Materials Literature
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Polyester Polyols from Glycolyzed PET Waste: Efect of Glycol Type on Kinetics of Polyesterification*hydroxyl to carboxyl ratio, to obtain the polyester polyols.The kinetics of polyesterification of the three glycolyzed PET products with adipic acid under conditions comparable to commercial scale processing is reported…
The cofactor requirements of dehydroquinate synthase from Escherichia coli have been characterized. The homogeneous enzyme, purified from the overproducing strain RB791 (pJB14), is a monomeric metalloenzyme of Mr = 39,000 that contains 1 mol of tightly bound Co(II) according to atomic absorption analysis. The holoenzy…
Helical complexes formed between fd DNA and reductively methylated fd gene 5 protein were indistinguishable by electron microscopy from complexes formed with the nonmethylated protein. 13C NMR spectroscopy of 13C-enriched N epsilon, N epsilon-dimethyllsyl residues of the protein showed that three of these residues (Ly…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTLong-range electron transfer in multisite metalloproteinsHarry B. Gray and Bo G. MalmstroemCite this: Biochemistry 1989, 28, 19, 7499–7505Publication Date (Print):September 19, 1989Publication History Published online1 May 2002Published inissue 19 September 1989https://pubs.…
Different approaches to the theoretical study of the local centres in solids are discussed. Particular attention is paid to the embedded-cluster models. There are given the mathematical formulation, the computational scheme and applications for some local centres on/in graphite monolayers of the moderately large embed…
Molecular dynamics computer simulations have been made of the ordered low-temperature and orientationally disordered high-temperature phases of crystalline sodium nitrate. The interionic force model used in the simulations is based on a rigid-ion representation of the electrostatic interactions, supplemented by a set…
The laser-induced deposition of high-purity aluminum metal has been achieved by pyrolytic decomposition of trimethylamine aluminum hydride. The chemical structure of the precursor affords a high ambient vapor pressure which results in rapid rates of aluminum film formation. In addition, the precursor is nonpyrophoric,…
We suggest that weak electron tunneling between layers is responsible for the experimentally observed dramatic deviations from two-dimensional behavior in the magnetoresistance in the metallic phase of the quasi-two-dimensional conductors (TMTSF${)}_{2}$${\mathrm{ClO}}_{4}$ and (TMTSF${)}_{2}$${\mathrm{PF}}_{6}$. We p…
The kinetics of electrochemical doping of polyaniline films has been studied using in situ ESR experiments. It has been found that the kinetics and the doping level achieved during a potential-reading step depend on the previous electrochemical events undergone by the sample. It is shown that slow relaxation process t…
(C3H7NH3)2PbCl4 is a new member of the family of perovskite-type layer compounds. Calorimetric, X-ray diffraction, and dieletric measurements show the occurrence of a structural phase transition at Tc ≈ 339 K, from an orthorhombic room temperature phase (ORT) with space group Pnma (Z = 4) to a monoclinic high temperat…
Frequency and temperature dependences of dielectric constant (ϵ′) and dielectric loss (ϵ″) are studied for glassy Se and Se100−xTex alloys where 2 ≦ x ≦ 25. The measurements are made in the audio-frequency range (120 Hz to 10 kHz) and in the temperature range 100 to 330 K. The results indicate that in glassy Se, ϵ′ an…
Needle crystal growth in the presence of kinetic effects and anisotropic surface energy is studied. Within the boundary layer model it is shown that at the dimensionless undercooling Δ > 1, instead of a parabolic dendrite, an “angular” dendrite, having planar sections far from the tip, grows. At Δ c > 1 needle crystal…
Electrical transport properties of a sintered yttrium aluminum garnet (YAG) doped with Ca or Mg have been investigated as a function of temperature and partial pressure of oxygen. Conductivity and ionic transport measurements show Ca- and Mg-doped YAG to be mixed ionic-electronic p-type conductors exhibiting an activa…
Room-temperature photoluminescence (PL) and electrolyte electroluminescence (EL) spectra of polycrystalline CdS samples, in air and in contact with aqueous electrolytes, have been studied as a function of the atmosphere and temperature of annealing, light excitation intensity and wavelength, applied bias, electrolyte…
Optical absorption (\ensuremath{\sim}1--5 eV) in rf-deposited hydrogenated (20--40 at. %) amorphous ``diamondlike'' carbon films has been studied as a function of heat treatment. For E\ensuremath{\gtrsim}2.5 eV a Tauc behavior is exhibited. Optical band gaps ${E}_{g}$ are \ensuremath{\lesssim}2.4 eV. At lower energies…
Deposition of Cu in ultrahigh vacuum on a clean Pd{001} surface leads to the growth of a new crystalline Cu phase with body-centered-tetragonal (bct) structure well ordered up to about 10 layers. A low-energy electron-diffraction (LEED) analysis of 6-layer films finds the bulk lattice parameters to be a=2.75 A\r{} and…
The bulk band structure of the IV-VI semiconductors PbSe and PbTe was determined experimentally through angle-resolved photoemission from cleaved PbSe(100) and PbTe(100) surfaces, using synchrotron radiation for photoexcitation. By analyzing spectra recorded in electron emission normal to the surface over a wide range…
Iron-bismuthate glassy semiconductors were prepared in a range of compositions and their electrical transport properties were measured in the temperature range of 100–500 K. The electrical data were analyzed in the light of the models of polaronic hopping conduction. The analysis showed that the high-temperature condu…
Accurate and explicitly electron-correlated wave functions have been used to determine the dynamic hyperpolarizability tensor (γ) and the dynamic field-gradient polarizabilities (B and C) for helium. The γ-tensor is related to nonlinear optical processes such as the Kerr effect, second- and third-harmonic generation a…
1,3-Bis(2-chloroethyl)-1-nitrosourea (BCNU) has been found to be an effective chemotherapeutic agent against brain tumors. However, because it has a very short half-life in plasma, the exposure of neoplastic cells to BCNU is very brief. The delivery of BCNU may be enhanced by using controlled release polymers. We meas…