Bayesian Analysis of Multi-Stratum Designs and Probability-based Optimal Designs with Separation.

PhDIndustrial experimental design is an important area under design of experiments and factorial design hold a rm place in industrial experiments. The generalization of factorial designs results in split-plot type designs when complete randomization of runs is not possible. More speci cally, hard-to-set factors lead naturally to split-plot type designs and mixed models. Mixed models are used to analyze multi-stratum designs as each stratum may have a random e ect on the responses. The study of random e ects in mixed models might be di cult using likelihood methods because of small number of groups or whole plots in multi-stratum and split-plot designs. Also, zero estimates of variance components could be due to estimating multiple variance components in a hierarchical model. Therefore, likelihood-based inference is often unreliable with the variance components being particularly di cult to estimate for small samples. A Bayesian method considering some noninformative or weakly informative priors for variance components could be a useful tool to solve the problem. Fuel economy experiments, conducted by Shell Global Solutions UK, fall under small sample trap during variance components estimation. Using SAS procedure MIXED, experimenters estimated the variance components to be zero which were unrealistic. Also, the experimenters were unsure about the parameter estimates obtained by likelihood method from linear mixed models. Therefore, we looked for an alternative to compare and found the Bayesian platform to be appropriate. Bayesian methods assuming some non-informative and weakly informative priors enable us to compare the parameter estimates and the variance components. Pro le likelihood and bootstrap based methods veri ed that Bayesian point and interval estimates are not absurd. Also, simulation studies have assessed the quality of likelihood and Bayesian estimates in this study. A polypropylene experiment was conducted by four Belgian automobile industries to look for economical plasma treatments which lead to a good adhesion to various coatings. The e ects of several additives were also studied in addition to the plasma treatments. The likelihood-based estimates were not reliable completely due to the existence of moderate number of whole-plots. Also, some of the variance components due to batch were zero for some coatings. Assuming noninformative priors for xed e ects and some weakly informative priors for variance components we have obtained more sensible estimates of variance components which were inestimable or poorly estimated by the likelihood-based method using SAS procedure GLIMMIX. In this study, the Bayesian methods appeared to give comparable results with classical methods. One response variable in the polypropylene experiment was categorical which was converted to binary to see the e ects of additives on the outcome of interest. Unfortunately for binary responses we failed to obtain estimates of the logistic parameters for some of the coatings as the system did not converge. One of the reasons for this was due to having the separation problem in the data. When one or more explanatory variables completely separate the responses, the problem is known as separation. This problem causes the non-existence of likelihood estimates of logistic regression parameters. We have done some novel methodological works on the separation issue to minimize the problem in the light of optimal design techniques. Though the information based D-optimality criterion is widely used in practice, it fails to handle the separation problem appropriately. We have proposed new probability-based optimality criteria to handle the separation problem at the design stage of a study. Our proposed criteria Ps- and DPs- might be worthwhile to take into account reduction of the separation problem. However, Ps-criterion alone is not suitable to deal with separation problem as it produces worse designs in terms of precision of the parameter estimates, i.e. with respect to D-optimality. On the other hand the compound DPs-criterion makes a balance between D- and Ps-optimality and produces better designs. To make designs less sensitive to parameter misspeci cation, pseudo-Bayesian design criterion DPSB- has been proposed. Simulation studies have veri ed that Bayesian designs perform better than non-Bayesian designs by providing less bias, less median squared errors and above all less probability of separation. Thus, newly devised Bayesian and non-Bayesian design criteria could be useful in practice to control separation problem at the design stage of a study.DTA scholarshi

Declaration Effect of Cash & Stock Dividends on Share Price: An Empirical Study on Dhaka Stock Exchange

This study analyzes the impact of different types of dividend declaration, namely stock and cash dividends. Using event study method, MAAR and CAAR, this study found no evidence of abnormal returns on the declaration day for either of the types of dividends. However, significant negative returns are reported on days prior to the declaration day for stock dividend, indicating speculative nature of the investors. Furthermore, it provides positive returns during the post-announcement period as the investors realize the chance of potential gains. However, as far as cash dividend is concerned companies listed under DSE do not provide any significant abnormal returns during the 60 days event window.  For CAAR, no significant return is reported for cash dividend, while stock dividend provided a maximum 5.6% abnormal returns during the post announcement period

Outcome of classical and reversal stapedotomy in otosclerosis

Classical and reversal stapedotomy both are exclusively done in otosclerosis but definite information regarding surgical advances, postoperative results, complications and information about how and in which patients these surgical techniques should exclusively be used are a source of continuous discussions. This prospective observational study was conducted in the Department of Otolaryngology-Head & Neck Surgery, Bangabandhu Sheikh Mujib Medical University, Shahbagh, Dhaka from July 2019 to December 2020 o compare the outcomes of classical and reversal stapedotomy in patients with otosclerosis. Total 28 cases of otosclerosis who underwent stapedotomy were divided in to two groups i.e. Group A (classical stapedotomy) & Group B (reversal stapedotomy) with 14 patients in each group. All patients were followed up post-operatively up to 3 months with Pure-tone audiometry (PTA). There is no significant difference between classical and reversal stapedotomy approach in terms of hearing improvement and complications. Chorda tympani injury was the main complication in both the groups. Regarding hearing gain and complications there was no significant difference between classical and reversal stapedotomy approach. BSMMU J 2022; 15(2): 121-12

In vitro release and cytotoxicity study of encapsulated sulfasalazine within LTSP micellar/ liposomal and TSP micellar/niosomal nano-formulations

The micelles/liposome formulation for the first time has been constructed via thin-film hydration method containing soy lecithin (L), tween 80 (T), squalene (S), and polyvinyl alcohol (P) (LTSP nanoparticles). Similar ingredients except for lecithin were used for preparing micellar/niosomal vesicular SSZ nano formulation (TSP nanoparticles). The percent drug loading and encapsulation efficiency of SSZ was 7.39% and 98.5 ± 0.3 % for the 7.5:100 (w/w) ratio of SSZ: total weight of LTSP, while the percent drug loading and encapsulation efficiency of SSZ was 4.7% and 62.85 ± 0.3 % in the TSP nano formulation. Dynamic light scattering (DLS) and trans- mission electron microscopy (TEM) results showed that both formulations formed spherical micelles and vesicles with globule sizes of 25 ± 1.2 nm and 100 ± 20.5 nm respectively. The cell toxicity evaluations showed that both LTSP and TSP nano formulations without drug were nontoxic (at the range of this experiment) for Human Dermal Fibroblasts (HDF) as a normal cell line, but SSZ loaded nano formulation exhibited increased cell toxicity with half-maximal inhibitory concentration (IC50) of 940 mM for SSZ alone to near 240 mM for SSZ loaded nano formulation (approximately four times). In vitro release experiments exhibited sustained release of SSZ from both nano formulations. The LTSP micellar/liposomal and TSP micellar/niosomal nano formulation for SSZ delivery can be considered as appropriate approaches for improving its bioavailability and probably they are good candidates for future clinical investigations

Improved anti-inflammatory and anticancer properties of celecoxib loaded zinc oxide and magnesium oxide nanoclusters: A molecular docking and density functional theory simulation

Present study offers great prospects for the adsorption of anti-inflammatory celecoxib molecule (CXB) over the surface of zinc oxide (Zn12O12) and magnesium oxide (Mg12O12) nanoclusters in several environments by performing robust theoretical calculations. Density functional theory (DFT), time-dependent density functional theory (TDDFT) and molecular docking calculations have been extensively carried out to predict the foremost optimum site of CXB adsorption. It has been observed that the CXB molecule prefers to be adsorbed by its SO2 site on the Zn-O and Mg-O bonds of the Zn12O12 and Mg12O12 nanoclusters instead of NH2 and NH sites, where electrostatic interactions dominate over the bonding characteristics of the conjugate complexes. Furthermore, the presence of interactions between the CXB molecule and nanoclusters has also been evidenced by the UV–Vis absorption spectra and IR spectra. Molecular docking analysis has revealed that both adsorption states including CXB/Zn12O12 and CXB/Mg12O12 have good inhibitory potential against protein tumor necrosis factor alpha (TNF-α) and Interleukin-1 (IL-1), and human epidermal growth factor receptor 2 (HER2). Hence they might be explored as efficient TNF-α, IL-1, and HER2 inhibitors. Hence from the study, it can be anticipated that these nanoclusters can behave as an appropriate biomedical carrier for the CXB drug delivery

Association of Low-Birth Weight with Malnutrition in Children under Five Years in Bangladesh: Do Mother's Education, Socio-Economic Status, and Birth Interval Matter?

Malnutrition in children under five years remains a significant problem in Bangladesh, despite substantial socio-economic progress and a decade of interventions aimed at improving it. Although several studies have been conducted to identify the important risk factors of malnutrition, none of them assess the role of low birth weight (LBW) despite its high prevalence (36%). This study examines the association between LBW and malnutrition using data from the Bangladesh Demographic and Health Survey (BDHS) 2011 and provides practical guidelines for improving nutritional status of children.Malnutrition in children is measured in terms of their height-for-age, weight-for-height, and weight-for-age. Children whose Z-scores for either of these indices are below two standard deviations (-2SD) from median of WHO's reference population are considered as stunted, wasted or underweight, respectively. The association between malnutrition and LBW was investigated by calculating adjusted risk-ratio (RR), which controls for potential confounders such as child's age and sex, mother's education and height, length of preceding-birth-interval, access to food, area of residence, household socio-economic status. Adjusted RR was calculated using both Cochran-Mantel-Haenszel approach and multivariable logistic regression models controlling for confounder.The prevalence of malnutrition was markedly higher in children with LBW than those with normal birth-weights (stunting: 51% vs 39%; wasting: 25% vs 14% and underweight: 52% vs 33%). While controlling for the known risk factors, children with LBW had significantly increased risk of becoming malnourished compared to their counter part with RR 1.23 (95% CI:1.16-1.30), 1.71 (95% CI:1.53-1.92) and 1.47 (95% CI: 1.38-1.56) for stunting, wasting and underweight, respectively. The observed associations were not modified by factors known to reduce the prevalence of malnutrition, such as higher education of mother, better household socio-economic conditions and longer birth-interval.Higher education of mother, better household socio-economic conditions and prolonged birth intervals alone are not sufficient in bringing about substantial reductions in prevalence of child malnutrition in Bangladesh. Targeted interventions should be designed to reduce prevalence of LBW in addition to improving mother's education and other socio-demographic conditions

Determinants of children ever born among ever-married women in Bangladesh: evidence from the Demographic and Health Survey 2017–2018

Objective: To investigate the prevalence of the number of children ever born (CEB) and its associated determinants among women aged 15–49 years in Bangladesh. Study design and setting: We used clustered data extracted from the last two Bangladesh Demographic and Health Surveys (BDHS 2014 and BDHS 2017–2018). A two-stage stratified sampling was used in both surveys. Mixed logistic regression modelling approach for binary responses was adapted to accommodate clustering effects via the generalised linear mixed model framework. Participants: The study is based on 15 924 ever-married women in BDHS 2017–2018 (14 119 in BDHS 2014) of Bangladesh. Results: As per the latest BDHS 2017–2018, 42.1% of reproductive women had three or more children. Age at first marriage (p<0.001, OR 0.74, 95% CI 0.666 to 0.825), age at first birth (p<0.001, OR0.54, 95% CI 0.480 to 0.607), place of residence (p<0.001, OR 0.79, 95% CI 0.712 to 0.872), exposure of media (p<0.001, OR 0.71, 95% CI 0.647 to 0.768), religion (p<0.001, OR 1.47, 95% CI 1.277 to 1.690), husband’s desire more child (p<0.001, OR 1.60, 95% CI 1.428 to 1.784), women empowerment (p<0.001, OR 1.19, 95% CI 1.075 to 1.3) and wealth index (p<0.001, OR1.61, 95% CI 0.435 to 1.796) were found to be statistically significant determinants of the number of CEB among ever-married women. The number of CEB among women was negatively associated with their own educational status (p<0.001) and husbands level of education (p<0.001). Conclusion: The CEB appears to be higher among women who were married before 18 years, Muslim, illiterate, living in rural areas, had first birth before 20 years, non-exposure of media and husband’s desire for more children

Risk ratios and 95% confidence intervals measuring association between low birth weight (LBW) and stunting.

<p>Risk ratios and 95% confidence intervals measuring association between low birth weight (LBW) and stunting.</p