| 1. |
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| 2. |
- Hansen, Helle Ploug, et al.
(författare)
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Kobling mellem teori og praksis
- 2013
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Ingår i: Læring i og af klinisk praksis. - 9788717042421 ; , s. 136-146
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Bokkapitel (refereegranskat)abstract
- Abstract in Danish Kapitlet sætter fokus på kobling mellem teori og praksis. Vi argumenterer for, at teoribevidsthed er nødvendig for studerende og sundhedsprofessionelle, her sygeplejersker, for at kunne reflektere, forstå, håndtere og udvikle handlinger, interaktioner og sygepleje i klinisk praksis. Først redegør vi kort for forståelser af teori og praksis. Dernæst præsenterer vi en case fra klinisk praksis. Vi analyserer casen ved hjælp af en argumentationsmodel, her Toulmins argumentationsmodel. Den kan betragtes som et redskab til at styrke sygeplejestuderendes og vejlederes viden om og færdigheder i at kunne reflektere over og begrunde sin sygepleje. Vi argumenterer for, at en manglende teoribevidsthed kan fratage patienten sin stemme i mødet med sundhedsprofessionelle, og at patienten dermed risikerer at blive ”fængslet” i en magtrelation; samtidigt risikerer de sundhedsprofessionelle at ”fængsle sig selv”, de studerende og hinanden i sygeplejerskekollektivets forforståelser.
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| 3. |
- Iversen, Morten Hvitfeldt, et al.
(författare)
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High resolution profiles of vertical particulate organic matter export off Cape Blanc, Mauritania : Degradation processes and ballasting effects
- 2010
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Ingår i: Deep Sea Research Part I. - : Elsevier BV. - 0967-0637 .- 1879-0119. ; 57:6, s. 771-784
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Tidskriftsartikel (refereegranskat)abstract
- Vertical carbon fluxes between the surface and 2500 m depth were estimated from in situ profiles of particle size distributions and abundances me/asured off Cape Blanc (Mauritania) related to deep ocean sediment traps. Vertical mass fluxes off Cape Blanc were significantly higher than recent global estimates in the open ocean. The aggregates off Cape Blanc contained high amounts of ballast material due to the presence of coccoliths and fine-grained dust from the Sahara desert, leading to a dominance of small and fast-settling aggregates. The largest changes in vertical fluxes were observed in the surface waters (<250 m), and, thus, showing this site to be the most important zone for aggregate formation and degradation. The degradation length scale (L), i.e. the fractional degradation of aggregates per meter settled, was estimated from vertical fluxes derived from the particle size distribution through the water column. This was compared with fractional remineralization rate of aggregates per meter settled derived from direct ship-board measurements of sinking velocity and small-scale 02 fluxes to aggregates measured by micro-sensors. Microbial respiration by attached bacteria alone could not explain the degradation of organic matter in the upper ocean. Instead, flux feeding from zooplankton organisms was indicated as the dominant degradation process of aggregated carbon in the surface ocean. Below the surface ocean, microbes became more important for the degradation as zooplankton was rare at these depths.
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| 4. |
- Iversen, M. H., et al.
(författare)
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Temperature effects on carbon-specific respiration rate and sinking velocity of diatom aggregates - potential implications for deep ocean export processes
- 2013
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 10:6, s. 4073-4085
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Tidskriftsartikel (refereegranskat)abstract
- Most deep ocean carbon flux profiles show low and almost constant fluxes of particulate organic carbon (POC) in the deep ocean. However, the reason for the non-changing POC fluxes at depths is unknown. This study presents direct measurements of formation, degradation, and sinking velocity of diatom aggregates from laboratory studies performed at 15 degrees C and 4 degrees C during a three-week experiment. The average carbon-specific respiration rate during the experiment was 0.12+/-0.03 at 15 degrees C, and decreased 3.5-fold when the temperature was lowered to 4 degrees C. No direct influence of temperature on aggregate sinking speed was observed. Using the remineralisation rate measured at 4 degrees C and an average particle sinking speed of 150 m d(-1), calculated carbon fluxes were similar to those collected in deep ocean sediment traps from a global data set, indicating that temperature plays a major role for deep ocean fluxes of POC.
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| 5. |
- Klawonn, Isabell, et al.
(författare)
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ANAEROBIC PROCESSES IN CYANOBACTERIAL AGGREGATES IN AERATED SURFACE WATERS
- 2013
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Konferensbidrag (refereegranskat)abstract
- The coupling of aerobic and anaerobic processes in cyanobacterial aggregates was investigated. Major pathways of the nitrogen cycle (N2 fixation, nitrification, denitrification, anaerobic ammonium oxidation (anammox) and dissimilatory nitrate reduction to ammonium (DNRA)) were measured via the isotope pairing technique in individual cyanobacterial colonies (Nodularia spumigena) collected in the Baltic Sea. Oxygen and N2O fluxes were measured with microsensors. High rates of dark respiration in Nodularia aggregates reached the limit set by O2-diffusion from the surrounding water to Nodularia colonies creating anoxic microzones within aggregates. The release of NH4+ deriving from N2 fixation supplied the microbial community with dissolve inorganic nitrogen (DIN), and we proofed the potential of nitrification, denitrification and DNRA in anoxic aggregates. Hence, mm-large aggregates of cyanobacteria and attached bacteria are not just sites of N2 fixation but also meet the physical/chemical constraints (oxic–anoxia interface, DIN, OM) for coupled aerobic and anaerobic processes to occur in fully aerated waters. These results may also apply for other particulate material (marine snow) in marine and freshwater systems which would be of major significance for the global nitrogen cycle.
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| 6. |
- Ploug, Helle, et al.
(författare)
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A novel method to measure particle sinking velocity in vitro, and its comparison to three other in vitro methods
- 2010
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Ingår i: Limnology and Oceanography. - : Wiley. - 1541-5856. ; 8, s. 386-393
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Tidskriftsartikel (refereegranskat)abstract
- We introduce a novel, simple method to measure sinking velocity of particles and aggregates in roller tanks. Using this noninvasive method, it is possible to follow changes in sinking velocities on the same aggregates during time and to make paired measurements of aggregate sinking velocity and composition. Particles and aggregates are video recorded in roller tanks, and their sinking velocity is derived from the orbital trajectories. This new method is compared with three other methods (using roller tanks, a vertical flow system, and a sedimentation column), which have not previously been inter-calibrated. Agar spheres and diatom aggregates were used as model particles in all experimental systems. No method showed significantly different sinking velocities of agar spheres compared with those calculated by theory. Paired measurements showed that sinking velocities from 70 to 700 m d(-1) were linearly correlated between different methods. Highest sinking velocities were measured in a sedimentation column followed by those measured in roller tanks and in the vertical flow system, respectively. The average difference of sinking velocity measured with the different methods ranged from 8% to 11% for agar spheres, and up to 20% for diatom aggregates.
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| 7. |
- Ploug, Helle, et al.
(författare)
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Carbon and nitrogen fluxes associated with the cyanobacterium Aphanizomenon sp. in the Baltic Sea
- 2010
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Ingår i: The ISME journal. - : Springer Science and Business Media LLC. - 1751-7362 .- 1751-7370. ; 4:9, s. 1215-1223
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Tidskriftsartikel (refereegranskat)abstract
- Carbon and nitrogen fluxes in Aphanizomenon sp. colonies in the Baltic Sea were measured using a combination of microsensors, stable isotopes, mass spectrometry, and nanoscale secondary ion mass spectrometry (nanoSIMS). Cell numbers varied between 956 and 33 000 in colonies ranging in volume between 1.4 x 10(-4) and 230 x 10(-4) mm(-3). The high cell content and their productivity resulted in steep O-2 gradients at the colony-water interface as measured with an O-2 microsensor. Colonies were highly autotrophic communities with few heterotrophic bacteria attached to the filaments. Volumetric gross photosynthesis in colonies was 78 nmol O-2 mm(-3) h(-1). Net photosynthesis was 64 nmol O-2 mm(-3) h(-1), and dark respiration was on average 15 nmol O-2 mm(-3) h(-1) or 16% of gross photosynthesis. These volumetric photosynthesis rates belong to the highest measured in aquatic systems. The average cell-specific net carbon-fixation rate was 38 and 40 fmol C cell(-1) h(-1) measured by microsensors and by using stable isotopes in combination with mass spectrometry and nanoSIMS, respectively. In light, the net C:N fixation ratio of individual cells was 7.3 +/- 3.4. Transfer of fixed N-2 from heterocysts to vegetative cells was fast, but up to 35% of the gross N-2 fixation in light was released as ammonium into the surrounding water. Calculations based on a daily cycle showed a net C: N fixation ratio of 5.3. Only 16% of the bulk N-2 fixation in dark was detected in Aphanizomenon sp. Hence, other organisms appeared to dominate N-2 fixation and NH4+ release during darkness.
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| 8. |
- Ploug, Helle, et al.
(författare)
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Carbon, nitrogen and O(2) fluxes associated with the cyanobacterium Nodularia spumigena in the Baltic Sea
- 2011
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Ingår i: The ISME Journal. - : Springer Science and Business Media LLC. - 1751-7362 .- 1751-7370. ; 5:9, s. 1549-1558
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Tidskriftsartikel (refereegranskat)abstract
- Photosynthesis, respiration, N(2) fixation and ammonium release were studied directly in Nodularia spumigena during a bloom in the Baltic Sea using a combination of microsensors, stable isotope tracer experiments combined with nanoscale secondary ion mass spectrometry (nanoSIMS) and fluorometry. Cell-specific net C-and N(2)-fixation rates by N. spumigena were 81.6 +/- 6.7 and 11.4 +/- 0.9 fmol N per cell per h, respectively. During light, the net C: N fixation ratio was 8.0 +/- 0.8. During darkness, carbon fixation was not detectable, but N(2) fixation was 5.4 +/- 0.4 fmol N per cell per h. Net photosynthesis varied between 0.34 and 250 nmol O(2) h(-1) in colonies with diameters ranging between 0.13 and 5.0 mm, and it reached the theoretical upper limit set by diffusion of dissolved inorganic carbon to colonies (>1 mm). Dark respiration of the same colonies varied between 0.038 and 87 nmol O(2) h (1), and it reached the limit set by O(2) diffusion from the surrounding water to colonies (>1 mm). N(2) fixation associated with N. spumigena colonies (41mm) comprised on average 18% of the total N(2) fixation in the bulk water. Net NH(4)(+) release in colonies equaled 8-33% of the estimated gross N(2) fixation during photosynthesis. NH(4)(+) concentrations within light-exposed colonies, modeled from measured net NH(4)(+) release rates, were 60-fold higher than that of the bulk. Hence, N. spumigena colonies comprise highly productive microenvironments and an attractive NH(4)(+) microenvironment to be utilized by other (micro) organisms in the Baltic Sea where dissolved inorganic nitrogen is limiting growth.
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| 9. |
- Svedén, Jennie, et al.
(författare)
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Kvävefixerare göder haven
- 2012
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Ingår i: "Havsutsikt". ; :1, s. 12-13
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Tidskriftsartikel (populärvet., debatt m.m.)
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