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  • Polymer and Materials Science  (5)
  • 21.10.−k  (1)
  • Biology  (1)
  • 1
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    In:  http://aquaticcommons.org/id/eprint/1604 | 3 | 2011-09-29 20:18:37 | 1604 | Aquatic Plant Management Society, Inc.
    Publication Date: 2021-07-09
    Description: Burial and removal techniques with seed bags were usedto examine the viability and longevity ofMelaleuca quinquenerviaseeds at four field sites representing different soil typesand hydrological conditions in South Florida. Seed viabilitywas determined over different burial durations in the soilthrough a combination of germination tests and 2,3,5-triphenyl-tetrazolium chloride (TTC) treatments. Control seedskept dry at 25 C in the laboratory maintained same viabilityof ca. 15% over the 3-year study. In the field, seed viability decreasedwith increased burial duration.(PDF has 4 pages.)
    Keywords: Management ; Biology ; Limnology ; Melaleuca ; paper bark tree ; seed viability ; germination ; dormancy ; Florida ; invasive plants ; Australia
    Repository Name: AquaDocs
    Type: article , TRUE
    Format: application/pdf
    Format: application/pdf
    Format: 39-42
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  • 2
    ISSN: 1434-601X
    Keywords: 21.10.−k ; 27.60. +j
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A new high-spin isomeric state with a half-life of ≥2μs was found in144Pm by observing the14N(136Xe,6n)144Pm reactions. The excitation energy and spin of the isomer were estimated to be ∼7.4 MeV and ∼27+, respectively. Filling gas in a recoil ion separator was used as the target material.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0959-8103
    Keywords: acrylonitrile ; copolymer ; methylacrylate ; hydration ; melting ; solid-state transition ; double melting transition ; double crystallization ; dipole-dipole interaction ; 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: The effect of chemical composition of copolymers of acrylonitrile (AN) and methylacrylate (MA) on the hydration and thermal transition behaviour was investigated. An increase of the MA content considerably depressed both Tm and Tc of the hydrated polymers. A double melting and crystallization transition behaviour was observed when the hydrated polymer was reheated after cooling from the molten state. The separation between primary and secondary peaks was more notable in the second heating scan than in the first heating scan. A novel solid-state transition was observed in the dried acrylic polymers which had experienced hydration and melting in the wet state, followed by drying in the open state at 200°C.
    Additional Material: 7 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 50 (1993), S. 1065-1073 
    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: The microstructure and fracture properties of diglycidyl ether of bisphenol A (DGEBA) epoxy resins modified with phenolic hydroxyl-terminated polysulfone (PSF) and cured with diaminodiphenyl sulfone (DDS) hardener have been investigated as a function of the molecular weight and concentration of PSF. The microstructure changed from a typical particulate structure to a phase-inverted structure as the molecular weight and/or the concentration of the modifier increased. The fracture toughness, measured by compact tension tests, increased with the microstructural changes toward the phase-inverted structure. The microstructural changes observed have been interpreted in terms of variation in the reaction mechanisms as determined by near-infrared spectroscopy. The level of minor reactions such as etherification and homopolymerization reactions increased with increasing molecular weight and/or concentration of the modifier, in line with the tendencies observed in microstructure and fracture toughness. In the system containing 20 wt% of Mn 10,000 PSF, about 30% of the epoxy groups were consumed by etherification and homopolymerization reactions, whereas none of these reactions occurred in the unmodified system. The increase in minor reactions in the modified systems may be to be due to the restricted molecular mobility, resulting from the increase of system viscosity caused by the modification. This increase in viscosity also reduced the rate of phase separation. The degree of heterogeneity in the epoxy network must increase with the increasing side reactions. The formation of the heterogeneous epoxy network and the slowdown of phase separation will prevent a uniform precipitation of the modifier and finally result in a heterogeneous partially phase-inverted structure or the completely phase-inverted structure, depending on the amount of modifier incorporated over the critical concentration. © 1993 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 50 (1993), S. 1511-1518 
    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: We have studied an epoxy resin formulation consisting of the diglycidyl ether of bisphenol-A (DGEBA), modified with phenolic hydroxyl-terminated polysulfone (PSF) and cured with an aromatic amine curing agent, diaminodiphenyl sulfone (DDS). A range of microstructures and fracture properties have been obtained by controlling the formulation cure conditions (cure temperature and cure cycle in an isothermal mode). The chemical conversion of the cured resins has been monitored by near-infrared spectroscopy (NIR). Although only a single material formulation was used, three distinct types of microstructure were identified by scanning electron microscope (SEM) observations on samples prepared at different cure temperatures. Surprisingly, the thermal and fracture properties of the cured samples did not vary noticeably, in spite of the significant microstructure variations. The consistency of these fracture toughness results with cure temperature changes was an unexpected result in the light of our earlier observations of a strong dependence of fracture toughness on cure temperature in neat resin systems. The difference in behavior between neat and modified resins reveals that the fracture toughness of the latter is dependent on a combination of the microstructure and the matrix resin properties. This hypothesis was also supported by an observation of high fracture thoughness in a sample cured in a two-step process, which we believe is due to the optimum microstructure and matrix resin properties, being achieved separately during precure and postcure, respectively. The increase in fracture toughness values caused by the modification (ΔGIC) was calculated from the fracture toughness values of neat and modified resins, prepared under the same cure conditions, using a proposed theoretical equation. © 1993 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 48 (1993), S. 1303-1312 
    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: The glass transition temperature (Tg), water- and solvent-absorption characteristics, fracture toughness, and tensile properties of a diglycidyl ether of bisphenol-A (DGEBA) -based epoxy resin (Epikote 8283) cured with an aromatic amine curing agent, 4,4' -diaminodiphenyl sulfone (DDS), were studied as a function of cure temperature and cure cycle (one-step or two-step cure). The glass transition temperature (which depends on the extent of cure) shows a linear increase with increasing cure temperature and levels off toward the cure temperature of 200°C. Water and solvent uptake tended to increase with increasing cure temperature and, hence, with cross-linking level. Fracture toughness, tensile strength, strain to break, and tensile fracture energy also increased significantly with increasing final cure temperature regardless of cure cycle. In contrast, the small strain properties such as modulus, yield stress, and yield strain were not influenced greatly by cure temperature and cure cycle. From these results, we infer that the large strain properties of the resin are not inversely proportional to the cross-link density of the network as reported in many publications, 1 but, rather, that they are dependent on other structural parameters such as free volume and the flexibility of the cross-linked chains. © 1993 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 18 (1980), S. 2949-2958 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Various wholly aromatic polyamides based on m-and p-phenylene diamines and isophthaloyl and terephthaloyl chloride have been synthesized and their thermal properties and oxygen index values have been studied. The effect of different substituents on the aromatic ring of the diamine have been explored by comparing their differential thermal analysis (DTA) and thermogravimetric analysis (TGA) behavior, their relative char yields at 700°C, and their oxygen indices. The —Cl, —NO2, and —OH substituted polyamides have been found to produce the highest char yields. The high char yields are probably associated with crosslinking occurring at high temperatures. Attempts at correlating char yield with oxygen index indicated enhancement for the chlorosubstituted aramids.
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