Search results for "swelling"
showing 10 items of 192 documents
An insight on the thermo-mechanical behaviour of a shale
2016
In recent years, several shale formations have been employed in geo-energy related engineering fields that foresee the presence of high thermal loads or significant temperature variations. Such thermal conditions are related to a need to reach great depths (several hundred of meters), as in the case of CO2 sequestration and Enhanced Geothermal System (EGS) technologies, or to the presence of thermal sources, as in the context of nuclear waste geological disposal. In addition, thermal changes can occur in shale formations through the injection of drilling and fracturing fluids at great depths, where a higher temperature with respect to the one of the injected fluid is encountered as a result…
Etude de la variabilité des propriétés physiques et hydrodynamiques d'un sol argileux sous l'effet de conduites en protection intégrée contre les adv…
2015
Integrated weed management (IWM)-based cropping systems are of great interest due to their significant reduction of herbicide inputs by using a complex combination of agricultural techniques. The main objective of our work was to contribute to the environmental dimension of the multi-criteria evaluation of IWM-based cropping systems which were set up since 2000 on the experimental domain of the National Institute for Agronomical Research (INRA) to Bretenière (France). The variability of physical and hydrodynamic soil properties involved in the transfer of water through the vadose zone was studied for the 5 cropping systems present on the experimental site (1 reference cropping system and 4 …
Photocrosslinking of dextran and polyaspartamide derivatives: a combination suitable for colon-specific drug delivery.
2007
Abstract The aim of this study was to prepare and characterize novel hydrogels with polysaccharide–polyaminoacid structure, able to undergo an enzymatic hydrolysis in the colon and potentially useful for treating inflammatory bowel diseases (IBD). Starting materials were methacrylated dextran (DEX-MA) and methacrylated α,β-poly(N-2-hydroxyethyl)- dl -aspartamide (PHM). These polymers were photocrosslinked by exposure of their aqueous solutions at 313 nm without photoinitiators. Different samples, shaped as microparticles, were obtained as a function of polymer concentration and irradiation time. FT-IR analysis confirmed the occurrence of a co-crosslinking between DEX-MA and PHM in all exper…
Spreading Depression Induces Permanent Cell Swelling Under Penumbra Conditions
2000
Background. Spreading depression (SD) is known to go along with temporary breakdown of ion gradients and cell swelling which spontaneously normalizes. Here, the effects of SD at reduced flow conditions as encountered in the ischemic penumbra are examined.
Reversible swelling of polyanion/polycation multilayer films in solutions of different ionic strength
1996
Immersion of consecutively adsorbed polyanion/polycation multilayer films in solutions of different ionic strength causes reversible thickness changes. Swelling of the films up to 18% was observed after soaking the films in aqueous solutions of NaCl at concentrations up to 1.0 mol/l. X-ray reflectivity clearly shows that the thickness changes are reversible within experimental error and that the films seem to get smoother after several cycles of immersion in salt solutions and in pure water. The extent of swelling depends on the internal film structure, namely on the number of polyanion/polycation interfaces in a film of a given thickness. Interestingly, the swelling levels off at salt conc…
Salt partitioning in ionized, thermo-responsive hydrogels: perspective to water desalination
2021
Charged hydrogels are capable of swelling in aqueous salt solutions, whereby part of the salt ions is repelled due to the presence of fixed charged groups inside the hydrogel. This effect creates a concentration gradient between the absorbed solution and the surrounding fluid known as salt partitioning, offering a potential for these materials to be employed to desalinate saltwater. If the charged hydrogels are thermo-sensitive as well, then the purer, absorbed solution can be recovered by shrinking the hydrogels upon temperature change. To tailor that potential in water-purification and desalination applications, the main parameters influencing the salt partitioning, the deswelling of the …
The Swelling Behavior of Polyelectrolyte Multilayers in Air of Different Relative Humidity and in Water
2002
The swelling properties of physisorbed polyelectrolyte multilayer self-assemblies with alternating polyion charge in humid air and in aqueous environment were investigated via X-ray and neutron reflectometry as well as optically, using surface plasmon spectroscopy. The sorption behavior was similar to that found for neutral polymers and was related to an internal screening of the charges of the adjacent layers owing to the high entanglement of the polyelectrolyte chains and the resulting low mobility of the polymer segments. The screening was found to be incomplete only in the top layer, resulting in a net charged surface.
Influence of Thermal Annealing on the Thermodynamic and Mass-Transfer Kinetic Properties of d- and l-Phenylalanine Anilide on Imprinted Polymeric Sta…
1999
An investigation of the material, chromatographic, thermodynamic, and kinetic properties of thermally treated (i.e., annealed) polymeric stationary phases imprinted with l-phenylalanine anilide (l-PA) was carried out. The imprinting procedure of the solid phase used in this study was the same as for the untreated imprinted stationary phase studied previously. However, after polymerization, these new stationary phases were treated at elevated temperatures (50, 120, 140, and 160 °C) for 24 h. The treatment at 120 and 140 °C led to a larger decrease in the retention of l-PA than that of d-PA. The polymer treated at 160 °C could no longer resolve the d,l-PA racemate. The heat treatments were ac…
A Novel Gas Chromatographic Method to Measure Sorption of Dense Gases into Polymers
2006
A novel experimental approach to determine the solubility of gaseous compounds inside polymers is here described. The method is based on the gas chromatographic determination of the composition of the fluid phase at equilibrium with the polymer. To take into account the effect of the volume swelling on the measurement a suitable probe, nonabsorbable by the polymer, was added to the fluid phase. Under the adopted configuration the apparatus can operate up to 35 MPa and 80°C. This experimental technique has been used to determine the solubility of carbon dioxide in poly(vinylidene fluoride) using argon as a probe. The latter was chosen because it is negligibly absorbed by the polymer and does…
Radiation synthesis of polyaspartamide functionalised hydrogels for sustained release of fragrances
2005
The aim of the present investigation is to assess the possibility of obtaining a biocompatible material device which is able to deliver oil-soluble fragrances in air over a length of time. Aqueous solutions of polyaspartamide functionalised with glycidyl methacrylate have been cross linked through gamma irradiation in the presence of a lipophilic model fragrance, emulsified prior to irradiation. Two emulsification conditions have been considered at two different concentrations of both fragrance and surfactant in water. Chemical hydrogels have been obtained in correspondence to two irradiation absorbed doses and have been characterised for their solubility properties and swelling ability in …