| 441. |
- Ignell, Rickard
(författare)
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Olfaction in Desert Locusts- Anatomy, Function and Plasticity of the Central Olfactory System
- 2001
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The anatomy, function and plasticity of the primary olfactory centre, the antennal lobe (AL), of the desert locust Schistocerca gregaria was investigated using a number of neuroanatomical and neurophysiological methods. Anatomical characterisation of the AL in a number of orthopteran species made it possible to deduce a model concerning the evolution of microglomeruli. These neuropil structures, constituting the first relay centres in the olfactory information pathway of the desert locust, seem to have evolved through fragmentation of multicompartmented unique glomeruli elicited by changes in the architecture of olfactory receptor- and projection neurons. The function and plasticity of the AL was investigated by characterising the response characteristics of olfactory projection neurons in 1st, 3rd, 5th and adult solitary and gregarious locusts by means of intracellular recording and staining methods while stimulating with behaviourally relevant odours. This characterisation revealed stage- and phase-dependent plasticity in the olfactory pathway, including changes and differences in response spectra and sensitivity of olfactory projection neurons. These changes were linked with morphological changes within the AL. Plasticity of olfactory information processing and aggregation behaviour in adult gregarious locusts was also studied in relation to age and juvenile hormone (JH) level. Locusts containing a high level of JH, i. e. old locusts and locusts injected with JH, displayed an impairment of the central olfactory system that was reflected in a diminished behavioural response to the main adult aggregation pheromone component, phenylacetonitrile. Locusts containing a low level of JH, on the other hand, displayed a fully functional olfactory system and a positive response to the tested pheromone component. The morphology and ramification pattern of immunocytochemically identified aminergic and neuropeptidergic neurons were investigated as a first step toward unravelling their potential role in olfactory information processing. This study revealed a number of novel interneurons innervating the AL showing immunoreactivity to serotonin, histamine, locustatachykinin, leucokinin and FMRFamide.
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| 442. |
- Kaplan, Jed O
(författare)
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Geophysical Applications of Vegetation Modeling
- 2001
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis describes the development and selected applications of a global vegetation model, BIOME4. The model is applied to problems in high-latitude vegetation distribution and climate, trace gas production, and isotope biogeochemistry. It demonstrates how a modeling approach, based on principles of plant physiology and ecology, can be applied to interdisciplinary problems that cannot be adequately addressed by direct observations or experiments. The work is relevant to understanding the potential effects of climate change on the terrestrial biosphere and the feedbacks between the biosphere and climate. BIOME4 simulates the distribution of 15 high-latitude biomes, including five tundra vegetation types, for the present day using observed climate, and the LGM, mid-Holocene, and a "greenhouse" scenario for 2100 using the output of GCMs. In the LGM simulations, the high-latitudes show a marked increase in the area of graminoid and forb tundra, which is also the predominant feature in the paleodata. This vegetation has no widespread modern analog; it was favored by the cold, dry climate, and supported large mammoth populations. Mid-Holocene simulations indicate a modest, asymmetrical northward advance of the Arctic treeline compared to present, with greatest extension in central Siberia (up to 300 km), and little to no change in the Western Hemisphere. This result is in good agreement with pollen and megafossil data from the same period. Differential warming of the continents in response to increased high-latitude solar radiation is hypothesized to account for the asymmetry. Vegetation changes in the 2100 projection, which assumes a continued exponential increase in atmospheric GHG concentrations, are more radical than those simulated for the mid-Holocene. The year-round forcing due to GHGs increases both summertime and annual temperatures in the high latitudes by up to double the mid-Holocene anomaly. However the potential treeline advances and biome shifts in our simulation are unlikely to be realized within 100 years, because of the time required for migration and establishment of new vegetation types. Potential natural wetland area for the present day was simulated by BIOME4 as 11.0 x 106 km2. This value is higher than other estimates but includes small (< 50 km2) and seasonal wetlands which have not been included in previous surveys. The wetland CH4 source was simulated as 140 Tg yr-1. At the LGM, simulated wetland area was increased by 15% but CH4 emissions were 24% less than the present-day. The simulated reduction in the CH4 source is due to substrate limitation induced by low atmospheric CO2 concentrations at the LGM. The 100% increase in atmospheric CH4 concentrations measured in ice cores between the LGM and the preindustrial Holocene may not be due to changes in CH4 source strength alone, as other trace gases influence the atmospheric CH4 sink. The stable carbon isotope composition of the terrestrial biosphere was simulated by BIOME4 and compared to measurements at the leaf, ecosystem and troposphere scales. Model simulations are correlated within one standard deviation to measured means at the PFT and biome scales, and at six Northern Hemisphere CO2 monitoring stations. Global carbon isotope discrimination in the terrestrial biosphere averaged 18.6‰ for potential natural vegetation and 18.1‰ when an agricultural land-use mask was applied. These simulated values are slightly higher than previous estimates, but consistent with measurements. This information is important for the interpretation of contemporary atmospheric observations in terms of carbon sources and sinks on land and in the ocean.
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| 443. |
- Larsson, Mattias
(författare)
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Neural Interfaces to the Odour World of Scarab Beetles
- 2001
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Antennal detection and central nervous integration of behaviourally relevant odours in scarab beetles (Coleoptera: Scarabaeidae) was investigated, using the two Japanese scarabs Anomala cuprea and Phyllopertha diversa (Rutelinae), and the Central African fruit chafer Pachnoda marginata (Cetoniinae) as model species. Electrophysiological single cell recordings in A. cuprea and P. diversa characterized odour detection by antennal olfactory receptor neurons tuned to plant odours (flower odours, green leaf volatiles) and sex pheromones. In both species, dose-response tests showed that plant compounds as well as sex pheromone components were detected by specialized types of receptor neurons, each type responding preferentially to a single compound. Responses of antennal receptor neurons in P. marginata to single compounds in fruit extracts were investigated using single cell recordings, while stimulating with fruit compounds eluting one by one from a gas chromatograph. Olfactory receptor neurons in this species also responded to single compounds or a few structurally related compounds, in spite of generally high stimulus concentrations. The receptor neurons responding to the fruit volatiles could be grouped into 28 types, responding to a total of more than 50 compounds. The attractiveness of 35 electrophysiologically active fruit compounds was evaluated in a 2-choice olfactometer. Half of these compounds were attractive to P. marginata, while the others showed no attractiveness as single compounds. A mixture of three compounds not attractive by themselves was attractive to P. marginata males, showing that some compounds have behavioural relevance only as components of a blend. In P. marginata, 27 fruit compounds detected by antennal receptor neurons were used as stimuli in intracellular studies of odour integration by interneurons in the antennal lobe of the brain. Lucifer Yellow-filled interneurons consisted of uniglomerular and multiglomerular projection neurons, plus some local neurons, which all had multiglomerular arborizations and a dense focus in a single glomerulus. Most interneurons had narrow response spectra, responding to single or up to a handful of compounds, while the multiglomerular projection neuron responded to almost all stimuli. Almost all interneurons responded to attractive single compounds, while non-attractive compounds generally eliciting no or very weak responses.
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| 444. |
- Persson, Maria
(författare)
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The Threat to the Baltic Salmon - a Combination of Persistent Pollutants, Parasite and Oxidative Stress
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Atlantic salmon (Salmo salar) from the Baltic Sea suffer from a reproduction disease known as the M74-syndrome. Newly hatched fry develop nerve disorders and die between 3-5 days after the first symptoms are seen. This is a maternally transmitted disease that is casued by a thiamine (vitamin B1) deficiency. The factor(s) that casue(s) this thiamine deficiency are largely unknown. However, several theories have been put forward including persistent pollutant exposure, parasite infestation, fungal or viral infections, thiminase-containing prey or genetic variation in salmon. In the second paper I have measured persistent pollutant concentrations in a Baltic salmon population and correlated that with stress levels in the liver (CYP1A1 and EROD) as well as genetic variation in the expression of the AH receptor (which aids in breaking down pollutants in the body). However, I suspected that there was a large within-fish variation in lipids (and thereby in lipophilic pollutant concentration) in salmon. Therefore, I measured lipid- and pollutant- variation within salmon in paper II, and discuss how such within-fish variation may have consequences both methodologically during sampling, but also for PCB intake in humans after consumption of fish. To further look into stress factors that may affect Atlantic salmon and give rise to a thiamine deficiency, I wanted to investigate nutrient uptake in intestinal parasites of salmon. In paper III, I measured stable isotopes of carbon and nitrogen and found that the cestode Eubothrium crassum and Atlantic salmon differ in nutrient uptake. It seems like parasites rely mainly on passive uptake, and can (when there is an excess of nutrients in the host) benefit from lipid rich hosts by accumulating excess lipids. In paper IV, I wanted to see if E. crassum can accumulate persistent pollutants from the diet. I collected salmon and parasites from salmon intestines as well as sprat from salmon stomachs (sprat is prey both for salmon and for parasites). It was found that salmon accumulate persistent pollutants from the prey, whereas parasites did not. In addition, salmon biomagnified all biphenyl congeners from the diet, whereas parasites seemed unable to biomagnify pollutants. In paper III and IV, the literature on nutrient uptake and biomagnification are discussed. In paper V, PCB and DDT concentrations were measured in three populations of salmon from the Baltic Sea and the two largest lakes in Sweden. The Baltic Sea salmon were the most contaminted on a wet weight basis. Pollutant concentrations in Swedish salmon were compared to concentrations in the rest of the world by an examination of the literature, and it was found that European salmon were more contaminated than salmon from North- or South America
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| 445. |
- Pirzadeh, Pardis
(författare)
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Ecotoxicological assessment by microcosm tests on plankton communities
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The aim of this thesis is to present a short-term plankton community toxicity test in laboratory microcosms, with which the effect of the test substance on species abundance and composition of the community is evaluated. This laboratory microcosm is an intermediate between single-species tests and outdoor mesocosm tests. The brominated flame retardant HBCDD was chosen as the reoccurring test substance in three experiments. It was applied at similar nominal exposure concentrations in toxicity experiments performed in test systems with different grades of complexity. One experiment was performed in an outdoor artificial pond in which cylinders were inserted to isolate replicate mesocosms. The other experiments were performed in a greenhouse environment in 10 L microcosms with sediment and water from a eutrophic lake and brackish water estuary. The short-time plankton community toxicity test proposed in this work was successful in detecting structural changes in plankton community composition due to exposure to anthropogenic chemicals. Several prerequisites for a sensitive community toxicity test were fulfilled. Ecological interactions, like competition and predation, were present and made detection of community level responses like secondary effects possible. The community which developed in the 10 L microcosms included many plankton species. This is important for a sensitive and representative evaluation of the toxic effect. The rich plankton community and a maintained balance between the autotroph and heterotroph communities during the course of the experiment were possible due to the sediment compartment. The sediment acts as a seed-bank from which plankton continuously hatch and enter the water volume. Lake water inoculation did not increase the species richness and made no change in plankton community composition. Using artificial water decreases both work-load and costs, considerably. Another important issue in the evaluation of toxicity tests is the variance of test endpoints between replicates. The minimal detectable difference from control (MDD) which mirrors the variability of test endpoints was compared between the mesocosm experiment and the two microcosm experiments. The three lowest MDD values were more or less in the same range between the experiments and ranged between 5-39%. A possible increase in MDD was observed with increased experimental duration. An exposure period of 7 days is considered optimal in detecting clear community level responses at a minimum time. The effects of the test compounds in the three experiments were evaluated with population level and community level metrics. Judging from the results, no single toxic endpoint was found to be the most sensitive one. This stresses the importance of analysing both community and population metrics.
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| 446. |
- Törneman, Niklas
(författare)
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Spatial variability linking carbon resource heterogeneity and microorganisms; causes and consequences
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Organic carbon and bacteria have a high variability at different scales in the soil, and organic carbon may be a limiting factor for growth of soil bacteria. Thus, it can be expected that these co-vary at different scales in the soil. In this thesis, I have studied the spatial interaction between soil bacteria and natural and contaminant (polycyclic aromatic hydrocarbon, PAH) organic carbon. The overall objective was to suggest reasons why there is an absence or presence of co-variation between them. The spatial patterns of PAHs at a creosote contaminated site were clearly related to their water solubility. The microbial community fingerprint (PLFA analysis) co-varied with PAH concentrations while microbial community diversity was positively correlated to PAH concentrations. Taken together it was demonstrated that a diverse gram-negative bacterial community with a patchy spatial distribution similar to the PAH spatial distribution dominated the creosote contaminated site. Catabolic genes for PAH degradation in bacteria had a more even distribution across the site although hotspots and/or cold spots of PAH concentrations and catabolic genes often coincided.Bacterial biomass and soil respiration was spatially autocorrelated and positively dependent on PAH concentrations. PAH biodegradation lacked a spatial pattern and was uncoupled from most microbial and abiotic soil properties. The results indicated that creosote rather than PAHs was a major carbon source for the microbial community and that PAH biodegradation was controlled by a multitude of soil properties simultaneously, each with its own spatial pattern.In soil peat cores, pore water flow rate had a significant non-linear effect on respiration and methane production while the amount and type of dissolved organic carbon (DOC) remained unimportant for respiration. In contrast, in carbon limited river water, both the quality and quantity of DOC had a clear effect on respiration and bacterial growth efficiency.The main factor determining microbial biomass, community composition, and activity were both the amount and the type of organic carbon regardless of any toxic effects of the carbon.
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| 447. |
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| 448. |
- Mukherjee, Sritama, et al.
(författare)
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Evaluating sustainability for water and wastewater treatment technologies
- 2023
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Ingår i: Technological Solutions for Water Sustainability. - : IWA Publishing. ; , s. 191-199
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- High-performance water and wastewater treatment have become feasible with the development of innovative and advanced technologies that may have the potential to have an impact on health and the environment. At the same time, they can be helpful in protecting the environment and meet specific social needs in a more sustainable way. New purification techniques have the potential to lead to the sustainable development of clean water, understand global environmental challenges and seek ways to improve them. Water treatment processes become more environmentally friendly by reducing energy consumption, removing toxic and essential substances and making products sustainable during the synthesis phase. This chapter discusses water treatment in the context of India, the necessity and methods of assessing sustainability, as well as examples of technological assessments for sustainability.
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| 449. |
- Kong, Xiangrui
(författare)
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Molecular investigations of atmospherically relevant interface processes: ice formation and water accommodation on ice and organic surfaces
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Clouds and aerosols play important roles in the climate system by affecting on atmospheric chemistry, the radiation budget of the atmosphere, and the water cycle including the formation of precipitation. Climate models with predictive power require quantitative descriptions of aerosols and clouds, but several key processes remain to be fully understood. One important example is the formation and growth of ice particles in clouds. Organic compounds also form secondary organic aerosol and coatings on existing particles including ice nuclei and ice cloud particles, which further complicate the description of cloud processes. To improve the understanding of these processes, some fundamental investigations of atmospherically relevant interface interactions are carried out, and the results and findings are summarized and discussed in this thesis. The investigations use a newly developed environmental molecular beam (EMB) technique as the main experimental method. The principle, design and demonstration of the EMB method are described in detail. The method allows for ice surface investigations at temperatures up to 213 K, and it is employed to study gas-surface interactions under conditions relevant to the troposphere. The main findings of this thesis are related to three research themes: (1) Ice formation via deposition mode nucleation on hydrophobic and hydrophilic surfaces is characterized. The critical supersaturation required to activate nucleation on various surfaces increases rapidly with decreasing temperature below 200 K, and adsorbed organic compounds are observed to influence the nucleation, structure and growth rate of ice. (2) Water uptake by bare ice and coated ice surfaces is investigated. The accommodation and desorption kinetics for water on bare ice is quantitatively described by a precursor model. Coatings on ice have a significant impact on water uptake, and adsorption of acids commonly found in the atmosphere tends to enhance water accommodation. (3) Water interactions with surfaces on condensed organic phases and organic coatings on graphite are characterized. Bulk accommodation is inefficient on solid organic surfaces, while water uptake is efficient on liquid phases. The surface layer on condensed n-butanol is shown to change gradually from solid to liquid over a 10 K temperature span around the bulk melting temperature, with major implications for water uptake. The thesis includes the development of new experimental methods and an improved molecular-level understanding of processes at gas-solid and gas-liquid interfaces, and thereby contributes to a better description of cloud and aerosol processes in the environment.
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| 450. |
- Sveinbjörnsson, Kári
(författare)
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Preparation and Characterization of Lead Halide Perovskites : Towards sustainable, cost-effective and upscalable solar cell manufacture
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The perovskite solar cell (PSC) is a recent contender within the photovoltaic research field. In a matter of a few years, the power conversion efficiency (PCE) of the PSC has catapulted from 4% to above 22%, which represents one of the fastest developments in the field. The PSC band-gap tunability makes them interesting for use in tandem solar cells with other established solar cell technologies. This thesis focuses on exploring the photophysics of the perovskite material as well as the development of different perovskite preparation processes and materials for potential use in large-scale manufacture and tandem solar cell applications.First, the photoconductivity of a perovskite film deposited on different metal oxide nanoparticle layers is investigated. The results show that the perovskite can generate free charge carriers without the presence of an electron acceptor.Secondly, we constructed PSCs with a conducting carbon-nanotube film, as a replacement for both the hole-selective layer and the metallic back electrode, which yielded a PCE of 15.5%. Furthermore, we explored the preparation of semitransparent PSCs for tandem solar cells by using atomic-layer deposition (ALD) for depositing a thin electron-selective metal-oxide layer. We were successful using ALD directly on a perovskite layer without damage to the perovskite. Although the PSCs did not yield high PCE, the study marks a step in further development for direct ALD deposition onto the perovskite.Finally, we developed two different methods concerning sustainable manufacture of PSCs. The first method was based on the synthesis of the mixed-ion (FAPbI3)0.87(MAPbBr3)0.17 perovskite in ambient air, which had hitherto only been possible in inert atmosphere. The best PSC was obtained by depositing the perovskite onto a 50°C warm substrate in ambient air yielding a PCE of 17.7%. In the second method, only non-hazardous solvents, water and isopropanol, were used in the synthesis of Cs0.1FA0.9Pb(I0.83Br0.17)3. It is the first publication of mixed inorganic and organic cation perovskite synthesis using a two-step preparation procedure with only non-hazardous solvents and the process yielded a PCE of 13.0%. The method allows for complete ionic control of the perovskite and further variation and improvements are therefore possible.
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