Analysis of a new cross flow heat exchanger flow arrangement - Extension to several rows

The present paper presents a theoretical analysis of a cross flow heat exchanger with a new flow arrangement comprehending several tube rows. The thermal performance of the proposed flow arrangement is compared with the thermal performance of a typical counter cross flow arrangement that is used in chemical, refrigeration, automotive and air conditioning industries. The thermal performance comparison has been performed in terms of the following parameters: heat exchanger effectiveness and efficiency, dimensionless entropy generation, entransy dissipation number, and dimensionless local temperature differences. It is also shown that the uniformity of the temperature difference field leads to a higher thermal performance of the heat exchanger. In the present case this is accomplished thorough a different organization of the in-tube fluid circuits in the heat exchanger. The relation between the recently introduced "entransy dissipation number" and the conventional thermal effectiveness has been obtained in terms of the "number of transfer units". A case study has been solved to quantitatively to obtain the temperature difference distribution over two rows units involving the proposed arrangement and the counter cross flow one. It has been shown that the proposed arrangement presents better thermal performance regardless the comparison parameter. (C) 2012 Elsevier Masson SAS. All rights reserved.

Facial Profile Evaluation of Isolated Pierre Robin Sequence

Objective: To evaluate numerically the facial profile of children with isolated Pierre Robin sequence (PRS) and to compare them with a control group that has no pathologies and exhibits regular and balanced facial growth, with no skeletal alterations. Patients: Eighty-three children aged 5 to 10 years (PRS group, n = 60; control group, n = 23) were selected. Setting: Hospital for Rehabilitation of Craniofacial Anomalies, University of Sao Paulo (HRAC-USP). Children from the control group were taken from the program of Interceptive Orthodontics at HRAC-USP. Design: Angular and ratio analyses of the facial profiles in both groups were realized through digital photographs. The PRS group was subdivided into two groups-complete and incomplete-according to the sagittal extension of the cleft palate, to investigate the possible influence of cleft extension on the face. Results: The facial convexity angle and the facial inferior third angle were considerably higher in the PRS groups than in the control group and were not significantly different between PRS groups. Nasolabial angle did not differ between groups. Conclusion: The facial profile was more convex in individuals with PRS than in those with regular facial growth and with no pathology. The mandible was responsible for the convexity of the profile in PRS because of its lack off anterior projection. An important relationship between the extension of the cleft palate and alterations in facial profile in PRS was not observed.

Musculoskeletal reported symptoms among aircraft assembly workers: a multifactorial approach

The aim of this study was to evaluate factors associated with reported work-related musculoskeletal symptoms among aircraft assembly workers. Population consisted of 552 (491 men/61 women) workers who performed tasks related to the work of aircraft assembly. Participants completed a comprehensive questionnaire, including socio-demographic information, habits/lifestyles, working conditions, and work organization. Workers also answered the Nordic Musculoskeletal Questionnaire to obtain data on musculoskeletal symptoms. Multivariate logistic regression was performed to analyze factors associated with musculoskeletal reported symptoms. Results showed that body regions with the highest prevalence of reported musculoskeletal symptoms were similar when referred the past twelve months and the past seven days. Significant factors associated with musculoskeletal symptoms included variables related to conflicts at work, sleep problems, mental fatigue, and lack of time for personal care and recovery. Working time in the industry was associated only with reports for the last seven days and regular physical activity off-work seems to be a positive factor in preventing musculoskeletal symptoms for the past twelve months. The results highlight the multi-factorial nature of the problem. Actions to prevent musculoskeletal diseases at the aircraft assembly work should consider multiple interventions that would promote better recovery between work shifts.

Trans-Planckian problem in the healthy extension of Horava-Lifshitz gravity

Planck scale physics may influence the evolution of cosmological fluctuations in the early stages of cosmological evolution. Because of the quasiexponential redshifting, which occurs during an inflationary period, the physical wavelengths of comoving scales that correspond to the present large-scale structure of the Universe were smaller than the Planck length in the early stages of the inflationary period. This trans-Planckian effect was studied before using toy models. The Horava-Lifshitz (HL) theory offers the chance to study this problem in a candidate UV complete theory of gravity. In this paper we study the evolution of cosmological perturbations according to HL gravity assuming that matter gives rise to an inflationary background. As is usually done in inflationary cosmology, we assume that the fluctuations originate in their minimum energy state. In the trans-Planckian region the fluctuations obey a nonlinear dispersion relation of Corley-Jacobson type. In the "healthy extension" of HL gravity there is an extra degree of freedom which plays an important role in the UV region but decouples in the IR, and which influences the cosmological perturbations. We find that in spite of these important changes compared to the usual description, the overall scale invariance of the power spectrum of cosmological perturbations is recovered. However, we obtain oscillations in the spectrum as a function of wave number with a relative amplitude of order unity and with an effective frequency which scales nonlinearly with wave number. Taking the usual inflationary parameters we find that the frequency of the oscillations is so large as to render the effect difficult to observe.

Photoconduction action spectra of regio-regular poly(3-hexylthiopene):TiO2 diodes

The development of polymer-based photovoltaic devices brings the promise of low-cost and lightweight solar energy conversion systems. This technology requires new materials and device architectures with enhanced efficiency and lifetime, which depends on the understanding of charge-transport mechanisms. Organic films combined with electronegative nanoparticles may form systems with efficient dissociation of the photogenerated excitons, thus increasing the number of carriers to be collected by the electrodes. In this paper we investigate the steady-state photoconductive action spectra of devices formed by a bilayer of regio-regular poly(3-hexylthiophene) (RRP3HT) and TiO2 sandwiched between ITO and aluminum electrodes (ITO/TiO2:RRP3HT/Al). Photocurrents were measured for distinct bias voltages with illumination from either side of the device. Heterojunction structures were prepared by spin coating a RRP3HT film on an already deposited TiO2 layer on ITO. Symbatic and antibatic curves were obtained and a model for photocurrent action spectra was able to fit the symbatic responses. The quantum yield increased with the electric field, indicating that exciton dissociation is a field-assisted process as in an Onsager mechanism. Furthermore, the quantum yield was significantly higher when illumination was carried out through the ITO electrode onto which the TiO2 layer was deposited, as the highly electronegative TiO2 nanoparticles were efficient in exciton dissociation.

Low dynamic muscle strength and its associations with fatigue, functional performance, and quality of life in premenopausal patients with systemic lupus erythematosus and low disease activity: a case–control study

Abstract Background The purpose of the present study was to compare dynamic muscle strength, functional performance, fatigue, and quality of life in premenopausal systemic lupus erythematosus (SLE) patients with low disease activity versus matched-healthy controls and to determine the association of dynamic muscle strength with fatigue, functional performance, and quality of life in SLE patients. Methods We evaluated premenopausal (18–45 years) SLE patients with low disease activity (Systemic lupus erythematosus disease activity index [SLEDAI]: mean 1.5 ± 1.2). The control (n = 25) and patient (n = 25) groups were matched by age, physical characteristics, and the level of physical activities in daily life (International Physical Activity Questionnaire IPAQ). Both groups had not participated in regular exercise programs for at least six months prior to the study. Dynamic muscle strength was assessed by one-repetition maximum (1-RM) tests. Functional performance was assessed by the Timed Up and Go (TUG), in 30-s test a chair stand and arm curl using a 2-kg dumbbell and balance test, handgrip strength and a sit-and-reach flexibility test. Quality of life (SF-36) and fatigue were also measured. Results The SLE patients showed significantly lower dynamic muscle strength in all exercises (leg press 25.63%, leg extension 11.19%, leg curl 15.71%, chest press 18.33%, lat pulldown 13.56%, 1-RM total load 18.12%, P < 0.001-0.02) compared to the controls. The SLE patients also had lower functional performance, greater fatigue and poorer quality of life. In addition, fatigue, SF-36 and functional performance accounted for 52% of the variance in dynamic muscle strength in the SLE patients. Conclusions Premenopausal SLE patients with low disease activity showed lower dynamic muscle strength, along with increased fatigue, reduced functional performance, and poorer quality of life when compared to matched controls.

Inclusão de crianças com deficiência na escola regular numa região do município de São Paulo: conhecendo estratégias e ações

A inclusão de alunos com necessidades educacionais especiais no ensino regular depende da preparação da comunidade escolar para promover a participação de todos os alunos. Foi objetivo deste estudo conhecer, do ponto de vista do professor do ensino fundamental da rede pública municipal, as estratégias pedagógicas que utilizavam para a inclusão de crianças com deficiência na classe comum. Para isso foram realizadas entrevistas semiestruturadas individuais e, posteriormente, grupais com 11 professores de cinco escolas, um representante do Centro de Formação e Acompanhamento à Inclusão e um coordenador pedagógico. As entrevistas foram gravadas e transcritas. Após diversas leituras foi possível identificar como temáticas principais: sentidos e imaginários do professor sobre a deficiência, formação do professor para efetivação do processo de inclusão, bem como a utilização de estratégias pedagógicas diferenciadas e formação de rede de apoio na escola. Os entrevistados utilizavam estratégias gerais como aula expositiva, debates, e específicas como: avaliação dos alunos, adaptação do material, atividades em duplas, parceria com o professor da sala de apoio e acompanhamento à inclusão. Parte dos entrevistados trouxe uma visão com relação aos alunos com deficiência permeada de possibilidades, acreditando no potencial de aprendizagem dos mesmos, enquanto para outros, o discurso centrou-se, sobretudo, na impossibilidade da aprendizagem. Os docentes identificaram a necessidade de apoio institucional para seu trabalho, incluindo possibilidades de formação a partir das demandas cotidianas. Responder às necessidades levantadas é parte dos desafios para implementar a Educação Inclusiva na perspectiva da Educação para Todos, para a efetivação dos direitos de crianças com necessidades educacionais especiais.

Chain extension of poly (ethylene terephthalate) by reactive extrusion with secondary stabilizer

Poly(ethylene tereftalate) (PET) is a polymer highly susceptible to the hydrolytic reactions that occur during applications and mainly in thermomechanical processing. These reactions lead to the decrease of molecular weight of the polymer, limiting the recycling number of the material. The reactive extrusion of the PET in presence of chain extenders is an alternative to recover mechanical and rheological properties that were depreciated by the polymer degradation. In this study, PET wastes from nonwoven fabrics production were extruded in presence of the secondary stabilizer Irgafos 126 (IRG) on variable concentrations. The results showed that Irgafos 126 increased molecular weight, decreased crystallinity and changed processing behavior of the PET, similarly to the effects produced by the well-known chain extender pyromellitic dianhydride (PMDA), showing that the secondary stabilizer Irgafos 126 can also act as a chain extender for the PET.

Impacto da orientação para a prática regular de atividade física dois anos após o parto

OBJETIVOS: avaliar as modificações na prática de atividade física (AF) e as barreiras para adoção de um estilo de vida saudável em mulheres que receberam orientações nutricionais e de AF durante a gestação e no primeiro ano após o parto. MÉTODOS: estudo de coorte com 57 mulheres (Grupo Controle = 29 e Grupo Intervenção = 28), e idade média igual a 28 (±6) anos. As informações foram obtidas através de entrevistas em visita domiciliar (durante a intervenção) e inquérito telefônico (um ano após o término da intervenção), utilizou-se questionário de AF. Para análise das barreiras foi realizada uma entrevista semiestruturada com questões abertas, as quais foram codificadas e agrupadas para análise dos dados. Foram realizados testes de qui-quadrado, Mann-Whitney U e Friedman. RESULTADOS: aos seis meses, apenas 30% das mulheres do grupo Intervenção realizavam AF no lazer pelo menos 120 minutos por semana, contra 10% do grupo Controle, reduzindo para 18% e 4%, respectivamente, dois anos após o parto. As principais barreiras à prática de AF regular foram: falta de tempo (44%), cuidado com os filhos (37%), trabalho (21%), afazeres domésticos (21%) e comodismo (26%). CONCLUSÕES: futuros programas devem priorizar a aquisição de conhecimento, visando à adoção de um estilo de vida ativo no pós-parto, considerando as barreiras maternas.

Inclusão do portador de necessidades especiais no ensino regular: revisão da literatura

OBJETIVOS: Analisar criticamente a inclusão do portador de necessidades especiais no ensino regular brasileiro, considerando aspectos sociais e jurídicos, por meio de revisão de literatura. ESTRATÉGIA DE PESQUISA: A pesquisa bibliográfica foi conduzida em bases de dados de acesso público: LILACS, SciELO, Portal Cochrane e IUSDATA, sendo esta última da Biblioteca da Faculdade de Direito da Universidade de São Paulo, considerando todos os artigos publicados até o mês de dezembro de 2010. Como estratégia de busca foram utilizados os seguintes termos livres: educação inclusiva, educação especial, proposta inclusiva e portador de necessidades especiais. CRITÉRIOS DE SELEÇÃO: Durante a busca, foram avaliados e selecionados apenas os estudos cujo resumo ou corpo do artigo tivesse relação com o objetivo proposto. ANÁLISE DE DADOS : Os artigos potencialmente relevantes para a revisão foram apresentados em uma ficha protocolar contendo critérios de elegibilidade do estudo, métodos utilizados, características do grupo de artigos analisado, tipo de intervenção realizada e resultados obtidos no estudo. Os artigos classificados como opinião de especialistas, apesar de apresentarem baixo nível de evidência científica, foram incluídos no trabalho, pois são frequentemente encontrados na literatura sobre o assunto. RESULTADOS: Foram encontrados 1.399 artigos, e após leitura dos resumos foram selecionados 120 artigos potencialmente relevantes considerando-se o objetivo da pesquisa. Destes, 67 artigos foram citados em mais de uma base de dados, o que resultou em 53 artigos para serem lidos na íntegra. Após a leitura dos 53 artigos, foram excluídos 15 que não se enquadravam nos critérios de inclusão. Desta forma, 38 estudos foram incluídos e analisados. CONCLUSÃO: Após a análise crítica da literatura da área conclui-se que, até o momento, de maneira geral, a escola recebe, mas há muito a percorrer para incluir os alunos portadores de necessidades especiais, embora o país possua o escopo da inclusão. Assim, faz-se necessário o estabelecimento de diretrizes e ações políticas visando uma inclusão efetiva.

Sharp estimates for eigenvalues of integral operators generated by dot product kernels on the sphere

We obtain explicit formulas for the eigenvalues of integral operators generated by continuous dot product kernels defined on the sphere via the usual gamma function. Using them, we present both, a procedure to describe sharp bounds for the eigenvalues and their asymptotic behavior near 0. We illustrate our results with examples, among them the integral operator generated by a Gaussian kernel. Finally, we sketch complex versions of our results to cover the cases when the sphere sits in a Hermitian space.

One-repetition maximum test and isokinetic leg extension and flexion: correlations and predicted values

The most typical maximum tests for measuring leg muscle performance are the one-repetition maximum leg press test (1RMleg) and the isokinetic knee extension/flexion (IKEF) test. Nevertheless, their inter-correlations have not been well documented, mainly the predicted values of these evaluations. This correlational and regression analysis study involved 30 healthy young males aged 18-24y, who have performed both tests. Pearson's product moment correlation between 1RMleg and IKEF varied from 0.20 to 0.69 and the more exact predicted test was to 1RMleg (R2 = 0.71). The study showed correlations between 1RMleg and IKEF although these tests are different (isotonic vs. isokinetic) and provided further support for cross determination of 1RMleg and IKEF by linear and multiple linear regression analysis.