Bibliothek

X
Ihre Suchhistorie ist leer.
feed icon rss

Ihre E-Mail wurde erfolgreich gesendet. Bitte prüfen Sie Ihren Maileingang.

Leider ist ein Fehler beim E-Mail-Versand aufgetreten. Bitte versuchen Sie es erneut.

Vorgang fortführen?

Exportieren
  • 1
    Digitale Medien
    Digitale Medien
    Paleolimnological evidence for the recent acidification of Llyn Hir, Dyfed, Wales (1989)
    Springer
    Journal of paleolimnology 2 (1989), S. 245-262 
    Details
    ISSN: 1573-0417
    Schlagwort(e): acidification ; diatoms ; sediment chemistry ; magnetic stratigraphy ; soot ; paleolimnology ; Wales
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract A variety of paleolimnological techniques, coupled with historical data on land-use and fisheries, are used to evaluate the magnitude, timing, and causes of acidification of Llyn Hir, a moorland lake in central Wales. pH reconstruction based on diatom analysis suggests a gradual decline in lakewater pH beginning ca. 1870 and intensifying in the mid-1930's, with a total decline of 1.1 pH units between 1870 and 1984. This pH decline correlates with increased sedimentary concentrations of carbonaceous particles, trace metals, and magnetic minerals, which indicate the local deposition of atmospherically transported products of fossil-fuel combustion. Pollen data and the historical record show no significant alterations in land-use or catchment vegetation, indicating that acidification of Llyn Hir is a result of the increased deposition of atmospheric pollutants, not of land-use and vegetation change.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00195475
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 2
    Digitale Medien
    Digitale Medien
    The relationship between diatoms and surface water quality in the Høylandet area of Nord-Trøndelag, Norway (1997)
    Springer
    Hydrobiologia 348 (1997), S. 69-80 
    Details
    ISSN: 1573-5117
    Schlagwort(e): diatoms ; water quality ; acidification ; pH calibration
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Although the ecological effects of surface wateracidification are now well researched, factorscontrolling the abundance and occurrence of aquaticorganisms in unpolluted acid-sensitive systems arepoorly known. The Høylandet region in central Norwayexperiences relatively low levels of atmosphericpollution and its surface waters, although acid, arenot significantly acidified. Hence lakes and streamsin this region were selected to study the influence ofwater chemistry on diatom algae. Relationships betweenthe two were explored using the multivariate techniqueof canonical correspondence analysis (CCA). Theprincipal water chemistry variables influencingspecies composition of periphytic diatoms were foundto be pH and water colour. Furthermore, therelationship between species abundance and pH wassufficiently strong to enable reconstruction of wateracidity from diatom data. Establishing the nature ofaquatic communities in atmospherically clean butgeologically sensitive regions is an important meansof identifying control systems against which therecovery of acidified lakes in polluted regions can beassessed. The Høylandet region has the potential toprovide a Europe-wide control system of this naturebut much further work is required to follow up andextend the results of this preliminary study.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1003085116632
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 3
    Digitale Medien
    Digitale Medien
    The use of infrared spectroscopy for determination of polypropylene stereoregularity (1988)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 36 (1988), S. 279-293 
    Details
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: This study examines the application of infrared (IR) spectrometry to the determination of polypropylene (PP) stereoregularity. The use of the absorption bands at 998 cm-1 and 841 cm-1 as indices of isotacticity and bands at 1167 cm-1 and 973 cm-1 as internal references have been explored. Calibration curves relating various absorption ratios to isotacticity as measured by 13C nuclear magnetic resonance are reported. The ratios A998/A973 and A841/A973 are the most useful and provide linear correlations with isotacticity. The effect of instrument type on the calibration has been investigated for both dispersive and Fourier transform type IR spectrometers. For samples annealed at room temperature the average of measurements on the same set of PP films by five instruments provide the calibrations: A998/A973 = 1.08 ± 0.02 (mm)-0.15 ± 0.03; and A841/A973 = 0.84 ± 0.06 (mm)-0.04 ± 0.02. High temperature annealing increases the crystallinity of the samples and the corresponding value of the absorption ratio but is not necessary for obtaining reproducible calibration curves.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/app.1988.070360203
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 4
    Digitale Medien
    Digitale Medien
    DSC studies of tactic polypropylenes: The correlation of polymer stereochemistry with thermal properties (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 41 (1990), S. 1095-1114 
    Details
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: A large number of polypropylene samples, of isotacticities spanning the range 0.35 to 1.00 mm, have been examined by differential scanning calorimetry (DSC) in order to establish a calorimetric index for determining stereostructure. Crystallization studies show that the crystallization onset temperature decreases in step with reduced isotacticity. However, samples prepared with supported catalysts show significantly lower crystallization onset temperatures than those from conventional catalysts which is believed to be due to differences in the inter- or intramolecular distribution of stereodefects. Furthermore, whole and fractionated samples cannot be fitted by one calibration curve. However, the enthalpy of crystallization is found to be related to the isotacticity by an equation of the form: log ΔH = m log (isotacticity) + c. This relationship is found to be applicable to samples from all types of catalysts examined and to both whole and fractionated samples. Fusion curves have been determined for “as received” as well as conditioned and annealed samples but the melting temperatures are not found to be a reliable guide to isotacticity. The respective enthalpies of fusion are found to follow the same logarithmic relationship stated above and thus can also be used as a basis for a calorimetric isotactic index. Examination of glass transition and related heat capacity data does not provide any clear-cut alternative index.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/app.1990.070410519
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
Schließen ⊗
Diese Webseite nutzt Cookies und das Analyse-Tool Matomo. Weitere Informationen finden Sie hier...