Matemaattis-luonnontieteellinen tiedekunta (a part of 2017)

 

A temporary collection for the newest 2017 master's thesis (not yet in the official "Matemaattis-luonnontieteellinen tiedekunta" collection) and some manually added (after 2017-10-30) older master's thesis.

Recent Submissions

  • Leinonen, Jani (Helsingin yliopisto, 2017)
    Korkean entropian metalliseokset ovat materiaalifysiikan tärkeä uusi osa-alue. Ne voivat mahdollisesti olla materiaalikehityksen tulevaisuus, ja niillä on havaittu perinteisiin metalliseoksiin verrattuna selvästi poikkeavia ominaisuuksia. Usean eri alkuaineen muodostamat seokset omaavat perinteisiä metalliseoksia huomattavasti korkeamman konfiguraatioentropian. Korkealla entropialla on merkittävä vaikutus metalliseoksen ominaisuuksiin. Tutkimuksessa käsitellään korkean entropian muodostumista ideaalisten hiukkasten satunnaisesti täyttämissä kuutioissa. Kuution täyttävät hiukkaset ovat ideaalisia palloja, joiden ainut ominaisuus on hiukkastyyppi. Hiukkaskuution entropian odotusarvo määritetään Monte Carlo -simulaation tuottamasta statistiikasta. Statistiikka kerätään tarkoitusta varten kirjoitetulla Pythonohjelmalla. Entropian muodostuminen eri hiukkastyyppimäärillä esitetään muodostamalla kuvaajat Matlab-ohjelmistolla, ja taulukoimalla tärkeimmät tulokset. Entropian kuvaajan muoto pysyy samanlaisena riippumatta hiukkaskuution koosta. Entropian kasvu hidastuu tasaisesti, kun kuution sisältämien hiukkastyyppien määrää kasvatetaan. Entropian kasvu näyttäisi lopulta lähes pysähtyvän noin 8 – 10 eri hiukkastyypin kohdalla. Tämän jälkeen hiukkastyyppien lisääminen ei enää merkittävästi kasvata kuution konfiguraatioentropiaa. Hiukkastyyppimäärän kasvaessa kuution entropiajakauma muuttuu eksponentiaalisesta jakaumasta nopeasti kohti normaalijakauman tyylistä jakaumaa.
  • Sahari, Aleksi (Helsingin yliopisto, 2017)
    Chiral amine is an interesting motive, commonly seen in pharmaceuticals and in chiral auxiliaries and ligands. They are often made from imines and N-heteroarenes by hydrogenation or nucleophilic addition. Traditionally metallic Lewis acids, with chiral ligands, have been used to catalyse these reactions. Recently, interest has grown towards metal-free catalytic systems and this thesis will focus on two emerging fields: chiral counter-ion directed catalysis and asymmetric hydrogenations with frustrated Lewis pairs. In chiral counter-ion directed catalysis, the chiral catalyst is an organic ion that can bind together with a reagent of opposite charge, where the main binding force is electronic interaction of the ion-pair. Common motives are deprotonated phosphates and disulphonamides. They allow close contact between the ion-pair, which is beneficial for high enantioselectivity. They can also act as a proton shuttle, which speeds up the reaction. Usually the catalyst has a chiral pocket, where the charged group is deeply embedded and surrounded by bulky aromatic groups. These bulky groups orient the reagent, so that the nucleophilic addition is blocked from one side. Imines and N-heteroarenes are excellent reagents for chiral anion catalysis, since they can be easily made cationic by protonation or acetylation. All major reaction types of these substrates can be done with acceptable yields and enantioselectivity. Frustrated Lewis pair consists of a Lewis acidic and basic group together in one molecule or in two separate ones. Classical Lewis reactivity is kinetically blocked by bulky substituents and therefore they can exist together in a solution. The pair has high thermodynamical energy, which can be used to activate small molecules, for example by splitting dihydrogen into hydride and proton. The activated hydrogen can be catalytically transferred to imines and N-heteroarenes to reduce them. Detailed mechanisms for general hydrogen activation and hydrogen transfer are presented, with some insights into structure-activity relationships. If a chiral group is introduced to the frustrated Lewis pair, chiral amines can be obtained. Generally, the activity and enantioselectivity are lower than with organometal catalyst alternatives, but with certain small imines and N-heteroarenes results are the best seen in asymmetric catalytic hydrogenation. The field hasn’t been yet much explored, but these exceptional results should encourage further studies.
  • Honkalammi, Henri (Helsingin yliopisto, 2017)
    Propargyl or methacrylate end-functionalized polylactides are important intermediates in polymer synthesis towards their application in the biomedical field. Through these intermediates hydrophobic polylactides are post polymerized with hydrophilic monomers or coupled with preformed hydrophilic homopolymers to obtain amphiphilic copolymers that possess qualities that they wouldn’t otherwise have. These systems show a unique property: self-assembly into micellar structures that can be utilized in drug delivery applications. Polylactides (PLA) offer biocompatibility and biodegradability to its non-toxic and non-carcinogenic metabolites for these biomedical applications. Understanding the synthesis, modification and processing of PLA in this light is a cornerstone for successful development of new PLA-based biomaterials. This thesis gives an overview of polylactide end functionalization, their post polymerization and documents attempts to synthesize different end functional polylactides. The experimental part of this thesis focuses on the synthesis of propargyl and methacrylate end-functionalized PLA:s with different chain lengths and their characterization with the appropriate polymer characterization techniques.
  • Alanen, Osku (Helsingin yliopisto, 2017)
    Prostate cancer remains one of the most frequently diagnosed cancers in men. While its localized form is typically slowly advancing, the aggressive and metastasized forms are responsible for a significant amount of deaths in men in developed countries. Thus, more reliable methods of diagnosis are currently highly sought-after. Prostate Specific Membrane Antigen (PSMA) remains a highly-researched receptor of choice, which has been found to be overexpressed in majority of prostate cancers. Several PSMA-targeting inhibitors with suitable radioisotopes are already being utilized for PET imaging (18F, 68Ga) and treatment (177Lu) of prostate cancer, with new radiotracers possessing improved characteristics being highly sought-after. Fluoroglycosylation is a typical method of altering the properties of radiotracers, leading into more desirable tracer characteristics, such as increased renal excretion due to the compound’s increased hydrophilicity. This can be achieved with chemical reactions, such as oxime formation, where the molecule is conjugated with a fluorine-containing carbohydrate. The aim of this study was to develop two 18F-labeled PSMA inhibitors via oxime formation by utilizing two 18F-labeled carbohydrates: 5-[18F]fluoro-5-deoxyribose ([18F]9) and 2-[18F]fluoro-2-deoxy-D-glucose ([18F]12). The precursor 3 moiety was successfully synthesized by utilizing an amide coupling reaction (yield 56%), followed by acid-catalyzed deprotection. The purification of precursor 3 was achieved by high-performance liquid chromatography (HPLC) with a yield of 29%. The precursor moiety was conjugated with [18F]9 and [18F]12 via oxime formation to yield compounds [19F]4 (yield 39%) and [19F]5 (yield 39%), respectively. This was followed by the synthesis of their respective radioisotopes, [18F]4 and [18F]5. [18F]9 exhibited more favorable labeling characteristics with precursor 3 compared to those of [18F]12, likely due to its readily-available aldehydic form, and milder reaction conditions. Conjugation of [18F]9 with precursor 3 moiety was successfully achieved in 15 minutes at room temperature in the presence of 0.3 M anilinium acetate buffer, with a radiolabeling yield up to 91% (1.5 mM peptide concentration). Comparably, conjugation with [18F]12 was achieved in 30 minutes at 85 ℃ in the presence of aniline, with a radiolabeling yield of 57% (9.8 mM peptide concentration). Minor by-product formation was also evident with [18F]5 while the reaction appeared more specific with [18F]4. Purification of [18F]4 was achieved by HPLC, yielding the radiotracer with 98% radiochemical purity. Similarly, purification of [18F]5 was demonstrated with HLPC using a smaller batch, yielding the product with a radiochemical purity of 88%. Minor degradation of the oxime ether bond into free [18F]9 or [18F]12 was evident as a function of time in an acidic environment, especially with [18F]5. The lipophilicity of the compounds was also demonstrated by the shake-flask method. Both compounds were found to be highly hydrophilic, with LogD7.4 values of –2.8±0.3 and -3.1±0.2 for [18F]5 and [18F]4, respectively. Further experiments should be made to optimize the radiosynthesis protocols for higher activities, and to determine the minimum peptide concentration and reaction time needed for the oxime ether formation. Additionally, the molar activities of the compounds should be determined. Also, the IC50 inhibition potency of PSMA with [18F]4 should be evaluated prior to any in vivo trials to better evaluate its potential as a possible PSMA inhibitor.
  • Mykkänen, Aino (Helsingin yliopisto, 2017)
    Vetyä halutaan varastoida sen suuren gravimetrisen energiatiheyden (142 MJ/kg) takia ja koska se olisi hiilidioksipäästötön energiankantaja. Vetyä on perinteisesti varastoitu joko paineistettuna kaasuna tai kryogeenisenä nesteenä, mutta näiden menetelmien ongelmina ovat olleet muun muassa niiden vaatimat korkeat paineet ja alhaiset lämpötilat. Yksi keino päästä näistä ongelmista eroon, on varastoida vetyä nestemäisiin orgaanisiin vedynkantajiin (LOHC), joita voidaan vedyttää ja joista voidaan poistaa vetyä reversiibelisti. LOHC-yhdisteet ovat yhdistepareja, jotka koostuvat vetyvajaasta aromaattisesta tai heteroamaattisesta yhdisteestä ja saman yhdisteen vedytetystä muodosta eli ali- tai heterosyklisesta yhdisteestä. Kirjallisuuskatsauksessa käsitellään vedyn ominaisuuksia, tuotantoa ja eri varastointimene-telmiä vedylle, LOHC-yhdisteiden toimintaperiaatteita vedyn varastoinnissa, LOHC-yhdisteiltä vaadittuja ominaisuuksia sekä karbatsolien, kinolien ja syklisten hiilivetyjen käyttöä LOHC-yhdisteinä. Kaikista näistä yhdisteryhmistä käsitellään vedytykseen ja vedyn poistoon vaadittavat katalyytit ja olosuhteet. Lisäksi karbatsoleista ja kinoleista käsitellään vedytyksen ja vedyn poiston mekanismit. Tutkielman kokeellisessa osuudessa tutkittiin kinaldiinin, kinoliinin, N-etyylikarbatsolin, dibentsyylitolueenin, 1-metyylinaftaleenin ja lutidiinin vedytystä Pt/C-, Pd/C-, Ru/Al2O3- ja Rh/AlO(OH)-katalyyteilla. Lisäksi tehtiin vedyn poistoja yhdisteille, jotka olivat onnistuneiden vedytyskokeiden tuotteita. Nämä yhdisteet olivat tetrahydrokinaldiini, tetrahydrokinoliini ja dodekahydro-N-etyylikarbatsoli.
  • Xia, Jingwen (Helsingin yliopisto, 2017)
    Hyaluronic acid (HA) hydrogels are interesting biomaterials for drug delivery and tissue engineering applications. Glycidyl ether derivatives have gained much interests due to their thermo-responsive properties. Thermo-responsive random copolymers of glycidyl methyl ether (GME) and epoxyhexane (EH) were synthesized. Once their properties were studied, they were grafted onto hyaluronic acid to obtain gelation at temperatures above the phase transition temperature of poly (GME-EH). PGME is a water-soluble polymer at low temperatures, but phase separates at 57.3oC. The transition temperature of PGME is too high to be utilized in medical applications. Thus a hydrophobic monomer EH was used to decrease the transition temperature of PGME via copolymerization. Several samples of random copolymers poly (GME-EH) were successfully synthesized by anionic ring opening polymerization (AROP). The transition temperature of copolymers was characterized by NMR, turbidimetry and micro-calorimetry respectively to study the phase transition behavior. Tetraoctylammonium bromide was used as initiator resulting with a bromide as the end group. Bromide was substituted by azide group to be used in click chemistry reaction with alkyne-functional HA. The reaction of the azide group on the end of copolymer chain was detected by FT-IR spectroscopy. Grafting was achieved by click chemistry following copper-catalyzed azide-alkyne cycloaddition (CuAAC) procedure. Rheology was used to study the gelation of the final product: thermo-responsive hyaluronic acid hydrogel. However, for different reasons the final product failed to form a gel.
  • Tear, Jing Ying Crystal (Helsingin yliopisto, 2017)
    Extracellular vesicles (EVs) are bilayer nanoparticles ranging from 40 nm to 5 μm in size and are mainly categorized as exosomes, microparticles, and apoptotic bodies. Recent studies reveal their involvement in various metabolic mechanisms in the human body. In particular, certain types of platelet-derived EVs found in plasma and serum are related to blood coagulation diseases and strokes. Merely, the diversity and heterogeneity of EVs in cellular systems and the lack of their isolation and detection methods are known about EVs. The fact is that a wide range of nomenclatures and basic questions regarding their morphology, size, and phenotype has remained debatable. As a result, there is a need to discover and standardize a simple and robust protocol for the isolation and detection of EVs. The literature part of the thesis covers an overview of what is defined as EVs and their functions undertaken, followed by a summary of the conventional methods for isolation and detection of EVs. The literature part finally concludes with an insight into upcoming and novel isolation and detection methods. Ultracentrifugation is the “golden” method used in the isolation of EVs. The long extraction times and varying reproducibility makes ultracentrifugation less viable, resulting in the exploration of other methods including size exclusion chromatography and immunoaffinity methods. Currently, none of these techniques are able to effectively distinguish between subtypes of EVs and matrix contaminants such as proteins remaining in the isolates. Each isolation method has its own edging advantages and disadvantages. Nevertheless, immunoaffinity methods showed greater potential in EVs extraction due to their high specificity and selectivity to process purified EVs samples. Detection methods are hindered by the minute sizes of EVs and the presence of contaminants in the isolates. Most detection methods involve the use of antibodies to detect or microscopic imaging to verify their presence based on their morphology. The trend is, however, skewing towards more reliable detection methods such as the use of mass spectrometry and microfluidic devices. The aim of the experimental portion is the ability to isolate purified platelet-derived EVs from complex human plasma samples and enable fast isolation of EVs. The use of immunoaffinity chromatography using antibody immobilized carbonyldiimidazole (CDI) monolithic disk was explored. Studies using specific platelet EV biomarker, anti-human CD61 antibody had successfully isolated platelet-derived EVs from plasma samples. In these studies, diluted plasma in phosphate buffer saline (PBS) solution (1:20 v/v) was injected through the housing setup containing the anti-human CD61 antibody immobilized monolithic disk. The eluate was obtained by injection of carbonate-bicarbonate solution and neutralized with hydrochloric acid. Detection analyses were then performed with nanoparticle tracking analysis (NTA), protein assays, Western blot and transmission electron microscopy (TEM). The average particle counts obtained in plasma isolates were found to achieve 10,000 particles more than isolates obtained after ultra-centrifugation reported in the literature. Positive presence of cytosolic protein TSG101 and transmembrane protein CD9 in Western blots, and transmission electron microscopic images of circular bilayer particles confirmed the isolation of platelet-derived EVs. Optimization studies also showed the inverse relationship between the flow rate in isolation step and the yield of platelet-derived EVs obtained. Affinity chromatography using antibody immobilized monolithic disk proved its success in the quick isolation (≤45 minutes) of platelet-derived EVs from plasma samples. The fast, miniaturized, compact setup, and simple methodology make the method viable for automation such as high throughput screening and suitable for applications of microfluidic microchips and censoring techniques on-line coupled for non-invasive and portable diagnostics.
  • Koskinen, Outi (Helsingin yliopisto, 2017)
    Lignin (wood in Latin) is a natural amorphous, aromatic polymer that acts as the essential glue and support that gives vascular plants their structural rigidity and colour. It is found mostly between but also within the plant cells and in the cell walls. Lignin consists of p-coumaryl (almost exclusively in grasses), coniferyl (common in softwoods) and sinapyl alcohol (common in hardwoods) monomers that form dimers with different linkage types depending on the types of monomer radicals combined together. As the result of lignin biosynthesis is a complex aromatic network where the β – aryl ether (β-O-4) linkage type is the most abundant one between monomer units. Within each type there is a lot of variation: lignins differ from species to species, and from one tissue to the next in the same plant--even within different parts of the same cell. Pulping industry separates lignin from biomass and the lignin waste is combusted on-site as energy for steam generation. Lignin is however potentially a renewable source of aromatic platform compounds that are important in other fields of industry. Many of these platform chemicals are currently obtained from fossil fuel sources. Hence there is an environmentally friendly need to develop efficient methods to convert lignin into high-value products. Rigid molecular structure of lignin and the abundant amount of hydrogen bonds in it makes it highly recalcitrant towards conventional solvents and mild reaction conditions. In addition a considerable sulfur content from the pulping processes establishes a catalyst poison. Thus the processing methods for lignin valorization need to be optimized with proper reaction conditions and effective catalysts while keeping the costs as reasonable as possible. This thesis is divided into literature and experimental sections. The literature section discusses about the chemical structure and biosynthesis of lignin, industrial view of lignin and a short review of recently examined studies of processing methods on lignin concentrating on hydrogen-dependent methods and ionic liquids as the hydrogen source. The experimental section concentrates on a novel ionic liquid in the studies with hydrogenation and hydrogen lysis of aileron, a widely used lignin model compound.
  • Hornytzkyj, Seppo (Helsingin yliopisto, 2017)
    Artists’ pigments identified from paintings can be used for dating paintings, for the examination of painting techniques of different artists and thereby aiding the attribution of their artworks, for recognizing copies and forgeries and for answering questions and solving problems related to conservation and restoration of paintings. From an analytical point of view, the most important pigments are those known as traditional artists’ pigments that had come into use before the 1920’s, as most analytical research in the field focuses on paintings that have been made before this. The main methods used for the identification of traditional artists’ pigments are SEM-EDS, EDXRF-spectrometry, Raman spectrometry and XRD. Polarized light microscopy has mainly been used for the visual characterization of pigment particles and thin-sections taken from paintings. If applied to the identification of pigment particles, a complementary method has always been used to confirm the result. Polarized light microscopy allows the assessment of a large variety of optical properties of pigment particles. There is, however, no systematic compilation of them available. The current work was launched to examine whether polarized light microscopy can be utilized to identify pigment particles in traditional artists’ pigments based on their optical properties only. I applied standard polarized light microscopy augmented by IR microscopy, the Chelsea filter technique, and phase contrast microscopy. The research material of the work comprises the ten most common traditional blue artists’ pigments: azurite, synthetic azurite, lazurite, synthetic lazurite (ultramarine) cobalt blue, cerulean blue, smalt, Egyptian blue, Prussian blue, and indigo. Most of the pigments examined were acquired from 1440-1915 oil paintings on wood, canvas, or paper; these paintings had been under conservation and restoration in the Ateneum and Sinebrychoff art museum in 2000--2012. Pigment particles were detached from the paintings with a tungsten needle under a binocular microscope and were transferred into a thermoplastic immersion liquid for polarized light microscopy. The identity of all the examined pigment particles was confirmed using SEM-EDS or an FTIRspectrometer. The results obtained were compared to pre-existing literature data, and a two-fold classification scheme for optical properties of pigment particles is proposed, primary and secondary. The former are found in all of the examined pigment particles, whereas the latter are commonly observed but not necessarily present in every pigment particle. Primary properties are the particle size, particle shape, particle size range, optical sign, extinction, refractive index, relief, color observed with the Chelsea filter, IR transmission and IR luminescense. For each of the blue pigments examined, five to seven primary properties, specific to the pigment, could be observed. This allows optical identification of the ten blue pigments. The technique may also be developed for the identification of other than blue artists’ pigments.
  • Kähkönen, Mervi (Helsingin yliopisto, 2017)
    Fracturing of the ore and wall rock in Pyhäsalmi mine was analysed from 3D-photographs, using Structural Suite –add-on to Surpac. Observations of geological structures were also made. The suitability of 3D-photographing method to observe rock mass movement was also tested. 33 fracture zones, which differ from the main joint direction, were observed from the pictures. In particularly, fracture zones that trend from southwest to northeast and pierce the ore body from the middle, were prominent. There was also a zone of rock inclusions, almost at the same direction and same location, as the southwest to northeast trending fracture zones are. Presumably, from southwest to northeast trending fracture zones have been noticed earlier on the basis of the seismic events. Gently dipping fracture zones were also noted, in which dip direction was mostly towards north or south. In wall rock, there were pegmatite veins, singular joints and possibly small-scale faults, which were gently dipping toward north or south. Apparently clearly visible rock mass movement did likely not occur during the monitoring period. It is not possible to observe small-scale movement with 3D-photographs, but large scale movement can possibly be observed from the pictures. Avainsanat – Nyckelord – Keywords Pyhäsalmi, mine, 3D-photogrammetry, 3D-photograph, 3D, fracture, fracturing, rock, rock mechanic, rock mass movement Säilytyspaikka – Förvaringställe – Where deposited Muita tietoja
  • Martikainen, Noora (Helsingin yliopisto, 2017)
    In the Neoprotezoic Era (1.0Ga – 540Ma) the earth’s climate changed by multiple large glaciations and supercontinent formations and break-ups. Climate changes can be seen from the carbon isotope record, where the steep negative excursions indicate glaciation. The Neoproterozoic Era is known for the Snowball Earth events, when the earth has been covered by snow even in the equator. At the same time, there was Rodinia supercontinent break-up and continent regroup, which led to Mozambique Ocean to form and close during the East African orogen 650 – 620 Ma ago. The Taita Hills is located in South Kenya and lies in the Mozambique Belt. Taita Hills is divided into the Kurase and Kasigau groups. The Kurase group is considered to be metasediments from a continental shelf and the Kasigau group from the continental margin. The Kurase group contains multiple sedimentary carbonate rock layers, which are surveyed by Horkel et al. (1979) and offers a base for this study. The sedimentary carbonate rock samples were analysed with MP-AES for the elemental concentrations of Ca, Mg, Fe, Sr and Mn and for the δ13C and δ18O composition of carbonate. Three of the samples were calcites (Mg/Ca ratio 0.00 – 0.04) and 45 were dolomites (Mg/Ca 0.38 – 0.61). The δ13C values varies from -1.55 to 6.96‰ and the δ18O composition were between -10.2 and -0.66‰. The Mn/Sr ratio indicates that the samples have retained primary δ13C composition. The δ13C composition differs remarkably between the calcite and the dolomite samples, which might indicate that the calcite carbonates have a secondary composition even if the Mn/Sr ratio is low. The positive δ13C values represents the interglacial time. The δ13C compositions of the global δ13C record indicate that the Taita Hills region sedimentary carbonate rocks were precipitated before or after the Sturtian Snowball Earth event.
  • Alatarvas, Raisa (Helsingin yliopisto, 2017)
    The Landsort Deep is the deepest part of the Baltic Sea. It is located just south from the postulated margins of the early Weichselian glacial, and the deep displays a high-resolution sediment sequence from late Weichselian and Holocene. The physical properties and characterisation of late and postglacial sediments from the Landsort Deep enabled the interpretation of the sediment responses to late Weichselian and Holocene glacial settings. The sediment stratigraphy of the Landsort Deep reflects variations of salinity in the Baltic Sea Basin, and it enables the identification of four major stages in the history of the Baltic Sea: Baltic Ice Lake, Yoldia Sea, Ancylus Lake and Littorina Sea. The samples studied are from cores from Hole M0063C. The cores were recovered during the Integrated Ocean Drilling Program (IODP) Expedition 347, “Baltic Sea Paleoenvironment”. Site M0063 is divided into seven lithostratigraphic units, and the samples are from Unit VI (54–93 ambsf) and Unit V (48–54 ambsf). Sediment analyses and the interpretation of the sedimentary environment of Units VI and V are based on grain-size analysis by laser diffractometry, loss on ignition (LOI) determination, and on the IODP Expedition 347 physical properties dataset. The uniquely long varved glacial clay sequence of Units VI and V gives indications of the Scandinavian Ice Sheet and the sedimentation of the Baltic Sea Basin responded to climate fluctuations. The lowermost part of the thick sediment column comprising Units VI and V, displays ice-proximal settings, and the upper part represents ice-distal settings. The correlation of the sedimentary features to well-known geological events in the Baltic Sea region enabled the relative age determination of the Units VI and V. The sediments are deposited during the Baltic Ice Lake stage and the transition into the Yoldia Sea stage, roughly estimated between 13.5 and 11.5 ka. Comparison to different late and postglacial settings e.g. marine and terrestrial, illustrated conformities in various glacial sedimentary settings.
  • Luostarinen, Tiia (Helsingin yliopisto, 2017)
    The Arctic regions are believed to be most strongly affected by the climate change, with the rapid loss of sea ice during the past decades and amplified polar warming showing a clear signal of recent warming. To understand the future climate change and its mechanisms, past reconstructions of the climate variability are needed. The oceanographic conditions in Kongsfjorden, NW Svalbard, are strongly related to the characteristics of the West Spitsbergen Current (WSC), which transports Atlantic Water (AW) and therefore also heat and salt into the Arctic Ocean. It has previously been shown that changes in the inflow of AW can have a major impact on the environment of the Svalbard area. This study aims to elucidate the fluctuations of AW and to reconstruct the sea surface temperatures in Kongsfjorden during the last 500 years. Marine subfossil diatom assemblages from Kongsfjorden, NW Svalbard, were used to investigate sea surface temperatures (SST) and sea ice variability in high temporal resolution. A 49 cm long marine sediment core was analyzed for diatoms and grain size at 1.0 cm intervals. Diatoms were only abundant in the top 16 cm of the core. The AMS 14C dates suggest that the diatom data represents ca. the last 500 years. The diatom-based SST reconstruction based on the North Atlantic surface sediment sample calibration data set and WAPLS transfer function method indicates temperature variation between 4.1 to 6.0 ˚C with a mean temperature of 4.8 ˚C. The qualitative sea ice reconstruction is based on the Marginal Ice Zone (MIZ) diatom assemblage, and the results are compared with factor analysis results. A cooling trend both in SST and sea ice during the Little Ice Age can be seen throughout the past 500 years with a very recent warming during the past decades. Grain size is dominated by clay and silt, but in the upper 15 cm of the core the coarser sand fraction increases to up to 40 %, indicating change in depositional conditions. The sea ice has been present in the area throughout the past 500 years, and the changes in both SST and MIZ species reflect the changes of the different water masses in the area. A gradual warming of 1.6 °C since LIA is seen, indicating a recent increase in the AW inflow that corresponds to the measured modern temperature of 5.8 ˚C.
  • Aho, Noora (Helsingfors universitet, 2017)
    Cytochrome bc1, also known as complex III, is the third enzyme of the electron transfer chain in cellular respiration, which is the main process generating energy in living cells. Complex III operates by oxidizing ubiquinol, and transferring two electrons to cytochrome c, while reducing ubiquinone. The electron transfer is coupled to proton translocation across the inner mitochondrial membrane. Thus, complex III contributes to generation of a proton electrochemical gradient, which is required for the function of ATP synthase. Cardiolipins (CLs), constituting up to 20 mol % of lipids in the inner mitochondrial membrane, have an important role in the structure and dynamics of the membrane, as well as in maintaining the correct function of the whole electron transfer chain. Cardiolipins are especially vulnerable to oxidation by reactive oxygen species (ROS) due to their dimeric structure with four doubly unsaturated acyl chains. Cytochrome bc1 is one of the main producers of ROS in mitochondria, increasing the exposure of tightly bound CLs to oxidation. Oxidative stress and CL oxidation have been associated with, for instance, programmed cell death and aging, and developing Alzheimer's and Parkinson's diseases. The objective of this thesis was to build a new computational model of cytochrome bc1 in a membrane, and to study the lipid interactions of complex III using atomistic molecular dynamics simulations. A model system with a high-resolution structure of complex III, embedded in a multicomponent bilayer mimicking the inner mitochondrial membrane was constructed. Four atomistic simulations of 1 μs each were performed to reveal possible cardiolipin binding sites and to examine the effects of CL oxidation on the complex. Altogether, eight CL binding sites on cytochrome bc1 were found, out of which two have not been suggested previously. The key residues of each binding site were listed, to compare with earlier results, and to identify the new binding sites in detail. In order to investigate the effects of CL oxidation, carboxylic acid and hydroperoxyl groups were attached to the acyl chains of three crystallographically resolved CLs. The oxidized region of the CL tails changed the nature of interactions with the protein and the surrounding water. As the tail was oxidized, the results showed an increase in the number of water molecules surrounding it. Additionally, the oxidized tails were found to affect the configuration of CL by bending the tail towards the lipid headgroup, or by reaching out to the water interface of the opposite leaflet. Normally, the acyl chains of CL mostly interact with the nonpolar residues of the protein. After oxidation, the number of polar and charged amino acids in the vicinity of the acyl chain increased.
  • Hautala, Suvi-Maria (Helsingfors universitet, 2017)
    Kiihtyvyys on keskeinen suure fysiikan opiskelussa, mutta oppilailla on siihen liittyviä monia ennakkokäsityksiä. Ennakkokäsityksiä ei voi korjata ulkoapäin annetulla tiedolla, vaan oppilaiden on ensin ymmärrettävä, että heidän käsityksensä ovat virheellisiä. Ennakkokäsitykset onkin huomioitava opetusta suunniteltaessa. Tämän työn yhtenä tavoitteena on esitellä kokeita, joissa kiihtyvyyttä havainnollistetaan kiihtyvyysanturilla ja joita voi mahdollisesti käyttää kiihtyvyyteen liittyvien ennakkokäsitysten korjaamiseen. Kokeiden todellista vaikutusta ei tässä työssä testata. Kaikissa töissä käytetään kiihtyvyyden mittaamiseen Vernierin valmistamaa WDSS-anturia, jolla voi mitata voimaa, korkeutta ja kiihtyvyyttä kolmeen suuntaan. Kokeet tehdään myös ultraääni- tai voima-anturilla, jonka jälkeen pohditaan, toiko kiihtyvyysanturi näihin kokeisiin jotain uutta aiemmin käytettyihin antureihin verrattuna. Kokeissa, joissa ennakkokäsityksen perusteella ei ole kiihtyvyyttä, kiihtyvyysanturi mahdollistaa kiihtyvyyden mittaamisen ja tuo niihin kokeisiin siten konkretiaa. Normaalikiihtyvyys on esimerkiksi aiemmin mitattu voiman kautta, mutta kiihtyvyysanturilla sitä pystytään mittaamaan suoraan. Kokeita tehtäessä havaitaan myös, ettei kiihtyvyysanturilla voi tehdä kokeita, joissa anturin kallistuskulma suhteessa pystysuoraan muuttuu. Käytetyn kiihtyvyysanturin toimintaperiaate on sellainen, ettei se tee eroa kiihtyvyyden ja gravitaation kiihtyvyyden suuntaisen komponentin välille.