Promoting adherence to antiretroviral therapy: the experience from a primary care setting in Khayelitsha, South Africa.

OBJECTIVE: To describe the approach used to promote adherence to antiretroviral therapy (ART) and to present the outcomes in the first primary care public sector ART project in South Africa. DESIGN: The study is a prospective open cohort, including all adult patients naive to previous ART who received antiretroviral treatment in Khayelitsha, from May 2001 to the end of 2002. Patients were followed until their most recent visit before 31 July 2003. METHODS: Plasma viral load was determined at 3, 6, 12, 18 and 24 months after ART was initiated, and CD4 cell counts 6-monthly. Kaplan-Meier estimates were determined for the cumulative proportions of patients surviving, and patients with viral load suppression and viral rebound. RESULTS: A total of 287 patients were initiated on triple therapy. The probability of survival was 86.3% at 24 months. The median CD4 cell count gain was 288 cells/microliters at 24 months. Viral load was less than 400 copies/ml in 89.2, 84.2 and 69.7% of patients at 6, 12 and 24 months, respectively. The cumulative probability of viral rebound (two consecutive HIV-RNA measurements above 400 copies/ml) after achieving an HIV-RNA measurement below 400 copies/ml was 13.2% at 18 months. CONCLUSION: The study shows that, with a standard approach to patient preparation and strategies to enhance adherence, a cohort of patients on ART can be retained in a resource-limited setting in a developing country. A high proportion of patients achieved suppression of viral replication. The subsequent probability of viral rebound was low

Indications for grain growth and mass decrease in cold dust disks around Classical T Tauri stars in the MBM 12 young association

We report detection of continuum emission at 850 and 450 micron from disks around four Classical T Tauri stars in the MBM 12 (L1457) young association. Using a simple model we infer masses of 0.0014-0.012 M_sun for the disk of LkHa 263 ABC, 0.005-0.021 M_sun for S18 ABab, 0.03-0.18 M_sun for LkHa 264 A, and 0.023-0.23 M_sun for LkHa 262. The disk mass found for LkHa 263 ABC is consistent with the 0.0018 M_sun inferred from the scattered light image of the edge-on disk around component C. Comparison to earlier 13CO line observations indicates CO depletion by up to a factor 300 with respect to dark-cloud values. The spectral energy distributions (SED) suggest grain growth, possibly to sizes of a few hundred micron, but our spatially unresolved data cannot rule out opacity as an explanation for the SED shape. Our observations show that these T Tauri stars are still surrounded by significant reservoirs of cold material at an age of 1-5 Myr. We conclude that the observed differences in disk mass are likely explained by binary separation affecting the initial value. With available accretion rate estimates we find that our data are consistent with theoretical expectations for viscously evolving disks having decreased their masses by ~30%.Comment: 15 pages, 3 figures, uses aastex. ApJ Letters, in pres

A Millimeter-Wave Galactic Plane Survey With The BICEP Polarimeter

In addition to its potential to probe the Inflationary cosmological paradigm, millimeter-wave polarimetry is a powerful tool for studying the Milky Way galaxy's composition and magnetic field structure. Towards this end, presented here are Stokes I, Q, and U maps of the Galactic plane from the millimeter-wave polarimeter BICEP covering the Galactic longitude range 260 - 340 degrees in three atmospheric transmission windows centered on 100, 150, and 220 GHz. The maps sample an optical depth 1 < AV < 30, and are consistent with previous characterizations of the Galactic millimeter-wave frequency spectrum and the large-scale magnetic field structure permeating the interstellar medium. Polarized emission is detected over the entire region within two degrees of the Galactic plane and indicates that the large-scale magnetic field is oriented parallel to the plane of the Galaxy. An observed trend of decreasing polarization fraction with increasing total intensity rules out the simplest model of a constant Galactic magnetic field throughout the Galaxy. Including WMAP data in the analysis, the degree-scale frequency spectrum of Galactic polarization fraction is plotted between 23 and 220 GHz for the first time. A generally increasing trend of polarization fraction with electromagnetic frequency is found, which varies from 0.5%-1.5%at frequencies below 50 GHz to 2.5%-3.5%above 90 GHz. The BICEP and WMAP data are fit to a two-component (synchrotron and dust) model showing that the higher frequency BICEP data are necessary to tightly constrain the amplitude and spectral index of Galactic dust. Furthermore, the dust amplitude predicted by this two-component fit is consistent with model predictions of dust emission in the BICEP bands

The Vega Debris Disk -- A Surprise from Spitzer

We present high spatial resolution mid- and far-infrared images of the Vega debris disk obtained with the Multiband Imaging Photometer for Spitzer (MIPS). The disk is well resolved and its angular size is much larger than found previously. The radius of the disk is at least 43" (330 AU), 70"(543 AU), and 105" (815 AU) in extent at 24, 70 and 160 um, respectively. The disk images are circular, smooth and without clumpiness at all three wavelengths. The radial surface brightness profiles imply an inner boundary at a radius of 11"+/-2" (86 AU). Assuming an amalgam of amorphous silicate and carbonaceous grains, the disk can be modeled as an axially symmetric and geometrically thin disk, viewed face-on, with the surface particle number density following an r^-1 power law. The disk radiometric properties are consistent with a range of models using grains of sizes ~1 to ~50 um. We find that a ring, containing grains larger than 180 um and at radii of 86-200 AU from the star, can reproduce the observed 850 um flux, while its emission does not violate the observed MIPS profiles. This ring could be associated with a population of larger asteroidal bodies analogous to our own Kuiper Belt. Cascades of collisions starting with encounters amongthese large bodies in the ring produce the small debris that is blown outward by radiation pressure to much larger distances where we detect its thermal emission. The dust production rate is >~10^15 g/s based on the MIPS results. This rate would require a very massive asteroidal reservoir for the dust to be produced in a steady state throughout Vega's life. Instead, we suggest that the disk we imaged is ephemeral and that we are witnessing the aftermath of a large and relatively recent collisional event, and subsequent collisional cascade.Comment: 13 pages, 17 figures, accepted for publication in ApJ. (Figures 2, 3a, 3b and 4 have been degraded to lower resolutions.

Continuum and CO/HCO+ Emission from the Disk Around the T Tauri Star LkCa 15

We present OVRO Millimeter Array lambda = 3.4 - 1.2 mm dust continuum and spectral line observations of the accretion disk encircling the T Tauri star LkCa 15. The 1.2 mm dust continuum emission is resolved, and gives a minimum diameter of 190 AU and an inclination angle of 57+/-5 degrees. There is a noticeable, but at present poorly constrained, decrease in the continuum spectral slope with frequency that may result from the coupled processes of grain growth and dust settling. Imaging of the fairly intense emission from the lowest rotational transitions of CO, 13CO and HCO+ reveals a rotating disk and emission extends to 750 AU and the characteristic radius of the disk is determined to be around 425 AU (HWHM) based on model fits to the CO velocity field. The disk mass derived from the CO isotopologues with ``typical'' dense cloud abundances is still nearly two orders of magnitude less than that inferred from the dust emission, which is probably due to extensive molecular depletion in the cold, dense disk midplane. N2H+ 1-0 emission has also been detected which, along with HCO+, sets a lower limit to the fractional ionization of 10^{-8} in the near-surface regions of protoplanetary disks. This first detection of N2H+ in circumstellar disks has also made possible a determination of the N2/CO ratio (~2) that is at least an order of magnitude larger than those in the envelopes of young stellar objects and dense clouds. The large N2/CO ratio indicates that our observations probe disk layers in which CO is depleted but some N2 remains in the gas phase. Such differential depletion can lead to large variations in the fractional ionization with height in the outer reaches of circumstellar disks, and may help to explain the relative nitrogen deficiency observed in comets.Comment: Submitted to ApJ, 28 pages, 7 figure

TurbEFA: an interdisciplinary effort to investigate the turbulent flow across a forest clearing

the atmosphere within turbulence closure models is mainly limited by a realistic three-dimensional (3D) representation of the vegetation architecture. Within this contribution we present a method to record the 3D vegetation structure and to use this information to derive model parameters that are suitable for numerical flow models. A mixed conifer forest stand around a clearing was scanned and represented by a dense 3D point cloud applying a terrestrial laser scanner. Thus, the plant area density (PAD) with a resolution of one cubic meter was provided for analysis and for numerical simulations. Multi-level high-frequency wind velocity measurements were recorded simultaneously by 27 ultrasonic anemometers on 4 towers for a period of one year. The relationship between wind speed, Reynolds stress and PAD was investigated and a parametrization of the drag coefficient CD by the PAD is suggested. The derived 3D vegetation model and a simpler model (based on classical forest assessments of the site) were applied in a boundary layer model (BLM) and in large-eddy simulations (LES). The spatial development of the turbulent flow over the clearing is further demonstrated by the results of a wind tunnel experiment. The project showed, that the simulation results were improved significantly by the usage of realistic vegetation models. 3D simulations are necessary to depict the influence of heterogeneous canopies on the turbulent flow. Whereas we found limits for the mapping of the vegetation structure within the wind tunnel, there is a considerable potential for numerical simulations. The field measurements and the LES gave new insight into the turbulent flow in the vicinity and across the clearing. The results show that the zones of intensive turbulence development can not be restricted to the locations found in previous studies with more idealized canopies

Dust and the Infrared Kinematic Properties of Early-Type Galaxies

We have obtained spectra and measured the stellar kinematics in a sample of 25 nearby early-type galaxies (with velocity dispersions from less than 100 km/s to over 300 km/s) using the near-infrared CO absorption bandhead at 2.29 microns. Our median uncertainty for the dispersions is ~10%. We examine the effects of dust on existing optical kinematic measurements. We find that the near-infrared velocity dispersions are in general smaller than optical velocity dispersions, with differences as large as 30%. The median difference is 11% smaller, and the effect is of greater magnitude for higher dispersion galaxies. The lenticular galaxies (18 out of 25) appear to be causing the shift to lower dispersions while the classical ellipticals (7 out of 25) are consistent between the two wavelength regimes. If uniformly distributed dust causes these differences, we would expect to find a correlation between the relative amount of dust in a galaxy and the fractional change in dispersion, but we do not find such a correlation. We do see correlations both between velocity dispersion and CO bandhead equivalent width, and velocity dispersion and Mg2 index. The differences in dispersion are not well explained by current models of dust absorption. The lack of correlation between the relative amount of dust and shift in dispersion possibly suggets that dust does not have a similar distribution from galaxy to galaxy. The CO equivalent widths of these galaxies are quite high (>10 angstroms for almost all), requiring the light at these wavelengths to be dominated by very cool stars.Comment: 17 pages, 14 figures, accepted to The Astronomical Journa

IRAS 21391+5802: The Molecular Outflow and its Exciting Source

We present centimeter and millimeter observations of gas and dust around IRAS 21391+5802, an intermediate-mass source embedded in the core of IC 1396N. Continuum observations from 3.6 cm to 1.2 mm are used to study the embedded objects and overall distribution of the dust, while molecular line observations of CO, CS, and CH3OH are used to probe the structure and chemistry of the outflows in the region. The continuum emission at centimeter and millimeter wavelengths has been resolved into three sources separated about 15 arcsec from each other, and with one of them, BIMA 2, associated with IRAS 21391+5802. The dust emission around this source shows a very extended envelope, which accounts for most of the circumstellar mass of 5.1 Msun. This source is powering a strong molecular outflow, elongated in the E--W direction, which presents a complex structure and kinematics. While at high outflow velocities the outflow is clearly bipolar, at low outflow velocities the blueshifted and redshifted emission are highly overlapping, and the strongest emission shows a V-shaped morphology. The outflow as traced by CS and CH3OH exhibits two well differentiated and clumpy lobes, with two prominent northern blueshifted and redshifted clumps. The curved shape of the clumps and the spectral shape at these positions are consistent with shocked material. In addition, CS and CH3OH are strongly enhanced toward these positions with respect to typical quiescent material abundances in other star-forming regions.Comment: 41 pages, including 11 figures, accepted for publication in ApJ (July 1); available at http://www.am.ub.es/~robert/Papers.html#las

Linearized model Fokker-Planck collision operators for gyrokinetic simulations. II. Numerical implementation and tests

A set of key properties for an ideal dissipation scheme in gyrokinetic simulations is proposed, and implementation of a model collision operator satisfying these properties is described. This operator is based on the exact linearized test-particle collision operator, with approximations to the field-particle terms that preserve conservation laws and an H-Theorem. It includes energy diffusion, pitch-angle scattering, and finite Larmor radius effects corresponding to classical (real-space) diffusion. The numerical implementation in the continuum gyrokinetic code GS2 is fully implicit and guarantees exact satisfaction of conservation properties. Numerical results are presented showing that the correct physics is captured over the entire range of collisionalities, from the collisionless to the strongly collisional regimes, without recourse to artificial dissipation.Comment: 13 pages, 8 figures, submitted to Physics of Plasmas; typos fixe