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- Backman, J.S.K., et al.
(författare)
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Increased Nitrification in Acid Coniferous Forest Soil Due to High Nitrogen Deposition and Liming
- 2003
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Ingår i: Scandinavian Journal of Forest Research. - : Informa UK Limited. - 0282-7581 .- 1651-1891. ; 18:6, s. 514-524
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Tidskriftsartikel (refereegranskat)abstract
- This study investigated whether liming stimulates the potential nitrification of acid forest soils in southern Sweden, and whether such stimulation (if present) is more pronounced in areas receiving high nitrogen (N) deposition. A short-term (30 h) soil-slurry incubation technique was used, which reduces the risk of bacterial growth, nitrate immobilization and denitrification during the incubation. The nitrate and nitrite produced were measured after biological conversion to nitrous oxide. The investigation was performed 6-7 yrs after the liming at four coniferous forest sites in the central and western parts of southern Sweden, which receive low and high deposition of N, respectively. Overall, liming had increased pH significantly down to 10 cm soil depth, but at 20 cm depth there was no difference between the limed and non-limed soil. In cases when liming had affected the total N pool and the potential nitrification, this was also limited to the uppermost 10 cm. It seems likely that the effects of liming on the potential nitrification were dependent on N availability, which is in turn influenced by N mineralization, trees' demands for N, and atmospheric N inputs. The strongest stimulatory effect of liming on the potential nitrification was seen on the west coast, indicating that these sites had the highest availability of ammonia for nitrifiers. However, liming also increased nitrification at one of the sites in south-central Sweden, which could have been mediated by increased rates of N mineralization.
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- Backman, J.S.K., et al.
(författare)
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Liming induces growth of a diverse flora of ammonia-oxidising bacteria in acid spruce forest soil as determined by SSCP and DGGE
- 2003
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Ingår i: Soil Biology and Biochemistry. - 0038-0717 .- 1879-3428. ; 35:10, s. 1337-1347
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Tidskriftsartikel (refereegranskat)abstract
- The autotrophic ammonia-oxidising bacterial (AOB) community composition was studied in acid coniferous forest soil profiles at a site in southwestern Sweden 6 years after liming. Liming caused a significant increase in pH in the organic horizons, while the mineral soil was unaffected. The AOB communities were studied by single-strand conformation polymorphism (SSCP) in parallel with denaturing gradient gel electrophoresis (DGGE) analysis of partial 16S rRNA genes amplified by PCR using primers reported to be specific for ß-Proteobacteria AOB, followed by nucleotide sequencing. High genetic diversity of Nitrosospira-like sequences was found in the limed soil profiles, whereas no AOB-like sequences were detected in the control soil at any depth, according to both the SSCP and DGGE analyses. This clearly showed that liming induced growth of a diverse flora of AOB at this forest site. Both Nitrosospira cluster 2 and cluster 4 sequences were present in the limed soil profiles, regardless of soil pH, but we found a higher number of sequences affiliated with cluster 4. The high lime dose seemed to affect the AOB community more than the low dose, and its effects reached deeper into the soil profile. Seven different Nitrosospira-like sequences were found 10 cm under the litter layer in the soil limed with the high dose, but only two in the soil amended with the low lime dose. © 2003 Elsevier Ltd. All rights reserved.
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- Backman, L, et al.
(författare)
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Functional changes in brain activity during priming in Alzheimer's disease
- 2000
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Ingår i: JOURNAL OF COGNITIVE NEUROSCIENCE. - : M I T PRESS. - 0898-929X. ; 12:1, s. 134-141
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Tidskriftsartikel (refereegranskat)abstract
- Patients with Alzheimer's disease (AD) are often impaired on certain forms of implicit memory, such as word-stem completion priming (WSCP). Lesion data suggest that deficient WSCP may be associated with abnormal functioning in the posterior neocortex. Usi
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- Bengtsson, M., et al.
(författare)
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Plant odor analysis of apple : Antennal response of codling moth females to apple volatiles during phenological development
- 2001
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Ingår i: Journal of Agricultural and Food Chemistry. - : American Chemical Society (ACS). - 0021-8561 .- 1520-5118. ; 49:8, s. 3736-3741
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Tidskriftsartikel (refereegranskat)abstract
- Volatile compounds were collected from apple branches (Malus domestica) at different developmental stages, and the antennal response of codling moth females (Cydia pomonella) to these compounds was recorded by electroantennography coupled to gas chromatography. Presence of a range of terpenoid compounds, many of which had antennal activity, was characteristic for volatile collections from branches with leaves, and from small green apples. Nine compounds from branches with leaves and green fruit consistently elicited an antennal response: methyl salicylate, (E)-beta -farnesene, fi-caryophyllene, 4,8-dimethyl-1,3(E),7-nonatriene, (Z)3-hexenol, (Z,E)-alpha -farnesene, linalool, germacrene D, and (EE)-alpha -farnesene. The bouquet emitted from flowering branches contained in addition several benzenoid compounds which were not found after bloom. Small green apples, which are the main target of codling moth oviposition during the first seasonal flight period, released very few esters. In comparison, fully grown apples released a large number of esters, but fewer terpenoids. The study of apple volatiles eliciting an antennal response, together with a survey of the seasonal change in the release of these compounds, is the first step toward the identification of volatiles mediating host-finding and oviposition in codling moth females.
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- Brus, E, et al.
(författare)
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Bed Material Consumption in Biomass Fired Fluidised Bed Boilers Due to Risk of Bed Agglomeration : Coating Formation and Possibilities for Regeneration
- 2003
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Ingår i: Industrial Combustion. - 2075-3071. ; :2, s. 1-12
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Tidskriftsartikel (refereegranskat)abstract
- Previous studies have shown that many biomass fuels result in critical agglomeration temperatures in the same range as typical operating process temperatures for fluidised beds. As soon as a sufficiently thick coating on the bed particles has been formed, the risk for severe agglomeration and defluidisation is often significant. Frequent bed change is therefore the normally method applied to ensure problem-free operation, but this is associated with additional costs and not sustainable on a long-term basis.The objectives of the present work were therefore to; i) collect full-scale bed material samples to determine coating characteristics and growth as functions of time; ii) estimate the critical coating thickness/age of the bed particles by SEM/EDS analysis and experimental determinate the agglomeration temperatures for the collected bed material; iii) experimentally evaluate if size fractionation and mechanical treatment could be used to reduce the bed material consumption.Bed material samples from two bubbling and two circulating full-scale fluidised bed boilers, with previous documented bed agglomeration problems, were collected. All plants used typical wood-based fuel mixtures. The coating formation rates on the bed particles were found to be significant, with an initial rate of some mm per day, but decreasing with time. The coating material was generally found to consist of Ca- and Mg-silicates as well as P, although the form in which it was present was not determined. The experimentally determined fuel specific agglomeration temperatures were found to agree well with the corresponding critical temperatures for the full-scale bed materials, as well as with the experiences reported by the different plant operators. The critical coating thickness was found to be relatively thin (
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