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PubMed1995

A risk assessment for lead in birds.

Ecotoxicologists and ecologists have examined the effects of pollutants on individuals and populations largely in terms of one or only a few effects. Yet the recent trend toward a holistic approach to ecological risk assessment suggests that a rigorous paradigm should be applied to toxicants, from hazard identification to risk characterization. Recent discussions have recognized that an up-front problem formulation phase is more critical in ecological risk assessment than it is for human health risk assessment. In this article a modified environmental health risk assessment paradigm is used to examine the risk of lead to birds. This risk analysis is largely conceptual, based on laboratory and field data, and incorporates information currently available. The model expands the hazard identification phase to create a target identification phase that includes the identification of receptors, endpoints, relationships, spatial and temporal scales, and indicators. The target identification phase is unique to the particular hazard, species, population, or community being examined. Lead can cause mortality, or can indirectly affect populations through effects on the food base, avian behavior, reproductive success, and recruitment. Lead can (1) decrease the abundance and availability of prey, (2) bioaccumulate in prey causing increased lead toxicosis in predators, or (3) increase prey availability by interfering with its hiding or escape behavior. Moreover, lower abundance of prey can lead to starvation or nutrient deficiencies, which amplify the absorption and retention of lead. Lead also causes decreases in clutch and egg size, mortality of embryos and nestlings, depression of growth, and deficits in behavior that affect survival. Lead decreases migratory behavior, and increases vulnerability to cold stress, hunters, and other predators. Research needs for evaluating the risk of lead in birds include obtaining data on (1) metal dynamics within various tissues as a function of dose and time since initial exposure, (2) low-level effects on embryos, (3) effects on chicks following fledging and in the period prior to recruitment, (4) effects on adult foraging skills and reproductive behavior, and (5) the relationship between effects from exposure in the laboratory and those from exposure in the wild. This latter point is extremely important, particularly if wild birds have other means of ridding the body of lead not available or less apparent to laboratory birds.

Animals↗

PubMed1997

Robust proofs of NP-hardness for protein folding: general lattices and energy potentials.

This paper addresses the robustness of intractability arguments for simplified models of protein folding that use lattices to discretize the space of conformations that a protein can assume. We present two generalized NP-hardness results. The first concerns the intractability of protein folding independent of the lattice used to define the discrete protein-folding model. We consider a previously studied model and prove that for any reasonable lattice the protein-structure prediction problem is NP-hard. The second hardness result concerns the intractability of protein folding for a class of energy formulas that contains a broad range of mean force potentials whose form is similar to commonly used pair potentials (e.g., the Lennard-Jones potential). We prove that protein-structure prediction is NP-hard for any energy formula in this class. These are the first robust intractability results that identify sources of computational complexity of protein-structure prediction that transcend particular problem formulations.

Models, Chemical↗

PubMed1985

An appraisal of goals for residency training in internal medicine.

The goals for residency training in internal medicine were assessed by faculty and house staff members at one university-based program using a 38-item questionnaire based largely upon American Board of Internal Medicine criteria. The respondents rated each item according to its ideal importance, its actual emphasis in training, and the respondents' degree of satisfaction with their own level of accomplishment for that item. Faculty and house staff members shared similar perceptions of ideal goals and actual emphases of training, with both groups rating clinical judgment, gathering data, and formulating problems as the most important. Both groups also tended to rate highly as ideal goals those items that they considered to be their own professional strengths and that reflected their current respective roles in medical training. This trend was the most apparent for faculty members in ratings of academic skills and for house staff members in ratings of technical proficiency and patient management skills. The tendency to idealize one's own professional role and strengths may inhibit needed changes in residency training.

Clinical Competence↗

PubMed1991

Clinical behaviors and skills that faculty from 12 institutions judged were essential for medical students to acquire.

This paper describes a 1988-1989 collaborative mail survey of faculty opinion about clinical behaviors and skills that students should be expected to demonstrate prior to graduation from undergraduate medical school (hereafter called "exit objectives"). Selected faculty from 12 American and Canadian medical schools indicated whether each of 77 objectives was essential for every student to know or demonstrate prior to graduation; useful but not essential at the undergraduate level; or not applicable to their undergraduate program. Their responses provide a glimpse into faculty expectations regarding some of the exit behaviours and skills they deemed essential. Forty-two percent (32) of the 77 objectives were regarded as essential by 75% or more of the faculty members who responded. Essential objectives involved conducting organ system examinations, formulating problems and hypotheses, and gathering fundamental interview, physical, and screening examination data, including emergency examinations of the airway and circulatory systems. Other essential objectives involved collaboration and communication, demonstrating concern for legal and ethical values, and keeping abreast of current information within the discipline. Exit objectives related to the diagnosis and management of specific conditions were regarded as useful but not essential at the undergraduate level. Implications for medical education are discussed.

Canada↗

PubMed1979

Automated medical screening in an urban county jail.

A machine-administered, branch-chain automated medical history (AMH) was evaluated as a medical intake screening tool for inmates of a large metropolitan county jail. The reproducibility, validity, sensitivity and specificity of the AMH were measured and found comparable to other previously reported AMH systems. The AMH did not produce intake screening data comparable to that obtained by trained face to face medical interviewers. This, in addition to the time and personnel effort required for administering the AMH while preventing vandalization of the equipment, made the AMH impractical for use in the county jail setting. Physicians used only 21 per cent of the positive AMH responses when they were asked to formulate problem lists from the AMH data. Physicians who used the AMH in clinical settings complained that "the AMH data seem as often wrong as right." The authors observed that the number of true-positive AMH responses was matched by an almost equal number of false-positve and false-negative responses. This may account for the physician's subjective response. If so, this represents a problem to be addressed by future AMH systems. Physicians used only 55.8 per cent of the intake screening information obtained by nurse practitioners. This was also somewhat lower than expected. For this reason, medical historical information in the county jail setting might be most efficiently obtained by the provider who has clinical responsibility for prescribing treatment.

Attitude of Health Personnel↗

PubMed2003

Tokamak equilibria with reversed current density.

Observations of nearly zero toroidal current in the central region of tokamaks (the "current hole") raises the question of the existence of toroidal equilibria with very low or reversed current in the core. The solutions of the Grad-Shafranov equilibrium equation with hollow toroidal current density profile including negative current density in the plasma center are investigated. Solutions of the corresponding eigenvalue problem provide simple examples of such equilibrium configurations. More realistic equilibria with toroidal current density reversal are computed using a new equilibrium problem formulation and computational algorithm which do not assume nested magnetic surfaces.

Journal Article↗

PubMed2001

Ecological risk assessment framework for low-altitude aircraft overflights: I. Planning the analysis and estimating exposure.

An ecological risk assessment framework for low-altitude aircraft overflights was developed, with special emphasis on military applications. The problem formulation and exposure analysis phases are presented in this article; an analysis of effects and risk characterization is presented in a companion article. The intent of this article is threefold: (1) to illustrate the development of a generic framework for the ecological risk assessment of an activity, (2) to show how the U.S. Environmental Protection Agency's ecological risk assessment paradigm can be applied to an activity other than the release of a chemical, and (3) to provide guidance for the assessment of ecological risks from low-altitude aircraft overflights. The key stressor for low-altitude aircraft overflights is usually sound, although visual and physical (collision) stressors may also be significant. Susceptible and regulated wildlife populations are the major assessment endpoint entities, although plant communities may be impacted by takeoffs and landings. The exposure analysis utilizes measurements of wildlife locations, measurements of sound levels at the wildlife locations, measurements of slant distances from aircraft to wildlife, models that extrapolate sound from the source aircraft to the ground, and bird-strike probability models. Some of the challenges to conducting a risk assessment for aircraft overflights include prioritizing potential stressors and endpoints, choosing exposure metrics that relate to wildlife responses, obtaining good estimates of sound or distance, and estimating wildlife locations.

Aircraft↗

PubMed2001

Ecological risk assessment framework for low-altitude aircraft overflights: II. Estimating effects on wildlife.

An ecological risk assessment framework for aircraft overflights has been developed, with special emphasis on military applications. This article presents the analysis of effects and risk characterization phases; the problem formulation and exposure analysis phases are presented in a companion article. The framework addresses the effects of sound, visual stressors, and collision on the abundance and production of wildlife populations. Profiles of effects, including thresholds, are highlighted for two groups of endpoint species: ungulates (hoofed mammals) and pinnipeds (seals, sea lions, walruses). Several factors complicate the analysis of effects for aircraft overflights. Studies of the effects of aircraft overflights previously have not been associated with a quantitative assessment framework; therefore no consistent relations between exposure and population-level response have been developed. Information on behavioral effects of overflights by military aircraft (or component stressors) on most wildlife species is sparse. Moreover, models that relate behavioral changes to abundance or reproduction, and those that relate behavioral or hearing effects thresholds from one population to another are generally not available. The aggregation of sound frequencies, durations, and the view of the aircraft into the single exposure metric of slant distance is not always the best predictor of effects, but effects associated with more specific exposure metrics (e.g., narrow sound spectra) may not be easily determined or added. The weight of evidence and uncertainty analyses of the risk characterization for overflights are also discussed in this article.

Aircraft↗

PubMed2002

Risk and systems theory.

The last few decades have seen increasingly widespread use of risk assessment and management techniques as aids in making complex decisions. However, despite the progress that has been made in risk science, there still remain numerous examples of risk-based decisions and conclusions that have caused great controversy. In particular, there is a great deal of debate surrounding risk assessment: the role of values and ethics and other extra-scientific factors, the efficacy of quantitative versus qualitative analysis, and the role of uncertainty and incomplete information. Many of the epistemological and methodological issues confronting risk assessment have been explored in general systems theory, where techniques exist to manage such issues. However, the use of systems theory and systems analysis tools is still not widespread in risk management. This article builds on the Alachlor risk assessment case study of Brunk, Haworth, and Lee to present a systems-based view of the risk assessment process. The details of the case study are reviewed and the authors' original conclusions regarding the effects of extra-scientific factors on risk assessment are discussed. Concepts from systems theory are introduced to provide a mechanism with which to illustrate these extra-scientific effects The role of a systems study within a risk assessment is explained, resulting in an improved view of the problem formulation process The consequences regarding the definition of risk and its role in decision making are then explored.

Acetamides↗

PubMed2004

Applying the partitioned multiobjective risk method (PMRM) to portfolio selection.

The analysis of risk-return tradeoffs and their practical applications to portfolio analysis paved the way for Modern Portfolio Theory (MPT), which won Harry Markowitz a 1992 Nobel Prize in Economics. A typical approach in measuring a portfolio's expected return is based on the historical returns of the assets included in a portfolio. On the other hand, portfolio risk is usually measured using volatility, which is derived from the historical variance-covariance relationships among the portfolio assets. This article focuses on assessing portfolio risk, with emphasis on extreme risks. To date, volatility is a major measure of risk owing to its simplicity and validity for relatively small asset price fluctuations. Volatility is a justified measure for stable market performance, but it is weak in addressing portfolio risk under aberrant market fluctuations. Extreme market crashes such as that on October 19, 1987 ("Black Monday") and catastrophic events such as the terrorist attack of September 11, 2001 that led to a four-day suspension of trading on the New York Stock Exchange (NYSE) are a few examples where measuring risk via volatility can lead to inaccurate predictions. Thus, there is a need for a more robust metric of risk. By invoking the principles of the extreme-risk-analysis method through the partitioned multiobjective risk method (PMRM), this article contributes to the modeling of extreme risks in portfolio performance. A measure of an extreme portfolio risk, denoted by f(4), is defined as the conditional expectation for a lower-tail region of the distribution of the possible portfolio returns. This article presents a multiobjective problem formulation consisting of optimizing expected return and f(4), whose solution is determined using Evolver-a software that implements a genetic algorithm. Under business-as-usual market scenarios, the results of the proposed PMRM portfolio selection model are found to be compatible with those of the volatility-based model. However, under extremely unfavorable market conditions, results indicate that f(4) can be a more valid measure of risk than volatility.

Journal Article↗

PubMed1990

Homecare at the end of life. A study of fifteen patients.

The study is a part of a research project on death in a sector of a large city, involved cooperation with the Franciscan Aid "home care team". The purpose was to study death in the home setting. Fifteen deaths were registered. Participant observation in the care of 14 patients were made--a total of 83 visits to homes, 2-15 visits per patient. In one case the author had contact with the relatives, after the death had occurred. Most of the patients had cancer. Their age varied from 28 to 80 years. The observations were recorded immediately after each visit. After the death of a patient a structured interview with the closest relatives and the nurse responsible were made. Their statements were used as a basis for formulating problems for the further study and the clarification of quantitative data. Results showed that the patients who chose to leave the hospital and remain at home often had negative experiences in hospital. All the patients in this study received good palliative treatment at home. All patients were also informed about their condition. One-third of the patients were readmitted to hospital during the final days.

Adult↗

PubMedDate not supplied

Prediction of muscle recruitment and its effect on joint reaction forces during knee exercises.

This study examined the hypothesis that muscle recruitment of the tibiofemoral joint and joint reaction forces during isometric and isokinetic exercises depends on the existing degrees of freedom of the knee and the direction and type of external load applied during exercise. When three-dimensional knee joint rotation was considered (three degrees of freedom), antagonistic muscle activities were predicted using an inverse dynamic problem formulation and muscle modeling optimization procedures. The results showed that the antagonistic activities of flexors during knee flexion/extension exercise increased the joint compressive forces and decreased the anterior tibial shear forces. Comparison of different knee joint modeling assumptions indicated that modeling a single degree of freedom in flexion/extension for the knee will underestimate the antagonistic muscle function.

Biomechanical Phenomena↗

PubMed1990

Theoretical prediction of muscle forces on the mandible during bite.

We present a mathematical model to determine the contribution of each muscle acting on the mandible in the development of a given bite force. We give special attention to the representation of the widely radiated temporalis and account for the attachment of the external pterygoid to the capsular ligament. An optimization technique based on minimizing the maximum stress occurring in the muscles is used to resolve the statically indeterminant nature of the problem formulated. The theoretically predicted values of the muscle forces are compared to experimental results taken from the literature.

Bite Force↗

PubMed1993

Multiple minima in inverse hyperthermia temperature estimation problems.

Using one-, two-, and three-dimensional numerical simulation models it is shown that multiple minima solutions exist for some inverse hyperthermia temperature estimation problems. This is a new observation that has important implications for all potential applications of these inverse techniques. The general conditions under which these multiple minima occur are shown to be solely due to the existence of symmetries in the bio-heat transfer model used to solve the inverse problem. General rules for determining the number of these global minimum points in the unknown parameter (perfusion) space are obtained for several geometrically symmetric (with respect to the sensor placement and the inverse case blood perfusion model) one-, two-, and three-dimensional problem formulations with multiple perfusion regions when no model mismatch is present. As the amount of this symmetry is successively reduced, all but one of these global minima caused by symmetry become local minima. A general approach for (a) detecting when the inverse algorithm has converged to a local minimum, and (b) for using that knowledge to direct the search algorithm toward the global minimum is presented. A three-dimensional, random perfusion distribution example is given which illustrates the effects of the multiple minima on the performance of a state and parameter estimation algorithm. This algorithm attempts to reconstruct the entire temperature field during simulated hyperthermia treatments based on knowledge of measured temperatures from a limited number of locations.

Algorithms↗

PubMed1987

The use of decision analysis for organizational design: reorganizing a community hospital.

Organizational design is presented as a decision process, with specific structures seen as providing alternative choices. To illustrate this, the authors present the case of a major metropolitan hospital that used the process to coordinate service delivery (nursing care versus patient care) and service focus (product oriented versus function oriented). Through interviews with more than 40 hospital administrators and staff, the authors created a list of 20 attributes, and used simple multi-attribute utility analysis to generate six design alternatives. The decision makers unanimously chose one alternative, even though potential for significant conflict existed because of differing values and objectives. The authors find decision analytic techniques useful for both the problem formulation and for generating and evaluating structural alternatives, and conclude that in this case consensus was facilitated by the decision process used.

Data Collection↗

PubMed1988

Consultation letters as a method for assessing in-training performance in a department of medicine.

This study examined the feasibility of using outpatient consultation letters as a means of assessing the clinical performance of clerks and house staff in a large teaching hospital. A total of 222 assessments were obtained based on samples of consultation problems from two clinical services. The method involved a two-stage rating scale based on the performance areas of Data Base, Problem Formulation, Diagnostic Tests, Management and Overall Assessment. The technique was investigated in terms of the objectivity, reliability, validity and efficiency of the performance ratings. Product-moment coefficients were used to assess inter- and intrarater agreement in scoring the consultation letters. These analyses identified a consistent difficulty in assessing the category of Data Base. For the remaining performance categories, interrater coefficients in the range .19-.76 and intrarater coefficients in the range .23-.96 were obtained. Other preliminary findings indicated good potential for a reliable and valid assessment. The method is technically feasible, and is based on a novel and reasonably unobtrusive approach to assessing trainee performance in a clinical setting.

Canada↗

PubMed2000

Gas chromatography/mass spectrometry identification and quantification of isazophos in a famphur pour-on and in bovine tissues after a toxic exposure.

A sample identified as "Warbex pour-on," expected to contain 13.2% famphur, and bovine tissue samples from 2 heifers that died after exhibiting signs of organophosphate intoxication were analyzed by gas chromatography/mass spectrometry (GC/MS). A product formulation problem was suspected because brain cholinesterase activities were depressed in both animals. Electron impact (EI) GC/MS of the pour-on revealed 9.7% famphur and an unidentified peak with approximately 76% of the peak area of the famphur. The unidentified peak showed a molecular ion at m/z 313, with a single Cl isotope cluster. Methane chemical ionization (MeCI) MS confirmed the molecular weight at 313 (1 Cl). A search on the molecular formula C9H17N3O3PSCl yielded a single match, isazophos. EI and MeCI GC/MS of reference isazophos confirmed the identity of the suspect peak. The concentration of isazophos in the pour-on was determined to be 6.0%. Famphur and isazophos were identified by their EI spectra and GC retention times in extracts of liver and brain from the 2 deceased animals. A GC/MS procedure utilizing selected ion monitoring (SIM) was developed for quantification of isazophos in liver, kidney, muscle, and fat of additional affected animals sacrificed at various times after exposure. Isazophos remained in animal tissues for as long as 94 days after topical exposure. Isazophos was present in fetal liver 70 days after exposure of the dam. High levels (6-3,500 ppm) of isazophos and famphur remained on the skin at 39 days postexposure.

Animals↗

PubMed2003

Nuclear waste transportation: case studies of identifying stakeholder risk information needs.

The U.S. Department of Energy (DOE) is responsible for the cleanup of our nation's nuclear legacy, involving complex decisions about how and where to dispose of nuclear waste and how to transport it to its ultimate disposal site. It is widely recognized that a broad range of stakeholders and tribes should be involved in this kind of decision. All too frequently, however, stakeholders and tribes are only invited to participate by commenting on processes and activities that are near completion; they are not included in the problem formulation stages. Moreover, it is often assumed that high levels of complexity and uncertainty prevent meaningful participation by these groups. Considering the types of information that stakeholders and tribes need to be able to participate in the full life cycle of decision making is critical for improving participation and transparency of decision making. Toward this objective, the Consortium for Risk Evaluation with Stakeholder Participation (CRESP) participated in three public processes relating to nuclear waste transportation and disposal in 1997-1998. First, CRESP organized focus groups to identify concerns about nuclear waste transportation. Second, CRESP conducted exit surveys at regional public workshops held by DOE to get input from stakeholders on intersite waste transfer issues. Third, CRESP developed visual tools to synthesize technical information and allow stakeholders and tribes with varying levels of knowledge about nuclear waste to participate in meaningful discussion. In this article we share the results of the CRESP findings, discuss common themes arising from these interactions, and comment on special considerations needed to facilitate stakeholder and tribal participation in similar decision-making processes.

Communication↗