The growth and characterisation of zinc telluride for use as a nuclear radiation detector

As grown ZnTe is a highly conductive p-type semiconductor. In an attempt to produce highly resistive material suitable for fabrication into nuclear radiation detectors various dopants have been added during the Bridgman growth process to try to compenate the shallow acceptor defects that are responsible for the as grown electrical conductivity. Van der Pauw resistivity measurements an samples from each boule have showed that indium and aluminiun doping offers a consistant way of producing the high resistivity material. In total 12 devices were fabricated from the indium, aluminium and the one boule of high resistivity lead doped material but it was found that only one device, from an aluminium doped boule, was able to detect nuclear radiation. Further studies on this device showed that it was capable of detecting alpha-particles but not gamma-rays and also that it exhibited the normaI polarisation efect. In an attempt to correlate device performance (or lack of it) with the presence of point defects in the material all of the material was subject to studies using electrical, optical and magnetic resonance techniques. The information gathered in these ways has proven, to a great extent, to be inconclusive.TSC studies on indium doped material revealed the presence of two hole trapping levels. One defect with an activation energy of Ev +0.0geV was found to be present in all samples whereas the activation energy of the deeper defect was found to vary from sample to sample. Only one defect, with an activation energy of Ev +0. 13eV, was observed in the aluminium doped material and was suggested as being the (VznAlzn)' A centre. The concentrations of the defects found using this method give an indication why indium doped material did not act as a detector.The presence of the deep Fe+ centre has been observed using EPR. The observation of this signal has been correlated with with near infra-red luminescence common to ZnTe and observed in these samples suggesting the involvement of the Fe+ centre in the luminescence process.The signs of the shallow donor g-factors in CdS in ZnS in ZnSe and in the mixed crystal ZnS₀.₆Se₀.₄ have, for the first time, been measured directly through ODMR experiments which employ circularly polarised microwaves. In all cases the sign was measured to be positive and provides unequivical experimental conformation of the theoretical calculations carried out by Cardonna. ODMR studies on the 695 run bound exciton emission in CdS₀.₉₈Te₀.₂ indicate that this emission does indeed involve the Te pair bound exciton and is the first reported observation of such ODMR signals. These measurements serve to confirm the Te₂ bound exciton assignment to this emission by Goede et al

Annual Survey of Virginia Law: Medical Malpractice the Year in Review

In its 1989 session, the General Assembly amended several medical malpractice statutes. Perhaps the most important changes expanded the definition of health care provider under the Medical Malpractice Act (the Act ), and clarified the qualification requirements for expert witnesses

Toward a better understanding of the comparatively high prostate cancer incidence rates in Utah

BACKGROUND: This study assesses whether comparatively high prostate cancer incidence rates among white men in Utah represent higher rates among members of the Church of Jesus Christ of Latter-day Saints (LDS or Mormons), who comprise about 70% of the state's male population, and considers the potential influence screening has on these rates. METHODS: Analyses are based on 14,693 histologically confirmed invasive prostate cancer cases among men aged 50 years and older identified through the Utah Cancer Registry between 1985 and 1999. Cancer records were linked to LDS Church membership records to determine LDS status. Poisson regression was used to derive rate ratios of LDS to nonLDS prostate cancer incidence, adjusted for age, disease stage, calendar time, and incidental detection. RESULTS: LDS men had a 31% (95% confidence interval, 26% – 36%) higher incidence rate of prostate cancer than nonLDS men during the study period. Rates were consistently higher among LDS men over time (118% in 1985–88, 20% in 1989–92, 15% in 1993–1996, and 13% in 1997–99); age (13% in ages 50–59, 48% in ages 60–69, 28% in ages 70–79, and 16% in ages 80 and older); and stage (36% in local/regional and 17% in unstaged). An age- and stage-shift was observed for both LDS and nonLDS men, although more pronounced among LDS men. CONCLUSIONS: Comparatively high prostate cancer incidence rates among LDS men in Utah are explained, at least in part, by more aggressive screening among these men

Self protecting data for de-perimeterised information sharing

The emergence of high-speed networks, Grid Computing, Service-Oriented Architectures, and an ever increasing ambient connection to mobile Internet has enabled an underpinning infrastructure for the development of dynamically formed, collaborative working groups known as Virtual Organisations (VOs). VOs provide strong motivation for investigation into the infrastructure, and in particular the security necessary to protect the information and resources shared within a VO, both while resident on local machines and when allowed to move beyond the secure boundary of a local organisational network perimeter and into the realm of the distributed VO. Traditional access control systems are perimeter- centric, meaning they apply the controls to both internal and external requests for access to information within or at the perimeter of their information system. • This paper presents the initial results of the JISC funded SPIDER project, being led by Cardiff University. Through case based example, the research investigates the limitations to granularity and persistent control over information when using the perimeter- centric approach in a collaborative working environment

Cannabis and other drug use among trauma patients in three South African cities, 1999 - 2001

Objective. To assess the extent of cannabis and other drug use among patients presenting with recent  injuries at trauma units in Cape Town, Port Elizabeth and Durban from 1999 to 2001.Design. Cross-sectional surveys were conducted during a 4- week period at each of the above sites in  1999, 2000 and 2001. The concept of an idealised week was used to render representative samples.Outcome measures. Cause of injury and biological markers toassess use of cannabis, methaqualone (Mandrax), opiates, cocaine, amphetamine, and  methamphetamine.Results. Over half of all patients tested experienced violent injuries. Excluding opiates, across sites and over time between 33% and 62% of patients tested positive for at least one drug  (N = 1 565). In most cases the drugs were cannabis and/ or methaqualone. While no inter-city differences were found,male patients were typically more likely to test positive for drugs in general and specific drugs such as  cannabis and the cannabis/methaqualone ('white pipe') combination than female patients. Drug positivity was higher in 2001 than in the previous 2 years in Cape Town, and patients injured as a result of violence in Cape Town and Durban were more likely to test positive for drugs than patients with certain other types of injuries.Conclusions. Drug use among trauma patients has remained consistently high for each of the 3 study periods. Efforts to combat the abuse of drugs such as cannabis and methaqualone would appear to be paramount in reducing the burden of injuries on health care services. The study has raised numerous issues requiring further research