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排序方式: 共有861条查询结果,搜索用时 15 毫秒
31.
Anca Giorgiana Grigoras Marieta Constantin Vasile Cristian Grigoras Simona Isabela Dunca Lacramioara Ochiuz 《Reactive and Functional Polymers》2013,73(9):1249-1254
The physico-chemical properties of three grafted pullulans (P) having linked poly(3-acrylamidopropyl)trimethylammonium chloride (pAPTAC) as side chains (P-g-pAPTAC1, P-g-pAPTAC2 and P-g-pAPTAC3 with 22.53, 29.05, and 34.51 (wt.%) of pAPTAC content in polymer, respectively) and possessing polyelectrolyte character were determined by light scattering analysis. All grafted pullulan aqueous solutions were tested in the presence of 0.5 M NaCl, KCl, NaNO3 or KNO3. The biggest associations were recorded in 0.5 M NaCl aqueous solutions for P-g-pAPTAC1, P-g-pAPTAC2 and P-g-pAPTAC3 according to the maximum values for Rg extracted from MALLS (multiangle laser light scattering) measurements. Also, the dominant conformation in salted solution of these polyelectrolytes was random coil as Debye plot analysis revealed. Antibacterial activity was tested by Kirby–Bauer diffusion method and all grafted pullulans dissolved in aqueous solutions of 0.5 M NaCl have developed inhibition zone against Staphylococcus aureus (ATCC 25923). 相似文献
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Summary: Syndiotactic polystyrene (sPS)/organophilic clay nanocomposites were obtained by in situ coordination‐insertion polymerization of styrene. Two cationic surfactants (alkylammonium and alkylphosphonium) were used for the intercalation of montmorillonite (MMT). For each organically modified clay, three protocols were performed using an MAO‐activated hemi‐metallocene catalyst, in order to compare the influence of experimental conditions on the composite microstructure and on its thermal stability. The microstructures of nanocomposites were investigated by wide angle X‐ray scattering and DSC. Partially exfoliated or intercalated materials were obtained in all cases and a decrease of crystallinity is observed. Thermal properties were also studied by DSC and thermogravimetric analysis. The presence of clay does not have a strong influence on the sPS thermal transitions but the thermal decomposition process of the material was slowed down in the presence of few organoclay percents, particularly in the degradation beginning. The influence of these two organically modified clays on the thermal stability of the material is discussed.
34.
Effect of P2O5 on the Structural and Magnetic Properties of Magnetite‐Based Glass‐Ceramics 下载免费PDF全文
Viorel Sandu Simona Greculeasa Andrei Kuncser Victor Kuncser 《Journal of the American Ceramic Society》2016,99(12):4013-4021
The specific morphology and magnetic properties of magnetite‐based glass‐ceramics obtained by crystallization of Fe‐containing borosilicate glassmelts in the presence of P2O5 as nucleating agent are investigated. We found that the distribution of the tiny nanoparticles of magnetite determines the low temperature response to magnetic field. The observed effects are discussed with respect to the following factors: (1) the existence of a multimodal size distribution of the tiny grains as revealed by Mössbauer spectroscopy, magnetometry, and high‐resolution electron microscopy; (2) the existence of a disordered layer at the grain surface which is driven by field in a magnetically ordered state; and (3) the interplay between the relaxation mechanisms in different temperature ranges. 相似文献
35.
Methane steam reforming is the most common industrial process used for almost the 50% of the world’s hydrogen production. Commonly, this reaction is performed in fixed bed reactors and several stages are needed for separating hydrogen with the desired purity. The membrane reactors represent a valid alternative to the fixed bed reactors, by combining the reforming reaction for producing hydrogen and its separation in only one stage. This article deals with the recent progress on methane steam reforming reaction, giving a short overview on catalysts utilization as well as on the fundamentals of membrane reactors, also summarizing the relevant advancements in this field. 相似文献
36.
Righi V Di Nunzio M Danesi F Schenetti L Mucci A Boschetti E Biagi P Bonora S Tugnoli V Bordoni A 《Lipids》2011,46(7):627-636
It is well recognized that a high dietary intake of long-chain polyunsaturated fatty acids (LC-PUFA) has profound benefits
on health and prevention of chronic diseases. In particular, in recent years there has been a dramatic surge of interest in
the health effects of n-3 LC-PUFA derived from fish, eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids. Notwithstanding,
the metabolic fate and the effects of these fatty acids once inside the cell has seldom been comprehensively investigated.
Using cultured neonatal rat cardiomyocytes as model system we have investigated for the first time, by means of high-resolution
magic-angle spinning nuclear magnetic resonance (HR-MAS NMR) spectroscopy in combination with gas chromatography (GC), the
modification occurring in the cell lipid environment after EPA and DHA supplementation. The most important difference between
control and n-3 LC-PUFA-supplemented cardiomyocytes highlighted by HR-MAS NMR spectroscopy is the increase of signals from
mobile lipids, identified as triacylglycerols (TAG). The observed increase of mobile TAG is a metabolic response to n-3 LC-PUFA
supplementation, which leads to an increased lipid storage. The sequestration of mobile lipids in lipid bodies provides a
deposit of stored energy that can be accessed in a regulated fashion according to metabolic need. Interestingly, while n-3
LC-PUFA supplementation to neonatal rat cardiomyocytes causes a huge variation in the cell lipid environment, it does not
induce detectable modifications in water-soluble metabolites, suggesting negligible interference with normal metabolic processes. 相似文献
37.
Orazio A. Attanasi Stefano Berretta Lucia De Crescentini Gianfranco Favi Gianluca Giorgi Fabio Mantellini Simona Nicolini 《Advanced Synthesis \u0026amp; Catalysis》2011,353(4):595-605
The zinc(II) triflate‐catalyzed synthesis of highly functionalized pyrroles is described. The sequence involves the preliminary preparation of α‐aminohydrazones by Michael addition of primary amines to 1,2‐diaza‐1,3‐dienes. The treatment of these intermediates with dialkyl acetylenedicarboxylates produces α‐(N‐enamino)‐hydrazones that are converted into the corresponding pyrroles. The substituents on the carbon in position four of 1,2‐diaza‐1,3‐dienes drive the regioselectivity of the ring closure process. Starting from 4‐aminocarbonyl‐1,2‐diaza‐1,3‐dienes only dialkyl 1‐substituted 5‐aminocarbonyl‐1H‐pyrrole‐2,3‐dicarboxylates are achieved by Lewis acid‐catalyzed ring closure. A screening of several Lewis/Brønsted acid catalysts is performed. Zinc(II) triflate is the most efficient catalyst. Under similar reaction conditions, employing 4‐alkoxycarbonyl‐1,2‐diaza‐1,3‐dienes, only 4‐hydroxy‐1H‐pyrrole‐2,3‐dicarboxylates are synthesized. These latter reactions can be accomplished regioselectively also in one pot. Using 4‐aminocarbonyl‐1,2‐diaza‐1,3‐dienes, diamines and dialkyl acetylenedicarboxylates the sequence provides the corresponding α,ω‐di(N‐pyrrolyl)alkanes. 相似文献
38.
39.
Influence of catalyst pretreatments on volatile organic compounds oxidation over gold/iron oxide 总被引:4,自引:0,他引:4
Simona Minic Salvatore Scir Carmelo Crisafulli Signorino Galvagno 《Applied catalysis. B, Environmental》2001,34(4):277-285
This paper reports a study on the influence of calcination pretreatments on the catalytic behaviour of the Au/iron oxide system towards the combustion of some representative volatile organic compounds (2-propanol, ethanol, methanol, acetone and toluene). The catalytic activity of Au/Fe2O3 samples towards the total oxidation to CO2 has been found to be strongly dependent on the catalyst pretreatment, decreasing on increasing the calcination temperature. On the basis of characterisation data (XPS, FT-IR, XRD, BET surface area) it has been proposed that the catalytic behaviour is related to the gold state and/or the iron oxide phase. It appears plausible to suggest that the gold oxidation state and/or the particle size play a key role in the catalytic combustion of volatile organic compounds. 相似文献
40.
Dr. Mariafrancesca Hyeraci Dr. Marialuigia Colalillo Prof. Luca Labella Prof. Fabio Marchetti Prof. Simona Samaritani Dr. Valeria Scalcon Prof. Maria Pia Rigobello Prof. Lisa Dalla Via 《ChemMedChem》2020,15(15):1464-1472
Platinum(II) complexes of the type [Pt(Cl)(PPh3){(κ2-N,O)-(1{C(R)=N(OH)-2(O)C6H4})}] with R=Me, H, ( 1 and 2 ) were synthesized and characterized. Single-crystal X-ray diffraction confirmed the proposed (SP4-3) configuration for 1 . Study of the antiproliferative activity, performed on a panel of human tumor cell lines and on mesothelial cells, highlighted complex 2 as the more effective. In particular, it showed a remarkable cytotoxicity in ovarian carcinoma cells (A2780) and interestingly, a significant antiproliferative effect on cisplatin resistant cells (A2780cis). Investigation into the intracellular mechanism of action demonstrated that 2 had a lower ability to platinate DNA than did cisplatin, which was taken as reference, and a notably higher uptake in resistant cells. A significant accumulation in mitochondria, along with the ability to induce concentration-dependent mitochondrial membrane depolarization and intracellular reactive oxygen species production, allowed us to propose a mitochondrion-mediated pathway as responsible for the interesting cytotoxic profile of complex 2 . 相似文献