Materials Literature
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The relation between fracture surface morphology and the three-dimensional structure of crack fronts is investigated through direct observation of brittle cracks in gels. A key notion in this investigation is the discontinuity of the crack front, whose advancement creates the fracture surface. We discuss the significa…
It is suggested that the appearance of Jordan blocks in the normal form of the recursion (transfer) matrix is responsible for high temperature superconductivity and related phenomena. Several published observations are discussed to support this idea. The draft of a quantum chemical theory is given for a more complete…
Polycrystalline samples of Ln 1/2 Sr 1/2 MnO 3 (Ln = La, Pr, La 0.33 Nd 0.67, Nd, Nd 0.5 Sm 0.5, Sm, and Gd) and Ln 1/2 Ca 1/2 MnO 3 (Ln = La, Pr, La 0.5 Nd 0.5, Nd, Sm, and Y 0.5 Sm 0.5 ) have been prepared, and structure determinations have been carried out at room temperature using high-resolution synchrotron X-ray…
We have studied the adsorption of two structurally similar forms of hemoglobin (met-Hb and HbCO) to a hydrophobic self-assembled methyl-terminated thiol monolayer on a gold surface, by using a Quartz Crystal Microbalance (QCM) technique. This technique allows time-resolved simultaneous measurements of changes in frequ…
The electronic properties of comb structures composed of one-dimensional atomic wires of alkali elements are studied. The wires and network of wires are assumed to be formed either on substrates or through networks of metal filled nanotubes. A tight-binding model is used to model the electronic structure of the wires…
Photoresponsive cholesteric (Ch) liquid crystals (LCs) showing reflection of visible light were prepared by the addition of chiral molecules and azobenzene molecules in a host nematic LC. The Ch–isotropic phase transition temperature and wavelength of reflected light were controlled by varying the enantiomer excess. S…
The electrical transport properties of have been investigated using complex-plane impedance analysis and dielectric measurements with measurements of four-probe dc conductivities and magnetic susceptibilities. The temperature dependencies of the bulk conductivities obtained by impedance analysis, and dielectric relaxa…
The dielectric ageing characteristics of a commercial cobalt-doped ceramic have been determined over a range of applied field strengths (field amplitude from 0.1 to 2.0 kV ) and temperatures (30, 60, ). P - E (polarization-electric field) hysteresis data were obtained, from which the internal bias field , polarization…
peer reviewed
Films of manganese doped zinc silicate have been deposited using the charged liquid cluster beam technique. The deposition conditions were found to have a large impact on the morphology and photoluminescence intensity of these films. The photoluminescence intensity was maximized at a manganese content near δ=0.04 in (…
A full partial structure factor analysis of vitreous germania has been obtained by a combination of neutron diffraction, x-ray diffraction, and anomalous x-ray scattering. The results are consistent with the identification of the first three peaks in the average neutron and x-ray structure factors with intermediate-ra…
The Zr57Cu20Al10Ni8Ti5 alloy solidifies into an amorphous phase upon rapid quenching or casting at low cooling rates. However, the amorphous alloys formed at different cooling rates exhibit different crystallization behavior. The slowly cooled bulk amorphous alloys prepared by copper mold casting reveal a first crysta…
Field emission data from aligned graphitic nanofibers have been obtained. The aligned nanofibers are 50–100 nm in diameter and 6–10 μm in length, with a density of 109–1010/cm2. The fibers were grown on polycrystalline nickel substrate by plasma-assisted hot filament chemical vapor deposition using a gas mixture of ni…
The critical behavior of the metal-insulator (MI) transition around ${x}_{c}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.16$ has been investigated for single crystals of ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{MnO}}_{3}$ by measurements of low-temperature resistivity and specific heat. The e…
Phase pure nanotube films were grown on silicon substrates by a microwave plasma under conditions which normally are used for the growth of chemical vapor deposited diamond films. However, instead of using any pretreatment leading to diamond nucleation we deposited metal clusters on the silicon substrate. The resultin…
We have observed two types of optical second harmonic spectra of ${\mathrm{Mn}}^{3+}$ ions in hexagonal ${\mathrm{YMnO}}_{3},$ one of which is caused by the noncentrosymmetric ferroelectric ordering of charges, whereas the other is due to the centrosymmetric antiferromagnetic ordering of spins. Partial overlapping bet…
We study the effect of Coulomb correlations on the ultrafast optical dynamics of small metal particles. We demonstrate that a surface-induced dynamical screening of the electron-electron interactions leads to quasiparticle scattering with collective surface excitations. In noble-metal nanoparticles, it results in an i…
Crack propagation is studied in a two dimensional decagonal model quasicrystal. The simulations reveal the dominating role of highly coordinated atomic environments as structure-intrinsic obstacles for both dislocation motion and crack propagation. For certain overloads, these obstacles and the quasiperiodic nature of…
A 4,4‘-diphenylmethane diisocyanate (4,4‘-MDI)-based poly(ester)−poly(urethane) has been synthesized as selectively 2 H labeled at the MDI methylene. The 2 H NMR spectrum showed that this elastomer consisted of a rigid and mobile component over a wide temperature range, with the mobile component increasing with temper…
The fracture behavior of poly(vinyl chloride) filled with ground calcium carbonate particles during a tensile test was studied. The particles were prepared by crushing natural raw crystalline limestone. For this purpose, 10–50 parts of the particles having two different mean sizes (2 and 8 μm) without further surface…