A pure S-wave covariant model for the nucleon

Using the manifestly covariant spectator theory, and modeling the nucleon as a system of three constituent quarks with their own electromagnetic structure, we show that all four nucleon electromagnetic form factors can be very well described by a manifestly covariant nucleon wave function with zero orbital angular momentum. Since the concept of wave function depends on the formalism, the conclusions of light-cone theory requiring nonzero angular momentum components are not inconsistent with our results. We also show that our model gives a qualitatively correct description of deep inelastic scattering, unifying the phenomenology at high and low momentum transfer. Finally we review two different definitions of nuclear shape and show that the nucleon is spherical in this model, regardless of how shape is defined.Comment: 20 pages and 10 figures; greatly expanded version with new fits and discussion of DIS; similar to published versio

Covariant nucleon wave function with S, D, and P-state components

Expressions for the nucleon wave functions in the covariant spectator theory (CST) are derived. The nucleon is described as a system with a off-mass-shell constituent quark, free to interact with an external probe, and two spectator constituent quarks on their mass shell. Integrating over the internal momentum of the on-mass-shell quark pair allows us to derive an effective nucleon wave function that can be written only in terms of the quark and diquark (quark-pair) variables. The derived nucleon wave function includes contributions from S, P and D-waves.Comment: 13 pages and 1 figur

The bright side of the dark side: covert politics as an alternative to the negative impacts of coercive change

This study examines practitioners as individual actors by focusing on a general manager's individual account. With a two-week episode of political maneuvering as a starting point, the case shows how skilful strategizing on the part of the general manager is at the origin of significant organizational change. Specifically, the paper has three purposes. First, to offer insights to practitioners and scholars regarding how powerful managers purposefully seek to influence organizational context in a non-disclosed fashion. Second, to illustrate how single case microstudies open a route to understanding events that would otherwise be unattainable. The third, and most important, is to apply organizational politics concepts to characterize managerial covert political action in the implementation of a deliberate strategy. Specifically, emphasis is put on how contextual characteristics relate to political action. How they constrain and enable politics, and facilitate the use and maintenance of concealed motives

Mechanical and wear behaviours of nano and microfilled polymeric composite: effect of filler fraction and size

The addition of ceramic reinforced material, SiC particles, to resin matrices, results in the improvement of the overall performance of the composite, allowing the application of these materials as tribo-materials in industries such as: automotive, aeronautical and medical. Particle-reinforced polymeric composites are widely used as biomaterials, for example as dental filler materials and bone cements. These reinforced composites have improved mechanical and tribological performance and have higher values of elastic modulus and hardness, and also reduce the shrinkage during the polymerisation compared with resin matrices. However, the effect of the filler level in mechanical and tribological behaviour is not quite understood. The aim of this work is to determine the influence of the particle volume fraction and particle size in the wear loss of the composites and their antagonists. Reciprocating wear tests were conducted using a glass sphere against resin polyester silica reinforced composite in a controlled medium, with an abrasive slurry or distilled water. For 6 μm average particle dimension, seven particles contents were studied ranging from 0% to 46% of filler volume fraction (FVF). Afterwards, filler volume fractions of 10% and 30% were selected; and, for these percentages, 7 and 4 average particle dimensions were tested and were evaluated regarding their wear behaviour, respectively. The reinforcement particle dimensions used ranged from 0.1 μm to 22 μm with the 10% filler fraction, and for 30% of filler content the range extended from 3 μm to 22 μm. The results allow us to conclude that in an abrasive slurry medium the composite abrasion resistance decreases with the increase of the particle volume fraction, in spite of the accompanying rise in hardness and elastic modulus. With constant FVF, and abrasive slurry, the composite wear resistance increases with increasing average particle dimension. In a distilled water medium and with several FVF values, the minimum wear was registered for a median particle content of 24%. In this medium and with constant FVF the highest wear resistance occurred for average reinforcement particles of 6 μm. The removal mechanisms involved in the wear process are discussed, taking into account the systematic SEM observations to evaluate the wear mechanisms

Fatores Preditivos do Stress Parental

Criar um filho é um desafio de grande responsabilidade e exige profundas transformações e adaptações na vida dos pais, sendo que os comportamentos parentais são influenciados por causas múltiplas, nomeadamente o stress parental, as variáveis sociodemográficas tais como o estatuto socioeconómico, o número de filhos, o género e idade dos pais, entre muitos outros. Esta pesquisa visa conhecer as características sociodemográficas e laborais dos pais das crianças que frequentam o 2º ciclo do Colégio João de Barros, conhecer as características sociodemográficas e escolares das crianças que frequentam o 2º ciclo do Colégio João de Barros e avaliar o nível de stress parental dos pais das crianças que frequentam o 2º ciclo do Colégio João de Barros. Para além destes objetivos, pretende-se também determinar a relação existente entre o nível de stress parental dos pais das crianças que frequentam o 2º ciclo do Colégio João de Barros e algumas características sociodemográficas e laborais e determinar a relação existente entre o nível de stress parental dos pais das crianças que frequentam o 2º ciclo do Colégio João de Barros e algumas características sociodemográficas e escolares das crianças que frequentam o 2º ciclo do Colégio João de Barros. A amostra é constituida por 50 encarregados de educação e 50 crianças a frequentarem o 2º ciclo do Colégio João de Barros. Foram definidos dois grupos de amostra e para cada grupo foi utilizado um instrumento de colheita de dados. Para o grupo dos encarregados de educação, aplicou-se um questionário sociodemográfico e laboral para avaliar as características sociais e laborais dos encarregados de educação das crianças e a “Escala de Stress Parental” para avaliar os níveis de stress experimentado pelos pais. Relativamente às crianças, aplicou-se um questionário relativo a dados sociodemográficos e escolares. Os resultados revelaram baixos níveis de stress parental, assim como a não existência de relação estatisticamente significativa entre os níveis de stress parental e as características sociodemográficas e laborais recolhidas, tal como algumas características sociodemográficas e escolares relativamente às crianças. No entanto surgiram resultados interessantes, nomeadamente a relação existente entre os rendimentos dos pais e os níveis de preocupações parentais e a relação existente entre a inexistência de irmãos e os elevados níveis de falta de controlo

About the efficiency behavior of the Portuguese manufacturing firms during the financial crisis

This work studies some effects of the World Financial Crisis on firms in terms of efficiency scores, by measuring how 23K units used inputs and produced outputs, obtained from a set of Portuguese manufacturing firms on three time periods: pre-crisis (2006-2008), pretroika (2009-2011) and troika (2012-2013). We adopt a non-parametric approach, which combines Multidirectional Efficiency Analysis (MEA) with other techniques as cluster analysis, principal component analysis and dimensionality testing, to examine three empirical hypotheses: H(1) the performance of the portuguese firms in the manufacturing sector has been adversely affected by the financial crisis felt in Portugal in the troika years; H(2) due to the financial crisis, the manufacturing sector acquired long-term debt deliberately; and H(3) the financial crisis has affected substantially the food subsector. The results indicate that H(1) is confirmed, but not totally, H(2) is confirmed and H(3) is rejected. We also found surprisingly good affine fittings between inputs and capital, and outputs and EBIT with really good p-values. Hence, we also propose a reduction of the dimensionality of the MEA model, when it is possible to apply model fitting. If the reduction results in one input and one output, we give procedures to visualize and compare between efficiencies scores.info:eu-repo/semantics/publishedVersio

Identifying the Azobenzene/Aniline reaction intermediate on TiO2-(110) : a DFT Study

Density functional theory (DFT) calculations, both with and without dispersion corrections, have been performed to investigate the nature of the common surface reaction intermediate that has been shown to exist on TiO2(110) as a result of exposure to either azobenzene (C6H5N═NC6H5) or aniline (C6H5NH2). Our results confirm the results of a previous DFT study that dissociation of azobenzene into two adsorbed phenyl imide (C6H5N) fragments, as was originally proposed, is not energetically favorable. We also find that deprotonation of aniline to produce this surface species is even more strongly energetically disfavored. A range of alternative surface species has been considered, and while dissociation of azobenzene to form surface C6H4NH species is energetically favored, the same surface species cannot form from adsorbed aniline. On the contrary, adsorbed aniline is much the most stable surface species. Comparisons with experimental determinations of the local adsorption site, the Ti–N bond length, the molecular orientation, and the associated C 1s and N 1s photoelectron core level shifts are all consistent with the DFT results for adsorbed aniline and are inconsistent with other adsorbed species considered. Possible mechanisms for the hydrogenation of azobenzene required to produce this surface species are discussed

On the use of hedonic regression models to measure the effect of energy efficiency on residential property transaction prices : evidence for Portugal and selected data issues

Using a unique dataset containing information of around 256 thousand residential property sales, this paper discloses a clear sales premium for most energy efficient dwellings, which is more pronounced for apartments (13%) than for houses (5 to 6%). Cross-country comparisons support the finding that energy efficiency price premiums are higher in the Portuguese residential market than in central and northern European markets. Results emphasize the relevance of data issues in hedonic regression models. They illustrate how the use of appraisal prices, explanatory variables with measurement errors, and the omission of variables associated with the quality of the properties, may seriously bias energy efficiency partial effect estimates. These findings provide valuable information not only to policy-makers, but also to researchers interested in this area.info:eu-repo/semantics/publishedVersio