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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 29 (1994), S. 1097-1100 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Conductive silicon carbide particles were incorporated into an insulating cristobalite ceramic matrix to produce composite materials with a sizeable positive temperature coefficient (PTC) effect. A large drop in resistivity with silicon carbide content at room temperature, or percolation behaviour, was observed. The PTC effect of the composites, which resulted from the thermal expansion of the cristobalite ceramic matrix, was a maximum with five orders of magnitude for the specimen with 25 vol% silicon carbide. The PTC transition temperature of the composites was at 260 °C, which coincided exactly the reversible high-low phase inversion temperature of the cristobalite ceramic matrix.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 1994-02-01
    Print ISSN: 0022-2461
    Electronic ISSN: 1573-4803
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Springer
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Bulletin of mathematical biology 56 (1994), S. 323-336 
    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract A simple chemical model of the idiotypic network of immune systems, namely the AB model, has been developed by De Boeret al. The complexity of the system, such as the steady states, periodic oscillations and chaotic motions, has been examined by the authors mentioned above. In the present paper, the periodic motions and chaotic behaviours exhibited by the system are intuitively described. To clarify in which parameter domains concerned the system exhibits periodic oscillations and in which parameter domains the system demonstrates chaotic behaviours the Lyapounov exponent is explored. To characterize the strangeness of the attractors, the fractal dimension problem is worked out.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of cluster science 5 (1994), S. 265-285 
    ISSN: 1572-8862
    Keywords: Designed synthesis ; transition metal clusters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Designed synthesis for some transition metal clusters involving bridging-sulfido ligands is reviewed. The basic concept with the use of reactive fragments as building blocks is described. It is shown that the sulfido ligands with lone-pair electrons and the unsaturated coordination sites play important roles in this rational synthesis. The relationship between the metallic coordination types of the sulfido ligands and their assembling activity in the compounds is summarized. Examples of the six kinds of “unit construction” with reactive fragments as building blocks are shown, indicating clearly that the “unit construction” is a reasonable way in the synthesis of transition metal clusters involving bridging sulfido ligands. Finally, the potential application of the “unit construction” schemes in the synthesis of transition metal clusters involving other bridging ligands is presented.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Earth, moon and planets 66 (1994), S. 49-52 
    ISSN: 1573-0794
    Keywords: Comet ; Jupiter/P ; Radio Burst
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract On July 21, 1994, 13 h - 15 h UT, decametric bursts had been recorded at frequencies from 24.0 MHz to 28.5 MHz in Xin Xiang station (longitude =-113.8°, latitude =35.3°), Henan province, China. Three maps of the three hour data are presented. Some of the bursts appears to be relative to the impact of the fragment S(No. 5) of the comet SL-9.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-0630
    Keywords: 41.80.Gg ; 68.55.−a ; 79.60.Eq
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Bombardment of silicon surfaces by low-energy (300–1000 eV) nitrogen ions has been investigated as a potential process for growing ultrathin films at relatively low temperatures (〈500°C). The thicknesses and chemical states of the obtained films are analysed using ellipsometry, X-ray Photoelectron Spectroscopy (XPS), and Auger Electron Spectroscopy (AES). All the analyses show that ultrathin (∽ 60 Å) silicon nitride films have been directly grown on silicon substrates. Detailed studies of the influence of different process parameters on the obtained films have been carried out. The thicknesses of the obtained films appear to increase with ion energy. The nitridation is found to be a rapid process which can be divided into two steps. The thicknesses are also observed to vary slightly with substrate temperature. The average active energy of nitridation rates is about 3.5 meV which indicates nonthermal process kinetics. For AES analysis, the films are found to be nitrogen-rich ones with the stoichiometric factor x≈1.7 larger than that of pure silicon nitride (x=1.33). In both AES and XPS studies, the chemical state of the silicon atoms resembles the existence of silicon oxynitride films of low oxygen concentration. The growth mechanism is also discussed briefly.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Applied microbiology and biotechnology 40 (1994), S. 780-785 
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract. Temperature and pH had only a slight effect on the astaxanthin content of a Phaffia rhodozyma mutant, but influenced the maximum specific growth rate and cell yield profoundly. The optimum conditions for astaxanthin production were 22° C at pH 5.0 with a low concentration of carbon source. Astaxanthin production was growth-associated, and the volumetric astaxanthin concentration gradually decreased after depletion of the carbon source. The biomass concentration decreased rapidly during the stationary growth phase with a concomitant increase in the cellular content of astaxanthin. Sucrose hydrolysis exceeded the assimilation rates of d-glucose and d-fructose and these sugars accumulated during batch cultivation. d-Glucose initially delayed d-fructose uptake, but d-fructose utilization commenced before glucose depletion. In continuous culture, the highest astaxanthin content was obtained at the lowest dilution rate of 0.043 h−1. The cell yield reached a maximum of 0.48 g cells·g−1 glucose utilized between dilution rates of 0.05 h−1 and 0.07 h−1 and decreased markedly at higher dilution rates.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Acta mechanica solida Sinica 7 (1994), S. 97-104 
    ISSN: 0894-9166
    Keywords: microcracks ; phase transformation ceramics ; stiffness ; strength
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Microcracks exert a large influence on the behavior of phase transformation ceramics. In this paper, the cause of microcracking is interpreted and the interaction between transformation particles and microcracks is described to estimate the stiffness and strength through the modified equivalent inclusion method by the authors. Three point bend experiments on Al2O3/ZrO2 ceramics are performed and a comparison between the theoretical and measured results confirms the rationality of the analytical model proposed in this paper and the important role of microcracks.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-203X
    Keywords: Medicago sativa ; Alfalfa ; Transformation ; Agrobacterium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The trait for somatic embryogenesis is being introduced sexually into alfalfa (Medicago sativa) breeding populations to facilitate genetic transformation of this crop. Cocultivation experiments were conducted with an agronomically-improved embryogenic clone from one such population as well as with two other embryogenic clones, one of which was the source of the embryogenic trait in the breeding populations. Transgenic plants were produced from the agronomically-improved clone whereas none were produced from the other two clones. Among the 16 transgenic plants analyzed there was a range in both copy number and number of integration sites for the NPT-II gene; those plants regenerated after a prolonged selection phase in vitro generally had the highest numbers in both respects. There was no evidence of sectoral chimerism of the transgene in a subsample of transgenic plants analyzed by PCR.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 70 (1994), S. 449-461 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract. The responses of “complex” simple cells to sharp and blurred ramp edges were studied. These responses are quite similar to those in the case of lines, which implies that phase information cannot be used to discriminate between ramp edges and lines. Furthermore, if the maximum of the modulus is used as a position estimate, a systematic bias toward the ramp side results, and this bias increases with edge blur. In contrast, a local extremum in the real part of the cell responses provides a precise position estimate, even for strongly blurred edges. Possible multiscale detection strategies are discussed in the context of a syntactical visual reconstruction. This is illustrated by an explanation of Mach bands as perceived at trapezoidal edges, including Ratliff’s Mach-band cancellation stimulus, and criteria for local probability summation in the prediction of Mach-band detection thresholds are presented.
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