ATR-FTIR spectroscopic studies of the structure and permeability of sulfonated poly(ether sulfone) membranes. Part 2.—Water diffusion processes

1996 ◽  
Vol 92 (15) ◽  
pp. 2737-2743 ◽  
Author(s):  
Márcia R. Pereira ◽  
Jack Yarwood
Keyword(s):  
Diffusion Processes ◽  
Spectroscopic Studies ◽  
Water Diffusion ◽  
Sulfonated Poly

Controlled release of a highly hydrophilic API from lipid microspheres obtained by prilling: Analysis of drug and water diffusion processes with X-ray-based methods

2012 ◽  
Vol 158 (3) ◽  
pp. 393-402 ◽  
Author(s):  
Perrine Pivette ◽  
Vincent Faivre ◽  
Lucia Mancini ◽  
Claire Gueutin ◽  
Georges Daste ◽  
...  
Keyword(s):  
Controlled Release ◽  
Diffusion Processes ◽  
Water Diffusion ◽  
X Ray

Spectroscopic Studies of Liquid Structure and Solvation

2004 ◽  
Author(s):  
W. Ronald Fawcett
Keyword(s):  
Electromagnetic Radiation ◽  
Diffusion Processes ◽  
Rotational Diffusion ◽  
Relaxation Times ◽  
Liquid Structure ◽  
Spectroscopic Studies ◽  
Distribution Functions ◽  
Spectroscopic Techniques ◽  
Complex Ions ◽  
Structure Of Solutions

Spectroscopy involves the study of the interactions of electromagnetic radiation with matter. In the case of liquids, radiation of a wide range of frequencies, and thus energies, has been used, all the way from radio-frequency waves to X-rays. Experiments involving neutrons, which are associated with very short wavelengths, are also important. In the spectroscopic experiment the incident radiation may be either absorbed or scattered and the experimental information is obtained by examining the intensity and direction of the radiation after it has passed through the sample. Several spectroscopic techniques will be considered in this chapter. X-ray and neutron diffraction techniques are powerful tools for studying the structure of liquids and have been introduced in chapter 2. They may also be used to study the structure of solutions and determine distribution functions for both the solute and solvent. The feasibility of these experiments depends on the number of different nuclei involved in the system. UV-visible spectroscopy is mainly used to study electronic transitions in polyatomic species. These species are often complex ions formed between the electrolyte and the solvent, or between the cation and one or more anions. Vibrational spectroscopy involves electromagnetic radiation of lower energy, usually in the infrared region. It is used to study intramolecular vibrational modes and how they are altered by the environment in solution. It can also be used to study the bonds formed between solute and solvent in the solvation process. Finally, nuclear magnetic resonance spectroscopy and its application to the study of solvation will be discussed. This is a particularly powerful technique because it provides information about the environment of a given nucleus, and experiments specific to a given nucleus can be carried out provided the nucleus has a non-zero magnetic moment. Several other spectroscopic techniques are commonly used [G1] but those considered here provide a representative picture of what can be learnt from those experiments. One should remember that the atoms and molecules in liquids are not motionless but in a state of flux determined by the intermolecular interactions and temperature. From the study of microwave spectroscopy discussed in chapter 4, it was found that rotational diffusion processes in liquids are characterized by relaxation times the order of a few picoseconds.

Meridional Circulation, Turbulence, and Diffusion Processes in Stars

1976 ◽  
Vol 32 ◽  
pp. 109-116 ◽  
Author(s):  
S. Vauclair
Keyword(s):  
Convection Zone ◽  
Diffusion Processes ◽  
Meridional Circulation ◽  
Diffusion Time ◽  
Work In Progress ◽  
First Results ◽  
Stellar Envelopes ◽  
And Diffusion ◽  
Turbulence And Diffusion ◽  
Hr Diagram

This paper gives the first results of a work in progress, in collaboration with G. Michaud and G. Vauclair. It is a first attempt to compute the effects of meridional circulation and turbulence on diffusion processes in stellar envelopes. Computations have been made for a 2 Mʘstar, which lies in the Am - δ Scuti region of the HR diagram.Let us recall that in Am stars diffusion cannot occur between the two outer convection zones, contrary to what was assumed by Watson (1970, 1971) and Smith (1971), since they are linked by overshooting (Latour, 1972; Toomre et al., 1975). But diffusion may occur at the bottom of the second convection zone. According to Vauclair et al. (1974), the second convection zone, due to He II ionization, disappears after a time equal to the helium diffusion time, and then diffusion may happen at the bottom of the first convection zone, so that the arguments by Watson and Smith are preserved.

Ergodic Control of Diffusion Processes

2009 ◽  
Author(s):  
Ari Arapostathis ◽  
Vivek S. Borkar ◽  
Mrinal K. Ghosh
Keyword(s):  
Diffusion Processes ◽  
Ergodic Control

Spectroscopic studies of Pd (II) complexes with cysteine and its di- and tripeptides

1987 ◽  
Vol 84 ◽  
pp. 443-448 ◽  
Author(s):  
Teresa Kowalik ◽  
Brigitte Decock-Le Reverend ◽  
Claude Loucheux ◽  
Damien Ficheux ◽  
Henryk Kozlowski
Keyword(s):  
Spectroscopic Studies
Sign in / Sign up

Export Citation Format

Share Document