Sur un nouveau materiau pour l'enregistrement magnetique derive du dioxyde de chrome

A new ferromagnetic ternary oxide of formula Cr_1?xIr_xO₂ (0 < x < 0.3) has been prepared and ajusted. Thanks to iron doping a high coercive field ($\text{H}{}_{\mathrm{<mtext>c</mtext>}}\text{? 600}\text{Oe}$) can be obtained in appropriate conditions for an irridium content as low as $\text{x}\text{? 5.10}{}^{\mathrm{?4}}$. Such a material is promising for magnetic recording.     

Internal morphology of a fiber-reinforced cement

The fracture of a fiber-reinforced cement, investigated by scanning electron microscopy, shows different types of areas with emergence and imbrication of fibers. Particular well-monocrystallized ettringite (“flower-like” crystallization), generally not encountered in hydrated pure portland cement paste, can be observed in some voids or cavities. This phenomenon is due to the macroporous texture of the material.     

A high spin configuration for six-coordinated iron (IV) in an oxygen lattice

A simple model for the variation of crystal field and of covalency with the distortion of FeO₆ octahedra shows that Fe (IV) with ground term 5A_1g (d¹_xyd¹_yzd¹_zxd¹_z2d⁰_x2?_y2) can be stabilized in an elongated FeO₆ octahedron. Such an electronic configuration has been found actually in a Sr_0.5La_1.5Li_0.5Fe_0.5O₄ phase with K₂NiF₄ structure. Structural ($\text{c}\text{a}\text{? 3.46}$), magnetic (Curie constant $\text{C}\text{? 3.06}$) and Mössbauer resonance (isomer shift at room temperature relative to metallic Fe $\text{δ ? ? 0.19}\text{mms}{}^{\mathrm{?1}}$) studies illustrate this electronic configuration.     

Nightmare behavior: A review.

Reviews objective reports, surveys, observations, and studies relating to nightmare behavior. Physiological correlates of nightmares including the relationship of homeostatic imbalances and production of nightmares are examined. Investigations are criticized on the basis of inadequate numbers of Ss, absence of controls, excessive reliance on self-reports, poor reliability and validity, and lack of experimental control over independent variable under study. Possible improvements in existing methodology are considered, and suggestions for further research are offered. Psychogenic theories accounting for production of nightmare dreams are reviewed. In addition, recent applications of behavioral methodology to treatment of pathological nightmare behavior are surveyed. (49 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Un exemple de chaînes antiferromagnetiques alternees de spin 12: CuWO4

The ordering of Cu and W atoms in the distorted wolframite structure of CuWO₄ gives rise to zigzag chains of edge sharing CuO₆ octahedra linked by similar chains of WO₆ octahedra. The existence of two kinds of connections between the CuO₆ octahedra leads to alternating antiferromagnetic interactions along the chains. The magnetic behavior is explained using a Heisenberg type model of Duffy and Barr with the largest exchange integral : J = ? 67 K and an alternation parameter : a = 0.8. k_B EPR measurements have shown that threedimensional ordering occurs at $\text{T}{}_{\mathrm{N}}\text{? 24}\text{K}$.     

Une modelisation du comportement magnetique d'un compose de l'iridium pentavalent: LaLi12Ir12O3

A new interpretation is proposed for the magnetic properties of perovskite-type iridium (+V) oxide $\text{LaLi}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{Ir}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{O}{}_3$. In its unusual +5 oxidation state iridium has a t⁴_2ge⁰_g configuration. The magnetic susceptibility has been calculated assuming cubic symmetry of the crystal field and a Coulomb repulsion of the same order of magnitude than spin-orbit coupling. Fitting of the experimental data leads to a single spin-orbit constant $\text{ζ ? 3470}\text{cm}{}^{\mathrm{?1}}$ close to that of previously investigated Ir(+V) compounds.     

The Esclangon diagram for voltage and current along a transmission line

This article offers a simple graphic construction that shows the variation of current and voltage along an electric line for a steady sinusoidal operation. The method complements the use of formula applications and the Smith chart, thus making for a good and easy understanding of transmission-line operation.     

Theoretical atomic inner-shell energy levels, 70 ≤ Z ≤ 106

Theoretical 1s, 2s, $\text{2p}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$, and $\text{2p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ energy levels in neutral atoms with 70 ≤ Z ≤ 106 are listed. The computations are relativistic and include complete relaxation. The electric energies are based on Dirac-Hartree-Slater wave functions; a first-order correction to the local approximation is made. The Breit-interaction energy and vacuum-polarization energy are listed separately, and a self-energy correction is included. These calculations differ from earlier work by the authors in that a more accurate, frequency-dependent expression for the Breit energy is employed, a Fermi (rather than uniform) distribution of the nuclear charge is assumed, and a screened self-energy correction is applied to the 1s, 2s, $\text{2p}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$, and $\text{2p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ levels. Comparison of results with 1967 experimental values adopted by Bearden and new work of Borchert shows better agreement than is provided by earlier calculations with frequency-independent Breit interaction and a uniform nuclear charge distribution.     

Influence de la pression partielle d'oxygene sur la nature des defauts ponctuels dans Ca2LaFe3O8+x

The type of point defects in non-stoichiometric Ca₂LaFe₃O_8+x ferrite has been studied by measuring the variation of electrical conductivity with oxygen partial pressure at various temperatures. Several ordering possibilities occur. The oxygen atoms inserted, mostly 1-charged, have a strong tendency to couple at sufficient oxygen pressure and at low temperature. Interstitial oxygen atoms in the lattice vacancies induce structural evolution as non-stoichiometry becomes significant enough.