Subcritical crack growth and in vitro lifetime prediction of resin composites with different filler distributions

Objectives. Verify the influence of different filler distributions on the subcritical crack growth (SCG) susceptibility, Weibull parameters (m and sigma(0)) and longevity estimated by the strength-probability-time (SPT) diagram of experimental resin composites. Methods. Four composites were prepared, each one containing 59 vol% of glass powder with different filler sizes (d(50) = 0.5; 0.9; 1.2 and 1.9 mu m) and distributions. Granulometric analyses of glass powders were done by a laser diffraction particle size analyzer (Sald-7001, Shimadzu, USA). SCG parameters (n and sigma(f0)) were determined by dynamic fatigue (10(-2) to 10(2) MPa/s) using a biaxial flexural device (12 x 1.2 mm; n = 10). Twenty extra specimens of each composite were tested at 10(0) MPa/s to determine m and sigma(0). Specimens were stored in water at 37 degrees C for 24 h. Fracture surfaces were analyzed under SEM. Results. In general, the composites with broader filler distribution (C0.5 and C1.9) presented better results in terms of SCG susceptibility and longevity. C0.5 and C1.9 presented higher n values (respectively, 31.2 +/- 6.2(a) and 34.7 +/- 7.4(a)). C1.2 (166.42 +/- 0.01(a)) showed the highest and C0.5 (158.40 +/- 0.02(d)) the lowest sigma(f0) value (in MPa). Weibull parameters did not vary significantly (m: 6.6 to 10.6 and sigma(0): 170.6 to 176.4 MPa). Predicted reductions in failure stress (P-f = 5%) for a lifetime of 10 years were approximately 45% for C0.5 and C1.9 and 65% for C0.9 and C1.2. Crack propagation occurred through the polymeric matrix around the fillers and all the fracture surfaces showed brittle fracture features. Significance. Composites with broader granulometric distribution showed higher resistance to SCG and, consequently, higher longevity in vitro. (C) 2012 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Analysis of energy dissipation in stirred suspension polymerisation reactors using computational fluid dynamics

This work evaluates the spatial distribution of normalised rates of droplet breakage and droplet coalescence in liquidliquid dispersions maintained in agitated tanks at operation conditions normally used to perform suspension polymerisation reactions. Particularly, simulations are performed with multiphase computational fluid dynamics (CFD) models to represent the flow field in liquidliquid styrene suspension polymerisation reactors for the first time. CFD tools are used first to compute the spatial distribution of the turbulent energy dissipation rates (e) inside the reaction vessel; afterwards, normalised rates of droplet breakage and particle coalescence are computed as functions of e. Surprisingly, multiphase simulations showed that the rates of energy dissipation can be very high near the free vortex surfaces, which has been completely neglected in previous works. The obtained results indicate the existence of extremely large energy dissipation gradients inside the vessel, so that particle breakage occurs primarily in very small regions that surround the impeller and the free vortex surface, while particle coalescence takes place in the liquid bulk. As a consequence, particle breakage should be regarded as an independent source term or a boundary phenomenon. Based on the obtained results, it can be very difficult to justify the use of isotropic assumptions to formulate particle population balances in similar systems, even when multiple compartment models are used to describe the fluid dynamic behaviour of the agitated vessel. (C) 2011 Canadian Society for Chemical Engineering

Low mechanical ventilation times and reintubation rates associated with a specific weaning protocol in an intensive care unit setting: a retrospective study

OBJECTIVES: A number of complications exist with invasive mechanical ventilation and with the use of and withdrawal from prolonged ventilator support. The use of protocols that enable the systematic identification of patients eligible for an interruption in mechanical ventilation can significantly reduce the number of complications. This study describes the application of a weaning protocol and its results. METHODS: Patients who required invasive mechanical ventilation for more than 24 hours were included and assessed daily to identify individuals who were ready to begin the weaning process. RESULTS: We studied 252 patients with a median mechanical ventilation time of 3.7 days (interquartile range of 1 to 23 days), a rapid shallow breathing index value of 48 (median), a maximum inspiratory pressure of 40 cmH2O, and a maximum expiratory pressure of 40 cm H2O (median). Of these 252 patients, 32 (12.7%) had to be reintubated, which represented weaning failure. Noninvasive ventilation was used postextubation in 170 (73%) patients, and 15% of these patients were reintubated, which also represented weaning failure. The mortality rate of the 252 patients studied was 8.73% (22), and there was no significant difference in the age, gender, mechanical ventilation time, and maximum inspiratory pressure between the survivors and nonsurvivors. CONCLUSIONS: The use of a specific weaning protocol resulted in a lower mechanical ventilation time and an acceptable reintubation rate. This protocol can be used as a comparative index in hospitals to improve the weaning system, its monitoring and the informative reporting of patient outcomes and may represent a future tool and source of quality markers for patient care.

EROD activity and genotoxicity in the seabob shrimp Xiphopenaeus kroyeri exposed to benzo[a]pyrene (BaP) concentrations

Seabob shrimp Xiphopenaeus kroyeri is a marine species that lives in shallow waters of coastal environments, often impacted by polycyclic aromatic hydrocarbons (PAH) pollution. In the present study, seabob shrimp were exposed for 96 h to benzo[a]pyrene (BaP) at the nominal concentrations of 100, 200, 400 and 800 microg.L-1. Animals of the control groups were exposed either to clean water or to the BaP-carrier (DMSO). At the end of the exposures, muscle tissues were sampled for BaP uptake assessment and hepatopancreas and hemolymph for EROD enzyme activity and hemocytes DNA damage, respectively. EROD activity and DNA damage increased significantly as a function of BaP exposure concentrations. Significant correlations between BaP uptake and both EROD activity and DNA damage suggest that they can be used as suitable tools for integrated levels of study on the biomarkers of PAH exposure.

Leptospiral Immunoglobulin-like Proteins Interact With Human Complement Regulators Factor H, FHL-1, FHR-1, and C4BP

Leptospira, the causative agent of leptospirosis, interacts with several host molecules, including extracellular matrix components, coagulation cascade proteins, and human complement regulators. Here we demonstrate that acquisition of factor H (FH) on the Leptospira surface is crucial for bacterial survival in the serum and that these spirochetes, besides interacting with FH, FH related-1, and C4b binding protein (C4BP), also acquire FH like-1 from human serum. We also demonstrate that binding to these complement regulators is mediated by leptospiral immunoglobulin-like (Lig) proteins, previously shown to interact with fibronectin, laminin, collagen, elastin, tropoelastin, and fibrinogen. Factor H binds to Lig proteins via short consensus repeat domains 5 and 20. Competition assays suggest that FH and C4BP have distinct binding sites on Lig proteins. Moreover, FH and C4BP bound to immobilized Ligs display cofactor activity, mediating C3b and C4b degradation by factor I. In conclusion, Lig proteins are multifunctional molecules, contributing to leptospiral adhesion and immune evasion.

Culture medium of diluted skimmed milk for the production of nisin in batch cultivations

Nisin is a promising alternative to chemical preservatives for use as a natural biopreservative in foods. This bacteriocin has also potential biomedical applications. Lactic acid bacteria are commonly cultivated in expensive standard complex media. We have evaluated the cell growth and nisin production of Lactococcus lactis in a low-cost natural medium consisting of diluted skimmed milk in a 2-L bioreactor. The assays were performed at 30 degrees C for 56 h, at varying agitation speeds and airflow rates: (1) 200 rpm (no airflow, and airflow at 0.5, 1.0 and 2.0 L/min); (2) 100 rpm (no airflow, and airflow at 0.5 L/min). Nisin activity was evaluated using agar diffusion assays. The highest nisin concentration, 49.88 mg/L (3.3 log AU/mL or 1,995.29 AU/mL), was obtained at 16 h of culture, 200 rpm and no airflow (k(L)a = 5.29 x 10(-3)). These results show that a cultivation medium composed of diluted skimmed milk supports cell growth to facilitate nisin biosynthesis.

Effect of dental tissue conditioners and matrix metalloproteinase inhibitors on type I collagen microstructure analyzed by Fourier transform infrared spectroscopy

This study aimed to evaluate the chemical interaction of collagen with some substances usually applied in dental treatments to increase the durability of adhesive restorations to dentin. Initially, the similarity between human dentin collagen and type I collagen obtained from commercial bovine membranes of Achilles deep tendon was compared by the Attenuated Total Reflectance technique of Fourier Transform Infrared (ATR-FTIR) spectroscopy. Finally, the effects of application of 35% phosphoric acid, 0.1M ethylenediaminetetraacetic acid (EDTA), 2% chlorhexidine, and 6.5% proanthocyanidin solution on microstructure of collagen and in the integrity of its triple helix were also evaluated by ATR-FTIR. It was observed that the commercial type I collagen can be used as an efficient substitute for demineralized human dentin in studies that use spectroscopy analysis. The 35% phosphoric acid significantly altered the organic content of amides, proline and hydroxyproline of type I collagen. The surface treatment with 0.1M EDTA, 2% chlorhexidine, or 6.5% proanthocyanidin did not promote deleterious structural changes to the collagen triple helix. The application of 6.5% proanthocyanidin on collagen promoted hydrogen bond formation. (c) 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2012.

Avaliação da morfometria renal através do método ultrassonográfico de fêmeas caprinas (Capra hircus) normais da raça Saanen

A utilização de técnicas ultrassonográficas na área de Medicina Veterinária está cada vez mais presente e a capacitação nesta área tornou-se indispensável para o clínico, auxiliando-o na obtenção de informações rápidas e valiosas das afecções patológicas que podem acometer os animais. O exame ultrassonográfico renal revelou-se de grande importância neste âmbito, com o objetivo de avaliar e mensurar os parâmetros morfométricos renais normais de fêmeas caprinas (Capra hircus). Por meio de técnicas ultrassonográficas procedeu-se o estudo de 30 fêmeas da raça Saanen, divididas em três grupos: fêmeas com idade inferior a 6 meses (3,0±1,0 meses), de 6-18 meses (9,0±4,3 meses) e com idade superior a 18 meses (46,3±17,4 meses). Realizaram-se imagens dos rins, em secções longitudinais, medidas de comprimento e largura e, em secções transversais, medidas de altura (ou espessura). Com estes valores calcularam-se volumes renais, corticais e medulares, além da relação cortico-medular. Com relação ao comprimento renal os grupos com idade inferior a 6 meses, de 6-18 meses e com idade superior a 18 meses obtiveram média e desvio padrão de 4,20±0,36cm, 5,56±0,40cm e 6,77±0,64cm, respectivamente. Tratando-se do volume renal, estes grupos apresentaram média e desvio padrão de 17,02±3,99cm³, 19,99±5,86cm³; e, 41,23±13,05cm³. Comparou-se a equivalência métrica das médias entre os dois rins de forma que os parâmetros volumétricos e lineares renais com diferença entre si são comprimento renal, volume renal e volume cortical para o grupo de fêmeas com idade de 6-18 meses, e comprimento renal e comprimento medular para o grupo com idade superior a 18 meses. Entre diferentes grupos observou-se que somente o comprimento medular esquerdo apresentou média equivalente em todos os grupos, ou seja, entre o grupo com idade inferior a 6 meses e o grupo com idade de 6-18 meses e, entre este último e o grupo com idade superior a 18 meses. Os resultados mostraram correlações diretas e positivas entre peso corporal e idade com os parâmetros lineares e volumétricos, a relação cortico-medular esquerda foi a única que apresentou correlação significativa com o peso (r= -0,365; P = 0,047). Para aqueles parâmetros que apresentaram correlação significativa foi realizada análise de regressão, obtendo-se a linha de melhor ajuste das variáveis.

Análise da confiabilidade e reprodutibilidade da goniometria em relação à fotogrametria na mão

OBJETIVO: Avaliar a confiabilidade intra e interexaminadores e a reprodutibilidade da goniometria em relação à fotogrametria na mão, comparando os ângulos da abdução de polegar, flexão da AIFP do II dedo e flexão da AMCF do V dedo. MÉTODOS: PARTIciparam deste estudo 30voluntários foram divididos em 3 grupos, um grupo de 10 estudantes de Fisioterapia, outro por 10 fisioterapeutas e o terceiro com 10 terapeutas da mão. Cada avaliador realizou as medidas no mesmo molde de mão, utilizando o goniômetro e em seguidadois softwares de fotogrametria, o CorelDraw® e o ALCimagem®. RESULTADOS: Os resultados revelaram que os grupos e os métodos propostos apresentam confiabilidade interexaminadores no geral classificada como excelente (ICC 0,998 I.C. 95% 0,995 - 0,999). Na avaliação intraexaminadores, foi encontrado excelente nível de confiabilidade entre os três grupos. Na comparação entre os grupos para cada ângulo e cada método, observou-se que não houve diferença significativa entre os grupos para a maioria das medidas. CONCLUSÃO: A goniometria e a fotogrametria são métodos confiáveis e reprodutíveis para avaliação de medidas na mão. Porém, pela escassez de referências semelhantes, necessita-se de estudos aprofundados para definição de parâmetros de normalidade entre os métodos nas articulações da mão. Nível de Evidência II, Estudo Diagnóstico.

Anti-Toxocara spp. antibodies in an adult healthy population: serosurvey and risk factors in Southeast Brazil.

Objective: To evaluate the frequency of anti-Toxocara spp. antibodies in an adult healthy population. Methods: The study was performed by interviewing 253 blood donors, from 19 to 65 years of age, in a hematological centre in Presidente Prudente, São Paulo, southeast Brazil. A survey was applied to blood donors in order to evaluate the possible factors associated to the presence of antibodies, including individual (gender and age), socioeconomic (scholarship, familial income and sanitary facilities) and habit information (contact with soil, geophagy, onycophagy and intake of raw/undercooked meat) as well as the presence of dogs or cats in the household. ELISA test was run for detection of the anti-Toxocara spp. IgG antibodies. Bivariate analysis followed by logistic regression was performed to evaluate the potential risk factors associated to seropositivity. Results: The overall prevalence observed in this study was 8.7% (22/253). Contact with soil was the unique risk factor associated with the presence of antibodies (P=0.0178 ; OR=3.52; 95% CI=1.244-9.995) Conclusions. The results of this study reinforce the necessity in promoting preventive public health measures, even for healthy adult individual, particularly those related to the deworming of pets to avoid the soil contamination, and hygiene education of the population.