CSI Collecting

Holloway, E. (2014). Complex specified information (CSI) collecting. In J. Bartlett, D. Halsmer, M. R. Hall (Eds.), Engineering and the ultimate (pp. 153-166). Broken Arrow, OK Blyth Institute Press. 

Selective excitation is an efficient method of data collection for samples in which the value of the relaxation time (TRc j) is less than three times the T value of the sample. The smallest possible value of 77 eff is given by n times the data acquisition time for each sample, where n is the number of coils. In cases where very high spectral resolution is required, a large number of coils are used, and/or where the samples have short T values, this method may be of limited use. The use of multiple receivers interfaced with a number of arrays, each containing a smaller number of coils, can potentially overcome this limitation. Alternatively, a one-dimensional CSI method can be used, with the proviso of losses in S/N or potentially longer acquisition times, as mentioned earlier. 

We are here attempting to distinguish between two distinct types of event with different pulse shape characteristics. The first is a scintillation event in the CsI(Tl) crystal, for which a typical yield wiU give 52,000 optical photons per MeV energy deposit. When combined with the light collection and photodiode quantum efficiencies, this gives an overall conversion efficiency (OCE) of - 40 electrons/keV. The temporal decay of light from Csl... 

To evaluate the performance of the detector, 15000 events were collected in the CsI(Tl)-PD detector while it was simultaneously illuminated with Am and Na sources giving lines at 60, 511 and 1275 keV. At the same time a reference spectrum was collected with a standard Nal(Tl)-photomultiplier system. The pulse-shape spectrum for the raw events is shown in Figure 2. Two clear peaks are seen, easily distinguishing the fast events from the silicon and the slower scintillation events. The rise-time spectrum for the Si events is distorted as the readout system was too slow to accurately determine the rise-times of the fastest events. 

GC was introduced very early as the technique of choice for the detection and identification of accelerants in debris from arson cases because of its high selectivity and sensitivity. But to use the full potential of the technique the methods of recovery of traces of common accelerants from fire debris had to be developed and adjusted. The used methods include solvent extraction, direct headspace analysis, and enrichment by adsorbent-based techniques. In the past, the most common concentration steps prior to the analysis have been (heated) headspace direct injection using a gastight syringe for analyte collection and GC injection or headspace adsorption techniques, mostly using charcoal followed by carbon disulfide (CSi) elution. Some of these procedures have been quite effective and are standardized by... 

A study of this type of a plastic waste has been performed at CSI using samples that came from two different experimental collection systems, the first in plastic boxes (internal volume 3 m ), and the second in arranged plastic areas inside... 

When I wrote the first edition of this book in 1994 the use of infrared miCTOscopy in forensic science was new. Since then the proliferation of CSI -type TV shows has plaeed forensic science, and to a point infrared microscopy, squarely in the public eye. This is appropriate since there are many real-world applications of infrared microscopy in forensic science. One application is the analysis of hair and clothing fibers collected at crime scenes, which may lead to someone s arrest. The spectrum of one of the author s hairs (NOT from a crime seene) measured with a micro-ATR accessory is shown in Figure 6.10. 

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