747 research outputs found
Environmental Correlates of Physical Activity Among African-American Adults
The purpose of this cross-sectional study was to identify perceived environmental correlates of meeting physical activity guidelines among African-American adults living in Southern Nevada. Trained interviewers phoned potential participants who lived in the 12 zip codes of Clark County, Nevada with the highest proportions of African-American residents. Respondents (n=237) answered 52 health-related and demographic questions. Slightly less than 50% of participants met physical activity guidelines. A factor analysis procedure produced two environmental variables, neighborhood safety and environmental supports for physical activity. Age, gender and educational attainment (p\u3c.05) predicted the meeting of those guidelines (R2=.214), while neighborhood support for physical activity, neighborhood safety, and BMI failed to do so. This finding suggests that environmental factors are not strong predictors of physical activity among African- American adults, although environmental supports for physical activity approached significance. Future studies should consider assessing additional aspects of the built environment as an influence on physical activity
Intelligent sampling for the measurement of structured surfaces
Uniform sampling in metrology has known drawbacks such as coherent spectral aliasing and a lack of efficiency in terms of measuring time and data storage. The requirement for intelligent sampling strategies has been outlined over recent years, particularly where the measurement of structured surfaces is concerned. Most of the present research on intelligent sampling has focused on dimensional metrology using coordinate-measuring machines with little reported on the area of surface metrology. In the research reported here, potential intelligent sampling strategies for surface topography measurement of structured surfaces are investigated by using numerical simulation and experimental verification. The methods include the jittered uniform method, low-discrepancy pattern sampling and several adaptive methods which originate from computer graphics, coordinate metrology and previous research by the authors. By combining the use of advanced reconstruction methods and feature-based characterization techniques, the measurement performance of the sampling methods is studied using case studies. The advantages, stability and feasibility of these techniques for practical measurements are discussed
Cracking During Nanoindentation and its Use in the Measurement of Fracture Toughness
Results of an investigation aimed at developing a technique by which the fracture toughness of a thin film or small volume can be determined in nanoindentation experiments are reported. The method is based on the radial cracking which occurs when brittle materials are deformed by a sharp indenter such as a Vickers or Berkovich diamond. In microindentation experiments, the lengths of radial cracks have been found to correlate reasonably well with fracture toughness, and a simple semi-empirical method has been developed to compute the toughness from the crack lengths. However, a problem is encountered in extending this method into the nanoindentation regime with the standard Berkovich indenter in that there are well defined loads, called cracking thresholds, below which indentation cracking does not occur in most brittle materials. We have recently found that the problems imposed by the cracking threshold can be largely overcome by using an indenter with the geometry of the comer of a cube. For the cube-corner indenter, cracking thresholds in most brittle materials are as small as 1 mN ({approximately}0.1 grams). In addition, the simple, well-developed relation between toughness and crack length used for the Vickers indenter in the microindentation regime can be used for the cube-corner indenter in the nanoindentation regime provided a different empirical constant is used
TokaMaker: An open-source time-dependent Grad-Shafranov tool for the design and modeling of axisymmetric fusion devices
In this paper, we present a new static and time-dependent MagnetoHydroDynamic
(MHD) equilibrium code, TokaMaker, for axisymmetric configurations of
magnetized plasmas, based on the well-known Grad-Shafranov equation. This code
utilizes finite element methods on an unstructured triangular grid to enable
capturing accurate machine geometry and simple mesh generation from
engineering-like descriptions of present and future devices. The new code is
designed for ease of use without sacrificing capability and speed through a
combination of Python, Fortran, and C/C++ components. A detailed description of
the numerical methods of the code, including a novel formulation of the
boundary conditions for free-boundary equilibria, and validation of the
implementation of those methods using both analytic test cases and cross-code
validation is shown. Results show expected convergence across tested polynomial
orders for analytic and cross-code test cases
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Cracking during nanoindentation and its use in the measurement of fracture toughness
Results of an investigation aimed at developing a technique by which the fracture toughness of a thin film or small volume can be determined in nanoindentation experiments are reported. The method is based on the radial cracking which occurs when brittle materials are deformed by a sharp indenter such as a Vickers or Berkovich diamond. In microindentation experiments, the lengths of radial cracks have been found to correlate reasonably well with fracture toughness, and a simple semi-empirical method has been developed to compute the toughness from the crack lengths. However, a problem is encountered in extending this method into the nanoindentation regime with the standard Berkovich indenter in that there are well defined loads, called cracking thresholds, below which indentation cracking does not occur in most brittle materials. We have recently found that the problems imposed by the cracking threshold can be largely overcome by using an indenter with the geometry of the comer of a cube. For the cube-corner indenter, cracking thresholds in most brittle materials are as small as 1 mN ({approximately}0.1 grams). In addition, the simple, well-developed relation between toughness and crack length used for the Vickers indenter in the microindentation regime can be used for the cube-corner indenter in the nanoindentation regime provided a different empirical constant is used
Clubbing masculinities: Gender shifts in gay men's dance floor choreographies
This is an Author's Accepted Manuscript of an article published in Journal of Homosexuality, 58(5), 608-625, 2011 [copyright
Taylor & Francis], available online at: http://www.tandfonline.com/10.1080/00918369.2011.563660This article adopts an interdisciplinary approach to understanding the intersections of gender, sexuality, and dance. It examines the expressions of sexuality among gay males through culturally popular forms of club dancing. Drawing on political and musical history, I outline an account of how gay men's gendered choreographies changed throughout the 1970s, 80s, and 90s. Through a notion of “technologies of the body,” I situate these developments in relation to cultural levels of homophobia, exploring how masculine expressions are entangled with and regulated by musical structures. My driving hypothesis is that as perceptions of cultural homophobia decrease, popular choreographies of gay men's dance have become more feminine in expression. Exploring this idea in the context of the first decade of the new millennium, I present a case study of TigerHeat, one of the largest weekly gay dance club events in the United States
Anti-Human Immunodeficiency Virus, Toxicity in Cell Culture, and Tolerance in Mammals of a Water-Soluble Fullerene
Rapid Quantification of Dynamic and Spall Strength of Metals Across Strain Rates
The response of metals and their microstructures under extreme dynamic
conditions can be markedly different from that under quasistatic conditions.
Traditionally, high strain rates and shock stresses are measured using
cumbersome and expensive methods such as the Kolsky bar or large spall
experiments. These methods are low throughput and do not facilitate
high-fidelity microstructure-property linkages. In this work, we combine two
powerful small-scale testing methods, custom nanoindentation, and laser-driven
micro-flyer shock, to measure the dynamic and spall strength of metals. The
nanoindentation system is configured to test samples from quasistatic to
dynamic strain rate regimes (10 s to 10 s). The
laser-driven micro-flyer shock system can test samples through impact loading
between 10 s to 10 s strain rates, triggering spall
failure. The model material used for testing is Magnesium alloys, which are
lightweight, possess high-specific strengths and have historically been
challenging to design and strengthen due to their mechanical anisotropy. Here,
we modulate their microstructure by adding or removing precipitates to
demonstrate interesting upticks in strain rate sensitivity and evolution of
dynamic strength. At high shock loading rates, we unravel an interesting
paradigm where the spall strength of these materials converges, but the failure
mechanisms are markedly different. Peak aging, considered to be a standard
method to strengthen metallic alloys, causes catastrophic failure, faring much
worse than solutionized alloys. Our high throughput testing framework not only
quantifies strength but also teases out unexplored failure mechanisms at
extreme strain rates, providing valuable insights for the rapid design and
improvement of metals for extreme environments
Photochemistry of Furyl- and Thienyldiazomethanes: Spectroscopic Characterization of Triplet 3-Thienylcarbene
Photolysis (λ \u3e 543 nm) of 3-thienyldiazomethane (1), matrix isolated in Ar or N2 at 10 K, yields triplet 3-thienylcarbene (13) and α-thial-methylenecyclopropene (9). Carbene 13 was characterized by IR, UV/vis, and EPR spectroscopy. The conformational isomers of 3-thienylcarbene (s-E and s-Z) exhibit an unusually large difference in zero-field splitting parameters in the triplet EPR spectrum (|D/hc| = 0.508 cm–1, |E/hc| = 0.0554 cm–1; |D/hc| = 0.579 cm–1, |E/hc| = 0.0315 cm–1). Natural Bond Orbital (NBO) calculations reveal substantially differing spin densities in the 3-thienyl ring at the positions adjacent to the carbene center, which is one factor contributing to the large difference in D values. NBO calculations also reveal a stabilizing interaction between the sp orbital of the carbene carbon in the s-Z rotamer of 13 and the antibonding σ orbital between sulfur and the neighboring carbon—an interaction that is not observed in the s-E rotamer of 13. In contrast to the EPR spectra, the electronic absorption spectra of the rotamers of triplet 3-thienylcarbene (13) are indistinguishable under our experimental conditions. The carbene exhibits a weak electronic absorption in the visible spectrum (λmax = 467 nm) that is characteristic of triplet arylcarbenes. Although studies of 2-thienyldiazomethane (2), 3-furyldiazomethane (3), or 2-furyldiazomethane (4) provided further insight into the photochemical interconversions among C5H4S or C5H4O isomers, these studies did not lead to the spectroscopic detection of the corresponding triplet carbenes (2-thienylcarbene (11), 3-furylcarbene (23), or 2-furylcarbene (22), respectively)
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