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951.
Udo Pachner 《Geometriae Dedicata》1978,7(4):443-453
Ohne Zusammenfassung 相似文献
952.
Dr. Udo Simon 《Mathematische Zeitschrift》1968,106(1):36-46
Ohne Zusammenfassung 相似文献
953.
Andrade LH Lima SM Novatski A Udo PT Astrath NG Medina AN Bento AC Baesso ML Guyot Y Boulon G 《Physical review letters》2008,100(2):027402
This Letter reports the formation of Ti3+ in OH- free aluminosilicate glass melted under vacuum condition, with a very long lifetime (170 micros) and broad emission band shifted towards the visible region. This lifetime value was attributed to the trapping of the excited electrons by the glass defects and detrapping by thermal energy, and it is 2 orders of magnitude higher than those published for Ti3+ doped materials. Our results suggest that this glass is a promising system to overcome the challenge of extending the spectral range of traditional tunable solid state lasers towards the visible region. 相似文献
954.
Photodissociation experiments were carried out at 193 nm for single HCl molecules which are adsorbed on the surface of large Ar n clusters and small (HCl)m complexes which are embedded in the interior of these clusters. For the surface case the size dependence is measured for the average sizes n=140-1000. No cage exit events are observed in agreement with the substitutional position of the molecule deeply buried in the outermost shell. This result is confirmed by a molecular dynamics simulation of the pickup process under realistic conditions concerning the experiment and the interaction potentials. The calculations of the dissociation process employ the surface hopping model. For the embedded case the average sizes covered are m=3 and 6 and n=8-248. The kinetic energy of the H atom fragments is measured exhibiting peaks at zero and around 2.0 eV which mark completely caged and unperturbed fragments, respectively. The ratio of theses peaks strongly depends on the cluster size and agrees well with theoretical predictions for one and two closed icosahedral shells, in which the nonadiabatic coupling of all states was accounted for. 相似文献
955.
The UM06-2X/aug-cc-pVTZ//UM06-2X/6-311G(d) theoretical models of representative singlet trans-2′-substituted cyclobutylcarbenes were computed. The :CH-group of carbenes with an ERG is bent toward the c-C4H7-ring’s proximal C1′–C2′ single bond. The :CH-group of carbenes with an EWG is bent toward the c-C4H7-ring’s distal C1′–C4′ single bond. The contrasting stereoelectronic effect was computationally tested using trimethylsilyl vs. bromo substituents to determine if exo-1- and exo-2-substituted bicyclo[2.1.0]pentanes would be produced in diastereomeric excess. 相似文献
956.
Sherif Ashraf Fahmy Fortuna Ponte Iten M. Fawzy Emilia Sicilia Udo Bakowsky Hassan Mohamed El-Said Azzazy 《Molecules (Basel, Switzerland)》2020,25(24)
P-sulfonatocalix[n]arenes have demonstrated a great potential for encapsulation of therapeutic drugs via host-guest complexation to improve solubility, stability, and bioavailability of encapsulated drugs. In this work, guest-host complexes of a third-generation anticancer drug (oxaliplatin) and p-4-sulfocalix[n]arenes (n = 4 and 6; p-SC4 and p-SC6, respectively) were prepared and investigated, using 1H NMR, UV, Job’s plot analysis, and DFT calculations, for use as cancer therapeutics. The peak amplitude of the prepared host-guest complexes was linearly proportional to the concentration of oxaliplatin in the range of 1.0 × 10−5 M−1 to 2.1 × 10−4 M−1. The reaction stoichiometry between either p-SC4 or p-SC6 and oxaliplatin in the formed complexes was 1:1. The stability constants for the complexes were 5.07 × 104 M−1 and 6.3 × 104 M−1. These correspond to complexation free energy of −6.39 and −6.52 kcal/mol for p-SC4 and p-SC6, respectively. Complexation between oxaliplatin and p-SC4 or p-SC6 was found to involve hydrogen bonds. Both complexes exhibited enhanced biological and high cytotoxic activities against HT-29 colorectal cells and MCF-7 breast adenocarcinoma compared to free oxaliplatin, which warrants further investigation for cancer therapy. 相似文献
957.
Zhiqiang Liu Yudha P. Budiman Ya-Ming Tian Dr. Alexandra Friedrich Mingming Huang Prof. Dr. Stephen A. Westcott Prof. Dr. Udo Radius Prof. Dr. Todd B. Marder 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(71):17267-17274
We report herein a mild procedure for the copper-catalyzed oxidative cross-coupling of electron-deficient polyfluorophenylboronate esters with terminal alkynes. This method displays good functional group tolerance and broad substrate scope, generating cross-coupled alkynyl(fluoro)arene products in moderate to excellent yields. Thus, it represents a simple alternative to the conventional Sonogashira reaction. 相似文献
958.
The bicyclic alkenylidenes 9 (bicyclo[3.2.1]oct-2-en-8-ylidene) and 17 (bicyclo[3.3.1]non-2-en-9-ylidene) were claimed to be stabilized foiled carbenes. Our B3LYP and MP2 computations confirm previous experimental data. Moreover, they show that these carbenes are very reactive and rearrange rapidly, mainly through a 1,2-vinyl shift by overcoming a low barrier (1.2 to 5.4 kcal/mol). This is in contrast to the high barriers (up to 30 kcal/mol) predicted for the same type of rearrangements in norborn-2-en-7-ylidene derivatives. In 17 and bicyclo[4.1.1]oct-2-en-7-ylidene (23), the divalent carbon atom is even bent away from the double bond! 相似文献
959.
DFT calculations have been performed to study the course of dichlorocarbene insertion reactions into alkanes and to better understand the regio- and stereoselectivities observed. At the B3LYP/6-31G(d) level of theory, the selectivity of dichlorocarbene insertions into a number of hydrocarbons agrees well with the obtained experimental results. The reactivity of a specific C-H bond is determined by the capacity of the remaining alkyl fragment to effectively delocalize the partial positive charge buildup during the reaction. This activity can readily be estimated by calculation of the hydride transfer potential (HTP). A comparison with the structure and the stability of the corresponding cation is useful to emphasize the origins of the selectivity. Dichlorocarbene is also predicted to react efficiently with acidic C-H bonds through a nucleophilic-electrophilic mechanism. In principle, an attack of a carbene on an appropriately substituted three-membered ring may lead to fragmentation of the molecule. 相似文献
960.
Computational resources can be used more efficiently by introducing reduced-order models, instead of solving large systems of equations of the original model. In this contribution, the Krylov subspace method, a reduced-order modeling method, is studied and compared to the modal decomposition for a rubber wheel model. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献