We study the buildup of the bimodal galaxy population using the NEWFIRM Medium-Band Survey, which provides excellent redshifts and well-sampled spectral energy distributions of 2,000 galaxies with K ...< 22.8 at 0.4 < z < 2.2. We first show that star-forming galaxies and quiescent galaxies can be robustly separated with a two-color criterion over this entire redshift range. We then study the evolution of the number density and mass density of quiescent and star-forming galaxies, extending the results of the COMBO-17, DEEP2, and other surveys to z = 2.2. The mass density of quiescent galaxies with M 3 X 1010 M increases by a factor of ~10 from z ~ 2 to the present day, whereas the mass density in star-forming galaxies is flat or decreases over the same time period. Modest mass growth by a factor of ~2 of individual quiescent galaxies can explain roughly half of the strong density evolution at masses >1011 M , due to the steepness of the exponential tail of the mass function. The rest of the density evolution of massive, quiescent galaxies is likely due to transformation (e.g., quenching) of the massive star-forming population, a conclusion which is consistent with the density evolution we observe for the star-forming galaxies themselves, which is flat or decreasing with cosmic time. Modest mass growth does not explain the evolution of less massive quiescent galaxies (~1010.5 M ), which show a similarly steep increase in their number densities. The less massive quiescent galaxies are therefore continuously formed by transforming galaxies from the star-forming population.
We select 25,000 galaxies from the NEWFIRM Medium Band Survey (NMBS) to study the rest-frame U - V color distribution of galaxies at 0 < z approx< 2.5. The five unique NIR filters of the NMBS enable ...the precise measurement of photometric redshifts and rest-frame colors for 9900 galaxies at 1 < z < 2.5. The rest-frame U - V color distribution at all z approx< 2.5 is bimodal, with a red peak, a blue peak, and a population of galaxies in between (the green valley). Model fits to the optical-NIR spectral energy distributions and the distribution of MIPS-detected galaxies indicate that the colors of galaxies in the green valley are determined largely by the amount of reddening by dust. This result does not support the simplest interpretation of green valley objects as a transition from blue star forming to red quiescent galaxies. We show that correcting the rest-frame colors for dust reddening allows a remarkably clean separation between the red and blue sequences up to z approx 2.5. Our study confirms that dusty-starburst galaxies can contribute a significant fraction to red-sequence samples selected on the basis of a single rest-frame color (i.e., U - V), so extra care must be taken if samples of truly 'red and dead' galaxies are desired. Interestingly, of galaxies detected at 24 mum, 14% remain on the red sequence after applying the reddening correction.
In order to reproduce the high-mass end of the galaxy mass distribution, some process must be responsible for the suppression of star formation in the most massive of galaxies. Commonly active ...galactic nuclei (AGN) are invoked to fulfil this role, but the exact means by which they do so is still the topic of much debate, with studies finding evidence for both the suppression and enhancement of star formation in AGN hosts. Using the ZFOURGE (FourStar Galaxy Evolution) and NMBS (Newfirm Medium Band Survey) galaxy surveys, we investigate the host galaxy properties of a mass-limited (M greater than or equal to 10... M...), high-luminosity (L... > 10... W Hz...) sample of radio-loud AGN to a redshift of z = 2.25. In contrast to low-redshift studies, which associate radio-AGN activity with quiescent hosts, we find that the majority of z > 1.5 radio-AGN are hosted by star-forming galaxies. Indeed, the stellar populations of radio-AGN are found to evolve with redshift in a manner that is consistent with the non-AGN mass-similar galaxy population. Interestingly, we find that the radio-AGN fraction is constant across a redshift range of 0.25 less than or equal to z < 2.25, perhaps indicating that the radio-AGN duty cycle has little dependence on redshift or galaxy type. We do however see a strong relation between the radio-AGN fraction and stellar mass, with radio-AGN becoming rare below ~10... M... or a halo mass of 10... M... This halo-mass threshold is in good agreement with simulations that initiate radio-AGN feedback at this mass limit. Despite this, we find that radio-AGN host star formation rates are consistent with the non-AGN mass-similar galaxy sample, suggesting that while radio-AGN are in the right place to suppress star formation in massive galaxies they are not necessarily responsible for doing so. (ProQuest: ... denotes formulae/symbols omitted.)
The hepatic iron concentration (HIC) is widely used in clinical practice and in research; however, data on the variability of HIC among biopsy sites are limited. One aim of the present study was to ...determine the variability of HIC within both healthy and cirrhotic livers.
Using colorimetric methods, we determined HIC in multiple large (microtome) and small (biopsy-sized) paraffin-embedded samples in 11 resected livers with end-stage cirrhosis. HIC was also measured in multiple fresh samples taken within 5 mm of each other ("local" samples) and taken at sites 3-5 cm apart ("remote" samples) from six livers with end-stage cirrhosis and two healthy autopsy livers.
The within-organ SD of HIC was 13-1553 microg/g (CV, 3.6-55%) for microtome samples and 60-2851 microg/g (CV, 15-73%) for biopsy-sized samples. High variability of HIC was associated with mild to moderate iron overload, because the HIC SD increased with increasing mean HIC (P <0.002). Livers with mean HIC >1000 microg/g exhibited significant biological variability in HIC between sites separated by 3-5 cm (remote sites; P <0.05). The SD was larger for biopsy-sized samples than for microtome samples (P = 0.02).
Ideally, multiple hepatic sites would be sampled to obtain a representative mean HIC.
Abstract
We investigate the relationship between the black hole accretion rate (BHAR) and star formation rate (SFR) for Milky Way (MW) and Andromeda (M31)-mass progenitors from z = 0.2 to 2.5. We ...source galaxies from the Ks-band-selected ZFOURGE survey, which includes multiwavelength data spanning 0.3–160 μm. We use decomposition software to split the observed spectral energy distributions (SEDs) of our galaxies into their active galactic nuclei (AGNs) and star-forming components, which allows us to estimate BHARs and SFRs from the infrared (IR). We perform tests to check the robustness of these estimates, including a comparison with BHARs and SFRs derived from X-ray stacking and far-IR analysis, respectively. We find that, as the progenitors evolve their relative black hole–galaxy growth (i.e. their BHAR/SFR ratio) increases from low to high redshift. The MW-mass progenitors exhibit a log–log slope of 0.64 ± 0.11, while the M31-mass progenitors are 0.39 ± 0.08. This result contrasts with previous studies that find an almost flat slope when adopting X-ray-/AGN-selected or mass-limited samples and is likely due to their use of a broad mixture of galaxies with different evolutionary histories. Our use of progenitor-matched samples highlights the potential importance of carefully selecting progenitors when searching for evolutionary relationships between BHAR/SFRs. Additionally, our finding that BHAR/SFR ratios do not track the rate at which progenitors quench casts doubts over the idea that the suppression of star formation is predominantly driven by luminous AGN feedback (i.e. high BHARs).
Given the widespread interest in antioxidant nutrients, we have developed a new procedure that will permit the automated determination of plasma ascorbic acid (AA) concentration with a Roche Fara ...centrifugal analyzer. After the deproteinization of plasma with metaphosphoric acid, AA is oxidized to dehydroascorbic acid by AA oxidase. The product is coupled to o-phenylenediamine to produce a chromophore for which the absorbance is measured at 340 nm. The procedure allows much faster throughput than conventional HPLC methods while yielding results that correlate well and provide improved precision. Linearity extends beyond the reference range of 26.1-84.6 micromol/L, and severe hemolysis is the only interference identified.
Brown adipose tissue (BAT) has attracted scientific interest as an antidiabetic tissue owing to its ability to dissipate energy as heat. Despite a plethora of data concerning the role of BAT in ...glucose metabolism in rodents, the role of BAT (if any) in glucose metabolism in humans remains unclear. To investigate whether BAT activation alters whole-body glucose homeostasis and insulin sensitivity in humans, we studied seven BAT-positive (BAT(+)) men and five BAT-negative (BAT(-)) men under thermoneutral conditions and after prolonged (5-8 h) cold exposure (CE). The two groups were similar in age, BMI, and adiposity. CE significantly increased resting energy expenditure, whole-body glucose disposal, plasma glucose oxidation, and insulin sensitivity in the BAT(+) group only. These results demonstrate a physiologically significant role of BAT in whole-body energy expenditure, glucose homeostasis, and insulin sensitivity in humans, and support the notion that BAT may function as an antidiabetic tissue in humans.
Iron deficiency anemia is known to impair cognitive and psychomotor development. The zinc protoporphyrin/heme (ZPP/H) ratio is a simple, accurate, and sensitive laboratory screening test that detects ...early iron depletion before the onset of anemia. The objective of this work was to evaluate this test in a primary pediatric practice setting.
The iron status of a cohort of 361 children was screened during routine examinations at a community pediatric practice. Whole blood hemoglobin concentration, hematocrit ratio, serum transferrin saturation, ferritin concentration, and the ZPP/H ratio were measured. The ZPP/H ratio then was evaluated as a single indicator of iron status by comparing it with other tests for detecting the onset of iron deficiency and for monitoring recovery after iron supplementation.
Significant age- and sex-related differences in the ZPP/H ratio were found. In this cohort, serum ferritin concentration and the ZPP/H ratio independently identified the same fraction of iron-deficient patients (3%-4%), and both tests were more specific than was either hemoglobin or hematocrit. A concordance of three iron status parameters changed the prediction of iron deficiency to </=1%. Children <3 years of age and adolescent girls had significantly higher ZPP/H results.
The prevalence of iron deficiency anemia in the typical healthy American pediatric population is low, but iron deficiency without anemia remains relatively common at some stages of development. Increase in the ZPP/H ratio is demonstrated to be a sensitive, specific, and cost-effective test for identifying preanemic iron deficiency in a community pediatric practice. anemia, nutrition, development.
A nested case-control study was conducted to assess the relation between serum levels of selenium and retinol and the subsequent risk of cancer. During the years 1972-1984, in northwest Washington ...State, 156 cases of cancer were identified among members of two employee cohorts from whom specimens had been previously obtained and stored. Two hundred eighty-seven controls were selected from these cohorts and matched to cases on the basis of employer, age, sex, race, and date of blood draw. Selenium and retinol levels were measured by neutron activation and high pressure liquid chromatography, respectively. Information on known cancer risk factors was collected by telephone interviews of subjects and next of kin. Levels of selenium and retinol were unassociated with the incidence of cancer of all sites combined, both overall and within subgroups defined by age, sex, levels of the other micronutrient, time between blood draw and diagnosis, smoking status, and family history of cancer. These findings suggest that neither serum levels of selenium nor those of retinol have an appreciable effect on the risk of cancer.
OBJECTIVE: Increased zinc protoporphyrin/heme (ZPP/H) ratio has been used in pediatrics to screen for iron deficiency and lead poisoning. This study was conducted to determine whether common ...hereditary hemoglobin disorders (α- and β-thalassemia traits, hemoglobin E) found in U.S. minority groups are associated with an increase in the ZPP/H ratio in an iron-sufficient population.
METHODS: The database was compiled from hemoglobinopathy screens performed between 1987 and 1993 at a regional referral laboratory in Washington State. ZPP/H ratio and hemoglobin type were obtained for 326 subjects between the ages of 15 and 49 years of age who were iron sufficient (serum ferritin levels ≥50 μg/L).
RESULTS: The mean ZPP/H ratio was significantly higher (
p <0.01) for subjects with β-thalassemia trait (87 ± 32 μmol/mol), α-thalassemia trait (73 ± 37 μmol/mol), and hemoglobin E disorders (73 ± 24 μmol/mol) than for subjects with normal hemoglobin values (60 ± 8 μmol/mol). Fifty-one percent of subjects with β-thalassemia trait, 22% with hemoglobin E, and 20% with α-thalassemia trait had elevated ZPP/H ratios (>80 μmol/mol), compared with only 1.5% with normal hemoglobin values.
CONCLUSIONS: The ZPP/H ratio is elevated in common hereditary hemoglobin disorders that mimic the microcytic anemia of iron deficiency, even in individuals without associated nutritional iron deficiency. For children who are treated for presumed iron deficiency, failure of the ZPP/H ratio to return to normal after adequate iron treatment, especially if microcytosis persists, indicates that a hereditary hemoglobin disorder may be present. (J P
EDIATR 1996;129:105-10)
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