Dynamic Characterisation Techniques

The desirability of using a non-invasive in-situ probe has already been discussed. There is, however, a problem, in that standard characterisation techniques are unable to penetrate bulky reaction vessels. As a result of this, little is known about the reaction dynamics or kinetics of intercalation reactions. A non-invasive probe which can interrogate a typical intercalation process is required. It is also necessary to employ short data collection times in order that kinetic information may be obtained. X-ray powder diffraction is a highly appropriate tool. It is non-invasive, and is a powerful characterisation technique when used in combination with ex-situ analyses. 

Structural studies of biomaterials using double quantum solid state NMR have been reviewed by Drobny et al. Both the theory and practice of doublequantum solid state NMR techniques for determining the secondary structures of surface-adsorbed peptides and proteins are presented. In particular, the use of solid state NMR dipolar techniques to provide the high-resolution structural and dynamic characterisation of a hydrated biomineralisation protein, salivary statherin, adsorbed to its biologically relevant hydroxyapatite surface is presented. This article also reviews NMR data on peptides designed to adsorb from aqueous solutions onto highly porous hydrophobic surfaces with specific helical secondary structures. 

During the last two decades, dynamic light scattering has evolved into a major characterisation technique for colloidal suspensions. A recent interlaboratory study into the characterisation of colloidal silica (Braun et al. 2011) showed that state-of-the-art DLS instrumentation facilitate a highly reproducible and very reliable acquisition of correlation function and corresponding mean particle size cum-... 

Static and dynamic scattering techniques are spectroscopic characterisation methods in the sense of Sect. 2.2. These techniques evaluate the functional dependency of measurement signals on a spectral parameter, i.e. on time, space, or classically on wavelength or frequency. The major advantage of spectroscopic methods is the reduced sample preparation (no fractionation), but they involve the inversion problem. That is, the spectrum is a—most frequently incomplete and discrete— nonlinear projection of the size distribution. Beside the scattering techniques, there are further spectroscopic methods which are based on the extinction of radiation or on any other response of the particle system to an external field. This section describes optical, acoustic, and electroacoustic methods that have gained relevance for the characterisation of colloidal suspensions. 

Schoff [2] has described the use of dynamic mechanical techniques in the characterisation of commercial organic coatings. Such techniques have become valuable methods for the determination of basic viscoelastic properties, following and measuring cure, and... 

More detailed aspects of protein function can be obtained also by force-field based approaches. Whereas protein function requires protein dynamics, no experimental technique can observe it directly on an atomic scale, and motions have to be simulated by molecular dynamics (MD) simulations. Also free energy differences (e.g. between binding energies of different protein ligands) can be characterised by MD simulations. Molecular mechanics or molecular dynamics based approaches are also necessary for homology modelling and for structure refinement in X-ray crystallography and NMR structure determination. 

Steam distillation is a process whereby organic liquids may be separated at temperatures sufficiently low to prevent their thermal decomposition or whereby azeotropes may be broken. Fats or perfume production are examples of applications of this technique. The vapour-liquid equilibria of the three-phase system is simplified by the usual assumption of complete immiscibility of the liquid phases and the validity of the Raoult and Dalton laws. Systems containing more than one volatile component are characterised by complex dynamics (e.g., boiling point is not constant). 

Polypropylene compositions containing magnesium hydroxide, with and without magnesium stearate surface treatment, were characterised at low and high shear rates using dynamic and capillary measurement techniques [36]. A significant reduction in viscosity was observed when surface treatment was present, particularly at low shear rates. In addition, with this system, the yield stress for the onset of flow was markedly reduced (Compare magnesium hydroxide variants A and E in Fig. 9). 

Thermal analysis is a group of techniques in which a physical property of a substance is measured as a function of temperature when the sample is subjected to a controlled temperature program. Single techniques, such as thermogravimetry (TG), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), dielectric thermal analysis, etc., provide important information on the thermal behaviour of materials. However, for polymer characterisation, for instance in case of degradation, further analysis is required, particularly because all of the techniques listed above mainly describe materials only from a physical point of view. A hyphenated thermal analyser is a powerful tool to yield the much-needed additional chemical information. In this paper we will concentrate on simultaneous thermogravimetric techniques. 

The problem with sulfide catalysts (hydrotreatment) is to determine the active centres, which represent only part of their total surface area. Chemisorption of O2, CO and NO is used, and some attempts concern NIL, pyridine and thiophene. Static volumetric methods or dynamic methods (pulse or frontal mode) may be used, but the techniques do not seem yet reliable, due to the possible modification (oxidation) of the surface or subsurface regions by O2 or NO probe molecules or the kinetics of adsorption. CO might be more promising. Infrared spectroscopy, especially FTIR seems necessary to characterise co-ordinativcly unsaturated sites, which are essential for catalytic activity. CO and NO can also be used to identify the chemical nature of sites (sulfided, partially reduced or reduced sites). For such... 

Solid-state NMR is one of the most powerful spectroscopic techniques for the characterisation of molecular structures and dynamics.1 This is because NMR parameters are highly sensitive to local chemical environments and molecular properties. One advantage of solid-state NMR is that it enables dealing with quadrupolar nuclei, which most of the NMR-accessible nuclei are in the periodic table. Moreover, it provides an opportunity to obtain information regarding the orientation dependence of the fundamental NMR parameters. In principle, such NMR parameters are expressed by second-rank tensors and it is the anisotropy that is capable of yielding more detailed information concerning the molecular properties. 

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