Acquisition and Spread of Antimicrobial Resistance: A tet(X) Case Study

Understanding the mechanisms leading to the rise and dissemination of antimicrobial resistance (AMR) is crucially important for the preservation of power of antimicrobials and controlling infectious diseases. Measures to monitor and detect AMR, however, have been significantly delayed and introduced much later after the beginning of industrial production and consumption of antimicrobials. However, monitoring and detection of AMR is largely focused on bacterial pathogens, thus missing multiple key events which take place before the emergence and spread of AMR among the pathogens. In this regard, careful analysis of AMR development towards recently introduced antimicrobials may serve as a valuable example for the better understanding of mechanisms driving AMR evolution. Here, the example of evolution of tet(X), which confers resistance to the next-generation tetracyclines, is summarised and discussed. Initial mechanisms of resistance to these antimicrobials among pathogens were mostly via chromosomal mutations leading to the overexpression of efflux pumps. High-level resistance was achieved only after the acquisition of flavin-dependent monooxygenase-encoding genes from the environmental microbiota. These genes confer resistance to all tetracyclines, including the next-generation tetracyclines, and thus were termed tet(X). ISCR2 and IS26, as well as a variety of conjugative and mobilizable plasmids of different incompatibility groups, played an essential role in the acquisition of tet(X) genes from natural reservoirs and in further dissemination among bacterial commensals and pathogens. This process, which took place within the last decade, demonstrates how rapidly AMR evolution may progress, taking away some drugs of last resort from our arsenal.     

Coverage optimization algorithm based on VF-CS in mobile sensor network

A random placement of large-scale sensor network in the outdoor environment often causes low coverage.An area coverage optimization algorithm of mobile sensor network (MSN) based on virtual force perturbation and Cuckoo search (VF-CS) was proposed.Firstly,the virtual force of the sensor nodes within the Thiessen polygon was analyzed based on the partitioning of Voronoi diagram of the monitoring area.Secondly,the force of polygon vertices and neighbor nodes was taken as the perturbation factor for updating the node’s location of the Cuckoo search (CS).Finally,the VF-CS guided the node to move so as to achieve the optimal coverage.The simulation results demonstrate that the proposed algorithm has higher coverage and shorter average moving distance of nodes than the Voronoi diagram based algorithms in literatures.     

新型树启发式搜索算法的机器人路径规划

面对三维空间移动机器人从起始点到终止点的最短路径问题,提出一种新型的边缘点树启发式搜索(TreeEP)算法,该方法将地图空间进行密度可调的三维离散化处理,根据障碍安全距离筛选出障碍物的可靠边缘点信息,再利用树扩散架构选出最能引导搜索方向的潜力点进行扩散搜索,最终得出最短路径。提出局部调整策略,得到改进的Tree-EP算法。实验结果表明,在带障碍复杂地形最短路径搜索应用中,提出的Tree-EP算法与已有方法相比,能找到更短的移动路径。     

预压力对压电驱动履带移动系统的性能影响

为了提高夹心式压电驱动移动系统的机械输出性能，提出了一种U型预压力调节机构，并开展了预压力对夹心式压电驱动履带移动系统输出性能影响关系的实验研究。首先，针对U型预压力调节机构的安装对夹心式压电振子的振动特性影响关系开展了有限元仿真分析，发现U型预压力调节机构始终处在夹心式压电振子的两相工作模态振动节点位置；其次，开展了夹心式压电驱动履带移动系统的原理样机的预压力调节测试实验，确定了系统的最大输出牵引力及其所对应的最佳预压力；最后，在最佳预压力工作状态下，开展了原理样机的牵引力特性、越障性能以及模拟月壤环境下的运动特性实验。研究结果表明，在最佳预压力工作状态下，夹心式压电驱动履带移动系统的机械输出性能最佳，为其进一步在月面巡视器上的应用提供了技术支持和试验基础。     

Specific smartphone uses and how they relate to anxiety and depression in university students: a cross-cultural perspective

ABSTRACT

People around the world spend hours of their daily lives using smartphones; therefore, it is important to conduct cross-cultural research on the effects of smartphone use on health and well-being as culture influences values, motivations and communication patterns. The purpose of this study was to explore 5 popular uses of the smartphone – messaging, browsing the Internet, posting social content, reading social content, and playing games – how they relate to anxiety and depression scores, and how they vary depending on the country of the participants: Spain, the United States, and Colombia. In all three countries the ranking of most popular uses was the same: (1) Messaging, (2) Reading social content, and (3) Browsing the Internet. In the USA, game playing contributed to anxiety scores whereas reading social content was a protective factor; regarding depression scores, text messaging was a contributing factor. In Spain, browsing the Internet contributed to anxiety scores; regarding depression scores, messaging was a contributing factor and posting social content was a protective factor. In Colombia, no specific use influenced anxiety scores; regarding depression scores, only game playing was a protective factor. Our results showed that in all the countries, problematic smartphone use contributed to anxiety scores.     

《移动商务》课程信息化教学设计

伴随着教育信息化和混合式教学的浪潮,许多课程都开始了信息化的教学改革。本文以《移动商务》课程为例,从课程定位、课程目标、课程设计、课程实施、课程评价五个方面对该课程的信息化教学予以总结,希望进一步提高《移动商务》课程的教学效果。     

煤矿井下避难硐室系统的构建与应用分析

为进一步减少煤矿事故发生后的人员伤亡、财产损失，在分析国内外煤矿井下避难系统发展的基础上，以何家塔煤矿井下避难硐室系统的构建设计与应用为例，详细介绍了井下避难硐室系统的分类、结构构成、功能需求和配套设施等，并通过紧急避险疏散时间的校验计算，提出避难硐室距离采掘工作面以不超过1 000 m为宜，且应按照“地面最安全，先逃生后避险”原则进行避险救援，为国内其他矿井避难硐室的构建应用和相关标准的制定提供了参考。     

车载移动测量系统定位准确度测试方法研究

阐述了移动测量系统的定位准确度需求,对圆概率法、均方差法和中误差法三种位置准确度评估方法进行分析比较,并在标准试验场内开展了车载GNSS/INS定位准确度测试。实验证明:中误差法的评估结果最准确,其误差小于1 m,明显优于圆概率法和均方差法。     

Modeling,tracking, vibration and balance control of an underactuated mobile manipulator (UMM)

This paper presents an underactuated mobile manipulator (UMM) and focuses on solving modeling, tracking, and vibration- and balance-control problems. Although the study has been directed at warehousing applications, the developed techniques are general and can be applied to other applications. The derivation of equations of motion of the UMM, disturbance analysis, and model validation are investigated to reveal the actual system dynamics. Additionally, a simple but effective strategy is also developed to solve the equilibrium point and balance problem. Based on the dynamic model, two control architectures are proposed: Model Predictive Control (MPC) and MPC+Proportional-Integral (PI) with integral actions, respectively, and they can also be applied to other robotic systems. Compared to other MPC-based control strategies, the proposed controllers require less effort to implement in practice. Finally, simulations, experiments, and robustness verification are conducted and discussed, and the results are satisfactory.     

基于改进蚁群算法的三维路径规划

针对移动机器人在海水环境中的三维路径规划问题容易陷入局部最优和收敛慢等瑕疵，根据三维环境全局信息来改进蚁群算法以提高实时性和收敛速度。改进蚁群算法的启发函数，采用局部信息和全局信息结合动态地改进信息素更新方式，以及根据三维空间中路径的平坦程度和光滑度二阶微分分别增加了一阶微分和二阶微分来再次修改信息素更新规则。仿真对比实验结果显示改进后的蚁群算法克服了收敛速度慢、容易陷入局部最优的缺点。