Field detection

M. D. Bingham, Field Detection and Implications of Mercury in Natural Gas, Soc. Petrol Engrs. Production Engrg, 120—124 (May, 1990). 

Distributions of pesticide concentrations in potential food items for avian species are required to estimate the contribution of food to exposure of birds in different regions where the test chemical may be used. On treated fields, detectable CEF residues were found in 102 of 207 earthworm samples. No earthworm samples collected from control fields (N = 28) contained detectable CEF. Average CEF concentrations in earthworms reached maxima 1-4 days post-application (Table 3). Mean CEF residues in earthworms fell below 0.1 qg g after 8 days post-application. This... 

Snyder, A. P Maswadeh, W. M. Parsons, J. A. Tripathi, A. Meuzelaar, H. L. C. Dworzanski, J. P. Kim, M. G. Field detection of Bacillus spore aerosols with standalone pyrolysis-gas chromatography-ion mobility spectrometry. Field Anal. Chem. Technol. 1999, 3, 315-326. 

A novel concept for colorimetric field detection ofpolynitroaromatic explosives was described by Arbuthnot et al. It is based on colorimetric changes that occur... 

Detection of TATP in the field has been problematic. Technologies have been developed that focus on the peroxide group. Of these tests, the most commonly available are field detection kits that rely on color changes brought on by chemical reactions. Mistral s PDK (Peroxide Detection Kit) offers chemical screening... 

FIGURE 9.2 Sketch of far-field detection of CARS waves generated in the focal volume. The figure shows the yz cross-section of the excitation volume. O is the origin of the coordinate system and also the center of the focal volume and O is a far-field point on the optical axis. The coordinates of the points in the near-field are represented by (x,y,z) and those of the points in the far-field by (X,Y,Z) in cartesian coordinate system. The outgoing arrows around the near-field points represent the CARS waves generated in the focal volume. The incoming arrows at the far-field points represent the contributions from the individual points in the focal volume. 

Solving these gas and vapor detection problems will require a variety of new sensors, sensor systems, and instruments. Field detection of airborne chemicals can be somewhat arbitrarily divided into three distinct situations. The first case is when a spill or leak results in a single compound occurring in air far in excess of its background concentration. The second case is when one or several trace constituent(s) occur in a complex background ("needle-in-the-haystack" problem). The third case is when a complete analysis is needed for all minor as well as major constituents of a complex mixture. The first case is the one specifically addressed by the approaches discussed in this review article. The second and... 

The presented examples of recent achievements in immunosensor development show the tremendous progress in this field. Detection limits lower continuously, miniaturized setups by keeping the possibility of automated production progressed, and procedures for detection are constantly simplified. Direct immobilization of the receptor antibody by photochemical reactions enables the production of ready to use immunosensors in few steps. With photovoltaic components, time consuming and expensive labeling procedures of the analyte can be avoided. 

For almost 20 years, the optical waveguide sensor has been used for the label-free, evanescent-field detection of chemical or biological reactions taking place in the close vicinity of the waveguide surface. This includes numerous applications within the fields of chemical and biological sensing, where in... 

The magnetic ordering was also monitored via 57Fe Mossbauer spectra at 4.2 and 295 K. The four crystallographically independent iron sites could be distinguished in the Mossbauer spectra. The isomer shifts at 4.2 and 295 K are similar for the four iron sites. As expected, the hyperfine fields detected at the iron nuclei are about 20% larger at 4.2 K. They range between 23.5 and 36.3 T. 

Faraday detection as described in Section 3.1., is the traditional method for recording NQR signals. As discussed earlier, Faraday detection sensitivity is limited by the detector s own thermal noise. The desire for improved detection sensitivity has driven the search for non-traditional methods and lower noise Faraday methods of RF magnetic field detection. In this section, several methods that have been applied to NQR signal detection will be discussed. 

J. Yinon, Field detection and monitoring explosives, Trends in Analytical Chemistry, 21... 

At the beginning of the Triad field investigation, only the uppermost two 1 -ft intervals at each location were analyzed in the field. Ultraviolet fluorescence test kits, which require 5 min per sample for collection and analysis, were used for field detection of PAH and TPH at all sampling locations. A percentage of the PAH and TPH samples were sent to an off-site laboratory for independent collaboration of the field results. 

There are two approaches which enhance observation of 1-2 nm supported metal crystallites. One is annular dark field or Z-con-trast detection (16) and the other is called axial dark field (17). These techniques can be easily utilized for simple catalyst compositions. The annular dark field detection method analyzes elastically scattered electrons at wide angles from the central beam. The scattering angle is a function of atomic number. Consequently, elements such as platinum are effectively observed in low atomic number supports such as Al203 or Si02 (18). The method is also effective in detecting larger crystallites in support particles... 

Kirschvink, J.L., and Gould, J.L., Biogenic magnetite as a basis for magnetic field detection in animals. Biosystems, 13, 181, 1981. 

Single Enzyme Experiments with Wide Field Detection Schemes... 

Only one well contained O2 greater than the field detection limit of 0.05 mg/L... 

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