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  • Springer  (308)
  • 1995-1999  (294)
  • 1960-1964  (3)
  • 1935-1939  (8)
  • 1920-1924
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  • 1
    Electronic Resource
    Electronic Resource
    Propionyl-CoA carboxylase of Myxococcus xanthus: catalytic properties and function in developing cells (1998)
    Springer
    Archives of microbiology 170 (1998), S. 179-184 
    Details
    ISSN: 1432-072X
    Keywords: Key wordsMyxococcus xanthus ; Propionyl-CoA ; carboxylase ; Acetyl-CoA carboxylase ; Kinetic constant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An acyl-coenzyme A carboxylase that carboxylates acetyl-CoA, butyryl-CoA, propionyl-CoA, and succinyl-CoA was purified from Myxococcus xanthus. Since the enzyme showed maximal rates of carboxylation with propionyl-CoA, the enzyme is thought to be propionyl-CoA carboxylase. The apparent K m values for acetyl-CoA, butyryl-CoA, propionyl-CoA, and succinyl-CoA were found to be 0.2, 0.2, 0.03, and 1.0 mM, respectively. The native enzyme has a molecular mass of 605–615 kDa and is composed of nonidentical subunits (α and β) with molecular masses of 53 and 56 kDa, respectively. The enzyme showed maximal activity at pH 7.0–7.5 and at 25–30°C, and was affected by variation in concentrations of ATP and Mg2+. During development of M. xanthus, the propionyl-CoA carboxylase activity increased gradually, with maximum activity observed during the sporulation stage. Previous work has shown that a propionyl-CoA-carboxylase-deficient mutant of M. xanthus reduces levels of long-chain fatty acids. These results suggest that the propionyl-CoA carboxylase is also responsible for the carboxylation of acetyl-CoA to malonyl-CoA used for the synthesis of long-chain fatty acids during development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002030050631
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  • 2
    Electronic Resource
    Electronic Resource
    Structural study of fucoidan from Cladosiphon okamuranus tokida (1999)
    Springer
    Glycoconjugate journal 16 (1999), S. 19-26 
    Details
    ISSN: 1573-4986
    Keywords: fucoidan ; sulfated fucan ; seaweed
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A structural study was carried out on a fucoidan isolated from the brown seaweed Cladosiphon okamuranus. The polysaccharide contained fucose, glucuronic acid and sulfate in a molar ratio of about 6.1 : 1.0 : 2.9. The results of Smith degradation showed that this polysaccharide has a linear backbone of 1→3-linked α-fucopyranose with a half sulfate substitution at the 4-positions, and a portion of the fucose residues was O-acetylated. The data obtained from partial acid hydrolysis, a methylation analysis and NMR spectra indicated that the α-glucuronic acid residue is linked to the 2-positions of the fucose residues, which were not substituted by a sulfate group. These results indicated that the average structure of this fucoidan is as follows: -[(→3Fuc-4(±OSO3-)α1−)5→3[GlcAα1→2]Fucα1−]n−. (Half of each fucose residue was sulfated. One O-acetyl ester was present in every 6 fucose residues.)
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006945618657
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  • 3
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    Single crystals of Dy1-xGdxVO4 for magnetic applications (1998)
    Springer
    Details
    Publication Date: 1998-05-01
    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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    PAPER CURRENT
  • 4
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    Propionyl-CoA carboxylase of Myxococcus xanthus : catalytic properties and function in developing cells (1998)
    Springer
    Details
    Publication Date: 1998-08-03
    Print ISSN: 0302-8933
    Electronic ISSN: 1432-072X
    Topics: Biology
    Published by Springer
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  • 5
    Electronic Resource
    Electronic Resource
    Synthesis of polymers bearing azo-dye chromophore with photocrosslinkable moiety for nonlinear optics (1996)
    Springer
    Polymer bulletin 36 (1996), S. 407-414 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Novel photocrosslinkable second-order nonlinear optical(NLO) polymers were synthesized from radical homopolymerization of 4-[N-ethyl-N-(2-methacryloyloxyethyl)]amino-4′-(2-cinnamoyloxyethyloxycarbonyl)-2′-nitroazobenzene(MACN) or copolymerization of MACN with 2-(cinnamoxyloxy)ethyl methacrylate(CM), and from polycondensation of 4-[N,N-bis(2-hydroxyethyl)]amino-4′-(2-cinnamoyloxyethyloxycarbonyl)-2′-nitroazobenzene(HACN) with p-phenylenediacyloyl chloride(PD). For the purpose of obtaining an optimized condition of UV irradiation for poling treatment involving photocrosslinking, photoreactivity of these NLO polymer films was investigated. There was observed considerably different photoreaction behavior, especially in photofading of the NLO chromophore, between MACN polymer and HACNPD polycondensate; the latter faded more rapidly than the former. A reason for this phenomenon was considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00315056
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  • 6
    Electronic Resource
    Electronic Resource
    High output power operation of 1.3-μm strained MQW lasers with low threshold currents at high temperature (1996)
    Springer
    Optical and quantum electronics 28 (1996), S. 503-511 
    Details
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract We have investigated the temperature dependencies of the slope efficiency and the threshold current for strained multiquantum well (MQW) lasers as a parameter of the well number. Smaller well numbers mean larger temperature dependencies of the slope efficiency and the threshold current, while larger well numbers mean larger internal loss and broadening of the photoluminescence linewidth of the MQW structure. Furthermore, the change in the slope efficiency with temperature change is related to the change in internal loss. In this work, the 1.3-μm strained MQW laser with a compressive strain of 1.0% and 7 wells shows the highest output power of 6.8 mW for an injection current of 50 mA and the lowest threshold current of 5.5 mA at 85°C, and the lowest variation in output power of 2.0 dB from 25–85°C at injection current of 50 mA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00943618
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  • 7
    Electronic Resource
    Electronic Resource
    Blue Luminescence from Silicon Nanoparticles Suspended in Organic Liquids (1999)
    Springer
    Journal of cluster science 10 (1999), S. 359-380 
    Details
    ISSN: 1572-8862
    Keywords: Silicon ; nanoparticles ; luminescence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract We have prepared several nanometer-sized silicon colloids in organic liquids in the range from 3.7 to 9.8 nm with a constant weight density of 1 mg/ml by a gas evaporation technique. The blue–green luminescent energy was found to be independent of size, in contrast to its intensity and optical absorption, which showed a clear size effect. Special emphasis is placed on the advantage of using a colloidal system: controllability of mass density in a unit volume, isolation of each particle, selection of wide band-gap substances, capability of absolute quantum efficiency, and easy surface modification. As an example of the above advantages, we have determined the absolute quantum yield as a function of size. From the quantum yield thus derived and the proposed model that combines surface as well as volume effects, experimentally obtained parameters such as the diffusion velocity of an electron–hole pair and the initial flight distance of this pair are found to be consistent with those obtained from other data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021981714227
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  • 8
    Electronic Resource
    Electronic Resource
    Cu/Ni colloidal dispersions stabilised by calcium and barium stearates for the amination of oxo-alcohols (1996)
    Springer
    Catalysis letters 40 (1996), S. 123-130 
    Details
    ISSN: 1572-879X
    Keywords: Cu/Ni colloidal dispersion ; barium stearate ; calcium stearate ; protective colloid ; amination of oxo-alcohols ; tertiary amine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Bimetallic Cu/Ni colloidal dispersions (the core catalyst) stabilised by a combination of calcium and barium stearates as protective colloids (catalyst C) showed a remarkable catalytic activity-several times higher than that of the core catalyst stabilised by barium stearate only (catalyst A) for the amination reaction of low reactive oxo-alcohols, having steric hindrance by branched alkyls, with dimethylamine to prepare N,N-dimethyl tertiary amines. Application of the catalyst C for the same amination reaction of dodecyl alcohol could be performed at a lower catalyst concentration of even 100 ppm based on copper at 220° C with a tertiary amine yield of 92% in a three hours' reaction. The reaction mixture containing catalyst C formed a gel at room temperature and formed a stable homogeneous solution with acetone as a polar solvent. It is postulated that water-repellency of calcium stearate and further incorporation of barium stearate as a second promoter yields a doubly stabilised structure for the core catalyst resulting in a remarkable increase in catalytic activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00807469
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  • 9
    Electronic Resource
    Electronic Resource
    Cellulose/poly(acryloyl morpholine) composites: synthesis by solution coagulation/bulk polymerization and analysis of phase structure (1998)
    Springer
    Cellulose 5 (1998), S. 123-134 
    Details
    ISSN: 1572-882X
    Keywords: cellulose ; poly(acryloyl morpholine) ; composite ; interpenetrating polymer network
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Cellulose/poly(acryloyl morpholine) (CELL/PACMO) compo sites were synthesized by bulk polymerization in the gel state of cellulose impregnated with reactive ACMO monomer. The thermal transition behaviour and phase structure of the CELL/PACMO composites obtained in film form were investigated by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and solid-state 13C NMR spectroscopy. For compositions rich in PACMO (CELL ≤ 30 wt %), it was revealed by DSC and DMA that the synthesized samples gave a composition-dependent Tg value higher than that of PACMO homopolymer, and the magnitude of the lowering of their dynamic modulus E′ in the glass transition region became extremely small in comparison with the corresponding drop in E′ noted for plain PACMO samples. These observations were interpreted as being due to the development of an interpenetrating polymer network (IPN)-type organization, resulting from successful fixation of an original netw ork structure of cellulose gels into the polymerized bulks. From the measurements of proton spin-lattice relaxation times in the NMR study, the IPN-like composites were estimated to be substantially homogeneous on a scale of a few nanometers. 0969--0239 © 1998 Blackie Academic & Professional
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009224931504
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  • 10
    Electronic Resource
    Electronic Resource
    Lattice path counting andM/M/c queueing systems (1995)
    Springer
    Queueing systems 19 (1995), S. 193-214 
    Details
    ISSN: 1572-9443
    Keywords: M/M/c queue ; transient solution ; lattice path counting ; depth of path
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract We apply the lattice path counting method to the analysis of the transientM/M/c queueing system. A closed-form solution is obtained for the probability of exactlyi arrivals andj departures within a time interval of lengtht in anM/M/c queueing system that is empty at the initial time. The derivation of the probability is based on the counting of paths from the origin to(i,j) on thexy-plane, that have exactly rd x-steps whose depth from the liney=x isd (d=0,1,...,c−1). The closed-form solution has an expression useful for numerical calculation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01148946
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