Materials Literature
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Limits fixed in Codes for the chemical characteristics of cements have been established with semi-empirical methods, given the complexity of influencing phenomena, without correspondence between these values and the physico-chemical or mechanical properties as durability or strength. Knowledge of statistical distribut…
In Colombian ways and means, since the application of no traditional constructive systems is growing up, and having recourse to the new Seismic Construction Code, it is necessary to work with cement mortars of defined and reproducible characteristics. An analysis of the variability affecting the mortars behaviour was…
A close relationship was found between the pH of soil suspensions in the SMP buffer solution (pHsmp) and the potential acidity of soils (H + Al) extracted by a neutral calcium acetate solution (r = 0.98), for twenty six soil samples of the State of Sao Paulo, Brazil, This relationship was represented by the equation l…
The equations of acoustoelasticity are formulated in both natural and initial frames of reference and applied to investigate the propagation of ultrasonic waves in orthotropic elastic solids with initial stresses. The foundation of the equations is re-examined for the purpose of applying them to the measurement of res…
A system which shows a relatively large blue-phase range is investigated. Owing to the small value of the cholesteric pitch the blue-phase shows no Bragg-reflections in visible light. Nevertheless, electric-field induced birefringence shows quite large values. The response times are a few tens of microseconds below 10…
Abstract When natural rubber is epoxidized under carefully controlled conditions, it can be converted to a totally new polymer with some properties more akin to speciality rubbers and some properties that appear to be advantageous for tire treads. Three levels of epoxidation have been extensively evaluated. They were…
The quinoid-benzenoid-diimine form, (=(C6H4)=N-(C6H4)-N=)x of “polyaniline” shows excellent cathode characteristics including recyclability when used in conjunction with a zinc anode in an aqueous electrolyte of (l. 0M ZnCl2 + 0. 5M NH4Cl) having a pH of ∼ 4. The reduced form of this material, (-(C6H4)-N(H)-(C6H4)-N(H…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTExcited-state properties of a triply ortho-metalated iridium(III) complexK. A. King, P. J. Spellane, and Richard J. WattsCite this: J. Am. Chem. Soc. 1985, 107, 5, 1431–1432Publication Date (Print):March 1, 1985Publication History Published online1 May 2002Published inissue…
“Polyaniline” has been synthesized in various forms both chemically and electrochemically in aqueous media. The qulnoid-benzenoid-diimine form, an insulator, is doped by dilute aqueous protonic acids to the metallic regime ([sgrave] = 5 ohm−1cm−1; compressed pellet) to give the corresponding iminium salt. This represe…
ABSTRACT: Effective interresidue contact energies for proteins in solution are estimated from the numbers of residue-residue contacts observed in crystal structures of globular proteins by means of the quasi-chemical approximation with an approximate treatment of the effects of chain connectivity. Employing a lattice…
Starting from the dielectric function of a two-band model, a generalised Horie formula (1959) for the wavevector-dependent frequency omega p (q), of the valence plasmon is derived. The dispersion is determined by band-structure effects and the q-dependence of the oscillator strength. The latter is calculated using kp…
For part II, see ibid., vol.17, p.4725 (1984). Measurements of the inelastic neutron scattering spectrum of molten MgCl 2 show directly the existence of a weak soft mode in the momentum transfer range 1.5<Q<1.8 AA -1 . Such modes are not directly observed in molten CaCl 2 and have not been seen in other molten salts.…
Resistivity and X-ray diffraction measurements have been made for the quasi-one-dimensional conductors (MSe 4 ) 2 I (M=Ta and Nb). (TaSe 4 ) 2 I is known to undergo a phase transition at T c approximately=260K. A phase transition of (NbSe 4 ) 2 I was found to take place at T c approximately=210K. Non-linear conduction…
The problem of low-frequency current noise with a 1/ f spectrum in solids (flicker noise) is reviewed. The fundamental general properties of this noise are described: frequency-dependence of the spectral density, time-dependence of the correlation function, form of the distribution function of the fluctuations, depend…
§ 1. Root System Belonging to a Quadratic Form § 2. Marked Extended Affine Root System (R
The authors present a systematic approach to the derivation of empirical potential parameters for binary oxides; they also consider their modification for use in mixed oxide systems. Shell-model potentials are used but, unlike the case of the alkali halides within which polarisability and short-range interaction param…
A strategy for the synthesis of chiral molecules that receives growing popularity among organic chemists employs the photochemically mediated [2 + 2] cycloaddition reaction. These reactions can be performed on a multigram scale and often proceed with high yield and with stereocontrol. These features, in combination wi…
The design, synthesis, and study of electrically conductive molecular and polymeric substances constitute a new scientific endeavor involving the interaction of chemists, physicists, and materials scientists. The strategies, developments, and challenges in these two closely related fields are analyzed via a class of m…
The fluoresence spectrum of europium(+III) doped LaMgB5O10 was studied at 77 and 300K under U.V. and visible dye laser excitation. A phenomenological crystal field analysis was conducted on the basis of the observed 34 7 F 0-5 level energies. A descending symmetry method from D 2d to C 2v and C 2 symmetries was used i…
The energy, the elastic dipole tensor and the entropy of point defects in ionic crystals are usually calculated by the Mott-Littleton approach, which treats a single defect in an infinite crystal. The authors suggest that there may be advantages, particularly for the dipole tensor and the entropy, in performing the ca…