miun.sePublikationer
Ändra sökning
Avgränsa sökresultatet
1234567 51 - 100 av 726
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Träffar per sida
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
Markera
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 51. Berglund, Per
    et al.
    Hedenström, Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Preparation of 2-, 3-, and 4-methylcarboxylic acids and the corresponding alcohols of high enantiopurity by lipase catalyzed esterification2001Ingår i: Enzymes in Nonaqueous Solvents: Methods and Protocols, Humana Press, 2001, s. 307-317Kapitel i bok, del av antologi (Övrigt vetenskapligt)
  • 52.
    Berglund, Per
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Holmquist, M
    Hedenström, Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Hult, K
    Högberg, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    2-Methylalkanoic Acids Resolved by Esterification Catalysed by Candida rugosa: Alcohol Chain Length and Enantioselectivity1993Ingår i: Tetrahedron: Asymmetry, ISSN 0957-4166, Vol. 4, nr 8, s. 1869-1878Artikel i tidskrift (Refereegranskat)
  • 53.
    Berglund, Per
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Holmquist, M
    Hult, K
    Högberg, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Alcohols as Enantioselective Inhibitors in a Lipase Catalysed Esterification of a Chiral Acyl Donor1995Ingår i: Biotechnology Letters, ISSN 0141-5492, Vol. 17, nr 1, s. 55-60Artikel i tidskrift (Refereegranskat)
  • 54. Bergström, G
    et al.
    Wassgren, A.-B.
    Högberg, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Hedenström, Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Hefetz, Abraham
    Simon, Dan
    Ohlsson, T
    Löfqvist, J
    Species specific, Two-Component, Volatile Signals in two Sympatric Ant-lion Species: Synclysis baetica and Acanthaclisis occitanica (Neuroptera, Myrmeleontidae1992Ingår i: Journal of Chemical Ecology, ISSN 0098-0331, Vol. 17, nr 7, s. 1177-1188Artikel i tidskrift (Refereegranskat)
  • 55. Bergström, Gunnar
    et al.
    Wassgren, A.-B.
    Anderbrant, O
    Fägerhag, Jonas
    Edlund, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Hedenström, Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Högberg, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Geri, C
    Auger, M. A.
    Varama, M
    Hansson, B. S.
    Löfqvist, J
    Sex pheromone of the pine sawfly Diprion pini (Hymenoptera: Diprionidae): Chemical identification, synthesis and biological activity1995Ingår i: Experientia, ISSN 0014-4754, Vol. 51, nr 4, s. 370-380Artikel i tidskrift (Refereegranskat)
  • 56. Bergström, Gunnar
    et al.
    Wassgren, Ann-Britt
    Anderbrant, Olle
    Ochieng, Samuel
    Östrand, Fredrik
    Hansson, Bill S.
    Hedenström, Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Högberg, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Sex Pheromone of the Pine Sawfly Microdiprion pallipes (Hymenoptera: Diprionidae)1998Ingår i: Naturwissenschaften, ISSN 0028-1042, Vol. 85, nr 5, s. 244-248Artikel i tidskrift (Refereegranskat)
  • 57. Bhupinderpal-Singh,
    et al.
    Nordgren, A
    Ottosson Löfvenius, Mikael
    Högberg, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Mellander, Per- Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Högberg, P
    Large-scale girdling of Scots pine boreal forest reveals controls and estimates of mycorrhizal root soil heterotrophic respiration2003Ingår i: Proceedings Third International Symposium on the Dynamics of Physiological Processes in Woody Roots. Perth, Western Australia 29 Sept – 3 Oct, 2003, 2003Konferensbidrag (Övrigt vetenskapligt)
  • 58. Bishop, Kevin
    et al.
    Nyberg, L
    Stähli, Manfred
    Lindström, G
    Mellander, Per-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Ottosson Löfvenius, Mikael
    Tjäle och avrinning från boreal skogsmark - en studie inom Vindelns Försöksparker.2000Bok (Övrigt vetenskapligt)
  • 59.
    Björklund, Glenn
    et al.
    Mittuniversitetet, Fakulteten för humanvetenskap, Institutionen för hälsovetenskap.
    Pettersson, Sofia
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Schagatay, Erika
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Performance predicting factors in prolonged exhausting exercise of varying intensity2007Ingår i: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 99, nr 4, s. 423-429Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Several endurance sports, e.g. road cycling, have a varying intensity profile during competition. At present, few laboratory tests take this intensity profile into consideration. Thus, the purpose of this study was to examine the prognostic value of heart rate (HR), lactate (La−1), potassium (K+), and respiratory exchange ratio (RER) performance at an exhausting cycling exercise with varying intensity. Eight national level cyclists performed two cycle tests each on a cycle ergometer: (1) a incremental test to establish VO2max, maximum power (W max), and lactate threshold (VO2LT), and (2) a variable intensity protocol (VIP). Exercise intensity for the VIP was based upon the VO2max obtained during the incremental test. The VIP consisted of six high intense (HI) workloads at 90% of VO2max for 3 min each, interspersed by five middle intense (MI) workloads at 70% of VO2max for 6 min each. VO2 and HR were continuously measured throughout the tests. Venous blood samples were taken before, during, and after the test. Increases in HR, La-, K+, and RER were observed when workload changed from MI to HI workload (P < 0.05). Potassium and RER decreased after transition from HI to MI workloads (P < 0.05). There was a negative correlation between time to exhaustion and decrease in La- concentration during the first MI (r = −0.714; P = 0.047). Furthermore, time to exhaustion correlated with VO2LT calculated from the ramp test (r = 0.738; P = 0.037). Our results suggest that the magnitude of decrease of La−1 between the first HI workload and the consecutive MI workload could predict performance during prolonged exercise with variable intensity

  • 60. Björn, Lars Olof
    et al.
    Ekelund, Nils
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Dinoflagellater: Hopplock från livets smörgåsbord2005Ingår i: Svensk Botanisk Tidskrift, ISSN 0039-646X, Vol. 99, nr 1, s. 7-16Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The dinoflagellates constitute a group within the protistan supergroup Alveolata, and can be referred neither to the plant nor the animal kingdom. They swim about using two flagella and are able to orient using various stimuli. About half the living dinoflagellate species are capable of oxygenic photosynthesis, but most of them complement this with capture of prey. Some live ebtirely by capturing small organisms, others are parasites. Some species are able to emit light. The group has a long evolutionary history, and almost as many extinct species as extant ones have been described. Most remarkable is the way the photosynthetically potent dinoflagellates have aquiered their chloroplasts by endosymbiosis with photosynthetic organisms from many different groups. In some cases repeated endosymbiontic events have taken place.

  • 61. Björn, Lars Olof
    et al.
    Ekelund, Nils
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Koraller och deras fotosyntetiska endosymbionter, zooxantellerna.2006Ingår i: Svensk Botanisk Tidskrift, ISSN 0039-646X, Vol. 100, nr 4, s. 263-270Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
  • 62. Björn, Lars-Olof
    et al.
    Ekelund, Nils
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Koraller och zooxantheller: ett marint partnerskap2006Ingår i: Svensk botanisk tidskrift, ISSN 0039-646X, Vol. 100, nr 4, s. 263-270Artikel i tidskrift (Refereegranskat)
    Abstract [sv]

    De flesta revbildande koraller lever i ett ömsesidigt beroende med så kallade zooxanteller, encelliga alger som lever inuti koralldjuret och som med hjälp av sin fotosyntes bidrar till försörjningen.

  • 63. Branström, J.
    et al.
    Norgren, Sven
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Sandström, P.
    Ruel, K.
    Höglund, Hans
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Compression wood in knots and the effect on surface roughness.2005Ingår i: proceedings from IMPC 2005, 2005Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

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

  • 64. Bratt, Katarina
    et al.
    Sunnerheim, Kerstin
    Bryngelsson, Susanne
    Fagerlund, Amelie
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Engman, Lars
    Andersson, Rolf E
    Dimberg, Lena H
    Avenanthramides in Oats (Avena Sativa L.) and Structure-Activity Relationships2003Ingår i: Journal of Agricultural and Food Chemistry, ISSN 0021-8561, E-ISSN 1520-5118, Vol. 51, nr 3, s. 594-600Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Eight avenanthramides, amides of anthranilic acid (1) and 5-hydroxyanthranilic acid (2), respectively, and the four cinnamic acids p-coumaric (p), caffeic (c), ferulic (f), and sinapic (s) acid, were synthesized for identification in oat extracts and for structure−antioxidant activity studies. Three compounds (2p, 2c, and 2f) were found in oat extracts. As assessed by the reactivity toward 1,1-diphenyl-2-picrylhydrazyl (DPPH), all avenanthramides except 1p showed activity. Initially, the antioxidant activity of the avenanthramides decreased in a similar order as for the corresponding cinnamic acids, that is: sinapic > caffeic > ferulic > p-coumaric acid. The avenanthramides derived from 2 were usually slightly more active than those derived from 1. All avenanthramides inhibited azo-initiated peroxidation of linoleic acid. 1c and 1s were initially the most effective compounds. The relative order of antioxidant activities was slightly different for the DPPH and the linoleic acid assays run in methanol and chlorobenzene, respectively.

  • 65.
    Breistein, Palle
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Karlsson, Staffan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Hedenström, Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Chiral pyrrolidinium salts as organocatalysts in stereoselective 1,4-conjugate addition of N-methylpyrrole to cyclopent-1-ene carbaldehyde2006Ingår i: Tetrahedron: Asymmetry, ISSN 0957-4166, Vol. 17, nr 1, s. 107-111Artikel i tidskrift (Refereegranskat)
  • 66.
    Bydén Sjöbom, Malin
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Edlund, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Dependence of Alkyl Chain Asymmetry on the Phase Equilibria of Three Catanionic Surfactant Mixtures Containing Dodecyltrimethylammonium Chloride-Sodium Alkylcarboxylate-Water2002Ingår i: Langmuir, ISSN 0743-7463, Vol. 18, nr 22, s. 8309-8317Artikel i tidskrift (Refereegranskat)
  • 67.
    Bydén Sjöbom, Malin
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Edlund, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Lindström, Birger
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    BinaBinary Phase Equilibria and Structure of the Two α-Methyl-Substituted Surfactants Sodium (R)-2-Methyldecanoate and Racemic Sodium 2-Methyldecanoate ry Phase Exuilibria and Structure of the Chiral α-Methylsubstituted Surfactants Sodium (R)-2-Methyldecanoate and Racemic Sodium 2-Methyldecanoate1999Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 15, nr 8, s. 2654-2660Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study, we present the binary phase diagrams for the aqueous systems of the alkyldecanoic salts racemic sodium 2-methyldecanoate and sodium (R)-2-methyldecanoate, respectively. Both systems form a micellar solution phase, as well as a normal hexagonal, a cubic, and a lamellar liquid crystalline phase. They also form a very narrow intermediate phase, situated between the hexagonal and cubic liquid crystalline phases. The methods used for characterization were crossed polaroids, polarizing optical microscope and 2H NMR quadrupolar splittings combined with SAXS studies. The cubic phase gave a well-resolved SAXS diffraction pattern, with eight peaks present, which establishes the bicontinuous cubic structure as Ia3d. A significant difference in these two phase diagrams, compared to those of unsubstituted alkanoates with the same chain length, is the very low Krafft boundary.

  • 68.
    Bydén Sjöbom, Malin
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Hedenström, Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Edlund, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Binary Phase Equilibria of Three alfa-Methylsubstituted Sodium Alkanoate Surfactant Systems.2003Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, Vol. 257, nr 2, s. 333-336Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work, we continue our study of methyl -substituted surfactants and present the aqueous binary phase diagrams of racemic sodium 2-methyloctanoate, -nonanoate, and -dodecanoate, respectively. All systems have very low Krafft temperatures within the solution phase, between 1 and 4 degreesC. The phase sequences of the two shorter surfactants are very similar to those of the unsubstituted sodium octanoate, although with somewhat different range of existence for the phases formed. The sodium 2-methyldodecanoate system is different from the unsubstituted sodium dodecanoate system, as the former seems to lack a hexagonal phase. The surfactant systems were delineated using H-2 NMR splittings and crossed polarizers, and combined with SAXS for determination of phase structure. 

  • 69.
    Bydén Sjöbom, Malin
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Marques, Eduardo
    Edlund, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Khan, Ali
    Phase Equilibria of the Mixed Didodecyldimethylammonium Bromide-Taurodeoxycholate-Water System with a Large Solution Region.2005Ingår i: Colloids and Surfaces, ISSN 0166-6622, E-ISSN 1873-4340, Vol. 269, nr 1-3, s. 87-95Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The phase behavior over the entire concentration range for the system didodecyldimethylammonium bromide (DDAB)-sodium taurodeoxycholate (STDC)-water, at 25 degrees C, has been investigated, with emphasis on the DDAB-rich part. Polarizing microscopy, SAXS, H-2 NMR and H-1 self-diffusion NMR have been used in combination as probing techniques for phase behavior and microstructure. The system forms four major phases, all deriving from the respective binary surfactant systems. The two lamellar phases originating from the binary DDAB-water axis (D-I and D-II, at 3-30 and 83-91 wt.% DDAB, respectively) are only able to incorporate small amounts of STDC. The D-II phase solubilizes a comparatively higher amount of bile salt (up to ca. 6 wt.%), while the D, phase takes up less than 0.25 wt.%. From the STDC-water axis, a solution phase and a "hexagonal-like" liquid crystalline phase are derived, at 0-26 and 37-60 wt.% of STDC, respectively. Heterogeneous regions are also indicated on the basis of NMR and SAXS data. The most striking feature is the large extension of the isotropic solution phase, which originates from the water corner and curves toward the DDAB-rich side of the phase diagram. Even though at the upper limit of the solution phase the amount of water is reduced to 10 wt.%, the measured water and DDAB self-diffusion coefficients exclude the possibility of reverse-type structures.

  • 70.
    Bylund, Dan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Chemometric tools for enhanced performance in liquid chromatography-mass spectrometry2001Doktorsavhandling, monografi (Övrigt vetenskapligt)
  • 71.
    Bylund, Dan
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Bergens, Arne
    Jacobsson, S P.
    Optimisation of chromatographic separations by use of a chromatographic response function, empirical modelling and multivariate analysis1997Ingår i: Chromatographia, ISSN 0009-5893, Vol. 44, nr 1/2, s. 74-80Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The chiral separation of the drug substance R,S-oxybutynin chloride on a reversed phase HPLC system has been optimised by use of empirical modelling and multivariate analysis. The separation was characterised by a new chromatographic response function developed to modulate both quality of separation and retention time. The study includes a comparison between three different multivariate techniques (multi-layer feed-forward neural networks, multiple linear regression and partial least squares regression) of their capabilities to model the new chromatographic response function and predict its value for new experiments. It was indicated that the most accurate models were achieved with neural networks, although partial least squares regression could also be used to solve the problem since it gives the major directions for the optimal settings of the variables.

  • 72.
    Bylund, Dan
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Danielsson, Rolf
    Malmquist, Gunnar
    Markides, Karin A
    Chromatographic alignment by warping and dynamic programming as a pre-processing tool for PARAFAC modelling of liquid chromatography-mass spectrometry data2002Ingår i: Journal of Chromatography A, ISSN 0021-9673, Vol. 961, nr 2, s. 237-244Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Solutes analysed with LC–MS are characterised by their retention times and mass spectra, and quantified by the intensities measured. This highly selective information can be extracted by multiway modelling. However, for full use and interpretability it is necessary that the assumptions made for the model are valid. For PARAFAC modelling, the assumption is a trilinear data structure. With LC–MS, several factors, e.g. non-linear detector response and ionisation suppression may introduce deviations from trilinearity. The single largest problem, however, is the retention time shifts not related to the true sample variations. In this paper, a time warping algorithm for alignment of LC–MS data in the chromatographic direction has been examined. Several refinements have been implemented and the features are demonstrated for both simulated and real data. With moderate time shifts present in the data, pre-processing with this algorithm yields approximately trilinear data for which reasonable models can be made.

  • 73.
    Bylund, Dan
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Danielsson, Rolf
    Markides, Karin E
    Peak purity assessment in liquid chromatography-mass spectrometry2001Ingår i: Journal of Chromatography A,, ISSN 0021-9673, Vol. 915, nr 1/2, s. 43-52Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Fixed-size moving window evolving factor analysis and base peak chromatograms have been used for peak purity detection in data generated with LC–MS. The two methods were evaluated with both real and simulated data and were found to be fast and complementary to each other. When a possibly impure peak is detected, it is suggested that further information can be obtained from local principal component analysis modelling and comparative mass chromatogram plots.

  • 74.
    Bylund, Dan
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Norström, Sara
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Essén, Sofia
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Lundström, Ulla
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Analysis of low molecular mass organic acids in natural waters by ion exclusion chromatography tandem mass spectrometry2007Ingår i: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1176, nr 1-2, s. 89-93Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A sensitive and selective method for the analysis of aliphatic low molecular mass organic acids (LMMOAs) in natural waters is presented. The method is based on separation with ion exclusion chromatography and detection with electrospray ionization tandem mass spectrometry (LC-MS/MS). The extra selectivity gained by applying MS/MS allows for a minimum of sample preparation and the use of a sub-optimal mobile phase regarding chromatographic resolution. Instead the mobile phase, comprising aqueous formic acid With methanol as organic modifier, was mainly optimized for maximum sensitivity and long term MS stability. Detection limits for malonic, fumaric, maleic, succinic, citraconic, glutaric, malic, alpha-ketoglutaric, tartaric, shikimic, trans-aconitic, cis-aconitic, isocitric and citric acid were in the range 1-50 nM, while the detection limits for pyruvic, oxalic and lactic acid were around 250 nM for an injection volume of 100 mu L. Due to their metal-chelating properties, these LMMOAs are all considered to affect the bioavailability of metals and to be involved in soil forming processes. It is thus of interest to be able to monitor their presence in natural waters, and the method developed within this work was successfully applied for the analysis of LMMOAs in soil solution and stream water samples.

  • 75.
    Bylund, Dan
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Samskog, J
    Jacobsson, S.P.
    Markides, K.E.
    Classification of lactate dehydrogenase of different origin by liquid chromatography-mass spectrometry and multivariate analysis2003Ingår i: Journal of the American Society for Mass Spectrometry, ISSN 1044-0305, E-ISSN 1879-1123, Vol. 14, nr 3, s. 236-240Artikel i tidskrift (Refereegranskat)
  • 76.
    Bång, Åsa
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Genetic variation and gene flow in riparian populations of Filipendula ulmaria2007Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
  • 77.
    Bång, Åsa
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Go with the flow?: Filipendula ulmaria, a common riparian plant species2006Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
  • 78.
    Bång, Åsa
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Holm, Svante
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Nilsson, Christer
    Control of plant species diversity in riparian corridors: Konferens OIKOS 20022002Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    previous study has shown that plant communities differ floristically between impoundments but remain similar within impoundments in a regulated river. The same pattern did not occur among plant species in a free-flowing river which instead showed a continuous change in species composition from the headwaters to the coast. This strongly suggests that the dispersal of plants is obstructed when dams are built on rivers. The present project will specifically study whether dams also affect the genetic diversity among and between populations of plant species. Filipendula ulmaria will be used as a first test species. A second question is whether tributaries have any impact on the distribution of genetic diversity of plant species within impoundments. A third question deals with the impact of seed and pollen dispersal on the genetic diversity among and between plant species populations. The project combines field sampling, field experiments and laboratory methods such as isoenzymes, microsatellites and other DNA-methods.

  • 79.
    Bång, Åsa
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Jonsson, Bengt Gunnar
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Holm, Svante
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Effects of pollination distance on reproductive success in Filipendula ulmariaManuskript (preprint) (Övrigt vetenskapligt)
  • 80.
    Bång, Åsa
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Jägbrant, Veronica
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Holm, Svante
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Spatial genetic structure of a common riparian plant species, Meadowsweet (Filipendula ulmaria) in northern SwedenManuskript (Övrigt vetenskapligt)
  • 81.
    Bång, Åsa
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Jägbrant, Veronica
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Nilsson, Christer
    Holm, Svante
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Differences in spatial genetic structure of riparian Filipendula ulmaria between an within river catchments in northern SwedenManuskript (preprint) (Övrigt vetenskapligt)
  • 82.
    Bång, Åsa
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Nilsson, Christer
    Holm, Svante
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    The potential role of tributaries as seed sources to an impoundment in northern Sweden: a field experiment with seed mimics2007Ingår i: Rivers Research and Applications: an international journal devoted to river research and management, ISSN 1535-1459, E-ISSN 1535-1467, Vol. 23, nr 10, s. 1049-1057Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Fragmentation and flow regulation of rivers by large dams are known to obstruct the longitudinal dispersal of waterborne plant propagules between impoundments, and to affect plant community composition. However, even several decades after a dam has been built, impoundments may still have a relatively species-rich riparian flora. We hypothesized that free-flowing tributaries act as the major gene pools for such impoundments, thus alleviating the fragmenting effect large dams have on the main channel. The importance of tributaries as seed sources was tested by releasing wooden seed mimics in three different-sized (0.22-6.93 m3 s-1) tributaries of an impoundment in the Ume River in northern Sweden. In each tributary seed mimics were released, during the spring flood peak, from three points approximately 1, 2 and 3 km upstream the outlet in the impoundment. The importance of a tributary as a seed source increased with tributary size. Of the 9000 released seed mimics 1.5 % reached the impoundment; 1.2 % of the 9000 originated from the largest tributary and 0.3 % from the middle-sized one. The smallest tributary retained all its mimics.

  • 83.
    Bång, Åsa
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Nilsson, Christer
    Holm, Svante
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    What is the role of tributaries as seed sources for a run-of-river impoundment: a field experiment: Konferens SISORL 20042004Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    The reservoirs in impounded rivers are blocked by dams, implying that plant seeds, especially waterborne ones, have trouble dispersing between reservoirs. We examined whether the tributaries have an important role in the dispersal of seeds to a specific reservoir. We did this by releasing small, coloured wooden cubes in three tributaries of the Stensele reservoir in northern Sweden, one small, one middle-sized and one large-sized. This work was carried out in spring during major flood. At the day of cube release, we counted the number of cubes that dispersed from the tributaries out into the reservoir. In summer, we collected the cubes that had stranded on the banks of the tributaries to learn how far they had spread within each stream. Our examinations showed that a big stream disperses most seeds the longest distance. The smaller the stream, the shorter the distance the seeds were spread, and the fewer the seeds that reached the reservoir. We concluded that large tributaries have an important role in dispersing plants to reservoirs of impounded rivers.

  • 84.
    Bökman, C.F.
    et al.
    Clinical Chemistry Laboratory, Falun Central Hospital, Falun.
    Bylund, Dan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Markides, K.E.
    Department of Analytical Chemistry, Uppsala University, Uppsala.
    Sjöberg, P.J.R.
    Department of Analytical Chemistry, Uppsala University, Uppsala .
    Relating chromatographic retention and electrophoretic mobility to the ion distribution within electrosprayed droplets2006Ingår i: Journal of the American Society for Mass Spectrometry, ISSN 1044-0305, E-ISSN 1879-1123, Vol. 17, nr 3, s. 318-324Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ions that are observed in a mass spectrum obtained with electrospray mass spectrometry can be assumed to originate preferentially from ions that have a high distribution to the surface of the charged droplets. In this study, a relation between chromatographic retention and electrophoretic mobility to the ion distribution (derived from measured signal intensities in mass spectra and electrospray current) within electrosprayed droplets for a series of tetraalkylammonium ions, ranging from tetramethyl to tetrapentyl, is presented. Chromatographic retention in a reversed-phase system was taken as a measure of the analyte's surface activity, which was found to have a large influence on the ion distribution within electrosprayed droplets. In addition, different transport mechanisms such as electrophoretic migration and diffusion can influence the surface partitioning coefficient. The viscosity of the solvent system is affected by the methanol content and will influence both diffusion and ion mobility. However, as diffusion and ion mobility are proportional to each other, we have, in this study, chosen to focus on the ion mobility parameter. It was found that the influence of ion mobility relative to surface activity on the droplet surface partitioning of analyte ions decreases with increasing methanol content. This effect is most probably coupled to the decrease in droplet size caused by the decreased surface tension at increasing methanol content. The same observation was made upon increasing the ionic strength of the solvent system, which is also known to give rise to a decreased initial droplet size. The observed effect of ionic strength on the droplet surface partitioning of analyte ions could also be explained by the fact that at higher ionic strength, a larger number of ions are initially closer to the droplet surface and, thus, the contribution of ionic transport from the bulk liquid to the liquid/air surface interface (jet and droplet surface), attributable to migration or diffusion will decrease.

  • 85.
    Carl, Bernd
    et al.
    Universität Jena.
    Schiebold, Cornelia
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Ein direkter Ansatz zur Untersuchung von Solitonengleichungen2000Ingår i: Jahresbericht der Deutschen Mathematiker-Vereinigung (Teubner), ISSN 0012-0456, E-ISSN 1869-7135, Vol. 102, nr 3, s. 102-148Artikel i tidskrift (Refereegranskat)
  • 86.
    Carl, Bernd
    et al.
    Universität Jena.
    Schiebold, Cornelia
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Nonlinear equations in soliton physics and operator ideals1999Ingår i: Nonlinearity, ISSN 0951-7715, E-ISSN 1361-6544, Vol. 12, nr 2, s. 333-364Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An operator-theoretic method for the investigation of nonlinear equations in soliton physics is discussed comprehensively. Originating from pioneering work of Marchenko, our operator-method is based on new insights into the theory of traces and determinants on operator ideals. Therefore, we give a systematic and concise approach to some recent developments in this direction which are important in the context of this paper. Our method is widely applicable. We carry out the corresponding arguments in detail for the Kadomtsev-Petviashvili equation and summarize the results concerning the Korteweg-de Vries and the modified Korteweg-de Vries equation as well as for the sine-Gordon equation. Exactly the same formalism works in the discrete case, as the treatment of the Toda lattice, the Langmuir and the Wadati lattice shows.

  • 87. Carlsson, F.
    et al.
    Vetterli, A.
    Pocock, Tessa
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Ekelund, Nils
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Falk, Stefan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    A comparative study including Clamydomonas reinhardtii and Chlamydomonas raudensis Ettl. strains SAG 49.72 and UWO 241 focusing on phototaxis.2005Ingår i: Proceedings of the 6th European Workshop Biotechnology of Microalgae, 2005Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Phototaxis is movement induced by light; this phenomenon has been detected in several solitary green algae species and generally works as a balancing force against gravitaxis, creating a system for optimum vertical placing in relation to irradiance, (energy -demands/restrictions). We study phototaxis in the mesophilic green algae, Chlamydomonas reinhardtii and C. raudensis SAG 49.72, relative to phototaxis in the from Antarctica newly isolated obligate psychrophilic strain of C. Raudensis (UWO 241) (henceforth called UWO 241). This species has some unusual movement patterns (Pocock et. al 2004) which function is yet to be revealed. Phototactic movement has not earlier been monitored in the normal conditions (high salinity, low temperature) for this strain, though when exposed to extreme temperatures (25C) the organism displays movement patterns interpreted as positive phototaxis. (Pocock et. al 2004). This behaviour should lead to a more rapid destruction of the organism due to the damaging high light (high energy input). The study shows that the three species responds different to light stimuli, when temperature is set to 12 C (culturing temperature) or the respective optimum culture temperatures. Light response curves of phototaxis in the range of 0,5 to 3000 μmol quanta m-2 s-1, shows that C. raudensis SAG 49.72 produce positive phototaxis over the entire range while C. reinhardtii mainly shows negative reactions. UWO 241 seem to be unaffected by irradiance, thus showing only nondirectional behaviour. In a second set of experiments the cells were kept in Petri dishes and exposed to 3000 μmol quanta m-2 s-1 under 40 min, in a temperature range of 5C to 25C for each sample. The results show that C. reinhardtii was negatively phototactic at 5C, switching to positive phototaxis at 25C.

  • 88.
    Carlsson, Lena
    et al.
    Umeå University.
    Yu, Ji-Guo
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Moza, Monica
    Biomedicum Helsinki, Finland.
    Carpen, Olli
    University of Turku, Turku University Central Hospital, Finland.
    Thornell, Lars-Eric
    Umeå University.
    Myotilin - a prominent marker of myofibrillar remodelling2007Ingår i: Neuromuscular Disorders, ISSN 0960-8966, E-ISSN 1873-2364, Vol. 17, nr 1, s. 61-68Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Myofibrillar remodelling with insertion of sarcomeres is a typical feature of biopsies taken from persons suffering of exercise-induced delayed onset muscle soreness. Here we studied the presence of the sarcomeric protein myotilin in eccentric exercise related lesions. Myotilin is a component of sarcomeric Z-discs and it binds several other Z-disc proteins, i.e. alpha-actinin, filamin C, F-actin and FATZ. Myotilin has previously been shown to be present in nemaline rods and central cores and to be mutated in limb girdle muscular dystrophy 1A (LGMD1A) and in a subset of myofibrillar myopathies, indicating an important role in Z-disc maintenance. Our findings on non-diseased muscle affected by eccentric exercise give new information on how myotilin is associated to myofibrillar components upon remodelling. We show that myotilin was present in increased amount in lesions related to Z-disc streaming and events leading to insertion of new sarcomeres in pre-existing myofibrils and can therefore be used as a marker for myofibrillar remodelling. Interestingly, myotilin is preferentially associated with F-actin rather than with the core Z-disc protein alpha-actinin during these events. This suggests that myotilin has a key role in the dynamic molecular events mediating myofibrillar assembly in normal and diseased skeletal muscle.

  • 89.
    Carlsson, Ralf
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Shell gravel deposits on the Åland Islands, southwestern Finland, with special reference to the molluscan assemblages2002Ingår i: Boreas, ISSN 0300-9483, E-ISSN 1502-3885, Vol. 31, nr 2, s. 203-211Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Twenty-six shell gravel sites at elevations between 3 and 35 m a.s.l. were found on the Aland Islands. The faunal composition was determined on 14 of these locations and Mytilus edulis and Macoma bulthic a were found everywhere. Another common species was Hydrobia ulvae. while H. ventrosa, Littorina saxatilis and Cerasto-derma glaucum were more sporadic. This species assemblage implies that the salinity of the area as about 10parts per thousand. when the animals lived there. The deposits on the N-NE hilltops generally have southerly to westerly aspect, while those of the south-central hilltops are easterly. On the basis of a C-14-dated stratified deposit it is suggested that each deposit was formed during a relatively short period of time. As a hilltop emerged from the sea. glacial debris was flushed down. Shell-bearing molluscs colonized the bare rock surface and were flushed down and formed the shell gravel deposit as the shoreline displacement continued. At a later stage. as the more concave part of the hilltop was subject to wave action. erosion was weaker and the shell gravel deposit was covered by beach sand. Since the hills may be of different elevation, it is concluded that trying to date ancient shorelines from shell gravel deposits is not justified. as each deposit originates from the hill with which it is associated.

  • 90. Cienciala, Emil
    et al.
    Mellander, Per-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Kučera, Jiří
    Opluštilov, Magda
    Ottosson-Löfvenius, Mikaell
    Bishop, Kevin
    The effect of a north-facing forest edge on tree water use in a boreal Scots pine stand2002Ingår i: Canadian Journal of Forest Research, ISSN 0045-5067, E-ISSN 1208-6037, Vol. 32, nr 4, s. 693-702Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Tree water use and growth increment were studied in a north-facing forest edge of a 70 year old mono-specific stand of Scots pine (Pinus sylvestris) trees growing on poor sandy soils in the northern boreal zone of Sweden. The forest edge in this study bordered a clear-cut established two decades ago. There were differences in water use and growth increment during the growing season between trees growing at the forest edge and trees growing in the forest interior. These differences were likely related to soil conditions, such as access to soil moisture, soil temperature and soil frost conditions, whereas an effect of above ground microclimate was not found. The estimated tree water use and growth increment over one growing season tended to be larger for trees at the edge zone relative to those from the interior. The variability of the measured tree water fluxes was high, especially for the edge zone trees. There were also structural differences between the two groups of trees, most notably in the radial profile of conductive xylem, in tree height and in green crown length, but these differences were on the limits of statistical significance. The estimated seasonal transpiration was low, about 70 mm when estimated exclusively for trees from the forest interior and 107 mm when estimated exclusively for trees at the forest edge. This illustrates the likely magnitude of water use enhancement due to the conditions specific to forest edge.

  • 91. Dahlberg, Anders
    et al.
    Hysing, Erik
    Olsson, Jan
    Kruys, Nicholas
    Silfvering, Göran
    Niemälä, Jari
    Jonsson, Bengt Gunnar
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Vedlevande arters ekologi: kunskaper för skötsel av död ved2005Ingår i: Död ved i levande skogar: hur mycket behövs och hur kan målet nås?, Stockholm: Naturvårdsverket , 2005, s. 110-Kapitel i bok, del av antologi (Övrigt vetenskapligt)
    Abstract [sv]

    Betydelsen av död ved i skogen för biologisk mångfald är väl dokumenterad. Sveriges riksdag har fastställt 15 miljömål och varje mål är uppdelat i flera delmål. I ett av dessa mål, Levande skogar, konstateras att kvantiteten av hård död ved måste öka med åtminstone 40 procent i hela landet och betydligt mer i områden, där biologisk mångfald är speciellt hotad. Men än så länge finns inget detaljerat långsiktigt mål. Syftet med den här studien var att undersöka: 1. Vilken kvalitet och kvantitet av död ved behövs i skogen för att bevara mångfalden? 2. Var i landskapet är det viktigast att öka mängden död ved? 3. Hur når vi målet? Arbetet har baserats på litteraturöversikter och frågeformulär till markägare, avverkningsentreprenörer och tjänstemän inom skogsnäringen. Olika scenarier baserade på litteraturgranskningen framställdes via datorsimulationer, där mängden och spridningen av död ved varierade med en beräknad ökningstakt. Utifrån dessa studier kan vi dra följande slutsatser: 1. Somliga arter är specialiserade och kräver ett rikligt utbud av död ved (50 m3/ha eller mer). Dessa arter kan endast bevaras i skyddade områden. 2. Brukade skogar utanför skyddade områden med 20 m3 död ved/ha tycks vara högkvalitativa habitat för många arter. 3. I områden dominerade av skog bör sådana habitat täcka mellan 10 och 30 procent av landskapet. 4. Dessa områden bör lokaliseras i anslutning till skyddade områden och områden med sällsynta arter. 5. Om den här strategin antas, kommer medelvärdet för hela Sverige vara 10 m3 död ved/ha. 6. För att kunna nå det målet 2030 måste mängden död ved öka med 40 procent varje årtionde (vilket innebär en exponentiell ökning). 7. Men ännu viktigare än att nå ett visst medelvärde för hela Sverige är, att så snabbt som möjligt öka förekomsten av död ved i anslutning till områden med hotade arter. 8. Det gäller att så snabbt som möjligt identifiera dessa hotade områden/ biotoper och för det ändamålet behöver regionala bristanalyser tas fram. 9. Men död ved behövs även utanför speciellt rika områden, som en resurs för kommande generationer samt som spridningskorridor mellan olika “hot-spots”. Där kan mängden död ved vara mindre och ökningsgraden lägre. 10. Förutom ökningen av död ved är det viktigt med en större variation av olika kvaliteter samt en kontinuerlig tillförsel. 11. Att öka mängden död ved snabbt i hotade områden (hot-spots) enbart med hjälp av frivilliga åtgärder, kommer troligen att bli svårt. Därför kan olika nya slags politiska åtgärder vara nödvändiga (såsom ekonomisk kompensation). 12. För att definiera målet mer i detalj, behövs mer kunskap om den kritiska tröskeln, spridningsmöjligheter, habitat och substratanspråk samt populationsbiologi för några arter.

  • 92.
    Dahlström, Niklas
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Function and dynamics of woody debris in boreal forest streams2005Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The work in this thesis deals with (1) the effects of woody debris on stream channel morphology and retention of organic material, and (2) the dynamics of woody debris and its relation to riparian forest history and composition. The studied stream reaches are situated in mature, productive forests in the boreal zone of Sweden. Wood variables were important predictors of the frequency of debris dams, pool area, the proportion of pools formed by wood, and variation in the bankfull channel width. Pools formed by woody debris were mainly created by damming and had larger surface areas and residual depths than pools formed by other agents. Stream reaches intersecting old-growth forest (with minor influence of forest management) had coarser and longer woody debris pieces, greater amounts of wood, more debris dams, and wood-formed pools compared to streams surrounded by forests influenced by selective logging. The influence of past forest management on the quality and quantity of woody debris in streams were analyzed by using dendrochrnological methods. Selective loggings and absence of forest fires after 1831 resulted in lower input rates and a gradual replacement of pine by sruce over time. Residence times in stream channels of woody debris (>10 cm in basal diameter) were long and the oldest dated pieces of pine and spruce were over 300 and 100 years, respectively. Dynamics of woody debris were explored by comparing wood volumes and characteristics between stream channels and their riparianforests and between old growth and managed sites. Wood volumes recorded in the stream channels exceeded, but were related to, the volumes found in the riparian forests. Limited input of woody debris by bank cutting and absence of slope processes suggest that recruitment processes of woody debri to stream channels are similar as in riparian forests and slow decay in channels results in greater volumes. The retentiveness of organic material in stream channels was examined by using release and capture experiments in multiple reaces during varying discharges using different sizes of leaf mimics. Sixty eight percent of the variation in retention was explained by a multiple regression model including discharge and leaf mimic siz. Between 44 and 80% of the variation in retention among reaches was explained by channel constraint, gravel coverage, and woody debris variables as the most important. Estimates from a partial least squares (PLS) model suggest an increase in mean transport distances by 22 to 53% in managed forest streams compared to old growth conditions and in a low wood scenario, mean transport distances increased by 38 to 99% with larger increases for higher discharges and larger particle sizes. To regain more pristine conditions of stream channels, management and restoration are needed to increase the amount of woody debris that recreates lost channel structures and increaes the retention of organic material.

  • 93.
    Dahlström, Niklas
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Jönsson, Karin
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Input processes and decomposition rates of large woody debris in a boreal forest stream2001Ingår i: Tree Rings and People: An International Conference on the Future of Dendrochronology, Davos, Switzerland September 22-26, 2001, 2001Konferensbidrag (Övrigt vetenskapligt)
  • 94.
    Dahlström, Niklas
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Jönsson, Karin
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Nilsson, Christer
    Long-term dynamics of large woody debris in a managed boreal forest stream.2005Ingår i: Forest Ecology and Management, ISSN 0378-1127, E-ISSN 1872-7042, Vol. 210, nr 1-3, s. 363-373Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Little is known about how past forest management in Sweden influenced the quantity and quality of large woody debris (LWD) in streams. The present study provides information of the long-term dynamics of LWD in a reach of a boreal stream intersecting a managed forest. Dendrochronological methods were used to reconstruct mortality years of the pieces of LWD and the general history of fire and cuttings of the surrounding riparian forest. Today, spruce dominates among the living trees, whereas the LWD is dominated by birch in the forest and by pine in the stream. Fire frequency prior to active fire suppression was similar to values reported from boreal forests. Pine trees were more abundant in the riparian forest before selective logging operations and active fire suppression began in the 1800s. Many of the pieces of LWD found in the stream today died more than 200 years ago and derived from a cohort of pines that generated in the early 1600s. Pine LWD in stream channels is highly resistant to decomposition and can reside for more than 300 years. A substantial amount of the LWD found today in managed forest streams in boreal Sweden most likely derives from the time before extensive human influence and is likely to decrease further in the future. Management of riparian forests to ascertain future supply of long-lived LWD in streams should target to increase the proportion of pine trees.

  • 95.
    Dahlström, Niklas
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Nilsson, Christer
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Influence of Woody Debris on Channel Structure in Old Growth and Managed Forest Streams in Central Sweden2004Ingår i: Environmental Management, ISSN 0364-152X, E-ISSN 1432-1009, Vol. 33, nr 3, s. 376-384Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Anecdotal information suggests that woody debris have had an important channel-forming role in Swedish streams and rivers, but there are few data to support this view. We identified 10 streams within near-natural and 10 streams within managed forest landscapes in central Sweden, and quantified their channel characteristics and content of woody debris. All pieces of woody debris greater than 0.5 m in length and greater than 0.05 m in base diameter were included. The near-natural forests were situated in reserves protected from forest cutting, whereas the managed forests had previously faced intensive logging in the area adjacent to the stream, The two sets of streams did not differ in general abiotic characteristics such as width, slope, or boulder cover, but the number of wood pieces was twice as high and the wood volume almost four times as high in the near-natural streams. This difference resulted in a higher frequency of debris dams in the near-natural streams. Although the total pool area did not differ between the two sets of streams, the wood-formed pools were larger and deeper, and potentially ecologically more important than other pools. In contrast to what has been believed so far, woody debris can be a channel-forming agent also in steeper streams with boulder beds. In a step-wise multiple regression analysis, pool area was positively and most strongly related to the quantity of woody debris, whereas channel gradient and wood volume were negatively related. The frequency of debris dams increased with the number of pieces of woody debris, but was not affected by other variables. The management implications of this study are that the wood quantity in streams in managed forests would need to be increased if management of streams will target more pristine conditions.

  • 96.
    Dahlström, Niklas
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Nilsson, Christer
    The dynamics of coarse woody debris in boreal Swedish forests are similar between stream channels and adjacent riparian forests2006Ingår i: Canadian Journal of Forest Research, ISSN 0045-5067, E-ISSN 1208-6037, Vol. 36, nr 5, s. 1139-1148Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Although numerous studies have focused on the dynamics of coarse woody debris (CWD) in boreal Fennoscandian forests, information on CWD in streams remains limited. To achieve a better understanding of CWD dynamics in streams we compared amounts and characteristics of CWD between streams and adjacent riparian forests in old-growth and managed forest sites, respectively. We also identified distances to the sources of CWD and evaluated these in relation to the lateral zonation of riparian trees. CWD volumes found in the stream channels were related to, but exceeded, the volumes found in the adjacent forest. In-channel volumes separated by species were better correlated with terrestrial volumes of CWD than with volumes of living trees. Tree species appeared to be zoned across the riparian zone, with slightly higher abundances of deciduous trees and lower abundances of Scots pine trees close to the stream. Similar to upland forests, riparian forests were dominated by coniferous tree species, mainly Norway spruce (Picea abies (L.) Karst.). These findings suggest large similarities in CWD input between streams and riparian forests and substantially slower decomposition rates in stream channels compared with those in riparian forest. The results provide an improved basis for creating reliable models of CWD supply and maintenance in streams based on knowledge of forest development and CWD dynamics in the terrestrial environment. Site productivity could potentially be used to predict CWD volumes in stream channels under pristine conditions.

  • 97. Danielsson, Rolf
    et al.
    Bylund, Dan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Markides, Karin E
    Matched filtering with background suppression for improved quality of base peak chromatograms and mass spectra in liquid chromatography-mass spectrometry2002Ingår i: Analytica Chimica Acta, ISSN 0003-2670, Vol. 454, nr 2, s. 167-184Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A time domain filter that combines the properties of matched filtering and two-fold differentiation is presented. The filter coefficients are given by the second derivative of a Gaussian model peak, controlled by the setting of two parameters related to the chromatographic system. The fundamental characteristics of the filter were derived, and its applicability demonstrated for real liquid chromatography–mass spectrometry (LC–MS) data. The filter is primarily intended as a fast pre-processing step, for a mass chromatogram with 320 scans over 700 mass channels the computation time was 0.6 s on a standard PC. Base peak chromatograms with improved peak detection capability and mass spectra useful for compound identification were obtained with filtered data. The most significant effect of the described filter is background reduction due to the differentiation, which in combination with the matched filter can be performed with maintained or even improved signal-to-noise ratio.

  • 98.
    Danilov, Roman A
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Studies on phytoplankton successions under the ice cover in Sundsvall Bay (the eastern coast of Sweden): A comparison of descriptive and multivariate methods2001Ingår i: Russian journal of ecology, ISSN 1067-4136, E-ISSN 1608-3334, Vol. 32, nr 5, s. 334-337Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Changes of the phytoplankton community during winter in the zone of industrial pollution were studied using cluster analysis. The results indicated that, compared to the descriptive methods conventionally used for monitoring phytoplankton communities, this method can be more efficient in revealing latent tendencies in their spatial and temporal dynamics.

  • 99.
    Danilov, Roman A
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Ekelund, Nils
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Applicability of growth rate, cell shape and motility of Euglena gracilis as physiological parameters for bioassessment at lower concentrations of toxic substances: an experimental approach.2001Ingår i: Environmental Toxicology, ISSN 1520-4081, E-ISSN 1522-7278, Vol. 16, nr 1, s. 78-83Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The responses of the growth rate, motility, and cell shape in the green flagellate Euglena gracilis to different concentrations of waste water substances from the pulp and paper industry were tested in a long-term study (7 days). Samples before (uncleaned sample) and after (cleaned sample) the treatment in a cleaning system were studied. The influence of different doses of UV-B radiation on cell shape and motility was also investigated. No statistically significant effects of increasing concentrations of the waste substances both before and after the cleaning process (except inhibition by the undiluted uncleaned effluent) on the growth rate in E. gracilis were observed. Cell shape turned out to be an unreliable physiological parameter for assessing the toxicity at lower concentrations of waste water substances. No significant patterns could be observed in the response of the cell shape to the different concentrations of the waste water substances or to UV-B radiation. Motility has been concluded to be a more sensitive parameter than cell shape. However, no clear patterns were observed in the response of the motility to the different concentrations of the waste water substances studied. Increasing concentrations of the uncleaned sample demonstrated a defense against UV-B radiation, due to the high absorbance in the UV-B range, when effects on motility were examined. We conclude that contrary to the results reported in the literature earlier, cell shape and motility of E. gracilis are not universal physiological parameters for bioassessment at lower concentrations of toxic substances, including metals such as copper and zinc from the pulp and paper industry. The long-duration tests had, in general, higher significance than those of short duration.

  • 100.
    Danilov, Roman A
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Ekelund, Nils
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Periphyton communities on natural substrata in eu-, meso- and oligotrophic lakes at higher latitude2002Ingår i: Biologia (Bratislava), ISSN 0006-3088, E-ISSN 1336-9563, Vol. 57, nr 4, s. 433-436Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Natural epiphyton and epilithon communities were studied in eu-, meso- and oligotrophic lakes at latitude of 62degrees54' N in Vasternorrlands region of Sweden. The samples of epiphyton as well as epilithon (three per lake) were identical and specific for each lake studied. Both epiphytic and epilithic communities consisted of members of three classes of algae - Cyanophyceae, Chlorophyceae and Bacillariophyceae. The highest species diversity was detected within Chlorophyceae while Cyanophyceae and Bacillariophyceae contained the same amount of species. In general, epiphyton and epilithon shared 44% of species identified. However, both epiphyton and epilithon showed distinct patterns between lakes of different trophic level. Epiphyton in the eutrophic lakes were clearly dominated by Cyanophyceae (Bacillariophyceae co-dominated in one of the eutrophic lakes). Both mesotrophic and oligotrophic lakes were signed by high abundance of Chlorophyceae and almost complete absence of Bacillariophyceae and Cyanophyceae. Epilithic communities in the oligotrophic lakes had higher species diversity than those in the meso- and eutrophic lakes studied. Chlorophyceae were dominant in two eutrophic lakes and Cyanophyceae only in one eutrophic lake, Chlorophyceae as well as Bacillariophyceae were abundant in the oligotrophic lakes. Cluster analysis based on species presence-absence led to a sufficient resolution between both epiphytic and epilithic communities of eutrophic environments, on the one hand, and epiphytic and epilithic communities of meso- and oligotrophic environments, on the other.

1234567 51 - 100 av 726
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf