Local phase transitions

Eles, P.T., and Michal, C.A. "Strain dependent local phase transitions observed during controlled supercontraction reveal mechanisms in spider silk". Macromolecules 37(4), 1342-1345 (2004). 

Various quantities, such as the fraction of repeating xmits (monomers) captured at the interface (which serves as an order parameter of the localization phase transition) and the components of the polymer radius of gyration parallel (I g ) and perpendicular (/ gj ) to the phase boundary between the immiscible hquids, can be then studied in order to verify the predictions of the pertinent scaling analysis by comparison with results from Monte Carlo simulations [36,45-47]. As an example, we show the changing degree of copolymer localization (Fig. 8a) and the ensuing... 

Write-once media, in most cases based on burning pits in an organic or inorganic layer which melts, evaporates or decomposes under the Influence of the laser beam. Another possibility is inducing a local phase transition, e.g. from polycrystalline to amorphous. Read-out is done at a lower intensity. 

Inhomogeneous stresses produced by localized defects may induce local phase transitions above the normal phase transition temperature Tc, causing the material to have mixed low and high symmetry phases in certain temperature regions. Such a two-phase mixture is usually very sensitive to external fields or stresses since the phase change among the mixture becomes barrierless even for a first order phase transition [10]. 

As follows from the 6H- and 3C-SiC microhardness temperature dependences, there is a local phase transition at temperatures lower than 40°C and pressure about 29 GPa with the formation of closely packed and more plastic phases. The activation energy of dislocation move-... 

As revealed by soHd-state NMR, dragline fibers undergo a collapse of amino acid chains when contacting with water. The inter-chain hydrogen bonds are broken by hydration, leading to local phase transitions to a rubbery state in the process of supercontraction (Figure 6.6). As a result, supercontracted silk exhibit rubber-like mechanical responses [55]. 

Besides the chemical composition, porosity is another property of stone which has great influence on its preservation. An increased porosity increases the exposed surface and pores allow movement of materials such as water and its solutes through the stones. If the pores are blocked or reduced in diameter such substances may be trapped within resulting in increased local interior damage. Exposure to the climatic elements is one important source of decay. Freeze-thaw cycles, in particular, result in pressures on the pore walls of the stone s interior from changes in volume during the phase transition... 

For the analysis heat and mass transfer in concrete samples at high temperatures, the numerical model has been developed. It describes concrete, as a porous multiphase system which at local level is in thermodynamic balance with body interstice, filled by liquid water and gas phase. The model allows researching the dynamic characteristics of diffusion in view of concrete matrix phase transitions, which was usually described by means of experiments. 

An ordering phase transition is characterized by a loss of symmetry the ordered phase has less symmetry than the disordered one. Hence, an ordering process leads to the coexistence of different domains of the same ordered phase. An interface forms whenever two such domains contact. The thermodynamic behavior of this interface is governed by different forces. The presence of the underlying lattice and the stability of the ordered domains tend to localize the interface and to reduce its width. On the other hand, thermal fluctuations favor an interfacial wandering and an increase of the interface width. The result of this competition depends strongly on the order of the bulk phase transition. 

Pd(lll). However, Pd(lll) shows little or no evidence for the stoichiometric 2Bi + L + 3L process. This could be due to the presence of longer range order on the single crystal than on the Pd particles, leading to processes more akin to two dimensional phase transitions on the Pd(lll) crystal surface, rather than a more local species conversion on the small metal crystallites. 

In general terms, the phenomena described above belong to the class of phase transitions and critical phenomena in confined spaces. From the field of statistical physics, some far-reaching results applying to such problems are knovm. One fruitful concept used in statistical physics is the correlation length (see, e.g., [64]). The correlation length describes how a local field quantity evaluated at one point in space is correlated with the same quantity at another point. As an example, the correlation length crfor density fluctuations in a fluid is defined via... 

In this second edition the text has been revised and new scientific findings have been taken into consideration. For example, many recently discovered modifications of the elements have been included, most of which occur at high pressures. The treatment of symmetry has been shifted to the third chapter and the aspect of symmetry is given more attention in the following chapters. New sections deal with quasicrystals and other not strictly crystalline solids, with phase transitions and with the electron localization function. There is a new chapter on nanostructures. Nearly all figures have been redrawn. 

A hysteresis cycle in the molar susceptibility measurements has been observed for [Ni2(Medpt)2(N3)2(/r-N3)2] (883). This has been ascribed to a phase transition caused by an asymmetrization process of the rhombus-like centrosymmetric [Ni-(N3)2-Ni] core that occurs with falling temperature. The asymmetrization transition can be explained in terms of a second-order Jahn-Teller distortion, taking into account the local symmetry of the dinuclear [Ni-(N3)2-Ni] entity (D2h, rhombic symmetry) before the arrangement.2128... 

Phase transitions of the PS-fo-PI system have been extensively studied. The morphological transition from the I phase to the G phase proceeds through nucleation and growth. The difference in the geometrical characteristics of these two phases induces considerable local distortion of both morphologies... 

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