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201.
A short overview of integrated waveguide demultiplexers for different applications in future highly inte- grated optical communication systems is presented. Some fabricated devices based on amorphous silicon nanowire technology are described. 相似文献
202.
Janusz Dabrowski Krystyna Kamieska-Trela Lech Kozerski 《Magnetic resonance in chemistry : MRC》1974,6(1):43-44
13C magnetic resonance spectra of nine quaternary ammonium salts of the general formula R1C1(O)C2H?C3HNR34Cl (where R1, R4 = alkyl) were obtained and compared with those of the parent amino compounds. The chemical shift differences between these two classes of compounds are qualitatively accounted for by π-electron density changes. Steric effects and hyperconjugation of the alkyl substituents are also discussed. 相似文献
203.
204.
Zbigniew Kisiel Adam Kranicki Lech Pszczkowski Steven T. Shipman Leonardo Alvarez-Valtierra Brooks H. Pate 《Journal of Molecular Spectroscopy》2009,257(2):177-186
The rotational spectrum of the bromoform molecule is complicated by overlap of extensive hyperfine splitting structure of three bromine nuclei belonging to four isotopic species of comparable abundance. We have been able to achieve an unambiguous assignment of this spectrum on the basis of complete hyperfine patterns of the lowest-J rotational transitions recorded at conditions of supersonic expansion with chirped-pulse, broadband Fourier transform microwave spectroscopy. The mm-wave rotational spectrum was then also studied up to J = 131 and 318 GHz, and extensive measurements are reported for four isotopic species of HCBr3 and four DCBr3 species. Precise values of many spectroscopic constants have been determined from global fits of all measurements for a given isotopic species and have been substantiated by comparisons among the various isotopic species and with results of ab initio calculations. The experimental measurements allowed determination of the axial rotational constant C for the symmetric top species, evaluation of nuclear quadrupole hyperfine splitting constants in the principal quadrupole axes of the bromine nucleus, and extension of the range of known values of the h3 splitting constant. The rz geometry of HCBr3 was also determined. 相似文献
205.
We prove that every digraph D with n≥7, n≥+6 vertices and at least (n−k−1)(n−1)+k(k+1) arcs contains all symmetric cycles of length at most n−k−2, an almost symmetric cycle of length n−k−1, and with some exceptions, also an almost symmetric cycle of length n−k. Consequently, D contains all orientations of cycles of length at most n−k, unless D is an exception.
The research was partially supported by the AGH University of Science and Technology grant No 11 420 04 相似文献
206.
Adam S. Plaziak Lech Celewicz Jaroslaw Spychala Krzysztof Golankiewicz 《Journal of mass spectrometry : JMS》1989,24(1):55-58
The electron impact mass spectra of N-(1H-2-oxo-4-pyrimidinyl) amino acids are discussed. It was established that thermal elimination of water took place prior to mass fragmentation of all these compounds with the formation of bicyclic structures. The fragmentation of bicyclic ions led to 1H-2-oxo-pyrimidinyl species. 相似文献
207.
The paper is concerned with order-topological characterizations of topological Riesz spaces, in particular spaces of measurable functions, not containing Riesz isomorphic or linearly homeomorphic copies of or .
208.
Let X be an F-space and \({\boldsymbol x=(x_n)}\) be a sequence of vectors in X. Ideals \({\mathcal{C}(\boldsymbol x)}\) of subseries convergence are considered. In particular, we show that a characterization of the class of Banach spaces not containing c 0 obtained by using the ideals \({\mathcal{C}(\boldsymbol x)}\) breaks down in every Fréchet space not isomorphic to a Banach space. On the other hand, the result can be extended to some F-spaces via the definition of a new class of F-spaces satisfying a stronger version of the condition (O) of Orlicz. A theorem discriminating between the finite and infinite dimensional case is obtained about the family \({\mathcal{C}(X)}\) of all ideals associated with the F-space X. 相似文献
209.
Lech Chmurzyński 《Journal of solution chemistry》1992,21(2):171-178
Acid dissociation constants in methanol for eight substituted pyridine N-oxides having a wide range of acid-base properties, [quinoline N-oxide (bi-cyclic amine N-oxide) and pyridine (heterocyclic amine)] have been determined using the potentiometric titration method. A linear correlation between ourmethanol data and aqueous pK
a
values from the literature has been found. As in polar aprotic solvents cationic homoconjugation phenomenon has been found to be present for sufficiently basic N-oxides. The tendency of substituted pyridine N-oxides towards cationic homoconjugation in methanol is weaker than in polar aprotic solvents and increases with increasing basicity of N-oxides. It has also been found that, in contrast to polar aprotic solvents, the cationic homoconjugation phenomenon in methanol is much more pronounced for heterocyclic amines than their N-oxides. 相似文献
210.
Lech Chmurzyski Grayna Wawrzyniak Zygmunt Warnke Zenon Pawlak 《Journal of heterocyclic chemistry》1997,34(1):215-219
The applicability of the direct method of pKa determination in the case of protonated heterocyclic amine N-oxides in a series of polar non-aqueous (aprotic and amphiprotic) solvents has been tested. The method is based on the pH determination of the non-aqueous solution of complex salt (the semiperchlorate in this case) formed by the N-oxides studied. The direct method not only provides for quick (one data point per each pKa determined), but also relatively accurate estimates of acidic dissociation constants. It has been experimentally shown on the example of substituted pyridine N-oxides that this method is precise enough in all studied non-aqueous solvents when applied to compounds of not too low basicity (the pKa being of the order of 5 or higher). To prove this, the pKa values of protonated monocyclic N-oxides obtained by the direct method have been compared with those resulting from the potentiometric titration curve. The agreement between the results found by using both methods is very good in most cases, the differences being within standard deviations. Based upon this observation it can be inferred that the pKa values of protonated bicyclic N-oxides in solvents studied determined by using the direct method can be also considered reliable, especially in the case of polar aprotic solvents. 相似文献