Materials Literature
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Mutants of Escherichia coli unable to synthesize a functional pyruvate formate-lyase (PFL) are severely impaired in their capacity to grow by glucose fermentation. In a functional complementation assay designed to isolate the pfl gene from Clostridium butyricum, we fortuitously identified a gene that did not encode a…
In this study ultraviolet photoemission spectroscopy was employed to correlate the electron affinity and Schottky barrier height of Cu films on type-IIb ($p$-type) diamond (100), (111), and (110) surfaces. Furthermore, field emission measurements were correlated with the effective electron affinity of the samples. Pri…
We have measured the complex dielectric permittivity for ceramic samples of ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{FeO}}_{3}$ $(0.2<~x<~0.8),$ which, unlike ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{MnO}}_{3}$ and ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{CoO…
Thermoelectric power (TEP) properties of carbon nanotubule bundles were measured in the range 4.2--300 K. It was found that the TEP is positive over the whole temperature range, and increases with the increase of temperature. Above 30 K it can be well described by a formula $S(\ensuremath{\mu}V)=0.181T\ensuremath{-}{(…
Electrical resistance and magnetoresistance of the HCl doped polyaniline (PANI) in aqueous ethanol medium and polyaniline–methyl cellulose dispersion (PANI–MC) has been investigated at low temperature down to 1.8 K and in magnetic field up to 8 T. The weaker temperature dependence of resistivity characterized by the r…
We present the first experimental characterization in molecular fragile glass-formers of a "prepeak" that appears significantly below the main peak of the static structure factor. The temperature and density dependences of this prepeak are studied via elastic neutron scattering experiments under high pressure (up to 3…
We report on spin-flip Raman scattering and on Raman scattering by acoustic phonons in CdS nanocrystals embedded in a glass matrix. We discuss both the spin-flip and the acoustic-phonon Raman spectra on the basis of the interaction of size-quantized electronic excitations with nonconfined acoustic vibrations. The pola…
Persistent photoconductivity (PPC) has been observed in boron-doped Si1−xGex/Si quantum wells. The decay kinetics of the PPC effect can be well described by a stretched-exponential function, Ippc(t)=Ippc(0)exp[−(t/τ)β](0&lt;β&lt;1), which is usually observed in many disorder materials. Through the studies of t…
We report a self-consistent tight-binding atomic-relaxation model for titanium dioxide. We fit the parameters of the model to first-principles electronic structure calculations of the band structure and energy as a function of lattice parameters in bulk rutile. We report the method and results for the surface structur…
Local structures around Mn in ${\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{As}$ ($x=0.005$ and 0.074) films have been studied using Mn $K$-edge extended x-ray-absorption fine structure. In the ${\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{As}$ films, Mn atoms are substituted into the Ga sites…
The ac conductivity, σac of BaSnO3 has been measured in the temperature range 310–520 K and frequency range 100 Hz–1 MHz. Below 420 K the conductivity is almost independent of temperature while between 420 and 520 K it is temperature dependent. At 100 kHz the activation energy of these two regions is 0.08 and 0.35 eV,…
In contrast to their hydrocarbon analogues which exhibit only nematic mesophases, poly{5-[[[2‘,5‘-bis[(4‘‘-( n -(dimethylsiloxyl)alkoxy)benzoyl)oxy]benzyl]oxy]carbonyl]bicyclo[2.2.1]hept-2-ene}s and their low-molar-mass model compounds exhibit smectic C mesophases. Since nematic liquid crystals can be forced into laye…
Temperature and frequency dependence of the real (ε′) and imaginary (ε″) parts of the dielectric permittivity of Ba(Ti1−yYy)O3 (0.028⩽y⩽0.258) ceramic samples were studied in the temperature range 12–500 K at 102, 103, and 104, and 105 Hz. The permittivity peaks are rounded and frequency dispersive when y&gt;0.028…
Silicified microcrystalline cellulose (SMCC) has been compared with a standard grade of microcrystalline cellulose (MCC) using several physicochemical techniques in order to elucidate any chemical or polymorphic changes in the material that could be attributed to the silicification process. Samples of SMCC, MCC and dr…
Since the rejuvenation of interest in the rare earth manganites owing to their potential use as magnetoresistive sensors, there has been adequate research to arrive at some evaluation of the potential for these materials in a variety of technologies that would use the peculiar properties of these materials. The magnet…
Scanning tunneling microscopy and first-principles atomic orbital based calculations have been used to study ${\mathrm{TiO}}_{2}(110)1\ifmmode\times\else\texttimes\fi{}2.$ A structure is proposed that resolves the controversy surrounding the surface morphology. Our model is simple, in that it consists only of atoms in…
The dilithium salts of N, N ‘, N ‘‘-tris(trimethylsilyl)diethylenetriamine ( 1 ), N -methyl- N ‘, N ‘‘-bis(trimethylsilyl)diethylenetriamine ( 2 ), and N -methyl- N ‘, N ‘‘-bis(diisopropyl)diethylenetriamine ( 3 ) reacted in THF, at −40 °C, with AlCl 3 affording monomeric aluminum chloride derivatives 4 (55% yield), 5…
Although theoretical understanding of doped mixed–valence manganites that exhibit colossal magnetoresistance (CMR) is still incomplete, the general observation of a systematic correlation at a given temperature between the magnetization and resistance both above and below the Curie temperature Tc can provide a phenome…
The morphology of a family of four 3-miktoarm star terpolymers of polystyrene (PS), polyisoprene (PI), and polymethyl methacrylate (PMMA) was studied. For three of the samples, the molecular weight of the PMMA block was systematically varied while that of the PS and PI blocks were held fixed. In the fourth sample, the…
The old coordinate driving procedure to find transition structures in chemical systems is revisited. The well-known gradient criterion, ∇E(x)=0, which defines the stationary points of the potential energy surface (PES), is reduced by one equation corresponding to one search direction. In this manner, abstract curves c…