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- Risgaard-Petersen, N., et al.
(författare)
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Evidence for complete denitrification in a benthic foraminifer
- 2006
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 443:7107, s. 93-96
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Tidskriftsartikel (refereegranskat)abstract
- Benthic foraminifera are unicellular eukaryotes found abundantly in many types of marine sediments. Many species survive and possibly reproduce in anoxic habitats(1), but sustainable anaerobic metabolism has not been previously described. Here we demonstrate that the foraminifer Globobulimina pseudospinescens accumulates intracellular nitrate stores and that these can be respired to dinitrogen gas. The amounts of nitrate detected are estimated to be sufficient to support respiration for over a month. In a Swedish fjord sediment where G. pseudospinescens is the dominant foraminifer, the intracellular nitrate pool in this species accounted for 20% of the large, cell-bound, nitrate pool present in an oxygen-free zone. Similarly high nitrate concentrations were also detected in foraminifera Nonionella cf. stella and a Stainforthia species, the two dominant benthic taxa occurring within the oxygen minimum zone of the continental shelf off Chile. Given the high abundance of foraminifera in anoxic marine environments(1-3), these new findings suggest that foraminifera may play an important role in global nitrogen cycling and indicate that our understanding of the complexity of the marine nitrogen cycle is far from complete.
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- Schmid, M. C., et al.
(författare)
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Anaerobic ammonium-oxidizing bacteria in marine environments: widespread occurrence but low diversity
- 2007
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Ingår i: Environmental Microbiology. - : Wiley. - 1462-2912 .- 1462-2920. ; 9:6, s. 1476-1484
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Tidskriftsartikel (refereegranskat)abstract
- Laboratory and field studies have indicated that anaerobic ammonium oxidation (anammox) is an important process in the marine nitrogen cycle. In this study 11 additional anoxic marine sediment and water column samples were studied to substantiate this claim. In a combined approach using the molecular methods, polymerase chain reaction (PCR), qualitative and quantitative fluorescence in situ hybridization (FISH), as well as N-15 stable isotope activity measurements, it was shown that anammox bacteria were present and active in all samples investigated. The anammox activity measured in the sediment samples ranged from 0.08 fmol cell(-1) day(-1) N-2 in the Golfo Dulce (Pacific Ocean, Costa Rica) sediment to 0.98 fmol cell(-1) day(-1) N-2 in the Gullmarsfjorden (North Sea, Sweden) sediment. The percentage of anammox cell of the total population (stained with DAPI) as assessed by quantitative FISH was highest in the Barents Sea (9% +/- 4%) and in most of the samples well over 2%. Fluorescence in situ hybridization and phylogenetic analysis of the PCR products derived from the marine samples indicated the exclusive presence of members of the Candidatus 'Scalindua' genus. This study showed the ubiquitous presence of anammox bacteria in anoxic marine ecosystems, supporting previous observations on the importance of anammox for N cycling in marine environments.
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- Bosch, H, et al.
(författare)
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Needs transilation
- 2008
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Ingår i: GEBURTSHILFE UND FRAUENHEILKUNDE. - 0016-5751. ; 68:4, s. 425-425
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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- Falk, Sven, et al.
(författare)
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Brain area-specific effect of TGF-beta signaling on Wnt-dependent neural stem cell expansion
- 2008
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Ingår i: Cell Stem Cell. - : Elsevier BV. - 1934-5909. ; 2:5, s. 472-483
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Tidskriftsartikel (refereegranskat)abstract
- Regulating the choice between neural stem cell maintenance versus differentiation determines growth and size of the developing brain. Here we identify TGF-beta signaling as a crucial factor controlling these processes. At early developmental stages, TGF-beta signal activity is localized close to the ventricular surface of the neuroepithelium. In the midbrain, but not in the forebrain, Tgfbr2 ablation results in ectopic expression of Wnt1/beta-catenin and FGF8, activation of Wnt target genes, and increased proliferation and horizontal expansion of neuroepithelial cells due to shortened cell-cycle length and decreased cell-cycle exit. Consistent with this phenotype, self-renewal of mutant neuroepithelial stem cells is enhanced in the presence of FGF and requires Wnt signaling. Moreover, TGF-beta signal activation counteracts Wnt-incluced proliferation of midbrain neuroepithelial cells. Thus, TGF-beta signaling controls the size of a specific brain area, the dorsal midbrain, by antagonizing canonical Wnt signaling and negatively regulating self-renewal of neuroepithelial stem cells.
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- Gustafson, Johan, et al.
(författare)
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Oxygen-induced step bunching and faceting of Rh(553): Experiment and ab initio calculations
- 2006
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121 .- 1550-235X. ; 74:3
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Tidskriftsartikel (refereegranskat)abstract
- Using a combined experimental and theoretical approach, we show that the initial oxidation of a Rh(553) surface, a surface vicinal to (111), undergoes step bunching when exposed to oxygen, forming lower-index facets. At a pressure of about 10(-6) mbar and a temperature of 380 degrees C this leads to (331) facets with one-dimensional oxide chains along the steps, coexisting with (111) facets. Further increase of the pressure and temperature results in (111) facets only, covered by an O-Rh-O surface oxide. Our density functional theory calculations provide an atomistic understanding of the observed behavior.
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- Lidin, Sven, et al.
(författare)
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Incommensurate Stistaite-Order Made to Order
- 2009
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 48:12, s. 5497-5503
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Tidskriftsartikel (refereegranskat)abstract
- The stistaite SbSn phase contg. 40-57 at.% Sb was investigated by using single crystal x-ray diffraction and EDX to yield a simple relation between the modulated structure and compn. Stistaite is incommensurately ordered over its entire stability region.
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- Woolhead, G., et al.
(författare)
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"Tu" or "Vous?". A European qualitative study of dignity and communication with older people in health and social care settings
- 2006
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Ingår i: Patient Education and Counseling. - : Elsevier BV. - 0738-3991 .- 1873-5134. ; 61:3, s. 363-371
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Tidskriftsartikel (refereegranskat)abstract
- Objective: To examine the experiences of communication between older people and health and social care providers in six European countries. Methods: Focus groups were carried out with groups of older people (91 focus groups, 391 participants), and health and social care professionals (85 focus groups, 424 participants), in order to gain insights into concepts of good communications. Data collection and analysis continued concurrently according to the method of constant comparison. Results: Different styles of communication between professionals and older people were found to be capable of enhancing or jeopardising dignity. The use of appropriate forms of address, listening, giving people choice, including them, respecting their need for privacy and politeness, and making them feel valued emerged as significant ways to maintain older peoples' sense of self-worth and dignity. Despite being aware of good communication practices, health and social care professionals often failed to implement them. Lack of time, staff, resource scarcity, regulation and bureaucracy were cited as barriers, as was a lack of awareness and effort. Conclusions and practice implications: The findings have important implications for health and social care professionals when they engage with older people. © 2005 Elsevier Ireland Ltd. All rights reserved.
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