Philip Davies

What is Evidence-based Education?

This paper argues that education should become more evidence-based. The distinction is made between using existing research and establishing high-quality educational research. The need for high-quality systematic reviews and appraisals of educational research is clear. Evidence-based education is not a panacea, but is a set of principles and practices for enhancing educational policy and practice.

Communication disorders: Planning a service to meet the needs

This paper reviews the size of the speech and language-disabled population in the United Kingdom by client groups and attempts to determine (1) those for whom speech therapy might be appropriate, (2) what pattern and level of speech therapy is appropriate and (3) how many speech therapists are required to provide this pattern and level of speech therapy. It is concluded that under present patterns of speech therapy provision, approximately 26 qualified speech therapists may be required per 100,000 population. However, it is argued that speech therapy may be trying to do too much and may be venturing into areas in which little, if anything, is known about its effectiveness. In conclusion, the paper argues that solutions to the current problems of speech therapy provision must come from the demand and the supply sides of the speech therapy service. The importance of treatment evaluation and further knowledge about patterns of spontaneous recovery are also discussed.

Complementary methods to investigate the development of clogging within a horizontal sub-surface flow tertiary treatment wetland.

A combination of experimental methods was applied at a clogged, horizontal subsurface flow (HSSF) municipal wastewater tertiary treatment wetland (TW) in the UK, to quantify the extent of surface and subsurface clogging which had resulted in undesirable surface flow. The three dimensional hydraulic conductivity profile was determined, using a purpose made device which recreates the constant head permeameter test in-situ. The hydrodynamic pathways were investigated by performing dye tracing tests with Rhodamine WT and a novel multi-channel, data-logging, flow through Fluorimeter which allows synchronous measurements to be taken from a matrix of sampling points. Hydraulic conductivity varied in all planes, with the lowest measurement of 0.1md(-1) corresponding to the surface layer at the inlet, and the maximum measurement of 1550md(-1) located at a 0.4m depth at the outlet. According to dye tracing results, the region where the overland flow ceased received five times the average flow, which then vertically short-circuited below the rhizosphere. The tracer break-through curve obtained from the outlet showed that this preferential flow-path accounted for approximately 80% of the flow overall and arrived 8h before a distinctly separate secondary flow-path. The overall volumetric efficiency of the clogged system was 71% and the hydrology was simulated using a dual-path, dead-zone storage model. It is concluded that uneven inlet distribution, continuous surface loading and high rhizosphere resistance is responsible for the clog formation observed in this system. The average inlet hydraulic conductivity was 2md(-1), suggesting that current European design guidelines, which predict that the system will reach an equilibrium hydraulic conductivity of 86md(-1), do not adequately describe the hydrology of mature systems.

Approaches to evidence-based teaching

It is timely that such a distinguished group as the Association for Medical Education in Europe should be holding a major international conference on `A Critical Appraisal of Medical Education’ , given the broad and growing interest throughout the world in evidence-based medicine (EBM), evidence-based health care (EBHC) and evidencebased policy and practice (EBPP). A recent meeting in London, England brought together educationalists, health care researchers and social scientists from the United States and Europe to discuss the development of an international collaboration on systematic reviews of the effects of social and educational interventions (Davies et al., 1999). One consequence of that meeting was the formation of the Campbell Collaboration, which will establish an electronic database of systematic reviews of the effects of social and education interventions, in a similar way to the high quality reviews of health care interventions that are provided by the Cochrane Collaboration. There are also initiatives in the United Kingdom, and in other countries, to establish centres of evidencebased policy and practice in education, and to improve the accessibility to teachers, students and educational policy makers of the best evidence of teaching and learning effectiveness. A critical approach to medical education is not new. Even a cursory search of databases such as MEDLINE and ERIC, or a casual perusal of journals such as Medical Education,Medical Teacher and Academic Medicine, indicates at least two decades of debate about the most effective ways of teaching medica l underg raduates, and of organising the professional development of doctors and other health care personnel. Some of this literature reports on controlled evaluations of different teaching methods and curricula arrangements. Other papers and articles in this literature report on less controlled trials, or on descriptive studies, or are more theoretical discussions of the principles, objectives and methods of medical education. Medical and other health care education inevitably involves teaching and learning by adults. Consequently, it is important that it uses teaching methods that are appropriate for adult learners, that understand the learning needs of adults, and that are based on the best empirical evidence of the most effective ways of teaching adults. This paper will review some of the main principles of adult learning, will present some of the ways in which these principles have been put into practice in medical and health care education, and will consider the available evidence on the effectiveness of different teaching methods and curricula arrangements in medical education. Principles of adult learning

Solar thermophotovoltaics: brief review and a new look

Abstract Solar thermophotovoltaics (STPV) should theoretically give very high conversion efficiencies but there are technical drawbacks and, consequently, there have been few if any practical demonstrations. Some articles on STPV are reviewed with the aim of pointing out the main design concepts. Although generally the receiver is a cavity relying on extremely high solar concentration at its mouth, such high concentration is not fundamentally necessary, rather a correctly chosen ratio of etendue subtended between the radiator and solar cell to that subtended between the radiator and the sun. For an ideal system, the efficiency limit is the same as that for a sun-driven Carnot engine. For real cells, the improvement given by a STPV over direct conversion is mainly a result of the current enhancement. We introduce a concept of bypass, so radiation just above the bandgap energy goes straight to the cell, and show that for silicon cells, the performance is potentially better than for normal STPV. The authors hope to stimulate fresh thought about STPV.

A comparative assessment of waste incinerators in the UK

The uptake in Europe of Energy from Waste (EfW) incinerator plants has increased rapidly in recent years. In the UK, 25 municipal waste incinerators with energy recovery are now in operation; however, their waste supply chains and business practices vary significantly. With over a hundred more plant developments being considered it is important to establish best business practices for ensuring efficient environmental and operational performance. By reviewing the 25 plants we identify four suitable case study plants to compare technologies (moving grate, fluidised bed and rotary kiln), plant economics and operations. Using data collected from annual reports and through interviews and site visits we provide recommendations for improving the supply chain for waste incinerators and highlight the current issues and challenges faced by the industry. We find that plants using moving grate have a high availability of 87-92%. However, compared to the fluidised bed and rotary kiln, quantities of bottom ash and emissions of hydrogen chloride and carbon monoxide are high. The uptake of integrated recycling practices, combined heat and power, and post incineration non-ferrous metal collections needs to be increased among EfW incinerators in the UK. We conclude that one of the major difficulties encountered by waste facilities is the appropriate selection of technology, capacity, site, waste suppliers and heat consumers. This study will be of particular value to EfW plant developers, government authorities and researchers working within the sector of waste management.

Sun-tracking mechanism using equatorial and ecliptic axes

Abstract The question of how to construct a sun-tracking structure for concentration photovoltaics is addressed. A new concept that uses, in addition to the familiar equatorial axis, a second axis perpendicular to the ecliptic plane, is proposed. With the approximation that the earths orbit is circular, the required motion about both these axes is of constant velocity. However, the eccentricity of the earths orbit introduces a tracking error of ±2° whose correction would require a small variation in the velocity of rotation about the ecliptic axis throughout the year. The foreseen advantage of the proposed system is the ease of control.

Edge-ray principle of nonimaging optics

Some form of the edge-ray principle is used to design most nonimaging systems. (Only systems based on geometrical optics are considered.) For proving certain statements of this principle, the optical system is considered to be surrounded by an enclosure that any ray emerging from the system must intersect. A phase space, of topology Sphere × Disk, corresponding to the intersection of rays with the enclosure is introduced, and the system gives rise to a mapping f among points of this space. The proofs hold only if f is continuous, which is not the case for all real systems. Discontinuities in f may be caused by (1) tangential incidence of a ray with a surface, (2) incidence where the radius of curvature of a surface is zero, (3) transition from refraction to total internal reflection, and (4) intersection of different types of optical surface. Although the condition of the continuity of f is used in the proofs, even among systems in which continuity is absent it is difficult in practice to find counterexamples to the edge-ray principle formulated.

Remedial therapy and functional recovery in a total population of first-stroke patients.

A consecutive series of 155 patients with a first-ever stroke and who were registered with the Oxfordshire Community Stroke Project (OCSP) were followed up. Their receipt of remedial therapy was recorded and their functional recovery was measured using the Barthel index of activities of daily living. Only a minority of patients received remedial therapy during the first 6 months after stroke. Those who were admitted to hospital during the first month following their stroke, or who were severely dependent, were significantly more likely to receive remedial therapy than those who remained in the community or were less dependent. A comparison of functional recovery amongst a matched subsample of patients who received remedial therapy and those who did not showed that there was comparable recovery amongst patients who did not receive remedial therapy.

DesaLink:solar powered desalination of brackish groundwater giving high output and high recovery

Desalination of groundwater is essential in many arid areas that are far from both seawater and fresh water resources. The ideal groundwater desalination system should operate using a sustainable energy source and provide high water output per land area and cost. To avoid discharging voluminous brine, it should also provide high recovery. To achieve these aims, we have designed DesaLink, a novel approach to linking the solar Rankine cycle to reverse osmosis (RO). To achieve high recovery without the need for multiple RO stages, DesaLink adopts a batch mode of operation. It is suited to use with a variety of solar thermal collectors including linear Fresnel reflectors (LFR). For example, using a LFR occupying 1,000m of land and providing steam at 200°C and 15.5 bar, DesaLink is predicted to provide 350m of fresh water per day at a recovery ratio of 0.7, when fed with brackish groundwater containing 5,000ppm of sodium chloride. Here, we report preliminary experiments to assess the feasibility of the concept. We study the effects of longitudinal dispersion, concentration polarisation and describe a pilot experiment to demonstrate the batch process using a materials testing machine. In addition, we demonstrate a prototype of DesaLink running from compressed air to simulate steam.