NIST experiment's data acquired before space shuttle tragedy. (General Developments).NIST (National Institute of Standards & Technology, Washington, DC, www.nist.gov) The standards-defining agency of the U.S. government, formerly the National Bureau of Standards. It is one of three agencies that fall under the Technology Administration (www.technology. scientists used an experiment aboard the STS-107 mission of the space shuttle space shuttle, reusable U.S. space vehicle. Developed by the National Aeronautics and Space Administration (NASA), it consists of a winged orbiter, two solid-rocket boosters, and an external tank. Columbia to look for a particular type of flow behavior, never before seen in a pure liquid, that may have practical applications in products ranging from paints and plastics to foods and pharmaceuticals. Almost all of the data from the experiment--sent by telemetry telemetry Highly automated communications process by which data are collected from instruments located at remote or inaccessible points and transmitted to receiving equipment for measurement, monitoring, display, and recording. to the ground during the mission--were acquired before the tragic loss of the shuttle orbiter and its seven-member crew on Feb. 1, 2003. The "Critical Viscosity of Xenon-2" (CVX CVX ChevronTexaco (stock symbol) CVX Comunidad de Vida Cristiana (Christian Life Community) CVX Code Veronica X (game) CVX Critical Viscosity of Xenon CVX Carrier, Experimental 2) experiment measured the changes in viscosity (resistance to flow) of a xenon xenon (zē`nŏn) [Gr.,=strange], gaseous chemical element; symbol Xe; at. no. 54; at. wt. 131.29; m.p. −111.9°C;; b.p. −107.1°C;; density 5.86 grams per liter at STP; valence usually 0. sample as it was stirred rapidly and approached the "critical point." Xenon, an inert gas inert gas or noble gas, any of the elements in Group 18 of the periodic table. In order of increasing atomic number they are: helium, neon, argon, krypton, xenon, and radon. , exhibits unusual behavior near its critical point, at which it turns into a milky fluid with properties between those of a liquid and a gas. The experiment was conducted in the microgravity mi·cro·grav·i·ty n. 1. An environment in which there is very little net gravitational force, as of a free-falling object, an orbit, or interstellar space. 2. of orbit because the changes in viscosity that take place in the critical state cannot be measured accurately in Earth's gravity. The experimental data should reveal whether xenon exhibits "shear thinning," meaning its usual resistance to flow is weakened by a large shear rate. Although predicted for decades, shear thinning has never been observed near the critical point of any pure fluid. Xenon, a pure fluid with a very simple structure and a critical temperature just below room temperature, is convenient for such experiments. The data may help scientists better understand shear thinning in complex fluids such as paints and foods (e.g., whipped cream), which need to flow easily during application and stand firm afterwards. The latest results will expand on those gathered during a 1997 NIST space shuttle experiment, which accurately measured the viscosity of xenon and revealed a viscosity increase of 37%--double the best measurements on Earth. That experiment also showed that xenon, when close to the critical point, is partly elastic; that is, it can "stretch" as well as flow. CONTACT: Robert Berg, (301) 975-2466; robert.berg@nist.gov or Michael Moldover, (301) 975-2459; michael.moldover@nist.gov. |
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