Detection and measurement

Geiger counter A device used to detect and measure amounts of radioactivity. 

For trace quantities of less than 100 ppm, the most successful method — and the most costly— is neutron activation. The sample is subjected to neutron bombardment in an accelerator where oxygen 16 is converted to unstable nitrogen 16 having a half-life of seven seconds. This is accompanied by emission of (J and 7 rays which are detected and measured. Oxygen concentrations as low as 10 ppm can be detected. At such levels, the problem is to find an acceptable blank sample. 

Chemiluminescence has been studied extensively (2) for several reasons (/) chemiexcitation relates to fundamental molecular interactions and transformations and its study provides access to basic elements of reaction mechanisms and molecular properties (2) efficient chemiluminescence can provide an emergency or portable light source (J) chemiluminescence provides means to detect and measure trace elements and pollutants for environmental control, or clinically important substances (eg, metaboHtes, specific proteins, cancer markers, hormones, DNA) and (4) classification of the hioluminescent relationship between different organisms defines their biological relationship and pattern of evolution. 

R. A. Smith, F. E. Jones, and R. P. Chasmar, The Detection and Measurement of Infrared Kadiation Oxford University Press, London, 1968. 

G. E. KnoU, Kadiation detection and Measurement 2nd ed., John Wiley Sons, Inc., New York, 1989. 

The complete description of the number of Auger electrons that are detected in the energy distribution of electrons coming from a surface under bombardment by a primary electron beam contains many factors. They can be separated into contributions from four basic processes, the creation of inner shell vacancies in atoms of the sample, the emission of electrons as a result of Auger processes resulting from these inner shell vacancies, the transport of those electrons out of the sample, and the detection and measurement of the energy distribution of the electrons coming from the sample. 

BS 50054 Electrical apparatus for the detection and measurement of combustible gases. General requirements and test methods Various... 

BS EN 45544 Electrical apparatus for the direct detection and measurement of toxic gases and vapours ... 

Cullis, C.R, and Firth, J.G. (ed.) (1988) Detection and Measurement of Hazardous Gases, Hememann, London. Daugherty, J., (1997) Assessment of Chemical Exposures Calculation Methods for Environmental Professionals, Lewis Publishing, London. 

Much of the biological work with colchicine in recent years has lain in its use to detect and measure certain types of cellular activity, and in the study of the effects it produces when applied to growing plants. 

Much of the study of kinetics constitutes a study of catalysis. The first goal is the determination of the rate equation, and examples have been given in Chapters 2 and 3, particularly Section 3.3, Model Building. The subsection following this one describes the dependence of rates on pH, and most of this dependence can be ascribed to acid—base catalysis. Here we treat a very simple but widely applicable method for the detection and measurement of general acid-base or nucleophilic catalysis. We consider aqueous solutions where the pH and p/f concepts are well understood, but similar methods can be applied in nonaqueous media. 

These use crystalline materials in which the electrical properties of the material are changed when it undergoes slight deformation by, for example, the application of mechanical pressure. The principal effect is to cause a change in the frequency at which the material resonates. This change in resonant frequency can be detected and measured, so giving an indication of the change in pressure. 

Nitration results from fuel combustion in engines. The products formed are highly acidic and they may leave deposits in combustion areas. Nitration will accelerate oil oxidation. Infrared analysis is used to detect and measure nitration products. 

While ideally structures should be designed and fabricated so that environment-sensitive cracking is avoided, in practice it is sometimes necessary to live with the problem. This implies an ability to detect and measure the size of cracks before they reach the critical size that may result in catastrophic failure. Such inspection has important implications for plant design, which should be such as to allow inspection at relevant locations. The latter are regions of high residual stress (welded, bolted or riveted joints) and regions of geometrical discontinuity (notches, crevices, etc.) where stress or environment concentration may occur. 

A note on the assays of coelenterazine and luciferase activity. The methods for measuring coelenterazine and the corresponding luciferases are given in Appendix C5. Special attention must be paid to the fact that coelenterazine in aqueous buffer solutions spontaneously emits a low level of chemiluminescence in the absence of any luciferase, which is greatly enhanced by the presence of various substances, including egg yolk, BSA and various surfactants (especially, hexadecyltrimethylammonium bromide). Therefore, the utmost care must be taken in the detection and measurement of a low level of... 

Coelenterazine can be detected and measured with a coelenterazine luciferase, i.e. a luciferase specific to coelenterazine. As the coelenterazine luciferase, the luciferases from the sea pansy Renilla and the copepods Gaussia and Pleuromamma are commercially available. Certain kinds of decapod shrimps, such as Oplophoms and Heterocarpus, contain a large amount of luciferase, and the luciferases purified from them are most satisfactory for the assay of coelenterazine considering their high activities and high quantum yields. Even partially purified preparations of these luciferases are satisfactory for most measurements. The author routinely uses purified Oplophoms luciferase. 

The amount of Cypridina luciferase is measured with Cypridina luciferin. However, the detection and measurement of a trace amount of the luciferase is extremely difficult, for the reason explained below. 

Ashley, C. C., and Campbell, A. K., eds. (1979). Detection and Measurement of Free Ca2+ in Cells. Elsevier/North-Holland Biomedical Press, Amsterdam. 

Nondestructive NAA can thus be used for the detection and measurement of Ba, Sb (and also Cu) from residue samples collected from the floor surface after the single firing of a handgun. By constructing a unique distribution pattern of these residues, it is possible to establish the flight path of the bullet and the proximity of the gun with respect to the target. The development of this information, particularly in the absence of a firearm, a bullet or an eyewitness, can be of considerable value in criminal investigations... 

Microwave measurements are typically performed at frequencies between 8 and 40 Gc/s. The sensitivity with which photogenerated charge carriers can be detected in materials by microwave conductivity measurements depends on the conductivity of the materials, but it can be very high. It has been estimated that 109-1010 electronic charge carriers per cubic centimeter can be detected. Infrared radiation can, of course, also be used to detect and measure free electronic charge carriers. The sensitivity for such measurements, however, is several orders of magnitude less and has been estimated to be around 1015 electronic charge carriers per cubic centimeter.1 Microwave techniques, therefore, promise much more sensitive access to electrochemical mechanisms. 

FosterRL. 1974. Detection and measurement of ambient organophosphate pesticides. ProcAnnuInd Air Pollut Control Conf 4 66-98. 

---