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71.
Summary: Having developed a theoretical model of hyperbranched polymerization involving AB2 and B2 monomers we present preliminary results of a test of its validity for the system consisting of 4,4-bis(4-hydroxyphenyl)pentanoic acid (AB2 monomer) and bisphenol A (B2 monomer). The monomers reacted at room temperature to yield the title hyperbranched polyesters. Diisopropylcarbodiimide (condensation water remover) along with an effective catalyst were used for that purpose. The total of AB2 monomer was introduced at once to a reactor containing B2 core monomer or it was divided into 3 or 5 equal portions and each of them introduced after the monomers previously present have reacted to a predetermined conversion. GPC measurements of the resulting molecular mass distribution gave inconclusive results because of poor reproducibility of polymer isolation/purification procedure and/or insufficient accuracy of GPC technique. 相似文献
72.
Klaudia Stando Ewa Korzeniewska Ewa Felis Monika Harnisz Sylwia Bajkacz 《Molecules (Basel, Switzerland)》2022,27(14)
Manure is a major source of soil and plant contamination with veterinary drugs residues. The aim of this study was to evaluate the uptake of 14 veterinary pharmaceuticals by parsley from soil fertilized with manure. Pharmaceutical content was determined in roots and leaves. Liquid chromatography coupled with tandem mass spectrometry was used for targeted analysis. Screening analysis was performed to identify transformation products in the parsley tissues. A solid-liquid extraction procedure was developed combined with solid-phase extraction, providing recoveries of 61.9–97.1% for leaves and 51.7–95.6% for roots. Four analytes were detected in parsley: enrofloxacin, tylosin, sulfamethoxazole, and doxycycline. Enrofloxacin was detected at the highest concentrations (13.4–26.3 ng g−1). Doxycycline accumulated mainly in the roots, tylosin in the leaves, and sulfamethoxazole was found in both tissues. 14 transformation products were identified and their distribution were determined. This study provides important data on the uptake and transformation of pharmaceuticals in plant tissues. 相似文献
73.
Sulodexide (SDX), a purified glycosaminoglycan mixture used to treat vascular diseases, has been reported to exert endothelial protective effects against ischemic injury. However, the mechanisms underlying these effects remain to be fully elucidated. The emerging evidence indicated that a relatively high intracellular concentration of reduced glutathione (GSH) and a maintenance of the redox environment participate in the endothelial cell survival during ischemia. Therefore, the aim of the present study was to examine the hypothesis that SDX alleviates oxygen–glucose deprivation (OGD)-induced human umbilical endothelial cells’ (HUVECs) injury, which serves as the in vitro model of ischemia, by affecting the redox state of the GSH: glutathione disulfide (GSSG) pool. The cellular GSH, GSSG and total glutathione (tGSH) concentrations were measured by colorimetric method and the redox potential (ΔEh) of the GSSG/2GSH couple was calculated, using the Nernst equation. Furthermore, the levels of the glutamate–cysteine ligase catalytic subunit (GCLc) and the glutathione synthetase (GSS) proteins, a key enzyme for de novo GSH synthesis, were determined using enzyme-linked immunoassay (ELISA). We demonstrated that the SDX treatment in OGD conditions significantly elevated the intracellular GSH, enhanced the GSH:GSSG ratio, shifting the redox potential to a more pro-reducing status. Furthermore, SDX increased the levels of both GCLc and GSS. The results show that SDX protects the human endothelial cells against ischemic stress by affecting the GSH levels and cellular redox state. These changes suggest that the reduction in the ischemia-induced vascular endothelial cell injury through repressing apoptosis and oxidative stress associated with SDX treatment may be due to an increase in GSH synthesis and modulation of the GSH redox system. 相似文献
74.
Dr. Bruno Mattia Bizzarri Dr. Paola Manini Dr. Valeria Lino Prof. Marco d'Ischia Dr. Michail Kapralov Prof. Eugene Krasavin Klaudia Mráziková Prof. Jiří Šponer Dr. Judit E. Šponer Prof. Ernesto Di Mauro Prof. Raffaele Saladino 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(65):14919-14928
Formation and structural modification of oxygenated polycyclic aromatic hydrocarbons (oxyPAHs) by UV irradiation on minerals have recently been proposed as a possible channel of PAH transformation in astrochemical and prebiotic scenarios of possible relevance for the origin of life. Herein, it is demonstrated that high-energy proton-beam irradiation in the presence of various meteorites, including stony iron, achondrite, and chondrite types, promotes the conversion of two representative oxyPAH compounds, 1-naphthol and 1,8-dihydroxynaphthalene, to complex mixtures of oxygenated and oligomeric derivatives. The main identified products include polyhydroxy derivatives, isomeric dimers encompassing benzofuran and benzopyran scaffolds, and, notably, a range of quinones and perylene derivatives. Addition of urea, a prebiotically relevant chemical precursor, expanded the range of identified species to include, among others, quinone diimines. Proton-beam irradiation of oxyPAH modulated by nitrogen-containing compounds such as urea is proposed as a possible contributory mechanism for the formation and processing of insoluble organic matter in meteorites and in prebiotic processes. 相似文献
75.
W. Bell A. Breakstone G. Claesson H. B. Crawley G. M. Dallavalle K. Doroba D. Drijard F. Fabbri A. Firestone M. A. Faessler H. G. Fischer S. Y. Fung S. Garpman W. Geist G. Giacomelli R. Gokieli M. Gorbics C. R. Gruhn P. Hanke M. Heiden W. Herr T. J. Ketel E. E. Kluge J. W. Lamsa T. Lohse I. Lund R. Mankel W. T. Meyer G. Mornacchi T. Nakada I. Otterlund M. Panter H. Pugh A. Putzer K. Rauschnabel B. Rensch F. Rimondi M. Schmelling L. Schroeder R. Sosnowski E. Stenlund T. J. M. Symons M. Szczekowski R. Szwed O. Ullaland R. Walczak D. Wegener M. Wunsch 《Zeitschrift für Physik A Hadrons and Nuclei》1986,325(1):7-14
Inelasticαα anddd collisions were studied at a centre-of-mass energy √S NN=31.2 GeV per nucleon-nucleon collision, using the Split-Field Magnet (SFM) detector at the CERN ISR. In this paper we show the inclusive and semi-inclusive rapidity distributions of protons, compare them with predictions of the Lund model, and calculate the average rapidity loss for participant protons. From the negative particles we calculate the inelasticity of the interaction, the average energy per particle, and the degree of isotropy of the produced hadrons. 相似文献
76.
77.
The phase equilibria in the total range of component concentrations in the V2O5-Cr2O3 system up to 1000 °C were studied by means of phase powder diffraction and DTA. Two compounds exist in the system: CrVO4, melting incongruently at 860±5 °C, and Cr2V4O13, which decomposes in the solid state at 640±5 °C to CrVO4(s) and V2O5(s). At 645±5 °C, CrVO4 and V2O5 form a eutectic mixture with the CrVO4 content not exceeding 2% mol.
Zusammenfassung Mittels DTA und Pulverdiffraktionsaufnahmen wurde das Phasengleichgewicht des Systems V2O5-Cr2O3 bis 1000 °C im gesamten Konzentrationsbereich untersucht. Innerhalb des Systemes existieren zwei Verbindungen: CrVO4 mit einem inkongruentem Schmelzpunkt bei 860±5 °C und Cr2V4O13, das sich in festem Zustand bei 640±5 °C in CrVO4(s) und V2O5(s) zersetzt. Bei 645±5 °C bilden CrVO4 und V2O5 ein eutektisches Gemisch mit einem maximalen CrVO4-Gehalt von 2 mol%.
DTA V25-Cr23 1000° . : CrVO4, 860±5° Cr2V4O13, 640±5° CrVO4 V2O5, 645±5° CrVO4, 2 %.相似文献
78.
Brereton Richard G. Jansen Jeroen Lopes João Marini Federico Pomerantsev Alexey Rodionova Oxana Roger Jean Michel Walczak Beata Tauler Romà 《Analytical and bioanalytical chemistry》2018,410(26):6691-6704
Analytical and Bioanalytical Chemistry - The contribution of chemometrics to important stages throughout the entire analytical process such as experimental design, sampling, and explorative data... 相似文献
79.
Studies on the three-component system Al2O3-V2O5-MoO3 have shown the existence of a new compound with molecular formula AlVMoO7. The synthesis conditions and X-ray characteristics of this compound and its melting temperature, 690±10°C, are reported.
Zusammenfassung Einleitende Untersuchungen am Dreikomponentensystem Al2O3-V2 O5-MoO3 zeigten die Existenz einer neuen, noch nicht publizierten Verbindung der Formel AlVMoO7. Die Synthese der Verbindung sowie ihre röntgenographischen Eigenschaften wurden beschrieben. Ihr Schmelzpunkt beträgt 690±10°C.相似文献
80.
Feature selection is a valuable technique in data analysis for information-preserving data reduction. This paper describes a feature selection approach for hierarchical clustering based on genetic algorithms using a fitness function that tries to minimize the difference between the dissimilarity matrix of the original feature set and the one of the reduced feature sets. Clustering trees based on reduced feature sets are comparable with those based on the complete feature set. Special measures to favor small reduced feature sets are discussed. 相似文献