Energy of bond defects in quantum spin chains obtained from local approximations and from exact diagonalization

We study the influence of ferromagnetic and antiferromagnetic bond defects on the ground-state energy of antiferromagnetic spin chains. In the absence of translational invariance, the energy spectrum of the full Hamiltonian is obtained numerically, by an iterative modification of the power algorithm. In parallel, approximate analytical energies are obtained from a local-bond approximation, proposed here. This approximation results in significant improvement upon the mean-field approximation, at negligible extra computational effort.Comment: 3 pages, 2 figures. Manuscript accepted by Journal of Magnetism and Magnetic Materials, special issue for LAWMMM 2007 conferenc

The Rise and Halt of Economic Development in Brazil, 1945-2004: Industrial Catching-up, Institutional Innovation and Financial Fragility

development, catch-up, institutions

Development of a first-contact protocol to guide assessment of adult patients in rehabilitation services networks

OBJECTIVE: This paper describes the development of the Protocol for Identification of Problems for Rehabilitation (PLPR), a tool to standardize collection of functional information based on the International Classification of Functioning, Disability and Health (ICF). DEVELOPMENT OF THE PROTOCOL: The PLPR was developed for use during the initial contact with adult patients within a public network of rehabilitation services. Steps to develop the protocol included: survey of the ICF codes most used by clinical professionals; compilation of data from functional instruments; development and pilot testing of a preliminary version in the service settings; discussion with professionals and development of the final version. The final version includes: user identification; social and health information; brief functional description (BFD); summary of the BFD; and PLPR results. Further testing of the final version will be conducted. CONCLUSIONS: The protocol standardizes the first contact between the user and the rehabilitation service. Systematic use of the protocol could also help to create a functional database that would allow comparisons between rehabilitation services and countries over time

Factors associated with walking, moderate and vigorous physical activities in adolescents

This study aimed at investigating the relationship between a set of variables (adolescents' gender, age, economic level, nutritional status, and fathers' educational level) and physical activity practices. The sample consisted of 578 students from a public school, aged between 11 and 16 years. The International Physical Activity Questionnaire (IPAQ, version 8, short form) was applied in order to measure their physical activity practices. Chi-square, independent t test and one-way ANOVA were implemented. Thirteen percent of adolescents were physically inactive and no significant difference was found between gender (p > .05). Compared to boys, girls spent more time in walking (p = .019) and vigorous activities (p = .017). Adolescents aged 14-16 years spent more time in walking compared with those aged 11-12 years (p = .026) and 13-year-olds (p = .006). There was a positive association between economic level and time spent in moderate physical activity (p = .034)

Expressão de HLA-DR em nervo periférico de esclerose lateral amiotrófica

To investigate the possibility of local antigen presentation within the peripheral nerve in amyotrophic lateral sclerosis (ALS), cryostat sections of 83 peripheral nerve biopsies were stained for the demonstration of HLA-DR using a monoclonal antibody. Forty samples showed increased expression of HLA-DR in endoneurium. The phenotypic characteristics of the HLA-DR positive cells are chiefly Schwann cells, using S-100 protein as a marker. We did not detect any co-expression between HLA-DR and NF (axons) and HLA-DR and myelin marker. We also detected co-expression between HLA-DR and NGFr in a majority of HLA-DR positive cells. Inflammatory cells were infrequent, being detected only in 11 cases, predominantly around epineurial blood vessels. Motor and sensory nerve biopsies performed simultaneously showed higher expression of HLA-DR in motor nerves in 2 out of 4 patients. The significance of these findings is not clear. The presence of endoneurial cells expressing HLA-DR suggests that an autoimmune mechanism may be involved in ALS having Schwann as the main target.Para investigar a possibilidade de comprometimento auto imune no nervo periférico de pacientes com esclerose lateral amiotrófica (ELA) 83 biópsias do nervo periférico de 79 pacientes (51 sexo masculino, 28 sexo feminino) com média de idade de 62 anos (variação de 19 a 82) foram congeladas e coradas para demonstração de HLA-DR usando anticorpo monoclonal. Quarenta amostras (48%) mostraram expressão nitidamente aumentada de HLA-DR na região endoneural. Usando proteína S-100 como marcador, demonstramos que HLA-DR se expressava principalmente nas células de Schwann. Não encontramos co-expressão com HLA-DR usando anticorpos antineurofilamento ou antimielina, mas detectamos co-expressão de HLA-DR e anti-receptor de fator de crescimento nervoso na maioria das células HLA-DR positivas. Células inflamatórias foram encontradas ocasionalmente, sendo detectadas em somente 11 casos, predominantemente ao redor de vasos sanguíneos epineurais. Biópsias de nervo sensitivo e motor feitas simultaneamente mostraram maior expressão de HLA-DR em nervos motores de 2 dos 4 pacientes. A significância desses achados ainda não é clara. A presença de células endoneurais expressando HLA-DR sugere que mecanismos auto imunes podem estar envolvidos na ELA tendo a célula de Schwann como um dos principais alvos.Escola Paulista de MedicinaColumbia University College of Physicians and Surgeons Division of NeuropathologyUNIFESP, EPMSciEL

Consistency analysis of a nonbirefringent Lorentz-violating planar model

In this work analyze the physical consistency of a nonbirefringent Lorentz-violating planar model via the analysis of the pole structure of its Feynman propagators. The nonbirefringent planar model, obtained from the dimensional reduction of the CPT-even gauge sector of the standard model extension, is composed of a gauge and a scalar fields, being affected by Lorentz-violating (LIV) coefficients encoded in the symmetric tensor $\kappa_{\mu\nu}$. The propagator of the gauge field is explicitly evaluated and expressed in terms of linear independent symmetric tensors, presenting only one physical mode. The same holds for the scalar propagator. A consistency analysis is performed based on the poles of the propagators. The isotropic parity-even sector is stable, causal and unitary mode for $0\leq\kappa_{00}<1$. On the other hand, the anisotropic sector is stable and unitary but in general noncausal. Finally, it is shown that this planar model interacting with a $\lambda|\varphi|^{4}-$Higgs field supports compactlike vortex configurations.Comment: 11 pages, revtex style, final revised versio

Can timber provision from Amazonian production forests be sustainable?

Around 30 Mm3 of sawlogs are extracted annually by selective logging of natural production forests in Amazonia, Earth's most extensive tropical forest. Decisions concerning the management of these production forests will be of major importance for Amazonian forests' fate. To date, no regional assessment of selective logging sustainability supports decision-making. Based on data from 3500 ha of forest inventory plots, our modelling results show that the average periodic harvests of 20 m3 ha−1 will not recover by the end of a standard 30 year cutting cycle. Timber recovery within a cutting cycle is enhanced by commercial acceptance of more species and with the adoption of longer cutting cycles and lower logging intensities. Recovery rates are faster in Western Amazonia than on the Guiana Shield. Our simulations suggest that regardless of cutting cycle duration and logging intensities, selectively logged forests are unlikely to meet timber demands over the long term as timber stocks are predicted to steadily decline. There is thus an urgent need to develop an integrated forest resource management policy that combines active management of production forests with the restoration of degraded and secondary forests for timber production. Without better management, reduced timber harvests and continued timber production declines are unavoidable

On the equivalence between Implicit Regularization and Constrained Differential Renormalization

Constrained Differential Renormalization (CDR) and the constrained version of Implicit Regularization (IR) are two regularization independent techniques that do not rely on dimensional continuation of the space-time. These two methods which have rather distinct basis have been successfully applied to several calculations which show that they can be trusted as practical, symmetry invariant frameworks (gauge and supersymmetry included) in perturbative computations even beyond one-loop order. In this paper, we show the equivalence between these two methods at one-loop order. We show that the configuration space rules of CDR can be mapped into the momentum space procedures of Implicit Regularization, the major principle behind this equivalence being the extension of the properties of regular distributions to the regularized ones.Comment: 16 page