Materials Literature
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A new noncontact calorimetric method has been developed based on inductive heating of a metallic spherical bulk sample by a power-modulated radio-frequency field under ultrahigh vacuum conditions. From the pyrometrically measured temperature response the specimen’s external (due to radiative heat loss) and internal re…
The initial permeability of soft polycrystalline ferrites exhibits thermal hysteresis when the temperature is cycled from above the Curie temperature T c to below. The temperature loops are classified into two categories according to the presence or absence of a secondary peak (SP), in addition to the Hopkinson peak,…
A model pair potential is calculated for Mn-Mn pairs in Al using a Green's function method. The pair potential has a preferred spacing of 4.7 \AA{}. The energy resulting from these Mn-Mn interactions strongly favors the ${\mathrm{Al}}_{6}$Mn, \ensuremath{\alpha}-AlMnSi, and icosahedral quasicrystal structures relative…
A striking evolution of the I-V curves is observed in a single sample (i.e., for a given realization of quenched disorder) of the charge density wave conductor ${\mathrm{NbSe}}_{3}$ in the presence of an external rf field of varying amplitude. This yields qualitatively different ``depinning transitions'' from the pinn…
The observation of photoluminescence (PL) spectral shifts during anodization of porous Si and after immersion in different chemical solutions is reported. These shifts in the PL spectra are attributed to changes in the surface chemistry achieved by changing the composition of the electrolyte in which the samples are i…
Synthetic amphiboles of the richterite―Ti-richterite series have been examined by synchrotron X-ray absorption spectroscopy to determine the oxidation state and coordination of Ti in their structure. The Ti K-edge in the amphiboles is displaced to energy values higher than that of Ti metal (4966.0 eV) and consists of…
The abundance of the structural units in alkali silicate melts, supercooled liquids, and glasses determined in-situ from 25 to 1651°C has been used to estimate the enthalpy (ΔH) for the disproportionation reaction, Si 2 O 5 (2Q 3 ) ↔ SiO 3 (Q 2 ) + SiO 2 (Q 4 ). The enthalpies are in the range of -34 to 30 kJ/mol with…
Synchrotron radiation photoemission spectroscopy suggests that the room temperature grown Au/Si(111) interface is an abrupt interface with the contact made by metallic Au and bulk Si. Si 2p core level spectra show no sign of an interface component, but only the surface reacted and bulk Si components during the growth…
In the present review on the rod-based sulphosalt structures we describe the fundamental features of their large- to medium-scale crystal chemistry. The principal, lozenge-shaped rods in these structures represent portions based on the SnS or PbS archetype, with their surfaces being alternatively of the pseudotetragon…
A modification of an earlier technique, to measure the distribution of space charge in the insulation of a coaxial cable, under both DC and AC electric fields, is described. The mathematical analysis is developed on the basis of acoustic waves propagating in media with cylindrical geometry. In order to measure the cha…
Raman spectra of diamond powders with size less than 2 μm have been measured as a function of the particle size. The Raman line was found to become more asymmetric with some tailing towards lower Raman shifts, broader, and weaker with decreasing particle size. The observed result can be explained by a phonon confineme…
Abstract The performance of acrylic (50:50 MMA/BuA) latexes was investigated as a function of fusion level using high speed tensile testing. The structure of the copolymer was varied via the addition of molecular weight modifiers to the emulsion polymerizations. Chain transfer agent (CBr 4 ) was used to reduce the cop…
Abstract Surface graft polymerization of a hydrophobic monomer, 2,2,3,3,3‐pentafluoropropyl methacrylate (5FMA), onto hydrophilic poly(vinyl alcohol) (PVA) and cellulose films was studied after corona discharge of the films. It was found that grafting strongly depended on the reaction medium; especially, addition of a…
Abstract The depression of the glass transition temperature by water was studied in a set of polyurethanes in which the soft segment consisted of polyethylene oxide (sample I) or a block copolymer of poly(propylene oxide) terminated with poly(ethylene oxide) in various proportions (sample set II). DSC measurements wer…
We have performed the first computer simulation of a twisted nematic liquid crystal using non-spherical hard particles in modified periodic boundary conditions. The director profiles are stable, suggesting that the technique may usefully complement conventional simulations of unperturbed liquid crystals. We make preli…
The demagnetizing tensor for ferromagnets is generalized to include interactions between uniformly magnetized bodies. This “mutual” demagnetizing tensor is symmetric, has a trace of zero, and has other simple geometric properties. The tensor is then used to develop an expression for the macroscopic magnetic field in n…
Adenosine 5'-monophosphate (AMP) deaminase from baker's yeast is an allosteric enzyme containing a single AMP binding site and two ATP regulatory sites per polypeptide [Merkler, D. J., & Schramm, V. L. (1990) J. Biol Chem. 265, 4420-4426]. The enzyme contains 0.98 +/- 0.17 zinc atom per subunit. The X-ray crystal stru…
The authors have measured angle-resolved ultraviolet photoemission spectra from epitaxially grown thin films of CuBr with (111) orientation. Their analysis allows the determination of an experimental valence band dispersion very near Gamma -L-direction of the bulk Brillouin zone. These results show fair agreement with…
We describe reversible holographic effects in azo-dye doped liquid crystals. Surface-stabilized holograms are recorded at 514 nm using beams polarized parallel to the molecular director of the liquid crystals. While these holograms persist for several hours in the dark, complete erasure is achieved in a few seconds by…
New lines in the low temperature luminescence spectra of lightly aluminum doped p-type films of 3C, 6H, and 4H SiC are identified and associated with the recombination of a neutral aluminum acceptor four particle bound exciton complex.