Development of new dominant selectable markers for the nonconventional yeasts Ogataea polymorpha and Candida famata

Nonconventional yeast Candida famata and Ogataea polymorpha are interesting organisms for basic and applied studies. O. polymorpha is methylotrophic thermotolerant yeast capable of xylose alcoholic fermentation whereas C. famata is capable of riboflavin overproduction. Still, the new tools for molecular research of these species are needed. The aim of this study was to develop the new dominant selective markers for C. famata and O. polymorpha usable in metabolic engineering experiments. In this work, the BSD gene from Aspergillus terreus coding for blasticidin S deaminase, O. polymorpha AUR1 gene required for sphingolipid synthesis and IMH3 gene, which encodes IMP dehydrogenase, were tested as the new dominant selective marker genes. Our results showed that AUR1 and IMH3 genes could be used as dominant selective markers for O. polymorpha with frequencies of transformation of 40 and 20 transformants per microgram of DNA, respectively. The IMH3 gene was successfully used as the marker for construction of O. polymorpha strains with increased ethanol production from xylose due to overexpression of TAL1, TKL1 and AOX1 genes. The BSD gene from A. terreus, conferring resistance to blasticidin, was found to be efficient for selection of C. famata transformants.     

受限空间内天然气爆炸反应过程模拟分析

为定量研究受限空间内天然气爆炸反应动力学特征，开展了3个方面的研究工作，①建立了基于激波管的天然气爆炸过程数值分析模型；②将天然气气相燃烧动力学反应分解为53种反应组分、325种基元反应，给出了朗金―雨贡尼关系式和正激波的压强比、密度比和温度比计算方法；③利用化学反应模拟软件CHEMKIN构建天然气燃烧过程机理文件，对激波诱导受限空间内天然气混气爆炸过程进行数值模拟，讨论了反应过程、初始压力和空间尺寸对天然气爆炸过程的影响，并绘制了天然气爆炸温度、压力变化特征曲线。结果表明：采用入射激波模拟混气引爆过程中体系温度会出现跳跃式上升随之向下扰动；混气被引爆后温度逐步提高，在温度达到峰值时压力随之提高；提高初始压力将缩短混气引爆时间，高的初始压力可以得到更为迅速的反应速度和更高的爆炸压力；空间尺寸对散热作用的影响高于其对活性基团消毁作用的影响，小尺寸空间条件下可以获得更迅速的爆炸升压速度。     

Ni@N-doped graphene nanosheets and CNTs hybrids modified separator as efficient polysulfide barrier for high-performance lithium sulfur batteries

Lithium-sulfur batteries (LSBs) have been regarded as one of the most promising energy storage systems to break through the upper limit of lithium-ion batteries. However, the rampant diffusions of soluble lithium polysulfides (LiPSs) in the electrolyte induced the shuttle effect between anode and cathode, resulting in low sulfur utilization, low energy efficiency and short cycling life. Herein, we prove the rational design and construction of Ni nanoparticles filled in vertically grown N-doped bamboo-like carbon nanotubes (CNTs) on graphene nanosheets (Ni@NG-CNTs) as efficient polysulfide barrier for high-performance LSBs. The unique design integrates graphene nanosheets and CNTs into hierarchical architectures with one-dimensional (1D) CNTs, two-dimensional (2D) ultrathin nanosheets and abundant carbon nanocages. This design provides large surface area for lithium polysulfides (LiPSs) adsorption, accelerates electron transport and enhances electrochemical redox of LiPSs. Benefiting from the unique structural features, the LSBs with the Ni@NG-CNTs as polysulfide barrier keep high reversible specific capacities of 309.1 and 265.0 mAh·g⁻¹ at 5 and 10 C rates after 500 cycles. This work provides a new strategy for constructing self-assembled hybrids of CNTs and graphene nanosheets with abundant carbon nanocages for high-performance LSBs.

     

Structure of turbulent rich hydrogen‐air premixed flames

In the present article, series of experiments were conducted to study the structure characteristics of premixed flames in turbulent rich hydrogen‐air mixtures within a constant‐volume turbulent combustion system, 7 equivalence ratios (1.2, 1.4, 1.6, 1.8, 2.0, 2.2, and 2.5), and 5 turbulent intensity (0, 0.494, 0.742, 1.080, and 1.309 m/s) were studied. With the increase of turbulent intensity, the cellularity degree was obviously enhanced for turbulence promoted the formation and the development of initial cracks by wrinkling flame‐front; furthermore, the enhanced hydrodynamic instability was also one important reason. Turbulence would change the linear growth of critical radius to equivalence ratio into nonlinear, but the variation extents had limitation. The wrinkling index of flame‐front would rise as flame expanded, and the wrinkling index on flames with similar size would be increased with the increase of turbulence once the turbulent intensity was sufficiently high. From the variations of the root mean square of related oscillation on flame‐front, it could be found that the partial amount of oscillation induced by sole turbulence was declined as flame expanded for the breakup of large eddies.     

Joining of dense Si3N4 ceramics with tape cast Lu-Al-Si-O-N interlayer

Lu-Al-Si-O-N tapes with different thickness were used to join gas pressure sintered Si₃N₄ ceramics. The microstructure of the joints and the influences of the joint thickness and joining temperature on the bonding strength of the as-joined Si₃N₄ ceramics have been investigated. The highest bonding strength about ~ 300 MPa of the joined specimens was achieved by using 450 µm interlayer at 1450 °C. The existence of Si₃N₄ nanowires was beneficial for the improvement of the bonding strength by interweaving the oxynitride glass matrix in the joint region.