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PubMed2000

Application of a mixed normal mixture model for the estimation of Mastitis-related parameters.

The current methodology for estimating genetic parameters for SCC (SCS) does not account for the difference in SCS between healthy cows and cows with an intramammary infection (IMI). We propose a two-component finite mixed normal mixture model to estimate IMI prevalence, separate SCS subpopulation means, individual posterior probabilities of IMI, and SCS variance components. The theory is presented and the expectation-conditional maximization algorithm is utilized to compute maximum likelihood estimates. The methodology is illustrated on two simulated data sets based on the current knowledge of SCS parameters. Maximum likelihood estimates of IMI prevalence and SCS subpopulation means were close to simulated values, except for the estimate of IMI prevalence when both subpopulations were almost confounded. Individual posterior probabilities of IMI were always higher among infected than among healthy cows. Error and additive variance components obtained under the mixture model were closer to simulated values than restricted maximum likelihood estimates obtained assuming a homogeneous SCS distribution, especially when subpopulations were completely separated and when mixing proportion was highest. Convergence was linear and rapid when priors were chosen with caution. The advantages of the methodology are demonstrated, and its feasibility for large data sets is discussed.

Algorithms↗
PubMed1996

Binary choice in patients with prefrontal or posterior brain damage. A relative judgement theory analysis.

Binary choice task has been poorly evaluated in patients with focal brain damage. We assessed the decision process in normal subjects and patients with frontal or posterior brain damage using a unimanual two-choice response time (CRT) paradigm. The decision was manipulated by varying the response probability and parameters were analysed with the relative judgement theory. The results suggest that the binary decision process is spared in patients with focal lesions and that their longer CRT is mainly related to slowing the perceptual or motor stages. The prominent role of the left hemisphere in binary choice received support.

Adult↗
PubMed2004

Waves in a reaction-transport system with memory, long-range interactions, and transmutations.

We develop a theory of wave propagation into an unstable state for a system of integral equations with memory, long-range interactions, and transmutations. In particular we use continuous-time random walk theory to describe the transport and transmutation processes. We use a hyperbolic scaling and Hamilton-Jacobi formalism to derive formulas for the speed of propagation of the traveling wave generated by the system in the long-time large-distance limit. Our theory is valid for arbitrary waiting-time, jump-length and, transmutation probability density functions and the propagation speed can generally be found numerically. However, we illustrate our theory by considering an example where analytic results are possible--that is, for a system of Markovian reaction-transport equations. We derive formulas to determine the propagation speed in both the so-called weakly coupled and strongly coupled cases.

Journal Article↗
PubMed1988

On the probability of interaction between elementary radiation-induced chromosomal injuries.

Within the Theory of Dual Radiation Action, the heuristically useful function, gamma(chi), that two energy depositions, a distance chi apart, will result in observable damage can be written in terms of two more fundamental quantities: One, s(chi), describes the structure of the sensitive matrix of the cell. The other, g(chi), describes the probability that two elementary injuries, a distance chi apart, will combine to produce observable damage. A priori, the known enhancement exhibited by gamma(chi) at nanometer separations could be due to an enhancement of s(chi), g(chi) or both. For the endpoint of chromatid exchanges in Chinese hamster cells, gamma(chi) has been evaluated from experimental data and s(chi) from a model system. From these g(chi) has been estimated and is roughly constant below approximately 1 micron, decreasing rapidly at larger separations. Thus the enhanced short-range effect appears to be a function more of the spatial characteristics of the target rather than the probability of damage interaction.

Algorithms↗
PubMed1999

Strength of evidence, judged probability, and choice under uncertainty.

This paper traces, within subjects, the relationship between assessed strength of evidence, judgments of probability, and decisions under uncertainty. The investigation relies on the theoretical framework provided by support theory (Tversky & Koehler, 1994; Rottenstreich & Tversky, 1997), a nonextensional model of judgment under uncertainty. Fans of professional basketball (N = 50) judged the probability that each of eight teams, four divisions, and two conferences would win the National Basketball Association championship. Additionally, participants rated the relative strength of each team, judged the probability that a given team would win the championship assuming a particular pairing in the finals, priced prospects contingent on the winner of the championship, and made choices between chance prospects. The data conformed to the major tenets of support theory, and the predicted relationships between assessed strength of evidence, hypothetical support, judged probabilities, and choices under uncertainty also held quite well.

Adult↗
PubMed1985

More than skin deep: a self-consistency approach to the psychology of cosmetic surgery.

Underlying attitudes about the general self and the specific body part operated on in cosmetic surgery were investigated. It was hypothesized that female cosmetic surgery patients would feel less favorably toward their noses, faces, or breasts than toward their overall self. These marked inconsistencies would cause "normal" individuals to seek practical solutions of enhancing the esteem of the particular body part, to make it consistent with their general view of themselves. Forty female cosmetic surgery patients were tested before and 2 and 4 months after surgery. In all, 12 hypotheses were made within the general self-consistency framework and 11 were upheld at levels ranging from 0.02 to 0.001. Self-consistency theory accurately represents the female cosmetic surgery patient as a normal woman in terms of self-esteem who is attempting to remediate a consciously felt inconsistency between general and specific body-part esteem. Cosmetic surgery seems to reduce this inconsistency.

Adult↗
PubMedDate not supplied

To test or not to test--to treat or not to treat: the decision-threshold approach to patient management.

The inability to consider explicitly factors that should enter into clinical judgment compromises physician efforts to make cost-effective decisions regarding diagnostic testing and treatment. The authors describe the decision-threshold approach, a decision-analysis strategy that helps physicians identify an optimal test-treatment decision based upon the prior probability of disease, the characteristics of the test (sensitivity, specificity, risk), and the benefits/costs of treatment. They also present a microcomputer graphics program that makes the decision-threshold approach readily available to physicians.

Computer Graphics↗
PubMed2005

Inferential structure determination.

Macromolecular structures calculated from nuclear magnetic resonance data are not fully determined by experimental data but depend on subjective choices in data treatment and parameter settings. This makes it difficult to objectively judge the precision of the structures. We used Bayesian inference to derive a probability distribution that represents the unknown structure and its precision. This probability distribution also determines additional unknowns, such as theory parameters, that previously had to be chosen empirically. We implemented this approach by using Markov chain Monte Carlo techniques. Our method provides an objective figure of merit and improves structural quality.

Algorithms↗
PubMed1999

The Effects of Framing, Reflection, Probability, and Payoff on Risk Preference in Choice Tasks.

A meta-analysis of Asian-disease-like studies is presented to identify the factors which determine risk preference. First the confoundings between probability levels, payoffs, and framing conditions are clarified in a task analysis. Then the role of framing, reflection, probability, type, and size of payoff is evaluated in a meta-analysis. It is shown that bidirectional framing effects exist for gains and for losses. Presenting outcomes as gains tends to induce risk aversion, while presenting outcomes as losses tends to induce risk seeking. Risk preference is also shown to depend on the size of the payoffs, on the probability levels, and on the type of good at stake (money/property vs human lives). In general, higher payoffs lead to increasing risk aversion. Higher probabilities lead to increasing risk aversion for gains and to increasing risk seeking for losses. These findings are confirmed by a subsequent empirical test. Shortcomings of existing formal theories, such as prospect theory, cumulative prospect theory, venture theory, and Markowitz's utility theory, are identified. It is shown that it is not probabilities or payoffs, but the framing condition, which explains most variance. These findings are interpreted as showing that no linear combination of formally relevant predictors is sufficient to capture the essence of the framing phenomenon. Copyright 1999 Academic Press.

Journal Article↗
PubMed2003

Skeletal implications of prostate cancer.

This manuscript reviews the theories behind the propensity of prostate cancer to cause bone metastases and skeletal implications of the prostate cancer biology and treatment modalities. The escape of tumor cells from the primary tumor in the prostate to secondary tumor sites in the axial skeleton probably occurs before the primary tumor is detected. Several theories offer explanations for the observed proclivity of prostate tumors to selectively colonize the axial skeleton. The interaction between the tumor cells and cells that populate bone marrow, in particular osteoblasts and osteoclasts, is important for creating a 'fertile' environment where tumor cells can establish and grow. Prostate cancer cells are capable of producing growth factors that can affect both osteoblasts, resulting in osteoblastic bone formation, and osteoclasts, resulting in excessive bone resorption. In addition to the capability to progress from testosterone-dependent to testosterone-independent phenotype, the hallmark of metastatic prostate cancer is osteosclerosis similar to one induced experimentally in nude rats using CWR22 human prostate cancer cell line. Metastatic bone disease caused by excessive bone formation and bone resorption is the major cause of morbidity in patients with prostate cancer. The most common symptoms include pain, pathological fractures, spinal cord compression, cranial nerve palsies, bone marrow suppression and hypercalcemia. The introduction of prostate-specific antigen in clinical practice created a shift to where more prostate cancer patients with early disease receive androgen ablation treatment, which in return causes more bone loss and cancer-associated osteoporosis. Introduction of third generation bisphosphonates to treat skeletal consequences of malignancy further stressed the important interaction between the bone marrow stroma and cancer cells. Nevertheless, animal models and human prostate tumor cell lines that mimic all aspects of skeletal conditions in prostate cancer patients including osteoblastic bone response are needed to develop and screen for novel therapeutic and diagnostic modalities.

Journal Article↗
PubMed2000

Overlapping generations can promote altruistic behavior.

We use an inclusive fitness model to study the evolution of altruism in a patch-structured population in which there is positive probability of breeder survival from one generation to the next. We find first that breeder survival promotes altruism and second that there is a marked difference between benefits of fecundity and benefits of survival. Under the first altruism is more strongly favored, and under the second altruism is less strongly favored than in a randomly mixing population.

Altruism↗
PubMed1995

Reliability of maximum number of simultaneously open channels as an estimator for the number of channels in single-channel recordings.

The single-channel recording technique has revolutionized the electrophysiological study of the ion channels. Interpretation of single-channel recordings often requires the exact number of channels present in a given patch--for example, derivation of the probability of a channel being open--and most theories handling gating kinetics assume that there is only one channel in the patch. Most investigators have estimated the number of channels as the number of maximal simultaneously open channels observed. Although this method is easy to understand and apply, examination of the validity of such estimation has not been much conducted before. As an attempt for such an examination, we have applied computer simulation method in order to obtain practically useful aids in judging the reliability of such estimates. Results show that (i) large estimated values (for example, larger than 10) are likely to be incorrect, and (ii) when the estimated value is small and the derived probability of a channel being open is within a certain range, the estimated number of channels is most likely to be correct.

Animals↗
PubMed1989

[Event related brain potentials and signal detection: decision confidence and signal probability].

This paper is concerned with the relation of two components of the late positive complex, P300 and slow wave, to parameters of signal detection theory. In the first experiment, basically a replication of Squires et al., signal probability was 50% and a six point rating scale was used for subjects' answers. Whereas for the P300 the well known relation to subjective confidence (and thus to response criteria) was confirmed, a similar relation could not be found for the slow wave. In the second experiment the local signal probability was varied from 25% to 75% on a trial to trial basis. Under these conditions neither the P300 nor the slow wave exhibited a relation to signal-probability, whilst the relation to decision-confidence was preserved.

Adult↗
PubMed1996

Jungian metapsychology and neurobiological theory.

This paper deals with brain research and depth psychology. Because brain research is becoming significantly more sophisticated and increasingly able to assay the neurobiology of subjective (i.e., mental) events in vivo, it is suggested that any school of depth psychology will probably not survive as a mainstream treatment modality if its theory and practice is found to be in frank variance with the findings of the modern neurosciences. Jung's psychology is compared to Freud's and shown to be reasonably consonant with such findings. Historical highlights of Jung's non-reductive way of conceptualizing and working are presented and put in the context of more recent scientifically defensible concepts (emergence, supervenience, complexity theory) from the fields of both philosophy of science and philosophy of mind. These concepts postulate a hierarchical model of reality which permits an exploration of the mind/brain relationship without resorting to reductionism or dualism. A sense of the present struggle is conveyed between the proponents of these and more traditional scientific concepts. Finally, the nature of mind/brain confluence is elucidated by examples from the areas of learning, memory and the capacity to symbolize in order to illustrate how clinical practices and observations familiar to experience depth therapists and also in agreement with Jungian theory are compatible with neuroscientific findings. A research suggestion is offered.

Brain↗
PubMed2002

Universality of small scale turbulence.

The proposed universality of small scale turbulence is investigated for a set of measurements in a cryogenic free jet with a variation of the Reynolds number (Re) from 8500 to 10(6) (max(R(lambda) approximately 1200). The traditional analysis of the statistics of velocity increments by means of structure functions or probability density functions is replaced by a new method which is based on the theory of Markov processes. It gives access to a more complete characterization by means of joint probabilities of finding velocity increments at several scales. Based on this more comprehensive method, our results are very far from a possible universal state, even for R(lambda) above 1000.

Journal Article↗