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  • 201.
    Neuman, Magnus
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Edvardsson, Sverker
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Edström, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Solving the radiative transfer equation with a mathematical particle method2015Ingår i: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 40, nr 18, s. 4325-4328Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We solve the radiative transfer equation (RTE) using a recently proposed mathematical particle method, originally developed for solving general functional equations. We show that, in the case of the RTE, it gives several advantages, such as handling arbitrary boundary conditions and phase functions and avoiding numerical instability in strongly forward-scattering media. We also solve the RTE, including fluorescence, and an example is shown with a fluorescence cascade where light is absorbed and emitted in several steps. We show that the evaluated particle method is straightforward to implement, which is in contrast with many traditional RTE solvers, but a potential drawback is the tuning of the method parameters.

  • 202.
    Niga, Petru
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Örtegren, Jonas
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Klaman, Marianne
    Innventia.
    Blohm, Erik
    Innventia.
    Lofthus, Jon
    Innventia.
    Hybrid package printing. Assessment of the influence of paper media parameters for inkjet printing on flexographic printed paper.2014Ingår i: Narrow WebTech, ISSN 1617-206X, nr 1, s. 16-22Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Hybrid printing combining inkjet technology with flexography can be used to add customer specific information in the production of packaging and print. However, in order to improve print quality a comprehensive understanding of the mechanisms governing print quality is required. In this work, inkjet printing using three aqueous inkjet inks was performed on top of flexographic printouts on four paper substrates. The flexographic film contained tone values ranging from 0 to 100% ink coverage. Line quality and print density of the inkjet print were evaluated in order to estimate the influence of paper parameters on the print quality. Specifically, it was found that for the system studied, the flexographic film essentially dictates the surface energy while keeping the porosity and the surface roughness of the paper unaltered. These findings are further supported by micrograph images.

  • 203.
    Nilsson, Christina
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Modifiering av låssystem2016Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Syftet med detta projekt har varit att identifiera problem gällande ett elektroniskt låssystem som företaget Uniper använder på sina vattenkraftsanläggningar. Låsen är i form av elektroniska hänglås och låscylindrar. Miljön som dessa lås är placerade i kan vara både fuktig och kall vilket har gjort att låsen inte fungerar som de ska. Målsättning har varit att identifiera varför inte låsen fungerar och hitta lösningar som gör det möjligt att använda låsen i kalla och fuktiga miljöer. Låsen har demonterats och deras funktion, komponenter och material har analyserat för att hitta felkällor. För att lära sig mer om tätningslösningar och hur dessa utformas så har litteratur och webbaserade källor studerats inom området. Projektet har resulterat i ett flertal rekommendationer om justeringar av låskonstruktionerna så som byte utav tätningar och måttjusteringar. Även externa skydds i form av manschetter på hänglåsbygeln och skyddsplattor har tagits fram. Dusch- och frystester har genomförts på befintliga och modifierade lås och det var tydligt att de inte tålde kombinationen av vatten och kyla speciellt bra. Ett lås med alla de rekommenderade modifieringarna har inte testats. Vad det är som gör att en tätning inte fungerar kan vara svårt att identifiera då det är så många saker som ska vara uppfyllda för att en tätning ska fungera bra. Det kan exempelvis vara att tätningen är för stor eller att ytorna den tätar mot har en för grov yttextur, men det kan också vara en kombination av flera saker. Vidare bör flera tester genomföras på lås med alla modifieringar applicerade för att kunna se om de löser problemet och uppfyller målen för projektet.

     

  • 204.
    Niskanen, Tomas
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Huvudtitel: Testrigg: Utveckling av laborationsutrustning2018Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
  • 205.
    Niskanen, Tomas
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Lyftkran: En effektivisering av hjälpmedel för individuellt anpassade fordon2016Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Ortman är ett företag med inriktning mot individuell anpassning av fordon. I företaget finns behov av att studera brister i funktionen av en lyftkran som hjälper kunder att lyfta in hjälpmedel som väger över 120 kg i sina fordon. Marknaden är studerad av Ortman och de finner ingen lösning på problemet och önskar att bygga sin egen kon­struktion. Uppdraget är att skapa en förstudie om en kommande lösning angående problemet. Företaget önskar att bli självständiga med en produkt som klarar av att lyfta in hjälpmedel med vikter upp till 200 kg som målvikt. Önskemål från företaget är att huvudfunktionen och aktiviteterna ska vara den samma som den tidigare produkten. De verifierbara målen med uppdraget är att påbörja ett digitalt konstruktionsunderlag med hjälp av Solidworks som uppfyller målet att lyfta 200 kg vikt och har en livslängd på sex år. Med en lämplig designmetodik, togs den inköpta lyftkranens styrkor och svagheter fram från en belastningsanalys. I konceptframtagningen användes belastningsanalysen med en modifierad designprocess, på grund av de tidsramar som projektet omfattade. Process utfördes i följande ordning en förundersökning, en framtagning av kravspecifikationen med tillhörande funktionsanalys samt en konceptgenerering. För att kontrollera att målet blir uppfyllt mot kravspecifikationen, genomfördes då en jämförelse av den nuvarande produkten mot den frambearbetade konstruk­tionslösningen med en belastningsanalys. I analysen på det nya konceptet utfördes justeringar, för att kontrollera att projektet uppnår de verifierbara målen. Slutligen blev inte konceptet helt klart eftersom en vidare bearbetning behövs göras, på infästningen av lyftarmen. Då den komponenten passerar sträckgränsen för materialets egenskaper. En vidare studie om hur en utformning skall se ut behövs därmed göras. I diskussionen tas materialfrågor upp. Att använda ett material med högre E-modul skulle kunna vara en lösning på dem problem som finns men är ekonomisk mer kostsamt. De slutsatser som framgår är att lösningarna med tjockare komponenter skulle bidra med en högre belastning och eventuellt inte lösa problemet med lastproblemet utan istället öka påkänningarna av konstruktionen negativt.      

  • 206.
    Novikova, P. Y.
    et al.
    Gregor Mendel Institute, Austrian Academy of Sciences, Vienna Biocenter (VBC), Vienna, Austria.
    Hohmann, N.
    Centre for Organismal Studies Heidelberg, University of Heidelberg, Heidelberg, Germany .
    Nizhynska, V.
    Gregor Mendel Institute, Austrian Academy of Sciences, Vienna Biocenter (VBC), Vienna, Austria.
    Tsuchimatsu, T.
    Gregor Mendel Institute, Austrian Academy of Sciences, Vienna Biocenter (VBC), Vienna, Austria.
    Ali, J.
    Department of Plant Physiology, Ruhr-Universität Bochum, Bochum, Germany.
    Muir, G.
    Vienna Graduate School of Population Genetics, Institut für Populationsgenetik, Vetmeduni, Vienna, Austria .
    Guggisberg, A.
    Institute of Integrative Biology, ETH Zurich, Zurich, Switzerland .
    Paape, T.
    Department of Evolutionary Biology and Environmental Studies, University of Zurich, Zurich, Switzerland .
    Schmid, K.
    Institute of Plant Breeding, Seed Science and Population Genetics, University of Hohenheim, Stuttgart, Germany .
    Fedorenko, O. M.
    Institute of Biology, Karelian Research Center, Russian Academy of Sciences, Petrozavodsk, Russian Federation .
    Holm, Svante
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Säll, T.
    Department of Biology, Lund University, Lund, Sweden .
    Schlötterer, C.
    Institut für Populationsgenetik, Vetmeduni, Vienna, Austria .
    Marhold, K.
    Department of Botany, Faculty of Science, Charles University, Prague, Czech Republic .
    Widmer, A.
    Department of Plant Physiology, Ruhr-Universität Bochum, Bochum, Germany .
    Sese, J.
    Artificial Intelligence Research Center, National Institute of Advanced Industrial Science and Technology, Tokyo, Japan .
    Shimizu, K. K.
    Department of Evolutionary Biology and Environmental Studies, University of Zurich, Zurich, Switzerland .
    Weigel, D.
    Max Planck Institute for Developmental Biology, Tübingen, Germany .
    Krämer, U.
    Department of Plant Physiology, Ruhr-Universität Bochum, Bochum, Germany .
    Koch, M. A.
    Centre for Organismal Studies Heidelberg, University of Heidelberg, Heidelberg, Germany .
    Nordborg, M.
    Gregor Mendel Institute, Austrian Academy of Sciences, Vienna Biocenter (VBC), Vienna, Austria .
    Sequencing of the genus Arabidopsis identifies a complex history of nonbifurcating speciation and abundant trans-specific polymorphism2016Ingår i: Nature Genetics, ISSN 1061-4036, E-ISSN 1546-1718, Vol. 48, nr 9, s. 1077-1082Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The notion of species as reproductively isolated units related through a bifurcating tree implies that gene trees should generally agree with the species tree and that sister taxa should not share polymorphisms unless they diverged recently and should be equally closely related to outgroups. It is now possible to evaluate this model systematically. We sequenced multiple individuals from 27 described taxa representing the entire Arabidopsis genus. Cluster analysis identified seven groups, corresponding to described species that capture the structure of the genus. However, at the level of gene trees, only the separation of Arabidopsis thaliana from the remaining species was universally supported, and, overall, the amount of shared polymorphism demonstrated that reproductive isolation was considerably more recent than the estimated divergence times. We uncovered multiple cases of past gene flow that contradict a bifurcating species tree. Finally, we showed that the pattern of divergence differs between gene ontologies, suggesting a role for selection. © 2016 Nature America, Inc. All rights reserved.

  • 207.
    Novikova, Polina Yu
    et al.
    Gregor Mendel Inst, Vienna, Austria; Vienna Grad Sch Populat Genet, Vienna, Austria.
    Tsuchimatsu, Takashi
    Gregor Mendel Inst, Vienna, Austria.
    Simon, Samson
    Université de Lille, France.
    Nizhynska, Viktoria
    Gregor Mendel Inst, Vienna, Austria.
    Voronin, Viktor
    Gregor Mendel Inst, Vienna, Austria.
    Burns, Robin
    Gregor Mendel Inst, Vienna, Austria.
    Fedorenko, Olga M.
    Russian Acad Sci, Petrozavodsk, Russia.
    Holm, Svante
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Saell, Torbjoern
    Lund Univ, Dept Biol, Lund.
    Prat, Elisa
    INRA CNRGV, Castanet Tolosan, France.
    Marande, William
    INRA CNRGV, Castanet Tolosan, France.
    Castric, Vincent
    Univ Lille, France.
    Nordborg, Magnus
    Gregor Mendel Inst, Vienna, Austria.
    Genome Sequencing Reveals the Origin of the Allotetraploid Arabidopsis suecica2017Ingår i: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 34, nr 4, s. 957-968Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Polyploidy is an example of instantaneous speciation when it involves the formation of a new cytotype that is incompatible with the parental species. Because new polyploid individuals are likely to be rare, establishment of a new species is unlikely unless polyploids are able to reproduce through self-fertilization (selfing), or asexually. Conversely, selfing (or asexuality) makes it possible for polyploid species to originate from a single individual-a bona fide speciation event. The extent to which this happens is not known. Here, we consider the origin of Arabidopsis suecica, a selfing allopolyploid between Arabidopsis thaliana and Arabidopsis arenosa, which has hitherto been considered to be an example of a unique origin. Based on whole-genome re-sequencing of 15 natural A. suecica accessions, we identify ubiquitous shared polymorphism with the parental species, and hence conclusively reject a unique origin in favor of multiple founding individuals. We further estimate that the species originated after the last glacial maximum in Eastern Europe or central Eurasia (rather than Sweden, as the name might suggest). Finally, annotation of the self-incompatibility loci in A. suecica revealed that both loci carry non-functional alleles. The locus inherited from the selfing A. thaliana is fixed for an ancestral non-functional allele, whereas the locus inherited from the outcrossing A. arenosa is fixed for a novel loss-offunction allele. Furthermore, the allele inherited from A. thaliana is predicted to transcriptionally silence the allele inherited from A. arenosa, suggesting that loss of self-incompatibility may have been instantaneous.

  • 208.
    Nylander, Andreas
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Quality Tool Concept: Requirements for better life expectancy assessment2016Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Sund Birsta AB is a Swedish company that develops, markets and delivers a wide range of equipment, from single machines to complete handling systems for the steel industry. As a world leading machine manufacturer with machines all over the world it’s important for Sund Birsta to assist their customers with a first-class service that includes a good life expectancy assessment of wear parts. The overall purpose of the project is to develop a tool that is able to make a good estimation of the life span of Sund Birsta’s wear parts. The main goal is to create a concept for a method, rather than a finished, ready to use prototype. The initial stage in this project is to select a machine or machine element according to predetermined criteria and make the method as general as possible to be able to apply it to other machine elements. The project resulted in a concept consisting of data collection, analysis, storage and evaluation of data. The concrete and variable goals were met and a steady foundation for a future quality tool was developed. There is still a lot of work to do before a complete tool is ready for use but the concept is in such a state that it can be used to start collecting and analyzing data. Some data collecting methods need more work before it can be executed, for example the Programmable Logic-Controller-data (PLC-data), while maintenance and service data is ready for collection. When more data is collected it will be possible to start using it for life expectancy assessment by, for example, linear regression or other data analyzing methods.

  • 209.
    Nyström, Jonas
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Konstruktion av stålstruktur för konstverk: Dimensionering av ramverk2015Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Erik Olof Wiklund arbetar med konst och litteratur som ofta relaterar till hembygden och dess plats i samtiden. Wiklund är uppvuxen i Alfta, Hälsingland och tycker om att avbilda lokala platser och historiska byggnader i området. Det arbete som konstnären nu vill utföra är en fullskalig modell av en hälsingegård. Denna ska dock se ut som att den kommer upp ur marken. Wiklund behöver hjälp med skapandet av någon form av bärande struktur. Projektets övergripande syfte är därför att skapa och dimensionera en stålstruktur så att den kan bära konstverket samt tåla väderförhållandena som råder. Byggnaden som ska konstrueras kommer att utsättas för en del laster, t.ex. snö- och vindlaster. Metoden som använts består av litteraturstudie, förstudie, cad-modellering, simulering och analys. Vid simulering läggs tre krafter på. Dessa är kraften från vikten av snölasten samt vikt på brädor, fönster och tak, kraften från trycket av vindlasten samt gravitationskraften (som verkar på stålkonstruktionen). Simuleringen avgör om ytterligare cad-modellering behövs för att konstruktionen ska hålla. Materialet som simuleras heter EN 1.4301 och är det material som vanligen benämns rostfritt stål. Det resultat som erhållits känns rimligt med tanke på att det simulerats så pass många gånger att något eventuellt beräkningsfel i simuleringen bör ha upptäckts. Modellen uppfyller de krav som ställts på den och ska tåla de påfrestningar som uppstår på grund av väderförhållanden.

  • 210.
    Nyström, Jonas
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Gradin, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Thörnberg, Benny
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för elektronikkonstruktion.
    An experimental study of the chipping process with focus on energy consumption and chipping angles2018Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 33, nr 3, s. 460-467Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A series of chipping experiments were performed under both dynamic and quasi-static conditions in a laboratory wood chipper (dynamic) and in a MTS-servohydraulic testing machine (quasi-static). One aim with the experiments was to investigate the rate dependency of the energy consumption during chipping. Another aim was to try to determine the load per unit knife edge length required to initiate cutting. The experiments were carried out using different combinations of spout and edge angles. It was found that for large edge angles (keeping the spout angle constant at 30 °30^\circ ) there was a slight rate dependency such that the energy consumption was larger at higher cutting rates which is quite in opposite of what is expected if wood is assumed to be a viscoelastic material. It was also found that to determine the force at initiation of cutting, is not a trivial task. Both Acoustic Emission monitoring and visual inspection was used to this end. The wood species used in this study was pine (Pinus silvestris). 

  • 211.
    Näslin, Joel
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Persson, Rickard
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Minskning av en friktionskopplings temperaturberoende2018Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
  • 212.
    Näslund, Lars-Åke
    et al.
    Linkoping Univ, Thin Film Phys Div, Dept Phys Chem & Biol IFM, SE-58183 Linkoping, Sweden.
    Ingason, Arni S.
    Linkoping Univ, Thin Film Phys Div, Dept Phys Chem & Biol IFM, SE-58183 Linkoping, Sweden.
    Holmin, Susanne
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap. Permascand AB, SE-84010 Ljungaverk, Sweden.
    Rosen, Johanna
    Linkoping Univ, Thin Film Phys Div, Dept Phys Chem & Biol IFM, SE-58183 Linkoping, Sweden.
    Formation of RuO(OH)(2) on RuO2-Based Electrodes for Hydrogen Production2014Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, nr 28, s. 15315-15323Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The catalytic and durable electrode coating of ruthenium dioxide (RuO2), applied on nickel (Ni) substrates, is today utilized as electrocatalytic cathodes for hydrogen production, e.g., in the chlor-alkali process and alkaline water electrolysis. The drawback is, however, the sensitivity to reverse currents obtained during power shutdowns, e.g., at maintenance, where the RuO2-based electrodes can be severely damaged unless polarization rectifiers are employed. Through the material characterization techniques X-ray diffraction and X-ray photoelectron spectroscopy, we can now reveal that RuO2 coatings, when exposed to hydrogen evolution at industrially relevant conditions, transforms into ruthenium oxyhydroxide (RuO(OH)(2)). The study further shows that as the hydrogen evolution proceeds the formed RuO(OH)(2) reduces to metallic ruthenium (Ru).

  • 213.
    Näslund, Lars-Åke
    et al.
    Department of Physics, Chemistry, and Biology (IFM), Linköping University,.
    Sánchez-Sánchez, Carlos M.
    Instituto Universitario de Electroquímica, Universidad de Alicante.
    Ingason, Árni S.
    Uppsala universitet Fysiska sektionen Institutionen för fysik och astronomi Materialfysik .
    Bäckström, Joakim
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Herrero, Enrique
    Instituto Universitario de Electroquímica, Universidad de Alicante.
    Rosen, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik.
    Holmin, Susanne
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad Fysik.
    The Role of TiO2 Doping on RuO2-Coated Electrodes for the Water Oxidation Reaction2013Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, nr 12, s. 6126-6135Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Electrochemical water splitting into H2 and O2 presents a significant and challenging energy loss due to the high overpotential required at the anode. Today, in industrially relevant applications, dimensionally stable anodes (DSA) based on the electrocatalytic active RuO2 are conventionally utilized. To enhance the resistance against corrosion, incorporation of TiO2 in the RuO2-coated electrodes is widely employed. In the present work we have used scanning electrochemical microscopy (SECM) to demonstrate that TiO2-doped RuO2-coated electrodes, in addition to being more durable, also show an electrocatalytic activity that is, on average, 13% higher as compared to the pure RuO2-coated electrodes. We also demonstrate that cracks in the pure RuO2 coating are the most active zones, probably because Ti from the Ti support has diffused into the first applied layer of the RuO2 coating. To reveal the nature of this enhanced activity for water oxidation displayed on TiO2-doped RuO2 electrodes, we have employed X-ray photoelectron spectroscopy (XPS) for material characterization. The results show that the electrocatalytic activity enhancement displayed on the mixed (Ru1−x:Tix)O2 coating is promoted through a charge transfer from the RuO2 to the TiO2, which provides new and more reactive sites designated as activated RuO2δ+.

  • 214.
    Näslund, Robin
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Lundström, Adam
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Uppborrningsverktygsbalansering: Metoder för balansering av roterande verktyg2015Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Företaget som initierat det här projektet behöver ta fram en metod för automatiserad balansering av roterande verktyg för skärande bearbet-ning, med fokus på uppborrningsverktyg. Dessa verktyg kan ha olika dimensioner och olika balansfel. Företaget vill därför att metoden ska kunna balansera verktygen oavsett dimension och balansfel. Denna balansering kommer att tas fram med hjälp av ett optimeringsverktyg som valts att kallas ”NX optimization” som finns i det datorstödda design-programmet Siemens NX. Optimeringsverktyget arbetar med sex olika algoritmer och har olika inställningar som måste testas för att hitta de optimala inställningarna för balanseringen. Rapporten kommer att gå igenom olika förslag på balanseringsgeometrier som kan användas för att balansera verktyget. Förslagen testades därefter med optimerings-verktyget för att kunna fatta beslut om vilken geometri som är mest lämpad. Rapporten går även igenom hur balansgeometrierna tas fram i programmet Siemens NX samt hur optimeringen ställs in för bästa möjliga resultat. För att kunna fatta beslut om dessa inställningar har tester gjorts på de olika inställningar som kan ställas in i optimerings-verktyget. Resultaten som har erhållits pekar på att många inställningar såsom konvergenskriterier och konvergenshastighet inte har någon inverkan på optimeringsresultatet. Från resultaten kunde tre förslag på balanseringstyper väljas. Dessa balanseringstyper har valts att kallas ”fyra hål”, ”fyra planfräsningar” och ”enkel planfräsning”. De balanse-ringsgeometrier som valdes kan balansera flera olika verktyg och anses därför vara lämpliga balanseringstyper. Från resultaten kunde även förslag på vilken algoritm som borde användas vid optimering ges. Lexicographic var den algoritm som ansågs som mest lämpad på grund av dess precision och arbetstid.

  • 215.
    Olin, Håkan
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Svensson, Krister
    Althoff, Fredrik
    Danilov, Andrey
    Measurement device for electron microscope2003Patent (Övrig (populärvetenskap, debatt, mm))
  • 216.
    Olin, Håkan
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Zhang, Renyun
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Soap film coating2014Patent (Övrig (populärvetenskap, debatt, mm))
  • 217.
    Olofsson, Madelen
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    On the investigation of chemical parameters reflecting microbial activity linked to nutrient availability in forest soil2015Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    As agrarian society developed, the most fertile soils able to sustain the nutritional requirements needed for high crop yield were assigned to farming, while the more penurious soils were left to uphold the forest ecosystems. Some temperate forests are developed on acidic soils considered to be nutrient poor, as much of the inorganic nutrients are entrapped in poorly weatherable soil minerals and not easily accessed by plant roots. In an undisturbed ecosystem, the largest contribution of available nutrients comes from the recycling of organically bound nutrients via the decomposition of dead plant material. If biomass is removed, for instance with a more intensified exploitation of the forest ecosystems including whole tree harvesting, this source of nutrients is consequently decreased. The importance of soil mineral weathering as a source of nutrients, and especially that promoted by soil biota, is thereby emphasized.

    This thesis addresses biotic parameters associated with mineral weathering. Different aspects of soil solution sampling strategies and analysis of different organic ligands as well as biomarkers for the estimation of fungal biomass were investigated. These chemical parameters were also evaluated as indicators of microbial activity in relation to mineral nutrient availability in soil.

    With the assumption that the current nutrient status of a soil will affect the microbial interest of certain minerals as sources of inorganic nutrients, a mineral amendment trial was performed in a Swedish boreal forest soil. Overall, the amended soil presented good nutrient status, but with a possible shortage of iron. Due to this, it was hypothesized that the amended mineral with the highest iron content i.e. biotite would cause an elevation of microbial activity in its vicinity when compared to the bulk soil.

    The level of microbial activity in the vicinity of the amended minerals was evaluated via quantification of organic acids and siderophores, as well as estimation of fungal biomass and enzymatic activity.

    The highest microbial activity was measured for the O horizon of the investigated podzol, although nothing indicated an elevated association with the amended minerals. In the E horizon, however, elevation in microbial activity was observed in the vicinity of the biotite mineral when compared with bulk soil, although only a few of the investigated parameters differed significantly when evaluated separately.  

    To enable this study, a highly sensitive analytical method employing liquid chromatography and mass spectrometry was developed to quantify a number of hydroxamate siderophores. On-line pre-concentration enabled detection of these organic ligands in the pico-molar range – a necessity when analyzing natural samples.

    Furthermore, an analytical method was developed for the estimation of fungal biomass via quantification of chitin-derived glucosamine, which also employed liquid chromatography and tandem mass spectrometry. Unlike currently available methods, the one presented in this thesis did not involve analyte derivatization, which resulted in high sample throughput while simultaneously avoiding complications involved with the additional derivatization procedure.

    The distribution of a group of organic ligands known as aromatic low molecular mass organic acids was also studied in a boreal forest podzol soil. Different sampling and samples preparation techniques, namely tension-lysimeters, soil centrifugation and liquid-soil extraction, were compared when analyzing soil solution components. Significant differences in analyte amount and species type were found between these sampling techniques. Some of the differences could be accounted for by variation in soil composition at different depths of the investigated podzol, but others could be attributed to structural differences within the studied analyte group. This clearly illustrated the intricacy of sampling and analysis when working with a sample matrix as complex and diverse as soil.

    As previously, liquid chromatography and mass spectrometry was used to quantify the analytes of interest. A highly sensitive analytical method was developed that was able to detect eleven aromatic low molecular mass organic acids in the nano-molar range. High selectivity was ensured by applying multiple reaction monitoring enabled by collision induced fragmentation of the analytes.

     

  • 218.
    Olofsson, Madelen
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Bylund, Dan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Analysis of hydroxamate siderophores in soil solution using liquid chromatography with mass spectrometry and tandem mass spectrometry with on-line sample preconcentration2015Ingår i: Journal of Separation Science, ISSN 1615-9306, E-ISSN 1615-9314, Vol. 38, nr 19, s. 3305-3312Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A liquid chromatography-electrospray ionization-mass spectrometry method was developed to quantitatively and qualitatively analyze thirteen hydroxamate siderophores (ferrichrome, ferrirubin, ferrirhodin, ferrichrysin, ferricrocin, ferrioxamine B, D1, E and G, neocoprogen I and II, coprogen and triacetylfusarinine C). Samples were pre-concentrated on-line via switch-valve setup prior to analyte separation on a Kinetex C18 column. Gradient elution was performed using a mixture of an ammonium formate buffer and acetonitrile. Total analysis time including column conditioning was 20.5 minutes. Analyte were fragmented by applying collision induced dissociation, enabling structural identification via tandem mass spectrometry. Limit of detection values for the selected ion monitoring method ranged from 71 pM to 1.5 nM with corresponding values of two to nine times higher for the multiple reaction monitoring method. The liquid chromatography-mass spectrometry method resulted in a robust and sensitive quantification of hydroxamate siderophores as indicated by retention time stability, linearity, sensitivity, precision and recovery. The analytical error of the methods, assessed trough random-order, duplicate analysis of soil samples extracted with a mixture of 10 mM phosphate buffer and methanol, appears negligible in relation to between-sample variations. 

  • 219.
    Olofsson, Madelen
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Bylund, Dan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Effects of mineral amendment on soil chemistry parameters reflecting microbial activity in a Swedish boreal forest soilManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    Samples of apatite, biotite and oligoclase were incubated in different soil horizons of a boreal forest podzol in central Sweden. After four years, soil from the bulk and the surfaces of the minerals were extracted and analyzed in regard to fungal biomass, enzymatic activity, low molecular mass organic acids and hydroxamate siderophores.  The nutrient status of the study area was evaluated using historical data from foliar and soil solution analysis. Soil solution indicated a possible shortage of P in the mineral soil even though foliar content was above target levels. The foliar analysis instead revealed possible shortage of Fe. Apatite is the primary source of inorganic P in soil and biotite is rich in Fe compared to the soil at the site, and it was hypothesized that both minerals could be attractive sources of weatherable mineral nutrients, hence associated with higher microbial activity. Parameters measured as indicators of microbial activity revealed few significant (p<0.05) differences between the minerals and bulk soil in the O horizon, probably due to large variations among replicates, although an overall higher microbial activity was found in the bulk soil. In the E horizon a distinct trend appeared indicating higher levels of low molecular mass organic acids, enzymatic activity and fungal biomass associated with the biotite mineral, although this observation was only found to be significant for some of the parameters when analyzed individually. No clear trends were observed in the B horizon.

  • 220.
    Olofsson, Madelen
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Bylund, Dan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Liquid Chromatography with Electrospray Ionization and Tandem Mass Spectrometry Applied in the Quantitative Analysis of Chitin-Derived Glucosamine for a Rapid Estimation of Fungal Biomass in Soil2016Ingår i: International Journal of Analytical Chemistry, ISSN 1687-8760, E-ISSN 1687-8779, artikel-id 9269357Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This method employs liquid chromatography-tandem mass spectrometry to rapidly quantify chitin-derived glucosamine for estimating fungal biomass. Analyte retention was achieved using hydrophilic interaction liquid chromatography, with a zwitter-ionic stationary phase (ZIC-HILIC), and isocratic elution using 60 % 5 mM ammonium formate buffer (pH 3.0) and 40 % ACN. Inclusion of muramic acid, and its chromatographic separation from glucosamine, enabled calculation of the bacterial contribution to the latter. Galactosamine, an isobaric isomer to glucosamine, found in significant amounts in soil samples, was also investigated. The two isomers form the same precursor and product ions, and could not be chromatographically separated using this rapid method. Instead, glucosamine and galactosamine were distinguished mathematically, using the linear relationships describing the differences in product ion intensities for the two analytes. The m/z transitions of 180→72 and 180→84 were applied for the detection of glucosamine and galactosamine and that of 252→126 for muramic acid. Limits of detection were in the pico-molar range for all included analytes. The total analysis time was 6 min, providing a high sample through-put method.

  • 221.
    Olofsson, Madelen
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Norström, Sara
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Bylund, Dan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Evaluation of sampling and sample preparation procedures for the determination of aromatic acids and their distribution in a podzol soil using liquid chromatography-tandem mass spectrometry2014Ingår i: Geoderma, ISSN 0016-7061, E-ISSN 1872-6259, Vol. 232-234, s. 373-380Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work the distribution of free and weekly adsorbed aromatic acids (phthalic acid and ten phenolicacids; gallic, p-hydroxybenzoic, salicylic, vanillic, protocatechuic, p-coumaric, syringic, sinapic, ferulic and caffeicacid), which could participate in weathering and soil formation processes, were studied for O, E and Bhorizons in a podzol soil in central Sweden. For the analysis a simple and rapid quantitative and qualitative liquidchromatography–tandem mass spectrometry method (using gradient elution) was developed with LODs rangingfrom 5 to 25 nM. Different soil solution sampling techniques (tension-lysimeter and soil centrifugation) and soilextraction with either 10 mM phosphate buffer (pH 7.2) or 50:50 (v/v) 10 mM phosphate buffer:MeOHwere compared. All eleven acids were found in detectable or trace concentrations. The most abundant aromaticacids were vanillic and phthalic acid with concentrations around 1 μM for O and E horizon respectively.Lysimeter samples resulted in the lowest concentrations followed by centrifugation samples. Ingeneral, buffer:MeOH extraction resulted in the highest concentrations for the O horizon, likely due toMeOH's ability to compete for hydrophobic sites on soil organic matter (SOM). Then again, pure bufferwith its higher ion strength, interfering with the acids electrostatic interactions with clay particles, leads tohigher extracted concentrations for the E and B horizons. Since the efficiency of the extraction solutions, to alarge extent, depends on the sample properties, a general approach is hard to appoint. However, the extractionof substituted cinnamic acids is in general facilitated by adding MeOH to the extraction solution. The use of statisticalmethods for the evaluation of the results showed a large and significant difference in aromatic acid concentrationsreceived using different sampling techniques and sample preparations. In fact, sampling methodsresulted in higher variations in aromatic acid concentrations than sampled horizon.

  • 222.
    Olsen, Martin
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Örtegren, Jonas
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Zhang, Renyun
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Reza, Salim
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för elektronikkonstruktion.
    Andersson, Henrik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för elektronikkonstruktion.
    Olin, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Schottky model for triboelectric temperature dependence2018Ingår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, nr 1, artikel-id 5293Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The triboelectric effect, charging by contact, is the working principle in a device called a triboelectric nanogenerator. They are used as efficient energy transducers in energy harvesting. In such generators the charging of surfaces at contact is followed by a separation of the surfaces increasing the electrical energy which can subsequently be used. Different materials have different triboelectric potentials leading to charging at contact. The temperature dependence of the charging has just recently been studied: the triboelectric effect is decreasing with temperature for a generator of Al-PTFE-Cu. Here, we suggest a mechanism to explain this effect assuming ion transfer using a two-level Schottky model where the two levels corresponds to the two surfaces. The difference in binding energy for ions on the two surfaces then enters the formula for charging. We fit the triboelectric power density as a function of temperature obtained from a two-level Schottky model to measured data for nanogenerators made of Al-PTFE-Cu found in three references. We obtain an average separation energy corresponding to a temperature of 365 K which is of the right magnitude for physically adsorbed atoms. We anticipate that this model could be used for many types of triboelectric nanogenerators.

  • 223.
    Orelund, Jonas
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Fire regimes and anthropogenic impacts in a boreal forest landscape2015Självständigt arbete på avancerad nivå (masterexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Forest fires are historically one of the dominant disturbances in boreal forest landscapes. The last 150 years of fire suppression have basically removed this disturbance from Fennoscandia. To remediate this, restoration fires are commonly used in protected areas as a conservation method. However, their application require understanding of past fire intervals in both inhabited and uninhabited areas of importance. In this study, fires of the past 700 years are dated in both space and time in a 15800 ha boreal forest landscape in the middle of Sweden. In total 222 wood samples have been analyzed representing 632 individual fire scars. Standard dendrochronological methods were used for the construction of a ring width chronology used for cross dating the fire scared wood samples. The spatial and temporal patterns of these fires are combined with information on historical human activities, such as local slash and burn settlements, armed conflicts and forest management. The earliest dated fire occurred in 1232 A.D. The frequency of fires increased in the 1600s, approximately at the same time as human population and activity increases. In the second part of 1800s, detected forest fires decreases significantly. Together with historical information, the results indicate links between size and frequencies of fires and human land use during most of the studied time period. However, in the early phases of the time sequence studied (1400s to 1500s), fire regime may be considered controlled by natural dynamics and climate. The fire interval in an average point in space at that time was 40 years, and an area approximately equal to the studied area burned each century.

  • 224.
    Osong, Sinke H.
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Norgren, Sven
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Pettersson, Gunilla
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Engstrand, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Còrdova, Armando
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Afewerki, Samson
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Alimohammadzadeh, Rana
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Processing of nanocellulose and applications relating to CTMP-based paperboard and foams2016Ingår i: International Mechanical Pulping Conference 2016, IMPC 2016, TAPPI Press, 2016, s. 87-93Konferensbidrag (Refereegranskat)
    Abstract [en]

    Although remarkable success has been made in the production of nanocellulose through several processing methods, it still remain a challenge to reduce the overall energy consumption, to use green chemistry and sustainable approach in order to make it feasible for industrial production of this novel nanomaterial. Herein, we have developed a new eco-friendly and sustainable approach to produce nanocellulose using organic acid combined with high-shear homogenisation, made hydrophobisation of nanocellulose and cross-linked the modified nanocellulosic material. Also, TEMPO-mediated oxidised nanocellulose was produced in order to compare the processing route with that of mild organic acid hydrolysis. Freeze-dried 3D structure of TEMPO-derived nanocellulose foam materials made fi-om bleached sulphite pulp and CTMP, respectively. Further, there is growing interest in using nanocellulose or microfibrillated cellulose (MFC) as an alternative paper sfrength additive in papermaking, and in using chemi-thermomechanical pulp (CTMP) with high freeness in producing CTMP-based paperboard with high bulk properties. To achieve greater strength improvement results, particularly for packaging paperboards, different proportions of cationic starch (CS) or MFC can be used to significantly improve the z-strength, with only a slight increase in sheet density. Research in this area is exploring CS or MFC as potential strength additives in CTMP-based paperboard, which is interesting from an industrial perspective. The mean grammage of the CTMP handsheets produced was approximately 150 g m~, and it was found that blending CTMP with CS or MFC yielded handsheets with significantly improved z-strength, tensile index, burst index and other strength properties at similar sheet densities.

  • 225.
    Osong, Sinke Henshaw
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Dahlström, Christina
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Forsberg, Sven
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap. Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Andres, Britta
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Engstrand, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Norgren, Sven
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Engström, Ann-Christine
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Nanofibrillated cellulose/nanographite composite films2016Ingår i: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 23, nr 4, s. 2487-2500Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Though research into nanofibrillated cellulose (NFC) has recently increased, few studies have considered co-utilising NFC and nanographite(NG) in composite films, and, it has, however been a challenge to use high-yield pulp fibres (mechanical pulps) to produce this nanofibrillar material. It is worth noting that there is a significant difference between chemical pulp fibres and high-yield pulp fibres, as the former is composed mainly of cellulose and has a yield of approximately 50 % while the latter is consist of cellulose, hemicellulose and lignin, and has a yield of approximately 90 %. NFC was produced by combining TEMPO (2,2,6,6-tetramethypiperidine-1-oxyl)-mediated oxidation with the mechanical shearing of chemi-thermomechanical pulp (CTMP) and sulphite pulp (SP); the NG was produced by mechanically exfoliating graphite. The different NaClO dosages in the TEMPO system differently oxidised the fibres, altering their fibrillation efficiency. NFC-NG films were produced by casting in a Petri dish. We examine the effect of NG on the sheet-resistance and mechanical properties of NFC films. Addition of 10 wt% NG to 90 wt% NFC of sample CC2 (5 mmol NaClO CTMP-NFC homogenised for 60 min) improved the sheet resistance, i.e. from that of an insulating pure NFC film to 180 Omega/sq. Further addition of 20 (CC3) and 25 wt% (CC4) of NG to 80 and 75 wt% respectively, lowered the sheet resistance to 17 and 9 Omega/sq, respectively. For the mechanical properties, we found that adding 10 wt% NG to 90 wt% NFC of sample HH2(5 mmol NaClO SP-NFC homogenised for 60 min) improved the tensile index by 28 %, tensile stiffness index by 20 %, and peak load by 28 %. The film's surface morphology was visualised using scanning electron microscopy, revealing the fibrillated structure of NFC and NG. This methodology yields NFC-NG films that are mechanically stable, bendable, and flexible.

  • 226.
    Ottosson, Elisabet
    et al.
    Swedish Univ Agr Sci, BioCtr, Dept Forest Mycol & Plant Pathol, SE-75007 Uppsala, Sweden.
    Kubartova, Ariana
    Swedish Univ Agr Sci, BioCtr, Dept Forest Mycol & Plant Pathol, SE-75007 Uppsala, Sweden.
    Edman, Mattias
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Jönsson, Mari
    Swedish Univ Agr Sci, Swedish Species Informat Ctr, SE-75007 Uppsala, Sweden.
    Lindhe, Anders
    Swedish Univ Agr Sci, BioCtr, Dept Forest Mycol & Plant Pathol, SE-75007 Uppsala, Sweden.
    Stenlid, Jan
    Swedish Univ Agr Sci, BioCtr, Dept Forest Mycol & Plant Pathol, SE-75007 Uppsala, Sweden.
    Dahlberg, Anders
    Swedish Univ Agr Sci, BioCtr, Dept Forest Mycol & Plant Pathol, SE-75007 Uppsala, Sweden.
    Diverse ecological roles within fungal communities in decomposing logs of Picea abies2015Ingår i: FEMS Microbiology Ecology, ISSN 0168-6496, E-ISSN 1574-6941, Vol. 91, nr 3, artikel-id fiv012Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Fungal communities in Norway spruce (Picea abies) logs in two forests in Sweden were investigated by 454-sequence analyses and by examining the ecological roles of the detected taxa. We also investigated the relationship between fruit bodies and mycelia in wood and whether community assembly was affected by how the dead wood was formed. Fungal communities were highly variable in terms of phylogenetic composition and ecological roles: 1910 fungal operational taxonomic units (OTUs) were detected; 21% were identified to species level. In total, 58% of the OTUs were ascomycetes and 31% basidiomycetes. Of the 231 337 reads, 38% were ascomycetes and 60% basidiomycetes. Ecological roles were assigned to 35% of the OTUs, accounting for 62% of the reads. Wood-decaying fungi were the most common group; however, other saprotrophic, mycorrhizal, lichenized, parasitic and endophytic fungi were also common. Fungal communities in logs formed by stem breakage were different to those in logs originating from butt breakage or uprooting. DNA of specific species was detected in logs many years after the last recorded fungal fruiting. Combining taxonomic identification with knowledge of ecological roles may provide valuable insights into properties of fungal communities; however, precise ecological information about many fungal species is still lacking.

  • 227.
    Ottosson, Elisabet
    et al.
    Uppsala Biocenter, Department of Forest Mycology and Plant Pathology, Swedish University of Agricultural Sciences, Sweden.
    Nordén, Jenni
    Microbial Evolution Research Group, Department of Biosciences, University of Oslo, Norway.
    Dahlberg, Anders
    Uppsala Biocenter, Department of Forest Mycology and Plant Pathology, Swedish University of Agricultural Sciences, Sweden.
    Edman, Mattias
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Jönsson, Mari
    Swedish Species Information Centre, Swedish University of Agricultural Sciences, Sweden.
    Larsson, Karl-Henrik
    Natural History Museum, University of Oslo, Norway.
    Olsson, Jörgen
    Department of Wildlife, Fish, and Environmental Studies, Swedish University of Agricultural Sciences, Sweden.
    Penttillä, Reijo
    Finnish Forest Research Institute, Finland.
    Stenlid, Jan
    Uppsala Biocenter, Department of Forest Mycology and Plant Pathology, Swedish University of Agricultural Sciences, Sweden.
    Ovaskainen, Otso
    Metapopulation Research Group, Department of Biosciences, University of Helsinki, Finland.
    Species associations during the succession of wood-inhabiting fungal communities2014Ingår i: Fungal ecology, ISSN 1754-5048, E-ISSN 1878-0083, Vol. 11, s. 17-28Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We studied fungal succession in decaying wood by compiling time-series data of fruit body observations. We tested the hypothesis that the presence of a primary species affects the probability of a succeeding species occurring later on the same log. Significant associations were detected for 15 species pairs; these were consistent with earlier findings on cooccurrence patterns in single time surveys. We used enrichment analysis to test if species with particular life-history attributes were more often associated with the occurrence of a succeeding species, or vice versa. White rot fungi and fungi abundant as mycelia were more often associated with the occurrence of succeeding species, compared to brown rot fungi and species with low mycelial abundance. Our results indicate that certain primary species cause priority effects and non-random co-occurrence patterns in the field. These successional patterns are likely to be connected both with substrate modification and species interactions.

  • 228.
    Palo, Thomas
    et al.
    SLU i Umeå.
    Öhmark, Sara
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Iason, Glenn
    The James Hutton Institute.
    Distribution Of Winter Browsing By Moose: Evidence Of Long-Term Stability In Northern Sweden2015Ingår i: Alces, ISSN 0835-5851, Vol. 51, s. 35-43Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Predicting spatial distribution of large herbivore foraging is important for successfulmanagement, but accurate predictions remain elusive against a background of multiple causes modifiedby environmental stochasticity. Moose (Alces alces) might prefer to browse areas with high plant density,but if snow depth co-varies with plant density, this could restrict access to these sites and force useof sites with lower plant density and snow depth. Moose browsing was measured in 72 plots distributedwithin the subarctic birch (Betula spp.) forest landscape at Abisko in northern Sweden in 1996. In 2010,the same plots were revisited and the measurements repeated. A generalized linear model predictedmoose browsing on birch in 2010 from the browsing pattern on birch measured in 1996. The modelsuggested that neither total density of willow and birch stems nor snow depth were influential of foragingdistribution of birch at multiple spatial scales. The spatial scale at which clustering of browsing on birchoccurred, coincided with the scale of clustering of birch and willow (Salix spp.) stems at distances of1000–2500 m; at lesser distance browsing was distributed randomly. We concluded that moose demonstratestability in spatial browsing patterns after 14 years which corresponds to 3–4 generations of moose,and that plant density represents a cue for moose only at certain scales. Predictability of feeding sites isvaluable for long-term moose and forest management, and conservation planning.

  • 229.
    Palo-Nieto, Carlos
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Afewerki, Samson
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Anderson, Mattias
    AlbaNova Univ Ctr, KTH Royal Inst Technol, Sch Biotechnol, Div Ind Biotechnol, SE-10691 Stockholm, Sweden.
    Tai, Cheuk-Wai
    Stockholm Univ, Dept Mat & Environm Chem, Berzelii Ctr EXSELENT Porous Mat, S-10691 Stockholm, Sweden.
    Berglund, Per
    AlbaNova Univ Ctr, KTH Royal Inst Technol, Sch Biotechnol, Div Ind Biotechnol, SE-10691 Stockholm, Sweden.
    Cordova, Armando
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap. Stockholm Univ, Dept Mat & Environm Chem, Berzelii Ctr EXSELENT Porous Mat, S-10691 Stockholm, Sweden.
    Integrated Heterogeneous Metal/Enzymatic Multiple Relay Catalysis for Eco-Friendly and Asymmetric Synthesis2016Ingår i: ACS Catalysis, ISSN 2155-5435, E-ISSN 2155-5435, Vol. 6, nr 6, s. 3932-3940Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Organic synthesis is in general performed using stepwise transformations where isolation and purification of key intermediates is often required prior to further reactions. Herein we disclose the concept of integrated heterogeneous metal/enzymatic multiple relay catalysis for eco-friendly and asymmetric synthesis of valuable molecules (e.g., amines and amides) in one-pot using a combination of heterogeneous metal and enzyme catalysts. Here reagents, catalysts, and different conditions can be introduced throughout the one-pot procedure involving multistep catalytic tandem operations. Several novel cocatalytic relay sequences (reductive amination/amidation, aerobic oxidation/reductive amination/amidation, reductive amination/kinetic resolution and reductive amination/ dynamic kinetic resolution) were developed. They were next applied to the direct synthesis of various biologically and optically active amines or amides in one-pot from simple aldehydes, ketones, or alcohols, respectively.

  • 230.
    Pavinatto, Adriana
    et al.
    University of São Paulo, Brazil.
    Delezuk, Jorge A.M.
    University of São Paulo, Brazil.
    Souza, Adriano L.
    University of São Paulo, Brazil.
    Pavinatto, Felippe J.
    University of São Paulo, Brazil.
    Volpati, Diogo
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap. São Carlos Institute of Physics, University of São Paulo, USP, P.O. Box 369, São Carlos, SP, Brazil .
    Miranda, Paulo B.
    University of São Paulo, Brazil.
    Campana-Filho, Sérgio P.
    University of São Paulo, Brazil.
    Oliveira Jr., Osvaldo N.
    University of São Paulo, Brazil.
    Experimental evidence for the mode of action based on electrostatic and hydrophobic forces to explain interaction between chitosans and phospholipid Langmuir monolayers2016Ingår i: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 145, s. 201-207Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The interaction between chitosans and Langmuir monolayers mimicking cell membranes has been explained with an empirical scheme based on electrostatic and hydrophobic forces, but so far this has been tested only for dimyristoyl phosphatidic acid (DMPA). In this paper, we show that the mode of action in such a scheme is also valid for dipalmitoyl phosphatidyl choline (DPPC) and dipalmitoyl phosphatidyl glycerol (DPPG), whose monolayers were expanded and their compressibility modulus decreased by interacting with chitosans. In general, the effects were stronger for the negatively charged DPPG in comparison to DPPC, and for the low molecular weight chitosan (LMWChi) which was better able to penetrate into the hydrophobic chains than the high molecular weight chitosan (Chi). Penetration into the hydrophobic chains was confirmed with polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS) and sum frequency generation (SFG) spectroscopy. A slight reduction in conformational order of the lipid chains induced by the chitosans was quantitatively estimated by measuring the ratio between the intensities of the methyl (r+) and methylene (d+) peaks in the SFG spectra for DPPG. The ratio decreased from 35.6 for the closely packed DPPG monolayer to 7.0 and 6.6 for monolayers containing Chi and LMWChi, respectively. Since in both cases there was a significant phospholipid monolayer expansion, the incorporation of chitosans led to chitosan-rich and lipid-rich condensed domains, which mantained conformational order for their hydrophobic tails. The stronger effects from LMWChi are ascribed to an easier access to the hydrophobic tails, as corroborated by measuring aggregation in solution with dynamic light scattering, where the hydrodynamic radius for LMWChi was close to half of that for Chi. Taken together, the results presented here confirm that the same mode of action applies to different phospholipids that are important constituents of mammalian (DPPC) and bacterial (DPPG) cell membranes.

  • 231.
    Pe'er, G.
    et al.
    UFZ-Helmholtz Centre for Environmental Research, Department of Conservation Biology, Permoserstr. 15, Leipzig, 04318, Germany.
    Mcneely, J. A.
    Cornell University, Rue Mauverney 28, 1196 Gland, Ithaca, NY, 14850, United States.
    Dieterich, M.
    University of Hohenheim, Institute for Landscape and Vegetation Ecology, August von Hartmannstr. 3, D-70599 Stuttgart, Germany.
    Jonsson, Bengt Gunnar
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Selva, N.
    Institute of Nature Conservation, Polish Academy of Sciences, Mickiewicza 33, 31-120 Krakow, Poland.
    Fitzgerald, J. M.
    Society for Conservation Biology, 1017 O Street, N.W., Washington, DC 20001, United States.
    Nesshöver, C.
    UFZ-Helmholtz Centre for Environmental Research, Department of Conservation Biology, Permoserstr. 15, Leipzig, 04318, Germany.
    IPBES: Opportunities and Challenges for SCB and Other Learned Societies2013Ingår i: Conservation Biology, ISSN 0888-8892, E-ISSN 1523-1739, Vol. 27, nr 1, s. 1-3Artikel i tidskrift (Refereegranskat)
  • 232.
    Persson, Johan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    On dynamic crack growth in discontinuous materials2015Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    In this thesis work numerical procedures are developed for modeling dynamic fracture of discontinuous materials, primarily materials composed of a load-bearing network. The models are based on the Newtonian equations of motion, and does not require neither stiffness matrices nor remeshing as cracks form and grow. They are applied to a variety of cases and some general conclusions are drawn. The work also includes an experimental study of dynamic crack growth in solid foam. The aims are to deepen the understanding of dynamic fracture by answering some relevant questions, e.g. What are the major sources of dissipation of potential energy in dynamic fracture? What are the major differences between the dynamic fracture in discontinuous network materials as compared to continuous materials? Is there any situation when it would be possible to utilize a homogenization scheme to model network materials as continuous? The numerical models are compared with experimental results to validate their ability to capture the relevant behavior, with good results. The only two plausible dissipation mechanisms are energy spent creating new surfaces, and stress waves, where the first dominates the behavior of slow cracks and the later dominates fast cracks. In the numerical experiments highly connected random fiber networks, i.e. structures with short distance between connections, behaves phenomenologically like a continuous material whilst with fewer connections the behavior deviates from it. This leads to the conclusion that random fiber networks with a high connectivity may be treated as a continuum, with appropriately scaled material parameters. Another type of network structures is the ordered networks, such as honeycombs and semi-ordered such as foams which can be viewed as e.g. perturbed honeycomb grids. The numerical results indicate that the fracture behavior is different for regular honeycombs versus perturbed honeycombs, and the behavior of the perturbed honeycomb corresponds well with experimental results of PVC foam.

  • 233.
    Persson, Johan
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Engberg, Birgitta A.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Granfeldt, Thomas
    Valmet AB.
    Feeding of double disc refiners - modeling of particle flow2018Ingår i: IMPC 2018, Trondheim, Norway, 2018Konferensbidrag (Refereegranskat)
    Abstract [en]

    Improvements to the energy efficiency of double disk refiners are hampered by the feeding rate in tothe machine. This study aims to evaluate parameters towards a complete model, which will help tobring clarity to the limiting factors in feeding rate. A combined computational fluid dynamic anddiscrete element model is used to evaluate the flowrate of a hopper discharge unaided, and aided by agas flow with varying density. The results of the study shows that it is essential to capture the exactgeometry of the double disk feeding in relation to the woodchips in the complete model. The resultsalso shows that while it is essential to include the gas phase in the full model, the model is not sensitiveto small variance in the density of the gas.

  • 234.
    Persson, Johan
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Isaksson, Per
    Applied Mechanics, Ångström Laboratory, Uppsala University, Box 534, SE-75121 Uppsala, Sweden.
    A mechanical particle model for analyzing rapid deformations and fracture in 3D fiber materials with ability to handle length effects2014Ingår i: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146, Vol. 51, nr 11-12, s. 2244-2251Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A mechanical model for analyses of rapid deformation and fracture in three-dimensional fiber materials is derived. Large deformations and fractures are handled in a computationally efficient and robust way. The model is truly dynamic and computational time and memory demand scales linearly to the number of structural components, which make the model well suited for parallel computing. The specific advantages, compared to traditional continuous grid-based methods, are summarized as: (1) Nucleated cracks have no idealized continuous surfaces. (2) Specific macroscopic crack growth or path criteria are not needed. (3) The model explicitly considers failure processes at fiber scale and the influence on structural integrity is seamlessly considered. (4) No time consuming adaptive re-meshing is needed. The model is applied to simulate and analyze crack growth in random fiber networks with varying density of fibers. The results obtained in fracture zone analyses show that for sufficiently sparse networks, it is not possible to make predictions based on continuous material assumptions on a macroscopic scale. The limit lies near the connectivity l(c)/L = 0.1, where is the ratio between the average fiber segment length and the total fiber length. At ratios l(c)/L < 0.1 the network become denser and at the limit l(c)/L -> 0, a continuous continuum is approached on the macroscopic level. (C) 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license.

  • 235.
    Persson, Johan
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Isaksson, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    A particle-based method for mechanical analyses of planar fiber-based materials2013Ingår i: International Journal for Numerical Methods in Engineering, ISSN 0029-5981, E-ISSN 1097-0207, Vol. 93, nr 11, s. 1216-1234Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A new discrete element model to deal with rapid deformation and fracture of flat fibrous materials is derived. The method is based on classical mechanical theories and is a combination of traditional particle dynamics and nonlinear engineering beam theory. It is assumed that a fiber can be seen as a beam that is represented by discrete particles, which are moving according to Newton's laws of motion. Damage is dealt with by fracture of fiber-segments and fiberfiber bonds when the potential energy of a segment or bond exceeds the critical fracture energy. This allows fractures to evolve as a result of material properties only. To validate the model, four examples are shown and compared with analytical results found in literature. Copyright (c) 2013 John Wiley & Sons, Ltd.

  • 236.
    Persson, Johan
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Isaksson, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Gradin, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Dynamic mode I crack growth in a notched foam specimen under quasi static loadingManuskript (preprint) (Övrigt vetenskapligt)
  • 237.
    Persson, Johan
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Per, Isaksson
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Modeling rapidly growing cracks in planar materials with a view to micro structural effects2015Ingår i: International Journal of Fracture, ISSN 0376-9429, E-ISSN 1573-2673, Vol. 192, nr 2, s. 191-201Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Dynamic fracture behavior in both fairly continuous materials and discontinuous cellular materials is analyzed using a hybrid particle model. It is illustrated that the model remarkably well captures the fracture behavior observed in experiments on fast growing cracks reported elsewhere. The material's microstructure is described through the configuration and connectivity of the particles and the model's sensitivity to a perturbation of the particle configuration is judged. In models describing a fairly homogeneous continuous material, the microstructure is represented by particles ordered in rectangular grids, while for models describing a discontinuous cellular material, the microstructure is represented by particles ordered in honeycomb grids having open cells. It is demonstrated that small random perturbations of the grid representing the microstructure results in scatter in the crack growth velocity. In materials with a continuous microstructure, the scatter in the global crack growth velocity is observable, but limited, and may explain the small scattering phenomenon observed in experiments on high-speed cracks in e.g. metals. A random perturbation of the initially ordered rectangular grid does however not change the average macroscopic crack growth velocity estimated from a set of models having different grid perturbations and imply that the microstructural discretization is of limited importance when predicting the global crack behavior in fairly continuous materials. On the other hand, it is shown that a similar perturbation of honeycomb grids, representing a material with a discontinuous cellular microstructure, result in a considerably larger scatter effect and there is also a clear shift towards higher crack growth velocities as the perturbation of the initially ordered grid become larger. Thus, capturing the discontinuous microstructure well is important when analyzing growing cracks in cellular or porous materials such as solid foams or wood.

  • 238.
    Pettersson, M.
    et al.
    Prosthetic Dentistry Department of Odontology Faculty of Medicine, Umeå University, Umeå.
    Kelk, P.
    Department of Integrative Medical Biology Faculty of Medicine, Umeå University, Umeå.
    Belibasakis, G. N.
    Section of Oral Microbiology and Immunology Institute of Oral Biology Center of Dental Medicine, University of Zürich, Zürich, Switzerland.
    Bylund, Dan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Molin Thorén, M.
    Prosthetic Dentistry Department of Odontology Faculty of Medicine, Umeå University, Umeå.
    Johansson, A.
    Molecular Periodontology Department of Odontology Faculty of Medicine, Umeå University, Umeå.
    Titanium ions form particles that activate and execute interleukin-1β release from lipopolysaccharide-primed macrophages2017Ingår i: Journal of Periodontal Research, ISSN 0022-3484, E-ISSN 1600-0765, Vol. 52, nr 1, s. 21-32Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Background and Objective: Peri-implantitis is a destructive inflammatory process characterized by destruction of the implant-supporting bone. Inflammasomes are large intracellular multiprotein complexes that play a central role in innate immunity by activating the release of proinflammatory cytokines. Although inflammasome activation has previously been linked to periodontal inflammation, there is still no information on a potential association with peri-implantitis. The aim of this study was to examine cytotoxic and proinflammatory effects, including inflammasome activation, of metals used in dental implants, in an in vitro model, as well as from clinical tissue samples. Material and methods: Human macrophages were exposed to different metals [titanium (Ti), cobalt, chromium and molybdenum] in a cell-culture assay. Cytotoxicity was determined using the neutral red uptake assay. Cytokine secretion was quantified using an ELISA, and the expression of genes of various inflammasome components was analysed using quantitative PCR. In addition, the concentrations of interleukin-1β (IL-1β) and Ti in mucosal tissue samples taken in the vicinity of dental implants were determined using ELISA and inductively coupled plasma mass spectrometry, respectively. Results: Ti ions in physiological solutions stimulated inflammasome activation in human macrophages and consequently IL-1β release. This effect was further enhanced by macrophages that have been exposed to lipopolysaccharides. The proinflammatory activation caused by Ti ions disappeared after filtration (0.22 μm), which indicates an effect of particles. Ti ions alone did not stimulate transcription of the inflammasome components. The Ti levels of tissue samples obtained in the vicinity of Ti implants were sufficiently high (≥ 40 μm) to stimulate secretion of IL-1β from human macrophages in vitro. Conclusion: Ti ions form particles that act as secondary stimuli for a proinflammatory reaction.

  • 239.
    Piirainen, Robert
    et al.
    Sundsvall Cty Hosp, Dept Lab Med, Sundsvall.
    Englund, Erling
    Sundsvall Cty Hosp, Dept Res & Dev, Sundsvall.
    Henriksson, Anders E.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap. Sundsvall Cty Hosp, Dept Lab Med, Sundsvall.
    The impact of seasonal variation of 25-hydroxyvitamin D and parathyroid hormone on calcium levels2016Ingår i: Clinical Biochemistry, ISSN 0009-9120, E-ISSN 1873-2933, Vol. 49, nr 12, s. 850-853Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Background: Primary hyperparathyroidism is often diagnosed by high calcium levels in blood. It is well known that calcium levels are dependent on vitamin D and Parathyroid hormone (PTH). Since vitamin D has a seasonal variation the calcium levels might also be influenced by seasonal variation. If a seasonal variation in calcium levels exists, this must be considered in the investigation of suspected hyperparathyroidism. The aim of the present study was to investigate the possible influence and magnitude of the seasonal variation of vitamin D and PTH on calcium levels. Method: In the present study the individual seasonal variation of 25-hydroxyvitamin D [25(OH) D], PTH and calcium in 69 healthy volunteers living at latitudes with extremely variable seasonal exposure to sunlight have been investigated. Results: As expected the 25(OH) D levels were significantly higher (42%) in summer compared to winter. PTH levels were significantly lower (7%) in summer than in winter. The mean serum concentration of calcium was 1% higher in August than in February, however not statistically significant. A good agreement between summer and winter calcium values was confirmed by Bland-Altman analysis. Conclusion: This study did not show any clinically important influence of seasonal variation of 25(OH) D and PTH on calcium that may influence a clinician's decision to investigate suspected hyperparathyroidism.

  • 240.
    Plötner, Björn
    et al.
    Max Planck Institute of Molecular Plant Physiology, Potsdam-Golm, Germany.
    Nurmi, Markus
    Max Planck Institute of Molecular Plant Physiology, Potsdam-Golm, Germany.
    Fischer, Axel
    Max Planck Institute of Molecular Plant Physiology, Potsdam-Golm, Germany.
    Watanabe, Mutsumi
    Max Planck Institute of Molecular Plant Physiology, Potsdam-Golm, Germany.
    Schneeberger, Korbinian
    Max Planck Institute for Plant Breeding, Cologne, Germany.
    Holm, Svante
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Vaid, Neha
    Max Planck Institute of Molecular Plant Physiology, Potsdam-Golm, Germany.
    Schöttler, Mark Aurel
    Max Planck Institute of Molecular Plant Physiology, Potsdam-Golm, Germany.
    Walther, Dirk
    Max Planck Institute of Molecular Plant Physiology, Potsdam-Golm, Germany.
    Hoefgen, Rainer
    Max Planck Institute of Molecular Plant Physiology, Potsdam-Golm, Germany.
    Weigel, Detlef
    Max Planck Institute for Developmental Biology, Tübingen, Germany.
    Laitinen, Roosa A. E.
    Max Planck Institute of Molecular Plant Physiology, Potsdam-Golm, Germany.
    Chlorosis caused by two recessively interacting genes reveals a role of RNA helicase in hybrid breakdown in Arabidopsis thaliana2017Ingår i: The Plant Journal, ISSN 0960-7412, E-ISSN 1365-313X, Vol. 91, nr 2, s. 251-262Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Hybrids often differ in fitness from their parents. They may be superior, translating into hybrid vigour or heterosis, but they may also be markedly inferior, because of hybrid weakness or incompatibility. The underlying genetic causes for the latter can often be traced back to genes that evolve rapidly because of sexual or host-pathogen conflicts. Hybrid weakness may manifest itself only in later generations, in a phenomenon called hybrid breakdown. We have characterized a case of hybrid breakdown among two Arabidopsis thaliana accessions, Shahdara (Sha, Tajikistan) and Lövvik-5 (Lov-5, Northern Sweden). In addition to chlorosis, a fraction of the F2 plants have defects in leaf and embryo development, and reduced photosynthetic efficiency. Hybrid chlorosis is due to two major-effect loci, of which one, originating from Lov-5, appears to encode an RNA helicase (AtRH18). To examine the role of the chlorosis allele in the Lövvik area, in addition to eight accessions collected in 2009, we collected another 240 accessions from 15 collections sites, including Lövvik, from Northern Sweden in 2015. Genotyping revealed that Lövvik collection site is separated from the rest. Crosses between 109 accessions from this area and Sha revealed 85 cases of hybrid chlorosis, indicating that the chlorosis-causing allele is common in this area. These results suggest that hybrid breakdown alleles not only occur at rapidly evolving loci, but also at genes that code for conserved processes.

  • 241.
    Pocock, Tessa
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap. Smart Lighting ERC, Rensselaer Polytechnic InstituteTroy, NY, United States.
    Falk, Stefan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Negative Impact on Growth and Photosynthesis in the Green Alga Chlamydomonas reinhardtii in the Presence of the Estrogen 17alpha-Ethynylestradiol2014Ingår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 9, nr 10, s. e109289-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    It is well known that estrogenic compounds affect development of fertilized eggs of many species of birds, fish and amphibians through disrupted activity of carbonic anhydrase (CA). The most potent activity comes from the most commonly occurring synthetic sterol, 17alpha-Ethynylestradiol (EE2). Less is known about the responses of aquatic phytoplankton to these compounds. Here we show for the first time that, in comparision to the control, the addition of 7 microM EE2 reduced the growth rate of the green alga Chlamydomonas reinhardtii by 68% for cells grown at high CO2. When cells were grown in ambient air (low Ci) with a fully activated carbon concentrating mechanism through the induction of CA activity, the growth rates were reduced by as much as 119%. A reduced growth rate could be observed at EE2 concentrations as low as 10 pM. This was accompanied by a reduced maximum capacity for electron transport in photosystem II as determined by a lower FV/FM for low Ci-grown cells, which indicates the involvement of CAH3, a CA specifically located in the thylakoid lumen involved in proton pumping across the thylakoid membranes. These results were in agreement with an observed reduction in the chloroplastic affinity for Ci as shown by a strong increase in the Michaelis-Menten K0.5 for HCO3-. In itself, a lowering of the growth rate of a green alga by addition of the sterol EE2 warrants further investigation into the potential environmental impact by the release of treated waste water.

  • 242.
    Pokorny, T.
    et al.
    Institute of Sensory Ecology, Heinrich-Department of Animal Ecology, Evolution and Biodiversity, Ruhr University Bochum, 44780 Bochum, Germany .
    Hannibal, M.
    Institute of Sensory Ecology, Heinrich-Heine University Düsseldorf, 40225 Düsseldorf, Germany .
    Quezada-Euan, J. J. G.
    Departamento de Apicultura, Universidad Autónoma de Yucatán, Mérida, Yucatán, 97100, Mexico .
    Hedenström, Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Sjöberg, Natalia
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Bång, Joakim
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Eltz, T.
    Department of Animal Ecology, Evolution and Biodiversity, Ruhr University Bochum, 44780 Bochum, Germany .
    Acquisition of species-specific perfume blends: Influence of habitat-dependent compound availability on odour choices of male orchid bees (Euglossa spp.)2013Ingår i: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 172, nr 2, s. 417-425Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Male orchid bees (Euglossini, Apidae, Hymenoptera) expose species-specific blends of volatile chemicals (perfume bouquets) during their courtship display. The perfumes are acquired by collecting fragrant substances from environmental sources, which are then accumulated in specialised hind leg pouches. To balance the perfume composition, the males need to find and collect the required substances in specific relative amounts while facing seasonal, local or habitat-dependent differences in compound availability. Experience-dependent choice of odours, i.e. 'learned avoidance' of recently collected components, has been proposed as the mechanism that mediates the accumulation of the stereotypical compound ratios. In the present study, we used the presence of certain compounds in male hind leg pouches as proxy for the respective local compound availability, and investigated whether differences in content are correlated with differences in chemical choice assays. Our results suggest that volatile availability differs between localities (n = 16) as well as habitats (n = 2; coastal vs. inland) across the Yucatán peninsula, Mexico, for both studied species. Male Euglossa dilemma showed a pronounced preference for benzyl benzoate and eugenol at locations where those compounds were rare in hind leg extracts, as predicted by the learned avoidance model. No equivalent correlations were found for Euglossa viridissima. This is the first study to combine chemical analyses of perfumes with bioassays of odour choice. It strengthens the view that negative feedback from collected odours modifies future chemical choice and helps males to acquire specific perfume blends. © 2013 Springer-Verlag Berlin Heidelberg.

  • 243.
    Rahaman, G M Atiqur
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Image analysis approach for modeling color predictions in printing2014Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
  • 244.
    Rahaman, G. M. Atiqur
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Norberg, O.
    Umea Univ, Dept Appl Phys & Elect, Umea, Sweden.
    Edström, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Experimental analysis for modeling color of halftone images2015Ingår i: Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), Springer, 2015, Vol. 9016, s. 69-80Konferensbidrag (Refereegranskat)
    Abstract [en]

    Reflectance models such as the monochrome Murray–Davies (MD) and the Neugebauer color equations make inaccurate predictions owing to changes in reflectance or tristimulus values (TSVs) of halftone dots and the paper between the dots. In this paper, we characterize the change of micro-TSVs as a function of printed area in spectral halftone image by a power function and compare its prediction efficiency using theoretically and experimentally measured limiting TSVs assuming dots of uniform thickness. We found that experimentally accounting for dot thickness variations as solid and mixed areas more precisely explained the single-model parameter that captured the observed lateral light scattering effect. The results showed that incorporating empirically modeled TSVs of the dots and the paper between dots, as well as introducing a new term addressing mixed area in the MD equation, produced CIE ΔE* ab in the range 1.22–1.76, and the overall gain was more than 1 ΔE* ab.

  • 245.
    Rahaman, G M Atiqur
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Norberg, Ole
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Edström, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Extension of Murray-Davies tone reproduction model by adding edge effect of halftone dots2014Ingår i: Proceedings of SPIE - The International Society for Optical Engineering, San Francisco, California, United States: SPIE - International Society for Optical Engineering, 2014, s. Art. no. 90180F-Konferensbidrag (Refereegranskat)
    Abstract [en]

    We propose expanding the Murray-Davies formula by adding the effect of edges of solid inks in a halftoned image. The expanded formula takes into account the spectral reflectance of paper white, full tone ink and mixed area scaled by the fractional area coverages. Here, mixed area mainly refers to the edge of an inked dot where the density is very low, and lateral exchange of photons can occur. Also, in such area the paper micro components may have higher scattering power than ink, especially, in uncoated paper. Our methodology uses cyan, magenta and yellow separation ramps printed on different papers by impact and non-impact based printing technologies. The samples include both frequency and amplitude modulation halftoning methods of various print resolutions. Based on pixel values, the captured microscale halftoned image is divided into three categories: solid ink, mixed area, and unprinted paper between the dots. The segmented images are then used to measure the fractional area coverage that the model receives as parameters. We have derived the characteristic reflectance spectrum of mixed area by rearranging the expanded formula and replacing the predicted term with the measured value using half of the maximum colorant coverage. Performance has clearly improved over the Murray-Davies model with and without dot gain compensation, more importantly, preserving the linear additivity of reflectance of the classical physics-based model.

  • 246.
    Rahaman, G M Atiqur
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Norberg, Ole
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Edström, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Microscale halftone color image analysis: perspective of spectral color prediction modeling2014Ingår i: Proceedings of SPIE - The International Society for Optical Engineering: Color Imaging XIX: Displaying, Processing, Hardcopy, and Applications, San Francisco, California, United States: SPIE - International Society for Optical Engineering, 2014, s. Art. no. 901506-Konferensbidrag (Refereegranskat)
    Abstract [en]

    A method has been proposed, whereby k-means clustering technique is applied to segment microscale single color halftone image into three components—solid ink, ink/paper mixed area and unprinted paper. The method has been evaluated using impact (offset) and non-impact (electro-photography) based single color prints halftoned by amplitude modulation (AM) and frequency modulation (FM) technique. The print samples have also included a range of variations in paper substrates. The colors of segmented regions have been analyzed in CIELAB color space to reveal the variations, in particular those present in mixed regions. The statistics of intensity distribution in the segmented areas have been utilized to derive expressions that can be used to calculate simple thresholds. However, the segmented results have been employed to study dot gain in comparison with traditional estimation technique using Murray-Davies formula. The performance of halftone reflectance prediction by spectral Murray-Davies model has been reported using estimated and measured parameters. Finally, a general idea has been proposed to expand the classical Murray-Davies model based on experimetal observations. Hence, the present study primarily presents the outcome of experimental efforts to characterize halftone print media interactions in respect to the color prediction models. Currently, most regression-based color prediction models rely on mathematical optimization to estimate the parameters using measured average reflectance of a large area compared to the dot size. While this general approach has been accepted as a useful tool, experimental investigations can enhance understanding of the physical processes and facilitate exploration of new modeling strategies. Furthermore, reported findings may help reduce the required number of samples that are printed and measured in the process of multichannel printer characterization and calibration.

  • 247.
    Rahaman, G M Atiqur
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Norberg, Ole
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Edström, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    The effect of media interactions in predicting spectral reflectance by color prediction models2013Konferensbidrag (Refereegranskat)
  • 248.
    Rahaman, G M Atiqur
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Parkkinen, Jussi
    School of Engineering, Monash University, Sunway Campus, Malaysia.
    Hauta-Kasari, Markku
    SIB Labs., School of Computing, University of Eastern Finland, Finland.
    Norberg, Ole
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Retinal Spectral Image Analysis Methods using Spectral Reflectance Pattern Recognition2013Ingår i: Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), Berlin Heidelberg: Springer, 2013, Vol. 7786, s. 224-238Konferensbidrag (Refereegranskat)
    Abstract [en]

    Conventional 3-channel color images have limited information andquality dependency on parametric conditions. Hence, spectral imaging andreproduction is desired in many color applications to record and reproduce thereflectance of objects. Likewise RGB images lack sufficient information tosuccessfully analyze diabetic retinopathy. In this case, spectral imaging may bethe alternative solution. In this article, we propose a new supervised techniqueto detect and classify the abnormal lesions in retinal spectral reflectance imagesaffected by diabetes. The technique employs both stochastic and deterministicspectral similarity measures to match the desired reflectance pattern. At first, itclassifies a pixel as normal or abnormal depending on the probabilistic behaviorof training spectra. The final decision is made evaluating the geometricsimilarity. We assessed several multispectral object detection methodsdeveloped for other applications. They could not proof to be the solution. Theresults were interpreted using receiver operating characteristics (ROC) curvesanalysis.

  • 249.
    Razaz, Ghadir
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Investigation of the Drawbacks in the Aluminium Alloys Casting Process2017Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
  • 250.
    Razaz, Ghadir
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Carlberg, Torbjörn
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Casting practices influencing inclusion distributions in billets2013Ingår i: Light Metals, ISSN 0147-0809, s. 987-991Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A macro-etching method has been used to analyze the distribution and amount of inclusions along billets and on cross sections. Main parameters that have been varied are holding time before casting and amount of liquid remaining after casting. The result show that short holding times, in the order of 10 minutes, give increased amount of inclusions in the beginning of the billets, but holding times in the range from 30 to 60 minutes do not show any significant differences. If the melt remaining in the furnace after casting is less than about 3000 kg, the inclusion density increases towards the end of the ingots. The distribution of inclusions over the cross section of billets show that most inclusions are found in the centre of the billets, however, at increased total amount of inclusions, they tend to appear evenly over the whole cross sections. The results are discussed based on convection in furnace and settling rates and convection at solidification front.

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