Irradiation measurements, methods

PGNAA involves the measurement of the prompt y rays emitted when the nuclei first absorb the neutrons. By energy and intensity analysis of the prompt y spectrum it is possible to reveal the elements present and determine their concentrations. Because the analysis is carried out during the irradiation, the method is quicker than delayed NAA, but it needs special equipment on site at the reactor to record the y spectrum whilst the sample is being irradiated (Glascock et al. 1984, Glascock 1994). It can, however, measure some elements more efficiently than delayed NAA (e.g., Pb), since it does not require the daughter nucleus to be radioactively unstable. 

A procedure for determination of lipid hydroperoxides in human plasma is based on kinetic measurement of the CL of luminol (124) with hemin (75a) catalysis . CLD of microperoxidase-catalyzed oxidation of luminol (124) or isoluminol (190) was applied to detection and determination of amino acid hydroperoxides after exposure to UV and y-irradiation A method for determination of hydroperoxides in the phospholipids of cultured cells uses isoluminol (190) and microperoxidase as catalyst " . Simultaneous determination of phosphatidylcholine hydroperoxides and cholesteryl ester hydroperoxides in human serum is carried out by quantitative extraction of the lipids, HPLC separation by column switching and CLD using isoluminol (190) with microperoxidase catalysis . ... 

Also, the method how the ablation parameters are acquired can have a pronounced influence on the results. The ablation rate can be defined either as the depth of the ablation crater after one pulse at a given fluence, or as the slope of a linear fit of a plot of the ablation depth versus the pulse number for a given fluence. Very different ablation rates can result from the two different measurement methods. This is especially the case for materials where ablation does not start with the first pulse, but after multiple pulses, or if the ablation crater depth after one pulse is too small to be measured. The process that occurs if ablation does not start with the first laser pulse is called incubation. It is related to physical or chemical modifications of the material by the first few laser pulses, which often results in an increase of the absorption at the irradiation wavelength [32,33], for example, the formation of double bonds in poly (methylmethacrylate) (PMMA). Incubation is normally observed only for polymers with low absorption coefficients at the irradiation wavelength. 

The main application fields of dosimetry in radiation processing include installation, operational and performance qualification, and routine process control. The selection of suitable routine dosimetry systems depends on the actual measurement to be carried out. Various characteristics should be considered, such as accurate and reproducible response, dose and dose rate range, energy of radiation, environmental effects on the response, stability before, during, and after irradiation, and method of evaluation. 

In order to examine the lifetime of the colored species of 2a, 2p, and 1 more quantitatively, KBr pellets (0.5 wt %) of the three crystals were prepared and were irradiated with UV light at room temperature. A new absorption band appeared around 3,400 cm", which was assigned to the N-H stretching vibration mode of the produced trans-keto form. From the intensity change of the band, the rate constant K and lifetime t were calculated for the three crystals. The observed lifetime T values for 2a, 2p, and 1 are 17,780, and 1,200 min, respectively. Although it was reported that 1 has a lifetime of 40 d from the change of the UV reflectance spectra [29], the lifetime from the IR spectra is only 20 h. Probably the lifetime seems to depend strongly on the measurement methods. 

Webb, A.R., Kift, R., Thiel, S., Blumthaler, M. An empirical method for the conversion of spectral UV irradiance measurements to actinic flux data. Atmos. Environ. 36, 4044—4397 (2002b)... 

X-ray fluorescence A method of analysis used to identify and measure heavy elements in the presence of each other in any matrix. The sample is irradiated with a beam of primary X-rays of greater energy than the characteristic X-radiation of the elements in the sample. This results in the excitation of the heavy elements present and the emission of characteristic X-ray energies, which can be separated into individual wavelengths and measured. The technique is not suitable for use with elements of lower atomic number than calcium. 

The concentration of Ni in a new alloy is determined by a neutron activation analysis using the method of external standards. A 0.500-g sample of the alloy and a 1.000-g sample of a standard alloy known to contain 5.93% w/w Ni are irradiated with neutrons in a nuclear reactor. When irradiation is complete, the sample and standard are allowed to cool, and the gamma-ray activities are measured. Given that the activity is 1020 cpm for the sample and 3540 cpm for the standard, determine the %w/w Ni in the alloy. 

Riboflavin can be assayed by chemical, en2ymatic, and microbiological methods. The most commonly used chemical method is fluorometry, which involves the measurement of intense yeUow-green fluorescence with a maximum at 565 nm in neutral aqueous solutions. The fluorometric deterrninations of flavins can be carried out by measuring the intensity of either the natural fluorescence of flavins or the fluorescence of lumiflavin formed by the irradiation of flavin in alkaline solution (68). The later development of a laser—fluorescence technique has extended the limits of detection for riboflavin by two orders of magnitude (69,70). 

X-Ray Fluorescence (XRF) is a nondestructive method used for elemental analysis of materials. An X-ray source is used to irradiate the specimen and to cause the elements in the specimen to emit (or fluoresce) their characteristic X rays. A detector s)rstem is used to measure the positions of the fluorescent X-ray peaks for qualitative identiflcation of the elements present, and to measure the intensities of the peaks for quantitative determination of the composition. All elements but low-Z elements—H, He, and Li—can be routinely analyzed by XRF. 

NAA cannot be used for some important elements, such as aluminum (in a Si or Si02 matrix) and boron. The radioactivity produced from silicon directly interferes with that ftom aluminum, while boron does not produce any radioisotope following neutron irradiation. (However, an in-beam neutron method known as neutron depth profiling C3J be used to obtain boron depth profiles in thin films. ) Another limitation of NAA is the long turn-around time necessary to complete the experiment. A typical survey measurement of all impurities in a sample may take 2-4 weeks. 

Data are provided as measured data or prepared data, representing typical data for a period of several years. Design reference years (DRY) established using methods developed with the framework of the lEA (International Energy Agency) represent characteristic data for a period of 10 years, condensed into a one-year data set. Internal coherence, e.g., between solar irradiation and air temperature, is maintained. For the United States, typical meteorological year (TMY) files are based on measurements in the period 1954 through 1972. 

Method A A solution of the azidoquinoline (5 mmol) in 3M KOMe in MeOH (40 mL) and dioxane (40 mL) was irradiated under N2 using a water-cooled, 125-W medium-pressure Hg lamp until all the azide [as measured by the disappearance of u(N3) at 2120 cm" 1 or by TLC] had reacted (4-10h). The photolysate was left to stand at 20 C for 24h then neutralized cautiously by the addition of 4M IICI in MeOH. The solvent was removed under reduced pressure and the crude product was purified initially by column chromatography on alumina (Type H, toluene), then finally by crystallization (petroleum ether). 

The method involves the irradiation of a sample with polychromatic X-rays (synchrotron radiation) which inter alia promote electrons from the innermost Is level of the sulfur atom to the lowest unoccupied molecular orbitals. In the present case these are the S-S antibonding ct -MOs. The intensity of the absorption lines resulting from these electronic excitations are proportional to the number of such bonds in the molecule. Therefore, the spectra of sulfur compounds show significant differences in the positions and/or the relative intensities of the absorption lines [215, 220, 221]. In principle, solid, liquid and gaseous samples can be measured. 

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