Non-collinear coupling between magnetic adatoms in carbon nanotubes

The long range character of the exchange coupling between localized magnetic moments indirectly mediated by the conduction electrons of metallic hosts often plays a significant role in determining the magnetic order of low-dimensional structures. In addition to this indirect coupling, here we show that the direct exchange interaction that arises when the moments are not too far apart may induce a non-collinear magnetic order that cannot be characterized by a Heisenberg-like interaction between the magnetic moments. We argue that this effect can be manipulated to control the magnetization alignment of magnetic dimers adsorbed to the walls of carbon nanotubes.Comment: 13 pages, 5 figures, submitted to PR

The role of the equation of state and the space-time dimension in spherical collapse

We study the spherically symmetric collapse of a fluid with non-vanishing radial pressure in higher dimensional space-time. We obtain the general exact solution in the closed form for the equation of state ($P_r = \gamma \rho$) which leads to the explicit construction of the root equation governing the nature (black hole versus naked singularity) of the central singularity. A remarkable feature of the root equation is its invariance for the three cases: (${D+1}, {\gamma = -1}$), (${D}, {\gamma = 0}$) and (${D - 1}, {\gamma = 1}$) where $D$ is the dimension of space-time. That is, for the ultimate end result of the collapse, $D$-dimensional dust, ${D+1}$ - AdS (anti de Sitter)-like and ${D-1}$ - dS-like are absolutely equivalent.Comment: 4 Pages, RevTeX, no figures, minor changes, new references added, Detailed version to follo

Protein kinase C inhibitor and irradiation-induced apoptosis: Relevance of the cytochrome c-mediated caspase-9 death pathway

Caspases are a family of cysteine proteases that constitute the apoptotic cell death machinery, We report the importance of the cytochrome c-mediated caspase-9 death pathway for radiosensitization by the protein kinase C (PKC) inhibitors staurosporine (STP) and PKC-412. In our genetically defined tumor cells, treatment with low doses of STP or the conventional PKC-specific inhibitor PKC-412 in combination with irradiation (5 Gy) potently reduced viability, enhanced mitochondrial cytochrome c release into the cytosol, and specifically stimulated the initiator caspase-9. Whereas treatment with each agent alone had a minimal effect, combined treatment resulted in enhanced caspase-3 activation. This was prevented by broad-range and specific caspase-9 inhibitors and absent in caspase-9-deficient cells. The tumor suppressor p53 was required for apoptosis induction by combined treatment but was dispensable for dose-dependent STP-induced caspase activation. These results demonstrate the requirement for an intact caspase-9 pathway for apoptosis-based radiosensitization by PKC inhibitors and show that STP induces apoptosis independent of p53

About the efficiency behavior of the Portuguese manufacturing firms during the financial crisis

This work studies some effects of the World Financial Crisis on firms in terms of efficiency scores, by measuring how 23K units used inputs and produced outputs, obtained from a set of Portuguese manufacturing firms on three time periods: pre-crisis (2006-2008), pretroika (2009-2011) and troika (2012-2013). We adopt a non-parametric approach, which combines Multidirectional Efficiency Analysis (MEA) with other techniques as cluster analysis, principal component analysis and dimensionality testing, to examine three empirical hypotheses: H(1) the performance of the portuguese firms in the manufacturing sector has been adversely affected by the financial crisis felt in Portugal in the troika years; H(2) due to the financial crisis, the manufacturing sector acquired long-term debt deliberately; and H(3) the financial crisis has affected substantially the food subsector. The results indicate that H(1) is confirmed, but not totally, H(2) is confirmed and H(3) is rejected. We also found surprisingly good affine fittings between inputs and capital, and outputs and EBIT with really good p-values. Hence, we also propose a reduction of the dimensionality of the MEA model, when it is possible to apply model fitting. If the reduction results in one input and one output, we give procedures to visualize and compare between efficiencies scores.info:eu-repo/semantics/publishedVersio

Black string corrections in variable tension braneworld scenarios

Braneworld models with variable tension are investigated, and the corrections on the black string horizon along the extra dimension are provided. Such corrections are encrypted in additional terms involving the covariant derivatives of the variable tension on the brane, providing profound consequences concerning the black string horizon variation along the extra dimension, near the brane. The black string horizon behavior is shown to be drastically modified by the terms corrected by the brane variable tension. In particular, a model motivated by the phenomenological interesting case regarding Eotvos branes is investigated. It forthwith provides further physical features regarding variable tension braneworld scenarios, heretofore concealed in all previous analysis in the literature. All precedent analysis considered uniquely the expansion of the metric up to the second order along the extra dimension, what is able to evince solely the brane variable tension absolute value. Notwithstanding, the expansion terms aftermath, further accomplished in this paper from the third order on, elicits the successive covariant derivatives of the brane variable tension, and their respective coupling with the extrinsic curvature, the Weyl tensor, and the Riemann and Ricci tensors, as well as the scalar curvature. Such additional terms are shown to provide sudden modifications in the black string horizon in a variable tension braneworld scenarioComment: 12 pages, 5 figures, accepted in PR

Síntese de Ferritas Dopadas Com Cobre à Partir da Reciclagem de Baterias Ion-Li (CuFe2O4-LiBs) e Suas Aplicações na Descoloração do Corante Azul de Metileno Pelo Processo Foto Fenton Heterogêneo e Como Pseudocapacitor Eletroquímico

Neste estudo, foi utilizado um método de co-precipitação para a síntese de Fe2O3/ Fe3O4 e CuFe2O4-A a partir de reagentes comerciais e CuFe2O4-LiB a partir de cobre reciclado do coletor de corrente de uma bateria de íon lítio (LiBs). A difração de raios X identificou a estrutura tetragonal de CuFe2O4-LiB. A microscopia eletrônica de varredura e a microscopia eletrônica de transmissão mostraram aglomerados de partículas esféricas nanométricas. As propriedades fotocatalíticas foram analisadas monitorando a descoloração do azul de metileno (AM) em um processo foto-Fenton heterogêneo na presença de radiação solar. As condições ideais para a descoloração de AM, determinadas usando um planejamento fatorial, foram 10 mg de CuFe2O4, pH 7 e 0,3 mol.L-1 e H2O2. A eficiência da descoloração foi de 96,1% em 45 minutos de reação. A análise da solução de AM após a descoloração mostrou uma redução de 32,3% na demanda química de oxigênio (DQO) após 105 minutos de reação. A cromatografia de íons detectou ácidos fórmicos e acéticos como produtos de degradação de AM e a espectrometria de emissão óptica de plasma indutivamente acoplada mostrou a presença de íons de ferro e cobre na solução tratada (sistema I) em concentrações aceitáveis pela legislação. A CuFe2O4-LiB mostrou ser um catalisador eficiente para a descoloração/degradação de AM por reações de foto-Fenton heterogênea. A voltametria cíclica foi utilizada para a caracterização eletroquímica de eletrodos compostos por CuFe2O4-LiB. Os eletrodos CuFe2O4-LiB mostraram grande reversibilidade, eficiência de carga e uma capacitância específica de 2,4 F.g-1 (10,0 mV.s-1), que são características favoráveis para pseudocapacitores. Este estudo investigou a multifuncionalidade de CuFe2O4-LiB como fotocatalisador para a descoloração e degradação de corante AM sob radiação solar e como pseudocapacitor. Portanto, este estudo é de interesse científico, econômico, ambiental e social

Biometria de frutos em um plantio de açaí em Porto Velho, Rondônia.

O objetivo deste trabalho foi realizar a biometria de frutos em um plantio de açaí em Porto Velho, Rondônia

Spinor Fields Classification in Arbitrary Dimensions and New Classes of Spinor Fields on 7-Manifolds

A classification of spinor fields according to the associated bilinear covariants is constructed in arbitrary dimensions and metric signatures, generalizing Lounesto's 4D spinor field classification. In such a generalized classification a basic role is played by the geometric Fierz identities. In 4D Minkowski spacetime the standard bilinear covariants can be either null or non-null -- with the exception of the current density which is invariably different from zero for physical reasons -- and sweep all types of spinor fields, including Dirac, Weyl, Majorana and more generally flagpoles, flag-dipoles and dipole spinor fields. To obtain an analogous classification in higher dimensions we use the Fierz identities, which constrain the covariant bilinears in the spinor fields and force some of them to vanish. A generalized graded Fierz aggregate is moreover obtained in such a context simply from the completeness relation. We analyze the particular and important case of Riemannian 7-manifolds, where the Majorana spinor fields turn out to have a quite special place. In particular, at variance with spinor fields in 4D Minkowski spacetime that are classified in six disjoint classes, spinors in Riemannian 7-manifolds are shown to be classified, according to the bilinear covariants: (a) in just one class, in the real case of Majorana spinors; (b) in four classes, in the most general case. Much like new classes of spinor fields in 4D Minkowski spacetime have been evincing new possibilities in physics, we think these new classes of spinor fields in seven dimensions are, in particular, potential candidates for new solutions in the compactification of supergravity on a seven-dimensional manifold and its exotic versions.Comment: 15 page

Análise do comércio do caranguejo-uçá, Ucides cordatus (Linnaeus, 1763), no município de Macapá-AP.

O caranguejo-uçá é um importante recurso pesqueiro que se encontra sobre explorado em todo litoral brasileiro. Desempenha papel tanto econômico, quando fonte de renda para os atores da cadeia produtiva, quanto ecológico, na manutenção dos ecossistemas de mangues. No Amapá têm ocorrência em três municípios (Amapá, Calçoene e Oiapoque), e é comercializado principalmente no município de Macapá, tornando de fundamental importância a caracterização desta atividade, uma vez que este é o primeiro estudo sobre o comércio da espécie no Estado. Durante nove meses (outubro/2008 a junho/2009) foram realizadas visitas mensais (n=32) às feiras do Mercado Central do Igarapé das Mulheres para aplicação de entrevistas com os vendedores de caranguejo, e para o levantamento de dados biométricos de largura e comprimento do tefalotórax (CC e LC) dos animais comercializados. Aleatoriamente, foram adquiridos 854 exemplares machos que apresentaram LC média de 85,4 mm e CC médio de 65 mm. Verificou-se que os caranguejos comercializados são capturados principalmente nos municípios amapaenses. Os resultados obtidos indicam que há alterações de preço durante o ano, e que essa oscilação está relacionada à oferta com que este recurso é disponibilizado. Os dados obtidos mostram ainda, que houve comercialização durante o período de defeso na Feira do Mercado Central e que os animais comercializados procedem em maior parte de municípios paraenses. De modo geral, concluímos que a Portaria Estadual está sendo respeitada em relação ao tamanho mínimo de captura e a não comercialização de fêmeas, no entanto, os caranguejos continuam a serem comercializados no período legalmente proibido