Moduli spaces for Bondal quivers

Given a sufficiently nice collection of sheaves on an algebraic variety V, Bondal explained how to build a quiver Q along with an ideal of relations in the path algebra of Q such that the derived category of representations of Q subject to these relations is equivalent to the derived category of coherent sheaves on V. We consider the case in which these sheaves are all locally free and study the moduli spaces of semistable representations of our quiver with relations for various stability conditions. We show that V can often be recovered as a connected component of such a moduli space and we describe the line bundle induced by a GIT construction of the moduli space in terms of the input data. In certain special cases, we interpret our results in the language of topological string theory.Comment: 17 pages, major revisio

Reviews

Managing Change in Higher Education: A Learning Environment Architecture by Peter Ford and eight other authors, Buckingham: Society for Research into Higher Education and the Open University Press, 1996. ISBN 0–335–19791–4. 161 pages, paperback. No price indicated

Reviews

Europe In the Round CD‐ROM, Guildford, Vocational Technologies, 1994

Forum: Is Public Archaeology a menace?

So sang my friend, colleague, and then-office manager Ron Melander in about 1971, in a song he wrote about me. I quote it here to help establish my bona fides in "public archaeology." I began my career as an amateur archaeologist (some would use less complimentary terms) and am now engaged in ending it similarly. In its course I've worked as an academic and applied professional archaeologist, often -if not always- with a strong tilt toward public involvement, participated in the development of "cultural resource management" (CRM)1, worked and published in that milieu, and incidentally was involved in U.S. archaeological politics at the time when C.R. McGimsey more or less invented the term "public archaeology" (McGimsey 1972). I had qualms about the term then, and I have qualms about it now. I want to explain why

Epidemiological determinants of spread of causal agent of severe acute respiratory syndrome in Hong Kong.

BACKGROUND: Health authorities worldwide, especially in the Asia Pacific region, are seeking effective public-health interventions in the continuing epidemic of severe acute respiratory syndrome (SARS). We assessed the epidemiology of SARS in Hong Kong. METHODS: We included 1425 cases reported up to April 28, 2003. An integrated database was constructed from several sources containing information on epidemiological, demographic, and clinical variables. We estimated the key epidemiological distributions: infection to onset, onset to admission, admission to death, and admission to discharge. We measured associations between the estimated case fatality rate and patients' age and the time from onset to admission. FINDINGS: After the initial phase of exponential growth, the rate of confirmed cases fell to less than 20 per day by April 28. Public-health interventions included encouragement to report to hospital rapidly after the onset of clinical symptoms, contact tracing for confirmed and suspected cases, and quarantining, monitoring, and restricting the travel of contacts. The mean incubation period of the disease is estimated to be 6.4 days (95% CI 5.2-7.7). The mean time from onset of clinical symptoms to admission to hospital varied between 3 and 5 days, with longer times earlier in the epidemic. The estimated case fatality rate was 13.2% (9.8-16.8) for patients younger than 60 years and 43.3% (35.2-52.4) for patients aged 60 years or older assuming a parametric gamma distribution. A non-parametric method yielded estimates of 6.8% (4.0-9.6) and 55.0% (45.3-64.7), respectively. Case clusters have played an important part in the course of the epidemic. INTERPRETATION: Patients' age was strongly associated with outcome. The time between onset of symptoms and admission to hospital did not alter outcome, but shorter intervals will be important to the wider population by restricting the infectious period before patients are placed in quarantine

Stability and BPS branes

We define the concept of Pi-stability, a generalization of mu-stability of vector bundles, and argue that it characterizes N=1 supersymmetric brane configurations and BPS states in very general string theory compactifications with N=2 supersymmetry in four dimensions.Comment: harvmac, 18 p

Transmission dynamics of the etiological agent of SARS in Hong Kong: impact of public health interventions.

We present an analysis of the first 10 weeks of the severe acute respiratory syndrome (SARS) epidemic in Hong Kong. The epidemic to date has been characterized by two large clusters-initiated by two separate "super-spread" events (SSEs)-and by ongoing community transmission. By fitting a stochastic model to data on 1512 cases, including these clusters, we show that the etiological agent of SARS is moderately transmissible. Excluding SSEs, we estimate that 2.7 secondary infections were generated per case on average at the start of the epidemic, with a substantial contribution from hospital transmission. Transmission rates fell during the epidemic, primarily as a result of reductions in population contact rates and improved hospital infection control, but also because of more rapid hospital attendance by symptomatic individuals. As a result, the epidemic is now in decline, although continued vigilance is necessary for this to be maintained. Restrictions on longer range population movement are shown to be a potentially useful additional control measure in some contexts. We estimate that most currently infected persons are now hospitalized, which highlights the importance of control of nosocomial transmission

Staying informed: superintendents and their experience with evidence-based research in the West Virginia public school system

The purpose of this study was to explore the sources used by West Virginia public school superintendents to stay informed; how useful they find evidence-based research; the perceptions they have regarding the overall usefulness/credibility of evidence-based research; the barriers that exist to the use of evidence-based research; and whether there are relationships between selected demographic variables and superintendents’ consumption of evidence-based research. Data were collected using a 10-question researcher adapted survey administered to 59 superintendents in West Virginia. This study continues the work of Treadway (2015) and Hoylman (2017) in the local public education arena. The most relied upon source of information by superintendents was their own professional experience. Evidence-based research was identified as useful, to a degree, in executing professional duties, but was not identified as a frequently relied upon source of information by superintendents; paradoxically, superintendents reported using evidence-based research to inform board of education members, policymakers, members of the general public, and in public relations. For superintendents to effectively inform policymaking, they must be efficient consumers of evidence-based research, fellowship with members of professional organizations, and develop methods of succinctly communicating evidence-based research to policymakers

Chandra Observations of the Dwarf Nova WX Hyi in Quiescence

We report Chandra observations of the dwarf nova WX Hyi in quiescence. The X-ray spectrum displays strong and narrow emission lines of N, O, Mg, Ne, Si, S and Fe. The various ionization states implied by the lines suggest that the emission is produced within a flow spanning a wide temperature range, from T ~ 10^6 K to T >~ 10^8 K. Line diagnostics indicate that most of the radiation originates from a very dense region, with n ~ 10^{13}-10^{14} cm^{-3}. The Chandra data allow the first tests of specific models proposed in the literature for the X-ray emission in quiescent dwarf novae. We have computed the spectra for a set of models ranging from hot boundary layers, to hot settling flows solutions, to X-ray emitting coronae. WX Hyi differs from other dwarf novae observed at minimum in having much stronger low temperature lines, which prove difficult to fit with existing models, and possibly a very strong, broad O VII line, perhaps produced in a wind moving at a few x 10^3 km/s. The accretion rate inferred from the X-rays is lower than the value inferred from the UV. The presence of high-velocity mass ejection could account for this discrepancy while at the same time explaining the presence of the broad O VII line. If this interpretation is correct, it would provide the first detection of a wind from a dwarf nova in quiescence.Comment: accepted to ApJ; 19 pages, 3 figures, 1 tabl