Ordered phase in the two-dimensional randomly coupled ferromagnet

True ground states are evaluated for a 2d Ising model with random near neighbor interactions and ferromagnetic second neighbor interactions (the Randomly Coupled Ferromagnet). The spin glass stiffness exponent is positive when the absolute value of the random interaction is weaker than the ferromagnetic interaction. This result demonstrates that in this parameter domain the spin glass like ordering temperature is non-zero for these systems, in strong contrast to the 2d Edwards-Anderson spin glass.Comment: 7 pages; 9 figures; revtex; new version much extende

Les Pierres Branlantes de Beuville (Calvados) : Pierre à cupules

Doranlo , Vetel J. Les Pierres Branlantes de Beuville (Calvados) : Pierre à cupules. In: Bulletin de la Société préhistorique de France, tome 10, n°12, 1913. pp. 5-21

Dynamic evidence for a 2d - 3d crossover in the Ising spin glass Fe0.35Mg0.65Br2

We report on magnetic dynamic properties in the Ising spin glass Fe 0.35Mg0.65Br2. The ac susceptibility curves have been deduced from direct susceptibility and Faraday rotation measurements over a wide frequency range extending from 100 kHz down to 0.05 Hz. The temperature dependence of the characteristic relaxation time cannot be fitted by either a power or an Arrhenius law over the whole frequency range. We show that this system exhibits a dimensional 2d-3d crossover when lowering the temperature.Nous présentons une étude du comportement critique dynamique du verre de spin de type Ising Fe0.35Mg0.65Br2. Les courbes de susceptibilités alternatives ont été déduites de mesures directes et de mesures par effet Faraday sur une large gamme de fréquence allant de 100 kHz à 0.05 Hz. La dépendance en température du temps de relaxation caractéristique du système ne peut être représentée ni par une loi de puissance ni par une loi d'Arrhénius sur toute la gamme de fréquence. Nous montrons que ce système présente un crossover de dimensionalité 2d-3d quand la température décroît

The geometry and emplacement of conical sandstone intrusions

Conical sandstone intrusions with a geometry comparable with that of many igneous sills have been identified using 3D seismic data from large areas of the North Sea and Faeroe-Shetland Basins. These intrusions are of reservoir scale, ranging from 100 to 2000 m or so in diameter, 50-300 m in height, and 1-80 m in thickness (aperture). They are concentrated in specific stratigraphic intervals in the Cenozoic fills of both basins. Two geometrical end members are recognised and defined here: 'apical cones' and 'flat-based bowls'. The former consist of inward dipping conical inclined sheets meeting at a prominent apex and the latter of similarly dipping discordant margins climbing from the edges of a concordant sheet. Both end members are associated with domal folds that are interpreted as resulting from the hydraulic elevation of the overburden during intrusion, and which are analogous to similar structures associated with bowl-shaped igneous sills. Measurements of aperture (ω) versus distance exhibit systematic relationships with the structural relief of these folds, offering a potentially predictive method for estimation of sandstone intrusion aperture and reservoir volume prior to drilling. A growth model for these end-member geometries is presented, drawing on existing theory for igneous sill emplacement. Aperture versus distance plots (ω -X) are used to illustrate two contrasting models for aperture inflation during propagation, but these require much further data before any specific growth model can be adopted. © 2008 Elsevier Ltd. All rights reserved

STATIC AND DYNAMIC CRITICAL BEHAVIOUR OF THE SPIN GLASS Fe0.35Mg0.65Br2

We present results concerning the static and dynamic behaviour of the new Ising spin glass Fe0.35Mg0.65Br2. The analysis of the static magnetisation leads to conclude to a transition at finite Tc = 1.9 K with γ = 2 and β = 0.4. Dynamics confirm this feature and we find critical exponent zv ~ 10

The location of europium in Eu³⁺-exchanged zeolite-Y as determined by extended X-ray absorption fine structure (EXAFS) investigations at 77 K

Eu L3-edge EXAFS has been used to investigate the location of Eu3+ cations in an Eu3+-exchanged zeolite-Y, with a framework Si/Al molar ratio of 13.5 ± 2.0, as a function of heat treatment up to 200 °C. All of the EXAFS data were recorded from samples cooled to 77 K following ion-exchange and heat treatment. The interpretation of the EXAFS data, in conjunction with a geometrical modelling approach, for the sample subject only to ion-exchange at 60 °C is consistent with hydrated Eu3+ cations being directly bound to framework oxygen atoms (O4) of free six-membered rings that border the supercages of the zeolite-Y structure. The hydrated Eu3+ cations are displaced from the high-symmetry SII sites. The coordination environment of the Eu3+ cation in the sample heated to 100 °C is similar to that in the as-exchanged sample. Heating of the Eu3+-exchanged zeolite-Y at 200 °C results in migration of the Eu3+ cations into the sodalite cages where, as partially hydrated species, they are coordinated to three framework oxygen atoms in such a way as to be displaced from SI′ sites