排序方式: 共有113条查询结果,搜索用时 265 毫秒
91.
A series of new thiourea catalysts prepared from natural amino acids have been applied in organocatalytic asymmetric Michael additions of α-nitrocyclohexanone to nitroalkenes. The resulting addition products are formed with excellent enantioselectivities (up to an er of 98:2) in good yields (up to 90%). 相似文献
92.
A synergistic catalytic system for the first asymmetric addition of aldehydes to in situ generated prochiral oxocarbenium ions has been developed. The dual catalytic protocol allows the simultaneous activation of both electrophile and nucleophile and provides access to a variety of valuable chiral 2H-chromenes with excellent enantioselectivities. 相似文献
93.
Margareta Socaciu Carmina Plosceanu Iuliana Cuculescu I. Muşcutariu 《Phase Transitions》2013,86(4):249-257
The use is described of absorption spectroscopy for determining phase transitions in the mesogenic compound cholesteryl myristate (CM) and in binary mixtures of terephthalbis-butyl-aniline (TBBA) and cholesteryl myristate. The temperature dependence of the optical densities in the visible region at phase transitions is reported. The transition temperatures obtained with this method are in good agreement with the results obtained with other methods. 相似文献
94.
We demonstrate that nonlinear electrical transport through a two-terminal nanoscale sample is not symmetric in the magnetic field B. More specifically, we have measured the lowest order B-asymmetric terms in single-walled carbon nanotubes. Theoretically, these terms can be used to infer both the strength of electron-electron interactions and the handedness of the nanotube. Consistent with theory, we find that at high temperatures the B-linear term is small and has a constant sign independent of Fermi energy, while at low temperatures it develops mesoscopic fluctuations. We also find surprising magnetoresistance at zero bias in the metallic regime. 相似文献
95.
Prof. Dr. C. Drăgulescu E. Petrovici Iuliana Lupu 《Monatshefte für Chemie / Chemical Monthly》1974,105(6):1176-1183
Complex compounds of divalent metal chlorides (CaCl2, NiCl2, MnCl2, CoCl2, CuCl2, CdCl2, PdCl2) are described, which had been obtained in a double complexation reaction in non aqueous media with nitro compounds and SbCl5:M
II(CH3NO2)
m
(SbCl6)2 (m=4, 6),M
II(C6H5NO2)
m
(SbCl6) (m=2, 3),M
II(-C10H7NO2)2(SbCl6)2. Synthesis, analytical results and i.r. spectra are discussed. 相似文献
96.
Gruia MI Oprea E Gruia I Negoita V Farcasanu IC 《Molecules (Basel, Switzerland)》2008,13(5):1195-1206
Lonicera caerulea is a species of bush native to the Kamchatka Peninsula (Russian Far East) whose berries have been extensively studied due to their potential high antioxidant activity. The aim of our work was to investigate the in vivo effects of the antioxidant action of Lonicera caerulea berry extracts on the dynamics of experimentally-induced tumors. Our data showed that aqueous Lonicera caerulaea extracts reduced the tumor volume when administered continuously during the tumor growth and development stages, but augmented the tumor growth when the administration of extracts started three weeks before tumor grafting. Prolonged administration of Lonicera caerulaea berry extracts induced the antioxidant defense mechanism in the tumor tissues, while surprisingly amplifying the peripheral oxidative stress. 相似文献
97.
The infrared absorption properties of a-SiC:H thin films dependence with the dc magnetron power density were investigated. The films were deposited in a mixture of CH4, H2 and Ar. The target used was polycrystalline Si. We found that the dc magnetron power density has an important contribution to the film composition. There is a strong dependence of the Si-H and Si-C bonds with the dc power density. 相似文献
98.
Petre Badica Nicolae Dan Batalu Mariana Carmen Chifiriuc Mihail Burdusel Mihai Alexandru Grigoroscuta Gheorghe Virgil Aldica Iuliana Pasuk Andrei Kuncser Marcela Popa Angelo Agostino Lorenza Operti Santanu Kumar Padhi Valentina Bonino Marco Truccato 《Molecules (Basel, Switzerland)》2021,26(19)
Pristine high-density bulk disks of MgB2 with added hexagonal BN (10 wt.%) were prepared using spark plasma sintering. The BN-added samples are machinable by chipping them into desired geometries. Complex shapes of different sizes can also be obtained by the 3D printing of polylactic acid filaments embedded with MgB2 powder particles (10 wt.%). Our present work aims to assess antimicrobial activity quantified as viable cells (CFU/mL) vs. time of sintered and 3D-printed materials. In vitro antimicrobial tests were performed against the bacterial strains Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 25923, Enterococcus faecium DSM 13590, and Enterococcus faecalis ATCC 29212; and the yeast strain Candida parapsilosis ATCC 22019. The antimicrobial effects were found to depend on the tested samples and microbes, with E. faecium being the most resistant and E. coli the most susceptible. 相似文献
99.
Beatrice-Cristina Ivan Florea Dumitrascu Adriana Iuliana Anghel Robert Viorel Ancuceanu Sergiu Shova Denisa Dumitrescu Constantin Draghici Octavian Tudorel Olaru George Mihai Nitulescu Mihaela Dinu Stefania-Felicia Barbuceanu 《Molecules (Basel, Switzerland)》2021,26(21)
A series of new pyrrole derivatives were designed as chemical analogs of the 1,4-dihydropyridines drugs in order to develop future new calcium channel blockers. The new tri- and tetra-substituted N-arylpyrroles were synthesized by the one-pot reaction of 1-methyl-3-cyanomethyl benzimidazolium bromide with substituted alkynes having at least one electron-withdrawing substituent, in 1,2-epoxybutane, acting both as the solvent and reagent to generate the corresponding benzimidazolium N3-ylide. The structural characterization of the new substituted pyrroles was based on IR, NMR spectroscopy as well as on single crystal X-ray analysis. The toxicity of the new compounds was assessed on the plant cell using Triticum aestivum L. species and on the animal cell using Artemia franciscana Kellogg and Daphnia magna Straus crustaceans. The compounds showed minimal phytotoxicity on Triticum rootlets and virtually no acute toxicity on Artemia nauplii, while on Daphnia magna, it induced moderate to high toxicity, similar to nifedipine. Our research indicates that the newly synthetized pyrrole derivatives are promising molecules with biological activity and low acute toxicity. 相似文献
100.
Iuliana Oita Hadewych Halewyck Bert Thys Bart Rombaut Yvan Vander Heyden 《Analytica chimica acta》2012
The development of capillary electrophoretic applications aiming to provide reliable stability assessment of viral suspensions, to detect subviral particles from cell extracts or to study the interactions between virus particles and various biomolecules, cannot be done without a thorough understanding of the sample matrix contribution to the observed electrophoretic behaviour. The present study thoroughly investigates the effect of the sample matrix on the electrophoretic behaviour of poliovirus injected as sample plugs of 1%, 5% and 12% effective capillary length. The effect of the sample matrix for three different poliovirus batches was evaluated. Additionally, simulated samples, obtained from concentrated poliovirus suspensions of high purity and diluted with commonly used lab buffers in order to obtain samples with either high or low conductivities, were also investigated. The goal of the study was to obtain a better understanding of the effect of the sample matrix on the signal enhancement, in order to define a general approach allowing a repeatable capillary electrophoretic (CE) separation of poliovirus from complex samples. This study clearly demonstrates that the sample matrix has an important influence on the sensitivity of the CE poliovirus separations. Translation of these observations into routine practice involves several compromises and a set of rules in order to reduce day-to-day variation and to maximize sensitivity. 相似文献