Data Storage Layer

The Data Persistence Layer can be a thick layer that resides in the application middleware or a thin layer in the application middleware combined with some stored procedures in the database. The former makes the Data Persistence Layer independent of the underline RDBMS that is being used. The latter provides better performance because the number of network calls can be reduced. Either way, a wed-defined interface between the Business Layer and the Data Storage Layer is the key. 

The data storage layers are composed mostly of small magnetic particles in a polymer film. The... 

The practical use of photochromic dyes as memory layers in erasable and rewritable data storage disks fails not only because of their physical limitations (lacking sensitivity, insufficient stabiHty, low number of cycles), but also because the diode lasers required for switching in the visible range (wavelength between 450 and 600 nm) and the uv-range (around 350 nm) are not available. 

The birefringence of substrate materials for optical data storage devices requires special attention, especially in the case of EOD(MOR) disks. Birefringence has no importance for glass substrates (glass does not exhibit any significant birefringence) and is only a subordinate factor for polymeric protective layers of aluminum substrates because of their reflective read/write technique. 

Pure aluminum is soft, light, and malleable. It is the most common metal in the Earth s crust (ca. 8 %). Small amounts of Cu or Mg additives make it hard and firm. The surface is passivated with an oxide layer. Produced by fused-salt molten flux electrolysis. Cannot be welded, but is nevertheless optimal for airplanes (in which case it is riveted), construction units (windows, frames), and utensils such as cans, foil, and tubes. Increasingly found in cars in order to minimize weight. Tiny holes are burnt into extremely thin aluminum films in data-storage units. It has no function in physiology, but Al ions in the bloodstream can be detrimental. 

Data storage and access This is the database access layer along with a logical layer above it to coordinate shared access to the data. 

The fully chlorinated copper phthalocyanine is used as precursor for the synthesis of IR-absorbers, applied in optical recording layers for data storage [27],... 

Several lanthanide metals can be found in certain types of magnetic data storage disks for computers. Gadolinium, terbium, and dysprosium are among the elements often sandwiched with iron and cobalt in thin layers to make these devices. 

Optical data storage media fall into three main classes [26] (Figure 6.9). Read only media comprise the CD in its audio and CD-ROM formats and DVD, also of the CD format but having about six to ten times the data capacity of a CD-ROM, depending upon whether one or two recording layers are used. These read only media are mainly dedicated to entertainment. As seen from Figure 6.9, the systems which use organic dyes are WORM (write-once-read-many), CD-R, and DVD-R. 

Dithiolene complexes, and more specifically the nickel derivatives, are involved in materials used for optical data storage, such as compact disc or laser disc read-only memory (CD- or LD-ROM), and also in copiers or photography related devices. In the latter case, it is the IR-absorbing property that is exploited. Some of these compounds can be found in reviews by Mueller-Westerhoff et al. (353, 354). Recent patents are given as examples in references (458—481). In the field of optical storage, short reviews were published in 1988 (482) and 1990 (362, 483). Here, the dithiolene complexes act as inhibitors of the laser-induced fading of the colored thin layers of the optical discs. They also act as an antioxidant and increase the photostability of the cyanine dyes that constitute the recording layer. Contrary to what was observed for the two... 

The features of InChl make it usable as a unique identifier of a molecular structure as well as a format for data storage (with limitations implied by its design, such as the absence of atom coordinates and charge localization, or delocalization of hydrogen atoms, which makes it impossible to distinguish between individual tautomeric forms without the presence of the fixed hydrogen layer). 

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