Structural analysis by diffusion

Structural Analysis by Diffusion Measurements SBS Block Copolymers and Polyethylene... 

Inherent structure analysis of diffusion via molecular dynamics of a deeply supercooled binary Lennard-Jones fluid have provided renewed impetus to the decisive role played by thermodynamic factors [52,53]. The location of the mode crossover temperature and the onset of super-Arrhenius behavior were related to the static structure of the liquid via the potential energy hypersurface [52,53],... 

Nicholson C, Sykova E (1998) Extracellular space structure revealed by diffusion analysis. Trends Neurosci 21 207-215... 

FIG. 23 Comparison of various one-parameter diffusion models. (Reproduced with permission from Ref. 448, Analysis of Diffusion and Structure in Polyacrylamide Gels by Nuclear Magnetic Resonance, M.S. Thesis, Florida State University, Copyright 1997, Brigita Penke.)... 

The diffusion of an impurity atom in a crystal, say K in NaCl, involves other considerations that influence diffusion. In such cases, the probability that the impurity will exchange with the vacancy will depend on factors such as the relative sizes of the impurity compared to the host atoms. In the case of ionic movement, the charge on the diffusing species will also play a part. These factors can also be included in a random-walk analysis by including jump probabilities of the host and impurity atoms and vacancies, all of which are likely to vary from one impurity to another and from one crystal structure to another. All of these alterations can be... 

The solids analysis described above can be taken to yet another level by correlating the color measurement to chemical properties. An excellent model system is vanadium pyrophosphate (VPO), which is a well-known catalyst for butane oxidation to maleic anhydride. During the synthesis of the catalyst precursor, solid V2O5 particles are dispersed in a mixture of benzyl alcohol and i-butanol. In this slurry phase, the vanadium is partly reduced. Addition of phosphoric acid leads to a further reduction and the formation of the VPO structure. With a diffuse reflectance (DR) UV-vis probe by Fiberguide Ind., the surface of the suspended solid particles could be monitored during this slurry reaction. Four points can be noted from Figure 4.4 ... 

Chapter 5- The coordination polymer [Zn(tmbdc)(dmso)2]-2(DMSO) (tmbdc = 2,3,5,6-tetramethyl-l,4-benzenedicarboxylate) has been synthesized by layer diffusion in DMSO (dimethyl sulfoxide) solution. The compound contains ID chain formed by octahedraly coordinated Zn ion chelated by the carboxyl groups of tmbdc. In another recently reported coordination polymer [Zn2(bdc)2(dmso)2]-5(DMSO) (bdc = 1,4-benzenedicarboxylate) prepared under the same condition, pairs of Zn ions are bridged by four carboxyl groups to form paddle-wheel sub unit and the 2D (4,4) net structure. Analysis of the structures reveals that the substituents of the ligands determine the coordination environments of zinc ions and the coordination modes of the carboxyls, and thus the final structures of the coordination polymers. 

The total acidity deterioration and the acidity strength distribution of a catalyst prepared from a H-ZSM-5 zeolite has been studied in the MTG process carried out in catalytic chamber and in an isothermal fixed bed integral reactor. The acidity deterioration has been related to coke deposition. The evolution of the acidic structure and of coke deposition has been analysed in situ, by diffuse reflectance FTIR in a catalytic chamber. The effect of operating conditions (time on stream and temperature) on acidity deterioration, coke deposition and coke nature has been studied from experiments in a fixed integral reactor. The technique for studying acidity yields a reproducible measurement of total acidity and acidity strength distribution of the catalyst deactivated by coke. The NH3 adsorption-desorption is measured by combination of scanning differential calorimetry and the FTIR analysis of the products desorbed. 

As had been observed with some 7-butyrolactones and antibiotic substances, it appeared likely that the above interspecific stimulation events are mediated by some diffusible metabolites produced by stimulator strains. To study the details of the interspecific stimulation events, Yamanaka et al80 isolated the activity principle that stimulated growth and development of Streptomyces tanashiensis from culture supernatant of S. griseus. As a result of structural analysis of the purified preparation, the substance was determined to be desferrioxamine E (synonym, nocardamine Figure 7). 

Schultz TP, Glasser WG (1986) Quantitative structural analysis of lignin by diffuse reflectance Fourier transform infrared spectromety Holzforschung 40 (Suppl) 37-44 Schultz TP, Nicholas DD (1987) Fourier transform infrared spectrometry Detection of incipient brown rot decay in wood Int Analyst 41 35-39 Sjostrom M, Wold, S, Lindberg W, Persson J-A, Martens H (1983) A multivariate calibration problem in analytical chemistry solved by partial least-squares models in latent variables Anal Chim Acta 150 61-70... 

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