Dynamical Vacuum in Quantum Cosmology

By regarding the vacuum as a perfect fluid with equation of state p=-rho, de Sitter's cosmological model is quantized. Our treatment differs from previous ones in that it endows the vacuum with dynamical degrees of freedom. Instead of being postulated from the start, the cosmological constant arises from the degrees of freedom of the vacuum regarded as a dynamical entity, and a time variable can be naturally introduced. Taking the scale factor as the sole degree of freedom of the gravitational field, stationary and wave-packet solutions to the Wheeler-DeWitt equation are found. It turns out that states of the Universe with a definite value of the cosmological constant do not exist. For the wave packets investigated, quantum effects are noticeable only for small values of the scale factor, a classical regime being attained at asymptotically large times.Comment: Latex, 19 pages, to appear in Gen. Rel. Gra

Commentaries on viewpoint : physiology and fast marathons

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Influência de diferentes sistemas de colheita na qualidade do café (Coffea arabica L.) Influence of different harvest systems on quality of coffee (Coffea arabica L.)

Com o objetivo de avaliar a influência da colheita na qualidade do café, foram estudados seis diferentes sistemas. O experimento foi conduzido na fazenda Rancho Fundo, município de Campos Gerais, MG, no Departamento de Ciência dos Alimentos da UFLA e no Centro Tecnológico do Sul de Minas da EPAMIG. Em uma lavoura da cultivar Acaiá Cerrado, foram sorteadas, ao acaso, dezoito parcelas com trinta metros de comprimento. A colheita foi realizada quando a lavoura apresentava aproximadamente 20% de frutos verdes. Um terço do café derriçado de cada parcela era formado pela mistura de frutos provenientes da lavoura. O restante do café foi lavado e separado em frutos-bóia e verde/cereja. Os diferentes tipos de café foram colocados no terreiro de secagem até atingirem o teor de água de 11% (b.u.). Após a secagem, o café foi beneficiado e submetido às seguintes avaliações: polifenóis, açúcares totais, redutores e não-redutores, sólidos solúveis totais, acidez titulável total e prova de xícara. Analisando os resultados obtidos, apesar de terem sido observadas diferenças significativas entre os valores médios de polifenóis, açúcares, sólidos solúveis e acidez titulável para os diferentes sistemas de colheita, não foi possível estabelecer uma associação definida entre sistema de colheita e composição química. Não foi possível também distinguir, a partir da prova de xícara, diferenças na qualidade do café em função do sistema de colheita, pois, todas as amostras analisadas apresentaram bebida classificada como mole, apenas mole e dura.Aiming to evaluating the influence of the harvest on coffee quality, six harvest systems with different mechanization level were studied. The present work was developed on the Rancho Fundo farm, Campos Gerais town, MG, in the Food Science Department of the UFLA and in the “Centro Tecnológico do Sul de Minas” of EPAMIG. In a crop of the Acaiá Cerrado cultivars were randomized eighteen plots with thirty meters long each. The harvest was performed when the crop was presenting about 20 % of green fruits. A third of the ripped coffee from each plot was maintained with the mixture of fruit from the crop. The rest of the coffee was washed and separated in float and green/cherry fruits. The different coffees were placed on the drying yard till the water content of 11%(w.b.). After drying, the coffee was processed and submitted to the following evaluation: polyphenol, total, reducing and non-reducing sugars, total soluble solids, total titrable acidity and cup proof. Considering the results obtained, in spite of significant differences was observed among the average values of polyphenol content, sugar content, soluble solids and titrable acidity, for the different mechanized harvest, it was not possible to establish a definite association between harvest system and chemical composition. It was not possible to distinguish on the basis of the cup proof, differences in coffee quality in terms of the harvest system because in all the samples analyzed the drink was classified as soft, only soft and hard

Determinação do coeficiente de cultura (Kc) e eficiência do uso de água do alecrim-pimenta irrigado

Objetivou-se com este estudo determinar os coeficientes de cultura (Kc), a eficiência do uso de água (EUA) do alecrim-pimenta contemplando a produção de biomassa e óleo essencial. O experimento foi conduzido em lisímetro de drenagem, no Instituto de Ciências Agrárias da Universidade Federal de Minas Gerais, em Montes Claros, MG. O delineamento experimental utilizado foi em blocos casualizados, cujos tratamentos correspondiam a sete lâminas de água (0,5; 0,75; 1,0; 1,2; 1,4; 1,65 e 1,9 ETo), e três repetições. A evapotranspiração potencial de referência utilizada no cálculo das lâminas de irrigação foi obtida pelo método de Penman-Monteith. Os tratamentos foram submetidos à análise de regressão. Os resultados indicam que o alecrim-pimenta apresenta resposta positiva ao aumento da lâmina d'água aplicada. O tratamento responsável pelo maior índice de eficiência do uso da água, foi o tratamento 6 (1,65 ETo), com 1,26 kg m-3 para a produção de matéria fresca em função da lâmina aplicada. A produtividade de óleo essencial foi de 59,12 kg ha-1 aos 120 dias após transplantio, para o tratamento 7 (1,9 ETo). Os coeficientes de cultura (Kc) médios determinados em todo o ciclo da cultura, variaram de 0,98 na fase inicial, 1,20 no desenvolvimento vegetativo e 1,52 no florescimento

Water stress before harvest of pepper-rosmarin

The objective of this work was to assess the effect of different periods of water stress before harvest of pepper-rosmarin (Lippia sidoides) on the contents of essential oil and flavonoids. The experiment was carried out during 270 days of cultivation, with drainage lysimeters, in a completely randomized block design with five treatments: 0, 2, 4, 6, and 8 days of water suppression before harvest, with four replicates. Fresh and dry matter yield, essential oil content, total flavonoids content, and water potential and temperature of leaves were determined. There was a decrease of approximately 50% in oil content and of 60% in total flavonoid content with the reduction of leaf water potential in 0.3 MPa. Essential oil is more sensitive to water stress than total flavonoids

Assessment of loose and adhered urban street sediments and trace metals: a study in the city of Po double dagger os de Caldas, Brazil

This study aims to quantify and characterise sediments accumulated in the street gutters in an urban area of Po double dagger os de Caldas, Brazil. The main research questions are: What type of urban areas, e.g. those under construction, produce most sediments and what are the main characteristics of such sediments? What differences, e.g. granulometry, can be found in loose and adhered sediments? What trace metals can be found in the sediments?Fieldwork was carried out in a residential area of Po double dagger os de Caldas, Brazil. Ten samplings were conducted between May and August 2013 to collect sediments from road gutters. The collected sediments were then divided into 'loose' and 'adhered', depending on whether they were collected in a first, gentle, sweeping with soft bristled brush or in a subsequent sweeping with a stiff bristled brush. Granulometric curves were drawn for both types of sediments. Fine sediment analyses (aecurrency sign63 mu m) were performed on samples from the last five samplings. Two techniques were used to look for trace elements: energy dispersive X-ray fluorescence (EDXRF) and inductively coupled plasma-atomic emission spectrometry (ICP-AES).Larger amounts of sediments were collected after lower intensity rainfall events. Higher intensity events seemed to wash the sediments away. A correlation was found between areas under construction and sediment mass production. A characteristic range of granulometries (medium sand), found in our study is in accordance with studies by other authors. An important presence of heavy metals (Cr, Cd, Pb, Zn, Ni and Cu) was detected and characterised. As and Sn were also detected even though they are not often mentioned in the literature on urban soil pollutants.Areas under construction were found to produce more sediments than other areas. The trace metals found in highest concentrations were Pb and As. The heavy metal concentration decreases after wet periods, showing that they are carried by runoff. It is expected that this study may serve as an input for establishing diffuse pollution control and mitigation strategies for the accumulation of pollutants in the urban environment