Ellipsoids representing physical

Here g is the gravitational field on the physical surface of the earth, y the normal field on the surface S. At the same time, dT/dv and dy/dv have the same values along line V at both surfaces. This is the boundary condition for the disturbing potential and therefore we have to find the harmonic function regular at infinity and satisfying Equation (2.301) on the surface S. In this case, the physical surface of the earth is represented by S formed by normal heights, plotted from the reference ellipsoid. In other words, by leveling the position of the surface S becomes known. 

The gradient of the electric field is the second derivative of the electrostatic potential, and as such, it obeys certain symmetries The EFG is a symmetric tensor with zero trace. This mean that it can be represented as a physical object An ellipsoid where off-diagonal elements represents reorientation of the principal axes system (See Figure 10). 

The crystal structure found represents an average of these two possibilities. If the anisotropic displacement parameters do not correspond to ellipsoids but to other quadratic surfaces that are not everywhere positive, the atomic displacement parameters may lose their physical significance (they become nonpositive definite). 

Attempts to consider a hkl dependence of the broadening in the Rietveld method were made by using different approaches involving ellipsoid, quartic and quadratic forms, either representing the modulation of the average sizes /,fc/and / /and microstrain hki, or used for a purely phenomenological qualitative fit without trying to extract any physical parameters. 

In order to elucidate relationships between surface active and film forming properties of food proteins, it is useful to examine the surface active properties of proteins whose physical and molecular properties are well characterized e.g. -casein, bovine serum albumin (BSA), lysozyme ( ), and -lactoglobulin (b-Lg) (2jL). These represent a range of tertiary structures for soluble proteins. Lysozyme is a rigid and roughly ellipsoidal molecule, whereas the hydrophobic -casein molecule is mostly a random coil structure. The b-Lg molecule consists almost entirely of antiparallel -sheet strands organized into a flattened cone ( ). 

A physically similar situation may be set up by allowing a drop of water to rest on a hot horizontal surface, such as a heated metal plate. If the surface is sufficiently hot, the drop will essentially float on an insulating layer of steam, in a friction-free situation. It is then possible for the drop to be set into oscillation between its original state of circular symmetry and an ellipsoidal shape as shown in Fig. 2.1. The oscillation represents a state of dynamic equilibrium between the inertia of the moving matter in the drop and the surface tension which attempts to maintain it in a symmetrical configuration. 

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