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  • 801.
    Witos, Joanna
    et al.
    Univ Helsinki, Dept Chem, Chem Anal Lab, FIN-00014 Helsinki, Finland..
    Samuelsson, Jörgen
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper.
    Cilpa-Karhu, Geraldine
    Univ Helsinki, Dept Chem, Chem Anal Lab, FIN-00014 Helsinki, Finland..
    Metso, Jari
    Nat Inst Hlth & Welf, Publ Hlth Genom Unit, Biomedicum, FIN-00290 Helsinki, Finland..
    Jauhiainen, Matti
    Nat Inst Hlth & Welf, Publ Hlth Genom Unit, Biomedicum, FIN-00290 Helsinki, Finland..
    Riekkola, Marja-Liisa
    Univ Helsinki, Dept Chem, Chem Anal Lab, FIN-00014 Helsinki, Finland..
    Partial filling affinity capillary electrophoresis including adsorption energy distribution calculations: towards reliable and feasible biomolecular interaction studies2015Ingår i: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 140, nr 9, s. 3175-3182Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work, a method to study and analyze the interaction data in free solution by exploiting partial filling affinity capillary electrophoresis (PF-ACE) followed by adsorption energy distribution calculations (AED) prior model fit to adsorption isotherms will be demonstrated. PF-ACE-AED approach allowed the possibility to distinguish weak and strong interactions of the binding processes between the most common apolipoprotein E protein isoforms (apoE2, apoE3, apoE4) of high density lipoprotein (HDL) and apoE-containing HDL2 with major glycosaminoglycan (GAG) chain of proteoglycans (PGs), chondroitin-6-sulfate (C6S). The AED analysis clearly revealed the heterogeneity of the binding processes. The major difference was that they were heterogeneous with two different adsorption sites for apoE2 and apoE4 isoforms, whereas interestingly for apoE3 and apoE-containing HDL2, the binding was homogeneous (one site) adsorption process. Moreover, our results allowed the evaluation of differences in the binding process strengths giving the following order with C6S: apoE-containing HDL2 > apoE2 > apoE4 > apoE3. In addition, the affinity constant values determined could be compared with those obtained in our previous studies for the interactions between apoE isoforms and another important GAG chain of PGs - dermatan sulfate (DS). The success of the combination of AED calculations prior to non-linear adsorption isotherm model fit with PF-ACE when the concentration range was extended, confirmed the power of the system in the clarification of the heterogeneity of biological processes studied.

  • 802.
    Wäne, Gerd
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Fibre surface properties of kraft pulp: The influence of wood raw material, bleaching and storage2009Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The aim of this thesis was to study the fibre surface properties of Birch (Betula ssp.), Eucalyptus (E. urograndis and E. globulus) and Spruce (Picea Abies) pulps bleached using two different methods: ECF (Elementary Chlorine Free) and TCF (Totally Chlorine Free). The hardwood pulps were subjected to a hot acidic stage prior to ECF bleaching in order to remove hexenuronic acid. The effect of prolonged storage (ageing) on the fibre surface properties was studied for all of the pulps.

    The characteristics of the fibre surfaces were determined by measuring the dynamic contact angle of single fibres (DCA) and by using Electron Spectroscopy for Chemical Analysis (ESCA) and Time of Flight Secondary Ion Mass Spectroscopy (ToF-SIMS). The correlation between the fibre surface properties and the sizing efficiency of the hardwood pulps were evaluated by measuring the amount of alkyl ketene dimer (AKD) needed to reach a certain water absorption level(measured as Cobb60).

    The birch pulp was more hydrophilic than the eucalyptus pulps, thus requiring more AKD to reach a certain water absorption value, and also had a lower DCA. The introduction of a hot acidic stage (A stage) in the ECF bleaching sequence applied to the hardwood pulps (i.e. A/D(EP)DD versus D(EP)DD) lowered, as expected, the total fibre charge due to the removal of hexenuronic acids groups (HexA). According to the DCA measurements all of the pulps became more hydrophilic after the A/D(EP)DD bleaching than after the D(EP)DD bleaching sequence. The sizing ability of the pulps, measured as the AKD demand to a certain Cobb60 value, showed that the AKD demand was more or less the same for the eucalyptus pulps regardless of the bleaching sequence used. The birch pulp, on the other hand, required somewhat less AKD in the A/D(EP)DD sequence than in the D(EP)DD.

    The AKD demand to a certain Cobb60 value decreased further for the bleached birch and E. globulus pulps after ageing due to an increase in the fibre surface hydrophobicity. ESCA analysis revealed an increase of surface extractives on the pulps after ageing, which was also supported by ToF-SIMS analysis. It was concluded that there was an increase in fatty acids, fatty acid salts and possibly even sterols and glycerides on the fibre surfaces due to ageing. A migration of these components from the interior of the fibre wall to the fibre surface during ageing was verified in this study.

    The TCF and ECF bleached softwood pulps also showed differences in their fibre surface properties that were tangible and thereby measurable. The dynamic contact angle was highest for the TCF bleached softwood fibres, i.e. these were more hydrophobic. Although changes caused by ageing were much more pronounced for the ECF fibres, all pulps became more hydrophobic upon ageing.

    The hydrophobicity of pulp fibres can be determined using DCA, which is a rather rapid and economically viable analysis. Using this information, a paper/board mill can base its sizing strategy on scientific findings.

    The ageing effects seen on the fibre surfaces in the form of the migration of extractives might be an important parameter from an industrial point of view, especially when pulps are stored and/or transported for a long time period. Nowadays it is quite common for pulps to be shipped around the world and subjected to warm and humid conditions. It is therefore probable that the properties of the pulp change in such a way that the papermaking process requires adjustment.

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  • 803.
    Wäne, Gerd
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Germgård, Ulf
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Aspects on the AKD demand of hardwood kraft pulps before and after ageing2009Ingår i: Appita journal, ISSN 1038-6807, Vol. 62, nr 2, s. 123-129Artikel i tidskrift (Refereegranskat)
  • 804.
    Wäne, Gerd
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Germgård, Ulf
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Pulp and Fibre surface properties of bleached hardwood Kraft Pulps: Influence of an A-stage2009Ingår i: Paperi ja puu, ISSN 0031-1243, Vol. 91, nr 7-8, s. 58-64Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Hexenuronic acids in kraft pulps increase the demand for bleaching chemicals and cause brightness reversion of the bleached pulps during storage. They can, however, be removed by the use of hot acid treatments in e.g. the bleaching sequence, which is commonly used for eucalyptus in the pulp industry today. In this work three kraft hardwood pulps (two eucalyptus and one birch) were selected to study the influence on the surface properties of the pulps of a hot acidic stage (A stage) introduced prior to a standard ECF bleaching sequence. The sequences compared were A/D(EP)DD and D(EP)DD. The results were compared before and after the pulps were aged at room temperature for about eight months.

  • 805. Yang, Li
    Spectral model of halftone on a fluorescent substrate2005Ingår i: J.Imaging Science Technology 49 (2005), 179-184Artikel i tidskrift (Refereegranskat)
  • 806. Yang, Li
    What has been overlooked in Kubelka-Munk Theory?2005Konferensbidrag (Övrig (populärvetenskap, debatt, mm))
  • 807. Yang, Li
    et al.
    Fogden, A.
    Pauler, N.
    Sävborg, Ö.
    Kruse, B.
    A novel method for studying ink penetration of a print2005Ingår i: Nordic Pulp and Paper Research Journal 40(2005),423-429Artikel i tidskrift (Refereegranskat)
  • 808. Yang, Li
    et al.
    Fogden, A.
    Pauler, N.
    Sävborg, Ö.
    Kruse, B.
    Studying ink penetration by microscopic and spectroscopic techniques2006Ingår i: J.Imaging Science and TechnologyArtikel i tidskrift (Refereegranskat)
  • 809. Yang, Li
    et al.
    Kruse, B.
    Studying ink penetration by microscopic and spectroscopic techniques2005Konferensbidrag (Övrig (populärvetenskap, debatt, mm))
  • 810. Yang, Li
    et al.
    Miklavcic, S.J.
    Revised Kubelka-Munk theory.III: A general theory of light propagation in scattering and absorptive media2005Ingår i: J.Optical Society of America A 22(9), 1866-1873, (2005)Artikel i tidskrift (Refereegranskat)
  • 811. Yang, Li
    et al.
    Miklavcic, S.J.
    Theory of light propagation incorporation scattering and absorption in turbid media2005Ingår i: Optics Letter 30(7), 792-794, 2005Artikel i tidskrift (Refereegranskat)
  • 812. Yusuf, Abdul Aleem
    Improvement of Oxygen Barrier Properties by Enzyme Technology2012Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
  • 813.
    Zdanowicz, Magdalena
    et al.
    West Pomeranian Univ Technol, Inst Polymer, Ul Pulaskiego 10, PL-70322 Szczecin, Poland.
    Johansson, Caisa
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper.
    Mechanical and barrier properties of starch-based films plasticized with two- or three component deep eutectic solvents2016Ingår i: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 151, s. 103-112Artikel i tidskrift (Refereegranskat)
  • 814.
    Zeb, Hassan
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap.
    Bleaching of Old Newsprint Paper at Metsä Tissue2011Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
  • 815.
    Zethelius, Thea
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Natriumkarbonat som alternativ alkalikälla till natriumhydroxid: Impregnering och blekning av kemitermomekanisk massa2019Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Arbetet handlade om att ta reda på om det går att byta ut natriumhydroxid mot natriumkarbonat som alkalikälla på CTMP-linjen, och gjordes på uppdrag av Stora Enso Skoghalls bruk. De områdena som studerades var impregnering och blekning av CTMP (kemitermomekanisk pappersmassa) samt hantering av natriumkarbonatlösning.

    Natriumkarbonatens löslighet vid olika temperaturer verifierades, blekning av CTMP med natriumkarbonat och natriumhydroxid utfördes, titrering av natriumhydroxid och natriumkarbonat mot natriumbisulfitlösning och en enklare laborationsimpregnering gjordes. Även aspekten av utrustning, kostnader och eventuell utfällning av kalciumkarbonat studerades.

    Resultaten visade att det krävs mer natriumkarbonat för att ersätta natriumhydroxid än vad man trott och att det totalt sett blir dyrare. Det finns dock en möjlighet att andra delar av bruket kan utföra bytet av alkali och gå med större vinst än vad CTMP-linjen går med förlust. Försöken visade även på temperaturökning vid tillredning av natriumkarbonatlösningen, utfällning av kristallsoda och behov av att den befintliga utrustningen kompletteras utifrån rekommendationer från kemikalieleverantören. Tidigare studier visade på eventuella försämringar av papperskvaliteten när natriumkarbonat används vid blekning av CTMP.

    Trots att natriumkarbonat är ett billigare alternativ till natriumhydroxid, och att det teoretiskt sett skulle fungera bra som en utbrytare, är det mycket som man behöver ta hänsyn till vad gäller natriumkarbonat och det krävs eftertanke för att saker ska görs på rätt sätt. Utifrån resultaten kan man dra slutsatsen att det inte ser ut som en bra ide att utföra bytet.

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  • 816.
    Zhang, Y.
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Forssén, Patrik
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Fornstedt, Torgny
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Gulliksson, M.
    Orebrov Univ, Sch Sci & Technol, Dept Math, Orebro, Sweden.
    Dai, X.
    Zhejiang Univ, City Coll, Sch Comp Sci, Hangzhou, Zhejiang, Peoples R China.
    An adaptive regularization algorithm for recovering the rate constant distribution from biosensor data2018Ingår i: Inverse Problems in Science and Engineering, ISSN 1741-5977, E-ISSN 1741-5985, Vol. 26, nr 10, s. 1464-1489Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present here the theoretical results and numerical analysis of a regularization method for the inverse problem of determining the rate constant distribution from biosensor data. The rate constant distribution method is a modern technique to study binding equilibrium and kinetics for chemical reactions. Finding a rate constant distribution from biosensor data can be described as a multidimensional Fredholm integral equation of the first kind, which is a typical ill-posed problem in the sense of J. Hadamard. By combining regularization theory and the goal-oriented adaptive discretization technique, we develop an Adaptive Interaction Distribution Algorithm (AIDA) for the reconstruction of rate constant distributions. The mesh refinement criteria are proposed based on the a posteriori error estimation of the finite element approximation. The stability of the obtained approximate solution with respect to data noise is proven. Finally, numerical tests for both synthetic and real data are given to show the robustness of the AIDA.

  • 817.
    Zhang, Ye
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013). Örebro Universitet Sverige.
    Lin, Guang-Liang
    Zhejiang Univ, Dept Math, Hangzhou 310027, Zhejiang, Peoples R China..
    Forssén, Patrik
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Gulliksson, Marten
    Örebro Universitet, Sweden..
    Fornstedt, Torgny
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Cheng, Xiao-Liang
    Zhejiang Univ, Dept Math, Hangzhou 310027, Zhejiang, Peoples R China..
    A regularization method for the reconstruction of adsorption isotherms in liquid chromatography2016Ingår i: Inverse Problems, ISSN 0266-5611, E-ISSN 1361-6420, Vol. 32, nr 10, artikel-id 105005Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Determining competitive adsorption isotherms is an open problem in liquid chromatography. Since traditional experimental trial-and-error approaches are too complex and expensive, a modern technique of obtaining adsorption isotherms is to solve the inverse problem so that the simulated batch separation coincides with actual experimental results. This is a typical ill-posed problem. Moreover, in almost all cases the observed concentration at the outlet is the total response of all components, which makes the problem more difficult. In this work, we tackle the ill-posedness with a new regularization method, which is based on the fact that the adsorption isotherms do not depend on the injection profile. The proposed method transfers the original problem to an optimization problem with a time-dependent convection-diffusion equation constraint. Iterative algorithms for solving constraint optimization problems for both the equilibrium-dispersive and the transport-dispersive models are developed. The mass transfer resistance is also estimated by the proposed inverse method. A regularization parameter selection method and the convergence property of the proposed algorithm are discussed. Finally, numerical tests for both synthetic problems and real-world problems are given to show the efficiency and feasibility of the proposed regularization method.

  • 818. Åsberg, Dennis
    Modeling of Overloaded Gradient Elution in Reversed-Phase Liquid Chromatography2012Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
  • 819.
    Åsberg, Dennis
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Karlsson, Anders
    AstraZeneca R and D, Mölndal, Sweden.
    Samuelsson, Jörgen
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Kaczmarski, Krzysztof
    Poland.
    Fornstedt, Torgny
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Analytical method development in the quality by design framework2014Ingår i: American Laboratory, ISSN 0044-7749, Vol. 46, nr 9, s. 12-15Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The development of analytical methods in the Quality by Design (QbD) framework is currently gaining great momentum in the pharmaceutical industry. Presented here is a case study in which a pharmaceutical Quality Control (QC) method was developed using HPLC. The possibilities of continuous improvements during the method’s lifetime are demonstrated by switching to ultrahigh performance liquid chromatography (UHPLC).

  • 820.
    Åsberg, Dennis
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper.
    Leśko, Marek
    Department of Chemical and Process Engineering, Rzeszów University of Technology.
    Enmark, Martin
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper.
    Samuelsson, Jörgen
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper.
    Kaczmarski, Krzysztof
    Department of Chemical and Process Engineering, Rzeszów University of Technology.
    Fornstedt, Torgny
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper.
    Fast estimation of adsorption isotherm parameters in gradient elution preparative liquid chromatography. II: The competitive case2013Ingår i: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1314, nr Nov, s. 70-76Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Abstract Experimental competitive adsorption isotherms were successfully determined directly from overloaded elution profiles in gradient elution mode using an extended inverse method. This approach differs from the existing methods in one important aspect – no isocratic experiments are necessary which makes it possible to study adsorption of substances whose retention factors vary strongly with the mobile-phase composition. The approach was verified with simulated binary data and with experimental data from gradient separations of a cyclohexanone/cycloheptanone mixture. For the synthetic data, the original adsorption isotherm parameters were found using a two-step estimation procedure. In the first step analytical peaks were used to estimate the “analytical” part of the Langmuir equation and in the second step the association equilibrium parameters were estimated from two simulated overloaded elution profiles. For the experimental data, a three-step approach was used. The two first steps were used to reduce the calculation time so that parameter estimation could be performed on an ordinary computer. In the first step, analytical peaks were used to estimate the “analytical” part of the bi-Langmuir equation. In the second step, initial guesses for all other parameters were determined separately for each solute using the faster Rouchon algorithm. In the final and third step, the more accurate orthogonal collocation on finite elements algorithm, was used to fine-tune the isotherm parameters. The model could accurately predict the shape of overloaded elution profiles. The shape of the adsorption isotherms agreed well with those determined with the standard isocratic method, although the numerical values were not the same. The extended inverse method is well suited for process optimization where few experiments and accurate predictions are important.

  • 821.
    Åsberg, Dennis
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper.
    Samuelsson, Jörgen
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper.
    Lesko, Marek
    Department of Chemical and Process Engineering, Rzeszów University of Technology, PL-35 959 Rzeszów, Poland.
    Cavazzini, Alberto
    Department of Chemical and Pharmaceutical Sciences, University of Ferrara, IT-44 121 Ferrara, Italy.
    Kaczmarski, Krzysztof
    Department of Chemical and Process Engineering, Rzeszów University of Technology, PL-35 959 Rzeszów, Poland.
    Fornstedt, Torgny
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper.
    Method transfer from high-pressure liquid chromatography to ultra-high-pressure liquid chromatography. II. Temperature and pressure effects2015Ingår i: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1401, s. 52-59Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The importance of the generated temperature and pressure gradients in ultra-high-pressure liquid chromatography (UHPLC) are investigated and compared to high-pressure liquid chromatography (HPLC). The drug Omeprazole, together with three other model compounds (with different chemical characteristics, namely uncharged, positively and negatively charged) were used. Calculations of the complete temperature profile in the column at UHPLC conditions showed, in our experiments, a temperature difference between the inlet and outlet of 16 degrees C and a difference of 2 degrees C between the column center and the wall. Through van't Hoff plots, this information was used to single out the decrease in retention factor (k) solely due to the temperature gradient. The uncharged solute was least affected by temperature with a decrease in k of about 5% while for charged solutes the effect was more pronounced, with k decreases up to 14%. A pressure increase of 500 bar gave roughly 5% increase in k for the uncharged solute, while omeprazole and the other two charged solutes gave about 25, 20 and 15% increases in k, respectively. The stochastic model of chromatography was applied to estimate the dependence of the average number of adsorption/desorption events (n) and the average time spent by a molecule in the stationary phase (tau(s)) on temperature and pressure on peak shape for the tailing, basic solute. Increasing the temperature yielded an increase in n and decrease in tau(s) which resulted in less skew at high temperatures. With increasing pressure, the stochastic modeling gave interesting results for the basic solute showing that the skew of the peak increased with pressure. The conclusion is that pressure effects are more pronounced for both retention and peak shape than the temperature effects for the polar or charged compounds in our study. (C) 2015 Elsevier B.V. All rights reserved.

  • 822.
    Östberg, Linda
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Laboratory Preparation of Viscose2011Konferensbidrag (Refereegranskat)
  • 823.
    Östberg, Linda
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Some Aspects on Pulp Pre-treatment Prior to Viscose Preparation2012Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Large amounts of carbon disulphide are consumed in the conventional production of viscose. Until a novel, eco-friendly, wood-based process for the production of cellulose textile fibres has been developed and implemented, it is important to try to find ways to improve the conventional viscose process, e.g. in terms of reducing the carbon disulphide requirement of the process. The aim of this thesis was to reduce the amount of carbon disulphide consumed in the preparation of high-viscosity viscose by pre-treating pulps with enzymes. It also aimed at investigating and linking the different measurements of reactivity, i.e. gamma number, Fock reactivity and Kw, and determining the sensitivity of the gamma number to the hemicellulose content of pulp. Reactivity was measured as Fock reactivity and gamma number. The gamma number of viscose solutions remained unchanged when an enzyme stage was used prior to the viscose process. The gamma number analysis was found to be selective not only to cellulose but also to the hemicellulosic material. It was verified that both cellulose and hemicellulose molecules in the pulp material were substituted in the viscose preparation stages, showing that the gamma number of the pulp is due to both substituted cellulose and substituted hemicelluloses. The mechanisms responsible for the Fock reactivity, or the filter-clogging value (Kw) on the one hand and the gamma number on the other, are probably not the same. It was speculated that the analysis method employed in Fock´s test and the filter-clogging value measure the results on a fibre level, whereas the gamma number measures changes mainly on a molecular level. This could explain the difference in the levels of reactivity found in this study.

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    KUS_2012_23
  • 824.
    Östberg, Linda
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Germgård, Ulf
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Some Aspects of the Reactivity of Pulp Intended for High-Viscosity Viscose: Influence on the Reactivity and the Gamma Number2011Konferensbidrag (Övrig (populärvetenskap, debatt, mm))
  • 825.
    Östberg, Linda
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Germgård, Ulf
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Some Aspects on the Reactivity of a Dissolving Pulp when used for Viscose PreparationIngår i: O papelArtikel i tidskrift (Refereegranskat)
  • 826.
    Östberg, Linda
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Håkansson, Helena
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Germgård, Ulf
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap.
    Some aspects of the reactivity of pulp intended for high-viscosity viscose2012Ingår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 7, nr 1, s. 743-755Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The original objective of this study was to reduce the consumption of carbon disulphide in the preparation of high-viscosity viscose by pre-treating two softwood pulps with enzymes prior to the viscose stages. Reactivity can, however, be measured in different ways and the methods used in this study are Fock´s test of the pulp and the gamma number of the viscose solution prior to regeneration. It was found that whilst the reactivity of a pulp that had been subjected to enzyme pretreatment increased according to Fock´s test, it did not increase when the gamma number obtained in a standardized viscose preparation process was used. This unexpected difference that was discovered between the two reactivity tests made it difficult to analyze the impact of the enzyme stage on reactivity; the underlying reasons for the different reactivity results obtained were therefore investigated first. The conclusion that may be drawn from this investigation is that Fock´s test measures the extent to which carbon disulphide reacts with a pulp sample during a standardized test whereas the gamma number measures the resulting degree of xanthate substitution on the cellulose backbone. These two reactivity tests are thus not totally correlated. It was concluded that the gamma number was the more relevant of the two tests since it reflects the dissolution ability of a pulp in the viscose preparation, which is a very basic property of viscose. A higher gamma number also means that the coagulation time in the spinning process is prolonged; this is beneficial as it can be used to increase the tenacity of the viscose fibres. Measuring the reactivity according to Fock´s test, on the contrary, provides more dubious results as the test has no undisputed correlation to the viscose preparation process.

  • 827.
    Östberg, Linda
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Kvarnlöf, Niklas
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Germgård, Ulf
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    The hemicellulose content in two chemical pulps and its influence on Fock´s test and the gamma number of the resulting viscose dope2013Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 28, nr 3, s. 4s. 377-380Artikel i tidskrift (Refereegranskat)
  • 828.
    Östberg, Linda
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Kvarnlöf, Niklas
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Germgård, Ulf
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    The Influence of the Hemicellulose Content in Dissolving Pulps on the Gamma Number of Viscose DopesIngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669Artikel i tidskrift (Refereegranskat)
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