6,923 research outputs found
The question of ‘alternatives’ within food and drink markets and marketing: introduction to the special issue
The question of 'alternatives' within food and drink markets and marketing: introduction to the special issu
Revealing charge-tunneling processes between a quantum dot and a superconducting island through gate sensing
We report direct detection of charge-tunneling between a quantum dot and a
superconducting island through radio-frequency gate sensing. We are able to
resolve spin-dependent quasiparticle tunneling as well as two-particle
tunneling involving Cooper pairs. The quantum dot can act as an RF-only sensor
to characterize the superconductor addition spectrum, enabling us to access
subgap states without transport. Our results provide guidance for future
dispersive parity measurements of Majorana modes, which can be realized by
detecting the parity-dependent tunneling between dots and islands.Comment: 6 pages, 4 figures, supplemental material included as ancillary fil
Resting state correlates of subdimensions of anxious affect
Resting state fMRI may help identify markers of risk for affective disorder. Given the comorbidity of anxiety and depressive disorders and the heterogeneity of these disorders as defined by DSM, an important challenge is to identify alterations in resting state brain connectivity uniquely associated with distinct profiles of negative affect. The current study aimed to address this by identifying differences in brain connectivity specifically linked to cognitive and physiological profiles of anxiety, controlling for depressed affect. We adopted a two-stage multivariate approach. Hierarchical clustering was used to independently identify dimensions of negative affective style and resting state brain networks. Combining the clustering results, we examined individual differences in resting state connectivity uniquely associated with subdimensions of anxious affect, controlling for depressed affect. Physiological and cognitive subdimensions of anxious affect were identified. Physiological anxiety was associated with widespread alterations in insula connectivity, including decreased connectivity between insula subregions and between the insula and other medial frontal and subcortical networks. This is consistent with the insula facilitating communication between medial frontal and subcortical regions to enable control of physiological affective states. Meanwhile, increased connectivity within a frontoparietal-posterior cingulate cortex-precunous network was specifically associated with cognitive anxiety, potentially reflecting increased spontaneous negative cognition (e.g., worry). These findings suggest that physiological and cognitive anxiety comprise subdimensions of anxiety-related affect and reveal associated alterations in brain connectivity
The housing first model (HFM) fidelity index: designing and testing a tool for measuring integrity of housing programs that serve active substance users
Background
The Housing First Model (HFM) is an approach to serving formerly homeless individuals with dually diagnosed mental health and substance use disorders regardless of their choice to use substances or engage in other risky behaviors. The model has been widely diffused across the United States since 2000 as a result of positive findings related to consumer outcomes. However, a lack of clear fidelity guidelines has resulted in inconsistent implementation. The research team and their community partner collaborated to develop a HFM Fidelity Index. We describe the instrument development process and present results from its initial testing.
Methods
The HFM Fidelity Index was developed in two stages: (1) a qualitative case study of four HFM organizations and (2) interviews with 14 HFM "users". Reliability and validity of the index were then tested through phone interviews with staff members of permanent housing programs. The final sample consisted of 51 programs (39 Housing First and 12 abstinence-based) across 35 states.
Results
The results provided evidence for the overall reliability and validity of the index.
Conclusions
The results demonstrate the index’s ability to discriminate between housing programs that employ different service approaches. Regarding practice, the index offers a guide for organizations seeking to implement the HFM
Impact of Short-Range Scattering on the Metallic Transport of Strongly Correlated 2D Holes in GaAs Quantum Wells
Understanding the non-monotonic behavior in the temperature dependent
resistance, R(T), of strongly correlated two-dimensional (2D) carriers in clean
semiconductors has been a central issue in the studies of 2D metallic states
and metal-insulator-transitions. We have studied the transport of high mobility
2D holes in 20nm wide GaAs quantum wells (QWs) with varying short-range
disorder strength by changing the Al fraction x in the Al_xGa_{1-x}As barrier.
Via varying the short range interface roughness and alloy scattering, it is
observed that increasing x suppresses both the strength and characteristic
temperature scale of the 2D metallicity, pointing to the distinct role of
short-range versus long-range disorder in the 2D metallic transport in this
correlated 2D hole system with interaction parameter r_s~ 20.Comment: accepted for publication in Phys Rev
Evolution of Mass Outflow in Protostars
We have surveyed 84 Class 0, Class I, and flat-spectrum protostars in
mid-infrared [Si II], [Fe II] and [S I] line emission, and 11 of these in
far-infrared [O I] emission. We use the results to derive their mass outflow
rates. Thereby we observe a strong correlation of mass outflow rates with
bolometric luminosity, and with the inferred mass accretion rates of the
central objects, which continues through the Class 0 range the trend observed
in Class II young stellar objects. Along this trend from large to small
mass-flow rates, the different classes of young stellar objects lie in the
sequence Class 0 -- Class I/flat-spectrum -- Class II, indicating that the
trend is an evolutionary sequence in which mass outflow and accretion rates
decrease together with increasing age, while maintaining rough proportionality.
The survey results include two which are key tests of magnetocentrifugal
outflow-acceleration mechanisms: the distribution of the outflow/accretion
branching ratio b, and limits on the distribution of outflow speeds. Neither
rule out any of the three leading outflow-acceleration,
angular-momentum-ejection mechanisms, but they provide some evidence that disk
winds and accretion-powered stellar winds (APSWs) operate in many protostars.
An upper edge observed in the branching-ratio distribution is consistent with
the upper bound of b = 0.6 found in models of APSWs, and a large fraction
(0.31) of the sample have branching ratio sufficiently small that only disk
winds, launched on scales as large as several AU, have been demonstrated to
account for them.Comment: Version submitted to ApJ: 36 pages, 3 tables, 8 figure
Hubble Space Telescope Observations of the Draco Dwarf Spheroidal
We present an F606W-F814W color-magnitude diagram for the Draco dwarf
spheroidal galaxy based on Hubble Space Telescope WFPC2 images. The luminosity
function is well-sampled to 3 magnitudes below the turn-off. We see no evidence
for multiple turnoffs and conclude that, at least over the field of the view of
the WFPC2, star formation was primarily single-epoch. If the observed number of
blue stragglers is due to extended star formation, then roughly 6% (upper
limit) of the stars could be half as old as the bulk of the galaxy. The color
difference between the red giant branch and the turnoff is consistent with an
old population and is very similar to that observed in the old, metal-poor
Galactic globular clusters M68 and M92. Despite its red horizontal branch,
Draco appears to be older than M68 and M92 by 1.6 +/- 2.5 Gyrs, lending support
to the argument that the ``second parameter'' which governs horizontal branch
morphology must be something other than age. Draco's observed luminosity
function is very similar to that of M68, and the derived initial mass function
is consistent with that of the solar neighborhood.Comment: 16 pages, AASTeX, 9 postscript figures, figures 1 and 2 available at
ftp://bb3.jpl.nasa.gov/pub/draco/. Accepted for publication in the
Astronomical Journa
Observations and Implications of the Star Formation History of the LMC
We present derivations of star formation histories based on color-magnitude
diagrams of three fields in the LMC from HST/WFPC2 observations. A significant
component of stars older than 4 Gyr is required to match the observed
color-magnitude diagrams. Models with a dispersion-free age-metallicity
relation are unable to reproduce the width of the observed main sequence;
models with a range of metallicity at a given age provide a much better fit.
Such models allow us to construct complete ``population boxes'' for the LMC
based entirely on color-magnitude diagrams; remarkably, these qualitatively
reproduce the age-metallicity relation observed in LMC clusters. We discuss
some of the uncertainties in deriving star formation histories. We find,
independently of the models, that the LMC bar field has a larger relative
component of older stars than the outer fields. The main implications suggested
by this study are: 1) the star formation history of field stars appears to
differ from the age distribution of clusters, 2) there is no obvious evidence
for bursty star formation, but our ability to measure bursts shorter in
duration than 25% of any given age is limited by the statistics of the
observed number of stars, 3) there may be some correlation of the star
formation rate with the last close passage of the LMC/SMC/Milky Way, but there
is no dramatic effect, and 4) the derived star formation history is probably
consistent with observed abundances, based on recent chemical evolution models.Comment: Accepted by AJ, 36 pages including 12 figure
WFPC2 Observations of the Cooling Flow Elliptical in Abell 1795
We present WFPC2 images of the core of the cooling flow cD galaxy in Abell
1795. An irregular, asymmetric dust lane extends 7 \h75 kpc in projection to
the north-northwest. The dust shares the morphology observed in the H
and excess UV emission. We see both diffuse and knotty blue emission around the
dust lane, especially at the ends. The dust and emission features lie on the
edge of the radio lobes, suggesting star formation induced by the radio source
or the deflection of the radio jets off of pre-existing dust and gas. We
measure an apparent R significantly less than 3.1, implying that the
extinction law is not Galactic in the dust lane, or the presence of line
emission which is proportional to the extinction. The dust mass is at least
2 M\solar\ and is more likely to be 6.5 M\solar.Comment: 14 pages, LaTeX, Figure 4 included, Postscript Figs. 1-3 available at
ftp://astro.nmsu.edu/pub/JASON/A1795/, accepted for publication in ApJ
Letter
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