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  • 1
    Electronic Resource
    Electronic Resource
    Microwave dielectric properties of strained (Ba0.4Sr0.6)TiO3 thin films (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 5448-5451 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ferroelectric Ba0.4Sr0.6TiO3 (BST) thin films grown on (001) MgO by pulsed laser deposition show a strong correlation between their structure and their microwave dielectric properties. Epitaxially grown BST films are observed by x-ray diffraction to be tetragonally distorted. The oxygen deposition pressure affects the magnitude of the tetragonal distortion (the ratio of in-plane and surface normal lattice parameters, D=a/c) of the deposited BST films. D varied from 0.996 to 1.004 at oxygen deposition pressure of 10–800 mTorr. The dielectric properties of BST films measured at microwave frequencies (1–20 GHz) exhibit an oxygen deposition pressure dependent dielectric constant (ε=100–600), and quality factor Q (1/tan δ=10–60). The BST film grown at the oxygen deposition pressure of 200 mTorr exhibits the highest figure of merit [% tuning in ε×Q0V, where % tuning is 100×(ε0−εb)/ε0, and ε0 and εb are dielectric constant at 0 and 80 kV/cm]. This corresponds to the film with the lowest distortion (D=1.001). The observed microwave properties of the films are explained by a phenomenological thermodynamic theory based on the strain along in-plane direction of the films. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1314619
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  • 2
    Electronic Resource
    Electronic Resource
    Percolation study on electrical resistivity of SiC/Si3N4 composites with segregated distribution (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 2593-2598 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Experimental and theoretical studies are made to account for the formation of segregated networks in SiC/Si3N4 particulate composite. It was observed in the present experimental work that fine SiC particles are uniformly dispersed along boundaries of Si3N4 matrix grains. The proposed theoretical model takes into account the volume fraction of dispersed particles necessary to form a percolating network as a function of the size ratio of SiC particle to Si3N4 grain. Threshold particle loading for percolation is estimated by applying a modified two-dimensional bond percolation model and then electrical resistivity of the composite by using percolation and general effective media equations. Both predicted values of threshold particle loading and electrical resistivity were found to agree closely with the present experimental values. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367020
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  • 3
    Electronic Resource
    Electronic Resource
    A stable Ti-based quasicrystal (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 3230-3232 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The thermal stability of the icosahedral phase (i phase) in Ti45Zr38Ni17 alloys is demonstrated. As-cast alloys containing initially only the C14 hexagonal Laves and α-solid-solution phases transformed primarily to the icosahedral phase upon annealing in vacuum for 64 h at 570 °C. This confirms previous evidence for i-phase stability and firmly establishes this quasicrystal as the first nonaluminum stable icosahedral phase. Diffraction data show that this stable i phase is primitive; energy dispersive x-ray spectroscopy measurements place its composition near Ti41.5Zr41.5Ni17. These and other results suggest that the structure of this i phase is similar to that of i(AlLiCu). © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.119133
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  • 4
    Electronic Resource
    Electronic Resource
    Microwave properties of tetragonally distorted (Ba0.5Sr0.5)TiO3 thin films (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 1185-1187 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A strong correlation is observed between the structure and the microwave dielectric properties of epitaxial Ba0.5Sr0.5TiO3 (BST) thin films deposited onto (001) MgO by pulsed laser deposition. Films were deposited at 750 °C in an oxygen pressure that was varied from 3 to 1000 mTorr. The tetragonal distortion (ratio of in-plane and surface normal lattice parameters, D=a/c) of the films depends on the oxygen deposition pressure. D varied from 0.996 at 3 mTorr to 1.003 at 800 mTorr. At microwave frequencies (1–20 GHz), BST films with low distortion have higher dielectric constants (ε∼500), and lower dielectric loss (tan δ∼0.02) compared to films with higher distortion. The correlation of the microwave properties with the film structure can be attributed to stresses and polarizability in the film. The BST film grown at the oxygen deposition pressure of 50 mTorr exhibits a large dielectric constant change and a low dielectric loss at the same time, which corresponds to the film in low stress (D=1.0004). For tunable microwave applications, BST films with low stress are desirable in order to achieve both low dielectric loss and large tunability. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.125977
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  • 5
    Electronic Resource
    Electronic Resource
    DEMETHYLATION OF PECTIN USING ACID AND AMMONIA (1978)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 43 (1978), S. 0 
    Details
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The kinetics of deesterification of high-ester citrus pectin, using acid, ammonia, or a treatment with acid followed by ammonia in isopropanol was studied with respect to the changes in methyl ester groups, molecular weight, and the formation of acid amide groups. It was found that: (1) Higher concentrations of acid or ammonia at low temperature resulted in less depolymerization for a certain decrease in ester groups; (2) The conversion of methoxyl groups to acid amide groups approached unity as temperature was lowered and ammonia concentration increased. A linear relationship between the increase in amide content and the decrease in esterification was found; (3) In treatments using hydrochloric acid followed by ammonia, a long acid treatment and a short ammonia treatment resulted in a maximum retention of apparent molecular weight. However, this treatment gave a smaller number of acid amide groups in the final product. Depending on the selection of ammonia concentration and temperature, a wide range of acid amide levels was possible. It was also possible to predict the conditions needed for deesterification to give certain apparent molecular weights and ratios of amide levels to ester levels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2621.1978.tb09739.x
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  • 6
    Electronic Resource
    Electronic Resource
    FORMULATION AND CHARACTERISTICS OF LOW-ESTER GELS FROM SUNFLOWER PECTIN (1978)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 43 (1978), S. 0 
    Details
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Sunflower pectins extracted from a 1:1 mixture of heads and stalks contained 98.5% galacturonic acid of molecular weight 122,200 with ester and acetyl contents of 29.4 and 1.4%, respectively. Gel firmness and strength were evaluated over the ranges of pH 3.0–4.7,15–30 mg Ca++/g pectin, 0.75–1.25% pectin and 10–50% sucrose in the gel formulation. Conditions of pH 4.3, 22.5 mg Ca++/g pectin, 1% pectin and 30% sucrose were optimal for gel firmness and strength. The sunflower pectin gel was particularly sensitive to pH and calcium concentration which had marked influences on pectin solubility, pregelation, brittleness and granularity. A high proportion of free carboxyl groups (69.1%), and possibly nonrandom distribution of demethoxylated groups on the pectin molecules, appeared responsible for the high sensitivity of sunflower pectins to ionic conditions in the gel formulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2621.1978.tb02408.x
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  • 7
    Electronic Resource
    Electronic Resource
    Mitochondrial cytochrome b sequence variation in Korean salmonids (2000)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 56 (2000), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The complete 1141 bp mitochondrial cytochrome b sequences were determined for lenok Brachymystax lenok, cherry salmon Oncorhynchus masou masou, Ishikawa's cherry salmon O. m. ishikawai, chum salmon O. keta, rainbow trout O. mykiss, and an albino mutant of rainbow trout. Common substitutions detected in these species were transitional mutations. There were no significant differences in the intraspecific variation of the cytochrome b genes. Interspecific divergences were greater than intraspecific variation. The level of variation ranged from 8·026–15·686%. The cherry salmon was closer to chum salmon than to rainbow trout, and the lenok was the most distantly related species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.2000.tb02130.x
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  • 8
    Electronic Resource
    Electronic Resource
    CHEMICAL AND GELATION CHARACTERISTICS OF AMMONIA-DEMETHYLATED SUNFLOWER PECTINS (1978)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 43 (1978), S. 0 
    Details
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Sunflower head and stalk pectins were demethylated by ammonia-ethanol treatments over a range of concentrations, duration and temperature conditions. The de-esterification treatments decreased the methoxyl and acetyl contents of the pectins and their molecular weights. The associated increases in proportions of acid amide and free carboxyl groups on the polygalacturonic acid molecules were greater in the modified pectins extracted from a head:stalk mixture (1:1 ratio) than in the modified head pectin samples. For all modified pectins there was a general increase in firmness and strength of the prepared gels as the percent esterification decreased from 32 to 14% in these samples. The modified head pectins were superior to those from the head-stalk mixture in pectin solubility, absence of pregelation, and gel smoothness, elasticity, uniformity and stability. The improved gel characteristics of the demethylated pectins were attributed to the increase in acid amide groups and greater randomization of free carboxyl groups in the pectin molecules. The optimum pH of 4.3 for gel formation in the unmodified and most demethylated samples was higher than that of a commercial low-ester pectin, suggesting a particular application in high pH dessert gels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2621.1978.tb02514.x
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  • 9
    Electronic Resource
    Electronic Resource
    EFFECT OF CHEMICAL COMPOSITION ON COMPRESSIVE MECHANICAL PROPERTIES OF LOW ESTER PECTIN GELS (1978)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 43 (1978), S. 0 
    Details
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Low-ester pectin gels were prepared by acid and a combination of acid and ammonium hydroxide demethylation. The chemical compositional data such as percent esterification, acid amide, free carboxyl, galacturonic acid and apparent molecular weight of the gels were determined. The maximum stress, modulus of elasticity and relaxation time prior to fracture of the low ester pectin gels were evaluated using a universal testing machine. Significant correlations were obtained between (a) relaxation time during fracture propagation and percent esterification; (b) maximum stress and molecular weight; and (c) maximum stress and percent acid amide groups. It was also found that percent acid amide groups in the pectin contributed to the strength of the gels over and above the effect of decreasing percent free carboxyl groups.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2621.1978.tb02357.x
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  • 10
    Electronic Resource
    Electronic Resource
    Characteristics and Sintering Behavior of Yttria Powders Synthesized by the Combustion Process (1999)
    Springer
    Journal of materials science 18 (1999), S. 411-413 
    Details
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006609523568
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