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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Agroforestry systems 1 (1983), S. 277-297 
    ISSN: 1572-9680
    Keywords: pine ; pasture ; cattle ; integrated management
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Native forages of southern United States are frequently low in nutrients and poorly digestible, while improved pastures are the opposite. Since this area produces rapid growth of pines, which is a major use of the land, the integration of pines, pastures, and cattle seem to offer an efficient and economical form of management. Therefore, in a 20-year study Coastal bermuda (Cynodon dactylon), dallis (Paspalum dilatatum), and Pensacola bahia (P. notatum) grasses were grown in pastures with no trees, and with slash pine (Pinus elliottii) spaced 3.7 x 3.7 and 6.1 x 6.1 m. The trees were grown free of competition for 3 years, grasses were established during the 4th year, and grazing by yearling cattle began the 5th year. The pastures were then fertilized, grazed, and burned for 15 years. Increasing tree canopies reduced forage production of all grasses. Bahiagrass was the most shade tolerant, while Coastal bermuda was the least. Liveweight gains during the 15 years of grazing totaled 3933, 2302, and 1518 kg/ha from pastures with no pines and slash pine spaced 6.1 x 6.1 and 3.7 x 3.7, respectively. Survival of slash pine was low due to heavy attacks by southern pine coneworm and southern fusiform rust. However, the trees grew rapidly and averaged 19.0 and 16.9 m in height, 30.0 and 33.3 cm in diameter, and 181.4 and 90.7 m3/ha of pulpwood after 20 years from the 3.7 x 3.7 and 6.1 x 6.1 spacings, respectively. Slash pine at these spacings planted in undisturbed, native vegetation were 16.0 and 15.7 m tall, 19.6 and 23.4 cm in diameter, and produced 145.5 and 63.6 m3/ha of pulpwood. Combining the production of pines and beef on improved pasture offers an opportunity for multiple-product yields. Since this approach to agroforestry is not trouble-free, good management is required. Landowners, especially those with small holdings, should consider these alternatives to single-product management when planning their cropping system.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Agroforestry systems 2 (1984), S. 31-41 
    ISSN: 1572-9680
    Keywords: agroforestry ; cattle ; Pinus elliottii ; Paspalum notatum ; Cynodon dactylon ; pasture ; pulpwood production
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract When combining pine and cattle production on improved pastures, grazing may have to be delayed for several years until trees are large enough to resist injury. During this period forage would be lost unless harvested for hay. This study in south Georgia, USA, examined hay production during the first 3 years, cattle production during the next 3 years, and effects of this management system on survival and growth of slash pine(Pinus elliottii) planted in widely-spaced rows within the pastures. Pines were planted at 225 trees/ha in configurations of 3.0 x 14.6 or 4.9 x 9.1 m in pastures recently sprigged or seeded with Coastal bermudagrass (Cynodon dactylon) or Pensacola bahiagrass(Paspalum notatum). Pastures were fertilized annually and cut for hay four or five times each year. Wide-row spacings permitted haying operations, but tree rows and turning areas removed 5 to 8 percent of the area from production. However, hay yields and liveweight gains by yearling cattle were near normal for this locale. Slash pine planted in these fertilized pastures survived well, grew rapidly, and only a few trees were killed during haying operations. After 6 years, 83 percent of the trees survived and averaged 6.5 m in height and 13.2 cm in diameter. Cattle killed a few trees by rubbing during the 4th year. Wide-row spacing of pines permits harvesting forage for hay while waiting for the trees to become large enough to permit grazing. This approach to agroforestry produces annual returns to the landowner while awaiting maturity of the pines.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 26 (1981), S. 1705-1717 
    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: Model graft copolymers were synthesized by grafting acrylamide onto dextran (M̄w = 500,000) utilizing the Fe(II)/H2O2 initiation system. Aqueous size exclusion chromatography (SEC) was used to determine the effects of changing reaction parameters on hydrodynamic dimensions of the resulting graft copolymers. It was also possible to optimize reaction conditions yielding the highest viscosity graft copolymer with the least amount of homopolyacrylamide and unreacted substrate. The molecular structures of the graft copolymers were determined by elemental analysis, SEC, and solution viscometry. Selective hydrolysis of the dextran backbone allowed determination of average molecular weight of acrylamide grafts, number of grafting sites, and average molecular weight of the graft copolymers. Rheological studies indicated viscosity and pseudoplastic behavior were largely related to the graft length of the polyacrylamide side chains.
    Additional Material: 11 Ill.
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  • 4
    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: Compositional analyses of random copolymers of acrylamide with sodium-2-sulfoethyl methacrylate and with sodium-2-acrylamido-2-methylpropane sulfonate have been performed utilizing elemental analysis, infrared spectroscopy, and C13 NMR. A mathematical method involving nitrogen to sulfur ratios has been developed to eliminate errors which often arise from associated water in hydrophilic copolymers. The ratios of infrared absorbances at 1043 cm-1 and 1664 cm-1 were used to determine the composition of AM - NaAMPS copolymers; likewise, absorbance ratios at 1040 cm-1 and 3200 cm-1 were utilized for determination of the AM - NaSEM copolymer composition. Carbon-13 NMR spectra of the copolymers were also obtained, and characteristic peaks were utilized to quantitate copolyer composition. The results obtained by elemental analyses, infrared spectroscopic studies, and NMR were in excellent agreement. These techniques are of great value for determining composition of hygroscopic copolymers which can crosslink or form strong intramolecular hydrogen bonds, often precluding further characterization.
    Additional Material: 11 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 29 (1984), S. 713-730 
    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: Dilute solution viscosity of a series of random copolymers of acrylamide (AM) with sodium-2-acrylamido-2-methylpropane sulfonate (NaAMPS) and with sodium-2-sulfoethylmethacrylate (NaSEM) has been studied using a four-bulb shear dilution capillary viscometer. The hydrodynamic volume of the copolymers in aqueous media was determined as a function of salt concentration, temperature, shear rate, and time. A linear relationship was observed between the intrinsic viscosity [η]0 and the reciprocal of the square root of ionic strength in sodium chloride solutions, with salt concentrations varying from 0.043M to 0.257M. Negative temperature coefficients for [η]0 indicate a decrease in the hydrodynamic volume of the ionic polymer molecules with increasing temperature. The relative zero-shear-intrinsic-viscosity change in distilled water to 0.257M sodium chloride aqueous media is used to elucidate viscosity-structure relationships. A maximum value is reached for this parameter at a composition of about 30 mol % of ionic comonomers for AM-NaAMPS and AM-NaSEM copolymer series.
    Additional Material: 14 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 19 (1981), S. 2229-2241 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Model graft copolymers were synthesized by grafting acrylamide onto dextran (Mw = 500,000) utilizing an initiation method in which a Ce(IV)/HNO3 solution was added to the dextran solution in order to allow coplexation prior to monomer addition. Three synthetic reaction parameters were optimized on the basis of conversion and solution viscosity: monomer concentration, dextran concentration, and nitric acid concentration. Molar ratios of [Ce(IV)]/[dextran] were changed systematically to affect the number and length of the acrylamide grafts. The number of grafting sites and graft chain lengths, determined by selective hydrolysis of the carbohydrate backbone, were in good agreement with those theortically predicted from knowledge of initiation efficiency and monomer conversion. Rheological studies of the model graft copolymers were conducted in aqueous solutions as a function of temperature, added salt, and copolymer concentration.
    Additional Material: 8 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 22 (1984), S. 49-60 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Studies were conducted on grafting of acrylamide (AM) and sodium-2-acrylamido-2-methylpropane sulfonate (NaAMPS) comonomers onto dextran utilizing Ce(IV) induced initiation. The effects of reaction temperature, the Ce(IV)/dextran ratio, and the AM/NaAMPS ratio on grafting yield were investigated. The graft copolymerization behavior can be explained by exchange of the AMPS anion with one of the ligands on the Ce(IV) initiator. Oxidative modification of the dextran substrate improved the yield of graft copolymer. The dextran-g-poly(acrylamido-co-sodium-2-acrylamido-2-methylpropane sulfonate) samples prepared by this method were characterized as to copolymer composition and molecular weight utilizing elemental analysis, dilute solution viscometry, and aqueous size exclusion chromatography. Relationships of molecular weight and charge density to kinematic viscosity and salt sensitivity are discussed.
    Additional Material: 4 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 22 (1984), S. 3633-3647 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The copolymerizations of acrylamide (AM) with N-(1,1-dimethyl-3-oxybutyl)acrylamide (DAAM) and with N,N-dimethylacrylamide (DMAM) have been studied. The values of r1,r2 have been determined to be 0.75 for the AM-DAAM pair and 0.86 for the AM-DMAM pair. The molecular weights of the copolymers were found to decrease with an increase in the feed composition of DAAM or DMAM. The microstructure was predicted for a wide range of feed compositions through a knowledge of reactivity ratios. These model structures are utilized for assessment of structure/dilute solution relationships reported in a subsequent paper in this series.
    Additional Material: 6 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 20 (1982), S. 817-838 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Random copolymers of acrylamide with sodium-2-sulfoethyl methacrylate and with sodium-2-acrylamido-2-methylpropane sulfonate were synthesized in aqueous solutions utilizing persulfate initiators. Copolymer compositions were determined by elemental analysis and by infrared spectroscopic methods. Monomer reactivity ratios were calculated using Fineman-Ross, Kelen-Tüdos, and/or Mayo-Lewis techniques at appropriate conversions. The copolymer microstructure, including mean sequence length distributions, was calculated from reactivity ratios. Membrane osmometry and viscometry measurements were utilized to estimate molecular weight and size. The large dimensions of these polyelectrolytes in aqueous solutions, as well as their inherent hydrogen bonding capacity and pseudoplasticity, make these copolymers excellent candidates for application as mobility control agents in enhanced oil recovery.
    Additional Material: 10 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 22 (1984), S. 3649-3660 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dilute solution properties of copolymers of acrylamide (AM) with N-(1,1-dimethyl-3-oxybutyl)acrylamide (DAAM) and with N,N-dimethylacrylamide (DMAM) have been studied as a function of composition, temperature, time, and added electrolytes sodium chloride and calcium chloride. Unlike the AM-DMAM copolymers, the AM-DAAM copolymers show solution viscosity increases in the presence of added NaCl and CaCl2 and decreases with increasing temperature which are related to copolymer composition. The unusual viscosity behavior of the DAAM-AM copolymers is suspected to be due to chain extension resulting from intramolecular hydrogen bonding and other cooperative associations along the macromolecular backbone.
    Additional Material: 10 Ill.
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