Archive for the ‘Technology’ Category

Single-molecule mechanics, gender, culture and mathematics performance, effect of tubulent driven instabilities on insect flight, and magnetic stabilization

June 3, 2009

Here are some interesting papers from the latest PNAS.

  1. Characterizing the resistance generated by a molecular bond as it is forcibly separated — L B Freund

    The goal of measurements of the resisting force generated by a molecular bond as it is being forcibly separated under controlled conditions is to determine functional characteristics of the bond. Here, we establish the dependence of force history during unbinding on both those parameters chosen to characterize the bond itself and the controllable loading parameters. This is pursued for the practical range of behavior in which unbinding occurs diffusively rather than ballistically, building on the classic work of Kramers. For a bond represented by a one-dimensional energy landscape, modified by a second time-dependent energy profile representing applied loading, we present a mathematical analysis showing the dependence of the resistance of the bond-on-bond well shape, general time dependence of the imposed loading, and stiffness of the loading apparatus. The quality of the result is established through comparison with full numerical solutions of the underlying Smoluchowski equation.

    A commentary on the paper is also available here.

  2. Gender, culture, and mathematics performance — J S Hyde and J E Mertz

    Using contemporary data from the U.S. and other nations, we address 3 questions: Do gender differences in mathematics performance exist in the general population? Do gender differences exist among the mathematically talented? Do females exist who possess profound mathematical talent? In regard to the first question, contemporary data indicate that girls in the U.S. have reached parity with boys in mathematics performance, a pattern that is found in some other nations as well. Focusing on the second question, studies find more males than females scoring above the 95th or 99th percentile, but this gender gap has significantly narrowed over time in the U.S. and is not found among some ethnic groups and in some nations. Furthermore, data from several studies indicate that greater male variability with respect to mathematics is not ubiquitous. Rather, its presence correlates with several measures of gender inequality. Thus, it is largely an artifact of changeable sociocultural factors, not immutable, innate biological differences between the sexes. Responding to the third question, we document the existence of females who possess profound mathematical talent. Finally, we review mounting evidence that both the magnitude of mean math gender differences and the frequency of identification of gifted and profoundly gifted females significantly correlate with sociocultural factors, including measures of gender equality across nations.

  3. Turbulence-driven instabilities limit insect flight performance — S A Combes and R Dudley

    Environmental turbulence is ubiquitous in natural habitats, but its effect on flying animals remains unknown because most flight studies are performed in still air or artificially smooth flow. Here we show that variability in external airflow limits maximum flight speed in wild orchid bees by causing severe instabilities. Bees flying in front of an outdoor, turbulent air jet become increasingly unstable about their roll axis as airspeed and flow variability increase. Bees extend their hindlegs ventrally at higher speeds, improving roll stability but also increasing body drag and associated power requirements by 30%. Despite the energetic cost, we observed this stability-enhancing behavior in 10 euglossine species from 3 different genera, spanning an order of magnitude in body size. A field experiment in which we altered the level of turbulence demonstrates that flight instability and maximum flight speed are directly related to flow variability. The effect of environmental turbulence on flight stability is thus an important and previously unrecognized determinant of flight performance.

  4. Magnetic stabilization and vorticity in submillimeter paramagnetic liquid tubes — J M D Coey et al

    It is possible to suppress convection and dispersion of a paramagnetic liquid by means of a magnetic field. A tube of paramagnetic liquid can be stabilized in water along a ferromagnetic track in a vertical magnetic field, but not in a horizontal field. Conversely, an “antitube” of water can be stabilized in a paramagnetic liquid along the same track in a transverse horizontal field, but not in a vertical field. The stability arises from the interaction of the induced moment in the solution with the magnetic field gradient in the vicinity of the track. The magnetic force causes the tube of paramagnetic liquid to behave as if it were encased by an elastic membrane whose cross-section is modified by gravitational forces and Maxwell stress. Convection from the tube to its surroundings is inhibited, but not diffusion. Liquid motion within the paramagnetic tube, however, exhibits vorticity in tubes of diameter 1 mm or less—conditions where classical pipe flow would be perfectly streamline, and mixing extremely slow. The liquid tube is found to slide along the track almost without friction. Paramagnetic liquid tubes and antitubes offer appealing new prospects for mass transport, microfluidics, and electrodeposition.

The potential is just unimaginable

May 5, 2009

For a device like this — called jerk-o-meter, which belongs to a class called sociometer:

Say you’re on a first date. Your eyes glaze a bit as the guy you’re with drones on about his ex-girlfriend’s mean-as-a-snake personality, about his garage’s sporty contents, about the dead-boring novel he’s reading (alas, one of your favorites). He’s cute, and there was a hint of chemistry between you over the antipasto, but as the entrée portion of the evening wears on, you see he’s way too self-absorbed. This dance you’ve danced before, and to no good end; preferable to dancing it again would be a solo evening with a book, Ben, and Jerry.

All at once, though, something shifts; you notice a new patterning to your date’s word flow and a stilling of his body. He looks right at you and asks to hear more about your love of all things Italy. Better yet, he listens actively as your answer, with an openness that’s winning you over. He smiles, and you smile, and all at once there’s hope for the dessert course.

What just happened? Cute Guy was jerk-o-metered. That is, he had been wired for your date — wired to a device that sent feedback on his social-signaling behavior, and that helped him make a mid-course correction (one that netted you some overdue attention).

As Alexander Pentland writes in Honest Signals, the jerk-o-meter is real, just one example of a class of devices called sociometers. Pentland, who heads the Human Dynamics Lab at MIT, thinks that sociometers will revolutionize our understanding of human communication.

You might even be able to demand, in some future date, that all your audience are wired before they show up for your lecture 🙂

The Open-House stories

April 26, 2009

I had the good fortune to be one of the coordinators from our Department for the Institute Open House held on the 18th of April. We had plenty of crowd in our Materials Science lab — to take a look at our crystal structure and defect models, to look at the creep experiment, to see the shape memory alloy, and of course, to see liquid nitrogen and ductile to brittle transition. One of the highlights from the Department is the demonstrations/exhibitions of the products developed by our design students; many of these products have made it to the newspapers too.

Here are the links to the news stories:

[1] Nivesh Pandya and Rajesh Kumar Dwivedi’s potato sowing machine

[2] No power fridge, room heating fan, and water saving dish washer

[3] Foldable (into a suitcase) table and chair, winter fans, and no-power refrigerator

Here are a couple of photographs of Chandrabhan Prajapati’s “no-power refrigerator” which was a real hit!Solar refrigeratorSolar refigerator poster

Finally, one of our grad students. Mohd Zaheer Khan Yusufzai’s poster on friction stir welding of mild steels also got an award (and, one of the first prizes) from the alumni.

It was great fun getting to know many of our students and their work, as well as interacting with students from outside and explaining them some of the things that we have been doing!

Update: A couple of photographs — of the manual farming machine of Aniruddh and Karan. In his mail to me Karan explains:

In hills, step farming is done and the main problem is that the tractors cannot be taken there for various agricultural purposes like ploughing, leveling, seeding etc. Humans can easily access the hills for this purpose and hence manual power can be utilized to make a small vehicle which can do these tasks altogether. The tasks performed by the vehicle are as follows: 1. Ploughing 2. Seeding 3. Leveling 4. Spraying 5. Storage while working The advantages of the multi-tasking vehicle are: 1. It can be easily taken anywhere into the hills for agricultural purposes. 2. It requires manual power, which is available in plenty. 3. There is no consumption of fuel.

Karan -- farming machineFarming machine close-up

The relevance of Snow

March 26, 2009

And his Two Cultures ideas — Peter Dizikes at NY Times Book Review (link via John Hawks):

There is nothing wrong with referring to Snow’s idea, of course. His view that education should not be too specialized remains broadly persuasive. But it is misleading to imagine Snow as the eagle-eyed anthropologist of a fractured intelligentsia, rather than an evangelist of our technological future. The deeper point of “The Two Cultures” is not that we have two cultures. It is that science, above all, will keep us prosperous and secure. Snow’s expression of this optimism is dated, yet his thoughts about progress are more relevant today than his cultural typologies.

After all, Snow’s descriptions of the two cultures are not exactly subtle. Scientists, he asserts, have “the future in their bones,” while “the traditional culture responds by wishing the future did not exist.” Scientists, he adds, are morally “the soundest group of intellectuals we have,” while literary ethics are more suspect. Literary culture has “temporary periods” of moral failure, he argues, quoting a scientist friend who mentions the fascist proclivities of Ezra Pound, William Butler Yeats and Wyndham Lewis, and asks, “Didn’t the influence of all they represent bring Auschwitz that much nearer?” While Snow says those examples are “not to be taken as representative of all writers,” the implication of his partial defense is clear.

Snow’s essay provoked a roaring, ad hominem response from the Cambridge critic F. R. Leavis — who called Snow “intellectually as undistinguished as it is possible to be” — and a more measured one from Lionel Trilling, who nonetheless thought Snow had produced “a book which is mistaken in a very large way indeed.” Snow’s cultural tribalism, Trilling argued, impaired the “possibility of rational discourse.”

A very interesting piece!

On focussing sound

January 28, 2009

A really cool video (of course) from TED!

On the three kinds of innovations

January 22, 2009

D Balasubramanian, in his latest Speaking of Science column in The Hindu, summarises a talk delivered by Kiran Mazumdar-Shaw of Biocon at IISc during IISc’s centenary celebrations on the three kinds of innovations, namely, incremental, evolutionary and breakthrough; he also gives some examples of successful breakthrough innovations:

The third is what she terms “breakthrough innovation”. This involves the creation of a radically new product, service, process or business model. Breakthrough is about new technology and novel products that are derived from experimental innovation. The electric car “Reva” or Biocon’s own “oral insulin” exemplify this.

Apart from Biocon’s oral insulin, let me quote another example. This comes from the innovative idea of DR. R. A. Mashelkar, then at the Council of Scientific & Industrial Research (CSIR), termed the New Millennium Indian Technology Leadership Initiative or NMITLI.

In one of the projects under this scheme, CSIR brought together a few eye research centres, a CISR research laboratory (CCMB at Hyderabad) and the Bangalore-based company Xcyton, and urged them to produce a DNA-based “chip” that would detect microbial infection of the eye, and point out whether the pathogen is a bacterium, fungus, or virus. This novel diagnostic chip is now in the market. The last and the most challenging category is “experimental innovation”, which in reality is close to, or identical to, invention. The driver here is the next practice.

One of the innovations that Balasubramanian talks about, namely Reva car, is my favourite too!

Swinging the ball and other such manoeuvres!

January 13, 2009

Yesterday, I heard a nice lecture by Dr David James of Sheffield Hallam University on Sports Engineering in general, and on the engineering aspects of cricket, in particular. Here is a summary based on my notes (and, my understanding, of course!)

Dr. James began his lecture with an introduction to sports Engineering and how the idea to use the scientific and engineering ideas to understand sports related mechanics is not really novel — apparently, Isaac Newton talked about the irregular flight of tennis balls (though, a cursory google search to locate the article tells me that it is Lord Rayleigh who wrote a piece titled thus — see here for example). He went on to mention some other recent pieces of engineering work that had been carried out at his university and elsewhere — helmut and bike design specialised for individual athletes (as in UK cycle racing team which, I understand is winning almost all the competitions across the globe, thanks to such design philosophy). However, sometimes the sports traditions are at variance with the engineering goals; for example, he feels that the tennis racket design has probably damaged the character of the game a bit. Also, sometimes, the sports engineer and the sports regulation authorities might not see eye-to-eye on issues; for example, a piece of research related to determining the 3D position of a football by triangulation using six receivers placed at different locations with the transmitter being at the centre of the football was discarded when the relevant authorities did not show enough interest in pursuing it.

After the preliminaries, Dr. James discussed the engineering aspects of cricket: here, he spent most of his time in describing the dynamics of ball delivery, the flight of the ball, the bounce of the ball off the pitch and the measures that ground staff can take to make the pitches neither too batsmen-friendly not too bowler-friendly. He ended his presentation with a short discussion on bat technology. The entire talk lasted for about one-and-a-half hours (though, I did not realise that at that time).

The first interesting result is the recording and analysis of how bowlers bowl the ball in a live match; using a high speed camera that records 600 frames per second located perpendicular to the pitch and focussed on one end, Dr. James recorded a huge number of ball bounces off the pitch and measured the impact speeds. Schematically, the curve of the frequencies of bowling at various impact speeds looked something like this:

cric-ball-bowling-dataThe bowlers thus use three ranges of speeds: 45-60 mph for spin, 60 to 70 mph for swing, and above 70 till up to 95 or so for fast. In his experience, nobody bowled at more than 100 mph.

After mentioning Rabindra B Mehta (of NASA) as the authority on ball aerodynamics (many papers of whose you can get via a google search), Dr James went on to discuss the swing and reverse swing in cricket balls; he also showed a couple of videos of windtunnel experiments to support his conclusions. As I understood, the usual swing (apparently, it is called the magnus effect in sports engineering in general) is due to the differences in the surface finish — for low velocities, on the smooth side, the ball has a laminar flow with a boundary layer that separates from the ball surface relatively early, while, on the seam side, the boundary layer is thicker, hugs the ball surface much longer, and the flow pattern is turbulent — resulting in a wake behind the ball which is at an angle — resulting in swing. By the way, this need for turbulence so that the wake behind the ball is minimal (and hence the drag) is the reason why gold balls have dimples, football is made up of patches, tennis balls have felt on top of them and so on. On the other hand, for balls which are bowled at much higher velocities, even on the smoother side, the flow patterns are turbulent, and now, soemtimes, the wake could be such that it is at an angle which produces the reverse swing effect. Dr. james also described that in simulations they have observed an effect similar to this: if a football is kicked with very less of spin — say, one rotation for the full length of its flight — since in games other than cricket, it is the spin that gives rise to the magnus effect — the ball might traverse a zigzag path in air. I understand, in volleyball too, some players can produce a reverse magnus effect while serving.

The section on the ball bounce and the pitch properties of the talk concentrated on answering the question, namely, that whether the ground staff, with a set of given number of experiments, determine the quality of the pitch and modify it according to their requirements. Apparently, the answer is yes; it involves a prescription in terms of the rolling regimes for the pitch (which bascially determines how hard the pitch is going to be — affecting how the ball bounces off its surface) and the water management in terms of keeping just the required amount of moisture (which affects the coefficient of friction between the ball and the pitch). The idea here is to consider the ball and the pitch as a system of springs and dashpots; determine the constants for these springs and dashpots by dropping the balls on rigis surfaces and by dropping hammers on the pitch; from these values, using an empirical model (which is obtained by fitting curves to actual experiments of bouncing balls off pitches), we can determine the coefficients of restitution and and coefficients of friction. During these discussions, Dr James mentioned about using clay tubes that are nearly a few feet deep but small in diameter to repair pitches — basically, by using these clay tubes as some sort of nails. It was cool!

Finally, he told why he does not think the bats will improve tremendously in the years to come — because of the restrictions — namely, that the blade should be of wood. The only thing that can be improved is by making the handles stiffer (and also energy absorbant — so that no vibrations are felt by the player — or, make it so stiff that the heavy vibrations are of such small amplitude that the player does not feel them either); however, the limitation here is the fact that the handle is to be connected to a blade which has very different stiffness properties.

After a couple of questions (and a discussion on how it is easy to tune pitches in places like Australia where you can put lots of clay and allow the sun to dry it to get the required pitch properties, which, can not be done in England given the weather conditions), we adjourned for refreshments.

PS: Dr. James has promised to send me some material that is in public domain — like his PhD thesis on pitches for example, which I will host in some page and leave the links here.

Chandrayaan news!

November 1, 2008

The spacecraft is now circling the Earth in an orbit whose apogee (farthest point to Earth) lies at 267,000 km (Two lakh sixty seven thousand km) and perigee (nearest point to Earth) at 465 km. In this orbit, Chandrayaan-1 takes about six days to go round the Earth once.

From this ISRO press release. I would have loved some colour pictures too — but, you know, black and white pictures have a charm of their own!

Micro-microscope or a scope on a chip!

August 5, 2008

An interesting news item:

Researchers have developed a micro-microscope. Writing in the journal Proceedings of the National Academy of Sciences, scientists at Caltech describe the creation of an on-chip, lens-free microscope that they say could be built for about ten dollars. The device uses a screen of tiny holes mounted above a CCD sensor to image liquids flowing through microscopic channels in the chip. Such a microscope chip could provide high-resolution microscopic images in field instruments for taks such as blood screening and water testing.

Link via Seed’s Daily Zeitgeist.

Here is the PNAS article in question, Lensless high-resolution on-chip optofluidic microscopes for and cell imaging:

Low-cost and high-resolution on-chip microscopes are vital for reducing cost and improving efficiency for modern biomedicine and bioscience. Despite the needs, the conventional microscope design has proven difficult to miniaturize. Here, we report the implementation and application of two high-resolution (≈0.9 μm for the first and ≈0.8 μm for the second), lensless, and fully on-chip microscopes based on the optofluidic microscopy (OFM) method. These systems abandon the conventional microscope design, which requires expensive lenses and large space to magnify images, and instead utilizes microfluidic flow to deliver specimens across array(s) of micrometer-size apertures defined on a metal-coated CMOS sensor to generate direct projection images. The first system utilizes a gravity-driven microfluidic flow for sample scanning and is suited for imaging elongate objects, such as ; and the second system employs an electrokinetic drive for flow control and is suited for imaging cells and other spherical/ellipsoidal objects. As a demonstration of the OFM for bioscience research, we show that the prototypes can be used to perform automated phenotype characterization of different mutant strains, and to image spores and single cellular entities. The optofluidic microscope design, readily fabricable with existing semiconductor and microfluidic technologies, offers low-cost and highly compact imaging solutions. More functionalities, such as on-chip phase and fluorescence imaging, can also be readily adapted into OFM systems. We anticipate that the OFM can significantly address a range of biomedical and bioscience needs, and engender new microscope applications.

Have fun!

Science and engineering approaches

June 27, 2008

Here is another take on the Wired piece of Chris Anderson — this time around, by Seth Roberts:

Varangy wonders what I think about this editorial by Chris Anderson, the editor of Wired. Anderson says “faced with massive data, this approach to science — hypothesize, model, test — is becoming obsolete.” Anderson confuses statistical models with scientific ones. As far as the content goes, I’m completely unconvinced. Anderson gives no examples of this approach to science being replaced by something else.

For me, the larger lesson of the editorial is how different science is from engineering. Wired is mainly about engineering. I’m pretty sure Anderson has some grasp of the subject. Yet this editorial, which reads like something a humanities professor would write, shows that his understanding doesn’t extend to science. It reminds me why I didn’t want to be a doctor. (Which is like being an engineer.) It seemed to me that a doctor’s world is too constrained: You deal with similar problems over and over. I wanted more uncertainty, a bigger canvas. That larger canvas came along when I tried to figure out why I was waking up too early. Rather than being like engineering (applying what we already know), this was true science: I had no idea what the answer was. There was a very wide range of possibilities. Science and engineering are two ends of a dimension of problem-solving. The more you have an idea what the answer will be, the more it is like engineering. The wider the range of possible answers, the more it is like science. Making a living requires a steady income: much more compatible with engineering than science. I like to think my self-experimentation has a kind of wild flavor which is the flavor of “raw” science, whereas the science most people are familiar with is “pasteurized” science — science tamed, made more certain, more ritualistic, so as to make it more compatible with making a living. Sequencing genes, for example, is pasteurized science. Taking an MRI of the brain while subjects do this or that task is pasteurized science. Pasteurized science is full of rituals and overstatements (e.g., “correlation does not equal causation”, “the plural of anecdote is not data”) that reduce unpleasant uncertainty, just as pasteurization does. Pasteurized science is more confusable with engineering.

There’s one way in which Anderson is right about the effects of more data. It has nothing to do with the difference between petrabytes and gigabytes (which is what Anderson emphasizes), but it is something that having a lot more data enables: Making pictures. When you can make a picture with your data, it becomes a lot easier to see interesting patterns in it.

By the way, is Seth correct about being a doctor? I do not think so; having read Atul Gawande and Oliver Sacks, I do see that most of the problems that they face and their approach to them is more science-y than engineering.

By the same token, even though engineering might be applying what we already know, in real world, there is no such clear distinction; and, even in cases where there is, the problems that one comes across are so varied, we do not know enough to start applying — and, in any case, innovation is all about applying some ideas which others have not even thought of as relevant for the problems in hand.

In other words, while I agree with Seth that Anderson’s piece reads rather naive about the scientific methodology, I am not sure if the naivette can be attributed to his training as an engineer.