1H NMR Spectral Simplification with Chiral Solvating Agents and with Achiral and Chiral Lanthanide Shift Reagents. Cis-4,5-Dihydro-4-Methyl-5-Phenyl-2-Oxazolamine, “Cis-4-Methylaminorex,” a Potent Stimulant and Anorectic

Abstract

The 60 MHz ¹H NMR spectra of racemic (+)-cis-4,5-dihydro-4-methyl-5-phenyl-2-oxazolamine, 1, have been studied at 28° in CDC1₃, solution with the achiral lanthanide shift reagent (LSR), tris(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato) europium(III), 2, and the chiral reagent tris[3?(heptafluoropropylhydroxymethy1ene)-d-camphor-ato]europium(III), 3. Additional NMR studies were performed at 400 MHz in CDC1, solution at 24° using the chiral solvating agents (CSA), (E)-(-)-2,2,2-trifluoro-1- (9-anthryl) ethanol, 4, and (R) - (+) -α-methoxy- α-(trifluoromethy1)phenylacetic acid, 5. Substantial enantiomeric shift differences, for the CH₃, signal of 1 using 3 or 5, and for the ortho aryl protons using4, which should make possible direct optical purity determinations of 1. Accurate 400 MHz data f o r chemical shifts and vicinal coupling constants of, of racemic cis-1 are presented, and compared with values for (optically active) (-)-trans-1; some dfferences are seen compared to previously reported data. solution. The LSR and CSA results are compared and Some additional data were obtained in C₆D₆ discussed.     

NMR Studies of Drugs. Applications of Lanthanide Shift Reagents to Afloqualone,an Axially Chiral Quinazolinone.

The skeletal muscle relaxant, aflogualone, 1, has been studied by ¹H NMR in CDC1₃ at 60 and 300 MHz in the presence of added chiral [Eu(HFC)₃] or achiral [Eu(FOD)₃] lanthanide shift reagents (LSR). With Eu(HFC)₃, significant enantiomeric shift differences, ΔΔδ, can be induced for most of the nuclei of 1, with near-baseline resolution obtainable for the H-5 signals of each enantiomer, indicating excellent analytical potential for direct determination of enantiomeric excess of samples of 1. Observation of ΔΔδ directly confirms hindered rotation about the bond between N (3) and the 2-methylphenyl group, i.e., the N (sp²) - C(sp²) bond, leading to axial chirality in 1 with slow rotation on the NMR timescale. Assignments are supported by 2D COSY spectra at 300 MHz. Relative lanthanide-induced shift magnitudes for the protons of 1 are compared.     

有线电视HFC传输系统的光纤应用

指出了同轴电缆在CATV系统中作为干线传输的缺点；引入HFC概念，从光纤的传输特性出发，着重阐述了HFC传输系统的几种调制方式、HFC组网方式及光纤接入的应用类型。     

基于有线电视HFC网的Internet高速接入构想

通过对电信网与有线电视HFC网进行比较，阐明在有线电视HFC网上实现Internet高速接入的优势，并对此高速接入方案中的双向传输方法、数字调制技术、MAC和Cable Modem的应用提出了一些构想和遴选方案。     

带膨胀机的HFC134a与HFO1234yf制冷系统分析

对带膨胀机的R134a与R1234yf制冷系统进行理论分析,并与不带膨胀机的系统进行比较。研究表明:HFC134a的排气温度明显高于HFO1234yf,HFC134a的排气温度随着蒸发温度的升高而降低,HFO1234yf的排气温度随着蒸发温度的升高而升高;HFC134a与HFO1234yf的单位制冷量都是随着蒸发温度的升高而增大,但HFC134a的单位制冷量明显高于HFO1234yf,其平均高于HFO1234yf约34.9kW/kg;HFO1234yf压缩机输入功率明显高于HFC134a,HFC134a的系统COP高于HFO1234yf的系统COP,且二者都是随着蒸发温度的升高而升高。在制冷系统中加入膨胀机后,对HFC134a产生了显著的影响,在蒸发温度-10℃时变化最为明显,其单位制冷量增大32%,压缩机输入功率降低12.1%,系统COP降低19.8%,膨胀机的加入并没有影响HFO1234yf系统,其各项参数均未发生明显变化。在HFO1234yf制冷系统中应用膨胀机的效果逊于HFC134a制冷系统。     

泰达HFC双向网络结构特点

对泰达网络系统进行了概述，介绍了HFC双向网络结构的特点，对建设过程中产生的问题进行总结，提出网络在不断的建设、发展、延伸中，会不断地产生一些新问题，需要及时解决、改进和完善。     

提高HFC网络性能的相关方法

概述了在IEEE802．14标准[1]中提高HFC网络性能的几种相关的算法和因素，仿真的结果表明这些方法对提高HFC网络性能是有效的。其结果对前端的设计有一定的实现意义。     

依靠科技进步保障电视节目的安全传输

论述了泰达有线电视网络设备管理系统(网管系统)建设的基本架构和设计原则,阐述了该网管系统的具体功能和应用,并说明了在实际运营使用中,通过对系统信息传输结构及软件模块的调整改进、充实完善,提高了系统的有效管理、拓展了实际应用范围,保障了电视节目的安全传输与播出。     

核电站空间系统HCFC22冷水机组替代工质性质的研究

以核电站大型空调系统替代工质冷水机组的国产化为背景,考虑以HFC134a作为HCFC22替代工质的主要选择对象,对HFC134a和HCFC22的物理性质,、循环特性和系统特性进行了详细的比较和研究,在此基础上对采用替代工质时存在的技术问题进行了讨论。     

用代理服务器提高HFC远端数据服务

混合光纤／同轴电缆网络由于具有近１ＧＨｚ的用户接入频带而被视为仅次于光纤到户的宽带数据接入方式。但由于环境射频噪声等因素的影响导致数据传输服务的误码率增大、使得数据服务提高受到一定的限制。