SETI bioastro: FW: Physics News Update 784

From: LARRY KLAES (ljk4_at_msn.com)
Date: Fri Jul 07 2006 - 08:57:38 PDT

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    >From: physnews_at_aip.org
    >Reply-To: physnews_at_aip.org
    >To: ljk4_at_MSN.COM
    >Subject: Physics News Update 784
    >Date: Fri, 7 Jul 2006 11:17:59 -0400
    >
    >PHYSICS NEWS UPDATE
    >The American Institute of Physics Bulletin of Physics News
    >Number 784 July 7, 2006 by Phillip F. Schewe, Ben Stein,
    >and Davide Castelvecchi www.aip.org/pnu
    >
    >RED OXYGEN. A new evolutionary crystallography algorithm predicts
    >the structure of crystals under a range of extreme pressure and
    >temperature conditions on the basis of the chemical composition
    >alone. One of these crystals would be a form of red-colored oxygen.
    >Predicting crystal structures is difficult even for simple solids,
    >partly because of the task of sorting among the astronomical number
    >of possible ways given atoms can compose a basic repeatable unit
    >cell. Artem Oganov, a scientist at ETH Zurich, and Colin W. Glass, a
    >PhD student, approach the problem by combining electronic structure
    >calculations and a specifically developed evolutionary algorithm. In
    >exploring the myriad atomic arrangements, they proceed in a
    >step-by-step, continual-optimization fashion that avoids
    >configurations less likely to succeed. This makes the algorithm very
    >efficient and allows the researchers to make certain specific
    >predictions. One example is calcium carbonate (CaCO3) at very high
    >pressures. Oganov's team for the first time predicted two new
    >stable structures for this mineral. By now, both structures have
    >been confirmed in experiments by Japanese colleagues. Oganov and
    >Glass have also solved the structures crystalline oxygen at high
    >pressure. Oxygen is unique from the chemical point of view. The
    >only magnetic molecular element known, under pressure it loses its
    >magnetism and turns red. The structure of red oxygen, which remained
    >unknown for a long time, seems to be finally solved and turns out to
    >be unique; that is, it does not manifest itself in any other
    >element. At even higher pressure oxygen is known to turn black in
    >color and become superconducting, which happens because of the
    >increased interactions between the O2 molecules. The ETH
    >researchers also predict a new stable phase of sulphur and several
    >new metastable forms of carbon. (Journal of Chemical Physics, 28
    >June 2006; lab website at http://olivine.ethz.ch/~artem/ ; ETH
    >Laboratory of Crystallography, 41(0)44 632 37 52,
    >a.oganov_at_mat.ethz.ch)
    >
    >SQUEEZED LIGHT AND GRAVITY WAVES. A proven method for reducing the
    >noise in high-precision optical measurements will soon be applied to
    >the search for gravitational waves. The most likely way such waves
    >will be detected is by observing their subtle effects on suspended
    >mirrors in detectors like the Laser Interferometer
    >Gravitational-wave Observatory (LIGO). At LIGO, laser light is
    >split into two beams which reflect many times from mirrors suspended
    >at the ends of two long pipes positioned at right angles. The two
    >beams are brought back together to form an interference pattern.
    >This procedure is adjusted so that a photodetector is positioned at
    >a null in the pattern; that is, it normally sees no photons coming
    >its way. The plan is that a passing gravity wave would ever so
    >slightly move the suspended mirrors in the two pipes
    >(which are otherwise insulated from ordinary kinds of vibration)
    >relative to each other, which in turn would disturb the interference
    >pattern. Suddenly the photodetector would record photons, heralding
    >a gravity wave. One problem with this scheme is "shot noise," the
    >quantum-based uncertainty in our knowledge of how many photons are
    >present in a laser beam at any moment. Fluctuations in photon
    >number could trigger a false positive reading. Physicists at the
    >Max Planck Institute (Hannover) and the University of Hannover are
    >hoping to reduce the quantum noise inherent in this interferometric
    >approach to gravity wave detection by squeezing light. Squeezed
    >light is produced when quantum noise in one or the other of two
    >complementary variables describing a light beam (such as phase and
    >amplitude) is greatly reduced at the expense of the other by sending
    >the light through (a series of) special optical crystals. The use
    >of squeezed light reduces quantum noise in a number of
    >optoelectronic applications. Usually the squeezed light approach is
    >applied at megahertz frequencies, but the Hannover researchers have
    >for the first time gotten it to work at all the detection
    >frequencies pertinent for LIGO including frequencies below a hundred
    >hertz, the expected frequency range of gravitational waves arriving
    >from some distant coalescing black holes in the universe. According
    >to Henning Vahlbruch(henning.vahlbruch_at_aei.mpg.de) a squeezed-light
    >control scheme would help reduce noise and raise the sensitivity of
    >gravity wave detectors. (Valbruch et al., Physical Review Letters,
    >7 July 2006; website at
    >http://www.geo600.uni-hannover.de/~schnabel/ )
    >
    >***********
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