364 research outputs found
Can Leaders Step Outside of the Gender Box? An Examination of Leadership and Gender Role Stereotypes
This study examined gender stereotypes for leaders using a more indirect method than is typical in stereotype research. Rather than reveal the leader\u27s gender, this study used vignettes in which the leader\u27s gender was unknown. Consistent with their hypothesis, the authors found that participants were more likely to infer a male (female) gender identity than a female (male) gender identity when presented with a leader using a masculine (feminine) style. They also hypothesized that a leader using a gender-consistent leadership style would be viewed more positively than a leader using a gender-inconsistent style. Contrary to this hypothesis, results revealed that men using a gender-inconsistent (feminine) style were actually evaluated more positively than men using a gender-consistent style. It is interesting that a perceived female leader who used a gender-inconsistent (masculine) style was evaluated more positively than a perceived male leader who used a masculine style, but only by female participants. Possible explanations for these results are discussed
The Characteristics of Northern Black Churches with Community Health Outreach Programs
OBJECTIVES. The Black church has a long history of addressing unmet health and human service needs, yet few studies have examined characteristics of churches involved in health promotion. METHODS. Data obtained from a survey of 635 Black churches in the northern United States were examined. Univariate and multivariate statistical procedures identified eight characteristics associated with community health outreach programs: congregation size, denomination, church age, economic class of membership, ownership of church, number of paid clergy, presence of other paid staff, and education level of the minister. RESULTS. A logistic regression model identified church size and educational level of the minister as the strongest predictors of church-sponsored community health outreach. The model correctly classified 88% of churches that conduct outreach programs. Overall, the model correctly classified 76% of churches in the sample. CONCLUSIONS. Results may be used by public health professionals and policy makers to enlist Black churches as an integral component for delivery of health promotion and disease prevention services needed to achieve the Year 2000 health objectives for all Americans
Exponential potentials and cosmological scaling solutions
We present a phase-plane analysis of cosmologies containing a barotropic
fluid with equation of state , plus a scalar
field with an exponential potential where . In addition to the well-known inflationary
solutions for in which the scalar field energy density tracks that of the barotropic
fluid (which for example might be radiation or dust). We show that the scaling
solutions are the unique late-time attractors whenever they exist. The
fluid-dominated solutions, where at late times, are
always unstable (except for the cosmological constant case ). The
relative energy density of the fluid and scalar field depends on the steepness
of the exponential potential, which is constrained by nucleosynthesis to
. We show that standard inflation models are unable to solve
this `relic density' problem.Comment: 6 pages RevTeX file with four figures incorporated (uses RevTeX and
epsf). Matches published versio
Magellan/M2FS and MMT/Hectochelle Spectroscopy of Dwarf Galaxies and Faint Star Clusters within the Galactic Halo
We present spectroscopic data for 16369 stellar targets within and/or toward
38 dwarf spheroidal galaxies and faint star clusters within the Milky Way halo
environment. All spectra come from observations with the multi-object,
fiber-fed echelle spectrographs M2FS at the Magellan/Clay telescope or
Hectochelle at the MMT, reaching a typical limiting magnitude G < 21. Data
products include processed spectra from all observations and catalogs listing
estimates -- derived from template model fitting -- of line-of-sight velocity
(median uncertainty 1.1 km/s) effective temperature (234 K), (base10 logarithm
of) surface gravity (0.52 dex in cgs units), [Fe/H] (0.38 dex) and [Mg/Fe]
(0.24 dex) abundance ratios. The sample contains multi-epoch measurements for
3720 sources, with up to 15 epochs per source, enabling studies of intrinsic
spectroscopic variability. The sample contains 6078 likely red giant stars
(based on surface gravity), and 4494 likely members (based on line-of-sight
velocity and Gaia-measured proper motion) of the target systems. The number of
member stars per individual target system ranges from a few, for the faintest
systems, to ~ 850 for the most luminous. For most systems, our new samples
extend over wider fields than have previously been observed; of the likely
members in our samples, 823 lie beyond twice the projected halflight radius of
their host system, and 42 lie beyond 5 Rhalf.Comment: Published September 2023 in The Astrophysical Journal Supplement
Series, processed spectra and catalogs publicly available at the Zenodo
database doi:10.5281/zenodo.783792
Spectroscopic Confirmation of the Sixth Globular Cluster in the Fornax Dwarf Spheroidal Galaxy
The Fornax dwarf spheroidal galaxy has an anomalous number of globular
clusters, five, for its stellar mass. There is a longstanding debate about a
potential sixth globular cluster (Fornax~6) that has recently been
`rediscovered' in DECam imaging. We present new Magellan/M2FS spectroscopy of
the Fornax~6 cluster and Fornax dSph. Combined with literature data we identify
members of the Fornax~6 cluster that this overdensity is indeed a
star cluster and associated with the Fornax dSph. The cluster is significantly
more metal-rich (mean metallicity of ) than
the other five Fornax globular clusters () and more
metal-rich than the bulk of Fornax. We measure a velocity dispersion of
corresponding to anomalously high
mass-to-light of 15M/L258 at 90\% confidence when calculated assuming
equilibrium. Two stars inflate this dispersion and may be either Fornax field
stars or as yet unresolved binary stars. Alternatively the Fornax~6 cluster may
be undergoing tidal disruption. Based on its metal-rich nature, the Fornax 6
cluster is likely younger than the other Fornax clusters, with an estimated age
of Gyr when compared to stellar isochrones. The chemodynamics and star
formation history of Fornax shows imprints of major events such as infall into
the Milky Way, multiple pericenter passages, star formation bursts, and/or
potential mergers or interactions. Any of these events may have triggered the
formation of the Fornax~6 cluster.Comment: 17 pages, 9 figures. Accepted to ApJ. Data catalogs included.
Comments welcom
A new view of k-essence
K-essence models, relying on scalar fields with non-canonical kinetic terms,
have been proposed as an alternative to quintessence in explaining the observed
acceleration of the Universe. We consider the use of field redefinitions to
cast k-essence in a more familiar form. While k-essence models cannot in
general be rewritten in the form of quintessence models, we show that in
certain dynamical regimes an equivalence can be made, which in particular can
shed light on the tracking behaviour of k-essence. In several cases, k-essence
cannot be observationally distinguished from quintessence using the homogeneous
evolution, though there may be small effects on the perturbation spectrum. We
make a detailed analysis of two k-essence models from the literature and
comment on the nature of the fine tuning arising in the models.Comment: 7 pages RevTeX4 file with four figures incorporate
Effective Iterative Techniques for Fingerprinting Design IP
Fingerprinting is an approach that assigns a unique
and invisible ID to each sold instance of the intellectual property
(IP). One of the key advantages fingerprinting-based intellectual
property protection (IPP) has over watermarking-based IPP is the
enabling of tracing stolen hardware or software. Fingerprinting
schemes have been widely and effectively used to achieve this goal;
however, their application domain has been restricted only to static
artifacts, such as image and audio, where distinct copies can be
obtained easily. In this paper, we propose the first generic fingerprinting
technique that can be applied to an arbitrary synthesis
(optimization or decision) or compilation problem and, therefore
to hardware and software IPs.
The key problem with design IP fingerprinting is that there is a
need to generate a large number of structurally unique but functionally
and timing identical designs. To reduce the cost of generating
such distinct copies, we apply iterative optimization in an incremental
fashion to solve a fingerprinted instance. Therefore, we
leverage on the optimization effort already spent in obtaining previous
solutions, yet we generate a uniquely fingerprinted new solution.
This generic approach is the basis for developing specific fingerprinting
techniques for four important problems in VLSI CAD:
partitioning, graph coloring, satisfiability, and standard-cell placement.
We demonstrate the effectiveness of the new fingerprinting-based
IPP techniques on a number of standard benchmarks
The Kinematics, Metallicities, and Orbits of Six Recently Discovered Galactic Star Clusters with Magellan/M2FS Spectroscopy
We present Magellan/M2FS spectroscopy of four recently discovered Milky Way
star clusters (Gran 3, Gran 4, Garro 01, LP 866) and two newly discovered open
clusters (Gaia 9, Gaia 10) at low Galactic latitudes. We measure line-of-sight
velocities and stellar parameters ([Fe/H], , , [Mg/Fe])
from high resolution spectroscopy centered on the Mg triplet and identify 20-80
members per star cluster. We determine the kinematics and chemical properties
of each cluster and measure the systemic proper motion and orbital properties
by utilizing Gaia astrometry. We find Gran 3 to be an old, metal-poor (mean
metallicity of [Fe/H]=-1.84) globular cluster located in the Galactic bulge on
a retrograde orbit. Gran 4 is an old, metal-poor ([Fe/H]}=-1.84) globular
cluster with a halo-like orbit that happens to be passing through the Galactic
plane. The orbital properties of Gran 4 are consistent with the proposed
LMS-1/Wukong and/or Helmi streams merger events. Garro 01 is an old, metal-rich
([Fe/H]=-0.30) globular cluster on a near circular orbit in the outer disk.
Gaia 9 and Gaia 10 are among the most distant known open clusters at
and most metal-poor with [Fe/H]~-0.50,-0.46 for Gaia
9 and Gaia 10, respectively. LP 866 is a nearby, metal-rich open cluster
([Fe/H]). The discovery and confirmation of multiple star clusters in
the Galactic plane shows the power of {\it Gaia} astrometry and the star
cluster census remains incomplete.Comment: 19 pages, 15 figures, submitted to MNRAS, associated data products
available at https://doi.org/10.5281/zenodo.780912
Stellar kinematics of dwarf galaxies from multi-epoch spectroscopy: application to Triangulum II
We present new MMT/Hectochelle spectroscopic measurements for 257 stars
observed along the line of sight to the ultra-faint dwarf galaxy Triangulum II.
Combining with results from previous Keck/DEIMOS spectroscopy, we obtain a
sample that includes 16 likely members of Triangulum II, with up to 10
independent redshift measurements per star. To this multi-epoch kinematic data
set we apply methodology that we develop in order to infer binary orbital
parameters from sparsely sampled radial velocity curves with as few as two
epochs. For a previously-identified (spatially unresolved) binary system in
Tri~II, we infer an orbital solution with period , semi-major axis , and a systemic velocity that we then use in the analysis of Tri~II's
internal kinematics. Despite this improvement in the modeling of binary star
systems, the current data remain insufficient to resolve the velocity
dispersion of Triangulum II. We instead find a 95% confidence upper limit of
Old Stellar Populations of the Small Magellanic Cloud
We present WFPC2 and ground-based VI photometry of NGC 121 and a nearby field
in the outer SMC. For NGC 121, we measure a true distance modulus of (m-M)0 =
18.96 +/- 0.04 (distance of 61.9 +/- 1.1 kpc), age of 10.6 +/- 0.5 Gyr,
metallicity of [Fe/H] = -1.03 +/- 0.06, and initial mass of 4.1 +/- 0.4 x 10^5
Msun, assuming a Salpeter IMF with lower cutoff at 0.1 Msun. In the outer SMC
field, we find evidence of stars covering a wide range of ages -- from 2 Gyr
old to at least 9-12 Gyr old. We have measured the distance, extinction, and
star formation history (past star formation rates and enrichment history) using
a CMD fitting algorithm. The distance modulus of the SMC is measured to be
(m-M)0 = 18.88 +/- 0.08, corresponding to a distance of 59.7 +/- 2.2 kpc. The
overall star formation rate appears to have been relatively constant over this
period, although there may be small gaps in the star forming activity too small
to be resolved. The lack of current star-forming activity is a selection
effect, as the field was intentionally chosen to avoid recent activity. The
mean metallicity of this field has increased from an average of [Fe/H] = -1.3
+/- 0.3 for stars older than 8 Gyr to [Fe/H] = -0.7 +/- 0.2 in the past 3 Gyr.Comment: 29 pages, 14 figures accepted for publication in Ap
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