From studies performed with well characterized substrates and polystyrene with a narrow M distribution, the measured values of T, p, and 0 at the theta point have been found to agree closely with the theories of Silberberg and Scheutjens and Fleer. Furthermore, it has been shown that the measured root-mean-square thickness of the adsorbed layer can be predicted semiquantitatively by the loop-train-tail conformation model. [Pg.61]

Table 4-2 reports the electrostatic and non-electrostatic components of AGsoi in water for the series of compounds included in the study computed from MST calculations. The deviation between experimental and calculated free energies of hydration is in general small, as noted in a mean signed errors (mse) close to zero and a root-mean square deviation around 0.9 kcal/mol, which compares with the statistical parameters obtained in the parametrization of the MST model [15]. [Pg.108]

Ellipsometry determines a certain average thickness th of the adsorbed layer. However, what is important for the evaluation of polymer conformations in this layer is the root-mean square thickness t. Hence, it is necessary to find a way of relating t to th. McCrackin and Colson66 studied this problem for several distributions of segments and found tnn, = th/l-5 for the exponential distribution and t - th/1.74 for the Gaussian distribution. Takahashi et al.67 showed that t = th/1.63 for the one-train and two-tail model (see Eqs. (B-110) and (B-lll)). [Pg.37]

An example from recent works is the study of the dynamics of unentangled PEO chains in 35% PEO/65% PMMA by quasielastic neutron scattering (Niedzwiedz et al., 2007), and in 25% PEO/75% PMMA by molecular dynamics simulations (Brodeck et al., 2010). The Rouse model has the mean-square displacement, (r (r)>, of a chain segment, which increases proportionally to the square root of time according to [Pg.235]

The challenge is then to achieve the same degree of accuracy in the derived values of the experimental electron density. Recent studies have shown that in some cases this is indeed within the reach of the present-day modelling techniques [3-5]. When the major sources of experimental error have been corrected for the typical root mean square electron density residual can reach values as low as 0.05 e A-3, with maxima below 0.20eA-3 in absolute value. The observed residuals are usually due to the [Pg.12]

NMR Self-Diffusion of Desmopressin. The NMR-diffusion technique (3,10) offers a convenient way to measure the translational self-diffusion coefficient of molecules in solution and in isotropic liquid crystalline phases. The technique is nonperturbing, in that it does not require the addition of foreign probe molecules or the creation of a concentration-gradient in the sample it is direct in that it does not involve any model dependent assumptions. Obstruction by objects much smaller than the molecular root-mean-square displacement during A (approx 1 pm), lead to a reduced apparent diffusion coefficient in equation (1) (10). Thus, the NMR-diffusion technique offers a fruitful way to study molecular interactions in liquids (11) and the phase structure of liquid crystalline phases (11,12). [Pg.256]

Figure 6.4.7 shows the interpretation of two sets of relaxation data obtained from a specific site, Trp9, in the polypeptide backbone of gramicidin A [24]. From powder pattern studies it has been shown that the local motions occur about an axis consistent with the C, —C ,+i axis, and that the motion is a librational motion of about 20° [21], quite similar to the indole side-chain described earlier. The data in Fig. 6.4.7 has been interpreted in light of this experimentally defined motional model. However, the field-dependent relaxation data suggests that the amplitude is much less than 20°, in fact it is closer to a root mean square amplitude of 5°. However, this apparent [Pg.226]

Table 2. Scale factors for ab initio model vibrational frequencies adapted from (Scott and Radom 1996). Please note that these scale factors are determined by comparing model and measured frequencies on a set gas-phase molecules dominated by molecules containing low atomic-number elements (H-Cl). These scale factors may not be appropriate for dissolved species and molecules containing heavier elements, and it is always a good idea to directly compare calculated and measured frequencies for each molecule studied. The root-mean-squared (rms) deviation of scaled model frequencies relative to measured frequencies is also shown, giving an indication of how reliable each scale factor is. |

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