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  • Polymer and Materials Science  (4)
  • Pseudotsuga menziesii  (2)
  • Regulation  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Contrasting modes of photosynthetic enzyme regulation in oxygenic and anoxygenic prokaryotes (1984)
    Springer
    Archives of microbiology 139 (1984), S. 124-129 
    Details
    ISSN: 1432-072X
    Keywords: Photosynthesis ; Regulation ; Thioredoxin ; Cyanobacterium ; Chromatium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Enzymes that are regulated by the ferredoxin/thioredoxin system in chloroplasts — fructose-1,6-bisphosphatase (FBPase), sedoheptulose-1,7-bisphosphatase purified from two different types of photosynthetic prokaryotes (cyanobacteria, purple sulfur bacteria) and tested for a response to thioredoxins. Each of the enzymes from the cyanobacterium Nostoc muscorum, an oxygenic organism known to contain the ferredoxin/thioredoxin system, was activated by thioredoxins that had been reduced either chemically by dithiothreitol or photochemically by reduced ferredoxin and ferredoxin-thioredoxin reductase. Like their chloroplast counterparts, N. muscorum FBPase and SBPase were activated preferentially by reduced thioredoxin f. SBPase was also partially activated by thioredoxin m. PRK, which was present in two regulatory forms in N. muscorum, was activated similarly by thioredoxins f and m. Despite sharing the capacity for regulation by thioredoxins, the cyanobacterial FBPase and SBPase target enzymes differed antigenically from their chloroplast counterparts. The corresponding enzymes from Chromatium vinosum, an anoxygenic photosynthetic purple bacterium found recently to contain the NADP/thioredoxin sytem, differed from both those of cyanobacteria and chloroplasts in showing no response to reduced thioredoxin. Instead, C. vinosum FBPase, SBPase, and PRK activities were regulated by a metabolite effector, 5′-AMP. The evidence is in accord with the conclusion that thioredoxins function in regulating the reductive pentose phosphate cycle in oxygenic prokaryotes (cyanobacteria) that contain the ferredoxin/thioredoxin system, but not in anoxygenic prokaryotes (photosynthetic purple bacteria) that contain the NADP/thioredoxin system. In organisms of the latter type, enzyme effectors seem to play a dominant role in regulating photosynthetic carbon dioxide assimilation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00401986
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  • 2
    Electronic Resource
    Electronic Resource
    The ferredoxin/thioredoxin system of enzyme regulation in a cyanobacterium (1981)
    Springer
    Archives of microbiology 130 (1981), S. 14-18 
    Details
    ISSN: 1432-072X
    Keywords: Thioredoxin ; Cyanobacterium ; Ferredoxin ; Nostoc ; Regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cell-free preparations of the cyanobacterium (bluegreen alga) Nostoc muscorum were assayed for thioredoxins and enzymes catalyzing the ferredoxin and NADP-linked reduction of thioredoxin. Nostoc was found to have two different thioredoxins: one of approximate molecular weight 16,000 (designated Nostoc thioredoxin f) that selectively activated chloroplast fructose 1,6-bisphosphatase, and another of approximate molecular weight 9,000 (designated Nostoc thioredoxin m) that selcetively activated chloroplast NADP-malate dehydrogenase. The two thioredoxins could be reduced either chemically with dithiothreitol or photochemically with ferredoxin and ferredoxin-thioredoxin reductase which, like the recently found regulatory iron-sulfur protein ferralterin, was present in Nostoc cells. Nostoc ferredoxin-thioredoxin reductase appeared to be similar to its chloroplast counterpart in enzyme specificity, molecular weight, and spectral properties. The Nostoc and spinach chloroplast ferredoxin-thioredoxin reductases as well as their thioredoxins, ferredoxins, and chlorophyll containing membranes were interchangeable in activating chloroplast fructose 1,6-bisphosphatase and NADP-malate dehydrogenase. There was no evidence for an NADP-linked thioredoxin reductase such as that of E. coli. The results are in accord with the conclusion that the cyanobacteria resemble higher plants in having a functional ferredoxin/thioredoxin system rather than an NADP/thioredoxin system typical of other bacteria.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00527065
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  • 3
    Electronic Resource
    Electronic Resource
    Direct impacts of sheep upon Douglas-fir trees in two agrosilvopastoral systems (1992)
    Springer
    Agroforestry systems 19 (1992), S. 223-232 
    Details
    ISSN: 1572-9680
    Keywords: agroforestry ; browsing ; debarking ; sheep ; deer ; Pseudotsuga menziesii
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Livestock may provide important service and production functions in agroforestry systems. However, use of livestock in conifer/improved pasture agrosilvopastoral systems is currently limited by concerns about potential damage to trees by livestock. Effects of sheep grazing on Douglas-fir (Pseudotsuga menziesii) trees in two patterns of sheep/pasture/conifer agroforest (cluster and grid plantations) were studied from 4 years after planting (1983) until the first precommercial thinning at age 10 years (1988). Trees averaged over 1 m in height when grazing began in summer 1983. Some browsing of tree lateral branches by sheep occurred regardless of grazing season in 1983–1985. However, the 2 to 10% of current year's lateral branch growth removed by grazing sheep was too low to impact tree growth. Sheep removed the terminal leaders from only 3 to 9% of trees each year during 1983–1985. Most browsing of terminals occurred in the summer when other forages had become mature and were relatively unpalatable to sheep. Less than 13% of agroforest trees were debarked by sheep each year during 1983–1987. By the end of grazing in 1987, less than 8% of agroforest trees had sustained a level of debarking likely to impact future growth (〉50% of tree circumference debarked). Grazing had no discernible effect upon tree diameter or height in any year (P 〉 0.05). Total tree mortality attributable to sheep grazing during 1983–1987 was only 0.9%, including three trees girdled by sheep and two debarked trees which were subsequently attacked by insects. Overall, grazing had no detrimental impact on timber stand growth or mortality.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00118780
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  • 4
    Electronic Resource
    Electronic Resource
    Productivity of two Douglas fir/subclover/sheep agroforests compared to pasture and forest monocultures (1996)
    Springer
    Agroforestry systems 34 (1996), S. 305-313 
    Details
    ISSN: 1572-9680
    Keywords: spatial pattern ; silvopastoral ; intercropping ; polyculture ; Pseudotsuga menziesii ; Trifolium subterraneum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Resource sharing between tree and forage plant components in silvopastoral systems includes a complex set of facilitative and competitive interactions. To the extent that facilitation exceeds competition, agroforests are expected to outyield monocultures of their components. Pasture and Douglas fir (Pseudotsuga menziesii) tree production of young agroforests was compared to pasture and forest monocultures under both grid and cluster patterns of tree planting near Corvallis, Oregon, USA, during 1983–1987. The height and diameter growth of forest and agroforest trees was similar, regardless of tree planting pattern. Five-year average annual forage production was 6500, 5800, and 2800 kg ha−1 on pasture, agroforest, and forest plots, respectively. The total cumulative 1982–1987 above-ground phytomass yield of forage plus trees was similar for pasture and conventional grid forest monocultures. The total productivity of agroforests, however, was over 30% greater than either pasture or forest components grown in monoculture. Approximately 1.6 ha (0.96 ha forest + 0.64 ha pasture) of monocultures would be needed to equal the productivity of 1 ha of agroforest.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00046930
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  • 5
    Electronic Resource
    Electronic Resource
    Viscoelastic properties of plasticized polymers (1963)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 7 (1963), S. 393-397 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Stress relaxation master curves were obtained for polystyrene, polymethyl methacrylate, and polyvinyl chloride, all plasticized with dioctylphthalate. The plasticized polyvinyl chloride results were quite different from the others, and this was tentatively ascribed to borderline crystallinity.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1963.070070136
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  • 6
    Electronic Resource
    Electronic Resource
    Solution properties of phosphonitrilic fluoroelastomersPaper was presented, in part, at the Technology Assessment and Planning Conference-Phosphazene and Phosphazene High Polymers, Army Materials and Mechanics Research Center, Watertown, Mass., May 20-22, 1975. (1976)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 14 (1976), S. 1379-1395 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of phosphonitrilic fluoroelastomers which have excellent solvent resistance and low temperature flexibility, and which perform well under a broad range of service conditions, have been developed. The solution properties of one of these polymers were studied more extensively in order to develop suitable quality control procedures and to gain a better understanding of the polymer structure. Solvents for these procedures were established, fractionation procedures were developed, and intrinsic viscosity, osmotic pressure, and light-scattering measurements were conducted. We found this polymer to have a very broad molecular weight distribution. And, although fractionation by molecular weight was effected, the fractions retained a broad molecular weight distribution. Our data do not indicate significant branching for this polymer. As a result of our studies, we have theorized that a supermolecular structure may be present in this polymer.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1976.170140607
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  • 7
    Electronic Resource
    Electronic Resource
    Further results concerning rubber elasticity and chain configuration (1962)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 61 (1962), S. S23 
    Details
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1962.1206117135
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  • 8
    Electronic Resource
    Electronic Resource
    Rubber elasticity and chain configuration (1961)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 54 (1961), S. 175-192 
    Details
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Various theories accounting for the existence of a front factor in the equation of state for rubber elasticity are reviwed. It is shown that a front factor which may be different from unity exists whether or not intramolecular energy effects are present. A unified theory is presented which is applicable both to Gaussian chains and to chains with intramolecular folding energy. Stress-temperature measurements were used to obtain values of the intramolecular folding energy ∊′ for numerous crosslinked polyacrylates and polymethacrylates. The values of ∊′ for almost all of the polyacrylates were found to be approximately zero; the values of ∊′ for the polymethacrylates varied generally between -350 and -700 cal./mole, indicating a preference for folded configurations. The front factors were also determined for these crosslinked polymers at 60°C. The front factor appears relatively independent of the degree of crosslinking. There appears to be a general trend to smaller front factors as the size of the alkyl chain increases in both series. An interpretation in terms of network interpenetration is given in the text. The variation of ∊′ with copolymer composition has been determined for a series of butyl acrylate-butyl methacrylate copolymers. The value of ∊′ for isotactic amorphous poly(1-pentene) was also measured and found to be zero. Finally, the effect of diluent on the front factor is discussed for the case where diluent is present during the crosslinking process and for the case where it is added after crosslinking.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1961.1205415913
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