340 resultados para Quintic Threefold


Relevância:

10.00% 10.00%

Publicador:

Resumo:

The nature of tetrahedral molecular fragments is investigated in SiSe2 glasses using the molecular-dynamics method. The glass consists of both edge-sharing (ES) and corner-sharing tetrahedra. The ES tetrahedra are the building blocks of chain-like-molecular fragments. The two-edge-sharing tetrahedra are the nucleus, and corner-sharing configurations provide connecting hinges between fragments. Statistics of rings and fragments reveals that threefold and eightfold rings are most abundant, chainlike fragments that are typically 10-15 angstrom long occur mostly in eightfold rings, and the longest fragments occur in elevenfold rings.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Superoxide radical (O2-) is a free radical that may be involved in various toxic processes. Cu-Zn superoxide dismutase catalyses the dismutation of the superoxide free radical and protects cells from oxidative damage, and it has been used clinically. The concentration of Ni2+ and Cu-Zn superoxide dismutase activity were measured in lungs of rats at time intervals of 5, 12, 19, 26, 33, and 40 days following an intratracheal injection of 127 nmol of NiCl2. Nickel chloride increased nickel content and resulted in a significant increase of Cu-Zn superoxide dismutase activity in lungs. This elevation of Cu-Zn superoxide dismutase activity was highest on the 12th day (approximately threefold) and is at levels comparable to controls rats on day 40 onwards. Since Cu-Zn superoxide dismutase activity was increased in lung throughout our experimental period without corresponding increases of Cu2+ and Zn2+, we speculate that the elevation of Cu-Zn superoxide dismutase activity might be due to an increased half-life of the enzyme, induced by nickel.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Relevância:

10.00% 10.00%

Publicador:

Resumo:

In three-dimensional trapped Bose-Einstein condensate (BEC), described by the time-dependent Gross-Pitaevskii-Ginzburg equation, we study the effect of initial conditions on stability using a Gaussian variational approach and exact numerical simulations. We also discuss the validity of the criterion for stability suggested by Vakhitov and Kolokolov. The maximum initial chirp (initial focusing defocusing of cloud) that can lead a stable condensate to collapse even before the number of atoms reaches its critical limit is obtained for several specific cases. When we consider two- and three-body nonlinear terms, with negative cubic and positive quintic terms, we have the conditions for the existence of two phases in the condensate. In this case, the magnitude of the oscillations between the two phases are studied considering sufficient large initial chirps. The occurrence of collapse in a BEC with repulsive two-body interaction is also shown to be possible.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Tuberculosis (TB), caused by Mycobacterium tuberculosis, remains the leading cause of mortality due to a bacterial pathogen. According to the 2004 Global TB Control Report of the World Health Organization, there are 300,000 new cases per year of multi-drug resistant strains (MDR-TB), defined as resistant to isoniazid and rifampicin, and 79% of MDR-TB cases are now super strains, resistant to at least three of the four main drugs used to treat TB. Thus there is a need for the development of effective new agents to treat TB. The shikimate pathway is an attractive target for the development of antimycobacterial agents because it has been shown to be essential for the viability of M. tuberculosis, but absent from mammals. The M. tuberculosis aroG-encoded 3-deoxy-d-arabino-heptulosonate 7-phosphate synthase (mtDAHPS) catalyzes the first committed step in this pathway. Here we describe the PCR amplification, cloning, and sequencing of aroG structural gene from M. tuberculosis H37Rv. The expression of recombinant mtDAHPS protein in the soluble form was obtained in Escherichia coli Rosetta-gami (DE3) host cells without IPTG induction. An approximately threefold purification protocol yielded homogeneous enzyme with a specific activity value of 0.47 U mg-1 under the experimental conditions used. Gel filtration chromatography results demonstrate that recombinant mtDAHPS is a pentamer in solution. The availability of homogeneous mtDAHPS will allow structural and kinetics studies to be performed aiming at antitubercular agents development. © 2004 Elsevier Inc. All rights reserved.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Nitensidine A is a guanidine alkaloid isolated from Pterogyne nitens, a common plant in South America. To gain insight into the biological activity of P. nitens-produced compounds, we examined herein their biological effects on osteoclasts, multinucleated giant cells that regulate bone metabolism by resorbing bone. Among four guanidine alkaloids (i.e., galegine, nitensidine A, pterogynidine, and pterogynine), nitensidine A and pterogynine exhibited anti-osteoclastic effects at 10 μM by reducing the number of osteoclasts on the culture plate whereas galegine and pterogynidine did not. The anti-osteoclastic activities of nitensidine A and pterogynine were exerted in a concentration-dependent manner, whereas nitensidine A exhibited an approximate threefold stronger effect than pterogynine (IC50 values: nitensidine A, 0.93 ± 0.024 μM; pterogynine, 2.7 ± 0.40 μM). In the present study, the anti-osteoclastic effects of two synthetic nitensidine A derivatives (nitensidine AT and AU) were also examined to gain insight into the structural features of nitensidine A that exert an anti-osteoclastic effect. The anti-osteoclastic effect of nitensidine A was greatly reduced by substituting the imino nitrogen atom in nitensidine A with sulfur or oxygen. According to the differences in chemical structures and anti-osteoclastic effects of the four guanidine alkaloids and the two synthetic nitensidine A derivatives, it is suggested that the number, binding site, and polymerization degree of isoprenyl moiety in the guanidine alkaloids and the imino nitrogen atom cooperatively contribute to their anti-osteoclastic effects. © 2013 Springer Science+Business Media Dordrecht.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Pós-graduação em Enfermagem (mestrado profissional) - FMB

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The bursting of the property bubble – subprime mortgage crisis – in 2007 in the United States has engendered panic, recession fears and turmoil in the global financial system. Although the United States economy grew by 0.6 per cent in the last quarter of 2007, down from 4.9 per cent in the previous quarter, day by day worsening scenarios emerge, from escalating oil prices, to a depreciating dollar and financial institutions’ bailout by the Federal Reserve. Many economists and policy makers share the view that a subprime-led recession – i.e. two consecutive quarters with negative growth – is inevitable and will be much deeper and longer than the 2001 dot-com downturn. Moreover, the critical situation of the financial system has driven some analysts to argue that should the monetary policy response fails to restore confidence among investors, the outcome would be the worst crisis seen since the Great Depression. This pessimism is not only among specialists. Indeed, in late March 2008 the Consumer Confidence Index in the United States recorded its lowest level since February 1992. A recession in the United States will undoubtedly have an important impact on the world economy, despite the continuous rapid growth experienced by emerging economies, particularly China and India. The purpose of this article is threefold: first, to characterize the current situation in the United States economy; second, to discuss the economic policy responses; and finally, to elaborate on how Caribbean economies may be affected.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

OBJETIVO: Os ferimentos penetrantes com comprometimento simultâneo das cavidades torácica e abdominal (FTA), além da dificuldade diagnóstica, merecem especial atenção em relação à conduta adotada para o tratamento do espaço pleural. O objetivo do presente estudo foi identificar os principais fatores relacionados à incidência de empiema pleural em pacientes com ferimentos penetrantes localizados na transição toracoabdominal. MÉTODO: Utilizando-se o modelo estatístico de regressão logística múltipla, os autores analisaram 110 pacientes com ferida toracoabdominal penetrante, submetidos à drenagem pleural fechada e laparotomia. A complicação empiema pleural foi estudada quanto à incidência e fatores envolvidos. Considerou-se o nível alfa igual a 0,05. RESULTADOS: Do total, 91 (82,7%) pacientes eram do sexo masculino e 19 (17,3%) do feminino. A faixa etária situou-se entre 13 e 63 anos. Os FTA foram causados por projétil de arma de fogo em 60 casos (54,5%) e por arma branca em 50 casos (45,5%). O empiema pleural incidiu em quatro (3,6%) dos pacientes estudados. Na análise estatística a incidência de empiema pleural esteve relacionada com: lesão de víscera oca (OR=3,1386, p=0.4005); lesão do lado esquerdo do diafragma (OR= 12,98, p=0,1178) e choque hemorrágico à admissão (OR=23,9639, p=0,0250). CONCLUSÕES: A chance da ocorrência de empiema pleural foi cerca de três vezes maior em pacientes com lesão de víscera oca e, de 13 vezes se a esta lesão estava associada à lesão do lado esquerdo do diafragma; aumentando para 24 vezes se estes pacientes apresentavam, concomitantemente, estado de choque hemorrágico à admissão.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Este artigo apresenta um modelo para o fomento da autonomia dos aprendentes, mostra alguns resultados alcançados na aplicação desse modelo e discute desafios ainda a serem enfrentados. O modelo comporta a investigação de áreas problemáticas do processo individual de aprendizagem de cada sujeito, a identificação de seus estilos preferenciais de aprender, o uso de ferramentas tecnológicas para melhorar a autonomia na aprendizagem, o desenvolvimento de um leque maior de estratégias de aprendizagem de línguas e a implementação de rotinas de auto-monitoramento e auto-avaliação. Este modelo tem sido aplicado nos últimos três anos com alunos de Letras cursando Licenciaturas em Alemão, Francês ou Inglês. Três ordens de resultados emergem dos dados da pesquisa: primeiramente, o modelo provou sua eficácia em prover um andaime para a aprendizagem autônoma de línguas dos alunos; em segundo lugar, as experiências de aprendizagem autônoma vividas pelos futuros professores de línguas poderão ser espelhadas em suas vidas profissionais futuras com seus próprios alunos; finalmente, os dados emanados dos participantes da pesquisa podem lançar uma luz sobre a variedade de maneiras pelas quais as pessoas aprendem no contexto local.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)