2,349 research outputs found

    Transport properties of a molecule embedded in an Aharonov-Bohm interferometer

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    We theoretically investigate the transport properties of a molecule embedded in one arm of a mesoscopic Aharonov-Bohm interferometer. Due to the presence of phonons the molecule level position (ϔd\epsilon_d) and the electron-electron interaction (UU) undergo a \emph{polaronic shift} which affects dramatically the electronic transport through the molecular junction. When the electron-phonon interaction is weak the linear conductance presents Fano-line shapes as long as the direct channel between the electrodes is opened. The observed Fano resonances in the linear conductance are originated from the interference between the spin Kondo state and the direct path. For strong enough electron-phonon interaction, the electron-electron interaction is renormalized towards negative values, {\it i.e.} becomes effectively attractive. This scenario favors fluctuations between the empty and doubly occupied charge states and therefore promotes a charge Kondo effect. However, the direct path between the contacts breaks the electron-hole symmetry which can efficiently suppress this charge Kondo effect. Nevertheless, we show that a proper tuning of the gate voltage is able to revive the Kondo resonance. Our results are obtained by using the Numerical Renormalization approximation to compute the electronic spectral function and the linear conductance.Comment: 17 pages, 12 figure

    Photocatalytic Aminodecarboxylation of Carboxylic Acids

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    Aminodecarboxylation of unactivated alkyl carboxylic acids has been accomplished utilizing an organic photocatalyst. This operationally simple reaction utilizes readily available carboxylic acids to chemoselectively generate reactive alkyl intermediates that are not accessible via conventional two-electron pathways. The organic radical intermediates are efficiently trapped with electrophilic diazo compounds to provide aminated alkanes.Division of Chemistry. Grant Number: 146517

    Mitogen and Stress-Activated Kinases 1 and 2 Mediate Endothelial Dysfunction

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    Inflammation promotes endothelial dysfunction, but the underlying mechanisms remain poorly defined in vivo. Using translational vascular function testing in myocardial infarction patients, a situation where inflammation is prevalent, and knock-out (KO) mouse models we demonstrate a role for mitogen-activated-protein-kinases (MAPKs) in endothelial dysfunction. Myocardial infarction significantly lowers mitogen and stress kinase 1/2 (MSK1/2) expression in peripheral blood mononuclear cells and diminished endothelial function. To further understand the role of MSK1/2 in vascular function we developed in vivo animal models to assess vascular responses to vasoactive drugs using laser Doppler imaging. Genetic deficiency of MSK1/2 in mice increased plasma levels of pro-inflammatory cytokines and promoted endothelial dysfunction, through attenuated production of nitric oxide (NO), which were further exacerbated by cholesterol feeding. MSK1/2 are activated by toll-like receptors through MyD88. MyD88 KO mice showed preserved endothelial function and reduced plasma cytokine expression, despite significant hypercholesterolemia. MSK1/2 kinases interact with MAPK-activated proteins 2/3 (MAPKAP2/3), which limit cytokine synthesis. Cholesterol-fed MAPKAP2/3 KO mice showed reduced plasma cytokine expression and preservation of endothelial function. MSK1/2 plays a significant role in the development of endothelial dysfunction and may provide a novel target for intervention to reduce vascular inflammation. Activation of MSK1/2 could reduce pro-inflammatory responses and preserve endothelial vasodilator function before development of significant vascular disease

    Time delay for one-dimensional quantum systems with steplike potentials

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    This paper concerns time-dependent scattering theory and in particular the concept of time delay for a class of one-dimensional anisotropic quantum systems. These systems are described by a Schr\"{o}dinger Hamiltonian H=−Δ+VH = -\Delta + V with a potential V(x)V(x) converging to different limits VℓV_{\ell} and VrV_{r} as x→−∞x \to -\infty and x→+∞x \to +\infty respectively. Due to the anisotropy they exhibit a two-channel structure. We first establish the existence and properties of the channel wave and scattering operators by using the modern Mourre approach. We then use scattering theory to show the identity of two apparently different representations of time delay. The first one is defined in terms of sojourn times while the second one is given by the Eisenbud-Wigner operator. The identity of these representations is well known for systems where V(x)V(x) vanishes as ∣x∣→∞|x| \to \infty (Vℓ=VrV_\ell = V_r). We show that it remains true in the anisotropic case Vℓ=ÌžVrV_\ell \not = V_r, i.e. we prove the existence of the time-dependent representation of time delay and its equality with the time-independent Eisenbud-Wigner representation. Finally we use this identity to give a time-dependent interpretation of the Eisenbud-Wigner expression which is commonly used for time delay in the literature.Comment: 48 pages, 1 figur

    Treatment of acute rhinitis with a nasal spray containing tramazoline and essential oils: a multicenter, uncontrolled, observational trial

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    BACKGROUND: In this observational trial, data were collected on the effectiveness and tolerability/safety of a nasal spray containing tramazoline and essential oils (trade name Rhinospray((R)) Plus) used for symptomatic treatment of acute rhinitis due to common cold. METHODS: The trial was performed in 300 children, adolescents and adults, who were to be treated with Rhinospray((R)) Plus for up to 4 times per day for up to 10 days. Primary endpoints were the change from baseline to final visit in the mean of three single symptom scores (blocked nose, sneezing, and runny nose) and the mean improvement in two quality-of-life parameters (ability to perform normal daytime activities and quality of sleep). RESULTS: A total of 108 children, 30 adolescents and 162 adults were treated with Rhinospray((R)) Plus. No patient discontinued prematurely. There was a mean reduction of 2.0 +/- 0.6 (standard deviation) in nasal symptom scores from baseline to final visit; 297 of 300 of patients (99.0 %) reported an improvement. The mean value for improvement in quality-of-life parameters was 1.3 +/- 0.5. Improvement in daytime activities was reported by all 300 patients (100.0 %) and in quality of sleep by 292 patients (97.4 %). Effectiveness and tolerability were rated as 'very good' or 'good' by 95.4 % and 97.4 % of patients, respectively; the investigators rated effectiveness and tolerability as 'very good' or 'good' for 97.4 % and 100.0 % of patients, respectively. No adverse events were reported. CONCLUSIONS: Community-based patients reported a relief in acute rhinitis symptoms and improvement in quality of life as a result of treatment with Rhinospray((R)) Plus. Treatment was well-tolerated

    A network analysis to identify pathophysiological pathways distinguishing ischaemic from non-ischaemic heart failure

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    Aims Heart failure (HF) is frequently caused by an ischaemic event (e.g. myocardial infarction) but might also be caused by a primary disease of the myocardium (cardiomyopathy). In order to identify targeted therapies specific for either ischaemic or non‐ischaemic HF, it is important to better understand differences in underlying molecular mechanisms. Methods and results We performed a biological physical protein–protein interaction network analysis to identify pathophysiological pathways distinguishing ischaemic from non‐ischaemic HF. First, differentially expressed plasma protein biomarkers were identified in 1160 patients enrolled in the BIOSTAT‐CHF study, 715 of whom had ischaemic HF and 445 had non‐ischaemic HF. Second, we constructed an enriched physical protein–protein interaction network, followed by a pathway over‐representation analysis. Finally, we identified key network proteins. Data were validated in an independent HF cohort comprised of 765 ischaemic and 100 non‐ischaemic HF patients. We found 21/92 proteins to be up‐regulated and 2/92 down‐regulated in ischaemic relative to non‐ischaemic HF patients. An enriched network of 18 proteins that were specific for ischaemic heart disease yielded six pathways, which are related to inflammation, endothelial dysfunction superoxide production, coagulation, and atherosclerosis. We identified five key network proteins: acid phosphatase 5, epidermal growth factor receptor, insulin‐like growth factor binding protein‐1, plasminogen activator urokinase receptor, and secreted phosphoprotein 1. Similar results were observed in the independent validation cohort. Conclusions Pathophysiological pathways distinguishing patients with ischaemic HF from those with non‐ischaemic HF were related to inflammation, endothelial dysfunction superoxide production, coagulation, and atherosclerosis. The five key pathway proteins identified are potential treatment targets specifically for patients with ischaemic HF

    The SPLASH Survey: Kinematics of Andromeda's Inner Spheroid

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    The combination of large size, high stellar density, high metallicity, and Sersic surface brightness profile of the spheroidal component of the Andromeda galaxy (M31) within R_proj ~ 20 kpc suggest that it is unlike any subcomponent of the Milky Way. In this work we capitalize on our proximity to and external view of M31 to probe the kinematical properties of this "inner spheroid." We employ a Markov chain Monte Carlo (MCMC) analysis of resolved stellar kinematics from Keck/DEIMOS spectra of 5651 red giant branch stars to disentangle M31's inner spheroid from its stellar disk. We measure the mean velocity and dispersion of the spheroid in each of five spatial bins after accounting for a locally cold stellar disk as well as the Giant Southern Stream and associated tidal debris. For the first time, we detect significant spheroid rotation (v_rot ~ 50 km/s) beyond R_proj ~ 5 kpc. The velocity dispersion decreases from about 140 km/s at R_proj = 7 kpc to 120 km/s at R_proj = 14 kpc, consistent to 2 sigma with existing measurements and models. We calculate the probability that a given star is a member of the spheroid and find that the spheroid has a significant presence throughout the spatial extent of our sample. Lastly, we show that the flattening of the spheroid is due to velocity anisotropy in addition to rotation. Though this suggests that the inner spheroid of M31 more closely resembles an elliptical galaxy than a typical spiral galaxy bulge, it should be cautioned that our measurements are much farther out (2 - 14 r_eff) than for the comparison samples.Comment: Accepted for publication in Ap
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