1,869 research outputs found
Increasing the detectability of external influence on precipitation by correcting feature location in GCMs
Understanding how precipitation varies as the climate changes is essential to determining the true impact of global warming. This is a difficult task not only due to the large internal variability observed in precipitation but also because of a limited historical record and large biases in simulations of precipitation by general circulation models (GCMs). Here we make use of a technique that spatially and seasonally transforms GCM fields to reduce location biases and investigate the potential of this bias correction to study historical changes. We use two versions of this bias correctionâone that conserves intensities and another that conserves integrated precipitation over transformed areas. Focussing on multimodel ensemble means, we find that both versions reduce RMS error in the historical trend by approximately 11% relative to the Global Precipitation Climatology Project (GPCP) data set. By regressing GCMs' historical simulations of precipitation onto radiative forcings, we decompose these simulations into anthropogenic and natural time series. We then perform a simple detection and attribution study to investigate the impact of reducing location biases on detectability. A multiple ordinary least squares regression of GPCP onto the anthropogenic and natural time series, with the assumptions made, finds anthropogenic detectability only when spatial corrections are applied. The result is the same regardless of which form of conservation is used and without reducing the dimensionality of the fields beyond taking zonal means. While âdetectabilityâ is dependent both on the exact methodology and the confidence required, this nevertheless demonstrates the potential benefits of correcting location biases in GCMs when studying historical precipitation, especially in cases where a signal was previously undetectable
The EDGE-CALIFA Survey: Interferometric Observations of 126 Galaxies with CARMA
We present interferometric CO observations, made with the Combined Array for Millimeter-wave Astronomy (CARMA) interferometer, of galaxies from the Extragalactic Database for Galaxy Evolution survey (EDGE). These galaxies are selected from the Calar Alto Legacy Integral Field Area (CALIFA) sample, mapped with optical integral field spectroscopy. EDGE provides good-quality CO data (3Ď sensitivity before inclination correction, resolution âź1.4 kpc) for 126 galaxies, constituting the largest interferometric CO survey of galaxies in the nearby universe. We describe the survey and data characteristics and products, then present initial science results. We find that the exponential scale lengths of the molecular, stellar, and star-forming disks are approximately equal, and galaxies that are more compact in molecular gas than in stars tend to show signs of interaction. We characterize the molecular-to-stellar ratio as a function of Hubble type and stellar mass and present preliminary results on the resolved relations between the molecular gas, stars, and star-formation rate. We then discuss the dependence of the resolved molecular depletion time on stellar surface density, nebular extinction, and gas metallicity. EDGE provides a key data set to address outstanding topics regarding gas and its role in star formation and galaxy evolution, which will be publicly available on completion of the quality assessment.Fil: Bolatto, Alberto. University of Maryland; Estados UnidosFil: Wong, Tony. University of Illinois at Urbana; Estados UnidosFil: Utomo, Dyas. University of California at Berkeley; Estados UnidosFil: Blitz, Leo. University of California at Berkeley; Estados UnidosFil: Vogel, Stuart N.. University of Maryland; Estados UnidosFil: SĂĄnchez, SebastiĂĄn F.. Universidad Nacional AutĂłnoma de MĂŠxico; MĂŠxicoFil: Barrera-Ballesteros, Jorge. University Johns Hopkins; Estados UnidosFil: Cao, Yixian. University of Illinois; Estados UnidosFil: Colombo, Dario. Max Planck Institut Fur Radioastronomie; AlemaniaFil: Dannerbauer, Helmut. Universidad de La Laguna; EspaĂąaFil: GarcĂa-Benito, RubĂŠn. Instituto de AstrofĂsica de AndalucĂa; EspaĂąaFil: Herrera-Camus, Rodrigo. Max Planck Institute fĂźr Extraterrestrische Physik; AlemaniaFil: Husemann, Bernd. Max-Planck-Institut fĂźr Astronomie; AlemaniaFil: Kalinova, Veselina. Max Planck Institut fĂźr Radioastronomie; AlemaniaFil: Leroy, Adam K.. Ohio State University; Estados UnidosFil: Leung, Gigi. Max-Planck-Institut fĂźr Astronomie; AlemaniaFil: Levy, Rebecca C.. University of Maryland; Estados UnidosFil: Mast, Damian. Observatorio Astronomico de la Universidad Nacional de Cordoba; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂŠcnicas. Centro CientĂfico TecnolĂłgico Conicet - CĂłrdoba; ArgentinaFil: Ostriker, Eve. University of Princeton; Estados UnidosFil: Rosolowsky, Erik. University of Alberta; CanadĂĄFil: Sandstrom, Karin M.. University of California at San Diego; Estados UnidosFil: Teuben, Peter. University of Maryland; Estados UnidosFil: Van De Ven, Glenn. Max-Planck-Institut fĂźr Astronomie; AlemaniaFil: Walter, Fabian. Max-Planck-Institut fĂźr Astronomie; Alemani
Design and rationale of the high-sensitivity Troponin T Rules Out Acute Cardiac Insufficiency Trial
BACKGROUND:
Acute heart failure (AHF) is a common presentation in the Emergency Department (ED), and most patients are admitted to the hospital. Identification of patients with AHF who have a low risk of adverse events and are suitable for discharge from the ED is difficult, and an objective tool would be useful.
METHODS:
The highly sensitive Troponin T Rules Out Acute Cardiac Insufficiency Trial (TACIT) will enroll ED patients being treated for AHF. Patients will undergo standard ED evaluation and treatment. High-sensitivity troponin T (hsTnT) will be drawn at the time of enrollment and 3 hours after the initial draw. The initial hsTnT draw will be no more than 3 hours after initiation of therapy for AHF (vasodilator, loop diuretic, noninvasive ventilation). Treating clinicians will be blinded to hsTnT results. We will assess whether hsTnT, as a single measurement or in series, can accurately predict patients at low risk of short-term adverse events.
CONCLUSION:
TACIT will explore the value of hsTnT measurements in isolation, or in combination with other markers of disease severity, for the identification of ED patients with AHF who are at low risk of short-term adverse events
Natriuretic peptides and integrated risk assessment for cardiovascular disease. an individual-participant-data meta-analysis
BACKGROUND: Guidelines for primary prevention of cardiovascular diseases focus on prediction of coronary heart disease and stroke. We assessed whether or not measurement of N-terminal-pro-B-type natriuretic peptide (NT-proBNP) concentration could enable a more integrated approach than at present by predicting heart failure and enhancing coronary heart disease and stroke risk assessment.
METHODS: In this individual-participant-data meta-analysis, we generated and harmonised individual-participant data from relevant prospective studies via both de-novo NT-proBNP concentration measurement of stored samples and collection of data from studies identified through a systematic search of the literature (PubMed, Scientific Citation Index Expanded, and Embase) for articles published up to Sept 4, 2014, using search terms related to natriuretic peptide family members and the primary outcomes, with no language restrictions. We calculated risk ratios and measures of risk discrimination and reclassification across predicted 10 year risk categories (ie, <5%, 5% to <7¡5%, and âĽ7¡5%), adding assessment of NT-proBNP concentration to that of conventional risk factors (ie, age, sex, smoking status, systolic blood pressure, history of diabetes, and total and HDL cholesterol concentrations). Primary outcomes were the combination of coronary heart disease and stroke, and the combination of coronary heart disease, stroke, and heart failure.
FINDINGS: We recorded 5500 coronary heart disease, 4002 stroke, and 2212 heart failure outcomes among 95â617 participants without a history of cardiovascular disease in 40 prospective studies. Risk ratios (for a comparison of the top third vs bottom third of NT-proBNP concentrations, adjusted for conventional risk factors) were 1¡76 (95% CI 1¡56-1¡98) for the combination of coronary heart disease and stroke and 2¡00 (1¡77-2¡26) for the combination of coronary heart disease, stroke, and heart failure. Addition of information about NT-proBNP concentration to a model containing conventional risk factors was associated with a C-index increase of 0¡012 (0¡010-0¡014) and a net reclassification improvement of 0¡027 (0¡019-0¡036) for the combination of coronary heart disease and stroke and a C-index increase of 0¡019 (0¡016-0¡022) and a net reclassification improvement of 0¡028 (0¡019-0¡038) for the combination of coronary heart disease, stroke, and heart failure.
INTERPRETATION: In people without baseline cardiovascular disease, NT-proBNP concentration assessment strongly predicted first-onset heart failure and augmented coronary heart disease and stroke prediction, suggesting that NT-proBNP concentration assessment could be used to integrate heart failure into cardiovascular disease primary prevention
DNA cruciform arms nucleate through a correlated but non-synchronous cooperative mechanism
Inverted repeat (IR) sequences in DNA can form non-canonical cruciform
structures to relieve torsional stress. We use Monte Carlo simulations of a
recently developed coarse-grained model of DNA to demonstrate that the
nucleation of a cruciform can proceed through a cooperative mechanism. Firstly,
a twist-induced denaturation bubble must diffuse so that its midpoint is near
the centre of symmetry of the IR sequence. Secondly, bubble fluctuations must
be large enough to allow one of the arms to form a small number of hairpin
bonds. Once the first arm is partially formed, the second arm can rapidly grow
to a similar size. Because bubbles can twist back on themselves, they need
considerably fewer bases to resolve torsional stress than the final cruciform
state does. The initially stabilised cruciform therefore continues to grow,
which typically proceeds synchronously, reminiscent of the S-type mechanism of
cruciform formation. By using umbrella sampling techniques we calculate, for
different temperatures and superhelical densities, the free energy as a
function of the number of bonds in each cruciform along the correlated but
non-synchronous nucleation pathways we observed in direct simulations.Comment: 12 pages main paper + 11 pages supplementary dat
A Solvable Regime of Disorder and Interactions in Ballistic Nanostructures, Part I: Consequences for Coulomb Blockade
We provide a framework for analyzing the problem of interacting electrons in
a ballistic quantum dot with chaotic boundary conditions within an energy
(the Thouless energy) of the Fermi energy. Within this window we show that the
interactions can be characterized by Landau Fermi liquid parameters. When ,
the dimensionless conductance of the dot, is large, we find that the disordered
interacting problem can be solved in a saddle-point approximation which becomes
exact as (as in a large-N theory). The infinite theory shows a
transition to a strong-coupling phase characterized by the same order parameter
as in the Pomeranchuk transition in clean systems (a spontaneous
interaction-induced Fermi surface distortion), but smeared and pinned by
disorder. At finite , the two phases and critical point evolve into three
regimes in the plane -- weak- and strong-coupling regimes separated
by crossover lines from a quantum-critical regime controlled by the quantum
critical point. In the strong-coupling and quantum-critical regions, the
quasiparticle acquires a width of the same order as the level spacing
within a few 's of the Fermi energy due to coupling to collective
excitations. In the strong coupling regime if is odd, the dot will (if
isolated) cross over from the orthogonal to unitary ensemble for an
exponentially small external flux, or will (if strongly coupled to leads) break
time-reversal symmetry spontaneously.Comment: 33 pages, 14 figures. Very minor changes. We have clarified that we
are treating charge-channel instabilities in spinful systems, leaving
spin-channel instabilities for future work. No substantive results are
change
When One Hemisphere Takes Control: Metacontrol in Pigeons (Columba livia)
Vertebrate brains are composed of two hemispheres that receive input, compute, and interact to form a unified response. How the partially different processes of both hemispheres are integrated to create a single output is largely unknown. In some cases one hemisphere takes charge of the response selection--a process known as metacontrol. Thus far, this phenomenon has only been shown in a handful of studies with primates, mostly conducted in humans. Metacontrol, however, is even more relevant for animals like birds with laterally placed eyes and complete chiasmatic decussation since visual input to the hemispheres is largely different.Homing pigeons (Columba livia) were trained with a color discrimination task. Each hemisphere was trained with a different color pair and therefore had a different experience. Subsequently, the pigeons were binocularly examined with two additional stimuli that combined the positive color of one hemisphere with a negative color that had been shown to the other, omitting the availability of a coherent solution and confronting the pigeons with a conflicting situation. Some of the pigeons responded to both stimuli, indicating that none of the hemispheres dominated the overall preference. Some birds, however, responded primarily to one of the conflicting stimuli, showing that they based their choice on the left- or right-monocularly learned color pair, indicating hemispheric metacontrol.We could demonstrate for the first time that metacontrol is a widespread phenomenon that also exists in birds, and thus in principle requires no corpus callosum. Our results are closely similar to those in humans: monocular performance was higher than binocular one and animals displayed different modes of hemispheric dominance. Thus, metacontrol is a dynamic and widely distributed process that possibly constitutes a requirement for all animals with a bipartite brain to confront the problem of choosing between two hemisphere-bound behavioral options
Garden and landscape-scale correlates of moths of differing conservation status: significant effects of urbanization and habitat diversity
Moths are abundant and ubiquitous in vegetated terrestrial environments and are pollinators, important herbivores of wild plants, and food for birds, bats and rodents. In recent years, many once abundant and widespread species have shown sharp declines that have been cited by some as indicative of a widespread insect biodiversity crisis. Likely causes of these declines include agricultural intensification, light pollution, climate change, and urbanization; however, the real underlying cause(s) is still open to conjecture. We used data collected from the citizen science Garden Moth Scheme (GMS) to explore the spatial association between the abundance of 195 widespread British species of moth, and garden habitat and landscape features, to see if spatial habitat and landscape associations varied for species of differing conservation status. We found that associations with habitat and landscape composition were species-specific, but that there were consistent trends in species richness and total moth abundance. Gardens with more diverse and extensive microhabitats were associated with higher species richness and moth abundance; gardens near to the coast were associated with higher richness and moth abundance; and gardens in more urbanized locations were associated with lower species richness and moth abundance. The same trends were also found for species classified as increasing, declining and vulnerable under IUCN (World Conservation Union) criteria
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