1,977 research outputs found
Parametrizing the Stellar Haloes of Galaxies
We study the stellar haloes of galaxies out to 70-100 kpc as a function of
stellar mass and galaxy type by stacking aligned and band images from a
sample of 45508 galaxies from SDSS DR9 in the redshift range
and in the mass range r. We derive surface brightness profiles to a depth of
almost . We find that the
ellipticity of the stellar halo is a function of galaxy stellar mass and that
the haloes of high concentration () galaxies are more elliptical than
those of low concentration () galaxies. The - colour profile of
high concentration galaxies reveals that the - colour of the stellar
population in the stellar halo is bluer than in the main galaxy, and the colour
of the stellar halo is redder for higher mass galaxies. We further demonstrate
that the full two-dimensional surface intensity distribution of our galaxy
stacks can only be fit through multi-component S\'{e}rsic models. Using the
fraction of light in the outer component of the models as a proxy for the
fraction of accreted stellar light, we show that this fraction is a function of
stellar mass and galaxy type. For high concentration galaxies, the fraction of
accreted stellar light rises from to for galaxies in the stellar
mass range from to . The fraction of
accreted light is much smaller in low concentration systems, increasing from
to over the same mass range. This work provides important
constraints for the theoretical understanding of the formation of stellar
haloes of galaxies.Comment: Submitted to MNRAS, 18 pages, 19 figure
Degree Distribution of Competition-Induced Preferential Attachment Graphs
We introduce a family of one-dimensional geometric growth models, constructed
iteratively by locally optimizing the tradeoffs between two competing metrics,
and show that this family is equivalent to a family of preferential attachment
random graph models with upper cutoffs. This is the first explanation of how
preferential attachment can arise from a more basic underlying mechanism of
local competition. We rigorously determine the degree distribution for the
family of random graph models, showing that it obeys a power law up to a finite
threshold and decays exponentially above this threshold.
We also rigorously analyze a generalized version of our graph process, with
two natural parameters, one corresponding to the cutoff and the other a
``fertility'' parameter. We prove that the general model has a power-law degree
distribution up to a cutoff, and establish monotonicity of the power as a
function of the two parameters. Limiting cases of the general model include the
standard preferential attachment model without cutoff and the uniform
attachment model.Comment: 24 pages, one figure. To appear in the journal: Combinatorics,
Probability and Computing. Note, this is a long version, with complete
proofs, of the paper "Competition-Induced Preferential Attachment"
(cond-mat/0402268
Use of probiotic Lactobacillus preparation to prevent diarrhoea associated with antibiotics: randomised double blind placebo controlled trial
Objective To determine the efficacy of a probiotic drink containing Lactobacillus for the prevention of any diarrhoea associated with antibiotic use and that caused by Clostridium difficile.
Design Randomised double blind placebo controlled study.
Participants 135 hospital patients (mean age 74) taking antibiotics. Exclusions included diarrhoea on admission, bowel pathology that could result in diarrhoea, antibiotic use in the previous four weeks, severe illness, immunosuppression, bowel surgery, artificial heart valves, and history of rheumatic heart disease or infective endocarditis.
Intervention Consumption of a 100 g (97 ml) drink containing Lactobacillus casei, L bulgaricus, and Streptococcus thermophilus twice a day during a course of antibiotics and for one week after the course finished. The placebo group received a longlife sterile milkshake.
Main outcome measures Primary outcome: occurrence of antibiotic associated diarrhoea. Secondary outcome: presence of C difficile toxin and diarrhoea.
Results 7/57 (12%) of the probiotic group developed diarrhoea associated with antibiotic use compared with 19/56 (34%) in the placebo group (P=0.007). Logistic regression to control for other factors gave an odds ratio 0.25 (95% confidence interval 0.07 to 0.85) for use of the probiotic, with low albumin and sodium also increasing the risk of diarrhoea. The absolute risk reduction was 21.6% (6.6% to 36.6%), and the number needed to treat was 5 (3 to 15). No one in the probiotic group and 9/53 (17%) in the placebo group had diarrhoea caused by C difficile (P=0.001). The absolute risk reduction was 17% (7% to 27%), and the number needed to treat was 6 (4 to 14).
Conclusion Consumption of a probiotic drink containing L casei, L bulgaricus, and S thermophilus reduce the incidence of antibiotic associated diarrhoea and C difficile associated diarrhoea. This has the potential to decrease morbidity, healthcare costs, and mortality if used routinely in patients aged over 50
Characteristics of young people accessing recently implemented Community Forensic Child and Adolescent Mental Health Services (F:CAMHS) in England: insights from national service activity data
Children and young people in contact with forensic child and adolescent mental health services present with more complex needs than young people in the general population. Recent policy in child and adolescent mental health has led to the
implementation of new workstreams and programmes to improve service provision. This research examines the characteristics of children and young people referred to recently commissioned Community Forensic Child and Adolescent Services
(F:CAMHS) and service activity during the frst 24 months of service. The study is a national cohort study to describe the
population and investigate service provision and access across England. Secondary data on 1311 advice cases and 1406 referrals are included in analysis. Findings show that 71.9% of the sample had accessed mainstream CAMHS before their referral,
50.9% had experienced/witnessed multiple traumatic events and 58.4% of young people presented with multiple difculties.
The results of the study highlight the complexity of the cohort and a need for interagency trauma-informed working. This is
the frst study to describe the characteristics of children and young people referred to Community F:CAMHS and provides
valuable information on pathways and needs to inform service policy and provision
Evidence-Based Practice: Knowledge, Attitude, Practice and Perceived Barriers to Practice among Nurses in Oman
OBJECTIVES: The aim of this study was to describe nurses’ practices, attitudes, knowledge/skills and
perceived barriers in relation to evidence-based practice (EBP) in Oman. METHODS: This descriptive cross-sectional
study was conducted between February and November 2012. A self-reported 24-item questionnaire was used to
measure EBP practices, attitudes and knowledge/skills among a convenience sample of 600 nurses working in four
governmental hospitals in Muscat, Oman. Responses were scored on a one to seven rating scale. Barriers to EBP
were measured on a five-point Likert scale using two subscales. Descriptive statistics and general linear regression
were used to analyse the data. RESULTS: A total of 414 nurses were included in the study. The greatest barriers to
developing EBP among nurses were insufficient time for research (3.51 ± 0.97) and insufficient resources to change
practices (3.64 ± 0.99). Nurses with more years of experience reported increased use of EBP (P <0.01), more positive
attitudes towards EBP (P <0.001) and fewer barriers to research (P <0.01). Significant positive correlations were
found between years of experience and practice (r = 0.16) and attitudes (r = 0.20). Nurses with a baccalaureate
degree reported fewer barriers to research than those qualified at a diploma level (P <0.001). Nurses who perceived
more barriers to research reported less use of EBP (P <0.001), less positive attitudes towards EBP (P <0.001)
and limited EBP knowledge/skills (P <0.001). CONCLUSION: These findings provide a basis for enhancing nursing
practices, knowledge and skills. Continuing education for nurses and minimising barriers is crucial to increasing
the use of EBP in Oma
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