Evaluation of the benchmark dose for point of departure determination for a variety of chemical classes in applied regulatory settings

Repeated-dose studies received by the New Substances Assessment and Control Bureau (NSACB) of Health Canada are used to provide hazard information toward risk calculation. These studies provide a point of departure (POD), traditionally the NOAEL or LOAEL, which is used to extrapolate the quantity of substance above which adverse effects can be expected in humans. This project explored the use of benchmark dose (BMD) modeling as an alternative to this approach for studies with few dose groups. Continuous data from oral repeated-dose studies for chemicals previously assessed by NSACB were reanalyzed using U.S. EPA benchmark dose software (BMDS) to determine the BMD and BMD 95% lower confidence limit (BMDL(05) ) for each endpoint critical to NOAEL or LOAEL determination for each chemical. Endpoint-specific benchmark dose-response levels , indicative of adversity, were consistently applied. An overall BMD and BMDL(05) were calculated for each chemical using the geometric mean. The POD obtained from benchmark analysis was then compared with the traditional toxicity thresholds originally used for risk assessment. The BMD and BMDL(05) generally were higher than the NOAEL, but lower than the LOAEL. BMDL(05) was generally constant at 57% of the BMD. Benchmark provided a clear advantage in health risk assessment when a LOAEL was the only POD identified, or when dose groups were widely distributed. Although the benchmark method cannot always be applied, in the selected studies with few dose groups it provided a more accurate estimate of the real no-adverse-effect level of a substance.     

Single process plan scheduling with genetic algorithms

AIn this paper, a genetic algorithm model for scheduling manufacturing resources is developed for the case when there is only one process plan available per job, hence there is no routeing flexibility. The scheduling objectives considered are minimizing the makespan and mean flow time. Genetic algorithms design issues are discussed and the working of the employed genetic operators is explained in detail. Parameters for the genetic algorithms used for single process plan scheduling SPPS problems are set through extensive experimentation. Finally, the genetic algorithms approach is compared with several other approaches in terms of optimality of solution and computAuthors: ing time. It was observed that in most cases the genetic algorithms approach performed better than other approaches both in terms of finding an optimal or near optimal solution as well as computing time.     

Detecting outliers in GARCH(p,q) models

This article is concerned with the outliers in GARCH models. An iterative procedure is given for testing the presence of any type of the four common outliers. Since the distribution of test statistic cannot be obtained analytically, its distributional behavior is investigated via a simulation study. The simulation study is based on estimation of residuals standard deviation (σ_ν), which are obtained using two methods, median absolute deviation method (MAD), and omit-one method. The proposed procedure is employed for testing the presence of outliers in weekly light oil price Indexes of Iran during 1997 to 2010.     

Demographic transition in Arab countries: A new perspective

This paper provides a new perspective on the fertility transition in Arab countries. It shows that the story of Arab fertility must be retold: the story is of a region with the highest fertility preferences, exhibiting reluctance to change due to the stranglehold of cultural forces, and just starting to respond to development forces. The paper shows that Arab regional experience is quite comparable to that of other developing countries and that, though the fertility decline occurred at a somewhat later date, the pace of decline more than compensates for this delay. Furthermore, the probing of country level experiences and forces underlying the transition shows the diversities of these experiences and the exaggeration of the role of cultural specificity. It also demonstrates that a large part of the decline in Arab fertility is due to changes in nuptiality. For some segments of society and some countries, these changes are not paralleled by increased opportunities for women to have more fulfilling lives. For these women, the fertility decline is not necessarily improving the quality of their lives and cannot be equated with progress and development.     

How do you measure trust in social institutions and health professionals? A systematic review of the literature (2012–2021)

The importance of measuring trust in health systems has been accentuated due to its correlation with important health outcomes aimed at reducing COVID-19 transmission. A systematic review published almost a decade ago identified gaps in measures including the lack of focus on trust in systems, inconsistency regarding the dimensionality of trust and need for research to strengthen the validity of measures. Given developments in our understandings of trust since its publication, we sought to identify new scales developed, existing ones adapted in response to identified gaps, and agendas for future research. Using the PRISMA approach for systematic reviews, we conducted a search in four databases. A total of 26 articles were assessed. Twelve new scales were identified, while 14 were adapted for different settings and populations. Literature continues to focus on measuring trust in health professionals rather than systems. Various shortcomings were identified, including some articles not mentioning the dimensions included in the scale and suboptimal use of validity and reliability testing and/or reporting. Moreover, a variety of terms were used for dimensions. Future research is needed to address these gaps and consequently, to understand their correlation with health behaviors and outcomes more accurately.