3,542 research outputs found
Gravitational waves from pulsars with measured braking index
We study the putative emission of gravitational waves (GWs) in particular for
pulsars with measured braking index. We show that the appropriate combination
of both GW emission and magnetic dipole brakes can naturally explain the
measured braking index, when the surface magnetic field and the angle between
the magnetic dipole and rotation axes are time dependent. Then we discuss the
detectability of these very pulsars by aLIGO and the Einstein Telescope. We
call attention to the realistic possibility that aLIGO can detect the GWs
generated by at least some of these pulsars, such as Vela, for example.Comment: 6 pages and 4 figure
The critical coupling likelihood method: a new approach for seamless integration of environmental and operating conditions of gravitational wave detectors into gravitational wave searches
Any search effort for gravitational waves (GWs) using interferometric detectors like LIGO needs to be able to identify if and when noise couples into the detector’s output signal. The critical coupling likelihood (CCL) method has been developed to characterize potential noise coupling and in the future aid GW search efforts. By testing two hypotheses about pairs of channels, CCL is able to identify undesirable coupled instrumental noise from potential GW candidates. Our preliminary results show that CCL can associate up to ∼80% of observed artifacts with SNR ⩾ 8 with local noise sources, while reducing the duty cycle of the instrument by ≲ 15%. An approach like CCL will become increasingly important as GW research moves into the advanced LIGO era, going from the first GW detection to GW astronomy
Neuromorphometric characterization with shape functionals
This work presents a procedure to extract morphological information from
neuronal cells based on the variation of shape functionals as the cell geometry
undergoes a dilation through a wide interval of spatial scales. The targeted
shapes are alpha and beta cat retinal ganglion cells, which are characterized
by different ranges of dendritic field diameter. Image functionals are expected
to act as descriptors of the shape, gathering relevant geometric and
topological features of the complex cell form. We present a comparative study
of classification performance of additive shape descriptors, namely, Minkowski
functionals, and the nonadditive multiscale fractal. We found that the proposed
measures perform efficiently the task of identifying the two main classes alpha
and beta based solely on scale invariant information, while also providing
intraclass morphological assessment
Most published meta-regression analyses based on aggregate data suffer from methodological pitfalls: a meta-epidemiological study.
BACKGROUND
Due to clinical and methodological diversity, clinical studies included in meta-analyses often differ in ways that lead to differences in treatment effects across studies. Meta-regression analysis is generally recommended to explore associations between study-level characteristics and treatment effect, however, three key pitfalls of meta-regression may lead to invalid conclusions. Our aims were to determine the frequency of these three pitfalls of meta-regression analyses, examine characteristics associated with the occurrence of these pitfalls, and explore changes between 2002 and 2012.
METHODS
A meta-epidemiological study of studies including aggregate data meta-regression analysis in the years 2002 and 2012. We assessed the prevalence of meta-regression analyses with at least 1 of 3 pitfalls: ecological fallacy, overfitting, and inappropriate methods to regress treatment effects against the risk of the analysed outcome. We used logistic regression to investigate study characteristics associated with pitfalls and examined differences between 2002 and 2012.
RESULTS
Our search yielded 580 studies with meta-analyses, of which 81 included meta-regression analyses with aggregated data. 57 meta-regression analyses were found to contain at least one pitfall (70%): 53 were susceptible to ecological fallacy (65%), 14 had a risk of overfitting (17%), and 5 inappropriately regressed treatment effects against the risk of the analysed outcome (6%). We found no difference in the prevalence of meta-regression analyses with methodological pitfalls between 2002 and 2012, nor any study-level characteristic that was clearly associated with the occurrence of any of the pitfalls.
CONCLUSION
The majority of meta-regression analyses based on aggregate data contain methodological pitfalls that may result in misleading findings
Agropastoral Systems an Alternative to Revert Pasture Degradation in the Cerrados of Brazil: Preliminary Results
A long term experiment was set to test the hypothesis that agropastoral systems could improve crop and animal production, being more profitable and sustainable relative to economical, biological and environmental aspects, than continuous and traditional crop and grazing pasture systems. Five farming systems are being tested: two traditional (continuous soybean annual cropping and continuous pasture cropping) and three agropastoral systems (two combinations of four by four years of rotational crop-pasture systems and one by three years of crop-pasture rotation). Animal production in continuous pasture cropping measured as liveweight gain/ha (LWG) are declining along the years in the sub-treatment without fertilizer maintenance. After five cycles of animal performance evaluation, average yields were 397 as compared to 444 kg of LWG/ha, in fertilized pasture. Agropastoral systems, in the other hand, have shown promising results of LWG, either in the one by three or in the four by four cropping combination, with animal production ranking from 547 to 789 kg of LWG/ha/year. Soil fertility in agropastoral systems increased substantially
The Critical Coupling Likelihood Method: A new approach for seamless integration of environmental and operating conditions of gravitational wave detectors into gravitational wave searches
Any search effort for gravitational waves (GW) using interferometric
detectors like LIGO needs to be able to identify if and when noise is coupling
into the detector's output signal. The Critical Coupling Likelihood (CCL)
method has been developed to characterize potential noise coupling and in the
future aid GW search efforts. By testing two hypotheses about pairs of
channels, CCL is able to identify undesirable coupled instrumental noise from
potential GW candidates. Our preliminary results show that CCL can associate up
to of observed artifacts with , to local noise sources,
while reducing the duty cycle of the instrument by . An approach
like CCL will become increasingly important as GW research moves into the
Advanced LIGO era, going from the first GW detection to GW astronomy.Comment: submitted CQ
Viscosupplementation for knee osteoarthritis: systematic review and meta-analysis
Objective: To evaluate the effectiveness and safety of viscosupplementation for pain and function in patients with knee osteoarthritis.
Design: Systematic review and meta-analysis of randomised trials.
Data sources Searches were conducted of Medline, Embase, and the Cochrane Central Register of Controlled Trials (CENTRAL) databases from inception to 11 September 2021. Unpublished trials were identified from the grey literature and trial registries.
Eligibility criteria for study selection: Randomised trials comparing viscosupplementation with placebo or no intervention for knee osteoarthritis treatment.
Main outcome measures: The prespecified primary outcome was pain intensity. Secondary outcomes were function and serious adverse events. Pain and function were analysed as standardised mean differences (SMDs). The prespecified minimal clinically important between group difference was −0.37 SMD. Serious adverse events were analysed as relative risks.
Methods: Two reviewers independently extracted relevant data and assessed the risk of bias of trials using the Cochrane risk of bias tool. The predefined main analysis was based only on large, placebo controlled trials with ≥100 participants per group. Summary results were obtained through a random effects meta-analysis model. Cumulative meta-analysis and trial sequential analysis under a random effects model were also performed.
Results: 169 trials provided data on 21 163 randomised participants. Evidence of small study effects and publication biases was observed for pain and function (Egger’s tests with P<0.001 and asymmetric funnel plots). Twenty four large, placebo controlled trials (8997 randomised participants) included in the main analysis of pain indicated that viscosupplementation was associated with a small reduction in pain intensity compared with placebo (SMD −0.08, 95% confidence interval −0.15 to −0.02), with the lower bound of the 95% confidence interval excluding the minimal clinically important between group difference. This effect corresponds to a difference in pain scores of −2.0 mm (95% confidence interval −3.8 to −0.5 mm) on a 100 mm visual analogue scale. Trial sequential analysis for pain indicated that since 2009 there has been conclusive evidence of clinical equivalence between viscosupplementation and placebo. Similar conclusions were obtained for function. Based on 15 large, placebo controlled trials on 6462 randomised participants, viscosupplementation was associated with a statistically significant higher risk of serious adverse events than placebo (relative risk 1.49, 95% confidence interval 1.12 to 1.98).
Conclusion: Strong conclusive evidence indicates that viscosupplementation leads to a small reduction in knee osteoarthritis pain compared with placebo, but the difference is less than the minimal clinically important between group difference. Strong conclusive evidence indicates that viscosupplementation is also associated with an increased risk of serious adverse events compared with placebo. The findings do not support broad use of viscosupplementation for the treatment of knee osteoarthritis
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