Layers textures

Phase conversion of the solid bulk material, leading to layered textures of h-BN on c-BN crystals. 

Shell brooch is made from the shiny inner nacreous layer of shell. The layered texture of the nacre is clearly visible. 

Rock varnish (often called desert varnish when seen in drylands) is a paper-thin mixture of about two-thirds clay minerals cemented to the host rock by typically one-fifth manganese and iron oxyhydroxides. Upon examination with secondary and backscattered electron microscopy, the accretionary nature of rock varnish becomes obvious, as does its basic layered texture imposed by clay minerals (Dorn and Oberlander, 1982). Manganese enhancement, two orders of magnitude above crustal values, remains the geochemical anomaly of rock varnish and a key to understanding its genesis. 

The number of research papers dedicated to micas is enormous, but knowledge of them is limited and not as extensive as that of other rock-forming minerals, for reasons mostly relating to their complex layer texture that makes obtaining crystals suitable for careful studies with the modem methods time-consuming, painstaking work. 

The most rigid cholesteric biopolymers have other types of layer textures, the monopole structures or Robinson spherulites discussed in the previous section the layers are approximately along concentric spheres (positive Gaussian curvature). An extensive study and review of cholesteric spherulites in materials of biological interest can be foimd in Bouligand and Livolant [57]. 

The sizes and optical properties of these Au(lll) textured islands can be controlled by the evaporation conditions and subsequent annealing (see Fig. 2). The influence of the evaporation parameters on the gold layer texture were extensively studied [85-88]. 

When an electric or magnetic field is applied to a liquid crystal cell, a texture transition occurs to minimize the free energy of the system. These texture changes in cholesteric liquid crystals are physically similar to the Frederiks transition in a nematic liquid crystal and result in a significant change in the optical properties of the layer. Texture transitions have been reviewed previously [8, 9] with allowance made for the sign of the dielectric or diamagnetic anisotropy, the initial texture, and the direction of the applied field. Here, we consider only the instability of the planar cholesteric texture, which has been widely discussed in recent literature. 

As might be expected, this simple picture does not hold perfectly. The coefficient of friction tends to increase with increasing velocity and also is smaller if the pavement is wet [14]. On a wet road, /x may be as small as 0.2, and, in fact, one of the principal reasons for patterning the tread and sides of the tire is to prevent the confinement of a water layer between the tire and the road surface. Similarly, the texture of the road surface is important to the wet friction behavior. Properly applied, however, measurements of skid length provide a conservative estimate of the speed of the vehicle when the brakes are first applied, and it has become a routine matter for data of this kind to be obtained at the scene of a serious accident. 

Berrett J F, Molino F, Porte G, Diat O and Lindner P 1996 The shear-induced transition between oriented textures and layer-sliding-mediated flows in a micellar cubic crystal J. Phys. Condens Matters 9513-17... 

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. 

Antireflection coatings are used over the silicon surface which, without the coating, reflects ca 35% of incident sunlight. A typical coating consists of a single layer of a transparent dielectric material with a refractive index of ca 2, which is between the index of siUcon and ait or cover material. Materials such as titanium dioxide, tantalum pentoxide, Ta20, or siUcon nitride, Si N, ca 0.08-p.m thick are common. The coating and a physically textured... 

The mixed Hquid is pumped into the area, where it cures and forms a slab. It may be poured in two layers to eliminate imperfections in the base. The first layer may be a preformed mbber slab which is glued to the base, or a mixture of reground mbber and binders or mbber and polyurethane. A textured surface maybe imparted to the second coat with sand or chips. 

Humus The dark organic material in soils, produced by the decomposition of soils. The matter that remains after the bulk of detritus has beenconsumed (leaves, roots). Humus mixes with top layers of soil (rock particles), supplies some of the nutrients needed by plants -increases acidity of soil inorganic nutrients more soluble under acidic conditions, become more available, EX. wheat grows best at pH 5.5-7.0. Humus modifies soil texture, creates loose, crumbly texture, that allows water to soak in and nutrients retained permits air to be incorporated into soil. 

A univocal confirmation of the development of crystalline aggregation in the fiber is the occurrence of layer reflexes Oil, HI, ill, and 101 on the textural x-ray diffraction pattern. The details of organization of the space lattice are defined by the parameters of the unit cell and the number of polymers felling into one cell. The data, established by different authors, are presented in Table 2. Daubenny and Bunn s [8] pioneer findings are considered the most probable for space lattices occurring in PET fibers. 

The value of the angle of tilting of the texture can be determined from the analysis of x-ray fiber diagrams. As Urbanczyk noted [18], the position of layer reflexes oil and ill or the position of equatorial reflexes 010 and 100 can be analyzed. In the first case, the tilting angle of the texture (v ) can be determined from the equation ... 

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