Effect of the pH on the Antibacterial Potential and Cytotoxicity of Different Plasma-Activated Liquids

In this study, different plasma-activated liquids were evaluated for their antimicrobial effects against Escherichia coli, as well as for their cytotoxicity on mammalian cells. The PALs were prepared from distilled (DIS), deionized (DI), filtered (FIL), and tap (TAP) water. Additionally, 0.9% NaCl saline solution (SAL) was plasma-activated. These PALs were prepared using 5 L/min air gliding arc plasma jet for up to 60.0 min of exposure. Subsequently, the physicochemical properties, such as, the oxidation-reduction potential (ORP), the pH, the conductivity, and the total dissolved solids (TDS) were characterized by a water multiparameter. The PALs obtained showed a drastic decrease in the pH with increasing plasma exposure time, in contrast, the conductivity and TDS increased. In a general trend, the UV-vis analyses identified a higher production of the following reactive species of nitrogen and oxygen (RONS), HNO₂, H₂O₂, NO₃⁻, and NO₂⁻. Except for the plasma-activated filtered water (PAW-FIL), where there was a change in the position of NO₂⁻ and NO₃⁻ at some pHs, The higher production of HNO₂ and H₂O₂-reactive species was observed at a low pH. Finally, the standardized suspensions of Escherichia coli were exposed to PAL for up to 60.0 min. The plasma-activated deionized water (PAW-DI pH 2.5), plasma-activated distilled water (PAW-DIS pH 2.5 and 3), and plasma-activated tap water (PAW-TAP 3.5) showed the best antimicrobial effects at exposure times of 3.0, 10.0, and 30.0 min, respectively. The MTT analysis demonstrated low toxicity of all of the PAL samples. Our results indicate that the plasma activation of different liquids using the gliding arc system can generate specific physicochemical conditions that produce excellent antibacterial effects for E. coli with a safe application, thus bringing future contributions to creating new antimicrobial protocols.     

滑动弧放电等离子体去除甲苯的实验研究

为了研究滑动弧放电等离子体对挥发性有机物的净化效果,选取甲苯作为代表物质进行实验研究,观察了电极间隔、电极材料、电极厚度、氧气含量、水汽含量、气流温度、污染物质量浓度等参数对去除率的影响。在输入体积能耗为0.26 kWh/m3、电极间隔为3 mm、电极厚4 mm、气体流量0.8 m3/h、甲苯质量浓度为7 850 mg/L的实验条件下,甲苯的去除率达到90%,反应器的能量利用率达到最大26.92 g/kWh;制作电极的金属材料对反应器的性能影响不大;甲苯去除率随着氧气含量、水汽含量和气流溫度的增加而增加,随着污染物浓度的增加而降低。     

Structural mechanics of filamentous cyanobacteria

Filamentous cyanobacteria, forming long strands of connected cells, are one of the earliest and most successful forms of life on Earth. They exhibit self-organized behaviour, forming large-scale patterns in structures like biomats and stromatolites. The mechanical properties of these rigid structures have contributed to their biological success and are important to applications like algae-based biofuel production. For active polymers like these cyanobacteria, one of the most important mechanical properties is the bending modulus, or flexural rigidity. Here, we quantify the bending stiffness of three species of filamentous cyanobacteria, of order Oscillatoriales, using a microfluidic flow device where single filaments are deflected by fluid flow. This is complemented by measurements of Young’s modulus of the cell wall, via nanoindentation, and the cell wall thickness. We find that the stiffness of the cyanobacteria is well-captured by a simple model of a flexible rod, with most stress carried by a rigid outer wall. Finally, we connect these results to the curved shapes that these cyanobacteria naturally take while gliding, and quantify the forces generated internally to maintain this shape. The measurements can be used to model interactions between cyanobacteria, or with their environment, and how their collective behaviour emerges from such interactions.     

滑动索系结构的统一分析方法——冷冻-升温法

结构工程中存在大量的滑动索系结构,但目前还没有有效的计算方法求解这种结构的内力和变形,因而使得这种结构的理论研究滞后于它的工程应用。提出了一种新颖、有效、通用的处理方法,称为冷冻-升温法(FHM),能有效地解决采用钢索滑移节点对计算结构内力和变形存在的困难。通过对不同算例进行分析,说明了这种方法的通用性和有效性。     

载气比对滑动弧裂解丙烷组分影响的研究

为了提升脉冲爆轰发动机的点火性能达到稳定点火起爆的目的,在氮气气氛下采用高压直流滑动弧放电等离子体裂解器对气体燃料-丙烷进行裂解实验。将进气流量中丙烷和氮气的摩尔比定义为载气比,在不同载气比下进行试验,得到丙烷转化率制氢能耗、氢气选择性和裂解产物中不同组分的体积分数,并分析能量输入密度对丙烷转化率的影响。结果表明,当进气流量中的载气比从1降低至0.2时,丙烷转化率由97.4%逐渐降低至91.8%,输入能量密度随载气比的增大逐渐降低;丙烷/氮气混合气经过等离子体作用后的裂解产物中,氢气体积分数最高,为81.80%,乙炔次之,体积分数为7.90%;丙烷/氮气混合气裂解产物中碳氢化合物各组分体积分数随载气比的增加有所增大;当载气比为0.8时,高压直流滑动弧放电等离子体可获得较高氢气选择性的同时,还可以保持较低的制氢能耗。研究结果可对碳氢燃料航空航天发动机辅助点火燃烧提供一定参考。     

类HTV-2高超声速滑翔飞行器的本体光辐射特性分析

第二代"猎鹰"高超声速技术飞行器(Falcon Hypersonic Technology Vehicle 2,HTV-2)长时间在大气层中飞行时,气动热是导致本体光辐射特性的主要原因。气动热预测和复杂结构传热温度求解是本体光辐射特性研究的关键。基于类HTV-2高超声速滑翔飞行器的结构以及飞行弹道特点,建立了适用于高超声速滑翔飞行器的气动热、三维有限元传热和本体光辐射耦合计算方法。在算法验证的基础上,通过计算获得了类HTV-2高超声速滑翔飞行器沿假定弹道飞行的本体光辐射特性。结果表明,红外探测器从地面70°方向观测的辐射强度大于从天上-70°方向观测的辐射强度;中波3~5μm光辐射强度明显大于长波8~12μm和短波0.4~0.7μm,因此选择3~5μm波段更有利于对类HTV-2高超声速滑翔飞行器进行探测。     

气液滑动弧放电降解4-氯酚溶液的研究

用10kV高压产生直接与废水接触的气液滑动弧放电非平衡等离子体降解水中4-氯酚。实验研究表明:由于液滴的存在改变了电极间的介电常数和局部电场,气液滑动弧放电的电压波形比纯气流滑动弧放电更加不规则,起弧电压更低:从溶液COD降解效果来看,当不锈钢作为电极材料时, 4-氯酚降解效果比铝和铜电极材料好;当空气作为载气时,经过76min的等离子体处理,溶液的COD值由1679.2mg／L降到190mg／L,相当于COD降解率为88．68％;增大气液混合比能够提高4-氯酚的降解效果;同时检测了H2O2和O3的生成量和溶液pH、电导率的变化。     

滑翔增程弹箭滑控段弹体运动模式对增程效率的影响

增程技术是弹箭技术重点发展方向之一,而滑翔增程是目前采用的较为有效的ー种弹箭增程技术。阐述了滑翔增程弹箭的飞行过程,建立了滑翔增程弹箭的滑翔段弾道模型,在滑翔控制段弹体分别采用俯仰滑翔飞行和旋转滑翔飞行,分析了在滑'翔控制段弹体的两种运动模式对弹箭增程效率的影响。仿真结果表明：在滑翔控制段弹体釆用俯仰滑翔飞行,增程效率高,但在滚转控制过程中控制系统复杂,对舵机的要求高;在滑翔控制段弹体采用旋转滑翔飞行,增程效率较低,但整个控制过程中控制系统简单,对舵机的要求低。     

一种起重机大车铁楔子防风锁定装置的设计

由于起重机经常使用于室外场地,易受大风吹袭,因此其大车铁楔子防风锁定装置往往会出现一些故障,甚至引起安全事故.本文设计了一种起重机大车铁楔子防风锁定装置,并对其进行了静力学和动力学分析.结果表明,此防风锁定装置安全可靠,为起重机的安全性设计提供了理论参考依据.     

风力发电机滑动偏航系统载荷特性分析

偏航控制过程中,滑动式偏航系统载荷特性是影响风力发电偏航系统安全可靠性的关键因素,现以2 MW风力发电机为研究对象,采用IEC标准中Von Kamman谱模拟湍流风,考虑重力载荷、气动载荷及惯性载荷的影响,建立风力发电机组模型,基于Bladed软件仿真风力发电机偏航时机组的动态特性,研究偏航时风况、偏航速度及偏航角度对滑动式偏航系统荷载的影响规律,为风力发电机的运行维护及改进设计提供依据。研究结果表明,偏航过程中同时变桨,变桨速率对偏航轴承的荷载有重要影响。湍流强度影响偏航轴承的疲劳和极端载荷的波动情况,偏航速度越大,偏航轴承处极限荷载越大。