229 research outputs found

    A Supercondutividade e o Formalismo de Nambu.

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    Neste trabalho foi realizado um estudo da transição de fase supercondutora, no qual delineia a termodinâmica envolvida numa descrição de campo médio (parâmetro de ordem). O modelo de Landau-Ginzburg, para descrever a termodinâmica envolvendo a transição de fase, utiliza um funcional dependente do parâmetro de ordem. A energia livre dada em função deste parâmetro, fornece os elementos essenciais para se extrair o comportamento da entropia, calor específico e o número de superelétrons. Contudo, este modelo não explica como o par de elétrons consegue superar a energia de repulsão Coulombiana e se estabilizar. Usando o formalismo de Nambu é possível expor como isto ocorre. Por outro lado, as cerâmicas supercondutoras (ex. Hg, Re- 1223, estudada no grupo de Física Aplica da UFES), são constituídas de grãos interpenetrantes que formam um conjunto de microjunções Josephson (os weak-links). Sendo assim podem-se usar os conceitos deste tipo de junção para apresentar os processos físicos microscópicos envolvidos nos supercondutores de altas temperaturas. Por fim na dissertação descreve-se a formação deste tipo de junção

    Supercondutividade e a transição de fase supercondutora: Misturas de duas fases na cerâmica (Hg,Re 1223)

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    O foco deste trabalho é a investigação das duas fases intrínsecas de supercondutores estruturais, utilizando como objeto de estudo a resposta magnética e a sua composição granular. Ao investigar a susceptibilidade magnética ac na cerâmica policristalina a base de mercúrio dopada com rênio (Hg0.82Re0.18Ba2Ca2Cu3O8.16) (Hg,Re)- 1223) com o precursor com teor ótimo de oxigênio, pulverizada (reduzida a pó e peneirada) foi possível determinar a temperatura crítica da amostra e observar que ela depende do tamanho de cada do grão. Para a partícula de 20 μm foi encontrada somente uma temperatura crítica de 133K, porém são observadas duas temperaturas críticas (133K e 98 K) ao ser reduzir ainda mais o tamanho da partícula, a uma escala mesoscópica de 600 nm. Este fato foi elucidado por uma extensão da teoria de Ginzburg-Landau utilizando dois parâmetros de ordem para parametrizar o campo escalar complexo e fazendo a conexão com o modelo microscópico responsável por descrever as peculiaridades destes tipos de grãos

    Extra-ocular muscle cells from patients with Graves' ophthalmopathy secrete α (CXCL10) and β (CCL2) chemokines under the influence of cytokines that are modulated by PPARγ

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    To our knowledge, no study has evaluated the involvement of T helper (Th)1- and Th2-chemokines in extra-ocular muscle (EOM) myopathy in "patients with thyroid-associated ophthalmopathy" (TAO-p). We tested the effects of interferon (IFN)γ and tumor necrosis factor (TNF)α stimulation, and of increasing concentrations of peroxisome proliferator-activated receptor (PPAR)γ agonists (pioglitazone or rosiglitazone; 0.1μM-20μM), on Th1-chemokine [C-X-C motif ligand (CXCL)10] and Th2-chemokine [C-C motif ligand (CCL)2] secretion in primary EOM cultures from TAO-p vs. control myoblasts. Moreover, we evaluated serum CXCL10 and CCL2 in active TAO-p with prevalent EOM involvement (EOM-p) vs. those with prevalent orbital fat expansion (OF-p). Serum CXCL10 was higher in OF-p and EOM-p vs. controls, while serum CCL2 was not significantly different in controls, or in OF-p and EOM-p. We showed the expression of PPARγ in EOM cells. In primary EOM cultures from TAO-p: a) CXCL10 was undetectable in the supernatant, IFNγ dose-dependently induced it, whereas TNFα did not; b) EOM produced basally low amounts of CCL2, TNFα dose-dependently induced it, whereas IFNγ did not; c) the combination of TNFα and IFNγ had a significant synergistic effect on CXCL10 and CCL2 secretion; and d) PPARγ agonists have an inhibitory role on the modulation of CXCL10, while they stimulate CCL2 secretion. EOM participates in the self-perpetuation of inflammation by releasing both Th1 (CXCL10) and Th2 (CCL2) chemokines under the influence of cytokines, in TAO. PPARγ agonist activation plays an inhibitory role on CXCL10, but stimulates the release of CCL2

    Assessing climate risk to support urban forests in a changing climate

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    We thank Leslie Brandt and Gregory McPherson (USDA Forest Service, USA), Jakub Kronenberg (University of Lodz, Poland), Shawn Landry (University of South Florida, USA) and Per Anker Pedersen (Faculty of Landscape and Society, Norwegian University of Life Sciences) for their thoughts and contributions. MER, PR, SP and MGT thank Leigh Staas (Macquarie University) and funding from the Hort Frontiers Green Cities Fund, part of the Hort Frontiers strategic partnership initiative developed by Hort Innovation, with coinvestment from Macquarie University, Western Sydney University and the NSW Department of Planning, Industry and Environment and contributions from the Australian Government. DNB acknowledges support from the Research Council of Norway to the ENABLE project through the BiodivERsA COFUND 2015-2016 call for research proposals. BW acknowledges support from FORMAS (dia.nr 2016-20098). Finally, we thank the anonymous reviewers for their critical observations and thoughtful contributions that improved this work. The opinions and findings expressed in this paper are those of the authors and should not be construed to represent any official USDA or US Government determination or policy.Societal Impact Statement Globally, cities are planning for resilience through urban greening initiatives as governments understand the importance of urban forests in improving quality of life and mitigating climate change. However, the persistence of urban forests and the ecosystem benefits they provide are threatened by climate change, and systematic assessments of causes of tree dieback and mortality in urban environments are rare. Long-term monitoring studies and adaptive management are needed to identify and prevent climate change-driven failures and mortality. Research and monitoring when coupled with systematic forecasting will enable governments to incorporate climate change resilience into urban forestry planning. Future scenarios in which urban forests are resilient or in decline will depend on the management and planning actions we make today.The management of urban forests is a key element of resilience planning in cities across the globe. Urban forests provide ecosystem services as well as other nature-based solutions to 4.2 billion people living in cities. However, to continue to do so effectively, urban forests need to be able to thrive in an increasingly changing climate. Trees in cities are vulnerable to extreme heat and drought events, which are predicted to increase in frequency and severity under climate change. Knowledge of species' vulnerability to climate change, therefore, is crucial to ensure provision of desired ecosystem benefits, improve species selection, maintain tree growth and reduce tree mortality, dieback and stress in urban forests. Yet, systematic assessments of causes of tree dieback and mortality in urban environments are rare. We reviewed the state of knowledge of tree mortality in urban forests globally, finding very few frameworks that enable detection of climate change impacts on urban forests and no long-term studies assessing climate change as a direct driver of urban tree dieback and mortality. The effects of climate change on urban forests remain poorly understood and quantified, constraining the ability of governments to incorporate climate change resilience into urban forestry planning.Hort Frontiers Green Cities Fund, Hort Frontiers strategic partnership initiativeResearch Council of NorwaySwedish Research Council Formas 2016-2009

    FOOT: a new experiment to measure nuclear fragmentation at intermediate energies

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    Summary: Charged particle therapy exploits proton or 12C beams to treat deep-seated solid tumors. Due to the advantageous characteristics of charged particles energy deposition in matter, the maximum of the dose is released to the tumor at the end of the beam range, in the Bragg peak region. However, the beam nuclear interactions with the patient tissues induces fragmentation both of projectile and target nuclei and needs to be carefully taken into account. In proton treatments, target fragmentation produces low energy, short range fragments along all the beam range, which deposit a non negligible dose in the entry channel. In 12C treatments the main concern is represented by long range fragments due to beam fragmentation that release their dose in the healthy tissues beyond the tumor. The FOOT experiment (FragmentatiOn Of Target) of INFN is designed to study these processes, in order to improve the nuclear fragmentation description in next generation Treatment Planning Systems and the treatment plans quality. Target (16O and 12C nuclei) fragmentation induced by –proton beams at therapeutic energies will be studied via an inverse kinematic approach, where 16O and 12C therapeutic beams impinge on graphite and hydrocarbon targets to provide the nuclear fragmentation cross section on hydrogen. Projectile fragmentation of 16O and 12C beams will be explored as well. The FOOT detector includes a magnetic spectrometer for the fragments momentum measurement, a plastic scintillator for ΔE and time of flight measurements and a crystal calorimeter to measure the fragments kinetic energy. These measurements will be combined in order to make an accurate fragment charge and isotopic identification. Keywords: Hadrontherapy, Nuclear fragmentation cross sections, Tracking detectors, Scintillating detector

    Clonal chromosomal mosaicism and loss of chromosome Y in elderly men increase vulnerability for SARS-CoV-2

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    The pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, COVID-19) had an estimated overall case fatality ratio of 1.38% (pre-vaccination), being 53% higher in males and increasing exponentially with age. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, we found 133 cases (1.42%) with detectable clonal mosaicism for chromosome alterations (mCA) and 226 males (5.08%) with acquired loss of chromosome Y (LOY). Individuals with clonal mosaic events (mCA and/or LOY) showed a 54% increase in the risk of COVID-19 lethality. LOY is associated with transcriptomic biomarkers of immune dysfunction, pro-coagulation activity and cardiovascular risk. Interferon-induced genes involved in the initial immune response to SARS-CoV-2 are also down-regulated in LOY. Thus, mCA and LOY underlie at least part of the sex-biased severity and mortality of COVID-19 in aging patients. Given its potential therapeutic and prognostic relevance, evaluation of clonal mosaicism should be implemented as biomarker of COVID-19 severity in elderly people. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, individuals with clonal mosaic events (clonal mosaicism for chromosome alterations and/or loss of chromosome Y) showed an increased risk of COVID-19 lethality
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