Bayesian analysis of capture-recapture model and diagnostic test in clinical trials

2014 ◽  
Author(s):  
◽  
Dan Zheng
Keyword(s):  
Clinical Trials ◽  
Simulation Study ◽  
Behavioral Response ◽  
Bayesian Method ◽  
Original Method ◽  
Potential Bias ◽  
The Em Algorithm ◽  
Em Method ◽  
Capture Recapture ◽  
Simulation Results

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] Capture-recapture models have been widely used to estimate the size of a target wildlife population. There are three major sources of variations that can affect capture probabilities: time (i.e., capture probabilities vary with time or trapping occasion), behavioral response (i.e., capture probabilities vary due to a trap response of animals to the first capture), and heterogeneity (i.e., capture probabilities vary by individual animal). There are eight models regarding possible combinations of these factors, including M0, Mt, Mb, Mh, Mtb, Mth, Mbh, and Mtbh. A capture-recapture model (Mb model) was created to present the behavioral response effect. The objective Bayesian analysis for the population size was developed and compared with common maximum likelihood estimates (MLEs). Simulation results demonstrate the advantages of the objective Bayesian over MLEs. Two real examples about a deer mouse are presented and one R package (OBMbpkg) was built for application. Companion diagnostics (CDx) for personalized medicine is commonly applied to in vitro diagnostic (IVD) industry and clinical trials for specific disease or treatment with biomarkers (e.g. molecular targets). The Bayesian method with Gibbs sampler was used to estimate the potential bias caused by imperfect CDx under the targeted design, where only patients with a positive diagnosis were enrolled the clinical trials. A simulation study was conducted to evaluate the performance of the Bayesian method and to compare with the EM algorithm. The Bayesian model selection method with G-prior was used to test treatment effects of targeted drugs for patients with biomarkers under the targeted design. A simulation study was conducted to evaluate the performance of the Bayesian method and to compare it with the original method and EM method when sample size is small. Eventually a biomarker-stratified design was studied, while patients enrolled in clinical trials could be divided into two groups (i.e., those with a positive or negative diagnosis). Both the EM algorithm and Bayesian method were used to estimate the potential bias caused by imperfect CDx. Simulation results demonstrate the advantages of the Bayesian method over the original method and EM method.

scholarly journals Treatment for mitochondrial diseases

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Tongling Liufu ◽  
Zhaoxia Wang
Keyword(s):  
Clinical Trials ◽  
Nuclear Dna ◽  
Mitochondrial Diseases ◽  
Cochrane Collaboration ◽  
Potential Bias ◽  
Leber Hereditary Optic Neuropathy ◽  
Pharmacological Agents ◽  
Unpublished Studies ◽  
New Treatment ◽  
Allotopic Expression

AbstractMitochondrial diseases are predominantly caused by mutations of mitochondrial or nuclear DNA, resulting in multisystem defects. Current treatments are largely supportive, and the disorders progress relentlessly. Nutritional supplements, pharmacological agents and physical therapies have been used in different clinical trials, but the efficacy of these interventions need to be further evaluated. Several recent reviews discussed some of the interventions but ignored bias in those trials. This review was conducted to discover new studies and grade the original studies for potential bias with revised Cochrane Collaboration guidelines. We focused on seven published studies and three unpublished studies; eight of these studies showed improvement in outcome measurements. In particular, two of the interventions have been tested in studies with strict design, which we believe deserve further clinical trials with a large sample. Additionally, allotopic expression of the ND4 subunit seemed to be an effective new treatment for patients with Leber hereditary optic neuropathy.

All standard materials flat reflector made by transformation electromagnetics

2014 ◽  
Vol 6 (2) ◽  
pp. 201-206 ◽  
Author(s):  
Mark Clemente Arenas ◽  
Anne Claire Lepage ◽  
Xavier Begaud ◽  
Paul Henri Tichit ◽  
André de Lustrac
Keyword(s):  
Design Methodology ◽  
Dielectric Material ◽  
Dielectric Materials ◽  
Original Method ◽  
Classical Solutions ◽  
Radiation Characteristics ◽  
Mathematical Relation ◽  
Simulation Results ◽  
Half Power ◽  
Realistic Structure

In this paper, the design methodology of a flat reflector composed with standard dielectric material and using transformation electromagnetics (TE) is presented. First, the mathematical relation between a flat reflector and a parabolic one is described. The TE principle is then described. Some realization issues are highlighted, leading to approximations and compromises in order to design a more realistic structure. In this way, a flat reflector made only with standard dielectric materials is presented, using an original method to achieve the desired spatial permittivity variation. The simulation results of different configurations for the flat reflector are presented and compared to classical solutions in order to prove the thickness reduction and the improvement of radiation characteristics in terms of gain and half-power beamwidth.

Underestimation of treatment effects in sequentially monitored clinical trials that did not stop early for benefit

2018 ◽  
Vol 28 (10-11) ◽  
pp. 3027-3041 ◽  
Author(s):  
Ian C Marschner ◽  
I Manjula Schou
Keyword(s):  
Clinical Trial ◽  
Clinical Trials ◽  
Treatment Effect ◽  
Interim Analysis ◽  
Experimental Treatment ◽  
Final Analysis ◽  
Effect Estimate ◽  
Effectiveness Analysis ◽  
Simulation Results ◽  
Meta Analyses

In recent years, there has been a prominent discussion in the literature about the potential for overestimation of the treatment effect when a clinical trial stops at an interim analysis due to the experimental treatment showing a benefit over the control. However, there has been much less attention paid to the converse issue, namely, that sequentially monitored clinical trials which did not stop early for benefit tend to underestimate the treatment effect. In meta-analyses of many studies, these two sources of bias will tend to balance each other to produce an unbiased estimate of the treatment effect. However, for the interpretation of a single study in isolation, underestimation due to interim analysis may be an important consideration. In this paper, we discuss the nature of this underestimation, including theoretical and simulation results demonstrating that it can be substantial in some contexts. Furthermore, we show how a conditional approach to estimation, in which we condition on the study reaching its final analysis, may be used to validly inflate the observed treatment difference from a sequentially monitored clinical trial. Expressions for the conditional bias and information are derived, and these are used in supplied R code that computes the bias-adjusted estimate and an associated confidence interval. As well as simulation results demonstrating the validity of the methods, we present a data analysis example from a pivotal clinical trial in cardiovascular disease. The methods will be most useful when an unbiased treatment effect estimate is critical, such as in cost-effectiveness analysis or risk prediction.

scholarly journals Performance Analysis of a Grid-Connected Rooftop Solar Photovoltaic System

Electronics ◽  
2019 ◽  
Vol 8 (8) ◽  
pp. 905 ◽  
Author(s):  
Akpolat ◽  
Dursun ◽  
Kuzucuoğlu ◽  
Yang ◽  
Blaabjerg ◽  
...  
Keyword(s):  
Performance Analysis ◽  
Simulation Study ◽  
Alternative Energy ◽  
Sunshine Duration ◽  
Clean Energy ◽  
Photovoltaic System ◽  
Solar Photovoltaic ◽  
Pv System ◽  
Simulation Results ◽  
Rooftop Solar

Turkey is among the countries largely dependent on energy import. This dependency has increased interest in new and alternative energy sources. Installation of rooftop solar photovoltaic systems (RSPSs) in Turkey is increasing continuously regarding geographical and meteorological conditions. This paper presents an insight into the potential situation for Turkey and a simulation study for the RSPS designing and calculation for the faculty building at Marmara University in Istanbul. This simulation study demonstrates that 84.75-kWp grid-connected RSPS can produce remarkable power. The system is performed in detail with the PV*SOL software (Premium 2017 R8 - Test Version, Valentin Software GmbH, Berlin, Germany). Detailed financial and performance analysis of the grid-connected RSPS for faculty building with various parameters is also carried out in this study. According to the simulation results, the system supplies 13.2% of the faculty buildings’ annual electrical energy consumption. The annual savings value of faculty buildings’ electrical consumption is approximately 90,298 kWh energy which costs roughly $7296. A photovoltaic (PV) system installation for the faculty building, which has considerable potential for solar energy and sunshine duration, is indispensable for clean energy requirements and was supported by the simulation results. This paper can be considered to be a basic feasibility study prior to moving on to the implementation project.

Foraging efficiency of a predator flock for randomly moving prey: A simulation study

2016 ◽  
Vol 30 (09) ◽  
pp. 1650135
Author(s):  
Sang-Hee Lee ◽  
Ohsung Kwon
Keyword(s):  
Foraging Behavior ◽  
Simulation Study ◽  
Food Resources ◽  
Foraging Efficiency ◽  
Prey Detection ◽  
Time Step ◽  
Detection Ability ◽  
Simulation Results ◽  
Flocking Behavior ◽  
Iteration Time

Flocking behavior of animals is highly advantageous for taking food resources. The degree of the advantage is related to the ability of flock members to detect their prey and the mobility of prey individuals. In this study, to explore the relation, we constructed a model to simulate a predator flock and its randomly moving prey. The predator members have the prey detection ability, which was characterized as sensing distance, [Formula: see text], and a sensing angle, [Formula: see text]. The mobility of the prey individuals was characterized as the maximum traveling distance of an iteration time step, [Formula: see text]. The relative flock foraging efficiency, [Formula: see text], was defined as [Formula: see text]. [Formula: see text] and [Formula: see text] represent the spent time for the flock to eat all prey individuals and to uptake the last remaining 10% prey, respectively. Simulation results showed that [Formula: see text] increased, maximized, and decreased with the increase of [Formula: see text], regardless of [Formula: see text]. As the number of prey, [Formula: see text], increased, the tendency of the increasing and decreasing was diluted. The result was briefly discussed in relation to the flock foraging behavior and the development of the model toward applications for real ecosystems.

Simulation Study of the Hydraulic System of Concrete Pumping Truck Based on AMESim

2012 ◽  
Vol 170-173 ◽  
pp. 1920-1925
Author(s):  
Chang Ge Fan ◽  
Fa Lin Zeng ◽  
De Hua Li ◽  
Lei Liu
Keyword(s):  
Simulation Study ◽  
Hydraulic System ◽  
Hydraulic Cylinder ◽  
Hydraulic Shock ◽  
Buffer Effect ◽  
Concrete Pumping ◽  
Working Principle ◽  
Simulation Results ◽  
The Relationship ◽  
Buffer Structure

The working principle of concrete pumping hydraulic system was analyzed. And base on the AMESim software, the complete simulation model of concrete pumping hydraulic system was built. A simulation was made to get the dynamic characteristics curve of hydraulic cylinder velocity and displacement at some specific conditions. The simulation results indicate that the model is reasonable. Comparative simulations of the pumping hydraulic system with different positions of buffer structure were carried out to study the relationship between buffer effect and the buffer position which can be used to provide theory basis for deeper study of the hydraulic shock.

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