Materials Literature
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The Green's function method with the symmetry decoupling scheme has been used in the present paper to investigate the antiferroelectric phase transition in squaric acid (H2C4O4) crystal. It is shown that the phase transition is of first order. The transition temperature Tc and the order parameter Sc at transition poin…
Abstract In order to study the synthesis and properties of polysulfonamides containing thiophene links, 2,2‐bis(5‐chlorosulfonyl‐2‐thienyl)propane [BCTP], 2,2‐bis(5‐chlorosulfonyl‐2‐thienyl)butane [BCTB], 1,1‐bis(5‐chlorosulfonyl‐2‐thienyl)cyclohexane [BCTC], and 2,4‐dichlorosulfonyl thiophene [DCST] were prepared and…
The authors present an experimental and theoretical study of the interplay of the superconductivity (SC) and the charge density wave (CDW) formations in the quasi-one-dimensional conductor NbSe 3 . The application of high pressure or the doping of impurities results in the coexistence of the SC and CDW and then raises…
The epipelic diatoms from various water bodies from the south-western part of the Hornsund fiord area are presented. Altogether, 157 taxa (127 species together with their variants and forms) have been identified. The flora consists almost entirely of diatoms from the order Pennales which is represented predominantly B…
Some years ago Varotsos (1980) suggested a model for the calculation of the bulk modulus of mixed ionic crystals. It was shown initially that this model gives excellent results for the KCl-KBr mixed system. Giri and Mitra (1986) have recently indicated that it can be applied to the mixed systems CaF 2 -SrF 2 and GaP-G…
One of the intrinsic instabilities of permanent magnets is magnetic aftereffect. The magnetic field and temperature dependences of the magnetic aftereffect constant, S v , were measured for a Sm 2 Co 17 sintered magnet under the effective magnetic field, H eff , ranging from -230 to -700 kA/m and at a temperature rang…
New data concerning the refractive-index profiles in Ag/Na ion-exchanged waveguides are obtained using a parabolic-segment reconstruction method. The profiles can be described as second-order polynomials, but with a mean curvature b = 2·8 which is significantly greater than the originally suggested value 0·64. The pro…
Some of the spectroscopic properties of the promethium ion (Pm/sup 3+/) were investigated in order to assess its feasibility for laser action. The fluorescence spectra and decays from the /sup 5/F/sub 1.2/ manifolds were measured in 11 dielectric materials. The calculated peak emission cross sections are comparable to…
A logarithmic increase of resistance with decreasing temperature and a negative magnetoresistance have been observed on low stage acceptor graphite fiber intercalation compounds (GACs) at low temperature. These results may be explained within the framework of the recent theories of weak localization and electron-elect…
Abstract Electrical resistivities ϱ and lattice parameters of quasi‐two‐dimensional crystals of monoclinic η‐Mo 4 O 11 and orthorhombic γ‐Mo 4 O 11 are measured under hydrostatic pressure up to 1.2 GPa at room temperature. Both crystals have negative pressure coefficients of ϱ, which can be qualitatively explained by…
Les cristaux de scolecite sont constitues de secteurs de croissance {110}, {010} et {111} de symetrie triclinique alors que l'analyse par diffraction RX indique une symetrie monoclinique. Existence de deux types de maclages: l'un du a un arrangement asymetrique des ions calcium et des molecules d'eau, et l'autre du a…
Abstract A quasi‐steady state model, based on two parallel modes of diffusion and a polycondensation reaction at the inside surface of a microcapsule, is formulated to compute the time of this microencapsulation process. The predicted times of encapsulation are in agreement with observed values reported in patents. It…
Resistivity measurements on Cu/Mo multilayered films have been performed and the in-plane resistivities interpreted with a model based on the Boltzmann kinetic theory as derived by Dimmich (1985). Theoretical calculations are in excellent agreement with the experimental data at two different temperatures. On the basis…
Abstract A quantitative simultaneous determination method by X-ray powder diffractometry is described for calcium sulfate and calcium carbonate in airborne dusts. In order to eliminate the mutual interference among diffraction peaks, and to avoid the presence of the hydration isomers of calcium sulfate, dust samples w…
An empirical core model construction procedure for pressurized water reactor (PWR) in-core fuel management problems is presented that (a) incorporates the effect of composition changes in all the control zones in the core on a given fuel assembly, (b) is valid at all times during the cycle for a given range of control…
Morphological and chemical properties of brown forest soils and podzolic soils developed on paleozoic shale under beech and/or cryptomeria have been studied with special reference to the eluviation-illuviation characteristics of Fe and Al. Mobilization of Al was observed even in brown forest soils and its pattern was…
Cristallisation dans P4 2 /n. Confirmation de la structure decrite par Strunz: alternance d'octaedres Fe(OH) 6 et Ge(OH) 6 relies par un sommet, dans un reseau tridimensionnel. La baisse de symetrie par rapport a un systeme cubique est accomplie par rotation rigide de ces polyedres. Les longueurs de liaison Fe−O et Ge…
Abstract Bright apple green millimeter-sized crystals of tavorite from the Tip Top pegmatite, near Custer, South Dakota are triclinic, space group , with refined unit-cell parameters a = 5.340(2), b = 7.283(2), c = 5.110(2)Å, α = 109.29(2)°, β = 97.86(3)°, γ = 106.32(3)°, V = 174.1(3)Å 3 , a:b:c = 0.7332:1:0.7016, Z =…
The structure of rhombohedral PbZr0.75Ti0.25O3 has been refined at liquid nitrogen and room temperatures (low temperature form) and at 105°C (high temperature form) using neutron diffraction data. Rotations of oxygen octahedra, characteristic for the low temperature phase, amount to ±5.3 and ±3.2 degrees for the forme…
In relation to the temperature effect in cavitation damage, the collapse of a single bubble in water over a wide range of temperatures was experimentally studied. A spark-induced bubble was observed by using a high speed camera and the impulsive pressure caused by the bubble collapse was measured by means of a pressur…