Brown University

About: Brown University is a education organization based out in Providence, Rhode Island, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 35778 authors who have published 90896 publications receiving 4471489 citations. The organization is also known as: brown.edu & Brown.

Anomalous Strength Characteristics of Tilt Grain Boundaries in Graphene

Abstract: Graphene in its pristine form is one of the strongest materials tested, but defects influence its strength. Using atomistic calculations, we find that, counter to standard reasoning, graphene sheets with large-angle tilt boundaries that have a high density of defects are as strong as the pristine material and, unexpectedly, are much stronger than those with low-angle boundaries having fewer defects. We show that this trend is not explained by continuum fracture models but can be understood by considering the critical bonds in the strained seven-membered carbon rings that lead to failure; the large-angle boundaries are stronger because they are able to better accommodate these strained rings. Our results provide guidelines for designing growth methods to obtain sheets with strengths close to that of pristine graphene.

Randomized Trial of Lifestyle Modification and Pharmacotherapy for Obesity

Abstract: background Weight-loss medications are recommended as an adjunct to a comprehensive program of diet, exercise, and behavior therapy but are typically prescribed with minimal or no lifestyle modification. This practice is likely to limit therapeutic benefits. methods In this one-year trial, we randomly assigned 224 obese adults to receive 15 mg of sibutramine per day alone, delivered by a primary care provider in eight visits of 10 to 15 minutes each; lifestyle-modification counseling alone, delivered in 30 group sessions; sibutramine plus 30 group sessions of lifestyle-modification counseling (i.e., combined therapy); or sibutramine plus brief lifestyle-modification counseling delivered by a primary care provider in eight visits of 10 to 15 minutes each. All subjects were prescribed a diet of 1200 to 1500 kcal per day and the same exercise regimen. results At one year, subjects who received combined therapy lost a mean (±SD) of 12.1±9.8 kg, whereas those receiving sibutramine alone lost 5.0±7.4 kg, those treated by lifestyle modification alone lost 6.7±7.9 kg, and those receiving sibutramine plus brief therapy lost 7.5±8.0 kg (P<0.001). Those in the combined-therapy group who frequently recorded their food intake lost more weight than those who did so infrequently (18.1±9.8 kg vs. 7.7±7.5 kg, P=0.04). conclusions The combination of medication and group lifestyle modification resulted in more weight loss than either medication or lifestyle modification alone. The results underscore the importance of prescribing weight-loss medications in combination with, rather than in lieu of, lifestyle modification.

Stochastic relaxation, Gibbs distributions and the Bayesian restoration of images*

Abstract: We make an analogy between images and statistical mechanics systems. Pixel gray levels and the presence and orientation of edges are viewed as states of atoms or molecules in a lattice-like physical system. The assignment of an energy function in the physical system determines its Gibbs distribution. Because of the Gibbs distribution, Markov random field (MRF) equivalence, this assignment also determines an MRF image model. The energy function is a more convenient and natural mechanism for embodying picture attributes than are the local characteristics of the MRF. For a range of degradation mechanisms, including blurring, non-linear deformations, and multiplicative or additive noise, the posterior distribution is an MRF with a structure akin to the image model. By the analogy, the posterior distribution defines another (imaginary) physical system. Gradual temperature reduction in the physical system isolates low-energy states (‘annealing’), or what is the same thing, the most probable states under the Gib...

Comprehensive analysis of the chromatin landscape in Drosophila melanogaster

Abstract: Chromatin is composed of DNA and a variety of modified histones and non-histone proteins, which have an impact on cell differentiation, gene regulation and other key cellular processes. Here we present a genome-wide chromatin landscape for Drosophila melanogaster based on eighteen histone modifications, summarized by nine prevalent combinatorial patterns. Integrative analysis with other data (non-histone chromatin proteins, DNase I hypersensitivity, GRO-Seq reads produced by engaged polymerase, short/long RNA products) reveals discrete characteristics of chromosomes, genes, regulatory elements and other functional domains. We find that active genes display distinct chromatin signatures that are correlated with disparate gene lengths, exon patterns, regulatory functions and genomic contexts. We also demonstrate a diversity of signatures among Polycomb targets that include a subset with paused polymerase. This systematic profiling and integrative analysis of chromatin signatures provides insights into how genomic elements are regulated, and will serve as a resource for future experimental investigations of genome structure and function.