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Search Results: 1 - 10 of 68987 matches for " Gregório Silva Neto "
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On Stable Hypersurfaces with Vanishing Scalar Curvature
Gregório Silva Neto
Mathematics , 2013,
Abstract: We will prove that \emph{there are no stable complete hypersurfaces of $\mathbb{R}^4$ with zero scalar curvature, polynomial volume growth and such that $\dfrac{(-K)}{H^3}\geq c>0$ everywhere, for some constant $c>0$}, where $K$ denotes the Gauss-Kronecker curvature and $H$ denotes the mean curvature of the immersion. Our second result is the Bernstein type one \emph{there is no entire graphs of $\mathbb{R}^4$ with zero scalar curvature such that $\dfrac{(-K)}{H^3}\geq c>0$ everywhere}. At last, it will be proved that, if there exists a stable hypersurface with zero scalar curvature and $\dfrac{(-K)}{H^3}\geq c>0$ everywhere, that is, with volume growth greater than polynomial, then its tubular neighborhood is not embedded for suitable radius.
Monotonicity formula for complete hypersurfaces in the Hyperbolic space and applications
Hilário Alencar,Gregório Silva Neto
Mathematics , 2015,
Abstract: In this paper we prove a monotonicity formula for the integral of the mean curvature for complete and proper hypersurfaces of the hyperbolic space and, as consequences, we obtain a lower bound for the integral of the mean curvature and that the integral of the mean curvature is infinity.
Poincaré and mean value inequalities for hypersurfaces in Riemannian manifolds and applications
Hilário Alencar,Gregório Silva Neto
Mathematics , 2015,
Abstract: In the first part of this paper we prove some new Poincar\'e inequalities, with explicit constants, for domains of any hypersurfaces of Riemannian manifolds with sectional curvature bounded from above, involving the first and the second symmetric functions of the eigenvalues of the second fundamental form of such hypersurfaces. We apply these inequalities to derive some isoperimetric inequalities and to estimate the volume of domains enclosed by compact self-shrinkers in terms of its scalar curvature. In the second part of the paper we prove some mean value inequalities and as consequences we derive some monotonicity results involving the integral of the mean curvature.
Eigenvalue estimates for a class of elliptic differential operators on compact manifolds
Hilário Alencar,Gregório Silva Neto,Detang Zhou
Mathematics , 2013,
Abstract: The motivation of this paper is to study a second order elliptic operator which appears naturally in Riemannian geometry, for instance in the study of hypersurfaces with constant $r$-mean curvature. We prove a generalized Bochner-type formula for such a kind of operators and as applications we obtain some sharp estimates for the first nonzero eigenvalues in two special cases. These results can be considered as generalizations of the Lichnerowicz-Obata Theorem.
Stable hypersurfaces with zero scalar curvature in Euclidean space
Hilário Alencar,Manfredo do Carmo,Gregório Silva Neto
Mathematics , 2015,
Abstract: In this paper we prove some results concerning stability of hypersurfaces in the four dimensional Euclidean space with zero scalar curvature. First we prove there is no complete stable hypersurface with zero scalar curvature, polynomial growth of integral of the mean curvature, and with the Gauss-Kronecker curvature bounded away from zero. We conclude this paper giving a sufficient condition for a regular domain to be stable in terms of the mean and the Gauss-Kronecker curvatures of the hypersurface and the extrinsic diameter of the domain.
Padr es espaciais de deposi o de fezes por bovinos de corte em áreas de pastagem Spatial patterns of deposition of feces by beef cattle in pasture
Sabino Pereira da Silva Neto,Rodrigo Gregório da Silva,Antonio Clementino dos Santos,Francismar Rodrigues Gama
Revista Brasileira de Saúde e Produ??o Animal , 2011,
Abstract: Por meio desta pesquisa objetivou-se obter informa es sobre o padr o de deposi o das fezes de bovinos da ra a Nelore na fase de recria, em áreas de pastagem cultivadas com e sem sombreamento natural, com auxílio da geoestatística, no período das águas. As informa es foram coletadas no mês de mar o de 2010, característico do ter o final do período central da esta o chuvosa. Foi realizada análise geoestatística dos dados bem como análise descritiva para obten o das médias, medianas, variancias, CV, assimetrias e curtoses. Para o teste de normalidade dos dados foi utilizado o Kolmogorov Smirnov. As áreas com sombreamento e sem sombreamento apresentaram dependência espacial moderada e forte, respectivamente. A área com arboriza o apresentou melhor distribui o na deposi o das fezes, enquanto a área sem sombreamento teve elevada concentra o das fezes junto ao bebedouro, cocho, depress es e área de sombra. Observou-se que quanto mais próximo das depress es, maior a deposi o de fezes. A análise geoestatística permitiu visualizar o padr o de deposi o de fezes por bovinos em área de pastagem sob lota o contínua. The survey aimed to collect information on deposition pattern of feces of Nelore catlle in growing phases on pasture with and without natural shading with the use of Geostatistics in rainy season. Information was collected in March 2010, including the central period of rainy season. Data geostatistical analysis was conducted and also the descriptive analysis, obtaining the mean, median, variance, CV, skewness and kurtosis. To teste data normality the Kolmogorov-Smirnov was used. Areas with shading and no shading showed moderate and strong spatial dependent. The area with afforestation had better distribution in the deposition of feces while the area without shading had higher concentration of feces along the drinker, trough, depressions and shaded area. As closer to the depressions, the a greater deposition of feces. The geostatistical analysis allowed visualizing the pattern of feces deposition by cattle in pasture under continuous stocking.
Atividade física, consumo de lipídios e fatores de risco para aterosclerose em adolescentes
Campos, Wagner de;Stabelini Neto, Antonio;Bozza, Rodrigo;Ulbrich, Anderson Zampier;Bertin, Renata Labronici;Mascarenhas, Luis Paulo Gomes;Silva, Sérgio Gregório da;Sasaki, Jeffer Eidi;
Arquivos Brasileiros de Cardiologia , 2010, DOI: 10.1590/S0066-782X2010005000033
Abstract: background: atherosclerosis is the coronary disease that most often affects the adult brazilian population. although it is a predominantly adult disease, the risk factors can appear in young individuals. objective: to verify the association between the physical activity level (pal) and the consumption of lipids with the risk factors for atherosclerosis in adolescents. methods: a total of 260 boys and 237 girls aged 10-18 years were assessed. the pal was estimated based on the activity record proposed by bouchard et al. the consumption of lipids was assessed through the food frequency questionnaire developed by sichieri and everhart. blood pressure was measured using a mercury-column sphygmomanometer. total cholesterol (tc), hdl-c and triglycerides (tg) were measured by the enzymatic-colorimetric method. ldl-c was calculated by friedewald's formula. the statistical analysis was carried out through logistic regression, with a level of significance set at p < 0.05. results: regarding the pal, 17.3% of the boys and 22.6% of the girls were classified as sedentary. as for the diet, 54% and 48.6% of the boys and girls, respectively, presented a consumption of lipids above the recommended level. boys with high tc and ldl-c levels had a higher or to be sedentary than their more active peers. high levels of ldl-c were associated with the excessive consumption of saturated fats in both sexes. conclusion: the results reinforce the previous evidence that young people must be encouraged since an early age to adopt a more physically active lifestyle, associated to more adequate dietary habits.
Mitochondria in the midgut epithelial cells of sugarcane borer parasitized by Cotesia flavipes (Cameron, 1891)
Pinheiro, DO.;Silva, MD.;Gregório, EA.;
Brazilian Journal of Biology , 2010, DOI: 10.1590/S1519-69842010000100023
Abstract: the sugarcane borer diatraea saccharalis (lepidoptera: crambidae) has been controlled by cotesia flavipes (hymenoptera: braconidae); however, very little is known about the effect of the parasitism in the host organs, including the midgut. this work aims to verify mitochondrial alteration in the different midgut epithelial cells of d. saccharalis parasitized by c. flavipes. midgut fragments (anterior and posterior region) of both non-parasitized and parasitized larvae were processed for transmission electron microscopy. the mitochondria of midgut epithelial cell in the parasitized larvae exhibit morphological alteration, represented by matrix rarefaction and vacuolisation. these mitochondrial alterations are more pronounced in the anterior midgut region during the parasitism process, mainly in the columnar cell.
O trágico em A hora e a vez de Augusto Matraga: uma leitura nietzschiana
Gregório, Paulo Henrique da Silva;
Pandaemonium Germanicum , 2010, DOI: 10.1590/S1982-88372010000200009
Abstract: this article presents a study of the short story "a hora e a vez de augusto matraga", by guimar?es rosa, which investigates how the tragic appears in this literary work and how it might represent a redemption signal to the main character. the study is based on nietzsche's concept of the tragedy, constituted by the fusion between two opposite impulses. they are related to apollo and dionysus' spirits that represent appearance and essence, respectively.
A NATUREZA COMO FATO POLITICAMENTE DECISóRIO: POLêMICAS SOBRE OS DIREITOS HUMANOS THE NATURE AS POLITICALLY DECISIVE FACT: POLEMICS ON HUMAN RIGHTS
Sertório de Amorim e Silva Neto
Philósophos : Revista de Filosofia , 2009, DOI: 10.5216/phi.v13i1.4869
Abstract: The paper investigates the context of origin and some controversy about human rights. Its intent is to present the paradox of these rights, the fact that they nevertheless serve to modern political emancipation and the defence of equality and freedom, involving also the bourgeois selfishness and totalitarian political regimes of the century XX assuming both the metaphysical and sublime form as of thing, nature crude and corruptible, gross and corruptible nature. What we want to discuss in this article are the reflections of the political assimilation of an abstract concept such human nature. O artigo investiga o contexto de origem e algumas polêmicas acerca dos direitos humanos. Seu intento é apresentar o paradoxo destes direitos, o fato de que eles, n o obstante sirvam à emancipa o política moderna e à defesa da igualdade e da liberdade, impliquem ainda o egoísmo burguês e os regimes totalitários.Objeto da especula o dos filósofos e mais atualmente das ciências positivistas, o conceito de natureza é bastante ambíguo, assumindo tanto a forma metafísica e sublime, quanto a forma de coisa, natureza bruta e corruptível. O que se deseja discutir neste artigo s o os reflexos políticos da assimila o de um conceito t o abstrato e indeterminado como o de natureza humana.
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