Projective toric varieties as fine moduli spaces of quiver representations

This paper proves that every projective toric variety is the fine moduli space for stable representations of an appropriate bound quiver. To accomplish this, we study the quiver $Q$ with relations $R$ corresponding to the finite-dimensional algebra $\bigl(\bigoplus_{i=0}^{r} L_i \bigr)$ where $\mathcal{L} := (\mathscr{O}_X,L_1, ...c, L_r)$ is a list of line bundles on a projective toric variety $X$. The quiver $Q$ defines a smooth projective toric variety, called the multilinear series $|\mathcal{L}|$, and a map $X \to |\mathcal{L}|$. We provide necessary and sufficient conditions for the induced map to be a closed embedding. As a consequence, we obtain a new geometric quotient construction of projective toric varieties. Under slightly stronger hypotheses on $\mathcal{L}$, the closed embedding identifies $X$ with the fine moduli space of stable representations for the bound quiver $(Q,R)$.Comment: revised version: improved exposition, corrected typos and other minor change

On Educational Performance Measures

Quantitative school performance measures (QPMs) are playing an ever larger role in education systems on both sides of the Atlantic. In this paper we outline the rationale for the use of such measures in education, review the literature relating to several important problems associated with their use, and argue that they nonetheless have a positive role to play in improving the educational quality. We delineate several institutional reforms which would help schools to respond "positively" to QPMs, emphasizing the importance of agents' flexibility to change the way they work, and the importance of a sound knowledge base regarding "what works" in raising attainment. We suggest that the present institutional setups in both England and the US too often hold schools accountable for outcomes over which they have little control – but that such problems are far from insurmountable.performance measures, education incentives, school quality

Redundancy for electric motors in spacecraft applications

The parts of electric motors which should be duplicated in order to provide maximum reliability in spacecraft application are identified. Various common types of redundancy are described. The advantages and disadvantages of each are noted. The principal types are illustrated by reference to specific examples. For each example, constructional details, basic performance data and failure modes are described, together with a discussion of the suitability of particular redundancy techniques to motor types

General Practitioners' perceptions of the route to evidence-based medicine: a questionnaire survey

Objectives: To determine the attitude of general practitioners towards evidence based medicine and their related educational needs. Design: A questionnaire study of general practitioners. Setting: General practice in the former Wessex region, England. Subjects: Randomly selected sample of 25% of all general practitioners (452), of whom 302 replied. Main outcome measures: Respondents' attitude towards evidence based medicine, ability to access and interpret evidence, perceived barriers to practising evidence based medicine, and best method of moving from opinion based to evidence based medicine. Results: Respondents mainly welcomed evidence based medicine and agreed that its practice improves patient care. They had a low level of awareness of extracting journals, review publications, and databases (only 40% knew of the Cochrane Database of Systematic Reviews), and, even if aware, many did not use them. In their surgeries 20% had access to bibliographic databases and 17% to the world wide web. Most had some understanding of the technical terms used. The major perceived barrier to practising evidence based medicine was lack of personal time. Respondents thought the most appropriate way to move towards evidence based general practice was by using evidence based guidelines or proposals developed by colleagues. Conclusion: Promoting and improving access to summaries of evidence, rather than teaching all general practitioners literature searching and critical appraisal, would be the more appropriate method of encouraging evidence based general practice. General practitioners who are skilled in accessing and interpreting evidence should be encouraged to develop local evidence based guidelines and advice

Mixed-Income Housing Developments: Promise and Reality

This paper examines the rationale for mixed-income approaches to affordable housing development, as well as the record of such developments in meeting their objectives, from the perspective of housing developers and those responsible for designing housing programs and policies. The drivers of the recent, renewed emphasis on a mixed-income housing projects are also examined and analyzed. The potential benefits this mixed-income approaches are summarized based on existing literature and interviews with key informants. Overall, this paper finds mixed-income approaches can have an important role in getting additional affordable units built, ensuring high-quality housing, and deconcentrating poverty. However, mixed-income housing is not a silver bullet to overcoming the difficult challenges faced by families seeking to escape from poverty or the realities of housing markets. Because mixed-income developments are complex, present unique risks, and often house fewer needy families than other types of development, mixed-income approaches must carefully consider the local housing market, the population to be served, financing options, the scale of the project, and the community context. This paper concludes by discussing the implications of these findings and suggests guiding questions for developers and policy makers considering mixed-income projects and policies

Attrition and Health in Ageing Studies: Evidence from ELSA and HRS

In this paper we present results of an investigation into observable characteristics associated with attrition in ELSA and the HRS, with a particular focus on whether attrition is systematically related to health outcomes and socioeconomic status (SES). Investigating the links between health and SES is one of the primary goals of the ELSA and HRS, so attrition correlated with these outcomes is a critical concern. We explored some possible reasons for these differences. Survey maturity, mobility, respondent burden, interviewer quality, and differing sampling methods all fail to account for the gap. Differential respondent incentives may play some role, but the impact of respondent incentive is difficult to test. Apparently, cultural differences between the US and Europe population in agreeing to participate and remain in scientific surveys are a more likely explanation.health, attrition

Disease Prevalence, Disease Incidence, and Mortality in the United States and in England

We find disease incidence and prevalence are both higher among Americans in age groups 55-64 and 70-80 indicating that Americans suffer from higher past cumulative disease risk and experience higher immediate risk of new disease onset compared to the English. In contrast, age specific mortality rates are similar in the two countries with an even higher risk among the English after age 65. Our second aim explains large financial gradients in mortality in the two countries. Among 55-64 year olds, we estimate similar health gradients in income and wealth in both countries, but for 70-80 year old, we find no income gradient in UK. Standard behavioral risk factors (work, marriage, obesity, exercise, and smoking) almost fully explain income gradients among 55-64 years old in both countries and a significant part among Americans 70-80 years old. The most likely explanation of no English income gradient relates to their income benefit system. Below the median, retirement benefits are largely flat and independent of past income and hence past health during the working years. Finally, we report evidence using a long panel of American respondents that their subsequent mortality is not related to large changes in wealth experienced during the prior ten year period.health

New Zealand information on the Internet: the Power to Find the Knowledge

In a world of apparently ubiquitous information, does knowledge still equal power? Whatever the answer to this question, we will not have power unless we can retrieve our knowledge. Despite the advances of the last decades, issues remain in finding information on the Web relating to Aotearoa. These include: the efficiency with which the global search engines index the NZ web space, searching for macronised words, the quality of Wikipedia information about NZ, and the availability of open access NZ research

Webometric Evaluation of Institutional Repositories

This research project investigated (a) whether there is a relationship between the Web Impact Factor (WIF) of an institutional repository, and conventional measures of research quality of the institution; and (b) whether a relatively new search engine, Blekko (http://blekko.com/) was a viable tool for webometric investigation. Blekko was used to count links made to the institutional repositories of Australasian universities. The WIF was calculated as the number of inlinks to the repository, divided by the number of documents at the repository. At the time of the research, Blekko's coverage of many of the institutional repositories was inconsistent, so only a subset of the repositories was used in the analysis, and the results are inconclusive. However there appeared to be a small correlation between the WIF of a repository and the QS World Ranking; and for Australian institutions, the WIF of a repository and the institution's ERA score

Benchmarking Google Scholar with the New Zealand PBRF Research Assessment Exercise

Google Scholar was used to generate citation counts to the web-based research output of New Zealand Universities. Total citations and hits from Google Scholar correlated with the research output as measured by the official New Zealand Performance-Based Research Fund (PBRF) exercise. The article discusses the use of Google Scholar as a cybermetric tool and methodology issues in obtaining citation counts for institutions. Google Scholar is compared with other tools that provide web citation data: Web of Science, SCOPUS, and the Wolverhampton Cybermetric Crawler