5,063 research outputs found
Enhanced nasopharyngeal infection and shedding associated with an epidemic lineage of emm3 group A Streptococcus
Background:
A group A Streptococcus (GAS) lineage of genotype emm3, sequence type 15 (ST15) was
associated with a six month upsurge in invasive GAS disease in the UK. The epidemic lineage
(Lineage C) had lost two typical emm3 prophages, Ī¦315.1 and Ī¦315.2 associated with the
superantigen ssa, but gained a different prophage (Ī¦UK-M3.1) associated with a different
superantigen, speC and a DNAse spd1.
Methods and Results:
The presence of speC and spd1 in Lineage C ST15 strains enhanced both in vitro mitogenic
and DNAse activities over non-Lineage C ST15 strains. Invasive disease models in Galleria
mellonella and SPEC-sensitive transgenic mice, revealed no difference in overall invasiveness
of Lineage C ST15 strains compared to non-Lineage C ST15 strains, consistent with clinical
and epidemiological analysis. Lineage C strains did however markedly prolong murine nasal
infection with enhanced nasal and airborne shedding compared to non-Lineage C strains.
Deletion of speC or spd1 in two Lineage C strains identified a possible role for spd1 in airborne
shedding from the murine nasopharynx.
Conclusions:
Nasopharyngeal infection and shedding of Lineage C strains was enhanced compared to nonLineage
C strains and this was, in part, mediated by the gain of the DNase spd1 through prophage acquisition
Emergence of a novel lineage containing a prophage in emm/M3 group A Streptococcus associated with upsurge in invasive disease in the UK
A sudden increase in invasive Group A Streptococcus (iGAS) infections associated with emm/M3 isolates during the winter of 2008/09 prompted the initiation of enhanced surveillance in England. In order to characterise the population of emm/M3 GAS within the UK and determine bacterial factors that might be responsible for this upsurge, 442 emm/M3 isolates from cases of invasive and non-invasive infections during the period 2001ā2013 were subjected to whole genome sequencing. MLST analysis differentiated emm/M3 isolates into three sequence types (STs): ST15, ST315 and ST406. Analysis of the whole genome SNP-based phylogeny showed that the majority of isolates from the 2008ā2009 upsurge period belonged to a distinct lineage characterized by the presence of a prophage carrying the speC exotoxin and spd1 DNAase genes but loss of two other prophages considered typical of the emm/M3 lineage. This lineage was significantly associated with the upsurge in iGAS cases and we postulate that the upsurge could be attributed in part to expansion of this novel prophage-containing lineage within the population. The study underlines the importance of prompt genomic analysis of changes in the GAS population, providing an advanced public health warning system for newly emergent, pathogenic strains
Sharks of the order Carcharhiniformes from the British Coniacian, Santonian and Campanian (Upper Cretaceous).
Bulk sampling of phosphate-rich horizons within the British Coniacian to Campanian (Upper Cretaceous) yielded very large samples of shark and ray teeth. All of these samples yielded teeth of diverse members of the Carcharhiniformes, which commonly dominate the fauna. The following species are recorded and described: Pseudoscyliorhinus reussi (Herman, 1977) comb. nov., Crassescyliorhinus germanicus (Herman, 1982) gen. nov., Scyliorhinus elongatus (Davis, 1887), Scyliorhinus brumarivulensis sp. nov., ? Palaeoscyllium sp., Prohaploblepharus riegrafi (MĆ¼ller, 1989) gen. nov., ? Cretascyliorhinus sp., Scyliorhinidae inc. sedis 1, Scyliorhinidae inc. sedis 2, Pteroscyllium hermani sp. nov., Protoscyliorhinus sp., Leptocharias cretaceus sp. nov., Palaeogaleus havreensis Herman, 1977, Paratriakis subserratus sp. nov., Paratriakis tenuis sp. nov., Paratriakis sp. indet. and ? Loxodon sp. Taxa belonging to the families ?Proscylliidae, Leptochariidae, and Carcharhinidae are described from the Cretaceous for the first time. The evolutionary and palaeoecological implications of these newly recognised faunas are discussed
Collaborative multidisciplinary learning : quantity surveying studentsā perspectives
The construction industry is highly fragmented and is known for its adversarial culture, culminating
in poor quality projects not completed on time or within budget. The aim of this study is thus to
guide the design of QS programme curricula in order to help students develop the requisite
knowledge and skills to work more collaboratively in their multi-disciplinary future workplaces.
A qualitative approach was considered appropriate as the authors were concerned with gathering an
initial understanding of what students think of multi-disciplinary learning. The data collection
method used was a questionnaire which was developed by the Behaviours4Collaboration (B4C)
team.
Knowledge gaps were still found across all the key areas where a future QS practitioner needs to be
collaborative (either as a project contributor or as a project leader) despite the need for change
instigated by the multi-disciplinary (BIM) education revolution.
The study concludes that universities will need to be selective in teaching, and innovative in
reorienting, QS education so that a collaborative BIM education can be effected in stages, increasing
in complexity as the studentsā technical knowledge grows. This will help students to build the
competencies needed to make them future leaders. It will also support programme currency and
delivery
Changes in microphytobenthos fluorescence over a tidal cycle: implications for sampling designs
Intertidal microphytobenthos (MPB) are important primary producers and provide food for herbivores in soft sediments and on rocky shores. Methods of measuring MPB biomass that do not depend on the time of collection relative to the time of day or tidal conditions are important in any studies that need to compare temporal or spatial variation, effects of abiotic factors or activity of grazers. Pulse amplitude modulated (PAM) fluorometry is often used to estimate biomass of MPB because it is a rapid, non-destructive method, but it is not known how measures of fluorescence are altered by changing conditions during a period of low tide. We investigated this experimentally using in situ changes in minimal fluorescence (F) on a rocky shore and on an estuarine mudflat around Sydney (Australia), during low tides. On rocky shores, the time when samples are taken during low tide had little direct influence on measures of fluorescence as long as the substratum is dry. Wetness from wave-splash, seepage from rock pools, run-off, rainfall, etc., had large consequences for any comparisons. On soft sediments, fluorescence was decreased if the sediment dried out, as happens during low-spring tides on particularly hot and dry days. Surface water affected the response of PAM and therefore measurements used to estimate MPB, emphasising the need for care to ensure that representative sampling is done during low tide
Comprehension as social and intellectual practice: Rebuilding curriculum in low socioeconomic and cultural minority schools
This article reframes the concept of comprehension as a social and intellectual practice. It reviews current approaches to reading instruction for linguistically and culturally diverse and low socioeconomic students, noting an emphasis on comprehension as autonomous skills. The Four Resources model (Freebody & Luke, 1990) is used to make the case for the integration of comprehension instruction with an emphasis on student cultural and community knowledge, and substantive intellectual and sociocultural content in elementary school curricula. Illustrations are drawn from research underway on the teaching of literacy in primary schools in low SES communities
DBI Inflation using a One-Parameter Family of Throat Geometries
We demonstrate the possibility of examining cosmological signatures in the
DBI inflation setup using the BGMPZ solution, a one-parameter family of
geometries for the warped throat which interpolate between the Maldacena-Nunez
and Klebanov-Strassler solutions. The warp factor is determined numerically and
subsequently used to calculate cosmological observables including the scalar
and tensor spectral indices, for a sample point in the parameter space. As one
moves away from the KS solution for the throat the warp factor is qualitatively
different, which leads to a significant change for the observables, but also
generically increases the non-Gaussianity of the models. We argue that the
different models can potentially be differentiated by current and future
experiments.Comment: 17 pages, 10 figures; v2: section 4 expanded, references added; v3:
typos fixe
Chord distribution functions of three-dimensional random media: Approximate first-passage times of Gaussian processes
The main result of this paper is a semi-analytic approximation for the chord
distribution functions of three-dimensional models of microstructure derived
from Gaussian random fields. In the simplest case the chord functions are
equivalent to a standard first-passage time problem, i.e., the probability
density governing the time taken by a Gaussian random process to first exceed a
threshold. We obtain an approximation based on the assumption that successive
chords are independent. The result is a generalization of the independent
interval approximation recently used to determine the exponent of persistence
time decay in coarsening. The approximation is easily extended to more general
models based on the intersection and union sets of models generated from the
iso-surfaces of random fields. The chord distribution functions play an
important role in the characterization of random composite and porous
materials. Our results are compared with experimental data obtained from a
three-dimensional image of a porous Fontainebleau sandstone and a
two-dimensional image of a tungsten-silver composite alloy.Comment: 12 pages, 11 figures. Submitted to Phys. Rev.
Regular Conjugacy Classes in the Weyl Group and Integrable Hierarchies
Generalized KdV hierarchies associated by Drinfeld-Sokolov reduction to grade
one regular semisimple elements from non-equivalent Heisenberg subalgebras of a
loop algebra \G\otimes{\bf C}[\lambda,\lambda^{-1}] are studied. The graded
Heisenberg subalgebras containing such elements are labelled by the regular
conjugacy classes in the Weyl group {\bf W}(\G) of the simple Lie algebra
\G. A representative w\in {\bf W}(\G) of a regular conjugacy class can be
lifted to an inner automorphism of \G given by , where is the defining vector of an subalgebra
of \G.The grading is then defined by the operator and any grade one regular element from the
Heisenberg subalgebra associated to takes the form , where and is included in an
subalgebra containing . The largest eigenvalue of is
except for some cases in , . We explain how these Lie
algebraic results follow from known results and apply them to construct
integrable systems.If the largest eigenvalue is , then
using any grade one regular element from the Heisenberg subalgebra associated
to we can construct a KdV system possessing the standard \W-algebra
defined by as its second Poisson bracket algebra. For \G a classical
Lie algebra, we derive pseudo-differential Lax operators for those
non-principal KdV systems that can be obtained as discrete reductions of KdV
systems related to . Non-abelian Toda systems are also considered.Comment: 44 pages, ENSLAPP-L-493/94, substantial revision, SWAT-95-77. (use
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