ASP Conf.Ser. 10 (2001) 269 We summarise the properties of the Sloan Digital Sky Survey (SDSS) project,
discuss our software infrastructure, and outline the architecture of the SDSS
image processing ...pipelines.
We then discuss two of the algorithms used in the SDSS image processing; the
KL-transform based modelling of the spatial variation of the PSF, and the use
of galaxy models in star/galaxy separation.
We conclude with the first author's personal opinions on the challenges that
the astronomical community faces with major software projects.
Pharmacokinetic models rarely undergo external validation in vulnerable populations such as critically ill infants, thereby limiting the accuracy, efficacy, and safety of model-informed dosing in ...real-world settings. Here, we describe an opportunistic approach using dried blood spots (DBS) to evaluate a population pharmacokinetic model of metronidazole in critically ill preterm infants of gestational age (GA) ≤31 weeks from the Metronidazole Pharmacokinetics in Premature Infants (PTN_METRO, NCT01222585) study. First, we used linear correlation to compare 42 paired DBS and plasma metronidazole concentrations from 21 preterm infants mean (SD): post natal age 28.0 (21.7) days, GA 26.3 (2.4) weeks. Using the resulting predictive equation, we estimated plasma metronidazole concentrations (ePlasma) from 399 DBS collected from 122 preterm and term infants mean (SD): post natal age 16.7 (15.8) days, GA 31.4 (5.1) weeks from the Antibiotic Safety in Infants with Complicated Intra-Abdominal Infections (SCAMP, NCT01994993) trial. When evaluating the PTN_METRO model using ePlasma from the SCAMP trial, we found that the model generally predicted ePlasma well in preterm infants with GA ≤31 weeks. When including ePlasma from term and preterm infants with GA >31 weeks, the model was optimized using a sigmoidal Emax maturation function of postmenstrual age on clearance and estimated the exponent of weight on volume of distribution. The optimized model supports existing dosing guidelines and adds new data to support a 6-hour dosing interval for infants with postmenstrual age >40 weeks. Using an opportunistic DBS to externally validate and optimize a metronidazole population pharmacokinetic model was feasible and useful in this vulnerable population.
We summarize the plans for and the current status of the Sloan Digital Sky Survey, a digital imaging and spectroscopic survey of \(\pi\) steradians in the northern Galactic cap. The CCD photometric ...survey will produce images in five bands to limiting magnitudes of order 23. The spectroscopic survey will obtain redshifts of \(10^6\) galaxies (a complete sample to a limiting magnitude \(r' \sim 18\)) and \(10^5\) quasars (\(g' \sim 19\)). Repeated imaging of a 200 deg\(^2\) strip in the southern Galactic cap will yield information about variable objects and a co-added photometric catalog roughly two magnitudes deeper than the northern survey. A dedicated 2.5-meter telescope, a large multi-CCD camera, and two fiber-fed double spectrographs are under construction and should be operational by fall of 1995. The main galaxy redshift sample will have a median redshift \(\langle z \rangle \approx 0.1\).
Astron.J.133:2222-2241,2007 (Abridged) We study the two-point correlation function of a uniformly
selected sample of 4,426 luminous optical quasars with redshift $2.9 \le z\le
5.4$ selected over 4041 ...deg$^2$ from the Fifth Data Release of the Sloan
Digital Sky Survey. For a real-space correlation function of the form
$\xi(r)=(r/r_0)^{-\gamma}$, the fitted parameters in comoving coordinates are
$r_0 = 15.2 \pm 2.7 h^{-1}$ Mpc and $\gamma = 2.0 \pm 0.3$, over a scale range
$4\le r_p\le 150 h^{-1}$ Mpc. Thus high-redshift quasars are appreciably more
strongly clustered than their $z \approx 1.5$ counterparts, which have a
comoving clustering length $r_0 \approx 6.5 h^{-1}$ Mpc. Dividing our sample
into two redshift bins: $2.9\le z\le 3.5$ and $z\ge 3.5$, and assuming a
power-law index $\gamma=2.0$, we find a correlation length of $r_0 = 16.9 \pm
1.7 h^{-1}$ Mpc for the former, and $r_0 = 24.3 \pm 2.4 h^{-1}$ Mpc for the
latter. Following Martini & Weinberg, we relate the clustering strength and
quasar number density to the quasar lifetimes and duty cycle. Using the Sheth &
Tormen halo mass function, the quasar lifetime is estimated to lie in the range
$4\sim 50$ Myr for quasars with $2.9\le z\le 3.5$; and $30\sim 600$ Myr for
quasars with $z\ge 3.5$. The corresponding duty cycles are $0.004\sim 0.05$ for
the lower redshift bin and $0.03\sim 0.6$ for the higher redshift bin. The
minimum mass of halos in which these quasars reside is $2-3\times 10^{12}\
h^{-1}M_\odot$ for quasars with $2.9\le z\le 3.5$ and $4-6\times 10^{12}\
h^{-1}M_\odot$ for quasars with $z\ge 3.5$.
Background
The proportion of proposed new treatments that are 'successful' is of ethical, scientific, and public importance. We investigated how often new, experimental treatments evaluated in ...randomized controlled trials (RCTs) are superior to established treatments.
Objectives
Our main question was: "On average how often are new treatments more effective, equally effective or less effective than established treatments?" Additionally, we wanted to explain the observed results, i.e. whether the observed distribution of outcomes is consistent with the 'uncertainty requirement' for enrollment in RCTs. We also investigated the effect of choice of comparator (active versus no treatment/placebo) on the observed results.
Search methods
We searched the Cochrane Methodology Register (CMR) 2010, Issue 1 in The Cochrane Library (searched 31 March 2010); MEDLINE Ovid 1950 to March Week 2 2010 (searched 24 March 2010); and EMBASE Ovid 1980 to 2010 Week 11 (searched 24 March 2010).
Selection criteria
Cohorts of studies were eligible for the analysis if they met all of the following criteria: (i) consecutive series of RCTs, (ii) registered at or before study onset, and (iii) compared new against established treatments in humans.
Data collection and analysis
RCTs from four cohorts of RCTs met all inclusion criteria and provided data from 743 RCTs involving 297,744 patients. All four cohorts consisted of publicly funded trials. Two cohorts involved evaluations of new treatments in cancer, one in neurological disorders, and one for mixed types of diseases. We employed kernel density estimation, meta‐analysis and meta‐regression to assess the probability of new treatments being superior to established treatments in their effect on primary outcomes and overall survival.
Main results
The distribution of effects seen was generally symmetrical in the size of difference between new versus established treatments. Meta‐analytic pooling indicated that, on average, new treatments were slightly more favorable both in terms of their effect on reducing the primary outcomes (hazard ratio (HR)/odds ratio (OR) 0.91, 99% confidence interval (CI) 0.88 to 0.95) and improving overall survival (HR 0.95, 99% CI 0.92 to 0.98). No heterogeneity was observed in the analysis based on primary outcomes or overall survival (I2 = 0%). Kernel density analysis was consistent with the meta‐analysis, but showed a fairly symmetrical distribution of new versus established treatments indicating unpredictability in the results. This was consistent with the interpretation that new treatments are only slightly superior to established treatments when tested in RCTs. Additionally, meta‐regression demonstrated that results have remained stable over time and that the success rate of new treatments has not changed over the last half century of clinical trials. The results were not significantly affected by the choice of comparator (active versus placebo/no therapy).
Authors' conclusions
Society can expect that slightly more than half of new experimental treatments will prove to be better than established treatments when tested in RCTs, but few will be substantially better. This is an important finding for patients (as they contemplate participation in RCTs), researchers (as they plan design of the new trials), and funders (as they assess the 'return on investment'). Although we provide the current best evidence on the question of expected 'success rate' of new versus established treatments consistent with a priori theoretical predictions reflective of 'uncertainty or equipoise hypothesis', it should be noted that our sample represents less than 1% of all available randomized trials; therefore, one should exercise the appropriate caution in interpretation of our findings. In addition, our conclusion applies to publicly funded trials only, as we did not include studies funded by commercial sponsors in our analysis.
Astrophys.J.Suppl.Ser.148:243-274,2003 We present a catalog of 799 clusters of galaxies in the redshift range z_est
= 0.05 - 0.3 selected from ~400 deg^2 of early SDSS commissioning data along
the ...celestial equator. The catalog is based on merging two independent
selection methods -- a color-magnitude red-sequence maxBCG technique (B), and a
Hybrid Matched-Filter method (H). The BH catalog includes clusters with
richness \Lambda >= 40 (Matched-Filter) and N_gal >= 13 (maxBCG), corresponding
to typical velocity dispersion of \sigma_v >~ 400 km s^{-1} and mass (within
0.6 h^{-1) Mpc radius) >~ 5*10^{13} h^{-1} M_sun. This threshold is below Abell
richness class 0 clusters. The average space density of these clusters is
2*10^{-5} h^3 Mpc^{-3}. All NORAS X-ray clusters and 53 of the 58 Abell
clusters in the survey region are detected in the catalog; the 5 additional
Abell clusters are detected below the BH catalog cuts. The cluster richness
function is determined and found to exhibit a steeply decreasing cluster
abundance with increasing richness. We derive observational scaling relations
between cluster richness and observed cluster luminosity and cluster velocity
dispersion; these scaling relations provide important physical calibrations for
the clusters. The catalog can be used for studies of individual clusters, for
comparisons with other sources such as X-ray clusters and AGNs, and, with
proper correction for the relevant selection functions, also for statistical
analyses of clusters.
Astron.J.130:873,2005 We investigate the extent to which the Palomar-Green (PG) Bright Quasar
Survey (BQS) is complete and representative of the general quasar population by
comparing with imaging ...and spectroscopy from the Sloan Digital Sky Survey. A
comparison of SDSS and PG photometry of both stars and quasars reveals the need
to apply a color and magnitude recalibration to the PG data. Using the SDSS
photometric catalog, we define the PG's parent sample of objects that are not
main-sequence stars and simulate the selection of objects from this parent
sample using the PG photometric criteria and errors. This simulation shows that
the effective U-B cut in the PG survey is U-B < -0.71 (rather than the intended
U-B < -0.44), implying a color-related incompleteness. As the color
distribution of bright quasars peaks near U-B=-0.7 and the 2-sigma error in U-B
is comparable to the full width of the color distribution of quasars, the color
incompleteness of the BQS is approximately 50% and essentially random with
respect to U-B color for z<0.5. There is, however, a bias against bright
quasars at 0.5 < z < 1, which is induced by the color-redshift relation of
quasars (although quasars at z>0.5 are inherently rare in bright surveys in any
case). We find no evidence for any other systematic incompleteness when
comparing the distributions in color, redshift, and FIRST radio properties of
the BQS and a BQS-like subsample of the SDSS quasar sample. However, the
application of a bright magnitude limit biases the BQS toward the inclusion of
objects which are blue in g-i, in particular compared to the full range of g-i
colors found among the i-band limited SDSS quasars, and even at i-band
magnitudes comparable to those of the BQS objects.
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