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- Agnemo, Roland, 1944-
(författare)
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Ligniners reaktioner med alkalisk väteperoxid
- 1981
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Under alkaline conditions hydrogen peroxide can be used either as a 1ignin-degrading or a 1ignin-preserving bleaching agent. If heavy metal ions are present and/or silicate is absent in the reaction medium, hydrogen peroxide decomposes via hydroxyl radicals and superoxide ions to oxygen and water. These decomposition products are able to react for example with phenolic lignin structures and thereby cause a partial degradation of lignin. In such a system peroxide could act as a bleaching and delignifying agent at the same time and these properties can be utilized for the bleaching of chemical pulps.In order to elucidate the factors which influence the degradation of phenolic structures by oxidation with alkaline hydrogen peroxide the lignin model compounds-methylsyringyl alcohol was studied.By determining the first order reaction rate constants for the oxidation, the main results which were obtained indicate that phenolic lignin structures can be efficiently degraded especially if:A. The pH in the bleaching liquor is close to the pK -valueàfor hydrogen peroxide.B. The ionic strength in the bleaching medium is as high as possible.C. A fixed amount of heavy metal ions (manganese) is added to the bleaching liquor.In the presence of silicate and diethylentriaminepenta-acetic acid (DTPA) hydrogen peroxide is stabilized against decomposition. Under these conditions alkaline hydrogen peroxide is able to react only with lignin units containing conjugated carbonyl groups such as quinone, aryl-oe-carbonyl and cinnamaldehyd structures, leading to an elimination of the chromophoric structures without any substantial dissolution of lignin. In this part of work we have elucidated the kinetic behavior and the reaction products from lignin model compounds of the aryl-of- carbonyl and cinnamaldehyde types.1,2-Diarylpropan-1,3,-diol structures constitute an important building unit in native lignins. We have demonstrated that under hydrogen peroxide bleaching conditions the model compound 2,3--bis(4-hydroxy-3-methoxyphenyl)-3-ethoxy-propanol was converted to stilbenes, ûe. structures which when present in pulps may contribute to a rapid yellowing. The results obtained with model compounds under simulated lignin retaining bleaching conditions demonstrate that there are possibilities to improve the bleaching of mechanical pulps with hydrogen peroxide if:A. The remaining heavy metal ions complexed with DTPA are present in their lowest valence states.B. The concentration of hydroperoxy ions can be maintained at a high level at the lowest possible pH-value.
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| 2. |
- Allergren, Björn, et al.
(författare)
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Studiehandbok
- 1981
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Rapport (övrigt vetenskapligt/konstnärligt)
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| 3. |
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| 4. |
- Andersson, Per, et al.
(författare)
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Thermal conductivity, heat capacity and phase diagrams of the trichloroethanes under pressure : II. 1,1,2-trichloroethane
- 1981
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Ingår i: Molecular Crystals and Liquid Crystals. - : Taylor & Francis. - 1542-1406 .- 1563-5287 .- 0026-8941. ; 69:1-2, s. 157-166
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Tidskriftsartikel (refereegranskat)abstract
- The thermal conductivity, λ, the heat capacity per unit volume, ρcp, and the phase diagram of 1,1,2-trichloroethane have been investigated in the temperature range 115 to 300 K and at pressures up to 2.5 GPa. The transient hot-wite method was used for the simultaneous measurement of λ and ρcp. Only solid phases I and II were detected, in agreement with the known phase diagram. A phase I-II transition was detected at about 200K and 0.1 GPa, which are conditions under which it had not priviously been observed. It was doubtful whether phase I could be retained metastably to low temperatures at low pressures with the most rapid cooling rate we were able to employ. The thermal resistivity of phase I was proportioned to temperature. The thermal resistivity of phase II contained an additional constant term, which we inferred to be a residual contribution associated with static structural imperfection in this phase.
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| 5. |
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| 6. |
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| 7. |
- Backman, Lars, 1951-
(författare)
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Counter-current distribution of interacting molecules : simulation of distribution behaviour and application to protein-protein interactions
- 1981
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Associations of biological macromolecules with other macromolecules, with larger assemblies of macromolecules and with themselves are widely encountered phenomena. In principle, these interactions can be studied with any method able to differentiate between free molecules and complexes formed. The most extensively used techniques are sedimentation equilibrium and velocity, elastic light scattering and molecular sieve chromatography. This thesis describes an alternative technique; counter-current distribution in aqueous two-phase systems.The counter-current distribution behaviour of a solute depends on its size and surface properties including charge and hydrophobicity. Since the surface properties of a complex formed most probably differ from those of the solutes participating in the association, complex formation should lead to changes in the average distribution behaviour of each solute. Consequently, the presence of one solute should affect the counter-current distribution of another solute if they interact with each other.In order to establish the boundary conditions and the potential as well as limitations of the counter-current distribution technique, the distribution behaviour of homogeneous and heterogeneous association equilibria have been simulated.The model developed for describing the distribution behaviour of heterogeneous associations has been tested using the well characterized interaction between bovine serum albumin and L-tryptophan. It was demonstrated that the theoretical model could predict the experimental distribution behaviour of these two molecules.However, the primary aim of the counter-current distribution experiments has been to gain insight into protein-protein interactions. The metabolically linked enzymes, malate dehydrogenase and aspartate aminotransferase, have been studied in order to determine if there is also a physical link between these two enzymes. The results showed that the cytosolic enzymes as well as the mitochondrial forms associate while the cytoplasmic enzymes did not display any association with the mitochondrial forms. Thus, an organelle specific interaction between malate dehydrogenase and aspartate aminotransferase was demonstrated.Hemoglobin and carbonic anhydrase are functionally linked through the Bohr effect. Thus, the binding of oxygen by hemoglobin in the lung capillaries is associated with the binding of protons which are formed by the catalytic action of carbonic anhydrase. From the counter- current distribution experiments it was possible to conclude that humain carbonic anhydrase II, the high activity form, associates with human hemoglobin whereas carbonic anhydrase I, the low activity form, did not show any affinity for hemoglobin.
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| 8. |
- Batten, David F., 1947-
(författare)
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Entropy, information theory and spatial input-output analysis
- 1981
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Interindustry transactions recorded at a macro level are simply summations of commodity shipment decisions taken at a micro level. The resulting statistical problem is to obtain minimally biased estimates of commodity flow distributions at the disaggregated level, given various forms of aggregated information. This study demonstrates the application of the entropy-maximizing paradigm in its traditional form, together with recent adaptations emerging from information theory, to the area of spatial and non-spatial input-output analysis. A clear distinction between the behavioural and statistical aspects of entropy modelling is suggested. The discussion of non-spatial input-output analysis emphasizes the rectangular and dynamic extensions of Leontief's original model, and also outlines a scheme for simple aggregation, based on a criterion of minimum loss of information. In the chapters on spatial analysis, three complementary approaches to the estimation of interregional flows are proposed. Since the static formulations cannot provide an accurate picture of the gross interregional flows between any two sectors, Leontief's dynamic framework is adapted to the problem. The study concludes by describing a hierarchical system of models to analyse feasible paths of economic development over space and time.
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| 9. |
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| 10. |
- Björkman, Sven, et al.
(författare)
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Thermic and tremorogenic effects of thyroliberin (TRH) in reserpine-treated mice--the non-involvement of GABA-ergic mechanisms.
- 1981
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Ingår i: Journal of Pharmacy and Pharmacology (JPP). - : Oxford University Press (OUP). - 0022-3573 .- 2042-7158. ; 33:9, s. 580-585
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Tidskriftsartikel (refereegranskat)abstract
- Administration of thyroliberin (TRH) to reserpinized mice causes tremor and counteracts the hypothermia in a dose-dependent fashion. The thyroliberin response is inhibited by gamma-hydroxybutyric acid (GHB) and baclofen, but not by other, more specific GABA-ergic agents, such as THIP, gamma-acetylenic GABA, and sodium valproate. Picrotoxin neither potentiates nor inhibits the thyroliberin actions. Nor are the thyroliberin effects dependent on cholinergic, monoaminergic or histaminergic mechanisms. The results repudiate a current hypothesis, that the peptide actions may be mediated by GABA-ergic pathways in the brain.
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