Molecular Simulation of Gas Solubility in Nitrile Butadiene Rubber

Molecular simulation is used to compute the solubility of small gases in nitrile butadiene rubber (NBR) with a Widom particle-insertion technique biased by local free volume. The convergence of the method is examined as a function of the number of snapshots upon which the insertions are performed and the number of insertions per snapshot and is compared to the convergence of the unbiased Widom insertion technique. The effect of varying the definition of local free volume is also investigated. The acrylonitrile content of the polymer is altered to examine its influence on the solubility of helium, CO₂, and H₂O, and the solubilities of polar gases are found to be enhanced relative to those of nonpolar gases, in qualitative agreement with experiment. To probe this phenomenon further, the solubilities are decomposed into contributions from the neighborhoods of different atoms, using a Voronoi cell construction, and a strong bias is found for CO₂ and H₂O in particular to be situated near nitrogen sites in the elastomer. Temperature is shown to suppress the solubility of CO₂ and H₂O but to increase that of helium. Increasing pressure is found to suppress the solubility of all gases but at different rates, according to a balance between their molecular sizes and electrostatic interactions with the polymer. These results are relevant to the use of NBR seals at elevated temperatures and pressures, such as in oil and gas wells.

Hospital-based caesarean section in the Arab region: an overview

This article provides an overview of hospital-based rates of caesarean delivery in 18 Arab countries and the association between these rates and selected demographic and socioeconomic characteristics. Data on caesarean section were based on 2 of the most recent national hospital-based surveys in each country and on published studies based on hospital samples. High levels of caesarean delivery were found in Egypt (26% in 2003), followed by Sudan (20% in 1993). Six countries and the West Bank area of Palestine had rates >15% and 11 countries and Gaza had rates between 5% and 15%. The findings indicate an increasing trend of caesarean section delivery in the region. Policies aiming at reducing surgical deliveries should seek to identify and address these risk factors.

Trends in the prevalence and determinants of caesarean section delivery in Jordan: evidence from three demographic and health surveys, 1990--2002

This paper explores recent levels and trends in the prevalence of Caesarean section (C-section) delivery in Jordan during the period 1990--2002 and examines the impact of socio-demographic, healthcare and spatial characteristics on C-sections there. The study used three national data sets from the Jordan Demographic and Health Survey (JDHS) program conducted in 1990, 1997 and 2002. The JDHS surveys were based on large, nationally representative samples of 16,296, 7335 and 7825 households. Rates of C-section delivery were calculated based on the last birth for each woman delivering in hospitals. Associations between C-section delivery and selected covariates were estimated using Chi2 tests and odds ratios from binary logistic regression models. Hospital-based C-sections increased consistently, from 8.5% in 1990, to 12.9% in 1997, to 17.8% in 2002. The rate of increase in C-section delivery was slightly higher in private hospitals than in public ones. Multiple births, child birth weight, old age at birth and antenatal visits were important determinants of C-section. Place of residence and place of delivery were not consistently associated with C-section. Unexpectedly, mother's education was also not associated with Caesarean section. The final model, based on the three merged data sets, showed a strong association between year of the survey and C-section, reflecting the substantial increase in C-section rates over time. Also, the odds ratio of C-section from multiple births was significantly higher in 2002 compared with 1990. Halting the increase in C-section deliveries, especially in private hospitals, should become a priority for health professionals and policy makers in Jordan. Further in-depth studies are needed, however, to better monitor and analyze changes in C-section rates for identifying ways to reduce the prevalence of this surgical procedure.

Maternal cultural participation and child health status in a Middle Eastern context: evidence from an urban health study

BACKGROUND

The negative effect of poverty on child health has been well established. However, rapid urbanization in developing countries prompts new research questions relating to socio-cultural practices and other related variables in these settings.

OBJECTIVE

To examine the association between maternal cultural participation and child health status in impoverished neighbourhoods of Beirut, Lebanon.

METHODS

A cross-sectional survey of 1241 mothers with children aged less than 5 years was conducted from randomly selected households in three impoverished neighbourhoods of diverse ethnic and religious make-up. The outcome variable was child health status (good/bad) as assessed by the mother. Maternal variables, including cultural participation, education, demographic and environmental/structural factors, were studied. Descriptive statistics and bivariate associations were provided using Pearson's chi-square tests. Unadjusted and adjusted odds ratios were then obtained from binary logistic regression models.

RESULTS

Two indicators of maternal cultural participation, namely watching entertaining television and attending movies/art exhibitions, were found to be significantly associated with child health status after controlling for other risk factors. The quality of water, the quality of local health services and maternal education were also significantly associated with child health status. Household income, child gender and household dampness had no significant association with child health status in this context.

CONCLUSION

Maternal cultural participation was a significant predictor of child health status in impoverished urban communities. Improving child health through culturally focused interventions for mothers, especially in deprived areas, may be greatly important.

Poverty

This glossary addresses the complex nature of poverty and raises some conceptual and measurement issues related to poverty in the public health literature, with a focus on poor countries.

The recent rise in Palestinian fertility: permanent or transient?

The purpose of this paper is to describe trends in fertility and fertility change in the West Bank and Gaza Strip during the years 1968-1992, with a particular focus on the recent rise in fertility. The paper is based primarily on vital registration data. The findings show that the fertility transition has been well underway in the West Bank since 1985, with a lull during the Intifada period. No indication of a fertility transition in the Gaza Strip was found. An examination of the age pattern of fertility reveals that Palestinian fertility has been increasingly shifting toward younger ages, with a particular concentration in the age group 15-24 during the Intifada period. A decomposition analysis of the fertility rates shows that the recent rise in fertility is essentially due to changes in marital structure, but also to increased fertility within marriage among younger women. No evidence of increased fertility among older women is found. Some implications of the findings are discussed.

Intravesical administration of radiolabelled tumour-associated monoclonal antibody in bladder cancer

Considerable progress has been made over the past decade in the use of tumour-associated monoclonal antibodies (mAbs) as carriers of cytotoxic agents in the management of several malignancies. In the present study we investigated the tumour localization and biodistribution of the mAb HMFG1 to bladder cancer following intravesical administration. HMFG1, which has been raised against the polymorphic epithelial mucin (PEM), was labelled with 125I and administered intravesically 2 h and 24 h before cystoscopy. During cystoscopy, biopsies were taken from the normal bladder and the malignant lesion. Tissue samples were tested for HMFG1 immunostaining and for radioactivity with the use of a gamma-counter. The mean ratio of tumour to normal uptake for 125I-HMFG1 was 5.81 +/- 1.23, at 2 h and 2.17 +/- 0.42 at 24 h. No radioactivity was detected in the blood. We conclude that HMFG1 could be used intravesically for the successful delivery of a cytotoxic agent.