Vacuum fluctuations of a scalar field near a reflecting boundary and their effects on the motion of a test particle

The contribution from quantum vacuum fluctuations of a real massless scalar field to the motion of a test particle that interacts with the field in the presence of a perfectly reflecting flat boundary is here investigated. There is no quantum induced dispersions on the motion of the particle when it is alone in the empty space. However, when a reflecting wall is introduced, dispersions occur with magnitude dependent on how fast the system evolves between the two scenarios. A possible way of implementing this process would be by means of an idealized sudden switching, for which the transition occurs instantaneously. Although the sudden process is a simple and mathematically convenient idealization it brings some divergences to the results, particularly at a time corresponding to a round trip of a light signal between the particle and the wall. It is shown that the use of smooth switching functions, besides regularizing such divergences, enables us to better understand the behavior of the quantum dispersions induced on the motion of the particle. Furthermore, the action of modifying the vacuum state of the system leads to a change in the particle energy that depends on how fast the transition between these states is implemented. Possible implications of these results to the similar case of an electric charge near a perfectly conducting wall are discussed.Comment: 17 pages, 8 figure

Performance of the modified Becke-Johnson potential

Very recently, in the 2011 version of the Wien2K code, the long standing shortcome of the codes based on Density Functional Theory, namely, its impossibility to account for the experimental band gap value of semiconductors, was overcome. The novelty is the introduction of a new exchange and correlation potential, the modified Becke-Johnson potential (mBJLDA). In this paper, we report our detailed analysis of this recent work. We calculated using this code, the band structure of forty one semiconductors and found an important improvement in the overall agreement with experiment as Tran and Blaha [{\em Phys. Rev. Lett.} 102, 226401 (2009)] did before for a more reduced set of semiconductors. We find, nevertheless, within this enhanced set, that the deviation from the experimental gap value can reach even much more than 20%, in some cases. Furthermore, since there is no exchange and correlation energy term from which the mBJLDA potential can be deduced, a direct optimization procedure to get the lattice parameter in a consistent way is not possible as in the usual theory. These authors suggest that a LDA or a GGA optimization procedure is used previous to a band structure calculation and the resulting lattice parameter introduced into the 2011 code. This choice is important since small percentage differences in the lattice parameter can give rise to quite higher percentage deviations from experiment in the predicted band gap value.Comment: 10 pages, 2 figures, 5 Table

Hydrogen via reforming aqueous ammonia and biomethane co-products of wastewater treatment: environmental and economic sustainability

Green H2 is increasingly viewed as a key energy carrier for the fight against climate change. Wastewater treatment plants (WWTPs) have the unique potential to be centres of renewable H2 generation with the growing availability of two attractive feedstocks: biomethane and ammonia. An innovative and novel method of ammonia recovery from digestate liquor followed by a state-of-the-art H2 production process named NWaste2H2 is demonstrated for a case-study WWTP. The recovered ammonia is used alongside biomethane for H2 production and its diversion from conventional biological treatment has two other crucial benefits, with reductions in both associated electricity demand and emissions of nitrous oxide, an extremely potent greenhouse gas. Process modelling, supported by extensive experiments in a packed-bed reactor at bench-scale, demonstrate the prized capability of simultaneously performing steam methane reforming and ammonia decomposition to generate a H2-rich syngas with yields close to equilibrium values. Greenhouse gas emission abatement from the replacement of diesel buses and reduced N2O emissions from biological treatment could save up to 17.2 kg CO2 equivalent (CO2e) per year for each person served by the WWTP. An in-depth economic study illustrates the ability to achieve a positive net present value with a 10% discount factor as early as 5.8 years when the H2 is prepared and sold to power fuel cell electric buses

O pensamento social de universitários sobre beleza e cirurgia estética

O estudo objetivou identificar as representações sociais de homens e mulheres com diferentes formações acadêmicas, a respeito de beleza e da cirurgia estética. Pesquisa de natureza descritiva e comparativa, com delineamento transversal, com a participação de 120 universitários; plano de investigação multimétodo desenhado por A.S. de Rosa através de questionário semiestruturado, autoaplicável, dividido em cinco par- tes; envolvendo análise estatística descritiva, relacional e análise textual de redes associativas. Os resultados destacam diferenças significativas nas representações sociais dos grupos em relação aos objetos sociais, beleza e cirurgia estética, em termos de conteúdo, avaliações e dimensões sociopsicológicas. A proximidade dos indivíduos e grupos com o corpo confirma parcialmente as evidências das variáveis influentes em termos de gênero e formação acadêmica dos participantes nas repre- sentações dos objetos pesquisados. The study aimed to identify the social representations of men and women with different academic backgrounds, regarding beauty and aesthetic surgery. This study is a descriptive and comparative research, with cross-sectional design, based on the par- ticipation of 120 university students; Multi-method research plan designed by A.S. de Rosa through a semi-structured, self-administered questionnaire, divided into five parts; involv- ing descriptive and relational statistical analysis, and textual analysis of associative networks. The results highlight significant differences in the social representations of the groups in relation to social objects, beauty and aesthetic surgery, in terms of contents, assessments and socio-psychological dimensions. The proximity of individuals and groups to the body partially confirms the evidence of influential variables in terms of gender and academic training of the participants in the representations of the objects surveyed

Concentração de ânions no perfil de solo tratado sucessivamente com lodo de esgoto.

Resumo: Uma das preocupações quanto ao uso agrícola de lodo de esgoto é a lixiviação de ânions no perfil do solo, principalmente o nitrato, que podem atingir o lençol freático e contaminar as coleções hídricas após aplicações sucessivas do resíduo. O objetivo foi avaliar a concentração de nitrato, nitrito e sulfato no perfil do solo de 1 a 5 metros de profundidade após seis aplicações anuais de doses superestimadas de lodo de esgoto, seguidas de dez anos de cultivo sem adição do resíduo em poço escavado em uma área experimental. Observaram-se o acúmulo de sulfato até 2 metros de profundidade e as maiores concentrações de nitrato a 4 e 5 metros de profundidade, indicando maior movimentação deste ânion em relação aos demais. Abstract: One concern about using sewage sludge in agriculture is the leaching of anions through the soil profile, particularly nitrate, which could contaminate groundwater after successive residue applications. IN this study, anions concentrations were evaluated through the soil profile (1 to 5 m of depth) after six annual applications of superdoses of sewage sludge followed by 10 years of cultivation without adding the residue using a well excavated at an experimental area. Sulfate accumulation was observed until 2m of depth and mayor nitrate concentrations at 4 and 5m of depth, indicating more intense leaching of this anion

Growth analysis of chickpea (Cicer arietinum L.)

Com a finalidade de avaliar o padrão de crescimento do grão-de-bico, variedade IAC-Marrocos, realizou-se um experimento na Estação Experimental de Monte Alegre do Sul, SP, nos anos agrícolas de 1987 e 1988. Semanalmente eram feitas coletas de plantas e após a separação das partes, eram obtidos os pesos secos, bem como o índice de área foliar. Esses dados foram analisados com modelos de regressão linear e exponencial ajustados para as matérias secas de grão, de folha e total e para os índices de área foliar e de crescimento. Baseando-se na análise de crescimento conclui-se que o grão-de-bico é uma planta que pode ser recomendada como alternativa para a cultura de inverno em condições climáticas semelhantes às do presente estudo.An experiment to study the growing pattern of a chickpea variety, IAC-Marrocos, was carried out at the Monte Alegre Experimental Station, SP, during 1987 and 1988. The dry matter production of all parts of the plant, as well the leaf area index, were weekly evaluated. Exponential quadratic models of regression were adjusted to total dry matter, leaf dry matter and leaf area index, and a linear model to dry matter of grain. Based on the growth analysis it was concluded that the chickpea is a rustic eatable plant that can be recommended as an alternative winter crop for similar climatic conditions as those of the experiment