@database PhysUPDATE.328.doc @remark Converted with HTML2Guide ©1997 Mark Harman @wordwrap @node MAIN "PhysUPDATE.328.doc" Date: Fri, 4 Jul 1997 04:30:21 +0100 (BST)From: physnews@aip.orgPHYSICS NEWS UPDATE The American Institute of Physics Bulletin of Physics NewsNumber 328 July 2, 1997 by Phillip F. Schewe and Ben SteinTHE MARS PATHFINDER spacecraft arrives July 4 at itsdestination where, after firing retrorockets and deploying aparachute and numerous airbags, it will bounce to a halt on whatwas probably an ancient floodplain. After this, its missionaryrover will venture forth to taste rocks and make movies. Thelocal weather forecast calls for blue skies and wispy clouds with asmall chance of a dust storm (currently 600 miles to the south),in which case the sky will be pink. In September another craft,the Mars Global Surveyor, will take up orbit around Mars. (Forthe latest update, view the JPL website: mpfwww.jpl.nasa.gov/)STORING AN OPTIMUM AMOUNT OF INFORMATION IN APHOTON or any other quantum particle is possible even in thepresence of noise, researchers have concluded (B. Schumacher etal., Physical Review A, July 1997; A.S. Holevo, upcoming inIEEE Transactions on Information Theory). A photon has manydifferent quantum states, each of which can be made to represent adifferent digit. Furthermore, one can store many digitssimultaneously in a single photon by putting it into a combinationor "superposition" of many states. However, quantum mechanicsprevents a measuring device from perfectly distinguishing betweenall these different states. Previously, physicists discovered that themaximum amount of information that can be read from a photoncan be no greater than the amount of entropy, or disorder, itacquires when a range of quantum states is created to representdifferent digits. Now, the researchers show that this upper limit canbe reached, even in a noisy environment, by utilizing severalstrategies, such as employing only those quantum states that aremost distinguishable. These findings provide insights into how littleenergy is required to store a message. (For more details, go towww.aip.org/physnews/preview; Ben Schumacher, KenyonCollege, 614-427-5832)HOLLOW NANOPARTICLE LUBRICANTS, consisting offullerene-like tungsten disulfide balls, have performed well infriction and durability tests, and may be superior to other solid-statelubricants, which usually come in powdered form. The 100-nmWS2 balls (much smaller than conventional powder grains, micronsacross) are nested like some carbon nanotubes, but flexible. This,their chemical inertness, and the tendency to roll rather than slidewhen pushed, should make the nanoparticles a good lubricant at themicron scale, or as an additive in other lubricants. Scientistsworking at the Weizmann Institute and at the Center forTechnological Education in Israel are now able to make gramamounts of the lubricant. (L. Rapoport et al., Nature, 19 June1997.)ONE MEASURE OF A NATION'S SCIENTIFIC STRENGTH isthe number of papers it generates and the citations those papersreceive. For the period 1992-96, these were the top producers ofpapers in a select set of journals: US (1.3 million), UK (300,000),Japan (281,000), and Germany (259,000). Ranked according tocitations per paper, the order becomes Switzerland (5.66), US(5.03), Netherlands (4.46), Sweden (4.38), and UK (4.19).The EU nations lumped together and the US each have a 36% shareof total citations. The general trend these past 15 years has been forthe US citation rate to remain high but for its citation share to giveground to the EU and to Asian/Pacific nations. (ISI ScienceWatch,May/June; also Nature, 5 June 1997.) @endnode