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  • 151.
    Ekelund, Nils
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Report on fieldwork at Husvik, South Georgia: October - December 1990. "Studies on the effects of ultraviolet radiation on phytoplankton of Sub-Antarctic lakes and ponds1992Ingår i: Swedish Antarctic Research Programme 1990/91, , s. 54-57Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
  • 152.
    Ekelund, Nils
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    The effect of UV-B radiation and humic substances on growth and motility of the flagellate, Euglena gracilis.1993Ingår i: Journal of Plankton Research, ISSN 0142-7873, E-ISSN 1464-3774, Vol. 15, s. 715-722Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effects of ultraviolet-B radiation (UV-B, 250–315 nm) were determined on Euglena gracilis with respect to speed, phototactic orientation, specific growth rate, and in the presence of humic substances. Humic substances had a protective effect when studying the speed and specific growth rate. However, the degree of phototactic orientation decreased in UV-B radiation both with and without humic substances. The inhibition of O2 evolution and speed was most pronounced when using cutoff filters WG280 and WG295. The photosynthetic inhibitor DCMU (10–6 M) did not have any effect on the speed, but the 02 evolution decreased to zero. The effect of different wavelengths in the UV-B region on the speed of E.gracilis showed the maximum sensitivity at 280 and 290 nm.

  • 153.
    Ekelund, Nils
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    The effects of UV-B radiation on dinoflagellates1991Ingår i: Journal of plant physiology (Print), ISSN 0176-1617, E-ISSN 1618-1328, Vol. 138, s. 274-278Artikel i tidskrift (Refereegranskat)
  • 154.
    Ekelund, Nils
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Till sjöelefanter i mittoceanen1998Ingår i: Senior posten, nr 4Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
  • 155.
    Ekelund, Nils
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Växters fotosyntes vid förändrade miljöförhållanden2001Ingår i: Fauna och flora : populär tidskrift för biologi, ISSN 0014-8903, Vol. 96, nr 1, s. 15-24Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
  • 156.
    Ekelund, Nils
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Aronsson, Andreas
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Changes in chlorophyll a fluorescence in Euglena gracilis and Chlamydomonas reinhardtii after exposure to wood-ash.2007Ingår i: Environmental and Experimental Botany, ISSN 0098-8472, E-ISSN 1873-7307, Vol. 59, nr 1, s. 92-98Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Recycling of wood-ash to boreal forests has been suggested to prevent depletion of essential soil nutrient or reduce the negative effects of acidification of surface waters. This study investigated the effects of different concentrations of wood-ash (5, 10 and 12.5 mg l-1 diluted in cultivating medium) on chlorophyll a fluorescence in Euglena gracilis and Chlamydomonas reinhardtii. The green alga C. reinhardtii was more susceptible to wood-ash solutions than the flagellate E. gracilis. Two different forms of wood-ash solutions were tested. In the first solution no adjustment of pH was made. In the second, the pH was adjusted to 7. Wood-ash forms a very strong alkaline reaction if no adjustment of pH is made. The results show that no negative effect on fluorescence yield, electron transport rate (ETR), photochemical quenching (qP) or non-photochemical quenching (NPQ) was observed in E. gracilis. In contrast, C. reinhardtii displayed strong inhibition at concentrations of 10 and 12.5 mg l-1 with non-adjusted pH. The negative effects of high pH on the photosynthetic capacity in C. reinhardtii could either be related to the destruction of the ∆pH across the thylakoid or other parts in the photosynthetic systems that are negatively affected by changing pH. Elevated pH levels in aquatic ecosystems constitute a major environmental stress factor to the phytoplankton community and may lead to loss of diversity among primary producers. If wood-ash application was to become general practice in or near aquatic ecosystems the ash may need to be treated accordingly to avoid rapid changes in pH.

  • 157.
    Ekelund, Nils
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Aronsson, Andreas
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Flagellaten Euglena gracilis rörelseförmåga kan avslöja graden av giftighet (kadmium) i vatten med hjälp av metoden ECOTOX. (Orientation of the flagellate Euglena gracilis can identify the toxicity (cadmium) of water using the automatic biotest ECOTOX).2004Ingår i: Vatten, ISSN 0042-2886, Vol. 60, nr 2, s. 77-84Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The interest in testing of water and wastewater for toxic compounds has increased in the last few years with rising pollutant levels from industry and with rising sensibility towards environmental problems. In order to get an early warning signal of environmental conditions the use of unicellular organism are recommended since they respond quickly and are easy to handle. An early warning system, called ECOTOX, for monitoring of water quality has been developed by a research group in Germany (Prof. D.-P. Häder). ECOTOX use movement parameters of the flagellate Euglena gracilis as orientation in the gravity field, the motility and the velocity of the cells. These parameters have been found to be sensitive to toxic compounds. In the present study it was shown that cadmium affect gravitaxis, motility, velocity and compactness of the cells negatively in the concentration interval of 10 to 15 mg l-1 after 24 and 48 h. After short time of incubation (minutes) with cadmium there is an inhibition of the different movements parameters starting at the concentration of 25 mg l-1. Like other biomonitoring systems ECOTOX can be used to detect changes in quality of aquatic systems.

  • 158.
    Ekelund, Nils
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Danilov, Roman
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Effects of autumnal stratification on phytoplankton communities in Lake Solumsjö, Sweden: Application of diversity indices and multivariate methods2000Ingår i: Biologia (Bratislava), ISSN 0006-3088, E-ISSN 1336-9563, Vol. 55, nr 4, s. 357-362Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Effects of autumnal stratification on phytoplankton communities at different depths were studied in Lake Solumsjö, NE Sweden. Species number, Shannon-Weaver’s, Margalef’s and Menhinick’s indices as well as cluster analyses using presence-absence with abundance matrices were applied. All diversity indices used clearly indicated higher diversity in epilimnion compared to that in hypolimnion. This pattern can be explained by sole dominance of Trachelomonas volvocinopsis under predominantly anoxic conditions and high concentrations of iron and manganese below the thermal gradient. Stratification disappeared between September 29 and October 4, thus leading to homogenisation of water column and similar phytoplankton communities at all depths. Cluster analyses using presence-absence with abundance matrices turned out to be a powerful tool when studying temporal changes in phytoplankton communities as a result of stratification patterns. Two distinct clusters at depths of 0, 2 and 10 m were clearly separated: one containing algal communities during stratification and one containing algal communities after the thermal gradient disappeared. At the depth of 5 m more homogeny between phytoplankton communities under stratified and mixed conditions was observed.

  • 159.
    Ekelund, Nils
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Danilov, Roman
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    The influence of selenium on photosynthesis and light-enhanced dark respiration (LEDR) in the flagellate Euglena gracilis after exposure to ultraviolet radiation2001Ingår i: Aquatic Sciences, ISSN 1015-1621, E-ISSN 1420-9055, Vol. 63, nr 4, s. 457-465Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Photodamage of photosynthesis arises from oxidative damage. One of the protective mechanisms is to convert excessive absorbed energy into thermal radiation. Another mechanism could be to strengthen the antioxidative capacity of plants and algae. Selenium is important in antioxidation in humans and may play a role in antioxidative mechanisms in plants. The aim of this investigation was to study the role of selenium in "light-enhanced dark respiration" (LEDR) and photosynthesis in the flagellate Euglena gracilis, after exposure to ultraviolet radiation (UV-radiation). Selenium was added into the growth medium at different concentrations of selenite (10-7, 10-8, 10-9 and 10-10 M, Na2SeO3 · 5H2O). E. gracilis were given six different light pulses with a photon fluence rate of 59, 163, 600, 1180, 2080 and 3340 μmol m-2 s-1 and periods of darkness between the light pulses. Photosynthetic saturation occurred at irradiances higher than 600 μmol m-2 s-1 and at the highest irradiance the photosynthetic rate decreased due to photoinhibition. Without any exposure to UV-radiation (UV-A, 320-400 nm, of 1.02 W m-2 plus UV-B, 280-320 nm, of 0.73 W m-2) LEDR increased with increasing photon fluence rate. After 40 min exposure to UV-radiation, photosynthetic rate and LEDR as functions of photon fluence rate were reduced. Neither in control (no UV-radiation) or when measured immediately after exposure to UV-radiation selenium had no stimulating effects on photosynthesis and LEDR. However, after UV-treatment and 24 h of recovery the presence of selenium led to an increase in photosynthesis and LEDR at higher irradiances. The results indicates that selenium might play a role in the repair mechanisms in E. gracilis after UV treatments.

  • 160.
    Ekelund, Nils
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Nielsen, Tom
    Influence of solar ultraviolet radiation on carbon fixation, oxygen evolution and motility of marine phytoplankton1995Ingår i: FEMS Microbiology Ecology, ISSN 0168-6496, E-ISSN 1574-6941, Vol. 18, s. 281-288Artikel i tidskrift (Refereegranskat)
  • 161.
    Ekelund, Nils
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Nielsen, Tom
    Inhibition and adaptation of photosynthesis in marine phytoplankton as an effect of ultraviolet radiation1998Rapport (Övrigt vetenskapligt)
  • 162.
    Engqvist, Cecilia
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Forsberg, Sven
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Norgren, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Edlund, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Andreasson, B
    Karlsson, O
    Lund University.
    Interactions between single latex particles and silica surfaces studied with AFM2007Ingår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 302, nr 1-3, s. 197-203Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The spreading of single styrene-acrylic latex particles on silicon oxide surfaces was studied using atomic force microscopy (AFM). Three latexes with different glass transition temperature (Tg) were used and the effects of temperature, time and preparation method were investigated. Particle sizes and shape were measured with AFM and the contact angles were calculated. The observed rate for the spreading of latex particles was low and it took several days before the particles reached steady state, even at temperatures well above their Tg. The experimental particle spreading results deviated with two orders of magnitude from predictions using the WLF equation for polymer diffusion. The deviation could be attributed to polymer-surface interactions that slowed down the particle spreading. The work of adhesion was calculated using two models. The results from using the regular Young-Dupré equation and a modified version of this equation that also included the mechanical properties (E-modulus and Poisson�s ratio) of the latexes, were compared. For soft latex particles the results from the two models agreed well and were of the order of 75 J/m2, but for glassy latexes the Young-Dupré equation underestimated the work of adhesion.

  • 163. Ericsson, T S
    et al.
    Berglund, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Östlund, L
    History and forest biodiversity of woodland key habitats in south boreal Sweden2005Ingår i: Biological Conservation, ISSN 0006-3207, E-ISSN 1873-2917, Vol. 122, nr 2, s. 289-303Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Forest exploitation has destructed forest habitats in Fermoscandia during last centuries. Vital components of existing forest biodiversity have been identified as small (a few ha) woodland key habitats (WKHs). Many WKHs in boreal forest landscapes are assumed to represent remnant near-natural forests from before the phase of industrial forest exploitation. Thus, WKHs are supposed to (i) exhibit a low degree of exploitation, (ii) have old-growth characteristics and (iii) host Red-list species. Yet, WKHs' history and biodiversity have not been systematically investigated. Thus, their conservation values remain unclear. This study investigates history and biodiversity of 15 WKHs in central Sweden with retrospective methods and field studies. We analyze (1) forest structure before, during and after the forest exploitation period, (2) existing biodiversity, i.e. species and structural elements, and (3) to what extent human activities (forestry) have influenced current biodiversity. Our results indicate that forest structure within the areas that currently are classified as WKHs has changed dramatically since the mid-19th century, when forests were unaffected by logging. The results suggest that fire-suppression during last century, gradually increased logging until mid-20th century and abandonment by modern forestry during the late 20th century, are main causes behind this transformation. Less than 10% of studied WKHs had biological features that resembled those of pristine boreal forests. Thus, most studied WKHs cannot be classified as near-natural or remnants of pristine forest. We Suggest that the program for WKHs give more focus to pre-industrial forest structure, local historical aspects being seriously regarded and ecological restoration efforts being introduced.

  • 164.
    Eriksson, Carina
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Högberg, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Månsson, Per
    Schlyter, Fredrik
    Sjödin, Kristina
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Strategier i sökandet efter gnaghämmare mot snytbaggen, Hylobius abietis: Föredrag, 19:e Organikerdagarna i Linköpng 20042004Konferensbidrag (Övrigt vetenskapligt)
  • 165.
    Eriksson, Carina
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Månsson, P
    Sjödin, Kristina
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Searching for Pine Weevil Antifeedants: Finding an Active Compound in Bark from Linden, Tilia cordata: Joint meeting of International Society of Chemical Ecology and Phytochemical Society of North America, Ottawa, Canada 20042004Konferensbidrag (Övrigt vetenskapligt)
  • 166.
    Eriksson, Carina
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Schlyter, F
    Sjödin, Kristina
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Benzaldehyde, cinnamic aldehyde and related compounds as antifeedants against the pine weevil, Hylobius abietis: A study of structure-activity relationships.Manuskript (Övrigt vetenskapligt)
  • 167.
    Eriksson, Carina
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Schlyter, F
    Sjödin, Kristina
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Högberg, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Syntes av 2,6-disubstituerade piperidinalkaloider, potentiella gnaghämmare mot snytbaggen Hylobius abietis: 20:e Organikerdagarna, 12-15 juni 2006, Kalmar, föredrag2006Konferensbidrag (Övrigt vetenskapligt)
  • 168.
    Eriksson, Carina
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Sjödin, Kristina
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Schlyter, Fredrik
    Swedish University of Agricultural Sciences, Alnarp.
    Högberg, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Synthesis of (+)- and (-)-dihydropinidine by diastereoselective dimethylzinc promoted allylation of 2-methyltetrahydropyridine-N-oxide with allylboronic ester.2006Ingår i: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 17, nr 7, s. 1074-1080Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The enantiomers of the naturally occurring alkaloid dihydropinidine 1, potential antifeedants against the pine weevil, Hylobius abietis, were prepared by diastereoselective, dimethylzinc mediated addition of pinacolyl 2-propenylboronate 14 to nitrones (R)- and (S)-2-methyl tetrahydropyridine-N-oxide 3, prepared from d- and l-alanine, respectively.

  • 169.
    Eriksson, Carina
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Smitt, O.
    Schlyter, F.
    Sjödin, Kristina
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Högberg, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Antifeedants for Protection of Pines and Spruces against the Pine Weevil, Hylobius abietis: International Society of Chemical Ecology, Annual Meeting 2001, Lake Tahoe, USA2001Konferensbidrag (Övrigt vetenskapligt)
  • 170.
    Eriksson, Carina
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Smitt, Olof
    Schlyter, Fredrik
    Sjödin, Kristina
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Högberg, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Searching for Pine Weevil Antifeedants, Strategy and Synthesis2002Ingår i: 19th annual meeting of International Society of Chemical Ecology, 2002, Hamburg, Germany, 2002, s. 217-Konferensbidrag (Övrigt vetenskapligt)
  • 171. Eriksson, Malin
    et al.
    Pettersson, Gunilla
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Wågberg, Lars
    Application of polymeric multilayers of starch onto wood fibres to enhance strength properties of paper2005Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 20, nr 3, s. 270-275Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Polyelectrolyte multilayers of cationic and anionic starch have been used to enhance the strength properties of paper. All starches used in this investigation had a degree of substitution around 0.065. Optical reflectometry showed that a combination of cationic and anionic starch could form polyelectrolyte multilayers onto silicon oxide surfaces. The same combination of starches was then applied to unbeaten, bleached softwood kraft fibres to form three layers, i.e. a cationic/anionic/cationic starch combination. The results showed a significant increase in the paper strength properties in terms of tensile index, strain at break, and Scott Bond. The adsorbed amount of starch in the sheets, determined using an enzymatic method, was found to increase with each successive starch treatment. The increased paper strength was not only due to the increase in adsorbed amount of starch; rather, the chemical composition of the starch was also important. Cationic starch with high amylose content had a more positive effect on the paper strength properties. Furthermore, it was observed that anionic starch, despite being adsorbed in large amounts, did not contribute to the increase in tensile strength or strain at break to the same extent as did cationic starch. However, the out-of-plane properties, measured as Scott Bond properties, increased with the adsorbed amount, regardless of the chemical composition of the starch used in the outermost layer.

  • 172.
    Eriksson, Malin
    et al.
    Royal Institute of Technology, Stockholm.
    Torgnysdotter, Annsofie
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Wågberg, Lars
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Surface modification of wood fibres using the polyelecrolyte multilayer technique: Effects on fibre joint and paper strength properties2006Ingår i: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 45, nr 15, s. 5279-5286Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Polyallylamine hydrochloride (PAH) and poly(acrylic acid) (PAA) were used to modify wood fibers by means of the polyelectrolyte multilayer (PEM) technique. Hand sheets and fiber crosses were prepared from the PEM-treated fibers. The sheet strength and fiber-fiber joint strength were evaluated, and the contact zone of the fiber-fiber joint was characterized using a recently developed staining technique. The nonjoined surface area of the paper sheets was estimated by determining nitrogen adsorption via BET analysis, and the results were compared with those of the light scattering measurements frequently used to determine the degree of “bonding” in paper. Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy was used to analyze chemical effects. It was shown that the PEM treatment of fibers increased the strength properties of the sheets through an increase in the number of fiber-fiber joints, increasing the degree of contact in a fiber-fiber joint and creating covalent bonding in the fiber-fiber joint.

  • 173.
    Essén, Sofia
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Hydroxamate Siderophores and Low Molecular Mass Organic Acids in Terrestrial and Aquatic Environments Determined by Liquid Chromatography Mass Spectrometry2007Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Siderophores are low molecular mass organic compounds with high iron(III) stability constants. They are produced by many microorganisms, often in combination with low molecular mass organic acids (LMMOAs). Both siderophores and LMMOAs accelerate mineral weathering, thereby enhancing mineral nutrient availability. Siderophore concentrations in natural environments, however, are largely unknown. In the present work, analytical methods based on liquid chromatography (LC) electrospray ionization mass spectrometry (ESI‐MS) were developed and used for concentration determination of selected hydroxamate siderophores and LMMOAs. The use of capillary LC with on‐line pre‐concentration via column switching enabled siderophore quantification with detection limits of 0.1 ‐ 5 nM. Through solid phase extraction even lower detection limits were achieved. In Swedish podzol soil solutions concentrations up to 12 nM ferricrocin and 2 nM ferrichrome were found in the upper soil layes. Additionally, in axenic pine (Pinus sylvestris) seedling cultures, the ectomycorrhizal fungus Hebeloma crustuliniforme was shown to produce ferricrocin as the main siderophore. Moreover, ferricrocin was found in enriched Baltic Sea cyanobacterial populations at concentrations up to 1 nM, while concentrations up to 0.05 nM ferrioxamine B were determined in Baltic Sea surface waters during cyanobacterial blooms. Siderophores have strong affinities for some actinides and may affect radionuclide mobilization in deep subsurface nuclear wase repositories. Two subsurface bacterial strains were shown to produce siderophores under aerobic conditions, i.e. Pseudomonas stutzeri produced mainly ferrioxamine E and Pseudomonas fluorescens produced one pyoverdin siderophore. Siderophores produced by aerobically grown P. stutzeri were not observed either in anaerobic cultures or in deep subsurface water samples.

  • 174.
    Essén, Sofia
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Bylund, Dan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Holmström, Sara
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Moberg, M
    Uppsala University.
    Lundström, Ulla
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Quantification of hydroxamate siderophores in soil solutions of podzolic soil profiles in Sweden2006Ingår i: Biometals, ISSN 0966-0844, E-ISSN 1572-8773, Vol. 19, nr 3, s. 269-282Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Concentrations up to 2 and 12 nM of the hydroxamate siderophores ferrichrome and ferricrocin, respectively, were identified in soil solutions of podzolic forest soils at four sites in both northern and southern Sweden. No ferrichrysin was detected. As with the dissolved organic carbon and low molecular mass organic acids, the highest concentrations of the siderophores were found in the upper layers i.e. the mor layer, the eluvial and upper illuvial horizons. At the southern sites, the concentrations of ferrichrome and ferricrocin were both of similar magnitude and did not differ between the two sites. In contrast, soil solutions at the two northern sites contained more ferricrocin than ferrichrome; the ferricrocin concentrations were also higher at the northern sites than at the southern sites. Analyses were performed by high performance liquid chromatography with a porous graphitic carbon column on which ferrichrome, ferricrocin and ferrichrysin were separated. Detection by electrospray ionization mass spectrometry (ESI-MS) combined with on-line sample pre-concentration, by means of column-switching, enabled detection limits of 0.1-0.2 nM for ferrichrome, ferrichrysin and ferricrocin. The structural identities of the siderophores were further verified by MS/MS fragmentation. Fragmentation of ferrichrome, ferricrocin and ferrichrysin occured mainly via peptide cleavage. The most intense fragments were typified by the loss of one of the three iron(III) chelating hydroxamate residues, i.e N5-acyl-N5-hydroxy ornithine.

  • 175.
    Essén, Sofia
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Johnson, Anna
    Bylund, Dan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Pedersen, Karsten
    Lundström, Ulla
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Siderophore production by Pseudomonas stutzeri under aerobic and anaerobic conditions2007Ingår i: Applied and Environmental Microbiology, ISSN 0099-2240, E-ISSN 1098-5336, Vol. 73, nr 18, s. 5857-5864Artikel i tidskrift (Refereegranskat)
  • 176.
    Fagerlund, Amelie
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Shanks, David
    Sunnerheim, Kerstin
    Engman, Lars
    Frisell, Håkan
    Protective effects of synthetic and naturally occurring antioxidants in pulp products2003Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 18, s. 176-181Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Various types of natural and synthetic antioxidants when added to handsheets of pulp in low concentrations (0.2% weight%) could significantly reduce the emission of hexanal. The most efficient compounds caused a 90% reduction after eight weeks. Their capacity to inhibit brightness reversion was limited.

  • 177.
    Falk, Stefan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Competition for photosynthetic energy between CO2- and NH4+-uptake in Selenastrum minutum: 5th European workshop on biotechnology in algae2003Konferensbidrag (Övrigt vetenskapligt)
  • 178.
    Falk, Stefan
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Pocock, Tessa
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Vetterli, Adrien
    Huner, N.P.A.
    Synergistic effects of salinity and temperature in an extremophilic Antarctic alga (Chlamydomonas raudensis UWO 241). Photosynt. Res. 91: 298-2992007Ingår i: Proceedings from the 14th International Conference on Photosynthesis, Glasgow, 2007: Published in Photosynthesis Research, vol 91: 298-299, 2007, s. 298-299Konferensbidrag (Övrigt vetenskapligt)
  • 179. Figueroa, Felix
    et al.
    Nygård, Charlotta
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Ekelund, Nils
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Gomez, Ivan
    Photobiological characteristics and photosynthetic UV responses in two Ulva species (Chlorophyta) from southern Spain.2003Ingår i: Journal of Photochemistry and Photobiology. B: Biology, ISSN 1011-1344, E-ISSN 1873-2682, Vol. 72, nr 1-3, s. 35-44Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effect of different wavebands of artificial UV (UVB and UVA) and photosynthetically active radiation (PAR) was assessed in two species of the genus Ova, U. olivascens and U rotundata, from southern Spain in order to test for possible differences in acclimation of photosynthesis. Both species share similar morphology but are subject to different light environments: U. rotundata is an estuarine alga, inhabiting subtidal locations, while U. olivascens is an intertidal, sun-adapted organism. Algae were exposed to three different UV conditions, PAR + UVA + UVB, PAR + UVA and PAR for 7 d. Short-term exposure (6 h) was also carried out, using two PAR levels, 150 and 700 mumol m(-2) s(-1). Pigment contents and photosynthesis vs. irradiance curves from oxygen evolution were used to contrast sun- and shade adaptation between these species. O-2-based net photosynthesis (P-max) and PAM-chlorophyll fluorescence (optimal quantum yield, F-v/F-m) were used as parameters to evaluate photoinhibition of photosynthesis in the experiments. The results underline different photobiological characteristics among species: the subtidal U rotundata had higher contents of pigments (Chl a, Chl b and carotenoids) than the sun-adapted U olivascens, which resulted in higher thallus absorptance and P-I parameters characterized by higher photosynthetic efficiency at limiting irradiances (alpha) and lower saturating points for photosynthesis (E-k). After 7 d exposure, photoinhibition of F-v/F-m was close to 40-45% in both species. Differences between UV treatments were seen in U. rotundata after 5 0 and after 7 d in U olivascens, in which PAR + UVA impaired strongly photosynthesis (80%). Such patterns were correlated with a progressive decrease in pigment contents, specially chlorophylls. In short-term (6 h) exposures, combinations of UVA + UVB and high PAR level resulted in high rates of photoinhibition of chlorophyll fluorescence (68-92%) in U rotundata, whereas in U. olivascens photoinhibition ranged between 42% and 53%. Photoinhibition under low PAR combined to UV radiation was lower than observed under high PAR. Net O-2-P-max revealed similar response among the species, with maximal photoinhibition rates close to 60% in algae incubated under high PAR + UVA + UVB. In the case of UV exposure in combination with low PAR, the highest photoinhibition rates were measured in U. rotundata. 

  • 180.
    Fjellström, Helena
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    The Photostabilising Effect of Coating Layers on CTMP‐based Papers2006Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
  • 181.
    Fjellström, Helena
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Höglund, Hans
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Forsberg, Sven
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Paulsson, Magnus
    Inhibition of light-induced brightness reversion of high-yield pulps: the UV-screening properties of coating layers containing kaolin or calcium carbonate pigments2007Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 22, nr 3, s. 350-355Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A newly developed method making it possible to study the reflectance/transmittance of thin coating layers and to link this to the inhibition of the light-induced yellowing, was used to describe the photo-stabilising properties of different types of commercial kaolin and calcium carbonate pigments. A base paper produced from a hydrogen-peroxide-bleached birch chemithermomechanical pulp (CTMP) was used throughout the study.The transmittance of the coating layers in the UV-region (300-385 nm) was found to be very low (below 1.0% at coat weights < 5g/m2) for all of the tested pigments, it strongly depends on the coat weight especially for coat weights below 10 g/m2. The kaolin pigments examined were found to be better in inhibiting the brightness reversion compared to the calcium carbonate pigments, even though the differences between the pigment types were only a few brightness units. The coating layer was, however, able to conceal some of the colour formed through the light-induce brightness reversion. For example, a coating layer consisting of kaolin pigments (coat weight of 15.6 g/m2) could conceal about 30% of the discoloration of the CTMP base paper.

  • 182.
    Fjellström, Helena
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Höglund, Hans
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Forsberg, Sven
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Paulsson, Martin
    Rundlöf, Mats
    A novel method of studying the ability of coating layer to retard the photo-yellowing of the base paper2007Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 22, nr 3, s. 343-349Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A method was developed which made it possible to study the reflectance/transmittance of thin coating layers and to link this to the inhibition of the light-induced yellowing. The ability of a coating layer to retard the photo-yellowing of a hydrogen-peroxide-bleached birch chemithermomechanical pulp (CTMP) is exemplified using this method. It is shown that the repeatability of the model system is excellent, even for coat weights below 10 g/m2. Furthermore, the transmittance in the UV-region is strongly correlated with the coating layers ability to protect the birch CTMP against photo-yellowing.

  • 183.
    Fjellström, Helena
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Höglund, Hans
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Paulsson, M
    Forsberg, Sven
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Influence of coating formulation on light-induced brightness stability of mechanical and chemimechanical pulp sheets2005Ingår i: International Mechanical Pulping Conference: IMPC 2005, Oslo, Norway, 7-9 June 2005, 2005, s. 339-343Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    The light-induced brightness reversion of different types of high-yield pulps has been studied under accelerated and long-term ambient ageing conditions. It was found that accelerated ageing (xenon lamp used as light source) overestimates the yellowing tendencies of hardwood pulps, whereas it was possible to predict the yellowing characteristics of softwood pulps. The lignin content of the pulps was found to be correlated to the degree of photo-yellowing for long-term ambient ageing. A model system was developed which made it possible to study the reflectance/transmittance of thin coating layers and to link this to the inhibition of the light-induced yellowing. The yellowing characteristics of a coated birch CTMP is exemplified using the evolved model system.

  • 184.
    Fjellström, Helena
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Höglund, Hans
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Paulsson, M.
    Rundlöf, Magnus
    Discolouration of mechanical and chemimechanical pulps: influence of wood raw material, process and ageing method2008Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 23, nr 1, s. 14-18Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The change in colour of a wide range of unbleached and bleached high-yield pulps was assessed using the CIELAB colour system. The influence of ageing method, pulping process and wood raw material is discussed.

  • 185.
    Fjellström, Helena
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Höglund, Hans
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Paulsson, Magnus
    Light-induced yellowing of mechanical and chemimechanical pulp sheets: influence of wood raw material, process and ageing method2007Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 22, nr 1, s. 117-123Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The light-induced brightness reversion of different types of unbleached and bleached high-yield pulps was studied under both accelerated and long-term ambient light-induced ageing conditions. It was found that accelerated ageing conditions that mimic indoor daylight exposures overestimate the yellowing tendencies of hardwood high-yield pulps (especially aspen pulps) compared to long-term ambient aging with no indirect sunlight present. It was, however, possible to predict the yellowing characteristics of softwood high-yield pulps. The lignin content of the pulps was found to be strongly correlated with the degree of photo-yellowing in the case of long-term ambient light-induced ageing. The presence of small amounts of birch chemithermomechanical pulp (CTMP) in a fine paper furnish resulted in extensive light-induced discoloration. The extent of photo-yellowing was found to be nearly linearly related to the amount of birch CTMP in the paper.

  • 186.
    Fjellström, Helena
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Höglund, Hans
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Paulsson, Magnus
    Forsberg, Sven
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    A novel method for studying the photo-stabilising properties of coating layers2006Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    A new model system was developed which made it possible to study the reflectance and transmittance of thin coating layers (<10 g/m2) in a reproducible way, and to link this to the inhibition of the light-induced yellowing (Figure 1). The UV/VIS-screening properties of coatings of different coat weights containing common pigments such as kaolin, calcium carbonate (ground or precipitated) and titanium dioxide will be reported. The ability of a coating layer to protect a birch CTMP from light-induced discoloration will be exemplified using the evolved model system. An estimation of the contribution of different wavelength regions of the illuminating light to the photo-yellowing of various types of materials will also be shown. The developed method is a valuable tool for future photo-yellowing studies as well as for optimisation of the pigment coating formulation for various paper grades.

  • 187. Fleischmann, E
    et al.
    Jonsson, Bengt-Gunnar
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Sjögren-Gulve, Per
    Focal species modeling for biodiversity conservation2000Ingår i: The use of population viability analyses in conservation planning, Copenhagen: Munksgaard , 2000, s. 85-99Konferensbidrag (Övrigt vetenskapligt)
  • 188. Forsgard, N.
    et al.
    Sjöberg, P.
    Bylund, Dan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Andersson, M.
    Pettersson, J.
    Screening and identification of aluminium-containing biomolecules by column-switched LC-ICP-MS and LC-ESI-MS/MS2007Ingår i: Journal of Analytical Atomic Spectrometry, ISSN 0267-9477, E-ISSN 1364-5544, Vol. 22, nr 11, s. 1397-1402Artikel i tidskrift (Refereegranskat)
  • 189.
    Forsström, Jennie
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Fundamental Aspects on the Re-use of Wood Based Fibres: Porous Structure of Fibres and Ink Detachment2004Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    In this work, different aspects on the re-use of wood based fibres have been studied, focusing on ink detachment of flexographic ink from model cellulose surfaces and changes in porous structure of kraft fibres following different treatments. New model systems for evaluation of ink detachment and ink-cellulose interactions were used. Ink detachment was studied using Impinging jet cell equipment, taking into consideration the influence of storage conditions, surface roughness and surface energy of the cellulose substrate. A micro adhesion measurement apparatus (MAMA) was used to directly study ink-cellulose interactions, from which the adhesive properties between ink and cellulose, having various surface energies, could be derived. UV-light, elevated temperatures, longer storage time, decreased surface energy, i.e. making the cellulose surface more hydrophobic, and high surface roughness all negatively affected ink detachment. Attenuated total reflectance - fourier transform infra red (ATR-FTIR) and atomic force microscopy (AFM) was used to evaluate structural and chemical changes of ink and cellulose upon storage at elevated temperature or under UV-light. After storage at elevated temperatures, ATR-FTIR spectra indicated that a hydrolysis or an oxidative reaction took place as a peak at 1710 cm-1 appeared. AFM revealed that storage at elevated temperatures caused the latex particles present in the ink to form a film, most likely due to annealing. Less ink detached from hydrophobic cellulose surfaces. Ink detachment decreased for rougher cellulose substrates due to an increased molecular contact area.

     

    Fibre pore structure and water retaining ability influenced fibre/fibre joint strength and different paper strength properties. Investigations took into account the effect of pulp yield, counter-ion types, pH, salt, hornification and strength enhancing additives. Nuclear magnetic resonance relaxation (NMR), inverse size exclusion chromatography (ISEC) and water retention value (WRV) measured the changes that occur in the fibre wall upon varying the conditions. Each different measuring technique contained unique information such that a combination of the techniques was necessary to give as complete a picture as possible over the changes that occurred in the fibre wall upon varying the conditions for the fibre. A correlation between fibre pore radius and sheet strength properties was found, suggesting that fibres with larger pores allow for a larger molecular contact area between fibres to be formed during drying and consolidation of the paper. Fibre/fibre joint strength, fibre flexibility, and the number of efficient fibre/fibre contacts also controlled sheet strength. The effect of different strength enhancing additives on fibre pore structure and paper strength was investigated. Larger pores in the fibres allowed for additives to penetrate into the fibre wall. Additives with low molecular mass (Mw) penetrated into the fibre wall to a larger extent than additives with a high Mw, causing an embrittlement of the fibre. However, low Mw additives gave higher sheet tensile strength despite a leveling out in strength at high additions, indicating that the fibre wall can only adsorb a limited amount of chemical. Polyallylamine hydrochloride (PAH) and polyelectrolyte complexes (PEC) of PAH and polyacrylic acid (PAA) were added separately to the pulp. PEC significantly improved both tensile strength and Z-strength, whereas PAH alone did not increase the strength properties to the same extent unless the sheets were heated to 150°C for 10 minutes. The results suggested that the effect of PEC was dominated by an improvement in fibre/fibre joint strength, whereas the effect of PAH was significantly affected by an improvement of the intra-fibre bond strength

     

  • 190.
    Forsström, Jennie
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Eriksson, Malin
    Wågberg, Lars
    A new technique for evaluating ink–cellulose interactions: initial studies of the influence of surface energy and surface roughness2005Ingår i: Journal of Adhesion Science and Technology, ISSN 0169-4243, E-ISSN 1568-5616, Vol. 19, nr 9, s. 783-798Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ink–cellulose interactions were evaluated using a new technique in which the adhesion properties between ink and cellulose were directly measured using a Micro-Adhesion Measurement Apparatus (MAMA). The adhesion properties determined with MAMA were used to estimate the total energy release upon separating ink from cellulose in water. The total energy release was calculated from interfacial energies determined via contact angle measurements and the Lifshitz–van der Waals/acid–base approach. Both methods indicated spontaneous ink release from model cellulose surfaces, although the absolute values differed because of differences in measuring techniques and different ways of evaluation. MAMA measured the dry adhesion between ink and cellulose, whereas the interfacial energies were determined for wet surfaces. The total energy release was linked to ink detachment from model cellulose surfaces, determined using the impinging jet cell. The influences of surface energy and surface roughness were also investigated. Increasing the surface roughness or decreasing the surface energy decreased the ink detachment due to differences in the molecular contact area and differences in the adhesiom properties.

  • 191.
    Forsström, Jennie
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Torgnysdotter, Annsofie
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Wågberg, Lars
    Influence of fibre/fibre joint strength and fibre flexibiity on the strentgh of papers from unbleached kraft fibres.2005Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 20, nr 2, s. 186-191Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The joint strength between single fibres and its influence on strength properties of papers was evaluated, taking into account the effect of pulp yield, ionic form of the carboxyl groups and drying. Fibre/fibre joint strength stayed almost constant for pulps with yield between 45 % and 50 %. Further increasing the pulp yield increased the joint strength until a maximum value was reached at a pulp yield of 57 %, after which the joint strength decreased. Joint strength correlated well to paper tensile strength for never dried fibres, i.e. a lower joint strength resulted in lower sheet tensile index. The decrease in sheet tensile index was not as pronounced as the decrease in joint strength. Changing counter-ion from Na+ to Ca2+ or H+ did not affect fibre flexibility, although it reduced the joint strength as the molecular contact area decreased due to a reduced swelling upon changing the counter-ions. Drying the high yield pulp lowered both the joint strength and the sheet tensile index to the same extent. The sheet tensile index, for the low yield pulp, decreased much more than the fibre/fibre joint strength after drying the fibres. In conclusion, a combination of a lower fibre flexibility, resulting in fewer contact points between fibres in the sheet, and a lower joint strength after drying was responsible for the reduction in sheet tensile index.

  • 192.
    Forsström, Jennie
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Wågberg, Lars
    Influence of different deinking efficiency of waterbased flexographic ink from model cellulose surfaces and sheets2004Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 19, nr 2, s. 250-256Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The influence of UV-light, temperature, atmospheric

    environment and storage time on the ink detachment of

    water-based flexographic ink printed on model cellulose surfaces

    was investigated using an impinging jet cell equipment. The

    printed surfaces were deinked using a NaOH solution (pH = 10)

    and the deinking process was monitored using a microscope

    equipped with a CCD camera. Images were collected at different

    time intervals during the detachment process and image

    analysis was used to quantify the ink detachment from the surface.

    Hand sheets, (the same pulp as used for model surface

    preparation) were also printed and stored under the same conditions,

    after which they were reslushed and deinked. The deinking

    efficiency of the recycled sheets was evaluated using

    brightness and ERIC (Effective Residual Ink Concentration)

    values. It was shown that UV-light had a negative effect on ink

    detachment both from the model cellulose surfaces and from

    the hand sheets. At storage temperatures of 55°C, (dark conditions

    were used) a large negative effect was observed for the

    cellulose surfaces while only a small effect on the ink detachment

    could be seen for the hand sheets. Ink detachment from

    the hand sheets became more difficult when increasing the storage

    temperature above 55°C, as detected as a decrease in

    brightness of the recycled and deinked sheets. A further increase

    in the storage temperature to 105°C gave poorer ink detachment

    efficiency than storage under UV-light for the hand sheets.

    Air had a more negative effect on ink detachment than nitrogen.

  • 193.
    Fraver, Shawn
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Disturbance dynamics of old-growth Picea rubens forests of northern Maine2005Ingår i: Journal of Vegetation Science, ISSN 1100-9233, E-ISSN 1654-1103, Vol. 16, nr 5, s. 597-610Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Question: How have the spatial and temporal aspects of past disturbance shaped the current structure and composition of old-growth Picea rubens forests?Location: Northern Maine, USA.Methods: We established three 50 m x 50 m plots in old-growth Picea rubens forests and mapped the location of trees and saplings. We extracted increment cores from canopy trees, and recorded growth releases indicating past disturbance. By linking spatial data (tree positions) and temporal data (dated growth releases), we reconstructed the location and size of former canopy gaps back to 1920, and determined a more general disturbance chronology extending as far back as 1740.Results: We found no evidence of stand-replacing disturbances. The disturbance dynamic includes pulses of moderate-severity disturbances caused by wind storms and hostspecific disturbance agents (spruce budworm, spruce bark beetle) interposed upon a background of scattered smaller canopy gaps. Consequently, rates of disturbance fluctuated considerably overtime. Reconstructed canopy gaps were temporally and spatially scattered; during disturbance peaks, they were both larger and more numerous.Conclusions: Despite peaks in disturbance, several of which created relatively large gaps, this system has experienced no significant change in species composition. Instead, the shade-tolerant Picea rubens has maintained canopy dominance. The patch dynamics described here consist of dramatic structural, not compositional, changes to the forest. The persistence of Picea rubens is attributed to a combination of traits: (1) abundance of advance regeneration; (2) ability to endure suppression and respond favourably to release; and (3) longevity relative to ecologically similar species.

  • 194.
    Fraver, Shawn
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Ringvall, Anna
    Jonsson, Bengt-Gunnar
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Refining volume estimates of down woody debris2007Ingår i: Canadian Journal of Forest Research, ISSN 0045-5067, E-ISSN 1208-6037, Vol. 37, nr 13, s. 627-633Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Down woody debris (DWD) plays a vital role in forest ecosystem structure and function. Although volume is likely the most common metric used to characterize DWD, an evaluation of the formulae used for volume estimation on individual DWD pieces has received little attention. We determined actual volume of 155 diverse DWD pieces (types, species, lengths, and diameters) by detailed field measurements. By comparing the actual and calculated volumes from six commonly used formulae, we assessed their bias, precision, and accuracy. Based on observed DWD forms, we developed a new formula, namely the “conic-paraboloid”, which was included in the assessment. Among the formulae that require length and two end diameter measurements, the conic-paraboloid had the lowest bias, highest precision, and hence greatest accuracy. Newton’s and the centroid formulae had higher accuracy yet require more field measurements. Smalian’s, conical frustum, and average-of-ends formulae had poor performance relative to the others. Accuracy of all formulae decreased with increasing piece length. Thus, partitioning pieces into two, three, and four sections for additional measurement improved accuracy. As decay advances, pieces become progressively more elliptical in cross section. Using the cross-sectional area derived from only the long axis of the ellipse leads to substantial volume overestimates for well-decayed DWD. [ABSTRACT FROM AUTHOR]

  • 195.
    Fraver, Shawn
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Seymour, R S
    Speer, J H
    White, A S
    Dendrochronological reconstruction of spruce budworm outbreaks in northern Maine, USA2007Ingår i: Canadian Journal of Forest Research, ISSN 0045-5067, E-ISSN 1208-6037, Vol. 37, nr 3, s. 523-529Artikel i tidskrift (Refereegranskat)
  • 196.
    Fraver, Shawn
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    White, A S
    Identifying growth releases in dendrochronological studies of forest disturbance2005Ingår i: Canadian Journal of Forest Research, ISSN 0045-5067, E-ISSN 1208-6037, Vol. 35, nr 7, s. 1648-1656Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Information on historical disturbances is vital to our understanding of current forest conditions. Dendro chronological methods provide one means of reconstructing disturbance histories in temperate and boreal forests. In particular, the dates of significant growth releases recorded on surviving trees provide strong inferential evidence of past disturbance events. The most common method of detecting releases (the percent-increase method) expresses the postevent growth increase as a percentage of the preevent rate. Despite its widespread use, the method is known to be overly sensitive at low rates of prior growth and overly stringent at high rates. We present an alternative method that directly follows the percent-increase method, but instead of dividing the postevent growth rate by the preevent rate, we simply subtract the two. If the difference exceeds a predetermined species-specific threshold, the event is considered a release. This absolute-increase method has convenient properties that remedy the shortcomings of the percent-increase method. We tested the validity of the absolute-increase thresholds by binary logistic regressions, and we compared the absolute- and percent-increase methods by various methods. We conclude that for the species evaluated in this study, the absolute-increase method represents an improvement over the standard percent-increase method.

  • 197.
    Fredriksson, Mattias
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Forsberg, Sven
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Wood Fibre Composites with High Fibre Content2005Rapport (Övrigt vetenskapligt)
  • 198.
    Fredriksson, Mattias
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Petersson, Patrik
    Jörntén-Karlsson, Magnus
    Axelsson, Bengt-Olof
    Bylund, Dan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    An objective comparison of pre-processing methods for enhancement of liquid chromatography-mass spectrometry data2007Ingår i: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1172, nr 2, s. 135-150Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Four data pre-processing methods have been applied with different settings to data sets obtained from the analysis of a pharmaceutical drug and its degradation products by liquid chromatography�mass spectrometry (LC�MS). The methods compared were the frequently used component detection algorithm (CODA) and three kinds of digital filters�matched filtration (MF), Gaussian second derivative (GSD) and Savitzky�Golay. The aim was to evaluate the performance and robustness of these methods for extracted ion chromatogram (XIC), total ion chromatogram (TIC) and base peak chromatogram (BPC) in the presence of different types of noise. In accordance with theory, the best improvements in signal-to-noise ratio (S/N) of the XICs were obtained with MF under the ideal case with random white noise. However, when highly coloured noise was present, it was found that no improvements in XIC S/N could be obtained with any of the pre-processing methods studied. GSD and CODA did, however, improve the S/N for both TIC and BPC. GSD and CODA also significantly reduced the background in the spectral domain, thereby facilitating the interpretation of the mass spectra. Another advantage associated with CODA and to some extent also with GSD is their data reduction ability.

  • 199.
    Friman, Linda
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    The influence of Iron and Some Other Metals on the Optical Properties of Thermomechanical Pulps2004Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
  • 200.
    Friman, Linda
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Höglund, Hans
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Högberg, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Agnemo, Roland
    Tannin-iron impregnated thermomechanical pulp: Part I: Effects of extractions and heat on brightness2004Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 19, nr 2, s. 229-236Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Tannins are polyphenolic compounds found mainly in bark. When reacting with iron, they form strongly coloured complexes, which through contamination from the bark may induce a brightness decrease of mechanical pulps. Wood itself contains phenolic compounds, which can form coloured complexes with iron. We have investigated gallotannin as a model for metal-binding sites in the pulp. The behaviour of tannin-iron complexes in solution and in pulp has been studied. In aqueous solution, the tannin-iron complexes can be decolourised by the addition of diethylenetriaminepentaacetic acid (DTPA). The colour of the tannin-iron complexes was very pH-dependent. Thus in solution, these were decolourised at low pH and at high pH the spectral characteristics were changed substantially. We have studied the effects on brightness and heatinduced brightness loss of the impregnation of thermomechanical pulp (TMP) with 30 parts per million iron (ppm i.e. mg/kg) either as iron or tannin-iron as well as the possibility to decrease such effects by using various solvent extractions. The tannin-iron impregnation causes a decrease in ISO-brightness of approximately 3% and an increase in the light absorption coefficient (k) by approximately 2 m(2)/kg at the tannin-iron absorbance maximum. 565 run. These effects are approximately ten times higher than those observed for the Pulp only impregnated with iron. Extraction with 1% by weight of DTPA provides a way to reduce the brightness decrease induced by the tanniniron complexes and the observed decrease can be attributed to removal of iron from the pulp. Acid extraction was the most efficient way to reduce the iron content in the pulps and to decoulorise the tannin-iron impregnated pulp. However, after acid extraction of iron impregnated Pulps, new chromophores were evidently formed. Addition of the reducing agent, sulphite, to extractions had no effect on the iron removal or the brightness of the impregnated pulps. The heat-induced brightness loss is not influenced by the addition of tannin-iron or iron. The brightness loss caused by heat was lower for pulps extracted with DTPA.

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