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  • Chemistry  (2)
  • Stream limnology  (1)
  • inshore  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Observations of seasonal changes in diatoms at inshore localities near Davis Station, East Antarctica (1986)
    Springer
    Hydrobiologia 139 (1986), S. 3-12 
    Details
    ISSN: 1573-5117
    Keywords: antarctic ; habitats ; diatoms ; sea ice ; benthos ; inshore
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Seventy-five diatom taxa were identified from net plankton samples collected inshore during winter, spring and summer 1977–8 near Davis Station, East Antarctica. Species richness was found to be higher in winter than in summer; this is the first time this trend has been reported in antarctic coastal regions. When these taxa were grouped according to the general habitats in which they normally occur, the benthic assemblages dominated the planktonic ones. Of the plankton, most species were of oceanic origin in winter and late summer and are thought to have been swept inshore by a cyclonic gyre which is known to occur in summer but has not been studied in winter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00770237
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  • 2
    Electronic Resource
    Electronic Resource
    Environmental conditions and phytoplankton in the Mwenda River, a small intermittent river flowing into Lake Kariba (1985)
    Springer
    Hydrobiologia 126 (1985), S. 81-89 
    Details
    ISSN: 1573-5117
    Keywords: Stream limnology ; water chemistry ; tropical river phytoplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Small intermittent rivers play an important role in the limnology of African lakes. The Mwenda River occurs on the southern shore of Lake Kariba. Its flow is governed by the incidence of tropical thunderstorms. During the dry period the river is reduced to a series of turbid pools. Physicochemically the river behaves similarly to a sheltered region of the lake. One river station deviates from the normal pattern because of the insulating effect of a Salvinia mat, and because of its permanent connection with the lake. River flooding flushes both nutrients and major ions into the lake. River phytoplankton populations peak prior to the flushing out of the river. Diatom populations are composed of cosmopolitan tropical taxa.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00008391
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  • 3
    Electronic Resource
    Electronic Resource
    The influence of molecular weight distribution on melt viscosity, melt elasticity, processing behavior and properties of polystyrene (1969)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 9 (1969), S. 164-171 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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: The influence of molecular weight and molecular weight distribution on the melt rheological behavior of two polystrenes of approximately the same weight average molecular weight, but of widely different molecular weight distribution, was determined. Then, using a series of capillaries with different length-to-diameter ratios in an Instron Capillary Rheometer, the entrance correction methods of E. B. Bagley and the relationships of W. Philippoff and F. H. Gaskins, the recoverable shear strain (SR) in the melt at the capillary wall for these mono- and polydisperse polystyrenes was determined. Shear modulus (G) and normal stress (PN) were calculated using the relationships: G = τRC/SR and PN = 2τRC SR, where τRC is the corrected shear stress at the capillary wall. These are compared to values obtained using a Weissenberg Rheogonimeter. These two polystyrenes were also injection molded into an ASTM specimen mold over a wide range of stock temperature, using a 12 OZ. in-line reciprocating screw injection press, and evaluated for mechanical property values. The effects of the elasticity parameters (SR G & PN) and their magnitude on the rheology, processability and mechanical properties of these polystyrenes are discussed.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760090304
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  • 4
    Electronic Resource
    Electronic Resource
    Application of the rheology of monodisperse and polydisperse polystyrenes to the analysis of injection molding behavior (1966)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 6 (1966), S. 373-376 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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: Monodisperse and polydisperse polystyrenes of equal weight average molecular weight (Mw) are evaluated for melt flow behavior in an Instron capillary rheometer and for injection molding behavior in a 12 ounce in-line reciprocationg screw injection molding machine. The influence of molecular weight distribution on the shape of the flow curves is deconstrated over a wide range of shear rate and temperature. The influence is also reflected in injection molding behavior as defined by pressure to fill or flash the mold at a given melt temperature. Studies of capillary rheometer data for correlation with injection moling beghavior indicate poor agreement when low shear rate viscosity data are used. Good agrement is foun using high shear rate viscosity data in the range 103 to 104 sec-1 Striking crossover points on melt rheology and injection colding area diagram curvs are found with the monodisperse and polydisperse polystyrenes of the same M These crossovers shift with melt temperature and make possible the determination of a “controlling shear rate” for the injection molding process. This is found to be 3500 sec-1 for short shot and 6200 sec-1 for flash with the ASTM test specimen mold used in this study.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760060416
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