1,870 research outputs found
False-negative malaria rapid diagnostic test results and their impact on community-based malaria surveys in sub- Saharan Africa
Surveillance and diagnosis of Plasmodium falciparum malaria relies predominantly on rapid diagnostic tests (RDTs). However, false-negative RDT results are known to occur for a variety of reasons, including operator error, poor storage conditions, pfhrp2/3 gene deletions, poor performance of specific RDT brands and lots, and low-parasite-density infections. We used RDT and microscopy results from 85,000 children enrolled in Demographic Health Surveys and Malaria Indicator Surveys from 2009 to 2015 across 19 countries to explore the distribution of and risk factors for false-negative RDTs in Sub40 Saharan Africa, where malaria’s impact is greatest. We sought to (i) identify spatial and demographic patterns of false-negative RDT (FN-RDT) results, defined as a negative RDT but positive gold-standard microscopy test, and (ii) estimate the percentage of infections missed within community-based malaria surveys due to FN-RDT results. Across all studies, 19.9% [95% CI: 19.0 – 20.9] of microscopy-positive subjects were negative by RDT. The distribution of FN-RDT results was spatially heterogeneous. The variance in FN-RDT results was best explained by the prevalence of malaria, with an increase in FN46 RDT results observed at lower transmission intensities, among younger subjects, and in urban areas. The observed proportion of FN-RDT results was not predicted by differences in RDT brand or lot performance alone. These findings characterise how the probability of detection by RDTs varies in different transmission settings and emphasize the need for careful interpretation of prevalence estimates based on surveys employing RDTs alone. Further studies are needed to characterise the cost-effectiveness of improved malaria diagnostics (e.g. PCR or highly sensitive RDTs) in community52 based surveys, especially in regions of low transmission intensity or high urbanicity
Effect of an extract of Centella asiatica on the biodistribution of sodium pertechnetate (Na<sup>99m</sup>TcO<sub>4</sub>) and on the fixation of radioactivity on blood constituents
This study evaluates the effects of an acute treatment with a Centella asiatica (CA) extract on the biodistribution of the radiopharmaceutical Na99mTcO4 and on the fixation of technetium-99m on blood constituents. Wistar rats were treated with CA extract and, 1 hour after, Na99mTcO4 was administered; organs/tissues were withdrawn and weighted. The radioactivity was counted to calculate the percentage of activity per gram (%ATI/g). Also, blood samples were withdrawn, plasma (P), blood cells (BC), insoluble fraction (IF) and soluble fractions of P and BC were isolated and the radioactivity was counted to calculate the percentage of activity (%ATI). Data indicated that the acute treatment with CA extract changed significantly (p99mTcO4 and the fixation of the technetium-99m on blood constituents in an acute treatment
Competition and Selection Among Conventions
In many domains, a latent competition among different conventions determines
which one will come to dominate. One sees such effects in the success of
community jargon, of competing frames in political rhetoric, or of terminology
in technical contexts. These effects have become widespread in the online
domain, where the data offers the potential to study competition among
conventions at a fine-grained level.
In analyzing the dynamics of conventions over time, however, even with
detailed on-line data, one encounters two significant challenges. First, as
conventions evolve, the underlying substance of their meaning tends to change
as well; and such substantive changes confound investigations of social
effects. Second, the selection of a convention takes place through the complex
interactions of individuals within a community, and contention between the
users of competing conventions plays a key role in the convention's evolution.
Any analysis must take place in the presence of these two issues.
In this work we study a setting in which we can cleanly track the competition
among conventions. Our analysis is based on the spread of low-level authoring
conventions in the eprint arXiv over 24 years: by tracking the spread of macros
and other author-defined conventions, we are able to study conventions that
vary even as the underlying meaning remains constant. We find that the
interaction among co-authors over time plays a crucial role in the selection of
them; the distinction between more and less experienced members of the
community, and the distinction between conventions with visible versus
invisible effects, are both central to the underlying processes. Through our
analysis we make predictions at the population level about the ultimate success
of different synonymous conventions over time--and at the individual level
about the outcome of "fights" between people over convention choices.Comment: To appear in Proceedings of WWW 2017, data at
https://github.com/CornellNLP/Macro
Path probability density functions for semi-Markovian random walks
In random walks, the path representation of the Green's function is an
infinite sum over the length of path probability density functions (PDFs). Here
we derive and solve, in Laplace space, the recursion relation for the n order
path PDF for any arbitrarily inhomogeneous semi-Markovian random walk in a
one-dimensional (1D) chain of L states. The recursion relation relates the n
order path PDF to L/2 (round towards zero for an odd L) shorter path PDFs, and
has n independent coefficients that obey a universal formula. The z transform
of the recursion relation straightforwardly gives the generating function for
path PDFs, from which we obtain the Green's function of the random walk, and
derive an explicit expression for any path PDF of the random walk. These
expressions give the most detailed description of arbitrarily inhomogeneous
semi-Markovian random walks in 1D
Effects of Noise on Ecological Invasion Processes: Bacteriophage-mediated Competition in Bacteria
Pathogen-mediated competition, through which an invasive species carrying and
transmitting a pathogen can be a superior competitor to a more vulnerable
resident species, is one of the principle driving forces influencing
biodiversity in nature. Using an experimental system of bacteriophage-mediated
competition in bacterial populations and a deterministic model, we have shown
in [Joo et al 2005] that the competitive advantage conferred by the phage
depends only on the relative phage pathology and is independent of the initial
phage concentration and other phage and host parameters such as the
infection-causing contact rate, the spontaneous and infection-induced lysis
rates, and the phage burst size. Here we investigate the effects of stochastic
fluctuations on bacterial invasion facilitated by bacteriophage, and examine
the validity of the deterministic approach. We use both numerical and
analytical methods of stochastic processes to identify the source of noise and
assess its magnitude. We show that the conclusions obtained from the
deterministic model are robust against stochastic fluctuations, yet deviations
become prominently large when the phage are more pathological to the invading
bacterial strain.Comment: 39 pages, 7 figure
Molecular characterization of Vibrio cholerae outbreak strains with altered El Tor biotype from southern India
Forty-four Vibrio cholerae isolates collected over a 7-month period in Chennai, India in 2004 were characterized for gene traits, antimicrobial susceptibility and genomic fingerprints. All 44 isolates were identified as O1 El Tor Ogawa, positive for various toxigenic and pathogenic genes viz. ace, ctxB, hlyA, ompU, ompW, rfbO1, rtx, tcpA, toxR and zot. Nucleotide sequencing revealed the presence of cholera toxin B of classical biotype in all the El Tor isolates, suggesting infection of isolates by classical CTXΦ. Antibiogram analysis showed a broad-spectrum antibiotic resistance that was also confirmed by the presence of resistant genes in the genomes. All isolates contained a class 1 integron and an SXT constin. However, isolates were sensitive to chloramphenicol and tested negative for the chloramphenicol resistant gene suggesting a deletion in SXT constin. Fingerprinting analysis of isolates by ERIC- and Box PCR revealed similar DNA patterns indicating the clonal dissemination of a single predominant V. cholerae O1 strain throughout the 2004 outbreak in Chennai
neXtProt: a knowledge platform for human proteins
neXtProt (http://www.nextprot.org/) is a new human protein-centric knowledge platform. Developed at the Swiss Institute of Bioinformatics (SIB), it aims to help researchers answer questions relevant to human proteins. To achieve this goal, neXtProt is built on a corpus containing both curated knowledge originating from the UniProtKB/Swiss-Prot knowledgebase and carefully selected and filtered high-throughput data pertinent to human proteins. This article presents an overview of the database and the data integration process. We also lay out the key future directions of neXtProt that we consider the necessary steps to make neXtProt the one-stop-shop for all research projects focusing on human proteins
Relationship between Structure, Entropy and Diffusivity in Water and Water-like Liquids
Anomalous behaviour of the excess entropy () and the associated scaling
relationship with diffusivity are compared in liquids with very different
underlying interactions but similar water-like anomalies: water (SPC/E and
TIP3P models), tetrahedral ionic melts (SiO and BeF) and a fluid with
core-softened, two-scale ramp (2SRP) interactions. We demonstrate the presence
of an excess entropy anomaly in the two water models. Using length and energy
scales appropriate for onset of anomalous behaviour, the density range of the
excess entropy anomaly is shown to be much narrower in water than in ionic
melts or the 2SRP fluid. While the reduced diffusivities () conform to the
excess entropy scaling relation, for all the systems
(Y. Rosenfeld, Phys. Rev. A {\bf 1977}, {\it 15}, 2545), the exponential
scaling parameter, , shows a small isochore-dependence in the case of
water. Replacing by pair correlation-based approximants accentuates the
isochore-dependence of the diffusivity scaling. Isochores with similar
diffusivity scaling parameters are shown to have the temperature dependence of
the corresponding entropic contribution. The relationship between diffusivity,
excess entropy and pair correlation approximants to the excess entropy are very
similar in all the tetrahedral liquids.Comment: 24 pages, 4 figures, to be published in Journal of Physical Chemistry
Spontaneous haemorrhage of an adrenal angiomyolipoma: case report
Background
Angiomyolipomas are rare mesenchymal tumours arising from the perivascular epithelioid cells consisting of variable amounts of adipose, thick-walled blood vessels and smooth muscle cells. These benign tumours commonly occur in the kidney with only a few case reports of adrenal angiomyolipomas which have the potential to reach a large size and haemorrhage.
Case presentation
A 45-year-old lady presented with a 3-week history of right loin pain, nausea and vomiting. A CT scan revealed a right adrenal angiomyolipoma measuring 6.3 × 6.8 cm with associated haemorrhage. The lesion was successfully treated with right open adrenalectomy, and histology confirmed the diagnosis of adrenal angiomyolipoma. The patient remained well with no evidence of recurrence at the 36-month follow-up.
Conclusion
Adrenal angiomyolipomas are rare benign tumours that have the ability to reach a large size and potential to bleed. Here, we report the second case of spontaneous haemorrhage in an adrenal angiomyolipoma, which was successfully treated with open adrenalectomy
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