1,618 research outputs found
The spectral content of SDO/AIA 1600 and 1700 \AA\ filters from flare and plage observations
The strong enhancement of the ultraviolet emission during solar flares is
usually taken as an indication of plasma heating in the lower solar atmosphere
caused by the deposition of the energy released during these events. Images
taken with broadband ultraviolet filters by the {\em Transition Region and
Coronal Explorer} (TRACE) and {\em Atmospheric Imaging Assembly} (AIA 1600 and
1700~\AA) have revealed the morphology and evolution of flare ribbons in great
detail. However, the spectral content of these images is still largely unknown.
Without the knowledge of the spectral contribution to these UV filters, the use
of these rich imaging datasets is severely limited. Aiming to solve this issue,
we estimate the spectral contributions of the AIA UV flare and plage images
using high-resolution spectra in the range 1300 to 1900~\AA\ from the Skylab
NRL SO82B spectrograph. We find that the flare excess emission in AIA 1600~\AA\
is { dominated by} the \ion{C}{4} 1550~\AA\ doublet (26\%), \ion{Si}{1}
continua (20\%), with smaller contributions from many other chromospheric lines
such as \ion{C}{1} 1561 and 1656~\AA\ multiplets, \ion{He}{2} 1640~\AA,
\ion{Si}{2} 1526 and 1533~\AA. For the AIA 1700~\AA\ band, \ion{C}{1} 1656~\AA\
multiplet is the main contributor (38\%), followed by \ion{He}{2} 1640 (17\%),
and accompanied by a multitude of other, { weaker} chromospheric lines, with
minimal contribution from the continuum. Our results can be generalized to
state that the AIA UV flare excess emission is of chromospheric origin, while
plage emission is dominated by photospheric continuum emission in both
channels.Comment: Accepted for publication in ApJ Skylab NRL SO82B data used in this
work available at http://dx.doi.org/10.5525/gla.researchdata.68
A White Light Megaflare on the dM4.5e Star YZ CMi
On UT 2009 January 16, we observed a white light megaflare on the dM4.5e star
YZ CMi as part of a long-term spectroscopic flare-monitoring campaign to
constrain the spectral shape of optical flare continuum emission. Simultaneous
U-band photometric and 3350A-9260A spectroscopic observations were obtained
during 1.3 hours of the flare decay. The event persisted for more than 7 hours
and at flare peak, the U-band flux was almost 6 magnitudes brighter than in the
quiescent state. The properties of this flare mark it as one of the most
energetic and longest-lasting white light flares ever to be observed on an
isolated low-mass star. We present the U-band flare energetics and a flare
continuum analysis. For the first time, we show convincingly with spectra that
the shape of the blue continuum from 3350A to 4800A can be represented as a sum
of two components: a Balmer continuum as predicted by the Allred et al
radiative hydrodynamic flare models and a T ~ 10,000K blackbody emission
component as suggested by many previous studies of the broadband colors and
spectral distributions of flares. The areal coverage of the Balmer continuum
and blackbody emission regions vary during the flare decay, with the Balmer
continuum emitting region always being significantly (~3-16 times) larger.
These data will provide critical constraints for understanding the physics
underlying the mysterious blue continuum radiation in stellar flares.Comment: 12 pages, 4 figures, accepted by Astrophysical Journal Letter
Drug-related stigma and access to care among people who inject drugs in Vietnam.
Introduction and aimsThere are considerable challenges faced by people with a history of injecting drug use (PWID) in Vietnam, including drug-related stigma and lack of access to healthcare. Seeking and utilising healthcare, as well as harm reduction programs for PWID, are often hampered by drug-related stigma. This study aimed to examine the impacts of drug-related stigma on access to care and utilisation of harm reduction programs among PWID in Vietnam.Design and methodsA cross-sectional study was conducted in two provinces in Vietnam, PhĂș Thá» and Vinh PhĂșc. The study participants completed the survey by using Audio Computer-Assisted Self-Interview between late 2014 and early 2015. Linear multiple regression models and logistic regression models were used to assess the relationship among drug-related stigma, access to care and utilisation of harm reduction programs, including methadone maintenance treatment (MMT) and needle exchange programs (NEP).ResultsA total of 900 PWID participated in this study. Drug-related stigma was significantly associated with lower level of access to care, but not with utilisation of MMT or NEP. Older age was positively associated with higher levels of access to care. Levels of education were positively correlated with access to care, as well as utilisation of MMT and NEP.Discussion and conclusionsThis study underscores the need for future interventions to reduce drug-related stigma in society and in health-care settings to improve PWID's utilisation of care services. Special attention should be paid to younger PWID and those with lower levels of education
The F-CHROMA grid of 1D RADYN flare models
Context: Solar flares are the result of the sudden release of magnetic energy
in the corona. Much of this energy goes into accelerating charged particles to
high velocity. These particles travel along the magnetic field and the energy
is dissipated when the density gets high enough, primarily in the solar
chromosphere. Modelling this region is difficult because the radiation energy
balance is dominated by strong, optically thick spectral lines.
Aims: Our aim is to provide the community with realistic simulations of a
flaring loop with an emphasis on the detailed treatment of the chromospheric
energy balance. This will enable a detailed comparison of existing and upcoming
observations with synthetic observables from the simulations, thereby
elucidating the complex interactions in a flaring chromosphere.
Methods: We used the 1D radiation hydrodynamics code RADYN to perform
simulations of the effect of a beam of electrons injected at the apex of a
solar coronal loop. A grid of models was produced, varying the total energy
input, the steepness, and low-energy cutoff of the beam energy spectrum.
Results: The full simulation results for a grid of models are made available
online. Some general properties of the simulations are discussed.Comment: 11 pages, 9 figures. Accepted for publication in Astronomy &
Astrophysic
The removal of thermally aged films of triacylglycerides by surfactant solutions
Thermal ageing of triacylglycerides (TAG) at high temperatures produces films which resist removal using aqueous surfactant solutions. We used a mass loss method to investigate the removal of thermally aged TAG films from hard surfaces using aqueous solutions of surfactants of different charge types. It was found that cationic surfactants are most effective at high pH, whereas anionics are most effective at low pH and a non-ionic surfactant is most effective at intermediate pH. We showed that the TAG film removal process occurs in several stages. In the first ââlag phaseââ no TAG removal occurs; the surfactant first partitions into the thermally aged film. In the second stage, the TAG film containing surfactant was removed by solubilisation into micelles in the aqueous solution. The effects of pH and surfactant charge on the TAG removal process correlate with the effects of these variables on the extent of surfactant partitioning to the TAG film and on the maximum extent of TAG solubilisation within the micelles. Additionally, we showed how the TAG removal is enhanced by the addition of amphiphilic additives such as alcohols which act as co-surfactants. The study demonstrates that aqueous surfactant solutions provide a viable and more benign alternative to current methods for the removal of thermally aged TAG films
Landau-Ginzburg String Vacua
We investigate a class of (2,2) supersymmetric string vacua which may be
represented as Landau--Ginzburg theories with a quasihomogeneous potential
which has an isolated singularity at the origin. There are at least three
thousand distinct models in this class. All vacua of this type lead to Euler
numbers which lie in the range . The Euler
characteristics do not pair up completely hence the space of Landau--Ginzburg
ground states is not mirror symmetric even though it exhibits a high degree of
symmetry. We discuss in some detail the relation between Landau--Ginzburg
models and Calabi--Yau manifolds and describe a subtlety regarding
Landau--Ginzburg potentials with an arbitrary number of fields. We also show
that the use of topological identities makes it possible to relate
Landau-Ginzburg theories to types of Calabi-Yau manifolds for which the usual
Landau-Ginzburg framework does not apply.Comment: 92p
Morinda citrifolia
Introduction. Noni (Morinda citrifolia) has been used for many years as an anti-inflammatory agent. We tested the efficacy of Noni in women with dysmenorrhea. Method. We did a prospective randomized double-blind placebo-controlled trial in 100 university students of 18 years and older over three menstrual cycles. Patients were invited to participate and randomly assigned to receive 400âmg Noni capsules or placebo. They were assessed for baseline demographic variables such as age, parity, and BMI. They were also assessed before and after treatment, for pain, menstrual blood loss, and laboratory variables: ESR, hemoglobin, and packed cell volume. Results. Of the 1027 women screened, 100 eligible women were randomized. Of the women completing the study, 42 women were randomized to Noni and 38 to placebo. There were no significant differences in any of the variables at randomization. There were also no significant differences in mean bleeding score or pain score at randomization. Both bleeding and pain scores gradually improved in both groups as the women were observed over three menstrual cycles; however, the improvement was not significantly different in the Noni group when compared to the controls. Conclusion. Noni did not show a reduction in menstrual pain or bleeding when compared to placebo
Circular Ribbon Flares and Homologous Jets
Solar flare emissions in the chromosphere often appear as elongated ribbons
on both sides of the magnetic polarity inversion line (PIL), which has been
regarded as evidence of a typical configuration of magnetic reconnection.
However, flares having a circular ribbon have rarely been reported, although it
is expected in the fan--spine magnetic topology involving reconnection at a
three-dimensional (3D) coronal null point. We present five circular ribbon
flares with associated surges, using high-resolution and high-cadence halpha
blue wing observations obtained from the recently digitized films of Big Bear
Solar Observatory. In all the events, a central parasitic magnetic field is
encompassed by the opposite polarity, forming a circular PIL traced by filament
material. Consequently, a flare kernel at the center is surrounded by a
circular flare ribbon. The four homologous jet-related flares on 1991 March 17
and 18 are of particular interest, as (1) the circular ribbons brighten
sequentially, with co-spatial surges, rather than simultaneously, (2) the
central flare kernels show an intriguing "round-trip" motion and become
elongated, and (3) remote brightenings occur at a region with the same magnetic
polarity as the central parasitic field and are co-temporal with a separate
phase of flare emissions. In another flare on 1991 February 25, the circular
flare emission and surge activity occur successively, and the event could be
associated with magnetic flux cancellation across the circular PIL. We discuss
the implications of these observations combining circular flare ribbons,
homologous jets, and remote brightenings for understanding the dynamics of 3D
magnetic restructuring.Comment: Ap.J., accepte
Culture change in elite sport performance teams: Examining and advancing effectiveness in the new era
Reflecting the importance of optimizing culture for elite teams, Fletcher and Arnold (2011) recently suggested the need for expertise in culture change. Acknowledging the dearth of literature on the specific process, however, the potential effectiveness of practitioners in this area is unknown. The present paper examines the activity's precise demands and the validity of understanding in sport psychology and organizational research to support its delivery. Recognizing that sport psychologists are being increasingly utilized by elite team management, initial evidence-based guidelines are presented. Finally, to stimulate the development of ecologically valid, practically meaningful knowledge, the paper identifies a number of future research directions
A falls prevention programme to improve quality of life, physical function and falls efficacy in older people receiving home help services: study protocol for a randomised controlled trial
BACKGROUND:
Falls and fall-related injuries in older adults are associated with great burdens, both for the individuals, the health care system and the society. Previous research has shown evidence for the efficiency of exercise as falls prevention. An understudied group are older adults receiving home help services, and the effect of a falls prevention programme on health-related quality of life is unclear. The primary aim of this randomised controlled trial is to examine the effect of a falls prevention programme on quality of life, physical function and falls efficacy in older adults receiving home help services. A secondary aim is to explore the mediating factors between falls prevention and health-related quality of life.
METHODS:
The study is a single-blinded randomised controlled trial. Participants are older adults, aged 67 or older, receiving home help services, who are able to walk with or without walking aids, who have experienced at least one fall during the last 12 months and who have a Mini Mental State Examination of 23 or above. The intervention group receives a programme, based on the Otago Exercise Programme, lasting 12 weeks including home visits and motivational telephone calls. The control group receives usual care. The primary outcome is health-related quality of life (SF-36). Secondary outcomes are leg strength, balance, walking speed, walking habits, activities of daily living, nutritional status and falls efficacy. All measurements are performed at baseline, following intervention at 3 months and at 6 months' follow-up. Sample size, based on the primary outcome, is set to 150 participants randomised into the two arms, including an estimated 15-20% drop out. Participants are recruited from six municipalities in Norway.
DISCUSSION:
This trial will generate new knowledge on the effects of an exercise falls prevention programme among older fallers receiving home help services. This knowledge will be useful for clinicians, for health managers in the primary health care service and for policy makers
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