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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
281

Super Duplex Stainless Steel Surfaces and their Effects on Marine Biofouling

Falk, Adrian January 2017 (has links)
Some of the world’s most ancient, but still viable, organisms have since the beginning of maritime caused problems for the industry. The problems affect both the longlivety and efficiency of ships which is caused by the mere presence of organisms attached to the ship hulls. The organisms, called biofoulers, causes problems with longlivety related to moisture and crevice corrosion which break down the hull material. The problem regarding efficiency of the ship is related to the added hydrodynamical resistance that the biofoulers cause. To limit fouling in the marine industry, paint poisonous to the biofoulers is applied to prohibit growth. Until recent the paint seemed to be a long-term solution but severe damage to the sea life has been traced to the use of antifouling paint. This master thesis aims on exploring one putative solution to the problems related to biofouling. In a maritime perspective, advanced stainless steels are modern materials with use limited to fittings and certain high strength parts. However, in 2014 a small ship constructed completely in super duplex stainless steel 2507 was launched. Immediately the longlivety of the ship increased by several times. The approach was that no antifouling paint was necessary, but biofoulers will grow on the now non-poisonous surface. Surprisingly, in some areas of the ship the biofoulers adhered seemed to detach when driving the ship in certain speeds. This lead to the initiative to examine this mechanism further in the form of this master thesis. The master thesis was held at Sandvik Materials TechnologyAB. The main hypothesis was that adhesion of biofoulers will decrease with decreasing surface roughness. Few studies on the subject stainless steel, biofouling and surface roughness have been performed. Even fewer studies on stainless steel with metallic surface coatings and biofoulers have been performed why another hypothesis was driven: There are surface coatings which will affect growth and adhesion of biofoulers. 22 different stainless steel 2507, 3207 and 316L surface setups were produced by either polishing, coating, bending or magnetizing. Plates were analysed before being immersed in natural seawater in Brest, France for 70 days. After 70 days, the plates were taken up and two major tests were performed at site; fouling amount rank analysis and barnacle adhesion strength measurements. SEM and GDOES were used in the post-experment analysis. No sign of corrosion on the plates were found. The data was processed and results were obtained: Maximum corrosion potential, surface roughness, barnacle adhesion strength and biofouling has quite strong or strong correlations. The lowest barnacle mean adhesion strength was measured to 0.02 MPa. In practical, based on experimental formulated formulas, the low adhesion barnacles would detach in a water flow of 11 m/s.
282

Enzymatic cleavage of HMGB1

Rensing, Merlin January 2017 (has links)
Alarmins and damage associated molecular pattern (DAMP) are endogenous proteins with distinct and various intracellular roles that when released extracellularly act as startingsignals for inflammatory immune responses. The endogenous protein High mobility group box 1 (HMGB1) acts as a DAMP and has been shown to drive progression of multiple inflammatory and autoimmune diseases. During homeostasis HMGB1 is localized in the nucleus of almost any cell, where its main function is organization of the DNA and regulation of transcription. Upon cell death or immune cell activation HMGB1 can be translocated into the cytoplasm for subsequent release into the extracellular space. Extracellular HMGB1 can act as a DAMP by activating several receptors of the immune system. Recent studies focus on HMGB1 release and functional regulation due to prost-translational modifications (PTMs) on cysteine residues. However, little is known about enzymatic regulation of HMGB1. The aim of this thesis was to investigate the possibility of proteolytic processing of HMGB1 by enzymes, which play a crucial role in inflammatory diseases and their progression. We utilized an in vitro model that mimics natural conditions of the autoimmune disease arthritis. Enzymatic digestion of HMGB1 was performed in kinetics studies using the neutrophilic enzymes cathepsin G, neutrophil Elastase as well as matrix metalloproteinase-3, which is released from tissues at the site of inflammation. We defined that HMGB1 is a novel substrate of all of the tested enzymes. All enzymes induced different cleavage pattern. In conclusion, my findings open up the possibility for future studies involving the observed fragments of HMGB1 and their functional features. It also demonstrated that HMGB1 is affected by protease modifications in a disease relevant environment.
283

Genetic Aspects of Environmental Disturbances in Marine Ecosystems : Studies of the Blue Mussel in the Baltic Sea

Larsson, Josefine January 2017 (has links)
Anthropogenic environmental changes can serve as drivers for evolutionary responses in wild populations. To predict the long-term impact of anthropogenic changes on populations, it is crucial to understand the genetic effects caused by these disturbances. The Baltic Sea is considered to be one of the world’s most contaminated seas, and the increase of anthropogenic chemical pollution is a major threat to its ecosystems. This thesis assesses the impact of harbors and sewage treatment plants on physiological traits and genetic structure of resident populations of blue mussels at replicated sites in the Baltic Sea. The initial evaluation of the overall genetic pattern in blue mussel populations in the Swedish West Coast, the Baltic Proper and the Bothnian Sea found genetic differentiation between the three water basins and a low genetic differentiation within each basin, especially within the Baltic Proper. Despite the low genetic differentiation among blue mussels within the Baltic Proper, a parallel genetic differentiation associated with sewage treatment plant effluents was found in this basin. This included genomic regions with a high degree of differentiation between reference sites and sites affected by sewage plants effluent. This genetic differentiation is suggested to be due to post-dispersal selection acting in each generation. In contrast, no parallel genetic differentiation was associated with harbors. We identified five genomic regions in blue mussels, showing strong signs of selection, shared among three out of four replicated reference sites and sites affected by sewage effluents in the Baltic Proper i.e. Askö, Tvärminne and Karlskrona. An initial characterization of these genomic regions revealed functions related to immune and endocrine responses, oxidative stress and shell formation. Our results indicate that selection caused by sewage effluents involves multiple loci. The same genomic regions are found across different locations in the Baltic Proper but there are also unique genomic regions at each location. No genotoxic or histopathological effects were found among blue mussels from sewage effluent-affected areas but a higher frequency of histological abnormalities in the digestive gland were observed in mussels from harbors. / Evolutionära anpassningar till miljöstörningar i marina ekosystem: genetisk ekotoxikologi i Östersjön
284

The surrounding landscape’s impact on species density in species-rich grasslands

Eningsjö, Frida January 2017 (has links)
When the agricultural revolution took place, the biodiversity decreased and during the last century more than 90 % of the area of species-rich grasslands has been lost. Fragmentation has occurred with the area lost and insects, e.g. butterflies, suffer because of this. I investigated the impact that surrounding landscapes have on vegetation in species-rich grasslands, by using data from NILS and land use land cover data. I used the area of grassland, forest, water and arable land at radii from 100 m to 40000 m. All landscape structures showed a significant effect on the species density, but at different ranges. Arable and forest were both positive at large radii. Water had a negative effect at short ranges but positive at large ranges. The same was shown for grassland, and that is likely explained by grassland making up a very small proportion of the total area. In conclusion, species density in species-rich grasslands can partly be explained by the surrounding landscape. These results have implication for reserve selection, monitoring and restoration.
285

Elevernas upplevelse av hälsa, stress och avslappningsövningar i en skola som aktivt arbetar med avslappning

Holm, Maria January 2017 (has links)
Syftet med studien var att undersöka hur elever upplever stress, hälsa och avslappningsövningar, i en skola där lärarna aktivt arbetar med hälsofrågor och avslappningsmetoder med eleverna. Undersökningen utgår från en kvalitativ forskningsansats med semistrukturerade intervjuer. Totalt nio elever intervjuades, tre elever från tre olika klasser. Vidare intervjuades de tre klasslärarna om hur de arbetar med hälsorelaterade frågor och strategier, för att förebygga stress hos elever. Lärarna beskrev tre olika avslappningsmetoder som används med eleverna. Två av metoderna utförs oftast och massage, som är en av dessa, är mest omtyckt bland eleverna. Både lärarna och några elever upplevde att avslappningsmetoderna sänker  ljudnivån på timmarna samt ger ett vänligare klimat i klassen. Eleverna upplever att de lär sig om hälsa och dess betydelse. Resultatet visade att eleverna själva tycker att de inte är stressade och att de har en god hälsa, sover bra samt äter bra mat i skolan. Slutsatsen är att eleverna som går på en skola som aktivt arbetar med hälsofrågor och avslappningsmetoder inte upplever sig stressade. Resultaten i denna studie kan ge idéer till andra verksamma lärare hur man kan arbeta för att förebygga uppkomsten av stress.
286

Hårfollikelns struktur, funktion och hårpigmenteringens genetiska reglering hos däggdjuren : Samt hur detta kan användas som modell i gymnasieksolan för att ge en djupare förståelse för genetiska interaktioner / The Function and Structure of the Hair Follicle, and the Genetical Regulation of Hair Pigmentation in Mammals : And how it can be Used as a Model in Upper Secondary School to Attain a Deeper Understanding of Genetical Interactions

Söderlund, Leo January 2020 (has links)
Hårfollikeln är en struktur som hittas hos alla däggdjur. Hår skyddar kroppen från UV-ljus, medverkar i kroppens värmereglering och har flera kommunikativa funktioner. Hårets varierande färg inom och mellan arter är både en fascinerande och intresseväckande egenskap som länge har studerats som en modell för genetisk nedärvning. I denna litteraturstudie ges en genomgång av hårfollikelns struktur och funktion, genetiken bakom hårets pigmentering samt didaktiska utmaningar i genetikundervisningen. Interaktioner mellan generna MC1R, ASIP (agouti) och POMC förklaras och exemplifieras. Dessutom diskuteras hur fårfollikeln och de pigmentreglerande generna kan användas i gymnasieskolan som ett exempel för komplicerade genetiska interaktioner. / The hair follicle is a structure found in all mammals. Hair protects the body from UV-induced damage, assists the body in its thermoregulation and has several communicative functions. The great variation in hair colour, both within and between species, is a captivating and intriguing trait that has been used as a model for genetic inheritance for a long time. This literature review features the structure and function of the hair follicle, the genetics behind the pigmentation of the hair as well as didactic challenges in teaching genetics. Interactions between the genes MC1R, ASIP (agouti) and POMC is both explained and illustrated. This review also discusses how the hair follicle and the genes regulating pigmentation can be used as an example of intricate genetic interactions in the upper secondary school. / <p>På grund av Covid-19 skedde presentation, opponering och respondering skriftligt på distans.</p>
287

Design av passageflyktöppningar: Substrats påverkan på nedströmspassage av mört (Rutilus rutilus) / The design of passageway entrances: The effect of substrate on downstream passage of roach (Rutilus rutilus)

Möller, Rebecka January 2021 (has links)
Vattenkraftens effekter på vandrande fiskarter har varit kända länge och väldigt få har de anpassningar som behövs för att vara funktionella för både upp-och nedströmsvandring för migrerande arter. Numera vet man det även finns ett behov för svagsimmande arter att använda fiskpassager och för att underlätta för dessa så har man testat olika alternativ som ska fungera för flera olika arter, bl.a. att placera substrat i form av sten eller grus i kulvertar. Vilket har visat sig vara effektivt för just svagsimmande arter genom att det sänker energikostnaden att passera och ökar attraktionen till en mer naturlig struktur. För att öka kunskapen om substrat har en effekt även vid nedströmspassage, så utfördes en experimentell studie om hur substrat påverkar nedströmspassage för mört vid avledning vid ingången till en passageöppning i en artificiell strömränna. Mörten märktes med PIT-tags och kameror placerades ut i olika vinklar för att analysera mörtens beteende. Resultatet visade att mörtar utan substrat hade en snabbare passagetid än mörtar med substrat, men även att mörtar utan substrat tog sig till flyktöppningen snabbare än mörtar med substrat. Orsaken till den långsammare passagetiden kan bero på att substratet framkallade turbulens som därmed fördröjde mörten till att undersöka flyktrännan, då inget annat beteende skiljde mellan de olika behandlingarna. Ytterligare analyser hade behövts av mörtens beteende innan flyktöppningen för att se var de blev fördröjde och då kanske få reda på orsaken. Att fortsätta undersöka fiskars beteende är viktigt för att kunna få fram fungerande alternativ på förbättringar för migrerande fiskar, det måste vara funktionellt för fler arter för att kunna gynna både miljön, naturen och vattenkraften. / The effects of hydropower on migratory fish species have been known for a long time, but very few are adapted for both upstream and downstream migration. Nowadays it is known that there is also a need for weak-swimming species to be able to use fish passages and to facilitate these, various alternatives have been tested that are functional for several different species, for instance placing substrate in the form of stone or gravel in culverts. Which has proven to be effective for weak-swimming species, because it lowers the energy cost of passing and increases the attraction to a more natural structure. In order to increase knowledge about substrate and if it also has an effect on downstream passage, an experimental study was carried out on how substrate affects downstream passage for roach through a bypass. The roach were marked with PIT-tags and cameras were placed at different angles to analyze the3roach´s behavior. The results showed that roach without substrate had a quicker passage time than roach with substrate and that roach without substrate reached the bypass faster than roach with substrate. The reason for the slower passage time may be due to the substrate causing turbulence and therefore delayed the roach to examine the bypass, as no other behavior differed between the different treatments. Further analyzes had been needed of the roach behavior before the bypass to be able to see where they were delayed and then perhaps find out what caused it. Continuing to investigate fish behavior is important in order to be able to develop alternatives to improvements for migratory fish, it must be functional for more species in order for the environment, nature and hydropower to benefit from the measure.
288

Blommor och bin på schemat : En studie angående högstadieelevers uppfattningar om sex- och samlevnadsundervisningens innehåll och användbarhet / Let's talk about the birds and the bees : A study focusing on pupils perceptions of the content and utility of sex education in secondary school

Paulander, Emma, Karlsson, Jennie January 2021 (has links)
No description available.
289

Förhoppningarna över CAR-T celler som behandlingsmetod mot hematologisk cancer

Löfås, Mathilda January 2018 (has links)
Olika typer av blodcancer är några av de vanligast förekommande cancerformerna i världen. Ju tidigare sjukdomen upptäcks och beroende på vilken typ av blodcancer någon drabbats av ser prognosen i många fall god ut då dagens behandlingsmetoder under flera år effektiviserats. Dock finns det fall där patienter inte svarar på traditionella terapier som cytostatika och stålning eller gånger där sjukdomen kommer tillbaka i aggressivare former. I dessa fall krävs andra metoder för att försöka behandla och bota cancern.   En metod som på senare tid fått mycket uppmärksamhet i forskarvärlden är användandet av kroppens egna immunceller som behandlingsform mot blodcancer. Genom att rena fram en patients egna T-celler från ett blodprov, kan dessa sedan genetiskt modifieras till att känna igen specifika tumörassocierade antigener (TAA) som bara vissa typer av cancerceller uttrycker. Metoden går ut på att T-cellerna får chimära antigen-receptorer (CAR), som uttrycks på cellytan, där CAR-T cellerna sedan injiceras tillbaka till patienten. CAR-T cellerna känner igen cancercellerna och attackerar sedan, med målet att patienten efter behandlingen inte ska ha några cancerceller kvar i kroppen.   Kliniska försök gjorda på patienter med olika typer av blodcancer har visat lovande resultat, särskilt gällande patienter som fått återfall av blodcancertypen Akut Lymfatisk Leukemi (ALL). De som fått delta i studierna har haft mycket dåliga prognoser och har innan blivit behandlade med de konventionella behandlingsterapierna, men utan eller med mycket dåligt resultat. Förhoppningar som väckts från dessa forskningsresultat har lett till diskussion att CAR-T celler kan komma att förändra cancervården och i framtiden kanske vara en lika vanlig behandlingsmetod som strålning eller kemoterapi. Dock kvarstår många problem som forskarna måste lyckas lösa innan CAR-T celler kan räknas som konventionell. Bland annat finns stora risker att patienter vid behandling kan drabbas av cytokinfrisläppningssyndrom (CRS, eng. cytokine release syndrome), där immunförsvaret kan attackera kroppens egna organ som i värsta fall kan leda till döden. Cancercellerna kan även komma tillbaka efterbehandling, då de har utvecklat en resistens mot CAR-T cellerna. Metoder för att undvika dessa toxiska responser och göra T-cellerna mer effektiva är bara några av de problem som kvarstår.
290

Effects of fine woody debris on juvenile brown trout (Salmo trutta) and drifting invertebrates

Enefalk, Åsa January 2014 (has links)
In boreal forest streams, woody debris is an important habitat component. Stream invertebrates and salmonids such as brown trout benefit from in-stream wood. The studies presented in this thesis explore how drifting stream invertebrates respond to addition of fine woody debris, and how young-of-the-year (0+) brown trout behave in habitats with and without fine woody debris. The first paper reports results from a field experiment where fine woody debris was added to streams, and invertebrate drift was measured in order to detect impacts of the fine woody debris on drift density, biomass and taxon diversity. In the end of the season, the fine woody debris-affected drift samples showed higher density, biomass and taxon diversity than the control samples. In the second paper, I describe effects of fine woody debris on 0+ brown trout, studied in laboratory stream channels. Trout were tested in habitats without fine woody debris, with an intermediate fine woody debris density, and with a high fine woody debris density. Swimming activity and foraging time were significantly lower when fine woody debris was present than when it was absent. More time was spent sheltering at the high fine woody debris density than at the intermediate one. The increasing exploitation of fine woody debris for biofuel purposes should be considered in relation to the effects on brown trout and stream invertebrate habitat. / <p>Artikel 1 ingick i avhandlingen som manuskript med titeln "Effects of fine wood addition on invertebrate drift in boreal forest streams". Nu publicerad.</p>

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