| 1. |
- Seppä, H., et al.
(författare)
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Spatial structure of the 8200 cal yr BP event in northern Europe
- 2007
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Ingår i: Climate of the Past. - : Copernicus GmbH. - 1814-9324 .- 1814-9332. ; 3:2, s. 225-236
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Tidskriftsartikel (refereegranskat)abstract
- A synthesis of well-dated high-resolution pollen records suggests a spatial structure in the 8200 cal yr BP event in northern Europe. The temperate, thermophilous tree taxa, especially Corylus, Ulmus, and Alnus, decline abruptly between 8300 and 8000 cal yr BP at most sites located south of 61° N, whereas there is no clear change in pollen values at the sites located in the North-European tree-line region. Pollen-based quantitative temperature reconstructions and several other, independent palaeoclimate proxies, such as lacustrine oxygen-isotope records, reflect the same pattern, with no detectable cooling in the sub-arctic region. The observed patterns challenges the general view of the wide-spread occurrence of the 8200 cal yr BP event in the North Atlantic region. An alternative explanation is that the cooling during the 8200 cal yr BP event took place mostly during the winter and spring, and the ecosystems in the south responded sensitively to the cooling during the onset of the growing season. In contrast, in the sub-arctic area, where the vegetation was still dormant and lakes ice-covered, the cold event is not reflected in pollen-based or lake-sediment-based records.
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| 2. |
- Antonsson, S., et al.
(författare)
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A comparative study of the impact of the cooking process on oxygen delignification
- 2003
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Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 18:4, s. 388-394
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Tidskriftsartikel (refereegranskat)abstract
- The impact of oxygen delignification on chemical pulps of a given kappa number manufactured in different ways (using kraft, prehydrolysis kraft and magnesium sulphite cooking) has been investigated. The prehistory of the pulps proves to be a very important factor in determining the response to oxygen delignification, i.e. the degree of delignification. It is shown that this is not due to different amounts of hexenuronic acid (HexA) in the different pulps, although this is an important factor behind the high residual kappa number after oxygen delignification of birch kraft pulp. Oxygen delignification of sulphite pulps proves to be efficient even at kappa numbers significantly lower than 10. These pulps show the greatest yield loss over the oxygen delignification. It is likely that Lignin Carbohydrate Complexes (LCC) complexes play a very important role in limiting the speed of reaction of oxygen delignification. Due to the very different prehistories of the pulps investigated, it is probable that the LCC:s are native and not formed during cooking.
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| 3. |
- Antonsson, T., et al.
(författare)
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The effect of cooling rate on the solidification of INCONEL 718
- 2005
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Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science. - : Springer Science and Business Media LLC. - 1073-5615 .- 1543-1916. ; 36:1, s. 85-96
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Tidskriftsartikel (refereegranskat)abstract
- The superalloy INCONEL 718 (IN718) is a commonly used material in aerospace and turbine components. The advantage of this type of material with sluggish precipitation-hardening kinetics is that IN718 is readily weldable. Both wrought and cast parts are used and welded together. While the alloy has been studied previously, new production processes such as laser treatment demand better knowledge of the solidification process in IN718. especially at high cooling rates. In this investigation. the solidification process was studied over a wide range of cooling rated by three different experimental techniques: differential thermal analysis (DTA), mirror furnace (MF), and levitation casting. The solidification sequence and the reaction temperatures were identified. The microstructure and the change in growth morphology were also studied. Segregation measurements were performed, and the distribution of Nb was analyzed in detail for the different types of samples. because of its strong impact on the solidification sequence and microstructure. New observations are that the latent heat decreases and the effective partition coefficient increases with increasing cooling rate. The diffusion rate also seems to be enhanced in the first part of primary solidified dendrites. It is suggested that the new observations can be explained by an increased number of lattice defects formed in the solid as the cooling rate increases.
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| 4. |
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| 5. |
- Dolhem, Franck, 1975, et al.
(författare)
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Modular synthesis of ChiraClick ligands: A library of P-chirogenic phosphines
- 2007
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Ingår i: Journal of Combinatorial Chemistry. - : American Chemical Society (ACS). - 1520-4774 .- 1520-4766. ; 9:3, s. 477-486
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Tidskriftsartikel (refereegranskat)abstract
- A library of novel and diverse P-chirogenic phosphine ligands containing a triazole moiety (ChiraClick ligands) were prepared in high yield in a modular fashion that allows for variation of both the phosphine and the triazole structure, as well as giving access to the two enantiomers of the ligand.
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| 6. |
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| 7. |
- Ekmark, I., et al.
(författare)
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Fluid and kinetic studies of tokamak disruptions using Bayesian optimization
- 2024
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Ingår i: Journal of Plasma Physics. - : Cambridge University Press (CUP). - 0022-3778 .- 1469-7807. ; 90:3
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Tidskriftsartikel (refereegranskat)abstract
- When simulating runaway electron dynamics in tokamak disruptions, fluid models with lower numerical cost are often preferred to more accurate kinetic models. The aim of this work is to compare fluid and kinetic simulations of a large variety of different disruption scenarios in ITER. We consider both non-activated and activated scenarios; for the latter, we derive and implement kinetic sources for the Compton scattering and tritium beta decay runaway electron generation mechanisms in our simulation tool Dream (Hoppe et al., Comput. Phys. Commun., vol. 268, 2021, 108098). To achieve a diverse set of disruption scenarios, Bayesian optimization is used to explore a range of massive material injection densities for deuterium and neon. The cost function is designed to distinguish between successful and unsuccessful disruption mitigation based on the runaway current, current quench time and transported fraction of the heat loss. In the non-activated scenarios, we find that fluid and kinetic disruption simulations can have significantly different runaway electron dynamics, due to an overestimation of the runaway seed by the fluid model. The primary cause of this is that the fluid hot-tail generation model neglects superthermal electron transport losses during the thermal quench. In the activated scenarios, the fluid and kinetic models give similar predictions, which can be explained by the significant influence of the activated sources on the runaway dynamics and the seed.
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| 8. |
- Hughes, K, et al.
(författare)
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Calmodulin-dependent kinase II mediates T cell receptor/CD3- and phorbol ester-induced activation of IkappaB kinase.
- 2001
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 276:38, s. 36008-36013
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Tidskriftsartikel (refereegranskat)abstract
- Numerous fundamental biological processes involve the NFkappaB family of transcription factors. The mechanisms by which this family of proteins is regulated are therefore of widespread importance. In most cells, NFkappaB is bound to inhibitory IkappaB proteins and sequestered in the cytoplasm. NFkappaB-inducing signals result in activation of a large multisubunit kinase complex, IKK, which phosphorylates IkappaB. IkappaB is subsequently degraded, releasing NFkappaB, which translocates to the nucleus. We previously reported that inhibitors of the calcium-binding protein calmodulin (CaM) prevent phorbol ester-induced phosphorylation of IkappaB. Here we show that KN93, an inhibitor of CaM-dependent kinases (CaMKs), also inhibits the phosphorylation of IkappaB. The effect of both CaM and CaMK inhibitors on IkappaB phosphorylation is due to the inhibition of the activity of CaMK II because neither drug has any effect when a derivative of CaMK II that is insensitive to these inhibitors is expressed. When CaMK II is inhibited, phorbol ester is no longer able to activate IKK, placing CaMK II in the signaling pathway that leads to IKK activation. CaM and CaMK inhibitors also block T cell receptor/CD3-induced activation but have no effect on the ability of the cytokine tumor necrosis factor alpha or the phosphatase inhibitor calyculin A to induce degradation of IkappaB. Finally we show that expression of a constitutively active CaMK II results in the activation of NFkappaB. The results identify CaMK II as a mediator of IKK activation specifically in response to T cell receptor/CD3 and phorbol ester stimulation.
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| 9. |
- Jarfors, A. E. W, et al.
(författare)
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Deformation enhanced liquid phase sintering (DELPS) : A study on the use of partial adiabatic melting during powder consolidation
- 2002
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Ingår i: Journal of Materials Processing Technology. - 0924-0136 .- 1873-4774. ; 127:2, s. 159-164
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Tidskriftsartikel (refereegranskat)abstract
- The presence of a liquid phase enhances the pore closure of a porous body, which is used in liquid phase sintering (LPS). During LPS, a substantial grain growth may occur by coalescence or Ostwald ripening, thus a short time in the liquid state is advantageous. Furthermore, it has been shown that during the initial stage of LPS, agglomerates are disintegrated and a significant reduction of grain size occurs. Heavy deformation causes an adiabatic temperature increase, which may result in a partial melting of the powder. Short-time duration deformation-assisted LPS, so called deformation enhanced LPS (DELPS), may thus be a suitable route for the fabrication of difficult-to-form materials. The present study is a feasibility test of DELPS. Three different types of materials were tested. The first type was an Al-Si with the possibility to form a large fraction of liquid phase. The second type was a W-based powder mixture yielding a low fraction liquid. The third type was a Ni-Al powder mixture exhibiting an exothermal behaviour when reaction occurs. The powders were hot compacted in a flexible die allowing large deformations. The specimens were examined and the composition of the phases were analysed. All of the samples, but one, showed near full density (>98%). Evidence of melting was found and in the W-base and the Ni-Al powder mixtures, and reaction had occurred in the Ni-Al mixture. © 2002 Elsevier Science B.V. All rights reserved.
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| 10. |
- Kron, J., et al.
(författare)
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Air gap formation during solidification in cylindrical castings of pure aluminium and eutectic Al-Si
- 2002
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Ingår i: International Journal of Cast Metals Research. - : Informa UK Limited. - 1364-0461 .- 1743-1336. ; 14:5, s. 275-285
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Tidskriftsartikel (refereegranskat)abstract
- Casting of aluminium and eutectic Al-Si in a cylindrical mould has been performed. The air gap formed between the inner mould wall and the solidified shell was measured throughout the solidification process. Simultaneously the temperature distribution in the metal and the mould was measured. Calculations of the shrinkage of the metal were performed. The shrinkage due to thermal contraction was found to be too small to fit the measurements. A new model for the solidification process and the air gap formation was used, where the effect of the formation and condensation of lattice defects was considered. The condensation of lattice defects was used to explain the shrinkage and the air gap found experimentally.
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