Materials Literature
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The phytoplankton of lake Zempoala was studied from April 1996 to July 1997. The taxonomy, ecology and geographical distribution of species show that their presence is more common in temperate than tropical areas. Seasonal variations in patching, density and dominant species of the phytoplankton are corresponding with…
The crystal structure of α-Sr2P2O7, distrontium diphosphate, has been refined by X-ray diffraction using single crystals grown from a SrLiPO4-P2O5 melt cooled between 1323 and 1073 K. The fully anisotropic refinement confirms the centrosymmetric Pnma space group, but also reveals a strong anisotropy along the b direct…
The potentialities of polarization microscopy has been greatly increased by using specific stains for selective enhancement of the optical anisotropy of a macromolecular constituent of cells and tissues. Such stainings have proved to be especially useful in exploring the spatial orientation pattern of the extracellula…
In situ scanning tunneling microscopy measurements of Pd single-crystal domains during hydrogen charging/discharging cycles in 0.25 M KOH at 298 K allowed us to follow deformations produced by the Pd ⇔ β(H−Pd) phase transition in real time. The stress produced by this transition leads to elastic deformations involving…
First-principles calculations of the band structure of peptide nanotubes are presented. It is shown that these nanotubes are insulators with wide band gaps, and that they act as an inert vessel where foreign atoms could be incorporated; hardly any interaction takes place between the tube wall and guest atoms.
The reconstruction of the shape of biological macromolecules in solution from small-angle scattering data is an important task for understanding the structure-function relationship. In the last few decades, the multipole expansion method was used to attack this problem. Here we present an improvement of the existing t…
The second-harmonic generation (SHG) yield of both evaporated and spin-coated films of some tri-substituted subphthalocyanines has been measured for three linear polarizations of the fundamental beam. Partial molecular ordering in the spin-coated films was achieved by the corona poling technique. For the evaporated fi…
Rhenium glass microspheres composed of metallic rhenium particles dispersed within a magnesium alumino borate glass matrix were produced by sintering ReO2 powder and glass frit at 1050 degrees C. The in vitro chemical durability of radioactive and nonradioactive microspheres was determined from chemical corrosion test…
Nanosized neutral silicon-carbon compound clusters produced by a laser vaporization source have been analyzed in the gas phase and deposited at room temperature on various substrates in an ultrahigh vacuum environment to produce nanostructured thin films. The electronic structure has been probed by complementary techn…
A study of charge transport in the crystalline phase of the columnar liquid crystal, hexakis(n-hexyloxy)triphenylene, HAT6, is reported. A simple model is introduced and fitted to observations of photocurrent transient decays in the crystalline phase of HAT6. From these a quasi one-dimensional trapping process is infe…
A cobaltite, Bi 3.7 Sr 11.4 Co 8 O 28 - δ, with a “tubular” structure derived from the 2201-type has been synthesized for the first time. This oxide represents, like the homologous manganese phase, the n = 2 member of the large structural [Bi 2 Sr 2 MO 6 ] n [Sr 8 M 6 O 16 ±δ ] family (M = Cu, Co, Mn). Although its st…
Epiclusianone [3-benzoyl-4-hydroxy-6,6-dimethyl-1,5,7-tris(3-methyl-2-butenyl)bicyclo[3.3.1]non-3-ene-2,9-dione] is a new isomeric form of the C33H42O4 compound identified by X-ray diffraction analysis. Structure comparison with the known clusianone evidences a case of epimerism in one of the chiral C atoms. A compari…
DNA and RNA polymerases use divalent metal ions for catalysis. Crystal structures of several polymerases reveal that two acidic residues are involved in coordinating two metal ions at the catalytic centre. Bacteriophage RNA polymerases contain a highly conserved C-terminus with the carboxylate positioned near the acti…
The luminescence decay kinetics of homogeneously and delta-doped ZnS:Mn thin film phosphors was investigated. A quantitative model based on the hopping model of energy transfer theory was developed to described the concentration quenching phenomenon in ZnS:Mn. The model predicted the dependence of the energy transfer…
The presence of a parasitic surface film of 80 nm thickness has been observed by x-ray reflectivity on the top of some p+ type porous silicon layers, related to a contamination of the substrate. After testing several methods to clean the substrate and to avoid this film, it was found that a 300 °C thermal annealing of…
Electrode processes at redox electrodes consist of mass transport to and from the electrode|electrolyte interface and of charge transfer across this interface. At n-type semiconductor electrodes, charge transfer may involve either direct exchange of conduction band electrons or direct exchange of valence band holes, a…
Analytical description of photoelectron and Auger-electron transport in solids requires values of the transport cross sections ${\ensuremath{\sigma}}_{\mathrm{tr}}$ for electron energies between 50 and 2000 eV. An analytical formula is proposed to provide needed values of ${\ensuremath{\sigma}}_{\mathrm{tr}}$ for ener…
We have re-investigated the well-studied hydrogen covered Si(100) surface using high resolution electron energy loss spectroscopy (HREELS) with a spectral resolution down to 13 cm1, representing an improvement by a factor of 3–4 compared to earlier work. For the first time in HREELS, it has been possible to clearly di…
A detailed study of coupled porous silicon (PS) microcavities (PSM's) is reported. The samples are investigated by room temperature photoluminescence and reflectivity. A splitting of the eigenmodes of the coupled cavity structure is observed, as well as a difference between the intensities of the cavity peaks related…
The dielectric behavior of pulsed laser deposited ferroelectric (Pb1−xLax)(Zr0.65Ti0.35)O3 films (PLZT x/65/35, x=0–9.75 at. %) has been studied experimentally. Epitaxial stoichiometric PLZT films were formed on a pulsed laser deposited layer of La0.5Sr0.5CoO3 (LSCO) on MgO (100) single-crystal substrates. The dielect…