Development of a quantitative risk assessment model for Salmonella enteritidis in pasteurized liquid eggs

Since Kraepelin delineated dementia praecox as a disease entity construct, epidemiological studies conducted since the beginning of the century have produced remarkably consistent estimates of its prevalence, incidence and lifetime risk across various populations and geographic areas. A similar pattern emerged from the WHO ten-country study on first-contact incidence of schizophrenia. The diagnostic concept of dementia praecox originally used by Kraepelin and that of schizophrenia employed in the WHO studies were found to overlap extensively, indicating continuity over time. However, the findings of a similar incidence of schizophrenia in diverse populations and across time periods are unusual for a multifactorial disease and are compatible with at least two alternative interpretations that have different implications for the search for genetic and environmental causes of the disorder.     

The linearized multistage model and the future of quantitative risk assessment

The linearized multistage (LMS) model has for over 15 years been the default dose-response model used by the U.S. Environmental Protection Agency (USEPA) and other federal and state regulatory agencies in the United States for calculating quantitative estimates of low-dose carcinogenic risks from animal data. The LMS model is in essence a flexible statistical model that can describe both linear and non-linear dose-response patterns, and that produces an upper confidence bound on the linear low-dose slope of the dose-response curve. Unlike its namesake, the Armitage-Doll multistage model, the parameters of the LMS do not correspond to actual physiological phenomena. Thus the LMS is 'biological' only to the extent that the true biological dose response is linear at low dose and that low-dose slope is reflected in the experimental data. If the true dose response is non-linear the LMS upper bound may overestimate the true risk by many orders of magnitude. However, competing low-dose extrapolation models, including those derived from 'biologically-based models' that are capable of incorporating additional biological information, have not shown evidence to date of being able to produce quantitative estimates of low-dose risks that are any more accurate than those obtained from the LMS model. Further, even if these attempts were successful, the extent to which more accurate estimates of low-dose risks in a test animal species would translate into improved estimates of human risk is questionable. Thus, it does not appear possible at present to develop a quantitative approach that would be generally applicable and that would offer significant improvements upon the crude bounding estimates of the type provided by the LMS model. Draft USEPA guidelines for cancer risk assessment incorporate an approach similar to the LMS for carcinogens having a linear mode of action. However, under these guidelines quantitative estimates of low-dose risks would not be developed for carcinogens having a non-linear mode of action; instead dose-response modelling would be used in the experimental range to calculate an LED10* (a statistical lower bound on the dose corresponding to a 10% increase in risk), and safety factors would be applied to the LED10* to determine acceptable exposure levels for humans. This approach is very similar to the one presently used by USEPA for non-carcinogens. Rather than using one approach for carcinogens believed to have a linear mode of action and a different approach for all other health effects, it is suggested herein that it would be more appropriate to use an approach conceptually similar to the 'LED10*-safety factor' approach for all health effects, and not to routinely develop quantitative risk estimates from animal data.     

Obstetric risk assessment

Obstetric risk assessment is an important component of comprehensive obstetric care. It is a tool used to evaluate the medical, psychosocial, familial, and environmental factors that increase the chance of an adverse outcome. Such outcomes may involve the mother, the infant, or both. Risk assessment collects and organizes data obtained from a pertinent history, physical examination, and laboratory assessment into an accurate and easily retrievable medical record. It can be used to adapt diagnostic or therapeutic management plans, arrange consultation or shared care with another specialist, or tailor anticipatory guidance and patient and family education.     

Building a successful risk-based competency assessment model

The requirement to verify and ensure the competency of staff members to perform their assigned duties is here to stay. This article describes a model for decision making about competency assessment frequency. Implementation of the model should be accompanied by a systematic review of learning needs and performance improvement data. Education sessions designed to address identified learning needs or to support performance improvement activities should occur before or concurrent with competency assessment. The result is a cost-effective, efficient use of resources to accomplish the goal of ongoing assessment and improvement of staff competency. When staff member competency improves, the likelihood of a positive patient outcome increases. Our model provides a structured, defensible mechanism to link competency assessment with improvements in patient care quality.     

Team assessment utilizing a many-facet Rasch model

As organizations begin to implement work teams, their assessment will ultimately reflect compensation strategies that move away from individual assessment. This will involve not only using multiple raters, but also the use of multiple criteria. Team assessment using multiple raters and multiple criteria is therefore necessitated; however, this can produce differences in ratings due to the leniency or severity of the individual team raters. This study analyzed the ratings of individual members on 31 different teams across 12 different criteria of team performance. Utilizing the many-facet Rasch model, statistical differences between the teams and 12 criteria were calculated.     

Outcome after aneurysmal subarachnoid haemorrhage: the use of a graphical model in the assessment of risk factors

In 102 consecutive prospectively identified patients with subarachnoid haemorrhage (SAH) we have analysed the severity of the initial haemorrhage and the direct and indirect effects of adverse factors on outcome. The data we recorded included delay in diagnosis, risk groups, Doppler measurements, angiographic findings, surgical events and outcome at 1 year. By using a temporal graphical chain model, the associations between all variables and possible causal pathways were statistically determined. The severity of the initial haemorrhage, as determined by means of a clinical assessment and CT scanning, allowed low-, medium- and high-risk patient groups and a statistically predictable outcome to be identified. The overall management mortality was 13.7% at 1 year; 70.6% had a favourable outcome and 15.7% were severely disabled. Outcome was directly associated with risk group (p = 0.0038) and rebleeding (p = 0.0000). Delayed diagnosis led to a poorer outcome (p = 0.014)--an indirect association probably due to rebleeding. Adverse surgical events led to a significantly poorer outcome in high-risk patients. No significant relationship was found either between age and risk group (p = 0.7784) or between age and outcome (p = 0.6418). Preoperative clinical (WFNS) grade was unreliable in predicting outcome. It is the particular risk group, determined by the initial SAH, that indicates the individual patient's outcome. Management strategies can reduce preventable adverse events such diagnostic delay and rebleeding. Future studies should stratify patients according to risk group, delay in diagnosis and rebleeding in order to enable a clearer comparison to be made of treatment methods.     

Suicide risk assessment in a college student population.

A group of 211 students at a midwestern university completed the Suicidal Behaviors Questionnaire (M. M. Linehan & S. L. Nielsen, 1981), Adult Suicidal Ideation Questionnaire (W. M. Reynolds, 1991a), Multi-Attitude Suicide Tendency Scale (I. Orbach et al., 1991), Beck Helplessness Scale (A. T. Beck, A. Weissman, D. Lester, & L. Trexler, 1974), and the Reasons for Living Inventory (M. M. Linehan, L. J. Goodstein, S. L. Nielsen, & J. A. Chiles, 1983) to determine if this group of commonly used self-report measures can distinguish between individuals with high and low levels of suicidal ideation and history of self-harmful behaviors. Exploratory principal-axis factor analysis resulted in an interpretable 2-factor solution accounting for 36.2% of the variance in suicidality. Support for convergent validity of the chosen measures was also found. It appears that rapid, accurate assessment of university student suicide risk is possible. Implications for reduction of suicide risk in this segment of the population are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Similarity and discrimination: A selective review and a connectionist model.

The 1st part of this article evaluates the extent to which 2 elemental theories of conditioning, stimulus sampling theory and the R. A. Rescorla-A. R. Wagner (1972) theory, are able to account for the influence of similarity on discrimination learning. A number of findings are reviewed that are inconsistent with predictions derived from these theories, either in their present form or in various modified forms. The 2nd part of the article is concerned with developing an alternative, configural account for discrimination learning. In contrast to previous configural theories, the present version is set within the framework of a connectionist network. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A closed-chest canine model for cross-sectional echocardiographic study

Cross-sectional echocardiography has been limited in the intact dog due to the intervening lobes of the left lung. Previous echo studies of the canine heart have utilized implanted transducers, catheter-tip transducers, or opened-chest preparations. The pericardial cradle technique described in this paper provides an acoustical window for echo studies of the entire heart in the closed-chest dog that has several advantages over these prior preparations. The left lung was retained by attaching the pericardium to the thoracic wall in a simple prestudy operation. Cross-sectional real-time echocardiographic studies have been performed on 52 anesthetized animals that were prepared in this manner. The studies were video taped for frame-by-frame analysis.     

基于不确定性分析的矿区重金属健康风险评价模型

利用区间数表示水环境中重金属质量浓度的不确定性,构建了基于不确定性分析的矿区重金属健康风险评价模型。选取Cu、Pb、Zn、Cd、Ni和As为评价因子,将模型应用于2007—2009年某铜矿区周围地表水健康风险评价中。评价结果表明:2007—2009年,该矿区周围地表水健康风险水平介于Ⅱ～Ⅵ级之间,其中Ⅴ级比例最多;A环境监测点的地表水健康风险等级分别为Ⅱ、Ⅱ、Ⅴ,B环境监测点的地表水健康风险等级分别为Ⅴ、Ⅵ、Ⅴ,说明B环境监测点的地表水健康风险水平较高;而在3年中,A环境监测点的地表水健康风险等级有所提高,说明A环境监测点的地表水环境质量有恶化趋势。     

基于云物元模型的国内矿业项目并购财务风险预警评价

国内矿业项目并购是一项充满风险的投资活动,其中财务风险是其成功与否的重要因素,因此,对国内矿业项目并购的财务风险进行预警评价具有重要意义.首先采用专家调查法对财务风险的主要影响因素进行了识别;其次建立了风险预警评价指标体系,采用德尔菲法确定了预警评价指标的权重;最后将云模型引入到物元分析中,建立了基于云物元模型的国内矿业项目并购财务风险预警评价模型,并将模型运用到实际案例中,利用Matlab软件编程计算出各评价指标的隶属度,得出该案例并购财务风险等级为一般,预警信号为黄灯,评价结果与实际较为吻合.     

Duration discrimination by rats

A psychophysical procedure was used to determine the difference limen for the duration of a signal that ranged from .5 to 8.0 sec. The accuracy of three rats in keeping track of the duration was assumed to be limited by three factors: (a) inattention to the signal on some trials, (b) variability in starting to time the duration when the signal begins (and/or in stopping to time the duration when the signal ends), and (c) factors related to signal duration itself. A generalized Weber model provided a better approximation to the growth in the difference limen as a function of signal than a generalized Counter model.     

Sperm competition games: a prospective analysis of risk assessment

We develop the logic of assessment of sperm competition risk by individual males where the mechanism of sperm competition follows a 'loaded raffle' (first and second inseminates of a female have unequal prospects). Male roles (first or second to mate) are determined randomly. In model 1, males have no information about the risk associated with individual females and ejaculation strategy depends only on the probability, q, that females mate twice. Evolutionarily stable strategy (ESS) ejaculate expenditure increases linearly from zero with q, and reduces with increasing inequality between ejaculates, though the direction of the loading (which role is favoured) is unimportant. In model 2, males have perfect information and can identify each of three risk states: females that will (1) mate just once ('no risk'), (2) mate twice but have not yet mated ('future risk'), and (3) mate twice and have already mated ('past risk'). The ESS is to ejaculate minimally with 'no risk' females, and to expand equally with 'past' and 'future' risk females; the direction of the competitive loading is again unimportant. Expenditure again increases with risk, but is now non-zero at extremely low risk. Model 3 examines three cases of partial information where males can identify only one of the three risk states and cannot distinguish between the other two: they therefore have just two information sets or 'contexts'. Expenditure in both contexts typically rises non-linearly from zero with q, but (whatever the loading direction) expenditure is higher in the context with higher risk (e.g. if contexts are 'mated' and 'virgin', males spend more with mated females). However, in highly loaded raffles, sperm expenditure can decrease over part of the range of risk. Also, the direction of the loading now affects expenditure. Biological evidence for the predictions of the models is summarized and discussed.     

Mixture risk assessment: a case study of Monsanto experiences

Monsanto employs several pragmatic approaches for evaluating the toxicity of mixtures. These approaches are similar to those recommended by many national and international agencies. When conducting hazard and risk assessments, priority is always given to using data collected directly on the mixture of concern. To provide an example of the first tier of evaluation, actual data on acute respiratory irritation studies on mixtures were evaluated to determine whether the principle of additivity was applicable to the mixture evaluated. If actual data on the mixture are unavailable, extrapolation across similar mixtures is considered. Because many formulations are quite similar in composition, the toxicity data from one mixture can be extended to a closely related mixture in a scientifically justifiable manner. An example of a family of products where such extrapolations have been made is presented to exemplify this second approach. Lastly, if data on similar mixtures are unavailable, data on component fractions are used to predict the toxicity of the mixture. In this third approach, process knowledge and scientific judgement are used to determine how the known toxicological properties of the individual fractions affect toxicity of the mixture. Three examples of plant effluents where toxicological data on fractions were used to predict the toxicity of the mixture are discussed. The results of the analysis are used to discuss the predictive value of each of the above mentioned toxicological approaches for evaluating chemical mixtures.     

Application of a statistical model to simple discrimination learning in human subjects.

(This reprinted article originally appeared in Journal of Experimental Psychology, 1955, Vol 50, 81–88. The following abstract of the original article appeared in PA, Vol 30:4111.) Ss had to predict which of a pair of reinforcing lights would appear following a signal. Uniform reinforcement (conditioning phase) or nonreinforcement (extinction phase) was given in the presence of one stimulus set and 50% random reinforcement in the presence of the other. Correspondence of theory and data, although by no means perfect, tended to support the view that discrimination learning in this situation is a simple resultant of effects of reinforcement and nonreinforcement. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Familial breast cancer risk assessment

A family, with a strong history of dominant breast and ovarian cancer, is described. Using highly polymorphic microsatellite markers within the BRCA1 breast cancer gene on chromosome 17q21; three affected sisters, their father and a paternal second cousin once removed, are shown to share the same "abnormal" haplotype. Because of this informative linkage, the carrier status of the unaffected siblings can be established by determining whether they inherited their father's "normal" or "abnormal" haplotype. Presymptomatic diagnosis is important in decisions regarding prophylactic surgery or follow-up care. However, the widespread general population presymptomatic DNA testing of breast cancer is currently not recommended because of inherent problems in the sensitivity and specificity of DNA testing.     

Caries prediction: a review of the literature

Since Jenner and Pasteur, various vaccines have been developed and administered in immunization program conducted by WHO in order to diminish the circulation of pathogenic agents and eradicate some diseases. Risks associated with immunization are revealed by the collection and assessment of adverse events reported after the use of these drugs. They vary according to the type of vaccines. With high rates of immunization and a low incidence of infectious diseases, adverse events receive increasing attention. Frequent and mostly expected adverse events are reported in clinical trials. Unexpected rare adverse events are reported after marketing authorization by spontaneous reporting and post marketing surveillance studies. Post marketing surveillance should be adapted to vaccines (vaccino-vigilance) and should take into account the risk linked to the disease they may protect against. Adverse events are often temporally associated with vaccines, that does not mean they are causally related. Specific studies should be conducted to assess the causal relationship between vaccines and post immunization adverse events. In order to reduce the risk associated with immunization, a strict follow-up of recommendations, warnings and contraindications in addition to appropriate information being delivered to both vaccinees and physicians are required.     

基于未确知测度模型的稀土原地浸矿地下水污染风险评价

通过识别原地浸矿地下水污染风险因子,建立了基于未确知测度理论的原地浸矿地下水污染风险评价模型,运用信息熵理论确定评价指标的权重,采用置信度识别准则来评价地下水污染的风险等级,选取了pH值、溶解性固体（COD）、硫酸盐、氯化物、高锰酸钾指数、硝酸盐、氨氮、氟化物、六价铬、收液巷道母液监控收液系统、水平孔监控收液系统、垂直孔监控收液系统、气象系统日降雨量和月累计雨量等14项三级指标作为未确知测度模型的判别指标,对国内某稀土原地浸矿前、浸矿中、浸矿后以及私采矿区分别进行了地下水污染风险评价,评价结果与该矿山的实际情况较吻合.研究结果表明,模型指标选择合理,未确知测度模型运用合理,该模型具有一定的实际运用价值,为稀土原地浸矿地下水污染风险提供了较好的评价方法.