Materials Literature
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Summary Southern yellow pine wood surfaces were modified under cold plasma conditions in order to create water repellent characteristics. The surface chemistry of the plasma “polymerized” hexamethyldisiloxane (PHMDSO) deposited onto wood surfaces was investigated using Electron Spectroscopy for Chemical Analysis (ESCA…
We have used in situ x-ray diffraction to measure strain curves of single crystals of 92% Pb(Zn1/3Nb2/3)O3–8% PbTiO3 poled in the 〈001〉 direction. We observed shifts in the (002) and (330) peaks as functions of applied voltage (in the 〈001〉 direction), thereby measuring the crystallographic strain. Our measurements co…
PbTiO 3 /SrTiO 3 superlattices were grown on (001) SrTiO3 substrates by reactive molecular beam epitaxy (MBE). Sharp superlattice reflections were observed by x-ray diffraction. High-resolution transmission electron microscopy of a [(PbTiO3)10/(SrTiO3)10]15 superlattice revealed that the PbTiO3/SrTiO3 interface struct…
A nanoporous structure was produced in the samples of graphite after ball milling at ambient temperature. The specific internal surface area of the micropores, as determined using the t-plot method, is higher than the external surface area of particles and mesopores. Phase transformations from hexagonal to turbostrati…
Below 360 mK, ${\mathrm{Fe}}_{8}$ magnetic molecular clusters are in the pure quantum relaxation regime and we show that the predicted ``square-root time'' relaxation is obeyed, allowing us to develop a new method for watching the evolution of the distribution of molecular spin states in the sample. We measure as a fu…
We have employed elevated temperature scanning tunneling microscopy to elucidate the reactivity and surface structure of the $(1\ifmmode\times\else\texttimes\fi{}2)$ reconstructed $\mathrm{TiO}{}_{2}(110)$ surface. We find two distinctly different ordered surface reconstructions depending upon the level of bulk reduct…
First principles molecular dynamics (MD) simulations, of water adsorption on the $\mathrm{MgO}[100]$ surface, was performed to determine the molecular structure and chemical nature of the adsorbed water at varying coverage. Dissociative adsorption was stabilized by hydrogen bond donation from neighboring water molecul…
Many experiments have been done to determine the relative strength of different knots, and these show that the break in a knotted rope almost invariably occurs at a point just outside the `entrance' to the knot. The influence of knots on the properties of polymers has become of great interest, in part because of their…
We examine scaling in two-dimensional simulations of dendritic growth at low undercooling, as well as in three-dimensional pivalic acid dendrites grown on NASA's USMP-4 Isothermal Dendritic Growth Experiment. We report new results on self-similar evolution in both the experiments and simulations. We find that the time…
In doped CuGeO3 systems, such as (Cu1-xZnx)GeO3 and Cu(Ge1-xSix)O3, the spin-Peierls (SP) ordering (Txc. They thus concluded that there is a compositional phase boundary between two distinct magnetic phases. To clarify the nature of two phases, we performed neutron-scattering measurements on (Cu1-xMgx)GeO3 single crys…
Neutron and synchrotron diffraction data provide the first observation of changes in the crystal symmetry at the metal-insulator transition in $R{\mathrm{NiO}}_{3}$ perovskites. At high temperatures, ${\mathrm{YNiO}}_{3}$ is orthorhombic and metallic but below ${T}_{\mathrm{MI}}\phantom{\rule{0ex}{0ex}}=\phantom{\rule…
The thermal properties of blends of poly(ether ether ketone) (PEEK) and poly(ether imide) (PEI) prepared by screw extrusion were investigated by differential scanning calorimetry. From the thermal analysis of amorphous PEEK–PEI blends which were obtained by quenching in liquid nitrogen, a single glass transition tempe…
The emulsion polymerization of methyl methacrylate initiated by ultrasound has been studied at ambient temperature using sodium lauryl sulfate as the surfactant. The investigation includes the: (1) nature and source of the free radical for the initiation process; (2) effects of different types of cavitation; and (3) d…
Ab initio electronic structure theory has been applied to study the effects of β-halogenation on the structure, ionization potentials (IP), and electronic spectra of free-base (PH2) and zinc porphyrins (ZnP). Electronic and infrared (IR) spectra of β-octahalogenated free-base (β-PX8H2; X=F, Cl, Br) and zinc porphyrins…
Effects of hydrostatic pressure on Raman spectra have been investigated in mixed-valence (MV) gold complexes Cs2Au2X6 (X=Cl and Br). We have observed pressure-induced deactivation of the Raman-active Au-X stretching modes at various temperatures, indicating a pressure-induced phase transition from the MV state to a si…
Flavin reductases use flavins as substrates and are distinct from flavoenzymes which have tightly bound flavins. The reduced flavin can serve to reduce ferric complexes and iron proteins. In Escherichia coli, reactivation of ribonucleotide reductase is achieved by reduced flavins produced by flavin reductase. The crys…
Radial basis function (RBF) neural network models for the simultaneous estimation of flash point ( T f ) and boiling point ( T b ) based on 25 molecular functional groups and their first-order molecular connectivity index ( 1 χ) have been developed. The success of the whole modeling process depended on a network optim…
We report the results of P31 NMR measurements on trioctylphosphine oxide (TOPO) passivated InP quantum dots. The spectra show distinct surface-capping sites, implying a manifold of crystal–ligand bonding configurations. Two In 31P surface components are resolved and related to different electronic surroundings. With d…
The charge carrier mobility in a ladder-type poly(paraphenylene) (MeLPPP) and a phenylamino-substituted poly(phenylenevinylene) (PPV) derivative (PAPPV) has been studied in detail by using the time-of-flight (TOF) method. In most cases, the TOF signals feature characteristics of nondispersive charge transport in terms…
We propose a new method of calculating nonlinear optical responses of interacting electronic systems. In this method, the total Hamiltonian (system + system-pump interaction) is transformed into a different form that (apparently) does not have a system-pump interaction. The transformed Hamiltonian, which we call the p…