Pitch color

The cholesteric phase maybe considered a modification of the nematic phase since its molecular stmcture is similar. The cholesteric phase is characterized by a continuous change in the direction of the long axes of the molecules in adjacent layers within the sample. This leads to a twist about an axis perpendicular to the long axes of the molecules. If the pitch of the heHcal stmcture is the same as a wavelength of visible light, selective reflection of monochromatic light can be observed in the form of iridescent colors. 

Paint is one of the most common and widely used materials in home and building constmction and decoration (see Building materials). Its broad use comes from its abiHty to provide not only improved appearance and decoration but also protection of a substrate to which it is appHed. Evidence of the historical uses of paint goes back over 25,000 years to cave paintings found in Europe. The Bible describes pitch being used to coat and protect Noah s Ark. Over 10,000 years ago in the Middle East, various minerals and metals such as lime, siHca, copper and iron oxides, and chalk were mixed and reacted to produce many colors. Resins from plant sap and casein were also used. Over 2000 years ago in Asia, resins refined from insect secretions and sap from trees were used to make clear lacquers and varnishes (2). 

Asphalt [8052-42-4] is defined by the American Society for Testing and Materials (ASTM) (1) as a dark brown to black cementitious material in which the predominating constituents are bitumens that occur in nature or are obtained in petroleum processing. Bitumen is a generic term defined by ASTM as a class of black or dark-colored (soHd, semisoHd, or viscous) cementitious substances, natural or manufactured, composed principally of high molecular weight hydrocarbons, of which asphalts, tars, pitches, and asphaltites are typical. 

Distillation. Most fatty acids are distilled to produce high quaHty products having exceUent color and a low level of impurities. Distillation removes odor bodies and low boiling unsaponifiable material in a light ends or heads fraction, and higher boiling material such as polymerized material, triglycerides, color bodies, and heavy decomposition products are removed as a bottoms or pitch fraction. The middle fractions sometimes can be used as is, or they can be fractionated (separated) into relatively pure materials such as lauric, myristic, palmitic, and stearic acids. 

Observable Characteristics - Physical State (as shipped) Liquid Color Light amber to red to black, depending on grade Odor Characteristic like pinetree pitch. 

Schwarz-manganerz, n. haiismannlte. -meer, n. Black Sea. -mehl, n, dark-colored flour, esp. rye flour, -ol, n. black oil, specif, a dark, pasty, boiled linseed oil, -pech, n. black pitch, common pitch, -pulver, n. black powder, ... 

Steinkohlenteer, m. coal tar. -benzin, n. benzene benzol(e), -blase,/. coal-tar still, -essenz, /. first light oil. -farbe, /. coal-tar color, -kampher, m. naphthalene, -dl, n. coal-tar oil (leichtes, light oil schweres, heavy oil), -pech, n. coal-tar pitch, -prl-parat, n. coal-tar preparation, coal-tar prod uct-... 

Thermotropic cholesterics have several practical applications, some of which are very widespread. Most of the liquid crystal displays produced use either the twisted nematic (see Figure 7.3) or the supertwisted nematic electrooptical effects.6 The liquid crystal materials used in these cells contain a chiral component (effectively a cholesteric phase) which determines the twisting direction. Cholesteric LCs can also be used for storage displays utilizing the dynamic scattering mode.7 Short-pitch cholesterics with temperature-dependent selective reflection in the visible region show different colors at different temperatures and are used for popular digital thermometers.8... 

Active area Pitch size Color coordinates Voltage Panel current Pixel current Luminance Luminous efficiency Power efficiency Power consumption... 

Fasting was necessary he insisted on weeks without meat. As well, Balsamo purchased and sacrificed nine live cockerels (a magical number, as everyone knew). They had to be black, white, and red three of each color in an expression of natural sympathy with the sparkling jewels of the hoard. He d also insisted they undertake ritual ablutions of the skin, followed by the application of special herbs, balms, unguents, and holy oils. All this he accompanied with chants in a high-pitched voice, like the Arabs when they prayed to Allah. 

Fig. 18. TLS analysis of the palindromic DNA on the NCP. (a) Composite motions of the DNA gyres looking at the ventral surface with the DNA colored by atom type. The two gyres reflect the structural asymmetry of the NCP with non-coincident axes of motion and different orientations for the primary axis of motion. The ventral gyre TLS axes more closely resemble the composite motions of the individual H3 H4 dimers (Fig. 17c), the dorsal TLS axes resemble the composite motion of the tetramer. (b) The composite motions of the DNA gyres are shown in a view down the dyad axis. The DNA is shown in a surface representation colored by atom type. Note that axes of motion appear parallel and in plane with the pitch of the DNA. In this view the ventral surface is on the bottom of the image.

Thermotropic chiral LCs whose pitch vary strongly with temperature can be used as crude thermometers since the color of the material will change as the pitch is changed. LC color transitions are used on many aquarium and pool thermometers. Other LC materials change color when stretched or stressed. Thus, LC sheets are often used in industry to look for hot spots, map heat flow, measure stress distribution patterns, etc. The LC in fluid form is used to detect electrically generated hot spots for failure analysis in the semiconductor industry. LC memory units with extensive capacity were used in Space Shuttle navigation equipment. 

What we really are is a web of interconnections, the summation of all of our relationships, all the people we know and those we are still to meet. It s not that we are in the web, the web is what we are. Vowel sounds change the colors pitch and tone alter the shape of the enclosing... 

Lithographic Printing Ink.—The composition of lithographic writing ink has boon already given. That which is employed to taka impressions on paper from engraved plates, with a view to their transference to the stona, may be composed as follows -—Tallow, wax, and soap, of each four ounces shellaa, throe ounces gum-mastic, two and a half ounces black pitch, one ounce and a half to which add lamp-black to color. 

Crown ethers of the type discussed in this section have been used as sensors, membranes, or materials for chromatography. Shinkai used cholesterol-substituted crown ether 10 as a sensor for chirality in chiral ammonium compounds (Scheme 16). It was found that the pitch of the cholesteric phase exhibited by 10 was changed upon addition of the chiral salt. As the wavelength of reflection for incident light depends on the pitch, a color change was observed that was visible to the naked eye [45, 46]. Such chirality sensing systems were known before but chromophores had to be bound to the crown ether in order to observe color changes [47]. This problem could be overcome by 10, which uses intrinsic properties of the chiral nematic phase. 

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