853 research outputs found

    Quantum Electro and Chromodynamics treated by Thompson's heuristic approach

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    In this work we apply Thompson's method (of the dimensions and scales) to study some features of the Quantum Electro and Chromodynamics. This heuristic method can be considered as a simple and alternative way to the Renormalisation Group (R.G.) approach and when applied to QED-lagrangian is able to obtain in a first approximation both the running coupling constant behavior of alpha(mu) and the mass m(mu).The calculations are evaluated just at d_c=4, where d_c is the upper critical dimension of the problem, so that we obtain the logarithmic behavior both for the coupling alpha and the excess of mass Delta m on the energy scale mu. Although our results are well-known in the vast literature of field theories,it seems that one of the advantages of Thompson's method, beyond its simplicity is that it is able to extract directly from QED-lagrangian the physical (finite) behavior of alpha(mu) and m(mu), bypassing hard problems of divergences which normally appear in the conventional renormalisation schemes applied to field theories like QED. Quantum Chromodynamics (QCD) is also treated by the present method in order to obtain the quark condensate value. Besides this, the method is also able to evaluate the vacuum pressure at the boundary of the nucleon. This is done by assumming a step function behavior for the running coupling constant of the QCD, which fits nicely to some quantities related to the strong interaction evaluated through the MIT-bag model.Comment: RevTex, 25 pages, no figure

    Parametrização do modelo CANEGRO para as cultivares brasileiras de cana-de-açúcar.

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    O objetivo do presente trabalho foi a parametrização do modelo CANEGRO para a as cultivares brasileiras IAC 91-1099 e SP 89 1115.Trabalho apresentado na V Mostra de Trabalhos de Estagiários e Bolsistas, Campinas, out. 2009

    Variation of the speed of light with temperature of the expanding universe

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    From an extended relativistic dynamics for a particle moving in a cosmic background field with temperature T, we aim to obtain the speed of light with an explicit dependence on the background temperature of the universe. Although finding the speed of light in the early universe much larger than its current value, our approach does not violate the postulate of special relativity. Moreover, it is shown that the high value of the speed of light in the early universe was drastically decreased before the beginning of the inflationary period. So we are led to conclude that the theory of varying speed of light should be questioned as a possible solution of the horizon problem.Comment: 3 pages and 1 figure; Phys. Rev. D86, 027703 (2012

    The Landscape of Immunotherapy for Retroperitoneal Sarcoma

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    Significant multidisciplinary scientific effort has been undertaken to understand the heterogeneous family of neoplasms that comprise soft tissue sarcomas. Within this family of neoplasms, outcomes for retroperitoneal sarcomas (RPS) are currently limited given a lack of effective therapies. In this review, we focus on immunotherapy and its relationship with the common RPS histologic subtypes. Although initial outcomes for RPS patients with immune checkpoint inhibition alone have been somewhat disappointing, subsequent analyses on histologies, the tumor microenvironment, sarcoma immune class, tumor infiltrating lymphocytes and genetic analysis for tumor mutational burden have yielded insight into the interplay between sarcomas and immunotherapy. Such approaches have all provided critical insight into the environment and characterization of these tumors, with targets for potential immunotherapy in future clinical trials. With this insight, molecularly tailored combination treatments for improving response rates and oncologic outcomes for RPS are promising

    Parametrização do modelo DSSAT/CANEGRO para as cultivares brasileiras de cana-de-açúcar.

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    A parametrização do modelo DSSAT/CANEGRO para a realidade brasileira tem grande importância para a obtenção de uma ferramenta capaz de otimizar o planejamento da produção sucroalcooleira nacional e analisar os impactos do aquecimento global na cultura da cana-de-açúcar no Brasil. O trabalho foi realizado com as cultivares IAC 91-1099 e SP 89-1115. Os dados biométricos foram coletados na APTA em Piracicaba-SP e analisados na Embrapa Informática Agropecuária em Campinas-SP, comparando-se com os dados gerados pelo modelo. Verificou-se que é possível parametrizar os dados de perfilhamento e altura de colmo, com bons resultados, porém a parametrização do IAF necessita de mais estudos. Essas análises indicam possibilidades promissoras para o uso do modelo CANEGRO para as cultivares brasileiras.CBA 2009

    Heart Rate Variability as a Biomarker for Predicting Stroke, Post-stroke Complications and Functionality

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    © The Author(s) 2018. Background: Heart rate variability (HRV) is a non-invasive measure of the function of the autonomic nervous system, and its dynamic nature may provide a means through which stroke and its associated complications may be predicted, monitored, and managed. Objective: The objective of this review is to identify and provide a critique on the most recent uses of HRV in stroke diagnosis/management and highlight areas that warrant further research. Methods: The MEDLINE, CINAHL, and OVID MEDLINE databases were canvassed using a systematic search strategy, for articles investigating the use of HRV in stroke diagnosis and management. Initial paper selections were based on title alone, and final paper inclusion was informed by a full-text critical appraisal. Results: The systematic search returned 98 records, of which 51 were unique. Following screening, 22 records were included in the final systematic review. The included papers provided some information regarding predicting incident stroke, which largely seems to be best predicted by time- and frequency-domain HRV parameters. Furthermore, post-stroke complications and functionality are similarly predicted by time- and frequency-domain parameters, as well as non-linear parameters in some instances. Conclusions: Current research provides good evidence that HRV parameters may have utility as a biomarker for stroke and for post-stroke complications and/or functionality. Future research would benefit from the integration of non-linear, and novel parameters, the hybridisation of HRV parameters, and the expansion of the utilisation of predictive regression and hazard modelling

    Doubly Special Relativity with a minimum speed and the Uncertainty Principle

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    The present work aims to search for an implementation of a new symmetry in the space-time by introducing the idea of an invariant minimum speed scale (VV). Such a lowest limit VV, being unattainable by the particles, represents a fundamental and preferred reference frame connected to a universal background field (a vacuum energy) that breaks Lorentz symmetry. So there emerges a new principle of symmetry in the space-time at the subatomic level for very low energies close to the background frame (vVv\approx V), providing a fundamental understanding for the uncertainty principle, i.e., the uncertainty relations should emerge from the space-time with an invariant minimum speed.Comment: 10 pages, 8 figures, Correlated paper in: http://www.worldscientific.com/worldscinet/ijmpd?journalTabs=read. arXiv admin note: substantial text overlap with arXiv:physics/0702095, arXiv:0705.4315, arXiv:0709.1727, arXiv:0805.120

    Arquitetura foliar e coeficiente de extinção de radiacao solar para duas variedades de cana-de-açúcar.

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    O objetivo do trabalho foi avaliar um método computacional para a determinação do ângulo de inserção foliar (AIF) em cana-de-açúcar com base em imagens digitais, em comparação com medidas de campo segundo uma metodologia tradicional, para duas cultivares de cana-de-açúcar (IAC91-1099 e SP89-1115). Além dessa comparação, estimou-se o coeficiente de extinção (K) para radiação solar, observando-se a propagação do erro de estimativa do AIF nesta estimativa. Os ângulos medidos e os estimados não tiveram diferença estatisticamente significativa a 5% de probabilidade com o teste Tukey, com exceção da folha +2 na cultivar SP89-1115. Isso, contudo, não resultou em diferença na determinação do K medido e estimado. A cultivar SP89-1115 obteve K maior do que o estimado para a cultivar IAC91-1099, variando entre 0,44 e 0,74 considerando valores calculados para as 12:00. Considerando a variação horária de K, os valores oscilaram entre 0,5 e 6,5. Podemos concluir que o método computacional é valido para estimar o ângulo de inserção foliar e existe diferença entre as duas cultivares no ângulo de inserção ocasionando diferença no cálculo do K.CBA 2009

    Condutância foliar e transpiração em cafeeiro irrigado de cinco anos de cultivo.

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    O objetivo deste trabalho foi determinar a condutância estomática e a transpiração de cafeeiro irrigado e sua relação com variáveis climáticas. O experimento foi executado em Piracicaba, SP, Brasil, em cafeeiro cultivar Mundo Novo Apuatã, com 5 anos de plantio, cultivado a pleno sol. As medições nos cinco dias estudados indicaram que a condutância estomática e a transpiração do cafeeiro responderam à variação da temperatura do ar, do saldo de radiação e do vento, sendo mais evidente no dia 24/09/2002. A condutância estomática variou de aproximadamente 0,20 cm s-1 até 0,05 cm s-1 e a transpiração de 6,0 mg m-2s-1 a 0,5 mg m-2s-1 no decorrer dos dias analisados.CBA 2009

    The Future of Targeted Therapy for Leiomyosarcoma

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    Leiomyosarcoma (LMS) is an aggressive subtype of soft tissue sarcoma that arises from smooth muscle cells, most commonly in the uterus and retroperitoneum. LMS is a heterogeneous disease with diverse clinical and molecular characteristics that have yet to be fully understood. Molecular profiling has uncovered possible targets amenable to treatment, though this has yet to translate into approved targeted therapies in LMS. This review will explore historic and recent findings from molecular profiling, highlight promising avenues of current investigation, and suggest possible future strategies to move toward the goal of molecularly matched treatment of LMS. We focus on targeting the DNA damage response, the macrophage-rich micro-environment, the PI3K/mTOR pathway, epigenetic regulators, and telomere biology
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