763 research outputs found
Hubble Space Telescope Wide Field Camera 3 Identifies an = 1 Kpc Dual Active Galactic Nucleus in the Minor Galaxy Merger SDSS J0924+0510 at z = 0.1495
Kiloparsec-scale dual active galactic nuclei (AGNs) are active supermassive
black hole pairs co-rotating in galaxies with separations of less than a few
kpc. Expected to be a generic outcome of hierarchical galaxy formation, their
frequency and demographics remain uncertain. We have carried out an imaging
survey with the Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) of AGNs
with double-peaked narrow [O III] emission lines. HST/WFC3 offers high image
quality in the near-infrared (NIR) to resolve the two stellar nuclei, and in
the optical to resolve [O III] from ionized gas in the narrow-line regions.
This combination has proven to be key in sorting out alternative scenarios.
With HST/WFC3 we are able to explore a new population of close dual AGNs at
more advanced merger stages than can be probed from the ground. Here we show
that the AGN SDSS J0924+0510, which had previously shown two stellar bulges,
contains two spatially distinct [O III] regions consistent with a dual AGN.
While we cannot completely exclude cross-ionization from a single central
engine, the nearly equal ratios of [O III] strongly suggest a dual AGN with a
projected angular separation of 0."4, corresponding to a projected physical
separation of = 1 kpc at redshift z = 0.1495. This serves as a proof of
principle for combining high-resolution NIR and optical imaging to identify
close dual AGNs. Our result suggests that studies based on low-resolution
and/or low-sensitivity observations may miss close dual AGNs and thereby may
underestimate their occurrence rate on kpc scales.Comment: 11 pages, 8 figures; ApJ in pres
Chandra X-ray and Hubble Space Telescope Imaging of Optically Selected kiloparsec-Scale Binary Active Galactic Nuclei I. Nature of the Nuclear Ionizing Sources
Kiloparsec-scale binary active galactic nuclei (AGNs) signal active
supermassive black hole (SMBH) pairs in merging galaxies. Despite their
significance, unambiguously confirmed cases remain scarce and most have been
discovered serendipitously. In a previous systematic search, we optically
identified four kpc-scale binary AGNs from candidates selected with
double-peaked narrow emission lines at redshifts of 0.1--0.2. Here we present
Chandra and Hubble Space Telescope Wide Field Camera 3 (WFC3) imaging of these
four systems. We critically examine and confirm the binary-AGN scenario for two
of the four targets, by combining high angular resolution X-ray imaging
spectroscopy with Chandra ACIS-S, better nuclear position constraints from WFC3
F105W imaging, and direct starburst estimates from WFC3 F336W imaging; for the
other two targets, the existing data are still consistent with the binary-AGN
scenario, but we cannot rule out the possibility of only one AGN ionizing gas
in both merging galaxies. We find tentative evidence for a systematically
smaller X-ray-to-[O III] luminosity ratio and/or higher Compton-thick fraction
in optically selected kpc-scale binary AGNs than in single AGNs, possibly
caused by a higher nuclear gas column due to mergers and/or a viewing angle
bias related to the double-peak narrow line selection. While our result lends
some further support to the general approach of optically identifying kpc-scale
binary AGNs, it also highlights the challenge and ambiguity of X-ray
confirmation.Comment: 18 emulateapj pages, 5 figures, ApJ in pres
Free Farm Produce in the Outpatient Psychiatry Waiting Room: A Feasibility Study
Background: People with mental illness suffer worse physical health and die significantly earlier than do those in the general population. Preventable cardiovascular disease is the most common cause of morbidity and mortality among this patient population. There is inadequate access to minimally disruptive health services tailored for the psychiatric patient population. Methods: The intervention brings free vegetables and eggs from the Farm at Penny Lane (Pittsboro, NC) to a local outpatient mental health clinic (Carrboro, NC). The intervention also incorporates education on healthy eating for patients in the clinic waiting room. Using observational data and survey data, I collected feedback on the feasibility and acceptability of this intervention from patients, clinic staff, farm staff, and medical students. Results: All stakeholders rated the service favorably. Suggestions for improvement included organizing recipe demonstrations, recruiting more volunteers to help at the farm, and providing more bags for patients to carry the produce. Medical students noted lack of time to be the main obstacle to helping implement the intervention. Conclusion: While the intervention received favorable feedback, more rigorous effectiveness research will help better characterize the specific strengths of the intervention and their effects on long-term health outcomes. Future iterations may consider adding more research personnel and employing a different research design. Researchers interested in pursuing such interventions will need to consider the culture of the study community, existing infrastructure and resources, and research designs that will best fit the main objective of their study.Master of Public Healt
Biochemical and Genetic Conservation of Fission Yeast DSK1 and Human SRPK1
Arginine/serine-rich (RS) domain-containing proteins and their phosphorylation by specific protein kinases constitute control circuits to regulate pre-mRNA splicing and coordinate splicing with transcription in mammalian cells. We present here the finding that similar SR networks exist in Schizosaccharomyces pombe. We previously showed that Dsk1 protein, originally described as a mitotic regulator, displays high activity in phosphorylating S. pombe Prp2 protein (spU2AF59), a homologue of human U2AF65. We now demonstrate that Dsk1 also phosphorylates two recently identified fission yeast proteins with RS repeats, Srp1 and Srp2, in vitro. The phosphorylated proteins bear the same phosphoepitope found in mammalian SR proteins. Consistent with its substrate specificity, Dsk1 forms kinase-competent complexes with those proteins. Furthermore, dsk1+ gene determines the phenotype of prp2+ overexpression, providing in vivo evidence that Prp2 is a target for Dsk1. The dsk1-null mutant strain became severely sick with the additional deletion of a related kinase gene. Significantly, human SR protein-specific kinase 1 (SRPK1) complements the growth defect of the double-deletion mutant. In conjunction with the resemblance of dsk1+ and SRPK1 in sequence homology, biochemical properties, and overexpression phenotypes, the complementation result indicates that SRPK1 is a functional homologue of Dsk1. Collectively, our studies illustrate the conserved SR networks in S. pombe consisting of RS domain-containing proteins and SR protein-specific kinases and thus establish the importance of the networks in eucaryotic organisms
The Sloan Digital Sky Survey Reverberation Mapping Project: Post-Starburst Signatures in Quasar Host Galaxies at z < 1
Quasar host galaxies are key for understanding the relation between galaxies
and the supermassive black holes (SMBHs) at their centers. We present a study
of 191 broad-line quasars and their host galaxies at z < 1, using high
signal-to-noise ratio (SNR) spectra produced by the Sloan Digital Sky Survey
Reverberation Mapping project. Clear detection of stellar absorption lines
allows a reliable decomposition of the observed spectra into nuclear and host
components, using spectral models of quasar and stellar radiations as well as
emission lines from the interstellar medium. We estimate age, mass (M*), and
velocity dispersion (sigma*) of the host stars, the star formation rate (SFR),
quasar luminosity, and SMBH mass (Mbh), for each object. The quasars are
preferentially hosted by massive galaxies with M* ~ 10^{11} Msun characterized
by stellar ages around a billion years, which coincides with the transition
phase of normal galaxies from the blue cloud to the red sequence. The host
galaxies have relatively low SFRs and fall below the main sequence of
star-forming galaxies at similar redshifts. These facts suggest that the hosts
have experienced an episode of major star formation sometime in the past
billion years, which was subsequently quenched or suppressed. The derived Mbh -
sigma* and Mbh - M* relations agree with our past measurements and are
consistent with no evolution from the local Universe. The present analysis
demonstrates that reliable measurements of stellar properties of quasar host
galaxies are possible with high-SNR fiber spectra, which will be acquired in
large numbers with future powerful instruments such as the Subaru Prime Focus
Spectrograph.Comment: ApJ in pres
Effect of Ca2+ on the Steady-State and Time-Resolved Emission Properties of the Genetically Encoded Fluorescent Sensor CatchER
We previously designed a calcium sensor CatchER (a GFP-based Calcium sensor for detecting high concentrations in the high calcium concentration environment such as ER) with a capability for monitoring calcium ion responses in various types of cells. Calcium binding to CatchER induces the ratiometric changes in the absorption spectra, as well as an increase in fluorescence emission at 510 nm upon excitation at both 395 and 488 nm. Here, we have applied the combination of the steady-state and time-resolved optical methods and Hydrogen/Deuterium isotope exchange to understand the origin of such calcium-induced optical property changes of CatchER. We first demonstrated that calcium binding results in a 44% mean fluorescence lifetime increase of the indirectly excited anionic chromophore. Thus, CatchER is the first protein-based calcium indicator with the single fluorescent moiety to show the direct correlation between the lifetime and calcium binding. Calcium exhibits a strong inhibition on the excited-state proton transfer nonadiabatic geminate recombination in protic (vs deuteric) medium. Analysis of CatchER crystal structures and the MD simulations reveal the proton transfer mechanism in which the disrupted proton migration path in CatchER is rescued by calcium binding. Our finding provides important insights for a strategy to design calcium sensors and suggests that CatchER could be a useful probe for FLIM imaging of calcium in situ
Cardiovascular safety of exenatide BID: an integrated analysis from controlled clinical trials in participants with type 2 diabetes
It is important for patients that treatments for diabetes not increase cardiovascular (CV) risk. The objective of this analysis was to examine retrospectively the CV safety of exenatide BID, a GLP-1 receptor agonist approved for treating hyperglycemia in patients with type 2 diabetes not adequately controlled with diet and exercise. Individual participant data was pooled to assess the relative risk (RR) of CV events with exenatide BID versus a pooled comparator (PC) group treated with either placebo or insulin from 12 controlled, randomized, clinical trials ranging from 12-52 weeks. Mean baseline values for HbA1c (8.33-8.38%), BMI (31.3-31.5 kg/m2), and duration of diabetes (8 y) were similar between groups. Trials included patients with histories of microvascular and/or macrovascular disease. Customized primary major adverse CV events (MACE) included stroke, myocardial infarction, cardiac mortality, acute coronary syndrome, and revascularization procedures. The Primary MACE RR (0.7; 95% CI 0.38, 1.31), calculated by the Mantel-Haenszel method (stratified by study), suggested that exenatide use (vs. PC) did not increase CV risk; this result was consistent across multiple analytic methods. Because the trials were not designed to assess CV outcomes, events were identified retrospectively from a list of preferred terms by physicians blinded to treatment. Other limitations included the low number of CV events, the short duration of trials (≤1 y), and a single active comparator (insulin). The results of these analyses are consistent with those of a recent retrospective analysis of a large insurance database that found that patients treated with exenatide twice daily were less likely to have a CV event than were patients treated with other glucose-lowering therapies
The Sloan Digital Sky Survey Reverberation Mapping Project: Velocity Shifts of Quasar Emission Lines
Quasar emission lines are often shifted from the systemic velocity due to
various dynamical and radiative processes in the line-emitting region. The
level of these velocity shifts depends both on the line species and on quasar
properties. We study velocity shifts for the line peaks of various narrow and
broad quasar emission lines relative to systemic using a sample of 849 quasars
from the Sloan Digital Sky Survey Reverberation Mapping (SDSS-RM) project. The
coadded (from 32 epochs) spectra of individual quasars have sufficient
signal-to-noise ratio (SNR) to measure stellar absorption lines to provide
reliable systemic velocity estimates, as well as weak narrow emission lines.
The sample also covers a large dynamic range in quasar luminosity (~2 dex),
allowing us to explore potential luminosity dependence of the velocity shifts.
We derive average line peak velocity shifts as a function of quasar luminosity
for different lines, and quantify their intrinsic scatter. We further quantify
how well the peak velocity can be measured for various lines as a function of
continuum SNR, and demonstrate there is no systematic bias in the line peak
measurements when the spectral quality is degraded to as low as SNR~3 per SDSS
pixel. Based on the observed line shifts, we provide empirical guidelines on
redshift estimation from [OII]3728, [OIII]5008, [NeV]3426, MgII, CIII],
HeII1640, broad Hbeta, CIV, and SiIV, which are calibrated to provide unbiased
systemic redshifts in the mean, but with increasing intrinsic uncertainties of
46, 56, 119, 205, 233, 242, 400, 415, and 477 km/s, in addition to the
measurement uncertainties. These more realistic redshift uncertainties are
generally much larger than the formal uncertainties reported by the redshift
pipelines for spectroscopic quasar surveys, and demonstrate the infeasibility
of measuring quasar redshifts to better than ~200 km/s with only broad lines.Comment: matched to the published version; minor changes and conclusions
unchange
Mendelian randomization shows a causal effect of low vitamin D on multiple sclerosis risk.
ObjectiveWe sought to estimate the causal effect of low serum 25(OH)D on multiple sclerosis (MS) susceptibility that is not confounded by environmental or lifestyle factors or subject to reverse causality.MethodsWe conducted mendelian randomization (MR) analyses using an instrumental variable (IV) comprising 3 single nucleotide polymorphisms found to be associated with serum 25(OH)D levels at genome-wide significance. We analyzed the effect of the IV on MS risk and both age at onset and disease severity in 2 separate populations using logistic regression models that controlled for sex, year of birth, smoking, education, genetic ancestry, body mass index at age 18-20 years or in 20s, a weighted genetic risk score for 110 known MS-associated variants, and the presence of one or more HLA-DRB1*15:01 alleles.ResultsFindings from MR analyses using the IV showed increasing levels of 25(OH)D are associated with a decreased risk of MS in both populations. In white, non-Hispanic members of Kaiser Permanente Northern California (1,056 MS cases and 9,015 controls), the odds ratio (OR) was 0.79 (p = 0.04, 95% confidence interval (CI): 0.64-0.99). In members of a Swedish population from the Epidemiological Investigation of Multiple Sclerosis and Genes and Environment in Multiple Sclerosis MS case-control studies (6,335 cases and 5,762 controls), the OR was 0.86 (p = 0.03, 95% CI: 0.76-0.98). A meta-analysis of the 2 populations gave a combined OR of 0.85 (p = 0.003, 95% CI: 0.76-0.94). No association was observed for age at onset or disease severity.ConclusionsThese results provide strong evidence that low serum 25(OH)D concentration is a cause of MS, independent of established risk factors
- …