ItemUncertainty of the optical spectral transmittance(Tartu Ülikool, 2023) Chehreghan, Zeinab; Ansko, Ilmar; Tartu Ülikool. Loodus- ja täppisteaduste valdkondDetermination of the optical filter spectral transmittance takes place at Tartu Observatory and is one of the accredited methods of the Tartu University Testing Centre. Comprehensive characterization of the measurement setup forms the experimental part of this master thesis. The measurement principles, instrumentation, and techniques are described in detail. In conclusion, the uncertainty contributions were quantified, and recommendations were given in order to improve the measurement setup. The thesis can be used as step-bystep instructions when reproducing the characterization of similar systems. ItemOrganic Constituents of Atmospheric Aerosols in a Hemi-boreal Forest(Tartu Ülikool, 2022) Flores March, Nieves Maria; Junninen, Heikki; Tartu Ülikool. Loodus- ja täppisteaduste valdkondAtmospheric aerosols have been demonstrated to be a highly dynamic system, playing a significant role in climate change and human health. In nature, ecosystems like boreal forests can modify the atmospheric particles producing a warming or cooling effect on climate. However, the regional and global impact of boreal forest on climate is still difficult to determine, especially due to the heterogeneous chemistry of aerosol samples, the need for multiple instruments for identification, and their limited library of compounds. In this thesis, to overcome these issues, we used a molecular networking technique based on the Global Natural Products Social web platform in combination with Nuclear Magnetic Resonance (NMR) to perform a screening of organic aerosols during the winter spring, and summer seasons from a Hemi-boreal forest. The aerosol samples were recollected in a glass filter weekly from SMEAR Station (Estonia) and analyzed by Gas Chromatography Mass spectrometry and NMR. A variety of chemical functional groups including carboxylic acids, phthalates, and organophosphate among the most abundant were annotated in the studied seasons. Furthermore, it was analyzed the presence of n-alkanol, carboxylic acid, and nalkane to evaluate any hydrocarbon contamination. Phthalates-based compounds like Dibutyl phthalate (~20.59% in winter), and Bis(2-ethylhexyl) phthalate (~3.87% in summer), altogether with organophosphates like Tris(2,4-di-tert-butylphenyl) phosphate (~24.13% in spring) and tris(2,4-di-tertbutylphenyl) phosphite (~5.13% in summer) were annotated as a possible air pollutant. Besides that, conifer burning tracers such as 7-Oxodehydroabietic (~1.18% in spring) and dehydroabietic acid (~0.49% in summer) were annoted. These finding presented in this work gives an insightful impact on the atmospheric aerosol composition presented in a Hemi-boreal forest using a straightforward and versatile technique such as molecular networking. ItemDevelopment of method for boron determination in basalt fibers(Tartu Ülikool, 2022) Mamun, Faisal-Al; Paiste, Päärn; Mõtlep, Riho; Tartu Ülikool. Loodus- ja täppisteaduste valdkondThe main objective of the present thesis was to develop a method to determine the boron content of boron doped basalt fibers. Two types of samples were investigated: natural basalt powders doped with H3BO3 were used for method development and the method was applied to basalt fiber samples from two different fiber producers. Na2O2 based alkaline fusion with different sample masses and the use of HCl and HNO3 for dissolution of fusion residues was investigated. The results show that using 10:1 flux to sample ratio and HCl as dissolving acid allows for full digestion of sample and determination of boron content by MP-AES analysis. Results from the analysis of commercial basalt fibers revealed that fibers from one producer, contrary to the suppliers claim, did not contain any boron, highlighting the need for quality check and the development of method to do that. ItemValidating the pyroelectric radiometer(Tartu Ülikool, 2021) Duong, Thi Kim Ngan; Ansko, Ilmar; Tartu Ülikool. Loodus- ja täppisteaduste valdkondThis master’s thesis describes the in-lab validation of the electrically calibrated pyroelectric radiometer (ECPR). The ECPR was inter-compared with two reflection-type trap detectors, a FEL lamp, and an absolute electrical substitution pyrheliometer. All the instruments have valid calibration certificates. The measurement methods, uncertainty analysis, and results are presented. The ���� numbers in all cases were satisfying. ItemDevelopment of Li column chemistry procedure for calcium carbonate material(Tartu Ülikool, 2021) Zhang, Nanyun; Paiste, Päärn; Tartu Ülikool. Loodus- ja täppisteaduste valdkondThe main objective of the study was to develop a relatively fast and robust column to isolate Li from the matrix components in solutions prepared from carbonate materials. Four parameters, eluent concentration, matrix loading, Li and acid concentration in sample solutions, were used to evaluate the column's efficiency and robustness. The thesis results show that Li and acid concentration in the sample solution do not affect the Li isolation, but the elution range of higher matrix loading will shift to the smaller range. The whole eluting procedure with optimized concentration 0.3 M HCl only takes around 4 hours. The ��7 Li values with uncertainties (2σ) of samples prepared using the developed set-up were highly consistent with the reference values and the comparative measurement. ItemSignal upscaling with the sequential addition of reagents for enhancement of detection sensitivity(Tartu Ülikool, 2021) Nasirova, Naila; Evard, Hanno; Lavõgina, Darja; Tartu Ülikool. Loodus- ja täppisteaduste valdkondIn the present study, a simplified model system for signal upscaling using sequential addition of reagents was aimed to be developed using gold nanoparticles (AuNPs). For achieving this goal, two approaches were investigated: streptavidin-biotin and click chemistry. In the streptavidin-biotin approach, modified parameters were the following: concentration of biotin-AuNPs, blocking of the plate surface with biotin solution, incubation time, and detergent concentration. In the click chemistry approach, varied parameters were: different additives in PBS, vortexing and sonication of AuNPs (derivatized with azide and alkyne), the concentration of a detergent solution. Two types of measurements were made in these approaches: absorbance at 572 nm (corresponding to AuNP absorption maximum) and brightfield microscopy (for assessment of homogeneity of the formed surface). Although signal upscaling could not be achieved during this thesis, the knowledge gained from this experience will be used as the basis for further research. ItemEffect of soil sample preparation on fatty acid biomarker content(Tartu Ülikool, 2021) Kasaju, Manju; Vahter, Tanel; Herodes, Koit; Tartu Ülikool. Loodus- ja täppisteaduste valdkondDifferent techniques for the pre-treatments were applied at various time frames to evaluate their impact on fatty acid biomarkers content for the soil sampled from Suurmetsa, Põlva County, Estonia, one from the arable field the other from grassland. The fatty acids were extracted by the PLFA method and analysed by using GC-FID. The study included eight bacterial biomarkers (i15:0, a15:0, i16:0, a17:0, 17:0, 10Me17:0 ,10Me18:0, cy19:0),total fungal biomass 18:2ꙍ6,9 and AM fungal biomass by group specific NLFA (16:1ꙍ5). Three pre-treatment methods ( Freezing and Lyophilization, Silica gel, and Hot Air Oven) on four different time frame (0, 8, 24, 48) was carried out. Comparing different pre-treatment methods showed both freezing and lyophilization, and the silica gel method is adequate to identify fatty acid biomarkers content. Still, soil pre-treatment should be done as early as possible to get better results. However, for studying general ecological patterns, whichever approaches, or treatment methods can be chosen. ItemDevelopment of a high-throughput method for soil fatty acid derivatization and analysis(Tartu Ülikool, 2021) Aleihela Yamannalage, Ayesh Piyara Wipulasena; Vahter, Tanel; Herodes, Koit; Tartu Ülikool. Loodus- ja täppisteaduste valdkondThe Bligh and Dyer method of extraction and separation of phospholipid fatty acids (PLFAs) and neutral lipid fatty acids (NLFAs) has been extensively used in soil microbial community studies. A high throughput method of soil fatty acid analysis was developed which involves the extraction of fatty acids, separation of the fatty acids to PLFAs and NLFAs using solid-phase extraction technique, and subjecting the fatty acids to mild alkaline methanolysis prior to analysis using a GC-FID. Where possible stages were modified to be carried on a 96 well plate multi-tier unit, increasing the sample throughput and decreasing the overall consumption of solvents, cost of analysis, and time. The novel high throughput method showed comparable biomass and community characteristics to that of the standard method and thus, could be proposed as a novel method of fatty acid analysis. ItemIsotopic stability of mass reference materials and possible use as isotopic reference materials(Tartu Ülikool, 2020) Gonzales Ferraz, Margarita Esmeralda; Kirsimäe, Kalle; Sepp, Holar; Tartu Ülikool. Loodus- ja täppisteaduste valdkondNatural isotope variation or fractionation depends on equilibrium and kinetic processes affecting the individual isotope. The purpose of the of this work is to determine the stability and reproducibility of historical data of δ(15N/14N) abbreviated as δ15N, and the δ(13C/12C), abbreviated as δ13C, of total N and C in three solid samples (Aspartic acid, Nicotinamide and Acetanilide). These three samples contain N and C. The primary reference material for relative N isotope-ratio measurements (δ15N) used were atmospheric nitrogen gas (N2), which is widespread and homogeneous and by convention, has a δ15N consensus value of 0‰. The primary reference material for relative C isotope-ratio measurements (δ13C) is the L-SVEC lithium carbonate which have consensus value of -46.6±0‰ on the Vienna Peedee Belemnite (VPDB scale. The secondary references used were IAEAN1 (+0.4±0.2‰), IAEAN2 (+20.3±0.2‰) for δ15N and IAEACH3 (-24.724±0.041‰), IAEACH6 (-10.449±0.033‰) for δ13C. The δ15N and δ13C data were provided for the Laboratory of Isotope Ration Mass Spectrometry (IRMS) of the Department of Geology University of Tartu. The δ15N and δ13C measurements were made with a Delta V Plus CF-IRMS, which alternately measures the isotope-amount ratios of the sample N2 and CO2 gases and one or more injections of the working reference N2 and CO2 gases. From the data and results obtained for uncertainties for the data provided for the 2014-2020, we obtained the following results: for Aspartic acid δ15N (-7.0±1.6 ‰), δ13C (2.0±28.6‰), for Nicotinamide δ15N (-2.0±1.0 ‰), δ13C (-34.5±0.7‰) and for Acetanilide δ15N (1.1±1.1 ‰), δ13C ( -27.0±0.9‰). These uncertainties probably could be due to fractionation process happening during sample preparation and transformation to gas before entering the IRMS. From the analysis of the stability we can conclude that the Aspartic acid (+35.1774 to -31.2543), Nicotinamide (-34.1254 to-34.7113) and Acetanilide (-26.5022 to -27.2740) are more stable for δ13C, but unstable for δ15N during, during 2014-2020. Lastly there is a good long-term reproducibility (SRW) only for Acetanilide and Nicotinamide with % RSD pooled of 1% for δ13C. ItemNitrogen removal in anaerobic ammonium oxidation process-based bioelectrochemical system.(Tartu Ülikool, 2020) Nava, Antonio Ivan Manuell; Zekker, Ivar; Priks, Hans; Tartu Ülikool. Loodus- ja täppisteaduste valdkondNitrogen removal process was studied in a microbial electrosynthesis (BES) system at different applied voltages. Three different inoculation methods were compared and cyclic voltammograms were generated to evaluate changes on the bioelectrodes. Results from this study showed that after electrode inoculation gradually lowering the applied potential over a long period of time results in improvement of the nitrogen removal rates. Cyclic voltammetry sowed a strong correlation between the nitrogen removal efficiency of a biocathode and its specific capacitance. This study contributes to the idea that an electrical potential of -0.5 V could result in an increase of ~30% on the nitrogen removal rate of a bioelectrode using anammox process. ItemSimultaneous determination of selected antimicrobial agents in sewage sludge by pressurized liquid extraction and LC -MS/MS(Tartu Ülikool, 2020) Osagu, Joshua Onyeka; Herodes, Koit; Tartu Ülikool. Loodus- ja täppisteaduste valdkondIn the present study, an efficient analytical method for the simultaneous determination of an amphenicol, sulfonamides (SAs) and fluoroquinolones (FQs) in a sewage sludge matrix was developed by high performance liquid chromatography in tandem with mass spectrometry (LCMS). The selected antibiotics were extracted from the sewage sludge sample by pressurized liquid extraction (PLE) followed by solid phase extraction (SPE) as a clean-up step. Compounds separation was achieved using a mobile phase gradient composition of hexafluoro-isopropanol buffer and methanol. Recoveries of all eight compounds were in the range from 69% to 166%. Limit of quantification ranged from 0.6 ng/g for FQs to 9.3 ng/g for SAs. As most of the compounds showed significant matrix effects, the method was validated using the standard addition method which reduced this effect very significantly. ItemThe optimization of conditions for the start-up of anammox bacteria seeded with non-specific biomass(Tartu Ülikool, 2020) Ijegbai, Ohimai Kelvin; Zekker, Ivar; Tartu Ülikool. Loodus- ja täppisteaduste valdkondStart-up of anammox bacteria mediated nitrogen removal from synthetic and reject water sources was investigated using a sequential batch reactor (SBR) inoculated with non-specific seed sludge (aerobic and anaerobic sludge types). The effect of anammox reaction intermediate hydrazine was also tested. A simplified SBR setup was implemented controlling pH and temperature at 7.5 – 8.3 and 30 ± 0.5 °C respectively. This condition was stabilized and adapted to favour the cultivation of anammox bacteria from scratch. The system was started with an initial ammonium concentration from inoculum sludge and was supplemented with synthetic and reject water at 10 mg L-1 to 110 mg L-1 with a hydraulic retention time (HRT) of 2 – 3 days during the entire period of start-up. The use synthetic ammonium and nitrite as nitrogen source as well as reject water created three distinct period of salinity: low, high and optimum salinity period. Reject water gave the optimum salinity period of less than 0.5 g L-1 with significantly higher nitrogen removal rate observed. Nitrogen removal efficiency of 87 % was achieved. Spiking with different concentration of hydrazine was carried out. 5 mg N2H4 L-1 indicated optimum concentration that enhanced anammox activity during batch testing, achieving specific nitrogen removal rate of 0.72 mg N/ g MLSS/d. Addition of trace hydrazine for short-term was able to enhance nitrogen removal rate (NRR) and nitrogen loading rate (NLR) by approximate 100 % after inhibition by high C/N ratio. Nitrogen loading rate increased during the entire start-up period of 193 days from 0.08 kg N m-3L-1 to 0.1 kg N m-3L-1. Specific nitrogen (NH4+ + NO2-) removal rate of 0.127 g N L-1 d-1 was achieved. The start-up of anammox bacteria in suspended granular biomass was successful after 65 days of operation, with hydrazine significantly accelerating anammox activity. ItemDetermination of antibacterials in river water by solid phase extraction using LC -MS/MS(Tartu Ülikool, 2020) Iftikhar, Waseem Ahmad; Herodes, Koit; Tartu Ülikool. Loodus- ja täppisteaduste valdkondAnalytical method was developed for the detection of fluoroquinolones (FQs), sulfonamides and Amphenicol in Emajogi river in Tartu City. The compounds were simultaneously extracted from river water using solid phase extraction (SPE). Identification and quantification was done through Liquid chromatography – tandem mass spectrometry (LC-MS/MS) in selected reaction monitoring (MRM) mode.The recovery of FQs ranged 62% for Enrofloxacin to 76% Marbofloxacin and 68% Florfenicol ,69% sulfamethoxazole. Limit of Quantification ranged from 0.1 ngg-1 for SA’s ,0.6 - 1.5 ngg-1 for FQ’s, and 0.9ngg-1 for FF. The method was developed and valdated for river water analysis of samples from upstream, midpoint and down stream of the WWTP. The method developed may be used for a more in-depth study on the occurence and fate of these commonly used pharmaceuticals in river water bodies. ItemX-Ray Photoelectron Spectroscopy Studies of Carbon-Based Electrocatalytic Materials(Tartu Ülikool, 2020) Danilian, Dmytro; Kikas, Arvo; Kisand, Vambola; Tammeveski, Kaido; Tartu Ülikool. Loodus- ja täppisteaduste valdkondX-ray photoelectron spectroscopy (XPS) was used for investigation of carbon-based electrocatalysts. According to the measurements, in a majority of samples, the main components were carbon, nitrogen and oxygen, as expected. In metal-nitrogen-carbon catalysts, the presence of iron and cobalt, introduced during preparation, was proved and in carbide-derived carbon catalysts zirconium and silicon were found. The results of N1s measurements showed 7 different nitrogen species in samples such as pyridinic-N, pyrrolic-N, amines/metal-Nx, imine-N, graphitic-N, NO and bulk N-H. The quantitative analysis of C1s demonstrated 7 states of carbon (sp2 C, sp3 C, C-O-C, C=O, C-O=C, π-π*, and carbide) with significant dominance of sp2 carbon. In O1s spectrum the following different oxygen-containing groups were observed: metal oxide, O=C-OH carboxyl, C=O carbonyl, C-O, C-OH, and chemisorbed O. The chemical composition of the samples was determined. The study of different carbon-oxygen functionalities and nitrogen species on the catalyst surface was of particular importance. The electrocatalytic properties of the catalyst material for the oxygen reduction reaction are related to the active sites on the catalyst surface. Determined peaks agree, in general, well with literature findings in different electrocatalysts. ItemCharacterization of a Temperature Measurement System for Use in Vacuum(Tartu Ülikool, 2020) Akintola, Adeyinka Jimoh; Vendt, Riho; Allik, Mari; Jain, Ayush; Tartu Ülikool. Loodus- ja täppisteaduste valdkondThermal vacuum tests must be performed to ensure the survivability of the spacecraft during the development and performance validation stages. To carry out these tests, vacuum compatible temperature sensors are placed on different sub-systems of a spacecraft in a vacuum chamber. For the reliability of this test, the temperature sensors to be used need to be calibrated. This work, therefore, aims at improving the temperature measurement system currently used for thermal vacuum testing at the Tartu Observatory, University of Tartu. A suitable vacuum compatible sensor was selected and calibrated in the climatic chamber using the existing measurement system available at the observatory and a new measurement system introduced in this work. Both measurement systems were characterized, and measurement and uncertainty models were designed and estimated for the measurements carried out both in the climatic chamber and in the vacuum chamber. ItemFunctional Interactions of metalloprotein YbeY, involved in ribosomal metabolism, with the putative metal efflux protein YbeX(Tartu Ülikool, 2019) Sarigül, Ismail; Maiväli, Ülo; Tenson, Tanel; Tartu Ülikool. Loodus- ja täppisteaduste valdkondYbeY is a putative ribosomal endoribonuclease which has been implicated, among other things, to be involved in quality control of 70S ribosomes, in 17S pre-rRNA maturation and in ribosomal degradation. However, controversy reigns over its mode of action, substrates, co-factors, and interaction partners. Proposed interactors of YbeY include ribosomal protein S11, Era, YbeZ, and SpoT. In many bacteria ybeY is located in the ybeZYX-Int operon, where ybeZ encodes a PhoH subfamily protein with NTP hydrolase domain and ybeX encodes a putative Cobalt/Magnesium efflux protein. Depletion of YbeY and YbeX have largely overlapping phenotypes, including accumulation of 17S pre-rRNA and an approximately 1 kb 16S rRNA cleavage product, sensitivity to heat shock, and to the protein synthesis inhibitors chloramphenicol and erythromycin. Overexpression of the YbeY partially rescues the some of the phenotypes of ΔybeX. Taken together our results indicate a functional interaction between ybeY and ybeX. ItemOxygen reduction on platinum nanoparticles deposited onto chromium carbide-derived carbon support(Tartu Ülikool, 2019) Nguyen, Huy Qui Vinh; Kasuk, Heili; Nerut, Jaak; Tartu Ülikool. Loodus- ja täppisteaduste valdkondPolymer electrolyte membrane fuel cells are very promising energy conversion devices, which have already found application in public transportation. However, one of the obstacles in the even wider application is the sluggishness of oxygen reduction reaction (ORR) at the cathode. Therefore, there is room for development in the field of catalysis synthesis. This study aimed to develop novel carbon support material for the platinum catalyst and to study ORR on the new catalyst. The carbon supports were synthesized from chromium carbide using chlorination at various temperatures (800-900°C). The platinum nanoparticles were deposited onto the chromium carbide-derived carbon supports by two different methods. Thermogravimetric analysis, X-ray diffraction and low-temperature nitrogen adsorption/desorption methods were used to characterize the structure of catalyst and catalyst support. ORR was studied with cyclic voltammetry and rotating disk electrode methods. The catalysts showed high activity towards ORR in 0.1 M HClO4 solution. ItemIsosorbide-based monomers and novel stiff biobased polymers(Tartu Ülikool, 2019) Faisal, Mahvish; Vares, Lauri; Matt, Livia; Tartu Ülikool. Loodus- ja täppisteaduste valdkondThe goal of this work was to explore the synthesis of bioderived isosorbide based monomers and corresponding biobased polymers. The attractive features of isosorbide derivatives as monomers are linked to their rigidity, chirality, nontoxicity and the matter of fact that they are derived from biobass. Firstly, this thesis presents the synthesis of mono- and bis-cyclic carbonate monomers with CO2 which is an inexpensive, abundant and renewable feedstock. In particular, the reactivity of (salen)Co–I catalyst was exploited for the synthesis of valuable isosorbide based cyclic carbonates. Secondly, novel isosorbide amino alcohols were obtained by the direct amination of epoxides with aqueous ammonia. These amines were reacted with isosorbeide bis-epoxies to form corresponding thermosets. Finally, the thermal properties of the synthesized polymeric materials were studied by TGA and DSC techniques. ItemDetermination of Amino Acids in Bee Products by Diethyl ethoxymethylenemalonate Derivatization Using LC-ESI-MS/MS(Tartu Ülikool, 2019) Bùi, Nguyên Kim Ngân; Herodes, Koit; Tartu Ülikool. Loodus- ja täppisteaduste valdkondAmino acid content of honey and royal jelly has been used for the product authentication, geographical and botanical origin evaluation, indication of freshness and nutritional value. In this thesis analytical method was tested and improved for analysis of the concentration of free amino acids in Vietnamese monofloral (Robusta coffee) honey and Royal Jelly by derivatization with diethyl ethoxymethylenemalonate (DEEMM) using liquid chromatography coupled to mass spectrometry (LC-MS/MS). The derivatization proceeds under aqueous conditions and is sufficiently fast reaction for most amino acids. Limits of quantitation at ng g-1 level were achieved for most amino acids. The method has good repeatability and recovery in general. Determined amino acid contents agree, in general, well with literature findings in different honey and royal jelly samples. The differences found may be indicative of botanical/geographical origin of these bee products. ItemError Analysis in Fe-Rich Geological Samples by X-Ray Fluorescence Spectroscopy: Fundamental Parameter Method(Tartu Ülikool, 2019) Ishola, Rasheed Adeyemi; Aruväli, Jaan; Kirsimäe, Kalle; Tartu Ülikool. Loodus- ja täppisteaduste valdkondThe purpose of this study was to develop and validate X-ray fluorescence spectrometry (XRF) method, the application of Fundamental Parameter method on Fe-rich geological samples major and trace elements, the analysis of pressed powder formulation. XRF is a widely used method of so-called non-destructive analysis of the chemical composition of various solids determination. XRF method is relatively simple and inexpensive but non-quantitative analysis was hampered by several problems, such as matrix materials, for example, variability in the composition of the mineral. During operation of the instrument measurement parameters were optimized to eliminate matrix effect, lines overlap and interference. The method used to evaluate three different Fe / Al-rich and the associated deposition laterite matrix compatible certified reference material into which the theoretical intensity of the analytical lines which were compared to the measured intensity of the subject, and from the calibration curve was developed in which the samples were quantitated. Fundamental parameters measured with the standards and the geological composition of the samples of unknown composition, and characterized by a variety of validation - accuracy, linearity, trueness, accuracy and uncertainty. The test method was used to estimate the uncertainty of the Nordtest which the composition of the standards measurements repeated on different days was evaluated in a systematic component and a random component.