5,817 research outputs found
Measuring the Efficiency and Productivity of British Universities: An Application of DEA and the Malmquist Approach
This paper uses data envelopment analysis to examine the technical efficiency (TE) of 45 British universities in the period 1980/81 to 1992/93. This period was chosen primarily because it was characterized by major changes in public funding and in student : staff ratios. To shed light on the causes of variations in efficiency, TE is decomposed into pure technical efficiency (PTE), congestion efficiency (CE) and scale efficiency (SE). The analysis indicates that there was a substantial rise in the weighted geometric mean TE score during the study period, although this rise was most noticeable between 1987/88 and 1990/91. The rising TE scores are attributed largely to the gains in PTE and CE, with SE playing a minor role. The Malmquist approach is then used to distinguish between changes in technical efficiency and intertemporal shifts in the efficiency frontier. The results reveal that total factor productivity rose by 51.5% between 1980/81 and 1992/93, and that most of this increase was due to a substantial outward shift in the efficiency frontier during this period.Efficiency; Productivity; Universities; DEA; Malmquist
Teaching public policy in East Asia: aspirations, potentials and challenges
10.1080/13876988.2012.724965Journal of Comparative Policy Analysis145376-39
The coupling of a young stellar disc with the molecular torus in the Galactic centre
The Galactic centre hosts, according to observations, a number of early-type
stars. About one half of those which are orbiting the central supermassive
black hole on orbits with projected radii 0.03 pc form a coherently
rotating disc. Observations further reveal a massive gaseous torus and a
significant population of late-type stars. In this paper, we investigate, by
means of numerical N-body computations, the orbital evolution of the stellar
disc, which we consider to be initially thin. We include the gravitational
influence of both the torus and the late-type stars, as well as the
self-gravity of the disc. Our results show that, for a significant set of
system parameters, the evolution of the disc leads, within the lifetime of the
early-type stars, to a configuration compatible with the observations. In
particular, the disc naturally reaches a specific - perpendicular - orientation
with respect to the torus, which is indeed the configuration observed in the
Galactic centre. We, therefore, suggest that all the early-type stars may have
been born within a single gaseous disc.Comment: Accepted for publication in MNRAS; 9 pages, 4 figures, 1 tabl
Core-Level X-Ray Photoemission Satellites in Ruthenates: A New Mechanism Revealing the Mott Transition
Ru 3d core-level x-ray photoemission spectra of various ruthenates are
examined. They show in general two-peak structures, which can be assigned as
the screened and unscreened peaks. The screened peak is absent in a Mott
insulator, but develops into a main peak in the metallic regime. This spectral
behavior is well explained by the dynamical mean-field theory calculation for
the single-band Hubbard model with on-site core-hole potential using the exact
diagonalization method. The new mechanism of the core-level photoemission
satellite can be utilized to reveal the Mott transition phenomenon in various
strongly correlated electron systems, especially in nano-scale devices and
phase-separated materials.Comment: 4 pages, 5 figures, submitted to PR
First principles predictions of thermophysical properties of refrigerant mixtures
We present pair potentials for fluorinated methanes and their dimers with CO2 based on ab initio potential energy surfaces. These potentials reproduce the experimental second virial coefficients of the pure fluorinated methanes and their mixtures with CO2 without adjustment. Ab initio calculations on trimers are used to model the effects of nonadditive dispersion and induction. Simulations using these potentials reproduce the experimental phase-coexistence properties of CH3F within 10% over a wide range of temperatures. The phase coexistence curve of the mixture of CH2F2 and CO2 is reproduced with an error in the mole fractions of both phases of less than 0.1. The potentials described here are based entirely on ab initio calculations, with no empirical fits to improve the agreement with experiment
High angular resolution integral-field spectroscopy of the Galaxy's nuclear cluster: a missing stellar cusp?
We report on the structure of the nuclear star cluster in the innermost 0.16
pc of the Galaxy as measured by the number density profile of late-type giants.
Using laser guide star adaptive optics in conjunction with the integral field
spectrograph, OSIRIS, at the Keck II telescope, we are able to differentiate
between the older, late-type ( 1 Gyr) stars, which are presumed to be
dynamically relaxed, and the unrelaxed young ( 6 Myr) population. This
distinction is crucial for testing models of stellar cusp formation in the
vicinity of a black hole, as the models assume that the cusp stars are in
dynamical equilibrium in the black hole potential. Based on the late-type stars
alone, the surface stellar number density profile, , is flat, with . Monte Carlo simulations of
the possible de-projected volume density profile, n(r) ,
show that is less than 1.0 at the 99.73 % confidence level. These
results are consistent with the nuclear star cluster having no cusp, with a
core profile that is significantly flatter than predicted by most cusp
formation theories, and even allows for the presence of a central hole in the
stellar distribution. Of the possible dynamical interactions that can lead to
the depletion of the red giants observable in this survey -- stellar
collisions, mass segregation from stellar remnants, or a recent merger event --
mass segregation is the only one that can be ruled out as the dominant
depletion mechanism. The lack of a stellar cusp around a supermassive black
hole would have important implications for black hole growth models and
inferences on the presence of a black hole based upon stellar distributions.Comment: 35 pages, 5 tables, 12 figures, accepted by Ap
Metagenome sequencing of the microbial community of a solar saltern crystallizer pond at cáhuil lagoon, chile.
Cáhuil Lagoon in central Chile harbors distinct microbial communities in various solar salterns that are arranged as interconnected ponds with increasing salt concentrations. Here, we report the metagenome of the 3.0- to 0.2-µm fraction of the microbial community present in a crystallizer pond with 34% salinity
The Distribution of Stars and Stellar Remnants at the Galactic Center
Motivated by recent observations that suggest a low density of old stars
around the Milky Way supermassive black hole, models for the nuclear star
cluster are considered that have not yet reached a steady state under the
influence of gravitational encounters. A core of initial radius 1-1.5 pc
evolves to a size of approximately 0.5 pc after 10 Gyr, roughly the size of the
observed core. The absence of a Bahcall-Wolf cusp is naturally explained in
these models, without the need for fine-tuning or implausible initial
conditions. In the absence of a cusp, the time for a 10-solar-mass black hole
to spiral in to the Galactic center from an initial distance of 5 pc can be
much greater than 10 Gyr. Assuming that the stellar black holes had the same
phase-space distribution initially as the stars, their density after 5-10 Gyr
is predicted to rise very steeply going into the stellar core, but could remain
substantially below the densities inferred from steady-state models that
include a steep density cusp in the stars. Possible mechanisms for the creation
of the parsec-scale initial core include destruction of stars on centrophilic
orbits in a pre-existing triaxial nucleus, inhibited star formation near the
supermassive black hole, or ejection of stars by a massive binary. The
implications of these models are discussed for the rates of gravitational-wave
inspiral events, as well as other physical processes that depend on a high
density of stars or stellar mass black holes near Sagittarius A*.Comment: ApJ, accepte
Transition Layer for the Heterogeneous Allen-Cahn Equation
We consider the equation \e^{2}\Delta u=(u-a(x))(u^2-1) in ,
on , where is a
smooth and bounded domain in , the outer unit normal to
\pa\Omega, and a smooth function satisfying in \ov{\Omega}.
We set , and to be respectively the zero-level set of
, {a>0} and {a<0}. Assuming on and on
, we show that there exists a sequence \e_j \to 0 such that
the above equation has a solution u_{\e_j} which converges uniformly to on the compact sets of \O_{\pm} as .Comment: 25 page
Predicting live birth, preterm and low birth weight infant after in-vitro fertilisation: a prospective study of 144018 treatment cycles
Background
The extent to which baseline couple characteristics affect the probability of live birth and adverse perinatal outcomes after assisted conception is unknown.
Methods and Findings
We utilised the Human Fertilisation and Embryology Authority database to examine the predictors of live birth in all in vitro fertilisation (IVF) cycles undertaken in the UK between 2003 and 2007 (n = 144,018). We examined the potential clinical utility of a validated model that pre-dated the introduction of intracytoplasmic sperm injection (ICSI) as compared to a novel model. For those treatment cycles that resulted in a live singleton birth (n = 24,226), we determined the associates of potential risk factors with preterm birth, low birth weight, and macrosomia. The overall rate of at least one live birth was 23.4 per 100 cycles (95% confidence interval [CI] 23.2–23.7). In multivariable models the odds of at least one live birth decreased with increasing maternal age, increasing duration of infertility, a greater number of previously unsuccessful IVF treatments, use of own oocytes, necessity for a second or third treatment cycle, or if it was not unexplained infertility. The association of own versus donor oocyte with reduced odds of live birth strengthened with increasing age of the mother. A previous IVF live birth increased the odds of future success (OR 1.58, 95% CI 1.46–1.71) more than that of a previous spontaneous live birth (OR 1.19, 95% CI 0.99–1.24); p-value for difference in estimate <0.001. Use of ICSI increased the odds of live birth, and male causes of infertility were associated with reduced odds of live birth only in couples who had not received ICSI. Prediction of live birth was feasible with moderate discrimination and excellent calibration; calibration was markedly improved in the novel compared to the established model. Preterm birth and low birth weight were increased if oocyte donation was required and ICSI was not used. Risk of macrosomia increased with advancing maternal age and a history of previous live births. Infertility due to cervical problems was associated with increased odds of all three outcomes—preterm birth, low birth weight, and macrosomia.
Conclusions
Pending external validation, our results show that couple- and treatment-specific factors can be used to provide infertile couples with an accurate assessment of whether they have low or high risk of a successful outcome following IVF
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