Ruthenium/Iridium Ratios in the Cretaceous-tertiary Boundary Clay: Implications for Global Dispersal and Fractionation Within the Ejecta Cloud

Ruthenium (Ru) and iridium (Ir) are the least mobile platinum group elements (PGE's) within the Cretaceous-Tertiary (K-T) boundary clay (BC). The Ru/Ir ratio is, therefore, the most useful PGE interelement ratio for distinguishing terrestrial and extraterrestrial contributions to the BC. The Ru/Ir ratio of marine K-T sections (1.77 +/- 0.53) is statistically different from that of the continental sections (0.93 +/- 0.28). The marine Ru/Ir ratios are chondritic (C1 = 1.48 +/- 0.09), but the continental ratios are not. We discovered an inverse correlation of shocked quartz size (or distance from the impact site) and Ru/Ir ratio. This correlation may arise from the difference in Ru and Ir vaporization temperature and/or fractionation during condensation from the ejecta cloud. Postsedimentary alteration, remobilization, or terrestrial PGE input may be responsible for the Ru/Ir ratio variations within the groups of marine and continental sites studied. The marine ratios could also be attained if approximately 15 percent of the boundary metals were contributed by Deccan Trap emissions. However, volcanic emissions could not have been the principal source of the PGE's in the BC because mantle PGE ratios and abundances are inconsistent with those measured in the clay. The Ru/Ir values for pristine Tertiary mantle xenoliths (2.6 +/- 0.48), picrites (4.1 +/- 1.8), and Deccan Trap basalt (3.42 +/- 1.96) are all statistically distinct from those measured in the K-T BC

Parallel processors and nonlinear structural dynamics algorithms and software

The adaptation of a finite element program with explicit time integration to a massively parallel SIMD (single instruction multiple data) computer, the CONNECTION Machine is described. The adaptation required the development of a new algorithm, called the exchange algorithm, in which all nodal variables are allocated to the element with an exchange of nodal forces at each time step. The architectural and C* programming language features of the CONNECTION Machine are also summarized. Various alternate data structures and associated algorithms for nonlinear finite element analysis are discussed and compared. Results are presented which demonstrate that the CONNECTION Machine is capable of outperforming the CRAY XMP/14

Changing Diagnostic Methods and Increased Detection of Verotoxigenic Escherichia coli, Ireland

The recent paradigm shift in infectious disease diagnosis from culture-based to molecular-based approaches is exemplified in the findings of a national study assessing the detection of verotoxigenic Escherichia coli infections in Ireland. The methodologic changes have been accompanied by a dramatic increase in detections of non-O157 verotoxigenic E. coli serotypes

Reducing substance misuse and related problems: How can unhealthy alcohol users and problem drug users be effectively intervened with in general hospital settings?

Background: There is a high prevalence of unhealthy alcohol use and problem drug use among patients presenting to general hospital settings. However, many unhealthy alcohol users and problem drug users in these settings are not even aware, or do not acknowledge that they have such problems. Their presentation to hospital for the treatment of other conditions offers an opportunity to engage with them. However, there is uncertainty over how best to identify, assess and intervene with this population. Aim: To investigate how unhealthy alcohol users or problem drug users can be effectively identified, assessed and intervened with when they present to general hospital settings for the treatment of other conditions. Methods: This thesis is based on six published papers that used systematic review, meta-regression and Delphi methods. Main findings: To date, research on interventions for unhealthy alcohol use in general hospital settings has focused on brief interventions (BIs). Multiple session BIs are likely to be beneficial for unhealthy alcohol use in these settings. Where targeted screening and intervention is the strategy of choice, a focus on gastroenterology and emergency medicine is a promising way to target resources for unhealthy alcohol use. There is lack of evidence on how to effectively identify and intervene with problem drug users. The available evidence favours the ASSIST as the problem drug use screening instrument of choice. There is also lack of evidence to inform which comprehensive substance misuse assessment package to use in these settings. Conclusions: There is still need for robustly designed research on how to effectively identify, assess and intervene with unhealthy alcohol users and problem drug users within general hospital settings. It is to be hoped that the body of work presented in this thesis will, effectively, contribute to the development stage for other primary research in the future

The AMSC mobile satellite system

The American Mobile Satellite Consortium (AMSC) Mobile Satellite Service (MSS) system is described. AMSC will use three multi-beam satellites to provide L-band MSS coverage to the United States, Canada and Mexico. The AMSC MSS system will have several noteworthy features, including a priority assignment processor that will ensure preemptive access to emergency services, a flexible SCPC channel scheme that will support a wide diversity of services, enlarged system capacity through frequency and orbit reuse, and high effective satellite transmitted power. Each AMSC satellite will make use of 14 MHz (bi-directional) of L-band spectrum. The Ku-band will be used for feeder links

Mobile satellite service in the United States

Mobile satellite service (MSS) has been under development in the United States for more than two decades. The service will soon be provided on a commercial basis by a consortium of eight U.S. companies called the American Mobile Satellite Consortium (AMSC). AMSC will build a three-satellite MSS system that will offer superior performance, reliability and cost effectiveness for organizations requiring mobile communications across the U.S. The development and operation of MSS in North America is being coordinated with Telesat Canada and Mexico. AMSC expects NASA to provide launch services in exchange for capacity on the first AMSC satellite for MSAT-X activities and for government demonstrations

Tracking of Carbon Monoxide Poisoning Using Michigan Emergency Department and Hospital Records

Objectives: Among all deaths due to poisonings, carbon monoxide (CO) is the leading cause. Development of a surveillance system to track CO poisoning is a recommended public health activity. Initial steps to develop such a system are discussed. Methods: Michigan hospitals provided face sheets and discharge summaries of hospitalized and emergency department visits for CO poisonings. Reports were divided into three categories; intentional poisoning, non-work-related poisoning, and work related poisoning. The characteristics of the three groups, including demographics, sources of exposure, carboxyhemoglobin levels, and time of year were described. Results: There were 847 cases of CO poisoning reported. Another 312 cases were estimated to have been diagnosed and to have required treatment in the emergency department but were not reported. Most cases were male, aged 22-44 years. The overall incidence rate for the state was 5.83 CO poisonings per 100,000 individuals. Conclusions: A CO surveillance system using hospital and ED data as proposed in a CDC/CSTE initiative is feasible. Useful information about source of exposure can be generated to prioritize public health intervention. A more comprehensive system using additional data sources such as poison control center data would increase the timeliness of the reports received

The Deep Space Network: A Radio Communications Instrument for Deep Space Exploration

The primary purpose of the Deep Space Network (DSN) is to serve as a communications instrument for deep space exploration, providing communications between the spacecraft and the ground facilities. The uplink communications channel provides instructions or commands to the spacecraft. The downlink communications channel provides command verification and spacecraft engineering and science instrument payload data