Compact discs

GaAs, GaAlAs, and GaP based laser diodes are manufactured using the LPE, MOCVD, and molecular beam epitaxy (MBE) technologies (51). The short wavelength devices are used for compact disc (CD) players, whereas the long wavelength devices, mostly processed by MBE, are used in the communication field and in quantum well stmctures. 

Nevertheless, the market in compact disc equipment is increasing, and computer data storage has expanded rapidly, as well as telecommunication by sateUite and the use of high frequency devices. 

The growth rate of 4-cumylphenol is expected to parallel the growth rate of polycarbonates, particularly the grades used to produce compact discs (see Table 3). 

Many database producers provide online access to thek databases or distribute thek databases on compact disc read-only-memory (CD-ROM) and so are also considered vendors or producer/vendors. Whereas numerical growth in vendors is indicated (Fig. 1), the success of the database industry is largely a result of the transition of the information industry from paper-based to computer-based services (see Computer technology Informiation RETRIEVAL, Inforitation STORAGE MATERIALS). Thus industry growth can also be measured in terms of the increase in use of computer-readable databases as exemplified by the number of searches. 

For many years vinyl chloride-vinyl acetate copolymers had two main uses, in flooring compositions and for long playing gramophone records. Whereas the former application remains strong, the use in gramophone records has dropped sharply, particularly since the widespread acceptance of polycarbonate-based compact discs. 

PMMA has not been able to compete in the field of compact discs, the market having gone to the polycarbonates (see Chapter 20). It is, however, suitable for optical data storage using large video discs. Large-scale acceptance in the field of optical fibres has been held back by problems of obtaining material of an acceptable level of purity. 

To reduce melt viscosity an aliphatic dicarhoxylic acid may be used to partially replace the carbonic acid derivative. Easy-flow grades with a melt flow rate of 80 are now available in order to meet the stringent flow requirements involved in compact disc production. Such an improvement in flow rate is, however, at the expense of heat distortion temperature. 

ATSDR s Toxicological Profiles on compact disc. (Lewis Publishers, 1997 CRC Press, Inc.). 

Hazardous Substances Data Bank (HSDB) on compact disc from the Canadian Center for Occupational Health and Safety (can buy at CCOHS web site). "The HSDB(R) (Hazardous Substances Data Bank(R)) database contains data profiles on 4,500 potentially toxic chemical substances. It is created and updated by specialists at the U.S. National Library of Medicine. Compiled from an extensive range of authoritative sources, HSDB is widely recognized as a reliable and practical source of health and safety information. Much of the data is peer reviewed. 

NIOSHTIC on compact disc from the Canadian Center for Occupational Health and Safety (ean buy at CCOHS web site). "NIOSHTIC(R) is a bibliographie database which provides comprehensive international coverage of documents on occupational health and safety, as well as related fields. It eontains detailed summaries of over 200,000 articles, reports and publications, spanning over 100 years. NIOSHTIC(R) sources include over 160 scientific and technical journals, NIOSH reports (published and unpublished), NIOSH research bibliographies, abstracts from CIS Abstracts, and personal files from respected professionals on selected topics. 

TLVs and other Occupational Exposure Values—1995 on compact disc from the American Conference of Governmental Industrial Hygienists. 

Just as many small-molecule materials, polymers also form glasses [4]. Actually, most polymeric materials of everyday use are made of polymer glasses, polystyrene (PS) cups or compact discs made of polycarbonates, for instance. In many respects polymer glasses are very similar to small-molecule glasses, and there is nothing special about them. However, on the other hand, the special aspects of polymer materials allow specific studies beyond characteristic studies on small-molecule glasses. 

To maximize control in setting tolerances there is usually a minimum and a maximum limit on thickness, based on the process to be used such as those in Tables 3-6 to 3-9. Each plastic has its own range that depends on its chemical structure, composition (additives, etc.), and melt-processing characteristics. Any dimensions and tolerances are theoretically possible, but they could result in requiring special processing equipment, which usually becomes expensive. There are of course products that require and use special equipment such as polycarbonate compact discs (CDs) to meet extremely tight tolerances. 

The pace of development has increased with the commercialization of more engineering plastics and high performance plastics that were developed for load-bearing applications, functional products, and products with tailored property distributions. Polycarbonate compact discs, for example, are molded into a very simple shape, but upon characterization reveal a distribution of highly complex optical properties requiring extremely tight dimension and tolerance controls (3,223). 

The basic steps of the IM process produce unique structures in all molded products, whether they are miniature (micro) electronic components, compact discs, or large automotive bumpers. These structures have frequently been compared to plywood with several distinct layers, each with a different set of properties. In all IM products, a macroscopic skin-core structure results from the flow of melt into an empty cavity. Identifiable zones or regions within the skin are directly... 

Why Do We Need to Know This Material The existence of compounds is central to the science of chemistry and by seeing how bonds form between atoms, we come to see how chemists design new materials. Research into artificial blood, new pharmaceuticals, agricultural chemicals, and the polymers used in materials such as compact discs, cellular phones, and synthetic fibers is based on an understanding of how atoms link together. 

C07-0007. A compact disc player uses light of frequency 3.85 X lO s to read the information on the disc, (a) What is this light s wavelength (b) In what portion of the electromagnetic spectrum (visible, ultraviolet, and so on) does this wavelength fall (c) What is the energy of one mole of photons at this frequency ... 

One application of modem solid-state electronic devices is semiconductor materials that convert electrical energy into light. These light-emitting diodes (LEDs) are used for visual displays and solid-state lasers. Many indicator lights are LEDs, and diode lasers read compact discs in a CD player. The field of diode lasers is expanding particularly rapidly, driven by such applications as fiber optic telephone transmission. 

Iowa Drug Information Service. A bibliographical database with access to full text, IDIS [98] provides access to the therapeutic and clinical pharmaceutic English language journal literature from 17 countries. FDA Summary Basis of Approval documents are indexed and available in full text. Updated monthly, the database contains over 450,000 records from 1966 forward with bibliographic citation, keyword indexes, and, for over 60% of citations, the author s abstract. IDIS is commercially available in microfiche, compact disc, and web formats and via DataStar, DIALOG. 

Glassy amorphous polymers exhibit excellent dimensional stability and are frequently transparent. Everyday examples include atactic polystyrene, polycarbonate, and polymethylmethacrylate (Plexiglas ), which we encounter in such applications as bus shelters, motorcycle windshields, and compact disc cases. 

The functional groups that typically participate in this type of polymerization are carboxyl, amine, and alcohol groups. Examples of step growth polymers include polyesters and nylons, which are often spun into fibers used to manufacture carpeting and fabrics, and polycarbonates, which are converted into compact discs, jewel cases, and the large bottles used in water coolers. 

PVC is used to make pipes, rods, and compact discs. 

In the disc method, the powder is compressed by a punch in a die to produce a compacted disc, or tablet. The disc, with one face exposed, is then rotated at a constant speed without wobble in the dissolution medium. For this purpose the disc may be placed in a holder, such as the Wood et al. [Ill] apparatus, or may be left in the die [112]. The dissolution rate, dmldt, is determined as in a batch method, while the wetted surface area is simply the area of the disc exposed to the dissolution medium. The powder x-ray diffraction patterns of the solid after compaction and of the residual solid after dissolution should be compared with that of the original powder to test for possible phase changes during compaction or dissolution. Such phase changes would include polymorphism, solvate formation, or crystallization of an amorphous solid [113],... 

The first BioCD took its inspiration from the compact disc. The compact disc was invented in 1970 by Claus Campaan of Phillips Laboratory. The concept is purely digital and uses null interferometers that are far from quadrature, as appropriate for the readout of two binary intensity states. The interferometers were common-path and stable, as required for the mechanical environment of portable compact disc readers. The original BioCD used the same physics as the compact disc, but modified the on-disc microstructures to change from the digital readout to an analog readout that operated in quadrature for sensitive detection of surface-bound proteins7,8. Because the quadrature condition is established by diffraction off of microstructures on the disc, this is called the microdiffraction-class (MD-Class) of BioCD. 

Zhao, M. Nolte, D. Cho, W. Regnier, F. Varma, M. Lawrence, G. Pasqua, J., High speed interferometric detection of label free immunoassays on the biological compact disc, Clin. Chem. 2006, 52, 2135 2140... 

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