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  • Articles  (395)
  • Springer  (375)
  • American Physical Society (APS)  (20)
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  • Articles  (395)
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  • 1
    Electronic Resource
    Electronic Resource
    Reduction of post-weld shift in semiconductor laser packaging (1996)
    Springer
    Optical and quantum electronics 28 (1996), S. 1741-1746 
    Details
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract A reduction of post-weld shift (PWS) in semiconductor laser packaging using a laser welding technique is presented. It is found that the PWS and its association with the power coupling loss of the laser packaging can be reduced under proper pressure constraint. Characteristics of defect mechanisms in laser welding techniques for semiconductor laser packaging are also investigated experimentally. The results in the stainless-to-Kovar joints show that the surface cracks are dependent on the Au thickness on the Kovar material. The low solubility of gold in the Kovar is identified as the defect mechanism for surface cracks. Preliminary reliability data demonstrated that these laser packages without crack defects in the welded joints are reliable.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00698539
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  • 2
    Electronic Resource
    Electronic Resource
    Corrosion inhibition of steel by thiourea and cations under incomplete cathodic protection in a 3.5% NaCl solution and seawater (1999)
    Springer
    Journal of applied electrochemistry 29 (1999), S. 911-918 
    Details
    ISSN: 1572-8838
    Keywords: cathodic protection ; cations ; inhibition ; NaCl solution ; seawater ; thiourea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract This study investigates corrosion inhibition of steel using thiourea and cations such as aluminium, calcium and magnesium under cathodic control in a 3.5% NaCl solution and in seawater. Steel protection in a 3.5% NaCl solution is normally incomplete under a cathodic potential less electronegative than −1.100 V. However, the protection can be enhanced by nearly 50% by adding either 50 ppm aluminium ion or 75 ppm thiourea in solution, and by almost 90% by the combined use of these additions. This study also analyzes how combining inhibitors and cathodic control may be used to protect steel. Moreover, this investigation monitors pH in the solution, measures zero-resistance current between the graphite-steel couple, as well as analyses cathode reaction products. A mechanism is also proposed to interpret the combined effects of inhibitors and cathodic control on the protection of steel.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003533800038
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  • 3
    Electronic Resource
    Electronic Resource
    Consistency and replaceability for conull matrices (1968)
    Springer
    Mathematische Zeitschrift 105 (1968), S. 208-212 
    Details
    ISSN: 1432-1823
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01109899
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  • 4
    Electronic Resource
    Electronic Resource
    The nucleic acid content of some edible mushrooms (1982)
    Springer
    Applied microbiology and biotechnology 15 (1982), S. 237-240 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary An improved method for the determination of nucleic acid content in edible mushrooms is described. Details of tissue homogenization and extraction are also included. In regard to the limit suggested by the Protein Advisory Group of the United Nations System, the amount of nucleic acids found in Agaricus bisporus, Pleurotus cystidiosus, Pleurotus sajor-caju and Volvariella volvacea indicates that it is safe to consume mushrooms as daily vegetable. No significant changes have been found in the nucleic acid content of V. volvacea at different degrees of maturity. V. volvacea loses around 20% of its nucleic acids upon boiling for 10 min. Possible reasons for the discrepancy between the present finding and that given in an earlier report have been discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00499963
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  • 5
    Electronic Resource
    Electronic Resource
    Microbial respiration and biomass (substrate-induced respiration) in soils of old-growth and regenerating forests on northern Vancouver Island, British Columbia (1996)
    Springer
    Biology and fertility of soils 23 (1996), S. 145-152 
    Details
    ISSN: 1432-0789
    Keywords: Basal respiration ; Metabolic quotient (qCO2) ; Microbial biomass ; Substrate-induced respiration (SIR) ; Fumigation-extraction (FE) ; Clear-cutting ; Humus ; Greenhouse effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In studying the basal respiration, microbial biomass (substrate-induced respiration, SIR), and metabolic quotient (qCO2) in western red cedar (Thuja plicata Donn ex D. Don)-western hemlock [(Tsuga heterophylla Raf.) Sarg.] ecosystems (old-growth forests, 3- and 10-year-old plantations) on northern Vancouver Island, British Columbia, Canada, we predicted that (1) soil basal respiration would be reduced by harvesting and burning, reflecting the reduction in microbial biomass and activities; (2) the microbial biomass would be reduced by harvesting and slash-burning, due to the excessive heat of the burning or due to reduced substrate availability; (3) microbial biomass in the plantations would tend to recover to the preharvesting levels with growth of the trees and increased substrate availability; and (4) microbial biomass measured by the SIR method would compare well with that measured by the fumigation-extraction (FE) method. Decaying litter layer (F), woody F (Fw) and humus layer (H) materials were sampled four times in the summer of 1992. The results obtained supported the four predictions. Microbial biomass was reduced in the harvested and slash-burned plots. Both SIR and FE methods provided equally good estimates of microbial biomass in the samples [SIR microbial C (mg g-1)=0.227+0.458 FE microbial C (mg g-1), r=0.63, P=0.0001] and proved suitable for microbial biomass measurements in this strongly acidic soil. Basal respiration was significantly greater in the old-growth forests than in the young plantations (P〈0.05) in both F and H layers, but not in the Fw layer. For the 3- and 10-year-old plantations, there was no difference in basal respiration in F, Fw, and H layers. Basal respiration was related to changes in air temperature, precipitation, and the soil moisture contant at the time of sampling. The qCO2 values were higher in the old-growth stands than in the plantations. Clear-cutting followed by prescribed burning did not increase soil microbial respiration, but CO2 released from slash-burning and that contributed from other sources may be of concern to increasing atmospheric CO2 concentrations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00336055
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  • 6
    Electronic Resource
    Electronic Resource
    Microbial respiration and biomass (substrate-induced respiration) in soils of old-growth and regenerating forests on northern Vancouver Island, British Columbia (1996)
    Springer
    Biology and fertility of soils 23 (1996), S. 145-152 
    Details
    ISSN: 1432-0789
    Keywords: Key words Basal respiration ; Metabolic quotient (qCO2) ; Microbial biomass ; Substrate-induced respiration (SIR) ; Fumigation-extraction (FE) ; Clear-cutting ; Humus ; Greenhouse effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In studying the basal respiration, microbial biomass (substrate-induced respiration, SIR), and metabolic quotient (qCO2) in western red cedar (Thuja plicata Donn ex D. Don)-western hemlock [(Tsuga heterophylla (Raf.) Sarg.] ecosystems (old-growth forests, 3- and 10-year-old plantations) on northern Vancouver Island, British Columbia, Canada, we predicted that (1) soil basal respiration would be reduced by harvesting and burning, reflecting the reduction in microbial biomass and activities; (2) the microbial biomass would be reduced by harvesting and slash-burning, due to the excessive heat of the burning or due to reduced substrate availability; (3) microbial biomass in the plantations would tend to recover to the preharvesting levels with growth of the trees and increased substrate availability; and (4) microbial biomass measured by the SIR method would compare well with that measured by the fumigation-extraction (FE) method. Decaying litter layer (F), woody F (Fw) and humus layer (H) materials were sampled four times in the summer of 1992. The results obtained supported the four predictions. Microbial biomass was reduced in the harvested and slash-burned plots. Both SIR and FE methods provided equally good estimates of microbial biomass in the samples [SIR microbial C (mg g–1)=0.227+0.458 FE microbial C (mg g–1), r=0.63, P=0.0001] and proved suitable for microbial biomass measurements in this strongly acidic soil. Basal respiration was significantly greater in the old-growth forests than in the young plantations (P〈〉;0.05) in both F and H layers, but not in the Fw layer. For the 3- and 10-year-old plantations, there was no difference in basal respiration in F, Fw, and H layers. Basal respiration was related to changes in air temperature, precipitation, and the soil moisture contant at the time of sampling. The qCO2 values were higher in the old-growth stands than in the plantations. Clear-cutting followed by prescribed burning did not increase soil microbial respiration, but CO2 released from slash-burning and that contributed from other sources may be of concern to increasing atmospheric CO2 concentrations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00336055
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  • 7
    Electronic Resource
    Electronic Resource
    Quantum chemical study of relative reactivities of a series of amines and nitriles: Relevance to prebiotic chemistry (1975)
    Springer
    Journal of molecular evolution 5 (1975), S. 131-152 
    Details
    ISSN: 1432-1432
    Keywords: Quantum Calculations ; Reactivity ; Nitriles ; Amines Prebiotic Chemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Using the Iterative Extended Huckel Theory (IEHT) calculations of the electron distribution and orbital energies of a series of thirteen amines, nitriles and amino-nitriles relevant to prebiotic and cosmo-chemistry have been carried out. Ground state properties such as the energy and nature of the highest occupied (HOMO) and lowest empty (LEMO) molecular orbitals, net atomic charges and number of nonbonding electrons have been identified as criteria for correlating the relative nucleophilicity of amine and nitrile nitrogens and the electrophilicity of nitrile and other unsaturated carbon atoms. The results of such correlations can be partially verified by known chemical behavior of these compounds and are used to predict and understand their role in prebiotic organic synthesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01732518
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  • 8
    Electronic Resource
    Electronic Resource
    The possible role of solid surface area in condensation reactions during chemical evolution: Reevaluation (1976)
    Springer
    Journal of molecular evolution 8 (1976), S. 357-380 
    Details
    ISSN: 1432-1432
    Keywords: Clays ; Apatite ; Fluctuating System ; Prebiotic Environments ; Chemical Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Published data on adsorption and condensation of amino acids, purine and pyrimidine bases, sugars, nucleosides, and nucleotides are analyzed in connection with Bernal's hypothesis that clays and other minerals may have provided the most likely surface for adsorption and condensation of these molecules in prebiotic times. Using surface concentration and reaction rate as the main criteria for the feasibility of condensation reactions, four types of prebiotic environments were analyzed: (1) an ocean-sediment system, (2) a dehydrated lagoon bed produced by evaporation, (3) the surface of a frozen sediment, and (4) a fluctuating system where hydration (rainstorms, tidal variations, flooding) and dehydration (evaporation) take place in a cyclic manner. With the possible exception of nucleotides, low adsorption of organomonomers on sediment surfaces of a prebiotic ocean (pH 8) is expected, and significant condensation is considered unlikely. In dehydrated and frozen systems, high surface concentrations are probable and condensation is more likely. In fluctuating environments, condensation rates will be enhanced and the size distribution of the oligomers formed during dehydration may be influenced by a “redistribution mechanism” in which adsorbed oligomers and monomers are desorbed and redistributed on the solid surface during the next hydration-dehydration cycle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01739261
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  • 9
    Electronic Resource
    Electronic Resource
    Quantum chemical study of the thermodynamics, kinetics of formation and bonding of H2CN: Relevance to prebiotic chemistry (1974)
    Springer
    Journal of molecular evolution 3 (1974), S. 209-224 
    Details
    ISSN: 1432-1432
    Keywords: Quantum Calculation ; Thermodynamics ; Kinetics ; H2CN ; Prebiotic Chemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Using the Iterative Extended Huckel Theory (IEHT), energy-conformation studies have been carried out for H2CN (I),trans-HCNH (IIA), andcis-HCNH (IIB), three possible isomers formed by addition of a hydrogen atom to hydrogen cyanide. Calculations show that the order of decreasing thermodynamic stability is I $$ 〉 $$ IIA 〉 IIB. Results of a series of calculations designed to simulate the stepwise addition of a hydrogen atom to hydrogen cyanide to form both I and IIA indicate that formation of I is also kinetically favored over IIA. Calculated properties of the minimum energy conformers of I and IIA and the nature of the bonding in them are described. The calculated distribution of the unpaired electron density in I compares favorably with results obtained empirically from the ESR spectra of a radical formed by addition of H atoms to HCN. The potential role of H2CN (I) as a reactive intermediate in prebiotic organic synthesis and its possible relevance to interstellar organic chemistry are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01797454
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  • 10
    Electronic Resource
    Electronic Resource
    A hierarchical algorithm for making sparse matrices sparser (1992)
    Springer
    Mathematical programming 56 (1992), S. 1-30 
    Details
    ISSN: 1436-4646
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract IfA is the (sparse) coefficient matrix of linear equality constraints, for what nonsingularT is ≡TA as sparse as possible, and how can it be efficiently computed? An efficient algorithm for thisSparsity Problem (SP) would be a valuable pre-processor for linearly constrained optimization problems. In this paper we develop a two-pass approach to solve SP. Pass 1 builds a combinatorial structure on the rows ofA which hierarchically decomposes them into blocks. This determines the structure of the optimal transformation matrixT. In Pass 2, we use the information aboutT as a road map to do block-wise partial Gauss-Jordan elimination onA. Two block-aggregation strategies are also suggested that could further reduce the time spend in Pass 2. Computational results indicate that this approach to increasing sparsity produces significant net reductions in simplex solution time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01580890
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