Conformational transitions of a semiflexible polymer in nematic solvents

Conformations of a single semiflexible polymer chain dissolved in a low molecular weight liquid crystalline solvents (nematogens) are examined by using a mean field theory. We takes into account a stiffness and partial orientational ordering of the polymer. As a result of an anisotropic coupling between the polymer and nematogen, we predict a discontinuous (or continuous) phase transition from a condensed-rodlike conformation to a swollen-one of the polymer chain, depending on the stiffness of the polymer. We also discuss the effects of the nematic interaction between polymer segments.Comment: 4 pages, 4 figure

Brain Amyloid Deposition is Associated With Lower Instrumental Activities of Daily Living Abilities in Older Adults : results from the MAPT Study

BACKGROUND: Brain amyloid deposition is one of the key pathological hallmarks underlying the cognitive changes associated with Alzheimer's disease. Growing interest has been given to the earliest clinical manifestations of amyloid plaques. However, the relationship between amyloid status and activities of everyday function remains largely unknown. In the present study, we examined the relationship between instrumental activities of daily living performance (using the ADL-PI score) and amyloid status in older adults. METHODS: Cross-sectional analyses of data from the Multidomain Alzheimer Preventive Trial (MAPT) were performed. Volunteers underwent a brain 18F-AV45 positron emission tomography examination. Bivariate analysis and regression models were conducted to study the relationships between brain amyloid deposition and the total ADL-PI score. RESULTS: We included 271 participants (women = 60%; age = 76\ub14 years). Amyloid positron emission tomography was positive (standard uptake value 651.17) for 103 participants (38%). The ADL-PI score was lower in amyloid positive participants than in their amyloid negative counterparts (38.8 vs 40.3, p = .007). This association was also confirmed in regression models adjusted for age, gender, and familial history of Alzheimer's disease (odds ratio = 0.94; 95% confidence interval 0.89-0.99; p = .02). This finding was consistent in cognitively normal individuals and in those with mild cognitive impairment, using the clinical dementia rating scale. CONCLUSIONS: This study highlighted an association between early functional limitations and brain amyloid deposition in elderly subjects. These symptoms could be the clinical manifestations of amyloid plaques even in the absence of overt dementia. Further prospective studies are warranted for examining the evolution of ADL-PI score over the course of Alzheimer's disease

A Framework for Modeling DNA Based Molecular Systems

Abstract. In this paper, we propose a framework for a discrete event simulator for simulating the DNA based nano-robotical systems. We describe a physical model that captures the conformational changes of the solute molecules. We also present methods to simulate various chemical reactions due to the molecular collisions, including hybridization, dehybridization and strand displacement. The feasibility of such a framework is demonstrated by some preliminary results. 1 Introduction and Related Work Recent research has explored DNA as a material for self-assembly of nanoscale object