18 research outputs found
The chemical abundance analysis of normal early A- and late B-type stars
Modern spectroscopy of early-type stars often aims at studying complex
physical phenomena. Comparatively less attention is paid to identifying and
studying the "normal" A- and B-type stars and testing how the basic atomic
parameters and standard spectral analysis allow one to fit the observations. We
wish to stablish whether the chemical composition of the solar photosphere can
be regarded as a reference for early A- and late B-type stars. We have obtained
optical high-resolution, high signal-to-noise ratio spectra of three slowly
rotating early-type stars (HD 145788, 21 Peg and pi Cet) that show no obvious
sign of chemical peculiarity, and performed a very accurate LTE abundance
analysis of up to 38 ions of 26 elements (for 21 Peg), using a vast amount of
spectral lines visible in the spectral region covered by our spectra. We
provide an exhaustive description of the abundance characteristics of the three
analysed stars with a critical review of the line parameters used to derive the
abundances. We compiled a table of atomic data for more than 1100 measured
lines that may be used in the future as a reference. The abundances we obtained
for He, C, Al, S, V, Cr, Mn, Fe, Ni, Sr, Y, and Zr are compatible with the
solar ones derived with recent 3D radiative-hydrodynamical simulations of the
solar photosphere. The abundances of the remaining studied elements show some
degree of discrepancy compared to the solar photosphere. Those of N, Na, Mg,
Si, Ca, Ti, and Nd may well be ascribed to non-LTE effects; for P, Cl, Sc and
Co, non-LTE effects are totally unknown; O, Ne, Ar, and Ba show discrepancies
that cannot be ascribed to non-LTE effects. The discrepancies obtained for O
(in two stars) and Ne agree with very recent non-LTE abundance analysis of
early B-type stars in the solar neighbourhood.Comment: Accepted for publication on Astronomy and Astrophysic
LSST: from Science Drivers to Reference Design and Anticipated Data Products
(Abridged) We describe here the most ambitious survey currently planned in
the optical, the Large Synoptic Survey Telescope (LSST). A vast array of
science will be enabled by a single wide-deep-fast sky survey, and LSST will
have unique survey capability in the faint time domain. The LSST design is
driven by four main science themes: probing dark energy and dark matter, taking
an inventory of the Solar System, exploring the transient optical sky, and
mapping the Milky Way. LSST will be a wide-field ground-based system sited at
Cerro Pach\'{o}n in northern Chile. The telescope will have an 8.4 m (6.5 m
effective) primary mirror, a 9.6 deg field of view, and a 3.2 Gigapixel
camera. The standard observing sequence will consist of pairs of 15-second
exposures in a given field, with two such visits in each pointing in a given
night. With these repeats, the LSST system is capable of imaging about 10,000
square degrees of sky in a single filter in three nights. The typical 5
point-source depth in a single visit in will be (AB). The
project is in the construction phase and will begin regular survey operations
by 2022. The survey area will be contained within 30,000 deg with
, and will be imaged multiple times in six bands, ,
covering the wavelength range 320--1050 nm. About 90\% of the observing time
will be devoted to a deep-wide-fast survey mode which will uniformly observe a
18,000 deg region about 800 times (summed over all six bands) during the
anticipated 10 years of operations, and yield a coadded map to . The
remaining 10\% of the observing time will be allocated to projects such as a
Very Deep and Fast time domain survey. The goal is to make LSST data products,
including a relational database of about 32 trillion observations of 40 billion
objects, available to the public and scientists around the world.Comment: 57 pages, 32 color figures, version with high-resolution figures
available from https://www.lsst.org/overvie
Coastal Upwelling Supplies Oxygen-Depleted Water to the Columbia River Estuary
Low dissolved oxygen (DO) is a common feature of many estuarine and shallow-water
environments, and is often attributed to anthropogenic nutrient enrichment from
terrestrial-fluvial pathways. However, recent events in the U.S. Pacific
Northwest have highlighted that wind-forced upwelling can cause naturally
occurring low DO water to move onto the continental shelf, leading to
mortalities of benthic fish and invertebrates. Coastal estuaries in the Pacific
Northwest are strongly linked to ocean forcings, and here we report observations
on the spatial and temporal patterns of oxygen concentration in the Columbia
River estuary. Hydrographic measurements were made from transect (spatial
survey) or anchor station (temporal survey) deployments over a variety of wind
stresses and tidal states during the upwelling seasons of 2006 through 2008.
During this period, biologically stressful levels of dissolved oxygen were
observed to enter the Columbia River estuary from oceanic sources, with minimum
values close to the hypoxic threshold of 2.0 mg L−1. Riverine
water was consistently normoxic. Upwelling wind stress controlled the timing and
magnitude of low DO events, while tidal-modulated estuarine circulation patterns
influenced the spatial extent and duration of exposure to low DO water. Strong
upwelling during neap tides produced the largest impact on the estuary. The
observed oxygen concentrations likely had deleterious behavioral and
physiological consequences for migrating juvenile salmon and benthic crabs.
Based on a wind-forced supply mechanism, low DO events are probably common to
the Columbia River and other regional estuaries and if conditions on the shelf
deteriorate further, as observations and models predict, Pacific Northwest
estuarine habitats could experience a decrease in environmental quality
Novel Blood Pressure Locus and Gene Discovery Using Genome-Wide Association Study and Expression Data Sets From Blood and the Kidney.
Elevated blood pressure is a major risk factor for cardiovascular disease and has a substantial genetic contribution. Genetic variation influencing blood pressure has the potential to identify new pharmacological targets for the treatment of hypertension. To discover additional novel blood pressure loci, we used 1000 Genomes Project-based imputation in 150 134 European ancestry individuals and sought significant evidence for independent replication in a further 228 245 individuals. We report 6 new signals of association in or near HSPB7, TNXB, LRP12, LOC283335, SEPT9, and AKT2, and provide new replication evidence for a further 2 signals in EBF2 and NFKBIA Combining large whole-blood gene expression resources totaling 12 607 individuals, we investigated all novel and previously reported signals and identified 48 genes with evidence for involvement in blood pressure regulation that are significant in multiple resources. Three novel kidney-specific signals were also detected. These robustly implicated genes may provide new leads for therapeutic innovation
The genetics of blood pressure regulation and its target organs from association studies in 342,415 individuals
To dissect the genetic architecture of blood pressure and assess effects on target-organ damage, we analyzed 128,272 SNPs from targeted and genome-wide arrays in 201,529 individuals of European ancestry and genotypes from an additional 140,886 individuals were used for validation. We identified 66 blood pressure loci, of which 17 were novel and 15 harbored multiple distinct association signals. The 66 index SNPs were enriched for cis-regulatory elements, particularly in vascular endothelial cells, consistent with a primary role in blood pressure control through modulation of vascular tone across multiple tissues. The 66 index SNPs combined in a risk score showed comparable effects in 64,421 individuals of non-European descent. The 66-SNP blood pressure risk score was significantly associated with target-organ damage in multiple tissues, with minor effects in the kidney. Our findings expand current knowledge of blood pressure pathways and highlight tissues beyond the classic renal system in blood pressure regulation
Effects of Anacetrapib in Patients with Atherosclerotic Vascular Disease
BACKGROUND:
Patients with atherosclerotic vascular disease remain at high risk for cardiovascular events despite effective statin-based treatment of low-density lipoprotein (LDL) cholesterol levels. The inhibition of cholesteryl ester transfer protein (CETP) by anacetrapib reduces LDL cholesterol levels and increases high-density lipoprotein (HDL) cholesterol levels. However, trials of other CETP inhibitors have shown neutral or adverse effects on cardiovascular outcomes.
METHODS:
We conducted a randomized, double-blind, placebo-controlled trial involving 30,449 adults with atherosclerotic vascular disease who were receiving intensive atorvastatin therapy and who had a mean LDL cholesterol level of 61 mg per deciliter (1.58 mmol per liter), a mean non-HDL cholesterol level of 92 mg per deciliter (2.38 mmol per liter), and a mean HDL cholesterol level of 40 mg per deciliter (1.03 mmol per liter). The patients were assigned to receive either 100 mg of anacetrapib once daily (15,225 patients) or matching placebo (15,224 patients). The primary outcome was the first major coronary event, a composite of coronary death, myocardial infarction, or coronary revascularization.
RESULTS:
During the median follow-up period of 4.1 years, the primary outcome occurred in significantly fewer patients in the anacetrapib group than in the placebo group (1640 of 15,225 patients [10.8%] vs. 1803 of 15,224 patients [11.8%]; rate ratio, 0.91; 95% confidence interval, 0.85 to 0.97; P=0.004). The relative difference in risk was similar across multiple prespecified subgroups. At the trial midpoint, the mean level of HDL cholesterol was higher by 43 mg per deciliter (1.12 mmol per liter) in the anacetrapib group than in the placebo group (a relative difference of 104%), and the mean level of non-HDL cholesterol was lower by 17 mg per deciliter (0.44 mmol per liter), a relative difference of -18%. There were no significant between-group differences in the risk of death, cancer, or other serious adverse events.
CONCLUSIONS:
Among patients with atherosclerotic vascular disease who were receiving intensive statin therapy, the use of anacetrapib resulted in a lower incidence of major coronary events than the use of placebo. (Funded by Merck and others; Current Controlled Trials number, ISRCTN48678192 ; ClinicalTrials.gov number, NCT01252953 ; and EudraCT number, 2010-023467-18 .)
Brain repair after stroke—a novel neurological model
Following stroke, patients are commonly left with debilitating motor and speech impairments. This article reviews the state of the art in neurological repair for stroke and proposes a new model for the future. We suggest that stroke treatment--from the time of the ictus itself to living with the consequences--must be fundamentally neurological, from limiting the extent of injury at the outset, to repairing the consequent damage. Our model links brain and behaviour by targeting brain circuits, and we illustrate the model though action observation treatment, which aims to enhance brain network connectivity. The model is based on the assumptions that the mechanisms of neural repair inherently involve cellular and circuit plasticity, that brain plasticity is a synaptic phenomenon that is largely stimulus-dependent, and that brain repair required both physical and behavioural interventions that are tailored to reorganize specific brain circuits. We review current approaches to brain repair after stroke and present our new model, and discuss the biological foundations, rationales, and data to support our novel approach to upper-extremity and language rehabilitation. We believe that by enhancing plasticity at the level of brain network interactions, this neurological model for brain repair could ultimately lead to a cure for stroke