833 research outputs found
Cytokine gene polymorphisms in preterm infants with necrotising enterocolitis: genetic association study
BACKGROUND The inflammatory cytokine cascade is implicated in the pathogenesis of necrotising enterocolitis (NEC). Genetic association studies of cytokine polymorphisms may help to detect molecular mechanisms that are causally related to the disease process. AIM To examine associations between the common genetic variants in candidate inflammatory cytokine genes and NEC in preterm infants. METHODS Multi-centre case-control and genetic association study. DNA samples were collected from 50 preterm infants with NEC and 50 controls matched for gestational age and ethnic group recruited to a multi-centre case-control study. Ten candidate single-nucleotide polymorphisms in cytokines previously associated with infectious or inflammatory diseases were genotyped. The findings were included in random-effects meta-analyses with data from previous genetic association studies. RESULTS All allele distributions were in Hardy-Weinberg equilibrium. None of the studied cytokine polymorphisms was significantly associated with NEC. Four previous genetic association studies of cytokine polymorphisms and NEC in preterm infants were found. Meta-analyses were possible for several single-nucleotide polymorphisms. These increased the precision of the estimates of effect size but did not reveal any significant associations. CONCLUSIONS The available data are not consistent with more than modest associations between these candidate cytokine variant alleles and NEC in preterm infants. Data from future association studies of these polymorphisms may be added to the meta-analyses to obtain more precise estimates of effects sizes.The study was funded by Tenovus (Scotland)
Candida parapsilosis infection in very low birthweight infants
In a UK national surveillance study, we found that Candida parapsilosis accounted for one quarter of all cases of invasive fungal infection in very low birthweight infants. C parapsilosis was associated with fewer deep-seated infections than C albicans, but mortality was similar. Ongoing surveillance is needed to monitor the epidemiology of invasive fungal infection in very low birthweight infants.This study was partly supported by an educational grant provided
by Pfizer UK
Theoretical He I Emissivities in the Case B Approximation
We calculate the He I case B recombination cascade spectrum using improved
radiative and collisional data. We present new emissivities over a range of
electron temperatures and densities. The differences between our results and
the current standard are large enough to have a significant effect not only on
the interpretation of observed spectra of a wide variety of objects but also on
determinations of the primordial helium abundance.Comment: Accepted to ApJ
The Early Evolution of Massive Stars: Radio Recombination Line Spectra
Velocity shifts and differential broadening of radio recombination lines are
used to estimate the densities and velocities of the ionized gas in several
hypercompact and ultracompact HII regions. These small HII regions are thought
to be at their earliest evolutionary phase and associated with the youngest
massive stars. The observations suggest that these HII regions are
characterized by high densities, supersonic flows and steep density gradients,
consistent with accretion and outflows that would be associated with the
formation of massive stars.Comment: ApJ in pres
Planetary Nebula Abundances and Morphology: Probing the Chemical Evolution of the Milky Way
This paper presents a homogeneous study of abundances in a sample of 79
northern galactic planetary nebulae whose morphological classes have been
uniformly determined. Ionic abundances and plasma diagnostics were derived from
selected optical line strengths in the literature, and elemental abundances
were estimated with the Ionization Correction Factor developed by Kingsbourgh &
Barlow (1994). We compare the elemental abundances to the final yields obtained
from stellar evolution models of low-and intermediate-mass stars, and we
confirm that most Bipolar planetary nebulae have high nitrogen and helium
abundance, and are the likely progeny of stars with main-sequence mass larger
than 3 solar masses. We derive =0.27, and discuss the implication of such
a high ratio in connection with the solar neon abundance. We determine the
galactic gradients of oxygen and neon, and found Delta log (O/H)/Delta R=-0.01
dex/kpc$ and Delta log (Ne/H)/Delta R=-0.01 dex/kpc. These flat PN gradients do
not reconcile with galactic metallicity gradients flattening with time.Comment: The Astrophysical Journal, in pres
Involvement of protein kinase C in the phosphorylation of an insulin-granule membrane protein
A Search for "Dwarf" Seyfert Nuclei. III. Spectroscopic Parameters and Properties of the Host Galaxies
We have completed an optical spectroscopic survey of the nuclear regions (r <
200 pc) of a large sample of nearby galaxies. Although the main objectives of
the survey are to search for low-luminosity active galactic nuclei and to
quantify their luminosity function, the database can be used for a variety of
other purposes. This paper presents measurements of the spectroscopic
parameters for the 418 emission-line nuclei, along with a compilation of the
global properties of all 486 galaxies in the survey. Stellar absorption
generally poses a serious obstacle to obtaining accurate measurement of
emission lines in nearby galactic nuclei. We describe a procedure for removing
the starlight from the observed spectra in an efficient and objective manner.
The main parameters of the emission lines (intensity ratios, fluxes, profile
widths, equivalent widths) are measured and tabulated, as are several stellar
absorption-line and continuum indices useful for studying the stellar
population. Using standard nebular diagnostics, we determine the probable
ionization mechanisms of the emission-line objects. The resulting spectral
classifications provide extensive information on the demographics of
emission-line nuclei in the local universe. This new catalog contains over 200
objects showing spectroscopic evidence for recent star formation and an equally
large number of active galactic nuclei, including 46 which show broad H-alpha
emission. These samples will serve as the basis of future studies of nuclear
activity in nearby galaxies.Comment: To appear in the Astrophysical Journal Supplements. LaTex, 31 pages,
plus an additional 23 figures and 5 tables. AASTex macro aaspp4.st
Improving Predictions for Helium Emission Lines
We have combined the detailed He I recombination model of Smits with the
collisional transitions of Sawey & Berrington in order to produce new accurate
helium emissivities that include the effects of collisional excitation from
both the 2 (3)S and 2 (1) S levels. We present a grid of emissivities for a
range of temperature and densities along with analytical fits and error
estimates.
Fits accurate to within 1% are given for the emissivities of the brightest
lines over a restricted range for estimates of primordial helium abundance. We
characterize the analysis uncertainties associated with uncertainties in
temperature, density, fitting functions, and input atomic data. We estimate
that atomic data uncertainties alone may limit abundance estimates to an
accuracy of 1.5%; systematic errors may be greater than this. This analysis
uncertainty must be incorporated when attempting to make high accuracy
estimates of the helium abundance. For example, in recent determinations of the
primordial helium abundance, uncertainties in the input atomic data have been
neglected.Comment: ApJ, accepte
Riparian buffer strips: their role in the conservation of insect pollinators in intensive grassland systems
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