251 research outputs found
Inhalant Use Among Native American Adolescents: A Comparison of Users and Nonusers at Intemountain Intertribal School
The objective of this study was to investigate a population of identified inhalant users at Intermountain Intertribal School, comparing and contrasting two user groups to a control group of nonusers on a number of selected research variables. The subjects included 42 identified inhalant users. Subjects were further classified into two user groups: one-time users and repeat users, and 20 nonusers. The nonuser group comprised the control group. Each subject was individually interviewed and administered the research and data collection instruments. In addition, other essential information was taken from permanent school records.
A one-way analysis of variance was computed to ascertain the relationship between group membership and 11 selected research variables. A discriminant function analysis was computed to determine differences in the 11 research variables as well as to classify and predict group membership. A descriptive analysis of a questionnaire was also reported.
Statistically significant differences were found among the three research groups on six of the 11 variables. The discriminant function correctly classified 72% of the subjects, and analysis of the group centroids indicated that the greatest distinctions among the groups were between the nonuser group and the repeat user group. The data present a pattern of inhalant use similar to other populations. The importance of early identification and treatment as well as preventative programs is discussed. Implications of the study and recommendations for further research were made
Intrinsic metrics for non-local symmetric Dirichlet forms and applications to spectral theory
We present a study of what may be called an intrinsic metric for a general regular Dirichlet form. For such forms we then prove a Rademacher type theorem. For strongly local forms we show existence of a maximal intrinsic metric (under a weak continuity condition) and for Dirichlet forms with an absolutely continuous jump kernel we characterize intrinsic metrics by bounds on certain integrals. We then turn to applications on spectral theory and provide for (measure perturbation of) general regular Dirichlet forms an Allegretto-Piepenbrinck type theorem, which is based on a ground state transform, and a Shnol type theorem. Our setting includes Laplacian on manifolds, on graphs and α-stable processes
Wind Accretion and State Transitions in Cygnus X-1
We present the results of a spectroscopic monitoring program (from 1998 to
2002) of the H-alpha emission strength in HDE 226868, the optical counterpart
of the black hole binary, Cyg X-1. The H-alpha profiles consist of (1) a P
Cygni component associated with the wind of the supergiant, (2) emission
components that attain high velocity at the conjunctions and that probably form
in enhanced outflows both towards and away from the black hole, and (3) an
emission component that moves in anti-phase with the supergiant's motion. We
argue that the third component forms in accreted gas near the black hole, and
the radial velocity curve of the emission is consistent with a mass ratio of
M_X / M_opt = 0.36 +/- 0.05. We find that there is a general anti-correlation
between the H-alpha emission strength and X-ray flux in the sense that when the
H-alpha emission is strong (W_\lambda < -0.5 Angstroms) the X-ray flux is
weaker and the spectrum harder. On the other hand, there is no correlation
between H-alpha emission strength and X-ray flux when H-alpha is weak. During
the low/hard X-ray state, the strong wind is fast and the accretion rate is
relatively low, while in the high/soft state the weaker, highly ionized wind
attains only a moderate velocity and the accretion rate increases. We argue
that the X-ray transitions from the normal low/hard to the rare high/soft state
are triggered by episodes of decreased mass loss rate in the supergiant donor
star.Comment: 45 pages, 16 figures, ApJ, in pres
Transitioning from Episodic to Sustained Care in Humanitarian Service
Background: Humanitarian missions serve populations needing care and usually provide short term interventions. Traditionally, care provided through humanitarian agencies like VOSH International has been episodic, consisting of a short-term mission placing a team in country for several days. There have been discussions that episodic care is a short term measure which impedes the systematic development of a long term solution to providing the necessary health care. The move toward sustained care is a step in the direction of improving the public health in developing countries.
Method: A survey instrument was mailed to the 26 VOSH chapters in the United States and Canada. Results were tabulated and analyzed.
Results: Sixteen completed surveys were returned for a response rate of 62%. In a one-year period, missions were carried out in 13 countries. There is a strong tendency toward continuity of care with 81% of respondents returning to locations of previous missions and 69% targeting the same population base. There is also a trend toward providing sustained care (such as establishment of a fixed clinical facility) with half responding affirmatively. Nineteen percent of chapters have been involved in the development or enhancement of departments, schools or colleges of optometry in the developing world.
Conclusion: It is exhibited in this study that most teams return to the same areas for future missions and collaborate with other partners with different expertise to create an ongoing presence. This model provides acute care for those needing immediate attention but also enhances the local infrastructure to develop a plan for long term care of this population. This allows for the opportunity to address immediate concerns, build rapport with the community, and use that goodwill and expertise to create long term change. While episodic humanitarian missions have made a profound impact, transitioning from episodic to sustained care improves overall quality of care, expanded services and long-term impact
Radial Velocities of Six OB Stars
We present new results from a radial velocity study of six bright OB stars
with little or no prior measurements. One of these, HD 45314, may be a
long-period binary, but the velocity variations of this Be star may be related
to changes in its circumstellar disk. Significant velocity variations were also
found for HD 60848 (possibly related to nonradial pulsations) and HD 61827
(related to wind variations). The other three targets, HD 46150, HD 54879, and
HD 206183, are constant velocity objects, but we note that HD 54879 has
H emission that may originate from a binary companion. We illustrate
the average red spectrum of each target.Comment: Accepted for publication in PASP July 2007 issu
The N Enrichment and Supernova Ejection of the Runaway Microquasar LS 5039
We present an investigation of new optical and ultraviolet spectra of the
mass donor star in the massive X-ray binary LS 5039. The optical band spectral
line strengths indicate that the atmosphere is N-rich and C-poor, and we
classify the stellar spectrum as type ON6.5 V((f)). The N-strong and C-weak
pattern is also found in the stellar wind P Cygni lines of N V 1240 and C IV
1550. We suggest that the N-enrichment may result from internal mixing if the
O-star was born as a rapid rotator, or the O-star may have accreted N-rich gas
prior to a common-envelope interaction with the progenitor of the supernova. We
re-evaluated the orbital elements to find an orbital period of P=4.4267 +/-
0.0010 d. We compared the spectral line profiles with new non-LTE,
line-blanketed model spectra, from which we derive an effective temperature
T_eff = 37.5 +/- 1.7 kK, gravity log g = 4.0 +/- 0.1, and projected rotational
velocity V sin i = 140 +/- 8 km/s. We fit the UV, optical, and IR flux
distribution using a model spectrum and extinction law with parameters E(B-V)=
1.28 +/- 0.02 and R= 3.18 +/- 0.07. We confirm the co-variability of the
observed X-ray flux and stellar wind mass loss rate derived from the H-alpha
profile, which supports the wind accretion scenario for the X-ray production in
LS 5039. Wind accretion models indicate that the compact companion has a mass
M_X/M_sun = 1.4 +/- 0.4, consistent with its identification as a neutron star.
The observed eccentricity and runaway velocity of the binary can only be
reconciled if the neutron star received a modest kick velocity due to a slight
asymmetry in the supernova explosion (during which >5 solar masses was
ejected).Comment: 38 pages, 9 figures; 2004, ApJ, 600, Jan. 10 issue, in press
Discussion revised thanks to comments from P. Podsiadlowsk
Comparison of the ICare® rebound tonometer with the Goldmann tonometer in a normal population
The aim of this study was to evaluate the accuracy of measurement of intraocular pressure (IOP) using a new induction/impact rebound tonometer (ICare) in comparison with the Goldmann applanation tonometer (AT). The left eyes of 46 university students were assessed with the two tonometers, with induction tonometry being performed first. The ICare was handled by an optometrist and the Goldmann tonometer by an ophthalmologist. In this study, statistically significant differences were found when comparing the ICare rebound tonometer with applanation tonometry (AT) (p < 0.05). The mean difference between the two tonometers was 1.34 +/- 2.03 mmHg (mean +/- S.D.) and the 95% limits of agreement were +/-3.98 mmHg. A frequency distribution of the differences demonstrated that in more than 80% of cases the IOP readings differed by <3 mmHg between the ICare and the AT. In the present population the ICare overestimates the IOP value by 1.34 mmHg on average when compared with Goldmann tonometer. Nevertheless, the ICare tonometer may be helpful as a screening tool when Goldmann applanation tonometry is not applicable or not recommended, as it is able to estimate IOP within a range of +/-3.00 mmHg in more than 80% of the populatio
Mass and Angular Momentum Transfer in the Massive Algol Binary RY Persei
We present an investigation of H-alpha emission line variations observed in
the massive Algol binary, RY Per. We give new radial velocity data for the
secondary based upon our optical spectra and for the primary based upon high
dispersion UV spectra. We present revised orbital elements and an estimate of
the primary's projected rotational velocity (which indicates that the primary
is rotating 7 times faster than synchronous). We use a Doppler tomography
algorithm to reconstruct the individual primary and secondary spectra in the
region of H-alpha, and we subtract the latter from each of our observations to
obtain profiles of the primary and its disk alone. Our H-alpha observations of
RY Per show that the mass gaining primary is surrounded by a persistent but
time variable accretion disk. The profile that is observed outside-of-eclipse
has weak, double-peaked emission flanking a deep central absorption, and we
find that these properties can be reproduced by a disk model that includes the
absorption of photospheric light by the band of the disk seen in projection
against the face of the star. We developed a new method to reconstruct the disk
surface density distribution from the ensemble of H-alpha profiles observed
around the orbit, and this method accounts for the effects of disk occultation
by the stellar components, the obscuration of the primary by the disk, and flux
contributions from optically thick disk elements. The resulting surface density
distribution is elongated along the axis joining the stars, in the same way as
seen in hydrodynamical simulations of gas flows that strike the mass gainer
near trailing edge of the star. This type of gas stream configuration is
optimal for the transfer of angular momentum, and we show that rapid rotation
is found in other Algols that have passed through a similar stage.Comment: 39 pages, 12 figures, ApJ in press, 2004 June 20 issu
The variable X-ray spectrum of Markarian 766 - I. Principal components analysis
Aims: We analyse a long XMM-Newton spectrum of the narrow-line Seyfert 1
galaxy Mrk 766, using the marked spectral variability on timescales >20ks to
separate components in the X-ray spectrum. Methods: Principal components
analysis is used to identify distinct emission components in the X-ray
spectrum, possible alternative physical models for those components are then
compared statistically. Results: The source spectral variability is
well-explained by additive variations, with smaller extra contributions most
likely arising from variable absorption. The principal varying component,
eigenvector one, is found to have a steep (photon index 2.4) power-law shape,
affected by a low column of ionised absorption that leads to the appearance of
a soft excess. Eigenvector one varies by a factor 10 in amplitude on
time-scales of days and appears to have broad ionised Fe K-alpha emission
associated with it: the width of the ionised line is consistent with an origin
at about 100 gravitational radii. There is also a strong component of
near-constant emission that dominates in the low state, whose spectrum is
extremely hard above 1 keV, with a soft excess at lower energies, and with a
strong edge at Fe K but remarkably little Fe K-alpha emission. Although this
component may be explained as relativistically-blurred reflection from the
inner accretion disc, we suggest that its spectrum and lack of variability may
alternatively be explained as either (i) ionised reflection from an extended
region, possibly a disc wind, or (ii) a signature of absorption by a disc wind
with a variable covering fraction. Absorption features in the low state may
indicate the presence of an outflow.Comment: 14 pages, accepted for publication in Astronomy & Astrophysic
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