Calix[4]azulene
Azulene reacts with paraformaldehyde in the presence of florisil to give excellent yields of calix[4]azulene.
Materials Literature
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Optical properties of point defects in SiO2 from time-dependent density functional theory
We have studied the optical absorptions of a series of point defects in SiO2 by means of time-dependent density functional response theory (TD-DFT). The structure of the defects has been described with cluster models and atomic orbital basis functions. For each center the lowest singlet→singlet and singlet→triplet (fo…
Antiferromagnetism inCaCu3Ti4O12studied by magnetic Raman spectroscopy
For ${\mathrm{CaCu}}_{3}{\mathrm{Ti}}_{4}{\mathrm{O}}_{12}$---an insulator that exhibits a giant dielectric response above 100 K---${\mathrm{Cu}}^{2+}$ antiferromagnetic spin ordering has been investigated by magnetic Raman scattering and magnetization measurements. Below the N\'eel temperature, ${T}_{N}=25\mathrm{K},…
Improvement of properties of silica‐filled natural rubber compounds using polychloroprene
Abstract Because silica has strong filler–filler interactions, a silica‐filled rubber compound is characterized by a poor dispersion of the filler. Properties of silica‐filled natural rubber (NR) compounds were improved using polychloroprene (chloroprene rubber [CR]). The bound rubber content of the compound increases…
Determination and Tailoring the Pore Entrance Size in Ordered Silicas with Cage-like Mesoporous Structures
A practical approach to the determination of the pore entrance size in ordered silicas with cage-like mesoporous structures (OSCMSs) is proposed. A fundamental insight into the OSCMS pore connectivity is gained, including the control of the pore entrance size by post-synthesis surface modification, and by selection of…
Filling factors, structural, and electronic properties ofC60molecules in single-wall carbon nanotubes
We report recent measurements of the electronic and structural properties of bulk samples of ${\mathrm{C}}_{60}$ molecules encapsulated in single-wall carbon nanotubes (so-called peapods) using electron-energy-loss spectroscopy in transmission. We demonstrate that ${\mathrm{C}}_{60}$ peapods with a single-wall carbon…
Electronic structure and tunneling resonance spectra of nanoscopic aluminum islands
The electronic structure of nanoscopic oxide-coated aluminum islands is investigated using a tight-binding model that incorporates the geometry, chemistry and disorder of the particle. The oxide coat is found to significantly increase the volume accessible to electrons at the Fermi level. The level statistics agree wi…
Elastic Interactions of Cells
Biological cells in soft materials can be modeled as anisotropic force contraction dipoles. The corresponding elastic interaction potentials are long-ranged ($\sim 1/r^3$ with distance $r$) and depend sensitively on elastic constants, geometry and cellular orientations. On elastic substrates, the elastic interaction i…
Anisotropic, Fermi-Surface-Induced Variation in T_c in MgB_2 Alloys
Using coherent-potential to describe disorder, Gaspari-Gyorffy approach to evaluate electron-phonon coupling, and Allen-Dynes equation to calculate T_c, we show that in Mg_{1-x}M_{x}B_{2} (M = Al,Li or Zn) alloys (i) the way T_c changes depends on the location of the added/modified k-resolved states on the Fermi surfa…
Comment on "Bounding and approximating parabolas for the spectrum of Heisenberg spin systems" by Schmidt, Schnack and Luban
Recently, Schmidt et al. proved that the energy spectrum of a Heisenberg spin system (HSS) is bounded by two parabolas, i.e. lines which depend on the total spin quantum number S as S(S+1). The prove holds for homonuclear HSSs which fulfill a weak homogenity condition. Moreover, the extremal values of the exact spectr…
Soft versus Hard Dynamics for Field-driven Solid-on-Solid Interfaces
Analytical arguments and dynamic Monte Carlo simulations show that the microstructure of field-driven Solid-on-Solid interfaces depends strongly on the dynamics. For nonconservative dynamics with transition rates that factorize into parts dependent only on the changes in interaction energy and field energy, respective…
Carbon nanotubes band assignation, topology, Bloch states, and selection rules
Various properties of the energy band structures (electronic, phonon, etc.), including systematic band degeneracy, sticking and extremes, following from the full line group symmetry of the single-wall carbon nanotubes are established. The complete set of quantum numbers consists of the angular and linear quasimomenta…
Molecular wire-nanotube interfacial effects on electron transport
We discuss the conductance of a molecular bridge between mesoscopic electrodes supporting low-dimensional transport and bearing an internal structure. As an example for such nanoelectrodes we assume semi-infinite (carbon) nanotubes. In the Landauer scattering matrix approach, we show that the conductance of this hybri…
Mechanical, adhesive and thermodynamic properties of hollow nanoparticles
When sheets of layered material like C, WS$_2$ or BN are restricted to finite sizes, they generally form single- and multi-walled hollow nanoparticles in order to avoid dangling bonds. Using continuum approaches to model elastic deformation and van der Waals interactions of spherical nanoparticles, we predict the vari…
Extrinsic magnetotransport phenomena in ferromagnetic oxides
Magnetic oxides show a variety of extrinsic magnetotransport phenomena: grain-boundary, tunnelling and domain-wall magnetoresistance. In view of these phenomena the role of some magnetic oxides is outstanding: these are believed to be half-metallic having only one spin-subband at the Fermi level. These fully spin-pola…
Organic Functionalization of Carbon Nanotubes
A very general and versatile method for functionalizing different types of carbon nanotubes is described, using the 1,3-dipolar cycloaddition of azomethine ylides. Approximately one organic group per 100 carbon atoms of the nanotube is introduced, to yield remakably soluble bundles of nanotubes, as seen in transmissio…
THE INFLUENCE OF NATURE OF COKE ON KINETICS OF CATALYST REGENERATION
Experiments have been carried out to study the effects of coke composition on combustion parameters and burn-off time in the regeneration of coke-deactivated supported alumina catalyst. At high temperatures, results showed that the combustion behaviour is dependent on coke type as oxidizable and reduceable coke profil…
Multilayer TiC/TiN diffusion barrier films for copper
TiC/TiN thin films deposited by reactive magnetron sputtering on Si (100) substrates were investigated by transmission electron microscopy for microstructure and by deep level transient spectroscopy (DLTS) for diffusion barrier against copper. TiN thin films deposited on Si substrates at a substrate temperature of 600…
Enhanced dielectric properties of SrTiO3 epitaxial thin film for tunable microwave devices
The performance of tunable microwave devices based on heteroepitaxial YBa2Cu3Ox/SrTiO3 films on (001) LaAlO3 substrates has been evaluated. It was ascertained that “out-of-plane” SrTiO3 lattice parameter is the relevant factor in determining both device agility and dielectric loss. After high temperature annealing (11…
Integrally gated carbon nanotube-on-post field emitter arrays
Multiwalled carbon nanotubes were grown using chemical vapor deposition on the tops of blunt vertical silicon posts in cells having a horizontal gate aperture of conventional field emitter design. We obtained over 1 mA total emission current from a single array, or 0.3 μA per cell at 40 V. In addition to the low volta…