684 research outputs found
Testing for Network and Spatial Autocorrelation
Testing for dependence has been a well-established component of spatial
statistical analyses for decades. In particular, several popular test
statistics have desirable properties for testing for the presence of spatial
autocorrelation in continuous variables. In this paper we propose two
contributions to the literature on tests for autocorrelation. First, we propose
a new test for autocorrelation in categorical variables. While some methods
currently exist for assessing spatial autocorrelation in categorical variables,
the most popular method is unwieldy, somewhat ad hoc, and fails to provide
grounds for a single omnibus test. Second, we discuss the importance of testing
for autocorrelation in data sampled from the nodes of a network, motivated by
social network applications. We demonstrate that our proposed statistic for
categorical variables can both be used in the spatial and network setting
Higher Powers in Gravitation
We consider the Friedmann-Robertson-Walker cosmologies of theories of gravity
that generalise the Einstein-Hilbert action by replacing the Ricci scalar, R,
with some function, f(R). The general asymptotic behaviour of these cosmologies
is found, at both early and late times, and the effects of adding higher and
lower powers of R to the Einstein-Hilbert action is investigated. The
assumption that the highest powers of R should dominate the Universe's early
history, and that the lowest powers should dominate its future is found to be
inaccurate. The behaviour of the general solution is complicated, and while it
can be the case that single powers of R dominate the dynamics at late times, it
can be either the higher or lower powers that do so. It is also shown that it
is often the lowest powers of R that dominate at early times, when approach to
a bounce or a Tolman solution are generic possibilities. Various examples are
considered, and both vacuum and perfect fluid solutions investigated.Comment: 30 pages, 9 figure
Thermodynamic analysis of inverted bifurcation
We present a thermodynamic analysis of inverted bifurcation
in binary mixtures heated from below. From this analysis it
follows that an inverted bifurcation is caused by the competition
between a stabilizing effect with a long relaxation time and a
destabilizing effect with a short relaxation time. These
conditions are precisely the same as those that give rise to
overstability. This might explain why overstability and inverted
bifurcation occur in the same systems
A meta-analysis of long-term effects of conservation agriculture on maize grain yield under rain-fed conditions
Conservation agriculture involves reduced tillage, permanent soil cover and crop rotations to enhance soil fertility and to supply food from a dwindling land resource. Recently, conservation agriculture has been promoted in Southern Africa, mainly for maize-based farming systems. However, maize yields under rain-fed conditions are often variable. There is therefore a need to identify factors that influence crop yield under conservation agriculture and rain-fed conditions. Here, we studied maize grain yield data from experiments lasting 5 years and more under rain-fed conditions. We assessed the effect of long-term tillage and residue retention on maize grain yield under contrasting soil textures, nitrogen input and climate. Yield variability was measured by stability analysis. Our results show an increase in maize yield over time with conservation agriculture practices that include rotation and high input use in low rainfall areas. But we observed no difference in system stability under those conditions. We observed a strong relationship between maize grain yield and annual rainfall. Our meta-analysis gave the following findings: (1) 92% of the data show that mulch cover in high rainfall areas leads to lower yields due to waterlogging; (2) 85% of data show that soil texture is important in the temporal development of conservation agriculture effects, improved yields are likely on well-drained soils; (3) 73% of the data show that conservation agriculture practices require high inputs especially N for improved yield; (4) 63% of data show that increased yields are obtained with rotation but calculations often do not include the variations in rainfall within and between seasons; (5) 56% of the data show that reduced tillage with no mulch cover leads to lower yields in semi-arid areas; and (6) when adequate fertiliser is available, rainfall is the most important determinant of yield in southern Africa. It is clear from our results that conservation agriculture needs to be targeted and adapted to specific biophysical conditions for improved impact
The High Burden of Cholera in Children: Comparison of Incidence from Endemic Areas in Asia and Africa
Cholera is an often forgotten disease affecting the world's forgotten people. When a large cholera outbreak occurs, the disease appears briefly on the radar of public attention. Some unfortunate populations around the world suffer recurrent episodes of cholera but their plight goes unnoticed. We established cholera surveillance in impoverished areas in Jakarta (Indonesia), Kolkata (India), and Beira (Mozambique) where the disease is known to occur regularly. The cholera burden was calculated using the site population as the denominator and the number of cholera cases as the numerator. The lowest overall rate was in Jakarta with 0.5 cases per 1000 population per year. The incidence was three times higher in Kolkata (1.6/1000/year) and eight times higher in Beira (4.0/1000/year), adding to the growing impression of the large cholera problem in Africa. In all sites, children are the most affected. Estimates such as these are useful when considering where and among whom interventions against the disease are most needed. Improvement of water supply and sanitation is the best strategy against cholera and other diarrheal diseases but may not be achievable in these impoverished areas in the near future. Other immediate, short- to medium-term strategies such as vaccination against cholera may be useful
NEMF mutations that impair ribosome-associated quality control are associated with neuromuscular disease
A hallmark of neurodegeneration is defective protein quality control. The E3 ligase Listerin (LTN1/Ltn1) acts in a specialized protein quality control pathway—Ribosome-associated Quality Control (RQC)—by mediating proteolytic targeting of incomplete polypeptides produced by ribosome stalling, and Ltn1 mutation leads to neurodegeneration in mice. Whether neurodegeneration results from defective RQC and whether defective RQC contributes to human disease have remained unknown. Here we show that three independently-generated mouse models with mutations in a different component of the RQC complex, NEMF/Rqc2, develop progressive motor neuron degeneration. Equivalent mutations in yeast Rqc2 selectively interfere with its ability to modify aberrant translation products with C-terminal tails which assist with RQC-mediated protein degradation, suggesting a pathomechanism. Finally, we identify NEMF mutations expected to interfere with function in patients from seven families presenting juvenile neuromuscular disease. These uncover NEMF’s role in translational homeostasis in the nervous system and implicate RQC dysfunction in causing neurodegeneration
Functional Annotation and Identification of Candidate Disease Genes by Computational Analysis of Normal Tissue Gene Expression Data
Background: High-throughput gene expression data can predict gene function through the ‘‘guilt by association’ ’ principle: coexpressed genes are likely to be functionally associated. Methodology/Principal Findings: We analyzed publicly available expression data on normal human tissues. The analysis is based on the integration of data obtained with two experimental platforms (microarrays and SAGE) and of various measures of dissimilarity between expression profiles. The building blocks of the procedure are the Ranked Coexpression Groups (RCG), small sets of tightly coexpressed genes which are analyzed in terms of functional annotation. Functionally characterized RCGs are selected by means of the majority rule and used to predict new functional annotations. Functionally characterized RCGs are enriched in groups of genes associated to similar phenotypes. We exploit this fact to find new candidate disease genes for many OMIM phenotypes of unknown molecular origin. Conclusions/Significance: We predict new functional annotations for many human genes, showing that the integration of different data sets and coexpression measures significantly improves the scope of the results. Combining gene expression data, functional annotation and known phenotype-gene associations we provide candidate genes for several geneti
Interleukin-10 Overexpression Promotes Fas-Ligand-Dependent Chronic Macrophage-Mediated Demyelinating Polyneuropathy
BACKGROUND:Demyelinating polyneuropathy is a debilitating, poorly understood disease that can exist in acute (Guillain-Barré syndrome) or chronic forms. Interleukin-10 (IL-10), although traditionally considered an anti-inflammatory cytokine, has also been implicated in promoting abnormal angiogenesis in the eye and in the pathobiology of autoimmune diseases such as lupus and encephalomyelitis. PRINCIPAL FINDINGS:Overexpression of IL-10 in a transgenic mouse model leads to macrophage-mediated demyelinating polyneuropathy. IL-10 upregulates ICAM-1 within neural tissues, promoting massive macrophage influx, inflammation-induced demyelination, and subsequent loss of neural tissue resulting in muscle weakness and paralysis. The primary insult is to perineural myelin followed by secondary axonal loss. Infiltrating macrophages within the peripheral nerves demonstrate a highly pro-inflammatory signature. Macrophages are central players in the pathophysiology, as in vivo depletion of macrophages using clodronate liposomes reverses the phenotype, including progressive nerve loss and paralysis. Macrophage-mediate demyelination is dependent on Fas-ligand (FasL)-mediated Schwann cell death. SIGNIFICANCE:These findings mimic the human disease chronic idiopathic demyelinating polyneuropathy (CIDP) and may also promote further understanding of the pathobiology of related conditions such as acute idiopathic demyelinating polyneuropathy (AIDP) or Guillain-Barré syndrome
Study of decays to the final state and evidence for the decay
A study of decays is performed for the first time
using data corresponding to an integrated luminosity of 3.0
collected by the LHCb experiment in collisions at centre-of-mass energies
of and TeV. Evidence for the decay
is reported with a significance of 4.0 standard deviations, resulting in the
measurement of
to
be .
Here denotes a branching fraction while and
are the production cross-sections for and mesons.
An indication of weak annihilation is found for the region
, with a significance of
2.4 standard deviations.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2016-022.html,
link to supplemental material inserted in the reference
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