1,911 research outputs found
Mental Health And The Role Of The States
Researchers from the State Health Care Spending Project -- a collaboration between The Pew Charitable Trusts and the John D. and Catherine T. MacArthur Foundation -- sought to better understand the country's mental health challenges and, in particular, the states' role in addressing them. The project found that:In 2013, approximately 44 million adults -- 18.5 percent of the population 18 and older -- were classified as having a mental illness. Of these, 10 million had a serious mental illness. The rate of serious mental illness varied from state to state.In 2009, the most recent year for which national mental health data are available, 22 billion (15 percent) in 2009. This total does not include state and local Medicaid expenditures. Counting those contributions brings total state and local spending up to $35.5 billion (24 percent).This report is intended to help federal, state, and local policymakers working to address the country's mental health challenges to better understand their prevalence, treatment, and funding trends
The Sloan Lens ACS Survey. IX. Colors, Lensing and Stellar Masses of Early-type Galaxies
We present the current photometric dataset for the Sloan Lens ACS (SLACS)
Survey, including HST photometry from ACS, WFPC2, and NICMOS. These data have
enabled the confirmation of an additional 15 grade `A' (certain) lens systems,
bringing the number of SLACS grade `A' lenses to 85; including 13 grade `B'
(likely) systems, SLACS has identified nearly 100 lenses and lens candidates.
Approximately 80% of the grade `A' systems have elliptical morphologies while
~10% show spiral structure; the remaining lenses have lenticular morphologies.
Spectroscopic redshifts for the lens and source are available for every system,
making SLACS the largest homogeneous dataset of galaxy-scale lenses to date. We
have developed a novel Bayesian stellar population analysis code to determine
robust stellar masses with accurate error estimates. We apply this code to
deep, high-resolution HST imaging and determine stellar masses with typical
statistical errors of 0.1 dex; we find that these stellar masses are unbiased
compared to estimates obtained using SDSS photometry, provided that informative
priors are used. The stellar masses range from 10^10.5 to 10^11.8 M and
the typical stellar mass fraction within the Einstein radius is 0.4, assuming a
Chabrier IMF. The ensemble properties of the SLACS lens galaxies, e.g. stellar
masses and projected ellipticities, appear to be indistinguishable from other
SDSS galaxies with similar stellar velocity dispersions. This further supports
that SLACS lenses are representative of the overall population of massive
early-type galaxies with M* >~ 10^11 M, and are therefore an ideal
dataset to investigate the kpc-scale distribution of luminous and dark matter
in galaxies out to z ~ 0.5.Comment: 20 pages, 18 figures, 5 tables, published in Ap
An enhanced surface passivation effect in InGaN/GaN disk-in-nanowire light emitting diodes for mitigating Shockley-Read-Hall recombination
We present a detailed study of the effects of dangling bond passivation and the comparison of different sulfide passivation processes on the properties of InGaN/GaN quantum-disk (Qdisk)-in-nanowire based light emitting diodes (NW-LEDs). Our results demonstrated the first organic sulfide passivation process for nitride nanowires (NWs). The results from Raman spectroscopy, photoluminescence (PL) measurements, and X-ray photoelectron spectroscopy (XPS) showed that octadecylthiol (ODT) effectively passivated the surface states, and altered the surface dynamic charge, and thereby recovered the band-edge emission. The effectiveness of the process with passivation duration was also studied. Moreover, we also compared the electro-optical performance of NW-LEDs emitting at green wavelength before and after ODT passivation. We have shown that the Shockley–Read–Hall (SRH) non-radiative recombination of NW-LEDs can be greatly reduced after passivation by ODT, which led to a much faster increasing trend of quantum efficiency and higher peak efficiency. Our results highlighted the possibility of employing this technique to further design and produce high performance NW-LEDs and NW-lasers
Further evidence for large central mass-to-light ratios in early-type galaxies: the case of ellipticals and lenticulars in the Abell~262 cluster
We present radially resolved spectroscopy of 8 early-type galaxies in
Abell~262, measuring rotation, velocity dispersion, and
coefficients along three axes, and line-strength index profiles of Mg, Fe and
H. Ionized-gas velocity and velocity dispersion is included for 6
galaxies. We derive dynamical mass-to-light ratios and dark matter densities
from orbit-based dynamical models, complemented by the galaxies' ages,
metallicities, and -elements abundances. Four galaxies have significant
dark matter with halos about 10 times denser than in spirals of the same
stellar mass. Using dark matter densities and cosmological simulations,
assembly redshifts \zdm\approx 1-3, which we found earlier for Coma. The
dynamical mass following the light is larger than expected for a Kroupa stellar
IMF, especially in galaxies with high velocity dispersion \sigeff inside the
effective radius \reff. This could indicate a `massive' IMF in massive
galaxies. Alternatively, some dark matter in massive galaxies could follow the
light closely. Combining with our comparison sample of Coma early-types, we now
have 5 of 24 galaxies where (1) mass follows light to 1-3\,\reff, (2) the
dynamical mass-to-light ratio {of all the mass that follows the light is large
( in the Kron-Cousins band), (3) the dark matter fraction is
negligible to 1-3\,\reff. Unless the IMF in these galaxies is particularly
`massive' and somehow coupled to the dark matter content, there seems a
significant degeneracy between luminous and dark matter in some early-type
galaxies. The role of violent relaxation is briefly discussed.Comment: 62 pages, 13 figures, 8 tables, accepted for publication in A
Hydrogen bonding in duplex DNA probed by DNP enhanced solid-state NMR N-H bond length measurements
Numerous biological processes and mechanisms depend on details of base pairing and hydrogen bonding in DNA. Hydrogen bonds are challenging to quantify by X-ray crystallography and cryo-EM due to difficulty of visualizing hydrogen atom locations but can be probed with site specificity by NMR spectroscopy in solution and the solid state with the latter particularly suited to large, slowly tumbling DNA complexes. Recently, we showed that low-temperature dynamic nuclear polarization (DNP) enhanced solid-state NMR is a valuable tool for distinguishing Hoogsteen base pairs (bps) from canonical Watson-Crick bps in various DNA systems under native-like conditions. Here, using a model 12-mer DNA duplex containing two central adenine-thymine (A-T) bps in either Watson-Crick or Hoogsteen confirmation, we demonstrate DNP solid-state NMR measurements of thymine N3-H3 bond lengths, which are sensitive to details of N-H···N hydrogen bonding and permit hydrogen bonds for the two bp conformers to be systematically compared within the same DNA sequence context. For this DNA duplex, effectively identical TN3-H3 bond lengths of 1.055 ± 0.011 Å and 1.060 ± 0.011 Å were found for Watson-Crick A-T and Hoogsteen A (syn)-T base pairs, respectively, relative to a reference amide bond length of 1.015 ± 0.010 Å determined for N-acetyl-valine under comparable experimental conditions. Considering that prior quantum chemical calculations which account for zero-point motions predict a somewhat longer effective peptide N-H bond length of 1.041 Å, in agreement with solution and solid-state NMR studies of peptides and proteins at ambient temperature, to facilitate direct comparisons with these earlier studies TN3-H3 bond lengths for the DNA samples can be readily scaled appropriately to yield 1.083 Å and 1.087 Å for Watson-Crick A-T and Hoogsteen A (syn)-T bps, respectively, relative to the 1.041 Å reference peptide N-H bond length. Remarkably, in the context of the model DNA duplex, these results indicate that there are no significant differences in N-H···N A-T hydrogen bonds between Watson-Crick and Hoogsteen bp conformers. More generally, high precision measurements of N-H bond lengths by low-temperature DNP solid-state NMR based methods are expected to facilitate detailed comparative analysis of hydrogen bonding for a range of DNA complexes and base pairing environments
Stellar populations of bulges at low redshift
This chapter summarizes our current understanding of the stellar population
properties of bulges and outlines important future research directions.Comment: Review article to appear in "Galactic Bulges", Editors: Laurikainen
E., Peletier R., Gadotti D., Springer Publishing. 34 pages, 12 figure
The SLUGGS Survey: Calcium Triplet-based Spectroscopic Metallicities for Over 900 Globular Clusters
Although the colour distribution of globular clusters in massive galaxies is
well known to be bimodal, the spectroscopic metallicity distribution has been
measured in only a few galaxies. After redefining the calcium triplet
index-metallicity relation, we use our relation to derive the metallicity of
903 globular clusters in 11 early-type galaxies. This is the largest sample of
spectroscopic globular cluster metallicities yet assembled. We compare these
metallicities with those derived from Lick indices finding good agreement. In 6
of the 8 galaxies with sufficient numbers of high quality spectra we find
bimodality in the spectroscopic metallicity distribution. Our results imply
that most massive early-type galaxies have bimodal metallicity, as well as
colour, distributions. This bimodality suggests that most massive galaxies
early-type galaxies experienced two periods of star formation.Comment: 23 pages, 13 figures. Accepted for publication in MNRAS. For more
information about the SLUGGS Survey please see http://sluggs.swin.edu.a
Clustering properties of galaxies selected in stellar mass: Breaking down the link between luminous and dark matter in massive galaxies from z=0 to z=2
We present a study on the clustering of a stellar mass selected sample of
18,482 galaxies with stellar masses M*>10^10M(sun) at redshifts 0.4<z<2.0,
taken from the Palomar Observatory Wide-field Infrared Survey. We examine the
clustering properties of these stellar mass selected samples as a function of
redshift and stellar mass, and discuss the implications of measured clustering
strengths in terms of their likely halo masses. We find that galaxies with high
stellar masses have a progressively higher clustering strength, and amplitude,
than galaxies with lower stellar masses. We also find that galaxies within a
fixed stellar mass range have a higher clustering strength at higher redshifts.
We furthermore use our measured clustering strengths, combined with models from
Mo & White (2002), to determine the average total masses of the dark matter
haloes hosting these galaxies. We conclude that for all galaxies in our sample
the stellar-mass-to-total-mass ratio is always lower than the universal
baryonic mass fraction. Using our results, and a compilation from the
literature, we furthermore show that there is a strong correlation between
stellar-mass-to-total-mass ratio and derived halo masses for central galaxies,
such that more massive haloes contain a lower fraction of their mass in the
form of stars over our entire redshift range. For central galaxies in haloes
with masses M(halo)>10^13M(sun) we find that this ratio is <0.02, much lower
than the universal baryonic mass fraction. We show that the remaining baryonic
mass is included partially in stars within satellite galaxies in these haloes,
and as diffuse hot and warm gas. We also find that, at a fixed stellar mass,
the stellar-to-total-mass ratio increases at lower redshifts. This suggests
that galaxies at a fixed stellar mass form later in lower mass dark matter
haloes, and earlier in massive haloes. We interpret this as a "halo downsizing"
effect, however some of this evolution could be attributed to halo assembly
bias.Comment: Accepted for publication in MNRAS. 19 pages, 8 figures and 3 tables
The Two Phases of Galaxy Formation
Cosmological simulations of galaxy formation appear to show a two-phase
character with a rapid early phase at z>2 during which in-situ stars are formed
within the galaxy from infalling cold gas followed by an extended phase since
z<3 during which ex-situ stars are primarily accreted. In the latter phase
massive systems grow considerably in mass and radius by accretion of smaller
satellite stellar systems formed at quite early times (z>3) outside of the
virial radius of the forming central galaxy. These tentative conclusions are
obtained from high resolution re-simulations of 39 individual galaxies in a
full cosmological context with present-day virial halo masses ranging from 7e11
M_sun h^-1 < M_vir < 2.7e13 M_sun h^-1 and central galaxy masses between 4.5e10
M_sun h^-1 < M_* < 3.6e11 M_sun h^-1. The simulations include the effects of a
uniform UV background, radiative cooling, star formation and energetic feedback
from SNII. The importance of stellar accretion increases with galaxy mass and
towards lower redshift. In our simulations lower mass galaxies (M_* > 1.7e11 M_sun h^-1) assembly is dominated by accretion and
merging with about 80 per cent of the stars added by the present-day. In
general the simulated galaxies approximately double their mass since z=1. For
massive systems this mass growth is not accompanied by significant star
formation. The majority of the in-situ created stars is formed at z>2,
primarily out of cold gas flows. We recover the observational result of
archaeological downsizing, where the most massive galaxies harbor the oldest
stars. We find that this is not in contradiction with hierarchical structure
formation. Most stars in the massive galaxies are formed early on in smaller
structures, the galaxies themselves are assembled late.Comment: 13 pages, 13 figures, accepted for publication in Ap
Stellar population gradients in brightest cluster galaxies
We present the stellar population and velocity dispersion gradients for a
sample of 24 brightest cluster galaxies (BCGs) in the nearby Universe for which
we have obtained high quality long-slit spectra at the Gemini telescopes. With
the aim of studying the possible connection between the formation of the BCGs
and their host clusters, we explore the relations between the stellar
population gradients and properties of the host clusters as well as the
possible connections between the stellar population gradients and other
properties of the galaxies. We find mean stellar population gradients (negative
{\Delta}[Z/H]/log r gradient of -0.285{\pm}0.064; small positive {\Delta}log
(age)/log r gradient of 0.069{\pm}0.049; and null {\Delta}[E/Fe]/log r gradient
of -0.008{\pm}0.032) that are consistent with those of normal massive
elliptical galaxies. However, we find a trend between metallicity gradients and
velocity dispersion (with a negative slope of -1.616{\pm}0.539) that is not
found for the most massive ellipticals. Furthermore, we find trends between the
metallicity gradients and K-band luminosities (with a slope of 0.173{\pm}0.081)
as well as the distance from the BCG to the X-ray peak of the host cluster
(with a slope of -7.546{\pm}2.752). The latter indicates a possible relation
between the formation of the cluster and that of the central galaxy.Comment: 23 pages, 18 figures, accepted for publication in MNRAS. arXiv admin
note: text overlap with arXiv:1104.2376v
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