Structural memory

The reactivation of enzymes (after their partial inactivation in an acid medium) upon passing into a medium of pH 8 is also of great importance for oral use (Fig. 25). Enzymes immobilized in crosslinked polyelectrolytes are characterized by a structural memory even after considerable inactivation. Under changed conditions, this leads to a considerable or almost complete reactivation of the enzyme, whereas in the reactivation of a free enzyme in solution under similar conditions the enzymatic activity is restored on a lower level. 

The conversion of the mixed metal oxides into LDHs has been variously referred to as regeneration, reconstruction, restoration, rehydration or the calcination-rehydration process , structural memory effect or simply memory effect . This method is usually employed when large guests are intercalated. It also avoids the competitive intercalation of inorganic anions arising from the metal salts. The procedure is more complicated than coprecipitation or ion-exchange methods, however, and amorphous phases are often produced simultaneously. 

Tonucci. R.J. ct al. "Nanochannet Array Glass. Science. 783 tOcioher 30. (992). Tse. J.S, and D.D. Klug "Structural Memory in Prcssure-Amorphized AIP04." Science. 1559 (Match 20. 1992). 

March Advanced Organic Chemistry Reactions, Mechanisms, and Structure Memory Quantum Theory of Magnetic Resonance Parameters Pitzer and Brewer (Revision of Lewis and Randall) Thermodynamics Plowman Enzyme Kinetics... 

Perfectly elastic deformation and perfectly viscous flow are idealizations that are approximately realized in some limiting conditions. In general the condensed matter has a fading structural memory, and the velocity with which a system that has been perturbed forgets the configuration that it had in the past roughly defines its solid or liquid nature. In ordinary liquids, molecular... 

Water, sodium ion, and hydroxide ion concentrations have been measured within the membrane phase as a function of bulk caustic solution concentration and temperature. These internal membrane concentrations are important because of their influence on the membrane polymer morphology, structural memory, plasticity and the resultant effects on its internal resistance, viscoelasticity and material transport. In addition, the self-diffusion coefficient of the sodium ions in various Nafion membranes has been measured as a function of temperature and external caustic concentration... 

The effect of structural memory in a wave field has been exsemplarily studied by the IR-spectroscopy method on films made from mixtures of butadiene-styrene and acrylic latex as models of polymeric membranes. The strengthening of the interphase interaction in heterophase systems that can cause change of their local and transmitting mobility has been observed. It has been shown, that the response of polymeric dispersed systems and compositions on influence of nonlinear vibrations proves their influence on deformation properties, like orientation phenomena in solid polymers (where Rebinder s effect can take place) that it is possible to consider as a way of polymer modifications, including the obtaining of nanicomposites, polymeric biocarriers, etc. 

Non-volatile MNOS and MNS memory structures with an embedded sheet of Si nanocrystals have been prepared by low pressure chemical vapour deposition using a S13N4 control layer and SiO2 or S13N4 tunnel layers. Si nanocrystals improved the charging behaviour of the MNOS structures. Memory window width of 1.3 V and 2.0 V was achieved for charging pulses of 9 V and 10 V, 100 ms, respectively. 

Kozlov, G. V Shustov, G. B. Dolbin, L V Structural memory of the polyarylates macromolecular coil fractal analysis. Proceedings of XVII Mendeleev s Congress by General and Applied Chemistry Achievements and Perspectives of Chemical Science. Kazan, 21-26 October 2003, p. 442. 

Kozlov, G. V Shustov, G. B. Fractal analysis of the structural memory of macromolecular coil of polyarylates. Reports of Adygskoi (Cheikesskoi) International Academy of Sciences, 2007, 9(2), 138-141. 

The influence of the thermal and chemical history on the active state of powdered iron(III) oxide was assessed from values of the activation energy of radon diffusion, determined from the experimental results of DSA at temperatures below 0.5Tm, where is the melting point in Kelvin [16]. In this temperature range the activation energy of radon diffusion reflects the concentration and type of non-equilibrium defects remaining in the structure of iron(III) oxide after the decomposition of initial iron salts used for the preparation of the oxide samples. Hedvall [18] called this phenomenon the structure memory of solids . 

More recently, a closer inspection of the transient stress rheology for thickening systems has revealed more complicated patterns, such as structural memory effects. Berret et al. [78] and Oeschlager et al. [93,107] have observed that the transient mechanical response also depended on the thermal and shear histories. Samples having been treated thermally, e.g., heated up to 90 °C for 2h, behaved very differently from samples freshly prepared or already sheared. The induction time couid last several hours, and was not proportional to the inverse shear rate, as mentioned previously. It was concluded that the lack of reproducibility under certain thermal and shear conditions might indicate that these surfactant solutions were characterized by long-lived metastable states. 

All real substances are viscoelastic. How they respond in particular situations depends on the rate of testing compared with the rate of spontaneous structural reorganization at the molecular level [1]. As depicted in Fig. 3.3, the neighbors of molecules in an ordinary liquid weU above its glass-transition temperature Tg change rapidly through the action of Brownian motion. Local structural memory - the... 

There are a number of techniques that have been successfully applied to synthesize modified hydrotalcites (48). The most commonly method used is the co-precipitation of two metal salts in alkaline solution at a constant pH value of about 10. Another method uses the classical ion exchange process in which the guest anions are exchanged with the anions in the interlayer spaces of preformed layered double hydroxides to produce specific anion intercalated modified hydrotalcites. StiU another method is a lattice reconstruction after heating, i.e., calcination, which is based on the structural memory effect of these materials, due to which the original structure is reproduced after rehydration. 

Thermal history as one of key factors in developing the catalytic active structure of metastable nature, minimizing in the same time the tendency of its reconstruction towards the initial structure (memory effect) ... 

A tetrahedral Ga4L coordination capsule 575, a derivative of the labile achiral ligand syntone 348, is reported in [69] to exhibit structural memory (i.e., retention of chirality of a cage framework). Although its molecular composition has been altered, chirality of the coordination capsule serves as a structural reporter, preserving the... 

Ziegler M, Davis AV, Johnson DW, Raymond KN (2003) Supramolecular chirality a reporter of structural memory. Angew Chem Int Ed 42(6) 665-668... 

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