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  • 51.
    Palm-Espling, Maria
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Andersson, David C.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Björn, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Linusson, Anna
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Wittung-Stafshede, Pernilla
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Determinants for simultaneous binding of copper and platinum to human chaperone Atox1: hitchhiking not hijacking2013Inngår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 8, nr 7, artikkel-id e70473Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cisplatin (CisPt) is an anticancer agent that has been used for decades to treat a variety of cancers. CisPt treatment causes many side effects due to interactions with proteins that detoxify the drug before reaching the DNA. One key player in CisPt resistance is the cellular copper-transport system involving the uptake protein Ctr1, the cytoplasmic chaperone Atox1 and the secretory path ATP7A/B proteins. CisPt has been shown to bind to ATP7B, resulting in vesicle sequestering of the drug. In addition, we and others showed that the apo-form of Atox1 could interact with CisPt in vitro and in vivo. Since the function of Atox1 is to transport copper (Cu) ions, it is important to assess how CisPt binding depends on Cu-loading of Atox1. Surprisingly, we recently found that CisPt interacted with Cu-loaded Atox1 in vitro at a position near the Cu site such that unique spectroscopic features appeared. Here, we identify the binding site for CisPt in the Cu-loaded form of Atox1 using strategic variants and a combination of spectroscopic and chromatographic methods. We directly prove that both metals can bind simultaneously and that the unique spectroscopic signals originate from an Atox1 monomer species. Both Cys in the Cu-site (Cys12, Cys15) are needed to form the di-metal complex, but not Cys41. Removing Met10 in the conserved metal-binding motif makes the loop more floppy and, despite metal binding, there are no metal-metal electronic transitions. In silico geometry minimizations provide an energetically favorable model of a tentative ternary Cu-Pt-Atox1 complex. Finally, we demonstrate that Atox1 can deliver CisPt to the fourth metal binding domain 4 of ATP7B (WD4), indicative of a possible drug detoxification mechanism.

  • 52. Paulo, Carlos
    et al.
    Kenney, Janice P L
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Persson, Per
    Dittrich, Maria
    Effects of Phosphorus in Growth Media on Biomineralization and Cell Surface Properties of Marine Cyanobacteria Synechococcus2018Inngår i: Geosciences, ISSN 2076-3263, Vol. 8, nr 12, artikkel-id UNSP 471Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Through geological time, cyanobacterial picoplankton have impacted the global carbon cycle by sequestrating CO2 and forming authigenic carbonate minerals. Various studies have emphasized the cyanobacterial cell envelopes as nucleation sites for calcium carbonate formation. Little is known, however, about how environmental conditions (e.g., nutrient content) trigger a cell surface and its properties and, consequently, influence biomineralization. Our study aims to understand how phosphorus (P) concentration impacts the properties of cell surfaces and cell–mineral interactions. Changes to the surface properties of marine Synechococcus strains grown under various P conditions were characterized by potentiometric titrations, X-ray photoelectron spectroscopy (XPS), and tip-enhanced Raman spectroscopy (TERS). Biomineralization experiments were performed using cyanobacterial cells, which were grown under different P concentrations and exposed to solutions slightly oversaturated with respect to calcium carbonate. We observed the changes induced by different P conditions in the macromolecular composition of the cyanobacteria cell envelope and its consequences for biomineralization. The modified properties of cell surfaces were linked to carbonate precipitation rates and mineral morphology from biomineralization experiments. Our analysis shows that the increase of phosphoryl groups and surface charge, as well as the relative proportion of polysaccharides and proteins, can impact carbonate precipitation by picocyanobacteria.

  • 53. Privalova, Elena
    et al.
    Rasi, S.
    Mäki-Arvela, P.
    Eränen, K.
    Rintala, D.
    Murzin, D. Yu.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    CO2 capture from biogas: absorbent selection2013Inngår i: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 3, nr 9, s. 2979-2994Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The development of proper biogas upgrading technology offers a viable means to utilize biogas in conventional power systems. In this paper, various molecular and ionic solvent systems were evaluated for CO2 removal from biogas in a loop reactor system. The performance of amine solutions, ionic liquids and their mixtures, amino acid salts and solutions blended with piperazine was compared in terms of their CO2 loading capacity. The experimental results revealed that addition of small amounts of piperazine can increase the efficiency of abovementioned solutions on average by 30 vol%. The CO2 capturing capacity of the most promising solvents was in the range of 50-60 L CO2/L absorbent. The regeneration of the solvent mixtures can be challenging since the solvents could loose 16-43 vol% of their initial efficiency upon CO2 release. Ionic liquid [C4mim][acetate] was found to be an efficient VOCs scrubbing media. Moreover, upon use of this ionic liquid, the amount of identified volatile organic compounds (VOCs) in the studied samples was reduced by 65 wt%, while the use of 15 wt% aqueous N-methyldiethanolamine (MDEA) resulted only in 32 wt% reduction in the amount of VOCs.

  • 54.
    Ramstedt, Madeleine
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Leone, Laura
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Bacterial surfaces in geochemistry: how can x-ray photoelectron spectroscopy help?2019Inngår i: Analytical geomicrobiology: a handbook of instrumental techniques / [ed] Janice P. L. Kenney, Harish Veeramani, Daniel S. Alessi, Cambridge: Cambridge University Press , 2019, s. 262-287Kapittel i bok, del av antologi (Annet vitenskapelig)
    Abstract [en]

    Processes occurring at surfaces and interfaces are very important in environmental systems, necessitating surface-specific characterization tools that can help us understand processes at and specific properties of surfaces and interfaces, and their role in biogeochemical systems. This chapter describes the use and application of X-ray photoelectron spectroscopy (XPS) to study interfacial processes of relevance for geomicrobiology. Examples are given from studies determining cell wall composition, acid–base properties, cell surface charge, metal adsorption onto bacterial cells, and bacterial surface–induced precipitation of secondary minerals. As XPS is an ultrahigh-vacuum technique, several sample preparation methods have been applied to enable analysis of bacterial samples, including analysis of freeze-dried samples as well as frozen bacterial suspensions. These are described and discussed alongside advantages and disadvantages of different approaches, with a special focus on fast-freezing and the cryogenic technique.

  • 55.
    Rebbling, Anders
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Boström, Dan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik. Luleå University of Technology, Department of Engineering Sciences & Mathematics, Energy Engineering.
    Understanding reactivity using fuel design - phosphorus vs kaolin in combustion of stem wood2016Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    The fate of various ash-forming elements determine how well a fuel will perform in a given thermochemical energy conversion process. In order understand ash-related process problems it is particularly important in which compounds alkali metal ions, for biomass this primarily means K+ and Na+, are bonded. Their low charge and relatively large ionic radii leads to poor bond strengths in compounds where they provide the only Lewis acid component, i.e. electron acceptor. This can be remedied by trying to bond alkali metal ions to stronger, predominantly molecular Lewis bases which is the case in for instance arkanite, K2SO4 – the targeted reaction product when (NH4)2SO4 is added in the flue gas to reduce KCl formation. Another approach is to bond alkali in bottom or bed ash, by including Lewis base forming elements such as phosphorus or the additive kaolin which is dominated by kaolinite. This route attempts to promote formation of high-temperature melting compounds with at least one alkali metal ion per phosphate or other starting molecule.

    While the understanding of how phosphorus reacts in combustion process is increasing it is valuable to understand how it will react in presence of other elements or molecules that play an important role for alkali capture. This will be of interest in situations where the base fuels may be combusted with addition of sulphur or kaolin, for instance. If the base fuels has a high concentration of phosphorus the amount of additive may need to be adjusted according to what phosphates will form, and if they will form even in the presence of the amending additives. Using the inherent composition of the fuel to decide suitable strategies for additive choice or possibly co-combustion is a key component of fuel design.

    The aim of this study is to investigate the relative Lewis base potential for capture of alkali metal ions between phosphates and kaolin. This is made by adding highly available phosphorus in the form of di-ammonium hydrogen phosphate, (NH4)2HPO4, and kaolin, a mineral where kaolinite is the main constituent for capturing alkali to the fuel blend. The fuel chosen is stem wood where the amount of Lewis acid forming elements greatly surpass that of Lewis base forming elements found in the ash forming matter.

  • 56.
    Reyes, Diana Carolina Alban
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Gorzsas, Andras
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Stridh, Kjell
    de Wit, Paul
    Sundman, Ola
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Alkalization of dissolving cellulose pulp with highly concentrated caustic at low NaOH stoichiometric excess2017Inngår i: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 165, s. 213-220Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present a quantitative study, using Raman spectroscopy combined with multivariate data analysis, to determine the degree of activation of softwood sulphite dissolving cellulose pulp by aqueous sodium hydroxide. We have chosen industrially relevant conditions, including low stoichiometric ratio of NaOH/Anhydroglucose Unit (AGU) <2 and highly concentrated caustic (>= 45% w/w [NaOH]). A design of experiments is used to investigate the effects of simultaneous variation of a set of key parameters on the degree of activation (i.e. transformation to alkali cellulose, denoted as DoA): (a) the NaOH/AGU stoichiometric ratio, denoted (r); (b) the concentration of NaOH, denoted [NaOH]; (c) temperature, denoted (T); and (d) reaction time, denoted (t). Solid-state C-13 CP/MAS NMR spectroscopy was applied to investigate the reproducibility of the experiments and to select the range for (t). According to the model, (r) is found to have a statistically significant effect on DoA (increasing from DoA= 6-30% at the lowest (r)=0.8, to DoA= 48-87% at the highest (r)=1.8), together with [NaOH]. The influence of [NaOH] depends strongly on (r). The other studied variables are found to be insignificant in the model and has a complicated influence on the activation. In particular, (T) is found to be unimportant in the studied range (30-60 degrees C), but increasing (t) from 5 to 25 min shows a positive influence on DoA, depending on both (r) and [NaOH]. A mercerisation mechanism that is controlled by diffusion is proposed to explain these phenomena. 

  • 57. Rodríguez, Juanjo
    et al.
    Gallampois, Christine
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Timonen, Sari
    Andersson, Agneta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF). Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Sinkko, Hanna
    Haglund, Peter
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Berglund, Åsa M. M.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Ripszam, Matyas
    Figueroa, Daniela
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Tysklind, Mats
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Rowe, Owen
    Effects of Organic Pollutants on Bacterial Communities Under Future Climate Change Scenarios2018Inngår i: Frontiers in Microbiology, ISSN 1664-302X, E-ISSN 1664-302X, Vol. 9, artikkel-id 2926Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Coastal ecosystems are highly dynamic and can be strongly influenced by climate change, anthropogenic activities (e.g. pollution) and a combination of the two pressures. As a result of climate change, the northern hemisphere is predicted to undergo an increased precipitation regime, leading in turn to higher terrestrial runoff and increased river inflow. This increased runoff will transfer terrestrial dissolved organic matter (tDOM) and anthropogenic contaminants to coastal waters. Such changes can directly influence the resident biology, particularly at the base of the food web, and can influence the partitioning of contaminants and thus their potential impact on the food web. Bacteria have been shown to respond to high tDOM concentration and organic pollutants loads, and could represent the entry of some pollutants into coastal food webs. We carried out a mesocosm experiment to determine the effects of: 1) increased tDOM concentration, 2) organic pollutant exposure, and 3) the combined effect of these two factors, on pelagic bacterial communities. This study showed significant responses in bacterial community composition under the three environmental perturbations tested. The addition of tDOM increased bacterial activity and diversity, while the addition of organic pollutants led to an overall reduction of these parameters, particularly under concurrent elevated tDOM concentration. Furthermore, we identified 33 bacterial taxa contributing to the significant differences observed in community composition, as well as 35 bacterial taxa which responded differently to extended exposure to organic pollutants. These findings point to the potential impact of organic pollutants under future climate change conditions on the basal coastal ecosystem, as well as to the potential utility of natural bacterial communities as efficient indicators of environmental disturbance.

  • 58.
    Rzhepishevska, Olena I.
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Limanska, Nataliia
    Galkin, Mykola
    Lacoma, Alicia
    Lundquist, Margaretha
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Sokol, Dmytro
    Hakobyan, Shoghik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Queen Mary University of London, London, UK.
    Sjöstedt, Anders
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi.
    Prat, Cristina
    Ramstedt, Madeleine
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Characterization of clinically relevant model bacterial strains of Pseudomonas aeruginosa for anti-biofilm testing of materials2018Inngår i: Acta Biomaterialia, ISSN 1742-7061, E-ISSN 1878-7568, Vol. 76, s. 99-107Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    There is a great interest in developing novel anti-biofilm materials in order to decrease medical device-associated bacterial infections causing morbidity and high healthcare costs. However, the testing of novel materials is often done using bacterial lab strains that may not exhibit the same phenotype as clinically relevant strains infecting medical devices. Furthermore, no consensus of strain selection exists in the field, making results very difficult to compare between studies. In this work, 19 clinical isolates of Pseudomonas aeruginosa originating from intubated patients in an intensive care unit have been characterized and compared to the lab reference strain PAO1 and a rmlC lipopolysaccharide mutant of PAO1. The adhesion and biofilm formation was monitored, as well as cell properties such as hydrophobicity, zeta potential and motility. Two groups of isolates were observed: one with high adhesion to polymer surfaces and one with low adhesion (the latter including PAO1). Furthermore, detailed biofilm assays in a flow system were performed using five characteristic isolates from the two groups. Confocal microscopy showed that the adhesion and biofilm formation of four of these five strains could be reduced dramatically on zwitterionic surface coatings. However, one isolate with pronounced swarming colonized and formed biofilm also on the antifouling surface. We demonstrate that the biofilm properties of clinical isolates can differ greatly from that of a standard lab strain and propose two clinical model strains for testing of materials designed for prevention of biofilm formation in the respiratory tract. The methodology used could beneficially be applied for screening of other collections of pathogens to identify suitable model strains for in vitro biofilm testing.

    Statement of Significance: Medical-device associated infections present a great challenge in health care. Therefore, much research is undertaken to prevent bacterial colonization of new types of biomaterials. The work described here characterizes, tests and presents a number of clinically relevant bacterial model strains for assessing biofilm formation by Pseudomonas aeruginosa. Such model strains are of importance as they may provide better predictability of lab testing protocols with respect to how well materials would perform in an infection situation in a patient. Furthermore, this study uses the strains to test the performance of polymer surfaces designed to repel bacterial adhesion and it is shown that the biofilm formation for four out of the five tested bacterial strains was reduced.

    Fulltekst tilgjengelig fra 2020-06-12 00:00
  • 59.
    Rölin, Lisa
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Metallanalys i salthaltigt vatten En studie i spektrala och icke-spektrala interferenser2012Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
  • 60. Saeid, Soudabeh
    et al.
    Kråkström, Matilda
    Tolvanen, Pasi
    Kumar, Narendra
    Eränen, Kari
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Kronberg, Leif
    Eklund, Patrik
    Peurla, Markus
    Aho, Atte
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Salmi, Tapio
    Advanced Oxidation Process for Degradation of Carbamazepine from Aqueous Solution: Influence of Metal Modified Microporous, Mesoporous Catalysts on the Ozonation Process2020Annet (Annet vitenskapelig)
    Abstract [en]

    Carbamazepine (CBZ), a widely used pharmaceutical compound, is one of the most detected drugs in surface waters. The purpose of this work was to identify an active and durable catalyst, which, in combination with an ozonation process, could be used to remove CBZ and its degradation products. It was found that the CBZ was completely transformed after ozonation within the first minutes of the treatment. However, the resulting degradation products, 1-(2-benzaldehyde)-4-hydro-(1H,3H)-quinazoline-2-one (BQM) and 1-(2-benzaldehyde)-(1H,3H)-quinazoline-2,4-dione (BQD), were more resistant during the ozonation process. The formation and degradation of these products were studied in more detail and a thorough catalytic screening was conducted to reveal the reaction kinetics of both the CBZ and its degradation products. The work was performed by non-catalytic ozonation and with six different heterogeneous catalysts (Pt-MCM-41-IS, Ru-MCM-41-IS, Pd-H-Y-12-EIM, Pt-H-Y-12-EIM, Pd-H-Beta-300-EIM and Cu-MCM-41-A-EIM) operating at two temperatures 20 &deg;C and 50 &deg;C. The influence of temperature on degradation kinetics of CBZ, BQM and BQD was studied. The results exhibited a notable difference in the catalytic behavior by varying temperature. The higher reactor temperature (50 &deg;C) showed a higher activity of the catalysts but a lower concentration of dissolved ozone. Most of the catalysts exhibited higher removal rate for BQM and BQD compared to non-catalytic experiments in both temperatures. The Pd-H-Y-12-EIM catalyst illustrated a higher degradation rate of by-products at 50 &deg;C compared to other catalysts.

  • 61. Salam, Abdus
    et al.
    Al Mamoon, Hassan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Ullah, Md Basir
    Ullah, Shah M.
    Measurement of the atmospheric aerosol particle size distribution in a highly polluted mega-city in Southeast Asia (Dhaka-Bangladesh)2012Inngår i: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 59, s. 338-343Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Aerosol particle size distribution was measured with an aerodynamic particle sizer (APS) spectrometer continuously from January 21 to April 24, 2006 in Dhaka, Bangladesh. Particles number, surface and mass distributions data were stored automatically with Aerosol Instrument Manager (AIM) software on average every half an hour in a computer attached to the APS. The grand total average of number, surface and mass concentrations were 8.2 x 10(3) +/- 7.8 x 10(3) particles cm(-3), 13.3 x 10(3) +/- 11.8 x 10(3) mu m(2) cm(-3) and 3.04 +/- 2.10 mg m(-3), respectively. Fine particles with diameter smaller than 1.0 mu m aerodynamic diameter (AD) dominated the number concentration, accounted for 91.7% of the total particles indicating vehicular emissions were dominating in Dhaka air either from fossil fuel burning or compressed natural gas (CNGs). The surface and mass concentrations between 0.5 and 1.0 mu m AD were about 56.0% and 26.4% of the total particles, respectively. Remarkable seasonal differences were observed between winter and pre-monsoon seasons with the highest monthly average in January and the lowest in April. Aerosol particles in winter were 3.79 times higher for number, 3.15 times for surface and 2.18 times for mass distributions than during the pre-monsoon season. Weekends had lower concentrations than weekdays due to less vehicular traffic in the streets. Aerosol particles concentrations were about 15.0% (ranging from 9.4% to 17.3%) higher during traffic peak hours (6:00am-8:00pm) than off hours (8:00pm-6:00am). These are the first aerosol size distribution measurements with respect to number, surface and mass concentrations in real time at Dhaka, Bangladesh.

  • 62. Salmi, Tapio
    et al.
    Eränen, Kari
    Tolvanen, Pasi
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Åbo Akademi University, Johan Gadolin Process Chemistry Centre (PCC), Laboratory of Industrial Chemistry and Reaction Engineering, Turku/Åbo, Finland.
    Russo, Vincenzo
    Determination of kinetics and equilibria of heterogeneously catalyzed gas-phase reactions in gradientless autoclave reactors by using the total pressure method: Methanol synthesis2019Inngår i: Chemical Engineering Science, ISSN 0009-2509, E-ISSN 1873-4405Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Rapid methods are very valuable in the determination of the kinetic and mass transfer effects for heterogeneously catalyzed reactions. The total pressure method is a classical tool in the measurement of the kinetics of gas-phase reactions, but it can be successfully applied to the kinetic measurements of gas-phase processes enhanced by solid catalysts. A general theory for the analysis of heterogeneously catalyzed gas-phase kinetics in gradientless batch reactors was presented for the case of intrinsic kinetic control and combined kinetic-diffusion control in porous catalysts. The concept was applied to gas-phase synthesis of methanol from carbon monoxide and hydrogen on a commercial copper-based catalyst (CuO/ZnO/Al2O3 R3-12 BASF). The reaction temperature was 180–210 °C and the initial total pressure was varied between 11 and 21 bar in a laboratory-scale autoclave reactor equipped with a rotating basket for the catalyst particles. The initial molar ratios CO-to-H2 were approximately 1:2, 1:3 and 1:4. The experimental data from methanol synthesis were compared with numerical simulations and a good agreement between the experiments and model simulations was achieved. The predicted equilibrium agrees with previously reported values.

  • 63.
    Sandberg Hiltunen, Maria
    Umeå universitet, Samhällsvetenskapliga fakulteten, Enheten för demografi och åldrandeforskning (CEDAR).
    A new approach to quantify and analyse tRNA sequence dataManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    A novel quantitative multivariate approach for describing and analyse tRNA sequence data is presented. This approach is based on a multivariate chemical description of each nucleoside in the sequence. 30 theoretically calculated descriptors were used to characterize 63 nucleosides, and principal component analysis was used to extract the main variation from this multivariate description. The resulting four principal properties were interpreted as (PPa) size/bulk of the nucleoside, (PPb) polarity/hydrophobicity of the nucleoside, (PPc) electronic properties of the nucleoside and (PPd)polarity and size of the ribose moiety. These principal properties may be used to translate the tRNA letter sequence data into a quantitative chemical representation. We demonstrate the use of this quantitative description with a multivariate analysis of a set of tRNA sequences. This analysis gives models that are interpretable in terms of wich sequence positions, and nucleoside properties that discriminate the different isoacceptors. This approach is applicable on all kinds of RNA sequence data and gives information that is complementary to current sequence analysis techniques.

  • 64.
    Shanmugam, Kavitha
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Tysklind, Mats
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Upadhyayula, Venkata K.K.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Use of Liquefied Biomethane (LBM) as a Vehicle Fuel for Road Freight Transportation: A Case Study Evaluating Environmental Performance of Using LBM for Operation of Tractor Trailers2018Inngår i: Procedia CIRP, ISSN 2212-8271, E-ISSN 2212-8271, Vol. 69, s. 517-522Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The environmental performance of Liquefied Biomethane (LBM) and Diesel operated Tractor Trailer (TT) is compared using the Life Cycle Assessment (LCA) study. In this study we consider, raw biogas produced from an anaerobic digestion process of a Wastewater Treatment Plant (WWTP) in Umea, Sweden, which is then upgraded and liquefied to LBM and used as a fuel for TTs. Currently, the WWTP in Umea is utilizing biogas, produced onsite for cogeneration of heat and electricity, thereby meeting its energy needs. A system expansion approach is applied where electricity and heat equivalent to amount of biogas displaced for LBM production is supplied from Swedish grid (SE) mix and incineration of wood chips respectively. Correspondingly, the biogas avoided for cogeneration of electricity and heat is accounted in the study. The equivalent functional unit chosen for the LCA study is “16,000,000 ton-km of a TT transporting products and goods”. The study is modelled using SimaPro LCA Software. The ReCiPe Midpoint (H) impact assessment methodology is used to quantify ten selected and relevant midpoint environmental impacts. When compared with Diesel TT system, LBM TT exhibits superior environmental performance in seven out of ten impact categories measured than the Diesel TT system. The highest reduction is seen in Global Warming Potential (GWP) and Fossil Depletion Potential (FDP) impacts thereby suggesting that LBM derived from raw biogas of WWTP an environmentally preferred alternative to diesel for operation of TTs. However, this value proposition can have other trade-offs such as increase in eutrophication and ecotoxicity impacts. Further, replacing diesel with LBM for TT operation may not have any significant environmental benefits when electricity is drawn from carbon intensive grid mixes (e.g. coal).

  • 65.
    Sharifi, Tiva
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Gracia-Espino, Eduardo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Chen, Anran
    Hu, Guangzhi
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Oxygen Reduction Reactions on Single- or Few-Atom Discrete Active Sites for Heterogeneous Catalysis2019Inngår i: Advanced Energy Materials, ISSN 1614-6832, artikkel-id 1902084Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The oxygen reduction reaction (ORR) is of great importance in energy-converting processes such as fuel cells and in metal-air batteries and is vital to facilitate the transition toward a nonfossil dependent society. The ORR has been associated with expensive noble metal catalysts that facilitate the O-2 adsorption, dissociation, and subsequent electron transfer. Single- or few-atom motifs based on earth-abundant transition metals, such as Fe, Co, and Mo, combined with nonmetallic elements, such as P, S, and N, embedded in a carbon-based matrix represent one of the most promising alternatives. Often these are referred to as single atom catalysts; however, the coordination number of the metal atom as well as the type and nearest neighbor configuration has a strong influence on the function of the active sites, and a more adequate term to describe them is metal-coordinated motifs. Despite intense research, their function and catalytic mechanism still puzzle researchers. They are not molecular systems with discrete energy states; neither can they fully be described by theories that are adapted for heterogeneous bulk catalysts. Here, recent results on single- and few-atom electrocatalyst motifs are reviewed with an emphasis on reports discussing the function and the mechanism of the active sites.

  • 66.
    Sharifi, Tiva
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Kwong, Wai Ling
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Berends, Hans-Martin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Larsen, Christian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Messinger, Johannes
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Maghemite nanorods anchored on a 3D nitrogen-doped carbon nanotubes substrate as scalable direct electrode for water oxidation2016Inngår i: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 41, nr 1, s. 69-78Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A hybrid catalyst 3D electrode for electrochemical water oxidation to molecular oxygen is presented. The electrode comprises needle shaped maghemite nanorods firmly anchored to nitrogen doped carbon nanotubes, which in turn are grown on a conducting carbon paper that acts as efficient current collector. In 0.1 M KOH this hybrid electrode reaches a current density of 1 mA/cm(2) (geometric surface) at an overpotential of 362 mV performing high chronoamperometric stability. The electrochemical attributes point toward efficient catalytic processes at the surface of the maghemite nanorods, and demonstrate a very high surface area of the 3D electrode, as well as a firm anchoring of each active component enabling an efficient charge transport from the surface of the maghemite rods to the carbon paper current collector. The latter property also explains the good stability of our hybrid electrode compared to transition metal oxides deposited on conducting support such as fluorine doped tin oxide. These results introduce maghemite as efficient, stable and earth abundant oxygen evolution reaction catalyst, and provide insight into key issues for obtaining practical electrodes for oxygen evolution reaction, which are compatible with large scale production processes. 

  • 67. Shuaishuai, Wang
    et al.
    Qing, Zhang
    CongCong, Chen
    Yuxi, Guo
    Reddy, Gadi Madhusudhan
    Jin, Yu
    Ulrika, Westerlind
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Yunpeng, Liu
    Xuefeng, Cao
    G., Wang Peng
    Lei, Li
    Facile Chemoenzymatic Synthesis of O-Mannosyl Glycans2018Inngår i: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 57, nr 30, s. 9268-9273Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Abstract O?Mannosylation is a vital protein modification involved in brain and muscle development whereas the biological relevance of O-mannosyl glycans has remained largely unknown owing to the lack of structurally defined glycoforms. An efficient scaffold synthesis/enzymatic extension (SSEE) strategy was developed to prepare such structures by combining gram-scale convergent chemical syntheses of three scaffolds and strictly controlled sequential enzymatic extension catalyzed by glycosyltransferases. In total, 45 O-mannosyl glycans were obtained, covering the majority of identified mammalian structures. Subsequent glycan microarray analysis revealed fine specificities of glycan-binding proteins and specific antisera.

  • 68.
    Shukla, Shashi Kant
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Khokarale, Santosh G.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Bui, Thai Q.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Industrial Chemistry and Reaction Engineering, Department of Chemical Engineering, Johan Gadolin Process Chemistry Centre, Åbo Akademi University, Åbo-Turku, Finland.
    Ionic Liquids: Potential Materials for Carbon Dioxide Capture and Utilization2019Inngår i: Frontiers in Materials, ISSN 2296-8016, Vol. 6, artikkel-id 42Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    The nonvolatility, structure-tunability and high CO2 uptake capacity render ionic liquids (ILs) the most exciting materials for the carbon dioxide (CO2) capture and fixation to value-added chemicals. The aim of this mini-review is to give a brief idea about the development of the potential ILs for CO2 capture, the mechanism involved in the CO2 binding and the application of ILs in the conversion of CO2 to useful chemicals. The mechanisms and nature of interactions in between IL-CO2 have been discussed in terms of the nature of cation, anion, presence of functional group and the extent of interaction between the components of ILs. The fixation of CO2 to linear and cyclic carbonates and electroreduction of CO2 to carbon-rich fuels in ILs has been accounted in detail. At the end, future challenges in terms of commercializing the ILs for CO2 capture and utilization technology are discussed.

  • 69. Sjollema, Jelmer
    et al.
    Zaat, Sebastian A.J.
    Fontaine, Veronique
    Ramstedt, Madeleine
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Luginbuehl, Reto
    Thevissen, Karin
    Li, Jiuyi
    van der Mei, Henny C.
    Busscher, Henk J.
    In vitro methods for the evaluation of antimicrobial surface designs2018Inngår i: Acta Biomaterialia, ISSN 1742-7061, E-ISSN 1878-7568, Vol. 70, s. 12-24Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Bacterial adhesion and subsequent biofilm formation on biomedical implants and devices are a major cause of their failure. As systemic antibiotic treatment is often ineffective, there is an urgent need for antimicrobial biomaterials and coatings. The term “antimicrobial” can encompass different mechanisms of action (here termed “antimicrobial surface designs”), such as antimicrobial-releasing, contact-killing or non-adhesivity. Biomaterials equipped with antimicrobial surface designs based on different mechanisms of action require different in vitro evaluation methods. Available industrial standard evaluation tests do not address the specific mechanisms of different antimicrobial surface designs and have therefore been modified over the past years, adding to the myriad of methods available in the literature to evaluate antimicrobial surface designs. The aim of this review is to categorize fourteen presently available methods including industrial standard tests for the in vitro evaluation of antimicrobial surface designs according to their suitability with respect to their antimicrobial mechanism of action. There is no single method or industrial test that allows to distinguish antimicrobial designs according to all three mechanisms identified here. However, critical consideration of each method clearly relates the different methods to a specific mechanism of antimicrobial action. It is anticipated that use of the provided table with the fourteen methods will avoid the use of wrong methods for evaluating new antimicrobial designs and therewith facilitate translation of novel antimicrobial biomaterials and coatings to clinical use. The need for more and better updated industrial standard tests is emphasized. Statement of Significance European COST-action TD1305, IPROMEDAI aims to provide better understanding of mechanisms of antimicrobial surface designs of biomaterial implants and devices. Current industrial evaluation standard tests do not sufficiently account for different, advanced antimicrobial surface designs, yet are urgently needed to obtain convincing in vitro data for approval of animal experiments and clinical trials. This review aims to provide an innovative and clear guide to choose appropriate evaluation methods for three distinctly different mechanisms of antimicrobial design: (1) antimicrobial-releasing, (2) contact-killing and (3) non-adhesivity. Use of antimicrobial evaluation methods and definition of industrial standard tests, tailored toward the antimicrobial mechanism of the design, as identified here, fulfill a missing link in the translation of novel antimicrobial surface designs to clinical use.

  • 70.
    Sjögren, Rickard
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Stridh, Kjell
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Skotare, Tomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Trygg, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Sartorius Stedim Data Analytics, Umeå, Sweden.
    Multivariate patent analysis: using chemometrics to analyze collections of chemical and pharmaceutical patents2018Inngår i: Journal of Chemometrics, ISSN 0886-9383, E-ISSN 1099-128X, artikkel-id e3041Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Abstract Patents are an important source of technological knowledge, but the amount of existing patents is vast and quickly growing. This makes development of tools and methodologies for quickly revealing patterns in patent collections important. In this paper, we describe how structured chemometric principles of multivariate data analysis can be applied in the context of text analysis in a novel combination with common machine learning preprocessing methodologies. We demonstrate our methodology in 2 case studies. Using principal component analysis (PCA) on a collection of 12338 patent abstracts from 25 companies in big pharma revealed sub-fields which the companies are active in. Using PCA on a smaller collection of patents retrieved by searching for a specific term proved useful to quickly understand how patent classifications relate to the search term. By using orthogonal projections to latent structures (O-PLS) on patent classification schemes, we were able to separate patents on a more detailed level than using PCA. Lastly, we performed multi-block modeling using OnPLS on bag-of-words representations of abstracts, claims, and detailed descriptions, respectively, showing that semantic variation relating to patent classification is consistent across multiple text blocks, represented as globally joint variation. We conclude that using machine learning to transform unstructured data into structured data provide a good preprocessing tool for subsequent chemometric multivariate data analysis and provides an easily interpretable and novel workflow to understand large collections of patents. We demonstrate this on collections of chemical and pharmaceutical patents.

  • 71.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Inorganic chemistry and bioenergy - an unexpected match?2019Konferansepaper (Annet vitenskapelig)
  • 72.
    Skoglund, Nils
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik. Energy Engineering, Department of Engineering Sciences & Mathematics, Luleå University of Technology, Luleå, Sweden.
    Werner, Kajsa
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Nylund, Göran M.
    University of Gothenburg, Department of Marine Sciences - Tjärnö.
    Pavia, Henrik
    University of Gothenburg, Department of Marine Sciences - Tjärnö.
    Albers, Eva
    Chalmers University of Technology, Department of Biology and Biological Engineering, Division Industrial Biotechnology.
    Broström, Markus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Combustion of seaweed: a fuel design strategy2017Inngår i: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 165, s. 155-161Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The high ash content and varying ash composition in algal biomass is often mentioned as problematic if to beused for thermal energy conversion. This paper suggests an approach where detailed information on ash compositionand predicted ash formation reactions are basis for successful remedies enabling the use of fuels consideredto be difficult. The procedure is demonstrated on seaweed (Saccharina latissima) cultivated for biorefinery purposes. The ash composition of the seaweed was found suitable for co-combustion with Miscanthus x giganteus, an energy crop high in alkali and silicon. Fuel mixtures were combusted in a bubbling fluidized bed reactorand ash samples were analyzed by SEM-EDS and XRD. The results showed that Ca from the seaweed was veryreactive and thus efficient in solving the silicatemelting problems. The fuel design approach was proven successfuland the potential for using otherwise difficult seaweed fuels in synergetic co-combustion was demonstrated.

  • 73.
    Skotare, Tomas
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Sjögren, Rickard
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Surowiec, Izabella
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Nilsson, David
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Trygg, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Sartorius Stedim Data Analytics, 907 36 Umeå, Sweden.
    Visualization of descriptive multiblock analysis2018Inngår i: Journal of Chemometrics, ISSN 0886-9383, E-ISSN 1099-128XArtikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Abstract Understanding and making the most of complex data collected from multiple sources is a challenging task. Data integration is the procedure of describing the main features in multiple data blocks, and several methods for multiblock analysis have been previously developed, including OnPLS and JIVE. One of the main challenges is how to visualize and interpret the results of multiblock analyses because of the increased model complexity and sheer size of data. In this paper, we present novel visualization tools that simplify interpretation and overview of multiblock analysis. We introduce a correlation matrix plot that provides an overview of the relationships between blocks found by multiblock models. We also present a multiblock scatter plot, a metadata correlation plot, and a variation distribution plot, that simplify the interpretation of multiblock models. We demonstrate our visualizations on an industrial case study in vibration spectroscopy (NIR, UV, and Raman datasets) as well as a multiomics integration study (transcript, metabolite, and protein datasets). We conclude that our visualizations provide useful tools to harness the complexity of multiblock analysis and enable better understanding of the investigated system.

  • 74.
    Skrobonja, Aleksandra
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Gojkovic, Zivan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Soerensen, Anne L.
    Westlund, Per-Olof
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Funk, Christiane
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Björn, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Uptake Kinetics of Methymerucy in a Freshwater Alga Exposed to Methylmercury Complexes with Environmentally Relevant Thiols2019Inngår i: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 53, nr 23, s. 13757-13766Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cellular uptake of dissolved methylmercury (MeHg) by phytoplankton is the most important point of entry for MeHg into aquatic food webs. However, the process is not fully understood. In this study we investigated the influence of chemical speciation on rate constants for MeHg accumulation by the freshwater green microalga Selenastrum capricornutum. We used six MeHg–thiol complexes with moderate but important structural differences commonly found in the environment. Rate constants for MeHg interactions with cells were determined for the MeHg–thiol treatments and a control assay containing the thermodynamically less stable MeHgOH complex. We found both elevated amounts of MeHg associated with whole cells and higher MeHg association rate constants in the control compared to the thiol treatments. Furthermore, the association rate constants were lower when algae were exposed to MeHg complexes with thiols of larger size and more “branched” chemical structure compared to complexes with simpler structure. The results further demonstrated that the thermodynamic stability and chemical structure of MeHg complexes in the medium is an important controlling factor for the rate of MeHg interactions with the cell surface, but not for the MeHg exchange rate across the membrane. Our results are in line with uptake mechanisms involving formation of MeHg complexes with cell surface ligands prior to internalization.

  • 75.
    Souihi, Nabil
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Multivariate Synergies in Pharmaceutical Roll Compaction: The quality influence of raw materials and process parameters by design of experiments2014Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Roll compaction is a continuous process commonly used in the pharmaceutical industry for dry granulation of moisture and heat sensitive powder blends. It is intended to increase bulk density and improve flowability. Roll compaction is a complex process that depends on many factors, such as feed powder properties, processing conditions and system layout. Some of the variability in the process remains unexplained. Accordingly, modeling tools are needed to understand the properties and the interrelations between raw materials, process parameters and the quality of the product. It is important to look at the whole manufacturing chain from raw materials to tablet properties.

    The main objective of this thesis was to investigate the impact of raw materials, process parameters and system design variations on the quality of intermediate and final roll compaction products, as well as their interrelations. In order to do so, we have conducted a series of systematic experimental studies and utilized chemometric tools, such as design of experiments, latent variable models (i.e. PCA, OPLS and O2PLS) as well as mechanistic models based on the rolling theory of granular solids developed by Johanson (1965).

    More specifically, we have developed a modeling approach to elucidate the influence of different brittle filler qualities of mannitol and dicalcium phosphate and their physical properties (i.e. flowability, particle size and compactability) on intermediate and final product quality. This approach allows the possibility of introducing new fillers without additional experiments, provided that they are within the previously mapped design space. Additionally, this approach is generic and could be extended beyond fillers. Furthermore, in contrast to many other materials, the results revealed that some qualities of the investigated fillers demonstrated improved compactability following roll compaction.

    In one study, we identified the design space for a roll compaction process using a risk-based approach. The influence of process parameters (i.e. roll force, roll speed, roll gap and milling screen size) on different ribbon, granule and tablet properties was evaluated. In another study, we demonstrated the significant added value of the combination of near-infrared chemical imaging, texture analysis and multivariate methods in the quality assessment of the intermediate and final roll compaction products. Finally, we have also studied the roll compaction of an intermediate drug load formulation at different scales and using roll compactors with different feed screw mechanisms (i.e. horizontal and vertical). The horizontal feed screw roll compactor was also equipped with an instrumented roll technology allowing the measurement of normal stress on ribbon. Ribbon porosity was primarily found to be a function of normal stress, exhibiting a quadratic relationship. A similar quadratic relationship was also observed between roll force and ribbon porosity of the vertically fed roll compactor. A combination of design of experiments, latent variable and mechanistic models led to a better understanding of the critical process parameters and showed that scale up/transfer between equipment is feasible.

  • 76.
    Souihi, Nabil
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Dumarey, Melanie
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Wikström, Håkan
    Tajarobi, Pirjo
    Fransson, Magnus
    Svensson, Olof
    Josefson, Mats
    Trygg, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    A Quality by Design approach to investigate the effect of mannitol and dicalcium phosphate qualities on roll compaction2013Inngår i: International Journal of Pharmaceutics, ISSN 0378-5173, E-ISSN 1873-3476, Vol. 447, nr 1-2, s. 47-61Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Roll compaction is a continuous process for solid dosage form manufacturing increasingly popular within pharmaceutical industry. Although roll compaction has become an established technique for dry granulation, the influence of material properties is still not fully understood. In this study, a quality by design (QbD) approach was utilized, not only to understand the influence of different qualities of mannitol and dicalcium phosphate (DCP), but also to predict critical quality attributes of the drug product based solely on the material properties of that filler. By describing each filler quality in terms of several representative physical properties, orthogonal projections to latent structures (OPLS) was used to understand and predict how those properties affected drug product intermediates as well as critical quality attributes of the final drug product. These models were then validated by predicting product attributes for filler qualities not used in the model construction. The results of this study confirmed that the tensile strength reduction, known to affect plastic materials when roll compacted, is not prominent when using brittle materials. Some qualities of these fillers actually demonstrated improved compactability following roll compaction. While direct compression qualities are frequently used for roll compacted drug products because of their excellent flowability and good compaction properties, this study revealed that granules from these qualities were more poor flowing than the corresponding powder blends, which was not seen for granules from traditional qualities. The QbD approach used in this study could be extended beyond fillers. Thus any new compound/ingredient would first be characterized and then suitable formulation characteristics could be determined in silico, without running any additional experiments.

  • 77.
    Souihi, Nabil
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Nilsson, David
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Josefson, Mats
    Trygg, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Near-infrared chemical imaging (NIR-CI) on roll compacted ribbons and tablets - multivariate mapping of physical and chemical properties2015Inngår i: International Journal of Pharmaceutics, ISSN 0378-5173, E-ISSN 1873-3476, Vol. 483, nr 1-2, s. 200-211Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Near-infrared chemical imaging (NIR-CI) is an attractive technique within the pharmaceutical industry, where tools are continuously in demand to assess the quality of the intermediate and final products. The present paper demonstrates how NIR-CI in combination with multivariate methods was utilized to spatially map physical properties and content of roll compacted ribbons and tablets. Additionally, extracted textural parameters from tablet images were correlated to the design parameters of the roll compaction process as well as to the physical properties of the granules. The results established the use of NIR-CI as a complementary nondestructive tool to determine the ribbon density and map the density distribution across the width and along the length of the ribbons. For the tablets, the compaction pressure developed during compression increased with the lateral distance from the center. Therefore, NIR-CI can be an effective tool to provide information about the spatial distribution of the compaction pressures on the surface of the tablet. Moreover, low roll compaction roll force correlated to a heterogeneous type of texture in the API chemical image. Overall, texture analysis of the tablets enabled efficient investigation of the spatial variation and could be used to advance process understanding. Finally, orthogonal projections to latent structures (O2PLS) model facilitated the understanding of the interrelationships between textural features, design parameters and physical properties data by separately joint and unique variations.

  • 78.
    Souihi, Nabil
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Reynolds, Gavin
    Tajarobi, Pirjo
    Wikström, Håkan
    Haeffler, Gunnar
    Josefson, Mats
    Trygg, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Roll compaction process modeling: transfer between equipment and impact of process parameters2015Inngår i: International Journal of Pharmaceutics, ISSN 0378-5173, E-ISSN 1873-3476, Vol. 484, nr 1-2, s. 192-206Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study the roll compaction of an intermediate drug load formulation was performed using horizontally and vertically force fed roll compactors. The horizontally fed roll compactor was equipped with an instrumented roll technology allowing the direct measurement of normal stress at the roll surface, while the vertically fed roll compactor was equipped with a force gauge between the roll axes. Furthermore, characterization of ribbons, granules and tablets was also performed. Ribbon porosity was primarily found to be a function of normal stress, exhibiting a quadratic relationship thereof. A similar quadratic relationship was also observed between roll force and ribbon porosity of the vertically fed roll compactor. The predicted peak pressure (Pmax) using the Johanson model was found to be higher than the measured normal stress, however, the predicted Pmax correlated well with the ribbon relative density/porosity and the majority of downstream properties of granules and tablets, demonstrating its use as a scale-independent parameter. A latent variable model was developed for both the horizontal and vertical fed roll compactors to express ribbon porosity as a function of geometric and process parameters. The model validation, performed with new data, resulted in overall good predictions. This study successfully demonstrated the scale up/transfer between two different roll compactors and revealed that the combined use of design of experiments, latent variable models and in silico predictions result in better understanding of the critical process parameters in roll compaction.

  • 79.
    Stenberg, Mia
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    In silico tools in risk assessment: of industrial chemicals in general and non-dioxin-like PCBs in particular2012Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Industrial chemicals in European Union produced or imported in volumes above 1 tonne annually, necessitate a registration within REACH. A common problem, concerning these chemicals, is deficient information and lack of data for assessing the hazards posed to human health and the environment. Animal studies for the type of toxicological information needed are both expensive and time consuming, and to that an ethical aspect is added. Alternative methods to animal testing are thereby requested. REACH have called for an increased use of

    in silico tools for non-testing data as structure-activity relationships (SARs), quantitative structure-activity relationships (QSARs), and read-across. The main objective of the studies underlying this thesis is related to explore and refine the use of in silico tools in a risk assessment context of industrial chemicals. In particular, try to relate properties of the molecular structure to the toxic effect of the chemical substance, by using principles and methods of computational chemistry. The initial study was a survey of all industrial chemicals; the Industrial chemical map was created. A part of this map was identified including chemicals of potential concern. Secondly, the environmental pollutants, polychlorinated biphenyls (PCBs) were examined and in particular the non-dioxin-like PCBs (NDL-PCBs). A set of 20 NDL-PCBs was selected to represent the 178 PCB congeners with three to seven chlorine substituents. The selection procedure was a combined process including statistical molecular design for a representative selection and expert judgements to be able to include congeners of specific interest. The 20 selected congeners were tested in vitro in as much as 17 different assays. The data from the screening process was turned into interpretable toxicity profiles with multivariate methods, used for investigation of potential classes of NDL-PCBs. It was shown that NDL-PCBs cannot be treated as one group of substances with similar mechanisms of action. Two groups of congeners were identified. A group including in general lower chlorinated congeners with a higher degree of ortho substitution showed a higher potency in more assays (including all neurotoxic assays). A second group included abundant congeners with a similar toxic profile that might contribute to a common toxic burden. To investigate the structure-activity pattern of PCBs effect on DAT in rat striatal synaptosomes, ten additional congeners were selected and tested in vitro. NDL-PCBs were shown to be potent inhibitors of DAT binding. The congeners with highest DAT inhibiting potency were tetra- and penta-chlorinated with 2-3 chlorine atoms in ortho-position. The model was not able to distinguish the congeners with activities in the lower μM range, which could be explained by a relatively unspecific response for the lower ortho chlorinated PCBs.

  • 80. Sugano, Yasuhito
    et al.
    Kumar, Narendra
    Peurla, Markus
    Roine, Jorma
    Aho, Atte
    Bobacka, Johan
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Åbo Akademi, University Faculty of Science and Engineering, Turku, Finland.
    Specific Electrocatalytic Oxidation of Cellulose at Carbon Electrodes Modified by Gold Nanoparticles2016Inngår i: ChemCatChem, ISSN 1867-3880, E-ISSN 1867-3899, Vol. 8, nr 14, s. 2401-2405Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The influence of the size and oxidation state of Au nanoparticles (AuNPs) as electrocatalysts for the electro-oxidation of cellulose was studied. Carbon paper electrodes modified with AuNPs were used as the electrocatalysts for the electro-oxidation of cellulose dissolved in 1.3 m NaOH. The size and oxidation state of the AuNPs were determined by using SEM, TEM, and X-ray photoelectron spectroscopy. Both the size and the oxidation state of the AuNPs were found to influence the electrocatalytic properties of the electrode, as studied by using cyclic voltammetry, square wave voltammetry, and electrochemical impedance spectroscopy. The carbon paper electrodes decorated with AuNPs (less than 25 nm) that consist of metallic Au gave rise to a significantly higher electrocatalytic activity than a bare polycrystalline Au electrode.

  • 81.
    Sundberg, Peter
    et al.
    Research Institutes of Sweden, RISE Bioeconomy/Biorefinery and Energy.
    Fagerström, Jonathan
    Åbo Akademi University, Faculty of Science and Engineering, Energy and Environmental Engineering.
    Rebbling, Anders
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Hermansson, Sven
    Research Institutes of Sweden, RISE Bioeconomy/Biorefinery and Energy.
    Tullin, Claes
    Research Institutes of Sweden, RISE Bioeconomy/Biorefinery and Energy.
    Boström, Dan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Engineering.
    Boman, Christoffer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Biomass and peat co-combustion in full scale grate boilers - a primary measure for reduction of fine particle emissions2017Konferansepaper (Fagfellevurdert)
  • 82.
    Sundman, Ola
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    The 7th workshop on cellulose, regenerated cellulose and cellulose derviatives2016Konferanseproceedings (Annet vitenskapelig)
  • 83.
    Sundman, Ola
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Albán Reyes, Diana Carolina
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Svedberg, Anna
    MoRe Research.
    Hellström, Sara
    Domsjö Fabriker AB.
    Differences in crystalline structure between fines and bulk cellulose in a softwood sulphite dissolving pulp2015Inngår i: 4th EPNOE International Polysaccaride Conference: Polysaccharides and polysaccharide-based materials: from science to industry, 2015Konferansepaper (Annet vitenskapelig)
  • 84.
    Tang, Shi
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. LunaLEC AB, Tvistevagen 47, SE-90719 Umea, Sweden.
    Murto, Petri
    Xu, Xiaofeng
    Larsen, Christian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. LunaLEC AB, Tvistevagen 47, SE-90719 Umea, Sweden.
    Wang, Ergang
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. LunaLEC AB, Tvistevagen 47, SE-90719 Umea, Sweden.
    Intense and Stable Near-Infrared Emission from Light-Emitting Electrochemical Cells Comprising a Metal-Free Indacenodithieno[3,2-b]thiophene-Based Copolymer as the Single Emitter2017Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 29, nr 18, s. 7750-7759Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report on the synthesis, characterization, and application of a series of metal-free near-infrared (NIR) emitting alternating donor/acceptor copolymers based on indacenodithieno[3,2-b]thiophene (IDTT) as the donor unit. A light-emitting electrochemical cell (LEC), comprising a blend of the copolymer poly[indacenodithieno[3,2-b]thiophene-2,8-diyl-alt-2,3-diphenyl-5,8-di(thiophen-2-y1)- quinoxaline-5,5'-diy1] and an ionic liquid as the single-layer active material sandwiched between two air-stable electrodes, delivered NIR emission (lambda(peak) = 705 nm) with a high radiance of 129 mu W/cm(2) when driven by a low voltage of 3.4 V. The NIR-LEC also featured good stress stability, as manifested in that the peak NIR output from a nonencapsulated device after 24 h of continuous operation only had dropped by 3% under N-2 atmosphere and by 27% under ambient air. This work accordingly introduces IDTT-based donor/acceptor copolymers as functional metal-free electroluminescent materials in NIR-emitting devices and also provides guidelines for how future NIR emitters should be designed for further improved performance.

  • 85. Toth, Geza
    et al.
    Halonen, Niina
    Maklin, Jani
    Kukkola, Jarmo
    Kordas, Krisztian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Microelectronics and Materials Physics Laboratories, EMPART Research Group of Infotech Oulu, Department of Electrical Engineering, University of Oulu, Finland.
    Thermal management of micro hotspots in electric components with carbon nanotubes2013Inngår i: International Journal of Nanotechnology, ISSN 1475-7435, E-ISSN 1741-8151, Vol. 10, nr 1-2, s. 57-62Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The excellent thermal and electrical conductivity as well as the remarkable mechanical properties of Carbon Nanotubes (CNTs) all point towards an unbeatable and facile route towards replacing traditional thermal management materials, like copper, in the electronics industry. In spite of that, the technology is still suffering from considerable challenges. In order to realise an actual electronics, which uses CNTs for thermal management, inevitable trade-offs have to be made. Our work is focusing on proposing novel ideas and manufacturing techniques which show a reasonable potential and could justify the practicality of this technology. The paper is reporting on the recent results in hotspot removal by using tailored multi-layer chips and CNTs grown directly on the heat affected zone.

  • 86.
    Trygg, Johan
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Aberg, K. Magnus
    13th Scandinavian Symposium on Chemometrics2014Inngår i: Journal of Chemometrics, ISSN 0886-9383, E-ISSN 1099-128X, Vol. 28, nr 8, s. 604-605Artikkel i tidsskrift (Annet vitenskapelig)
  • 87. Wigestrand, Mattis B.
    et al.
    Stenberg, Mia
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Waalas, S Ivar
    Fonnum, Frode
    Andersson, Patrik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Non-dioxin-like PCBs inhibit [3H]WIN-35,428 binding to dopamine active transporter:  a structure activity relationship study2013Inngår i: Naunyn-Schmiedeberg's Archives of Pharmacology, ISSN 0028-1298, E-ISSN 1432-1912Artikkel i tidsskrift (Annet vitenskapelig)
  • 88.
    Winberg, Mikael
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för naturvetenskapernas och matematikens didaktik.
    Learning by computer-simulated laboratory exercises – effects on learning outcomes.2001Konferansepaper (Annet vitenskapelig)
  • 89.
    Winberg, Mikael
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för naturvetenskapernas och matematikens didaktik.
    Using PCA for analysis of questionnaires, a journey into the affective domain.2001Konferansepaper (Fagfellevurdert)
  • 90.
    Winberg, Mikael
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för naturvetenskapernas och matematikens didaktik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Berg, A
    Lunberg, B
    Computer simulated acid-base titrations as prelab: effects on learning outcome2001Konferansepaper (Fagfellevurdert)
  • 91.
    Winberg, Mikael
    et al.
    Umeå universitet, Fakultet för lärarutbildning, Matematik, teknik och naturvetenskap.
    Berg, Anders
    Umeå universitet, Fakultet för lärarutbildning, Matematik, teknik och naturvetenskap.
    Students' cognitive focus during a chemistry laboratory exercise: Effects of a computer simulated prelab2007Inngår i: Journal of research in science teaching, ISSN 0022-4308, Vol. 44, nr 8, s. 1098-2736Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    To enhance the learning outcomes achieved by students, learners undertook a computer-simulated activity based on an acid-base titration prior to a university-level chemistry laboratory activity. Students were categorized with respect to their attitudes toward learning. During the laboratory exercise, questions that students asked their assistant teachers were used as indicators of cognitive focus. During the interviews, students' frequency and level of spontaneous use of chemical knowledge served as an indicator of knowledge usability. Results suggest that the simulation influenced students toward posing more theoretical questions during their laboratory work and, regardless of attitudes, exhibiting a more complex, correct use of chemistry knowledge in their interviews. A more relativistic student attitude toward learning was positively correlated with interview performance in both the control and treatment groups.

  • 92.
    Winberg, Mikael
    et al.
    Umeå universitet, Fakultet för lärarutbildning, Matematik, teknik och naturvetenskap.
    Hedman, Leif
    Umeå universitet, Samhällsvetenskapliga fakulteten, Institutionen för psykologi.
    Student attitudes toward learning, level of pre-knowledge and instruction type in a computer-simulation: effects on flow experiences and perceived learning outcomes2008Inngår i: Instructional science, ISSN 0020-4277, E-ISSN 1573-1952, Vol. 36, nr 4, s. 269-287Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Attitudes toward learning (ATL) have been shown to influence students’ learning outcomes. However, there is a lack of knowledge about the ways in which the interaction between ATL, the learning situation, and the level of students’ prior knowledge influence affective reactions and conceptual change. In this study, a simulation of acid-base titrations was examined to assess the impact of instruction format, level of prior knowledge and students’ ATL on university-level students, with respect to flow experiences (Csikszentmihalyi, 1990) and perceived conceptual change. Results show that the use of guiding instructions was correlated with a perceived conceptual change and high levels of “Challenge,” “Enjoyment,” and “Concentration,” but low sense of control during the exercise. Students who used the open instructions scored highly on the “Control flow” component, but their perceived learning score was lower than that for the students who used the guiding instructions. In neither case did students’ ATL or their pre-test results contribute strongly to students’ flow experiences or their perceived learning in the two different learning situations.

  • 93. Xu, Jing
    et al.
    Marsac, Remi
    Costa, Dominique
    Cheng, Wei
    Wu, Feng
    Boily, Jean-Francois
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Hanna, Khalil
    Co-Binding of Pharmaceutical Compounds at Mineral Surfaces: Molecular Investigations of Dimer Formation at Goethite/Water Interfaces2017Inngår i: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 51, nr 15, s. 8343-8349Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The emergence of antibiotic and anti-inflammatory agents in aquatic and terrestrial systems is becoming a serious threat to human and animal health worldwide. Because pharmaceutical compounds rarely exist individually in nature, interactions between various compounds can have unforeseen effects on their binding to mineral surfaces. This work demonstrates this important possibility for the case of two typical antibiotic and anti-inflammatory agents (nalidixic acid (NA) and niflumic acid (NFA)) bound at goethite (alpha FeOOH) used as a model mineral surface. Our multidisciplinary study, which makes use of batch sorption experiments, vibration spectroscopy and periodic density functional theory calculations, reveals enhanced binding of the otherwise weakly bound NFA caused by unforeseen intermolecular interactions with mineral-bound NA. This enhancement is ascribed to the formation of a NFA NA dimer whose energetically favored formation (-0.5 eV compared to free molecules) is predominantly driven by van der Waals interactions. A parallel set of efforts also showed that no. cobinding occurred with sulfamethoxazole (SMX) because of the lack of molecular interactions with coexisting contaminants. As such, this article raises the importance of recognizing drug cobinding, and lack of cobinding, for predicting and developing policies on the fate of complex mixtures of antibiotics and anti-inflammatory agents in nature.

  • 94.
    Zhe, Li
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Relative influences of uncertainty in physical-chemical property data and variability in climate parameters in determining the fate of PCBs2011Independent thesis Advanced level (degree of Master (Two Years)), 30 poäng / 45 hpOppgave
    Abstract [en]

    Persistent organic pollutants (POPs) present a class of substances which are of high concern due to their toxicity and ecotoxicity, long-range atmospheric transport and resistance to degradation. A combination of analytical measurement and modeling researchis a powerful means for understanding chemical fate and behavior. Among all availablemodeling approaches, multi-compartmental fugacity modeling is a common and relatively simpleway to simulate the concentrations and distributions of pollutants. This approach isalso applied hereto study a well-studiedgroup of POPs –polychlorinated biphenyls (PCBs).

    Climate changeis potentially one of the largest global environmental problems facing society today. Climate change resulting from anthropogenic activities may impact the transport, fate and exposure of POPs due to alterations in climatic and landscape properties (e.g. temperature, windspeed, precipitation etc.). Modeling studies have previously been carried out to investigate their influence on POPs fate under defined scenarios.However, in previous work the uncertainty of chemical properties has not been considered. We hypothesize that the uncertainties in physical-chemical parameters could actually cause a greater impact predicted concentrations than variability in climate parameters such as temperature, wind speed and precipitation.

    To test the hypothesis, a 4-compartment Level III fugacity model –ChemCAN spreadsheet model is used. A combination of8 climate variables, 3 physical-chemical properties and 4 degradation properties are chosen to investigate how the variability and uncertainty affect the environmental fate of 6 selected PCBs congeners. In total, 18 forecasts are createdin the investigation and outputs provided forconcentrations, distributions, total amounts, long-range transport potential indicators and persistence of the chemicals. We arbitrarily model the Japan region for which we had environmental parameterization in the ChemCAN model. Monte-Carlo simulations areundertakenusing the

    Crystal Ball®computer software to perform correlation and sensitivity analyses, in order to specifically examine andcompare the influence brought from variability and uncertainty.Datafor climate variablesarecollected and calculated from Intergovernmental Panel on Climate Change –Data Distribution Centre (IPCC-DDC), while thosefor chemical propertyuncertainty arecollected and calculated from literature sources/methods.

    The results are interpreted focusing on the two types of analyses –correlation and sensitivity. Within the correlation analysis between climate variables and PCB fate predictions, temperature is the most important factor affecting total amount, concentrations and distributions, especially in the atmosphere compartment. It alsoinfluencesthefugacity of the PCBs in each media, as well asthe reactive residence times. The uncertainty of temperature increases resulting fromclimate change has more influence thanvariability in mean temperature however. Precipitation hardly has any influence onPCB fate,althoughthe change in precipitationdue to climate changecould affect distributions in surface water and surface soil for light chlorinated PCBs congeners due to the extremely high coefficient of variation. Wind speedalso has little impact onpredictions other than for long-range transport potential descriptors, namely characteristic transport distance and transfer efficiency. Wind speed also affectsthe advective residence timein theair compartment forPCBs.Within the correlation analysis between properties and PCB fate predictions, all the chosen 3 physical-chemical properties, vapor pressure, water solubility and water-octanol partition coefficient, significantly affect the predictions. Vapor pressure has more influence onpredictions related to air and more significantly on lighter PCBs, while water solubility and the water-octanol partition coefficient mostly affect the heavier PCBs, especially

    MSc. Thesis in Environmental Chemistry

    II

    the predicted outcomes in water and sediment. Despite a fairly small uncertainty inphysical-chemical propertiescompared to many other chemicals, the influence on PCB fate is noticeable. Degradation properties, which have a rather high uncertainty, also significantly affect PCB environmental fate and degradation half-lives in air and soil have much more significant influence than those in water and sediment.

    In the sensitivity analysis, variability and uncertainty are assembled into a single simulation. When excluding degradation properties, it could be concluded that uncertainty inphysical-chemical properties is usually dominant forPCBs. One notable exception isthat precipitation change has a greaterinfluence on PCB-8, which is also the lightestincluded inthe study. If degradation propertiesare included, degradation half-lives in air and soil are always the dominantsource of uncertainty to predictions.

    The main conclusion of this thesis is that the uncertainty in chemical property datais generally more important than variability in climate parameters in controlling variance in predicted environmental concentrations.This supports the hypothesis of that was raised at the beginning of this study.

     

     

  • 95. Öhman, Anders
    et al.
    Lycksell, P O
    Juréus, A
    Langel, U
    Bartfai, T
    Gräslund, A
    NMR study of the conformation and localization of porcine galanin in SDS micelles. Comparison with an inactive analog and a galanin receptor antagonist.1998Inngår i: Biochemistry, ISSN 0006-2960, E-ISSN 1520-4995, Vol. 37, nr 25Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Galanin is a 29/30-residue neuro-endocrine peptide which performs its many important physiological functions via a membrane-bound receptor. By using two-dimensional proton NMR spectroscopy, complete relaxation matrix analysis, and simulated annealing, the conformation of porcine galanin was determined in a membrane-mimicking solvent containing sodium dodecyl sulfate (SDS) micelles. The final family of calculated structures displays three well-defined beta- or gamma-turn regions, comprising residues 1-5, 7-10, and 24-27, but has otherwise a random conformation. The receptor-interacting N-terminal part, residues 1-5, was found to be best defined with a backbone RMSD value of 0.12 A. The mode of association between galanin and the SDS micelle was determined by observing the broadening effect on proton resonances, when spin-labeled 5- and 12-doxyl stearate molecules were added. It was concluded that galanin is located close to the surface of the micelle with two regions, residues 6-9 and 24-29, as well as two single residues, 18 and 21, reaching out into the aqueous solvent. Additional NMR studies were carried out on an inactive analogue, Ala2-galanin, and an antagonist M40. The results show that the proton resonances of galanin and M40 have identical chemical shifts in the N-terminal receptor-interacting region, indicating similar solution structures in this region. For Ala2-galanin, the same region displays a spectral heterogeneity with chemical shifts clearly different from the other two peptides, indicative of different secondary structures. These results may provide a structural background for the antagonist activity of M40 and the hormonal inactivity of Ala2-galanin, as compared to galanin.

  • 96.
    Öhman, Anders
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för farmakologi och klinisk neurovetenskap, Klinisk neurovetenskap.
    Rak, Alexey
    Dontsova, Maria
    Garber, Maria B
    Härd, Torleif
    NMR structure of the ribosomal protein L23 from Thermus thermophilus.2003Inngår i: Journal of Biomolecular NMR, ISSN 0925-2738, E-ISSN 1573-5001, Vol. 26, nr 2Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The ribosomal protein L23 is a component of the large ribosomal subunit in which it is located close to the peptide exit tunnel. In this position L23 plays a central role both for protein secretion and folding. We have determined the solution structure of L23 from Thermus thermophilus. Uncomplexed L23 consists of a well-ordered part, with four anti-parallel beta-strands and three alpha-helices connected as beta-alpha-beta-alpha-beta-beta-alpha, and a large and flexible loop inserted between the third and fourth beta-strand. The observed topology is distantly related to previously known structures, primarily within the area of RNA biochemistry. A comparison with RNA-complexed crystal structures of L23 from T. thermophilus, Deinococcus radiodurans and Haloarcula marismourtui, shows that the conformation of the well-ordered part is very similar in the uncomplexed and complexed states. However, the flexible loop found in the uncomplexed solution structure forms a rigid extended structure in the complexed crystal structures as it interacts with rRNA and becomes part of the exit tunnel wall. Structural characteristics of importance for the interaction with rRNA and with the ribosomal protein L29, as well as the functional role of L23, are discussed.

  • 97.
    Österlund, Lise-Lotte
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Redox models in chemistry:  A depiction of the conceptions held by secondary school students of redox reactions2010Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    According to previous research, students show difficulties in learning redox reactions. By the historical development different redox models exist to explain redox reactions, the oxygen model, the hydrogen model, the electron model and the oxidation number model. This thesis reports about three studies concerning conceptions held by secondary school students of redox reactions. A textbook analysis is also included in the thesis.

    The first study was an investigation of the students’ use of redox models in inorganic contexts, their use of the activity series of metals, and the students’ ability to transfer redox knowledge. Then the students’ work with an open-ended biochemical task, where the students had access of the textbook was studied. The students talk about redox reactions, the questions raised by the students, what resources used to answer the questions and what kind of talk developed were investigated. A textbook analysis based on chemistry books from Sweden and one book from England was performed. The redox models used as well as the dealing with redox related learning difficulties was studied. Finally, the students’ conceptions about redox in inorganic, organic and biochemistry after completed chemistry courses were studied.

    The results show that the students were able to use the electron model as a tool to explain inorganic redox reactions and the mutuality of oxidation and reduction was fundamental. The activity series of metals became a tool for the prediction of reducing agent in some reactions. Most of the students rejected that oxygen is a prerequisite for a redox reaction. In the biochemical task the resource most used to answer the raised questions were the students’ consultation of the textbook – together or individually. Most questions resulted in short answers and the majority of these questions were answered. Questions concerning redox were analysed by the students and integrated into a chemical context but they could neither identify the substances oxidised or reduced nor couple the concepts to transfer of hydrogen atoms. The majority of these redox questions became unanswered. The textbook helped the students to structure a poster as well as to answer basic chemistry questions. For questions about organic and biochemical redox, the book was of no help. The textbook analysis showed that all historical redox models are used. Different models are used in inorganic, organic and biochemistry. The mutuality of oxidation and reduction is treated differently in subject areas. The textbooks did not help the reader linking the different redox models that were used. Few redox-related learning difficulties are addressed in the books. After completed chemistry courses the students had major problems to justify a redox reaction explained by transfer of hydrogen atoms both in the organic and biochemistry examples.

  • 98. Škvarla, Jiří
    et al.
    Kaňuchová, Mária
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Girová, Anna
    Brezáni, Ivan
    Cryo-XPS: A new technique for the quantitative analysis of the structure of electric double layer at colloidal particles?2020Inngår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 586, artikkel-id 124234Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    There is a long-lasting uncertainty as to the structure of the metal oxide/water interface. Various structures have especially been invoked to rationalize the seemingly anomalous silica/water interface. But, none of them seems to be approved in a quantitative and systematic way. We show that the concentration ratio of monovalent counterions and coions around colloidal silica spheres, as detected by the cryo-XPS technique, follows fundamental theoretical predictions of either Boltzmann or Donnan distribution. It is suggested that the reason of the dual response is the formation of the swelling gel layer on the silica surface due to its longer contact with water.

12 51 - 98 of 98
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