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PubMed1982

An empirical approach to the statistical analysis of mutagenesis data from the Salmonella test.

A number of recent papers have suggested basing the statistical analysis of Salmonella (Ames) mutagenicity test results on a mathematical model of the complete dose-response curve. For most mutagens at low doses the curve increases linearly; then, as the dose increases, the curve may flatten and finally turn downwards due primarily to effects of toxicity. The exact mechanism underlying this shape is, however, not well understood and is likely to vary for different chemicals. A different approach is to assume that the initial part of the curve is linear and to base the statistical analysis solely on this region, reasoning that it contains most of the interpretable information about the mutagenesis dose response. In this paper a formal method of deciding which points are on the initial linear part of the curve is described, and a statistical method is proposed for analyzing these points. Computer simulations are used to examine the properties of the procedure and comparisons are made with a previously proposed mathematical model of the whole curve. It is concluded that the method suggested here provides a very satisfactory, robust method for the standard analysis of Salmonella data.

Dose-Response Relationship, Drug↗
PubMedDate not supplied

A semi-empirical approach for determination of low-energy gamma-emmiters in sediment samples with coaxial Ge-detectors.

A simple method for the determination in sediment samples of low-energy gamma-emitters with coaxial Ge detectors and using a cylindrical sample geometry is outlined. This method allows an easy estimation of self-absorption effects by knowing the apparent densities and the composition of the investigated samples. As calibration matrixes solid samples enriched in known amounts of natural radionuclides emitting low-energy gamma rays were used. In this way, the difficult homogenisation steps needed when liquid spikes are added to a solid blank for manufacturing the calibration sample are avoided. The method has been carefully checked and validated by applying it to sediment samples with known activities of some low-energy gamma-ray emitters. Additionally, these sediment measurements have allowed to evaluate the magnitude and importance of the self-absorption corrections.

Algorithms↗
PubMed2006

How do forensic scientists learn to become competent in casework reporting in practice: a theoretical and empirical approach.

In their day-to-day work, carrying out complex tasks, forensic scientists use a combination of explicit, codified standard operating procedures and tacit knowledge developed through their ongoing practice. We show that tacit knowledge is an integral part of the activities of expert forensic science practitioners who continually add to their knowledge repertoire by engaging other scientists through communities of practice. We wish to shed fresh light on the gaining of tacit knowledge by forensic scientists during their apprentice formative years, termed as legitimate peripheral participation. In quantifying tacit knowledge exchanges, we use social network analysis, a methodology for the analysis of social structures, to map relational knowledge flows between forensic scientists within communities of practice at the Forensic Science Laboratory, Ireland. This paper sheds light on the importance of tacit knowledge within the training regime of forensic scientists and its recognition as equal to the part played by explicit knowledge.

Forensic Sciences↗
PubMed2000

The cognitive-energetic model: an empirical approach to attention-deficit hyperactivity disorder.

Attention Deficit/Hyperactivity Disorder (ADHD) is a childhood psychiatric disorder which when carefully defined, affects around 1% of the childhood population [Swanson JM, Sergeant JA, Taylor E, Sonuga-Barke EJS, Jensen PS, Canwell DP. Attention-deficit hyperactivity disorder and hyperkinetic disorder. Lancet 1998;351:429-433]. The primary symptoms: distractibility, impulsivity and overactivity vary in degree and association in such children, which led DSM IV to propose three subgroups. Only one of these subgroups, the combined subtype: deficits in all three areas, meets the ICD-10 criteria. Since the other two subtypes are used extensively in North America (but not in Europe), widely different results between centres are to be expected and have been reported. Central to the ADHD syndrome is the idea of an attention deficit. In order to investigate attention, it is necessary to define what one means by this term and to operationalize it in such a manner that others can test and replicate findings. We have advocated the use of a cognitive-energetic model [Sanders, AF. Towards a model of stress and performance. Acta Psychologica 1983;53: 61-97]. The cognitive-energetic model of ADHD approaches the ADHD deficiency at three distinct levels. First, a lower set of cognitive processes: encoding, central processing and response organisation is postulated. Study of these processes has indicated that there are no deficits of processing at encoding or central processing but are present in motor organisation [Sergeant JA, van der Meere JJ. Convergence of approaches in localizing the hyperactivity deficit. In Lahey BB, Kazdin AE, editors. Advancements in clinical child psychology, vol. 13. New York: Plenum press, 1990. p. 207-45; Sergeant, JA, van der Meere JJ. Additive factor methodology applied to psychopathology with special reference to hyperactivity. Acta Psychologica 1990;74:277-295]. A second level of the cognitive-energetic model consists of the energetic pools: arousal, activation and effort. At this level, the primary deficits of ADHD are associated with the activation pool and (to some extent) effort. The third level of the model contains a management or executive function system. Barkley [Barkley RA, Behavioral inhibition, sustained attention, and executive functions: constructing a unifying theory of ADHD. Psychological Bulletin 1997;121:65-94] reviewed the literature and concluded that executive function deficiencies were primarily due to a failure of inhibition. Oosterlaan, Logan and Sergeant [Oosterlaan J, Logan GD, Sergeant JA. Response inhibition in ADHD, CD, comorbid ADHD + CD, anxious and normal children: a meta-analysis of studies with the stop task. Journal of Child Psychology and Psychiatry 1998;39:411-426] demonstrated that this explanation was not specific to ADHD but also applied to children with the associated disorders of oppositional defiant and conduct disorder. Other executive functions seem to be intact, while others, are deficient. It is argued here that the cognitive-energetic model is a useful guide for determining not only ADHD deficiencies and associated disorders but also linking human cognitive neuroscience studies with neurobiological models of ADHD using animals [Sadile AG. Multiple evidence of a segmental defect in the anterior forebrain of an animal model of hyperactivity and attention deficits. Neuroscience and Biobehavioral Reviews, in press; Sagvolden T, Sergeant JA. Attention-deficit hyperactivity disorder: from brain dysyfunctions to behaviour. Behavioural Brain Research 1998;94:1-10]. A plea for an integrated attack on this research problem is made and the suggestion that conceptual refinement between levels of analysis is essential for further fundamental work to succeed is offered here.

Animals↗
PubMed2003

Biological nonlocality and the mind-brain interaction problem: comments on a new empirical approach.

Up to now, we have been faced with an age old fundamental dilemma posed by the mind-brain interaction problem, i.e. how is it that the mind which is subjective and immaterial, can interact with the brain which is objective and material? Analysis of recent experiments appears to indicate that quantum mechanics may have a role to play in the resolution of the mind-brain interaction problem in the form of biological entanglement and nonlocality. In addition to this analysis, when coupled with ongoing and proposed experiments, may help us to simultaneously resolve related issues such as whether mental events can initiate neural events, the transference of conscious subjective experience, the measurement problem and the binding problem.

Brain↗
PubMed1996

An empirical approach to informed consent in ovarian cancer.

The study was designed to define and compare the professional and the reasonable-person standards for provision of information to ovarian cancer patients, and to determine if patient information priorities could be anticipated by surrogate patients. Physicians treating ovarian cancer patients, women treated for the disease, and well lay women imagining themselves to have the disease used a visual analog scale to judge the importance of 57 questions that they might want answered before treatment decisions are made. On the basis of median importance scores, all groups judged questions relating to life expectancy as most important. Overall, judgments of the patient groups agreed well with one another; doctor-patient agreement was significant but smaller than between-patient agreement. Predicting an individual's judgments from his/her group, however, was very poor for all groups. Life experience and demographic characteristics rarely improved our ability to predict an individual's judgments.

Adult↗
PubMed2003

The elusiveness of coffee aroma: new insights from a non-empirical approach.

Aroma is central to a pleasurable eating/drinking experience but is one of the most labile components of food. Coffee is an outstanding example. Attempts to avoid or control aroma degradation are often frustrated by ignorance of the microscopic mechanisms that are responsible for it. One of the processes most frequently invoked is radical formation, yet the identity of the radicals and their involvement in aroma degradation are poorly understood at the molecular level. Here a step forward in the fundamental understanding of this complex problem is taken by identifying the most relevant radicals and their products using first-principles calculations. Over 100 radicals originating from key aroma compounds found in coffee and other foods have been studied and classified according to an unambiguous criterion: their thermodynamic stability relative to common radical sources. This classification scheme predicts that most aroma molecules are resistant to both peroxidation and attack from phenolic antioxidants but are unstable with respect to radicals such as .OH. Dimers--generated from radical reactions--were also considered, and the most volatile species, which may further contribute to coffee aroma degradation, were focused on. Those--which are very few indeed--that have this potential have been identified.

Coffee↗
PubMed2001

Quality of life in breast cancer patients: a cluster analytic approach. Empirically derived subgroups of the EORTC-QLQ BR 23--a clinically oriented assessment.

Quality of life (QOL) questionnaires are integrated into clinical trials in order to evaluate different treatments, and rarely used in a diagnostic sense. The aim of this study was to identify clinically meaningful subgroups by means of established QOL tools. Since January 1995, a field study funded by the German Ministry of Health was conducted to evaluate quality of care of breast cancer patients in eastern Thuringia. During the follow-up period, the European Organization of Research and Treatment of Cancer (EORTC), Quality of Life C30 and the breast specific module BR23 were mailed. One-hundred-fifty-eight women answered both questionnaires. A cluster analysis was performed to distinguish subgroups on the basis of QOL-BR23 scores. According to the QOL outcomes, four subgroups could be described. There was a strong relation to operative treatment (p < 0.05), while no association with the adjuvant treatment strategy was observed. The subsets identified on the basis of BR23 scores were significantly related to all C30 domains. It was possible to demonstrate the clinical validity in terms of clinical and sociodemographic data. No association was found with the marital status or the highest level of education, while a worsening of the financial situation was associated. It could be shown that a distinction of patient subgroups based on clinically meaningful BR23 data is possible. Subgroups with specific profiles could be identified. In the future, the characterisation of subgroups could provide a possibility to generate indications for specific supportive interventions.

Aged↗
PubMed2003

Toward an empirical approach to evidentiary ruling.

This paper responds to criticisms/misconstruals of our measure of the maximum probative value of evidence (D. Davis & W. C. Follette, 2002), and our conclusions regarding the potentially prejudicial role of "intuitive profiling" evidence, including motive. We argue that R. D. Friedman and R. C. Park's (2003) criticisms and example cases are largely based on inappropriate violation of the presumption of innocence. Further, we address the merits of our absolute difference measure of probative value versus those of the Bayesian likelihood ratio championed by D. H. Kaye and J. J. Koehler (2003). We recommend methods for presentation of measures of evidence utility that convey complexities of interdependence between new and existing evidence. Finally, we propose a "probable cause" standard for admission of potentially prejudicial evidence, dictating that admissibility of such evidence should be contingent upon other substantial evidence of guilt.

Bias↗
PubMed2004

Microbial life and temperature: a semi empirical approach.

Many groups have examined the effect of temperature on the survival of microorganisms, resulting in the development of several models. Some of these models are based on the Arrhenius equation and the others are based on multidimensional response surface equations. We argue that the former are inadequate and the latter lack biological meaning. We show that an equation (the GLE equation) deduced from the Theory of Rate Processes is more accurate than the Arrhenius equation. The excellent standard deviation values of the apparent free energy of activation obtained with the GLE equation for microbial growth, embryogenic and other processes show that this equation is more suitable than the Arrhenius equation. The GLE equation shows how temperature affects survival. Thus, organisms survive longer at low temperatures than at normal temperatures. The recent discovery of microorganisms in Siberian permafrost samples that are several million years old, in deep oil fields, mines and other extreme habitats appears to be consistent with the GLE equation. Another example, the enhanced resistance of spores at extreme temperatures can be easily explained by their high apparent free energy of activation We also examined the implications of the GLE equation on food sterilization practices and on exobiology.

Bacterial Physiological Phenomena↗