Generalization of the ordinary state-based peridynamic model for isotropic linear viscoelasticity

This paper presents a generalization of the original ordinary state-based peridynamic model for isotropic linear viscoelasticity. The viscoelastic material response is represented using the thermodynamically acceptable Prony series approach. It can feature as many Prony terms as required and accounts for viscoelastic spherical and deviatoric components. The model was derived from an equivalence between peridynamic viscoelastic parameters and those appearing in classical continuum mechanics, by equating the free energy densities expressed in both frameworks. The model was simplified to a uni-dimensional expression and implemented to simulate a creep-recovery test. This implementation was finally validated by comparing peridynamic predictions to those predicted from classical continuum mechanics. An exact correspondence between peridynamics and the classical continuum approach was shown when the peridynamic horizon becomes small, meaning peridynamics tends toward classical continuum mechanics. This work provides a clear and direct means to researchers dealing with viscoelastic phenomena to tackle their problem within the peridynamic framework.     

Sequential analysis of hair mercury levels in relation to fish diet of an Amazonian population, Brazil

Several studies in the Amazonian Basin have shown that riverine populations are exposed to methylmercury through fish consumption. It has been suggested that seasonal variations in hair mercury observed through sequential analyses may be related to the changes in fish species ingested by the local communities. The aim of the present study was to investigate the relationship between fish-eating practices and seasonal variation in mercury exposure. A group of 36 women from a village located on the banks of the Tapajós River, a major tributary of the Amazon, comprised the present study population. An interview-administered questionnaire was used to gather information on socio-demographic characteristics, fish-eating practices and other relevant information. The women also provided hair samples of at least 24 cm in length for mercury analysis. Hair total and inorganic mercury concentration was measured using a cold vapor atomic absorption analytical method. Trigonometric regression analysis was done to assess the seasonal variation of total mercury levels. Variations in inorganic mercury were examined by repeated measures analysis of variance, and analysis of contrast variable with a polynomial transformation. The results showed that hair mercury levels varied with the season. Higher levels were observed in months corresponding to the dry season, with lower levels in the rainy season. Herbivorous fish predominated the diet for 47.2% of the women during the dry season, but this rose to 72.2% during the rainy season. Those who reported eating fish daily had higher mercury levels in hair compared to those who only ate fish a few times per week. Retrospective mercury analyses, evaluated by the quantity of mercury present in each centimeter of hair, indicate that mean mercury level of the population decreased over the 2 years prior to the study. The percentage of inorganic mercury over the total mercury in hair increased towards the extremities of the hair strand. Higher percentages of inorganic mercury were found for the group who ate more fish (on a daily consumption basis). These results support the assumption that there are seasonal variations in methylmercury exposure and also a relationship between type of fish species consumed and the resulting hair mercury levels.     

Expression and detection of pap-, sfa-, and afa-encoded fimbrial adhesin systems among uropathogenic Escherichia coli

Thirty-five Escherichia coli isolates from young children and women with pyelonephritis, cystitis, or asymptomatic bacteriuria were characterized genotypically and phenotypically. The isolates were examined genotypically by using DNA probes specific for the hemolysis gene and for the pap, sfa, and afa adhesin systems. Genes for the adhesin systems were also detected by polymerase chain reaction, using multigene amplification. The isolates were serotyped, tested for hemolysin production, and classified for their adhesion specificity by hemagglutination and by binding specificity assays. Twenty-seven of the 35 isolates were pap positive. Results showed that pap-positive isolates expressing class I or class II G adhesins were more frequent in cases of pyelonephritis than in cases of cystitis and asymptomatic bacteriuria. Expression of the class III G adhesins was more frequent in isolates from cystitis and asymptomatic bacteriuria than in isolates from pyelonephritis. Multiple adhesin systems and hemolysin were more frequently found in isolates from cases of pyelonephritis than in isolates from cases of cystitis and asymptomatic bacteriuria. There was perfect correlation between the results obtained by polymerase chain reaction and and those obtained by hybridization.     

Angiotensin II effect on plasma steroids in selective hypoaldosteronism

The effect of angiotensin II infusion on plasma pregnenolone, progesterone, corticosterone and aldosterone was investigated in 4 cases of established hypoaldosteronism, in 4 elderly controls in the same age range and in 6 young normals. In young and old normals, angiotensin II induced the expected dose response increase in aldosterone while corticosterone usually decreased progressively during the infusion. Progesterone levels were not significantly different in young and old subjects and no change was observed during angiotensin II infusion. Baseline pregnenolone levels were significantly lower in elderly controls and angiotensin II elicited a slight decrease in pregnenolone in the two control groups. In selective hypoaldosteronism, baseline plasma aldosterone concentrations were very low and the aldosterone response to angiotensin II was blunted. Plasma corticosterone and progesterone levels were in a comparable range to normals throughout the study. Contrary to control subjects, a dose dependent increase in pregnenolone was observed during angiotensin II infusion in the patient group. These results suggest that the anomalies of steroid biosynthesis found in selective hypoaldosteronism could be contributing factors to the hypoaldosteronism in some patients.     

Making space for women: civil society organizations,gender and hydropower development in the Mekong region

Large-scale hydropower development disrupts local livelihoods and resource access. Adverse impacts are often greater for women than men, but also large for children, the elderly, poorer households and ethnic minorities. Burdens of resettlement often fall disproportionately on already disadvantaged individuals. The purpose of this study was to evaluate how international, national and local civil society organizations (CSOs) have addressed gender in hydropower development in the Mekong Region. Four CSO orientations are distinguished: communitarian, environmentalist, knowledge-based and feminist. Common activities of CSOs were to share information, to expand participation and to mobilize development. The extent to which these activities were promoted and appear to be making space for women depended on the types of CSOs and women and men targeted or otherwise involved.     

Thermochemistry of the combustion of gas phase and condensed phase detonation products in an explosive fireball

This paper uses the thermochemical behaviour of reacting species to differentiate between the combustion of gas phase and condensed phase detonation products in the fireball of an explosion. Experiments were carried out involving the detonation 15 g charges of C-4 and Detasheet-C explosives in a closed vessel. The initial partial pressure of oxygen in the vessel was varied in order to control the extent of the secondary afterburn reactions, and the total heat release was measured using the calorimeter that contained the closed vessel. A simple model that independently describes the evolution of heat from the gas phase and condensed phase detonation products as a function of oxygen consumption was developed, and was used to show that condensed phase products react much more effectively in the fireball than gas phase reactions, because the transport properties of particulates entrained in a turbulent flow gives them an advantage when it comes to the manner in which they mix with the surrounding air. An additional set of trials employing the entrainment of an external combustible material further confirms the importance of particle combustion in explosive fireballs.     

A genetic polymorphism of the peroxisome proliferator-activated receptor gamma gene influences plasma leptin levels in obese humans

OBJECTIVE: To determine whether adverse perinatal outcome is associated with asthma or asthma medication use during pregnancy. METHODS: A retrospective cohort study was conducted of women who resided in Halifax County, Nova Scotia, and delivered between 1991 and 1993. Asthmatic women were classified into three groups, according to medication usage: no medications, beta agonists only, and steroids with or without other asthma medications. Outcomes compared among asthmatic and nonasthmatic women included maternal complications (pregnancy-induced hypertension, cesarean delivery, gestational diabetes, preterm birth, and antepartum and postpartum hemorrhage) and neonatal outcomes (low birth weight, congenital malformations, hyperbilirubinemia, and respiratory distress syndrome). RESULTS: The cohort included 817 asthmatic women and 13,709 nonasthmatic women. Overall, the prevalence of pregnancies complicated by asthma increased from 4.8% in 1991 to 6.9% in 1993. Asthmatic women were at increased risk for antepartum and postpartum hemorrhage, independent of medication usage. Asthmatic women taking steroids were at increased risk for pregnancy-induced hypertension (odds ratio [OR] 1.7; 95% confidence interval [CI] 1.0, 2.9). The only significant difference in neonatal outcome between asthma medication groups and nonasthmatic women was of an increased risk of hyperbilirubinemia in infants of women taking steroids (OR 1.9; 95% CI 1.1, 3.4). CONCLUSION: Risk of antepartum and postpartum hemorrhage is increased in asthmatic women, independent of medication usage. The increased incidence of neonatal hyperbilirubinemia and the borderline increased risk of pregnancy-induced hypertension may be complications of steroid use or may be related to poorly controlled asthma.