The IINS, IR and DFT studies of hydrogen bonds in 6-Furfuryl and 6-Benzylaminopurines

FTIR and IINS spectra of 6-Furfurylaminopurine (6-FAP) and 6-Benzylaminopurine (6-BAP) taken at different temperatures have been analysed and compared with the spectra calculated by the ab initio DFT/B3LYP method and the semiempirical PM3 method in the isolated molecule approximation, for the tautomers N3-H, N7-H and N9-H, and dimers with hydrogen bonds. For 6-FAP the best agreement between the calculated and experimental (at 20 K) spectra has been found for the N9-H tautomer, whose structure was established by X-ray diffraction. For 6-BAP the analogous agreement for the N9-H tautomer structure has been poor and much better for the N7-H tautomer. The vibrational spectra calculated for dimers of the molecules studied involved in hydrogen bonds, permitted also an interpretation of the bands whose positions and FWHM in the FTIR spectra changed with temperature.     

Small angle neutron scattering studies on nonaqueous dispersions of calcium carbonate Part 2. Determination of the form factor for concentric spheres

Colloidal dispersions of calcium carbonate, stabilised primarily by a surface active agent, in both toluene and dodecane have been examined by small angle neutron scattering. A model has been developed to simulate the scattering behaviour of the particles and is based on the idea of a concentric sphere with a homogeneous layer of adsorbed material surrounding a core particle. Computations based on the model show a wide variation of scattering behaviour with variation of the coherent scattering length of the dispersion medium. These predictions were confirmed by experiment. A method is described for analysis of the experimental data which leads to a determination of the thickness of the adsorbed layer, the radius of the core particle and the standard deviation of core particle radius.     

有机锗氨基酸酯类系列化合物的快原子轰击质谱规律

为增强有机锗化合物的生物活性，合成了一系列有机锗氨基酸酯类倍半氧化物，并重点研究了它们的快原子轰击质谱（ＦＡＢＭＳ）。研究结果表明：该系列化合物的各碎片离子峰与其组成及结构均有很好的对应关系及很强的规律性     

New NIST sediment SRM for inorganic analysis

NIST maintains a portfolio of more than 1300 standard reference materials (SRM), more than a third of these relating to measurements in the biological and environmental fields. As part of the continuous renewal and replacement efforts, a set of new marine sediments has been recently developed covering organic and inorganic determinations. This paper describes the steps taken in sample preparation, homogeneity assay, and analytical characterization and certification with specific emphasis on SRM 2702 inorganics in marine sediment. Neutron activation analysis showed the SRM to be highly homogeneous, opening the possibility for use with solid sampling techniques. The certificate provides certified mass fraction values for 25 elements, reference values for eight elements, and information values for 11 elements, covering most of the priority pollutants with small uncertainties of only several percent relative. The values were obtained by combining results from different laboratories and techniques using a Bayesian statistical model. An intercomparison carried out in field laboratories with the material before certification illustrates a high commutability of this SRM.Electronic Supplementary Material Supplementary material is available in the online version of this article at     

K3MnH5, das erste salzartige Manganhydrid

K₃MnH₅, the First Salt-like Manganese Hydride K₃MnH₅ and K₃MnD₅ were synthesized by the reaction of potassium hydride (deuteride) with manganese powder under a hydrogen pressure above 3000 bar at 875 K. X-ray investigations on powdered samples and elastic neutron diffraction experiments on the deuterated compound at the time-of-flight spectrometer LAD in the temperature range 5–600 K led to the complete structure determination. The atomic arrangement is isotypic with that of Cs₃[CoCl₄]Cl (space group: 14/mcm, Z = 4). The structure of K₃MnH₅ contains isolated [MnH₄]^2?-tetrahedra and additional hydrogen ions which are exclusively coordinated by potassium cations. The magnetic susceptibilities show Curie-Weiss behaviour. At temperatures below 50 K there are obviously antiferromagnetic interactions.     

Comparison of Electrospray Ionization and Fast Atom Bombardment Mass Spectrometry for the Analysis of Saponins from Alfalfa,Clover, and Mungbeans

The determination of seven saponins in crude plant extracts by electrospray ionization mass spectrometry (ESI-MS) and fast atom bombardment mass spectrometry (FAB-MS) is described. Distinct protonated and natriated (Na-adduct) molecular ions in ESI-MS spectra readily provide molecular weight information, which can be further verified using clusters of molecular ions. Saponin mixtures can be analyzed by ESIMS on varying the potential difference between the capillary and skimmer in the ESI source to decompose impurities. ESI-MS uses less amount of sample than that required by FAB-MS. ESI-MS does not produce structural information, however. The FAB-MS spectra consist mainly of protonated and deprotonated molecular ions with limited structural information. (-)-FAB-MS is more suitable for analyzing saponin samples than the (+)-FAB-MS.     

Dispersion of silica nano-particles in sol-gel hybrid resins for fabrication of multi-scale hybrid nanocomposite

Multi-scale hybrid nanocomposites containing both ∼15 nm silica colloids and ∼2 nm oligosiloxanes in a methacryl polymer matrix were newly designed and fabricated. Colloidal silica sols were dispersed in methacryl oligosiloxanes nano-hybrid resins synthesized by sol-gel reaction of methacryloxypropylmethoxysilane and diphenylsilanediol. On the basis of TEM and SANS analyses, it was confirmed that the silica colloids were compatibly dispersed and different sizes of colloidal silica and oligosiloxanes co-exist in the solutions. Multi-scale hybrid nanocomposites fabricated by UV and thermal curing with incorporation of silica colloids in the nano-hybrid materials show enhanced mechanical and thermal characteristics.     

Synthese und Struktur von Li3RhH6, einem ternären Hydrid mit isolierten [RhH6]3−-Oktaedern

Synthesis and Structure of Li₃RhH₆ — a Ternary Hydride with Isolated [RhH₆]^3? Octahedra The ternary rhodium hydride Li₃RhH₆ was synthesized by the reaction of lithium hydride with rhodium under a hydrogen pressure of 80 bar. X-ray investigations on powdered samples and an elastic neutron diffraction experiment on the deuterated compound led to the complete structure determination (space group: Pnma, Z = 4). The atomic arrangement is isotypic to the Na₃RhH₆ structure type. The crystal structure contains isolated [RhH₆]^3? octahedra, which are separated by the lithium ions.     

Sol-Gel Routes to Zeolite Membranes and Thin Films

The synthesis of zeolite membranes and thin films using the secondary growth process is briefly described. In this process colloidal zeolite particles (sols) are prepared hydrothermally and then subsequently deposited on substrates to produce uniform layers of controlled thickness, as illustrated with silicalite and zeolite-A. The formation and growth of the zeolite sols has been investigated in situ by small angle neutron scattering (SANS). SANS measurements on silicalite sols at progressively higher concentrations have provided details of the colloid interactions which lead to zeolite gel-layer structures which are uniform and free of defects.     

不同热管工质对热管冷却反应堆堆芯物理参数的影响与分析

热管冷却反应堆采用非能动传热技术,热响应速度快,可避免堆芯单点失效,具有功率密度大、寿命长、环境适应性强、工作性能稳定等特点,是目前空间核反应堆研究的热点。本文基于清华大学开发的反应堆蒙特卡洛中子输运程序RMC (Reactor Monte Carlo code),以美国爱荷华国家实验室(Idaho National Laboratory, INL)设计的热管冷却反应堆INL Design A为研究对象,选取3种热管工质开展热管冷却反应堆堆芯物理计算。计算结果表明：锂热管工质不仅拥有很好的热物性参数,并且使用锂热管工质的热管冷却反应堆缓发中子有效份额最大、中子能谱较硬、燃耗反应性损失最小、增殖性能最佳,有利于热管冷却反应堆堆芯小型化与长寿命。因此,推荐锂为热管冷却反应堆的热管工质。