Birks’ method

In the Birks method the two reciprocal decay times are expressed as functions of the rate constants by Eq. (15.28) (which also results from Eq. (15.26)). 

The kinetics were successfully solved, using an extension of the Birks method, by measuring the decays as a function of temperature, and globally fitting the data, under a number of reasonable assumptions on the temperature dependence of the rate constants [58]. 

Alternatively, fundamental parameter methods (FPM) may be used to simulate analytical calibrations for homogeneous materials. From a theoretical point of view, there is a wide choice of equivalent fundamental algorithms for converting intensities to concentrations in quantitative XRF analysis. The fundamental parameters approach was originally proposed by Criss and Birks [239]. A number of assumptions underlie the application of theoretical methods, namely that the specimens be thick, flat and homogeneous, and that, for calibration purposes, the concentrations of all the elements in the reference material be known (having been determined by alternative methods). The classical formalism proposed by Criss and Birks [239] is equivalent to the fundamental influence coefficient formalisms (see ref. [232]). In contrast to empirical influence coefficient methods, in which the experimental intensities from reference materials are used to compute the values of the coefficients, the fundamental influence coefficient approach calculates... 

Two techniques, phase and pulse fluorometry, are used for the direct measurement of fluorescence decay rates, and their principles are described by Birks and Munro (1967), Parker (1968), and Birks (1970). The photon sampling method has proved useful and versatile. This is an iterative technique in which single photons are counted as a function of the time at which they appear after excitation and a complete decay curve is built up. (For recent references see e.g. Zimmerman et al., 1973, 1974). Wider use of the photon sampling technique will increase the precision of lifetimes obtained and extend the range of compounds studied to those with shorter lifetimes or very low fluorescence yields. 

If no direct measurement of the fluorescence lifetime is available the relations between the radiative lifetime and the fluorescence and absorption spectra can be used in conjunction with the quantum yield to obtain an indication of the fluorescence lifetime. Birks and Munro (1967) have reviewed the methods of calculating the radiative lifetime. In general these methods are limited to specific groups of compounds. For example, Favaro et al. (1973) applied Stickler and Berg s (1962) formula to the spectral data obtained from an excited state acid-base study of some styrylpyridines and found a lack of quantitative agreement between the measured and calculated lifetimes. 

The Birk-Perone system, a flash photolysis experiment with subsequent second-order decay, is a little more interesting because it can, with an unsuitable simulation method, lead to negative concentration values. The simultaneous reactions are... 

While vibrational spectroscopy is a well-known method of determining the structures of stable compounds, new techniques open up new possibilities of also analyzing unstable species. In analogy to 0=C=0, which is discussed in Section 4.2.2.2.2, the isoelectronic unstable species HN=C-NH was studied by FTIR methods. The two CN stretching vibrations are similar to those of CO2 i aj(CN) = 2104.70 cm i/j(CN) = 1285 cm (Birk and Winnewisser, 1986). An unstable carbon oxide, the linear species 0=C=C=C=C=C=0, was also investigated in the gas-phase (Holland et al., 1988) and as a matrix isolated species (Maier et al., 1988). 

Clegg RM. Methods Enzymol. 1992 211 353 Selvin PR. Methods Enzymol. 1995 246 300 Birks JB. Acta Phys. Polon. 1968 34 603... 

X-ray spectrometry is of such wide interest today as a means of chemical analysis that it has been given book-length treatment by several authors Jenkins and DeVries [G.29], Birks [G.31], Jenkins [G.41], and Bertin [G.46]. In addition, a book by Jenkins [G.37] presents worked-out problems arising in practical spectrometry, and [7.18] contains many papers on energy-dispersive methods and microanalysis. 

Uniaxial Compression - Williams Method This method was developed by Williams, Birks and Bhatta-charya24. A compact is first formed in a split mould by applying an axial compressive force, the mould is then removed to leave a cylindrical specimen with its axis vertical. The compressive vertical stress needed to cause failure of the specimen is then found and this is the unconfined yield stress for the consolidating stress used in the compaction of the specimen. The failure function is found by forming a number of compacts under different consolidating stresses and finding the unconfined yield stress for each specimen. 

Cardoso. A.C., Sohmini, A.G., Premazzi, G., Birk, S., Hale, P., Rafael, T. and Serrano, M.L. (2005) Report on harmonisation of freshwater biological methods, European Commission, Joint Research Centre, Ispra, EUR 21769 EN. 

Benjamin, E.J. Conley, D.L. On-line HPLC method for clean-up and analysis of hydrocortisone and sulconazole nitrate in a cream. Int.J.Pharm., 1983, 13, 205—217 Gandelman, M.S. Birks, J.W. Liquid chromatographic detection of cardiac glycosides, saccharides and hydrocortisone based on the photoreduction of 2-tert-butylanthraquinone. Anal.Chim.Acta, 1983, 155, 159-171... 

Kennedy, A.R. B.F. Szuhaj. Method of making soybean Bowman-Birk inhibitor concentrate and use of same as a human cancer preventative and therapy. U.S. Patent 5,217,717 June 8, 1993. 

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