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Uranium bearing dissolved organic matter in the porewaters of uranium contaminated lake sediments
Breda Novotnik, Wei Chen, R. Douglas Evans, 2018, original scientific article

Abstract: Uranium (U) mobility in the environment strongly depends on its oxidation state and the presence of complexing agents such as inorganic carbon, phosphates, and dissolved organic matter (DOM). Despite the importance of DOM in U mobility, the exact mechanism is still poorly understood. Therefore, the aim of our investigation was to characterise sediment porewater DOM in two lakes in Ontario, Canada (Bow and Bentley Lakes) that were historically contaminated with U and propose possible composition of UO2-bearing DOM. Depth profiles of U concentrations in porewaters and total sediment digests reveal U levels of up to 1.3 mg L−1 in porewater and up to 0.8 mg−1 g in sediment. Depth profiles of U did not correlate with Fe, Mn, SO4 2−, or Eh profiles. Therefore, porewater DOM was analysed and taken into consideration as the primary source of U mobility. Porewater DOM in each sediment section (1 cm sections, 20 cm core length) was analysed by high-resolution electrospray ionisation mass spectrometry. PCA analyses of porewater DOM mass spectra showed grouping and clear separation of DOM in sediment sections with elevated U concentrations in comparison to sections with background U concentrations. Several criteria were set to characterise UO2-bearing DOM and more than 70 different molecules were found. The vast majority of these UO2-DOM compounds fell in the category of carboxyl-containing aliphatic molecules (H/C between 0.85 and 1.2 and O/C≤0.4) and had a mean value of m/z about 720.
Found in: ključnih besedah
Summary of found: ...length) was analysed by high-resolution electrospray ionisation mass spectrometry. PCA analyses of porewater DOM mass spectra...
Keywords: Uranium Lake sediments Porewater Disolved organic matter High resolution mass spectrometry
Published: 09.10.2019; Views: 2063; Downloads: 0
.pdf Fulltext (1,48 MB)

Quantitative detection of Microcystis aeruginosa in fresh water using single domain antibodies (VHHs)
Ario de Marco, Dorota Korte, Hanna Budasheva, Mladen Franko, Elisa Mazzega, Sandra Oloketuyi, Gbenga Folorunsho Oginni, published scientific conference contribution abstract

Found in: ključnih besedah
Summary of found: ...thermal lens spectrometry, nanobodies, fluobodies, cyanobacteria...
Keywords: thermal lens spectrometry, nanobodies, fluobodies, cyanobacteria
Published: 18.11.2019; Views: 2516; Downloads: 98
.pdf Fulltext (15,09 KB)

A multi-thermal-lens approach to evaluation of multi-pass probe beam configuration in thermal lens spectrometry
Humberto Cabrera, Leja Goljat, Dorota Korte, Ernesto Marin, Mladen Franko, original scientific article

Abstract: In this work, a recently proposed thermal lens instrument based on multi-pass probe beam concept is investigated and described as a multi-thermal-lens equivalent system. A simulation of the photothermal lens signal formation in a multi-thermal-lens equivalent configuration of the system is performed and validated by comparing the experimental signals of single, dual and ten-pass configurations to theoretically calculated values. The theoretically predicted enhancement of the signal is 9 to 10-fold for a weak thermal lens when comparing the ten-pass configuration with the conventional single-pass thermal lens system. Experimentally achieved signal enhancement in the ten-pass system is 8.3 for pure ethanol sample and between 8 and 9 for solutions with different concentrations of the Fe(II) - 1,10-Phenanthroline complex. Additionally, a value of 9.1 was calculated as the ratio of the slopes of the calibration lines obtained using the ten-pass and single-pass configurations. The achieved limit of detection for determination of Fe(II), in the ten-pass configuration, was 0.4 µgL-1, with a relative standard deviation around 4.5%, which compares favorably with previously reported results for TLS determination of Fe(II) in thin samples using low excitation power. For the multi-pass configuration the linear range of measurement is reduced when compared to the single-pass configuration. This is explained by the theoretical analysis of the photothermal signal under multi-pass condition, which shows the important contribution of the nonlinear term in the theoretical expression for the photothermal signal. The ten-pass configuration, which is presented and validated experimentally for the first time, offers important signal enhancement needed in recently developed TLS instruments with tunable, low power excitation sources.
Found in: ključnih besedah
Keywords: Thermal lens spectrometry, Photothermal detection, Trace determination, Chemical sensor
Published: 10.12.2019; Views: 2053; Downloads: 0
.pdf Fulltext (656,75 KB)

Mineral element composition in grain of awned and awnletted wheat (Triticum aestivum L.) cultivars tissue-specific iron speciation and phytate and non-phytate ligand ratio
Hiram Castillo Michel, Iztok Arčon, Paula Pongrac, Katarina Vogel-Mikuš, 2020, original scientific article

Abstract: In wheat (Triticum aestivum L.), the awns—the bristle-like structures extending from lemmas—are photosynthetically active. Compared to awned cultivars, awnletted cultivars produce more grains per unit area and per spike, resulting in significant reduction in grain size, but their mineral element composition remains unstudied. Nine awned and 11 awnletted cultivars were grown simultaneously in the field. With no difference in 1000-grain weight, a larger calcium and manganese—but smaller iron (Fe) concentrations—were found in whole grain of awned than in awnletted cultivars. Micro X-ray absorption near edge structure analysis of different tissues of frozen-hydrated grain cross-sections revealed that differences in total Fe concentration were not accompanied by differences in Fe speciation (64% of Fe existed as ferric and 36% as ferrous species) or Fe ligands (53% were phytate and 47% were non-phytate ligands). In contrast, there was a distinct tissue-specificity with pericarp containing the largest proportion (86%) of ferric species and nucellar projection (49%) the smallest. Phytate ligand was predominant in aleurone, scutellum and embryo (72%, 70%, and 56%, respectively), while nucellar projection and pericarp contained only non-phytate ligands. Assuming Fe bioavailability depends on Fe ligands, we conclude that Fe bioavailability from wheat grain is tissue specific.
Found in: ključnih besedah
Summary of found: ...phytate, iron, awn, X-ray fluorescence, X-ray absorption spectrometry, phosphorus, sulphur, nicotianamine...
Keywords: biofortification, phytate, iron, awn, X-ray fluorescence, X-ray absorption spectrometry, phosphorus, sulphur, nicotianamine
Published: 16.01.2020; Views: 1800; Downloads: 0
.pdf Fulltext (2,63 MB)

Implementation of high performance liquid chromatography coupled to thermal lens spectrometry (HPLC‑TLS) for quantification of pyranoanthocyanins during fermentation of Pinot Noir grapes
Lorena Butinar, Jelena Topič Božič, Natka Ćurko, Karin Kovačević Ganić, Branka Mozetič Vodopivec, Dorota Korte, Mladen Franko, 2020, original scientific article

Abstract: In this work high performance liquid chromatography coupled to thermal lens spectrometry (HPLC-TLS) was applied for monitoring of vinylphenolic pyranoanthocyanins formation during the fermentation of Pinot Noir wines. Vinylphenolic pyranoanthocyanins are wine pigments, present in low concentrations, but very important for wine colour stability. Fermentation process was conducted with four different yeast strains, used as starters, either in sequential fermentation of non-Saccharomyces with S. cerevisiae yeast or as single fermentation with S. cerevisiae yeasts in order to test the applicability of developed method for monitoring of selected compounds in real wine fermentation experiments. The developed HPLC-TLS method showed higher sensitivity compared to HPLC coupled to diode array detection (DAD) technique for particular wine colour compounds. Obtained limits of detection (LODs), were 6- and 22-times lower in comparison to HPLC–DAD in gradient and isocratic elution mode, respectively, whereas limits of quantification (LOQs) 5 and 18-times lower. Lower LODs enabled earlier observation of vinylphenolic pyranoanthocyanins formation during fermentation (already at day 7) in the case of HPLC-TLS method in gradient mode, while by using HPLC–DAD in gradient elution mode the formation of vinylphenolic pyranoanthocyanins was noticed only after 12 days of fermentation.
Found in: ključnih besedah
Keywords: Thermal lens spectrometry (TLS), High performance liquid chromatography (HPLC), Pyranoanthocyanins, Wine, Yeasts
Published: 18.06.2020; Views: 1979; Downloads: 0
.pdf Fulltext (1,94 MB)

Evaluation of recently-proposed secondary organic aerosol models for a case study in Mexico City
Katja Džepina, R. M. Volkamer, Sasha Madronich, P. Tulet, I. M. Ulbrich, Q. Zhang, C. D. Cappa, P. J. Ziemann, Jose L. Jimenez, 2009, original scientific article

Abstract: Recent field studies have found large discrepancies in the measured vs. modeled SOA mass loadings in both urban and regional polluted atmospheres. The reasons for these large differences are unclear. Here we revisit a case study of SOA formation in Mexico City described by Volkamer et al. (2006), during a photochemically active period when the impact of regional biomass burning is minor or negligible, and show that the observed increase in OA/Delta CO is consistent with results from several groups during MILAGRO 2006. Then we use the case study to evaluate three new SOA models: 1) the update of aromatic SOA yields from recent chamber experiments (Ng et al., 2007); 2) the formation of SOA from glyoxal (Volkamer et al., 2007a); and 3) the formation of SOA from primary semivolatile and intermediate volatility species (P-S/IVOC) (Robinson et al., 2007). We also evaluate the effect of reduced partitioning of SOA into POA (Song et al., 2007). Traditional SOA precursors (mainly aromatics) by themselves still fail to produce enough SOA to match the observations by a factor of similar to similar to 7. The new low-NOx aromatic pathways with very high SOA yields make a very small contribution in this high-NOx urban environment as the RO2 center dot+NO reaction dominates the fate of the RO2 center dot radicals. Glyoxal contributes several mu g m(-3) to SOA formation, with similar timing as the measurements. P-S/IVOC are estimated from equilibrium with emitted POA, and introduce a large amount of gas-phase oxidizable carbon that was not in models before. With the formulation in Robinson et al. (2007) these species have a high SOA yield, and this mechanism can close the gap in SOA mass between measurements and models in our case study. However the volatility of SOA produced in the model is too high and the O/C ratio is somewhat lower than observations. Glyoxal SOA helps to bring the O/C ratio of predicted and observed SOA into better agreement. The sensitivities of the model to some key uncertain parameters are evaluated.
Found in: ključnih besedah
Summary of found: ...polycyclic aromatic-hydrocarbons, positive matrix factorization, mass- spectrometry, volatility measurements...
Keywords: polycyclic aromatic-hydrocarbons, positive matrix factorization, mass-spectrometry, volatility measurements
Published: 11.04.2021; Views: 1004; Downloads: 0
.pdf Fulltext (1,18 MB)

An anti-HER2 nanobody binds to its antigen HER2 via two independent paratopes
Daniele Ubbiali, Sandra Oloketuyi, Ario De Marco, Barbara Medagli, Sara Fortuna, Gregor Ilc, Marta S. Semrau, Gregor Bajc, Claudio Iacobucci, Matic Kovačič, Marco Orlando, 2021, original scientific article

Found in: ključnih besedah
Summary of found: ...NMR, cross-linking, mass spectrometry, nanobodies, modelling, rational mutagenesis...
Keywords: NMR, cross-linking, mass spectrometry, nanobodies, modelling, rational mutagenesis
Published: 15.04.2021; Views: 1011; Downloads: 0
.pdf Fulltext (3,07 MB)

Molekularna karakterizacija lebdećih čestica slobodne troposfere sa Opservatorija Pico planine
Sumit Kumar, J. A. Perlinger, D. Helmig, J. Hueber, Swarup China, B. Zhang, R. Chris Owen, Katja Džepina, Claudio Mazzoleni, Paulo Fialho, 2017, published scientific conference contribution abstract

Abstract: Long-range transported free tropospheric aerosol was sampled at the PMO (38°28’15’’N, 28°24’14’’W; 2225 m amsl) on Pico Island of the Azores in the North Atlantic. Filter-collected aerosol during summer 2012 was analysed for organic and elemental carbon, and inorganic ions. The average aerosol ambient concentration was 0.9 µg m-3. Organic aerosol contributed the majority of mass (57%), followed by sulphate (21%) and nitrate (17%). Filter-collected aerosol was positively correlated with on-line aerosol measurements of black carbon, light scattering and number concentration. Water-soluble organic compounds (WSOC) from 9/24 and 9/25 samples collected during a pollution event were analysed with ultrahigh-resolution FT-ICR MS. FLEXPART analysis showed the air masses were very aged (>12 days). ~4000 molecular formulas were assigned to each of the mass spectra between m/z 100-1000. The majority of the assigned molecular formulas have unsaturated structures with CHO and CHNO elemental compositions. WSOC have an average O/C of ~0.45, relatively low compared to O/C of other aged aerosol, which might be the result of evaporation and fragmentation during long-range transport. The increase in aerosol loading during 9/24 was linked to biomass burning emissions from North America by FLEXPART and MODIS fire counts. This was confirmed with WSOC biomass burning markers and with the morphology and mixing state of particles as determined by SEM. The presence of markers characteristic of aqueous-phase reactions of biomass burning phenolic species suggests that the aerosol collected at Pico had undergone cloud processing. The air masses on 9/25 were more aged (~15 days) and influenced by marine emissions, as indicated by organosulphates and species characteristic for marine aerosol (e.g. fatty acids). The change in air masses for the two samples was corroborated by the changes in ozone, ethane, propane, morphology of particles, as well as by FLEXPART. In this presentation we will presents the first detailed molecular characterization of free tropospheric aged aerosol intercepted at the PMO.
Found in: ključnih besedah
Summary of found: ...Atmospheric aerosol, Free troposphere, Mass spectrometry, Pico mountain observatory...
Keywords: Atmospheric aerosol, Free troposphere, Mass spectrometry, Pico mountain observatory
Published: 26.05.2021; Views: 918; Downloads: 0
.pdf Fulltext (8,36 MB)

Chemical (in)stability of interfaces between different metals and Bi[sub]2Se[sub]3 topological insulator
Sandra Gardonio, Matjaž Valant, Katja Ferfolja, Mattia Fanetti, 2018, published scientific conference contribution abstract

Abstract: In recent years a classification of materials based on their topological order gained popularity due to the discovery of materials with special topological character – topological insulators (TI). TI have different band structure than regular insulators or conductors. They are characterized by a band gap in the bulk of the material, but at the surface they possess conductive topological surface states (TSS) that cross the Fermi level. TSS are a consequence of the non-trivial bulk band structure and have properties that differ from ordinary surface states. They are robust toward contamination and deformation of the surface. Additionally, they are also spin polarized, which means that an electron spin is locked to a crystal momentum and, therefore, backscattering during transport is suppressed [1]. Due to their specific properties the TI could be used in fields of spintronics, quantum computing and catalysis [2]. The investigation of the interfaces between metals and the TI has not been given much attention even though its characterization is interesting from fundamental physics and applicative point of view. (In)stability of the contacts with metal electrodes, in a form of a chemical reaction or diffusion, has to be taken into account since it can affect the transport properties of the material or increase the contact resistance. Our research is dedicated to the study of the metal/TI interfaces, in particular to Bi2Se3 with deposited metals that are relevant for electrical contacts (Au, Ag, Pt, Cr, Ti). The thermal and chemical stability of the interfaces are of fundamental importance for understanding the contact behavior, therefore, we focused our work to the characterization of these properties. The metal/TI interfaces are investigated mainly with an electron microscopy (SEM, TEM, STM), EDX microanalysis and XRD. Our previous studies showed that the interface between Bi2Se3, and Ag deposited either chemically or from a vapor phase, results in the formation of new phases already at room temperature [3]. On the contrary, Au deposited on the Bi2Se3 surface shows very limited reactivity and is stable at RT, but diffusion and coalescence of the metal are observed starting from 100 °C [4]. In this contribution, we will present further characterization on the evolution of the Ag/Bi2Se3 and Au/Bi2Se3 interfaces, show preliminary results about recently investigated systems (Pt/Bi2Se3, Ti/Bi2Se3) and compare the thermal and chemical stability of the systems under investigation.
Found in: ključnih besedah
Summary of found: ...thermal lens spectrometry, photothermal beam deflection spectroscopy, dye remediation, photothermal...
Keywords: thermal lens spectrometry, photothermal beam deflection spectroscopy, dye remediation, photothermal technique, photocatalytic degradation, reactive blue 19, TiO2 modification
Published: 20.08.2021; Views: 996; Downloads: 0
.pdf Fulltext (100,42 KB)

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