Resolution terms

Usually, the top peaks of the translation search are then submitted to a low resolution quick rigid-body refinement, for which quick algorithms have been devised (Huber and Schneider, 1985 Navaza and Saludjian, 1997).The resolution is usually taken to be 12-4 Angstroms or so if one wants to use the low resolution terms, one should use a solvent effect correction technique (Fokine and Urzhumtsev, 2002). 

The sum of peak-valley ratios was used as the resolution term in a composite optimization criterion, which otherwise corresponds to eqn.(4.30). Berridge also added a term to describe the contribution of the number of peaks (n). With this, the complete optimization criterion became... 

Figure 3 shows the influence of temperature and iso-. , propanol volume fraction in the term (a—l/a). There are examples of different situations for pairs 5-6 and j 4—5, the (a l/a) term is markedly influenced by the g-isopropanol volume fraction the column temperature g also exerts an important influence on this term for pairs -s 2-3 and 4—5. It is interesting to note that both J parameters T and V) have important and similar effects on pairs 4—5 and 2-3 in this resolution term. For these... 

It should be emphasized that the stated resolution of a particular structure determination does not necessarily reflect the clarity of the features present in the electron density map, or the accuracy of the model based on the map. That is, many 3.0 A resolution electron density maps are far more interpretable in terms of protein structure, and the amino acid side groups more recognizable, than are some maps that include higher resolution terms. This is because resolution says nothing about the accuracy of the structure factors used to compute the map. In particular, it gives no indication of the quality of the phase determination, the mean phase error, which is the essential factor that influences contrast between the electron density of the protein and the background noise level in the Fourier map. 

FIGURE 10.9 In (a) is an optical diffraction pattern of the two-dimensional molecular crystal in (b). In (c) the resolution of the terms used to produce the transform are limited, and a degraded image of the molecules results in (d). When only very low resolution terms are included in the backtransform as in (e), the periodicity of the pattern in (f) remains clear, but the image of the molecule making up the pattern becomes virtually uninterpretable. 

Figure 26 The effect of resolution on FTs. (a) A picture of a duck and its FT. (b) A back transform of the duck using only the low-resolution terms of the FT. Only the general shape of the duck is discernible the details are lost. Reproduced from the web-based book Book of Fourier, University of York, UK, with permission from Kewin Cowtan reimplemented by I. Karonen.

HR2 High mass resolution with high spatial resolution (term trade... 

From (1) it is clear that the phase contrast can be interpreted simply in terms of tbe variation (second order derivative) of the projected image density, and increases with improving resolution of the system, in agreement with the findings of [3]. 

This works for any veetor f, and we eould write the proeess in general in terms of the resolution of the identity as... 

The separation of a racemic mixture into its enantiomeric components is termed resolution The first resolution that of tartaric acid was carried out by Louis Pasteur m 1848 Tartaric acid IS a byproduct of wine making and is almost always found as its dextrorotatory 2R 3R stereoisomer shown here m a perspective drawing and m a Fischer projection... 

The fundamental resolution equation incorporates the terms involving the thermodynamics and kinetics of the chromatographic system ... 

Equations 12.21 and 12.22 contain terms corresponding to column efficiency, column selectivity, and capacity factor. These terms can be varied, more or less independently, to obtain the desired resolution and analysis time for a pair of solutes. The first term, which is a function of the number of theoretical plates or the height of a theoretical plate, accounts for the effect of column efficiency. The second term is a function of a and accounts for the influence of column selectivity. Finally, the third term in both equations is a function of b, and accounts for the effect of solute B s capacity factor. Manipulating these parameters to improve resolution is the subject of the remainder of this section. 

One of the simplest ways to improve resolution is to adjust the capacity factor for solute B. If all other terms in equation 12.21 remain constant, increasing k improves resolution. As shown in Figure 12.11, however, the effect is greatest when the... 

Another approach to improving resolution is to use thin films of stationary phase. Capillary columns used in gas chromatography and the bonded phases commonly used in HPLC provide a significant decrease in plate height due to the reduction of the Hs term in equation 12.27. 

In general terms, the main function of the magnetic/electric-sector section of the hybrid is to be able to resolve m/z values differing by only a few parts per million. Such accuracy allows highly accurate measurement of m/z values and therefore affords excellent elemental compositions of ions if these are molecular ions, the resulting compositions are in fact molecular formulae, which is the usual MS mode. Apart from accurate mass measurement, full mass spectra can also be obtained. The high-resolution separation of ions also allows ions having only small mass differences to be carefully selected for MS/MS studies. 

Examples of prolate near-symmetric rotors are the s-trans and s-cis isomers of crotonic acid, shown in Figure 5.8, the a axis straddling a chain of the heavier atoms in both species. The rotational term values for both isomers are given approximately by Equation (5.37) but, because A and B are different for each of them, their rotational transitions are not quite coincident. Figure 5.9 shows a part of a low-resolution microwave spectmm of crotonic acid in which the weaker series of lines is due to the less abundant s-cis isomer and the stronger series is due to the more abundant s-trans isomer. 

The NEP may be written in terms of the detector element active area, the number of detector pixels elements cormected for additive output the electronic noise bandwidth B and the detector element detectivity, D. Typically = 1, but may be increased for improved sensitivity with an attendant loss in resolution. 

The long-term stability of the nonaqueous coating films under elevated temperature and moderate humidity is reported to be better than aqueous coatings (30). Furthermore, color resolution and sensitivity of reacted nonaqueous coating films ate excellent. 

The fineness of the grid pattern, called resolution, is quantified in terms of pixels per linear distance. Common practice for commercial quaUty images assumes that photographic images can be reproduced accurately using about 300 pixels per inch (120 pixels/cm). 

Although performance varies with the isotopes for which they are intended, and with the balance in the design between resolution and efficiency, the overall sensitivity of a y-camera collimator is on the order of 5000 counts/(MBqmin) (several hundred counts/(/iCi-min)). In terms of photons detected per photon emitted, this is equivalent to about 2 x lO ". In other words, about two photons out of 10,000 emitted arrives at the crystal. This necessitates exposure times that range from several minutes to the better part of an hour. Fortunately, the large number of photons available from a modest injected radioactive dose more than offsets the poor detector sensitivity. The camera s abiUty to resolve small objects, however, is ultimately limited by the collimator inefficiency. 

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