222 research outputs found
An Economic Analysis of Unemployment in Trinidad and Tobago
Unemployment is regarded as one of the most challenging economic problems facing the governments of the Caribbean. Although there are variations in the measurement of unemployment, official estimates obtained from labor force surveys indicate that in 1995 the unemployment rate ranged from 7. 8 percent in Antigua/Barbuda to 19. 7 percent in Barbados. This paper explores unemployment in Trinidad and Tobago.
Labor Market Regulation and Employment in the Caribbean
This research project focuses on the demand side of the labor market by examining the impact which labor market regulations have had on employment creation in the English-speaking Caribbean countries of Barbados, Jamaica and Trinidad and Tobago. Although a recent IADB report on labor market reform in Latin America and the Caribbean indicates that the English-speaking Caribbean countries have a lower level of labor market inflexibility than Latin American countries, the regulatory environment in both the labor and commodity markets has had some adverse impact on employment creation in the region (IADB, 1996). Results from a study of the operations of the labor market in the Caribbean Group for Cooperation in Economic Development (CGCED) suggest that these regulatory measures do have some effect on the operation of businesses in the region (see Abt Associates, 1998).
Molecular Gas in the Lensed Lyman Break Galaxy cB58
We have used the IRAM Plateau de Bure Interferometer to map CO(3-2) emission
from the gravitationally lensed Lyman break galaxy MS1512-cB58. This is the
first detection of a molecular emission line in any Lyman break system; its
integrated intensity implies a total molecular gas mass of 6.6e9 Msun, while
its width implies a dynamical mass of 1.0e10 csc^2i Msun (for a flat Lambda=0.7
cosmology). These estimates are in excellent concordance with nearly all
parameters of the system measured at other wavelengths, and yield a consistent
picture of past and future star formation with no obvious discrepancies
requiring explanation by differential lensing. In particular, we find that the
age and remaining lifetime of the current episode of star formation are likely
to be similar; the surface densities of star formation and molecular gas mass
are related by a Schmidt law; and the fraction of baryonic mass already
converted into stars is sufficient to account for the observed enrichment of
the interstellar medium to 0.4 Zsun. Barring substantial gas inflow or a major
merger, the stars forming in the current episode will have mass and coevality
at z=0 similar to those of a spiral bulge. Assuming cB58 is a typical Lyman
break galaxy apart from its magnification, its global parameters suggest that
the prescriptions for star formation used in some semi-analytic models of
galaxy evolution require moderate revision, although the general prediction
that gas mass fraction should increase with redshift is validated. [abridged]Comment: 41 pages, 6 figures, accepted by Ap
Terahertz electrometry via infrared spectroscopy of atomic vapor
In recent years, the characterisation of radiation falling within the so-called âterahertz (THz) gapâ has become an ever more prominent issue due to the increasing use of THz systems in applications such as nondestructive testing, security screening, telecommunications, and medical diagnostics. THz detection technologies have advanced rapidly, yet traceable calibration of THz radiation remains challenging. In this paper, we demonstrate a system of electrometry in which a THz signal can be characterized using laser spectroscopy of highly excited (Rydberg) atomic states. We report on proof-of-principle measurements that reveal a minimum detectable THz electric field amplitude of 1.070.06 V/m at 1.06 THz (3 ms detection), corresponding to a THz power at the atomic cell of approximately 3.4 nW. Due to the relative simplicity and cryogen-free nature of this system, it has the potential to provide a route to a SI traceable âatomic candleâ for THz calibration across the terahertz frequency range, and provide an alternative to calorimetric methods
The Unusual Infrared Object HDF-N J123656.3+621322
We describe an object in the Hubble Deep Field North with very unusual
near-infrared properties. It is readily visible in Hubble Space Telescope
NICMOS images at 1.6um and from the ground at 2.2um, but is undetected (with
signal-to-noise <~ 2) in very deep WFPC2 and NICMOS data from 0.3 to 1.1um. The
f_nu flux density drops by a factor >~ 8.3 (97.7% confidence) from 1.6 to
1.1um. The object is compact but may be slightly resolved in the NICMOS 1.6um
image. In a low-resolution, near-infrared spectrogram, we find a possible
emission line at 1.643um, but a reobservation at higher spectral resolution
failed to confirm the line, leaving its reality in doubt. We consider various
hypotheses for the nature of this object. Its colors are unlike those of known
galactic stars, except perhaps the most extreme carbon stars or Mira variables
with thick circumstellar dust shells. It does not appear to be possible to
explain its spectral energy distribution as that of a normal galaxy at any
redshift without additional opacity from either dust or intergalactic neutral
hydrogen. The colors can be matched by those of a dusty galaxy at z >~ 2, by a
maximally old elliptical galaxy at z >~ 3 (perhaps with some additional
reddening), or by an object at z >~ 10 whose optical and 1.1um light have been
suppressed by the intergalactic medium. Under the latter hypothesis, if the
luminosity results from stars and not an AGN, the object would resemble a
classical, unobscured protogalaxy, with a star formation rate >~ 100 M_sun/yr.
Such UV-bright objects are evidently rare at 2 < z < 12.5, however, with a
space density several hundred times lower than that of present-day L* galaxies.Comment: Accepted for publication in the Astrophysical Journal. 27 pages,
LaTeX, with 7 figures (8 files); citations & references updated + minor
format change
Modeling CO Emission: II. The Physical Characteristics that Determine the X factor in Galactic Molecular Clouds
We investigate how the X factor, the ratio of H_2 column density (NH2) to
velocity-integrated CO intensity (W), is determined by the physical properties
of gas in model molecular clouds (MCs). We perform radiative transfer
calculations on chemical-MHD models to compute X. Using integrated NH2 and W
reproduces the limited range in X found in observations, resulting in a mean
value X=2\times10^20 s/cm^2/K^1/km^1 from the Galactic MC model. However, in
limited velocity intervals, X can take on a much larger range due to CO line
saturation. Thus, X strongly depends on both the range in gas velocities and
volume densities. The temperature (T) variations within individual MCs do not
strongly affect X, as dense gas contributes most to setting X. For fixed
velocity and density structure, gas with higher T has higher W, yielding X ~
T^-1/2 for T~20-100 K. We demonstrate that the linewidth-size scaling relation
does not influence the X factor - only the range in velocities is important.
Clouds with larger linewidths, regardless of the linewidth-size relation, have
a higher W, corresponding to a lower value of X, scaling roughly as X ~
sigma^-1/2. The "mist" model, consisting of optically thick cloudlets with
well-separated velocities, does not accurately reflect the conditions in a
turbulent MC. We propose that the observed cloud-average values of X ~ XGal is
simply a result of the limited range in NH2, temperatures, and velocities found
in Galactic MCs - a ~constant value of X therefore does not require any
linewidth-size relation, or that MCs are virialized objects. Since gas
properties likely differ (slightly) between clouds, masses derived through a
standard X should only be considered as a rough first estimate. For
temperatures T~10-20 K, velocity dispersions ~1-6 km/s, and NH2~2-20\times10^21
cm^-2, we find cloud-averaged X ~ 2-4\times10^20 s/cm^2/K^1/km^1 for
Solar-metallicity models.Comment: 24 pages, including 21 Figures, Accepted to MNRA
An Analysis of Private School Closings
We add to the small literature on private school supply by exploring exits of K-12 private schools. We find that the closure of private schools is not an infrequent event, and use national survey data from the National Center for Education Statistics to study closures of private schools. We assume that the probability of an exit is a function of excess supply of private schools over the demand, as well as the school's characteristics such as age, size, and religious affiliation. Our empirical results generally support the implications of the model. Working Paper 07-0
A new pedigree with thrombomodulin-associated coagulopathy in which delayed fibrinolysis is partially attenuated by co-inherited TAFI deficiency
ACKNOWLEDGEMENTS We thank NIHR BioResource volunteers for their participation, and gratefully acknowledge NIHR BioResource centres, NHS Trusts and staff for their contribution. We thank the National Institute for Health Research and NHS Blood and Transplant. The views expressed are those of the authors and not necessarily those of the NHS, the NIHR or the Department of Health and Social Care. S.K.W. was supported during this work by the Medical Research Council (MR/K023489/1) and is now funded through an NIHR-funded Academic Clinical Lectureship. K.D. is supported as a HSST trainee by NHS Health Education England. N.J.M. and C.S.W. are supported by the British Heart Foundation (PG/15/82/31721). J.C.M. is a fellow of the Research Foundation Flanders (FWO Vlaanderen; 1137717N). A.D.M. is supported by the NIHR Biomedical Research Centre at the University Hospitals Bristol National Health Service Foundation Trust and the University of Bristol. We thank Prof Paul Declerck and Prof Ann Gils, University Leuven, Belgium for the kind gift of the MA-T12D11 antibody. We acknowledge technical assistance from Dorien Leenaerts, University of Antwerp, Belgium and Michela Donnarumma, University of Aberdeen, UK.Peer reviewedPublisher PD
Incorporating Alternative Polygenic Risk Scores into the BOADICEA Breast Cancer Risk Prediction Model
Background: The multifactorial risk prediction model BOADI-CEA enables identification of women at higher or lower risk of developing breast cancer. BOADICEA models genetic susceptibility in terms of the effects of rare variants in breast cancer susceptibility genes and a polygenic component, decomposed into an unmeasured and a measured component -the polygenic risk score (PRS). The current version was developed using a 313 SNP PRS. Here, we evaluated approaches to incorporating this PRS and alternative PRS in BOADICEA.Methods: The mean, SD, and proportion of the overall polygenic component explained by the PRS (a2) need to be estimated. a was estimated using logistic regression, where the age-specific log-OR is constrained to be a function of the age-dependent polygenic relative risk in BOADICEA; and using a retrospective likelihood (RL) approach that models, in addition, the unmeasured polygenic component.Results: Parameters were computed for 11 PRS, including 6 variations of the 313 SNP PRS used in clinical trials and imple-mentation studies. The logistic regression approach underestimates a, as compared with the RL estimates. The RL a estimates were very close to those obtained by assuming proportionality to the OR per 1 SD, with the constant of proportionality estimated using the 313 SNP PRS. Small variations in the SNPs included in the PRS can lead to large differences in the mean.Conclusions: BOADICEA can be readily adapted to different PRS in a manner that maintains consistency of the model.Impact : The methods described facilitate comprehensive breast cancer risk assessment
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