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排序方式: 共有119条查询结果,搜索用时 15 毫秒
41.
André V.-H. Soares Sumeet S. Kale Udo Armbruster Fabio B. Passos Shubhangi B. Umbarkar Mohan K. Dongare Andreas Martin 《国际化学动力学杂志》2019,51(8):634-640
Glycerol acetylation is a very interesting reaction for studies of consecutive kinetics. In this short communication, we present a pseudo-homogeneous model for the synthesis of triacetyl glycerol from the reaction of glycerol and acetic acid over strongly acidic Amberlyst-15 and Amberlyst-70 catalysts, considering a dimerization of diacetyl glycerol (DAG) into diglycerol tetraacetate as a parallel reaction and compare the results with a model without side reactions. The best fits were obtained for apparent zeroth-order dimerization and first-order consecutive reactions in the presence of acetic acid in excess and with removal of water. An adaptation was made for DAG. The proposed model shows that the formation of DAG is faster than the consumption of glycerol, which could be an explanation for the occurrence of DAG dimerization instead of other parallel reactions in acetylation. 相似文献
42.
43.
H. Saitovitch P. R. J. Silva A. M. Rodriguez J. Weberszpil F. B. Passos M. Schmal 《Hyperfine Interactions》1994,84(1):563-567
The effect of indium addition on alumina-supported platinum catalysts was investigated by measurements of hyperfine interactions. Via lime differential perturbed angular correlation spectroscopy (TDPAC) on111Cd, Pt/Al2O3 catalysts were studied in the flow of a heptane/H2 gas stream. The results indicate that some amount of indium sticks to platinum which is then dispersed on the support surface. The amount of In that is free from platinum is mobile under reaction conditions, being capable of diluting platinum particles and draining off coke precursors from the platinum surface.Researcher from Consejo Nac. Invest. Cient. Tecn., CONICET, Argentina. 相似文献
44.
Célia?Fonseca?Guerra Tushar?van der?Wijst F.?Matthias?BickelhauptEmail author 《Structural chemistry》2005,16(3):211-221
We have theoretically analyzed Watson–Crick AT and GC base pairs in which purine C8 and/or pyrimidine C6 positions carry a substituent X = H, F, Cl or Br, using the generalized gradient approximation (GGA) of density functional theory at BP86/TZ2P. The purpose is to study the effects on structure and hydrogen bond strength if X = H is substituted by a halogen atom. Furthermore, we wish to explore the relative importance of electrostatic attraction versus orbital interaction in the above multiply hydrogen-bonded systems, using a quantitative bond energy decomposition scheme. We find that replacing X = H by a halogen atom has relatively small yet characteristic effects on hydrogen bond lengths, strengths and bonding mechanism. In general, it reduces the hydrogen-bond-accepting- and increases the hydrogen-bond-donating capabilities of a DNA base. The orbital interaction component in these hydrogen bonds is found for all substituents (X = H, F, Cl, and Br) to contribute about 41% of the attractive interactions and is thus of the same order of magnitude as the electrostatic component, which provides the remaining 59% of the attraction. 相似文献
45.
Nonlinear Dynamics - We study super-Bloch oscillations of ultracold atoms loaded in a lattice potential. We consider nonlinear contribution emerging from a mean-field approximation for the... 相似文献
46.
Robson Matos Mohamed F. Meidine John F. Nixon Bernadette F. Trigo Passos Edgar Niecke Detlef Barion 《Journal of organometallic chemistry》1990,390(3)
Different types of ligating behaviour of the R
R′ ring system are reported; the sp2 hybridised phosphorus is the donor atom in Pt(0), W(0) and Rh(I) complexes, whereas ligation of the sp3 hybridised phosphorus atom is preferred by Pd(II), and both phosphorus atoms are ligated in dinuclear Pt(II) systems. 相似文献
47.
A static thermoelectroelastic problem for an infinite transversally isotropic body containing a spheroidal cavity is explicitly solved. The symmetry axis of the spheroid coincides with the anisotropy axis of the body. It is assumed that at a rather large distance from the cavity the body is in a uniform heat flow directed along the anisotropy axis. Formulas are derived for the stress components and the projections of the electric displacement vector near the cavity, which depend on the heat-flow value, cavity geometry, and the thermoelectroelastic properties of the material. The solution of the problem for a body with a disk-like crack is obtained as a partial case from the solution of the problem for a piezoceramic body with a spheroidal cavity. The stress intensity factors for the force and electric fields are determined near the crack 相似文献
48.
An explicit solution is constructed for the static problem of thermoelectroelasticity for an infinite transversally isotropic
body with a heat-insulated elliptic crack located in the isotropy plane. It is assumed that at a large distance from the crack
the body is affected by a uniform heat flow perpendicular to the crack plane. Formulas are derived for the stress intensity
factors at the crack end, which depend on the value of the heat flow, crack geometry, and the thermoelectroelastic properties
of the piezoceramic body.
Translated from Prikladnaya Mekhanika, Vol. 36, No. 2, pp. 72–82, February, 2000. 相似文献
49.
Marinho V. L. Pocrifka L. A. Passos R. R. 《Journal of Solid State Electrochemistry》2018,22(5):1517-1524
Journal of Solid State Electrochemistry - In the last decades, the ethylene glycol has been considered as another option of fuel, in both acid and alkaline solutions, for fuel cells application.... 相似文献
50.