Materials Literature
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Abstract This chapter covers the field of channelling and its effects for electrons traversing thin crystals in the transmission geometry. Channelling effects in the reflection or RHEED geometry, where the beam makes a glancing angle with the crystal surface, are treated in Vol. 2, chapter 3. Backscattered channelling…
Saccharomyces cerevisiae has both cytoplasmic and mitochondrial C1-tetrahydrofolate (THF) synthases. These trifunctional isozymes are central to single-carbon metabolism and are responsible for interconversion of the THF derivatives in the respective compartments. In the present work, we have used 13C NMR to study fol…
An X-ray structure analysis of a crystal of mutant Asp229----Ala of cyclodextrin glycosyltransferase from Bacillus circulans (Ec 2.4.1.19) that had been shortly exposed to beta-cyclodextrin showed density corresponding to a maltose bound at the catalytic center. The crystal structure was refined to an R-factor of 18.7…
The effect of thermal annealing and surface coverage on porous silicon photoluminescence was studied in situ in an ultrahigh vacuum chamber. These investigations correlated simultaneously temperature, surface coverage, and photoluminescence intensity. The surface coverage was monitored using transmission Fourier trans…
Changes in dangling bond densities in porous silicon were measured and results indicate a relatively low dangling bond density (roughly 3×1016 bonds/cm3) in as-prepared samples, which increases by a factor of 6–7 upon quenching of the photoluminescence (PL). The electron spin resonance (ESR) data suggest the presence…
Grafted polymer layers are well known as stabilizing agents in colloidal dispersions. Here we show how these polymer ``brushes'' may also deeply modify wetting phenomena by favoring the formation of stable wetting layers of microscopic size. We discuss in particular the influence of a solvated polymer layer on the wet…
The mode coupling theory for supercooled liquid dynamics finds a beta -relaxation regime on mesoscopic timescales. It is caused by the interplay between nonlinear interactions of density fluctuations and phonon-assisted hopping transport. In this regime all correlation functions and spectra can be expressed in terms o…
Absorption spectra from 0.94--5.58 eV are obtained for gas-phase neutral silicon clusters ${\mathrm{Si}}_{18}$--${\mathrm{Si}}_{41}$ using resonant one- and two-color photodissociation spectroscopy. The spectra of all clusters are essentially identical. Above 3.0 eV, they exhibit six sharp absorption peaks with cross…
We present the first investigation of the growth kinetics of diamond films grown homoepitaxially by hot-filament chemical vapor deposition on (100), (110), and (111) natural diamond substrates. Growth rates on the various faces exhibited different functional dependencies on CH4 flow rate, being linear on (100), slight…
We study theoretically the equilibrium behavior of the lamellar phase of an A-B diblock copolymer melt. Each lamellar layer is an A-B,B-A repeat unit and n such layers are confined between, and parallel to, two identical flat plates. We find that the configurations with a half-odd-integer number of layers occur only w…
It is proposed that the first sharp diffraction peak (FSDP) in the structure factor of network glasses and liquids is a pre-peak in the concentration-concentration structure factor due to the chemical ordering of interstitial voids around cation-centred clusters in the structure. This model can predict quantitatively…
Experimental investigations of the diffusion in crystalline metals and alloys under irradiation are reviewed emphasizing those experiments, in which atom transport was directly observed. Three types of results will be considered: (i) radiation-enhanced self- and impurity diffusion, (ii) segregation of components in ho…
When two bodies of liquid merge, their interfaces must also rupture and rearrange into one. Virtually no information is available concerning the small-scale dynamics of this process. Molecular dynamics simulations of coalescence in systems of about 10,000 Lennard-Jones particles have been performed, arranged so as to…
Cost and weight savings achieved by the use of composites have allowed these materials to displace their metal counterparts in space applications. Epoxy matrix based carbon fiber reinforced composites, such as Fiberite 934, have been used for a number of years. Relative to these systems, cyanate esters offer a number…
Dielectric, thermal, and elastic properties of Cs2CuCl4 crystals are studied at temperature from 80 K to their melting point. No anomalies typical of incommensurate phase transitions are observed. The changes in ϵ33 as well as in the c33 and c23 components of the elasticity tensor suggest the possibility of a phase tr…
The crystal structure of the cubic phase of the complex perovskite Pb2CoWO6 is investigated by single crystal X-ray diffraction and neutron powder diffraction. Both experiments lead to the same conclusion. The Pb atom is not on the special position of the prototype structure, but displaced from this position along the…
A model explaining all the features of the complex thermoluminescence (TL) process in ${\mathrm{CdF}}_{2}$:Eu is presented, based on extensive optical and EPR studies. It is shown that two types of europium centers are active in the TL process: the charge-compensated ${\mathrm{Eu}}^{3+\mathrm{\ensuremath{-}}}$${\mathr…
Abstract We are investigating the bulk and interfacial chemistry of polyimide (PI) exposed to heat and relative humidity (RH) stress (85°C/85% RH) over long periods to understand the long‐term reliability aspects of PI for microelectronic applications. The PI surface chemistry and the PI–Si interface chemistry was fol…
Micro-Raman spectroscopy is applied to evaluate change of the crystal quality in molecular beam epitaxial GaAs layers on Si after rapid thermal annealing (RTA). The forbidden transverse optical phonon is observed in the GaAs layers especially near the interface. In the as-grown state, the Raman frequency of the longit…
Abstract The crystallization of poly(ethylene terephthalate) (PET) in its blends with other thermoplastics such as poly(phenylene sulfide) (PPS), high‐density polyethylene (HDPE), poly(methyl methacrylate) (PMMA), aromatic polyamide, and a co ‐polyester is reported. The nonisothermal crystallization and melting behavi…