The Charm of the Proton and the Λc+\Lambda _c^{+} Production

We propose a two component model for charmed baryon production in $pp$ collisions consisting of the conventional parton fusion mechanism and fragmentation plus quarks recombination in which a $ud$ valence diquark from the proton recombines with a $c$-sea quark to produce a $\Lambda_c^+$. Our two-component model is compared with the intrinsic charm two-component model and experimental data.Comment: 6 pages, LaTex, 2 figures included, aipproc.sty included. Talk presented at Simposio Latino Americano de Fisica de Altas Energias, Merida, Mexico, November 199

Superconducting Kondo phase in an orbitally-separated bilayer

The nature of superconductivity in heavy-fermion materials is a subject under intense debate, and controlling this many-body state is central for its eventual understanding. Here, we examine how proximity effects may change this phenomenon, by investigating the effects of an additional metallic layer on the top of a Kondo-lattice, and allowing for pairing in the former. We analyze a bilayer Kondo Lattice Model with an on-site Hubbard interaction, $-U$, on the additional layer, using a mean-field approach. For $U=0$, we notice a drastic change in the density-of-states due to multiple-orbital singlet resonating combinations. It destroys the well-known Kondo insulator at half filling, leading to a metallic ground state, which, in turn, enhances antiferromagnetism through the polarization of the conduction electrons. For $U\neq 0$, a superconducting Kondo state sets in at zero temperature, with the occurrence of unconventional pairing amplitudes involving $f$-electrons. We establish that this remarkable feature is only possible due to the proximity effects of the additional layer. At finite temperatures we find that the critical superconducting temperature, $T_c$, decreases with the interlayer hybridization. We have also established that a zero temperature superconducting amplitude tracks $T_c$, which reminisces the BCS proportionality between the superconducting gap and $T_c$.Comment: 11 pages, 10 figure

Determinação de aflatoxinas em milho por cromatografia líquida de alta eficiência com detecção por fluorescência - CLAE/DF.

bitstream/item/84132/1/2009-CTE-0158.pd

The half-filled extended Hubbard model on a square lattice: Phase boundaries from determinant quantum Monte Carlo simulations

The extended Hubbard model (EHM) describes fermions on a lattice coupled through on-site, $U$, and first-neighbor, $V$, interactions. In the context of high-$T_c$ cuprates, antiferromagnetic fluctuations may lead to an attractive channel, hence to superconductivity. Despite interest in the two-dimensional version of the model, the current knowledge about the phase diagram is still far from complete. Here, we report on the results of extensive determinant quantum Monte Carlo simulations for this model at half filling, in which we have used the average sign of the product of fermionic determinants as an additional observable to locate critical points. We arrive at a ground state phase diagram in the $U$-$V$ plane in which the boundaries involving antiferromagnetic, charge-ordered, $s$- and $d$-wave superconductivity, and phase-separated phases are quantitatively set with good accuracy. We have also proposed a partial phase diagram, $T_c(U,V)$, featuring critical temperatures for the CDW and $s$-wave superconducting phases

Agricultura familiar e políticas públicas: o impacto do Pronaf no Rio Grande do Sul.

A aparição do Programa Nacional de Fortalecimento da Agricultura Familiar (PRONAF) marca um momento singular na trajetória do processo de intervenção estatal na agricultura e no mundo rural do Brasil. Apesar de avanços no aperfeiçoamento e ampliação do universo de cobertura, o programa permanece ancorado numa ambigüidade básica tanto em termos do público-alvo a ser beneficiado quanto aos objetivos essenciais que persegue, onde, na retórica oficial, mesclam-se orientações tipicamente produtivistas com compromissos mais amplos, como a geração de empregos, a inclusão social e o desenvolvimento territorial. O artigo em questão desenvolve uma análise do PRONAF à luz de recente pesquisa realizada no Estado do Rio Grande do Sul, inserida no contexto de um convênio firmado entre o PCT/IICA-PRONAF e a Fundação de Economia de Campinas - FECAMP para montar um sistema de acompanhamento das ações do Ministério do Desenvolvimento Agrário e avaliar os impactos deste programa. Os dados finais mostram fortes evidências de diferenciação social dentre os produtores familiares

Magnetic impurities in a charge-ordered background

We investigate how magnetic impurities may affect a system exhibiting charge-density wave (CDW) in its ground state. We consider a disordered Hubbard-Holstein model with a homogeneous electron-phonon interaction, but with a (randomly chosen) fraction of sites displaying a non-zero Coulomb repulsion, $U$, and perform state-of-the-art finite-temperature quantum Monte Carlo simulations. For a single magnetic impurity, charge-charge correlations hamper the spin-spin ones around the repulsive site, thus requiring a strong enough value of $U$ to create non-negligible antiferromagnetic (AFM) correlations. As the number of magnetic impurities increases, these AFM correlations become deleterious to CDW order and its features. First, the critical temperature is drastically reduced, and seems to vanish around 40$\%$ of impurities (for fixed $U/\lambda=2$), which we correlate with the classical percolation threshold. We also notice that just a small amount of disorder suffices to create a \textit{bad insulating} state, with the suppression of both Peierls and spin gaps, even within the charge-ordered phase. Finally, we have also found that pairing correlations are enhanced at large doping, driven by the competition between CDW and AFM tendencies

Obtenção de gases combustíveis via transformação termoquímica de Eucalyptus grandis em reator de leito fluidizado.

Mestrado (Tecnologias) - Universidade de Brasília, Brasília, DF. Orientador: Fabricio Machado Silva. Coorientador CNPAE: Rossano Gambetta

Processamento de carnes de caprinos e ovinos.

A caprinocultura e a ovinocultura são atividades que apresentam destaque no agronegócio brasileiro, mas para consolidar um papel expressivo nas economias regionais há necessidade de serem desenvolvidas ações de natureza profissional capazes de oferecerem produtos de qualidade, sejam animais vivos ou seus produtos processados. Destacaremos as principais etapas que devem ser executadas para a produção de carcaças, e de cortes padronizados para carnes, e produção de peles de boa qualidade.bitstream/item/200085/1/Apostila-PROCESSAMENTO-DE-CARNE-2012.pd