Quantized fields and gravitational particle creation in f(R) expanding universes

The problem of cosmological particle creation for a spatially flat, homogeneous and isotropic Universes is discussed in the context of f(R) theories of gravity. Different from cosmological models based on general relativity theory, it is found that a conformal invariant metric does not forbid the creation of massless particles during the early stages (radiation era) of the Universe.Comment: 14 pages, 2 figure

Phantom Accretion by Black Holes and the Generalized Second Law of Thermodynamics

The accretion of a phantom fluid with non-zero chemical potential by black holes is discussed with basis on the Generalized Second Law of thermodynamics. For phantom fluids with positive temperature and negative chemical potential we demonstrate that the accretion process is possible, and that the condition guaranteeing the positiveness of the phantom fluid entropy coincides with the one required by Generalized Second Law. In particular, this result provides a complementary confirmation that cosmological phantom fluids do not need to have negative temperatures

Международный культурно-академический обмен: опыт личного и научного роста

В этой статье описывается опыт трех студентов, участвовавших в программе международной академической мобильности в рамках специальности Металлургическое машиностроение. Это отчет о пребывании студентов в России в Уральском федеральном университете, который стал возможным благодаря Федеральному университету Оуро Прето (UFOP) и Совету по международным делам (CAINT). Обмен, который проходил с начала февраля до конца июля, стал возможностью для приобретения новых научных, культурных и социальных знаний, в том числе знаний в области бизнеса, экономики и менеджмента. Надеемся на стимулирование специальности «Международная мобильность» на высшем уровне, в виду ее важности для улучшения академического образования и повышения уровня подготовки выпускников из Бразилии путем научного и культурного обмена.This article has objective describe an experience of three students to integrate a program of International Mobility Academic, during the graduate in Metallurgical Engineering. It is an account of students experience at Russia, at Ural Federal University, made possible by Federal University of Ouro Preto – (UFOP) and Coordinating international affairs – (CAINT). The exchange experience, that is preview to have started on February and end on July, had possibility the acquisition of new scientific knowledge, cultural and social, including learning Business, Economic and Management. As a contribution, hope to stimulate and intensify the International Mobility specialty in the ambit of graduate, considering the it important to improvement of academic education and the excellence on superior graduate Brazilian by scientific exchange and culture on exterior

Synthesis of Dehydrodipeptide and N-ethyl-dehydrodipeptide Derivatives with an α-Aminoisobutyric Acid Residue

Several dipeptides with an N-benzyloxycarbonyl or an N-(tert-butyloxycarbonyl) α-aminoisobutyric acid residue and a β-hydroxyamino acid methyl ester were subjected to dehydration to form dehydrodipeptide derivatives. N-Ethylation of these dipeptides using triethyloxonium tetrafluoroborate with potassium tert-butoxide as auxiliary base led to complex mixtures that failed to render pure products. However, when the 4-nitrophenylsulfonyl protecting group was substituted for the benzyloxycarbonyl or tert-butyloxycarbonyl groups and N,N-diisopropylethylamine was substituted for potassium tert-butoxide, the dehydrodipeptide derivatives were selectively N-alkylated at the amino terminal nitrogen in fair to high yields. Alternatively, N-ethylation can be carried out prior to dehydration. Thus, through a combination of dehydration and N-ethylation procedures, it was possible to obtain dipeptides with α-aminoisobutyric acid and dehydroamino acid residues, which are N-alkylated at the amino terminal nitrogen.Foundation for Science and Technology (FCT) – Portugal and Fundo Europeu de Desenvolvimento Regional (FEDER) for financial support to Chemistry Centre of University of Minho. The NMR spectrometer Bruker Avance II+ 400 is part of the National NMR Network and was purchased in the framework of the National Program for Scientific Re-equipment; contract REDE/1517/RMN/2005, with funds from POCI 2010, FEDER and FCT.info:eu-repo/semantics/publishedVersio

Chemical Potential and the Nature of the Dark Energy: The case of phantom

The influence of a possible non zero chemical potential $\mu$ on the nature of dark energy is investigated by assuming that the dark energy is a relativistic perfect simple fluid obeying the equation of state (EoS), $p=\omega \rho$ ($\omega <0, constant$). The entropy condition, $S \geq 0$, implies that the possible values of $\omega$ are heavily dependent on the magnitude, as well as on the sign of the chemical potential. For $\mu >0$, the $\omega$-parameter must be greater than -1 (vacuum is forbidden) while for $\mu < 0$ not only the vacuum but even a phantomlike behavior ($\omega <-1$) is allowed. In any case, the ratio between the chemical potential and temperature remains constant, that is, $\mu/T=\mu_0/T_0$. Assuming that the dark energy constituents have either a bosonic or fermionic nature, the general form of the spectrum is also proposed. For bosons $\mu$ is always negative and the extended Wien's law allows only a dark component with $\omega < -1/2$ which includes vacuum and the phantomlike cases. The same happens in the fermionic branch for $\mu 0$ are permmited only if $-1 < \omega < -1/2$. The thermodynamics and statistical arguments constrain the EoS parameter to be $\omega < -1/2$, a result surprisingly close to the maximal value required to accelerate a FRW type universe dominated by matter and dark energy ($\omega \lesssim -10/21$).Comment: 7 pages, 5 figure

Evolução da pobreza e concentração de renda no meio rural de pernambuco: 2003-2011.

Esta pesquisa visa demonstrar como evoluem a pobreza e concentração de renda no meio rural de Pernambuco por meio de análises nos microdados da Pesquisa Nacional por Amostra de Domicílios (Pnad) usando índices Foster-Greer-Thorbecke (FGT) e o índice de concentração de Gini. Os resultados mostram que a pobreza e concentração de renda não têm tendência de aumento ou queda estatisticamente definida no período analisado, entre 2003 e 2011

Pancreatic Stromal Tumor of Nerve Sheath Origin Treated by Pancreatoduodenectomy

A pancreatic sarcoma of nerve sheath origin is reported in a 28-year-old female patient, who presented with melaena. Preoperative imaging showed an 8.5 cm diameter mass in the head of pancreas. There was bleeding from the papilla of Vater at endoscopy and a highly vascular lesion on arteriography. The patient was submitted to proximal pancreatoduodenectomy and remains symptom-free at 1 year follow-up

Synthesis of N-alkyl-C α, α-dimethylglycine derivatives

The application of trialkyloxonium tetrafluoroborates for N-alkylation of the nonnatural amino acid Cα, α-dimethylglycine is described. Several methyl esters of dimethylglycine protected with different amine protecting groups were subject to N-ethylation or N-methylation with triethyloxonium tetrafluoroborate or trimethyloxonium tetrafluoroborate, respectively. The corresponding N-akyl-Cα, α-dimethylglycine derivatives were obtained in good to high yields. Removal of the methyl ester rendered amino acid derivatives ready for application in peptide synthesis.Foundation for Science and Technology (FCT) – Portugal and Fundo Europeu de Desenvolvimento Regional (FEDER) for financial support to Chemistry Centre of University of Minho. The NMR spectrometer Bruker Avance II+ 400 is part of the National NMR Network and was purchased in the framework of the National Program for Scientific Re-equipment; contract REDE/1517/RMN/2005, with funds from POCI 2010, FEDER and FCT.info:eu-repo/semantics/publishedVersio

Participação escolar: representações dos alunos do 3º ciclo de Aveiro (Portugal)

Este artigo propõe uma reflexão sobre a relação intrínseca entre democracia e educação, particularmente na vertente relacionada com a participação dos discentes nas decisões da escola. Neste sentido e, no quadro do regime de autonomia das escolas portuguesas, importa identificar os espaços formais e informais que são proporcionados aos jovens na tomada de decisões da vida organizativa da escola para compreendermos o papel desta na promoção e capacitação dos jovens para o exercício de uma cidadania ativa. O modo de vida democrático constrói-se através de oportunidades de aprendizagem acerca do mesmo, nomeadamente pela vivência de experiências participativas no contexto escolar. Em 2009, realizámos um estudo, no âmbito da dissertação de uma dissertação de mestrado em Ciências da Educação da Universidade de Aveiro, Portugal, em duas escolas públicas do ensino básico, do Concelho de Aveiro, abrangendo uma população composta por 240 alunos do 8º e 9º ano de escolaridade e 14 delegados de turma. Os resultados mostram que os alunos possuem uma débil participação formal e informal, apesar de o Decreto-lei n. 115-A/98 prever a possibilidade de cada escola, no âmbito da sua autonomia, poder promover e criar espaços de efetiva participação dos alunos. A análise dos instrumentos de autonomia das escolas estudadas revela que a participação dos alunos é assumida, ainda, como um ideal e não já como um efetivo projeto de concretização. Concluímos, pois, que as escolas ainda mantêm uma centralização das decisões nos professores, verificando-se, por parte dos alunos, uma participação formal, passiva e ritualizad