8,806 research outputs found
Cooperative mixing induced surface roughening in bilayer metals: a possible novel surface damage mechanism
Molecular dynamics simulations have been used to study a collective atomic
transport phenomenon by repeated Ar irradiations in the Ti/Pt interfacial
system. The ion-induced injection of surface atoms to the bulk, the ejection of
bulk atoms to the top layers together with surface erosion is strongly enhanced
by interfacial mixing. This process leads to a dense interfacial material, and
broadening of the interface region. The process scales with the relative
difference of the atomic masses. We find that surface roughening and
interfacial mixing is strongly coupled via an enhanced counterflow material
transport normal to the surface which might be a novel surface damage
mechanism. This cooperative phenomenon is active when the bilayer system is
subjected to a high dose ion irradiation (multiple ion irradiations) and leads
to surface cavity growth.Comment: 6 pages, 6 figures. accepted in Nucl. Instrum. Meth.
Prevalence and measurement of anxiety in samples of patients with heart failure
© 2016 Wolters Kluwer Health, Inc. Objectives: Rates of anxiety in patients with heart failure (HF) vary widely, and not all assessment instruments used in this patient population are appropriate. It is timely to consolidate the evidence base and establish the prevalence and variance of anxiety in HF samples. Methods: A systematic review, meta-analysis, and meta-regression were conducted to identify the prevalence, variance, and measurement of anxiety in patients with HF. Results: A total of 14,367 citations were identified, with 73 studies meeting inclusion criteria. A random effects pooled prevalence of 13.1% (95% confidence interval [CI], 9.25%-16.86%) for anxiety disorders, 28.79% (95% CI, 23.30%-34.29) for probable clinically significant anxiety, and 55.5% (95% CI, 48.08%-62.83%) for elevated symptoms of anxiety was identified. Rates of anxiety were highest when measured using the Brief Symptom Scale-Anxiety scale (72.3%) and lowest when measured using the Generalised Anxiety Disorder-7 (6.3%). Conclusion: Many patients with HF would benefit if screened for anxiety and treated. The conceptualization and measurement of anxiety accounted for most variance in prevalence rates. The Generalised Anxiety Disorder-7 or the Hospital Anxiety and Depression Scale appear to be the most appropriate instruments for this clinical population, with evidence to suggest they can discriminate between depression and anxiety, omit somatic items that may contaminate identification of anxiety in a population with physical comorbidities, and provide thresholds with which to differentiate patients and target treatments. Although there are limitations with the collation of diverse measurement methods, the current review provides researchers and clinicians with a more granular knowledge of prevalence estimates of anxiety in a population of HF patients.The research was funded through an interdisciplinary doctoral studentship jointly funded by the Medical Research Council and the Economics and Social Research Council
Dilatonic current-carrying cosmic strings
We investigate the nature of ordinary cosmic vortices in some scalar-tensor
extensions of gravity. We find solutions for which the dilaton field condenses
inside the vortex core. These solutions can be interpreted as raising the
degeneracy between the eigenvalues of the effective stress-energy tensor,
namely the energy per unit length U and the tension T, by picking a privileged
spacelike or timelike coordinate direction; in the latter case, a phase
frequency threshold occurs that is similar to what is found in ordinary neutral
current-carrying cosmic strings. We find that the dilaton contribution for the
equation of state, once averaged along the string worldsheet, vanishes, leading
to an effective Nambu-Goto behavior of such a string network in cosmology, i.e.
on very large scales. It is found also that on small scales, the energy per
unit length and tension depend on the string internal coordinates in such a way
as to permit the existence of centrifugally supported equilibrium
configuration, also known as vortons, whose stability, depending on the very
short distance (unknown) physics, can lead to catastrophic consequences on the
evolution of the Universe.Comment: 10 pages, ReVTeX, 2 figures, minor typos corrected. This version to
appear in Phys. Rev.
Secondary Physical Education Teachers’ Perceptions of Adolescent Females’ Cardiovascular Fitness
Cardiovascular fitness levels in physical education have decreased for males and females in an inner-city high school, with female cardiovascular fitness decreasing the most. Cardiovascular fitness is important because participating in cardio exercises decreases health issues such as obesity and cardio problems. The purpose of this qualitative research study was to explore the views of teachers regarding low cardiovascular fitness among adolescent females in physical education and how a professional development could help teachers to address the problem. Bandura’s social learning theory was used as the study’s conceptual framework. Semistructured and open-ended interview questions were used to collect data from 6 veteran PE teachers to address the research questions regarding teachers’ experiences in promoting cardiovascular exercises, levels of participation in cardiovascular exercises, and perceptions of professional development to help ameliorate the problem. Participant responses to the open-ended interview questions were analyzed by coding common words to create categories to develop themes. Qualitative findings revealed that participants started to notice low cardiovascular endurance in 9th grade, that professional development was not geared towards improving female adolescent activities nor assisting PE teachers in how to model these. A professional development, via the proposed project, was developed that will provide activities that can be used by both new and seasoned physical education teachers. Social change will occur in that implementation of the ideas shared in project may lead to a healthier and physically active lifestyle when students reach adulthood
Commensurate Itinerant Antiferromagnetism in BaFe2As2: 75As-NMR Studies on a Self-Flux Grown Single Crystal
We report results of 75As nuclear magnetic resonance (NMR) experiments on a
self-flux grown single crystal of BaFe2As2. A first-order antiferromagnetic
(AF) transition near 135 K was detected by the splitting of NMR lines, which is
accompanied by simultaneous structural transition as evidenced by a sudden
large change of the electric field gradient tensor at the As site. The NMR
results lead almost uniquely to the stripe spin structure in the AF phase. The
data of spin-lattice relaxation rate indicate development of anisotropic spin
fluctuations of the stripe-type with decreasing temperature in the paramagnetic
phase.Comment: 7 pages, 7 figures, accepted for publication in J. Phys. Soc. Jp
Establishing and sustaining high-quality services for people with young onset dementia: The perspective of senior service providers and commissioners
OBJECTIVES: We aimed to understand the facilitators to developing and sustaining high-quality services for people with young onset dementia (YOD) and their families/supporters. DESIGN: This qualitative study used semi-structured interviews with commissioners and service managers, analyzed using inductive thematic analysis. SETTING: A purposive sample of providers was selected from diverse areas and contrasting YOD services. PARTICIPANTS: Eighteen senior staff from YOD services and two dementia service commissioners took part. MEASUREMENTS: For commissioners, key interview topics were experiences of commissioning YOD services, perceived facilitators or barriers, and how future guidance should be structured for ease of use. For service providers, key topics explored experiences of delivering YOD services; what was achievable or challenging; how the service was funded; how it linked with broader provision for YOD in the area; and how guidance should be structured. RESULTS: Recorded interviews lasted 30–40 minutes. Seven key facilitators to the development and sustaining of YOD services were identified: having knowledgeable, committed local champions; involvement of people living with YOD and family supporters; initial delivery within existing resources; partnership working within and between sectors; having a reflective, supportive organizational culture; gathering evidence of impact; and having wider support and guidance. CONCLUSIONS: Improvements in provision for those with YOD and their families need to be built on understanding of service-level and interpersonal influences as well as on understanding of YOD itself. Our findings highlight a set of facilitators which need to be in place to establish and sustain high-quality YOD services that fit the local context
Good practice in needs-based post-diagnostic support for people with young onset dementia: findings from the Angela Project
Evidence on post-diagnostic support for people with young onset dementia is scarce. Previous studies have employed a problem-focused approach; however, evidence on ‘what works’ in real-life practice is essential to develop recommendations for service design and delivery. This study aimed to provide insight into ‘what works’ from the perspectives of people with young onset dementia and their supporters. We gathered free-text responses on positive service experiences via a UK cross-sectional survey. Inductive thematic analysis was used to identify the objectives of positive services and the needs these met. Follow-up interviews enabled in-depth insights from people with diverse diagnoses, ages and social situations. These were analysed using a template drawn from the survey. The 233 survey respondents gave 856 examples of positive support. Analysis of 24 follow-up interviews led to 16 themes clustered under three superordinate themes: ‘maintaining autonomy’, ‘being myself’ and ‘togetherness’. We found that positive services address the disruptions to sense of agency, selfhood and meaningful relationships that are experienced by those with young onset dementia. The study provides an in-depth understanding of the needs met by positive services for younger people with dementia. Our nuanced findings on good practice can inform age-specific guidelines for young onset dementia and indicate how personalisation can work in practice to help people with young onset dementia to maintain identity, autonomy and connections
How non-linear scaling relations unify dwarf and giant elliptical galaxies
Dwarf elliptical galaxies are frequently excluded from bright galaxy samples
because they do not follow the same linear relations in diagrams involving
effective half light radii R_e or mean effective surface brightnesses _e.
However, using two linear relations which unite dwarf and bright elliptical
galaxies we explain how these lead to curved relations when one introduces
either the half light radius or the associated surface brightness. In
particular, the curved _e - R_e relation is derived here. This and other
previously misunderstood curved relations, once heralded as evidence for a
discontinuity between faint and bright elliptical galaxies at M_B ~ -18 mag,
actually support the unification of such galaxies as a single population whose
structure (i.e. stellar concentration) varies continuously with stellar
luminosity and mass.Comment: 4 pages including 2 figures, to appear in "A Universe of dwarf
galaxies", Conf. Proc. (Lyon, June 14-18, 2010
Systematic variation of the stellar Initial Mass Function with velocity dispersion in early-type galaxies
An essential component of galaxy formation theory is the stellar initial mass
function (IMF), that describes the parent distribution of stellar mass in star
forming regions. We present observational evidence in a sample of early-type
galaxies (ETGs) of a tight correlation between central velocity dispersion and
the strength of several absorption features sensitive to the presence of
low-mass stars. Our sample comprises ~40,000 ETGs from the SPIDER survey
(z<0.1). The data, extracted from the Sloan Digital Sky Survey, are combined,
rejecting both noisy data, and spectra with contamination from telluric lines,
resulting in a set of 18 stacked spectra at high signal-to-noise ratio (S/N>
400 per A). A combined analysis of IMF-sensitive line strengths and spectral
fitting is performed with the latest state-of the art population synthesis
models (an extended version of the MILES models). A significant trend is found
between IMF slope and velocity dispersion, towards an excess of low-mass stars
in the most massive galaxies. Although we emphasize that accurate values of the
IMF slope will require a detailed analysis of chemical composition (such as
[a/Fe] or even individual element abundance ratios), the observed trends
suggest that low-mass ETGs are better fit by a Kroupa-like IMF, whereas massive
galaxies require bottom-heavy IMFs, exceeding the Salpeter slope at velocity
dispersions above 200km/s.Comment: 5 pages, 4 figures, accepted for publication in MNRAS Letter
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