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The Smoluchowski coagulation equation is considered to be one of the most fundamental equations of the classical description of matter alongside with the Boltzman, Navier-Stokes and Euler equations. It has applications from physical chemistry to astronomy. In this thesis, a new existence result of measure valued solutions to the coagulation equation is proven. The proven existence result is stronger and more general than a previously claimed result. The proven result holds for a generic class of coagulation kernels, including various kernels used in applications. The coagulation equation models binary coagulation of objects characterized by a strictly positive real number called size, which often represents mass or volume in applications. In binary coagulation, two objects can merge together with a rate characterized by the so-called coagulation kernel. Time evolution of the size distribution is given by the coagulation equation. Traditionally the coagulation equation has two forms, discrete and continuous, which are referring to whether the objects sizes can take discrete or continuous values. A similar existence result to the one proven in this thesis has been obtained for the continuous coagulation equation, while the discrete coagulation equation is often favored in applications. Being able to study both discrete and continuous systems and their mixtures at the same time has motivated the study of measure valued solutions to the coagulation equation. After motivating the existence result proven in this thesis, its proof is organized into four Steps described at the end of the introduction. The needed mathematical tools and their connection to the four Steps are presented in chapter 2. The precise mathematical statement of the existence result is given in chapter 3 together with Step 1, where the coagulation equation will be regularized using a parameter ε ∈ (0, 1) into a more manageable regularized coagulation equation. Step 2 is done in chapter 4 and it consists of proving existence and uniqueness of a solution f_ε for each regularized coagulation equation. Step 3 and Step 4 are done in chapter 5. In Step 3, it will be proven that the regularized solutions {f_ε} have a converging subsequence in the topology of uniform convergence on compact sets. Step 4 finishes the existence proof by verifying that the subsequence’s limit satisfies the original coagulation equation. Possible improvements and future work are outlined in chapter 6.

The conventional understanding and model of development is based on economic growth. This dominant way of creating development has consequences to natural, cultural and social environments, which cannot be overlooked. The transformations within these environments are increasingly connected to the prevailing socio-economic model of neoliberalism, but are often not considered in its contextualization at a local scale. The processes of production of space and nature under the neoliberal doctrine have led to economic restructuration and to conformation of geographies of neoliberal environment, which together transform localities. There is an increasing need to investigate how the local inhabitants understand and experience these processes and their outcomes. In this research, place is introduced as an insight to observe these problematics. Place in this research is understood as a changing and dynamic terrain, which articulates experiences of development. This research is qualitative case study which investigates the consequences of production of space and nature in Curepto, Chile. Curepto is one of the localities where the implementation of a normative framework for economic growth has resulted in extensive areas of foreign tree species monoculture and important physical and socio-spatial transformations related to them. The primary aim of this research is to investigate the local inhabitants' accounts of these transformations. The thesis investigates how the locality has changed, but focuses on what these changes have meant for the local community and their sense of place. Physical, sociocultural and emotive dimensions of place as well as their transformations were investigated using qualitative methods, mainly semi-structured interviews. Residents were interviewed both in urban and rural districts. The findings of this research indicate that the forest industry and tree plantations have been important drivers behind the physical and socio-spatial transformations. The extensive plantations of pine and eucalyptus have changed the physical environment and these transformations are reflected in the social and cultural geography. Environmental degradation, changed circumstances of land property, loss of native forests and drought constitute transformations that affect livelihoods negatively especially in the rural districts, and come in parallel with a loss of local tradition and culture. The meaningful space the inhabitants experience diminishes and is made more one-sided, as access to the natural environment becomes more difficult and the interaction with it is lost. Although transformations within place are considered negative, the meaningful relation inhabitants have with place remains positive. Participants redetermine their practices and livelihoods, and re-articulate the relation with their surroundings in order to stay in their place. The local community lives in a space that is both familiar and foreign to them, loved and hated at the same time.

Perovskites are a class of materials that possess many interesting properties with a wide range of technological applications in the field of optoelectronics and photovoltaics. In recent years, perovskites have gained considerable attention as an inexpensive and easy-to-synthesize light absorbing material for so-called organic-inorganic solar cells. In this study we wish to examine the structural and electronic properties of CH3NH3PbI3 organohalide lead perovskites. Charge transport behaviour between the light harvesting perovskite and the underlying electron transport mesostructure are some of the factors that affect the Power Conversion Efficiencies (PCE) of these devices. Therefore, advanced characterization methods were used to investigate the structural and electronic changes that may occur at the interface. Scanning electron microscopy (SEM) was used to survey the structure and morphology of the samples. It was found that the titania grain sizes were 20-25 nm in size and the perovskite grain sizes from 200 nm to 500 nm. The samples were prepared using a solution processing method, which is widely considered as one of the most cost effective ways for crystal growth. However, our studies show that this method does not provide a full perovskite coverage of the surface (14.4% of surface uncovered) which reduces the light harvesting yield. X-ray diffraction (XRD) was employed to study the crystal structure of the sample. It was concluded that the titania was in the anatase phase and the perovskite in a tetragonal crystal system (space group: I4/mcm), with a cell size of a=8.89 A and c=12.68 A. Moreover, our XRD results reveal the existence of a PbI2 crystal phase, indicating an incomplete conversion of the precursors to the perovskite phase. In order to probe the changes that occur at the interface and to elucidate the electron transport mechanisms, X-ray photoelectron spectroscopy (XPS) was conducted and the core-level spectra was investigated. A shift of 0.44 eV in the binding energy of the Ti 2p line was observed between the titania samples and the titania/perovskite. We hypothesize the origin of this shift to be due to a local screening effect, or the formation of a barrier between the perovskite and the titania that is hindering charge transport and is preventing the compensation for the surface charges lost during photoionization. Based on the findings presented in this thesis we suggest, as a possible research direction for the future, UV Photoelectron Spectroscopy (UPS) for constructing the band alignment schemes with the PbI2 layer included and a thorough investigation of the substrate effects and the synthesis routes on the charge transport dynamics of these systems.

Earlier, vast majority of the experiment were performed with PIXE exclusively, with protons as an impinging particle. Due to the concurrence of various phenomena in nuclear and atomic physics like the significant development of the theory of the inner-shell ionization in ion-atom collision, higher sensitivity due to heavy-ions, larger scattering cross-section and larger stopping cross-section HIXE turns out to be a useful technique. While cross-section of heavy-ion beam at energy few MeV and above have been measured and reported, experimental data for high-energy heavy ions against heavy targets are lack. In this study, X-ray production cross-section induced by iodine ions with energies from 15MeV to 45MeV, produced by 5MV tandem accelerator, have been measured for multiple compounds of thin targets of Ti, Cu, Zn, Ru, Nb, Ta, W and Au in a direct way. Simultaneous measurement of the X-ray data and ERDA data were taken with the help of the x-ray detector and ERDA detector placed at an angle of 1200 and 300 respectively. Measured cross-section was compared against the ECPSSR and ECPSSR-UA cross-section calculated by the program ISICS11. Experimental cross-section was found above both of the ECPSSR and ECPSSR-UA data. Thickness of the target from ERDA data were used for the direct calculation of the X-ray production cross-section for 15MeV iodine energy beam. Additionally, measured cross-section along with the ECPSSR data was compared against the average reduced velocity parameter.

High-intensity and -amplitude focused ultrasound has been used to induce cavitation for decades. Well known applications are medical (lithotripsy and histotripsy) and industrial ones (particle cleaning, erosion, sonochemistry). These applications often use low frequencies (0.1-5 MHz), which limits the spatial precision of the actuation, and the chaotic nature of inertial cavitation is rarely monitored or compensated for, constituting a source of uncertainty. We demonstrate the use of high-frequency (12 MHz) high-intensity (ISPTA=90 W/cm2 ) focused-ultrasound- induced cavitation to locally remove solid material (pits with a diameter of 20 µm to 200 µm) for non- contact sampling. We demonstrate breaking cohesion (aluminium) and adhesion (thin film on a substrate, i.e. marker ink on microscope glass). The eroded surfaces were analyzed with a scanning acoustic microscope (SAM). We present the assembly and the characterization of a focused ultrasound transducer and show quantification of the effect of different sonication parameters (amplitude, cycle count, burst count, defocus) on the size and shape of the resulting erosion pits. The quantitative precision of this method is achieved by systematic calibration measurements, linking the resulting erosion to acoustic parameters to ensure repeatability (sufficient probability of cavitation), and inertial cavitation monitoring of the focal echoes. We discuss the usability of this method for localized non-contact sampling.

Biological soil crust, biocrust, is a significant contributor to biogeochemical cycles through nitrogen and carbon cycling. Further, it stabilizes soil, facilitates water infiltration, and mitigates soil erosion. The global biocrust cover is believed to decrease by about 25-40% in the next 60 years due to climate change and intensification in land use. Research on biocrust in arctic and subarctic regions is limited, much of the knowledge comes from lower latitudes in arid and semiarid ecosystems. Cold-adapted biocrust might respond differently to increasing temperatures when compared with warm-adapted biocrust. Therefore, it is fundamental to research biocrust in arctic and subarctic regions when looking at how fast the climate is changing in the Northern hemisphere. Temporal variations of soil respiration in subarctic biocrust have not been studied systematically before. This research project focuses on the effects of warming on soil respiration in biocrust, on a diurnal and a seasonal scale. It also focuses on species composition changes of vascular plants in the warming experiment where warming was induced with open-top chambers (OTCs). Soil respiration, temperature, soil water content, as well as plant species composition changes were measured during three field trips that each lasted four days during the growing season of 2021. The results show that soil respiration was lower in September when compared with measurements done in June and July. The highest values of soil respiration were observed during mid-day and the lowest during evenings and nights. The temperatures of OTC plots were, on average, 1.16 °C higher than control plots, and OTC plots had significantly lower soil water content than control plots. During this research, the soil respiration increased with higher temperature but was not different between control and OTC plots during any time of day or month measured. Soil water content did not affect soil respiration significantly, while temperature did. These findings might be explained by less soil water content within warmer plots, but warmth and moisture have been shown to increase soil respiration. In other words, less soil water content might countereffect the increase of soil respiration due to warming. Some vascular plant species were more likely to be found within or outside the warming plots. Dwarf willow, Salix herbacea, decreased in cover within OTC plots. Previous research has shown that warming significantly reduces pollen shed and time of pollen shedding for S. herbacea, which might decrease its abundance within OTC plots. Alpine bistort, Bistorta vivipara, increased in cover within OTC plots compared to control plots. Warming experiments on B. vivipara have shown positive effects on reproductive parameters, which might increase its abundance within warmed OTC plots. Sheep also prefer grazing on B. vivipara. Therefore, it might have less cover in control plots, given that OTCs exclude grazing and that many sheep roam the studied site during the growing season. Vascular plant cover was greater within control plots when compared with warmed plots. Previous results at the same site after one year of warming, from summer 2019, showed more vascular plant cover within the OTC plots when compared with control plots. The results of this research might indicate that vascular plants are gradually affected by the warming and are transitioning towards a new equilibrium. The results of this research are ground for further studies on subarctic ecosystems dominated by biocrust. Many biotic and abiotic factors affect carbon cycles. For future modelling of predicted effects of climate change, having better knowledge on how subarctic ecosystems respond to warming is essential for a better understanding of the functions and feedbacks in a global context.

Tutkielmassa pyritään kertomaan lyhyt tarinanomainen esitys kaaosteoriasta. Esitys tarkastelee ja selittää kaaosteoriaan olennaisesti liittyviä käsitteitä kuten deterministisyys ja alkuarvoherkkyys. Oleellisesti tutkielma kertoo kaaosteorian isänäkin pidetyn Edward Norton Lorenzin tarinan maailman ensimmäisen kaaottisen systeemin löytymisestä ja sitä myötä alkuarvoherkkyyden käsitteen syntymisestä. Tutkielman tarkoitus on näyttää aiheeseen perehtymättömällekin lukijalle mistä kaaosteoriassa on kyse sekä miksi se on merkityksellistä. Johdantokappaleen jälkeinen luku on jaettu kolmeen osaan, jotka käsittelevät kaaosteorian asettumista tieteenhistorian jatkumoon, käsitettä deterministisyys ja tapahtumaketjua, jonka seurauksena Edward Norton Lorenz teki tieteellisen löytönsä. Kolmas luku selittää helposti lähestyttävin esimerkein käsitteen alkuarvoherkkyys, joka tunnetaan paremmin myös nimellä perhosvaikutus. Neljännessä luvussa esitellään dynaamisen systeemin käsite selittäen sen olennaisuuden maailman tapahtumia esitettäessä ja formuloitaessa matemaattisesti. Luvussa paneututaan myös matemaattisemmin käsitteeseen deterministisyys. Luku 5 tutustuttaa lukijan tutkielman tärkeimpien lukujen 6,7 ja 8 ymmärtämiseen tarvittaviin matemaattisiin menetelmiin kuten Taylorin sarjateoriaan useammassa ulottuvuudessa, Jacobiaaniin sekä linearisaatioon. Luku 6 esittelee tutkielman pääaiheen, Lorenz-systeemin, määritellen sen matemaattisesti sekä kuvaillen sen ominaisuuksia yksinkertaista sääsysteemiä mallintavana systeeminä. Luvussa käydään läpi myös Lorenz-systeemin ymmärtäminen vektorikentän käsitteen kautta ja systeemin ratkaisupolun geometrinen representaatio. Luvussa tutkitaan myös onko Lorenz-systeemi alkuarvoherkkä kaikkialla lähtöavaruudessa. Luvun lopussa näytetään myös erittäin kuvaannollisti kuinka Lorenz-systeemin käyttäytymisen ennustaminen on käytännössä mahdotonta. Luvussa 7 Lorenz-systeemi osoitetaan alkuarvoherkäksi seuraamalla systeemin aikakehitystä. Oleellisesti kahden alkuarvoiltaan miltein identtisten ratojen välistä etäisyyttä mittaavan vektorin aikakehitystä seuraamalla näytetään, että radat erkanevat toisistaan erittäin nopeasti. Viimeinen luku esittää lyhyen yleisanalyysin alkuarvoherkkien systeemien aikakehityksestä. Luku esittelee myös kaaosteoriaan olennaisesti liittyvät käsitteet attraktori ja outo attraktori. Luvun loppuun on vielä tiivistetty tutkielman otsikkoa kunnioittaen kaaoksen suppea selitys listaten kolme päätekijää kaaoksen käsitettä matemaattisesti määrittämään.

Free mobile applications (apps) available on app marketplaces are largely monetized through mobile advertising. The number of clicks received on the advertisements (ads) and thus the revenue gained from them can be increased by showing targeted ads to users. Mobile advertising networks collect a variety of privacy sensitive information about users and use it to build advertising profiles. To target ads at individual users based on their interests, these advertising profiles are typically linked with the users' unique device identifiers, such as the advertising ID used in Android. Advertising profiles may contain a large amount of privacy sensitive information about users, which can attract adversaries to attempt gaining access to this information. Mobile devices are known to leak privacy sensitive information such as device identifiers in clear text. This poses a potential privacy risk, since an adversary might exploit the leaked identifiers to learn privacy sensitive details about a victim by sampling personalized ads targeted at the victim. This thesis explores the behavior of mobile ad networks regarding data collection and ad targeting, as well as the possibility of an attack where leaked device identifiers are exploited to request ads targeted at a victim. We investigated these problems in the context of four popular Android ad libraries that support ad targeting, using a custom app and simulated user profiles designed for this purpose. Our findings indicate that it is possible to use sniffed identifiers to impersonate another user for requesting ads, and to some degree, this can result in receiving ads specific to the victim's profile. In the case of some ad networks, the lack of ad targeting causes it to be infeasible to conduct an attack to request ads targeted at the victim.

With the fast growing number of scientific papers produced every year, browsing through scientific literature can be a difficult task: formulating a precise query is not often possible if one is a novice in a given research field or different terms are often used to describe the same concept. To tackle some of these issues, we build a system based on topic models for browsing the arXiv repository. Through visualizing the relationship between keyphrases, documents and authors, the system allows the user to better explore the document search space compared to traditional systems based solely on query search. In this paper, we describe the design principles and the functionality supported by this system as well as report on a short user study.

Finding and exploring relevant information from a huge amount of available information is crucial in today’s world. The information need can be a specific and precise search or a broad exploratory search, or even something between the two. Therefore, an entity-based search engine could provide a solution for combining these two search goals. The focus in this study is to 1) study previous research articles on different approaches for entity-based information retrieval and 2) implement a system which tries to provide a solution for both information need and exploratory information search, regardless of whether the search was made by using basic free form query or query with multiple entities. It is essential to improve search engines to support different types of information need in the incessantly expanding information space.