Materials Literature
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Weak metal-arene interactions have been investigated in Zn, Cd, Hg, and Ni complexes of meso-tetraaryl m- and p-benziporphyrin (1 and 2) and of the new compound, m-benziporphodimethene (3). Compounds 1-3 incorporate the phenylene moiety into a macrocyclic structure so as to facilitate the interaction between the arene…
We present ab initio density functional calculations that show P (Al) dopant atoms in small hydrogen-terminated Si crystals to be negatively (positively) charged. These signs of the dopant charges are reversed relative to the same dopants in bulk Si. We predict this novel reversal of the dopant charge (and electronic…
This paper presents a large-scale assembly method to deposit discrete multiwalled carbon nanotubes (MWCNTs) across gaps present in an electrode array. A parametric study showed that MWCNTs dispersed in a liquid could be deposited to individually span gaps by combining an alternating current (ac) and a direct current (…
We show that elongated nanowires can be grown on crystal surfaces by allowing large strained two-dimensional islands to desorb by varying the adatom supersaturation or chemical potential. The width of the wires formed in this process is determined by a competition between the repulsive elastic interactions of the long…
Based on density functional calculations, we propose that ZrMn_2 is a polymorphic material. We predict that at low temperatures the cubic C15, and the hexagonal C14 and C36 structures of the Laves phase compound ZrMn_2 are nearly equally stable within 0.3 kJmol^{-1} or 30 K. This degeneracy occurs when the Mn atoms ma…
We report on the achievement of a two-dimensional electron gas in completely undoped In[0.75]Al[0.25]As/In[0.75]Ga[0.25]As metamorphic quantum wells. Using these structures we were able to reduce the carrier density, with respect to reported values in similar modulation-doped structures. We found experimentally that t…
We discuss materials based on arrays of metallic magnetic cylindrical structures near ferromagnetic resonance with applied magnetic fields at microwave frequencies. We have found that the materials have a negative refraction index when the appropriate structure is chosen. Numerical FDTD simulations were performed, aft…
Although the clean Si(001) and Ge(001) surfaces are very similar, experiments to date have shown that dimer-vacancy (DV) defects self-organize into vacancy lines (VLs) on Si(001), but not on Ge(001). In this paper, we perform empirical-potential calculations aimed at understanding the differences between the vacancies…
We develop a lattice mean field theory for ferromagnetic ordering in diluted magnetic semiconductors by taking into account the spatial fluctuations associated with random disorder in the magnetic impurity locations and the finite mean free path associated with low carrier mobilities. Assuming a carrier-mediated indir…
We show that the correlation between morphological fluctuations of two interfaces confining a quantum well strongly suppresses a contribution of interface disorder to inhomogeneous line width of excitons. We also demonstrate that only taking into account these correlations one can explain all the variety of experiment…
The paper presents numerical simulations performed on dielectric properties of two-dimensional binary composites on eleven regular space filling tessellations. First, significant contributions of different parameters, which play an important role in the electrical properties of the composite, are introduced both for d…
We report Raman and time-resolved photoluminescence spectroscopic studies of multiwalled BN and B x C y N z nanotubes. The Raman spectroscopy shows that the as-grown B x C y N z nanotubes are radially phase separated into BN shells and carbon shells. The photoluminescence decay process is characterized by two time con…
We present an investigation of the influence of structural distortions in charge-carrier doped ${\mathrm{La}}_{1\ensuremath{-}x}{M}_{x}{\mathrm{CoO}}_{3}$ by substituting ${\mathrm{La}}^{3+}$ with alkaline-earth metals of strongly different ionic sizes, that is, $M={\mathrm{Ca}}^{2+},$ ${\mathrm{Sr}}^{2+},$ and ${\mat…
We propose structural and electronic properties of recently synthesized SiC nanotubes. The nanotubes with a Si to C ratio of 1:1 exhibit rich morphologies and are shown to belong to two distinct categories that are close in energies but show significant differences in electronic and transport properties. Similarities…
The synthesis and characterization of novel biodegradable elastomers , exemplified by poly(1,8‐octanediol‐ co ‐citric acid), is reported. Biodegradation, mechanical, and biocompatibility data suggest very good potential for use as porous scaffolds in cardiovascular tissue engineering (see Figure). Material properties…
Control of silk fibroin concentration in aqueous solutions via osmotic stress was studied to assess relationships to gel formation and structural, morphological, and functional (mechanical) changes associated with this process. Environmental factors potentially important in the in vivo processing of aqueous silk fibro…
Abstract A novel emulsion polymerization technique referred to as emulsifier‐minor emulsion polymerization was achieved by the copolymerization of methyl methacrylate, butyl acrylate, and styrene (MMA‐BA‐St) with a combination of water‐soluble ionic monomers [methacrylic acid (MAA) or acrylic acid (AA)] and nonionic m…
The functionalization of phosphorus-containing dendrimers was easily achieved through thioacylation reactions involving new dendrimers capped with dithioester end groups and various functionalized amines. These reactions were successfully applied to the first generation (12 end groups) and the third generation of the…
Wir haben ein Bild! Citrat und andere Zwischenstufen des Citrat-Zyklus lassen sich durch zeitaufgelöste Fluoreszenzspektroskopie unter Verwendung eines Eu3+-Tetracyclin-Komplexes als Fluoreszenzsonde bildlich darstellen (siehe Bild). Die zeitliche Auflösung ermöglicht die Unterscheidung verschiedener Zwischenstufen oh…
The N\'eel temperature ${T}_{N},$ electronic specific heat coefficient ${\ensuremath{\gamma}}_{e},$ band structures and the effective exchange constant ${J}_{0}$ of the ${L1}_{0}$-type MnIr alloy system have been investigated. The value of ${T}_{N}$ is highest among Mn alloy systems, being 1145 K for the alloy with 50…