Long-range Effects on the Pyroelectric Coefficient and Dielectric Susceptibility of a Ferroelectric Bilayer

Long-range effects on the pyroelectric coefficient and susceptibility of a ferroelectric bilayer with a ferroelectric interfacial coupling are investigated by use of the transverse Ising model within the framework of mean-field theory. The effects of the interfacial coupling and the transverse field on the pyroelectric coefficient and susceptibility of the bilayer are investigated by taking into account the long-range interaction. It is found that the pyroelectric coefficient and susceptibility increase with the decrease of the magnitude of the long-range interaction and the interfacial coupling when the temperature is lower than the phase transition temperature. We also find that the strong long-range interaction, the large transverse field and weak interfacial coupling can lead to the disappearance of some of the peaks of the pyroelectric coefficient and susceptibility of the ferroelectric bilayer. The phase transition temperature increases with the increase of the strength of the long-range interaction, which is similar to the results obtained in ferroelectric multi-layers or superlattice.Comment: 23 pages, 11 figure

Superfluid to normal phase transition and extreme regularity of superdeformed bands

We derive the exact semiclassical expression for the second inertial parameter $\cal B$ for the superfluid and normal phases. Interpolation between these limiting values shows that the function ${\cal B}(I)$ changes sign at the spin $I_c$, which is critical for a rotational spectrum. The quantity $\cal B$ turns out to be a sensitive measure of the change in static pairing correlations. The superfluid-to-normal transition reveals itself in the specific variation of the ratio ${\cal B}/{\cal A}$ versus spin $I$ with the plateau characteristic of the normal phase. We find this dependence to be universal for normal deformed and superdeformed bands. The long plateau with a small value ${\cal B}/{\cal A}\sim A^{-8/3}$ explains the extreme regularity of superdeformed bands.Comment: 30 pages in LaTeX, 6 figures (PostScript). To be published in Yadernaya Fizika (Physics of Atomic Nuclei), special edition dedecated to the 90th birthday of Prof. I. I. Gurevit

Microscopic Study of Superdeformed Rotational Bands in 151Tb

Structure of eight superdeformed bands in the nucleus 151Tb is analyzed using the results of the Hartree-Fock and Woods-Saxon cranking approaches. It is demonstrated that far going similarities between the two approaches exist and predictions related to the structure of rotational bands calculated within the two models are nearly parallel. An interpretation scenario for the structure of the superdeformed bands is presented and predictions related to the exit spins are made. Small but systematic discrepancies between experiment and theory, analyzed in terms of the dynamical moments, J(2), are shown to exist. The pairing correlations taken into account by using the particle-number-projection technique are shown to increase the disagreement. Sources of these systematic discrepancies are discussed -- they are most likely related to the yet not optimal parametrization of the nuclear interactions used.Comment: 32 RevTeX pages, 15 figures included, submitted to Physical Review

Iron Behaving Badly: Inappropriate Iron Chelation as a Major Contributor to the Aetiology of Vascular and Other Progressive Inflammatory and Degenerative Diseases

The production of peroxide and superoxide is an inevitable consequence of aerobic metabolism, and while these particular "reactive oxygen species" (ROSs) can exhibit a number of biological effects, they are not of themselves excessively reactive and thus they are not especially damaging at physiological concentrations. However, their reactions with poorly liganded iron species can lead to the catalytic production of the very reactive and dangerous hydroxyl radical, which is exceptionally damaging, and a major cause of chronic inflammation. We review the considerable and wide-ranging evidence for the involvement of this combination of (su)peroxide and poorly liganded iron in a large number of physiological and indeed pathological processes and inflammatory disorders, especially those involving the progressive degradation of cellular and organismal performance. These diseases share a great many similarities and thus might be considered to have a common cause (i.e. iron-catalysed free radical and especially hydroxyl radical generation). The studies reviewed include those focused on a series of cardiovascular, metabolic and neurological diseases, where iron can be found at the sites of plaques and lesions, as well as studies showing the significance of iron to aging and longevity. The effective chelation of iron by natural or synthetic ligands is thus of major physiological (and potentially therapeutic) importance. As systems properties, we need to recognise that physiological observables have multiple molecular causes, and studying them in isolation leads to inconsistent patterns of apparent causality when it is the simultaneous combination of multiple factors that is responsible. This explains, for instance, the decidedly mixed effects of antioxidants that have been observed, etc...Comment: 159 pages, including 9 Figs and 2184 reference

Facile and efficient synthesis of 3β-hydroxy-eupholanost-8-en-24-one

The epoxidation of the natural product α-euphol followed by cleavage of the obtained epoxide with BF3-etherate, provides 3β-hydroxy-eupholanost-8-en-24-one in satisfactory overall yield

Magnetic properties of the spin-1/2 Ising ferromagnetic thin films with 2 alternating superlattice configuration

The magnetic properties in a finite ferromagnetic superlattice are studied. The spin-(1)/(2) Ising model with alternating intralayer parameters is used within the effective field theory, which is based on a probability distribution technique that accounts for the self-correlation function. The transition temperatures are calculated as a function of the intra- and interlayer exchange interactions and of the surface exchange interaction. The magnetization profiles are also studied

Phase diagram of spin-1/2 Ising semi-infinite and film ferromagnets with spin-3/2 overlayers

Within the framework of the effective field theory, we examine the phase diagrams of a spin-1/2 Ising film, with a spin-3/2 atoms on the top and bottom surfaces, and the corresponding semi-infinite system. In particular, the effects of surface single-ion anisotropy on the phase diagram and critical value for surface ordering are clarified. The system shows the existence of a critical value of the ratio of the surface interaction to the bulk one above which the surface magnetism appears. This critical value moves to lower values when D-s increases. The critical surface temperature exhibits a characteristic behavior namely when large negative D-s are selected

Facile and efficient synthesis of 3β-hydroxy-eupholanost-8-en-24-one

The epoxidation of the natural product α-euphol followed by cleavage of the obtained epoxide with BF3-etherate, provides 3β-hydroxy-eupholanost-8-en-24-one in satisfactory overall yield

Magnetic properties of the spin-1/2 transverse ferromagnetic bilayer system with disordered interfaces

The effects of an applied transverse magnetic field on the magnetic properties in a ferromagnetic bilayer system with disordered interfaces consisting of spin-1/2 atoms are investigated using the effective field theory. The magnetization protiles and the phase diagrams. namcl, T-c versus the concentration p, T-c versus the interlayer exchange interaction and T-c versus the transverse field plots are discussed. It is shown that the existence of the disordered interfaces may severely affect the phase diagrams of T-c When the transverse field is applied and the interlayer exchange interaction is selected as the large value. some characteristic effects due to them can be obtained in the critical properties of the system. such as the reentrant phenomenon observed for special cases. (C) 2002 Published by Elsevier Science B.V