279 research outputs found
Qualitative data analysis in cross-cultural projects
Large-scale research projects, conducted in a cross-European context, are increasingly attractive to educational researchers and policy-makers. However, this form of comparative research across cultures brings problems concerning the standardization of data collection and analysis, particularly where ethnographic research is concerned, as it prioritizes a full range of qualitative research strategies. This paper outlines the use of a universal model and the approaches recently taken by two research teams and contrasts these with another recent nine-partner comparative European study that used ethnographic methods. We then describe the analytical procedures used in the project, which encouraged participant observation and individual researcher interpretation in order to generate grounded accounts and outline how they were culturally sensitive and meaningful to research teams who used varied analytical approaches. However, this raised difficult issues for the 'final' analysis and the production of a loosely coupled research report. Our pragmatic solution was a process of 'qualitative synthesis' whereby individual partner reports were collated by the Project Director and treated as data and a grounded theory approach was applied to generate tentative theory in respect of creative learning. The paper concludes by arguing that data generated by a loosely coupled approach to qualitative comparative research which uses a wide range of data collection methods can be effectively analysed with a qualitative synthesis
Dual Purpose Lyot Coronagraph Masks for Simultaneous High-Contrast Imaging and High-Resolution Wavefront Sensing
Directly imaging Earth-sized exoplanets with a visible-light coronagraph
instrument on a space telescope will require a system that can achieve
raw contrast and maintain it for the duration of observations
(on the order of hours or more). We are designing, manufacturing, and testing
Dual Purpose Lyot coronagraph (DPLC) masks that allow for simultaneous
wavefront sensing and control using out-of-band light to maintain high contrast
in the science focal plane. Our initial design uses a tiered metallic focal
plane occulter to suppress starlight in the transmitted coronagraph channel and
a dichroic-coated substrate to reflect out-of-band light to a wavefront sensing
camera. The occulter design introduces a phase shift such that the reflected
channel is a Zernike wavefront sensor. The dichroic coating allows higher-order
wavefront errors to be detected which is especially critical for compensating
for residual drifts from an actively-controlled segmented primary mirror. A
second-generation design concept includes a metasurface to create
polarization-dependent phase shifts in the reflected beam, which has several
advantages including an extended dynamic range. We will present the focal plane
mask designs, characterization, and initial testing at NASA's High Contrast
Imaging Testbed (HCIT) facility.Comment: To appear in the Proceedings of the SPIE, Techniques and
Instrumentation for Detection of Exoplanets X
Learning to Teach About Ideas and Evidence in Science : The Student Teacher as Change Agent
A collaborative curriculum development project was set up to address the lack of good examples of teaching about ideas and evidence and the nature of science encountered by student teachers training to teach in the age range 11-16 in schools in England. Student and teacher-mentor pairs devised, taught and evaluated novel lessons and approaches. The project design required increasing levels of critique through cycles of teaching, evaluation and revision of lessons. Data were gathered from interviews and students' reports to assess the impact of the project on student teachers and to what extent any influences survived when they gained their first teaching posts. A significant outcome was the perception of teaching shifting from the delivery of standard lessons in prescribed ways to endeavours demanding creativity and decision-making. Although school-based factors limited newly qualified teachers' chances to use new lessons and approaches and therefore act as change-agents in schools, the ability to critique curriculum materials and the recognition of the need to create space for professional dialogue were durable gains
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HIV Treatment as Prevention: Systematic Comparison of Mathematical Models of the Potential Impact of Antiretroviral Therapy on HIV Incidence in South Africa
Background: Many mathematical models have investigated the impact of expanding access to antiretroviral therapy (ART) on new HIV infections. Comparing results and conclusions across models is challenging because models have addressed slightly different questions and have reported different outcome metrics. This study compares the predictions of several mathematical models simulating the same ART intervention programmes to determine the extent to which models agree about the epidemiological impact of expanded ART. Methods and Findings: Twelve independent mathematical models evaluated a set of standardised ART intervention scenarios in South Africa and reported a common set of outputs. Intervention scenarios systematically varied the CD4 count threshold for treatment eligibility, access to treatment, and programme retention. For a scenario in which 80% of HIV-infected individuals start treatment on average 1 y after their CD4 count drops below 350 cells/”l and 85% remain on treatment after 3 y, the models projected that HIV incidence would be 35% to 54% lower 8 y after the introduction of ART, compared to a counterfactual scenario in which there is no ART. More variation existed in the estimated long-term (38 y) reductions in incidence. The impact of optimistic interventions including immediate ART initiation varied widely across models, maintaining substantial uncertainty about the theoretical prospect for elimination of HIV from the population using ART alone over the next four decades. The number of person-years of ART per infection averted over 8 y ranged between 5.8 and 18.7. Considering the actual scale-up of ART in South Africa, seven models estimated that current HIV incidence is 17% to 32% lower than it would have been in the absence of ART. Differences between model assumptions about CD4 decline and HIV transmissibility over the course of infection explained only a modest amount of the variation in model results. Conclusions: Mathematical models evaluating the impact of ART vary substantially in structure, complexity, and parameter choices, but all suggest that ART, at high levels of access and with high adherence, has the potential to substantially reduce new HIV infections. There was broad agreement regarding the short-term epidemiologic impact of ambitious treatment scale-up, but more variation in longer term projections and in the efficiency with which treatment can reduce new infections. Differences between model predictions could not be explained by differences in model structure or parameterization that were hypothesized to affect intervention impact
Pitfalls of Practicing Cancer Epidemiology in Resource-limited Settings: the Case of Survival and Loss to Follow-up after a Diagnosis of Kaposiâs Sarcoma in Five Countries across Sub-Saharan Africa
Background: Survival after diagnosis is a fundamental concern in cancer epidemiology. In resource-rich settings, ambient clinical databases, municipal data and cancer registries make survival estimation in real-world populations relatively straightforward. In resource-poor settings, given the deficiencies in a variety of health-related data systems, it is less clear how well we can determine cancer survival from ambient data.
Methods: We addressed this issue in sub-Saharan Africa for Kaposiâs sarcoma (KS), a cancer for which incidence has exploded with the HIV epidemic but for which survival in the region may be changing with the recent advent of antiretroviral therapy (ART). From 33 primary care HIV Clinics in Kenya, Uganda, Malawi, Nigeria and Cameroon participating in the International Epidemiologic Databases to Evaluate AIDS (IeDEA) Consortia in 2009â2012, we identified 1328 adults with newly diagnosed KS. Patients were evaluated from KS diagnosis until death, transfer to another facility or database closure.
Results: Nominally, 22 % of patients were estimated to be dead by 2 years, but this estimate was clouded by 45 % cumulative lost to follow-up with unknown vital status by 2 years. After adjustment for site and CD4 count, agelost.
Conclusions: In this community-based sample of patients diagnosed with KS in sub-Saharan Africa, almost half became lost to follow-up by 2 years. This precluded accurate estimation of survival. Until we either generally strengthen data systems or implement cancer-specific enhancements (e.g., tracking of the lost) in the region, insights from cancer epidemiology will be limited
LOFAR 150-MHz observations of SS 433 and W50
We present Low-Frequency Array (LOFAR) high-band data over the frequency range 115-189 MHz for the X-ray binary SS 433, obtained in an observing campaign from 2013 February to 2014 May. Our results include a deep, wide-field map, allowing a detailed view of the surrounding supernova remnant W50 at low radio frequencies, as well as a light curve for SS 433 determined from shorter monitoring runs. The complex morphology of W50 is in excellent agreement with previously published higher frequency maps; we find additional evidence for a spectral turnover in the eastern wing, potentially due to foreground free-free absorption. Furthermore, SS 433 is tentatively variable at 150 MHz, with both a debiased modulation index of 11 per cent and a ç 2 probability of a flat light curve of 8.2 Ăâ 10 -3 . By comparing the LOFAR flux densities with contemporaneous observations carried out at 4800 MHz with the RATAN-600 telescope, we suggest that an observed ~0.5-1 Jy rise in the 150-MHz flux density may correspond to sustained flaring activity over a period of approximately 6 months at 4800 MHz. However, the increase is too large to be explained with a standard synchrotron bubble model. We also detect a wealth of structure along the nearby Galactic plane, including the most complete detection to date of the radio shell of the candidate supernova remnant G38.7-1.4. This further demonstrates the potential of supernova remnant studies with the current generation of low-frequency radio telescopes
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