Robustness of differentiation cascades with symmetric stem cell division

Stem cells (SCs) perform the task of maintaining tissue homeostasis by both self-renewal and differentiation. While it has been argued that SCs divide asymmetrically, there is also evidence that SCs undergo symmetric division. Symmetric SC division has been speculated to be key for expanding cell numbers in development and regeneration after injury. However, it might lead to uncontrolled growth and malignancies such as cancer. In order to explore the role of symmetric SC division, we propose a mathematical model of the effect of symmetric SC division on the robustness of a population regulated by a serial differentiation cascade and we show that this may lead to extinction of such population. We examine how the extinction likelihood depends on defining characteristics of the population such as the number of intermediate cell compartments. We show that longer differentiation cascades are more prone to extinction than systems with less intermediate compartments. Furthermore, we have analysed the possibility of mixed symmetric and asymmetric cell division against invasions by mutant invaders in order to find optimal architecture. Our results show that more robust populations are those with unfrequent symmetric behaviour.     

Power‐law conductivity in polythiophene/copper(II) acetylacetonate composites

This paper reports the charge transport mechanism of polythiophene (PT) matrix composites having various concentrations of copper(II) acetylacetonate. Characterization and structural analyses of the samples were carried out via Fourier transform infrared spectroscopy, atomic absorption spectroscopy, differential scanning calorimetry, thermogravimetric analysis and scanning electron microscopy (SEM). The alternating current electrical properties were investigated as a function of temperature. The change of free energy of adsorption calculated from the Langmuir adsorption isotherm showed that metal ions were electrostatically adsorbed onto polymer chains. Significant morphological changes were observed from SEM images of PT depending on doping process which in turn affected the thermal degradation of PT. The charge transport mechanism determined from a power law showed that there was one frequency‐dependent conductivity region for PT, while there were two regions for the composites in contrast to studies reported in the literature. © 2013 Society of Chemical Industry     

空气超声波检漏仪检测方法

提出空气超声波检漏仪的检测方法,采用替代法,通过对频率响应、最小检出能力和测量范围三个参数的检测,实现了对空气超声波检测仪性能的评判。实验结果表明,对于市场上常见的空气超声波检测仪,该检测方法可以有效地评判其性能。     

Channel and feature selection for a surface electromyographic pattern recognition task

The objective of this research is to select a reduced group of surface electromyographic (sEMG) channels and signal-features that is able to provide an accurate classification rate in a myoelectric control system for any user. To that end, the location of 32 sEMG electrodes placed around-along the forearm and 86 signal-features are evaluated simultaneously in a static-hand gesture classification task (14 different gestures). A novel multivariate variable selection filter method named mRMR-FCO is presented as part of the selection process. This process finds the most informative and least redundant combination of sEMG channels and signal-features among all the possible ones. The performance of the selected set of channels and signal-features is evaluated with a Support Vector Machine classifier.     

基于经验模态分解的桥式起重机振动模态分析

以机械系统模态分析理论为基础，分析了桥式起重机简支梁模型振动特性，提出了基于经验模态分解的桥式起重机模态分析方法。简支梁振动响应通过经验模态分解处理得到固有模态函数，分析表明固有模式函数与振动模式函数具有较高的一致性。最后通过简支梁振动实验验证了桥式起重机EMD分析方法的可实现性。基于EMD的桥式起重机模态分析方法对于在用、维修和改造桥式起重机的模态分析具有重要意义。     

Perceived similarity in face measurement

Automatic face recognition is a widely used biometric identification method, since it is based on standard video surveillance systems and does not require the collaboration of the person to be recognised. The recognition process involves decisions based on the face measurement results. The reliability and robustness of the recognition procedure are critical factors, strongly affected by influence quantities, such as face-camera relative orientation and position, illumination and expression. To improve performance it makes sense to imitate the recognition process in humans, who succeed in recognising faces even from poor quality images. It is therefore interesting to investigate the perception of similarity between faces, with the aim of gaining insight into the process of human face recognition. We report on an investigation that has been carried out by original methods developed in our laboratory for the direct measurement of perceptual quantities. Such methods have been implemented for two complementary recognition procedures, based either on the global appearance of a face or on the detection of specific repere points.     

中国BT项目关键成功因素研究

中国不少地方政府采取BT模式建设公共项目,但许多BT项目最终并未取得成功,因此有必要对BT项目关键成功因素进行研究。首先梳理BT项目实施流程及工作内容,结合BT项目成功标准,初步归纳影响BT项目成功的关键因素,然后用问卷调查方法对初步关键成功因素进行修正和确认,得到关键成功因素清单,然后扩大问卷调查范围确定各关键成功因素的重要性,并对重要性的调查结果从整体和按角色进行对比分析,所得结果对BT项目中的业主、实施方、监理等各参与方都有借鉴作用。     

The optimal control related to Riemannian manifolds and the viscosity solutions to Hamilton–Jacobi–Bellman equations

In this paper we study the optimal stochastic control problem for stochastic differential equations on Riemannian manifolds. The cost functional is specified by controlled backward stochastic differential equations in Euclidean space. Under some suitable assumptions, we conclude that the value function is the unique viscosity solution to the associated Hamilton–Jacobi–Bellman equation which is a fully nonlinear parabolic partial differential equation on Riemannian manifolds.     

Effect of DBD plasma excitation characteristics on turbulent separation over a hump model

In this paper, the effect of dielectric-barrier discharge plasma excitation characteristics on turbulent boundary layer separation over a hump is investigated using computational fluid dynamics. Four different turbulence models were used for verification. The Reynolds stress model showed the best agreement with the experimental data, in general. Based on the verification and validation, the effect of duty cycle and excitation frequency on the turbulent flow separation were investigated. The results showed that the pulsed plasma excitation could effectively suppress the flow separation by mixing augmentation. With increasing duty cycle and excitation frequency, the flow separation first increased, then decreased again. The optimal duty cycle was 0.75 and the optimal excitation frequency was 50 Hz.     

Learning with dynamic and static visualizations: Realistic details only benefit learners with high visuospatial abilities

Learning environments can nowadays easily be enriched with different presentation formats of visualizations, because computer graphics technology is constantly and rapidly developing. This study investigates the effectiveness of dynamic compared to static visualizations. Moreover, the influence of realistic details in the visualizations as well as learners’ prerequisites in terms of their visuospatial abilities were addressed. Eighty university students were randomly assigned to four conditions of a two-by-two between subjects design with the two independent variables dynamism and realism. Learning outcomes were measured by means of a verbal factual knowledge test about the terminology and visuospatial details and a pictorial recognition test about the dynamic processes. Data analyses revealed no effects for factual knowledge. With respect to recognition, learners with dynamic visualizations outperformed learners with static visualizations. Furthermore, there was an interaction between learners’ visuospatial abilities and the degree of realism in the visualization: learners with lower visuospatial abilities showed better recognition with schematized visualizations, whereas learners with higher visuospatial abilities showed better recognition with realistic visualizations. The results imply that when designing instructional materials, both the type of knowledge that has to be acquired as well as learners’ prerequisites such as their visuospatial abilities need to be considered.