Quantum phase transitions in alternating spin-(1/2, 5/2) Heisenberg chains

The ground state spin-wave excitations and thermodynamic properties of two types of ferrimagnetic chains are investigated: the alternating spin-1/2 spin-5/2 chain and a similar chain with a spin-1/2 pendant attached to the spin-5/2 site. Results for magnetic susceptibility, magnetization and specific heat are obtained through the finite-temperature Lanczos method with the aim in describing available experimental data, as well as comparison with theoretical results from the semiclassical approximation and the low-temperature susceptibility expansion derived from Takahashi's modified spin-wave theory. In particular, we study in detail the temperature vs. magnetic field phase diagram of the spin-1/2 spin-5/2 chain, in which several low-temperature quantum phases are identified: the Luttinger Liquid phase, the ferrimagnetic plateau and the fully polarized one, and the respective quantum critical points and crossover lines

Mechanical characterization of Iroko wood using small specimens

Despite their favorable physical and mechanical properties for structural use, tropical woods, such as Iroko (Milicia excelsa), present knowledge gaps to be filled mainly about their mechanical characterization, which currently limit their use or result in under- or overdimensioned structural elements. Visual classification, one of the most used methods for characterizing wood, is inaccurate in the case of Iroko due to the wide variety of geographical locations in which this species can be found. In addition, mechanical characterization using test pieces with structural dimensions leads to high and impractical costs. In this context, this study aims to verify the mechanical properties of Iroko (imported from the Republic of the Congo) from small size specimens, a process that is currently standardized only for softwoods, and to verify the correlation of different properties through bending properties and ultrasound tests. Prior to the bending tests, the speed of propagation of ultrasonic waves was measured using the direct method. The results obtained show a good correlation between density and bending properties and the velocity of propagation of ultrasonic waves

Discussão sobre a regularização da piscicultura brasileira: da produção à comercialização.

Introdução. Regularização de projetos aquícolas. Regularização de projetos aquícolas. Exemplos da abertura de empresa rural em outros países. Registro de Aquicultor e Licença de Aquicultor. Espécies cultiváveis. Exemplos de permissão de espécies exóticas para cultivo em outros países. Resumo do processo de regularização das pisciculturas em águas da União. Licenciamento ambiental de projetos de piscicultura. Particularidades do licenciamento em viveiros escavados, barragem e PCH e águas Estaduais. Custos do processo de regularização da área aquícola no Brasil. Exemplos internacionais sobre a regularização das áreas produtivas. Outorga de direito de uso de recursos hídricos para a piscicultura. Exemplos internacionais sobre cessão de uso das áreas produtivas. Regularização da produção. Incentivos para a produção. Tarifa da energia elétrica. Contribuição previdenciária. Regularização na comercialização. Despesca e Abate. Transporte. Guia de trânsito animal e outros documentos. Problemas causados pela falta de Inspeção Sanitária. Registros de estabelecimentos de processamento de pescado. SISB - Uma opção. Considerações Finais. Referências. Anexo 1 - Referências de interesse

Zeta function method and repulsive Casimir forces for an unusual pair of plates at finite temperature

We apply the generalized zeta function method to compute the Casimir energy and pressure between an unusual pair of parallel plates at finite temperature, namely: a perfectly conducting plate and an infinitely permeable one. The high and low temperature limits of these quantities are discussed; relationships between high and low temperature limits are estabkished by means of a modified version of the temperature inversion symmetry.Comment: latex file 9 pages, 3 figure

Spontaneous emission of an atom near a wedge

It is a well known fact that non-trivial boundary conditions affect the interaction between atoms and the always present quantized electromagnetic field. In this paper, we focus on how the spontaneous emission rate of a given excited atom is altered when placed inside a perfectly conducting wedge. We begin by briefly presenting the formalism on which our calculations are founded, proceeding then to a long but straightforward calculation of the transition rate. We present results for a general atom but, for the sake of simplicity, we narrow them down to an effective two-level system in our numerical investigations. From these we conclude that the results are physically sound.Comment: 10 pages, version replaced to match the published on

Kinetic Energy Rate of the Rain Drops Based on the Impact Signal Analysis

The erosive potential of precipitation can be evaluated by the kinetic energy transferred to the soil by the impact of the rain drop. A kinetic energy rate of the rain drops was estimated by the disdrometer classifying impact signals. This equation in the form of power presented an adjustment measure between the rain rate and rainfall quantity of 97% and 95% for continental and maritime rains, respectively. The exponent of the power equation, initially, shows no dependence on the type of rainfall. However, the multiplicative factor presented variation, which can be adjusted according to rainfall events. This equation was validated by the coefficient of determination, the average absolute error and the confidence error. The kinetic energy of precipitation, associated to certain types of soil, will allow the determination of the potential of the erosion caused by the rains.Korea Meteorological Administration Researc

Prevalência e fatores de risco associados à mastite subclínica em rebanhos fornecedores de agroindústrias familiares de Rondônia.

A contagem de células somáticas (CCS) é o indicador geral da saúde do úbere e é utilizada como indicador universal da qualidade do leite. Embora vários fatores possam estar associados à variação na CCS, a ocorrência de mastite é considerada o principal fator, sendo o limite de 200.000 células/ml o mais indicado para estimar uma nova infecção intramamária. O objetivo do trabalho foi estimar a prevalência e os fatores de risco associados à mastite subclínica em rebanhos fornecedores de agroindústrias familiares com serviço de inspeção do estado de Rondônia

Fatores de risco associados à qualidade microbiológica do leite de rebanhos fornecedores de agroindústrias familiares.

Dentre os parâmetros que caracterizam a qualidade do leite, o atendimento ao limite definido na legislação para contagem bacteriana se caracteriza por um desafio à cadeia produtiva de Rondônia. O objetivo do trabalho foi identificar os fatores de risco associados à contagem bacteriana do leite de rebanhos fornecedores de agroindústrias familiares do estado