Multifrequency

It is possible to build very powerful, and very compact monofrequency instruments, but the same technology cannot be used in multifrequency instruments. 

These equations are the coupled system of discrete equations that define the rigorous forward problem. Note that we can take advantage of the convolution form for indices (i — I) and (j — J). Then, by exciting the conductive media with a number N/ oi frequencies, one can obtain the multifrequency model. The kernels of the integral equations are described in [13] and [3j. 

We present in this paper an eddy current imaging system able to give an image of three-dimensional flaws. We implement a multifrequency linearized model for solving the 2590... 

Fig. 48. Multifrequency modulus and tan 5 vs temperature plots. To convert N/m to psi, multiply by 1.45 x. ...

The multifrequency EPR and Mdssbauer properties of the [FesSJ in C. vinosum NiFe-hydrogenase are particularly interesting since they provide evidence of magnetic interactions with nearby paramagnetic species (151, 154, 155). The magnetically isolated form exhibits a well-resolved, almost axial EPR signal, g = 2.018, 2.016, 2.002, indicative of minimal conformational heterogeneity. However, a com-... 

Multifrequency EPR spectroscopy was applied to study Fe(III)-MCM-41 mesoporous molecular sieves with incorporated carotenoids (Konovalova et al. 2003). 

Multifrequency HF-EPR permits precise determination of the g-values of the exchange-coupled organic radical metal ion species, provides parameters for accurate simulation of the EPR spectra, and allows determination of detailed information about the radicals themselves and their environment (Gerfen et al. 1993, Un et al. 1995, Bar et al. 2001, Ivancich et al. 2001). 

Carotenoid radical intermediates generated electrochemically, chemically, and photochemically in solutions, on oxide surfaces, and in mesoporous materials have been studied by a variety of advanced EPR techniques such as pulsed EPR, ESEEM, ENDOR, HYSCORE, and a multifrequency high-held EPR combined with EPR spin trapping and DFT calculations. EPR spectroscopy is a powerful tool to characterize carotenoid radicals to resolve -anisotropy (HF-EPR), anisotropic coupling constants due to a-protons (CW, pulsed ENDOR, HYSCORE), to determine distances between carotenoid radical and electron acceptor site (ESEEM, relaxation enhancement). 

Ivancich, A., P. Dorlet et al. (2001). Multifrequency high-field EPR study of the tryptophanyl and tyrosyl radical intermediates in wild-type and the W191G mutant of cytochrome c peroxidase. J. Am. Chem. Soc. 123 5050-5058. 

Konovalova, T. A., L. D. Kispert et al. (2004). Multifrequency high-field electron paramagnetic resonance characterization of the peroxyl radical. Location in horse heart myoglobin oxidized by H202. J. Phys. Chem. BIOS 11820-11826. 

Selected Papers from the Recent Literature High Field)Multifrequency EPR ... 

In the next section of this chapter, we will review a variety of instrumentation approaches to the FLIM experiment. In particular, we describe conventional systems as well as those designed to observe variation in a, and systems designed for the collection of multifrequency data. In this context, we will also look at data collection strategies and the subsequent first pass analysis of the acquired... 

Examination of Eqs. (2.9-2.11) suggests that having frequency domain lifetimes measured at a variety of frequencies is desirable, as it will allow a mixture of fluorophores to be determined. With this in mind, two approaches may be taken to obtain multifrequency results. The first of these is simply to make a series of FLIM measurements while stepping through a predetermined set of frequencies. In practice, this is of limited utility for biological systems because of photo-induced damage to the specimen. 

Spectral FLIM involves measuring the apparent lifetimes in a preparation at many wavelengths with the assistance of a spectrograph or a series of filters (see also Chapter 4, Figs. 4.7 and 4.8 depicting hyperspectral FLIM in the time domain). The goal of the measurement is similar to that of the multifrequency approach ... 

Hedstrom, J., Sedarous, S. and Prendergast, F. G. (1988). Measurements of fluorescence lifetimes by use of a hybrid time-correlated and multifrequency phase fluorometer. Biochemistry 27, 6203-8. 

Pardi, L.A., Krzystek, J., Telser, J., and Brunei, L.-C. 2000. Multifrequency EPR spectra of molecular oxygen in solid air. Journal of Magnetic Resonance 146 375-378. 

Finally, we note that, to the best of our knowledge, only one report exists about EPR spectra of non-Kramers lanthanide ions in molecular magnets. In 2012, Hill and coworkers [51] performed a multifrequency study on powder and single crystal samples of NagHofWgOj H20, in both the pure form and when doped into the isostructural Y3+ derivative. While crystallizing in a triclinic unit cell, the symmetry of the lanthanide ion in this family is very close to Did. For this reason, susceptibility data had been previously fitted by a purely axial Hamiltonian [50]. 

A.2. Multifrequency Detection Analog Parallel Cross-Correlation... 

J. R. Alcala, E Gratton, and D. M. Jameson, A multifrequency phase fluorometer using the harmonic content of a mode-locked laser, Analytical Instrumentation 14, 225-250 (1985). 

In the upper panel of Figure 13.6, the emission is drawn assuming a modulation frequency of 30 MHz and a lifetime of 9 nsec. Using the equations above, the phase angle is 59.5° and the demodulation factor is 0.5. (For further details, the reader is referred to Lakowicz(66)). Additionally, multifrequency phase and modulation instruments that operate over a range of frequencies have been described(67, flS) and simple instruments are possible if only one or several discrete frequencies are required (Figure 13.6, lower panel). 

Figure 14.15. Multifrequency phase-modulation curves of 4 nM BPE-thyroxine donor conjugate ( ) of donor in the presence of CY5-anti-thyroxine IgG acceptor conjugate (a) and of both donor and acceptor in the presence of a nearly saturating amount of thyroxine ( ). (From Ref. 34 with permission).

F. V Bright, Multifrequency phase fluorescence study of hapten-antibody complexation, Anal. Chem. 61, 309-313 (1989). 

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