Efficiency calibration

The X-ray sources have been designed to allow direct calibration efficiency/energy without knowledge of the decay schemes. For the list of radionuclides and their properties see Table 4.14. Beyond 3.5 MeV, no radionuclide is usable as a reference. The usual methods of calibration used at low energies (sets of different sources or multigamma sources) cannot be applied. 

Apart from CompAct, aU of the programs referred to use the inverse of Equation (6.13) to convert peak count rate, R, to source strength, S, i.e. sample activity, calculating the efficiency, e, from the calibrated efficiency function. Ideally, the program would also fold into the uncertainty of the peak area measurement the additional uncertainties due to interpolation of the calibration curve. 

The linear relation between the PSL signal and neutron fluence was established to exist over three decades up to 6. lO cm. The IP-ND can be used as fast and efficient neutron monitors at rather low neutron fluxes. However, for neutron dosimetry individual IP-ND must be calibrated individually since their sensitiviy can differ from one plate to another. In Gd/film based direct NR the film fog below the exposure dose of about 8.10 cm is the limiting factor. 

Tajima and co-workers [108] determined the surface excess of sodium dode-cyl sulfate by means of the radioactivity method, using tritiated surfactant of specific activity 9.16 Ci/mol. The area of solution exposed to the detector was 37.50 cm. In a particular experiment, it was found that with 1.0 x 10" Af surfactant the surface count rate was 17.0 x 10 counts per minute. Separate calibration showed that of this count was 14.5 X 10 came from underlying solution, the rest being surface excess. It was also determined that the counting efficiency for surface material was 1.1%. Calculate F for this solution. 

In the ideal case for REMPI, the efficiency of ion production is proportional to the line strength factors for 2-photon excitation [M], since the ionization step can be taken to have a wavelength- and state-mdependent efficiency. In actual practice, fragment ions can be produced upon absorption of a fouitli photon, or the ionization efficiency can be reduced tinough predissociation of the electronically excited state. It is advisable to employ experimentally measured ionization efficiency line strengdi factors to calibrate the detection sensitivity. With sufficient knowledge of the excited molecular electronic states, it is possible to understand the state dependence of these intensity factors [65]. 

Standardizing the Method Equations 10.32 and 10.33 show that the intensity of fluorescent or phosphorescent emission is proportional to the concentration of the photoluminescent species, provided that the absorbance of radiation from the excitation source (A = ebC) is less than approximately 0.01. Quantitative methods are usually standardized using a set of external standards. Calibration curves are linear over as much as four to six orders of magnitude for fluorescence and two to four orders of magnitude for phosphorescence. Calibration curves become nonlinear for high concentrations of the photoluminescent species at which the intensity of emission is given by equation 10.31. Nonlinearity also may be observed at low concentrations due to the presence of fluorescent or phosphorescent contaminants. As discussed earlier, the quantum efficiency for emission is sensitive to temperature and sample matrix, both of which must be controlled if external standards are to be used. In addition, emission intensity depends on the molar absorptivity of the photoluminescent species, which is sensitive to the sample matrix. 

Table 15. Decay Data for Radionuclides Useful for the Energy and Efficiency Calibration of 7-Ray Detectors...

Presented approach enables an efficient approach to the choice of the proper calibration cur ve, having two terms. Method was tested on big amount of standar ds of brass, bronze and aluminium alloys. 

Calibrated machine. When brake and pulley or dynamometer methods are not possible, the test motor may be loaded onto a calibrated generator. The efficiency curve of the generator must be available. 

A particular strength of Equation (7) is that the intensity ratio is formed between mea-surements of the same X-ray energy in both the unknown and standard. This procedure has significant advant es First, there is no need to know the spectrometer s efficiency, a value that is very difficult to calibrate absolutely, since it appears as a multiplicative factor in both terms and therefore cancels. Second, an exact knowledge of the inner shell ionization cross section or fluorescence yields is not needed, since they also cancel in the ratio. 

The original motivation for the preparation of regular metallic multilayers of carefully controlled periodicity was the need for X-ray reflectors, both to calibrate unknown X-ray wavelengths and to function as large and efficient monochromators, especially for soft X-rays of wavelengths of several A. This was first done by... 

Figure 6.3 shows a comparison of elution patterns of standard polystyrene between a linear-type column and a standard-type column. Because of the high linearity of its calibration curve, the linear series has improved the efficiency of oligomer domain separation. 

The linear column (PSS SDV 5 /mm linear) has a wider molar mass fractionation range while keeping the analysis time roughly the same. Therefore the slope of the calibration curve is much steeper and the resolution will be poorer in this case. The second column with a single pore size (PSS SDV 5 /mm 1000 A) separates only below 50,000 Da, but does this very efficiently in the same time. 

Overall resolution can be improved by simply adding another column of the same type, thus decreasing the slope of the calibration curve and increasing the efficiency of the system. 

Normally a calibration curve—molar mass against the total retention volume—exists for every GPC column or column combination. As a measure of the separation efficiency of a given column (set) the difference in the retention of two molar masses can be determined from this calibration curve. The same eluent and the same type of calibration standards have to be used for the comparison of different columns or sets. However, this volume difference is not in itself sufficient. In a first approximation the cross section area does not contribute to the separation. Dividing the retention difference by the cross section area normalizes the retention volume for different diameters of columns. The ISO standard method (3) contains such an equation... 

Most size exclusion chromatography (SEC) practitioners select their columns primarily to cover the molar mass area of interest and to ensure compatibility with the mobile phase(s) applied. A further parameter to judge is the column efficiency expressed, e.g., by the theoretical plate count or related values, which are measured by appropriate low molar mass probes. It follows the apparent linearity of the calibration dependence and the attainable selectivity of separation the latter parameter is in turn connected with the width of the molar mass range covered by the column and depends on both the pore size distribution and the pore volume of the packing material. Other important column parameters are the column production repeatability, availability, and price. Unfortunately, the interactive properties of SEC columns are often overlooked. 

Column manufacturers normally provide basic information about their columns, such as plate count, particle size, exclusion limit, and calibration curve. This information is necessary and fundamental, however, it is not sufficient to allow users to make an intelligent decision about a column for a specific application. For example, separation efficiency, the dependence of separation efficiency on the mobile phase, the ability to separate the system peaks from the polymer peak, the symmetry of the polymer peak, and the possible interaction with polymers are seldom provided. 

The catalytic efficiency increases, under comparable conditions (pH, concentration of catalyst, etc.) in the sequence Cl < Br - S(CH3)2 < SCN < SC(NH2)2 < I . Titration with a calibrated solution of NaN02 (usually 0.05 to 0.10 m) is used for the analytical determination of aromatic amines, dissolved in aqueous H2S04 or HC1. Here nucleophilic catalysis is achieved by adding KBr. This allows a titration to be completed much faster than without that addition. 

Anionic polymerizations carried out in aprotic solvents with an efficient initiator may lead to molecular weight control (Mn is determined by the monomer to initiator mole ratio) and low polydispersity indices. The chains are linear and the monomer units are placed head-to-tail. Such polymers are commonly used as calibration samples and for investigation of structure-properties relationships. 

This first step makes necessary a correction of the atmosphere aberrations by means of an adaptive optics or at the minimum a tip tilt device. If the turbulence induces high aberrations the coupling efficiency is decreased by a factor VN where N is the number of spatial modes of the input beam. Note that tilt correction is also mandatory in a space mission as long as instabilities of the mission platform may induce pointing errors. Figure 10 (left) illustrates the spatial filtering operation. This function allows a very good calibration of... 

In Fig. 4.39, results for spiked placebo and for the verum tablets are given for compound A (bold lines) and B all horizontal bars should be at 100%, and the vertical lines should be centered at the same height. The gray trendlines, particularly for the LO- and Hl-range A-values indicate a systematic difference in response between tbe calibration solutions and the spiked placebo tablets (extraction efficiency, interference, etc.). For same ranges, the verum-tablets assays either underestimate the content of A by 4—5%, or A is underdosed. For compound A the repeatability figures are as follows (%-of-nom-inal, see file Fig4 39.dat), see Table 4.36. 

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