The Distance to the Coma Cluster from Surface Brightness Fluctuations

We report on the first determination of the distance to the Coma Cluster based on surface brightness fluctuation (SBF) measurements obtained from Hubble Space Telescope WFPC2 observations of the bright E0 galaxy NGC 4881 in the Coma Cluster and ground-based observations of the standard E1 galaxy NGC 3379 in the Leo-I group. Relative distances based on the I-band fluctuation magnitude, I(SBF), are strongly dependent on metallicity and age of the stellar population. However, the radial changes in the stellar populations of the two giant ellipticals, NGC 3379 and NGC 4881, are well described by published Mg_2 gradients, and the ground-based measurements of I(SBF) at several radial points in NGC 3379 are used to calibrate I(SBF) in terms of the Mg_2 index. The distance to NGC 3379, assumed to be identical to the average SBF distance of the Leo-I group, is combined with the new SBF measurements of NGC 4881 to obtain a Coma Cluster distance of 102+-14 Mpc. Combining this distance with the cosmic recession velocity of Coma (7186+-428 km/s), we find the Hubble constant to be H_0 = 71+-11 km/s/Mpc.Comment: 12 pages, LaTex, includes aaspp4.sty and 3 eps figures. To appear in ApJ Letter

Total joint replacement in sub-Saharan Africa:a systematic review

Outcomes of arthroplasty in sub-Saharan Africa are not widely reported. To our knowledge, this systematic review is the first to explore this topic. Scopus, EMBASE, Medline and PubMed databases were searched, utilising MeSH headings and Boolean search strategies. All papers from South Africa were excluded. Twelve papers reporting 606 total hip replacements (THRs) and 763 total knee replacements (TKRs) were included. Avascular necrosis was the most common indication for THR, whereas osteoarthritis was the main indication for TKR. HIV prevalence of up to 33% was seen. Improvements were seen in patient-reported outcome measures in both THR and TKR. The dislocation rate in THR was 1.6%. The deep infection rate was 1.6% for TKRs and 0.5% for THRs. Positive results were reported, with comparable complications to high-income countries. However, there is likely to be significant reporting bias and the introduction of mandatory registries would enable more accurate monitoring across the region

Impact of alcohol on memory:a systematic review

This chapter reviews the literature in psychology on acute alcohol intoxication and memory. Special emphasis is placed on empirical studies that have systematically examined alcohol’s effects on memory performance in forensic contexts. Three aspects of memory performance are considered, including memory accuracy (i.e. the ability of the complainant to accurately distinguish between correct and incorrect information about the crime), memory reliability (i.e. the probability that information recalled by the complainant at a given level of certainty is correct), and completeness (i.e. the quantity of information reported by the complainant). The review also documents the major theoretical perspectives on memory and acute alcohol intoxication. A total of 19 studies are reviewed. The results show that different memory performance measures are relevant depending on whether we are policy makers formulating interview guidance or decision makers evaluating the strength of memory evidence in a given case. Overall, the research to date indicates that acute alcohol intoxication during rape affects the completeness, but not the accuracy and reliability of what is remembered

On the unification of dwarf and giant elliptical galaxies

The near orthogonal distributions of dwarf elliptical (dE) and giant elliptical (E) galaxies in the mu_e-Mag and mu_e-log(R_e) diagrams have been interpreted as evidence for two distinct galaxy formation processes. However, continuous, linear relationships across the alleged dE/E boundary at M_B = -18 mag - such as those between central surface brightness (mu_0) and (i) galaxy magnitude and (ii) light-profile shape (n) - suggest a similar, governing formation mechanism. Here we explain how these latter two linear trends necessitate a different behavior for dE and E galaxies, exactly as observed, in diagrams involving mu_e (and also _e). A natural consequence is that the distribution of dEs and Es in Fundamental Plane type analyses that use the associated intensity I_e, or _e, are expected to appear different. Together with other linear trends across the alleged dE/E boundary, such as those between luminosity and color, metallicity, and velocity dispersion, it appears that the dEs form a continuous extension to the E galaxies. The presence of partially depleted cores in luminous (M_B < -20.5 mag) Es does however signify the action of a different physical process at the centers (< ~300 pc) of these galaxies.Comment: 5 pages from the proceedings of the 2004 conference "Penetrating bars through masks of cosmic dust: the Hubble tuning fork strikes a new note". Edited by D. L. Block, I. Puerari, K. C. Freeman, R. Groess, and E. K. Bloc

Near-Field Analysis of Terahertz Pulse Generation From Photo-Excited Charge Density Gradients

Excitation of photo-current transients at semiconductor surfaces by subpicosecond optical pulses gives rise to emission of electromagnetic pulses of terahertz (THz) frequency radiation. To correlate the THz emission with the photo-excited charge density distribution and the photo-current direction, we mapped near-field and far-field distributions of the generated THz waves from GaAs and Fe-doped InGaAs surfaces. The experimental results show that the charge dynamics in the plane of the surface can radiate substantially stronger THz pulses than the charge dynamics in the direction normal to the surface, which is generally regarded as the dominant origin of the emission

Empirical Models for Dark Matter Halos. III. The Kormendy relation and the log(rho_e)-log(R_e) relation

We have recently shown that the 3-parameter density-profile model from Prugniel & Simien provides a better fit to simulated, galaxy- and cluster-sized, dark matter halos than an NFW-like model with arbitrary inner profile slope gamma (Paper I). By construction, the parameters of the Prugniel-Simien model equate to those of the Sersic R^{1/n} function fitted to the projected distribution. Using the Prugniel-Simien model, we are therefore able to show that the location of simulated (10^{12} M_sun) galaxy-sized dark matter halos in the _e-log(R_e) diagram coincides with that of brightest cluster galaxies, i.e., the dark matter halos appear consistent with the Kormendy relation defined by luminous elliptical galaxies. These objects are also seen to define the new, and equally strong, relation log(rho_e) = 0.5 - 2.5log(R_e), in which rho_e is the internal density at r=R_e. Simulated (10^{14.5} M_sun) cluster-sized dark matter halos and the gas component of real galaxy clusters follow the relation log(rho_e) = 2.5[1 - log(R_e)]. Given the shapes of the various density profiles, we are able to conclude that while dwarf elliptical galaxies and galaxy clusters can have dark matter halos with effective radii of comparable size to the effective radii of their baryonic component, luminous elliptical galaxies can not. For increasingly large elliptical galaxies, with increasingly large profile shapes `n', to be dark matter dominated at large radii requires dark matter halos with increasingly large effective radii compared to the effective radii of their stellar component.Comment: AJ, in press. (Paper I can be found at astro-ph/0509417

Analytical expressions for the deprojected Sersic model

The Sersic model has become the standard to parametrize the surface brightness distribution of early-type galaxies and bulges of spiral galaxies. A major problem is that the deprojection of the Sersic surface brightness profile to a luminosity density cannot be executed analytically for general values of the Sersic index. Mazure & Capelato (2002) used the Mathematica computer package to derive an expression of the Sersic luminosity density in terms of the Meijer G function for integer values of the Sersic index. We generalize this work using analytical means and use Mellin integral transforms to derive an exact, analytical expression for the luminosity density in terms of the Fox H function for all values of the Sersic index. We derive simplified expressions for the luminosity density, cumulative luminosity and gravitational potential in terms of the Meijer G function for all rational values of the Sersic index and we investigate their asymptotic behaviour at small and large radii. As implementations of the Meijer G function are nowadays available both in symbolic computer algebra packages and as high-performance computing code, our results open up the possibility to calculate the density of the Sersic models to arbitrary precision.Comment: 9 pages, accepted for publication in Astronomy and Astrophysic

Weak homology of elliptical galaxies

We start by studying a small set of objects characterized by photometric profiles that have been pointed out to deviate significantly from the standard R^{1/4} law. For these objects we confirm that a generic R^{1/n} law, with n a free parameter, can provide superior fits (the best-fit value of n can be lower than 2.5 or higher than 10), better than those that can be obtained by a pure R^{1/4} law, by an R^{1/4}+exponential model, and by other dynamically justified self--consistent models. Therefore, strictly speaking, elliptical galaxies should not be considered homologous dynamical systems. Still, a case for "weak homology", useful for the interpretation of the Fundamental Plane of elliptical galaxies, could be made if the best-fit parameter n, as often reported, correlates with galaxy luminosity L, provided the underlying dynamical structure also follows a systematic trend with luminosity. We demonstrate that this statement may be true even in the presence of significant scatter in the correlation n(L). Preliminary indications provided by a set of "data points" associated with a sample of 14 galaxies suggest that neither the strict homology nor the constant stellar mass--to--light solution are a satisfactory explanation of the observed Fundamental Plane (abridged).Comment: 34 pages, 11 figures, accepted by Astronomy and Astrophysic

Short-term rhGH increases PIIINP, a biomarker of endothelial dysfunction

Objectives: In arterial hypertension, amino-terminal propeptide of type III procollagen (PIIINP) is elevated in arterial aneurysm tissue and associated with a poor prognosis following acute myocardial infarction (MI). Recombinant human growth hormone (rhGH) administration attenuates endothelial dysfunction but increases PIIINP. This study was conducted to establish if short-term rhGH administration affects PIIINP, endothelial function and selected cardiovascular disease (CVD) risk factors, in healthy males. Design: Method: Male subjects (n=48) were randomly assigned into two groups: (1): control group (C) n=24, mean ± SD, age 32 ± 11 years; height 1.8 ± 0.06 metres; (2): rhGH administration group (rhGH) n=24, mean ± SD, age 32 ± 9 years; height 1.8 ± 0.07 metres. Blood pressure (BP), heart rate (HR), arterial pulse wave velocity (APWV), and biochemical indices were investigated. Results: PIIINP (0.28±0.1 vs. 0.42±0.2, U/ml); Insulin like growth factor-I (159±54 vs. 323±93, ng.mL-1); resting HR (72±14 vs. 78±11, b.p.m.) and rate pressure product (RPP) (90±18 vs. 97±14, bpm x mm.Hg x 10-2) all significantly increased (P<0.05). Total cholesterol (4.7±0.9 vs. 4.4±0.7, mmol.L-1); high sensitivity C-reactive protein (1.77±2.1 vs. 1.29±1.6, mg.L-1); serum homocysteine (13.2±4.0 vs. 11.7±3.1, μmol.L-1) and APWV (9.97±1.38 vs. 9.18±1.6, m.s-1) all significantly decreased (P<0.05). Conclusion: Paradoxically, there was an improvement in CVD inflammatory markers and APWV; but PIIINP and resting RPP increased. Elevated PIIINP may have a confounding adverse effect on the endothelium, but may also provide clinical prognostic information in monitoring arterial hypertension, left ventricular function in the sub-acute phase following MI and endothelial function in aortic aneurysms