Spectral gradient

Knowledge of the pKa value is crucial for analyzing both lipophilicity and solubility of ionizable compounds, as discussed above. Ionization equilibria also affect several toxicokinetic parameters, such as intestinal absorption, membrane permeability, protein binding, and metabolic transformations. Therefore, much research has been invested in developing both experimental and computational tools for pKa determination. Experimentally, two high-throughput methods exist spectral gradient analysis and capillary electrophoresis. However, the most definitive methods are still... 

Even if the intrinsic fluorescence spectrum of the thylakoid membrane is constant, there are several possible causes for such a spectral gradient. Wavelength dependence of reabsorption and/or point-spread functions can, in principle, give rise to such a dependence of the spectra on the position of the probing fluorescence (e.g., whether the position is at the central part or near the edge). These two possible artifacts were ruled out in our previous work, based on measurements of wavelength dependence of transmission and point-spread function [21]. 

Object Phase curve P(a) Min. Inversion Max. Polarization spectral gradient Rate of increase dP/dX,] =S0 (% per pm)... 

We can say nothing about the average spectral dependence of polarization for gas-rich comets because of different gas contributions in the blue and red domain of spectra. It was shown only for comet Tabur [38] that correcting for the gas contamination changed the value of spectral gradient from 0.2%/1000 to 0.84%/1000, which is close to the m ean value for dust-rich comets. 

Figure 6. Variations of tiie degree of linear polmization with wavelength for dust-rich comets, Hale-Bopp, and Giacobini-Zinner (a). Spectral gradient of polarization versus phase angle for dust-rich comets (b).

The integral of the temperature gradient of the spectral power density from wavelength Xl to X2, is readily calculable using the Planck radiation law (5). Constant emissivity is assumed for equation 3. 

Membrane depolarization can be measured by members of a class of fluorophores (commonly referred to as the carbocyanine dyes) which have been designed to partition into the membrane, where their orientation and spectral properties change with changes in the electrochemical gradient across the membrane (18). 3,3 -dipropyl-... 

Although the overall cost of the conjugate gradient algorithm may be higher than that of some of the iterative algorithms described in Section III.B, the algorithm allows us easily to restrict the spectral and temporal stmcture of optimal pulses and enables us to incorporate the exact form of the laser-molecule interactions. 

Different product sorts (20-22,24-26) are marked in the score plot of spectral NIR measurements (Fig. 4). Sorts 23 and 31 are in separate classes outside the range of this plot. A gradient is seen in the plot, indicating the chemical differences among the sorts the %DE are increasing in the 20->25/26 direction while the opposite holds for the Ca-based gel strength measm-ements. 

Figure 4. Score plots from a PCA of NIR R spectral data (2nd derivative). Left PC 1 versus PC 3 shows a clear segregation of sorts 23 and 31. Right PC 1 versus PC 2 (without sorts 23 and 31) shows a more distinct sort gradient/classification than the one produced by the chemical data.

In the stochastic theory of lineshape developed by Blume [31], the spectral lines are calculated under the influence of a time-dependent Hamiltonian. The method has been successfully applied to a variety of dynamic effects in Mossbauer spectra. We consider here an adaptation due to Blume and Tjon [32, 33] for a Hamiltonian fluctuating between two states with axially symmetric electric field gradients (efg s), the orientation of which is parallel or perpendicular to each other. The present formulation is applicable for states with the same... 

Spatially localized NMR spectroscopy was performed using a sample composed of a monoolein-D20 dispersion forming a cubic liquid-crystalline phase [41]. The spectra were selected from a slice of 300-pm thickness. The direction of the gradient was along the spinning axis. A spectral resolution was obtained that had never been observed before when selecting the whole volume of the sample. 

Another issue of concern is the amplitude of magnetic field gradients required for solids imaging. For spectra up to a few kHz wide, standard frequency encoding schemes can be used to obtain reasonable spatial resolution. This will not work for broader lines, but it is well known that phase encoding is much more tolerant to line broadening and can be used for spectral widths in excess of 100 kHz with no major loss in spatial resolution. 

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