对DSC单峰纯度测定法的评述

指出了当前流行的差示扫描量热法DSC单峰法测样品纯度所基于的假定有一些不确切的地方,并用计算机动态摸拟了DSC实验过程,结果证实了本文的论断。     

SAPO-34分子筛骨架稳定性的研究

利用差热分析，原位ＸＲＤ技术，高温条件下的焙烧和水蒸气处理并关联其催化性能变化，研究了ＳＡＰＯ－３４分子筛的热及水热稳定性，差热分析结果表明，ＳＡＰＯ－３４的骨架破坏温度高于１３００Ｋ，原位ＸＲＤ跟踪研究证实，ＳＡＰＯ－３４分子筛原粉在高温焙烧以除掉有机胺及随后的降温过程中无明显的骨架破坏；而焙烧型ＳＡＰＯ－３４在空气中放置一定时间后，水分子吸附微孔中明业降低样品的ＸＲＤ峰强度，且降低幅度随放置时     

微分脉冲极谱同时测定三种碱性氨基酸的研究

应用微分脉冲极谱，在ｐＨ９．０ ＮａＢ４Ｏ７－ ＣＨ３ＣＨＯ－Ｃｏ２＋－ ＮａＯＨ组成的极谱底液，扫描电位－ ０．８０～－ １．６０ Ｖ、振幅 ２０ｍＶ、扫描速度５ｍＶ／ｓ、一滴汞周期２ｓ的条件下进行连续扫描测量三种碱性氨基酸，获得三个灵敏 度和分辨率均较高的极谱峰图。该法简便快速，稳定可靠，为测量各种蛋白质中的三种磁性氨基酸提供一种新途 径。     

PBT／PET共混体系的协同效应

ＰＢＴ、ＰＥＴ具有良好相容性，且两种聚合物分子链间存在相互作用，它们的共混体系在熔体降温结晶过程中以及溶液中均表现出协同效应。虽然ＰＢＴ、ＰＥＴ在共混体系中各自形成晶区，但熔体降温结果过程中只能观察到一个结晶放热峰，当ＰＢＴ／ＰＥＴ共混物中两组份分子链段数目相近时，熔体降温结晶峰温较低，峰形变宽，共混体系的结晶程度降低在溶液中两组份分子链段数目相近时，共混物特性粘度（η）值最大，分子链的均方根末端     

Selenium speciation in foods: Preliminary results on potatoes

The present paper deals with the speciation of selenium in potatoes (enriched or not in selenium). The study was carried out by using differential pulse cathodic stripping voltammetry (DPCSV) for quantifying selenium. Results obtained provide evidence that the selenium content in the protein fraction is rather independent from the selenium added to the plants during their growth. On the contrary, the amount of Se in the non-protein fraction (water and starch) in Se-enriched sample is significantly higher than in non-enriched one, suggesting that it is the main selenium-storing site. In this fraction the Se(VI)/Se(IV) ratio seems independent from selenium application but it may be related to the redox conditions. The accumulation of selenium in the non-protein fraction is tentatively ascribed to the “Se–starch interaction” that should be able to modulate both the Se absorption into proteins and, possibly, its toxic effect for the plant itself.     

Voltammetric behaviour and determination of moxifloxacin in pharmaceutical products and human plasma

The oxidative behaviour of moxifloxacin was studied at a glassy carbon electrode in different buffer systems using cyclic, differential pulse, and Osteryoung square-wave voltammetry. The oxidation process was shown to be irreversible over the entire pH range studied (2.0–10.0) and was diffusion-controlled. The methods were performed in Britton–Robinson buffer and the corresponding calibration graphs were constructed and statistical data were evaluated. When the proposed methods were applied at pH 6.0 linearity was achieved from 4.4×10^–7 to 1.0×10^–5 mol L^–1. Applicability to tablets and human plasma analysis was illustrated. Furthermore, a high-performance liquid chromatographic method with diode-array detection was developed. A calibration graph was established from 4.0×10^–6 to 5.0×10^–5 mol L^–1 moxifloxacin. The described methods were successfully employed with high precision and accuracy for estimation of the total drug content of human plasma and for pharmaceutical dosage forms of moxifloxacin.     

DSC法研究液晶物质2-(4-烷氧苯基)6-取代苯并噻唑的相变热性质

The phase transitions of a new group of mesogens, 2-(4-alkoxyphenyl)-6-substituted benzothiazoles were thermodynamically studied by DSC, and their transition temperatures and enthalpy changes were measured, from which the transition entropy changes were calculated. The results obtained were discussed. In addition, the phe-nomenon of super-cooling of the compounds were quantitatively observed.     

Polymer crystallization dynamics,as reflected by differential scanning calorimetry. Part 2: Numerical simulations

With the aid of a model for the kinetics of polymer crystallization, as put forward in previous publications, the shape of DSC-curves and their position on the temperature scale were simulated for various conditions of heat transfer in the apparatus. It turns out that the outcome is very dependent on the assumptions made with respect to these heat transfer conditions. For the ideal condition — no temperature differences between sample, pan and furnace — an invariable shape is predicted for the DSC-curves. They only shift to lower temperatures with increasing cooling rates. For more realistic conditions, the curves not only shift but become broader and their maxima decrease. They show a more familiar appearance. These calculations are very involved, however, A simple balance equation is shown to yield equivalent results, if a dimensionless characteristic number like the Nusselt number remains considerably smaller than one. This number contains an effective heat transfer coefficient between sample and furnace which, surprisingly, should not be too high. Apparently, the heat capacity of the pan does not play an important role under these conditions. This is investigated in Appendix II. Appendix I describes the procedure of the numerical simulations.     

Voltammetry in Undiluted Acetic Acid. In Situ Determination of Water

Water present in undiluted acetic acid can be monitored in situ with Pt and Au microelectrodes using differential pulse and square‐wave voltammetries. Both reduction and oxidation peaks can be obtained. The best quantitative analytical results were obtained for the anodic peak, the Pt microelectrode, and differential pulse voltammetry. The anodic water peak is located at +1.55 V vs. the quasi reference Pt electrode. The voltammetric peak obtained at Pt electrode is apparently not a diffusional one, however, the calibration plot obtained by employing this peak is linear over a wide concentration range, up to 4 mol dm^?3. The detection limit has been estimated as 2.3 mM or 0.0043 v/v%. The developed method may be particularly useful, since the Karl Fischer method can not be used to determine water in glacial acetic acid due to the estrification reaction of acetic acid with methanol. A voltammetric wave of undiluted acetic acid could not be obtained in the positive and negative ranges of potential.     

On the minimal time function for distributed control systems in Banach spaces

In this paper, it is shown that the minimal time function is locally Lipschitz continuous for the control systemx=Ax+u in a Banach spadeE, under either of two conditions:A is linear and generates aC ₀-semigroup of bounded linear operators; orA is nonlinear, possibly multivalued, and dissipative. The main tool used for the nonlinear case is a result of Barbu concerning the null controllability of the system.