scholarly journals Development of a dynamic interactive web tool to enhance understanding of multi-state model analyses: MSMplus

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Nikolaos Skourlis ◽  
Michael J. Crowther ◽  
Therese M-L. Andersson ◽  
Paul C. Lambert
Keyword(s):  
Complex Disease ◽  
Transition Probabilities ◽  
R Package ◽  
State Model ◽  
Web Tool ◽  
Transition Intensity ◽  
Web Tools ◽  
State Models ◽  
Disease Pathways ◽  
Meaningful Communication

Abstract Background Multi-state models are used in complex disease pathways to describe a process where an individual moves from one state to the next, taking into account competing states during each transition. In a multi-state setting, there are various measures to be estimated that are of great epidemiological importance. However, increased complexity of the multi-state setting and predictions over time for individuals with different covariate patterns may lead to increased difficulty in communicating the estimated measures. The need for easy and meaningful communication of the analysis results motivated the development of a web tool to address these issues. Results MSMplus is a publicly available web tool, developed via the Shiny R package, with the aim of enhancing the understanding of multi-state model analyses results. The results from any multi-state model analysis are uploaded to the application in a pre-specified format. Through a variety of user-tailored interactive graphs, the application contributes to an improvement in communication, reporting and interpretation of multi-state analysis results as well as comparison between different approaches. The predicted measures that can be supported by MSMplus include, among others, the transition probabilities, the transition intensity rates, the length of stay in each state, the probability of ever visiting a state and user defined measures. Representation of differences, ratios and confidence intervals of the aforementioned measures are also supported. MSMplus is a useful tool that enhances communication and understanding of multi-state model analyses results. Conclusions Further use and development of web tools should be encouraged in the future as a means to communicate scientific research.

scholarly journals Development of a dynamic interactive web tool to enhance understanding of multi-state model analyses: MSMplus

2021 ◽  
Author(s):  
Nikolaos Skourlis ◽  
Michael J. Crowther ◽  
Therese M-L. Andersson ◽  
Paul C. Lambert
Keyword(s):  
Complex Disease ◽  
Transition Probabilities ◽  
State Model ◽  
Web Tool ◽  
Transition Intensity ◽  
Web Tools ◽  
State Models ◽  
Disease Pathways ◽  
Over Time ◽  
Meaningful Communication

Abstract Background: Multi-state models are used in complex disease pathways to describe a process where an individual moves from one state to the next, taking into account competing states during each transition. In a multi-state setting, there are various measures to be estimated that are of great epidemiological importance. However, increased complexity of the multi-state setting and predictions over time for individuals with different covariate patterns may lead to increased difficulty in communicating the estimated measures. The need for easy and meaningful communication of the analysis results motivated the development of a web tool to address these issues. Results: MSMplus is a publicly available web tool, developed in RShiny, with the aim of enhancing the understanding of multi-state model analyses results. The results from any multi-state model analysis are uploaded to the application in a pre-specified format. Through a variety of user-tailored interactive graphs, the application contributes to an improvement in communication, reporting and interpretation of multi-state analysis results as well as comparison between different approaches. The predicted measures that can be supported by MSMplus include, among others, the transition probabilities, the transition intensity rates, the length of stay in each state, the probability of ever visiting a state and user defined measures. Representation of differences, ratios and confidence intervals of the aforementioned measures are also supported. MSMplus is a useful tool that enhances communication and understanding of multi-state model analyses results. Conclusions: Further use and development of web tools should be encouraged in the future as a means to communicate scientific research.

scholarly journals webSalvador, a Web Tool for the Luria-Delbrük Experiment

2021 ◽  
Vol 10 (20) ◽  
Author(s):  
Qi Zheng
Keyword(s):  
User Interface ◽  
R Package ◽  
Web Tool ◽  
R Language ◽  
Web Tools ◽  
Fluctuation Experiment ◽  
Mutation Research

ABSTRACT Existing Web tools for the Luria-Delbrück fluctuation experiment do not offer many desirable capabilities that are vital to mutation research. webSalvador offers these capabilities via a user interface that allows researchers to access most of the functions in the R package rSalvador without having to learn the R language.

scholarly journals Developmental State and Ethnic Federalism in Ethiopia:

2019 ◽  
Vol 3 (1) ◽  
pp. 95-127
Author(s):  
Zekarias Beshah Abebe
Keyword(s):  
Cultural Diversity ◽  
Economic Restructuring ◽  
Developmental State ◽  
The Other ◽  
State Model ◽  
Ethnic Federalism ◽  
State Models ◽  
Liberal Approach ◽  
The Right

The ethnic federalization of the post-1991 Ethiopia and the subsequent adoption of developmental state paradigm are the two most important pillars for the country’s political and economic restructuring. An interventionist developmental state model is opted for against the dominant narrative of the non-interventionist neo-liberal approach as the right path to conquer poverty: a source of national humiliation. On the other hand, ethnically federated Ethiopia is considered as an antidote to the historical pervasive mismanagement of the ethno-linguistic and cultural diversity of the polity. The presence of these seemingly paradoxical state models in Ethiopia makes it a captivating case study for analysis. Ethiopia’s experiment of pursuing a developmental state in a decentralized form of governance not only deviates from the prevalent pattern but also is perceived to be inherently incompatible due to the competing approaches that characterize the two systems. This article argues that the way in which the developmental state is being practiced in Ethiopia is eroding the values and the very purposes of ethnic federalism. Its centralized, elitist and authoritarian nature, which are the hallmark of the Ethiopian developmental state, defeats the positive strides that ethnic federalism aspires to achieve, thereby causing discontent and disenfranchisement among a swathe of the society. The article posits that the developmental state can and should be reinvented in a manner that goes in harmony with the ideals of ethnic federalism. The notion of process-based leadership remains one way of reinventing the Ethiopian developmental state model.  

scholarly journals Forecasting the Long-Run Behavior of the Stock Price of Some Selected Companies in the Malaysian Construction Sector: A Markov Chain Approach

2020 ◽  
Vol 5 (2) ◽  
pp. 296-308
Author(s):  
Wajeeh Mustafa Sarsour ◽  
Shamsul Rijal Muhammad Sabri
Keyword(s):  
Markov Model ◽  
Stock Prices ◽  
Stock Price ◽  
Transition Probabilities ◽  
Return Time ◽  
Price Increase ◽  
State Model ◽  
Construction Sector ◽  
Long Run ◽  
Three State Model

The fluctuations in stock prices produce a high risk that makes investors uncertain about their investment decisions. The present paper provides a methodology to forecast the long-term behavior of five randomly selected equities operating in the Malaysian construction sector. The method used in this study involves Markov chains as a stochastic analysis, assuming that the price changes have the proparty of Markov dependency with their transition probabilities. We identified a three-state Markov model (i.e., increase, stable, fall) and a two-state Markov model (i.e., increase and fall). The findings suggested that the chains had limiting distributions. The mean return time was computed for respective equities as well as to determine the average duration to return to a stock price increase. The analysis might aid investors in improving their investment knowledge, and they will be able to make better decisions when an equity portfolio possesses higher transition probabilities, higher limiting distribution, and lowest mean return time in response to a price increase. Finally, our investigations suggest that investors are more likely to invest in the GKent based on the three-state model, while VIZIONE seems to be a better investment choice based on a two-state model.

scholarly journals THE IMPORTANCE OF MAINTAINING PHYSICAL ACTIVITY FOR TRANSITIONS BETWEEN COGNITIVE STATES: A COORDINATED ANALYSIS

2019 ◽  
Vol 3 (Supplement_1) ◽  
pp. S911-S911
Author(s):  
Tomiko Yoneda ◽  
Jonathan Rush ◽  
Nathan A Lewis ◽  
Jamie E Knight ◽  
Jinshil Hyun ◽  
...  
Keyword(s):  
Physical Activity ◽  
Life Expectancy ◽  
Transition Probabilities ◽  
Cognitive Changes ◽  
Total N ◽  
Older Adulthood ◽  
Cognitive States ◽  
Total Life Expectancy ◽  
State Models ◽  
The Impact

Abstract Although existing research shows that physical activity (PA) protects against cognitive decline, it is unclear if maintenance of PA throughout older adulthood influences the timing of onset or transitions through cognitive states. Further understanding of modifiable lifestyle factors that protect against cognitive changes characteristic of both normal aging and pathological aging, such as Alzheimer’s disease and other dementias, is imperative. Data were drawn from fourteen longitudinal studies of aging from Europe and America (total N=53,069). Controlling for demographics and chronic conditions, multi-state models were independently fit between datasets to investigate the impact of PA (computed based on Metabolic Equivalent of Task Method) on the likelihood of transitioning through three cognitive states, while also accounting for death as a competing risk factor. Random effects meta-analysis of transition probabilities indicated that more PA was associated with a reduced risk of transitioning from normal cognition to mildly impaired cognition (HR=0.90, CI’s=0.84, 0.97, p=0.007) and death (HR=0.24, CI’s=0.06, 0.92, p=0.04), as well as an increased likelihood of transitioning from severe impairment back to mild impairment (HR=1.09, CI’s=1.01, 1.17, p=0.03). Engagement in national minimum recommendations for PA (~150 minutes/week) increased total life expectancy for 70 year old males and females by 4.08 and 5.47 years, respectively. These results suggest that engaging in at least 150 minutes of physical activity per week in older adulthood contributes to delays in onset of mild cognitive impairment, substantially increases life expectancy, and may also diminish the symptoms that contribute to poor cognitive performance at the severely impaired stage.

scholarly journals Calculation of LTC Premiums Based on Direct Estimates of Transition Probabilities

2005 ◽  
Vol 35 (2) ◽  
pp. 455-469 ◽  
Author(s):  
Florian Helms ◽  
Claudia Czado ◽  
Susanne Gschlößl
Keyword(s):  
Life History ◽  
Generalized Estimating Equations ◽  
Transition Matrix ◽  
Transition Probabilities ◽  
State Model ◽  
Link Function ◽  
History Of ◽  
The Relationship ◽  
Pseudo Values ◽  
Almost Unbiased

In this paper we model the life-history of LTC-patients using a Markovian multi-state model in order to calculate premiums for a given LTC-plan. Instead of estimating the transition intensities in this model we use the approach suggested by Andersen et al. (2003) for a direct estimation of the transition probabilities. Based on the Aalen-Johansen estimator, an almost unbiased estimator for the transition matrix of a Markovian multi-state model, we calculate so-called pseudo-values, known from Jackknife methods. Further, we assume that the relationship between these pseudo-values and the covariates of our data are given by a GLM with the logit as link-function. Since the GLMs do not allow for correlation between successive observations we use instead the “Generalized Estimating Equations” (GEEs) to estimate the parameters of our regression model. The approach is illustrated using a representative sample from a German LTC portfolio.

scholarly journals A hybrid landmark Aalen-Johansen estimator for transition probabilities in partially non-Markov multi-state models

2021 ◽  
Author(s):  
Niklas Maltzahn ◽  
Rune Hoff ◽  
Odd O. Aalen ◽  
Ingrid S. Mehlum ◽  
Hein Putter ◽  
...  
Keyword(s):  
Statistical Power ◽  
Transition Probabilities ◽  
Real Data ◽  
Testing Procedure ◽  
Data Application ◽  
Stratification Method ◽  
Model Complex ◽  
Markov Assumption ◽  
State Models ◽  
Disability Education

AbstractMulti-state models are increasingly being used to model complex epidemiological and clinical outcomes over time. It is common to assume that the models are Markov, but the assumption can often be unrealistic. The Markov assumption is seldomly checked and violations can lead to biased estimation of many parameters of interest. This is a well known problem for the standard Aalen-Johansen estimator of transition probabilities and several alternative estimators, not relying on the Markov assumption, have been suggested. A particularly simple approach known as landmarking have resulted in the Landmark-Aalen-Johansen estimator. Since landmarking is a stratification method a disadvantage of landmarking is data reduction, leading to a loss of power. This is problematic for “less traveled” transitions, and undesirable when such transitions indeed exhibit Markov behaviour. Introducing the concept of partially non-Markov multi-state models, we suggest a hybrid landmark Aalen-Johansen estimator for transition probabilities. We also show how non-Markov transitions can be identified using a testing procedure. The proposed estimator is a compromise between regular Aalen-Johansen and landmark estimation, using transition specific landmarking, and can drastically improve statistical power. We show that the proposed estimator is consistent, but that the traditional variance estimator can underestimate the variance of both the hybrid and landmark estimator. Bootstrapping is therefore recommended. The methods are compared in a simulation study and in a real data application using registry data to model individual transitions for a birth cohort of 184 951 Norwegian men between states of sick leave, disability, education, work and unemployment.

scholarly journals Stakeholder participation and the use of web technology for MPA management

2013 ◽  
Vol 4 (2) ◽  
pp. 260 ◽  
Author(s):  
Markantonatou Vasiliki ◽  
Manuel Meidinger ◽  
Marcello Sano ◽  
Eleni Oikonomou ◽  
Giuseppe Di Carlo ◽  
...  
Keyword(s):  
Marine Protected Areas ◽  
Stakeholder Participation ◽  
Web Technology ◽  
Web Tool ◽  
Community Based ◽  
Web Tools ◽  
New Information ◽  
Wide Range ◽  
High Quality Information ◽  
Stakeholder Preferences

Stakeholder participation has received increased attention as a key process for enhancing mitigation of conflicts between different interests for the same resources and transparent decision-making in marine protected areas (MPAs). A wide range of advanced web tools is available nowadays that integrate stakeholder participation by generating new information and allow interaction between actors in MPA management. However, such technologies are frequently used without much consideration regarding the complexity of the decision to be made and the heterogeneity of stakeholder preferences and understanding in order to be related to these technologies. In order to understand how technology corresponds to the changing needs of MPA management, we have reviewed a range of different participation strategies adopted by web technology, based on a set of criteria that define a successful participation approach. We start from simple towards more sophisticated tools that have been developed worldwide in order to better inform decisions, and contribute to more effective and efficient MPA management. Finally, we draw a theoretical framework for the development of a community-based web tool with the capacity to incorporate the philosophy of stakeholder participation by generating new and high quality information flow for effective MPA management.

Estimating the magnitude of carcinogenic effects in long-term animal studies

1995 ◽  
Vol 14 (8) ◽  
pp. 643-653
Author(s):  
N. Stallard ◽  
A. Whitehead
Keyword(s):  
Conventional Method ◽  
Animal Studies ◽  
Mortality Rates ◽  
State Model ◽  
Carcinogenic Effects ◽  
State Models ◽  
Peto Test ◽  
Modelling Approach

Carcinogenicity studies seek to compare the incidence of tumours in animals exposed to the substance under inves tigation and animals used as controls. The conventional method of analysis is the Peto test, which assumes that tumours are either instantly fatal or have no effect on mor tality and requires a judgement to be made regarding the lethality of each tumour. Such an assumption seems unre alistic and the judgement is often difficult to make and unreliable. The need for such a judgement and the assumption of extreme lethality can be removed by using parametric multi-state models. In this modelling approach the transition of animals between the states 'alive without a tumour', 'alive with a tumour' and 'dead' is modelled mathematically. This paper compares the Peto test with tests based on two parametric multi-state models in terms of the sensitiv ity of the tests to detect carcinogenicity. The sensitivity, or power, is shown to be low for commonly used numbers of animals, depending chiefly on the expected total number of animals with tumours. The Omar and Whitehead multi state model is found to be slightly more powerful than the Dewanji et al. model and at least as powerful as the Peto test. Provided the parametric assumptions are appropri ate, this method thus gives a test that is more sensitive than the Peto test and enables estimation of tumour onset and mortality rates without the requirement of tumour lethality judgements.

scholarly journals Activation and inactivation of single calcium channels in snail neurons.

1984 ◽  
Vol 83 (5) ◽  
pp. 751-769 ◽  
Author(s):  
A M Brown ◽  
H D Lux ◽  
D L Wilson
Keyword(s):  
Waiting Time ◽  
Single Channel ◽  
Waiting Times ◽  
State Model ◽  
Ca Channel ◽  
Snail Neurons ◽  
Channel Opening ◽  
Three State Model ◽  
State Models ◽  
Ca Currents

Activation and inactivation properties of Ca currents were investigated by studying the behavior of single Ca channels in snail neurons. The methods described in the previous paper were used. In addition, a zero-phase digital filter has been incorporated to improve the analysis of latencies to first opening, or waiting times. It was found that a decrease in the probability of single channel opening occurred with time. This was especially marked at 29 degrees C and paralleled the inactivation observed in macroscopic currents. The fact that a single channel was observed means that there is a significant amount of reopening from the "inactivated" state. Small depolarizations at 18 degrees C showed little inactivation. From these measurements, histograms of single channel open, closed, and waiting times were analyzed to estimate the rate constants of a three-state model of activation. Two serious discrepancies with the model were found. First, waiting time distributions at -20 mV were slower than those predicted by parameters obtained from an analysis of the single channel closed times. Second, it was shown that the time and the magnitude of the peak of the waiting time histogram were inconsistent with a three-state model. It is concluded that a minimum of four states are involved in activation. Some four-state models may be eliminated from further consideration. However, a comprehensive model of Ca channel kinetics must await further measurements.

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