253 research outputs found
A novel approach to HIV prevention: understanding multi-level influences on HIV pre-exposure prophylaxis (PREP) uptake and outreach among African Americans.
This dissertation examined and provided basis for addressing factors related to HIV pre-exposure prophylaxis (PrEP) engagement, outreach, and uptake among high-risk African American youth groups in Louisville, KY. This qualitative dissertation study was designed through the lens of an interpretive framework of social constructivism which holds that multiple realities and interpretations exist and are socially constructed through the lived experiences of individuals and their interactions with others. Thus, lived experiences of various African American youth groups in Louisville as well as key informants of AIDS service organizations (ASOs) across the U.S. (including Louisville) were explored to develop a deeper understanding of the barriers and facilitators to PrEP engagement, outreach, and uptake among African American youth priority groups. Seven chapters delineate the dissertation path. Chapter one provides a background and introduces the research problem and study rationale. Chapter two presents a detailed review of the literature; provides a focused overview of the epidemiologic landscape of HIV among African Americans in the U.S. as well as in Kentucky; influences on PrEP uptake among African Americans; and gaps in the literature. Chapter three outlines the methods utilized to answer the various research questions. Chapters four, five, and six each function as distinct manuscripts addressing the various research questions. Findings revealed multi-level/multifaceted factors influencing PrEP-use among African Americans. These include intrapersonal factors (PrEP awareness/knowledge, perceived HIV risk and PrEP need, fears/reservations about PrEP, and acceptability of PrEP), interpersonal relationships, sociocultural issues (stigma, homophobia, and homonegativity), and systemic and structural factors (such as cost of PrEP medication, insurance coverage, availability and accessibility of PrEP, and responses to PrEP engagement strategies of AIDS service organizations). Strategies and lessons learned from a national sample of ASOs informed the development of a context specific framework for successfully implementing PrEP outreach among African American groups. This dissertation addresses gaps in literature by utilizing findings to create a framework that serves as recommendations for other ASOs, including Louisville ASOs, seeking to improve PrEP service delivery and outreach among African American priority groups
The first direct measurement of ¹²C (¹²C,n) ²³Mg at stellar energies
Neutrons produced by the carbon fusion reaction ¹²C(¹²C,n)²³Mg play an important role in stellar nucleosynthesis. However, past studies have shown large discrepancies between experimental data and theory, leading to an uncertain cross section extrapolation at astrophysical energies. We present the first direct measurement that extends deep into the astrophysical energy range along with a new and improved extrapolation technique based on experimental data from the mirror reaction ¹²C(¹²C,p)²³Na. The new reaction rate has been determined with a well-defined uncertainty that exceeds the precision required by astrophysics models. Using our constrained rate, we find that ¹²C(¹²C,n)²³Mg is crucial to the production of Na and Al in Pop-III Pair Instability Supernovae. It also plays a non-negligible role in the production of weak s-process elements as well as in the production of the important galacti
In-beam spectroscopy of medium- and high-spin states in Ce
Medium and high-spin states in Ce were investigated using the
Cd(Ne, ) reaction and the Gammasphere array. The level
scheme was extended up to an excitation energy of MeV and spin 93/2
. Eleven bands of quadrupole transitions and two new dipole bands are
identified. The connections to low-lying states of the previously known,
high-spin triaxial bands were firmly established, thus fixing the excitation
energy and, in many cases, the spin parity of the levels. Based on comparisons
with cranked Nilsson-Strutinsky calculations and tilted axis cranking covariant
density functional theory, it is shown that all observed bands are
characterized by pronounced triaxiality. Competing multiquasiparticle
configurations are found to contribute to a rich variety of collective
phenomena in this nucleus.Comment: 20 pages, 11 figure
Tidal waves in Pd 102: A phenomenological analysis
Rotational and electromagnetic properties of the yrast band in Pd102 are analyzed in terms of a phenomenological phonon model that includes anharmonic terms. Both the moment of inertia and B(E2)'s are well reproduced by the model, providing an independent confirmation of the multiphonon picture recently proposed. The (empirical) dependence of the phonon-phonon interaction on the phonon frequency, in Ru, Pd, and Ru isotopes, follows the expectations from particle-vibration coupling
Static quadrupole moments of nuclear chiral doublet bands
The static quadrupole moments (SQMs) of nuclear chiral doublet bands are
investigated for the first time taking the particle-hole configuration
with triaxial deformation
parameters in the range as examples. The
behavior of the SQM as a function of spin is illustrated by analyzing the
components of the total angular momentum. It is found that in the region of
chiral vibrations the SQMs of doublet bands are strongly varying with ,
whereas in the region of static chirality the SQMs of doublet bands are almost
constant. Hence, the measurement of SQMs provides a new criterion for
distinguishing the modes of nuclear chirality. Moreover, in the high-spin
region the SQMs can be approximated by an analytic formula with a
proportionality to for both doublet bands. This provides a way to
extract experimentally the triaxial deformation parameter for chiral
bands from the measured SQMs.Comment: 7 pages, 4 figure
Direct Evidence for Octupole Deformation in Ba and the Origin of Large Moment Variations in Reflection-Asymmetric Nuclei
Despite the more than one order of magnitude difference between the measured
dipole moments in Ba and Ba, the strength of the octupole
correlations in Ba are found to be as strong as those in Ba
with a similarly large value of determined as
48() W.u. The new results not only establish unambiguously the
presence of a region of octupole deformation centered on these neutron-rich Ba
isotopes, but also manifest the dependence of the electric dipole moments on
the occupancy of different neutron orbitals in nuclei with enhanced octupole
strength, as revealed by fully microscopic calculations.Comment: 6 pages, 5 figures, accepted for publication in Phys. Rev. Let
Evidence for Multiple Chiral Doublet Bands in Ce
Two distinct sets of chiral-partner bands have been identified in the nucleus
Ce. They constitute a multiple chiral doublet (MD), a phenomenon
predicted by relativistic mean field (RMF) calculations and observed
experimentally here for the first time. The properties of these chiral bands
are in good agreement with results of calculations based on a combination of
the constrained triaxial RMF theory and the particle-rotor model.Comment: Minor changes based on referee reviews and corrections of some typo
Probing the single-particle character of rotational states in F using a short-lived isomeric beam
A beam containing a substantial component of both the ,
ns isomeric state of F and its , 109.77-min ground
state has been utilized to study members of the ground-state rotational band in
F through the neutron transfer reaction , in inverse kinematics.
The resulting spectroscopic strengths confirm the single-particle nature of the
13/2 band-terminating state. The agreement between shell-model
calculations, using an interaction constructed within the shell, and our
experimental results reinforces the idea of a single-particle/collective
duality in the descriptions of the structure of atomic nuclei
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