7,172 research outputs found

    Gamma-widths, lifetimes and fluctuations in the nuclear quasi-continuum

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    Statistical γ\gamma-decay from highly excited states is determined by the nuclear level density (NLD) and the γ\gamma-ray strength function (γ\gammaSF). These average quantities have been measured for several nuclei using the Oslo method. For the first time, we exploit the NLD and γ\gammaSF to evaluate the γ\gamma-width in the energy region below the neutron binding energy, often called the quasi-continuum region. The lifetimes of states in the quasi-continuum are important benchmarks for a theoretical description of nuclear structure and dynamics at high temperature. The lifetimes may also have impact on reaction rates for the rapid neutron-capture process, now demonstrated to take place in neutron star mergers.Comment: CGS16, Shanghai 2017, Proceedings, 5 pages, 3 figure

    Renal function, sodium and water homeostasis in patients with idiopathic extrahepatic portal vein thrombosis compared with normal healthy controls

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    Objectives. To determine whether portal hypertension in the absence of liver disease contributes to changes in renal function and renal sodium and water handling.Methods. Nine patients with extrahepatic portal vein thrombosis (PVT) with normal liver function and histology were compared with 9 matched healthy control subjects. All underwent standard measurements of glomerular filtration rate and effective renal blood flow using inulin and paraaminohippuric acid (PAH) clearances, respectively. Sodium excretion and renin and aldosterone levels were studied before, during and after an intravenous saline infusion,Results. At baseline there were no differences in inulin clearance, PAH clearance, fractional excretion of sodium and free water excretion. During and after the saline infusion both groups showed a significant increase in sodium excretion with a reduction in water excretion, while the PAH and inulin clearances remained unchanged. Although aldosterone and renin levels both fell after the infusion, aldosterone levels were significantly lower in the PVT group. There were no other significant differences between the PVT and control groups.Conclusion. Renal function and sodium and water handling were comparable in healthy controls and patients with PVT. It is unlikely that portal hypertension alone plays a significant role in the impaired ability to excrete sodium and water in patients with liver cirrhosi

    The prognostic value of pulmonary artery compliance in cardiogenic shock.

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    The aim of this study was to evaluate the pathophysiological role and the prognostic significance of pulmonary artery compliance (C <sub>PA</sub> ), a measure of right ventricular pulsatile afterload, in cardiogenic shock. We retrospectively included 91 consecutive patients with cardiogenic shock due to primary left ventricular failure, monitored with a pulmonary artery catheter within the first 24 h. C <sub>PA</sub> was calculated as the ratio of stroke volume to pulmonary artery pulse pressure, and we determined whether C <sub>PA</sub> predicted mortality and whether it performed better than other pulmonary hemodynamic variables. The overall in-hospital mortality in our cohort was 27%. Survivors and nonsurvivors had comparable left ventricular ejection fraction, systolic, diastolic and mean pulmonary artery pressure, transpulmonary gradient, diastolic pressure gradient, and pulmonary vascular resistance at 24 h. In contrast, C <sub>PA</sub> was the only pulmonary artery variable significantly associated with mortality in univariate and multivariate analyses. Mortality increased from 4.5% at the highest quartile of C <sub>PA</sub> (3.6-6.5 mL/mmHg) to 43.5% at the lowest quartile (0.7-1.7 mL/mmHg). In 64 patients with a PAC inserted immediately upon admission, we calculated the trend of C <sub>PA</sub> between admission and 24 h. This trend was positive in survivors (+0.8 ± 1.3 ml/mmHg) but negative in nonsurvivors (-0.1 ± 1.0 mL/mmHg). The lower C <sub>PA</sub> in nonsurvivors was associated with more severe right ventricular systolic dysfunction. In conclusion, a reduced compliance of the pulmonary artery promotes right ventricular dysfunction and is independently associated with mortality in cardiogenic shock. Future studies should evaluate the impact on pulmonary arterial compliance and right ventricular afterload of therapies used in cardiogenic shock

    “A Process of Controlled Serendipity”: An Exploratory Study of Historians’ and Digital Historians’ Experiences of Serendipity in Digital Environments

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    We investigate historians\u27 experiences with serendipity in both physical and digital environments through an online survey. Through a combination of qualitative and quantitative data analyses, our preliminary findings show that many digital historians select a specific digital environment because of the expectation that it may elicit a serendipitous experience. Historians also create heuristic methods of using digital tools to integrate elements of serendipity into their research practice. Four features of digital environments were identified by participants as supporting serendipity: exploration, highlighted triggers, allowed for keyword searching and connected them to other people

    Spectra of Discrete Schr\"odinger Operators with Primitive Invertible Substitution Potentials

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    We study the spectral properties of discrete Schr\"odinger operators with potentials given by primitive invertible substitution sequences (or by Sturmian sequences whose rotation angle has an eventually periodic continued fraction expansion, a strictly larger class than primitive invertible substitution sequences). It is known that operators from this family have spectra which are Cantor sets of zero Lebesgue measure. We show that the Hausdorff dimension of this set tends to 11 as coupling constant λ\lambda tends to 00. Moreover, we also show that at small coupling constant, all gaps allowed by the gap labeling theorem are open and furthermore open linearly with respect to λ\lambda. Additionally, we show that, in the small coupling regime, the density of states measure for an operator in this family is exact dimensional. The dimension of the density of states measure is strictly smaller than the Hausdorff dimension of the spectrum and tends to 11 as λ\lambda tends to 00

    Rabl's model of the interphase chromosome arrangement tested in Chinise hamster cells by premature chromosome condensation and laser-UV-microbeam experiments

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    In 1885 Carl Rabl published his theory on the internal structure of the interphase nucleus. We have tested two predictions of this theory in fibroblasts grown in vitro from a female Chinese hamster, namely (1) the Rabl-orientation of interphase chromosomes and (2) the stability of the chromosome arrangement established in telophase throughout the subsequent interphase. Tests were carried out by premature chromosome condensation (PCC) and laser-UV-microirradiation of the interphase nucleus. Rabl-orientation of chromosomes was observed in G1 PCCs and G2 PCCs. The cell nucleus was microirradiated in G1 at one or two sites and pulse-labelled with 3H-thymidine for 2h. Cells were processed for autoradiography either immediately thereafter or after an additional growth period of 10 to 60h. Autoradiographs show unscheduled DNA synthesis (UDS) in the microirradiated nuclear part(s). The distribution of labelled chromatin was evaluated in autoradiographs from 1035 cells after microirradiation of a single nuclear site and from 253 cells after microirradiation of two sites. After 30 to 60h postincubation the labelled regions still appeared coherent although the average size of the labelled nuclear area fr increased from 14.2% (0h) to 26.5% (60h). The relative distance dr, i.e. the distance between two microirradiated sites divided by the diameter of the whole nucleus, showed a slight decrease with increasing incubation time. Nine metaphase figures were evaluated for UDS-label after microirradiation of the nuclear edge in G1. An average of 4.3 chromosomes per cell were labelled. Several chromosomes showed joint labelling of both distal chromosome arms including the telomeres, while the centromeric region was free from label. This label pattern is interpreted as the result of a V-shaped orientation of these particular chromosomes in the interphase nucleus with their telomeric regions close to each other at the nuclear edge. Our data support the tested predictions of the Rabl-model. Small time-dependent changes of the nuclear space occupied by single chromosomes and of their relative positions in the interphase nucleus seem possible, while the territorial organization of interphase chromosomes and their arrangement in general is maintained during interphase. The present limitations of the methods used for this study are discussed

    A note on fermions in holographic QCD

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    We study the fermionic sector of a probe D8-brane in the supergravity background made of D4-branes compactified on a circle with supersymmetry broken explicitly by the boundary conditions. At low energies the dual field theory is effectively four-dimensional and has proved surprisingly successful in recovering qualitative and quantitative properties of QCD. We investigate fluctuations of the fermionic fields on the probe D8-brane and interpret these as mesinos (fermionic superpartners of mesons). We demonstrate that the masses of these modes are comparable to meson masses and show that their interactions with ordinary mesons are not suppressed.Comment: 21+1 pp, 1 figure; v2: typos corrected, refs. adde
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