4,315 research outputs found

    Black string corrections in variable tension braneworld scenarios

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    Braneworld models with variable tension are investigated, and the corrections on the black string horizon along the extra dimension are provided. Such corrections are encrypted in additional terms involving the covariant derivatives of the variable tension on the brane, providing profound consequences concerning the black string horizon variation along the extra dimension, near the brane. The black string horizon behavior is shown to be drastically modified by the terms corrected by the brane variable tension. In particular, a model motivated by the phenomenological interesting case regarding Eotvos branes is investigated. It forthwith provides further physical features regarding variable tension braneworld scenarios, heretofore concealed in all previous analysis in the literature. All precedent analysis considered uniquely the expansion of the metric up to the second order along the extra dimension, what is able to evince solely the brane variable tension absolute value. Notwithstanding, the expansion terms aftermath, further accomplished in this paper from the third order on, elicits the successive covariant derivatives of the brane variable tension, and their respective coupling with the extrinsic curvature, the Weyl tensor, and the Riemann and Ricci tensors, as well as the scalar curvature. Such additional terms are shown to provide sudden modifications in the black string horizon in a variable tension braneworld scenarioComment: 12 pages, 5 figures, accepted in PR

    The Volumetric Contraction of Dental Gypsum Materials on Setting

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    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67364/2/10.1177_00220345530320030801.pd

    Waveform control of orientation-dependent ionization of DCl in few-cycle laser fields

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    Strong few-cycle light fields with stable electric field waveforms allow controlling electrons on time scales down to the attosecond domain. We have studied the dissociative ionization of randomly oriented DCl in 5 fs light fields at 720 nm in the tunneling regime. Momentum distributions of D+ and Cl+ fragments were recorded via velocity-map imaging. A waveformdependent anti-correlated directional emission of D+ and Cl+ fragments is observed. Comparison of our results with calculations indicates that tailoring of the light field via the carrier envelope phase permits the control over the orientation of DCl+ and in turn the directional emission of charged fragments upon the breakup of the molecular ion

    Stability and asymptotic behavior of periodic traveling wave solutions of viscous conservation laws in several dimensions

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    Under natural spectral stability assumptions motivated by previous investigations of the associated spectral stability problem, we determine sharp LpL^p estimates on the linearized solution operator about a multidimensional planar periodic wave of a system of conservation laws with viscosity, yielding linearized L1LpLpL^1\cap L^p\to L^p stability for all p2p \ge 2 and dimensions d1d \ge 1 and nonlinear L1HsLpHsL^1\cap H^s\to L^p\cap H^s stability and L2L^2-asymptotic behavior for p2p\ge 2 and d3d\ge 3. The behavior can in general be rather complicated, involving both convective (i.e., wave-like) and diffusive effects

    Measuring the Magnetic Field on the Classical T Tauri Star TW Hydrae

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    We present infrared (IR) and optical echelle spectra of the Classical T Tauri star TW Hydrae. Using the optical data, we perform detailed spectrum synthesis to fit atomic and molecular absorption lines and determine key stellar parameters: Teff = 4126 \pm 24 K, log g = 4.84 \pm 0.16, [M/H] = -0.10 \pm 0.12, vsini = 5.8 \pm 0.6 km/s. The IR spectrum is used to look for Zeeman broadening of photospheric absorption lines. We fit four Zeeman sensitive Ti I lines near 2.2 microns and find the average value of the magnetic field over the entire surface is 2.61 \pm 0.23 kG. In addition, several nearby magnetically insensitive CO lines show no excess broadening above that produced by stellar rotation and instrumental broadening, reinforcing the magnetic interpretation for the width of the Ti I lines. We carry out extensive tests to quantify systematic errors in our analysis technique which may result from inaccurate knowledge of the effective temperature or gravity, finding that reasonable errors in these quantities produce a 10% uncertainty in the mean field measurement.Comment: The tar file includes one Tex file and four .eps figures. The paper is accepted and tentatively scheduled for the ApJ 1 December 2005, v634, 2 issue. ApJ manuscript submission # 6310

    Structural model correlation using large admissible perturbations incognate space

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    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76957/1/AIAA-10863-901.pd

    Identification of the slow E3 transition 136mCs -> 136Cs with conversion electrons

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    We performed at ISOLDE the spectroscopy of the decay of the 8- isomer in 136Cs by and conversion-electron detection. For the first time the excitation energy of the isomer and the multipolarity of its decay have been measured. The half-life of the isomeric state was remeasured to T1/2 = 17.5(2) s. This isomer decays via a very slow 518 keV E3 transition to the ground state. In addition to this, a much weaker decay branch via a 413 keV M4 and a subsequent 105 keV E2 transition has been found. Thus we have found a new level at 105 keV with spin 4+ between the isomeric and the ground state. The results are discussed in comparison to shell model calculations.Comment: Phys. Rev. C accepted for publicatio

    CHEMICALLY MODIFIED PHOTOSYNTHETIC BACTERIAL REACTION CENTERS: CIRCULAR DICHROISM, RAMAN RESONANCE, LOW TEMPERATURE ABSORPTION, FLUORESCENCE AND ODMR SPECTRA AND POLYPEPTIDE COMPOSITION OF BOROHYDRIDE TREATED REACTION CENTERS FROM Rhodobacter sphaeroides R26

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    Reaction centers from Rhodobacter sphaeroides have been modified by treatment with sodium borohydride similar to the original procedure [Ditson et al., Biochim. Biophys. Acta 766, 623 (1984)], and investigated spectroscopically and by gel electrophoresis. (1) Low temperature (1.2 K) absorption, fluorescence, absorption- and fluorescence-detected ODMR, and microwave-induced singlet-triplet absorption difference spectra (MIA) suggest that the treatment produces a spectroscopically homogeneous preparation with one of the ‘additional’ bacteriochlorophylls being removed. The modification does not alter the zero field splitting parameters of the primary donor triplet (TP870). (2) From the circular dichroism and Raman resonance spectra in the1500–1800 cm-1 region, the removed pigment is assigned to BchlM, e.g. the "extra" Bchl on the "inactive" M-branch. (3) A strong coupling among all pigment molecules is deduced from the circular dichroism spectra, because pronounced band-shifts and/or intensity changes occur in the spectral components assigned to all pigments. This is supported by distinct differences among the MIA spectra of untreated and modified reaction centers, as well as by Raman resonance. (4) The modification is accompanied by partial proteolytic cleavage of the M-subunit. The preparation is thus spectroscopically homogeneous, but biochemically heterogenous

    A New Differential Absorption Lidar to Measure Sub-Hourly Fluctuation of Tropospheric Ozone Profiles in the Baltimore - Washington D.C. Region

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    Tropospheric ozone profiles have been retrieved from the new ground based National Aeronautics and Space Administration (NASA) Goddard Space Flight Center TROPospheric OZone DIfferential Absorption Lidar (GSFC TROPOZ DIAL) in Greenbelt, MD (38.99 N, 76.84 W, 57 meters ASL) from 400 m to 12 km AGL. Current atmospheric satellite instruments cannot peer through the optically thick stratospheric ozone layer to remotely sense boundary layer tropospheric ozone. In order to monitor this lower ozone more effectively, the Tropospheric Ozone Lidar Network (TOLNet) has been developed, which currently consists of five stations across the US. The GSFC TROPOZ DIAL is based on the Differential Absorption Lidar (DIAL) technique, which currently detects two wavelengths, 289 and 299 nm. Ozone is absorbed more strongly at 289 nm than at 299 nm. The DIAL technique exploits this difference between the returned backscatter signals to obtain the ozone number density as a function of altitude. The transmitted wavelengths are generated by focusing the output of a quadrupled Nd:YAG laser beam (266 nm) into a pair of Raman cells, filled with high pressure hydrogen and deuterium. Stimulated Raman Scattering (SRS) within the focus generates a significant fraction of the pump energy at the first Stokes shift. With the knowledge of the ozone absorption coefficient at these two wavelengths, the range resolved number density can be derived. An interesting atmospheric case study involving the Stratospheric-Tropospheric Exchange (STE) of ozone is shown to emphasize the regional importance of this instrument as well as assessing the validation and calibration of data. The retrieval yields an uncertainty of 16-19 percent from 0-1.5 km, 10-18 percent from 1.5-3 km, and 11-25 percent from 3 km to 12 km. There are currently surface ozone measurements hourly and ozonesonde launches occasionally, but this system will be the first to make routine tropospheric ozone profile measurements in the Baltimore-Washington DC area
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