Mass storage, computer data

The main interest in this book is the use of laser addressable dyes in optical data recording, specifically WORM (write once read many times) used in the industrial and institutional arena for the mass storage of data, and CD-R used in smaller scale computing, educational and entertainment outlets. 

Data curves together with all associated parameters are stored on mass storage media. At retrieval, the stored curves and the related parameter are loaded and can be modified. After retrieval, (I) data can be plotted as multiple kinetic curves, and each individual curve, can be the average of several stored experiments, (2) spectra can be constructed at selected times from a file of kinetic curves recorded at various wavelengths, (3) computer simulation can be carried out and compared immediately with the kinetic data, as discussed below. 

Magnetic tapes These are low-speed mass storage devices with significant capacity (10 to 20 million words). They are seldomly found on process control computers and they are used to store off-line large programs and large amounts of data. 

The current practice is to rely on minicomputers with more efficient programs and faster mass storage devices to speed up the data handling and processing. (There is not much we can do about data acquisition.) Since, if the 2-D experiment is performed in any detail, the computation (and plotting) time could take many hours even with a modern minicomputer, we should rethink about how the experiments should be performed. Basically, we are back to the pre-FFT situation when it was unthinkable to do an on-line FT experiment. We believe that it makes much sense to process 2-D NMR data offline on large computers designed for ultra fast computations and let the minicomputer concentrate on data acquisition. 

The interpretation of spectroscopic data for the identification and structure elucidation of organic compounds is largely an empirical process and relies heavily on the use of previously accumulated reference data. Compilation of computer-readable spectroscopic data bases is nowadays feasible because most commercially available spectrometers have small built-in computers for the digital acquisition of measured spectroscopic data they are also equipped with a suitable mass storage device to store spectra or selected spectral data, or they provide the facility to transfer the recorded spectra to a more powerful external computer. If the computer-readable spectroscopic data are suitably organized, the analyst is provided with a very powerful tool for the identification of a compound, a group of compounds or a structure by means of suitable software, thereby avoiding the slow and tedious manual work otherwise involved [67,69]. 

Since deadtimes in this type of spectrometer are quite long ( 60 fis), the system must normally operate with deadtime losses in the 10 to 60% range. Consequently, most multichannel analyzers are equipped with an electronic means of deadtime correction, such that the observed spectrum represents the true number of photons arriving at the detector during the period of data accumulation. In addition to the ability to display the spectrum on a cathode-ray tube or television monitor, the analyzer can usually drive an X-Y plotter to produce a permanent copy. Alternatively, the contents of the analyzer memory can be printed as the number of counts in each channel, listed by channel number. Most quantitative fluorescence spectrometers include a personal computer with approximately 2-6 megabytes of memory plus some form of mass storage. In such a system the computer may control specimen presentation, the excitation conditions, and data accumulation in the multichannel analyzer. At the end of data acquisition for each specimen the computer analyzes the spectrum in the multichannel analyzer, computes the raw element intensities, corrects for interelement effects, and computes the concentration of each element. 

The amount of acquired data on the computer is limited by its memory capacity, as well as the capacity of its mass storage media. A normal microcomputer has a hard disk of around 200 MBytes. Assum-... 

The computer performs under control of a real time executive system that selects the specific application program required for the task to be performed. The application program, in turn, controls the GC-MS system via the interface and communicates with the user via the terminal concerning the experimental analysis to be performed. The disc memory is used for mass storage of application programs and experimental data. The results are printed on the user terminal. The electrostatic printer plotter permits optional graphical display of the data and results. 

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