Materials Literature
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The fundamental issues of symmetry related to chirality are discussed and applied to simple situations relevant to liquid crystals. The authors show that any chiral measure of a geometric object is a pseudoscalar (invariant under proper rotations but changing sign under improper rotations) and must involve three-point…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTMesoporous Silicate Sequestration and Release of ProteinsYong-Jin Han, Galen D. Stucky, and Alison ButlerView Author Information Department of Chemistry and Biochemistry and the Materials Research Laboratory University of California Santa Barbara, California 93106-9510…
Abstract Smectites are one of the most important groups of phyllosilicates found in soils and sediments, and certainly one of the most difficult to study. New information about the formation mechanisms, impact of structural features on surface properties, and long-term stability of smectites can best be gained from th…
We have peformed neutron diffraction measurements on melt-grown polycrystalline samples of ${\mathrm{Nd}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{MnO}}_{3}$ $(0.49<~x<~0.75).$ A systematic transformation of the crystalline and magnetic structures of this system was observed. This can be consistently explaine…
In this article, the second part of a two‐part study, we report on the mechanical behavior of Ti 3 SiC 2 . In particular, we have evaluated the mechanical response of fine‐grained (3–5 μm) Ti 3 SiC 2 in simple compression and flexure tests, and we have compared the results with those of coarse‐grained (100–200 μm) Ti…
One way to increase the rate of an electrochemical process is to increase the area of the interface between the electrode and the electrolyte. A novel polymer electrode, with a very high effective surface area and a nanometer-scale continuous conducting network that extends into a large volume, is presented and its pr…
Diffraction intensities can be evaluated by two distinct procedures: summation integration and profile fitting. Equations are derived for evaluating the intensities and their standard errors for both cases, based on Poisson statistics. These equations highlight the importance of the contribution of the X-ray backgroun…
We propose a novel strategy using fullerenes for the construction of solar energy conversion systems that mimic the primary electron transfer events in photosynthesis. Redox-active fullerenes such as C60 and C70 were covalently bound to a porphyrin and the photophysical properties of the resulting compounds were inves…
X-ray-diffraction studies of nanometer-sized particles of zinc sulfide show a significant reduction in the zinc-blende-to-wurtzite phase transition temperature, as compared to the bulk value. Five nanoparticle samples were annealed in vacuum at temperatures increasing from room temperature (23 \ifmmode^\circ\else\text…
A metal nanoshell consists of a nanometer-scale dielectric core surrounded by a thin metallic shell. The plasmon resonance of metal nanoshells displays a geometric tunability controlled by the ratio of the core radius to the total radius. For gold-coated Au2S this ratio varies from 0.6 to 0.9, yielding a plasmon reson…
The advantages of combining carbon nanotubes with conjugated polymers for high-efficiency photovoltaic devices are explored in this article. The preparation and optical properties of a composite of multiwalled carbon nanotubes (MWNTs) and poly(p-phenylene vinylene) (PPV) are reported and the efficiency of a photovolta…
Tailoring of porous materials involves not only chemical synthetic techniques for tailoring microscopic properties such as pore size, pore shape, pore connectivity, and pore surface reactivity, but also materials processing techniques for tailoring the meso- and the macroscopic properties of bulk materials in the form…
The application of broken symmetry density functional calculations to homobinuclear and heterobinuclear transition metal complexes produces good estimates of the exchange coupling constants as compared to experimental data. The accuracy of different hybrid density functional theory methods was tested. A discussion is…
It has been shown recently that in many cases strain anisotropy in powder diffraction can be well accounted for by the dislocation model of the mean square strain. The practical application assumes knowledge of the individual contrast factors C of dislocations related to particular Burgers, line and diffraction vector…
X-ray diffraction images from two-dimensional position-sensitive detectors can be characterized as thick or thin, depending on whether the rotation-angle increment per image is greater than or less than the crystal mosaicity, respectively. The expectations and consequences of the processing of thick and thin images in…
Novel organic−inorganic hybrid mesoporous materials have been synthesized, in which organic and inorganic oxide moieties are distributed homogeneously at the molecular level in the framework, forming a covalently bonded network. They are highly ordered at the mesoscale, with two- and three-dimensional hexagonal symmet…
Nabiasite, ideally BaMn 9 [(V,As)O 4 ] 6 (OH) 2 , is a new mineral which occurs in rhodochrosite-, friedelite- and barite-bearing veinlets crosscutting Mn ores at the historic Pla de Labasse deposit near the Nabias hamlet, Central Pyrenees, France. These syn-genetic exhalative ores are embedded in Lower Carboniferous…
A helium-gas-pressure apparatus with optical-reflectivity detection tested with a spin-transition solid, Jelena Jeftic, Nieves Menéndez, AndréWack, Epiphane Codjovi, Jorge Linarès, Antoine Goujon, Gérard Hamel, Stefan Klotz, Gérard Syfosse, François Varret
The energy dissipation of Tb 3+ /Eu 3+ cations in both heterolanthanide multinuclear polyoxometalates, K 15 H 3 [Tb 1.4 Eu 1.6 (H 2 O) 3 (SbW 9 O 33 )(W 5 O 18 ) 3 ]·25.5H 2 O and Na 7 H 19 [Tb 4.3 Eu 1.7 O 2 (OH) 6 (H 2 O) 6 Al 2 (Nb 6 O 19 ) 5 ]·47H 2 O is studied by crystal structures, emission and excitation spect…
High molecular weight poly( l -glutamic acid) was chemically modified with a spiropyran reagent to give polypeptides containing 35 and 85 mol % spiropyran units in the side chains. To investigate the photochromic and conformational behavior in acid conditions, the polypeptides were dissolved in hexafluoro-2-propanol (…