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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.
121

Does eutrophication cause greater growth of epiphytic algae on the seagrass Zostera marina?

Ljung, Angelica January 2024 (has links)
The most common eelgrass along the Swedish coast is Zostera marina. It is an ecosystem engineer which provides both nature and humans with important ecosystem services and various ecosystem functions. Eutrophication is one of the main reasons why the Swedish coast has lost a lot of Z. marina meadows. When there is more nitrogen in the ocean, it is an advantage for epiphytic algae so that they can grow faster. The epiphytic algae grow on Z. marina and reduce Z. marina from receiving light. And therefore, the aim of my thesis is to investigate the effect of eutrophication on the growth of epiphytic algae on Z. marina. I took water samples at 8 different locations (spanning 7.21 km) along the coast of Halmstad, from the mouth of river Nissan, which I hypothesize to be a main source of nitrogen, to the open sea. From the water samples nitrogen, absorbance and TOC was measured to see if there was any difference in the water composition from Nissan's outlet and seawards. Z. marina leaves were taken from two different sites on one occasion to investigate the degree of epiphytic algae on the leaves. I found that the nitrogen concentration was decreasing from the outlet of Nissan River along coast towards the open sea. Also, the growth of epiphytic algae on Z. marina was decreasing from the outlet of Nissan River along the coast towards the open sea. The growth of epiphytic algae on Z. marina was not solely dependent of the concentration of nitrogen. In Scandinavia, Z. marina meadows are one of the most diverse coastal ecosystems. On otherwise sandy and species-poor substrates, Z. marina is an important habitat for a rich epiflora and fauna so a more integrated understanding in both management and science of Z. marina's stress responses is needed.
122

Effekter av dammutrivning på kvicksilverhalten hos gädda / The effects of dam removal on mercury concentration in pike

Wiener, Jessica January 2024 (has links)
Sammanfattning Dammutrivningar blir alltmer vanligt på grund av att många är föråldrade och kostar mer att driva och underhålla än vinsten de ger i energi. Effekten av utrivningar på halten miljögifter i fiskar är relativt okänd, men det finns observationer som indikerar att det dammutrivningar kan minska kvicksilverhalten i fiskar. Syftet med min studie var att undersöka skillnaderna i kvicksilverhalten hos gädda (Esox lucius), mellan sjöar som har fått dammen i sjöutloppet utriven respektive dammen intakt. Jag undersökte 66 provtagningar från 18 oligotrofa svenska skogssjöar. I sjöar där dammutrivning skett innehöll en medelstor gädda 500 ng/g kvicksilver, medan motsvarande värde i sjöar med dammen intakt var 740 ng/g kvicksilver. Det fanns ingen signifikant effekt av vare sig antal år efter utrivning eller provtagningsår. Kvicksilverhalten var nära förknippad med gäddans längd och varierade mellan sjöar, och i fyra av sjöarna, översteg mätningarna 1000n ng/g (gränsvärdet för konsumtion inom EU) medan gäddor från de andra sjöarna hade värden som mestadels under detta gränsvärde. / Abstract Dam removals are becoming increasingly common because many are outdated and cost more to operate and maintain than the value of that they provide in energy. The effect of dam removal on the level of environmental toxins in fish is relatively unknown, but there are observations that indicate that dam removal can reduce mercury concentrations in fish. The aim of my study was to investigate differences in the mercury concentration of pike (Esox lucius) between lakes that have had their outlet dams removed and those that have their dams intact. I examined 66 samples from 18 oligotrophic Swedish forest lakes.n lakes where the dam had been removed, a pike of average length contained 500 ng/g mercury, whereas the corresponding value for lakes with the dam intact was 740 ng/g of mercury. There was no significant effect of the number of years after removal or sampling year. The mercury concentration was closely associated to pike length and varied between the lakes, and in four of the lakes, all measurements exceeded 1000 ng/g (the limit value for consumption in EU), whereas most pike from the other lakes had values below this limit value.
123

Makrofager som stimulerats med Cutibacterium acnes ökar sitt uttryck av CCL22 mRNA / Macrophages stimulated with Cutibacterium acnes increases its expression of CCL22 mRNA

Lundell, Sandra January 2019 (has links)
Prostatacancer är en av världens vanligaste cancerformer. Varje år diagnostiseras ungefär 1,3 miljoner män världen över med prostatacancer och trots det vet man inte de bakomliggande orsakerna. Det finns flera studier som visar att det finns en koppling mellan infektion och olika typer av cancer och Cutibacterium acnes återfinns i hög utsträckning i prostatacancervävnad. Det har därför föreslagits att det finns ett samband mellan infektion av C. acnes och prostatacancer. Närvaro av tumörassocierade makrofager har visats sig vara gynnande för olika typer av cancer och från dessa makrofager frisätts kemokiner, bland annat CCL22. CCL22 kan vara inblandad i en lokal hämning av immunförsvaret som ofta förknippas med tillväxt av cancer. I detta arbete odlas makrofager från blodgivare med C. acnes för att ta reda på om makrofagerna ökar sitt uttryck av CCL22 mRNA. Genom att analysera resultaten från en kvantitativ realtids-PCR indikeras det att makrofager som behandlats med C. acnes signifikant ökar sitt uttryck av CCL22 mRNA. Sammanfattningsvis bedöms resultaten från detta arbete styrka uppfattningen att det kan finnas en koppling mellan C. acnes och orsakerna bakom prostatacancer men mer arbete återstår för att kunna klargöra dess relevans. / Prostate cancer is one of world´s most common forms of cancer. Every year about 1.3 million men around the world are diagnosed with prostate cancer and even so we cannot fully explain the etiology. There have been several studies indicating that there is a correlation between infection and different forms of cancer. Cutibacterium acnes (C.acnes) can be found to a large extent in prostate cancer tissue and a correlation between infection of C. acnes and prostate cancer has therefore been suggested. The presence of tumor-associated macrophages has been shown to favor various types of cancer. Several chemokines including CCL22 are released from these macrophages. CCL22 may be involved in a local inhibition of the immune system that is often associated with cancer growth. In this work, macrophages from a blood donor are grown with C. acnes to find out if the macrophages increase their expression of CCL22 mRNA after this exposure. By analyzing the results of a quantitative real-time PCR for CCL22 mRNA, it was demonstrated that macrophages treated with C. acnes significantly increase their expression of CCL22 mRNA. In conclusion, the results of this work indicate that there could be a link between C. acnes and the causes of prostate cancer, but more work remains to be able to clarify its relevance.
124

Våtmarksfåglar i Stjärnarp, en inventering av nyanlagd våtmark utanför Halmstad, Halland / Wetland birds in Stjärnarp, an inventory of a recently constructed wetland outside of Halmstad, Halland

Dejenfelt, Pontus January 2019 (has links)
Genom en kombinerad linjetaxering och revirkartering av nyanlagd våtmark i Stjärnarpsdalen utanför Halmstad under april-juni 2018 har jag undersökt artsammansättning, antal individer och par samt häckningskriteria hos fågelarter på plats. En jämförelse har gjorts med fem andra våtmarker i Halland i fråga om artsammansättning och häckninggskriteria för att undersöka om ålder eller storlek hos våtmarker har en effekt på dessa. Efter flertalet besök i Stjärnarp observerades totalt 55 arter varav 31 nyttjade våtmarken för antingen häckning, födosök eller rastade. Totalt 19 arter visade tecken på häckning inom våtmarkens gränser, varav endast fem arter slutligen fick ut avkomma. Hos samtliga undersökta våtmarker varierade antal arter mer under 2018, när de var av olika ålder, jämfört med när de alla var ungefär ett år gamla. Jag fann inga signifikanta korrelationer, beroenden eller skillnader mellan undersökta variabler, med undantag för signifikant korrelation och beroende mellan antal möjliga häckningar och area hos våtmarker. Enligt flera källor kan våtmarkers egenskaper och utformning ha stor betydelse för fåglars förekomst, t ex våtmarkens storlek, ålder, vattendjup, skötsel, placering, närvaro av fisk och mycket mer. I denna studie har Stjärnarp visats hysa arter som bl a häckar, och flera dessa arter indikerar på egenskaper som tidig succession, näringsrikt vatten, öppna strandängar och mer. Beroende på vad för fåglar och annan biologisk mångfald man vill gynna här i framtiden är planering och kontinuerligt uppföljningsarbete viktigt för att se om och hur fågelfaunan förändras samt vad det kan bero på. / By doing a transect inventory combined with territory mapping at a recently constructed wetland in the area of Stjärnarp outside of Halmstad, during April-June in 2018, I have investigated species composition, species abundance and reproductive criteria shown by the bird species in the area. A comparison was made with five other wetlands in the county of Halland in matter of species composition and reproductive criteria to overlook if the age or area of the wetlands have an impact. After several visits in Stjärnarp, a total of 55 species of birds were recorded, of which 31 species were using the wetland area for reproduction, foraging or resting. Among all examined wetlands species richness varied more during 2018, when of different ages, compared to when they were about one year old. Overall analysis wasn’t significant for correlations, regressions or differences between the investigated variables of this study, though there were a significant correlation and regression between the amount of possibly reproductive species and the area of wetlands. According to others, characteristics of wetlands can have great impact on the presence of birds, e.g. size and age of wetlands, water depth, maintenance, location, presence of fish and more. According to this study, several reproductive species in particular have indicated attributes in Stjärnarp, e.g. early succession, nutrient rich waters, open meadows and more. Depending on what species or other biodiversity people which to benefit in the future, planning and continuous studies are needed here to find out if and how bird communities change with time, and to what causes. / LIFE - Goodstream
125

Facial width-to-height ratio as a cue of threat : An ERP study

Eldblom, Hans January 2018 (has links)
The late positive potential (LPP) is an event-related potential (ERP) component associated with increased affective processing. Studies have shown that stimuli with high evolutionary significance (e.g. a threatening face) induce increased activity over centro-parietal areas of the brain. In an electrophysiological context, this is hypothesized to be indexed by greater LPP amplitudes. The facial width-to-height ratio (fWHR) is a facial-masculinity metric which refers to cheekbone width, divided by upper facial height (top of the lip to between the brows). For the first time, LPP amplitudes were examined in subjects upon observing faces with high vs. low facial fWHRs. Prior studies suggest that faces with high fWHRs are perceived as more threatening than faces with low fWHRs. Consequently, fWHR has by some researchers been proposed to serve as a cue of threat. Two separate tasks in the present study were used to investigate this. In the aggression task, males with high fWHRs were judged as more aggressive. Moreover, when put in a threatening context, high fWHR faces also elicited greater LPP amplitudes in subjects compared to faces with low fWHRs. Conversely, in the self-regulation task, differences in LPP amplitudes did not reach significance. In this task, statistical power was low due to few blocks/trials in the ERP experiment and subjects were not primed on threat, which may explain the non-significant results. Taken together, the results provide modest support to the theory that fWHR serve as a cue of threat. Future studies will need to take the present study’s limitations into consideration
126

Elevers intressen och åsikter om biologiundervisningen i gymnasieskolan - Ett redskap för kunskapsförmedling från lärare till elev

Fransson, Sofia January 2018 (has links)
Denna studie handlar om elevers intresse för naturvetenskapliga ämnen, och då främst biologiämnet. Den svenska läroplanen för gymnasieskolan sägs vila på en demokratisk grund. Denna studie visar att detta inte alltid är fallet. Tidigare studier har visat att det finns en skillnad i intresse för de olika naturvetenskapliga ämnena, beroende på ditt biologiska kön, där kvinnor oftast visade ett större intresse för biologi, och särskilt inom de områden som är kopplade till vård, såsom hälsa, skönhet och medicin, medan män tenderade att ha ett större intresse för kemi, fysik och teknik (Schreiner & Sjøberg 2010; Adolfsson et al. 2011). Denna studie visar ett annat resultat, men detta motbevisar inte tidigare forskning. Nästan alla elever i denna studie uttrycker ett intresse för människokroppen och dess funktioner. Men anledningen till varför, är inte möjligt att klargöra utan vidare undersökning. Som i tidigare studier har denna studie visat att elevernas intressen för ett specifikt ämne ökar deras motivation för att lära sig mer om det. Denna typ av motivation kallas för inre motivation (Deci & Ryan 2000). Ett av de viktigaste resultaten av denna studie är lärarens roll. Denna studie är avsedd att fungera som ett verktyg för kunskapsförmedling för lärare i praktiken. Därför är det viktig kunskap att en lärares inverkan påverkar studenternas motivation att lära sig om ett specifikt ämne. Hur en lärare går till väga för att lära ut ett ämne och lärarens inställning till ämnet eller en del av ett ämne kan så småningom påverka den kunskap eleverna tar med sig.
127

The effect of imperfect resource conversion and recurring perturbations on byproduct cross- feeding chains in digital communities

Frejborg, Filippa January 2021 (has links)
The gut microbiome plays a vital role in human health. Disturbances of this microbial system is associated with diseases such as obesity and inflammatory bowel disease. In populations of microbial species, many organisms partake in byproduct cross-feeding interactions, where byproducts from one organism are consumed by other microbes. Using the digital evolution software Avida, I studied the effect of recurring perturbations and imperfect resource conversion on the evolution of byproduct cross-feeding chains in digital communities. To investigate the effect of perturbation and conversion rate on digital organisms, I evolved digital communities for 200,000 updates in an unperturbed environment that could hold 50 different resource types, each produced as a byproduct of consuming another resource. At 200,000 updates, 50 or 60 % of all organisms were removed at various intervals during periods of different lengths, with a conversion rate less than 100 % between resources in the byproduct chain. I found that 0.9 conversion rate caused communities to evolve longer cross-feeding chains. A conversion rate of 0.5 resulted in communities with much shorter chains, more similar in length to byproduct chains in the human gut. Perturbation events seem to affect chain length only under certain conditions when energy is lost between resources, for example when 60 % of all organisms were removed every 50th update on average. It appears that conversion loss makes digital communities more robust against the effects of perturbations, and that it might protect these communities from going extinct.
128

Effects of recurring perturbations on byproduct cross-feeding chain lengths in a digital microbiome

Schwarz, Johanna January 2021 (has links)
The human gut microbiome is a complex ecosystem with hundreds of species interacting with each other and the host. One function of the microbiome is to break down undigested nutrients into smaller nutrients, sometimes available for uptake by the host. The digestion of such macromolecules can involve several species where one feeds on another’s byproducts, forming a large cross-feeding network. The method of digital evolution can be of great aid in studying such complex ecosystems by creating models of the studied system. In this study, the digital evolution software Avida was used to study the effects of perturbations in the system on byproduct cross-feeding chain length. Intense perturbations were found to shorten the chain lengths in general whereas weaker perturbations had either a small or no effect. When perturbations ceased, most byproduct chains displayed recovery to lengths similar to the preperturbation lengths. This indicates that byproduct chain lengths may be kept short by common ecological mechanisms alone, explaining why very long chains are rarely observed while still theoretically possible.
129

Är Sveriges områdesskydd klimatanpassat? : En geografisk analys över hur mycket av Sveriges skyddade natur som påverkas vid en havsnivåhöjning.

Korall, Elin January 2020 (has links)
På grund av klimatförändringarna och den globala uppvärmningen sker en pågående havsnivåhöjning. IPCC har i sina klimatscenarier kommit fram till att havet förväntas stiga mellan 28 cm och 98 cm till år 2100, vilket kommer att leda till stora konsekvenser för människa och samhälle. Förhöjda havsnivåer förväntas även ha en stor påverkan på kustnära naturvärden, bland annat för ett flertal Natura 2000-naturtyper. Den här studien visar för första gången vilka nationella effekter en havsnivåhöjning kan ha på skyddad natur i Sverige. Studien har undersökt hur stor andel av svenska naturreservat och Natura 2000-naturtyper som kommer att påverkas vid de projicerade havsnivåförändringarna i tre av IPCC:s klimatscenarier. Mellan 34 och 102 reservat kommer att förlora minst 5% av sin totalyta beroende på scenario, detta motsvarar landförluster med ca 750-4640 hektar. Av Sveriges totala yta kommer minst 5% hos 14-15 naturtyper att hamna under havsytan. Fyra av de naturtyper som förväntas drabbas hårdast vid det högsta scenariot är; Driftvallar (46%), Glasörtstränder (85%), Salta strandängar (42%) och Strandängar vid Östersjön (44%). Forskning har däremot visat på att en god förvaltning av omgivande mark är av yttersta vikt för naturtypers och arters överlevnad, exempelvis kan vissa naturtyper förflytta sig inåt land när havet stiger. Det krävs därför en klimatanpassad och adaptiv naturvård där hotade naturtyper och naturvärden ges möjlighet att sprida sig till lämpligare miljöer allteftersom klimatet förändras. / Due to climate change and global warming, there is an ongoing sea level rise. IPCC has published four climate scenarios that show the projected changes in climate until the year 2100. The global sea levels are estimated to rise between 28 and 98 cm, which will result in great consequences for coastal landscape and protected nature. This study is the first in Sweden to analyze which consequences a sea level rise will have on protected nature in Sweden. A geographical analysis has been made of how much of the Swedish nature reserves and Natura 2000-habitat types that are going to be covered by the sea in three of the climate scenarios. The sea will cover more than 5% of the total area in 34-102 nature reserves depending on which scenario takes place, which means a loss of 750-4640 hectares. More than 5% of 14-15 Natura 2000-habitat types in Sweden will be covered by the sea. Four of the habitat types that are most affected in the worst scenario are; Annual vegetation of drift lines (46%), Salicornia and other annuals colonizing mud and sand (85%), Atlantic salt meadows (42%) and Boreal Baltic coastal meadows (44%). Recent research has shown that habitat loss due to climate change and sea level rise can be avoided if species and habitats are allowed to move inland, and that management of surrounding areas are of high importance in conservation biology. It is therefore essential to use conservation strategies that are adapted to sea level rise.
130

Optimization of an In-Vitro System for Testing Developmental Neurotoxicity Induced by Oestrogen, Androgen and Thyroid Disruption

Awoga, Roseline Ayowumi January 2021 (has links)
In recent times, endocrine disrupting chemicals (EDCs) have been associated with the rise in neurodevelopmental disorders such as autism, attention deficit hyperactivity disorder (ADHD) and decreased intelligence quotient (IQ) in children. This effect is suspected to be induced at pre-/peri-natal development, via an alteration in hormonal signaling, thus interfering with neuronal differentiation, with subsequent effect on normal brain development and function in exposed children. This issue increases the need for chemical screening for potential developmental neurotoxicity (DNT) effect. The current available EDC induced DNT test guideline is based on in-vivo testing that requires animal use. Here, a multipotent neural progenitor cell line, the C17.2 cell-line, generated from neural stem cells of the external germinal layer of mouse cerebellum, with potential to differentiate to neurons or astrocytes, is introduced for in-vitro EDC induced DNT testing. This project focused on optimizing the C17.2 cell-line for the detection of EDC-induced DNT with emphasis on the disruption of the oestrogen, androgen, and thyroid hormone systems. It aimed at validating the involvement of oestrogen, androgen, and thyroid hormone on molecular and cellular endpoints relevant for the differentiation of the C17.2 cells.  Herein, the cells were exposed to the hormonal agonist and antagonist at a range of concentrations for a 10-day differentiation period. After exposure, LDH, viability assay and morphological changes (percentage of neurons in culture and neurite outgrowth) were evaluated. The results showed no morphological changes induced by androgen receptor (AR) agonist/antagonist at relevant physiological concentrations. The thyroid receptor (TR) agonist and antagonist on the other hand showed a response in the form of increased neurite outgrowth in relation to the negative control at a concentration range of 40-200 nM and 40 nM respectively. The oestrogen receptor (ER) antagonist at 100 nM also increased percentage neuron in culture. Additionally, in-silico analysis of microarray and RNA sequencing data were used to map out target genes regulated by ER, AR and TR and involved in neurodevelopment. With this approach, 29 marker genes were identified. Validation of the marker genes by means of gene expression (qPCR) was carried out, ER and TR agonist/antagonist were observed to modulate the expression of examined genes. In summary, the model could not be established for detecting EDC induced DNT via androgenic and oestrogenic pathway, while it is a promising model for identifying DNT induced by thyroid hormone signalling disruption.

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