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- Eschen, R, et al.
(author)
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Carbon addition alters vegetation composition on ex-arable fields
- 2007
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In: Journal of Applied Ecology. - : Wiley. - 1365-2664 .- 0021-8901. ; 44:1, s. 95-104
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Journal article (peer-reviewed)abstract
- 1. Recent changes in European agricultural policy have led to measures to reverse the loss of species-rich grasslands through the creation of new areas on ex-arable land. Ex-arable soils are often characterized by high inorganic nitrogen (N) levels, which lead to the rapid establishment of annual and fast-growing perennial species during the initial phase of habitat creation. The addition of carbon (C) to the soil has been suggested as a countermeasure to reduce plant-available N and alter competitive interactions among plant species. 2. To test the effect of C addition on habitat creation on ex-arable land, an experiment was set up on two recently abandoned fields in Switzerland and on two 6-year-old restoration sites in the UK. Carbon was added as a mixture of either sugar and sawdust or wood chips and sawdust during a period of 2 years. The effects of C addition on soil parameters and vegetation composition were assessed during the period of C additions and 1 year thereafter. 3. Soil nitrate concentrations were reduced at all sites within weeks of the first C addition, and remained low until cessation of the C additions. The overall effect of C addition on vegetation was a reduction in above-ground biomass and cover. At the Swiss sites, the addition of sugar and sawdust led to a relative increase in legume and forb cover and to a decrease in grass cover. The soil N availability, composition of soil micro-organisms and vegetation characteristics continued to be affected after cessation of C additions. 4. Synthesis and applications. The results suggest that C addition in grassland restoration is a useful management method to reduce N availability on ex-arable land. Carbon addition alters the vegetation composition by creating gaps in the vegetation that facilitates the establishment of late-seral plant species, and is most effective when started immediately after the abandonment of arable fields and applied over several years.
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- Hedlund, Emma, et al.
(author)
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Improved determination of the gas flow rate for UHV and leak metrology with laser refractometry
- 2006
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In: Measurement science and technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 17:10, s. 2767-2772
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Journal article (peer-reviewed)abstract
- A system often used for vacuum metrology purposes in order to calibrate vacuum gauges in the UHV region and to calibrate gas leak rates is the throughput system, employing the continuous ( or dynamic) expansion method. An important component in such systems is the flowmeter, which has to deliver a pure and well-determined gas flow into the system. To determine the generated gas flow, a number of factors including the pressure inside the flowmeter have to be determined. However, it has turned out that the calibration uncertainty when measuring the pressure in the flowmeter gives a main contribution to the total uncertainty (of typically about 0.1%) for the generated flow, thereby limiting the accuracies of the generated vacuum pressure as well as gas leak rates in UHV metrology. A feasibility study is reported in this paper about the possibility of using laser refractometry to monitor dynamic gas density in situ in the flowmeter, as an alternative and possibly more accurate means of determining the generated gas flow, thereby potentially improving the calibration gas leak rates in the range 10(-8) - 10(-4) Pa m(3) s(-1).
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- Hedlund, Julia, 1975, et al.
(author)
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Change of Colloidal and Surface Properties of Mytilus edulis Foot Protein 1 in the Presence of an Oxidation (NaIO4) or a Complex-Binding (Cu2+) Agent
- 2009
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In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 10:4, s. 845-849
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Journal article (peer-reviewed)abstract
- Quartz crystal microbalance with dissipation monitoring (QCM-D) was used to study the viscoelastic properties of the blue mussel, Mytilus edulis, foot protein 1 (Mefp-1) adsorbed on modified hydrophobic gold surfaces. The change in viscoelasticity was studied after addition of Cu2+ and Mn2+, which theoretically could induce metal complex formation with 3,4-dihydroxyphenylalanine (DOPA) moieties. We also used NaIO4, a nonmetal oxidative agent known to induce di-DOPA formation. Reduction in viscoelasticity of adsorbed Mefp-1 followed the order of NaIO4 > Cu2+ > buffer control > Mn2+. We also studied the formation of molecular aggregates of Mefp-1 in solution with the use of dynamic light scattering (DLS). We found that addition of Cu2+, but not Mn2+, induced the formation of larger DLS-detectable aggregates. Minor aggregate formation was found with NaIO4. With the analytical resolution of small angle X-ray scattering (SAXS), we could detect differences in the molecular structure between NaIO4- and Cu2+-treated Mefp-1 aggregates. We concluded from this study that Cu2+ could participate in intermolecular cross-linking of the Mefp-1 molecule via metal complex formation. Metal incorporation in the protein most likely increases the abrasion resistance of the Mefp-1 layer. NaIO4, on the other hand, resulted in mainly intramolecular formation of di-DOPA, but failed to induce larger intermolecular aggregation phenomena. The described methodological combination of surface sensitive methods, like QCM-D, and bulk sensitive methods, like DLS and SAXS, generates high resolution results and is an attractive platform to investigate intra- and intermolecular aspects of assembly and cross-linking of the Mefp proteins.
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