Photovoltaic technologies

Photovoltaics is already a billion dollar industry. It is experiencing rapid growth as concerns over fuel supplies and carbon emissions mean that governments and individuals are increasingly prepared to ignore its current high costs. It will become truly mainstream when its costs are comparable to other energy sources. At the moment, it is around four times too expensive for competitive commercial production. Three generations of photovoltaics have been envisaged that will take solar power into the mainstream. Currently, photovoltaic production is 90% first-generation and is based on silicon wafers. These devices are reliable and durable, but half of the cost is the silicon wafer and efficiencies are limited to around 20%. A second generation of solar cells would use cheap semiconductor thin films deposited on low-cost substrates to produce devices of slightly lower efficiency. A number of thin-film device technologies account for around 5–6% of the current market. As second-generation technology reduces the cost of active material, the substrate will eventually be the cost limit and higher efficiency will be needed to maintain the cost-reduction trend. Third-generation devices will use new technologies to produce high-efficiency devices. Advances in nanotechnology, photonics, optical metamaterials, plasmonics and semiconducting polymer sciences offer the prospect of cost-competitive photovoltaics. It is reasonable to expect that cost reductions, a move to second-generation technologies and the implementation of new technologies and third-generation concepts can lead to fully cost- competitive solar energy in 10–15 years

Low-level support for socially isolated older people: An evaluation of telephone befriending

In May 2005 Help the Aged and Zurich Community Trust launched a two year national programme ‘A Call in Time’. The purpose of the programme was to provide low level support and befriending services via the telephone to older people who are lonely, isolated or vulnerable. Eight projects were funded across the country. Following the launch of the programme, Help the Aged commissioned the Centre for Health Promotion Research at Leeds Metropolitan University to undertake an evaluation of the programme and to investigate the direct impact of low level support on older people who are vulnerable, isolated or lonely using the telephone as a specific tool of befriending. The main objectives of the evaluation were to: * Measure and identify the effectiveness of telephone befriending services for older people with regards to their mental and physical well-being and their quality of life and the extent to which services were of preventive value. * Examine the components parts of each model of telephone befriending and identify ‘models of good practice’. All eight telephone befriending schemes functioning within a variety of different parameters were included in the evaluation. The participants in this research included project co-ordinators, project volunteers and older people who were in receipt of the services

The use of telephone befriending in low level support for socially isolated older people--an evaluation.

There is increasing policy recognition that the alleviation of social isolation and loneliness in older people should be prioritised. Recently, technology, such as telephone networks and the Internet, has received attention in supporting isolated and lonely older people. Despite lack of evidence, telephone befriending has been considered an effective low-level method to decrease loneliness among older people. This study evaluated the impact of a national befriending scheme for isolated and/or lonely older people, involving eight project sites across the UK 2007-2008. The purpose was to assess the impact of different models of telephone-based befriending services on older people's health and well-being. A mixed methods approach was used. This paper reports on the findings from 40 in-depth interviews with older service recipients. The most important finding was that the service helped older people to gain confidence, re-engage with the community and become socially active again. Three topics were identified: why older people valued the service, what impact it had made on their health and well-being and what they wanted from the service. In addition, nine subthemes emerged: life is worth living, gaining a sense of belonging, knowing they had a friend, a healthy mind is a healthy body, the alleviation of loneliness and anxiety, increased self-confidence, ordinary conversation, a trusted and reliable service, the future--giving something back. In conclusion, the findings present in-depth qualitative evidence of the impact of telephone befriending on older people's well-being. Befriending schemes provide low-cost means for socially isolated older people to become more confident and independent and develop a sense of self-respect potentially leading to increased participation and meaningful relationships

Clustering Time Series from Mixture Polynomial Models with Discretised Data

Clustering time series is an active research area with applications in many fields. One common feature of time series is the likely presence of outliers. These uncharacteristic data can significantly effect the quality of clusters formed. This paper evaluates a method of over-coming the detrimental effects of outliers. We describe some of the alternative approaches to clustering time series, then specify a particular class of model for experimentation with k-means clustering and a correlation based distance metric. For data derived from this class of model we demonstrate that discretising the data into a binary series of above and below the median improves the clustering when the data has outliers. More specifically, we show that firstly discretisation does not significantly effect the accuracy of the clusters when there are no outliers and secondly it significantly increases the accuracy in the presence of outliers, even when the probability of outlier is very low

IFSWF Report on Compliance with the Santiago Principles: Admirable but Flawed Transparency

Sarah Bagnall and Edwin M. Truman examine the International Forum of Sovereign Wealth Funds (IFSWF) report, which claims to be "a solid, initial step toward a better understanding of the IFSWF and of the Santiago Principles," and find this to be largely true, with a few limitations. The report, released July 7, 2011, is a self-assessment of the voluntary compliance of 21 member sovereign wealth funds (SWFs) with the Generally Accepted Principles and Practices of SWFs, issued in October 2008. Bagnall and Truman find that the extent of compliance with the Santiago Principles is somewhat exaggerated. In addition, some of the 21 funds have substantially lower rates of compliance than others, which is not reported. However, the report is frank about many of the issues that arise with respect to the interpretation of its results, for example regarding the application of the principles on investment policies and on nonfinancial restrictions on SWF investment decisions. Ultimately, presentation may obscure some results in the IFSWF report, but Bagnall and Truman find the report credible and admirable.

Helium ion microscopy and energy selective scanning electron microscopy – two advanced microscopy techniques with complementary applications

Both scanning electron microscopes (SEM) and helium ion microscopes (HeIM) are based on the same principle of a charged particle beam scanning across the surface and generating secondary electrons (SEs) to form images. However, there is a pronounced difference in the energy spectra of the emitted secondary electrons emitted as result of electron or helium ion impact. We have previously presented evidence that this also translates to differences in the information depth through the analysis of dopant contrast in doped silicon structures in both SEM and HeIM. Here, it is now shown how secondary electron emission spectra (SES) and their relation to depth of origin of SE can be experimentally exploited through the use of energy filtering (EF) in low voltage SEM (LV-SEM) to access bulk information from surfaces covered by damage or contamination layers. From the current understanding of the SES in HeIM it is not expected that EF will be as effective in HeIM but an alternative that can be used for some materials to access bulk information is presented

Self-assembled germanium islands grown on (001) silicon substrates by low-pressure chemical vapor deposition

The time evolution of self-assembled Ge islands, during low-pressure chemical vapor deposition (LPCVD) of Ge on Si at 650 Deg C using high growth rates, has been investigated by atomic force microscopy, transmission electron microscopy, and Rutherford backscattering spectrometry. We have found three different island structures The smallest islands are "lens-shaped" and characterized by a rather narrow size distribution, ~4nm high and ~20nm wide. Next to form are a distinct population of multifaceted "dome shaped" islands, up to 25nm high and 80-150 nm wide. Finally, the largest islands that form are square-based truncated pyramids with a very narrow size distribution ~50nm high and ~250nm wide. The pyramidal islands normally seen in the intermediate size range (~150nm) are not observed. The small lens-shaped islands appear to be defect free, while some of the multifaceted islands as well as all the large truncated pyramids contain misfit dislocations. The existence of multifaceted islands, in the size range where multifaceted "dome shaped" islands have previously been reported, is attributed to the high growth rate used. Furthermore, under the growth conditions used, the truncated-pyramid-shaped islands are characterized by a very narrow size distribution

Suppression of backscattered diffraction from sub-wavelength ‘moth-eye’ arrays

The eyes and wings of some species of moth are covered with arrays of nanoscale features that dramatically reduce reflection of light. There have been multiple examples where this approach has been adapted for use in antireflection and antiglare technologies with the fabrication of artificial moth-eye surfaces. In this work, the suppression of iridescence caused by the diffraction of light from such artificial regular moth-eye arrays at high angles of incidence is achieved with the use of a new tiled domain design, inspired by the arrangement of features on natural moth-eye surfaces. This bio-mimetic pillar architecture contains high optical rotational symmetry and can achieve high levels of diffraction order power reduction. For example, a tiled design fabricated in silicon and consisting of domains with 9 different orientations of the traditional hexagonal array exhibited a ~96% reduction in the intensity of the ?1 diffraction order. It is suggested natural moth-eye surfaces have evolved a tiled domain structure as it confers efficient antireflection whilst avoiding problems with high angle diffraction. This combination of antireflection and stealth properties increases chances of survival by reducing the risk of the insect being spotted by a predator. Furthermore, the tiled domain design could lead to more effective artificial moth-eye arrays for antiglare and stealth applications

A radiographic study of ossification in the spine and limbs of the human fetus

Until recently relatively little has been known about factors which affect growth and development in early life. and which have a fundamental influence on later adult life. Thus pre- and postnatal growth and development must be studied as a continuum for they have a profound effect on ultimate physical and mental development. However, legal and ethical problems governing the availability of human fetal material diminish the prospects for assembling large comprehensive surveys. Because of this, there is often inaccuracy and inconsistency in many reports of human fetal development and, in particular, the study of certain regions has been considerably neglected. Ossification of the human fetal spine and limbs is one such example. The initial purpose of the present study was an attempt to increase knowledge in an area where there appears to be substantial gaps. [Continues.