Application of heat conduction calorimetry to high explosives

This paper describes some thermal analysis experiments conducted on high explosive samples. These employ differential scanning calorimetry to monitor thermal effects at elevated temperatures (around 200 °C) and heat conduction calorimetry to record thermal effects at much lower temperatures (below 100 °C).The work shows that, due to the generally high thermal stability of many high explosive compositions, heat generation rates are very low, if detectable at all, at normal storage temperatures, even when using a very sensitive instrument. The sensitivity and reproducibility of this technique has been investigated in detail by Wilker et al. [S. Wilker, U. Ticmanis, G. Pantel, Detailed investigation of sensitivity and reproducibility of heat flow calorimetry, in: Proceedings of the 11th Symposium on Chemical Problems Connected with the Stability of Explosives, Sweden, 1998] and shown to be capable of recording heat generation rates of less than a microwatt. This allows continuous measurement of decomposition processes in nitrate ester based propellants at temperatures as low as 40 °C. However, the measurement of very low levels of heat generation is difficult, time consuming and therefore expensive. If the assumption is made that the life limiting process is invariably the slow decomposition of the energetic component, this will frequently lead to very long service lifetime predictions.A number of possible complications are identified. Firstly, due to its low detection threshold, a heat conduction calorimeter may detect other reactions which will not lead to failure, but which may still dominate the heat flow signal. Secondly, the true failure process may generate little energy and be overlooked. In view of these considerations, at present it seems unwise to rely on heat conduction microcalorimetry as the only tool for the assessment of the life of high explosive energetic systems.Based on examples of life terminating processes in high explosives during storage and use, it is clear that decomposition of the energetic material is not invariably the cause of system failure. It is also by no means the only reaction that may take place in, and be observed by, a heat conduction calorimeter.     

Solventless injecction for packed column supercritical fluid chromatography

The adverse effects of injection solvent strength on microbore packed column SFC band broadening are demonstrated and a solventless injection system that eliminates these effects is introduced. The injection system removes solvent in a GC-like manner using a retention gap and an on-column capillary GC syringe. The analyte is delivered to the analytical column in a solvent-free plug of supercritical fluid mobile phase.     

C2H4-K体系中振动态至电子态传能的研究

用TEA CO_2激光将C_2H_4分子激发到高振动激发态，高振动激发态的C_2H_4分子与基态的K原子碰撞发生振动态→电子态（V→E）传能过程，根据提出的能级组模型，对测得的时间分辨原子荧光信号进行处理，获得温度在453－663 K范围内，C_2H_4-K体系中V→E传能速率的数量级为10~(-10)/cm~3·molecule~(－1)·s~(－1)，对应的碰撞传能截面约为0.30～0.80 nm．随着反应温度升高，V→E传能截面减小．上述实验结果表明碰撞体间吸引相互作用在这种非共振的V→E传能过程中起主要作用．利用多极相互作用势下的碰撞络合物模型对实验结果进行了讨论．     

A convergent synthesis of octadeca-2E, 13Z-dienyl acetate, a pheromone component ofSynanthedon tipuliformis C.

A convergent synthesis of octadeca-2E, 13Z-dienyl acetate, a pheromone component ofSynanthedon tipuliformis C., has been developed. The synthesis is based on cross-coupling of 8-iodooct-2E-en-I-ol THP ether with dec-5Z-enyl bromide catalyzed by CuBr. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1529–1531, August, 1997.     

Synthesis and characterization of sulfone-containing polyesters derived from 4,4′-dicarboxydiphenyl sulfone by direct polycondensation

Several sulfone-containing polyesters having inherent viscosities 0.43-0.19 dL g^?1 were prepared by direct polycondensation of 4,4′-dicarboxydiphenyl sulfone (DCDPS) with various aromatic and aliphatic diols, by p-toluenesulfonyl chloride and N,N′-dimethylformamide in pyridine solution. The polyesters were examined by elementary analysis, IR spectra, inherent viscosity, x-ray diffraction, solubility, DSC, and TGA. The diffraction diagram showed that all polyesters were crystalline except that obtained from bisphenol-A. All polymers were soluble in sulfonic acid (18M), phenol and p-chlorophenol, but not in acetone and toluene. These polymers obtained from aromatic bisphenols lost no mass below 325°C, but 10% loss of mass was recorded above 396°C in nitrogen. DCDPS copolymerized with isophthalic acid (IPA) and bisphenol-A had inherent viscosity up to 0.49 dL g^?1, with relatively narrow distribution of molar mass . © 1995 John Wiley & Sons, Inc.     

A statistical method to detect chromosomal regions with DNA copy number alterations using SNP-array-based CGH data

Single nucleotide polymorphism (SNP) arrays were used to detect chromosomal regions with DNA copy number alterations. Current statistical methods for microarray-based comparative genomic hybridization (array-CGH) analysis generally assume certain relationships among adjacent markers on the same chromosome, and these assumptions may be questionable. For an SNP-array-based CGH study, multiple normal reference SNP arrays were collected. In order to utilize these normal reference SNP arrays, we derived an empirical distribution of signal ratios for each SNP marker. With an assumed threshold value for the overall error rate control and the defined signal ratio ranges for chromosomal amplification and deletion, we proposed a procedure to identify chromosomal alteration regions based on several bootstrapped one-sample t-tests and the false discovery rate control. When we have multiple arrays for different individuals with the same disease, our method can also be used to detect SNP markers for chromosomal alteration regions that are common among these individuals. We applied our method to a published SNP array data set for breast carcinoma cell lines. For an individual with breast cancer, numerous chromosomal alteration regions were identified. Compared to results of previous studies, our method identified more chromosomal alteration regions, with some being implicated in the literature to harbor genes associated with breast cancer. For multiple cancer arrays, our results suggested the existence of common chromosomal alteration regions. However, a high proportion of false positives also indicated that genetic variations among different individuals with breast cancer can be present.     

Phenol methylation over CrPO4 and CrPO4?AlPO4 catalysts

The vapor-phase catalytic alkylation of phenol with methanol and dimethyl carbonate on a series of differently prepared CrPO₄ (Cr/P=1) and CrPO₄-AlPO₄ (CrAIP) catalysts, has been studied at different temperatures (473–673 K). The reaction is first order in phenol, giving a mixture of O- and C-alkylated products (C-alkylation taking place preferentially at theortho-position). Moreover, dimethyl carbonate is a better methylating agent than methanol.     

光解苯半醌和2-羟基-2-丙基自由基的CIDEP谱

用高时间分辨ＥＳＲ波谱仪测量了光解苯半醌和２－羟基－２－丙基自由基的ＣＩＤＥＰ谱,苯半醌自由基的ＣＩＤＥＰ属ＴＭ机理,实验研究了微波功率,溶液浓度对苯半醌自由基的ＣＩＤＥＰ谱时间演化的影响,２－羟基－２－丙基自由基的ＣＩＤＥＰ属ＲＰＭ机理,实验研究了自旋极化的生成环境。     

Successive substitution titration of calcium and magnesium with EGTA using thallium oxide electrode for indication

Summary It is demonstrated that magnesium can be titrated with EGTA in the presence of CaEDTA complex. On the basis of this substitution reaction, calcium and magnesium are successively titrated with EGTA, if an appropriate amount of CaEDTA is added after having reached the end point for calcium. Both end points are indicated amperometrically using a thallium oxide anode. The method has been tested for analysis of tap and mineral water. Larger amounts of manganese(II) render the calcium result too high. Moreover, the indication of both end points is affected by the electrode position of an inactive MnO₂-layer onto the Tl₂O₃-layer. Reducing agents destroy the Tl₂O₃-layer. These interferences can be overcome by addition of an appropriate amount of manganate(VII) to the sample.

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Sukzessive Substitutionstitration von Calcium und Magnesium mit ÄGTA, indiziert mit der Thalliumoxidelektrode

Zusammenfassung Magnesium kann mit ÄGTA in Gegenwart des CaÄDTA-Komplexes titriert werden. Auf der Grundlage dieser Substitutionstitration können Calcium und Magnesium nacheinander mit ÄGTA titriert werden, wenn nach dem Endpunkt für Calcium eine ausreichende Menge CaÄDTA zugesetzt wird. Beide Endpunkte werden amperometrisch mit Hilfe einer Thalliumoxidelektrode angezeigt. Die Methode wurde an Leitungswasser und Mineralwasser geprüft. Größere Mengen Mangan(II) bewirken zu hohe Calciumwerte. Darüber hinaus wird die Indikation beider Endpunkte dadurch beeinträchtigt, daß sich eine inaktive MnO₂-Schicht auf der Tl₂O₃-Schicht elektrolytisch abscheidet. Reduzierende Stoffe zerstören die Tl₂O₃-Schicht. Diese Störungen können durch Zugabe von Permanganat vermieden werden.

     

Preparation and structural characterization of a hexanuclear molybdenum (II) cluster containing carboxylate ligands (Bu4N)2[Mo6(μ3-Cl)8(O2CMe)6]

The hexamolybdenum cluster complex [Mo₆(₃-Cl)₈(O₂CMe)₆]^2–, 1 was isolated as the Bu₄N⁺ salt in 71% yield from the reaction of (Bu₄N)₂[Mo₆(₃-Cl)₈Cl₆] with AgO₂CMe in CH₂Cl₂ solvent. The compound was characterized by single crystal X-ray diffraction analysis. The cluster contains an octahedral arrangement of six molybdenum atoms with eight chloride ligands bridging the eight trianglar faces and six carboxylate ligands terminally coordinated through one oxygen atom to each of the six molybdenum atoms. Crystal data: space group =P2₁/n,a=10.713(3)Å,b=14.43(1)Å,c=21.919(4)Å, =94.37(2)°,Z=2, 1965 reflections,R=0.036.