29,077 research outputs found
Objective structured clinical examinations (OSCEs), psychiatry and the clinical assessment of skills and competencies (CASC) : same evidence, different judgement
Background: The Objective Structured Clinical Examination (OSCE), originally developed in the 1970’s, has been
hailed as the "gold standard" of clinical assessments for medical students and is used within medical schools
throughout the world. The Clinical assessment of Skills and Competencies (CASC) is an OSCE used as a clinical
examination gateway, granting access to becoming a senior Psychiatrist in the UK.
Discussion: Van der Vleuten’s utility model is used to examine the CASC from the viewpoint of a senior
psychiatrist. Reliability may be equivalent to more traditional examinations. Whilst the CASC is likely to have
content validity, other forms of validity are untested and authenticity is poor. Educational impact has the potential
to change facets of psychiatric professionalism and influence future patient care. There are doubts about
acceptability from candidates and more senior psychiatrists.
Summary: Whilst OSCEs may be the best choice for medical student examinations, their use in post graduate
psychiatric examination in the UK is subject to challenge on the grounds of validity, authenticity and educational
impact
QCD corrections to the hadronic production of a heavy quark pair and a W-boson including decay correlations
We perform an analytic calculation of the one-loop amplitude for the W-boson
mediated process 0 \to d u-bar Q Q-bar l-bar l, retaining the mass for the
quark Q. The momentum of each of the massive quarks is expressed as the sum of
two massless momenta and the corresponding heavy quark spinor is expressed as a
sum of two massless spinors. Using a special choice for the heavy quark spinors
we obtain analytic expressions for the one-loop amplitudes which are amenable
to fast numerical evaluation. The full next-to-leading order (NLO) calculation
of hadron+hadron \to W(\to e nu) b b-bar with massive b-quarks is included in
the program MCFM. A comparison is performed with previous published work.Comment: 45 pages, 17 figure
Magneto-optical determination of the electron-solid phase-boundary
We have obtained a two-dimensional electron-solid phase diagram in the extreme magnetic quantum limit by studying the temperature dependence of the radiative recombination of electrons in a GaAs/AlxGa1-xAs heterojunction with holes bound to a delta-layer, 250 A away in the GaAs, of Be acceptors. The low-energy shoulder to the luminescence line, indicating the presence of the electron solid, is seen to disappear at a filling-factor-dependent critical temperature. We observe no shoulder above a filling factor of 0.25, and the critical temperature falls to below 0.4 K at filling factors 1/5 and 1/7
Effects of the Running of the QCD Coupling on the Energy Loss in the Quark-Gluon Plasma
Finite temperature modifies the running of the QCD coupling alpha_s(k,T) with
resolution k. After calculating the thermal quark and gluon masses
selfconsistently, we determine the quark-quark and quark-gluon cross sections
in the plasma based on the running coupling. We find that the running coupling
enhances these cross sections by factors of two to four depending on the
temperature. We also compute the energy loss dE/dx of a high-energy quark in
the plasma as a function of temperature. Our study suggests that, beside
t-channel processes, inverse Compton scattering is a relevant process for a
quantitative understanding of the energy loss of an incident quark in a hot
plasma.Comment: 14 pages, 6 figure
Electroweak supersymmetric effects on high energy unpolarized and polarized single top production at LHC
We consider various processes of single top production at LHC in the
theoretical framework of the MSSM and examine the role of the supersymmetric
electroweak one-loop corrections in a special moderately light SUSY scenario,
in an initial parton-pair c.m. high energy range where a logarithmic asymptotic
expansion of Sudakov type can be used. We show that the electroweak virtual
effects are systematically large, definitely beyond the relative ten percent
size, particularly for a final pair where a special enhancement is
present. We show then in a qualitative way the kind of precision tests of the
model that would be obtainable from accurate measurements of the energy
distributions of the various cross sections and of the top polarization
asymmetries.Comment: 30 pages, 9 figure
Irrotational dust with Div H=0
For irrotational dust the shear tensor is consistently diagonalizable with
its covariant time derivative: , if
and only if the divergence of the magnetic part of the Weyl tensor vanishes:
. We show here that in that case, the consistency of the Ricci
constraints requires that the magnetic part of the Weyl tensor itself vanishes:
.Comment: 19 pages. Latex. Also avaliable at
http://shiva.mth.uct.ac.za/preprints/text/lesame2.te
Weak Interaction Sum Rules for Polarized top-antitop Production at LHC
We consider two polarization asymmetries in the process of top-antitop
production at LHC. We show that the theoretical predictions for these two
quantities, at the strong and electroweak partonic one-loop level, are free of
QCD and QED effects. At this perturbative level we derive two sum rules, that
relate measurable quantities of top-antitop production to genuinely weak
inputs. This would allow to perform two independent tests of the candidate
theoretical model, with a precision that will be fixed by the future
experimental accuracies of the different polarization measurements. A tentative
quantitative illustration of this statement for a specific MSSM scenario is
enclosed, and a generalization to include two other future realistic
measurements is also proposed.Comment: 13 pages, 3 figures, local report number adde
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