461 research outputs found
Evolution of cosmic string configurations
We extend and develop our previous work on the evolution of a network of
cosmic strings. The new treatment is based on an analysis of the probability
distribution of the end-to-end distance of a randomly chosen segment of
left-moving string of given length. The description involves three distinct
length scales: , related to the overall string density, , the
persistence length along the string, and , describing the small-scale
structure, which is an important feature of the numerical simulations that have
been done of this problem. An evolution equation is derived describing how the
distribution develops in time due to the combined effects of the universal
expansion, of intercommuting and loop formation, and of gravitational
radiation. With plausible assumptions about the unknown parameters in the
model, we confirm the conclusions of our previous study, that if gravitational
radiation and small-scale structure effects are neglected, the two dominant
length scales both scale in proportion to the horizon size. When the extra
effects are included, we find that while and grow,
initially does not. Eventually, however, it does appear to scale, at a much
lower level, due to the effects of gravitational back-reaction.Comment: 61 pages, requires RevTex v3.0, SUSSEX-TH-93/3-4,
IMPERIAL/TP/92-93/4
Impact of analytic provenance in genome analysis
Many computational methods are available for assembly and annotation of newly sequenced microbial genomes. However, when new genomes are reported in the literature, there is frequently very little critical analysis of choices made during the sequence assembly and gene annotation stages. These choices have a direct impact on the biologically relevant products of a genomic analysis - for instance identification of common and differentiating regions among genomes in a comparison, or identification of enriched gene functional categories in a specific strain. Here, we examine the outcomes of different assembly and analysis steps in typical workflows in a comparison among strains of Vibrio vulnificus
How does the early life environment influence the oral microbiome and determine oral health outcomes in childhood?
The first 1000 days of life, from conception to 2 years, are a critical window for the influence of environmental exposures on the assembly of the oral microbiome, which is the precursor to dental caries (decay), one of the most prevalentmicrobially induced disorders worldwide. While it is known that the human microbiome is susceptible to environmental exposures, there is limited understanding of the impact of prenatal and early childhood exposures on the oral microbiome trajectory and oral health. A barrier has been the lack of technology to directly measure the foetal "exposome", which includes nutritional and toxic exposures crossing the placenta. Another barrier has been the lack of statistical methods to account for the high dimensional data generated by-omic assays. Through identifying which early life exposures influence the oral microbiome and modify oral health, these findings can be translated into interventions to reduce dental decay prevalence.Christina Jane Adler, Kim-Anh LĂȘ Cao, Toby Hughes, Piyush Kumar, Christine Austi
Variability in the area, energy and time costs of wintering waders responding to disturbance
Birdsâ responses to human disturbance are interesting due to their similarities to anti-predator behaviour, and understanding this behaviour has practical applications for conservation management by informing measures such as buffer zones to protect priority species. To understand better the costs of disturbance and whether it will impact on population size, studies should quantify time-related responses as well as the more commonly reported flight initiation distance (FID). Using waders wintering on an estuarine area, we experimentally disturbed foraging birds on the Wash Embayment, UK, by walking towards them and recording their responses (FID, alert time, time spent in flight, time taken to resume feeding, and total feeding time lost). We present data for 10 species of conservation concern: Curlew Numenius arquata, Oystercatcher Haematopus ostralegus, Bar-tailed Godwit Limosa lapponica, Grey Plover Pluvialis squatarola, Redshank Tringa totanus, Knot Calidris canutus, Turnstone Arenaria interpres, Ringed Plover Charadrius hiaticula, Sanderling Calidris alba and Dunlin Calidris alpina. Larger species responded more strongly, response magnitude was greater under milder environmental conditions, and responses varied over both small and large spatial scales. The energetic costs of individual responses, however, were low relative to daily requirements and disturbance events were unlikely to be frequent enough to seriously limit foraging time. We suggest, therefore, that wintering wader populations on the Wash are not currently significantly negatively impacted by human disturbance during the intertidal foraging period. This is also likely to be the case at other estuarine sites with comparable access levels, visitor patterns, invertebrate food availability and environmental conditions
Adhesion of Listeria monocytogenes to materials commonly found in domestic kitchens
The aim of this work was to investigate the adhesion of Listeria monocytogenes ATCC 15313 to glass,
granite, marble, polypropylene from a bowl (PPb), polypropylene from a cutting board (PPcb) and stainless
steel (SS), which are materials commonly used in kitchens. Marble and granite were chosen because they are
applied as kitchen bench covers and pavements in many countries and there are no literature reports on their
behaviour in terms of microbial adhesion. The effect of surface hydrophobicity and roughness on the
adhesion process was also analysed. The results showed that the highest extent of adhesion of
L. monocytogenes occurred to stainless steel, followed by glass and in less extent to the other materials
studied. However, it was not possible to establish a correlation between surface hydrophobicity or roughness
and the extent of adhesion of L. monocytogenes. The adherence of L. monocytogenes should be dependent on
other factors, like the presence of exopolymers and surface charge.Fundação para a CiĂȘncia e a Tecnologia (FCT
On the gravitational, dilatonic and axionic radiative damping of cosmic strings
We study the radiation reaction on cosmic strings due to the emission of
dilatonic, gravitational and axionic waves. After verifying the (on average)
conservative nature of the time-symmetric self-interactions, we concentrate on
the finite radiation damping force associated with the half-retarded minus
half-advanced ``reactive'' fields. We revisit a recent proposal of using a
``local back reaction approximation'' for the reactive fields. Using
dimensional continuation as convenient technical tool, we find, contrary to
previous claims, that this proposal leads to antidamping in the case of the
axionic field, and to zero (integrated) damping in the case of the
gravitational field. One gets normal positive damping only in the case of the
dilatonic field. We propose to use a suitably modified version of the local
dilatonic radiation reaction as a substitute for the exact (non-local)
gravitational radiation reaction. The incorporation of such a local
approximation to gravitational radiation reaction should allow one to complete,
in a computationally non-intensive way, string network simulations and to give
better estimates of the amount and spectrum of gravitational radiation emitted
by a cosmologically evolving network of massive strings.Comment: 48 pages, RevTex, epsfig, 1 figure; clarification of the domain of
validity of the perturbative derivation of the string equations of motion,
and of their renormalizabilit
Enacting corporate governance of health care safety and quality: a dramaturgy of hospital boards in England
The governance of patient safety is a challenging concern for all health systems. Yet, while the role of executive Boards receives increased scrutiny, the area remains theoretically and methodologically underdeveloped. Specifically, we lack a detailed understanding of the performative aspects at play: what Board members say and do to discharge their accountabilities for patient safety. This article draws on qualitative data from overt non-participant observation of four NHS hospital Foundation Trust Boards in England. Applying a dramaturgical framework to explore scripting, setting, staging and performance, we found important differences between case study sites in the performative dimensions of processing and interpretation of infection control data. We detail the practices associated with these differences - the legitimation of current performance, the querying of data classification, and the naming and shaming of executives â to consider their implications
Human Milk Oligosaccharides in the Milk of Mothers Delivering Term versus Preterm Infants.
Human milk oligosaccharides (HMOs) are a major component of human milk, and play an important role in protecting the infant from infections. Preterm infants are particularly vulnerable, but have improved outcomes if fed with human milk. This study aimed to determine if the HMO composition of preterm milk differed from that of term milk at equivalent stage of lactation and equivalent postmenstrual age. In all, 22 HMOs were analyzed in 500 samples of milk from 25 mothers breastfeeding very preterm infants (< 32 weeks of gestational age, < 1500g of birthweight) and 28 mothers breastfeeding term infants. The concentrations of most HMOs were comparable at equivalent postpartum age. However, HMOs containing α-1,2-linked fucose were reduced in concentration in preterm milk during the first month of lactation. The concentrations of a number of sialylated oligosaccharides were also different in preterm milk, in particular 3'-sialyllactose concentrations were elevated. At equivalent postmenstrual age, the concentrations of a number of HMOs were significantly different in preterm compared to term milk. The largest differences manifest around 40 weeks of postmenstrual age, when the milk of term infants contains the highest concentrations of HMOs. The observed differences warrant further investigation in view of their potential clinical impact
LENDA, a Low Energy Neutron Detector Array for experiments with radioactive beams in inverse kinematics
The Low Energy Neutron Detector Array (LENDA) is a neutron time-of-flight
(TOF) spectrometer developed at the National Superconducting Cyclotron Lab-
oratory (NSCL) for use in inverse kinematics experiments with rare isotope
beams. Its design has been motivated by the need to study the spin-isospin
response of unstable nuclei using (p, n) charge-exchange reactions at
intermediate energies (> 100 MeV/u). It can be used, however, for any reaction
study that involves emission of low energy neutrons (150 keV - 10 MeV). The
array consists of 24 plastic scintillator bars and is capable of registering
the recoiling neutron energy and angle with high detection efficiency. The
neutron energy is determined by the time-of-flight technique, while the
position of interaction is deduced using the timing and energy information from
the two photomultipliers of each bar. A simple test setup utilizing radioactive
sources has been used to characterize the array. Results of test measurements
are compared with simulations. A neutron energy threshold of < 150 keV, an
intrinsic time (position) resolution of \sim 400 ps (\sim 6 cm) and an
efficiency > 20 % for neutrons below 4 MeV have been obtained.Comment: Version accepted for publication in Nucl. Instr. Methods A. Revised
text, 2 new figures added (one in section 4 and one in section 7
Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment
This paper describes an analysis of the angular distribution of W->enu and
W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with
the ATLAS detector at the LHC in 2010, corresponding to an integrated
luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and
the missing transverse energy, the W decay angular distribution projected onto
the transverse plane is obtained and analysed in terms of helicity fractions
f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV
and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw
> 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour,
are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017
+/- 0.030, where the first uncertainties are statistical, and the second
include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables,
revised author list, matches European Journal of Physics C versio
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