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81.
Katritzky AR Akhmedov NG Abdel-Fattah AA Wang M Rostek CJ Maender OW 《Magnetic resonance in chemistry : MRC》2004,42(5):424-435
Nucleophilic addition of alkyl- and benzylthiols to benzoquinone diimine (1) gave the corresponding 3-alkylthio- or 3-benzylthio-1,4-phenylenediamines (2-5). However, addition of aryl- or heteroarylthiols to 1 formed 2-arylthio- or 2-heteroarylthio-1,4-phenylenediamines (6-14). The structures of 2-14, obtained in 55-91% yields, were confirmed in CDCl3 or DMSO-d6 solution using 1D (NOE difference, coupled 13C NMR spectra, APT and DEPT) and 2D NMR techniques [DQCOSY, NOESY, HETCOR and heteronuclear multiple bond coherence (HMBC)] that resulted in unambiguous proton and carbon NMR resonance assignments. The substituent-induced 13C NMR chemical shift differences were calculated in 2-14 relative to carbon atoms in the model compound N1-(1,3-dimethylbutyl)-N4-phenyl-1,4-phenylenediamine (DMBPPD) (15) (a reduced form of benzoquinone diimine). 相似文献
82.
83.
It is proved that the apparent transverse velocities β_(app) and the spectral powers at 10GHz P_(10) of the cores of known superluminal sources are correlated. An interpretation ofthis result within the framework of the relativistic jet model shows that the jet Lorentzfactor γ depends on the intrinsic luminosity of the sources. The probable existence of twosubpopulations of the superluminal sources is shown by a linear regression analysis. "Small"sources f i.e. the sources without extended emission or with a distance from the core tothe outer edge of the lobe<20 kpc, show lower β_(app) than the "large" objects; this can beinterpreted as an orientation effect. Since all BL Lac objects belong to the "small" class,this result sheds new light on such a question as why these sources have lower apparent ve-locities than the "classical" superluminal quasars. 相似文献
84.
《Surface and interface analysis : SIA》2005,37(10):802-808
B‐doped Si multiple delta‐layers (MDL) were developed as certified reference materials (CRM) for secondary ion mass spectrometry (SIMS) depth profiling analysis. Two CRMs with different delta‐layer spacing were grown by ion beam sputter deposition (IBSD). The nominal spacing of the MDL for shallow junction analysis is 10 nm and that for high energy SIMS is 50 nm. The total thickness of the film was certified by high resolution transmission electron microscopy (HR‐TEM). The B‐doped Si MDLs can be used to evaluate SIMS depth resolution and to calibrate the depth scale. A consistency check of the calibration of stylus profilometers for measurement of sputter depth is another possible application. The crater depths measured by a stylus profilometer showed a good linear relationship with the thickness measured from SIMS profiling using the calibrated film thickness for depth scale calibration. The sputtering rate of the amorphous Si thin film grown by sputter deposition was found to be the same as that of the crystalline Si substrate, which means that the sputtering rate measured with these CRMs can be applied to a real analysis of crystalline Si. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
85.
Equilibrium molecular dynamics (MD) simulations have been performed in both the NVT and NPT ensembles to study the structural and dynamical properties of fully occupied methane clathrate hydrates at 50, 125, and 200 K. Five atomistic potential models were used for water, ranging from fully flexible to rigid polarizable and nonpolarizable. A flexible and a rigid model were utilized for methane. The phonon densities of states were evaluated and the localized rattling modes for the methane molecules were found to couple to the acoustic phonons of the host lattice. The calculated methane density of states was found to be in reasonable agreement with available experimental data. 相似文献
86.
Comparison of equilibrium and nonequilibrium models of a CSTR with total condenser focused on the multiple steady states and
dynamic behaviour was carried out. The steady-state behaviour of the model system, MTBE synthesis from methanol and isobutene
in a reactive distillation column, was studied in terms of the input parameters, i. e. feed flow rate of methanol or butenes, reflux ratio, and mass of catalyst. The dynamic behaviour of the system during the
start-up was investigated and perturbations of manipulated variables were found to cause transitions between the parallel
steady states.
Presented at the 33rd International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 22–26 May
2006. 相似文献
87.
A constrained form of the Weber problem is formulated in which no path is permitted to enter a prespecified forbidden region of the plane. Using the calculus of variations the shortest path between two points which does not intersect is determined. If is unconstrained distance, we denote the shortes distance along a feasible path by . The constrained Weber problem is, then: given points and positive weights wj, j = 1,2,…,n, find a point such that is a minimum.An algorithm is formulated for the solution of this problem when is Euclidean distance and is a single circular region. Numerical results are presented. 相似文献
88.
New Experimental Insight into the Nature of Metal−Metal Bonds in Digallium Compounds: J Coupling between Quadrupolar Nuclei 下载免费PDF全文
Dr. Libor Kobera Scott A. Southern Dr. Gyandshwar Kumar Rao Prof. Dr. Darrin S. Richeson Prof. Dr. David L. Bryce 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(28):9565-9573
Multiple bonding between atoms is of ongoing fundamental and applied interest. Here, we report a multinuclear (1H, 13C, and 71Ga) solid‐state magnetic resonance spectroscopic study of digallium compounds which have been proposed, albeit somewhat controversially, to contain single, double, and triple Ga?Ga bonds. Of particular relevance to the nature of these bonds, we have carried out two‐dimensional 71Ga J/D‐resolved NMR experiments which provide a direct measurement of J(71Ga,71Ga) spin–spin coupling constants across the gallium?gallium bonds. When placed in the context of clear‐cut experimental data for analogous singly, doubly, and triply bonded carbon spin pairs or boron spin pairs, the 71Ga NMR data clearly support the notion of a different bonding paradigm in the gallium systems. Our findings are consistent with an increasing role across the purported gallane–gallene–gallyne series for classical and/or slipped π‐type bonding orbitals. 相似文献
89.
Competitive location problems can be characterized by the fact that the decisions made by others will affect our own payoffs. In this paper, we address a discrete competitive location game in which two decision-makers have to decide simultaneously where to locate their services without knowing the decisions of one another. This problem arises in a franchising environment in which the decision-makers are the franchisees and the franchiser defines the potential sites for locating services and the rules of the game. At most one service can be located at each site, and one of the franchisees has preferential rights over the other. This means that if both franchisees are interested in opening the service in the same site, only the one that has preferential rights will open it. We consider that both franchisees have budget constraints, but the franchisee without preferential rights is allowed to show interest in more sites than the ones she can afford. We are interested in studying the influence of the existence of preferential rights and overbidding on the outcomes for both franchisees and franchiser. A model is presented and an algorithmic approach is developed for the calculation of Nash equilibria. Several computational experiments are defined and their results are analysed, showing that preferential rights give its holder a relative advantage over the other competitor. The possibility of overbidding seems to be advantageous for the franchiser, as well as the inclusion of some level of asymmetry between the two decision-makers. 相似文献
90.
Zhou Yan Bing Xia Ming Hua Qiu Ding Li Sheng Hong Xi Xu 《Biomedical chromatography : BMC》2013,27(11):1560-1567
A rapid and reliable method was established for simultaneous determination of main triterpenoids in Ganoderma lucidum spores using ultra‐high‐performance liquid chromatography coupled with triple quadrupole mass spectrometry (UPLC‐TQ‐MS). The established method was validated in terms of linearity, sensitivity, precision, accuracy and stability, and was successfully applied to determine the contents of 10 main triterpenoids in different batches of G. lucidum spores. The analysis results showed that moderate levels of triterpenoids were found in G. lucidum spores. In addition, a MS full scan with a daughter ion scan experiment was performed to identify the potential derivatives of triterpenoids present in G. lucidum spores. As a result, a total of 22 triterpenoids from different G. lucidum spores were unequivocally or tentatively identified via comparisons with authentic standards and literatures. This method provides both qualitative and quantitative results without the need for repetitive UPLC‐MS analyses, thereby increasing efficiency and productivity, making it suitable for high‐throughput applications. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献