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301.
302.
Krystyna Bogdanowicz-Szwed Aleksandra Pa?asz 《Monatshefte für Chemie / Chemical Monthly》2001,41(6):393-401
Reaction of 1-(phenylsulfenyl)-, 1-(phenylsulfinyl)-, and 1-(phenylsulfonyl)-2- propanones as well as 2-(phenylsulfonyl)-acetophenone
with 2-(3-methyl-2-butenyloxy)- and 2-((E)-3-phenyl-2-propenyloxy)-benzaldehydes yielded the corresponding Knoevenagel condensation products. The latter compounds underwent intramolecular cycloadditions affording cis-fused 2H-pyran derivatives as the major products. 相似文献
303.
Paweł Groch Katarzyna Dziubek Krystyna Czaja Marzena Białek Katarzyna Adamczyk‐Tomiak Stanisław Rabiej Beata Dudziec 《Journal of polymer science. Part A, Polymer chemistry》2017,55(23):3918-3934
Copolymerization of ethylene with iso‐butyl substituted monoalkenyl(siloxy)‐ or monoalkenylsilsesquioxane (POSS) comonomers over bis(phenoxy‐imine) and salen‐type titanium and zirconium catalysts was studied. It was found that the polyreaction performance was significantly depended by the kind of the catalyst and by the structure and concentration of POSS in the feed. The POSS comonomer was efficiently incorporated into the polymer chain at up to 0.2 mol %. The differences in the copolymer compositions as the functions of the catalyst kind and the POSS comonomer were observed, including the varied number‐average sequence length of ethylene and unsaturated end groups, as determined by 1H NMR and FT‐IR. The presence of POSS comonomers affected also the melting and crystallization behavior of the copolymers, as evidenced by DSC, because of influence on the polymer chain arrangement. The POSS units could act as the nucleating agents. Moreover, the crystal and structural parameters of ethylene/POSS copolymers were evaluated on the basis of X‐ray results, and the limited self‐aggregation of POSS incorporated into the polymer chain, the small number and size of POSS aggregates, and the increased crystallinity degree of copolymers were demonstrated. The ethylene/POSS copolymers produced by postmetallocenes offered also high thermal stability and interesting morphological properties. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3918–3934 相似文献
304.
Krystyna T. Baliska Louis V. Quintas Jerzy Szymaski 《Random Structures and Algorithms》1994,5(1):3-12
A random recursive forest is defined as a union of random recursive trees. We find the expected number of trees in the uniform random recursive forest as well as the number of vertices of given degree, the maximum degree, the height of vertices, the order of branches, the root of the component containing a given vertex, and the last root of such forests. © 1994 John Wiley & Sons, Inc. 相似文献
305.
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
306.
Zofia Krystyna Drzazga Aneta Kluczewska-Gałka Anna Michnik Michał Kaszuba Hanna Trzeciak 《Journal of fluorescence》2011,21(3):851-857
Autofluorescence of the mandible and femur bones taken from newborn rats (7-, 14- and 28-day old) was studied. Endogenous
fluorophores were excited with 231 nm, 291 nm, 340 nm and 360 nm wavelengths. Modifications in content and microenvironment
of both noncolagenous and collagenous constituents of bone tissue as well as metabolic coenzymes during the bone formation
with age were reflected in fluorescence emission spectra. The increase of emission from peptide bonds and tryptophan residues
was noted with rat age while for collagen and metabolic coenzymes at the first 2 weeks only. After maternal administration
of indinavir the changes in fluorescence intensity and shifts in position of peak maximum were found. The distinct drop of
emission from peptide bonds and tryptophan residues in studied bones was detected. In the case of collagen and metabolic coenzymes
the red shift of peak maximum was revealed. Fluorescence spectroscopy could be used to follow bone development in newborn
rats and effect of maternal indinavir administration on offspring. 相似文献
307.
Justyna Piechocka Anna Gramza-Michaowska Krystyna Szymandera-Buszka 《Molecules (Basel, Switzerland)》2021,26(15)
Phenolic compounds and thiamine may serve as therapies against oxidative stress-related neurodegenerative diseases. However, it is important to note that these components show high instability under changing conditions. The study’s aim was to determine the impact of the thiamine concentration (hydrochloride—TH and pyrophosphate—TP; in the range 0.02 to 20 mg/100 g on the indices of the chelating properties and reducing power, and free radicals scavenging indices of EGCG, EGC, ECG and caffeine added from 0.04 to 6.0 mg/100 g. Our research confirmed that higher concentrations of TH and TP can exhibit significant activity against the test antioxidant indices of all components. When above 5.0 mg/100 g of thiamine was used, the radical scavenging abilities of the compound decreased in the following order: EGCG > ECG > EGC > caffeine. The highest correlation was found for the concentration of thiamine pyrophosphate to 20.0 mg/100 g and EGCG. Knowledge of the impact of factors associated with the concentration of both EGCG, EGC, ECG or caffeine and thiamine on their activity could carry weight in regulating the quality supplemented foods, especially of nutrition support for people of all ages were oral, enteral tube feeding and parenteral nutrition). 相似文献
308.
An improved and simplified analytical method which offers rapid, accurate determination and identification of phenolic compounds in honey samples is reported. The honey samples were diluted by acidified water (pH 2), and analyzed by HPLC–ESI-MS/MS. Simultaneously determination of phenolic acids and flavonoids was carried out by a liquid chromatography–mass spectrometry. Comparison between atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI) was performed by analysis of standards. Fragmentation of analytes for subsequent selective Multiple Reaction Monitoring (MRM) analysis was investigated in negative mode. Sample preparation without separation of sugars and clean-up procedure, followed by fast chromatographic separation using a narrow-bore column C18 (50 mm × 2.1 mm, 3 μm) allowed the analysis to be completed in a short run time. LODs were ranged between 1 and 15 ng L−1 for p-coumaric acid and naringenin, respectively. The method was applied for determination of phenolic acids and flavonoids in honey samples from different botanical origin. 相似文献
309.
Renaud Marquis Dr. Krystyna Kulikiewicz Dr. Sergei Lebedkin Dr. Manfred M. Kappes Prof. Dr. Charles Mioskowski Dr. Stéphane Meunier Dr. Alain Wagner Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(42):11187-11196
Syntheses of chiral 6,15‐dihydronaphtho[2,3‐c]pentaphene derivatives of opposite configurations are reported. Starting from anthracene, the strategy involves two key steps: a Diels–Alder reaction on a prochiral dianthraquinone, and an enantiomeric resolution using (?)‐menthol. The final molecules exhibit very strong optical activity, as shown by their circular dichroism spectra, and are examples of chiral facial amphiphiles. Their adsorption at the surface of single‐walled carbon nanotubes (SWNTs) has also been studied, and has been found to occur preferentially on 0.8–1.0 nm diameter nanotubes among the population of a high‐pressure CO conversion (HiPco) SWNT sample (0.8–1.2 nm). The synthesised facial amphiphiles act as nano‐tweezers for the diameter‐selective solubilisation of SWNTs in water. The expected optical activities of the SWNT samples solubilised by each of the chiral amphiphiles have been studied by circular dichroism spectroscopy, but the results are not yet conclusive. 相似文献
310.
Andrzej Zwierzak Krystyna Osowska-Pacewicka 《Monatshefte für Chemie / Chemical Monthly》1984,115(1):117-120
The effective, one-step transformation of diethyl hydrogen phosphate into diethyl phosphoramides by using hexamethyltriaminodibromophosphorane prepared in situ is described.
Direkte Umwandlung von Diethylhydrogenphosphat in Diethylphosphoramid (Kurze Mitteilung)
Zusammenfassung Es wird eine effiziente, einstufige Umwandlung von Diethylhydrogenphosphat in Diethylphosphoramid unter Verwendung vonin situ erzeugten Hexamethyltriaminodibromophosphoran beschrieben.相似文献