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Search Results: 1 - 10 of 2939 matches for " Joanne Hughes "
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Determining Photometric Metallicities of dSph Stellar Populations
Joanne Hughes,George Wallerstein
Physics , 2011,
Abstract: If there are so few upper red-giant branch stars in the SDSS-discovered dwarf galaxies, how can we find the true population structure without extensive spectroscopy? We review recent photometric and spectroscopic studies of the Ultra-Faint Dwarf Galaxies, and determine a new method of estimating [Fe/H] with a combination of Washington and Stromgren filters, using Bootes I dSph as an example. We can use the CT1by filters alone to achieve 0.3 dex resolution in [Fe/H], and 0.5 Gyr resolution in age. Both the Washington and Stromgren filters, C and v, are sensitive to CN-variations; however, in stars with a large deficiency of heavy elements the CN bands are weak and not important. The [Fe/H]-sensitivity of the Washington and Stromgren combination is at least twice as great as the SDSS filters, and this work maintains that resolution on the lower red-giant branch, where other calibrations fail.
Age and Metallicity Effects in Omega Centauri
Joanne Hughes,George Wallerstein
Physics , 1999,
Abstract: We have observed (with vby filters) a field north of the core of the most massive globular cluster in our galaxy, Omega Centauri. We have found a correlation of age and metallicity in a region which avoids the dense core and the inhomogeneous foreground dust emission shown by the IRAS satellite. Our observations show that the comparatively metal-rich stars (as defined by the (b-y) and m_1 colors) are younger than the metal-poor stars by at least 3 Gyr. This correlation of metallicity with age suggests that Omega Cen has enriched itself over a timescale of about 3 Gyr, and possibly longer. It is remarkable that ejecta from stellar winds combined with supernovae of type II failed to disperse the cluster's interstellar matter at an earlier epoch, but were captured by the cluster instead. Star formation would have ceased as type Ia supernovae dispersed the remaining interstellar matter. This work and other recent evidence suggests that Omega Cen could have been part of a small satellite galaxy in which all the activity occurred before it was captured by the Milky Way.
The coherence of small island sea-level with the wider ocean: a model study
Joanne Williams,Christopher W. Hughes
Ocean Science Discussions (OSD) , 2012, DOI: 10.5194/osd-9-3049-2012
Abstract: Studies comparing tide gauge measurements with sea level from nearby satellite altimetry have shown good agreement for some islands, and poor agreement for others, though no explanation has been offered. Using the 1/12° OCCAM ocean model, we investigate the relationship between sea level at small, open-ocean islands, and offshore sea level. For every such island or seamount in the model, we compare the shallow-water sea level with the steric and bottom pressure variability in a neighboring ring of deep water. We find a latitude-dependent range of frequencies for which off-shore sea level is poorly correlated with island sea level. This poor coherence occurs in a spectral region for which steric signals dominate, but are unable to propagate as baroclinic Rossby waves. This mode of decoupling does not arise because of island topography, as the same decoupling is seen between deep ocean points and surrounding rings.
The coherence of small island sea level with the wider ocean: a model study
Joanne Williams,Chris W. Hughes
Ocean Science (OS) & Discussions (OSD) , 2013, DOI: 10.5194/os-9-111-2013
Abstract: Studies comparing tide gauge measurements with sea level from nearby satellite altimetry have shown good agreement for some islands and poor agreement for others, though no explanation has been offered. Using the 1/12° OCCAM ocean model, we investigate the relationship between sea level at small, open-ocean islands and offshore sea level. For every such island or seamount in the model, we compare the shallow-water sea level with the steric and bottom pressure variability in a neighbouring ring of deep water. We find a latitude-dependent range of frequencies for which off-shore sea level is poorly correlated with island sea level. This poor coherence occurs in a spectral region for which steric signals dominate, but are unable to propagate as baroclinic Rossby waves. This mode of decoupling does not arise because of islands bathymetry, as the same decoupling is seen between deep ocean points and surrounding rings.
Photometric Observations of Omega Centauri: Multi-Wavelength Observations of Evolved Stars
Joanne Hughes,George Wallerstein,Floor van Leeuwen
Physics , 2001,
Abstract: We present multi-wavelength observations of the northern population of Omega Cen from the main-sequence turn-off to high on the red giant branch. We show that the best information about the metallicity and age of the stars can be gained from combining vby, B-I and V-I colors (in the absence of spectroscopy). We confirm our results for the main-sequence turn-off stars: there is at least a 3 Gyr age spread. We use proper motion studies to confirm cluster membership at and above the level of the horizontal branch, and we show that the age spread is maintained amongst stars from the subgiant branch through the red giants. The available evidence suggests that Omega Cen is the core of a disrupted dwarf galaxy.
The Effects of Living in Segregated vs. Mixed Areas in Northern Ireland: A Simultaneous Analysis of Contact and Threat Effects in the Context of Micro-Level Neighbourhoods
Katharina Schmid,Nicole Tausch,Miles Hewstone,Joanne Hughes
International Journal of Conflict and Violence , 2008,
Abstract: This study examines the consequences of living in segregated and mixed neighbourhoods on ingroup bias and offensive action tendencies, taking into consideration the role of intergroup experiences and perceived threat. Using adult data from a cross-sectional survey in Belfast, Northern Ireland, we tested a model that examined the relationship between living in segregated (N = 396) and mixed (N = 562) neighbourhoods and positive contact, exposure to violence, perceived threat and outgroup orientations. Our results show that living in mixed neighbourhoods was associated with lower ingroup bias and reduced offensive action tendencies. These effects were partially mediated by positive contact. However, our analysis also shows that respondents living in mixed neighbourhoods report higher exposure to political violence and higher perceived threat to physical safety. These findings demonstrate the importance of examining both social experience and threat perceptions when testing the relationship between social environment and prejudice.
A novel SNP in COMT is associated with alcohol dependence but not opiate or nicotine dependence: a case control study
Joanne Voisey, Christopher D Swagell, Ian P Hughes, Bruce R Lawford, Ross MD Young, C Morris
Behavioral and Brain Functions , 2011, DOI: 10.1186/1744-9081-7-51
Abstract: To determine whether COMT is important in substance dependence, rs165774 and rs4680 were genotyped and haplotyped in patients with nicotine, alcohol and opiate dependence.The rs165774 SNP was associated with alcohol dependence. However, it was not associated with nicotine or opiate dependence. Individuals with alcohol dependence were more than twice as likely to carry the GG or AG genotypes compared to the AA genotype, indicating a dominant mode of inheritance. The rs4680 SNP showed a weak association with alcohol dependence at the allele level that did not reach significance at the genotype level but it was not associated with nicotine or opiate dependence. Analysis of rs165774/rs4680 haplotypes also revealed association with alcohol dependence with the G/G haplotype being almost 1.5 times more common in alcohol-dependent cases.Our study provides further support for the importance of the COMT in alcohol dependence in addition to schizophrenia. It is possible that the rs165774 SNP, in combination with rs4680, results in a common molecular variant of COMT that contributes to schizophrenia and alcohol dependence susceptibility. This is potentially important for future studies of comorbidity. As our participant numbers are limited our observations should be viewed with caution until they are independently replicated.Catechol-O-methyl transferase (COMT) is an enzyme involved in the degradation of dopamine [1] and is encoded by the COMT gene. This lies in a region that has been strongly implicated in schizophrenia [2-4]. The COMT gene is located on chromosome 22q11 and association studies have identified a number of polymorphisms that are associated with schizophrenia [5-11]. One of the more interesting polymorphisms is rs4680 that encodes either valine or methionine at amino acid position 158, with the substitution shown to alter COMT enzyme activity [12]. The only other non-synonymous polymorphism in COMT that has been found to be associated with schizophrenia is rs626
Female Headship and Life History Research: Using Emotional Turning Points  [PDF]
Joanne Cliffe
Creative Education (CE) , 2016, DOI: 10.4236/ce.2016.718258
Abstract: A natural line of enquiry for women studying women’s lives is to use life history. Life history helps us to know and understand a subject’s identity. It distinguishes what people are “trying to do” and provides a framework to comprehend a person’s actions so an individual is a dynamic, rather than reflexive participant in her own life. Life history reflects the lived experience of those being researched as they construct their identity through recounting their stories and gaining a deeper understanding of themselves. This paper draws on stories recounted by female headteachers with an emphasis on the rich tapestry of their life experiences and their associated learning through positive and/or negative events. It is the outcomes of these events where the focus lies; particularly how the headteachers made effective use of emotional “turning points” in their lives. Their subsequent actions provide insight and possible contributions to future headship preparation programmes. Findings from two studies provide the data from which the paper is based. The first explored the career paths of seven female secondary school headteachers making sole use of life history interviews; the second was a through five-year longitudinal investigation of another seven secondary school female headteachers with a focus on emotional intelligence which used a range of methods, including life history interviews and psychometric tests (including emotional intelligence tests).
Passion for Beauty: A Model for Learning  [PDF]
Conrad Hughes
Creative Education (CE) , 2012, DOI: 10.4236/ce.2012.33053
Abstract: This essay investigates the idea that effective teaching entails a passion for the beauty of the subject matter being taught. The first part gives a summative overview of the last 72 years of constructivism with references to educational research and discussion on content, cognition and attitudes. This overview is set against the problem of increasing pressure on students and teachers in an age where university places are difficult to secure and students are not always motivated. The second part of the essay investigates the issue of student motivation. Forced learning will be discussed, the problems of trying to cater for student motivation through pedagogy and curriculum, and finally the idea of the muse, arguing that the most effective learning must involve some degree of passion for the subject from the teacher that the student integrates and appropriates. The conclusion of the essay considers passion for beauty as the core element of good learning and how this should be valorized openly and not seen as opposing constructivist pedagogy.
CD8+ T-Cell Interleukin-7 Receptor Alpha Expression as a Potential Indicator of Disease Status in HIV-Infected Children
Tanvi S. Sharma, Jane Hughes, Amarylis Murillo, Joanne Riley, Andreia Soares, Francesca Little, Charles D. Mitchell, Willem A. Hanekom
PLOS ONE , 2008, DOI: 10.1371/journal.pone.0003986
Abstract: Background Initiation and modification of antiretroviral therapy in HIV-infected children depend on viral load and CD4+ T-cell count. However, these surrogates have limitations, and complementary immunological markers to assess therapeutic response are needed. Our aim was to evaluate CD8+ T-cell expression of CD127 as a marker of disease status in HIV-infected children, based on adult data suggesting its usefulness. We hypothesized that CD127 expression on CD8+ T-cells is lower in children with more advanced disease. Methods In a cross-sectional evaluation, we used flow cytometry to measure CD127+ expression on CD8+ T-cells in whole blood from HIV-infected children with varying disease status. This was compared with expression of CD38 on this subset, currently used in clinical practice as a marker of disease status. Results 51 HIV-infected children were enrolled. There was a strong positive correlation between CD127 expression on CD8+ T-cells and CD4+ T-cell count, and height and weight z-scores, and a strong negative correlation between CD127 expression and viral load. In contrast, we found no association between CD38 expression and these disease status markers. Conclusions CD8+ T-cell CD127 expression is significantly higher in children with better HIV disease control, and may have a role as an immunologic indicator of disease status. Longitudinal studies are needed to determine the utility of this marker as a potential indicator of HIV disease progression.
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