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  • 101.
    Danilov, Roman A
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Ekelund, Nils G A
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Phytoplankton communities at different depths in two eutrophic and two oligotrophic temperate lakes at higher latitude during the period of ice cover2001Ingår i: Acta Protozoologica, ISSN 0065-1583, E-ISSN 1689-0027, Vol. 40, nr 3, s. 197-201Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Phytoplankton communities at different depths and at different locations within each lake were studied during the period of ice cover (from January to March) in two eutrophic and two oligotrophic lakes in North-Eastern Sweden. Cryptophyceae, Dinophyceae and Euglenophyceae were dominant during the whole period of investigation in eutrophic environments. Bacillariophyceae, Chlorophyceae, Chrysophyceae and Cyanophyceae were only occasionally found both in eutrophic and oligotrophic lakes. Both in eutrophic and oligotrophic lakes diversity as well as abundance of phytoplankton were considerably higher immediately under ice than near the bottom. No differences in horizontal distribution of phytoplankton assemblages were detected within each lake. However, vertical differences were more profound. It is speculated that both light availability and increased ion concentration under the ice cover can be viewed as main factors determining phytoplankton communities.

  • 102.
    Danilov, Roman
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Ekelund, Nils
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Autumn phytoplankton assemblages in temperate lakes of different eutrophication level in the middle part of Sweden2000Ingår i: Nordic Journal of Botany, ISSN 0107-055X, E-ISSN 1756-1051, Vol. 20, nr 2, s. 225-232Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Phytoplankton assemblages were studied during autumn 1998 in oligo-, meso- and eutrophic lakes in central Sweden (62°54'N). Differences in phytoplankton assemblages have been detected both in space and time. In eutrophic lakes coccoid Chlorophyceae dominated quantitatively during September and October. Diatoms were the most diverse group in all types of lakes in September and in meso- and oligotrophic lakes in October. In November Cryptophyceae became the most abundant group in all lakes. The total richness of species decreased in the meso- and oligotrophic environments in November compared to September and October, whilst in the eutrophic environment it remained almost unchanged. Cluster analyses, using both presence-absence and presence-absence in combination with abundance matrices, showed similar results and a good resolution between the lakes of different eutrophication conditions. We conclude that the phytoplankton assemblages of the lakes studied depended on the trophic conditions and thus they can be used for resolution between different eutrophication levels.

  • 103.
    Danilov, Roman
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Ekelund, Nils
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Comparative studies on the usefulness of seven ecological indices for the marine coastal monitoring close to the shore on the swedish east coast2001Ingår i: Environmental Monitoring & Assessment, ISSN 0167-6369, E-ISSN 1573-2959, Vol. 66, nr 3, s. 265-279Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The simultaneous behaviour of seven ecological indices (Hurlbert's, Margalef's, Menhinick's, Shannon's, species number, Jaccard's and saprobic index) was studied based on phytoplankton data close to the shore on the East coast of Sweden during the summer 1998. The sampling stations had a similar eutrophication level and were located in bays. Standard phytoplankton databases were used in calculating the indices, which were later compared using cluster analysis. Hurlbert's, Margalef's, Menhinick's, Shannon's and species number indices, as measure of community diversity, produced similar trends which often differed from those based on Jaccard's index of similarity. However, the simultaneous use of these indices was found meaningful as a possible part of the monitoring close to the shore. The application of a saprobic index lead to erroneous conclusions in the studied case.

  • 104.
    Danilov, Roman
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Ekelund, Nils
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Comparison of usefulness of three types of artificial substrata (glass, wood and plastic) when studying settlement patterns of periphyton in lakes of different trophic status2001Ingår i: Journal of Microbiological Methods, ISSN 0167-7012, E-ISSN 1872-8359, Vol. 45, nr 3, s. 167-170Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Usefulness of three types of artificial substrata (glass, wood and plastic) was tested when studying settlement patterns of periphyton in lakes of different trophic status. Strictly eu-, meso- and oligotrophic lakes in central Sweden were chosen as objects of the study. Glass slides, glass tubes, pieces of plastic (PVC) and pieces of wood of similar dimensions were placed for 9 weeks in July-August vertically 3 cm above bottom at a total depth of ca. 30 cm. Substrata were located at well-illuminated places without any other submerged objects (like macrophytes and stones), which could potentially affect colonisation patterns by algae. Periphyton communities, which colonised both the glass tubes and the pieces of wood tested, were specific enough to enable a clear classification of the lakes studied in eu-, meso- and oligotrophic. Glass tubes turned out to be the most favourable substratum when investigating settlement patterns of periphyton in this study. Although also colonised by periphytic species, wood did not support the same diversity and abundance of species as glass did. No algae were detected on the plastics studied. The plastics were covered entirely by a slime layer of bacteria. It is discussed if the nature of plastics could have some inhibitory effects on algal growth or the slime layer itself may have prevented settlement of algal spores.

  • 105.
    Danilov, Roman
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Ekelund, Nils
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Correlation between different levels of waste substances from the forest industry and the growth rate of Euglena gracilis1998Rapport (Övrigt vetenskapligt)
  • 106.
    Danilov, Roman
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Ekelund, Nils
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Effects of copper on growth rate, cell shape, motility and photosynthesis in the green flagellate Euglena gracilis in a long-term experiment2000Ingår i: Biologia (Bratislava), ISSN 0006-3088, E-ISSN 1336-9563, Vol. 55, nr 4, s. 413-418Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The green flagellate Euglena gracilis was treated for seven days with concentrations of copper ranging from 0.02 mg L-1 to 2.0 mg L-1. No inhibiting effects were detected in any physiological parameters measured. In general, it seems that enhanced copper concentrations stimulated photosynthetic efficiency (PE) of E. gracilis. Concentrations of copper reported to be critical for the other algae studied (from 0.10 mg L-1 to 0.14 mg L-1) did not show any severe negative effects on E. gracilis. An unusual trend was observed where an increase in PE was followed by an increase in light irradiance necessary to achieve light compensation point. High capacity of E. gracilis to adapt to copper stress is being discussed as a possible explanation for the trends detected.

  • 107.
    Danilov, Roman
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Ekelund, Nils
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Effects of Cu2+, Ni2+, Pb2+, Zn2+ and pentachlorophenol on photosynthesis and motility in Chlamydomonas reinhardtii in short-term exposure experiments.2001Ingår i: BMC Ecology, ISSN 1472-6785, Vol. 1, nr 1Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Background: Heavy metals, especially copper, nickel, lead and zinc, have adverse effects on terrestrial and in aquatic environments. However, their impact can vary depending on the nature of organisms. Taking into account the ability of heavy metals to accumulate in sediments, extended knowledge of their effects on aquatic biota is needed. In this context the use of model organisms (often unicellular), which allows for rapid assessment of pollutants in freshwater, can be of advantage. Pentachlorophenol has been extensively used for decades as a bleaching agent by pulpand paper industry. Pentachlorophenol tends to accumulate in the nature. We aim to determine if photosynthesis and motility can be used as sensitive physiological parameters in toxicological studies of Chlamydomonas reinhardtii, a motile green unicellular alga. It is discussed if photosynthesis and motility can be used as sensitive physiological parameters in toxicological studies. Results: The concentrations studied ranged from 0.1 to 2.0 mg l-1 for copper, nickel, lead and zinc, and from 0.1 to 10.0 mg l-1 for pentachlorophenol. Exposure time was set to 24 h. Copper and pentachlorophenol turned out to be especially toxic for photosynthetic efficiency (PE) in C. reinhardtii. Conclusion: Copper and pentachlorophenol turned out to be especially toxic for PE in C. reinhardtii. Zinc has been concluded to be moderately toxic while nickel and lead had stimulatory effects on the PE. Because of high variance, motility was not considered a reliable physiological parameter when assessing toxicity of the substances using C. reinhardtii. © 2001 Danilov and Ekelund, licensee BioMed Central Ltd.

  • 108.
    Danilov, Roman
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Ekelund, Nils
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Effects of different levels of UV-B radiation on marine epilithic communities: a short-term microcosm study2000Ingår i: Scientia Marina, ISSN 0214-8358, E-ISSN 1886-8134, Vol. 64, nr 4, s. 363-368Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Epilithic communities from brackish coastal water of the east coast of Sweden were studied in order to reveal their responses to different levels of UV-B radiation. The experiment was conducted for seven days in an indoor microcosm system. The epilithic communities were exposed daily to different doses of UV-B radiation: 1, 3, 5 and 7 hours, respectively. The intensity of the UV-B radiation used was similar to that in natural environments. After seven days clear shifts both in species composition and community structure were observed. All species of diatoms showed negative correlation with enhanced levels of UV-B. On the other hand, abundance of cyanobacteria was positively correlated with enhanced levels of UV-B (Calothrix aeruginea, R=0.49;Oscillatoria amphibia, R=0.93; Pseudanabaena mucicola, R=0.26). Communities dominated by diatoms and green algae at the initial stage of the experiment did show a drastic decrease in diatom abundance under UV-B stress and finally became dominated by cyanobacteria. Among green algae the abundance of Cladophora sericea correlated positively (R=0.33) with enhanced exposure to UV-B, while Monoraphidium-species exhibited negative correlation to UV-B. Otherwise, no significant correlation between other green algae species identified and UV-B stress could be detected. We conclude that UV-B radiation, even at lower levels, is capable to induce severe changes to marine epilithic communities. The trends revealed in the present study predict a shift from communities dominated by diatoms and green algae to those dominated by cyanobacteria.

  • 109.
    Danilov, Roman
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Ekelund, Nils
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Effects of increasing doses of UV-B radiation on photosynthesis and motility in Chlamydomonas reinhardtii2000Ingår i: Folia microbiologica (Prague), ISSN 0015-5632, E-ISSN 1874-9356, Vol. 45, nr 1, s. 41-44Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Effects of increasing doses of UV-B radiation on photosynthetic efficiency (PE) and motility inChlamydomonas reinhardtii were investigated. The exposure time ranged from 10 to 120 min at 0.73 W/m2 UV-B radiation. A decrease in compensation points (CP) was followed by an increase in PE on extending the UV-B treatment up to 60 min. The subsequent increase in PE was accompanied by increasing CPs. Enhanced doses of UV-B radiation thus have a stimulatory effect on the PE inC. reinhardtii. No inhibitory effects could be detected. No statistically significant differences in motility could be observed due to an extremely high variation of values.

  • 110.
    Danilov, Roman
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Ekelund, Nils
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Effects of pH on the growth rate, motility and photosynthesis in Euglena gracilis2001Ingår i: Folia microbiologica (Prague), ISSN 0015-5632, E-ISSN 1874-9356, Vol. 46, nr 6, s. 549-554Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The influence of pH 3-10 on the growth, motility and photosynthesis in Euglena gracilis was demonstrated during a 7-d cultivation. The cells did not survive at pH <4 and >8, highest growth rate being detected at pH 7. Motility followed a similar pattern as growth rate. Photosynthetic response curves were shown to be of the same type over the whole pH range. High respiration was characteristic for cells grown at pH 5 and 6, the lowest one at 7. At high and also at low pH more active respiration was found which can be considered as a protective response on proton stress. Respiration was not completely inhibited with potassium cyanide. Photosynthesis was the most effective at pH 6; lower and higher pH decreased photosynthetic efficiency. pH affected more the growth rate than the photosynthesis.

  • 111.
    Danilov, Roman
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Ekelund, Nils
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Effects of short-term and long-term aluminium stress on photosynthesis, respiration and reproductive capacity in a unicellular green flagellate (Euglena gracilis).2002Ingår i: Acta Hydrochimica et Hydrobiologica, ISSN 0323-4320, E-ISSN 1521-401X, Vol. 30, nr 4, s. 190-196Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Effects of short-term (1 h exposure) and long-term (7 d exposure) aluminium stress on photosynthesis and reproductive capacity have been studied in Euglena gracilis strain Z. Following concentrations of Altot (added as AlCl3) were tested: 0.5 mg L-1, 1.0 mg L-1, 1.5 mg L-1, 2.5 mg L-1, 7.5 mg L-1, 10.0 mg L-1, and 15.0 mg L-1 Al, respectively. Growth rates at different aluminium concentrations did not show significant differences, except at 15.0 mg L-1 Al. Initial respiration was higher in long-term than in the short-term experiments. It is supposed that an energy-dependent mechanism of excretion of aluminium ions has been active in the stressed cells. Consequently, the cells of E. gracilis after long-term exposure to aluminium are believed to be more acclimatised to the aluminium stress. Photosynthetic efficiency (PE) has been negatively affected by aluminium in all experiments performed. Differences between control algae and those treated with aluminium were significant in all cases. PE in long-term experiments was in general significantly higher at all concentrations of aluminium studied, compared to the short-term experiments. The aluminium concentrations tested led only to a general decrease in PE while the level of decrease was not especially concentration-dependent. In general, aluminium tolerance of E. gracilis can be estimated as low, especially by short-term exposure. However, good acclimatisation capacity of this green flagellate to aluminium doses by long-term exposure can be supposed.

  • 112.
    Danilov, Roman
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Ekelund, Nils
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Effects of solar radiation, humic substances and nutrients on phytoplankton biomass in Lake Solumsjö, Sweden.2001Ingår i: Hydrobiologia, ISSN 0018-8158, Vol. 444, nr 1-3, s. 203-212Artikel i tidskrift (Refereegranskat)
  • 113.
    Danilov, Roman
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Ekelund, Nils
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Influence of chlorophyll concentrations on the reliability of measurements with an oxygen electrode when studying photosynthetic efficiency in bioassays using microalgae2000Ingår i: Journal of Applied Phycology, ISSN 0921-8971, E-ISSN 1573-5176, Vol. 12, nr 1, s. 63-67Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Euglena gracilis and Chlamydomonas reinhardtii were used as model organisms to establish the best conditions for studying photosynthetic efficiency using the Light Pipetteexperimental system, which enables sensitive detection of changes in oxygen evolution/consumption and an easy collection and digitalisation of data. Chlorophyll concentrations of 0.005, 0.025, 0.050 and 0.075 mg mL-1 were investigated using different light regimes. Cultures of E. gracilis at the same chlorophyll concentration absorbed more light (measured at 580 μmol m-2 s-1) than those of C. reinhardtii. Cell density had a considerable effect on the reliability of measurements. Chlorophyll concentrations between 0.025 mg(Chl) ml-1 and 0.050 mg(Chl) ml-1 can be recommended when applying the Light Pipette system in bioassays using microalgae.

  • 114.
    Danilov, Roman
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Ekelund, Nils
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Influence of waste water from the paper industry and UV-B radiation on the photosynthetic efficiency of Euglena gracilis1999Ingår i: Journal of Applied Phycology, ISSN 0921-8971, E-ISSN 1573-5176, Vol. 11, s. 157-163Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The green flagellate Euglena gracilis has been used as a model organism to elucidate the possible large-scale and short-term effects of waste substances from the pulp and paper industry on photosynthetic efficiency (PE). Different concentrations of waste substances before and after treatment in a cleaning system were studied. The uncleaned sample at concentrations up to 1:10 and the cleaned sample at concentrations up to 1:5 showed stimulating effects on the PE after 7 days of incubation compared to the control. The effects of waste substances on the PE of E. gracilis were also studied in combination with short-term studies (20 and 40 min) of ultraviolet-B radiation (UV-B, 280–320 nm). It was shown that increasing concentrations of the uncleaned sample had continuously stimulating effects on the PE and worked protectively against UV-B radiation. The cleaned sample exhibited no effects, or negative effects, on the PE of E. gracilis together with UV-B radiation compared to the experiments with only UV-B radiation. At the concentration 1:1 of the cleaned sample an increase in the PE was detected due to the high concentration of the coloured substances and a decrease in the UV-B penetration. PE revealed itself to be highly sensitive for detecting toxic effects on E. gracilis and is thus very promising for use in regular toxicity tests of waste water from pulp and paper industry.

  • 115.
    Danilov, Roman
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Ekelund, Nils
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Responses of photosynthetic efficiency, cell shape and motility in Euglena gracilis (Euglenophyceae) to short-term exposure to heavy metals and pentachlorophenol2001Ingår i: Water, Air and Soil Pollution, ISSN 0049-6979, E-ISSN 1573-2932, Vol. 132, nr 1-2, s. 61-73Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Euglena gracilis was exposed for 24 hr to concentrations of copper, nickel, lead and zinc ranging from 0.1 to 2.0 mg L-1 and to pentachlorophenol ranging from 0.1 to 10.0 mg L-1. Photosynthetic efficiency (PE) was inhibited by increasing concentrations of the heavy metals. Nickel was found to be the least toxic of the metals to E. gracilis, while the other three metals exhibited similar levels of toxicity. Treatment with pentachlorophenol caused unusual responses of the photosynthetic apparatus probably due to the especially high toxicity of this substance. Both cell shape and motility turned out to be insensitive physiological parameters for the toxicity testing of the substances studied.

  • 116.
    Danilov, Roman
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Ekelund, Nils
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Summer phytoplankton dynamics close to the shore in three brackish water bays on the East coast of Sweden (Gulf of Bothnia)2000Ingår i: Thaiszia – J. Botany, Kosice, ISSN 1210-0420, Vol. 9, s. 131-142Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Three brackish water bays between Härnösand and Sundsvall on the East coast of Sweden (Gulf of Bothnia) were investigated between June and August 1998 in order to reveal summer phytoplankton dynamics close to the coast. All samples were collected at depth of 0,5 m. The results obtained show patterns in phytoplankton dynamics. In the spring Bacillariophyceae dominated, followed by an increase in Dinophyceae and small flagellates of Prasinophyceae and Cryptophyceae. Chlorophyceae were represented during the whole period of investigation especially with species of Monoraphidium, which often dominated or subdominated. In total 84 phytoplankton species were identified. Cluster analyses based on similarities in species’ diversity and their abundance made it easy to distinguish between the bays close to Härnösand and the Bay of Sundsvall. However, no clear differences were found between the sampling stations within the Bay of Sundsvall.

  • 117.
    Danilov, Roman
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Ekelund, Nils
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    The efficiency of seven diversity and one similarity indices based on phytoplankton data for assessing the level of eutrophication in lakes in central Sweden1999Ingår i: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 234, s. 15-23Artikel i tidskrift (Refereegranskat)
  • 118.
    Danilov, Roman
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Ekelund, Nils
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    The use of epiphyton and epilithon data as a base for calculating ecological indices in monitoring of eutrophication in lakes in central Sweden2000Ingår i: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 248, s. 63-70Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Eutrophication was monitored with the aid of one similarity and seven diversity indices in the lakes of different trophic levels (eutrophic, mesotrophic and oligotrophic) in central Sweden. The ecological indices were applied separately to epiphyton and epilithon communities. Epiphyton turned out to be inappropriate for assessing eutrophication in the lakes studied. On the other hand, Hurlbert's, Simpson's and the similarity indices turned out to be promising environmental tools when applied to the data of epilithon.

  • 119.
    Danilov, Roman
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Ekelund, Nils
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Using the green flagellate Euglena gracilis Klebs as physiological dosimeter: is a long-term bioassay more significant than a short-term one?2001Ingår i: Turkish journal of botany, ISSN 1300-008X, Vol. 25, s. 43-44Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The use of short-term tests with E. gracilis Klebs in order to assess toxicity cannot be viewed as absolutely preferable.At least in the case with wastewater from the pulp and paper industry, 7 day-tests could lead to more explanatory and significantresults.

  • 120. D'Arrigo, P
    et al.
    Högberg, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Pedrocchi-Fantoni, G
    Servi, S
    Old and New Synthetic Capacities of Baker's Yeast1994Ingår i: Biocatalysis, ISSN 0886-4454, Vol. 9, nr 1-4, s. 299-312Artikel i tidskrift (Refereegranskat)
  • 121.
    de Bruijn, Robert
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Cardiovascular and hematological responses to voluntary apnea in humans2007Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    This thesis deals with cardiovascular and hematological responses to voluntary apnea in

    humans, with a special focus on O2 usage and storage. Humans, and many other air‐breathing

    animals, respond to apnea (breath holding) with a collection of interacting cardiovascular

    reflexes, which are collectively called the diving response. In humans, the main characteristics of

    the diving response are a reduction in heart rate (bradycardia), decreased cardiac output,

    peripheral vasoconstriction and increased arterial blood pressure. Another response during

    apnea in mammals, more recently also observed in man, is a transient increase in hemoglobin

    concentration across a series of apneas, probably due a reduction in spleen size. There may also

    be long‐term effects on erythropoiesis in the apneic diver, as suggested by high hemoglobin

    levels observed in divers. The focus of the included studies are the short transient diving

    response (I), the more slowly occurring transient hematological changes to apnea, most likely

    related to a reduction in spleen size (II), and the possible effects of repeated apnea on serum

    erythropoietin concentration (III).

    I) The aim was to study the effects of body immersion on the O2‐conserving effect of the

    human diving response. The results showed that, regardless of body immersion, apnea with face

    immersion causes a stronger cardiovascular diving response compared to during apnea alone,

    leading to a smaller reduction in arterial oxygen saturation levels. Thus the diving response is

    triggered and conserves O2 even during whole‐body immersion, which has previously only been

    observed during apnea without whole‐body immersion.

    II) The aim was to study hematological responses to voluntary repeated maximal‐duration

    apneas in divers and non‐divers. Increases in hemoglobin concentration were found across a

    series of 3 apneas in elite breath‐hold divers, elite cross‐country skiers and untrained subjects.

    However a larger increase in hemoglobin was found in divers compared to non‐divers, which

    suggests a possible training effect of their extensive apnea‐specific training. In contrast, physical

    endurance training does not appear to affect the hematological response to apnea.

    III) The aim was to study the effects of serial voluntary apnea on the serum erythropoietin

    concentration. In a comparison between elite breath‐hold divers and subjects untrained in apnea,

    divers were found to have a 5% higher resting hemoglobin concentration. An average maximum

    increase in erythropoietin of 24 % was found in untrained subjects after 15 maximal duration

    apneas, preceded by 1 min of hyperventilation. This suggests a possible erythropoietic effect of

    apnea‐induced hypoxia, which may connect the increased resting hemoglobin found in divers to

    their apnea‐specific training.

    It was concluded from these studies that man responds to apnea with a series of different

    adjustments in order to limit O2 usage and increase O2 storage: The classical diving response is

    effectively restricting O2‐consumption also during full immersion, the spleen related hemoglobin

    increase occurs in both divers and non‐divers with different levels of physiological training, but

    is more prominent in divers, and finally, the observed high levels of hemoglobin concentration in

    divers may be related to enhanced erythropoiesis during dive training.

  • 122.
    de Bruijn, Robert
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Richardson, Matt
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Schagatay, Erika
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    The function of the human diving response in the immersed diver2003Ingår i: Annual Meeting of the European Underwater and Baromedical Society, Copenhagen, Denmark, 2003Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Background: Much previous research has used apneic face immersion as a model for studying the diving response and its oxygen-conserving effect, however there are few direct comparisons to apneic face immersion with the body immersed. Therefore, it is not settled if the oxygen conserving effect revealed in the dry-body model persists in the immersed diver. In this study we compared the diving response and its effect on arterial oxygen saturation between apnea in horizontal dry-body and immersed-body conditions. Methods: Twelve individually determined near-maximal apneas of the same duration were completed by 17 healthy untrained subjects at rest. Three apneas in each of four categories were performed: dry-body apnea (DA), dry-body, face-immersion apnea (DFIA), immersed-body apnea (IA), and immersed-body, face-immersion apnea (IFIA), in a weighted order. For the face and body immersions, mean water temperature (± SD) was 23.1 ±0.12oC and mean air temperature was 23.3 ±0.32oC. Heart rate and arterial haemoglobin saturation were recorded non-invasively with a pulse oximeter. Results: The diving response was similar for both the dry-body and the immersed body-categories. In all 4 categories the heart rate was reduced. The heart rate reduction in DFIA and IFIA categories was more pronounced than in the DA and IA categories. Heart rate reduction during DA and DFIA was 10% (±1.6) and 18% (±2.8) respectively (P<0.01), while heart rate reduction during IA and IFIA was 9% (±2.6) and 18% (±3.1) respectively (P<0.01). In both the DFIA and IFIA categories there was less desaturation compared to the DA and IA categories (DA vs. DFIA P<0.001, IA vs. IFIA P<0.05). Conclusion: Face immersion enhances the apneic diving response both in the dry- and immersed-body conditions, and is associated with a less pronounced arterial oxygen desaturation. We conclude that the immersed diver may benefit from an oxygen conserving diving response. This study also shows that the dry-body model can be useful for studying the diving response.

  • 123.
    de Bruijn, Robert
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Richardson, Matthew
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Haughey, Helena
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Björklund, Glenn
    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.
    High hemoglobin levels in divers may be a result of apnea induced EPO-production2005Ingår i: FASEB JOURNAL, 2005, s. A211-A212Konferensbidrag (Refereegranskat)
    Abstract [en]

    Oxygen storage capacity is important for apneic duration and affects performance in endurance sports. We studied if hemoglobin concentration (Hb) was different in divers compared to endurance athletes and untrained subjects and if any differences could be connected to training-induced erythropoietin (EPO) -production. We first compared Hb in 3 groups of subjects: 13 elite apneic divers (35±4 years), 13 elite cross-country skiers (20±1 years) and 23 untrained subjects (29±1 years) with similar weight and height. After 20 min of horizontal rest blood samples were drawn and analysed for Hb using standard methods. In a second experiment, we compared EPO levels before and after a series of 15 maximal apneas in air in 9 previously untrained volunteers (302 years). Apneas were spaced by 2 minutes, the last minute with hyperventilation to produce durations long enough to induce hypoxia. Values were also compared to the EPO levels of a control day without apneas. The apneic divers had higher Hb than untrained subjects (P<0.05) and skiers (P<0.01). After apnea training in untrained subjects EPO levels increased in all subjects, with a mean peak value after 3 h, where the increase was 135 % of the pre apnea value (P<0.05). No increase was observed during the same time period of the control day. We concluded that higher Hb levels in apneic divers may be a result of enhanced EPO-production due to the apnea training.

  • 124.
    de Bruijn, Robert
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Richardson, Matthew
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Haughey, Helena
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Holmberg, Hans-Christer
    Mittuniversitetet, Fakulteten för humanvetenskap, Institutionen för hälsovetenskap.
    Björklund, Glenn
    Mittuniversitetet, Fakulteten för humanvetenskap, Institutionen för hälsovetenskap.
    Schagatay, Erika
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Hemoglobin levels in elite divers, elite skiers and untrained humans2004Konferensbidrag (Övrigt vetenskapligt)
  • 125.
    de Bruijn, Robert
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Richardson, Matthew
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Milling, U
    Lemon, H
    Schagatay, Erika
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Erythropoietin production as a result of repeated apneas2004Konferensbidrag (Refereegranskat)
    Abstract [en]

    Background: It has been known for decades that high altitude hypoxia will lead to increased erythropoiesis. Hypoxia in mainly the kidney results in an increased production of erythropoietin (EPO) stimulating erythropoiesis. High altitude natives display a higher haemoglobin concentration than sea level residents, which in turn increase their haemoglobin concentration as part of the adaptation to altitude. Another group of humans exposed to hypoxia is apneic divers, which may endure transient acute hypoxia, spaced by periods of normal breathing. We recently found higher haemoglobin levels in elite apneic divers, compared to groups of elite skiers and untrained subjects, suggesting that apnea training may induce erythropoiesis in humans. It is well known that diving mammals display high haemoglobin concentrations, and the beneficial effects are obvious: A larger oxygen store before diving prolongs the aerobic dive limit, and a higher haemoglobin concentration may speed up recovery after apneas and act as a buffer against acidosis during the dive. Although our group comparisons reveal a higher haemoglobin concentration in divers, it cannot be determined whether this is a training effect or genetically determined i.e. if individuals with higher concentrations of haemoglobin are more prone to take up apneic diving. Methods: To investigate if apnea training can induce EPO production, 5 previously untrained volunteers (3 men and 2 women, mean ageSD 28 5.5 years) performed 15 maximal apneas in a horizontal position in air. The apneas were grouped in 3 series of 5 apneas and spaced by 2 minutes of which 1 minute was spent slightly hyperventilating, to produce apneas sufficiently long to induce hypoxia. Series were spaced by 10 minutes resting periods. To determine EPO levels, venous blood samples were taken before apneas and directly after the last apnea series, followed by samples 1, 2, 3 and 5 hours after the apneas. Results: Mean baseline EPO before the apneas was 10.2 U/L. In all subjects EPO levels increased during the 5 hours period after the apneas. The time for EPO-peak values were different among individuals. The mean peak value occurred after 3 h, where the mean increase was 12 % of the pre apnea reference value. Conclusion: The results suggest that apnea induced intermittent hypoxia could lead to increased erythropoiesis. The evaluation of these findings in a larger group of subjects, including measurements of the individual circadian variations in EPO production, is in progress.

  • 126. de Jong, Johnny
    et al.
    Dahlberg, A
    Almstedt, M
    Jonsson, Bengt-Gunnar
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Hysing, E
    Silverling, G
    Mer död ved i skogen: en förutsättning för tusentals arters överlevnad2004Ingår i: Fauna och flora, ISSN 0014-8903, Vol. 99, nr 2, s. 36-41Artikel i tidskrift (Övrigt vetenskapligt)
  • 127. De la Rosa, M. P.
    et al.
    Holmström, Sara J. M.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Sposito, G
    Tebo, B. M.
    Bargar, J
    Systematic study of the effect of pH on the structure and reactivity of Mn oxide produced by Bacillus sp., strain SG-1: Gordon Research Conferences - Environmental Bioinorganic Chemistry 2006. Proctor Academy , Andover, NH, USA, 18-23 June, 2006 ; Poster2006Konferensbidrag (Refereegranskat)
  • 128. Deng, N.X.
    et al.
    Ferahi, M.
    Uesaka, Tetsu
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Pressroom runnability: comprehensive analyses of pressroom and mill databases2005Ingår i: Annual Meeting of the Pulp and Paper Technical Association of Canada (PAPTAC): Book C, Pulp and Paper Technical Association of Canada, 2005, s. C217-228Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

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

  • 129. Deng, X.
    et al.
    Ferahi, M.
    Uesaka, Tetsu
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Pressroom Runnability: A Comprehensive Analysis of Press Room and Mill Database2007Ingår i: Pulp & paper Canada, ISSN 0316-4004, Vol. 108, nr 2, s. 42-51Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 130.
    Denson Hill, C
    et al.
    SUNY Stony Brook, New York.
    Porten, Egmont
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    The H-Principle and Pseudoconcave CR Manifolds2005Ingår i: Contemporary Mathematics, ISSN 0271-4132, E-ISSN 1098-3627, Vol. 50, s. 117-125Artikel i tidskrift (Refereegranskat)
  • 131.
    Dijkstra, F. A.
    et al.
    Laboratory of Soil Science and Geology, PO Box 37, 6700 AA Wageningen, PAYS-BAS.
    Geibe, Christine
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Holmström, Sara
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Lundström, Ulla
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    van Breemen, N.
    Laboratory of Soil Science and Geology, PO Box 37, 6700 AA Wageningen, PAYS-BAS.
    The effect of organic acids on base cation leaching from forest floor under six north American tree species2001Ingår i: European Journal of Soil Science, ISSN 1351-0754, E-ISSN 1365-2389, Vol. 52, nr 2, s. 205-214Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Organic acidity and its degree of neutralization in the forest floor can have large consequences for base cation leaching under different tree species. We investigated the effect of organic acids on base cation leaching from the forest floor under six common North American tree species. Forest floor samples were analysed for exchangeable cations and forest floor solutions for cations, anions, simple organic acids and acidic properties. Citric and lactic acid were the most common of the acids under all species. Malonic acid was found mainly under Tsuga canadensis (hemlock) and Fagus grandifolia (beech). The organic acids were positively correlated with dissolved organic carbon and contributed significantly to the organic acidity of the solution (up to 26%). Forest floor solutions under Tsuga canadensis contained the most dissolved C and the most weak acidity among the six tree species. Under Tsuga canadensis we also found significant amounts of strong acidity caused by deposition of sulphuric acid from the atmosphere and by strong organic acids. Base cation exchange was the most important mechanism by which acidity was neutralized. Organic acids in solution from Tsuga canadensis, Fagus grandifolia, Acer rubrum (red maple) and Quercus rubra (red oak) were hardly neutralized while much more organic acidity was neutralized for Acer saccharum (sugar maple) and Fraxinus americana (white ash). We conclude that quantity, nature and degree of neutralization of organic acids differ among the different tree species. While the potential for base cation leaching with organic acids from the forest floor is greatest under Tsuga canadensis, actual leaching with organic anions is greatest under Acer saccharum and Fraxinus americana under which the forest floor contains more exchangeable cations than does the strongly acidified forest floor under Tsuga canadensis.

  • 132. Drolet, F
    et al.
    Uesaka, Tetsu
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    A Stochastic Structure Model for Predicting sheet Consolidation and Print Uniformity2005Ingår i: 13th fundamental research symposium, Cambridge, 11-16 sept. 2005, 2005, s. 1139-1154Konferensbidrag (Refereegranskat)
  • 133. Dynesius, Mats
    et al.
    Jansson, Roland
    Johansson, Mats E
    Nilsson, Christer
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Intercontinental similarities in riparian-plant diversity and sensitivity to river regulation.2004Ingår i: Ecological Applications, ISSN 1051-0761, E-ISSN 1939-5582, Vol. 14, nr 1, s. 173-191Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We asked whether assemblages of species with separate evolutionary histories differed in their response to similar human interventions. We assessed this by comparing the response of riparian plant communities to river regulation on two different continents. We compared free-flowing and regulated rivers between boreal parts of North America (Alberta and British Columbia) and Europe (Sweden), using a standardized Sampling protocol and the same field staff on both continents. Although the two regions shared few species, both riparian plant-species diversity along free-flowing rivers and the response to different kinds of flow regulation were similar between the continents. The number of riparian-plant species and their amount of cover differed among types of water-level regime, but the continental affiliation of a river-margin site did not statistically explain any of the variation. Within continents, the local flora of the regulated river-margin sites was largely similar in species composition to the free-flowing ones, but the sites along storage reservoirs were more species-poor. The similarity in the response to regulation between the continents suggests that general guidelines for rehabilitation of degraded boreal rivers are. a realistic goal.The number of species and genera, plant cover, and species numbers in most trait groups (classified according to growth form and life span) were similar between free-flowing river margins in Europe and North America. Moreover, the regional native species pools of northern Sweden and Alberta were similar in size and composition of species groups, despite the fact that only 27% of the species in Alberta were found in northern Sweden. This is presumably because the floras share a common Tertiary origin and because the regions have had largely similar late-Tertiary and Quaternary histories. The most pronounced difference between the continents was that we found no exotic species on the 183 Swedish river margin sites, whereas 9% of the species found in all 24 North American plots taken together were exotics. All North American exotics found have occurred in Europe since prehistoric times, and the difference in exotic richness most likely reflects a difference in the number of species humans have transferred from one continent to another, rather than a difference in invasibility between the regions.

  • 134.
    Edlund, Håkan
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Berglund, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Jensen, M
    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.
    Resolution of 2-Methylalkanoic Acids: Enantioselective Esterification with Long Chain Alcohols Catalysed by Candida rugosa Lipase1996Ingår i: Acta Chemica Scandinavica, ISSN 0904-213X, Vol. 50, nr 8, s. 666-671Artikel i tidskrift (Refereegranskat)
  • 135.
    Edlund, Håkan
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Bydén, Malin
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Lindström, Birger
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Khan, Ali
    Phase Equilibria and Structure of the 1-dodecyl Pyridinium Bromide-Dodecane-Water System1998Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 204, nr 2, s. 312-319Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 136.
    Edlund, Håkan
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Bydén, Malin
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Lindström, Birger
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Khan, Ali
    Ternary Phase Equilibria of the 1.dodecyl Pyridinium Bromide-Dodecanol-Water System1997Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 196, nr 2, s. 231-240Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 137.
    Edlund, Håkan
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Khan, A
    La Mesa, C
    Formation of a Liquid Crystalline Phase in the Sodium Taurodeoxycholate-Water System1998Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 14, s. 3691-3697Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 138.
    Edlund, Håkan
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Norgren, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Different Types of Aggregation and Aggregate Structures in Aqueous Kraft Lignin Solutions. 2002Ingår i: Proceedings. 7th EWLP, 2002, s. 297-300Konferensbidrag (Övrigt vetenskapligt)
  • 139.
    Edlund, Håkan
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Norgren, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Ion Specific Differences in Salt Induced Precipitation of Kraft Lignin2002Ingår i: Proceedings 7th EWLP, Turku, Finland, Aug 26–29, 2002, 2002, s. 75-78Konferensbidrag (Refereegranskat)
  • 140.
    Edlund, Håkan
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Sadaghiani, Alireza
    Khan, Ali
    Phase Behaviour and Phase Structure for Catanionic Surfactant Mixtures: DoTAC-SN-Water System1997Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 13, s. 4953-4963Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 141.
    Edman, Mattias
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Gustafsson, Mårten
    Stenlid, Jan
    Jonsson, Bengt Gunnar
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Ericson, Lars
    Spore deposition of wood-decaying fungi: Importance of landscape composition2004Ingår i: Ecography, ISSN 0906-7590, E-ISSN 1600-0587, Vol. 27, nr 1, s. 103-111Artikel i tidskrift (Refereegranskat)
  • 142.
    Edman, Mattias
    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.
    Spatial pattern of downed logs and wood-living fungi in an old-growth spruce forest2001Ingår i: Journal of Vegetation Science, ISSN 1100-9233, E-ISSN 1654-1103, Vol. 12, nr 5, s. 609-620Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Since many wood-living forest species are influenced by the dynamics of coarse woody debris (CWD), information about the spatial pattern of CWD under natural conditions is essential to understand species distributions. In this study we examined the spatial pattern of downed logs and wood-decaying fungi in an old-growth boreal Picea abies forest in northwestern Sweden that is governed by gap-phase dynamics. The spatial pattern of wood-decaying fungi was studied to draw conclusions about species dispersal abilities. A total of 684 logs with a diameter 10 cm were mapped and analysed with Ripley's K-function. The distribution of all logs taken together displayed a significant aggregated pattern up to 45 m. The different decay stages also deviated from random expectations. Fairly fresh logs and logs in the middle decay stage were clumped up to about 25 and 35 m respectively, and late decayed logs aggregated up to 95 m. Logs with diameters from 10-29 cm were aggregated up to 25 m, whereas logs ≥30 cm diameter were randomly distributed. The result suggests that gap-dynamics do have an impact on the spatial pattern of the CWD, creating fine-scale clumping. The random distribution of large logs may result from the slightly regular spacing of large living trees. The spatial patterns of 16 species (n 20) of wood-decaying fungi were analysed with Ripley's K-function. Three patterns were aggregated, for Gloeophyllum sepiarium, Coniophora olivacea and Vesiculomyces citrinus. These results indicate that the distribution of most species at the stand level is generally not influenced by dispersal limitations.

  • 143.
    Edman, Mattias
    et al.
    Swedish University of Agricultural Sciences, Umeå.
    Jönsson, Mari
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Jonsson, Bengt Gunnar
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Fungi and wind strongly influence the temporal availability of logs in an old-growth spruce forest2007Ingår i: Ecological Applications, ISSN 1051-0761, E-ISSN 1939-5582, Vol. 17, nr 2, s. 482-490Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Coarse woody debris (CWD) is a key habitat for many species in forest ecosystems. To ensure the long-term survival of such species, forest management regimes must include measures that promote dead wood dynamics similar to those of natural forests. Thus, information on CWD dynamics under natural conditions is required, including data pertaining to the underlying agents of disturbance. This study examines modes of mortality, decay rates, and temporal patterns in the availability of Picea abies logs in a Swedish old-growth forest affected by internal, small-scale disturbance. All 684 logs in a 6.6-ha plot were mapped and classified into one of six decay classes. Logs in the early stages of decay were examined for the presence of heart-rot fungi. Six years later all logs were re-inventoried, including newly formed logs. Matrix models based on the transition rates between decay classes showed that it took about 60 years for 90% of the logs to decay beyond class 6 (a deformed trunk with soft wood). Large logs (≥26 cm) decayed 40% more slowly than small logs (≤25 cm). The initial volume of logs was 37.6 m3/ha but increased to 44.8 m 3/ha after six years. In addition, there was a large shift in the decay-class distribution. The volume of logs in early and late decay classes increased by 71% and 45%, respectively, while the volume of logs in the intermediate decay classes decreased by 32%. The fluctuations appear to result from pulses in mortality, driven by a combination of strong winds and the heart-rot fungus, Phellinus chrysoloma, which was present in more than 30% of all logs at an early stage of decay. These results show that large temporal fluctuations in dead wood also occur in the absence of large-scale disturbance, and that heart-rot fungi are important factors driving the overall dynamics of dead wood. Since many wood-inhabiting species are naturally rare and have very specific substrate demands, such temporal variability in dead wood availability may have effects on biodiversity and should be taken into account when designing small, protected forest areas.

  • 144.
    Edman, Mattias
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Jönsson, Mari
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Jonsson, Bengt Gunnar
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Small-scale fungal- and wind-mediated disturbances strongly influence the temporal availability of logs in an old-growth Picea abies forest2007Manuskript (preprint) (Övrigt vetenskapligt)
  • 145.
    Edman, Mattias
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Kruys, Nicholas
    Jonsson, Bengt Gunnar
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Local dispersal sources strongly affect colonization patterns of wood-decaying fungi on experimental spruce logs2004Ingår i: Ecological Applications, ISSN 1051-0761, E-ISSN 1939-5582, Vol. 14, nr 3, s. 893-901Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Coarse woody debris (CWD) is an important habitat for many species in forest ecosystems. However, forestry has decreased the abundance of CWD so that many wood-dependent species have become threatened. To alleviate this problem, guidelines for a more biodiversity-oriented forestry focus on increasing CWD in managed forests. Unfortunately, how this increase is to be allocated on a landscape scale is not well understood. The present study reports an experiment in which freshly cut logs of varying sizes were placed in stands with contrasting abundance of natural CWD and subsequently varying pools of wood-inhabiting species. The first six years of colonization by wood fungi show that local abundance and composition of the fungal flora strongly influenced colonization. Higher species richness was observed in CWD-rich sites, and several species were more frequent on the experimental logs at CWD-rich sites. The strong within-site effect is interpreted as resulting from high spore deposition from the local species pool. This is supported by spore deposition estimates of Fomitopsis rosea, a red-listed species that only occurred on experimental logs at the CWD-rich sites. F. rosea had a 9-180 times higher spore deposition at the CWD-rich sites compared to the CWD-poor sites. The species richness and composition on small logs differed from that of large logs with higher richness on the latter. The results strongly suggest that restoration efforts would be more efficient if directed toward sites close to CWD-rich sites and that preferably large logs should be created.

  • 146.
    Ekelund, N. G. A.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Interactions between photosynthesis and 'light-enhanced dark respiration' (LEDR) in the flagellate Euglena gracilis after irradiation with ultraviolet radiation2000Ingår i: Journal of Photochemistry and Photobiology. B: Biology, ISSN 1011-1344, E-ISSN 1873-2682, Vol. 55, nr 1, s. 63-69Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effects of ultraviolet radiation (UV-A, 315-400 nm plus UV-B, 280-315 nm) on photosynthesis and 'light-enhanced dark respiration' (LEDR) in Euglena gracilis have been investigated by using light pulses (80 s) with increasing photon fluence rates of 59, 163, 600, 1180, 2080 and 3340 mu mol m(-2) s(-1) and dark periods between the light pulses. LEDR is estimated as the maximum rate of oxygen consumption after a period of Light minus the rate of oxygen consumption 30 s after the maximum rate. Without any exposure to UV radiation, the photosynthetic rate and LEDR increase with increasing photon fluence rate. After 20 and 40 min exposures to UV radiation, the photosynthetic rate and LEDR as functions of photon fluence rate are reduced. After a 20 min UV treatment respiration is greater than photosynthesis after the first light pulse of 59 mu mol m(-2) s(-1) radiation, and especially at higher photon fluence rates photosynthesis is lower than the control values. The inhibitory effects of UV radiation on photosynthetic rate and LEDR are greater after a 40 min UV exposure than after a 20 min exposure. Only at 600 mu mol m(-2) s(-1) is the rate of oxygen evolution greater than that of oxygen consumption after a 40 min UV treatment. Both photosynthetic rate and LEDR are inhibited by the photosynthetic inhibitor DCMU (10(-5) M) in a similar way, which indicates close regulatory interactions between photosynthesis and LEDR. Potassium cyanide (KCN) inhibits dark respiration more than it inhibits LEDR. Dark respiration is not affected to the same degree by UV radiation as are photosynthesis and LEDR.

  • 147.
    Ekelund, Nils
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Effects of protein synthesis inhibitors on photoinhibition by UV–B (280-320 nm) radiation in the flagellate Euglena gracilis1996Ingår i: Scienta Marina, Vol. 60, nr 1, s. 95-100Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Irradiation of the flagellate Euglena gracilis by UV-B radiation resulted in inhibition of photosynthesis and motility. After 2 h of UV-B radiation (1.2 W m super(-2)) the rates of photosynthesis did not completely recover until after 24 h in visible light. After 24 h in darkness the rate of photosynthesis was lower but the recovery time in darkness after UV-B radiation was about the same as in the visible light. In the presence of lincomycin, inhibitor of chloroplast protein synthesis, therecovery of photoinhibition was totally blocked for up to 16 h recovery in visible light. However, after 24 h recovery in visible light together with lincomycin, photosynthesis was partially recovered but recovery in darkness together with lincomycindid not give any reparation at all of photosynthesis. The inhibition of motility had a slower recovery phase and had not fully recovered even after 72 h in visible light.

  • 148.
    Ekelund, Nils
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Forøget ultraviolet stråling og dens betydning for havmiljøet.”1992Ingår i: Naturens Verden, Vol. 2, s. 57-63Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
  • 149.
    Ekelund, Nils
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    ”Hej då, sjöelefanter och pingviner – hoppas vi ses igen.”1998Ingår i: Senior posten, nr 5Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
  • 150.
    Ekelund, Nils
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Influence of UV-B radiation on light-response curves, absorption spectra and motility of four phytoplankton species1994Ingår i: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 91, s. 696-702Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Several unicellular algae were exposed to artificial UV-B (280-320 nm) radiation after adaptation to high (43 W m-2) and low (19 W m-2) visible light. UV-B radiation had different effects on rates of photosynthesis. motility and absorption spectra for these species. Photosynthesis of Euglena gracilis and the diatom Phaeodactylum tricornum was more sensitive to UV-B inhibition than that of the dinoflagellates Heterocapsa triquetra and Prorocentrum minimum. Not only UV-B radiation but light had a photoinhibitory effect on photosynthesis in all four organisms. The effect on photosynthesis was observed both on the quantum yield and on the light saturation rate of photosynthesis

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