34 posts · 20,601 views
The blog contains short notes and explanatory essays on eclectic topics that interests me. The science/research content is mostly on thermal and fluid science and mathematics.
Arunn
34 posts
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- September 1, 2010
- 02:32 PM
- 34 views
Blood Flow and Fahraeus Effect
by Arunn in Unruled Notebook
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 [...]... Read more »
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
- August 31, 2010
- 08:33 AM
- 35 views
Blood Viscosity in Capillaries
by Arunn in Unruled Notebook
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 [...]... Read more »
R. Fahraeus and T. Lindqvist. (1931) The viscosity of the blood in narrow capillary tubes. American Journal of Physiology, 562-568. info:/
- August 23, 2010
- 01:59 PM
- 49 views
Yawns help cool the brain?
by Arunn in Unruled Notebook
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."
Shouldn't I yawn anymore in a department meeting conducted in an air conditioned room? ... Read more »
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
- May 21, 2010
- 10:52 AM
- 209 views
Inner Life of Mesoorganisms
by Arunn in Unruled Notebook
The title of both this note and the paper it discusses is inspired by a 1970s classic paper by Nobel Laureate Edward Purcell on Life at low Reynolds number. With simple physics, that paper gave insights about micro-organisms (bacteria, sperms … Continue reading →... Read more »
van de Meent JW, Tuval I, & Goldstein RE. (2008) Nature's microfluidic transporter: rotational cytoplasmic streaming at high Péclet numbers. Physical review letters, 101(17), 178102. PMID: 18999789
- December 10, 2009
- 01:21 PM
- 542 views
Blood: Clot, Flow and Slip
by Arunn in Unruled Notebook
By 2020 seventy percent of the heart patients of the World, a study suggests, would be in India. The cause seems genetic. The gene that codes the enzyme called PON1 is defective in Indians and predisposes them to heart ailments and diabetes. Coupled with degenerating lifestyle – eating habits – leads to such a dire [...]... Read more »
Kaoui, B., Biros, G., & Misbah, C. (2009) Why Do Red Blood Cells Have Asymmetric Shapes Even in a Symmetric Flow?. Physical Review Letters, 103(18). DOI: 10.1103/PhysRevLett.103.188101
- December 5, 2009
- 10:34 AM
- 423 views
Quantifying Research Quality using Article Level Metrics
by Arunn in Unruled Notebook
Quantifying research quality is a buzz-activity in academia for the last two decades. The irony is lost in the paper work. For reasons best left out in this essay, this activity has come to stay in our academics. One such quantifying-quality measure (QQM) evolved recently is the Impact Factor (IF) of journals [1] that publish [...]
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Neylon, C., & Wu, S. (2009) Article-Level Metrics and the Evolution of Scientific Impact. PLoS Biology, 7(11). DOI: 10.1371/journal.pbio.1000242
- November 18, 2009
- 12:19 PM
- 463 views
Why do Toucans have large bill
by Arunn in Unruled Notebook
What can one do with the nose? If one were Cleopatra of Egypt, she could rule Rome. If one were the unfortunate Sphinx of Egypt, his form minus the nose could become the wonderment of the World. If one were Tycho Brahe, he could remove the nose, for polishing amidst a heated debate or duel, [...]... Read more »
Tattersall, G., Andrade, D., & Abe, A. (2009) Heat Exchange from the Toucan Bill Reveals a Controllable Vascular Thermal Radiator. Science, 325(5939), 468-470. DOI: 10.1126/science.1175553
- October 7, 2009
- 01:27 PM
- 532 views
Pennes Bioheat Transfer Equation
by Arunn in Unruled Notebook
It can be argued that one of the most influential articles ever published in the Journal of Applied Physiology is the Analysis of tissue and arterial blood temperatures in the resting human forearm by Harry H. Pennes, which appeared in Volume 1, No. 2, published in August, 1948. Thus begins Prof. Wissler, his 1998 revisit [...]... Read more »
PENNES HH. (1948) Analysis of tissue and arterial blood temperatures in the resting human forearm. Journal of applied physiology, 1(2), 93-122. PMID: 18887578
- September 30, 2009
- 02:09 AM
- 547 views
Where should that new store or temple be?
by Arunn in Unruled Notebook
Where should a business set up its new commercial store – chain or single – to maximize its profit? There may be a demand for the store in a sparsely populated region but it may be wiser to locate the store in a densely populated region for more profit. Is there a definite correlation between population density and commercial facility density?
Similarly, if the government or citizen group wants to locate a public facility – temples, toilets, grocery store, fire station – where should that be? It is not for profit, but should be easily accessible by many. Is there a suggestive correlation in this situation?
The answer to the above two questions is yes.... Read more »
Um, J., Son, S., Lee, S., Jeong, H., & Kim, B. (2009) Scaling laws between population and facility densities. Proceedings of the National Academy of Sciences, 106(34), 14236-14240. DOI: 10.1073/pnas.0901898106
- September 9, 2009
- 11:45 AM
- 605 views
When a Mobius ring is dropped into a fluid
by Arunn in Unruled Notebook
We have heard of the Mobius band. A one sided strip, it is a topological peculiarity. Over the decades it has popped up in several places in knowledge-space: the self-induction free Mobius resistor, the Mobius gear, the shape of the trajectory the Solar wind plasma assume in their route to chaos when interacting with the [...]... Read more »
Leweke, T., Thompson, M., & Hourigan, K. (2009) Motion of a Möbius band in free fall. Journal of Fluids and Structures, 25(4), 687-696. DOI: 10.1016/j.jfluidstructs.2009.04.007
- April 14, 2009
- 01:07 AM
- 968 views
Stefan and the Polar Ice Caps
by Arunn in Unruled Notebook
Melting of polar ice caps is a topic of current interest due to global warming and its impact. But not long back in human history, in times of lesser pollution and implication, the inverse problem of solidification or growth of polar ice was of interest. During mid nineteenth century Arctic expeditions to study polar ice [...]... Read more »
Crepeau, J. (2007) Josef Stefan: His life and legacy in the thermal sciences. Experimental Thermal and Fluid Science, 31(7), 795-803. DOI: 10.1016/j.expthermflusci.2006.08.005
- April 10, 2009
- 03:29 AM
- 918 views
Stefan and the T to the fourth power law
by Arunn in Unruled Notebook
The working of Stefan’s diathermometer to measure the thermal conductivity was explained earlier. Here we recount how the diathermometer helped also in the prediction of the T to the fourth power law of electromagnetic radiation purely by experimental means. It was an instance of scientific advancement, where the experimental outcome preceded the theoretical support. We [...]... Read more »
Crepeau, J. (2007) Josef Stefan: His life and legacy in the thermal sciences. Experimental Thermal and Fluid Science, 31(7), 795-803. DOI: 10.1016/j.expthermflusci.2006.08.005
- April 6, 2009
- 03:33 PM
- 793 views
Stefan and the Diathermometer
by Arunn in Unruled Notebook
Once in a while, it is useful to revisit the history of inventions and discoveries that we now take for granted. Such revisits to the masters and their works provide a perspective on how to think about the unknown from whatever was known - right or wrong. Instances where a correct discovery results from wrong [...]... Read more »
Crepeau, J. (2007) Josef Stefan: His life and legacy in the thermal sciences. Experimental Thermal and Fluid Science, 31(7), 795-803. DOI: 10.1016/j.expthermflusci.2006.08.005
- March 23, 2009
- 04:15 PM
- 904 views
Vortices behind a bat wing
by Arunn in Unruled Notebook
Discusses a computer simulation of vortices behind a bat in flight that won an award in the 2007 Visualization Challenge Winners.... Read more »
Lester, B. (2007) 2007 Visualization Challenge Winners. Science, 317(5846), 1858-1863. DOI: 10.1126/science.317.5846.1858
- February 11, 2009
- 01:05 AM
- 847 views
Visualizing Physics and Porous Medium Heterogeneity
by Arunn in Unruled Notebook
New Journal of Physics, the open access journal, came up with an issue dedicated to visualizing physics resulting in some pretty pictures. I could spot one close to my research: Quantifying spatial heterogeneity from images.... Read more »
Pomerantz, A., & Song, Y. (2008) Quantifying spatial heterogeneity from images. New Journal of Physics, 10(12), 125012. DOI: 10.1088/1367-2630/10/12/125012
- December 29, 2008
- 11:25 PM
- 798 views
Lotus Effect and Superhydrophobic Coatings using Carbon Nano Tubes
by Arunn in Unruled Notebook
Mimicking the intricate natural structure of the surface of lotus leaves, through a structure of micron-level-3-D pattern coated with nanometeric layer of wax.... Read more »
Srinivasan, S., Praveen, V., Philip, R., & Ajayaghosh, A. (2008) Bioinspired Superhydrophobic Coatings of Carbon Nanotubes and Linear π Systems Based on the “Bottom-up” Self-Assembly Approach. Angewandte Chemie International Edition. DOI: 10.1002/anie.200802097
- December 5, 2008
- 09:56 PM
- 783 views
Effect of Temperature-Dependent Viscosity in Porous Medium Flows
by Arunn in Unruled Notebook
For channel or pipe flows, a theoretical hydraulic model usually relates the longitudinal pressure drop to the flow rate. The situation remains more or less the same, if we introduce a porous medium in such channel flows. ... Read more »
Narasimhan, A., & Lage, J. (2001) Modified Hazen-Dupuit-Darcy Model for Forced Convection of a Fluid With Temperature-Dependent Viscosity. Journal of Heat Transfer, 123(1), 31. DOI: 10.1115/1.1332778
- November 20, 2008
- 10:29 PM
- 740 views
Lotus Leaves, Hydrophobic and Omniphobic Surfaces
by Arunn in Unruled Notebook
Surfaces can be hydrophobic. Like Lotus leaves. Now they can be omniphobic - repel both water and oil.... Read more »
Cheng, Y., Rodak, D., Wong, C., & Hayden, C. (2006) Effects of micro- and nano-structures on the self-cleaning behaviour of lotus leaves. Nanotechnology, 17(5), 1359-1362. DOI: 10.1088/0957-4484/17/5/032
- November 11, 2008
- 11:03 PM
- 643 views
Individual and Empire in Academics
by Arunn in Unruled Notebook
ResearchBlogging.orgIndividual or Empire? Should we remain individual scientists or should I forge or join a research group for pursuing research. This is not an age old question, if we reckon the time span of human thought and scientific inquiry.... Read more »
A. Bejan. (2008) Constructal Self-organization of Research: Empire Building Versus the Individual Investigator. Int. J. of Design Nature and Ecodynamics, 3(3), 1-13. DOI: http://journals.witpress.com/pages/paperinfo.asp?PaperID
- November 6, 2008
- 06:50 PM
- 750 views
Firing Fungus
by Arunn in Unruled Notebook
Fungus eject their spores to the surrounding by different mechanisms. One such mechanism is the squirt gun type, the fluid dynamics of which is explained. ... Read more »
Yafetto, L., Carroll, L., Cui, Y., Davis, D., Fischer, M., Henterly, A., Kessler, J., Kilroy, H., Shidler, J., Stolze-Rybczynski, J.... (2008) The Fastest Flights in Nature: High-Speed Spore Discharge Mechanisms among Fungi. PLoS ONE, 3(9). DOI: 10.1371/journal.pone.0003237
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