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Sökning: WFRF:(Norström H)

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1.
  • Daniau, A. -L, et al. (författare)
  • predictability of biomass burning in response to climate changes
  • 2012
  • Ingår i: Global Biogeochemical Cycles. - 0886-6236 .- 1944-9224. ; 26, s. GB4007-
  • Tidskriftsartikel (refereegranskat)abstract
    • Climate is an important control on biomass burning, but the sensitivity of fire to changes in temperature and moisture balance has not been quantified. We analyze sedimentary charcoal records to show that the changes in fire regime over the past 21,000 yrs are predictable from changes in regional climates. Analyses of paleo-fire data show that fire increases monotonically with changes in temperature and peaks at intermediate moisture levels, and that temperature is quantitatively the most important driver of changes in biomass burning over the past 21,000 yrs. Given that a similar relationship between climate drivers and fire emerges from analyses of the interannual variability in biomass burning shown by remote-sensing observations of month-by-month burnt area between 1996 and 2008, our results signal a serious cause for concern in the face of continuing global warming.
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  • Steen, Mårten, et al. (författare)
  • Functional characterization of Factor V-Ile359Thr, a novel mutation associated with thrombosis.
  • 2004
  • Ingår i: Blood. - : American Society of Hematology. - 1528-0020 .- 0006-4971. ; 103:9, s. 3381-3387
  • Tidskriftsartikel (refereegranskat)abstract
    • A missense mutation, FV-IIe359Thr (FV Liverpool), associated with thrombosis has recently been described. This mutation creates an additional potential N-linked glycosylation site (Asn-X-Ser/Thr) in factor V (FV) at Asn357 that could interfere with secretion and/or protein interactions. To investigate the molecular pathology of FV-IIe359Thr, the mutation was created by site-directed mutagenesis and expressed together with other mutations that could help explain the phenotype (FV-Arg306GIn/IIe359Thr/Arg679GIn, FV-IIe359Thr/Arg506GIn/Arg679GIn, and FV-Asn357GIn/IIe359Thr). The FV-IIe359Thr was secreted normally and had full procoagulant activity. Western blot analysis showed that FV-IIe359Thr migrated more slowly, while the FV-Asn357GIn/IIe359Thr was indistinguishable from FV-wild type (FV-WT), indicating that FV-IIe359Thr was expressed with an additional carbohydrate chain. Activated protein C (APC)-mediated inactivation in an FVa degradation assay showed that the IIe359Thr mutation significantly reduced the cleavage at Arg306 both in the presence and absence of protein S, whereas the cleavage at Arg506 was unaffected. When tested in an FVIIIa degradation assay, the FV-IIe359Thr variant exhibited equally low APC cofactor activity as FV Leiden (FVArg506GIn). In conclusion, the IIe359Thr mutation appears to affect anticoagulation by 2 mechanisms, impeding the APCmediated down-regulation of the FVa molecule and additionally being a poor APC cofactor for the down-regulation of FVIIIa. These findings explain the association of the FV-IIe359Thr mutation with thrombosis. (C) 2004 by The American Society of Hematology.
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  • Blom, Hans-Olof, et al. (författare)
  • Removal of RSE induced damages in silicon
  • 1986
  • Ingår i: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - 0734-2101 .- 1520-8559. ; 4:3, s. 752-
  • Tidskriftsartikel (refereegranskat)
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  • Blum, Kristin M., et al. (författare)
  • Removal of 30 active pharmaceutical ingredients in surface water under long-term artificial UV irradiation
  • 2017
  • Ingår i: Chemosphere. - : Elsevier BV. - 0045-6535 .- 1879-1298. ; 176, s. 175-182
  • Tidskriftsartikel (refereegranskat)abstract
    • This study investigated the i) kinetics, and ii) proportion of photolysis of 30 relatively stable active pharmaceutical ingredients (APIs) during artificial UV irradiation for 28 d in ammonium acetate buffer, filtered and unfiltered river water. Buffer was included to control removal kinetics under stable pH conditions and without particulate matter. Dark controls were used to determine removal due to other processes than photolysis and calculate the proportion of photolysis of the total removal. The removal of each API in each matrix was determined using online solid phase extraction/liquid chromatography tandem mass spectrometry (online SPE/LC-MS/MS). Most APIs transformed during the 28 d of UV irradiation and the dark controls showed that photolysis was the major removal process for the majority of the APIs studied. The half-lives ranged from 6 h (amitriptyline) in unfiltered river water to 884 h (37 d, carbamazepine) in buffer. In unfiltered river water, the proportion of APIs with short half-lives (<48 h) was much higher (29%) than in the other matrices (4%), probably due to additional organic carbon, which could have promoted indirect photolysis. Furthermore, two APIs, memantine and fluconazole, were stable in all three matrices, while alprazolam was stable in buffer and unfiltered river water and four additional APIs were stable in buffer. Considering the relatively long-term UV-exposure, this study enabled the investigation of environmentally relevant half-lives in natural waters. Many APIs showed high persistence, which is environmentally concerning and emphasizes the importance of further studies on their environmental fate and effects.
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  • Dierikx, Cindy, et al. (författare)
  • A European multicenter evaluation study to investigate the performance on commercially available selective agar plates for the detection of carbapenemase producing Enterobacteriaceae
  • 2022
  • Ingår i: Journal of Microbiological Methods. - : Elsevier. - 0167-7012 .- 1872-8359. ; 193
  • Tidskriftsartikel (refereegranskat)abstract
    • The European Food Safety Authority (EFSA) advised to prioritize monitoring carbapenemase producing Enterobacteriaceae (CPE) in food producing animals. Therefore, this study evaluated the performance of different commercially available selective agars for the detection of CPE using spiked pig caecal and turkey meat samples and the proposed EFSA cultivation protocol. Eleven laboratories from nine countries received eight samples (four caecal and four meat samples). For each matrix, three samples contained approximately 100 CFU/g CPE, and one sample lacked CPE. After overnight enrichment in buffered peptone water, broths were spread upon Brilliance™ CRE Agar (1), CHROMID® CARBA (2), CHROMagar™ mSuperCARBA™ (3), Chromatic™ CRE (4), CHROMID® OXA-48 (5) and Chromatic™ OXA-48 (6). From plates with suspected growth, one to three colonies were selected for species identification, confirmation of carbapenem resistance and detection of carbapenemase encoding genes, by methods available at participating laboratories. Of the eleven participating laboratories, seven reported species identification, susceptibility tests and genotyping on isolates from all selective agar plates. Agars 2, 4 and 5 performed best, with 100% sensitivity. For agar 3, a sensitivity of 96% was recorded, while agar 1 and 6 performed with 75% and 43% sensitivity, respectively. More background flora was noticed for turkey meat samples than pig caecal samples. Based on this limited set of samples, most commercially available agars performed adequately. The results indicate, however, that OXA-48-like and non-OXA-48-like producers perform very differently, and one should consider which CPE strains are of interest to culture when choosing agar type.
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  • Johansson, Katarina, et al. (författare)
  • Celiac disease and upper secondary school achievement in Sweden : A retrospective cohort study
  • 2022
  • Ingår i: BMC Pediatrics. - : BioMed Central (BMC). - 1471-2431. ; 22:1
  • Tidskriftsartikel (refereegranskat)abstract
    • BACKGROUND: Both undiagnosed celiac disease and some chronic childhood diseases are associated with lower academic achievement. However, there is little knowledge of achievements in those diagnosed with celiac disease. Our aim was to investigate school achievements in upper secondary school among Swedish adolescents with celiac disease.METHODS: We performed a retrospective cohort study using register data. We analyzed choice of upper secondary school program, completion of upper secondary school including achievements of basic eligibility for college/university, and final grade in individuals with celiac disease diagnosed before 15 years of age, born 1991-97. We compared with the Swedish population of the same birth years. Analyses were adjusted for sex, year of birth, living region at 17 years of age, and parental education as well as income.RESULTS: The cohort included 734 074 individuals, whereof 3 257 (62% females) with celiac disease. There was no significant difference in choice of upper secondary school program. No significant difference was found in completion or achieving basic eligibility for college/university in adjusted analyses. The mean final grade in the celiac disease group was 13.34 (standard deviation 4.85) compared to 12.78 (standard deviation 5.01) in the reference population (p < 0.001), out of a maximum of 20. The effect of celiac disease on final grade remained in adjusted analyses (p = 0.012).CONCLUSIONS: We found that diagnosed celiac disease does not negatively affect school achievements in upper secondary school. This finding suggests the diagnosis, treatment and follow-up programs of celiac disease could reverse potential deleterious academic processes.
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  • Katrantsiotis, Christos, et al. (författare)
  • Climate changes in the Eastern Mediterranean over the last 5000 years and their links to the high-latitude atmospheric patterns and Asian monsoons
  • 2019
  • Ingår i: Global and Planetary Change. - : Elsevier BV. - 0921-8181 .- 1872-6364. ; 175, s. 36-51
  • Tidskriftsartikel (refereegranskat)abstract
    • This research aims to improve the knowledge of the mid to late Holocene climate changes and the underlying drivers in the eastern Mediterranean. We focus on the Peloponnese peninsula, SW Greece, characterized by a W-E rainfall/temperature gradient and a strong climate-sensitivity to shifts in the large-scale atmospheric patterns. A radiocarbon-dated sediment core, taken from the ancient Lake Lerna, a former lake in NE Peloponnese, was analyzed for distribution and hydrogen isotope (δD) composition of n-alkanes and bulk organic geochemistry (δ13C, TOC). The predominantly macrophyte (submerged/floating)-derived δD23 profile exhibits the largest long-term fluctuation in the record and co-varies with δD of long-chain n-alkanes providing evidence for precipitation and temperature changes over the last 5000 years. The Lerna δD23 signal is sometimes in agreement with other n-alkane δD records from SW Peloponnese indicating wetter conditions in the peninsula at ca 5000–4600, ca 4500–4100, ca 3000–2600 (more unstable in SW) and after ca 700 cal BP with drier periods at ca 4100–3900 and ca 1000–700 cal BP. Conversely, a NE-SW climate see-saw is revealed at ca 4600–4500, ca 3200, ca 2600–1800, and ca 1200–1000 cal BP when the δD23 Lerna exhibits more positive trends (drier in NE) with a reversal at ca 3900–3300, ca 3200–3000 and ca 1800–1300 cal BP. These opposing and sometimes similar signals between NE and SW Peloponnese can be explained by the relative dominance of high-latitude atmospheric patterns over the peninsula. A similar signal would be expected when the North Atlantic Oscillation (NAO) exerts the main control with NAO (+) creating conditions of reduced moisture. The dipole pattern is likely driven by shifts in North Sea–Caspian Atmospheric pattern (NCP), which account for the present-day regional climate variability with NCP (+) leading to wetter and colder conditions in NE Peloponnese. The Asian monsoonal system likely has an additional impact on the δD variabilities through influencing the summer temperatures. There is a consistency between the Peloponnesian δD signals and monsoonal records after ca 4000 cal BP confirming the actualistic models. Strong monsoonal periods coincide with cooler summers (lower δD values) in Lerna, due to the northerly winds, the Etesians. On the contrary, SW Peloponnese is dominated by warmer conditions during the same periods as the area is located on the lee side of the mountain and highly influenced by the adiabatic warming associated with the subsidence over the Eastern Mediterranean.
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  • Katrantsiotis, Christos, et al. (författare)
  • Late quaternary hydroclimate variability in Madagascar and its connection to atmospheric circulation patterns
  • 2024
  • Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier. - 0031-0182 .- 1872-616X. ; 649
  • Tidskriftsartikel (refereegranskat)abstract
    • Large uncertainties still exist about the long-term mechanisms influencing the hydroclimate variability of southeast Africa where proxy data and model simulations indicate rainfall dipoles between subtropical and tropical areas. The topography of Madagascar, located off the southeastern coast of Africa, modulates these dipoles while its climate is influenced by the position of the Intertropical Convergence Zone (ITCZ) and the Subtropical High as well as the sea surface temperature (SST) of SW Indian Ocean. The island can thus be considered a key location for the understanding of the tropical SE African climatic variability and the interplay between atmospheric patterns. However, the scarcity of continuous records from Madagascar has made the evolution of regional late Quaternary climate and its driving mechanisms difficult to assess. Here, we present a 26-kyr record of the deuterium/hydrogen isotope ratio (δD) of biomarkers (n-alkanes) from the central eastern part of the island at Antananarivo at around 1250 m a.s.l. Preliminary summary pollen data are also presented as a comparison. The δD profiles of aquatic plant and terrestrial plant-derived n-alkanes generally exhibit similar trends implying that they all record changes in the isotope composition of source water, namely meteoric water that recharges soil and lake waters. In this tropical region, the δD variability of precipitation is mainly influenced by the amount effect reflecting the intensity of precipitation associated with the monsoon. We observe: (i) stable and wet conditions during the Last Glacial Maximum, (ii) drier conditions from 18.5 to 15 ka (ka before present) during the Heinrich Stadial 1 (iii) high humidity after 15 ka culminating at the Younger Dryas (YD), (iv) drier conditions from 11.7 ka to 8.2 ka, (v) a return to humid climate until 2.8 ka, and (vi) an arid phase followed by increased wetness after 0.9 ka, although the record is likely influenced by human-induced vegetation changes the last 1.2 ka. This climate signal is similar to other records from the Mozambique Channel but opposite to records from the East African mainland and the subtropical southern Africa, especially between 20 and 25°S. Although there is a good correspondence of our record with insolation- driven migrations of ITCZ during the LGM and the early Holocene, the dipoles are largely consistent with the modern rainfall anomaly and are best explained by the interlinked effects of the SST changes and the variability of the Mozambique Channel Trough.
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  • Katrantsiotis, Christos, et al. (författare)
  • Seasonal variability in temperature trends and atmospheric circulation systems during the Eemian (Last Interglacial) based on n-alkanes hydrogen isotopes from Northern Finland
  • 2021
  • Ingår i: Quaternary Science Reviews. - Amsterdam : Elsevier. - 0277-3791 .- 1873-457X. ; 273, s. 107250-107250
  • Tidskriftsartikel (refereegranskat)abstract
    • The Last Interglacial warm period, the Eemian (ca. 130-116 thousand years ago), serves as a reference for projected future climate in a warmer world. However, there is a limited understanding of the seasonal characteristics of interglacial climate dynamics, especially in high latitude regions. In this study, we aimto provide new insights into seasonal trends in temperature and moisture source location, linked to shifts in atmospheric circulation patterns, for northern Fennoscandia during the Eemian. Our study is based on the distribution and stable hydrogen isotope composition (dD) of n-alkanes in a lake sediment sequence from the Sokli paleolake in NE Finland, placed in a multi-proxy framework. The dD values of predominantly macrophyte-derived mid-chain n-alkanes are interpreted to reflect lake water dD variability influenced by winter precipitation dD (dDprec), ice cover duration and deuterium (D)-depleted meltwater. The dD values of terrestrial plant-derived long-chain n-alkanes primarily reflect soil water dD variability modulated by summer dDprec and by the evaporative enrichment of soil and leaf water. The dDprec variability in our study area is mostly attributed to the temperature effect and the moisture source location linked to the relative dominance between D-depleted continental and polar air masses and Denriched North Atlantic air masses. The biomarker signal further corroborates earlier diatom-based studies and pollen-inferred January and July temperature reconstructions from the same sediment sequence. Three phases of climatic changes can be identified that generally follow the secular variationsin seasonal insolation: (i) an early warming trend succeeded by a period of strong seasonality (ii) a midoptimum phase with gradually decreased seasonality and cooler summers, and (iii) a late climatic instability with a cooling trend. Superimposed on this trend, two abrupt cooling events occur in the early and late Eemian. The Sokli dD variability is generally in good agreement with other North Atlantic and Siberian records, reflecting major changes in the atmospheric circulation patterns during the Eemian as a response to orbital and oceanic forcings.
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  • Nilsson, T., et al. (författare)
  • Effects of local alcohol prevention initiatives in Swedish municipalities, 2006–2014
  • 2020
  • Ingår i: Substance Use & Misuse. - : Informa UK Limited. - 1082-6084 .- 1532-2491. ; 55:6, s. 1008-1020
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Several components of the Swedish alcohol policy, e.g., pricing and availability, weakened when Sweden joined the EU in 1995. To counteract the possible negative effects of this, emphasis was placed on the local level as an important arena of alcohol prevention. Thus, considerable efforts were made to strengthen alcohol prevention in Swedish municipalities. Objectives: The aim of this study was to examine whether local alcohol prevention reduced consumption and alcohol-related harm in Swedish municipalities. Methods: Alcohol prevention was monitored using a composite measure called the Alcohol Prevention Magnitude Measure (APMM), with subcategories of staff and budget, inspections and licenses, policy, activities, and cooperation. APMM and its categories were analysed in relation to alcohol consumption and harm over time, 2006–2014. A fixed effects model was used with 63% (N¼182, consumption) and 71% (N¼207, harm) of 290 Swedish municipalities, respectively, included in the analyses. Results: The main results suggest that when APMM increases with 1 percent, the alcohol-related mortality decreases with 0.26 percent, controlled for changes in population size, median income, unemployment, and post-secondary education. In light of this result, the estimated effect of APMM on alcohol consumption (sales) is small (0.02 percent decrease); possible explanations for this are discussed in the article. Conclusion:The overall results indicate that local alcohol prevention initiatives in Sweden have reduced some forms of alcohol-related harm, not least alcohol-related mortality, during the period 2006–2014. Further studies are needed to assess the generalizability of the present study.
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  • Norström, Christer, et al. (författare)
  • Special section on factory communication systems
  • 2005
  • Ingår i: IEEE Transactions on Industrial Informatics. - 1551-3203 .- 1941-0050. ; 1:3, s. 149-150
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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  • Norström, Elin, et al. (författare)
  • Biomarker hydrogen isotope composition (D) as proxy for Holocene hydroclimatic change and seismic activity in SW Peloponnese, Greece
  • 2018
  • Ingår i: Journal of Quaternary Science. - : Wiley. - 0267-8179 .- 1099-1417. ; 33:5, s. 563-574
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a 6000-year-long record tracing hydroclimate changes in SW Greece, based on hydrogen isotope composition of aquatic plant-derived n-C-23 alkanes (D-C23) in a sediment core from the Messenian plain, Peloponnese. The D-C23 record co-varies with other eastern Mediterranean records, suggesting relatively wetter conditions c. 6-4.5ka, followed by progressively drier conditions leading up to maximum aridity c. 2.8 ka. This arid phase was interrupted by a shift in D-C23 between 3.3 and 3.1ka inferring wetter conditions and/or tentative responses to anthropogenic water regulating activities during the Late Bronze Age. After 2.7ka, a return to more humid conditions was followed by increased dryness and stronger seasonality contrasts from c. 2.0ka. The D-C23 record shows three short-lived excursions (5.7, 5.3, 2.8ka), where isotope values dropped by >20 parts per thousand and immediately stabilized again. The events were paralleled by abrupt increases in sedimentation rates. We hypothesize that the isotopic shifts represent a response to mixing of ground water systems during tectonic events, followed by sealing of seismically derived cracks in the active fault. The outcome of the study is promising for future expansion of isotope-based proxies on sediments in the region, to reconstruct both hydroclimate and past seismic activity.
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  • Norström, Elin, et al. (författare)
  • Chemotaxonomy in some Mediterranean plants and implications for fossil biomarker records
  • 2017
  • Ingår i: Geochimica et Cosmochimica Acta. - : Elsevier BV. - 0016-7037 .- 1872-9533. ; 219, s. 96-110
  • Tidskriftsartikel (refereegranskat)abstract
    • The increasing utilization of n-alkanes as plant-derived paleo-environmental proxies calls for improved chemotaxonomic control of the modern flora in order to calibrate fossil sediment records to modern analogues. Several recent studies have investigated long-chain n-alkane concentrations and chain-length distributions in species from various vegetation biomes, but up to date, the Mediterranean flora is relatively unexplored in this respect. Here, we analyse the n-alkane concentrations and chain-length distributions in some of the most common species of the modern macchia and phrygana vegetation in south western Peloponnese, Greece. We show that the drought adapted phrygana herbs and shrubs, as well as some of the sclerophyll and gymnosperm macchia components, produce high concentrations of n-alkanes, on average more than double n-alkane production in local wetland reed vegetation. Furthermore, the chain-length distribution in the analysed plants is related to plant functionality, with longer chain lengths associated with higher drought adaptive capacities, probably as a response to long-term evolutionary processes in a moisture limited environment. Furthermore, species with relatively higher average chain lengths (ACL) showed more enriched carbon isotope composition in their tissues (delta C-13(plant)), suggesting a dual imprint from both physiological and biochemical drought adaptation. The findings have bearings on interpretation of fossil sedimentary biomarker records in the Mediterranean region, which is discussed in relation to a case study from Agios Floros fen, Messenian plain, Peloponnese. The 6000 year long n-alkane record from Agios Floros (ACL, delta C-13(wax)) is linked to the modern analogue and then evaluated through a comparison with other regional-wide as well as local climate and vegetation proxy-data. The high concentration of long chain n-alkanes in phrygana vegetation suggests a dominating imprint from this vegetation type in sedimentary archives from this ecotone.
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  • Norström, Elin, et al. (författare)
  • Evaluation of anhydrosugars as a molecular proxy for paleofire activity : A case study on a Holocene sediment core from Agios Floros, Peloponnese, Greece
  • 2021
  • Ingår i: Organic Geochemistry. - : Elsevier BV. - 0146-6380 .- 1873-5290. ; 153
  • Tidskriftsartikel (refereegranskat)abstract
    • The anhydrosugars, levoglucosan, mannosan and galactosan, are regarded as suitable molecular indicators of natural biomass combustion. Here, we evaluate summed anhydrosugars (SAS) as a paleofire indicator in a 6000 year-long fossil core from Agios Floros fen, Peloponnese, Greece, by analyzing charcoal fragments in parallel, throughout the sediment sequence. Modern surface soil samples from the same region were analysed for the presence of SAS, confirming the biomarker as an indicator of recent fire activity. The highest SAS concentrations in the fossil core were found in sections representing periods of wet conditions, both on local and regional scales and regionally widespread arboreal vegetation. Low amounts, or the absence, of SAS in the fossil core were associated with periods of dryness, regional dominance of non-arboreal vegetation and the presence of a fen rather than a lake ecosystem at the site. Micro-charcoal fragments were generally more abundant under these conditions. This suggests that SAS yield and deposition may vary with fuel availability and fire behavior, which in turn is affected by climate, local moisture and vegetation type. Forest fires result in more SAS compared to grass fires. SAS yield is also favored by low-temperature fires sustained under wet climate conditions. Preservation of SAS is likely to be compromised in the only seasonally wet fen ecosystem under the dry and warm Mediterranean climate conditions. The moist and shallow conditions in the wetland during hot summer months probably promote oxidation and biodegradation of the labile SAS molecules, compared to the more robust charcoal fragments. Thus, a multiproxy approach - using several proxies, both for fire, hydroclimate and vegetation change - is preferred when aiming to reconstruct past biomass burning from wetland ecosystems in a Mediterranean environment. The micro-charcoal record from Agios Floros reveals significant fire activity between 4400 and 2800 cal yr BP. This partly overlaps the Bronze Age period, associated with intense human environmental interaction and climate change in this area of Peloponnese, Greece.
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  • Norström, Elin, et al. (författare)
  • Late Quaternary vegetation dynamics and hydro-climate in the Drakensberg, South Africa
  • 2014
  • Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 105, s. 48-65
  • Tidskriftsartikel (refereegranskat)abstract
    • Abstract A multi-proxy study of a sediment sequence from Braamhoek wetland, covering the last c. 16,000 years, reveals a record of regional climate and vegetation dynamics in the Drakensberg region, South Africa, including signals from both the organic sediment fraction (fossil pollen, charcoal, n-alkane abundance, n-alkane δ13C, TOC) and the inorganic fraction (mineral magnetic properties). The reconstruction, supported by a robust chronology, indicates two major periods of increased regional wetness during the late Pleistocene to early Holocene phase (c. 13,800–12,600 cal yr BP; c. 10,200–8500 cal yr BP) and one during the late Holocene (c. 2000 cal yr BP to present). Drier conditions are recorded during the Younger Dryas (c. 12,600–11,300 cal yr BP) and mid-Holocene (c. 7000–2000 cal yr BP). A major decline in fynbos vegetation during the early Holocene suggests a shift towards warmer temperatures and possibly towards less pronounced winter rains in eastern South Africa from c. 8500 cal yr BP. Comparison with records from interior of South Africa show relatively high inter-site variability, however, the Braamhoek moisture proxies do co-vary with the speleothem isotope records from Makapansgat, suggesting a similar hydro-climate evolution in eastern and interior parts of the summer rainfall region during the studied period. On multi-millennial time scales, an inverse hydro-climatological pattern is evident between these two South African records and reconstructions from tropical locations in southeast Africa. Such a rainfall dipole between eastern tropical and southern Africa, has previously been identified on shorter time scales, i.e. on inter-annual to millennial scales. The Braamhoek study suggests that a similar dipole pattern is acting also on a multi-millennial perspective. These long-term precipitation anomalies are tentatively coupled to teleconnections from multi-millennial changes in the dynamics of the Indian Ocean Dipole (IOD) and El Niño-Southern Oscillation (ENSO).
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  • Norström, Elin, et al. (författare)
  • Leaf wax delta D inferring variable medieval hydroclimate and early initiation of Little Ice Age (LIA) dryness in southern Mozambique
  • 2018
  • Ingår i: Global and Planetary Change. - : Elsevier BV. - 0921-8181 .- 1872-6364. ; 170, s. 221-233
  • Tidskriftsartikel (refereegranskat)abstract
    • A sediment sequence from a coastal, hydrologically isolated lake in southern Mozambique was analysed for leaf wax delta D, n-alkane abundance (ACL) and bulk organic geochemistry (delta C-13, TOC, %N), providing a record of past rainfall variability and savanna dynamics over the last 1500 years. The delta D-wax a rainfall reconstruction reveals a stable hydroclimate between 500-700 CE, while ACL and delta C-13 together with previous pollen data suggest savanna vegetation was characterized by a relatively dense woody cover. Highly variable hydroclimate conditions are inferred by delta D-wax between 800-1350 CE, with repeated centennial scale intervals of extreme dry and wet conditions overlapping the Medieval Climate Anomaly (MCA; 950-1250 CE). Savanna tree cover stayed relatively intact over this phase. After ca 1250 CE, a progressive change towards drier conditions was initiated, leading up to maximum aridity during the AD 1700s, a period associated with the Little Ice age (LIA; 1500-1850 CE). Tree cover was now replaced by a more grass-dominated savanna. The clear antiphase rainfall patterns between Nhaucati and equatorial East African proxy records gives support to the notion that Indian Ocean sea surface temperature (SST) gradients act as modulator of southern African climate on a multi-decadal time scale, possibly forced by long-term El Nino Southern Oscillation (ENSO) variability. We suggest that strong ENSO variability and greater occurrence of La Nina events triggered the generally wet and unstable MCA in southern Africa. From around 1250 CE, a shift towards a predominance of El Nino induced drier conditions in south-east Africa during the LIA. Our study of vegetation and hydroclimate proxies in parallel suggests that savanna tree and shrub cover was relatively resilient to the abrupt shifts in hydroclimate over the MCA, but more sensitive to the long-term progressive drying over the LIA.
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  • Norström, H., et al. (författare)
  • Formation of a buried collector layer in RF-bipolar devices by ion implantation
  • 2006
  • Ingår i: MICROELECTRONICS JOURNAL. - : Elsevier BV. - 0026-2692. ; 37:11, s. 1366-1371
  • Tidskriftsartikel (refereegranskat)abstract
    • High-dose implantation of arsenic (As) buried collector layer formation for bipolar/BiCMOS processes has been studied. Wafers with and without screen oxide were subjected to high-dose implants with different energies. Some wafers were given a low-temperature anneal before XTEM and SIMS analyses. Defects observed after As implants of 6E15 cm(-2) through screen oxide after low-temperature anneal were annihilated at the subsequent high-temperature steps, but the direct implant of As into the silicon is preferred since fewer defects are generated and there is no knock-on of oxygen into the material. Fabricated devices showed excellent electrical performance. However, the upper limit (dose and/or energy) at which perfect recrystallization does no longer occur has not been defined and the process limit is consequently not established.
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46.
  • Norström, Sara H, et al. (författare)
  • Influences of dissolved organic carbon on stream water chemistry in two forested catchments in central Sweden
  • 2010
  • Ingår i: Biogeochemistry. - : Springer. - 0168-2563 .- 1573-515X. ; 101:1-3, s. 229-241
  • Tidskriftsartikel (refereegranskat)abstract
    • Stream water chemistry in two headwater streams draining two small, adjacent catchments in Bispgården, central Sweden was studied during the 2003 and 2004 growing seasons. The two catchments closely resemble each other in regard to size, shape and drainage density, with the major difference found in the area of wetland lining the streambeds. The emphasis of the study was to investigate the stream water chemistry of these closely resembling catchments, regarding the quality and quantity of dissolved organic carbon (DOC) and its influence on the concentrations of di- and trivalent cations. The streams showed significant differences in the content and size distribution of DOC and in the distribution of cations between the different size fractions. For both streams the high flow events induced by precipitation influenced the chemistry of the streams through increase of organic matter and its associated cations. Fanbergsbäcken, with relatively low pH and high DOC concentration, had a greater amount of high molecular mass (HMM) DOC to which approximately 75% of Al and Fe and about 50% of Ca and Mg were associated. Gråbergsbäcken, with a higher pH and lower DOC level, had approximately 65% of Al, 40% of Fe and 30% of Ca and Mg associated to its HMM DOC fraction. Sixteen different low molecular mass organic acids were found in the stream water, of which oxalic and lactic acid were present in the highest concentrations.
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47.
  • Norström, Sara H, et al. (författare)
  • Initial effects of wood ash application to soil and soil solution chemistry in a small, boreal watershed
  • 2012
  • Ingår i: Geoderma. - : Elsevier. - 0016-7061 .- 1872-6259. ; 187, s. 85-93
  • Tidskriftsartikel (refereegranskat)abstract
    • With the conception that whole tree harvesting leads to an impoverishment of forest soils wood ash application is recommended, with the foremost benefits being increased pH in soil and subsequent surface waters, and recycling of nutrients from the wood ash.In this investigation a small boreal catchment in central Sweden was studied for two years before and two years after treatment with the maximum recommended dose, 3 tonnes/ha, of crushed, self-hardened wood ash. The sampling area was situated in a slope towards a stream, to include the effect on both recharge- and discharge areas with different soil constitutions. The soil solution chemistry, exchangeable pool of cations and potential heavy metal accumulation in berries were studied. Temporary increases in soil solution concentration were found for K in the recharge area and Ca and SO4 in the discharge area when comparing ashed and control areas. No change in exchangeable cations was observed during the study period, and no increase of heavy metals in bilberries did occur. These small changes in the constitution of the soil solution do not suggest wood ash application as a method to improve soil quality in an initial phase.
  •  
48.
  • Norström, Sara H (författare)
  • Soil and stream water chemistry in a boreal catchment - interactions, influences of dissolved organic matter and effects of wood ash application
  • 2010
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Two small bordering catchments in Bispgården, Central Sweden, wereinvestigated in regard to soil solution and stream water chemistry during the frostfree seasons of 2003-2007. Both catchments were drained by first order streams,Fanbergsbäcken and Gråbergsbäcken, and in Fanbergsbäckens catchment anextensive investigation of the soil and soil solution chemistry was conducted bylysimeter and centrifugation sampling. The area of intensive soil solutioninvestigation was situated in a slope towards a stream incorporating a rechargearea, with podzolic soil, and a discharge area close to the stream with an arenosolsoil. Samples were continuously taken in both the recharge- and the discharge areaof the slope, and stream water was sampled in the streams of both catchments. Themain variables of interest of the study were the interactions, the influence ofdissolved organic carbon and the effects of wood ash application to soil solutionand stream water.The natural variations and the interactions between soil solution and streamwater were monitored during 2003-2004. In soil solution, most of the investigatedsubstances tended to increase during the growing season, due to weathering andmicrobial degradation of biota. Ca, Mg, Al and Fe were highly associated todissolved organic carbon (DOC) throughout the catchment. The low molecularfraction of DOC seemed to have a higher impact on the soil processes in therecharge area, while high molecular DOC was more important for transport ofcations in the discharge area and the stream water.The concentration of different substances in the two streams differedsignificantly, even though the catchments were similar in size, shape andforestation. The seasonal patterns of most of the substances measured weresignificantly correlated between the streams, however. Cations and pH correlatedwell with DOC and flow. The flow pattern driven by precipitation seems to be thedriver of the stream water chemistry.Wood ash was applied at a dosage of 3 ton/ha to one of the catchments in theautumn of 2004, to investigate the initial effects on the soil solution- and streamwater chemistry. WAA is recommended by the Swedish Forest Agency tocounteract acidification in soil and runoff that may be caused by an intensivebiomass harvesting. The impact of the WAA was studied during 2005-2006.Compared to the control temporarily higher concentrations of K, Ca and SO4 wereobserved in the soil solution of the ashed area. In the stream water the effects of theWAA were easier to distinguish due to higher sampling frequency. The strongesteffect was seen for K, but increases in the stream water were also noted for DOC,Ca, Mg, Si, Cl and malonate. No increase in pH could be statistically verifiedhowever, and overall the initial effects of the WAA seem mild.
  •  
49.
  • Norström, Thor, 1948-, et al. (författare)
  • Alcohol, suppressed anger and violence
  • 2010
  • Ingår i: Addiction. - : Wiley. - 0965-2140 .- 1360-0443. ; 105:9, s. 1580-1586
  • Tidskriftsartikel (refereegranskat)abstract
    • Aims Is alcohol related causally to violence, and if so, is the effect of drinking contingent on suppressed anger such that it is strongest among individuals who are highly inclined to withhold angry feelings? We addressed these questions by analysing panel data using a method that diminishes the effects of confounding factors. Design We analysed data on heavy episodic drinking and violent behaviour from the second (1994) and third (1999) waves of the Young in Norway Longitudinal Study ( n = 2697; response rate: 67%). The first difference method was applied to estimate the association between these behaviours, implying that changes in the frequency of violence were regressed on changes in the frequency of drinking. Hence, the effects of time-invariant confounders were eliminated. Analyses were conducted for the whole sample, and for groups scoring low, medium and high on a short version of the STAXI anger suppression scale. Findings Changes in drinking were related positively and significantly to changes in violent behaviour, but the alcohol effect varied with the level of suppressed anger: it was strongest in the high-anger group (elasticity estimate = 0.053, P = 0.011) and weakest (and insignificant) in the low-anger group (elasticity estimate = 0.004, P = 0.806). Conclusions Alcohol use may be related causally to violence, but the effect of drinking is confined to individuals who are inclined to suppress their angry feelings. [ABSTRACT FROM AUTHOR]
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50.
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