1,184 research outputs found
Sociocultural Risk Factors for Elevated Perceived Stress among African American Smokers
Introduction: African Americans experience unique stressors that may inhibit smoking cessation and enhance relapse rates. Few studies, however, have focused on risk factors for perceived stress among treatment seekers. Because African Americans are less likely to quit compared to the larger community, understanding factors associated with perceived stress among smokers has the potential to improve intervention outcomes. This study examined psychosocial and cultural correlates of stress in a sample of African American participants in a randomized controlled trial.
Methods: At baseline, participants reported demographic factors and completed assessments of smoking history, alcohol use, friend and household smoking, weight concerns, acculturation, depressive symptoms, and perceived stress (N = 325). Bivariate associations were examined, followed by multiple regression analyses to test independent relationships. The sample was comprised of mostly middle-aged males, with at least a high school education, who were single, and reported low household income. Participants were moderately nicotine dependent and smoked 18 cigarettes per day for 26 years.
Results: Perceived stress was inversely associated with age (r = -.16, p = .004), education (r = -.11, p = .04), household income (r = -.11, p = .047), and positively associated with being male (r = .13, p = .02). Stress perceptions were positively related to cigarettes per day (r = .11, p = .049), nicotine dependence (r = .20, p = .001), drinking frequency (r = .15, p = .008), drinking intensity (r = .14, p=.02), and inversely related to smoking duration (r = -.12, p = .03). We found positive associations between perceived stress and household smokers (r = .18, p = .004), and friends who smoke (r = .15, p = .01).
Perceived stress was also positively associated with post-cessation weight concern (r = .14, p = .01), a traditional African American cultural orientation; r = .12, p = .04), and depressive symptoms (r = .65, p
Conclusion: These findings have important intervention implications. Many of the risk factors for distress among African American smokers are modifiable. Interventions should prioritize addressing depression, household smoking environment, and stress among younger smokers, in addition to managing other stress-enhancing concerns like alcohol use
Two-stage athermal solidification of semiflexible polymers and fibers
We study how solidification of model freely rotating polymers under athermal
quasistatic compression varies with their bond angle . All systems
undergo two discrete, first-order-like transitions: entanglement at followed by jamming at . For , systems are in a
"gas" phase wherein all chains remain free to translate and reorient. For
, systems are in a
liquid-like phase wherein chains are entangled. In this phase, chains'
rigid-body-like motion is blocked, yet they can still locally relax via
dihedral rotations, and hence energy and pressure remain extremely small. The
ability of dihedral relaxation mechanisms to accommodate further compression
becomes exhausted, and systems rigidify, at . At and slightly
above , the bulk moduli increase linearly with the pressure rather
than jumping discontinuously, indicating these systems solidify via rigidity
percolation. The character of the energy and pressure increases above
can be characterized via chains' effective aspect ratio
. Large- (small-) systems'
jamming is bending-dominated and is similar to that observed in systems
composed of straight fibers. Small- (large-)
systems' jamming is dominated by the degree to which individual chains'
dihedrals can collapse into compact, tetrahedron-like structures. For
intermediate , chains remain in highly disordered globule-like
configurations throughout the compression process; jamming occurs when
entangled globules can no longer even locally relax away from one another
Delvocid® and sodium chloride effects on the stability of a corn-based liquid supplement containing urea, monensin, vitamin A and trace minerals
Call number: LD2668 .T4 1979 D54Master of Scienc
Building Resilience in a Major City Evacuation Plan Using Simulation Modeling
This study provides data on the optimal staff, materials, space, and time resources required to operate a regional hub reception center, a “short-term facility with the goal to process and transport displaced survivors (evacuees) to temporary or permanent shelters following a catastrophic incident,” (Regional Catastrophic Planning Team, 2012). The facility will process approximately 20,000 evacuees over its entire seven-day duration following a disaster to assist in community resilience. The study was performed using a model created using the computer simulation software, AnyLogic. The results of the study demonstrated that the goals set forth by the Illinois-Indiana-Wisconsin Regional Catastrophic Planning Team could be improved upon and that the largest contributing factor to optimizing the RHRC is finding the optimal number of total staff members to operate the facility
Simulations and Measurements of the Background Encountered by a High-Altitude Balloon-Borne Experiment for Hard X-ray Astronomy
We have modelled the hard X-ray background expected for a high-altitude
balloon flight of the Energetic X-ray Telescope Experiment (EXITE2), an imaging
phoswich detector/telescope for the 20--600 keV energy range. Photon and
neutron-induced contributions to the background are considered. We describe the
code and the results of a series of simulations with different shielding
configurations. The simulated hard X-ray background for the actual flight
configuration agrees reasonably well (within a factor of 2) with the
results measured on the first flight of EXITE2 from Palestine, Texas. The
measured background flux at 100 keV is 4 10 counts
cm s keV.Comment: 17 pages Latex (uses aaspp4.sty) plus 7 postscript figures: available
in file figs.tar.g
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Environmental exposures during windows of susceptibility for breast cancer: a framework for prevention research.
BackgroundThe long time from exposure to potentially harmful chemicals until breast cancer occurrence poses challenges for designing etiologic studies and for implementing successful prevention programs. Growing evidence from animal and human studies indicates that distinct time periods of heightened susceptibility to endocrine disruptors exist throughout the life course. The influence of environmental chemicals on breast cancer risk may be greater during several windows of susceptibility (WOS) in a woman's life, including prenatal development, puberty, pregnancy, and the menopausal transition. These time windows are considered as specific periods of susceptibility for breast cancer because significant structural and functional changes occur in the mammary gland, as well as alterations in the mammary micro-environment and hormone signaling that may influence risk. Breast cancer research focused on these breast cancer WOS will accelerate understanding of disease etiology and prevention.Main textDespite the plausible heightened mechanistic influences of environmental chemicals on breast cancer risk during time periods of change in the mammary gland's structure and function, most human studies of environmental chemicals are not focused on specific WOS. This article reviews studies conducted over the past few decades that have specifically addressed the effect of environmental chemicals and metals on breast cancer risk during at least one of these WOS. In addition to summarizing the broader evidence-base specific to WOS, we include discussion of the NIH-funded Breast Cancer and the Environment Research Program (BCERP) which included population-based and basic science research focused on specific WOS to evaluate associations between breast cancer risk and particular classes of endocrine-disrupting chemicals-including polycyclic aromatic hydrocarbons, perfluorinated compounds, polybrominated diphenyl ethers, and phenols-and metals. We outline ways in which ongoing transdisciplinary BCERP projects incorporate animal research and human epidemiologic studies in close partnership with community organizations and communication scientists to identify research priorities and effectively translate evidence-based findings to the public and policy makers.ConclusionsAn integrative model of breast cancer research is needed to determine the impact and mechanisms of action of endocrine disruptors at different WOS. By focusing on environmental chemical exposure during specific WOS, scientists and their community partners may identify when prevention efforts are likely to be most effective
The Minimum Backlog Problem
We study the minimum backlog problem (MBP). This online problem arises, e.g.,
in the context of sensor networks. We focus on two main variants of MBP.
The discrete MBP is a 2-person game played on a graph . The player
is initially located at a vertex of the graph. In each time step, the adversary
pours a total of one unit of water into cups that are located on the vertices
of the graph, arbitrarily distributing the water among the cups. The player
then moves from her current vertex to an adjacent vertex and empties the cup at
that vertex. The player's objective is to minimize the backlog, i.e., the
maximum amount of water in any cup at any time.
The geometric MBP is a continuous-time version of the MBP: the cups are
points in the two-dimensional plane, the adversary pours water continuously at
a constant rate, and the player moves in the plane with unit speed. Again, the
player's objective is to minimize the backlog.
We show that the competitive ratio of any algorithm for the MBP has a lower
bound of , where is the diameter of the graph (for the discrete
MBP) or the diameter of the point set (for the geometric MBP). Therefore we
focus on determining a strategy for the player that guarantees a uniform upper
bound on the absolute value of the backlog.
For the absolute value of the backlog there is a trivial lower bound of
, and the deamortization analysis of Dietz and Sleator gives an
upper bound of for cups. Our main result is a tight upper
bound for the geometric MBP: we show that there is a strategy for the player
that guarantees a backlog of , independently of the number of cups.Comment: 1+16 pages, 3 figure
Valve-sparing and valve-replacing techniques for aortic root replacement in patients with Marfan syndrome: Analysis of early outcome
ObjectiveA prospective, international registry study was initiated to provide contemporary comparative data on short-term clinical outcomes after aortic valve-sparing and aortic valve-replacing root operations in patients with Marfan syndrome. The purpose of this initial report is to describe the study design and to compare early outcomes in the first 151 enrolled patients.MethodsWe assessed 30-day outcomes in 151 patients who met strict Ghent diagnostic criteria for Marfan syndrome and underwent aortic root replacement with either valve-replacing (n = 46) or valve-sparing techniques (n = 105) at one of 18 participating centers. In the valve replacement group, a mechanical composite valve graft was used in 39 (85%) patients and a bioprosthetic valve in 7 (15%). In the valve-sparing group, David V procedures were performed in 57 (54%) patients, David I in 38 (36%), David IV in 8 (8%), Florida sleeve in 1 (1%), and Yacoub remodeling in 1 (1%).ResultsNo in-hospital or 30-day deaths occurred. Despite longer crossclamp and cardiopulmonary bypass times in the valve-sparing group, there were no significant between-group differences in postoperative complications. Thirty-day valve-related complications occurred in 2 (4%) patients undergoing valve replacement and in 3 (3%) undergoing valve-sparing procedures (P = .6).ConclusionsThe analysis of early outcomes revealed that valve-sparing techniques were the most common approach to root replacement in patients with Marfan syndrome in these centers. The complexity of valve-sparing root replacement did not translate into any demonstrable adverse early outcomes. Subsequent analysis will compare the 3-year durability of these two surgical approaches
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