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排序方式: 共有467条查询结果,搜索用时 15 毫秒
81.
Chemically crosslinked polyimide organic–inorganic composite nanofiltration membranes suitable for application in harsh organic solvents were successfully prepared by phase inversion of dope solutions. TiO2 nanoparticles were dispersed in these dope solutions, comprising polyimide (PI) in N,N-dimethylformamide/1,4-dioxane. The impact of TiO2 on the resulting PI membranes was investigated using SEM, TGA, water contact angle, dope viscosity measurements and mechanical strength. The presence of TiO2 nanoparticles within the membrane matrix was proved by the detection of a peak characteristic of TiO2 in the WAXS pattern. SEM pictures of the cross-section of the PI/TiO2 membranes showed dramatically changed morphology compared to reference membranes with no TiO2 addition. Macrovoids present in reference membranes were suppressed by increasing loading of TiO2 nanoparticles, and eventually disappeared completely at a TiO2 loading above 3 wt.%. Decreasing water contact angle and an increase in ethanol flux indicated that hydrophilicity increased as nanoparticle loading increased. The effect of TiO2 on the functional performance of the membranes was evaluated by measuring flux and rejection using cross-flow filtration. Perhaps surprisingly, the presence of TiO2 improved the compaction resistance of the membranes, whereas rejection and steady flux were almost unaltered. 相似文献
82.
Let Λ be an algebraic set and let (n is even) be a polynomial mapping such that for each there is r(λ) > 0 such that the mapping g
λ = g(· , λ) restricted to the sphere S
n
(r) is an immersion for every 0 < r < r (λ), so that the intersection number I(g
λ|S
n
(r)) is defined. Then is an algebraically constructible function.
I. Karolkiewicz and A. Nowel supported by the grant BW/5100-5-0286-7. 相似文献
83.
Quantitative EPR study on free radicals in the natural polyphenols interacting with metal ions and other environmental pollutants 总被引:1,自引:0,他引:1
Jezierski A Czechowski F Jerzykiewicz M Golonka I Drozd J Bylinska E Chen Y Seaward MR 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2002,58(6):1293-1300
Quantitative electron paramagnetic resonance (EPR) method was applied to characterise radicals stabilised in polyphenolic matrices of various biogenic materials: lichens, mosses, composts, soils, peats, brown coals and sewage sludge sediments. The investigations were carried out on raw materials and extracted fractions of humic acids (HA). General trends of g value and spin concentration changes were found. These parameters in lichens strongly depend on lichen species and air pollution. Determination of the g value and semiquinone spin concentration allows to assess degree of transformation of organic matter in compost, soil, peat and lignite. Application of gaseous ammonia as a base penetrating the organic matrices extends the possibilities and usefulness of the method. Interaction of metal ions with humic materials is illustrated by interaction of VO2+ ion with peat and lignite HA as well as demineralised (raw and carbonised) brown coal. Our investigations demonstrate that quantitative EPR is a rapid and effective monitoring method to study the influence of various environmental factors on substances containing polyphenolic matrices. 相似文献
84.
Bury W Justyniak I Prochowicz D Wróbel Z Lewiński J 《Chemical communications (Cambridge, England)》2012,48(59):7362-7364
Two unique adducts of an oxozinc carboxylate cluster with H(2)O and THF were isolated and structurally characterized, [Zn(4)(μ(4)-O)(O(2)CR)(6)(H(2)O)(THF)]·2(THF) and [Zn(4)(μ(4)-O)(O(2)CR')(6)(THF)(3)] (where R = benzoate and R' = 9-antracenecarboxylate anion). The study shows that the zinc centers of the Zn(4)O core can easily form unique coordination environments without breaking of the Zn-O(carboxylate) bonds. 相似文献
85.
Kamila Malecka Iwona Grabowska Jerzy Radecki Anna Stachyra Anna Góra‐Sochacka Agnieszka Sirko Hanna Radecka 《Electroanalysis》2012,24(2):439-446
The working principle of a genosensor is based on the mechanism of ion‐channel mimetic sensors. The analytical signals generated upon hybridization processes were recorded by a redox active marker [Fe(CN)6]3?/4? present in the sample solution using voltammetric techniques. The developed genosensor was suitable for determination of 20‐mer complementary oligonucleotide sequence, and also of the PCR products containing the complementary 20‐mer sequence in various positions, with detection limits in the 10 pM range. The noncomplementary 20‐mer oligonucleotide sequence as well as the PCR product without complementary region generated very weak response. The good discrimination of the position of the complementary part in the PCR products was observed. 相似文献
86.
Bury W Justyniak I Prochowicz D Rola-Noworyta A Lewiński J 《Inorganic chemistry》2012,51(13):7410-7414
An atom-efficient and mild synthesis of a series of oxozinc carboxylates [Zn(4)(μ(4)-O)(O(2)CR)(6)] [where R = Ph (2a), p-PhC(6)H(4) (2b), p-MeC(6)H(4) (2c), and p-MeSC(6)H(4) (2d)] from well-defined alkylzinc precursors and H(2)O is described. The molecular and crystal structures of the resulting complexes have been determined by single-crystal X-ray diffraction. A closer examination of their crystal structure provides a direct picture of the effect of the nature of substituents on the molecular self-assembly of the octahedral oxozinc through noncovalent interactions. It was revealed that these discrete oxozinc clusters can form diverse types of noncovalent assemblies ranging from structures representing zeolitic topologies in the case of 2a to soft porous materials with gated voids or open channels for the remaining molecular clusters. 相似文献
87.
Paulina Mierzejewska Michal Kunc Magdalena Agnieszka Zabielska-Kaczorowska Barbara Kutryb-Zajac Iwona Pelikant-Malecka Alicja Braczko Patrycja Jablonska Pawel Romaszko Patrycja Koszalka Jolanta Szade Ryszard Tomasz Smolenski Ewa Maria Slominska 《Experimental & molecular medicine》2021,53(9):1402
Our recent studies identified a novel pathway of nicotinamide metabolism that involves 4-pyridone-3-carboxamide-1-β-D-ribonucleoside (4PYR) and demonstrated its endothelial cytotoxic effect. This study tested the effects of 4PYR and its metabolites in experimental models of breast cancer. Mice were divided into groups: 4T1 (injected with mammary 4T1 cancer cells), 4T1 + 4PYR (4PYR-treated 4T1 mice), and control, maintained for 2 or 21 days. Lung metastasis and endothelial function were analyzed together with blood nucleotides (including 4PYR), plasma amino acids, nicotinamide metabolites, and vascular ectoenzymes of nucleotide catabolism. 4PYR metabolism was also evaluated in cultured 4T1, MDA-MB-231, MCF-7, and T47D cells. An increase in blood 4PYR in 4T1 mice was observed at 2 days. 4PYR and its metabolites were noticed after 21 days in 4T1 only. Higher blood 4PYR was linked with more lung metastases in 4T1 + 4PYR vs. 4T1. Decreased L-arginine, higher asymmetric dimethyl-L-arginine, and higher vascular ecto-adenosine deaminase were observed in 4T1 + 4PYR vs. 4T1 and control. Vascular relaxation caused by flow-dependent endothelial activation in 4PYR-treated mice was significantly lower than in control. The permeability of 4PYR-treated endothelial cells was increased. Decreased nicotinamide but enhanced nicotinamide metabolites were noticed in 4T1 vs. control. Reduced N-methylnicotinamide and a further increase in Met2PY were observed in 4T1 + 4PYR vs. 4T1 and control. In cultured breast cancer cells, estrogen and progesterone receptor antagonists inhibited the production of 4PYR metabolites. 4PYR formation is accelerated in cancer and induces metabolic disturbances that may affect cancer progression and, especially, metastasis, probably through impaired endothelial homeostasis. 4PYR may be considered a new oncometabolite.Subject terms: Mechanisms of disease, Pathogenesis, Breast cancer 相似文献
88.
Natalia Pachura Robert Kupczyski Kamila Lewandowska Maciej Wodarczyk Marta Klemens Piotr Kuropka Renata Nowaczyk Magorzata Krzystek-Korpacka Iwona Bednarz-Misa Tomasz Sozaski Krystyna Pogoda-Sewerniak Antoni Szumny 《Molecules (Basel, Switzerland)》2022,27(11)
Ilex paraguariensis, the holly tree, is a plant with recognized biological properties, whose aqueous infusions are known as “Yerba mate”, that regulate lipid metabolism, reduce obesity, and improve brain stimulation. In the present study, the effect of standardized saponin and terpenoid fractions of a European taxon, Ilex aquifolium, on blood biochemical parameters in a rat model of metabolic disorder, (fa/fa) Zucker, are presented. The profiles of the volatile fractions of two species and six European varieties of Ilex were investigated. After selecting the best variety, the saponin and terpenoid fractions were isolated and standardized, and animals were fed 10 mg kg−1 b.w. for 8 weeks. A statistically significant decrease in liver adiposity was observed, confirmed by histology and quantitative identification (gas chromatography–mass spectrometry analyses of hepatic lipids. RT-qPCR analysis of gene expression in the aorta revealed that the administration of the terpenoid fraction downregulated LOX-1, suggesting a reduction in atherosclerotic stimuli. In addition, a statistically significant reduction (p < 0.05) in PPARγ for the saponin fraction was observed in the liver. The expression of the ACAT-1 gene in the liver, responsible for the formation of cholesterol esters, increased significantly in the group receiving the terpenoid fraction compared to the control, which was also confirmed by the analysis of individual blood biochemical parameters. The opposite effect was observed for saponins. Taking the above into account, it is shown for the first time that Ilex aquifolium can be a source of compounds that positively influence lipid metabolism. 相似文献
89.
Elena Sinkiewicz-Darol Iwona Adamczyk Katarzyna ubiech Gabriela Pilarska Magdalena Twaruek 《Molecules (Basel, Switzerland)》2022,27(11)
Breast milk is the optimal food for infants and toddlers, providing basic nutrients. It is also a source of many biologically active substances. Among them are hormones responsible for metabolic balance. One of the hormones taken in with breast milk by a breastfed baby is leptin. This hormone is involved in the regulation of appetite, informing the brain about the body’s energy resources. Having the correct mechanisms related to the action of leptin is a factor reducing the risk of obesity. The natural presence of leptin in the composition of breast milk suggests that it has a specific role in shaping the health of a breastfed child. Obesity as a disease of civilization affects more and more people, including children. The development of this disease is multifaceted and determined by many factors, including genetic and environmental factors such as eating habits and low physical activity. Behind obesity, there are complex mechanisms in which many elements of the human body are involved. Understanding the effects of breastfeeding as a natural source of leptin can help prevent childhood obesity and development of this disease in future life. 相似文献
90.
ukasz Lewandowski Iwona Bednarz-Misa Alicja Z. Kucharska Agnieszka Kubiak Patrycja Kasprzyk Tomasz Sozaski Dominika Przybylska Narcyz Pirecki Magorzata Krzystek-Korpacka 《Molecules (Basel, Switzerland)》2022,27(13)
Despite the fact that phytochemicals of Cornaceae species have long been discussed as possible auxiliary agents in contemporary treatment, the insights on their properties remain relatively scarce. This study focuses on Cornus mas L. (Cornelian cherry), the extracts of which are reported to exert a pleiotropic effect shown in both in vivo and in vitro studies. This study aimed to explore the cytotoxic effect of extracts from fruits of red (Cornus mas L. ‘Podolski’) and yellow (Cornus mas L. ‘Yantarnyi’ and ‘Flava’) Cornelian cherries on two melanoma cell lines (A375 and MeWo). The extracts were characterized in the context of the concentration of bioactive compounds of antioxidative properties. Cytotoxicity was investigated with the use of the following two assays: SRB and MTT. An additional, alternative protocol for the SRB assay was used in this study so as to account for possible bias. Cytotoxicity was assessed as a difference in the whole time series of cell viability, instead of analyzing differences in raw values (often found in the literature). Both extracts from Cornus mas L. induced cytotoxicity in both A375 and MeWo cell lines, although the response of these cells was different. Moreover, based on this study, there is no evidence for claiming a different magnitude of cytotoxicity between these two extracts. 相似文献