1,508 research outputs found
Reliability analysis of reinforced concrete structures with a methodology to account stochastic effects of material properties
Neste trabalho é dada uma ênfase especial à inclusão das incertezas na avaliação do comportamento estrutural, objetivando uma melhor representação das caracterÃsticas do sistema e uma quantificação da importância destas incertezas no projeto. É tratado o problema da análise de confiabilidade de estruturas, incluindo o efeito da variabilidade espacial das suas propriedades. Para tanto, é proposto um modelo de elementos finitos para a representação do comportamento do concreto armado para cargas de curta e longa duração, o qual inclui as principais caracterÃsticas observadas neste material. Também é desenvolvido um modelo para a geração de campos estocásticos multidimensionais não Gaussiano para as propriedades do material e que é independente da malha de elementos finitos. Um exemplo da geração de campos estocásticos bidimensionais não Gaussianos numa placa quadrada de aço é apresentado em primeiro lugar. Posteriormente, a análise de confiabilidade é realizada em relação a uma função de estado limite, a qual estabelece que a flecha na secção localizada no centro do vão de uma viga de concreto armado não deve ultrapassar um valor prescrito. Finalmente, a influência dos efeitos de longa duração na confiabilidade de uma viga de concreto armado é estudada, com e sem a consideração da corrosão da armadura.In this paper, special emphasis is given to the inclusion of uncertainties in the evaluation of structural behaviour aiming at a better representation of the system characteristics and the quantification of the importance of these uncertainties in the project. It deals with the structural reliability analysis problem accounting the effect of spatial variability of material properties. To this end it is proposed a finite element model to represent the behaviour of reinforced concrete for short and long-term loads, which includes the main features observed in this material. It was developed a model for the generation of multidimensional non-Gaussian stochastic fields for the material properties that is independent of the finite element mesh. First, an example of a two-dimensional non-Gaussian stochastic field generation in a square steel plate is presented. Latter, the reliability analysis is performed to a limit state function based on prescribed values of mid-span displacements on a simply-supported reinforced beam. Finally, the influence of long-term effects on the reliability of a reinforced concrete beam is studied considering the effect of steel reinforcement corrosion.Peer Reviewe
Intercellular communication between osteocytes and stem cells:implications for bone tissue engineering
Intercellular communication between osteocytes and stem cells:implications for bone tissue engineering
Fast and slow-twitching muscles are differentially affected by reduced cholinergic transmission in mice deficient for VAChT: A mouse model for congenital myasthenia
Congenital myasthenic syndromes (CMS) result from reduced cholinergic transmission at neuromuscular junctions (NMJs). While the etiology of CMS varies, the disease is characterized by muscle weakness. To date, it remains unknown if CMS causes long-term and irreversible changes to skeletal muscles. In this study, we examined skeletal muscles in a mouse line with reduced expression of Vesicular Acetylcholine Transporter (VAChT, mouse line herein called VAChT-KDHOM). We examined this mouse line for several reasons. First, VAChT plays a central function in loading acetylcholine (ACh) into synaptic vesicles and releasing it at NMJs, in addition to other cholinergic nerve endings. Second, loss of function mutations in VAChT causes myasthenia in humans. Importantly, VAChT-KDHOM present with reduced ACh and muscle weakness, resembling CMS. We evaluated the morphology, fiber type (myosin heavy chain isoforms), and expression of muscle-related genes in the extensor digitorum longus (EDL) and soleus muscles. This analysis revealed that while muscle fibers atrophy in the EDL, they hypertrophy in the soleus muscle of VAChT-KDHOM mice. Along with these cellular changes, skeletal muscles exhibit altered levels of markers for myogenesis (Pax-7, Myogenin, and MyoD), oxidative metabolism (PGC1-alpha and MTND1), and protein degradation (Atrogin1 and MuRF1) in VAChT-KDHOM mice. Importantly, we demonstrate that deleterious changes in skeletal muscles and motor deficits can be partially reversed following the administration of the cholinesterase inhibitor, pyridostigmine in VAChT-KDHOM mice. These findings reveal that fast and slow type muscles differentially respond to cholinergic deficits. Additionally, this study shows that the adverse effects of cholinergic transmission, as in the case of CMS, on fast and slow type skeletal muscles are reversible
A sequential quadratic programming algorithm that combines merit function and filter ideas
A sequential quadratic programming algorithm for solving nonlinear programming problems is presented. The new feature of the algorithm is related to the definition of the merit function. Instead of using one penalty parameter per iteration and increasing it as the algorithm progresses, we suggest that a new point is to be accepted if it stays sufficiently below the piecewise linear function defined by some previous iterates on the (f,C2²)-space. Therefore, the penalty parameter is allowed to decrease between successive iterations. Besides, one need not to decide how to update the penalty parameter. This approach resembles the filter method introduced by Fletcher and Leyffer [Math. Program., 91 (2001), pp. 239-269], but it is less tolerant since a merit function is still used. Numerical comparison with standard methods shows that this strategy is promising.33737
STILF - A spatiotemporal interval logic formalism for reasoning about events in remote sensing data
Although several studies perform time series analysis using remote sensing data provided by Earth observation satellites, few have been explored concerning the reasoning about land use change using these data. Besides, exists the challenge of make the best use of big Earth observation data sets to represent change. In this context, this work presents a new formalism - STILF (Spatiotemporal Interval Logic Formalism), and shows how to use it for reasoning about land use change using big Earth observation data. Extending the ideas from Allen’s interval temporal logic, we introduce predicates holds(o, p, t) and occur(o, p, Te) to build a general framework to reason about events. Events can be defined as complete entities on their respective time intervals and their lifetime is limited while objects persist in time, with a defined begin and end. Since events are intrinsically related to the objects they modify, a geospatial event formalism should specify not only what happens, but also which objects are affected by such changes. The formalism proposed and predicates extended from Allen''''''''s ideas can model and capture changes using big Earth observation data, and also allows reasoning about land use trajectories in regional or global areas. Examples for tropical forest area application is presented to better understand our proposal using STILF. For the future, the proposed formalism will be include other temporal analysis tools to thinking about events related the land use and cover change
The Impact of the Malolactic Fermentation in the Volatile Composition of Trincadeira Wine Variety
Use of commercial starters for malolactic fermentation (MLF) is a
common practice, and outcomes of this procedure are very relevant for wine
producers because aroma attributes might change according to the strain
used.
MLF was carried out in the Trincadeira wine variety in three batches:
spontaneously and with inoculation of two different commercial starters. Wine
extracts before and after MLF were obtained through liquid–liquid extraction.
Gas chromatography/ion trap mass spectrometry analysis allowed the detection
of 21 compounds, some of them tentatively identified through electron
impact spectra comparison with a database, through interpretation of multistage
mass spectrometry and chemical ionization mass spectrometry spectra
and confirmation by comprehensive multidimensional gas chromatography/
time of flight-mass spectrometry (GC ¥ GC/ToF-MS).
After MLF, an increase in ethyl lactate, g-butyrolactone and diethyl
succinate and a drop in isoamyl acetate, ethyl octanoate, ethyl decanoate,
2,3-dimethyl-hexan-3-ol, propanol, isobutanol and 2,3-butanediol was
observed. The concentrations of the 10 compounds are statistically different in
wines before and after MLF, and wines after MLF show significant differences
for the nine compounds
Tin determination in fistula seals from Conimbriga and Augusta Emerita
info:eu-repo/semantics/publishedVersio
Estudo da associação entre receio de queda e análise postural na população sénior
Os factores biológicos, doenças e causas externas podem influenciar a fase de envelhecimento. A queda é considerada como uma causa externa já que é um evento não esperado, no qual o indivÃduo muda de posição em relação à sua posição inicial, o que poderá acarretar sérios problemas para o idoso. A queda ocorre devido à perda total do equilÃbrio postural, podendo estar relacionada à insuficiência súbita dos mecanismos neurais e osteoarticulares envolvidos na manutenção da postura. O objectivo deste estudo foi de analisar os resultados obtidos em diferentes tipos de testes de avaliação do equilÃbrio em associação entre o receio de queda e a postura corporal de forma a observar ou não se existe uma correlação entre o risco de quedas e o equilÃbrio em dois grupos distintos de idosas. Metodologia: A amostra foi constituÃda por 41 sujeitos do sexo feminino, 21 mulheres incluÃram o grupo de força (GF, 67,33 ± 4,61 anos de idade, 1,55 ± 0,08 [m] de estatura e 74,08 ± 11,79 [kg] de massa corporal) e outras vinte no grupo aeróbio (GA, 65,35 ±3,01 anos de idade, 1,56 ± 0,09 [m] de estatura e 69,43 ± 10,03 [kg] de massa corporal). A avaliação postural estática foi feita pelo teste SAPo; os fatores de risco através da Escala de Berg; a avaliação dos problemas de mobilidade pelo Teste Tinetti; o risco de queda e a capacidade de transferência, relacionado com o equilÃbrio dinâmico pelo Time Up & Go; o medo de cair o Falls Efficacy Scale. A normalidade da distribuição foi avaliada com o teste de Shapiro-Wilk, como analise exploratoria. Foram calculadas as estatÃsticas descritivas (média ± 1 DP) de todas as variáveis dependentes seleccionadas. Como estatÃstica inferencial fez-se recurso ao teste T de Student para nÃveis de significância P ≤ 0,05. Os alinhamentos segmentares e ângulos articulares analisados sugerem que o GA tende apresentar uma postura ortostática que procura promover uma quantidade inferior de esforço e/ou de sobrecarga mecânica sobre o aparelho locomotor do que o GF. Relativamente aos testes de equilÃbrio realizados à s utentes do programa mais idade mais saúde, conclui-se que não existem diferenças significativas, quer a nÃvel de equilÃbrio estático ou dinâmico. Na avaliação da associação do risco de queda e da avaliação da postura corporal, pode-se observar nas tabelas acima, que não existem diferenças significativas intra-grupos, isto é, tanto o grupo de força como o grupo aeróbio não sofrem risco de queda segundo a avaliação da sua postura. Por outro lado, quando a avaliação foi realizada com a junção de ambos os grupos, podem-se observar diferenças significativas na associação do risco de queda com a postugrafia (*0,05). Conclusão: Tudo indica que as senhoras que frequentam o programa não estão sujeitas a riscos acrescidos de queda
Distribution of non-LEE-encoded type 3 secretion system dependent effectors in enteropathogenic Escherichia coli
Enteropathogenic Escherichia coli (EPEC) are important human gastroenteritis agents. The prevalence of six non-LEE genes encoding type 3 translocated effectors was investigated. The nleC, cif and nleB genes were more prevalent in typical than in atypical EPEC, although a higher diversity of genes combinations was observed in atypical EPEC.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento CientÃfico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de NÃvel Superior (CAPES)Universidade Federal de São Paulo (UNIFESP) Departamento de Microbiologia, Imunologia e ParasitologiaUniversidade Estadual Paulista Julio de Mesquita Filho Instituto de Biociências Departamento de Microbiologia e ImunologiaUNIFESP, Depto. de Microbiologia, Imunologia e ParasitologiaSciEL
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