Search results for "Oxide"
showing 10 items of 6424 documents
Halogen-Bonded Co-Crystals of Aromatic N-oxides : Polydentate Acceptors for Halogen and Hydrogen Bonds
2017
The C-ethyl-2-methylresorcinarene (1) forms 1:1 in-cavity complexes with aromatic N,N′-dioxides, only if each of the aromatic rings has an N−O group. The structurally different C-shaped 2,2′-bipyridine N,N′-dioxide (2,2′-BiPyNO) and the linear rod-shaped 4,4′-bipyridine N,N′-dioxide (4,4′-BiPyNO) both form 1:1 in-cavity complexes with the host resorcinarene in C4v crown and C2v conformations, respectively. In the solid state, the host–guest interactions between the 1,3-bis(4-pyridyl)propane N,N′-dioxide (BiPyPNO) and the host 1 stabilize the unfavorable anti-gauche conformation. Contrary to the N,N′-dioxide guests, the mono-N-oxide guest, 4-phenylpyridine N-oxide (4PhPyNO), does not form an…
Grafting of polymer chains on the surface of carbon nanotubes via nitroxide radical coupling reaction
2016
Poly(butylene succinate)/MWCNTs nanocomposites with improved dispersion and with nanotubes embedded/immobilized into the polymer matrix were here prepared by an alternative "grafting to" method based on thenitroxide radical coupling reaction. Poly(butylene succinate) (PBS) was grafted on the surface of TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy) modified multi-walled carbon nanotubes (MWCNTs) via a nitroxide radical coupling reaction. TEMPO functionalized MWCNTs (MWCNTs-g-TEMPO) were synthesized using the Cu(I)-catalyzed azide/alkyne click chemistry approach and the covalent bond of the nitroxide moieties onto the MWCNTs was confirmed via electron paramagnetic resonance (EPR) spectroscopy.…
Synthesis of oxide-supported vanadium catalysts and their activity in ethylene polymerization
1999
The activity of oxide-supported vanadium-based catalyst systems (VOCl 3/Et 2AlCl) in low-pressure ethylene polymerization and the properties of the resulting polyethylenes were studied in relation to the type and mode of modification of the oxide support. Alumina, silica and an un"conventional silica-type material prepared by the sol-gel process were used as supports. Results are compared with those obtained earlier with a catalyst supported on MgCl 2(THF) 2. Of the oxides studied, the silica-type sol-gel material dehydrated and subsequently modified with Et 2AlCl proved to be the best carrier for a vanadium catalyst. The polyethylene prepared by using this catalyst support was found to exh…
Influence of different dehydration levels on volatile profiles, phenolic contents and skin hardness of alkaline pre-treated grapes cv Muscat of Alexa…
2020
A dehydration experiment was carried out on Vitis vinifera L. cv Muscat of Alexandria (synonym Zibibbo) following the process for the production of renowned special dessert wines produced on Pantelleria island (Sicily, Italy). Harvested berries were pre-treated in a sodium hydroxide dipping solution (45 g/L, dipped for 185 s, 25 °
Effect of Hot Dip Galvanized Steel Surface Chemistry and Morphology on Titanium Hexafluoride Pretreatment
2017
Titanium hexafluoride pretreatments are known to improve paint adhesion and function as a barrier between the coating and the hot dip galvanized (HDG) steel surface. Interactions at the zinc/pretreatment interface are of utmost importance for the formation of pretreatment layers and the corrosion resistance of color coated hot dip galvanized steels. Removal rate of inert aluminum oxide from HDG steel samples by chemical dissolution was studied. XPS measurements showed that the surface Al2O3 layer thickness decreased rapidly already at mild alkaline cleaning, while complete removal of Al required severe etching. Low reactivity of an Al2O3-rich surface was confirmed by impaired formation of a…
Modification of PVDF nanoparticles by controlled free radical graft copolymerization in supercritical carbon dioxide
2014
PVDF (polyvinylidenefluoride) membranes are widely used in microfiltration (MF) and ultrafiltration (UF) due to their excellent processability, chemical resistance, well-controlled porosity, and good thermal properties [1]. Moreover this polymer is also frequently adopted in bio-medical devices owing to its good biocompatibility [2]. On the other hand, the use of PVDF membranes in biomedical applications is limited to some extent by the hydrophobicity of their exposed area, which mainly arises from the nature of the pore surface. Prompted by these considerations in the present work we have studied the modification of PVDF nanoparticles with hydroxyethylmethacrylate (HEMA) thus obtaining a m…
The C–I･･･⁻O–N⁺ Halogen Bonds with Tetraiodoethylene and Aromatic N-oxides
2020
The nature of C–I⋯⁻O–N⁺ interactions, first of its kind, between non-fluorinated tetraiodoethylene XB-donor and pyridine N-oxides (PyNO) are studied by single-crystal X-ray diffraction (SCXRD) and Density Functional Theory (DFT) calculations. Despite the non-fluorinated nature of the C2I4, the I⋯O halogen bond distances are similar to well-known perfluorohaloalkane/-arene donor-PyNO analogues. With C2I4, oxygens of the N-oxides adopt exclusively 2-XB-coordination in contrast to the versatile bonding modes observed with perfluorinated XB-donors. The C2I4 as the XB donor forms with PyNO’s one-dimensional chain polymer structures in which the C2I4⋯(μ-PyNO)2⋯C2I4 segments manifesting two bondin…
Rayleigh-instability-driven dewetting of thin Au and Ag films on indium-tin-oxide surface under nanosecond laser irradiations
2013
Investigations have been carried out on laser-beam-induced nanoparticle (NP) formation in thin (5 nm) Au and Ag films on indium-tin-oxide substrate. After the irradiation the films were observed to break-up into NPs through a dewetting mechanism. This mechanism was investigated as a Rayleigh-instability- driven process. In fact, for each used laser fluence, the resulting Au and Ag NPs' mean size and surface-to-surface mean distance were quantified and correlated between them in the framework of the Rayleigh-instability theory showing an excellent agreement. © The Institution of Engineering and Technology 2013.
Physical inactivity increases oxidative stress, endothelial dysfunction, and atherosclerosis.
2005
Objective— Sedentary lifestyle is associated with increased cardiovascular events. The underlying molecular mechanisms are incompletely understood. Reactive oxygen species (ROS) contribute to endothelial dysfunction and atherosclerosis. An important source of vascular ROS is the NADPH oxidase. Methods and Results— C57BL6 mice were subjected to regular housing (physical inactivity) or voluntary training on running wheels (6 weeks). Inactivity increased vascular lipid peroxidation to 148±9% and upregulated superoxide release to 176±17% (L-012 chemiluminescence) and 188±29% (cytochrome C reduction assay), respectively. ROS production was predominantly increased in the endothelium and the medi…