179 research outputs found
Idiopathic immunoglobulin A nephropathy in children and adolescents
Immunoglobulin A nephropathy is now recognized as the glomerular disease most often associated with progressive renal failure in patients around the world. In many cases it is not known when the disease starts to inflict glomerular injury, but recent studies that have shown genetically determined abnormalities in glycosylation of the IgA molecule suggest that this may begin in early life. This review focuses on recent advances in our understanding of IgA nephropathy, with special emphasis on clinical aspects of the disease when it presents in children and adolescents. In addition, the sections dealing with therapeutic options for patients with IgA nephropathy concentrate on studies that have been carried out on children. Whenever possible, data from randomized controlled clinical trials have formed the basis for recommendations. Unfortunately, this is not always possible, because of the lack of such trials in patients with IgA nephropathy
Diffuse HI Disks in Isolated Galaxies
In order to investigate the contribution of diffuse components to their total
HI emission, we have obtained high precision HI line flux densities with the
100m Green Bank Telescope for a sample of 100 isolated spiral and irregular
galaxies which we have previously observed with the 43m telescope. A comparison
of the observed HI line fluxes obtained with the two different telescopes,
characterized by half-power beam widths of 9 arcmin and 21 arcmin respectively,
exploits a ``beam matching'' technique to yield a statistical determination of
the occurrence of diffuse HI components in their disks. A simple model of the
HI distribution within a galaxy well describes ~75 % of the sample and accounts
for all of the HI line flux density. The remaining galaxies are approximately
evenly divided into two categories: ones which appear to possess a
significantly more extensive HI distribution than the model predicts, and ones
for which the HI distribution is more centrally concentrated than predicted.
Examples of both extremes can be found in the literature but little attention
has been paid to the centrally concentrated HI systems. Our sample has
demonstrated that galaxies do not commonly possess extended regions of low
surface brightness HI gas which is not accounted for by our current
understanding of the structure of HI disks. Eight HI-rich companions to the
target objects are identified, and a set of extragalactic HI line flux density
calibrators is presented.Comment: 26 page
CD4 Count At Presentation For HIV Care In The United States And Canada: Are Those Over 50 Years More Likely To Have A Delayed Presentation?
We assessed CD4 count at initial presentation for HIV care among [greater than or equal to]50-year-olds from 1997-2007 in 13 US and Canadian clinical cohorts and compared to <50-year-olds. 44,491 HIV-infected individuals in the North American AIDS Cohort Collaboration on Research and Design (NA-ACCORD) were included in our study. Trends in mean CD4 count (measured as cells/mm3) and 95% confidence intervals ([,]) were determined using linear regression stratified by age category and adjusted for gender, race/ethnicity, HIV transmission risk and cohort. From 1997-2007, the proportion of individuals presenting for HIV care who were [greater than or equal to]50-years-old increased from 17% to 27% (p-value < 0.01). The median CD4 count among [greater than or equal to]50 year-olds was consistently lower than younger adults. The interaction of age group and calendar year was significant (p-value <0.01) with both age groups experiencing modest annual improvements over time (< 50-year-olds: 5 [4 , 6] cells/mm3; [greater than or equal to]50-year-olds: 7 [5 , 9] cells/mm3), after adjusting for sex, race/ethnicity, HIV transmission risk group and cohort; however, increases in the two groups were similar after 2000. A greater proportion of older individuals had an AIDS-defining diagnosis at, or within three months prior to, first presentation for HIV care compared to younger individuals (13% vs. 10%, respectively). Due to the increasing proportion, consistently lower CD4 counts, and more advanced HIV disease in adults [greater than or equal to]50-year-old at first presentation for HIV care, renewed HIV testing efforts are needed.
 
Far-Ultraviolet Observations of RR Lyrae Stars in the Core of NGC 1851
There are extraordinarily few far ultraviolet observations of RR Lyrae stars
in the literature. We present Hubble Space Telescope FUV (~1600 A) imaging of
the core of the globular cluster NGC 1851. Eleven new variables whose light
curves are consistent with those of RR Lyr stars are discovered, increasing the
total number of RR Lyr known in this cluster by a substantial amount. In
agreement with basic physical theory, the observed amplitude of the variables
in the FUV is enormous compared with the century of past optical observations,
ranging up to 4 mag. HST STIS FUV observations of cluster cores may prove an
especially effective means of obtaining a near-complete census of RR Lyr stars,
combining high angular resolution, suppression of luminous red stars, and data
where the stellar pulsation amplitudes are greatly enhanced. Attention is also
drawn to a peculiar blue object in the cluster that is most probably a low mass
x-ray binary system in quiescence.Comment: Accepted for publication in The Astronomical Journal, Vol. 128, Nov.
2004, 13 pages, 4 figures, AASTeX v5.
The SEGUE Stellar Parameter Pipeline. II. Validation with Galactic Globular and Open Clusters
We validate the performance and accuracy of the current SEGUE (Sloan
Extension for Galactic Understanding and Exploration) Stellar Parameter
Pipeline (SSPP), which determines stellar atmospheric parameters (effective
temperature, surface gravity, and metallicity) by comparing derived overall
metallicities and radial velocities from selected likely members of three
globular clusters (M 13, M 15, and M 2) and two open clusters (NGC 2420 and M
67) to the literature values. Spectroscopic and photometric data obtained
during the course of the original Sloan Digital Sky Survey (SDSS-I) and its
first extension (SDSS-II/SEGUE) are used to determine stellar radial velocities
and atmospheric parameter estimates for stars in these clusters. Based on the
scatter in the metallicities derived for the members of each cluster, we
quantify the typical uncertainty of the SSPP values, sigma([Fe/H]) = 0.13 dex
for stars in the range of 4500 K < Teff < 7500 K and 2.0 < log g < 5.0, at
least over the metallicity interval spanned by the clusters studied (-2.3 <
[Fe/H] < 0). The surface gravities and effective temperatures derived by the
SSPP are also compared with those estimated from the comparison of the
color-magnitude diagrams with stellar evolution models; we find satisfactory
agreement. At present, the SSPP underestimates [Fe/H] for
near-solar-metallicity stars, represented by members of M 67 in this study, by
about 0.3 dex.Comment: 56 pages, 8 Tables, 15 figures, submitted to the Astronomical Journa
CD4 count at presentation for HIV care in the United States and Canada: Are those over 50 years more likely to have a delayed presentation?
We assessed CD4 count at initial presentation for HIV care among ≥50-year-olds from 1997-2007 in 13 US and Canadian clinical cohorts and compared to <50-year-olds. 44,491 HIV-infected individuals in the North American AIDS Cohort Collaboration on Research and Design (NA-ACCORD) were included in our study. Trends in mean CD4 count (measured as cells/mm3) and 95% confidence intervals ([,]) were determined using linear regression stratified by age category and adjusted for gender, race/ethnicity, HIV transmission risk and cohort. From 1997-2007, the proportion of individuals presenting for HIV care who were ≥50-years-old increased from 17% to 27% (p-value < 0.01). The median CD4 count among ≥50 year-olds was consistently lower than younger adults. The interaction of age group and calendar year was significant (p-value <0.01) with both age groups experiencing modest annual improvements over time (< 50-year-olds: 5
[4 , 6] cells/mm3; ≥50-year-olds: 7
[5 , 9] cells/mm3), after adjusting for sex, race/ethnicity, HIV transmission risk group and cohort; however, increases in the two groups were similar after 2000. A greater proportion of older individuals had an AIDS-defining diagnosis at, or within three months prior to, first presentation for HIV care compared to younger individuals (13% vs. 10%, respectively). Due to the increasing proportion, consistently lower CD4 counts, and more advanced HIV disease in adults ≥50-year-old at first presentation for HIV care, renewed HIV testing efforts are needed
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