2,398 research outputs found
Dust masses of disks around 8 Brown Dwarfs and Very Low-Mass Stars in Upper Sco OB1 and Ophiuchus
We present the results of ALMA band 7 observations of dust and CO gas in the
disks around 7 objects with spectral types ranging between M5.5 and M7.5 in
Upper Scorpius OB1, and one M3 star in Ophiuchus. We detect unresolved
continuum emission in all but one source, and the CO J=3-2 line in two
sources. We constrain the dust and gas content of these systems using a grid of
models calculated with the radiative transfer code MCFOST, and find disk dust
masses between 0.1 and 1 M, suggesting that the stellar mass / disk
mass correlation can be extrapolated for brown dwarfs with masses as low as
0.05 M. The one disk in Upper Sco in which we detect CO emission, 2MASS
J15555600, is also the disk with warmest inner disk as traced by its H - [4.5]
photometric color. Using our radiative transfer grid, we extend the correlation
between stellar luminosity and mass-averaged disk dust temperature originally
derived for stellar mass objects to the brown dwarf regime to , applicable to spectral types
of M5 and later. This is slightly shallower than the relation for earlier
spectral type objects and yields warmer low-mass disks. The two prescriptions
cross at 0.27 L, corresponding to masses between 0.1 and 0.2 M
depending on age.Comment: 9 pages,6 figures, accepted to ApJ on 26/01/201
Randomized Clinical Trial of Azithromycin vs. Erythromycin for the Treatment of Chlamydia Cervicitis in Pregnancy
Objective: The purpose of this study was to prospectively test the null hypothesis that there is no
difference in the clinical effectiveness of azithromycin and erythromycin for the treatment of chlamydia
cervicitis in pregnancy
Growth of children receiving a dehydrated potato-soy protein concentrate or corn-soy blend as part of a food aid program in Northern Senegal
Rations distributed by food aid programs are intended to improve the growth of undernourished children. In practice, food programs target individual children and provide a supplement to the family that is intended to increase the energy and nutrient intake of undernourished children. Multiple food rations are available yet few studies have compared their differential effect on the growth of children. The objective of the study was to compare growth in undernourished Senegalese children who received a newly developed dehydrated potato-soy protein concentrate blend (PSB) to those supplemented with the currently available corn-soy blend (CSB). The first child at each site was randomly assigned to receive PSB or CSB and subsequent children alternately received PSB or CSB. Eligibility for obtaining the food ration was basedon criteria determined by the USAID (P.L. 480) Title II Food Aid Program. Children received iso-caloric amounts of the two supplements each month (23,000kcals). Weight, height and mid-upper arm circumference (MUAC) were taken over a fourmonth period. Z-scores were calculated for weight-for-age (WAZ), weight-for-height (WHZ) and for length/height-for-age measures (HAZ).The study was conducted at 7 clinics which served as food distribution sites in northern Senegal. The study enrolled348 children 18-56 months old with a weight-for-age z-score below the �yellow� zone of the locally available growth chart (equivalent to WAZ < -1.0). WAZ and HAZ significantly increased over time but there was no difference between the two ration groups. In a subset of 280 children (145 PSB, 135 CSB) who attended all four appointments and received the full complement of ration, there was significant and equivalent increase for both groups in WAZ and WHZ. These findings indicate thatchildren participating in the food aid program significantly improved their growth over a four-month period. Using the new PSB as a ration had the same impact on growth as the standard CSB and required less fuel to prepare
Intrinsic charge transport on the surface of organic semiconductors
The novel technique based on air-gap transistor stamps enabled realization of
the intrinsic (not dominated by static disorder) transport of the
electric-field-induced charge carriers on the surface of rubrene crystals over
a wide temperature range. The signatures of the intrinsic transport are the
anisotropy of the carrier mobility, mu, and the growth of mu with cooling. The
anisotropy of mu vanishes in the activation regime at lower temperatures, where
the charge transport becomes dominated by shallow traps. The deep traps,
deliberately introduced into the crystal by X-ray radiation, increase the
field-effect threshold without affecting the mobility. These traps filled above
the field-effect threshold do not scatter the mobile polaronic carriers.Comment: 10 pages, 4 figure
Improving methods for analysing anti-malarial drug efficacy trials: molecular correction based on length-polymorphic markers msp-1, msp-2 and glurp.
BACKGROUND:Drug efficacy trials monitor the continued efficacy of front-line drugs against falciparum malaria. Over-estimates of efficacy result in a country retaining a failing drug as first-line treatment with associated increases in morbidity and mortality, while under-estimating drug effectiveness leads to removal of an effective treatment with substantial practical and economic implications. Trials are challenging: they require long durations of follow-up to detect drug failures, and patients are frequently re-infected during that period. Molecular correction based on parasite genotypes distinguishes reinfections from drug failures to ensure the accuracy of failure rate estimates. Several molecular correction "algorithms" are proposed, but which is most accurate and/or robust remains unknown. METHODS:We used pharmacological modelling to simulate parasite dynamics and genetic signals that occur in patients enrolled in malaria drug clinical trials. We compared estimates of treatment failure obtained from a selection of proposed molecular correction algorithms against the known "true" failure rate in the model. FINDINGS:(i) Molecular correction is essential to avoid substantial over-estimates of drug failure rates. (ii) The current WHO-recommended algorithm consistently under-estimates the true failure rate. (iii) Newly-proposed algorithms produce more accurate failure rate estimates; the most accurate algorithm depends on the choice of drug, trial follow-up length, and transmission intensity. (iv) Long durations of patient follow-up may be counterproductive; large numbers of new infections accumulate and may be misclassified, over-estimating drug failure rate. (v) Our model was highly consistent with existing in vivo data. INTERPRETATION:The current WHO-recommended method for molecular correction and analysis of clinical trials should be re-evaluated and updated
Panchromatic observations and modeling of the HV Tau C edge-on disk
We present new high spatial resolution (<~ 0.1") 1-5 micron adaptive optics
images, interferometric 1.3 mm continuum and 12CO 2-1 maps, and 350 micron, 2.8
and 3.3 mm fluxes measurements of the HV Tau system. Our adaptive optics images
reveal an unusually slow orbital motion within the tight HV Tau AB pair that
suggests a highly eccentric orbit and/or a large deprojected physical
separation. Scattered light images of the HV Tau C edge-on protoplanetary disk
suggest that the anisotropy of the dust scattering phase function is almost
independent of wavelength from 0.8 to 5 micron, whereas the dust opacity
decreases significantly over the same range. The images further reveal a marked
lateral asymmetry in the disk that does not vary over a timescale of 2 years.
We further detect a radial velocity gradient in the disk in our 12CO map that
lies along the same position angle as the elongation of the continuum emission,
which is consistent with Keplerian rotation around an 0.5-1 Msun central star,
suggesting that it could be the most massive component in the triple system. We
use a powerful radiative transfer model to compute synthetic disk observations
and use a Bayesian inference method to extract constraints on the disk
properties. Each individual image, as well as the spectral energy distribution,
of HV Tau C can be well reproduced by our models with fully mixed dust provided
grain growth has already produced larger-than-interstellar dust grains.
However, no single model can satisfactorily simultaneously account for all
observations. We suggest that future attempts to model this source include more
complex dust properties and possibly vertical stratification. (Abridged)Comment: 26 pages, 11 figures, editorially accepted for publication in Ap
Laboratory phenomics predicts field performance and identifies superior indica haplotypes for early seedling vigour in dry direct-seeded rice
Seedling vigour is an important agronomic trait and is gaining attention in Asian rice (Oryza sativa) as cultivation practices shift from transplanting to forms of direct seeding. To understand the genetic control of rice seedling vigour in dry direct seeded (aerobic) conditions we measured multiple seedling traits in 684 accessions from the 3000 Rice Genomes (3K-RG) population in both the laboratory and field at three planting depths. Our data show that phenotyping of mesocotyl length in laboratory conditions is a good predictor of field performance. By performing a genome wide association study, we found that the main QTL for mesocotyl length, percentage seedling emergence and shoot biomass are co-located on the short arm of chromosome 7. We show that haplotypes in the indica subgroup from this region can be used to predict the seedling vigour of 3K-RG accessions. The selected accessions may serve as potential donors in genomics-assisted breeding programs
Confinement effects on glass forming liquids probed by DMA
Many molecular glass forming liquids show a shift of the glass transition T-g
to lower temperatures when the liquid is confined into mesoporous host
matrices. Two contrary explanations for this effect are given in literature:
First, confinement induced acceleration of the dynamics of the molecules leads
to an effective downshift of T-g increasing with decreasing pore size. Second,
due to thermal mismatch between the liquid and the surrounding host matrix,
negative pressure develops inside the pores with decreasing temperature, which
also shifts T-g to lower temperatures. Here we present dynamic mechanical
analysis measurements of the glass forming liquid salol in Vycor and Gelsil
with pore sizes of d=2.6, 5.0 and 7.5 nm. The dynamic complex elastic
susceptibility data can be consistently described with the assumption of two
relaxation processes inside the pores: A surface induced slowed down relaxation
due to interaction with rough pore interfaces and a second relaxation within
the core of the pores. This core relaxation time is reduced with decreasing
pore size d, leading to a downshift of T-g proportional to 1/d in perfect
agreement with recent differential scanning calorimetry (DSC) measurements.
Thermal expansion measurements of empty and salol filled mesoporous samples
revealed that the contribution of negative pressure to the downshift of T-g is
small (<30%) and the main effect is due to the suppression of dynamically
correlated regions of size xi when the pore size xi approaches
JWST imaging of edge-on protoplanetary disks. I. Fully vertically mixed 10m grains in the outer regions of a 1000 au disk
Scattered light imaging of protoplanetary disks provides key insights on the
geometry and dust properties in the disk surface. Here we present JWST
2--21\,m images of a 1000\,au-radius edge-on protoplanetary disk
surrounding an 0.4\, young star in Taurus, 2MASS\,J04202144+2813491.
These observations represent the longest wavelengths at which a protoplanetary
disk is spatially resolved in scattered light. We combine these observations
with HST optical images and ALMA continuum and CO mapping. We find that the
changes in the scattered light disk morphology are remarkably small across a
factor of 30 in wavelength, indicating that dust in the disk surface layers is
characterized by an almost gray opacity law. Using radiative transfer models,
we conclude that grains up to m in size are fully coupled to
the gas in this system, whereas grains m are strongly settled
towards the midplane. Further analyses of these observations, and similar ones
of other edge-on disks, will provide strong empirical constraints on disk
dynamics and evolution and grain growth models. In addition, the 7.7 and
12.\,m JWST images reveal an X-shaped feature located above the warm
molecular layer traced by CO line emission. The highest elevations at which
this feature is detectable roughly match the maximal extent of the disk in
visible wavelength scattered light as well as of an unusual kinematic signature
in CO. We propose that these phenomena could be related to a disk wind
entraining small dust grains.Comment: Accepted for publication in the Astronomical Journa
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