Number 458, November 18, 1999 by Phillip F. Schewe and Ben Stein
THE SHADOW OF A PLANET slipping across the face of a distant star has been detected, for the first time, by veteran extrasolar-planet stalkers Geoffrey Marcy of UC Berkeley and Paul Butler of the Carnegie Institution, working with Greg Henry of Tennessee State University. Prior indirect "sightings" of extrasolar planets consisted of small feints in the apparent position of the stars caused by the suspected gravity pull of an orbiting planet. Astronomers have felt that from among the growing sample of such planets (up to 25 as of now) a few (whose orbits would be viewed at Earth edge-on) might be detected directly as they pass in front of the star. One such candidate was HD 209458. Prediction of a planetary transit for the night of November 7 proved accurate and a 1.7% dimming in the star's light was seen. (Announcement made in an International Astronomical Union circular.)
MICROFLUIDICS CAN BE DRIVEN BY HEAT rather than by electric fields. Microfluidics is to the mixing of fluids (including studies of blood, DNA, etc.) what integrated circuits are to the processing of electrical signals: transactions occur quickly, controllably, in a very small space. But instead of excavating small channels in a substrate and propelling tiny fluid volumes around the nano-sized system of aqueducts customary in microfluidics (see Update 367), Princeton professor Sandra M. Troian and Dawn Kataoka, now at Sandia Laboratories(CA), have moved tiny liquid rivulets around a silicon wafer using temperature gradients. The capillary movement of the micro-fluids can be programmed because (1) the liquid surface tension varies with temperature and even a gradient of 3 or 4 K will cause a fluid to seek out a cold region, and (2) a lithographically applied pattern of chemical modifications on the substrate (the equivalent of an invisible scent marker or a chemical levee) further constrains the droplet rivercourses. Thus streams of hydrophilic and hydophobic molecules, zooming across the substrate along neighboring lanes, can be shunted together at some desired meeting point. The advantages of thermo-capillary action over electronic-driven fluidics are that the use of high electric fields and the precision carving of channels are not necessary; everything happens on a plane, making easier the task of building micro-electromechanical (MEMS) "labs-on-a-chip." Troian (609-258-4574, email@example.com) will report on her research at the APS division of fluid dynamics meeting in New Orleans, November 21-23: www.nd.edu/~apsnd/)
HYDROGEN STORAGE IN NANOTUBES. Hydrogen is a potent fuel: combined with oxygen it can power spacecraft to the Moon. Storing such a dangerous substance, however, is difficult. Physicists at MIT have now succeeded in canning hydrogen inside carbon nanotubes. Actually, hydrogen sausage has been encased in a carbon skin before, but the MIT efforts are the first to achieve reliably such a high hydrogen uptake (one hydrogen for every two carbons) at room temperature. And like a jack-in-the-box, the hydrogens came shooting out of the tubes (80% of them anyway) when the packing pressure was relaxed. (Liu et al., Science, 5 November 1999.)
THE ONLINE JOURNAL PUBLISHING SERVICE (OJPS) constitutes a shopping mall for the physics journals published by the American Institute of Physics (AIP), many of its member societies, and other scientific and engineering societies. From this site one can handily visit the homepage for such journals as Physical Review, Applied Physics Letters, Optics Letters, and Chaos. Nonsubscribers can view tables of contents and look at all the abstracts, including those from some issues not yet published. (You can even search the full SPIN database of abstracts if you have a subscription to at least one of the OJPS journals.) In general the full texts are available only to subscribers, although a few prominent articles are supplied to science writers via a separate website called Physics News Select Articles.