Motion artefact

The fluctuations of isolated steps have been studied, both theoretically - using Langevin theory, Monte Carlo simulations of SOS models, as well as exact methods, and experimentally by scanning tunneling microscopy (caution is needed in the measurements to avoid artefacts of tip assisted motions of the steps O-... 

The vibrational wavefunction depends only on the nuclear coordinates qnuc. The nuclei move in a fixed electronic potential that is often approximated as a harmonic potential (dashed curve in Figure 1.10) to determine vibrational wavefunctions near the potential s bottom. The electronic wavefunction carries the complete information about the motion and distribution of electrons. It still depends on both sets of coordinates qe and qnuc, but the latter are now fixed parameters rather than independent variables the nuclei are considered to be fixed in space. The BO assumption is a mild approximation that is entirely justified in most cases. Not only does it enormously simplify the mathematical task of solving Equation 1.5, it also has a profound impact from a conceptual point of view The notions of stationary electronic states and of a PES are artefacts of the BO approximation. It does break down, however, when two electronic states come close in energy and it must be abandoned for the treatment of radiationless decay processes (see Section 2.1.5). 

As described in the previous section, the challenges of size reduction, comfort, battery life, and motion artefacts remain unsolved in current portable pregnancy monitors. In general, these issues have been addressed by the wireless sensor network (WSN) community. More specifically, they are researched under the name of wireless body area network (WBAN) (Gonzalez-Valenzuela et al., 2013 Yang, 2006 Latre et al., 2010 Chen et al., 2010). 

Increases display dynamic range (increased sensitivity) Susceptible to tissue motion artefacts... 

Intestinal hyperaemia is a sign of active disease in the inflamed intestine, which can be detected by Doppler sonography. Tissue motion artefacts (peristalsis) sometimes make the assessment difficult, but visualisation of vessels by using contrast harmonic imaging at a low MI is not restricted by peristalsis (Fig. 20.1). 

Artefacts either occur from unwanted motion or as a result of the magnetic field gradient (Mirowitz 1999). 

Motion artefacts result from tissue movement during the period of data acquisition, which may be either voluntary or involuntary. In children, voluntary movements are not an infrequent problem because of their reduced understanding and compliance. In the young or uncooperative child, the use of sedation or general anaesthesia may be needed to achieve satisfactory immobility. 

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