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PubMed1994

Handedness as a continuous variable with dextral shift: sex, generation, and family handedness in subgroups of left- and right-handers.

Percentages of left-handed relatives were compared between subgroups of left-handers and of right-handers to test the prediction that the subgroups are ordered for probability of carrying the rs +/gene (hypothesized by the right-shift theory of handedness). Data included families of undergraduates and Open University students who described their children as well as other relatives. Linear relationships were found between subgroup order and percentage of left-handed relatives. In agreement with previous evidence that some right-writers with weak sinistral preferences (class 2) are in fact more dextral than consistent right-handers (class 1), class 2 tended to have fewer left-handed relatives than class 1 in both samples. Left writers with weak dextral tendencies (class 7) tended to have more left-handed relatives that consistent left-handers (class 8). Comparisons of the distribution of subgroup handedness in undergraduates and their parents revealed strong effects for sex and for generation. In both cases, the main contrasts were not between left-handers and right-handers but between left-handers plus right-handers with weak dextrality and right-handers with strong dextrality. The findings are consistent with the theory that the relevant factor is not handedness as such but, rather, the absence or presence of the rs +/gene.

Adolescent↗
PubMed1993

The true meaning of 'exotic species' as a model for genetically engineered organisms.

The exotic or non-indigenous species model for deliberately introduced genetically engineered organisms (GEOs) has often been misunderstood or misrepresented. Yet proper comparisons of of ecologically competent GEOs to the patterns of adaptation of introduced species have been highly useful among scientists in attempting to determine how to apply biological theory to specific GEO risk issues, and in attempting to define the probabilities and scale of ecological risks with GEOs. In truth, the model predicts that most projects may be environmentally safe, but a significant minority may be very risky. The model includes a history of institutional follies that also should remind workers of the danger of oversimplifying biological issues, and warn against repeating the sorts of professional misjudgements that have too often been made in introducing organisms to new settings. We once expected that the non-indigenous species model would be refined by more analysis of species eruptions, ecological genetics, and the biology of select GEOs themselves, as outlined. But there has been political resistance to the effective regulation of GEOs, and a bureaucratic tendency to focus research agendas on narrow data collection. Thus there has been too little promotion by responsible agencies of studies to provide the broad conceptual base for truly science-based regulation. In its presently unrefined state, the non-indigenous species comparison would overestimate the risks of GEOs if it were (mis)applied to genetically disrupted, ecologically crippled GEOs, but in some cases of wild-type organisms with novel engineered traits, it could greatly underestimate the risks. Further analysis is urgently needed.

Bacterial Physiological Phenomena↗
PubMed1982

Decision theory model of the emergency medical triage process.

The major objective of this research project was to apply the scientific discipline of decision-making to the problem of identifying the appropriate receiving hospital for persons injured in accidents. This problem, which is usually referred to as the prehospital triage process, is enormously important in terms of maximizing the critically injured patient's chances for survival. The long term objective of this research program, for which this project was a pilot study, is to develop an interactive computer system to support decisions regarding triage of patients at the scene of medical emergencies. The completed system will offer guidance to the paramedic in deciding whether to transport the emergency victim to the nearest hospital for stabilization and further evaluation or directly to the hospital best equipped to deal with the specific conditions of the victim.

Accidents↗
PubMed2006

Spectroscopic properties of Nd3+ doped transparent oxyfluoride glass ceramics.

In this paper, the spectroscopic properties of Nd(3+) doped transparent oxyfluoride glass ceramics containing LaF(3) nano-crystals were systematically studied. The formation and distribution of LaF(3) nano-crystals in the glass matrix were investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Based on Judd-Ofelt theory, the intensity parameters Omega(t) (t=2, 4, 6), spontaneous emission probability, radiative lifetime, radiative quantum efficiency, width of the emission line and stimulated emission cross-section of Nd(3+) were evaluated. Particularly, the effect of Nd(3+) doping level on them was discussed. With the increase of Nd(3+) concentration in the glass ceramic, the experimental luminescence lifetime, radiative quantum efficiency and stimulated emission cross-section vary from 353.4 micros, 78.3% and 1.86 x 10(-20)cm(2) to 214.7 micros, 39.9% and 1.52 x 10(-20)cm(2), respectively. The comparative study of Nd(3+) spectroscopic parameters in different hosts suggests that the investigated glass ceramic system is potentially applicable as laser materials for 1.06 microm emission.

Ceramics↗
PubMed1999

Role of infections in atherosclerosis.

A growing amount of epidemiologic, experimental, and clinical evidence has linked infection as a risk factor to variousatherosclerotic diseases including acute myocardial infarction and cerebral infarction. Bacteremic infections with and without endocarditis carry a high risk for both stroke and acute myocardial infarction. During the last decade, chronic bacterial infections such as Chlamydia pneumoniae and dental infections have been associated as risk factors for various atherosclerotic diseases. These chronic bacterial infections are risk factors for acute cardiovascular events, but they may also have some role in the etiopathogenesis of atherosclerotic process itself. There are many known mechanisms that might explain the observed association of infection and atherosclerotic diseases, but it is probable that these mechanisms are complex and multifactorial and probably differ from infection to infection and from patient to patient. Infection theory is by no means against classic risk factor theory in the etiopathogenesis of atherosclerosis. Infection may also act as a synergistic risk factor together with classic risk factors in the development of various atherosclerotic diseases.

Arteriosclerosis↗
PubMed1971

Theory of threshold fluctuations in nerves. I. Relationships between electrical noise and fluctuations in axon firing.

Relations describing threshold fluctuation phenomena in nerves are derived by calculating the approximate response of the Hodgkin-Huxley (HH) axon to electrical noise. We use FitzHugh's reduced phase space approximation and describe the dynamics of a noisy nerve by a two-dimensional brownian motion. The theory predicts the functional form and parametric dependence of the relation between probability of firing and stimulus strength. Expressions are also obtained for the firing probability as a function of stimulus duration and for the distribution of latency times as a function of stimulus strength.

Action Potentials↗
PubMed1979

A systems-theory approach to the analysis of multiexponential fluorescence decay.

A mathematical model of the fluorescence decay experiment based on linear systems theory is presented. The model suggests an experimental technique that increases the probability of correctly determining the decay constants of a multicomponent system. The use of moment methods for data analysis improves accuracy by combining information obtained from several discrete experiments. Examples are presented to show that the analysis of a three component system composed of known standards is improved as the number of experimental determinations is increased from one to four. The discrete measurements are made by changing the excitation and emission wavelengths.

Carbazoles↗
PubMed1996

Theoretical uncertainty of measurements using quantitative polymerase chain reaction.

Current quantitative polymerase chain reaction (PCR) protocols are only indicative of the quantity of a target sequence relative to a standard, because no means of estimating the amplification rate is yet available. The variability of PCR performed on isolated cells has already been reported by several authors, but it could not be extensively studied, because of lack of a system for doing kinetic data acquisition and of statistical methods suitable for analyzing this type of data. We used the branching process theory to simulate and analyze quantitative kinetic PCR data. We computed the probability distribution of the offspring of a single molecule. We demonstrated that the rate of amplication has a severe influence on the shape of this distribution. For high values of the amplification rate, the distribution has several maxima of probability. A single amplification trajectory is used to estimate the initial copy number of the target sequence as well as its confidence interval, provided that the amplification is done over more than 20 cycles. The consequence of possible molecular fluctuations in the early stage of amplification is that small copy numbers result in relatively larger intervals than large initial copy numbers. The confidence interval amplitude is the theoretical uncertainty of measurements using quantitative PCR. We expect these results to be applicable to the data produced by the next generation of thermocyclers for quantitative applications.

Biometry↗
PubMed1980

Effect of myocardial infarction on the peak amplitude of high frequency QRS potentials.

Studies based on analysis of QRS notching and slurring have suggested an increase in high frequency QRS potentials following myocardial infarction (MI). We investigated the sensitivity and specificity of an indirect, but easily quantitated index of high frequency potentials--the peak-to-peak amplitude of the high frequency signal. A commercially-available micro-processor ECG system was employed with a QRS-averaging program to reduce random noise and an 80-300 Hz filter to selectively record higher frequency potentials. High frequency ECGs were recorded in leads II, III and aVF in 40 normal men and 41 patients with prior inferior MI. Peak-to-peak amplitude of the high frequency signal was less than or equal to 35 micro V in one or more of these leads in 18 of 41 MI patients (44%) compared with only 1 of 40 normals (2.5%) (P < 0.001). In the infarct group, reduced peak amplitude of the high frequency signal was also noted in some leads where the standard ECG did not show pathologic Q waves. This diminution in peak amplitude probably reflects a reduction in high frequency voltage. Therefore, contrary to previous theory, MI may actually cause a decrease in high frequency potentials as part of an overall loss of electromotive force or a slowing of conduction associated with myocardial necrosis. Quantitative high frequency QRS measurements may be of critical value in selected cases.

Adult↗
PubMed1985

Bio-informational equivalence.

Combined, the ideas of modern genetics and those of evolutionary process form the central explanatory concepts of biological science. Over the past 30 years or so, those concepts have merged with the idea that biological processes--at every level of organization--are equivalent to information transactions. The latter idea is here called the concept of bio-informational equivalence. It appears in one or other of three basic forms or else in some combination of them. According to the view adopted in this paper, bio-informational equivalence, in all its forms, has a deeply anthropocentric core which makes it unsuited for its present role as a quasi-theoretical perspective in biological science.

Animals↗
PubMed1992

A multicenter questionnaire investigation of attitudes toward hand hygiene, assessed by the staff in fifteen hospitals in Denmark and Norway.

A questionnaire survey was carried out anonymously among 2557 health care workers in Denmark and Norway to identify and quantify factors that affect the handwashing behavior of physicians, nurses, and other staff groups who perform direct patient care. For number of daily patient contacts physicians reported significantly fewer instances of hand hygiene (HH) per day than did those in other medical professions. Male physicians reported significantly fewer HH per day than did their female colleagues. Significant differences were found among staff groups in emphasis on factors motivating and discouraging HH. The main motivating factor for all groups, however, was an awareness that HH is important for the prevention of infection. Skin problems from frequent handwashing and the use of agents that irritate and dry the skin were the main reasons for disinclination toward HH. The number of points given to these statements correlated well with the stated frequency of HH in staff groups with relatively many (9 to 24) patient contacts per day. Many studies have revealed low standards of HH in health care settings. Whenever HH is taught, the significance of HH for the prevention of infection is always stressed. The participants in this survey were well aware of this significance, but there is still a discrepancy between theory and practice. Goal-specific strategies to improve HH practices would probably be more effective if more were done to minimize the factors that health care workers find detrimental to HH. Continual evaluation of the possibly detrimental effects of current hand washing agents should also be carried out.

Attitude of Health Personnel↗
PubMed1995

On the generalization of the receiver operating characteristic analysis to the population of readers and cases with the jackknife method: an assessment.

RATIONALE AND OBJECTIVES: A new methodology that analyzes receiver operating characteristic (ROC) data sets based on jackknifing and that considers both case and reader variability has been proposed. The purpose of this investigation was to compare results using this method to those using commonly reported methodology. METHODS: ROC data sets using discrete and continuous rating scales were analyzed using the proposed jackknifing method, and results were compared to analysis of the same data sets using the paired t test. RESULTS: The two methodologies did not result in the same significance levels, and in some cases, the difference was sufficient to affect conclusions regarding comparisons of diagnostic modalities. The probability value for the jackknifing procedure is based on large sample distribution theory, and its appropriateness is unknown for sample sizes used in practice. Also, the jackknifing technique was found to be sensitive to outliers resulting when data from the computer programs used to estimate area under the ROC curve failed to converge. CONCLUSION: Although the proposed methodology yields reasonable results, several fundamental and practical issues must be addressed before it can be used widely as the analytic method of choice in ROC studies comparing different imaging techniques or reading environments.

Analysis of Variance↗
PubMed2003

A theoretical framework for understanding the effects of simultaneous base-rate and payoff manipulations on decision criterion learning in perceptual categorization.

Observers completed perceptual categorization tasks in which base rates and payoffs were manipulated separately or simultaneously across a range of category discriminabilities. Decision criterion estimates from the simultaneous base-rate/payoff conditions were closer to optimal than those predicted from the independence assumption, in line with predictions from the flat-maxima hypothesis. A hybrid model that instantiated the flat-maxima and competition between reward and accuracy maximization hypotheses was applied to the data as well as used in a reanalysis of C. J. Bohil and W.J. Maddox's (2001) study. The hybrid model was superior to a model that incorporated the independence assumption, suggesting that violations of the independence assumption are to be expected and are well captured by the flat-maxima hypothesis, without requiring any additional assumptions.

Decision Making↗