Glass models

Another widely studied phenomenon in alkah borate glasses is the mixed alkah effect, the nonlinear change in glass properties when a second kind of alkah oxide is added into the single-alkali glass. Models have been suggested to explain the mixed alkah effect (144), but a universally accepted model has not been developed as of this writing. 

Derrida and Flyvberg [flyvb88] and Derrida and Bessis [derrida88] have examined the overlap between two attractors by looking at the probability that two randomly chosen initial state.s evolve toward the same attractor. These studies find that the distribution is very similar to that found in certain spin-glass models. 

Aquaporins. Figure 1 (a) The hour-glass model. The scheme depicts the six transmembrane helices (H1-H6), the connecting loops A-E, including the helical parts of loops B ((H)B) and E (E(H)), and the conserved NPA (Asn-Pro-Ala) motif of canonical aquaporins. (b) Structure of the conserved NPA motif region, flanked by the indicated helices, (c) Crystallographic structure of AQP1 tetramer. The four water pores in atetramer are indicated [1]. 

Wood and Hill consider that the role of fluoride in these glasses is uncertain. Phase-separation studies suggest that the structure of the glass might relate to the crystalline species formed, in which case a microcrystallite glass model is appropriate. But other evidence cited above on the structure-breaking role of fluoride is compatible with a random network model. 

L. F. Cugliandolo, J. Kurchan, G. Parisi, and F. Ritort, Matrix models as solvable glass models. Phys. Rev. Lett. 74, 1012-1015 (1995). 

L. F. Cugliandolo and J. Kurchan, Analytical solution of the off-equilibrium dynamics of a long-range spin-glass model. Phys. Rev. Lett. 71, 173-176 (1993). 

The Beuhler-Friedman model becomes essentially identical to the earlier Stern-glass model at high velocities. It is also quite similar to the well known model of Parilis and KishinerskiP with the major difference being the method used to calculate the number of energetic electrons produced within the target. 

Most of the simple fitness functions, including the spin-glass models and the AW-modcl, are isotropic (Schuster and Stadler, 1994). However, it is expected that real sequence spaces are highly anisotropic with most regions devoid of fitness, and functional regions that are rich with landscape features. A real protein landscape can appear isotropic in two ways. The first is if a subset of the space is defined—for instance, only the functional sequences are considered. Further, the landscape can... 

A modified form of the quantum FDT in an out-of-equilibrium situation, allowing for the description of aging effects, has been proposed in [46,47] for mean-field spin-glass models. Here, we propose a modified form of the quantum FDT which can conveniently be applied to the displacement of the free quantum Brownian particle—that is, to the problem of diffusion.9... 

Herbert Hauptman, a mathematician turned crystallographer and chemistry Nobel laureate for 1985, has devoted a lot of attention to close packing of spheres in the icosahedron. Figure 9-31 shows one of his beautiful stained-glass models. 

Figure 9-31. Herbert Hauptman (photograph by the authors) and one of his stained-glass models—an icosahedron—with densely packed spheres (photograph courtesy of Herbert Hauptman, Buffalo, New York).

Experimental. A Parr model 1221 oxygen bomb calorimeter was modified for isothermal operation and to ensure solution of nitrogen oxides (2). The space between the water jacket and the case was filled with vermiculite (exploded mica) to improve insulation. A flexible 1000-watt heater (Cenco No. 16565-3) was bent in the form of a circle to fit just within the jacket about 1 cm. above the bottom. Heater ends were soldered through the orifices left by removing the hot and cold water valves. A copper-constantan thermocouple and a precision platinum resistance thermometer (Minco model S37-2) were calibrated by comparison with a National Bureau of Standards-calibrated Leeds and Northrup model 8164 platinum resistance thermometer. The thermometer was used to sense the temperature within the calorimeter bucket the thermocouple sensed the jacket temperature. A mercury-in-glass thermoregulator (Philadelphia Scientific Glass model CE-712) was used to control the jacket temperature. 

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