Materials Literature
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We have studied the influence of the patterning procedure on the critical current density of high-$T_c$ YBa$_2$Cu$_3$O$_{7-δ}$ thin rings using the nonlinear ac susceptibility method. At no applied dc magnetic field we have found that laser ablation degrades strongly the critical current density whereas ion beam etchi…
A microscopically motivated theory of glassy dynamics based on an underlying random first order transition is developed to explain the magnitude of free energy barriers for glassy relaxation. A variety of empirical correlations embodied in the concept of liquid "fragility" are shown to be quantitatively explained by s…
Novel vegetable oil derived macromonomers were synthesized by the chemical modification of castor, lesquerella and vernonia oils. The castor oil derivative has been successfully copolymerized into vinyl-acrylic and all-acrylic latexes designed for use as architectural coatings. The castor oil derived monomer provides…
Starting from rapidly quenched NdδFe13.1B(2.05⩽δ⩽147.6) alloys and by appropriate annealing, the microstructure was tailored from strongly interacting Nd2Fe14B grains to magnetically isolated single domain Nd2Fe14B grains embedded in a nonmagnetic Nd-rich matrix (α-Nd and γ-Nd). This change in microstructure was found…
ZnS layers were grown by metalorganic vapor phase epitaxy on GaAs substrates using diethylzinc, ditertiarybutyl sulphide, and triallylamine as organometallic sources. After postgrowth rapid thermal annealing, the ZnS layers showed p-type conductivity with hole concentrations up to 1018 cm−3. Photoluminescence measurem…
We compare the large magnetoresistive response of slightly nonstoichiometric Ag2±δTe for a wide range of hole (p⩽8×1017 cm−3) and electron (n⩽4×1018 cm−3) carrier densities. In the p-type material alone, a characteristic peak in the resistivity ρ(T,H) is dramatically enhanced and moves to higher temperature with incre…
Perfectly c-axis oriented micrometer thick Na0.5K0.5NbO3(NKN) films have been prepared on a thermally grown ultrathin SiO2 template layer onto a Si(001) wafer by the pulsed laser deposition technique. A x-ray diffraction θ–2θ scan reveals multiple-cell structuring of single phase NKN film along the polar axis, while f…
Using atomistic pseudopotential wave functions we calculate the quasiparticle gap, the optical gap and the electron and hole addition energies of CdSe nanocrystals. We find that the quasiparticle gap and the addition energies depend strongly on the dielectric constant of the surrounding material, while the optical gap…
Small-angle X-ray scattering (SAXS), which determines the radius of gyration, R(g), and the pair distance distribution function, was used to investigate the conformational changes of calmodulin (CaM) on binding to an antagonist, trifluoperazine (TFP), with or without Ca(2+) in solution. We previously applied this SAXS…
The dynamic conductance of carbon nanotubes was investigated using the nonequilibrium Green's function formalism within the context of a tight-binding model. Specifically, we have studied the ac response of tubes of different helicities, both with and without defects, and an electronic heterojunction. Because of the i…
Gas-tube protector units are used in telecom network interface device boxes and central office switching gears to provide protection from lightning and alternating current power cross faults on the telecom network. Current gas discharge tube (GDT) protector units are unreliable from the standpoint of mean turn-on volt…
The strong influence of nuclear spins on resonant quantum tunneling in the molecular cluster Fe8 is demonstrated for the first time by comparing the relaxation rate of the standard Fe8 sample with two isotopic modified samples: (i) 56Fe is replaced by 57Fe, and (ii) a fraction of 1H is replaced by 2H. By using a recen…
Current and its noise in a ferromagnetic double tunnel barrier device with a small spacer particle were studied in the framework of the sequential tunneling approach. Analytical formulae were derived for electron tunneling through the spacer particle containing only a single energy level. It was shown that Coulomb int…
Granular materials react to shear stresses differently than do ordinary fluids. Rather than deforming uniformly, materials such as dry sand or cohesionless powders develop shear bands: narrow zones containing large relative particle motion leaving adjacent regions essentially rigid[1,2,3,4,5]. Since shear bands mark a…
We measured thermal conductivity $\ensuremath{\kappa}$, thermoelectric power $S$, and electric conductivity $\ensuremath{\sigma}$ of ${\mathrm{La}}_{5/8\ensuremath{-}x}{\mathrm{Pr}}_{x}{\mathrm{Ca}}_{3/8}{\mathrm{MnO}}_{3}$, showing an intricate interplay between metallic ferromagnetism (FM) and charge ordering (CO) i…
The oxygen-deficient double perovskite YBaCo2O5, containing corner-linked CoO5 square pyramids as principal building units, undergoes a paramagnetic to antiferromagnetic spin ordering at 330 K. This is accompanied by a tetragonal to orthorhombic distortion. Below 220 K orbital ordering and long-range Co(2+)/Co(3+) cha…
GaAs has been selectively grown in a hexagonally ordered array of nanometer-scale holes with a density as high as ∼1011/cm2 by metalorganic chemical vapor deposition. This array of holes was created using block copolymer lithography, in which a thin layer of diblock copolymer was used as an etching mask to make dense…
We have developed a process to fabricate well-aligned, patterned, carbon nanotube field emitters on glass substrates. The process consists of depositing and patterning a nickel-based metal line on the glass substrate followed by a bias-enhanced microwave plasma chemical vapor deposition to grow carbon nanotube emitter…
The effects of impurities and local structural defects on the conductance of metallic carbon nanotubes are calculated using an ab initio pseudopotential method within the Landauer formalism. Substitutionally doped boron or nitrogen produces quasibound impurity states of a definite parity and reduces the conductance by…
Using low-resistance electrical contacts, we have measured the intrinsic high-field transport properties of metallic single-wall carbon nanotubes. Individual nanotubes appear to be able to carry currents with a density exceeding 10(9) A/cm(2). As the bias voltage is increased, the conductance drops dramatically due to…