Reverse-Engineering Self-Organized Behavior in Myxococcus xanthus Biofilms

Myxococcus xanthus ( M. xanthus ) is a gram-negative, rod-shaped soil-dwelling predatory bacterium. It can move on solid surfaces forming cooperative single-species biofilm in which various self-organizing patterns are observed. Under distinct environmental conditions, these bacteria can swarm outward, form travelling waves or aggregate into fruiting bodies as a result of diverse intercellular interactions, signaling and coordinated cell motility. M. xanthus colony actively expands when food is plentiful, but stops this under nutritional stress and thereafter aggregates into fruiting bodies where individual cells transform into spores. When in direct contact with their prey, M. xanthus cells form traveling cell-density waves called ripples to facilitate their predation. These patterns play an important role in maximizing M. xanthus adaption to the changing environment. While these phenomena have been studied using traditional experimental microbiology and genetics, recently it is becoming clear that system biology approach greatly complements traditional laboratory work. This thesis shows my effort to deepen the understanding of self-organization in microorganisms using statistical image processing techniques and agent-based modeling. Statistical image processing results illustrate that aggregation into fruiting bodies is a highly non-monotonic yet spontaneous process without long-range signal transduction. The agent-based model of aggregation accurately reproduces the final steady states of an aggregation process but fails to reproduce the experimental dynamics. The agent-based modeling for predatory ripples quantitatively reproduces all observed patterns based on three simple experimentally observed rules: regular cellular reversals, side-to-side contact induced early reversals and refractory period after each cellular reversal. Moreover, the agent-based model predicts that predatory ripples speed up the swarm expansion into the prey region and keep individual M. xanthus cells in the prey region longer. These predictions are all quantitatively verified by experimental observations. The combination of statistical image analysis and agent-based modeling brings greater understanding of self-organizing patterns in M. xanthus and will be essential for further research on similar patterns in other microorganisms and higher organisms

Type-enhanced Ensemble Triple Representation via Triple-aware Attention for Cross-lingual Entity Alignment

Entity alignment(EA) is a crucial task for integrating cross-lingual and cross-domain knowledge graphs(KGs), which aims to discover entities referring to the same real-world object from different KGs. Most existing methods generate aligning entity representation by mining the relevance of triple elements via embedding-based methods, paying little attention to triple indivisibility and entity role diversity. In this paper, a novel framework named TTEA -- Type-enhanced Ensemble Triple Representation via Triple-aware Attention for Cross-lingual Entity Alignment is proposed to overcome the above issues considering ensemble triple specificity and entity role features. Specifically, the ensemble triple representation is derived by regarding relation as information carrier between semantic space and type space, and hence the noise influence during spatial transformation and information propagation can be smoothly controlled via specificity-aware triple attention. Moreover, our framework uses triple-ware entity enhancement to model the role diversity of triple elements. Extensive experiments on three real-world cross-lingual datasets demonstrate that our framework outperforms state-of-the-art methods

Numerical Simulation of the Effect of Gravitational Direction on Particle Deposition in Pulmonary Acinus under the Condition of Breath Holding

A two-dimensional CFD simulation is conducted to study the effect of the gravitational direction on particle deposition in pulmonary acinus when the breath is held for a short time. The results show that for the large particles (particle diameters of 1 μm, 2 μm, and 3 μm), gravity is the dominant force, and for the small particles (particle diameter of 0.01 μm), the Brownian force is significant. Under the action of either force, the deposition time of particles is short and an equilibrium state can be reached quickly. However, for the medium-sized particles (particle diameters of 0.1 μm and 0.5 μm), the deposition time of particles is elongated because both gravity and Brownian force become weak. Meanwhile, the directions of applied gravity relative to the pulmonary acinus affect the deposition zone of these particles. Therefore, the gravitational direction has no effect on the total deposition fraction of the pulmonary acinus, but can change the local deposition fraction. Applying gravity along the +x direction would increase the local deposition fraction in some specific generations in comparison with the situation along the –y direction. The present study can provide a reliable theoretical basis for further studies on pulmonary mass transport and inhalation therapy. 摘要: 本文通过现有的肺腺泡区的二维几何模型,对由吸气转入屏气后肺腺泡区域的颗粒物沉积特性以及屏气状况下–y 重力方向和+x 重力方向对颗粒在肺腺泡内沉积的影响进行模拟.结果表明:在屏气情况下,粒径大(1μm , 2μm, 3μm) 的颗粒运动受重力主导,粒径小(0.01μm) 的颗粒运动受布朗力主导,它们的沉积率随屏气时间的增加而快速增加,很快达到稳定;而中间粒径(0.1μm , 0.5μm) 的颗粒运动受重力和布朗力作用相当,沉积缓慢.不同重力方向会影响颗粒沉积到不同的位置,所以重力方向对肺腺泡整体沉积率几乎没有影响,但能影响肺腺泡特定区域的沉积率,与–y 重力方向相比, +x 重力方向能增加某些特定区域的沉积率.本文二维肺腺泡内颗粒物沉积的特性研究,将为肺部物质输运以及呼吸系统吸入疗法的深入研究提供可靠的理论依据.中图分类号: 0368; R318 文献标志码:A 文章编号: 1672-6030 (2018) 01-0066-07 Keywords: pulmonary acinus, breath holding, particle deposition, gravitational direction, total deposition fraction, regional deposition fraction, 关键词: 肺腺泡, 屏气, 颗粒沉积, 重力方向, 整体沉积率, 分级沉积

Experimental Study on the Thermoplastic Dripping and Flame Spread Behaviors of Energized Electrical Wire under Reduced Atmospheric Pressure

Flame spread over wire surface is different from other solid fires as it is usually accompanied by melting and dripping processes. Although the related behaviors at reduced pressure (20–100 kPa) are significant to those fire risk evaluations, very few studies have been undertaken on this matter. Therefore, the thermoplastic dripping and flame spread behaviors of energized polyethylene insulated copper wires were investigated experimentally at reduced pressure. It was known from experimental results that the dripping frequency increases, showing a relatively smooth (linear) and rapid (power) increasing trends under high and low electrical currents, respectively. A short-period flame disappearance was observed during the dripping process, which is unique for the energized wire at reduced pressure. The bright flame can disappear for several seconds and then show again after the dripping. While at 20 kPa or lower, the wire flame would turn to a completed extinguishment after the dripping. A critical dripping point was proposed to show the minimal required electrical current to sustain the flame spearing. The critical current changes smoothly during 100–80 kPa and decreases rapidly at 80–60 kPa. Additionally, the dripping phenomenon can stop or delay the flame spread, partly because of the short-term flame disappearance

Parallel Optimization for Large Scale Interferometric Synthetic Aperture Radar Data Processing

Interferometric synthetic aperture radar (InSAR) has developed rapidly over the past years and is considered as an important method for surface deformation monitoring, benefiting from growing data quantities and improving data quality. However, the handing of SAR big data poses significant challenges for related algorithms and pipeline, particularly in large-scale SAR data processing. In addition, InSAR algorithms are highly complex, and their task dependencies are intricate. There is a lack of efficient optimization models and task scheduling for InSAR pipeline. In this paper, we design parallel time-series InSAR processing models based on multi-thread technology for high efficiency in processing InSAR big data. These models concentrate on parallelizing critical algorithms that have high complexity, with a focus on deconstructing two computationally intensive algorithms through loop unrolling. Our parallel models have shown a significant improvement of 10–20 times in performance. We have also developed a parallel optimization tool, Simultaneous Task Automatic Runtime (STAR), which utilizes a data flow optimization strategy with thread pool technology to address the problem of low CPU utilization resulting from multiple modules and task dependencies in the InSAR processing pipeline. STAR provides a data-driven pipeline and enables concurrent execution of multiple tasks, with greater flexibility to keep the CPU busy and further improve CPU utilization through predetermined task flow. Additionally, a supercomputing-based system has been constructed for processing massive InSAR scientific big data and providing technical support for nationwide surface deformation measurement, in accordance with the framework of time series InSAR data processing. Using this system, we processed InSAR data with the volumes of 500 TB and 700 TB in 5 and 7 days, respectively. Finally we generated two maps of land surface deformation all over China

Which Position is Better? A Survey on User Preference for Ambient Light Positions

With the development of intelligent automotive products, in-vehicle ambient lighting has received increasing attention, as shown by the growing number of models on the market with in-vehicle ambient lighting installed and the growing range of ambient lighting installation positions. Currently, there is no industry guideline for the appropriate position of ambient lights. Therefore, this study investigated user preference for 15 ambient light positions and explored whether driving experience, demographic variables, and ambient light usage experience influence user preference for ambient light positions. This study used two indicators to measure users&#39; preference for ambient light positions, aesthetic evaluation and favourite ranking. The results of 479 valid questionnaires showed that users&rsquo; preference for 15 ambient light positions can be divided into three categories. The ambient light positions with high preference were those surrounding the centre screen, armrest and centre screen bottom. Users had a low preference for the upper front windshield, steering wheel, bottom of left and right windows, A-pillar and rear view mirror. It was also found that users&#39; aesthetic evaluation of each position was influenced by gender and experience with ambient lighting. Male drivers, users with ambient lights currently installed in their vehicles and users with more frequent use of ambient lights showed a higher aesthetic evaluation for each position, indicating a more open attitude toward ambient lighting. The results of this study can provide a reference for the layout of in-vehicle ambient lighting, help relevant practitioners determine in-vehicle ambient light positions that better meet user needs, and suggest that ambient light layouts should be designed to better match the characteristics of consumer groups.</p

Effect of particle-particle interaction on dielectrophoretic single particle trap in a sudden contraction flow

Dielectrophoretic (DEP) force is significant in manipulating tiny objects in micro/nano scale. To study the effect of electric interaction force on particle manipulation, a microstructure consisting of a pair of strip electrodes and a sudden contraction micro-channel was constructed. Besides DEP force and hydrodynamic force acting on single particle, the numerical model also involved electric interaction force and force moment on two particles. The analyses revealed that the particle-particle interaction force was in the same order as that of DEP force on single trapped particle. The interaction force resulted in trapping single particle failure under continuous DEP force. Thus, pulsed DEP force, turning on/off DEP force at a given time interval, was suggested. During the “off” period, the velocity difference of the two particles located at sudden contraction micro-channel enlarged the gap between them and further weakened the particle-particle interaction. By a proof-of-concept experiment, both the trapping behavior of single particle and that of two particles were in good agreement with the model. With carefully controlled parameters, the reliable function of retaining single particle was realized by pulsed DEP. Keywords: DEP, Single particle, Interaction force, Pulsed DE