584 research outputs found
Um modelo baseado no indivÃduo para estudo da transmissão da anemia infecciosa equina por mutuca no Pantanal brasileiro.
Resumo. A Anemia Infeciosa Equina (AIE) é uma doença causada por um retrovÃrus e transmitida pelo inseto hematófago conhecido como mutuca (tabanÃdeo), sendo observada nas últimas décadas a prevalência de 50% entre os animais de serviço no Pantanal brasileiro. Este trabalho apresenta um modelo baseado no indivÃduo para analisar a dinâmica de transmissão da AIE pela mutuca no Pantanal. Considerando um perÃodo de 40 anos de simulação, os resultados mostram que a mutuca não pode ser responsável sozinha pela alta prevalência da doença na região, sendo necessário estudos mais detalhados das práticas de manejo usadas.SBIAgro 2013
Uso da modelagem baseada no indivÃduo para estudo da dinâmica de propagação de doença no cavalo pantaneiro.
Este trabalho objetiva o uso da modelagem baseada no indivÃduo (MBI) para analisar a dinâmica de propagação da anemia infecciosa equina (AIE) em cavalos de serviço usando o software TerraME, desenvolvido pelo INPE.CIIC 2013. No 13605
Creating pseudo Kondo-resonances by field-induced diffusion of atomic hydrogen
In low temperature scanning tunneling microscopy (STM) experiments a cerium
adatom on Ag(100) possesses two discrete states with significantly different
apparent heights. These atomic switches also exhibit a Kondo-like feature in
spectroscopy experiments. By extensive theoretical simulations we find that
this behavior is due to diffusion of hydrogen from the surface onto the Ce
adatom in the presence of the STM tip field. The cerium adatom possesses
vibrational modes of very low energy (3-4meV) and very high efficiency (> 20%),
which are due to the large changes of Ce-states in the presence of hydrogen.
The atomic vibrations lead to a Kondo-like feature at very low bias voltages.
We predict that the same low-frequency/high-efficiency modes can also be
observed at lanthanum adatoms.Comment: five pages and four figure
Evaluating public sentiment towards transport policies: A causal analysis of the motorbike ban in Hanoi
Controversial transport policies, such as the proposed ban on non-electric motorbikes in Hanoi, Vietnam, often challenge the status quo and spur resistance among road users. This paper aims to unpack the causal implications of the motorbike ban, with an emphasis on elucidating potential transformations in urban mobility patterns and public sentiment in Hanoi. The research methodology is rooted in an mixed-methods approach. It begins by applying Spatial Propensity Score Matching (SPSM) to a bespoke transport survey to mitigate geographical confounding in the identification of the ban’s causal effects on societal attitudes and behaviours. Subsequently, it applies Ordinal Logistic Regression to quantify the causal influences of diverse socio-economic and demographic factors on public opinion towards the motorbike ban. Together, these methods yield a robust analysis of the policy’s prospective impacts.
Through this framework, the study provides insights into the key factors influencing individual’s opinion on controversial transport policies, such as the motorbike ban in Hanoi. Specifically, the approach reveals 4 key geographical insights into socioeconomic status, public transport perception, motorbike dependency, and automobile affinity among people in Hanoi
New insights into nuclear physics and weak mixing angle using electroweak probes
Using the new results on coherent elastic neutrino-nucleus scattering data in cesium-iodide provided by the COHERENT experiment, we determine a new measurement of the average neutron rms radius of Cs-133 and I-127. In combination with the atomic parity violation (APV) experimental result, we derive the most precise measurement of the neutron rms radii of Cs-133 and I-127, disentangling for the first time the contributions of the two nuclei. By exploiting these measurements we determine the corresponding neutron skin values for Cs-133 and I-127. These results suggest a preference for models which predict large neutron skin values, as corroborated by the only other electroweak measurements of the neutron skin of Pb-208 performed by PREX experiments. Moreover, for the first time, we obtain a data-driven APV+COHERENT measurement of the low-energy weak mixing angle with a percent uncertainty, independent of the value of the average neutron rms radius of Cs-133 and I-127, that is allowed to vary freely in the fit. The value of the low-energy weak mixing angle that we found is slightly larger than the standard model prediction
Long-range Kondo signature of a single magnetic impurity
The Kondo effect, one of the oldest correlation phenomena known in condensed
matter physics, has regained attention due to scanning tunneling spectroscopy
(STS) experiments performed on single magnetic impurities. Despite the
sub-nanometer resolution capability of local probe techniques one of the
fundamental aspects of Kondo physics, its spatial extension, is still subject
to discussion. Up to now all STS studies on single adsorbed atoms have shown
that observable Kondo features rapidly vanish with increasing distance from the
impurity. Here we report on a hitherto unobserved long range Kondo signature
for single magnetic atoms of Fe and Co buried under a Cu(100) surface. We
present a theoretical interpretation of the measured signatures using a
combined approach of band structure and many-body numerical renormalization
group (NRG) calculations. These are in excellent agreement with the rich
spatially and spectroscopically resolved experimental data.Comment: 7 pages, 3 figures + 8 pages supplementary material; Nature Physics
(Jan 2011 - advanced online publication
The significance of sample mass in the analysis of steroid estrogens in sewage sludges and the derivation of partition coefficients in wastewaters
Optimization of an analytical method for determination of steroid estrogens, through minimizing sample size, resulted in recoveries >84%, with relative standard deviations <3% and demonstrated the significance of sample size on method performance. Limits of detection were 2.1–5.3 ng/g. Primary sludges had estrogen concentrations of up to one order of magnitude less than those found in biological sludges (up to 994 ng/g). However, partition coefficients were higher in primary sludges (except estriol), with the most hydrophobic compound (ethinylestradiol) exhibiting the highest Kp value, information which may be of value to those involved in modeling removal during wastewater treatment
Impact of the Dresden-II and COHERENT neutrino scattering data on neutrino electromagnetic properties and electroweak physics
Coherent elastic neutrino-nucleus scattering (CEνNS) represents a powerful tool to investigate key electroweak physics parameters and neutrino properties since its first observation in 2017 by the COHERENT experiment exploiting the spallation neutron source at Oak Ridge National Laboratory. In light of the recent detection of such a process with antineutrinos produced by the Dresden-II reactor scattering off a germanium detector, we revisit the limits so far set on the neutrino magnetic moments, charge radii and millicharges as well as on the weak mixing angle. In order to do so, we also include the contribution of elastic neutrino-electron scattering, whose effect becomes non negligible in some beyond the Standard Model theories. By using different hypotheses for the germanium quenching factor and the reactor antineutrino flux, we provide a measurement of the weak mixing angle at the low-energy scale of the Dresden-II reactor experiment and, thanks to a combined analysis with the latest cesium iodide and argon data set released by the COHERENT Collaboration, we deliver updated limits for the neutrino electromagnetic properties. Interestingly, we are able to set a new best upper limit on the electron neutrino charge radius and significantly improve the other CE nu NS-related limits on the neutrino electric charge and magnetic moment
Fundamentos para a estruturação, desenvolvimento e gestão de redes de pesquisa: o caso da Rede AgroHidro da Embrapa.
A Empresa Brasileira de Pesquisa Agropecuária (Embrapa), uma instituição pública ligada ao Ministério da Agricultura, Pecuária e Abastecimento (Mapa), do governo federal brasileiro, instituiu a Rede AgroHidro para estudar as interações da agricultura com os recursos hÃdricos de bacias hidrográficas em diferentes biomas brasileiros. Para isto realizou-se uma pesquisa quanti-qualitativa de caráter longitudinal. Na primeira fase levantaram-se informações junto aos integrantes da Rede, sobre os aspectos relativos à s competências individuais e à estrutura e gestão da Rede. Na segunda identificaram-se os elementos favorecedores da estruturação, desenvolvimento e gestão da Rede. Concluiu-se que os aspectos organizacionais e as relações e influências destes nas interações sociais ocorridas na Rede devem favorecer ações de troca de dados, informações, conhecimentos e experiências para facilitar a execução das atividades de Pesquisa, Desenvolvimento e Inovação (PD&I); promover uma gestão compartilhada para desenvolver vÃnculos entre os pares; estimular a organização de informações nas diversas áreas de conhecimentos e temas que envolvam as necessidades da Rede; e fortalecer as relações entre os pares a partir do estabelecimento de princÃpios comunicacionais voltados para autonomia crÃtica, dialogismo, corresponsabilidade entre os pares e pensamento complexo. Quanto aos aspectos relacionados à gestão, desenvolvimento e estruturação da Rede AgroHidro concluiu-se que as competências humanas e organizacionais existentes na Rede; o modelo de gestão praticado pelos diversos gestores que a integram; o excesso de burocracia; e o estabelecimento de papéis/atribuições claras entre os seus integrantes são fatores que favorecem, em maior ou menor grau, a estruturação, desenvolvimento e gestão da Rede.ADM 2017
Kondo Conductance in an Atomic Nanocontact from First Principles
The electrical conductance of atomic metal contacts represents a powerful
tool to detect nanomagnetism. Conductance reflects magnetism through anomalies
at zero bias -- generally with Fano lineshapes -- due to the Kondo screening of
the magnetic impurity bridging the contact. A full atomic-level understanding
of this nutshell many-body system is of the greatest importance, especially in
view of our increasing need to control nanocurrents by means of magnetism.
Disappointingly, zero bias conductance anomalies are not presently calculable
from atomistic scratch. In this Letter we demonstrate a working route
connecting approximately but quantitatively density functional theory (DFT) and
numerical renormalization group (NRG) approaches and leading to a
first-principles conductance calculation for a nanocontact, exemplified by a Ni
impurity in a Au nanowire. A Fano-like conductance lineshape is obtained
microscopically, and shown to be controlled by the impurity s-level position.
We also find a relationship between conductance anomaly and geometry, and
uncover the possibility of opposite antiferromagnetic and ferromagnetic Kondo
screening -- the latter exhibiting a totally different and unexplored zero bias
anomaly. The present matching method between DFT and NRG should permit the
quantitative understanding and exploration of this larger variety of Kondo
phenomena at more general magnetic nanocontacts.Comment: 11 pages, 3 figures. Supplementary materials under request at
[email protected]
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