Bulk detection

To give an example both sensitivity coefficients are evaluated for the current sensor (see Sect. 10.3 for details). For the bulk detection of glucose this results in A bulk (rad) = 5.6 x 102 AC (g/ml), whereas for the adsorption of proteins on the sensor surface the overall sensitivity of the sensor is evaluated as A< >layer (rad) = 2.0 x 10 5 Am/A (fg/mm2). Measuring the phase change A< >,-, between any of the two channels i and j can thus give an estimation on the change in analyte concentrations between those two channels. If one channel (e.g., channel N) is used as a reference channel, then ACV = 0 and AmN = 0 and absolute analyte concentrations can be determined. 

Instrumentation for revealing the presence of bulk quantities of concealed drugs will differ from those developed to find evidence of minute quantities on surfaces. Bulk detection is concerned with amounts ranging from grams to kilograms [4], Bulk detection is done by manual inspection, X-ray, CT scans, and acoustic inspection. X-ray or CT scanners used as bulk detectors have sensitivity of 2-10 g, and suspect items are subsequently confirmed by chemical analysis. Hand-held acoustic inspection instruments such as the Acoustic Inspection Device (AID) and the Ultrasonic Pulse Echo (UPE) developed by Pacific Northwest National Laboratories/Battelle, can be used for analysis of cargo liquids in sealed containers of various sizes within seconds [5]. The acoustical velocity and attenuation of multiple echoes returned to the instrument is evaluated by software which compares the data to the shipping manifest. 

The functional components of a bomb are a control system, detonator, booster, and a main charge. Such threats can often be recognized from their shape. These can be viewed as bulk detection issues, historically addressed by imaging techniques such as sight or touch. Other threats may take no particular physical form and can only be recognized by their chemical composition. These are often trace detection issues, historically detected by the sense of taste or smell. 

In the congressional research service (CRS) report for the USA Congress (2005), Shea and Morgan [75] included chemical luminescence as one of the trace detection techniques for aviation security. They point out that bulk detection of explosives on airline passengers is of interest and that these systems detect only bulk quantities of explosives, so they would not raise nuisance alarms on passengers who have recently handled explosives for innocuous reasons. They also mention that trace detection techniques would also detect bulk quantities of explosives and may raise security concerns about passengers who have been in contact with explosives. 

Integration of mass spectrometry with other technologies, i.e., bulk detection systems, would greatly enhance the detection capabilities of such integrated systems. 

It is an empirical finding that the diffraction patterns of many organic explosives display prominent diffraction peaks that lend themselves to material identification [13]. XDI is sensitive to a wide range of explosives, and its low false-alarm rate (FAR) when confronted with the harmless materials that comprise the vast majority of suitcase contents is unsurpassed by alternative bulk detection techniques. 

Trace portals could also be used for bulk detection because of the likelihood that a mass of explosive concealed on the person would present an adequate chemical signature. The combination of a trace and anomaly portal would provide a powerful multi-sensor platform that would offset the limitations of the individual technologies. Currently, a commercially available multi-sensor explosives detection personnel portal that combines trace and anomaly methods does not exist. 

The book includes several chapters on vapor and trace detection chemiluminescence, mass spectrometry, ion mobility spectrometry, electrochemical methods, and micro mechanical sensors, such as microcantilevers. Other chapters deal with bulk detection techniques neutron techniques, nuclear quadrupole resonance, X-ray diffraction imaging, millimeter-wave imaging, terahertz imaging, and laser techniques. Special chapters are devoted to personnel portals and to biological detection. 

M. Krausa in H. Schubert and A. Kuznetsov, Bulk Detection of Explosives Advanced techniques against Terrorism , NATO Sciences Series, in press. http //www.lennartz-electronic.de/Pages/MOSES/MOSES home e.html... 

Energy of radio frequency absorption Information depth Bulk Detectability >1%... 

Liquid explosives are a novel threat that has been of particular interest since August 2006, when British poliee disrupted a plot to bomb aircraft using liquids. The DHS is evaluating technologies to detect liquid explosives. Its efforts are mainly focused on bulk detection, such as scanners to test the contents of bottles. Like solid explosives, however, liquids might be found through trace detection, if the trace detection system is designed to look for them. 

While bulk detection of dyes is suggestive of filtration and elucidates renal function, imaging the distribution of dyes in the kidney might provide additional insight into renal... 

DETECTION METHODOLOGY BULK DETECTION AND TRACE DETECTION... 

Two methods are primarily used to detect hidden explosives, as shown in Figure 21.1 bulk detection, which determines the existence of suspicious objects such as knives, firearms, and explosive devices from their shapes and trace detection, which detects the presence of explosive contaminants by chemical analysis of vapor from objects. 

In bulk detection, physical imaging technology, which features the use of X-rays, neutron beams, and electromagnetic waves, for example, is applied to identify explosives and explosive devices by exposing the size, shape, and weight of the suspicious object in an image. 

However, it is difficult to determine the identity of the object because the molecules of explosives consist of carbon, nitrogen, oxygen, and hydrogen, and furthermore, the elemental characteristics of the explosives are similar to those of food and common goods. Therefore, the false-positive rate of bulk detection is relatively high, namely, 10% or more. 

In trace detection, on the other hand, chemical analysis methods are applied to check for the existence of trace contamination of explosives on a passenger s body, clothes, and luggage [1]. Trace detection methods have higher selectivity capabilities than bulk detection methods, and the false-positive rate is typically below 1%. However, even if an explosive contamination is confirmed or detected on a bag or passenger, the bag or passenger may not actually be carrying the explosive device at that time. 

The bulk and trace detection methods have different characteristics, and they complement each other s weak points. Therefore, the combined use of bulk detection and trace detection is effective to improve security at important facilities. Bulk detection is a popular meliiod that has been widely used, but trace detection technologies have become increasingly necessary as security concerns have grown. For example, wiping tests for luggage using ion mobility spectroscopy or chemiluminescence detection have been implemented as part of aviation security. 

FIGURE 21.1 Detection methods for hidden explosive devices bulk detection and trace detection. 

Methods for bulk analysis and particle analysis of nuclear materials for detection of undeclared activities were described in a review article (Piksaikin et al. 2006). The bulk detection methods included radiometry (alpha, beta, and gamma spectrometry) based on the natural decay of the radionuclides, including the use of 234Th/23°Th gamma activity ratio for age determination (see detailed discussion later) and ratio that should be about 21 for undisturbed ores higher in mining... 

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