Compressive Behavior of Hybrid Composites
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Fraction of the CoMoS phases accessible to NO in Co–Mo hydrodesulfurization catalysts
It is established by using Co-Mo model sulfide catalysts, XAFS and FTIR that Co atoms constituting CoMoS phases are not oxidized by NO adsorption and that only 55% of the CoMoS phases is susceptible to NO adsorption even at the maximum coordinative unsaturation attainable under usual HDS reaction conditions (623-673 K…
Manipulation of anchoring strength in an azo-dye side chain polymer by photoisomerization
The generation of surface anisotropy by photochemical means has been proposed as an attractive method to align liquid crystals. In this paper, we present an experimental study of the alignment induced on a liquid crystal by a polymer film containing azo-dye groups in the side chain. Optical measurements were performed…
Computational Materials: Modeling and Simulation of Nanostructured Materials and Systems
The paper provides details on the structure and implementation of the Computational Materials program at the NASA Langley Research Center. Examples are given that illustrate the suggested approaches to predicting the behavior and influencing the design of nanostructured materials such as high-performance polymers, com…
Efficient anodic pyridination of poly(3-hexylthiophene) toward post-functionalization of conjugated polymers
Nucleophilic substitution reaction of poly(3-hexylthiophene) (P3HT) with pyridine derivatives as nucleophile was demonstrated in anodic oxidation process. The key reaction involves efficient nucleophilic attack of the pyridine derivatives toward thiophene rings in partly oxidized polymer, i.e., doped state, in the sim…
Magnetic ordering in the rutile molecular magnetsMII[N(CN)2]2(M=Ni,Co, Fe, Mn,Ni0.5Co0.5,andNi0.5Fe0.5)
Rietveld refinement of powder neutron diffraction data, combined with group theory considerations, is used to determine the magnetic structures of the binary metal dicyanamide, ${M}^{\mathrm{II}}[{\mathrm{N}(\mathrm{CN})}_{2}{]}_{2}$ where $M=\mathrm{Ni},$ Co, Fe, Mn, ${\mathrm{Ni}}_{0.5}{\mathrm{Co}}_{0.5},$ and ${\m…
Handedness reversal of circular Bragg phenomenon due to negative real permittivity and permeability
When the real parts of the permittivity and the permeability dyadics of a structurally chiral, magnetic-dielectric material are reversed in sign, the circular Bragg phenomenon displayed by the material is proved here to suffer a change which indicates that the structural handedness has been, in effect, reversed. Addit…
Metal impurities in an oxide: Ab initiostudy of electronic and structural properties of Cd in rutileTiO2
In this work we undertake the problem of a transition metal impurity in an oxide. We present an ab initio study of the relaxations introduced in ${\mathrm{TiO}}_{2}$ when a Cd impurity substitutionally replaces a Ti atom. Using the full-potential linearized-augmented-plane-wave method, we obtain relaxed structures for…
Numerical study of electromagnetic waves interacting with negative index materials
We study numerically the electromagnetic scattering properties of structures with negative indices of refraction. To perform this analysis, we utilize a commercial finite-element based electromagnetic solver (HFSS, Ansoft), in which a negative index material can be formed from mesh elements whose permittivity and perm…
Synthesis of meso-β doubly linked porphyrin tapesElectronic supplementary information (ESI) available: 1H NMR spectra. See http://www.rsc.org/suppdata/cc/b3/b302032k/
The oxidation of 5,15-bis(3,5-di-tert-butylphenyl) Ni(II)-porphyrin 1b with Sc(OTf)3 and DDQ led to production of meso-beta doubly linked Ni(II)-porphyrin tapes that have large pi-electronic communications over the arrays.
Metamaterial endoscope for magnetic field transfer: near field imaging with magnetic wires
We report on the development and use of a highly anisotropic magnetic metamaterial for near-field imaging. The material consists of an array of Swiss Roll structures, resonant near 21.3 MHz, with a peak value of relative permeability ~35. At this peak, the material transfers an input magnetic field pattern to the outp…
Experimental and theoretical verification of focusing in a large, periodically loaded transmission line negative refractive index metamaterial
We have previously shown that a new class of Negative Refractive Index (NRI) metamaterials can be constructed by periodically loading a host transmission line medium with inductors and capacitors in a dual (high-pass) configuration. A small planar NRI lens interfaced with a Positive Refractive Index (PRI) parallel-pla…
Regenerating evanescent waves from a silver superlens
We investigated a precursor of superlensing: regenerating evanescent waves by excitation of a surface plasmon. Because the permittivity of a silver slab approaches -1, we experimentally observed a broadening of surface-plasmon bandwidth. Our study identifies a means to access deep subwavelength features by use of a me…
�?erenkov radiation in materials with negative permittivity and permeability
The mathematical solution for Cerenkov radiation in a novel medium, left-handed medium (LH medium), which has both negative permittivity and permeability, is introduced in this paper. It is shown that the particle motion in the LH medium generates power that propagates backward. In this paper, both dispersion and diss…
Electronic compressibility and charge imbalance relaxation in cuprate superconductors
In the material SmLa$_{1-x}$Sr$_x$CuO$_{4-δ}$ with alternating intrinsic Josephson junctions we explain theoretically the relative amplitude of the two plasma peaks in transmission by taking into account the spatial dispersion of the Josephson Plasma Resonance in $c$ direction due to charge coupling. From this and the…
Gallium adsorption on (0001) GaN surfaces
We study the adsorption behavior of Ga on (0001) GaN surfaces combining experimental specular reflection high-energy electron diffraction with theoretical investigations in the framework of a kinetic model for adsorption and ab initio calculations of energy parameters. The measurement of a Ga/GaN adsorption isotherm a…
Thickness dependence of the properties of epitaxial MgB2 thin films grown by hybrid physical-chemical vapor deposition
We have studied the effect of deposition rate and layer thickness on the properties of epitaxial MgB2 thin films grown by hybrid physical-chemical vapor deposition on 4H-SiC substrates. The MgB2 film deposition rate depends linearly on the concentration of B2H6 in the inlet gas mixture. We found that the superconducti…
Pressure-induced intermediate-to-low spin state transition inLaCoO3
Synchrotron x-ray powder-diffraction experiments reveal that the transition from a magnetic intermediate spin (IS) state ${t}_{2g}^{5}{e}_{g}^{1}$ to a nonmagnetic low-spin ground state ${t}_{2g}^{6}$ in ${\mathrm{LaCoO}}_{3}$ normally observed when cooling manifests itself under pressure by an anomalously low bulk mo…
Structure of the icosahedral Ti-Zr-Ni quasicrystal
The atomic structure of the icosahedral Ti-Zr-Ni quasicrystal is determined by invoking similarities to periodic crystalline phases, diffraction data, and the results from ab initio calculations. The structure is modeled by decorations of the canonical-cell tiling geometry. The initial decoration model is based on the…
Perfect cylindrical lenses
A slab of negatively refracting material is known to focus light and if 1 n = the focussing will be perfect, producing an image which is an exact replica of the object. Magnifying the image requires a new design concept in which the surface of the negatively refracting lens is curved. Here we show how a hollow cylinde…