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| 2. |
- Abrahamsson, Katarina, 1957, et al.
(författare)
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Variations of biochemical parameters along a transect in the Southern Ocean, with special emphasis on volatile halogenated organic compounds
- 2004
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Ingår i: Deep-sea research. Part II, Topical studies in oceanography. - : Elsevier BV. - 0967-0645. ; 51:22-24, s. 2745-2756
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Tidskriftsartikel (refereegranskat)abstract
- A number of parameters of biogeochemical interest were monitored along a north-southerly transect (S 43-S 63degrees) in the Atlantic Sector of the Southern Ocean from the 8th to the 20th of December 1997. Changes in total dissolved inorganic carbon (C-T) and total alkalinity (A(T)) were mostly dependent on temperature and salinity until the ice edge was reached. After this point only a weak correlation was seen between these. Highest mean values of C-T and A(T) were observed in the Winter Ice Edge (WIE) (2195 and 2319 mumol kg(-1), respectively). Lowest mean AT (2277 mumol kg(-1)) was observed in the Sub-Antarctic Front (SAF), whereas lowest mean CT concentration (2068 mumol kg(-1)) was associated with the Sub-Tropical Front (STF). The pH in situ varied between 8.060 and 8.156 where the highest values were observed in the southern part of the Antarctic Polar Front (APF) and in the Summer Ice Edge (SIE) Region. These peaks were associated with areas of high chlorophyll a (chl a) and tribromomethane values. In the other areas the pH in situ was mainly dependent on hydrography. Bacterial abundance decreased more than one order of magnitude when going from north to south. The decrease appeared to be strongly related to water temperature and there were no elevated abundances at frontal zones. Microphytoplankton dominated in the SAF and APF, whereas the nano- and picoplankton dominated outside these regions. Volatile halogenated compounds were found to vary both with regions, and with daylight. For the iodinated compounds, the highest concentrations were found north of the STF. Brominated hydrocarbons had high concentrations in the STF, but elevated concentrations were also found in the APF and SIE regions. No obvious correlation could be found between the occurrence of individual halocarbons and chl a. On some occasions trichloroethene and tribromomethane related to the presence of nano- and microplankton, respectively.
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- Balksten, Kristin, 1977-, et al.
(författare)
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Permeability in lime plaster in relation to durability of covered materials
- 2004
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Ingår i: Proceedings of the 32nd IAHS World Congress on Housing – Sustainability of the Housing Projects. Trento, Italy 2004.. ; 1
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Konferensbidrag (refereegranskat)abstract
- In restoration of old buildings, lime plasters are used for reasons of authenticity and for technicalreasons as well. In many traditional constructions, there is wood behind the plasters or there is old limemortar in the masonry. For the durability of both these underlying materials, it is important that therelative humidity, RH is not too high under a long time of exposure. This can lead to an accelerateddegradation process of wood and leaching of lime in mortars. To prevent this, the plaster must have aproper permeability.The permeability of a material determines its ability to transport gas and moisture. In lime plasters,permeability affects hardening, carbonation as well as durability of the underlying materials. In thepresent paper, eleven mixtures of lime mortar were studied. The binders used were lime slaked in fourdifferent ways, hydraulic lime and cement.The following measurements were made to analyse the permeability and the pore structure of thesamples. Gas permeability and draining curves give an indication of rate of carbonation. Vapourpermeability shows the ability of plaster to transmit moisture at different RH. Thin sections were madefor microscopically investigations of the samples.The investigations show that both the vapour permeability and gas permeability decreases with anincreased amount of hydraulic binder in the lime plasters. Even small amounts of hydraulic binderhave a significant effect.By connecting these results with examples from reality, the picture becomes clearer. In the medievaltown Visby in Sweden, there are several examples of both rotten wood and disintegrated lime mortars.It is constructions from 13th to 19th centuries and low permeable cementitious plasters have coveredthem all, during the middle of the 20th century.
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| 4. |
- Balksten, Kristin, 1977-, et al.
(författare)
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The pore structure in lime plaster as a key to understanding moisture transportation properties and frost damages
- 2004
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Ingår i: 10th International Congress on the Deterioration and Conservation of Stone. ; 2, s. 1033-1040
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Konferensbidrag (refereegranskat)abstract
- The pore structure is of great importance for a materials ability to hold and transport gasand moisture. In lime plaster, it affects hardening, carbonation as well as durability againstfrost damage. In the present paper, eleven mixtures of lime mortar were studied withrespect to frost damages. The binders used were lime slaked in four different ways,hydraulic lime and cement.Several analyses were made to characterize the transport properties and the porestructure of the materials; density, porosity, sorption curves, capillary water suction andthin sections. This study shows that there is a correlation between pore structure andimportant material properties. By studying these parameters, it is possible to get a goodpicture of the materials ability to resist frost damages. The study also gives an indication ofwhat materials in the mortar such as binders, aggregates and water, give a good porestructure.
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| 6. |
- Blennow, Jörgen, 1966, et al.
(författare)
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Active High Voltage Insulation
- 2002
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Ingår i: Journal of Electrostatics. ; 55:2, s. 159-172
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Tidskriftsartikel (refereegranskat)
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| 7. |
- Carlsson, Per-Anders, 1972, et al.
(författare)
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A transient in situ FTIR and XANES study of CO oxidation over Pt/Al2O3 catalysts
- 2004
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Ingår i: Journal of Catalysis. - : Elsevier BV. - 0021-9517 .- 1090-2694. ; 226:2, s. 422-434
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Tidskriftsartikel (refereegranskat)abstract
- We report experimental results for the oxidation of CO over supported Pt/Al2O3 catalysts operating in oxygen excess at atmospheric pressure. To study the reaction kinetics under transient conditions we have employed step changes of the O2 concentration by intermittently switching off the O2 supply at various temperatures ranging from 523 to 623 K. Detailed in situ FTIR and XANES data for CO coverage and the chemical state of Pt, respectively, are presented together with the CO conversion, which in both cases was monitored by mass spectrometry. A red-shift of the vibrational frequency of linearly bonded CO which correlates with a blue-shift of the Pt LIII binding energy indicates that the Pt catalyst initially is partially oxidised and gradually reduced when the O2 supply is switched off. Control experiments with a NO2 oxidised Pt/Al2O3 catalyst support these findings. A hysteresis in the catalytic activity due to the different rates whereby Pt is oxidised and reduced as a function of gas-phase composition is observed. The activation energy for the Pt oxide reduction (decomposition) process is estimated to be about 50 kJ/mol. The results further emphasise that the conventional three-step Langmuir-Hinshelwood (LH) scheme used to interpret CO oxidation on Pt surfaces must be complemented by a Pt oxidation and reduction mechanism during transient conditions. Moreover, FTIR data suggest that during the extinction, the partially oxidised platinum surface is reduced by chemisorbed CO which should be explicitly accounted for in the modeling of the reaction mechanism.
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