Approximate solutions for the skyrmion

We reconsider the Euler-Lagrange equation for the Skyrme model in the hedgehog ansatz and study the analytical properties of the solitonic solution. In view of the lack of a closed form solution to the problem, we work on approximate analytical solutions. We show that Pade approximants are well suited to continue analytically the asymptotic representation obtained in terms of a power series expansion near the origin, obtaining explicit approximate solutions for the Skyrme equations. We improve the approximations by applying the 2-point Pade approximant procedure whereby the exact behaviour at spatial infinity is incorporated. An even better convergence to the exact solution is obtained by introducing a modified form for the approximants. The new representations share the same analytical properties with the exact solution at both small and large values of the radial variable r.Comment: 15 pages, 5 figures. 1 Reference adde

Approximate solutions for the single soliton in a Skyrmion-type model with a dilaton scalar field

We consider the analytical properties of the single-soliton solution in a Skyrmion-type Lagrangian that incorporates the scaling properties of quantum chromodynamics (QCD) through the coupling of the chiral field to a scalar field interpreted as a bound state of gluons. The model was proposed in previous works to describe the Goldstone pions in a dense medium, being also useful for studying the properties of nuclear matter and the in-medium properties of mesons and nucleons. Guided by an asymptotic analysis of the Euler-Lagrange equations, we propose approximate analytical representations for the single soliton solution in terms of rational approximants exponentially localized. Following the Pad\'e method, we construct a sequence of approximants from the exact power series solutions near the origin. We find that the convergence of the approximate representations to the numerical solutions is considerably improved by taking the expansion coefficients as free parameters and then minimizing the mass of the Skyrmion using our ans\"atze for the fields. We also perform an analysis of convergence by computation of physical quantities showing that the proposed analytical representations are very useful useful for phenomenological calculations.Comment: 13 pages, 3 eps figures, version to be published in Phys.Rev.

Valoração econômica da perda de solo na cultura de cana-de-açúcar colhida crua e queimada no município de Campos dos Goytacazes.

Este trabalho foi realizado no Município de Campos dos Goytacazes, RJ e teve como objetivo valorar economicamente as perdas de solo em relação aos nutrientes perdidos na cultura de cana-de-açúcar sob dois sistemas distintos de colheita, cana-de-açúcar crua e queimada em áreas de baixada e de tabuleiro. Utilizou-se a Universal Soil Loss Equation ? USLE e o método do custo de reposição de nutrientes, para realizar a estimação econômica das perdas de solo. Os resultados mostram que a taxa de perda de solo da cana-de-açúcar queimada foi quatro vezes maior quando comparada à taxa para cana-de-açúcar colhida crua para ambas as áreas estudadas. O custo de reposição dos nutrientes perdidos no cultivo da cana-de-açúcar sob sistema de colheita com queima prévia apresentou um valor de R$10,53 por hectare, já o custo para área com cana crua foi de R$ 2,61 por hectare em área de baixada e de R$43,59 por hectare para cana queimada e R$ 10,89 para cana crua em tabuleiro. Dessa forma, o sistema de manejo da colheita da cana crua contribui ambientalmente e economicamente para a preservação da fertilidade do solo

A Catalog of Dermatology Utilities: A Measure of the Burden of Skin Diseases

Utilities are measures of quality of life that reflect the strength of individuals' preferences or values for a particular health outcome. As such, utilities represent a measure of disease burden. The aim of this article is to introduce the concept of utilities to the dermatology community and to present a catalog of dermatology utilities obtained from direct patient interviews. Our data are based on 236 total subjects from Grady Hospital (Atlanta, GA), Stanford Medical Center (Palo Alto, CA), and Parkland Hospital (Dallas, TX). The mean time trade-off utilities ranged from 0.640 for blistering disorders to 1.000 for alopecia, cosmetic, and urticaria. The mean utility across all diagnoses was 0.943. We present utilities for 17 diagnostic categories and discuss the underlying reasons for the significant disease burden that these utilities represent. We also present these dermatology categories relative to noncutaneous diseases to place the cutaneous utilities in perspective and to compare the burden of disease. We have demonstrated that skin diseases have considerable burden of disease and provided a preliminary repository of utility data for future researchers and policy makers

Otimização azotada no Capim-elefante para fins energéticos.

Conduziu-se uma experiência não irrigada com um delineamento de blocos casualizados, num esquema de parcelas sub-sub-divididas sob cinco doses de Azoto, quatro de Fósforo e três repetições para cada tratamento, em Alegre (ES), para estimar níveis de adubação das cultivares. Utilizou-se a função de produção para obter o máximo físico e óptimo económico. As cultivares constituíram as parcelas, o fósforo as sub-parcelas e o azoto as sub-sub-parcelas. Observou-se a ausência de significância para o fósforo e para as suas interações. E significância para os outros fatores. Realizou-se uma análise envolvendo os fatores Genótipo e Azoto por meio do modelo estatístico de parcela sub-sub-dividida. A estimativa da produtividade (t ha-1) obteve um ajuste estatístico significativo (p < 0,05) ao modelo de segunda ordem. Os resultados indicaram respostas positivas na produtividade física em função da adubação azotada. A receita líquida operacional foi positiva para cvs. Guaçu/IZ.2, Cameroon-Piracicaba e Cana DÁfrica, com os respectivos valores R$326,80; R$ 219,54 e R$281,49 sem utilização do azoto, devido ao baixo preço da tonelada do capim (R$ 41,82) e elevado preço da tonelada do azoto (R$ 2.670,00). Conclui-se que há possibilidade de manipular a produção de capim-elefante para fins energéticos sem a utilização da adubação azotada

Agent based modelling helps in understanding the rules by which fibroblasts support keratinocyte colony formation

Background: Autologous keratincoytes are routinely expanded using irradiated mouse fibroblasts and bovine serum for clinical use. With growing concerns about the safety of these xenobiotic materials, it is desirable to culture keratinocytes in media without animal derived products. An improved understanding of epithelial/mesenchymal interactions could assist in this. Methodology/Principal Findings: A keratincyte/fibroblast o-culture model was developed by extending an agent-based keratinocyte colony formation model to include the response of keratinocytes to both fibroblasts and serum. The model was validated by comparison of the in virtuo and in vitro multicellular behaviour of keratinocytes and fibroblasts in single and co-culture in Greens medium. To test the robustness of the model, several properties of the fibroblasts were changed to investigate their influence on the multicellular morphogenesis of keratinocyes and fibroblasts. The model was then used to generate hypotheses to explore the interactions of both proliferative and growth arrested fibroblasts with keratinocytes. The key predictions arising from the model which were confirmed by in vitro experiments were that 1) the ratio of fibroblasts to keratinocytes would critically influence keratinocyte colony expansion, 2) this ratio needed to be optimum at the beginning of the co-culture, 3) proliferative fibroblasts would be more effective than irradiated cells in expanding keratinocytes and 4) in the presence of an adequate number of fibroblasts, keratinocyte expansion would be independent of serum. Conclusions: A closely associated computational and biological approach is a powerful tool for understanding complex biological systems such as the interactions between keratinocytes and fibroblasts. The key outcome of this study is the finding that the early addition of a critical ratio of proliferative fibroblasts can give rapid keratinocyte expansion without the use of irradiated mouse fibroblasts and bovine serum

Portuguese validation of the Internet Addiction Test: An empirical study

Abstract Background and aims Research into Internet addiction (IA) has increased greatly over the last decade. Despite its various definitions and general lack of consensus regarding its conceptualisation amongst researchers, instruments for measuring this phenomenon have proliferated in a number of countries. There has been little research on IA in Portugal and this may be partly due to the absence of standardised measurement tools for assessing IA. Methods This study attempted to address this issue by adapting a Portuguese version of the Internet Addiction Test (IAT) via a translation-back translation process and Confirmatory Factor Analysis in a sample of 593 Portuguese students that completed a Portuguese version of the IAT along with questions related to socio-demographic variables. Results The findings suggested that the IAT appears to be a valid and reliable instrument for measuring IA among Portuguese young adults as demonstrated by its satisfactory psychometric properties. However, the present findings also suggest the need to reword and update some of the IAT's items. Prevalence of IA found in the sample was 1.2% and is discussed alongside findings relating to socio-demographic correlates. Limitations and implications of the present study are also discussed. Conclusions The present study calls for a reflection of the IAT while also contributing to a better understanding of the basic aspects of IA in the Portuguese community since many health practitioners are starting to realise that Internet use may pose a risk for some individuals