Anisotropy differences

The intensity of this ripple effect is very small indeed, amounting to only a few parts per 100,000. While this anisotropy (differences in quantity depending on direction) is exceedingly small, it is not at all insignificant. Indeed, astronomers believe that these tiny variations in CMB may be related to differences of distribution of matter in the early universe and are, therefore, a possible key to the later formation of stars and galaxies. 

Maciel (66) in studying vinyl a Sn compounds (Table VII) has noted that there is little correlation between proton and carbon resonances (due probably to geometric-anisotropy differences) but that 3Ca and SC of vinyl a compounds are similar to the corresponding phenyl compounds. He concluded that common inductive, resonance, and anisotropy effects must be operating in both systems. 

Another important difference between nonamorphous solids and single molecules is anisotropy (different space directions are not equivalent). No anisotropic effect is observed in the gas phase with no applied field because of the averaging process caused by the random orientation of molecules. In contrast,... 

Formation testers are measurement instruments that retrieve reservoir fluid samples from wells during pauses in drilling operations. Various practical questions arise. A type of reverse invasion problem appears how long must pumps be operated in order to obtain true formation fluids and not mud filtrate contaminants How do pump power requirements vary in permeable versus tight zones Can measured pressure transients be interpreted for rock characteristics like permeability and anisotropy Different answers are obtained depending on the fluid model assumed. Later in this book, we will consider constant density, immiscible, two-phase flows with and without mudcake effects. For now we assume transient, compressible, single-phase flow, but within this framework, we formulate and solve a very general problem. 

Figure 4.11. Chemical shift anisotropy different orientations of the axis of the bond between two nuclei, A and B, in applied field Bq result in nucleus B experiencing different shielding or deshielding effects.

This automatic velocity measurement method (AUTO-V) has also been suecessfijlly applied to other materials sueh as non-ferrous metals and even eeramics and plasties. The only requirement for this type of sequential velocity and thickness measurement is a certain isotropy of the material materials having anisotropie properties will lead to incorrect thickness readings due to the velocity difference in the two orthogonal directions. 

MAS Si speetnim of a sample of sodium disilieate (Na Si O,) erystallized from a glass is shown as an example. Whilst the statie speetnim elearly indieates an axial ehemieal shift powder pattern, it gives no evidenee of more than one silieon site. The MAS speetnim elearly shows four resolved lines from the different polymorphs present in die material whose widths are 100 times less than the ehemieal shift anisotropy. 

Shearing of the data is perfonned to obtam isotropic spectra in the FI dimension and to facilitate easy extraction of the ID slices for different peaks. Shearing is a projection of points that lie on a line with a slope equal to the anisotropy axis onto a line that is parallel to the F2 axis [24]- Shearing essentially achieves the same as the split-t experiment or delayed acquisition of the echo. Although sheared spectra may look more attractive, they do not add any extra infomiation and they are certainly not necessary for the extraction of QIS and values. 

Let us consider tire case of a donor-acceptor pair where tire acceptor, after capturing excitation from tire donor, can emit a photon of fluorescence. If tire excitation light is linearly polarized, tire acceptor emission generally has a different polarization. Common quantitative expressions of tliis effect are tire anisotropy of fluorescence, r, or tire degree of polarization,... 

The correlation is difficult in the case of thiazole and substituted thiazoles because of different effects field effect and anisotropy of hetero-atoms (110), which are very difficult to describe and calculate. When the importance of these two effeas is determined it is then possible to have a good correlation between tt electron densities and corrected chemical... 

Anisotropy in metals and composite materials is common as a result of manufacturing history. Anisotropic materials often display significantly different results when tested along different planes. This appHes to indentation hardness tests as well as any other test. 

Coercivity of Thin-Film Media. The coercivity ia a magnetic material is an important parameter for appHcations but it is difficult to understand its physical background. It can be varied from nearly zero to more than 2000 kA/m ia a variety of materials. For thin-film recording media, values of more than 250 kA / m have been reported. First of all the coercivity is an extrinsic parameter and is strongly iafluenced by the microstmctural properties of the layer such as crystal size and shape, composition, and texture. These properties are directly related to the preparation conditions. Material choice and chemical inborn ogeneties are responsible for the Af of a material and this is also an influencing parameter of the final In crystalline material, the crystalline anisotropy field plays an important role. It is difficult to discriminate between all these parameters and to understand the coercivity origin ia the different thin-film materials ia detail. 

Oriented In-Plane Texture. In this kind of film the properties (H and in the various in-plane directions (texture and nontexture directions) are different. The texture of the film can be supported by the texture of the substrate and the crystal lattice can be smaller in the texture direction than in the transverse direction. This can be the source for strain-induced magnetic anisotropy (magnetostriction). It is also found that the crystal is aligned in the texture direction (92). 

It generally is accepted that the mechanism of coercivity in the Alnicos is incoherent rotation of single-domain particles of the a -phase based on shape anisotropy. As coercivity increases, the larger the aspect ratio of the tods and the smoother thek surface becomes the difference between the saturation polarizations of the two phases also increases. It is thought that Ti increases the coercivity of Alnico because of an increased aspect ratio of the rods and a smoother surface. 

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