| 1. |
- Hagelqvist, Alina
(författare)
-
Sludge from pulp and paper mills for biogas production : Strategies to improve energy performance in wastewater treatment and sludge management
- 2013
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The production of pulp and paper is associated with the generation of large quantities of wastewater that has to be purified to avoid severe pollution of the environment. Wastewater purification in pulp and paper mills combines sedimentation, biological treatment, chemical precipitation, flotation and anaerobic treatment, and the specific combination of techniques is determined by the local conditions. Wastewater treatment generates large volumes of sludge that after dewatering can be incinerated and thus used for bio-energy production. Sludge is currently viewed as biofuel of poor quality due to its high water content, and some mills treat it solely as a disposal problem.Two strategies have been identified as feasible options to improve the energy efficiency of sludge management. One is drying using multi-effect evaporation followed by incineration. The other is anaerobic digestion of the wet sludge to produce methane.This thesis explores the energy balances of sludge management strategies in pulp and paper mills with special focus on anaerobic digestion. The first part consists of a system analysis, used to evaluate some wastewater treatment processes and sludge management, and the second part of empirical studies of anaerobic digestion of pulp and paper mill sludge. It was shown that the use of energy for aeration in aerobic biological treatment should be kept to the minimum required for acceptable quality of the processed water. Additional aeration for reduction of the generated sludge will only result in reduced energy generation in a subsequent methane generation stage. In the second part of the thesis, it is shown that anaerobic digestion is a feasible option for sludge management as it leads to production of high value biogas. Co-digestion with grass silage, cow/pig manure or municipal sewage sludge should then be used to counteract the low nitrogen content of pulp and paper mill sludge.
|
|
| 2. |
- Nilsson, R. Anders, 1976-
(författare)
-
Dangerous Liaisons : Why Ex-Combatants Return to Violence. Cases from the Republic of Congo and Sierra Leone
- 2008
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- After disarming and demobilizing, why do some ex-combatants re-engage in organized vio-lence, while others do not? Even though former fighters have been identified as a major source of insecurity in post-civil war societies due to their military know-how, there have been few efforts to systematically examine this puzzle. This study fills this research gap by comparing the presence or absence of organized violence in different ex-combatant communi-ties – all the former fighters that used to belong to the same armed faction and who share a common, horizontal identity based on shared war-and peacetime experiences. It does so by analyzing six ex-combatant communities in two countries: ex-Cobra, Cocoye and Ninja in the Republic of Congo and ex-AFRC, CDF and RUF in Sierra Leone. More specifically, three concepts – remarginalization (former fighters’ lack of political influence, personal security or economic assistance), remobilizers (individuals who have the will, capacity and skills to coordinate organized violence in a post-conflict setting) and relationships (whether or not remobilizers share social or material bonds, conducive for war, with ex-combatant communi-ties and each other) – are applied to the six cases, in order to explain why relatively many former CDF, Cobra, Ninja and RUF fighters resorted to violence, while no or hardly any ex-AFRC and Cocoye combatants did the same. Contrary to assumptions found in previous research, this study finds that structural factors, relating to remarginalization, have little ex-planatory value in themselves. Being a rule, rather than an exception, remarginalization can best be understood as a background variable, creating conducive conditions for violence to take place. Instead, the main determinants of ex-combatant violence are whether former fight-ers have access to regional or domestic elites in the market for experienced fighters and to second-tier individuals – such as former mid-level commanders – who can act as intermediar-ies between the two. By utilizing relationships based on selective incentives and social net-works, these two kinds of remobilizers are able to generate the needed enticements and feel-ings of affinity, trust or fear, to convince ex-combatants to resort to arms. These findings demonstrate that the outbreak of ex-combatant violence can only be understood by more clearly incorporating an actor perspective, focusing on three levels of analysis: the elite, mid-level and grass-root.
|
|
| 3. |
- Almlöf Ambjörnsson, Heléne, 1968-
(författare)
-
Mercerization and Enzymatic Pretreatment of Cellulose in Dissolving Pulps
- 2013
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis deals with the preparation of chemically and/or enzymatically modified cellulose. This modification can be either irreversible or reversible. Irreversible modification is used to prepare cellulose derivatives as end products, whereas reversible modification is used to enhance solubility in the preparation of regenerated cellulose.The irreversible modification studied here was the preparation of carboxymethyl cellulose (CMC) using extended mercerization of a spruce dissolving pulp. More specifically the parameters studied were the effect of mercerization at different proportions of cellulose I and II in the dissolving pulp, the concentration of alkali, the temperature and the reaction time. The parameters evaluated were the degree of substitution, the filterability and the amount of gel obtained when the resulting CMC was dissolved in water. Molecular structures of CMC and its gel fractions were analysed by using NIR FT Raman spectroscopy. It was found that the alkali concentration in the mercerization stage had an extensive influence on the subsequent etherification reaction. FT Raman spectra of CMC samples and their gel fractions prepared with low NaOH concentrations (9%) in the mercerization stage indicated an incomplete transformation of cellulose to Na-cellulose before carboxymethylation to CMC. Low average DS values of the CMC, i.e. between 0.42 and 0.50 were obtained. Such CMC dissolved in water resulted in very thick and semi solid gum-like gels, probably due to an uneven distribution of substituents along the cellulose backbone. FT Raman spectra of CMC samples and their gel fractions mercerized at higher alkaline concentration, i.e. 18.25 and 27.5% in the mercerization stage, indicated on the other hand a complete transformation of cellulose to Na-cellulose before carboxymethylation to CMC. Higher average DS values of the CMC, i.e. between 0.88 and 1.05 were therefore obtained. When dissolved in water such CMC caused gel formation especially when prepared from dissolving pulp with a high fraction of cellulose II.The reversible modification studied was the dissolution of cellulose in NaOH/ZnO. Here the effect of enzyme pretreatment was investigated by using two mono-component enzymes; namely xylanase and endoglucanase, used in consecutive stages. It was found that although the crystallinity and the specific surface area of the dissolving pulp sustained minimal change during the enzymatic treatment; the solubility of pulp increased in a NaOH/ZnO solution from 29% for untreated pulp up to 81% for enzymatic pretreated pulp.
|
|
| 4. |
- Magnusson, Karin, 1981-
(författare)
-
Poly-and oligothiophenes : Optical probes for multimodal fluorescent assessment of biological processes
- 2015
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- One interesting class of molecules in the research field of imaging biological processes is luminescent conjugated polythiophenes, LCPs. These fluorescent probes have a flexible backbone consisting of repetitive thiophene units. Due to this backbone, the probes possess unique abilities to give rise to different spectral signatures depending on their target and environment. LCPs are a polydispersed material meaning there is an uneven distribution of lengths of the probe. Recently, monodispersed chemically well-defined material denoted luminescent conjugated oligothiophenes, LCOs, with an exact number of repetitive units and distinct sidechain functionalities along the backbone has been developed. LCOs have the advantages of being smaller which leads to higher ability to cross the blood brain barrier. The synthesis of minor chemical alterations is also more simplified due to the well-defined materials.During my doctoral studies I have used both LCPs and LCOs to study biological processes such as conformational variation of protein aggregates in prion diseases and cellular uptake in normal cells and cancer cells. The research has generally been based on the probes capability to emit light upon irradiation and the interaction with their targets has mainly been assessed through variations in fluorescence intensity, emission-and excitation profiles and fluorescence lifetime decay. These studies verified the utility of LCPs and LCOs for staining and discrimination of both prion strains and cell phenotypes. The results also demonstrated the pronounced influence minor chemical modifications have on the LCO´s staining capacity.
|
|
| 5. |
- Nilsson, Charlotte, 1985-
(författare)
-
Phosphorus recovery from sewage sludge : Implications of incineration and enrichment potential of produced ashes
- 2024
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Sewage sludge is a promising source for phosphorus recovery, but it also contains contaminants (organics, metals) which must be removed. The most commonly used practice is incineration, where organic contaminants are decomposed. This treatment entirely alters the chemical profile of the material, and information regarding this transformation is crucial for development of durable handling and recovery processes. The aims of this project were to; 1)study the chemical speciation of phosphorus and metals in sewage sludge and their ashes after incineration; 2)evaluate the impact of iron and aluminium on the phosphorus redistribution following incineration, and 3)investigate the potential for sewage sludge ashes to function as sorbents for phosphorus and metals. Sludge and ashes from 10 municipal wastewater treatment plants in Sweden were sampled and characterized for their elemental composition, mineral components, leachability and chemical speciation. Major elements were Fe and Al (added in the wastewater treatment process), Ca, Mg, Na and K. Phosphorus was predominantly associated with aluminium and iron in the sludge, but after incineration there was a shift to calcium associated species, which is preferred for phosphorus recovery. This alteration was hampered by high concentrations of aluminium, why its concentration should be kept at a minimum. The incineration caused changes in speciation, where more ordered mineral phases where created, hematite being the major component. The ashes were successfully used as sorbents for both metals and phosphorus. Adsorption isotherms and inter particle-diffusion modelling indicated that the sorption takes place in two stages, where the first is a rapid process on the surfaces, while the second is slower and includes interactions with the pores of the material.
|
|
| 6. |
- Pettersson, John H.-O. 1981-
(författare)
-
The Origin of the Genus Flavivirus and the Ecology of Tick-Borne Pathogens
- 2013
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The present thesis examines questions related to the temporal origin of the Flavivirus genus and the ecology of tick-borne pathogens. In the first study, we date the origin and divergence time of the Flavivirus genus. It has been argued that the first flaviviruses originated after the last glacial maximum. This has been contradicted by recent analyses estimating that the tick-borne flaviviruses emerged at least before 16,000 years ago. It has also been argued that the Powassan virus was introduced into North America at the time between the opening and splitting of the Beringian land bridge. Supported by tip date and biogeographical calibration, our results suggest that this genus originated circa 120,000 (156,100–322,700) years ago if the Tamana bat virus is included in the genus, or circa 85,000 (63,700–109,600) years ago excluding the Tamana bat virus. In the second study we estimate the prevalence of tick-borne encephalitis virus (TBEV) in host-seeking Ixodes ricinus from 29 localities in Sweden and compare our data with those of neighbouring countries. Nymphs and adult ticks were screened for TBEV using a real-time PCR assay. The mean TBEV prevalence for all tick stages combined was 0.26% for Sweden and 0.28% for all Scandinavian countries, excluding Iceland. The low prevalence of TBEV in nature may partly be explained by the fact that TBEV occurs in spatially small foci and that the inclusion of ticks from non-infected foci will reduce the prevalence estimate. In the third and fourth study, we conducted the first large-scale investigations to estimate the prevalence and geographical distribution of Anaplasma spp. and Rickettsia spp. in host-seeking larvae, nymphs and adults of I. ricinus ticks in Sweden. Ticks were collected from several localities in central and southern Sweden and were subsequently screened for the presence of Anaplasma spp. and Rickettsia spp. using a real-time PCR assay. For all active tick stages combined, the mean prevalence of Anaplasma spp. and Rickettsia spp. in I. ricinus in Sweden was estimated to 1.1% and 4.8%, respectively. It was also shown that A. phagocytophilum and R. helvetica are the main Anaplasma and Rickettsia species occurring in Sweden.
|
|
| 7. |
- Sellberg, Jonas A., 1985-
(författare)
-
X-ray scattering and spectroscopy of supercooled water and ice
- 2014
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis presents experimental studies of water and ice at near-atmospheric pressures using intense x-rays only accessible at synchrotrons and free-electron lasers. In particular, it focuses on the deeply supercooled, metastable state and its implications on ice nucleation.The local structure of the liquid phase was studied by x-ray scattering over a wide temperature range extending from 339 K down to 227 K. In order to be able to study the deeply supercooled liquid, micron-sized water droplets were evaporatively cooled in vacuum and probed by ultrashort x-ray pulses. This is to date the lowest temperature at which measurements of the structure have been performed on bulk liquid water cooled from room temperature. Upon deep supercooling, the structure evolved toward that of a low-density liquid with local tetrahedral coordination. At ~230 K, where the low-density liquid structure started to dominate, the number of droplets containing ice nuclei increased rapidly. The estimated nucleation rate suggests that there is a “fragile-to-strong” transition in the dynamics of the liquid below 230 K, and its implications on water structure are discussed.Similarly, the electronic structure of deeply supercooled water was studied by x-ray emission spectroscopy down to 222 K, but the spectral changes expected from the structural transformation remained absent and explanations are discussed. At high fluence, the non-linear dependence of the x-ray emission yield indicated that there were high valence hole densities created during the x-ray pulse length due to Auger cascades, resulting in reabsorption of the x-ray emission.Finally, the hydrogen-bonded network in water was studied by x-ray absorption spectroscopy and compared to various ices. It was found that the pre-edge absorption cross-section, which is associated with distorted hydrogen bonds, could be minimized for crystalline ice grown on a hydrophobic BaF2(111) surface with low concentration of nucleation centers.
|
|
| 8. |
- Styf, Elisabeth
(författare)
-
Styrelsens ansvar för den interna kontrollen
- 2011
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Intern kontroll fick ökad uppmärksamhet i svenskt näringsliv i och med att en svensk kod för bolagsstyrning (Koden) gavs ut 2004. Att övervaka och bedöma den interna kontrollen är ett komplext och omfattande ansvar som är svårt att överblicka för en enskild styrelseledamot.Viss forskning har bedrivits under 2000-talet inom bolagsstyrning och intern kontroll. Revisionsutskottets möjlighet att säkerställa den interna kontrollen och minska riskerna för felaktigheter i den finansiella rapporteringen har bl.a. studerats. När arbetet med den här avhandlingen påbörjades fanns i huvudsak endast forskning som baserade sig på andra länders regelsystem. Svensk bolagsstyrning har till stora delar påverkats av regelsystemen i de anglosaxiska länderna, men vissa förhållanden är specifika för bolag som är noterade på svenska börser. Det är därför angeläget att studera bolagsstyrning och intern kontroll från ett svensktperspektiv.I avhandling ges en genomgång av Koden och dess formulering av styrelsens ansvar för intern kontroll. Syftet är att undersöka hur tydligt styrelsens ansvar har formulerats i Kodens regelverk samt vilka förutsättningar styrelsen har att följa reglerna. En empirisk studie genomfördes under 2007–2008, då ett 80-tal svenska börsföretag var berörda av Koden. I studien intervjuas tio styrelseledamöter om hur de upplever sitt ansvar för företagets interna kontroll och sin roll gentemot övriga bolagsorgan, dvs. ägarna, företagsledningen och revisorerna. Som ett komplement till intervjuerna analyseras 2007 års internkontrollrapporter för de företag där styrelseledamöterna varit verksamma.När Koden gavs ut hade vare sig regelsättarna eller svenska styrelseledamöter en tydlig bild över innebörden och nyttan av intern kontroll. Tidigare studier om bolagsstyrning visar att det tar tid innan förändringar får genomslag. Även denna studie visar att förändringar sker successivt. I de företag som analyserats pågår ett arbete som syftar till att förbättra den interna kontrollen. För att nå framgång i arbetet har styrelseledamöterna anammat ett pragmatiskt synsätt på sitt ansvar, som till stor del innebär att de förlitar sig på samarbete med företagsledningen. I stället för att utöva strikt kontroll och övervakning, söker styrelseledamöterna skapa en effektiv företagskultur där de tillsammans med företagsledningen strävar efter en god intern kontroll i bolaget.I likhet med tidigare forskningsresultat visar denna studie att kravet på revisionsutskott medfört att kontakterna mellan styrelsen och revisorerna har underlättats. Mötena i revisionsutskottet ger styrelsen en möjlighet att fördjupa sig i frågor om intern kontroll och finansiell rapportering. Dock saknas mer handfasta riktlinjer om vad revisorernas rapportering på utskottsmötena bör innehålla. Det finns en risk för ett förväntningsgap mellan styrelseledamöterna och revisorerna beträffande rapporteringens innehåll, och på vilket sätt den bör kommuniceras.Studien visar att internkontrollrapporteringen vid de undersökta företagen är alltför generell för att läsaren ska kunna få en uppfattning om företagets riskhanteringsprocess och kontrollåtgärder. Genom att komplettera Kodens Vägledning med förtydligande och metodbeskrivningar för riskbedömning skulle rapporteringen kunna göras mer informativ.Vidare visar studien att Kodens otydliga definition av internrevision återspeglas i styrelseledamöternas uppfattning om internrevisionens roll i internkontrollfrågor. Vare sig Koden eller Kodens vägledning beskriver internrevisionens roll och ansvar eller hur den kan bidra till att ge styrelsen ökad kunskap om bolagets interna kontrollstruktur.Kodens regler baseras på självreglering, vilket möjliggör för styrelsen att frångå reglerna och i stället ge en förklaring till varför dessa inte följs. Det ställs därför krav på att aktörer, såsom investerare, regelsättare och medier, intresserar sig för den information som lämnas eller inte lämnas, i styrelsens internkontrollrapportering. Om ingen efterfrågar informationen eller ställer krav på innehållet kommer intresset att minska, och företagens brist på god intern kontroll kommer endast att få fokus i samband med företagsskandaler.
|
|
| 9. |
- Sun, Xiaojiao, 1981-
(författare)
-
High Affinity Synthetic Molecular Binders for Proteins : Design, Synthesis and Evaluation
- 2012
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis describes the design and synthesis of small molecule derivatives and their polypeptide conjugates as high affinity binders for proteins: the D-dimer protein (D-dimer), a biomarker for diagnosis of thromboembolic diseases; human myeloperoxidase (MPO), a biomarker for cardiovascular diseases; and chitinases, potential targets for asthma therapy. The interactions between the synthetic binder molecules and those proteins were evaluated by surface plasmon resonance (SPR) biosensor analysis and fluorescence spectroscopy. Competition SPR experiments or other methods proved that the small molecule components of the binder molecules were critical for binding and specifically bound to the original binding site of small molecules. The binder molecules consisted of a 42-residue helix-loop-helix polypeptide conjugated to a small molecule via aliphatic spacers of suitable length. The small molecules could be any type of moderately binding structure. In the binder development for the D-dimer, the tetrapeptide GPRP with a dissociation constant Kd of 25 μM was used and the affinity of 4C15L8GPRP obtained was estimated to be approximately 3 nM. In the binder development for MPO, salicylhydroxamic acid (SHA) with Kd of 2 μM was used and the affinity of 4C37L34C11SHA obtained was estimated to be approximately 0.4 nM. In the binder development for chitinases, a theobromine derivative (pentoxifylline) with a Kd of 43±10 μM was used and the affinity of 4C37L34-P obtained was estimated to be considerably higher than that of pentoxifylline. The binder molecules were identified from a 16-membered pool of candidates obtained by conjugating the small molecules to each member of a set of 16 designed polypeptides. The affinities were greatly enhanced by 2-3 orders of magnitude, compared to the small molecule. The polypeptides did not bind to the proteins with measurable affinities. The discovery of these new synthetic binders for protein targets can pave the way to diagnostic tests in vivo or in vitro, independent of antibodies.
|
|
| 10. |
- Wallménius, Katarina, 1983-
(författare)
-
Studies of Spotted Fever Rickettsia - Distribution, Detection, Diagnosis and Clinical Context : With a Focus on Vectors and Patients in Sweden
- 2016
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The spotted fever rickettsia, Rickettsia helvetica, is an endemic tick-borne bacteria in Sweden. It causes infections in humans, manifested as aneruptive fever, headache, arthralgia and myalgia, and sometimes an inoculation eschar or a rash. There have also been two known cases of human infections with R. felis in Sweden.The present thesis starts by investigating dispersal of ticks and Rickettsia spp. by migrating birds flying from Africa to Europe. Almost 15,000 birds were searched and 734 ticks collected, mainly of the species Hyalomma marginatum complex. Almost half (48%) of the ticks were infected with Rickettsia spp., 96% of which was R. aeschlimannii, the remaining R. africae and undefined species.The next study focused on questing ticks over a large area in Sweden and determining the prevalence of Rickettsia spp., Anaplasma spp. and Coxiella burnetii. Rickettsia spp. was found in 9.5-9.6% of the ticks and A. phagocytophilum in 0.7%; no C. burnetii was found.The last three papers in the thesis focused on the clinical presentation of rickettsiosis, the symptoms associated with the infection in general and particularly in patients with neurological complications. A tick-exposed population in Sweden was investigated to gain a better understanding of symptoms due to rickettsioses, also in relation to co-infections with other tick-borne bacteria. Based on symptoms, it was not possible to distinguish what pathogen caused the infections. Most patients had erythema migrans, some had serological reactions to Rickettsia spp., Borrelia spp. or co-infections by Rickettsia spp., Borrelia spp. and/or Anaplasma spp. In the fourth and fifth papers, we found associations between antibodies against Rickettsia spp. and sudden deafness (in 10-24% of patients) and facial nerve paralysis (in 8.3-25% of patients). In three patients R. felis was detected in the cerebrospinal fluids. Briefly, the thesis helps to clarify our knowledge about tick dispersal, shows a narrower prevalence estimate of Rickettsia spp. in Swedish ticks, and illuminates symptoms of rickettsioses and co-infections with other tick-borne infections. It also shows that presence of erythema migrans may be explained by more than Lyme disease and indicates a possible association between rickettsiosis and sudden deafness and facial nerve paralysis.
|
|
