1,096 research outputs found

    The Two-Point Function and the Effective Magnetic Field in Diluted Ising Models on the Cayley Tree

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    Some results on the two-point function and on the analytic structure of the momenta of the effective fugacity at the origin for a class of diluted ferromagnetic Ising models on the Cayley tree are presented.Comment: 22 page

    Aspects of Two-Level Systems under External Time Dependent Fields

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    The dynamics of two-level systems in time-dependent backgrounds is under consideration. We present some new exact solutions in special backgrounds decaying in time. On the other hand, following ideas of Feynman, Vernon and Hellwarth, we discuss in detail the possibility to reduce the quantum dynamics to a classical Hamiltonian system. This, in particular, opens the possibility to directly apply powerful methods of classical mechanics (e.g. KAM methods) to study the quantum system. Following such an approach, we draw conclusions of relevance for ``quantum chaos'' when the external background is periodic or quasi-periodic in time.Comment: To appear in J. Phys. A. Mathematical and Genera

    Converging Perturbative Solutions of the Schroedinger Equation for a Two-Level System with a Hamiltonian Depending Periodically on Time

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    We study the Schroedinger equation of a class of two-level systems under the action of a periodic time-dependent external field in the situation where the energy difference 2epsilon between the free energy levels is sufficiently small with respect to the strength of the external interaction. Under suitable conditions we show that this equation has a solution in terms of converging power series expansions in epsilon. In contrast to other expansion methods, like in the Dyson expansion, the method we present is not plagued by the presence of ``secular terms''. Due to this feature we were able to prove absolute and uniform convergence of the Fourier series involved in the computation of the wave functions and to prove absolute convergence of the epsilon-expansions leading to the ``secular frequency'' and to the coefficients of the Fourier expansion of the wave function

    Hyperuricemia in Chronic Kidney Disease: a Role Yet To Be Explained

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    The role of uric acid as an independent risk factor for chronic kidney disease development and progression is still a matter of discussion. Several observational studies showed a positive association between hyperuricemia and the progression of kidney dysfunction, but others did not, which probably derived from different biases and studies insufficiencies. Moreover, the results from studies on patients in hemodialysis and peritoneal dialysis are even more controversial, with some evidence pointing towards a protective role of uric acid in hemodialysis patients, but not in peritoneal dialysis. In addition to most evidence suggesting a role of uric acid in chronic kidney disease pathogenesis and progression, pharmacological treatment of asymptomatic hyperuricemia is still not indicated, with no consensus on either the uric acid level at which treatment would be beneficial, or the target-level to achieve. There are several studies on the renal benefits of xanthine oxidase inhibitors allopurinol and febuxostat, with heterogeneous results. Most of them showed a renoprotective effect of both drugs, delaying renal disease progression. However, the different results found in other studies makes it difficult to draw definitive conclusions. Despite recent evidence pointing toward an important role of uric acid in the pathogenesis and progression of kidney disorders, and the benefits of its treatment, there are still several unanswered questions, and well-conducted studies are needed to make valid conclusions.info:eu-repo/semantics/publishedVersio

    Technological innovation in banking services: an exploratory analysis to perceptions of the front office employee

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    It is widely recognized that the increased intensity of competition in the banking sector has had direct implications for financial institutions' approach to customers and how they define their business strategy. Considering that the current economic stance embraces innovation and technology as fundamental elements of strategic management and business and economic development, new approaches to the relationship between technological innovation and financial services are essential in achieving competitive advantage. Based on this premise, the purpose of this paper is to analyze the main effects of technological innovation on financial services at the bank branch level by evaluating responses from front office employees. The results show that information and communication technologies are an important lever in the modernization of the sector. Practical implications, strengths and limitations of our empirical study are also presente

    A relação Universidade-Indústria: um caso de transferência da tecnologia em engenharia mecânica e Gestão Industrial

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    A inovação nas pequenas e médias empresas industriais do ramo da Engenharia Mecânica émuitas vezes inexistente ou incipiente, podendo ser facilmente incrementada através de umestreito relacionamento e cooperação com as Universidades e/ou os seus Institutos deInterface. Neste contexto, a Universidade do Porto, através do Departamento de EngenhariaMecânica e Gestão Industrial da Faculdade de Engenharia, fundou em 1986 o INEGI -Instituto de Engenharia Mecânica e Gestão Industrial, com a missão de reforçar a cooperaçãoentre esta Universidade e o meio empresarial. O INEGI participa activamente, há 21 anos, nodesenvolvimento da indústria nacional contribuindo com conhecimento e competênciasdistintas na área da Engenharia Mecânica e Gestão Industrial, assumindo a missão de:Contribuir para o aumento da competitividade da indústria nacional através da investigação edesenvolvimento, demonstração, transferência de tecnologia e formação nas áreas deconcepção e projecto, materiais, produção, energia, manutenção, gestão industrial eambiente. Desde a sua criação, o INEGI tem tido um crescimento sustentado, tendodesenvolvido mais de 1300 projectos para organizações públicas e privadas, estando nestemomento numa fase de internacionalização, através do estabelecimento de protocolos eprojectos conjuntos com instituições internacionais.Esta comunicação pretende demonstrar as vantagens que as empresas podem obter, através deuma ligação ás Universidades e Institutos de Interface, no desenvolvimento de materiais,produtos e processos tecnológicos, permitindo assim aumentar a sua competitividade. Asáreas de intervenção dos projectos inovadores aqui focados abrangem uma grande variedadede temas multidisciplinares, desde as energias renováveis, desenvolvimento de processostecnológicos e sistemas mecânicos, materiais compósitos, prototipagem rápida e tecnologiasavançadas de produção e gestão industrial

    Limitations and perceived delays for diagnosis and staging of lung cancer in Portugal: A nationwide survey analysis

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    Background We aimed to identify the perception of physicians on the limitations and delays for diagnosing, staging and treatment of lung cancer in Portugal. Methods Portuguese physicians were invited to participate an electronic survey (Feb-Apr-2020). Descriptive statistical analyses were performed, with categorical variables reported as absolute and relative frequencies, and continuous variables with non-normal distribution as median and interquartile range (IQR). The association between categorical variables was assessed through Pearson’s chi-square test. Mann-Whitney test was used to compare categorical and continuous variables (Stata v.15.0). Results Sixty-one physicians participated in the study (45 pulmonologists, 16 oncologists), with n = 26 exclusively assisting lung cancer patients. Most experts work in public hospitals (90.16%) in Lisbon (36.07%). During the last semester of 2019, responders performed a median of 85 (IQR 55–140) diagnoses of lung cancer. Factors preventing faster referral to the specialty included poor articulation between services (60.0%) and patients low economic/cultural level (44.26%). Obtaining National Drugs Authority authorization was one of the main reasons (75.41%) for delaying the begin of treatment. The cumulative lag-time from patients’ admission until treatment ranged from 42–61 days. Experts believe that the time to diagnosis could be optimized in around 11.05 days [IQR 9.61–12.50]. Most physicians (88.52%) started treatment before biomarkers results motivated by performance status deterioration (65.57%) or high tumor burden (52.46%). Clinicians exclusively assisting lung cancer cases reported fewer delays for obtaining authorization for biomarkers analysis (p = 0.023). Higher waiting times for surgery (p = 0.001), radiotherapy (p = 0.004), immunotherapy (p = 0.003) were reported by professionals from public hospitals. Conclusions Physicians believe that is possible to reduce delays in all stages of lung cancer diagnosis with further efforts from multidisciplinary teams and hospital administration.This work was supported by AstraZeneca. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

    Biodiversity and characterization of marine mycota from Portuguese waters

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    Biodiversity and characterization of marine mycota from Portuguese waters.— The occurrence, diversity and similarity of marine fungi detected by the sum of direct and indirect observations in Fagus sylvatica and Pinus pinaster baits submerged at two Portuguese marinas are analyzed and discussed. In comparison with the data already published in 2010, the higher number of specimens considered in this study led to the higher number of very frequent taxa for these environments and substrata; the significant difference in substrata and also in fungal diversity detected at the two environments is also highlighted, in addition to the decrease in fungal similarity. Because the identification of Lulworthia spp., Fusarium sp., Graphium sp., Phoma sp. and Stachybotrys sp. down to species level was not possible, based only on the morphological characterization, a molecular approach based on the amplification of the LSU rDNA region was performed with isolates of these fungi. This was achieved for three isolates, identified as Fusarium solani, Graphium eumorphum and Stachybotrys chartarum. To achieve this with the other isolates which are more complex taxa, the sequencing of more regions will be considered.Biodiversidad y caracterización de los hongos marinos de las aguas portuguesas.— Se analiza y discute la presencia, la diversidad y la similitud de los hongos marinos detectados mediante la suma de observaciones directas e indirectas utilizando cebos de Fagus sylvatica y Pinus pinaster sumergidos en dos puertos deportivos portugueses. En comparación con los datos ya publicados en 2010, el mayor número de especímenes aquí considerados condujo a un mayor número de taxones muy frecuentes en estos sustratos y medios ambientales; también debe destacarse la diferencia significativa en los sustratos y también en la diversidad fúngica en los dos medios ambientales, además de la disminución de la similitud fúngica. Dado que no fue posible la identificación de Lulworthia spp., Fusarium sp., Graphium sp., Phoma sp., y Stachybotrys sp. hasta el nivel de especie, basándose únicamente en la caracterización morfológica, se llevó a cabo un estudio molecular basado en la amplificación de la región LSU ADNr con extractos de dichos hongos. Ello se consiguió en tres extractos puros, identificados como de Fusarium solani, Graphium eumorphum y Stachybotrys chartarum. Para llevar a cabo este proceso con otros extractos puros pertenecientes a taxones más complejos, se considerará la secuenciación de más regiones.publishe
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