Characterization of the Nocardiopsin Biosynthetic Gene Cluster Reveals Similarities to and Differences from the Rapamycin and FK‐506 Pathways

Macrolide‐pipecolate natural products, such as rapamycin ( 1 ) and FK‐506 ( 2 ), are renowned modulators of FK506‐binding proteins (FKBPs). The nocardiopsins, from Nocardiopsis sp. CMB‐M0232, are the newest members of this structural class. Here, the biosynthetic pathway for nocardiopsins A–D ( 4 – 7 ) is revealed by cloning, sequencing, and bioinformatic analyses of the nsn gene cluster. In vitro evaluation of recombinant NsnL revealed that this lysine cyclodeaminase catalyzes the conversion of L ‐lysine into the L ‐pipecolic acid incorporated into 4 and 5 . Bioinformatic analyses supported the conjecture that a linear nocardiopsin precursor is equipped with the hydroxy group required for macrolide closure in a previously unobserved manner by employing a P450 epoxidase (NsnF) and limonene epoxide hydrolase homologue (NsnG). The nsn cluster also encodes candidates for tetrahydrofuran group biosynthesis. The nocardiopsin pathway provides opportunities for engineering of FKBP‐binding metabolites and for probing new enzymology in nature's polyketide tailoring arsenal.     

Ti-MCM-36: a new mesoporous epoxidation catalyst

Ti-containing MCM-36 catalyst was synthesized from a Ti-MCM-22 precursor (P) via surfactant swelling followed by polymeric silica pillaring. Mesoporous region with ca. 2.8 nm pore size was created by expansion between lamellar crystalline sheets in Ti-MCM-22 (P). Characterization of Ti-MCM-36 was conducted using XRD, BET surface area measurement, ICP, and UV-vis spectroscopy. Catalytic performances in 1-hexene and propylene epoxidation reactions using H₂O₂ as an oxidant demonstrated superior performance of Ti-MCM-36 over Ti-MCM-22 or TS-1.     

运用Factsage计算CaO熔剂对镁铬砖相结构的影响

运用Factsage软件计算了镁铬砖耐火材料中主要氧化物MgO、Cr₂O₃,与造渣剂CaO的相图、初液形成相的温度来研究对镁铬砖耐火材料的影响。计算结果表明：在铜冶炼的温度下镁铬砖会和加入的CaO反应形成MgO的固溶体、CaO的固溶体及CaCr₂O₄。其中对镁铬砖耐火材料影响最大就是CaCr₂O₄。形成的相全部都是高熔点氧化物,冶炼温度高于1864.34℃会形成初液相。     

鱼腥草袋装方便食品加工

介绍了鱼腥草袋装方便的加工工艺。针对加工及贮藏中易出现的产品包泽，脆度劣变的现象，探讨了提高产品质量的有效措施。     

Synthesis and processing of nanostructured WC-Co materials

In this study a novel approach, termed the integrated mechanical and thermal activation (IMTA) process, was used to synthesize nanostructured WC-Co powder. As a result of the integration of mechanical and thermal activation, nanostructured WC-Co powder was synthesized below 1000°C, starting from WO₃, CoO and graphite powder mixtures. Furthermore, consolidation of the nanostructured WC-Co powder via high velocity oxy-fuel (HVOF) thermal spraying and solid state sintering was investigated. The results demonstrated the feasibility of converting the nanostructured WC-Co powder to coatings and bulk components, the properties of which are either comparable to or better than that of the conventional coarse-grained counterparts.     

Poly(vinylpyrrolidone) coated iron nanoparticles in polar aprotic solvent

Poly(vinylpyrrolidone) (PVP) coated iron nanoparticles which show well-defined core-shell structures have been successfully synthesized in a polar aprotic solvent. In this approach, PVP was employed not as capping agent, but as coating polymer directly applied to the metallic (iron) core nanoparticles. The morphologies, structures, compositions and magnetic properties of the products were investigated by transmission electron microscopy (TEM), X-ray powder diffraction (XRD), energy dispersive X-ray spectroscopy (EDXS), SQUID magnetometry and FTIR spectroscopy.     

300MW锅炉引风机增容改造后叶片断裂原因分析及对策

某电厂300MW锅炉在增容改造后运行不到6000h,接连发生引风机叶片断裂事故。经分析,其直接原因是振动引起疲劳失效,引风机长期在失速、喘振不稳定工作区运行是引起叶片振动疲劳破坏的主要原因。通过对叶片进行焊接加强环等措施,来有效防止类似事故的发生。     

A novel two-degree-of-freedom spherical ultrasonic motor using three travelling-wave type annular stators

In order to promote the tolerance and controllability of the multi-degree-of-freedom(M-DOF) ultrasonic motor, a novel two-degree-of-freedom(2-DOF) spherical ultrasonic motor using three traveling-wave type annular stators was put forward. Firstly,the structure and working principle of this motor were introduced, especially a spiral spring as the preload applied component was designed for adaptive adjustment. Then, the friction drive model of 2-DOF spherical motor was built up from spatial geometric relation between three annular stators and the spherical rotor which was used to analyze the mechanical characteristics of the motor.The optimal control strategy for minimum norm solution of three stators’ angular velocity was proposed, using Moore-Penrose generalized inverse matrix. Finally, a 2-DOF prototype was fabricated and tested, which ran stably and controllably. The maximum no-load velocity and stall torque are 92 r/min and 90 m N·m, respectively. The 2-DOF spherical ultrasonic motor has compact structure, easy assembly, good performance and stable operation.