Recent Advances in Lipase-Mediated Preparation of Pharmaceuticals and Their Intermediates

Biocatalysis offers an alternative approach to conventional chemical processes for the production of single-isomer chiral drugs. Lipases are one of the most used enzymes in the synthesis of enantiomerically pure intermediates. The use of this type of enzyme is mainly due to the characteristics of their regio-, chemo- and enantioselectivity in the resolution process of racemates, without the use of cofactors. Moreover, this class of enzymes has generally excellent stability in the presence of organic solvents, facilitating the solubility of the organic substrate to be modified. Further improvements and new applications have been achieved in the syntheses of biologically active compounds catalyzed by lipases. This review critically reports and discusses examples from recent literature (2007 to mid-2015), concerning the synthesis of enantiomerically pure active pharmaceutical ingredients (APIs) and their intermediates in which the key step involves the action of a lipase.     

井下矿安全管理的新模式

我国多数大中型矿山已经转入井下生产,安全问题一直倍受人们的关注.通常的安全管理均由单位的安全部门专门负责检查、监督.这样的安全管理有着自身的弊端,要想搞好井下安全生产,必须做到安全职能部门与各类专业技术管理人员齐抓共管,才能达到安全生产的真正目的.     

浅谈喷雾在矿山通风除尘中的应用

针对矿山井下尘源及特点，结合矿山原有的通风系统进行风网改造，采用喷雾进行井下通风除尘。     

浅析施工企业财务风险与化解

在建筑业竞争激烈的今天,施工企业面临的财务风险与日俱增,结合施工企业的特点及所面临的财务风险,对如何规避与化解财务风险进行探讨.     

活塞式混凝土湿喷机喷射脉动产生原因与消除方法探讨

国内开发的活塞式湿喷机虽然在结构上与国外产品并无多大不同,但却没有掌握泵送喷射过程消除"脉动"的方法.分析活塞式混凝土湿喷机喷射过程产生"脉动"现象的两个主要原因分别为:(1)由于活塞式湿喷机在进行活塞切换时的切换时间造成了混凝土喷射过程的"脉动";(2)活塞式湿喷机在吸料过程混凝土缸吸料不足,使混凝土不能完全填充混凝土缸,从而造成喷射时的"脉动"产生.针对这两个主要原因提出两种对应解决方案"筑峰填谷"法和"充浆单元"法."筑峰填谷法"核心思想就是让双活塞在交替往复推送混凝土时的速度可调,即在双柱塞刚刚完成切换时让活塞以较快的速度向前推送一小段行程,然后再以正常的速度向前推进.这样就在正常的输送中形成了混凝土的一个"堆积",这个"堆积"(比喻成波峰)在较长输送管路内被削弱正好可以填补刚刚由于双活塞切换而成的混凝土"断续"(比喻成波谷)使不连续现象得以改善."充浆单元"法就是强制填充两主混凝土缸以保证其100%填充,使输送管路的空气段(或称该气体间隔)最小,即输送泵缸的填充是靠外界高压来帮助完成的,而不是靠大气压.由于这种方式加快了填充速度,切换过程的有效时间重叠被充分利用从而保证了双缸在切换时间内都向输送管路推送混凝土.这种积极因素避免了混凝土柱状体变成静止,也就避免了输送管路中混凝土圆柱再重新加速以及输送高压使混凝土柱状体再次发生磨损和断裂,客观上降低了能耗.更重要的是由于活塞每次推送混凝土都被完全充满,因此提高了混凝土输出量,保证了一个比较均匀的输送流量速度,消除了"脉动"现象,也能使喷浆尾部的软管不再摆动.在研制成的"煤矿井下的湿喷作业系统"中应用了"筑峰填谷"法,并进行了试验验证.     

Quantum measurements on finite dimensional systems: relabeling and mixing

Quantum measurements are mathematically described by positive operator valued measures (POVMs). Concentrating on finite dimensional systems, we show that one can limit to extremal rank-1 POVMs if two simple procedures of mixing and relabeling are permitted. We demonstrate that any finite outcome POVM can be obtained from extremal rank-1 POVMs with these two procedures. In particular, extremal POVMs with higher rank are just relabelings of extremal rank-1 POVMs and their structure is therefore clarified.     

Esterification of Free Fatty Acids Using Layered Carboxylates and Hydroxide Salts as Catalysts

Layered lanthanum and copper(II) laurates were tested as catalysts for methanolic esterification of lauric acid (C₁₂). Factorial design evidenced a positive effect of reaction temperature and amount of catalyst on ester conversion, while the acid:alcohol molar ratio (MR) had a negative effect. With lanthanum laurate, 90.5% conversion was reached at 140???C with 10% catalyst and MR of 6:1. Although the highest conversion with copper(II) laurate converted 81.5% under the same conditions, results were better with a lower amount of catalyst (78% ester at 140???C with 2% catalyst and MR of 6:1). A calcium hydroxide succinate was also investigated showing better catalytic performance than the well-known CaO, under mild reaction conditions (120???C with 1% catalyst and MR of 3:1). Although layered carboxylates can be successively reused, the layered calcium hydroxide salt transformed into inactive CaCO₃ in the second reuse reaction.     

Part Load Performance Characteristics of a Low-Heat Rejection Diesel Engine Fueled with Biodiesel

This experimental study focused on improving performance characteristics of a low-heat rejection (LHR) diesel engine operating with biodiesel fuel. To ensure LHR conditions, the cylinder head and valves of the test engine were coated with a Y2O3-ZrO2 (yttria-stabilized zirconia) layer of 0.35?mm thickness over a NiCrAl bond coat of 0.15?mm thickness. The fuel used in the engine tests was produced from sunflower oil with transesterification methods. The engine test results showed that brake-specific fuel consumption (BSFC) and brake thermal efficiency were improved with biodiesel usage and thermal barrier coating (TBC) application. Further, exhaust gas temperature was decreased with use of biodiesel, while it was increased with TBC application.     

Magnetic Properties of Zn1?x Ni x O (0.25≤x≤ 0.50) Prepared by Solid-State Reactions

In this study the origin of ferromagnetism in ZnO-based bulk systems has been investigated using Ni-doped ZnO samples, Zn_1−x Ni _x O with 0.25≤x≤0.50, prepared by solid-state reactions. The structural characterizations indicated that the Ni²⁺ ions almost uniformly distributed in all the samples, and the samples have hexagonal wurtzite structure; however, when x is increased toward 0.50, a new NiO phase is formed. A ferromagnetism (FM) has been observed for all the samples at and below the room temperature. In other words, the room temperature results of (M–H) curves show that the FM observed is intrinsic for all the Ni-doped ZnO samples. However, the saturated magnetizations decrease gradually with increasing Ni concentration. This indicates that, in addition to FM, the excessive doping of Ni in ZnO also causes an antiferromagnetic (AFM) contribution which increases with increasing Ni amount. This result is also supported by the magnetization against temperature measurements. Furthermore, the trend of the ac-susceptibility (χ) versus temperature curves, measured under an ac-magnetic field of 100 Oe, also support our conclusion about the antiferromagnetic contribution to ferromagnetism in our samples.