Edge effects in game-theoretic dynamics of spatially structured tumours

Cancer dynamics are an evolutionary game between cellular phenotypes. A typical assumption in this modelling paradigm is that the probability of a given phenotypic strategy interacting with another depends exclusively on the abundance of those strategies without regard for local neighbourhood structure. We address this limitation by using the Ohtsuki–Nowak transform to introduce spatial structure to the go versus grow game. We show that spatial structure can promote the invasive (go) strategy. By considering the change in neighbourhood size at a static boundary—such as a blood vessel, organ capsule or basement membrane—we show an edge effect that allows a tumour without invasive phenotypes in the bulk to have a polyclonal boundary with invasive cells. We present an example of this promotion of invasive (epithelial–mesenchymal transition-positive) cells in a metastatic colony of prostate adenocarcinoma in bone marrow. Our results caution that pathologic analyses that do not distinguish between cells in the bulk and cells at a static edge of a tumour can underestimate the number of invasive cells. Although we concentrate on applications in mathematical oncology, we expect our approach to extend to other evolutionary game models where interaction neighbourhoods change at fixed system boundaries.     

A reference-based Hirschian similarity measure for journals

Hirsch’s concept of h-index was used to define a similarity measure for journals. The h-similarity is easy to calculate from the publicly available data of the Journal Citation Reports, and allows for plausible interpretation. On the basis of h-similarity, a relative eminence indicator of journals was determined: the ratio of the JCR impact factor to the weighted average of that of similar journals. This standardization allows journals from disciplines with lower average citation level (mathematics, engineering, etc.) to get into the top lists.     

Wavelet-based distortion measure for binary images

Abstract

This paper proposes an objective distortion measure for binary images. Whereas most previously proposed measures decide the distortion weight of a distorted pixel based on the relationship with the neighbouring pixels in the spatial domain, we observe the characteristics of distorted pixels in multi-spectral spatial-frequency bands. Similarities between the binary wavelet transform and the human visual system are utilised to obtain the distortion weight. When we decide the distortion weight of a distorted pixel, we consider flatness, edge orientation and texture complexity of the distorted pixel at each level of binary wavelet decomposition. Experimental results on various sample images show that the proposed measure is more adequate to human than previously proposed measures.     

An efficient similarity measure technique for medical image registration

In this paper, an efficient similarity measure technique is proposed for medical image registration. The proposed approach is based on the Gerschgorin circles theorem. In this approach, image registration is carried out by considering Gerschgorin bounds of a covariance matrix of two compared images with normalized energy. The beauty of this approach is that there is no need to calculate image features like eigenvalues and eigenvectors. This technique is superior to other well-known techniques such as normalized cross-correlation method and eigenvalue-based similarity measures since it avoids the false registration and requires less computation. The proposed approach is sensitive to small defects and robust to change in illuminations and noise. Experimental results on various synthetic medical images have shown the effectiveness of the proposed technique for detecting and locating the disease in the complicated medical images.     

Effect of yoga on visual perception and visual strain

Visual perception implies that additional features of a visual stimulus are extracted and cognized. Yoga practice improved the response to a flickering light stimulus, so that it continues to be perceived as ‘flickering’ (rather than fused) at higher frequencies. This response was observed in both children and adults when the ‘critical flicker fusion frequency’ was measured at the end of the yoga programme compared to before. Following yoga, the degree of optical illusion perceived (using the Müller–Lyer lines) was also reduced. A recent randomized controlled trial on 118 professional computer users, randomized as yoga and wait-list control groups, showed that two months of yoga practice reduced subjective reports of symptoms of dry eye and objective evidence of visual fatigue in these professionals. Hence, yoga practice has potential applications especially in those occupations requiring good visual perceptual sensitivity and minimal visual strain.     

Quantifying a similarity of classes of texture images

To quantify the concept of similarity between classes of images three measures and algorithms of calculation are proposed. The first measure is calculated through the frequency of misclassification of subimages sampled randomly from images. The second one is calculated through the cross membership of the mass center of a class in a feature space. The third measure is defined through the membership of subimages, using the distance between each subimage and the mass center of a class in a feature space. We study these measures, classifying images in the coordinated clusters representation (CCR) feature space with the minimum distance classifier. A database of images of Rosa Porri?o granite tiles, previously classified by three human experts, is used in the experiments. The calculated similarity between classes is in excellent accordance with the qualitative evaluation by the human experts.     

非线性耦合双稳系统的振动共振与随机共振

单一双稳系统受到弱周期信号和噪声的作用能产生随机共振.而在高、低两种不同频率信号作用下则能产生振动共振,将两个双稳系统经非线性耦合而成为耦合双稳系统,并在低频、高频信号和噪声的作用下研究了耦合双稳系统对低频信号的响应特性,给出了高频信号参数和耦合系数对振动共振和随机共振的影响关系,结果表明通过调节高频信号幅值或耦合系数大小能产生振动共振或随机共振,并构建了耦合双稳系统原理框图,为随机共振的控制及其利用提供了新的理论方法,数值仿真结果与理论分析结论完全吻合.     

Wideband enhancement of television images for people with visual impairments

Wideband enhancement was implemented by detecting visually relevant edge and bar features in an image to produce a bipolar contour map. The addition of these contours to the original image resulted in increased local contrast of these features and an increase in the spatial bandwidth of the image. Testing with static television images revealed that visually impaired patients (n = 35) could distinguish the enhanced images and preferred them over the original images (and degraded images). Most patients preferred a moderate level of wideband enhancement, since they preferred natural-looking images and rejected visible artifacts of the enhancement. Comparison of the enhanced images with the originals revealed that the improvement in the perceived image quality was significant for only 22% of the patients. Possible reasons for the limited increase in perceived image quality are discussed, and improvements are suggested.     

Optical head tracking for functional magnetic resonance imaging using structured light

An accurate motion-tracking technique is needed to compensate for subject motion during functional magnetic resonance imaging (fMRI) procedures. Here, a novel approach to motion metrology is discussed. A structured light pattern specifically coded for digital signal processing is positioned onto a fiduciary of the patient. As the patient undergoes spatial transformations in 6 DoF (degrees of freedom), a high-resolution CCD camera captures successive images for analysis on a computing platform. A high-speed image processing algorithm is used to calculate spatial transformations in a time frame commensurate with patient movements (10-100 ms) and with a precision of at least 0.5 microm for translations and 0.1 deg for rotations.     

真假目标红外图像相似度检测算法

本文提出了真,假目标红外图像相似性定量的计算方法.该方法应用小波变换将真、假目标的红外图像分解为不用层次的子图像;利用Harris角点检测算子提取不用层次子图像的特征点,构成特征点集;并利用改进的Hausdorff距离计算出特征点集之间的Hausdorff距离.该距离越小说明真、假目标的红外图像越相似,也就说明假目标的红外示假效果越好.实验结果证明该算法能客观准确的计算出真、假目标红外图像的相似度,计算过程快速.     

A similarity coefficient measure and machine-parts grouping in cellular manufacturing systems

For more than three decades, similarity coefficient measures one of the important tools for solving group technology problems have gained the attention of the research community in cellular manufacturing systems. A new similarity coefficient measure that uses a set of important characteristic properties for grouping is developed here for use as an intermediate tool to form cohesive cells. A mathematical model that uses this similarity coefficient for optimally solving the cell-formation problems in cellular manufacturing is developed. A heuristic procedure that improves the optimal methodology in term of solution capability of the large instances is devised for an efficient solution. Both the optimal methodology and the heuristic are applied to some well-known problems from literature to compare the grouping efficiencies. The similarity coefficient and the solution methodologies developed are able to solve the cell formation problems efficiently.     

The formation of features for recognizing complex images based on stochastic geometry

The theory of obtaining the features of pattern recognition based on stochastic geometry and having a three-functional structure (triplet features) is presented. The effectiveness of the proposed method of forming features for recognizing complex-structured and semantically saturated images is proved. A practical example of the formation of features for images from the area of medical diagnostics is considered. __________ Translated from Izmeritel’naya Tekhnika, No. 2, pp. 56–61, February, 2008.     

Deterministic stochastic resonance in a bistable semiconductor system

The phenomenon of deterministic stochastic resonance has been experimentally observed and studied for the first time in a bistable semiconductor system with an S-shaped current-voltage characteristic exhibiting a transition to chaos via intermittency. Spectral regions featuring amplification of an external signal and phase locking are determined as dependent on the frequency and amplitude of the external signal and the control parameter.     

随机共振技术在探潜中的应用

潜艇在低速航行时,由于辅机的工作和螺旋桨转动,导致了声频在甚低频段(0~100 Hz)内有较强的线谱。在声源较弱时,由于信噪比太低,传统的Demon谱分析方法无法辨别出线谱成分。这在一定程度上限制了声呐在低信噪比情况下的探潜性能。根据随机共振理论的非线性检测目标手段,运用扫频式随机共振技术,对低信噪比情况下的潜艇线谱噪声进行处理,从而增强了线谱能量,以提高检测信噪比。根据该理论,运用扫频随机共振方法对潜艇甚低频段线谱进行了数据处理,使得检测结果提高了8 dB,实际运用的目标检测距离提高1倍以上。充分体现了该理论的工程实用价值。     

Transfer operators for contractive Markov systems and stochastic stability of the invariant measure

We consider contractive Markov systems, a generalization due to Werner of iterated function systems that contract on average. We study a transfer operator for such systems and determine an appropriate function space on which this operator acts quasi-compactly and has good spectral perturbation properties. We discuss how these results apply to the stochastic stability of the invariant measure.     

Optoelectronic parallel watershed implementation for segmentation of magnetic resonance brain images

An optoelectronic implementation for the morphological watershed transform is proposed. Fiber-optic programmable logic arrays are used in the implementation because of their high fan factors at high clock speeds. Image segmentation is one of the main applications of the watershed transform. Based on the optoelectronic implementation, an algorithm for the segmentation of axial magnetic resonance (MR) head images to extract information on brain matter is presented. Simulation results for the different steps of the segmentation process are presented.     

Signal amplification under stochastic resonance in vanadium dioxide film

The phenomenon of stochastic resonance with an input signal gain of 1.6 times was observed in the planar structure that is connected in series with the loading resistor and has a VO₂ conducting channel. It was shown that the signal-to-noise ratio transferring in the circuit can reach 250 times.