Potential of Silver Nanoparticles in Overcoming the Intrinsic Resistance of Pseudomonas aeruginosa to Secondary Metabolites from Carnivorous Plants

Carnivorous plants are exemplary natural sources of secondary metabolites with biological activity. However, the therapeutic antimicrobial potential of these compounds is limited due to intrinsic resistance of selected bacterial pathogens, among which Pseudomonas aeruginosa represents an extreme example. The objective of the study was to overcome the intrinsic resistance of P. aeruginosa by combining silver nanoparticles (AgNPs) with secondary metabolites from selected carnivorous plant species. We employed the broth microdilution method, the checkerboard titration technique and comprehensive phytochemical analyses to define interactions between nanoparticles and active compounds from carnivorous plants. It has been confirmed that P. aeruginosa is resistant to a broad range of secondary metabolites from carnivorous plants, i.e., naphthoquinones, flavonoids, phenolic acids (MBC = 512 µg mL⁻¹) and only weakly sensitive to their mixtures, i.e., extracts and extracts’ fractions. However, it was shown that the antimicrobial activity of extracts and fractions with a significant level of naphthoquinone (plumbagin) was significantly enhanced by AgNPs. Our studies clearly demonstrated a crucial role of naphthoquinones in AgNPs and extract interaction, as well as depicted the potential of AgNPs to restore the bactericidal activity of naphthoquinones towards P. aeruginosa. Our findings indicate the significant potential of nanoparticles to modulate the activity of selected secondary metabolites and revisit their antimicrobial potential towards human pathogenic bacteria.     

Activity of Oritavancin and Its Synergy with Other Antibiotics against Mycobacterium abscessus Infection In Vitro and In Vivo

Background: Pulmonary disease caused by Mycobacterium abscessus (M. abscessus) spreads around the world, and this disease is extremely difficult to treat due to intrinsic and acquired resistance of the pathogen to many approved antibiotics. M. abscessus is regarded as one of the most drug-resistant mycobacteria, with very limited therapeutic options. Methods: Whole-cell growth inhibition assays was performed to screen and identify novel inhibitors. The IC₅₀ of the target compounds were tested against THP-1 cells was determined to calculate the selectivity index, and then time–kill kinetics assay was performed against M. abscessus. Subsequently, the synergy of oritavancin with other antibiotics was evaluated by using checkerboard method. Finally, in vivo efficacy was determined in an immunosuppressive murine model simulating M. abscessus infection. Results: We have identified oritavancin as a potential agent against M. abscessus. Oritavancin exhibited time-concentration dependent bactericidal activity against M. abscessus and it also displayed synergy with clarithromycin, tigecycline, cefoxitin, moxifloxacin, and meropenem in vitro. Additionally, oritavancin had bactericidal effect on intracellular M. abscessus. Oritavancin significantly reduced bacterial load in lung when it was used alone or in combination with cefoxitin and meropenem. Conclusions: Our in vitro and in vivo assay results indicated that oritavancin may be a viable treatment option against M. abscessus infection.     

折流板换热器的数值模拟及场协同分析

在PHOENICS—3 .5 .1程序的基础上, 采用多孔介质模型, 以及体积多孔度、表面渗透度和各向异性的分布阻力来处理换热器内的管束; 用分布热源考虑管侧流体对壳侧流体的影响,对单弓形折流板换热器的壳程流场和温度场做了数值模拟。结果表明: (1) 采用换热器三维流动计算模型和k—ε湍流模型能较好地模拟折流板换热器内的流场分布; (2) 通过数值模拟可直观地了解换热器内的流动状态, 确定换热器的高、低速区和旋涡区。低速区和旋涡区换热效果差,管子易结垢, 而高速区换热效率高, 但管子易被冲蚀, 且阻力较大, 应予改进; (3) 换热器中间段的场协同性较好, 出入口处的场协同性较差, 应尽量减小其结构尺寸, 或采用导流筒式结构。     

橡胶防老剂的协同作用及发展趋势

介绍了橡胶防老剂协同作用的分类及其机理,并综述了不同协同作用防老剂的研究进展,指出聚合型大分子质量化、超细微粒化、反应型和绿色环保型等新品种的开发是防老剂研发未来的发展趋势.     

Optimization design of slotted fin by numerical simulation coupled with genetic algorithm

Using a novel method that couples genetic algorithm (GA) with numerical simulation, the geometric configuration for a two-dimensional slotted fin has been optimized in this paper. The objective of optimization is to maximize the heat transfer capacity of slotted fin, and minimize the pressure drop penalty of fluid flow through the fin. The key of this method is the fitness function of GA, which were (j/j₀)/(f/f₀) and j/j₀. In this complex multiparameter problem, the numerical simulation is a crucial step to calculate the Colburn factor j and friction factor f. The results showed that for two-dimensional slotted fin considered, the j factor is increased by 229.22%, the f factor is increased by 196.30%, and the j/f ratio was increased by 11.11% at Re = 500 based on optimal integrated performance (j/j₀)/(f/f₀); the j factor is increased by 479.08% at Re = 500 based on optimal heat exchange capacity j/j₀. The feasibility of optimal designs was verified by the field synergy principle.     

农业非点源污染控制最佳管理措施(BMPs)研究

农业面源污染控制最佳管理措施(BMPs)是欧美发达国家广泛采用控制农业非点源污染的一种有效措施。本文主要介绍BMPs的基本概念及目前广泛应用的工程性和非工程性的BMPs。并对我们农业非点源污染控制BMPs的实施提出了相关建议。     

缩放管内自旋流强化传热的场协同分析

建立了周期性单元模型,采用数值模拟方法分析了缩放管内带衰减性自旋流的三维湍流流动中的场协同现象,研究轴向不同位置速度场与温度场的演变过程。结果表明,切向速度对强化传热影响很大,自旋流纵向涡使轴向速度和切向速度在同一数量级;自旋流改善了湍流中心区与边壁区流体速度场与温度梯度场的协同程度,使传热得到了强化。     

复合翅片传热与流动特性的数值模拟

结合纵向涡发生器和开缝的优点,提出一种复合强化传热翅片,并对该种翅片的传热与流动特性进行数值计算.由于翅片结构比较复杂,在三角形小翼及X形开缝区域应用阶梯逼近进行网格划分.复合翅片的强化作用在于两方面:一是在三角形小翼和X形开缝后的流场均产生了纵向涡,对流体产生较强的扰动;二是带状开缝的间断表面抑制了边界层的增长,平均...     

Two energy conservation principles in convective heat transfer optimization

Improving heat transfer performance is very beneficial to energy conservation because heat transfer processes widely existed in energy utilization systems. In this contribution, in order to effectively optimize convective heat transfer, such two principles as the field synergy principle and the entransy dissipation extremum principle are investigated to reveal the physical nature of the entransy dissipation and its intrinsic relationship with the field synergy degree. We first established the variational relations of the entransy dissipation and the field synergy degree with the heat transfer performance, and then derived the optimization equation of the field synergy principle and made comparison with that of the entransy dissipation extremum principle. Finally the theoretical analysis is then validated by the optimization results in both a fin-and-flat tube heat exchanger and a foursquare cavity. The results show that, for prescribed temperature boundary conditions, the above two optimization principles both aim at maximizing the total heat flow rate and their optimization equations can effectively obtain the best flow pattern. However, for given heat flux boundary conditions, only the optimization equation based on the entransy dissipation extremum principle intends to minimize the heat transfer temperature difference and could get the optimal velocity and temperature fields.     

菱形折流杆换热器传热研究

针对圆杆折流杆结构换热器只有在较高壳程流速时才能达到较高传热效率,以及目前缺乏折流杆换热器壳程支撑结构场协同关系定量计算关系式的情况,开展了新型菱形折流杆换热器的传热研究。运用实验方法获得换热器壳程传热关联式,验证了新结构良好的传热效率;利用CFD软件直观地得到了换热器壳程流场和温度场分布。通过对壳程能量方程的无因次变换,得到了壳程速度场和温度梯度场的场协同角的定量关联式,证实了新结构具有更好的场协同关系。