The unitarity problem for the BTZ black hole can possibly be solved by a coordinate transformation in which the event horizon is extended to a wormhole. In a model proposed by S.N. Solodukhin, this is done by the addition of a wormhole parameter $\lambda$ to the BTZ black hole line element. This thesis studies the changes in the spacetime geometry that comes with the addition of such a parameter. The focus of study are geodesic behaviour and possible bound states of waves. Investigating a possible source of the wormhole, the stress-energy tensor ansatz for a perfect fluid is also tested. The thesis concludes that there are notable changes to the spacetime depending on the presence of either a black hole or a wormhole. These changes includes orbital trajectories of geodesics and localized bound states of waves. The changes are most notable for $\lambda>1$ but also detectable for small parameter corrections. The wormhole spacetime can however not be generated by a simple addition of matter in a perfect fluid form.

The use of cash in the Swedish society is decreasing, leaving room for digital payment methods to ascend. However, mobile payment solutions are not as established in Sweden compared to other countries. The objective of this thesis is twofold; map the current market of mobile payments solutions in Swedish in store retail and identify the opportunities and obstacles facing this market, both from a security perspective. Furthermore, the future potential of mobile payment solutions in Sweden will be assessed. To fullfil the purpose of this thesis, an empirical study consisting of qualitative interviews and a quantitative survey were conducted. The interviews brought the perspective of businesses and financial institutions that influence the payment market, whilst the data from the survey provided the perspective and attitudes of private users. The studied payment solutions were Apple Pay, Samsung Pay and Swish’s BLE solution. Apple Pay and Samsung Pay were found to be secure solutions, but with varying availability and compatibility for the users. Swish is a compatible payment solution for the users but is lacking in technical infrastructure. A lack of knowledge regarding security and availability of these solutions was found to have prevented widespread adoption by the population. Mobile payment solutions were perceived as useful and easy to use by the private users. Conclusions are that mobile payment solutions have a high market potential in Sweden if their availability improves. Swish’s BLE solution has the highest potential due to its popularity amongst users, under the circumstance that merchants invest in the BLE receivers.

The present project aims to provide the γ-ray source spectrum (the gamma energies and their intensities) for a nuclear fuel, given its physical dimensions, its enrichment and the detailed knowledge of the burnup history. In a nuclear reactor, the nuclide concentrations within the nuclear fuel change due to nuclear transmutation caused by neutron irradiation and due to the radioactive decay during and after the irradiation. This alteration in the fuel composition is simulated in this project with a burnup-mode simulation using the reactor physics code Serpent 2. A second Serpent 2 photon-mode simulation follows as to evaluate the γ-radiation spectrum from the respective nuclides produced in the first simulation. Finally, the γ-ray mass attenuation coefficients for selected energies are evaluated by combining the fuel elemental concentrations with the corresponding mass attenuation coefficients for fresh fuel based on NIST XCOM database. To facilitate the repeated evaluation of the γ-ray source spectrum, a custom-made MATLAB® function, GetEmissions, that initiates the Serpent 2 simulations was created. This function utilizes the user input data, which are the fuel dimensions, the fuel enrichment and the burnup history, as to automatically create an input for the Serpent 2 code. Afterwards, it executes burnup and photon simulations, and finally extracts the data sought for, which are the emitted by the fuel γ-ray energies and their intensities (γ-ray source spectrum). In addition, for the given fuel characteristics, the function provides the mass attenuation coefficient for a selected γ-ray passing the fuel. Using the GetEmissions function, the gamma spectra from ten nuclear burnup history cases representing a scan through low and high burnup and short, medium and long cooling times are calculated. The resulting top ten gamma energies are listed by absolute intensity, and information about the mother nuclide and the decay is provided.

Arktis är ett känsligt område som påverkas kraftigt av de globala klimatförändringarna. Temperaturökningen leder bland annat till att permafrost tinar, isar smälter och nederbörden ökar. Klimatförändringar sker snabbt i Arktis och det finns en del forskning om varför dessa förändringar sker, men mer forskning behövs. Det finns även mycket direkt påverkan i Arktis orsakat av människan, till exempel dammbyggen, och hur dessa påverkar Arktis hydrologi är lite mer osäkert. Mätningar visar bland annat att vattenflöden i Arktis floder har ökat under de senaste decennierna. Målet med det här projektet var att undersöka hur dammar i Kanada påverkat vattenflödena i Arktis floder. Ett dammsystem bestående av två vattenkraftsdammar, W.A.C. Bennett och Peace Canyon, och en vattenförsörjningsdamm, Glenmore, valdes för studien. Frågeställningen var dels att se hur påverkan på vattenflödet skiljer sig mellan dammar med olika funktioner och dels att se hur dammarna respektive klimatet påverkat månadsoch årsmedelflödena över tid. De dammar som undersöktes valdes ut med hjälp av ArcGIS, ett geografiskt informationssystem. I urvalsprocessen togs det hänsyn till att dammarna skulle vara tillräckligt stora, ha mätstationer precis nedströms dammen samt mätstationer i närheten som var opåverkade av dammarna. De mätstationer som var opåverkade av dammarna räknades som klimatreferenser. Önskemålet var att erhålla tidsserier tillräckligt långa för att inkludera både tiden före, under och efter dammbyggnationen. För trendanalysen av datan användes Mann-Kendalls test. Analyserna visade att vattenflödet påverkas på olika sätt av en vattenkraftsdamm och en vattenförsörjningsdamm, vilket var förväntat. Det sågs inget entydigt stöd för att klimatförändringarna påverkat vattenflödet, då inte alla opåverkade mätstationer uppvisade signifikanta trender. Signifikanta trender sågs främst för perioden 1969 till nutid, framför allt i mätstationer påverkade av damm. Om det är dammarna eller klimatet som ligger bakom dessa trender är ännu oklart, fler framtida studier krävs.

Many applications share a substantial and yet unmet need for prediction and control of interactions between surfaces and proteins or living cells. Examples are blood-contacting biomaterials, biosensors, and non-toxic anti-biofouling coatings for ship hulls. The main focus of this thesis work has been the synthesis, characterization and properties of a group of coatings, designed for such applications. Many types of substrates, particularly plastics, were coated directly with ultrathin, hydrophilic polymer coatings, using a newly developed polymerization method initiated by short-wavelength ultraviolet light. The thesis contains eight papers and an introduction aimed to provide a context for the research work. The common theme, discussed and analyzed throughout the work, has been the minimization of non-specific binding of proteins to surfaces, thereby limiting the risk of uncontrolled attachment of cells and higher organisms. This has mainly been accomplished through the incorporation of monomer units bearing poly(ethylene glycol) (PEG) side chains in the coatings. Such PEG-containing “protein resistant” coatings have been used in this work as matrices for biosensor applications, as blood-contacting inert surfaces and as antibiofouling coatings for marine applications, with excellent results. The properties of the coatings, and their interactions with proteins and cells, have been thoroughly characterized using an array of techniques such as infrared spectroscopy, ellipsometry, atomic force microscopy, surface plasmon resonance and neutron reflectometry. In addition, other routes to fabricate coatings with high protein resistance have also been utilized. For instance, the versatility of the fabrication method has enabled the design of gradients with varying electrostatic charge, affecting the protein adsorption and leading to protein resistance in areas where the charges are balanced. This thesis also describes a novel application of imaging surface plasmon resonance for the investigation of the surface exploration behavior of marine biofouling organisms, in particular barnacle larvae. This technique allows for real-time assessment of the rate of surface exploration and the deposition of protein-based adhesives onto surfaces, a process which was previously very difficult to investigate experimentally. In this thesis, the method was applied to several model surface chemistries, including the hydrogels described above. The new method promises to provide insights into the interactions between biofouling organisms and a surface during the critical stages prior to permanent settlement, hopefully facilitating the development of antibiofouling coatings for marine applications.

In 2015, the United nations presented the 17 Global Goals that would put an end to extreme poverty, inequality and climate change by 2030. One of these goals was clean water and sanitation. In 2015 1.8 billion people did not have access to clean water. Because of the contaminated water, one million people die every year worldwide. Africa, and especially Ghana, has had a high development in the recent years. The population has grown and more resources are needed. Clean water in Ghana is not a given matter, three million people live without access to clean water. To work towards the Global Goal water can be clean locally. A simple and cheap way is to build slow sand filters, which also are the purpose of this project. These filters purify the water mechanically, chemically and biologically. The biologically purification takes place in the biolayer that grows on the sand inside the filter and it consumes contaminants in the water. It takes about a month for the biolayer to be fully developed and clean the water to its full potential. The positive aspects with sand filters are that people get healthier and can save money that can be invested in education or business. It can also reduce the need for water in plastic bags or bottles and would reduce littering. The companies that produce this water could end their business and air pollutions would be reduced as well.   During this project, slow sand filters have been tested and evaluated in Sweden and Ghana with the purpose to develop a theoretical filter that benefits the biolayer under local conditions in Ghana, this was of the one aims. Experiments in Sweden showed that the flow decreased with increased sand height and decreased hydraulic head. In Ghana three filters were built with the sand heights 30, 50 and 80 cm to clean 7 litres of drinking water for a family of four. None of these produced drinkable water by WHO’s and EU’s standards.   The next aim was to understand which chemical and physical factors that effected the development of the biolayer. The detected relations were absolute conductivity, total alkalinity, coliform bacteria and oxidantial reduction potential which were between the biolayer in the 30 and 50 filters.   The flow rate in Ghana was too high and to lower it, a new diffuser with smaller holes would be built to get the recommended flow of 0,4 m3/m2/h. A too high flow broke the bound between the biolayer and made an uncomfortable environment. A sedimentation should be installed before the sand filter to reduce the variations of the incoming water such as turbidity, suspended solids etc., so the biolayer would flourish. It was not enough dissolved oxygen in the water so the pause period would be decreased to 12 hours to get more oxygen in the filter each day. For a sand filter to work as planned a lot of attention should be given to the filter. It is a system that should be used all the time for the best purification. To build a filter takes a lot of time and it also takes time for the biolayer to develop. If it is not going to be used much, another treatment method should be used.   The last aim was to evaluate the cost of the materials that could be bought locally to the filter. One filter cost about 130 GHS. / 2015 tog Förenta nationerna fram de 17 globala målen för att få ett slut på extrem fattigdom, ojämlikhet och klimatförändringen till år 2030. Ett av dessa mål handlar om rent vatten och sanitet. 2015 var det 1,8 miljarder människor som inte hade tillgång till rent vatten. På grund av det förorenade vattnet dör en miljon människor i hela världen varje år. Afrika, och speciellt Ghana, har haft en snabb utveckling de senaste åren. Folkmängden har ökat och mer naturresurser behövs. Rent vatten i Ghana är inte en självklarhet, tre miljoner människor lever idag utan tillgång till rent vatten i Ghana. Ett sätt för att jobba mot det globala målet är rening av vatten lokalt. Ett enkelt och billigt sätt är att bygga långsamsandfilter, vilket även var syftet med denna studien. Dessa filter renar vattnet mekaniskt, kemiskt och biologiskt. Den biologiska reningen sker av en biofilm som växer på sanden inuti filtret som konsumerar föroreningar i vattnet. Det tar ungefär en månad för biofilmen att bli färdigutvecklad och rena vattnet till sin fulla potential. Det positiva med sandfilter är att människorna skulle bli friskare och spara pengar som kan investeras på utbildning eller företag. Ur miljöpunkt skulle reduktionen av köpt vatten i plastpåsar och flaskor minska nedskräpningen och företagen som producerar dessa kan avsluta produktionen och därmed minska luftföroreningar.   Under detta projekt har långsamsandfilter utvärderats både i Sverige och Ghana för att utveckla ett nytt teoretiskt filter som gynnar tillväxten av biofilm under lokala förhållanden i Ghana, vilket var ett mål. Experimenten i Sverige visade att flödet sjönk med ökad sandhöjd, men även med minskat hydrauliskt tryck. I Ghana byggdes tre filter med sand höjderna 30, 50 och 80 cm för att rena 7 liter dricksvatten till en familj på fyra. Ingen av dessa lyckades producera drickbart vatten enligt WHO:s och EU:s standarder.   Nästa mål var att förstå vilka av de kemiska och fysiska faktorer som påverkade biofilmstillväxten. Det förhållanden som upptäcktes var absolut konduktivitet, total alkalinitet, coliform bacteria och oxidential reduction potential vilket fanns i 30 och 50 filtret.   Flödet i Ghana var för högt, så för att minska det skulle en diffusör med mindre hål byggas för att få det rekommenderade flödet 0,4 m3/m2/h. Ett för högt flöde gjorde sönder bindingen mellan biofilmen och skapade en otrivsam miljö. En sedimentation skulle installeras innan sandfiltret för att minska variationer på ingående vatten i filtret för att få biofilmen att trivas bättre. Det fanns för lite löst syre i vattnet och om pausperioden minskas till 12 timmar skulle mer syre i filtret varje dag. För att ett sandfilter ska fungera som planerat måste mycket tid läggas på filtret. Sandfilter är ett system som bör används ofta för bästa rening. Att bygga ett filter kräver mycket tid, samt att det tar tid innan biofilmen har utvecklats. Om sandfiltret inte kommer används mycket föreslås att en annan metod används istället.   Det sista målet var att utvärdera kostnaden av materialen som kunde köpas lokalt till filtret. Ett filter kostade runt 130 GHS.

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A customers propensity to buy a certain product is a widely researched field and is applied in multiple industries. In this thesis it is showed that using binary classification on data from Scandinavian Airlines can predict their customers propensity to book a flight within the next coming seven days. A comparison between logistic regression and support vector machine is presented and logistic regression with reduced number of variables is chosen as the final model, due to it's simplicity and accuracy. The explanatory variables contains exclusively booking history, whilst customer demographics and search history is showed to be insignificant.

Rhodamine B (RB) as a fluorescent dye has toxic effects in the environment, humanity and potentially harmful to ecological systems, therefore it needs to be removed. Adsorption is a simple and cost friendly approach, but the adsorption capacity of the reported adsorbents needs to improve. Herein, the preparations of C@titania core-shell nanoparticles for the efficient elimination of RB from simulated textile wastewater was studied. The nanoparticles were prepared by first coating a layer of titania gel on ZIF-8 and HKUST-1 nanoparticles via hydrolysis of Titanium butoxide (TBOT) and followed by carbonization. XRD, FTIR, SEM, TEM, and N2 adsorption-desorption analysis was used to explore the obtained products. The adsorption for RB in the simulated textile wastewater with different pH was investigated. TEM pictures visibly illustrate the core-shell structures with a thickness of the titania layer of 14 to 25 nm. N2 adsorption-desorption results display the textural characteristics of the products with mainly meso-pores and a relative high surface area of 107 and 43 m2 g-1 for C@titania core-shell prepared from ZIF-8 and HKUST respectively. The equilibrium adsorption capacities have its climax at pH 7. The maximum RB adsorption capacities of the C@titania core-shell nanoparticles prepared from ZIF-8 and HKUST are 174.4 and 106.3 mg g-1, which is higher than the parental carbons. The C@titania nanoparticles can be easily made and their RB adsorption capacities is relatively high. The results show that the C@titania nanoparticles are potential candidates for elimination of RB from water.

Nanoparticles combining metal oxides TiO2 and graphene derivatives (reduced graphene oxide and multi-walled carbon nanotubes) were synthesised via wet chemistry methods. The materials were investigated through a series of techniques (scanning electron microscopy, X-ray diffraction, photoluminescence and UV-visible spectrophotometry). The electronic features of the materials were examined by cyclic voltammetry, and some photocatalysis testing was performed, using a solar light simulator and Rhodamine B as a pollutant in water. It was found that addition of the graphene derivative enhanced the electrical properties of the substance, which theoretically should reflect positively in the photocatalytic skill. However, photocatalysis was not found more efficient with the composites, compared to the pristine materials. Further, SnO2@ZnO core@shell nanoparticles were synthesised by wet chemistry methods. These materials were investigated by the mentioned methods and preliminary photocatalysis testing was executed, where the composites were found functional, although further testing is required.