234 research outputs found
A Spectroscopic Survey of the Fields of 28 Strong Gravitational Lenses: Implications for
Strong gravitational lensing provides an independent measurement of the
Hubble parameter (). One remaining systematic is a bias from the
additional mass due to a galaxy group at the lens redshift or along the
sightline. We quantify this bias for more than 20 strong lenses that have
well-sampled sightline mass distributions, focusing on the convergence
and shear . In 23% of these fields, a lens group contributes a 1%
convergence bias; in 57%, there is a similarly significant line-of-sight group.
For the nine time delay lens systems, is overestimated by 11%
on average when groups are ignored. In 67% of fields with total
0.01, line-of-sight groups contribute more convergence than
do lens groups, indicating that the lens group is not the only important mass.
Lens environment affects the ratio of four (quad) to two (double) image
systems; all seven quads have lens groups while only three of 10 doubles do,
and the highest convergences due to lens groups are in quads. We calibrate the
- relation: with a rms scatter of 0.34 dex.
Shear, which, unlike convergence, can be measured directly from lensed images,
can be a poor predictor of ; for 19% of our fields, is
. Thus, accurate cosmology using strong gravitational lenses
requires precise measurement and correction for all significant structures in
each lens field.Comment: 34 pages, 11 figures, accepted for publication in Ap
Universities and community-based research in developing countries: community voice and educational provision in rural Tanzania
The main focus of recent research on the community engagement role of universities has been in developed countries, generally in towns and cities and usually conducted from the perspectives of universities rather than the communities with which they engage. The purpose of this paper is to investigate the community engagement role of universities in the rural areas of developing countries, and its potential for strengthening the voice of rural communities. The particular focus is on the provision of primary and secondary education. The paper is based on the assumption that in order for community members to have both the capacity and the confidence to engage in political discourse for improving educational capacity and quality, they need the opportunity to become involved and well-versed in the options available, beyond their own experience. Particular attention is given in the paper to community-based research (CBR). CBR is explored from the perspectives of community members and local leaders in the government-community partnerships which have responsibility for the provision of primary and secondary education in rural Tanzania. The historical and policy background of the partnerships, together with findings from two case studies, provide the context for the paper
Revisiting Frederic Engelâs hypothesis: how The Lomas determine the distribution of preceramic archaeology on Peruâs southern coast
FrĂ©dĂ©ric Engel (1981:24), el pionero de los estudios del PrecerĂĄmico en el PerĂș, argumentĂł que la distribuciĂłn de los sitios arqueolĂłgicos durante el Holoceno temprano fue determinada por âla capacidad de las lomasâ âoasis estacionales producidos por la humedad oceĂĄnica que estĂĄn presentes a lo largo de la costa del PerĂșâ una proposiciĂłn que aĂșn se encuentra en debate. Nosotros evaluaremos las ideas de Engel basĂĄndonos en datos de sitios arqueolĂłgicos del PrecerĂĄmico Medio (hasta 4500 años cal AP) ubicados dentro y cerca de las lomas de la costa sur del PerĂș.The pioneer of Preceramic archaeology in Peru, FrĂ©dĂ©ric Engel (1981: 24), argued that archaeological site distribution during the Early Holocene, was defined by the âfog oasis situationâ of lomas âthe seasonal oases sustained by ocean fogs that flourish along the arid Pacific coast of Peruâ a proposition that remains much debated. Here we reassess Engelâs ideas using archaeological findings from Middle Preceramic archaeological sites (to c. 4500 cal BP) from alongside and within the lomas of the south coast of Peru.Sociedad Argentina de AntropologĂ
Explaining Foreign Holdings of Asia's Debt Securities: The Feldstein-Horioka Paradox Revisited
Variation in the psychosocial determinants of the intention to prescribe hormone therapy prior to the release of the Women's Health Initiative trial: a survey of general practitioners and gynaecologists in France and Quebec
BACKGROUND: Theory-based approaches are advocated to improve our understanding of prescription behaviour. This study is an application of the theory of planned behaviour (TPB) with additional variables. It was designed to assess which variables were associated with the intention to prescribe hormone therapy (HT). In addition, variations in the measures across medical specialities (GPs and gynaecologists) and across countries (France and Quebec) were investigated. METHODS: A survey among 2,000 doctors from France and 1,044 doctors from Quebec was conducted. Data were collected by means of a self-administered questionnaire. A clinical vignette was used to elicit doctors' opinions. The following TPB variables were assessed: attitude, subjective norm, perceived behavioural control, attitudinal beliefs, normative beliefs and power of control beliefs. Additional variables (role belief, moral norm and practice pattern-related factors) were also assessed. A stepwise logistic regression was used to assess which variables were associated with the intention to prescribe HT. GPs and gynaecologists were compared to each other within countries and the two countries were compared within the specialties. RESULTS: Overall, 1,085 doctors from France returned their questionnaire and 516 doctors from Quebec (response rate = 54% and 49%, respectively). In the overall regression model, power of control beliefs, moral norm and role belief were significantly associated with intention (all at p < 0.0001). The models by specialty and country were: for GPs in Quebec, power of control beliefs (p < 0.0001), moral norm (p < 0.01) and cytology and hormonal dosage (both at p < 0.05); for GPs in France, power of control beliefs and role belief (both at p < 0.0001) and perception of behavioural control (p < 0.05) and cessation of menses (p < 0.01); for gynaecologists in Quebec, moral norm and power of control beliefs (both at p = 0.01); and for gynaecologists in France, power of control beliefs (p < 0.0001), and moral norm, role belief and lipid profile (all at p < 0.05). CONCLUSION: In both countries, compared with GPs, intention to prescribe HT was higher for gynaecologists. Psychosocial determinants of doctors' intention to prescribe HT varied according to the specialty and the country thus, suggesting an influence of contextual factors on these determinants
The 2.5 m Telescope of the Sloan Digital Sky Survey
We describe the design, construction, and performance of the Sloan Digital
Sky Survey Telescope located at Apache Point Observatory. The telescope is a
modified two-corrector Ritchey-Chretien design which has a 2.5-m, f/2.25
primary, a 1.08-m secondary, a Gascoigne astigmatism corrector, and one of a
pair of interchangeable highly aspheric correctors near the focal focal plane,
one for imaging and the other for spectroscopy. The final focal ratio is f/5.
The telescope is instrumented by a wide-area, multiband CCD camera and a pair
of fiber-fed double spectrographs. Novel features of the telescope include: (1)
A 3 degree diameter (0.65 m) focal plane that has excellent image quality and
small geometrical distortions over a wide wavelength range (3000 to 10,600
Angstroms) in the imaging mode, and good image quality combined with very small
lateral and longitudinal color errors in the spectroscopic mode. The unusual
requirement of very low distortion is set by the demands of
time-delay-and-integrate (TDI) imaging; (2) Very high precision motion to
support open loop TDI observations; and (3) A unique wind baffle/enclosure
construction to maximize image quality and minimize construction costs. The
telescope had first light in May 1998 and began regular survey operations in
2000.Comment: 87 pages, 27 figures. AJ (in press, April 2006
Progressive Activation of CD127+132â Recent Thymic Emigrants into Terminally Differentiated CD127â132+ T-Cells in HIV-1 Infection
AIM: HIV infection is associated with distortion of T-cell homeostasis and the IL-7/IL7R axis. Progressive infection results in loss of CD127+132- and gains in CD127-132+ CD4+ and CD8+ T-cells. We investigated the correlates of loss of CD127 from the T-cell surface to understand mechanisms underlying this homeostatic dysregulation. METHODS: Peripheral and cord blood mononuclear cells (PBMCs; CBMC) from healthy volunteers and PBMC from patients with HIV infection were studied. CD127+132-, CD127+132+ and CD127-132+ T-cells were phenotyped by activation, differentiation, proliferation and survival markers. Cellular HIV-DNA content and signal-joint T-cell receptor excision circles (sjTRECs) were measured. RESULTS: CD127+132- T-cells were enriched for naĂŻve cells while CD127-132+ T-cells were enriched for activated/terminally differentiated T-cells in CD4+ and CD8+ subsets in health and HIV infection. HIV was associated with increased proportions of activated/terminally differentiated CD127-132+ T-cells. In contrast to CD127+132- T-cells, CD127-132+ T-cells were Ki-67+Bcl-2(low) and contained increased levels of HIV-DNA. NaĂŻve CD127+132- T-cells contained a higher proportion of sjTRECs. CONCLUSION: The loss of CD127 from the T-cell surface in HIV infection is driven by activation of CD127+132- recent thymic emigrants into CD127-132+ activated/terminally differentiated cells. This process likely results in an irreversible loss of CD127 and permanent distortion of T-cell homeostasis
Landscape of somatic single nucleotide variants and indels in colorectal cancer and impact on survival
Colorectal cancer (CRC) is a biologically heterogeneous disease. To characterize its mutational profile, we conduct targeted sequencing of 205 genes for 2,105 CRC cases with survival data. Our data shows several findings in addition to enhancing the existing knowledge of CRC. We identify PRKCI, SPZ1, MUTYH, MAP2K4, FETUB, and TGFBR2 as additional genes significantly mutated in CRC. We find that among hypermutated tumors, an increased mutation burden is associated with improved CRC-specific survival (HR=0.42, 95% CI: 0.21-0.82). Mutations in TP53 are associated with poorer CRC-specific survival, which is most pronounced in cases carrying TP53 mutations with predicted 0% transcriptional activity (HR=1.53, 95% CI: 1.21-1.94). Furthermore, we observe differences in mutational frequency of several genes and pathways by tumor location, stage, and sex. Overall, this large study provides deep insights into somatic mutations in CRC, and their potential relationships with survival and tumor features. Large scale sequencing study is of paramount importance to unravel the heterogeneity of colorectal cancer. Here, the authors sequenced 205 cancer genes in more than 2000 tumours and identified additional mutated driver genes, determined that mutational burden and specific mutations in TP53 are associated with survival odds
"Don't wait for them to come to you, you go to them". A qualitative study of recruitment approaches in community based walking programmes in the UK
<p>Abstract</p> <p>Background</p> <p>This study aimed to examine the experiences of walking promotion professionals on the range and effectiveness of recruitment strategies used within community based walking programmes within the United Kingdom.</p> <p>Methods</p> <p>Two researchers recruited and conducted semi-structured interviews with managers and project co-ordinators of community based walking programmes, across the UK, using a purposive sampling frame. Twenty eight interviews were conducted, with community projects targeting participants by age, physical activity status, socio-demographic characteristics (i.e. ethnic group) or by health status. Three case studies were also conducted with programmes aiming to recruit priority groups and also demonstrating innovative recruitment methods. Data analysis adopted an approach using analytic induction.</p> <p>Results</p> <p>Two types of programmes were identified: those with explicit health aims and those without. Programme aims which required targeting of specific groups adopted more specific recruitment methods. The selection of recruitment method was dependent on the respondentâs awareness of âwhat worksâ and the resource capacity at their disposal. Word of mouth was perceived to be the most effective means of recruitment but using this approach took time and effort to build relationships with target groups, usually through a third party. Perceived effectiveness of recruitment was assessed by number of participants rather than numbers of the right participants. Some programmes, particularly those targeting younger adult participants, recruited using new social communication media. Where adopted, social marketing recruitment strategies tended to promote the âsocialâ rather than the âhealthâ benefits of walking.</p> <p>Conclusions</p> <p>Effective walking programme recruitment seems to require trained, strategic, labour intensive, word-of-mouth communication, often in partnerships, in order to understand needs and develop trust and motivation within disengaged sedentary communities. Walking promotion professionals require better training and resources to deliver appropriate recruitment strategies to reach priority groups.</p
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