Estudo da instabiliadade estrutural de tubos compósitos finos submetidos à pressão hidrostática externa

Tubos de materiais compósitos poliméricos são amplamente utilizados como componentes estruturais em situações onde estão sujeitos a pressões externas ou cargas compressivas. Neste contexto, pode ocorrer o colapso do tubo, governado pela instabilidade ou pelo limite de resistência do material. Portanto, a predição da instabilidade é um fator crítico de projeto. Muitos parâmetros podem afetar as predições de instabilidade estrutural, e estas são normalmente realizadas por análises computacionais, incorporando no modelo geométrico as imperfeições da estrutura real. Entretanto, em um estágio inicial de projeto estes dados não estão disponíveis, exigindo abordagem alternativa para essas predições. Neste trabalho, foram estudados tubos compósitos de parede fina produzidos por enrolamento filamentar (filament winding), sujeitos à pressão hidrostática externa com o objetivo de predizer instabilidades. Algumas soluções analíticas conhecidas foram avaliadas por comparação com o método dos elementos finitos, sendo que duas delas apresentaram grandes desvios relativos. Foi então desenvolvido um procedimento numérico-experimental de caracterização das propriedades mecânicas dos materiais envolvidos por calibração com dados experimentais representativos. As variáveis do problema de instabilidade foram avaliadas por uma análise de sensibilidade, elencando-as em ordem de influência, onde se destacaram a espessura do tubo e o módulo longitudinal do tubo. As propriedades calibradas foram implementadas em análises por elementos finitos lineares e não-lineares de instabilidade, e os resultados foram comparados com dados experimentais de ensaios em câmara hiperbárica. Também foram avaliadas estimativas de amplitude de imperfeição geométrica dos tubos produzidos, implementando-as nas análises não-lineares de elementos finitos com base nos primeiros modos de instabilidade bifurcacionais de cada tubo. Os resultados obtidos apresentaram boa correlação numérico-experimental.Polymer composite tubes are widely used as structural components in situations where they are subject to external pressures or compressive loads. In this context, the collapse of the tube may be governed by structural instability or the material strength limit. Therefore, the prediction of structural instability is a critical design factor. Many parameters can affect structural instability predictions, and these are usually performed by computational analysis, incorporating in the geometric model geometrical imperfections of the real structure. However, at an early design stage these data are not available, demanding an alternative approach for these predictions. In this work, thin-walled composite tubes produced by filament winding, subjected to external hydrostatic pressure were analyzed in order to predict instabilities. Some widely known analytical solutions were evaluated by comparison with the finite element method, and two of them presented large relative deviations. A numerical-experimental procedure was then developed to characterize the mechanical properties of the materials involved by calibration with representative experimental data. The variables of the instability problem were evaluated by a sensitivity analysis, listing them in order of influence, where tube thickness and longitudinal modulus were the most influential. The calibrated properties were implemented in linear and nonlinear finite element analyses of instability, and the results were compared with experimental data obtained in tests in a hyperbaric chamber. Geometrical imperfection amplitude estimates of the produced tubes were also evaluated, implementing them in a nonlinear finite element analysis based on the first modes of bifurcational instability of each tube. The obtained results presented good numerical-experimental correlation

Severe shifts of Zostera marina epifauna: comparative study between 1997 and 2018 on the Swedish Skagerrak coast

The interaction between bottom-up and top-down processes in coastal ecosystems has been scarcely studied so far. Temporal changes in trophic interactions of Zostera marina along the Swedish west coast are relatively well studied, with the exception of epifaunal communities. Epifauna was used as a model study to explore resource (bottom-up) or predator (top-down) regulated in a vegetated ecosystem. We conducted a 21-year comparative study (1997 and 2018) using epifauna of 19 Zostera marina meadows along the Swedish Skagerrak coast. Large changes were observed in the composition of small (0.2–1 mm) and large (> 1 mm) epifauna. In the small-sized epifauna, the nematode Southernia zosterae and harpacticoids showed an increase of 90% and a decrease of 50% of their abundances, respectively. In the large-sized epifauna, the polychaete Platynereis dumerilii and chironomid larvae were absent in 1997 but thrived in 2018 (> 2000 ind. m−2 ). Mesoherbivores (Idoteids and gammarids) were locally very abundant in 1997 but disappeared in 2018. An 83% decline of mytilids settling in Zostera marina leaves was observed. Our results showed that epifauna is predominantly top-down regulated. An in tegrative framework of the study area is outlined to shed light on the causes and consequences of the en vironmental shifts reported in Zostera meadows from the northern Skagerrak area throughout the last three decades.info:eu-repo/semantics/publishedVersio

Histological evaluation of the effect of low-level laser on distraction osteogenesis in rabbit mandibles

Objectives: This study evaluated the action of low level laser therapy (LLLT) on the percentage of newly formed bone in rabbit mandibles that underwent distraction osteogenesis (DO). Study design: Ten rabbits underwent bone lengthening according to the following protocol: Latency ? 3 days; Activation ? 7 days 0.7 mm/d; and Consolidation ? 10 days. The control group was composed of 4 rabbits. The experimental group, composed of 6 rabbits, received infrared GaAlAs LLLT (?=830 nm, P=40 mW) according to the following protocol: point dose of 10 J/cm2 applied directly on the bone site that underwent DO during bone consolidation at 48-hour intervals. Results: The percentage of newly formed bone was greater in the LLLT group (57.89%) than in the control group (46.75%) (p=0.006). Conclusion: The results suggest that LLLT had a positive effect on the percentage of newly formed bone. Betterquality bone sites may allow early removal of the osteogenic distractors, thus shortening total treatment time

Randomized crossover comparison of proportional assist ventilation and patient-triggered ventilation in extremely low birth weight infants with evolving chronic lung disease

Background: Refinement of ventilatory techniques remains a challenge given the persistence of chronic lung disease of preterm infants. Objective: To test the hypothesis that proportional assist ventilation ( PAV) will allow to lower the ventilator pressure at equivalent fractions of inspiratory oxygen (FiO(2)) and arterial hemoglobin oxygen saturation in ventilator-dependent extremely low birth weight infants in comparison with standard patient-triggered ventilation ( PTV). Methods: Design: Randomized crossover design. Setting: Two level-3 university perinatal centers. Patients: 22 infants ( mean (SD): birth weight, 705 g ( 215); gestational age, 25.6 weeks ( 2.0); age at study, 22.9 days ( 15.6)). Interventions: One 4- hour period of PAV was applied on each of 2 consecutive days and compared with epochs of standard PTV. Results: Mean airway pressure was 5.64 ( SD, 0.81) cm H2O during PAV and 6.59 ( SD, 1.26) cm H2O during PTV ( p < 0.0001), the mean peak inspiratory pressure was 10.3 ( SD, 2.48) cm H2O and 15.1 ( SD, 3.64) cm H2O ( p < 0.001), respectively. The FiO(2) ( 0.34 (0.13) vs. 0.34 ( 0.14)) and pulse oximetry readings were not significantly different. The incidence of arterial oxygen desaturations was not different ( 3.48 ( 3.2) vs. 3.34 ( 3.0) episodes/ h) but desaturations lasted longer during PAV ( 2.60 ( 2.8) vs. 1.85 ( 2.2) min of desaturation/ h, p = 0.049). PaCO2 measured transcutaneously in a subgroup of 12 infants was similar. One infant met prespecified PAV failure criteria. No adverse events occurred during the 164 cumulative hours of PAV application. Conclusions: PAV safely maintains gas exchange at lower mean airway pressures compared with PTV without adverse effects in this population. Backup conventional ventilation breaths must be provided to prevent apnea-related desaturations. Copyright (c) 2007 S. Karger AG, Base

Avaliação experimental dos efeitos da fixação interna (Ti, 1,5mm), no crescimento craniofacial pós-natal de coelhos por meio de análise morfométrica indireta

The purpose of the present investigation is to verify whether the potential for postnatal craniofacial bonegrowth in rabbits is impaired by the use of titanium microplates and microscrews in areas of rapid bone growth.To this end, 20 animals in their seventh week of life were divided into two groups: in the experimental group,a microplate with four holes was fixed on the right-hand side transversely to the coronal cranial suture; in thecontrol group, only two screws were placed, one on either side of the right coronal suture at a distancecorresponding to the two outer holes on the microplate. The animals were killed and manually decapitated inthe 17th postoperative week. An evaluation of bone growth was performed through indirect morphometric measurements by the tridimensional analysis of the craniofacial volumes using computed tomography. Astatistically significant difference was found when the partial direct volumes of the two groups were compared.It is thus possible to state that the use of internal rigid fixation in regions of rapid growth in growing rabbitsproduces dimensional changes

Avaliação experimental dos efeitos da fixação interna (Ti, 1,5mm) no crescimento craniofacial pós-natal de coelhos, por meio de análise morfométrica direta

In order to investigate the influence of internal rigid fixation on postnatal craniofacial growth, twenty rabbitswere randomly divided into two groups - experimental and control. In the experimental group, in theseventh postnatal week, one 1.5-mm straight microplate was transversely fixed to the coronal cranial suture.In the control group, also in the seventh postnatal week, a microscrew was placed on each side of the righthandside of the coronal suture at a distance equal to that separating the outer holes of the microplate. Allthe animals were sacrificed, at the age of 24 weeks, in the 17th postoperative week and an evaluation ofbone growth was performed using direct morphometric measurements of the anteroposterior distance indry skulls. An anteroposterior shortening of the lambdoid frontal distance was observed, both by comparing the right and left sides in the same specimen and by comparing the same side in the two groups. The righthandside was found to be smaller in the experimental group. It is believed that internal rigid fixationthrough areas of rapid bone growth in the skulls of rabbits at the age of development is able to inducechanges in the size of the skull

CARACTERIZAÇÃO DO SOLO EM ÁREA SUBMETIDA A DERRAMAMENTO DE LIXIVIADO DECORRENTE DE ATERRO SANITÁRIO

http://dx.doi.org/10.5902/2236130810939Population growth and consumerism in contemporary civilizations created, make the volume of waste generated is ever increasing, there is increasingly a need to give a correct destination of those materials that are discarded. Landfills are a counterpoint to the old way of disposal of solid waste, the landfill. With the major differences in soil sealing and coverage of periodic layers of trash with a layer of earth. Leaching and decomposition are natural processes that lead to formation of leachate. Therefore, this study aims to present the characterization of the soil in an area under the resulting slurry spill landfill, located in the municipality of Seberi-RS. Soil samples were collected from berehole manual, in 11(eleven) different points, two white dots. The results of laboratory analyzes show that the concentrations of potassium, have an average of 358,55 ± 147,87 mg kg-1, the concentrations of calcium showed an average of 1276,84 ± 398,8 mg kg-1the percentage of clay had an average of 47,55 ± 10,11 %, pH values   in H2O had an average area of  5,2 ± 0,29, the area showed a mean of 3,43 ± 1.63% Aluminum concentrations showed a mean of 6,54 ± 4,20 mg kg-1. Some parameters when compared with white spots were considered a minor change, but it can be assumed that the exposed area is less vulnerable to contamination.http://dx.doi.org/10.5902/2236130810939O crescimento populacional e o consumismo criado nas civilizações contemporâneas fazem que o volume de resíduos gerados seja cada vez mais crescente, desta forma, surge a cada vez mais a necessidade de se dar um destino correto a esses materiais que são descartados. Os aterros sanitários fazem um contraponto à antiga forma de disposição dos resíduos sólidos, o lixão. Tendo como principais diferenças a impermeabilização do solo e a cobertura periódica das camadas de lixo com uma camada de terra. A lixiviação e a decomposição são processos naturais que conduzem a formação do chorume. Desta forma este estudo tem como objetivo, apresentar a caracterização do solo em área submetida a derramamento de chorume decorrente de aterro sanitário, localizado no município de Seberi-RS. As amostras de solo foram coletadas através de tradagem manual, em 11 (onze) pontos diferentes, sendo dois pontos brancos. Os resultados das análises de laboratório, mostram que, as concentrações de Potássio, apresentam uma média de 358,55 ± 147,87 mg kg-1, as concentrações de Cálcio apresentaram uma média de 1276,84 ± 398,8 mg kg-, as porcentagens de argila apresentaram uma média de 47,55 ± 10,11 %, os valores de pH em H2O apresentaram uma média na área de 5,2 ± 0,29, a área apresentou uma média de matéria orgânica de 3,43±1,63 %, as concentrações de Alumínio apresentaram uma média de 6,54 ± 4,20 mg kg-1. Alguns parâmetros quando comparados aos pontos considerados brancos apresentaram uma pequena alteração, porém pode-se considerar que a área exposta é pouco vulnerável a contaminação

INDICATIVO DE CONTAMINAÇÃO AMBIENTAL POR METAIS PESADOS EM ATERRO SANITÁRIO

http://dx.doi.org/10.5902/2236130814441The manure is a dark liquid, which contains high concentrations of organic and inorganic compounds. This fluid can contain heavy metals, suspended solids and organic compounds derived from the degradation of substances that are metabolized as carbohydrates, proteins and fats. By virtue of the place where you can reach and contaminate soil and surface and underground water resources, threatening the population living near the area. This study aimed to analyze the concentrations of heavy metals barium, copper and chromium in soil occupied by the landfill. To collect soil auger were performed on 10 different sites and depths. To determine the metal has been used the technique of fluorescence X-ray Energy Dispersive and with the aid of specialized software 10 were Surfer generating the data to the maps. All metals cited in this study indicate soil contamination at some sites and depths, highlighting the point 8 a share of 538.94 m, obtaining concentrations of barium, copper and chromium indicating relation of the surface flow and sub-surface water contaminated by these elements, with the results obtained it can be seen the potential of metal contamination in soil displaced by landfill.http://dx.doi.org/10.5902/2236130814441O chorume é um liquido escuro, que contém altas concentrações de compostos orgânicos e inorgânicos. Esse líquido pode conter metais pesados, sólidos suspensos e compostos orgânicos originados da degradação de substâncias que são metabolizadas, como carboidratos, proteínas e gorduras. Em virtude do local onde se encontra poderá atingir e contaminar o solo e recursos hídricos superficiais e subterrâneos, pondo em risco a população que vive nas proximidades da área. O presente trabalho teve como objetivo analisar as concentrações dos metais pesados bário, cobre e cromo em solo ocupado por aterro sanitário. Para coleta do solo foram realizadas tradagens em 10 diferentes pontos e profundidades. Para determinação dos metais foi utilizado a técnica de Fluorescência de Raios-X por Energia dispersiva e com auxilio do software Surfer 10 foram especializados os dados gerando-se os cartogramas. Todos os metais citados no presente trabalho indicam contaminação do solo em alguns pontos e profundidades, destacando-se o ponto 8 a uma cota de 538,94 m, obtendo concentrações de Bário, Cobre e Cromo indicando relação do fluxo superficial e sub superficial da água com contaminação por estes elementos, com os resultados obtidos pode-se constatar o potencial de contaminação por metais em solo ocupado pelo Aterro Sanitário