Search results for "Diffusion"
showing 10 items of 1615 documents
Lèvy flights Superdiffusion: An Introduction
2008
After a short excursion from discovery of Brownian motion to the Richardson "law of four thirds" in turbulent diffusion, the article introduces the Lévy flight superdiffusion as a self-similar Lévy process. The condition of self-similarity converts the infinitely divisible characteristic function of the Lévy process into a stable characteristic function of the Lévy motion. The Lévy motion generalizes the Brownian motion on the base of the α-stable distributions theory and fractional order derivatives. The further development of the idea lies on the generalization of the Langevin equation with a non-Gaussian white noise source and the use of functional approach. This leads to the Kolmogorov'…
Pellets based on polyuronates: Relationship between gelation and release properties
2017
International audience; Three polyuronates: amidated low methoxyl pectin (ALMP), low methoxyl pectin (LMP) and polygalacturonic acid (PGA) were used to encapsulate rutin in pellets, and they were characterized by different techniques (macroscopic properties, Calcium and rutin release). The ability of the three polyuronates to bind calcium ions and the viscoelastic properties of gels were performed to relate the properties of the pellets to the gel structures. The pellets size, the water content, the water uptake, the release of calcium and rutin varied depending on the polyuronate used. The pellets size of ALMP were smaller than LMP and PGA with a lower water content, but this matrix was mo…
Transfers of small analytes in a multiphasic stirred fruit yoghurt model
2007
International audience; The transfer of small analytes in a multiphasic stirred fruit yoghurt model, made of a pectin gel aimed to mimic fruit pieces and of a dairy gel done with milk acidified by glucono-δ-lactone hydrolysis, have been studied. The concentration gradients between the pectin gel and the dairy gel were the driving force for the migration of small analytes (i.e. water, protons and colorants). Water migrated from the dairy to the pectin gel, causing modifications in the water content of both gels and an equilibration of their water activity at 0.938±0.003. Inversely, protons migrated from the pectin to the dairy gel. These changes in composition of both gels being likely to ha…
Theoretical space-time modelling of the diffusion of raw materials and manufactured objects
2013
International audience; Workgroup 3 of ArchaeDyn II programme focuses its study on the diffusion systems of ancient products. In order to be able to structure data in GIS in an appropriate way, we propose a general theoretical modelling integrating the different components of the diffusion systems, and identifying their interactions and the factors affecting the location of products and their transfers. Three dimensions are considered: the Time, the Space and the Function of places. A product's pathway can be apprehended efficiently by distinguishing spatial entities as well as functional entities. This modelling highlights the fact that the approach through the simple notion of "site" is n…
Decay estimates for time-fractional and other non-local in time subdiffusion equations in R^d
2016
We prove optimal estimates for the decay in time of solutions to a rather general class of non-local in time subdiffusion equations in R d . An important special case is the timefractional diffusion equation, which has seen much interest during the last years, mostly due to its applications in the modeling of anomalous diffusion processes. We follow three different approaches and techniques to study this particular case: (A) estimates based on the fundamental solution and Young’s inequality, (B) Fourier multiplier methods, and (C) the energy method. It turns out that the decay behaviour is markedly different from the heat equation case, in particular there occurs a critical dimension phenom…
The adsorption of water vapor on super absorbent product at low temperatures and low mass.
2006
The adsorption isotherms of water vapor on super absorbent product have the same form of type III isotherm at ambient temperature with the hysteresis phenomena. For temperatures lower than ambient, the isotherms become deformed because of the chains effect. The polymer is characterized by a multilayer adsorption, which occurs before a full-course is complete. During adsorption reactions, the polymer undergoes rearrangement polymeric network, which results from a cooperative diffusion of the water molecules and from a chain spacing followed by an expansion of the polymeric network. Three types of water molecules adsorbed on polymer were identified: strongly dependent water, adsorbed water, a…
Characterization of microscopic disorder in reconstructed porous materials and assessment of mass transport-relevant structural descriptors
2016
The targeted optimization of the functional properties of porous materials includes the understanding of their transport properties and thus requires knowledge about the relationship between material synthesis, resulting in three-dimensional material morphology, and relevant transport properties. In this Perspective, we present our views and results on the characterization of microscopic disorder in functional porous materials, which are widely used today as fixed beds in adsorption, separation, and catalysis. This allows us to identify structural parameters that impact their mass transport properties and eventually their overall performance in technological operations. We address this comp…
Advances in Fourier transform infrared spectroscopy of natural glasses: From sample preparation to data analysis
2014
Fourier transform infrared spectroscopy (FTIR) is an analytical technique utilized to measure the concentrations of H and C species in volcanic glasses. Water and CO2 are the most abundant volatile species in volcanic systems. Water is present in magmas in higher concentrations than CO2 and is also more soluble at lower pressures, and, therefore it is the dominant volatile forming bubbles during volcanic eruptions. Dissolved water affects both phase equilibria and melt physical properties such as density and viscosity, therefore, water is important for understanding magmatic processes. Additionally, quantitative measurements of different volatile species using FTIR can be achieved at high s…
Soil CO2 degassing on Mt Etna (Sicily) during the period 1989?1993: discrimination between climatic and volcanic influences
1995
Wide variations were measured in the diffuse CO2 flux through the soils in three selected areas of Mt Etna between August 1989 and March 1993. Degassing of CO2 from the area of Zafferana Etnea-S. Venerina, on the eastern slope of the volcano, has been determined to be more strongly influenced by meteorological parameters than the other areas. The seasonal component found in the data from this area has been excluded using a filtering algorithm based on the best fitting equation calculated from the correlation between CO2 flux values and those of air temperature. The filtered data appear to have variations temporally coincident with those from the other areas, thus suggesting a common and pro…
Tectonothermal Evolution of the Broadly Rifted Zone, Ethiopian Rift
2019
The Broadly Rifted Zone (BRZ) of southern Ethiopia is a long-lived and structurally complex segment of the East African Rift System. However, due to poor surface exposure of early synrift strata and a dearth of subsurface data, the evolution of the BRZ remains poorly understood. We present new apatite (U-Th-Sm)/He and augmented apatite fission track low-temperature thermochronology data from the Beto and Galana basin boundary fault systems to constrain the tectonothermal evolution of the western and eastern BRZ, respectively. Time-temperature reconstructions suggest that East African Rift System-related extension began concurrently across the BRZ in the early Miocene (20–17 Ma), at least 6 …