1,829 research outputs found

    Parametric Evolution for a Deformed Cavity

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    We consider a classically chaotic system that is described by a Hamiltonian H(Q,P;x), where (Q,P) describes a particle moving inside a cavity, and x controls a deformation of the boundary. The quantum-eigenstates of the system are |n(x)>. We describe how the parametric kernel P(n|m) = , also known as the local density of states, evolves as a function of x-x0. We illuminate the non-unitary nature of this parametric evolution, the emergence of non-perturbative features, the final non-universal saturation, and the limitations of random-wave considerations. The parametric evolution is demonstrated numerically for two distinct representative deformation processes.Comment: 13 pages, 8 figures, improved introduction, to be published in Phys. Rev.

    Reduction of circulating cholesterol and apolipoprotein levels during sepsis

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    Sepsis with multiple organ failure is frequently associated with a substantial decrease of cholesterol levels. This decrease of cholesterol is strongly associated with mortality suggesting a direct relation between inflammatory conditions and altered cholesterol homeostasis. The host response during sepsis is mediated by cytokines and growth factors, which are capable of influencing lipid metabolism. Conversely lipoproteins are also capable of modulating cytokine production during the inflammatory response. Therefore the decrease in circulating cholesterol levels seems to play a crucial role in the pathophysiology of sepsis. In this review the interaction between cytokines and lipid metabolism and its clinical consequences will be discussed

    Study of the growth parameters involved in synthesizing boron carbide filaments Final report

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    Boron carbide whiskers - growth, mechanical properties and crystalline perfection, and incorporation in composite material

    Localization in Strongly Chaotic Systems

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    We show that, in the semiclassical limit and whenever the elements of the Hamiltonian matrix are random enough, the eigenvectors of strongly chaotic time-independent systems in ordered bases can on average be exponentially localized across the energy shell and decay faster than exponentially outside the energy shell. Typically however, matrix elements are strongly correlated leading to deviations from such behavior.Comment: RevTeX, 5 pages + 3 postscript figures, submitted to Phys. Rev. Let

    Quantum-Mechanical Non-Perturbative Response of Driven Chaotic Mesoscopic Systems

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    Consider a time-dependent Hamiltonian H(Q,P;x(t))H(Q,P;x(t)) with periodic driving x(t)=Asin(Ωt)x(t)=A\sin(\Omega t). It is assumed that the classical dynamics is chaotic, and that its power-spectrum extends over some frequency range ω<ωcl|\omega|<\omega_{cl}. Both classical and quantum-mechanical (QM) linear response theory (LRT) predict a relatively large response for Ω<ωcl\Omega<\omega_{cl}, and a relatively small response otherwise, independently of the driving amplitude AA. We define a non-perturbative regime in the (Ω,A)(\Omega,A) space, where LRT fails, and demonstrate this failure numerically. For A>AprtA>A_{prt}, where AprtA_{prt}\propto\hbar, the system may have a relatively strong response for Ω>ωcl\Omega>\omega_{cl}, and the shape of the response function becomes AA dependent.Comment: 4 pages, 2 figures, revised version with much better introductio

    Study of the growth parameters involved in synthesizing boron carbide filaments

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    Growth and deposition zone geometry effects on boron carbide whisker production, mechanical properties, and composite application

    Global Diffusion in a Realistic Three-Dimensional Time-Dependent Nonturbulent Fluid Flow

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    We introduce and study the first model of an experimentally realizable three-dimensional time-dependent nonturbulent fluid flow to display the phenomenon of global diffusion of passive-scalar particles at arbitrarily small values of the nonintegrable perturbation. This type of chaotic advection, termed {\it resonance-induced diffusion\/}, is generic for a large class of flows.Comment: 4 pages, uuencoded compressed postscript file, to appear in Phys. Rev. Lett. Also available on the WWW from http://formentor.uib.es/~julyan/, or on paper by reques

    Marine stratocumulus aerosol-cloud relationships in the MASE-II experiment: Precipitation susceptibility in eastern Pacific marine stratocumulus

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    Observational data on aerosol-cloud-drizzle relationships in marine stratocumulus are presented from the second Marine Stratus/Stratocumulus Experiment (MASE-II) carried out in July 2007 over the eastern Pacific near Monterey, California. Observations, carried out in regions of essentially uniform meteorology with localized aerosol enhancements due to ship exhaust (“ship tracks”), demonstrate, in accord with those from numerous other field campaigns, that increased cloud drop number concentration Nc and decreased cloud top effective radius r_e are associated with increased subcloud aerosol concentration. Modulation of drizzle by variations in aerosol levels is levels is clearly evident. Variations of cloud base drizzle rate R_(cb) are found to be consistent with the proportionality, R_(cb) / H^3/N_c, where H is cloud depth. Simultaneous aircraft and A-Train satellite observations are used to quantify the precipitation susceptibility of clouds to aerosol perturbations in the eastern Pacific region

    Evaluation of Methicillin-Resistant Staphylococcus aureus Carriage and High Livestock Production Areas in North Carolina through Active Case Finding at a Tertiary Care Hospital

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    : Recent reports from the Netherlands document the emergence of novel multilocus sequence typing (MLST) types (e.g., ST-398) of methicillin-resistant Staphylococcus aureus (MRSA) in livestock, particularly swine. In Eastern North Carolina (NC), one of the densest pig farming areas in the United States, as many as 14% of MRSA isolates from active case finding in our medical center have no matches in a repetitive sequence-based polymerase chain reaction (rep-PCR) library. The current study was designed to determine if these non-matched MRSA (NM-MRSA) were geographically associated with exposure to pig farming in Eastern NC. While residential proximity to farm waste lagoons lacked association with NM-MRSA in a logistic regression model, a spatial cluster was identified in the county with highest pig density. Using MLST, we found a heterogeneous distribution of strain types comprising the NM-MRSA isolates from the most pig dense regions, including ST-5 and ST-398. Our study raises the warning that patients in Eastern NC harbor livestock associated MRSA strains are not easily identifiable by rep-PCR. Future MRSA studies in livestock dense areas in the U.S. should investigate further the role of pig–human interactions
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