1,566 research outputs found
Probability Density Functions to Represent Magnetic Fields at the Solar Surface
Numerical simulations of magneto-convection and analysis of solar magnetogram
data provide empirical probability density functions (PDFs) for the
line-of-sight component of the magnetic field. In this paper, we theoretically
explore effects of several types of PDFs on polarized Zeeman line formation. We
also propose composite PDFs to account for randomness in both field strength
and orientation. Such PDFs can possibly mimic random fields at the solar
surface.Comment: To appear in "Magnetic Coupling between the Interior and the
Atmosphere of the Sun", eds. S.S. Hasan and R.J. Rutten, Astrophysics and
Space Science Proceedings, Springer-Verlag, Heidelberg, Berlin, 200
Challenges of Incorporating Digital Health Technology Outcomes in a Clinical Trial: Experiences from PD STAT.
Digital health technologies (DHTs) have great potential for use as clinical trial outcomes; however, practical issues need to be addressed in order to maximise their benefit. We describe our experience of incorporating two DHTs as secondary/exploratory outcome measures in PD STAT, a randomised clinical trial of simvastatin in people with Parkinson's disease. We found much higher rates of missing data in the DHTs than the traditional outcome measures, in particular due to technical and software difficulties. We discuss methods to address these obstacles in terms of protocol design, workforce training and data management
Challenges of Incorporating Digital Health Technology Outcomes in a Clinical Trial: Experiences from PD STAT
\ua9 2022 - The authors. Published by IOS Press.Digital health technologies (DHTs) have great potential for use as clinical trial outcomes; however, practical issues need to be addressed in order to maximise their benefit. We describe our experience of incorporating two DHTs as secondary/exploratory outcome measures in PD STAT, a randomised clinical trial of simvastatin in people with Parkinson\u27s disease. We found much higher rates of missing data in the DHTs than the traditional outcome measures, in particular due to technical and software difficulties. We discuss methods to address these obstacles in terms of protocol design, workforce training and data management
Recommended from our members
Circulating C3 is Necessary and Sufficient for Induction of Autoantibody-Mediated Arthritis in a Mouse Model
Objective. For the inflammation characteristic of rheumatoid arthritis, the relative contribution of mediators produced locally in the synovium versus those circulating systemically is unknown. Complement factor C3 is made in rheumatoid synovium and has been proposed to be a crucial driver of inflammation. The aim of this study was to test, in a mouse model of rheumatoid arthritis, whether C3 synthesized within the synovium is important in promoting inflammation. Methods. Radiation bone marrow chimeras between normal and C3â/â mice were constructed in order to generate animals that expressed or lacked expression of C3 only in hematopoietic cells. Parabiotic mice were made by surgically linking C3â/â mice to irradiated wild-type mice to obtain animals having C3 only in the circulation. Arthritis was induced by injection of serum from arthritic K/BxN mice.Results In bone marrow chimeras, synthesis of C3 by radioresistant cells was necessary and sufficient to confer susceptibility to serum-transferred arthritis. Parabionts having C3 only in the circulation remained sensitive to arthritis induction, and the cartilage of these arthritic mice contained deposits of C3. Conclusion. In a mouse model in which the alternative pathway of complement activation is critical to the induction of arthritis by autoantibodies, circulating C3 was necessary and sufficient for arthritis induction.Stem Cell and Regenerative Biolog
A qualitative evidence synthesis of employees' views of workplace smoking reduction or cessation interventions
Background
The need to reduce smoking rates is a recognised public health policy issue in many countries. The workplace offers a potential context for offering smokersâ programmes and interventions to assist smoking cessation or reduction. A qualitative evidence synthesis of employeesâ views about such programmes might explain why some interventions appear effective and others not, and can be used to develop evidence-based interventions for this population and setting.
Methods
A qualitative evidence synthesis of primary research exploring employeesâ views about workplace interventions to encourage smoking cessation, including both voluntary programmes and passive interventions, such as restrictions or bans. The method used was theory-based âbest fitâ framework synthesis.
Results
Five relevant theories on workplace smoking cessation were identified and used as the basis for an a priori framework. A comprehensive literature search, including interrogation of eight databases, retrieved 747 unique citations for the review. Fifteen primary research studies of qualitative evidence were found to satisfy the inclusion criteria. The synthesis produced an evidence-based conceptual model explaining employeesâ experiences of, and preferences regarding, workplace smoking interventions.
Conclusion
The synthesis suggests that workplace interventions should employ a range of different elements if they are to prove effective in reducing smoking among employees. This is because an employee who feels ready and able to change their behaviour has different needs and preferences from an employee who is not at that stage. Only a multi-faceted intervention can satisfy the requirements of all employees
Hemispherical power asymmetry: parameter estimation from CMB WMAP5 data
We reexamine the evidence of the hemispherical power asymmetry, detected in
the CMB WMAP data using a new method. At first, we analyze the hemispherical
variance ratios and compare these with simulated distributions. Secondly,
working within a previously-proposed CMB bipolar modulation model, we constrain
model parameters: the amplitude and the orientation of the modulation field as
a function of various multipole bins. Finally, we select three ranges of
multipoles leading to the most anomalous signals, and we process corresponding
100 Gaussian, random field (GRF) simulations, treated as observational data, to
further test the statistical significance and robustness of the hemispherical
power asymmetry. For our analysis we use the Internally-Linearly-Coadded (ILC)
full sky map, and KQ75 cut-sky V channel, foregrounds reduced map of the WMAP
five year data (V5). We constrain the modulation parameters using a generic
maximum a posteriori method.
In particular, we find differences in hemispherical power distribution, which
when described in terms of a model with bipolar modulation field, exclude the
field amplitude value of the isotropic model A=0 at confidence level of ~99.5%
(~99.4%) in the multipole range l=[7,19] (l=[7,79]) in the V5 data, and at the
confidence level ~99.9% in the multipole range l=[7,39] in the ILC5 data, with
the best fit (modal PDF) values in these particular multipole ranges of A=0.21
(A=0.21) and A=0.15 respectively. However, we also point out that similar or
larger significances (in terms of rejecting the isotropic model), and large
best-fit modulation amplitudes are obtained in GRF simulations as well, which
reduces the overall significance of the CMB power asymmetry down to only about
94% (95%) in the V5 data, in the range l=[7,19] (l=[7,79]).Comment: 24 pages, 10 figures; few typos corrected; published in JCA
"Best fit" framework synthesis: refining the method
Background
Following publication of the first worked example of the âbest fitâ method of evidence synthesis for the systematic review of qualitative evidence in this journal, the originators of the method identified a need to specify more fully some aspects of this particular derivative of framework synthesis.
Methods and Results
We therefore present a second such worked example in which all techniques are defined and explained, and their appropriateness is assessed. Specified features of the method include the development of new techniques to identify theories in a systematic manner; the creation of an a priori framework for the synthesis; and the âtestingâ of the synthesis. An innovative combination of existing methods of quality assessment, analysis and synthesis is used to complete the process. This second worked example was a qualitative evidence synthesis of employeesâ views of workplace smoking cessation interventions, in which the âbest fitâ method was found to be practical and fit for purpose.
Conclusions
The method is suited to producing context-specific conceptual models for describing or explaining the decision-making and health behaviours of patients and other groups. It offers a pragmatic means of conducting rapid qualitative evidence synthesis and generating programme theories relating to intervention effectiveness, which might be of relevance both to researchers and policy-makers
Magnetic Coupling in the Quiet Solar Atmosphere
Three kinds of magnetic couplings in the quiet solar atmosphere are
highlighted and discussed, all fundamentally connected to the Lorentz force.
First the coupling of the convecting and overshooting fluid in the surface
layers of the Sun with the magnetic field. Here, the plasma motion provides the
dominant force, which shapes the magnetic field and drives the surface dynamo.
Progress in the understanding of the horizontal magnetic field is summarized
and discussed. Second, the coupling between acoustic waves and the magnetic
field, in particular the phenomenon of wave conversion and wave refraction. It
is described how measurements of wave travel times in the atmosphere can
provide information about the topography of the wave conversion zone, i.e., the
surface of equal Alfv\'en and sound speed. In quiet regions, this surface
separates a highly dynamic magnetic field with fast moving magnetosonic waves
and shocks around and above it from the more slowly evolving field of high-beta
plasma below it. Third, the magnetic field also couples to the radiation field,
which leads to radiative flux channeling and increased anisotropy in the
radiation field. It is shown how faculae can be understood in terms of this
effect. The article starts with an introduction to the magnetic field of the
quiet Sun in the light of new results from the Hinode space observatory and
with a brief survey of measurements of the turbulent magnetic field with the
help of the Hanle effect.Comment: To appear in "Magnetic Coupling between the Interior and the
Atmosphere of the Sun", eds. S.S. Hasan and R.J. Rutten, Astrophysics and
Space Science Proceedings, Springer-Verlag, Heidelberg, Berlin, 200
- âŠ