Search results for " alcohol"
showing 10 items of 578 documents
Manganese(iv) oxamato-catalyzed oxidation of secondary alcohols to ketones by dioxygen and pivalaldehyde
1998
A new manganese(IV) oxamato complex possessing a bis(moxo) dimanganese core has been synthesized, magnetically and structurally characterized, and found to catalyze the aerobic oxidation of secondary alcohols to ketones with cooxidation of pivalaldehyde to pivalic acid with good yields and high selectivities. Ruiz Garcia, Rafael, Rafael.Ruiz@uv.es ; Fernandez Picot, Isabel, Isabel.Fernandez@uv.es ; Pedro Llinares, Jose Ramon, Jose.R.Pedro@uv.es ; Rosello Arce, Antonio Luis, Antonio.L.Rosello@uv.es ; Castro Bleda, Isabel, Isabel.Castro@uv.es
Xyloglucan-based hydrogel films for wound dressing: Structure-property relationships
2017
Thin xyloglucan-based hydrogel films have been synthetized and characterized in the prospect of producing wound dressings. Polyvinyl alcohol (PVA) and glycerol (Gro) were added to have an optimal combination of softness, conformability and resilience. Physical hydrogels have been transformed into permanent covalent hydrogels by reaction with glutaraldehyde (GA). Network structure-process-property relationships are discussed on the account of the results of several complementary characterizations: FTIR, rheology, thermal analysis, morphological analysis, moisture retention and swelling measurements. Selected formulations were also subjected to preliminary in vitro cytotoxicity tests. The phy…
Influence of different parameters on drug release from hydrogel systems to a biomembrane model. Evaluation by differential scanning calorimetry techn…
2000
A comparative study on the drug release capacity of four water swellable polymeric systems was carried out by differential scanning calorimetry (DSC). The polymeric systems chosen were alpha,beta-polyaspartahydrazide (PAHy) crosslinked by glutaraldehyde (GLU) (PAHy-GLU) or by ethyleneglycoldiglycidylether (EGDGE), (PAHy-EGDGE), polyvinylalcohol (PVA) crosslinked by glutaraldehyde (PVA-GLU) and alpha,beta-poly(N-hydroxyethyl)-DL-aspartamide (PHEA) by gamma irradiation (PHEA-gamma matrices). The degree of crosslinking for PAHy-GLU, PAHy-EGDGE and PVA-GLU samples was about 0.4 and 0.8. These hydrogels were characterized as free of drugs and were loaded with diflunisal (DFN) (approximately 2.5%…
Development and evaluation of occlusive systems employing polyvinyl alcohol for transdermal delivery of sumatriptan succinate
2010
The aim of the present study was to develop a sumatriptan succinate transdermal system for applying migraine treatments efficiently and easily. For this system polyvinyl alcohol was employed as a matrix and Azone((R)) was added as a permeability enhancer. The physical characteristics, mechanical properties, and in vivo bioadhesion of the systems were evaluated, as was in vitro permeation across porcine skin. A uniform distribution of the drug in the matrix was observed, and moisture uptake values were constant. With regard to mechanical parameters, occlusive layer inclusion made the system more resistant, and no significant differences were detected with respect to other systems. Although A…
Novel GTA-PVA Fricke gels for three-dimensional dose mapping in radiotherapy
2017
Abstract One of the most recent and promising developments in radiotherapy dosimetry was the introduction of 3D radiation-sensitive gels. These gels present tissue equivalent composition and density, so they also serve as phantoms, and their response is largely independent of radiation quality and dose rate. Some gels are infused with ferrous sulfate and rely on the radiation-induced oxidation of ferrous ions to ferric ions (Fricke-gels). These formulations suffer from spontaneous-oxidation and diffusion of ferric ions after irradiation; chelating agents such as xylenol-orange significantly reduces the latter. Other gel types consist of dispersed monomers, and rely on radiation-induced cros…
Spray-Drying, Solvent-Casting and Freeze-Drying Techniques: a Comparative Study on their Suitability for the Enhancement of Drug Dissolution Rates.
2019
Purpose Solid dispersions (SDs) represent the most common formulation technique used to increase the dissolution rate of a drug. In this work, the three most common methods used to prepare SDs, namely spray-drying, solvent-casting and freezedrying, have been compared in order to investigate their effect on increasing drug dissolution rate. Methods Three formulation strategies were used to prepare a polymer mixture of polyvinyl-alcohol (PVA) and maltodextrin (MDX) as SDs loaded with the following three model drugs, all of which possess a poor solubility: Olanzapine, Dexamethasone, and Triamcinolone acetonide. The SDs obtained were analysed and compared in terms of drug particle size, drug-lo…
Structure and the metal-support interaction of the Au/Mn oxide catalysts
2010
Gold catalysts with loading 1 and 10 wt % were-prepared by deposition precipitation method with urea over mesoporous manganese oxide, obtained through a surfactant-assisted procedure by using cetyltrimethylammonium bromide (CTAB), followed by treatment with sulphuric acid. For comparison, Au(10 wt %) was also deposited over commercial CeO2 and SiO2 supports. The materials were characterized by XRD and EXAFS at the Mn K and Au L-III edges and XPS. Moreover, the analyses were performed on the samples treated under 1%CO/He, at 250 degrees C for 90 min. The structural and surface results of the as prepared manganese oxide confirmed the formation of gamma-MnO2 along with some amorphous Mn3O4 upo…
Thalassiosira pseudonana diatom as biotemplate to produce a macroporous ordered carbon-rich material
2008
Abstract Ordered macroporous–mesoporous carbonaceous materials were produced as a direct replica of the Thalassiosira pseudonana diatom by infiltration of the skeleton with furfuryl alcohol. The final carbon-rich material preserves the macropores of the diatom acting as bio-template and new hierarchical macro–mesopores appears as the silica is eliminated through chemical etching. The final solid can be described as an organized array of carbon macrotubes. In order to understand the progressive silica etching and the subsequent effect on the final carbon material, different etching reagents have been used. Moreover, the similar pore topology of T. pseudonana and the well known MCM-41 mesopor…
Experimental and theoretical investigations of lignin-urea-formaldehyde wood adhesive: Density functional theory analysis
2021
Abstract In view of its chemical structure, lignin has recently become an interesting candidate for various applications. This work serves to optimize the isolation process of lignin from sugar industry by-product (bagasse can, molasses beet) applying alkali treatment. For this purpose, the effect of alkali and sulfuric acid concentrations have been studied ranging from 10% (w/v) to 20% (w/v) and 1.5 M–3 M, respectively. Moreover, the isolated lignins were characterized by different complementary analysis such as FT-IR and TGA/DTG. The aim behind this work is to reduce formaldehyde emissions and improving mechanical as well as physical properties of wood adhesive. Lignin was added with diff…
Self assembled hydrophobic nanoclusters of poly(methyl methacrylate) embedded into polyvinyl alcohol based hydrophilic matrix: Preparation and water …
2009
Hydrophilic matrices containing nanosized clusters of hydrophilic moieties have demonstrated potential applications in biomedical field. A novel hydrogel containing nanosized domains (20–35 nm) of hydrophobic moieties of poly(methyl methacrylate) (PMMA) was prepared by grafting crosslinked poly(acrylic acid-co-methyl methacrylate) chains onto polyvinyl alcohol (PVA) backbone using an efficient redox system. The graft copolymerization process was investigated to observe the influence of gel components on the kinetic parameters of grafting such as rate of grafting (Rg), grafting yield (Gy) and grafting efficiency (Ge). The prepared graft nanohydrogel was evaluated for its water sorption poten…