Detection, multi-frequency

In multi-target situations the association of the detected beat frequencies at the FFT output to different targets is not trivial. Therefore, a... 

Phase shift fluorimetry, the other important method for measuring fluorescent lifetimes, also continues to be developed and improved. The effects of Inaccurate reference lifetimes on the interpretation of frequency domain fluorescence data can be removed or minimized by a least squares analysis method.The direct collection of multi-frequency data for obtaining fluorescence lifetimes can be achieved by the use of digital parallel acquisition in frequency domain fluorimetry. Frequency domain lifetime measurement has been used for on-line fluorescence lifetime detection of eluents in chromatography. An unusual use of frequency domain measurement which has been reported is for the examination of photon migration in living tissue. Photons in the... 

In summary, dielectric properties differ between healthy and injured lungs due to atelectasis caused by mechanical ventilation. It is shown that detection of more or less collapsed lung tissue was possible by analysing differences in electrical impedanceat different frequencies. This can be a promising feature for multi-frequency BIT devices. More studies are needed to evaluate additional diseases, such as pulmonary edema or pneumonic infiltrates. 

The advances in technology in the last years led to the development and optimization of new ESR methods such as high field/multi-frequency ESR [29-31], double resonance [32, 33], and pulse methods [34-36]. The improvements in resolution brought by these methods have made possible analysis and interpretation of more complex systems and detection and characterization of transient paramagnetic intermediates inaccessible before. 

Photoionization ti me-of-fli ght mass spectrometry is almost exclusively the method used in chemical reaction studies. The mass spectrometers, detectors and electronics are almost identical. A major distinction is the choice of ionizing frequency and intensity. For many stable molecules multi photon ionization allowed for almost unit detection efficiency with controllable fragmentation(20). For cluster systems this has been more difficult because high laser intensities generally cause extensive dissociation of neutrals and ions(21). This has forced the use of single photon ionization. This works very well for low i oni zati on potential metals ( < 7.87 eV) if the intensity is kept fairly low. In fact for most systems the ionizing laser must be attenuated. A few very small... 

Based on this principle, multi-nuclei instruments were initially built. They kept the frequency fixed while scanning the magnetic field over a wide range. This allowed the qualitative and global detection of elements by their characteristic resonance frequency (Table 9.2 and Fig. 9.5). 

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