The Stellar Mass Spectrum in the Young Populous Cluster NGC 1866

The young populous cluster NGC 1866 in the Large Magellanic Cloud LMC), which is probably one of the most massive object formed in the LMC during the last ~ 3 Gyr, appears to have an unexpectedly high mass-to-light ratio. From its velocity dispersion Fischer et al. (1992) find its mass to be (1.35 " 0.25) x 105 Mu. The luminosity of this cluster is MV = -8.93 " 0.13, corresponding to LV = (3.2 " 0.4) x 105 LV (u). This yields M/LV = 0.42 " 0.09 in solar units. For a cluster of age 0.1 Gyr such a relatively high mass-to-light ratio requires a mass spectrum with an exponent x = 1.72 " 0.09; or x = 1.75 " 0.09 if mass loss by evolving stars is taken into account.Comment: To be published in the October 1999 issue of the Publications of the Astronomical Society of the Pacifi

Shear-free perfect fluids with a solenoidal electric curvature

We prove that the vorticity or the expansion vanishes for any shear-free perfect fluid solution of the Einstein field equations where the pressure satisfies a barotropic equation of state and the spatial divergence of the electric part of the Weyl tensor is zero.Comment: 9 page

Rotating solenoidal perfect fluids of Petrov type D

We prove that aligned Petrov type D perfect fluids for which the vorticity vector is not orthogonal to the plane of repeated principal null directions and for which the magnetic part of the Weyl tensor with respect to the fluid velocity has vanishing divergence, are necessarily purely electric or locally rotationally symmetric. The LRS metrics are presented explicitly.Comment: 6 pages, no figure

Spectro-Morphology of Galaxies

We present a quantitative method to classify galaxies, based on multi-wavelength data and elaborated from the properties of nearby galaxies. Our objective is to define an evolutionary method that can be used for low and high redshift objects. We estimate the concentration of light (C) at the galaxy center and the 180 degree-rotational asymmetry (A), computed at several wavelengths, from ultraviolet (UV) to I-band. The variation of the indices of concentration and asymmetry with the wavelength reflects the proportion and the distribution of young and old stellar populations in galaxies. In general C is found to decrease from optical to UV, and A is found to increase from optical to UV: the patchy appearance of galaxies in UV with no bulge is often very different from their counterpart at optical wavelengths, with prominent bulges and more regular disks. The variation of C and A with the wavelength is quantified. By this way, we are able to distinguish five types of galaxies that we call spectro-morphological types: compact, ringed, spiral, irregular and central-starburst galaxies, which can be differentiated by the repartition of their stellar populations. We discuss in detail the morphology of galaxies of the sample, and describe the morphological characteristics of each spectro-morphological type. We apply spectro-morphology to three objects at a redshift z=1 in the Hubble Deep Field North, that gives encouraging results for applications to large samples of high-redshift galaxies. This method of morphological classification could be used to study the evolution of the morphology with the redshift and is expected to bring observational constraints on scenarios of galaxy evolution.Comment: Accepted for publication in Astronomy & Astrophysic

Shearfree perfect fluids with solenoidal magnetic curvature and a gamma-law equation of state

We show that shearfree perfect fluids obeying an equation of state p=(gamma -1) mu are non-rotating or non-expanding under the assumption that the spatial divergence of the magnetic part of the Weyl tensor is zero.Comment: 11 page

On the negative spectrum of two-dimensional Schr\"odinger operators with radial potentials

For a two-dimensional Schr\"odinger operator $H_{\alpha V}=-\Delta-\alpha V$ with the radial potential $V(x)=F(|x|), F(r)\ge 0$, we study the behavior of the number $N_-(H_{\alpha V})$ of its negative eigenvalues, as the coupling parameter $\alpha$ tends to infinity. We obtain the necessary and sufficient conditions for the semi-classical growth $N_-(H_{\alpha V})=O(\alpha)$ and for the validity of the Weyl asymptotic law.Comment: 13 page

Changing priorities in maternal and perinatal health in Gert Sibande District, South Africa

Gert Sibande District is a predominantly rural district in Mpumalanga Province, South Africa (SA), with a population of just over 1.1 million. It has a high prevalence of HIV infection and pregnancy-related hypertensive disease. In 2010 the district was one of the worst-performing health districts in SA, with a maternal mortality ratio of 328.0 per 100 000 births. Various programmes were introduced between 2010 and 2017 to address major causes of maternal and perinatal morbidity and mortality in the district. The focus has been on HIV-related morbidity, the direct obstetric causes of maternal and perinatal morbidity and mortality, and health systems strengthening. During the period 2010 - 2017, there was a steady decline in institutional maternal mortality with a drop of 71% in maternal deaths over a period of 6 years, from 328.0 per 100 000 births to 95.0. However, the ratio levelled off in 2016 and 2017, mainly as a result of a changing disease profile. The stillbirth rate showed a decline of 24.4% over a period of 8 years. With perseverance, rapid response and evidence-based strategies it was possible to more than halve the institutional maternal mortality ratio within 6 years. However, with the changing disease profile, conditions such as hypertensive disease in pregnancy should be prioritised and new strategies developed to further reduce maternal and perinatal mortality and morbidity

Local cosmic string in generalised scalar tensor theory

A recent investigation shows that a local gauge string with a phenomenological energy momentum tensor, as prescribed by Vilenkin, is inconsistent in Brans-Dicke theory. In this work it has been shown that such a string is consistent in a more general scalar tensor theory where $\omega$ is function of the scalar field.A set of solutions of full nonlinear Einstein's equations for interior region of such a string are presented.Comment: 7 pages, latex format, minor changes according to referee's suggestions, revised version submitted in Phys.Rev.

Silent universes with a cosmological constant

We study non-degenerate (Petrov type I) silent universes in the presence of a non-vanishing cosmological constant L. In contrast to the L=0 case, for which the orthogonally spatially homogeneous Bianchi type I metrics most likely are the only admissible metrics, solutions are shown to exist when L is positive. The general solution is presented for the case where one of the eigenvalues of the expansion tensor is 0.Comment: 11 pages; several typos corrected which were still present in CGQ version; minor change