2,250 research outputs found
Shrinking a large dataset to identify variables associated with increased risk of Plasmodium falciparum infection in Western Kenya
Large datasets are often not amenable to analysis using traditional single-step approaches. Here, our general objective was to apply imputation techniques, principal component analysis (PCA), elastic net and generalized linear models to a large dataset in a systematic approach to extract the most meaningful predictors for a health outcome. We extracted predictors for Plasmodium falciparum infection, from a large covariate dataset while facing limited numbers of observations, using data from the People, Animals, and their Zoonoses (PAZ) project to demonstrate these techniques: data collected from 415 homesteads in western Kenya, contained over 1500 variables that describe the health, environment, and social factors of the humans, livestock, and the homesteads in which they reside. The wide, sparse dataset was simplified to 42 predictors of P. falciparum malaria infection and wealth rankings were produced for all homesteads. The 42 predictors make biological sense and are supported by previous studies. This systematic data-mining approach we used would make many large datasets more manageable and informative for decision-making processes and health policy prioritization
Supersolidity, entropy and frustration
We study the properties of t-t'-V model of hard-core bosons on the triangular
lattice that can be realized in optical lattices. By mapping to the spin-1/2
XXZ model in a field, we determine the phase diagram of the t-V model where the
supersolid characterized by the ordering pattern (x,x,-2x') ("ferrimagnetic" or
SS A) is a ground state for chemical potential \mu >3V. By turning on either
temperature or t' at half-filling \mu =3V, we find a first order transition
from SS A to the elusive supersolid characterized by the (x,-x,0) ordering
pattern ("antiferromagnetic" or SS C). In addition, we find a large region
where a superfluid phase becomes a solid upon raising temperature at fixed
chemical potential. This is an analog of the Pomeranchuk effect driven by the
large entropic effects associated with geometric frustration on the triangular
lattice.Comment: 4 pages, igures, LaTe
Field Theory And Second Renormalization Group For Multifractals In Percolation
The field-theory for multifractals in percolation is reformulated in such a
way that multifractal exponents clearly appear as eigenvalues of a second
renormalization group. The first renormalization group describes geometrical
properties of percolation clusters, while the second-one describes electrical
properties, including noise cumulants. In this context, multifractal exponents
are associated with symmetry-breaking fields in replica space. This provides an
explanation for their observability. It is suggested that multifractal
exponents are ''dominant'' instead of ''relevant'' since there exists an
arbitrary scale factor which can change their sign from positive to negative
without changing the Physics of the problem.Comment: RevTex, 10 page
Episodic Star Formation Coupled to Reignition of Radio Activity in 3C 236
We present Hubble Space Telescope UV and optical imaging of the radio galaxy
3C 236, whose relic 4 Mpc radio jet lobes and inner 2 kpc CSS radio source are
evidence of multiple epochs of AGN activity. Our data confirm the presence of
four bright knots of FUV emission in an arc along the edge of the inner
circumnuclear dust disk in the galaxy's nucleus, as well as FUV emission
cospatial with the nucleus itself. We interpret these to be sites of recent or
ongoing star formation. We present photometry of these knots, as well as an
estimate for the internal extinction in the source using the Balmer decrement
from SDSS spectroscopy. We estimate the ages of the knots by comparing our
extinction-corrected photometry with stellar population synthesis models. We
find the four knots cospatial with the dusty disk to be young, of order 10^7 yr
old. The FUV emission in the nucleus is likely due to an episode of star
formation triggered ~10^9 yr ago. We argue that the young 10^7 yr old knots
stem from an episode of star formation that was roughly coeval with the event
resulting in reignition of radio activity, creating the CSS source. The 10^9 yr
old stars in the nucleus may be associated with the previous epoch of activity
that generated the 4 Mpc relic source, before it was cut off by exhaustion or
interruption. The ages of the knots, considered in context with the disturbed
morphology of the nuclear dust and the double-double morphology of the "old"
and "young" radio sources, present evidence for an episodic AGN/starburst
connection. We suggest that the AGN fuel supply was interrupted for ~10^7 yr
due to a minor merger event and has now been restored, and the resultant
non-steady flow of gas toward the nucleus is likely responsible for both the
new episode of infall-induced star formation and also the multiple epochs of
radio activity.Comment: 15 pages, 7 figures. Accepted for publication in ApJ
Lactobacillli expressing llama VHH fragments neutralise Lactococcus phages
<p>Abstract</p> <p>Background</p> <p>Bacteriophages infecting lactic acid bacteria (LAB) are widely acknowledged as the main cause of milk fermentation failures. In this study, we describe the surface-expression as well as the secretion of two functional llama heavy-chain antibody fragments, one binding to the major capsid protein (MCP) and the other to the receptor-binding proteins (RBP) of the lactococcal bacteriophage p2, by lactobacilli in order to neutralise lactococcal phages.</p> <p>Results</p> <p>The antibody fragment VHH5 that is directed against the RBP, was fused to a c-<it>myc </it>tag and expressed in a secreted form by a <it>Lactobacillus </it>strain. The fragment VHH2 that is binding to the MCP, was fused to an E-tag and anchored on the surface of the lactobacilli. Surface expression of VHH2 was confirmed by flow cytometry using an anti-E-tag antibody. Efficient binding of both the VHH2 and the secreted VHH5 fragment to the phage antigens was shown in ELISA. Scanning electron microscopy showed that lactobacilli expressing VHH2 anchored at their surface were able to bind lactococcal phages. A neutralisation assay also confirmed that the secreted VHH5 and the anchored VHH2 fragments prevented the adsorption of lactococcal phages to their host cells.</p> <p>Conclusion</p> <p>Lactobacilli were able to express functional VHH fragments in both a secreted and a cell surface form and reduced phage infection of lactococcal cells. Lactobacilli expressing llama heavy-chain antibody fragments represent a novel way to limit phage infection.</p
Absolute Flux Calibration of the IRAC Instrument on the Spitzer Space Telescope using Hubble Space Telescope Flux Standards
The absolute flux calibration of the James Webb Space Telescope will be based
on a set of stars observed by the Hubble and Spitzer Space Telescopes. In order
to cross-calibrate the two facilities, several A, G, and white dwarf (WD) stars
are observed with both Spitzer and Hubble and are the prototypes for a set of
JWST calibration standards. The flux calibration constants for the four Spitzer
IRAC bands 1-4 are derived from these stars and are 2.3, 1.9, 2.0, and 0.5%
lower than the official cold-mission IRAC calibration of Reach et al. (2005),
i.e. in agreement within their estimated errors of ~2%. The causes of these
differences lie primarily in the IRAC data reduction and secondarily in the
SEDs of our standard stars. The independent IRAC 8 micron band-4 fluxes of
Rieke et al. (2008) are about 1.5 +/- 2% higher than those of Reach et al. and
are also in agreement with our 8 micron result.Comment: 16 pages, 6 figure
External perceptions of successful university brands
Branding in universities has become an increasingly topical issue, with some institutions committing substantial financial resources to branding activities. The particular characteristics of the sector present challenges for those seeking to build brands and it therefore seems to be timely and appropriate to investigate the common approaches of those institutions perceived as having successful brands.
This study is exploratory in nature, seeking to investigate how successfully UK universities brand themselves, whether they are distinct and if the sector overall communicates effectively. This is approached through examining the perspective of opinion formers external to universities but closely involved with the sector ā a key stakeholder group in UK higher education
Overall, the researchās exploratory nature aims to further the debate on effective branding in UK higher education.
The findings and conclusions identify some issues surrounding university branding activity; most UK universities were considered to be distinct from one another, but few were seen to have real fully formed brands. Although a number of institutions that were seen as having more āsuccessfulā brands were identified, it was argued that whilst many UK universities communicate their brand well enough to key stakeholders, they fail to consistently do this across all audiences. It was also suggested that UK universities may concentrate on areas of perceived immediate strategic importance (in terms of branding) to an extent where others are neglected
Characterization of CRISPR-Cas systems in the Ralstonia solanacearum species complex
Clustered regularly interspaced short palindromic repeats (CRISPRs) are composed of an array of short DNA repeat sequences separated by unique spacer sequences that are flanked by associated (Cas) genes. CRISPRāCas systems are found in the genomes of several microbes and can act as an adaptive immune mechanism against invading foreign nucleic acids, such as phage genomes. Here, we studied the CRISPRāCas systems in plantāpathogenic bacteria of the Ralstonia solanacearum species complex (RSSC). A CRISPRāCas system was found in 31% of RSSC genomes present in public databases. Specifically, CRISPRāCas types IāE and IIāC were found, with IāE being the most common. The presence of the same CRISPRāCas types in distinct Ralstonia phylotypes and species suggests the acquisition of the system by a common ancestor before Ralstonia species segregation. In addition, a Cas1 phylogeny (IāE type) showed a perfect geographical segregation of phylotypes, supporting an ancient acquisition. Ralstoniasolanacearum strains CFBP2957 and K60T were challenged with a virulent phage, and the CRISPR arrays of bacteriophageāinsensitive mutants (BIMs) were analysed. No new spacer acquisition was detected in the analysed BIMs. The functionality of the CRISPRāCas interference step was also tested in R. solanacearum CFBP2957 using a spacerāprotospacer adjacent motif (PAM) delivery system, and no resistance was observed against phage phiAP1. Our results show that the CRISPRāCas system in R. solanacearum CFBP2957 is not its primary antiviral strategy
Increasing Dominance - the Role of Advertising, Pricing and Product Design
Despite the empirical relevance of advertising strategies in concentrated markets, the economics literature is largely silent on the effect of persuasive advertising
strategies on pricing, market structure and increasing (or decreasing) dominance. In a simple model of persuasive advertising and pricing with differentiated goods,
we analyze the interdependencies between ex-ante asymmetries in consumer appeal, advertising and prices. Products with larger initial appeal to consumers will
be advertised more heavily but priced at a higher level - that is, advertising and price discounts are strategic substitutes for products with asymmetric initial appeal.
We find that the escalating effect of advertising dominates the moderating effect of pricing so that post-competition market shares are more asymmetric than pre-competition differences in consumer appeal. We further find that collusive advertising (but competitive pricing) generates the same market outcomes, and that network effects lead to even more extreme market outcomes, both directly and via
the effect on advertising
Shear Alignment and Instability of Smectic Phases
We consider the shear flow of well-aligned one-component smectic phases, such
as thermotropic smectics and lamellar diblock copolymers, below the critical
region. We show that, as a result of thermal fluctuations of the layers,
parallel () alignment is generically unstable and perpendicular ()
alignment is stable against long-wavelength undulations. We also find,
surprisingly, that both and are stable for a narrow window of values
for the anisotropic viscosity.Comment: To appear in PRL. Revtex, 1 figure
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