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91.
Shimbo Y Gorecka E Pociecha D Araoka F Goto M Takanishi Y Ishikawa K Mieczkowski J Gomola K Takezoe H 《Physical review letters》2006,97(11):113901
A polarization reorientation process has been studied by means of optical second-harmonic generation in an optically uniaxial smectic phase of an asymmetric bent-core liquid crystal. A nontilted polar smectic order with a biaxial order is induced by applying an electric field to the uniaxial nonpolar smectic phase. This phenomenon was well simulated by the two-dimensional Langevin process, i.e., electric-field-induced continuous molecular reorientation against thermal agitation. The simulation suggests that about 200s of molecules form a polar domain and cooperatively respond to the applied field. The existence of the polar domains and their reorientation are consistent to the dielectric measurement; a high dielectric constant of about 60 at the kHz range is markedly suppressed by applying a bias field. 相似文献
92.
Zbigniew Ka?u?a Arkadiusz KazimierskiKrzysztof Lewandowski Kinga SuwińskaBeata Szcz?sna Marek Chmielewski 《Tetrahedron》2003,59(31):5893-5903
Starting from (l)-ethyl lactate and 4-vinyloxy-azetidin-2-one the diastereomeric (4S,6R)- and (4S,6S)-4-methyl-5-oxa-3-methylene and 3-oxo-cephams were obtained. The formation of the cepham skeleton proceeds with a diastereomeric excess up to 80%, depending on catalyst and reaction conditions. For comparison, the corresponding racemic cephams lacking a methyl at C-4 or with a gem-dimethyl group at C-4 were synthesized. 相似文献
93.
Anna Przybylska-Balcerek Tomasz Szablewski Renata Cegielska-Radziejewska Tomasz Gral Danuta Kurasiak-Popowska Kinga Stuper-Szablewska 《Molecules (Basel, Switzerland)》2022,27(5)
Problems related with biological contamination of plant origin raw materials have a considerable effect on prevention systems at each stage of food production. Concerning the antimicrobial action of phenolic acids, studies were undertaken to investigate antibacterial properties against bacterial strains of Escherichia coli (EC), Pseudomonas fluorescence (PF), Micrococcus luteus (ML) and Proteus mirabilis (PM), as well as antifungal properties targeting microscopic fungi Fusarium spp., extracts of phenolic compounds coming from inoculated grain from various genotypes of cereals. This study evaluated the antimicrobial action of phenolic acids extracts obtained from both naturally infested and inoculated with microorganisms. For this purpose a total of 24 cereal cultivars were selected, including 9 winter and 15 spring cultivars. The analyses showed a bactericidal effect in the case of 4 extracts against Micrococcus luteus (ML), 14 extracts against Pseudomonas fluorescence (PF), 17 extracts against Escherichia coli (EC) as well as 16 extracts against Proteus mirabilis (PM). It was found that 3 out of the 24 extracts showed no antibacterial activity. In turn, fungicidal action was observed in the case of 17 extracts against Fusarium culmorum (FC) (NIV), 16 extracts against FC (3AcDON), 12 extracts against Fusarium graminearum (FG) (3AcDON), while 12 other extracts showed antifungal action against FG (NIV) and 19 extracts against Fusarium langsethiae (FL). Based on the conducted analyses it was found that grain of small-grained cereals exposed to fungal infection is a source of bioactive compounds exhibiting antimicrobial properties. It was observed that the qualitative and quantitative profiles of polyphenols vary depending on the cereal cultivar. This extracts may be used to develop an antimicrobial preparation applicable in organic farming. 相似文献
94.
Dr. Anna Kamecka Prof. Andrzej Kapturkiewicz M.Sc. Patryk Wójcik Prof. Kinga Suwińska Dr. Joanna Masternak 《欧洲无机化学杂志》2023,26(33):e202300438
The paper deals with the synthesis of a series of cationic [Pt(ppz)2(N^N)]2+ complexes containing deprotonated 1-phenyl-1H-pyrazole as cyclometallating (C^N) ligands and α-diimines (N^N) in the form of water-soluble salts with OTf− (trifluoromethanesulfonate) counter ions. These complexes were obtained from cis-[Pt(ppz)2Cl2] through chloride ligands substitution with α-diimines. The complexes were identified by means of NMR spectroscopy and their molecular structures were confirmed by X-ray crystallography. The photophysical properties of these complexes were studied in detail. These complexes showed strong luminescence in MeOH/EtOH 1 : 1 glasses at 77 K but were almost non-emitting in MeCN solutions at room temperature. Their emission properties were compared to analogues IrIII complexes. 相似文献
95.
Copper(II) on a 4?Å molecular sieve support catalyses the chemoselective addition of alkyl- and arylmagnesium halides to chalcones. Only the 1,4-addition products were obtained in high yields. 相似文献
96.
97.
Zbigniew Grobelny Marek Matlengiewicz Sylwia Golba Justyna Jurek-Suliga Andrzej S. Swinarew Kinga Skrzeczyna 《International Journal of Polymer Analysis and Characterization》2015,20(3):206-222
Mono- and dipotassium salts of dipropylene glycol were applied for the polymerization of propylene oxide in mild conditions, i.e., tetrahydrofuran solution at ambient temperature. The structure of polymers was investigated by use of 13C NMR and MALDI-TOF techniques. The structure depends strongly on the kind of initiator and additives that are used such as coronand 18-crown-6 and dipropylene glycol. The lowest unsaturation, represented by allyloxy starting groups, has the polymer obtained by use of monopotassium salt without the ligand. The highest unsaturation degree is for the polymer synthesized in the presence of dipotassium salt–activated 18-crown-6. This polymer, obtained at high initial monomer concentration and low initial concentration of initiator, consists of two fractions, i.e., a low molar mass fraction (Mn = 9400) containing mainly macromolecules with alkoxide starting and end groups and a much higher molar mass fraction (Mn = 29500 g/mol) containing macromolecules with allyloxy starting groups and alkoxide or hydroxyl end groups. Addition of free glycol to this system decreases the molar mass of polymers. Similar results were obtained by use of dipotassium salts of other glycols. The mechanisms of the studied processes are discussed. 相似文献
98.
Three different modes of hydroformylation/aldol reaction sequences involving either acid-catalysed aldol reactions, Mukaiyama aldol addition of pre-formed enolsilanes or aldol addition of in situ generated boron enolates can be applied to unsaturated ketones and ketoesters to afford the corresponding carbocyclic aldol adducts in good yields proceeding through the intermediate activated ketoaldehydes. In selected cases, complimentary, synthetically useful diastereoselectivities were observed in the products. 相似文献
99.
J. Orbán Kinga Pozsonyi Krisztina Szarka Szilvia Barkó Emőke Bódis D. Lőrinczy 《Journal of Thermal Analysis and Calorimetry》2006,84(3):619-623
The thermodynamic properties of the ADP- and ATP-actin filaments were
compared by the method of differential scanning calorimetry. The lower melting
point for the ADP-F-actin filament (58.4 vs. 64.5°C for ATP-F-actin) indicated
that compared to the ATP-actin filaments its structure was less resistant
to heat denaturation. The detailed thermodynamic characterisation of the proteins
was carried out by the analysis of the calorimetric enthalpy, the entropy
and the free enthalpy changes. All of the determined parameters gave lower
values to the ADP-actin filaments than to the ATP-actin filaments. The calculated
values of the activation energy also demonstrated that compared to the ADP-F-actin
the ATP-F-actin was thermodynamically more resistant to the denaturing effect
of heat.
Based on all of this information we have concluded that the actin
filament prepared from ADP containing magnesium saturated actin monomers at
pH 8.0 is thermodynamically less stable than the ones obtained from ATP-actin
monomers. 相似文献
100.
Vyacheslav Boyko Roman Rodik Oksana Danylyuk Lyudmila Tsymbal Yaroslav Lampeka Kinga Suwinska Janusz Lipkowski Vitaly Kalchenko 《Tetrahedron》2005,61(52):12282-12287
The synthesis of new calix[4]arenes bearing two or four tetrazole liganting groups at the upper rim is decribed. The structures of tetrakis-tetrazolecalix[4]arene and its palladium dichloride (2:2) complex are examined by X-ray crystallography. 相似文献