25,547 research outputs found
High-resolution iron-line spectroscopy
Methods of resolving the iron lines, the most common X-ray emission lines in both galactic and extragalactic X-ray sources, are reviewed. A self-focussing crystal spectrometer is shown to be the most suitable instrument, and the optimum crystal geometry is spherical (Schnopper and Taylor 1980). The principles of operation of such a spherical crystal imaging spectrometer are examined and its sensitivity is shown to be two orders of magnitude better than a focal plane crystal spectrometer on AXAF. A Spacelab version of this payload would be very cost-effective
MULTICOLLINEARITY IN REGRESSION WITH QUADRATIC REGRESSORS
Research Methods/ Statistical Methods,
Biological Information, Causality and Specificity - an Intimate Relationship
In this chapter we examine the relationship between biological information, the key
biological concept of specificity, and recent philosophical work on causation. We begin
by showing how talk of information in the molecular biosciences grew out of efforts to
understand the sources of biological specificity. We then introduce the idea of ‘causal
specificity’ from recent work on causation in philosophy, and our own, information
theoretic measure of causal specificity. Biological specificity, we argue, is simple the
causal specificity of certain biological processes. This, we suggest, means that causal
relationships in biology are ‘informational’ relationships simply when they are highly
specific relationships. Biological information can be identified with the storage,
transmission and exercise of biological specificity. It has been argued that causal
relationships should not be regarded as informational relationship unless they are
‘arbitrary’. We argue that, whilst arbitrariness is an important feature of many causal
relationships in living systems, it should not be used in this way to delimit biological
information. Finally, we argue that biological specificity, and hence biological
information, is not confined to nucleic acids but distributed among a wide range of
entities and processes
Health systems analysis of eye care services in Zambia: evaluating progress towards VISION 2020 goals.
BACKGROUND: VISION 2020 is a global initiative launched in 1999 to eliminate avoidable blindness by 2020. The objective of this study was to undertake a situation analysis of the Zambian eye health system and assess VISION 2020 process indicators on human resources, equipment and infrastructure. METHODS: All eye health care providers were surveyed to determine location, financing sources, human resources and equipment. Key informants were interviewed regarding levels of service provision, management and leadership in the sector. Policy papers were reviewed. A health system dynamics framework was used to analyse findings. RESULTS: During 2011, 74 facilities provided eye care in Zambia; 39% were public, 37% private for-profit and 24% owned by Non-Governmental Organizations. Private facilities were solely located in major cities. A total of 191 people worked in eye care; 18 of these were ophthalmologists and eight cataract surgeons, equivalent to 0.34 and 0.15 per 250,000 population, respectively. VISION 2020 targets for inpatient beds and surgical theatres were met in six out of nine provinces, but human resources and spectacles manufacturing workshops were below target in every province. Inequalities in service provision between urban and rural areas were substantial. CONCLUSION: Shortage and maldistribution of human resources, lack of routine monitoring and inadequate financing mechanisms are the root causes of underperformance in the Zambian eye health system, which hinder the ability to achieve the VISION 2020 goals. We recommend that all VISION 2020 process indicators are evaluated simultaneously as these are not individually useful for monitoring progress
Cosmic Gravitational Shear from the HST Medium Deep Survey
We present a measurement of cosmic shear on scales ranging from 10\arcsec
to 2\arcmin in 347 WFPC2 images of random fields. Our result is based on
shapes measured via image fitting and on a simple statistical technique;
careful calibration of each step allows us to quantify our systematic
uncertainties and to measure the cosmic shear down to very small angular
scales. The WFPC2 images provide a robust measurement of the cosmic shear
signal decreasing from at 10\arcsec to at 130\arcsec .Comment: 4 pages 2 Postscript figures, uses emulateapj.cls Astrophysical
Journal Letters, December 1, 200
Conveying troublesome concepts : using an open-space learning activity to teach mixed-methods research in the health sciences
In the past decade, there has been a groundswell of interest in the use of mixed-methods approaches to conduct research in the health sciences. However, there remains a paucity of diverse teaching materials, curricula and activities to support the continued expansion of education and innovation in mixed-methods research. Here, we report the development and evaluation of an open-space learning activity and tool to aid teaching the concept of synthesis in mixed-methods research. We detail the iterations of the teaching activity and tool as they were developed, we report student feedback, and we discuss the utility of the activity and tool for introducing the concept of synthesis in mixed-methods research within health science and related fields
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