Analysis and simulation on the performance of a gyro-penitron amplifier

A cylindrical waveguide gyro-peniotron amplifier is analysed theoretically in this paper. By a ballistic method and directly using the energy conservation in the beam-wave system, a set of interaction equations for the cylindrical waveguide gyro-peniotron amplifier is derived. Computer simulation shows that under defined conditions an interaction efficiency of 47%, an output power of 240kW at a gain of 22. 5 dB and a 3 dB-instantaneous bandwidth of 1. 9% for a central frequency of 35GHz, TE₀₃ mode gyro-peniotron amplifier could be achieved. The influence of the operation parameters on the amplifier performance is also presented.     

苦味酸荧光光化学传感器在药物分析中的应用

苦味酸水浴液对固定在增塑的聚氯乙烯（ＰＶＣ）膜中的蒽有可逆荧光熄灭作用，据此研制了测定苦味酸的荧光光化学传感器。该传感器的敏感膜的最佳组成为６～８ｍｇ蒽、５０ｍｇＰｖＣ粉、１００ｍｇ邻苯二甲酸二异辛酯。测定苦味酸的浓度范围为３．０４×１０￣（－６）～６．１６×１０￣（－３）ｍｏｌ／Ｌ，重现性良好，响应时间为５～４０秒，该传感器选择性好，许多常见亲脂明离子不干扰测定，可用于药物奎宁及辛可宁的间接测定。     

ULTRASONICALLY DISPERSED POTASSIUM AS DEPROTONATING AND COUPLING AGENT──SYNTHESIS OF 1，6－DINITRILES IN SITU

ＵＬＴＲＡＳＯＮＩＣＡＬＬＹ　ＤＩＳＰＥＲＳＥＤ　ＰＯＴＡＳＳＩＵＭ　ＡＳ　ＤＥＰＲＯＴＯＮＡＴＩＮＧ　ＡＮＤ　ＣＯＵＰＬＩＮＧ　ＡＧＥＮＴ──ＳＹＮＴＨＥＳＩＳ　ＯＦ　１，６－ＤＩＮＩＴＲＩＬＥＳ　ＩＮ　ＳＩＴＵＵＬＴＲＡＳＯＮＩＣＡＬＬＹＤＩＳＰ...     

Photoacoustic Spectrometry Investigation and Determination of Rare Earth Ions Ho3+ and Nd3+ in a Solution

A home-made high sensitive photoacoustic transducer was used to determine the photoacoustic signal in a solution. The photoacoustic spectra of Ho in different solvents were measured and comparedwith its absorption spectrum. The affection factors of photoacousticsensitivity are discussed. The trivalent rare earth ions Ho3+ and Nd3+in an aqueous acetonitrile solution were determined. The detection limit is 5×10-8 mol/L for Ho3+ and 1.0 ×10-7 mol/L for Nd3+, and corresponds to the absorbance of 1.5×10 and 6.3×10-7.respectively.     

Effects of thioamide substitutions on the conformation and stability of alpha- and 3(10)-helices

Thiopeptides, formed by replacing the amide oxygen atom with a sp(2) sulfur atom, are useful in protein engineering and drug design because they confer resistance to enzymatic degradation and are predicted to be more rigid. This report describes our free molecular dynamics simulations with explicit water and free energy calculations on the effects of thio substitutions on the conformation of alpha-helices, 3(10)-helices, and their relative stability. The most prominent structural effect of thio substitution is the increase in the hydrogen bond distance from 2.1 A for normal peptides to 2.7 A for thiopeptides. To accommodate for the longer C[double bond]S...H-N hydrogen bond, the (phi, psi) dihedral angles of the alpha-helix changed from (-66 degrees, -42 degrees) to (-68 degrees, -38 degrees), and the rise per turn increased from 5.5 to 6.3 A. For 3(10)-helices, the (phi, psi) dihedral angles (-60 degrees, -20 degrees) and rise per turn (6.0 A) changed to (-66 degrees, -12 degrees) and 6.8 A, respectively. In terms of relative stability, the most prominent change upon thio substitution is the decrease in the free energy difference, Delta A(alpha --> 3(10)), from 14 to 3.5 kcal/mol. Therefore, normal peptides are less likely to form 3(10)-helix than are thiopeptides. Component analysis of the Delta A(alpha --> 3(10)) reviews that the entropy advantage of the 3(10)-helix for both Ac-Ala(10)-NHMe and Act-Alat(10)-NHMe is attributed to the 3(10)-helix being more flexible than the alpha-helix. Interestingly, upon thio substitution, this differential flexibility is even more apparent because the alpha-helix conformation of Act-Alat(10)-NHMe becomes more rigid due to the bulkier sulfur atom.     

手性毛细管色谱法测定人尿中美芬妥英对映体的含量及其在代谢分型中的应用

 采用手性毛细管色谱柱和ＦＩＤ检测器建立了人尿中美芬妥英（ＭＰ）对映体的定量分析方法。尿样用二氯乙烷提取，用酸、碱洗涤得以纯化，测得各对映体的最低检测限为６０μｇ／Ｌ。在１１５～６９０μｇ／Ｌ浓度范围内，标准曲线呈良好的线性关系，ｒ＞０．９９，日内、日间精密度ＲＳＤ＜６．５％，Ｓ－ＭＰ的平均回收率为７４．４１％，Ｒ－ＭＰ的平均回收率为７３．７８％。并以ＭＰ为探针药物，对３２名志愿者的尿样进行了ＭＰ氧化代谢分型研究。