Oil Drop Trap is Set for a Lone Quark SLAC . The drip consists of tiny droplets of silicone oil. 7micrometers in diameter, falling languidly between 2 electrically charged plates while a CCD video camera records their movements. Robert Millikan applied 85 years ago in his classic measurement of the charge of a single electron. Martin Perl hoping to find a droplet bearing a still smaller morself of charge - a quark, a fundamental particles that make up protons and neutrons. No free quarks spotted in the first round. QCD theory of the strong force binds quarks. /*---------------------------------------------------------------------*/ Tuning a Catalyst for New Plastics Adding boron to carbon rings lets researchers "tune", or adjust, the electronic behavior of this catalyst. If plastics are big business, the catalysts that create many of them are the keys. Indeed without them, plastic production, currently worth hundreds of bbillions of dollars annually, would be hobbled because there would be no way to link the small chemical building blocks from which plastics are made. One breed of catalysts that link building blocks called alpha-olefins typically employ rings of carbons to do their jobs. But now researchers, bby inserting bboron atoms into the carbon rings, are developing a new class of catalysts - an possibly whole new classes of polymers too. 3/6/96 issue of journal of the american chemical society , a group of chemists at the University of rochester in New York and the university of Michigan in Ann Arbor report that boron atoms, in combination with different chemical groups attached to them, can change how electrons are distributed throughout the catalyst molecule. That should give scientists a new way to "tune" , or change, the catalyst's electronic properties. Because those properties help determine which olefins the catalyst will link together and how they assemble, increased tunability should lead to new types of polymers, possibly with different molecular weights or densities, says Guillermo Bazan, one author of the report. Just what those polymers will look like and how they will behave "is impossible to predict", he says. But although the researchers have not yet created a catalytic choir, just one compound humming a single note, it performs as well as current catalysts, and thus is "a promising first step," says Francis Timmers, a catalysis expert at the Dow Chemical Company's Central REsearch LAboratories in Midland, Michigan. Catalysts of this type, known as metallocenes, typically consist of a single metal atom, such as zirconium, surrounded by a pair of all- carbon rings, which are in turn linked to other chemical groups. One end of the growing polymer chain binds near the metal, while together the rings and dangling groups control access of the olefin building blocks to that interior complex, forcing them to bind in one preferred orientation to the end of the chain. Bazan and his colleagues found that adding boron atoms to the rings shakes things up a bit. Boron is electron-hungry and tends to borrow electrons from other atoms in the catalyst, atoms either in the surrounding chemical groups or the core atom itself. That change in the distribution of electrons in the catalyst molecule is what alters the catalyst's interaction with the olefin building blocks. Along with Arthur Ashe and his colleagues at Michigan, Bazan and his Rochester group found they could control this electron distribution by adding specific groups to the borons. The researchers linked the borons to nitrogen-containing amine groups and then inserted the borons into a pair of carbon rings surrounding a zirconium atom. as a result of this configuration, each boron grabbed a pair of electrons from the nearby nitrogen, leaving those around the metal undistrubed. That made the catalyst behave just like an ordinary catalyst with all-carbon rings and produce polyethlene and other polymers as effectively as conventional metallocene catalysts. The researchers next plan to replace the amines with carbon-based phenyl rings. These rings should not give up electrons to the boron atoms, which should therefore scavenge electrons from the zirconium - altering the metal's electronic and catalytic behavior. If so, polymer catalysts may soon be singing some new tunes. /*---------------------------------------------------------------------*/ Isolated Neutron Stars INSs are only active for a fraction of their lifetime 10^10 years. Violent and short nonthermal phase they are visible as radio pulsars for 10^6.5 years. They cool after being born in a supernova, neutron stars maintain a surface temperature of > 10^5K for the same time period. Thus about 10^-3 of the INS population might be deted either as radio pulsars or through their thermal surface emission, assuming they are sufficiently hot and luminous to be picked up by the current generation of xray, UV and optical telescopes, which only sample a small volume of our galaxy. When the radio mechanism fades away and their surface temperature drops, the INss become invisible and just sit there, making up a fraction of the galactic dark baryonic matter. They can be revived by a companion from which they start accreting matter and become millisecond pulsars. They can no longer be considered isolated self powered by either rotation or latent heat. /*---------------------------------------------------------------------*/ Intermittently Flowing Rivers of Magnetic Flux Computer simulated trajectories of east votices moving in superconductor with pinning sites. STrong pinning produces a few vortex channels with heavy traffic, weak pinning induces a different network of much broader vortex trails. The vortex channels also become wider at higher temperatures, when pinning is weaker.