Materials Literature
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Using various ultraviolet laser excitation lines between 199.8 nm (50 034 cm -1 ) and 266 nm (37 583 cm -1 ), emission transitions have been observed and assigned for the first time from the 3 P 2 term of Tm 3+, located near 37 500 cm -1 . The most intense transitions are to the terminal 3 H 6 and 3 F 4 states, and ar…
Abstract A series of oligomeric, hydroxy‐terminated silarylene–siloxane prepolymers of various lengths were prepared via dehydrogenative coupling between 1,4‐bis(dimethylsilyl)benzene [H(CH 3 ) 2 SiC 6 H 4 Si(CH 3 ) 2 H] and excess 1,4‐bis(hydroxydimethylsilyl)benzene [HO(CH 3 ) 2 SiC 6 H 4 Si(CH 3 ) 2 OH] in the pres…
The factors that govern the materials chemistry of a variety of new catalysts are identified and illustrated. Prominence is given mainly to nanoporous (and some nanoparticle) catalysts, which are of high relevance in ‘clean’ technology and ‘green’ chemistry. In particular, molecular sieve catalysts for the regioselect…
The structures of an optically isotropic cubic phase and a bluish colored phase exhibited in an (R,S) dichiral compound with fluorines have been investigated. Not only the bluish colored phase but also the cubic phase exhibit circular dichroism, being confirmed to be chiral phases. Based on the analysis of several X-r…
We present a single-orbital double-exchange model, coupled with cooperative phonons (the so called breathing modes of the oxygen octahedra in manganites). The model is studied with Monte Carlo simulations. For a finite range of doping and coupling constants, a first-order metal-insulator phase transition is found, whi…
This communication describes scanning tunnelling microscopy investigations of the electronic properties of singlewalled carbon nanotubes (SWNTs). First, the unique relationship between the atomic structure and electronic properties of SWNTs is presented. Second, structural defects in nanotubes are addressed, and quant…
Highly saddle shaped iron(III) porphyrin complex 1 showing a novel spin crossover process between the S = 3/2 and S = 1/2 has been crystallographically analyzed at 298, 180, and 80 K. As the temperature is lowered, the lattice contraction has occurred specifically along the b-axis. Correspondingly, the iron-pyridine b…
Electrolysis of benzylthiocyanate, benzyl chloride, p-methylbenzyl chloride, p-methoxybenzyl chloride, or toluene in acetonitrile, at platinum electrodes in a two compartments cell divided by a glass-frit diaphragm, affords 2,6-dimethyl-4-arylpyridine-3,5-dicarbonitrile as major product.
We report on upconversion luminescence in ${\mathrm{Y}}_{3}{\mathrm{Ga}}_{5}{\mathrm{O}}_{12}$ codoped with ${\mathrm{Cr}}^{3+}$ and ${\mathrm{Yb}}^{3+}.$ This is, to our knowledge, the first upconversion process directly involving ${\mathrm{Cr}}^{3+}.$ At low temperature excitation around 10 314 ${\mathrm{cm}}^{\math…
In comparison with their symmetrical analogues, unsymmetrically substituted Cu-Salen complexes show mesophases with lowered melting points. For terminally substituted complexes, symmetrical ones (R(1) = R(2)) have only an S(A) phase, while for unsymmetrical alkoxy substitution a monotropic S(E) phase occurs and the me…
Two new A-type proanthocyanidins have been isolated from Ecdysanthera utilis and identified as epicatechin-(4beta-->8,2beta-->O-->7)-epicatechin-(4beta-->8)-epicatechin (5) and epicatechin-(4beta-->8)-epicatechin-(4beta-->8,2beta-->O-->7)-epicatechin-(4beta-->8)-epicatechin (6), respectively. The structure-related com…
The preparation and crystal structure determination of the iron(III) compound of formula [(NH(4))(2)[Fe(2)O(ox)(2)Cl(2)].2H(2)O](n) (1) (ox = oxalate dianion) are reported here. Complex 1 crystallizes in the orthorhombic system, space group Fdd2, with a = 14.956(7) A, b = 23.671(9) A, c = 9.026(4) A, and Z = 8. The st…
Manuscript received: 2 January 2002. Final version: 4 February 2002.
Abstract Corona discharge treatment (CDT) is a surface modification technique commonly used to treat plastic films prior to adhesive bonding, printing with inks, lamination to other films and other coating applications. In this study, the treatment conditions are, in energy terms, representative of those used in indus…
We report on the new type of photoinduced magnetization in ferromagnetic (Ga,Mn)As thin films. Optically generated spin-polarized holes change the orientation of ferromagnetically coupled Mn spins and cause a large change in magnetization, being 15% of the saturation magnetization, without the application of a magneti…
We have studied the dependence of impurity vs. band effects in the appearance of inverse giant magnetoresistance (IGMR) in Cu/Fe superlattices whit Cr. Current in plane (CIP) and current perpendicular to the plane (CPP) geometries are considered. For the calculation of the conductivities we have used the linearized Bo…
The phase-transition sequence of a ferroelectric perovskite such as BaTiO_3 can be simulated by computing the statistical mechanics of a first-principles derived effective Hamiltonian [Zhong, Vanderbilt and Rabe, Phys. Rev. Lett. 73, 1861 (1994)]. Within this method, the effect of an external pressure (in general, of…
We have investigated the melting behavior of ultra-thin copper nanowires using classical molecular dynamics simulations. The caloric curves of cylindrical multi-shell copper nanowires showed an insight into the specific phase transition. The melting temperature of copper nanowires is linearly proportional with the num…
On the basis of high pressure diamond-anvil compression studies for the precious metals Ru, Ir, and Os we report the surprising discovery that metallic osmium has a lower compressibility than covalently bonded diamond. We also find that Ir and Ru are as incompressible as Re. In addition, we have performed first princi…
Recently, a new orthorhombic phase has been discovered in the ferroelectric system $(1\ensuremath{-}x)\mathrm{Pb}({\mathrm{Zn}}_{1/3}{\mathrm{Nb}}_{2/3}){\mathrm{O}}_{3}\ensuremath{-}x{\mathrm{PbTiO}}_{3}$ $(\mathrm{PZN}\ensuremath{-}x\mathrm{PT})$ for $x=9%,$ and for $x=8%$ after the application of an electric field.…