2,115 research outputs found
The development of QUADAS : a tool for the quality assessment of studies of diagnostic accuracy included in systematic reviews
BACKGROUND: In the era of evidence based medicine, with systematic reviews as its cornerstone, adequate quality assessment tools should be available. There is currently a lack of a systematically developed and evaluated tool for the assessment of diagnostic accuracy studies. The aim of this project was to combine empirical evidence and expert opinion in a formal consensus method to develop a tool to be used in systematic reviews to assess the quality of primary studies of diagnostic accuracy. METHODS: We conducted a Delphi procedure to develop the quality assessment tool by refining an initial list of items. Members of the Delphi panel were experts in the area of diagnostic research. The results of three previously conducted reviews of the diagnostic literature were used to generate a list of potential items for inclusion in the tool and to provide an evidence base upon which to develop the tool. RESULTS: A total of nine experts in the field of diagnostics took part in the Delphi procedure. The Delphi procedure consisted of four rounds, after which agreement was reached on the items to be included in the tool which we have called QUADAS. The initial list of 28 items was reduced to fourteen items in the final tool. Items included covered patient spectrum, reference standard, disease progression bias, verification bias, review bias, clinical review bias, incorporation bias, test execution, study withdrawals, and indeterminate results. The QUADAS tool is presented together with guidelines for scoring each of the items included in the tool. CONCLUSIONS: This project has produced an evidence based quality assessment tool to be used in systematic reviews of diagnostic accuracy studies. Further work to determine the usability and validity of the tool continue
Antiferromagnetism in metals: from the cuprate superconductors to the heavy fermion materials
The critical theory of the onset of antiferromagnetism in metals, with
concomitant Fermi surface reconstruction, has recently been shown to be
strongly coupled in two spatial dimensions. The onset of unconventional
superconductivity near this critical point is reviewed: it involves a subtle
interplay between the breakdown of fermionic quasiparticle excitations on the
Fermi surface, and the strong pairing glue provided by the antiferromagnetic
fluctuations. The net result is a logarithm-squared enhancement of the pairing
vertex for generic Fermi surfaces, with a universal dimensionless co-efficient
independent of the strength of interactions, which is expected to lead to
superconductivity at the scale of the Fermi energy. We also discuss the
possibility that the antiferromagnetic critical point can be replaced by an
intermediate `fractionalized Fermi liquid' phase, in which there is Fermi
surface reconstruction but no long-range antiferromagnetic order. We discuss
the relevance of this phase to the underdoped cuprates and the heavy-fermion
materials.Comment: Talk at SCES 2011; 19 pages, 12 figures; (v2) corrected typo
Electronic Liquid Crystal Phases of a Doped Mott Insulator
The character of the ground state of an antiferromagnetic insulator is
fundamentally altered upon addition of even a small amount of charge. The added
charges agglomerate along domain walls at which the spin correlations, which
may or may not remain long-ranged, suffer a phase shift. In two
dimensions, these domain walls are ``stripes'' which are either insulating, or
conducting, i.e. metallic rivers with their own low energy degrees of freedom.
However, quasi one-dimensional metals typically undergo a transition to an
insulating ordered charge density wave (CDW) state at low temperatures. Here it
is shown that such a transition is eliminated if the zero-point energy of
transverse stripe fluctuations is sufficiently large in comparison to the CDW
coupling between stripes. As a consequence, there exist novel,
liquid-crystalline low-temperature phases -- an electron smectic, with
crystalline order in one direction, but liquid-like correlations in the other,
and an electron nematic with orientational order but no long-range positional
order. These phases, which constitute new states of matter, can be either high
temperature supeconductors or two-dimensional anisotropic ``metallic''
non-Fermi liquids. Evidence for the new phases may already have been obtained
by neutron scattering experiments in the cuprate superconductor,
La_{1.6-x}Nd_{0.4}Sr_xCuO_{4}.Comment: 5 pages in RevTex with two figures in ep
Smeared versus localised sources in flux compactifications
We investigate whether vacuum solutions in flux compactifications that are
obtained with smeared sources (orientifolds or D-branes) still survive when the
sources are localised. This seems to rely on whether the solutions are BPS or
not. First we consider two sets of BPS solutions that both relate to the GKP
solution through T-dualities: (p+1)-dimensional solutions from
spacetime-filling Op-planes with a conformally Ricci-flat internal space, and
p-dimensional solutions with Op-planes that wrap a 1-cycle inside an everywhere
negatively curved twisted torus. The relation between the solution with smeared
orientifolds and the localised version is worked out in detail. We then
demonstrate that a class of non-BPS AdS_4 solutions that exist for IASD fluxes
and with smeared D3-branes (or analogously for ISD fluxes with anti-D3-branes)
does not survive the localisation of the (anti) D3-branes. This casts doubts on
the stringy consistency of non-BPS solutions that are obtained in the limit of
smeared sources.Comment: 23 pages; v2: minor corrections, added references, version published
in JHE
Tau protein, A beta 42 and S-100B protein in cerebrospinal fluid of patients with dementia with Lewy bodies
The intra vitam diagnosis of dementia with Lewy bodies (DLB) is still based on clinical grounds. So far no technical investigations have been available to support this diagnosis. As for tau protein and beta-amyloid((1-42)) (Abeta42), promising results for the diagnosis of Alzheimer's disease ( AD) have been reported; we evaluated these markers and S-100B protein in cerebrospinal fluid (CSF), using a set of commercially available assays, of 71 patients with DLB, 67 patients with AD and 41 nondemented controls (NDC) for their differential diagnostic relevance. Patients with DLB showed significantly lower tau protein values compared to AD but with a high overlap of values. More prominent differences were observed in the comparison of DLB patients with all three clinical core features and AD patients. Abeta42 levels were decreased in the DLB and AD groups versus NDC, without significant subgroup differences. S-100B levels were not significantly different between the groups. Tau protein levels in CSF may contribute to the clinical distinction between DLB and AD, but the value of the markers is still limited especially due to mixed pathology. We conclude that more specific markers have to be established for the differentiation of these diseases. Copyright (C) 2005 S. Karger AG, Basel
Surveillance strategies for Classical Swine Fever in wild boar – a comprehensive evaluation study to ensure powerful surveillance
Surveillance of Classical Swine Fever (CSF) should not only focus on livestock, but must also include wild boar. To prevent disease transmission into commercial pig herds, it is therefore vital to have knowledge about the disease status in wild boar. In the present study, we performed a comprehensive evaluation of alternative surveillance strategies for Classical Swine Fever (CSF) in wild boar and compared them with the currently implemented conventional approach. The evaluation protocol was designed using the EVA tool, a decision support tool to help in the development of an economic and epidemiological evaluation protocol for surveillance. To evaluate the effectiveness of the surveillance strategies, we investigated their sensitivity and timeliness. Acceptability was analysed and finally, the cost-effectiveness of the surveillance strategies was determined. We developed 69 surveillance strategies for comparative evaluation between the existing approach and the novel proposed strategies. Sampling only within sub-adults resulted in a better acceptability and timeliness than the currently implemented strategy. Strategies that were completely based on passive surveillance performance did not achieve the desired detection probability of 95%. In conclusion, the results of the study suggest that risk-based approaches can be an option to design more effective CSF surveillance strategies in wild boar
The Herschel Exploitation of Local Galaxy Andromeda (HELGA) II: Dust and Gas in Andromeda
We present an analysis of the dust and gas in Andromeda, using Herschel
images sampling the entire far-infrared peak. We fit a modified-blackbody model
to ~4000 quasi-independent pixels with spatial resolution of ~140pc and find
that a variable dust-emissivity index (beta) is required to fit the data. We
find no significant long-wavelength excess above this model suggesting there is
no cold dust component. We show that the gas-to-dust ratio varies radially,
increasing from ~20 in the center to ~70 in the star-forming ring at 10kpc,
consistent with the metallicity gradient. In the 10kpc ring the average beta is
~1.9, in good agreement with values determined for the Milky Way (MW). However,
in contrast to the MW, we find significant radial variations in beta, which
increases from 1.9 at 10kpc to ~2.5 at a radius of 3.1kpc and then decreases to
1.7 in the center. The dust temperature is fairly constant in the 10kpc ring
(ranging from 17-20K), but increases strongly in the bulge to ~30K. Within
3.1kpc we find the dust temperature is highly correlated with the 3.6 micron
flux, suggesting the general stellar population in the bulge is the dominant
source of dust heating there. At larger radii, there is a weak correlation
between the star formation rate and dust temperature. We find no evidence for
'dark gas' in M31 in contrast to recent results for the MW. Finally, we
obtained an estimate of the CO X-factor by minimising the dispersion in the
gas-to-dust ratio, obtaining a value of (1.9+/-0.4)x10^20 cm^-2 [K kms^-1]^-1.Comment: 19 pages, 18 figures. Submitted to ApJ April 2012; Accepted July 201
Recommendations by Cochrane Review Groups for assessment of the risk of bias in studies
<p>Abstract</p> <p>Background</p> <p>Assessing the risk of bias in individual studies in a systematic review can be done using individual components or by summarizing the study quality in an overall score.</p> <p>Methods</p> <p>We examined the instructions to authors of the 50 Cochrane Review Groups that focus on clinical interventions for recommendations on methodological quality assessment of studies.</p> <p>Results</p> <p>Forty-one of the review groups (82%) recommended quality assessment using components and nine using a scale. All groups recommending components recommended to assess concealment of allocation, compared to only two of the groups recommending scales (P < 0.0001). Thirty-five groups (70%) recommended assessment of sequence generation and 21 groups (42%) recommended assessment of intention-to-treat analysis. Only 28 groups (56%) had specific recommendations for using the quality assessment of studies analytically in reviews, with sensitivity analysis, quality as an inclusion threshold and subgroup analysis being the most commonly recommended methods. The scales recommended had problems in the individual items and some of the groups recommending components recommended items not related to bias in their quality assessment.</p> <p>Conclusion</p> <p>We found that recommendations by some groups were not based on empirical evidence and many groups had no recommendations on how to use the quality assessment in reviews. We suggest that all Cochrane Review Groups refer to the Cochrane Handbook for Systematic Reviews of Interventions, which is evidence-based, in their instructions to authors and that their own guidelines are kept to a minimum and describe only how methodological topics that are specific to their fields should be handled.</p
Single-cell insights into immune dysregulation in rheumatoid arthritis flare versus drug-free remission
The Need for Compliance Verification in Collaborative Business Processes
Compliance constrains processes to adhere to rules, standards, laws
and regulations. Non-compliance subjects enterprises to litigation and financial
fines. Collaborative business processes cross organizational and regional
borders implying that internal and cross regional regulations must be complied
with. To protect customs’ data, European enterprises must comply with the EU
data privacy regulation (general data protection regulation - GDPR) and each
member state’s data protection laws. An example of non-compliance with
GDPR is Facebook, it is accused for breaching subscriber trust. Compliance
verification is thus essential to deploy and implement collaborative business
process systems. It ensures that processes are checked for conformance to
compliance requirements throughout their life cycle. In this paper we take a
proactive approach aiming to discuss the need for design time preventative
compliance verification as opposed to after effect runtime detective approach.
We use a real-world case to show how compliance needs to be analyzed and
show the benefits of applying compliance check at the process design stag
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