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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of polymers and the environment 3 (1995), S. 121-131 
    ISSN: 1572-8900
    Keywords: Biodegradation ; poly(β-hydroxybutyrate) ; testing ; carbon balance ; carbon dioxide evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Establishing carbon balances has been proven to be an applicable and powerful tool in testing biodegradability of polymers. In controlled degradation tests at a 4-L scale with the model polymer poly(β-hydroxybutyrate) (PHB), it was shown that the degree of degradation could not be determined with satisfactory accuracy from CO2 release alone. Instead, the course of degradation was characterized by means of establishing carbon balances for the degradation of PHB withAcidovorax facilis and a mixed culture derived from compost. Different analytical methods for determining the different carbon fractions were adapted to the particular test conditions and compared. Quantitative determination of biomass and residual polymer were the main problems in establishing carbon balances. Amounts of biomass derived from protein measurements depend strongly on assumptions of the protein content of the biomass. Selective oxidation of biomass with hypochlorite was used as alternative, but here problems arose from insoluble metabolic products. Determination of soluble components with the method of chemical oxygen demand (COD) also includes empirical assumptions but seems acceptable if the dissolved carbon fraction is in the range of some 10% total carbon. Results confirm both analytical assays and theoretical approaches, in ending up at values very close to 100%, within an acceptable standard deviation range under test conditions comparable to standard test practice.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of polymers and the environment 4 (1996), S. 9-20 
    ISSN: 1572-8900
    Keywords: Copolyesters ; biodegradability ; aliphatic diol ; adipic acid ; terephthalic acid ; aromatic oligomers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Model oligo esters of terephthalic acid with 1,2-ethanediol, 1,3-propanediol, and 1,4-butanediol have been investigated with regard to their biodegradability in different biological environments. Well-characterized oligomers with weight-average molar masses of from 600 to 2600 g/mol exhibit biodegradation in aqueous systems, soil, and compost at 60°C. SEC investigations showed a fast biological degradation of the oligomer fraction consisting of 1 or 2 repeating units, independent of the diol component used for polycondensation, while polyester oligomers with degrees of polymerization higher than 2 were stable against microbial attack at room temperature in a time frame of 2 months. At 60°C in a compost environment chemical hydrolysis also degrades chains longer than two repeating units, resulting in enhanced degradability of the oligomers. Metabolization of the monomers and the dimers as well by the microorganisms could be confirmed by comparing SEC measurements and carbon balances in a “Sturm test” experiment. Based on these results degradation characteristics of potential oligomer intermediates resulting from a primary chain scission from copolyesters consisting of aromatic and aliphatic dicarbonic acids can be predicted depending on their composition. These results will have an evident influence on the evaluation of the biodegradability of commercially interesting copolyesters and lead to new ways of tailor-made designing of new biodegradable materials as well.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1939
    Keywords: Browsing tolerance ; Clipping ; Compensatory growth capacity ; Herbivory tolerance ; Meristematic potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Inherent relative growth rate has been suggested as a major determinant of plant species' capacity to regrow and compensate for tissues lost to herbivores. We investigated: 1) the relationship between compensatory growth capacity and relative growth rate (RGR) in six semiarid-land shrubs following removal in winter or spring of 90% of the previous year's growth, 2) the influence of loss of buds on production of new growth and 3) the relationship between meristematic potential and the capacity to produce new growth in four of the six semiarid-land shrub species. Four-year-old plants growing under field conditions were used in the study. The species with the highest inherent growth rate, sagebrush [Artemisia tridentata ssp. vaseyana (Rydb.) Beetle], died following the severe clipping treatments. The other five species exactly compensated for lost tissues. Inherent growth rates and compensatory growth capacity of the shrubs were not correlated. Loss of 90% of the buds on the previous year's growth did not limit production of new growth. Instead, shrubs that lost buds produced more new growth biomass than the controls. The shrub species had significantly different meristematic potential. Curlleaf mountain mahogany (Cercocarpus ledifolius Nutt.) and serviceberry (Amelanchier alnifolia Nutt.) had the greatest and least number of buds and long shoots per plant, respectively. The number of long shoots produced following bud removal was positively correlated with new growth biomass, while the percentage of long shoots produced at the basal position on twigs was negatively correlated with new growth biomass. Our results suggest that inherent growth rate is not likely to influence production of new growth following browsing when resources for growth are not limiting. In contrast, the ability of a shrub to initiate long shoot growth is likely to influence production of new growth even when resources for growth are abundant.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-2242
    Keywords: Apomixis ; Wheat ; Barley ; Rye ; Wide hybridization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Four hybrids were obtained between three Australian Elymus taxa and three cereal grains: wheat, rye, and barley. Mean meiotic metaphase-I configurations were 41.14 I, 0.42 rod II, 0.003 ring II, and 0.01 III for E. scabrus var ‘plurinervis’ x Triticum aestivum (1 hybrid plant), 22.27 I, 2.63 rod II, 0.06 ring II, and 0.12 III for E. scabrus var ‘scabrus’ x Secale cereale (4 hybrid plants), and 26.65 I, 0.66 rod II, 0.00 ring II, and 0.01 III for E. scabrus var ‘plurinervis’ x Hordeum vulgare (13 hybrid plants). The I genome of barley also paired very little in a BIII hybrid of apomictic E. rectisetus x H. vulgare (2 hybrid plants). Megasporogenesis in this BIII hybrid was at least facultatively apomeiotic, with the same sort of nuclear elongation, apomeiotic division, and dyad formation seen previously in E. rectisetus itself. All four hybrid combinations were sterile. While spike morphology in the E. scabrus x T. aestivum and E. scabrus x H. vulgare hybrids were intermediate to their parents, E. scabrus x S. cereale and E. rectisetus x H. vulgare looked like their maternal parents.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The viscosity level in the range of the Newtonian viscosity η0, as well as in the shear rate dependent range (non-Newtonian-viscosity, η = f(\documentclass{article}\pagestyle{empty}\begin{document}$$ \mathop \gamma \limits^. $$\end{document})) of polymer solutions can be determined on the basis of a molecular modelling. Prerequisite is the information about the molecular parameters of the individual molecules  -  found in most cases in handbooks  -  and the result of the one-point measurement of η0 in the concentrated range.In addition, a criterium for shear stability was obtained, predicting the boundary range between a stable and a degraded polymer solution. This criterium holds for the laminar as well as for the turbulent flow. So, answers could be given to technologically interesting questions about the stability of the solutions.Under modified considerations, these results may be applied to polymer melts.
    Notes: Das Viskositätsniveau im Bereich der Ruhescherviskosität η0 (Newtonscher Bereich) sowie im schergeschwindigkeitsabhängigen Bereich (nicht-Newtonscher Bereich (η = f(\documentclass{article}\pagestyle{empty}\begin{document}$$ \mathop \gamma \limits^. $$\end{document})) von Polymerlösungen kann auf der Basis molekularer Modellierungen bestimmt werden. Voraussetzung hierfür ist die Kenntnis der molekularen Parameter des Einzelmoleküls, welche in vielen Fällen Handbüchern entnommen werden könen, und das Ergebnis einer Einpunktmessung von η0 in konzentrierter Lösung. Darüber hinaus wurde ein Stabilitätskriterium erarbeitet, das den Grenzbereich zwischen einer scherstabilen und einer degradierten Polymerlösung vorhersagt. Dieses Kriterium ist sowohl für den laminaren als auch für den turbulenten Strömungszustand verwendbar, wodurch anwendungstechnologisch bedeutsame Fragestellungen bezüglich der Stabilität beantwortet werden können.Die Ergebnisse sind unter einer modifizierten Betrachtungsweise auf Polymerschmelzen übertragbar.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Publication Date: 2011-06-14
    Description: Author(s): J. M. Mueller, R. J. Charity, R. Shane, L. G. Sobotka, S. J. Waldecker, W. H. Dickhoff, A. S. Crowell, J. H. Esterline, B. Fallin, C. R. Howell, C. Westerfeldt, M. Youngs, B. J. Crowe, III, and R. S. Pedroni Neutron elastic-scattering angular distributions were measured at beam energies of 11.9 and 16.9 MeV on 40,48 Ca targets. These data plus other elastic-scattering measurements, total and reaction cross-sections measurements, ( e , e ′ p ) data, and single-particle energies for magic and doubly magic nuclei... [Phys. Rev. C 83, 064605] Published Mon Jun 13, 2011
    Keywords: Nuclear Reactions
    Print ISSN: 0556-2813
    Electronic ISSN: 1089-490X
    Topics: Physics
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  • 7
    Publication Date: 2014-08-13
    Description: This work employs in situ measurement data and constructive simulations to examine the underlying physical mechanisms that drive spacecraft plume interactions with the space environment in low Earth orbit. The study centers on observations ofthe enhanced flux of plasma generated during a maneuver of Space Shuttle Endeavour as part of the Sensor Test for Orion Relative Navigation Risk Mitigation (STORRM) experiment in May 2011. The Canary electrostatic analyzer (ESA) instrument mounted on the port-side truss of the International Space Station (ISS) indicated an elevated ion current during the shuttle maneuver. The apparent source of enhanced ion current is a result of interaction of the spacecraft thruster plume with the rarefied ambient ionosphere, which generates regions of relatively high-density plasma through charge exchange between the neutral plume and ambient ions. To reconstruct this event, unsteady simulation data were generated using a combined direct simulation Monte Carlo/Particle in Cell methodology, which employed detailed charge-exchange cross section data and a magnetic field model. The simulation provides local plasma characteristics at the ESA sensor location, and a sensor model is subsequently used to transform the local properties into a prediction of measured ion current. The predicted and observed total current are presented as a function of time over a 30 second period of pulsed thruster firings. A strong correlation is observed in the temporal characteristics of the simulated and measured total current, and good agreement is also achieved in the total current predicted by the model. These results support conclusions that: (1) the enhanced flux of plasma observed by the ESA instrument is associated with Space Shuttle thruster firings, and (2) the simulation model captures the essential features of the plume interactions based on the observation data.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 8
    Publication Date: 1992-06-01
    Print ISSN: 0029-8549
    Electronic ISSN: 1432-1939
    Topics: Biology
    Published by Springer
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  • 9
    Publication Date: 1985-09-10
    Print ISSN: 0148-0227
    Electronic ISSN: 2156-2202
    Topics: Geosciences
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  • 10
    Publication Date: 1981-02-10
    Print ISSN: 0148-0227
    Electronic ISSN: 2156-2202
    Topics: Geosciences
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