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981.
Preparation of the title compound ( 4 ) is described. An important transannular effect between the two unconjugated s-cis-butadiene chromophores is observed by comparison of the UV. spectra of the dimethylidene-oxanorbornane 3 and the tetramethylidene-oxanor-bornane 4 . 相似文献
982.
ab initio STO 3g calculations on 2,3-episulfonionorbornanes and 2-norbornyl cations substituted at C(5) or C(6) suggest that homoconjugated carbonyl group and related (-M, -I) functions can be remote electron-donors. 相似文献
983.
We have determined the magnitudes of all possible four-, five- and six-bond HH couplings in four 2-pyrone derivatives. Substituents exert a negligible effect on the couplings. The allylic couplings are position-specific (J34 = 1·2; J45 ≤ 0·2; J56 = 0.8) and the observed pattern of alternating magnitudes is indicative of π-bond fixation. The allylic couplings can be translated into π-bond orders which agree well with results of recently published SCF-MO calculations on 2-pyrone. Finally, comparison of long range coupling constant data for 4,6-dimethyl-2-pyrone with those for related cyclic anhydrides and trans-1,3-pentadiene further supports the picture of 2-pyrone as a slightly perturbed butadiene, in agreement with extensive chemical and physical evidence. 相似文献
984.
P. Vogel 《Czechoslovak Journal of Physics》1961,11(9):644-651
Deviations of nuclear magnetic moments of oddA nuclei from the Schmidt lines are explained by configuration mixing. The general results obtained are applied to several nuclei and the magnitudes of the admixture coefficients necessary to explain the deviations are estimated. The results show that the deviations can be successfully explained only for those nuclei, in which possible configuration admixtures give contributions to the magnetic moment linear in the admixture coefficient.
This work was done as a diploma thesis at the Faculty of Technical and Nuclear Physics, Technical University, Prague.
In conclusion I want to thank Dr. L. Trlifaj for suggesting this subject and for his guidance in its realization. 相似文献
A . , . , , , .
This work was done as a diploma thesis at the Faculty of Technical and Nuclear Physics, Technical University, Prague.
In conclusion I want to thank Dr. L. Trlifaj for suggesting this subject and for his guidance in its realization. 相似文献
985.
986.
Théodore Vogel 《Annali di Matematica Pura ed Applicata》1976,108(1):137-147
Résumé Après avoir rappelé et précisé les résultats qu'il avait précédemment obtenus dans l'étude des systèmes dynamiques affaiblis,
l'auteur traite du cas des systèmes commandés, et de certains problèmes inverses, notamment de ceux de la détection et de
l'accessibilité.
A Dario Graffi pour son 70-ème anniversaire
Entrata in Redazione il 8 maggio 1975. 相似文献
987.
Eguchi K Enomoto S Furuno K Ikeda H Ikeda K Inoue K Ishihara K Iwamoto T Kawashima T Kishimoto Y Koga M Koseki Y Maeda T Mitsui T Motoki M Nakajima K Ogawa H Owada K Piquemal F Shimizu I Shirai J Suekane F Suzuki A Tada K Tajima O Takayama T Tamae K Watanabe H Busenitz J Djurcic Z McKinny K Mei DM Piepke A Yakushev E Berger BE Chan YD Decowski MP Dwyer DA Freedman SJ Fu Y Fujikawa BK Goldman J Heeger KM Lesko KT Luk KB Murayama H Nygren DR Okada CE Poon AW Steiner HM Winslow LA Horton-Smith GA 《Physical review letters》2004,92(7):071301
Data corresponding to a KamLAND detector exposure of 0.28 kton yr has been used to search for nu;(e)'s in the energy range 8.3相似文献
988.
By carrying out random walk simulations we systematically study the effects of various types of complex molecular dynamics on (2)H NMR experiments in solids. More precisely, we calculate one-dimensional (1D) (2)H NMR spectra and the results of two dimensional (2D) (2)H NMR experiments in time domain, taking into account isotropic as well as highly restricted motions which involve rotational jumps about different finite angles. Although the dynamical models are chosen to mimic the primary and secondary relaxation in supercooled liquids and glasses, we do not intend to describe experimental results quantitatively but rather to show general effects appearing for complex reorientations. We carefully investigate whether 2D (2)H NMR in time domain, which was originally designed to measure correlation times of ultraslow motions (tau >/= 1 ms), can be used to obtain shorter tau, too. It is demonstrated that an extension of the time window to tau >/= 10 &mgr;s is possible when dealing with exponential relaxation, but that it will fail if there is a distribution of correlation times G(lgtau). Vice versa, we show that 1D (2)H NMR spectra, usually recorded to look at dynamics with tau in the microsecond regime, are also applicable for studying ultraslow motions provided that the loss of correlation is achieved step by step. Therefore, it is useful to carry out 1D and 2D NMR experiments simultaneously in order to reveal the mechanism of complex molecular motions. In addition, we demonstrate that highly restricted dynamics can be clearly observed in 1D spectra and in 2D NMR in time domain if long solid-echo delays and large evolution times are applied, respectively. Finally, unexpected observations are described which appear in the latter experiment when considering very broad distributions G(lgtau). Because of these effects, time scale and geometry of a considered motion cannot be extracted from a straightforward analysis of experimental results. Copyright 2000 Academic Press. 相似文献
989.
Dr. Jing Sun Julian Vogel Lisa Chen A. Lennart Schleper Tim Bergner Prof. Dr. Alexander J. C. Kuehne Prof. Dr. Max von Delius 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(13):e202104116
The aqueous self-assembly of amphiphiles into aggregates such as micelles and vesicles has been widely investigated over the past decades with applications ranging from materials science to drug delivery. The combination of characteristic properties of nucleic acids and amphiphiles is of substantial interest to mimic biological self-organization and compartmentalization. Herein, we present ribose- and ribonucleotide-based amphiphiles and investigate their self-assembly as well as their fundamental reactivity. We found that various types of aggregates are formed, ranging in size from nanometers to micrometers and all amphiphiles exhibit aggregation-induced emission (AIE) in solution as well as in the solid state. We also observed that the addition of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) leads to rapid and selective dimerization of the amphiphiles into pyrophosphates, which decreases the critical aggregation concentration (CAC) by a factor of 25 when compared to the monomers. Since the propensity for amphiphile dimerization is correlated with their tendency to self-assemble, our results may be relevant for the formation of rudimentary compartments under prebiotic conditions. 相似文献
990.
Vera Seidl Dr. Angel H. Romero Dr. Frank W. Heinemann Dr. Andreas Scheurer Dr. Carola S. Vogel Prof. Dr. Tobias Unruh Prof. Dr. Peter Wasserscheid Prof. Dr. Karsten Meyer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(20):e202200100
Adding to the versatile class of ionic liquids, we report the detailed structure and property analysis of a new class of asymmetrically substituted imidazolium salts, offering interesting thermal characteristics, such as liquid crystalline behavior, polymorphism or glass transitions. A scalable general synthetic procedure for N-polyaryl-N’-alkyl-functionalized imidazolium salts with para-substituted linker (L) moieties at the aryl chain, namely [LPhmImHR]+ (L=Br, CN, SMe, CO2Et, OH; m=2, 3; R=C12, PEGn; n=2, 3, 4), was developed. These imidazolium salts were studied by single-crystal X-ray diffraction (SC-XRD), NMR spectroscopy and thermochemical methods (DSC, TGA). Furthermore, these imidazolium salts were used as N-heterocyclic carbene (NHC) ligand precursors for mononuclear, first-row transition metal complexes (MnII, FeII, CoII, NiII, ZnII, CuI, AgI, AuI) and for the dinuclear Ti-supported Fe-NHC complex [(OPy)2Ti(OPh2ImC12)2(FeI2)] (OPy=pyridin-2-ylmethanolate). The complexes were studied concerning their structural and magnetic behavior via multi-nuclear NMR spectroscopy, SC-XRD analyses, variable temperature and field-dependent (VT-VF) SQUID magnetization methods, X-band EPR spectroscopy and, where appropriate, zero-field 57Fe Mössbauer spectroscopy. 相似文献