Radiation artifact

In addition to these equatorial reflections, Corey and Wyckoff reported three others, at 51.0 A (faint), 81.8 A (medium), and 115 A (medium). Bear has pointed out that the central regions of the x-ray pattern given by feather rachis are confused by radiation artifacts related to the strong reflections, and that this is probably the soim e of these three large equatorial spacings. If we accept this interpretation, the equatorial reflections of feather keratin are all accounted for by our unit. 

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. 

A more complex but faster and more sensitive approach is polarization modulation (PM) IRLD. For such experiments, a photoelastic modulator is used to modulate the polarization state of the incident radiation at about 100 kHz. The detected signal is the sum of the low-frequency intensity modulation with a high-frequency modulation that depends on the orientation of the sample. After appropriate signal filtering, demodulation, and calibration [41], a dichroic difference spectrum can be directly obtained in a single scan. This improves the time resolution to 400 ms, prevents artifacts due to relaxation between measurements, and improves sensitivity for weakly oriented samples. However, structural information can be lost since individual polarized spectra are not recorded. Pezolet and coworkers have used this approach to study the deformation and relaxation in various homopolymers, copolymers, and polymer blends [15,42,43]. For instance, Figure 7 shows the relaxation curves determined in situ for miscible blends of PS and PVME [42]. The (P2) values were determined... 

V. Mazel, P. Richardin, D. Debois, D. Touboul, M. Cotte, A. Brunelle, P. Walter and O. Laprevote, Identification of ritual blood in African artifacts using ToF SIMS and synchrotron radiation microspectroscopies, Analytical Chemistry, 79, 9253 9260 (2007). 

Bigazzi, G., Ercan, T., Oddone, M., Ozdogan, M. and Yegingil, Z. (1993). Application of fission track dating to archaeometry provenance studies of prehistoric obsidian artifacts. Nuclear Tracks and Radiation Measurements 22 757-762. 

Even more elegantly, the local resolution is improved by irradiation with very intense focused femtosecond laser pulses outside the absorption range of the fluoro-phore (e.g., in the near-infrared). The very intense focus of the laser beam—and only this—will excite the fluorophore by nonresonant two-photon absorption. Artifacts by scattered primary radiation are ruled out and the local resolution is comparable to a confocal microscope. In addition, the damage of the sample by laser light absorption is reduced to a minimum. 

M. H. Miles and B. F. Bush, Radiation measurements at China Lake Real or artifacts Proc. ICCF-7 (7th Int. Conf. Cold Fusion), Vancouver, BC, Canada, April 1998, p. 101. 

Suppose that you measure the intensity of radiation from carbon-14 in an ancient piece of wood to be 6 percent of what it would be in a freshly cut piece of wood. How old is this artifact ... 

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