1,452 research outputs found
Annealing of defects in Fe after MeV Heavy ion irradiation
We report study of recovery dynamics, followed by in-situ resistivity
measurement after 100 MeV oxygen ion irradiation, in cold rolled Fe at 300K.
Scaling behavior with microstructural density and temperature of sample have
been used to establish stress induced defects formed during irradiation as a
new type of sink. The dynamics after irradiation has been shown to be due to
migration of defects to two types of sinks i.e. stress induced defect as
variable sinks and internal surfaces as fixed sinks. Experimental data obtained
under various experimental conditions have been fitted to theoretical curves.
Parameters thus obtained from fitting are employed to establish effect of
electronic energy loss and temperature on recovery dynamics and stress
associated with variable sinks.Comment: 12 pages, 7 figures. Europhysics Letter (in press
Pinching instabilities in superconducting strings
Superconducting cosmic strings can exhibit longitudinal, pinching
instabilities in some regions of the parameter space. We make predictions about
the onset of this instability using the thin string approximation (TSA) and
develop an improved analysis that remains applicable for small wavelength
perturbations, where the TSA breaks down. We use simulations of perturbed
strings to assess the accuracy of the TSA, test the predictions of our new
analysis and demonstrate an improvement over previous methods in the
literature. Notably, it appears that the instabilities are typically present
for a larger range of magnetic strings than previously expected, and we show
examples of pinching instabilities also occurring in electric strings. However,
both our simulations and predictions agree that strings near the chiral limit
are free from pinching instabilities and in particular our results support our
previously published claim that vortons can be stable to all classical
perturbations if they are sufficiently large.Comment: 14 pages, 7 figure
Global monopoles in the two-Higgs-doublet-model
We discuss monopoles formed due to the spontaneous breakdown of a global
symmetry within the global two-Higgs doublet model. We explain
that the Higgs sector dynamics can be described in terms of two vectors one of
which is null, for , with 5 independent
components describing the Higgs family symmetry and another, , with 3
independent components related to the ``would-be'' Goldstone bosons. When
formed from random initial conditions we find that monopoles are formed with a
charged vacuum in the centre which couples the two fields together. We find a
spherical symmetric solution which is an approximately uniform, unit winding of
the sphere in both the and vectors. These global monopoles are
closely related to the Nambu monopole. The additional complexity and structure
contained in these monopoles does not appear to prevent the scaling of their
density.Comment: 12 pages, 4 figure
Diagnostic accuracy of PAT-POPS and ManChEWS for admissions of children from the emergency department
Background
The Pennine Acute Trust (PAT) Paediatric Observation Priority Score (PAT-POPS) is a specific emergency department (ED) physiological and observational aggregate scoring system, with scores of 0–18. A higher score indicates greater likelihood of admission. The Manchester Children’s Early Warning System (ManChEWS) assesses six physiological observations to create a trigger score, classified as Green, Amber or Red.
Methods
Prospectively collected data were used to calculate PAT-POPS and ManChEWS on 2068 patients aged under 16 years (mean 5.6 years, SD 4.6) presenting over 1 month to a UK District General Hospital Paediatric ED. Receiver operating characteristics (ROC) comparison, using STATA V.13, was used to investigate the ability of ManChEWS and PAT-POPS to
predict admission to hospital within 72 h of presentation
to the ED.
Results
Comparison of the area under the ROC curve indicates that the ManChEWS ROC is 0.67 (95% CI 0.64 to 0.70) and the PAT-POPS ROC is 0.72 (95% CI 0.68 to 0.75). The difference is statistically significant. At a PAT-POPS cut-off of ≥2, 80% of patients had their admission risk correctly classified ( positive likelihood ratio 3.40, 95% CI 2.90 to 3.98) whereas for ManChEWS with a cut off of ≥Amber only 71% of
patients were correctly classified ( positive likelihood ratio 2.18, 95% CI 1.94 to 2.45).
Conclusions
PAT-POPS is a more accurate predictor of admission risk than ManChEWS. Replacing ManChEWS with PAT-POPS would appear to be clinically appropriate in a paediatric ED. This needs validation in a multicentre study
A modified monomolecular film test for micro-quantities of lipids in foods
This bulletin is a report on Department of Poultry Husbandry research project 17, Egg Utilization--P. [3].Digitized 2007 AES.Includes bibliographical references (page 30)
Melting as a String-Mediated Phase Transition
We present a theory of the melting of elemental solids as a
dislocation-mediated phase transition. We model dislocations near melt as
non-interacting closed strings on a lattice. In this framework we derive simple
expressions for the melting temperature and latent heat of fusion that depend
on the dislocation density at melt. We use experimental data for more than half
the elements in the Periodic Table to determine the dislocation density from
both relations. Melting temperatures yield a dislocation density of (0.61\pm
0.20) b^{-2}, in good agreement with the density obtained from latent heats,
(0.66\pm 0.11) b^{-2}, where b is the length of the smallest
perfect-dislocation Burgers vector. Melting corresponds to the situation where,
on average, half of the atoms are within a dislocation core.Comment: 18 pages, LaTeX, 3 eps figures, to appear in Phys. Rev.
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