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31.
Continuous flow methodology is described which allows the in situ generation of the highly effective oxidising agent HOF·MeCN from fluorine and wet acetonitrile and immediate reaction with alkenes to afford epoxides in high yield. The HOF·MeCN continuous flow oxidising system provides an environmentally benign process that is suitable for large scale synthesis and is atom efficient, because the only by-product is hydrogen fluoride which, in principle, could be recycled to produce fluorine by electrolysis. 相似文献
32.
A flow injection manifold incorporating UV-photocatalytic oxidation for the determination of chemical oxygen demand (COD) in freshwater is reported. The method utilises the UV-photocatalytic oxidation of organic compounds instead of conventional heating (used in the standard method), with acidified potassium permanganate as the oxidant. Sodium oxalate, d-glucose and potassium hydrogen phthalate were used as COD standards. A 100 microL sample solution was injected into a 0.3 mol L(-1) H2SO4 carrier stream containing 0.1 mol L(-1) (NH4)2SO4, merged with a permanganate solution (8 x 10(-4) mol L(-1)) and passed through a 250 cm FEP (fluoroethylene polymer) photo-reaction coil wound around a 15 W UV lamp. The sample throughput was 30 h(-1), with an LOD (blank plus 3sigma) of 0.5 mg COD L(-1) and a linear range of 0.5-50 mg COD L(-1) (D-glucose, r2 = 0.9966). The method had good precision with relative standard deviations of 2.7% at 5 mg COD L(-1) and 1.2% at 20 mg COD L(-1) (n = 12) for glucose. Results for a COD certified reference material (QC Demand Quality Control Standard) were in good agreement with the certified COD value. Recovery from Tamar River water samples for all three COD standards was 83.0-111.0% and the COD values determined were in good agreement with those of a permanganate index reference method. 相似文献
33.
Graham Sandford Andrzej Tadeusiak Judith A.K. Howard 《Journal of fluorine chemistry》2007,128(10):1216-1220
A short series of bromo- and nitro-polyfluorobenzene derivatives gave the corresponding tetrahydroquinoxaline systems upon reaction with N,N′-dimethylethylene diamine. This annelation strategy gives useful quantities of functionalised tetrahydroquinoxaline systems which may be interesting scaffolds for the drug discovery arena. 相似文献
34.
In medical
products, shelf-life after thermoplastic processing and sterilization is important,
and ionizing radiation has become a preferred sterilization mode for medical
devices. We have employed successfully thermal analytical methods to predict
shelf-life for many polyolefin materials. However, as the material of construction
becoming more sophisticated: multiphase alloys and blends, multi-layer constructions
etc., issues existed that require clarification as to what extent these methodologies
are applicable.
We
have employed thermal analytical methods in conjunction with spectroscopic
and morphological methods to study the applicability and limitation of these
techniques. Results were combined with real life and simulated aging experiments
and presented in this article. 相似文献
35.
The TDDFT method is first applied in a series of tetra-nuclear transition metal clusters studies for nonlinear optical properties. The results indicate that the charge transfer inside the metal core [MCu3X4] (M=W, Mo; X=S, O, Cl, Se, Br) makes contribution to the optical nonlinearity. It is possible to enhance the hyperpolarizability by substituting the ligands of the clusters. 相似文献
36.
Yu-Ming ZHENG Hong-Min LIU Ben-Hao SA Zhong-Dao LU Zhong-Qi WANG Xiao-Ze ZHANG 《理论物理通讯》1993,19(1):71-74
A simple Monte Carlo simulation and even a partition method can be used to reproduce quite well the power law behavior between the factorial moment and the charge interval of fragment charge distributions from the multifragmentation of 197Au nucleus bombarding emulsion at~1 GeV/nucleon. This indicates that the above power law seems not to be a unique precursor of the intermittent behavior in nuclear multifragmentations. 相似文献
37.
The charge dispersion of fragments in high energy p+Cu,Kr and Xe reactions are calculated by statistical model and Monte Carlo technique.The corresponding data are reproduced quite well.It is shown that the charge dispersions are all nearly gaussian.The mass dependence of the most probable fragment charge reflects the rest target memory effect. 相似文献
38.
Following the method developed by the authors,recently,the equation of state of hot nuclei(238U in concrete) before break-up was investigated numerically.The isotherms are drawn in the plan of the general pressure P versus volume VRT. They are similar to those of Van der Waals gas.The critical temperature of phase transition should correspond to the isotherm with one turning point only.It turns out that the data of mass yield distribution can be reproduced by many pairs of parameters T and VRT (freeze-out temperature and freeze-out volume) varying in certain range.For each isotherm (each T),the data are always best reproduced by the value of VRT located at the maximum general pressure within two phases coexistence region. 相似文献
39.
LU ZhongDao SA BenHao Masanori Matsuda Junichi Nagata Atsushi Nakamura Osamu Miyamura 《中国物理C(英文版)》2000,24(8):743-747
The Λ multiplicity and Λ/p ratio are studied by hadron transportation-string fragmentation model in relativistic heavy ion collisions. Firstly, the dependence of Λ multiplicity and Λ/p ratio on the system size and the collision centrality is studied. It shows that the Λ and p multiplicities go up as the increase of system size and the increase of collision centrality. However, their ratio keeps almost a constant. The effect of Λ annihilation cross section to Λ multiplicity and Λ/p ratio is also studied. It is found that this effect is weak: Λ multiplicity and Λ/p ratio have a little amount of increase by the decrease of Λ annihilation cross section. Even the cross section is down to zero, Λ/p ratio is only 1.2 in 200A GeV AuAu head on collision. The Λ/p ratio is obtained to be 0.28 in pp collision, lying in the range of experimental data:0.2—0.3. It is also obtained that the ratio in AA collisions is 3—5 times of that in pp collision. 相似文献
40.
M P Bernstein S A Sandford 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》1999,55(12):2455-2466
We present the 2335-2325 cm-1 infrared spectra and band positions, profiles and strengths (A values) of solid nitrogen and binary mixtures of N2 with other molecules at 12 K. The data demonstrate that the strength of the infrared forbidden N2 fundamental near 2328 cm-1 is moderately enhanced in the presence of NH3, strongly enhanced in the presence of H2O and very strongly enhanced (by over a factor of 1000) in the presence of CO2, but is not significantly affected by CO, CH4, or O2. The mechanisms for the enhancements in N2-NH3 and N2-H2O mixtures are fundamentally different from those proposed for N2-CO2 mixtures. In the first case, interactions involving hydrogen-bonding are likely the cause. In the latter, a resonant exchange between the N2 stretching fundamental and the 18O = 12C asymmetric stretch of 18O12C16O is indicated. The implications of these results for several astrophysical issues are briefly discussed. 相似文献