Isotropization of Bianchi type models and a new FRW solution in Brans-Dicke theory

Using scaled variables we are able to integrate an equation valid for isotropic and anisotropic Bianchi type I, V, IX models in Brans-Dicke (BD) theory. We analyze known and new solutions for these models in relation with the possibility that anisotropic models asymptotically isotropize, and/or possess inflationary properties. In particular, a new solution of curve ($k\neq0$) Friedmann-Robertson-Walker (FRW) cosmologies in Brans-Dicke theory is analyzed.Comment: 15 pages, 4 postscript figures, to appear in Gen. Rel. Grav., special issue dedicated in honour of Prof. H. Dehne

Folding studies of immunoglobulin-like β-sandwich proteins suggest that they share a common folding pathway

AbstractBackground: Are folding pathways conserved in protein families? To test this explicitly and ask to what extent structure specifies folding pathways requires comparison of proteins with a common fold. Our strategy is to choose members of a highly diverse protein family with no conservation of function and little or no sequence identity, but with structures that are essentially the same. The immunoglobulin-like fold is one of the most common structural families, and is subdivided into superfamilies with no detectable evolutionary or functional relationship.Results: We compared the folding of a number of immunoglobulin-like proteins that have a common structural core and found a strong correlation between folding rate and stability. The results suggest that the folding pathways of these immunoglobulin-like proteins share common features.Conclusions: This study is the first to compare the folding of structurally related proteins that are members of different superfamilies. The most likely explanation for the results is that interactions that are important in defining the structure of immunoglobulin-like proteins are also used to guide folding

Uma análise de soft systems methodology e sua utilização para melhoria do processo de desenvolvimento de cultivares em uma instituição de pesquisa agropecuária.

O objetivo desse artigo é apresentar algumas contribuições para enriquecer a reflexão sobre a Soft Systems Methodology (SSM) e contribuir para a sua prática em situações diversas do mundo organizacional. A SSM é explorada em um caso prático de aplicação na Embrapa Milho e Sorgo, com o objetivo de propor melhorias para o Processo de Desenvolvimento de Cultivares da empresa. O foco é direcionado para as características metodológicas da intervenção, enfatizando a adaptação feita ao processo de aplicação da SSM para se ajustar às contingências da situação. Ao final, avalia-se que a utilização da metodologia na forma flexível apresentada pode contribuir para o alcance de bons resultados para a organização

Neutrino Spin Flavor Precession and Leptogenesis

We argue that \Delta L=2 neutrino spin flavor precession, induced by the primordial magnetic fields, could have a significant impact on the leptogenesis process that accounts for the baryon asymmetry of the universe. Although the extra galactic magnetic fields is extremely weak at present time (about 10^{-9} Gauss), the primordial magnetic filed at the electroweak scale could be quite strong (of order 10^{17} Gauss). Therefore, at this scale, the effects of the spin flavor precession are not negligible. We show that the lepton asymmetry may be reduced by 50% due to the spin flavor precession. In addition, the leptogenesis will have different feature from the standard scenario of leptogenesis, where the lepton asymmetry continues to oscillate even after the electroweak phase transition.Comment: 5 pages, one figure. References adde

Implicit Beliefs About Change: A Theory-Grounded Measure Applied to Community Organizations Serving Children, Youth, and Families

The aim of this study was to design and evaluate a theory-grounded measure that taps staff beliefs about the possibility for change in an organization which serves children, youth and families at the community level. The rationale for measuring staff beliefs about change derived from a motivation theory that features two contrasting beliefs structures (entity vs. incremental), and the goals and behavioral dispositions associated with each (Dweck & Leggett, 1988). Twenty-nine individuals associated with the community-based organization completed the newly developed Implicit Beliefs About Change Scale (IBACS) and participatedi n a semi-structured interview. Quantitative analyses indicated that the IBACS has good internal consistency, and yields sufficient response variance. Content analysis of the semi-structured interviews, used to assess the scale\u27s construct validity, uncovered distinctive and theory-consistent behavioral dispositions among those staff members whose beliefs regarding change could be characterized as either incremental or entity in nature. Implications for staff development and future research are discussed

Conformal Couplings in Induced Gravity

It is found that the induced gravity with conformal couplings requires the conformal invariance in both classical and quantum levels for consistency. This is also true for the induced gravity with an extended conformal coupling interacting with torsion.Comment: 10 pages, Revtex3.0, to appear in General Relativity and Gravitatio

Modeling the Spatiotemporal Epidemic Spreading of COVID-19 and the Impact of Mobility and Social Distancing Interventions

On 31 December, 2019, an outbreak of a novel coronavirus, SARS-CoV-2, that causes the COVID-19 disease, was first reported in Hubei, mainland China. This epidemics'' health threat is probably one of the biggest challenges faced by our interconnected modern societies. According to the epidemiological reports, the large basic reproduction number R0~3.0, together with a huge fraction of asymptomatic infections, paved the way for a major crisis of the national health capacity systems. Here, we develop an age-stratified mobility-based metapopulation model that encapsulates the main particularities of the spreading of COVID-19 regarding (i) its transmission among individuals, (ii) the specificities of certain demographic groups with respect to the impact of COVID-19, and (iii) the human mobility patterns inside and among regions. The full dynamics of the epidemic is formalized in terms of a microscopic Markov chain approach that incorporates the former elements and the possibility of implementing containment measures based on social distancing and confinement. With this model, we study the evolution of the effective reproduction number R(t), the key epidemiological parameter to track the evolution of the transmissibility and the effects of containment measures, as it quantifies the number of secondary infections generated by an infected individual. The suppression of the epidemic is directly related to this value and is attained when R<1. We find an analytical expression connecting R with nonpharmacological interventions, and its phase diagram is presented. We apply this model at the municipality level in Spain, successfully forecasting the observed incidence and the number of fatalities in the country at each of its regions. The expression for R should assist policymakers to evaluate the epidemics'' response to actions, such as enforcing or relaxing confinement and social distancing

A spherical scalar-tensor galaxy model

We build a spherical halo model for galaxies using a general scalar-tensor theory of gravity in its Newtonian limit. The scalar field is described by a time-independent Klein-Gordon equation with a source that is coupled to the standard Poisson equation of Newtonian gravity. Our model, by construction, fits both the observed rotation velocities of stars in spirals and a typical luminosity profile. As a result, the form of the new Newtonian potential, the scalar field, and dark matter distribution in a galaxy are determined. Taking into account the constraints for the fundamental parameters of the theory (lambda,alpha), we analyze the influence of the scalar field in the dark matter distribution, resulting in shallow density profiles in galactic centers.Comment: 14 pages, 16 plots set in 7 figures, typos and references adde

Avaliação de linhagens de milho quanto à ocorrência de grãos ardidos.

Trabalho apresentado no 42º Congresso Brasileiro de Fitopatologia, 2009, Rio de Janeiro, RJ

Scalar-field Pressure in Induced Gravity with Higgs Potential and Dark Matter

A model of induced gravity with a Higgs potential is investigated in detail in view of the pressure components related to the scalar-field excitations. The physical consequences emerging as an artifact due to the presence of these pressure terms are analysed in terms of the constraints parting from energy density, solar-relativistic effects and galactic dynamics along with the dark matter halos.Comment: 26 pages, 3 figures, Minor revision, Published in JHE