217 research outputs found
Volume limited dependent Galactic model parameters
We estimated 34 sets of Galactic model parameters for three intermediate
latitude fields with Galactic longitudes l=60, l=90, and l=180, and we
discussed their dependence on the volume. Also, we confirmed the variation of
these parameters with absolute magnitude and Galactic longitude. The star
samples in two fields are restricted with bright and unit absolute magnitude
intervals, (4,5], and (5,6], whereas for the third field a larger absolute
magnitude interval is adopted, (4,10]. The limiting apparent magnitudes of star
samples are g=15 and g=22.5 mag which provide space densities within distances
in the line of sight 0.9 and 25 kpc. The Galactic model parameters for the thin
disc are not volume dependent. However, the ones for thick disc and halo do
show spectacular trends in their variations with volume, except for the
scalelength of the thick disc. The local space density of the thick disc
increases, whereas the scaleheight of the same Galactic component decreases
monotonically. However, both model parameters approach asymptotic values at
large distances. The axial ratio of the halo increases abruptly for the volumes
where thick disc is dominant, whereas it approaches an asymptotic value
gradually for larger volumes, indicating a continuous transition from disclike
structure to a spherical one at the outermost region of the Galaxy. The
variation of the Galactic model parameters with absolute magnitude can be
explained by their dependence on the stellar luminosity, whereas the variation
with volume and Galactic longitude at short distances is a bias in analysis.Comment: 12 pages, including 8 figures and 5 tables, accepted for publication
in PAS
The stellar metallicity distribution in intermediate latitude fields with BATC and SDSS data
Based on the Beijing-Arizona-Taiwan-Connecticut (BATC) and Sloan Digital Sky
Survey (SDSS) photometric data, we adopt SEDs fitting Method to evaluate the
metallicity distribution for \sim40,000 main-sequence stars in the Galaxy.
According to the derived photometric metallicities of these sample stars, we
find that the metallicity distribution shift from metal-rich to metal-poor with
the increase of distance from the Galactic center. The mean metallicity is
about of 1.5 \pm 0.2dex in the outer halo and 1.3 \pm 0.1 dex in the inner
halo. The mean metallicity smoothly decreases from -0.4 to -0.8 in interval 0 <
r \leq 5 kpc. The fluctuation in the mean metallicity with Galactic longitude
can be found in interval 4 < r \leq 8 kpc. There is a vertical abundance
gradients d[Fe/H]/dz\sim -0.21 \pm 0.05 dex kpc-1 for the thin disk (z \leq 2
kpc). At distance 2 < z \leq 5 kpc, where the thick disk stars are dominated,
the gradients are about of -0.16 \pm0.06 dex kpc-1, it can be interpreted as a
mixture of stellar population with different mean metallicities at all z
levels. The vertical metallicity gradient is - 0.05 \pm0.04 dex kpc-1 for the
halo (z > 5 kpc). So there is little or no metallicity gradient in the halo
The Information Of The Milky Way From 2MASS Whole Sky Star Count: The Structure Parameters
The Ks band differential star count of the Two Micron All Sky Survey (2MASS)
is used to derive the global structure parameters of the smooth components of
the Milky Way. To avoid complication introduced by other fine structures and
significant extinction near and at the Galactic plane, we only consider
Galactic latitude |b| > 30 degree data. The star count data is fitted with a
threecomponent model: double exponential thin disk and thick disk, and a power
law decay oblate halo. Using maximum likelihood the best-fit local density of
thin disk is n0 = 0.030 +- 0.002 stars/pc^3. The best-fit scale-height and
length of the thin disk are Hz1 = 360+-10 pc and Hr1 = 3.7+-1.0 kpc, and those
of the thick disk are and Hz2 = 1020+-30 pc and Hr2 = 5.0+-1.0 kpc, the local
thick-to-thin disk density ratio is f2 = 7+-1%. The best-fit axis ratio, power
law index and local density ratio of the oblate halo are kappa = 0.55+-0.15, p
= 2.6+-0.6 and fh = 0.20+-0:10%, respectively. Moreover, we find some
degeneracy among the key parameters (e.g. n0,Hz1, f2 and Hz2). Any pair of
these parameters are anticorrelated to each other. The 2MASS data can be
well-fitted by several possible combinations of parameters. This is probably
the reason that there is a wide range of values for the structure parameters in
literature similar to this study. Since only medium and high Galactic latitude
data are analyzed, the fitting is very insensitive to the scale-lengths of the
disks.Comment: 25 pages, 4 figures, accepted by ApJ on July 15 201
Fluoromycobacteriophages for rapid, specific, and sensitive antibiotic susceptibility testing of Mycobacterium tuberculosis
Rapid antibiotic susceptibility testing of Mycobacterium tuberculosis is of paramount importance as multiple- and extensively- drug resistant strains of M. tuberculosis emerge and spread. We describe here a virus-based assay in which fluoromycobacteriophages are used to deliver a GFP or ZsYellow fluorescent marker gene to M. tuberculosis, which can then be monitored by fluorescent detection approaches including fluorescent microscopy and flow cytometry. Pre-clinical evaluations show that addition of either Rifampicin or Streptomycin at the time of phage addition obliterates fluorescence in susceptible cells but not in isogenic resistant bacteria enabling drug sensitivity determination in less than 24 hours. Detection requires no substrate addition, fewer than 100 cells can be identified, and resistant bacteria can be detected within mixed populations. Fluorescence withstands fixation by paraformaldehyde providing enhanced biosafety for testing MDR-TB and XDR-TB infections. © 2009 Piuri et al
Participatory learning and action cycles with women s groups to prevent neonatal death in low-resource settings: A multi-country comparison of cost-effectiveness and affordability.
WHO recommends participatory learning and action cycles with women's groups as a cost-effective strategy to reduce neonatal deaths. Coverage is a determinant of intervention effectiveness, but little is known about why cost-effectiveness estimates vary significantly. This article reanalyses primary cost data from six trials in India, Nepal, Bangladesh and Malawi to describe resource use, explore reasons for differences in costs and cost-effectiveness ratios, and model the cost of scale-up. Primary cost data were collated, and costing methods harmonized. Effectiveness was extracted from a meta-analysis and converted to neonatal life-years saved. Cost-effectiveness ratios were calculated from the provider perspective compared with current practice. Associations between unit costs and cost-effectiveness ratios with coverage, scale and intensity were explored. Scale-up costs and outcomes were modelled using local unit costs and the meta-analysis effect estimate for neonatal mortality. Results were expressed in 2016 international dollars. The average cost was 61-135 to $1627. The intervention was highly cost-effective when using income-based thresholds. Variation in cost-effectiveness across trials was strongly correlated with costs. Removing discounting of costs and life-years substantially reduced all cost-effectiveness ratios. The cost of rolling out the intervention to rural populations ranges from 1.2% to 6.3% of government health expenditure in the four countries. Our analyses demonstrate the challenges faced by economic evaluations of community-based interventions evaluated using a cluster randomized controlled trial design. Our results confirm that women's groups are a cost-effective and potentially affordable strategy for improving birth outcomes among rural populations
Synthesis, antitubercular activity and mechanism of resistance of highly effective thiacetazone analogues
Defining the pharmacological target(s) of currently used drugs and developing new analogues with greater potency are both important aspects of the search for agents that are effective against drug-sensitive and drug-resistant Mycobacterium tuberculosis. Thiacetazone (TAC) is an anti-tubercular drug that was formerly used in conjunction with isoniazid, but removed from the antitubercular chemotherapeutic arsenal due to toxic side effects. However, several recent studies have linked the mechanisms of action of TAC to mycolic acid metabolism and TAC-derived analogues have shown increased potency against M. tuberculosis. To obtain new insights into the molecular mechanisms of TAC resistance, we isolated and analyzed 10 mutants of M. tuberculosis that were highly resistant to TAC. One strain was found to be mutated in the methyltransferase MmaA4 at Gly101, consistent with its lack of oxygenated mycolic acids. All remaining strains harbored missense mutations in either HadA (at Cys61) or HadC (at Val85, Lys157 or Thr123), which are components of the bhydroxyacyl-ACP dehydratase complex that participates in the mycolic acid elongation step. Separately, a library of 31 new TAC analogues was synthesized and evaluated against M. tuberculosis. Two of these compounds, 15 and 16, exhibited minimal inhibitory concentrations 10-fold lower than the parental molecule, and inhibited mycolic acid biosynthesis in a dose-dependent manner. Moreover, overexpression of HadAB HadBC or HadABC in M. tuberculosis led to high level resistance to these compounds, demonstrating that their mode of action is similar to that of TAC. In summary, this study uncovered new mutations associated with TAC resistance and also demonstrated that simple structural optimization of the TAC scaffold was possible and may lead to a new generation of TAC-derived drug candidates for the potential treatment of tuberculosis as mycolic acid inhibitors
Protocol for the cost-consequence and equity impact analyses of a cluster randomised controlled trial comparing three variants of a nutrition-sensitive agricultural extension intervention to improve maternal and child dietary diversity and nutritional status in rural Odisha, India (UPAVAN trial)
BACKGROUND: Undernutrition causes around 3.1 million child deaths annually, around 45% of all child deaths. India has one of the highest proportions of maternal and child undernutrition globally. To accelerate reductions in undernutrition, nutrition-specific interventions need to be coupled with nutrition-sensitive programmes that tackle the underlying causes of undernutrition. This paper describes the planned economic evaluation of the UPAVAN trial, a four-arm, cluster randomised controlled trial that tests the nutritional and agricultural impacts of an innovative agriculture extension platform of women's groups viewing videos on nutrition-sensitive agriculture practices, coupled with a nutrition-specific behaviour-change intervention of videos on nutrition, and a participatory learning and action approach. METHODS: The economic evaluation of the UPAVAN interventions will be conducted from a societal perspective, taking into account all costs incurred by the implementing agency (programme costs), community and health care providers, and participants and their households, and all measurable outcomes associated with the interventions. All direct and indirect costs, including time costs and donated goods, will be estimated. The economic evaluation will take the form of a cost-consequence analysis, comparing incremental costs and incremental changes in the outcomes of the interventions, compared with the status quo. Robustness of the results will be assessed through a series of sensitivity analyses. In addition, an analysis of the equity impact of the interventions will be conducted. DISCUSSION: Evidence on the cost and cost-effectiveness of nutrition-sensitive agriculture interventions is scarce. This limits understanding of the costs of rolling out or scaling up programs. The findings of this economic evaluation will provide useful information for different multisectoral stakeholders involved in the planning and implementation of nutrition-sensitive agriculture programmes. TRIAL REGISTRATION: ISRCTN65922679 . Registered on 21 December 2016
Production of phi mesons at mid-rapidity in sqrt(s_NN) = 200 GeV Au+Au collisions at RHIC
We present the first results of meson production in the K^+K^- decay channel
from Au+Au collisions at sqrt(s_NN) = 200 GeV as measured at mid-rapidity by
the PHENIX detector at RHIC. Precision resonance centroid and width values are
extracted as a function of collision centrality. No significant variation from
the PDG accepted values is observed. The transverse mass spectra are fitted
with a linear exponential function for which the derived inverse slope
parameter is seen to be constant as a function of centrality. These data are
also fitted by a hydrodynamic model with the result that the freeze-out
temperature and the expansion velocity values are consistent with the values
previously derived from fitting single hadron inclusive data. As a function of
transverse momentum the collisions scaled peripheral.to.central yield ratio RCP
for the is comparable to that of pions rather than that of protons. This result
lends support to theoretical models which distinguish between baryons and
mesons instead of particle mass for explaining the anomalous proton yield.Comment: 326 authors, 24 pages text, 23 figures, 6 tables, RevTeX 4. To be
submitted to Physical Review C as a regular article. Plain text data tables
for the points plotted in figures for this and previous PHENIX publications
are (or will be) publicly available at http://www.phenix.bnl.gov/papers.htm
Bacterial immunostat: Mycobacterium tuberculosis lipids and their role in the host immune response
Positive feedback and noise activate the stringent response regulator Rel in mycobacteria
Phenotypic heterogeneity in an isogenic, microbial population enables a
subset of the population to persist under stress. In mycobacteria, stresses
like nutrient and oxygen deprivation activate the stress response pathway
involving the two-component system MprAB and the sigma factor, SigE. SigE in
turn activates the expression of the stringent response regulator, rel. The
enzyme polyphosphate kinase 1 (PPK1) regulates this pathway by synthesizing
polyphosphate required for the activation of MprB. The precise manner in which
only a subpopulation of bacterial cells develops persistence, remains unknown.
Rel is required for mycobacterial persistence. Here we show that the
distribution of rel expression levels in a growing population of mycobacteria
is bimodal with two distinct peaks corresponding to low (L) and high (H)
expression states, and further establish that a positive feedback loop
involving the mprAB operon along with stochastic gene expression are
responsible for the phenotypic heterogeneity. Combining single cell analysis by
flow cytometry with theoretical modeling, we observe that during growth,
noise-driven transitions take a subpopulation of cells from the L to the H
state within a "window of opportunity" in time preceding the stationary phase.
We find evidence of hysteresis in the expression of rel in response to changing
concentrations of PPK1. Our results provide, for the first time, evidence that
bistability and stochastic gene expression could be important for the
development of "heterogeneity with an advantage" in mycobacteria.Comment: Accepted for publication in PLoS On
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