Search results for "solution"

Mesoscopic and Microscopic Investigation on Poly(vinyl alcohol) Hydrogels in the Presence of Sodium Decylsulfate

2007

The structure of poly(vinyl alcohol) (PVA) hydrogels formed as a result of freeze/thaw treatments of aqueous solutions of the polymer (11 wt % PVA) in the freshly prepared state is analyzed through the combined use of small (SANS) and ultrasmall (USANS) angle neutron scattering techniques. The structure of these hydrogels may be described in terms of polymer rich regions, with dimensions of the order of 1-2 microm, dispersed in a water rich phase, forming two bicontinuous phases. The PVA chains in the polymer rich phase form a network where the cross-linking points are mainly crystalline aggregates of PVA having average dimensions of approximately 45 A. The structural organization of freeze…

E-beam crosslinked, biocompatible functional hydrogels incorporating polyaniline nanoparticles

2012

Abstract PANI aqueous nanocolloids in their acid-doped, inherently conductive form were synthesised by means of suitable water soluble polymers used as stabilisers. In particular, poly(vinyl alcohol) (PVA) or chitosan (CT) was used to stabilise PANI nanoparticles, thus preventing PANI precipitation during synthesis and upon storage. Subsequently, e-beam irradiation of the PANI dispersions has been performed with a 12 MeV Linac accelerator. PVA-PANI nanocolloid has been transformed into a PVA-PANI hydrogel nanocomposite by radiation induced crosslinking of PVA. CT-PANI nanoparticles dispersion, in turn, was added to PVA to obtain wall-to-wall gels, as chitosan mainly undergoes chain scission…

1993

In a new theoretical approach the separation of a pair of chain molecules (measured thermodynamically by the second osmotic virial coefficient A2) is treated as a two-step process: In the first step the molecules are detached from each other by the addition of solvent—keeping their dimensions constant—and in the second step the now isolated coils are allowed to relax into their equilibrium dimensions. For the description of the second step, in which only segments belonging to one molecule take part, an intra-molecular interaction parameter is introduced on the basis of the intrinsic viscosity. The present two-parameter approach yields A2 = A + σ M−(1−a) for the dependence of A2 on the molec…

A Viscosity Equation for Minimizers of a Class of Very Degenerate Elliptic Functionals

2013

We consider the functional $$J(v) = \int_\varOmega\bigl[f\bigl(|\nabla v|\bigr) - v\bigr] dx, $$ where Ω is a bounded domain and f:[0,+∞)→ℝ is a convex function vanishing for s∈[0,σ], with σ>0. We prove that a minimizer u of J satisfies an equation of the form $$\min\bigl(F\bigl(\nabla u, D^2 u\bigr), |\nabla u|-\sigma\bigr)=0 $$ in the viscosity sense.

Microgels of polyaspartamide and poly(ethylene glycol) derivatives obtained by γ-irradiation

2002

Abstract The copolymer PHG based on α , β -poly( N -2-hydroxyethyl)- dl -aspartamide (PHEA) functionalized with glycidyl methacrylate has been exposed in aqueous solution to a γ -ray source at different irradiation doses (2, 2.5 and 3.5 kGy), alone or in combination with poly(ethylene glycol)dimethacrylate (PEGDMA) or poly(ethylene glycol)diacrylate (PEGDA). The irradiation produces microgel systems that have been characterized by viscosity measurements. Lyophilization of microgels gives rise to samples able to swell instantaneously in water whereas their treatment with acetone produces swellable microparticles that have been characterized.

Effect of TiO2 on the mullite formation and mechanical properties of alumina porcelain

2010

Abstract The effect of adding TiO 2 to standard alumina porcelain on its microstructure and flexural strength was investigated. A series of alumina porcelain bodies containing increasing amounts of TiO 2 were prepared by extruding mixtures of raw materials and TiO 2 . Porcelain rods were fired under industrial scheduling in a manufacturing kiln. The overall degree of crystalline and amorphous phase content within the porcelain bodies was quantitatively determined using a Rietveld analysis. Results indicated a higher amount of mullite formation in porcelain bodies containing TiO 2 . Examination of the product materials using field emission scanning electron microscopy showed a high density o…

Die viskosität von polymerlösungen in der nähe von oberen und unteren entmischungstemperaturen

1977

Die Viskositat flussiger Mischungen zeigt in der Nahe des kritischen Entmischungspunktes eine charakteristische Temperaturabhangigkeit. fur Polymerlosungen ist diese Erscheinung bei der oberen kritischen Entmischungstemperatur gut untersucht, wahrend in der Umgebung der unteren kritischen Entmischungstemperatur keine derartigen Messungen vorliegen. ES wurden Viskositatsmessungen im System Cyclohexan/Polystyrol (obere kritische Entmischungstemperatur) und im System Orthotrimethylformiat/Diathylather/Polystyrol (untere kritische Entmischungstemperatur) durchgefuhrt. Beim ersten System ergab sich qualitative Ubereinstimmung mit den Ergebnissen von Debye und Mitarbeitern. Die Untersuchungen in …

LST retrieval algorithm adapted to the Amazon evergreen forests using MODIS data

2018

Abstract Amazonian tropical forests play a significant role in global water, carbon and energy cycles. Considering the importance of this biome and climate change projections, the monitoring of vegetation status of these rainforests becomes of significant importance. In this context vegetation temperature is presented as a key variable linked with plant physiology. In particular some studies showed the relationship between this variable and the CO2 absorption capacity and biomass loss of these tropical forests proving the potential use of vegetation temperature in the monitoring of the vegetation status. Nevertheless, the use of thermal remote sensing data over tropical forests still has so…

Picosecond absorption spectroscopy: Methods and applications in photophysical and photochemical systems

1985

EDGE: explorer of diffuse emission and gamma-ray burst explosions

2009

How structures on various scales formed and evolved from the early Universe up to present time is a fundamental question of astrophysical cosmology. EDGE will trace the cosmic history of the baryons from the early generations of massive star by Gamma-Ray Burst (GRB) explosions, through the period of cluster formation, down to very low redshifts, when between a third and one half of the baryons are expected to reside in cosmic filaments undergoing gravitational collapse by dark matter (Warm Hot Intragalactic Medium: WHIM). In addition EDGE, with its unprecedented observational capabilities, will provide key results on several other topics. The science is feasible with a medium class mission …