Resolution improvement

Since it does not appear that a lower limit was set as to what constitutes OOS, a similarly legalistic situation holds as when the infamous Delaney clause was on the books What today still passes as < 105% (105.005. .. 105.049, assuming an instrumental resolution equivalent to 0.1), will become OOS if instrumental resolution improves by a factor of 10. 

Once an electron density map has become available, atoms may be fitted into the map by means of computer graphics to give an initial structural model of the protein. The quality of the electron density map and structural model may be improved through iterative structural refinement but will ultimately be limited by the resolution of the diffraction data. At low resolution, electron density maps have very few detailed features (Fig. 6), and tracing the protein chain can be rather difficult without some knowledge of the protein structure. At better than 3.0 A resolution, amino acid side chains can be recognized with the help of protein sequence information, while at better than 2.5 A resolution solvent molecules can be observed and added to the structural model with some confidence. As the resolution improves to better than 2.0 A resolution, fitting of individual atoms may be possible, and most of the... 

Brown, R. S. Lennon, J. J. Mass resolution improvement by incorporation of pulsed ion extraction in a matrix-assisted laser desorption/ionization linear time-of-flight mass spectrometer. Anal. Chem. 1995,67,1998-2003. 

R. S. Brown and J. J. Lennon. Mass Resolution Improvement by Incorporation of Pulsed Ion Extraction in a Matrix-Assisted Laser Desorption/Ionization Linear Time-of-Flight Mass Spectrometer. Anal. Chem., 67(1995) 1998-2003. 

Columns filled with polymer solutions are extremely simple to prepare, and the packing can easily be replaced as often as desired. These characteristics make the pseudostationary phases excellent candidates for use in routine CEC separations such as quality control applications where analysis and sample profiles do not change much. However, several limitations constrain their widespread use. For example, the sample capacity is typically very low, pushing typical detection methods close to their sensitivity limits. Additionally, the migration of the pseudostationary phase itself may represent a serious problem, e. g., for separations utilizing mass spectrometric detection. The resolution improves with the concentration of the pseudostationary phase. However, the relatively low solubility of current amphiphilic polymers does not enable finding the ultimate resolution limits of these separation media [88]. 

Fig. 4.25. The influence of relative slit width settings on peak shape and resolution on a magnetic sector instrument. The peak shape first changes from flat-topped (left) to Gaussian (middle) and finally resolution improves at cost of peak height (right).

Regarding the three adjustable parameters for Savitsky-Golay derivatives, the window width essentially determines the amount of smoothing that accompanies the derivative. For rather noisy data, it can be advantageous to use higher window widths, although this also deteriorates the resolution improvement of the derivative. The polynomial order is typically set to two, meaning that the derivative is calcnlated based on the best fits of the local data windows to a second-order polynomial. The derivative order, of conrse, dictates... 

Selected entries from Methods in Enzymology [vol, page(s)] Analysis, software for, 207, 717 barrier models, 207, 818 closed and open time estimation, 207, 755 data acquisition, 207, 747 modal behavior analysis, 207, 757 multiple channel problem, 207, 756 single-channel [extraction of kinetic information, 207, 765 measurement in tissue slices, 207, 220] synaptic, resolution improvement in patch clamp recording, 207, 216 whole-cell recording in calcium channel, 207, 181 fluctuation analysis, 207, 192. 

The solutions illustrated in Schell s original publication were indeed entirely positive and showed some resolution improvement over the inverse-filter estimates. The improvement in these examples was not, however, as great as we have come to expect from the best of the newer methods and may not in fact demonstrate the method s real potential. The method does bring with it in a very explicit way, however, the idea that the Fourier spectrum may be extended, on the basis of a knowledge of positivity. Previous studies had focused on the finite extent constraint to achieve this objective. 

Detailed analysis of the chemical shifts demands higher resolution than a basic ESCA spectrometer can provide. The needed resolution improvement may be achieved experimentally by monochromatizing the x rays and/or by high-resolution energy analysis of the electrons. Either way, because of the reduced slit widths required, penalties are paid in decreased signal-to-noise ratio and longer observation time. Furthermore, the problem of sample charging (Section IV.D) is typically more severe when monochromatized x rays are used (Brundle and Baker, 1981). 

Because infrared spectrophotometry is detector noise limited, a profitable trade-off is possible between signal-to-noise ratio and resolution. Such a trade-off may be useful when deconvolution is used to recover resolution lost by opening monochromator slits to increase acquisition rates. In any system where degrading the resolution improves the signal-to-noise ratio nonlinearly, a potentially useful trade-off is possible. 

Deconvolution, the inverse operation of recovering the original function o from the convolution model as given in Eq. (1), employs procedures that almost always result in an increase in resolution of the various components of interest in the data. However, there are many broadening and degrading effects that cannot be explicitly expressed as a convolution integral. To consider resolution improvement alone, it is instructive to consider other viewpoints. The uncertainty principle of Fourier analysis provides an interesting perspective on this question. 

For FTS data, artifact removal is a consideration that is as important as resolution improvement for most researchers in this field. Interferogram continuation methods are not as yet widely known in this area. Methods currently in widespread use that are effective in artifact removal involve the multiplication of the interferogram by various window functions, an operation called apodization. A carefully chosen window function can be very effective in suppressing the artifacts. However, the peaks are almost always broadened in the process. This can be understood from the uncertainty principle. A window that reduces the function most strongly closest to the end points will yield a transform for the modified function that must be broader than it was originally. Alternatively we may employ the convolution... 

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