Materials Literature
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The kinetics of acetylene hydrogenation in the presence of a large excess of ethylene was studied in a laboratory flow reactor. Experiments were carried out using a Pd/α-Al 2 O 3 commercial catalyst and a simulated cracker gas mixture (H 2 /C 2 H 2 = 50; 60% C 2 H 4; 30% H 2, and traces of CO), at varying temperature…
The role of metal–metal bonding interactions is reviewed in the context not only of cluster chemistry, but also in linear gold(I) compounds. The latter, although much weaker than the former, can lead to interesting infinite and catenane structures which arise from supramolecular interactions.
4-Urazoylbenzoic acid groups are attached to the chain ends of polyisobutylene. The cooperative assembling process of these polar groups is studied by DSC and dielectric and dynamic mechanical spectroscopy. The melting of the ordered clusters occurs in the temperature range 380−390 K. Distortions within the U4A cluste…
The first observation of a ligand-driven light-induced spin-state change (LD-LISC effect) in a transition-metal complex is reported. The compounds under investigation are of the type Fe(II)L(4)X(2), where L is a cis/trans photoisomerizable ligand. For an iron(II) spin-state change to result from ligand cis <--> trans…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTPolyhydroxybutyrate Synthase: Evidence for Covalent CatalysisJ. Wodzinska, K. D. Snell, A. Rhomberg, A. J. Sinskey, K. Biemann, and J. StubbeView Author Information Departments of Chemistry and Biology Massachusetts Institute of Technology Cambridge, Massachusetts 0213…
A new series of liquid-crystalline Schiff base lanthanide compounds of the general formula (L‘‘H) 2 L‘‘MX 2 was prepared (L‘‘H = H 2 n +1 C n OC 6 H 3 (OH)CHNC m H 2 m +1; n = 7, 12; m = 14, 18; M = La, Tb, Dy, Er, Nd, Ho, Eu, Pr, and Gd; X = NO 3 or Cl). The thermal behavior of these complexes was examined by polariz…
A thermodynamic model is given for phase separation induced by the increase of network elasticity during free-radical cross-linking polymerization. The importance of network elasticity in the field of polymer dispersed liquid crystals is stressed. The concept of a conversion−phase diagram is introduced as an attractiv…
By conjugating proteins with a common pH-sensitive fluorescent label, fluorescein isothiocyanate (FITC), and controlling the ionic strength, we provide a means to decrease the characteristic length scale of the total internal reflection fluorescence (TIRF) technique by two orders of magnitude. The usual characteristic…
Fluorescence resonance energy transfer is a powerful tool for studying nanometer-scale distances in biological macromolecules under physiological conditions. Using luminescent lanthanides instead of conventional fluorophores as donor molecules in energy transfer measurements offers many technical advantages and opens…
The importance of two buried salt bridges in barnase in the stability of its folded state, the major transition rate for unfolding, and a folding intermediate has been analyzed by protein engineering, kinetic, and thermodynamic studies. The aspartate residues in the bridges Arg69-Asp93 and Arg83-Asp75 were replaced by…
Magnetic properties of the layered materials Cu 2 (OH) 3 ( n -C m H 2 m +1 COO) ( m = 0, 1, 7, 8, and 9) have been examined. X-ray powder diffraction patterns indicate that the interlayer distance increases in the order of m . The interlayer distances of the m = 0 and 1 materials are shorter than the molecular heights…
We demonstrate that a surfactant-stabilized molten globule intermediate exists for recombinant human growth hormone (rhGH), is very hydrophobic, and tends to form aggregates. Characterization of this intermediate included equilibrium denaturation measured by electron paramagnetic resonance (EPR) and CD spectroscopy, a…
A phylogeny of the diatoms was inferred from comparisons of nuclear-encoded small subunit ribosomal RNA coding regions using maximum likelihood, weighted maximum parsimony, and neighbor-joining distance methods with Jukes and Cantor, Kimura, Gamma, van de Peer, and LogDet evolutionary models. Analyses of 30 taxa in 11…
We report an extensive ab initio study of the electric dipole polarizability and hyperpolarizability of carbon monoxide. The bond length dependence of the molecular properties has been determined from finite-field complete fourth-order many-body perturbation theory and coupled cluster calculations with very large, wel…
The zinc alkoxy(siloxy) complex {Zn[OSi(O t Bu) 3 ] 2 } 2 has been prepared and studied as a molecular precursor to zinc orthosilicate, Zn 2 SiO 4 . This complex, prepared by reaction of ZnMe 2 with HOSi(O t Bu) 3, has been characterized by X-ray crystallography as a dimer with two four-coordinate zinc centers. It cle…
ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTRedox Behavior of Polyaniline−Transition Metal Complexes in SolutionMasayoshi Higuchi, Daisuke Imoda, and Toshikazu HiraoView Author Information Department of Applied Chemistry, Faculty of Engineering, Osaka University, Yamada-oka,…
We use atomic force microscopy (AFM) with phase detection imaging (PDI) in order to study the surface microdomain morphology of thick (i.e., ca. 2 mm) films of triblock copolymers. We present here the results obtained on a poly(methyl methacrylate)- block -polybutadiene- block -poly(methyl methacrylate) (PMMA- b -PBD-…
Nickel-containing mesoporous materials MCM-41 and AlMCM-41 have been prepared by synthesis and ion exchange. These materials are catalytically active for ethylene dimerization and 1-butene isomerization. The catalytic activity for the dimerization reaction is shown to be due to nickel(I) species, while the 1-butene di…
Carbon spheres have been synthesized using a mixed-valent oxide-catalytic carbonization process in macroscopic quantities and at low cost. The technique uses natural gas and reusable catalysts and produces no environmental waste or pollution. The product is all solid spheres (∼210 nm) comprised of layered graphitic fl…
We show how to measure dynamic specific heat and thermal conductivity of a solid or liquid sample using the 3ω technique, which is an ac-modulation method where we use a heater simultaneously as the sensor. By varying the width of the heater relative to the thermal decay length, one can choose the proper regime to mea…