Determination of maternal risk factors of preterm delivery: Adjusted for sparse data bias; results from a population-based case-control study in Iran

Objective To determine the maternal risk factors associated with preterm delivery in Iran. Methods A population-based case-control study was conducted including 48 women having preterm delivery (case group) and 100 women having term delivery (control group) between March 2007 and March 2012 in the maternity hospitals of the Selseleh County, Lorestan province, Iran. Information regarding maternal risk factors was collected by structured interview and reviewing the medical records. The maternal risk factors associated with preterm delivery were identified using univariate and multivariable logistic regression analysis after adjusting the sparse data bias. The area under the receiver operating characteristic (ROC) curves was estimated to evaluate the discrimination power of the statistical models. Results Multivariable analysis demonstrated that multiparty (odds ratio OR, 14.23; 95% confidence interval CI, 1.60-127.05), history of gestational diabetes (OR, 0.10; 95% CI, 0.01-0.99), thyroid dysfunction (OR, 97.32; 95% CI, 5.78-1,637.80), urinary tract infection (OR, 16.60; 95% CI, 3.20-85.92), and taking care during pregnancy (OR, 0.12; 95% CI, 0.03-0.50) had significant impact on preterm delivery after adjusting the potential confounders. The area under the ROC curve for the aforementioned maternal risk factors was 0.86 (95% CI, 0.80-0.92). Conclusion Our study provides evidence for the associations between multiparty, history of gestational diabetes, thyroid dysfunction, urinary tract infection, as well as taking care during pregnancy, and preterm delivery. © 2020 Korean Society of Obstetrics and Gynecology

The effects of material formulation and manufacturing process on mechanical and thermal properties of epoxy/clay nanocomposites

A holistic study was conducted to investigate the combined effect of three different pre-mixing processes, namely mechanical mixing, ultrasonication and centrifugation, on mechanical and thermal properties of epoxy/clay nanocomposites reinforced with different platelet-like montmorillonite (MMT) clays (Cloisite Na+, Cloisite 10A, Cloisite 15 or Cloisite 93A) at clay contents of 3–10 wt%. Furthermore, the effect of combined pre-mixing processes and material formulation on clay dispersion and corresponding material properties of resulting composites was investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), flexural and Charpy impact tests, Rockwell hardness tests and differential scanning calorimetry (DSC). A high level of clay agglomeration and partially intercalated/exfoliated clay structures were observed regardless of clay type and content. Epoxy/clay nanocomposites demonstrate an overall noticeable improvement of up to 10 % in the glass transition temperature (Tg) compared to that of neat epoxy, which is interpreted by the inclusion of MMT clays acting as rigid fillers to restrict the chain mobility of epoxy matrices. The impact strength of epoxy/clay nanocomposites was also found to increase by up to 24 % with the addition of 3 wt% Cloisite Na+ clays. However, their flexural strength and hardness diminished when compared to those of neat epoxy, arising from several effects including clay agglomeration, widely distributed microvoids and microcracks as well as weak interfacial bonding between clay particles and epoxy matrices, as confirmed from TEM and SEM results. Overall, it is suggested that an improved technique should be used for the combination of pre-mixing processes in order to achieve the optimal manufacturing condition of uniform clay dispersion and minimal void contents

Biplot Analysis of Three Carthamus Species and their F2 Hybrids Evaluated under Drought Stress in Seedling Stage

Drought stress is one of the most important environmental factors affecting growth, development and production of crop plants. Drought tolerance in germination and seedling growth stage is very important especially for crop production in dry regions. Sufficient genetic diversity in cultivated species of safflower is limited and seems to be of potential benefit in search of wild species. In this study drought tolerance of three Crathamus species and their respective F2 hybrids (direct and reciprocal from paired crosses) was evaluated under four levels of osmotic potential of polyethylene glycol (0, -5, -10 and -15 bars) using a factorial experiment based on the completely randomized design with three replications. Increasing water stress levels caused significantly more reductions in the germination, root length, shoot length, root dry weight, shoot dry weight and seedling dry weight of cultivated genotypes as compared with wild species C. palaestinus (Cp), C. oxyacanthus (Co) and their F2 progenies indicating that wild species sustained more moisture stress tolerance than cultivated species. Results of drought tolerance indices (such as TOL and STI) also confirmed that wild species and F2 progenies had more drought tolerance in germination stage. Biplot analysis, according to principle component analysis (PCA), indicated that C. tinctorius was the most sensitive and the hybrids of C. oxyacanthus × C. palestinus were the most drought tolerant genotypes which can be due to heterosis. Results also showed that the F2 hybrids from crosses between cultivated species (C. tinctorius) and wild species (C. oxyacanthus and C. palestinus) had high tolerance to drought stress and can be used for developing drought tolerant genotypes in inter-specific hybridization breeding programs