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Search Results: 1 - 10 of 174723 matches for " Sarah E. Harris "
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Red giants in the outer halo of the elliptical galaxy NGC 5128 / Centaurus A
Sarah A. Bird,Chris Flynn,William E. Harris,Mauri Valtonen
Physics , 2014, DOI: 10.1051/0004-6361/201423418
Abstract: We used VIMOS on VLT to perform $V$ and $I$ band imaging of the outermost halo of NGC 5128 / Centaurus A ($(m-M)_0=27.91\pm0.08$), 65 kpc from the galaxy's center and along the major axis. The stellar population has been resolved to $I_0 \approx 27$ with a $50\%$ completeness limit of $I_0 = 24.7$, well below the tip of the red-giant branch (TRGB), which is seen at $I_0 \approx 23.9$. The surface density of NGC 5128 halo stars in our fields was sufficiently low that dim, unresolved background galaxies were a major contaminant in the source counts. We isolated a clean sample of red-giant-branch (RGB) stars extending to $\approx 0.8$ mag below the TRGB through conservative magnitude and color cuts, to remove the (predominantly blue) unresolved background galaxies. We derived stellar metallicities from colors of the stars via isochrones and measured the density falloff of the halo as a function of metallicity by combining our observations with HST imaging taken of NGC 5128 halo fields closer to the galaxy center. We found both metal-rich and metal-poor stellar populations and found that the falloff of the two follows the same de Vaucouleurs' law profiles from $\approx 8$ kpc out to $\approx$ 70 kpc. The metallicity distribution function (MDF) and the density falloff agree with the results of two recent studies of similar outermost halo fields in NGC 5128. We found no evidence of a "transition" in the radial profile of the halo, in which the metal-rich halo density would drop rapidly, leaving the underlying metal-poor halo to dominate by default out to greater radial extent, as has been seen in the outer halo of two other large galaxies. If NGC 5128 has such a transition, it must lie at larger galactocentric distances.
The Inner Halo of M87: A First Direct View of the Red-Giant Population
Sarah Bird,William E. Harris,John P. Blakeslee,Chris Flynn
Physics , 2010, DOI: 10.1051/0004-6361/201014876
Abstract: An unusually deep (V,I) imaging dataset for the Virgo supergiant M87 with the Hubble Space Telescope ACS successfully resolves its brightest red-giant stars, reaching M_I(lim) = -2.5. After assessing the photometric completeness and biasses, we use this material to estimate the metallicity distribution for the inner halo of M87, finding that the distribution is very broad and likely to peak near [m/H] ~ -0.4 and perhaps higher. The shape of the MDF strongly resembles that of the inner halo for the nearby giant E galaxy NGC 5128. As a byproduct of our study, we also obtain a preliminary measurement of the distance to M87 with the TRGB (red-giant branch tip) method; the result is (m-M)_0 = 31.12 +- 0.14 (d = 16.7 +- 0.9 Mpc). Averaging this result with three other recent techniques give a weighted mean d(M87) = (16.4 +- 0.5) Mpc.
Patient related factors in frequent readmissions: the influence of condition, access to services and patient choice
Sue E Kirby, Sarah M Dennis, Upali W Jayasinghe, Mark F Harris
BMC Health Services Research , 2010, DOI: 10.1186/1472-6963-10-216
Abstract: A retrospective analysis was performed on emergency department data collected from a regional hospital in NSW Australia in 2008. Frequently readmitted patients were defined as those with three or more admissions in a year. Clinical, service usage and demographic patient characteristics were examined for their influence on readmissions using multivariate analysis.The emergency department received about 20,000 presentations a year involving some 16,000 patients. Most patients (80%) presented only once. In 2008 one hundred and forty four patients were readmitted three or more times in a year. About 20% of all presentations resulted in an admission. Frequently readmitted patients were more likely to be older, have an urgent Triage classification, present with an unplanned returned visit and have a diagnosis of neurosis, chronic obstructive pulmonary disease, dyspnoea or chronic heart failure. The chronic ambulatory care sensitive conditions were strongly associated with frequent readmissions. Frequent readmissions were unrelated to gender, time, day or season of presentation or country of birth.Multivariate analysis of routinely collected hospital data identified that the factors associated with frequent readmission include the type of condition, urgency, unplanned return visit and age. Interventions to improve patient uptake of chronic disease management services and improving the availability of alternative non-hospital services should reduce the readmission rate in chronic disease patients.Emergency departments aim to provide treatment for more urgent and serious conditions. In Australia, the role of emergency departments has been specified as "prevention, diagnosis and management of acute and urgent aspects of illness and injury affecting patients of all age groups with a full spectrum of undifferentiated physical and behavioural disorders"[1]. However, many people who access emergency departments have complex social needs as well as a clinical condition requiring t
Prolonged Low Flow Reduces Reactive Hyperemia and Augments Low Flow Mediated Constriction in the Brachial Artery Independent of the Menstrual Cycle
Mark Rakobowchuk, Emily R. Parsloe, Sarah E. Gibbins, Emma Harris, Karen M. Birch
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0055385
Abstract: Non-invasive forearm ischemia-reperfusion injury and low flow induced vascular dysfunction models provide methods to evaluate vascular function. The role of oestrogen, an endogenous anti-oxidant on recovery from ischemia-reperfusion injury has not been evaluated nor has the impact of prolonged low flow on vascular function been established. Eight healthy women (33±10 yr) attended the lab during the follicular, ovulatory and mid-luteal phases of their menstrual cycles. After 30 minutes of rest, brachial artery vascular function was assessed by ultrasound measurements of diameter changes during 5 minutes of forearm ischemia and 3 minutes after. Subsequently, a 20-minute forearm ischemia period was completed. Further, vascular function assessments were completed 15, 30 and 45 minutes into recovery. Flow-mediated dilation, low-flow-mediated constriction, and reactive hyperaemia proximal to the area of ischemia were determined. Flow-mediated dilation was reduced at 15 minutes of recovery but recovered at 30 and 45 minutes (PRE: 7.1±1.0%, POST15:4.5±0.6%, POST30:5. 5±0.7% POST45:5.9±0.4%, p<0.01). Conversely, low-flow mediated constriction increased (PRE: ?1.3±0.4%, POST15: ?3.3±0.6%, POST30: ?2.5±0.5% POST45: ?1.5±0.12%, p<0.01). Reactive hyperaemia was reduced throughout recovery (p<0.05). Data were unaffected by menstrual phase. Prolonged low flow altered vascular function and may relate as much to increased vasoconstriction as with decreased vasodilation. Reductions in anterograde shear and greater retrograde shear likely modulate the brachial artery response, but the reduced total shear also plays an important role. The data suggest substantial alterations in vascular function proximal to areas of ischemia with potential clinical implications following reperfusion.
The Distribution of Returns  [PDF]
David E. Harris
Journal of Mathematical Finance (JMF) , 2017, DOI: 10.4236/jmf.2017.73041
Abstract: The distribution of the returns on investment depends on the rules in the economic system. The article reviews various return distributions, ranging from equity securities in equilibrium, to antiques bought at auction, to debt instruments with uncertain payouts. A general methodology is provided to construct distributions of returns.
Alzheimer's Disease Genes Are Associated with Measures of Cognitive Ageing in the Lothian Birth Cohorts of 1921 and 1936
Gillian Hamilton,Sarah E. Harris,Gail Davies,David C. Liewald,Albert Tenesa,John M. Starr,David Porteous,Ian J. Deary
International Journal of Alzheimer's Disease , 2011, DOI: 10.4061/2011/505984
Abstract: Alzheimer's disease patients have deficits in specific cognitive domains, and susceptibility genes for this disease may influence human cognition in nondemented individuals. To evaluate the role of Alzheimer's disease-linked genetic variation on cognition and normal cognitive ageing, we investigated two Scottish cohorts for which assessments in major cognitive domains are available: the Lothian Birth Cohort of 1921 and the Lothian Birth Cohort of 1936, consisting of 505 and 998 individuals, respectively. 158 SNPs from eleven genes were evaluated. Single SNP analyses did not reveal any statistical association after correction for multiple testing. One haplotype from TRAPPC6A was associated with nonverbal reasoning in both cohorts and combined data sets. This haplotype explains a small proportion of the phenotypic variability (1.8%). These findings warrant further investigation as biological modifiers of cognitive ageing. 1. Introduction Alzheimer’s disease (AD) is the most common neurodegenerative disease, and it is predicted to affect over a million people in the UK by 2025 (Dementia UK 2007 report). AD is characterised initially by impaired episodic memory [1] and, as the disease progresses, other cognitive deficits appear, particularly in attention and executive functions, semantic memory, language, and spatial orientation [2, 3]. AD is a genetically heterogeneous disease. Mutations in three genes (the amyloid precursor protein, APP; presenilin 1, PS1; presenilin 2, PS2) are known to cause a rare early-onset form of AD [4–6]. The most common form of AD occurs sporadically and with a late age at onset. Until recently, the only well-replicated risk factor for this form of AD was the ε4 allele of the apolipoprotein E (APOE) gene [7]. However, three recent genome-wide association studies (GWASs) have identified four new candidate genes for sporadic AD—BIN1, CLU, CR1, and PICALM—and one new genomic region near BLOC1S3/EXOC3L2/MARK4 [8–10]. Associations with CLU, CR1, and PICALM have been replicated [11–13]. Nonpathological age-related cognitive decline is a major and growing concern in developed societies [14]. General cognitive ability is an important predictor of life outcomes, including in old age. The determinants of normal cognitive ageing are not fully understood, but are likely to include both genetic and environmental influences [14]. Genetic influences on cognitive ability increase from about 30% in childhood to as much as 80% in later adulthood, and these decrease slightly in very old-age when, probably, stochastic effects become relatively more
Human Intelligence and Polymorphisms in the DNA Methyltransferase Genes Involved in Epigenetic Marking
Paul Haggarty,Gwen Hoad,Sarah E. Harris,John M. Starr,Helen C. Fox,Ian J. Deary,Lawrence J. Whalley
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0011329
Abstract: Epigenetic mechanisms have been implicated in syndromes associated with mental impairment but little is known about the role of epigenetics in determining the normal variation in human intelligence. We measured polymorphisms in four DNA methyltransferases (DNMT1, DNMT3A, DNMT3B and DNMT3L) involved in epigenetic marking and related these to childhood and adult general intelligence in a population (n = 1542) consisting of two Scottish cohorts born in 1936 and residing in Lothian (n = 1075) or Aberdeen (n = 467). All subjects had taken the same test of intelligence at age 11yrs. The Lothian cohort took the test again at age 70yrs. The minor T allele of DNMT3L SNP 11330C>T (rs7354779) allele was associated with a higher standardised childhood intelligence score; greatest effect in the dominant analysis but also significant in the additive model (coefficient = 1.40additive; 95%CI 0.22,2.59; p = 0.020 and 1.99dominant; 95%CI 0.55,3.43; p = 0.007). The DNMT3L C allele was associated with an increased risk of being below average intelligence (OR 1.25additive; 95%CI 1.05,1.51; p = 0.011 and OR 1.37dominant; 95%CI 1.11,1.68; p = 0.003), and being in the lowest 40th (padditive = 0.009; pdominant = 0.002) and lowest 30th (padditive = 0.004; pdominant = 0.002) centiles for intelligence. After Bonferroni correction for the number variants tested the link between DNMT3L 11330C>T and childhood intelligence remained significant by linear regression and centile analysis; only the additive regression model was borderline significant. Adult intelligence was similarly linked to the DNMT3L variant but this analysis was limited by the numbers studied and nature of the test and the association was not significant after Bonferroni correction. We believe that the role of epigenetics in the normal variation in human intelligence merits further study and that this novel finding should be tested in other cohorts.
A genetic association analysis of cognitive ability and cognitive ageing using 325 markers for 109 genes associated with oxidative stress or cognition
Sarah E Harris, Helen Fox, Alan F Wright, Caroline Hayward, John M Starr, Lawrence J Whalley, Ian J Deary
BMC Genetics , 2007, DOI: 10.1186/1471-2156-8-43
Abstract: Associations between cognitive ageing and 325 single nucleotide polymorphisms (SNPs), located in 109 genes implicated in oxidative stress and/or cognition, were examined in a unique cohort of relatively healthy older people, on whom we have cognitive ability scores at ages 11 and 79 years (LBC1921). SNPs showing a significant positive association were then genotyped in a second cohort for whom we have cognitive ability scores at the ages of 11 and 64 years (ABC1936). An intronic SNP in the APP gene (rs2830102) was significantly associated with cognitive ageing in both LBC1921 and a combined LBC1921/ABC1936 analysis (p < 0.01), but not in ABC1936 alone.This study suggests a possible role for APP in normal cognitive ageing, in addition to its role in Alzheimer's disease.Individuals differ in their cognitive skills, and in how much these cognitive skills change as people grow older. That is, there are individual differences in the trait (or level) of intelligence, and in the age-related change (or trajectory). We have previously shown that about 50% of the variance in trait intelligence is stable from the age of 11 to the age of 79[1]. In both the trait and the age-related change, the majority of the between-individual variation is accounted for by a common factor of general cognitive ability (or g)[2,3]. Both mild intellectual impairment (low trait intelligence) and accelerated age-related cognitive decline (increased downward trajectory in intelligence) have a major impact on society, because of the large number of individuals involved who have limited independence. In our increasingly 'ageing society', disabilities linked to cognitive ageing are a growing medical and social problem.There are environmental and genetic contributions to individual differences in trait intelligence and cognitive ageing[4,5]. Genetic influences account for more than 50% of the variability in adult cognitive abilities[6]. We have shown that genetic variation in some specific genes, e.g. A
Horizontally Acquired Glycosyltransferase Operons Drive Salmonellae Lipopolysaccharide Diversity
Mark R. Davies,Sarah E. Broadbent,Simon R. Harris,Nicholas R. Thomson,Marjan W. van der Woude
PLOS Genetics , 2013, DOI: 10.1371/journal.pgen.1003568
Abstract: The immunodominant lipopolysaccharide is a key antigenic factor for Gram-negative pathogens such as salmonellae where it plays key roles in host adaptation, virulence, immune evasion, and persistence. Variation in the lipopolysaccharide is also the major differentiating factor that is used to classify Salmonella into over 2600 serovars as part of the Kaufmann-White scheme. While lipopolysaccharide diversity is generally associated with sequence variation in the lipopolysaccharide biosynthesis operon, extraneous genetic factors such as those encoded by the glucosyltransferase (gtr) operons provide further structural heterogeneity by adding additional sugars onto the O-antigen component of the lipopolysaccharide. Here we identify and examine the O-antigen modifying glucosyltransferase genes from the genomes of Salmonella enterica and Salmonella bongori serovars. We show that Salmonella generally carries between 1 and 4 gtr operons that we have classified into 10 families on the basis of gtrC sequence with apparent O-antigen modification detected for five of these families. The gtr operons localize to bacteriophage-associated genomic regions and exhibit a dynamic evolutionary history driven by recombination and gene shuffling events leading to new gene combinations. Furthermore, evidence of Dam- and OxyR-dependent phase variation of gtr gene expression was identified within eight gtr families. Thus, as O-antigen modification generates significant intra- and inter-strain phenotypic diversity, gtr-mediated modification is fundamental in assessing Salmonella strain variability. This will inform appropriate vaccine and diagnostic approaches, in addition to contributing to our understanding of host-pathogen interactions.
Curating Knowledge and Curating Fun: An Analysis of the Expanding Roles of Children’s Museums  [PDF]
Sarah C. Harris, Flávio S. Azevedo, Anthony J. Petrosino
Creative Education (CE) , 2018, DOI: 10.4236/ce.2018.912138
Abstract: Museums constantly undergo shifts and changes in the roles and functions they serve in society. We report on the expanding roles of a children’s STEAM museum through a case study of two adult-only, fundraising events that the museum implemented. Drawing on both qualitative and quantitative measures, our analysis pursues two complementary threads. First, we seek to characterize those events in detail so that we might understand the events’ culture and functioning. Second, we look into the population who frequents the events, focusing specifically on various indicators of socio-economic status. By bringing these analytical threads together, we corroborate the finding that museums are expanding into?curating fun?experiences that are highly tailored to certain segments of the adult public. Importantly, attending to the empirical details of such processes, we further find that the observed changes1) directly impact the job demands and require?skills of children’s museum staff, 2) reify?the museum as an important economic agent in the community, and 3) potentially reproduce patterns of inequitable access to STEAM cultural capital, among others.
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