Inventions

Robot (household)

noreply@blogger.com (Toma) — Wed, 14 Apr 2010 02:14:05 PDT

The invention:

The first available personal robot, Hero 1 could
speak; carry small objects in a gripping arm, and sense light, motion,
sound, and time.

The people behind the invention:

Karel Capek (1890-1938), a Czech playwright
The Health Company, an American electronics manufacturer

Personal Robots

In 1920, the Czech playwright Karel Capek introduced the term
robot, which he used to refer to intelligent, humanoid automatons
that were subservient to humans. Robots such as those described
by Capek have not yet been developed; their closest counterparts
are the nonintelligent automatons used by industry and by private
individuals. Most industrial robots are heavy-duty, immobile machines
designed to replace humans in routine, undesirable, monotonous
jobs. Most often, they use programmed gripping arms to
carry out tasks such as spray painting cars, assembling watches,
and shearing sheep.
Modern personal robots are smaller, more mobile, less expensive
models that serve mostly as toys or teaching tools. In some
cases, they can be programmed to carry out activities such as walking
dogs or serving mixed drinks. Usually, however, it takes more
effort to program a robot to perform such activities than it does to
do them oneself.
The Hero 1, which was first manufactured by the Heath Company
in 1982, has been a very popular personal robot. Conceived
as a toy and a teaching tool, the Hero 1 can be programmed
to speak; to sense light, sound, motion, and time; and
to carry small objects. The Hero 1 and other personal robots are
often viewed as tools that will someday make it possible to produce
intelligent robots.

Hero 1 Operation
The concept of artificial beings serving humanity has existed
since antiquity (for example, it is found in Greek mythology). Such
devices, which are now called robots, were first actualized, in a
simple form, in the 1960’s. Then, in the mid-1970’s, the manufacture
of personal robots began. One of the first personal robots was
the Turtle, which was made by the Terrapin Company of Cambridge,
Massachusetts. The Turtle was a toy that entertained owners
via remote control, programmable motion, a beeper, and blinking
displays. The Turtle was controlled by a computer to which it
was linked by a cable.
Among the first significant personal robots was the Hero 1. This
robot, which was usually sold in the form of a $1,000 kit that had to
be assembled, is a squat, thirty-nine-pound mobile unit containing a
head, a body, and a base. The head contains control boards, sensors,
and a manipulator arm. The body houses control boards and related
electronics, while the base contains a three-wheel-drive unit that
renders the robot mobile.
The Heath Company, which produced the Hero 1, viewed it as
providing entertainment for and teaching people who are interested
in robot applications. To facilitate these uses, the following
abilities were incorporated into the Hero 1: independent operation
via rechargeable batteries; motion- and distance/position-sensing
capability; light, sound, and language use/recognition; a manipulator
arm to carry out simple tasks; and easy programmability.
The Hero 1 is powered by four rechargeable batteries arranged as
two 12-volt power supplies. Recharging is accomplished by means
of a recharging box that is plugged into a home outlet. It takes six to
eight hours to recharge depleted batteries, and complete charging is
signaled by an indicator light. In the functioning robot, the power
supplies provide 5-volt and 12-volt outputs to logic and motor circuits,
respectively.
The Hero 1 moves by means of a drive mechanism in its base. The
mechanism contains three wheels, two of which are unpowered
drones. The third wheel, which is powered for forward and reverse
motion, is connected to a stepper motor that makes possible directional
steering. Also included in the powered wheel is a metal disk with spaced reflective slots that helps Hero 1 to identify its position.
As the robot moves, light is used to count the slots, and the slot
count is used to measure the distance the robot has traveled, and
therefore its position.
The robot’s “senses,” located in its head, consist of sound, light,
and motion detectors as well as a phoneme synthesizer (phonemes
are sounds, or units of speech). All these components are connected
with the computer. The Hero 1 can detect sounds between 200 and
5,000 hertz. Its motion sensor detects all movement within a 15-foot
radius. The phoneme synthesizer is capable of producing most
words by using combinations of 64 phonemes. In addition, the robot
keeps track of time by using an internal clock/calendar.
The Hero 1 can carry out various tasks by using a gripper that
serves as a hand. The arm on which the gripper is located is connected
to the back of the robot’s head. The head (and, therefore, the
arm) can rotate 350 degrees horizontally. In addition, the arm contains
a shoulder motor that allows it to rise or drop 150 degrees vertically,
and its forearm can be either extended or retracted. Finally, a
wrist motor allows the gripper’s tip to rotate by 350 degrees, and the
two-fingered gripper can open up to a maximum width of 3.5
inches. The arm is not useful except as an educational tool, since its
load-bearing capacity is only about a pound and its gripper can exert
a force of only 6 ounces.
The computational capabilities of the robot are much more impressive
than its physical capabilities. Programming is accomplished
by means of a simple keypad located on the robot’s head, which
provides an inexpensive, easy-to-use method of operator-computer
communication. To make things simpler for users who want entertainment
without having to learn robotics, a manual mode is included
for programming. In the manual mode, a hand-held teaching
pendant is connected to Hero 1 and used to program all the
motion capabilities of the robot. The programming of sensory and
language abilities, however, must be accomplished by using the
keyboard. Using the keyboard and the various options that are
available enables Hero 1 owners to program the robot to perform
many interesting activities.

Consequences

The Hero 1 had a huge impact on robotics; thousands of people
purchased it and used it for entertainment, study, and robot design.
The Heath Company itself learned from the Hero 1 and later introduced
an improved version: Heathkit 2000. This personal robot,
which costs between $2,000 and $4,500, has ten times the capabilities
of Hero 1, operates via radio-controlled keyboard, contains a
voice synthesizer that can be programmed in any language, and
plugs itself in for recharging.
Other companies, including the Androbot Company in California,
have manufactured personal robots that sell for up to $10,000.
One such robot is the Androbot BOB (brains on board). It can guard
a home, call the police, walk at 2.5 kilometers per hour, and sing.
Androbot has also designed Topo, a personal robot that can serve
drinks. Still other robots can sort laundry and/or vacuum-clean
houses. Although modern robots lack intelligence and merely have
the ability to move when they are directed to by a program or by remote
control, there is no doubt that intelligent robots will be developed
in the future.

Richter scale

noreply@blogger.com (Toma) — Wed, 31 Mar 2010 08:29:11 PDT

The invention:

A scale for measuring the strength of earthquakes
based on their seismograph recordings.

The people behind the invention:

Charles F. Richter (1900-1985), an American seismologist
Beno Gutenberg (1889-1960), a German American seismologist
Kiyoo Wadati (1902- ), a pioneering Japanese seismologist
Giuseppe Mercalli (1850-1914), an Italian physicist,volcanologist, and meteorologist

Earthquake Study by Eyewitness Report

Earthquakes range in strength from barely detectable tremors to
catastrophes that devastate large regions and take hundreds of thousands
of lives. Yet the human impact of earthquakes is not an accurate
measure of their power; minor earthquakes in heavily populated regions
may cause great destruction, whereas powerful earthquakes in
remote areas may go unnoticed. To study earthquakes, it is essential
to have an accurate means of measuring their power.
The first attempt to measure the power of earthquakes was the
development of intensity scales, which relied on damage effects
and reports by witnesses to measure the force of vibration. The
first such scale was devised by geologists Michele Stefano de Rossi
and François-Alphonse Forel in 1883. It ranked earthquakes on a
scale of 1 to 10. The de Rossi-Forel scale proved to have two serious
limitations: Its level 10 encompassed a great range of effects, and its
description of effects on human-made and natural objects was so specifically
European that it was difficult to apply the scale elsewhere.
To remedy these problems, Giuseppe Mercalli published a revised
intensity scale in 1902. The Mercalli scale, as it came to be
called, added two levels to the high end of the de Rossi-Forel scale,
making its highest level 12. It also was rewritten to make it more
globally applicable. With later modifications by Charles F. Richter,
the Mercalli scale is still in use.
Intensity measurements, even though they are somewhat subjective, are very useful in mapping the extent of earthquake effects.
Nevertheless, intensity measurements are still not ideal measuring
techniques. Intensity varies from place to place and is strongly influenced
by geologic features, and different observers frequently report
different intensities. There is a need for an objective method of
describing the strength of earthquakes with a single measurement.

Measuring Earthquakes One Hundred Kilometers Away

An objective technique for determining the power of earthquakes
was devised in the early 1930’s by Richter at the California Institute
of Technology in Pasadena, California. The eventual usefulness of
the scale that came to be called the “Richter scale” was completely
unforeseen at first.
In 1931, the California Institute of Technology was preparing to
issue a catalog of all earthquakes detected by its seismographs in the
preceding three years. Several hundred earthquakes were listed,
most of which had not been felt by humans, but detected only by instruments.
Richter was concerned about the possible misinterpretations
of the listing. With no indication of the strength of the earthquakes,
the public might overestimate the risk of earthquakes in
areas where seismographs were numerous and underestimate the
risk in areas where seismographs were few.
To remedy the lack of a measuring method, Richter devised the
scale that now bears his name. On this scale, earthquake force is expressed
in magnitudes, which in turn are expressed in whole numbers
and decimals. Each increase of one magnitude indicates a tenfold jump
in the earthquake’s force. These measurements were defined for a
standard seismograph located one hundred kilometers fromthe earthquake.
By comparing records for earthquakes recorded on different devices at different distances,
Richter was able to create conversion tables
for measuring magnitudes for any instrument at any distance.

Impact

Richter had hoped to create a rough means of separating small,
medium, and large earthquakes, but he found that the scale was capable
of making much finer distinctions. Most magnitude estimates
made with a variety of instruments at various distances from earthquakes
agreed to within a few tenths of a magnitude. Richter formally
published a description of his scale in January, 1935, in the
Bulletin of the Seismological Society of America. Other systems of estimating
magnitude had been attempted, notably that of KiyooWadati,
published in 1931, but Richter’s system proved to be the most workable
scale yet devised and rapidly became the standard.
Over the next few years, the scale was refined. One critical refinement
was in the way seismic recordings were converted into magnitude.
Earthquakes produce many types of waves, but it was not
known which type should be the standard for magnitude. So-called
surface waves travel along the surface of the earth. It is these waves
that produce most of the damage in large earthquakes; therefore, it
seemed logical to let these waves be the standard. Earthquakes deep
within the earth, however, produce few surface waves. Magnitudes
based on surface waves would therefore be too small for these earthquakes.
Deep earthquakes produce mostly waves that travel through
the solid body of the earth; these are the so-called body waves.
It became apparent that two scales were needed: one based on
surface waves and one on body waves. Richter and his colleague
Beno Gutenberg developed scales for the two different types of
waves, which are still in use. Magnitudes estimated from surface
waves are symbolized by a capital M, and those based on body
waves are denoted by a lowercase m.
From a knowledge of Earth movements associated with seismic
waves, Richter and Gutenberg succeeded in defining the energy
output of an earthquake in measurements of magnitude. A magnitude
6 earthquake releases about as much energy as a one-megaton
nuclear explosion; a magnitude 0 earthquake releases about as
much energy as a small car dropped off a two-story building.

Charles F. Richter

Charles Francis Richter was born in Ohio in 1900. After his
mother divorced his father, she moved the family to Los Angles
in 1909. Aprecocious student, Richter entered the University of
Southern California at sixteen and transferred to Stanford University
a year later, majoring in physics. He graduated in 1920
and finished a doctorate in theoretical physics at the California
Institute of Technology in 1928.
While Richter was a graduate student at Caltech, Noble laureate
Robert A. Millikan lured him away from his original interest,
astronomy, to become an assistant at the seismology laboratory.
Richter realized that seismology was then a relatively new
discipline and that he could help it mature. He stayed with it—
and Caltech—for the rest of his university career, retiring as
professor emeritus in 1970. In 1971 he opened a consulting
firm—Lindvall, Richter and Associates—to assess the earthquake
readiness of structures.
Richter published more than two hundred articles about
earthquakes and earthquake engineering and two influential
books, Elementary Seismology and Seismicity of the Earth (with
Beno Gutenberg). These works, together with his teaching,
trained a generation of earthquake researchers and gave them a
basic tool, the Richter scale, to work with. He died in California
in 1985.

Rice and wheat strains

noreply@blogger.com (Toma) — Tue, 23 Mar 2010 05:00:03 PDT

The invention:

Artificially created high-yielding wheat and rice
varieties that are helping food producers in developing countries
keep pace with population growth
The people behind the invention:

Orville A. Vogel (1907-1991), an agronomist who developed
high-yielding semidwarf winter wheats and equipment for
wheat research
Norman E. Borlaug (1914- ), a distinguished agricultural
scientist
Robert F. Chandler, Jr. (1907-1999), an international agricultural
consultant and director of the International Rice Research
Institute, 1959-1972
William S. Gaud (1907-1977), a lawyer and the administrator of
the U.S. Agency for International Development, 1966-1969

The Problem of Hunger

In the 1960’s, agricultural scientists created new, high-yielding
strains of rice and wheat designed to fight hunger in developing
countries. Although the introduction of these new grains raised levels
of food production in poor countries, population growth and
other factors limited the success of the so-called “Green Revolution.”
Before World War II, many countries of Asia, Africa, and Latin
America exported grain toWestern Europe. After the war, however,
these countries began importing food, especially from the United
States. By 1960, they were importing about nineteen million tons of
grain a year; that level nearly doubled to thirty-six million tons in
1966. Rapidly growing populations forced the largest developing
countries—China, India, and Brazil in particular—to import huge
amounts of grain. Famine was averted on the Indian subcontinent
in 1966 and 1967 only by the United States shipping wheat to the region.
The United States then changed its food policy. Instead of contributing
food aid directly to hungry countries, the U.S. began working to help such countries feed themselves.
The new rice and wheat strains were introduced just as countries
in Africa and Asia were gaining their independence from the European
nations that had colonized them. The ColdWar was still going
strong, and Washington and other Western capitals feared that the
Soviet Union was gaining influence in the emerging countries. To
help counter this threat, the U.S. Agency for International Development
(USAID) was active in the ThirdWorld in the 1960’s, directing
or contributing to dozens of agricultural projects, including building
rural infrastructure (farm-to-market roads, irrigation projects,
and rural electric systems), introducing modern agricultural techniques,
and importing fertilizer or constructing fertilizer factories in
other countries. By raising the standard of living of impoverished
people in developing countries through applying technology to agriculture,
policymakers hoped to eliminate the socioeconomic conditions
that would support communism.

The Green Revolution

It was against this background thatWilliam S. Gaud, administrator
of USAID from 1966 to 1969, first talked about a “green revolution”
in a 1968 speech before the Society for International Development
in Washington, D.C. The term “green revolution” has
been used to refer to both the scientific development of highyielding
food crops and the broader socioeconomic changes in a
country’s agricultural sector stemming from farmers’ adoption of
these crops.
In 1947, S. C. Salmon, a United States Department of Agriculture
(USDA) scientist, brought a wheat-dwarfing gene to the United
States. Developed in Japan, the gene produced wheat on a short
stalk that was strong enough to bear a heavy head of grain. Orville
Vogel, another USDA scientist, then introduced the gene into local
wheat strains, creating a successful dwarf variety known as Gaines
wheat. Under irrigation, Gaines wheat produced record yields. After
hearing about Vogel’s work, Norman Borlaug, who headed
the Rockefeller Foundation’s wheat-breeding program in Mexico,
adapted Gaines wheat, later called “miracle wheat,” to a variety of
growing conditions in Mexico.
Success with the development of high-yielding wheat varieties
persuaded the Rockefeller and Ford foundations to pursue similar
ends in rice culture. The foundations funded the International Rice
Research Institute (IRRI) in Los Banos, Philippines, appointing as director
Robert F. Chandler, Jr., an international agricultural consultant.
Under his leadership, IRRI researchers cross-bred Peta, a tall variety
of rice from Indonesia, with Deo-geo-woo-gen, a dwarf rice from Taiwan,
to produce a new strain, IR-8. Released in 1966 and dubbed
“miracle rice,” IR-8 produced yields double those of other Asian rice
varieties and in a shorter time, 120 days in contrast to 150 to 180 days.
Statistics from India illustrate the expansion of the new grain varieties.
During the 1966-1967 growing season, Indian farmers planted
improved rice strains on 900,000 hectares, or 2.5 percent of the total
area planted in rice. By 1984-1985, the surface area planted in improved
rice varieties stood at 23.4 million hectares, or 56.9 percent of
the total. The rate of adoption was even faster for wheat. In 1966-
1967, improved varieties covered 500,000 hectares, comprising 4.2
percent of the total wheat crop. By the 1984-1985 growing season,
the surface area had expanded to 19.6 million hectares, or 82.9 percent
of the total wheat crop.
To produce such high yields, IR-8 and other genetically engineered
varieties of rice and wheat required the use of irrigation, fertilizers,
and pesticides. Irrigation further increased food production
by allowing year-round farming and the planting of multiple crops
on the same plot of land, either two crops of high-yielding grain varieties
or one grain crop and another food crop.
Expectations
The rationale behind the introduction of high-yielding grains in
developing countries was that it would start a cycle of improvement
in the lives of the rural poor. High-yielding grains would lead to
bigger harvests and better-nourished and healthier families. If better
nutrition enabled more children to survive, the need to have large
families to ensure care for elderly parents would ease. Ahigher survival
rate of children would lead couples to use family planning,
slowing overall population growth and allowing per capita food intake
to rise.
The greatest impact of the Green Revolution has been seen in
Asia, which experienced dramatic increases in rice production, and
on the Indian subcontinent, with increases in rice and wheat yields.
Latin America, especially Mexico, enjoyed increases in wheat harvests.
Subsaharan Africa initially was left out of the revolution, as
scientists paid scant attention to increasing the yields of such staple
food crops as yams, cassava, millet, and sorghum. By the 1980’s,
however, this situation was being remedied with new research directed
toward millet and sorghum.
Research is conducted by a network of international agricultural
research centers. Backed by both public and private funds, these
centers cooperate with international assistance agencies, private
foundations, universities, multinational corporations, and government
agencies to pursue and disseminate research into improved
crop varieties to farmers in the Third World. IRRI and the International
Maize and Wheat Improvement Center (IMMYT) in Mexico
City are two of these agencies.

Impact

Expectations went unrealized in the first few decades following
the green revolution. Despite the higher yields from millions of
tons of improved grain seeds imported into the developing world,
lower-yielding grains still accounted for much of the surface area
planted in grain. The reasons for this explain the limits and impact
of the Green Revolution.
The subsistence mentality dies hard. The main targets of Green
Revolution programs were small farmers, people whose crops provide
barely enough to feed their families and provide seed for the
next crop. If an experimental grain failed, they faced starvation.
Such farmers hedged their bets when faced with a new proposition,
for example, by intercropping, alternating rows of different grains
in the same field. In this way, even if one crop failed, another might
feed the family.
Poor farmers in developing countries also were likely to be illiterate
and not eager to try something they did not fully understand.
Also, by definition, poor farmers often did not have the means to
purchase the inputs—irrigation, fertilizer, and pesticides—required
to grow the improved varieties.
In many developing countries, therefore, rich farmers tended to be
the innovators. More likely than poor farmers to be literate, they also
had the money to exploit fully the improved grain varieties. They
also were more likely than subsistence-level farmers to be in touch
with the monetary economy, making purchases from the agricultural
supply industry and arranging sales through established marketing
channels, rather than producing primarily for personal or family use.
Once wealthy farmers adopted the new grains, it often became
more difficult for poor farmers to do so. Increased demand for limited
supplies, such as pesticides and fertilizers, raised costs, while
bigger-than-usual harvests depressed market prices.With high sales
volumes, owners of large farms could withstand the higher costs and
lower-per-unit profits, but smaller farmers often could not.
Often, the result of adopting improved grains was that small
farmers could no longer make ends meet solely by farming. Instead,
they were forced to hire themselves out as laborers on large farms.
Surges of laborers into a limited market depressed rural wages,
making it even more difficult for small farmers to eke out a living.
The result was that rich farmers got richer and poor farmers got
poorer. Often, small farmers who could no longer support their
families would leave rural areas and migrate to the cities, seeking
work and swelling the ranks of the urban poor.

Mixed Results

The effects of the Green Revolution were thus mixed. The dissemination
of improved grain varieties unquestionably increased
grain harvests in some of the poorest countries of the world. Seed
companies developed, produced, and sold commercial quantities of
improved grains, and fertilizer and pesticide manufacturers logged
sales to developing countries thanks to USAID-sponsored projects.
Along with disrupting the rural social structure and encouraging
rural flight to the cities, the Green Revolution has had other negative
effects. For example, the millions of tube wells sunk in India to
irrigate crops reduced groundwater levels in some regions faster
than they could be recharged. In other areas, excessive use of pesticides
created health hazards, and fertilizer use led to streams and
ponds being clogged by weeds. The scientific community became
concerned that the use of improved varieties of grain, many of
which were developed from the same mother variety, reduced the
genetic diversity of the world’s food crops, making them especially
vulnerable to attack by disease or pests.
Perhaps the most significant impact of the Green Revolution is
the change it wrought in the income and class structure of rural areas;
often, malnutrition was not eliminated in either the countryside
or the cities. Almost without exception, the relative position of peasants
deteriorated. Many analysts admit that the Green Revolution
did not end world hunger, but they argue that it did buy time. The
poorest of the poor would be even worse off without it.

Reserpine

noreply@blogger.com (Toma) — Tue, 23 Mar 2010 05:00:44 PDT

The invention: A drug with unique hypertension-decreasing effects
that provides clinical medicine with a versatile and effective
tool.
The people behind the invention:
Robert Wallace Wilkins (1906- ), an American physician and
clinical researcher
Walter E. Judson (1916- ) , an American clinical researcher
Treating Hypertension
Excessively elevated blood pressure, clinically known as “hypertension,”
has long been recognized as a pervasive and serious human
malady. In a few cases, hypertension is recognized as an effect
brought about by particular pathologies (diseases or disorders). Often,
however, hypertension occurs as the result of unknown causes.
Despite the uncertainty about its origins, unattended hypertension
leads to potentially dramatic health problems, including increased
risk of kidney disease, heart disease, and stroke.
Recognizing the need to treat hypertension in a relatively straightforward
and effective way, Robert Wallace Wilkins, a clinical researcher
at Boston University’s School of Medicine and the head of
Massachusetts Memorial Hospital’s Hypertension Clinic, began to
experiment with reserpine in the early 1950’s. Initially, the samples
that were made available to Wilkins were crude and unpurified.
Eventually, however, a purified version was used.
Reserpine has a long and fascinating history of use—both clinically
and in folk medicine—in India. The source of reserpine is the
root of the shrub Rauwolfia serpentina, first mentioned in Western
medical literature in the 1500’s but virtually unknown, or at least
unaccepted, outside India until the mid-twentieth century. Crude
preparations of the shrub had been used for a variety of ailments in
India for centuries prior to its use in the West.
Wilkins’s work with the drug did not begin on an encouraging
note, because reserpine does not act rapidly—a fact that had been
noted in Indian medical literature. The standard observation in
Western pharmacotherapy, however, was that most drugs work
rapidly; if a week has elapsed without positive effects being shown
by a drug, the conventional Western wisdom is that it is unlikely
to work at all. Additionally, physicians and patients alike tend to
look for rapid improvement or at least positive indications. Reserpine
is deceptive in this temporal context, andWilkins and his
coworkers were nearly deceived. In working with crude preparations
of Rauwolfia serpentina, they were becoming very pessimistic,
when a patient who had been treated for many consecutive
days began to show symptomatic relief. Nevertheless, only after
months of treatment did Wilkins become a believer in the drug’s
beneficial effects.

The Action of Reserpine

When preparations of pure reserpine became available in 1952,
the drug did not at first appear to be the active ingredient in the
crude preparations. When patients’ heart rate and blood pressure
began to drop after weeks of treatment, however, the investigators
saw that reserpine was indeed responsible for the improvements.
Once reserpine’s activity began, Wilkins observed a number of
important and unique consequences. Both the crude preparations
and pure reserpine significantly reduced the two most meaningful
measures of blood pressure. These two measures are systolic blood
pressure and diastolic blood pressure. Systolic pressure represents
the peak of pressure produced in the arteries following a contraction
of the heart. Diastolic pressure is the low point that occurs
when the heart is resting. To lower the mean blood pressure in the
system significantly, both of these pressures must be reduced. The
administration of low doses of reserpine produced an average drop
in pressure of about 15 percent, a figure that was considered less
than dramatic but still highly significant. The complex phenomenon
of blood pressure is determined by a multitude of factors, including
the resistance of the arteries, the force of contraction of the
heart, and the heartbeat rate. In addition to lowering the blood pressure,
reserpine reduced the heartbeat rate by about 15 percent, providing
an important auxiliary action.
In the early 1950’s, various therapeutic drugs were used to treat
hypertension. Wilkins recognized that reserpine’s major contribution
would be as a drug that could be used in combination with
drugs that were already in use. His studies established that reserpine,
combined with at least one of the drugs already in use, produced
an additive effect in lowering blood pressure. Indeed, at
times, the drug combinations produced a “synergistic effect,” which
means that the combination of drugs created an effect that was more
effective than the sum of the effects of the drugs when they were administered
alone. Wilkins also discovered that reserpine was most
effective when administered in low dosages. Increasing the dosage
did not increase the drug’s effect significantly, but it did increase the
likelihood of unwanted side effects. This fact meant that reserpine
was indeed most effective when administered in low dosages along
with other drugs.
Wilkins believed that reserpine’s most unique effects were not
those found directly in the cardiovascular system but those produced
indirectly by the brain. Hypertension is often accompanied
by neurotic anxiety, which is both a consequence of the justifiable
fears of future negative health changes brought on by
prolonged hypertension and contributory to the hypertension itself.
Wilkins’s patients invariably felt better mentally, were less
anxious, and were sedated, but in an unusual way. Reserpine
made patients drowsy but did not generally cause sleep, and if
sleep did occur, patients could be awakened easily. Such effects
are now recognized as characteristic of tranquilizing drugs, or
antipsychotics. In effect, Wilkins had discovered a new and important
category of drugs: tranquilizers.

Impact

Reserpine holds a vital position in the historical development of
antihypertensive drugs for two reasons. First, it was the first drug
that was discovered to block activity in areas of the nervous system
that use norepinephrine or its close relative dopamine as transmitter
substances. Second, it was the first hypertension drug to be
widely accepted and used. Its unusual combination of characteristics
made it effective in most patients.
Since the 1950’s, medical science has rigorously examined cardiovascular
functioning and diseases such as hypertension. Many
new factors, such as diet and stress, have been recognized as factors
in hypertension. Controlling diet and life-style help tremendously
in treating hypertension, but if the nervous system could not be partially
controlled, many cases of hypertension would continue to be
problematic. Reserpine has made that control possible.

Refrigerant gas

noreply@blogger.com (Toma) — Thu, 11 Mar 2010 09:24:44 PST

The invention: A safe refrigerant gas for domestic refrigerators,
dichlorodifluoromethane helped promote a rapid growth in the
acceptance of electrical refrigerators in homes.
The people behind the invention:
Thomas Midgley, Jr. (1889-1944), an American engineer and
chemist
Charles F. Kettering (1876-1958), an American engineer and
inventor who was the head of research for General Motors
Albert Henne (1901-1967), an American chemist who was
Midgley’s chief assistant
Frédéric Swarts (1866-1940), a Belgian chemist
Toxic Gases
Refrigerators, freezers, and air conditioners have had a major impact
on the way people live and work in the twentieth century.With
them, people can live more comfortably in hot and humid areas,
and a great variety of perishable foods can be transported and
stored for extended periods. As recently as the early nineteenth century,
the foods most regularly available to Americans were bread
and salted meats. Items now considered essential to a balanced diet,
such as vegetables, fruits, and dairy products, were produced and
consumed only in small amounts.

Through the early part of the twentieth century, the pattern of
food storage and distribution evolved to make perishable foods
more available. Farmers shipped dairy products and frozen meats
to mechanically refrigerated warehouses. Smaller stores and most
American households used iceboxes to keep perishable foods fresh.
The iceman was a familiar figure on the streets of American towns,
delivering large blocks of ice regularly.
In 1930, domestic mechanical refrigerators were being produced
in increasing numbers. Most of them were vapor compression machines,
in which a gas was compressed in a closed system of pipes
outside the refrigerator by a mechanical pump and condensed to a liquid. The liquid was pumped into a sealed chamber in the refrigerator
and allowed to evaporate to a gas. The process of evaporation
removes heat from the environment, thus cooling the interior of the
refrigerator.
The major drawback of early home refrigerators involved the
types of gases used. In 1930, these included ammonia, sulfur dioxide,
and methyl chloride. These gases were acceptable if the refrigerator’s
gas pipes never sprang a leak. Unfortunately, leaks sometimes
occurred, and all these gases are toxic. Ammonia and sulfur
dioxide both have unpleasant odors; if they leaked, at least they
would be detected rapidly. Methyl chloride however, can form a
dangerously explosive mixture with air, and it has only a very faint,
and not unpleasant, odor. In a hospital in Cleveland during the
1920’s, a refrigerator with methyl chloride leaked, and there was a
disastrous explosion of the methyl chloride-air mixture. After that,
methyl chloride for use in refrigerators was mixed with a small
amount of a very bad-smelling compound to make leaks detectable.
(The same tactic is used with natural gas.)
Three-Day Success
General Motors, through its Frigidaire division, had a substantial
interest in the domestic refrigerator market. Frigidaire refrigerators
used sulfur dioxide as the refrigerant gas. Charles F. Kettering,
director of research for General Motors, decided that Frigidaire
needed a new refrigerant gas that would have good thermal properties
but would be nontoxic and nonexplosive. In early 1930, he sent
Lester S. Keilholtz, chief engineer of General Motors’ Frigidaire division,
to Thomas Midgley, Jr., a mechanical engineer and selftaught
chemist. He challenged them to develop such a new gas.
Midgley’s associates, Albert Henne and Robert McNary, researched
what types of compounds might already fit Kettering’s specifications.
Working with research that had been done by the Belgian
chemist Frédéric Swarts in the late nineteenth and early twentieth
centuries, Midgley, Henne, and McNary realized that dichlorodifluoromethane
would have ideal thermal properties and the right
boiling point for a refrigerant gas. The only question left to be answered
was whether the compound was toxic.
The chemists prepared a few grams of dichlorodifluoromethane
and put it, along with a guinea pig, into a closed chamber. They
were delighted to see that the animal seemed to suffer no ill effects
at all and was able to breathe and move normally. They were briefly
puzzled when a second batch of the compound killed a guinea pig
almost instantly. Soon, they discovered that an impurity in one of
the ingredients had produced a potent poison in their refrigerant
gas. A simple washing procedure completely removed the poisonous
contaminant.
This astonishingly successful research project was completed in
three days. The boiling point of dichlorodifluoromethane is -5.6 degrees
Celsius. It is nontoxic and nonflammable and possesses excellent
thermal properties. When Midgley was awarded the Perkin
Medal for industrial chemistry in 1937, he gave the audience a
graphic demonstration of the properties of dichlorodifluoromethane:
He inhaled deeply of its vapors and exhaled gently into a jar
containing a burning candle. The candle flame promptly went out.
This visual evidence proved that dichlorodifluoromethane was not
poisonous and would not burn.
Impact
The availability of this safe refrigerant gas, which was renamed
Freon, led to drastic changes in the United States. The current patterns
of food production, distribution, and consumption are a direct
result, as is air conditioning. Air conditioning was developed early
in the twentieth century; by the late 1970’s, most American cars and
residences were equipped with air conditioning, and other countries
with hot climates followed suit. Consequently, major relocations
of populations and businesses have become possible. Since
World War II, there have been steady migrations to the “Sun Belt,”
the states spanning the United States from southeast to southwest,
because air conditioners have made these areas much more livable.
Freon is a member of a family of chemicals called “chlorofluorocarbons.”
In addition to refrigeration, it is also used as a propellant
in aerosols and in the production of polystyrene plastics. In 1974,
scientists began to suspect that chlorofluorocarbons, when released
into the air, might have a serious effect on the environment. They
speculated that the compounds might migrate into the stratosphere,
where they could be decomposed by the intense ultraviolet light
from the sunlight that is prevented from reaching the earth’s surface
by the thin but vital layer of ozone in the stratosphere. In the process,
large amounts of the ozone layer might also be destroyed—
letting in the dangerous ultraviolet light. In addition to possible climatic
effects, the resulting increase in ultraviolet light reaching the
earth’s surface would raise the incidence of skin cancers. As a result,
chemical manufacturers are trying to develop alternative refrigerant
gases that will not harm the ozone layer.

Radio interferometer

noreply@blogger.com (Toma) — Thu, 11 Mar 2010 09:22:36 PST

The invention: An astronomical instrument that combines multiple
radio telescopes into a single system that makes possible the
exploration of distant space.
The people behind the invention:
Sir Martin Ryle (1918-1984), an English astronomer
Karl Jansky (1905-1950), an American radio engineer
Hendrik Christoffel van de Hulst (1918- ), a Dutch radio
astronomer
Harold Irving Ewan (1922- ), an American astrophysicist
Edward Mills Purcell (1912-1997), an American physicist
Seeing with Radio
Since the early 1600’s, astronomers have relied on optical telescopes
for viewing stellar objects. Optical telescopes detect the
visible light from stars, galaxies, quasars, and other astronomical
objects. Throughout the late twentieth century, astronomers developed
more powerful optical telescopes for peering deeper into the
cosmos and viewing objects located hundreds of millions of lightyears
away from the earth.

In 1933, Karl Jansky, an American radio engineer with Bell Telephone
Laboratories, constructed a radio antenna receiver for locating
sources of telephone interference. Jansky discovered a daily radio
burst that he was able to trace to the center of the Milky Way
galaxy. In 1935, Grote Reber, another American radio engineer, followed
up Jansky’s work with the construction of the first dishshaped
“radio” telescope. Reber used his 9-meter-diameter radio
telescope to repeat Jansky’s experiments and to locate other radio
sources in space. He was able to map precisely the locations of various
radio sources in space, some of which later were identified as
galaxies and quasars.
Following World War II (that is, after 1945), radio astronomy
blossomed with the help of surplus radar equipment. Radio astronomy
tries to locate objects in space by picking up the radio waves that they emit. In 1944, the Dutch astronomer Hendrik Christoffel
van de Hulst had proposed that hydrogen atoms emit radio waves
with a 21-centimeter wavelength. Because hydrogen is the most
abundant element in the universe, van de Hulst’s discovery had explained
the nature of extraterrestrial radio waves. His theory later
was confirmed by the American radio astronomers Harold Irving
Ewen and Edward Mills Purcell of Harvard University.
By coupling the newly invented computer technology with radio
telescopes, astronomers were able to generate a radio image of a star
almost identical to the star’s optical image. Amajor advantage of radio
telescopes over optical telescopes is the ability of radio telescopes
to detect extraterrestrial radio emissions day or night, as well as their
ability to bypass the cosmic dust that dims or blocks visible light.
More with Less
After 1945, major research groups were formed in England, Australia,
and The Netherlands. Sir Martin Ryle was head of the Mullard
Radio Astronomy Observatory of the Cavendish Laboratory,
University of Cambridge. He had worked with radar for the Telecommunications
Research Establishment during World War II.
The radio telescopes developed by Ryle and other astronomers
operate on the same basic principle as satellite television receivers.
A constant stream of radio waves strikes the parabolic-shaped reflector
dish, which aims all the radio waves at a focusing point
above the dish. The focusing point directs the concentrated radio
beam to the center of the dish, where it is sent to a radio receiver,
then an amplifier, and finally to a chart recorder or computer.
With large-diameter radio telescopes, astronomers can locate
stars and galaxies that cannot be seen with optical telescopes. This
ability to detect more distant objects is called “resolution.” Like
optical telescopes, large-diameter radio telescopes have better resolution
than smaller ones. Very large radio telescopes were constructed
in the late 1950’s and early 1960’s (Jodrell Bank, England;
Green Bank, West Virginia; Arecibo, Puerto Rico). Instead of just
building larger radio telescopes to achieve greater resolution, however,
Ryle developed a method called “interferometry.” In Ryle’s
method, a computer is used to combine the incoming radio waves of two or more movable radio telescopes pointed at the same stellar
object.
Suppose that one had a 30-meter-diameter radio telescope. Its radio
wave-collecting area would be limited to its diameter. If a second
identical 30-meter-diameter radio telescope was linked with
the first, then one would have an interferometer. The two radio telescopes
would point exactly at the same stellar object, and the radio
emissions from this object captured by the two telescopes would be
combined by computer to produce a higher-resolution image. If the
two radio telescopes were located 1.6 kilometers apart, then their
combined resolution would be equivalent to that of a single radio
telescope dish 1.6 kilometers in diameter.
Ryle constructed the first true radio telescope interferometer at
the Mullard Radio Astronomy Observatory in 1955. He used combinations
of radio telescopes to produce interferometers containing
about twelve radio receivers. Ryle’s interferometer greatly improved
radio telescope resolution for detecting stellar radio sources, mapping
the locations of stars and galaxies, assisting in the discovery of “quasars” (quasi-stellar radio sources), measuring the earth’s rotation
around the Sun, and measuring the motion of the solar system
through space.
Consequences
Following Ryle’s discovery, interferometers were constructed at
radio astronomy observatories throughout the world. The United
States established the National Radio Astronomy Observatory (NRAO)
in rural Green Bank, West Virginia. The NRAO is operated by nine
eastern universities and is funded by the National Science Foundation.
At Green Bank, a three-telescope interferometer was constructed,
with each radio telescope having a 26-meter-diameter
dish. During the late 1970’s, theNRAOconstructed the largest radio
interferometer in the world, the Very Large Array (VLA). The VLA,
located approximately 80 kilometers west of Socorro, New Mexico,
consists of twenty-seven 25-meter-diameter radio telescopes linked
by a supercomputer. The VLA has a resolution equivalent to that of
a single radio telescope 32 kilometers in diameter.
Even larger radio telescope interferometers can be created with
a technique known as “very long baseline interferometry” (VLBI).
VLBI has been used to construct a radio telescope having an effective
diameter of several thousand kilometers. Such an arrangement
involves the precise synchronization of radio telescopes located
in several different parts of the world. Supernova 1987A in
the Large Magellanic Cloud was studied using a VLBI arrangement
between observatories located in Australia, South America,
and South Africa.
Launching radio telescopes into orbit and linking them with
ground-based radio telescopes could produce a radio telescope
whose effective diameter would be larger than that of the earth.
Such instruments will enable astronomers to map the distribution
of galaxies, quasars, and other cosmic objects, to understand the
origin and evolution of the universe, and possibly to detect meaningful
radio signals from extraterrestrial civilizations.

Radio crystal sets

noreply@blogger.com (Toma) — Thu, 11 Mar 2010 09:20:18 PST

The invention: The first primitive radio receivers, crystal sets led
to the development of the modern radio.
The people behind the invention:
H. H. Dunwoody (1842-1933), an American inventor
Sir John A. Fleming (1849-1945), a British scientist-inventor
Heinrich Rudolph Hertz (1857-1894), a German physicist
Guglielmo Marconi (1874-1937), an Italian engineer-inventor
James Clerk Maxwell (1831-1879), a Scottish physicist
Greenleaf W. Pickard (1877-1956), an American inventor
From Morse Code to Music
In the 1860’s, James Clerk Maxwell demonstrated that electricity
and light had electromagnetic and wave properties. The conceptualization
of electromagnetic waves led Maxwell to propose that
such waves, made by an electrical discharge, would eventually be
sent long distances through space and used for communication
purposes. Then, near the end of the nineteenth century, the technology
that produced and transmitted the needed Hertzian (or radio)
waves was devised by Heinrich Rudolph Hertz, Guglielmo Marconi
(inventor of the wireless telegraph), and many others. The resultant
radio broadcasts, however, were limited to the dots and
dashes of the Morse code.

Then, in 1901, H. H. Dunwoody and Greenleaf W. Pickard invented
the crystal set. Crystal sets were the first radio receivers
that made it possible to hear music and the many other types of
now-familiar radio programs. In addition, the simple construction
of the crystal set enabled countless amateur radio enthusiasts
to build “wireless receivers” (the name for early radios) and
to modify them. Although, except as curiosities, crystal sets were
long ago replaced by more effective radios, they are where it all
began.
Crystals, Diodes, Transistors, and Chips
Radio broadcasting works by means of electromagnetic radio
waves, which are low-energy cousins of light waves. All electromagnetic
waves have characteristic vibration frequencies and wavelengths.
This article will deal mostly with long radio waves of frequencies
from 550 to 1,600 kilocycles (kilohertz), which can be seen
on amplitude-modulation (AM) radio dials. Frequency-modulation
(FM), shortwave, and microwave radio transmission use higherenergy
radio frequencies.
The broadcasting of radio programs begins with the conversion
of sound to electrical impulses by means of microphones. Then, radio
transmitters turn the electrical impulses into radio waves that
are broadcast together with higher-energy carrier waves. The combined
waves travel at the speed of light to listeners. Listeners hear
radio programs by using radio receivers that pick up broadcast
waves through antenna wires and reverse the steps used in broadcasting.
This is done by converting those waves to electrical impulses
and then into sound waves. The two main types of radio
broadcasting are AM and FM, which allow the selection (modulation)
of the power (amplitude) or energy (frequency) of the broadcast
waves.
The crystal set radio receiver of Dunwoody and Pickard had
many shortcomings. These led to the major modifications that produced
modern radios. Crystal sets, however, began the radio industry
and fostered its development. Today, it is possible to purchase
somewhat modified forms of crystal sets, as curiosity items. All
crystal sets, original or modern versions, are crudeAMradio receivers
that are composed of four components: an antenna wire, a crystal
detector, a tuning circuit, and a headphone or loudspeaker.
Antenna wires (aerials) pick up radio waves broadcast by external
sources. Originally simple wires, today’s aerials are made to
work better by means of insulation and grounding. The crystal detector
of a crystal set is a mineral crystal that allows radio waves to
be selected (tuned). The original detectors were crystals of a leadsulfur
mineral, galena. Later, other minerals (such as silicon and carborundum)
were also found to work. The tuning circuit is composed
of 80 to 100 turns of insulated wire, wound on a 0.33-inch support. Some surprising supports used in homemade tuning circuits
include cardboard toilet-paper-roll centers and Quaker Oats
cereal boxes. When realism is desired in collector crystal sets, the
coil is usually connected to a wire probe selector called a “cat’s
whisker.” In some such crystal sets, a condenser (capacitor) and additional
components are used to extend the range of tunable signals.
Headphones convert chosen radio signals to sound waves that are
heard by only one listener. If desired, loudspeakers can be used to
enable a roomful of listeners to hear chosen programs.
An interesting characteristic of the crystal set is the fact that its
operation does not require an external power supply. Offsetting
this are its short reception range and a great difficulty in tuning or
maintaining tuned-in radio signals. The short range of these radio
receivers led to, among other things, the use of power supplies
(house current or batteries) in more sophisticated radios. Modern
solutions to tuning problems include using manufactured diode
vacuum tubes to replace crystal detectors, which are a kind of natural
diode. The first manufactured diodes, used in later crystal sets
and other radios, were invented by John Ambrose Fleming, a colleague
of Marconi’s. Other modifications of crystal sets that led to
more sophisticated modern radios include more powerful aerials,
better circuits, and vacuum tubes. Then came miniaturization,
which was made possible by the use of transistors and silicon chips.
Impact
The impact of the invention of crystal sets is almost incalculable,
since they began the modern radio industry. These early radio receivers
enabled countless radio enthusiasts to build radios, to receive radio
messages, and to become interested in developing radio communication
systems. Crystal sets can be viewed as having spawned all
the variant modern radios. These include boom boxes and other portable
radios; navigational radios used in ships and supersonic jet
airplanes; and the shortwave, microwave, and satellite networks
used in the various aspects of modern communication.
The later miniaturization of radios and the development of sophisticated
radio system components (for example, transistors
and silicon chips) set the stage for both television and computers.
Certainly, if one tried to assess the ultimate impact of crystal sets by
simply counting the number of modern radios in the United States,
one would find that few Americans more than ten years old own
fewer than two radios. Typically, one of these is run by house electric
current and the other is a portable set that is carried almost everywhere.

Radio

noreply@blogger.com (Toma) — Thu, 28 Jan 2010 01:53:42 PST

The invention: The first radio transmissions of music and voice
laid the basis for the modern radio and television industries.
The people behind the invention:
Guglielmo Marconi (1874-1937), an Italian physicist and
inventor
Reginald Aubrey Fessenden (1866-1932), an American radio
pioneer
True Radio
The first major experimenter in the United States to work with
wireless radio was Reginald Aubrey Fessenden. This transplanted
Canadian was a skilled, self-made scientist, but unlike American inventor
Thomas Alva Edison, he lacked the business skills to gain the
full credit and wealth that such pathbreaking work might have merited.
Guglielmo Marconi, in contrast, is most often remembered as
the person who invented wireless (as opposed to telegraphic) radio.
There was a great difference between the contributions of Marconi
and Fessenden. Marconi limited himself to experiments with
radio telegraphy; that is, he sought to send through the air messages
that were currently being sent by wire—signals consisting of dots
and dashes. Fessenden sought to perfect radio telephony, or voice
communication by wireless transmission. Fessenden thus pioneered
the essential precursor of modern radio broadcasting.
At the beginning
of the twentieth century, Fessenden spent much time and energy
publicizing his experiments, thus promoting interest in the
new science of radio broadcasting.
Fessenden began his career as an inventor while working for the
U.S. Weather Bureau. He set out to invent a radio system by which
to broadcast weather forecasts to users on land and at sea. Fessenden
believed that his technique of using continuous waves in the
radio frequency range (rather than interrupted waves Marconi had
used to produce the dots and dashes of Morse code) would provide
the power necessary to carry Morse telegraph code yet be effective
enough to handle voice communication. He would turn out to be
correct. He conducted experiments as early as 1900 at Rock Point,
Maryland, about 80 kilometers south ofWashington, D.C., and registered
his first patent in the area of radio research in 1902.
Fame and Glory
In 1900, Fessenden asked the General Electric Company to produce
a high-speed generator of alternating current—or alternator—
to use as the basis of his radio transmitter. This proved to be the first
major request for wireless radio apparatus that could project voices
and music. It took the engineers three years to design and deliver
the alternator. Meanwhile, Fessenden worked on an improved radio
receiver. To fund his experiments, Fessenden aroused the interest
of financial backers, who put up one million dollars to create the
National Electric Signalling Company in 1902.
Fessenden, along with a small group of handpicked scientists,
worked at Brant Rock on the Massachusetts coast south of Boston.
Working outside the corporate system, Fessenden sought fame and
glory based on his own work, rather than on something owned by a
corporate patron.
Fessenden’s moment of glory came on December 24, 1906, with
the first announced broadcast of his radio telephone. Using an ordinary
telephone microphone and his special alternator to generate
the necessary radio energy, Fessenden alerted ships up and down
the Atlantic coast with his wireless telegraph and arranged for
newspaper reporters to listen in from New York City. Fessenden
made himself the center of the show. He played the violin, sang,
and read from the Bible. Anticipating what would become standard
practice fifty years later, Fessenden also transmitted the sounds of a
phonograph recording. He ended his first broadcast by wishing those
listening “a Merry Christmas.” A similar, equally well-publicized
demonstration came on December 31.
Although Fessenden was skilled at drawing attention to his invention
and must be credited, among others, as one of the engineering
founders of the principles of radio, he was far less skilled at
making money with his experiments, and thus his long-term impact
was limited. The National Electric Signalling Company had a fine
beginning and for a time was a supplier of equipment to the United
Fruit Company. The financial panic of 1907, however, wiped out an
opportunity to sell the Fessenden patents—at a vast profit—to a corporate
giant, the American Telephone and Telegraph Corporation.
Impact
Had there been more receiving equipment available and in place,
a massive audience could have heard Fessenden’s first broadcast.
He had the correct idea, even to the point of playing a crude phonograph
record. Yet Fessenden, Marconi, and their rivals were unable
to establish a regular series of broadcasts. Their “stations” were experimental
and promotional.
It took the stresses of World War I to encourage broader use of
wireless radio based on Fessenden’s experiments. Suddenly, communicating
from ship to ship or from a ship to shore became a frequent
matter of life or death. Generating publicity was no longer
necessary. Governments fought over crucial patent rights. The Radio
Corporation of America (RCA) pooled vital knowledge. Ultimately,
RCA came to acquire the Fessenden patents. Radio broadcasting
commenced, and the radio industry, with its multiple uses
for mass communication, was off and running.

Guglielmo Marconi

Guglielmo Marconi failed his entrance examinations to the
University of Bologna in 1894. He had a weak educational background,
particularly in science, but he was not about to let
that—or his father’s disapproval—stop him after he conceived
a deep interest in wireless telegraphy during his teenage years.
Marconi was born in 1874 to a wealthy Italian landowner
and an Irish whiskey distiller’s daughter and grew up both in
Italy and England. His parents provided tutors for
him, but he and his brother often accompanied their
mother, a socialite, on extensive travels. He acquired
considerable social skills, easy self-confidence, and
determination from the experience.
Thus, when he failed his exams, he simply tried another
route for his ambitions. He and his mother persuaded
a science professor to let Marconi use a university
laboratory unofficially. His father thought it a
waste of time. However, he changed his mind when
his son succeeded in building equipment that could
transmit electronic signals around their house without wires, an
achievement right at the vanguard of technology.
Now supported by his father’s money, Marconi and his
brother built an elaborate set of equipment—including an oscillator,
coherer, galvanometer, and antennas—that they hoped
would send a signal outside over a long distance. His brother
walked off a mile and a half, out of sight, with the galvanometer
and a rifle. When the galvanometer moved, indicating a signal
had arrived from the oscillator, he fired the rifle to let Marconi
know he had succeeded. The incident is widely cited as the first
radio transmission.
Marconi went on to send signals over greater and greater
distances. He patented a tuner to permit transmissions at specific
frequencies, and he started theWireless Telegraph and Signal
Company to bring his inventions to the public; its American
branch was the Radio Corporation of America (RCA). He not
only grew wealthy at a young age; he also was awarded half of
the 1909 Nobel Prize in Physics for his work. He died in Rome
in 1937, one of the most famous inventors in the world.

Radar

noreply@blogger.com (Toma) — Wed, 09 Dec 2009 03:03:52 PST

The invention: An electronic system for detecting objects at great
distances, radar was a major factor in the Allied victory ofWorld
War II and now pervades modern life, including scientific research.
The people behind the invention:
Sir Robert Watson-Watt (1892-1973), the father of radar who
proposed the chain air-warning system
Arnold F. Wilkins, the person who first calculated the intensity
of a radio wave
William C. Curtis (1914-1976), an American engineer
Looking for Thunder
Sir RobertWatson-Watt, a scientist with twenty years of experience
in government, led the development of the first radar, an acronym
for radio detection and ranging. “Radar” refers to any instrument
that uses the reflection of radio waves to determine the
distance, direction, and speed of an object.
In 1915, during World War I (1914-1918), Watson-Watt joined
Great Britain’s Meteorological Office. He began work on the detection
and location of thunderstorms at the Royal Aircraft Establishment
in Farnborough and remained there throughout the
war. Thunderstorms were known to be a prolific source of “atmospherics”
(audible disturbances produced in radio receiving apparatus
by atmospheric electrical phenomena), andWatson-Watt
began the design of an elementary radio direction finder that
gave the general position of such storms.

Research continued after
the war and reached a high point in 1922 when sealed-off
cathode-ray tubes first became available. With assistance from
J. F. Herd, a fellow Scot who had joined him at Farnborough, he
constructed an instantaneous direction finder, using the new
cathode-ray tubes, that gave the direction of thunderstorm activity.
It was admittedly of low sensitivity, but it worked, and it was
the first of its kind.Watson-Watt did much of this work at a new site at Ditton Park,
near Slough, where the National Physical Laboratory had a field
station devoted to radio research. In 1927, the two endeavors were
combined as the Radio Research Station; it came under the general
supervision of the National Physical Laboratory, withWatson-Watt
as the first superintendent. This became a center with unrivaled expertise
in direction finding using the cathode-ray tube and in studying
the ionosphere using radio waves. No doubt these facilities
were a factor when Watson-Watt invented radar in 1935.
As radar developed, its practical uses expanded. Meteorological
services around the world, using ground-based radar, gave warning
of approaching rainstorms. Airborne radars proved to be a great
help to aircraft by allowing them to recognize potentially hazardous
storm areas. This type of radar was used also to assist research into
cloud and rain physics. In this type of research, radar-equipped research
aircraft observe the radar echoes inside a cloud as rain develops,
and then fly through the cloud, using on-board instruments to
measure the water content.
Aiming Radar at the Moon
The principles of radar were further developed through the discipline
of radio astronomy. This field began with certain observations
made by the American electrical engineer Karl Jansky in 1933
at the Bell Laboratories at Holmdell, New Jersey. Radio astronomers
learn about objects in space by intercepting the radio waves that
these objects emit.
Jansky found that radio signals were coming to Earth from space.
He called these mysterious pulses “cosmic noise.” In particular, there
was an unusual amount of radar noise when the radio antennas were
pointed at the Sun, which increased at the time of sun-spot activity.
All this information lay dormant until after World War II (1939-
1945), at which time many investigators turned their attention to interpreting
the cosmic noise. The pioneers were Sir Bernard Lovell at
Manchester, England, Sir Martin Ryle at Cambridge, England, and
Joseph Pawsey of the Commonwealth of Science Industrial Research
Organization, in Australia. The intensity of these radio waves was
first calculated by Arnold F.Wilkins.
As more powerful tools became available toward the end of
World War II, curiosity caused experimenters to try to detect radio
signals from the Moon. This was accomplished successfully in the
late 1940’s and led to experiments on other objects in the solar system:
planets, satellites, comets, and asteroids.
Impact
Radar introduced some new and revolutionary concepts into warfare,
and in doing so gave birth to entirely new branches of technology.
In the application of radar to marine navigation, the long-range
navigation system developed during the war was taken up at once
by the merchant fleets that used military-style radar equipment
without modification. In addition, radar systems that could detect
buoys and other ships and obstructions in closed waters, particularly
under conditions of low visibility, proved particularly useful
to peacetime marine navigation.
In the same way, radar was adopted to assist in the navigation of
civil aircraft. The various types of track guidance systems developed after the war were aimed at guiding aircraft in the critical last
hundred kilometers or so of their run into an airport. Subsequent
improvements in the system meant that an aircraft could place itself
on an approach or landing path with great accuracy.
The ability of radar to measure distance to an extraordinary degree
of accuracy resulted in the development of an instrument that
provided pilots with a direct measurement of the distances between
airports. Along with these aids, ground-based radars were developed
for the control of aircraft along the air routes or in the airport
control area.
The development of electronic computers can be traced back to
the enormous advances in circuit design, which were an integral part
of radar research during the war. During that time, some elements
of electronic computing had been built into bombsights and other
weaponry; later, it was realized that a whole range of computing operations
could be performed electronically. By the end of the war,
many pulse-forming networks, pulse-counting circuits, and memory
circuits existed in the form needed for an electronic computer.
Finally, the developing radio technology has continued to help
astronomers explore the universe. Large radio telescopes exist in almost
every country and enable scientists to study the solar system
in great detail. Radar-assisted cosmic background radiation studies
have been a building block for the big bang theory of the origin of
the universe.

Pyrex glass

noreply@blogger.com (Toma) — Wed, 02 Dec 2009 03:24:41 PST

The invention: Asuperhard and durable glass product with widespread
uses in industry and home products.
The people behind the invention:
Jesse T. Littleton (1888-1966), the chief physicist of Corning
Glass Works’ research department
Eugene G. Sullivan (1872-1962), the founder of Corning’s
research laboratories
William C. Taylor (1886-1958), an assistant to Sullivan
Cooperating with Science
By the twentieth century, Corning GlassWorks had a reputation
as a corporation that cooperated with the world of science to improve
existing products and develop new ones. In the 1870’s, the
company had hired university scientists to advise on improving the
optical quality of glasses, an early example of today’s common practice
of academics consulting for industry.
When Eugene G. Sullivan established Corning’s research laboratory
in 1908 (the first of its kind devoted to glass research), the task
that he undertook withWilliam C. Taylor was that of making a heatresistant
glass for railroad lantern lenses. The problem was that ordinary
flint glass (the kind in bottles and windows, made by melting
together silica sand, soda, and lime) has a fairly high thermal expansion,
but a poor heat conductivity. The glass thus expands
unevenly when exposed to heat. This condition can cause the glass
to break, sometimes violently. Colored lenses for oil or gas railroad
signal lanterns sometimes shattered if they were heated too much
by the flame that produced the light and were then sprayed by rain
or wet snow. This changed a red “stop” light to a clear “proceed”
signal and caused many accidents or near misses in railroading in
the late nineteenth century.

Two solutions were possible: to improve the thermal conductivity
or reduce the thermal expansion. The first is what metals do:
When exposed to heat, most metals have an expansion much greater
than that of glass, but they conduct heat so quickly that they expand
nearly equally throughout and seldom lose structural integrity from
uneven expansion. Glass, however, is an inherently poor heat conductor,
so this approach was not possible.
Therefore, a formulation had to be found that had little or no
thermal expansivity. Pure silica (one example is quartz) fits this description,
but it is expensive and, with its high melting point, very
difficult to work.
The formulation that Sullivan and Taylor devised was a borosilicate
glass—essentially a soda-lime glass with the lime replaced by
borax, with a small amount of alumina added. This gave the low thermal
expansion needed for signal lenses. It also turned out to have
good acid-resistance, which led to its being used for the battery jars
required for railway telegraph systems and other applications. The
glass was marketed as “Nonex” (for “nonexpansion glass”).
From the Railroad to the Kitchen
Jesse T. Littleton joined Corning’s research laboratory in 1913.
The company had a very successful lens and battery jar material,
but no one had even considered it for cooking or other heat-transfer
applications, because the prevailing opinion was that glass absorbed
and conducted heat poorly. This meant that, in glass pans,
cakes, pies, and the like would cook on the top, where they were exposed
to hot air, but would remain cold and wet (or at least undercooked)
next to the glass surface. As a physicist, Littleton knew that
glass absorbed radiant energy very well. He thought that the heatconduction
problem could be solved by using the glass vessel itself
to absorb and distribute heat. Glass also had a significant advantage
over metal in baking. Metal bakeware mostly reflects radiant energy
to the walls of the oven, where it is lost ultimately to the surroundings.
Glass would absorb this radiation energy and conduct it evenly to
the cake or pie, giving a better result than that of the metal bakeware.
Moreover, glass would not absorb and carry over flavors from
one baking effort to the next, as some metals do.
Littleton took a cut-off battery jar home and asked his wife to
bake a cake in it. He took it to the laboratory the next day, handing
pieces around and not disclosing the method of baking until all had
agreed that the results were excellent. With this agreement, he was
able to commit laboratory time to developing variations on the
Nonex formula that were more suitable for cooking. The result was
Pyrex, patented and trademarked in May of 1915.
Impact
In the 1930’s, Pyrex “Flameware” was introduced, with a new
glass formulation that could resist the increased heat of stovetop
cooking. In the half century since Flameware was introduced,
Corning went on to produce a variety of other products and materials:
tableware in tempered opal glass; cookware in Pyroceram, a
glass product that during heat treatment gained such mechanical
strength as to be virtually unbreakable; even hot plates and stoves
topped with Pyroceram.
In the same year that Pyrex was marketed for cooking, it was
also introduced for laboratory apparatus. Laboratory glassware
had been coming from Germany at the beginning of the twentieth
century; World War I cut off the supply. Corning filled the gap
with Pyrex beakers, flasks, and other items. The delicate blownglass
equipment that came from Germany was completely displaced
by the more rugged and heat-resistant machine-made Pyrex
ware.
Any number of operations are possible with Pyrex that cannot
be performed safely in flint glass: Test tubes can be thrust directly
into burner flames, with no preliminary warming; beakers and
flasks can be heated on hot plates; and materials that dissolve
when exposed to heat can be made into solutions directly in Pyrex
storage bottles, a process that cannot be performed in regular
glass. The list of such applications is almost endless.
Pyrex has also proved to be the material of choice for lenses in
the great reflector telescopes, beginning in 1934 with that at Mount
Palomar. By its nature, astronomical observation must be done
with the scope open to the weather. This means that the mirror
must not change shape with temperature variations, which rules
out metal mirrors. Silvered (or aluminized) Pyrex serves very well,
and Corning has developed great expertise in casting and machining
Pyrex blanks for mirrors of all sizes.

Propeller-coordinated machine gun

noreply@blogger.com (Toma) — Wed, 02 Dec 2009 03:22:10 PST

The invention: A mechanism that synchronized machine gun fire
with propeller movement to prevent World War I fighter plane
pilots from shooting off their own propellers during combat.
The people behind the invention:
Anthony Herman Gerard Fokker (1890-1939), a Dutch-born
American entrepreneur, pilot, aircraft designer, and
manufacturer
Roland Garros (1888-1918), a French aviator
Max Immelmann (1890-1916), a German aviator
Raymond Saulnier (1881-1964), a French aircraft designer and
manufacturer
French Innovation
The first true aerial combat ofWorldWar I took place in 1915. Before
then, weapons attached to airplanes were inadequate for any
real combat work. Hand-held weapons and clumsily mounted machine
guns were used by pilots and crew members in attempts to
convert their observation planes into fighters. On April 1, 1915, this
situation changed. From an airfield near Dunkerque, France, a
French airman, Lieutenant Roland Garros, took off in an airplane
equipped with a device that would make his plane the most feared
weapon in the air at that time.
During a visit to Paris, Garros met with Raymond Saulnier, a French
aircraft designer. In April of 1914, Saulnier had applied for a patent on
a device that mechanically linked the trigger of a machine
gun to a cam
on the engine shaft. Theoretically, such an assembly would allow the
gun to fire between the moving blades of the propeller. Unfortunately,
the available machine gun Saulnier used to test his device was a
Hotchkiss gun, which tended to fire at an uneven rate. On Garros’s arrival,
Saulnier showed him a new invention: a steel deflector shield
that, when fastened to the propeller, would deflect the small percentage
of mistimed bullets that would otherwise destroy the blade.
The first test-firing was a disaster, shooting the propeller off and
destroying the fuselage. Modifications were made to the deflector
braces, streamlining its form into a wedge shape with gutterchannels
for deflected bullets. The invention was attached to a
Morane-Saulnier monoplane, and on April 1, Garros took off alone
toward the German lines. Success was immediate. Garros shot
down a German observation plane that morning. During the next
two weeks, Garros shot down five more German aircraft.
German Luck
The German high command, frantic over the effectiveness of the
French “secret weapon,” sent out spies to try to steal the secret and
also ordered engineers to develop a similar weapon. Luck was with
them. On April 18, 1915, despite warnings by his superiors not to fly
over enemy-held territory, Garros was forced to crash-land behind
German lines with engine trouble. Before he could destroy his aircraft,
Garros and his plane were captured by German troops. The secret
weapon was revealed.
The Germans were ecstatic about the opportunity to examine
the new French weapon. Unlike the French, the Germans had the
first air-cooled machine gun, the Parabellum, which shot continuous
bands of one hundred bullets and was reliable enough to be
adapted to a timing mechanism.
In May of 1915, Anthony Herman Gerard Fokker was shown
Garros’s captured plane and was ordered to copy the idea. Instead,
Fokker and his assistant designed a new firing system. It is unclear
whether Fokker and his team were already working on a synchronizer
or to what extent they knew of Saulnier’s previous work in
France.Within several days, however, they had constructed a working
prototype and attached it to a Fokker Eindecker 1 airplane. The
design consisted of a simple linkage of cams and push-rods connected
to the oil-pump drive of an Oberursel engine and the trigger
of a Parabellum machine gun. The firing of the gun had to be timed
precisely to fire its six hundred rounds per minute between the
twelve-hundred-revolutions-per-minute propeller blades.
Fokker took his invention to Doberitz air base, and after a series of exhausting trials before the German high command, both on the
ground and in the air, he was allowed to take two prototypes of the
machine-gun-mounted airplanes to Douai in German-held France.
At Douai, two German pilots crowded into the cockpit with Fokker
and were given demonstrations of the plane’s capabilities. The airmen
were Oswald Boelcke, a test pilot and veteran of forty reconnaissance
missions, and Max Immelmann, a young, skillful aviator
who was assigned to the front.
When the first combat-ready versions of Fokker’s Eindecker 1
were delivered to the front lines, one was assigned to Boelcke, the
other to Immelmann. On August 1, 1915, with their aerodrome under attack from nine English bombers, Boelcke and Immelmann
manned their aircraft and attacked. Boelcke’s gun jammed, and he
was forced to cut off his attack and return to the aerodrome. Immelmann,
however, succeeded in shooting down one of the bombers
with his synchronized machine gun. It was the first victory credited
to the Fokker-designed weapon system.
Impact
At the outbreak of World War I, military strategists and commanders
on both sides saw the wartime function of airplanes as a
means to supply intelligence information behind enemy lines or as
airborne artillery spotting platforms. As the war progressed and aircraft
flew more or less freely across the trenches, providing vital information
to both armies, it became apparent to ground commanders
that while it was important to obtain intelligence on enemy
movements, it was important also to deny the enemy similar information.
Early in the war, the French used airplanes as strategic bombing
platforms. As both armies began to use their air forces for strategic
bombing of troops, railways, ports, and airfields, it became evident
that aircraft would have to be employed against enemy aircraft to
prevent reconnaissance and bombing raids.
With the invention of the synchronized forward-firing machine
gun, pilots could use their aircraft as attack weapons. Apilot finally
could coordinate control of his aircraft and his armaments with
maximum efficiency. This conversion of aircraft from nearly passive
observation platforms to attack fighters is the single greatest innovation
in the history of aerial warfare. The development of fighter
aircraft forced a change in military strategy, tactics, and logistics and
ushered in the era of modern warfare. Fighter planes are responsible
for the battle-tested military adage: Whoever controls the sky controls
the battlefield.

Polystyrene

noreply@blogger.com (Toma) — Wed, 18 Nov 2009 08:45:45 PST

The invention: A clear, moldable polymer with many industrial
uses whose overuse has also threatened the environment.
The people behind the invention:
Edward Simon, an American chemist
Charles Gerhardt (1816-1856), a French chemist
Marcellin Pierre Berthelot (1827-1907), a French chemist
Polystyrene Is Characterized
In the late eighteenth century, a scientist by the name of Casper
Neuman described the isolation of a chemical called “storax” from a
balsam tree that grew in Asia Minor. This isolation led to the first report
on the physical properties of the substance later known as “styrene.”
The work of Neuman was confirmed and expanded upon
years later, first in 1839 by Edward Simon, who evaluated the temperature
dependence of styrene, and later by Charles Gerhardt,
who proposed its molecular formula. The work of these two men
sparked an interest in styrene and its derivatives.
Polystyrene belongs to a special class of molecules known as
polymers.Apolymer (the name means “many parts”) is a giant molecule
formed by combining small molecular units, called “monomers.”
This combination results in a macromolecule whose physical
properties—especially its strength and flexibility—are significantly
different fromthose of its monomer components. Such polymers are
often simply called “plastics.”
Polystyrene has become an important material in modern society
because it exhibits a variety of physical characteristics that can be
manipulated for the production of consumer products. Polystyrene
is a “thermoplastic,” which means that it can be softened by heat
and then reformed, after which it can be cooled to form a durable
and resilient product.
At 94 degrees Celsius, polystyrene softens; at room temperature,
however, it rings like a metal when struck. Because of the glasslike
nature and high refractive index of polystyrene, products made from it are known for their shine and attractive texture. In addition,
the material is characterized by a high level of water resistance and
by electrical insulating qualities. It is also flammable, can by dissolved
or softened by many solvents, and is sensitive to light. These
qualities make polystyrene a valuable material in the manufacture
of consumer products.
Plastics on the Market
In 1866, Marcellin Pierre Berthelot prepared styrene from ethylene
and benzene mixtures in a heated reaction flask. This was the
first synthetic preparation of polystyrene. In 1925, the Naugatuck
Chemical Company began to operate the first commercial styrene/
polystyrene manufacturing plant. In the 1930’s, the Dow Chemical
Company became involved in the manufacturing and marketing of
styrene/polystyrene products. Dow’s Styron 666 was first marketed
as a general-purpose polystyrene in 1938. This material was
the first plastic product to demonstrate polystyrene’s excellent mechanical
properties and ease of fabrication.
The advent ofWorldWar II increased the need for plastics. When
the Allies’ supply of natural rubber was interrupted, chemists sought
to develop synthetic substitutes. The use of additives with polymer
species was found to alter some of the physical properties of those
species. Adding substances called “elastomers” during the polymerization
process was shown to give a rubberlike quality to a normally
brittle species. An example of this is Dow’s Styron 475, which
was marketed in 1948 as the first “impact” polystyrene. It is called
an impact polystyrene because it also contains butadiene, which increases
the product’s resistance to breakage. The continued characterization
of polystyrene products has led to the development of a
worldwide industry that fills a wide range of consumer needs.
Following World War II, the plastics industry revolutionized
many aspects of modern society. Polystyrene is only one of the
many plastics involved in this process, but it has found its way into
a multitude of consumer products. Disposable kitchen utensils,
trays and packages, cups, videocassettes, insulating foams, egg cartons,
food wrappings, paints, and appliance parts are only a few of
the typical applications of polystyrenes. In fact, the production of polystyrene has grown to exceed 5 billion pounds per year.
The tremendous growth of this industry in the postwar era has
been fueled by a variety of factors. Having studied the physical
and chemical properties of polystyrene, chemists and engineers
were able to envision particular uses and to tailor the manufacture
of the product to fit those uses precisely. Because of its low cost of
production, superior performance, and light weight, polystyrene
has become the material of choice for the packaging industry. The
automobile industry also enjoys its benefits. Polystyrene’s lower
density compared to those of glass and steel makes it appropriate
for use in automobiles, since its light weight means that using
it can reduce the weight of automobiles, thereby increasing gas
efficiency.
Impact
There is no doubt that the marketing of polystyrene has greatly
affected almost every aspect of modern society. Fromcomputer keyboards
to food packaging, the use of polystyrene has had a powerful
impact on both the quality and the prices of products. Its use is not,
however, without drawbacks; it has also presented humankind
with a dilemma. The wholesale use of polystyrene has created an
environmental problem that represents a danger to wildlife, adds to
roadside pollution, and greatly contributes to the volume of solid
waste in landfills.
Polystyrene has become a household commodity because it lasts.
The reciprocal effect of this fact is that it may last forever. Unlike natural
products, which decompose upon burial, polystyrene is very
difficult to convert into degradable forms. The newest challenge facing
engineers and chemists is to provide for the safe and efficient
disposal of plastic products. Thermoplastics such as polystyrene
can be melted down and remolded into new products, which makes
recycling and reuse of polystyrene a viable option, but this option
requires the cooperation of the same consumers who have benefited
from the production of polystyrene products.

Polyethylene

noreply@blogger.com (Toma) — Wed, 18 Nov 2009 08:43:29 PST

The invention: An artificial polymer with strong insulating properties
and many other applications.
The people behind the invention:
Karl Ziegler (1898-1973), a German chemist
Giulio Natta (1903-1979), an Italian chemist
August Wilhelm von Hofmann (1818-1892), a German chemist
The Development of Synthetic Polymers
In 1841, August Hofmann completed his Ph.D. with Justus von
Liebig, a German chemist and founding father of organic chemistry.
One of Hofmann’s students,William Henry Perkin, discovered that
coal tars could be used to produce brilliant dyes. The German chemical
industry, under Hofmann’s leadership, soon took the lead in
this field, primarily because the discipline of organic chemistry was
much more developed in Germany than elsewhere.
The realities of the early twentieth century found the chemical
industry struggling to produce synthetic substitutes for natural
materials that were in short supply, particularly rubber. Rubber is
a natural polymer, a material composed of a long chain of small
molecules that are linked chemically. An early synthetic rubber,
neoprene, was one of many synthetic polymers (some others were
Bakelite, polyvinyl chloride, and polystyrene) developed in the
1920’s and 1930’s. Another polymer, polyethylene, was developed
in 1936 by Imperial Chemical Industries. Polyethylene was a
tough, waxy material that was produced at high temperature and
at pressures of about one thousand atmospheres. Its method of
production made the material expensive, but it was useful as an insulating
material.
WorldWar II and the material shortages associated with it brought
synthetic materials into the limelight. Many new uses for polymers
were discovered, and after the war they were in demand for the production
of a variety of consumer goods, although polyethylene was

still too expensive to be used widely.

Organometallics Provide the Key
Karl Ziegler, an organic chemist with an excellent international
reputation, spent most of his career in Germany. With his international
reputation and lack of political connections, he was a natural
candidate to take charge of the KaiserWilhelm Institute for Coal Research
(later renamed the Max Planck Institute) in 1943. Wise planners
saw him as a director who would be favored by the conquering
Allies. His appointment was a shrewd one, since he was allowed to
retain his position after World War II ended. Ziegler thus played a
key role in the resurgence of German chemical research after the war.
Before accepting the position at the Kaiser Wilhelm Institute,
Ziegler made it clear that he would take the job only if he could pursue
his own research interests in addition to conducting coal research.
The location of the institute in the Ruhr Valley meant that
abundant supplies of ethylene were available from the local coal industry,
so it is not surprising that Ziegler began experimenting with
that material.
Although Ziegler’s placement as head of the institute was an important
factor in his scientific breakthrough, his previous research
was no less significant. Ziegler devoted much time to the field of
organometallic compounds, which are compounds that contain a
metal atom that is bonded to one or more carbon atoms. Ziegler was
interested in organoaluminum compounds, which are compounds
that contain aluminum-carbon bonds.
Ziegler was also interested in polymerization reactions, which
involve the linking of thousands of smaller molecules into the single
long chain of a polymer. Several synthetic polymers were known,
but chemists could exert little control on the actual process. It was
impossible to regulate the length of the polymer chain, and the extent
of branching in the chain was unpredictable. It was as a result of
studying the effect of organoaluminum compounds on these chain
formation reactions that the key discovery was made.
Ziegler and his coworkers already knew that ethylene would react
with organoaluminum compounds to produce hydrocarbons,
which are compounds that contain only carbon and hydrogen and
that have varying chain lengths. Regulating the product chain length
continued to be a problem.
At this point, fate intervened in the form of a trace of nickel left in a
reactor from a previous experiment. The nickel caused the chain
lengthening to stop after two ethylene molecules had been linked.
Ziegler and his colleagues then tried to determine whether metals
other than nickel caused a similar effect with a longer polymeric
chain. Several metals were tested, and the most important finding
was that a trace of titanium chloride in the reactor caused the deposition
of large quantities of high-density polyethylene at low pressures.
Ziegler licensed the procedure, and within a year, Giulio Natta
had modified the catalysts to give high yields of polymers with
highly ordered side chains branching from the main chain. This
opened the door for the easy production of synthetic rubber. For
their discovery of Ziegler-Natta catalysts, Ziegler and Natta shared
the 1963 Nobel Prize in Chemistry.
Consequences
Ziegler’s process produced polyethylene that was much more
rigid than the material produced at high pressure. His product also
had a higher density and a higher softening temperature. Industrial
exploitation of the process was unusually rapid, and within ten years
more than twenty plants utilizing the process had been built throughout
Europe, producing more than 120,000 metric tons of polyethylene.
This rapid exploitation was one reason Ziegler and Natta were
awarded the Nobel Prize after such a relatively short time.
By the late 1980’s, total production stood at roughly 18 billion
pounds worldwide. Other polymeric materials, including polypropylene,
can be produced by similar means. The ready availability
and low cost of these versatile materials have radically transformed
the packaging industry. Polyethylene bottles are far lighter
than their glass counterparts; in addition, gases and liquids do not
diffuse into polyethylene very easily, and it does not break easily.
As a result, more and more products are bottled in containers
made of polyethylene or other polymers. Other novel materials
possessing properties unparalleled by any naturally occurring material
(Kevlar, for example, which is used to make bullet-resistant
vests) have also been an outgrowth of the availability of low-cost
polymeric materials.

Polyester

noreply@blogger.com (Toma) — Tue, 03 Nov 2009 10:07:55 PST

The invention: Asynthetic fibrous polymer used especially in fabrics.
The people behind the invention:
Wallace H. Carothers (1896-1937), an American polymer
chemist
Hilaire de Chardonnet (1839-1924), a French polymer chemist
John R. Whinfield (1901-1966), a British polymer chemist
A Story About Threads
Human beings have worn clothing since prehistoric times. At
first, clothing consisted of animal skins sewed together. Later, people
learned to spin threads from the fibers in plant or animal materials
and to weave fabrics from the threads (for example, wool, silk,
and cotton). By the end of the nineteenth century, efforts were begun
to produce synthetic fibers for use in fabrics. These efforts were
motivated by two concerns. First, it seemed likely that natural materials
would become too scarce to meet the needs of a rapidly increasing
world population. Second, a series of natural disasters—
affecting the silk industry in particular—had demonstrated the
problems of relying solely on natural fibers for fabrics.
The first efforts to develop synthetic fabric focused on artificial
silk, because of the high cost of silk, its beauty, and the fact that silk
production had been interrupted by natural disasters more often
than the production of any other material. The first synthetic silk
was rayon, which was originally patented by a French count,
Hilaire de Chardonnet, and was later much improved by other
polymer chemists. Rayon is a semisynthetic material that is made
from wood pulp or cotton.
Because there was a need for synthetic fabrics whose manufacture
did not require natural materials, other avenues were explored. One
of these avenues led to the development of totally synthetic polyester
fibers. In the United States, the best-known of these is Dacron, which
is manufactured by E. I. Du Pont de Nemours. Easily made intthreads, Dacron is widely used in clothing. It is also used to make audiotapes
and videotapes and in automobile and boat bodies.
From Polymers to Polyester
Dacron belongs to a group of chemicals known as “synthetic
polymers.” All polymers are made of giant molecules, each of
which is composed of a large number of simpler molecules (“monomers”)
that have been linked, chemically, to form long strings. Efforts
by industrial chemists to prepare synthetic polymers developed
in the twentieth century after it was discovered that many
natural building materials and fabrics (such as rubber, wood, wool,
silk, and cotton) were polymers, and as the ways in which monomers
could be joined to make polymers became better understood.
One group of chemists who studied polymers sought to make inexpensive
synthetic fibers to replace expensive silk and wool. Their efforts
led to the development of well-known synthetic fibers such as
nylon and Dacron.
Wallace H. Carothers of Du Pont pioneered the development of
polyamide polymers, collectively called “nylon,” and was the first
researcher to attempt to make polyester. It was British polymer
chemists John R. Whinfield and J. T. Dickson of Calico Printers Association
(CPA) Limited, however, who in 1941 perfected and patented
polyester that could be used to manufacture clothing. The
first polyester fiber products were produced in 1950 in Great Britain
by London’s British Imperial Chemical Industries, which had secured
the British patent rights from CPA. This polyester, which was
made of two monomers, terphthalic acid and ethylene glycol, was
called Terylene. In 1951, Du Pont, which had acquired Terylene patent
rights for theWestern Hemisphere, began to market its own version
of this polyester, which was called Dacron. Soon, other companies
around the world were selling polyester materials of similar
composition.
Dacron and other polyesters are used in many items in the
United States. Made into fibers and woven, Dacron becomes cloth.
When pressed into thin sheets, it becomes Mylar, which is used in
videotapes and audiotapes. Dacron polyester, mixed with other materials,
is also used in many industrial items, including motor vehicle and boat bodies. Terylene and similar polyester preparations
serve the same purposes in other countries.
The production of polyester begins when monomers are mixed
in huge reactor tanks and heated, which causes them to form giant
polymer chains composed of thousands of alternating monomer
units. If T represents terphthalic acid and E represents ethylene glycol,
a small part of a necklace-like polymer can be shown in the following
way: (TETETETETE). Once each batch of polyester polymer
has the desired composition, it is processed for storage until it is
needed. In this procedure, the material, in liquid form in the hightemperature
reactor, is passed through a device that cools it and
forms solid strips. These strips are then diced, dried, and stored.
When polyester fiber is desired, the diced polyester is melted and
then forced through tiny holes in a “spinneret” device; this process
is called “extruding.” The extruded polyester cools again, while
passing through the spinneret holes, and becomes fine fibers called
“filaments.” The filaments are immediately wound into threads that
are collected in rolls. These rolls of thread are then dyed and used to
weave various fabrics. If polyester sheets or other forms of polyester
are desired, the melted, diced polyester is processed in other ways.
Polyester preparations are often mixed with cotton, glass fibers, or
other synthetic polymers to produce various products.
Impact
The development of polyester was a natural consequence of the
search for synthetic fibers that developed fromwork on rayon. Once
polyester had been developed, its great utility led to its widespread
use in industry. In addition, the profitability of the material spurred
efforts to produce better synthetic fibers for specific uses. One example
is that of stretchy polymers such as Helance, which is a form
of nylon. In addition, new chemical types of polymer fibers were developed,
including the polyurethane materials known collectively
as “spandex” (for example, Lycra and Vyrenet).
The wide variety of uses for polyester is amazing. Mixed with
cotton, it becomes wash-and-wear clothing; mixed with glass, it is
used to make boat and motor vehicle bodies; combined with other
materials, it is used to make roofing materials, conveyor belts,hoses, and tire cords. In Europe, polyester has become the main
packaging material for consumer goods, and the United States does
not lag far behind in this area.
The future is sure to hold more uses for polyester and the invention
of new polymers. These spinoffs of polyester will be essential in
the development of high technology.

Polio vaccine (Salk)

noreply@blogger.com (Toma) — Wed, 28 Oct 2009 09:34:01 PDT

The invention: Jonas Salk’s vaccine was the first that prevented polio,resulting in the virtual eradication of crippling polio epidemics.The people behind the invention:
Jonas Edward Salk (1914-1995), an American physician,
immunologist, and virologist
Thomas Francis, Jr. (1900-1969), an
American microbiologist
Cause for Celebration
Poliomyelitis (polio) is an infectious disease that can adversely
affect the central nervous system, causing paralysis and great muscle
wasting due to the destruction of motor neurons (nerve cells) in
the spinal cord. Epidemiologists believe that polio has existed since
ancient times, and evidence of its presence in Egypt, circa 1400 b.c.e.,
has been presented. Fortunately, the Salk vaccine and the later vaccine
developed by the American virologist Albert Bruce Sabin can
prevent the disease. Consequently, except in underdeveloped nations,
polio is rare. Moreover, although once a person develops polio,
there is still no cure for it, a large number of polio cases end without
paralysis or any observable effect.
Polio is often called “infantile paralysis.” This results from the
fact that it is seen most often in children. It is caused by a virus and
begins with body aches, a stiff neck, and other symptoms that are
very similar to those of a severe case of influenza. In some cases,
within two weeks after its onset, the course of polio begins to lead to
muscle wasting and paralysis.
On April 12, 1955, the world was thrilled with the announcement
that Jonas Edward Salk’s poliomyelitis vaccine could prevent the
disease. It was reported that schools were closed in celebration of
this event. Salk, the son of a New York City garment worker, has
since become one of the most well-known and publicly venerated
medical scientists in the world.
Vaccination is a method of disease prevention by immunization,
whereby a small amount of virus is injected into the body to prevent
a viral disease. The process depends on the production of antibodies
(body proteins that are specifically coded to prevent the disease
spread by the virus) in response to the vaccination. Vaccines are
made of weakened or killed virus preparations.
Electrifying Results
The Salk vaccine was produced in two steps. First, polio viruses
were grown in monkey kidney tissue cultures. These polio viruses
were then killed by treatment with the right amount of formaldehyde
to produce an effective vaccine. The killed-virus polio vaccine
was found to be safe and to cause the production of antibodies
against the disease, a sign that it should prevent polio.
In early 1952, Salk tested a prototype vaccine against Type I polio virus
on children who were afflicted with the disease and were thus
deemed safe from reinfection. This test showed that the vaccination greatly elevated the concentration of polio antibodies in these children.
On July 2, 1952, encouraged by these results, Salk vaccinated fortythree
children who had never had polio with vaccines against each of
the three virus types (Type I, Type II, and Type III). All inoculated children
produced high levels of polio antibodies, and none of them developed
the disease. Consequently, the vaccine appeared to be both safe in
humans and likely to become an effective public health tool.
In 1953, Salk reported these findings in the Journal of the American
Medical Association. In April, 1954, nationwide testing of the Salk
vaccine began, via the mass vaccination of American schoolchildren.
The results of the trial were electrifying. The vaccine was safe,
and it greatly reduced the incidence of the disease. In fact, it was estimated
that Salk’s vaccine gave schoolchildren 60 to 90 percent protection
against polio.
Salk was instantly praised. Then, however, several cases of polio
occurred as a consequence of the vaccine. Its use was immediately
suspended by the U.S. surgeon general, pending a complete examination.
Soon, it was evident that all the cases of vaccine-derived polio
were attributable to faulty batches of vaccine made by one
pharmaceutical company. Salk and his associates were in no way responsible
for the problem. Appropriate steps were taken to ensure
that such an error would not be repeated, and the Salk vaccine was
again released for use by the public.
Consequences
The first reports on the polio epidemic in the United States had
occurred on June 27, 1916, when one hundred residents of Brooklyn,
New York, were afflicted. Soon, the disease had spread. By August,
twenty-seven thousand people had developed polio. Nearly seven
thousand afflicted people died, and many survivors of the epidemic
were permanently paralyzed to varying extents. In New York City
alone, nine thousand people developed polio and two thousand
died. Chaos reigned as large numbers of terrified people attempted
to leave and were turned back by police. Smaller polio epidemics
occurred throughout the nation in the years that followed (for example,
the Catawba County, North Carolina, epidemic of 1944). A
particularly horrible aspect of polio was the fact that more than 70 percent of polio victims were small children. Adults caught it too;
the most famous of these adult polio victims was U.S. President
Franklin D. Roosevelt. There was no cure for the disease. The best
available treatment was physical therapy.
As of August, 1955, more than four million polio vaccines had
been given. The Salk vaccine appeared to work very well. There were
only half as many reported cases of polio in 1956 as there had been in
1955. It appeared that polio was being conquered. By 1957, the number
of cases reported nationwide had fallen below six thousand.
Thus, in two years, its incidence had dropped by about 80 percent.
This was very exciting, and soon other countries clamored for the
vaccine. By 1959, ninety other countries had been supplied with the
Salk vaccine.Worldwide, the disease was being eradicated. The introduction
of an oral polio vaccine by Albert Bruce Sabin supported
this progress.
Salk received many honors, including honorary degrees from
American and foreign universities, the LaskerAward, a Congressional
Medal for Distinguished Civilian Service, and membership in
the French Legion of Honor, yet he received neither the Nobel Prize
nor membership in the American National Academy of Sciences. It
is believed by many that this neglect was a result of the personal antagonism
of some of the members of the scientific community who
strongly disagreed with his theories of viral inactivation.

Polio vaccine (Sabin)

noreply@blogger.com (Toma) — Wed, 28 Oct 2009 09:30:05 PDT

The invention: Albert Bruce Sabin’s vaccine was the first to stimulate
long-lasting immunity against polio without the risk of causing
paralytic disease.
The people behind the invention:
Albert Bruce Sabin (1906-1993), a Russian-born American
virologist
Jonas Edward Salk (1914-1995), an American physician,
immunologist, and virologist
Renato Dulbecco (1914- ), an Italian-born American
virologist who shared the 1975 Nobel Prize in Physiology or
Medicine
The Search for a Living Vaccine
Almost a century ago, the first major poliomyelitis (polio) epidemic
was recorded. Thereafter, epidemics of increasing
frequency
and severity struck the industrialized world. By the 1950’s, as many
as sixteen thousand individuals, most of them children, were being
paralyzed by the disease each year.
Poliovirus enters the body through ingestion by the mouth. It
replicates in the throat and the intestines and establishes an infection
that normally is harmless. From there, the virus can enter the
bloodstream. In some individuals it makes its way to the nervous
system, where it attacks and destroys nerve cells crucial for muscle
movement. The presence of antibodies in the bloodstream will prevent
the virus from reaching the nervous system and causing paralysis.
Thus, the goal of vaccination is to administer poliovirus that
has been altered so that it cannot cause disease but nevertheless will
stimulate the production of antibodies to fight the disease.
Albert Bruce Sabin received his medical degree from New York
University College of Medicine in 1931. Polio was epidemic in 1931,
and for Sabin polio research became a lifelong interest. In 1936,
while working at the Rockefeller Institute, Sabin and Peter Olinsky
successfully grew poliovirus using tissues cultured in vitro. Tissue
culture proved to be an excellent source of virus. Jonas Edward Salk
soon developed an inactive polio vaccine consisting of virus grown
from tissue culture that had been inactivated (killed) by chemical
treatment. This vaccine became available for general use in 1955, almost
fifty years after poliovirus had first been identified.
Sabin, however, was not convinced that an inactivated virus vaccine
was adequate. He believed that it would provide only temporary
protection and that individuals would have to be vaccinated
repeatedly in order to maintain protective levels of antibodies.
Knowing that natural infection with poliovirus induced lifelong immunity,
Sabin believed that a vaccine consisting of a living virus
was necessary to produce long-lasting immunity. Also, unlike the
inactive vaccine, which is injected, a living virus (weakened so that
it would not cause disease) could be taken orally and would invade
the body and replicate of its own accord.
Sabin was not alone in his beliefs. Hilary Koprowski and Harold
Cox also favored a living virus vaccine and had, in fact, begun
searching for weakened strains of poliovirus as early as 1946 by repeatedly
growing the virus in rodents. When Sabin began his search
for weakened virus strains in 1953, a fiercely competitive contest ensued
to achieve an acceptable live virus vaccine.
Rare, Mutant Polioviruses
Sabin’s approach was based on the principle that, as viruses acquire
the ability to replicate in a foreign species or tissue (for example,
in mice), they become less able to replicate in humans and thus
less able to cause disease. Sabin used tissue culture techniques to
isolate those polioviruses that grew most rapidly in monkey kidney
cells. He then employed a technique developed by Renato Dulbecco
that allowed him to recover individual virus particles. The recovered
viruses were injected directly into the brains or spinal cords of
monkeys in order to identify those viruses that did not damage the
nervous system. These meticulously performed experiments, which
involved approximately nine thousand monkeys and more than
one hundred chimpanzees, finally enabled Sabin to isolate rare mutant
polioviruses that would replicate in the intestinal tract but not
in the nervous systems of chimpanzees or, it was hoped, of humans.
In addition, the weakened virus strains were shown to stimulate antibodies when they were fed to chimpanzees; this was a critical attribute
for a vaccine strain.
By 1957, Sabin had identified three strains of attenuated viruses that
were ready for small experimental trials in humans. Asmall group of
volunteers, including Sabin’s own wife and children, were fed the vaccine
with promising results. Sabin then gave his vaccine to virologists
in the Soviet Union, Eastern Europe, Mexico, and Holland for further
testing. Combined with smaller studies in the United States, these trials
established the effectiveness and safety of his oral vaccine.
During this period, the strains developed by Cox and by Koprowski
were being tested also in millions of persons in field trials
around the world. In 1958, two laboratories independently compared
the vaccine strains and concluded that the Sabin strains were
superior. In 1962, after four years of deliberation by the U.S. Public
Health Service, all three of Sabin’s vaccine strains were licensed for
general use.Consequences
The development of polio vaccines ranks as one of the triumphs of
modern medicine. In the early 1950’s, paralytic polio struck 13,500
out of every 100 million Americans. The use of the Salk vaccine
greatly reduced the incidence of polio, but outbreaks of paralytic disease
continued to occur: Fifty-seven hundred cases were reported in
1959 and twenty-five hundred cases in 1960. In 1962, the oral Sabin
vaccine became the vaccine of choice in the United States. Since its
widespread use, the number of paralytic cases in the United States
has dropped precipitously, eventually averaging fewer than ten per
year. Worldwide, the oral vaccine prevented an estimated 5 million
cases of paralytic poliomyelitis between 1970 and 1990.
The oral vaccine is not without problems. Occasionally, the living
virus mutates to a disease-causing (virulent) form as it multiplies in
the vaccinated person. When this occurs, the person may develop
paralytic poliomyelitis. The inactive vaccine, in contrast, cannot
mutate to a virulent form. Ironically, nearly every incidence of polio
in the United States is caused by the vaccine itself.
In the developing countries of the world, the issue of vaccination is
more pressing. Millions receive neither form of polio vaccine; as a result,
at least 250,000 individuals are paralyzed or die each year. The World
Health Organization and other health providers continue to work toward
the very practical goal of completely eradicating this disease.

Pocket calculator

noreply@blogger.com (Toma) — Wed, 21 Oct 2009 04:33:55 PDT

The invention: The first portable and reliable hand-held calculator
capable of performing a wide range of mathematical computations.
The people behind the invention:
Jack St. Clair Kilby (1923- ), the inventor of the
semiconductor microchip
Jerry D. Merryman (1932- ), the first project manager of the
team that invented the first portable calculator
James Van Tassel (1929- ), an inventor and expert on
semiconductor components
An Ancient Dream
In the earliest accounts of civilizations that developed number
systems to perform mathematical calculations, evidence has been
found of efforts to fashion a device that would permit people to perform
these calculations with reduced effort and increased accuracy.
The ancient Babylonians are regarded as the inventors of the first
abacus (or counting board, from the Greek abakos, meaning “board”
or “tablet”). It was originally little more than a row of shallow
grooves with pebbles or bone fragments as counters.
The next step in mechanical calculation did not occur until the
early seventeenth century. John Napier, a Scottish baron and mathematician,
originated the concept of “logarithms” as a mathematical
device to make calculating easier. This concept led to the first slide
rule, created by the English mathematician William Oughtred of
Cambridge. Oughtred’s invention consisted of two identical, circular
logarithmic scales held together and adjusted by hand. The slide
rule made it possible to perform rough but rapid multiplication and
division. Oughtred’s invention in 1623 was paralleled by the work
of a German professor,Wilhelm Schickard, who built a “calculating
clock” the same year. Because the record of Schickard’s work was
lost until 1935, however, the French mathematician Blaise Pascal
was generally thought to have built the first mechanical calculator,
the “Pascaline,” in 1645.Other versions of mechanical calculators were built in later centuries,
but none was rapid or compact enough to be useful beyond specific
laboratory or mercantile situations. Meanwhile, the dream of
such a machine continued to fascinate scientists and mathematicians.
The development that made a fast, small calculator possible did
not occur until the middle of the twentieth century, when Jack St.
Clair Kilby of Texas Instruments invented the silicon microchip (or
integrated circuit) in 1958. An integrated circuit is a tiny complex of
electronic components and their connections that is produced in or
on a small slice of semiconductor material such as silicon. Patrick
Haggerty, then president of Texas Instruments, wrote in 1964 that
“integrated electronics” would “remove limitations” that determined
the size of instruments, and he recognized that Kilby’s invention
of the microchip made possible the creation of a portable,
hand-held calculator. He challenged Kilby to put together a team to
design a calculator that would be as powerful as the large, electromechanical
models in use at the time but small enough to fit into a
coat pocket. Working with Jerry D. Merryman and James Van Tassel,
Kilby began to work on the project in October, 1965.
An Amazing Reality
At the outset, there were basically five elements that had to be designed.
These were the logic designs that enabled the machine to
perform the actual calculations, the keyboard or keypad, the power
supply, the readout display, and the outer case. Kilby recalls that
once a particular size for the unit had been determined (something
that could be easily held in the hand), project manager Merryman
was able to develop the initial logic designs in three days.Van Tassel
contributed his experience with semiconductor components to solve
the problems of packaging the integrated circuit. The display required
a thermal printer that would work on a low power source.
The machine also had to include a microencapsulated ink source so
that the paper readouts could be imprinted clearly. Then the paper
had to be advanced for the next calculation. Kilby, Merryman, and
Van Tassel filed for a patent on their work in 1967.
Although this relatively small, working prototype of the minicalculator
made obsolete the transistor-operated design of the much larger desk calculators, the cost of setting up new production lines
and the need to develop a market made it impractical to begin production
immediately. Instead, Texas Instruments and Canon of Tokyo
formed a joint venture, which led to the introduction of the
Canon Pocketronic Printing Calculator in Japan in April, 1970, and
in the United States that fall. Built entirely of Texas Instruments
parts, this four-function machine with three metal oxide semiconductor (MOS) circuits was similar to the prototype designed in 1967.
The calculator was priced at $400, weighed 740 grams, and measured
101 millimeters wide by 208 millimeters long by 49 millimeters
high. It could perform twelve-digit calculations and worked up
to four decimal places.
In September, 1972, Texas Instruments put the Datamath, its first
commercial hand-held calculator using a single MOS chip, on the
retail market. It weighed 340 grams and measured 75 millimeters
wide by 137 millimeters long by 42 millimeters high. The Datamath
was priced at $120 and included a full-floating decimal point that
could appear anywhere among the numbers on its eight-digit, lightemitting
diode (LED) display. It came with a rechargeable battery
that could also be connected to a standard alternating current (AC)
outlet. The Datamath also had the ability to conserve power while
awaiting the next keyboard entry. Finally, the machine had a built-in
limited amount of memory storage.Consequences
Prior to 1970, most calculating machines were of such dimensions
that professional mathematicians and engineers were either tied to
their desks or else carried slide rules whenever they had to be away
from their offices. By 1975, Keuffel&Esser, the largest slide rule manufacturer
in the world, was producing its last model, and mechanical
engineers found that problems that had previously taken a week
could now be solved in an hour using the new machines.
That year, the Smithsonian Institution accepted the world’s first
miniature electronic calculator for its permanent collection, noting
that it was the forerunner of more than one hundred million pocket
calculators then in use. By the 1990’s, more than fifty million portable
units were being sold each year in the United States. In general,
the electronic pocket calculator revolutionized the way in which
people related to the world of numbers.
Moreover, the portability of the hand-held calculator made it
ideal for use in remote locations, such as those a petroleum engineer
might have to explore. Its rapidity and reliability made it an indispensable
instrument for construction engineers, architects, and real
estate agents, who could figure the volume of a room and other
building dimensions almost instantly and then produce cost estimates
almost on the spot.

Plastic

noreply@blogger.com (Toma) — Wed, 14 Oct 2009 01:30:18 PDT

The invention: The first totally synthetic thermosetting plastic,
which paved the way for modern materials science.
The people behind the invention:
John Wesley Hyatt (1837-1920), an American inventor
Leo Hendrik Baekeland (1863-1944), a Belgian-born chemist,
consultant, and inventor
Christian Friedrich Schönbein (1799-1868), a German chemist
who produced guncotton, the first artificial polymer
Adolf von Baeyer (1835-1917), a German chemist
Exploding Billiard Balls
In the 1860’s, the firm of Phelan and Collender offered a prize of
ten thousand dollars to anyone producing a substance that could
serve as an inexpensive substitute for ivory, which was somewhat
difficult to obtain in large quantities at reasonable prices. Earlier,
Christian Friedrich Schönbein had laid the groundwork for a breakthrough
in the quest for a new material in 1846 by the serendipitous
discovery of nitrocellulose, more commonly known as “guncotton,”
which was produced by the reaction of nitric acid with cotton.
An American inventor, John Wesley Hyatt, while looking for a
substitute for ivory as a material for making billiard balls, discovered
that the addition of camphor to nitrocellulose under certain
conditions led to the formation of a white material that could be
molded and machined. He dubbed this substance “celluloid,” and
this product is now acknowledged as the first synthetic plastic. Celluloid
won the prize for Hyatt, and he promptly set out to exploit his
product. Celluloid was used to make baby rattles, collars, dentures,
and other manufactured goods.
As a billiard ball substitute, however, it was not really adequate,
for various reasons. First, it is thermoplastic—in other words, a material
that softens when heated and can then be easily deformed or
molded. It was thus too soft for billiard ball use. Second, it was
highly flammable, hardly a desirable characteristic. Awidely circulated, perhaps apocryphal, story claimed that celluloid billiard balls
detonated when they collided.
Truly Artificial
Since celluloid can be viewed as a derivative of a natural product,
it is not a completely synthetic substance. Leo Hendrik Baekeland
has the distinction of being the first to produce a completely artificial
plastic. Born in Ghent, Belgium, Baekeland emigrated to the
United States in 1889 to pursue applied research, a pursuit not encouraged
in Europe at the time. One area in which Baekeland hoped
to make an inroad was in the development of an artificial shellac.
Shellac at the time was a natural and therefore expensive product,
and there would be a wide market for any reasonably priced substitute.
Baekeland’s research scheme, begun in 1905, focused on finding
a solvent that could dissolve the resinous products from a certain
class of organic chemical reaction.
The particular resins he used had been reported in the mid-
1800’s by the German chemist Adolf von Baeyer. These resins were
produced by the condensation reaction of formaldehyde with a
class of chemicals called “phenols.” Baeyer found that frequently
the major product of such a reaction was a gummy residue that was
virtually impossible to remove from glassware. Baekeland focused
on finding a material that could dissolve these resinous products.
Such a substance would prove to be the shellac substitute he sought.
These efforts proved frustrating, as an adequate solvent for these
resins could not be found. After repeated attempts to dissolve these
residues, Baekeland shifted the orientation of his work. Abandoning
the quest to dissolve the resin, he set about trying to develop a resin
that would be impervious to any solvent, reasoning that such a material
would have useful applications.
Baekeland’s experiments involved the manipulation of phenolformaldehyde
reactions through precise control of the temperature
and pressure at which the reactions were performed. Many of these
experiments were performed in a 1.5-meter-tall reactor vessel, which
he called a “Bakelizer.” In 1907, these meticulous experiments paid
off when Baekeland opened the reactor to reveal a clear solid that
was heat resistant, nonconducting, and machinable. Experimentation proved that the material could be dyed practically any color in
the manufacturing process, with no effect on the physical properties
of the solid.
Baekeland filed a patent for this new material in 1907. (This patent
was filed one day before that filed by James Swinburne, a British electrical engineer who had developed a similar material in his
quest to produce an insulating material.) Baekeland dubbed his new
creation “Bakelite” and announced its existence to the scientific
community on February 15, 1909, at the annual meeting of the American
Chemical Society. Among its first uses was in the manufacture
of ignition parts for the rapidly growing automobile industry.
Impact
Bakelite proved to be the first of a class of compounds called
“synthetic polymers.” Polymers are long chains of molecules chemically
linked together. There are many natural polymers, such as cotton.
The discovery of synthetic polymers led to vigorous research
into the field and attempts to produce other useful artificial materials.
These efforts met with a fair amount of success; by 1940, a multitude
of new products unlike anything found in nature had been discovered.
These included such items as polystyrene and low-density
polyethylene. In addition, artificial substitutes for natural polymers,
such as rubber, were a goal of polymer chemists. One of the results
of this research was the development of neoprene.
Industries also were interested in developing synthetic polymers
to produce materials that could be used in place of natural fibers
such as cotton. The most dramatic success in this area was achieved
by Du Pont chemist Wallace Carothers, who had also developed
neoprene. Carothers focused his energies on forming a synthetic fiber
similar to silk, resulting in the synthesis of nylon.
Synthetic polymers constitute one branch of a broad area known
as “materials science.” Novel, useful materials produced synthetically
from a variety of natural materials have allowed for tremendous
progress in many areas. Examples of these new materials include
high-temperature superconductors, composites, ceramics, and
plastics. These materials are used to make the structural components
of aircraft, artificial limbs and implants, tennis rackets, garbage
bags, and many other common objects.

Photovoltaic cell

noreply@blogger.com (Toma) — Tue, 13 Oct 2009 07:48:40 PDT

Photovoltaic cell
The invention: Drawing their energy directly from the Sun, the
first photovoltaic cells powered instruments on early space vehicles
and held out hope for future uses of solar energy.
The people behind the invention:
Daryl M. Chapin (1906-1995), an American physicist
Calvin S. Fuller (1902-1994), an American chemist
Gerald L. Pearson (1905- ), an American physicist
Unlimited Energy Source
All the energy that the world has at its disposal ultimately comes
from the Sun. Some of this solar energy was trapped millions of years
ago in the form of vegetable and animal matter that became the coal,
oil, and natural gas that the world relies upon for energy. Some of this
fuel is used directly to heat homes and to power factories and gasoline
vehicles. Much of this fossil fuel, however, is burned to produce
the electricity on which modern society depends.
The amount of energy available from the Sun is difficult to imagine,
but some comparisons may be helpful. During each forty-hour
period, the Sun provides the earth with as much energy as the
earth’s total reserves of coal, oil, and natural gas. It has been estimated
that the amount of energy provided by the sun’s radiation
matches the earth’s reserves of nuclear fuel every forty days. The
annual solar radiation that falls on about twelve hundred square
miles of land in Arizona matched the world’s estimated total annual
energy requirement for 1960. Scientists have been searching for
many decades for inexpensive, efficient means of converting this
vast supply of solar radiation directly into electricity.
The Bell Solar Cell
Throughout its history, Bell Systems has needed to be able to
transmit, modulate, and amplify electrical signals. Until the 1930’s,
these tasks were accomplished by using insulators and metallic conductors. At that time, semiconductors, which have electrical properties
that are between those of insulators and those of conductors,
were developed. One of the most important semiconductor materials
is silicon, which is one of the most common elements on the
earth. Unfortunately, silicon is usually found in the form of compounds
such as sand or quartz, and it must be refined and purified
before it can be used in electrical circuits. This process required
much initial research, and very pure silicon was not available until
the early 1950’s.
Electric conduction in silicon is the result of the movement of
negative charges (electrons) or positive charges (holes). One way of
accomplishing this is by deliberately adding to the silicon phosphorus
or arsenic atoms, which have five outer electrons. This addition
creates a type of semiconductor that has excess negative charges (an
n-type semiconductor). Adding boron atoms, which have three
outer electrons, creates a semiconductor that has excess positive
charges (a p-type semiconductor). Calvin Fuller made an important
study of the formation of p-n junctions, which are the points at
which p-type and n-type semiconductors meet, by using the process
of diffusing impurity atoms—that is, adding atoms of materials that
would increase the level of positive or negative charges, as described
above. Fuller’s work stimulated interested in using the process
of impurity diffusion to create cells that would turn solar energy
into electricity. Fuller and Gerald Pearson made the first largearea
p-n junction by using the diffusion process. Daryl Chapin,
Fuller, and Pearson made a similar p-n junction very close to the
surface of a silicon crystal, which was then exposed to sunlight.
The cell was constructed by first making an ingot of arsenicdoped
silicon that was then cut into very thin slices. Then a very
thin layer of p-type silicon was formed over the surface of the n-type
wafer, providing a p-n junction close to the surface of the cell. Once
the cell cooled, the p-type layer was removed from the back of the
cell and lead wires were attached to the two surfaces. When light
was absorbed at the p-n junction, electron-hole pairs were produced,
and the electric field that was present at the junction forced
the electrons to the n side and the holes to the p side.
The recombination of the electrons and holes takes place after the
electrons have traveled through the external wires, where they do useful work. Chapin, Fuller, and Pearson announced in 1954 that
the resulting photovoltaic cell was the most efficient (6 percent)
means then available for converting sunlight into electricity.
The first experimental use of the silicon solar battery was in amplifiers
for electrical telephone signals in rural areas. An array of 432
silicon cells, capable of supplying 9 watts of power in bright sunlight,
was used to charge a nickel-cadmium storage battery. This, in
turn, powered the amplifier for the telephone signal. The electrical
energy derived from sunlight during the day was sufficient to keep
the storage battery charged for continuous operation. The system
was successfully tested for six months of continuous use in Americus,
Georgia, in 1956. Although it was a technical success, the silicon solar
cell was not ready to compete economically with conventional
means of producing electrical power.
Consequences
One of the immediate applications of the solar cell was to supply
electrical energy for Telstar satellites. These cells are used extensively
on all satellites to generate power. The success of the U.S. satellite program prompted serious suggestions in 1965 for the use of
an orbiting power satellite. A large satellite could be placed into a
synchronous orbit of the earth. It would collect sunlight, convert it
to microwave radiation, and beam the energy to an Earth-based receiving
station. Many technical problems must be solved, however,
before this dream can become a reality.
Solar cells are used in small-scale applications such as power
sources for calculators. Large-scale applications are still not economically
competitive with more traditional means of generating
electric power. The development of the ThirdWorld countries, however,
may provide the incentive to search for less-expensive solar
cells that can be used, for example, to provide energy in remote villages.
As the standards of living in such areas improve, the need for
electric power will grow. Solar cells may be able to provide the necessary
energy while safeguarding the environment for future generations.

Photoelectric cell

noreply@blogger.com (Toma) — Mon, 12 Oct 2009 00:38:22 PDT

The invention: The first devices to make practical use of the photoelectric
effect, photoelectric cells were of decisive importance in
the electron theory of metals.
The people behind the invention:
Julius Elster (1854-1920), a German experimental physicist
Hans Friedrich Geitel (1855-1923), a German physicist
Wilhelm Hallwachs (1859-1922), a German physicist
Early Photoelectric Cells
The photoelectric effect was known to science in the early
nineteenth century when the French physicist Alexandre-Edmond
Becquerel wrote of it in connection with his work on glass-enclosed
primary batteries. He discovered that the voltage of his batteries increased
with intensified illumination and that green light produced
the highest voltage. Since Becquerel researched batteries exclusively,
however, the liquid-type photocell was not discovered until
1929, when the Wein and Arcturus cells were introduced commercially.
These cells were miniature voltaic cells arranged so that light
falling on one side of the front plate generated a considerable
amount of electrical energy. The cells had short lives, unfortunately;
when subjected to cold, the electrolyte froze, and when subjected to
heat, the gas generated would expand and explode the cells.
What came to be known as the photoelectric cell, a device connecting
light and electricity, had its beginnings in the 1880’s. At
that time, scientists noticed that a negatively charged metal plate
lost its charge much more quickly in the light (especially ultraviolet
light) than in the dark. Several years later, researchers demonstrated
that this phenomenon was not an “ionization” effect because
of the air’s increased conductivity, since the phenomenon
took place in a vacuum but did not take place if the plate were positively
charged. Instead, the phenomenon had to be attributed to
the light that excited the electrons of the metal and caused them to
fly off: Aneutral plate even acquired a slight positive charge under the influence of strong light. Study of this effect not only contributed
evidence to an electronic theory of matter—and, as a result of
some brilliant mathematical work by the physicist Albert Einstein,
later increased knowledge of the nature of radiant energy—but
also further linked the studies of light and electricity. It even explained
certain chemical phenomena, such as the process of photography.
It is important to note that all the experimental work on
photoelectricity accomplished prior to the work of Julius Elster
and Hans Friedrich Geitel was carried out before the existence of
the electron was known.
Explaining Photoelectric Emission
After the English physicist Sir Joseph John Thomson’s discovery
of the electron in 1897, investigators soon realized that the photoelectric
effect was caused by the emission of electrons under the influence
of radiation. The fundamental theory of photoelectric emission
was put forward by Einstein in 1905 on the basis of the German
physicist Max Planck’s quantum theory (1900). Thus, it was not surprising
that light was found to have an electronic effect. Since it was
known that the longer radio waves could shake electrons into resonant
oscillations and the shorter X rays could detach electrons from
the atoms of gases, the intermediate waves of visual light would
have been expected to have some effect upon electrons—such as detaching
them from metal plates and therefore setting up a difference
of potential. The photoelectric cell, developed by Elster and Geitel
in 1904, was a practical device that made use of this effect.
In 1888,Wilhelm Hallwachs observed that an electrically charged
zinc electrode loses its charge when exposed to ultraviolet radiation
if the charge is negative, but is able to retain a positive charge under
the same conditions. The following year, Elster and Geitel discovered
a photoelectric effect caused by visible light; however, they
used the alkali metals potassium and sodium for their experiments
instead of zinc.
The Elster-Geitel photocell (a vacuum emission cell, as opposed to
a gas-filled cell) consisted of an evacuated glass bulb containing two
electrodes. The cathode consisted of a thin film of a rare, chemically
active metal (such as potassium) that lost its electrons fairly readily; the anode was simply a wire sealed in to complete the circuit. This anode
was maintained at a positive potential in order to collect the negative
charges released by light from the cathode. The Elster-Geitel
photocell resembled two other types of vacuum tubes in existence at
the time: the cathode-ray tube, in which the cathode emitted electrons
under the influence of a high potential, and the thermionic
valve (a valve that permits the passage of current in one direction only), in which it emitted electrons under the influence of heat. Like
both of these vacuum tubes, the photoelectric cell could be classified
as an “electronic” device.
The new cell, then, emitted electrons when stimulated by light, and
at a rate proportional to the intensity of the light. Hence, a current
could be obtained from the cell. Yet Elster and Geitel found that their
photoelectric currents fell off gradually; they therefore spoke of “fatigue”
(instability). It was discovered later that most of this change was
not a direct effect of a photoelectric current’s passage; it was not even
an indirect effect but was caused by oxidation of the cathode by the air.
Since all modern cathodes are enclosed in sealed vessels, that source of
change has been completely abolished. Nevertheless, the changes that
persist in modern cathodes often are indirect effects of light that can be
produced independently of any photoelectric current.
Impact
The Elster-Geitel photocell was, for some twenty years, used in
all emission cells adapted for the visible spectrum, and throughout
the twentieth century, the photoelectric cell has had a wide variety
of applications in numerous fields. For example, if products leaving
a factory on a conveyor belt were passed between a light and a cell,
they could be counted as they interrupted the beam. Persons entering
a building could be counted also, and if invisible ultraviolet rays
were used, those persons could be detected without their knowledge.
Simple relay circuits could be arranged that would automatically
switch on street lamps when it grew dark. The sensitivity of
the cell with an amplifying circuit enabled it to “see” objects too
faint for the human eye, such as minor stars or certain lines in the
spectra of elements excited by a flame or discharge. The fact that the
current depended on the intensity of the light made it possible to
construct photoelectric meters that could judge the strength of illumination
without risking human error—for example, to determine
the right exposure for a photograph.
A further use for the cell was to make talking films possible. The
early “talkies” had depended on gramophone records, but it was very
difficult to keep the records in time with the film. Now, the waves of
speech and music could be recorded in a “sound track” by turning the sound first into current through a microphone and then into light with
a neon tube or magnetic shutter; next, the variations in the intensity of
this light on the side of the film were photographed. By reversing the
process and running the film between a light and a photoelectric cell,
the visual signals could be converted back to sound.

Personal computer

noreply@blogger.com (Toma) — Mon, 12 Oct 2009 00:35:09 PDT

The invention: Originally a tradename of the IBM Corporation,
“personal computer” has become a generic term for increasingly
powerful desktop computing systems using microprocessors.
The people behind the invention:
Tom J. Watson, (1874-1956), the founder of IBM, who set
corporate philosophy and marketing principles
Frank Cary (1920- ), the chief executive officer of IBM at the
time of the decision to market a personal computer
John Opel (1925- ), a member of the Corporate Management
Committee
George Belzel, a member of the Corporate Management
Committee
Paul Rizzo, a member of the Corporate Management Committee
Dean McKay (1921- ), a member of the Corporate
Management Committee
William L. Sydnes, the leader of the original twelve-member
design team
Shaking up the System
For many years, the International Business Machines (IBM) Corporation
had been set in its ways, sticking to traditions established
by its founder, Tom Watson, Sr. If it hoped to enter the new microcomputer
market, however, it was clear that only nontraditional
methods would be useful. Apple Computer was already beginning
to make inroads into large IBM accounts, and IBM stock was starting
to stagnate onWall Street. A1979 BusinessWeek article asked: “Is
IBM just another stodgy, mature company?” The microcomputer
market was expected to grow more than 40 percent in the early
1980’s, but IBM would have to make some changes in order to bring
a competitive personal computer (PC) to the market.
The decision to build and market the PC was made by the company’s
Corporate Management Committee (CMC). CMC members
included chief executive officer Frank Cary, John Opel, George Belzel, Paul Rizzo, Dean McKay, and three senior vice presidents. In
July of 1980, Cary gave the order to proceed. He wanted the PC to be
designed and built within a year. The CMC approved the initial design
of the PC one month later. Twelve engineers, with William L.
Sydnes as their leader, were appointed as the design team. At the
end of 1980, the team had grown to 150.
Most parts of the PC had to be produced outside IBM. Microsoft
Corporation won the contract to produce the PC’s disk operating system
(DOS) and the BASIC (Beginner’s All-purpose Symbolic Instruction
Code) language that is built into the PC’s read-only memory
(ROM). Intel Corporation was chosen to make the PC’s central processing
unit (CPU) chip, the “brains” of the machine. Outside programmers
wrote software for the PC. Ten years earlier, this strategy
would have been unheard of within IBM since all aspects of manufacturing,
service, and repair were traditionally taken care of in-house.
Marketing the System
IBM hired a New York firm to design a media campaign for the
new PC. Readers of magazines and newspapers saw the character
of Charlie Chaplin advertising the new PC. The machine was delivered
on schedule on August 12, 1981. The price of the basic “system
unit” was $1,565. A system with 64 kilobytes of random access
memory (RAM), a 13-centimeter single-sided disk drive holding
160 kilobytes, and a monitor was priced at about $3,000. A system
with color graphics, a second disk drive, and a dot matrix printer
cost about $4,500.
Many useful computer programs had been adapted to the PC
and were available when it was introduced. VisiCalc from Personal
Software—the program that is credited with “making” the microcomputer
revolution—was one of the first available. Other packages
included a comprehensive accounting system by Peachtree
Software and a word processing package called Easywriter by Information
Unlimited Software.
As the selection of software grew, so did sales. In the first year after
its introduction, the IBM PC went from a zero market share to 28
percent of the market. Yet the credit for the success of the PC does
not go to IBM alone. Many hundreds of companies were able to produce software and hardware for the PC.Within two years, powerful
products such as Lotus Corporation’s 1-2-3 business spreadsheet
had come to the market. Many believed that Lotus 1-2-3 was the
program that caused the PC to become so phenomenally successful.
Other companies produced hardware features (expansion boards)
that increased the PC’s memory storage or enabled the machine to
“drive” audiovisual presentations such as slide shows. Business especially
found the PC to be a powerful tool. The PC has survived because
of its expansion capability.
IBM has continued to upgrade the PC. In 1983, the PC/XT was
introduced. It had more expansion slots and a fixed disk offering 10
million bytes of storage for programs and data. Many of the companies
that made expansion boards found themselves able to make
whole PCs. An entire range of PC-compatible systems was introduced
to the market, many offering features that IBM did not include
in the original PC. The original PC has become a whole family
of computers, sold by both IBM and other companies. The hardware
and software continue to evolve; each generation offers more computing
power and storage with a lower price tag.
Consequences
IBM’s entry into the microcomputer market gave microcomputers
credibility. Apple Computer’s earlier introduction of its computer
did not win wide acceptance with the corporate world. Apple
did, however, thrive within the educational marketplace. IBM’s
name already carried with it much clout, because IBM was a successful
company. Apple Computer represented all that was great
about the “new” microcomputer, but the IBM PC benefited from
IBM’s image of stability and success.
IBM coined the term personal computer and its acronym PC. The
acronym PC is now used almost universally to refer to the microcomputer.
It also had great significance with users who had previously
used a large mainframe computer that had to be shared with
the whole company. This was their personal computer. That was important
to many PC buyers, since the company mainframe was perceived
as being complicated and slow. The PC owner now had complete
control.

Penicillin

noreply@blogger.com (Toma) — Thu, 01 Oct 2009 08:30:10 PDT

The invention: The first successful and widely used antibiotic
drug, penicillin has been called the twentieth century’s greatest
“wonder drug.”
The people behind the invention:
Sir Alexander Fleming (1881-1955), a Scottish bacteriologist,
cowinner of the 1945 Nobel Prize in Physiology or Medicine
Baron Florey (1898-1968), an Australian pathologist, cowinner
of the 1945 Nobel Prize in Physiology or Medicine
Ernst Boris Chain (1906-1979), an émigré German biochemist,
cowinner of the 1945 Nobel Prize in Physiology or Medicine
The Search for the Perfect Antibiotic
During the early twentieth century, scientists were aware of antibacterial
substances but did not know how to make full use of them
in the treatment of diseases. Sir Alexander Fleming discovered penicillin
in 1928, but he was unable to duplicate his laboratory results
of its antibiotic properties in clinical tests; as a result, he did not recognize
the medical potential of penicillin. Between 1935 and 1940,
penicillin was purified, concentrated, and clinically tested by pathologist
Baron Florey, biochemist Ernst Boris Chain, and members
of their Oxford research group. Their achievement has since been regarded
as one of the greatest medical discoveries of the twentieth
century.
Florey was a professor at Oxford University in charge of the Sir
William Dunn School of Pathology. Chain had worked for two years
at Cambridge University in the laboratory of Frederick Gowland
Hopkins, an eminent chemist and discoverer of vitamins. Hopkins
recommended Chain to Florey, who was searching for a candidate
to lead a new biochemical unit in the Dunn School of Pathology.
In 1938, Florey and Chain formed a research group to investigate
the phenomenon of antibiosis, or the antagonistic association between
different forms of life. The union of Florey’s medical knowledge
and Chain’s biochemical expertise proved to be an ideal combination for exploring the antibiosis potential of penicillin. Florey
and Chain began their investigation with a literature search in
which Chain came across Fleming’s work and added penicillin to
their list of potential antibiotics.
Their first task was to isolate pure penicillin from a crude liquid
extract. A culture of Fleming’s original Penicillium notatum was
maintained at Oxford and was used by the Oxford group for penicillin
production. Extracting large quantities of penicillin from the
medium was a painstaking task, as the solution contained only one
part of the antibiotic in ten million. When enough of the raw juice
was collected, the Oxford group focused on eliminating impurities
and concentrating the penicillin. The concentrated liquid was then
freeze-dried, leaving a soluble brown powder.
Spectacular Results
In May, 1940, Florey’s clinical tests of the crude penicillin proved
its value as an antibiotic. Following extensive controlled experiments
with mice, the Oxford group concluded that they had discovered
an antibiotic that was nontoxic and far more effective against
pathogenic bacteria than any of the known sulfa drugs. Furthermore,
penicillin was not inactivated after injection into the bloodstream
but was excreted unchanged in the urine. Continued tests
showed that penicillin did not interfere with white blood cells and
had no adverse effect on living cells. Bacteria susceptible to the antibiotic
included those responsible for gas gangrene, pneumonia,
meningitis, diphtheria, and gonorrhea. American researchers later
proved that penicillin was also effective against syphilis.
In January, 1941, Florey injected a volunteer with penicillin
and found that there were no side effects to treatment with the
antibiotic. In February, the group began treatment of Albert Alexander,
a forty-three-year-old policeman with a serious staphylococci
and streptococci infection that was resisting massive doses of
sulfa drugs. Alexander had been hospitalized for two months after
an infection in the corner of his mouth had spread to his face,
shoulder, and lungs. After receiving an injection of 200 milligrams
of penicillin, Alexander showed remarkable progress, and for the
next ten days his condition improved. Unfortunately, the Oxford production facility was unable to generate enough penicillin to
overcome Alexander’s advanced infection completely, and he died
on March 15. A later case involving a fourteen-year-old boy with
staphylococcal septicemia and osteomyelitis had a more spectacular
result: The patient made a complete recovery in two months. In
all the early clinical treatments, patients showed vast improvement,
and most recovered completely from infections that resisted
all other treatment.
Impact
Penicillin is among the greatest medical discoveries of the twentieth
century. Florey and Chain’s chemical and clinical research
brought about a revolution in the treatment of infectious disease.
Almost every organ in the body is vulnerable to bacteria. Before
penicillin, the only antimicrobial drugs available were quinine, arsenic,
and sulfa drugs. Of these, only the sulfa drugs were useful for
treatment of bacterial infection, but their high toxicity often limited
their use. With this small arsenal, doctors were helpless to treat
thousands of patients with bacterial infections.
The work of Florey and Chain achieved particular attention because
ofWorldWar II and the need for treatments of such scourges
as gas gangrene, which had infected the wounds of numerous
World War I soldiers. With the help of Florey and Chain’s Oxford
group, scientists at the U.S. Department of Agriculture’s Northern
Regional Research Laboratory developed a highly efficient method
for producing penicillin using fermentation. After an extended search,
scientists were also able to isolate a more productive penicillin
strain, Penicillium chrysogenum. By 1945, a strain was developed that
produced five hundred times more penicillin than Fleming’s original
mold had.
Penicillin, the first of the “wonder drugs,” remains one of the
most powerful antibiotic in existence. Diseases such as pneumonia,
meningitis, and syphilis are still treated with penicillin. Penicillin
and other antibiotics also had a broad impact on other fields of medicine,
as major operations such as heart surgery, organ transplants,
and management of severe burns became possible once the threat of
bacterial infection was minimized.Florey and Chain received numerous awards for their achievement,
the greatest of which was the 1945 Nobel Prize in Physiology
or Medicine, which they shared with Fleming for his original discovery.
Florey was among the most effective medical scientists of
his generation, and Chain earned similar accolades in the science of
biochemistry. This combination of outstanding medical and chemical
expertise made possible one of the greatest discoveries in human
history.

Pap test

noreply@blogger.com (Toma) — Wed, 30 Sep 2009 03:20:23 PDT

The invention: A cytologic technique the diagnosing uterine cancer,
the second most common fatal cancer in American women.
The people behind the invention:
George N. Papanicolaou (1883-1962), a Greek-born American
physician and anatomist
Charles Stockard (1879-1939), an American anatomist
Herbert Traut (1894-1972), an American gynecologist
Cancer in History
Cancer, first named by the ancient Greek physician Hippocrates
of Cos, is one of the most painful and dreaded forms of human disease.
It occurs when body cells run wild and interfere with the normal
activities of the body. The early diagnosis of cancer is extremely
important because early detection often makes it possible to effect
successful cures. The modern detection of cancer is usually done by
the microscopic examination of the cancer cells, using the techniques
of the area of biology called “cytology, ” or cell biology.
Development of cancer cytology began in 1867, after L. S. Beale
reported tumor cells in the saliva from
a patient who was afflicted
with cancer of the pharynx. Beale recommended the use in cancer
detection of microscopic examination of cells shed or removed (exfoliated)
from organs including the digestive, the urinary, and the
reproductive tracts. Soon, other scientists identified numerous striking
differences, including cell size and shape, the size of cell nuclei,
and the complexity of cell nuclei.
Modern cytologic detection of cancer evolved from the work of
George N. Papanicolaou, a Greek physician who trained at the University
of Athens Medical School. In 1913, he emigrated to the
United States.
In 1917, he began studying sex determination of guinea pigs with
Charles Stockard at New York’s Cornell Medical College. Papanicolaou’s
efforts required him to obtain ova (egg cells) at a precise
period in their maturation cycle, a process that required an indicator
of the time at which the animals ovulated. In search of this indicator,
Papanicolaou designed a method that involved microscopic examination
of the vaginal discharges from female guinea pigs.
Initially, Papanicolaou sought traces of blood, such as those
seen in the menstrual discharges from both primates and humans.
Papanicolaou found no blood in the guinea pig vaginal discharges.
Instead, he noticed changes in the size and the shape of the uterine
cells shed in these discharges. These changes recurred in a fifteento-
sixteen-day cycle that correlated well with the guinea pig menstrual
cycle.
“New Cancer Detection Method”
Papanicolaou next extended his efforts to the study of humans.
This endeavor was designed originally to identify whether comparable
changes in the exfoliated cells of the human vagina occurred
in women. Its goal was to gain an understanding of the human menstrual
cycle. In the course of this work, Papanicolaou observed distinctive
abnormal cells in the vaginal fluid from a woman afflicted
with cancer of the cervix. This led him to begin to attempt to develop
a cytologic method for the detection of uterine cancer, the second
most common type of fatal cancer in American women of the
time.
In 1928, Papanicolaou published his cytologic method of cancer
detection in the Proceedings of the Third Race Betterment Conference,
held in Battle Creek, Michigan. The work was received well by the
news media (for example, the January 5, 1928, New YorkWorld credited
him with a “new cancer detection method”). Nevertheless, the
publication—and others he produced over the next ten years—was
not very interesting to gynecologists of the time. Rather, they preferred
use of the standard methodology of uterine cancer diagnosis
(cervical biopsy and curettage).
Consequently, in 1932, Papanicolaou turned his energy toward
studying human reproductive endocrinology problems related to
the effects of hormones on cells of the reproductive system. One example
of this work was published in a 1933 issue of The American
Journal of Anatomy, where he described “the sexual cycle in the human
female.” Other such efforts resulted in better understanding of reproductive problems that include amenorrhea and menopause.
It was not until Papanicolaou’s collaboration with gynecologist
Herbert Traut (beginning in 1939), which led to the publication of
Diagnosis of Uterine Cancer by the Vaginal Smear (1943), that clinical
acceptance of the method began to develop. Their monograph documented
an impressive, irrefutable group of studies of both normal
and disease states that included nearly two hundred cases of cancer
of the uterus.
Soon, many other researchers began to confirm these findings;
by 1948, the newly named American Cancer Society noted that the
“Pap” smear seemed to be a very valuable tool for detecting vaginal
cancer. Wide acceptance of the Pap test followed, and, beginning
in 1947, hundreds of physicians from all over the world
flocked to Papanicolaou’s course on the subject. They learned his
smear/diagnosis techniques and disseminated them around the
world.
Impact
The Pap test has been cited by many physicians as being the most
significant and useful modern discovery in the field of cancer research.
One way of measuring its impact is the realization that the
test allows the identification of uterine cancer in the earliest stages,
long before other detection methods can be used. Moreover, because
of resultant early diagnosis, the disease can be cured in more
than 80 percent of all cases identified by the test. In addition, Pap
testing allows the identification of cancer of the uterine cervix so
early that its cure rate can be nearly 100 percent.
Papanicolaou extended the use of the smear technique from
examination of vaginal discharges to diagnosis of cancer in many
other organs from which scrapings, washings, and discharges
can be obtained. These tissues include the colon, the kidney, the
bladder, the prostate, the lung, the breast, and the sinuses. In
most cases, such examination of these tissues has made it possible
to diagnose cancer much sooner than is possible by using
other existing methods. As a result, the smear method has become
a basis of cancer control in national health programs throughout the
world

Pacemaker

noreply@blogger.com (Toma) — Tue, 29 Sep 2009 02:43:43 PDT

The invention: A small device using transistor circuitry that regulates
the heartbeat of the patient in whom it is surgically emplaced.
The people behind the invention:
Ake Senning (1915- ), a Swedish physician
Rune Elmquist, co-inventor of the first pacemaker
Paul Maurice Zoll (1911- ), an American cardiologist
Cardiac Pacing
The fundamentals of cardiac electrophysiology (the electrical activity
of the heart) were determined during the eighteenth century;
the first successful cardiac resuscitation by electrical stimulation occurred
in 1774. The use of artificial pacemakers for resuscitation was
demonstrated in 1929 by Mark Lidwell. Lidwell and his
coworkers
developed a portable apparatus that could be connected to a power
source. The pacemaker was used successfully on several stillborn
infants after other methods of resuscitation failed. Nevertheless,
these early machines were unreliable.
Ake Senning’s first experience with the effect of electrical stimulation
on cardiac physiology was memorable; grasping a radio
ground wire, Senning felt a brief episode of ventricular arrhythmia
(irregular heartbeat). Later, he was able to apply a similar electrical
stimulation to control a heartbeat during surgery.
The principle of electrical regulation of the heart was valid. It was
shown that pacemakers introduced intravenously into the sinus
node area of a dog’s heart could be used to control the heartbeat
rate. Although Paul Maurice Zoll utilized a similar apparatus in
several patients with cardiac arrhythmia, it was not appropriate for
extensive clinical use; it was large and often caused unpleasant sensations
or burns. In 1957, however, Ake Senning observed that attaching
stainless steel electrodes to a child’s heart made it possible
to regulate the heart’s rate of contraction. Senning considered this to
represent the beginning of the era of clinical pacing.
Development of Cardiac Pacemakers
Senning’s observations of the successful use of the cardiac pacemaker
had allowed him to identify the problems inherent in the device.
He realized that the attachment of the device to the lower, ventricular
region of the heart made possible more reliable control, but
other problems remained unsolved. It was inconvenient, for example,
to carry the machine externally; a cord was wrapped around the
patient that allowed the pacemaker to be recharged, which had to be
done frequently. Also, for unknown reasons, heart resistance would
increase with use of the pacemaker, which meant that increasingly
large voltages had to be used to stimulate the heart. Levels as high
as 20 volts could cause quite a “start” in the patient. Furthermore,
there was a continuous threat of infection.
In 1957, Senning and his colleague Rune Elmquist developed a
pacemaker that was powered by rechargeable nickel-cadmium batteries,
which had to be recharged once a month. Although Senning
and Elmquist did not yet consider the pacemaker ready for human
testing, fate intervened.Aforty-three-year-old man was admitted to
the hospital suffering from an atrioventricular block, an inability of
the electrical stimulus to travel along the conductive fibers of the
“bundle of His” (a band of cardiac muscle fibers). As a result of this
condition, the patient required repeated cardiac resuscitation. Similar
types of heart block were associated with a mortality rate higher
than 50 percent per year and nearly 95 percent over five years.
Senning implanted two pacemakers (one failed) into the myocardium
of the patient’s heart, one of which provided a regulatory
rate of 64 beats per minute. Although the pacemakers required periodic
replacement, the patient remained alive and active for twenty
years. (He later became president of the Swedish Association for
Heart and Lung Disease.)
During the next five years, the development of more reliable and
more complex pacemakers continued, and implanting the pacemaker
through the vein rather than through the thorax made it simpler
to use the procedure. The first pacemakers were of the “asynchronous”
type, which generated a regular charge that overrode the
natural pacemaker in the heart. The rate could be set by the physician
but could not be altered if the need arose. In 1963, an atrialtriggered synchronous pacemaker was installed by a Swedish team.
The advantage of this apparatus lay in its ability to trigger a heart
contraction only when the normal heart rhythm was interrupted.
Most of these pacemakers contained a sensing device that detected
the atrial impulse and generated an electrical discharge only when
the heart rate fell below 68 to 72 beats per minute.
The biggest problems during this period lay in the size of the
pacemaker and the short life of the battery. The expiration of the
electrical impulse sometimes caused the death of the patient. In addition,
the most reliable method of checking the energy level of the
battery was to watch for a decreased pulse rate. As improvements
were made in electronics, the pacemaker became smaller, and in
1972, the more reliable lithium-iodine batteries were introduced.
These batteries made it possible to store more energy and to monitor
the energy level more effectively. The use of this type of power
source essentially eliminated the battery as the limiting factor in the
longevity of the pacemaker. The period of time that a pacemaker
could operate continuously in the body increased from a period of
days in 1958 to five to ten years by the 1970’s.
Consequences
The development of electronic heart pacemakers revolutionized
cardiology. Although the initial machines were used primarily to
control cardiac bradycardia, the often life-threatening slowing of
the heartbeat, a wide variety of arrhythmias and problems with cardiac
output can now be controlled through the use of these devices.
The success associated with the surgical implantation of pacemakers
is attested by the frequency of its use. Prior to 1960, only three
pacemakers had been implanted. During the 1990’s, however, some
300,000 were implanted each year throughout the world. In the
United States, the prevalence of implants is on the order of 1 per
1,000 persons in the population.
Pacemaker technology continues to improve. Newer models can
sense pH and oxygen levels in the blood, as well as respiratory rate.
They have become further sensitized to minor electrical disturbances
and can adjust accordingly. The use of easily sterilized circuitry
has eliminated the danger of infection. Once the pacemaker has been installed in the patient, the basic electronics require no additional
attention.With the use of modern pacemakers, many forms
of electrical arrhythmias need no longer be life-threatening.

Orlon

noreply@blogger.com (Toma) — Mon, 28 Sep 2009 07:28:33 PDT

The invention: A synthetic fiber made from polyacrylonitrile that
has become widely used in textiles and in the preparation of
high-strength carbon fibers.
The people behind the invention:
Herbert Rein (1899-1955), a German chemist
Ray C. Houtz (1907- ), an American chemist
A Difficult Plastic
“Polymers” are large molecules that are made up of chains of
many smaller molecules, called “monomers.” Materials that are
made of polymers are also called polymers,
and some polymers,
such as proteins, cellulose, and starch, occur in nature. Most polymers,
however, are synthetic materials, which means that they were
created by scientists.
The twenty-year period beginning in 1930 was the age of great
discoveries in polymers by both chemists and engineers. During
this time, many of the synthetic polymers, which are also known as
plastics, were first made and their uses found. Among these polymers
were nylon, polyester, and polyacrylonitrile. The last of these
materials, polyacrylonitrile (PAN), was first synthesized by German
chemists in the late 1920’s. They linked more than one thousand
of the small, organic molecules of acrylonitrile to make a polymer.
The polymer chains of this material had the properties that
were needed to form strong fibers, but there was one problem. Instead
of melting when heated to a high temperature, PAN simply
decomposed. This made it impossible, with the technology that existed
then, to make fibers.
The best method available to industry at that time was the process
of melt spinning, in which fibers were made by forcing molten
polymer through small holes and allowing it to cool. Researchers realized
that, if PAN could be put into a solution, the same apparatus
could be used to spin PAN fibers. Scientists in Germany and the
United States tried to find a solvent or liquid that would dissolve
PAN, but they were unsuccessful until World War II began.
Fibers for War
In 1938, the German chemist Walter Reppe developed a new
class of organic solvents called “amides.” These new liquids were
able to dissolve many materials, including some of the recently discovered
polymers. WhenWorldWar II began in 1940, both the Germans
and the Allies needed to develop new materials for the war effort.
Materials such as rubber and fibers were in short supply. Thus,
there was increased governmental support for chemical and industrial
research on both sides of the war. This support was to result in
two independent solutions to the PAN problem.
In 1942, Herbert Rein, while working for I. G. Farben in Germany,
discovered that PAN fibers could be produced from a solution of
polyacrylonitrile dissolved in the newly synthesized solvent dimethylformamide.
At the same time Ray C. Houtz, who was working for E.
I. Du Pont de Nemours inWilmington, Delaware, found that the related
solvent dimethylacetamide would also form excellent PAN fibers.
His work was patented, and some fibers were produced for use
by the military during the war. In 1950, Du Pont began commercial
production of a form of polyacrylonitrile fibers called Orlon. The
Monsanto Company followed with a fiber called Acrilon in 1952, and
other companies began to make similar products in 1958.
There are two ways to produce PAN fibers. In both methods,
polyacrylonitrile is first dissolved in a suitable solvent. The solution
is next forced through small holes in a device called a “spinneret.”
The solution emerges from the spinneret as thin streams of a thick,
gooey liquid. In the “wet spinning method,” the streams then enter
another liquid (usually water or alcohol), which extracts the solvent
from the solution, leaving behind the pure PAN fiber. After air drying,
the fiber can be treated like any other fiber. The “dry spinning
method” uses no liquid. Instead, the solvent is evaporated from the
emerging streams by means of hot air, and again the PANfiber is left
behind.
In 1944, another discovery was made that is an important part of
the polyacrylonitrile fiber story. W. P. Coxe of Du Pont and L. L.
Winter at Union Carbide Corporation found that, when PAN fibers
are heated under certain conditions, the polymer decomposes and
changes into graphite (one of the elemental forms of carbon) but still
keeps its fiber form. In contrast to most forms of graphite, these fibers
were exceptionally strong. These were the first carbon fibers
ever made. Originally known as “black Orlon,” they were first produced
commercially by the Japanese in 1964, but they were too
weak to find many uses. After new methods of graphitization were
developed jointly by labs in Japan, Great Britain, and the United
States, the strength of the carbon fibers was increased, and the fibers
began to be used in many fields.
Impact
As had been predicted earlier, PAN fibers were found to have
some very useful properties. Their discovery and commercialization
helped pave the way for the acceptance and wide use of polymers.
The fibers derive their properties from the stiff, rodlike structure
of polyacrylonitrile. Known as acrylics, these fibers are more
durable than cotton, and they are the best alternative to wool for
sweaters. Acrylics are resistant to heat and chemicals, can be dyed
easily, resist fading or wrinkling, and are mildew-resistant. Thus, after
their introduction, PAN fibers were very quickly made into
yarns, blankets, draperies, carpets, rugs, sportswear, and various
items of clothing. Often, the fibers contain small amounts of other
polymers that give them additional useful properties.
A significant amount of PAN fiber is used in making carbon fibers.
These lightweight fibers are stronger for their weight than any
known material, and they are used to make high-strength composites
for applications in aerospace, the military, and sports. A “fiber
composite” is a material made from two parts: a fiber, such as carbon
or glass, and something to hold the fibers together, which is
usually a plastic called an “epoxy.” Fiber composites are used in
products that require great strength and light weight. Their applications
can be as ordinary as a tennis racket or fishing pole or as exotic
as an airplane tail or the body of a spacecraft.