Pitches unique properties

The unique properties of liquid crystals have also provided opportunity for study of novel nonlinear optical processes. An example involves the ability to modify the pitch of cholesteric liquid crystals. Because a pseudo-wave vector may be associated with the period of pitch, a number of interesting Umklapp type phasematching processes (processes in which wave vector conservation is relaxed to allow the vector addition to equal some combination of the material pseudo-wave vectors rather than zero) are possible in these pseudo-one-dimensional media. Shen and coworkers have investigated these employing optical third harmonic generation (5.) and four-wavemixing (6). 

Lipases are found in a wide variety of bacteria, yeasts, and filamentous fungi. Due to their unique properties, lipases are used in all applications where fats are modified or need to be removed. In the detergent industry, lipases are added to laundry detergents for the removal of fat-containing stains. In the paper industry, lipases remove fatty pitches from... 

This division can also be viewed favorably from the perspective of functionality. Asymmetric materials possess certain unique properties, with the symmetry making interactions with other materials more selective and specific. An example is DNA, which is helical helicity is a special type of asymmetry where the pitch and diameter of the helix determine how the materials interact with their counterparts. Asymmetric catalysis follows the same principle. Furthermore, the interaction between hehcal nanomaterials and other materials can be tuned by using the surfactants on the helices, and manipulating this factor of symmetry will provide another handle to control the function of the materials. 

From the mechanical application point of view, asymmetric nanomaterials such as silica nanocoils should have a much greater compressibihty and expansibUity than symmetric nanowires or nanorods. This unique property may be employed to create unique appUcations. For example, the magnetically controlled opening and closing of pitches in the helical coils may be used as a drug deUvery vehicle, although until now this property has not been utilized, most likely due to the lack of manipulation of these asymmetric nanomaterials. 

Distillation By-Products. Of the CTO distiHation by-products, ie, pitch, heads, and DistiHed TaH Oil (DTO), only the last, a unique mixture of rosin and fatty acids, has significant commercial value. Pitch and heads are used as fuel the former has a fuel value of 41,800 kj/kg. TaH oil heads have outstanding solvent properties, but also have a bad odor, which is hard to remove. They contain a relatively high fraction of palmitic acid which can be recovered by crystallization. 

Because of their unique blend of properties, composites reinforced with high performance carbon fibers find use in many structural applications. However, it is possible to produce carbon fibers with very different properties, depending on the precursor used and processing conditions employed. Commercially, continuous high performance carbon fibers currently are formed from two precursor fibers, polyacrylonitrile (PAN) and mesophase pitch. The PAN-based carbon fiber dominates the ultra-high strength, high temperature fiber market (and represents about 90% of the total carbon fiber production), while the mesophase pitch fibers can achieve stiffnesses and thermal conductivities unsurpassed by any other continuous fiber. This chapter compares the processes, structures, and properties of these two classes of fibers. 

When an anode contains an appropriate amount of metals (or metal oxide), novel carbon materials such as SWNTs, metallofuJlerenes, filled nanocapsules, bam-boo -shaped tubes (23), nanochains (10), and MWNTs filled with metal carbides (24,25) are formed. Especially SWNTs are now attracting a great deal of interest from researchers in physics and materials science, because exotic electronic properties that vary between semiconducting and metallic states depending on how a graphene sheet is rolled (i.e., diameter and helical pitch of a tube) are predicted theoretically (26-28) and because unique quantum effects are revealed experimentally (29,30). 

Lyotropic liquid crystalline cellulose derivatives exhibit unique optical properties because of their helicoidal supramolecular structure.The chiro-optical properties of the helicoidal structure can be described by a pitch p (or its inverse, the twist p ) p = 2o/fi, where is the reflection wavelength and h is the mean refractive index of a sheet, and the corresponding handedness of the twist right-handed helicoidal structure being assigned to a positive pitch p > 0) and left-handed helicoidal structures to a negative pitch p < The nematic mesophase can be... 

Liquid crystalline phases formed by chiral molecules (i.e. molecules differing from their mirror image) show unique macroscopic properties. The best-known example is the cholesteric phase which is termodynamically equivalent to the nematic phase. In the later phase the free-energy of the system corresponds to a uniform director distribution in the whole sample. On the other hand in cholesterics the molecules tend to form a helical structure the helical axis being perpendicular to the director. A similar helical structure develops in the smectic C phase when the molecules are chiral. In this case the helical axis is parallel to the layer normal the tilt angle is constant while the azimuthal angle is rotating in space. The pitch of the helix in these systems is typically in the order of a micron. 

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