Materials Literature
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The magnetic and magnetotransport properties of the perovskite La0.67Ca0.33Mn0.9Fe0.1O3 have been investigated, and the spin-glass behavior with a spin freezing temperature of 42 K has been well confirmed for this compound. A metal-to-insulator transition and colossal magnetoresistance have been observed near its spin…
We study closely packed crystalline structures formed by slow lateral compression of a colloidal suspension of hard spheres in a thin wedge. In addition to the known sequence of structural transitions, a buckling mechanism was recently proposed to maximize the packing fraction $\ensuremath{\Phi}$ between one and two l…
We study the behaviour of total-energy supercell calculations for dipolar molecules and charged clusters. Using a cutoff Coulomb interaction within the framework of a plane-wave basis set formalism, with all other aspects of the method (pseudopotentials, basis set, exchange-correlation functional) unchanged, we are ab…
single crystals have been grown and characterized by experimental techniques such as high-resolution transmission electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy and optical and electrical measurements. The samples were prepared in single-crystal form from a melt. The structural analysis indic…
The thermal conductivity and diffusivity of lithium sulphate have been measured simultaneously, using the transient plane source technique over the temperature range 300 - 900 K. The thermal conductivity decreases slowly up to about 640 K, whereupon a distinct rise occurs, indicating the onset of a pre-transitional be…
We describe the development of a comprehensive theory of thermoluminescence (TL) supralinearity and sensitization, the unified interaction model (UNIM), based on both radiation absorption stage and recombination stage mechanisms. The UNIM incorporates both the track interaction model (TIM) for heavy charged particles…
The optical properties of GeO(2) glass were investigated to clarify its potentiality as an optical fiber material. Glass samples were prepared by the flame hydrolysis and the melting techniques, and their Rayleigh scattering and infrared absorption properties were examined. Optical fibers composed of a pure GeO(2) cor…
Significant improvements have been obtained for solid-state dye lasers with doped xerogels. By using longitudinal pumping with a frequency-doubled Q-switched Nd: YAG laser, we obtained as much as 86% slope efficiency and 5 x 10(5) pulses lifetime. Furthermore, newly prepared deoxygenated samples exhibited even greater…
We describe a high-resolution, high-bandwidth technique for determining the local viscoelasticity of soft materials such as polymer gels. Loss and storage shear moduli are determined from the power spectra of thermal fluctuations of embedded micron-sized probe particles, observed with an interferometric microscope. Th…
We have developed a new technique to measure viscoelasticity in soft materials such as polymer solutions, by monitoring thermal fluctuations of embedded probe particles using laser interferometry in a microscope. Interferometry allows us to obtain power spectra of fluctuating beads from 0.1 Hz to 20 kHz, and with sub-…
A theory of the hysteresis loop in ferromagnets controlled by the domain wall motion is presented. Domain walls are considered as plane or linear interfaces moving in a random medium under the action of the external ac magnetic field $H=H_0\sinωt$. We introduce important characteristics of the hysteresis loop, such as…
PE and PBT are known to be incompatible polymers. A grafted copolymer PBT-EVA has been generated as a compatibilizer in situ during the processing operation by redistributive transesterification between PBT and EVA in the presence of dibutyl tin oxide (DBTO). This copolymer has been isolated by selective extractions f…
Hybrid systems based on 3-trimethoxysilyl propyl methacrylate, tetramethylorthosilicate, and methyl methacrylate were developed for moisture protection and strengthening of glass objects. The hydrophobic behavior of the hybrid was obtained by adding different fluorinated precursors to the hybrid solution. Experimental…
In his Perspective, Engel discusses the diverse structural features of collagens, a ubiquitous fibrillar protein that forms the main support of skin and tendons. A unique example is reported in this issue by Coyne et al ., who describe the amino acid sequence of the specialized collagen that forms the byssal threads t…
To adhere to solid surfaces, marine mussels produce byssal threads, each of which is a stiff tether at one end and a shock absorber with 160 percent extensibility at the other end. The elastic extensibility of proximal byssus is extraordinary given its construction of collagen and the limited extension (less than 10 p…
The fcc-based structure of Yb2.75C60 is unique among metal-doped fullerene compounds, exhibiting long-range-ordered vacancies, significantly off-centered divalent Yb cations, and distorted, crystallographically inequivalent, orientationally ordered C60 anions. A simple electrostatic-energy analysis, which models the c…
The reversible reaction of a monomeric CuII complex to a cyclic hexamer (crystal structures shown below) is the first example interconversion between a potential guest complex and a complex that cannot function as a guest [Eq. (a)]. It is—like in living organisms—controlled by a very common external signal, namely pro…
Why don't we live in β-peptide world? This is a legitimate question in light of new findings by D. Seebach et al. and S. Gellman et al. on the secondary structures of β-peptides. Peptides composed of less than ten β-amino acid residues can from stable, secondary structure motifs like the 31-M-helix shown on the right.…
A highly ordered lamellar mesophase is exhibited by the thermally stable liquid-crystalline gold(I) dicarbene compounds presented here. The crystal structure of one of these compounds is depicted on the right.
The total energy differences between various SiC polytypes (3C, 6H, 4H, 2H, 15R and 9R) were calculated using the full-potential linear muffin-tin orbital method using the Perdew-Wang-(91) generalized gradient approximation to the exchange-correlation functional in the density functional method. Numerical convergence…