1,341 research outputs found
V, J, H and K Imaging of the Metal Rich Globular Cluster NGC 6528
New near-infrared observations of NGC6528 are presented. The JHK observations
complement a previous HST/NICMOS data set by Ortolani et al. (2001), in that
they sample a larger area, contain a more numerous sample of red giant stars,
and include the K band. Also, archival HST data sets (separated by 6.093 years)
were used to proper-motion decontaminate the near-infrared sample and extract a
clean VJHK catalogue. Using the present wide colour baseline, we compared the
cleaned colour-magnitude diagrams of NGC6528 with those of NGC 6553 and NGC104
and derived new estimates of reddening and distance, E(B-V)=0.55 and
(m-M)o=14.44 (7.7 kpc). Moreover, the morphology and location of the cleaned
red giant branch were used to derive a photometric estimate of the cluster
metallicity. The average of 10 metallicity indicators yields a mean value of
[M/H] ~ 0.0, and [Fe/H] ~-0.20 and +0.08 on the Zinn & West (1984) and Carretta
& Gratton (1997) revised metallicity scale, respectively. The best isochrone
fit to the cleaned K,V-K diagram is obtained for a 12.6 Gyr and Z=0.02
isochrone, i.e. the derived metallicity of NGC6528 turns out to be very close
to the mean of stars in the Baade's Window. Five AGB variable star candidates,
whose membership has to be confirmed spectroscopically, are bolometrically as
bright as the known long period variable stars in NGC6553. As discussed in
Guarnieri et al. (1997) for NGC6553, this may indicate that an `intermediate
age' population is not needed to account for the brightest stars in external
galaxies such as M32.Comment: 11 pages, 9 figures, A&A accepte
Development and Validation of a Composite Programmatic Assessment Tool for HIV Therapy
Background
We developed and validated a new and simple metric, the Programmatic Compliance Score (PCS), based on the IAS-USA antiretroviral therapy management guidelines for HIV-infected adults, as a predictor of all-cause mortality, at a program-wide level. We hypothesized that non-compliance would be associated with the highest probability of mortality.
Methods and Findings
3543 antiretroviral-naive HIV-infected patients aged â„19 years who initiated antiretroviral therapy between January 1, 2000 and August 31, 2009 in British Columbia (BC), Canada, were followed until August 31, 2010. The PCS is composed by six non-performance indicators based on the IAS-USA guidelines: (1) having <3 CD4 count tests in the first year after starting antiretroviral therapy; (2) having <3 plasma viral load tests in the first year after starting antiretroviral therapy; (3) not having drug resistance testing done prior to starting antiretroviral therapy; (4) starting on a non-recommended antiretroviral therapy regimen; (5) starting therapy with CD4 <200 cells/mm3; and (6) not achieving viral suppression within 6 months since antiretroviral therapy initiation. The sum of these six indicators was used to develop the PCS score - higher score indicates poorer performance. The main outcome was all-cause mortality. Each PCS component was independently associated with mortality. In the mortality analysis, the odds ratio (OR) for PCS â„4 versus 0 was 22.37 (95% CI 10.46â47.84).
Conclusions
PCS was strongly associated with all-cause mortality. These results lend independent validation to the IAS-USA treatment guidelines for HIV-infected adults. Further efforts are warranted to enhance the PCS as a means to further improve clinical outcomes. These should be specifically evaluated and targeted at healthcare providers and patients
Theories for the Fermi Scale
I give a short review of our present understanding of new theories of the
electroweak scale, with emphasis on recent progress. Plenary talk at the EPS
2007 Conference at Manchester.Comment: 14 pages, EPS 2007 Conferenc
The Status of GMSB After 1/fb at the LHC
We thoroughly investigate the current status of supersymmetry in light of the
latest searches at the LHC, using General Gauge Mediation (GGM) as a
well-motivated signature generator that leads to many different simplified
models. We consider all possible promptly-decaying NLSPs in GGM, and by
carefully reinterpreting the existing LHC searches, we derive limits on both
colored and electroweak SUSY production. Overall, the coverage of GGM parameter
space is quite good, but much discovery potential still remains even at 7 TeV.
We identify several regions of parameter space where the current searches are
the weakest, typically in models with electroweak production, third generation
sfermions or squeezed spectra, and we suggest how ATLAS and CMS might modify
their search strategies given the understanding of GMSB at 1/fb. In particular,
we propose the use of leptonic to suppress backgrounds.
Because we express our results in terms of simplified models, they have broader
applicability beyond the GGM framework, and give a global view of the current
LHC reach. Our results on 3rd generation squark NLSPs in particular can be
viewed as setting direct limits on naturalness.Comment: 44 pages, refs added, typos fixed, improved MC statistics in fig 1
General Messenger Gauge Mediation
We discuss theories of gauge mediation in which the hidden sector consists of
two subsectors which are weakly coupled to each other. One sector is made up of
messengers and the other breaks supersymmetry. Each sector by itself may be
strongly coupled. We provide a unifying framework for such theories and discuss
their predictions in different settings. We show how this framework
incorporates all known models of messengers. In the case of weakly-coupled
messengers interacting with spurions through the superpotential, we prove that
the sfermion mass-squared is positive, and furthermore, that there is a lower
bound on the ratio of the sfermion mass to the gaugino mass.Comment: 37 pages; minor change
The Secret to Successful User Communities: An Analysis of Computer Associatesâ User Groups
This paper provides the first large scale study that examines the impact of both individual- and group-specific factors on the benefits users obtain from their user communities. By empirically analysing 924 survey responses from individuals in 161 Computer Associates' user groups, this paper aims to identify the determinants of successful user communities. To measure success, the amount of time individual members save through having access to their user networks is used. As firms can significantly profit from successful user communities, this study proposes four key implications of the empirical results for the management of user communities
A HST/WFPC2 survey of bright young clusters in M31. I. VdB0, a massive star cluster seen at ~= 25 Myr
{Aims.} We introduce our imaging survey of possible young massive globular
clusters in M31 performed with the Wide Field and Planetary Camera 2 (WFPC2) on
the Hubble Space Telescope (HST). We present here details of the data reduction
pipeline that is being applied to all the survey data and describe its
application to the brightest among our targets, van den Bergh 0 (VdB0), taken
as a test case. {Methods.} The reddening, the age and the metallicity of the
cluster are estimated by comparison of the observed Color Magnitude Diagram
(CMD) with theoretical isochrones. {Results.} Under the most conservative
assumptions the stellar mass of VdB0 is M > 2.4 x 10^4 M_sun, but our best
estimates lie in the range ~ 4-9 x 10^4 M_sun. The CMD of VdB0 is best
reproduced by models having solar metallicity and age = 25 Myr. Ages smaller
than = 12 Myr and larger than = 60 Myr are clearly ruled out by the available
data. The cluster has a remarkable number of Red Super Giants (> 18) and a CMD
very similar to Large Magellanic Cloud clusters usually classified as young
globulars such as NGC 1850, for example. {Conclusions.} VdB0 is significantly
brighter (>~ 1 mag) than Galactic open clusters of similar age. Its present-day
mass and half-light radius (r_h=7.4 pc) are more typical of faint globular
clusters than of open clusters. However, given its position within the disk of
M31 it is expected to be destroyed by dynamical effects, in particular by
encounters with giant molecular clouds, within the next ~ 4 Gyr.Comment: 18 pages, 16 figures (quality of Figures 1,2,3 and 4 reduced).
Accepted for publication in Astronomy & Astrophysics. Minor revisions to
sect. 1.
Infrared Variability of Evolved Protoplanetary Disks: Evidence for Scale Height Variations in the Inner Disk
We present the results of a multi-wavelength multi-epoch survey of five
evolved protoplanetary disks in the IC 348 cluster that show significant
infrared variability. Using 3-8micron and 24micron photometry along with
5-40micron spectroscopy from the Spitzer Space Telescope, as well as
ground-based 0.8-5micron spectroscopy, optical spectroscopy and near-infrared
photometry, covering timescales of days to years, we examine the variability in
the disk, stellar and accretion flux. We find substantial variations (10-60%)
at all infrared wavelengths on timescales of weeks to months for all of these
young stellar objects. This behavior is not unique when compared to other
cluster members and is consistent with changes in the structure of the inner
disk, most likely scale height fluctuations on a dynamical timescale. Previous
observations, along with our near-infrared photometry, indicate that the
stellar fluxes are relatively constant; stellar variability does not appear to
drive the large changes in the infrared fluxes. Based on our near-infrared
spectroscopy of the Pa-beta and Br-gamma lines we find that the accretion rates
are variable in most of the evolved disks but the overall rates are probably
too small to cause the infrared variability. We discuss other possible physical
causes for the variability, including the influence of a companion, magnetic
fields threading the disk, and X-ray flares.Comment: Accepted to ApJ. 33 pages, emulate apj forma
Efficacy of ImageJ in the assessment of apoptosis
<p>Abstract</p> <p>Objective</p> <p>To verify the efficacy of ImageJ 1.43 n in determining the extent of apoptosis which is a complex and multistep process.</p> <p>Study Design</p> <p>Cisplatin in different concentrations was used to induce apoptosis in cultured Hep2 cells. Cell viability assay and nuclear image analysis of stained Hep2 cells were used to discriminate apoptotic cells and cells suspected to be undergoing apoptosis from control cells based on parameters such as nuclear area, circularity, perimeter and nuclear area factor (NAF), in association with visual morphology.</p> <p>Results</p> <p>Image analysis revealed a progressive and highly significant decrease in nuclear area factor detected in apoptotic cells and in cells suspected of undergoing apoptosis compared to the control cells (P-values < 0.01). Some of the other studied parameters showed also the same trend. This decrease was assumed to indicate DNA loss. Image analysis results correlated positively and significantly with the results obtained by cell viability assay (R = 0.958, P-value = 0.042). NAF was the most reliable parameter in assessment of apoptosis.</p> <p>Conclusion</p> <p>Nuclear area factor can be calculated using powerful free and open-source software. Consequently, a quantitative measure of apoptosis can be obtained that is linked to morphological changes. ImageJ 1.43 n may therefore provide a useful tool for the assessment and discrimination of apoptotic cells.</p> <p>Virtual slides</p> <p>The virtual slide(s) for this article can be found here:</p> <p><url>http://www.diagnosticpathology.diagnomx.eu/vs/5929043086367338</url></p
Networked buffering: a basic mechanism for distributed robustness in complex adaptive systems
A generic mechanism - networked buffering - is proposed for the generation of robust traits in complex systems. It requires two basic conditions to be satisfied: 1) agents are versatile enough to perform more than one single functional role within a system and 2) agents are degenerate, i.e. there exists partial overlap in the functional capabilities of agents. Given these prerequisites, degenerate systems can readily produce a distributed systemic response to local perturbations. Reciprocally, excess resources related to a single function can indirectly support multiple unrelated functions within a degenerate system. In models of genome:proteome mappings for which localized decision-making and modularity of genetic functions are assumed, we verify that such distributed compensatory effects cause enhanced robustness of system traits. The conditions needed for networked buffering to occur are neither demanding nor rare, supporting the conjecture that degeneracy may fundamentally underpin distributed robustness within several biotic and abiotic systems. For instance, networked buffering offers new insights into systems engineering and planning activities that occur under high uncertainty. It may also help explain recent developments in understanding the origins of resilience within complex ecosystems. \ud
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