4,532 research outputs found

    Effects of hydrogen bond and solvent polarity on the C=O strectching of bis(2-thienyl)ketone in solution

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    The optimized structural parameters, the absorption and the resonance Raman spectra have been investigated for the bis(2-thienyl)ketone in gas phase, in cyclohexane, methanol, and acetonitrile solvents by means of time dependent density functional theory calculations, the solvent electronic polarization effect on the solvation shift is examined and in well accordance with the calculation. The effect of increasing the polarity of the solvent is well represented by the polarizable continuum model, both for the absorption spectra and resonance Raman intensities. The Raman spectra of the C=O stretching mode, which is sensitive to the intermolecular interaction for bis(2-thienyl)ketone dissolved in solvents, were systematically studied. It was found that the hydrogen bond effect plays an important role in reducing the carbonyl stretching wavenumbers. The results of Raman shifts were interpreted through the dilution effect, solvation effects, and hydrogen bond-forming effects. Furthermore, the excitation profiles of several important Raman bands of bis(2-thienyl)ketone molecule in different solvents have been critically analyzed. The solvent effects on structural and symmetry properties of the molecule in S2 electronic state as well as the short-time photo relaxation dynamics have been discussed.published_or_final_versio

    Size and frequency of natural forest disturbances and the Amazon forest carbon balance

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    types: Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.Copyright © 2014 Macmillan Publishers Limited. All rights reserved.This is an open-access articleForest inventory studies in the Amazon indicate a large terrestrial carbon sink. However, field plots may fail to represent forest mortality processes at landscape-scales of tropical forests. Here we characterize the frequency distribution of disturbance events in natural forests from 0.01 ha to 2,651 ha size throughout Amazonia using a novel combination of forest inventory, airborne lidar and satellite remote sensing data. We find that small-scale mortality events are responsible for aboveground biomass losses of ~1.7 Pg C y(-1) over the entire Amazon region. We also find that intermediate-scale disturbances account for losses of ~0.2 Pg C y(-1), and that the largest-scale disturbances as a result of blow-downs only account for losses of ~0.004 Pg C y(-1). Simulation of growth and mortality indicates that even when all carbon losses from intermediate and large-scale disturbances are considered, these are outweighed by the net biomass accumulation by tree growth, supporting the inference of an Amazon carbon sink.NASA Earth System Science Fellowship (NESSF

    Doping the holographic Mott insulator

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    Mott insulators form because of strong electron repulsions, being at the heart of strongly correlated electron physics. Conventionally these are understood as classical "traffic jams" of electrons described by a short-ranged entangled product ground state. Exploiting the holographic duality, which maps the physics of densely entangled matter onto gravitational black hole physics, we show how Mott-insulators can be constructed departing from entangled non-Fermi liquid metallic states, such as the strange metals found in cuprate superconductors. These "entangled Mott insulators" have traits in common with the "classical" Mott insulators, such as the formation of Mott gap in the optical conductivity, super-exchange-like interactions, and form "stripes" when doped. They also exhibit new properties: the ordering wave vectors are detached from the number of electrons in the unit cell, and the DC resistivity diverges algebraically instead of exponentially as function of temperature. These results may shed light on the mysterious ordering phenomena observed in underdoped cuprates.Comment: 27 pages, 9 figures. Accepted in Nature Physic

    Towards strange metallic holography

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    We initiate a holographic model building approach to `strange metallic' phenomenology. Our model couples a neutral Lifshitz-invariant quantum critical theory, dual to a bulk gravitational background, to a finite density of gapped probe charge carriers, dually described by D-branes. In the physical regime of temperature much lower than the charge density and gap, we exhibit anomalous scalings of the temperature and frequency dependent conductivity. Choosing the dynamical critical exponent zz appropriately we can match the non-Fermi liquid scalings, such as linear resistivity, observed in strange metal regimes. As part of our investigation we outline three distinct string theory realizations of Lifshitz geometries: from F theory, from polarised branes, and from a gravitating charged Fermi gas. We also identify general features of renormalisation group flow in Lifshitz theories, such as the appearance of relevant charge-charge interactions when z2z \geq 2. We outline a program to extend this model building approach to other anomalous observables of interest such as the Hall conductivity.Comment: 71 pages, 8 figure

    Genetic determinants of co-accessible chromatin regions in activated T cells across humans.

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    Over 90% of genetic variants associated with complex human traits map to non-coding regions, but little is understood about how they modulate gene regulation in health and disease. One possible mechanism is that genetic variants affect the activity of one or more cis-regulatory elements leading to gene expression variation in specific cell types. To identify such cases, we analyzed ATAC-seq and RNA-seq profiles from stimulated primary CD4+ T cells in up to 105 healthy donors. We found that regions of accessible chromatin (ATAC-peaks) are co-accessible at kilobase and megabase resolution, consistent with the three-dimensional chromatin organization measured by in situ Hi-C in T cells. Fifteen percent of genetic variants located within ATAC-peaks affected the accessibility of the corresponding peak (local-ATAC-QTLs). Local-ATAC-QTLs have the largest effects on co-accessible peaks, are associated with gene expression and are enriched for autoimmune disease variants. Our results provide insights into how natural genetic variants modulate cis-regulatory elements, in isolation or in concert, to influence gene expression

    Perceptions of barriers to providing good cat care in Malaysian clinical practices

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    \ua9 The Author(s), 2023. Many veterinary practices around the world do not meet basic post-operative cat care, thereby compromising cat welfare. Understanding why the appropriate care is not always given is important. The current study used a mixed methods approach of two phases, to investigate the barriers Malaysian veterinarians face in seeking to provide good cat care in practice. Phase 1 involved a survey consisting of 14 questions which were divided into three sections (demographic details, basic management and barriers experienced by practices) and emailed to 143 Malaysian veterinarians. While for phase 2, 20 interviews were undertaken (recruited from the survey sample) to further elaborate on the results. A Thematic Analysis was conducted to extract the main barriers experienced by participants. A total of 49 veterinarians completed the survey. Over half of the respondents were senior veterinarians (i.e. those with two or more years in practice) (53.1%; n = 26) who were aware of the basic environmental provisions that cats need post-surgery such as bedding and toileting facilities (57.1%; n = 28). Cost (47%; n = 23) was the biggest restriction to good care provision. Interview findings showed that participants were aware of comfortable post-surgery environments helping recovery, but barriers were highlighted: workload factors and a lack of understanding of cat pain behaviours and associated stress. This suggested that participants had the knowledge required to provide good cat care but experienced difficulties putting this into practice. Therefore, to improve cat welfare in veterinary practice, instead of focusing purely on education, interventions to increase good cat care could include targeted elements that support behaviour change to overcome the barriers

    The impact of pesticide suicide on the geographic distribution of suicide in Taiwan: a spatial analysis

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    <p>Abstract</p> <p>Background</p> <p>Pesticide self-poisoning is the most commonly used suicide method worldwide, but few studies have investigated the national epidemiology of pesticide suicide in countries where it is a major public health problem. This study aims to investigate geographic variations in pesticide suicide and their impact on the spatial distribution of suicide in Taiwan.</p> <p>Methods</p> <p>Smoothed standardized mortality ratios for pesticide suicide (2002-2009) were mapped across Taiwan's 358 districts (median population aged 15 or above = 27 000), and their associations with the size of agricultural workforce were investigated using Bayesian hierarchical models.</p> <p>Results</p> <p>In 2002-2009 pesticide poisoning was the third most common suicide method in Taiwan, accounting for 13.6% (4913/36 110) of all suicides. Rates were higher in agricultural East and Central Taiwan and lower in major cities. Almost half (47%) of all pesticide suicides occurred in areas where only 13% of Taiwan's population lived. The geographic distribution of overall suicides was more similar to that of pesticide suicides than non-pesticide suicides. Rural-urban differences in suicide were mostly due to pesticide suicide. Areas where a higher proportion of people worked in agriculture showed higher pesticide suicide rates (adjusted rate ratio [ARR] per standard deviation increase in the proportion of agricultural workers = 1.58, 95% Credible Interval [CrI] 1.44-1.74) and overall suicide rates (ARR = 1.06, 95% CrI 1.03-1.10) but lower non-pesticide suicide rates (ARR = 0.91, 95% CrI 0.87-0.95).</p> <p>Conclusion</p> <p>Easy access to pesticides appears to influence the geographic distribution of suicide in Taiwan, highlighting the potential benefits of targeted prevention strategies such as restricting access to highly toxic pesticides.</p

    Search for Second-Generation Scalar Leptoquarks in ppˉ\bm{p \bar{p}} Collisions at s\sqrt{s}=1.96 TeV

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    Results on a search for pair production of second generation scalar leptoquark in ppˉp \bar{p} collisions at s\sqrt{s}=1.96 TeV are reported. The data analyzed were collected by the CDF detector during the 2002-2003 Tevatron Run II and correspond to an integrated luminosity of 198 pb1^{-1}. Leptoquarks (LQ) are sought through their decay into (charged) leptons and quarks, with final state signatures represented by two muons and jets and one muon, large transverse missing energy and jets. We observe no evidence for LQLQ production and derive 95% C.L. upper limits on the LQLQ production cross sections as well as lower limits on their mass as a function of β\beta, where β\beta is the branching fraction for LQμqLQ \to \mu q.Comment: 9 pages (3 author list) 5 figure
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