3,800 research outputs found
Vacuum Polarization by a Magnetic Flux Tube at Finite Temperature in the Cosmic String Spacetime
In this paper we analyse the effect produced by the temperature in the vacuum
polarization associated with charged massless scalar field in the presence of
magnetic flux tube in the cosmic string spacetime. Three different
configurations of magnetic fields are taken into account: a homogeneous
field inside the tube, a field proportional to and a
cylindrical shell with -function. In these three cases, the axis of the
infinitely long tube of radius coincides with the cosmic string. Because
the complexity of this analysis in the region inside the tube, we consider the
thermal effect in the region outside. In order to develop this analysis, we
construct the thermal Green function associated with this system for the three
above mentioned situations considering points in the region outside the tube.
We explicitly calculate in the high-temperature limit, the thermal average of
the field square and the energy-momentum tensor.Comment: 16 pages, 1 figur
From vortex molecules to the Abrikosov lattice in thin mesoscopic superconducting disks
Stable vortex states are studied in large superconducting thin disks (for
numerical purposes we considered with radius R = 50 \xi). Configurations
containing more than 700 vortices were obtained using two different approaches:
the nonlinear Ginzburg-Landau (GL) theory and the London approximation. To
obtain better agreement with results from the GL theory we generalized the
London theory by including the spatial variation of the order parameter
following Clem's ansatz. We find that configurations calculated in the London
limit are also stable within the Ginzburg-Landau theory for up to ~ 230
vortices. For large values of the vorticity (typically, L > 100), the vortices
are arranged in an Abrikosov lattice in the center of the disk, which is
surrounded by at least two circular shells of vortices. A Voronoi construction
is used to identify the defects present in the ground state vortex
configurations. Such defects cluster near the edge of the disk, but for large L
also grain boundaries are found which extend up to the center of the disk.Comment: 15 pages, 10 figures, RevTex4, submitted to Phys. Rev.
Assessment of N mineralization and leaching in soil using a new in-situ incubation method
RAMIRAN International ConferenceTowards sustainable soil management, the application of organic residues to the soil has to be based on criteria
sustained by experimental studies. Several methods for estimating the amount of N that mineralizes from landapplied
organic residues can be used but laboratory incubations has been the main methodology used due to several
advantages related to practical and economical aspects (Qafoku et al., 2001). However, this type of methodology is
performed under controlled temperature and moisture content, at optimal conditions for the mineralization process,
limiting the extrapolation of laboratory derived values to the field conditions (Hanselman et al., 2004). Since N
mineralization process can be affected by the dynamic of these factors, several authors consider field incubations as
a more realistic method to assess N mineralization (Subler et al., 1995; Halselman et al., 2004). Nevertheless, the
quality of the results obtained depends on the type of reactor devices used for measuring N mineralization under
these conditions. In fact, various reactors devices described in the specific literature, like buried bags (Eno, 1960) or
covered cylinders (Raison et al., 1987), reveal some disadvantages or limitations in monitoring N mineralization in
field conditions. More recently, refining reactor devices, by introducing exchange resins, promoted a more sensible
indicator comparatively to other methods since temperature, moisture content and aeration inside the containerized
soil are close to undisturbed soil (Halselman et al., 2004). Considering that resin-trap incubation is the most
promising in-situ technology in measuring nitrogen net mineralization rates from organic soil amendments, the aim
of the present study is to evaluate the quality of the results obtained by using a new in-situ incubation device for the
determination of N mineralization kinetics in the soil as well as the potential of nitrogen leaching as a potential
alternative use in field studies of N mineralization kinetics from organic residues applied to soils
Duration of Low Wage Employment: A Study Based on a Survival Model
This paper includes a survival analysis which attempts to explain the duration, as in the number of years a worker remains in a low wage situation. Explanatory variables take into account the characteristics of the employee, such as education, age, tenure with the company, gender and nationality, and the characteristics of the job and the company such as industry affiliation, number of employees, age of the company and location.low wage, survival, Portugal
Some remarks on particle size effects on the abrasion of a range of Fe based alloys
The low-stress three body abrasion behaviour of a range of steels was investigated. The tests were carried out in a rubber wheel tester (according to ASTM G65-94, reapproved in 2000) at room temperature. The abrasive particles used were angular alumina particles of four different sizes. The results showed that, in general, the smaller particles (50 8m and 125 8m average size) caused more damage. With these particles, observations of surface morphology indicarted a more intense cutting and ploughing action, leading to more damage, whereas bigger particles i.e. larger 250 8m and 560 8m particles produced less damage, and their action involved more plastic deformation type wear. The 304 SS had a lower abrasion resistance than the 310 SS. For the austentic and ferritic steels the subsurface deformation was larger for impact with the coarser particles. Variations in substrate hardness had no effect on the abrasive behaviour observed. On the whole, the hardest steel (mild steel in martensitic condition) showed the higher extent of damage, irrespective of particle size
Tecnologia de produção de ovinos no Ceará.
Resumo: Esse trabalho Ă© parte de um survey amplo sobre a produção de ovinos no Ceará, incluindo a análise das caracterĂsticas gerais das propriedades, perfil dos produtores, infraestrutura e nĂvel de capitalização, indicadores financeiros, aspectos comerciais e tecnologia de produção. O objeto geral desse artigo Ă© a descrição da tecnologia de produção adotada no estado. Para cumprir o objetivo, realizou-se uma pesquisa classificada quanto aos objetivos como descritiva e quanto Ă natureza ou abordagem do problema como qualitativa e quantitativa. Quanto ao delineamento o estudo caracterizou-se por uma ampla pesquisa de campo em 170 propriedades produtoras de ovinos no estado do Ceará. EstatĂsticas descritivas foram usadas na análise dos dados, com o uso do pacote estatĂstico SPSS, em especial o cálculo de mĂ©dias e freqĂĽĂŞncias. Estes cálculos permitiram observar que o sistema de produção dominante Ă© caracterizado por baixo nĂvel geral tecnolĂłgico em todas as áreas ? manejo, alimentação, reprodução e sanidade. Abstract: The work is part of an extensive survey about sheep production in the Ceará state of Brazil. The general objective of this paper is to describe the prevalent production technology in farms sheep in this state. This objective was achieved through a survey of 170 sheep farmers. Descriptive statistics was applied in the data analysis with the use of SPSS package. From the analysis, it was possible to identify the prevalence of low technological level in the production of sheep, either in production, management, reproduction e feedin
Dor em portadores de prĂłteses totais primárias da anca: causas e avaliação clĂnica
Apesar da prótese total primária da anca ser referenciada como uma das endopróteses com maior sucesso em Ortopedia, uma pequena percentagem de doentes desenvolve um quadro doloroso localizado na anca num curto, médio ou a longo prazo, que pode ou não ser provocado pelo implante.
A razĂŁo da persistĂŞncia da dor apĂłs a implantação de uma prĂłtese da anca pode ser sustentada por fatores intrĂnsecos, por fatores extrĂnsecos loco-regionais ou por outros fatores extrĂnsecos. O estudo das prĂłteses da anca nĂŁo pode ser feito isoladamente, deve estar integrado no complexo funcional vertebro-pĂ©lvico-femoral.
Assim, tendinopatias dos mĂşsculos glĂşteos, do psoas-ilĂaco, dos adutores, dos isquiotĂbiais ou as afeções da coluna lombar, da articulação sacroilĂaca ou do joelho homolateral e, ainda, afeções vasculares, nervosas e fatores psicolĂłgicos podem justificar a presença da dor.
Neste contexto, o desprendimento assĂ©tico e a infeção periprotĂ©tica sĂŁo dois importantes fatores que poderĂŁo estar na origem da dor na anca apĂłs uma prĂłtese total da anca e devem, desde logo, ser excluĂdos antes de se considerarem outras causas menos comuns. Se nĂŁo existir, aparentemente, uma razĂŁo que justifique a dor, o doente deve ser considerado como tendo uma infeção periprotĂ©tica atĂ© prova do contrário.
A anamnese e o exame fĂsico, complementados por provas laboratoriais sanguĂneas e do aspirado articular ou periarticular e, ainda, pelos exames imagiolĂłgicos, constituem os pilares sobre os quais assenta o diagnĂłstico das diferentes afeções que podem estar na gĂ©nese da dor. Com efeito, o hemograma com fĂłrmula leucocitária, a velocidade de sedimentação, a proteĂna C reativa, os exames radiográficos em diferentes incidĂŞncias, a ecografia, a artrocentese com estudo citolĂłgico, microbiolĂłgico, cultura e antibiograma do aspirado articular, a tomografia axial computorizada quando indicada, sĂŁo instrumentos valiosos para se conseguir alcançar um diagnĂłstico definitivo.
Identificada a etiologia da dor, torna-se possĂvel definir a estratĂ©gia terapĂŞutica mais indicada, que Ă© necessariamente diferente de um caso para outro.
Constitui um princĂpio crucial sĂł iniciar a terapĂŞutica apĂłs o conhecimento do diagnĂłstico, quer se trate de uma abordagem conservadora ou, sobretudo, de uma intervenção cirĂşrgica. As dores inexplicáveis, de causa desconhecida, nĂŁo encontram indicação para uma intervenção cirĂşrgica, assim como nĂŁo Ă© de aceitar a origem periarticular da dor sem terem sido eliminadas todas as causas de dor relacionadas com a prĂłtese.
A intervenção cirĂşrgica com a finalidade de se proceder a uma eventual recolocação artroplástica, sem prĂ©vio esclarecimento da etiologia da dor, nĂŁo Ă© uma boa prática produz, muitas vezes, um pobre resultado clĂnico
Short-term effects on soil properties and wheat production from secondary paper sludge application on two Mediterranean agricultural soils
This study was conducted under greenhouse conditions to evaluate the potential use of SPS as a fertilizer, amendment and/or liming
agent for wheat (Triticum aestivum L.). Two representative Mediterranean agricultural soils, a Cambic Arenosol (cmAR) and a Cromic
Cambisol (crCM) were used. Treatments included four sludge rates ranging from 0 to 40 g kg 1 (equivalent of 0, 38, 88 and
120 Mg ha 1). A significant increment in soil pH, organic carbon, N total, available P and exchangeable K were observed in both soils.
Sludge application significantly increased N and decreased Zn, Mn and Cu concentrations in wheat. Wheat grain yields were reduced by
33% and 37% when 120 Mg SPS ha 1 was applied to cmAR and crCM soils, respectively, due apparently to unavailability of Mg. However,
straw yields, with much lower Mg requirements, increased significantly with SPS rates. Secondary pulp mill sludge seems to be a
potential source of organic matter, N, P, K and a potential soil amendment liming agent for acid soils, when appropriate supplemental
fertilizer was provided. For grain crops grown in these soils, addition of Mg is required for proper nutrient balance
Impacto Alimentar Esofágico, um Dilema Diagnóstico
O impacto alimentar esofágico é uma situação que na maioria dos casos é secundária a patologia esofágica congénita ou adquirida, podendo constituir a primeira manifestação da doença.
Descreve-se um rapaz, 11 anos, saudável, com sialorreia e dor retrosternal que surgiram subitamente durante o jantar. Foi submetido a endoscopia digestiva alta, que revelou um fragmento de carne impactado no terço distal do esĂłfago (que foi extraĂdo) e estrias longitudinais na mucosa. A análise histolĂłgica das biĂłpsias esofágicas foi compatĂvel com eosinofilia esofágica. Iniciou terapĂŞutica com inibidor da bomba de protões com melhoria clĂnica e histolĂłgica. O diagnĂłstico diferencial das principais causas de impacto alimentar associadas a eosinofilia esofágica, nomeadamente esofagite eosinofĂlica, doença do refluxo gastroesofágico e eosinofilia esofágica respondedora a inibidor da bomba de protões, constitui um desafio clĂnico.info:eu-repo/semantics/publishedVersio
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