673 research outputs found
Participant Recruitment of African American College Students at an Historically Black College and University (HBCU): Challenges and Strategies for Health-Related Research
Lack of research participation among African Americans is problematic for population relevant health disparity research. The purpose of this paper is to identify and describe challenges and strategies in recruitment of African American college students for health related research being conducted at a small Historically Black College or University (HBCU). Upon completion of a recruitment and retention literature review, study investigators constructed and tested a culturally-specific, direct-appeal protocol to recruit participants. Major barriers to recruitment of African American college students included discrete sources of distrust, lack of understanding of the research process, and logistical concerns. Implementation of a culturally-specific, direct appeal protocol led to a significant improvement in recruitment and retention of student participants. It is imperative that researchers demystify scientific investigation as a first step towards building trust between themselves and target populations, particularly those from traditionally underrepresented groups. Reasons for distrust, a need for trust and trust building strategies are offered here
Tendency of spherically imploding plasma liners formed by merging plasma jets to evolve toward spherical symmetry
Three dimensional hydrodynamic simulations have been performed using smoothed
particle hydrodynamics (SPH) in order to study the effects of discrete jets on
the processes of plasma liner formation, implosion on vacuum, and expansion.
The pressure history of the inner portion of the liner was qualitatively and
quantitatively similar from peak compression through the complete stagnation of
the liner among simulation results from two one dimensional
radiationhydrodynamic codes, 3D SPH with a uniform liner, and 3D SPH with 30
discrete plasma jets. Two dimensional slices of the pressure show that the
discrete jet SPH case evolves towards a profile that is almost
indistinguishable from the SPH case with a uniform liner, showing that
non-uniformities due to discrete jets are smeared out by late stages of the
implosion. Liner formation and implosion on vacuum was also shown to be robust
to Rayleigh-Taylor instability growth. Interparticle mixing for a liner
imploding on vacuum was investigated. The mixing rate was very small until
after peak compression for the 30 jet simulation.Comment: 28 pages, 16 figures, submitted to Physics of Plasmas (2012
Multi-chord fiber-coupled interferometer with a long coherence length laser
This paper describes a 561 nm laser heterodyne interferometer that provides
time-resolved measurements of line-integrated plasma electron density within
the range of 10^15-10^18 cm^(-2). Such plasmas are produced by railguns on the
Plasma Liner Experiment (PLX), which aims to produce \mu s-, cm-, and
Mbar-scale plasmas through the merging of thirty plasma jets in a spherically
convergent geometry. A long coherence length, 320 mW laser allows for a strong,
sub-fringe phase-shift signal without the need for closely-matched probe and
reference path lengths. Thus only one reference path is required for all eight
probe paths, and an individual probe chord can be altered without altering the
reference or other probe path lengths. Fiber-optic decoupling of the probe
chord optics on the vacuum chamber from the rest of the system allows the probe
paths to be easily altered to focus on different spatial regions of the plasma.
We demonstrate that sub-fringe resolution capability allows the interferometer
to operate down to line-integrated densities of order 10^15 cm^(-2).Comment: submitted to Rev. Sci. Instrum. (2011
Graded Hecke algebras for disconnected reductive groups
We introduce graded Hecke algebras H based on a (possibly disconnected)
complex reductive group G and a cuspidal local system L on a unipotent orbit of
a Levi subgroup M of G. These generalize the graded Hecke algebras defined and
investigated by Lusztig for connected G.
We develop the representation theory of the algebras H. obtaining complete
and canonical parametrizations of the irreducible, the irreducible tempered and
the discrete series representations. All the modules are constructed in terms
of perverse sheaves and equivariant homology, relying on work of Lusztig. The
parameters come directly from the data (G,M,L) and they are closely related to
Langlands parameters.
Our main motivation for considering these graded Hecke algebras is that the
space of irreducible H-representations is canonically in bijection with a
certain set of "logarithms" of enhanced L-parameters. Therefore we expect these
algebras to play a role in the local Langlands program. We will make their
relation with the local Langlands correspondence, which goes via affine Hecke
algebras, precise in a sequel to this paper.Comment: Theorem 3.4 and Proposition 3.22 in version 1 were not entirely
correct as stated. This is repaired in a new appendi
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Evaluation of health and safety impacts of defense high-level waste in geologic repositories. Draft 1
This report is concerned with evaluating the health and safety aspects of defense waste disposal during both the operational and the post-closure phase of a repository. In each case, the evaluation includes three aspects: (1) an identification and discussion of the various factors which are expected to influence the health and safety impacts of the different disposal options for defense high-level waste, (2) an identification of the general assumptions which were used in estimating potential health and safety effects and a selection of appropriate models for estimating the health and safety impacts of the various disposal options, and (3) an analysis of the health and safety impacts for each disposal option for defense high-level waste. This report describes our initial results in these areas. Based on the evaluations presented in this report, our initial conclusion is that the potential health and safety impacts are not likely to vary significantly among the different disposal options that might be chosen for defense high-level waste, primarily because of the need to meet standards in all cases. The differences in estimated health and safety aspects for different options are in all cases much smaller than the uncertainties which will be associated with realistic estimates of these impacts
Studies of hepatic synthesis in vivo of plasma proteins, including orosomucoid, transferrin, α-antitrypsin, C8, and factor B
Serum protein types were determined in eight recipients and donors in cases of hepatic homotransplantation. A change from recipient type to donor type was observed for factor B, C8, orosomucoid, haptoglobin, transferrin, α1-antitrypsin, C3 and C6, but not for Gm and Inv immunoglobulin markers. The results indicate that all the proteins studied (except immunoglobulins) are produced primarily by the liver in vivo. © 1980
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