Resistência ao cisalhamento de vigas de concreto reforçado com fibras de aço

This research investigates the mechanical shear behavior of twelve reinforced concrete beams. The type of loading (normal or reverse), the presence or absence of steel fibers (30 kgf/m³), and the concrete compressive strength (40MPa, 60 MPa, or 80 MPa) were the mains test variables studied. The beams had nominally identical cross-sections, effective depths, and longitudinal and transverse reinforcements. The loads were increased at 10 kN intervals until shear failure occurred, defined by the yielding of the first stirrup. The ultimate shear loads observed in these tests were compared to three empirical and semi-empirical formulas proposed in the literature. Based on the test results it could be concluded that concrete compressive strength has no significant influence on the reduction of ultimate shear load caused by reverse loading. Reverse-loaded beams with fibers had approximately the same ultimate shear strength as concrete beams without fibers subjected to normal loading, regardless of the compressive strength of the concrete.Este trabalho investiga o comportamento ao esforço cortante de doze vigas em concreto com adição de fibras de aço. As principais variáveis estudadas foram o tipo de carregamento (normal ou reverso), a presença ou a ausência de fibras de aço (30kgf/m³) e a resistência do concreto à compressão (40 MPa, 60 MPa, ou 80 MPa). As vigas apresentavam seção transversal, altura útil e armaduras longitudinais e transversais nominalmente idênticas. Uma carga concentrada, no meio do vão da viga, foi aplicada em intervalos de 10 kN até a ruptura por cisalhamento, definida pelo escoamento do primeiro estribo em solicitação. A carga última de cisalhamento observada nos testes foi comparada com três formulas empíricas, e semi-empiricas, propostas na literatura. Baseando-se nos resultados dos testes, concluiu-se que a resistência à compressão do concreto não tem influencia significativa na parcela de redução da carga ultima de cisalhamento, promovida pela reversão do carregamento. Vigas sujeitas ao carregamento reverso e com fibras apresentaram, aproximadamente, a mesma resistência última de cisalhamento que as vigas sem fibras sujeitas ao carregamento normal, independentemente da resistência do concreto à compressão.78479

Avaliação experimental dos métodos de prevenção de fissuras na interface alvenaria de vedação e pilar de concreto

Cracks that form at the interfaces between masonry structures are common uncontrolled occurrences in buildings. Numerous methods have been proposed by the construction industry to address this problem. Cracks continuously form in the joints between concrete columns and masonry infill walls. In this study, the most common methods for preventing these types of cracks were evaluated in laboratory experiments. Column masonry models were constructed using different types of joints between concrete columns and masonry infill walls, such as steel bars and steel mesh. The efficiency of each type of joint method was evaluated by performing direct tensile tests (pullout tests) on the models and monitoring the evolution of the crack opening in the joint between the column and wall, as a function of load applied to the model. The results from this study indicate that the model composed of electrowelded wire mesh without steel angles is the best model for controlling cracking in the joints between concrete columns and masonry infill walls.As fissuras na interface alvenaria/estrutura são ocorrências patológicas comuns nas edificações e muitos são os métodos propostos pela indústria da construção que prometem evitar este problema. De caráter recorrente encontram-se as fissuras na ligação pilar de concreto e parede de alvenaria. Neste trabalho, são avaliados, em laboratório, os métodos mais usuais de prevenção deste tipo de fissura. Modelos pilar/alvenaria foram construídos utilizando-se diferentes tipologias de ligação entre o pilar de concreto e a parede de alvenaria, desde o usual ferro cabelo até telas de aço. A eficiência de cada um destes métodos de ligação foi avaliada por intermédio de ensaio dos modelos à tração direta, com o monitoramento da evolução da abertura da fissura na ligação pilar/parede em função do incremento de carga aplicada ao modelo. Os resultados desta pesquisa indicaram o modelo composto por tela metálica eletrossoldada, e sem cantoneira de aço, como a melhor técnica de controle da fissuração na ligação pilar de concreto e parede de alvenaria, dentre todos os modelos avaliados.76577

Reliability and validity of a sedentary behavior questionnaire for South American pediatric population: SAYCARE study

Background Multicenter studies from Europe and the United States have developed specifically standardized questionnaires for assessing and comparing sedentary behavior, but they cannot be directly applied for South American countries. The aim of this study was to assess the reliability and validity of the South American Youth Cardiovascular and Environmental (SAYCARE) sedentary behavior questionnaire. Methods Children and adolescents from seven South American cities were involved in the test-retest reliability (children: n = 55; adolescents: n = 106) and concurrent validity (children: n = 93; adolescents: n = 94) studies. The SAYCARE sedentary behavior questionnaire was administered twice with two-week interval and the behaviors were parent-reported for children and self-reported for adolescents. Questions included time spent watching television, using a computer, playing console games, passive playing (only in children) and studying (only in adolescents) over the past week. Accelerometer was used for at least 3 days, including at least one weekend day. We compared values of sedentary time, using accelerometers, by quartiles of reported sedentary behavior time and their sum. Results The reliability of sedentary behavior time was moderate for children (rho ≥0.45 and k ≥ 0.40) and adolescents (rho ≥0.30). Comparisons between the questionnaire and accelerometer showed a low overall agreement, with the questionnaire systematically underreporting sedentary time in children (at least, − 332.6 ± 138.5 min/day) and adolescents (at least, − 399.7 ± 105.0 min/day). Conclusion The SAYCARE sedentary behavior questionnaire has acceptable reliability in children and adolescents. However, the findings of current study indicate that SAYCARE questionnaire is not surrogate of total sedentary time

Inspiratory Muscle Training in the Intensive Care Unit: A New Perspective

BACKGROUND: Prolonged use of mechanical ventilation (MV) leads to weakening of the respiratory muscles, especially in patients subjected to sedation, but this effect seems to be preventable or more quickly reversible using respiratory muscle training. The aims of the study were to assess variations in respiratory and hemodinamic parameters with electronic inspiratory muscle training (EIMT) in tracheostomized patients requiring MV and to compare these variations with those in a group of patients subjected to an intermittent nebulization program (INP). METHODS: This was a pilot, prospective, randomized study of tracheostomized patients requiring MV in one intensive care unit (ICU). Twenty-one patients were randomized: 11 into the INP group and 10 into the EIMT group. Two patients were excluded in experimental group because of hemodynamic instability. RESULTS: In the EIMT group, maximal inspiratory pressure (MIP) after training was significantly higher than that before (P = 0.017), there were no hemodynamic changes, and the total weaning time was shorter than in the INP group (P = 0.0192). CONCLUSION: The EIMT device is safe, promotes an increase in MIP, and leads to a shorter ventilator weaning time than that seen in patients treated using INP.info:eu-repo/semantics/publishedVersio

Pathogen- and Host-Directed Antileishmanial Effects Mediated by Polyhexanide (PHMB)

BACKGROUND:Cutaneous leishmaniasis (CL) is a neglected tropical disease caused by protozoan parasites of the genus Leishmania. CL causes enormous suffering in many countries worldwide. There is no licensed vaccine against CL, and the chemotherapy options show limited efficacy and high toxicity. Localization of the parasites inside host cells is a barrier to most standard chemo- and immune-based interventions. Hence, novel drugs, which are safe, effective and readily accessible to third-world countries and/or drug delivery technologies for effective CL treatments are desperately needed. METHODOLOGY/PRINCIPAL FINDINGS:Here we evaluated the antileishmanial properties and delivery potential of polyhexamethylene biguanide (PHMB; polyhexanide), a widely used antimicrobial and wound antiseptic, in the Leishmania model. PHMB showed an inherent antileishmanial activity at submicromolar concentrations. Our data revealed that PHMB kills Leishmania major (L. major) via a dual mechanism involving disruption of membrane integrity and selective chromosome condensation and damage. PHMB's DNA binding and host cell entry properties were further exploited to improve the delivery and immunomodulatory activities of unmethylated cytosine-phosphate-guanine oligodeoxynucleotides (CpG ODN). PHMB spontaneously bound CpG ODN, forming stable nanopolyplexes that enhanced uptake of CpG ODN, potentiated antimicrobial killing and reduced host cell toxicity of PHMB. CONCLUSIONS:Given its low cost and long history of safe topical use, PHMB holds promise as a drug for CL therapy and delivery vehicle for nucleic acid immunomodulators

The Pierre Auger Observatory III: Other Astrophysical Observations

Astrophysical observations of ultra-high-energy cosmic rays with the Pierre Auger ObservatoryComment: Contributions to the 32nd International Cosmic Ray Conference, Beijing, China, August 201

Highlights from the Pierre Auger Observatory

The Pierre Auger Observatory is the world's largest cosmic ray observatory. Our current exposure reaches nearly 40,000 km$^2$ str and provides us with an unprecedented quality data set. The performance and stability of the detectors and their enhancements are described. Data analyses have led to a number of major breakthroughs. Among these we discuss the energy spectrum and the searches for large-scale anisotropies. We present analyses of our X$_{max}$ data and show how it can be interpreted in terms of mass composition. We also describe some new analyses that extract mass sensitive parameters from the 100% duty cycle SD data. A coherent interpretation of all these recent results opens new directions. The consequences regarding the cosmic ray composition and the properties of UHECR sources are briefly discussed.Comment: 9 pages, 12 figures, talk given at the 33rd International Cosmic Ray Conference, Rio de Janeiro 201