Search results for "2506"
showing 10 items of 112 documents
Behavior of alloying elements during anodizing of Mg-Cu and Mg-W alloys in a fluoride/glycerol electrolyte
2015
Anodizing of sputtering-deposited magnesium and Mg-0.75at.%Cu and Mg-1.23at.%W alloys has been carried out in a fluoride/ glycerol electrolyte. The aims of the study were to investigate the enrichment of alloying elements in the alloy immediately beneath the anodic film and the migration of alloying element species in the film. The specimens were examined by electron microscopy and ion beam analysis. An enrichment of copper is revealed in the Mg-Cu alloy that increases with the anodizing time up to ∼6×1015 Cu atoms cm-2. Copper species are then incorporated into the anodic film and migrate outwards. In contrast, no enrichment of tungsten occurs in the Mg-W alloy, and tungsten species are im…
Coagulation bath composition and desiccation environment as tuning parameters to prepare skinless membranes via diffusion induced phase separation
2015
Diffusion Induced Phase Separation (DIPS) is a currently used technique to produce porous membranes for a large variety of applications. A strong limitation is represented by the occurrence of a dense skin, which is formed during the process, highly reducing the membrane permeability. To overcome this issue, two modifications of the standard DIPS protocol were investigated: the use of coagulation baths composed by a solvent/nonsolvent mixture and the desiccation in a controlled environment, by modulating the partial pressure of nonsolvent vapor. An appropriate choice of coagulation bath composition, together with an appropriate desiccation protocol (i.e., the use of a nonsolvent vapor), wil…
Temperature-induced self-assembly of degalactosylated xyloglucan at low concentration
2015
Xyloglucan is a natural polysaccharide having a cellulose-like backbone and hydroxyl groups-rich side-chains. In its native form the polymer is water-soluble and forms gel only in presence of selected co-solutes. When a given fraction of galactosyl residues are removed by enzymatic reaction, the polymer acquires the ability to form a gel in aqueous solution at physiological temperatures, a property of great interest for biomedical/pharmaceutical applications. This work presents data on the effect of a temperature increase on degalactosylated xyloglucan dispersed in water at concentration low enough not to run into macroscopic gelation. Results obtained over a wide interval of length scales …
Influence of Drawing on the Antimicrobial and Physical Properties of Chlorhexidine-Compounded Poly(caprolactone) Monofilaments
2015
In this work, we prepared poly(caprolactone) (PCL) monofilaments incorporating different amounts of the antiseptic chlorhexidine diacetate (CHX) and evaluated the effect of "online" drawing during the melt spinning or of an "offline" cold drawing on the antimicrobial and physical properties of PCL/CHX monofilaments. The results showed that the drawing conditions strongly affected the properties of the threads. In particular, the filaments exhibited antimicrobial activity for all the draw ratios (DR) adopted, but on increasing DR the antibacterial efficiency reduced. These results were correlated with the CHX surface concentration and with the release kinetics.
Circular Dichroism of DNA G-Quadruplexes: Combining Modeling and Spectroscopy To Unravel Complex Structures
2016
We report on the comparison between the computational and experimental determination of electronic circular dichroism spectra of different guanine quadruplexes obtained from human telomeric sequences. In particular the difference between parallel, antiparallel, and hybrid structures is evidenced, as well as the induction of transitions between the polymorphs depending on the solution environment. Extensive molecular dynamics simulations (MD) are used to probe the conformational space of the different quadruplexes, and subsequently state-of-the-art hybrid quantum mechanics/molecular mechanics (QM/MM) techniques coupled with excitonic semiempirical Hamiltonian are used to simulate the macromo…
Halogen bonding stabilizes a cis-azobenzene derivative in the solid state : A crystallographic study
2017
Crystals oftrans- andcis-isomers of a fluorinated azobenzene derivative have been prepared and characterized by single-crystal X-ray diffraction. The presence of F atoms on the aromatic core of the azobenzene increases the lifetime of the metastablecis-isomer, allowing single crystals of thecis-azobenzene to be grown. Structural analysis on thecis-azobenzene, complemented with density functional theory calculations, highlights the active role of the halogen-bond contact (N...I synthon) in promoting the stabilization of thecis-isomer. The presence of a long aliphatic chain on the azobenzene unit induces a phase segregation that stabilizes the molecular arrangement for both thetrans- andcis-i…
Characterization and properties of PEO coatings on 7075 Al alloy grown in alkaline silicate electrolyte containing KMnO 4 additive
2017
Abstract Plasma electrolytic oxidation (PEO) was used to modify the surface of 7075 Al alloy by applying a bipolar pulsed-current in a silicate based electrolyte containing 0 to 3 g L− 1 KMnO4. For the coating produced in the base electrolyte, crystalline γ-Al2O3 was the main phase, while the coatings formed at the presence of KMnO4 consisted of α-Mn2O3 containing Si and Al oxides. A pancake structure was observed on surface of the coating produced in the base electrolyte, while a foam feature along with some volcano-like areas was detected on the surface of the coatings produced in the presence of KMnO4. The KMnO4 changed the discharge type leading to diminish the pores at the metal/coatin…
The Amorphous Semiconductor Schottky Barrier Approach to Study the Electronic Properties of Anodic Films on Ti
2017
A detailed study of the electronic properties of thin (>20 nm) anodic TiO2 potentiostatically grown on titanium in two different solutions is presented. The results show that the nature of the anodizing solution affects the electronic properties of the anodic film and, more specifically, the density of electronic states (DOS) distribution. Different DOS were derived from the experimental data analyzed according to the theory of amorphous semiconductor (a-SC) Schottky barrier. It is shown that the usual non-linear and frequency dependent Mott-Schottky plots are in agreement with expected theoretical behavior of a-SC Schottky barrier.
Pluronic nanoparticles as anti-oxidant carriers for polymers
2016
Abstract The immobilization of anti-oxidant stabilizers for polymers, particularly naturally occurring systems, can be considered a valuable route for preventing their migration, volatilization, thermo-degradation and decomposition at typical high processing temperatures, as well as for enhance their solubility in polymers. In this work, an innovative approach for the immobilization of naturally occurring stabilizer, through the encapsulation in copolymer nanoparticles, is proposed. Pluronic nanoparticles (PNPs), based on PEO-PPO-PEO, (PEO: poly (ethylene oxide); PPO: poly(propylene oxide)), without and with quercetin, Q, have been successfully formulated and the critical micellar condition…
Polymeric micelles as a new generation of anti-oxidant carriers
2017
A promising strategy to immobilize a natural stabilizer in polymeric films is presented. Par-Ticularly, nevadensin (N, a natural basil flavonoid) molecules have been encapsulated in Pluronic F-127 micelles [F127, a triblock copolymer poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide)] and the obtained nanoparticles have been introduced in poly(ethylene glycol), PEG [otherwise known as poly(ethylene oxide), PEO]. In order to verify the effectiveness of the micelles as anti-oxidant carriers, PEG-based films have been subjected to artificial weathering. The encapsulation of anti-oxidant molecules allows the enhancement of N solubility in PEG, leading to advanced materials with enh…