That is Weekend-Waste-Worthy Videos for you. A collection on Science and Music.

First some Science videos:

1) Grown-ups, watch this with a straight face at home. Remember to shoo away your six-year-olds with ‘this is heady science stuff that you need to grow up to appreciate’. TED Talk by Mary Roach on 10 things you didn’t know about orgasm.

2) Slowmo cameras can reveal more of our daily life activities. Mostly funny, some Science concepts also get explained along the way [video link].

3) What exactly is Schrondinger’s Cat concept trying to explain in quantum mechanics? Sixty symbols attempts a short explanation.

and

4) here is Brain Malow with science jokes, where not surprisingly, Schrondinger’s cat enters a bar and doesn’t…

5) A Brief History of Pretty Much Everything as a flipbook made entirely out of biro pens. Nice creativity.

This is the final piece for my AS art course, a flipbook made entirely out of biro pens. It’s something like 2100 pages long, and about 50 jotter books. I’d say I worked on and off it for roughly 3 weeks.

[source: DispleasedEskimo]

Now for some Music.

As I did earlier in Saturday Songs an eclectic collection of music across the World that I like…

1) Jeff Beck’s Bolero (a slow Spanish/Latin dance and music) on the guitar has its own charm

but

2) obviously stands no chance against the real western classical Bolero by Ravel (dare to pump up the volume at home – the only way to listen to this – as if in a concert hall)

3) At an young and appropriately impressionable age John “granny glass” Lennon was one of my heroes. So much so, I was wearing a granny glass and combing my hair parted in the middle, strumming my acoustic all through the night, just sitting here Watching the Wheels go round and round…

4) Here is some amazing gypsy syncopation much ahead of its time when done in 1980 by Tomatito in Bulerias. Tomatito is on the flamenco guitar. Clip is from Rito y Geografia del Toque DVD set. [video: marRicardo]

5) Go round and scrounge the World a million times with an open mind for imbibing the capricious richness of music as an art form, as an intellectual exercise, as entertainment or as a spiritual experience… I shall come back to my home land and its music for salvation.

Here is ikanaina a one hit wonder in the rAgam pushpalathika by M S Subbulakshmi with a deadly neraval in the interlude.

Neraval is a carnatic music creative embellishment, taking a line from the song and elaborating on it with musical variations within the scope of the rAga of the song.

Singing neraval is difficult. Even yesterday stalwarts have dared to safely leave out this section from their musical careers so that they don’t have to loose face having tried and failed. If you observe in concerts, even swara kalpanai can be attempted with reasonable success in rare rAgAs. But not neraval. Musicians only attempt neraval in safe and well tested rAgAs, with some available reference.

Judging with this backdrop, the above MSS neraval on an obscure rAgA is outstanding.

I heard a commendable recent rendition of this song by Sikkil Gurucharan.

What if Lord Shiva the destroyer is actually human who lived thousands of years ago and fought great battles to establish the balance between superpowers of allegorical Good and Evil? What if there did exist in reality a Rama Rajya – as prescribed by King Rama of Ayodhya, but practised by the people of the Indus valley Civilization? What if Manu (Manu Smriti author) is originally from SangamTamil, the kingdom of the Pandyas (an etymological origin for the word pundit), the present day Tamil Nadu. What if owing to some great calamity (ocean engulfing vast Southern lands) along with a select few pundits he has gone up to North until Harappa and Mohan-ja-daro, the cradle of the Indus Valley Civilization? What if Brahaspathi is a chief scientist of an advanced research laboratory with nice coherent scientific ideas and rational outlook? What if he could brew the divine nectar or immortality, amirtham (amruth for Northies) or somarasa in his laboratory almost as a modern day organic titration? What if the somarasa neutralizes oxidants – the toxins – from our body and prevents oxidation, thereby aging…

There are enough interesting thoughts and suggestions that engage you in The Immortals of Meluha, the first book of a promised trilogy by Amish, which I picked on a lark from the local book store.

The Immortals of Meluha is not commendable for its plot or language, but definitely recommendable as an engaging page turner with enough Hindu mythology to rediscover and philosophy to ruminate, rue or ignore.

The story is set around 1900 BC in India, known then a Sapt Sindh, the land of the seven rivers. A nice yarn at that. The Indus Valley civilization of Harappa and Mohan-ja-daro are the Meluhas or Suryavanshis, while the dwellers of present day Tibet, Bihar and nearby regions are the Chandravanshis. One tribe is very advanced in their thinking and technology , with organized roads, sanitation and drainage (required for an interesting reason), almost immortal but captive to their rules. The other tribe is not so advanced, dis-organized as a civilization, unbounded by any set of rules, mortals with diseases and strife and freedom. The eternal struggle between Good and Evil is depicted through the battles between these two dynasties. Both believe a savior or leader from outside their tribe will come to lead them to victory in a definitive battle to vanquish the other tribe. and then there were the Nagas, vile and willy, from a far off netherworld to complicate the issue.

Soon you realize the allegories and originals; the Devas and the Asuras, related puranic stories, Shiva and Sati, Nandhi and Veerabahu, Taksha and Tarakasura (nice little cameo as Tarak in the book) and so on.

The leader arrives from elsewhere (Kailash or Himalayas), takes sides, wins the battle. But did Good actually triumph? Read the book…

With names of the characters resembling their mythological originals and their deeds not too far off from the originals, the plot meanders after a while. And taking up Gods as characters has its limitations. Romance between Shiva and Sati (Parvathi) is stinky clean without a kiss. Thankfully, Shiva is human and humane, amorous and valorous, smokes pot and fights to kill. On the lighter side, even with the blatant Hanuman of Vayuputra tribe, the altered names of characters in the story, with clues to the originals, always brings a smile. And there are some romantic escapades and interludes to pep up the God-manly tale.

Having finished reading the book, I searched the web for more details on Amish and the book. Bad decision.

First I stumbled on an YouTube advertisement video for the book. Here it is. (Who is the Shiva model with that nice shoulder scar?)

YouTube Link

Then I stumbled on another series videos presenting an interview with Amish. [Start here]

He seems to be a cool guy with a humble outlook but that interview was a definite let down for me. Is that an advertisement strategy to proclaim his atheist past life, only to be changed by Lord Shiva forever now? Once, he didn’t want to enter the temple his wife went to (why should a true atheist refrain from entering temples that should anyway have no Gods?) but he says (in the interview) now he is a zealous convert with Lord Shiv(a) as fav-deity, going to temples, wearing even the rudraksha and an armchain and so on.

May be I shouldn’t blame him squarely when the interview poses questions on how to end world violence, assuming the answer is in the book or with the author.

Amish originally planned to write a book on his philosophy and interpretations about Hindu scriptures. Thankfully, well-wishers talked him out of it and gave this fiction-with-myth-philosophy idea. I liked the refreshing outlook he brought in the book with Shiva as a human with some novel interpretations of our scriptures and puranas. He cites Underworld by Graham Hancock (check out that book for more World myths questioned) for his Manu interpretations. He even argued nicely about the plausibility but futility of an ideal society.

And then he goes on to become a staunch theist with his favorite deity as Lord Shiva. At least in the interviews.

I don’t mind such incongruity in humans. We are carbon-based islands of capricious consciousness. But with such image-bursting information about the author, perhaps done as a promotion gig, the book I read isolates author-less. I wanted to read the other two parts of this trilogy. I still would. Somehow, that interview has doused my eagerness.

Lesson learnt: don’t read or listen to the web on things you already like or seem to know enough about.

Let me end on an approving note. If I can devour all the predictably racy and many-a-times half-way-through-rudderless page-turners of James Rollins, I would definitely read the other parts of Amish’s much tauter and unpretentious trilogy with a definitive philosophical message. At least the yarn is closer to my abode.

But one cannot also escape obvious pitfalls in re-interpreting mythologies or puranas known to us. The surprise element is absent for the reader. For instance, if I know some Shiva and Vishnu purana, I could get clairvoyant about the second part. Sati’s father, Takshit would be killed by the emissaries of Shiva. Shiva would soon come to wield a class of weapons of mass destruction and would annihilate the Worlds in a single shot. The third part could even feature the World’s earliest successful human-animal transplant and the result was Vinayaka. And so on…

Unless Amish plans to surprise. Let us see.

*****
Check also Official site | Amish | @Twitter

The dependence of apparent viscosity of human blood on the capillary size it is flowing through is identified as the Fahraeus-Lindqvist effect (1931). This was explained in the earlier Blood Flow in Capillaries note. There is a related but different effect called the Fahraeus effect (1929). This is the decrease in average concentration of red blood cells in human blood as the diameter of the glass tube in which it is flowing decreases.

The Fahraeus effect definitely influences the Fahraeus-Lindqvist effect but the former is not the only cause of the later. The F-L effect is also due to the slippage at the tube walls induced by the few-microns-thick blood plasma layer (without RBCs and WBCs, which migrate towards the axis).

We shall discuss the Fahraeus effect (1929) in some detail now.

Blood can be viewed as a suspension of cells in plasma. It consists of red blood cells or erythrocytes (RBCs), white blood cells or leukocytes (WBCs) and platelets. Hematocrit (Ht or HCT) is the proportion of blood volume in a region that is occupied by red blood cells. Another way of saying this is, hematocrit is the percentage of whole blood occupied by cellular elements. Normally, it is about 48 percent for men and 38 percent for women. The standard ’blood test’ that doctor’s prescribe include hematocrit in the complete blood count results, along with hemoglobin concentration, white blood cell count, and platelet count (check a ’blood test’ result next time).

Considering steady laminar fully-developed blood flow in a small tube, r₀ ≤ 150μm, whole blood separates into a cell-free plasma layer, δ ≈ 5μm, along the tube wall and enriched central core, 0 ≤ r ≤ (r₀ – δ). As a result, the tube hematocrit, H_t, is smaller than the out flow hematocrit, H₀, i.e., H_t < H₀. This is the Fahraeus effect (1929).

The migration of cells from the capillary or tube walls towards the tube centre causes an average cell speed greater than the average axial velocity component of the surrounding fluid. Imagine a region of the tube where the blood is homogeneous with RBCs distributed equally across the cross section. In this section, due to the presence of the tube wall, the fluid (liquid parts of the blood) velocity is less and progressively increases towards the axis, where there is no wall to brake the flow. This results in a parabolic cross sectional velocity profile under laminar flow – what is known as Poiseuille flow. When the RBCs migrate from near the wall towards the axis, the average speed of them increases, with a corresponding decrease in the surrounding fluid.

This migration and speeding results in a non-homogeneous RBC distribution in a cross section of the tube. All the RBCs have to squeeze near the axis and enjoy their life in the fast lane before getting discharged at the exit. In other words, the tube hematocrit (percent volume of RBCs) is less than that of the blood discharged from the end of the tube (the discharge hematocrit) at the exit.

There is also an entrance effect – usually present and hard to eliminate totally in an experiment – that could cause this lack of RBcs near the walls and could be mistakenly interpreted as Fahraeus effect. When blood comes into a tube from a mother reservoir, the RBCs in them – due to their solidity – act like human crowd near an exit door. they crowd towards the axis at the entrance of the tube. This is not Fahraeus effect and dies out farther away from the entrance of the tube. (regular fluid mechanists by now would already be irked with this explanation as they know already what I meant when I mentioned the phrase entrance effect).

So, in the absence of these kind of entrance effect, the (exit) discharge hematocrit from a tube must equal to that of the blood in the mother reservoir that feeds the tube (the so-called feed hematocrit). In between, due to Fahraeus effect, the tube hematocrit registers a decrease from the outflow or discharge hematocrit.

Enough English. Here is some mathematics to show the nature of the function that governs the dependence of hematocrit content of blood on the size of the capillaries. A simple mathematical treatment of the Fahraeus effect was shown in Sutera et al. (1970). As far as my limited knowledge goes, this seems to be the earliest analysis. I would stand corrected if an earlier reference is pointed. Another analysis is also presented in Kleinstrauer’s book [4], which we shall elaborate here.

For a tube of circular cross section with radius r₀, the averaged tube and outlet hematocrit can be defined as:

Tube hematocrit

… (1)

Outlet hematocrit

… (2)

with

and

… (5)

is the axial flow velocity that is a function of the radius (more near axis, less near tube walls).

Using Eqs. (1) and (2) one could write (how to do this is left as an exercise for those interested in trying out such details):

… (6)

Now assuming δ = 5μm, H_t < H₀ when r₀ < 500μm i.e. the critical radius when the Fahraeus effect becomes apparent. Here is a graph based on the functional relationship in the above equation. The graph shows the relationship between tube hematocrit and the plasma layer growth near the capillary wall.

The heterogeneous character of blood affects the blood viscosity when the length scale of the blood vessel (artery etc.) is comparable to the length scale of the components of the blood. When flowing through very large vessels, much larger than the size of the components of blood, blood exhibits as a homogeneous fluid (read on homogeneity and length scales). Hence, in those instances, blood viscosity exhibits Newtonian characteristic. Blood viscosity varies with concentration of components (e.g., amount of RBCs), and with diameter of blood vessel.

Small blood vessel diameter has the effect of reducing the apparent blood viscosity because the blood components like RBCs tend to concentrate near the center of the vessel. This induces a small layer of more homogeneous fluid to surround the vessel wall. The cell components then slide more freely as they flow downstream. For example, at a given concentration of RBCs (how many per volume of blood), the apparent blood viscosity reduces more than 50 percent (3 to less than 2 centipoise), when the blood vessel diameter reduces 10 times (say, from around 2 mm to 0.2 mm). Under these circumstances, blood viscosity differs from Newtonian characteristic.

Fahraeus effect has direct advantages for humans and serious implications during malfunction. Blood circulation in human body is a closed loop. Within this loop, blood requires to be pumped for flowing. Pumping requires energy (pressure-drop), which is provided by the heart. Clots and fats in the blood vessels (veins and arteries) increase the pumping power load of the heart – a potential reason for heart attack.

Interestingly, these mechanical resistance parameters also change with time because of blood flow induced re-modeling. There can be long-term changes in the capillary materials and geometric properties. Hypertension may cause thicker and stiffer arteries and a chronic artery-wall decrease may lead to localized lumen constrictions. Unlike rigid pipe networks we encounter in mechanical and other engineering constructions, bio-engineered arteries respond to what flows through them – blood flow conditions.

References

Sutera, S. P., Seshadri, V., Croce, P. A. and Hochmuth, R. M. (1970). Capillary blood flow: II. Deformable model cells in tube flow Microvascular Research, 2 (4), 420-433 DOI: 10.1016/0026-2862(70)90035-X

1. R. Fahraeus and T. Lindqvist Am. J. Physiol. 96 (1931), p. 562.

2. Fahraeus, R., (1929) The suspension stability of the blood. Physiol. Rev. 9, 241274.

3. Sutera, S. P., Seshadri, V., Croce, P. A. and Hochmuth, R. M., (1970) Capillary blood flow : II. Deformable model cells in tube flow. Microvasc. Res. 2, 420433.

4. C. Kleinstrauer, (2007) Bio-Fluid Dynamics, Taylor and Francis Pub.

More interesting and review papers related to this topic

5. Pries, A. R., Neuhaus, D. and Gaehtgens, P. (1992) Blood viscosity in tube flow: dependence on diameter and haematocrit. Am. J. Physiol. 263, H1770H1778.

6. Blair, G. W. S. (1958) The importance of the sigma phenomenon in the study of the flow of blood. Rheol. Acta 1, 123126. (review – to read)

7. Goldsmith, H. L., Cokelet, G. R. and Gaehtgens, P. 1989 Robin Fahraeus: evolution of his concepts in cardiovascular physiology. Am. J. Physiol. 257, H1005H1015. (review – to read)

8. Miguel Moyers-Gonsalez, R. G. Owens and J. Fang, (2008) Non-homogeneous constitutive model for human blood. Part 1. Model derivation and steady flow, J. Fluid Mech., vol. 617, pp. 327354. [DOI: http://dx.doi.org/10.1017/S002211200800428X ]

Blood flow has its peculiarities, in particular how the viscosity depends on the size of the capillary it flows through. To appreciate this, let us begin with a preamble of what is standard textbook behavior of common liquids like water. Liquids in general adhere to the Newtonian law of dynamic viscosity. When flowing, their shear rate is directly proportional to their strain rate or velocity gradient. The proportionality constant turns out to be the dynamic viscosity, a property defined by this relationship, known as the Newtonian law of viscosity. Based on this understanding, one could derive other interesting insights.

Poiseuille (and Hagen) around 1840 did experiments with water flow in capillaries and found a relationship between the applied pressure drop and the volume flow rate (or average liquid velocity for uniform cross section). They found under laminar flow conditions (Re_D ≤ 2000, read Pipe Turbulence essay for details) the pressure-drop (ΔP∕L) and average velocity U(m/s) are linearly related, with the constant of proportionality including the dynamic viscosity of the liquid (and the pipe geometry). This observation was also deduced as a particular viscous laminar flow solution for the Navier-Stokes equation, the momentum conservation statement for fluid flow.

For laminar flow of a liquid with average velocity U (m/s) through pipes of length L, with circular cross section of diameter D, one could write or a way to determine viscosity of the flowing fluid.

The outcome of the above findings is that capillaries (that ensure laminar flow) provide a standard way to measure the dynamic viscosity of the flowing liquid. Further, as one would expect for a constitutive property, the measured viscosity is independent of the capillary size (length or diameter), volume flow rate and applied pressure-drop. For instance, dynamic viscosity of water or air can be determined with fair accuracy this way in the laboratory [a difference could occur when temperature dependency of viscosity is strong].

So far so good. Enter blood; the situation gets different. Blood flow in a capillary vessel – as in our human body – behaves in a peculiar way. The viscosity of blood changes depending on the size of the capillary it flows through. In other words, Poiseuille’s relationship for viscosity (mentioned above) doesn’t hold for blood flow in capillaries, at least in a range of capillary diameters. This is called the Fahraeus – Lindqvist effect, named after Swedish haematologists Robert Sanno Fahraeus and Johan Torsten Lindqvist who reported it in their now classic paper [1] published in 1931.

The objective of their paper is quite clear:

The present investigation deals with the problem of the influence of the diameter of the capillary tube upon the viscosity of the blood and pays special attention to the conditions in capillary tubes which are as narrow as possible.

Interestingly, Fahraeus and Lindqvist are also knowledgeable on why they don’t want to use viscometers to measure the blood viscosity, when they write

Many investigators have used viscosimeters of Ostwalds type, where the blood from a reservoir is pressed by its own weight through a vertical capillary. This apparatus has, however, a great source of error. The red corpuscles have time to settle in the reservoir, during the experiment. The consequence of this will be that the concentration of the corpuscle suspension entering the capillary will change during different phases of the streaming. [...] This fact certainly explains the above mentioned result of Denning and Watson, who found the viscosity of horse blood increased in narrow tubes.

Based on the above results, they conclude in their paper:

[...] the viscosity of human blood is far from being a constant quantity, but changes with the diameter of the capillary tube. These growing narrower, the viscosity begins to decrease in capillaries [...] Very likely in a capillary tube of a diameter, for instance, of 0,03 mm., the values are only about 50 per cent of those obtained in a capillary tube of a diameter of 0.3 mm. [...] The law of Poiseuille does not apply to the flow of blood in capillary tubes of a diameter below about 0.3 mm.

The viscosity of the blood is not a constant quantity, but dependent on the diameter of the tube. Below a diameter of about 0.3 mm, the viscosity decreases strongly with reduced diameter of the tube. The viscosity decreases in small vessels (diameter D < 300μm) to a minimum of 1cP at D = 8μm.

Amazingly, for further reduction in capillary diameter, for capillaries with D ≤ 8μm, the blood viscosity increases. Eventually, the RBCs are unable to squeeze through the narrow vessel.

Current understanding is a decrease in blood viscosity is observed when it flows in capillaries with 30μm < d < 300μm. This is the Fahraeus – Lindqvist effect explained in the figures above. As a consequence the resistance to the flow of blood in the arterioles (and in the small veins) is considerably less than would be the case if the blood flow followed the Poiseuille relationship for its viscosity. However, for d < 10μm the hematocrit and apparent viscosity increase again, until even deformable RBCs cannot pass vessels with d ≤ 2.7μm. This behaviour is amply demonstrated in later experiments as collected in the figure below. Blood viscosity affects the power required from the heart. If the viscosity is too high, the required power increases; if the viscosity is too low, the required power again increases to hold the blood from flowing by gravitational effect. Due to heterogeneity in content, blood viscosity behaves differently from the viscosity of simple liquids.

Fahraeus effect has direct advantages for humans and serious implications during malfunction. Blood circulation in human body is a closed loop. Within this loop, blood requires to be pumped for flowing. Pumping requires energy (pressure-drop), which is provided by the heart. Clots and fats in the blood vessels (veins and arteries) increase the pumping power load of the heart – a potential reason for heart attack. Read about such issues in Blood: Clot, Flow and Slip

References

R. Fahraeus and T. Lindqvist (1931). The viscosity of the blood in narrow capillary tubes American Journal of Physiology, 96, 562-5681. R. Fahraeus and T. Lindqvist, The viscosity of the blood in narrow capillary tubes, Am. J. Physiol. 96 (1931), p. 562 – 568. [Link]

2. Bio-Fluid Dynamics by C. Kleinstrauer, CRC Press, Taylor and Francis Pub., 2007. 3. Blood: Clot, Flow and Slip

I have written earlier on How to stay calm and Oh to be a Teacher.

And now for something completely indifferent…

Imaginary Conversation 1

Why don’t you take this course?

I don’t know what is bio-heat transfer.

But, isn’t that the reason why you should take the course.

I might score a poor grade…

Yes, but if I assure you that you will certainly pass, will you give it a try?

I would like a better grade. I am not sure I would get that with your new elective. It is already vague. What if it turns out to be tough.

So you want me to assure you of a pass and also a better grade, even before you want to learn?

Well, no. But a better grade would not mess up my chances of winning a medal or a job or a graduate entry.

If I assure you of success in life even before you try, will you die young?

*****
Imaginary Conversation 2:

Do you want to work in bio heat transfer and fluid mechanics?

No. I don’t know biology.

You don’t need to know too much biology. Only basics in heat transfer and fluid mechanics are expected.

Will I get a job?

Look, since when you have heard of Ph.Ds being jobless in India? Joblessness is a status exclusive for PIGS trying to settle in the USA. You can be assured of a job here…

But will I get a GOOD job?

What do you mean?

With lot of salary…

More than me?

Er, no, thats not what I meant…

No, its okay. You may get one that way. I don�t know now. But there is always enough opportunity for Ph.D.s in any topic…

I want to finish quickly…

Just work on the problem I ask you to and things will be alright.

May be it will take longer to finish the degree in this new area than other research…

Actually, it could be the converse. The problems are fresh and there could be enough low hanging fruits for those who try early. So…

I also need to know about fruits?

Never mind…

*****

Imaginary Conversation 3:

What do you want to do?

I have worked on power plants for two years after my undergraduate. But now I want to work on something latest.

So, what is latest?

Nowadays it is either nano or bio…

So you want to work in nano or bio or both, like nano-bio…. hey, wait, i am not joking…check out this 2020 course list.

*****

Imaginary Conversation 4:

Why do you want to complain?

I cuppaxed; scored a poor grade; barely passed. lost my CGPA and gold pedal…

So…

The course is dead easy…it is impossible for me to score a poor grade in such a silly course.

So, you mean, you worked for that grade?

No, there is a screw-up; something doesn’t add up; i would like to place a formal charge against the instructor. He screwed me.

Are you sure? Why don’t you talk to the istructor and find out what happened?

I did. He doesn’t budge. I smell fish.

OK. Give a written complaint.

Here it is…

Hey, do you really mean all this? You don’t like him, do you?

Ya, sort of…when should I come back?

Tomorrow…

[...]

Okay, I talked with the instructor; checked your answer books…

Well…

You were right. There was indeed a mistake in the adding-up of marks…

Gee; see I was right…

No, no; It should have been the other way. You had actually failed the course.

Three-dimensional computer simulations of the turbulent-mixing dynamics of fluids.

Theses simulations provide density snapshots of a single plume of dense fluid (shown in red) descending into light fluid (shown in yellow). The simulations are of increasing resolution from left to right.

Photo courtesy of University of Chicago Center for Astrophysical Thermonuclear Flashes

Source: Flash Center computer code simulates cosmic explosions

Is there a fractal structure we see on that picture? Yes and no. Fractal structure is not present in all length scales of turbulent flows. A limited range of flows and scales can be investigated using the fractal approach. Elaboration requires separate write-ups, which in turn require free time, which in turn remind me i don’t have that now.

Anyway, this gives me a chance to goad you to read some of my earlier introductory essays on Turbulence:

• Turbulence
• Pipe Turbulence
• Turbulence in Flow around Bodies
• Simple Method to Detect Pipe Turbulence
• Distinct features of superfluid turbulence reported

It seems[*], cooler brain is more efficient. If yawns allow us to cool our brains, then they may allow us to think more clearly. In one study, researchers had humans hold either cold towels or warm towels to their foreheads: people yawned more frequently when exposed to the warm towels.

We don’t yawn when we are out in the sun, when our body skin temperature is probably higher than the core temperature. We may inhale higher temperature air and that doesn’t seem to be required to cool the brain. So we don’t yawn?

But does the air we breathe normally reach near the brain or anywhere near it to cool some parts of it? No it is not air that reaches the brain, but cool blood.

How do I know that?


From this Science Daily news item I gather,

Evidence shows that blood vessels in the nasal cavity and face send cool blood to the brain, and by breathing through the nose or by cooling the forehead, the brain is cooled, eliminating the need to yawn.

So one can take deep breathes to cool the brain continuously? I thought I sweat profusely on the forehead when I think too much and when am stressed – thermoregulation to drive away excess heat generated by excess metabolism in the hot brain? Isn’t that sufficient to cool my brain? I should prompt a yawn to send more cool blood to the brain? Or I should take deep breathes of cool air?

Also, my understanding is, humans have a much more efficient thermoregulatory mechanism to cool off. Sweating, vasodilation and vasoconstriction (enhancing or curbing blood flow to the skin surface by deforming capillaries). Cooling the brain by sending cooler blood through yawning seems far-fetched. Too little cooling (when quantified) accomplished per yawn, compared to sweating. May be the alveoli in the lung gets activated more through yawning and this makes them draw more oxygen rich air while breathing. And the blood exchanges more oxygen or just more blood pumps to the brain and so it requires more oxygen per volume in the lungs and that is why we yawn. I am just guessing but this seems plausible.

The above news item also states

The UAlbany researchers also suggest, again contrary to popular opinion, that yawning does not promote sleep but helps mitigate the need to sleep.

But that is not contrary to my or my mother’s opinion. We always thought yawning mitigated sleep. That is why we were asked to retire – not to avoid sleeping when our brains need that rest, i.e. we are actually tired. A simple ulta perspective of our common knowledge provides a grand psychological conclusion? And no other psychologist asks questions about these research or news items?

If the cooling the brain by yawning is true, an amusing long shot aside comes to mind: is this why we take oil-bath (sabbath)? To directly cool the brain that is. There, we can now navel-gaze our far more knowledgeable ancients. But then, I yawn profusely after an oil-bath…

Anyway, papers to read to understand if there is something in this:

1) GALLUP, A., MILLER, M., & CLARK, A. (2009). Yawning and thermoregulation in budgerigars, Melopsittacus undulatus Animal Behaviour, 77 (1), 109-113 DOI: 10.1016/j.anbehav.2008.09.014

2) Andrew C. Gallup, Gordon G. Gallup Jr. (2007). Yawning as a Brain Cooling Mechanism: Nasal Breathing and Forehead Cooling Diminish the Incidence of Contagious Yawning. Evolutionary Psychology, 5 (1), 92-101 [free PDF]

Andrew Gallup (one of the author of the above papers) says in a related 2008 Discovery News item

“Based on the brain cooling hypothesis, we suggest that there should be a thermal window in which yawning should occur,” Gallup said. “For instance, yawning should not occur when ambient temperatures exceed body temperature, as taking a deep inhalation of warm air would be counterproductive. In addition, yawning when it is extremely cold may be maladaptive, as this may send unusually cold air to the brain, which may produce a thermal shock.”

Basically this means I could yawn only at a narrow temperature range. Shouldn’t I yawn anymore in a department meeting conducted in an air conditioned room? Should I not yawn anymore as I doze off in the summer special train that takes me on a vacation trip to my hometown in sweltering heat that makes me inhale air at temperatures exceeding 40 degree Celcius, about 3 to 4 degrees more than my core body temperature?

Maybe I don’t have to read those papers after all. May be I should stop reading any research that is getting advertised on the web.

OK, another internet search saves my time. Somebody in the science blogosphere (is there one Bora?) had done that reading for me earlier, from which let me borrow this graph. The data is from an experiment conducted on budgerigars (parakeets?), which have relatively large brain compared to their body. The frequency and distribution of yawning versus ambient temperature is recorded in the graph, with a linear (er, linear one) and quadratic (obviously, curved) regression for the data.

Is that a regression / curve-fit for data? Wow. I hear bird noise. Launch a full frontal sixth order polynomial regression to make sense of that bird er, data noise.

There is a related comment by Mark H in the above Grrlscientist post, that seems to agree with my argument. I am recording it here for my notes.

“Cooling the brain” makes little sense in this context as our bodies have far more elaborate and effective mechanisms to do this. And there is a better and more plausible mechanism for yawning. That is physiologic splinting open of alveoli. As we breathe at rest our tidal volumes are quite low and the total minute ventilation of the alveoli is modest at rest. Especially as we slow down and are less active this ventilation gets quite low (like at bedtime when we’re sleepy). As a result, alveoli collapse causing atelectasis. To maintain airflow and splint alveoli back open we yawn, vastly increasing ventilation and opening pressure on the alveoli. This serves two purposes – keeping the lungs well ventilated and preserving the mucus transport function of the lungs that fails with collapse predisposing to infection.

Related News: 3Quarks Daily

[the top picture is taken from a definition for Sighage: v., To yawn or sigh repeatedly in an effort to subtly communicate one’s lack of interest in the current conversation. n., A series of long, exasperated, and often escalating sighs indicating extreme boredom.]

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Note [*] Cooler brain means what? cooler than my body core temperature of 37 degree Celsius? While functioning it should be cooler to also be efficient? Then an nonfunctional brain is more efficient?

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Heat and Mass Transfer in Biological Systems is a graduate elective course I offer this semester (July-Dec) for the second time. The course was inaugurated in 2009 and was received with moderate discontent.

This time I am tuning the course more as a research elective, with promised discussion about ongoing research in bio-heat transfer and bio-fluid dynamics.

Here is a tentative syllabus in pdf for the interested: ME556-Syllabus

There is a introduction to Bioheat Transfer. Also a separate page Biothermofluids Notes collects some notes related to this course.

And now for something completely indifferent.

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Imaginary Conversation 1

Why don’t you take this course?

I don’t know what is bio-heat transfer.

But, isn’t that the reason why you should take the course.

I might score a poor grade…

Yes, but if I assure you that you will certainly pass, will you give it a try?

I would like a better grade. I am not sure I would get that with your new elective. It is already vague. What if it turns out to be tough.

So you want me to assure you of a pass and also a better grade, even before you want to learn?

Well, no. But a better grade would not mess up my chances of winning a medal or a job or a graduate entry.

If I assure you of success in life even before you try, will you die young?

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Imaginary Conversation 2:

Do you want to work in bio heat transfer and fluid mechanics?

No. I don’t know biology.

But, you don’t need to know too much biology. Only basics in heat transfer and fluid mechanics are expected.

May be it will take more time to finish the degree…

Actually, it could be the converse. Just work on the problem I ask you to and things will be alright.

Will I get a job?

I don’t know. But there is always enough opportunity for Ph.D.s in any topic.

But I want to finish quickly…

The problems are fresh and there could be enough low hanging fruit for those who try early.

I need to know about fruits?

Never mind…

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Imaginary Conversation 3:

What do you want to do?

I have worked on power plants for two years after my undergraduate. But now I want to work on something latest.

So, what is latest?

Nowadays it is either nano or bio…

So you want to work in nano or bio or both, like nano-bio…. hey, wait, i am not joking…check out this 2020 course list.

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Imaginary Conversation 4:

Why do you want to complain?

I cuppaxed; scored a poor grade; barely passed. lost my CGPA and gold pedal…

So…

The course is dead easy…it is impossible for me to score a poor grade in such a silly course.

So, you mean, you worked for that grade?

No, there is a screw-up; something doesn’t add up; i would like to place a formal charge against the instructor. He screwed me.

Are you sure? Why don’t you talk to the istructor and find out what happened?

I did. He doesn’t budge. I smell fish.

OK. Give a written complaint.

Here it is…

Hey, do you really mean all this? You don’t like him, do you?

Ya, sort of…when should I come back?

Tomorrow…

[...]

Okay, I talked with the instructor; checked your answer books…

Well…

You were right. There was indeed a mistake in the adding-up of marks…

Gee; see I was right…

No, no; It should have been the other way. You had actually failed the course.

I got to spend a month of Summer 2010 as a Visiting Scientist at the ME Department of the Indian Institute of Science Bangalore, THE premier research institute of our country. Before I get castigated by blog-browsing colleagues, I hasten to add that the department I currently work is also among the top in this country.

Now for some pictures. As most of the artistic pictures about IISc (and for that matter, IITM) have already been taken by better cameras and candidates, posted and pasted, cussed and discussed in blogs, I offer only my shake-well-while-in-use nokia E52 view.

Some comments about the pictures could be originally bland.

[Show as slideshow]

[View with PicLens]

P.S. Ya, I also did some research at IISc. But you wouldn’t want to know about it through blogs, right?