14,446 research outputs found
The importance of social worlds: an investigation of peer relationships [Wider Benefits of Learning Research Report No. 29]
In the following report, we investigate the developing social worlds in late primary school, exploring the patterns in childrenâs general peer relationships, their closer and more significant friendships and bullying behaviours. Using cluster analysis, we identify unique groups of children characterized not only by their experiences of bullying and victimization, but the support and satisfaction they receive from their friendships and interactions between the ages of 8 and 10. We also expand past research by examining how childrenâs early development (ages 3 to 4) may predict their later designation as bullies and/or victims, and whether peer clusters relate to childrenâs contemporaneous and later adjustment
Natural Resource Access and Interracial Associations: Black and White Subsistence Fishing in the Mississippi Delta
Using qualitative data gathered over approximately twenty months, we examine how racial divisions between black and white fishers factor into access, harvesting strategies, and use of natural resources in subsistence fishing activities in the Mississippi Delta. Though both races engage in subsistence fishing for many of the same reasons -- a sense of autonomy and economic independence -- clear differences were manifest in their access, harvesting strategies, and utilization of the fish. We document these differences. We conclude that the social relations between white and black subsistence fishers, as they interact with and through the landscape, appear to perpetuate the characteristics of race relations in this region rather than redefine them
On the use of artificial neural networks for the analysis of survival data
Artificial neural networks are a powerful tool for analyzing data sets where there are complicated nonlinear interactions between the measured inputs and the quantity to be predicted. We show that the results obtained when neural networks are applied to survival data depend critically on the treatment of censoring in the data. When the censoring is modeled correctly, neural networks are a robust model independent technique for the analysis of very large sets of survival data
Large Area Mapping at 850 Microns. V. Analysis of the Clump Distribution in the Orion A South Molecular Cloud
We present results from a 2300 arcmin^2 survey of the Orion A molecular cloud
at 450 and 850 micron using the Submillimetre Common-User Bolometer Array
(SCUBA) on the James Clerk Maxwell Telescope. The region mapped lies directly
south of the OMC1 cloud core and includes OMC4, OMC5, HH1/2, HH34, and L1641N.
We identify 71 independent clumps in the 850 micron map and compute size, flux,
and degree of central concentration in each. Comparison with isothermal,
pressure-confined, self-gravitating Bonnor-Ebert spheres implies that the
clumps have internal temperatures T_d ~ 22 +/- K and surface pressures log
(k^-1 P cm^-3 K) = 6.0 +/- 0.2. The clump masses span the range 0.3 - 22 Msun
assuming a dust temperature T_d ~ 20 K and a dust emissivity kappa_850 = 0.02
cm^2 g^-1. The distribution of clump masses is well characterized by a
power-law N(M) propto M^-alpha with alpha = 2.0 +/- 0.5 for M > 3.0 Msun,
indicating a clump mass function steeper than the stellar Initial Mass
Function. Significant incompleteness makes determination of the slope at lower
masses difficult. A comparison of the submillimeter emission map with an H_2
2.122 micron survey of the same region is performed. Several new Class 0
sources are revealed and a correlation is found between both the column density
and degree of concentration of the submillimeter sources and the likelihood of
coincident H_2 shock emission.Comment: 44 pages, 17 figures, accepted by Ap
Hydrogen Balmer Line Broadening in Solar and Stellar Flares
The broadening of the hydrogen lines during flares is thought to result from
increased charge (electron, proton) density in the flare chromosphere. However,
disagreements between theory and modeling prescriptions have precluded an
accurate diagnostic of the degree of ionization and compression resulting from
flare heating in the chromosphere. To resolve this issue, we have incorporated
the unified theory of electric pressure broadening of the hydrogen lines into
the non-LTE radiative transfer code RH. This broadening prescription produces a
much more realistic spectrum of the quiescent, A0 star Vega compared to the
analytic approximations used as a damping parameter in the Voigt profiles. We
test recent radiative-hydrodynamic (RHD) simulations of the atmospheric
response to high nonthermal electron beam fluxes with the new broadening
prescription and find that the Balmer lines are over-broadened at the densest
times in the simulations. Adding many simultaneously heated and cooling model
loops as a "multithread" model improves the agreement with the observations. We
revisit the three-component phenomenological flare model of the YZ CMi
Megaflare using recent and new RHD models. The evolution of the broadening,
line flux ratios, and continuum flux ratios are well-reproduced by a
multithread model with high-flux nonthermal electron beam heating, an extended
decay phase model, and a "hot spot" atmosphere heated by an ultrarelativistic
electron beam with reasonable filling factors: 0.1%, 1%, and 0.1% of the
visible stellar hemisphere, respectively. The new modeling motivates future
work to understand the origin of the extended gradual phase emission.Comment: 31 pages, 13 figures, 2 tables, accepted for publication in the
Astrophysical Journa
`t Hooft Anomaly Matching for QCD
I present a set of theories which display non-trivial `t Hooft anomaly
matching for QCD with flavors. The matching theories are non-Abelian gauge
theories with "dual" quarks and baryons, rather than the purely confining
theories of baryons that `t Hooft originally searched for. The matching gauge
groups are required to have an dimensional representation. Such a
correspondence is reminiscent of Seiberg's duality for supersymmetric (SUSY)
QCD, and these theories are candidates for non-SUSY duality. However anomaly
matching by itself is not sufficiently restrictive, and duality for QCD cannot
be established at present. At the very least, the existence of multiple anomaly
matching solutions should provide a note of caution regarding conjectured
non-SUSY dualities.Comment: 8 pages, LaTeX, version to be published in PR
Liraglutide and renal outcomes in type 2 diabetes
In a randomized, controlled trial that compared liraglutide, a glucagon-like peptide 1 analogue, with placebo in patients with type 2 diabetes and high cardiovascular risk who were receiving usual care, we found that liraglutide resulted in lower risks of the primary end point (nonfatal myocardial infarction, nonfatal stroke, or death from cardiovascular causes) and death. However, the long-term effects of liraglutide on renal outcomes in patients with type 2 diabetes are unknown
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Reducing patientsâ exposures to asthma and allergy triggers in their homes: an evaluation of effectiveness of grades of forced air ventilation filters
Objective: Many interventions to reduce allergen levels in the home are recommended to asthma and allergy patients. One that is readily available and can be highly effective is the use of high performing filters in forced air ventilation systems. Methods: We conducted a modeling analysis of the effectiveness of filter-based interventions in the home to reduce airborne asthma and allergy triggers. This work used âeach pass removal efficiencyâ applied to health-relevant size fractions of particles to assess filter performance. We assessed effectiveness for key allergy and asthma triggers based on applicable particle sizes for cat allergen, indoor and outdoor sources of particles 70% for cat dander particles, fine particulate matter (PM2.5) and respiratory virus can lower concentrations of those asthma triggers and allergens in indoor air of the home by >50%. Very high removal efficiency filters, such as those rated a 16 on the nationally recognized Minimum Efficiency Removal Value (MERV) rating system, tend to be only marginally more effective than MERV12 or 13 rated filters. Conclusions: The results of this analysis indicate that use of a MERV12 or higher performing air filter in home ventilation systems can effectively reduce indoor levels of these common asthma and allergy triggers. These reductions in airborne allergens in turn may help reduce allergy and asthma symptoms, especially if employed in conjunction with other environmental management measures recommended for allergy and asthma patients
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