background: although the precise etiology of multiple sclerosis (ms) is unknown, it seems that both genetic and environmental factors are important. recent studies suggest that low serum vitamin d levels are important environmental factor in ms. the aim of this study was to compare the serum levels of vitamin d between ms patients and healthy subjects, and to determine its association with disa...

Conspecific negative density dependence (CNDD) is an important driver of stand-level tree diversity in temperate forests. CNDD can occur via two main processes. First, soil pathogens and herbivores form a halo high enemy surrounding established trees at local spatial scales. As result, seedlings saplings residing within this experience reduced growth survival. Second, intraspecific competition ...

BACKGROUND Double-adjustment can be used to remove confounding if imbalance exists after propensity score (PS) matching. However, it is not always possible to include all covariates in adjustment. We aimed to find the optimal imbalance threshold for entering covariates into regression. METHODS We conducted a series of Monte Carlo simulations on virtual populations of 5,000 subjects. We perfor...

We address the issue of variable selection in the regression model with very high ambient dimension, i.e., when the number of covariates is very large. The main focus is on the situation where the number of relevant covariates, called intrinsic dimension, is much smaller than the ambient dimension. Without assuming any parametric form of the underlying regression function, we get tight conditio...

PURPOSE This study tested the hypothesis that volunteering in environmental organizations in midlife is associated with greater physical activity and improved mental and physical health over a 20-year period. DESIGN AND METHODS The study used data from two waves (1974 and 1994) of the Alameda County Study, a longitudinal study of health and mortality that has followed a cohort of 6,928 adults...