Asymmetry ratio

Band Asymmetry. The peak asymmetry factor AF is often defined as the ratio of peak half-widths at 10% of peak height, that is, the ratio b/a, as shown in Fig. 11.2. When the asymmetry ratio lies outside the range 0.95-1.15 for a peak of k =2, the effective plate number should be calculated from the expression... 

The solvent used was 5 %v/v ethyl acetate in n-hexane at a flow rate of 0.5 ml/min. Each solute was dissolved in the mobile phase at a concentration appropriate to its extinction coefficient. Each determination was carried out in triplicate and, if any individual measurement differed by more than 3% from either or both replicates, then further replicate samples were injected. All peaks were symmetrical (i.e., the asymmetry ratio was less than 1.1). The efficiency of each solute peak was taken as four times the square of the ratio of the retention time in seconds to the peak width in seconds measured at 0.6065 of the peak height. The diffusivities obtained for 69 different solutes are included with other physical and chromatographic properties in table 1. The diffusivity values are included here as they can be useful in many theoretical studies and there is a dearth of such data available in the literature (particularly for the type of solutes and solvents commonly used in LC separations). 

Figure 7.17 shows the asymmetry ratios of a series of compounds (acids, bases, and neutrals) determined at iso-pH 7.4, under the influence of sink conditions created not by pH, but by anionic surfactant added to the acceptor wells (discuss later in the chapter). The membrane barrier was constructed from 20% soy lecithin in dodecane. All molecules show an upward dependence on lipophilicity, as estimated by octanol-water apparent partition coefficients, log KdaA). The bases are extensively cationic at pH 7.4, as well as being lipophilic, and so display the highest responses to the sink condition. They are driven to interact with the surfactant by both hydrophobic and electrostatic forces. The anionic acids are largely indifferent... 

Figure 7.17 Surfactant-induced sink asymmetry ratio versus octanol-water apparent...

Asymmetry ratio, defined as (Vd/VaXP /Pc0 )) where Vd and Va are donor and acceptor solution volumes, respectively, and the superscripts refer to the two possible directions of transport... 

In Figure 2, the mean square fluctuation 0 (Figure 2a), the asymmetry ratio r (Figure 2b), and the pressure p (Figure 2c) are plotted versus the average distance (z), for various values of Ac, using the first method. Figure 2d... 

The peak area errors for the two most studied de-convolution methods (i.e., perpendicular drop and linear tangential skim) are dependent on a complex combination of resolution, relative peak width, relative peak height, and asymmetry ratio [1]. Exponential skimming assumes that the tailing of the first peak can be described by an exponential decay and that the peaks are sufficiently resolved to determine the decay parameters. Nonetheless, some broad generalizations can be made ... 

FIGURE 9.7 In vitro permeation data. (A) Permeation of drugs through a Caco-2 cell monolayer. Good permeation is log Papp >—5 (>10-5 cm s-1). (B) Log of asymmetry ratios of permeation from basal to apical divided by permeation from apical to basal in MDCK cells. Ratios >1 indicate that the permeation from apical to basal is somewhat selectively hindered one reason for this could be an outwardly oriented efflux mechanism such as P-gp. This can be confirmed by elimination of die ratio >1 by an efflux inhibitor such as verapamil. Compounds 10 to 18 have been noted to be substrates for efflux. 

A good, uniformly packed and WCOT column should give an asymmetry ratio of between 0.9 and 1.2. 

If baseline drift has occurred then the peak height is measured from the mid point on the line joining start and end points of the peak and peak width at half height by drawing the horizontal vector to the line drawn at Aq.s parallel to the base line (Figure 8.4). Measurement of peak data assumes symmetrical peaks. Data from asymmetric peaks with an asymmetry ratio of greater than 1.2 will be less accurate. 

Fig. 7.10 Magnetic asymmetry ratios measured on a [Fe(2)/V(15)]3o sample in the vicinity of the Fe L-edges in reflection at the second superlattice peak prior (bold line) and after (light line) hydrogen exposure.

Liquid crystals consisting of rigid rods with asymmetry ratio x are easiest to understand so we discuss them first. If the concentration of rigid rods is small a particular rigid rod chosen at random can achieve every orientation and every location. It is not frustrated from doing so. However, as the... 

Flory gives for rigid rods the formula (25) xV =8 while we give (29) xV j=4. Here is the volume fraction of rigid rods and x the asymmetry ratio. If xVx is less than the critical value the chains can pack at random but when the critical value is exceeded the chains begin to order and a two phase system is formed. 

Conclusive additional evidence for the metallic nature of PAni and its blends with PMMA is provided by electron spin resonance (ESR) studies with the observation of a Dysonian line shape [104]. In both cases, the asymmetry ratio (A/B) decreases with decreasing temperature. The observed changes in the line shape from Dysonian to Lorentzian are thus seen to be a manifestation of the variation with temperature of the electrical conductivity (Figure 1.46). The g value is calculated as 2.00191 + 0.00005. The g value, which is close to the fi-ee spin value, confirms that the spins are indeed polarons. 

While the cross section is the fimdamental measurable quantity in scattering theory, it is frequently more convenient in X-ray scattering from magnetic materials to measure the asymmetry ratio (dichroism). This is defined as the difference divided by the sum of the cross section for the moment in one direction and the moment in the opposite direction. 

As shown by Lovesey and Collins (1996), the asymmetry ratio directly reflects the scattering amplitude rather than the cross section and emphasizes the interference between magnetic scattering and charge scattering. 

FIGURE 29 The asymmetry ratio of the lanthanides Gd through to Tm after Brown et al. (2007). The circles represent the experimental results measured on the XMaS beamline at the ESRF. The dashed line represents the full first-principles theory outlined in this section and yields at least good qualitative agreement with experiment. The full line is a simple model calculation that neglects all matrix elements and bases the asymmetry ratio on the DOS calculated using SIC-LSD theory. Note the features A and B that are discussed in the text. 

For the polystyrene/cyclohexanol system, = 1-0. This means that the polymer-rich domains will have to travel a composition distance that is equal to that of the solvent-rich domains in order to reach its binodal composition (symmetric case in Fig. 1.4.4). However, if the polymer composition asymmetry ratio is equal to about 2 (such as in Fig. 1.4.5), then half of the polymer-rich domains is believed to migrate to adjacent domains in order for the rest of the polymer-rich domains to continue to approach the binodal composition (Cahn, 1961). Since there is equal competition for polymer-rich material from every domain, then the position of the resulting holes (or cells) will be in a regular lattice position. Continued growth of structure should be based on the belief that the domains that are eaten up are those that are contiguous to the most number of polymer-rich domains. Also, as implied by the presence of distinct dominant frequencies for spinodal decomposition mechanism, the disappearance of contiguous polymer-rich domains should occur uniformly in space. 

This prediction is of the general form found in many SANS experiments, i-e-> 5(s = A -t- (B/T) where A and B are often empirically interpretated as entropic and enthalpic contributions, respectively. Note that for the present idealized thread model, B is always positive, but the molecular weight dependent A-factor can in general be positive or n ative depending on the precise values of the stiffness asymmetry ratio and blend composition. 

The asymmetry ratio R follows the evolution of the Dq F2 transition especially sensible to the crystal field. Parameter R increases when the covalent bonds with the neighbors are reinforced and when the symmetry of the site decreases. Crystal field theory enables to define certain parameters in order to characterize and distinguish the different europium site configuration. Crystal field parameter calculation involves some steps ... 

Employing very precise methods of measuring retention times as a means of determining the composition of unresolvable binary solute mixtures would be extremely valuable in the analyses of configurational isomers. Providing the retention time of a known mixture of the two components is available (in most instances one pure isomer and a 50% (w/v) mixture of one isomer in the other can be obtained) a calibration curve can be calculated theoretically. The asymmetry ratio of the peak for one pure component and the column efficiency for that component is usually the only further information required as the detector response factors for configurational isomers are generally identical. 

Our method based on the asymmetry ratio of the RIG signal which is unitless (24-25). 

Figure 2. First derivative traces of the EMG model simulation, using equations 7 and 8. A For i/a = 4 providing an asymmetry ratio (AR) of 2.52 B for tie = 1 providing an asymmetry ratio (AR) of 1.25 according to equation 5.

Figure 3. Asymmetry ratio versus the relative time position of the simulated first...

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