19,892 research outputs found
A Search for Intrinsic Polarization in O Stars with Variable Winds
New observations of 9 of the brightest northern O stars have been made with
the Breger polarimeter on the 0.9~m telescope at McDonald Observatory and the
AnyPol polarimeter on the 0.4~m telescope at Limber Observatory, using the
Johnson-Cousins UBVRI broadband filter system. Comparison with earlier
measurements shows no clearly defined long-term polarization variability. For
all 9 stars the wavelength dependence of the degree of polarization in the
optical range can be fit by a normal interstellar polarization law. The
polarization position angles are practically constant with wavelength and are
consistent with those of neighboring stars. Thus the simplest conclusion is
that the polarization of all the program stars is primarily interstellar.
The O stars chosen for this study are generally known from ultraviolet and
optical spectroscopy to have substantial mass loss rates and variable winds, as
well as occasional circumstellar emission. Their lack of intrinsic polarization
in comparison with the similar Be stars may be explained by the dominance of
radiation as a wind driving force due to higher luminosity, which results in
lower density and less rotational flattening in the electron scattering inner
envelopes where the polarization is produced. However, time series of
polarization measurements taken simultaneously with H-alpha and UV spectroscopy
during several coordinated multiwavelength campaigns suggest two cases of
possible small-amplitude, periodic short-term polarization variability, and
therefore intrinsic polarization, which may be correlated with the more widely
recognized spectroscopic variations.Comment: LaTeX2e, 22 pages including 11 tables; 12 separate gif figures; uses
aastex.cls preprint package; accepted by The Astronomical Journa
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Bump start needed: linking guidelines, policy and practice in promoting physical activity during and beyond pregnancy
First paragraph: There is compelling evidence that regular physical activity (PA) during pregnancy benefits both mother and baby.1 2 Notably, physical and psychological benefits are evident in the literature, such as marked reductions in the development of gestational diabetes and hypertensive disorders, alongside improvements in depressive symptoms and cardiorespiratory fitness.1 2 The evidence base has been reflected by recent policy initiatives, for example, in 2017 (relaunched in 2019), the UKâs chief medical officers (CMOs) published PA guidelines for pregnant women, which made substantial strides in unifying and translating the evidence into recommendations.1 The CMO guidelines are aimed at supporting health professionals to provide consistent, evidence-based PA messages to women throughout pregnancy.1 Recently, the Chartered Institute for the Management of Sport and Physical Activity have updated their professional standards for working with antenatal and postnatal clients to align with these CMO guidelines.3 However, not all women have access to professionals with this level of expertise and training, potentially limiting the impact of the CMO guidelines
Nonlinear propagation of light in Dirac matter
The nonlinear interaction between intense laser light and a quantum plasma is
modeled by a collective Dirac equation coupled with the Maxwell equations. The
model is used to study the nonlinear propagation of relativistically intense
laser light in a quantum plasma including the electron spin-1/2 effect. The
relativistic effects due to the high-intensity laser light lead, in general, to
a downshift of the laser frequency, similar to a classical plasma where the
relativistic mass increase leads to self-induced transparency of laser light
and other associated effects. The electron spin-1/2 effects lead to a frequency
up- or downshift of the electromagnetic (EM) wave, depending on the spin state
of the plasma and the polarization of the EM wave. For laboratory solid density
plasmas, the spin-1/2 effects on the propagation of light are small, but they
may be significant in super-dense plasma in the core of white dwarf stars. We
also discuss extensions of the model to include kinetic effects of a
distribution of the electrons on the nonlinear propagation of EM waves in a
quantum plasma.Comment: 9 pages, 2 figure
Counting reducible, powerful, and relatively irreducible multivariate polynomials over finite fields
We present counting methods for some special classes of multivariate
polynomials over a finite field, namely the reducible ones, the s-powerful ones
(divisible by the s-th power of a nonconstant polynomial), and the relatively
irreducible ones (irreducible but reducible over an extension field). One
approach employs generating functions, another one uses a combinatorial method.
They yield exact formulas and approximations with relative errors that
essentially decrease exponentially in the input size.Comment: to appear in SIAM Journal on Discrete Mathematic
306 KNEE CONFIDENCE AND PHYSICAL FUNCTION IN PERSONS WITH OR AT RISK FOR KNEE OSTEOARTHRITIS: DATA FROM THE OSTEOARTHRITIS INITIATIVE
Health System Performance for the High-Need Patient: A Look at Access to Care and Patient Care Experiences
Achieving a high-performing health system will require improving outcomes and reducing costs for high-need, high-cost patientsâthose who use the most health care services and account for a disproportionately large share of health care spending. Goal: To compare the health care experiences of adults with high needsâthose with three or more chronic diseases and a functional limitation in the ability to care for themselves or perform routine daily tasksâto all adults and to those with multiple chronic diseases but no functional limitations. Methods: Analysis of data from the 2009â2011 Medical Expenditure Panel Survey. Key findings: High-need adults were more likely to report having an unmet medical need and less likely to report having good patientâprovider communication. High-need adults reported roughly similar ease of obtaining specialist referrals as other adults and greater likelihood of having a medical home. While adults with private health insurance reported the fewest unmet needs overall, privately insured highneed adults reported the greatest difficulties having their needs met. Conclusion: The health care system needs to work better for the highest-need, most-complex patients. This study's findings highlight the importance of tailoring interventions to address their need
Animal Assisted Therapy in Pediatric Speech-Language Therapy with a Preschool Child with Severe Language Delay: A Single-Subject Design
Background: The application of animal assisted therapy (AAT) in provision of services is an emerging area of research in the allied health literature. Prior investigators have called for additional research concerning applications of animal assisted therapy in specific settings and patient populations.
Objectives: to (a) investigate the effect of animal assisted therapy on the quantity of vocalizations in a single child participant with severe speech delay, and (b) identify optimal animal assisted therapy practices in pediatric group speech-language therapy.
Design: A case study was conducted using ABA single-case design. The number of vocalizations produced by the participant was measured for 15-minute periods during four initial baseline (no animal assisted therapy) sessions, four sessions with the intervention condition (animal assisted therapy), and three additional baseline (no animal assisted therapy) sessions. Observations were also recorded concerning the interactions between the animal assisted therapy team, the participant, and other children in the group.
Results: The number of vocalizations increased markedly during the intervention phase, and the effect was nonreversible. The participant also demonstrated increased attention to tasks and activities during the intervention phase. An increase in unpredictable, forceful movements by the participant and other children was observed after 10-minutes.
Conclusions: Although the same degree of increase in vocalizations is not expected for every child exposed to animal assisted therapy, results suggest that animal assisted therapy is a potentially valuable tool for speech-language pathologists working with children who have severe delays in communication skills. Recommendations for future research include consideration of time limits for animal assisted therapy interventions, detailed advance planning with the handler to minimize stressors for the animal assisted therapy team, and ensuring adequate adult personnel for data collection and management of the intervention sessions
Fluorescent Silicon Clusters and Nanoparticles
The fluorescence of silicon clusters is reviewed. Atomic clusters of silicon
have been at the focus of research for several decades because of the relevance
of size effects for material properties, the importance of silicon in
electronics and the potential applications in bio-medicine. To date numerous
examples of nanostructured forms of fluorescent silicon have been reported.
This article introduces the principles and underlying concepts relevant for
fluorescence of nanostructured silicon such as excitation, energy relaxation,
radiative and non-radiative decay pathways and surface passivation.
Experimental methods for the production of silicon clusters are presented. The
geometric and electronic properties are reviewed and the implications for the
ability to emit fluorescence are discussed. Free and pure silicon clusters
produced in molecular beams appear to have properties that are unfavourable for
light emission. However, when passivated or embedded in a suitable host, they
may emit fluorescence. The current available data show that both quantum
confinement and localised transitions, often at the surface, are responsible
for fluorescence. By building silicon clusters atom by atom, and by embedding
them in shells atom by atom, new insights into the microscopic origins of
fluorescence from nanoscale silicon can be expected.Comment: 5 figures, chapter in "Silicon Nanomaterials Sourcebook", editor
Klaus D. Sattler, CRC Press, August 201
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