Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Probability Theory”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 973 records · Page 54Linked to original sources

A descriptive analysis of 10 years of research published in the Journal of Health Communication.

This article describes the contents of the articles from the first decade of The Journal of Health Communication (JOHC). Three hundred and twenty-one published articles were reviewed and coded to determine the characteristics of the researchers, the types of research presented, the common health topics covered, and the research designs used. The results led to the following profile of a typical article. Its primary author is a U.S. academic. It probably focuses on smoking, HIV/AIDS, or cancer. It is an empirical research study, more likely to use quantitative, specifically survey methods, rather than qualitative methods. It probably is not driven by theory. It is much more likely to examine mass media communication than interpersonal communication. Its purpose is just as likely to be audience analysis as message design, as evaluation of a planned communication intervention. If its purpose is to evaluate a planned communication intervention however, that intervention is almost certainly a successful one.

Bibliometrics↗

Approach to Gaussian stochastic behavior for systems driven by deterministic chaotic forces.

We consider skew-product dynamical systems that describe the stroboscopic dynamics of a damped particle subjected to a chaotic kick force. In a suitable scaling limit the dynamics converges to the Ornstein-Uhlenbeck process. We investigate the deterministic chaotic corrections in the vicinity of this Gaussian limit case for various examples of chaotic forces. We present numerical evidence that, for certain classes of chaotic forces, the deterministic chaotic corrections of the invariant density are universal. We provide analytical results for forces generated by Tchebyscheff maps and sketch a renormalization group theory in the space of probability densities.

Journal Article↗

Statistics of transmitted power in multichannel dissipative ergodic structures.

We use the random matrix theory (RMT) to study the probability distribution function and moments of the wave power transmitted inside systems with ergodic wave motion. The results describe either open multichannel systems or their closed counterparts with local-in-space internal dissipation. We concentrate on the regime of broken time-reversal invariance and employ two different analytical approaches: the exact supersymmetry method and a simpler technique that uses RMT eigenstatistics for closed nondissipative systems as an input. The results of the supersymmetric method were confirmed by numerical simulation. The simpler method is found to be adequate for closed systems with uniform dissipation, or in the limit of a large number of weak local dampers.

Journal Article↗

Logarithmic corrections in directed percolation.

We study directed percolation at the upper critical transverse dimension d=4, where critical fluctuations induce logarithmic corrections to the leading (mean-field) behavior. Viewing directed percolation as a kinetic process, we address the following properties of directed percolation clusters: the mass (the number of active sites or particles), the radius of gyration, and the survival probability. Using renormalized dynamical field theory, we determine the leading and the next to leading logarithmic corrections for these quantities. In addition, we calculate the logarithmic corrections to the equation of state that describes the stationary homogeneous particle density in the presence of a homogeneous particle source.

Journal Article↗

Spin noise spectroscopy in GaAs.

We observe the noise spectrum of electron spins in bulk GaAs by Faraday-rotation noise spectroscopy. The experimental technique enables the undisturbed measurement of the electron-spin dynamics in semiconductors. We measure exemplarily the electron-spin relaxation time and the electron Landé g factor in -doped GaAs at low temperatures and find good agreement of the measured noise spectrum with a theory based on Poisson distribution probability.

Journal Article↗

Binary halftone image resolution increasing by decision tree learning.

This paper presents a new, accurate, and efficient technique to increase the spatial resolution of binary halftone images. It makes use of a machine learning process to automatically design a zoom operator starting from pairs of input-output sample images. To accurately zoom a halftone image, a large window and large sample images are required. Unfortunately, in this case, the execution time required by most of the previous techniques may be prohibitive. The new solution overcomes this difficulty by using decision tree (DT) learning. Original DT learning is modified to obtain a more efficient technique (WZDT learning). It is useful to know, a priori, sample complexity (the number of training samples needed to obtain, with probability 1 - delta, an operator with accuracy epsilon): we use the probably approximately correct (PAC) learning theory to compute the sample complexity. Since the PAC theory usually yields an overestimated sample complexity, statistical estimation is used to evaluate, a posteriori, a tight error bound. Statistical estimation is also used to choose an appropriate window and to show that DT learning has good inductive bias. The new technique is more accurate than a zooming method based on simple inverse halftoning techniques. The quality of the proposed solution is very close to the theoretical optimal obtainable quality for a neighborhood-based zooming process using the Hamming distance to quantify the error.

Algorithms↗

Recursive noisy OR--a rule for estimating complex probabilistic interactions.

This paper focuses on approaches that address the intractability of knowledge acquisition of conditional probability tables in causal or Bayesian belief networks. We state a rule that we term the "recursive noisy OR" (RNOR) which allows combinations of dependent causes to be entered and later used for estimating the probability of an effect. In the development of this paper, we investigate the axiomatic correctness and semantic meaning of this rule and show that the recursive noisy OR is a generalization of the well-known noisy OR. We introduce the concept of positive causality and demonstrate its utility in axiomatic correctness of the RNOR. We also introduce concepts describing the ways in which dependent causes can work together as being either "synergistic" or "interfering." We provide a formalization to quantify these concepts and show that they are preserved by the RNOR. Finally, we present a method for the determination of Conditional Probability Tables from this causal theory.

Algorithms↗

The robustness of the "binormal" assumptions used in fitting ROC curves.

The binormal form is the most common model used to formally fit ROC curves to the data from signal detection studies that employ the "rating" method. The author lists a number of justifications that have been offered for this choice, ranging from theoretical considerations of probability laws and signal detection theory, to mathematical tractability and convenience, to empirical results showing that "it fits!" To these justifications is added another, namely that even if an alternative formulation based on another underlying form (e.g., power law) or model (e.g., binomial, Poisson, or gamma type distributions) were in fact correct, the binormal fit differs so little from the true form as to be of no practical consequence. Moreover, the small lack of fit is unlikely to be demonstrated in practice: it is obscured by the much larger variation that can be attributed to sampling of cases. In addition, even if a very large sample of cases could be studied, the small number of rating categories used does not permit seemingly very different models to be distinguished from one another.

Mathematical Computing↗

Accurate sensitivity in optically preamplified direct detection.

We present a novel model for calculating the bit error rate in optical communication systems in the case of on-off keying intensity modulation and optically preamplified direct detection. The model accounts for the intersymbol interference and is based on the Laguerre photon-count probability distribution predicted by photodetection theory. For a non-return-to-zero modulation format an accurate value of the sensitivity for a quantum-limited receiver of 33.9 photons/bit is obtained.

Journal Article↗

Recent developments in the psychobiology and pharmacotherapy of depression: optimising existing treatments and novel approaches for the future.

Effective antidepressants include monoamine oxidase inhibitors and tricyclic antidepressants, selective serotonin re-uptake inhibitors and novel agents, including serotonin and noradrenaline re-uptake inhibitors. Although effective, current treatments most often produce partial symptomatic improvement (response) rather than symptom resolution and optimal functioning (remission). While current pharmacotherapies target monoaminergic systems, different symptoms of major depressive disorder (MDD) may have distinct neurobiological underpinnings and other neurobiological systems are likely involved in the pathogenesis of MDD. In this article a review of current pharmacotherapeutic options for MDD, current understanding of the neurobiology and pathogenesis of MDD and a review of new and promising directions in pharmacological research will be provided. It is generally accepted that no single neurotransmitter or system is responsible for the dysregulation found in MDD. While agents that affect monoaminergic systems will likely continue to be first-line treatments for MDD for the foreseeable future, a number of new and novel agents, including corticotropin-releasing factor antagonists, substance P antagonists and antiglucocorticoids show considerable promise for refining treatment options. In order to better understand the neurobiology and treatment response of MDD, it is probable that more sophisticated theory-driven typologies of MDD will have to be developed.

Animals↗

Electrical stimulation: current concepts and indications.

The use of electrical stimulation in fracture management is increasing. Electrical stimulation has been found to offer a reasonable means of treatment for nonunions that have failed to respond to previous bone grafting over an extended period of time. The effective use of electrical stimulation devices requires an understanding of the various principles and concepts employed by the four types of stimulators currently available. While the exact mechanism of electrically-induced osteogenesis is uncertain, current theories indicate that several factors probably are involved and more than one mechanism may be responsible. There are significant differences in the clinical applications of the various types of electrical stimulators. Whether these differences are significant from a practical standpoint remains to be seen.

Animals↗

[Kos and Knidos].

The authors review the evidence concerning the antagonism between Cos and Cnidus and the alleged differences between their medical theories. They conclude that, most probably, the theoretical differences were negligible and the antagonism limited to professional competition between two groups of physicians sharing a common medical paradigm.

Greece, Ancient↗

Anomalous origin of the left coronary artery from the right pulmonary artery.

A previously unknown coronary artery anomaly is reported: origin of the left coronary artery from the right pulmonary artery. This unusual anomaly can probably be explained by the theory of dual embryonic development of the coronary arteries from angioblastic buds in the truncus arteriosus. It is thought that these buds anastomose with a capillary network that is developing on the surface of the ventricles. Complete repair of this lesion with restoration of a two-coronary artery system was accomplished in a 10-month-old baby. The coronary artery was detached from the pulmonary artery, with a button of pulmonary artery being retained around the coronary artery ostium. Direct systemic arterial flow to the left coronary artery was established by anastomosis of the left coronary to the right subclavian artery.

Coronary Vessel Anomalies↗

Selecting the sample for a research study.

Sample selection is a very important but sometimes underestimated part of a research study. Sampling theory describes two sampling domains: probability and nonprobability. Probability samples contain some type of randomization and consist of simple, stratified, systematic, cluster, and sequential types. Nonprobability samples lack randomization and consist of convenience or accidental, purposive, quota, volunteer, and expert types. The primary distinction between the two domains is that the probability sampling study findings can be generalized to the target population while the nonprobability sampling study findings can only be generalized to the institution where the sample was studied.

Humans↗

Interpretation of pathophysiology by laboratory data (3). A consultation program based on clinical laboratory data.

Based on previous studies, a consultation program using clinical laboratory data has been constructed. After converting all data into the standard deviation index (SDI), the score for preregistered diseases was calculated by integrating products of SDI and the weighting factors (WF) pre-determined empirically by medical experts for each item. Ten diseases in order of their maximum scores, the most predictable ones, and additional comments were printed out. The principle of our consultation program is based on the modified Bayesian theory which employs, instead of probability a posteriori, weighting factors (WF) corresponding to the grade of membership in the "fuzzy set" concept. Evaluations based on this interpretation performed 2-3 times during the clinical course in nine patients were found to agree qualitatively with each clinical course and diagnosis. This report also contains 1) an outline of the progress of this consultation program in Japan and abroad, 2) the actual level of acceptance of this system by physicians, 3) and the characteristics and problems of our program. We are now planning to report a quantitative evaluation of this program using many cases in some specified field, instead of one case of each disease.

Clinical Laboratory Techniques↗

Approximate interval estimation of the ratio of binomial parameters: a review and corrections for skewness.

Various methods for finding confidence intervals for the ratio of binomial parameters are reviewed and evaluated numerically. It is found that the method based on likelihood scores (Koopman, 1984, Biometrics 40, 513-517; Miettinen and Nurminen, 1985, Statistics in Medicine 4, 213-226) performs best in achieving the nominal confidence coefficient, but it may distribute the tail probabilities quite disparately. Using general theory of Bartlett (1953, Biometrika 40, 306-317; 1955, Biometrika 42, 201-203), we correct this method for asymptotic skewness. Following Gart (1985, Biometrika 72, 673-677), we extend this correction to the case of estimating the common ratio in a series of two-by-two tables. Computing algorithms are given and applied to numerical examples. Parallel methods for the odds ratio and the ratio of Poisson parameters are noted.

Algorithms↗

Adrenergic receptors and gastric secretion in dogs. Is a "tonic balance" relationship between vagal and beta 2-adrenergic activity a possibility?

The relative influence of adrenergic receptors on gastric acid secretion in the dog stomach with different vagal activity or "tone" is almost unknown. beta-adrenoceptors seem to be most important for the direct effect of adrenergic stimulation on acid secretion. In this study the effects of vagotomy and beta 2-adrenoceptor activity were studied in conscious gastric fistula dogs. Pentagastrin stimulated acid output was increased slightly in non-vagotomized dogs and to its prevagotomy level in vagotomized dogs after propranolol infusion. Practolol showed no such effect. Histamine stimulated acid secretion was not influenced significantly by beta-blockade. Similar dose-response curves were found for non-vagotomized dogs with high beta 2-adrenergic tone and dogs with low vagal tone (vagotomy) after pentagastrin and histamine stimulated acid secretion. This study indicates that a counterbalance between beta 2-adrenergic and cholinergic vagal tone exists. A "tonic balance theory" is suggested and is probably involved in the resulting acid secretion after vagotomy.

Adrenergic beta-Antagonists↗

[Congenital mesoblastic nephroma. Study of five cases and review of the literature (author's transl)].

Mesoblastic nephroma (individualized by Bolande in 1967) is a congenital renal tumor sometimes locally and regionally aggressive but never giving metastases, in contrast with nephroblastoma. It almost always occurs in the newborn. Therefore, every renal tumor discovered before twelve months must evoke mesoblastic nephroma. No preoperative adjuvant treatment must be used in infants under six months old. Considering five personal observations and review of literature, the authors expose the main etiologic and clinical characteristics of the disease, the gross and microscopic features which allow its diagnosis and the histogenetic theories of this curious lesion, probably border-line between neoplasias and dysplasias of renal parenchyma.

Child, Preschool↗