Wow! Really?

Do you know where you came from?

2017-08-27T18:07:00.000-07:00

Genetic test nowadays are dirt cheap. And your 23 chromosomes have amazing stories to tell, including details of your ancestry. In fact, white supremacist were quick to jump on the gene sequencing process to prove their "ethnic purity" only to find out that they weren’t all that pure after all. They were particularly disturbed to learn that all our distant ancestors were from Africa and we all were black! But I'm getting ahead of the story.

As you know, our 23 pairs of chromosomes are made of DNA, and everyone inherits half of their DNA from their mother and half from their father.

When DNA is passed from parents to their children, the two chromosomes in each pair are randomly shuffled together. What you may not know is that when the chromosomes are shuffled, long segments from a single recent ancestor are broken into shorter segments. In the next generation the grandparent's segments are reshuffled and their fragments become shorter yet, and sometimes just disappear. Etc, the more generations back you go the shorter the segment and the fewer there are.

A bit off topic, but sometimes mistakes occur and mutations are produced during the shuffling process. Most mutations are of no consequence, but sometimes they create problems, and sometimes they create solutions--meaning whatever occurs makes the organism more (or less) able to live in it’s environment, so it reproduces (or not) and the mutation is carried forward to new generations (or dies out). It’s an over simplification, but that’s essentially what evolution is all about—not so much “survival of the fittest” as it is “refinement of suitability” for a given environment(s). You get enough generations of changes and one species branches so far off you end up with something totally different, a new species.

Anyway, different unique patterns of DNA, called markers, are found throughout your genome and, thanks to millions of tests, some of them are known to be from different people (perhaps I should write it People) in specific places around the world. There are oodles of markers in your genome and when you combine evidence from the hundreds of thousands of markers you carry, a clear picture of where you’re from and when develops. While the probability that you share DNA with a particular ancestor decreases as we go back over the generations, your total number of genetic ancestors does increase. By the time we get back to tens of thousands of years ago you are essentially related to everyone who left any descendants to the present day. So, since 50,000+ years ago everyone lived in Africa, the majority of your ancestral genome traces back to those African ancestors.

Which raises the question, where did white folk come from? Using these same gene sequencing methods, we know that people who lived 7700 years ago, in what is today called Sweden, where probably the first to develop a light skin gene variant which survived in the gloomy north. Only about 5800 years ago light skin swept through the lower latitudes of Europe because by then people had acquired two light skin genes and the trait became much easier to inherit and thus more common.

Incidentally, 5800 years isn’t much on human timescale--hold your arms out to your side and modern man’s history spans from fingertip to fingertip. On that scale 5800 years ago is about where your wedding ring is, and you can remove all of modern technology from the steam engine to the iPhone with nail-clippers. A nail file would easily remove the entire history of gene sequencing.

Personally, I love that fact that we know all this in such detail that the genes have names and we know exactly where they are in our DNA. The oldest are called SLC24A5 (on the long arm of chromosome 15) and SLC45A2 (on the short arm of chromosome 5). You can actually see the long and short arms I’m referring to in the photos below. The arms on chromosome fifteen are hard to distinguish but obvious on five. There’s also a more recent third gene, HERC2/OCA2, that causes blue eyes and probably also contributes to light skin and blond hair.

As an even further digression, you might be amused to know that if you unraveled all you DNA it would stretch to the Sun and back 4 times. DNA molecules are 1.7 to 8.5 cm long when uncoiled, or about 5 cm on average. You have about 10 trillion cells in your body (not counting red blood cells which don’t contain a nucleus or DNA), so if you stretched the DNA in all the cells out, end to end, they'd stretch over 744 million miles. The sun is 93 million miles away, so your DNA would reach there and back about 4 times!

Farther afield, we share about 90 percent of yeast's genes, of all things—there are exact counterparts in humans. Even stranger, there are 223 genes in humans that exactly match for those in bacteria. What’s more, researchers have found that bacteria have a way to do what’s called lateral gene transfer and it’s particularly prevalent in cancer cells. Either cancer cells are prone to these intrusions or the incoming bacterial genes help to kick-start the transformation from healthy cells into cancerous ones. In fact mitochondria, the powerplant in our cells, are decedents of ancient bacteria, and have their own genes that they swap them among themselves. Amazingly, there are scientists that think mitochondria have their own genetic interest that may not align with ours. Kinda creepy to think we’re just perambulating hosts. We're zombies!

Were not the only one to be invaded by bacteria. Look out the window; everything you see that’s green is thanks to a similar process.

About 2 billion years ago some cyanobacterium started functioning as a cellular component in plants. Thanks to them plants can use water, hydrogen and sunlight to create sugars that power the plant. In the process they create oxygen, lucky for us. All the oxygen in the atmosphere (about 20% off it) comes from that process (photosynthesis). We wouldn’t be here if bacterium hadn’t invaded plant cells just like mitochondria invaded ours.

How do we know? Genetics, of course! All the plants on earth, from giant redwoods to tiny single algae diatoms found everywhere, came from one single alga cell that swallowed a cyanobacterium with the help of a bacterial parasite. Every single plant shares the same DNA structure.

Turns out humans with blue eyes have a single common ancestor too. We all have melanin in our iris that creates the browns and greens, but a genetic mutation affecting the OCA2 gene turned off a switch that produces melanin in eyes, and the blue is what’s left.

Wow! Really?

Fun with RADAR

2012-10-28T13:42:00.002-07:00

Say 'radar' and most people think of cops and a speed trap, FAA air traffic controllers following airplanes, or NASA engineers tracking rockets. But RAdio Detection And Ranging can be used for a lot of purposes including some that are simply fun. Especially when you can put a whole radar system on a 5mm x 5mm chip, like ViaSat managed to do.

If you stand in a canyon and yell, you'll hear an echo when the sound of your voice bounces off the side of the canyon and back to you. Like timing a thunderclap to judge the distance to a bolt of lightning, if you time the echo of your yell and know the speed of sound (roughly 1000 feet per second) you can estimate how far away the cliffs are and how close a thunderstorm is. Flash, one-thousand, two-thousand, three..,boom! Storm is about a half-mile away.

With radar, you essentially do the same thing except you use a radio signal instead of sound, and the signal propagates at almost the speed of light (about 11 inches per nanosecond). Send a pulse, listen carefully for a radio echo, and you can tell how far away something is by measuring how long it takes for the signal to go out and bounce back.

If you know the direction your antenna is pointing when you receive the signal you know where to look for the target. Compute the difference in position between two received signals and you can tell the direction your target is moving. Measure the change in frequency of your radio signal, and you can determine the speed of the target with respect to your antenna, although a target with zero speed may be traveling at a constant distance in a circle around you.

ViaSat has put all the radar electronics on a 5mm by 5mm chip. Add a power supply and an antenna and you're in business. It's not quite that easy of course, but that's essentially all you need.

ViaSat's chip is available for military and commercial applications that are a lot more serious, such as perimeter security, traffic management, and altimeters. In such applications the product has to survive challenging environmental conditions, take up up as little space as possible, use a tiny amount of power, and require no tweaking after it's installed—and do all that at a reasonable cost.

ViaSat's radar-on-a-chip is the only self-contained frequency modulated continuous wave radar sensor on a single chip. What's more, it can be easily tailored to different applications using digital interface software to control frequency and bandwidth. Best of all, it works over a wide temperature range because it continuously self-calibrates.

With those capabilities, the chip can be used by the military to control vehicles in driverless convoys, provide UAV navigation in tight spaces, or watch for small boat intruders when ships are in port. Civilian applications include adaptive cruise control so you don't have to brake and resume when traffic slows down.

ViaSat doesn't sell their chips retail, but a similar sensor will set you back only about $10. You won't be able to track passing aircraft or bust speeding drivers, but you could create a backup obstacle detector for your car or an intruder alarm for your house.

Or, just for fun, you could build a theremin—one of those weird-sounding electronic musical instruments. They date back to the 1920s when people used an antenna and oscillator to produce spooky sounds. With radar on a chip, you could do the same to measure the motion of your hands.

Radar isn't just about business and war, it can be fun too.

Satellite Solutions

2012-10-27T18:59:00.000-07:00

Technology is always in the news these days, but there's one spectacular device out there you've probably never heard of.

ViaSat-1, launched in late 2011, provides more capacity in one satellite than all other communications satellites over North America combined. It will help 1,000,000 technologically deprived web surfers on the ground, in the air, and on the high seas join the 21st Century.

If you rummage around online forums about broadband services you'll find grumps who complain that satellite services can be interrupted by something as common as rain. That used to be true, but engineers have found a solution so the ViaSat Exede service will do just that— exceed your expectations. Now it's just silly to worry about weather effects except under the most extreme circumstances.

Jim Petranovich, MIT grad and Chief Geek at ViaSat subsidiary Enerdyne, wrote a technical whitepaper that discusses the ways ViaSat reduces and prevents the affects of weather for users of the company's very special Ka-band (high frequency) satellites. I’ll translate the paper for you, but first a little background.

Bit buckets and fire hoses

ViaSat's high-capacity satellite uses spot beams to concentrate energy into smaller areas than conventional satellites. ViaSat-1 has 72 spot beams supported by 20 gateways. Each spot beam supplies nearly as much bandwidth as one entire old satellite. That means they can send more data, at a faster rate, to smaller user antennae.

Four spot beams on the satellite are usually supported by one ground station called a gateway. The gateways, connected to the Internet, beam data up to ViaSat-1. The satellite acts like a U-shaped pipe that collects a stream of data coming up and shoots it back down to you, wherever your bit bucket (antenna) is located to catch the data. In fact, ViaSat-1 is referred to, technically, as a bent-pipe satellite.

As an aside, the amount of energy an antenna can collect is based on size or aperture. The bigger the antenna—the bigger the bucket—the more energy they collect. So for very strong sources you don't need much aperture. A fire hose will fill a milk bucket, real quick like.

Telescopes work the same way--in a sense they're antennae too, photon buckets, receiving light energy instead of radio energy. That means I can use my little 3.5" telescope to look at the literally blinding Sun, and even need to add a special solar filter, like super-strong sunglasses. My 8" telescope collects over five times more light, so I can use that to observe dim deep-sky objects.

What's all that mean to you? ViaSat-1 has powerful transmitters, brighter or "hotter" than old satellites'. So your antenna only needs to be two and half feet in diameter--a Very Small Aperture Terminal or VSAT. In fact, ViaSat has a battery powered portable terminal for news-gathering organizations that packs into a suitcase that weighs under 50 pounds, antenna and all.

And, now, back to the weather. ViaSat can't make it stop raining, of course, but they have done something about how weather affects broadband satellite services.

Heavy rain, I mean heavy rain such as in Hurricane Sandy, or a blizzard of wet snow (such as in Hurricane Sandy), can be an issue—light rain and dry snow not so much. Gases in the atmosphere, clouds, and weird changes in the ionosphere, called scintillation, can reduce the strength of a satellite signal too, but those effects are small.

Singing in the rain

So how does ViaSat make sure even the worst weather doesn't affect your Facebook or Twitter experience?

To begin with, ViaSat-1 is "hotter" than older satellites, as we've said. With stronger down link signals, the reduction in strength caused by weather is less noticeable. Think of weather as blue food coloring and the satellite beam as a stream of water. If you add the coloring to a dribble from a faucet the water will be very blue. Put the same amount in our fire hose, and you won't even notice. Strong satellite signals simply overwhelm small weather effects.

This whole issue of the effect of rain on radio signals (satellite or terrestrial) has been studied to death. Researchers can tell you how raindrop size, drop oscillation, the angle the rain comes down, and temperature, impurities and host of other nitty-gritty details can affect reception.

But, to be clear, you'll seldom, if ever, notice weather issues using ViaSat's Exede service. One reason is that really heavy rain, strong enough to be a problem, is a rare event. Another reason weather is seldom a problem is that fancy network protocols (software sleuths) are used to detect and retransmit missing data.

In the case of streaming video, Internet applications expect micro-interruptions anyway, so the computer programs create a buffer that can be emptied while data is resent. They work like your water heater where a tank (buffer) of hot water is created so you can drain it off when needed without waiting for it to get hot. That's why you often have to wait for a YouTube or Netflix video to start, they're filling a buffer.

Okay, you say, but what if the weather is really awful, hurricane awful, and they're looking at the real possibility of signal fade? ViaSat has gotcha covered there too, with some really high tech solutions such as adaptive power control and adaptive coding and modulation.

Adaptive power control generally is only necessary when data is being sent by you to the satellite. Your little dish antenna and small amplifier have to yell most of the time for the satellite far away to hear you. If weather interferes with the satellite, and it's having trouble hearing you, it tells your system to take a deep breath and scream twice as loud for a while to make sure your email to finicky Aunt Martha isn't garbled.

Modern magic

Adaptive modulation, on the other hand, is one of those technologies that, when it's shown in a system diagram, deserves an arrow with a caption that says, "Here there be magic." One of the incantations the magicians use goes something like this: "Euler, Euler, phase-shift, quadraphase; sine wave, sine wave, lowpass, carrier. . .and . . . demodulate." Presto, you have double the bandwidth. But that's just a small part of the show that all happens at the speed of light out in space.

Adaptive coding, including forward error detection, means weather threats just evaporate. Forward error detection sounds like they're not just magicians but psychic too, correcting problems before they happen. But really they're just adding redundancy so your data doesn't have to be retransmitted. It's kinda sad all that magic is going on up there and we can't see it.

Like all magic, there's slight of hand at work behind the scenes at ViaSat, and it's fully understood by those in the know. All you need to know is that fancy software can adapt to changing conditions to adjust your instantaneous data rate and the amount of time the satellite allocates to your messages. You're not even aware anything changed.

Weather can potentially affect gateways, too, of course; and that can be a big problem because everyone supported by the gateway would be affected. But gateways use adaptive power control and adaptive modulation and coding, too. In some cases multiple gateways serve the same spot beams and end users. If weather threatens one gateway, another can be pick up the load without any interruption—more magic developed by ViaSat.

Another nifty trick that ViaSat uses is to put their ground stations outside the coverage area of the spot beams. So while it may be pouring where you are, say in the Gulf Coast or Florida, your gateway might be basking under clear skies in Albuquerque or Tucson.

The moral of the story

Even if it is raining on the gateway, by the way, signal strength is only loosely related to rain intensity. The signal path is generally on a diagonal up from the ground to the satellite located over the West Coast. In any event, the weather at your location has more effect on performance than at the gateway because they have big honking antennae and you just have the little dinky dish.

So you may have filed away in your brain that satellite broadband really isn't a good option because of weather problems. That's not the case anymore. That thought is just brain sludge, taking up space in your noggin along with the 1962 hit tune, Telstar performed by The Tornadoes.