12,108 research outputs found
A Geospatial Analysis of CDC-funded HIV Prevention Programs for African Americans in the United States
Given the increase in HIV/AIDS infection rates among racial and ethnic minorities, particularly African Americans, this study was undertaken as part of a larger research effort to examine the distribution of HIV prevention services focusing on African American populations within the United States. Data were gathered via a national survey of community-based organizations (CBOs) funded by the Centers for Disease Control and Prevention (CDC). A geocoded national database was constructed to identify, locate, and map these HIV prevention programs. A total of 1,020 CBOs responded to the survey, yielding a response rate of 70.3%. These CBOs administered a total of 3,028 HIV prevention programs. Data describing intervention types and persons served, combined with the address and service area of responding CBOs, were integrated with census data (2000) and analyzed by using a geographic information system (GIS). The results of our national level analysis show that HIV prevention services for African Americans have fair coverage where African Americans comprise a substantial proportion of the population in urban areas in northeastern states, but that HIV prevention services for African Americans are inadequately distributed in the southeastern states. A local-level analysis was conducted for Alabama, where 68% of HIV/AIDS cases are among African Americans. Specific interventions such as street and community outreach, health communications, and public information are fairly well provided to African Americans in more urban cities in Alabama, however, individual- and group-level interventions have poor coverage in rural areas where a large percentage of African-Americans live. Overall, our study illustrates that the use of GIS adds value when used with other data sources to provide prevention services that are accessible to the populations most in need
A study of liquid propellant autoignition
Data and theory pertinent to the autoignition of liquid oxygen/liquid hydrogen and liquid oxygen propellants were reviewed. Physical models of the processes supporting or contributing to autoignition were developed. Emphasis was placed on the description of the physical environment and its relationship to the autoignition phenomenon
Pion double charge exchange on 4He
The doubly differential cross sections for the He
reaction were calculated using both a two-nucleon sequential single charge
exchange model and an intranuclear cascade code. Final state interactions
between the two final protons which were the initial neutrons were included in
both methods. At incident pion energies of 240 and 270 MeV the low-energy peak
observed experimentally in the energy spectrum of the final pions can be
understood only if the contribution of pion production is included. The
calculated cross sections are compared with data.Comment: 25 pages, 9 figure
Generalized Phase Rules
For a multi-component system, general formulas are derived for the dimension
of a coexisting region in the phase diagram in various state spaces.Comment: In the revised manuscript, physical meanings of D's are explained by
adding three figures. 10 pages, 3 figure
Optical bistability involving planar metamaterial with broken structural symmetry
We report on a bistable light transmission through a planar metamaterial
composed of a metal pattern of weakly asymmetric elements placed on a nonlinear
substrate. Such structure bears the Fano-like sharp resonance response of a
trapped-mode excitation. The feedback required for bistability is provided by
the coupling between the strong antiphased trapped-mode-resonance currents
excited on the metal elements and the intensity of inner field in the nonlinear
substrate.Comment: 4 pages, 4 figure
The alpha-effect in cyclic secondary amines: new scaffolds for iminium ion accelerated transformations
Five-membered secondary amine heterocycles containing an α-heteroatom were prepared and shown to be ineffective as catalysts for the iminium ion catalysed Diels–Alder reaction between cinnamaldehyde and cyclopentadiene. Their six-membered counterparts proved to be highly active catalysts. In stark contrast, the catalytic activity observed when comparing the non α-heteroatom cyclic amines proline methyl ester and methyl pipecolinate showed the five-membered ring amine was significantly more active. Concurrent density functional theoretical calculations suggest a rationale for the observed trends in reactivity, highlighting that LUMO activation through an iminium ion intermediate plays a key role in catalytic activity
User interface design for mobile-based sexual health interventions for young people: Design recommendations from a qualitative study on an online Chlamydia clinical care pathway
Background: The increasing pervasiveness of mobile technologies has given potential to transform healthcare by facilitating clinical management using software applications. These technologies may provide valuable tools in sexual health care and potentially overcome existing practical and cultural barriers to routine testing for sexually transmitted infections. In order to inform the design of a mobile health application for STIs that supports self-testing and self-management by linking diagnosis with online care pathways, we aimed to identify the dimensions and range of preferences for user interface design features among young people. Methods: Nine focus group discussions were conducted (n=49) with two age-stratified samples (16 to 18 and 19 to 24 year olds) of young people from Further Education colleges and Higher Education establishments. Discussions explored young people's views with regard to: the software interface; the presentation of information; and the ordering of interaction steps. Discussions were audio recorded and transcribed verbatim. Interview transcripts were analysed using thematic analysis. Results: Four over-arching themes emerged: privacy and security; credibility; user journey support; and the task-technology-context fit. From these themes, 20 user interface design recommendations for mobile health applications are proposed. For participants, although privacy was a major concern, security was not perceived as a major potential barrier as participants were generally unaware of potential security threats and inherently trusted new technology. Customisation also emerged as a key design preference to increase attractiveness and acceptability. Conclusions: Considerable effort should be focused on designing healthcare applications from the patient's perspective to maximise acceptability. The design recommendations proposed in this paper provide a valuable point of reference for the health design community to inform development of mobile-based health interventions for the diagnosis and treatment of a number of other conditions for this target group, while stimulating conversation across multidisciplinary communities
Small Orbits
We study both the "large" and "small" U-duality charge orbits of extremal
black holes appearing in D = 5 and D = 4 Maxwell-Einstein supergravity theories
with symmetric scalar manifolds. We exploit a formalism based on cubic Jordan
algebras and their associated Freudenthal triple systems, in order to derive
the minimal charge representatives, their stabilizers and the associated
"moduli spaces". After recalling N = 8 maximal supergravity, we consider N = 2
and N = 4 theories coupled to an arbitrary number of vector multiplets, as well
as N = 2 magic, STU, ST^2 and T^3 models. While the STU model may be considered
as part of the general N = 2 sequence, albeit with an additional triality
symmetry, the ST^2 and T^3 models demand a separate treatment, since their
representative Jordan algebras are Euclidean or only admit non-zero elements of
rank 3, respectively. Finally, we also consider minimally coupled N = 2, matter
coupled N = 3, and "pure" N = 5 theories.Comment: 40 pages, 9 tables. References added. Expanded comments added to
sections III. C. 1. and III. F.
Muon-spin rotation measurements of the vortex state in SrRuO: type-1.5 superconductivity, vortex clustering and a crossover from a triangular to a square vortex lattice
Muon-spin rotation has been used to probe vortex state in SrRuO. At
moderate fields and temperatures a lattice of triangular symmetry is observed,
crossing over to a lattice of square symmetry with increasing field and
temperature. At lower fields it is found that there are large regions of the
sample that are completely free from vortices which grow in volume as the
temperature falls. Importantly this is accompanied by {\it increasing} vortex
density and increasing disorder within the vortex-cluster containing regions.
Both effects are expected to result from the strongly temperature-dependent
long-range vortex attractive forces arising from the multi-band chiral-order
superconductivity.Comment: 13 pages, 4 figure
Intrinsic Optical and Electronic Properties from Quantitative Analysis of Plasmonic Semiconductor Nanocrystal Ensemble Optical Extinction
The optical extinction spectra arising from localized surface plasmon
resonance in doped semiconductor nanocrystals (NCs) have intensities and
lineshapes determined by free charge carrier concentrations and the various
mechanisms for damping the oscillation of those free carriers. However, these
intrinsic properties are convoluted by heterogeneous broadening when measuring
spectra of ensembles. We reveal that the traditional Drude approximation is not
equipped to fit spectra from a heterogeneous ensemble of doped semiconductor
NCs and produces fit results that violate Mie scattering theory. The
heterogeneous ensemble Drude approximation (HEDA) model rectifies this issue by
accounting for ensemble heterogeneity and near-surface depletion. The HEDA
model is applied to tin-doped indium oxide NCs for a range of sizes and doping
levels but we expect it can be employed for any isotropic plasmonic particles
in the quasistatic regime. It captures individual NC optical properties and
their contributions to the ensemble spectra thereby enabling the analysis of
intrinsic NC properties from an ensemble measurement. Quality factors for the
average NC in each ensemble are quantified and found to be notably higher than
those of the ensemble. Carrier mobility and conductivity derived from HEDA fits
matches that measured in the bulk thin film literature
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