1,840 research outputs found
SLFs vårexkursion till södra Småland – en rapport.
No full textI april 2016 gick föreningens vårexkursion till trakterna runt Växjö, med några helt skilda miljöer som mål. Här redogör Emil Persson och Ulf Arup för exkursionen som innebar deltagarrekord med god marginal. Första dagen deltog hela 56 personer
Johan Söderberg, Ulf Jonsson et Christer Persson, A Stagnating Metropolis. The Economy and Demography of Stockholm, 1750-1850
No full textVerley Patrick. Johan Söderberg, Ulf Jonsson et Christer Persson, A Stagnating Metropolis. The Economy and Demography of Stockholm, 1750-1850. In: Annales. Économies, Sociétés, Civilisations. 48ᵉ année, N. 4, 1993. pp. 949-951
Fungal decomposition and transformation of molecular and colloidal fractions of dissolved organic matter extracted from boreal forest soil
No full textDissolved organic matter (DOM) plays a central role in soil carbon (C) dynamics, serving as both a substrate for microbial decomposers and a source of material stabilised via physical protection in molecular aggregates and associations with mineral particles. It is well established that soil microorganisms play a key role in mineral-associated C aggregates; however, their impacts on molecular aggregates is not clearly understood. Here, we examined the ability of an ectomycorrhizal fungus (Paxillus involutus) and a saprotrophic fungus (a strain of Gloeophyllum), two major functional groups of fungal decomposers in forest ecosystems, to decompose and process the molecular and colloidal size fractions of DOM. DOM was extracted by water from boreal forest soil, and the chemical composition and colloidal properties were followed over 11 days using nuclear magnetic resonance (NMR) spectroscopy and small-angle light and X-ray scattering techniques. Both fungi decompose various organic compounds into their molecular fractions in the presence of an energy source (i.e. glucose). The decomposition rate was significantly higher for Gloeophyllum than for P. involutus. When glucose was depleted, Gloeophyllum continued to decompose more complex carbohydrates, whereas the decomposition activity of P. involutus almost stopped. A large proportion of the C in the DOM was found in organic colloids. At later stages, Gloeophyllum but not P. involutus, significantly affected the colloids by promoting the formation of larger aggregates. Thus, saprotrophic fungi activity can significantly influence the colloidal properties of DOM. Our results support the view that ectomycorrhizal fungi decompose some of the soil organic C however, their overall capacity for DOM decomposition and transformation is significantly lower than that of saprotrophic fungi
Chemical composition and colloidal properties of dissolved organic matter in Norway spruce forest stands of different ages
No full textDissolved organic matter (DOM) is the most mobile and actively cycling fraction of soil carbon and acts as a carrier of nutrients and contaminants. It is consumed by microbes, photodegraded, or adsorbed in soils and sediments on its way to the ocean. Despite intensive research in the last two decades, the formation and fate of DOM in soils and its response to changes in land use and climate are poorly understood [1-3]. The changes in temperature and chemical composition of soils affect substantially the rates of microbial decomposition. It has previously been observed that afforestation had a positive effect on carbon stocks approximately 3 decades after land-use change [4]. The aim of this study was to identify the role of afforestation on the chemical composition and colloidal nature of DOM. We compared water extractable DOM from an organic horizon in three differently aged (35-, 61-, 90-years-old) Norway spruce stands growing in the same Tönnersjöheden area located at Simlångsdalen, south-west Sweden . Arable fields that were adjacent to each of these three forests served as control DOM samples and represented the soil material before afforestation. Chemical composition of DOM was inferred from 13C solid-state nuclear magnetic resonance (NMR), high-resolution 1H NMR, infrared spectroscopy (DRIFT) and elemental analysis measurements. Colloidal properties of DOM were investigated using small-angle X-ray and dynamic light scattering methods together with electrophoretic mobility measurements. The dialysis experiment was additionally performed in order to investigate the high molecular fraction of DOM.
Elemental analysis revealed an increase in the ratio between total organic C and total N with forest age and no differences between three field DOM extracts. 1H and 13C NMR results showed that both field and forest DOM extracts were dominated by carbohydrates and also contained carboxylic and aliphatic compounds. The aromatic structures were not detected using NMR. However, some features of aromatics and phenolics were detected in IR spectra, especially in forest cold DOM. Scattering data showed that field and forest DOM contained locally stable colloidal aggregates of ca. 100 nm in radius. The structures of these aggregates are consistent with a combination of globular and cluster-like colloids. Field DOM contained slightly higher fraction of clusters than forest DOM. According to the dialysis experiment the half of DOM was presented in high molecular weight fraction (> 12-14 kDa). Overall, our data suggest that DOM extracted from forest and field organic soils had similar chemical and colloidal properties. The relative composition was dictated more by temperature at which DOM was extracted
Ferrihydrite Nanoparticle Aggregation Induced by Dissolved Organic Matter
No full textFerrihydrite (Fh) nanoparticles are omnipresent in nature and often highly mobile because of their colloidal stability. Thus, Fh serves as a vector for iron as well as associated nutrients and contaminants. Here, we demonstrate, using small-angle X-ray scattering combined with cryo-transmission electron microscopy (cryo-TEM), that dissolved organic matter (DOM), extracted from a boreal forest soil, induce aggregation of Fh nanoparticles, of radius 3 nm, into fractal aggregates, having a fractal dimension D = 1.7. The DOM consists of both fractal-like colloids (>100 nm) and small molecular DOM, but the attractive Fh interparticle interaction was mediated by molecular DOM alone as shown by cryo-TEM. This highlights the importance of using soil extracts, including all size fractions, in studies of the colloidal behavior of DOM-mineral aggregates. The Fh nanoparticles also self-assemble during synthesis into aggregates with the same fractal dimension as the DOM-Fh aggregates. We propose that, in both the absence and presence of DOM, the aggregation is controlled by the Fh particle charge, and the process can be viewed as a linear polymerization into a self-avoiding random walk structure. The theoretical D value for this is 5/3, which is in close agreement with our Fh and DOM-Fh results
Änglar, Fresterskor och Älskarinnor - Kvinnobilder i Ulf Lundells rocklyrik
No full textKvinnobilderna i Ulf Lundells rocklyrik undersöks ur ett litteraturvetenskapligt perspektiv. Hur presenteras kvinnlig närvaro i texterna? Närmare 500 av Lundells rocktexter ligger till grund för undersökningen som tolkar skildringen av främst Änglar, Fresterskor och Älskarinnors förekomst i texterna
Swedish integration policy documents: a close dialogic reading
No full textSweden as the great welfare state where everybody is equally welcomed and cared for has for long been the prevailing view. Although Swedish integration policy seems to confirm this view, this is far removed from many people’s experienced reality. I argue that part of this disharmony lies in how West European languages contain and relate to an ‘identity’ construction, which perpetuates and is perpetuated through dichotomies that strengthen the social and political cogency of concepts such as ‘race’, ethnicity and culture. Based on this, I carry out a discourse analysis of Sweden’s major integration policy documents from the mid 1970s up to today.
After an eclectic reading of discourses on migration and integration terminology, ‘identity’ and language, I assert the centrality of ‘identity’ construction to everything we do. With this in mind, taking the dialogism promoted by the Bakhtinian Circle as the dichotomy to monologism, I carry out a close dialogic reading in the tradition of Lynn Pearce (1994) and Peter Stallybrass and Allon White (1986).
Contextualising the policy documents, I present the history of migration and integration from a Swedish perspective. Focusing on the last five decades, I divide the different historic tendencies into themes ranging from: emigration to labour migration, refugee migration and the European Union, and from immigrant policy to integration policy.
Believing that the conceptualisation and the handling of categorisation, segregation, culture, discrimination and racism are all central to a successful integration policy, I analyse the policy documents thematically accordingly. I show how the interdependence of the common ‘identity’ constructions and language sometimes obscures and frequently counteracts the intention of the author. As a result, I argue that the Bakhtinian Circle holds the key to a better understanding of the invincibility of stereotyping within racialised discourses, through applying absolute ‘identity’ constructions in monologic speech, and how this may be counteracted in order to strive for a dialogic approach to the world
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