The structure of force-free magnetic fields

Incontrovertible evidence is presented that the force-free magnetic fields exhibit strong stochastic behavior. Arnold’s solution is given with the associated first integral of energy. A subset of the solution is shown to be non-ergodic whereas the full solution is shown to be ergodic. The first integral of energy is applied to the study of these fields to prove that the equilibrium points of such magnetic configurations are saddle points. Finally, the potential function of the first integral of energy is shown to be a member of the Helmholtz family of solutions. Numerical results corroborate the theoretical conclusions and demonstrate the robustness of the energy integral, which remains constant for arbitrarily long computing time

Is geographic diversification sufficient to limit contract grower risk?

Lending and financial institutions have looked for a variety of ways to expand their portfolios into agriculture, but because of the risks associated with lending to farmers who lack traditional forms of collateral, they face price and yield risks, causing these inroads to be limited. Market-based instruments are readily available for price risk. Organised exchanges offering the most basic of these instruments, futures and options, have operated for a long time, providing transparency to the market and low-cost risk transfer tools for those able to access them. While the use of price risk management instruments is an incomplete solution, it has sufficient merits on its own and will make the overall burden of risk more bearable. The use of these instruments and multi-peril crop insurance products is expensive and does not provide full protection for financial lending institutions to limit their credit risk exposure. This article determines whether geographic diversification would be sufficient as a risk management tool for lending institutions to limit their credit risk.Geographic diversification, Contract grower, Risk, Lending, Rainfall, Yield, Agricultural Finance,

Issues Related to the Emergence of the Information Superhighway and California Societal Changes, IISTPS Report 96-4

The Norman Y. Mineta International Institute for Surface Transportation Policy Studies (IISTPS) at San José State University (SJSU) conducted this project to review the continuing development of the Internet and the Information Superhighway. Emphasis was placed on an examination of the impact on commuting and working patterns in California, and an analysis of how public transportation agencies, including Caltrans, might take advantage of the new communications technologies. The document reviews the technology underlying the current Internet “structure” and examines anticipated developments. It is important to note that much of the research for this limited-scope project was conducted during 1995, and the topic is so rapidly evolving that some information is almost automatically “dated.” The report also examines how transportation agencies are basically similar in structure and function to other business entities, and how they can continue to utilize the emerging technologies to improve internal and external communications. As part of a detailed discussion of specific transportation agency functions, it is noted that the concept of a “Roundtable Forum,” growing out of developments in Concurrent Engineering, can provide an opportunity for representatives from multiple jurisdictions to utilize the Internet for more coordinated decision-making. The report also included an extensive analysis of demographic trends in California in recent years, such as commute and recreational activities, and identifies how the emerging technologies may impact future changes

An Approach for Actions to Prevent Suicides on Commuter and Metro Rail Systems in the United States, MTI Report 12-33

The primary goals of this report are to discuss measures to prevent suicides on commuter and metro rail systems, and to outline an approach for suicide prevention on rail systems. Based on existing literature and analysis of data obtained from the Metrolink system in Southern California, it was found that most suicides occur near station platforms and near access points to the track. Suicides occurred most frequently when relatively more trains were in operation and in areas of high population density. There do not appear to be suicide “hot spots” (e.g., linked to mental hospitals in the proximity, etc.), based on data analyzed for U.S. systems. The suicide prevention measures range from relatively inexpensive signs posting call-for-help suicide hotline information to costly platform barriers that physically prevent people from jumping onto tracks in front of trains. Other prevention measures fall within this range, such as hotlines available at high frequency suicide locations, or surveillance systems that can report possible suicide attempts and provide the opportunity for intervention tactics. Because of the relatively low number of suicides on rail systems, as compared to the overall number of suicides in general, a cost-effective strategy for preventing suicides on rail systems should be approached in a very focused manner. The prevention measures executed by the rail authorities should be focused on the suicides occurring on the rail systems themselves, while the broader problem of suicides should be left to community-based prevention efforts. Moreover, prevention measures, such as surveillance and response, could “piggyback” on surveillance and response systems used for other purposes on the rail systems to make such projects economically feasible

Taking safety promotion and injury prevention “beyond interventionism”: Aligning activity theory with community based participatory research

No Abstrac

Bikesharing and Bicycle Safety

The growth of bikesharing in the United States has had a transformative impact on urban transportation. Major cities have established large bikesharing systems, including Boston, Chicago, Denver, Minneapolis-Saint Paul, New York City, Salt Lake City, the San Francisco Bay Area, Seattle, Washington DC, and others. These systems began operating as early as 2010, and no fatalities have occurred within the US as of this writing. However, three have happened in North America—two in Canada and one in Mexico. Bikesharing has some qualities that appear inherently unsafe for bicyclists. Most prominently, helmet usage is documented to be quite low in most regions. Bikesharing is also used by irregular bicyclists who are less familiar with the local terrain. In this study, researchers take a closer look at bikesharing safety from qualitative and quantitative perspectives. Through a series of four focus groups, they discussed bikesharing usage and safety with bikesharing members and nonmembers in the Bay Area. They further engaged experts nationwide from a variety of fields to evaluate their opinions and perspectives on bikesharing and safety. Finally, researchers conducted an analysis of bicycle and bikesharing activity data, as well as bicycle and bikesharing collisions to evaluate injury rates associated with bikesharing when compared with benchmarks of personal bicycling. The data analysis found that collision and injury rates for bikesharing are lower than previously computed rates for personal bicycling. Experts and focus group participants independently pointed to bikesharing rider behavior and bikesharing bicycle design as possible factors. In particular, bikesharing bicycles are generally designed in ways that promote stability and limited speeds, which mitigate the conditions that contribute to collisions. Data analysis also explored whether there was evidence of a “safety in numbers benefit” that resulted from bikesharing activity. However, no significant impact from bikesharing activity on broader bicycle collisions could be found within the regions in which they operate. Discussion and recommendations are presented in the conclusion

Suicides on Commuter Rail in California: Possible Patterns — A Case Study, Research Report 10-05

Suicides on rail systems constitute a significant social concern. Reports in local media, whether in newspapers, television, or radio, have brought awareness to this very sensitive and personal subject. This is also true for the San Francisco Bay Area. These events also cause severe trauma for the train operators and staff of the system as well as disruption and cost to society. The overall objective of this project was to conduct a pilot study to identify possible patterns in suicides associated with urban commuter rail systems in California. The Caltrain commuter rail system in the San Francisco Bay Area was used as the subject system for the pilot study. The primary intent of the data analysis was to determine whether suicides along the Caltrain tracks exhibited patterns. Pattern detection in this study was conducted primarily on the basis of time and location. Because the data were readily available, the gender factor was also included in the analysis, although this is not a factor that is connected to the rail system. It was concluded that the data did show some patterns for suicides with respect to time and location. Some of the patterns can be explained while the reasons for some are not immediately obvious. However, the patterns in the latter category did not indicate a particularly attractive location or possible source for suicides

An Overview of System Design Issues Related to Safety Aspects of Bicycle Infrastructure

The purpose of this report is to provide a critical review of the current practices and policies regarding infrastructure design for bicycling. The infrastructure is discussed primarily from a system perspective. The wide range of bicyclists’ physical characteristics (such as size, power, skill, response to road and traffic conditions) makes it challenging for the designer to design bicycle facilities with the same sophistication and safety as facilities for motor vehicles. An attempt should be made to integrate the design standards for motor vehicles and bicycles into common design manuals. Incompatibility of the standards may make it clear when separate facilities for bicyclists should be considered and when bicyclists should not be allowed on a road. Bicycling has been promoted based substantially on health benefits and the reduction of environmental impact without stating the risks of injury and death as well as musculoskeletal injuries resulting from overuse. This has led to an increase in the provision of bike paths and bicycle lanes, including re-designating general traffic lanes to exclusive use by bicyclists. A study1 showed that it is more cost-efficient to remove pollutants by allocating funds to improve traffic flow and public transportation than allocating those funds to some bicycle facilities. Re-designating general-use traffic lanes as bike lanes could also cause congestion, which could increase air pollution. Consideration should be given to promote bicycling for exercise and recreation on trails and to prohibit bicycling in areas where large differences in speed and crossing maneuvers at high speed could occur, such as in the vicinity of busy traffic interchanges. It is the author’s view that the way in which safety improvements for bicyclists is approached should be fundamentally changed. Decreasing fatalities and injuries should be considered for the transportation system as a whole instead of trying to decrease the fatalities and injuries to bicyclists alone by implementing countermeasures

It’s a Virtual Child!: Postgraduate students’ experiences in a developmental psychology class

The aim of this study was to explore postgraduate psychology students’ development, as facilitated by the use of an interactive web-based simulation programme, My Virtual Child©. A social constructivist developmental approach, with specific focus on cognitive development towards self-authorship, served as the overarching framework for the study. Participants included postgraduate students enrolled in a developmental psychology module. Multiple sources of data, such as reflective exercises, summative portfolio assignments and a focus group, were analysed using thematic analysis. Participants indicated that the My Virtual Child© programme provided them with an excellent opportunity for authentic, relevant and challenging learning experiences, whilst balancing theory and practice. Furthermore, it provided room for deliberate reflective activities, group interaction and the integration of a diversity of experiences. This programme therefore created a practical and pragmatic teaching environment for more engaging and theoretically rich learning, preparing students for self-authorship in a complex world

Epidemiological research methods. Part VII. Epidemiological research in health planning

CITATION: Yach, D. & Botha, J. L. 1987. Epidemiological research methods. Part VII. Epidemiological research in health planning. South African Medical Journal, 72:633-636.The original publication is available at http://www.samj.org.zaThe goal of epidemiology is to improve the health status of human populations. In our series thus far we have srressed the need to use the correct design for epidemiological studies, a sampling scheme that yields interpretable results, measurements that are both valid and reliable, and finally the appropriate analysis. These methodological considerations are of importance if the goal is to be reached. In this article we assume that most of these issues have been adequately dealt with and focus on how the results of epidemiological research can be used by health planners to improve the health status of regions and the country as a whole.Publisher’s versio