分枝杆菌生物被膜发育调控与抗生素耐药菌防控新措施研发

目前,已知的分枝杆菌属有170多种,是分枝杆菌科中唯一的属。该属的微生物在引起人类疾病的能力方面呈现多样化。分枝杆菌属包括人类病原体(结核分枝杆菌复合菌群和麻风分枝杆菌)和被称为非结核分枝杆菌(non-tuberculosis mycobacteria,NTM)的环境微生物。分枝杆菌的一个常见致病因素是生物被膜的形成。细菌生物被膜通常被定义为表面附着的细菌群落,也被认为是被包裹的微生物细胞的共享空间,包括各种胞外聚合物基质(extracellular polymeric substances,EPS),如多糖、蛋白质、淀粉样蛋白、脂类和胞外DNA (extracellular DNA,EDNA),以及膜小泡和类腐殖质微生物衍生的难降解物质。基质的组装和动力学主要由第二信使、信号分子或小RNA协调。完全破译细菌如何为基质提供结构,从而促进细胞外反应并从中受益,仍然是未来生物被膜研究的挑战。本文介绍了生物被膜五步发育模型和生物被膜形成的新模型,分析了生物被膜的致病性,与噬菌体、宿主免疫细胞的互作,同时解析了分枝杆菌生物被膜关键基因及调控网络,分枝杆菌生物被膜与耐药性,以期为临床上治疗由生物被膜引起的疾病提供基础。

Elastic Model of Flexure-Based Linkage under Motion Constrains and External Load

For a flexible mechanism with several-stage flexible linkage, the flexible linkage is equivalent to work under the actions of an external load and motion constrains. This paper aims to deal with a simplified elastic model on the kinematic characteristics of a flexure-based linkage under these conditions. The elastic modeling method was developed based on motion constrains and the elastic beam theorem(EBT). Effects of a constant force, an elastic force with a constant stiffness, and the materials were taken into account. The proposed modeling method was verified by comparing with the finite element method(FEM). Further, the developed modeling method was used to optimize a flexure-based mechanism based on a two-stage flexible linkage to realize a maximum displacement amplification ratio of 6.56. The flexure-based mechanism was employed to drive a miniature sucker, which performed with a negative pressure of 2.45 kPa at a frequency of 13.2 kHz.

USP18介导的蛋白质去ISG化及其在结核病等传染病中的作用

干扰素诱导基因15(interferon-stimulated gene 15,isg15)的表达受Ⅰ型干扰素诱导,该基因编码的蛋白ISG15可以分别通过E1、E2和E3酶的作用共价修饰靶蛋白,此过程被称为ISG化(ISGylation)。宿主蛋白的ISG化广泛参与天然免疫例如宿主的抗病毒过程。泛素特异性蛋白酶18(ubiquitin-specific protease 18,USP18)作为一种去泛素化酶(deubiquitinase,DUB)可以去除靶蛋白偶联的ISG15,并通过抑制Ⅰ型干扰素信号通路来抑制宿主的免疫应答。ISG15介导的ISG化和USP18介导的去ISG化(deISGylation)建立的动态平衡对结核病的发生、发展和转归有重要影响。此外,同ISG15一样,USP18也广泛参与病毒感染和宿主细胞抗病毒反应,多种先天性免疫疾病和免疫信号通路都受到USP18的调节。本文综述了ISG15和USP18相关的研究进展,重点介绍了ISG15介导的ISGylation和USP18介导的去ISG化在结核病及其他重要疾病中的调控作用,以期为靶向宿主蛋白的结核病等重要疾病防治提供新的策略。

Toxicity Test of Different Pesticides on Tobacco Root-knot Nematodes

[Objectives]This study was conducted to quickly screen out effective and safe agents for controlling tobacco root knot nematode disease.[Methods]Six pesticides were tested and screened indoors at five different concentrations.[Results]The six pesticides all had toxic effects on the second-instar larvae of tobacco root-knot nematode,and the corrected mortality was positively correlated with the concentration and time of the pesticides,with the correlation coefficients above 0.8.From the perspective of inhibitory activity,the order was fosthiazate>abamectin>emamectin benzoate>cadusafos>ethoprophos>carbosulfan.Four pesticides that can be used in the field were selected.[Conclusions]This study provides a theoretical basis for field pesticide selection.

Review of atomization mechanism and spray characteristics of a liquid jet in supersonic crossflow

The injection and atomization process of a liquid fuel jet is critical for an ignition start of a scramjet engine.Airwall-mounted crossflow injection strategy is widely used in scramjet combustors,avoiding high total pressure loss and allowing the liquid fuel to rapidly undergo atomization,mixing,and evaporation.In this review,research progress on a liquid jet in supersonic crossflow was evaluated from aspects of atomization mechanism and spray characteristics.When a liquid jet is injected into a supersonic crossflow,primary and secondary breakups occur successively.The surface instability of liquid can significantly affect the breakup process.This review discusses the current understanding of the breakup process and spray characteristics of a liquid jet in supersonic crossflow including the mechanism of atomization and the characteristics of distribution and atomization.The development of windward Rayleigh-Taylor(R-T)unstable waves is the main factor in column breakup.The development of Kelvin-Helmholtz(K-H)unstable waves along the circumferential direction of the jet or droplets is the main factor of surface and droplet breakups.The liquid-gas momentum ratio is the most important factor affecting the penetration depth.The span width of the liquid jet is affected by the windward area.Breakup and coalescence lead to a transformation of the size distribution of droplets from S-or C-shaped to I-shaped,and the velocity distribution of the droplets on the central symmetry plane has a mirrored S-shape.The droplet distribution on the spanwise cross-section retains a structure similar to an“Ω”shape.At last,some promising recommendations have been proposed,namely a theoretical predictive model which can describe the breakup mechanism of a liquid jet,the distribution characteristics and droplets size distribution of a liquid jet under a cavity combustion chamber,especially for enthalpy flows with complex wave structures.

Drag reduction characteristics of recirculation flow at rocket base in an RBCC engine under ramjet/scramjet mode

To reduce the drag generated by the recirculation flow at the rocket base in a RocketBased Combined Cycle(RBCC)engine operating in the ramjet/scramjet mode,a novel annular rocket RBCC engine based on a central plug cone was proposed.The performance loss mechanism caused by the recirculation flow at the rocket base and the influence of the plug cone configuration on the thrust performance were studied.Results indicated that the recirculation flow at the rocket base extended through the entire combustor,which creates an extensive range of the"low-kineticenergy zone"at the center and leads to an engine thrust loss.The plug cone serving as a surface structure had a restrictive effect on the internal flow of the engine,making it smoothly transit at the position of the large separation zone.The model RBCC engine could achieve a maximum thrust augmentation of 37.6%with a long plug cone that was twice diameter of the inner isolator.However,a shorter plug cone that was half diameter of the inner isolator proved less effective at reducing the recirculation flow for a supersonic flow and induced an undesirable flow fraction that diminished the thrust performance.Furthermore,the effectiveness of the plug cone increased with the flight Mach number,indicating that it could further broaden the operating speed range of the scramjet mode.

Effect of kerosene injection states on mixing and combustion characteristics in a cavity-based supersonic combustor

It has been found that the static pressure distribution along the axial direction of liquid kerosene is lower than that of the gaseous kerosene under the same flow condition and overall equivalent ratio from previous studies.To further investigate this phenomenon,a compressible two-phase parallel simulation method is utilized to analyze the mixing and combustion characteristics of gaseous and liquid kerosene jets in a cavity-based supersonic combustor.The numerical results are consistent with the experiments and demonstrate that gaseous injection leads to a cavity shear layer that dives deeper into the cavity,forming two recirculation zones in the front and rear of the cavity.In contrast,the cavity shear layer is closer to the mainstream during liquid injection,and only a large recirculation zone is formed in the rear of the cavity.As a result of the cavity shear layer and the recirculating flow,the fuel vapor of gaseous injection accumulates in the front of the cavity,while for the liquid injection,the fuel vapor disperses in the cavity,cavity shear layer,and the region above,and the rear of the cavity has a higher fuel vapor concentration than the front.This unique fuel distribution causes the combustion area to be concentrated in the cavity during the gaseous injection but dispersed inside and downstream of the cavity during the liquid injection.As a result,forming a thermal throat under the same conditions is more challenging during liquid injection,and the generated static pressure distribution is lower than that during the gaseous injection.