322 research outputs found
Recommended from our members
Data Envelopment Analysis: Measurement of Educational Efficiency in Texas
The purpose of this study was to examine the efficiency of Texas public school districts through Data Envelopment Analysis. The Data Envelopment Analysis estimation method calculated and assigned efficiency scores to each of the 931 school districts considered in the study. The efficiency scores were utilized in two phases. First, the school district efficiency scores were combined with school district student achievement to evaluate effectiveness with efficiency. A framework was constructed to graph the scores on an x-axis of student achievement scores and a y-axis of efficiency scores to further illustrate the data. The framework was evaluated with the full statewide sample and with school districts categorized into similar peer groups. Then, using variables selected from related scholarly literature, a regression analysis identified which factors impacted school district efficiency statewide. The non-discretionary variables included in the study were total student enrollment, the percentage of non-white students and the percentage of economically disadvantaged students. The discretionary variables selected included the teacher-to-student ratio, teachers’ average years of experience, the percentage of teachers with master’s degrees and the average teacher base salary. Amongst the seven factors selected for regression analysis, five statistically significant variables were identified as impacting statewide school district efficiency. All three non-discretionary variables were identified as statistically significant on efficiency and included total student enrollment, the percentage of non-white students and the percentage of economically disadvantaged students. Two discretionary factors showed statistically significant effects on efficiency which included teachers’ average years of experience and the percentage of teachers with master’s degrees. The teacher-to-student ratio and the average teacher base salary were ineffective in predicting efficiency. This study contributed to the understanding on educational efficiency. Data Envelopment Analysis has been employed mainly in the private sector to analyze efficiency in economics and business organizations. This study added to the educational research on selecting Data Envelopment Analysis as a primary estimation method for analyzing the efficiency of school systems
Physical and Psychological Adjustments Associated with Home and Family Management Problems of Selected Normal and Handicapped Homemakers
The purpose of this study was to determine some physical and
psychological adjustments associated with home and family management
problems of homemakers.
The hypotheses formulated were: (1) There is no significant difference
between the experimental and control groups either in the number of responses
made or the intensity of attitude expressed toward physical disability, homemaker's
role, family life, or life in general; (2) there is no significant
difference between paired subjects with respect to their attitude toward
these aforementioned factors; and (3) there is no correlation between the
duration of the disability and attitudes expressed toward these identical
factors.
The experimental group consisted of ten physically-disabled homemakers,
while the control group was comprised of ten normal ones, all
between the ages of twenty and fifty.
Personal interviews and case studies were utilized to collect data
concerning physical and psychological adjustments of test subjects. Two
somewhat structured interviews were conducted in the home of each subject.
Data were tabulated and treated statistically.
Major findings indicate that: (1) The two groups did not differ in
intensity of attitude toward selected aspects of personal and family life;
(2) paired test subjects were not significantly different in their attitudes
toward selected aspects of personal and family life; and (3) disabled homemakers
related the duration of disability to attitudes toward their disability
and selected aspects of personal and family living.
Two conclusions were drawn, namely: (1) Those homemakers who
reflected the greatest insight into educational opportunities for the handicapped
tended to reflect better understanding of inherent problems and to
have more wholesome attitudes toward life in general, and (2) disabled
homemakers were approachable in terms of assistance needed to strengthen
management practices, and sought resources available to them.
In light of the findings and conclusions, the following implications
for further study are identified: (1) Experimental use of specifically
trained management aides to implement multiple-purpose programs to assist
disabled homemakers; (2) experimentation to provide maximum help to
families confronted with temporary disability; and (3) investigation to
test for specific changes in attitudes in light of given conditions.
This study points up the nature and extent of problems faced by
disabled homemakers and their interest and concern for specific professional
help in their day-to-day living experiences
Modelling fully convective stars in eclipsing binaries: KOI-126 and CM Draconis
We present models of the components of the systems KOI-126 and CM Draconis,
the two eclipsing binary systems known to date to contain stars with masses low
enough to have fully convective interiors. We are able to model satisfactorily
the system KOI-126, finding consistent solutions for the radii and surface
temperatures of all three components, using a solar-like value of the
mixing-length parameter \alpha in the convection zone, and PHOENIX NextGen 1D
model atmospheres for the surface boundary conditions. Depending on the
chemical composition, we estimate the age of the system to be in the range 3-5
Gyr. For CM Draconis, on the other hand, we cannot reconcile our models with
the observed radii and T_eff using the current metal-poor composition estimate
based on kinematics. Higher metallicities lessen but do not remove the
discrepancy. We then explore the effect of varying the mixing length parameter
\alpha. As previously noted in the literature, a reduced \alpha can be used as
a simple measure of the lower convective efficiency due to rotation and induced
magnetic fields. Our models show a sensitivity to \alpha (for \alpha < 1.0)
sufficient to partially account for the radius discrepancies. It is, however,
impossible to reconcile the models with the observations on the basis of the
effect of the reduced \alpha alone. We therefore suggest that the combined
effects of high metallicity and \alpha reduction could explain the observations
of CM Draconis. For example, increasing the metallicity of the system towards
super-solar values (i.e. Z = 2 Z_sun) yields an agreement within 2 \sigma with
\alpha = 1.0.Comment: 7 pages, 4 figures, accepted for publication in MNRA
Fundamental properties of lower main-sequence stars
The field of exoplanet research has revitalized interest in M dwarfs, which
have become favorite targets of Doppler and transit surveys. Accurate
measurements of their basic properties such as masses, radii, and effective
temperatures have revealed significant disagreements with predictions from
stellar evolution theory in the sense that stars are larger and cooler than
expected. These anomalies are believed to be due to high levels of activity in
these stars. The evidence for the radius discrepancies has grown over the years
as more and more determinations have become available; however, fewer of these
studies include accurate determinations of the temperatures. The ubiquitous
mass-radius diagrams featured in many new discovery papers are becoming more
confusing due to increased scatter, which may be due in part to larger than
realized systematic errors affecting many of the published measurements. A
discussion of these and other issues is given here from an observer's
perspective, along with a summary of theoretical efforts to explain the radius
and temperature anomalies.Comment: 7 pages, to appear in the Proceedings of the 17th Cambridge Workshop
on Cool Stars, Stellar Systems, and the Sun, eds. K. Strassmeier & M.
Lopez-Morales (AN, Vol. 334
Orbital and physical parameters of eclipsing binaries from the ASAS catalogue - IV. A 0.61 + 0.45 M_sun binary in a multiple system
We present the orbital and physical parameters of a newly discovered low-mass
detached eclipsing binary from the All-Sky Automated Survey (ASAS) database:
ASAS J011328-3821.1 A - a member of a visual binary system with the secondary
component separated by about 1.4 seconds of arc. The radial velocities were
calculated from the high-resolution spectra obtained with the 1.9-m
Radcliffe/GIRAFFE, 3.9-m AAT/UCLES and 3.0-m Shane/HamSpec
telescopes/spectrographs on the basis of the TODCOR technique and positions of
H_alpha emission lines. For the analysis we used V and I band photometry
obtained with the 1.0-m Elizabeth and robotic 0.41-m PROMPT telescopes,
supplemented with the publicly available ASAS light curve of the system.
We found that ASAS J011328-3821.1 A is composed of two late-type dwarfs
having masses of M_1 = 0.612 +/- 0.030 M_sun, M_2 = 0.445 +/- 0.019 M_sun and
radii of R_1 = 0.596 +/- 0.020 R_sun, R_2 = 0.445 +/- 0.024 R_sun, both show a
substantial level of activity, which manifests in strong H_alpha and H_beta
emission and the presence of cool spots. The influence of the third light on
the eclipsing pair properties was also evaluated and the photometric properties
of the component B were derived. Comparison with several popular stellar
evolution models shows that the system is on its main sequence evolution stage
and probably is more metal rich than the Sun. We also found several clues which
suggest that the component B itself is a binary composed of two nearly
identical ~0.5 M_sun stars.Comment: 12 pages, 7 figures, 7 tables, to appear in MNRA
Identification of a novel botulinum neurotoxin gene cluster in Enterococcus
The deadly neurotoxins of Clostridium botulinum (BoNTs) comprise eight serotypes (A–G; X). The neurotoxin gene cluster encoding BoNT and its accessory proteins includes an operon containing an ntnh gene upstream of the boNT gene. Another operon contains either ha (haemagglutinin) or orfX genes (of unknown function). Here we describe a novel boNT gene cluster from Enterococcus sp. 3G1_DIV0629, with a typical ntnh gene and an uncommon orfX arrangement. The neurotoxin (designated putative eBoNT/J) contains a metallopeptidase zinc-binding site, a translocation domain and a target cell attachment domain. Structural properties of the latter suggest a novel targeting mechanism with consequent implications for application by the pharmaceutical industry. This is the first complete boNT gene cluster identified in a non-clostridial genome
Slow-transit constipation and criteria for colectomy: a cross-sectional study of 1568 patients.
BACKGROUND: Colectomy remains a treatment option for a minority of patients with slow-transit constipation (STC) refractory to conservative treatment. However careful patient selection is essential to maximize benefits and minimize risk of adverse outcome. This study determined the proportion of patients with chronic constipation that would meet criteria for colectomy based on recent European graded practice recommendations derived by expert consensus. METHODS: Retrospective application of graded practice recommendations was undertaken on a prospectively maintained data set of consecutive adult patients with chronic constipation who underwent whole-gut transit studies using radio-opaque markers. Primary analysis applied contraindications achieving high level of expert consensus (normal whole-gut transit as an absolute contraindication and faecal incontinence as a relative contraindication for colectomy). Secondary analysis applied contraindications with less certain consensus. RESULTS: Primary analysis of 1568 patients undergoing a whole-gut transit study between January 2004 and March 2016 found 208 (13.3 per cent) met published criteria to be selected for colectomy, with 974 excluded for normal whole-gut transit and 386 for faecal incontinence. Secondary analysis demonstrated high prevalence of other relative contraindications to colectomy: 165 concomitant upper gastrointestinal symptoms, 216 abdominal pain (including 126 irritable bowel syndrome), and 446 evacuation disorder. The majority of patients (416 of 594) had two or more relative contraindications. If these patients were excluded, only 26 (1.7 per cent) chronically constipated patients retrospectively met selection criteria for colectomy. CONCLUSIONS: The retrospective application of selection criteria is a limitation. However, the data highlight the high prevalence of factors associated with poor postoperative outcome and provide further caution to surgeons undertaking colectomy for STC
The X-ray luminous cluster underlying the bright radio-quiet quasar H1821+643
We present a Chandra observation of the only low redshift, z=0.299, galaxy
cluster to contain a highly luminous radio-quiet quasar, H1821+643. By
simulating the quasar PSF, we subtract the quasar contribution from the cluster
core and determine the physical properties of the cluster gas down to 3 arcsec
(15 kpc) from the point source. The temperature of the cluster gas decreases
from 9.0\pm0.5 keV down to 1.3\pm0.2 keV in the centre, with a short central
radiative cooling time of 1.0\pm0.1 Gyr, typical of a strong cool-core cluster.
The X-ray morphology in the central 100 kpc shows extended spurs of emission
from the core, a small radio cavity and a weak shock or cold front forming a
semi-circular edge at 15 arcsec radius. The quasar bolometric luminosity was
estimated to be 2 x 10^{47} erg per sec, requiring a mass accretion rate of 40
Msolar per yr, which corresponds to half the Eddington accretion rate. We
explore possible accretion mechanisms for this object and determine that Bondi
accretion, when boosted by Compton cooling of the accretion material, could
provide a significant source of the fuel for this outburst. We consider
H1821+643 in the context of a unified AGN accretion model and, by comparing
H1821+643 with a sample of galaxy clusters, we show that the quasar has not
significantly affected the large-scale cluster gas properties.Comment: 20 pages, 19 figures, accepted by MNRA
Stellar Processes Near the Massive Black Hole in the Galactic Center
A massive black hole resides in the center of most, perhaps all galaxies. The
one in the center of our home galaxy, the Milky Way, provides a uniquely
accessible laboratory for studying in detail the connections and interactions
between a massive black hole and the stellar system in which it grows; for
investigating the effects of extreme density, velocity and tidal fields on
stars; and for using stars to probe the central dark mass and probe
post-Newtonian gravity in the weak- and strong-field limits. Recent results,
open questions and future prospects are reviewed in the wider context of the
theoretical framework and physical processes that underlie them.
Contents: [1] Introduction (1.1) Astrophysical context (1.2) Science
questions (1.3) Scope and connections to related topics [2] Observational
overview: Stars in the Galactic center (2.1) The central 100 parsecs (2.2) The
central parsec [3] Stellar dynamics at extreme densities (3.1) Physical
processes and scales (3.2) The stellar cusp in the Galactic center (3.3) Mass
segregation (3.4) Stellar Collisions [4] Probing the dark mass with stellar
dynamics (4.1) Weighing and pinpointing the dark mass (4.2) Constraints on
non-BH dark mass alternatives (4.3) Limits on MBH binarity (4.4) High-velocity
runaway stars [5] Probing post-Newtonian gravity near the MBH (5.1)
Relativistic orbital effects (5.2) Gravitational lensing [6] Strong star-MBH
interactions (6.1) Tidal disruption (6.2) Dissipative interactions with the MBH
[7] The riddle of the young stars (7.1) The difficulties of forming or
importing stars near a MBH (7.2) Proposed solutions (7.3) Feeding the MBH with
stellar winds [8] Outlook (8.1) Progress report (8.2) Future directionsComment: Invited review article, to appear in Physics Reports. 101 p
Biological Case Against Downlisting the Whooping Crane and for Improving Implementation under the Endangered Species Act
The Whooping Crane (Grus americana; WHCR) is a large, long-lived bird endemic to North America. The remnant population migrates between Aransas National Wildlife Refuge, USA, and Wood Buffalo National Park, Canada (AWBP), and has recovered from a nadir of 15-16 birds in 1941 to ~540 birds in 2022. Two ongoing reintroduction efforts in Louisiana and the Eastern Flyway together total ~150 birds. Evidence indicates the U.S. Fish and Wildlife Service (USFWS) is strongly considering downlisting the species from an endangered to a threatened status under the Endangered Species Act (ESA). We examined the current status of the WHCR through the lens of ESA threat factors, the USFWS’s Species Status Assessment (SSA) framework, and other avian downlisting actions to determine if the action is biologically warranted. Our research indicates that WHCRs are facing an intensification of most threat drivers across populations and important ranges. The AWBP is still relatively small compared to other crane species and most birds of conservation concern. To date, only one avian species has been downlisted from an endangered status with an estimated population of \u3c3,000 individuals. Representation in terms of WHCRs historic genetic, geographic, and life history variation remains limited. Also, the lack of spatial connectivity among populations, reliance of the reintroduced populations on supplementation, and continued habitat loss suggest that WHCR populations may not be resilient to large stochastic disturbances. Given that reintroduced populations are not self-sustaining, neither supplies true redundancy for the AWBP. Proposed downlisting before recovery plan population criteria have been met is objectively unwarranted 3 and reflects USFWS inconsistency across ESA actions. Only by incorporating basic quantitative criteria and added oversight into ESA listing decisions can we avoid an action as misguided as downlisting the Whooping Crane without consideration of its recovery plan criteria or ostensibly its population ecology
- …