York University

About: York University is a education organization based out in Toronto, Ontario, Canada. It is known for research contribution in the topics: Population & Poison control. The organization has 18899 authors who have published 43357 publications receiving 1568560 citations.

Nonequilibrium Capillary Electrophoresis of Equilibrium Mixtures: A Universal Tool for Development of Aptamers

Abstract: Aptamers are DNA (or RNA) ligands selected from large libraries of random DNA sequences and capable of binding different classes of targets with high affinity and selectivity. Both the chances for the aptamer to be selected and the quality of the selected aptamer are largely dependent on the method of selection. Here we introduce selection of aptamers by nonequilibrium capillary electrophoresis of equilibrium mixtures (NECEEM). The new method has a number of advantages over conventional approaches. First, NECEEM-based selection has exceptionally high efficiency, which allows aptamer development with fewer rounds of selection. Second, NECEEM can be equally used for selecting aptamers and finding their binding parameters. Finally, due to its comprehensive kinetic capabilities, the new method can potentially facilitate selection of aptamers with predefined K(d), k(off), and k(on) of the aptamer-target interaction. In this proof-of-principle work, we describe the theoretical bases of the method and demonstrate its application to a one-step selection of DNA aptamers with nanomolar affinity for protein farnesyltransferase.

A Tutorial on Multilevel Survival Analysis: Methods, Models and Applications.

Abstract: Data that have a multilevel structure occur frequently across a range of disciplines, including epidemiology, health services research, public health, education and sociology. We describe three families of regression models for the analysis of multilevel survival data. First, Cox proportional hazards models with mixed effects incorporate cluster-specific random effects that modify the baseline hazard function. Second, piecewise exponential survival models partition the duration of follow-up into mutually exclusive intervals and fit a model that assumes that the hazard function is constant within each interval. This is equivalent to a Poisson regression model that incorporates the duration of exposure within each interval. By incorporating cluster-specific random effects, generalised linear mixed models can be used to analyse these data. Third, after partitioning the duration of follow-up into mutually exclusive intervals, one can use discrete time survival models that use a complementary log-log generalised linear model to model the occurrence of the outcome of interest within each interval. Random effects can be incorporated to account for within-cluster homogeneity in outcomes. We illustrate the application of these methods using data consisting of patients hospitalised with a heart attack. We illustrate the application of these methods using three statistical programming languages (R, SAS and Stata).

Evidence for decline in eastern North American bumblebees (Hymenoptera: Apidae), with special focus on Bombus affinis Cresson

Abstract: Bumblebees (Bombus spp.) have been declining rapidly in many temperate regions of the Old World. Despite their ecological and economic importance as pollinators, North American bumblebees have not been extensively surveyed and their conservation status is largely unknown. In this study, two approaches were used to determine whether bumblebees in that region were in decline spatially and temporally. First, surveys performed in 2004–2006 in southern Ontario were compared to surveys from 1971 to 1973 in the same sites to look at changes in community composition, in one of the most bumblebee diverse areas of eastern North America. Second, the extent of range decline for a focal species (Bombus affinis Cresson) was estimated by surveying 43 sites throughout its known native range in eastern Canada and the United States. Our study documents an impoverishment of the bumblebee community in southern Ontario over the past 35 years. Bombus affinis in particular was found to have declined drastically in abundance not only in southern Ontario but throughout its native range. The loss of any bumblebee species may result in cascading impacts on native fauna and flora and reduce agricultural production. Implications for the conservation of this important group of pollinators are discussed.

Effects of Exposure to Thin Media Images: Evidence of Self-Enhancement among Restrained Eaters

Abstract: The effects of viewing media-portrayed idealized body images on eating, self-esteem, body image, and mood among restrained and unrestrained eaters were examined. Study 1 found that restrained eaters (i.e., dieters), but not unrestrained eaters, rated both their ideal and current body sizes as smaller and disinhibited their food intake following exposure to idealized body images. These results suggest that restrained eaters are susceptible to a “thin fantasy” brought about by viewing ideal body images. Study 2 found that strengthening thinness attainability beliefs can further enhance the thin fantasy demonstrated by restrained eaters following exposure to idealized body images. Study 3 examined whether demand characteristics moderate these effects of media-portrayed idealized body images. As predicted, when explicit demand characteristics were present, participants reported feeling worse following exposure to thin models. The complexities of the media’s role in the development and maintenance of body diss...