Materials Literature
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Ligand-stabilized gold clusters may serve as model catalysts, and the packing of their gold atoms is therefore of great interest. The cluster of the stoichiometry Au 55 [P(C 6 H 5 ) 3 ] 12 Cl 6 is thought to be the smallest known defined compound in which the gold maintains a cubic dense packed metallic (ccp) state. W…
The X-ray structure of tyrosine phenol-lyase (TPL) complexed with a substrate analog, 3-(4'-hydroxyphenyl)propionic acid, shows that Arg 381 is located in the substrate binding site, with the side-chain NH1 4.1 A from the 4'-OH of the analog. The structure has been deduced at 2.5 A resolution using crystals that belon…
Complex formation between pyrazine derivatives and dimeric self-assembly of αααα-isomer of meso -tetrakis(2-carboxy-4-nonylphenyl)porphyrin Zn complex ( 1·Zn ) was investigated. Thermal atropisomerization of 1·Zn in a nonpolar solvent such as toluene gives the αααα-atropisomer exclusively. Vapor pressure osmometry for…
First-principles quantum calculations are potentially of great value for assessing the plausibility of proposed catalytic reaction mechanisms. The present analysis of reaction pathways and energetics for key elementary steps in the catalytic decomposition of NO to N 2 + O 2 by Cu-exchanged zeolites yields novel insigh…
The chemisorptive behavior of CO on several planar model monometallic and bimetallic Pd, Cu, and Au catalysts supported on thin film Al2O3 has been investigated using infrared reflection absorption spectroscopy (IRAS). For Pd and Cu monometallic catalysts, CO adsorption spectra indicate a high representation of low in…
The melt miscibility of atactic poly(propylene) (a-PP) with isotactic (i-PP) and syndiotactic poly(propylene) (s-PP), respectively, is investigated by diffusion experiments of i-PP/a-PP/i-PP or s-PP/a-PP/s-PP sandwich specimens using polarized light microscopy. It is shown that the system a-PP/i-PP is miscible in the…
The crystal structure of ${\mathrm{La}}_{1.2}$${\mathrm{Sr}}_{1.8}$${\mathrm{Mn}}_{2}$${\mathrm{O}}_{7}$ has been determined as a function of temperature in magnetic fields of 0 and 0.6 T. There is a significant magnetostriction at the Curie temperature ${\mathrm{T}}_{\mathrm{C}}$; the a axis contracts (\ensuremath{\D…
Porphyrin dimers linked in the meso -positions by bridges containing alkynes conjugated with the porphyrin π-systems display highly perturbed electronic absorption spectra. We have prepared a series of such dimers using meso -ethynyl nickel(II) octaethylporphyrin as the primary building block. The bridging units inclu…
The hydrothermal reactions of vanadium oxide and molybdenum oxide starting materials with divalent first-row transition metal cations in the presence of nitrogen donor chelating ligands yield the heterometallic hexanuclear clusters [{Zn(bipy)(2)}(2)V(4)O(12)] (2), [{Zn(phen)(2)}(2)V(4)O(12)].H(2)O (3.H(2)O), and [{Ni(…
Abstract The peculiar liquid crystalline behavior of two poly(urethane‐ester)s TDI‐C6C4 and TDI‐C6C8 is reported. Evidence is provided of the formation of two nematic mesophases, a cybotactic nematic and a conventional nematic mesophase, in TDI‐C6C8 and of one cybotactic nematic mesophase in TDI‐C6C4. IR spectroscopy…
Introduction and synopsis Foams can be made out of almost anything: metals, plastics, ceramics, glasses, and even composites. Their properties depend on two separate sets of parameters. There are those which describe the geometric structure of the foam – the size and shape of the cells, the way in which matter is dist…
Abstract Die Wirkungsweise von Rasensprengern, Parfumzerstäubern oder Tintenstrahldruckern beruht auf der Oberflächenspannung. Diese führt dazu, daß sich ein Flüssigkeitsstrahl unter Verringerung der Oberfläche einschnürt und Tropfen bildet. In der Nähe des singulären Punktes, in dem sich ein Tropfen abtrennt, gelten…
Thermal conductivity and thermal diffusivity of three rare earth oxide powders (Gadolinium oxide, Samarium oxide and Yttrium oxide) are measured experimentally using Transient Plane Source (TPS) technique at ambient temperature. An attempt has been made to accommodate the effect of porosity of the powders on thermal c…
Abstract Soil weathering is an important source of nutrient cations and P for development of forested ecosystems, but the rates at which these nutrients are released are not well known. Measurement of weathering products can be used in long‐term (5–10 yr) mesocosm studies to evaluate soil weathering rates. In this stu…
A new class of photochromic compounds, derivatives of 2,3-dihydro-2-spiro-4′-(2′,6′-di-tert-butylcyclohexadienon-2′,5′- one) erimidine is described and their photochromic and thermochromic rearrangements described.
A previous study (Snyder, C. R.; Marand, H.; Mansfield, M. L. Macromolecules 1996, 29, 7508) by the authors suggested that, within the context of the Lauritzen−Hoffman secondary surface nucleation theory, the apportionment factor for the free energy of crystallization (ψ LH ) and the retardation factor due to transpor…
Raman spectra have been recorded from 300--10 K for lanthanide hexachloroelpasolites, ${\mathrm{Cs}}_{2}$${\mathrm{NaLCl}}_{6}$. Electronic Raman-scattering intensity ratios have been calculated using Judd-Ofelt-Axe theory and are in reasonable agreement with experimental results, except for those cases where electron…
The electron-donating property of Na metal-doped MgO (Na/MgO) was studied by the ESR technique. The spin concentration of (CO) n x - ((CO) 2 - and/or (CO) 6 3 - ) radicals formed from adsorbed CO on a Na/MgO surface was much higher than that of the surface paramagnetic center formed by an electron released from sodium…
Abstract A brief discussion of selected synthetic strategies pursued in the field of molecular, macromolecular and supramolecular liquid crystals is made by reviewing some tandem historical events of the past 100 years of activity in this field. This survey will try to suggest the rational for the discovery, evolution…
The synthesis, mesophase morphology and transition temperatures of a series of 1,2,4,5-tetrasubstituted benzenes are described. The compounds have (4-tridecyloxyphenyl)carbonyloxy or (4-tridecyloxyphenyl)ethynyl as the peripheral substituents in all possible combinations ranging from the tetra-ester to the tetra-alkyn…