822 research outputs found
The problems with systematic reviews: a living systematic review
Objectives
Systematic reviews and meta-analyses are proliferating as they are an important building block to inform evidence-based guidelines and decision-making. Enforcement of best practice in clinical trials is firmly on the research agenda of good clinical practice, but there is less clarity as to how evidence syntheses that combine these studies can be influenced by bad practice. Our aim was to conduct a living systematic review of articles that highlight flaws in published systematic reviews to formally document and understand these problems.
Study Design and Setting
We conducted a comprehensive assessment of all literature examining problems, which relate to published systematic reviews.
Results
The first iteration of our living systematic review (https://systematicreviewlution.com/) has found 485 articles documenting 67 discrete problems relating to the conduct and reporting of systematic reviews which can potentially jeopardize their reliability or validity.
Conclusion
Many hundreds of articles highlight that there are many flaws in the conduct, methods, and reporting of published systematic reviews, despite the existence and frequent application of guidelines. Considering the pivotal role that systematic reviews have in medical decision-making due to having apparently transparent, objective, and replicable processes, a failure to appreciate and regulate problems with these highly cited research designs is a threat to credible science
Contribution to the Control of a MAS's Global Behaviour: Reinforcement Learning Tools
Reactive multi-agent systems present global behaviours uneasily linked to their local dynamics. When it comes to controlling such a system, usual analytical tools are difficult to use so specific techniques have to be engineered. We propose an experimental dynamical approach to enhance the control of the global behaviour of a reactive multi-agent system. We use reinforcement learning tools to link global information of the system to control actions. We propose to use the behaviour of the system as this global information. The behaviour of the whole system is controlled thanks to actions at different levels instead of building the behaviours of the agents, so that the complexity of the approach does not directly depend on the number of agents. The controllability is evaluated in terms of rate of convergence towards a target behaviour. We compare the results obtained on a toy example with the usual approach of parameter setting
The potential for tree planting strategies to reduce local and regional ecosystem impacts of agricultural ammonia emissions
Trees are very effective at capturing both gaseous and particulate pollutants from the atmosphere. But while studies have often focussed on PM and NOx in the urban environment, little research has been carried out on the tree effect of capturing gaseous emissions of ammonia in the rural landscape. To examine the removal or scavenging of ammonia by trees a long-range atmospheric model (FRAME) was used to compare two strategies that could be used in emission reduction policies anywhere in the world where nitrogen pollution from agriculture is a problem. One strategy was to reduce the emission source strength of livestock management systems by implementing two âtree-captureâ systems scenarios â tree belts downwind of housing and managing livestock under trees. This emission reduction can be described as an âon-farmâ emission reduction policy, as ammonia is âstoppedâ from dispersion outside the farm boundaries. The second strategy was to apply an afforestation policy targeting areas of high ammonia emission through two planting scenarios of increasing afforestation by 25% and 50%. Both strategies use trees with the aim of intercepting NH3 emissions to protect semi-natural areas. Scenarios for on-farm emission reductions showed national reductions in nitrogen deposition to semi-natural areas of 0.14% (0.2 kt NâNHx) to 2.2% (3.15 kt NâNHx). Scenarios mitigating emissions from cattle and pig housing gave the highest reductions. The afforestation strategy showed national reductions of 6% (8.4 kt NâNHx) to 11% (15.7 kt NâNHx) for 25% and 50% afforestation scenarios respectively. Increased capture by the planted trees also showed an added benefit of reducing long range effects including a decrease in wet deposition up to 3.7 kt NâNHx (4.6%) and a decrease in export from the UK up to 8.3 kt NâNHx (6.8%)
Observation of Scaling Violations in Scaled Momentum Distributions at HERA
Charged particle production has been measured in deep inelastic scattering
(DIS) events over a large range of and using the ZEUS detector. The
evolution of the scaled momentum, , with in the range 10 to 1280
, has been investigated in the current fragmentation region of the Breit
frame. The results show clear evidence, in a single experiment, for scaling
violations in scaled momenta as a function of .Comment: 21 pages including 4 figures, to be published in Physics Letters B.
Two references adde
D* Production in Deep Inelastic Scattering at HERA
This paper presents measurements of D^{*\pm} production in deep inelastic
scattering from collisions between 27.5 GeV positrons and 820 GeV protons. The
data have been taken with the ZEUS detector at HERA. The decay channel
(+ c.c.) has been used in the study. The
cross section for inclusive D^{*\pm} production with
and is 5.3 \pms 1.0 \pms 0.8 nb in the kinematic region
{ GeV and }. Differential cross
sections as functions of p_T(D^{*\pm}), and are
compared with next-to-leading order QCD calculations based on the photon-gluon
fusion production mechanism. After an extrapolation of the cross section to the
full kinematic region in p_T(D^{*\pm}) and (D^{*\pm}), the charm
contribution to the proton structure function is
determined for Bjorken between 2 10 and 5 10.Comment: 17 pages including 4 figure
Forward jet production in deep inelastic ep scattering and low-x parton dynamics at HERA
Differential inclusive jet cross sections in neutral current deep inelastic
ep scattering have been measured with the ZEUS detector. Three phase-space
regions have been selected in order to study parton dynamics where the effects
of BFKL evolution might be present. The measurements have been compared to the
predictions of leading-logarithm parton shower Monte Carlo models and
fixed-order perturbative QCD calculations. In the forward region, QCD
calculations at order alpha_s^1 underestimate the data up to an order of
magnitude at low x. An improved description of the data in this region is
obtained by including QCD corrections at order alpha_s^2, which account for the
lowest-order t-channel gluon-exchange diagrams, highlighting the importance of
such terms in parton dynamics at low x.Comment: 25 pages, 4 figure
Search for lepton-flavor violation at HERA
A search for lepton-flavor-violating interactions and has been performed with the ZEUS detector using the entire HERA I
data sample, corresponding to an integrated luminosity of 130 pb^{-1}. The data
were taken at center-of-mass energies, , of 300 and 318 GeV. No
evidence of lepton-flavor violation was found, and constraints were derived on
leptoquarks (LQs) that could mediate such interactions. For LQ masses below
, limits were set on , where
is the coupling of the LQ to an electron and a
first-generation quark , and is the branching ratio of
the LQ to the final-state lepton ( or ) and a quark . For
LQ masses much larger than , limits were set on the four-fermion
interaction term for LQs that couple to an electron and a quark
and to a lepton and a quark , where and are
quark generation indices. Some of the limits are also applicable to
lepton-flavor-violating processes mediated by squarks in -Parity-violating
supersymmetric models. In some cases, especially when a higher-generation quark
is involved and for the process , the ZEUS limits are the most
stringent to date.Comment: 37 pages, 10 figures, Accepted by EPJC. References and 1 figure (Fig.
6) adde
Multijet production in neutral current deep inelastic scattering at HERA and determination of alpha_s
Multijet production rates in neutral current deep inelastic scattering have
been measured in the range of exchanged boson virtualities 10 < Q2 < 5000 GeV2.
The data were taken at the ep collider HERA with centre-of-mass energy sqrt(s)
= 318 GeV using the ZEUS detector and correspond to an integrated luminosity of
82.2 pb-1. Jets were identified in the Breit frame using the k_T cluster
algorithm in the longitudinally invariant inclusive mode. Measurements of
differential dijet and trijet cross sections are presented as functions of jet
transverse energy E_{T,B}{jet}, pseudorapidity eta_{LAB}{jet} and Q2 with
E_{T,B}{jet} > 5 GeV and -1 < eta_{LAB}{jet} < 2.5. Next-to-leading-order QCD
calculations describe the data well. The value of the strong coupling constant
alpha_s(M_Z), determined from the ratio of the trijet to dijet cross sections,
is alpha_s(M_Z) = 0.1179 pm 0.0013(stat.) {+0.0028}_{-0.0046}(exp.)
{+0.0064}_{-0.0046}(th.)Comment: 22 pages, 5 figure
Measurement of (anti)deuteron and (anti)proton production in DIS at HERA
The first observation of (anti)deuterons in deep inelastic scattering at HERA
has been made with the ZEUS detector at a centre-of-mass energy of 300--318 GeV
using an integrated luminosity of 120 pb-1. The measurement was performed in
the central rapidity region for transverse momentum per unit of mass in the
range 0.3<p_T/M<0.7. The particle rates have been extracted and interpreted in
terms of the coalescence model. The (anti)deuteron production yield is smaller
than the (anti)proton yield by approximately three orders of magnitude,
consistent with the world measurements.Comment: 26 pages, 9 figures, 5 tables, submitted to Nucl. Phys.
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