| 1. |
- Abbasi, R., et al.
(författare)
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Observation of seasonal variations of the flux of high-energy atmospheric neutrinos with IceCube
- 2023
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Ingår i: European Physical Journal C. - : Springer. - 1434-6044 .- 1434-6052. ; 83:9
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Tidskriftsartikel (refereegranskat)abstract
- Atmospheric muon neutrinos are produced by meson decays in cosmic-ray-induced air showers. The flux depends on meteorological quantities such as the air temperature, which affects the density of air. Competition between decay and re-interaction of those mesons in the first particle production generations gives rise to a higher neutrino flux when the air density in the stratosphere is lower, corresponding to a higher temperature. A measurement of a temperature dependence of the atmospheric νμ flux provides a novel method for constraining hadronic interaction models of air showers. It is particularly sensitive to the production of kaons. Studying this temperature dependence for the first time requires a large sample of high-energy neutrinos as well as a detailed understanding of atmospheric properties. We report the significant (>10σ) observation of a correlation between the rate of more than 260,000 neutrinos, detected by IceCube between 2012 and 2018, and atmospheric temperatures of the stratosphere, measured by the Atmospheric Infrared Sounder (AIRS) instrument aboard NASA’s AQUA satellite. For the observed 10 % seasonal change of effective atmospheric temperature we measure a 3.5(3) % change in the muon neutrino flux. This observed correlation deviates by about 2-3 standard deviations from the expected correlation of 4.3 % as obtained from theoretical predictions under the assumption of various hadronic interaction models.
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| 2. |
- Abbasi, R., et al.
(författare)
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Limits on Neutrino Emission from GRB 221009A from MeV to PeV Using the IceCube Neutrino Observatory
- 2023
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Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 946:1
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Tidskriftsartikel (refereegranskat)abstract
- Gamma-ray bursts (GRBs) have long been considered a possible source of high-energy neutrinos. While no correlations have yet been detected between high-energy neutrinos and GRBs, the recent observation of GRB 221009A-the brightest GRB observed by Fermi-GBM to date and the first one to be observed above an energy of 10 TeV-provides a unique opportunity to test for hadronic emission. In this paper, we leverage the wide energy range of the IceCube Neutrino Observatory to search for neutrinos from GRB 221009A. We find no significant deviation from background expectation across event samples ranging from MeV to PeV energies, placing stringent upper limits on the neutrino emission from this source.
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| 3. |
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| 4. |
- Leebens-Mack, James H., et al.
(författare)
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One thousand plant transcriptomes and the phylogenomics of green plants
- 2019
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Ingår i: Nature. - : Nature Publishing Group. - 0028-0836 .- 1476-4687. ; 574:7780, s. 679-
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Tidskriftsartikel (refereegranskat)abstract
- Green plants (Viridiplantae) include around 450,000-500,000 species(1,2) of great diversity and have important roles in terrestrial and aquatic ecosystems. Here, as part of the One Thousand Plant Transcriptomes Initiative, we sequenced the vegetative transcriptomes of 1,124 species that span the diversity of plants in a broad sense (Archaeplastida), including green plants (Viridiplantae), glaucophytes (Glaucophyta) and red algae (Rhodophyta). Our analysis provides a robust phylogenomic framework for examining the evolution of green plants. Most inferred species relationships are well supported across multiple species tree and supermatrix analyses, but discordance among plastid and nuclear gene trees at a few important nodes highlights the complexity of plant genome evolution, including polyploidy, periods of rapid speciation, and extinction. Incomplete sorting of ancestral variation, polyploidization and massive expansions of gene families punctuate the evolutionary history of green plants. Notably, we find that large expansions of gene families preceded the origins of green plants, land plants and vascular plants, whereas whole-genome duplications are inferred to have occurred repeatedly throughout the evolution of flowering plants and ferns. The increasing availability of high-quality plant genome sequences and advances in functional genomics are enabling research on genome evolution across the green tree of life.
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| 5. |
- de Graauw, Th., et al.
(författare)
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The Herschel-Heterodyne Instrument for the Far-Infrared (HIFI)
- 2010
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 518, s. L6-
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Tidskriftsartikel (refereegranskat)abstract
- Aims: This paper describes the Heterodyne Instrument for the Far-Infrared (HIFI) that was launched onboard ESA's Herschel Space Observatory in May 2009. Methods: The instrument is a set of 7 heterodyne receivers that are electronically tuneable, covering 480-1250 GHz with SIS mixers and the 1410-1910 GHz range with hot electron bolometer (HEB) mixers. The local oscillator (LO) subsystem comprises a Ka-band synthesizer followed by 14 chains of frequency multipliers and 2 chains for each frequency band. A pair of auto-correlators and a pair of acousto-optical spectrometers process the two IF signals from the dual-polarization, single-pixel front-ends to provide instantaneous frequency coverage of 2 × 4 GHz, with a set of resolutions (125 kHz to 1 MHz) that are better than 0.1 km s-1. Results: After a successful qualification and a pre-launch TB/TV test program, the flight instrument is now in-orbit and completed successfully the commissioning and performance verification phase. The in-orbit performance of the receivers matches the pre-launch sensitivities. We also report on the in-orbit performance of the receivers and some first results of HIFI's operations. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.
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| 6. |
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| 7. |
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| 8. |
- Schweitzer, H., et al.
(författare)
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Innovating carbon-capture biotechnologies through ecosystem-inspired solutions
- 2021
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Ingår i: One Earth. - : Elsevier BV. - 2590-3330 .- 2590-3322. ; 4:1, s. 49-59
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Tidskriftsartikel (refereegranskat)abstract
- Rising atmospheric carbon concentrations affect global health, the economy, and overall quality of life. We are fast approaching climate tipping points that must be addressed, not only by reducing emissions but also through new innovation and action toward carbon capture for sequestration and utilization (CCSU). In this perspective, we delineate next-generation biotechnologies for CCSU supported by engineering design principles derived from ecological processes inspired by three major biomes (plant-soil, deep biosphere, and marine). These are to interface with existing industrial infrastructure and, in some cases, tap into the carbon sink potential of nature. To develop ecosystem-inspired biotechnology, it is important to identify accessible control points of CO2 and CH4 within a given system as well as value-chain opportunities that drive innovation. In essence, we must supplement natural biogeochemical carbon sinks with new bioengineering solutions. © 2020 The Authors Atmospheric carbon emissions are driving global tipping points that must be addressed by reducing emissions in combination with carbon capture for sequestration and utilization. We outline that there is much to be gained by translating ecological processes that underpin global carbon cycles into engineering principles that harness plant-soil, deep biosphere and marine microbiomes for creation of new value chains and access to Earth's major carbon storage pools. Rapid innovation is required, and biotechnology has a certain role to play. © 2020 The Authors
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| 9. |
- Gaudin, J., et al.
(författare)
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Time-resolved investigation of nanometer scale deformations induced by a high flux x-ray beam
- 2011
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Ingår i: Optics Express. - 1094-4087. ; 19:16, s. 15516-15524
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Tidskriftsartikel (refereegranskat)abstract
- We present results of a time-resolved pump-probe experiment where a Si sample was exposed to an intense 15 keV beam and its surface monitored by measuring the wavefront deformation of a reflected optical laser probe beam. By reconstructing and back propagating the wavefront, the deformed surface can be retrieved for each time step. The dynamics of the heat bump, build-up and relaxation, is followed with a spatial resolution in the nanometer range. The results are interpreted taking into account results of finite element method simulations. Due to its robustness and simplicity this method should find further developments at new x-ray light sources (FEL) or be used to gain understanding on thermo-dynamical behavior of highly excited materials. (C) 2011 Optical Society of America
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| 10. |
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| 11. |
- Korchynska, S, et al.
(författare)
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A hypothalamic dopamine locus for psychostimulant-induced hyperlocomotion in mice
- 2022
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Ingår i: Nature communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 13:1, s. 5944-
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Tidskriftsartikel (refereegranskat)abstract
- The lateral septum (LS) has been implicated in the regulation of locomotion. Nevertheless, the neurons synchronizing LS activity with the brain’s clock in the suprachiasmatic nucleus (SCN) remain unknown. By interrogating the molecular, anatomical and physiological heterogeneity of dopamine neurons of the periventricular nucleus (PeVN; A14 catecholaminergic group), we find that Th+/Dat1+ cells from its anterior subdivision innervate the LS in mice. These dopamine neurons receive dense neuropeptidergic innervation from the SCN. Reciprocal viral tracing in combination with optogenetic stimulation ex vivo identified somatostatin-containing neurons in the LS as preferred synaptic targets of extrahypothalamic A14 efferents. In vivo chemogenetic manipulation of anterior A14 neurons impacted locomotion. Moreover, chemogenetic inhibition of dopamine output from the anterior PeVN normalized amphetamine-induced hyperlocomotion, particularly during sedentary periods. Cumulatively, our findings identify a hypothalamic locus for the diurnal control of locomotion and pinpoint a midbrain-independent cellular target of psychostimulants.
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| 12. |
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| 13. |
- Allocca, Giancarlo, et al.
(författare)
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Validation of 'Somnivore', a Machine Learning Algorithm for Automated Scoring and Analysis of Polysomnography Data
- 2019
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Ingår i: Frontiers in Neuroscience. - : Frontiers Media S.A.. - 1662-4548 .- 1662-453X. ; 13
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Tidskriftsartikel (refereegranskat)abstract
- Manual scoring of polysomnography data is labor-intensive and time-consuming, and most existing software does not account for subjective differences and user variability. Therefore, we evaluated a supervised machine learning algorithm, Somnivore (TM), for automated wake-sleep stage classification. We designed an algorithm that extracts features from various input channels, following a brief session of manual scoring, and provides automated wake-sleep stage classification for each recording. For algorithm validation, polysomnography data was obtained from independent laboratories, and include normal, cognitively-impaired, and alcohol-treated human subjects (total n = 52), narcoleptic mice and drug-treated rats (total n = 56), and pigeons (n = 5). Training and testing sets for validation were previously scored manually by 1-2 trained sleep technologists from each laboratory. F-measure was used to assess precision and sensitivity for statistical analysis of classifier output and human scorer agreement. The algorithm gave high concordance with manual visual scoring across all human data (wake 0.91 +/- 0.01; N1 0.57 +/- 0.01; N2 0.81 +/- 0.01; N3 0.86 +/- 0.01; REM 0.87 +/- 0.01), which was comparable to manual inter-scorer agreement on all stages. Similarly, high concordance was observed across all rodent (wake 0.95 +/- 0.01; NREM 0.94 +/- 0.01; REM 0.91 +/- 0.01) and pigeon (wake 0.96 +/- 0.006; NREM 0.97 +/- 0.01; REM 0.86 +/- 0.02) data. Effects of classifier learning from single signal inputs, simple stage reclassification, automated removal of transition epochs, and training set size were also examined. In summary, we have developed a polysomnography analysis program for automated sleep-stage classification of data from diverse species. Somnivore enables flexible, accurate, and high-throughput analysis of experimental and clinical sleep studies.
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| 14. |
- Bjarnadottir, M, et al.
(författare)
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Intracellular accumulation of the amyloidogenic L68Q variant of cystatin C in NIH/3T3 cells
- 1998
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Ingår i: Molecular Pathology. - 1366-8714. ; 51:6, s. 317-326
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Tidskriftsartikel (refereegranskat)abstract
- AIM: To study the cellular transport of L68Q cystatin C, the cystatin variant causing amyloidosis and brain haemorrhage in patients suffering from hereditary cystatin C amyloid angiopathy (HCCAA). METHODS: Expression vectors for wild-type and L68Q cystatin C were constructed and used to transfect mouse NIH/3T3 cells. Stable cell clones were isolated after cotransfection with pSV2neo. Clones expressing human wild-type and L68Q cystatin C were compared with respect to secreted cystatin C by enzyme linked immunosorbent assay (ELISA), and for intracellular cystatin C by western blotting and immunofluorescence cytochemistry. Colocalisation studies in cells were performed by double staining with antibodies against human cystatin C and marker proteins for lysosomes, the Golgi apparatus, or the endoplasmic reticulum, and evaluated by confocal microscopy. RESULTS: Concentrations of human cystatin C secreted from transfected NIH/3T3 cells were similar to those secreted from human cells in culture. In general, clones expressing the gene encoding L68Q cystatin C secreted slightly lower amounts of the protein than clones expressing wild-type human cystatin C. Both immunofluorescence cytochemistry and western blotting experiments showed an increased accumulation of cystatin C in cells expressing the gene encoding L68Q cystatin C compared with cells expressing the gene for the wild-type protein. The intracellularly accumulating L68Q cystatin C was insoluble and located mainly in the endoplasmic reticulum. CONCLUSIONS: The cellular transport of human cystatin C is impeded by the pathogenic amino acid substitution Leu68-- >Gln. The resulting intracellular accumulation and increased localised concentration of L68Q cystatin C might be an important event in the molecular pathophysiology of amyloid formation and brain haemorrhage in patients with HCCAA.
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| 15. |
- Bossard, G., et al.
(författare)
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Integral invariants in maximally supersymmetric Yang-Mills theories
- 2011
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Ingår i: Journal of High Energy Physics (JHEP). - 1126-6708 .- 1029-8479. ; :5, s. 021-
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Tidskriftsartikel (refereegranskat)abstract
- Integral invariants in maximally supersymmetric Yang-Mills theories are discussed in spacetime dimensions 4 <= D <= 10 for SU(k) gauge groups. It is shown that, in addition to the action, there are three special invariants in all dimensions. Two of these, the single-and double-trace F-4 invariants, are of Chern-Simons type in D = 9, 10 and BPS type in D <= 8, while the third, the double-trace of two derivatives acting on F-4, can be expressed in terms of a gauge-invariant super-D-form in all dimensions. We show that the super-ten-forms for D = 10 F-4 invariants have interesting cohomological properties and we also discuss some features of other invariants, including the single-trace d(2)F(4), which has a special form in D = 10. The implications of these results for ultra-violet divergences are discussed in the framework of algebraic renormalisation.
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| 16. |
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| 17. |
- Croot, P. L., et al.
(författare)
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Trace metal/phytoplankton interactions in the Skagerrak
- 2002
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Ingår i: Journal of Marine Systems. - 0924-7963. ; 35:1-2, s. 39-60
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Tidskriftsartikel (refereegranskat)abstract
- Algal community species composition, as estimated by high performance liquid chromatography (HPLC) pigments and microscopy analysis, and trace metal speciation (Cu and Co) and distributions (Fe, Zn, Co and Cu) were measured along a summer transect across the Skagerrak. In waters of Baltic origin, with elevated trace metals levels, but very low macronutrients, a mix of dinoflagellates and haptophytes dominated the low biomass. In the Jutland current, which had high dissolved iron concentrations, a mixed bloom (4-6 mug/l chl a) of diatoms (major species-Leptocylindricus danica) and dinoflagellates (Ceratium sp.) was present. In the waters of the central Skagerrak derived from the North Sea, below the low salinity Baltic water, a large diatom (major species-L. danica) bloom (7.7 mug/l) was present at 35 in. This bloom formed below the pycnocline. and was located at the nutricline for silicate. The lowest concentrations of trace metals were found in the water of North Sea origin. Synechocoecus-like cyanobacteria were observed in the upper waters across the survey area, as were strong binding ligands for Cu, but no clear numerical relationship existed between them, as had been observed by Moffett [Deep-Sea Res. 42 (1995) 1273]m the Sargasso Sea. The [Co]/[Zn] hypothesis of Sunda and Huntsman [Limnol. Oceanogr, 40 (1995) 1404] for coccolithophorids and diatoms was examined using the field data collected. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 18. |
- Flivik, Gunnar, et al.
(författare)
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Improved acetabular pressurization gives better cement penetration : In vivo measurements during total hip arthroplasty
- 2004
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Ingår i: The Journal of Arthroplasty. - : Elsevier BV. - 0883-5403 .- 1532-8406. ; 19:7, s. 911-918
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Tidskriftsartikel (refereegranskat)abstract
- During total hip arthroplasty, the intraoperative cementation pressure was measured inside one of the acetabular anchorage holes. Patients were randomized to pressurization of cement with either a conventional pressurizer or a sequential method including individual pressurization of each anchorage hole. The pressure was correlated to the cement penetration measured on digital radiographs. The early peak pressures were higher for the sequential method, resulting in a significantly better penetration of 2.8 mm compared with 0.7 mm with the conventional pressurizer. We found a strong correlation between early peak cementation pressures and cement penetration into the cancellous bone of the anchoring holes, indicating a cause-effect relationship at this early stage. The highest peak pressures were achieved during the later cup insertion, but these pressures did not correlate with the cement penetration. We conclude that conventional methods for cement pressurization in the acetabulum may not be optimal. © 2004 Elsevier Inc. All rights reserved.
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| 19. |
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| 20. |
- Gromada, J, et al.
(författare)
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Glucagon-like peptide I increases cytoplasmic calcium in insulin-secreting beta TC3-cells by enhancement of intracellular calcium mobilization
- 1995
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Ingår i: Diabetes. - : American Diabetes Association. - 1939-327X .- 0012-1797. ; 44:7, s. 767-774
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Tidskriftsartikel (refereegranskat)abstract
- In the insulin-secreting beta-cell line beta TC3, stimulation with 11.2 mmol/l glucose caused a rise in the intracellular free Ca2+ concentration ([Ca2+]i) in only 18% of the tested cells. The number of glucose-responsive cells increased after pretreatment of the cells with glucagon-like peptide I (GLP-I)(7-36)amide and at 10(-11) mol/l; 84% of the cells responded to glucose with a rise in [Ca2+]i. GLP-I(7-36)amide induces a rapid increase in [Ca2+]i only in cells exposed to elevated glucose concentrations (> or = 5.6 mmol/l). The action of GLP-I(7-36)amide and forskolin involved a 10-fold increase in cytoplasmic cAMP concentration and was mediated by activation of protein kinase A. It was not associated with an effect on the membrane potential but required some (small) initial entry of Ca2+ through voltage-dependent L-type Ca2+ channels, which then produced a further increase in [Ca2+]i by mobilization from intracellular stores. The latter effect reflected Ca(2+)-induced Ca2+ release and was blocked by ryanodine. Similar increases in [Ca2+]i were also observed in voltage-clamped cells, although there was neither activation of a background (Ca(2+)-permeable) inward current nor enhancement of the voltage-dependent L-type Ca2+ current. These observations are consistent with GLP-I(7-36) amide inducing glucose sensitivity by promoting mobilization of Ca2+ from intracellular stores. We propose that this novel action of GLP-I(7-36)amide represents an important factor contributing to its insulinotropic action.
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| 21. |
- Gudberg, Christel, et al.
(författare)
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Individual differences in slow wave sleep architecture relate to variation in white matter microstructure across adulthood
- 2022
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Ingår i: Frontiers in Aging Neuroscience. - : Frontiers Media S.A.. - 1663-4365. ; 14
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Tidskriftsartikel (refereegranskat)abstract
- Sleep plays a key role in supporting brain function and resilience to brain decline. It is well known that sleep changes substantially with aging and that aging is associated with deterioration of brain structure. In this study, we sought to characterize the relationship between slow wave slope (SWslope)—a key marker of sleep architecture and an indirect proxy of sleep quality—and microstructure of white matter pathways in healthy adults with no sleep complaints. Participants were 12 young (24–27 years) and 12 older (50–79 years) adults. Sleep was assessed with nocturnal electroencephalography (EEG) and the Pittsburgh Sleep Quality Index (PSQI). White matter integrity was assessed using tract-based spatial statistics (TBSS) on tensor-based metrics such as Fractional Anisotropy (FA) and Mean Diffusivity (MD). Global PSQI score did not differ between younger (n = 11) and older (n = 11) adults (U = 50, p = 0.505), but EEG revealed that younger adults had a steeper SWslope at both frontal electrode sites (F3: U = 2, p < 0.001, F4: U = 4, p < 0.001, n = 12 younger, 10 older). There were widespread correlations between various diffusion tensor-based metrics of white matter integrity and sleep SWslope, over and above effects of age (n = 11 younger, 9 older). This was particularly evident for the corpus callosum, corona radiata, superior longitudinal fasciculus, internal and external capsule. This indicates that reduced sleep slow waves may be associated with widespread white matter deterioration. Future studies should investigate whether interventions targeted at improving sleep architecture also impact on decline in white matter microstructure in older adults.
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| 22. |
- Halbach, Laura, et al.
(författare)
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Tidewater Glaciers and Bedrock Characteristics Control the Phytoplankton Growth Environment in a Fjord in the Arctic
- 2019
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Ingår i: Frontiers in Marine Science. - : Frontiers Media SA. - 2296-7745. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- Meltwater discharge from tidewater glaciers impacts the adjacent marine environment. Due to the global warming, tidewater glaciers are retreating and will eventually terminate on land. Yet, the mechanisms through which meltwater runoff and subglacial discharge from tidewater glaciers influence marine primary production remain poorly understood, as data in close proximity to glacier fronts are scarce. Here, we show that subglacial meltwater discharge and bedrock characteristics of the catchments control the phytoplankton growth environment inside the fjord, based on data collected in close proximity to tidewater glacier fronts in Kongsfjorden, Svalbard from 26 to 31 July 2017. In the southern part of the inner fjord, glacial meltwater from subglacial discharge was rich in fine sediments derived from erosion of Devonian Old Red Sandstone and carbonate rock deposits, limiting light availability for phytoplankton (0.6 mg m(-3) Chl a on average, range 0.2-1.9 mg m(-3)). In contrast, coarser sediments derived from gneiss and granite bedrock and lower subglacial discharge rates were associated with more favourable light conditions facilitating a local phytoplankton bloom in the northern part of the inner fjord with mean Chl a concentration of 2.8 mg m(-3) (range 1.3-7.4 mg m(-3)). In the northern part, glacier meltwater was a direct source of silicic acid through weathering of the silica-rich gneiss and granite bedrock. Upwelling of the subglacial freshwater discharge plume at the Kronebreen glacier front in the southern part entrained large volumes of ambient, nutrient-rich bottom waters which led to elevated surface concentrations of ammonium, nitrate, and partly silicic acid. Total dissolved inorganic nitrogen transported to the surface with the upwelling of the subglacial discharge plume has a significant potential to enhance summer primary production in Kongsfjorden, with ammonium released from the seafloor being of particular importance. The transition from tidewater to land-terminating glaciers may, thus, reduce the input of nutrients to the surface layer with negative consequences for summer productivity.
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| 23. |
- Helge, E. Wulff, et al.
(författare)
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BMD in elite female triathletes is related to isokinetic peak torque without any association to sex hormone concentrations
- 2012
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Ingår i: Journal of Sports Medicine and Physical Fitness. - : Edizioni Minerva Medica. - 0022-4707 .- 1827-1928. ; 52:5, s. 489-500
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Tidskriftsartikel (refereegranskat)abstract
- Aim. Female endurance athletes suffering from low energy availability and reproductive hormonal disorders are at risk of low BMD. Muscle forces acting on bone may have a reverse site-specific effect. Therefore we wanted to test how BMD in female elite triathletes was associated to isokinetic peak torque (IPT) and reproductive hormone concentrations (RHC). A possible effect of oral contraceptives (OCON's) is taken into consideration. Methods. Eight female elite triathletes (training 8-24 hrs/wk) and seven sedentary controls, age 21-37 years, participated. Total body and regional BIVID (g.cm(-2)) were measured by DXA. IPT were measured during knee extension, and trunk extension and flexion (Nm). Serum RHC and biochemical bone markers were evaluated. Energy balance was estimated from 7-days training-and weighed food records. Results. Despite a high training volume, BMD in triathletes was not higher than in controls. In triathletes trunk flexion IPT, but not RHC, was a strong predictor of BMD in both total body and femur (0.70
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| 24. |
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| 25. |
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| 26. |
- Hoffmann, R., et al.
(författare)
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Implications of Glacial Melt-Related Processes on the Potential Primary Production of a Microphytobenthic Community in Potter Cove (Antarctica)
- 2019
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Ingår i: Frontiers in Marine Science. - : Frontiers Media SA. - 2296-7745. ; 6:October
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Tidskriftsartikel (refereegranskat)abstract
- The Antarctic Peninsula experiences a fast retreat of glaciers, which results in an increased release of particles and sedimentation and, thus, a decrease in the available photosynthetic active radiation (PAR, 400-700 nm) for benthic primary production. In this study, we investigated how changes in the general sedimentation and shading patterns affect the primary production by benthic microalgae, the microphytobenthos. In order to determine potential net primary production and respiration of the microphytobenthic community, sediment cores from locations exposed to different sedimentation rates and shading were exposed to PAR of 0-70 mu.mol photons m(-2)s(-1). Total oxygen exchange rates and microphytobenthic diatom community structure, density, and biomass were determined. Our study revealed that while the microphytobenthic diatom density and composition remained similar, the net primary production of the microphytobenthos decreased with increasing sedimentation and shading. By comparing our experimental results with in situ measured PAR intensities, we furthermore identified microphytobenthic primary production as an important carbon source within Potter Cove's benthic ecosystem. We propose that the microphytobenthic contribution to the total primary production may drop drastically due to Antarctic glacial retreat and related sedimentation and shading, with yet unknown consequences for the benthic heterotrophic community, its structure, and diversity.
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| 27. |
- Jamnik, P., et al.
(författare)
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Bioactivity of Cod and Chicken Protein Hydrolysates before and after in vitro Gastrointestinal Digestion
- 2017
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Ingår i: Food Technology and Biotechnology. - : Faculty of Food Technology and Biotechnology - University of Zagreb. - 1330-9862 .- 1334-2606. ; 55:3, s. 360-367
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Tidskriftsartikel (refereegranskat)abstract
- Bioactivity of cod (Gadus morhua) and chicken (Gallus domesticus) protein hydrolysates before and aft er in vitro gastrointestinal (GI) digestion was investigated using yeast Saccharomyces cerevisiae as a model organism. Both hydrolysates were exposed to in vitro GI digestion prior to cellular exposure to simulate digestion conditions in the human body and therefore investigate the role of modulations in the GI tract on the cell response. The effect of digested and undigested hydrolysates on intracellular oxidation, cellular metabolic energy and proteome level was investigated. No diff erence in the eff ect on intracellular oxidation activity was obtained between cod and chicken hydrolysates, while higher aff ect on intracellular oxidation was provided by digested hydrolysates, with relative values of intracellular oxidation of cod of (70.2 +/- 0.8) and chicken of (74.5 +/- 1.4) % than by undigested ones, where values of cod and chicken were (95.5 +/- 1.2) and (90.5 +/- 0.7) %, respectively. Neither species nor digestion had any eff ect on cellular metabolic energy. At proteome level, digested hydrolysates gave again signifi cantly stronger responses than undigested counterparts; cod peptides here also gave somewhat stronger response than chicken peptides. The knowledge of the action of food protein hydrolysates and their digests within live cells, also at proteome level, is important for further validation of their activity in higher eukaryotes to develop new functional food ingredients, such as in this case chicken and cod muscle-derived peptides.
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| 28. |
- Larsson, Jörgen, et al.
(författare)
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Picosecond X-ray diffraction studies of laser-excited acoustic phonons in InSb
- 2002
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Ingår i: Applied Physics A: Materials Science & Processing. - : Springer Science and Business Media LLC. - 1432-0630 .- 0947-8396. ; 75:4, s. 467-478
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Tidskriftsartikel (refereegranskat)abstract
- We have employed time-resolved X-ray diffraction with picosecond temporal resolution to measure the time-dependent rocking curves of laser-irradiated asymmetrically cut single InSb crystals. Coherent acoustic phonons were excited in the crystals by irradiation with 800-nm, 100-fs laser pulses at irradiances between 0.25 and 12 mJ/cm(2). The induced time-dependent strain profiles (corresponding to the coherent phonons) were monitored by diffracting collimated, monochromatic pulses Of X-rays from the irradiated crystals. Recording of the diffracted radiation with a fast low-jitter X-ray streak camera resulted in an overall temporal resolution of better than 2 ps. The strain associated with the coherent phonons modifies the rocking curve of the crystal in a time-dependent manner, and the rocking curve is recorded by keeping the angle of incidence of the X-rays upon the crystal fixed, but varying the energy of the incident X-rays around a central energy of 8.453 keV (corresponding to the peak of the rocking curve of the unperturbed crystal). The observed time-dependent diffraction from the irradiated crystals is in reasonable agreement with simulations over a wide range of energies from the unperturbed rocking-curve peak.
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| 29. |
- Leu, E., et al.
(författare)
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Fatty acid dynamics during the spring bloom in a High Arctic fjord: importance of abiotic factors versus community changes
- 2006
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Ingår i: Canadian Journal of Fisheries and Aquatic Sciences. - 0706-652X. ; 63:12, s. 2760-2779
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Tidskriftsartikel (refereegranskat)abstract
- We followed the fatty acid composition of particulate organic matter (POM) in a High Arctic fjord (79 degrees N; Svalbard, Norway) during and after the spring bloom. The content of essential polyunsaturated fatty acids (PUFAs) was highest (45% of total fatty acids) at the beginning of the bloom, well before the biomass maximum, and decreased linearly towards the end (30%). During the postbloom period, the concentrations of PUFAs remained stable, between 25% and 30%. Redundancy analysis was used to identify the environmental factors that explained the observed variability in the fatty acid composition of phytoplankton. A particular emphasis was put on the potential influence of high irradiances. During the spring bloom, nutrient availability (Si and N), as well as shifts in phytoplankton community composition and chlorophyll a, were shown to account for much of the pattern in fatty acid composition. During the postbloom period, particularly during periods of stratification, light had a pronounced effect on the fatty acid composition. In general, we found a decrease in the relative amount of PUFAs under high light intensities and nutrient limitation.
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| 30. |
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| 31. |
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| 32. |
- Mariani, G, et al.
(författare)
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Thrombosis in inherited factor VII deficiency
- 2003
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Ingår i: Journal of thrombosis and haemostasis : JTH. - : Elsevier BV. - 1538-7933 .- 1538-7836. ; 1:10, s. 2153-2158
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Tidskriftsartikel (refereegranskat)
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| 33. |
- Naylor, G. A, et al.
(författare)
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A sub-picosecond accumulating streak camera for x-rays
- 2001
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Ingår i: Measurement Science & Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 12:11, s. 1858-1864
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Tidskriftsartikel (refereegranskat)abstract
- An x-ray streak camera system uses a laser triggered photo-conductive switch to synchronize the high voltage ramp applied to its sweep plates to the photo-excitation of a sample. This technique allows the jitter. between successive sweeps to be kept below 100 fs compared to over 1 ps:using classical methods. By accumulating a stable pulsed x-ray signal over many sweeps, a very high dynamic range can be achieved whilst maintaining a sub-picosecond time resolution. The ultimate time resolution is limited by the dispersion of electrons in the streak tube. Whilst triggering with a laser at 900 Hz we have achieved a time resolution (FWHM) of 640 fs at a detection wavelength of 267 nm for a 60 s accumulation period, corresponding to over 50 000 sweeps.
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| 34. |
- Nilsson, Anders K., 1982, et al.
(författare)
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Nutraceutical Fatty Acid Production in Marine Microalgae and Cyanobacteria
- 2020
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Ingår i: Nutraceutical Fatty Acids from Oleaginous Microalgae: A Human Health Perspective. - : Scrivener Publishing LLC. - 9781119631729 ; , s. 23-76
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- In light of the potential negative impacts that fisheries and fish aquaculture have on marine ecosystems, alternative sources for long‐chain polyunsaturated fatty acids (LC‐PUFAs) for human consumption are warranted. n‐3 and n‐6 PUFAs have documented beneficial effects on human health and wellbeing. Of particular interest for their nutraceutical properties are the C20 and C22 LC‐PUFAs, represented by arachidonic acid (ARA) of the n‐6 series and eicosapentaenoic‐ and docosahexaenoic acid (EPA and DHA, respectively) of the n‐3 series. LC‐PUFAs can be endogenously synthesized from shorter‐chain precursor molecules by humans. However, this synthesis is limited to why it is often promoted that preformed LC‐PUFAs should be included in the diet, particularly EPA and DHA. Fatty fish and other seafood accumulate n‐3 LC‐PUFAs produced de novo at lower trophic levels, i.e., by marine microalgae and cyanobacteria, and are the main source of dietary EPA and DHA. In this chapter, we review LC‐PUFA biosynthesis pathways and the current use of photosynthetic marine microbes for nutraceutical oil production. Different cultivation techniques, as well as optimal growth conditions, are discussed in the context of future possibilities of exploring microalgae and cyanobacteria for large‐scale LC‐PUFA production.
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| 35. |
- Nordin, Steven, 1960-, et al.
(författare)
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A longitudinal descriptive study of self-reported abnormal smell and taste perception in pregnant women
- 2004
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Ingår i: Chemical Senses. - : Oxford University Press. - 0379-864X .- 1464-3553. ; 29:5, s. 391-402
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Tidskriftsartikel (refereegranskat)abstract
- Self-reported abnormal sensitivity, qualitative distortions and phantom sensations with respect to smell and taste was assessed with a longitudinal design, based on questions referring to gestational weeks 13–16 and 31–34 of pregnancy in comparison with 9–12 weeks post partum and with non-pregnant women with corresponding time durations and intervals. The results show that abnormal smell and/or taste perception was reported by 76% of the pregnant women, typically believed to be caused by their pregnancy. Increased smell sensitivity was found to be very common at the early stage of pregnancy (67% of all pregnant respondents) and occasionally accompanied by qualitative smell distortions (17%) and phantom smells (14%). The smell abnormalities were less common at the late pregnancy stage and almost absent post partum. Abnormal taste sensitivity was fairly commonly reported (26%), often described as increased bitter sensitivity and decreased salt sensitivity. These results, suggesting that abnormal smell and/or taste perception is experienced by a large majority of pregnant women, imply that further research is needed to understand to what extent these chemosensory changes may underlie food aversions and craving with implications for food intake during pregnancy.
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| 36. |
- Nylandsted Larsen, A., et al.
(författare)
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Tin-vacancy acceptor levels in electron-irradiated n-type silicon
- 2000
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 62:7, s. 4535-4544
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Tidskriftsartikel (refereegranskat)abstract
- Si crystals (n-type, fz) with doping levels between 1.5×1014 and 2×1016 cm-3 containing in addition ∼1018 Sn/cm3 were irradiated with 2-MeV electrons to different doses and subsequently studied by deep level transient spectroscopy, Mössbauer spectroscopy, and positron annihilation. Two tin-vacancy (Sn-V) levels at Ec-0.214 eV and Ec-0.501 eV have been identified (Ec denotes the conduction band edge). Based on investigations of the temperature dependence of the electron-capture cross sections, the electric-field dependence of the electron emissivity, the anneal temperature, and the defect-introduction rate, it is concluded that these levels are the double and single acceptor levels, respectively, of the Sn-V pair. These conclusions are in agreement with electronic structure calculations carried out using a local spin-density functional theory, incorporating pseudopotentials to eliminate the core electrons, and applied to large H-terminated clusters. Thus, the Sn-V pair in Si has five different charge states corresponding to four levels in the band gap.
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| 37. |
- Pattanaik, Bagmi, 1977, et al.
(författare)
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Production of the cyanotoxin nodularin-A multifactorial approach
- 2010
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Ingår i: Harmful Algae. - : Elsevier BV. - 1568-9883. ; 10:1, s. 30-38
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Tidskriftsartikel (refereegranskat)abstract
- Summer blooms in the Baltic Sea are dominated by the diazotrophic cyanobacteria Nodularia spumigena and Aphanizomenon sp. During the blooms, N. spumigena is concentrated to the water surface and exposed to high irradiances of both photosynthetic active radiation (PAR, 400-700 nm) and ultraviolet radiation (UVR, 280-400 nm), in addition, this organism is exposed to seasonal changes in nutrient conditions. N. spumigena produces nodularin, a hepatotoxin lethal to wild and domestic animals. It has been suggested that the accumulation of nodularin within the cell and the release from the cell are affected by different environmental factors. One laboratory experiment and two outdoor experiments were performed to investigate the interaction of two radiation treatments, PAR and PAR + UV-A + UV-B (PAB); three nutrient treatments, nutrient replete (NP), nitrogen limited (-N), and phosphorus limited (-P) and the presence and absence of Aphanizomenon sp. on intracellular as well as extracellular nodularin concentration in N. spumigena. In this study, we hypothesised that the interaction of ambient radiation, nutrient limitation, and the presence or absence of Aphanizomenon sp. would affect the accumulation and release of nodularin. We further hypothesised that the presence of Aphanizomenon sp. would increase the production and release of nodularin and that this increase would have a negative effect on the specific growth rate of this co-existing species. Significant interaction effects were found between the factors investigated. In all three experiments, the lowest intracellular nodularin concentrations were found under phosphorus limitation. The highest intra- and extracellular nodularin concentrations were observed under nitrogen limitation when shielded from UVR. In our opinion, further increase of nitrogen removal in e.g. sewage treatment, should consider a possible increased toxicity of the N. spumigena blooms. The presence of N. spumigena had no significant effect on the specific growth rate of Aphanizomenon sp. under different radiation and nutrient treatments. Thus, we conclude that although nodularin accumulation and release were dependent on different environmental conditions, it did not affect the co-existing species Aphanizomenon sp. (C) 2010 Elsevier B.V. All rights reserved.
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| 38. |
- Purple, R. J., et al.
(författare)
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Sleep-related memory consolidation in the psychosis spectrum phenotype
- 2020
-
Ingår i: Neurobiology of Learning and Memory. - : Elsevier. - 1074-7427 .- 1095-9564. ; 174
-
Tidskriftsartikel (refereegranskat)abstract
- Sleep and memory processing impairments range from mild to severe in the psychosis spectrum. Relationships between memory processing and sleep characteristics have been described for schizophrenia, including unaffected first-degree relatives, but they are less clear across other high-risk groups within the psychosis spectrum. In this study, we investigated high-risk individuals with accumulated risk-factors for psychosis and subthreshold symptoms. Out of 1898 screened individuals, 44 age- and sex-matched participants were sub-grouped into those with substantial environmental risk factors for psychosis and subthreshold psychotic symptoms (high-risk group) and those without these phenotypes (low-risk controls). Four groups (high/low risk, morning/evening training) were trained and tested in the laboratory for sustained attention, motor skill memory (finger-tapping task) and declarative memory (word-pair learning task) immediately after training, again after a night of EEG-recorded sleep at home or a period of daytime wakefulness, and again after 24 h from training. No differences in sustained attention or in memory consolidation of declarative and motor skill memory were found between groups for any time period tested. However, a group difference was found for rapid-eye movement (REM) sleep in relation to motor skill memory: the longer the total sleep time, particularly longer REM sleep, the greater the performance gain, which occurred only in high-risk individuals. In conclusion, our results suggest a gain in motor skill performance with sufficient sleep opportunity for longer REM sleep in high-risk individuals with subthreshold psychotic symptoms. Declarative memory did not benefit from sleep consolidation above or beyond that of the control group.
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| 39. |
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| 40. |
- Roleda, Michael Y., et al.
(författare)
-
Photosynthetic performance, DNA damage and repair in gametes of the endemic Antarctic brown alga Ascoseira mirabilis exposed to ultraviolet radiation
- 2007
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Ingår i: Austral Ecology. - : Wiley. - 1442-9985 .- 1442-9993. ; 32:8, s. 917-926
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Tidskriftsartikel (refereegranskat)abstract
- Stress physiology on the reproductive cells of Antarctic macroalgae remained unstudied. Ascoseira mirabilis is endemic to the Antarctic region, an isolated ecosystem exposed to extreme environmental conditions. Moreover, stratospheric ozone depletion leads to increasing ultraviolet radiation (280-400 nm) at the earth's surface, thus it is necessary to investigate the capacity of reproductive cells to cope with different UV irradiances. This study is aimed to investigate the impact of exposure to different spectral irradiance on the photosynthetic performance, DNA damage and gamete morphology of the A. mirabilis. Gametangia, gametes and zygotes of the upper sublittoral brown alga A. mirabilis were exposed to photosynthetically active radiation (PAR = P; 400-700 nm), P + UV-A radiation (UV-A, 320-400 nm) and P + UV-A + UV-B radiation (UV-B, 280-320 nm). Rapid photosynthesis versus irradiance curves of freshly released propagules were measured. Photosynthetic efficiencies and DNA damage (in terms of cyclobutane pyrimidine dimers) were determined after 1, 2, 4 and 8 h exposure as well as after 2 days of recovery in dim white light. Saturation irradiance (I-k) in freshly released propagules was 52 mu mol photons m(-2) s(-1). Exposure for 1 h under 22 mu mol photons m(-2) s(-1) of PAR significantly reduced the optimum quantum yield (F-v/F-m), suggesting that propagules are low light adapted. Furthermore, UVR significantly contributed to the photoinhibition of photosynthesis. Increasing dose as a function of exposure time additionally exacerbated the effects of different light treatments. The amount of DNA damage increased with the UV-B dose but an efficient repair mechanism was observed in gametes pre-exposed to a dose lower than 5.8 x 10(3) J m(-2) of UV-B. The results of this study demonstrate the negative impact of UV-B radiation. However, gametes of A. mirabilis are capable of photosynthetic recovery and DNA repair when the stress factor is removed. This capacity was observed to be dependent on the fitness of the parental sporophyte.
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| 41. |
- Roleda, Michael Y., et al.
(författare)
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Susceptibility of spores of different ploidy levels from Antarctic Gigartina skottsbergii (Gigartinales, Rhodophyta) to ultraviolet radiation
- 2008
-
Ingår i: Phycologia. - 0031-8884. ; 47:4, s. 361-370
-
Tidskriftsartikel (refereegranskat)abstract
- Haploid tetraspores and diploid carpospores from Antarctic Gigartina skottsbergii were exposed in the laboratory to photosynthetically active radiation (400-700 nm = P), P + ultraviolet (UV)-A radiation (320-700 nm = PA) and P + UV-A + UV-B radiation (280-700 nm = PAB). Photosynthetic performance, DNA damage and repair, spore mortality, and an initial characterization of the UV-absorbing mycosporine-like amino acids (MAAs) were studied. Rapid photosynthesis vs irradiance (E) curves of freshly released spores showed that both tetraspores and carpospores were low-light adapted (E-k = 44 +/- 2 and 54 +/- 2 mu mol photons m(-2) s(-1), respectively). The light-harvesting and photosynthetic conversion efficiencies were similar (alpha = 0.13), whereas photosynthetic capacity in terms of optimum quantum yield (F-v/F-m) and relative electron transport rate (rETR(max)) were significantly higher in carpospores. Photoinhibition and recovery of photosynthesis were not significantly different between spore ploidy but were significantly affected by radiation and exposure time treatments. Accumulation of DNA damage was UV-B dose dependent and significantly higher in tetraspores than in carpospores. After 2 days postcultivation, DNA lesions were completely repaired in spores exposed to UV-B dose less than 1.2 X 10(4) J m(-2). The dynamic recovery of photosynthetic capacity as well as effective DNA repair mechanism contributed to the relatively low spore mortality (4-14%). A substantial amount of UV-screening MAAs shinorine and palythine were observed for the first time in spores of Gigartinales. This study on stress and physiological characterization of seaweed propagules is important to understand recruitment dynamics and life history phase dominance in the field.
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| 42. |
- Romanov, Roman A., et al.
(författare)
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Molecular interrogation of hypothalamic organization reveals distinct dopamine neuronal subtypes
- 2017
-
Ingår i: Nature Neuroscience. - : Nature Publishing Group. - 1097-6256 .- 1546-1726. ; 20:2, s. 176-188
-
Tidskriftsartikel (refereegranskat)abstract
- The hypothalamus contains the highest diversity of neurons in the brain. Many of these neurons can co-release neurotransmitters and neuropeptides in a use-dependent manner. Investigators have hitherto relied on candidate protein-based tools to correlate behavioral, endocrine and gender traits with hypothalamic neuron identity. Here we map neuronal identities in the hypothalamus by single-cell RNA sequencing. We distinguished 62 neuronal subtypes producing glutamatergic, dopaminergic or GABAergic markers for synaptic neurotransmission and harboring the ability to engage in task-dependent neurotransmitter switching. We identified dopamine neurons that uniquely coexpress the Onecut3 and Nmur2 genes, and placed these in the periventricular nucleus with many synaptic afferents arising from neuromedin S+ neurons of the suprachiasmatic nucleus. These neuroendocrine dopamine cells may contribute to the dopaminergic inhibition of prolactin secretion diurnally, as their neuromedin S+ inputs originate from neurons expressing Per2 and Per3 and their tyrosine hydroxylase phosphorylation is regulated in a circadian fashion. Overall, our catalog of neuronal subclasses provides new understanding of. hypothalamic organization and function.
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| 43. |
- Sondhauss, Peter, et al.
(författare)
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Picosecond X-ray studies of coherent folded phonons in a multiple quantum well
- 2005
-
Ingår i: Physical Review Letters. - Lund Univ, Dept Phys, SE-22100 Lund, Sweden. European Synchrotron Radiat Facil, F-38043 Grenoble, France. Malmo Univ, Sch Technol & Soc, S-20506 Malmo, Sweden. Univ Oxford, Dept Phys, Clarendon Lab, Oxford OX1 3PU, England. : AMERICAN PHYSICAL SOC. - 1079-7114 .- 0031-9007. ; 94
-
Tidskriftsartikel (refereegranskat)abstract
- Coherent folded acoustic phonons in a multilayered GaSb/InAs epitaxial heterostructure were generated by femtosecond laser pulses and studied by means of ultrafast x-ray diffraction. Coherent phonons excited simultaneously in the fundamental acoustic branch and the first back-folded branch were detected. This represents the first clear evidence for phonon branch folding based directly on the atomic motion to which x-ray diffraction is sensitive. From a comparison of the measured phonon-modulated x-ray reflectivity with simulations, evidence was found for a reduction of the laser penetration depth. This reduction can be explained by the self-modulation of the refractive index due to photogenerated free carriers.
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| 44. |
- Stamenković, Marija, et al.
(författare)
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Desmids (Zygnematophyceae, Streptophyta) as a promising freshwater microalgal group for the fatty acid production: results of a screening study
- 2019
-
Ingår i: Journal of Applied Phycology. - : Springer Science and Business Media LLC. - 0921-8971 .- 1573-5176. ; 31:2, s. 1021-1034
-
Tidskriftsartikel (refereegranskat)abstract
- © 2018, Springer Nature B.V. This study aimed to investigate fatty acid content and productivity of the insufficiently investigated group of freshwater microalgae—desmids (Zygnematophyceae, Streptophyta)—and to estimate their commercial potential. A total of 29 desmid strains of various environmental preferences were grown in standard cultivation conditions to assess fatty acid concentration and composition and biomass productivity during the growth phases. Six desmid strains belonging to Cosmarium crenatum var. boldtianum, C. meneghinii, C. regnellii var. pseudoregnellii, C. leave, Staurastrum boreale, and S. punctulatum had distinctly high total fatty acid contents (> 200mgg−1 dry weight), among which C. crenatum had by far the highest average of total fatty acids (308.1mgg−1 dry weight). Despite that desmids were grown in a medium which was not enriched with nutrients and CO2, these six strains achieved moderate biomass productivity (up to 0.14g dry weight L−1day−1), while the fatty acid productivity was in the range 8–11.1mgL−1day−1. The relatively high amounts of linoleic and palmitic acids in C. crenatum var. boldtianum and C. meneghinii were comparable to those found in several commercially grown plants, indicating that fatty acid extracts of these desmids could be utilized in cosmetics, pharmacy, medicine, or in additional industrial applications. On the other hand, the high proportion of oleic acid in a new isolate of Staurastrum boreale, along with its relatively high biomass productivity and cell size, pointed that this strain might be used for further investigations regarding biodiesel production.
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| 45. |
- Stamenković, Marija, et al.
(författare)
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Fatty acids as chemotaxonomic and ecophysiological traits in green microalgae (desmids, Zygnematophyceae, Streptophyta): A discriminant analysis approach
- 2020
-
Ingår i: Phytochemistry. - : Elsevier BV. - 0031-9422. ; 170
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Tidskriftsartikel (refereegranskat)abstract
- © 2019 Elsevier Ltd Desmids (Zygnematophyceae) are a group of poorly studied green microalgae. The aim of the present study was to identify fatty acids (FAs) that could be used as biomarkers in desmids in general, and to determine FAs as traits within different ecophysiological desmid groups. FA profiles of 29 desmid strains were determined and analysed with respect to their geographic origin, trophic preference and age of cultivation. It appeared that merely FAs present in relatively large proportions such as palmitic, linoleic, α-linolenic and hexadecatrienoic acids could be used as biomarkers for reliable categorization of this microalgal group. Linear discriminant analysis applied to three a priori defined groups of desmids, revealed clear strain-specific characteristics regarding FA distribution, influenced by climate and trophic conditions at the source sites as well as by the age of culture and growth phase. Accordingly, when considering FAs for the determination of lower taxonomic ranks we recommend using the term “trait” instead of “biomarker”, as the latter designates unchangeable “fingerprint” of a specific taxon. Furthermore, despite that desmids were regarded as microalgae having stable genomes, long-term cultivation appeared to cause modifications in FA metabolic pathways, evident as a larger proportion of stearidonic acid in desmid strains cultivated over extensive time periods (>35 years).
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| 46. |
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| 47. |
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| 48. |
- Torstensson, Anders, et al.
(författare)
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Elevated temperature and decreased salinity both affect the biochemical composition of the Antarctic sea-ice diatom Nitzschia lecointei, but not increased pCO2
- 2019
-
Ingår i: Polar Biology. - : Springer Science and Business Media LLC. - 0722-4060 .- 1432-2056. ; 42:11, s. 2149-2164
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Tidskriftsartikel (refereegranskat)abstract
- © 2019, The Author(s). Areas in western Antarctica are experiencing rapid climate change, where ocean warming results in more sea ice melt simultaneously as oceanic CO2 levels are increasing. In this study, we have tested how increased temperature (from −1.8to 3°C) and decreased salinity (from 35 to 20 and 10) synergistically affect the growth, photophysiology and biochemical composition of the Antarctic sea-ice diatom Nitzschia lecointei. In a separate experiment, we also addressed how ocean acidification (from 400 to 1000µatm partial pressure of CO2) affects these key physiological parameters. Both positive and negative changes in specific growth rate, particulate organic carbon to particulate organic nitrogen ratio, chl a fluorescence kinetics, lipid peroxidation, carbohydrate content, protein content, fatty acid content and composition were observed when cells were exposed to warming and desalination. However, when cells were subjected to increased pCO2, only Fv/Fm, non-photochemical quenching and lipid peroxidation increased (by 3, 16 and 14%, respectively), and no other of the abovementioned biochemical properties were affected. These results suggest that changes in temperature and salinity may have more effects on the biochemical composition of N. lecointei than ocean acidification. Sea-ice algae are important component of polar food webs, and their nutritional quality may be affected as a result of altered environmental conditions due to climate change and sea ice melt.
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| 49. |
- Torstensson, Anders, et al.
(författare)
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Microalgal photophysiology and macronutrient distribution in summer sea ice in the Amundsen and Ross Seas, Antarctica
- 2018
-
Ingår i: Plos One. - : Public Library of Science (PLoS). - 1932-6203. ; 13:4
-
Tidskriftsartikel (refereegranskat)abstract
- Our study addresses how environmental variables, such as macronutrients concentrations, snow cover, carbonate chemistry and salinity affect the photophysiology and biomass of Antarctic sea-ice algae. We have measured vertical profiles of inorganic macronutrients (phosphate, nitrite + nitrate and silicic acid) in summer sea ice and photophysiology of ice algal assemblages in the poorly studied Amundsen and Ross Seas sectors of the Southern Ocean. Brine-scaled bacterial abundance, chl a and macronutrient concentrations were often high in the ice and positively correlated with each other. Analysis of photosystem II rapid light curves showed that microalgal cells in samples with high phosphate and nitrite + nitrate concentrations had reduced maximum relative electron transport rate and photosynthetic efficiency. We also observed strong couplings of PSII parameters to snow depth, ice thickness and brine salinity, which highlights a wide range of photoacclimation in Antarctic pack-ice algae. It is likely that the pack ice was in a post-bloom situation during the late sea ice season, with low photosynthetic efficiency and a high degree of nutrient accumulation occurring in the ice. In order to predict how key biogeochemical processes are affected by future changes in sea ice cover, such as in situ photosynthesis and nutrient cycling, we need to understand how physicochemical properties of sea ice affect the microbial community. Our results support existing hypothesis about sea-ice algal photophysiology, and provide additional observations on high nutrient concentrations in sea ice that could influence the planktonic communities as the ice is retreating.
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| 50. |
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