672 research outputs found
Toward Realistic Altruism: A Community-Based Field Experience
This is a study of the perceptions of preservice teachers engaged in a human services field experience and the college instructors responsible for teaching the Human Development course attached to the field experience. Student data came from semistructured focus group interviews and student journals maintained throughout the experience, faculty data from onc-onone semi-structured interviews. Using the constant comparative method, data for students and faculty were grouped as follows: a) what students do during their placements, b) benefits and challenges of the experience, c) connections built between their experiences in the field and in the classroom. Analysis indicated that while the experience is generally perceived as valuable, there are gaps between what students actually do and faculty perceptions. Also, certain types of placements are much more powerful than others in yielding desired results of empathy, awareness of diversity and teaching skills. Recommendations for increasing the benefits and minimizing knowledge gaps are discussed
Adsorption of Multi-block and Random Copolymer on a Solid Surface: Critical Behavior and Phase Diagram
The adsorption of a single multi-block -copolymer on a solid planar
substrate is investigated by means of computer simulations and scaling
analysis. It is shown that the problem can be mapped onto an effective
homopolymer adsorption problem. In particular we discuss how the critical
adsorption energy and the fraction of adsorbed monomers depend on the block
length of sticking monomers , and on the total length of the polymer
chains. Also the adsorption of the random copolymers is considered and found to
be well described within the framework of the annealed approximation. For a
better test of our theoretical prediction, two different Monte Carlo (MC)
simulation methods were employed: a) off-lattice dynamic bead-spring model,
based on the standard Metropolis algorithm (MA), and b) coarse-grained lattice
model using the Pruned-enriched Rosenbluth method (PERM) which enables tests
for very long chains. The findings of both methods are fully consistent and in
good agreement with theoretical predictions.Comment: 27 pages, 12 figure
On the stability of very massive primordial stars
The stability of metal-free very massive stars ( = 0; M = 120 - 500
\msol) is analyzed and compared with metal-enriched stars. Such zero-metal
stars are unstable to nuclear-powered radial pulsations on the main sequence,
but the growth time scale for these instabilities is much longer than for their
metal-rich counterparts. Since they stabilize quickly after evolving off the
ZAMS, the pulsation may not have sufficient time to drive appreciable mass loss
in Z = 0 stars. For reasonable assumptions regarding the efficiency of
converting pulsational energy into mass loss, we find that, even for the larger
masses considered, the star may die without losing a large fraction of its
mass. We find a transition between the - and -mechanisms for
pulsational instability at Z\sim 2\E{-4} - 2\E{-3}. For the most metal-rich
stars, the -mechanism yields much shorter -folding times, indicating
the presence of a strong instability. We thus stress the fundamental difference
of the stability and late stages of evolution between very massive stars born
in the early universe and those that might be born today.Comment: 7 pages, 5 figures. Minor changes, more results given in Table 1,
accepted for publication in Ap
Constraints on Supersymmetry from Relic Density compared with future Higgs Searches at the LHC
Among the theories beyond the Standard Model (SM) of particle physics
Supersymmetry (SUSY) provides an excellent dark matter (DM) candidate, the
neutralino. One clear prediction of cosmology is the annihilation cross section
of DM particles, assuming them to be a thermal relic from the early universe.
In most of the parameter space of Supersymmetry the annihilation cross section
is too small compared with the prediction of cosmology. However, for large
values of the tan beta parameter the annihilation through s-channel
pseudoscalar Higgs exchange yields the correct relic density in practically the
whole range of possible SUSY masses up to the few TeV range. The required
values of tan beta are typically around 50, i.e. of the order of top and bottom
mass ratio, which happens to be also the range allowing for Yukawa unification
in a Grand Unified Theory with gauge coupling unification. For such large
values of tan beta the associated production of the heavier Higgses, which is
enhanced by tan beta squared, becomes three orders of magnitude larger than the
production of a simlar SM-like Higgs and could be observable as one of the
first hints of new physics at the LHC.Comment: 12 pages, 5 figures, Published version in Phys. Lett. B with updated
references and minor correction
Patient-reported outcomes of periacetabular osteotomy from the prospective ANCHOR cohort study
BACKGROUND: Current literature describing the periacetabular osteotomy (PAO) is mostly limited to retrospective case series. Larger, prospective cohort studies are needed to provide better clinical evidence regarding this procedure. The goals of the current study were to (1) report minimum 2-year patient-reported outcomes (pain, hip function, activity, overall health, and quality of life), (2) investigate preoperative clinical and disease characteristics as predictors of clinical outcomes, and (3) report the rate of early failures and reoperations in patients undergoing contemporary PAO surgery. METHODS: A large, prospective, multicenter cohort of PAO procedures was established, and outcomes at a minimum of 2 years were analyzed. A total of 391 hips were included for analysis (79% of the patients were female, and the average patient age was 25.4 years). Patient-reported outcomes, conversion to total hip replacement, reoperations, and major complications were documented. Variables with a p value of ≤0.10 in the univariate linear regressions were included in the multivariate linear regression. The backward stepwise selection method was used to determine the final risk factors of clinical outcomes. RESULTS: Clinical outcome analysis demonstrated major clinically important improvements in pain, function, quality of life, overall health, and activity level. Increasing age and a body mass index status of overweight or obese were predictive of improved results for certain outcome metrics. Male sex and mild acetabular dysplasia were predictive of lesser improvements in certain outcome measures. Three (0.8%) of the hips underwent early conversion to total hip arthroplasty, 12 (3%) required reoperation, and 26 (7%) experienced a major complication. CONCLUSIONS: This large, prospective cohort study demonstrated the clinical success of contemporary PAO surgery for the treatment of symptomatic acetabular dysplasia. Patient and disease characteristics demonstrated predictive value that should be considered in surgical decision-making. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence
Analyzing Regional Variation in Health Care Utilization Using (Rich) Household Microdata
On the Adsorption of Two-State Polymers
Monte Carlo(MC) simulations produce evidence that annealed copolymers
incorporating two interconverting monomers, P and H, adsorb as homopolymers
with an effective adsorption energy per monomer, , that depends
on the PH equilibrium constants in the bulk and at the surface. The cross-over
exponent, is unmodified. The MC results on the overall PH ratio, the PH
ratio at the surface and in the bulk as well as the number of adsorbed monomers
are in quantitative agreement with this hypothesis and the theoretically
derived . The evidence suggests that the form of surface
potential does not affect but does influence the PH equilibrium.Comment: 22 pages, 10 figure
Measurements of branching fraction ratios and CP-asymmetries in suppressed B^- -> D(-> K^+ pi^-)K^- and B^- -> D(-> K^+ pi^-)pi^- decays
We report the first reconstruction in hadron collisions of the suppressed
decays B^- -> D(-> K^+ pi^-)K^- and B^- -> D(-> K^+ pi^-)pi^-, sensitive to the
CKM phase gamma, using data from 7 fb^-1 of integrated luminosity collected by
the CDF II detector at the Tevatron collider. We reconstruct a signal for the
B^- -> D(-> K^+ pi^-)K^- suppressed mode with a significance of 3.2 standard
deviations, and measure the ratios of the suppressed to favored branching
fractions R(K) = [22.0 \pm 8.6(stat)\pm 2.6(syst)]\times 10^-3, R^+(K) =
[42.6\pm 13.7(stat)\pm 2.8(syst)]\times 10^-3, R^-(K)= [3.8\pm 10.3(stat)\pm
2.7(syst]\times 10^-3, as well as the direct CP-violating asymmetry A(K) =
-0.82\pm 0.44(stat)\pm 0.09(syst) of this mode. Corresponding quantities for
B^- -> D(-> K^+ pi^-)pi^- decay are also reported.Comment: 8 pages, 1 figure, accepted by Phys.Rev.D Rapid Communications for
Publicatio
Search for the standard model Higgs boson in the H to ZZ to 2l 2nu channel in pp collisions at sqrt(s) = 7 TeV
A search for the standard model Higgs boson in the H to ZZ to 2l 2nu decay
channel, where l = e or mu, in pp collisions at a center-of-mass energy of 7
TeV is presented. The data were collected at the LHC, with the CMS detector,
and correspond to an integrated luminosity of 4.6 inverse femtobarns. No
significant excess is observed above the background expectation, and upper
limits are set on the Higgs boson production cross section. The presence of the
standard model Higgs boson with a mass in the 270-440 GeV range is excluded at
95% confidence level.Comment: Submitted to JHE
Search for New Physics with Jets and Missing Transverse Momentum in pp collisions at sqrt(s) = 7 TeV
A search for new physics is presented based on an event signature of at least
three jets accompanied by large missing transverse momentum, using a data
sample corresponding to an integrated luminosity of 36 inverse picobarns
collected in proton--proton collisions at sqrt(s)=7 TeV with the CMS detector
at the LHC. No excess of events is observed above the expected standard model
backgrounds, which are all estimated from the data. Exclusion limits are
presented for the constrained minimal supersymmetric extension of the standard
model. Cross section limits are also presented using simplified models with new
particles decaying to an undetected particle and one or two jets
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