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  • 1.
    Abbaszad Rafi, Abdolrahim
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. Azarbaijan Shahid Madani University, Tabriz, Iran.
    Hamidi, N.
    Azarbaijan Shahid Madani University, Tabriz, Iran.
    Bashir-Hashemi, A.
    University of Alabama, Tuscaloosa, AL, United States.
    Mahkam, M.
    Azarbaijan Shahid Madani University, Tabriz, Iran.
    Photo-Switchable Nanomechanical Systems Comprising a Nanocontainer (Montmorillonite) and Light-Driven Molecular Jack (Azobenzene-Imidazolium Ionic Liquids) as Drug Delivery Systems; Synthesis, Characterization, and in Vitro Release Studies2018In: ACS Biomaterials Science and Engineering, ISSN 2373-9878, Vol. 4, no 1, p. 184-192Article in journal (Refereed)
    Abstract [en]

    In this work, photoresponsive nanomechanical systems were prepared through the intercalation of positively charged photoswitching molecular jacks (azobenzene ionic liquids, Azo-ILs) within montmorillonite (MMT) layers (MMT@Azo-ILs). The study shows that MMT@Azo-ILs are photosensitive and the synthesized molecular jacks could change the basal distances of MMT layers upon UV irradiation. These changes come from changes in the structure and geometry of Azo molecules (i.e., cis-trans isomerization) between clay layers upon UV irradiation. The prepared photoresponsive nanomechanical systems were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), thermogravimetric analysis (TGA), energy-dispersive X-ray spectroscopy (EDX), field-emission scanning electron microscope (FE-SEM). Moreover, the in vitro release studies were performed in different conditions (upon UV irradiation and darkness) in pH 5.8 at 34 ± 1 °C, and it was found that the release rates from drug loaded MMT@Azo-ILs were higher upon UV irradiation in comparison with the release rates in darkness. According to the release studies, the prepared photoresponsive carriers might be considered as an excellent potential candidate in order to formulate smart sunscreens. © 2017 American Chemical Society.

  • 2.
    Afewerki, Samson
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Alimohammadzadeh, Rana
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Henshaw Osong, Sinke
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Tai, Cheuk-Wai
    The Arrhenius Laboratory, Stockholm University.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Córdova, Armando
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Eco-friendly design for scalable direct fabrication of nanocelluloseManuscript (preprint) (Other academic)
  • 3.
    Afewerki, Samson
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Cordova, Armando
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Cooperative Lewis Acids and Aminocatalysis2017In: Chiral Lewis Acids in Organic Synthesis / [ed] J. Mlynarski, Wiley-Blackwell , 2017, p. 345-374Chapter in book (Refereed)
    Abstract [en]

    This chapter describes the cooperative strategy of combining metal catalyst activation with aminocatalysis, with a focus on the metal acting as a Lewis acid catalyst. It gives examples where the metal catalyst promotes the reactivity of different substrates by the formation of reactive intermediates. These intermediates can act either as electrophiles or nucleophiles, which in turn can couple with nucleophilic enamine or electrophilic iminium intermediates formed between the carbonyl compounds and aminocatalyst. The chemical transformation ensues via the merging of the enamine and π‐allyl‐Pd complex via asymmetric counteranion‐direct catalysis (ACDC). Subsequently, several groups reported different co‐catalytic systems and chemical strategies for the α‐allylic alkylation of aldehydes and ketones. Cordova and coworkers reported the first example where iminium activation catalysis is combined with metal catalyst activation cooperatively. The stratagem was demonstrated for the catalytic enantioselective conjugate silyl addition to α,β‐unsaturated aldehydes.

  • 4.
    Alves, Luis
    et al.
    CQC, University of Coimbra, Portugal.
    Lindman, Björn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. CQC, University of Coimbra, Portugal; Lund University.
    Klotz, Björn
    BASF Personal Care and Nutrition GmbH, Düsseldorf, Germany.
    Böttcher, Axel
    BASF Personal Care and Nutrition GmbH, Düsseldorf, Germany.
    Haake, Hans-Martin
    BASF Personal Care and Nutrition GmbH, Düsseldorf, Germany.
    Antunes, Filipe E.
    CQC, University of Coimbra, Portugal.
    On the rheology of mixed systems of hydrophobically modified polyacrylate microgels and surfactants: Role of the surfactant architecture2018In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 513, p. 489-496Article in journal (Refereed)
    Abstract [en]

    Hypothesis The rheological control of suspensions is of key interest in the formulation design. A chemically cross-linked hydrophobically modified poly(acrylic acid) (HMCL-PAA), used as rheology modifier, is pH sensitive and shows swelling behavior above a critical pH due to the ionization of the acrylic acid groups. At low pH, HMCL-PAA suspensions are liquid and turbid. The binding of surfactants to HMCL-PAA, at low pH conditions, can result in significant changes on rheology and transparency of the polymeric suspensions, due to the swelling of the microgel particles. Experiments The influence of surfactants addition on the rheological properties and transparency of HMCL-PAA suspensions was determined. A systematic study was performed using different types of surfactants (ionic, non-ionic and zwitterionic). Findings The gelation efficiency of HMCL-PAA suspensions at low pH is strongly dependent on surfactant architecture: ionic surfactants are found to be much more efficient than non-ionic or zwitterionic surfactants. Ionic surfactants lead to a liquid-to-gel transition accompanied by an increase of transparency of the suspensions. Among the ionic surfactants, anionics show stronger interactions with the polymer. Also the surfactant hydrophobicity is relevant; the more hydrophobic the surfactant, the stronger is the binding to the polymer and thus the larger the particle swelling. 

  • 5.
    Alves, Luis
    et al.
    Univ Coimbra, Dept Chem, P-3004535 Coimbra, Portugal..
    Medronho, Bruno
    Univ Algarve, Fac Sci & Technol MEDITBIO, Campus Gambelas,Ed 8, P-8005139 Faro, Portugal..
    Antunes, Filipe E.
    Univ Coimbra, Dept Chem, P-3004535 Coimbra, Portugal..
    Topgaard, Daniel
    Lund Univ, Ctr Chem & Chem Engn, Dept Chem, Div Phys Chem, S-22100 Lund, Sweden..
    Lindman, Björn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. Nanyang Technol Univ, Mat Sci & Engn, Singapore 639798, Singapore.
    Dissolution state of cellulose in aqueous systems. 1. Alkaline solvents2016In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 23, no 1, p. 247-258Article in journal (Refereed)
    Abstract [en]

    The understanding of the state of dissolution of cellulose in a certain solvent is a critical step forward in the development of new efficient solvent systems for cellulose. Nevertheless, obtaining such information is not trivial. Recently, polarization transfer solid-state NMR (PTssNMR) was shown to be a very promising technique regarding an efficient and robust characterization of the solution state of cellulose. In the present study, combining PTssNMR, microscopic techniques and X-ray diffraction, a set of alkaline aqueous systems are investigated. The addition of specific additives, such as urea or thiourea, to aqueous NaOH based systems as well as the use of an amphiphilic organic cation, is found to have pronounced effects on the dissolution efficiency of cellulose. Additionally, the characteristics of the regenerated material are strongly dependent on the dissolution system; typically less crystalline materials, presenting smoother morphologies, are obtained when amphiphilic solvents or additives are used.

  • 6.
    Alves, Luis
    et al.
    Univ Coimbra, Dept Chem, P-3004535 Coimbra, Portugal..
    Medronho, Bruno
    Univ Algarve, Fac Sci & Technol MEDITBIO, Campus Gambelas,Ed 8, P-8005139 Faro, Portugal..
    Antunes, Filipe E.
    Univ Coimbra, Dept Chem, P-3004535 Coimbra, Portugal..
    Topgaard, Daniel
    Lund Univ, Ctr Chem & Chem Engn, Dept Chem, Div Phys Chem, SE-22100 Lund, Sweden..
    Lindman, Björn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. Nanyang Technol Univ, Mat Sci & Engn, Singapore 639798, Singapore.
    Dissolution state of cellulose in aqueous systems. 2. Acidic solvents2016In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 151, p. 707-715Article in journal (Refereed)
    Abstract [en]

    Cellulose is insoluble in water but can be dissolved in strong acidic or alkaline conditions. How well dissolved cellulose is in solution and how it organizes are key questions often neglected in literature. The typical low pH required for dissolving cellulose in acidic solvents limits the use of typical characterization techniques. In this respect, Polarization Transfer Solid State NMR (PT ssNMR) emerges as a reliable alternative. In this work, combining PT ssNMR, microscopic techniques and X-ray diffraction, a set of different acidic systems (phosphoric acid/water, sulfuric acid/glycerol and zinc chloride/water) is investigated. The studied solvent systems are capable to efficiently dissolve cellulose, although degradation occurs to some extent. PT ssNMR is capable to identify the liquid and solid fractions of cellulose, the degradation products and it is also sensitive to gelation. The materials regenerated from the acidic dopes were found to be highly sensitive to the solvent system and to the presence of amphiphilic additives in solution.

  • 7. Amenitsch, Hans
    et al.
    Edlund, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Khan, Ali
    Marques, Eduardo
    La Mesa, Camilo
    Bile Salts Form Lyotropic Liquid Crystals2003In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 213, no 1, p. 79-92Article in journal (Refereed)
    Abstract [en]

    A reinvestigation of the phase diagrams relative to some conjugated and non-conjugated bile salts in water has demonstrated the formation of lyotropic liquid crystalline phases, in contradiction with generally accepted statements. The phase behaviour is complex and the phase diagrams are unusual, compared to most surfactants and lipids. In particular, coexistence of liquid crystalline phases with crystals has been observed. The formation of liquid crystalline phases requires very long equilibration times and the thermal stability of the lyotropic phases is moderate. The observed structure is tentatively assumed to be of the reverse hexagonal type. Structural relations with currently accepted models for the organisation of bile salts into micelles and solid form have been found.

  • 8.
    Andersson, J
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Wågberg, Lars
    KTHB.
    Ageing of Flexographic Printed Model Cellulose Surfaces and Determination of the Mechanisms Behind Ageing2009In: Pulp & paper Canada, ISSN 0316-4004, Vol. 110, no 7-8, p. 34-38Article in journal (Refereed)
    Abstract [en]

    The influence of storage conditions on the ink detachment efficiency of

    water-based flexographic ink printed onto model cellulose surfaces and

    handsheets was investigated. It was shown that UV light, elevated

    temperatures, longer storage time, increasing surface roughness, and

    increasing surface hydrophobicity all had a negative effect on ink

    detachment. It was also shown that the ink's chemical and structural

    characteristics changed when stored at elevated temperatures. No

    chemical or structural changes could be observed for the ink when

    stored under UV light.

     

  • 9.
    Andersson, Kerstin
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Lignin in wastewater generated by mechalical pulping: Chemical characterisation and removal by adsorption2010Licentiate thesis, comprehensive summary (Other academic)
  • 10.
    Andersson, Kerstin I
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Eriksson, Marie
    SCA R&D Ctr, SE-85121 Sundsvall, Sweden.
    Norgren, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Removal of Lignin from Wastewater Generated by Mechanical Pulping Using Activated Charcoal and Fly Ash: Adsorption Isotherms and Thermodynamics2011In: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 50, no 13, p. 7722-7732Article in journal (Refereed)
    Abstract [en]

    Lignin-related material found in wastewater from thermomechanical pulping resists conventional biological treatment, entailing the use of advanced removal methods. In this work, the use of adsorption for removing lignin-related material was investigated. Activated charcoal and fly ash were used to study the adsorption behavior of lignin and to determine the adsorption capacities of these two adsorbents. Experimental data were fitted to various isotherm equations to find the best description of the sorption systems, and the corresponding thermodynamic parameters were calculated. Fly ash exhibited good sorption properties, although its sorption capacity was inferior to that of activated charcoal. Both the Freundlich and Langmuir equations provided reasonable models of the sorption processes, and the thermodynamic parameters indicated that sorption onto activated charcoal is endothermic, whereas sorption onto fly ash appears to be exothermic. Fly ash is a low-cost material that is often available on-site and offers an interesting alternative to high-cost advanced wastewater treatment systems for removing recalcitrant organic materials.

  • 11.
    Andersson, Kerstin I.
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Eriksson, Marie
    SCA R&D Ctr, SE-85121 Sundsvall, Sweden.
    Norgren, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Removal of Lignin from Wastewater Generated by Mechanical Pulping Using Activated Charcoal and Fly Ash: Adsorption Kinetics2011In: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 50, no 13, p. 7733-7739Article in journal (Refereed)
    Abstract [en]

    The possible application of adsorption for the removal of lignin-related material found in wastewater generated by mechanical pulping was investigated. Activated charcoal and fly ash were used as adsorbents in batch experiments. The lignin-related material exhibited properties well-suited for adsorption onto both adsorbents, although the sorption capacity of activated charcoal exceeds that of fly ash. The experimental data were fitted to pseudo-first- and pseudo-second-order rate kinetic expressions, and an attempt was made to find the rate-limiting step involved in the adsorption processes. The results showed that lignin adsorption onto both activated charcoal and fly ash follows pseudo-second-order rate kinetics and that both boundary-layer diffusion and intraparticle diffusion are likely involved in the rate-limiting mechanisms. Adsorption is an interesting option in advanced wastewater treatment, and fly ash appears to be a suitable low-cost adsorbent for recalcitrant organic pollutants.

  • 12.
    Andersson, Kerstin I
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Norgren, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Eriksson, Magnus
    SCA R and D Centre, Sundsvall, Sweden.
    Lignin removal from wastewater by adsorption2009In: Proceedings - 2009 International Mechanical Pulping Conference, IMPC 2009, 2009, p. 280-285Conference paper (Refereed)
    Abstract [en]

    Lignin contributes to residual COD in wastewater after biological treatment. Available methods for removal of recalcitrant material like lignin, e.g. chemical oxidation and coagulation, are associated with heavy operational expenses. Stringent discharge requirements demand new cost-effective methods for removal of recalcitrant COD. Adsorption is an important mechanism for lignin removal in biological wastewater treatment. A study of lignin, using activated carbon as a model adsorbent, was performed to learn more about the adsorption behaviour of lignin. At the adsorbent dose 4 g/L and an initial lignin concentration of 0.5 g/L, 77% of the lignin was removed after six hours. The adsorption kinetics was found to follow the pseudo second-order rate expression and no temperature dependency could be observed in the temperature range studied.

     

     

  • 13. Andreasson, Bo
    et al.
    Forsström, Jennie
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Wågberg, Lars
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    The porous structure of pulp fibres with different yields and its influence on paper strength2003In: Cellulose, ISSN 0969-0239, Vol. 10, no 2, p. 111-123Article in journal (Refereed)
    Abstract [en]

    The porous structure of the interior of papermaking fibres is a well-known important property of the fibres. Changes of this structure will influence tensile and burst strength of paper formed from the fibres and a change in pore size of the pores within the fibre wall is also important for the ability of molecules to diffuse in and out of the fibre wall. Relevant examples of this latter effect are the removal of lignin during cooking and the addition of performance chemicals during papermaking. In this paper, pore sizes and the pore size distribution of unbleached softwood fibres have been studied. A well-characterised fibre material consisting of laboratory cooked spruce and pine pulp of various lignin contents was used. Pore size and pore size distribution were measured by studies of the relaxation behaviour of 2H in fibres saturated with 2H2O. Beside this the total and surface charge of the fibres were also measured together with strength properties of papers from unbeaten fibres. For both pulps, there is a maximum in pore radius at a yield around 46%. Calculations of fibre wall volume from water retention values and yield levels show that there is a discontinuity in pore radius as a function of the fibre wall volume around a yield of 51%. It is suggested that this discontinuity is caused by the breakdown of the hemicellulose/lignin matrix within the fibre wall at this yield level. The strength of the papers formed from the fibres shows a correlation with the surface charge of the fibres. Based on the change in surface charge with yield and the change in total charge with yield, this correlation is suggested to be due to an opening up of the external part of the fibre wall. This stresses the importance of the chemical composition and physical structure of the outer layer of the fibre wall.

  • 14.
    Andreasson, Ulrika
    et al.
    SCA Packaging Research, Sundsvall, Sweden.
    Wågberg, Lars
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Ink release from printed surfaces: new methodology and initial insights to the true mechanisms behind ink detachment2001Report (Other academic)
  • 15.
    Andres, Britta
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Dahlström, Christina
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Blomquist, Nicklas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Norgren, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Cellulose binders for electric double-layer capacitor electrodes: The influence of cellulose quality on electrical properties2018In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 141, p. 342-349Article in journal (Refereed)
    Abstract [en]

    Cellulose derivatives are widely used as binders and dispersing agents in different applications. Binders composed of cellulose are an environmentally friendly alternative to oil-based polymer binding agents. Previously, we reported the use of cellulose nanofibers (CNFs) as binders in electrodes for electric double-layer capacitors (EDLCs). In addition to good mechanical stability, we demonstrated that CNFs enhanced the electrical performance of the electrodes. However, cellulose fibers can cover a broad range of length scales, and the quality requirements from an electrode perspective have not been thoroughly investigated. To evaluate the influence of fiber quality on electrode properties, we tested seven samples with different fiber dimensions that are based on the same kraft pulp. To capture the length scale from fibers to nanofibrils, we evaluated the performance of the untreated kraft pulp, refined fibers, microfibrillated cellulose (MFC) and CNFs. Electrodes with kraft pulp or refined fibers showed the lowest electrical resistivity. The specific capacitances of all EDLCs were surprisingly similar, but slightly lower for the EDLC with CNFs. The same electrode sample with CNFs also showed a slightly higher equivalent series resistance (ESR), compared to those of the other EDLCs. Graphite dispersions with MFC showed the best dispersion stability. 

  • 16.
    Backlund, Hans-Olof
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Höglund, Hans
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Gradin, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Study of tangential forces and temperature profiles in commercial refiners2003In: 2003 International Mechanical Pulping Conference, 2003, p. 379-388Conference paper (Refereed)
  • 17.
    Batchelor, Warren J.
    et al.
    Monash University, Australia.
    Westerlind, B. S.
    SCA Graphic Research, Sundsvall.
    Hägglund, R.
    SCA Packaging Research, Sundsvall.
    Gradin, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Effect of test conditions on measured loads and displacements in zero-span testing2006In: TAPPI Journal, ISSN 0734-1415, Vol. 5, no 10, p. 3-8Article in journal (Refereed)
    Abstract [en]

    Single fiber mechanical properties play a critical role in determining sheet mechanical properties, but fiber mechanical properties are rarely measured, because of the time-consuming nature of the tests. Zero-span strength is commonly used as a measure of fiber strength, but the results can vary with the test conditions. Modeling has shown that the load displacement curves are influenced by the thickness-to-span ratio, as there is a heterogeneous stress field in the thickness direction of the sample.

    This paper presents data on the effect of grammage on the loads and displacements in zero-span tests. Clamps were designed and made for a displacement-control led load frame. These clamps can test up to 10 plies of papers with,a span length from 0 to 3 mm. For the sake of comparison, tests were made using a commercial zero-span tester, which is load controlled but limited in span length and thickness of the tested material. Both machines were found to give comparable results. Isotropic 65 g/m(2) handsheets, 36 g/m(2) aluminum foil, and 42 g/m(2) greaseproof paper were tested as functions of sheet grammage. An intrinsic zero-span strength was defined as the y-axis intercept of a plot of zero-span strength versus grammage.

    Application:This paper demonstrates that the measured zero-span strength is always less than the intrinsic zero-span strength. The results show that, for best results, the grammage of the material tested should be minimized to obtain a measured value that is as close to the intrinsic value as possible.

  • 18.
    Becher, Paul G.
    et al.
    Swedish University of Agricultural Sciences, Alnarp.
    Lebreton, Sebastien
    Swedish University of Agricultural Sciences, Alnarp.
    Wallin, Erika
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Hedenström, Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Borrero, Felipe
    Colombian Corporation of Agricultural Research, Las Palmas, Bogota, Colombia.
    Bengtsson, Marie
    Swedish University of Agricultural Sciences, Alnarp.
    Joerger, Volker
    Staatliches Weinbauinstitut, Freiburg, Germany.
    Witzgall, Peter
    Swedish University of Agricultural Sciences, Alnarp.
    The Scent of the Fly2018In: Journal of Chemical Ecology, ISSN 0098-0331, E-ISSN 1573-1561, Vol. 44, no 5, p. 431-435Article in journal (Refereed)
    Abstract [en]

    (Z)-4-undecenal (Z4-11Al) is the volatile pheromone produced by females of the vinegar fly Drosophila melanogaster. Female flies emit Z4-11Al for species-specific communication and mate-finding. A sensory panel finds that synthetic Z4-11Al has a characteristic flavour, which can be perceived even at the small amounts produced by a single female fly. Since only females produce Z4-11Al, and not males, we can reliably distinguish between single D. melanogaster males and females, according to their scent. Females release Z4-11Al at 2.4 ng/h and we readily sense 1 ng synthetic Z4-11Al in a glass of wine (0.03 nmol/L), while a tenfold concentration is perceived as a loud off-flavour. This corroborates the observation that a glass of wine is spoilt by a single D. melanogaster fly falling into it, which we here show is caused by Z4-11Al. The biological role of Z4-11Al or structurally related aldehydes in humans and the basis for this semiochemical convergence remains yet unclear. 

  • 19.
    Berg, Jan-Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Wood and fibre mechanics related to the thermomechanical pulping process2008Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The main objective of this thesis was to improve the understanding of some aspects on wood and fibre mechanics related to conditions in the thermomechanical pulping process. Another objective was to measure the power distribution between the rotating plates in a refiner.

     

    The thesis comprises the following parts:

    –A literature review aimed at describing fracture in wood and fibres as related to the thermomechanical pulping process

    –An experimental study of fracture in wood under compression, at conditions similar to those in feeding of chips into preheaters and chip refiners

    –An experimental study of the effect of impact velocity on the fracture of wood, related to conditions of fibre separation in the breaker bar zone in a chip refiner

    –A micromechanical model of the deterioration of wood fibres, related to the development of fibre properties during the intense treatment in the small gap in the refining zone

    –Measurements of the power distribution in a refiner.

     

    The fracture in wood under compression was investigated by use of acoustic emission monitoring. The wood was compressed in both lateral and longitudinal directions to predict preferred modes of deformation in order to achieve desired irreversible changes in the wood structure. It was concluded that the most efficient compression direction in this respect is longitudinal. Preferable temperature at which the compression should be carried out and specific energy input needed in order to achieve substantial changes in the wood structure were also given.

     

    The fibre separation step and specifically the effect of impact velocity on the fracture energy were studied by use of a falling weight impact tester. The fracture surfaces were also examined under a microscope. An increase in impact velocity resulted in an increase in fracture energy.

    In the thermomechanical pulping process the fibres are subjected to lateral compression, tension and shear which causes the creation of microcracks in the fibre wall. This damage reduces the fibre wall stiffness. A simplified analytical model is presented for the prediction of the stiffness degradation due to the damage state in a wood fibre, loaded in uni-axial tension or shear. The model was based on an assumed displacement field together with the minimum total potential energy theorem. For the damage development an energy criterion was employed. The model was applied to calculate the relevant stiffness coefficients as a function of the damage state. The energy consumption in order to achieve a certain damage state in a softwood fibre by uniaxial tension or shear load was also calculated. The energy consumption was found to be dependent on the microfibril angle in the middle secondary wall, the loading case, the thicknesses of the fibre cell wall layers, and conditions such as moisture content and temperature. At conditions, prevailing at the entrance of the gap between the plates in a refiner and at relative high damage states, more energy was needed to create cracks at higher microfibril angles. The energy consumption was lower for earlywood compared to latewood fibres. For low microfibril angles, the energy consumption was lower for loading in shear compared to tension for both earlywood and latewood fibres. Material parameters, such as initial damage state and specific fracture energy, were determined by fitting of input parameters to experimental data.

    Only a part of the electrical energy demand in the thermomechanical pulping process is considered to be effective in fibre separation and developing fibre properties. Therefore it is important to improve the understanding of how this energy is distributed along the refining zone.

    Investigations have been carried out in a laboratory single-disc refiner. It was found that a new developed force sensor is an effective way of measuring the power distribution within the refining zone. The collected data show that the tangential force per area and consequently also the power per unit area increased with radial position.

    The results in this thesis improve the understanding of the influence of some process parameters in thermomechanical pulping related wood and fibre mechanics such as loading rate, loading direction, moisture content and temperature to separate the fibres from the wood and to achieve desired irreversible changes in the fibre structure. Further, the thesis gives an insight of the spatial energy distribution in a refiner during thermomechanical pulping.

     

     

  • 20.
    Berg, Jan-Erik
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Sandberg, Christer
    Braviken Paper Mill, Holmen Paper, SE-60188 Norrkoping, Sweden.
    Engberg, Birgitta A.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Low-consistency refining of mechanical pulp in the light of forces on fibres2015In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 30, no 2, p. 225-229Article in journal (Refereed)
    Abstract [en]

    The aim of this investigation was to find new approaches to evaluate the performance of low-consistency refiners. Data from a paper mill producing TMP from Norway spruce was used in order to find a possible way to calculate the power split between the zones in a TwinFlo refiner. An assumption of equal amount of fibres captured between overlapping bars was found successful in order to develop equations for the power split. The equations predicted equal power in both zones at equal disc gaps. The power was found to increase approximately linearly with decreasing disc gap over the range, 0.1-0.2 mm. The power split was essential to know for calculating refining intensities expressed as specific edge load and forces on fibres in the two zones. The reduction in fibre length was about 5% at 0.17 mm disc gap or at 0.03 N forces on fibres or at 0.7 J/m specific edge load. Disc gap, forces on fibres and specific edge load was found to predict fibre shortening approximately equally upon changes in power and flow rate through the refiner.

  • 21.
    Berg, Jan-Erik
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Sandberg, Christer
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. Holmen Paper, Braviken Paper Mill, Sweden.
    Engberg, Birgitta
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    LC Refining Intensity In The Light Of Forces On Fibres2014In: International Mechanical Pulping Conference, IMPC 2014, Espoo: Paper Engineers' Association (PI) , 2014Conference paper (Refereed)
    Abstract [en]

    The aim of this investigation was to find new approaches to evaluate the performance of a full sized two-zoned low-consistency refiner i.e. a refiner with two stators and one rotor in between. Data from a paper mill producing TMP from Norway spruce was used in order to find a possible way to calculate the power split between the two zones. An assumption of equal amount of fibres captured between overlapping bars was found successful in order to develop equations for the power split. The equations predicted equal power in both zones at equal disc gaps. The power was found to correlate approximately linearly with the disc gap. The power split was essential to know for calculating refining intensity expressed as specific edge load and forces on fibres in the two zones. The reduction in fibre length was about 5% at 0.17 mm disc gap corresponding to 0.03 N force on fibres and 0.7 J/m specific edge load. Disc gap, force on fibres and specific edge load was found to predict the fibre shortening with approximately equal sufficiency upon changes in power and flow rate through the refiner.

  • 22. Berglund, P
    et al.
    Vörde, Carin
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Högberg, Hans-Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Esterification of 2-Methylalkanoic Acids Catalysed by Lipase from Candida rugosa: Enantioselectivity as a Function of Water Activity and Alcohol Chainlength1994In: Biocatalysis and Biotransformation, ISSN 1024-2422, E-ISSN 1029-2446, Vol. 9, p. 123-130Article in journal (Refereed)
  • 23.
    Bergström, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Modelling Mechanics of Fibre Network using Discrete Element Method2018Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Low-density fibre networks are a fundamental structural framework of everyday hygiene products, such as baby diapers, incontinence and feminine care products, bathroom tissue and kitchen towels. These networks are a random assembly of fibres, loosely bonded and oriented in the plane direction.

    Designing such a complex network structure for better performance, better use of materials and lower cost is a constant challenge for product designers, requiring in-depth knowledge and understanding of the structure and properties on the particle (fibre) level.

    This thesis concerns the development of a computational design platform that will generate low-density fibre networks and test their properties, seamlessly, with the aim to deepening the fundamental understanding of the micromechanics of this class of fibre networks.

    To achieve this goal, we have used a particle-based method, the Discrete Element Method (DEM), to model the fibres and fibre networks. A fibre is modelled as a series of linked beads, so that one can consider both its axial properties (stretching and bending) and transverse properties (shearing,twisting and transverse compression). For manufacturing simulations, we developed the models for depositing fibres to form a fibre network, consolidating the fibre network, compressing to make a 3D-structured network, and creating creping. For testing the end-use performance, we have developed two models and investigated the micromechanics of the fibre network in uniaxial compression in the thickness direction (ZD) and in uniaxial tension in the in-plane direction.

    In the ZD-uniaxial compression of entangled (unbonded) fibrenetworks, the compression stress exhibits a power-law relationship with density, with a threshold density. During compression, the fibre deformation mode changed from fibre bending to the transverse compression of fibre. Accordingly, the transverse properties of the fibreshad a large impact on the constitutive relation. By considering a realistic value for the transverse fibre property, we were able to predict the valuesof the exponent widely observed in the experimental literature. We havefound that the deviation of the experimental values from those predictions by the earlier theoretical studies is due to the neglect of the transverse fibre property.

    For tensile properties of bonded networks, we have investigated scaling of network strength with density and fibre–fibre bond strength. The network strength showed beautiful scaling behaviour with both density and bond strength, with exponents 1.88 and 1.08 respectively. The elastic modulus of the network, on the other hand, showed a changing exponent(from 2.16 to 1.69) with density in accordance with previous results in the literature. We have also reconfirmed that, with increasing density, the deformation mode changes from bending to stretching. The predicted results for both elastic modulus and strength agreed very well with experimental data of fibre networks of varying densities reported in the literature.

    We have developed a computational platform, based on DEM, for accurately modelling a fibre network from its manufacturing process to product properties. This is a tool that allows a versatile design of materials and products used for hygiene products, providing a promising venue for exploring the parameter space of new material and process design.

  • 24.
    Bergström, Per
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Hossain, Shakhawath
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Uesaka, Tetsu
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Scaling Behaviour of Strength of 3D-, Semi-flexible-, Cross-linked Fibre NetworkManuscript (preprint) (Other academic)
  • 25.
    Björkqvist, Olof
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Htun, Myat
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Norgren, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    FORE – Ett nytt industrikombinat baserat på mekaniska massaprocesser2010In: Svensk papperstidning, Nordisk cellulosa, ISSN 1101-766X, no 2, p. 24-25Article in journal (Other (popular science, discussion, etc.))
  • 26.
    Björkqvist, T.
    et al.
    Department of Automation Science and Engineering, Tampere University of Technology, P.O.B 692, FIN-33100 Tampere, Finland.
    Engberg, Birgitta A.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Salminen, L. I.
    VTT Technical Research Center Finland, P.O.B. 1000, FIN-02044 VTT, Finland.
    Salmi, A.
    VTT Technical Research Center Finland, P.O.B. 1000, FIN-02044 VTT, Finland.
    Towards optimal defibration: Energy reduction by fatiguing pre-treatment2012In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 27, no 2, p. 168-172Article in journal (Refereed)
    Abstract [en]

    A motive for fatiguing wood prior to defibration would be to reduce the energy consumption needed in mechanical pulping processes. Therefore, the effects of fatiguing pre-treatment were here studied on wood samples, on defibration and also on produced paper. The results indicate that pre-fatiguing changes the mechanic response of wood to be more favorable for harsh defibration which in turn is positive for the process efficiency.

  • 27. Branström, J.
    et al.
    Norgren, Sven
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Sandström, P.
    Ruel, K.
    Höglund, Hans
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Compression wood in knots and the effect on surface roughness.2005In: proceedings from IMPC 2005, 2005Conference paper (Other academic)
    Abstract [en]

    The microstructural and ultrastructural characteristics of knot wood were examined and related to paper properties. Norway spruce (Picea abies) chips were laboratory fractionated and sorted into a knot containing assortment and a non knot containing reference assortment. The proportions of compression wood in these two assortments were then assessed and the two chip assortments refined in pilot refiners. The knot containing portion was divided into wood from the upper branch, wood from the lower branch compression wood and wood surrounding the branch. Fibres from the three knotwood portions and the reference chips were extracted and measurements were made of fibre properties including fibre length, fibre width and cell wall thickness. The two chip assortments were refined in a pilot plant and the surface properties of laboratory sheets were measured. The knot containing chips had adverse effects on several paper properties. However, no clear relationship was established between surface roughness and the presence of compression wood fibres in knot wood. (6 fig, 12 ref)

  • 28. Busson, Philippe
    et al.
    Örtegren, Jonas
    Ihre, Henrik
    Gedde, Ulf W.
    Hult, Anders
    Andersson, Gunnar
    Ferroelectric Liquid Crystalline Dendrimers: Synthesis, Thermal Behavior, and Electrooptical Characterization2001In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 34, p. 1221-1229Article in journal (Refereed)
    Abstract [en]

    The preparation and characterization of a series of novel ferroelectric liquid crystalline dendrimers are presented. End-capping of 1-, 2-, and 3-generation dendrimers based on 2,2-bis- (hydroxymethyl)propionic acid with mesogens gave surface-functionalized liquid crystalline compounds with 6, 12, and 24 mesogen-containing units, respectively. 4¢¢-((R)-1-Methylheptyloxy)phenyl 4-{4¢-[10- (hydroxycarbonyl)decyloxy]phenyl}benzoate was synthesized and used as a mesogen-containing unit. The purity and structure of each compound were determined by 1H NMR spectroscopy, size exclusion chromatography, and elemental analysis. Differential scanning calorimetry and optical microscopy were used to investigate the mesomorphic properties of the mesogen-functionalized dendrimers. The materials displayed a variety of mesophases, including the smectic C* phase. All the liquid crystalline dendrimers showed ferroelectricity, and tilt angle and spontaneous polarization measurements were performed. The obtained results show that the ferroelectric properties of the materials are independent of the generation number of the dendritic scaffold.

  • 29.
    Busson, Philippe
    et al.
    KTH.
    Örtegren, Jonas
    KTH.
    Ihre, Henrik
    KTH.
    Gedde, Ulf W.
    KTH.
    Hult, Anders
    KTH.
    Andersson, Gunnar
    Chalmers University of Technology.
    Eriksson, Anders
    Linköping University.
    Lindgren, Mikael
    Linköping University.
    Preparation of Mesogen-Functionalized Dendrimers for Second-Order Nonlinear Optics2002In: Macromolecules, ISSN 0024-9297, Vol. 35, p. 1663-1671Article in journal (Refereed)
    Abstract [en]

    Liquid crystalline dendrimers with peripheral mesogen-containing units have been prepared. Multistep synthesis with several selective reactions was used in the preparation of the mesogen-containing molecules, 4¢¢-[10-(hydroxycarbonyl)decyloxy]phenyl 4-[4¢-(2-(R)-octyloxy)-3¢-nitrophenyl]benzoate and 4¢¢- [10-(hydroxycarbonyl)decyloxy]biphenyl 4-[4¢-(2-(R)-octyloxy)-3¢-nitrophenyl]benzoate. Both molecules possessed an electron-accepting nitro group placed perpendicular to the long axis of the molecules in order to enhance the nonlinear optical activity. A second generation hydroxyl functional aliphatic dendrimer based on the dihydroxy acid, 2,2-bis(hydroxymethyl)propionic acid, was used as dendritic scaffold and was subsequently functionalized with the aforementioned groups. The purity and structure of the two liquid crystalline dendrimers were determined by 1H NMR spectroscopy, size exclusion chromatography, and elemental analysis. The synthesis of both the mesogen-containing units and the liquid crystalline dendrimers is described in detail. Investigation of the liquid crystalline properties of the materials by differential scanning calorimetry and optical microscopy showed that they exhibited different mesophases, including the chiral smectic C phase. Ferroelectric switching was observed in this tilted phase, and electrooptical properties, including tilt angle and spontaneous polarization measurements, were investigated. Finally, the nonlinear optical properties of one of the materials were preliminary characterized.

  • 30. Bäckström, Marie
    et al.
    Kolar, Marie-Claude
    Htun, Myat
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Characterisation of fines from unbleached kraft pulps and their impact on sheet properties2008In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 62, no 5, p. 546-552Article in journal (Refereed)
  • 31.
    Chen, Xu
    et al.
    State Key Laboratory of Coal Combustion, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, China.
    Yang, Haiping
    State Key Laboratory of Coal Combustion, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, China.
    Chen, Yingquan
    State Key Laboratory of Coal Combustion, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, China.
    Chen, Wei
    State Key Laboratory of Coal Combustion, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, China.
    Lei, Tingzhou
    Henan Academy of Sciences Institute of Energy Co., Ltd, Zhengzhou, Henan, China.
    Zhang, Wennan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Chen, Hanping
    State Key Laboratory of Coal Combustion, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, China.
    Catalytic fast pyrolysis of biomass to produce furfural using heterogeneous catalysts2017In: Journal of Analytical and Applied Pyrolysis, ISSN 0165-2370, E-ISSN 1873-250X, Vol. 127, p. 292-298Article in journal (Refereed)
    Abstract [en]

    Furfural is a valuable chemical, the production of furfural from renewable biomass resources becomes more attractive in recent years. In this study, biomass fast pyrolysis with heterogeneous catalysts (titanium compounds (TiN, TiO2 and TiOSO4) and metal nitrides (MoN, GaN and VN)) for furfural production was investigated experimentally by means of pyrolysis-gas chromatography/mass-spectrometry (Py-GC/MS). The measurement results indicated that TiN and GaN promoted the furfural compounds production notably mainly through direct decomposition of oligosaccharides. The formation of furfural was promoted when the amount of TiN was increased, and the yield of furfural formed was about 5.5 times the size of that from non-catalytic pyrolysis when TiN/cellulose mass ratio was 4. The furfural yield decreased when the pyrolysis residence time increased from 10 to 30 s, which suggests competitive reactions (formation of 1, 6-anhydro-beta.-D-glucopyranose) against the formation of furfural. TiN, as a catalyst for fast pyrolysis towards furfural production, can be well applied to agriculture biomass residues. Comparing three biomass residues: corncob, wheat straw and cotton stalk, corncob showed higher furfural yield due to the higher holocellulose content, while wheat straw showed higher furfural selectivity. 

  • 32.
    Cuomo, Francesca
    et al.
    Univ Molise, Campobasso, Italy.
    Cofelice, Martina
    Univ Molise, Campobasso, Italy.
    Venditti, Francesco
    Univ Molise, Campobasso, Italy.
    Ceglie, Andrea
    Univ Molise, Campobasso, Italy.
    Miguel, Maria
    Coimbra Univ, Coimbra, Portugal.
    Lindman, Björn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. Lund Univ, Lund.
    Lopez, Francesco
    Univ Molise, Campobasso, Italy.
    In-vitro digestion of curcumin loaded chitosan-coated liposomes2018In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 168, p. 29-34Article in journal (Refereed)
    Abstract [en]

    Liposomes are considered a major route for encapsulation of hydrophilic and hydrophobic molecules. Chitosan coated liposomes could represent an alternative way as a carrier for delivery of drugs in human body. In this study the preparation and applicability of chitosan-coated liposomes containing curcumin as well as curcumin loaded anionic liposomes were evaluated. The applicability of the carriers was tested by means of an in vitro digestion procedure allowing for measurement of the bioaccessibility of ingested curcumin. Values of diameter, polydispersity index and surface charge for curcumin loaded anionic liposomes obtained through dynamic light scattering and zeta-potential measurements were 129 nm, 0.095 and -49 mV, respectively. After chitosan-coating, diameter and polydispersity index remain unvaried while the surface charge gets positive. Slightly higher curcumin concentrations were found after the mouth and the stomach digestion phases when curcumin was loaded in anionic liposomes. On the contrary, after the intestinal phase, a higher percentage of curcumin was found when chitosan-coated liposomes were used as carrier, both in the raw digesta and in the bile salt micellar phase. It was shown that the presence of a positively charged surface allows a better absorption of curcumin in the small intestine phase, which increases the overall curcumin bioavailability. The mechanism behind these results can be understood from the composition of different environments generated by the digestive fluids that differently interact with anionic or cationic surfaces. 

  • 33.
    Cuomo, Francesca
    et al.
    Univ Molise, Dipartimento Agr, Ambiente Alimenti DIAAA, I-86100 Campobasso, Italy.
    Lopez, Francesco
    Univ Molise, Dipartimento Agr, Ambiente Alimenti DIAAA, I-86100 Campobasso, Italy.
    Piludu, Marco
    Univ Cagliari, Dipartimento Sci Biomed, I-09042 Monserrato, CA, Italy.
    Miguel, Maria G.
    Univ Coimbra, Dept Chem, P-3004535 Coimbra, Portugal.
    Lindman, Björn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. Lund Univ, Phys Chem, S-22100 Lund, Sweden.
    Ceglie, Andrea
    Univ Molise, Dipartimento Agr, Ambiente Alimenti DIAAA, I-86100 Campobasso, Italy.
    Release of small hydrophilic molecules from polyelectrolyte capsules: Effect of the wall thickness2015In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 447, p. 211-216Article in journal (Refereed)
    Abstract [en]

    Polymer nanocapsules assembled on cationic liposomes have been built through the layer-by-layer (LbL) technique. Chitosan and alginate, two biocompatible polyelectrolytes, were used to cover the template, where the Rhodamine B was previously loaded. The multishell formed with the alternate deposition of the polyelectrolytes, according to the principles of the LbL assembly, was supposed to change the permeability of the capsule wall. The thickness of the multishell was seen increasing with the number of layers deposited through the observations with the Transmission Electron Microscope. The permeability of the capsules was studied through Rhodamine B release assays. Nanocapsules with seven layers of polyelectrolytes released the dye slowly compared to the capsules with three or five layers. The Ritger-Peppas model was applied to investigate the release mechanisms and a non-Fickian transport behavior was detected regardless of the number of layers. Values of diffusion coefficients of Rhodamine B through the capsule wall were also calculated. (C) 2014 Elsevier Inc. All rights reserved.

  • 34.
    Córdova, Armando
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Afewerki, Samson
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Alimohammadzadeh, Rana
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Sanhueza, Italo
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Tai, Cheuk-Wai
    Stockholm University, Stockholm.
    Osong, Sinke H.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Ibrahem, Ismail
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    A sustainable strategy for production and functionalization of nanocelluloses2018In: Pure and Applied Chemistry, ISSN 0033-4545, E-ISSN 1365-3075Article in journal (Refereed)
    Abstract [en]

    A sustainable strategy for the neat production and surface functionalization of nanocellulose from wood pulp is disclosed. It is based on the combination of organocatalysis and click chemistry ("organoclick" chemistry) and starts with nanocellulose production by organic acid catalyzed hydrolysis and esterification of the pulp under neat conditions followed by homogenization. This nanocellulose fabrication route is scalable, reduces energy consumption and the organic acid can be efficiently recycled. Next, the surface is catalytically engineered by "organoclick" chemistry, which allows for selective and versatile attachment of different organic molecules (e.g. fluorescent probes, catalyst and pharmaceuticals). It also enables binding of metal ions and nanoparticles. This was exemplified by the fabrication of a heterogeneous nanocellulose-palladium nanoparticle catalyst, which is used for Suzuki cross-coupling transformations in water. The disclosed surface functionalization methodology is broad in scope and applicable to different nanocelluloses and cellulose based materials as well.

  • 35.
    Dahlström, Christina
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Quantitative microscopy of coating uniformity2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Print quality demands for coated papers are steadily growing, and achieving coating uniformity is crucial for high image sharpness, colour fidelity, and print uniformity. Coating uniformity may be divided into two scales: coating thickness uniformity and coating microstructure uniformity, the latter of which includes pigment, pore and binder distributions within the coating layer. This thesis concerns the investigation of both types of coating uniformity by using an approach of quantitative microscopy.First, coating thickness uniformity was analysed by using scanning electron microscope (SEM) images of paper cross sections, and the relationships between local coating thickness variations and the variations of underlying base sheet structures were determined. Special attention was given to the effect of length scales on the coating thickness vs. base sheet structure relationships.The experimental results showed that coating thickness had a strong correlation with surface height (profile) of base sheet at a small length scale. However, at a large length scale, it was mass density of base sheet (formation) that had the strongest correlation with coating thickness. This result explains well the discrepancies found in the literature for the relationship between coating thickness variation and base sheet structure variations. The total variance of coating thickness, however, was dominated by the surface height variation in the small scale, which explained around 50% of the variation. Autocorrelation analyses were further performed for the same data set. The autocorrelation functions showed a close resemblance of the one for a random shot process with a correlation length in the order of fibre width. All these results suggest that coating thickness variations are the result of random deposition of particles with the correlation length determined by the base sheet surface textures, such as fibre width.In order to obtain fundamental understandings of the random deposition processes on a rough surface, such as in paper, a generic particle deposition model was developed, and systematic analyses were performed for the effects of particle size, coat weight (average number of particles), levelling, and system size on coating thickness variation. The results showed that coating thickness variation3grows with coat weight, but beyond a certain coat weight, it reaches a plateau value. A scaling analysis yielded a universal relationship between coating thickness variation and the above mentioned variables. The correlation length of coating thickness was found to be determined by average coat weight and the state of underlying surfaces. For a rough surface at relatively low coat weight, the correlation length was typically in the range of fibre width, as was also observed experimentally.Non-uniformities within the coating layer, such as porosity variations and binder distributions, are investigated by using a newly developed method: field emission scanning electron microscopy (FESEM) in combination with argon ion beam milling technique. The combination of these two techniques produced extremely high quality images with very few artefacts, which are particularly suited for quantitative analyses of coating structures. A new evaluation method was also developed by using marker-controlled watershed segmentation (MCWS) of the secondary electron images (SEI).The high resolution imaging revealed that binder enrichment, a long disputed subject in the area, is present in a thin layer of a 500 nm thickness both at the coating surface and at the base sheet/coating interface. It was also found that the binders almost exclusively fill up the small pores, whereas the larger pores are mainly empty or depleted of binder.

  • 36.
    Dahlström, Christina
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Uesaka, Tetsu
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    New Insights into Coating Uniformity and Base Sheet Structures2009In: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 48, no 23, p. 10472-10478Article in journal (Refereed)
    Abstract [en]

    Base sheet structures, such as surface roughness and mass density distribution (formation), have been known to affect coating uniformity. However, the literature is not necessarily consistent in determining which structure controls coating uniformity. This study employed scanning electron microscopy (SEM) and image analysis, combined with autocorrelation and frequency analyses, to investigate the fundamental mechanisms of coating and to resolve some of the controversies in the literature regarding the base sheet effects. The results showed that coating thickness variation resembles a process of random deposition with leveling. At small length scales (in the size of fiber width), leveling causes a very strong dependence of coating thickness variations on the surface profile of the base sheet, whereas at larger length scales, coating thickness variation diminishes in its intensity by the same leveling effect, but still retains a significant correlation with base sheet structure, particularly formation. Frequency analyses clearly showed that the discrepancies in the results for the base sheet effects in the literature are due to the length scales used in the experiments, that is, the sampling area and the resolution of the measurements.

  • 37.
    Dahlström, Christina
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Uesaka, Tetsu
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Norgren, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Base Sheet Structures that Control Coating Uniformity: Effects of Length Scale2008In: TAPPI Advanced Coating Fundamentals Symposium Proceedings, TAPPI Press, 2008, p. 124-133Conference paper (Refereed)
    Abstract [en]

    Characterization of the base sheet properties and coating layer properties was performed by using scanning electron microscope (SEM) images of paper cross-sections and image analysis. Frequency analysis was used to study how the base sheet properties affect coating thickness uniformity at different length scales. Samples analysed were Lightweight Coated (LWC) base sheets blade-coated on only one side with coat weights of 12 and 22 g/m2. A number of images were taken in sequence giving a total length of more than 6 mm. The results showed that the surface height variations of the base sheet control coating uniformity in the entire examined length scale, but with different mechanisms. At short wavelengths the coating mechanism was “level coating” where the coating suspension fills small pores (“levels”), whereas at longer wavelengths the coating suspension follows the surface profile and “contour coating” becomes more prevalent. In other words, the level- and contour-coatings represent the coating mechanisms in different length scales. Surface height variations can be explained by base sheet thickness only at short wavelengths, but at all other wavelengths the surface height variations were very much independent of the base sheet structure properties measured.

  • 38. D'Arrigo, P
    et al.
    Högberg, Hans-Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Pedrocchi-Fantoni, G
    Servi, S
    Old and New Synthetic Capacities of Baker's Yeast1994In: Biocatalysis, ISSN 0886-4454, Vol. 9, no 1-4, p. 299-312Article in journal (Refereed)
  • 39. Deng, X.
    et al.
    Ferahi, M.
    Uesaka, Tetsu
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Pressroom Runnability: A Comprehensive Analysis of Press Room and Mill Database2007In: Pulp & paper Canada, ISSN 0316-4004, Vol. 108, no 2, p. 42-51Article in journal (Refereed)
    Abstract [en]

    Web break is an important runnability issue in the pressrooms. However, web breaks are rare events. Performance statistics for a large number of rolls are required to determine the causes of runnability problems with a reasonable level of confidence. To provide better insight into the main causes of web breaks, we analyzed seven pressroom/mill databases of sufficient size to produce reliable runnability statistics. The statistical "association" between strength properties (average) and break rate was examined using a Chi Square analysis method. We found that the statistical "association" between strength properties (average) and break rate varied considerably from one pressroom to the other (or from one mill to the other), depending on the pressroom operation (the variations of tension) and the quality of data from mills. However, among different strength properties, MD tensile strength has been most consistently associated with the break rate. CD tear strength did not consistently predict the runnability. We also found that strength uniformity had a significant impact on pressroom performance. Lastly, the pressroom data consistently showed that typical, macroscopic defects are now minority causes for web breaks and the majority of breaks are press-related or "unknown".

  • 40.
    Ding, Mingyue
    et al.
    Wuhan University, China.
    Ma, Longlong
    Chinese Academy of Sciences, China.
    Zhang, Qian
    Chinese Academy of Sciences, China.
    Wang, Chenguang
    Chinese Academy of Sciences, China.
    Zhang, Wennan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Wang, Tiejun
    Chinese Academy of Sciences, China.
    Enhancement of conversion from bio-syngas to higher alcohols fuels over K-promoted Cu-Fe bimodal pore catalysts2017In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 159, p. 436-441Article in journal (Refereed)
    Abstract [en]

    A novel K-promoted Cu-Fe bimodal derived catalyst was designed to optimize the catalytic activity and higher alcohols selectivity in higher alcohols synthesis (HAS). The characterization results indicated that the Cu-Fe bimodal derived catalyst presented the bimodal pore structures. The adding of K promoter increased the BET surface area and promoted the dispersion of Cu and Fe species in the bimodal pores without destroying the bimodal structure, whereas the excessive adding of potassium resulted in easily the aggregation of bimetal active species. Incorporation of moderate K content enhanced the reduction of Cu and Fe species and promoted the formation of active bimetal species for HAS, while the bimodal derived catalyst with excessive K content restrained the reduction of bimetal particles, decreasing the catalytic activity for higher alcohols synthesis. In addition, the gradual increasing of K content in the Cu-Fe bimodal derived catalyst strengthened the interaction of K and bimetal active species, which was combined with the “confinement effect” of bimodal pore structures, shifting product distribution towards C2 + OH.

  • 41.
    Duan, Ran
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Ibrahem, Ismail
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Edlund, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Norgren, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Acid-Catalyzed Synthesis of Foamed Materials from Renewable Sources2014In: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 53, no 45, p. 17597-17603Article in journal (Refereed)
    Abstract [en]

    In this study, lightweight biobased foamed materials were successfully synthesized by the modification of renewable polysaccharides, such as starch and microcrystalline cellulose. Low-cost and nontoxic organic acids were utilized as catalysts in the first-step esterification reaction of the synthesis. The effects of different reaction conditions on the water absorbency and weight loss of freeze-casted polysaccharide–citrate–chitosan foams are discussed. Physical properties, such as pore-size distributions and compressive stress–strain curves, of the foams were determined. The characterization results show that the amide bonds formed between the carboxylic acid groups of polysaccharide–citrate and the amino groups of chitosan are crucial to the foamed material’s performance.

  • 42.
    Duan, Ran
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Norgren, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Edlund, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Hedenström, Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Novel foamed materials from renewable sources2012In: 9th European Conference on Foams, Emulsions and Applications, 2012Conference paper (Refereed)
  • 43.
    Duan, Ran
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Norgren, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Hedenström, Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Ibrahem, Ismail
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Edlund, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    New approaches toward producing foamed materials from renewable sources.2013Conference paper (Refereed)
  • 44.
    Duan, Ran
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Westerlind, Bo
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Norgren, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Anugwom, Ikenna
    Technical Chemistry, Department of Chemistry, Chemical-Biological Centre, Umeå University; Laboratory of Industrial Chemistry and Reaction Engineering, Johan Gadolin Process Chemistry Centre, Åbo Akademi University, Finland.
    Virtanen, Pasi
    Technical Chemistry, Department of Chemistry, Chemical-Biological Centre, Umeå University.
    Mikkola, Jyri-Pekka
    Technical Chemistry, Department of Chemistry, Chemical-Biological Centre, Umeå University; Laboratory of Industrial Chemistry and Reaction Engineering, Johan Gadolin Process Chemistry Centre, Åbo Akademi University, Finland.
    Fibre stress-strain response of high temperature chemi-thermomechanical pulp treated with switchable ionic liquids2016In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 11, no 4, p. 8570-8588Article in journal (Refereed)
    Abstract [en]

    The removal of lignin from a high-temperature chemi-thermomechanical pulp (HT-CTMP) using a switchable ionic liquid prepared from an organic superbase (1,8-diazabicyclo-[5.4.0]-undec-7-ene (DBU)), monoethanol amine (MEA), and SO2 was investigated. The objective was to measure the fibre properties before and after removal of the lignin to analyse the contributions from lignin in the HT-CTMP fibre to the tensile properties. It was found that the fibre displacement at break - measured in zero span, which is related to fibre strain at break - was not influenced by the lignin removal in this ionic liquid system when tested dry. There was a small increase in displacement at break and a reduction in tensile strength at zero span when tested after rewetting. At short span, the displacement at break decreased slightly when lignin was removed, while tensile strength was almost unaffected when tested dry. Under rewetted conditions, the displacement at break increased and tensile strength decreased after lignin removal. Nevertheless, no dramatic differences in the pulp properties could be observed. Under the experimental conditions, treatment with the ionic liquid reduced the lignin content from 37.4 to 15.5 wt%.

  • 45.
    Ebrahimzadeh, PR
    et al.
    Chalmers University of Technology, Department of Polymeric and Textile Materials, S-412 96 Gothenburg, Sweden.
    Kubat, J
    Chalmers University of Technology, Department of Polymeric and Textile Materials, S-412 96 Gothenburg, Sweden.
    McQueen, DH
    Chalmers Innovation Center, Chalmers University of Technology, S-412 96 Gothenburg, Sweden.
    Dynamic mechanical characterization of mechanosorptive effects in wood and paper1996In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 54, no 4, p. 263-271Article in journal (Refereed)
    Abstract [en]

    Dynamic mechanical studies in dual cantilever and tensile stretching mode of Scots pine veneer, birch veneer and paper under stepwise humidity changes between 5% and 85% relative humidity are reported. The loss tangent (tan delta) shows a transient peak every time the relative humidity of the surrounding atmosphere is changed. In the bending mode a clamping arrangement that is freely movable in the longitudinal direction gives more distinct damping peaks than does a static fixture.

    There is a close relationship between the rate of sorption/desorption and the shape of the tan delta peak. In response to reduction of the rate of humidity change the damping transients slowly disappear. They also diminish in strength as the temperature is raised toward 60 degrees C. Their strengths increase as the measuring frequency is lowered toward 0.01 Hz. Also, when the samples are highly compressed or prestressed with static loads the peak heights are greatly reduced. The tans peaks become less distinct and eventually disappear when the amplitude of the vibration increases. Long time testing results in significant changes in the shapes of the tan delta versus time data.

    A working hypothesis is that these phenomena are closely related to molecular diffusion of water through the sample material. Simple estimates show that the relaxation time for a diffusion related process should be of the order of a minute.

  • 46.
    Edlund, Håkan
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Bydén, Malin
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Lindström, Birger
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Khan, Ali
    Phase Equilibria and Structure of the 1-dodecyl Pyridinium Bromide-Dodecane-Water System1998In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 204, no 2, p. 312-319Article in journal (Refereed)
    Abstract [en]

    The isothermal ternary phase diagram for the 1-dodecylpyridinium bromide/dodecane/water system was determined at 40°C by 2H NMR and polarizing microscopy methods. Two liquid crystalline phases, a large cubic area and a normal hexagonal phase, and one isotropic normal micellar solution phase were characterized, and their ranges of existence were determined. The micelles were found to be probably small and spherical at lower concentrations of surfactant, and were found to grow at higher concentrations and on addition of oil. The two-phase areas, L1 + H1 and H1 + I, are both very narrow. The comparatively large cubic area, containing 43-63 wt% surfactant and 3-10 wt% dodecane, is probably consistent of more than one structure. SAXS experiments indicate two different structures built of discrete micellar aggregates.

  • 47.
    Edlund, Håkan
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Bydén, Malin
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Lindström, Birger
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Khan, Ali
    Ternary Phase Equilibria of the 1.dodecyl Pyridinium Bromide-Dodecanol-Water System1997In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 196, no 2, p. 231-240Article in journal (Refereed)
    Abstract [en]

    The isothermal ternary phase diagram for the 1-dodecylpyridinium bromide (1-DPB)–water–dodecanol system was determined at 40°C, using2H NMR, polarizing microscopy, and SAXS methods. All of the phases were characterized, and their ranges of existence were determined. The surfactant is easy to dissolve in water, yielding a normal micellar solution phase. After the normal micellar phase, on the binary surfactant–water axis, a normal hexagonal liquid crystalline phase is found at higher surfactant concentrations. On addition of dodecanol, four more phases are formed, i.e. a cubic, a lamellar, and a reverse hexagonal phase, followed by a reverse micellar solution phase. The lamellar liquid crystalline phase dominates the ternary phase diagram. The structures of the liquid crystalline phases were further examined using SAXS measurements, and the results are discussed in terms of the critical packing parameter, cpp, and electrostatic forces. The SAXS experiments show a pronounced swelling of the rods in the hexagonal phase, from 28.5 to 33 Å on addition of dodecanol, whereas the cylindrical aqueous core of the reverse hexagonal phase has a diameter of 18–21 Å, depending on sample composition. The average bilayer thickness of the lamellar phase is about 24 Å.

  • 48.
    Edlund, Håkan
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Khan, A
    La Mesa, C
    Formation of a Liquid Crystalline Phase in the Sodium Taurodeoxycholate-Water System1998In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 14, p. 3691-3697Article in journal (Refereed)
    Abstract [en]

    The binary phase equilibria for the system sodium taurodeoxycholate-water have been studied. The system forms a liquid crystalline phase in addition to the previously known isotropic solution phase at 22 °C. 2H (water) NMR quadrupole splitting, SAXS data in combination with the polarizing microscopic texture observed for the liquid crystal indicate that the liquid crystalline phase consists of a hexagonal-type aggregate structure. A metastable liquid crystal, probably with lamellar-type structure, also appears to exist prior to the formation of the stable hexagonal phase. A micellar growth is measured with the NMR self-diffusion method for the isotropic solution phase. Electrical conductance experiments are used to determine the liquid crystal-solution thermal transition.

  • 49.
    Edlund, Håkan
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Sadaghiani, Alireza
    Khan, Ali
    Phase Behaviour and Phase Structure for Catanionic Surfactant Mixtures: DoTAC-SN-Water System1997In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 13, p. 4953-4963Article in journal (Refereed)
    Abstract [en]

    The phase behavior and phase structure of catanionic surfactant mixtures of DoTAC (dodecyltrimethylammonium chloride) and SN (sodium nonanoate) with water are studied by combined 2H NMR, SAXS, and microscopy techniques at 40 °C. The system forms a large isotropic micellar solution phase with excess water. As the concentration of total surfactant is increased, the solution phase coexists with different liquid crystalline phasesa lamellar phase at equimolar ratio of the two surfactants and hexagonal phases with excess DoTAC and excess SN. The lamellar and hexagonal liquid crystalline phases formed by the binary DoTAC system extensively swell with water on adding the anionic surfactant, and the swelling is more dramatic for the lamellar phase which extends to an equimolar ratio of the two surfactants. The mesophase of the short alkyl chain is incapable of solubilizing any substantial amounts of the long chain DoTAC molecules. SAXS data shows a decrease in bilayer thickness and an unchanged average area per polar group on adding SN into the lamellar phase. For the DoTAC-rich hexagonal phase, the diameter of the cylinder remains unchanged and the average area per polar headgroup is decreased in catanionic mixtures. The 2H NMR quadrupolar splitting values in the hexagonal liquid crystalline phase indicate that the polar headgroups are less extensively hydrated in catanionic mixtures compared to the hydration of the headgroups in the single surfactant systems. The 2H splitting value in the lamellar phase first decreases, going through a zero splitting value, and then the splitting increases again on a continuous decreasing of the total surfactant concentrations. Alkyl chain asymmetry is found to play a dominant role in the formation and stability of aggregates in catanionic surfactant mixtures.

  • 50.
    Edström, Per
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Neuman, Magnus
    Avramidis, Stefanos
    Andersson, Mattias
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Geometry Related Inter-Instrument Differences in Spectrophotometric Measurements2010In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 25, no 2, p. 221-232Article in journal (Refereed)
    Abstract [en]

    The L&W Elrepho d/0 and the Spectrolino 45/0 instruments are examined using paper samples with different properties. External factors that influence the measurements such as the sample background, the instrument calibration and the sample inhomogeneity are studied, and a methodology for their minimization is presented. Experimental measurements show that such external factors, if not minimized by proper routines, affect the inter-instrument differences far more (up to 4-5 Delta E-ab(star)) than the instrument geometry (the effect of which is small and of order 0.1 Delta E-ab(star)). The DORT2002 radiative transfer model is used to simulate differences caused by instrument geometry. The simulated and measured differences are found to agree in magnitude, and the differences are mapped against sample properties. It is observed that the 45/0 instrument detects higher reflectance from paper samples with negligible absorption and transmittance. When there is considerable absorption (dyed samples) or transmittance (thin samples), the d/0 instrument detects higher reflectance. The physical mechanism behind this behavior is studied and explained using DORT2002, and the instrument differences are shown to depend on the anisotropy of the reflected light. The model/measurement agreement is satisfactory as the characteristic behavior is captured in almost all cases studied. This new understanding is important for facilitating accurate data exchange between the paper and graphic arts industries, but also for interpretation of reflectance measurements in general.

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