排序方式: 共有18条查询结果,搜索用时 250 毫秒
1.
Electrical conduction in the temperature range of 120–370 K has been studied in sandwiched structures of Al/Ta2O5/Si. The tantalum oxide films were prepared by evaporation of tantalum on a p-Si crystal substrate, followed by oxidation
at a temperature of 600°C. The temperature-dependent current-voltage (I–V) characteristics are explained on the basis of a phonon-assisted tunnelling model. The same explanation is given for I–V data measured on Ta2O5 films by other investigators. From the comparison of experimental data with theory the density of states in the interface
layer is derived and the electron-phonon interaction constant is assessed.
相似文献
2.
Regina Janciene Zita Stumbreviciute Ausra Vektariene Lidija Kosychova Romualdas Sirutkaitis Algirdas Palaima Zita Staniulyte Benedikta D. Puodziunaite 《Heteroatom Chemistry》2008,19(1):72-81
A number of 1‐substituted 4H,5H,6H‐[1,3]thiazolo[3,2‐a][1,5]benzodiazepinium‐11‐bromides and S‐(2‐oxo‐2‐phenyl‐X‐(p)‐ethyl)‐3‐(2‐methyl‐1H‐benzimidazol‐1‐yl) propane (or butane) thioate hydrobromides were obtained by direct reaction of the 5‐acetyl(or formyl, or anilinocarbonyl)‐substituted tetrahydro‐1,5‐benzodiazepine‐2‐thiones with aromatic α‐bromoketones. 2‐[(1‐Acetyl‐2(or 3)‐methyl‐2,3‐dihydro‐1H‐1,5‐benzodiazepin‐4‐yl) sulfanyl]‐1‐phenylethanones as intermediates of the formation of thiazolo [3,2‐a][1,5]benzodiazepine and N‐substituted 2‐methyl‐1H‐benzimidazole derivatives have been synthesized. Semiempirical AM1 calculations of a mechanism and energetic parameters for the heptatomic nucleus rearrangement to benzimidazole ring are presented. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:72–81, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20414 相似文献
3.
RNA oligomers, carrying 2'-O-modified nucleosides, proved to be extremely useful in different antisense strategies, including RNAi. The 2'-O-alkyl modification, carrying an amino functionality, deserves special attention due to its ability to neutralize the negatively charged phosphate backbone, leading to improved physicochemical and pharmaceutical properties of antisense agents. Here, we report a very short, convenient, and straightforward synthesis of phosphoramidites for all four 2'-aminoethyl-modified natural ribonucleosides, where the aminoethyl group is introduced in a single alkylation step. 相似文献
4.
Experimental current-voltage characteristics and their temperature dependencies for AlGaAs Schottky barrier structures are shown to be in agreement with the recent theory of phonon-assisted tunneling. 相似文献
5.
6.
Romualdas Striela Gintaras Urbelis Jurgis Sūdžius Sigitas Stončius Rita Sadzevičienė Linas Labanauskas 《Tetrahedron letters》2017,58(17):1681-1683
The reactions of 2-amino-5-cyclopropylpyridine with organic nitrites in the presence of copper(II) halides in various organic solvents were investigated. Optimal reaction conditions for the Sandmeyer reaction were developed and successfully applied to the synthesis of useful building blocks, bromo and chlorocyclopropylpyridines. Aminocyclopropylpyridines were synthesized in high yields from the corresponding aminobromopyridines under standard Suzuki coupling conditions. 相似文献
7.
The acousto-optic control of light polarization due to diffraction by leaky acoustic waves in ZX-LiNbO? has been demonstrated. The randomly polarized light of 633 nm wavelength is converted by the anisotropic diffraction into two beams with mutually orthogonal polarizations, the relative intensities of which depend on the light incidence angle and acoustic frequency. Variation in acoustic frequency from 108 to 112 MHz rotates the polarization of the output optical beam by 90°. The acousto-optic control is accomplished entirely by electronic means and can be applied for implementation of fast polarization converters. 相似文献
8.
Romualdas Smicius Virginija Jakubkiene Milda M. Burbuliene Povilas Vainilavicius 《Monatshefte für Chemie / Chemical Monthly》2002,7(1):173-181
Treatment of 5-(6-methyl-2,4-dioxo-1,2,3,4-tetrahydro-3-pyrimidinyl)-methyl-1,3,4-oxadiazole-2-thione with haloalkanes yielded oxadiazole S-alkyl derivatives, whereas its reaction with formaldehyde and amines resulted in formation of oxadiazole N(3)-aminomethyl derivatives. The alkylation of 2-alkylsulfanyl-5-(6-methyl-2,4-dioxo-1,2,3,4-tetrahydro-3-pyrimidinyl)-methyl-1,3,4-oxadiazoles with methyl bromoacetate proceeded at the N(1)-position of pyrimidine to give 2-alkylsulfanyl-5-(1-methoxycarbonylmethyl-6-methyl-2,4-dioxo-1,2,3,4-tetrahydro-3-pyrimidinyl)-methyl-1,3,4-oxadiazoles, whereas aminomethylation, bromination, or nitration took place at position 5 of pyrimidine ring and afforded the corresponding 5-pyrimidine substituted derivatives. 相似文献
9.
Imidazole modification at C-5 of uridine that is part of tandem G-U wobble base pairs causes slight reduction of thermal stability (DeltaDeltaG(0)(310) < 0.4 kcal mol(-1)) and relatively small change in hydration of short RNA helices. 相似文献
10.
Povilas Vainilavicius Romualdas Smicius Virginija Jakubkiene Sigitas Tumkevicius 《Monatshefte für Chemie / Chemical Monthly》2001,132(7):825-831
Summary. In the reaction of 5-(6-methyl-2,4-dioxo-1,2,3,4-tetrahydro-3-pyrimidinyl)-methyl-1,3,4-oxadiazole-2-thione with hydrazine
hydrate, 5-(6-methyl-2,4-dioxo-1,2,3,4-tetrahydro-3-pyrimidinyl)-methyl-4-amino-1,2,4-triazole-3-thione was formed. The reactions
of the latter with ethyl bromoacetate and chloroacetonitrile in the presence of triethylamine proceeded under formation of
the corresponding S-alkylated derivatives, whereas from its reaction with ω-bromoacetophenone and ethyl 4-chloroacetoacetate
triazolothiadiazines were obtained. Treatment of the title compound with ethyl 2-chloroacetoacetate led to the formation of
5-(6-methyl-2,4-dioxo-1,2,3,4-tetrahydro-3-pyrimidinyl)-methyl-4-N-acetylamino-(3-ethoxy-carbonylmethylthio)-1,2,4-triazole.
Performing of the latter reaction without basic catalyst gave a triazolothiadiazine. Treatment of the S-alkylated derivatives
with sodium methoxide resulted in triazolothiadiazines via a cyclocondensation reaction.
Received November 20, 2000. Accepted January 15, 2001 相似文献