Scanning working principle

Figure 4.22 The working principle of positron emission tomography (PET) is based on the decay of F-labeled diagnostics, for example [ F]2-fluorodeoxyglucose ([ F]FDG) [85]. The y photon pairs resulting from positron-electron annihilation are detected left) and enable spatial resolution of the sites where the labeled diagnostics and their congeners are predominantly processed. [ F]FDG is particularly useful for identification of metabolically active areas with high glucose turnover, for example brain tumors (nght). The two PET scans show a healthy brain above) and a newly developed tumor below, arrow courtesy of Hamamatsu Photonics).

Beyond the working principle described so far, ellipsometry can also provide laterally resolved information. This is possible in a scanning process but also directly by imaging ellipsometry. The latter approach is illustrated, for example, by the work of Schmaljohann et al. [50] who exemplified the advantages of this technique for a micropattemed thermoresponsive coating. 

Biosensors Using Atomic Force Microscopes, Fig. 1 (a) Basic components and working principle of AFM. A sharp tip fixed at the end of a fiexible cantilever is raster scanned over the surface of a sample. As the tip interacts with the surface, the cantilever deflects, and its deflections are monitored by a laser and a photodiode and then used to reconstruct the topography of the sample, (b) A schematic diagram of AFM as a biosensor in detecting... 

CV shares essentially the same working principle with LSV, but the CV scans are repeated in triangular sweeps in both anodic and cathodic directions. Irreversible electrochemical reactions are readily detected in CV. Voltage sweep rate-dependent current features and scan-direction activated hysteresis of voltammograms serve as a useful metric for CV-based evaluations of slurry additives (Emery et al., 2005). The OCP (or oc) of a metal—solution interface has the same physical meaning as Ecorr for that system. While Econ is measured in the potentiodynamic mode, oc is generally determined in the potentiostatic mode as a function of time. The different nomenclatures are commonly used in view of these different methods used to measure the two parameters. 

Figure 9.1 Schematic illustrations of the working principle of (a) scanning tunneling...

Scanning electron microscopy (SEM) uses a focused electron beam to survey a surface of interest. The working principle of SEM is very similar to that of optical microscopy but with an approximately 250 times higher resolution. The electrons... 

The working principle of a commercially available instrument, latroscan TH-10, designed to scan the adsorbent-coated "Chromarods are depicted in Figure 2. The rod holder carrying the... 

We first experimented with the Quartz Crystal Microbalance (QCM) in order to measure the ablation rate in 1987 (12). The only technique used before was the stylus profilometer which revealed enough accuracy for etch rate of the order of 0.1 pm, but was unable to probe the region of the ablation threshold where the etch rate is expressed in a few A/pulse. Polymer surfaces are easily damaged by the probe tip and the meaning of these measurements are often questionable. Scanning electron microscopy (21) and more recently interferometry (22) were also used. The principle of the QCM was demonstrated in 1957 by Sauerbrey (22) and the technique was developed in thin film chemistiy. analytical and physical chemistry (24). The equipment used in this work is described in previous publications (25). When connected to an appropriate oscillating circuit, the basic vibration frequency (FQ) of the crystal is 5 MHz. When a film covers one of the electrodes, a negative shift <5F, proportional to its mass, is induced ... 

Cyclic voltammetry is a powerful tool for following mechanisms since varying the scan rate v is equivalent to varying the time-scale of observation, t. In order to obtain the rate constant k of the homogeneous C reaction, the CV is obtained as a function of the scan rate, with k of the reaction then being determined from working curves calculated from theoretical principles. 

Lin et al. 1985 Wade and Meyyappan 1987 Wey and Kessler 1989) the insonification is broadcast throughout the specimen, and the detection is by a focused optical probe that measures local surface tilt on the surface of the specimen. But in the scanning acoustic microscope both the illumination and the detection are performed by focusing elements and, since these are focused at the same point, the configuration may be described as confocal. The first con-focal acoustic microscopes worked in transmission and, although this is now of mainly historical interest, the transmission arrangement will be described first because in some respects it is simpler and will serve to introduce some principles. 

For the quantitation of chromatograms, the development condition found by the conventional TLC was transferred to another TLC system which uses a thin quartz rod coated with silica gel of 75 p thickness and may be called thin-layer-FID chromatography . The TLC system is equipped with a flame ionization detector (FID) and commercially available as a complete set (Iatron thinchrograph model TFG-10, Iatron Co., Ltd., Tokyo). The principle of sample scanning and device for FID are almost the same as those worked out by Padley57), Szakasits et al, and... 

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