Control and Characterization of Individual Grains and Grain Boundaries in Graphene Grown by Chemical Vapor Deposition

The strong interest in graphene has motivated the scalable production of high quality graphene and graphene devices. Since large-scale graphene films synthesized to date are typically polycrystalline, it is important to characterize and control grain boundaries, generally believed to degrade graphene quality. Here we study single-crystal graphene grains synthesized by ambient CVD on polycrystalline Cu, and show how individual boundaries between coalescing grains affect graphene's electronic properties. The graphene grains show no definite epitaxial relationship with the Cu substrate, and can cross Cu grain boundaries. The edges of these grains are found to be predominantly parallel to zigzag directions. We show that grain boundaries give a significant Raman "D" peak, impede electrical transport, and induce prominent weak localization indicative of intervalley scattering in graphene. Finally, we demonstrate an approach using pre-patterned growth seeds to control graphene nucleation, opening a route towards scalable fabrication of single-crystal graphene devices without grain boundaries.Comment: New version with additional data. Accepted by Nature Material

Implementation of Web-Based Respondent-Driven Sampling among Men who Have Sex with Men in Vietnam

Objective: Lack of representative data about hidden groups, like men who have sex with men (MSM), hinders an evidence-based response to the HIV epidemics. Respondent-driven sampling (RDS) was developed to overcome sampling challenges in studies of populations like MSM for which sampling frames are absent. Internet-based RDS (webRDS) can potentially circumvent limitations of the original RDS method. We aimed to implement and evaluate webRDS among a hidden population. Methods and Design: This cross-sectional study took place 18 February to 12 April, 2011 among MSM in Vietnam. Inclusion criteria were men, aged 18 and above, who had ever had sex with another man and were living in Vietnam. Participants were invited by an MSM friend, logged in, and answered a survey. Participants could recruit up to four MSM friends. We evaluated the system by its success in generating sustained recruitment and the degree to which the sample compositions stabilized with increasing sample size. Results: Twenty starting participants generated 676 participants over 24 recruitment waves. Analyses did not show evidence of bias due to ineligible participation. Estimated mean age was 22 year and 82% came from the two large metropolitan areas. 32 out of 63 provinces were represented. The median number of sexual partners during the last six months was two. The sample composition stabilized well for 16 out of 17 variables. Conclusion: Results indicate that webRDS could be implemented at a low cost among Internet-using MSM in Vietnam. WebRDS may be a promising method for sampling of Internet-using MSM and other hidden groups. Key words: Respondent-driven sampling, Online sampling, Men who have sex with men, Vietnam, Sexual risk behavio

Evidence-based Kernels: Fundamental Units of Behavioral Influence

This paper describes evidence-based kernels, fundamental units of behavioral influence that appear to underlie effective prevention and treatment for children, adults, and families. A kernel is a behavior–influence procedure shown through experimental analysis to affect a specific behavior and that is indivisible in the sense that removing any of its components would render it inert. Existing evidence shows that a variety of kernels can influence behavior in context, and some evidence suggests that frequent use or sufficient use of some kernels may produce longer lasting behavioral shifts. The analysis of kernels could contribute to an empirically based theory of behavioral influence, augment existing prevention or treatment efforts, facilitate the dissemination of effective prevention and treatment practices, clarify the active ingredients in existing interventions, and contribute to efficiently developing interventions that are more effective. Kernels involve one or more of the following mechanisms of behavior influence: reinforcement, altering antecedents, changing verbal relational responding, or changing physiological states directly. The paper describes 52 of these kernels, and details practical, theoretical, and research implications, including calling for a national database of kernels that influence human behavior

SUN-313 Depression, Subjective Stress and Serum Osteocalcin Concentrations in People with Type 2 Diabetes Mellitus

Abstract Serum osteocalcin is emerging as a potential marker of glucose homeostasis and risk of type 2 diabetes mellitus (T2DM). In mice, osteocalcin knockouts exhibit depressive-like behaviours but knockouts of a putative osteocalcin receptor, GPR158, are resistant to chronic unpredictable mild stress. Recently, osteocalcin release from bone has been suggested to mediate some aspects of the acute stress response. Here, we assess relationships between serum osteocalcin, depression and perceived stress in people with T2DM. Participants with T2DM were assessed for whether they met the DSM-5 criteria for Major Depressive Disorder using the research version of the Structured Clinical Interview for DSM-5 depression criteria (SCID-5RV). Subjective stress was assessed using the Perceived Stress Scale (PSS) with higher scores indicating greater subjective stress. Serum carboxylated (cOCN) and uncarboxylated (unOCN) osteocalcin were assayed from fasting morning blood by commercial ELISA. Among 87 participants (mean age 62.9±9.5, 52% women), 18 (26%) were experiencing a depressive episode (7 men, 11 women). Both serum unOCN and cOCN were associated with higher PSS scores in participants with depression (unOCN, r=0.566, p=0.014; cOCN, r=0.564, p=0.015) but not in those without depression (unOCN, r=0.002, p=0.985; cOCN, r=0.090, p=0.463). A significant interaction was found between depression and PSS scores predicting serum unOCN in a linear model adjusted for age, sex, body mass index, antidepressant use and HbA1c (F=6.225, p=0.015). The results are consistent with reports that osteocalcin release from bone may be a mediator of stress perception; however, among people with T2DM, this relationship was observed only among those currently experiencing a depressive episode.</jats:p