Single-Particle Green Functions in Exactly Solvable Models of Bose and Fermi Liquids

Based on a class of exactly solvable models of interacting bose and fermi liquids, we compute the single-particle propagators of these systems exactly for all wavelengths and energies and in any number of spatial dimensions. The field operators are expressed in terms of bose fields that correspond to displacements of the condensate in the bose case and displacements of the fermi sea in the fermi case. Unlike some of the previous attempts, the present attempt reduces the answer for the spectral function in any dimension in both fermi and bose systems to quadratures. It is shown that when only the lowest order sea-displacement terms are included, the random phase approximation in its many guises is recovered in the fermi case, and Bogoliubov's theory in the bose case. The momentum distribution is evaluated using two different approaches, exact diagonalisation and the equation of motion approach. The novelty being of course, the exact computation of single-particle properties including short wavelength behaviour.Comment: Latest version to be published in Phys. Rev. B. enlarged to around 40 page

Preservação da qualidade pós-colheita de araçá-vermelho através do tratamento com 1-metilciclopropeno e do acondicionamento em embalagens plásticas, sob refrigeração Postharvest quality preservation of red strawberry-guavas by treatment with 1-methylcyclopropene and fruit packaging in plastic films under refrigeration

O objetivo deste trabalho foi estudar o padrão respiratório e de produção de etileno, e os efeitos do tratamento com diferentes doses de 1-metilciclopropeno (1-MCP) e do acondicionamento em diferentes embalagens plásticas, associado à refrigeração, na preservação da qualidade pós-colheita de araçá-vermelho. Os frutos apresentaram comportamento climatérico de respiração e produção de etileno. Frutos tratados com doses crescentes de 1-MCP (0; 100; 300; 600 e 1.200 nL L-1) e armazenados a 10±1C/90±5% UR, durante 10 dias, apresentaram retardo substancial no amadurecimento, através da preservação da textura e inibição na mudança de cor da epiderme. Frutos acondicionados com diferentes filmes (polietileno de baixa densidade, policloreto de vinila e à base de náilon) apresentaram, em termos gerais, melhor preservação da textura e menores mudanças na cor da epiderme e perdas de massa fresca, durante armazenamento refrigerado (5C e 10C). Os resultados demonstram que os frutos de araçá-vermelho apresentam elevada perecibilidade, caracterizada pelas elevadas taxas respiratórias e de produção de etileno, sendo mais bem preservados quando refrigerados, e tratados com 1-MCP ou acondicionados em embalagens plásticas.<br>This work was carried out to study respiration and ethylene production behavior of red strawberry-guavas and to assess the preservation of fruit postharvest quality by treatment with different doses of 1-methylcyclopropene (1-MCP) and fruit packaging in plastic films, under refrigeration. Red strawberry-guavas exhibit a climacteric behavior of respiration and ethylene production. Fruits treated with increasing doses of 1-MCP (0, 100, 300, 600, and 1,200 nL L-1) and stored at 10±1C/90±5% RH for 10 days had a substantial delay in ripening, with a better retention of texture and inhibition in the change of the color of the skin. Fruits packed in different plastic films (low density polyethylene, vinyl polychloride, and nylon based films) showed, in general terms, a better retention of texture and green color of the skin, and lower mass loss during cold storage (at 5C and 10C). The results showed that red strawberry-guavas are highly perishable, as a result of their high respiration and ethylene production rates. This requires immediate storage under refrigeration, and the treatment with 1-MCP or fruit packing in plastic films to preserve their postharvest quality

Qualidade de goiaba-serrana em resposta à temperatura de armazenamento e ao tratamento com 1-metilciclopropeno Fruit quality of feijoas in response to storage temperature and treatment with 1-methylcyclopropene

Os objetivos deste trabalho foram caracterizar a fisiologia e avaliar os efeitos da temperatura e da aplicação de 1-metilciclopropeno (1-MCP) na qualidade pós-colheita de frutos de goiaba-serrana (Acca selowiana), em acessos do banco ativo de germoplasma da Empresa de Pesquisa Agropecuária e Extensão Rural de Santa Catarina. Os frutos foram colhidos na maturação comercial. Os genótipos Brasil (acesso 387) e Uruguai (acesso 454) foram avaliados quanto ao comportamento respiratório e de produção de etileno a 20ºC, e taxas respiratórias e alterações na cor da casca a 0, 5, 10, 20 e 30ºC. O genótipo Brasil (acesso 242) foi avaliado quanto ao amadurecimento a 4ºC, após tratamento com 1-MCP (0, 500 e 1.500 ppb). Os genótipos Brasil (acesso 387) e Uruguai (acesso 454) apresentaram comportamento climatérico, com picos de produção de etileno e de taxa respiratória aos 8 e 12 dias de armazenamento a 20ºC, respectivamente. Não houve diferença significativa entre as taxas respiratórias e de produção de etileno entre os genótipos, nessa temperatura. Houve aumento substancial na taxa respiratória em ambos os genótipos, com o aumento de 0 para 30ºC, com coeficiente metabólico de 3,5 aproximadamente. Com o aumento na temperatura, houve maior alteração na cor verde da epiderme, em frutos do tipo Brasil, e maior escurecimento da epiderme, em frutos do tipo Uruguai. Frutos do genótipo Brasil (acesso 242), tratados com 1-MCP e armazenados a 4ºC, apresentaram retardamento no amadurecimento.<br>The objectives of this work were to characterize the postharvest physiology and to evaluate the effects of temperature and treatment with 1-methylcyclopropene (1-MCP) on the postharvest quality of fruits of feijoa (Acca selowiana) accessions from the germplasm bank of Empresa de Pesquisa Agropecuária e Extensão Rural de Santa Catarina. Fruits were harvested at commercial maturity. The genotypes Brasil (accession no. 387) and Uruguai (accession no. 454) were evaluated for respiration and ethylene production at 20ºC, and respiration rates and skin color alterations at 0, 5, 10, 20, 30ºC. The genotype Brasil (accession no. 242) was evaluated for ripening at 4ºC, after treatment with 1-MCP (0, 500 and 1,500 ppb). Brasil (accession no. 387) and Uruguai (accession no. 454) exhibited a climacteric pattern, with a peak of ethylene evolution and respiration rate at the 8th and 12th days of storage at 20ºC, respectively. There was no significant difference for respiration rates and ethylene evolution between these genotypes at this temperature. There was a substantial increase of respiration rate in both genotypes with the increase in temperature from 0 to 30ºC, with a metabolic coefficient of approximately 3.5. With the increase in temperature, fruits of the genotype Brasil showed the greatest change of skin green color, while fruits of the genotype Uruguai exhibited the greatest darkening of skin. Feijoa fruits of genotype Brasil (accession no. 242) had delayed ripening when treated with 1-MCP and stored at 4ºC

The status of the ARGO experiment at YBJ

The ARGO-YBJ experiment, located at Yangbajing, Tibet, China, performed by a wide Sino-Italian collaboration, is designed to study cosmic rays, sub-TeV gamma ray sources and GeV Gamma Ray Burst (GRB) emission in the northern hemisphere, by means of detecting small size EAS (Extensive Air Shower) using a full coverage RPC (Resistive Plate Chamber) carpet. The central carpet of the detector is installed and put into operation to date, with 1900m2 of the carpet already operating since December 2004. With a trigger multiplicity of ≥60 hits, corresponding to a primary mode energy of 2 TeV, the angular resolution of EAS measurements is < 1o for showers with more than 500 recorded hits. We report the preliminary results of data taking performed during 2005: the all-sky survey for gamma ray sources and the search for GRBs, as well as the cosmic ray spectrum up to about 100TeV. The Forbush decrease of the cosmic ray flux during January, 2005 is observed using the ARGO data