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191.
L. Ionescu C. Picot M. Duval R. Duplessix H. Benoit J. P. Cotton 《Journal of Polymer Science.Polymer Physics》1981,19(7):1019-1031
General equations for small-angle neutron scattering are derived for block copolymers in dilute solution. The effects of excluded volume and polydispersity are examined. The applicability of the method of variable contrast to such systems is discussed. 相似文献
192.
193.
194.
Ionescu AR Bérces A Zgierski MZ Whitfield DM Nukada T 《The journal of physical chemistry. A》2005,109(36):8096-8105
The conformation of the six-membered ring of pyranosyl sugars has pronounced effects on the physical and chemical properties of carbohydrates. We present a method to determine key features of the potential energy surfaces, such as transition states associated with the inversion pathways of the model compounds cyclohexane, tetrahydropyran, p-dioxane, m-dioxane, s-trioxane, and 2-oxanol. Finally, we make the first determination of the pathways for inversion of penta-O-methyl-alpha-D-glucopyranose and penta-O-methyl-beta-D-glucopyranose. For both anomers, a transition state with five coplanar atoms with appreciable (O)E character was found. The method is based on constrained Car-Parrinello ab initio molecular dynamics, as implemented in the projector augmented-wave (PAW) method. The constraints are derived from the normal modes of six-membered rings and are described in terms of the canonical conformations (1)C(4) chair, (1,4)B boat, and (O)S(2) skew-boat. The PAW derived trajectories are in agreement with previous suggestions in the literature that pseudorotation is an important feature of such conformational interconversions. The dynamic nature as well as the internal coordinate-based constraints provide a method which can reliably accommodate pseudorotation. To determine semiquantitative energies, we recalculate key conformations using standard quantum mechanical calculations while keeping the ring dihedral angles frozen at their values found in the dynamics. In all cases where experimental barriers are known, our results are in excellent agreement. 相似文献
195.
Niculae I. Ionescu Monica Caldararu Cristian Hornoiu Cornel Munteanu 《Reaction Kinetics and Catalysis Letters》2007,91(2):257-262
The overall activation energy for the ignition of thermokinetic oscillations observed (in a dynamic calorimeter) during the
heterogeneous catalytic oxidation of methanol on Pd/LiAl5O8 were obtained and discussed by a PdOx redox cycle. 相似文献
196.
In this paper we discuss the extension of operators onL 1 R spaces to operators onL 1 E andP 1 E spaces (see Section 1), whereE is a Banach space. A necessary and sufficient condition for the existence of the extension to a spaceP 1 E is given (see Section 3) whenE has the weak Radon-Nikodym property. The paper contains certain applications to ergodic theory and a theorem giving a characterization of weakly conditionally compact sets. 相似文献
197.
M. V. Ionescu und H. Slusanschi 《Fresenius' Journal of Analytical Chemistry》1936,107(1-2):68-70
Ohne Zusammenfassung 相似文献
198.
N. I. Ionescu M. Chirca E. Meroiu J. Hercovici 《Reaction Kinetics and Catalysis Letters》1981,15(4):425-429
The kinetics of catalytic methylation of phenol on -alumina in the presence of water vapors was studied by means of a factorial experiment.
- .相似文献
199.
To further investigate the (19)F and (1)H nuclear hyperfine structure and Zeeman effect in the simplest singlet carbene, HCF, we recorded polarization quantum beat spectra (QBS) of the pure bending levels 2(0) (n) with n = 0-7 and combination bands 1(0) (1)2(0) (n) with n = 1-6 and 2(0) (n)3(0) (1) with n = 0-3 in the HCF A(1)A(")<--X(1)A(') system. The spectra were measured under jet-cooled conditions using a pulsed discharge source, both at zero field and under application of a weak magnetic field (<30 G). Analysis yielded the nuclear spin-rotation constants C(aa) and weak field Lande g(aa) factors. Consistent with a two-state model, the majority of observed vibrational levels exhibit a linear correlation of C(aa) and g(aa), and our analysis yielded effective (a) hyperfine constants for the (19)F and (1)H nuclei (in MHz) of 728(23) and 55(2), respectively. The latter was determined here owing to the high resolving power of QBS. The vibrational state selectivity of the (19)F hyperfine constants is discussed, and we suggest that the underlying Renner-Teller interaction may play an important role. 相似文献
200.
P. J. Plath N. I. Ionescu M. S. Chirca N. I. Jaeger M. Liauw U. Sydow 《Reaction Kinetics and Catalysis Letters》1994,53(2):391-396
The experimental bifurcation diagrams of the heterogeneous catalytic oxidation of methanol on Pd have been determined by changing the concentration of methanol or oxygen in the feed. Hopf bifurcations have been obtained. 相似文献