Fast scanning applications

The imaging protocol summarized above for PTFE (hands-on example 3) remains fully applicable for POM. Imaging at minimized forces F is obviously beneficial to reduce the contact area (which scales in a purely elastic approximation as F2/3) and thus to increase lateral resolution, while minimizing sample deformation. The resolution of the exposed POM crystal facet may require a careful adjustment of the relative scan angle, since periodicities are more clearly discernible in a near perpendicular (vertical direction of the image) orientation with respect to the fast scan direction (horizontal direction of the image). Hence, for the two periodicities observed, in, Fig. 3.15, the chain direction (see arrows) should be in an angle of 45° with respect to the fast scan direction in order to visualize both periodicities. 

Weh2 F.W. Wehrli, Fast-Scan Magnetic Resonance Principles and Applications, Raven Press,... 

The origins of SECM homogeneous kinetic measurements can be found in the earliest applications of ultramicroelectrodes (UMEs) to profile concentration gradients at macroscopic (millimeter-sized) electrodes (1,2). The held has since developed considerably, such that short-lived intermediates in electrode reactions can now readily be identified by SECM under steady-state conditions, which would be difficult to characterize by alternative transient UME methods, such as fast scan cyclic voltammetry (8). 

Fast scan voltammetry, in particular on microinterfaces, can be used for determination of charge-transfer rate constants. Impedance analysis can be used not only in analytical applications, but also to obtain a better understanding of surface phenomena (48) and adsorption (32). Microinterfaces, with their high own resistance, are well suited for impedance analysis derived from measurements of noise generated by electrochemical systems (49, 50). Understanding the phenomena peculiar to microinterfaces is essential to future studies of the electrochemistry of small domains. 

Turning initially to multidetection, and here first to simultaneous usage, an obvious application is to combine the gradient FIA techniques with the use of detectors that provide several signals at several values of the instrumental variables, which indeed gives FIA a doubly dynamic character. In these techniques, which have already been mentioned in Section 2.4, advantage can be taken by multidetectors, such as the fast-scan vol-tammetric detectors [288] or by inductively coupled plasma atomic emission spectroscopy [808] or by diode array detectors [1017, 1075, 1382]. Combined with the advantages offered by chemometrics, these multidetection procedures may in fact be extended to multideterminations. 

The cyclic voltammetry of the complexes tranj-lRu LXJ, where L = 4NH3 or 2en, X = Cl or Br etc., illustrates the application of the technique for obtaining detailed mechanistic information on reactions occurring subsequent to the initial redox process. At moderately fast scan rates, ca. 1 V s the redox behaviour is typical of a single reversible one-electron couple corresponding to the couple At slower scan rates, ca. 0.1 V s , a wave corresponding to the same... 

Potential applications of thermal analysis and calorimetry to quality control is not limited in any way to those discussed in this chapter. Once some physical or chemical characteristic of a material or process is known and can be examined and/or characterized by these techniques, it is only the imagination that limits the possibilities for quality control applications. Both traditional techniques (DSC, TG, DMA, isothermal calorimetry, etc.) and non-traditional techniques (temperature modeling, etc.) have been shown to have potential uses for quality control. With the introduction of many new techniques (fast scanning DSC, sample controlled thermal analysis (SCTA), modulated and other temperature programmed techniques, etc.), many more new opportunities will arise for providing quality control tools. 

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