Uses of synthetic

In conjunction with the increased use of synthetic fibers and blends of synthetic and natural fibers, and the modernisation of appHcation processes which has taken place simultaneously, the technique of textile whitening has been improved considerably. 

Polyolefin—ceUulose composites also are used in nonasbestos flooring felts, waUpapers, filter media, labels, embossable papers, and other nonwoven fabrics that are made on paper machines. Use of synthetic fibers in paper has been reviewed (103,104). 

Tlie structure of boehmite consists of double layers in wliich the oxygen ions exliibit cubic packing. Hydroxyl ions of one double layer are located over the depression between OH ions in the adjacent layer such that the double layers are linked by hydrogen bonds between hydroxyls in neighboring planes. Tliere is some technical production and use of synthetically produced boehmite. 

Another fire-related problem that has seen some research effort is that of smolder resistance of upholstery and bedding fabrics. Finishing techniques have been developed to make cotton smolder-resistant (152—156), but the use of synthetic barrier fabrics appears to provide a degree of protection. Work also has provided a means of producing cotton fabrics that have both smooth-dry and flame-retardant performance (150,151). In this case, the appHcation of FR treatment should be performed first, and DP treatment should be modified to accommodate the presence of the FR polymer on the fabric. 

Hydrogels, ie, gelatin and agar, have been known for a long time. In the late nineteenth century, Herschel proposed the use of jelly materials on the cornea for the correction of vision (108). In 1960, the use of synthetic hydrogels for contact lenses was proposed and several U.S. patents were obtained for the invention of cross-linked hydrophilic polymers, eg, systems based on 2-hydroxethyl methacrylate [868-77-9] (HEMA) (5) (109—112). 

Natural Sensitizing Dyes and Photodynamic Therapy. The chlorophylls are, of course, among the natural sensitizers for photosynthesis. Considerable iaterest exists ia chlorophyll and related pigments as photosensitizers ia biology and medicine (75), isomeric retinal chromophores as visual pigments (76,77), and the use of synthetic photosensitizers ia neurobiology (9), hematology (78), and photodynamic therapy (79). 

An example of a direct spectrophotometrical assay is the use of synthetic peptide -nitroanilide substrates to determine protease activity. The /)-nitroani1ine group Hberated from the substrates by the protease can be determined spectrophotometricaHy at 410 nm. An example of an indirect (coupled) spectrophotometric assay is the determination of a-amylase using -nitrophenyLmaltoheptaoside. Initially, the substrate is cleaved by the a-amylase and subsequentiy one of the reaction products, -nitrophenyLmaltotrioside, is cleaved by a-glucosidase, hberating -nitrophenyl, a chromophore... 

Anions of (3-keto esters are said to be synthetically equivalent to the enolates of ketones. The anion of ethyl acetoacetate is synthetically equivalent to the enolate of acetone, for example. The use of synthetically equivalent groups is a common tactic in synthetic organic chemistry. One of the skills that characterize the most creative practitioners of organic synthesis is an ability to recognize situations in which otherwise difficult transfonnations can be achieved through the use of synthetically equivalent reagents. 

The use of synthetic organic chemistry to create molecules that will alter in a useful way some disease process in a living system. 

Reduction of exhaust emissions is being tackled in two ways by engineers, including precombustion and postcombustion technology. One of the most effective methods now being researched and adopted includes use of synthetic fuel made from natural gas. This fuel is crystal clear, and just like water, it has no aromatics, contains no sulfur or heavy metals, and when used with a postcombustion device such as a catalytic converter any remaining NO, or other emissions can be drastically reduced. Estimates currently place the cost of this fuel at 1.50 per gallon, with availability in 2004 to meet the next round of stiff EPA exhaust emission standards. 

The natural supply of nitrogen available to plants from the nitrogen cycle is limited. To meet the growing demands for agriculture crops, nitrogen is added to soil in the form of fertilizers. An estimated one-third of the human population is fed as a result of the use of synthetic fertilizers. 

Worldwide use of synthetic rubber (not including thermoplastic elastomers) in 1997 was approximately 10.5 million metric tons. 

Prior to 1940, the use of synthetic elastomers in linings was negligible, but the advent of the Second World War, and the consequent loss of natural rubber sources to the Allies, led to the use of synthetic rubber, namely a styrene-butadiene copolymer which, whilst not having all the properties of natural rubber, proved to have adequate anti-corrosive performance. 

To our knowledge, the first work on the use of synthetic polyelectrolytes as models of hydrolase was reported by Steinhardt and Fuggit81). They used polystyrenesul-... 

Since 1945 the use of synthetic pesticides in the United States has grown 33-fold. The amounts of herbicides, insecticides, and fungicides used have changed with time due, in large part, to changes in agricultural practices and cosmetic standards (14, 15). At the same time, the toxicity and biological effectiveness of these pesticides have increased at least 10-fold (15). For example, in 1945 DDT was applied at a rate of about 2 kg/ha. With the more potent insecticides available now, similar effective insect control is achieved with pyrethroids and aldicarb applied at 0.1 kg/ha and 0.05 kg/ha, respectively. 

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