scholarly journals A new look at multi-stage models of cancer incidence

2018 ◽  
Author(s):  
Tyler Lian ◽  
Rick Durrett

AbstractMulti-stage models have long been used in combination with SEER data to make inferences about the mechanisms underlying cancer initiation. The main method for studying these models mathematically has been the computation of generating functions by solving hyperbolic partial differential equations. Here, we analyze these models using a probabilistic approach similar to the one Durrett and Moseley [7] used to study branching process models of cancer. This more intuitive approach leads to simpler formulas and new insights into the behavior of these models. Unfortunately, the examples we consider suggest that fitting multi-stage models has very little power to make inferences about the number of stages unless parameters are constrained to take on realistic values.

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 532
Author(s):  
A Jo ◽  
Myeong Jeong ◽  
Sang Lee ◽  
Young Moon ◽  
Sun Hwang

A multi-stage cold forging process was developed and complemented with finite element analysis (FEA) to manufacture a high-strength one-body input shaft with a long length body and no separate parts. FEA showed that the one-body input shaft was manufactured without any defects or fractures. Experiments, such as tensile, hardness, torsion, and fatigue tests, and microstructural characterization, were performed to compare the properties of the input shaft produced by the proposed method with those produced using the machining process. The ultimate tensile strength showed a 50% increase and the torque showed a 100 Nm increase, confirming that the input shaft manufactured using the proposed process is superior to that processed using the machining process. Thus, this study provides a proof-of-concept for the design and development of a multi-stage cold forging process to manufacture a one-body input shaft with improved mechanical properties and material recovery rate.


1974 ◽  
Vol 11 (3) ◽  
pp. 458-470 ◽  
Author(s):  
Howard J. Weiner

In a multitype critical age dependent branching process with immigration, the numbers of cell types born by t, divided by t2, tends in law to a one-dimensional (degenerate) law whose Laplace transform is explicitily given. The method of proof makes a correspondence between the moments in the m-dimensional case and the one-dimensional case, for which the corresponding limit theorem is known. Other applications are given, a possible relaxation of moment assumptions, and extensions are indicated.


1986 ◽  
Vol 23 (02) ◽  
pp. 283-296 ◽  
Author(s):  
Peter Donnelly

A general exchangeable model is introduced to study gene survival in populations whose size changes without density dependence. Necessary and sufficient conditions for the occurrence of fixation (that is the proportion of one of the types tending to 1 with probability 1) are obtained. These are then applied to the Wright–Fisher model, the Moran model, and conditioned branching-process models. For the Wright–Fisher model it is shown that certain fixation is equivalent to certain extinction of one of the types, but that this is not the case for the Moran model.


2018 ◽  
Vol 48 (10) ◽  
pp. 2459-2482 ◽  
Author(s):  
Hoa Pham ◽  
Darfiana Nur ◽  
Huong T. T. Pham ◽  
Alan Branford

2019 ◽  
Vol 65 (3) ◽  
pp. 197-203
Author(s):  
Olga Yu. Rebrova

Development of de novo clinical guidelines (CG) is a complex process that requires highly qualified personnel, an extended amount of time (from 1 to 3 years), and, consequently, substantial funding. In many countries there are limits to these resources, and so, as an alternative to the development of actual de novo CG, the expert community has developed simplified ways of preparing CG: adoption and adaptation. Adoption is the easiest option – it is simply translation of clinical guidelines developed by a credible foreign professional association into the native language. In this case, of course, translated guidelines should be attributed accurately as a translation, without claiming additional authorship by a local professional association. It may be stated that the local professional organization has discussed and approved the translated document. It is also possible to post comments. Another way – adaptation – is to adjust the CG, developed in one country, to the conditions and features of the healthcare system in another country. Adaptation is fundamentally more difficult than adoption. An adaptation procedure has been developed by ADAPTE, an international group of experts. Their detailed procedure, complete with commentaries, is freely available. The key stage of the multi-stage adaptation procedure is the assessment of the methodological quality of the adapted CG using the AGREE II questionnaire or its simplified version, AGREE GRS. An assessment of the relevance, consistency, acceptability and applicability of the CG is also performed. In situations of a pronounced shortage of resources, adoption of the CG is preferable, while under less constrained conditions – adaptation of the CG. Development of de novo CG in the context of an unlimited exchange of information seems inappropriate and unnecessarily costly. The compromise is an adaptation that serves, on the one hand, to significantly save various types of resources, and, on the other, to promote the methodology of evidence-based medicine in the national medical community.


Author(s):  
Sven Feja ◽  
Sören Witt ◽  
Andreas Speck

Business process models (BPM) are widely used for specification of software systems, as the basis for model driven software development. Hence, it is crucial to ensure that these BPMs fulfill the requirements they have to comply with. These requirements may originate from various domains. Many may be considered non-functional requirements. They are affecting privacy, security, as well as compliance or economic aspects. In order to avoid error-prone manual checking, automated checking techniques should be applied wherever possible. This requires expressing requirements in a formal manner. The common textual representations for such formal requirements are not well accepted in the modeling domain, since they are settled on a lower level of abstraction, compared to BPMs. In this chapter, the authors present the Business Application Modeler (BAM), which integrates formal requirement specification and automated checking with process modeling. On the one hand BAM supports different notations for process modeling. On the other hand a graphical notation, called G-CTL, for the formal specification of requirements is provided. G-CTL is based on temporal logic, and statements are expressed on the level of abstraction of the graphical process models. Furthermore BAM provides the ability to define selective views on process models. This allows complex domain specific annotations of processes as well as the assignment of responsibilities regarding functional domains. Moreover, BAM integrates into common requirements engineering processes.


Author(s):  
Angel L. Meroño-Cerdan ◽  
Pedro Soto-Acosta ◽  
Carolina Lopez-Nicolas

This study seeks to assess the impact of collaborative technologies on innovation at the firm level. Collaborative technologies’ influence on innovation is considered here as a multi-stage process that starts at adoption and extends to use. Thus, the effect of collaborative technologies on innovation is examined not only directly, the simple presence of collaborative technologies, but also based on actual collaborative technologies’ use. Given the fact that firms can use this technology for different purposes, collaborative technologies’ use is measured according to three orientations: e-information, e-communication and e-workflow. To achieve these objectives, a research model is developed for assessing, on the one hand, the impact of the adoption and use of collaborative technologies on innovation and, on the other hand, the relationship between adoption and use of collaborative technologies. The research model is tested using a dataset of 310 Spanish SMEs. The results showed that collaborative technologies’ adoption is positively related to innovation. Also, as hypothesized, distinct collaborative technologies were found to be associated to different uses. In addition, the study found that while e-information had a positive and significant impact on innovation, e-communication and e-workflow did not.


2020 ◽  
Vol 12 (1) ◽  
pp. 1-19
Author(s):  
Mostefai Abdelkader ◽  
Ignacio García Rodríguez de Guzmán

This paper formulates the process model matching problem as an optimization problem and presents a heuristic approach based on genetic algorithms for computing a good enough alignment. An alignment is a set of not overlapping correspondences (i.e., pairs) between two process models(i.e., BP) and each correspondence is a pair of two sets of activities that represent the same behavior. The first set belongs to a source BP and the second set to a target BP. The proposed approach computes the solution by searching, over all possible alignments, the one that maximizes the intra-pairs cohesion while minimizing inter-pairs coupling. Cohesion of pairs and coupling between them is assessed using a proposed heuristic that combines syntactic and semantic similarity metrics. The proposed approach was evaluated on three well-known datasets. The results of the experiment showed that the approach has the potential to match business process models effectively.


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