Scan process

Double-beam spectrophotometers. Most modern general-purpose ultraviolet/ visible spectrophotometers are double-beam instruments which cover the range between about 200 and 800 nm by a continuous automatic scanning process producing the spectrum as a pen trace on calibrated chart paper. 

Quadrupole mass spectrometers has been used mainly in CE—MS because they can be obtained at relatively low cost, possess small dimensions, and are easy to operate. As previously mentioned, the scanning process is relatively slow and allows operation of only a small fraction of the available ions, which is not suitable with very narrow CE peaks. The use of selected ion monitoring (SIM) mode greatly improves sensitivity and duty cycle, but it is not always appropriate for the detection of complex mixtures. This kind of analyzer is currently used as a low-resolution instrument and for quantitative determination. 

Fig. 1. 55. The function of eIF-2 in eucaryotic translation. eIF-2, the initiator protein for the translation is a regulatory GTPase that occurs in an active GTP-form and in an inactive GDP form (see ch. 5). The active eIF-2 GTP forms a complex with the initiator-tRNA, fMet-tRNA "" and the 40S subunit of the ribosome. This complex binds to the cap structure of mRNA to initiate the scanning process. eIF-2 undergoes an activation cycle typical for regulatory GTPases the inactive eIF-2 GDP fom is activated with the assistance of the eIF-2B protein into the active elF-2 GTP form. eIF-2B acts as a G-nucleotide exchange factor in the cycle (see ch. 5).

It is therefore frequently difficult to find punctual areas in the sample having a sufficient concentration of the desired analyte to be detected by the x-ray microanalysis system. Thus, identification and eventually quantitation of metals in dec-orative/protective layers of pictorial samples by SEM/EDX frequently require an accurate and often time-consuming scanning process. 

Data acquisition is actually a scanning process that converts the analog gel image into a digital image with the aid of computer-based techniques. 

Figure 18.12 Sketch of the PFM scanning process using a metal coated tip where the metal is partly removed, (a) As a result only the grain edges contribute to the PFM image, (b) An asymmetrical tip wear leads to an asymmetrical piezoresponse image.

The technique is called a scanning process because the beam of electrons are carefully directed across the sample until all the sample has been scanned. The analysis of all the radiation emitted is computed and a two-dimensional image is created either on a screen like a television screen or on a photographic plate. One disadvantage of this technique is that for nonconductors of electricity the sample has... 

The main purpose of developing the AMT system is to treat large substrate surfaces via a scanning process. In order to investigate the effectiveness of AMT plasma treatment of large substrate surfaces, large CRS panels of 17.8 cm x 17.8 cm and 25.4 cm X 25.4 cm were used as the substrate. The experimental results are shown in Figures 17.35 and 17.36. 

Once you start SCANDISK, you start the scanning process by selecting the type of scan you want to perform (Standard or Thorough) and clicking Start. 

Through the automation of the scanning process the method has become more rational and more reliable. New possibilities of evaluation and documentation result from connection to a computer. 

The most common analytical techniques used in (S)TEM are EDS and EELS. The combination of STEM and EDS and/or EELS can be used to analyze the specimen locally when stopping the scan process, the electron probe can be positioned at the point of interest. 

Fig. 10.7. Scanning process The surface is imaged line by line. While the tip continuously follows the surface, the measurement is taken at the positions denoted by black circles.

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