5,156 research outputs found
Increased tolerance to humans among disturbed wildlife.
Human disturbance drives the decline of many species, both directly and indirectly. Nonetheless, some species do particularly well around humans. One mechanism that may explain coexistence is the degree to which a species tolerates human disturbance. Here we provide a comprehensive meta-analysis of birds, mammals and lizards to investigate species tolerance of human disturbance and explore the drivers of this tolerance in birds. We find that, overall, disturbed populations of the three major taxa are more tolerant of human disturbance than less disturbed populations. The best predictors of the direction and magnitude of bird tolerance of human disturbance are the type of disturbed area (urbanized birds are more tolerant than rural or suburban populations) and body mass (large birds are more tolerant than small birds). By identifying specific features associated with tolerance, these results guide evidence-based conservation strategies to predict and manage the impacts of increasing human disturbance on birds
Value Computations in Ventral Medial Prefrontal Cortex during Charitable Decision Making Incorporate Input from Regions Involved in Social Cognition
Little is known about the neural networks supporting value computation during complex social decisions. We investigated this question using functional magnetic resonance imaging while subjects made donations to different charities. We found that the blood oxygenation level-dependent signal in ventral medial prefrontal cortex (VMPFC) correlated with the subjective value of voluntary donations. Furthermore, the region of the VMPFC identified showed considerable overlap with regions that have been shown to encode for the value of basic rewards at the time of choice, suggesting that it might serve as a common valuation system during decision making. In addition, functional connectivity analyses indicated that the value signal in VMPFC might integrate inputs from networks, including the anterior insula and posterior superior temporal cortex, that are thought to be involved in social cognition
Origin of magnetism and quasiparticles properties in Cr-doped TiO
Combining LSDA+ and an analysis of superexchange interactions beyond DFT,
we describe the magnetic ground states in rutile and anatase Cr-doped TiO.
In parallel, we correct our LSDA+ ground state through GW corrections
(@LSDA+) that reproduce the position of impurity states and the band
gaps in satisfying agreement with experiments. Because of the different
topological coordinations of Cr-Cr bonds in the ground states of rutile and
anatase, superexchange interactions induce either ferromagnetic or
antiferromagnetic couplings of Cr ions. In Cr-doped anatase, this interaction
leads to a new mechanism which stabilizes a ferromagnetic ground state, in
keeping with experimental evidence, without the need to invoke F-center
exchange.Comment: 5<pages, 4 figure
The bandstructure of gold from many-body perturbation theory
The bandstructure of gold is calculated using many-body perturbation theory
(MBPT). Different approximations within the GW approach are considered.
Standard single shot G0W0 corrections shift the unoccupied bands up by ~0.2 eV
and the first sp-like occupied band down by ~0.4 eV, while leaving unchanged
the 5d occupied bands. Beyond G0W0, quasiparticle self-consistency on the
wavefunctions lowers the occupied 5d bands by 0.35 eV. Globally, many-body
effects achieve an opening of the interband gap (5d-6sp gap) of 0.35 to 0.75 eV
approaching the experimental results. Finally, the quasiparticle bandstructure
is compared to the one obtained by the widely used HSE (Heyd, Scuseria, and
Ernzerhof) hybrid functional
Current density distribution mapping in polymer electrolyte membrane fuel cell
A non-uniform utilization of the active area due to inhomogeneous current density distribution is one of the main factors for poor fuel cell performance. Furthermore, it leads to hot points which can be responsible for thermal stress in the membrane electrode assemble (MEA). Therefore, it became extremely important to have a consistent technic to visualize in real time the current density and temperature distribution on the active area. For this purpose a printed circuit board (current scan lin® form S++) was used to measure the current density and temperature distribution. With this equipment it was possible to generate high resolution counters for these two variables. With these results the effect on the current density distribution by different flow fields design, oxygen stoichiometry, and temperature were analysed. Besides, these results can be used to provide crucial data for simulation work, in particular for validation purpose
Hydrogen production from sodium borohydride on a Ni-Ru catalyst : an electrochemical study
Previous work by the authors has demonstrated a high rate and high yield hydrolysis of sodium borohydride, in the presence of a Ni-Ru catalyst synthesized by wet chemistry. The catalyst has been fully characterized and utilized more than 300 times exhibiting high stability and durability. In this work, results of an electrochemical study are reported using the powder catalyst supported on a Ni foam in order to measure the open circuit potential during hydrogen production and to study the reaction using voltammetry and ac impedance. Production rates were as high as 10 Lmin-1gcat -1 at 65ºC. Electrochemical studies indicated that the hydrogen evolution mechanism corresponds to a Volmer- Heyrovsky type, suggested by a Tafel slope of 117 mVdec-1. Tafel region potentials are in agreement with values found for hydrolysis at the open circuit. The Langmuir-Hinshelwood mechanism explains the hydrolysis of sodium borohydride using a Ni-Ru catalyst. The role of Ni and Ru is briefly discussed
Hydrogen production by hydrolysis of sodium borohydride for PEM fuel cells feeding
In this work, hydrogen is produced by a hydrolysis process that uses sodium borohydride as a hydrogen carrier and storage media. High purity hydrogen is obtained at low temperatures with high volumetric and gravimetric storage efficiencies; reaction products are non-toxic. The produced hydrogen can be supply on-demand at specified flow by tailor made developed catalyst. Hydrogen feeding to a low power fuel cell was accomplished. According to experimental conditions conversion rates of 100% are possible. Catalyst is demonstrated to be reusable
Self-control in decision-making involves modulation of the vmPFC valuation system
Every day, individuals make dozens of choices between an alternative with higher overall value and a more tempting but ultimately inferior option. Optimal decision-making requires self-control. We propose two hypotheses about the neurobiology of self-control: (i) Goal-directed decisions have their basis in a common value signal encoded in ventromedial prefrontal cortex (vmPFC), and (ii) exercising self-control involves the modulation of this value signal by dorsolateral prefrontal cortex (DLPFC). We used functional magnetic resonance imaging to monitor brain activity while dieters engaged in real decisions about food consumption. Activity in vmPFC was correlated with goal values regardless of the amount of self-control. It incorporated both taste and health in self-controllers but only taste in non–self-controllers. Activity in DLPFC increased when subjects exercised self-control and correlated with activity in vmPFC
PALEO-PGEM v1.0: a statistical emulator of Pliocene–Pleistocene climate
We describe the development of the “Paleoclimate PLASIM-GENIE (Planet Simulator–Grid-Enabled Integrated Earth system model) emulator” PALEO-PGEM and its application to derive a downscaled high-resolution spatio-temporal description of the climate of the last 5×106 years. The 5×106-year time frame is interesting for a range of paleo-environmental questions, not least because it encompasses the evolution of humans. However, the choice of time frame was primarily pragmatic; tectonic changes can be neglected to first order, so that it is reasonable to consider climate forcing restricted to the Earth's orbital configuration, ice-sheet state, and the concentration of atmosphere CO2. The approach uses the Gaussian process emulation of the singular value decomposition of ensembles of the intermediate-complexity atmosphere–ocean GCM (general circulation model) PLASIM-GENIE. Spatial fields of bioclimatic variables of surface air temperature (warmest and coolest seasons) and precipitation (wettest and driest seasons) are emulated at 1000-year intervals, driven by time series of scalar boundary-condition forcing (CO2, orbit, and ice volume) and assuming the climate is in quasi-equilibrium. Paleoclimate anomalies at climate model resolution are interpolated onto the observed modern climatology to produce a high-resolution spatio-temporal paleoclimate reconstruction of the Pliocene–Pleistocene
Biomassa e estoques de nutrientes em vegetação de pousio sob diferentes manejos em sistema agroflorestal seqüencial de corte-e-trituração na Amazônia Oriental.
O manejo da vegetação de pousio é importante para manutenção da produtividade em sistemas agroflorestais seqüenciais. Durante o período de pousio, o sistema acumula nutrientes para as culturas agrícolas subseqüentes. A introdução de espécies leguminosas associadas à adubação fosfatada de baixa solubilidade pode promover o acúmulo de biomassa e os estoques de nutrientes influenciando positivamente na produtividade das culturas agrícolas. O estudo da biomassa e dos estoques de nutrientes nesses agroecossistemas pode fornecer subsídios para o seu manejo. Este artigo compara estimativas da biomassa e estoques de nutrientes de três vegetações de pousio submetidos a diferentes tratamentos: (1) pousio espontâneo; (2) pousio enriquecido com leguminosas arbóreas (Sclerolobium paniculatum Vogel e Inga edulis Mart.), e (3) pousio enriquecido com leguminosas arbóreas submetidas à adubação fosfatada de baixa solubilidade. O experimento foi conduzido por 23 meses, em um sistema agroflorestal seqüencial de corte-e-trituração no município de Marapanim, Amazônia Oriental. Os resultados mostraram que o sistema de pousio enriquecido com leguminosas arbóreas, submetidas ou não à adubação fosfatada de baixa solubilidade, acumula maiores massas secas e estoques de nutrientes que o sistema com pousio espontâneoEditores técnicos: Roberto Porro, Milton Kanashiro, Maria do Socorro Gonçalves Ferreira, Leila Sobral Sampaio e Gladys Ferreira de Sousa
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