49,023 research outputs found

    Prediction and analysis of long-term variability of temperature and salinity in the Irish Sea

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    The variability of temperature and salinity in the Irish Sea over the 40 year period 1960 - 1999 is investigated using a free-running fine-resolution local area model. The skill of the model to represent observed temperature and salinity variability is assessed using conductivity-temperature-depth survey data ( 3397 profiles) and a long time series of measurements from Cypris station (southwest of Isle of Man). This clearly demonstrates that the model can reproduce the observed seasonal and longer-term cycles in temperature, with mean and RMS errors of - 0.01 degrees C and 0.78 degrees C. Particularly apparent is the long-term warming trend at Cypris station and throughout the model domain. Model estimates of salinity are less accurate and are generally too saline (mean and RMS errors are 0.79 and 0.98 practical salinity units). Inaccuracies are likely to arise from boundary conditions and forcing (riverine and surface). However, while absolute values are not particularly well represented, the model reproduces many of the trends in the salinity variability observed at Cypris station, suggesting that the dominant physical processes in the Irish Sea, with timescales up to similar to 3 years, are well represented. The model is also used to investigate the variability in temperature stratification. While stratification is confined to approximately the same geographical area in each year of the simulation, there is significant variability in the timing of the onset and breakdown of stratification and in the peak surface to bed temperature difference. Together, these results suggest that a local area model with limited boundary conditions may be sufficiently accurate for climatic investigation of some (locally forced) parameter

    Study of photoconductive indium antimonide

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    Indium antimonide (InSb) material was assessed for use as photoconductive infrared detectors under low background conditions. Such detectors must be more rugged, and have lower capacitance, than the common photovoltaic InSb detector. Electronic grade n-type InSb was etched to 50 micrometers thickness, and tin and gold contacts were applied by evaporation. The test devices showed a relatively low ultimate impedance: 7 Mohms at 4.2 K. This was attributed to the presence of impurity levels of very shallow energies, and this material was judged unsuitable for low background detection

    Selective COX-2 inhibitors and risk of myocardial infarction

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    Selective inhibitors of cyclooxygenase- 2 ( COX- 2, ` coxibs') are highly effective anti-inflammatory and analgesic drugs that exert their action by preventing the formation of prostanoids. Recently some coxibs, which were designed to exploit the advantageous effects of non- steroidal anti-inflammatory drugs while evading their side effects, have been reported to increase the risk of myocardial infarction and atherothrombotic events. This has led to the withdrawal of rofecoxib from global markets, and warnings have been issued by drug authorities about similar events during the use of celecoxib or valdecoxib/ parecoxib, bringing about questions of an inherent atherothrombotic risk of all coxibs and consequences that should be drawn by health care professionals. These questions need to be addressed in light of the known effects of selective inhibition of COX- 2 on the cardiovascular system. Although COX- 2, in contrast to the cyclooxygenase-1 ( COX- 1) isoform, is regarded as an inducible enzyme that only has a role in pathophysiological processes like pain and inflammation, experimental and clinical studies have shown that COX- 2 is constitutively expressed in tissues like the kidney or vascular endothelium, where it executes important physiological functions. COX- 2- dependent formation of prostanoids not only results in the mediation of pain or inflammatory signals but also in the maintenance of vascular integrity. Especially prostacyclin ( PGI(2)), which exerts vasodilatory and antiplatelet properties, is formed to a significant extent by COX- 2, and its levels are reduced to less than half of normal when COX- 2 is inhibited. This review outlines the rationale for the development of selective COX- 2 inhibitors and the pathophysiological consequences of selective inhibition of COX- 2 with special regard to vasoactive prostaglandins. It describes coxibs that are currently available, evaluates the current knowledge on the risk of atherothrombotic events associated with their intake and critically discusses the consequences that should be drawn from these insights. Copyright (C) 2005 S. Karger AG, Basel

    Study of solution procedures for nonlinear structural equations

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    A method for the redution of the cost of solution of large nonlinear structural equations was developed. Verification was made using the MARC-STRUC structure finite element program with test cases involving single and multiple degrees of freedom for static geometric nonlinearities. The method developed was designed to exist within the envelope of accuracy and convergence characteristic of the particular finite element methodology used

    Evidence of induced innovation in US sectoral Capital´s shares

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    We use annual data on capital´s share and relative factor prices from 35 US industriesfrom 1960 to 2005 to test the induced innovation hypothesis. We derive, from a productionfunction framework, testable implications for the effect of contemporaneous and lagged factorprice ratios on capital´s share of production. The predicted effect is positive or negativedepending on the elasticity of substitution between labor and capital. From panel regressions, theestimated effect of the contemporaneous factor price ratio implies an elasticity of substitutionthat is less than unity, consistent with the consensus from the literature. Based on this, ournegative estimated effects for lagged price ratios are both statistically significant and consistentwith the induced innovation hypothesis.induced innovation, biased technical change, capital´s share, labor´s share, elasticityof substitution

    #cutting: non-suicidal self-injury (NSSI) on Instagram

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    Social media presents an important means for social interaction, especially among adolescents, with Instagram being the most popular platform in this age-group. Pictures and communication about non-suicidal self-injury (NSSI) can frequently be found on the internet. During 4 weeks in April 2016, n = 2826 (from n = 1154 accounts) pictures which directly depicted wounds on Instagram were investigated. Those pictures, associated comments, and user accounts were independently rated for content. Associations between characteristics of pictures and comments as well as weekly and daily trends of posting behavior were analyzed. Most commonly, pictures depicted wounds caused by cutting on arms or legs and were rated as mild or moderate injuries. Pictures with increasing wound grades and those depicting multiple methods of NSSI generated elevated amounts of comments. While most comments were neutral or empathic with some offering help, few comments were hostile. Pictures were mainly posted in the evening hours, with a small peak in the early morning. While there was a slight peak of pictures being posted on Sundays, postings were rather evenly spread across the week. Pictures of NSSI are frequently posted on Instagram. Social reinforcement might play a role in the posting of more severe NSSI pictures. Social media platforms need to take appropriate measures for preventing online social contagion

    Laser velocimeter systems analysis applied to a flow survey above a stalled wing

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    A laser velocimeter operating in the backscatter mode was used to survey the flow above a stalled wing. Polarization was used to separate the two orthogonal velocity components of the fringe-type laser velocimeter, and digital counters were used for data processing. The velocities of the kerosene seed particles were measured with less than 2 percent uncertainty. The particle velocity measurements were collected into histograms. The flow field survey was carried out above an aspect-ratio-8 stalled wing with an NACA 0012 section. The angle of attack was 19.5 deg, the Mach number was 0.49, and the Reynolds number was 1,400,000. The flow field was characterized by the periodic shedding of discrete vortices from near the crest of the airfoil

    Signatures of non-gaussianity in the isocurvature modes of primordial black hole dark matter

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    Primordial black holes (PBHs) are black holes which may have formed very early on during the radiation dominated era in the early universe. We present here a method by which the large scale perturbations in the density of primordial black holes may be used to place tight constraints on non-gaussianity if PBHs account for dark matter (DM). The presence of local-type non-gaussianity is known to have a significant effect on the abundance of primordial black holes, and modal coupling from the observed CMB scale modes can significantly alter the number density of PBHs that form within different regions of the universe, which appear as DM isocurvature modes. Using the recent \emph{Planck} constraints on isocurvature perturbations, we show that PBHs are excluded as DM candidates for even very small local-type non-gaussianity, fNL0.001|f_{NL}|\approx0.001 and remarkably the constraint on gNLg_{NL} is almost as strong. Even small non-gaussianity is excluded if DM is composed of PBHs. If local non-Gaussianity is ever detected on CMB scales, the constraints on the fraction of the universe collapsing into PBHs (which are massive enough to have not yet evaporated) will become much tighter.Comment: 23 pages, 11 figures. V2: minor corrections and changes, matches published versio

    Non-equilibrium fixed points of coupled Ising models

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    Driven-dissipative systems are expected to give rise to non-equilibrium phenomena that are absent in their equilibrium counterparts. However, phase transitions in these systems generically exhibit an effectively classical equilibrium behavior in spite of their non-equilibrium origin. In this paper, we show that multicritical points in such systems lead to a rich and genuinely non-equilibrium behavior. Specifically, we investigate a driven-dissipative model of interacting bosons that possesses two distinct phase transitions: one from a high- to a low-density phase---reminiscent of a liquid-gas transition---and another to an antiferromagnetic phase. Each phase transition is described by the Ising universality class characterized by an (emergent or microscopic) Z2\mathbb{Z}_2 symmetry. They, however, coalesce at a multicritical point, giving rise to a non-equilibrium model of coupled Ising-like order parameters described by a Z2×Z2\mathbb{Z}_2 \times \mathbb{Z}_2 symmetry. Using a dynamical renormalization-group approach, we show that a pair of non-equilibrium fixed points (NEFPs) emerge that govern the long-distance critical behavior of the system. We elucidate various exotic features of these NEFPs. In particular, we show that a generic continuous scale invariance at criticality is reduced to a discrete scale invariance. This further results in complex-valued critical exponents and spiraling phase boundaries, and it is also accompanied by a complex Liouvillian gap even close to the phase transition. As direct evidence of the non-equilibrium nature of the NEFPs, we show that the fluctuation-dissipation relation is violated at all scales, leading to an effective temperature that becomes "hotter" and "hotter" at longer and longer wavelengths. Finally, we argue that this non-equilibrium behavior can be observed in cavity arrays with cross-Kerr nonlinearities.Comment: 19+11 pages, 7+9 figure
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