892 resultados para negative dialectic
Resumo:
The effective refractive index of a kind of granular composite, which consists of granular metallic and magnetic inclusions with different radius embedded in a host medium, is theoretically investigated. Results show that for certain volume fractions of these two inclusions, the negative permittivity peak shifts to low frequency and the peak value increases with increasing radius ratio of the radius of magnetic granulae to that of metallic granulae. Simultaneously, peak value of permeability decreases with the radius ratio, and value peak shifts to high frequency with increasing volume fraction of magnetic inclusion. Therefore, the radius ratio can affect the effective refractive index considerably, and it is found that by adjusting the radius ratio, the refractive index may change between negative and positive values for certain volume fractions of the two inclusions. (c) 2005 Elsevier B.V. All rights reserved.
Resumo:
We deliver the general conditions on the synthetic proportions for a homogeneous mixture of ferro- and nonmagnetic substances to become left-handed. As an alternative for left-handed metamaterials, we consider mixing ferromagnetic materials with nonmagnetic microscopic particles. In the mixture, the ferromagnetic material provides the needed permeability via domain wall resonances at high frequencies, whereas the nonmagnetic material gives the required permittivity. Using the effective medium theory, we have found that when the concentration of the nonmagnetic particles falls into a certain range, the refractive index of the mixture is negative, n < 0, which includes the double negative ( epsilon < 0 and mu < 0) and other cases ( e. g. epsilon < 0 and mu > 0). We finally give the requirements on the microscopic material properties for the ferromagnetic materials to reach the domain wall resonances at high frequencies.
Resumo:
Negative ion element impurities breakdown model in HfO2 thin film was reported in this paper. The content of negative ion elements were detected by glow discharge mass spectrum analysis (GDMS); HfO2 thin films were deposited by the electron-beam evaporation method. The weak absorption and laser induced damage threshold (LIDT) of HfO2 thin films were measured to testify the negative ion element impurity breakdown model. It was found that the LIDT would decrease and the absorption would increase with increasing the content of negative ion element. These results indicated that negative ion elements were harmful impurities and would speed up the damage of thin film. (c) 2006 Elsevier B.V. All rights reserved.
Resumo:
We design and experimentally demonstrate some negative dispersion mirrors with optimized Gires-Tournois interferometers. The mirror structure is composed of 38 alternating Ta2O5 and SiO2 layers and could be regarded as two sections: high-reflectivity section consisting of a series of quarter-wavelength optical thickness stacks and negative-dispersion section consisting of only 13 layers. The designed mirrors exhibit the expected performance. These mirrors were fabricated by using ion beam sputtering. By adopting such mirrors, dispersion of a mode-locked femtosecond Ti:sapphire laser has been compensated for mostly. With two series of the mirrors, 32 fs and 15 fs pulses have been obtained respectively.
Resumo:
Background Although depressive symptoms in first episode psychosis have been associated with cannabis abuse, their influence on the long-term functional course of FEP patients who abuse cannabis is unknown. The aims of the study were to examine the influence of subclinical depressive symptoms on the long-term outcome in first episode-psychosis patients who were cannabis users and to assess the influence of these subclinical depressive symptoms on the ability to quit cannabis use. Methods 64 FEP patients who were cannabis users at baseline were followed-up for 5 years. Two groups were defined: (a) patients with subclinical depressive symptoms at least once during follow-up (DPG), and (b) patients without subclinical depressive symptoms during follow-up (NDPG). Psychotic symptoms were measured using the Positive and Negative Syndrome Scale (PANSS), depressive symptoms using the Hamilton Depression Rating Scale (HDRS)-17, and psychosocial functioning was assessed using the Global Assessment of Functioning (GAF). A linear mixed-effects model was used to analyze the combined influence of cannabis use and subclinical depressive symptomatology on the clinical outcome. Results Subclinical depressive symptoms were associated with continued abuse of cannabis during follow-up (beta=4.45; 95% confidence interval [CI]: 1.78 to 11.17; P=.001) and with worse functioning (beta=-5.50; 95% CI: -9.02 to -0.33; P=.009). Conclusions Subclinical depressive symptoms and continued cannabis abuse during follow-up could be predictors of negative outcomes in FEP patients.
Resumo:
The freshwater river systems and floodplains of Bangladesh are the breeding grounds for 13 endemic species of carps and barbs and a large number of other fish species, including a number of exotic carps and other species that have been introduced for aquaculture. Since 1967, breeding of endemic and exotic aquaculture species for seed producton through hypophysation techniques has become a common practice. The paper describes the present status of broodstock management, identifies problems, and suggests some guidelines to control negative selection and inbreeding in hatchery stocks in Bangladesh.
Resumo:
O estudo do fenômeno das adaptações e improvisações de materiais e equipamentos elaboradas no ambiente hospitalar é relativamente recente nas ciências da saúde. Pode-se inferir que esses artefatos decorrem predominantemente devido à adoção de políticas de recorte neoliberal, que gera carência qualitativa e quantitativa de recursos, material e humano, refletindo no gerenciamento administrativo e assistencial do cuidado. Objeto de estudo: as repercussões da prática de improvisar e de adaptar recursos materiais no processo de trabalho da enfermagem em ambiente hospitalar. Os objetivos foram: I) descrever as adaptações e improvisações de materiais e equipamentos no ambiente hospitalar; II) analisar as consequências das adaptações e improvisações de materiais e equipamentos para o processo de trabalho em enfermagem; III) discutir as concepções da prática das adaptações e improvisações para a qualidade do trabalho da enfermagem e para a saúde do cliente, na visão dos trabalhadores de enfermagem. Pesquisa qualitativa e descritiva, desenvolvida em um hospital geral situado no Rio de Janeiro. Os sujeitos foram vinte trabalhadores de enfermagem. A coleta de dados se deu por meio de entrevista semiestruturada e observação sistemática. O método de análise utilizado foi a análise de conteúdo. A partir da apropriação da técnica, emergiram três categorias empíricas: categoria 1: o contexto de criação das adaptações/improvisações no ambiente hospitalar; categoria 2: as adaptações e improvisações de recursos materiais presentes na organização e no processo de trabalho da enfermagem; categoria 3: A dialética da prática das adaptações e improvisações para a qualidade do trabalho da enfermagem e saúde do paciente. Os resultados consolidaram o entendimento de que as adaptações e improvisações surgem predominantemente devido a um contexto de precarização, que impelem os trabalhadores a elaborarem estas criações, a fim de assegurar que o processo de trabalho da enfermagem aconteça. Constatou-se que as adaptações e improvisações interferem no processo de trabalho, no sentido de aumentar o volume de trabalho, o modo operatório da enfermagem, o tempo gasto no processo de criação, os deslocamentos do profissional, a dificuldade do seguimento aos princípios científicos em situações emergenciais. No entanto, depreendeu-se que a enfermagem faz uma multiplicidade de adaptações e improvisações em prol da assistência, porém há concepções dialéticas, as quais simbolizam aspectos positivos e negativos para o trabalho de enfermagem e para a saúde do paciente. Conclui-se que o processo de trabalho na instituição não está em consonância com as necessidades práticas do trabalho da enfermagem, acarretando em sobrecargas, adaptações e improvisações, e em última instância, em transgressões do trabalho prescrito.