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PubMed1983

Models in administration and the dean's exercise of power and leadership.

As a result of the investigation into theories of leadership in today's society, it is probably safe to assume that any one of the models presented does not exist in pure form. Rather, the principles of one system predominate with a reflection of other systems becoming apparent in a given situation. In an institution where governance can best be classified as following the traditional model, the ability of the dean to arrive at immediate decisions in the day-to-day activities or to institute minor changes promptly is seriously hampered. Emergency situations which tend to arise in a department of nursing, especially in conjunction with the practice component, become exceedingly stressful. Independent action is stifled and unless the chief officer is cognizant of the nature of nursing, the potential for a high degree of professionalism is thwarted. The human relations model ameliorates some of these effects by promoting a degree of communication horizontally and by placing the immediate superior officer in a role which contributes to this communication process. The ingredient that is missing is the free exchange vertically which often translates into lack of support from the higher echelon. The dean's position lacks credibility; hence, the sense of power is lacking and effective leadership suffers. The human resources model best promotes a unified effort toward excellence in nursing for students and faculty alike by encouraging the continued development of all persons within the department.(ABSTRACT TRUNCATED AT 250 WORDS)

Administrative Personnel↗
PubMed1975

[Contribution to the knowledge of fatty tissue--containing tumors of the uterus (author's transl)].

Based on a case observation, the different types of fatty tissue-containing uterine tumors are discussed with regard to the literature. The different theories on the histogenesis of uterine lipomas are considered. Probably these lipomatous tumors arise from misplaced embryonic fat cells. With respect to the formal genesis, possible concordances with the uterine leiomyomas are pointed out.

Age Factors↗
PubMed1981

Transdifferentiation of chicken embryo neural retina into pigment epithelium: indications of its biochemical basis.

Neural retina from 8- to 9-day embryo chickens was grown in long-term cell culture in an experiment to test the hypothesis that one step during the in vitro transdifferentiation of neural retina into pigment cells occurs in response to stimulation of tricarboxylic acid (TCA) cycle activity. Time-lapse photography showed that pigment-cell formation occurs through the intermediate stages of 'undistinguished cells', 'pavement epithelium' and 'potential pigment cells'. Mitosis of undistinguished cells to pavement epithelium was proportional to malonate over most of the tested range of concentrations and was inhibited by succinate, which respectively depress and stimulate the TCA cycle. Conversely mitosis of pavement epithelium to potential pigment cells occurred in proportion to succinate concentration over most of the tested range and was inhibited by malonate, in support of the hypothesis under test. Melanin synthesis begins in a minority of 'pigment leader cells' uniquely stimulated by the lowest concentration of malonate, although higher concentrations blocked pigment synthesis in all cell types. The pigment leader cells appear to act as centres of influence upon neighbouring potential pigment cells, which subsequently also become pigmented. Lactate inhibited most or all of the steps in formation of pigment epithelium. Between three and five mitoses occur in the production of pigment cells, whereas multilayers and lentoid bodies seem to be formed by expansion of undistinguished cells, probably without mitosis. The observations lead to a general theory that metaplastic conversion between cell types in eye tissues may require the physical isolation of overtly differentiated, multipotent cells from 'leader' cells which normally hold them in physiological subjugation.

Animals↗
PubMedDate not supplied

[The elderly as victims of violent crime].

Up to now, victimology has only dealt with partial aspects of the situation of the elderly as victims of violent crime. Nevertheless, the Police Crime Statistics enable us to make the following three basic statements: In general, old people are less likely to become victims of violent crime (than young people). The acts of violence committed against the elderly are mainly ones in which there was a relationship between offender and victim before the offense. Elderly women are disproportionately more often victims of purse snatching. The increasing social isolation of old people constitutes not only a specific form of victimization, it probably also increases their susceptibility to become victims. The theory that old people have "a particularly pronounced fear of crime" cannot be generally proven. This question must be considered from differing points of view and depends largely on the individual vulnerability of the old people. In Germany, there has hardly been any empirical study of violence towards the elderly in institutions and in family households (so-called domestic violence). It is believed that more violence takes place in both than in generally assumed.

Aged↗
PubMed1980

Medical decisions.

In relation to the application of decision theory to medical problems, a description is given of the terms 'probability', 'utility' and 'coherence'. The use of utilities is illustrated by comparing the outcomes of various methods of palliating terminal renal failure. The use of Bayes' theorem in incorporating additional information is described. Reference is made to specific clinical applications of mathematical methods. Some general comments are made on the way in which clinical and other medical decisions are reached.

Bayes Theorem↗
PubMedDate not supplied

[Transient global amnesia and vascular risk factors].

INTRODUCTION: Transient global amnesia (TGA) is a clinical syndrome determined by an episode of less than 24 hours consisting of temporo-spatial disorientation with retrograde and anterograde amnesia followed by complete recovery. OBJECTIVES: To determine whether the presence or absence of vascular risk factors (VRF) in patients with TGA is associated with different clinical data and/or examination findings. PATIENTS AND METHODS: A retrospective study was made of two groups of 13 and 12 patients with TGA, who presented with and without VRF, respectively. The following variables were determined: VRF, age, a previous history of migraine, triggering factors, duration and repetition of the episodes, associated neurological symptoms and findings obtained by neuroimaging, eco-Doppler of the supra-aortic trunks and transcranial Doppler. The data were subjected to statistical analysis by univariate analysis with Fischer's exact probability test. RESULTS: The statistical studies showed no significant differences between the variables obtained in the two groups of patients. CONCLUSIONS: Transient global amnesia has been particularly related to migraine, epilepsy and cerebral vascular pathology, although its aetiology has not been fully determined. In this study we compare clinical data between the two groups of patients with and without VRF who have had TGA. The lack of significant differences between them tends to rule out a vascular aetiology as the sole cause of this syndrome. Recently Leao's propagated depression has been suggested as the physiopathological mechanism involved. According to this theory, the vascular pathology might act as the trigger but probably not as the aetiological factor. The findings of our study may support this thesis.

Aged↗
PubMed2001

Multidimensional Fechnerian Scaling: Basics.

Fechnerian scaling is a theory of how a certain (Fechnerian) metric can be computed in a continuous stimulus space of arbitrary dimensionality from the shapes of psychometric (discrimination probability) functions taken in small vicinities of stimuli at which these functions reach their minima. This theory is rigorously derived in this paper from three assumptions about psychometric functions: (1) that they are continuous and have single minima around which they increase in all directions; (2) that any two stimulus differences from these minimum points that correspond to equal rises in discrimination probabilities are comeasurable in the small (i.e., asymptotically proportional), with a continuous coefficient of proportionality; and (3) that oppositely directed stimulus differences from a minimum point that correspond to equal rises in discrimination probabilities are equal in the small. A Fechnerian metric derived from these assumptions is an internal (or generalized Finsler) metric whose indicatrices are asymptotically similar to the horizontal cross-sections of the psychometric functions made just above their minima. Copyright 2001 Academic Press.

Journal Article↗
PubMed1975

Epinephrine induced hyperglycemia in bulls and its relationship to polioencephalomalacia.

Data on blood glucose concentration in bulls affected with molasses associated polioencephalomalacia are controversial. It has been suggested that the brain lesions are related to a "hypoglycemic state" during the development of polioencephalomalacia. This paper reports the mobilization of glucose by means of the epinephrine test in three bulls fed two diets, one forage based and the other molasses based. The results showed significantly greater hyperglycemic responses in the animals during the molasses diet than during the forage one. This probably means that glucose stores (as glycogen) are higher in cattle consuming molasses than those consuming forage. Such hepatic glucose output is in disagreement with the hypoglycemia theory as the cause of the early stages of brain lesions and focuses the probable cause as being related to glucose utilization.

Animals↗
PubMedDate not supplied

Culture media and Chaos theory--predicting the unpredictable.

Undefined culture media have played a major role in diagnostic microbiology for 100 years. Chaos theory explains why increased knowledge of microbial systems has failed to predict defined nutritional requirements for the isolation of organisms. A brief description of Chaos theory is given and three microbiological areas of unpredictability are discussed: uncertain identity of isolates, unknown stress damage, unexplored variation of individual colony populations. Probably all living biological systems are non-linear, complex interactions and operate within Chaos theory.

Culture Media↗
PubMed1983

Clinical inferences and decisions--I. Diagnosis and Bayes' theorem.

Clinical decisions are based upon inferences derived from test evidence where data is collected as a means of hypothesis testing. In medicine, the initial expectation of a clinical state is rarely expressed in the classical scientific language of a null hypothesis where alternative outcomes are assumed to be equally probable, because clinical experience reinforces the maxim that common events occur commonly. The collection of test evidence in clinical practice, therefore, is directed towards overturning prior likelihoods for a clinically pathological state which are far from mere chance expectations. The extent to which any test evidence can modify such prior expectations not only depends on its relevance to the clinical state in question (i.e. the hypothesis) but also is largely influenced by the inherent error rates in the test itself. Clinical decision models should reflect these facts. Using examples from the field of ophthalmology, this paper presents a normative model using Bayes' theorem of conditional probabilities which provides a rational framework upon which to base or appraise clinical decisions. Parts II and III of the series will expand this clinical application of decision theory to show how it may be used in the absence of hard test evidence and also where a different emphasis or utility may be placed on false positive or false negative errors.

Bayes Theorem↗
PubMed1993

Human response to traumatic events: an integration of counterfactual thinking, hindsight bias, and attribution theory.

In documenting cognitive processes underlying persons' reactions to negative events, counterfactual thinking, hindsight bias, and attribution theory focus on distinct, although not unrelated, aspects of human information processing. Counterfactual thinking highlights the cognitive processing undertaken when persons imagine different courses of action that lead to alternative outcomes. Hindsight bias describes the inflated retrospective estimates individuals make regarding event probabilities that come with the advantage of knowledge about outcomes. And attribution theory concerns the affective and behavioral consequences that result from the perceived causes of events. This essay argues that a more comprehensive understanding of the processes underlying human response to traumatic events results from the integration of counterfactual thinking, hindsight bias, and attribution theory into a single model.

Adaptation, Psychological↗
PubMed2006

The most likely voltage path and large deviations approximations for integrate-and-fire neurons.

We develop theory and numerical methods for computing the most likely subthreshold voltage path of a noisy integrate-and-fire (IF) neuron, given observations of the neuron's superthreshold spiking activity. This optimal voltage path satisfies a second-order ordinary differential (Euler-Lagrange) equation which may be solved analytically in a number of special cases, and which may be solved numerically in general via a simple "shooting" algorithm. Our results are applicable for both linear and nonlinear subthreshold dynamics, and in certain cases may be extended to correlated subthreshold noise sources. We also show how this optimal voltage may be used to obtain approximations to (1) the likelihood that an IF cell with a given set of parameters was responsible for the observed spike train; and (2) the instantaneous firing rate and interspike interval distribution of a given noisy IF cell. The latter probability approximations are based on the classical Freidlin-Wentzell theory of large deviations principles for stochastic differential equations. We close by comparing this most likely voltage path to the true observed subthreshold voltage trace in a case when intracellular voltage recordings are available in vitro.

Action Potentials↗
PubMed1983

Receiver operating characteristic analysis of diagnostic skill.

In an effort to assess diagnostic skill, the authors collected estimates of the probability of positive results for 392 chest x-rays and 595 throat cultures from 56 pediatricians at different stages in training. Positivity rates were 28.6% for x-rays and 32.9% for throat cultures. The ability to predict the outcome of chest x-rays (pneumonia or not) improved with training on two measures: 1) "calibration," the accuracy of the guessed probability of positivity, and 2) "operating characteristic," the ability to sort patients with negative x-rays from patients with positive x-rays. Improvement was most marked in the ability to predict that a patient with a positive x-ray would have a positive x-ray. For throat culture results, no regular improvement was found with training either in calibration or in operating characteristic. Measurements of calibration and operating characteristic are useful for assessing the effect of training on diagnostic skill.

Clinical Competence↗
PubMed2000

Estimating probabilities of diabetes mellitus using neural networks.

Classification problems are often encountered in medical diagnosis. This paper presents an introduction to classification theory and shows how artificial neural networks can be used for classification. We also map out a bootstrapped procedure for interval estimation of posterior probabilities. The entire procedure is illustrated using the diabetes mellitus data in Pima Indians.

Diabetes Mellitus↗
PubMed1993

Psychological health-sickness (PHS) as a predictor of outcomes in dynamic and other psychotherapies.

This is the first dedicated review of quantitative studies on Sigmund Freud's proposition that the poorer the psychological health, the more limited are the benefits from treatment. Since observer-rated scales for psychological health-sickness were developed in 1949, many studies have applied them, and the majority show significant prediction of outcomes of psychotherapy, with correlations between .2 and .35. This article reviews (a) the main methods of measurement, (b) the record of predictive success, (c) validity studies, (d) the relation to psychiatric diagnosis, (e) prediction in forms of treatment other than psychotherapy, and (e) theories of why psychological health predicts outcomes of psychotherapy.

Humans↗
PubMed2006

Predicting fracture of the femoral neck.

A prediction of the probability of safe loading of the femoral neck, based on queueing theory, is presented. The following methods have been applied: (I) criterion of bone fracture was formulated, taking into consideration the complex state of stress-strain in the porosity zones of the bone; (II) tensile stresses around pores in the stretched zone of the bone were evaluated; (III) the influence of random events of the critical regimes of loading was modeled. The evaluation of the probability of safe loading of bones was obtained based on the levels of the tensile stresses, Young's moduli and ultimate tensile stresses which are affected by the increase in bone porosity and the distribution of the pores. Examples of analysis involving typical mechanical properties of bone in areas of vascular and lacunar-canalicular porosity are demonstrated. The ranges of initial average values of effective Young's moduli and ultimate tensile strengths were taken as 15.8-17.5GPa and 83-95MPa, respectively. The present analysis discovers the existence of three levels of safe loading: (1) a relatively safe level of the nominal tensile stresses (smaller than (2.8-3.2)MPa) where the probability of safe loading is of the order of 0.95 for the bone porosity which is less than 0.15; (2) an intermediate level of safety where the nominal tensile stresses are below (4.2-4.8)MPa and the probability of safe loading is 0.89 or higher, for the same level of bone porosity; (3) a critical level of safe loading where the nominal tensile stresses are about (8.3-9.5)MPa; they lead to sharp drop of probabilities of safe loading to 0.85-0.8 if the porosity is about 0.10 and to probabilities of 0.41-0.4 if the porosity is about 0.15.

Algorithms↗
PubMed1996

Variability of sex ratio, mating probability and egg production in an intestinal nematode in its fluctuating host population.

In dioecious parasites, the chances of co-occurring with the opposite sex depend on the sex ratio, abundance and distribution pattern of parasites within the host population. Theory suggests that if the abundance and degree of aggregation are very low, mating probability may decrease so much that the parasite population is vulnerable to extinction. Our aim is to determine the factors affecting the mating probability and egg production in Heligmosomum mixtum (Heligmosomidae), an intestinal nematode of the bank vole, Clethrionomys glareolus, at Pallasjärvi, Finnish Lapland. We also search for factors responsible for the persistence of H. mixtum in its fluctuating host population. The results showed that during high parasite abundance practically all nematode females co-occurred with males, but during a phase of very low abundance only 15% of females had a chance to mate. Comparison of observed mating probabilities and those predicted by a theoretical model (May & Woolhouse, 1993) showed that deviation from the assumption of complete aggregation between males and females results in underestimation of the mating probability. Sex ratio and the degree of aggregation showed a minor effect on mating probability. The sex ratio (proportion of females) of H. mixtum, which was female-biased (0.58), showed a negative correlation with the mean intensity of infection in the monthly samples (decreasing female-bias at high mean intensity), but no significant relation to the intensity of infection (number of worms in a host individual). The long-term persistence of H. mixtum in its strongly varying host population seems to be due to the high transmission efficiency and long life-span of the parasite.

Animals↗