A modified simplex method for multifactor optimization of selectivity in gas chromatography

A computer-assisted advanced simplex method is presented for the simultaneous optimization of multifactor ( stationary phase loading, carrier gas flow rate and column temperature ) for separation of ten compounds in gas chromatography. A three factors factorial design was used. The method was based on a special polynomial established from fifteen preliminary runs, using resolution as the selection criterion, with connection to a general simplex method. Excellent agreement is found between the predicted data and the experimental results, and most of experiments required in the general simplex method can be omitted.     

烯烃加成反应活性与烷基极化效应的关系

烯烃的自由基加成和亲电加成速率受不同的因素控制.对于仅仅含烷基取代的简单烯烃:(1)与OH自由基加成速率-log kOH可由π键上烷基极化效应指数的几何平均值GMPEIπ关联:-log kOH=a bGMPEIπ c(GMPEIπ)2; (2)与亲电试剂加成速率log k可由π键两端碳原子所连基团极化效应指数PEI(L)和PEI(S)关联:log k=a bPEI(L) cPEI(S),其中的PEI(L)和PEI(S)分别表示极化效应较大和较小的一端.     

STRUCTRE AND PROPERTIES OF COMPOSITE Ni/HARD CARBON FILMS PREPARED BY PLASMA DEPOSITION

IntroductionHardcarbonfilmsprcparcdb}'vari0usplasmaprocesscsareofc0nsidcrablcinterestbccauscofthcirunusualmcchanical-opticalandelcctricalpropertiesll~3l.Rccently,ithasReceive(IJl111c5,l9`)5;,.`,1iis()tI1ie)\tioII,1'ceil'edJtl1)'l4,l995*'I11isprojectiss[1pportcdh}tl1cNatiol1a1Nat[lntlScicl1ccI`()ul1dati()l1ofCl1il1aal1dtl1eI,aboraton'ofSolidI,ubricati()l1,l.al1/l10ulnstitutcofCl1cn1icalPh\'sics,111cChincscAcadcl11\'ofScicnccs.benfoundthattheinc0rporati0nofmetaIintocarbonfilmscangrcatl}'…     

Reaction of the carbonate radical with substituted anilines

Rate constants for the reaction of carbonate radical with aniline and some parasubstituted anilines have been determined by the flash photolysis technique. Using σ⁺ para values the rate constants at pH 8.5 correlate very well with the Hammett equation yielding ρ= − 1. The carbonate radical oxidises aniline giving the anilino radical. The products so formed have been identified through studies under conditions of continuous irradiation.     

Investigation on the Interaction of Bendazac with β-, Hydroxypropyl-β-, and γ-, yclodextrins

The interactions of Bendazac, a topical non-steroidal anti-inflammatory drug, with-cyclodextrin, hydroxypropyl--cyclodextrin and -cyclodextrinwere investigated to evaluate possibilities to improve the drug's poor water solubilityand eventually to enhance the topical delivery of Bendazac. Phase solubility studiesdemonstrated the ability of the selected cyclodextrins to complex with Bendazac andincrease drug solubility. The amount of solubilized Bendazac increased linearly withthe addition of each cyclodextrin according toA_L type plots. ¹³C-NMR studiesshowed that the Bendazac A-ring was included in the cavity of the three cyclodextrins.The -cyclodextrin was also able to include the B-ring of Bendazac, forminga complex where one drug molecule fitted into two cyclodextrin molecules. Equimolarsolid systems of the drug with each cyclodextrin carrier were prepared using varioustechniques (physical mixing, spray-drying and freeze-drying). The results of differential scanning calorimetry and Fourier transform infrared analysis, performed on the solid systems, demonstrated that freeze-dried and spray-dried products had a high degree of amorphization and agreed with the hypothesis of the existence of drug–cyclodextrin interaction in the solid state. The cyclodextrins tested were able to improve the dissolution of Bendazac. The dissolution profile of the drug was also affected by the physico-chemical properties of each solid system, the freeze-dried products being the most rapidly dissolving forms.     

直接酯化法合成PET反应条件对树脂结晶速率的影响

用直接酯化法合成了聚对苯二甲酸乙二酯（ＰＥＴ）。对缩聚反应温度、真空度及稳定剂等合条件对产物结晶速率的影响进行了研究。以ΔＴｃ＝Ｔｃ－Ｔｇ和ΔＴｃｏ＝Ｔｃｏ－Ｔｇ表征样品的结晶速率。结果表明，真空度一定，反应温度高则样品结晶速率慢；温度一定，真空度高样品结晶速率也慢。这两个因素的影响均是不可忽视的。     

热致液晶聚酯酰亚胺的非等温相转变动力学研究

以差示扫描量热法对热致液晶聚酯酰亚胺的结晶过程和液晶化过程的非等温相转变动力学行为进行了初步研究，根据Ｊｅｚｉｏｒｎｙ方法处理数据得到了表征聚合物非等温相转变动力参数Ｚｃ，Ｇｃ并对其进行了讨论，结果表明，在所研究的条件下聚合物的相转变过程基本上符事Ｊｅｚｉｏｒｎｙ结论，但两种相转变的成核与生长方式是不同的。     

The structure and electrochemical characteristics of La0.67Mg0.33 (Ni0.8Co0.1Mn0.1) x (x=2.5–5.0) multiphase alloys for nickel-metal hydride batteries

This paper presents results concerning structure and electrochemical characteristics of the La_0.67Mg_0.33 (Ni_0.8Co_0.1Mn_0.1) _x (x=2.5–5.0) alloy. It can be found from the result of the Rietveld analyses that the structures of the alloys change obviously with increasing x from 2.5 to 5.0. The main phase of the alloys with x=2.5–3.5 is LaMg₂Ni₉ phase with a PuNi₃-type rhombohedral structure, but the main phase of the alloys with x=4.0–5.0 is LaNi₅phase with a CaCu₅-type hexagonal structure. Furthermore, the phase ratio, lattice parameter and cell volume of the LaMg₂Ni₉phase and the LaNi₅ phase change with increasing x. The electrochemical studies show that the maximum discharge capacity increases from 214.7 mAh/g (x=2.5) to 391.1 mAh/g (x=3.5) and then decreases to 238.5 mAh/g (x=5.0). As the discharge current density is 1,200 mA/g, the high rate dischargeability (HRD) increases from 51.1% (x=2.5) to 83.7% (x=3.5) and then decreases to 71.6% (x=5.0). Moreover, the exchange current density (I ₀) of the alloy electrodes first increases and then decrease with increasing x from 2.5 to 5.0, which is consistent with the variation of the HRD. The cell volume reduces with increasing x in the alloys, which is detrimental to hydrogen diffusion and accordingly decreases the low-temperature dischargeability of the alloy electrodes.     

Analysis of the nonisothermal crystallization kinetics in three linear aromatic polyester systems

Melt or cold crystallization kinetics has a strong bearing on morphology and the extent of crystallization, which significantly affects the physical properties of polymeric materials. Nonisothermal crystallization kinetics are often analyzed by the classical Johnson–Mehl–Avrami–Kolmogorov (JMAK) model or one of its variants, even though they are based on an isothermal assumption. As a result, during the nonisothermal (e.g. constant heating or cooling rate) crystallization of polymeric material, different sets of model parameters are required to describe crystallization at different rates, thereby increasing the total number of model parameters. In addition, due to the uncorrelated nature of these model parameters with the cooling or heating rate, accurate modeling at any intermediate condition is not possible. In the present work, these two limitations of the conventional approach have been eliminated by exhibiting the existence of a functional relationship between cooling or heating rate and effective activation energy during nonisothermal melt or cold crystallization in three linear aromatic polyesters. Furthermore, it has been shown that when the JMAK model is used in conjunction with this functional relationship, it is possible to precisely predict the experimental nonisothermal melt or cold crystallization kinetics at any linear cooling or heating rate with a single set of model parameters.