3,905 research outputs found

    Recovering Classical Dynamics from Coupled Quantum Systems Through Continuous Measurement

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    We study the role of continuous measurement in the quantum to classical transition for a system with coupled internal (spin) and external (motional) degrees of freedom. Even when the measured motional degree of freedom can be treated classically, entanglement between spin and motion causes strong measurement back action on the quantum spin subsystem so that classical trajectories are not recovered in this mixed quantum classical regime. The measurement can extract localized quantum trajectories that behave classically only when the internal action also becomes large relative to ħ

    Lung Injury Pathways: Adenosine Receptor 2B Signaling Limits Development of Ischemic Bronchiolitis Obliterans Organizing Pneumonia

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    Purpose/Aim of the Study: Adenosine signaling was studied in bronchiolitis obliterans organizing pneumonia (BOOP) resulting from unilateral lung ischemia. Materials and Methods: Ischemia was achieved by either left main pulmonary artery or complete hilar ligation. Sprague–Dawley (SD) rats, Dahl salt sensitive (SS) rats and SS mutant rat strains containing a mutation in the A2B adenosine receptor gene (Adora2b) were studied. Adenosine concentrations were measured in bronchoalveolar lavage (BAL) by HPLC. A2A (A2AAR) and A2B adenosine receptor (A2BAR) mRNA and protein were quantified. Results: Twenty-four hours after unilateral PA ligation, BAL adenosine concentrations from ischemic lungs were increased relative to contralateral lungs in SD rats. A2BAR mRNA and protein concentrations were increased after PA ligation while miR27a, a negatively regulating microRNA, was decreased in ischemic lungs. A2AAR mRNA and protein concentrations remained unchanged following ischemia. A2BAR protein was increased in PA ligated lungs of SS rats after 7 days, and 4 h after complete hilar ligation in SD rats. SS-Adora2b mutants showed a greater extent of BOOP relative to SS rats, and greater inflammatory changes. Conclusion: Increased A2BAR and adenosine following unilateral lung ischemia as well as more BOOP in A2BAR mutant rats implicate a protective role for A2BAR signaling in countering ischemic lung injury

    <i>Campylobacter jejuni </i>infections and anti-GM1 antibodies in Guillain-Barré syndrome

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    The group of patients with Guillain-Barre syndrome (GBS) is very heterogenous with regard to antecedent infections, immunological parameters, clinical manifestations, and response to treatment. In this study, the presumed pathogenic factors anti-GM1 antibodies and Campylobacter jejuni infections were related to the clinical characteristics. Serum from 154 patients with GBS, 63 patients with other neurological diseases (OND), and 50 normal controls (NC) were tested for the presence of antibodies against GM1 and C. jejuni. Anti-GM1 antibodies were detected in 31 (20%) GBS patients, 5 (8%) OND patients, and in none of the NC. Evidence for a recent C. jejuni infection was found in 49 (32%) GBS patients and less often in OND patients (11%) or NC (8%). In GBS patients, the presence of anti-GM1 antibodies was significantly associated with C. jejuni infections. The subgroup of GBS patients with anti-GM1 antibodies suffered more often from a rapidly progressive and more severe neuropathy with predominandy distal distribution of weakness, without deficits of cranial nerves or sensory disturbances. The subgroup with C. jejuni infection also more often had a severe pure motor variant of GBS. Recovery of the patients with anti-GMl antibodies and C. jejuni infections was not as good after plasma exchange compared with intravenous immunoglobulins.</p

    Quantum And Classical Dynamics Of Atoms In A Magneto-optical Lattice

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    The transport of ultra-cold atoms in magneto-optical potentials provides a clean setting in which to investigate the distinct predictions of classical versus quantum dynamics for a system with coupled degrees of freedom. In this system, entanglement at the quantum level and chaos at the classical level arise from the coupling between the atomic spin and its center-of- mass motion. Experiments, performed deep in the quantum regime, correspond to dynamic quantum tunneling. This nonclassical behavior is contrasted with the predictions for an initial phase space distribution produced in the experiment, but undergoing classical Hamiltonian flow. We study conditions under which the trapped atoms can be made to exhibit classical dynamics through the process of continuous measurement, which localizes the probability distribution to phase space trajectories, consistent with the uncertainty principle and quantum back-action noise. This method allows us to analytically and numerically identify the quantum-classical boundary.Comment: Contribution to the Proceedings of the 7th Experimental Chaos Conference describing recent experimental and theoretical result

    Vortices and domain walls in a Chern-Simons theory with magnetic moment interaction

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    We study the structure and properties of vortices in a recently proposed Abelian Maxwell-Chern-Simons model in 2+12 +1 dimensions. The model which is described by gauge field interacting with a complex scalar field, includes two parity and time violating terms: the Chern-Simons and the anomalous magnetic terms. Self-dual relativistic vortices are discussed in detail. We also find one dimensional soliton solutions of the domain wall type. The vortices are correctly described by the domain wall solutions in the large flux limit.Comment: To be published in Phys RevD 23 pages, RevTex, 5 figure

    Photon number resolution using a time-multiplexed single-photon detector

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    Photon number resolving detectors are needed for a variety of applications including linear-optics quantum computing. Here we describe the use of time-multiplexing techniques that allows ordinary single photon detectors, such as silicon avalanche photodiodes, to be used as photon number-resolving detectors. The ability of such a detector to correctly measure the number of photons for an incident number state is analyzed. The predicted results for an incident coherent state are found to be in good agreement with the results of a proof-of-principle experimental demonstration.Comment: REVTeX4, 6 pages, 8 eps figures, v2: minor changes, v3: changes in response to referee report, appendix added, 1 reference adde
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