Background and study aims: Early neoplasia in Barrett's esophagus is difficult to detect and often overlooked during Barrett's surveillance. An automatic detection system could be beneficial, by assisting endo...
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Background and study aims: Early neoplasia in Barrett's esophagus is difficult to detect and often overlooked during Barrett's surveillance. An automatic detection system could be beneficial, by assisting endoscopists with detection of early neoplastic lesions. The aim of this study was to assess the feasibility of a computer system to detect early neoplasia in Barrett's esophagus. Patients and methods: Based on 100 images from 44 patients with Barrett's esophagus, a computer algorithm, which employed specific texture, color filters, and machine learning, was developed for the detection of early neoplastic lesions in Barrett's esophagus. The evaluation by one endoscopist, who extensively imaged and endoscopically removed all early neoplastic lesions and was not blinded to the histological outcome, was considered the gold standard. For external validation, four international experts in Barrett's neoplasia, who were blinded to the pathology results, reviewed all images. Results: The system identified early neoplastic lesions on a per-image analysis with a sensitivity and specificity of 0.83. At the patient level, the system achieved a sensitivity and specificity of 0.86 and 0.87, respectively. A trade-off between the two performance metrics could be made by varying the percentage of training samples that showed neoplastic tissue. Conclusion: The automated computer algorithm developed in this study was able to identify early neoplastic lesions with reasonable accuracy, suggesting that automated detection of early neoplasia in Barrett's esophagus is feasible. Further research is required to improve the accuracy of the system and prepare it for real-time operation, before it can be applied in clinical practice.
This paper presents a multimodal network design model with a computer algorithm to solve it. The selection of link improvements in the network is assumed to affect practical capacities as well as mean free times. The ...
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This paper presents a multimodal network design model with a computer algorithm to solve it. The selection of link improvements in the network is assumed to affect practical capacities as well as mean free times. The equilibrium flows and the modal shares are affected accordingly. The improvements are assumed to be continuous variables with concave marginal costs. This provided a good approximation for the behaviour of the discrete model. The algorithm is based on Hooke and Jeeves' Optimization Methodology which requires a solution of a multimodal equilibrium assignment problem for each functional evaluation. The algorithm is implemented in such a way that only some functional evaluations need a solution of an equilibrium problem, implying efficiency for large-scale problems. Computational results show that although flow congestion decreased due to link improvements, modal shares may change towards private users. The latter contributes to congestion again and possibly makes the overall decrease in congestion less significant. [ABSTRACT FROM AUTHOR]
Let M and P be Seifert 3-manifolds. Is there a degree one map f : M --> P ? The problem was completely solved by Hayat-Legrand, Wang, and Zieschang for all cases except when P is the Poincare homology sphere. We in...
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Let M and P be Seifert 3-manifolds. Is there a degree one map f : M --> P ? The problem was completely solved by Hayat-Legrand, Wang, and Zieschang for all cases except when P is the Poincare homology sphere. We investigate the remaining case by elaborating and implementing a computer algorithm that calculates the degree. As a result, we get an explicit experimental expression for the degree through numerical invariants of the induced homomorphism f(#) : pi(1)(M) --> pi(1)(P).
Objective: The aim of this study was to demonstrate the principle of supporting radiologists by using a computer algorithm to quantitatively analyse MRI morphological features used by radiologists to predict the prese...
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Objective: The aim of this study was to demonstrate the principle of supporting radiologists by using a computer algorithm to quantitatively analyse MRI morphological features used by radiologists to predict the presence or absence of metastatic disease in local lymph nodes in rectal cancer. Methods: A computer algorithm was developed to extract and quantify the following morphological features from MR images: chemical shift artefact;relative mean signal intensity;signal heterogeneity;and nodal size (volume or maximum diameter). Computed predictions on nodal involvement were generated using quantified features in isolation or in combinations. Accuracies of the predictions were assessed against a set of 43 lymph nodes, determined by radiologists as benign (20 nodes) or malignant (23 nodes). Results: Predictions using combinations of quantified features were more accurate than predictions using individual features (0.67-0.86 vs 0.58-0.77, respectively). The algorithm was more accurate when three-dimensional images were used (0.58-0.86) than when only middle image slices (two-dimensional) were used (0.47-0.72). Maximum node diameter was more accurate than node volume in representing the nodal size feature;combinations including maximum node diameter gave accuracies up to 0.91. Conclusion: We have developed a computer algorithm that can support radiologists by quantitatively analysing morphological features of lymph nodes on MRI in the context of rectal cancer nodal staging. We have shown that this algorithm can combine these quantitative indices to generate computed predictions of nodal status which closely match radiological assessment. This study provides support for the feasibility of computer-assisted reading in nodal staging, but requires further refinement and validation with larger data sets.
This paper applies mathematical ideas which arise from differential geometry and control theory to computer programming theory. For the sake of simplicity, most questions of logic and language are put to the side. A c...
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This paper applies mathematical ideas which arise from differential geometry and control theory to computer programming theory. For the sake of simplicity, most questions of logic and language are put to the side. A computer program is regarded as a collection of data, considered as a collection of cross-sections of a fiber space whose base is a discrete space. These distinguished cross-sections are called the trajectories of the computer program system. For the simplest von Neumann type of program, the base space is the nonnegative integers: The trajectories may then often be thought of as the orbits of a discretetime dynamical system. Feedback control theory enters when one attempts to provide a ‘rational’ way of generating such dynamical systems, satisfying certain conditions, such as termination and correctness. The greatest common divisor and bubble sort programs — standard examples in computer science textbooks — are treated as models for the development of a general theory.
Geometrically, we will also consider them as the discrete analogue of what are called path systems in differential geometry. These examples can also be treated as the analogue of closed-loop feedback control systems — themselves a sort of path system — that are ‘driven’ to the final answer by a process that is similar to the way that Lyapunov theory is used in the linear regulator problem of control theory. This use of the Lyapunov ideas of dynamical system theory gives a technique for proving the correctness and termination of some programs. In order to provide a mathematical structure to a programming theory that is, in some sense, analogous to the group-theoretic structure of fiber bundle differential geometry, an algebraic structure of a category which acts on the fiber space is associated with such programs. The computation of the binomial coefficients will also be treated as an example of a system of partial difference equations, leading to the description of some features of concur
作者：
Cash, GGEnvironmental Effects Branch
Health & Environmental Review Division Office of Pollution Prevention & Toxics U.S. Environmental Protection Agency SW USA
A fast computer algorithm is described which brings computation of the permanents of sparse matrices, specifically, chemical adjacency matrices, within the reach of a desktop computer. Examples and results are present...
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A fast computer algorithm is described which brings computation of the permanents of sparse matrices, specifically, chemical adjacency matrices, within the reach of a desktop computer. Examples and results are presented, along with a discussion of the relationship of the permanent to the Kekule structure count. Also presented is a C-language implementation which was deliberately written for ease of translation into other high-level languages.
It does not appear to be widely recognized that a computer can be a useful aid in the design of experiments as well as in the analysis of the data. The computer can be particularly useful in the administration of an e...
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It does not appear to be widely recognized that a computer can be a useful aid in the design of experiments as well as in the analysis of the data. The computer can be particularly useful in the administration of an experimental program and in developing experimental plans for those situations in which the classic designs (e.g., factorial and response surface) are not applicable. Such situations include irregularly-shaped experimental regions, mixture experiments and formulation studies, the need to construct unusual fractions of factorial designs, and experimental plans to estimate the parameters in nonlinear models. Several examples are presented to illustrate the practical problems encountered and how computer algorithms can be helpful in developing useful experimental designs.
In this study, a quadrupedal pronking gait robot modeling was carried out with Spring Loaded Inverted Pendulum model in stance phase. This is achieved by solving a natural problem in which the main goal is to enable t...
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In this study, a quadrupedal pronking gait robot modeling was carried out with Spring Loaded Inverted Pendulum model in stance phase. This is achieved by solving a natural problem in which the main goal is to enable the robot to walk and run in a stable condition regardless of the environmental conditions. In order to solve this problem, dynamic model and control of a quadrupedal robot were realized for a pronking gait. The stance and flight phase dynamic structures were solved in a sequential closed loop to obtain the equation of motion for pronking gait. Spring Loaded Inverted Pendulum model was used as a dynamic model to simplify the simulation, dynamic locomotion and experimental works of the system, and also to simplify the pronking gait concept. The quadrupedal robot with pronking gait was controlled by proportional-derivative control algorithm. As a result, all computer simulations have shown that the proposed control actions and methods are more effective and make the system control quite easy and successful. Crown Copyright (C) 2011 Published by Elsevier Ltd. All rights reserved.
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