| 1. |
- Hammarlund, Emma U., 1971-
(författare)
-
Ocean chemistry and the evolution of multicellularity
- 2012
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Oxygen has been assumed to be a vital trigger for the evolution of multicellular life forms on Earth, partly based on its power to promote substantial energy flux in cell respiration and partly as biosynthesis of compounds like collagen require oxygen. However, the co-evolution of large life and the Earth’s chemical environment is not well understood at present, and there is particular disagreement in the field about whether the Cambrian explosion of animal life forms was a chemical or biological event. Here, I discuss the evolution of multicellularity, divided in simple or complex forms, in light of the evolution of ocean water column chemistry in both the Proterozoic and the early Paleozoic. Even if the appearance of animals is confined to the Ediacaran, other fossil evidence of complex multicellularity can be argued to occur in the Paleo-, Meso- and Neoproterozic. These finds are, if anything, reason enough to keep searching for early experiments in complex multicellularity. In this search, we may have to expand our toolbox by looking at e.g. trace element aggregations and the isotopic composition of key elements. Research over the last couple of years have accentuated that much of the interval between the Ediacaran and the Devonian was dramatic with transitional ocean chemistry at the same time that large forms of animal life experienced dynamic radiation and ecological expansion. Results presented here describe some aspects of this time, including geochemistry from Chengjiang and a mechanism for preserving non-mineralized Cambrian animals that was partly dependent on specific ocean chemistry. Also, geochemical proxies using iron and molybdenum are used to infer a Paleozoic atmosphere with less than 50% of present levels of oxygen. The possibility that the subsequent rise is due to terrestrial plants and linked to the appearance of large predatory fish is discussed. Finally, the first mass extinction in the end-Ordovician is linked to low oxygen concentrations in the water column. It appears that more than oxygen was critical to allow the radiation of large life forms on Earth, but that chemistry and tectonic activity were intimately intertwined to biology, in a dance of permitting and being determined by certain aspects of ecology.
|
|
| 2. |
|
|
| 3. |
- Duc, Nguyen Thanh, 1980-
(författare)
-
Abiotic and biotic methane dynamics in relation to the origin of life
- 2012
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Methane (CH4) plays an important role in regulating Earth’s climate. Its atmospheric concentrations are related to both biotic and abiotic processes. The biotic one can be formed either by chemoautotrophic or heterotrophic pathways by methanogens. Abiotic CH4 formation can occur from several sequential reactions starting with H2 production by serpentinization of Fe-bearing minerals followed by Fischer-Tropsch Type reactions or thermogenic reactions from hydrocarbons. In the presence of suitable electron acceptors, microbial oxidation utilizes CH4 and contributes to regulating its emission. From the perspectives of astrobiology and Earth climate regulation, this thesis focuses on: (1) Dynamics of CH4 formation and oxidation in lake sediments (Paper I), (2) Constructing an automatic flux chamber to facilitate its emission measurements (Paper II), (3) dynamics of both abiotic and biotic CH4 formation processes related to olivine water interaction in temperature range 30 - 70°C (Paper III and IV). Paper I showed that potential CH4 oxidation strongly correlated to in situ its formation rates across a wide variety of lake sediments. This means that the oxidation rates could be enhanced in environments having the high formation rates. Thereby, the oxidation would likely be able to keep up with potentially increasing the formation rates, as a result diffusive CH4 release from freshwater sediments might not necessarily increase due to global warming. Paper II presented a new automated approach to assess temporal variability of its aquatic fluxes. Paper III and IV together revealed that H2 can be formed via olivine-water interaction. Abiotic CH4 formation was formed likely by Fischer-Tropsch Type reactions at low inorganic carbon concentration but by thermogenic processes at high inorganic carbon concentration. Paper IV showed that biotic methanogenic metabolism could harvest H2 and produce CH4. The dynamics of these processes seemed strongly affected by carbonate chemistry.
|
|
| 4. |
- Bohlin, Hanna, 1974-
(författare)
-
The influence by point sources on carbon, nitrogen and metals in two sedimentary environments
- 2005
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Sediments in two aquatic environments have been investigated. Both are anthropogenically affected and polluted. The focus has been on stable carbon and nitrogen isotopes, C/N ratios, and heavy metals. The first site is Höggarnsfjärden Bay in the inner parts of the Stockholm Archipelago, Sweden, where a garbage dump releases treated leach water. The effect on carbon and nitrogen in the sediment close to the discharge is large, but 1200 m downstream the effect is diluted by the background discharge of the town of Stockholm and the Lake Mälaren, which drains into the archipelago. The main source of the studied metals is not the garbage dump itself. The sediment close to the discharge shows high enrichment factors due to high sedimentation rate and adsorption, and low decomposition of organic matter. The metal enrichment factors of downstream sites are not higher than the upstream sites. The second site is Lake Verkasjön close to the north part of Lake Vättern, in the county of Örebro, Sweden. River Salaån flows through Lake Verkasjön on the way through a former mining area to Lake Vättern. Upstream of Lake Verkasjön an ore dressing plant site was used in 1877-1881 for extraction of zinc. During that period the sediment of Lake Verkasjön received high loadings of sulphidic tailings. Normal sedimentation after the event has lead to that the polluted sediment is found as a distinct layer at 18-22 cm. The layer is characterized by elevated metal concentrations, decreased organic matter content and increased stable carbon composition. The sediment that has accumulated above 18 cm works as a physicochemical barrier that seals the waste from the overlying sediment. At the time of the event the signal of aquatic production in the sediment changed; the sediment above the layer has an increased proportion of aquatically produced material, implying changed land use in the catchment area.
|
|
| 5. |
- Holm, Johan, 1960-
(författare)
-
Konstruktionen av en stormakt : Kungamakt, skattebönder och statsbildning 1595-1640
- 2007
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- State building has traditionally been viewed strictly as the prerogative of rulers. However, recent studies have been focusing more on the perspective of state building from below. Princes and central administrators needed the active support of their leading subjects. In most parts of Europe this meant the nobility and/or the rich merchant groups.In Sweden, however, there were few rich merchants and the nobility, lead by the old aristocracy, did not support the state that the Vasa kings wanted to build. So the kings turned to the only group left to support them, the Swedish landholding farmers. They were the major tax contributors and they were also a military force to be reckoned with. But if the kings wanted their support they also had to give them something in return. The more dependent the king was on their support, the more political influence the farmers could exercise.It has long been an issue of debate whether the Swedish peasants, a) could be considered as a proactive, political group, b) whether they actually had a political program of their own and c) if they were able to exercise a lasting influence upon the formation of the Swedish state. When examining the evidence it becomes clear that the taxpaying farmers can be considered as a political proactive group with a political program. It is also clear that they managed to influence the state building process. But this influence was closely tied to the current value of their support. Duke Karl (later Karl IX) badly needed the farmer’s support in his fight for the crown. His son, Gustav II Adolf, managed to gain the support of the nobility as well as the support of the farmers, consequently he did not need the farmers support as badly as his father. After the kings death in 1632 the nobility took control. They did not need the farmers support at all, and consequently the state formation process now took a path contrary to the farmer’s interests.The Swedish peasants did, however, manage to retain parts of their political influence and they maintained their position in the diet. In short, the Swedish taxpaying farmers were politically active subjects, they did have a political program of their own and they did, indeed, exercise a considerable influence on the state building process from below.
|
|
| 6. |
- Ivarsson, Magnus, 1975-
(författare)
-
Fossilized microorganisms in volcanic rocks from sub-seafloor environments
- 2008
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Fossilized microorganisms are focused in this thesis. Such organisms have been observed in drilled basalt samples from the Emperor Seamounts in the Pacific Ocean collected during ODP (Ocean Drilling Program) Leg 197. The fossilized microorganisms occur in veins where they are attached to the vein walls of altered basalt, volcanic glass or zeolites and entombed in secondary mineral phases like calcite, aragonite and gypsum. The fossilized microorganisms consist of various morphological types: sheaths, segmented filaments, twisted filaments, amorphous filaments and branched filaments. Fossilized cells are also found in association with the filaments as well as microbially produced tunnel structures.The work has mainly been divided in two parts: (1) proving biogenicity of the microfossils and (2) studying the paleoenvironment that prevailed while the microorganisms lived, as well as the interaction between the microorganisms and their environment. The first part has been focused on various instruments and methods with the aim of gathering as much data as possible regarding the biogenicity of the microfossils. The methods that have been used are ESEM/EDS, ToF-SIMS, Raman spectroscopy, laser ablation ICP-MS and staining with the pigment PI (propidium iodide) in combination with fluorescence light. The use of these methods have resulted in various data that, when combined, display a strong case for the biogenicity of the microfossils.The second part has been focused on the minerals in which the microfossils are preserved as well as mineral phases closely associated with the microfossils. Studying fluid inclusions present in the same minerals that the microfossils are found in has made it possible to reconstruct the conditions that prevailed at the moment of preservation regarding fluid composition, fluid temperatures and water depth. With laser ablation ICP-MS it has been possible to study micro-scale variations in iron isotopes within the microfossils and to indicate iron fractionation that has taken place during the involvement in iron oxidation reactions and precipitation of iron oxides. Association with various minerals and alteration products has shown that the microorganisms have been able to inhabit various mineral surfaces and micro-environments as the alteration of the ocean crust has proceeded and the conditions for a biosphere have changed. The work extends the present knowledge about the deep-sub-seafloor biosphere and shows that it probably inhabits much larger volumes of the ocean crusts around the world than was previously known. The work introduces new geological niches and new micro-structures to search for and to study in the ongoing search for traces of life in geological environments. This has implications for the exploration of the ocean crusts and sub-surface environments on Earth as well as future exploration for a fossil record on other planetary bodies like Mars.
|
|
| 7. |
- Neubeck, Anna, 1974-
(författare)
-
Low temperature olivine alteration ; an experimental approach
- 2011
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Water reacting with minerals to alter or dissolve them is a common phenomenon on Earth, leading to a unique chemical composition of the oceans and continents. The continuous circulation of elements and the chemical reactions between them creates the extraordinary environment prevailing on our Earth today and was probably an important requirement for the onset of life on our planet. Olivine is a mineral with the special property of being unstable at atmospheric pressures and temperatures due to its crystal structure and chemical composition. Hydrous alteration of olivine has the capacity to form molecular hydrogen (H2) and hydrated secondary products concurrent with the release of heat. H2 is considered to be crucial for the deep subsurface biosphere and is capable of reducing oxidized carbon species to CH4 and other hydrocarbons through the so-called Sabatier reaction or Fischer-Tropsch Type reactions which are important when studying the large scale CH4 outgassing on Mars or the CH4 seeps coupled to contemporary terrestrial ophiolites. This thesis investigates the potential abiotic formation of H2 and CH4 at low temperatures and pressures as well as under anoxic conditions but also looks at the potential for sustaining the growth of methanogenic archaea with olivine and water. The results suggest that olivine has the potential to form H2 and fuel the abiotic formation of CH4 at low temperatures and low concentrations of dissolved bicarbonate. At higher bicarbonate concentrations, precipitation of silica and carbonate are suggested to cover the reactive catalytic sites on the olivine surface.
|
|
| 8. |
|
|
| 9. |
- Ståhle, Göran, 1967-
(författare)
-
Det religiösa självet i praktik vid ett hinduiskt gudinnetempel : Ett kulturpsykologiskt angreppssätt för religionspsykologi
- 2004
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The main objective of this dissertation is to contribute to the psychology of religion in two ways. First, it adds to theory development in the field, and second, it provides an original field study of Hindu everyday-religiosity. This dual-focused objective is met through the development of theory for a practice-oriented cultural psychology of religion, grounded in a study of a Hindu goddess-temple in Banaras (Varanasi), India. The cultural psychological approach makes use of Bourdieu’s concept “habitus”. It is argued that employing this concept in theory development overcomes a dualism of culture and self, and provides an alternative to previous models in the psychology of religion that interpret religiosity in either intrapsychical or intersubjective terms. Further, it is argued that the concept can interpret culture-specific features in Hindu religiosity, such as an emphasis on practical activity and on a non-dualistic view of person and world.A model of a “Religious Self in Practice” is outlined, which integrates features from theories of “self as narrative practice” and Bell’s concept “ritualization”. The religious self is seen as a construction of relational and practical processes, a product of individuals participating in cultural practices of religiosity, manifested in a specific local site. Specific persons master the pre-given conventions of religious self-construction in individual, creative ways. The study argues that a temple is such a site in a Hindu context. Ethnography is used to study the cultural practices of the religious self at the site, and life story interview to study a sample of seven individual ways of mastering these practices. The study analyzes sacred status at the temple as being an interplay of individuals’ devotions and common practices of religiosity. This practical logic is also identified in the life stories of the devotees as narrative practice of the religious self in relation to the Goddess.
|
|
