Particle Identification Methods

As already mentioned, particle identification is achieved by energy-loss measurement (the AE- E method) or by velocity measurement (TOP method). 

For ERDA arrangements using high-energy heavy projectiles, mainly gas telescope detectors, are used for AF and F measurements [3.153, 3.165, 3.166]. In an ionization 

The total energy, E, is obtained from the total charge accumulated in both sections of the anode. The second part of the ionization chamber, which measures the energy E - AE, can be replaced by an SBD [3.167], and the first part, which measures the energy loss AE, by a transmission SBD [3.168, 3.169]. When SBDs are used to measure heavy ions, radiation damage of the detector by the ions must be taken into account. 

In TOP systems, particle energies are usually determined by SBDs in addition to particle velocities being obtained with a TOP set-up which primarily measures the time needed by a particle to pass the distance between two thin foils 0.5-1 m apart [3.170, 3.171]. The first foil delivers a start signal, the second a stop signal. The stop signal can also be obtained from the SBD, but usually foils provide better timing signals. 

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Although a number of secondary minerals have been predicted to form in weathered CCB materials, few have been positively identified by physical characterization methods. Secondary phases in CCB materials may be difficult or impossible to characterize due to their low abundance and small particle size. Conventional mineral identification methods such as X-ray diffraction (XRD) analysis fail to identify secondary phases that are less than 1-5% by weight of the CCB or are X-ray amorphous. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM), coupled with energy dispersive spectroscopy (EDS), can often identify phases not seen by XRD. Additional analytical methods used to characterize trace secondary phases include infrared (IR) spectroscopy, electron microprobe (EMP) analysis, differential thermal analysis (DTA), and various synchrotron radiation techniques (e.g., micro-XRD, X-ray absorption near-eidge spectroscopy [XANES], X-ray absorption fine-structure [XAFSJ). 

Since conventional virus detection methods are not suitable for the detection and identification of single virus particles, one method allowing the anal-... 

Beside the identification of single bacterial cell or spores by means of Raman spectroscopy, the localization of these cells inside partly complex matrices has to be performed. One approach is the combination of Raman spectroscopy, fluorescence spectroscopy and digital imaging techniques. This method was applied to detect traces of endospores and other biothreat organisms even in the presence of complex environmental matrices like bioaeroso-lic background, nasal mucin [67], or tap water [68], Another fully automated device was built to analyze bioaerosols in clean room environments, where prior to the Raman identification method a particle preselection took place [69]. 

A satisfactory test for the identification of FDR on a suspected firer has been sought by forensic scientists for many years. A satisfactory test would be one that is simple, reliable, fast, inexpensive, and conclusive. Until recently efforts have concentrated mainly on the detection of inorganic components of FDR and encompass qualitative and quantitative methods, culminating in the particle analysis method, which is the most informative method currently available. A brief outline of the most important developments follows. 

The development of the particle analysis method for FDR detection and identification involved consideration of how the particles are formed and of their physical and chemical nature.170,171... 

The detection and identification of the organic constituents in FDR has the potential to be used either as a screening technique or, much more likely, as a complementary technique to the particle analysis method. The particle analysis method has proved very satisfactory and has been well tried and tested in casework and court. The objective is to devise an efficient system for organic firearm residue detection that is entirely compatible with the particle analysis method. As a suspect may need to be examined for both firearm and explosive residue the method must also be compatible with organic explosive residue detection techniques. 

The analytical methods currently used by this laboratory are chromatography (GC/TEA HPLC/PDME) for explosive residues and the particle analysis method (SEM/EDX) for FDR. The latter method involves the detection and identification of individual FDR particles therefore any sampling technique must be nondestructive. 

Bagtzoglou AC (1990) Particle-grid methods with application to reacting flows and reliable solute source identification. PhD Dissertation, University of California Irvine, p 246... 

Nonlinear System Identification Particle-Based Methods... 

Nonlinear System Identification Particle-Based Methods, Fig. 1 The unscented Kalman filter process for a two-dimensional state... 

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