Change search
Refine search result
2345678 201 - 250 of 412
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 201. Eriksson, Björn
    et al.
    Dahl, Magnus
    Andersson, M.B.O.
    Blomberg, Lars G
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Changes in mobile phase ion distribution when combining pressurized flow and electric field2004In: Electrophoresis, 25 (2004) 3092-3097Article in journal (Refereed)
  • 202. Eriksson, Björn O.
    et al.
    Skuland, Inger Lill
    Andersson, Magnus B.O.
    Blomberg, Lars G
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    In-line application of electric field in capillary separation systems, Part II, Separation parameters affecting the conductivity2006In: Karlstad University Press, 2006:55, 2006Chapter in book (Other academic)
  • 203.
    Eriksson, Björn
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Skuland, Inger Lill
    Karlstad University, Faculty of Technology and Science.
    Andersson, Magnus
    Blomberg, Lars
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    In-line application of electric field in capillary separation systems Part II: Separation parameters affecting the conductivity2006Manuscript (preprint) (Other academic)
  • 204.
    Eriksson, Björn
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Skuland, Inger Lill
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Marlin, Nicola
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Andersson, Magnus
    Early Development, Pharmaceutical and Analytical Research & Development, AstraZeneca, Sweden.
    Blomberg, Lars
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    In-line application of electric field in capillary separation systems Part I: Joule heating, pH and conductivity2008In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 75, no 1, p. 83-90Article in journal (Refereed)
    Abstract [en]

    This study concerns the technique electric field-assisted capillary liquid chromatography. In this technique, an electric field is applied over the separation capillary in order to provide an additional selectivity. In this technique, the electric field is applied in-line in the separation capillary and here the electric current is the factor limiting the magnitude of applied electric field. The influence of Joule heating and other factors on the current in such systems has been investigated.

    The temperature in the capillary was first measured within a standard CE set-up, as function of effect per unit of length. Then the same cooling system was applied to an in-line set-up, to replicate the conditions between the two systems, and thus the temperature. Thus Joule heating effects could then be calculated within the in-line system. It was found that for systems applying an electric field in line, the direct influence from Joule heating was only relatively small.

    The pH in the capillary was measured in the in-line set-up using cresol red/TRIS solutions as pH probe. Significant changes in pH were observed and the results suggested that electrolysis of water is the dominant electrode reaction in the in-line system. In summary, the observed conductivity change in in-line systems was found to be mainly due to the pH change by hydrolysis of water, but primarily not due the temperature change in the capillary column.

  • 205.
    Erlandsson, Ann
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Effects of 177Lu-DOTA-Tyr3-octreotate on small cell lung cancer studied by immunohistochemistry, oral presentation2007Conference paper (Other (popular science, discussion, etc.))
  • 206.
    Erlandsson, Ann
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Effects of 177Lu-DOTA-Tyr3-octreotate on small cell lung cancer studied by immunohistochemistry, oral presentation2007Conference paper (Other (popular science, discussion, etc.))
  • 207.
    Erlandsson, Ann
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Idiotypic and antiidiotypic antibodies, Oral presentation2005Conference paper (Other (popular science, discussion, etc.))
  • 208.
    Erlandsson, Ann
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Eriksson, D
    Johansson, L
    Riklund, K
    Stigbrand, T
    Sundström, Birgitta
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    In vivo clearing of idiotypic antibodies with antiidiotypic antibodies and their derivatives2006In: Molecular Immunology 2006;42:599-604Article in journal (Refereed)
    Abstract [en]

    At immunolocalization of experimental tumors, idiotypic monoclonal antibodies, such as TS1 against cytokeratin 8, can be used to carry and deposit in vivo terapeutics in the tumor. These carriers also remain in the circulation and may cause negative side-effects in other tissues.

    In this report, several derivatives of the antiidiotypic antibody anti-TS1 were produced and tested for their clearing capacity of the idiotypic carrier antibody TS1. Intact monoclonal anri-TS1, scFv of a anti-TS1 and anti-TS1 Fab and Fab'2 fragments were produced by recombinant technology or by cleavage with Ficin. The scFv was tailored by use of the variable domain genes of the light and heavy chain from the hybridoma clone in combination with a (Gly4Ser)3-linker, followed by expression in E. coli. When tested for clearing capacity, the intact divalent antiidiotypic IgG was found to be the most efficient. The divalent Fab'2 and the monovalent Fab fragment also demonstrated significant clearing, but lower than the intact antiidiotypic IgG. The anti-TS1 scFv antibody when injected separately was not found to clear the idiotype, but could do so when preincubated with the idiotype. Rapid excretion and in vivo instability of this lowmolecular weight antibody fragment may be the major reasons. Similar results were obtained when the system was reversed and the 131I-labeled antiidiotype IgG was cleared with the idiotype Fab'2 fragment. It is concluded that both intact antiidiotypic IgG, Fab'2 and Fab fragments are able to clear the idiotypic antibodies. The experimental data support the conclusion that the Fc parts from both the idiotype and the antiidiotype may contribute to this elimination

  • 209.
    Erlandsson, Ann
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Forssell-Aronsson, Eva
    Seidal, Tomas
    Bernhardt, Peter
    Binding of TS1, an anti-keratin 8 antibody, in small cell lung cancer after 177Lu-DOTA-Tyr3-octreotate treatment: a histological study in xenografted mice2011In: EJNMMI Research, ISSN 2191-219X, E-ISSN 2191-219X, Vol. 1, no 19Article in journal (Refereed)
  • 210.
    Erlandsson, Ann
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Holm, P
    Jafari, R
    Stigbrand, T
    , Sundström
    ScFv construct and functional mapping of the monoclonal antiidiotypic antibody aTS12003Conference paper (Other (popular science, discussion, etc.))
  • 211.
    Erlandsson, Ann
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Holm, P
    Jafari, R
    Stigbrand, T
    Sundström, _
    ScFv construct and functional mapping of the monoclonal antiidiotypic antibody aTS12003Conference paper (Other (popular science, discussion, etc.))
  • 212.
    Erlandsson, Ann
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Holm, Patrik
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Jafari, Rozbeh
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Stigbrand, Torgny
    Sundström, Birgitta
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Functional mapping of the anti-idiotypic antibody anti-TS1 scFv using site-directed mutagenesis and kinetic analysis2010In: mAbs, ISSN 1942-0862, Vol. 2, no 6, p. 663-669Article in journal (Refereed)
  • 213.
    Erlandsson, Ann
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Johansson, A
    Ullén, A
    Stigbrand, T
    Sundström, Birgitta
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Interaction studies between the antigen cytokeratin 8 and idiotypic-antiidiotypic monoclonal antibodies1998Conference paper (Other (popular science, discussion, etc.))
  • 214.
    Erlandsson, Ann
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Larsson, Isabell
    Holmberg, M
    Bernhardt, Peter
    Förändringar i cell antal och somatostatin receptor typ 2 mRNA uttryck i en SCLC xenograft modell behandlad med 177Lu-DOTA-Tyr3-octreotate, muntlig presentation2010Conference paper (Other (popular science, discussion, etc.))
  • 215.
    Erlandsson, Ann
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Samuelsson, My
    Aldrin, Patrik
    Tornhamre, Susanne
    Kronisk myeloisk leukemi och LTC4S, oral presentation2010Conference paper (Other (popular science, discussion, etc.))
  • 216.
    Esguerra, Maricris
    et al.
    Sahlgrens Univ Hosp, Vasc Engn Ctr, Gothenburg, Sweden..
    Fink, Helen
    Sahlgrens Univ Hosp, Vasc Engn Ctr, Gothenburg, Sweden..
    Laschke, Matthias W.
    Univ Saarland, Inst Clin & Expt Surg, D-6650 Homburg, Saarland, Germany..
    Jeppsson, Anders
    Sahlgrens Univ Hosp, Dept Cardiothorac Surg, Gothenburg, Sweden..
    Delbro, Dick
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences. Sahlgrens Univ Hosp, Dept Surg, Gothenburg, Sweden.;Univ Karlstad, Sch Pure & Appl Nat Sci, Karlstad, Sweden..
    Gatenholm, Paul
    Chalmers, Dept Biol & Chem Engn, S-41296 Gothenburg, Sweden..
    Menger, Michael D.
    Univ Saarland, Inst Clin & Expt Surg, D-6650 Homburg, Saarland, Germany..
    Risberg, Bo
    Sahlgrens Univ Hosp, Vasc Engn Ctr, Gothenburg, Sweden..
    Intravital fluorescent microscopic evaluation of bacterial cellulose as scaffold for vascular grafts2010In: Journal of Biomedical Materials Research. Part A, ISSN 1549-3296, E-ISSN 1552-4965, Vol. 93A, no 1, p. 140-149Article in journal (Refereed)
    Abstract [en]

    Although commonly used synthetic vascular grafts perform satisfactorily in large caliber blood vessels, they are prone to thrombosis in small diameter vessels. Therefore, small vessels might benefit from tissue engineered vascular grafts. This study evaluated bacterial cellulose (BC) as a potential biomaterial for biosynthetic blood vessels. We implanted the dorsal skinfold chambers in three groups of Syrian golden hamsters with BC (experimental group), polyglycolic acid, or expanded polytetrafluorethylane (control groups). Following implantation, we used intravital fluorescence microscopy, histology, and immunochemistry to analyze the biocompatibility, neovascularization, and incorporation of each material over a time period of 2 weeks. Biocompatibility was good in all groups, as indicated by the absence of leukocyte acti-vation upon implantation. All groups displayed angiogenic response in the host tissue, but that response was highest in the polyglycolic acid group. Histology revealed vascularized granulation tissue Surrounding all three biomaterials, with many proliferating cells and a lack of apoptotic cell death 2 weeks after implantation. In conclusion, BC offers good biocompatibility and material incorporation compared with commonly used materials in vascular surgery. Thus, BC represents a promising new biomaterial for tissue engineering of vascular grafts. (C) 2009 Wiley Periodicals, Inc. J Biomed Mater Res 93A: 140-149, 2010

  • 217. Evans, C
    et al.
    Partyka, M
    van Stam, Jan
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences. Karlstad University, Faculty of Technology and Science, Materials Science.
    Naphthalene Complexation by .beta.-Cyclodextrin: Influence of Added Short Chain Branched and Linear Alcohols2000In: J. Incl. Phenom. Mol. Recog., 2000, 38, 381-396Article in journal (Refereed)
  • 218. Evans, CH
    et al.
    De Feyter, S
    Viaene, L
    van Stam, Jan
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences. Karlstad University, Faculty of Technology and Science, Materials Science.
    De Schryver, FC
    Bimolecular Processes of .alpha.-Terthiophene in a .beta.-Cyclodextrin Environment: An Exploratory Study1996In: J. Phys. Chem., 1996, 100, 2129-2135Article in journal (Refereed)
  • 219.
    Fjaeraa Alfredsson, Christina
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Nånberg, Eewa
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Effect of ellagic acid on proliferation, cell adhesion and apoptosis in SH-SY5Y human neuroblastoma cells2009In: Biomedicine and Pharmacotherapy, ISSN 0753-3322, E-ISSN 1950-6007, Vol. 63, no 4, p. 254-261Article in journal (Refereed)
    Abstract [en]

    Ellagic acid, a polyphenolic compound found in berries, fruits and nuts, has been shown to possess growth-inhibiting and apoptosis promoting activities in cancer cell lines in vitro. The objective of this study was to investigate the effect of ellagic acid in human neuroblastoma SH-SY5Y cells. In cultures of SH-SY5Y cells incubated with ellagic acid, time- and concentration-dependent inhibitory effects on cell number were demonstrated.Ellagic acid induced cell detachment, decreased cell viability and induced apoptosis as measured by DNA strand breaks. Ellagic acid-induced alterations in cell cycle were also observed. Simultaneous treatment with all-trans retinoic acid did not rescue the cells from ellagic acid effects. Furthermore, the results suggested that pre-treatment with all-trans retinoic acid to induce differentiation and cell cycle arrest did not rescue the cells from ellagic acid-induced cell death.

  • 220.
    Fornstedt, Torgny
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Edström, Lena
    Department of Physical and Analytical Chemistry, Uppsala University.
    Lämmerhofer, Michael
    Lindner, Wolfgang
    Forssén, Patrik
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    A Novel Optimization Strategy for Incorporating of Additives in the Modelling Aimed at Improved Process Optimization2010Conference paper (Refereed)
  • 221.
    Fornstedt, Torgny
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Forssén, Patrik
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Peterson, Patrik
    Astrazeneca.
    Edström, Lena
    Uppsala Universitet.
    Samie, Farzad
    Astrazeneca.
    Tatterton, Stephen
    Clarke, Adrian
    Astrazeneca.
    Why UHPLC Produces More Tailing Peaks Than HPLC, Why it Does Not Matter and How it Can be Addressed2012Conference paper (Refereed)
    Abstract [en]

    The purpose of this study is to demonstrate, with experiments and with computer simulations based on a firm chromatographic theory, that the wide spread perception of that the United States Pharmacopeia tailing factor must be lower than 2 (Tf < 2) is questionable when using the latest generation of LC equipment. It is shown that highly efficient LC separations like those obtained with sub-2 ÎŒm porous and 2.7 ÎŒm superficially porous particles (UHPLC) produce significantly higher Tf -values than the corresponding separation based on 3 ÎŒm porous particles (HPLC) when the same amount of sample is injected. Still UHPLC separations provide a better resolution to adjacent peaks. Expressions have been derived that describe how the Tf-value changes with particle size or number of theoretical plates. Expressions have also been derived that can be used to scale the injection volume based on particle size or number of theoretical plates to maintain the Tf-value when translating a HPLC separation to the corresponding UHPLC separation. An aspect that has been ignored in previous publications. Finally, data obtained from columns with different age/condition indicate that Tf-values should be complemented by a peak width measure to provide a more objective quality measure.

  • 222.
    Fornstedt, Torgny
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Peterson, Patrik
    Forssén, Patrik
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Karlsson, Anders
    Astrazeneca.
    HPLC vs UHPLC - a comparison of peak asymmetry and plan to step forward using Quality by Design (QbD) related to analytical methods2012Conference paper (Refereed)
    Abstract [en]

    The purpose of this study is to demonstrate, with experiments and with computer simulations based on a firm chromatographic theory, that the wide spread perception of that the United States Pharmacopeia tailing factor must be lower than 2 (Tf < 2) is questionable when using the latest generation of LC equipment. It is shown that highly efficient LC separations like those obtained with sub-2 m porous and 2.7 m superficially porous particles (UHPLC) produce significantly higher Tf-values than the corresponding separation based on 3 m porous particles (HPLC) when the same amount of sample is injected. Still UHPLC separations provide a better resolution to adjacent peaks. Expressions have been derived that describe how the Tf-value changes with particle size or number of theoretical plates. Expressions have also been derived that can be used to scale the injection volume based on particle size or number of theoretical plates to maintain the Tf-value when translating a HPLC separation to the corresponding UHPLC separation. This aspect has been ignored in previous publications. Finally, data obtained from columns with different age/condition indicate that Tf-values should be complemented by a peak width measure to provide a more objective quality measure. A plan to take a further step for using Quality by Design (QbD) related to analytical methods will also be presented [Ref 1]. Continuous improvement of an original HPLC method to an UHPLC method will be the used as a case study. The capability of the two methods will be deeply studied using mechanistic comparisons. Method criteria that must be fulfilled for the two chromatographic methods will be stated. [1] 2012 PDA Europe Workshop Quality by Design The Role of Analytical Science in Implementing QbD − Technical and Regulatory Aspects, Liverpool UK 6-7 March. This is an industrial – academic cooperation in the Fundamental Separation S

  • 223.
    Fornstedt, Torgny
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Samuelsson, Jörgen
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    A more reliable procedure for estimating interactions between drugs and biomolecules using biosensors: a comparison with chromatography2012Conference paper (Other academic)
    Abstract [en]

    This poster serves as background information to the corresponding lecture. Adsorption isotherms are essential in order to understand the interaction between small molecules such as pharmaceutical compounds and larger biomolecules. An adsorption isotherm describes the relationship of free substance in a solution with adsorbed substance to a surface, at a specific and constant temperature. Adsorption isotherms could be determined using several different method, all method have their pros and cons. In this study we are using two modern but principally different biosensors to determine interactions: quarts micro-balance (QCM) and Surface plasmon resonance (SPR) to determine interactions. For a long time adsorption isotherms has been determined solely by the chromatographic community. In this study we will present transformation of adsorption analysis tools from chromatography to biosensors, especially calculation of adsorption energy distribution prior adsorption model fit. We will also discuss how the experiments should be conducted. Guidelines will be given for the experimental setup and for when the chromatographic or a biosensor technique is to be preferred. This is a contribution from the Fundamental Separation Science Group in Karlstad www.separationscience.se

  • 224.
    Fornstedt, Torgny
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Samuelsson, Jörgen
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Determination of adsorption processes in modern chromatographic systems - Characterization, illustrations and guidlines how to avoid common pitfalls2010Conference paper (Refereed)
  • 225.
    Fornstedt, Torgny
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Samuelsson, Jörgen
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Insights into retention mechanisms and bio-molecular interactions gained from rigorous evaluation of adsorption data derived from HPLC and modern biosensors2012Conference paper (Refereed)
    Abstract [en]

    The estimation of reliable adsorption / equilibrium data are crucial for researchers in a wide range of fields such as analytical chemistry, biochemistry, chemical engineering, pharmacology and pharmacokinetics. Traditionally, equilibrium data are simply estimated from the statistically best-fitted model to adsorption data; but there are many dangerous pitfalls on this road. We have therefore recently improved several methods for adsorption isotherm determinations. As example, the accuracy of generating adsorption data by the elution by characteristic points (ECP) method was increased considerably by a new experimental approach that eliminated the post-loop dispersion; the method was also expanded to cover more different general types of adsorption isotherms than before. We have also made important improvements on the processing and evaluation of the data based on a firm theoretical basis. In this context, a new numerical tool was developed, calculation of the adsorption energy distribution (AED) allowing the estimation of the degree of heterogeneity of the interaction prior to the rival model fit. This concept has also been transposed to modern biosensors such as surface plasmon resonance (SPR) technology and continuous flow quartz crystal microbalance (QCM). We have utilized the improvements of generating and evaluation adsorption data to reveal more detailed information about molecular interactions in systems aimed at analytical and preparative separations and to understand better bio-molecular interactions derived from modern biosensors. This is a contribution from the Fundamental Separation Science Group in Karlstad www.separationscience.se

  • 226.
    Fornstedt, Torgny
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Samuelsson, Jörgen
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    The Tracer-pulse Experience €œ"reveiling the invisible iceberg"2010Conference paper (Refereed)
    Abstract [en]

    This Poster gives complementary material to the Lecture “Visualization of Chromatographic Surprises – The Helfferich Paradox Revisited. Here we will give more information on the remarkable deformations of invisible zones in the most simple and chromatographic system, unknown for most chromatographer. It is like reviling the part of the iceberg that is invisible, under the water.We recently described that “the injected sample molecules are not always found in the peak”. This happens if a small excess of molecules is injected into a column equilibrated with the same kind of molecules. Only one single peak will appear on the chromatogram (the system peak) while the injected molecules elute later in an invisible zone. The latter zones can be visualized by smart, but tedious, experimental procedures using either tracers or enantiomers. The phenomenon which was predicted by Helfferich in Science around 40 years ago was recently experimentally proven by us for the first time.As we continued to investigate the phenomena we could see that invisible zones containing the injected molecules take on the most strange and deformed shapes at higher sample loads. We will further show that a similar type of phenomenon appears in frontal analysis which results in invisible break-through and desorption curves. Depending on the conditions, the invisible breakthrough curves become more or less deformed. We explain the effects with the help of computer simulations which show an excellent agreement with experimental profiles of peaks and fronts.

    Single component, small perturbation

    Experimental Proof of a Chromatographic Paradox: Are the Injected Molecules in the Peak? Jörgen Samuelsson, Patrik Forsén, Morgan Stefansson and Torgny Fornstedt. Analytical Chemistry 2004, 76(4). 953-958.

    Single component, large perturbation

    Invisible Analyte Peak Deformations in Single-Component Liquid Chromatography” by Jörgen Samuelsson, Robert Arnell and Torgny Fornstedt. Analytical Chemistry (2006) 78 2765-2771.

    Single component, frontal analysis

    Discovery of invisible extra fronts in single-component frontal analysis in liquid chromatography by Jörgen Samuelsson and Torgny Fornstedt. Journal of Chromatography A (2006) 1114, 53-61.

    Multi-component, small perturbation

    Validation of the Tracer Pulse Method for Multi Component Liquid Chromatography- a Classical Paradox Revisited. Robert Arnell and Torgny Fornstedt. Analytical Chemistry (2006) 78, 4615-4623.

  • 227.
    Fornstedt, Torgny
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Samuelsson, Jörgen
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Edström, Lena
    A systematic investigation of deformations of overloaded peak shapes of basic compounds in reversed phase chromatography2010Conference paper (Refereed)
  • 228.
    Fornstedt, Torgny
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Samuelsson, Jörgen
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Edström, Lena
    Deformations of overloaded bands under pH-stable conditions in reversed phase chromatography2011In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1218, no 15, p. 1966-1973Article in journal (Refereed)
    Abstract

    It has recently been demonstrated, using mathematical models, how peculiar overloaded band profiles of basic compounds are due to the local pH in the column when using low capacity buffers. In this study, overloaded peak shapes resulting after injection of carefully pH matched samples close to the pKa of the chosen solute are investigated primarily on two columns; one hybrid silica C18 column (Kromasil Eternity) and one purely polymeric column (PLRP-S), the latter lacking C18 ligands. It was found that distorted peaks of the basic test compound appear even though there is no difference in pH between the injected sample solution and the eluent; the previous explanation to why these effects occur is based on a pH mismatch. Thus, the unusual band shapes are not due to an initial pH difference. Furthermore, it was observed that the effect does not appear on polymeric columns without C18 ligands, but only on columns with C18 ligands, independently of the base matrix (silica, hybrid silica, polymeric)

  • 229.
    Fornstedt, Torgny
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Samuelsson, Jörgen
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Edström, Lena
    Peak Deformations of Basic Compounds in Reversed Phase Chromatography Under pH-stable conditions2010Conference paper (Refereed)
  • 230.
    Fornstedt, Torgny
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Samuelsson, Jörgen
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Edström, Lena
    Department of Physical and Analytical Chemistry, Uppsala University.
    Forssén, Patrik
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Injection profiles in liquid chromatography. I. A fundamental investigation2010In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1217, no 26, p. 4306-4312Article in journal (Refereed)
    Abstract [en]

    This is a fundamental experimental and theoretical investigation on how the injection profile depends on important experimental parameters. The experiments revealed that the injection profile becomes more eroded with increased (i) flow rate, (ii) viscosity of the eluent, (iii) size of the solute, (iv) injection volume and (v) inner diameter of the injection loop capillary. These observations cannot be explained by a 1D-convection-diffusion equation, since it does not account for the effect of the parabolic flow and the radial diffusion on the elution profile. Therefore, the 1D model was expanded into a 2D-convection-diffusion equation with cylindrical coordinates, a model that showed a good agreement with the experimental injection profiles dependence on the experimental parameters. For a deeper understanding of the appearance of the injection profile the 2D model is excellent, but to account for injection profiles of various injection volumes and flow rates in preparative and process-chromatography using computer-optimizations, a more pragmatic approach must be developed. The result will give guidelines about how to reduce the extra-column variance caused by the injection profile. This is important both for preparative and analytical chromatography; in particular for modern analytical systems using short and narrow columns

  • 231.
    Fornstedt, Torgny
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Samuelsson, Jörgen
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Forssén, Patrik
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Transposing Advanced LC Theory to Modern Biosensors - Estimation of Bio-Molecular Interactions and Drug-Protein Interactions by Transposing LC-Theory to Biosensors2012Conference paper (Other academic)
    Abstract [en]

    This poster will also serves as background information to the lecture “Deeper insights in retention mechanisms and molecular interactions through improved methods for generating and evaluation adsorption data”. Adsorption isotherms are essential in order to understand the interaction between small molecules such as pharmaceutical compounds and larger biomolecules. An adsorption isotherm describes the relationship of free substance in a solution with adsorbed substance to a surface, at a specific and constant temperature. Adsorption isotherms could be determined using several different method, all method have their pros and cons. In this study we are using two modern but principally different biosensors to determine interactions: quarts micro-balance (QCM) and Surface plasmon resonance (SPR) to determine interactions. For a long time adsorption isotherms has been determined solely by the chromatographic community. In this study we will present transformation of adsorption analysis tools from chromatography to biosensors, especially calculation of adsorption energy distribution prior adsorption model fit. We will also discuss how the experiments should be conducted. Guidelines will be given for the experimental setup and for when the chromatographic or a biosensor technique is to be preferred. This is a contribution from the Fundamental Separation Science Group in Karlstad www.separationscience.se

  • 232.
    Fornstedt, Torgny
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Samuelsson, Jörgen
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Undin, Torgny
    Petersson, Patrik
    Törncrona, Anders
    Ekeroth,, Johan
    A New Approach for Characterization of Adsorption Processes in Analytical Chromatographic Systems by Combining Linear and Nonlinear Methods2010Conference paper (Refereed)
  • 233.
    Fornstedt, Torgny
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Samuelsson, Jörgen
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Undin, Torgny
    Törncrona,, Anders
    Deeper characterization of new hybrid silica phases - A combined experimental and theoretical approach2010Conference paper (Refereed)
  • 234.
    Forssén, Patrik
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Edström, Lena
    Uppsala University.
    Lämmerhofer, Michael
    Institute of Pharmaceutical Sciences, University of Tübingen, Germany.
    Samuelsson, Jörgen
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Karlsson, Anders
    Department of Molecular Biology, Göteborg University .
    Lindner, Wolfgang
    Department of Analytical Chemistry, University of Vienna, Austria.
    Fornstedt, Torgny
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences. Uppsalas universitet.
    Optimization strategies accounting for the additive in preparative chiral liquid chromatography2012In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1269, p. 279-286, article id SIArticle in journal (Refereed)
    Abstract [en]

    This study is an in-depth investigation on how numerical optimization strategies that also account forthe additive type and concentration, in preparative batch chromatography, should be performed. As amodel system, the separation of Z-(R,S)-2-aminobutyric acid enantiomers on a quinidine carbamate-based chiral stationary phase in polar organic mode was used, with different additive strengths of aceticacid or hexanoic acid in methanol. The inverse method was used to determine the competitive adsorp-tion isotherm parameters for the enantiomers and the additives. Three different optimization strategieswere examined: (1) injection volume optimization, (2) optimization of injection volume and additiveconcentration, and (3) full optimization including injection volume, additive concentration, sample con-centration and flow rate. It was concluded that (i) it is important to incorporate the additive concentrationin the optimization procedure to achieve the highest production rates, (ii) the full optimization strategyhad the overall best results, and (iii) the selection of additive is very important (here acetic acid additivewas superior to the hexanoic acid additive). By including the additive in the adsorption model and inthe numerical optimization it is not only possible to achieve higher production rates but also to properlyselect the additive that is most advantageous for the specific separation problem.

  • 235.
    Forssén, Patrik
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Edström, Lena
    Uppsala University.
    Samuelsson, Jörgen
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Fornstedt, Torgny
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Injection profiles in liquid chromatography II: Predicting accurate injection-profiles for computer-assisted preparative optimizations2011In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1218, no 34, p. 5794-5800Article in journal (Refereed)
    Abstract [en]

    In computer assisted optimization of liquid chromatography it has been known for some years that it is important to use experimental injection profiles, instead of rectangular ones, in order to calculate accurate elution bands. However, the incorrectly assumed rectangular profiles are still mostly used especially in numerical optimizations. The reason is that the acquisition of injection profiles, for each injection volume and each flow rate considered in a computer-assisted optimization requires a too large number of experiments. In this article a new function is proposed, which enables highly accurate predictions of the injection profiles and thus more accurate computer optimizations, with a minimum experimental effort. To model the injection profiles for any injection volume at a constant flow rate, as few as two experimental injection profiles are required. If it is desirable to also take the effect of flow rate on the injection profiles into account, then just two additional experiments are required. The overlap between fitted and experimental injection profiles at different flow rates and different injection volumes were excellent, more than 90%, using experimental injection profiles from just four different injection volumes at two different flow rates. Moreover, it was demonstrated that the flow rate has a minor influence on the injection profiles and that the injection volume is the main parameter that needs to be accounted for.

  • 236.
    Forssén, Patrik
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Samuelsson, Jörgen
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Fornstedt, Torgny
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Relative importance of column and adsorption parameters on the productivity in preparative liquid chromatography. I: Investigation of a chiral separation system2013In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1299, p. 58-63Article in journal (Refereed)
    Abstract [en]

    Starting out from an experimental chiral separation system we have used computer simulations for a systematic investigation on how the maximum productivity depends on changes in column length, packing particle size, column efficiency, back pressure, sample concentration/solubility, selectivity, retention factor of the first eluting component and monolayer saturation capacity. The study was performed by changing these parameters, one at a time, and then calculating the corresponding change in maximum productivity. The three most important parameters for maximum production rate was found to be (i) the selectivity (ii) the retention factor of the first eluting component and (iii) the column length. Surprisingly, the column efficiency and sample concentration/solubility were of minor importance. These findings can be used as rough guidelines for column selection, e.g. a low-efficiency column are more likely perform better, in terms of productivity, than a high-efficiency column that have higher retention factor for the first eluting component.

  • 237.
    Furster, Catrin
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Health Sciences. Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Hallerback, Maria Unenge
    Department of Psychiatry, County Council of Värmland, Värmland, Sweden; Child and Adolescent Psychiatry, Central Hospital, S-651 85, Karlstad, Sweden .
    The use of melatonin in Swedish children and adolescents-a register-based study according to age, gender, and medication of ADHD2015In: European Journal of Clinical Pharmacology, ISSN 0031-6970, E-ISSN 1432-1041, Vol. 71, no 7, p. 877-881Article in journal (Refereed)
    Abstract [en]

    The use of melatonin is increasing among Swedish children and adolescents despite deficient knowledge of usage in these groups. The aim of this study was to investigate the use of melatonin in Swedish children and adolescents according to age, gender, dosage, treatment duration, and use of attention deficit hyperactivity disorder (ADHD) medication. Data from the Swedish Prescribed Drug Register was analyzed for children and adolescents 0-19 years old in Sweden during 2006-2013. The number of new users of melatonin in 2013 was 4296 and 3093 among boys and girls, respectively. Girls started treatment with melatonin in older ages compared to boys. Regular users of melatonin were most common among boys 10-14 years. The average defined daily dose (DDD) per regular user was decreasing from 2.4 DDD in 2006 to 1.7 DDD in 2012. Among girls and boys 5-9 years who were regular users in 2010, over 40 and 50 %, respectively, were still regular users in 2013. In the age group 15-19 years, only about 10 % were still regular users in 2013. In 2013, 65 % of boys and 49 % of girls, using melatonin regularly, also used medication for ADHD regularly. More Swedish boys than girls used melatonin regularly. The boys started treatment earlier and more often combined regular use of melatonin with regular use of medication for ADHD. This indicates that girls and boys partly are prescribed melatonin for different reasons. About half of the younger children stayed on melatonin treatment for several years, while 90 % of adolescents (15-19 years) concluded their treatment.

  • 238. Gehlen, MH
    et al.
    De Schryver, FC
    Bhaskar Dutt, G
    van Stam, Jan
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences. Karlstad University, Faculty of Technology and Science, Materials Science.
    Boens, N
    Van der Auweraer, M
    Intermicellar Mobility of Probe and Quencher in Reverse Micelles Studied by Fluorescence Quenching1995In: J. Phys. Chem., 1995, 99, 14407-14413Article in journal (Refereed)
  • 239. Gensch, T
    et al.
    Hofkens, J
    van Stam, Jan
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences. Karlstad University, Faculty of Technology and Science, Materials Science.
    Faes, H
    Creutz, S
    Tsuda, K
    Jérôme, R
    Masuhara, H
    De Schryver, FC
    Transmission and confocal fluorescence microscopy, and time-resolved fluorescence spectroscopy combined with a laser trap: Investigation of optically trapped block copolymer micelles1998In: J. Phys. Chem. B, 1998, 102, 8440-8451Article in journal (Refereed)
  • 240.
    Gericke, Niklas
    et al.
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Drechsler, Michal
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Are Biology and Chemistry Models used from a 'Nature of Science' Perspective?: An analysis of Swedish Textbooks2006Conference paper (Refereed)
  • 241. Hao, X-Y
    et al.
    Castro, VM
    Berg, J
    Sundström, Birgitta
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Mannervik, B
    Isoenzyme-specific quantitative immunoassays for cytosolic glutathione transferases and measurement of the enzymes in blood plasma from cancer patients and in tumor cell lines1994In: Biochim Biophys Acta 1994;1225:223-230Article in journal (Refereed)
  • 242. Heegaard, N.H.H.
    et al.
    He, X.
    Blomberg, Lars G
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Binding of Ca2+, Mg2+ and heparin by human serum amyloid P component in affinity capillary electrophoresis2006In: Electrophoresis, 27 (2006) 2609-2615Article in journal (Refereed)
  • 243.
    Hegazy, Mohamed-Elamir F.
    et al.
    Natl Res Ctr, Pharmaceut Res Lab, Ctr Excellence Adv Sci, Cairo 12622, Egypt.;Natl Res Ctr, Chem Med Plants Dept, Giza 12622, Egypt..
    El-Beih, Ahmed A.
    Natl Res Ctr, Pharmaceut Res Lab, Ctr Excellence Adv Sci, Cairo 12622, Egypt.;Natl Res Ctr, Chem Nat & Microbial Prod Dept, Giza 12622, Egypt..
    Moustafa, Alaa Y.
    Sohag Univ, Dept Zool, Fac Sci, Sohag, Egypt..
    Hamdy, Abdelhamed A.
    Natl Res Ctr, Chem Nat & Microbial Prod Dept, Giza 12622, Egypt..
    Alhammady, Montaser A.
    Natl Inst Oceanog & Fisheries, Red Sea Branch, Hurghada, Egypt..
    Selim, Rehab M.
    Natl Res Ctr, Chem Nat & Microbial Prod Dept, Giza 12622, Egypt..
    Abdel-Rehim, Mohamed
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences. Natl Res Ctr, Pharmaceut Res Lab, Ctr Excellence Adv Sci, Cairo 12622, Egypt.;Karlstad Univ, Dept Chem & Biomed Sci, Fac Sci & Technol, SE-65188 Karlstad, Sweden.;Astra Zeneca, R&D, Dept Clin Pharmacol, S-15185 Sodertalje, Sweden.;Astra Zeneca, R&D, DMPK, S-15185 Sodertalje, Sweden..
    Pare, Paul W.
    Texas Tech Univ, Dept Chem & Biochem, Lubbock, TX 79409 USA..
    Cytotoxic Cembranoids from the Red Sea Soft Coral Sarcophyton glaucum2011In: Natural Product Communications, ISSN 1934-578X, E-ISSN 1555-9475, Vol. 6, no 12, p. 1809-1812Article in journal (Refereed)
    Abstract [en]

    One new cembrane diterpene, 2R,7R,8R-dihydroxydeepoxysarcophine (1), together with three known compounds, 7 alpha,8 beta-dihydroxydecpoxysarcophine (2), 7 beta-acetoxy-8 alpha-hydroxydeepoxysarcophine (3), and sarcophine (4), have been isolated from the Red Sea soft coral Sarcophyton glaucum. Their structures were determined using 1D and 2D NMR spectroscopy. 7 beta-Acetoxy-8 alpha-hydroxydeepoxysarcophine (3) exhibits cytotoxic activity against HepG2, HCT-116, and HeLa cells with IC(50) values of 3.6, 2.3, and 6.7 mu g/mL, respectively.

  • 244.
    Heidkamp, Hannah
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Carlsson, Gunilla
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    van Stam, Jan
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Polymer film formation studied with fluorescence microscopy and AFM2010In: Molecular Processes at Solid Surfaces: 10th Annual Surface and Colloid Symposium, 2010, p. 49-Conference paper (Refereed)
    Abstract [en]

    Thin polymer films are used in many applications such as paint, paper coatings and electronic devices. For these applications, it is important to have knowledge about the film formation process, since it affect the film morphology and the morphology is important for the applications.One method for studying film formation in situ is fluorescence microscopy. By labeling a target molecule or particle with a fluorophore, the targets movements can be traced as the solvent evaporates [1-3]. If information gained from studies of particle movements during film formation and wet state behavior are combined, information about the film formation process can be obtained. Examination of the final film surfaces with regular light microscopy and AFM gives additional information about the film formation.These methods have been used for studying the formation of negatively charged latex films. It was shown that the films are greatly affected by adding positively charged surfactants [4-5]. Since latex is a water-based system it has relatively long drying times. Systems based on high-vapor pressure organic solvents have much shorter drying times and the film formation occurs under non-equilibrium conditions. This results in incomplete phase separation, which in turn gives microstructures in the film. These microstructures are of great interest since they affect the properties of the film and its function [6-7]. Our aim is to develop the methods used for latex studies in order to be able to apply them to study film formation of polymer blends used for photovoltaic applications. The goal is to get more knowledge about the film forming process and a deeper understanding about the mechanisms behind the formation of microstructures.[1] Carlsson G., Warszynski P., van Stam J., J. Colloid Interface Sci., 2003, 267, 500-508[2] Carlsson G., van Stam J., Nord. Pulp Pap. Res. J., 2005, 20, 192-199[3] Carlsson G., Järnström L., van Stam J., J. Colloid Interface Sci., 2006, 298, 162-171[4] Heidkamp H., Master thesis, Karlstad University 2009.[5] Paakkonen, J., Master thesis, Karlstad University 2010.[6] Björström C.M., Magnusson K.O., Moons E., Synth. Metals, 2005, 152, 109-112[7] Moons E., J. Phys.: Condens. Matter, 2002, 14, 12235-12260

  • 245.
    Heidkamp, Hannah
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences. Karlstad University, Faculty of Technology and Science, Materials Science.
    Carlsson, Gunilla
    Karlstad University, Faculty of Technology and Science, Paper Surface Centre. Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences. Karlstad University, Faculty of Technology and Science, Materials Science.
    van Stam, Jan
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences. Karlstad University, Faculty of Technology and Science, Materials Science.
    Latex particle behavior studied in the wet state with fluorescence microscopy2010Conference paper (Refereed)
    Abstract

    Dispersions of latex are often used as model systems due to the well known properties of the latex particles. They can be made with a monodisperse distribution, different extent of cross linking and different surface charges. The behavior of latex particles in the wet state is important for both film formation and understanding what happens in the system when different additives are introduced. Latex is used in many different blends and one common additive is surfactants, both for stabilization during manufacturing and for adjusting the system features in different applications. A suitable method for studying latex dispersions in wet state is fluorescence microscopy. By adding latex particles with similar size and charge, marked with a fluorophore, particle movements can be followed even if the particle radius is below microscope resolution limit. This can be used for studying particle behavior in dispersions with different additives, in order to see how the additives affect the latex particles.



    By measuring the latex particles displacement, diffusion coefficients can be determined. This has been successfully used for both high and low latex volume fractions [1-3]. Since surfactants are a common additive, the focus in our studies lies on interactions between surfactants and negatively charged latex. When DoTAB (dodecyl trimethyl ammonium bromide), a cationic surfactant, is added to the latex dispersion, an interesting behavior can be seen. Both diffusion coefficients and conductivity measurements show that at a certain concentration, when DoTAB has neutralized the latex particles, aggregates are formed. When the DoTAB concentration is raised even more, the aggregates dissolve. Light scattering measurements give the same indications.



    Combined with other studies, such as film formation, the particle behavior gives important information about what happens in the system when different concentration of both latex and additives are used.



    [1] Carlsson G., Warszynski P. and van Stam J., J. Colloid Interface Sci., 2003, 267, 500-508 [2] Carlsson G., Järnström L. and van Stam J., J. Colloid Interface Sci., 2006, 298, 162-171

    [3] Carlsson G. and van Stam J., Nord. Pulp Pap. Res. J., 2005, 20, 192-199

  • 246.
    Heidkamp, Hannah
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Rogowski, Rafal
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Dzwilewski, Andrzej
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    van Stam, Jan
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Carlsson, Gunilla
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Morphology of polymer blends in films made by dip-coating2011Conference paper (Refereed)
    Abstract [en]

    Thin spincoated polymer films are used in various applications and there has been anincreasing demand to understand and get precise control over the film formation process. One of the most exciting applications is organic solar cells which have an active layer made of a polymer based blend. The film morphology has a strong effect on the efficiency of solar cells and therefore it is crucial to understand the film formation process in order to tailor thedesired morphology [1].

    In this study we are combining and comparing results from three different deposition processes: drop-casting, sphere-on-flat arrangement and dip-coating. We are using dip-coating to produce thin films of polymer blends with different morphologies under controlled conditions. The main goal is to gain a deeper insight into the processes that occur while solvent evaporates and to understand why certain structures are formed.

    Drop-casting allows for little control of the structure formation. In the sphere-on-flat arrangement a droplet of a solution is constrained between a half-sphere and the substrate, which provides more controllable conditions for the deposition process. For more precise control, dip-coating can be used, where a substrate is withdrawn from a solution at a constant speed.

    In this study we have used the polymer poly(3-hexylthiophene) (P3HT) and the fullerene derivative [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) dissolved in toluene. These components are the model system for studies on organic solar cells [1]. The dip-coated films show a wide variety of morphologies depending on the coating speed. This dependence can be rationalized by the different mechanisms occurring at low and high speeds: At low speeds, evaporation is dominant, [2] resulting in well ordered patterns. At high speeds, viscous forces become dominant, [2] yielding optically homogeneous films.

    [1] G. Dennler, M. C. Scharber, C. J. Brabec, Adv. Mat. 21, 1323-1338 (2009)

    [2] R. Z. Rogowski and A. A. Darhuber, Langmuir 26, 11485-93 (2010)

  • 247.
    Heidkamp, Hannah
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    van Stam, Jan
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Carlsson, Gunilla
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Dzwilewski, Andrzej
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Rogowski, Rafal
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Morphology of P3HT and PCBM blends in thin films obtained with different deposition methods2011Conference paper (Refereed)
    Abstract [en]

    Patterns and structures, formed when a semiconducting polymer blend in solution is subject to controlled evaporation, have been of great interest due to their influence on the performance of organic devices. By controlling the processes of pattern formation, function properties of organic semiconductor structures can be tailored, allowing for facile manufacturing of the active layers in organic devices, e.g. solar cells.

    By analyzing the morphologies of polymer blends resulting from different deposition methods, a deeper insight into the pattern formation process can be acquired. In this study, we have analyzed the morphology of blends of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) formed upon solvent evaporation. We used the following deposition methods: dip-coating, droplet evaporation within a constrained geometry and drop-casting. Dip-coated films revealed various types of morphology depending on the coating speed. At low coating speeds, where evaporation is the dominant factor, well-ordered patterns were obtained. When increasing the coating speed, viscous forces become dominant over evaporation yielding optically homogenous films [2]. Morphologically similar structures to those observed at low coating speeds, were also obtained with spatially constrained droplets. The blend morphologies were analyzed with polarized, fluorescence and atomic force microscopy [1].

    References:

    [1] C. M. Björström Svanström, J. Rysz, A. Bernasik, A. Budkowski, F. Zhang, O. Inganäs, M. R. Andersson, K. O. Magnusson, J. J. Benson-Smith, J. Nelson, and E. Moons, Adv. Mat. 21, 4398-4403 (2009)

    [2] R. Z. Rogowski and A. A. Darhuber, Langmuir 26, 11485-93 (2010)

  • 248.
    Heidkamp, Hannah
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    van Stam, Jan
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Carlsson, Gunilla
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Rogowski, Rafal
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Morphology of PCBM and P3HT blends in films made by dip-coating on homogeneous and chemically patterned surfaces,2011Conference paper (Refereed)
  • 249.
    Hellberg Lindqvist, Miriam
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Johansson, Nicklas
    Nilsson, Thomas
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Rova, Maria
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Expression of Chlorite Dismutase and Chlorate Reductase in the Prescence of Oxygen and/or Chlorate as the Terminal Electron Acceptor in Ideonella dechloratans2012In: Applied and Environmental Microbiology, ISSN 0099-2240, E-ISSN 1098-5336, Vol. 78, no 12, p. 4380-4385Article in journal (Refereed)
    Abstract [en]

    The ability of microorganisms to perform dissimilatory (per)chlorate reduction is, for most species, known to be oxygen sensitive. Consequently, bioremediation processes for the removal of oxochlorates will be disturbed if oxygen is present. We measured the expression of chlorite dismutase and chlorate reductase in the presence of different terminal electron acceptors in the chlorate reducer Ideonella dechloratans. Enzyme activity assays and mRNA analyses by real-time quantitative reverse transcription (qRT)-PCR were performed on cell extracts from cells grown aerobically with and without chlorate and on cells grown anaerobically in the presence of chlorate. Our results showed that both chlorite dismutase and chlorate reductase are expressed during aerobic growth. However, transfer to anaerobic conditions with chlorate resulted in significantly enhanced enzyme activities and mRNA levels for both enzymes. Absence of oxygen was necessary for the induction to occur, since chlorate addition under aerobic conditions produced neither increased enzyme activities nor higher relative levels of mRNA. For chlorite dismutase, the observed increase in activity was on the same order of magnitude as the increase in the relative mRNA level, indicating gene regulation at the transcriptional level. However, chlorate reductase showed about 200 times higher enzyme activity in anaerobically induced cells, whereas the increase in mRNA was only about 10-fold, suggesting additional mechanisms influence the enzyme activity.

  • 250.
    Hellberg Lindqvist, Miriam
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Nilsson, Thomas
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Rova, Maria
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Expression of chlorate reductase and chlorite dismutase in the chlorate-respiring bacterium Ideonella dechloratans2012Conference paper (Other academic)
2345678 201 - 250 of 412
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf