Self-organized Multilayer Films and Porous Nanocomposites of Gold Nanoparticles with Octa(3-aminopropyl)octasilsesquioxane

Successive deposition of octa(3-aminopropyl)octasilsesquioxane octahydrochloride and gold nanoparticles coated with carboxylate groups (Au–COO⁻) on glass substrates alternately under mild basic conditions led to systematic buildup of a gold colloidal multilayer. The driving force of the self-assembly was electrostatic interaction between ammonium cations of octa(3-aminopropyl)octasilsesquioxane octahydrochloride and carboxylate anions on Au–COO⁻. A linear increase of surface plasmon resonance of Au–COO⁻ with the deposited bilayers indicated the multilayer manipulation was reproducible. Porous nanocomposites were accomplished by precipitation of octa(3-aminopropyl)octasilsesquioxane octahydrochloride modified polystyrene (PS) latex particles and Au–COO⁻ followed by removal of the PS particles via tetrahydrofuran (THF) extraction. Porous nanocomposite films were obtained by layer-by-layer (LBL) self-assembly of the octa(3-aminopropyl)octasilsesquioxane octahydrochloride modified PS latex particles and Au–COO⁻ followed by removal of the PS particles via THF extraction. Dedicated to Professor Christopher W. Allen for his advances in inorganic ring and polymer chemistry.     

Structures and microhardness of nanostructured Cr–Ni-sputtered alloy

Nanostructured Cr–xNi alloys were prepared by magnetron sputtering in low pressure argon gas, where x varied from 0 to 20 at%. The structure and microhardness of the alloys were observed by TEM (microscopy) and Vickers hardness testing, respectively. The crystal structure of the sputtered alloys was BCC. The addition of nickel to chromium decreases the grain size of the Cr–Ni alloys and the grain sizes of the alloys changed from 88 nm for Cr to 30 nm for Cr-20 at% Ni alloys. The microhardness of the Cr–Ni alloys showed the maximum around 5 at% Ni. The increase in nickel content above 5 at% lowers the microhardness of the alloys, although the grain size of the Cr–Ni decreases. The abnormal tendency against grain size change was discussed in terms of the characteristics of the grain boundaries in the alloys.     

Extraction rates of amino acids by an emulsion liquid membrane with tri-n-octylmethylammonium chloride

The extraction rates of amino acids from alkaline aqueous solution into an emulsion liquid membrane containing tri-n-octylmethylammonium chloride as a carrier and Paranox 100 as an emulsifier were measured using a stirred transfer cell. The effects of agitation speed (0·33–0·66 rev s⁻¹), amino acid concentrations (0·5–50 mol m⁻³) and temperature (10–45°C) on the extraction rates were examined. The results were analyzed by a double-film model. The mass transfer coefficients of amino acids (0·26–1·58×10⁻⁵ m s⁻¹) and their complexes (0·60–1·72×10⁻⁵ m s⁻¹) were found to correlate well with the hydrophobicities of the amino acids. It was found that the surfactant layer influenced the mass transfer processes of both amino acids in the aqueous film and their complexes in the organic film. The permeation of amino acids with a large hydrophobicity through the emulsion liquid membrane was promoted by both high distribution and larger mass transfer rates. © 1998 Society of Chemical Industry     

(h,k)-Arbiters for h-out-of-k mutual exclusion problem

h-Out-of-k mutual exclusion is a generalization of the 1-mutual exclusion problem, where there are k units of shared resources and each process requests h (1hk) units at the same time. Though k-arbiter has been shown to be a quorum-based solution to this problem, quorums in k-arbiter are much larger than those in the 1-coterie for 1-mutual exclusion. Thus, the algorithm based on k-arbiter needs many messages. This paper introduces the new notion that each request uses different quorums depending on the number of units of its request. Based on the notion, this paper defines two (h,k)-arbiters for h-out-of-k mutual exclusion: a uniform (h,k)-arbiter and a (k+1)-cube (h,k)-arbiter. The quorums in each (h,k)-arbiter are not larger than the ones in the corresponding k-arbiter; consequently, it is more efficient to use (h,k)-arbiters than the k-arbiters. A uniform (h,k)-arbiter is a generalization of the majority coterie for 1-mutual exclusion. A (k+1)-cube (h,k)-arbiter is a generalization of square grid coterie for 1-mutual exclusion.     

Formation of IPN organic-inorganic polymer hybrids utilizing the photodimerization of thymine

Summary Formation of an interpenetrating polymer network (IPN) composed of organic polymer gel and silica gel in the form of polymer hybrids was conducted by utilizing the photodimerization of thymine bases. Thymine-modified poly(2-methyl-2-oxazoline) (POZO-T) was synthesized by the condensation reaction of partially hydrolyzed polyoxazoline and 1-(2-carboxyethyl)thymine. Organic-inorganic polymer hybrids were prepared from POZO-T and tetramethoxysilane (TMOS). Transparent and homogeneous polymer hybrids could be obtained. The photodimerization and the reverse reaction of thymine in the polymer hybrids were monitored by the UV absorption spectroscopy. Received: 27 March 2000/Revised version: 5 June 2000/Accepted: 15 June 2000     

EFFECT OF Ti CONTENT ON THE MICROSTRUCTURE AND PROPERTIES OF Si_3n_4/Si_3N_4 JOINT BRAZED USING Cu-Zn-Ti ALLOY

1.IntroductionWiththedevelopmentofaerospace,energyandelectronicindustries,advancedmaterialsarebecomingmoreandmoreimPOrtant.CerdricmaterialshavevariousadVantagessuchashighthermalresistance,corrosionresistanceandwearresistance,whichcansatisfymanyindustryreqUirements.However,becauseOfthehighbrittlenessandPOOrmachiningproperties,cerawhcmaterialsisverydifficulttobeusedasthestructurecomponentswithlargesizeorcomplicatedshapes.Therefore,weldingofceradricmaterialsisoneofthekeytechniqUesfortheirappl…     

Effect of bonding parameters on microstructure and properties of Si_3N_4/Si_3N_4 joint brazed by Cu-Zn-Ti filler alloy

1INTRODUCTION Si3N4ceramichashighthermalandwearingresistanceandisapromisingmaterialforhightem peratureapplications.However,itisdifficultto manufacturetheSi3N4ceramicworkpieceswithla gerdimensionsandcomplicatedshapesduetoitspoorworkabilityandlowductility.Inrecent20years,manystudieshavebeenfocusedonthetech niquesofceramicjoining,becausethejoiningtech niquescanbeusednotonlyforlow costandhigh reliabilitymanufacturingofceramicpartswith complicatedshapesbutalsoforrepairingofthece ramicpartsinw…     

Effects of Polyols and Organic Solvents on Thermostability of Lipase

The effects of polyols and organic solvents on the thermostability of lipase were studied. The thermodeactivation process of lipase obeyed a series deactivation model and four kinetic parameters were determined. The rate constant of the first deactivation process was found to be a key one. All the polyols used had a positive effect for stabilization of lipase and the extent of effect increased with polyol concentration and carbon number of polyol. The effect of organic solvents on the thermostability of lipase was investigated by incubating the lipase in the organic solvents before measuring their activities. The behavior of the thermodeactivation depended upon the organic solvents used; increased activity was observed in some solvents. © 1997 SCI     

Spatio-Temporal Receptive Field Measurement of Retinal Neurons by Random Pattern Stimulation and Cross Correlation

A method is developed for the measurement of the spatio-temporal receptive field (STRF) of neurons in the retina. The test input is an unsteady visual pattern randomly modulated in both space and time, and the output is the stochastic time course of the intracellular response. The STRF is expressed in terms of the spatio-temporal Wiener kernels calculated through a special cross-correlation algorithm between the response and the stimulus-related information. The method is an extension of existing white-noise identification techniques to include the spatial domain. Consideration is given to the practical implementation of the required stimulus pattern, and has led to several alternative approaches.