Materials Literature
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Optical pumping has been used to select Ar atoms in the metastable 3P2 or 3P0 state in a flowing afterglow reactor. The relative concentrations of the two metastable states were assigned from observation of the N2(C,v′) emission spectra. The isolated reactions of the Ar(3P2) and Ar(3P0) atoms with F2, NF3, Cl2, CCl4,…
The first example of transition metal co-ordination to ethereal like oxygens of a 9-metallocrown-3 ether is seen in FeIII[FeIII(salicylhydroximato)(MeOH)(acetate)]3 and leads to an unusual tetranuclear cluster which exhibits both inter- and intra-cluster antiferromagnetic interactions and an S= 5 ground state.
New experiments conducted in a turbulent flow reactor show kinetic characteristics of methanol oxidation that have not been observed previously. Data are presented for methanol oxidation at equivalence ratios in the range of 0.6−1.6 and initial temperatures or 1025-1090 K at atmospheric pressure. At intermediate exten…
The present study concerns the surface layered structure of the cast Ti. A commercial Ti was cast into a mold which was made of a phosphate-bonded Al2O3/SiO2 investment. Elemental analyses of the interfacial zone of the casting were made under an electron probe micro-analyzer. The interfacial zone was composed of four…
The bacterial phosphotransferase system (PTS) functions in a variety of regulatory capacities. One of the best characterized of these is the process by which the PTS regulates inducer uptake and catabolite repression. Early genetic and physiological evidence supported a mechanism whereby the phosphorylation state of a…
Poly[3-(3,6-dioxaheptyl)thiophene] has been synthesised by electropolymerisation; this highly conducting electroactive polymer exhibits specific interactions with lithium cations.
The nature of the possible liquid-crystalline phases that a molecular or colloidal system may exhibit depends sensitively on the shape of the constituent particles. Recent computer simulations on fluids of consisting of non-spherical hard-core molecules suggest that, in order to predict the relative stability of isotr…
1. Volume I-Mechanical Behavior and Properties of Composite Materials 2. Volume 2 -Micromechanical Materials Modeling 3. Volume 3-Processing and Fabrication Technology 4. Volume 4-Failure Analysis of Composite Materials 5. Volume 5-Design Studies 6. Volume 6-Test Methods
Issues related to the design of high-frequency transformers are discussed. An analysis of skin and proximity effects in the conductors and measurements of permeability and hysteresis loss in the magnetic material are combined in a computer-assisted study of the relationships between size, efficiency, and frequency. Ex…
The mechanism of electrical tree initiation in polyethylene subjected at AC, DC, and half-rectified AC voltages is studied by an optical technique which is at least two orders of magnitude more sensitive than partial discharge detection. For DC voltage up to 46 kV, no light emission or tree inception was detected in t…
The esperamicins represent a class of antitumor antibiotics characterized by an unusual chemical core structure and extremely potent cytotoxicity. The mechanism by which these drugs produce cytotoxicity was investigated and found to be related to the formation of single- and double-strand DNA breaks. Using five struct…
An analysis is given of experimental techniques for measuring the anchoring energy, W, of nematic liquid crystals with solid surfaces. Two novel methods for measuring W in homeotropically oriented samples are discussed. The first is based on the stabilization of the flexoelectric distortion by a magnetic field. In the…
A replica trick similar to that used in spin glass theory is implemented to study a structure of large heteropolymeric globule or a heteropolymeric melt with random quenched sequence of monomers of two types (A and B). It is shown that a microphase separation third order phase transition occurs when the system of torn…
Two classes of thermotropic polymers were synthesized containing the trans-azobenzene unit as both a mesogenic and a photochromic group. In the former class (I) the azobenzene unit is incorporated into the main chain of substituted polymalonates, while in the latter class (II) it is appended as a side chain substituen…
The adsorption of aromatic compounds by smectite exchanged with tetramethylammonium (TMA) has been studied. Aromatic compounds adsorbed by TMA–smectite are assumed to adopt a tilted orientation in a face-to-face arrangment with the TMA tetrahedra. The sorptive characteristics of TMA–smectite were influenced strongly b…
Femtosecond differential absorption measurements of the quantum-confined transitions in CdSe microcrystallites are reported. Spectral hole burning is observed, which is accompanied by an induced absorption feature on the high-energy side. The spectral position of the burned hole depends on the excitation wavelength. F…
An automatic procedure for building a protein polyalanine backbone from C alpha positions and 'spare parts' retrieved from a data base of 66 high-resolution protein structures is described. Protein backbones are constructed from overlapping fragments of variable length, which allows the backbone of regular secondary s…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTChemistry of yttrium triisopropoxide revisited. Characterization and crystal structure of Y5(.mu.5-O)(.mu.3-OPr-iso)4(.mu.2-OPr-iso)4(OPr-iso)5Olivier Poncelet, William J. Sartain, Liliane G. Hubert-Pfalzgraf, Kirsten Folting, and Kenneth G. CaultonCite this: Inorg. Chem. 19…
A detailed description of the method of crystallographic refinement by simulated annealing is presented. To test the method, it has been applied to a 1.5 Å resolution X-ray structure of crambin. The dependence of the success of the simulated annealing protocol with respect to the temperature of the heating stage is di…
Relaxation and diffusion in restricted geometrics excitation energy transfer and photoinduced electron transfer phenomena in some confined systems electron excitation transport in micelles, polymers, and multilayers electron excitation transport on polymer chains polymer structure and downchain electronic energy trans…