Tree LANS with collision avoidance : protocol, switch architecture, and performance

Packet collisions and their resolution create a performance bottleneck in random access LANs. A hardware solution to this problem is to use collision avoidance switches. These switches allow the implementation of random access protocols without the penalty of collisions among packets. We review and compare the designs of some tree LANs that use collision avoidance switches. They have the potential of combining the benefits of random access (low delay when traffic is light, simple and distributed, and therefore robust, protocols) with excellent network utilization and concurrency of transmission. The collision avoidance LANs we review are broadcast star, Hubnet-like tree, Tinker-Tree, and a treenet that allows concurrent broadcasts within non-intersecting subtrees. After this review, we present a slotted-time, infinite user analysis of the broadcast star network

Longitudinal investigation of medical student perceptions of a video-based guided study resource used to facilitate an eight week module in medicine

We use an action research approach to evaluate three successive cohorts of medical student perceptions of using a multi-faceted video-based guided study resource which provides academic (skills-based), social (motivation-based) and professional (clinical-based) interventions aimed at facilitating and enriching learning across an eight week module in the second year of the MBChB medical degree. Our findings show that whilst students value these video resources both as a revision tool and an aid to learning during the semester, they have specific critiques about several areas which would improve the project. We interpret our data to evidence a tangible beneficial argument for the use video-based learning objects to support student learning that is reliably reaffirmed by our longitudinal data

On the Transition and Migration of Flight Functions in the Airspace System

Since ~400 BC, when man first replicated flying behavior with kites, up until the turn of the 20th century, when the Wright brothers performed the first successful powered human flight, flight functions have become available to man via significant support from man-made structures and devices. Over the past 100 years or so, technology has enabled several flight functions to migrate to automation and/or decision support systems. This migration continues with the United States NextGen and Europe s Single European Sky (a.k.a. SESAR) initiatives. These overhauls of the airspace system will be accomplished by accommodating the functional capabilities, benefits, and limitations of technology and automation together with the unique and sometimes overlapping functional capabilities, benefits, and limitations of humans. This paper will discuss how a safe and effective migration of any flight function must consider several interrelated issues, including, for example, shared situation awareness, and automation addiction, or over-reliance on automation. A long-term philosophical perspective is presented that considers all of these issues by primarily asking the following questions: How does one find an acceptable level of risk tolerance when allocating functions to automation versus humans? How does one measure or predict with confidence what the risks will be? These two questions and others will be considered from the two most-discussed paradigms involving the use of increasingly complex systems in the future: humans as operators and humans as monitors

Health Effects of Indoor-Air Benzene in Anchorage Residences: A Study of Indoor-Air Quality in Houses with Attached Garages

Benzene is a known carcinogen. It affects white blood cells; it causes leukemia and aplastic anemia. It may also affect the immune system which is dependent on white blood cells.1 It has been removed from all household products, but it is still present in gasoline. Alaskan gasoline is particularly high in benzene (>5%). Gasoline refined in Alaska has high concentrations of benzene and other the aromatic compounds as much as 50% aromatics by volume. Leaving the aromatics in the gasoline helps cars start in the cold, but it also puts high concentrations of benzene in both the ambient and indoor air. We already knew from previous work done in Alaska by Bernard Goldstein in Valdez2 and the Anchorage Department of Health and Human Services in Anchorage3 that people were exposed to high ambient levels of benzene in the winter, and that there were high indoor benzene concentrations in homes with attached garages if the garage was used to store gasoline or gasoline powered engines. Benzene does not bioaccumulate in the body as dioxin or some pesticides do. But are its effects cumulative? Does a little dose of benzene everyday have the same effect as a large dose over less time? Benzene reduces CD4 cells in a dose-response manner at workplace concentrations less than 1 ppm (OSHA 8-hour exposure limit) in workers.4 People who live in homes with high benzene concentrations may be exposed 24 hours a day, seven days a week. There have been no studies of health effects of such environmental exposure to benzene. This study was done to determine three things: 1. What percentage of Anchorage homes with attached garages had high levels of indoor benzene? 2. Were the high levels of indoor benzene affecting the health of the residents? 3. Were residents more likely to develop asthma in homes with high levels of indoor benzene?Municipality of AnchorageIntroduction / Methods / Recruitment / Results / Laboratory Results / Smoking / Health Results / Demographics / Determining Risk Levels / Asthma Outcomes / Children / Work and Hobby Exposure / General Health / Conclusions / Bibliography / Appendice

The Recognition of STEMI by Paramedics and the Effect of Computer inTerpretation (RESPECT): a randomised crossover feasibility study

Background : The appropriate management of patients with ST-segment elevation myocardial infarction (STEMI) depends on accurate interpretation of the 12-lead ECG by paramedics. Computer interpretation messages on ECGs are often provided, but the effect they exert on paramedics’ decision-making is not known. The objective of this study was to assess the feasibility of using an online assessment tool, and collect pilot data, for a definitive trial to determine the effect of computer interpretation messages on paramedics’ diagnosis of STEMI. Methods : The Recognition of STEMI by Paramedics and the Effect of Computer inTerpretation (RESPECT) feasibility study was a randomised crossover trial using a bespoke, web-based assessment tool. Participants were randomly allocated 12 of 48 ECGs, with an equal mix of correct and incorrect computer interpretation messages, and STEMI and STEMI-mimics. The nature of the responses required a cross-classified multi-level model. Results : 254 paramedics consented into the study, 205 completing the first phase and 150 completing phase two. The adjusted OR for a correct paramedic interpretation, when the computer interpretation was correct (true positive for STEMI or true negative for STEMI-mimic), was 1.80 (95% CI 0.84 to 4.91) and 0.58 (95% CI 0.41 to 0.81) when the computer interpretation was incorrect (false positive for STEMI or false negative for STEMI-mimic). The intraclass correlation coefficient for correct computer interpretations was 0.33 for participants and 0.17 for ECGs, and for incorrect computer interpretations, 0.06 for participants and 0.01 for ECGs. Conclusions : Determining the effect of computer interpretation messages using a web-based assessment tool is feasible, but the design needs to take clustered data into account. Pilot data suggest that computer messages influence paramedic interpretation, improving accuracy when correct and worsening accuracy when incorrect

Promoting independence, health and well-being for older people: a feasibility study of computer-aided health and social risk appraisal system in primary care

Background - With population ageing, research is needed into new low-cost, scalable methods of effective promotion of health and wellbeing for older people. We aimed to assess feasibility, reach and costs of implementing a new tailored computer-aided health and social risk appraisal system in primary care. Methods - Design: Feasibility study. Setting: Five General Practices in London (Ealing) and Hertfordshire, United Kingdom (UK) Participants: Random sample of patients aged 65 + years. Intervention: The Multi-dimensional Risk Appraisal for Older people (MRA-O) system includes: 1) Postal questionnaire including health, lifestyle, social and environmental domains; 2) Software system generating a personalised feedback report with advice on health and wellbeing; 3) Follow-up of people with new concerning or complex needs by GPs or practice nurses. Evaluation: Feasibility of implementation; participant wellbeing, functional ability and quality of life; social needs, health risks, potential lifestyle changes; and costs of implementation. Results - Response rates to initial postal invitations were low (526/1550, 34%). Of these, 454/526 (86%) completed MRA-O assessments. Compared to local UK Census data on older people, participants were younger, more were owner-occupiers and fewer were from ethnic minority groups than expected. A range of problems was identified by participants, including pain in last week (269/438, 61.4%), low physical activity (173/453, 38.2%), sedentary lifestyle (174/447, 38.3%), falls (117/439, 26.7%), incontinence (111/441 25.2%), impaired vision 116/451 (25.7%), impaired hearing (145/431, 33.6%), depressed mood (71/451, 15.7%), impaired memory (44/444 9.9%), social isolation (46/449, 10.2%) and loneliness (31/442, 7.0%). Self-rated health was good/excellent in 312/437 (71.4%), and quality of life and well-being were slightly above age-specific population norms. Implementation costs were low. Practices reviewed medical records of 143/454 (31.5%) of participants as a consequence of their responses, and actively followed up 110/454 (24.2%) of their patients. Conclusions - A computer-aided risk appraisal system was feasible for General Practices to implement, yields useful information about health and social problems, and identifies individual needs. Participation rates were however low, particularly for the oldest old, the poorest, and ethnic minority groups, and this type of intervention may increase inequalities in access. Widespread implementation of this approach would require work to address potential inequalities