Change search
Refine search result
1 - 12 of 12
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Alriksson, Björn
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Ethanol from lignocellulose: Alkali detoxification of dilute-acid spruce hydrolysates2006Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Detoxification of dilute-acid lignocellulose hydrolysates by treatment with Ca(OH)2 (overliming) efficiently improves the production of fuel ethanol, but is associated with drawbacks like sugar degradation and CaSO4 precipitation. In factorial designed experiments, in which pH and temperature were varied, dilute-acid spruce hydrolysates were treated with Ca(OH)2, NH4OH or NaOH. The concentrations of sugars and inhibitory compounds were measured before and after the treatments. The fermentability was examined using the yeast Saccharomyces cerevisiae and compared with reference fermentations of synthetic medium without inhibitors. The treatment conditions were evaluated by comparing the balanced ethanol yield, which takes both the degradation of sugars and the ethanol production into account. Treatment conditions resulting in excellent fermentability and minimal sugar degradation were possible to find regardless of whether Ca(OH)2, NH4OH or NaOH was used. Balanced ethanol yields higher than those of the reference fermentations were achieved for hydrolysates treated with all three types of alkali. As expected, treatment with Ca(OH)2 gave rise to precipitated CaSO4. The NH4OH treatments gave rise to a brownish precipitate but the amounts of precipitate formed were relatively small. No precipitate was observed in treatments with NaOH. The possibility that the ammonium ions from the NH4OH treatments gave a positive effect as an extra source of nitrogen during the fermentations was excluded after experiments in which NH4Cl was added to the medium. The findings presented can be used to improve the effectiveness of alkali detoxification of lignocellulose hydrolysates and to minimize problems with sugar degradation and formation of precipitates.

  • 2.
    Alriksson, Björn
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Ethanol from lignocellulose: Management of by-products of hydrolysis2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Fuel ethanol can be produced from lignocellulosic materials, such as residues from agriculture and forestry. The polysaccharides of lignocellulose are converted to sugars by hydrolysis and the sugars can then be fermented to ethanol using microorganisms. However, during hydrolysis a wide range of by-products are also generated. By-product formation can affect ethanol yield and productivity. Management of by-products of hydrolysis is therefore important in the development of commercially viable production of cellulosic ethanol.

    Detoxification of inhibitory dilute-acid lignocellulose hydrolysates by treatment with Ca(OH)2 (overliming) efficiently improves the fermentability, but is associated with drawbacks like sugar degradation and CaSO4 precipitation. In factorial designed experiments, in which pH and temperature were varied, dilute-acid spruce hydrolysates were treated with Ca(OH)2, NH4OH or NaOH. The concentrations of sugars and inhibitory compounds were measured before and after the treatments. The fermentability was examined using the yeast Saccharomyces cerevisiae and compared with reference fermentations of synthetic medium without inhibitors. The treatment conditions were evaluated by comparing the balanced ethanol yield, which takes both the degradation of sugars and the ethanol production into account. Treatment conditions resulting in excellent fermentability and minimal sugar degradation were possible to find regardless of whether Ca(OH)2, NH4OH or NaOH was used. Balanced ethanol yields higher than those of the reference fermentations were achieved for hydrolysates treated with all three types of alkali. As expected, treatment with Ca(OH)2 gave rise to precipitated CaSO4. The NH4OH treatments gave rise to a brownish precipitate but the amounts of precipitate formed were relatively small. No precipitate was observed in treatments with NaOH. The findings presented can be used to improve the effectiveness of alkali detoxification of lignocellulose hydrolysates and to minimize problems with sugar degradation and formation of precipitates.

    Overexpression of different S. cerevisiae genes was investigated with the aim to engineer a biocatalyst with increased inhibitor tolerance. Overexpression of YAP1, a gene encoding a transcription factor, conveyed increased resistance to lignocellulose-derived inhibitors as well as to a dilute-acid hydrolysate of spruce.

    Recombinant Aspergillus niger expressing the Hypocrea jecorina endoglucanase Cel7B was cultivated on spent lignocellulose hydrolysate (stillage). The fungus simultaneously removed inhibitors present in the stillage and produced higher amounts of endoglucanase than when it was grown in a standard medium with comparable monosaccharide content. The concept can be applied for on-site production of enzymes in a cellulose-to-ethanol process and facilitate recycling of the stillage stream.

  • 3.
    Alriksson, Björn
    et al.
    Karlstad University, Division for Chemistry.
    Horváth, Ilona Sárvári
    Karlstad University, Division for Chemistry.
    Sjöde, Anders
    Karlstad University, Division for Chemistry.
    Nilvebrant, Nils-Olof
    Karlstad University, Division for Chemistry.
    Jönsson, Leif J
    Karlstad University, Division for Chemistry.
    Ammonium hydroxide detoxification of spruce acid hydrolysates.2005In: Applied Biochemistry and Biotechnology, ISSN 0273-2289, E-ISSN 1559-0291, Vol. 121-124, p. 911-22Article in journal (Refereed)
    Abstract [en]

    When dilute-acid hydrolysates from spruce are fermented to produce ethanol, detoxification is required to make the hydrolysates fermentable at reasonable rates. Treatment with alkali, usually by overliming, is one of the most efficient approaches. Several nutrients, such as ammonium and phosphate, are added to the hydrolysates prior to fermentation. We investigated the use of NH4OH for simultaneous detoxification and addition of nitrogen source. Treatment with NH4OH compared favorably with Ca(OH)2, Mg(OH)2, Ba(OH)2, and NaOH to improve fermentability using Saccharomyces cerevisiae. Analysis of monosaccharides, furan aldehydes, phenols, and aliphatic acids was performed after the different treatments. The NH4OH treatments, performed at pH 10.0, resulted in a substantial decrease in the concentrations of furfural and hydroxymethylfurfural. Under the conditions studied, NH4OH treatments gave better results than Ca(OH)2 treatments. The addition of an extra nitrogen source in the form of NH4Cl at pH 5.5 did not result in any improvement in fermentability that was comparable to NH4OH treatments at alkaline conditions. The addition of CaCl2 or NH4Cl at pH 5.5 after treatment with NH4OH or Ca(OH)2 resulted in poorer fermentability, and the negative effects were attributed to salt stress. The results strongly suggest that the highly positive effects of NH4OH treatments are owing to chemical conversions rather than stimulation of the yeast cells by ammonium ions during the fermentation.

  • 4.
    Alriksson, Björn
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Rose, Shaunita, H
    Department of Microbiology, University of Stellenbosch, South Africa.
    van Zyl, Wilhelm, H
    Department of Microbiology, University of Stellenbosch, South Africa.
    Sjöde, Anders
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Nilvebrant, Nils-Olof
    STFI-Packforsk AB, Stockholm, Sweden.
    Jönsson, Leif J.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Cellulase Production from Spent Lignocellulose Hydrolysates with Recombinant Aspergillus niger.2009In: Applied and Environmental Microbiology, ISSN 0099-2240, E-ISSN 1098-5336, Vol. 75, no 8, p. 2366-2374Article in journal (Refereed)
  • 5.
    An, Wei
    et al.
    Brookhaven National Laboratory, USA.
    Baber, Ashleigh E.
    Brookhaven National Laboratory, USA.
    Xu, Fang
    Stony Brook University, USA.
    Soldemo, Markus
    KTH.
    Weissenrieder, Jonas
    KTH.
    Stacchiola, Dario
    Brookhaven National Laboratory, USA.
    Liu, Ping
    Brookhaven National Laboratory, USA.
    Mechanistic Study of CO Titration on CuxO/Cu(111) (x <= 2) Surfaces2014In: ChemCatChem, ISSN 1867-3880, E-ISSN 1867-3899, Vol. 6, no 8, p. 2364-2372Article in journal (Refereed)
    Abstract [en]

    The reducibility of metal oxides is of great importance to their catalytic behavior. Herein, we combined ambient-pressure scanning tunneling microscopy (AP-STM), X-ray photoemission spectroscopy (AP-XPS), and DFT calculations to study the CO titration of CuxO thin films supported on Cu(111) (CuxO/Cu(111)) aiming to gain a better understanding of the roles that the Cu(111) support and surface defects play in tuning catalytic performances. Different conformations have been observed during the reduction, namely, the 44 structure and a recently identified (5-7-7-5) Stone-Wales defects (5-7 structure). The DFT calculations revealed that the Cu(111) support is important to the reducibility of supported CuxO thin films. Compared with the case for the Cu2O(111) bulk surface, at the initial stage CO titration is less favorable on both the 44 and 5-7 structures. The strong CuxO <-> Cu interaction accompanied with the charge transfer from Cu to CuxO is able to stabilize the oxide film and hinder the removal of O. However, with the formation of more oxygen vacancies, the binding between CuxO and Cu(111) is weakened and the oxide film is destabilized, and Cu2O(111) is likely to become the most stable system under the reaction conditions. In addition, the surface defects also play an essential role. With the proceeding of the CO titration reaction, the 5-7 structure displays the highest activity among all three systems. Stone-Wales defects on the surface of the 5-7 structure exhibit a large difference from the 44 structure and Cu2O(111) in CO binding energy, stability of lattice oxygen, and, therefore, the reduction activity. The DFT results agree well with the experimental measurements, demonstrating that by adopting the unique conformation, the 5-7 structure is the active phase of CuxO, which is able to facilitate the redox reaction and the Cu2O/Cu(111)<-> Cu transition.

  • 6.
    Anderson, Fredrik
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Rheological changes at the air-liquid interface and examining different kind of magnetic needles2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The main objective in this work was to learn how the instrument, the Interfacial Shear

    Rheometer (ISR400), worked and to investigate how the rheological properties, storage

    modulus (elasticity), G' and loss modulus (viscous), G'', changes when the surface

    pressure at the air-liquid interphase changes. The second objective were to examine the

    different kind of magnetic needles used in the experiments and to conclude which type of

    needle is best for its specific field of analysis.

    It was concluded that the relative heavy needle with mass 70.6 mg and length 50 mm

    was best for systems where the viscous and elastic components are significantly large,

    where the inertia of the needle is not dominant. It also worked of using the heavier needle

    for a system of phospholipids.

    For the hydroxystearic acid (HSA) experiment that were tested on NaCl sub-phase there

    was a clear improvement after switching from the heavy needle (mass 41.5 mg; length 51

    mm) to the relative lighter needle (mass 6.94 mg; length 34.7 mm). The values for the

    dynamic modulus therefore had a better agreement with reference literature.

    A spread layer of class II hydrophobins (HFBII) could be compressed to a surface

    pressure of 46 mNm-1. The G' and G'' values from the frequency sweep were discarded

    because the monolayer turned into a very viscous-like liquid, and the oscillating needle,

    after compression, was kind of stuck in the sub-phase and moved very staggering during

    a frequency sweep.

    The needle comparison experiment with silica particles 10 wt% Bindzil CC30 (BCC30),

    at pH 3.5 was done to see if there was any difference in the sensitivity for the needles at

    the interface which consisted of a pure 10 mM NaCl solution or a 10 mM NaCl solution

    with BCC30 added to it. The differences were negligible in terms of surface tension but

    there was a clear difference between the heavy needle and the light needle, when

    oscillating at higher frequencies (>≈6 rad/s).

    With this study, the understanding of ISR400 has increased largely. Several issues have

    been addressed and the results provide a good basis for further studies within the many

    areas the instrument can be used for. Despite the project's time limit, and the fact that the

    instrument was new and untested where the project was carried out, focus areas were

    prioritized so good results could be achieved within reasonable goals.

  • 7. Annergren, Göran
    et al.
    Kvarnlöf, Niklas
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Sulfitmassa: Översikt kring Processfrågor, Marknad och Framtid2014Report (Other academic)
    Abstract [sv]

    Karlstads universitet har tagit på sig uppgiften att försöka sammanställa det kunnande som idag finns inom landet kring sulfitmassa och sulfitprocesser. Eftersom antalet massabruk som tillverkar sulfitmassa sakta sjunker är detta en viktig uppgift för att i någon mån kunna behålla det stora kunnande som en gång fanns kring denna process.

    Denna rapport belyser bl.a. viktiga processfrågor kring framställningen av pappers- och dissolvingmassor från sulfitprocessen.

  • 8.
    Dabrowski, Patrik
    Karlstad University, Faculty of Health, Science and Technology (starting 2013).
    Rening av rökgaskondensat i ett fjärrvärmeverk: Återanvändning av rökgaskondensat som spädvatten2017Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    Arvika Fjärrvärme AB is manufacturing and distributing district heating to around 300 customers in Arvika. Heat production consists of a BFB boiler fed with GROT fuel (branches and peaks) and delivers a maximum power of 30 MW. In order to operate the plant, an average of 60 m3 of water per day is consumed from the urban water network. The water consumption is divided between water treatment, sooting and process cooling.

    In the processes, sulfur is dosed to obtain a more complete combustion of the hazardous flue gases that can occur. This is a result of previous thesis made for Arvika fjärrvärme. GROT is a fuel that contains high levels of moisture, which means that a high amount of condensate is formed during combustion, averaging 100 m3 per day. At present, condensate is sufficient to meet the condensate limit values ​​to be flushed into the drain. This is achieved by sand filtration and pH neutralization.

    Today, Arvika heat production is equipped with a purification stage for the feed water consisting of a softening filter and membrane filtration. This creates good conditions for cleaning the condensate and recirculating it in the process. Questions for this study are which hazardous substances the condensate can contain and how the condensate composition affected due to sulfur dosage. In addition, Arvika fjärrvärme wants to find out whether the purified condensate can replace the use of the urban water and, finally, if the condensate can be purified and used as feed water in the process.

    The execution of the work was based on a full-scale attempt in two operating cases of 9 and 18 MW. The tank collecting all condensate after purification in the sand filter and pH neutralization was coupled to the feed water purification stage. Thus, the condensate was pumped and purified in the softening filter and membrane filter. Assay substrates were collected before and after purification of the condensate.

    In addition to the topics that Arvika investigates, high levels of alkalinity were found in the condensate. The sulfur dosage that Arvika technology works with can be the cause of the high concentrations of sulphate. However, it appears that both the sulfate and alkalinity were purified in the membrane filter.

    The amount of condensate formed cannot completely replace the entire water requirement, but definitely large parts. The condensate can be used as feed water based on the retention rate for all substances. However, it appears that two substances, chloride and sulphate can create problems for the membrane filter. To investigate this, the condensate should be tested over a longer period of time to see the affect the chloride as well as the sulphate in the long run.

  • 9.
    Fredriksson, Mårten
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Syftet med NTA i kemi: Fjärdeklasselevers uppfattning av syftet jämfört med lärarens syfte2018Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The purpose of my study was to contribute with increased knowledge on what ideas fourth grade pupils have about the aims of NTA in chemistry, and if their ideas correspond with the teachers´ aims. The data collection is made through group interviews with fifteen pupils and their teacher. The answers in these interviews have been inductively categorized. The results have shown that pupils don´t see the aims of the NTA-boxes as the teacher have in mind. It seems like the pupils´ see aims in each lesson and focus on what is happening. The teacher, on the other hand, has a much more overall aim that originates from the curriculum, but which she doesn´t manage to fully communicate to the pupils. She also intends that the pupils should develop their capability of reasoning, which they do during classroom discussions. In addition to this, the pupils also find classroom discussions both interesting and educational. Time is given for classroom discussions which gives an opportunity for scientific literacy.

  • 10.
    Lorenz, Elin
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Utveckling av 2D-gelelektrofores för alkaliska proteiner i Ideonella dechloratans: En jämförelse mellan aeroba och anaeroba odlingsförhållanden2013Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    De flesta klorater som finns i naturen kommer från utsläpp av människan i flera storaindustrier. Kloraterna påverkar flera olika levande organismer och det är därför viktigt att tahand om dem efter utsläppen. Flera olika bakterier kan bryta ned klorat till klorid och syre, enav dessa är Ideonella dechloratans. Nedbrytningen sker med de alkaliska enzymernakloratreduktas och kloritdismutas under anaeroba förhållanden. I detta arbete har 2Dgelelektrofores utvecklats för alkaliska proteiner i Ideonella dechloratans i syfte att kunnajämföra proteinuttryck under olika odlingsförhållanden. Därefter har en jämförelse mellanaeroba och anaeroba odlingsförhållanden gjorts samt försök att detektera kloritdismutas.Resultatet har blivit att en metod har tagits fram som ger en hög grad av upplösning pågelerna från 2D-gelelektroforesen. Jämförelserna mellan aeroba och anaerobaodlingsförhållanden har visat att det finns stora skillnader i proteinuttryck mellan de bådaodlingsförhållandena. Fler proteiner syns i området pH 8-10 under anaerobaodlingsförhållanden jämfört med aeroba förhållanden. Försök till identifiering avkloritdismutas har gjorts för de anaeroba odlingsförhållandena, dock krävs det ytterligarearbete innan en säker identifiering kan göras.

  • 11.
    Moonen, Nele
    Karlstad University, Faculty of Health, Science and Technology (starting 2013).
    The cloning of the clrA gene of Ideonella dechloratans2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 12.
    Rantamäki, Anja
    Karlstad University, Faculty of Arts and Social Sciences (starting 2013), Department of Educational Studies.
    Hur får vi energi?: En kvalitativ semistruktuerad intervjustudie om barns uppfattningar kring kroppens energiprocesser.2018Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The purpose of this study is to investigate how preschool children between the age of 5 and 6 years reflect about energy processes connected to the body. The study was conducted with semi structured interviews with a preschool class and a preschool. The theoretical framework for the study is social constructivism. The study was conducted with communicative tools (a doll). The result of the study is most children relate food as an important source of energy. Children ́s perceptions about where they got the energy from, lies in the form of informal language, where they use the word energy when they feel alert and have strength to play. It differs from the science ́s descriptions of energy, that we obtain energy through cellular respiration. Children ́s perceptions about where they got the energy from are divided into five categories. The categories are: through food, through motion, through rest, through fluid and through oxygen. 

1 - 12 of 12
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf