High normal-state properties

In the second example BCS theory relates the appearance of a superconducting state to the breakdown of electromagnetic gauge symmetry by interaction with regular ionic lattice phonons and the creation of bosonic excitations. This theory cannot be extended to deal with high Tc ceramic superconductors and it correlates poorly with normal-state properties, such as the Hall effect, of known superconductors. It is therefore natural to look for alternative models that apply to all forms of superconductivity. 

In the previous Section we analysed the normal-state properties of high-7) superconductors, based on the Fermi-liquid picture. In this Section we discuss some aspects which seemingly contradict the Fermi liquid theory, in particular... 

It was realized at the outset that the normal state properties of the high-T cuprate superconductors are unusual and appear to violate the Landau Fermi liquid paradigm (Anderson 1987, Levi 1990, Levin et al. 1991, Laughlin 1988, Varma et al. 1989). Some researchers share the view that in so far as the normal state properties reflect the electronic structure that underlies high-To superconductivity, it will be necessary to develop an understanding of the normal state before the superconducting state can be imderstood. 

The anomalous normal state properties first identified in the high-Tc cuprate superconductors include the electrical resistivity and Hall effect. The electrical resistivity Pab T)... 

Discovery of a highly anisotropic vortex lattice, with conventional quantization in UPt3, a compound whose normal state properties are quite isotropic. 

Properties of Light and Heavy Hydrogen. Vapor pressures from the triple point to the critical point for hydrogen, deuterium, tritium, and the various diatomic combinations are Hsted in Table 1 (15). Data are presented for the equiUbrium and normal states. The equiUbrium state for these substances is the low temperature ortho—para composition existing at 20.39 K, the normal boiling point of normal hydrogen. The normal state is the high (above 200 K) temperature ortho—para composition, which remains essentially constant. 

A supercritical fluid is a state of matter achieved by high temperature and extremely high pressure, exceeding the so-called critical temperature and pressure for that substance. The solvent properties of a supercritical fluid are much improved over the normal solvent properties of that fluid. 

Most of our high Tc superconductors are highly inhomogeneous on a scale that is likely important for both normal state and superconducting properties. Some have taken this as evidence for... 

At high temperatures, ferroelectric materials transform to the paraelectric state (where dipoles are randomly oriented), ferromagnetic materials to the paramagnetic state, and ferroelastic materials to the twin-free normal state. The transitions are characterized through order parameters (Rao Rao, 1978). These order parameters are characteristic properties parametrized in such a way that the resulting quantity is unity for the ferroic state at a temperature sufficiently below the transition temperature, and is zero in the nonferroic phase beyond the transition temperature. Polarization, magnetization and strain are the proper order parameters for the ferroelectric. 

Raney Ni with additives is also used [77, 276]. In particular, valve metals are added to stabilize the catalyst structure [102,410, 411], thus decreasing the recrystallization and sintering which always takes place as the solution temperature is raised [412] (which points to the high energy state of such an electrode structure). In this respect, potential cycling has also been observed to be detrimental since it can induce recrystallization [407]. This is probably the reason why surface oxidation may be deleterious with Raney structures [390] while it normally results in improved electrocatalytic properties with bulk Ni electrodes [386]. However, after prolonged cathodic load resulting in deactivation, Raney Ni electrodes can be reactivated (temporarily) by means of anodic sweeps [405]. 

The fluorescence of polysilanes has received much attention in recent years, in part because of the discovery that some poly silanes are electroluminescent, and so may have applications in display technology. Fluorescence spectra, quantum yields, lifetimes and other properties for dialkylpolysilanes have been thoroughly investigated by Sun and coworkers.98 Dialkylpolysilanes exhibit fluorescence of a rather normal type, in which the emission is a mirror image of the absorption, with a rather small Stokes shift. This suggests that the emission takes place from a highly delocalized state, probably an... 

Probably the most widely reported information concerning petrolatum s effect on damaged skin was a 1992 article by Ghadially and coworkers.71 Newspapers across the United States reported the results of this study, which showed that, when applied to skin that had been damaged by acetone, petrolatum accelerated the recovery of the skin s normal barrier properties. It was noted that this is in contrast to materials that are highly impermeable to water vapor (such as polyethylene films) which hinder barrier repair. However, another publication has indicated that the repair of the permeability barrier in human skin is not delayed by occlusion.72... 

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