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  • Nutrient cycling  (2)
  • Polymer and Materials Science  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Fire in the Brazilian Amazon 2. Biomass, nutrient pools and losses in cattle pastures (1998)
    Springer
    Oecologia 113 (1998), S. 415-427 
    Details
    ISSN: 1432-1939
    Keywords: Key words Cattle pastures ; Deforestation ; Nutrient cycling ; Biomass burning ; Tropical forests
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Conversion to cattle pasture is the most common fate of the ≈426,000 km2 of tropical forest that has been deforested in the Brazilian Amazon. Yet little is known about the biomass, C, nutrient pools, or their responses to the frequent fires occurring in these pastures. We sampled biomass, nutrient pools and their losses or transformation during fire in three Amazonian cattle pastures with typical, but different, land-use histories. Total aboveground biomass (TAGB) ranged from to 53 to 119 Mg ha−1. Residual wood debris from the forests that formally occupied the sites composed the majority of TAGB (47–87%). Biomass of fine fuels, principally pasture grasses, was ≈16–29 Mg ha−1. Grasses contained as much as 52% of the aboveground K pool and the grass and litter components combined composed as much as 88% of the aboveground P pool. Fires consumed 21–84% of the TAGB. Losses of C to the atmosphere ranged from 11 to 21 Mg ha−1 and N losses ranged from 205 to 261 kg ha−1. Losses of S, P, Ca, and K were 〈33 kg ha−1. There were no changes in surface soil (0–10 cm) nutrient concentration in pastures compared to adjacent primary forests. Fires occur frequently in cattle pastures (i.e., about every 2 years) and pastures are now likely the most common type of land burned in Amazonia. The first 6 years of a pastures existence would likely include the primary forest slash fire and three pasture fires. Based upon our results, the cumulative losses of N from these fires would be 1935 kg ha−1 (equivalent to 94% of the aboveground pool of primary forest). Postfire aboveground C pools in old pastures are as low as 3% of those in adjacent primary forest. The initial primary forest slash fire and the repeated fires occurring in the pastures result in the majority of aboveground C and nutrient pools being released via combustion processes rather than decomposition processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050394
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Fire in the Brazilian Amazon: 1. Biomass, nutrient pools, and losses in slashed primary forests (1995)
    Springer
    Oecologia 104 (1995), S. 397-408 
    Details
    ISSN: 1432-1939
    Keywords: Tropical forests ; Biomass burning ; Carbon cycling ; Nutrient cycling ; Slash-and-burn
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Deforestation in the Brazilian Amazon has resulted in the conversion of 〉230,000 km2 of tropical forest, yet little is known on the quantities of biomass consumed or the losses of nutrients from the ecosystem. We quantified the above-ground biomass, nutrient pools and the effects of biomass burning in four slashed primary tropical moist forests in the Brazilian Amazon. Total above-ground biomass (TAGB) ranged from 292 Mg ha-1 to 436 Mg ha-1. Coarse wood debris (〉20.5 cm diameter) was the dominant fuel component. However, structure of the four sites were variable. Coarse wood debris comprised from 44% to 69% of the TAGB, while the forest floor (litter and rootmat) comprised from 3.7 to 8.0% of the TAGB. Total biomass consumption ranged from 42% to 57%. Fires resulted in the consumption of 〉99% of the litter and rootmat, yet 〈50% of the coarse wood debirs. Dramatic losses in C, N, and S were quantified. Lesser quantities of P, K, and Ca were lost by combustion processes. Carbon losses from the ecosystem were 58–112 Mg ha-1. Nitrogen losses ranged from 817 to 1605 kg ha-1 and S losses ranged from 92 to 122 kg ha-1. This represents losses that are as high as 56%, 68%, and 49% of the total above-ground pools of these nutrients, respectively. Losses of P were as high as 20 kg ha-1 or 32% of the above-ground pool. Losses to the atmosphere arising from primary slash fires were variable among sites due to site differences in concentration, fuel biomass, and fuel structure, climatic fluctuations, and anthropogenic influences. Compared to fires in other forest ecosystems, fires in slashed primary tropical evergreen forests result in among the highest total losses of nutrients ever measured. In addition, the proportion of the total nutrient pool lost from slash fires is higher in this ecosystem compared to other ecosystems due to a higher percentage of nutrients stored in above-ground biomass.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00341336
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Viscoelastic characterization of PVC plastisol melts for foam applicationsThis paper was presented at a Symposium on PVC Foams, American Chemical Society National Meeting, Philadelphia, Pennsylvania, April 1975 (1976)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 20 (1976), S. 1187-1198 
    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: Melt rheology and its time-temperature dependence have long been known to be fundamental properties associated with satisfactory expansion characteristics in vinyl foam. Since much is known about the relationship between rheology and material variables like polymer morphology and system composition, adequate rheological characterization should be quite helpful in polymer design and plastisol compounding.Earlier attempts to study the melt rheology of plasticized PVC foam systems were only partially successful because instrument limitations required that the material be studied at too high shear rate or temperature, or that behavior of specific compositions be extrapolated from data obtained at considerably higher plasticizer level.This paper deals with measurement of the viscoelastic behavior of melts from actual azodicarbonamide foam compositions. The Rheometrics Mechanical Spectrometer was used in the orthogonal mode to study both elastic modulus and loss modulus (viscosity) in the range of shear rates and temperatures which actually occur during commercial utilization of PVC foam compounds. The effects of changing vinyl resin types and plasticizer types and levels were explored.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1976.070200505
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Gelation and fusion profiles of PVC dispersion resins in plastisols (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 28 (1983), S. 807-822 
    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: Poly(vinyl chloride) (PVC) plastisols are used for coatings, films, sheets, foams, and rotational castings. In order to satisfy the requirements for the different applications, a variety of PVC dispersion resins are manufactured. The requirements for the plastisols are many: for example, good air release, viscosity stability, fine particle size, foamability, and good heat stability. Processability is another important requirement, which emphasizes the rheological behavior at room temperature and the gelation - fusion behavior. This paper documents research to fingerprint the gelation and fusion profiles of various PVC dispersion resins. The viscoelastic measurements were used to continuously monitor the changes of moduli during gelation and fusion under a heating rate which simulates the temperature profile of the processes. The effects of molecular weight, resin type, and copolymer on the gelation-fusion behavior are discussed.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1983.070280232
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    Paper (German National Licenses)
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