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71.
72.
V. A. Matyshak A. N. Il’ichev O. N. Sil’chenkova V. A. Sadykov V. N. Korchak 《Kinetics and Catalysis》2017,58(2):198-210
It has been demonstrated by quantitative spectrokinetic measurements that, on the surface of zirconia stabilized as a tetragonal phase, the rate-limiting step of the selective catalytic reduction of nitrogen oxides (SCR of NO x ) with propylene is the interaction of surface nitrates with C3H6 yielding organic nitro compounds. It is hypothesized that propylene reacts not with the nitrates themselves but with the activated complex NO2 ads whose structure is intermediate between the structures of the monodentate NO3 ? and NO2 species. Deep C3H6 oxidation exerts an adverse effect on the rate of the SCR of NO x with propylene, and the interaction between O2 and NO, which yields NO2 and NO3 ? stimulates further nitrogen reduction to N2. The effect of the reaction between oxygen and O2N?C n H m on the NO x reduction rate is variable and is determined by the C3H6/NO x ratio. A generalized scheme of the SCR of NO x with propylene on the surface of ZrO2 partially stabilized as a tetragonal phase has been developed by comparing experimental data of this study and data available from the literature. 相似文献
73.
A. V. Pashchenko V. P. Pashchenko V. K. Prokopenko Yu. F. Revenko A. S. Mazur V. A. Turchenko V. Ya. Sycheva V. V. Burkhovetskii A. G. Sil’cheva G. G. Levchenko 《Physics of the Solid State》2013,55(3):486-494
Ceramic samples of manganite perovskites La0.6 ? x Pr x Sr0.3Mn1.1O3 (x = 0?0.6) have been studied using the X-ray diffraction, resistive, magnetic (χac, 55Mn NMR), microscopic, and magnetoresistive methods. It has been found that an increase in the praseodymium concentration x leads to a transition from the rhombohedral R $\bar 3$ c (x = 0–0.3) to orthorhombic Pbnm (x = 0.4–0.6) perovskite structure. It has been shown that the real perovskite structure contains anion and cation vacancies, whose concentrations increase with an increase in the praseodymium concentration x. A decrease in the metal-insulator phase transition temperature T mi and the ferromagnetic-paramagnetic phase transition temperature T c with increasing x correlates with an increase in the concentration of vacancies weakening the high-frequency electronic exchange Mn3+ ? Mn4+. For compositions with x = 0 and 0.1, when the lattice contains not only vacancies but also nanostructured clusters with Mn2+ in the A-positions, there is an anomalous hysteresis. An analysis of the asymmetrically broadened 55Mn NMR spectra of the compounds has revealed a high-frequency electronic exchange of the ions Mn3+ Mn4+ in the B-positions and a local heterogeneity of their surrounding by other ions (La2+, Pr3+, Sr2+) and vacancies. The phase diagram has demonstrated that there is a strong correlation between the composition, imperfection of the perovskite structure, phase transition temperatures T mi and T c , and magnetoresistive properties. 相似文献
74.
Resorcin[4]arene-based tetrakis(N-hydantoinylamido)cavitand 1 forms a stable molecular capsule in the presence of suitable anionic guests such as CH(3)OSO(3)(-) or BF(4)(-) in C(2)D(2)Cl(4). Molecular capsule G(2)@1(2) is stabilized by the eight intermolecular imide N-H···O═C hydrogen bondings, two from each four paired hydantoinyl units, and the eight intramolecular amide N-H···O-CH(2)-O hydrogen bondings, four on each two cavitands. The formations of molecular capsules were confirmed by (1)H, 2D NOESY, and 2D-DOSY NMR. 相似文献
75.
V. A. Matyshak O. N. Sil’chenkova I. T. Ismailov V. F. Tret’yakov 《Kinetics and Catalysis》2012,53(1):91-100
The main reactions yielding hydrogen are the recombination of hydrogen atoms on copper clusters and methyl formate decomposition.
Methyl formate results from the interaction between the linear methoxy group and the formate complex located on CuO. The source
of CO2 appearing in the gas phase is the formate complex, and the source of CO is methyl formate. The rates of methoxy group conversion
and product formation over supports (ZrO2, CeO2, Ce0.8Zr0.2O2) and copper-containing catalysts (5%Cu/CeO2, 5%Cu/ZrO2, 2%Cu/Ce0.8Zr0.2O2, 2%Cu/Ce0.1Y0.1Zr0.8) are compared. The dominant process in methoxy group conversion over the supports and copper-containing catalysts is methanol
decomposition to H2 and CO and to H2 and CO2, respectively. The methoxy group conversion rate is proportional to the H2 and CO2 formation rate and is determined by the concentration of supported copper. 相似文献
76.
We study a few properties of fermions in an anisotropic harmonic trap in absence as well as in presence of an optical lattice. The density of states (DOS) and specific heat of the fermions are studied for different anisotropies. Analytical expressions for the DOS in a strongly anisotropic harmonic trap are derived. For a particular combined potential, where the fermions are hopping in a 3D lattice under a 2D harmonic potential, the Drude weight of the fermionic system is evaluated. The Drude weight is found to be flat in a wide range of fermion concentrations where it is almost temperature independent. 相似文献
77.
Matyshak V. A. Sil’chenkova O. N. Ismailov I. T. Tret’yakov V. F. 《Kinetics and Catalysis》2009,50(5):784-792
Formate and carbonate complexes and bridging and linear methoxy groups were detected on the surfaces of CeO2 and 5.0% Cu/CeO2 under the reaction conditions of methanol conversion using IR spectroscopy. The reaction products were H2, methyl formate, CO, CO2, and H2O. The bridging and linear methoxy groups were the sources of formation of bi- and monodentate formate complexes, respectively.
Methyl formate was formed as a result of the interaction of the linear methoxy group and the formate complex. The study demonstrated
that the recombination of hydrogen atoms on copper clusters and the decomposition of methyl formate were the main reactions
of hydrogen formation. Formate and carbonate complexes were the source of CO2 formation in the gas phase, and the decomposition of methyl formate was the source of CO. It was found that the addition
of water vapor to the reaction flow considerably decreased the rate of CO formation at a constant yield of hydrogen. The effects
of water vapor and oxygen on the course of surface reactions and the formation of products are discussed. To explain the mechanism
of methanol conversion, a scheme of surface reactions is proposed. 相似文献
78.
Within the framework of a model of nonlinear deformations of shape memory alloys (SMA) under phase and structural transformations
and for different statements of the problem, an analytical solution of the problem of stability of an SMA rod undergoing a
direct martensitic phase transformation under the action of a compressive load is obtained. It is shown that taking account
of the nonlinearity of the deformation process and structural transformation in the transition into the adjacent form of equilibrium
significantly changes the solution for sufficiently flexible rods. At the same time, taking into account the strains developed
in a phase transition is topical for thick-walled SMA elements. 相似文献
79.
Eun Sil Kim Bo Hyun Yoon Seung Min Lee Min Choi Eun Hye Kim Byong-Wook Lee Sang-Yeob Kim Chan-Gi Pack Young Hoon Sung In-Jeoung Baek Chang Hee Jung Tae-Bum Kim Jin-Yong Jeong Chang Hoon Ha 《Experimental & molecular medicine》2022,54(2):103
Despite the strong influence of the gut microbiota on atherosclerosis, a causal relationship between atherosclerosis pathophysiology and gut microbiota is still unverified. This study was performed to determine the impact of the gut microbiota on the pathogenesis of atherosclerosis caused by genetic deficiency. To elucidate the influence of the gut microbiota on atherosclerosis pathogenesis, an atherosclerosis-prone mouse model (C1q/TNF-related protein 9-knockout (CTRP9-KO) mice) was generated. The gut microbial compositions of CTRP9-KO and WT control mice were compared. Fecal microbiota transplantation (FMT) was performed to confirm the association between gut microbial composition and the progression of atherosclerosis. FMT largely affected the gut microbiota in both CTRP9-KO and WT mice, and all transplanted mice acquired the gut microbiotas of the donor mice. Atherosclerotic lesions in the carotid arteries were decreased in transplanted CTRP9-KO mice compared to CTRP9-KO mice prior to transplantation. Conversely, WT mice transplanted with the gut microbiotas of CTRP9-KO mice showed the opposite effect as that of CTRP9-KO mice transplanted with the gut microbiotas of WT mice. Here, we show that CTRP9 gene deficiency is related to the distribution of the gut microbiota in subjects with atherosclerosis. Transplantation of WT microbiotas into CTRP9-KO mice protected against the progression of atherosclerosis. Conversely, the transplantation of CTRP9-KO microbiotas into WT mice promoted the progression of atherosclerosis. Treating atherosclerosis by restoring gut microbial homeostasis may be an effective therapeutic strategy.Subject terms: Atherosclerosis, Experimental models of disease, Mechanisms of disease 相似文献
80.