24,343 research outputs found
On the Intracluster Medium in Cooling Flow & Non-Cooling Flow Clusters
Recent X-ray observations have highlighted clusters that lack entropy cores.
At first glance, these results appear to invalidate the preheated ICM models.
We show that a self-consistent preheating model, which factors in the effects
of radiative cooling, is in excellent agreement with the observations.
Moreover, the model naturally explains the intrinsic scatter in the L-T
relation, with ``cooling flow'' and ``non-cooling flow'' systems corresponding
to mildly and strongly preheated systems, respectively. We discuss why
preheating ought to be favoured over merging as a mechanism for the origin of
``non-cooling flow'' clusters.Comment: 4 pages, to appear in the proceedings of the "Multiwavelength
Cosmology" Conference held in Mykonos, Greece, June 2003, ed. M. Plionis
(Kluwer
Predictive validity of the HCR-20 for inpatient aggression:the effect of intellectual disability on accuracy
BackgroundPeople with intellectual disability (ID) account for a large proportion of aggressive incidents in secure and forensic psychiatric services. Although the Historical, Clinical, Risk Management 20 (HCR-20) has good predictive validity in inpatient settings, it does not perform equally in all groups and there is little evidence for its efficacy in those with ID.MethodA pseudo-prospective cohort study of the predictive efficacy of the HCR-20 for those with ID (n = 109) was conducted in a UK secure mental health setting using routinely collected risk data. Performance of the HCR-20 in the ID group was compared with a comparison group of adult inpatients without an ID (n = 504). Analysis controlled for potential covariates including security level, length of stay, gender and diagnosis.ResultsThe HCR-20 total score was a significant predictor of any aggression and of physical aggression for both groups, although the area under the curve values did not reach the threshold for a large effect size. The clinical subscale performed significantly better in those without an ID compared with those with. The ID group had a greater number of relevant historical and risk management items. The clinicians' summary judgment significantly predicted both types of aggressive outcomes in the ID group, but did not predict either in those without an ID.ConclusionsThis study demonstrates that, after controlling for a range of potential covariates, the HCR-20 is a significant predictor of inpatient aggression in people with an ID and performs as well as for a comparison group of mentally disordered individuals without ID. The potency of HCR-20 subscales and items varied between the ID and comparison groups suggesting important target areas for improved prediction and risk management interventions in those with ID
The scatter and evolution of the global hot gas properties of simulated galaxy cluster populations
We use the cosmo-OWLS suite of cosmological hydrodynamical simulations to
investigate the scatter and evolution of the global hot gas properties of large
simulated populations of galaxy groups and clusters. Our aim is to compare the
predictions of different physical models and to explore the extent to which
commonly-adopted assumptions in observational analyses (e.g. self-similar
evolution) are violated. We examine the relations between (true) halo mass and
the X-ray temperature, X-ray luminosity, gas mass, Sunyaev-Zel'dovich (SZ)
flux, the X-ray analogue of the SZ flux () and the hydrostatic mass. For
the most realistic models, which include AGN feedback, the slopes of the
various mass-observable relations deviate substantially from the self-similar
ones, particularly at late times and for low-mass clusters. The amplitude of
the mass-temperature relation shows negative evolution with respect to the
self-similar prediction (i.e. slower than the prediction) for all models,
driven by an increase in non-thermal pressure support at higher redshifts. The
AGN models predict strong positive evolution of the gas mass fractions at low
halo masses. The SZ flux and show positive evolution with respect to
self-similarity at low mass but negative evolution at high mass. The scatter
about the relations is well approximated by log-normal distributions, with
widths that depend mildly on halo mass. The scatter decreases significantly
with increasing redshift. The exception is the hydrostatic mass-halo mass
relation, for which the scatter increases with redshift. Finally, we discuss
the relative merits of various hot gas-based mass proxies.Comment: 31 pages (21 before appendices), 19 figures, 12 tables, accepted by
MNRAS after minor revisio
The impact of baryonic processes on the two-point correlation functions of galaxies, subhaloes and matter
The observed clustering of galaxies and the cross-correlation of galaxies and
mass provide important constraints on both cosmology and models of galaxy
formation. Even though the dissipation and feedback processes associated with
galaxy formation are thought to affect the distribution of matter, essentially
all models used to predict clustering data are based on collisionless
simulations. Here, we use large hydrodynamical simulations to investigate how
galaxy formation affects the autocorrelation functions of galaxies and
subhaloes, as well as their cross-correlation with matter. We show that the
changes due to the inclusion of baryons are not limited to small scales and are
even present in samples selected by subhalo mass. Samples selected by subhalo
mass cluster ~10% more strongly in a baryonic run on scales r > 1Mpc/h, and
this difference increases for smaller separations. While the inclusion of
baryons boosts the clustering at fixed subhalo mass on all scales, the sign of
the effect on the cross-correlation of subhaloes with matter can vary with
radius. We show that the large-scale effects are due to the change in subhalo
mass caused by the strong feedback associated with galaxy formation and may
therefore not affect samples selected by number density. However, on scales r <
r_vir significant differences remain after accounting for the change in subhalo
mass. We conclude that predictions for galaxy-galaxy and galaxy-mass clustering
from models based on collisionless simulations will have errors greater than
10% on sub-Mpc scales, unless the simulation results are modified to correctly
account for the effects of baryons on the distributions of mass and satellites.Comment: 15 pages, 9 figures. Replaced to match the version accepted by MNRA
Models of the ICM with Heating and Cooling: Explaining the Global and Structural X-ray Properties of Clusters
(Abridged) Theoretical models that include only gravitationally-driven
processes fail to match the observed mean X-ray properties of clusters. As a
result, there has recently been increased interest in models in which either
radiative cooling or entropy injection play a central role in mediating the
properties of the intracluster medium. Both sets of models give reasonable fits
to the mean properties of clusters, but cooling only models result in fractions
of cold baryons in excess of observationally established limits and the
simplest entropy injection models do not treat the "cooling core" structure
present in many clusters and cannot account for entropy profiles revealed by
recent X-ray observations. We consider models that marry radiative cooling with
entropy injection, and confront model predictions for the global and structural
properties of massive clusters with the latest X-ray data. The models
successfully and simultaneously reproduce the observed L-T and L-M relations,
yield detailed entropy, surface brightness, and temperature profiles in
excellent agreement with observations, and predict a cooled gas fraction that
is consistent with observational constraints. The model also provides a
possible explanation for the significant intrinsic scatter present in the L-T
and L-M relations and provides a natural way of distinguishing between clusters
classically identified as "cooling flow" clusters and dynamically relaxed
"non-cooling flow" clusters. The former correspond to systems that had only
mild levels (< 300 keV cm^2) of entropy injection, while the latter are
identified as systems that had much higher entropy injection. This is borne out
by the entropy profiles derived from Chandra and XMM-Newton.Comment: 20 pages, 15 figures, accepted for publication in the Astrophysical
Journa
Star formation quenching in simulated group and cluster galaxies: When, how, and why?
Star formation is observed to be suppressed in group and cluster galaxies
compared to the field. To gain insight into the quenching process, we have
analysed ~2000 galaxies formed in the GIMIC suite of cosmological
hydrodynamical simulations. The time of quenching varies from ~2 Gyr before
accretion (first crossing of r200,c) to >4 Gyr after, depending on satellite
and host mass. Once begun, quenching is rapid (>~ 500 Myr) in low-mass galaxies
(M* < 10^10 M_Sun), but significantly more protracted for more massive
satellites. The simulations predict a substantial role of outflows driven by
ram pressure -- but not tidal forces -- in removing the star-forming
interstellar matter (ISM) from satellite galaxies, especially dwarfs (M* ~ 10^9
M_Sun) where they account for nearly two thirds of ISM loss in both groups and
clusters. Immediately before quenching is complete, this fraction rises to ~80%
even for Milky Way analogues (M* ~ 10^10.5 M_Sun) in groups (M_host ~ 10^13.5
M_Sun). We show that (i) ISM stripping was significantly more effective at
early times than at z = 0; (ii) approximately half the gas is stripped from
`galactic fountains' and half directly from the star forming disk; (iii)
galaxies undergoing stripping experience ram pressure up to ~100 times the
average at a given group/cluster-centric radius, because they are
preferentially located in overdense ICM regions. Remarkably, stripping causes
at most half the loss of the extended gas haloes surrounding our simulated
satellites. These results contrast sharply with the current picture of
strangulation -- removal of the ISM through star formation after stripping of
the hot halo -- being the dominant mechanism quenching group and cluster
satellites.Comment: 24 pages, 21 figures; accepted by MNRA
Effects of negative energy balance on liver gene and protein expression during the early postpartum period and its impacts on dairy cow fertility
End of project reportNegative energy balance (NEB) is a severe metabolic affecting high yielding dairy cows early post partum with both concurrent and latent negative effects on cow fertility as well as on milk production and cow health. The seasonal nature of Irish dairy production necessitates high cow fertility and a compact spring calving pattern in order to maximise grass utilisation. Poor dairy cow reproductive performance currently costs the Irish cattle industry in excess of €400 million annually. High milk yields have been associated with lower reproductive efficiency, and it has been suggested that this effect is probably mediated through its effects on the energy balance of the cow during lactation. The modern high genetic merit dairy cow prioritises nutrient supply towards milk production in early lactation and this demand takes precedence over the provision of optimal conditions for reproduction. In this study we used the bovine Affymetrix 23,000 gene microarray, which contains the most comprehensive set of bovine genes to be assembled and provides a means of investigating the modifying influences of energy balance on liver gene expression.
Cows in severe negative energy balance (SNEB) in early lactation showed altered hepatic gene expression in metabolic processes as well as a down regulation of the insulin-like growth factor (IGF) system, where insulin like growth factor-1 (IGF-1), growth hormone receptor variant 1A (GHR1A) and insulin-like growth factor binding protein-acid labile subunit (IGFBP-ALS) were down regulated compared to the cows in the moderate negative energy balance MNEB group, consistent with a five-fold reduction in systemic concentrations of IGF1 in the SNEB group.Cows in SNEB showed elevated expression of key genes involved in the inflammatory response such as interleukin-8 (IL-8). There was a down regulation of genes involved in cellular growth in SNEB cows and moreover a negative regulator of cellular proliferation (HGFIN) was up regulated in SNEB cows, which is likely to compromise adaptation and recovery from NEB.
The puma method of analysis revealed that 417 genes were differentially regulated by EB (P<0.05), of these genes 190 were up-regulated while 227 were down-regulated, with 405 genes having known biological functions. From Ingenuity Pathway Analysis (IPA), lipid catabolism was found to be the process most affected by differences in EB status
Vine and Fruit Responses to Supplementary Irrigation and Canopy Management
Drip irrigation at 0.0, 0.2 or 0.4 of weekly Class A Pan evaporation was applied to grapevines cv. Shiraz in the Barossa Valley of South Australia. Irrigation resulted in a significant increase in yield and vegetative growth but also significantly changed wine composition and wine spectral measures. Canopy management by shoot positioning and treatment with ethephon, both designed to increase fruit exposure to sunlight, resulted in significant but small changes in wine quality measures. The implications of these treatments for the improvement of wine quality from irrigated vines are discussed
Salmonella in Irish pig farms; prevalence, antibiotic resistance and molecular epidemiology
The objective was to examine the prevalence of Salmonella in manure from 30 Irish pig farms and to characterize any recovered isolates in order to assess potential risks and epidemiological relationships. Salmonella was detected in the manure from finisher pigs in 50% of the herds investigated. S. Typhimurium was the predominant serotype recovered and the most common phage types were DT104 and DT104b. Nineteen of the 29 Salmonella isolates recovered were resistant to one or more antibiotics and 15 of these (all Typhimurium) were multi-resistant
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