Materials Literature
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The macroscopic electric polarization of a crystal is often defined as the dipole of a unit cell. In fact, such a dipole moment is ill defined, and the above definition is incorrect. Looking more closely, the quantity generally measured is differential polarization, defined with respect to a "reference state" of the s…
Thermoanalytical techniques have found widespread use as a quality-control tool for petroleum and related products. Pressure differential scanning calorimetry (PDSC) has been effectively used as an alternative method to estimate thermal-oxidation stability of middle-destillate fuels. In this paper, the fuels were rate…
Abstract The development of a modified Phillips reaction allows the synthesis of complicated heteroleptic ligands based on pyridine and 1 H ‐benzimidazole moieties. The key‐step formation of aromatic 1 H ‐benzimidazole rings from N ‐(2‐nitroaryl)arenecarboxamides significantly improves the possibilities of the classic…
A cornerstone reference in the field, this work analyzes available information on the corrosion resistance of zinc and its alloys both as solid materials and as coatings on steel, detailing the corrosion resistance of zinc in atmospheric, aqueous, underground and chemical environments. Corrosion Resistance of Zinc and…
Two extremely potent inhibitors of citrate synthase, carboxyl and primary amide analogues of acetyl coenzyme A, have been synthesized. The ternary complexes of these inhibitors with oxaloacetate and citrate synthase have been crystallized and their structures analyzed at 1.70- and 1.65-A resolution, respectively. The…
Absolute differential (in angle) and total scattering cross sections for low-energy (0.1-7.0 eV) electron scattering from neon have been measured. Both data sets have been analysed using phaseshift techniques and comparisons are made between the present cross sections and phaseshifts and similar data from previous swa…
Collagen-like peptides with potential for ion pair formation were studied to investigate the role of electrostatic interactions in the triple-helix conformation. Three peptides--(POG)10, the EK-containing peptide (POG)4EKG(POG)5, and T3-487, a peptide with 18 residues of type III collagen and a C-terminal (GPO)4 tail-…
Abstract Experimental data were obtained on the concentration dependence of the fraction of total filler–bound polymer, fraction of polymer in a coherent polymer–filler gel, and fraction of solvent‐dispersed filler particles in compounds of fume silica (Aerosil OX50) with natural rubber (NR) and styrene butadiene rubb…
The energy band gap of light-emitting porous silicon is determined by high-resolution electron energy loss spectroscopy, and the valence band edge of porous silicon with respect to its Fermi level is measured by ultraviolet photoelectron spectroscopy. By combining the results with that measured from clean Si, a pictur…
Abstract The chemical synthesis of polypyrrole in water, with FeCl 3 as an oxidant of pyrrole, was investigated. During these experiments in ambient air, a large evaporation of pyrrole was observed. Moreover, a kinetic study of pyrrole disappearance by high‐performance liquid chromatography (HPLC), with various FeCl 3…
Polycrystalline pyridinium perchlorate has been studied over a wide range of temperatures by differential thermal analysis, proton NMR spectra and relaxation, and dielectric permittivity measurements. Two solid-solid phase transitions at 232 and 248 K have been revealed and the pyridinium cation reorientations in all…
Highly localized, laser-excited optical modes of silver colloid fractal clusters were observed using photon scanning tunneling microscopy. The spatial distribution of the modes shows the frequency and polarization selectivity suggested by numerical simulations. The results verify the main concepts of the recently deve…
We investigate interactions between interfacial disequilibrium and compositional convection during the freezing of an alloy from below to form a mushy layer. A theoretical model is developed in which a stagnant mushy layer underlies a melt that is convecting vigorously, driven by compositional gradients associated wit…
An x-ray surface forces apparatus for simultaneously measuring forces and structures of confined complex fluids under static and flow conditions is described. This apparatus, combined with an intense synchrotron x-ray source, allows investigation of molecular orientations within a thin liquid crystal film confined bet…
The quinoxaline and phenazine dianions can each be stabilized by two lanthanocene units, which leads to the novel binuclear rare-earth complexes with short LaC and LaN contacts. These La–ligand contacts resemble those in “aromatic alkali-metal amides”. The phenazine complex is shown on the right.
Very flexible and antiaromatic versus relatively rigid and aromatic—that is the difference between [24]porphyrinogen 1 and its oxidation product [22]porphyrin dication 2. Although both compounds occur in the cis, trans, cis, trans configuration, the protons along the inner perimeter of 2 are shifted roughly 20.5 ppm u…
An energetically low-lying octet ground state and ferromagnetic exchange interactions between seven CuII ions characterize the magnetic behavior of the complex cation in 1, whose novel Cu7(OH)8 framework is shown on the right, bpym = 2,2′-bypyrimidine.
One equivalent of Ca2+ and Sr2+ ions induces the isomerization of the colorless spirobenzopyrans 1a (n = 1) and 1b (n = 2), respectively, to the colored merocyanines 2. Compounds of type 1 thus function as ion-selective chemical sensors.
Im Kampf um die Aromatizität gewinnt Benzol gegen [18]Annulen: Das erste voll durchkonjugierte, Benzol enthaltende Porphyrinanalogon 1 erweist sich als nicht‐18 π‐aromatisch, nur das Tautomer mit intakten benzoiden Aren wird beobachtet. 1 läßt sich in ca. 6% Ausbeute aus der entsprechenden Tripyrrandicarbonsäure und I…
In PbHfO3 single crystals the amplitude of the thermal vibrations for Pb ions in the high-temperature Pm3m phase, calculated from the Debye-Waller factor, reached unexpectedly large values. The random displacements of Pb ions were assumed and the new thermal vibration amplitude, which is more reasonable from the cryst…