2,199 research outputs found
A purple patch for evidence-based health policy?
The global focus on nation states' responses to the COVID-19 pandemic has rightly highlighted the importance of science and evidence as the basis for policy action. Those with a lifelong passion for evidence-based policy (EBP) have lauded Australia's and other nations' policy responses to COVID-19 as a breakthrough moment for the cause. This article reflects on the complexity of the public policy process, the perspectives of its various actors, and draws on Alford's work on the Blue, Red and Purple zones to propose a more nuanced approach to advocacy for EBP in health. We contend that the pathway for translation of research evidence into routine clinical practice is relatively linear, in contrast to the more complex course for translation of evidence to public policy - much to the frustration of health researchers and EBP advocates. Cairney's description of the characteristics of successful policy entrepreneurs offers useful guidance to advance EBP and we conclude with proposing some practical mechanisms to support it. Finally, we recommend that researchers and policy makers spend more time in the Purple zone to enable a deeper understanding of, and mutual respect for, the unique contributions made by research, policy and political actors to sound public policy
The number of beams in IMRT - theoretical investigations and implications for single-arc IMRT
The first purpose of this paper is to shed some new light on the old question
of selecting the number of beams in intensity-modulated radiation therapy
(IMRT). The second purpose is to illuminate the related issue of discrete
static beam angles vs. rotational techniques, which has recently re-surfaced
due to the advancement of volumetric arc therapy (VMAT). A specific objective
is to find analytical expressions that allow one to address the points raised
above. To make the problem mathematically tractable, it is assumed that the
depth dose is flat and that the lateral dose profile can be approximated by
polynomials, specifically Chebyshev polynomials of the first kind, of finite
degree. The application of methods known from image reconstruction then allows
one to answer the first question above as follows: The required number of beams
is determined by the maximum degree of the polynomials used in the
approximation of the beam profiles, which is a measure of the dose variability.
There is nothing to be gained by using more beams. In realistic cases, in which
the variability of the lateral dose profile is restricted in several ways, the
required number of beams is of the order of 10 to 20. The consequence of
delivering the beams with a `leaf sweep' technique during continuous rotation
of the gantry, as in VMAT, is also derived in analytical form. The main effect
is that the beams fan out, but the effect near the axis of rotation is small.
This result can serve as a theoretical justification of VMAT. Overall the
analytical derivations in this paper, albeit based on strong simplifications,
provide new insights into, and a deeper understanding of, the beam angle
problem in IMRT
Continuous macroscopic limit of a discrete stochastic model for interaction of living cells
In the development of multiscale biological models it is crucial to establish
a connection between discrete microscopic or mesoscopic stochastic models and
macroscopic continuous descriptions based on cellular density. In this paper a
continuous limit of a two-dimensional Cellular Potts Model (CPM) with excluded
volume is derived, describing cells moving in a medium and reacting to each
other through both direct contact and long range chemotaxis. The continuous
macroscopic model is obtained as a Fokker-Planck equation describing evolution
of the cell probability density function. All coefficients of the general
macroscopic model are derived from parameters of the CPM and a very good
agreement is demonstrated between CPM Monte Carlo simulations and numerical
solution of the macroscopic model. It is also shown that in the absence of
contact cell-cell interactions, the obtained model reduces to the classical
macroscopic Keller-Segel model. General multiscale approach is demonstrated by
simulating spongy bone formation from loosely packed mesenchyme via the
intramembranous route suggesting that self-organizing physical mechanisms can
account for this developmental process.Comment: 4 pages, 3 figure
Fermi Surface as the Driving Mechanism for Helical Antiferromagnetic Ordering in Gd-Y Alloys
The first direct experimental evidence for the Fermi surface (FS) driving the
helical antiferromagnetic ordering in a gadolinium-yttrium alloy is reported.
The presence of a FS sheet capable of nesting is revealed, and the nesting
vector associated with the sheet is found to be in excellent agreement with the
periodicity of the helical ordering.Comment: 4 pages, 4 figure
Recommended from our members
The martyrdom effect : when pain and effort increase prosocial contributions
Most theories of motivation and behavior (and lay intuitions alike) consider pain and effort to be deterrents. In contrast to this widely held view, we provide evidence that the prospect of enduring pain and exerting effort for a prosocial cause can promote contributions to the cause. Specifically, we show that willingness to contribute to a charitable or collective cause increases when the contribution process is expected to be painful and effortful rather than easy and enjoyable. Across five experiments, we document this “martyrdom effect,” show that the observed patterns defy standard economic and psychological accounts, and identify a mediator and moderator of the effect. Experiment 1 showed that people are willing to donate more to charity when they anticipate having to suffer to raise money. Experiment 2 extended these findings to a non-charity laboratory context that involved real money and actual pain. Experiment 3 demonstrated that the martyrdom effect is not the result of an attribute substitution strategy (whereby people use the amount of pain and effort involved in fundraising to determine donation worthiness). Experiment 4 showed that perceptions of meaningfulness partially mediate the martyrdom effect. Finally, Experiment 5 demonstrated that the nature of the prosocial cause moderates the martyrdom effect: the effect is strongest for causes associated with human suffering. We propose that anticipated pain and effort lead people to ascribe greater meaning to their contributions and to the experience of contributing, thereby motivating higher prosocial contributions. We conclude by considering some implications of this puzzling phenomenon. Copyright © 2011 John Wiley & Sons, Ltd
Attention and fluctuating attention in patients with dementia with lewy bodies and alzheimer disease
Background: Attentional deficits are described in the consensus clinical criteria for the operationalized diagnosis of dementia with Lewy bodies (DLB) as characteristic of the condition. In addition, preliminary studies have indicated that both attentional impairments and fluctuation of attentional impairments are more marked in patients with DLB than in patients with Alzheimer disease (AD), although neuropsychological function has not previously been examined in a large prospective cohort with confirmed diagnostic accuracy against postmortem diagnosis. Methods: A detailed evaluation of attention and fluctuating attention was undertaken in 155 patients with dementia (85 with DLB and 80 with AD) from a representative hospital dementia case register and 35 elderly controls using the Cognitive Drug Research Computerized Assessment System for Dementia Patients computerized neuropsychological battery. Operationalized clinical diagnosis was made using the consensus criteria for DLB and the National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer's Disease and Related Disorders Association criteria for AD. High levels of sensitivity and specificity have been achieved for the first 50 cases undergoing postmortem examination. Results: The groups were well matched for severity of cognitive impairments, bur the AD patients were older (mean age, 80 vs 78 years) and more likely to be female (55 vs 40). Patients with DLB were significantly more impaired than patients with AD on all measures of attention and fluctuating attention (for all comparisons, t � 2.5, P<.001), and patients from both dementia groups were significantly more impaired than elderly controls for all comparisons other than cognitive reaction time, which was significantly more impaired in DLB patients than controls but was comparable in controls and AD patients. There were, however, significant associations between the severity of cognitive impairment and the severity of both attentional deficits and fluctuations in attention. Conclusions: This large prospective study confirms that slowing of cognitive processing, attention, and fluctuations of attention are significantly more pronounced in DLB and AD patients, although fluctuating attention is common in patients with moderate-to-severe AD. Deficits of cognitive reaction rime appear to be specific to DLB, except in severe dementia. A detailed evaluation of attentional performance could make an important contribution to differential diagnosis, although the results need to be interpreted within the context of the overall severity of cognitive deficits
Thermodynamic Structure of the Solar Corona: Tomographic Reconstructions and MHD Modeling
We carry out a study of the global three-dimensional (3D) structure of the
electron density and temperature of the quiescent inner solar corona () by means of tomographic reconstructions and magnetohydrodynamic
simulations. We use differential emission measure tomography (DEMT) and the
Alfv\'en Wave Solar Model (AWSoM), in their latest versions. Two target
rotations were selected from the solar minimum between solar cycles (SCs) 23
and 24 and the declining phase of SC 24. We report in quantitative detail on
the 3D thermodynamic structure of the core and outer layers of the streamer
belt, and of the high latitude coronal holes (CH), as revealed by the DEMT
analysis. We report on the presence of two types of structures within the
streamer belt, loops with temperature decreasing/increasing with height (dubbed
down/up loops), as reported first in previous DEMT studies. We also estimate
the heating energy flux required at the coronal base to keep these structures
stable, found to be or order , consistently with
previous DEMT and spectroscopic studies. We discuss how these findings are
consistent with coronal dissipation of Alfv\'en waves. We compare the 3D
results of DEMT and AWSoM in distinct magnetic structures. We show that the
agreement between the products of both techniques is the best so far, with an
overall agreement , depending on the target rotation and the
specific coronal region. In its current implementation the ASWsoM model can not
reproduce down loops though. Also, in the source region of the fast and slow
components of the solar wind, the electron density of the AWSoM model increases
with latitude, opposite to the trend observed in DEMT reconstructions
Does ohmic heating influence the flow field in thin-layer electrodeposition?
In thin-layer electrodeposition the dissipated electrical energy leads to a
substantial heating of the ion solution. We measured the resulting temperature
field by means of an infrared camera. The properties of the temperature field
correspond closely with the development of the concentration field. In
particular we find, that the thermal gradients at the electrodes act like a
weak additional driving force to the convection rolls driven by concentration
gradients.Comment: minor changes: correct estimation of concentration at the anode,
added Journal-re
- …