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- Kierulf, H P, et al.
(författare)
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Seasonal glacier and snow loading in Svalbard recovered from geodetic observations
- 2022
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Ingår i: Geophysical Journal International. - : Oxford University Press (OUP). - 0956-540X .- 1365-246X. ; 229:1, s. 408-425
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Tidskriftsartikel (refereegranskat)abstract
- We processed time-series from seven Global Navigation Satellite System (GNSS) stations and one Very Long Baseline Interferometry (VLBI) station in Svalbard. The goal was to capture the seasonal vertical displacements caused by elastic response of variable mass load due to ice and snow accumulation. We found that estimates of the annual signal in different GNSS solutions disagree by more than 3 mm which makes geophysical interpretation of raw GNSS time-series problematic. To overcome this problem, we have used an enhanced Common Mode (CM) filtering technique. The time-series are differentiated by the time-series from remote station BJOS with known mass loading signals removed a priori. Using this technique, we have achieved a substantial reduction of the differences between the GNSS solutions. We have computed mass loading time-series from a regional Climatic Mass Balance (CMB) and snow model that provides the amount of water equivalent at a 1 km resolution with a time step of 7 d. We found that the entire vertical loading signal is present in data of two totally independent techniques at a statistically significant level of 95 per cent. This allowed us to conclude that the remaining errors in vertical signal derived from the CMB model are less than 0.2 mm at that significance level. Refining the land water storage loading model with a CMB model resulted in a reduction of the annual amplitude from 2.1 to 1.1 mm in the CM filtered time-series, while it had only a marginal impact on raw time-series. This provides a strong evidence that CM filtering is essential for revealing local periodic signals when a millimetre level of accuracy is required.
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- Moen, Oddvar, et al.
(författare)
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Differences in blood activation related to roller/centrifugal pumps and heparin-coated/uncoated surfaces in a cardiopulmonary bypass model circuit
- 1996
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Ingår i: Perfusion. - : SAGE Publications. - 0267-6591 .- 1477-111X. ; 11:2, s. 113-123
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Tidskriftsartikel (refereegranskat)abstract
- An in vitro model cardiopulmonary bypass (CPB) circuit consisting ot tubing, oxygenator and venous reservoirs with either a roller or a centrifugal pump, and with either heparin-coated (Carmeda Bioactive Surface, CBAS) or uncoated surfaces, was studied with respect to 'blood activation', using small-scale-based blood volume (450 + 500 ml). Sixteen circuits were tested in each pump group, eight with and eight without heparin-coated surfaces, by circulating heparinized fresh human blood for 72 hours at 30 degrees C. Blood plasma, sampled at defined intervals, was analysed for haemolysis (lactate dehydrogenase and potassium), complement activation (C3bc and C5b-9 (TCC)), complement lytic inhibitors (vitronectin and clusterin), coagulation activation (fibrinopeptide A), granulocyte (lactoferrin and myeloperoxidase) and platelet (beta-thromboglobulin) activation and contaminating endotoxin. The heparin coating significantly reduced the concentrations of C3bc, TCC, fibrinopeptide A, lactoferrin, myeloperoxidase and beta-thromboglobulin. The two pump types did not differ with respect to these parameters, but the roller pump caused significantly higher increases in plasma LDH and potassium and significantly greater reductions in clusterin and vitronectin than the centrifugal pump. Endotoxin concentration was low at the start and after 24 hours in all groups. These results confirm that heparin-coated CPB surfaces reduce blood activation, and suggest that centrifugal pumps cause less haemolysis and less reduction in lytic complement inhibitors than roller pumps.
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