| 11. |
- 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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| 12. |
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| 13. |
- Abramowicz, Marek A, 1945, et al.
(författare)
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Interpreting black hole QPOs
- 2004
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Ingår i: AIP Conference Proceedings. - 0094-243X. ; 714, s. 21-28
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- n all the microquasars with two hHz QPOs, the ratio of the frequencies is 3:2, supporting our suggestion that a non-linear resonance between two modes of oscillation in the accretion disk plays a role in exciting the observed modulations of the X-ray flux. We discuss the evidence in favor of this interpretation, and we relate the black hole spin to the frequencies expected for various types of resonances that may occur in nearly Keplerian disks in strong gravity. For those microquasars where the mass of the central X-ray source is known, the black hole spin can be deduced from a comparison of the observed and expected frequencies.
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| 14. |
- Abramowicz, Marek A, 1945, et al.
(författare)
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The importance of discovering A 3:2 twin-peak quasi-periodic oscillation in an ultraluminous X-ray source, or how to solve the puzzle of intermediate-mass black holes
- 2004
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Ingår i: Astrophysical Journal, Letters. - 0067-0049. ; 609:2, s. L63-L65
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Tidskriftsartikel (refereegranskat)abstract
- Recently, twin-peak quasi-periodic oscillations (QPOs) have been observed in a 3:2 ratio for three Galactic black hole microquasars with frequencies that have been shown to scale as 1/M, as expected for general relativistic motion near a black hole. It may be possible to extend this result to distinguish between the following two disparate models that have been proposed for the puzzling ultraluminous X-ray sources (ULXs): (1) an intermediate-mass black hole (M~103 M⊙) radiating very near the Eddington limit and (2) a conventional black hole (M~10 M⊙) accreting at a highly super-Eddington rate with its emission beamed along the rotation axis. We suggest that one could discriminate between these models by detecting the counterpart of a Galactic twin-peak QPO in a ULX: the expected frequency for the intermediate-mass black hole model is only about 1 Hz, whereas for the conventional black hole model the expected frequency would be the ~100 Hz value observed for the Galactic microquasars.
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| 15. |
- Abramowicz, Marek A, 1945, et al.
(författare)
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Twin peak QPOs frequencies in microquasars and Sgr A*. The resonance and other orbital models
- 2004
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Ingår i: Proceedings of RAGtime 4/5 Workshops on black holes and neutron stars, 14-16/13-15 October 2002/2003. - 8072482424
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In all four microquasars which show twin peak kHz QPOs, the ratio of the two frequencies is 3:2. This rather strongly supports the suggestion by Abramowicz, M. A. and Kluzniak [W. Abramowicz, M. A. and Kluzniak, W., (2001). A precise determination of black hole spin in GRO J1655-40. Astronomy and Astrophysics, 374:L19] that twin peak kHz QPOs are due to a resonance between some modes of accretion disk oscillations. Detailed studies of this suggestion revealed that several such non-linear resonances are present in nearly Keplerian disks in strong gravity. Here, we fit to observations predictions of the resonance hypothesis for two particular types of non-linear resonances between vertical and radial epicyclic frequencies. For three microquasars with known masses, the fits give an accurate estimate of the spin.
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| 16. |
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| 17. |
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| 18. |
- Adelbratt, Thomas, 1949
(författare)
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Beliefs about real life decision strategies
- 2004
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- What kind of behavior is seen as most adaptive for everyday decision makers? How do they invest their mental energy? Is it in complex information integration, which traditionally is considered rational, or in other cognitive procedures? With these underlying questions 25 subjects were encouraged to give written accounts of their decision strategies in real life. The instructions promoted sequential descriptions without being too obtrusive. All reports were contents analyzed and condensed to six reflective and six intuitive categories with contrasting qualities. These indicated that the subjects had good analytic intentions, but rarely employed any demanding strategies and were almost unaware of the possibility of using different integration rules. The subjects rather preferred other sorts of deliberation, in areas like strategic planning, social adjustment, value co-ordination, and assessment calibration. Several of these activities were focused on evaluative phenomena and quite often prepared for systematic restructuring of values, criterion levels, and attribute weights to simplify the process. A strong regulating factor was the intuitive influence from emotions, established principles, identity concepts, and wishful thinking. It is concluded that the relative priority of evaluative phenomena has certain advantages for the individual. The strategy is probably easier to understand and to justify. It has a more natural relation to fundamental needs, identity aspects, social ties, etc. Finally, it is in direct contact with the individual?s emotional life and thus a connecting bridge between analysis and intuition.
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| 19. |
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| 20. |
- Adermark, Louise, 1974, et al.
(författare)
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Ethanol acutely decreases astroglial gap junction permeability in primary cultures from defined brain regions
- 2004
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Ingår i: Neurochemistry International. - : Elsevier BV. - 0197-0186. ; 45:7, s. 971-978
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Tidskriftsartikel (refereegranskat)abstract
- The acute effect of hyperosmotic ethanol on gap junction permeability was examined in astroglial cells in primary culture from five different brain regions. Gap junction permeability was analyzed by measuring dye spreading from cell to cell with the low molecular weight dye Lucifer Yellow. Ethanol concentrations 25-300 mM significantly decreased dye spreading in cultures from the cerebral cortex in a dose-dependent but time-independent manner for up to 60 min. Besides cerebral cortex, exposure to 150 mM ethanol decreased dye spreading in astroglial cultures from the hippocampus and from the brain stem, while cultures from the olfactory bulb and from the hypothalamus were not significantly affected. The ethanol-induced decrease in dye spreading in cultures from the cerebral cortex was not mediated through changes in cell volume, osmolarity, protein kinase C (PKC) phosphorylation, intracellular pH, or intracellular calcium concentration ([Ca 2+ ] i ). The decrease in dye spreading was abolished upon incubation in sodium-reduced buffer, and after blockage of the Na + /K + /2Cl - cotransporter with furosemide. The results presented here indicate that ethanol-mediated decrease in dye spreading is directly or indirectly dependent on sodium. © 2004 Elsevier Ltd. All rights reserved.
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