Materials Literature
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A Monte Carlo method, namely, the ‘‘statistical counting method’’ (SCM) has been proposed for simulating the conformational entropy of a single free or confined linear self-avoiding random walk chains on the simple cubic lattice. For a free linear chain with length 1081, it is found from the calculated results of 100…
We present and compare results from Monte Carlo and self-consistent-field studies of a grafted brush of polyelectrolyte chains (of length N), interacting via a screened-Coulombic potential. We examine the brush under a variety of grafting and screening conditions and investigate the various régimes of this system. The…
We have studied the photoluminescence at 1.5 μm of the 4I13/2→4I15/2 transition of the Er3+ ion, incorporated as ErF3 into polycrystalline YF3, LuF3, and LaF3 films, deposited onto SiO2 or Si wafers. We conclude that LaF3 is an exceptionally suitable host for Er3+, since it permits high Er3+ concentrations, long lifet…
Raman measurements have been carried out on Si clusters embedded in porous Si (PS). Conspicuous new Raman peaks are observed, and are identified as surface modes of Si clusters and their combination with TA modes. Good agreement is achieved between the observed Raman peaks and calculated results. The Si clusters drop…
The Raman spectra of MoO3 implanted with 1, 2, and 4×1016 H+/cm2 have been recorded at room temperature. It was found that most of the Raman modes of Ag and Bg symmetry, which are observed between 100 and 1100 cm−1, decrease in intensity by the electronic screening of phonons as a result of the electron transfer from…
From an expression for the energy of a cell containing an antiferroelectric smectic liquid crystal with only nearest-neighbor interactions between layers we conclude the following: (1) a critical cell thickness exists at which the commensurability of the system changes from unity to higher values; (2) for negative die…
In single crystals of the dimer compound Cs3Y2Br9:10% Yb3+ below 31 K, both visible (VIS) and near-infrared (NIR) luminescence intensities were found to exhibit hysteresis as a function of incident NIR intensity and temperature. The optical bistability is intrinsic to Cs3Y2Br9:10% Yb3+ and not a result of an external…
The metC gene coding for cystathionine beta-lyase of Escherichia coli has been cloned and used to construct an overproducing E. coli strain. An efficient purification scheme has been developed and the purified enzyme has been crystallized by the hanging drop vapour diffusion method using either ammonium sulfate or pol…
We present a molecular theory of the phenomena of single-chain collapse and phase separation into a polymer-rich and a polymer-poor phase, which occur in polymer solutions below the Θ temperature. The theory extends the Fourier self-consistent approach of Allegra and Ganazzoli from the study of single-chain properties…
A photovoltaic cell with carbonaceous thin film/n-type silicon (C/n-Si) was fabricated. The carbonaceous thin film was deposited on an n-type single-crystal-silicon substrate by chemical-vapor deposition of 2,5-dimethyl-p-benzoquinone at 500 °C. Without light irradiation, the photovoltaic cell displayed an almost perf…
Plasma-deposited, hydrogenated carbon thin films were investigated by infrared analysis and high-energy ion analysis. The absolute quantities of hydrogen in the films, as measured by ion beam analysis, and the strength of the C–H vibrational bands around 3000 cm−1 were compared to determine the average absorption stre…
We describe a modification of conventional dynamic light scattering (DLS) using a CCD camera as optical area detector. Scattered intensity autocorrelation functions are determined using both ensemble- and time-averaging. Therefore, the new setup allows for much shorter measurement times compared to conventional DLS. O…
A physical picture of a conjugated chain as a collection of almost planar segments, separated by large angular breaks arises from a microscopic model which includes conjugation and steric interactions. The conjugation part of the standard phenomenological Hamiltonian for torsional motion is also derived from the model…
The lattice parameter and surface morphology of homoepitaxial SrTiO3 films were found to depend on the ambient oxygen pressure during growth. The homoepitaxial layers were grown by pulsed laser deposition with static ambient oxygen pressures of 100, 10, and 1 mTorr. The surface roughness of the films increased with in…
The binary liquid phase separation of aqueous solutions of γ-crystallins is utilized to gain insight into the microscopic interactions between these proteins. The interactions are modeled by a square-well potential with reduced range λ and depth ε. A comparison is made between the experimentally determined phase diagr…
Methanotrophs have promising applications in the bioremediation of chlorinated hydrocarbons and in the production of a biopolymer, poly-beta-hydroxybutyrate (PHB). Batch bioreactor culture conditions were studied for the accumulation of PHB by methane-grown Methylosinus trichosporium OB3b, and to evaluate the effect o…
Without a doubt, photochemically induced electron transfer in 1 proceeds stepwise. Triad 1 is one of the latest models of the photosynthetic reaction center. The rates of the individual steps in the electron transfer relay have been determined by ultra-fast laser spectroscopy.
Syntheses of a series of conjugated donor-acceptor chromophores, based on a strongly electron-withdrawing heterocyclic acceptor, have led to compounds with large second-order optical nonlinearities. Incorporation of one of these chromophores into polycarbonate at 20 percent weight loading yielded, after poling at 150…
The crosslinking reaction of poly(vinyl alcohol) (PVA) with 3,3′,4,4′-tetracarboxybenzophenone dianhydride, pyromellitic carboxylic acid anhydride, and Epiclon B-4400 as hardeners was studied either in solution or by differential scanning calorimetry. A catalyst agent had to be used in all cases. Depending on the conc…
Several microcrystalline celluloses prepared from viscose staple, bagasse, ramie, and cotton were evaluated by viscosimetry, X-ray diffraction and scanning and transmission electron microscopies. The changes in crystallinity, size of crystallites, grain-size distribution, morphological features, and degree of polymeri…