1,350 research outputs found
Overstating the evidence - double counting in meta-analysis and related problems
Background: The problem of missing studies in meta-analysis has received much attention. Less attention has been paid to the more serious problem of double counting of evidence.
Methods: Various problems in overstating the precision of results from meta-analyses are described and illustrated with examples, including papers from leading medical journals. These problems include, but are not limited to, simple double-counting of the same studies, double counting of some aspects of the studies, inappropriate imputation of results, and assigning spurious precision to individual studies.
Results: Some suggestions are made as to how the quality and reliability of meta-analysis can be improved. It is proposed that the key to quality in meta-analysis lies in the results being transparent and checkable.
Conclusions: Existing quality check lists for meta-analysis do little to encourage an appropriate attitude to combining evidence and to statistical analysis. Journals and other relevant organisations should encourage authors to make data available and make methods explicit. They should also act promptly to withdraw meta-analyses when mistakes are found
Economic footprint of California wildfires in 2018
Recent increases in the frequency and scale of wildfires worldwide have raised concerns about the influence of climate change and associated socioeconomic costs. In the western United States, the hazard of wildfire has been increasing for decades. Here, we use a combination of physical, epidemiological and economic models to estimate the economic impacts of California wildfires in 2018, including the value of destroyed and damaged capital, the health costs related to air pollution exposure and indirect losses due to broader economic disruption cascading along with regional and national supply chains. Our estimation shows that wildfire damages in 2018 totalled 27.7 billion (19%) in capital losses, 88.6 billion (59%) in indirect losses (all values in US$). Our results reveal that the majority of economic impacts related to California wildfires may be indirect and often affect industry sectors and locations distant from the fires (for example, 52% of the indirect losses—31% of total losses—in 2018 were outside of California). Our findings and methods provide new information for decision makers tasked with protecting lives and key production sectors and reducing the economic damages of future wildfires
Cancer-selective, single agent chemoradiosensitising gold nanoparticles
Two nanometre gold nanoparticles (AuNPs), bearing sugar moieties and/or thiol-polyethylene glycol-amine (PEG-amine), were synthesised and evaluated for their in vitro toxicity and ability to radiosensitise cells with 220 kV and 6 MV X-rays, using four cell lines representing normal and cancerous skin and breast tissues. Acute 3 h exposure of cells to AuNPs, bearing PEG-amine only or a 50:50 ratio of alpha-galactose derivative and PEG-amine resulted in selective uptake and toxicity towards cancer cells at unprecedentedly low nanomolar concentrations. Chemotoxicity was prevented by co-administration of N-acetyl cysteine antioxidant, or partially prevented by the caspase inhibitor Z-VAD-FMK. In addition to their intrinsic cancer-selective chemotoxicity, these AuNPs acted as radiosensitisers in combination with 220 kV or 6 MV X-rays. The ability of AuNPs bearing simple ligands to act as cancer-selective chemoradiosensitisers at low concentrations is a novel discovery that holds great promise in developing low-cost cancer nanotherapeutics
Revisiting Scalar and Pseudoscalar Couplings with Nucleons
Certain dark matter interactions with nuclei are mediated possibly by a
scalar or pseudoscalar Higgs boson. The estimation of the corresponding cross
sections requires a correct evaluation of the couplings between the scalar or
pseudoscalar Higgs boson and the nucleons. Progress has been made in two
aspects relevant to this study in the past few years. First, recent lattice
calculations show that the strange-quark sigma term and the
strange-quark content in the nucleon are much smaller than what are expected
previously. Second, lattice and model analyses imply sizable SU(3) breaking
effects in the determination on the axial-vector coupling constant that
in turn affect the extraction of the isosinglet coupling and the
strange quark spin component from polarized deep inelastic
scattering experiments. Based on these new developments, we re-evaluate the
relevant nucleon matrix elements and compute the scalar and pseudoscalar
couplings of the proton and neutron. We also find that the strange quark
contribution in both types of couplings is smaller than previously thought.Comment: 17 pages, Sec. II is revised and the pion-nucleon sigma term
extracted from the scattering data is discussed. Version to appear in JHE
Salience-based selection: attentional capture by distractors less salient than the target
Current accounts of attentional capture predict the most salient stimulus to be invariably selected first. However, existing salience and visual search models assume noise in the map computation or selection process. Consequently, they predict the first selection to be stochastically dependent on salience, implying that attention could even be captured first by the second most salient (instead of the most salient) stimulus in the field. Yet, capture by less salient distractors has not been reported and salience-based selection accounts claim that the distractor has to be more salient in order to capture attention. We tested this prediction using an empirical and modeling approach of the visual search distractor paradigm. For the empirical part, we manipulated salience of target and distractor parametrically and measured reaction time interference when a distractor was present compared to absent. Reaction time interference was strongly correlated with distractor salience relative to the target. Moreover, even distractors less salient than the target captured attention, as measured by reaction time interference and oculomotor capture. In the modeling part, we simulated first selection in the distractor paradigm using behavioral measures of salience and considering the time course of selection including noise. We were able to replicate the result pattern we obtained in the empirical part. We conclude that each salience value follows a specific selection time distribution and attentional capture occurs when the selection time distributions of target and distractor overlap. Hence, selection is stochastic in nature and attentional capture occurs with a certain probability depending on relative salience
Correcting Mortality for Loss to Follow-Up: A Nomogram Applied to Antiretroviral Treatment Programmes in Sub-Saharan Africa
Matthias Egger and colleagues present a nomogram and a web-based calculator to correct estimates of program-level mortality for loss to follow-up, for use in antiretroviral treatment programs
WNT signalling in prostate cancer
Genome sequencing and gene expression analyses of prostate tumours have highlighted the potential importance of genetic and epigenetic changes observed in WNT signalling pathway components in prostate tumours-particularly in the development of castration-resistant prostate cancer. WNT signalling is also important in the prostate tumour microenvironment, in which WNT proteins secreted by the tumour stroma promote resistance to therapy, and in prostate cancer stem or progenitor cells, in which WNT-β-catenin signals promote self-renewal or expansion. Preclinical studies have demonstrated the potential of inhibitors that target WNT receptor complexes at the cell membrane or that block the interaction of β-catenin with lymphoid enhancer-binding factor 1 and the androgen receptor, in preventing prostate cancer progression. Some WNT signalling inhibitors are in phase I trials, but they have yet to be tested in patients with prostate cancer
Understanding high pressure hydrogen with a hierarchical machine-learned potential
The hydrogen phase diagram has a number of unusual features which are
generally well reproduced by density functional calculations. Unfortunately,
these calculations fail to provide good physical insights into why those
features occur. In this paper, we parameterize a model potential for molecular
hydrogen which permits long and large simulations. The model shows excellent
reproduction of the phase diagram, including the broken-symmetry Phase II, an
efficiently-packed phase III and the maximum in the melt curve. It also gives
an excellent reproduction of the vibrational frequencies, including the maximum
in the vibrational frequency and negative thermal expansion. By
detailed study of lengthy molecular dynamics, we give intuitive explanations
for observed and calculated properties. All solid structures approximate to
hexagonal close packed, with symmetry broken by molecular orientation. At high
pressure, Phase I shows significant short-ranged correlations between molecular
orientations. The turnover in Raman frequency is due to increased coupling
between neighboring molecules, rather than weakening of the bond. The liquid is
denser than the close-packed solid because, at molecular separations below
2.3\AA, the favoured relative orientation switches from
quadrupole-energy-minimising to steric-repulsion-minimising. The latter allows
molecules to get closer together, without atoms getting closer but this cannot
be achieved within the constraints of a close-packed layer
Erratum: A review of trends and drivers of greenhouse gas emissions by sector from 1990 to 2018 (Environmental Research Letters (2021) 16 (073005) DOI: 10.1088/1748-9326/abee4e)
This corrigendum resolves an error in figure 17 and clarifies the scope of the cement sector in figure 2. Figure 17 in the original published manuscript depicts a Kaya identity for the agriculture, forestry and other land uses (AFOLU) sector. We unintentionally excluded land-use CO2 emissions from total greenhouse gas (GHG) emissions in this identity, and depicted only agricultural GHG emissions
Observation of a ppb mass threshoud enhancement in \psi^\prime\to\pi^+\pi^-J/\psi(J/\psi\to\gamma p\bar{p}) decay
The decay channel
is studied using a sample of events collected
by the BESIII experiment at BEPCII. A strong enhancement at threshold is
observed in the invariant mass spectrum. The enhancement can be fit
with an -wave Breit-Wigner resonance function with a resulting peak mass of
and a
narrow width that is at the 90% confidence level.
These results are consistent with published BESII results. These mass and width
values do not match with those of any known meson resonance.Comment: 5 pages, 3 figures, submitted to Chinese Physics
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