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At least 883 records · Page 49Linked to original sources

A trivariate distribution for the height, weight, and fat of adult men.

Using exploratory data analysis, probability plots, scatterplots, and computer animations to rotate and visualize the data, we fit a trivariate Normal distribution to data for the height, the natural logarithm of body weight, and the body fat for 646 men between the ages of 50 and 80 years as reported by the medical staff of the U.S. Veterans Administration's "Normative Aging Study" in Boston, MA. Although these data do not include any children, women, or young men, the measurements represent the best data that we could find through a 4-year search. We believe that these data are well measured and reliable for men in the specified age range and that these data reveal an interesting statistical pattern for use in probabilistic PBPK models.

Adipose Tissue↗

Coding of temporal information by activity-dependent synapses.

Synaptic transmission in the neocortex is dynamic, such that the magnitude of the postsynaptic response changes with the history of the presynaptic activity. Therefore each response carries information about the temporal structure of the preceding presynaptic input spike train. We quantitatively analyze the information about previous interspike intervals, contained in single responses of dynamic synapses, using methods from information theory applied to experimentally based deterministic and probabilistic phenomenological models of depressing and facilitating synapses. We show that for any given dynamic synapse, there exists an optimal frequency of presynaptic spike firing for which the information content is maximal; simple relations between this optimal frequency and the synaptic parameters are derived. Depressing neocortical synapses are optimized for coding temporal information at low firing rates of 0.5-5 Hz, typical to the spontaneous activity of cortical neurons, and carry significant information about the timing of up to four preceding presynaptic spikes. Facilitating synapses, however, are optimized to code information at higher presynaptic rates of 9-70 Hz and can represent the timing of over eight presynaptic spikes.

Action Potentials↗

Potential impact of a targeted cardiopulmonary resuscitation program for older adults on survival from private-residence cardiac arrest.

OBJECTIVE: Traditional cardiopulmonary resuscitation (CPR) training programs do not target older adults who are most likely to witness private-residence cardiac arrests and do not reliably result in a bystander who is likely to perform CPR in the event of an arrest. This study was performed to compare targeted CPR training programs for older adults (older than 50 years) that 1) increase numbers of CPR-trained bystanders of private-residence cardiac arrest or 2) increase the percentage of trained bystanders of private-residence cardiac arrest who perform CPR. A simultaneous outcome was to estimate the minimal significant survival benefit associated with each of the training programs. METHODS: A probabilistic simulation model was developed in Fortran95 that incorporated key out-of-hospital cardiac arrest elements, including witnessed arrests, CPR-trained witness, CPR provision, and impact of CPR on ventricular fibrillation. Input data were derived from published or publicly available data, including a large prospective cohort study of outcomes in Oakland County, MI. Monte Carlo simulation (n = 10,000) and sensitivity analyses (n = 40) were used to assess median and the empiric 95% confidence intervals [CIs] for incremental survival with either intervention. RESULTS: The baseline model, calibrated to the characteristics of the input-data community, established that, for private-residence cardiac arrests, 40.8% of cardiac arrest bystanders were trained in CPR; however, only 25.7% performed CPR. This yielded 4.81% survival (95% CI = 4.72 to 4.89). Modeling the impact on the baseline training level with increased CPR performance among trainees indicated that 75% of private-residence trained bystanders would need to perform CPR in order to reach a minimally significant improvement in survival (5.02%; 95% CI = 4.94 to 5.15). Similarly, targeted CPR training that would result in a significant survival benefit (to 5.01%; 95% CI = 4.93 to 5.09) would require that 70.8% of bystanders be trained. CONCLUSIONS: CPR training programs that focus on yielding 75% of trainees who perform CPR in the event of witnessing an arrest would have equivalent results to mass CPR training programs that result in 70% of bystanders being trained in CPR. However, the minimal survival benefit associated with these programs (around 0.2%) may prove either method costly with minimal effect.

Aged↗

Enhancing text categorization with semantic-enriched representation and training data augmentation.

OBJECTIVE: Acquiring and representing biomedical knowledge is an increasingly important component of contemporary bioinformatics. A critical step of the process is to identify and retrieve relevant documents among the vast volume of modern biomedical literature efficiently. In the real world, many information retrieval tasks are difficult because of high data dimensionality and the lack of annotated examples to train a retrieval algorithm. Under such a scenario, the performance of information retrieval algorithms is often unsatisfactory, therefore improvements are needed. DESIGN: We studied two approaches that enhance the text categorization performance on sparse and high data dimensionality: (1) semantic-preserving dimension reduction by representing text with semantic-enriched features; and (2) augmenting training data with semi-supervised learning. A probabilistic topic model was applied to extract major semantic topics from a corpus of text of interest. The representation of documents was projected from the high-dimensional vocabulary space onto a semantic topic space with reduced dimensionality. A semi-supervised learning algorithm based on graph theory was applied to identify potential positive training cases, which were further used to augment training data. The effects of data transformation and augmentation on text categorization by support vector machine (SVM) were evaluated. RESULTS AND CONCLUSION: Semantic-enriched data transformation and the pseudo-positive-cases augmented training data enhance the efficiency and performance of text categorization by SVM.

Algorithms↗

Coding of the contrasts in natural images by visual cortex (V1) neurons: a Bayesian approach.

Individual V1 neurons respond dynamically over only limited ranges of stimulus contrasts, yet we can discriminate contrasts over a wide range. Different V1 neurons cover different parts of the contrast range, and the information they provide must be pooled somehow. We describe a probabilistic pooling model that shows that populations of neurons with contrast responses like those in cat and monkey V1 would most accurately code contrasts in the range actually found in natural scenes. The pooling equation is similar to Bayes's equation; however, explicit inclusion of prior probabilities in the inference increases coding accuracy only slightly.

Animals↗

Probing intra- versus interchain kinetic preferences of L-Thr acylation on dimeric VibF with mass spectrometry.

We present a method to probe intra- and interchain activities within dimeric nonribosomal peptide synthetases. Utilizing domain inactivation and analytical mass mutants in conjunction with rapid-quench, mass spectrometry, and a probabilistic kinetic model, we have elucidated the pre-steady-state intra- and interchain rates and the corresponding flux of the acylation of L-Thr onto VibF. Although the intra rate is significantly faster than the inter rate, the data are most consistent with an even flux of covalent substrate loading where neither pathway dominates. These pre-steady-state results confirm previous steady-state in vitro mutant complementation studies of VibF. Extension of this methodology to other dimeric nonribosomal peptide synthetases, and to the related fatty acid and polyketide synthases, will further our biophysical understanding of their acyl-intermediate-processing pathways.

Acylation↗

Quasi-dynamic choice models: Melioration and ratio invariance.

There is continuing controversy about the behavioral process or processes that underlie the major regularities of free-operant choice such as molar matching and systematic deviations therefrom. A recent interchange between Vaughan and Silberberg and Ziriax concerned the relative merits of melioration, and a computer simulation of molecular maximizing. There are difficulties in evaluating theories expressed as computer programs because many arbitrary decisions must often be made in order to get the programs to operate. I therefore propose an alternative form of model that I term quasi-dynamic as a useful intermediate form of theory appropriate to our current state of knowledge about free-operant choice. Quasi-dynamic models resemble the game-theoretic analyses now commonplace in biology in that they can predict stable and unstable equilibria but not dynamic properties such as learning curves. It is possible to interpret melioration as a quasi-dynamic model. An alternative quasi-dynamic model for probabilistic choice, ratio invariance, has been proposed by Horner and Staddon. The present paper compares the predictions of melioration and ratio invariance for five experimental situations: concurrent variable-interval variable-interval schedules, concurrent variable-interval variable-ratio schedules, the two-armed bandit (concurrent random-ratio schedules), and two types of frequency-dependent schedule. Neither approach easily explains all the data, but ratio invariance seems to provide a better picture of pigeons' response to probabilistic choice procedures. Ratio invariance is also more adaptive (less susceptible to "traps") and closer to the original expression of the law of effect than pure hill-climbing processes such as momentary maximizing and melioration, although such processes may come in to play on more complex procedures that provide opportunities for temporal discrimination.

Journal Article↗

A probabilistic approach to high throughput drug discovery.

A methodology is presented in which high throughput screening experimental data are used to construct a probabilistic QSAR model which is subsequently used to select building blocks for a virtual combinatorial library. The methodology is based upon statistical probability estimation and not regression. The methodology is applied to the construction of two focused virtual combinatorial libraries: one for cyclic GMP phosphodiesterase type V inhibitors and one for acyl-CoA:cholesterol O-acyltransferase inhibitors. The results suggest that the methodology is capable of selecting combinatorial substituents that lead to active compounds starting with binary (pass/fail) activity measurements.

3',5'-Cyclic-GMP Phosphodiesterases↗

Optimizing the herd calving pattern with linear programming and dynamic probabilistic simulation.

Until recently, little attention has been paid to the influence of seasonal variation in performance and prices on the optimal calving pattern of a herd. A method was developed to determine the herd calving pattern that is farm-specific and optimal with use of linear programming. The required technical and economic parameters are calculated with a dynamic probabilistic simulation model of the dairy herd. The approach was illustrated with a situation in which the objective was to maximize the gross margin of the herd and the annual milk production of the herd was restricted, resulting in an optimal calving pattern: all heifers calved during August. When, in addition, only home-reared replacement heifers were allowed to enter the herd, heifer calvings took place from July to October. The gross margin was reduced by only Dfl. .13/100 kg of milk ($1 US = 1.80 Dfl.) as a result of the additional constraint. The sensitivity of the optimal calving pattern of herd was determined for lower reproductive performance and when seasonal price variation was ignored. The method described herein is a flexible tool for determining the optimal calving pattern of herd, taking into account farm-specific inputs and constraints.

Animal Feed↗

A systematic review and economic evaluation of magnetic resonance cholangiopancreatography compared with diagnostic endoscopic retrograde cholangiopancreatography.

OBJECTIVES: To compare the clinical and cost-effectiveness of magnetic resonance cholangiopancreatography (MRCP) with diagnostic endoscopic retrograde cholangiopancreatography (ERCP) for the investigation of biliary obstruction. DATA SOURCES: Electronic bibliographic databases, the reference lists of relevant articles and various health services research-related resources. REVIEW METHODS: The data sources were searched and selected studies were assessed using quality criteria. In total, 28 prospective diagnostic studies were identified reporting several suspected conditions plus one of patient satisfaction. Analyses were then performed to establish sensitivities, specificities, likelihood ratios and confidence intervals. The relative cost-effectiveness of adopting MRCP scanning in the investigation of the biliary tree was undertaken using a probabilistic economic model. RESULTS: The median sensitivity for choledocholithiasis (13 studies) was 93% and the median specificity 94%. The median likelihood ratio for a positive value was 15.75 and for a negative value 0.08. Reported sensitivities for malignancy were somewhat lower, ranging from 81 to 86%, and specificities ranged from 92 to 100%. There was some evidence that MRCP is an accurate diagnostic test in comparison to ERCP, although the quality of studies was moderate. Claustrophobia prevented at least some patients from having MRCP in ten of the 28 studies. The other 18 studies did not mention claustrophobia. The probability of avoiding unnecessary diagnostic ERCP is estimated at 30%. These patients could avoid the unnecessary risk of complications and death associated with diagnostic ERCP, and substantial cost saving would be gained. The overall expected cost saving associated with MRCP is GBP149; the overall expected gain in quality-adjusted life-year is estimated at 0.011. CONCLUSIONS: There is some evidence that MRCP is an accurate investigation compared with diagnostic ERCP, although the values for malignancy compared with choledocholithiasis were somewhat lower. The quality of studies was moderate. The limited evidence on patient satisfaction showed that patients preferred MRCP to diagnostic ERCP. The estimated clinical and economic impacts of diagnostic MRCP versus diagnostic ERCP are very favourable. The baseline estimate is that MRCP may both reduce cost and result in improved quality of life outcomes compared with diagnostic ERCP. Further research is suggested to compare MRCP and diagnostic ERCP with final diagnosis and also with the full range of target conditions; to examine patient satisfaction and ways of reducing problems with claustrophobia; to look at protocols to help identify who could most benefit from MRCP or ERCP; to assess the relative need and urgency of patient access to magnetic resonance imaging services, and also to determine how demand would affect availability and potential cost savings.

Cholangiopancreatography, Endoscopic Retrograde↗

A probabilistic approach to improved antibiotic therapy.

PTA is a decision-theoretic expert system that aims to assist clinicians in diagnosing and treating patients with pneumonia in the intensive care unit. Its underlying probabilistic network model includes knowledge for diagnosing pneumonia on the basis of the likelihood of tracheobronchial-tree colonisation by pathogens, and symptoms and signs actually present in the patient. Optimal antibiotic therapy is selected by balancing the expected efficacy of treatment, which is related to the likelihood of pathogen-specific pneumonias, against costs and side effects of treatment. In this article, the model underlying the system and results of a preliminary evaluation are described.

Anti-Bacterial Agents↗

Objectivity in psychosocial measurement: what, why, how.

This article raises and tries to answer questions concerning what objectivity in psychosocial measurement is, why it is important, and how it can be achieved. Following in the tradition of the Socratic art of maiuetics, objectivity is characterized by the separation of meaning from the geometric, metaphoric, or numeric figure carrying it, allowing an ideal and abstract entity to take on a life of its own. Examples of objective entities start from anything teachable and learnable, but for the purposes of measurement, the meter, gram, volt, and liter are paradigmatic because of their generalizability across observers, instruments, laboratories, samples, applications, etc. Objectivity is important because it is only through it that distinct conceptual entities are meaningfully distinguished. Seen from another angle, objectivity is important because it defines the conditions of the possibility of shared meaning and community. Full objectivity in psychosocial measurement can be achieved only by attending to both its methodological and its social aspects. The methodological aspect has recently achieved some notice in psychosocial measurement, especially in the form of Rasch's probabilistic conjoint models. Objectivity's social aspect has only recently been noticed by historians of science, and has not yet been systematically incorporated in any psychosocial science. An approach to achieving full objectivity in psychosocial measurement is adapted from the ASTM Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method (ASTM Committee E-11 on Statistical Methods, 1992).

Data Interpretation, Statistical↗

Lifetime cost of HIV care in France during the era of highly active antiretroviral therapy.

OBJECTIVE: To estimate the treatment and health care costs of HIV infection or AIDS in France during the era of highly active antiretroviral therapy (HAART). DESIGN: We used a clinical database of HIV-infected patients to calculate the resource use and cost of care for different stages of HIV infection. Costs were incorporated into a computer-based, probabilistic simulation model of the natural history and treatment of HIV infection to estimate the lifetime cost of treating patients with HIV disease. SETTING: A northern France HIV clinical cohort. PARTICIPANTS: 1232 HIV-infected patients followed from January 1994 through July 1998. RESULTS: In the absence of an AIDS-defining event, the average total cost of care ranged from 670 euros (1 euro=US $1.19) per person-month in the highest CD4 stratum (>500/microl) to 1060 euros per person-month in the lowest CD4 stratum (< or = 50/microl). The mean cost of care was estimated at 3370 euros per person-month during the initial months around the occurrence of an AIDS-defining event; at 1750 euros per person-month during the period spanning from 2 months after the diagnosis of specific AIDS-defining event to 1 month prior to death; and at 13010 euros per person-month in the final month prior to death. If clinical management of HIV infection began at a CD4 cell count of 378/microl, as in this cohort, the discounted lifetime cost of treating an HIV-infected French patient was estimated at 214000 euros. The undiscounted costs were 309000 euros over a projected life expectancy of 16.4 years. CONCLUSION: The cost of HIV disease varies widely depending upon the stage of illness. These estimates of stage-specific and lifetime costs of HIV care will assist health policy planners in assessing the burden of disease in the era of HAART and projecting future resource requirements.

Adult↗

Lifetime health effects and costs of diabetes treatment.

BACKGROUND: This article presents cost-effectiveness analyses of the major diabetes interventions as formulated in the revised Dutch guidelines for diabetes type 2 patients in primary and secondary care. The analyses consider two types of care: diabetes control and the treatment of complications, each at current care level and according to the guidelines. METHODS: A validated probabilistic diabetes model describes diabetes and its complications over a lifetime in the Dutch population, computing quality-adjusted life years and medical costs. Effectiveness data and costs of diabetes interventions are from observational current care studies and intensive care experiments. Lifetime consequences of in total sixteen intervention mixes are compared with a baseline glycaemic control of 10% HBA1C. RESULTS: The interventions may reduce the cumulative incidence of blindness, lower-extremity amputation, and end-stage renal disease by >70% in primary care and >60% in secondary care. All primary care guidelines together add 0.8 quality-adjusted life years per lifetime. CONCLUSION: In case of few resources, treating complications according to guidelines yields the most health benefits. Current care of diabetes complications is inefficient. If there are sufficient resources, countries may implement all guidelines, also on diabetes control, and improve efficiency in diabetes care.

Cost-Benefit Analysis↗

[Clinical and functional course of occupational asthma in pharmacologic treatment and during persistent exposure. A 3-year follow-up].

According to act 626/1994, employers have the duty to inform and train workers and their representatives. The implementation of training activities requires the following points: planning the training progra according to the needs of the target population, use of the methods aimed at promoting learning and the adoption of safe behaviour, setting-up of evaluation tools. The disciplines of risk perception and communication and adult training may provide useful contribution in this frame. At the light of the preliminary experiences in this field, the importance of the following items for workers, workers representatives and employers is emphasized: probabilistic causality models, role of cognitive and emotional factors in the learning process, definition of carcinogenic according to national and internationals organisation, meaning of TLV with respect to carcinogenic exposure, interaction between carcinogens in the case of multiple exposition, risk evaluation, preventive measures, transfer of carcinogen risk from workplace to domestic environment, due to lack of compliance with basic hygienic rules such proper use of work clothes.

Asthma↗

[Occupational asthma and rhinitis caused by colophony among linoleum production workers].

According to act 626/1994, employers have the duty to inform and train workers and their representatives. The implementation of training activities requires the following points: planning the training progra according to the needs of the target population, use of the methods aimed at promoting learning and the adoption of safe behaviour, setting-up of evaluation tools. The disciplines of risk perception and communication and adult training may provide useful contribution in this frame. At the light of the preliminary experiences in this field, the importance of the following items for workers, workers representatives and employers is emphasized; probabilistic causality models, role of cognitive and emotional factors in the learning process, definition of carcinogenic according to national and internationals organisation, meaning of TLV with respect to carcinogenic exposure, interaction between carcinogens in the case of multiple exposition, risk evaluation, preventive measures, transfer of carcinogen risk from workplace to domestic environment, due to lack of compliance with basic hygienic rules such proper use of work clothes.

Adult↗

[Part-time work at a hospital: study of atypical workers].

According to act 626/1994, employers have the duty to inform and train workers and their representatives. The implementation of training activities requires the following points: planning the training progra according to the needs of the target population, use of the methods aimed at promoting learning and the adoption of safe behaviour, setting-up of evaluation tools. The disciplines of risk perception and communication and adult training may provide useful contribution in this frame. At the light of the preliminary experiences in this field, the importance of the following items for workers, workers representatives and employers is emphasized: probabilistic causality models, role of cognitive and emotional factors in the learning process, definition of carcinogenic according to national and internationals organisation, meaning of TLV with respect to carcinogenic exposure, interaction between carcinogens in the case of multiple exposition, risk evaluation, preventive measures, transfer of carcinogen risk from workplace to domestic environment, due to lack of compliance with basic hygienic rules such proper use of work clothes.

Adult↗

Computer simulation of pathogen transmission in the medical intensive care unit: a comparison of two probabilistic methods.

The quantitative evaluation of pathogen transmission in the medical intensive care unit (MICU) is difficult given the small number of patients and the complexity and severity of illness. We sought to evaluate the suitability of a probabilistic computer model of our MICU, with which we could rapidly simulate infection control measures and other clinical interventions that would be impossible to perform in the real clinical setting

Computer Simulation↗