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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.
201

Investigating the EEG Error-Related Negativity in College Students with ADHD, Anxiety, and Depression

Canini, Mariacristina, Jones, Marissa R, Sawyer, Ben, Ashworth, Ethan, Sellers, Eric W 12 April 2019 (has links)
Error-related Negativity (ERN) is an event-related potential elicited by the commission of errors. It appears as a negative deflection peaking between 50ms and 100ms after an erroneous response. Previous literature demonstrated that individuals who suffer from either anxiety or depression display a higher ERN amplitude compared to a control group. It has also been shown that people with ADHD display a lower ERN amplitude, suggesting that traits of this disorder, such as impulsivity, impair sensitivity to errors. Based on these findings, we investigated which disorder has more weight on the variance in amplitude of the ERN. We recruited thirty-eight students at East Tennessee State University and gathered data on their level of anxiety, depression, and ADHD through completion of three surveys: the Beck Anxiety Inventory, Beck Depression Inventory, and the ADHD self-report scale. Subsequently, participants were asked to perform a modified Flanker task while their EEG neural activity was collected through a 32-channel EEG cap. ERN amplitude for error responses was significantly higher than ERN amplitude for correct responses. In addition, error responses produced a large P300 component of the event-related potential.
202

The Influence of Sex on the Osmoreceptor Modulation of Heat Loss Responses

Barrera Ramirez, Juliana A January 2014 (has links)
Females exhibit lower sudomotor response than males, which has been attributed to physiological differences between sexes. It is well accepted that non-thermal factors (i.e. baroreceptors and osmoreceptors) can influence thermoeffector responses. Even though there are sex-related differences in baroreceptor modulation of thermoeffector responses, it remains unknown if differences in osmoreceptor modulation could explain the lower sudomotor response in females. Therefore, we examined if there are sex-related differences in osmoreceptor modulation of sweating and cutaneous vascular conductance (CVC). A group of nine males and nine females were passively heated while in an isosmotic and hyperosmotic state. The onset and thermosensitivity of sweating and CVC were calculated and compared between groups and conditions. We show that the delay in onset of sweating and CVC is similar between sexes. However, thermosensitivity of sweating was lower in females than males. We conclude that hyperosmolality does not modulate the decreased sudomotor activity in females.
203

Dagvatten i Vegastaden : Stormwater in Vegastaden

Levander, Ellinor January 2005 (has links)
SammanfattningDetta examensarbete är utfört på Miljö- och stadsbyggnadsförvaltningen i Haninge kommun och är en utredning om hur dagvatten i den planerade stadsdelen Vegastaden kan hanteras. Vegastaden kommer att innebära 3000 nya bostäder, en ny pendeltågsstation och en ny anslutning till väg 73. Området där Vegastaden kommer att byggas är mycket kuperat och har varierande jordkapacitet. Vissa områden har växlande infiltrationsmöjligheter och består av morän- och hällområden, andra består av täta jordlager av lera med mycket liten genomsläpplighet. Drevviken, som är recipient för dagvattnet i Vegaområdet, är i dagsläget överbelastad med dagvatten så tyngdpunkten har lagts på lokalt omhändertagande av dagvatten. Dammar, trög avledning, våtmark, gröna tak, infiltration och översilningsytor diskuteras i rapporten som även innefattar beräkningar av vattenavrinning, undersökning av infiltrations- och översilningsmöjligheter, fördröjning samt dimensionering av diken och dammar. Examensarbetet ska ge en uppfattning om hur stor del av dagvattnet som kan hanteras genom LOD (lokalt omhändertagande av dagvatten) och ge en idé om hur stora ytor som behövs för fördröjning och rening i dammar. Haninges dagvattenstrategi som antogs i kommunfullmäktige i april 2005 har påverkat utformningen av examensarbetet. Under 1999 och 2000 byggdes en kretsloppsanpassad serviceanläggning, Green Zone, i Umeå som möjligtvis kan ge inspiration till hur dagvattnet i Vegastaden kan hanteras. Samtliga byggnader utformades med gröna tak och minskar avrinningen från hustaken med 50 %. För avrinningsberäkningar och dimensionering av dammar och diken har dataprogrammet Storm Tac använts. Olika scenarier presenteras där det visas hur mycket avrinningen kan reduceras genom olika åtgärder. Då inga åtgärder vidtas beräknas avrinningen till ca 195 506 m 3/år och med rejäla åtgärder i form av gröna tak och infiltrationsytor beräknas avrinningen till 88 137 m 3/år. För att ta hand om det dagvatten som måste ledas bort på grund av att det varken  avdunstar, infiltrerar eller tas upp av växter så har dammar dimensionerats. Beroende på hur stora åtgärder som vidtas för att minska avrinningen varierar dammarnas storlek mellan ca 1 800 m 2och 3 700 m 2. Infiltrationsytor bör läggas där de gör som störst nytta och gröna tak där infiltration en i marken är som sämst. Kan man inte i dagsläget bestämma till hur stor del dagvattnet ska tas omhand lokalt bör förutsättningarna för ett sådant omhändertagande i framtiden göras goda, genom att till exempel bygga taken med en lutning och konstruktion som i framtiden klarar gröna tak och minimera de hårdgjorda ytorna. Då grundvattnet står högt i området är ett dike knappast ett alternativ till bortledning av dagvatten, men däremot skulle en dagvattenkanal i betong klara av att leda bort vatten. Området kan klara sig med endast en damm vad gäller avrinning och rening och den förläggs lämpligast öster om järnvägsspåret där de lägsta punkterna finns. / AbstractThis thesis was carried out at the Environment- and town planning department in the municipality of Haninge and is an inquiry of how stormwater in the planned quarter, Vegastaden, can be managed. Vegastaden will involve 3000 new dwellings, a new commuter train station and a new connection with road 73. Drevviken, which is the recipient of stormwater in the neighbourhood of Vega, is overloaded with stormwater so the focus in this thesis is on local management of stormwater. Ponds, slow off leading, wet lands, green roofs, infiltration and filter strips are discussed in the thesis which even contains calculations of water run off, investigation of infiltration- and filter strips possibilities, slow off leading and dimensioning of swales and ponds. The thesis will give an apprehension of how large volume of the stormwater that can be handled through local handling of stormwater and give an idea of how large areas that will be needed for retardation and treatments in ponds. The stormwater strategy of Haninge was accepted in the municipal council in April 2005 and has influenced the model of this thesis. The area where Vegastaden will be built is very hilly and has varying ground capacity. Some areas have varying infiltration possibilities and consists of moraine and flat rocks, other areas consists of seal earth-layers of clay with minimal permeability. During 1999 and 2000 an ecocycle society service construction, Green Zone was built in Umeå which possibly can give inspiration in how to manage the storm water in Vegastaden. All the buildings were designed with green roofs which reduce run off from the roofs with 50 %. The computer program Storm Tac has been used for run off calculations and dimensioning of ponds and swales. Different scenes are introduced where it shows how much of the run off that can be reduced through different measures. When no measures are taken the run off is calculated to ca 195 506 m 3/year and with great measures in form of green roofs and filter strips the run off is calculated to ca 88 137 m 3/year. To manage the stormwater that has to be led off on account of no evaporation or infiltration ponds have been dimensioned. Depending on the measures taken to reduce the run off, the size of the ponds will vary between ca 800 m 2and 3700 m2. Filter strips should be placed where they do the greatest good and green roofs where the infiltration in the ground is the worst. If there is no way today to decide how much of the storm water that should be managed locally the conditions for such a management in the future should be favoured through for example green roof friendly roof constructions and to minimize the non-permeable surfaces. Because of the high ground water in the area a swale is hardly a good alternative when leading off storm water, but a stormwater canal of concrete should be able to lead off stormwater. The area should manage with only one pond regarding run off and treatment and is suitably placed east of the railway where the lowest parts are.
204

A conceptual model of the aquifer in Tiquipaya, Bolivia : A minor field study

Borggren-Franck, Emma, Lindberg, Ted January 2005 (has links)
SummaryThe area of study in this project is in Bolivia, South America. The specific area is theMunicipality of Tiquipaya, situated in Cochabamba valley. Cochabamba valley consists of a gently sloping plain bounded by steep slopes of the Cordillera. The vegetation in the Cordillera is mostly high steppe and high mountain prairie. The average annual precipitation is 600-1000 mm/ year. When it rains in the mountain range the rivers flow down to the valley with high velocity and cause great problems with erosion. In the valley the average annual precipitation is 500 mm/year and the land use is mostly agricultural. Because of the intense agriculture and the rapid population growth, Cochabamba Central Valley suffers a constant shortage of water. Different irrigation systems and groundwater from the aquifer supplies Tiquipaya with water.The aquifer in Tiquipaya is one out of three thick sedimentary bodies in the Central Valley. The aquifer is an alluvial fan delta and the thickness is approximately 500 m. It is recharged through infiltration from the mountain rivers, precipitation on the valley area and by irrigation. The discharge from the aquifer consists of wells and springs. There are 37 flowing springs in Tiquipaya and they have been in use for hundreds of years. During the last 10 years the habitants have noticed a decreasing amount of flow in the springs. This indicates that the groundwater level is sinking. In order to find out whether or not the aquifer reserve is decreasing a water balance is calculated. To estimate the recharge to the aquifer we had access to precipitation data, but we had to estimate the evapotranspiration and the percentage which infiltrates. Concerning the discharge we had access to specific spring data over two areas and a list of registered wells. We know that there are more wells then the ones registered, but we did not know how many and what flow rate they have. Based on the existing data and our assumptions we have estimated a possible discharge for the Tiquipaya area. To get a truthful picture of the reality, we have made three water balances based on different data and variations. The one we find most likely show that the aquifer is decreasing.The aquifer is under a lot of environmental threats. The town of Tiquipaya is situated on the aquifer and the town’s residual water is used as irrigation water without any treatment. Also the river beds, which are very permeable recharge zones, are being used as garbage heaps. Concerning the aquifer the most impending problems are the use of residual water and the garbage handling. To obtain a sustainable development the habitants' residual water and garbage have to be taken care of.As a conclusion we do not think that the actual situation in Tiquipaya is sustainable. The groundwater reserve is decreasing and can not supply enough water for the municipality. If the agriculture stays as intensive as it is today the municipality needs to supplement with water from watersheds outside of the Cochabamba Valley. This would also give the aquifer a chance to restore its reserve. The completion of the Misicuni project will hopefully provide Tiquipaya with the water supplement needed. In order to determine the exact extension and capacity of the aquifer more reliable data is needed. We recommend geophysical tests, drilling and field investigations to obtain this data. / Resumen El área de estudio de este proyecto es la municipalidad de Tiquipaya, situado en el valle central de Cochabamba, Bolivia. El valle central de Cochabamba consta de una llanura suavemente inclinada, limitada por las empinadas montañas de la ordillera. La vegetación en la Cordillera es principalmente estepa alta y pradera de montaña alta . La precipitación media anual es 600-1000 milímetros / año. Cuando llueve en la Cordillera los ríos fluyen al valle con una velocidad muy alta, causando grandes problemas con la erosión. En el valle la precipitación media anual es 500 milímetros / año y el uso de suelo es principalmente agrícola. Debido a la agricultura intensa y el rápido crecimiento de población, el valle central de Cochabamba se ve constantemente afectado por una escasez de agua. Diferentes sistemas de irrigación y agua subterránea del acuífero intentan proporcionar Tiquipaya con el agua. El acuífero en Tiquipaya es uno de tres cuerpos sedimentarios gruesos en el valle central. El acuífero es formada por depósitos aluviales que forman conos y abanicos con un espesor de 500 m. El acuífero es recargado a través de infiltración de los ríos de montaña, de la precipitación sobre el valle y por la irrigación.La descaraga del acuífero consta de pozos y vertientes. Hay 37 vertientes fluyendo en Tiquipaya y han sido usados durante cientos de años. Durante los últimnos 10 años los habitantes ha n notado una disminuación en el flujo de los vertientes. Esto indica que el nivel estático de agua está hundiendo. Para entender si la reserva de acuífero está disminuyendo o no, un balance hídrico es calculado. Para calcular la recarga del acuífero teníamos acceso à los datos de precipitación, pero tuvimos que calcular el evapotranspiración y los porcentajes que se infiltra. Al calcular la descarga teníamos acceso a datos específicos de los vertientes en dos áreas y una lista de pozos registrados. Sabemos que hay más pozos que los en la lista, pero no sabemos cuántos y qué flujo tienen. Basado en los datos existentes y nuestras suposiciones hemos calculado una descarga posible para la área de Tiquipaya. Para conseguir un modelo sincero de la realidad, hemos hecho tres balances de agua basados en diferentes datos y variaciónes. El balance que muestra que el acuífero está disminuyendo es el más probable. Para el acuífero hay muchas amenazas ambientales. El pueblo de Tiquipaya está situado sobre el acuífero y el agua residual del pueblo es usada en la irrigación sin cualquier trato. También las zonas de recarga son muy sensatas y se estan usando los lechos del río como basurales. Con respecto al acuífero de agua subterránea los problemas más inminentes son el uso del agua residual y el manejo de basura. Para obtener un desarrollo sostenible, los problemas de aguas residuales y basura tienen que ser solucionados. Como conclusión no pensamos que la situación actual en Tiquipaya sea sostenible. La reserva de agua subterránea está disminuyendo y no puede proporcionar suficiente agua para la municipalidad. Si la agricultura se queda tan intensiva como es hoy la municipalidad tiene que complementar con agua de aréas fuera del valle de Cochabamba. Esto también daría una oportunidad a la reserva del acuífero de restituirse. La terminación del proyecto de Misicuni posiblemente suministrará Tiquipaya con el suplemento de agua necesitado.Para determinar la extensión exacta y la capacidad del acuífero datos más  confiables son necesitados. Recomendamos pruebas geofísicas, pruebas de bombeo y investigaciones de campo para obtener estos datos.
205

Enhanced Radar Backscatter from the Ionosphere

Schlatter, Nicola January 2013 (has links)
Incoherent scatter radars are powerful ground based instruments for ionospheric measurements. By analysis of the Doppler shifted backscatter spectrum, containing the signature of electrostatic plasma waves, plasma bulk properties are estimated. Occasionally, the backscattered radar power is enhanced several orders of magnitude above the thermal backscatter level. These enhancements occur during naturally disturbed ionospheric conditions and in ionospheric modi_cation experiments, where a powerful radio wave is incident on the ionospheric plasma. In both of the cases the non-linearity is thought to be turbulence of electrostatic Langmuir waves. The Langmuir turbulence theory and models account for many features of enhanced ionospheric radar backscatter reported on in the literature. During disturbed conditions, with precipitation of auroral electrons, Langmuir turbulence is thought to be driven by a low energy electron beam. Optical and radar observations of naturally enhanced radar backscatter indicate Alfvénic type of aurora during events reported on in the literature. However, contrasting conclusions have been drawn from optical observations. While some reports suggest that enhanced radar backscatter is observed at the edge of auroral structures others suggest that the enhanced backscatter region and auroral precipitation are co-located. Optical imagers with a narrow field of view resolve auroral structures with tens of meters scale size. The cross beam resolution of radars, however, is limited by the width of the radar beam, typically several kilometers wide at auroral altitudes. By using several radar receivers for observations - radar interferometry - the cross beam resolution is increased. Simultaneous observations of enhanced radar backscatter with radar interferometry and narrow field of view optical observations will increase the understanding of the physical processes involved and will make it possible to associate auroral structures with the enhanced radar backscatter. An interferometric radar receiver system has been built and a calibration technique for the system developed. In ionospheric modification experiments, the Langmuir turbulence is driven by a powerful electromagnetic wave incident on the ionosphere and electrons are significantly accelerated. The acceleration of electrons is not yet fully understood. Ionospheric modification experiments and ground based measurements, as reported on herein, contribute to the understa / <p>QC 20130131</p>
206

Large-Scale Realistic Macro-Simulation of Vehicle Movement on Road Networks

Li, Nuosuola January 2013 (has links)
No description available.
207

The nutrient-color paradigm : A test based on a comperative analysis of lakes in four ecoregions in Sweden

Nordström, Viktoria January 2021 (has links)
The nutrient-color paradigm explains lake productivity as a function of the concentrations of nutrients and colored dissolved organic matter (CDOM) in the water column.  Specifically, the paradigm predicts that primary production decreases with increasing concentrations of CDOM due to reduced light penetration, and increases with nitrogen or phosphorus concentration because these are typically the growth limiting elements for phytoplankton. A key assumption of the nutrient-color paradigm is that these factors are independent, forming orthogonal axes of a habitat template. This thesis presents an empirical test of this assumption based on water chemistry data collected from Swedish lakes in four ecoregions with different land cover and land use characteristics. Lakes in southern Sweden have weak correlations between metrics of nutrient concentration and CDOM. In contrast, there were strong correlations between nutrient and CDOM concentrations in northern Sweden. These results indicate that the orthogonality assumption of nutrient-color paradigm only holds in some ecoregions, specifically those where there are substantial inorganic nutrient sources available like in southern Sweden due to agriculture and urbanization. I describe how this observation reconciles apparently contrasting patterns of primary production observed when comparing lakes in northern Sweden compared to those reported in the temperate ecoregions.
208

Miljöpåverkan i samband med begravningar och begravningsceremonier : En undersökning av möjlighet för nationella styrsystemför gravplatser samt en enkätstudie om attityder för frivilligt miljöarbete

Petersson, Maria January 2021 (has links)
Vid förändringar i klimat och förändrade vattenmönster kan föroreningar i markenhärledda från tidigare aktiviteter i samband med begravningar innebära ökade riskerför förorening av grundvatten i anslutning till gravplatser. Sjukdomsspridandepatogener uppkommer bara från kistbegravningar så den ökande trend avkremeringar som går att se i Sverige minskar dessa risker. Fler utförda kremeringaroch att askan koncentreras på begränsade ytor kan däremot innebära att markensbindande kapacitet av föroreningar överstigs och leder till att föroreningarna spridstill grundvattnet. Detta är något som måste utredas grundligare samt riskbedömas.För vätskor som används vid balsamering av avlidna är riskerna inte tillräckligtklarlagda hur de kan påverka den som utför balsameringsprocessen samt hur de kanpåverka miljön runt en gravplats, och då endast regionala föreskrifter bestämmervalet av balsameringsvätskor gör detta att flera olika nedbrytningsrester avbalsameringsvätskor kan finnas spridda över olika gravplatser. För att minska riskenmed att regnvatten kan föra med sig föroreningar och patogener från gravplatser tillnärliggande vattenkällor uppmuntras plantering av träd och gränsväxter som kanhjälpa till att hålla kvar vattenflödena inom gravplatsen. Studien har undersöktmöjligheten till nationella krav på riskbedömningar av gravplatser samt krav omväxter med fytoremedierade förmåga på de gravplatser det behövs. Då vart pastoratvar juridiskt självstyrande var nationellt bindande krav inte möjligt. Tvingandeåtgärder kunde bara komma från en myndighet exempelvis länsstyrelsen. Riktlinjeroch uttalade målsättningar fanns från Svenska kyrkans sida, som ansvarar förmajoriteten av Sveriges gravplatser, och stor fokus ägnades åt att ge stöd,information och utbildning från nationell nivå. Krav på begravningsbyråer ochflorister om att inte erbjuda produkter som kunde utgöra föroreningsrisker behövdeäven de komma från myndigheter då Svenska kyrkan inte hade mandat för att krävasådana begränsningar. Från utförd enkätundersökning, besvarad av 57 svenskabegravningsbyråer, inkom önskemål om att en certifiering skulle krävas både för attstarta upp en begravningsbyrå och för att få fortsätta driva den. Enkäten innehölläven önskemål om reglering av branschen och att utbildningen inte skulle kommafrån förbundet utan från myndigheter. Från enkäten gick att utläsa att även omkunden var i första rum behövde det inte automatiskt innebära att miljöhänsynbehövde uteslutas, en vacker begravning och ceremonier gick att kombinera medbra val ur miljösynpunkt. Studien såg möjlighet i att begravningsbyråer ochbranschorganisationen skulle kunna ta större ansvar i fråga om att bara erbjudakistor och urnor av miljömässigt fördelaktiga material. För maximal miljömässigvinst skulle ett förbud krävas av Riksdagen som i sin tur måste ha väl genomfördforskning för att grunda sitt beslut på, vilket i dagsläget saknas. / In the event of changes in climate and changes in water patterns, contamination inthe soil derived from previous activities in connection with funerals may entailincreased risks of contamination of groundwater in connection with burial sites.Disease-spreading pathogens arise only from coffin burials, so the increasing trendof cremations that can be seen in Sweden reduces these risks. More performedcremations and that the ash is concentrated on limiting areas can mean that thebinding capacity of the soil is exceeded, and that is something that must beinvestigated more thoroughly, and risk assessed. For liquids used in embalming thedead, the risks are not necessarily clear how they can affect the person performingthe process or the environment surrounding the graveyard and since only regionalregulations determine the choice of embalming fluids, this means that severaldifferent residues of embalming fluids may be scattered over different burial sites.To reduce the risk that rainwater can carry pollutants and pathogens from burialsites to nearby water sources, planting of trees and border plants is encouraged thatcan help maintain water flows within the burial site. The study has investigated thepossibility of national requirements for risk assessments of burial sites as well asrequirements for plants with phytoremediation ability in the burial sites that areneeded. As each pastorate was legally self-governing, nationally bindingrequirements were not possible. Compulsory measures could only come from anauthority such as the county administrative board. Guidelines and stated goals wereset by the Church of Sweden, which is responsible for the majority of Sweden'sgraveyards, and great focus was placed on providing support, information andeducation from the national level. Requirements for funeral homes and florists notto offer products that could pose pollution risks also needed to come fromauthorities as the Church of Sweden did not have a mandate to demand suchrestrictions. From a survey conducted, answered by 57 Swedish funeral homes,requests were received that a certification would be required both to start up afuneral home and to be allowed to continue running it. The survey also containedrequests for regulation of the industry and that the education would not come fromthe union but from authorities. From the survey it could be deduced that even if thecustomer was first priority, it did not automatically mean that environmentalconsiderations needed to be excluded, a beautiful funeral and ceremonies could becombined with good choices from an environmental point of view. The study sawthe possibility that funeral homes and the trade association could take greaterresponsibility in terms of only offering coffins and urns of environmentallyadvantageous materials. For maximum environmental benefit, a ban would berequired by the Riksdag, which in turn must have carried out well-conductedresearch to base its decision on, which is currently lackingIn the event of changes in climate and changes in water patterns, contamination inthe soil derived from previous activities in connection with funerals may entailincreased risks of contamination of groundwater in connection with burial sites.Disease-spreading pathogens arise only from coffin burials, so the increasing trendof cremations that can be seen in Sweden reduces these risks. More performedcremations and that the ash is concentrated on limiting areas can mean that thebinding capacity of the soil is exceeded, and that is something that must beinvestigated more thoroughly, and risk assessed. For liquids used in embalming thedead, the risks are not necessarily clear how they can affect the person performingthe process or the environment surrounding the graveyard and since only regionalregulations determine the choice of embalming fluids, this means that severaldifferent residues of embalming fluids may be scattered over different burial sites.To reduce the risk that rainwater can carry pollutants and pathogens from burialsites to nearby water sources, planting of trees and border plants is encouraged thatcan help maintain water flows within the burial site. The study has investigated thepossibility of national requirements for risk assessments of burial sites as well asrequirements for plants with phytoremediation ability in the burial sites that areneeded. As each pastorate was legally self-governing, nationally bindingrequirements were not possible. Compulsory measures could only come from anauthority such as the county administrative board. Guidelines and stated goals wereset by the Church of Sweden, which is responsible for the majority of Sweden'sgraveyards, and great focus was placed on providing support, information andeducation from the national level. Requirements for funeral homes and florists notto offer products that could pose pollution risks also needed to come fromauthorities as the Church of Sweden did not have a mandate to demand suchrestrictions. From a survey conducted, answered by 57 Swedish funeral homes,requests were received that a certification would be required both to start up afuneral home and to be allowed to continue running it. The survey also containedrequests for regulation of the industry and that the education would not come fromthe union but from authorities. From the survey it could be deduced that even if thecustomer was first priority, it did not automatically mean that environmentalconsiderations needed to be excluded, a beautiful funeral and ceremonies could becombined with good choices from an environmental point of view. The study sawthe possibility that funeral homes and the trade association could take greaterresponsibility in terms of only offering coffins and urns of environmentallyadvantageous materials. For maximum environmental benefit, a ban would berequired by the Riksdag, which in turn must have carried out well-conductedresearch to base its decision on, which is currently lacking
209

Mercury in Fossil Leaves as a Proxy for Tracking Large Igneous Province Volcanism / Kvicksilver i fossila blad som proxy för att undersöka förekomst av vulkanism från stor vulkanisk provins

Näslund, Johan January 2021 (has links)
During some mass extinctions, usually minor, world oceans also underwent anoxic to euxinic conditions, events called Oceanic anoxic events (OAEs). Such an event unfolded during the Toarcian (∼183 Ma), called the T-OAE which is suggested to have been caused by Karoo-Ferrar Large Igneous Province (LIP) volcanism. In the present day, volcanoes release extensive amounts of Hg, it has therefore been hypothesized that elevated mercury (Hg) levels in sediments can be used as a proxy to correlate the two. During the T-OAE, increased Hg-levels have been observed in marine records from numerous basins across multiple continents suggesting atmospheric Hg0 to have been significantly raised. Leaves have a substantial uptake of Hg0, therefore this study investigated the possibility of using fossil leaves as a proxy to detect raised levels of Hg0. Mercury analysis was conducted on leaves from the Toudahoe section, from Hubei Province (Southern China), where the T-OAE already has been located stratigraphically, in a section of Toarcian age, through paleoflora, elevated atmospheric PCO2, negative carbon isotope excursion (CIE) (characteristic negative shift of ∼3–9 ‰ interrupting a positive excursion), and raised global temperatures by ∼6°C. Raised levels of Hg were observed in leaves in, and leading up to, the beds suggested to represent the T-OAE. The observed elevated fossil-leaf Hg values directly coincide with elevated Hg-concentrations in marine sedimentary records from other basins, such as the Mochras borehole sedimentary archive from the Cardigan Bay Basin (UK),inferring elevated Hg in fossil leaves to be useful as a proxy, validating the stratigraphy and concluding that atmospheric Hg0 was significantly raised during, and leading up to, the T-OAE. It also suggests that episodes of volcanic activity happened before the onset of the T-OAE, while the main phase of Karoo-Ferrar volcanism took place during the T-OAE. Analysis on terrestrial sediments showed high Hg/TOC results in samples with low/ or high TOC-values, deducing that factors such as depositional environment, type of organic matter (OM) and clay- and sulfur content may affect the ratio, which needs to be analysed in order to produce a valid terrestrial Hg/TOC- record. Further, samples with TOC &lt;1% needs to be analysed for TOC multiple times, because of large analytical errors when carbon is very low.
210

Why Does It Always Rain On Me? : Properties of Alternative Durable Water Repellent Chemicals for Textiles

Schellenberger, Steffen January 2016 (has links)
Environmental pollution caused by persistent perfluoroalkyl acids (PFAAs) - Organic Chemicals with confirmed levels of toxicity and propensity for bioaccumulation - has given rise to global environmental concerns. Functional textiles Containing durable water repellents (DWRs) That are based on side-chain fluorinated polymers are Noted to be the major contributors to the release of Such environmental pollutants. This results from the release of impurities and Their Gradual degradation. Nevertheless, the properties of DWRs based on long chain perfluoroalkyl chains resulting thing into Exceptional Performance Materials Into the repellent textiles and are there fore hard to replace without detriment to textile quality. This thesis AIMS to characterise the currently available alternatives by DWR Assessing Their technical performance and potentiality as hazardous chemicals with respect to Estimated emission scenarios. Further More, The Work Carried out herein Suggests That by taking a segmented perspective of the textile market, the substitution of fluorinated materials with more environmentally benign alternatives where peak performance materials is not required might sacrifice a better solution. In addition, the thesis proposes Directions for Future Research That May be Considered essential for a more robust breakfest and understanding of the environmental fate of DWR Polymers and how best to defuse Reduce emissions of PFAAs.

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