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761.
Štefan Chromik Marianna Španková Jozef Liday Peter Lobotka 《Applied Surface Science》2008,254(12):3635-3637
Epitaxial MgO thin films have been grown on semiinsulating GaAs (0 0 1) substrates using electron beam (e-beam) evaporation. X-ray diffraction indicates c-axis oriented MgO with (0 0 2) reflection only and rocking curve widths ∼2.2-3°. Transmission electron microscopy (TEM) analyses confirm an epitaxial growth of the MgO films. We study the microstructure and the defects at the interface between the MgO film and the GaAs substrate. Auger electron Spectroscopy (AES) concentration depth profiles reveal no contamination of the MgO films by As and Ga at different temperatures of the deposition process. 相似文献
762.
János T. Csenki Ádám Mészáros Dr. Zsombor Gonda Dr. Zoltán Novák 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(63):15638-15643
The availability and synthesis of fluorinated enamine derivatives such as N-(3,3,3-trifluoropropenyl)heterocycles are challenging, especially through direct functionalization of the heterocyclic scaffold. Herein, a stereoselective N-trifluoropropenylation method based on the use of a bench-stable trifluoropropenyl iodonium salt is described. This reagent enables the straightforward trifluoropropenylation of various N-heterocycles under mild reaction conditions, providing trifluoromethyl enamine type moieties with high stereoselectivity and efficiency. 相似文献
763.
J��lius Czap Stanislav Jendrol�� Franti?ek Kardo? Jozef Mi?kuf 《Graphs and Combinatorics》2011,27(1):73-85
A face of a vertex coloured plane graph is called loose if the number of colours used on its vertices is at least three. The looseness of a plane graph G is the minimum k such that any surjective k-colouring involves a loose face. In this paper we prove that the looseness of a connected plane graph G equals the maximum number of vertex disjoint cycles in the dual graph G* increased by 2. We also show upper bounds on the looseness of graphs based on the number of vertices, the edge connectivity,
and the girth of the dual graphs. These bounds improve the result of Negami for the looseness of plane triangulations. We
also present infinite classes of graphs where the equalities are attained. 相似文献
764.
On-line preconcentration on a short C18 column, prior to HPLC with UV and electrochemical detection, has been used for determination of some phenylurea herbicides and their possible degradation products, substituted anilines, in water samples. With electrochemical detection the detection limit at a signal-to-noise ratio of 3 was 5 ppt for 4-chloroaniline and 4-bromoaniline and 7 ppt for 3,4-dichloroaniline; with UV detection the detection limit was ca 300 ppt for all analytes. 相似文献
765.
The crossing function of a graphG with orientable genusn is defined as a mapping \(f:\{ \not 0,1, \ldots ,n\} \to \{ \not 0,1,2, \ldots \} \) for whichf(k)=cr k (G) the crossing number ofG on the orientable surface of genusk. It is proved that any decreasing convex function \(f:\{ \not 0,1, \ldots ,n\} \to \{ \not 0,1,2, \ldots \} \) with \(f(n) = \not 0\) is the crossing function of some connected graph. 相似文献
766.
767.
The lowest-lying triplet and singlet potential energy surfaces for the O(3P) + C6H6 reaction were theoretically characterized using the "complete basis set" CBS-QB3 model chemistry. The primary product distributions for the multistate multiwell reactions on the individual surfaces were then determined by RRKM statistical rate theory and weak-collision master equation analysis using the exact stochastic simulation method. It is newly found that electrophilic O-addition onto a carbon atom in benzene can occur in parallel on two triplet surfaces, 3A' and 3A' '; the results predict O-addition to be dominant up to combustion temperatures. Major expected end-products of the addition routes include phenoxy radical + H*, phenol and/or benzene oxide/oxepin, in agreement with the experimental evidence. While c-C6H5O* + H* are nearly exclusively formed via a spin-conservation mechanism on the lowest-lying triplet surface, phenol and/or benzene oxide/oxepin are mainly generated from the lowest-lying singlet surface after inter-system crossing from the initial triplet surface. CO + c-C5H6 are predicted to be minor products in flame conditions, with a yield < or = 5%. The O + C6H6 --> c-C5H5* + *CHO channel is found to be unimportant under all relevant combustion conditions, in contrast with previous theoretical conclusions (J. Phys. Chem. A 2001, 105, 4316). Efficient H-abstraction pathways are newly identified, occurring on two different electronic state surfaces, 3B1 and 3B2, resulting in hydroxyl plus phenyl radicals; they are predicted to play an important role at higher temperatures in hydrocarbon combustion, with estimated contributions of ca. 50% at 2000 K. The overall thermal rate coefficient k(O + C6H6) at 300-800 K was computed using multistate transition state theory: k(T) = 3.7 x 10-16 x T 1.66 x exp(-1830 K/T) cm(3) molecule(-1) s(-1), in good agreement with the experimental data available. 相似文献
768.
The Monte Carlo method was used for generation of amorphous polyethylene configurations on a diamond lattice. Chain building was performed on the tetrahedral lattice of edges 36, 62 and 43 Å with periodic boundary conditions imposed.32 chains were generated, each with a length of 100 CH2-groups (resulting density = 0.81 g·cm−3). Small spherical volumes with a radius of 10 Å were chosen at random from the total volume for the calculation of rotational barriers. The rotating bond was chosen to be close to the center of this sphere. We employed the method of molecular mechanics in order to calculate the rotational barriers. The calculation was made for 578 rotating bonds and the obtained distribution of rotational barriers is approximated by the corresponding Γ-distribution. 相似文献
769.
Dr. Francesco Messa Dr. Andrea Nicola Paparella Dr. Dominik Veselý Prof. Jozef Krajčovič Dr. Paride Papadia Dr. Serena Perrone Prof. Antonio Salomone 《European journal of organic chemistry》2023,26(24):e202300309
The Pd-catalyzed amino- and alkoxycarbonylation of aryl iodides has been exploited, for the first time, in a bioinspired Deep Eutectic Solvent and under gas-free conditions, by using Mo(CO)6 as the CO source. The method allows for the preparation of carboxylic amides and esters in high yields (up to 99 %), short reaction time (2 h) and under mild reaction conditions (80 °C), with a low catalyst loading (2.5 mol %). Noteworthy, in the case of N-hexylbenzamide, it has been demonstrated that both the catalyst and DES can be used for four consecutive runs, with a moderate decrease of catalytic efficiency. The methodology has been also applied to the preparation of an Active Pharmaceutical Ingredient used for the treatment of human scabies and lice. 相似文献
770.
Four polymerizable glycidyl derivatives of sterically hindered amines were prepared from derivatives of 2, 2, 6, 6-tetramethyl-4-hydroxypiperidine and 14, 16-dioxo-7, 15-diazadispiro [5, 1, 5, 3] hexadecane. One of them is a stable nitroxyl derivative. 相似文献