521 research outputs found

    On the ecology of cold-water phytoplankton in the Baltic Sea

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    Increased anthropogenic loading of nitrogen (N) and phosphorus (P) has led to an eutrophication problem in the Baltic Sea, and the spring bloom is a key component in the biological uptake of increased nutrient concentrations. The spring bloom in the Baltic Sea is dominated by both diatoms and dinoflagellates. However, the sedimentation of these groups is different: diatoms tend to sink to the sea floor at the end of the bloom, while dinoflagellates to a large degree are been remineralized in the euphotic zone. Understanding phytoplankton competition and species specific ecological strategies is thus of importance for assessing indirect effects of phytoplankton community composition on eutrophication problems. The main objective of this thesis was to describe some basic physiological and ecological characteristics of the main cold-water diatoms and dinoflagellates in the Baltic Sea. This was achieved by specific studies of: (1) seasonal vertical positioning, (2) dinoflagellate life cycle, (3) mixotrophy, (4) primary production, respiration and growth and (5) diatom silicate uptake, using cultures of common cold-water diatoms: Chaetoceros wighamii, C. gracilis, Pauliella taeniata, Thalassiosira baltica, T. levanderi, Melosira arctica, Diatoma tenuis, Nitzschia frigida, and dinoflagellates: Peridiniella catenata, Woloszynskia halophila and Scrippsiella hangoei. The diatoms had higher primary production capacity and lower respiration rate compared with the dinoflagellates. This difference was reflected in the maximum growth rate, which for the examined diatoms range from 0.6 to 1.2 divisions d-1, compared with 0.2 to 0.3 divisions d-1 for the dinoflagellates. Among diatoms there were species specific differences in light utilization and uptake of silicate, and C. wighamii had the highest carbon assimilation capacity and maximum silicate uptake. The physiological properties of diatoms and dinoflagellates were used in a model of the onset of the spring bloom: for the diatoms the model could predict the initiation of the spring bloom; S. hangoei, on the other hand, could not compete successfully and did not obtain positive growth in the model. The other dinoflagellates did not have higher growth rates or carbon assimilation rates and would thus probably not perform better than S. hangoei in the model. The dinoflagellates do, however, have competitive advantages that were not included in the model: motility and mixotrophy. Previous investigations has revealed that the chain-forming P. catenata performs diurnal vertical migration (DVM), and the results presented here suggest that active positioning in the water column, in addition to DVM, is a key element in this species' life strategy. There was indication of mixotrophy in S. hangoei, as it produced and excreted the enzyme leucine aminopeptidase (LAP). Moreover, there was indirect evidence that W. halophila obtains carbon from other sources than photosynthesis when comparing increase in cell numbers with in situ carbon assimilation rates. The results indicate that mixotrophy is a part of the strategy of vernal dinoflagellates in the Baltic Sea. There were also indications that the seeding of the spring bloom is very important for the dinoflagellates to succeed. In mesocosm experiments dinoflagellates could not compete with diatoms when their initial numbers were low. In conclusion, this thesis has provided new information about the basic physiological and ecological properties of the main cold-water phytoplankton in the Baltic Sea. The main phytoplankton groups, diatoms and dinoflagellates, have different physiological properties, which clearly separate their life strategies. The information presented here could serve as further steps towards better prognostic models of the effects of eutrophication in the Baltic Sea.Övergödningen av Östersjön Ă€r ett vĂ€lkĂ€nt problem som förorsakas av mĂ€nskligt utslĂ€pp av kvĂ€ve och fosfor. MĂ„nga av dessa nĂ€ringsĂ€mnen blir tagna upp av algerna under vĂ„ren nĂ€r ljusets ökade intensitet sĂ€tter igĂ„ng en vĂ„rblomning hos algerna. DĂ€rför Ă€r kunskap om algernas vĂ€xt under denna period viktig för förstĂ„elsen av eutrofieringsprocesser i Östersjön. MĂ„lsĂ€ttningen av denna avhandling var att beskriva grundlĂ€ggande fysiologiska och ekologiska egenskaper hos alger som Ă€r vanliga under vĂ„rblomningen i Östersjön. Detta mĂ„l uppnĂ„ddes genom specifika studier av (1) lĂ„ngskiktig vertikal placering (2) dinoflagellateers livscykler (3) mixotrofi (4) primĂ€rproduktion, respiration och tillvĂ€xt och (5) kiselalgers silikatupptag. Arbetet blev utfört i havet utanför Hangö och med laboratoriekulturer av kiselalgerna: Chaetoceros wighamii, C. gracilis, Pauliella taeniata, Thalassiosira baltica, T. levanderi, Melosira arctica, Diatoma tenuis, Nitzschia frigida, och dinoflagellaterna: Peridiniella catenata, Woloszynskia halophila and Scrippsiella hangoei. Kiselalgerna hade högre primĂ€r produktion och lĂ€gre respiration Ă€n dinoflagellaterna. Denna skillnad reflekterades ocksĂ„ i den maximala tillvĂ€xthastigheten som för kiselalgerna var 0.6-1.2 delningar per dag och för dinoflagellaterna 0.2-0.3 delningar per dag. Bland kiselalgerna var det ocksĂ„ arts specifika skillnader i anvĂ€ndandet av ljus och upptagandet av silikat. C. wighamii hade den högsta primĂ€rproduktionen, silikatupptag och maximal tillvĂ€xthastighet. De fysiologiska egenskaperna hos kiselalgerna och dinoflagellaterna blev anvĂ€nda i en modell av tidpunkten för vĂ„rblomningen. För kiselalgerna kunde modellen förutspĂ„ vĂ„rblomingens början men dinoflagellaterna fick inte positiv vĂ€xt i modellen. Dessa arter finns i Östersjön under vĂ„ren och mĂ„ste dĂ€rför ha andra konkurrensegenskaper som inte var med i modellen sĂ„ som mobilitet och mixotrofi (förmĂ„gan till att uppta nĂ€ring i organisk form). Den kolonibildande dinoflagellaten P. catenata Ă€r en god simmare, och resultaten indikerar att aktiv positionering i vattenpelaren Ă€r viktigt för denna arts ekologiska strategi. Det var bevis för mixotrfi i S. hangoei eftersom arten producerar enzymet leucine aminopeptidase (LAP). Det var ocksĂ„ resultat som indirekt pekade mot mixtotrofi hos W. halophila eftersom tillvĂ€xten var mycket högre Ă€n fixeringsraten av karbon indikerade. Det ursprungliga antal dinoflagellater verkar ocksĂ„ vara mycket viktig för den biomassa som byggs upp under vĂ„rblomningen. Denna avhandling har beskrivit ny information om fysiologiska och ekologiska egenskaper hos algerna som Ă€r vanliga under vĂ„rblomningen i Östersjön. Detta Ă€r information som inte tidigare har funnits pĂ„ artnivĂ„

    The impact of changing cooling refrigerant in fresh whole salmon export to dry ice

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    Performance enhancement in cellular networks with dynamic cell sizing

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    Handwriting versus keyboarding in first grade: Which modality best supports written composition performance and learning?

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    PhD thesis in Reading researchAn important background for the present thesis is the increasing digitalisation in school, and more specifically, the Norwegian first-grade reality, where a growing number of schools provide students with personal digital devices to be used in initial writing instruction. The research that compares effects of handwriting and keyboarding on children’s early writing is, however, scarce, findings are inconsistent, and many of the studies suffer from methodological problems, for example, inadequate control of children’s prewriting experience (Wollscheid et al., 2016). The aim of the present thesis was therefore to investigate whether modality – handwriting on paper or keyboarding on digital tablet with text-to-speech functionality – affects first grader’s written composition performance and written composition learning, and whether these effects depend on children’s literacy skills (grapheme-phoneme mapping, first sound segmentation, blending, word reading, spelling and vocabulary) measured at school start. This was examined in a sample of Norwegian first graders from 18 schools, where five schools taught children to write by hand, five schools taught children to write by digital tablet postponing handwriting, and eight schools taught children to write both by hand and using a digital tablet. Children’s compositions were analysed for length and quality by formally assessing a set of text features related to both transcription (spacing, spelling and punctuation) and narrative sophistication (vocabulary, syntax and narrative structures). The text quality measures were specifically developed for assessing narratives by beginning writers which typically are short and simple. The statistical modelling was done using Bayesian methods, which allow for demonstrating evidence in both the presence and absence of effects. This thesis includes four articles. Article 1 is a philosophical discussion of how texts by beginning writers can be analysed from a quantitative viewpoint. The three remaining articles contribute to the thesis by empirically investigating the effects of modality on first graders’ written composition performance and written composition learning. Article 2 shows that first graders who are taught writing in both modalities from the start of school are likely to produce compositions of similar length and quality in both modalities. This article also shows that the lack of a modality effect on written composition performance does not depend on children’s literacy skills. For example, students with weaker literacy skills did not produce stories of higher quality in one or another modality. Article 3 demonstrates that first-grade students receiving instruction based on handwriting or digital tablets with otherwise minimal change to instruction, overall learn to compose text at the same rate throughout the first year of formal writing instruction. The students showed similar development in text length, syntactic complexity and accuracy, and narrative structures, regardless of learning to write by hand or with a digital tablet. Students writing with a digital tablet showed better performance in transcription accuracy (spelling, spacing and terminator accuracy), but showed little or no development of these text features through the first grade. Students writing by hand started at a lower performance level for transcription accuracy but showed improvement throughout the year. This difference in performance can probably be attributed to the text-to-speech functionality offered by the digital tablets. Article 4 shows that there were no interaction effects between modality and students’ literacy skills on learning to compose text. This means that there were, for example, no advantages related to learning to compose text with a digital tablet, or by hand, for students with weaker literacy skills. The conclusion of the thesis is that, in a context similar to the one studied here, modality does not substantially affect first-grade students’ written composition performance or written composition learning. Thus, it seems that instruction based on handwriting and instruction based on digital tablets can provide children with similar opportunities to develop their written composition skills in their first year of school. Before clear recommendations about the choice of modality for initial writing instruction can be made, future research should investigate the potential transition effects of going from learning to write in one modality to the other.En viktig bakgrunn for denne avhandlingen er den Ăžkende digitaliseringen i skolen, og mer spesifikt den norske fĂžrste-klasse-virkeligheten, der et Ăžkende antall skoler utstyrer elevene med personlige digitale enheter til bruk i skriveopplĂŠringen. Forskningen som sammenligner effektene av hĂ„ndskrift og tastaturskriving pĂ„ barns tidlige skriving er imidlertid knapp, funn er inkonsistente og mange av studiene lider av metodologiske svakheter, for eksempel utilstrekkelig kontroll av deltakernes tidligere skriveerfaring (Wollscheid et al., 2016). MĂ„let med denne avhandlingen var derfor Ă„ undersĂžke om modalitet – hĂ„ndskrift pĂ„ papir eller tastaturskriving pĂ„ nettbrett med tekst-til-tale funksjonalitet – pĂ„virker fĂžrsteklassingers prestasjon i og lĂŠring av tekstkomposisjon, og om disse modalitetseffektene avhenger av barnas literacyferdigheter (grafem-fonem-kunnskap, framlydsanalyse, fonologisk syntese, ordlesing, staving og vokabular) mĂ„lt ved skolestart. Dette ble undersĂžkt i et utvalg av norske fĂžrsteklassinger fra 18 skoler, hvorav fem skoler lĂŠrte barna Ă„ skrive for hĂ„nd, fem skoler utsatte hĂ„ndskriftsopplĂŠringen og lĂŠrte elevene Ă„ skrive pĂ„ digitalt nettbrett, og Ă„tte skoler lĂŠrte barna Ă„ skrive bĂ„de for hĂ„nd og pĂ„ digitalt nettbrett. Elevenes tekster ble analysert for lengde og kvalitet gjennom formell vurdering av et sett av teksttrekk knyttet bĂ„de til transkripsjon (staving, mellomromsbruk og tegnsetting) og narrativ kompleksitet (vokabular, syntaks og narrative strukturer). TekstkvalitetsmĂ„lene ble utviklet spesielt for Ă„ vurdere begynnerskriveres fortellinger, som typisk er korte og enkle. Den statistiske analysen ble gjort gjennom Bayesianske metoder, som kan bevise bĂ„de tilstedevĂŠrelse og fravĂŠr av effekter. Avhandlingen inkluderer fire artikler. Artikkel 1 er en vitenskapsteoretisk diskusjon av hvordan tekster av begynnerskrivere kan analyseres fra et kvantitativt perspektiv. De tre resterende artiklene bidrar til avhandlingen gjennom Ă„ empirisk undersĂžke modalitetseffekter pĂ„ fĂžrsteklassingers prestasjon i og lĂŠring av tekstkomposisjon. Artikkel 2 gir evidens for at fĂžrsteklassinger, som fra starten av fĂžrste klasse lĂŠrer Ă„ skrive i begge modaliteter, etter all sannsynlighet produserer fortellinger av lik lengde og kvalitet i begge modaliteter. Denne artikkelen viser ogsĂ„ at mangelen pĂ„ en modalitetseffekt pĂ„ prestasjon i tekstkomposisjon ikke avhenger av elevenes literacyferdigheter. For eksempel skrev ikke elever med svakere literacyferdigheter fortellinger av hĂžyere kvalitet i en av modalitetene. Artikkel 3 viser at fĂžrsteklasseelever som fĂ„r undervisning basert pĂ„ enten hĂ„ndskrift eller digitalt nettbrett, med ellers minimal forandring i undervisningen, i hovedsak lĂŠrer Ă„ komponere tekster i samme takt gjennom det fĂžrste Ă„ret med skriveopplĂŠring. Elevene viste lik utvikling av tekstlengde, syntaktisk kompleksitet og nĂžyaktighet og narrative strukturer, uavhengig av om de lĂŠrte Ă„ skrive for hĂ„nd eller pĂ„ digitalt nettbrett. Elever som skrev pĂ„ nettbrett, presterte bedre pĂ„ transkripsjonsnĂžyaktighet (stave-, mellomroms- og tegnsettingsnĂžyaktighet), men viste liten eller ingen utvikling av disse teksttrekkene gjennom fĂžrsteklasse. Elever som skrev for hĂ„nd, startet pĂ„ et lavere nivĂ„ i transkripsjonsnĂžyaktighet, men viste utvikling gjennom Ă„ret. Denne forskjellen i prestasjon kan sannsynligvis tilskrives tekst-til-tale funksjonaliteten pĂ„ de digitale nettbrettene. Artikkel 4 viser at det ikke var noen interaksjonseffekter mellom modalitet og elevenes literacyferdigheter pĂ„ lĂŠring av tekstkomposisjon. Det vil si at det var, for eksempel, ingen fordeler knyttet til Ă„ lĂŠre Ă„ komponere tekst pĂ„ digitalt nettbrett, eller for hĂ„nd, for elever med svakere literacyferdigheter. Konklusjonen i avhandlingen er at, i en kontekst lik den som er studert her, pĂ„virker ikke modalitet fĂžrsteklassingers prestasjon i tekstkomposisjon eller lĂŠring av tekstkomposisjon i vesentlig grad. Det ser altsĂ„ ut som at skriveopplĂŠring basert pĂ„ hĂ„ndskrift og skriveopplĂŠring basert pĂ„ nettbrett kan gi elever like muligheter for Ă„ utvikle ferdigheter i tekstkomposisjon det fĂžrste Ă„ret pĂ„ skolen. FĂžr klare anbefalinger om bruk av modalitet i begynneropplĂŠring kan gis, bĂžr framtidig forskning undersĂžke mulige overgangseffekter i Ă„ gĂ„ fra Ă„ lĂŠre Ă„ skrive i en modalitet til den andre modaliteten

    Aspects of self-organisation in cellular networks

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    An introduction to situation aware networks

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    The intramolecular ene reactions of some unsaturated acyloins

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    The reaction of 3ÎČ-tosyloxy-5α-cholesta-5,6ÎČ-diol with potassium t butoxide in t-butanol has been further investigated. 5ÎČ-Hydroxy-4,5-secocholest-3-en-6-one was synthesised. It was shown to undergo an ene reaction in decalin in a sealed tube at 200°C to give primarily 3ÎČ-methyl-A-nor-5ÎČ-cholestan-5-o1 -6-one and 6ÎČ-hydroxy-4(5-6α) abeo-cholestan-5-one. These primary products were further modified under the reaction conditions to give 3-methyl-B-nor-5ÎČ-cholest-2-en-4-one and 5ÎČ-cholestan-5-ol-6-one respectively. The cyclohexane analogue, 3-methyl-3-(3-butenyl)-2-hydroxy-cyclohexanl- one was synthesised. Heating under reflux in decalin gave 3ÎČ,7aÎČ-dimethyl- 3aÎČ-hydroxy-octahydro-4H-inden-4-one;5ÎČ,7aÎČ-dimethyl-3aÎČ-hydroxy-octahydro- 4H-inden-4-one and an unidentified minor product. The synthesis of 5-(2-propenyl)-5ÎČ-cholestan-2-ol-3-one was partially completed. The epimeric 5-(2-propenyl)-5ÎČ-cholestan-2-ol-3-one. was synthesised. The ene reaction was observed in refluxing toluene giving 2α,5-(1-methylethano)-5α-cholestan-2ÎČ-ol-3-one and 3α,5-(methyethano)-5α-cholestan-3ÎČ–ol-2-one. The ketone analogue, 5-(2-propenyl )-5α-cholestan-3-one underwent an ene reaction in decalin in a sealed tube at 250°C to give 2α,5-(1-methylethano) -5α-cholestan-3-one

    EntreprenĂžrskap i utdanningen - perspektiver og begreper

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    FormÄlet med denne rapporten er Ä gjennomgÄ teorigrunnlaget for entreprenÞrskap i utdanningen (EiU) og drÞfte hvordan det kan operasjonaliseres med hensyn til utforming av utdanningstilbud i entreprenÞrskap pÄ ulike nivÄer og pÄ ulike fagomrÄder i utdanningssystemet

    Adaptive coverage for UMTS macrocells based on situation awareness

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    Determining inorganic and organic nitrogen

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    Correction: Methods in Molecular Biology Volume1980 Page 243-243 Article Number107968 DOI 10.1007/7651_2019_252 Published 2020Nitrogen (N) is one of the key nutrients for algal growth and is an integral part of many cellular components, for example in proteins. Being able to determine the inorganic and organic pools of N is consequently critical for algal cultivation. In this chapter we present the methods we use for determining dissolved inorganic nitrogen (DIN), dissolved organic nitrogen (DON) and particulate organic nitrogen (PON). The methods presented here for DIN rely on colorimetric methods and those of DON and PON on filtration and high temperature catalytic oxidation.Peer reviewe
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