Modulator method

These modulation methods do not accelerate the electron-hole pairs and hence produce only a first-derivative Modulation Spectroscopy. Their line shapes are given by Equation (1), with m = 2. 

The fluorescent lifetime of chlorophyll in vivo was first measured in 1957, independently by Brody and Rabinowitch (62) using pulse methods, and by Dmitrievskyand co-workers (63) using phase modulation methods. Because the measured quantum yield was lower than that predicted from the measured lifetime, it was concluded that much of the chlorophyll molecule was non-fluorescent, suggesting that energy transfer mechanisms were the means of moving absorbed energy to reactive parts of the molecule. 

Both pulse and modulation methods permit an estimate of a spherical volume for a macromolecule and are especially useful for determining deviations from molecular sphericity. 

In the Miller method, a 5% contingency was used, plus a 10% allowance for miscellaneous unlisted equipment. This is equivalent to the 15% contingency used in the module method. 

Figure 5. Schematic of a Complementary Source Modulation method of correlation spectroscopy.

It can be readily seen from the above discussion that a simplistic version of the polarization modulation method for using Fourier Transform Infrared method would be to say that if one subtracted the message obtained from the vertical light from that obtained from the parallel light, the result will be information from the surface only. The relevant equation is shown below. 

Prior to describing the possible applications of laser-diode fluorometry, it is important to understand the two methods now used to measure fluorescence lifetimes these being the time-domain (Tl)/4 5 24 and frequency-domain (FD) or phase-modulation methods.(25) In TD fluorometry, the sample is excited by a pulse of light followed by measurement of the time-dependent intensity. In FD fluorometry, the sample is excited with amplitude-modulated light. The lifetime can be found from the phase angle delay and demodulation of the emission relative to the modulated incident light. We do not wish to fuel the debate of TD versus FD methods, but it is clear that phase and modulation measurements can be performed with simple and low cost instrumentation, and can provide excellent accuracy with short data acquisition times. 

There are two widely used methods for measuring fluorescence lifetimes, the time-domain and frequency-domain or phase-modulation methods. The basic principles of time-domain fluorometry are described in Chapter 1, Vol.l of this series(34) and those of frequency-domain in Chapter 5, Vol. 1 of this series.<35) Good accounts of time-resolved measurements using these methods are also given elsewhere/36,37) It is common to represent intensity decays of varying complexity in terms of the multiexponential model... 

The principal requirements for photomultipliers in both pulse and phase-modulation methods of measuring fluorescence lifetimes are as follows. 

The third block in Fig. 2.1 shows the various possible sensing modes. The basic operation mode of a micromachined metal-oxide sensor is the measurement of the resistance or impedance [69] of the sensitive layer at constant temperature. A well-known problem of metal-oxide-based sensors is their lack of selectivity. Additional information on the interaction of analyte and sensitive layer may lead to better gas discrimination. Micromachined sensors exhibit a low thermal time constant, which can be used to advantage by applying temperature-modulation techniques. The gas/oxide interaction characteristics and dynamics are observable in the measured sensor resistance. Various temperature modulation methods have been explored. The first method relies on a train of rectangular temperature pulses at variable temperature step heights [70-72]. This method was further developed to find optimized modulation curves [73]. Sinusoidal temperature modulation also has been applied, and the data were evaluated by Fourier transformation [75]. Another idea included the simultaneous measurement of the resistive and calorimetric microhotplate response by additionally monitoring the change in the heater resistance upon gas exposure [74-76]. 

The second module. Method, involves determining the level of verification and validation to which the user s methodology has been subjected. Verification is the general process used to decide whether a method in question is capable of producing accurate and reliable data. Validation is an experimental process involving external corroboration by other laboratories (internal or external) of methods or the use of reference materials to evaluate the suitability of methodology (1). A menu of choices includes (1) the method has only been verified, (2) the method has been both verified and validated, or (3) the method has been neither verified or validated. 

B. Chen and G. Womell, Preprocessed and postprocessed quantization index modulation methods for digital watermarking, in Proc. ofSPIE Vol. 3971 Security and Watermarking of Multimedia Contents II, pp. 48-59, (San Jose, (3a, USA), January 2000. 

A systematic study was conducted on clean Si(lll) surface with a clean W tip (Chen and Hamers, 1991). The entire curve of the dependence of the measured apparent barrier height, Eq. (8.27), with z-piezo displacement, was recorded. The experiment was performed under the condition that a clear 7X7 pattern was observed, which indicated that both the tip (near the apex atom) and the sample were clean. By carefully moving the tip back and forth, so as not to press into the sample surface too deeply, the entire process is completely reversible. The experimental barrier height measurements were performed using an ac modulation method, by applying a small 0.05 A modu-... 

As implied by this description, CD measurements by the modulation method are not absolute. The instrument must be calibrated using a standard well-known CD)2,6-8 Due to slow changes in the amplifier and other components, CD instruments must be calibrated regularly. 

Potential modulation method in elec-trodeposition of ZnO on indium tin oxide... 

To investigate the dynamic properties of ionic species present at very low concentration in apolar solvents the field modulation method is particularly suited In this... 

In this paper we review the field modulation method especially to indicate the applicability for the investigation of organic reaction mechanisms where ionic species may intervene. 

At increasing salt concentrations the conductance of all solutions investigated shows the emergence of other equilibria involving the ions and ion-pairs triple ions, quadrupoles. .. become stable species. Althought one expects from chemical relaxation theory the appearance of more relaxation processes, experimentally only one relaxation process, whatever the concentration of salt, is observed. This odd behavior is intimately related to the nature of equlllbriun perturbation and observation of the response in the field modulation method. 

The presence of small lead inclusions is easily established by using the x-ray modulation method on the microprobe. We believe that a lineal intercept analysis from pictures taken by this method is probably the most accurate if the electron microprobe is used. 

There are many excellent differential scanning calorimeter systems available which can be used to measure the specific heat which, when combined with the sample density can be used to give c . The thermal diffusivity (which can be important for thermal imaging systems if the target is not reticulated) can be measured directly on a pyroelectric substrate using the laser intensity modulation method described by Lang [23],... 

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