984 research outputs found
A qualitative study of Barbadian teachers' professional identity.
This study is a qualitative investigation of the professional identity structure of teachers in
Barbados, a small post-colonial Caribbean territory. The aim was to determine whether
Barbadian teachers regard themselves as professionals and to what extent their
occupational/professional identity structure could be described by a pre-conceptualized set
of categories. Data was collected from a focus group made up of teachers of both genders
from primary, secondary and tertiary educational institutions in the country. Teachers in
the study claim to be professionals despite acknowledging that teaching in Barbados is not
recognized as a profession. This seemingly paradoxical claim is explained by the fact that
teachers regard being a professional as an individual determination characterized by a
different set of criteria from those that define a profession. By making this claim,
Barbadian teachers appear to have mitigated the potential threat to the coherence of their
professional self-concept brought about by the perceived discrepancy between the
importance of their role as teachers and the non-recognition of teaching as a profession.
The empirical data supports the four pre-conceptualized identity categories but four
additional categories were uncovered. Overall, the findings support the contention that
professional identity is an aspect of the self-concept; consequently, it is subject to the
principle of self-concept maintenance
On the galactic chemical evolution of sulfur
Sulfur abundances have been determined for ten stars to resolve a debate in
the literature on the Galactic chemical evolution of sulfur in the halo phase
of the Milky Way. Our analysis is based on observations of the S I lines at
9212.9, 9228.1, and 9237.5 A for stars for which the S abundance was obtained
previously from much weaker S I lines at 8694.0 and 8694.6 A. In contrast to
the previous results showing [S/Fe] to rise steadily with decreasing [Fe/H],
our results show that [S/Fe] is approximately constant for metal-poor stars
([Fe/H] < -1) at [S/Fe] = +0.3. Thus, sulfur behaves in a similar way to the
other alpha elements, with an approximately constant [S/Fe] for metallicities
lower than [Fe/H] = -1. We suggest that the reason for the earlier claims of a
rise of [S/Fe] is partly due to the use of the weak S I 8694.0 and 8694.6 A
lines and partly uncertainties in the determination of the metallicity when
using Fe I lines. The S I 9212.9, 9228.1, and 9237.5 A lines are preferred for
an abundance analysis of sulfur for metal-poor stars.Comment: Accepted by A&A, 12 pages. Full article with figures in A&
A Dedicated M-Dwarf Planet Search Using The Hobby-Eberly Telescope
We present first results of our planet search program using the 9.2 meter
Hobby-Eberly Telescope (HET) at McDonald Observatory to detect planets around
M-type dwarf stars via high-precision radial velocity (RV) measurements.
Although more than 100 extrasolar planets have been found around solar-type
stars of spectral type F to K, there is only a single M-dwarf (GJ 876, Delfosse
et al. 1998; Marcy et al. 1998; Marcy et al. 2001) known to harbor a planetary
system. With the current incompleteness of Doppler surveys with respect to
M-dwarfs, it is not yet possible to decide whether this is due to a fundamental
difference in the formation history and overall frequency of planetary systems
in the low-mass regime of the Hertzsprung-Russell diagram, or simply an
observational bias. Our HET M-dwarf survey plans to survey 100 M-dwarfs in the
next 3 to 4 years with the primary goal to answer this question. Here we
present the results from the first year of the survey which show that our
routine RV-precision for M-dwarfs is 6 m/s. We found that GJ 864 and GJ 913 are
binary systems with yet undetermined periods, while 5 out of 39 M-dwarfs reveal
a high RV-scatter and represent candidates for having short-periodic planetary
companions. For one of them, GJ 436 (rms = 20.6 m/s), we have already obtained
follow-up observations but no periodic signal is present in the RV-data.Comment: 12 pages, 14 figures, accepted for publication in the Astronomical
Journa
Radial Velocity Variations in Pulsating Ap Stars III. The Discovery of 16.21 min Oscillations in Beta CrB
We present the analysis of 3 hrs of a rapid time series of precise stellar
radial velocity (RV) measurements (sigma = 4.5 m/s) of the cool Ap star Beta
CrB. The integrated RV measurements spanning the wavelength interval 5000-6000
Ang. show significant variations (false alarm probability = 10^-5) with a
period of 16.21 min (nu = 1028.17 micro Hz) and an amplitude of 3.54 +/- 0.56
m/s. The RV measured over a much narrower wavelength interval reveals one
spectral feature at 6272 Ang. pulsating with the same 16.21 min period and an
amplitude of 138 +/- 23 m/s. These observations establish Beta CrB to be a
low-amplitude rapidly oscillating Ap star.Comment: 5 Pages, 5 figure
The Relative and Unique Contributions of Emotion Dysregulation and Impulsivity to Posttraumatic Stress Disorder Among Substance Dependent Inpatients
Background: Despite elevated rates of posttraumatic stress disorder (PTSD) among substance use disorder (SUD) patients, as well as the clinical relevance of this co-occurrence, few studies have examined psychological factors associated with a PTSD–SUD diagnosis. Two factors worth investigating are emotion dysregulation and impulsivity, both of which are associated with PTSD and SUDs. Therefore, this study examined associations between PTSD and facets of emotion dysregulation and impulsivity within a sample of trauma-exposed SUD inpatients.
Methods: Participants were an ethnically diverse sample of 205 SUD patients in residential substance abuse treatment. Patients were administered diagnostic interviews and completed a series of questionnaires.
Results: Patients with PTSD (n = 58) reported significantly higher levels of negative urgency (i.e., the tendency to engage in impulsive behaviors when experiencing negative affect) and lower sensation seeking, as well as higher levels of emotion dysregulation and the specific dimensions of lack of emotional acceptance, difficulties engaging in goal-directed behavior when upset, difficulties controlling impulsive behaviors when distressed, limited access to effective emotion regulation strategies, and lack of emotional clarity. Further, overall emotion dysregulation emerged as a significant predictor of PTSD status, accounting for unique variance in PTSD status above and beyond facets of impulsivity (as well as other relevant covariates).
Conclusions: Results suggest that emotion dysregulation may contribute to the development, maintenance, and/or exacerbation of PTSD and highlight the potential clinical utility of targeting emotion dysregulation among SUD patients with PTSD
Exploring The Frequency Of Close-In Jovian Planets Around M Dwarfs
We discuss our high precision radial velocity results of a sample of 90 M dwarfs observed with the Hobby-Eberly Telescope and the Harlan J. Smith 2.7 m Telescope at McDonald Observatory, as well as the ESO VLT and the Keck I telescopes, within the context of the overall frequency of Jupiter-mass planetary companions to main sequence stars. None of the stars in our sample show variability indicative of a giant planet in a short period orbit, with a 3.8 M_Jup and a 3.5 M_Jup and a < 0.7 AU. Our results point toward a generally lower frequency of close-in Jovian planets for M dwarfs as compared to FGK-type stars. This is an important piece of information for our understanding of the process of planet formation as a function of stellar mass
Extracting quantum dynamics from genetic learning algorithms through principal control analysis
Genetic learning algorithms are widely used to control ultrafast optical
pulse shapes for photo-induced quantum control of atoms and molecules. An
unresolved issue is how to use the solutions found by these algorithms to learn
about the system's quantum dynamics. We propose a simple method based on
covariance analysis of the control space, which can reveal the degrees of
freedom in the effective control Hamiltonian. We have applied this technique to
stimulated Raman scattering in liquid methanol. A simple model of two-mode
stimulated Raman scattering is consistent with the results.Comment: 4 pages, 5 figures. Presented at coherent control Ringberg conference
200
Further evidence for the planet around 51 Pegasi
The discovery of the planet around the solar-type star 51 Pegasi marked a
watershed in the search for extrasolar planets. Since then seven other
solar-type stars have been discovered, of which several have surprisingly short
orbital periods, like the planet around 51 Peg. These planets were detected
using the indirect technique of measuring variations in the Doppler shifts of
lines in the spectra of the primary stars. But it is possible that oscillations
of the stars themselves (or other effects) could mimic the signature of the
planets, particularly around the short-period planets. The apparent lack of
spectral and brightness variations, however, led to widespread acceptance that
there is a planet around 51 Peg. This conclusion was challenged by the
observation of systematic variations in the line profile shapes of 51 Peg,
which suggested stellar oscillations. If these observations are correct, then
there is no need to invoke a planet around 51 Peg to explain the data. Here we
report observations of 51 Peg at a much higher spectral resolution than those
in ref.9, in which we find no evidence for systematic changes in the line
shapes. The data are most consistent with a planetary companion to 51 Peg.Comment: LaTeX, 6 pages, 2 figures. To appear in 8 January 1998 issue of
Natur
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