Monte Carlo model for nuclear collisions from SPS to LHC energies

A Monte Carlo model to simulate nuclear collisions in the energy range going from SPS to LHC, is presented. The model includes in its initial stage both soft and semihard components, which lead to the formation of color strings. Collectivity is taken into account considering the possibility of strings in color representations higher than triplet or antitriplet, by means of string fusion. String breaking leads to the production of secondaries. At this point, the model can be used as initial condition for further evolution by a transport model. In order to tune the parameters and see the results in nucleus-nucleus collisions, a naif model for rescattering of secondaries is introduced. Results of the model are compared with experimental data, and predictions for RHIC and LHC are shown.Comment: LaTeX, 48 pages, 6 tables, 15 postscript figures included using epsfi

J/psi suppression at SPS and RHIC in the comovers approach

The NA50 collaboration data on the $J/\psi$ suppression are compared with the results obtained in a comovers approach based on the Dual Parton Model (DPM). Predictions for the $J/\psi$ suppression versus the charged multiplicity - measured in the rapidity region of the dimuon trigger - are given for SPS and RHIC energies.Comment: 4 pages, contribution to QM200

Análise da situação da ATEPA (Assistência Técnica e Extensão Pesqueira e Aquícola) no Tocantins: perspectivas e entraves.

O presente estudo tem como objetivo geral analisar a situação dos serviços de ATEPA (Assistência Técnica e Extensão Pesqueira e Aquícola) no Tocantins e, especificamente, mapear e caracterizar as empresas prestadoras de ATEPA; e caracterizar o perfil dos extensionistas que atuam no setor pesqueiro. O estudo tem caráter exploratório-descritivo utilizando-se de fontes primárias, com o apoio da técnica de entrevista semi-estruturada, além de fontes secundárias.Organizado por: Sílvio Ricardo Maurano; AQUACIÊNCIA 2012

Specific heat and thermal conductivity in the mixed state of MgB2

The specific heat C and the electronic and phononic thermal conductivities kappa_e and kappa_{ph} are calculated in the mixed state for magnetic fields H near H_{c2}. The effects of supercurrent flow and Andreev scattering of the Abrikosov vortex lattice on the quasiparticles are taken into account. The resulting function C(H) is nearly linear while kappa_e(H) exhibits an upward curvature near H_{c2}. The slopes decrease with impurity scattering which improves the agreement with the data on MgB_2. The ratio of phonon relaxation times tau_n/tau_s = g(omega_0,H) for phonon energy omega_0, which is nearly a step function at omega_0 = 2Delta for the BCS state, is smeared out and tends to one for increasing H. This leads to a rapid reduction of kappa_{ph}(H) in MgB_2 for relatively small fields due to the rapid suppression of the smaller energy gap.Comment: 8 pages, 4 figures, accepted for publication in Phys. Rev. Letter

Formalização e geração de renda: o caso da assessoria à padaria artesanal comunitária "Mãos de Fibra".

Este relato de experiência é originado de um trabalho de extensão com o objetivo de oferecer assessoria técnica e especializada ao empreendimento econômico solidário Padaria Artesanal Comunitária ?Mãos de Fibra?, localizado na zona rural de Viçosa-MG. A Padaria tem a característica de ser predominantemente formada por mulheres rurais. Estas vêm desenvolvendo a produção e comercialização dos pães caseiros. Boa parte da produção resgata a tradição de receitas de seus antepassados. Nessa perspectiva, esta diversidade de produção de alimentos resultou na criação de um novo serviço, denominado ?lanchão?, servidos em eventos. Entre os objetivos específicos, as ações estão orientadas para a formalização do empreendimento em uma associação e para a agregação de valores aos produtos artesanais e agroindustriais já comercializados com a finalidade de qualificar a inserção do grupo em mercados especializados. Entre os resultados, percebe-se que houve melhorias na comunidade desde a formalização do empreendimento ?Associação dos Agricultores Familiares Mãos de Fibra?, pois permitiu a concretização de uma estrutura organizacional formal e autossustentável, possibilitando oferecer condições dignas de trabalho, aumentar a produção e otimizar os resultados econômicos e sociais. Assim, ao capacitar os membros do empreendimento, qualificou-se a possibilidade dessas famílias se tornarem agentes ativos e com papel destacado no processo de desenvolvimento comunitário, contribuindo para a sustentabilidade socioeconômica e criando condições que propiciem melhor renda e qualidade de vida

Two-dimensional quantum spin-1/2 Heisenberg model with competing interactions

We study the quantum spin-1/2 Heisenberg model in two dimensions, interacting through a nearest-neighbor antiferromagnetic exchange ($J$) and a ferromagnetic dipolar-like interaction ($J_d$), using double-time Green's function, decoupled within the random phase approximation (RPA). We obtain the dependence of $k_B T_c/J_d$ as a function of frustration parameter $\delta$, where $T_c$ is the ferromagnetic (F) transition temperature and $\delta$ is the ratio between the strengths of the exchange and dipolar interaction (i.e., $\delta = J/J_d$). The transition temperature between the F and paramagnetic phases decreases with $\delta$, as expected, but goes to zero at a finite value of this parameter, namely $\delta = \delta_c = \pi /8$. At T=0 (quantum phase transition), we analyze the critical parameter $\delta_c(p)$ for the general case of an exchange interaction in the form $J_{ij}=J_d/r_{ij}^{p}$, where ferromagnetic and antiferromagnetic phases are present.Comment: 4 pages, 1 figur

NIR spectroscopy of the Sun and HD20010 - Compiling a new linelist in the NIR

Context: Effective temperature, surface gravity, and metallicity are basic spectroscopic stellar parameters necessary to characterize a star or a planetary system. Reliable atmospheric parameters for FGK stars have been obtained mostly from methods that relay on high resolution and high signal-to-noise optical spectroscopy. The advent of a new generation of high resolution near-IR spectrographs opens the possibility of using classic spectroscopic methods with high resolution and high signal-to-noise in the NIR spectral window. Aims: We aim to compile a new iron line list in the NIR from a solar spectrum to derive precise stellar atmospheric parameters, comparable to the ones already obtained from high resolution optical spectra. The spectral range covers 10 000 {\AA} to 25 000 {\AA}, which is equivalent to the Y, J, H, and K bands. Methods: Our spectroscopic analysis is based on the iron excitation and ionization balance done in LTE. We use a high resolution and high signal-to-noise ratio spectrum of the Sun from the Kitt Peak telescope as a starting point to compile the iron line list. The oscillator strengths (log gf) of the iron lines were calibrated for the Sun. The abundance analysis was done using the MOOG code after measuring equivalent widths of 357 solar iron lines. Results: We successfully derived stellar atmospheric parameters for the Sun. Furthermore, we analysed HD20010, a F8IV star, from which we derived stellar atmospheric parameters using the same line list as for the Sun. The spectrum was obtained from the CRIRES- POP database. The results are compatible with the ones found in the literature, confirming the reliability of our line list. However, due to the quality of the data we obtain large errors.Comment: 9 pages and 9 figure