Materials Literature
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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…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTTheoretical and Experimental Evidence for SN2 Transition States in Oxidative Addition of Methyl Iodide to cis-[M(CO)2I2]- (M = Rh, Ir)Tim R. Griffin, David B. Cook, Anthony Haynes, Jean M. Pearson, Donato Monti, and George E. MorrisView Author Information Department of…
The study of very low temperature magnetic relaxation in nanostructured materials has provided the opportunity to observe the occurrence of quantum tunneling of magnetization (QTM) in many different systems. As the magnetization is a classical vector, this effect is also referred to as macroscopic quantum tunneling (M…
The morphological behavior of a series of well-defined A 2 B simple graft or “Y” architecture block copolymers is characterized via small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). This model architecture is formed by grafting a polystyrene block onto the center of a polyisoprene backbon…
The surface-enhanced Raman scattering (SERS) spectra of pyridine have been analyzed on the basis of a resonant charge transfer (CT) mechanism. The most intense bands recorded in the SERS at negative electrode potentials correspond with the normal modes that connect the equilibrium geometries of the neutral molecule an…
KBi 6.33 S 10 and K 2 Bi 8 S 13 were synthesized by the direct combination of K 2 S/Bi 2 S 3 at high temperature (>700 °C). The reaction of K 2 S/3.3Bi 2 S 3 at 800 °C revealed the presence of a new ternary sulfide KBi 6.33 S 10 ( I, 92% yield). The shiny, silver polycrystalline material crystallizes in the orthorhomb…
Crystalline, thermostable molecular sieve MCM-41 with hexagonal channel porosity is synthesized in a temperature-controlled microwave oven from aged precursor gels within about one hour.
A stochastic simulation method employing suitable experimentally based cross sections has been developed for probing the spatial distribution of energy loss and the trajectory of 100 eV to 1 MeV electrons in gaseous and liquid water. Elastic collisions and large-energy-loss inelastic collisions strongly influence the…
The equilibrium mixture of yeast enolase with substrate, 2-phospho-D-glycerate (2-PGA), and product, phosphoenolpyruvate (P-enolpyruvate), has been crystallized from solutions of poly(ethylene glycol) (PEG) at pH 8.0. Crystals belong to the space group C2 and have unit cell dimensions a = 121.9 A, b = 73.2 A, c = 93.9…
The peroxides from methylrhenium trioxide (MTO) and hydrogen peroxide, CH 3 ReO 2 (η 2 -O 2 ), A, and CH 3 Re(O)(η 2 -O 2 ) 2 (H 2 O), B, have been fully characterized in both organic and aqueous media by spectroscopic means (NMR and UV−vis). In aqueous solution, the equilibrium constants for their formation are K 1 =…
The synthesis of 2(3),9(10),16(17),23(24)-tetrasubstituted phthalocyanines from 1,2-dicyano-4-alkoxybenzenes or the corresponding isoindolines is reported. In each case, four isomers with D 2 h, C 4 h, C 2 v, and C s symmetry are obtained in the statistical expected yield. The separation of the C 4 h and the D 2 h iso…
A fluorescent polymer of 2-naphthol is prepared using the oxidative enzyme horseradish peroxidase encapsulated in the microstructured system of AOT/isooctane reversed micelles. The monomer, being amphiphilic, partitions to the oil−water interface with the hydroxyl moieties directed toward the microaqueous core. The en…
A model of packing for the ordered modification of the α form of syndiotactic polystyrene is suggested, through comparisons between calculated structure factors and experimental intensities observed in the X-ray fiber and electron diffraction patterns. The present analysis improves the preliminary model proposed in pr…
We have explored the use of chain end segregation as a means of controlling the properties of a polymer surface. Thin film blends of homopolystyrene (PS) and PS synthesized with low-energy oligotetrafluoroethylene chain ends (PS-TFE) were studied using neutron reflectivity. The fraction of PS-TFE that localizes near t…
The reaction of Mn(O(2)CPh)(2).2H(2)O and PhCO(2)H in EtOH/MeCN with NBu(n)(4)MnO(4) gives (NBu(n)(4))[Mn(4)O(2)(O(2)CPh)(9)(H(2)O)] (4) in high yield (85-95%). Complex 4 crystallizes in monoclinic space group P2(1)/c with the following unit cell parameters at -129 degrees C: a = 17.394(3) Å, b = 19.040(3) Å, c = 25.6…
UDP-galactose 4-epimerase catalyzes the conversion of UDP-galactose to UDP-glucose through a mechanism involving the transient reduction of NAD+. Here we describe the X-ray structures for epimerase complexed with NADH/UDP, and NAD+/UDP, refined to 1.8 and 2.0 angstrom, respectively. The alpha-carbon positions for the…
A literature review on space-charge electrets, covering the time period 1987 to 1996, is presented. The review starts out with a discussion of new inorganic and organic electret materials which also includes silicon based single and double layers. This is followed by a review of recent work on methods for measuring ch…
The Monte Carlo simulation technique (the bond fluctuation model) has been used for the study of the equilibrium conformations of comb-branched polymers consisting of a long flexible main chain and side chains grafted at a regular separation onto the main chain. The solvent has been supposed to be good (athermal) for…
The structural and electronic properties of bulk cubic and tetragonal tungsten trioxide are investigated using a periodic boundary condition ab initio Hartree−Fock method; a posteriori density functional corrections are used to estimate the effect of electron correlation on the energy. The forces involved in the bondi…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTConformational Flexibility in Dodecasubstituted PorphyrinsDaniel J. Nurco, Craig J. Medforth, Timothy P. Forsyth, Marilyn M. Olmstead, and Kevin M. SmithView Author Information Department of Chemistry University of California Davis, California 95616-5295 Cite this: J.…