16,990 research outputs found
A Comparison of Perceptions of Knowledge and Skills Held by Primary and Secondary Teachers: From the Entry to Exit of Their Preservice Programme
The purpose of this study was to investigate if there were differences in the levels of pedagogical knowledge and skills as perceived by the student teachers who were enrolled in the Primary and the Secondary Post Graduate Diploma in Education programme at the National Institute of Education in Singapore. 170 Primary and 426 Secondary student teachers participated in the study. The results showed that there were no significant differences at the beginning of the programme between the two cohorts. However, there were significant differences between the two groups at the end of programme, with the Primary student teachers tending to perceive themselves as gaining more pedagogical knowledge and skills by the end of their initial teacher preparation programme than the Secondary student teachers
The Potential Trajectory of Carbapenem-Resistant Enterobacteriaceae, an Emerging Threat to Health-Care Facilities, and the Impact of the Centers for Disease Control and Prevention Toolkit.
Carbapenem-resistant Enterobacteriaceae (CRE), a group of pathogens resistant to most antibiotics and associated with high mortality, are a rising emerging public health threat. Current approaches to infection control and prevention have not been adequate to prevent spread. An important but unproven approach is to have hospitals in a region coordinate surveillance and infection control measures. Using our Regional Healthcare Ecosystem Analyst (RHEA) simulation model and detailed Orange County, California, patient-level data on adult inpatient hospital and nursing home admissions (2011-2012), we simulated the spread of CRE throughout Orange County health-care facilities under 3 scenarios: no specific control measures, facility-level infection control efforts (uncoordinated control measures), and a coordinated regional effort. Aggressive uncoordinated and coordinated approaches were highly similar, averting 2,976 and 2,789 CRE transmission events, respectively (72.2% and 77.0% of transmission events), by year 5. With moderate control measures, coordinated regional control resulted in 21.3% more averted cases (n = 408) than did uncoordinated control at year 5. Our model suggests that without increased infection control approaches, CRE would become endemic in nearly all Orange County health-care facilities within 10 years. While implementing the interventions in the Centers for Disease Control and Prevention's CRE toolkit would not completely stop the spread of CRE, it would cut its spread substantially, by half
Estimating Negative Likelihood Ratio Confidence When Test Sensitivity is 100%: A Bootstrapping Approach
Objectives: Assessing high-sensitivity tests for mortal illness is crucial in emergency and critical care medicine. Estimating the 95% confidence interval (CI) of the likelihood ratio (LR) can be challenging when sample sensitivity is 100%. We aimed to develop, compare, and automate a bootstrapping method to estimate the negative LR CI when sample sensitivity is 100%.
Methods: The lowest population sensitivity that is most likely to yield sample sensitivity 100% is located using the binomial distribution. Random binomial samples generated using this population sensitivity are then used in the LR bootstrap. A free R program, “bootLR,” automates the process. Extensive simulations were performed to determine how often the LR bootstrap and comparator method 95% CIs cover the true population negative LR value. Finally, the 95% CI was compared for theoretical sample sizes and sensitivities approaching and including 100% using: (1) a technique of individual extremes, (2) SAS software based on the technique of Gart and Nam, (3) the Score CI (as implemented in the StatXact, SAS, and R PropCI package), and (4) the bootstrapping technique.
Results: The bootstrapping approach demonstrates appropriate coverage of the nominal 95% CI over a spectrum of populations and sample sizes. Considering a study of sample size 200 with 100 patients with disease, and specificity 60%, the lowest population sensitivity with median sample sensitivity 100% is 99.31%. When all 100 patients with disease test positive, the negative LR 95% CIs are: individual extremes technique (0,0.073), StatXact (0,0.064), SAS Score method (0,0.057), R PropCI (0,0.062), and bootstrap (0,0.048). Similar trends were observed for other sample sizes.
Conclusions: When study samples demonstrate 100% sensitivity, available methods may yield inappropriately wide negative LR CIs. An alternative bootstrapping approach and accompanying free open-source R package were developed to yield realistic estimates easily. This methodology and implementation are applicable to other binomial proportions with homogeneous responses
J/Psi Propagation in Hadronic Matter
We study J/ propagation in hot hadronic matter using a four-flavor
chiral Lagrangian to model the dynamics and using QCD sum rules to model the
finite size effects manifested in vertex interactions through form factors.
Charmonium breakup due to scattering with light mesons is the primary
impediment to continued propagation. Breakup rates introduce nontrivial
temperature and momentum dependence into the J/ spectral function.Comment: 6 Pages LaTeX, 3 postscript figures. Proceedings for Strangeness in
Quark Matter 2003, Atlantic Beach, NC, March 12-17, 2003; minor corrections
in version 2, to appear in J. Phys.
Burden of mild haemophilia A: Systematic literature review
Introduction Although the clinical manifestations of severe haemophilia A (HA) are well studied, the challenges, if any, of living with mild HA are not clearly delineated to date. Aim To assess available evidence of clinical risks and societal/economic impacts of disease in adult patients with mild HA using a systematic literature review. Methods Prespecified study selection criteria were applied in a comprehensive literature search. Included studies varied in design and reported outcomes of interest for adults (>= 13 years of age) with mild HA. Results Seventeen studies with a total of 3213 patients met eligibility criteria (published or presented in English, 1966-2017). Most studies were observational, and the outcomes reported were too sparse and dissimilar to support a formal meta-analysis. Mean annual bleeding rates ranged from 0.44 to 4.5 episodes per patient per year. Quality of life (QoL; SF-36 General Health) was impacted compared to healthy controls. Health care costs and productivity were seldom assessed and no robust comparisons to healthy controls were available. Conclusion Quantifying outcomes for adult patients with mild HA remains challenging, with estimates of key QoL and cost data often based on small data sets and without comparison to population norms. Therefore, the clinical impact of mild haemophilia may be under-represented and unmet needs may remain unaddressed. As paradigm-changing therapies for HA emerge, stronger knowledge of mild HA can guide the development of care options that minimize burden and enhance the QoL for this segment of the haemophilia community, and for the haemophilia community in totality
Regulation of Star Formation Rates in Multiphase Galactic Disks: a Thermal/Dynamical Equilibrium Model
We develop a model for regulation of galactic star formation rates Sigma_SFR
in disk galaxies, in which ISM heating by stellar UV plays a key role. By
requiring simultaneous thermal and (vertical) dynamical equilibrium in the
diffuse gas, and star formation at a rate proportional to the mass of the
self-gravitating component, we obtain a prediction for Sigma_SFR as a function
of the total gaseous surface density Sigma and the density of stars + dark
matter, rho_sd. The physical basis of this relationship is that thermal
pressure in the diffuse ISM, which is proportional to the UV heating rate and
therefore to Sigma_SFR, must adjust to match the midplane pressure set by the
vertical gravitational field. Our model applies to regions where Sigma < 100
Msun/pc^2. In low-Sigma_SFR (outer-galaxy) regions where diffuse gas dominates,
the theory predicts Sigma_SFR \propto Sigma (rho_sd)^1/2. The decrease of
thermal equilibrium pressure when Sigma_SFR is low implies, consistent with
observations, that star formation can extend (with declining efficiency) to
large radii in galaxies, rather than having a sharp cutoff. The main parameters
entering our model are the ratio of thermal pressure to total pressure in the
diffuse ISM, the fraction of diffuse gas that is in the warm phase, and the
star formation timescale in self-gravitating clouds; all of these are (in
principle) direct observables. At low surface density, our model depends on the
ratio of the mean midplane FUV intensity (or thermal pressure in the diffuse
gas) to the star formation rate, which we set based on Solar neighborhood
values. We compare our results to recent observations, showing good agreement
overall for azimuthally-averaged data in a set of spiral galaxies. For the
large flocculent spiral galaxies NGC 7331 and NGC 5055, the correspondence
between theory and observation is remarkably close.Comment: 49 pages, 7 figures; accepted by the Ap.
Radio Galaxy Zoo: The Distortion of Radio Galaxies by Galaxy Clusters
We study the impact of cluster environment on the morphology of a sample of
4304 extended radio galaxies from Radio Galaxy Zoo. A total of 87% of the
sample lies within a projected 15 Mpc of an optically identified cluster.
Brightest cluster galaxies (BCGs) are more likely than other cluster members to
be radio sources, and are also moderately bent. The surface density as a
function of separation from cluster center of non-BCG radio galaxies follows a
power law with index out to (Mpc), which
is steeper than the corresponding distribution for optically selected galaxies.
Non-BCG radio galaxies are statistically more bent the closer they are to the
cluster center. Within the inner (Mpc) of a cluster,
non-BCG radio galaxies are statistically more bent in high-mass clusters than
in low-mass clusters. Together, we find that non-BCG sources are statistically
more bent in environments that exert greater ram pressure. We use the
orientation of bent radio galaxies as an indicator of galaxy orbits and find
that they are preferentially in radial orbits. Away from clusters, there is a
large population of bent radio galaxies, limiting their use as cluster
locators; however, they are still located within statistically overdense
regions. We investigate the asymmetry in the tail length of sources that have
their tails aligned along the radius vector from the cluster center, and find
that the length of the inward-pointing tail is weakly suppressed for sources
close to the center of the cluster.Comment: 23 pages, 17 figures, 2 tables. Supplemental data files available in
The Astronomical Journal or contact autho
Transmission Through Carbon Nanotubes With Polyhedral Caps
We study electron transport between capped carbon nanotubes and a substrate,
and relate the transmission probability to the local density of states in the
cap. Our results show that the transmission probability mimics the behavior of
the density of states at all energies except those that correspond to localized
states in the cap. Close proximity of a substrate causes hybridization of the
localized state. As a result, new transmission paths open from the substrate to
nanotube continuum states via the localized states in the cap. Interference
between various transmission paths gives rise to antiresonances in the
transmission probability, with the minimum transmission equal to zero at
energies of the localized states. Defects in the nanotube that are placed close
to the cap cause resonances in the transmission probability, instead of
antiresonances, near the localized energy levels. Depending on the spatial
position of defects, these resonant states are capable of carrying a large
current. These results are relevant to carbon nanotube based studies of
molecular electronics and probe tip applications
The Global Evolution of Giant Molecular Clouds II: The Role of Accretion
We present virial models for the global evolution of giant molecular clouds.
Focusing on the presence of an accretion flow, and accounting for the amount of
mass, momentum, and energy supplied by accretion and star formation feedback,
we are able to follow the growth, evolution, and dispersal of individual giant
molecular clouds. Our model clouds reproduce the scaling relations observed in
both galactic and extragalactic clouds. We find that accretion and star
formation contribute contribute roughly equal amounts of turbulent kinetic
energy over the lifetime of the cloud. Clouds attain virial equilibrium and
grow in such a way as to maintain roughly constant surface densities, with
typical surface densities of order 50 - 200 Msun pc^-2, in good agreement with
observations of giant molecular clouds in the Milky Way and nearby external
galaxies. We find that as clouds grow, their velocity dispersion and radius
must also increase, implying that the linewidth-size relation constitutes an
age sequence. Lastly, we compare our models to observations of giant molecular
clouds and associated young star clusters in the LMC and find good agreement
between our model clouds and the observed relationship between H ii regions,
young star clusters, and giant molecular clouds.Comment: 23 Pages, 9 Figures. Accepted to Ap
An Algebraic Approach to Linear-Optical Schemes for Deterministic Quantum Computing
Linear-Optical Passive (LOP) devices and photon counters are sufficient to
implement universal quantum computation with single photons, and particular
schemes have already been proposed. In this paper we discuss the link between
the algebraic structure of LOP transformations and quantum computing. We first
show how to decompose the Fock space of N optical modes in finite-dimensional
subspaces that are suitable for encoding strings of qubits and invariant under
LOP transformations (these subspaces are related to the spaces of irreducible
unitary representations of U(N)). Next we show how to design in algorithmic
fashion
LOP circuits which implement any quantum circuit deterministically. We also
present some simple examples, such as the circuits implementing a CNOT gate and
a Bell-State Generator/Analyzer.Comment: new version with minor modification
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