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- Nordgren, A, et al.
(författare)
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Tree root and soil heterotrophic respiration as revealed by girdling of boreal Scots pine forest: : extending observations beyond the first year
- 2003
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Ingår i: Plant, Cell and Environment. - : Wiley. - 0140-7791. ; 26:8, s. 1287-1296
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Tidskriftsartikel (refereegranskat)abstract
- Limitations in available techniques to separate autotrophic (root) and soil heterotrophic respiration have hampered the understanding of forest C cycling. The former is here defined as respiration by roots, their associated mycorrhizal fungi and other micro-organisms in the rhizosphere directly dependent on labile C compounds leaked from roots. In order to separate the autotrophic and heterotrophic components of soil respiration, all Scots pine trees in 900 m2 plots were girdled to instantaneously terminate the supply of current photosynthates from the tree canopy to roots. Högberg et al. (Nature 411, 789-792, 2001) reported that autotrophic activity contributed up to 56% of total soil respiration during the first summer of this experiment. They also found that mobilization of stored starch (and likely also sugars) in roots after girdling caused an increased apparent heterotrophic respiration on girdled plots. Herein a transient increase in the δ13C of soil CO2 efflux after girdling, thought to be due to decomposition of 13C-enriched ectomycorrhizal mycelium and root starch and sugar reserves, is reported. In the second year after girdling, when starch reserves of girdled tree roots were exhausted, calculated root respiration increased up to 65% of total soil CO2 efflux. It is suggested that this estimate of its contribution to soil respiration is more precise than the previous based on one year of observation. Heterotrophic respiration declined in response to a 20-day-long 6 °C decline in soil temperature during the second summer, whereas root respiration did not decline. This did not support the idea that root respiration should be more sensitive to variations in soil temperature. It is suggested that above-ground photosynthetic activity and allocation patterns of recent photosynthates to roots should be considered in models of responses of forest C balances to global climate change
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- Ottosson Gadd, Tony, 1969, et al.
(författare)
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A 4G IP based wireless system proposal
- 2002
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Ingår i: Proceedings Radiovetenskap och Kommunikation 2002, Stockholm, Sweden. ; , s. 709-713
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Konferensbidrag (refereegranskat)
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- Ottosson Gadd, Tony, 1969, et al.
(författare)
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Towards 4G IP-based wireless systems
- 2001
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Ingår i: Proceedings Future Telecommunications Conference, Beijing, P.R. China. ; , s. 34-38
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Konferensbidrag (refereegranskat)
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- Ottosson, Tony, et al.
(författare)
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Joint source-channel and multiuser decoding for Rayleigh fading CDMA Channels
- 2000
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Ingår i: IEEE Transactions on Communications. - : IEEE Communications Society. - 0090-6778 .- 1558-0857. ; 48:1, s. 13-16
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Tidskriftsartikel (refereegranskat)abstract
- We consider joint source-channel and multiuser decoding for frequency-selective Rayleigh fading code-division multiple-access channels. The block source-channel encoder is defined by a vector quantizer, We investigate optimal (minimum mean-square error) decoding and user-separated decoding of lower complexity, The studied decoders are soft in the sense that they utilize all soft information available at the receiver. Simulations indicate significant performance gains of the introduced decoders compared with a tandem approach that uses maximum-likelihood multiuser detection plus table-lookup decoding.
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- Svensson, Arne, 1955, et al.
(författare)
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An OFDM based System Proposal for 4G Downlinks
- 2003
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Ingår i: Proceedings International Workshop on Multi-Carrier and Spread Spectrum for Future Generation Wireless Systems, Oberpfaffenhofen, Germany.
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Konferensbidrag (refereegranskat)
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- Törndahl, Tobias, 1974-
(författare)
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Atomic Layer Deposition of Copper, Copper(I) Oxide and Copper(I) Nitride on Oxide Substrates
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Thin films play an important role in science and technology today. By combining different materials, properties for specific applications can be optimised. In this thesis growth of copper, copper(I) oxide and copper(I) nitride on two different substrates, amorphous SiO2 and single crystalline α-Al2O3 by the so called Atomic Layer Deposition (ALD) techniques has been studied. This technique allows precise control of the growth process at monolayer level on solid substrates. Other characteristic features of ALD are that it produces films with excellent step coverage and good uniformity even as extremely thin films on complicated shaped substrates.Alternative deposition schemes were developed for the materials of interest. It was demonstrated that use of intermediate water pulses affected the deposition pathways considerably. By adding water, the films are thought to grow via formation of an oxide over-layer instead of through a direct reaction between the precursors as in the case without water.For growth of copper(I) nitride from Cu(hfac)2 and ammonia no film growth occurred without adding water to the growth process. The Cu3N films could be transformed into conducting copper films by post annealing. In copper growth from CuCl and H2 the water affected film growth on the alumina substrates considerably more than on the fused silica substrates. The existence of surface -OH and/or -NHx groups was often found to play an important role, according to both theoretical calculations and experimental results.
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