Coronary artery disease prevalence amongst patients undergoing valve replacement surgery: A South African perspective

Background: The prevalence of coronary artery disease (CAD) amongst patients presented for valve surgery has important implications for routine angiography. Information on the frequency of CAD in predominantly black patients presented for valve surgery in South Africa has not been published.Methods: A retrospective, descriptive study of 116 patients presented for valve surgery that underwent coronary angiography between 2010 and 2011 was performed. CAD was defined as stenosis of 70% or greater in one or more epicardial vessels or ≥50% in the left main coronary artery, as defined by quantitative coronary angiography.Results: Median age was 57.4 (IQR 43 - 67) years (56.9% females). Black patients represented 66.4%, whites 19.8%, and, coloured and Indian patients 13.8%. Hypertension and smoking were the most common cardiovascular risk factors (26.7% and 16.4% respectively). Diabetes mellitus, dyslipidaemia, chronic kidney disease and prior CAD occurred collectively in 15.5% of study subjects. HIV prevalence was 12%, half of whom were on antiretroviral therapy. An isolated valve lesion occurred in 69% of patients, with the remainder having 2 or more lesions. The most common valve lesion was aortic stenosis (43.1%), followed by mitral stenosis (36.2%), aortic regurgitation (29.3%), mitral regurgitation (25.9%) and tricuspid regurgitation (19%). The predominant aetiology was rheumatic heart disease (58.6%), followed by degenerative valve disease (24.1%). CAD was documented in 10 patients (8.6%), of whom 8 had single vessel disease and 2 had double vessel disease.Conclusion: The low prevalence of CAD found in younger, asymptomatic black patients without cardiovascular risk factors referred for valve surgery, raises the question of whether routine pre-operative coronary angiography in this sub-group is appropriate

Mammography Social Support for Women Living in a Midwestern City: Toward Screening Promotion via Social Interactions

Notwithstanding recommendations and interventions, the percentage of 50 – 74-year-old U.S. women who reported having had a mammography in the past two years remained below target coverage. Social interactions may influence mammography rates. To measure characteristics of social interactions in a Midwestern city as they relate to social support for mammography received by women older than 40 years of age. A cross-sectional study was conducted in Bloomington, Indiana, sending mail surveys to 3,000 telephone directory addresses selected by simple random sampling. An anonymous, self-administered, closed-ended, questionnaire with eight checklist items (for demographics) and six multipart semantic differential scale items (for social support), derived from validated instruments, was used. Social support for mammography in women who had undergone regular screening was analyzed using chi-square test and logistic regression. Of 450 respondents with valid responses, 91% were white; 47% were older than 80; 92% had good health insurance coverage; and 82% had undergone regular mammography. Healthcare workers provided the highest support, followed by children, siblings, and relatives. Friends, neighbors, and co-workers were least supportive. In social interactions, emotional support was the most prominent, followed by informational, appraisal, and instrumental supports. Having higher income and being married were associated with receiving greater support. Although mammography provides limited benefits after age 74, women older than 80 years of age received the highest support. Identifying the structural and functional characteristics of social interactions is important for: 1) designing interventions that enhance social support, and 2) expanding breast cancer screening via personalized approaches using existing social interactions

Untying the Gordian Knot: The Development of an Immunization Information Exchange

Legislative mandates require the sharing of immunization information among multiple stakeholders. This in turn requires the implementation of interoperable systems across various information systems. A key challenge to system interoperability is the need to integrate healthcare information and processes across different settings. This paper reports work in progress on the development of a student immunization Health Information Exchange (HIE). The system builds on a commercially available platform, appropriately modified on both front and backend, to meet the needs of school health professionals and other stakeholders involved in the production and maintenance of immunization information. We describe the situated change perspective as well as the iterative and incremental development process adopted for the project, and examine some of the lessons learned throughout

e+e−e^+e^- Pair Production from 10 GeV to 10 ZeV

At very high energies, pair production ($\gamma\to e^+e^-$) exhibits many interesting features. The momentum transfer from the target is very small, so the reaction probes the macroscopic properties of the target, rather than individual nuclei. Interference between interactions with different atoms reduces the pair production cross section considerably below the Bethe-Heitler values. At very high energies, photonuclear interactions may outnumber pair production. In contrast, in crystals, the interaction amplitudes may add coherently, greatly increasing the cross sections. Pair production in matter-free magnetic fields is also possible. The highest energy pair production occurs at high energy particle colliders. This article will compare pair production in these very different regimes.Comment: 37 pages with 9 figures. Invited Review for "Radiation Physics and Chemistry" Version for publication, incorporating comments by the referee, and by Gerhard Baur and Roman Le

Bremsstrahlung Suppression due to the LPM and Dielectric Effects in a Variety of Materials

The cross section for bremsstrahlung from highly relativistic particles is suppressed due to interference caused by multiple scattering in dense media, and due to photon interactions with the electrons in all materials. We present here a detailed study of bremsstrahlung production of 200 keV to 500 MeV photons from 8 and 25 GeV electrons traversing a variety of target materials. For most targets, we observe the expected suppressions to a good accuracy. We observe that finite thickness effects are important for thin targets.Comment: 52 pages, 13 figures (incorporated in the revtex LaTeX file

A comparison of methods for estimating Reynolds stress from ADCP measurements in wavy environments

Author Posting. © American Meteorological Society, 2011. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Atmospheric and Oceanic Technology 28 (2011): 1539–1553, doi:10.1175/JTECH-D-11-00001.1.Turbulent Reynolds stresses are now routinely estimated from acoustic Doppler current profiler (ADCP) measurements in estuaries and tidal channels using the variance method, yet biases due to surface gravity waves limit its use in the coastal ocean. Recent modifications to this method, including spatially filtering velocities to isolate the turbulence from wave velocities and fitting a cospectral model to the below-wave band cospectra, have been used to remove this bias. Individually, each modification performed well for the published test datasets, but a comparative analysis over the range of conditions in the coastal ocean has not yet been performed. This work uses ADCP velocity measurements from five previously published coastal ocean and estuarine datasets, which span a range of wave and current conditions as well as instrument configurations, to directly compare methods for estimating stresses in the presence of waves. The computed stresses from each were compared to bottom stress estimates from a quadratic drag law and, where available, estimates of wind stress. These comparisons, along with an analysis of the cospectra, indicated that spectral fitting performs well when the wave climate is wide-banded and/or multidirectional as well as when instrument noise is high. In contrast, spatial filtering performs better when waves are narrow-banded, low frequency, and when wave orbital velocities are strong relative to currents. However, as spatial filtering uses vertically separated velocity bins to remove the wave bias, spectral fitting is able to resolve stresses over a larger fraction of the water column.J. Rosman acknowledges funding from the National Science Foundation (OCE-1061108)

The spinorial geometry of supersymmetric heterotic string backgrounds

We determine the geometry of supersymmetric heterotic string backgrounds for which all parallel spinors with respect to the connection $\hat\nabla$ with torsion $H$, the NS$\otimes$NS three-form field strength, are Killing. We find that there are two classes of such backgrounds, the null and the timelike. The Killing spinors of the null backgrounds have stability subgroups K\ltimes\bR^8 in $Spin(9,1)$, for $K=Spin(7)$, SU(4), $Sp(2)$, $SU(2)\times SU(2)$ and $\{1\}$, and the Killing spinors of the timelike backgrounds have stability subgroups $G_2$, SU(3), SU(2) and $\{1\}$. The former admit a single null $\hat\nabla$-parallel vector field while the latter admit a timelike and two, three, five and nine spacelike $\hat\nabla$-parallel vector fields, respectively. The spacetime of the null backgrounds is a Lorentzian two-parameter family of Riemannian manifolds $B$ with skew-symmetric torsion. If the rotation of the null vector field vanishes, the holonomy of the connection with torsion of $B$ is contained in $K$. The spacetime of time-like backgrounds is a principal bundle $P$ with fibre a Lorentzian Lie group and base space a suitable Riemannian manifold with skew-symmetric torsion. The principal bundle is equipped with a connection $\lambda$ which determines the non-horizontal part of the spacetime metric and of $H$. The curvature of $\lambda$ takes values in an appropriate Lie algebra constructed from that of $K$. In addition $dH$ has only horizontal components and contains the Pontrjagin class of $P$. We have computed in all cases the Killing spinor bilinears, expressed the fluxes in terms of the geometry and determine the field equations that are implied by the Killing spinor equations.Comment: 73pp. v2: minor change

Charged-Particle Multiplicity in Proton-Proton Collisions

This article summarizes and critically reviews measurements of charged-particle multiplicity distributions and pseudorapidity densities in p+p(pbar) collisions between sqrt(s) = 23.6 GeV and sqrt(s) = 1.8 TeV. Related theoretical concepts are briefly introduced. Moments of multiplicity distributions are presented as a function of sqrt(s). Feynman scaling, KNO scaling, as well as the description of multiplicity distributions with a single negative binomial distribution and with combinations of two or more negative binomial distributions are discussed. Moreover, similarities between the energy dependence of charged-particle multiplicities in p+p(pbar) and e+e- collisions are studied. Finally, various predictions for pseudorapidity densities, average multiplicities in full phase space, and multiplicity distributions of charged particles in p+p(pbar) collisions at the LHC energies of sqrt(s) = 7 TeV, 10 TeV, and 14 TeV are summarized and compared.Comment: Invited review for Journal of Physics G -- version 2: version after referee's comment

Top quark physics in hadron collisions

The top quark is the heaviest elementary particle observed to date. Its large mass makes the top quark an ideal laboratory to test predictions of perturbation theory concerning heavy quark production at hadron colliders. The top quark is also a powerful probe for new phenomena beyond the Standard Model of particle physics. In addition, the top quark mass is a crucial parameter for scrutinizing the Standard Model in electroweak precision tests and for predicting the mass of the yet unobserved Higgs boson. Ten years after the discovery of the top quark at the Fermilab Tevatron top quark physics has entered an era where detailed measurements of top quark properties are undertaken. In this review article an introduction to the phenomenology of top quark production in hadron collisions is given, the lessons learned in Tevatron Run I are summarized, and first Run II results are discussed. A brief outlook to the possibilities of top quark research a the Large Hadron Collider, currently under construction at CERN, is included.Comment: 84 pages, 32 figures, accepted for publication by Reports on Progress in Physic