Computer simulation of plasma and N-body problems

The following FORTRAN language computer codes are presented: (1) efficient two- and three-dimensional central force potential solvers; (2) a three-dimensional simulator of an isolated galaxy which incorporates the potential solver; (3) a two-dimensional particle-in-cell simulator of the Jeans instability in an infinite self-gravitating compressible gas; and (4) a two-dimensional particle-in-cell simulator of a rotating self-gravitating compressible gaseous system of which rectangular coordinate and superior polar coordinate versions were written

A public health approach to hepatitis C control in low- and middle-income countries.

In light of new treatment regimens for hepatitis C, Amitabh Suthar and Anthony Harries outline a wider public health approach for tackling the disease

Radiative Transfer in Star Formation: Testing FLD and Hybrid Methods

We perform a comparison between two radiative transfer algorithms commonly employed in hydrodynamical calculations of star formation: grey flux limited diffusion and the hybrid scheme, in addition we compare these algorithms to results from the Monte-Carlo radiative transfer code MOCASSIN. In disc like density structures the hybrid scheme performs significantly better than the FLD method in the optically thin regions, with comparable results in optically thick regions. In the case of a forming high mass star we find the FLD method significantly underestimates the radiation pressure by a factor of ~100.Comment: 4 Pages; to appear in the proceedings of 'The Labyrinth of Star Formation', Crete, 18-22 June 201

The Inner Rim of YSO Disks: Effects of dust grain evolution

Dust-grain growth and settling are the first steps towards planet formation. An understanding of dust physics is therefore integral to a complete theory of the planet formation process. In this paper, we explore the possibility of using the dust evaporation front in YSO disks (`the inner rim') as a probe of the dust physics operating in circumstellar disks. The geometry of the rim depends sensitively on the composition and spatial distribution of dust. Using radiative transfer and hydrostatic equilibrium calculations we demonstrate that dust growth and settling can curve the evaporation front dramatically (from a cylindrical radius of about 0.5 AU in the disk mid-plane to 1.2 AU in the disk upper layers for an A0 star). We compute synthetic images and interferometric visibilities for our representative rim models and show that the current generation of near-IR long-baseline interferometers (VLTI, CHARA) can strongly constrain the dust properties of circumstellar disks, shedding light on the relatively poorly understood processes of grain growth, settling and turbulent mixing.Comment: 26 pages, 9 figures. Accepted for publication in Ap

Achieving universal access to antiretroviral therapy in a rural district in Malawi: how was it done?

Mexico AIDS Conference 200

Dowelled structural connections in laminated bamboo and timber

© 2016 The Authors. Structural sections of laminated bamboo can be connected using methods common in timber engineering, however the different material properties of timber and laminated bamboo suggest that the behaviour of connections in the two materials would not be the same. This study investigates the dowelled connection, in which a connector is passed through a hole in the material, and load is resisted by shear in the connector and embedment into the surrounding material. Steel dowels were used in a connection between a laminated bamboo member and a steel plate in a central slot in the bamboo, and the behaviour of this connection was compared with a similar connection in timber. The laminated bamboo was made from Moso bamboo (Phyllostachys pubescens) which had been treated by one of two preservative processes, either bleaching or caramelisation. Following testing, substantial qualitative differences between the bamboo and timber specimens were observed: the bamboo failed most often by the formation of a shear plug whereas the timber failed by a single split. The two preservative treatments resulted in different behaviour: the bleached bamboo had a degree of ductility roughly twice that of the caramelised bamboo. Digital image correlation provided full-field strain measurements, which gave further insight into the differences between the materials, particularly between bamboo and timber. Shear strain is dominant in the bamboo, compared with tensile strain perpendicular to grain in the timber. Numerical modelling showed that this difference in the strain field could be explained by the different orthotropic elastic and frictional properties of the two materials.The presented work is supported by a Leverhulme Trust Programme Grant, and EPSRC Grant EP/K023403/1

Outcomes and safety of concomitant nevirapine and rifampicin treatment under programme conditions in Malawi.

SETTING: Thyolo District Hospital, rural Malawi. OBJECTIVES: To report on 1) clinical, immunological and virological outcomes and 2) safety among human immunodeficiency virus (HIV) infected patients with tuberculosis (TB) who received concurrent nevirapine (NVP) and rifampicin (RMP) based treatment. DESIGN: Retrospective cohort study. METHODS: Analysis of programme data, June-December 2007. RESULTS: Of a total of 156 HIV-infected TB patients who started NVP-based antiretroviral treatment, 136 (87%) completed TB treatment successfully, 16 (10%) died and 5 (4%) were transferred out. Mean body weight and CD4 gain (adults) were respectively 4.4 kg (95%CI 3.3-5.4) and 140 cells/mm(3) (95%CI 117-162). Seventy-four per cent of patients who completed TB treatment and had a viral load performed (n = 74) had undetectable levels (<50 copies/ml), while 17 (22%) had a viral load of 50-1000 copies/ml. Hepatotoxicity was present in 2 (1.3%) patients at baseline. Two patients developed Grade 2 and one developed Grade 3 alanine transaminase enzyme elevations during TB treatment (incidence rate per 10 years of follow-up 4.2, 95%CI 1.4-13.1). There were no reported deaths linked to hepatotoxicity. CONCLUSIONS: In a rural district in Malawi, concomitant NVP and RMP treatment is associated with good TB treatment outcomes and appears safe. Further follow-up of patients would be useful to ascertain the longer-term effects of this concurrent treatment

Modelling the clumping-induced polarimetric variability of hot star winds

Clumping in the winds of massive stars may significantly reduce empirical mass-loss rates, and which in turn may have a large impact on our understanding of massive star evolution. Here, we investigate wind-clumping through the linear polarization induced by light scattering off the clumps. Through the use of an analytic wind clumping model, we predict the time evolution of the linear polarimetry over a large parameter space. We concentrate on the Luminous Blue Variables, which display the greatest amount of polarimetric variability and for which we recently conducted a spectropolarimetric survey. Our model results indicate that the observed level of polarimetric variability can be reproduced for two regimes of parameter space: one of a small number of massive, optically-thick clumps; and one of a very large number of low-mass clumps. Although a systematic time-resolved monitoring campaign is required to distinguish between the two scenarios, we currently favour the latter, given the short timescale of the observed polarization variability. As the polarization is predicted to scale linearly with mass-loss rate, we anticipate that all hot stars with very large mass-loss rates should display polarimetric variability. This is consistent with recent findings that intrinsic polarization is more common in stars with strong H$\alpha$ emission.Comment: 12 pages, 11 figures, accepted to A&