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  • 2751.
    Zerva, Anastasia
    et al.
    Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens .
    Papaspyridi, Lefki Maria
    Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens .
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Topakas, Evangelos
    National Technical University of Athens, School of Chemical Engineering, National Technical University of Athens, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Valorization of Olive Mill Wastewater for the Production of β-glucans from Selected Basidiomycetes2017Ingår i: Waste and Biomass Valorization, ISSN 1877-2641, E-ISSN 1877-265X, Vol. 8, nr 5, s. 1721-1731Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Purpose

    The aim of the present study was to investigate the feasibility of polysaccharides production by selected basidiomycetes in submerged culture. Olive mill wastewater (OMWW) was also tested as a potential substrate for polysaccharides production by mushroom strains, focusing on the simultaneous degradation and valorization of the waste material.

    Methods

    The tested strains were grown in two different substrates, and after biomass harvesting, polysaccharides were isolated using two different methods. The extracellular polysaccharides were isolated from the culture broth, with ethanol precipitation. The isolated fractions were partially characterized with FT-IR spectroscopy.

    Results

    All three strains performed well in both substrates. Maximum degradation performance of OMWW was achieved by Ganoderma lucidum, achieving 19.4% phenols reduction together with 47.56% decolorization. The extracellular polysaccharides (EPS) produced by all strains were found to be richer in total glucans during growth in semi-synthetic medium, compared to growth in OMWW-based medium. In regard to biomass polysaccharides, Pleurotus ostreatus biomass was found to be richer in glucans, reaching 8.68% (w/w) total glucan content when grown in semi-synthetic medium and 7.58% (w/w) when grown in OMWW-based medium. After purification of biomass polysaccharides with two methods, the fraction with the highest glucan content was found to be the one from G. lucidum after growth in semi-synthetic medium cultures, with 49.1% (w/w) total glucans. FT-IR spectra of the isolated samples revealed the bands corresponding to α- and β-glucosidic bonds, but also the existence of protein contamination.

    Conclusions

    Purification of biomass polysaccharides with two distinct methods revealed that α-amylase and Sevag treatments failed to remove completely α-glucans and proteins respectively, leading to the suggestion that these two steps could be omitted without significant impact. Moreover, the results imply that the valorization of OMWW might be feasible with the use of mushroom strains, leading to the production of important products, such as glucans.

  • 2752.
    Zerva, Anastasia
    et al.
    Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Zervakis, Georgios I.
    Agricultural University of Athens, Laboratory of General and Agricultural Microbiology.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Topakas, Evangelos
    National Technical University of Athens, School of Chemical Engineering, National Technical University of Athens, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Degradation of olive mill wastewater by the induced extracellular ligninolytic enzymes of two wood-rot fungi2017Ingår i: Journal of Environmental Management, ISSN 0301-4797, E-ISSN 1095-8630, Vol. 203:2, s. 791-798Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Olive mill wastewater (OMWW) is a major problem in olive oil – producing countries, due to its high organic load and concentration in phenols that are toxic for marine life, plants and soil microorganisms. In the present study, two mushroom species were tested in regard to their OMWW's oxidative capacity, Pleurotus citrinopileatus LGAM 28684 and Irpex lacteus LGAM 238. OMWW (25% v/v) degradation was investigated for several culture conditions, namely pH, agitation speed, nitrogen-based supplements and their concentration. The selected values were pH 6, agitation rate 150 rpm, 30 g L−1 corn steep liquor as nitrogen source for P. citrinopileatus and 20 g L−1 diammonium tartrate for I. lacteus. The two strains performed well in cultures supplemented with OMWW, generating very high titers of oxidative enzymes and achieving more than 90% color and phenols reduction within a 24 days cultivation period. In addition, the amount of glucans present in the fungal biomass was assessed. Hence, P. citrinopileatus and I. lacteus appear as potent degraders of OMWW with the ability to use the effluent as a substrate for the production of biotechnologically important enzymes and valuable fungal glucans. 

  • 2753.
    Zetterholm, Jonas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Forest based biorefinery supply chains - Identification and evaluation of economic, CO2, and resource efficiency2018Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Biorefineries for production of fuels, chemicals, or materials, can bean important contribution to reach a fossil-free economy. Large-scaleforest-based biorefineries are not yet cost competitive with their fossil counterparts and it is important to identify biorefinery supply chain configurations with good economic, CO2, and biomass performance if biorefineries are to be a viable alternative to the fossil refineries.

    Several factors influence the performance of biorefinery supply chains,e.g. type of conversion process, geographical localisation, and produc-tion capacity. These aspects needs to be analysed in conjunction to identify biorefineries with good supply chain performance. There ares everal approaches to improve the performance of biorefineries, wheree.g. integration with other industries can improve the economic perfor-mance by utilisation of excess heat and by-products. From a Swedish perspective the traditional forest industry is of interest as potential host industries, due to factors such as by-product availability, opportunity for heat integration, proximity to other biomass resources, and their experience in operating large-scale biomass supply chains.

    The objectives of this work were to investigate how different supply chain configurations influence the economic, biomass, and CO2 perfor-mance of thermochemical biorefineries integrated with forest industries,as well as methods for evaluating those supply chains.

    This work shows that there is an economic benefit for integration with the traditional forest industry for thermochemical biorefineries.This is especially true when the biorefinery concept can replace cur-rent old industrial equipment on site which can significantly improvethe economic performance of the biorefinery, highlighting the role the Swedish forest industry could play to reach a cost efficient large-scale implementation of lignocellulosic biorefineries.

    The cost for biomass is a large contributor to the total cost of biore-fineries and for traditional techno-economic evaluations, the biomass prices are considered as static variables. A large-scale biorefinery will likely have an impact on the biomass market, which could lead to both changes in the biomass price, as well as changed biomass demand for other industries. A framework where this is accounted for was intro-duced, combining a techno-economic perspective for evaluating the sup-ply chain performance, with a market model which identifies changes in biomass price and allocation due to the increased biomass competition.

    The biorefinery performance can be determined from several per-spectives and system boundaries, both from a plant-level and a national perspective. To facilitate a large-scale introduction of biorefineries and  maximise the benefit from their implementations, there is a need to identify biorefinery concepts with high performance considering severa system boundaries, which has been explored in this work.

  • 2754.
    Zetterholm, Jonas
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Mossberg, Johanna
    RISE Research Institutes of Sweden, Bioeconomy.
    Joakim, Lundgren
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Wetterlund, Elisabeth
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Evaluating investments in integrated biofuel production - factoring in uncertainty through real options analysis2019Ingår i: PROCEEDINGS OF ECOS 2019 / [ed] Wojciech Stanek, Paweł Gładysz, Sebastian Werle, Wojciech Adamczyk, 2019, s. 1921-1932Konferensbidrag (Refereegranskat)
    Abstract [en]

    In the endeavour to reduce CO2 emissions from the transport sector, biofuels from forest industry by-products are key. The adaptation of forest-based biorefinery technologies has so far been low which can partly be attributed to uncertainties in the form of policy instability, market prices, and technology costs. These uncertainties in combination with technology learning, which can be expected to reduce future investment costs, could make it favourable to postpone an investment decision. When applying real options theory, it is recognised that there is an opportunity cost associated with the decision to invest, since the option to wait for more favourable market conditions to occur is forfeited. In traditional discounted cash flow analysis, the impact of uncertainty and the value of reducing it (e.g. by waiting), is usually not taken into consideration. This paper uses a real options framework that incorporates the option to postpone an investment to reduce market uncertainties and wait for technology learning to occur. The focus is to investigate how the usage of an investment decision rule based on real options analysis affects technology choice, the economic performance, and when in time it is favourable to invest in pulp mill integrated biofuel production, compared with using a decision rule based on traditional discounted cash flow analysis. As an illustrative case study we examine a pulp mill which has the option, but not the obligation, to invest in either of two different biofuel production technologies that both use the pulp mill by-product black liquor as feedstock: (1) black liquor gasification followed by fuel synthesis, and (2) membrane separation of lignin followed by hydrodeoxygenation. With the usage of the real options framework and the inclusion of the uncertainties regarding future market prices and investment costs, the decision to invest is made later, compared with using traditional cash flow analysis. The usage of real options also reduces the likeliness of a net loss occurring if an investment is made, as well as increases the expected economic returns, showing the added economic value of flexibility in the face of uncertain future conditions.

  • 2755. Zevenhoven-Onderwater, Maria
    et al.
    Öhman, Marcus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Skrifvars, Bengt-Johan
    Backman, Rainer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi. Åbo Akademi University.
    Nordin, Anders
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Hupa, Mikko
    Bed agglomeration characteristics of wood-derived fuels in FBC2006Ingår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 20, nr 2, s. 818-824Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The agglomeration tendency of five Scandinavian forest-derived biomass fuels was studied using an advanced fuel analysis, i.e., a combination of chemical fractionation analysis, controlled bed defluidization tests, and SEM/EDX analysis of bed samples. It is shown that all five fuels have a tendency to form bed agglomerates when fired in a fluidized bed with silica sand as the bed material. The agglomeration appeared to proceed by formation of a sticky layer on bed particles gluing them together. The layers on the bed particles contained Si, Ca, and K, and, in some cases, P. The combination of advanced fuel analysis by SEM/EDX showed that the soluble fraction of Ca and K (i.e., leachable from the fuel with water and acetate) may be responsible for the formation of the layer. Silicon may mainly come from the bed particles.

  • 2756.
    Zhan, Caijuan
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Industriell bioteknologi.
    Hydrodynamics considerations in cells systems from ocean flow to perfusion cultivation process2019Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Microorganisms and animal cells are grown surrounded by fluid, which is providing them with nutrients and removing their waste products. In nature and industry processes, cells/microbes can be subject to aggressive environments, such as turbulent flow or shear flow. Hydrodynamics force generated in these flows can affect the distribution of cells/microbes and even lead to cell damage. Understanding the mechanism and exploring the effect of hydrodynamic force in these environments could make the prediction of cells’ hydrodynamic response more systematic. In pharmaceutical industry, perfusion process is recognized as an attractive option for biologics production due to its high productivity. However, there are still some challenges and limitations for further process improvement due to lack of information of cell response to hydrodynamic force and nutrients. In both cases, hydrodynamics plays an important role and similar tool can be used to achieve a deeper understanding of these processes. This thesis is mainly aiming to elucidate the influence of hydrodynamic forces on microorganisms or cells in nature and during bioprocesses. In particular, shear stress in a natural environment and in a bioreactor operated in perfusion mode is studied.

    This work mainly investigates hydrodynamics in nature and bioprocess including three flow cases. The first study investigates the effect of turbulence on marine life by performing direct numerical simulations (DNS) of motile micro-organisms in isotropic homogeneous turbulence. The clustering level of micro-organisms with one preferential swimming direction (e.g. gyrotaxis) is examined. The second study uses Computation Fluid Dynamics (CFD) to simulate the fluid flow inside a Wave bioreactor bag. The phenomenon of mixing, oxygen transfer rate and shear stress in nine different operating conditions of rocking speeds and angles are discussed. In the third study, the cellular response to shear force including growth and metabolism in a cell retention device such as hollow fiber filters during a perfusion process is analyzed. Theoretical calculations and experiment validation is performed to compare two filtration modes, tangential flow filtration (TFF) or alternating tangential flow filtration (ATF). Further optimizations regarding mixing and feeding are performed in a screening scale of in a perfusion system of stirred tank bioreactor with cell separation device.

    The main findings can be summarized as that spherical gyrotaxis swimmers show significant clustering, whereas prolate swimmers remain more uniformly distributed due to their large sensitivity to the local shear. These results could explain how pure hydrodynamic effects can alter the ecology of micro-organisms for instance by varying shape and their preferential orientation (paper I). The simulations of Wave bioreactors show that the mixing and shear stress increase with the rocking angle but that increasing rocking speeds are not systematically associated with increasing mixing and shear stress. A resonance phenomenon is responsible for the fact that the lowest studied rocking speed generates the highest fluid velocity, mixing and shear stress (paper II). Theoretical velocity profile-based calculations suggested a lower shear stress for ATF by a factor 0.637 compared to TFF. This is experimentally validated by cultures of HEK (human embryonic kidney) 293 cells subjected to shear stress by a perfusion system that affects growth and metabolism using these cell separation devices (paper III). Thanks to optimization of mixing and oxygen transfer in a screening system for perfusion process, very high cell densities above 100 x 106 cells/mL of mammalian cells were achieved (paper IV).

  • 2757.
    Zhan, Caijuan
    et al.
    KTH, Skolan för teknikvetenskap (SCI). KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Industriell bioteknologi.
    Hubert, Schwarz
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Industriell bioteknologi.
    Malm, Magdalena
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Proteinvetenskap, Proteinteknologi.
    Sellick, Christopher
    Rockberg, Johan
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Proteinvetenskap, Proteinteknologi.
    Chotteau, Véronique
    KTH, Skolan för teknikvetenskap (SCI). KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Industriell bioteknologi.
    Hydrodynamic shear stress in hollow filter for perfusion culture of human cellsManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    High cell density perfusion process is an economical way to produce biopharmaceuticals at high yield. To achieve high density of healthy cells, the cell culture conditions should be free from mechanically detriment. Human embryonic kidney (HEK) K293 cells, interesting for the production of therapeutic glycoproteins, are known as shear sensitive. In order to obtain the optimal hydrodynamics conditions with reduced mechanical damage, we investigated the fact of the shear stress compatible with HEK293 cells. We reviewed hollow filter based tangential flow filtration strategies, tangential flow filtration (TFF) and alternating tangential flow filtration (ATF). We studied shear stress introduced by these two flow filtration methods. By theoretical study, we obtained that lower shear stress introduced by alternating tangential flow filtration result in lower average shear stress comparing to tangential flow filtration with same flow rate.  In our experimental runs, we achieved different shear stress levels by applying different flow rates. 5-Days batch cultivations were performed to examine the influence of shear stress on cell growing and metabolic behaviour. We identified that the shear stress potentially reduce the growth rate and productivity of HEK293 cells and found the cell metabolism associated with shear stress levels. By documenting these cell responses to shear stress, we confirmed our theoretical results and could further optimize the hydrodynamic conditions for perfusion process of HEK 293 cells. 

  • 2758.
    Zhang, Qinglin
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    Dor, L.
    Yang, Weihong
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    Blasiak, Włodzimierz
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    CFD modeling of municipal solid waste gasification in a fixed-bed plasma gasification melting reactor2011Ingår i: Air Waste Manage. Assoc. - Int. Conf. Therm. Treat. Technol. Hazard. Waste Combustors, 2011, s. 252-278Konferensbidrag (Refereegranskat)
    Abstract [en]

    A steady CFD model is developed to simulate the gasification of municipal solid waste (MSW) in a moving-bed Plasma Gasification Melting (PGM) reactor. In this model, the Eulerian-Eulerian multiphase model is conducted, and the solid phase is treated as a plastic fluid. The conservation equations of both gas and solid phases are solved respectively. The momentum conservation equations of the solid phase are simplified by disregarding the interphase forces between gas and solid. Both heterogeneous reactions and homogeneous reactions are defined in this model to express the detailed gasification chemistry inside the reactor. A two-step pyrolysis model was used in this work, and the pyrolysis mechanisms of cellulosic and plastic fractions are considered separately. The predicted results of a base case are compared with the measured data of the trial reactor. The temperature distribution inside the PGM reactor is introduced. Based on the variation of temperature, the whole reaction shaft was divided into five layers. The 2D effect of the reactor is also discussed. The influence of two dimensionless parameters: the equivalence ratio (ER) and dimensionless plasma energy ratio (DPER) are introduced and discussed. With the variation of ER, two typical temperature distributions can be found for PGM reactor. The turning point of these two distributions stands in the ER range 0.120-0.133. This turning point is the optimal operation condition of PGM air gasification. It is also found that when the energy request for gasification is satisfied, further increment of DPER value does not significantly influence the characters of PGM process.

  • 2759. Zhang, Ranran
    et al.
    Elkhooly, Tarek A.
    Huang, Qianli
    Liu, Xujie
    Yang, Xing
    Yan, Hao
    Xiong, Zhiyuan
    Ma, Jing
    Feng, Qingling
    Shen, Zhijian
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). Tsinghua University, China.
    A dual-layer macro/mesoporous structured TiO2 surface improves the initial adhesion of osteoblast-like cells2017Ingår i: Materials science & engineering. C, biomimetic materials, sensors and systems, ISSN 0928-4931, E-ISSN 1873-0191, Vol. 78, s. 443-451Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A dual-layer TiO2 surface with hierarchical macro and mesoporous structure was prepared by a combinational approach of micro-arc oxidation followed by evaporation-induced self-assembly of nano-crystallites. The mesoporous layer contains pores with an average size of <10 nm and consists of anatase TiO2 nanocrystallites. The dual-layer hierarchical macro/mesoporous structured TiO2 surface improves the hydrophilicity and fibronectin adsorption ability in comparison with the sole macroporous or smooth TiO2 surface. With the formation of an additional mesoporous layer on macroporous TiO2 surface, the attached number of human osteogenic sarcoma cells (SaOS-2) increases in the initial incubation of 4 h but it does not show significant difference after 24 h compared to that attached on the macroporous or smooth surfaces. Whereas, it was noticed that SaOS-2 cells have larger spread area and more stress fibers on the macro/mesoporous structured surface than those on the other surfaces. To understand the intracellular mechanism of the initial cell adhesion on the macro/mesoporous surface, the Rho/ROCK pathway was investigated to reveal the topography-induced biological functions by introducing the ROCK inhibitor Y-27632 during cell culture. In the presence of Y-27632, cells on the macroporous surface and macro/mesoporous surface both show stellate appearance, with poor assembly stress fibers and long cell membrane protrusions. Cells on the smooth surface have larger spread areas compared to the former two surfaces. And the attached cells significantly reduced but there are no differences among the three surfaces. It reveals that the ROCK inhibitor invalidates the promotion of initial cell adhesion on the macro/mesoporous structure. This study may shed light on the mechanism behind the enhancement effect of macro/mesoporous structure for initial cell adhesion.

  • 2760. Zhang, Ranran
    et al.
    Elkhooly, Tarek A.
    Huang, Qianli
    Liu, Xujie
    Yang, Xing
    Yan, Hao
    Xiong, Zhiyuan
    Ma, Jing
    Feng, Qingling
    Shen, Zhijian
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). Tsinghua University, China.
    Effects of the hierarchical macro/mesoporous structure on the osteoblast-like cell response2018Ingår i: Journal of Biomedical Materials Research. Part A, ISSN 1549-3296, E-ISSN 1552-4965, Vol. 106, nr 7, s. 1896-1902Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To improve the success of medical devices, implants with strong surface bioactivity are urgently required. Coatings with a macroporous structure produced by micro-arc oxidation possess advantages, such as strong adhesion to substrate and excellent resistance to wear and corrosion. Mesoporous structures contain pores with sizes of 2-50 nm, which can endow the biomaterials with the ability to enhance osteogenesis and to be loaded with diverse drugs. Thus, in this study, we aimed to evaluate the effects of both macroporous and mesoporous structures using a hierarchical macro/mesoporous structure to modify the titanium implant surface. The behaviors of SaOS-2 human osteosarcoma cells on the macro/mesoporous structure, including initial adhesion, proliferation, alkaline phosphatase (ALP) activity, and collagen secretion, were investigated. Cells that attached on the macro/mesoporous surface showed the highest cell numbers and greatest spreading area after incubation for 1, 2, and 4 h compared with the polished smooth substrate and macroporous surface in the presence of fetal bovine serum (FBS). However, in the absence of FBS, cell adhesion on the polished substrate, macroporous structure, and macro/mesoporous structure did not differ significantly. Cell proliferation on the macroporous and macro/mesoporous surfaces increased compared with that on the smooth substrate surface. Furthermore, ALP activity and collagen secretion were enhanced on the macro/mesoporous structure. Our findings provided important insights into the cellular responses to macro/mesoporous structures in the field of implant surface modification.

  • 2761.
    Zhang, Wei
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för biokemi och organisk kemi.
    Modén, Olof
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för biokemi och organisk kemi.
    Mannervik, Bengt
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för biokemi och organisk kemi.
    Differences among allelic variants of human glutathione transferase A2-2 in the activation of azathioprine2010Ingår i: Chemico-Biological Interactions, ISSN 0009-2797, E-ISSN 1872-7786, Vol. 186, nr 2, s. 110-117Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Azathioprine has been clinically used for decades in connection with organ transplantation, autoimmune disease, and treatment of cancer. Toxic side-reactions are common and have been linked to the liberation of excessively high concentrations of 6-mercaptopurine and corresponding toxic metabolites. An allelic variant of thiopurine methyltransferase with low activity is associated with elevated concentrations of 6-mercaptopurine. However, other genetic markers remain to be identified in order to fully account for adverse reactions and efficacy failure. In the present study, we studied the five known allelic variants of human glutathione transferase A2-2 (GST A2-2) (EC2.5.1.18), abundantly expressed in liver and efficiently catalyzing the bioactivation of azathioprine to release 6-mercaptopurine. All five variants exhibited high activity with azathioprine, but allelic variant E of GST A2-2 displayed a 3-4-fold elevated catalytic efficiency compared to the other variants. High GST activity can lead to overproduction of 6-mercaptopurine, and the nature of the multiple forms of GSTs in a patient will obviously affect the metabolism of azathioprine. In addition to GST A2-2, the polymorphic GST M1-1 is also highly active with azathioprine. Considering our findings, it appears that the genotypic and phenotypic variations in the GST complement may influence the presentation of adverse reactions in patients treated with azathioprine. Clinical trials will be required to clarify the impact of the GST expression in comparison with the established biomarker thiopurine methyltransferase as predictors of adverse reactions.

  • 2762.
    Zhang, Wei
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för biokemi och organisk kemi.
    Modén, Olof
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för biokemi och organisk kemi.
    Tars, Kaspars
    Biomedical Research and Study Center, LV-1067 Riga, Latvia.
    Mannervik, Bengt
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för biokemi och organisk kemi.
    Structure-based redesign of GST A2-2 for enhanced catalytic efficiency with azathioprine2012Ingår i: Chemistry and Biology, ISSN 1074-5521, E-ISSN 1879-1301, Vol. 19, nr 3, s. 414-421Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Glutathione transferase (GST) A2-2 is the most efficient human enzyme in the biotransformation of the prodrug azathioprine (Aza). The activation of Aza has therapeutic potential for possible use of GSTs in targeted enzyme-prodrug treatment of diseases. Based on the assumed catalytic mechanism and computational docking of Aza to the active site of the enzyme, active-site residues were selected for construction of focused mutant libraries, which were thereafter screened for Aza activity. Mutants with elevated Aza activity were identified, DNA sequenced, and the proteins purified. The two most active mutants showed up to 70-fold higher catalytic efficiency than the parental GST A2-2. The structure of the most active triple mutant (L107G/L108D/F222H) enzyme was determined by X-ray crystallography demonstrating significant changes in the topography of the active site facilitating productive binding of Aza as a substrate. 

  • 2763.
    Zhang, Xiaolei
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    Micro-reaction Mechanism Study of the Biomass Thermal Conversion Process using Density Functional Theory2013Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Biomass, or bio-energy, is one of the most important alternative energies because of environmental concerns and the future shortage of fossil fuels. Multi-scaled bioenergy studies have been performed in the division of Energy and Furnace Technology, which included studies of macroscopic systems such as systems and reactors, modeling of computational fluid dynamics (CFD), and atomic/molecular level studies. The present thesis focus on the atomic/molecular level that based on quantum chemistry methods.

    The microscopic structure study of biomass is the first and an important step for the investigation of the biomass thermal conversion mechanism. Cellulose, hemicellulose, and lignin are the three most important components for biomass. The atomic interactions among these three main components were studied, including the hydrogen bond linkages between cellulose and hemicellulose, and the covalent bond linkages between hemicellulose and lignin.

    The decomposition of biomass is complicated and includes cellulose decomposition, hemicellulose decomposition, and lignin decomposition. As the main component of biomass, the mechanism of cellulose pyrolysis mechanism was focused on in this thesis. The study of this mechanism included an investigation of the pathways from cellulose to levoglucosan then to lower-molecular-weight species. Three different pathways were studied for the formation of levoglucosan from cellulose, and three different pathways were studied for the levoglucosan decomposition. The thermal properties for every reactant, intermediate, and product were obtained. The kinetics parameters (rate constant, pre-exponential factor, and activation energy) for every elementary step and pathway were calculated. For the formation of levoglucosan, the levoglucosan chain-end mechanism is the favored pathway due to the lower energy barrier; for the subsequent levoglucosan decomposition process, dehydration is a preferred first step and C-C bond scission is the most difficult pathway due to the strength of the C-C bonds.

    The biomass gasification process includes pyrolysis, char gasification, and a gas-phase reaction; Char gasification is considered to be the rate-controlling step because of its slower reaction rate. Char steam gasification can be described as the adsorption of steam on the char surface to form a surface complex, which may transfer to another surface complex, which then desorbs to give the gaseous products (CO and H2) and the solid product of the remaining char. The influences of several radicals (O, H, and OH) and molecules (H2 and O2) on steam adsorption were investigated. It was concluded that the reactivity order for these particles adsorbed onto both zigzag and armchair surfaces is O > H2 > H > OH > O2. For water adsorbs on both zigzag and armchair carbon surfaces, O and OH radicals accelerate water adsorption, but H, O2, and H2 have no significant influence on water adsorption.

    It was also shown that quantum chemistry (also known as molecular modeling) can be used to investigate the reaction mechanism of a macroscopic system. Detailed atomic/molecular descriptions can provide further understanding of the reaction process and possible products.

  • 2764.
    Zhang, Ye
    KTH, Skolan för bioteknologi (BIO), Industriell bioteknologi.
    High cell density perfusion process development for antibody producing Chinese Hamster Ovary cells2017Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Perfusion operation mode is currently under fast expansion in mammalian cell based manufacturing of biopharmaceuticals, not only for labile drug protein but also for stable proteins such as monoclonal antibodies (mAbs). Perfusion mode can advantageously offer a stable cell environment, long-term production with high productivity and consistent product quality. Intensified high cell density culture (HCDC) is certainly one of the most attractive features of a perfusion process due to the high volumetric productivity in a small footprint that it can provide. Advancements in single-use technology have alleviated the intrinsic complexity of perfusion processes while the maturing in cell retention devices has improved process robustness. The knowledge for perfusion process has been gradually built and the “continuous” concept is getting more and more acceptance in the field.

    This thesis presents the development of robust perfusion process at very high cell densities in various culture systems. Four HCDC perfusion systems were developed with industrial collaborators with three different mAb producing Chinese Hamster Ovary (CHO) cell lines: 1-2) WAVE Bioreactor™ Cellbag prototype equipped with cell separation by hollow fiber filter utilizing Alternating Tangential Flow (ATF) and Tangential Flow Filtration (TFF) techniques; 3) Fiber matrix based CellTank™ prototype; 4) Glass stirred tank bioreactor equipped with ATF. In all the systems, extremely high viable cell densities above 130 million viable cells per milliliter (MVC/mL) up to 214 MVC/mL were achieved. Steady states were maintained and studied at 20-30 MVC/mL and 100-130 MVC/mL for process development. Perfusion rate selection based on cell specific perfusion rate (CSPR) was systematically investigated and exometabolome study was performed to explore the metabolic footprint of HCDC perfusion process.

  • 2765.
    Zhang, Ye
    et al.
    KTH, Skolan för bioteknologi (BIO), Industriell bioteknologi.
    Zhan, Caijuan
    KTH, Skolan för bioteknologi (BIO), Industriell bioteknologi.
    Girod, Pierre-Alain
    Martiné, Alexandra
    Chotteau, Veronique
    KTH, Skolan för bioteknologi (BIO), Industriell bioteknologi.
    Optimization of the cell specific perfusion rate in high cell density perfusion processManuskript (preprint) (Övrigt vetenskapligt)
  • 2766.
    Zhang, Yu
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Polymerkemi.
    Heher, Philipp
    Ludwig Boltzmann Inst Expt & Clin Traumatol, Austrian Cluster Tissue Regenerat, Donaueschingenstr 13, A-1200 Vienna, Austria.;Trauma Care Consult GmbH, Gonzagagasse 11-25, A-1010 Vienna, Austria..
    Hilborn, Jöns
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Polymerkemi.
    Redl, Heinz
    Ludwig Boltzmann Inst Expt & Clin Traumatol, Austrian Cluster Tissue Regenerat, Donaueschingenstr 13, A-1200 Vienna, Austria.;Trauma Care Consult GmbH, Gonzagagasse 11-25, A-1010 Vienna, Austria..
    Ossipov, Dmitri A.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Polymerkemi.
    Hyaluronic acid-fibrin interpenetrating double network hydrogel prepared in situ by orthogonal disulfide cross-linking reaction for biomedical applications2016Ingår i: Acta Biomaterialia, ISSN 1742-7061, E-ISSN 1878-7568, Vol. 38, s. 23-32Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To strengthen the mechanical properties of a fibrin gel and improve its applicability as a scaffold for tissue engineering (TE) applications, a strategy for the in situ preparation of the interpenetrating network (IPN) of fibrin and hyaluronic acid (HA) was developed on the basis of simultaneous and orthogonal fibrinogenesis and disulfide cross-linking. The synthetic pathway included the preparation of mutually reactive HA derivatives bearing thiol and 2-dithiopyridyl groups. Combining thiol-derivatized HA with thrombin and 2-dithiopyridyl-modified HA with fibrinogen and then mixing the obtained liquid formulations afforded IPNs with fibrin-resembling fibrillar architectures at different ratios between fibrin and HA networks. The formation of two networks was confirmed by conducting reference experiments with the compositions lacking one of the four components. The composition of 2% (w/v) fibrin and 1% (w/v) HA showed the highest storage modulus (G'), as compared with the single network counterparts. The degradation of fibrin in IPN hydrogels was slower than that in pure fibrin gels both during incubation of the hydrogels in a fibrin-cleaving nattokinase solution and during the culturing of cells after their encapsulation in the hydrogels. Together with the persistence of HA network, it permitted longer cell culturing time in the IPN. Moreover, the proliferation and spreading of MG63 cells that express the hyaluronan receptor CD44 in IPN hydrogel was increased, as compared with its single network analogues. These results are promising for tunable ECM-based materials for TE and regenerative medicine. Statement of Significance The present work is devoted to in situ fabrication of injectable extracellular matrix hydrogels through simultaneous generation of networks of fibrin and hyaluronic acid (HA) that interpenetrate each other. This is accomplished by combination of enzymatic fibrin cross-linking with orthogonal disulphide cross-linking of HA. High hydrophilicity of HA prevents compaction of the fibrin network, while fibrin provides an adhesive environment for in situ encapsulated cells. The interpenetrating network hydrogel shows an increased stiffness along with a lower degradation rate of fibrin in comparison to the single fibrin network. As a result, the cells have sufficient time for the remodelling of the scaffold. This new approach can be applied for modular construction of in vitro tissue models and tissue engineering scaffolds in vivo.

  • 2767.
    Zhao, Ke
    KTH, Skolan för bioteknologi (BIO).
    Theoretical study of light-molecule nonlinear interactions2007Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The work presented in the thesis concerned theoretical study of light-matter nonlinear interactions. Two important aspects of such interactions have been examined, namely the nonlinear optical properties of a series of organic charge transfer molecules in solutions induced by the laser light and the propagation of the ultrafast high power laser through the nonlinear molecular medium.

    Special attention has been paid to understand the solvent effects on the two-photon absorption of a symmetrical diamino substituted distyrylbenzene chromophore, for which time-dependent density functional theory in combination with polarizable continuum model (PCM) have been employed. The dielectric medium alone has a rather small effect both on the bond length alternation and on the one-photon absorption spectrum, but noticeable effects on the two-photon absorption cross section. Both one- and two-photon absorptions are found to be extremely sensitive to the planarity of the molecule. Our calculations indicate that the experimentally observed anomalous solvent effect on the two-photon absorption of dialkylamino substituted distyrylbenzene chromophores can not be attributed to the intrinsic properties of a single molecule and its interaction with solvents. With the same theoretical approaches, two-photon absorption properties of interacting polar chromophores have been investigated to examine the validity of the widely used exciton model. Our first principles calculations have shown that the exciton model offers a conceptually simple interpretation for experimental observations, but is lack of predictability.

    The second part of the thesis is to investigate the propagation of ultrashort laser pulse through a one-dimensional asymmetric organic molecular medium by solving full Maxwell-Bloch equations using predictor-corrector finite-difference time-domain method. It focuses on the supercontinuum generation of spectra and the formation of attosecond pulses. It is shown that the supercontinuum generation is strongly modulated by both area and width of the pulse, which results from the interference between the splitting pulses in time-domain and is the implication of the time-energy uncertainty relation. The presence of permanent dipole moment in molecular medium has noticeable effects on the supercontinuum generation. Our calculations show that a well-shaped 132 attosecond pulse can be generated from a two femtosecond incoming pulse under certain conditions. Influences of carrier-envelope phase and time-dependent ionization on the spectral and temporal evolutions of the ultrashort pulses have also been discussed.

  • 2768.
    Zhao, Ke
    et al.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Ferrighi, Lara
    Centre for Theoretical and Computational Chemistry, Department of Chemistry, University of Tromsø.
    Frediani, Luca
    Centre for Theoretical and Computational Chemistry, Department of Chemistry, University of Tromsø.
    Wang, Chuan-Kui
    College of Physics and Electronics, Shandong Normal University, Jinan .
    Luo, Yi
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Solvent effects on two-photon absorption of dialkylamino substituted distyrylbenzene chromophore2007Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 126, nr 20Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Solvent effects on the two-photon absorption of a symmetrical diamino substituted distyrylbenzene chromophore have been studied using the density functional response theory in combination with the polarizable continuum model. It is shown that the dielectric medium has a rather small effect both on the bond length alternation and on the one-photon absorption spectrum, but it affects significantly the two-photon absorption cross section. It is found that both one- and two-photon absorptions are extremely sensitive to the planarity of the molecule, and the absorption intensity can be dramatically reduced by the conformation distortion. It has led to the conclusion that the experimentally observed anomalous solvent effect on the two-photon absorption of dialkylamino substituted distyrylbenzene chromophores cannot be attributed to the intrinsic properties of a single molecule and its interaction with solvents.

  • 2769.
    Zhao, Ke
    et al.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Liu, Ji-Cai
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Wang, Chuan-Kui
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Luo, Yi
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Modulation of supercontinuum generation and formation of an attosecond pulse from a generalized two-level medium2007Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 40, s. 1523-1534Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The propagation of ultrashort pulses in a generalized two- level system, consisting of permanent dipole moments, is simulated by solving the full Maxwell - Bloch equations. Special attention has been paid to the supercontinuum generation of spectra and the formation of attosecond ( as) pulses. It is found that the supercontinuum generation is strongly modulated by both area and width of the pulse, resulting from the interference between the splitting pulses in the time domain and the implication of the time - energy uncertainty relation. The effect of the permanent dipole moment on the supercontinuum generation is discussed in detail. Calculations show that a well- shaped 132 as pulse can be generated from a 2 fs incoming pulse under the condition where the permanent dipole moment difference between two levels is equal to the transition dipole moment between them. Influences of carrier- envelope phase and time- dependent ionization on the spectral and temporal evolution of the ultrashort pulses are also discussed at length.

  • 2770.
    Zhao, Ke
    et al.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Wang, Chuan-Kui
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Luo, Yi
    Shandong Normal Univ, Coll Phys & Elect, Jinan.
    Two-photon absorbation activities of interating dipolar chromophores: a DFT study.Manuskript (preprint) (Övrigt vetenskapligt)
  • 2771.
    Zhao, Ning-Wei
    KTH, Skolan för bioteknologi (BIO).
    Recent Progress in the Methods of Genome Sequencing2010Ingår i: Brazilian archives of biology and technology, ISSN 1516-8913, E-ISSN 1678-4324, Vol. 53, nr 2, s. 319-325Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Genome sequencing is a very important tool for the development of genetic diagnosis, drugs of gene engineering, pharmacogenetics, etc. As the HGP comes into people's ears, there is an emerging need for the genome sequencing. During the recent years, there are two different traditional strategies available for this target: shotgun sequencing and hierarchical sequencing. Besides these, many efforts are pursuing new ideas to facilitate fast and cost-effective genome sequencing, including 454 GS system, polony sequencing, single molecular array, nanopore sequencing, with each having different unique characteristics, but remains to be fully developed.

  • 2772.
    Zhao, Ning-Wei
    et al.
    KTH, Skolan för bioteknologi (BIO).
    Yao, Jin-Ting
    Characterization and sequence identification of angiotensin II by a novel method involving ultra-fast liquid chromatography assay coupled with matrix-assisted laser desorption/ionization quadrupole ion trap time-of-flight five tandem mass spectrometry analysis2010Ingår i: European journal of mass spectrometry, ISSN 1469-0667, E-ISSN 1751-6838, Vol. 16, nr 6, s. 663-671Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    High-throughput proteomics aims to investigate dynamically changing proteins expressed by a full organism, specific tissue or cellular compartment under certain conditions. High-sensitivity mass spectrometry has gradually become a significant tool for characterizing peptides. Here, we analyzed angiotensin II using ultra-fast liquid chromatography (UFLC) coupled with matrix-assisted laser desoprtion/ionization time-of-flight mass spectrometry (MALDI-ToF MS5). First, we applied UFLC in isolating and collecting the angiotensin II, and then Axima-Resonance (MALDI-QIT-ToF MS5) was adopted, which enables collision-induced dissociation-MS5 analysis for fine structural characterization of angiotensin II. Resultant MS, MS2, MS3 and MS4 spectra of interested [M+H](+) ions selected as precursor ions yielded detailed information about the sites of fragmentation as well as the amino acid sequence for angiotensin II; meanwhile, the average deviation between theoretical mass and actually measured mass from MS to MS5 spectra was only 0.32 Da. It indicated that Axima-Resonance was capable of analysing the peptide sequence accurately and providing the corresponding fragmentation information thoroughly, thus suggesting a potential strategy involving UFLC assay coupled with MALDI-QIT-ToF MS5 analysis for high-throughput proteomics studies in the future.

  • 2773.
    Zhou, Xiaojian
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Sain, Mohini
    Centre for Biocomposites and Biomaterials Processing, University of Toronto, University of Toronto, Centre for Biocomposites and Biomaterials Processing, Faculty of Forestry, University of Toronto.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Semi-rigid biopolyurethane foams based on palm-oil polyol and reinforced with cellulose nanocrystals2016Ingår i: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 83, s. 56-62Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study, water-blown biopolyurethane (BPU) foams based on palm oil were developed and cellulose nanocrystals (CNC) were incorporated to improve the mechanical properties of the foams. In addition, the foams were compared with petroleum polyurethane (PPU) foam. The foam properties and cellular morphology were characterized. The obtained results revealed that a low-density, semi-rigid BPU foam was prepared using a new formulation. CNC as an additive significantly improved the compressive strength from 54 to 117 kPa. Additionally, cyclic compression tests indicated that the addition of CNC increased the rigidity, leading to decreased deformation resilience. The dimensional stability of BPU foams was increased with increasing CNC concentration for both heating and freezing conditions.Therefore, the developed BPU nanocomposite foams are expected to have great potential as core material in composite sandwich panels as well as in other construction materials.

  • 2774.
    Zhou, Xiaojian
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Sethi, Jatin
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Geng, Shiyu
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Berglund, Linn
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Frisk, Nikolina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Aitomäki, Yvonne
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Sain, Mohini
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Dispersion and reinforcing effect of carrot nanofibers on biopolyurethane foams2016Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 110, s. 526-531Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study, carrot nanofibers (CNF) were used to enhance the performance of biobased castor oil polyol polyurethane nanocomposite foams. A method of dispersing CNF in the polyol was developed and the foam characteristics and CNF reinforcing effect were studied. Co-solvent-assisted mixing resulted in well-dispersed CNF in the polyol, and foams with 0.25, 0.5 and 1 phr CNF content were prepared. The reinforced nanocomposite foams displayed a narrow cell size distribution and the compressive strength and modulus were significantly elevated and the best compressive strength and modulus were reached with 0.5 phr CNF. Similarly, the modulus of the solid material was also significantly increased based on theoretical calculations. When comparing the foam performance, compressive strength and stiffness as a function of the density, the nanocomposite foams performs as commercial rigid PU foam with a closed cell structure. These results are very promising and we believe that these foams are excellent core materials for lightweight sandwich composites.

  • 2775.
    Zhu, Chuantao
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Dobryden, Illia
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Ryden, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Holmgren, Allan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Mathew, Aji P.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Adsorption Behavior of Cellulose and Its Derivatives toward Ag(I) in Aqueous Medium: An AFM, Spectroscopic, and DFT Study2015Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 31, nr 45, s. 12390-12400Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The aim of this study was to develop a fundamental understanding of the adsorption behavior of metal ions on cellulose surfaces using experimental techniques supported by computational modeling, taking Ag(I) as an example. Force interactions among three types of cellulose microspheres (native cellulose and its derivatives with sulfate and phosphate groups) and the silica surface in AgNO3 solution were studied with atomic force microscopy (AFM) using the colloidal probe technique. The adhesion force between phosphate cellulose microspheres (PCM) and the silica surface in the aqueous AgNO3 medium increased significantly with increasing pH while the adhesion force slightly decreased for sulfate cellulose microspheres (SCM), and no clear adhesion force was observed for native cellulose microspheres (CM). The stronger adhesion enhancement for the PCM system is mainly attributed to the electrostatic attraction between Ag(I) and the negative silica surface. The observed force trends were in good agreement with the measured zeta potentials. The scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) analyses confirmed the presence of silver on the surface of cellulose microspheres after adsorption. This study showed that PCM with a high content of phosphate groups exhibited a larger amount of adsorbed Ag(I) than CM and SCM and possible clustering of Ag(I) to nanoparticles. The presence of the phosphate group and a wavenumber shift of the P−OH vibration caused by the adsorption of silver ions on the phosphate groups were further confirmed with computational studies using density functional theory (DFT), which gives support to the above findings regarding the adsorption and clustering of Ag(I) on the cellulose surface decorated with phosphate groups as well as IR spectra.

  • 2776.
    Zhu, Chuantao
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Mathew, Aji P.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Morphology and surface interactions studies of nanocellulose using Atomic Force Microscopy2015Konferensbidrag (Övrig (populärvetenskap, debatt, mm))
    Abstract [en]

    Force interactions between native cellulose microsphere (CM), sulfate cellulose microsphere (SCM), phosphate cellulose microsphere (PCM) and glass substrate under the effect of silver ions in the model solution were investigated using atomic force microscopy (AFM). The special interest was the influence of Ag+ ions and pH on the interaction between the probe and glass substrate. The probe was functionalized with above three types of cellulose microspheres by gluing method using contact mode with AFM. Functionalized probe and glass substrate were immersed in aqueous Ag+ solutions (50mg/L) at various pH value (4.25, 5.07, 5.62 and 6.63). Zeta potential studies showed negatively charged surfaces for CM, SCM, PCM and silica powders in model Ag+ solutions. The analysis revealed a decrease of adhesion force for CM and SCM system but an increase of adhesion force for PCM system with the increase of pH. The possible mechanism of the interaction under the effects of Ag+ ions, pH, and functional group contents as well as the shape of the cellulose microspheres was discussed. The SEM and SEM-EDS analysis confirmed the presence of silver ions on the surface of the cellulose microspheres after adsorption and force measurements.

  • 2777.
    Zhu, Chuantao
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Mathew, Aji p.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Dobryden, Illia
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Adsorption behavior of cellulose and its derivatives for Ag+ in aqueous medium: An AFM and spectroscopy study2015Konferensbidrag (Refereegranskat)
    Abstract [en]

    Cellulose particles in micro and nano scales has shown excellent potential to adsorb water pollutants such as dyes, pesticides, bacteria and virus, and a wide range of heavy metal ions, including Ag(Ⅰ), U(Ⅱ), Fe(Ⅲ), Cu(Ⅱ), Ni(Ⅱ), Cr(Ⅲ) and Zn(Ⅱ) 1, 2. However, mechanisms of adsorption and desorption the contaminants to/from cellulose micro or nano particles are largely unknown. The aim of the study was to develop fundamental understanding about the interaction and adsorption behavior of silver ions on cellulose surfaces using colloidal probe and spectroscopy techniques. Force interactions between three types of cellulose microspheres viz. native cellulose microspheres (CM), sulfate cellulose microspheres (SCM), phosphate cellulose microspheres (PCM) and silica surface in AgNO3 solution were studied with atomic force microscopy (AFM). The AFM results were further elaborated by extensive spectroscopy investigations.

  • 2778.
    Zhu, Chuantao
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Department of Materials and Environmental Chemistry, Stockholm University.
    Soldatov, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Mathew, Aji
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Department of Materials and Environmental Chemistry, Stockholm University.
    Advanced microscopy and spectroscopy reveal the adsorption and clustering of Cu(II) onto TEMPO-oxidized cellulose nanofibers2017Ingår i: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 9, nr 22, s. 7419-7428Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    TEMPO (2,2,6,6-tetramethylpiperidine-1-oxylradical)-mediated oxidation nanofibers (TOCNF), as a biocompatible and bioactive material, have opened up a new application of nanocellulose for the removal of water contaminants. This development demands extremely sensitive and accurate methods to understand the surface interactions between water pollutants and TOCNF. In this report, we investigated the adsorption of metal ions on TOCNF surfaces using experimental techniques atthe nano and molecular scales with Cu(II) as the target pollutant in both aqueous and dry forms. Imaging with in situ atomic force microscopy (AFM), together with a study of the physiochemical properties of TOCNF caused by adsorption with Cu(II) in liquid, were conducted using the PeakForce Quantitative NanoMechanics (PF-QNM) mode at the nano scale. The average adhesion force between the tip and the target single TOCNF almost tripled after adsorption with Cu(II) from 50 pN to 140 pN. The stiffness of the TOCNF was also enhanced because the Cu(II) bound to the carboxylate groups and hardened the fiber. AFM topography, scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) mapping and X-ray photoelectron spectroscopy (XPS) indicated that the TOCNF were covered by copper nanolayers and/or nanoparticles after adsorption. The changes in the molecular structure caused by the adsorption were demonstrated by Raman and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR). This methodology will be of great assistance to gain qualitative and quantitative information on the adsorption process and interaction between charged entities in aqueous medium.

  • 2779.
    Zhu, Youjian
    et al.
    School of Energy and Power Engineering, Zhengzhou University of Light Industry, Zhengzhou, Henan 450002, People’s Republic of China.
    Piotrowska, Patrycja
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    van Eyk, Philip Joseph
    School of Chemical Engineering, University of Adelaide, Adelaide, South Australia 5005, Australia.
    Boström, Dan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Wu, Xuehong
    School of Energy and Power Engineering, Zhengzhou University of Light Industry, Zhengzhou, Henan 450002, People’s Republic of China.
    Boman, Christoffer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Broström, Markus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Zhang, Jun
    School of Energy and Power Engineering, Zhengzhou University of Light Industry, Zhengzhou, Henan 450002, People’s Republic of China.
    Kwong, Chi Wai
    School of Chemical Engineering, University of Adelaide, Adelaide, South Australia 5005, Australia.
    Wang, Dingbiao
    School of Chemical Engineering and Energy, Zhengzhou University, Zhengzhou, Henan 450001, People’s Republic of China.
    Cole, Andrew J
    MACRO, the Centre for Macroalgal Resources and Biotechnology, James Cook University, Townsville, Queensland 4811, Australia.
    de Nys, Rocky
    MACRO, the Centre for Macroalgal Resources and Biotechnology, James Cook University, Townsville, Queensland 4811, Australia.
    Gentili, Francesco G.
    Department of Wildlife, Fish, and Environmental Studies, Swedish University of Agricultural Sciences (SLU), 901 83 Umeå, Sweden.
    Ashman, Peter J.
    School of Chemical Engineering, University of Adelaide, Adelaide, South Australia 5005, Australia.
    Fluidized bed co-gasification of algae and wood pellets: gas yields and bed agglomeration analysis2016Ingår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 30, nr 3, s. 1800-1809Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Algae utilization in energy production has gained increasing attention as a result of its characteristics, such as high productivity, rapid growth rate, and flexible cultivation environment. In this paper, three species of algae, including a fresh water macroalgae, Oedogonium sp., a saltwater macroalgae, Derbersia tenuissima, and a microalgae species, Scenedesmus sp., were studied to explore the potential of using smaller amounts of algae fuels in blends with traditional woody biomasses in the gasification processes. Co-gasification of 10 wt % algae and 90 wt % Swedish wood pellets was performed in a fluidized bed reactor. The effects of algae addition on the syngas yield and carbon conversion rate were investigated. The addition of 10 wt % algae in wood increased the CO, H2, and CH4 yields by 3–20, 6–31, and 9–20%, respectively. At the same time, it decreased the CO2 yield by 3–18%. The carbon conversion rates were slightly increased with the addition of 10 wt % macroalgae in wood, but the microalgae addition resulted in a decrease of the carbon conversion rate by 8%. Meanwhile, the collected fly ash and bed material samples were analyzed using scanning electron microscopy combined with an energy-dispersive X-ray detector (SEM–EDX) and X-ray diffraction (XRD) technique. The fly ashes of wood/marcoalgae tests showed a higher Na content with lower Si and Ca contents compared to the wood test. The gasification tests were scheduled to last 4 h; however, only wood and wood/Derbersia gasification experiments were carried out without significant operational problems. The gasification of 10 wt % Oedogonium N+ and Oedogonium N– led to defluidization of the bed in less than 1 h, and the wood/Scenedesmus (WD/SA) test was stopped after 1.8 h as a result of severe agglomeration. It was found that the algae addition had a remarkable influence on the characteristics and compositions of the coating layer. The coating layer formation and bed agglomeration mechanism of wood/macroalgae was initiated by the reaction of alkali compounds with the bed particles to form low-temperature melting silicates (inner layer). For the WD/SA test, the agglomeration was influenced by both the composition of the original algae fuel as well as the external mineral contaminations. In summary, the operational problems experienced during the co-gasification tests of different algae–wood mixtures were assigned to the specific ash compositions of the different fuel mixtures. This showed the need for countermeasures, specifically to balance the high alkali content, to reach stable operation in a fluidized bed gasifier.

  • 2780. Zhu, Youjian
    et al.
    van Eyk, Philip J.
    Boman, Christoffer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Broström, Markus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Kirtania, Kawnish
    Piotrowska, Patrycja
    Boström, Dan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    de Nys, Rocky
    Bhattacharya, Sankar
    Gentili, Francesco G.
    Ashman, Peter J.
    Preliminary understanding on the ash behavior of algae during co-gasification in an entrained flow reactor2018Ingår i: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 175, s. 26-34Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Algae are considered as a promising alternative fuel to produce energy due to its advantages such as high production yield, short growth cycle and flexible growing environment. Unfortunately, ash-related issues restrict its thermochemical utilization due to the high ash content and especially the high alkali metal concentration. In this paper, the gasification performance and ash behavior were experimentally analysed for three macro- and micro-algal species. Clear differences in the proximate and ultimate compositions were found between the cultivated algae used in this study and macroalgae (seaweed) harvested from the marine environments. Algal biomass generally contained higher Na and P contents than lignocellulosic biomass. Microalgae also had a relatively high mineral content due to the impurities in the harvesting process which included centrifugal pumping followed by sedimentation. Co-gasification of 20 wt% algae with softwood was investigated using an entrained flow reactor. The addition of both macroalgal species Derbersia tenuissima and Oedogonium to softwood had a limited influence on the gas yields and carbon conversion. On the other hand, the addition of the microalgal species Scenedesmus significantly decreased the main gas yields and carbon conversion. Moreover, the addition of algae clearly changed the residual ash composition of the base fuel. Finally, a preliminary understanding of the ash behavior of the tested algae blends was obtained through the analysis of the fuel ashes and the collected residual ashes. Fouling and corrosion were presumably occurred during the co-gasification of wood/macroalgae blends in view of the high alkali metal content. Microalga Scenedesmus had a high mineral content which could potentially capture the alkali metal in the ash and mitigate fouling when gasified with softwood. The growing environment and harvesting method were found to be significantly affecting the ash behavior implying the need for careful consideration regarding co-gasification process.

  • 2781.
    Zieba, Agata
    et al.
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för immunologi, genetik och patologi. Uppsala universitet, Science for Life Laboratory, SciLifeLab.
    Ponten, Fredrik
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för immunologi, genetik och patologi. Uppsala universitet, Science for Life Laboratory, SciLifeLab.
    Uhlen, Mathias
    KTH Royal Inst Technol, Sci Life Lab, Stockholm, Sweden..
    Landegren, Ulf
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för immunologi, genetik och patologi. Uppsala universitet, Science for Life Laboratory, SciLifeLab.
    In situ protein detection with enhanced specificity using DNA-conjugated antibodies and proximity ligation2018Ingår i: Modern Pathology, ISSN 0893-3952, E-ISSN 1530-0285, Vol. 31, nr 2, s. 253-263Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Antibodies are important tools in anatomical pathology and research, but the quality of in situ protein detection by immunohistochemistry greatly depends on the choice of antibodies and the abundance of the targeted proteins. Many antibodies used in scientific research do not meet requirements for specificity and sensitivity. Accordingly, methods that improve antibody performance and produce quantitative data can greatly advance both scientific investigations and clinical diagnostics based on protein expression and in situ localization. We demonstrate here protocols for antibody labeling that allow specific protein detection in tissues via bright-field in situ proximity ligation assays, where each protein molecule must be recognized by two antibodies. We further demonstrate that single polyclonal antibodies or purified serum preparations can be used for these dual recognition assays. The requirement for protein recognition by pairs of antibody conjugates can significantly improve specificity of protein detection over single-binder assays.

  • 2782.
    Zimmermann, Tanja
    et al.
    Swiss Federal Laboratories for Materials Testing and Research (EMPA).
    Tingaut, P.
    Eyholzer, Christian
    Richter, Klaus
    Applications of nanofibrillated cellulose in polymer composites2012Konferensbidrag (Refereegranskat)
  • 2783. Zirk, Katrin
    et al.
    Langel, Ülo
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för neurokemi. University of Tartu, Estonia.
    Vectorization of splice-correcting oligonucleotides with cell-penetrating peptides2013Ingår i: Chimica oggi, ISSN 0392-839X, E-ISSN 1973-8250, Vol. 31, nr 2, s. 12-15Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Personalized medicine approaches based on different gene therapy settings have gained much attention lately. In order to enforce successful gene therapy, genetic material needs to be delivered into cells. Nucleic acids and their analogues are unable to do so and thus require assistance to reach their site of action residing in the cytoplasm or nucleus. Here we give a short review on recent advancements in cell-penetrating peptide mediated delivery of splice-correcting oligonucleotides. We report on different cell-penetrating peptides applied for vectorization of splice-correcting oligonucleotides using both covalent conjugation and non-covalent nanoparticle formation approach. While covalent conjugation has gained extensive interest, there have also been great advances in non-covalent complex formation.

  • 2784.
    Åberg, Katarina
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Pommer, Linda
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Nordin, Anders
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Syngas production by combined biomass gasification and in situ biogas reforming2015Ingår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 29, nr 6, s. 3725-3731Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    For small- to medium-sized streams of biogas (methane) produced at a biorefinery site where cost-efficient reforming by traditional methods are unavailable, combined biomass gasification and methane reforming could facilitate co-conversion and increase the H-2/CO ratio in the syngas from the gasification plant. In the present work, co-gasification of biomass with CH4 was evaluated by means of a parametric chemical equilibrium study for both wood/CH4 and black liquor/CH4 feedstocks and bench-scale fluidized-bed gasification experiments for a wood/peat/CH4 fuel mixture. The parametric study indicated that high-temperature, and steam and oxygen addition all facilitate a high conversion rate, i.e., methane reforming. Evaluating the influence of the gasification temperature on CH4 reforming and increasing the H-2/CO ratio experimentally demonstrated that high temperatures are required for efficient co-conversion.

  • 2785.
    Åhlin, Mikaela
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för biologisk grundutbildning.
    Mapping the binding site of the Hof1p SH3 domain in the Bnr1p FH1 domain2014Rapport (Övrigt vetenskapligt)
    Abstract [en]

    The unusual syndrome Wiskott-Aldrich Syndrome has been found to be linked to a mutation in a gene expressing the Wiskott-Aldrich Syndrome protein (WASp). Due to the conservation of certain mechanisms and the homologous proteins from lower to higher eukaryotes, yeast has been used to study the molecular mechanisms that underlie diseases in humans. The yeast WASp homologue, Las17p (Local Anaexthetic Sentivie 17) and the yeast homologye Vrpp of its (i.e. human WASp) partner protein known as WIP (WASp-interacting protein), have been studied with the intention to investigate the phenotypes that arise in cells deficient in Vrp1p. A protein-protein interaction is believed to occur in the absence of Vrp1p, the interaction between the SH3 domain of the yeast F-Bar protein Hof1p and the FH1 domain of the yeast formin protein Bnr1p. This interaction is thought to have pathological effects, such as inhibition of cell proliferation and other phenotypes.

    This study has been conducted in an attempt to map the binding site of Hof1p SH3 domain in the Bnr1p FH1 domain more specifically, based on previous studies suggesting that Fragment 1(755-905) of Bnr1p Full Interacting Fragment(755-1375), including the proline- rich FH1 domain, interacts with Hof1p SH3 domain in cells deficient in Vrp1p. Both Hof1p and Bnr1p are involved in the cytokinesis stagemof the yeast cell cycle. The hypothesis implies that the excessive interaction of Hof1p SH3 domain and Bnr1p FH1 domain may interrupt the cytokinesis, which thereby can lead to the growth of defects.

    There was no finding of binding site within the Bnr1p FH1 domain for the Hof1p SH3 domain during this study. This can be due to various reason as explained later. Even though, this study has cast some doubts on previously conducted studies.

  • 2786.
    Åkerlund, Elin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    Development of polymer based composite filaments for 3D printing2019Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The relatively new and still growing field of 3D-printing has opened up the possibilities to manufacture patient-specific medical devices with high geometrical accuracy in a precise and quick manner. Additionally, biocompatible materials are a demand for all medical applications while biodegradability is of importance when developing scaffolds for tissue growth for instance. With respect to this, this project consisted of developing biocompatible and bioresorbable polymer blend and composite filaments, for fused deposition modeling (FDM) printing. Poly(lactic acid) (PLA) and polycaprolactone (PCL) were used as supporting polymer matrix while hydroxyapatite (HA), a calcium phosphate with similar chemical composition to the mineral phase of human bone, was added to the composites to enhance the biological activity. PLA and PCL content was varied between 90–70 wt% and 10-30 wt%, respectively, while the HA content was 15 wt% in all composites. All materials were characterized in terms of mechanical properties, thermal stability, chemical composition and morphology. An accelerated degradation study of the materials was also executed in order to investigate the degradation behavior as well as the impact of the degradation on the above mentioned properties. The results showed that all processed materials exhibited higher mechanical properties compared to the human trabecular bone, even after degradation with a mass loss of around 30% for the polymer blends and 60% for the composites. It was also apparent that the mineral accelerated the polymer degradation significantly, which can be advantageous for injuries with faster healing time, requiring only support for a shorter time period.

  • 2787.
    Östrand, Therese
    Örebro universitet, Akademin för naturvetenskap och teknik.
    Analysis of CHS, MEB5.2, PDX1.3 and PR-5 expression in Arabidopsis thaliana ecotypes during UV-B irradiation.2010Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
  • 2788.
    Özdemir, Gonca
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design.
    Optimering av biogasproduktion från gödsel2009Självständigt arbete på grundnivå (kandidatexamen), 30 poäng / 45 hpStudentuppsats (Examensarbete)
    Abstract [en]

                          In this study, the bioconversion of manure and silage to biogas by an anaerobic digestion process in batch reactors was studied. Biogas is a valuable alternative energy source, mainly in rural areas. The main aim for the environment is to use biogas as a fuel instead of crude oil or natural gas. In this study, two different parameters were studied to observe the changes in methane productivity. The first three reactors were shaken once per week and the following three reactors were shaken 5 times per week. The results showed that mixing has no major effect on the methane production yield. In the second six reactors a mixture of 1% and 3% silage was added and the results were recorded. When the data from the reactors with just manure was compared to the reactors with 1% and 3% silage, it was seen that the silage increased the production rate and total gas produced. The process stabilization took a long time for digestion with the 3% silage possibly caused by release of too much fatty acids.

  • 2789.
    New EU criteria for endocrine disrupters: Consequences for the food chain2018Bok (Övrigt vetenskapligt)
    Abstract [en]

    Endocrine disruptors (EDs) are substances that adversely affect hormone function. The effects by EDs are thought to depend on both dose and timing of exposure, especially during foetal development. The upcoming EU regulation on identification of EDs, application biocides and pesticides, will have an impact on all actors of the food chain. The consequences of a ban of EDs in foods were discussed in a Nordic workshop (Uppsala, 29-30 Nov 2016) where risk assessors and managers from Nordic food authorities, industry, trade associations, consumer organizations and researchers were represented. It was recognized by all participants that a ban was particularly challenging for the production chain since there are few viable alternatives. A harmonized EU legislation based on scientific risk assessment was preferred compared to national specific legislation as it treats all the actors equally.

  • 2790. Oksman, Kristiina (Redaktör)
    Wood based composites: Proceedings from Nordic research course at Lövånger 22-27 March 19921992Rapport (Övrigt vetenskapligt)
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