Journal Tips from the American Institute of Physics: June 5, 2012

Newswise — The following are brief summaries of papers recently accepted for publication in journals of the American Institute of Physics (AIP): Physics of Fluids, Journal of Applied Physics, and Biomicrofluidics.

1. Mathematicians Model Heat Flow In Human Tears2. Thermal Conductivity of Argon at High Pressures and Temperatures3. New Ways to Stretch DNA and Other Organic Molecules

Copies of papers are available to journalists upon request at [email protected].

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1. Mathematicians Model Heat Flow in Human Tears

Mathematicians from the University of Delaware have created a new model of the fluid dynamics and heat flow in human tears. When people blink their eyes, a thin liquid film is spread across the surface of the eye. Experiments show that the surface of the tear film cools slightly after each blink, and for dry eye patients the rate of cooling can be even higher. The Delaware researchers set out to create a heat transfer model with enough detail to capture this experimentally observed cooling. Models that set a fixed temperature for the eyeball show the temperature of the tear film actually increasing slightly after each blink. A model that incorporates heat transfer into the eye through a thin layer likewise shows a temperature increase during the interblink period. But when the researchers incorporated heat transfer into a sufficiently thick region of tissue under the tear film, the model produced results comparable to the rate of cooling observed in vivo. Future work by the team may touch on better ways to model the lipid component of tears and the temperature dynamics during the motion of a blinking eyelid.

TITLE: “A model for the human tear film with heating from within the eye”JOURNAL: Physics of Fluids (pof.aip.org)AUTHORS: Longfei Li (1) and R. J. Braun (1)

(1) University of Delaware2. Thermal Conductivity of Argon at High Pressures and Temperatures

Diamond anvil cells (DACs) are used routinely in laboratories to apply extreme pressure to materials, recreating conditions that normally only occur deep in planetary interiors or during certain industrial manufacturing techniques. Under these conditions, however, it is difficult to measure how materials conduct heat. To better understand thermal conductivity, researchers from the United States and Sweden placed a thin film of iridium sandwiched between layers of argon in a DAC, subjected it to extreme pressure (50 gigapascals) and then used microsecond laser bursts to heat it to 2,500 degrees K. The researchers measured the temperature history of the iridium foil and used that data to calculate the thermal conductivity of the argon. Their results confirmed that one model, kinetic theory, better matched observations than another model, Green-Kubo formalism. These results are important for ongoing studies of how minerals behave in the Earth’s mantle and core.

TITLE: “Thermal conductivity of argon at high pressures and high temperatures”JOURNAL: Journal of Applied Physics (jap.aip.org)AUTHORS: Alexander F. Goncharov (1), Michael Wong (1,2), D. Allen Dalton (1), J.G.O. Ojwang (1), Viktor V. Struzhkin (1), Zuzana Konopkova (3), Peter Lazor (3)

(1) Carnegie Institution of Washington, Washington, D.C. (2) University of California, Berkeley(3) Uppsala University, Upsala, Sweden 3. New Ways to Stretch DNA and Other Organic MoleculesBy taking advantage of the unique patterns generated when two immiscible fluids flow together, scientists have developed a new tool for studying tiny biomolecules. Researchers at the National Taiwan University and the National Central University in Taiwan used a technique called two-phase microfluidics to stretch organic molecules in a systematic manner. The researchers created different types of flow patterns by controlling wall wettability of a microfluidic channel, the flow rate ratio of two fluids, and the Reynolds number, which is a ratio between the inertial and viscous forces in a fluid. By systematically varying these three parameters, the researchers could control the extension of a polymer string suspended in the fluid flow. Stretching polymers, proteins, DNA, and other organic macromolecules can reveal clues about what the molecules are made of and how they interact with other substances.

TITLE: “Polymer stretch in two-phase microfluidics: Effect of wall wettability”JOURNAL: Biomicrofluidics (bmf.aip.org)AUTHORS: Ssu-Wei Hu (1), Yu-Jane Sheng (1), and Heng-Kwong Tsao (2)

(1) Department of Chemical Engineering, National Taiwan University, Taipei, Taiwan(2) Department of Chemical and Materials Engineering, Department of Physics, National Central University, Jhongli, Taiwan

About American Institute of PhysicsThe American Institute of Physics (AIP) is an organization of 10 physical science societies, representing more than 135,000 scientists, engineers, and educators. As one of the world's largest publishers of scientific information in physics, AIP employs innovative publishing technologies and offers publishing services for its Member Societies. AIP's suite of publications includes 15 journals, three of which are published in partnership with other organizations; magazines, including its flagship publication Physics Today; and the AIP Conference Proceedings series. Through its Physics Resources Center, AIP also delivers valuable services and expertise in education and student programs, science communications, government relations, career services for science and engineering professionals, statistical research, industrial outreach, and the history of physics and other sciences.