Tracking spin and charge with spectroscopy in spin-polarised 1D systems

We calculate the spectral function of a one-dimensional strongly interacting chain of fermions, where the response can be well understood in terms of spinon and holon excitations. Upon increasing the spin imbalance between the spin species, we observe the single-electron response of the fully polarised system to emanate from the holon peak while the spinon response vanishes. For experimental setups that probe one-dimensional properties, we propose this method as an additional generic tool to aid the identification of spectral structures, e.g. in ARPES measurements. We show that this applies even to trapped systems having cold atomic gas experiments in mind.Comment: 5 pages, 4 figure

Aplicativo SIGMA EMBRAPA: versão 1.0 para Windows.

O aplicativo SIGMA Embrapa (Sistema de Gerenciamento de Manutenções) foi desenvolvido a fim de informatizar a Área de Manutenção e equipamentos Laboratoriais (AML), permitindo o registro dos serviçoes realizados, pesquisas no banco de dados e geração de relatórios.bitstream/CNPDIA/8890/1/CT28_98.pd

An SU(4) Model of High-Temperature Superconductivity and Antiferromagnetism

We present an SU(4) model of high-temperature superconductivity having many similarities to dynamical symmetries known to play an important role in microscopic nuclear structure physics and in elementary particle physics. Analytical solutions in three dynamical symmetry limits of this model are found: an SO(4) limit associated with antiferromagnetic order; an SU(2) X SO(3) limit that may be interpreted as a d-wave pairing condensate; and an SO(5) limit that may be interpreted as a doorway state between the antiferromagnetic order and the superconducting order. The model suggests a phase diagram in qualitative agreement with that observed in the cuprate superconductors. The relationship between the present model and the SO(5) unification of superconductivity and antiferromagnetic order proposed by Zhang is discussed.Comment: A long paper extended from the early version cond-mat/9903150; accepted by Phys. Rev.

Análise in silico de genes de defesa do café expressos em ramos infectados por Xylella fastidiosa.

Um dos problemas que afetam a cultura do café é o depauperamento da folha do cafeeiro (?Coffee Leaf Scorch? - CLS), causado pela bactéria Xylella fastidiosa. Esta bactéria forma agregados no xilema da planta, impossibilitando a passagem de água e nutrientes. Em virtude da importância econômica da cultura do café para o Brasil e das perdas causadas por X. fastidiosa, uma biblioteca de cDNA (RX1) foi construída utilizando ramos de cafeeiro infectados com esta bactéria e os ESTs (?Expressed sequence tags?) foram incluídos no banco de dados do CafEST (Genoma Funcional de Café). Com o objetivo de identificar genes potencialmente envolvidos nos processos de defesa de cafeeiro infectado com X. fastidiosa, foi realizada uma análise in silico dos ESTs de RX1. Foi analisado um total de 7502 seqüências, que foram agrupadas em 5483 clusters. A análise global baseada em ontologia de função molecular desses clusters revelou que a maior parte dos genes (cerca de 70%) está envolvida com metabolismo e processos fisiológicos celulares. Aproximadamente 1% dos ESTs está envolvido com estresse biótico e 2% com estresse abiótico. Foram encontrados ainda genes relacionados com a resposta a estímulos externos e ao estresse, diferenciação celular, entre outras funções. Dos 5483 clusters da biblioteca RX1, 2254 representam possivelmente genes únicos, pois não foram encontrados nas outras 37 bibliotecas do CafEST, construídas a partir de diferentes tecidos e condições biológicas. Muitos destes genes estão classicamente envolvidos com os processos de defesa da planta, incluindo aqueles que codificam para oxidases, peroxidases, lipoxigenases, proteínas de resistência, entre outros

Interrelation of Superconducting and Antiferromagnetic Gaps in High-Tc Compounds: a Test Case for a Microscopic Theory

Recent angle resolved photoemission (ARPES) data, which found evidence for a d-wave-like modulation of the antiferromagnetic gap, suggest an intimate interrelation between the antiferromagnetic insulator and the superconductor with its d-wave gap. This poses a new challenge to microscopic descriptions, which should account for this correlation between, at first sight, very different states of matter. Here, we propose a microscopic mechanism which provides a definite correlation between these two different gap structures: it is shown that a projected SO(5) theory, which aims at unifying antiferromagnetism and d-wave superconductivity via a common symmetry principle while explicitly taking the Mott-Hubbard gap into account, correctly describes the observed gap characteristics. Specifically, it accounts for both the dispersion and the order of magnitude difference between the antiferromagnetic gap modulation and the superconducting gap.Comment: 8 pages, 5 figure

A solvable model of the genesis of amino-acid sequences via coupled dynamics of folding and slow genetic variation

We study the coupled dynamics of primary and secondary structure formation (i.e. slow genetic sequence selection and fast folding) in the context of a solvable microscopic model that includes both short-range steric forces and and long-range polarity-driven forces. Our solution is based on the diagonalization of replicated transfer matrices, and leads in the thermodynamic limit to explicit predictions regarding phase transitions and phase diagrams at genetic equilibrium. The predicted phenomenology allows for natural physical interpretations, and finds satisfactory support in numerical simulations.Comment: 51 pages, 13 figures, submitted to J. Phys.

Energy efficiency of pasta waste and its effect on performance, carcass, and economic viability of broilers.

Abstract: The objective of this study was to determine the energy value of pasta waste through a metabolism trial and determine the best level of its inclusion in broiler diets. In the metabolism trial, sixty 14-day-old birds were assigned to two treatments (control diet and a diet in which 30% was replaced by the byproduct) with six replicates and five birds per experimental unit. In the performance trial, 525 one-day-old chicks were assigned to treatments consisting of five levels of pasta waste (0, 100, 200, 300, and 400 g kg−1) in the diet, with seven replicates and 15 birds per experimental unit, in a completely randomized design. The phases of up to 7, 21, 35, and 42 days of age were evaluated. At the end, two broilers with average weight were selected per plot for carcass evaluation. An economic analysis was undertaken. The calculated apparent metabolizable energy (AME) value of the waste was 3812 kcal kg−1, and its nitrogen-corrected AME was 3616 kcal kg−1. In the performance trial, no significant difference was detected from 1 to 7 days. However, in the other phases, a decreasing effect was observed on feed intake, weight gain, slaughter weight, hot- and cold-carcass weights, empty- and full-gizzard weights and yields, cuts (chest, drumstick, thigh, wings, and back), and feed conversion worsened. The revenue and gross margin alculated for the diets decreased with pasta waste. Therefore, pasta waste is not a viable alternative, except in the pre-starter phase of broilers