Comment on ``Validity of Feynman's prescription of disregarding the Pauli principle in intermediate states''

In a recent paper Coutinho, Nogami and Tomio [Phys. Rev. A 59, 2624 (1999); quant-ph/9812073] presented an example in which, they claim, Feynman's prescription of disregarding the Pauli principle in intermediate states of perturbation theory fails. We show that, contrary to their claim, Feynman's prescription is consistent with the exact solution of their example.Comment: 1 pag

Doped AB_2 Hubbard Chain: Spiral, Nagaoka and RVB States, Phase Separation and Luttinger Liquid Behavior

We present an extensive numerical study of the Hubbard model on the doped AB$_2$ chain, both in the weak coupling and the infinite-U limit. Due to the special unit cell topology, this system displays a rich variety of phases as function of hole doping ($\delta$) away from half-filling. Near half-filling, spiral states develop in the weak coupling regime, while Nagaoka itinerant ferromagnetism is observed in the infinite-U limit. For higher doping the system phase-separates before reaching a Mott insulating phase of short-range RVB states at $\delta=1/3$. Moreover, for $\delta>1/3$ we observe a crossover, which anticipates the Luttinger liquid behavior for $\delta > 2/3$.Comment: 11 pages, 13 figure

Some vine clones resistant to Plasmopora

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Conservation of Orbital Angular Momentum in Stimulated Down-Conversion

We report on an experiment demonstrating the conservation of orbital angular momentum in stimulated down-conversion. The orbital angular momentum is not transferred to the individual beams of the spontaneous down-conversion, but it is conserved when twin photons are taken individually. We observe the conservation law for an individual beam of the down-conversion through cavity-free stimulated emission.Comment: Submitted for publication in Phys. Rev. Let

Recent results in vine improvement regarding its resistance to downy and powdery mildews

Resistance to mildew remains very important under Portuguese conditions and induced mutations present a great interest to obtain it. γ -rays irradiation was applied to woody material and X-ray was used on in vitro cultures of stem apexes and leaf explants. After doses up to 2000 rad, two resistant mutants were selected: with γ -rays, the resistance being expressed as surrounding necrotic patches; with X-rays, the plant coming out from in vitro culture presented small necrotic patches. Concerning powdery mildew, we are developing new techniques for laboratorial inoculation, including a technique for sowing isolated spores. By using these, we can conduct studies on morphology and biology of the isolated colony, variability of the resistance within the rids varieties and genetic variability of the parasite. Some results concerning these areas are presented

Avaliação dos efeitos de um protocolo com a plataforma NINTENDO WII® nas dimensões cognitivas e físicas /equilíbrio e coordenação) em idosos

Objetivos: Avaliar e quantificar o impacto do tratamento de fisioterapia, utilizando exclusivamente a Nintendo Wii®, na Qualidade de Vida relacionada com a saúde dos sujeitos com 65 anos ou mais e as mudanças na cognição, equilíbrio, coordenação e desempenho das Atividades da Vida Diária após o protocolo; Inquirir o grau de adesão ao treino. Material e Métodos: 30 sujeitos em dois momentos de avaliação. Medidas aplicadas: SF-12, MSE, TUG e com tarefa cognitiva, Escala de Equilíbrio de Berg, avaliação da coordenação e Escala de Barthel. Intervenção durante 4 semanas, 2 por semana, 60 minutos, em 8 sessões. Resultados: Ganhos em todas as escalas, com significado estatístico na Escala de Saúde Mental Geral, componente do SF-12 (p=0,008), MMSE (p=0,007), TUG normal (p=0,003), TUG com tarefa cognitiva (p=0,028) e Protocolo de Avaliação da Coordenação proposto por O’Neil et al. (p=0,008). Da amostra 46,67% teve um Baixo Grau de Adesão, 30% Médio Grau de Adesão, e 23,33% Alto Grau de Adesão. Conclusões: Um protocolo de intervenção de 4 semanas com a Nintendo Wii Sports® (bowling) em sujeitos institucionalizados, apresenta benefícios na QV relacionada com a Saúde Metal e de cognição, e dimensão física da coordenação e capacidade para a dupla-tarefa