Compact discs structures

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 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... 

Microfabrication techniques Optical and compact discs Ceramic surface structures Catalyses... 

In addition to the construction industry, phenol has many other applications. It is used in pharmaceuticals, in herbicides and pesticides, and as a germicide in paints. It can be used to produce caprolactam, which is the monomer used in the production of nylon 6. Another important industrial compound produced from phenol is bisphenol A, which is made from phenol and acetone. Bisphenol A is used in the manufacture of polycarbonate resins. Polycarbonate resins are manufactured into structural parts used in the manufacture of various products such as automobile parts, electrical products, and consumer appliances. Items such as compact discs, reading glasses, sunglasses, and water bottles are made from polycarbonates. 

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 structures. 

Many ethylene derivatives having the general structure CH2=CHZ are also used as monomers for polymerization. The identity of Z affects the physical properties of the resulting polymer, making some polymers more suitable for one consumer product (e.g., plastic bags or food wrap) than another (e.g., soft drink bottles or compact discs). Polymerization of CH2=CHZ usually affords polymers with the Z groups on every other carbon atom in the chain. Table 15.2 lists some common monomers and polymers prepared industrially. 

Figure 22.16 Compact discs are made of polycarbonate and contain long chains of the structural unit shown. 

The Protein Data Bank (PDB) was established as a service to international science at the Brookhaven National Laboratory in the United States in 1971 to store and curate the atomic coordinates of macromo-lecular stmctures. Original versions of the whole data bank were distributed on magnetic tape to scientists, then on compact discs, and now they are freely available via the Internet (http //www.rcsb.org/). The PDB is part of the wwPDB whose mission is to ensure that the PDB archive remains an international resource with uniformly coded data. Other related sites are located in Japan (PDBj, http //www.pdbj.org/) and in Europe (MSD-EBI, http //www.ebi.ac.uk/msd/). In addition to coordinates, the PDB stores experimental diffraction data, and it provides many tools for analyzing and displaying structures. As of April 15, 2008, the PDB held 50,277 sets of atomic coordinates from proteins, nucleic acids, and carbohydrates determined by X-ray diffraction, NMR spectroscopy, and electron microscopy. About 5000 new stmctures are released each year, and the database is expected to treble to 150,000 by 2014. 

The Sadder division of Bio-Rad Laboratories (http // www.sadtler.com) has a product on compact disc containing 175,000 IR and 3,300 Raman spectra. For a subscription price the user gets the disc and an e-mailed code from Sadder that opens the disc for searches on one computer for a year. Once the code opens the disc, the user may perform unlimited lookups on one computer for one year. A lookup retrieves spectra by names or structures for comparison. In addition, the user may perform unlimited searches to identify or classify unknowns. Other databases for... 

We use commercially available relief structures such as compact discs (CDs), which have sub-500 nm features, as masters. Conventional CDs are made from a pre-patterned polycarbonate (PC) plastic layer covered with a thin sheet of aluminum (Al), and data on CDs is stored in a series of indentations packed in a spiral track. Each indentation in the PC layer is 110-nm deep and 690-nm wide separated by 1.2-pm areas, while the Al recording layer has the inverse features (Figure 1). These two layers, PC and Al, can be used to create two types of masters with complementary features. 

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