Zur Kenntnis der thermischen Zersetzung von Ammoniumhexafluoroscandat,-titanat,-vanadat und-chromat

Thermal analysis supported by kinetic calculations was applied exhaustively to these compounds. Under dynamic conditions, tetrafluorometallates(III), which as intermediates, could not be isolated, for the first three compounds. In each case, the final step was the pure metal(III) fluoride. Ammonium hexafluorochromate(III) decomposed directly to the pure chromium(III) fluoride. The decomposition rate of all compounds slowed down towards the end, probably for kinetic reasons. Polymorphic transitions of ammonium hexafluorotitanate(III) were observed at 35 and 100°C. Ammoniumhexafluoroscandate(III) underwent polymorphic transition at 47°C. The decomposition patterns for all these compounds were similar. Conditions for the preparation of pure ammonium tetrafluorometallates(III) of Sc, Ti and V are described.     

Influence of Urbach Energy,Temperature, and Longitudinal Position in the Active Layer on Carrier Diffusion Length in Perovskite Solar Cells

The diffusion length of charge carriers in the active layer of a perovskite solar cell (PSC) of the structure Glass/PEDOT: PSS/CH₃NH₃PbI₃/PC60BM/Al is modelled. It is found that the diffusion length depends on the position x in the active layer measured from the PEDOT: PSS interface, Urbach energy and temperature. By varying the voltage in the range from zero to , it is shown that the dependence of diffusion length on the position x in the active layer reduces at higher voltage. The combined influence of applied voltage and temperature on the diffusion length of charge carriers is investigated and it is found that in the low voltage range the diffusion length is temperature independent, but it becomes significantly temperature dependent at higher voltages. Also, it is found that the diffusion length decreases as the applied voltage increases and this reduction becomes much more significant at higher voltage and temperatures. The combined influence of applied voltage and Urbach energy on diffusion length of charge carriers reveals that the diffusion length decreases when both the applied voltage and Urbach energy increase. However, the reduction in the diffusion length due to the increase in Urbach energy becomes less significant at higher voltage.     

Non-empirical LCAO-MO-SCF-CI calculations on organic molecules with Gaussian type functions

This paper (Part I) describes the theoretical and computational bases of some non-empirical calculations on small organic molecules to be reported in later papers (Parts II et seq). Approximate solutions for the usual fixed nucleus electronic Hamiltonian, in the term of wave functions composed of Slater determinants, are discussed, with particular emphasis on their computational utility. Possible choices of basis functions, from which to form the determinants are examined, and the advantages of Gaussian type functions (GTF) centered on the component atoms are pointed out. Some of the properties of molecules which can be calculated using such approximate wave functions are outlined. Finally an attempt is made to discuss the current limitations of non-empirical calculations of the type described here, and some guesses are made about their future. Brief outlines as a set of appendices are given of the mathematical formalism and computational details of the calculations.     

开链冠醚Schiff碱-稀土配合物的合成、表征及近红外发光光谱研究

合成了3个新型开链冠醚Schiff碱-稀土离子三元配合物RE(H2L)(Mq)(NO3)3,其中RE=Nd3 ,Er3 ,Yb3 ,配体H2L=N,N-双(邻羟苯亚甲基)-3,6-二氧杂-1,8-二氨基辛烷,Mq为8-羟基喹哪啶.采用元素分析、红外光谱(IR)、紫外-可见吸收光谱(UV-vis)、热重-差热分析(TG-DTG)等手段对配合物的组成结构进行了表征.测定了3种新型结构稀土三元配合物在不同温度(77 K和300 K)时的近红外发光光谱.     

Reaction of methyl 4-nitrobenzenesulfonate with Br- in water-formamide tetradecyltrimethylammonium bromide micellar solutions

Summary The reaction methyl 4-nitrobenzenesulfonate + Br^- was studied in water-formamide tetradecyltrimethylammonium bromide micellar solutions. A pseudophase kinetic model was used to quantitatively rationalize the kinetic micellar effects observed     

The exo-selectivity of the new non-natural chiral auxiliary (+)-(1R,endo)-2-benzonorbornenol in an asymmetric aza-Diels-Alder reaction

The recently reported compound (+)-(1R,endo)-2-benzonorbornenol (2) proved to be an efficient chiral auxiliary in the asymmetric aza-Diels-Alder reaction between cyclopentadiene and the N-benzyl imine of its glyoxylate, which afforded a virtually all-exo mixture of cycloaducts with a 1S:1R diastereomeric ratio of 63:37.     

Single-strand conformation polymorphism-based analysis of mitochondrial cytochrome c oxidase subunit 1 reveals significant substructuring in hookworm populations

Sequence heterogeneity in a portion of the mitochondrial cytochrome c oxidase subunit 1 gene (pcox1) was measured for the hookworms, Ancylostoma caninum from Australia, A. duodenale from China, and Necator americanus from China and Togo using single-strand conformation polymorphism (SSCP) analysis combined with DNA sequencing. The pcox1 sequences were characterised for individual nematodes displaying genetic variation within each of the three species, and those were compared with pcox1 sequences of four other species of hookworm. While intraspecific variation in the pcox1 sequence ranged from 0.5 to 8.6% for A. caninum, 0.3 to 3.3% forA. duodenale, and 0.3 to 4.3% for N. americanus, interspecific differences varied from 4.8 to 12.9%. Sequence data also provided information on nucleotide compositions and substitution patterns. Genetically distinct groups were detected within A. caninum and A. duodenale, indicating significant population substructuring within these species. Also, N. americanus individuals from China all differed from those from Togo at four nucleotide positions, supporting a previous proposal (based on ribosomal DNA sequence data) that N. americanus may represent a species complex. The findings indicated the value of pcox1 sequence data and the mutation scanning approach for studying the genetic structures of hookworm populations, which should have important epidemiological relevance.     

二氧化铈还原表面上水煤气变换反应机理

采用原位红外，程序升温脱附，脉冲表面反应技术研究了ＣｅＯ２还原表面在中温变换反应条件下表面物种的生成及脱附，并根据研究结果归纳出水煤气变换反应机理。     

Modeling deoxyribose radicals by neutralization-reionization mass spectrometry. Part 1. Preparation,dissociations, and energetics of 2-hydroxyoxolan-2-yl radical,neutral isomers,and cations

Collisional neutralization of several isomeric C(4)H(7)O(2) cations is used to generate radicals that share some structural features with transient species that are thought to be produced by radiolysis of 2-deoxyribose. The title 2-hydroxyoxolan-2-yl radical (1) undergoes nearly complete dissociation when produced by femtosecond electron transfer from thermal organic electron donors dimethyl disulfide and N,N-dimethylaniline in the gas phase. Product analysis, isotope labeling ((2)H and (18)O), and potential energy surface mapping by ab initio calculations at the G2(MP2) and B3-PMP2 levels of theory and in combination with Rice-Ramsperger-Kassel-Marcus (RRKM) kinetic calculations are used to assign the major and some minor pathways for 1 dissociations. The major (approximately 90%) pathway is initiated by cleavage of the ring C-5[bond]O bond in 1 and proceeds to form ethylene and *CH(2)COOH as main products, whereas loss of a hydrogen atom forms 4-hexenoic acid as a minor product. Loss of the OH hydrogen atom forming butyrolactone (2, approximately 9%) and cleavage of the C-3[bond]C-4 bonds (<1%) in 1 are other minor pathways. The major source of excitation in 1 is by Franck-Condon effects that cause substantial differences between the adiabatic and vertical ionization of 1 (5.40 and 6.89 eV, respectively) and vertical recombination in the precursor ion 1(+) (4.46 eV). (+)NR(+) mass spectra distinguish radical 1 from isomeric radicals 2-oxo-(1H)oxolanium (3), 1,3-dioxan-2-yl (9), and 1,3-dioxan-4-yl (10) that were generated separately from their corresponding ion precursors.     

Determination of bismuth, indium and lead in geological samples by electrothermal AAS Part 2. Comparative study of palladium and molybdenum containing chemical modifiers*

A comparative and systematic study has been carried out of the effects of palladium and molybdenum containing chemical modifiers, such as Pd + Rh, Pd + Pt, Pd + Ru, Pd + Rh + Pt, Pd + Rh + Ru, Mo + Pd, Mo + Rh, Mo + Ru and Mo + Pt and additionally tartaric acid (TA) as a reducing agent together with mixed modifiers for the thermal stabilization of Bi, In and Pb in a Zeeman electrothermal atomic absorption spectrometer (ETAAS). The effect of the mass ratios of the mixed modifier components on the maximum pretreatment temperature for the analytes has been determined. The modifier mixtures of Pd + Rh + Pt, Mo + Pd + TA and Mo + Pt + TA were found to be especially powerful for the determination of Bi, In and Pb. These mixed modifiers could increase the ashing temperatures of the analytes up to 1250–1400° C. They were applied to the determination of Bi and Pb in dissolved geological reference samples and accuracy and precision of the method were thereby enhanced. The percent relative error was decreased from 20.0 to 0.4 for Bi and from 10.5 to 0.3 for Pb, depending on the sample type. Received: 9 May 1997 / Revised: 19 August 1997 / Accepted: 20 August 1997