Mõningate õhukeste kilede pinnauuringud

Väitekirja elektrooniline versioon ei sisalda publikatsioone.Titaan(IV)oksiid (TiO2) ja roostevaba teras (nii nimetatakse rauasulameid, mis sisaldavad olulisel määral kroomi) on materjalid, mida laialdaselt kasutatakse paljudes erinevates tänapäevastes rakendustes. Lisaks TiO2 tuntud kasutusaladele, nagu pigment valgetes värvides ja ultraviolettkiirguse neelaja päikesekreemides, võimaldab see materjal luua niinimetatud isepuhastuvaid aknaklaase. Seejuures akna isepuhastumine toimub kaheastmelisena: (i) päikesevalguse toimel orgaanilise ja mitteorgaanilise mustuse lagundamine (fotokatalüüsi abil) ja (ii) superhüdrofiilse pinna teke päikesevalguse abil (s.t. pind kuhu veetilkasid ei moodustu, vaid vesi katab pinna ühtlaselt) ning sellise pinna efektiivne puhastumine laguproduktidest tavalise vihmavee abil. Isepuhastuvad aknaklaasid on juba müügil, kuid nende efektiivsus vajab parandamist. Üheks võimaluseks parandada päikesevalguse neeldumist TiO2 (ja suurendada isepuhastuvuse efektiivsust), on lisada sobivaid lisandit (nn. dopeerida). Roostevaba teras on kasutusel paljudes valdkondades, näiteks meditsiinis, autotööstuses, ehitusel ja igas majapidamises lauanõudena. Roostevaba terasele annab korrosioonikindluse (s.t. vastupidavuse roostetamisele) tema pinnale tekkiv üliõhukene kroomirikas oksiidikiht. Kui roostevaba terast kasutada eriti spetsiifilistes tingimustes, nagu näiteks kõrgetel temperatuuridel, tuleb tema korrosioonikindlust tõsta. Üheks võimaluseks on terasesse viia lisandeid, näiteks titaani, räni ja alumiiniumi. Antud doktoritöös uuriti lisandita, koobalti ja nikli lisandiga TiO2 kilesid ning kroomirikkaid oksiidikihte erineval määral oksüdeeritud roostevaba terase pinnal. Koobalti ja nikli lisandiga TiO2 uuringutest selgus, et lisandid mõjutavad TiO2 füüsikalisi omadusi, nagu näiteks kristalliitide teket ja kasvu. Kui täpsemalt uurida, kuidas koobalti (või nikli) lisand TiO2 kristallvõresse läheb, selgub, et lisand moodustab muuhulgas ka selliseid ühendeid nagu CoTiO3 (või NiTiO3). Antud töös näidati, et koobalti (või nikli) lisandiga TiO2 neelab rohkem nähtavat valgust, kui ilma lisandita TiO2. Titaankarbiidiga rikastatud roostevaba terase uuringutest selgus, et kroomirikka kaitsva oksiidikihi moodustumine algas sulami pinnale juba siis, kui kasutati väga väikest kogust hapnikku. Esmalt oksüdeerus sulamis kiirelt kroom, seejärel raud. Nikkel ja titaankarbiid sulami pinnakihis ei oksüdeerunud. Lisaks moodustusid kaitsvas oksiidikihis veel ka Al2O3 ja SiOx.Titanium(IV) oxide (TiO2, titania) and stainless steels (iron alloys, which contain significant amount of chromium) are materials, which are widely used in a number of modern applications. Additionally to titania’s well known applications, such as pigment in white paints and ultraviolet light absorber in sunscreens, it allows to prepare so-called self-cleaning windows. Self-cleaning of windows works as a two-step process: (i) photocatalytic degradation of organic and inorganic pollutants, and (ii) washing away the products of degradation from super-hydrophilic surface (i.e. surface where water droplets are not formed, instead water covers surface uniformly). Self-cleaning windows are available in the market, but their efficiency needs improvement. One possible method to enhance sunlight absorption in TiO2 (and increase efficiency of self-cleaning process) is addition of certain impurity (i.e. doping). Stainless steels are widely used in different fields, for example in medicine, automotive industry, construction, and in every household as tableware. The key issue related to the corrosion resistance is the protective chromium-rich surface oxide layer, which forms on alloy. When stainless steel is used in specific conditions, for example, at high-temperatures, its corrosion resistance needs to be enhanced. One possibility is to introduce additives, such as titanium, silicon and aluminium. In this thesis, undoped, cobalt- and nickel-containing TiO2 films and chromium-rich oxide layers on the surface of different degree oxidized stainless steel were studied. From the studies of cobalt- and nickel-containing TiO2, it was revealed that impurities influence titania’s physical properties, for example, its crystallite formation and growth. It was observed that cobalt (or nickel) addition led to formation of CoTiO3 (or NiTiO3). It was also demonstrated that cobalt-containing (or nickel-containing) TiO2 absorbs more sunlight than virgin TiO2. Investigations of titanium carbide enriched stainless steel revealed that formation of chromium-rich protective oxide layer on the surface of alloy started, when very small oxygen exposures were used. First chromium oxidized rapidly, then iron oxidized. Nickel and titanium carbide did not oxidize in alloy surface layer. Additionally also Al2O3 and SiOx were present in protective oxide layer

Hoiakud COVID-19 vastu vaktsineerimise suhtes ja vaktsineerimises kõhklemisega seotud tegurid Eestis aastal 2021: rahvastikupõhise COVID-19-kiiruuringu tulemused

Taust ja eesmärk. Ehkki praeguseks on koroonapandeemia lõppenud ning COVID-19-vaktsiinid kaotanud aktuaalsuse, võib vaktsineerimises kõhklemist pidada tõsiseks rahvatervishoiu probleemiks. Artikli eesmärk on anda ülevaade COVID-19 vastu vaktsineerimise hoiakutest ning vaktsineerimises kõhklemisega seotud teguritest.Metoodika. Töö põhineb Tervise Arengu Instituudi 2021. aasta kevadel korraldatud COVIDi-kiiruuringu läbilõikelistel andmetel. Analüüsi kaasatud 3590 inimest vanuses 19–80 aastat jaotati kolme rühma: COVID-19 vaktsineerimise pooldajad, selles kahtlejadja vaktsineerimisest keeldujad. Leiti rühmade kaalutud levimused ning hinnangud vaktsineerimisega seotud väidetele. Logistilise regressioonanalüüsi abil leiti kohandatud šansisuhted (aOR).Tulemused. Vastajatest 81% suhtus COVID-19 vastu vaktsineerimisse pooldavalt, kahtlejaid oli 7% ja keeldujaid 11%. Enamik pidas vaktsiine efektiivseks, oluliseks ja usaldas tervishoiutöötaja soovitusi. Vaktsiine pidas ohutuks ja vaktsiiniteavet usaldas veidi enam kui pool (keeldujatest 17%). Vaktsineerimises kõhklesid sagedamini naised (aOR = 1,85), nooremad, muukeelsed (aOR = 1,86) ning madalama hariduse ja raske majandusliku olukorraga vastajad (aOR = 1,95) ning need, kes ei pidanud viirust ohtlikuks (aOR = 10,32).Järeldused. Vaktsineerimises kõhklemise võtmeteguriks on usaldus, seega on oluline leida lahendusi, kuidas tekitada usaldust rühmades, kus vaktsineerimises kõhklemine on suur. Üheks võimalikuks lahenduseks oleks riikliku vaktsineerimisstrateegia väljakujundamisel rakendada pandeemia-aegset kogemust

Progress in development of a new luminescence setup at the FinEstBeAMS beamline of the MAX IV laboratory

The main funding for the FinEstBeAMS beamline has been obtained from the European Union through the European Regional Development Fund (project “Estonian beamline to MAX-IV synchrotron”, granted to the University of Tartu) and from the Academy of Finland through the Finnish Research Infrastructure funding projects ( FIRI2010 , FIRI2013 , FIRI2014 ). The authors also acknowledge the funding contributions of the University of Oulu , University of Turku , Tampere University of Technology , the Estonian Research Council ( IUT 2-25 , IUT 2-26 , PRG-111 ), as well as the Estonian Centre of Excellence in Research “Advanced materials and high-technology devices for sustainable energetics, sensorics and nanoelectronics” TK141 (2014-2020.4.01.15-0011). The strategic funding of Finnish FIMAX consortium coordinating university , University of Oulu , for beamline personnel is also acknowledged. The authors thank the MAX IV Laboratory for financial and infrastructural support as well as for assistance during the construction of the FinEstBeaMS beamline.FinEstBeAMS is a new materials science beamline at the 1.5 GeV storage ring of the MAX IV Laboratory in Lund, Sweden. It has been built based on grazing incidence monochromatization of synchrotron light, which allows to cover a remarkably wide excitation energy range from ultraviolet to soft x-rays (4.5–1450 eV). A new mobile luminescence spectroscopy end station has been commissioned with design benefitting from the advantages of a high flux elliptically polarizing undulator light source. We report on the design of the luminescence end station, its technical realization and performance achieved so far. Special attention is paid to the experimental challenges for luminescence spectroscopy under grazing incidence excitation conditions. The first luminescence results obtained demonstrate a reliable performance of the advanced setup at FinEstBeAMS.Eesti Teadusagentuur IUT 2-25,PRG-111,IUT 2-26; European Commission; University of Tartu; Academy of Finland FIRI2010,FIRI2013,FIRI2014; Tampereen Teknillinen Yliopisto; Turun Yliopisto; European Regional Development Fund; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART

Gas-phase endstation of electron, ion and coincidence spectroscopies for diluted samples at the FinEstBeAMS beamline of the MAXIV 1.5GeV storage ring

Since spring 2019 an experimental setup consisting of an electron spectrometer and an ion time-of-flight mass spectrometer for diluted samples has been available for users at the FinEstBeAMS beamline of the MAXIV Laboratory in Lund, Sweden. The setup enables users to study the interaction of atoms, molecules, (molecular) microclusters and nanoparticles with short-wavelength (vacuum ultraviolet and X-ray) synchrotron radiation and to follow the electron and nuclear dynamics induced by this interaction. Test measurements of N-2 and thiophene (C4H4S) molecules have demonstrated that the setup can be used for many-particle coincidence spectroscopy. The measurements of the Ar3p photoelectron spectra by linear horizontal and vertical polarization show that angle-resolved experiments can also be performed. The possibility to compare the electron spectroscopic results of diluted samples with solid targets in the case of Co2O3 and Fe2O3 at the Co and Fe L-2,L-3-absorption edges in the same experimental session is also demonstrated. Because the photon energy range of the FinEstBeAMS beamline extends from 4.4eV up to 1000eV, electron, ion and coincidence spectroscopy studies can be executed in a very broad photon energy range

The prevalence of genital warts in the Baltic countries : Findings from national cross-sectional surveys in Estonia, Latvia and Lithuania

Objectives: To assess the prevalence and correlates of self-reported genital warts (GWs) among women and men aged 18-45 years in the Baltic countries. Methods: In 2011-2013 we performed a cross-sectional survey using a self-administered questionnaire to collect information on the history of clinically diagnosed GWs, sociodemographic characteristics and sexual behaviour. Probability sampling methods were used to invite 16 959 individuals representing the general population, of whom 7760 (45.8%) participated (Estonia: 1967 women, 1221 men; Latvia: 1525 women, 1525 men; Lithuania: 1522 women). Results: The estimated lifetime prevalence of clinically diagnosed GWs in women was 4.6% (95% CI 3.8 to 5.5) in Estonia, 2.9% (95% CI 2.0 to 3.6) in Latvia and 1.5% (95% CI 1.2 to 2.0) in Lithuania. Among men, the corresponding values were 2.8% (95% CI 1.9 to 4.0) in Estonia and 1.9% (95% CI 1.3 to 2.6) in Latvia. The mean age at first episode of clinically diagnosed GW was 24.6 years (95% CI 23.6 to 25.5) for women and 24.5 years (95% CI 22.9 to 26.0) for men. A lifetime history of clinically diagnosed GW was associated with a history of sexually transmitted infections other than GW (adjusted OR (AOR) 3.0, 95% CI 2.1 to 4.3 for women; AOR 5.3, 95% CI 3.0 to 9.2 for men), and a higher number (5+) of lifetime sexual partners (AOR 2.9, 95% CI 1.9 to 4.2 for women; AOR 2.1, 95% CI 1.2 to 3.9 for men). Men living comfortably within their household income had higher odds for GW (AOR 1.9, 95% CI 1.1 to 3.2). Conclusions: Our estimated prevalence of clinically diagnosed GWs was lower than estimates from the general population of other European countries.publishersversionPeer reviewe

E-Cigarette Use by Smoking Status in Estonia, 2012–2018

Background: In the context of declining smoking rates in Estonia, this study aims to analyze the recent trends in e-cigarette use and its associations with smoking status and sociodemographic factors. Methods: Nationally representative data from biennial cross-sectional health surveys in 2012–2018 (n = 9988) were used to describe the prevalence of smoking and e-cigarette use by smoking status in Estonia. Multivariate logistic regression analysis was used to describe the sociodemographic patterns of e-cigarette use in three subgroups: the general population, smokers, and ex-smokers. Results: The prevalence of current smoking decreased from 45.4% in 2012 to 31.5% in 2018 among men and from 26.6% to 20.0% among women. At the same time, e-cigarette use in the general population had increased to 3.7% among men and to 1.2% among women. The increase in the prevalence of e-cigarette use was statistically significant among men in the general population, smokers, and ex-smokers, but non-significant among women. In addition to period effects, e-cigarette use was patterned by age, gender, and education. Conclusion: In 2002–2018, the e-cigarette use had increased but smoking had decreased in Estonia. A timely and targeted tobacco policy may alleviate the harm of e-cigarette use from the public health perspective

Effects of Co Ion Addition and Annealing Conditions on Nickel Ferrite Gas Response

Pure and cobalt–ion-containing nickel ferrite samples Ni1–xCoxFe2O4 (x = 0, x = 0.01, x = 0.05 and x = 0.1) were prepared by using the sol–gel auto-combustion method. To form the desired structure after the auto-combustion process, the samples were annealed in air at 800 ◦C for 1 h, followed by slow cooling in air (2.5 ◦C/min) or rapid cooling by quenching in water. The influences of cobalt ion addition and the cooling rate on the electronic structure, morphology and electrical properties of Ni–Co ferrite were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The gas-sensing properties of pure and cobalt–ion-containing nickel ferrites were studied by using acetone as a test gas. The gas-response of nickel ferrite samples was strongly influenced by the cooling rate and cobalt addition. The effect was attributed to a change in the Ni3+ concentration and a restriction of the transduction of the chemical signal into an output electrical signal. It was demonstrated that the gas response of Ni1–xCoxFe2O4 tends to increase with decreasing cobalt ion content and with decreasing concentration of the point defects such as cation vacancies and Ni3+ ions

Synthesis of P-Type and N-Type Nickel Ferrites and Associated Electrical Properties

We used sol-gel auto combustion to synthesize nickel ferrites of p-type and n-type conductivity by controlling the relative amounts of nickel and iron during synthesis. The obtained samples have been characterized by XRD, FE-SEM, electrical measurements and XPS. We observe huge differences in the effect of grain size on the electrical resistivity between the p-type and the n-type material when the grain size increases from nano to micro scale during annealing at temperatures from 900 oC to 1300 oC. The observed resistivity decrease (due to grain size) is four orders of magnitude in the the n-type nickel ferrite, whereas the p-type material remains virtually unaffected. We rationalize this drastic difference to stem from a reverse contrast of the surface (grain shell) versus bulk (grain core) conductivity between p- and n-type ferrite. With the grain shells in p-type the easier charge carrier path the effect of scatter at grain boundaries is accordingly diminished, whereas in the n-type charge transport properties are controlled by (the number of) grain boundaries in a conduction path

In Situ X-ray Photoelectron Spectroscopic and Electrochemical Studies of the Bromide Anions Dissolved in 1-Ethyl-3-Methyl Imidazolium Tetrafluoroborate

Influence of electrode potential on the electrochemical behavior of a 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF4) solution containing 5 wt % 1-ethyl-3-methylimidazolium bromide (EMImBr) has been investigated using electrochemical and synchrotron-initiated high-resolution in situ X-ray photoelectron spectroscopy (XPS) methods. Observation of the Br 3d5/2 in situ XPS signal, collected in a 5 wt % EMImBr solution at an EMImBF4⁻vacuum interface, enabled the detection of the start of the electrooxidation process of the Br− anion to Br3− anion and thereafter to the Br2 at the micro-mesoporous carbon electrode, polarized continuously at the high fixed positive potentials. A new photoelectron peak, corresponding to B⁻O bond formation in the B 1s in situ XPS spectra at E ≤ −1.17 V, parallel to the start of the electroreduction of the residual water at the micro-mesoporous carbon electrode, was observed and is discussed. The electroreduction of the residual water caused a reduction in the absolute value of binding energy vs. potential plot slope twice to ca. dBE dE−1 = −0.5 eV V−1 at E ≤ −1.17 V for C 1s, N 1s, B 1s, F 1s, and Br 3d5/2 photoelectrons

Gas-Sensing Properties of Graphene Functionalized with Ternary Cu-Mn Oxides for E-Nose Applications

Chemiresistive gas sensors were produced by functionalizing graphene with a ~3 nm layer of mixed oxide xCu2O⸱yMnO using pulsed laser deposition (PLD) from a hopcalite CuMn2O4 target. Sensor response time traces were recorded for strongly oxidizing (NO2, O3) and reducing (NH3, H2S) poisonous gases at ppb and ppm levels, respectively. The morphology of the MOX layer was modified by growth temperature during PLD, resulting in the optimization of the sensor response. Differences in decomposition or oxidation rates on catalytically active metal oxide (MOX) were utilized to achieve partial selectivity for pairs of gases that have similar adsorption and redox properties. The predominant selectivity towards ozone in most samples at different measuring conditions remained difficult to suppress. A distinct selectivity for H2S emerged at higher measurement temperatures (100–150 °C), which was assigned to catalytic oxidation with O2. Several gas–MOX interaction mechanisms were advanced to tentatively explain the sensor behavior, including reversible electron transfer in the simplest case of NO2, decomposition via ionic transients for O3, and complex catalytic oxidative transformations for NH3 and H2S