7,989 research outputs found
Disorder effects at low temperatures in La_{0.7-x}Y_{x}Ca_{0.3}MnO_{3} manganites
With the aim of probing the effect of magnetic disorder in the
low-temperature excitations of manganites, specific-heat measurements were
performed in zero field, and in magnetic fields up to 9 T in polycrystalline
samples of La_{0.7-x}Y_{x}Ca_{0.3}MnO_{3}, with Y concentrations x=0, 0.10, and
0.15. Yttrium doping yielded the appearance of a cluster-glass state, giving
rise to unusual low-temperature behavior of the specific-heat. The main feature
observed in the results is a strong enhancement of the specific-heat linear
term, which is interpreted as a direct consequence of magnetic disorder. The
analysis was further corroborated by resistivity measurements in the same
compounds.Comment: 9 pages, 2 figure
Anisotropic superconducting properties of aligned MgB2 crystallites
Samples of aligned MgB2 crystallites have been prepared, allowing for the
first time the direct identification of an upper critical field anisotropy
Hc2^{ab}/Hc2^{c}= xi_{ab}/xi_{c} ~ 1.73; with xi_{o,ab} ~ 70 A, xi_{o,c} ~ 40
A, and a mass anisotropy ratio m_{ab}/m_{c} ~ 0.3. A ferromagnetic background
signal was identified, possibly related to the raw materials purity.Comment: 4 pages, 4 figures; Revised version to appear in Phys. Rev. Let
The first confirmation of V-type asteroids among the Mars crosser population
The Mars crossing region constitutes a path to deliver asteroids from the
Inner Main Belt to the Earth crossing space. While both the Inner Main Belt and
the population of Earth crossing asteroids contains a significant fraction of
asteroids belonging to the V taxonomic class, only two of such V-type asteroids
has been detected in the Mars crossing region up to now. In this work, we
searched for asteroids belonging to the V class among the population of Mars
crossing asteroids, in order to support alternative paths to the delivery of
this bodies into the Earth crossing region. We selected 18 candidate V-type
asteroids in the Mars crossing region using observations contained in the Sloan
Digital Sky Survey Moving Objects Catalog. Then, we observed 4 of these
candidates to take their visible spectra using the Southern Astrophysical
Research Telescope (SOAR). We also performed the numerical simulation of the
orbital evolution of the observed asteroids. We confirmed that 3 of the
observed asteroids belong to the V class, and one of these may follow a path
that drives it to an Earth collision in some tens of million years
Irreversible magnetization under rotating fields and lock-in effect on ErBa_2Cu_3O_7 single crystal with columnar defects
We have measured the irreversible magnetization M_i of an ErBa_2Cu_3O_7
single crystal with columnar defects (CD), using a technique based on sample
rotation under a fixed magnetic field H. This method is valid for samples whose
magnetization vector remains perpendicular to the sample surface over a wide
angle range - which is the case for platelets and thin films - and presents
several advantages over measurements of M_L(H) loops at fixed angles. The
resulting M_i(\Theta) curves for several temperatures show a peak in the CD
direction at high fields. At lower fields, a very well defined plateau
indicative of the vortex lock-in to the CD develops. The H dependence of the
lock-in angle \phi_L follows the H^{-1} theoretical prediction, while the
temperature dependence is in agreement with entropic smearing effects
corresponding to short range vortex-defects interactions.Comment: 7 pages, 6 figures, to be published in Phys. Rev.
What Do Fact Checkers Fact-check When?
Recent research suggests that not all fact checking efforts are equal: when and what is fact checked plays a pivotal role in effectively correcting misconceptions. In this paper, we propose a framework to study fact checking efforts using Google Trends, a signal that captures search interest over topics on the world's largest search engine. Our framework consists of extracting claims from fact checking efforts, linking such claims with knowledge graph entities, and estimating the online attention they receive. We use this framework to study a dataset of 879 COVID-19-related fact checks done in 2020 by 81 international organizations. Our findings suggest that there is often a disconnect between online attention and fact checking efforts. For example, in around 40% of countries where 10 or more claims were fact checked, half or more than half of the top 10 most popular claims were not fact checked. Our analysis also shows that claims are first fact checked after receiving, on average, 35% of the total online attention they would eventually receive in 2020. Yet, there is a big variation among claims: some were fact checked before receiving a surge of misinformation-induced online attention, others are fact checked much later. Overall, our work suggests that the incorporation of online attention signals may help organizations better assess and prioritize their fact checking efforts. Also, in the context of international collaboration, where claims are fact checked multiple times across different countries, online attention could help organizations keep track of which claims are "migrating" between different countries
Ex-utero intrapartum treatment (or EXIT procedure) in a case of cervical linfangiona
Introdução: Fetos com diagnóstico pré-natal de malformações anatómicas envolvendo a face e/ou o pescoço estão em risco de obstrução das vias aéreas desde o pós-natal imediato. A programação de medidas periparto que previnam a compressão das vias aéreas, mantendo uma adequada circulação fetal, é fundamental no prognóstico.
Caso Clínico: Feto com diagnóstico ecográfico, às 31 semanas de gestação, de volumosa massa cervical e facial, compatível com linfangioma quístico. O caso foi discutido em equipa multidisciplinar, tendo sido decidida a realização de cesariana associada ao procedimento EXIT às 39 semanas de gestação. Após exteriorização do polo cefálico, foi confirmada massa cervical e facial direita, sendo o feto sujeito a intubação oro-traqueal no primeiro minuto. Ao sexto dia de vida foi submetido a cirurgia, com excisão parcial da massa.
Conclusão: O procedimento EXIT permite a manutenção de uma adequada oxigenação fetal enquanto se estabelece uma via aérea patente. Uma adequada coordenação da equipa multidisciplinar é fundamental para o êxito da técnic
Quantum Hall resistance standards from graphene grown by chemical vapor deposition on silicon carbide
Replacing GaAs by graphene to realize more practical quantum Hall resistance
standards (QHRS), accurate to within in relative value, but operating
at lower magnetic fields than 10 T, is an ongoing goal in metrology. To date,
the required accuracy has been reported, only few times, in graphene grown on
SiC by sublimation of Si, under higher magnetic fields. Here, we report on a
device made of graphene grown by chemical vapour deposition on SiC which
demonstrates such accuracies of the Hall resistance from 10 T up to 19 T at 1.4
K. This is explained by a quantum Hall effect with low dissipation, resulting
from strongly localized bulk states at the magnetic length scale, over a wide
magnetic field range. Our results show that graphene-based QHRS can replace
their GaAs counterparts by operating in as-convenient cryomagnetic conditions,
but over an extended magnetic field range. They rely on a promising hybrid and
scalable growth method and a fabrication process achieving low-electron density
devices.Comment: 12 pages, 8 figure
Tristeza parasitária bovina em assentamentos rurais de Corumbá, MS: ocorrência e controle.
bitstream/CPAP/56594/1/CT66.pdfFormato Eletronico
Transcription factors involved in prostate gland adaptation to androgen deprivation
FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQAndrogens regulate prostate physiology, and exert their effects through the androgen receptor. We hypothesized that androgen deprivation needs additional transcription factors to orchestrate the changes taking place in the gland after castration and for the adaptation of the epithelial cells to the androgen-deprived environment, ultimately contributing to the origin of castration-resistant prostate cancer. This study was undertaken to identify transcription factors that regulate gene expression after androgen deprivation by castration (Cas). For the sake of comparison, we extended the analysis to the effects of administration of a high dose of 17 beta-estradiol (E2) and a combination of both (Cas+ E2). We approached this by (i) identifying gene expression profiles and enrichment terms, and by searching for transcription factors in the derived regulatory pathways; and (ii) by determining the density of putative transcription factor binding sites in the proximal promoter of the 10 most up- or down-regulated genes in each experimental group in comparison to the controls Gapdh and Tbp7. Filtering and validation confirmed the expression and localized EVI1 (Mecom), NFY, ELK1, GATA2, MYBL1, MYBL2, and NFkB family members (NFkB1, NFkB2, REL, RELA and RELB) in the epithelial and/or stromal cells. These transcription factors represent major regulators of epithelial cell survival and immaturity as well as an adaptation of the gland as an immune barrier in the absence of functional stimulation by androgens. Elk1 was expressed in smooth muscle cells and was up-regulated after day 4. Evi1 and Nfy genes are expressed in both epithelium and stroma, but were apparently not affected by androgen deprivation.96113FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ2009/16150-6Sem informaçã
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