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  • Canadian Science Publishing  (7)
  • American Institute of Physics (AIP)  (1)
  • Nature Publishing Group  (1)
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  • 1
    Electronic Resource
    Electronic Resource
    Electron-microscopic investigation of the morphology of a melt-crystallized polyaryletherketone (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 58 (1985), S. 2843-2853 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied the structure and morphology of the useful high-temperature/high-strength polymer polyaryletherketone (PEEK) by transmission electron microscopy and three-dimensional electron diffraction after finding suitable solvents (α-chloronaphthalene and benzophenone) that allowed casting of the required ultrathin polymer films. When crystallized from the melt, PEEK grows in the form of spherulites consisting of narrow lamellae and having the b axis of the unit cell radial. Additionally, at high temperatures in these ultrathin films, the spherulites attain an extraordinary cylindrical symmetry as a result of growth of their lamellae on edge, with the c crystallographic direction parallel to the film plane and the a direction corresponding to the cylinder axis. Reasons for this mode of growth are attributed to the highly anisometric molecular cross section normal to the chain direction, which favors crystal nucleation on the substrate with the bc plane. At lower temperatures during crystallization from the melt, a more random lamellar disposition is seen in these thin-film spherulites, although lamellae on edge still predominate. Crystallization by heating from the quenched glassy phase yields random lamellar aggregates and small spherulites. The glassy phase in ultrathin PEEK shows no consistent morphological features down to a level of resolution of 1.0 nm. Scanning electron microscopic examination of the free surfaces of bulk samples crystallized under controlled conditions both from the melt and from the glass, show that our findings from ultrathin films (with the exception of the quasicylindrical spherulitic substructure) also apply to these thicker specimens.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.335856
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Aqueous-phase source of formic acid in clouds (1983)
    [s.l.] : Nature Publishing Group
    Nature 304 (1983), S. 427-429 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] During the daytime, gaseous OH and HO2 radicals are photo-chemically produced in the atmosphere10-12. Within a cloud, these radicals can be rapidly scavenged by cloud droplets, thereby resulting in a source of free radicals to cloudwater13. Once in the aqueous phase, OH and HO2 initiate a complex ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/304427a0
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  • 3
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    Variation among Fraxinus families in foliar response to ozone (1979)
    Canadian Science Publishing
    Details
    Publication Date: 1979-03-01
    Description: Seedlings representing 10 open-pollinated families of Fraxinuspennsylvanica Marsh, and 2 of F. americana L. were exposed to 490 μg/m3 ozone (0.25 ppm) for 6 h at 24 °C and 75% relative humidity. At time of exposure, the seedlings were approximately 2 months old from seed and had three or four pairs of primary leaves. Both percentage of leaf surface injury and kind of injury varied significantly among families of the same and different species and between pairs of leaves at different nodal positions. Results reveal that total foliar ozone injury may be a complex of genetically independent symptom responses that should be distinguished in future studies of the genetics of ozone resistance.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Canadian Science Publishing
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  • 4
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    Influence of humidity and temperature during exposure on SO2-induced leaf necrosis of Virginia pine and river birch (1987)
    Canadian Science Publishing
    Details
    Publication Date: 1987-10-01
    Description: River birch and Virginia pine seedlings were exposed to 0.8 or 1.0 ppm SO2 (approximately 2100 and 2600 μg m−3, respectively) for 4 h at temperatures of 16, 24, and 32 °C and at relative humidities of 60, 75, and 90%, in all combinations. Virginia pine seedlings exhibited increased SO2-induced leaf necrosis with increasing temperature and with increasing humidity. For greenhouse-grown Virginia pine seedlings, the relationship between leaf necrosis and vapor pressure deficit was linear with a common negative slope but with different intercepts for each temperature. For Virginia pine seedlings grown outdoors, the relationship between leaf necrosis and vapor pressure deficit was also linear, but both slope and intercept changed with temperature. For river birch, temperature did not greatly affect the overall level of injury; instead, the response to humidity was negligible, linear, or quadratic, depending on temperature and on the conditions under which seedlings were grown. The effects of temperature and humidity on injury to Virginia pine are consistent with an explanation based on changes in leaf conductance; however, such an explanation cannot easily account for the observed response of river birch.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Canadian Science Publishing
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  • 5
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    Sulfur dioxide injury, sulfur content, and stomatal conductance of birch foliage (1981)
    Canadian Science Publishing
    Details
    Publication Date: 1981-03-01
    Description: Seedlings of three birch species were exposed biweekly to 2358 μg/m3 (0.9 ppm) SO2 for 2 h from May to September 1977. Leaf sulfur content of the birch foliage increased following exposure to SO2, but sulfur accumulation was not correlated with visible injury. Relative susceptibility was significantly correlated with preexposure leaf conductance rates of Betulanigra L. and B. papyrifera Marsh., but not for B. pubescens Ehrh. Leaf conductance rates were not correlated with sulfur accumulation.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Canadian Science Publishing
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  • 6
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    Discussion: Response of bark tissues to injury and infection (1984)
    Canadian Science Publishing
    Details
    Publication Date: 1984-06-01
    Description: Research of nonspecific defense processes in woody plants has focused on xylem. From these studies the concept of compartmentalization sensu Shigo was developed. Responses of bark to injury and infection, however, are understood poorly. This discussion summarizes evidence for the occurrence of processes similar in function to xylem compartmentalization in bark. We suggest that a developmental approach to research on woody plant responses to injury and infection could result in conceptual unity regarding structural and functional changes in both xylem and bark.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Canadian Science Publishing
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  • 7
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    Identification of Armillaria species isolated from bigtooth aspen based on rDNA RFLP analysis (1998)
    Canadian Science Publishing
    Details
    Publication Date: 1998-01-01
    Description: Restriction fragment length polymorphism analysis (RFLP) of the intergenic region (IGR-1) between the 3 ' end of the 26S ribosomal RNA gene and the 5 ' end of the 5S rRNA gene was used to identify 39 isolates of Armillaria species collected from live or recently dead bigtooth aspen (Populus grandidentata Michx.) trees and sucker sprouts in the Tioga State Forest, Pennsylvania. The unknown isolates were identified by comparing their restriction fragment patterns with 18 isolates of known Armillaria species common to the northeastern United States. Twenty of the unknown isolates (50%) were identified as either Armillaria gallica or Armillaria calvescens. Eighteen (46%) of the isolates were identified as Armillaria ostoyae. One isolate of Armillaria sinapina was obtained from a recently dead aspen tree. One isolate of Armillaria mellea, considered to be the most divergent of the Armillaria species, was obtained from basidiomes fruiting on a recently dead aspen tree near Berwick, Pennsylvania. In some instances, amplification of DNA was possible by adding mycelial scrapes directly to the polymerase chain reaction (PCR) mix, thus precluding the need for DNA extraction. Advancements in RFLP analysis may offer a method able to provide rapid and precise identification of most North American and European Armillaria isolates.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Canadian Science Publishing
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  • 8
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    Effect of SO2 on growth and sulfur content of hybrid poplar (1981)
    Canadian Science Publishing
    Details
    Publication Date: 1981-12-01
    Description: Growth of hybrid poplar clone NE-388 (Populusmaximowizii Henry × trichocarpa Torr. & Gray) was significantly reduced by repeated continuous 72-h exposures to 0.12 or 0.25 ppm SO2 for 6 or 14 weeks, respectively. Both dosages of SO2 induced significant defoliation of the oldest leaves. The sulfur content of abscised foliage ranged from 0.90 to 1.70% S dry weight basis compared with control values of 0.24 to 0.32% S. These sulfur values may provide information on the role of hybrid poplar in removing pollutants from the atmosphere.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Canadian Science Publishing
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  • 9
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    Major and trace element concentrations in surface organic layers, mineral soil, and white oak xylem downwind from a coal-fired power plant (1989)
    Canadian Science Publishing
    Details
    Publication Date: 1989-12-01
    Description: White oak (Quercusalba L.) xylem tissues, associated mineral soils (0 to 25 cm), and surface organic layers (O2 horizon) were sampled downwind from a 623 MW coal-fired power plant to determine whether major or trace element concentration patterns were affected by changes in emission stack heights during a 32-year operating period. Four sites with Hazleton (Typic Dystrochrept) soils located at 0.25, 1.2, 2.0, and 10.3 km downwind from the power plant were sampled. In surface O2 layers, Fe and Co concentrations varied inversely with distance from the power plant. Inductively coupled plasma–atomic emission spectroscopy was used to determine concentrations (ppm) of P, K, Ca, Mg, Fe, Mn, B, Na, Sr, Ba, Cu, Al, Si, Cr, Ni, Co, Pb, and Cd in xylem tissues during four separate time periods: one preoperation and three periods concurrent with power plant operation. Only Sr concentrations showed a consistent pattern of greatest accumulation in the xylem during periods when emission stacks were lowest, and at sites closest to the power plant. Potentially toxic elements were not detected at elevated levels in xylem tissues; however, xylem Sr may be a sensitive bioindicator of historical fly-ash deposition.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Canadian Science Publishing
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