| 1. |
- Abel, I, et al.
(författare)
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Overview of the JET results with the ITER-like wall
- 2013
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 53:10, s. 104002-
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Tidskriftsartikel (refereegranskat)abstract
- Following the completion in May 2011 of the shutdown for the installation of the beryllium wall and the tungsten divertor, the first set of JET campaigns have addressed the investigation of the retention properties and the development of operational scenarios with the new plasma-facing materials. The large reduction in the carbon content (more than a factor ten) led to a much lower Z(eff) (1.2-1.4) during L- and H-mode plasmas, and radiation during the burn-through phase of the plasma initiation with the consequence that breakdown failures are almost absent. Gas balance experiments have shown that the fuel retention rate with the new wall is substantially reduced with respect to the C wall. The re-establishment of the baseline H-mode and hybrid scenarios compatible with the new wall has required an optimization of the control of metallic impurity sources and heat loads. Stable type-I ELMy H-mode regimes with H-98,H-y2 close to 1 and beta(N) similar to 1.6 have been achieved using gas injection. ELM frequency is a key factor for the control of the metallic impurity accumulation. Pedestal temperatures tend to be lower with the new wall, leading to reduced confinement, but nitrogen seeding restores high pedestal temperatures and confinement. Compared with the carbon wall, major disruptions with the new wall show a lower radiated power and a slower current quench. The higher heat loads on Be wall plasma-facing components due to lower radiation made the routine use of massive gas injection for disruption mitigation essential.
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| 2. |
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| 3. |
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| 4. |
- Kim, Jongsik, et al.
(författare)
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Spatial and temporal variability of xylan distribution in differentiating secondary xylem of hybrid aspen
- 2012
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Ingår i: Planta. - : Springer Science and Business Media LLC. - 0032-0935 .- 1432-2048. ; 235, s. 1315-1330
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Tidskriftsartikel (refereegranskat)abstract
- Xylans occupy approximately one-third of the cell wall components in hardwoods and their chemical structures are well understood. However, the microdistribution of xylans (O-acetyl-4-O-methylglucuronoxylans, AcGXs) in the cell wall and their correlation with functional properties of cells in hardwood xylem is poorly understood. We demonstrate here the spatial and temporal distribution of xylans in secondary xylem cells of hybrid aspen using immunolocalization with LM10 and LM11 antibodies. Xylan labeling was detected earliest in fibers at the cell corner of the S-1 layer, and then later in vessels and ray cells respectively. Fibers showed a heterogeneous labeling pattern in the mature cell wall with stronger labeling of low substituted xylans (lsAcGXs) in the outer than inner cell wall. In contrast, vessels showed uniform labeling in the mature cell wall with stronger labeling of lsAcGXs than fibers. Xylan labeling in ray cells was detected much later than that in fibers and vessels, but was also detected at the beginning of secondary cell wall formation as in fibers and vessels with uniform labeling in the cell wall regardless of developmental stage. Interestingly, pit membranes including fiber-, vessel- and ray-vessel pits showed strong labeling of highly substituted xylans (hsAcGXs) during differentiation, although this labeling gradually disappeared during pit maturation. Together our observations indicate that there are temporal and spatial variations of xylan deposition and chemical structure of xylans between cells in aspen xylem. Differences in xylan localization between aspen (hardwood) and cedar (softwood) are also discussed.
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| 5. |
- Roach, Melissa, et al.
(författare)
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Fructokinase is required for carbon partitioning to cellulose in aspen wood
- 2012
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Ingår i: The Plant Journal. - 0960-7412 .- 1365-313X. ; 70:6, s. 967-977
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Tidskriftsartikel (refereegranskat)abstract
- Sucrose is the main transported form of carbon in several plant species, including Populus species. Sucrose metabolism in developing wood has therefore a central role in carbon partitioning to stem biomass. Half of the sucrose-derived carbon is in the form of fructose, but metabolism of fructose has received little attention as a factor in carbon partitioning to walls of wood cells. We show that RNAi-mediated reduction of FRK2 activity in developing wood of hybrid aspen (Populus tremula × tremuloides) led to the accumulation of soluble neutral sugars and a decrease in hexose phosphates and UDP-glucose, indicating that carbon flux to cell-wall polysaccharide precursors is decreased. Reduced FRK2 activity also led to thinner fiber cell walls with a reduction in the proportion of cellulose. No pleiotropic effects on stem height or diameter were observed. The results establish a central role for FRK2 activity in carbon flux to wood cellulose.
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| 6. |
- Romanelli, F, et al.
(författare)
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Overview of the JET results
- 2011
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 51:9
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Tidskriftsartikel (refereegranskat)abstract
- Since the last IAEA Conference JET has been in operation for one year with a programmatic focus on the qualification of ITER operating scenarios, the consolidation of ITER design choices and preparation for plasma operation with the ITER-like wall presently being installed in JET. Good progress has been achieved, including stationary ELMy H-mode operation at 4.5 MA. The high confinement hybrid scenario has been extended to high triangularity, lower ρ*and to pulse lengths comparable to the resistive time. The steady-state scenario has also been extended to lower ρ*and ν*and optimized to simultaneously achieve, under stationary conditions, ITER-like values of all other relevant normalized parameters. A dedicated helium campaign has allowed key aspects of plasma control and H-mode operation for the ITER non-activated phase to be evaluated. Effective sawtooth control by fast ions has been demonstrated with3He minority ICRH, a scenario with negligible minority current drive. Edge localized mode (ELM) control studies using external n = 1 and n = 2 perturbation fields have found a resonance effect in ELM frequency for specific q95values. Complete ELM suppression has, however, not been observed, even with an edge Chirikov parameter larger than 1. Pellet ELM pacing has been demonstrated and the minimum pellet size needed to trigger an ELM has been estimated. For both natural and mitigated ELMs a broadening of the divertor ELM-wetted area with increasing ELM size has been found. In disruption studies with massive gas injection up to 50% of the thermal energy could be radiated before, and 20% during, the thermal quench. Halo currents could be reduced by 60% and, using argon/deuterium and neon/deuterium gas mixtures, runaway electron generation could be avoided. Most objectives of the ITER-like ICRH antenna have been demonstrated; matching with closely packed straps, ELM resilience, scattering matrix arc detection and operation at high power density (6.2 MW m-2) and antenna strap voltages (42 kV). Coupling measurements are in very good agreement with TOPICA modelling. © 2011 IAEA, Vienna.
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| 7. |
- Sandquist, David, et al.
(författare)
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Anatomical and Immunocoverage Observations on SuSy, C4H, and Pectate Lyase Family Protein Down-regulated Aspens Genotypes
- 2015
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Ingår i: Bioresources. - 1930-2126. ; 10, s. 5016-5029
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Tidskriftsartikel (refereegranskat)abstract
- This study aims to complement previous studies on down-regulation of sucrose synthase and cinnamate 4-hydroxylase in hybrid aspen (Bjurhager et al. 2010; Gerber et al. 2014) with a quantitative anatomical comparison (Sandquist et al. 2015). The main focus was placed on evaluating quantitative modifications to fiber morphology and lignin composition. This was achieved by combining results from light-, electron-, and UV-microscopy together with histochemical staining. Overall there was good agreement between the morphological results in this study compared to the previously published chemical and physical reports, particularly on cinnamate 4-hydroxylase down-regulated aspen. The previously reported statistical correlations between fiber lumen area and plant diameter, and fiber length and tree height (Sandquist et al. 2015) have been further refined. Knock-down of genes coding for biologically important proteins such as sucrose synthase and cinnamate 4-hydroxylase had broad spanning morphological impacts. Down-regulated sucrose synthase genotype showed significantly reduced fiber development, possibly with altered S/G ratio. Down-regulated cinnamate 4-hydroxylase genotype showed an overall reduction of lignin in fibers as indicated from both chemical staining and UV-microscopy measurements. Down-regulated pectate lyase genotype showed no overall significant effects on fiber morphology, ultrastructural, nor lignin staining.
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| 8. |
- Sandquist, David, et al.
(författare)
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Microdistribution of xyloglucan in differentiating Poplar cells
- 2010
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Ingår i: Bioresources. - 1930-2126. ; 5, s. 796-807
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Tidskriftsartikel (refereegranskat)abstract
- Recent studies on the ultrastructure and composition of the gelatinous layer (g-layer) in poplar have reported findings of xyloglucan. Using correlated fluorescence, scanning- and transmission electron microscopy, we found evidence for xyloglucan present in and surrounding the g-layer, using the fucosylated xyloglucan specific CCRC-M1 antibody and the carbohydrate binding module FXG-14b. However, labeling of isolated gelatinous layer remained negative.
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| 9. |
- Sandquist, David, et al.
(författare)
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Microstructural characterization of 12 Poplar genotypes: morphology and composition
- 2010
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The promise of genotypic characterization as a tool, in combination with breeding programs, is to tailor and improve the raw material supply to the biomass industry. Gross chemical analysis can provide an overview of the total changes in chemistry, but only with microscopic analysis can detailed information about the spatial distribution of these changes be attained. Changes brought about by genetic transformation may often be subtle and difficult to define, as one change in biochemistry may lead to multiple changes in morphology and cell wall chemistry. Except in cases where these changes are extreme, which often limits the production of a phenotype. Because of naturally high variability, a complete understanding of genotypic characteristics is difficult without combining morphological and microdistribution measurements with statistical analysis. In the present work we describe the morphology and part of the composition for 12 FuncFiber genotypes. Samples for the genotypes where taken at 20 cm above soil level, and embedded in Technovit and LR White. Semi-thin LR White sections where used for chemical staining, using Toluidine Blue, Phloroglucinol and Maüle Reaction. The Toluidine Blue images were used in combination with the software Image Pro for the morphological measurements. Control staining to verify the lack of tension wood was carried out with Safranin and Astra blue on LR White sections. Semi-thin Technovit sections were used for immunofluorescence staining using the antibodies CCRC-M1 (xyloglucan), CCRC-M8 (arabinogalactan), LM-10 (xylan), JIM-5 and JIM-7 (pectins). To quantify the staining data, a plug-in for ImageJ was developed called FluoroJ. The main trends in the results show that significant differences are found either in morphology or cell wall chemistry for a given genotype, but rarely both. The immunolabelling and staining data presented provides overall trends for the presence of the different chemical components at tissue level. For further study, the material is also available for characterization at cellular and/or cell wall levels. Furthermore, the developed methodology allows for an increase in microscopic throughput, allowing for semi-automatic microscopic characterization and statistical evaluation. The data presented is a single measurement statistical evaluation and multivariate analysis is currently being conducted. In order to determine the effect of genotypes and lines a statistical model was developed
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| 10. |
- Sandquist, David
(författare)
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Poplar wood formation : genotypical influences on structure and chemistry
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Genotypical effects on wood formation in aspen (Populus tremula x tremuloides) have been studied at morphological, ultrastructural and micro-distributional levels. To characterize transgenically induced modifications, light-, fluorescence-, UV-, scanning- and transmission electron microscopy have been applied complemented by immunolabeling, histochemistry, multivariate statistics and image analysis. Tension wood formation in aspen has also been studied with a focus on xyloglucan micro-distribution. To perform quantitative screeing of wood immunofluorescenc, a novel image analysis protocol was developed and applied. The protocol performs immuno-signal isolation to calculate labeling ratio, termed coverage. Coverage is proportional to epitope availability, in relation to immunoprobe performance. The protocol was shown to perform favorably compared to operator supervised analysis and quantification. Morphological characterization of the twelve genotypes showed significant modifications only for fiber properties. Coverage characterization showed significant modifications for LM-10 (xylan) and JIM-5 (pectin) antibody labeling. In the cell wall architecture, structure is often as important as composition. The multivariate analysis confirms previously reported relationships between individual fiber measurements, and highlights novel immunolabeling relationships. The results show that detailed morphological and coverage characterization can be a valuable addition to the semi-high throughput screening of wood tissue. Utilizing two complementary probes the presence of xyloglucan during g-layer formation of tension wood in aspen was shown at the ultrastructural level. The observation of increased xyloglucan labeling between the g-layer and S2 strengthens the hypothesis that xyloglucan acts as conductor of tensional forces between the g-layer and the rest of the fiber wall.
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