The local structure of molten LaCl3 was investigated by X-ray absorption fine structure of the La K-edge. The nearest La3+-Cl− distance and coordination number were 2.89±0.01 Å and 7.4±0.5 from the curve fitting of the first peak in the Fourier transform magnitude |FT|. The coordination number larger than 6 suggests that the local structure of molten LaCl3 is not a simple octahedral coordination (LaCl6)3−, but 7-fold (LaCl7)4− and/or 8-fold (LaCl8)5− complexes. The first La3+-La3+ distance, of which correlation was observed as a weak second peak in the |FT|, was evaluated to be 4.9 Å. It suggests that the distorted corner-sharing connection of the complex species is predominant in the melt, in contrast with molten YCl3 in which the edge-sharing connection of the 6-fold (YCl6)3− mainly exists. 相似文献
A new complex of a chiral monoaza-crown ether, [R-(-)-2-ethyl-N-benzyl-4,7,10,13-tetraoxa-8,9-benzo-1-azacyclopentadec-8-ene...NaClO4], has been prepared and studied by x-ray diffraction. The compound crystallizes in space group P21 with cell dimensions a = 8.721(1), b = 16.318(2), c = 8.905(1) Å, = 100.80(1)°. The sodium cation is heptacoordinated and located significantly out of the best plane of the macrocycle ring. The donor atoms of the macrocycle are in the half-chair arrangement. 相似文献
The X-ray crystal structure of IX, perchlorate salt of R-(?-2-ethyl-N-benzyl-4,7,19,13-tetraoxa-8,9-benzo-1-azacyclopentadec-8-ene has been determined. In the molecule, the protonated nitrogen atom participates in two N-H?O hydrogen bonds. The unusually high proton affinity of aza crown ether leads to the formation of diastreomer instead of complex formation with chiral R-(+)-1-phenyl ethyl ammonium perchlorate and S-(?)-1-phenyl ethyl ammonium perchlorate. The complex ability of host ethers was evaluated in terms of structural modification. 相似文献
The gamma-irradiated single crystals of 2-Bromo-4′-methoxyaceto-phenone (2B4MA) were investigated using electron paramagnetic resonance (EPR) technique. Density-functional theory calculations were employed to investigate and identify the radicals that have been assumed to be formed upon irradiation of 2B4MA single crystals. The EPR spectra of 2B4MA were recorded at different orientations in the magnetic field at room temperature. Taking into account the chemical structure and experimental spectra of irradiated single crystal of 2B4MA, it was assumed that at least two different radicals were produced in the sample. Following this assumption, six possible radicals were modeled and EPR parameters were calculated by using the DFT, B3LYP/6-311+G(d), for the modeled radicals individually. The calculated hyperfine coupling constants and g-tensors were used as initial values for simulation studies. The three crystallographic axes on the simulated spectra were well matched with experimental spectra for the two modeled radicals. Thus, we identified the R1 type radical and R4 type radical as paramagnetic species produced in gamma-irradiated 2B4MA. 相似文献
Knowledge management is widely considered as a strategic tool to increase firm performance by enabling the reuse of organizational knowledge. Although many have studied knowledge management in a variety of business settings, the concept of tacit knowledge, especially the individual one, has not been explored in due detail. The objective of this study is to identify and prioritize individual tacit knowledge criteria and to explain their effects on firm performance. In the proposed methodology, first, the most prevalent individual tacit knowledge variables are identified by means of knowledge elicitation and feature selection methods. Then, the extracted variables were prioritized using machine learning methods and fuzzy Analytic Hierarchy Process (AHP). Support vector machine (SVM), logistic regression, and artificial neural networks are used as the first approach, followed by fuzzy AHP as the second approach. Based on the comparative analysis results, SVM (as the best-performed machine-learning technique) and fuzzy AHP methods were identified for the subsequent analysis. The results showed that both SVM and fuzzy AHP determined time efficiency of employees, communication between employees and supervisors, and innovative capability of employees as the most important tacit knowledge criteria. These findings are mostly supported by the extant literature, and collectively shows the synergistic nature of the utilized analytics approaches in determining individual tacit knowledge criteria.
Practical use of many bioelectronic and bioanalytical devices is limited by the need of expensive materials and time consuming fabrication. Here we demonstrate the use of nickel electrodes as a simple and cheap solid support material for bioelectronic applications. The naturally nanostructured electrodes showed a surprisingly high electromagnetic surface enhancement upon light illumination such that immobilization and electron transfer reactions of the model redox proteins cytochrome b5 (Cyt b5) and cytochrome c (Cyt c) could be followed via surface enhanced resonance Raman spectroscopy. It could be shown that the nickel surface, when used as received, promotes a very efficient binding of the proteins upon preservation of their native structure. The immobilized redox proteins could efficiently exchange electrons with the electrode and could even act as an electron relay between the electrode and solubilized myoglobin. Our results open up new possibility for nickel electrodes as an exceptional good support for bioelectronic devices and biosensors on the one hand and for surface enhanced spectroscopic investigations on the other hand. 相似文献
A novel fluoroionophore compound was synthesized from a boron dipyrromethene (BODIPY) fluorophore and 4′-formylbenzo-15-crown-5 ionophore groups. Photophysical properties of the BODIPY-crown compound were studied with UV–Vis and fluorescence spectroscopy. The effect of metalic cations (Li+, Na+, K+, Mg2+, Ca2+, Ba2+, Al3+, Fe3+, Cu2+, Co2+, Zn2+, Ag+, Hg2+, Pb2+) on the absorption and fluorescence spectra of compound 2 was investigated. Blue shifts were detected in UV–Vis spectra upon addition of some metal ions (Al3+ > Fe3+ > Na+). At the same time, the emission intensity of this complex increased due to binding of Na+ ion to the benzo crown cavity. Additionally, a decrease in the intensity of the 630 nm emission peak and an increase in the intensity of the 570 nm emission peak was observed in the fluorescence emission spectra following addition of Al3+ and Fe3+ ions. 相似文献
Solution Combustion Synthesis (SCS) and ConventionalCeramic Process (CCP) were applied for the preparation of magnesium pyroborate (Mg2B2O5) from Mg(NO3)2 · 6H2O and H3BO3. Structural and morphological properties of the products were comparatively examined by XRD and FT‐IR spectroscopic measurements as well as SEM and BET techniques. The effects of synthesis conditions on the properties of products were investigated throughly by optimizing the B/Mg molar ratio and reaction duration in CCP and by optimizing the fuel (carbohydrazide) quantity in SCS. Pure Mg2B2O5 (triclinicsuanite) was obtained by thermal treatment in CCP employing a B/Mg molar ratio of 3:1. It was found that the fuel must be in close proximity to the stoichiometric requirements in order to obtain the desired product in highly crystalline form from SCS. The Mg2B2O5 samples obtained by both methods exhibited similar structural properties but different morphologies. 相似文献
Abstract Graft polymerization of acrylamide (AAm) on 1, 1, 2, 2 tetrachloro-ethane (TCE) preswelled poly(ethylene terephthalate) (PET) films were performed with chemical initiation method using asobisiso-butyronitrile (AIBN) initiator. Temperature was found to have a greater effect on the swelling then the swelling time. Variation of the graft yield with polymerization temperature, time, AIBN concentration, AAm concentration, AIBN and AAm inclusion times were investigated. The optimum temperature for grafting was found to be 70°CC. The graft yield was observed to increase with polymerization time, AAm concentration, initiator and monomer diffusion time up to a saturation graft yield and then leveled off. An increase in AIBN concentration first enhanced the percent grafting then showed a decrease. The addition of some salts (Ni2+, Cr3+, Co2+, Cu2+) on the rate of grafting was also investigated. From the temperature dependence of the initial rate of grafting, the overall activation energy was found to be 4. 1 kcal/mol and relevant rate equation have been derived. The effect of grafting on film propities, such as water absorption capacity, intrinsic viscosity were determined. Grafted films were characterized by FTIR spectros-copy and scanning electron microscopy (SEM). 相似文献