4,153 research outputs found
Probing the Ionization State of the Universe at z>6
We present high signal-to-noise ratio Keck ESI spectra of the two quasars
known to have Gunn-Peterson absorption troughs, SDSS J1030+0524 (z=6.28) and
SDSS J1148+5251 (z=6.37). The Ly alpha and Ly beta troughs for SDSS J1030+0524
are very black and show no evidence for any emission over a redshift interval
of ~0.2 starting at z=6. On the other hand, SDSS J1148+5251 shows a number of
emission peaks in the Ly beta Gunn-Peterson trough along with a single weak
peak in the Ly alpha trough. The Ly alpha emission has corresponding Ly beta
emission, suggesting that it is indeed a region of lower optical depth in the
intergalactic medium at z=6.08.
The stronger Ly beta peaks in the spectrum of SDSS J1148+5251 could
conceivably also be the result of "leaks" in the IGM, but we suggest that they
are instead Ly alpha emission from an intervening galaxy at z=4.9. This
hypothesis gains credence from a strong complex of C IV absorption at the same
redshift and from the detection of continuum emission in the Ly alpha trough at
the expected brightness. If this proposal is correct, the quasar light has
probably been magnified through gravitational lensing by the intervening
galaxy. The Stromgren sphere observed in the absorption spectrum of SDSS
J1148+5251 is significantly smaller than expected based on its brightness,
which is consistent with the hypothesis that the quasar is lensed.
If our argument for lensing is correct, the optical depths derived from the
troughs of SDSS J1148+5251 are only lower limits (albeit still quite strong,
with tau(LyA)>16 inferred from the Ly beta trough.) The Ly beta absorption
trough of SDSS J1030+0524 gives the single best measurement of the IGM
transmission at z>6, with an inferred optical depth tau(LyA)>22.Comment: To appear in July 2003 AJ, 34 pages, 11 figures; minor changes/typos
fixe
Remembering Sir William Osler 100 years after his death: what can we learn from his legacy?
William Osler es un médico por antonomasia en la historia de la medicina. Como padre de la medicina hipocrática moderna trasladó las bases de la educación médica del siglo XIX de los salones de clase a la cabecera de los pacientes (figura), introdujo el uso rutinario del laboratorio y la autopsia como parte de la educación y la práctica médica, y trajo consigo la escolaridad, humildad y la humanidad en la relación médico–paciente. Fue muy querido por quienes lo conocían y respetado por su generación y por las que la siguieron. Brindó atención al paciente preocupándose antes que todo por la persona misma. Osler aún recibe elogios -con justicia merecidos- por avanzar el sitial de la ciencia, de las humanidades y del profesionalismo en la medicina (véase la sección referencias). Osler es menos reconocido por el control de errores, la biología variacional, el método científico y el humanismo—asuntos problemáticos para la medicina modernaWilliam Osler is a physician par excellence in the history of medicine. As father of modern Hippocratic medicine moved the foundations of medical education nineteenth century classrooms at the bedside of patients (Figure) introduced the routine use of laboratory and autopsy as part of education and medical practice and it brought schooling, humility and humanity in the doctor-patient relationship. He was loved by those who knew and respected by his generation and those that followed. It provided patient care caring first of all by the same person. Osler still receives praise, with justice merecidos- to advance the seat of science, humanities and professionalism in medicine (see the references section). Osler is less recognized for error control, variational biology, the scientific method and humanism-issues problematic for modern medicine
Enantioselective Synthesis of Dual Serotonergic Azanoradamantane SC-52491
A racemic synthesis of azanoradamantane (±)-3 was accomplished via Yamamoto\u27s MAD-catalyzed Diels-Alder protocol. Subsequently, a scalable asymmetric synthesis of azanoradamantane benzamide SC-52491 was carried out employing Helmchen\u27s asymmetric Diels-Alder methodology to construct all four contiguous asymmetric centers with the correct relative stereochemistry and in 99.3% e.e
A Model of Child Morbidity, Mortality and Health Interventions
A macro model of morbidity and mortality in children under five
years of age is presented. Monthly disease-specific incidence
and case fatality rates form the basis of the model and the
efficacy and coverage of disease-specific interventions alter
these values. In addition, frailty is modeled via relative risks
of mortality based on five groups, determined in the first month
by the birthweight distribution and at later ages by the
proportion of children surviving a given illness who become more
frail and the proportion not ill and with adequate nutrition who
become less frail. A validation of the model was carried out
using data from the comparison and treatment areas of the
Demographic Surveillance System in Matlab, Bangladesh. The model
very closely predicts the observed mortality level. Scenarios
for improvements in coverage of specific interventions in
settings in South Asia, West Africa and Andean South America are
modeled and their effects on mortality gauged. The model
provides a useful tool for those wishing to know the mortality
impact of specified mixes of interventions in a given setting.
Limitations of the model are considered and possible extensions
to address these are discussed
Evaluation of the Social Interaction Self-Statement Test with a Social Phobic Population
The convergent and discriminant validity of the Social Interaction Self-Statement Test (SISST) were evaluated in a sample of men and women awaiting treatment for fear and avoidance of social interactions. Partial correlations revealed that negative, but not positive, self-statement scores were generally related to self-report measures of anxiety and depression. Heart rate and subjective anxiety ratings derived from a behavioral simulation of a personally relevant anxiety-provoking situation were unrelated to SISST scores. However, subjects’ reports of negative thoughts obtained via the thought-listing procedure were related to the SISST negative self-statement scores, suggesting that the negative subscale of the SISST and the thought-listing procedure tap similar dimensions. Finally, the negative subscale of the SISST discriminated between social phobics whose primary fear involved social interactions and social phobics whose anxiety was confined to public-speaking situations. The findings support the use of the SISST with clinically socially anxious patients
DSM-III-R Subtypes of Social Phobia: Comparison of Generalized Social Phobics and Public Speaking Phobics
Social phobic patients who fear most or all social interaction situations are labeled generalized social phobics in DSM-III-R. Thirty-five patients who met this criterion were compared with 22 social phobic patients whose fears were restricted to public-speaking situations. Generalized social phobics were younger, less educated, and less likely to be employed, and their phobias were rated by clinical interviewers as more severe than those of public-speaking phobics. Generalized social phobics appeared more anxious and more depressed and expressed greater fears concerning negative social evaluation. They performed more poorly on individualized behavioral tests and differed from public-speaking phobics in their responses to cognitive assessment tasks. The two groups showed marked differences in their patterns of heart rate acceleration during the behavioral test. The implications of these findings for the classification and treatment of social phobic individuals are discussed
Discovery of a Classic FR-II Broad Absorption Line Quasar from the FIRST Survey
We have discovered a remarkable quasar, FIRST J101614.3+520916, whose optical
spectrum shows unambiguous broad absorption features while its double-lobed
radio morphology and luminosity clearly indicate a classic Fanaroff-Riley Type
II radio source. Its radio luminosity places it at the extreme of the recently
established class of radio-loud broad absorption line quasars (Becker et al.
1997, 2000; Brotherton et al. 1998). Because of its hybrid nature, we speculate
that FIRST J101614.3+520916 is a typical FR-II quasar which has been
rejuvenated as a broad absorption line (BAL) quasar with a Compact Steep
Spectrum core. The direction of the jet axis of FIRST J101614.3+520916 can be
estimated from its radio structure and optical brightness, indicating that we
are viewing the system at a viewing angle of > 40 degrees. The position angles
of the radio jet and optical polarization are not well-aligned, differing by 20
to 30 degrees. When combined with the evidence presented by Becker et al.
(2000) for a sample of 29 BAL quasars showing that at least some BAL quasars
are viewed along the jet axis, the implication is that no preferred viewing
orientation is necessary to observe BAL systems in a quasar's spectrum. This,
and the probable young nature of compact steep spectrum sources, leads
naturally to the alternate hypothesis that BALs are an early stage in the lives
of quasars.Comment: 14 pages, 6 postscript figures; accepted for publication in the
Astrophysical Journa
The determinants of use of maternal and child health services in Metro Cebu, the Philippines
The determinants of the use of family planning, prenatal care, childhood immunizations and oral rehydration salts (ORS) were studied with survey data of 8000 women in Metro Cebu, the Philippines. Polytomous logistic regression methods were used. The level of maternal education was the most consistent and important determinant of use of these four health services in both urban and rural areas. For example, the estimated odds of using modern contraception increased by six and eleven per cent for each additional year of schooling in urban and rural strata respectively. Economic status and access to service variables had less consistent patterns: women’s work status, for example, was associated only with contraceptive use
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