Optical discs

G. Bouwhuis, Prindples of Optical Disc Systems, Adam Hdgei, Bristol, U.K, 1985. 

In the computer industry, new read/write optical discs, capable of storing over 250 megabytes, utilize a thin coating consisting of a germanium, teUurium, and antimony compound (see Imaging TECHNOLOGY). 

At about four months gestation, mesenchymal cells emanating from the central hyaloid vessel at the optic disc invade the inner layers of the retina. These endothelial complexes develop into capillaries as vascularization proceeds anteriorly in all directions towards the ora serrata from the optic nerve. As this progresses, so the embryonic hyaloid vessels in the vitreous undeigo regression. These retinal vessels do not, however, reach the most anterior portion of the retina until 8 months gestation and the anterior temporal retinal periphery, ferthest removed from the optic nerve, is not vascularized until about full term (Flower and Patz, 1971). 

Optic nerve head (optic disc) cupping. 

Roth spots are rarely occurring (in less than 5% of IE cases), oval-shaped retinal hemorrhages with a pale center near the optic disc (Fig. 71-3D). 

Papilledema Edema of the optic disc typically associated with increased intracranial pressure. 

L A 50-year-old male ls seen in the emergency department (ED) with a blood pressure of 260/160 mmHg. Blurring optic discs with indistinct margins are seen on ophthalmologic examination. An intravenous drip of sodium nitroprusside is administered. What is the mechanism of action of sodium nitroprusside ... 

Arsenic acid Dietary levels of 350 mg/kg resulted in blindness and optic disc 6... 

Photopolymerization and photocrosslinking processes have been in use for many years in the electronics industry, for example in the making of printed circuit boards and in the fixation of color dots in TV tubes. More recent applications of light-induced chain crosslinking polymerization processes are the replication of optical discs (1,2) of aspherical lenses (3,4) and the in-line coating of optical fibers (5,6). 

Other fundus c/ anges - Attenuation of retinal arterioles fine granular pigmentary disturbances in the peripheral retina optic disc pallor and atrophy prominent choroidal patterns in advanced stage. 

Blurring of vision, hyperemia of optic disc and blindness. 

Kaida et al. (1,2) prepared optically anisotropic polymerizable liquid-crystal derivatives, (I) and (II), respectively, containing internal esters that were used in optical disc applications. 

A case of bilateral optic disc edema has been described (22). 

Stewart O, Walsh L, Pande M. Bilateral optic disc oedema associated with latanoprost. Br J Ophthalmol 1999 83(9) 1092-3. 

Of 199 patients, 16 developed significant worsening of retinopathy, including neovascularization, over 12 weeks 12 of the 16 had optic disc swelling, which necessitated laser therapy in three of them (3). This was mostly seen in patients using a high dose of IGF-I, but a longterm effect of low-dose IGF-I could not be excluded either. 

The excellent insulating and dielectric properties of BN combined with the high thermal conductivity make this material suitable for a huge variety of applications in the electronic industry [142]. BN is used as substrate for semiconductor parts, as windows in microwave apparatus, as insulator layers for MISFET semiconductors, for optical and magneto-optical recording media, and for optical disc memories. BN is often used as a boron dopant source for semiconductors. Electrochemical applications include the use as a carrier material for catalysts in fuel cells, electrodes in molten salt fuel cells, seals in batteries, and BN coated membranes in electrolysis cells for manufacture of rare earth metals [143-145]. 

The mechanism of WORM recording and indeed of all currently available optical disc media, whether erasible or write-once, depends upon the heat generated by a focused laser beam impinging on an absorbing medium. The energy, normally near-IR radiation, is transmitted to the absorbing material in a time much shorter than the time it takes for the heat generated to dissipate by thermal conduction. 

DVD Digital Video Disc, a high-capacity optical disc commonly used for storing movies or other video records. 

The larger proportion of archival and modern information is stored on materials with a limited life expectancy. These materials Include, paper, film, magnetic tape and optical disc. Paper, the major storage medium to date, is known to become brittle and discoloured with increasing age. This is particularly true of paper manufactured since the 1850 s. 

Theory of the transient photocurrent behaviour at the ORDE. The stationary optical disc electrode is assumed to be uniformly illuminated by parallel light which is switched on at time t = 0, and which produces a measurable concentration of photogenerated electrons on the particles denoted by c. The differential equation for the generation and transport of these electrons to the electrode surface, with concurrent homogeneous back reaction is set up with the following assumptions. 

Fig. 9.13. Typical light-on current time transient for colloidal CdS ([CdS] = Smolm 3) at a stationary optical disc electrode.

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... 

Pioneer Corp. of Japan has used PLA as a replacement for polycarbonate to manufacture an optical disc. 

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