Artifacts radiation-caused

The most important modem system of units is the SI system, which is based around seven primary units time (second, abbreviated s), length (meter, m), temperature (Kelvin, K), mass (kilogram, kg), amount of substance (mole, mol), current (Amperes, A) and luminous intensity (candela, cd). The candela is mainly important for characterizing radiation sources such as light bulbs. Physical artifacts such as the platinum-iridium bar mentioned above no longer define most of the primary units. Instead, most of the definitions rely on fundamental physical properties, which are more readily reproduced. For example, the second is defined in terms of the frequency of microwave radiation that causes atoms of the isotope cesium-133 to absorb energy. This frequency is defined to be 9,192,631,770 cycles per second (Hertz) —in other words, an instrument which counts 9,192,631,770 cycles of this wave will have measured exactly one second. Commercially available cesium clocks use this principle, and are accurate to a few parts in 1014. 

The simple backprojection has the problem of star pattern artifacts (Fig. 4.1a) caused by shining through radiations from adjacent areas of... 

Loss of crystallinity causes all diffraction contrast features in the TEM image to fade away. Moire fringes, lattice fringes, bend contours and the like will all lose contrast during irradiation [118]. Features that depend on orientation such as bend contours or dislocation strain field images will become smeared out, as directions in imperfect or very small crystals are less well defined (the reciprocal lattice spot increases in size). During irradiation, new contrast features -radiation artifacts - can appear temporarily and then fade with the rest. 

KBr pellets can be obtained by removing bound water at 110 °C for 2-3 h. [11]. Spectral enhancements have also been obtained by using photoacoustic FTIR methods, where IR radiation absorbed by analyte is detected as an acoustic wave generated in an inert gas in contact with the sample. PA-FTIR spectra of resin beads were found to be free of baseline artifacts caused by light scattering and sample inhomogeniety in typical FTIR experiments [12]. 

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