4,081 research outputs found
Distant Galaxy Clusters Identified From Optical Background Fluctuations
We present the first high redshift (0.3 < z < 1.1) galaxy clusters found by
systematically identifying optical low surface brightness fluctuations in the
background sky. Using spectra obtained with the Keck telescope and I-band
images from the Palomar 1.5m telescope, we conclude that at least eight of the
ten candidates examined are high redshift galaxy clusters. The identification
of such clusters from low surface brightness fluctuations provides a
complementary alternative to classic selection methods based on overdensities
of resolved galaxies, and enables us to search efficiently for rich high
redshift clusters over large areas of the sky. The detections described here
are the first in a survey that covers a total of nearly 140 sq. degrees of the
sky and should yield, if these preliminary results are representative, over 300
such clusters.Comment: Submitted to ApJ
Pediatric intestinal obstruction in Malawi: characteristics and outcomes
Abstract Background Intestinal obstruction (IO) is a common pediatric surgical emergency in sub-Saharan Africa with high morbidity and mortality, but little is known about its etiopathogenesis in Malawi. Methods Retrospective analysis of patients seen from February 2012 to June 2014 at Kamuzu Central Hospital in Lilongwe, Malawi (n = 3,407). Pediatric patients with IO were analyzed (n = 130). Results Overall, 57% of patients were male with a mean age of 3.5 ± 4.1 years. A total of 52% of patients underwent operative intervention. The overall mortality rate was 3%. Leading causes of IO were Hirschprung's 29%, anorectal malformation 18%, and intussusception 4%. Neonates and patients with congenital causes of IO underwent surgery less frequently than infants and/or children and patients with acquired causes, respectively. These groups also demonstrated increased number of days from admission to surgery. Conclusions Increasing pediatric-specific surgical education and/or training and expanding access to resources may improve mortality after IO in poor medical communities within sub-Saharan Africa
Cluster Galaxy Evolution from a New Sample of Galaxy Clusters at 0.3 < z < 0.9
(Abridged) We analyze photometry and spectroscopy of a sample of 63 clusters
at 0.3<z<0.9 drawn from the Las Campanas Distant Cluster Survey to empirically
constrain models of cluster galaxy evolution. Specifically, by combining data
on our clusters with those from the literature we parametrize the redshift
dependence of 1) M*_I in the observed frame; 2) the V-I color of the E/S0 red
sequence in the observed frames; and 3) the I-K' color of the E/S0 red sequence
in the observed frame. Using the peak surface brightness of the cluster
detection, S, as a proxy for cluster mass, we find no correlation between S and
M* or the location of the red envelope in V-I. We suggest that these
observations can be explained with a model in which luminous early type
galaxies (or more precisely, the progenitors of current day luminous early type
galaxies) form the bulk of their stellar populations at high redshift (>~ 5)
and in which many of these galaxies, if not all, accrete mass either in the
form of evolved stellar populations or gas that causes only a short term
episode of star formation at lower redshifts (1.5 < z < 2). Our data are too
crude to reach conclusions regarding the evolutionary state of any particular
cluster or to investigate whether the morphological evolution of galaxies
matches the simple scenario we discuss, but the statistical nature of this
study suggests that the observed evolutionary trends are universal in massive
clusters.Comment: 35 pages, accepted for publication in Ap
Associations of pubertal stage and body mass index with cardiometabolic risk in Hong Kong Chinese children: A cross-sectional study
Background: Puberty is associated with a clustering of cardiometabolic risk factors (CMRFs) during adolescence that are manifested in later life. Although anthropometric variables such as body mass index (BMI) can predict cardiometabolic risk in children and adolescents, it is not clear whether there is an interaction between pubertal stage and BMI associated with cardiometabolic risk in this age group. This paper examines the association of pubertal stage and BMI with CMRFs in Hong Kong Chinese children. Methods: A cross-sectional school-based study was conducted among 1985 (95.1%) students aged 6 to 18 years. Fasting lipid profile and plasma glucose, blood pressure, body weight, body height and waist circumference were measured. A self-reported pubertal stage questionnaire was used to assess pubertal stage of participants. Two cardiometabolic risk scores, alpha and beta, were constructed to quantify cardiometabolic risk. Cardiometabolic risk score alpha refers to the sum of z-scores of sex-specific, age-adjusted waist circumference, height-adjusted systolic and diastolic blood pressure, fasting plasma glucose, triglyceride and low-density lipoprotein cholesterol, and minus z-score of sex-specific age-adjusted high-density lipoprotein cholesterol. Cardiometabolic risk score beta includes all components of risk score alpha except waist circumference. Results: The interaction of BMI z-score (ZBMI) and pubertal stage demonstrated a significant increase in variance explained in cardiometabolic risk score alpha in boys (0.5%, p = 0.024) and girls (0.7%, p = 0.006) and in cardiometabolic risk score beta in boys (0.8%, p = 0.030) but not in girls (0.5%, p = 0.051). Conclusions: Pubertal stage has an interaction effect on the association of cardiometabolic risk by BMI in boys and may have a similar but lesser effect in girls.published_or_final_versio
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