ABSTRACT
For safe innovation, knowledge on potential human health impacts is essential. Ideally, these impacts are considered within a larger life-cycle-based context to support sustainable development of new applications and products. A methodological framework that accounts for human health impacts caused by inhalation of engineered nanomaterials (ENMs) in an indoor air environment has been previously developed. The objectives of this study are as follows: (i) evaluate the feasibility of applying the CF framework for NP exposure in the workplace based on currently available data; and (ii) supplement any resulting knowledge gaps with methods and data from the life cycle approach and human risk assessment (LICARA) project to develop a modified case-specific version of the framework that will enable near-term inclusion of NP human health impacts in life cycle assessment (LCA) using a case study involving nanoscale titanium dioxide (nanoTiO2 ). The intent is to enhance typical LCA with elements of regulatory risk assessment, including its more detailed measure of uncertainty. The proof-of-principle demonstration of the framework highlighted the lack of available data for both the workplace emissions and human health effects of ENMs that is needed to calculate generalizable characterization factors using common human health impact assessment practices in LCA. The alternative approach of using intake fractions derived from workplace air concentration measurements and effect factors based on best-available toxicity data supported the current case-by-case approach for assessing the human health life cycle impacts of ENMs. Ultimately, the proposed framework and calculations demonstrate the potential utility of integrating elements of risk assessment with LCA for ENMs once the data are available.
ABSTRACT
Longitudinal data can be used to estimate the transition intensities between healthy and unhealthy states prior to death. An illness-death model for history of stroke is presented, where time-dependent transition intensities are regressed on a latent variable representing cognitive function. The change of this function over time is described by a linear growth model with random effects. Occasion-specific cognitive function is measured by an item response model for longitudinal scores on the Mini-Mental State Examination, a questionnaire used to screen for cognitive impairment. The illness-death model will be used to identify and to explore the relationship between occasion-specific cognitive function and stroke. Combining a multi-state model with the latent growth model defines a joint model which extends current statistical inference regarding disease progression and cognitive function. Markov chain Monte Carlo methods are used for Bayesian inference. Data stem from the Medical Research Council Cognitive Function and Ageing Study in the UK (1991-2005).
Subject(s)
Bayes Theorem , Cognition Disorders/etiology , Models, Statistical , Stroke/mortality , Aged , Cognition Disorders/mortality , Humans , Markov Chains , Monte Carlo Method , Risk Factors , Stroke/complications , Time FactorsABSTRACT
For most allergenic foods, limited availability of threshold dose information within the population restricts the advice on action levels of unintended allergenic foods which should trigger advisory labeling on packaged foods. The objective of this paper is to provide guidance for selecting an optimal sample size for threshold dosing studies for major allergenic foods and to identify factors influencing the accuracy of estimation. A simulation study was performed to evaluate the effects of sample size and dosing schemes on the accuracy of the threshold distribution curve. The relationships between sample size, dosing scheme and the employed statistical distribution on the one hand and accuracy of estimation on the other hand were obtained. It showed that the largest relative gains in accuracy are obtained when sample size increases from N=20 to N=60. Moreover, it showed that the EuroPrevall dosing scheme is a useful start, but that it may need revision for a specific allergen as more data become available, because a proper allocation of the dosing steps is important. The results may guide risk assessors in minimum sample sizes for new studies and in the allocation of proper dosing schemes for allergens in provocation studies.
Subject(s)
Allergens/immunology , Food Hypersensitivity/diagnosis , Algorithms , Arachis/adverse effects , Arachis/immunology , Dose-Response Relationship, Immunologic , Food Hypersensitivity/immunology , Food Hypersensitivity/prevention & control , Humans , Models, Biological , No-Observed-Adverse-Effect Level , Risk AssessmentABSTRACT
A general joint modeling framework is proposed that includes a parametric stratified survival component for continuous time survival data, and a mixture multilevel item response component to model latent developmental trajectories given mixed discrete response data. The joint model is illustrated in a real data setting, where the utility of longitudinally measured cognitive function as a predictor for survival is investigated in a group of elderly persons. The object is partly to determine whether cognitive impairment is accompanied by a higher mortality rate. Time-dependent cognitive function is measured using the generalized partial credit model given occasion-specific mini-mental state examination response data. A parametric survival model is applied for the survival information, and cognitive function as a continuous latent variable is included as a time-dependent explanatory variable along with other explanatory information. A mixture model is defined, which incorporates the latent developmental trajectory and the survival component. The mixture model captures the heterogeneity in the developmental trajectories that could not be fully explained by the multilevel item response model and other explanatory variables. A Bayesian modeling approach is pursued, where a Markov chain Monte Carlo algorithm is developed for simultaneous estimation of the joint model parameters. Practical issues as model building and assessment are addressed using the DIC and various posterior predictive tests.
Subject(s)
Bayes Theorem , Markov Chains , Models, Statistical , Survival Analysis , Aged , Cognition , Female , Humans , Male , Monte Carlo Method , Surveys and QuestionnairesABSTRACT
In current psychological research, the analysis of data from computer-based assessments or experiments is often confined to accuracy scores. Response times, although being an important source of additional information, are either neglected or analyzed separately. In this article, a new model is developed that allows the simultaneous analysis of accuracy scores and response times of cognitive tests with a rule-based design. The model is capable of simultaneously estimating ability and speed on the person side as well as difficulty and time intensity on the task side, thus dissociating information that is often confounded in current analysis procedures. Further, by integrating design matrices on the task side, it becomes possible to assess the effects of design parameters (e.g., cognitive processes) on both task difficulty and time intensity, offering deeper insights into the task structure. A Bayesian approach, using Markov Chain Monte Carlo methods, has been developed to estimate the model. An application of the model in the context of educational assessment is illustrated using a large-scale investigation of figural reasoning ability.
Subject(s)
Cognition , Models, Statistical , Psychological Tests/statistics & numerical data , Psychometrics/statistics & numerical data , Reaction Time , Aptitude Tests/statistics & numerical data , Attention , Bayes Theorem , Concept Formation , Educational Measurement/statistics & numerical data , Humans , Pattern Recognition, Visual , Problem Solving , Reproducibility of ResultsABSTRACT
Influence of time and temperature on Salmonella enteritidis multiplication in experimentally injected eggs was examined. There was an increase in the number of S. enteritidis with the increase in temperature of egg storage. There was less increase of S. enteritidis in eggs stored at 4 degrees C than in eggs held at temperatures higher than 4 degrees C (P less than 0.05). These results suggest a possible method for monitoring commercial eggs for the presence of S. enteritidis. It was concluded that the chances of recovery of S. enteritidis can be increased 10(6)-fold or more by holding the eggs at temperatures of 21 or 27 degrees C for more than 20 days and culturing their contents.
Subject(s)
Ovum/microbiology , Salmonella enteritidis/growth & development , Animals , Chickens , Temperature , Time FactorsABSTRACT
A totally artificial heart--the Rostock totally artificial heart (Rostock TAH) was implanted in calves. We can give the following deductions after 27 examinations: -- The Rostock TAH was tested successfully in endurance test about 7 months; it show no sign of wear. -- The surgical technique of the implantation was standardised and a successful experimentation is possible. -- The longest survival time was 15 days. The hemodynamic early results were very good in 3 other animals. -- Modifications of the Rostock TAH were taken up relating to the dimensions of the artificial ventriculi and by mounting a screw cap for avoiding an air embolism. -- Adaption tests in the corpse show that the present form of the artificial heart is not ideal for a possible application in man. -- The problem is still existing in developing a suitable drive system locates intrathoracically. The present drive and control system on a pneumatic base is qualified only for the animal experiment but not for a possible application in man.
Subject(s)
Heart, Artificial , Anesthesia, General , Animals , Blood Pressure , Cattle , Humans , Methods , Preoperative CareABSTRACT
Echocardiography makes possible the analysis of cardiac structures and their dynamics. The presence of valvular disease and its severity can be determined by evaluation of variations in the intensity of reflection and alterations in the motion of valvular structures. The echocardiographic representation of cardiac chambers permits the detection of congenital and acquired structural defects as well as an evaluation of ventricular function. Echocardiography provides a non-invasive means of diagnostic analysis throughout the spectrum of heart diseases and can replace a number of invasive diagnostic procedures.