730 research outputs found
Monitoring environmental cleanliness on two surgical wards
Ten hand-touch sites were screened weekly on two surgical wards over two consecutive six-month periods. The results were analysed using hygiene standards, which specify 1) an aerobic colony count (ACC) >2.5cfu/cm2, and 2) presence of coagulase-positive staphylococci, as hygiene failures. Sites most often failing the standards were beds and hoist (64%: 33 of 52 weeks), bedside lockers (62%: 32 of 52) and overbed tables (44%: 23 of 52). Methicillin-susceptible/resistant Staphylococcus aureus (MSSA/MRSA) were more often recovered from lockers, overbed tables and beds. Recovery of MSSA/MRSA at any site was significantly associated with an ACC>2.5cfu/cm2 from that site (p=0.001; OR: 3.35 (95% CI 1.79, 6.28)). In addition, total ACC's>2.5cfu/cm2 each week were significantly associated with weekly bed occupancies >95% (p=0.0004; OR: 2.94 (95% CI 1.44, 6.02)). Higher microbial growth levels from hand-touch sites reflect weekly bed occupancies and indicate a risk for both resistant and susceptible S.aureus. These organisms are more likely to be recovered from near-patient sites on the ward
The Sachs-Wolfe Effect: Gauge Independence and a General Expression
In this paper we address two points concerning the Sachs-Wolfe effect: (i)
the gauge independence of the observable temperature anisotropy, and (ii) a
gauge-invariant expression of the effect considering the most general situation
of hydrodynamic perturbations. The first result follows because the gauge
transformation of the temperature fluctuation at the observation event only
contributes to the isotropic temperature change which, in practice, is absorbed
into the definition of the background temperature. Thus, we proceed without
fixing the gauge condition, and express the Sachs-Wolfe effect using the
gauge-invariant variables.Comment: 5 pages, closer to published versio
Suppression of static stripe formation by next-neighbor hopping
We show from real-space Hartree-Fock calculations within the extended Hubbard
model that next-nearest neighbor (t') hopping processes act to suppress the
formation of static charge stripes. This result is confirmed by investigating
the evolution of charge-inhomogeneous corral and stripe phases with increasing
t' of both signs. We propose that large t' values in YBCO prevent static stripe
formation, while anomalously small t' in LSCO provides an additional reason for
the appearance of static stripes only in these systems.Comment: 4 pages, 5 figure
The Primordial Gravitational Wave Background in String Cosmology
We find the spectrum P(w)dw of the gravitational wave background produced in
the early universe in string theory. We work in the framework of String Driven
Cosmology, whose scale factors are computed with the low-energy effective
string equations as well as selfconsistent solutions of General Relativity with
a gas of strings as source. The scale factor evolution is described by an early
string driven inflationary stage with an instantaneous transition to a
radiation dominated stage and successive matter dominated stage. This is an
expanding string cosmology always running on positive proper cosmic time. A
careful treatment of the scale factor evolution and involved transitions is
made. A full prediction on the power spectrum of gravitational waves without
any free-parameters is given. We study and show explicitly the effect of the
dilaton field, characteristic to this kind of cosmologies. We compute the
spectrum for the same evolution description with three differents approachs.
Some features of gravitational wave spectra, as peaks and asymptotic
behaviours, are found direct consequences of the dilaton involved and not only
of the scale factor evolution. A comparative analysis of different treatments,
solutions and compatibility with observational bounds or detection perspectives
is made.Comment: LaTeX, 50 pages with 2 figures. Uses epsfig and psfra
CBR Anisotropy from Primordial Gravitational Waves in Two-Component Inflationary Cosmology
We examine stochastic temperature fluctuations of the cosmic background
radiation (CBR) arising via the Sachs-Wolfe effect from gravitational wave
perturbations produced in the early universe. We consider spatially flat,
perturbed FRW models that begin with an inflationary phase, followed by a mixed
phase containing both radiation and dust. The scale factor during the mixed
phase takes the form , where are
constants. During the mixed phase the universe smoothly transforms from being
radiation to dust dominated. We find analytic expressions for the graviton mode
function during the mixed phase in terms of spheroidal wave functions. This
mode function is used to find an analytic expression for the multipole moments
of the two-point angular correlation function
for the CBR anisotropy. The analytic expression for the multipole
moments is written in terms of two integrals, which are evaluated numerically.
The results are compared to multipoles calculated for models that are {\it
completely} dust dominated at last-scattering. We find that the multipoles
of the CBR temperature perturbations for are
significantly larger for a universe that contains both radiation and dust at
last-scattering. We compare our results with recent, similar numerical work and
find good agreement. The spheroidal wave functions may have applications to
other problems of cosmological interest.Comment: 28 pgs + 6 postscript figures, RevTe
Pairing Correlations in a Generalized Hubbard Model for the Cuprates
Using numerical diagonalization of a 4x4 cluster, we calculate on-site s,
extended s and d pairing correlation functions (PCF) in an effective
generalized Hubbard model for the cuprates, with nearest-neighbor correlated
hopping and next nearest-neighbor hopping t'. The vertex contributions (VC) to
the PCF are significantly enhanced, relative to the t-t'-U model. The behavior
of the PCF and their VC, and signatures of anomalous flux quantization,
indicate superconductivity in the d-wave channel for moderate doping and in the
s-wave channel for high doping and small U.Comment: 5 pages, 5 figure
Limits on the gravity wave contribution to microwave anisotropies
We present limits on the fraction of large angle microwave anisotropies which
could come from tensor perturbations. We use the COBE results as well as
smaller scale CMB observations, measurements of galaxy correlations, abundances
of galaxy clusters, and Lyman alpha absorption cloud statistics. Our aim is to
provide conservative limits on the tensor-to-scalar ratio for standard
inflationary models. For power-law inflation, for example, we find T/S<0.52 at
95% confidence, with a similar constraint for phi^p potentials. However, for
models with tensor amplitude unrelated to the scalar spectral index it is still
currently possible to have T/S>1.Comment: 23 pages, 7 figures, accepted for publication in Phys. Rev. D.
Calculations extended to blue spectral index, Fig. 6 added, discussion of
results expande
Conformations of closed DNA
We examine the conformations of a model for a short segment of closed DNA.
The molecule is represented as a cylindrically symmetric elastic rod with a
constraint corresponding to a specification of the linking number. We obtain
analytic expressions leading to the spatial configuration of a family of
solutions representing distortions that interpolate between the circular form
of DNA and a figure-eight form that represents the onset of interwinding. We
are also able to generate knotted loops. We suggest ways to use our approach to
produce other configurations relevant to studies of DNA structure. The
stability of the distorted configurations is assessed, along with the effects
of fluctuations on the free energy of the various configurations.Comment: 39 pages in REVTEX with 14 eps figures. Submitted to Phys. Rev. E.
This manuscript updates, expands and revises, to a considerable extent, a
previously posted manuscript, entitled "Conformations of Circular DNA," which
appeared as cond-mat/970104
HOPX functions as a tumour suppressor in head and neck cancer.
Head and neck squamous cell carcinoma (HNSCC) is generalized term that encompasses a diverse group of cancers that includes tumours of the oral cavity (OSCC), oropharynx (OPSCC) and nasopharynx (NPC). Genetic alterations that are common to all HNSCC types are likely to be important for squamous carcinogenesis. In this study, we have investigated the role of the homeodomain-only homeobox gene, HOPX, in the pathogenesis of HNSCC. We show that HOPX mRNA levels are reduced in OSCC and NPC cell lines and tissues and there is a general reduction of HOPX protein expression in these tumours and OPSCCs. HOPX promoter methylation was observed in a subset of HNSCCs and was associated with a worse overall survival in HPV negative tumours. RNAseq analysis of OSCC cells transfected with HOPX revealed a widespread deregulation of the transcription of genes related to epithelial homeostasis and ectopic over-expression of HOPX in OSCC and NPC cells inhibited cell proliferation, plating efficiency and migration, and enhanced sensitivity to UVA-induced apoptosis. Our results demonstrate that HOPX functions as a tumour suppressor in HNSCC and suggest a central role for HOPX in suppressing epithelial carcinogenesis
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Evidence against water delivery by impacts within 10 million years of planetesimal formation
The quenched (rapidly-cooled) angrite meteorites, which formed in the inner Solar System, record large-scale planetary mixing in the first few Ma of Solar System history, and therefore, provide a unique opportunity to investigate the role of impacts in terms of water addition to the growing planetesimals. Here we investigate the H isotopic composition and H2O abundance of relict olivine grains that survived impact melting within Asuka (A) 12,209 and compare them with impact melt-produced groundmass fractions using in-situ nanoscale secondary ion mass spectrometry (NanoSIMS). These analyses test if the angrite parent body (APB) acquired a CC-like H isotopic composition before early large-scale impact mixing and/or acquired volatiles by subsequent impact(s). Furthermore, we analyse the H isotopic composition and H2O abundance of later-forming plutonic (NWA 4801), intermediate (NWA 10,463) and dunitic (NWA 8535) angrite meteorites to assess the role of impacts, in terms of volatile delivery, during the first 50 Ma of the inner Solar System history. The H isotopic composition of most quenched angrites appears to be affected by degassing. Consequently, we opt to use the weighted average ÎŽD of pyroxenes and olivines in the plutonic angrite, NWA 4801, to estimate the original composition of the APB (-235 ± 113 â° 1Ï, n = 18), in agreement with recent studies on the hydrogen isotopic signatures of mineral-hosted melt inclusions in D'Orbigny and Sahara 99,555. Additionally, we use the H2O abundances of NWA 4801 pyroxene (7.9 ± 1 ”g/g 2Ï) and olivine (6.1 ± 0.6 ”g/g 2Ï) to estimate the lower (85 to 110 ”g/g) and upper (519 to 1089 ”g/g) limits of the primitive APB mantle H2O content, implying that the APB was one of the most hydrated bodies in the early inner Solar System. The similarity of ÎŽD/H2O systematics in the relict olivine grains and groundmass olivine within A 12,209 argues against water delivery through impacts in the early inner Solar System. Overall, the non-carbonaceous reservoir in the inner Solar System appears to retain a single source of water, which isotopically resembles either water ice in carbonaceous chondrite parent bodies or fractionated nebula water
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