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Number 394, October 1, 1998 by Phillip F. Schewe and Ben Stein
A BLAST OF GAMMA LIGHT, representing the largest batch of energy to arrive at Earth from a star beyond our solar system, struck the upper reaches of our atmosphere on 27 August 1998. The 5-minute pulse of high-energy radiation momentarily disrupted some terrestrial radio traffic and sent detectors on several spacecraft off scale. The source of the blast is believed to be a neutron star previously known for its intermittent gamma and x-ray emissions. The potency of the August event, however, would seem to characterize the star as a very rare type of object that has come to be known as a magnetar, so named because the star's magnetic field is expected to be in the vicinity of 1015 gauss, 100 times larger than ordinary neutron stars, and essentially the largest known magnetic field in the universe. The gammas probably arise when magnetic forces crack open the star's crust. Ionized particles above the star ride the magnetic fields, spewing radiation as they go, creating a much more potent version of the solar flares seen on our sun. (Science News, 12 September 1998.)
THE PHYSICS OF THE IMMUNE SYSTEM. When antigens (viruses, poisons, etc.) invade the body, the vigilant immune system first senses the danger and then produces an appropriate response. To do this, the defenders, a fleet of lymphocytes possessing as many as 1011 molecular receptors, must perform a vast program of pattern recognition. A theory from the 1970's proposed that this process could be compared to a self-regulating multiply-connected network of agents. Physicists in Brazil have now taken the next step by simulating the immune performance with a system of cellular automatons, and have successfully modeled the actual behavior of the mouse immune system. Rita Maria Zorzenon dos Santos of the Universidade Federal Fluinense (011-55-21-620-6735, zorzenon@if.uff.br) and Americo Bernardes of the Universidade Federal de Ouro Preto have even been able to simulate correctly the effects of aging on the immune response. At the heart of their model is a "shape space" of possible receptor attributes including, for example, electrical charge, receptor geometry, and degree of activation. Zorzenon dos Santos believes that work on the immune system might offer insights into the behavior of complicated physics systems operating at far from equilibrium conditions. The next step for her immune research is the attempt to model the evolution of HIV infection and to study the way in which lymphocytes are activated in response to malaria. (Physical Review Letters, 5 October 1998.)
DNA-MEMBRANE SELF-ASSEMBLIES, materials formed by mixing DNA molecules with artificial versions of the membranes that form the protective coverings of cells, are highly organized at length scales from nanometers to microns, new experiments have confirmed. These materials, currently serving as gene delivery vehicles, are made of layers consisting of rows of equally spaced, single DNA molecules alternating with sheets of membrane. Using a 1-by-4 micron x-ray beam at the Advanced Photon Source in Argonne National Lab, a UC Santa Barbara-Argonne team showed that the molecules in these materials are aligned over length scales of microns. The spaces between molecules form organized arrays of "nanopores" which have many possible chemical applications. In addition, these materials can potentially serve as templates for the fabrication of inorganic nanostructures with geometries and features that were previously impossible to achieve. (G. Wong et al., Applied Physics Letters, October 5, 1998; J. Radler et al., Science, 7 February 1997; also see figure at Physics News Graphics.
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