Structural entropy

GEN.28. P. Glansdorff et 1. Prigogine, Entropie, structure et dynamique (Entropy, structure and dynamics), in Sadi Carnot et I Essor de la Thermodynamique, CNRS, Paris, 1974. 

Bourne, J.R. Davey R.J. (1976) The role of sol-vent-solute interactions in determining crystal growth mechanisms from solution. 1. The surface entropy structure. J. Cryst. Growth 36 278-286... 

Although beta decay and electron captures on stellar core nuclei do not produce energy in major ways they nevertheless play a crucial role in shifting the pathways of nuclear and thermodynamic evolution in the core conditions. These ultimately determine the mass of the core and its entropy structure which finally collapses in a supernova explosion. 

A novel approach for suppression of grain noise in ultrasonic signals, based on noncoherent detector statistics and signal entropy, is presented. The performance of the technique is demonstrated using ultrasonic B-scans from samples with coarse material structure. 

The classical computer tomography (CT), including the medical one, has already been demonstrated its efficiency in many practical applications. At the same time, the request of the all-round survey of the object, which is usually unattainable, makes it important to find alternative approaches with less rigid restrictions to the number of projections and accessible views for observation. In the last time, it was understood that one effective way to withstand the extreme lack of data is to introduce a priori knowledge based upon classical inverse theory (including Maximum Entropy Method (MEM)) of the solution of ill-posed problems [1-6]. As shown in [6] for objects with binary structure, the necessary number of projections to get the quality of image restoration compared to that of CT using multistep reconstruction (MSR) method did not exceed seven and eould be reduced even further. 

Returning to more surface chemical considerations, most literature discussions that relate adhesion to work of adhesion or to contact angle deal with surface free energy quantities. It has been pointed out that structural distortions are generally present in adsorbed layers and must be present if bulk liquid adsorbate forms a finite contact angle with the substrate (see Ref. 115). Thus both the entropy and the energy of adsorption are important (relative to bulk liquid). The... 

Thus the entropy of localized adsorption can range widely, depending on whether the site is viewed as equivalent to a strong adsorption bond of negligible entropy or as a potential box plus a weak bond (see Ref. 12). In addition, estimates of AS ds should include possible surface vibrational contributions in the case of mobile adsorption, and all calculations are faced with possible contributions from a loss in rotational entropy on adsorption as well as from change in the adsorbent structure following adsorption (see Section XVI-4B). These uncertainties make it virtually impossible to affirm what the state of an adsorbed film is from entropy measurements alone for this, additional independent information about surface mobility and vibrational surface states is needed. (However, see Ref. 15 for a somewhat more optimistic conclusion.)... 

Obviously die first law is not all there is to the structure of themiodynamics, since some adiabatic changes occur spontaneously while the reverse process never occurs. An aspect of the second law is that a state fimction, the entropy S, is found that increases in a spontaneous adiabatic process and remains unchanged in a reversible adiabatic process it caimot decrease in any adiabatic process. 

The hydrophobic effect. Water molecules around a non-polar solute form a cage-like structure, which ices the entropy. When two non-polar groups associate, water molecules are liberated, increasing the entropy. 

Side chain generation is often a source of error. It will be most reliable if certain rules of thumb are obeyed. Start with structurally conserved side chains and hold them fixed. Then look at the energy and entropy of rotamers for the remaining side chains. Conventional conformation search techniques are often used to place each side chain. 

When the film thickens beyond two or three molecular layers, the effect of surface structure is largely smoothed out. It should therefore be possible, as Hill and Halsey have argued, to analyse the isotherm in the multilayer region by reference to surface forces (Chapter 1), the partial molar entropy of the adsorbed film being taken as equal to that of the liquid adsorptive. By application of the 6-12 relation of Chapter 1 (with omission of the r" term as being negligible except at short distances) Hill was able to arrive at the isotherm equation... 

GW Carter Ir. Entropy, likelihood and phase determination. Structure 3 147-150, 1995. RL Dunbrack Ir, EE Cohen. Bayesian statistical analysis of protein sidecham rotamer preferences. Protein Sci 6 1661-1681, 1997. 

The thermodynamic stability of a protein in its native state is small and depends on the differences in entropy and enthalpy between the native state and the unfolded state. From the biological point of view it is important that this free energy difference is small because cells must be able to degrade proteins as well as synthesize them, and the functions of many proteins require structural flexibility. 

Both types of mutations have been made in T4 lysozyme. The chosen mutations were Gly 77-Ala, which caused an increase in Tm of 1 °C, and Ala 82-Pro, which increased Tm by 2 °C. The three-dimensional structures of these mutant enzymes were also determined the Ala 82-Pro mutant had a structure essentially identical to the wild type except for the side chain of residue 82 this strongly indicates that the effect on Tm of Ala 82-Pro is indeed due to entropy changes. Such effects are expected to be additive, so even though each mutation makes only a small contribution to increased stability, the combined effect of a number of such mutations should significantly increase a protein s stability. 

Further information on the effect of polymer structure on melting points has been obtained by considering the heats and entropies of fusion. The relationship between free energy change AF with change in heat content A// and entropy change A5 at constant temperature is given by the equation... 

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