2,018 research outputs found

    Comments on the Relativity of Shape

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    In this talk I address three topics related to the shape of hadrons: 1. The Lorentz contraction of bound states. Few dedicated studies of this exist - I describe a recent calculation for ordinary atoms (positronium). 2. Does the A-dependence of nuclear structure functions indicate a change of proton shape in the nuclear environment? (My short answer is no.) 3. The size of Fock states contributing to processes involving large momentum transfers. End-point configurations can be transversally extended and yet sufficiently short-lived to contribute coherently to hard scattering.Comment: Talk at the Workshop on the Shape of Hadrons, 27-29 April 2006 in Athens, Greece. 11 pages, 15 figure

    Raman detection of macular carotenoid pigments in intact human retina

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    Journal ArticlePURPOSE: To develop and test a novel noninvasive optical technique suitable for the objective measurement of macular carotenoid levels in human retina. METHODS: A resonance Raman scattering apparatus was constructed to measure carotenoid levels in flat-mounted human retinas and eyecups and in experimental animal eyes. Light from an argon laser was used to resonantly excite the electronic absorption of the carotenoid pigments, and scattered light was collected and analyzed by a Raman spectrometer. After carotenoid Raman measurements were completed on the retinal samples, macular carotenoid levels were determined by high-performance liquid chromatography (HPLC). RESULTS: Carotenoid resonance Raman scattering proved to be a highly sensitive and specific method for the noninvasive measurement of macular pigments in the human retina. Signal strength scaled linearly with actual macular carotenoid content as measured by HPLC. Our apparatus was also used to record resonance Raman signals from xanthophyll carotenoids stored in the retinal pigment epithelium of intact frog eyes. CONCLUSIONS: This new noninvasive optical method will facilitate studies of ocular carotenoid distributions and their role in degenerative diseases of the eye and may allow for the rapid screening of carotenoid levels in large populations at risk for vision loss from age-related macular degeneration, the leading cause of blindness in the elderly in the United States. A prototype clinical instrument is under development

    Resonances in rotationally inelastic scattering of OH(X2ΠX^2\Pi) with helium and neon

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    We present detailed calculations on resonances in rotationally and spin-orbit inelastic scattering of OH (X\,^2\Pi, j=3/2, F_1, f) radicals with He and Ne atoms. We calculate new \emph{ab initio} potential energy surfaces for OH-He, and the cross sections derived from these surfaces compare favorably with the recent crossed beam scattering experiment of Kirste \emph{et al.} [Phys. Rev. A \textbf{82}, 042717 (2010)]. We identify both shape and Feshbach resonances in the integral and differential state-to-state scattering cross sections, and we discuss the prospects for experimentally observing scattering resonances using Stark decelerated beams of OH radicals.Comment: 14 pages, 15 Figure

    Event Horizons in Numerical Relativity II: Analyzing the Horizon

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    We present techniques and methods for analyzing the dynamics of event horizons in numerically constructed spacetimes. There are three classes of analytical tools we have investigated. The first class consists of proper geometrical measures of the horizon which allow us comparison with perturbation theory and powerful global theorems. The second class involves the location and study of horizon generators. The third class includes the induced horizon 2-metric in the generator comoving coordinates and a set of membrane-paradigm like quantities. Applications to several distorted, rotating, and colliding black hole spacetimes are provided as examples of these techniques.Comment: 23 double column pages including 28 figures. Higher quality figures (big size!) available upon request (jmasso OR [email protected]

    Recent Developments in Precision Electroweak Physics

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    Developments in precision electroweak physics in the two years since the symposium are briefly summarized.Comment: Update on recent developments, prepared for the publication of the Proceedings of Alberto Sirlin Symposium, New York University, October 2000. 10 pages, 1 figur
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