Radiometric detectors

Because the spectral irradiance 1(1) enters in this definition, the correction factor is a function of total ozone (Q) and solar zenith angle (6), which are the main parameters that determine 1(1). It is obvious from (2), that /ri expresses actually the relative change in the weighted integral when the instrument s sensitivity is used as weighting function instead of the CIE, Because of the involvement of 1(1) in relative sense, 1(1) can be determined from model calculations, as far as total ozone and SZA are known. In practice, lookup tables can be constructed for each instrument, defining the correction factor fd, as functions of total ozone and SZA. These tables can be used thereafter for the conversion of the broadband detectors radiometric output to CIE weighted eiythemal irradiance. 

A large number of radiometric techniques have been developed for Pu analysis on tracer, biochemical, and environmental samples (119,120). In general the a-particles of most Pu isotopes are detected by gas-proportional, surface-barrier, or scintillation detectors. When the level of Pu is lower than 10 g/g sample, radiometric techniques must be enhanced by preliminary extraction of the Pu to concentrate the Pu and separate it from other radioisotopes (121,122). Alternatively, fission—fragment track detection can detect Pu at a level of 10 g/g sample or better (123). Chemical concentration of Pu from urine, neutron irradiation in a research reactor, followed by fission track detection, can achieve a sensitivity for Pu of better than 1 mBq/L (4 X 10 g/g sample) (124). 

In order to achieve detection limits below the ng mL-1 range only amperometric, chemiluminescence, radiometric, or conventional fluorescence (CF) can be applied (Table 4.41). Fluorescence detectors are generally about 100 times more sensitive and more selective than UV detectors. The selectivity of fluorescence detection is due to the fact that only aromatic and conjugated molecules can be analysed, and by applying specific excitation and emission wavelengths the selectivity can even be increased. Pre- or postcolumn derivatisation in HPLC is a technique that is most commonly performed prior to UV absorption or fluorescence detection... 

The main goal of the Planck instrument is to improve the accuracy of the measurement of the cosmic microwave background (CMB), in order to extract cosmological parameters that remain poorly constrained after the results of WMAP (Wilkinson microwave anisotropy probe) and of the best ground-based experiments. The basic idea of HFI-Planck is to use all the information contained in the CMB radiation, i.e. to perform a radiometric measurement limited by the quantum fluctuations of the CMB radiation itself. In these conditions, the accuracy is only limited by the number of detectors and by the duration of the observation. 

The second radiometric method, proposed by Kazarinov, ° is based upon a different principle. At the beginning of an experiment, the electrode is placed far from the detector, which is situated at the bottom of the cell,... 

Spjut and his associates heated levitated microparticles and measured their temperatures radiometrically. They levitated a microparticle in a bihyperbol-oidal quadrupole, and they irradiated the particle from opposite sides by splitting a cw CO2 laser beam and directing the beams by means of mirrors to illuminate the particle symmetrically (Spjut et al., 1987). The particle temperature was measured by multiple-color pyrometry (Spjut, 1987 Spjut and Bolsaitis, 1987) using narrow-band infrared detectors. The temperature... 

Traditional exploration for sandstone-type uranium deposits has centered on genetic models and radiometric methods (Morse 1969 Harshman 1970 Rubin 1970). However, these methods have become prohibitive for sandstone-type uranium deposits hidden at a depth of hundreds of metres (Riese et al. 1978). Radioactivity detectors are ineffective in regions where there is a relatively thin inactive overburden (Bowie etal. 1970). 

All methods of radiometric analysis involve, of course, the use. of various radiation detection devices, The devices available for measuring radioactivity will vary with the types of radiations emitted by the radioisotope and the kinds of radioactive material. Ionization chambers are used for gases Geiger-Miiller and proportional counters for solids liquid scintillation counters for liquids and solutions and solid crystal or semi-conductor detector scintillation counters for liquids and solids emitting high-energy radiations. Each device can be adopted to detect and measure radioactive material in another state, e.g., solids can be assayed in an ionization chamber. The radiations interact with the detector to produce a signal,... 

In principle, there are two ways to achieve the radiometric calibration of an instrument measuring solar radiation. The first is by comparison to a standard radiation source of known output and the second by comparison to a prototype standard instrument that is capable in measuring the same radiometric quantity. The fist can be applied to broadband detectors only if their spectral response over the whole range of the radiation source is known with sufficient accuracy. The second method requires that the standard instrument has exactly the same spectral response, which is rather unlikely to occur. 

Following the determination of the radiometric calibration of a detector, an additional step is required to achieve its calibration for the erythema response (CIE). Due to manufacturing limitations, the spectral sensitivity of broadband detectors deviates form the CIE biological action spectrum. Therefore, die requirement for a correction factor to enable the simulation of the CIE weighted irradiance by any of those commercial... 

The target acquisition system is likely to use an IR detector tuned to the typical emission spectrum of armored vehicles. It is understood, however, that a mm-band radiometric correlator is also being considered, the latter having the advantage of being less affected by environmental conditions than an IR system... 

Laser-induced fluorescence (LIF) has also been utilized as a highly sensitive detection principle for CE [48-51]. However, while the LIF detector is now able to achieve zeptomole (10 21) detection limits, conventional derivatization techniques are inefficient at these exceptional levels [52]. Also, CE has successfully been coupled with mass spectrometry (MS) [53], nuclear magnetic resonance (NMR) [54, 55], near-infrared fluorescence (NIRF) [56, 57], radiometric [58], flame photometric [59], absorption imaging [60], and electrochemical (conductivity, amperometric, and potentiometry) [61-63] detectors. A general overview of the main detection methods is shown is Table 1 [64]. 

Metabolite identification can be conducted on several levels, ranging from straightforward analyses for targeted species to more complex analyses utilizing radiometric detection, MS, and possibly other detectors. A process flow for profiling and characterization of metabolites by LC-MS is presented in Fig. 1.34. There is an increasing emphasis on quality metabolite data from relatively early in discovery (Fernandez-Metzler et al., 1999), and some of the fundamental approaches that can be used have been summarized by Anari and Baillie (2005). 

In this radiometric detection approach, the detection limit could be lowered by using a stopped-flow procedure that captured 89% of the eluted "Tc within a 2.5-mL flow-through counting cell. Continuous-flow and stopped-flow detector traces are... 

Three variants of one protocol are used to separate 17a-hydroxypregneno-lone and its metabolites, 17 cr-hydroxyprogesterone and its metabolites, and pregnenolone and its metabolites. The compounds have been separated on a silica gel column using a THF-hexane mobile phase in conjunction with a Flo-One Model HS radiometric detector from Radiomatic Instruments. 

Detectors are a very important element of radiometric measuring instrumentation and are used to measure activity based on the ionizing process in gases, liquids, and solids. The following detectors are used to measure ionizing radiation [5] ... 

The name quantum detector is given to a radiometric detector having equal or near equal response over the entire range to be measured, UV or VIS and calibrated in quantum units. As is the case for all meters, they may be calibrated for any... 

A radiometer is an electronic measuring device which when coupled to a proper sensing device, e.g., flat response radiometric detectors (quantum) and calibrated, measures most accurately the quantity of incident radiation falling on its sensor. These instruments are available for both the UV or VIS ranges. 

The flame ionization detector (FID), which, for fluorinated compounds, has the advantage of a greater linearity range in spite of its lower sensitivity in comparison with the electron capture detector (BCD), has been extensively applied to organic metal chelates in particular. Comparisons of the different detectors were carried out (Table 1.2) For special analyses such as the determination of SO2 by reaction to SO2F2 with the radioactive F-isotope or by utilization of H-labelled 3-diketon-ates, radiometric measurements for detection are employed ... 

Skin Keratin adducts Alkaline hydrolysis, derivatization LC/radiometric detector Not reported Noort et al. (2000a)... 

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