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71.
Elmira Popova 《Operations Research Letters》2004,32(3):283-287
The optimal structure of Bayesian group replacement policies for a parallel system of n items with exponential failure times and random failure parameter is presented. The paper contains a proof of the fact that it is optimal to observe the system only at failure times. For the case of two items operating in parallel the exact form of the policy is derived. 相似文献
72.
Samvel N. Sirakanyan Athina Geronikaki Viktor G. Kartsev Elmira K. Hakobyan Anush A. Hovakimyan 《合成通讯》2019,49(10):1262-1276
Taking into account previously obtained biological results on some polyheterocyclic compounds (containing different heteroatoms) and in particular on several 8-amino-5-isopropyl-2,2-dimethyl-10-(methylthio)-1,4-dihydro-2H-pyrano[4’’,3’’:4’,5’]pyrido[3’,2’:4,5]thieno[3,2-d]pyrimidines Ia-v we have carried out the synthesis of twentyone 8-amino-5-isobutyl-2,2-dimethyl-10-(methylthio)-1,4-dihydro-2H-pyrano[4’’,3’’:4’,5’]pyrido[3’,2’:4,5]thieno[3,2-d]pyrimidines 6. Therefore we have slightly modified the structure of the previously studied I introducing at C-5 an isobutyl group instead of the previously examined isopropyl ones in order to see if this variation (changing a little the lipophilicity) will affect the biological activity. Furthermore thieno[3,2-d]pyrimidine-8-thione 7 and their S-alkylated 8 were synthesized. Finally by alkylation of 5-isobutyl-2,2-dimethyl-10-thioxo-1,4,10,11-tetrahydro-2H-pyrano[4'',3'':4',5']pyrido[3',2':4,5]thieno[3,2-d]pyrimidin-8(9H)-one 3 with alkyl dichlorides (bifunctional reagents) we realized the cyclization of a thiazole or thiazine ring on the [b] side of the pyrimidine ring with formation of the new condensed pentaheterocyclic systems: pyrano[4'',3'':4',5']pyrido[3',2':4,5]thieno[3,2-d][1,3]thiazolo[3,2-a]pyrimidin-8-one 11 and pyrano[4''',3''':4'',5'']pyrido[3'',2'':4',5']thieno[3',2':4,5]pyrimido[2,1-b][1,3]thiazin-8-one 12. It was found that some of the synthesized compounds showed interesting antimicrobial activity (by agar diffusion method) against some gram-positive and gram-negative bacilli strains. 相似文献
73.
Nanomagnetic bisethylferrocene‐containing ionic liquid supported on silica‐coated iron oxide (Fe3O4@SiO2@Im‐bisethylFc [HC2O4]) as a novel catalyst was designed and synthesized. The described catalyst was recycled and used without change in the time and efficiency of the condensation reaction. The Fourier transform‐infrared spectroscopy (FT‐IR), scanning electron microscopy images, X‐ray diffraction patterns, energy‐dispersive X‐ray spectroscopy, transmission electron microscope and vibrating‐sample magnetometer results confirmed the formation of Fe3O4@SiO2@Im‐bisethylFc [HC2O4] magnetic nanoparticle. The novel bis‐coumarin derivatives were identified by 1H‐NMR, 13C‐NMR, FT‐IR and CHNS analysis. 相似文献
74.
Aydar Rakhmatullin Vasiliy V. Brusko Elmira R. Shcherbitskaya Ilya B. Polovov Rinat Bakirov Catherine Bessada 《Magnetic resonance in chemistry : MRC》2022,60(9):893-900
A family of three- and four-coordinated silver(I) complexes of formulas [Ag(PPh3)2L], [Ag(PPh3)L], and [AgL]n with N-thiophosphorylated thiourea and thioamide ligands of general formula RC(S)NHP(S)(OPri)2 [R = Ph, PhNH, iPrNH, tBuNH, NH2] have been studied by solid-state 109Ag and 31P CPMAS NMR spectroscopy. 109Ag NMR spectra have provided valuable structural information about Ag coordination, which is in good accordance with the available crystal structure data. The data presented in this work represent a significant addition to the available 109Ag chemical shifts and chemical shifts anisotropies. The silver chemical shift ranges for different P,S-environments and coordination state were discussed in detail. The 1J(31P–107/109Ag) and 2J(31P–31P) values were determined and analyzed. 相似文献
75.
Sergey A. Baskakov Yulia V. Baskakova Eugene N. Kabachkov Galina A. Kichigina Pavel P. Kushch Dmitriy P. Kiryukhin Svetlana S. Krasnikova Elmira R. Badamshina Sergey G. Vasil&#x;ev Timofey A. Soldatenkov Victor N. Vasilets Filipp O. Milovich Alexandre Michtchenko Oksana V. Veselova Vasiliy A. Yakimov Svetlana N. Ivanova Yury M. Shulga 《Molecules (Basel, Switzerland)》2022,27(18)
Cellulose HogC was produced by the modified traditional method with 35% yield from the stem of Sosnovsky hogweed and was characterized by elemental analysis, infrared (IR) spectroscopy, powder X-ray diffractometry, differential scanning calorimetry (DSC) and X-ray photoelectron spectroscopy (XPS). For HogC, the degree of crystallinity (approximately 70%) and the glass transition temperature (105–108 °C) were determined. It was found that the whiteness characteristic in the case of HogC was 92% and this significate was obtained without a bleaching procedure using chlorine-containing reagents. In this paper, the possibility of hydrophobization of HogC films by treatment with radiation-synthesized telomers of tetrafluoroethylene is shown. It was found that the contact angle of the telomer-treated cellulose film surface depended on the properties of the telomers (the chemical nature of the solvent, and the initial concentration of tetrafluoroethylene) and could reach 140 degrees. 相似文献
76.
Andrei V. Churakov Sergey S. Karlov Elmira Kh. Lermontova Galina S. Zaitseva Judith A. K. Howard 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(12):o761-o762
The title compound, C24H17F10N3O2, exhibits intramolecular N—H...O hydrogen bonding, as well as intramolecular Ar...ArF face‐to‐face interactions. The molecules are linked together by N—H...F—C hydrogen bonds, forming chains parallel to the a axis. Adjacent symmetry‐related chains are combined in double zipper‐like ribbons by parallel ArF...ArF offset π‐stacking interactions. 相似文献
77.
Liviu Leontie M. Caraman Igor Evtodiev Elmira Cuculescu Ana Mija 《physica status solidi (a)》2008,205(8):2052-2056
Bismuth oxide (Bi2O3) thin films with thickness in the range 20–160 nm have been deposited by d.c. reactive magnetron sputtering of Bi in an atmosphere Ar:O2 (1:1), onto single crystalline p‐GaSe (Cu) substrates. The optical constants, n and k, of oxide films have been determined from the analysis of the polarization ellipse of the reflected radiation from outer surface of Bi2O3/p‐GaSe structures. In the wavelength range 400–800 nm the refractive index of nanometric Bi2O3 films onto GaSe(Cu) decreases from 2.10 to 1.78 and it seen to increase at decreasing sample thickness. In order to determine the interaction mechanism between semiconducting oxide film and GaSe surface, the spectral characteristics of photocurrent through Bi2O3/p‐GaSe junction and optical absorption in the range 400–800 nm have been examined. As resulted from respective analyses, Bi2O3 film generates new valence bonds, which contribute to the increase in the density of localized states at Bi2O3/p‐GaSe (Cu) junction interface. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献