Crossing the Border: From Keto- to Imine Reduction in Short-Chain Dehydrogenases/Reductases

The family of NAD(P)H-dependent short-chain dehydrogenases/reductases (SDRs) comprises numerous biocatalysts capable of C=O or C=C reduction. The highly homologous noroxomaritidine reductase (NR) from Narcissus sp. aff. pseudonarcissus and Zt_SDR from Zephyranthes treatiae, however, are SDRs with an extended imine substrate scope. Comparison with a similar SDR from Asparagus officinalis (Ao_SDR) exhibiting keto-reducing activity, yet negligible imine-reducing capability, and mining the Short-Chain Dehydrogenase/Reductase Engineering Database indicated that NR and Zt_SDR possess a unique active-site composition among SDRs. Adapting the active site of Ao_SDR accordingly improved its imine-reducing capability. By applying the same strategy, an unrelated SDR from Methylobacterium sp. 77 (M77_SDR) with distinct keto-reducing activity was engineered into a promiscuous enzyme with imine-reducing activity, thereby confirming that the ability to reduce imines can be rationally introduced into members of the “classical” SDR enzyme family. Thus, members of the SDR family could be a promising starting point for protein approaches to generate new imine-reducing enzymes.     

Quaternion rational surfaces: Rational surfaces generated from the quaternion product of two rational space curves

A quaternion rational surface is a surface generated from two rational space curves by quaternion multiplication. The goal of this paper is to demonstrate how to apply syzygies to analyze quaternion rational surfaces. We show that we can easily construct three special syzygies for a quaternion rational surface from a μ-basis for one of the generating rational space curves. The implicit equation of any quaternion rational surface can be computed from these three special syzygies and inversion formulas for the non-singular points on quaternion rational surfaces can be constructed. Quaternion rational ruled surfaces are generated from the quaternion product of a straight line and a rational space curve. We investigate special μ-bases for quaternion rational ruled surfaces and use these special μ-bases to provide implicitization and inversion formulas for quaternion rational ruled surfaces. Finally, we show how to determine if a real rational surface is also a quaternion rational surface.     

河流下浅埋深薄基岩煤层部分开采可行性分析

控制覆岩破坏高度是实现水体下安全开采的关键。针对“浅埋深、薄基岩、坚硬顶板”河流下压覆煤炭资源的问题，采用数值模拟的方法，计算了巷柱式和房柱式等部分开采的覆岩破坏高度，并从防水煤岩柱留设、岩梁极限跨度以及煤柱稳定性3个方面论述河流下部分开采的可行性。研究结果表明，部分开采能够很好地控制覆岩破坏高度，煤岩柱厚度基本满足留设防水安全煤岩柱要求；由于上覆基岩柱中存在厚度大于10 m的粗砂岩，在跨度小于8.53 m的情况下可以支撑上覆岩层；设计煤柱安全系数为1.28～1.81，均满足要求。采用采6 m、留6 m的巷柱（窄条带）式开采是最佳方案，面积采出率为50%，按总采出率45%计算，可解放河流压覆区域约52万t煤炭。     

支撑掩护式液压支架的结构特点及合理应用

支撑掩护式支架是以支撑为主 ,掩护为辅的液压支架 ,用来控制采场顶板下沉断裂及冒落 ,保证控顶距内顶板完整和必要的回采空间。对支撑掩护式液压支架的结构特点及合理应用等进行了简要介绍。为保证支架的合理工作状态 ,应尽量缩短降架时间 ,快速移架 ,及时支护 ,并保持足够的支架初撑力     

生态建筑理性化表达的多样性

通过对生态建筑的本质与视觉表达多样性的挥讨,并举相应实例加以说明,从而认识到生态建筑多样化的表达方式正逐渐走向理性和科学。     

住房抵押贷款的理性违约及其风险的规避

分析了住房抵押贷款中借款人的理性违约，认为因住房贬值而导致的借款人理性违约，实质上是住房的价格风险在供款人和贷款人之间的重新再分配。基于对我国住房抵押贷款市场中缺乏违约风险规避机制的分析，作者提出了建立我国由政府性质的担保机构和商业保险公司共同提供保险的综合违约风险规避机制的设想。此外，就建立政府性质担保机构的问题进行了着重探讨，通过对美国联邦住房管理局（FHA）的住房抵押贷款互助保险基金（MMIF）的分析，并结合中国实际，得出了中国有必要设立政府性质担保机构的结论。     

运用合理低价评标法搞好招标管理

通过对合理低价评标法的分析,阐述了其在工作实践中所发挥的优势及运用该方法加强招标管理所要采取的必要措施,从而使投资效益在工程建设中得到充分发挥,并在激烈的竞争中使企业立于不败之地。     

浅议城中村建筑和规划的现状与未来

面对在中国城市普遍存在“城中村”的现象,调查了“城中村”目前的人居现状及人居环境中存在的大量问题,提出改造城中村的思路与模式,揭示“城中村”实现合理城市化的重要意义。     

热力站规模的合理选择

本文简要介绍了我国目前的供热状况和热力站的规模,并结合工程实例,采用静态分析的方法,对热力站不同规模的设计方案进行了经济分析、比较,考虑其适应条件及影响因素,得出热力站的合理规模。同时,文中针对目前热力站设计中存在的问题,提出了选择设计热力站时应遵循的一般原则及需注意的问题。     

浅谈工程投标报价

介绍了工程投标报价的编制原则、编制依据及方法,阐述了工程投标报价的策略,从不平衡报价、多方案报价法及突然报价法等方面探讨了投标决策的制定和投标技巧,并讲述了合理报价的计算方法,从而使投标单位中标后获得较多的利润。