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The pyrophoric compound Rb2[U(NH2)6] was obtained as a grey to black powder from the reaction of more than three equivalents of RbNH2 with UI3 in anhydrous liquid ammonia. During the process, UIII is oxidized to UIV and ammonia is reduced under evolution of H2. Rb2[U(NH2)6] crystallizes in the cubic crystal system, space group Fm3 m, with the lattice parameter a = 9.7870(12) Å, V = 937.4(2) Å3, Z = 4 at T = 293 K. It is isotypic to K2PtCl6. The compound contains the unprecedented hexaamidouranate(IV) anion [U(NH2)6]2–. 相似文献
23.
Kim Eklund Dr. Mikhail S. Kuklin Prof. Dr. Florian Kraus Prof. Antti J. Karttunen 《Chemphyschem》2020,21(8):802-808
Solid gold(I) fluoride remains as an unsynthesized and uncharacterized compound. We have performed a search for potential gold(I) fluoride crystal structures using USPEX evolutionary algorithm and dispersion-corrected hybrid density functional methods. Over 4000 AuF crystal structures have been investigated. Behavior of the AuF crystal structures under pressure was studied up to 25 GPa, and we also evaluated the thermodynamic stability of the hypothetical AuF crystal structures with respect to AuF3, AuF5, and Au3F8. Mixed-valence compound Au3[AuF4] with Au atoms in various formal oxidation states emerged as the thermodynamically most stable AuF species. 相似文献
24.
We present a method for simultaneous determination of the aminopolycarboxylic acids DTPA, EDTA and NTA in dishwashing detergents, paper mill waters, and natural waters by capillary electrophoresis (CE). The complexing agents were examined as their copper(II) complexes and separated by conventional CE with reversed polarity of the applied voltage. The optimum separation conditions were established by varying the pH and phosphate and tetradecyltrimethylammonium bromide (TTAB) concentrations in the run buffer. The separations were carried out in a fused-silica capillary (61 cm×75 m i.d.) filled with phosphate buffer (80 mmol L–1, TTAB concentration 0.5 mmol L–1, pH 7.1, voltage –20 kV) using direct UV detection at 191 and 254 nm. With this CE method all the peaks in the electropherograms were properly separated, the calibration plots gave good correlation coefficients and all three complexing agents could be detected in less than 4 min. Linear calibration plots were obtained for CuDTPA, CuEDTA and CuNTA; limits of detection were 0.03 mmol L–1 for all complexing agents and recoveries for all tested samples were within the range 104±7%. Results obtained from dishwashing detergent samples were found to be reliable and comparable with those from HPLC (R2=0.989) and UV–Vis (R2=0.985) methods. 相似文献
25.
Brake squeal, which usually falls in the frequency range between 1 and 16 kHz, has been one of the most difficult concerns associated with automotive brake systems since their inception. It causes customer dissatisfaction and increases warranty costs. Although substantial research has been conducted into predicting and eliminating brake squeal since the 1930s, it is still rather difficult to predict its occurrence. In this paper, the characteristics and current difficulties encountered in tackling brake squeal are first described. A review of the analytical, experimental and numerical methods used for the investigation of brake squeal is then given. Some of the challenges facing brake squeal research are outlined. 相似文献
26.
A Minkowski space formalism of finite-temperature quantum field theory is used to compute static thermodynamic quantities in the one- and two-loop approximation in an elegant and straightforward way using a generalization of Weinberg's tadpole method of calculating effective potentials. Systematic diagrammatic techniques for low- and high-temperature expansions are developed. Renormalizability by zero-temperature symmetric counterterms is proven for all orders in the loop expansion and demonstrated explicitly to two loops. Many useful computational techniques applicable to general finite temperature calculations are explained. 相似文献
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We introduce a method for finding the required control parameters for a quantum computer that yields the desired quantum algorithm without invoking elementary gates. We concentrate on the Josephson charge-qubit model, but the scenario is readily extended to other physical realizations. Our strategy is to numerically find any desired double- or triple-qubit gate. The motivation is the need to significantly accelerate quantum algorithms in order to fight decoherence. 相似文献
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Peak dispersion effects in nonaqueous capillary electrophoretic separations of aromatic anionic analytes were investigated in a propanolic background electrolyte solution. Poly(glycidylmethacrylate-co-N-vinylpyrrolidone) coating was applied to the capillary to suppress the electroosmotic flow and to improve the repeatability of the migration times. Electrical field strengths up to 2000 Vcm(-1) were applied in separations and the separation efficiencies were compared with theoretical values calculated on the basis of plate height theory. The contributions to the total plate height were calculated for injection plug length, diffusion, Joule heating, electromigration dispersion, analyte adsorption to the capillary wall, and detector slit aperture length. Analyte diffusion coefficients were measured by Taylor dispersion method, while distribution constants were measured chromatographically. Agreement between the calculated and empirical results was fairly good even though some approximations were required. In most cases the longitudinal diffusion contribution governed the total plate height, while the contribution of Joule heating was insignificant even at exceptionally high field strengths used. The relatively long detection slit aperture was found to influence the separation efficiency strongly, while the other dispersion sources that were investigated were of minor importance, except for adsorption in the case of one analyte. With all analytes, the dispersive effect of longitudinal diffusion was reduced as the field strength was increased, leading to enhanced migration velocities and faster separations. 相似文献