Alignment vibrational coordinates

Another descriptor based on eigenvalues is the EVA descriptor [66,67] (where EVA stands for EigenVAlue). The EVA descriptor is an example of a 3D descriptor that does not require alignment of the 3D structures (i.e., it is invariant to translation or rotation of the structure). It is based on the infrared spectrum of a molecule, which is related to the 3D structure. The molecular vibrations are calculated using a normal coordinate analysis (NCA) of the energy-minimized structure (e.g., using MOPAC AMI), and the eigenvalues from the NCA are used to derive the EVA descriptor (see Ref. 67). 

Orientation of Sensors. Tissue-, interface-, and structure-mounted sensors may be aligned as closely as possible with the axes of a biodynamic coordinate system (see, for example, Fig. 10.2), even though these may have inaccessible origins that are anatomical sites within the body. In practice, sensors are commonly oriented to record the component accelerations defined by the basicentric coordinate systems shown in Fig. 10.2 (ISO 2631-1, 1997 ISO 5349-1,2001), which have origins at the interface between the body and the vibrating surface. The location of accelerometers to record the handle vibration of specific power tools is described in an international standard (ISO 5349-2, 2001). 

For variational transition state theory, one requires the vibrational Hamiltonian only in a hypersurface perpendicular to the reaction coordinate. For such calculations the global CV treatments for chemical reactions reduce to an earlier method [8j] in which a local Cartesian system is erected at a point on the MEP, with one of the axes aligned with the tangent to the path. However, for reaction-path-based tunneling calculations, one must consider the globally curved nature of reaction coordinate. 

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