Post-blast detection of traces of explosives by means of Fourier transform infrared spectroscopy

Samples obtained from debris after explosions of about 30 g of energetic materials were analyzed by means of Fourier transform infrared (FTIR) spectroscopy using both, Globar and synchrotron infrared radiation at the ISMI beamline of the Singapore synchrotron light source (SSLS). Low- and high-strength-of-explosion blasts were performed during each test run with the same explosive material. From the spectroscopic measurements, traces of unreacted explosives were found on more than 200 different materials that served as sample catchers in the explosions.The integrality of the experiments done confirmed that FTIR spectroscopy is a sufficiently sensitive method to detect traces of explosives in post-blast residues even of high-strength explosions. The method requires only a minimal amount of sample and enables accurate and very fast identification of the presence of explosive material. Finally, the synchrotron radiation infrared source provided one order of magnitude higher sensitivity compared to the conventional Globar source.     

Optimization of Fermentation Conditions for the Biosynthesis of <Emphasis Type="SmallCaps">l</Emphasis>-Threonine by <Emphasis Type="Italic">Escherichia coli</Emphasis>

In this study, the fed-batch fermentation technique was applied to improve the yield of l-threonine produced by Escherichia coli TRFC. Various fermentation substrates and conditions were investigated to identify the optimal carbon source, its concentration and C/N ratio in the production of l-threonine. Sucrose was found to be the optimal initial carbon source and its optimal concentration was determined to be 70 g/L based on the results of fermentations conducted in a 5-L jar fermentor using a series of fed-batch cultures of E. coli TRFC. The effects of glucose concentration and three different feeding methods on the production of l-threonine were also investigated in this work. Our results showed that the production of l-threonine by E. coli was enhanced when glucose concentration varied between 5 and 20 g/L with DO-control pulse fed-batch method. Furthermore, the C/N ratio was a more predominant factor than nitrogen concentration for l-threonine overproduction and the optimal ratio of ammonium sulfate to sucrose (g/g) was 30. Under the optimal conditions, a final l-threonine concentration of 118 g/L was achieved after 38 h with the productivity of 3.1 g/L/h (46% conversion ratio from glucose to threonine).     

Merrifield树脂负载的固相法合成1-氨基-2,4-咪唑二酮

设计了两条新的固相有机合成路线合成了1-氨基-2,4-咪唑二酮化合物4. 一条是由Merrifield树脂负载的羟基苯甲醛1a～1c和氨基脲反应得到缩氨基脲树脂2a～2c, 再在乙醇钠存在下和氯乙酸乙酯成环, 经盐酸切割得到1-氨基-2,4-咪唑二酮; 另一条是将Merrifield树脂用二甲基亚砜氧化氯甲基末端醛化后, 与氨基脲反应得到负载的缩氨基脲6, 经环化、切割得到目标产物4. 这两种方法中用1 mol/L的盐酸代替三氟乙酸作为切割剂, 产物单一、操作简便、可定量反应, 是合成1-氨基-2,4-咪唑二酮化合物的新方法.     

Cytotoxic triterpenoid saponins from Ardisia pusilla

A new triterpenoid saponin,3-O-{β-D-xylopyranosyl-(1→2)-β-D-glucopyranosyl-(1→4)-[β-D-ghcopyranosyl-(1→2)]-α-L-arabinopyranosyl }-3β,16α,28α-trihydroxy-1313,28-epoxy-oleanan-30-al(ardipusilloside Ⅲ,1),together with two known sapo-nins,ardisiacrispins A(2)and B(3),were isolated from the whole plants ofArdisia pusilla A.DC.Their structures were elucidated by extensive spectral analysis and chemical evidences.Saponins 1 and 3 exhibited significant cytotoxicity against human glioblastoma U251MG cells.     

Two new triterpenes from Duchesnea indica

Two new triterpenes,2α,3β-dihydroxyurs-12-en-18,19-epoxy-28-oic acid(1)and 18,19-seco,2α,3α-dihydroxyl-19-oxo-urs-11, 13(18)-dien-28-oic acid(2)were isolated from the herbaceous part of Duchesnea indica.Their structures were elucidated by spectroscopic analysis,including 2D NMR technique.The isolated compounds exhibited moderate cytotoxic activities against HeLa and L929 cell lines.     

Synthesis, characterizations and crystal structures of new organoantimony(V) complexes with various isomers of fluoromethylbenzoate ligands

Six new organoantimony(V) complexes containing various isomers of fluoromethylbenzoate ligands [RC₆H₃COO]₂SbPh₃ and [RC₆H₃COO]SbPh₄ [R = 3-F-4-(CH₃) (1, 4), 4-F-2-(CH₃) (2, 5), 5-F-2-(CH₃) (3, 6)] have been synthesized by the reactions of triphenylantimony(V) dichloride or tetraphenylantimony(V) bromide with various isomers of fluoromethylbenzoate ligands in 1:2 or 1:1 stoichiometries. All the complexes have been characterized by elemental analysis, IR and NMR [¹H, ¹³C and ¹⁹F] studies. The crystal structures of complexes 1, 3, 4, 5 and 6 have been determined by X-ray single crystal diffraction. The structure of complexes show that the five-coordinated antimony(V) atom adopts a distorted trigonal bipyramidal geometry. Furthermore, weak but significant intermolecular C–H···O, C–H···F hydrogen bonds, C–H···pi stacking lead to aggregation and assembly of these complexes into 1D and 2D supramolecular frameworks.     

A technique for production of nanocrystalline cellulose with a narrow size distribution

Nanocrystalline cellulose (NCC) was prepared by sulfuric acid hydrolysis of microcrystalline cellulose. A differential centrifugation technique was studied to obtain NCC whiskers with a narrow size distribution. It was shown that the volume of NCC in different fractions had an inverse relationship with relative centrifugal force (RCF). The length of NCC whiskers was also fractionized by differential RCF. The aspect ratio of NCC in different fractions had a relatively narrow range. This technique provides an easy way of producing NCC whiskers with a narrow size distribution.     

不用汞盐溶液的废水化学需氧量的快速测定

对测定废水的化学需氧量(COD)的标准方法(GB/T 11914-1989)作了两点改进:用硫酸锰代替硫酸银作催化剂和用少量银盐代表汞盐作为氯离子的掩蔽剂.这一改进使氧化时间由原来的2 h缩短为6 min,而且彻底消除了由汞离子所带来的污染问题.试验所得优化的测定条件为:加热温度为160℃;回流时间为6 min;酸度为15 mol·L-1;硫酸锰的加入量为7.5 g·L-1及测定下限为100 mg·L-1COD.     

水包油型微乳液相色谱分离激素类药物的影响因素

采用水包油型微乳液相色谱(MELC)分离了6种激素类药物(醋酸可的松、泼尼松龙、己烯雌酚、炔雌醇、醋酸氟轻松及黄体酮)。考察了微乳流动相的组成成分(包括表面活性剂的浓度、油相种类、有机添加剂种类)及固定相孔径等对分离的影响。实验得到的最佳分离条件: 色谱柱为Venusil ASB C18 (T)(粒径5 μm,孔径30 nm,250 mm×4.6 mm),微乳流动相为30 g/L十二烷基硫酸钠(SDS)-0.8%正辛烷-6.6%正丁醇,流速为0.8 mL/min,检测波长为254 nm,柱温为35 ℃。该方法可用于甾体药物及其制剂的分离鉴别以及快速测定。     

Structure of Plastic Crystalline Succinonitrile: High‐Resolution in situ Powder Diffraction

The temperature dependent (150–290 K) crystal structure of the low‐temperature α‐phase, and high temperature β‐phase, of succinonitrile has been determined by high resolution in situ powder diffraction. The α‐phase has a monoclinic unit cell that contains four gauche molecules and belongs to the P2₁/a space group. The crystal undergoes a reversible first‐order phase transition at 233 K into the high temperature β‐phase. The lattice parameters increase with temperature and the phase transition leads to an abrupt 6.7 % increase in volume. The β‐phase crystallizes into a bcc‐structure that belongs to the space group. The high temperature phase; however, is a highly disordered plastic crystal at room temperature that contains both gauche and trans molecules. The non‐linearity in the overall isotropic temperature‐factor indicates other possible phase transitions in the temperature range of 233–250 K.