Repozitorij Univerze v Novi Gorici

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Saturation magnetisation as an indicator of the disintegration of barium hexaferrite nanoplatelets during the surface functionalisation
Klemen Lisjak, Iztok Arčon, Matic Poberžnik, Gabriela Herrero‑Saboya, Ali Tufani, Andraž Mavrič, Matjaž Valant, Patricija Hribar, Alenka Mertelj, Darko Makovec, Layla Martin‑Samos, 2023, izvirni znanstveni članek

Opis: Barium hexaferrite nanoplatelets (BHF NPLs) are permanent nanomagnets with the magnetic easy axis aligned perpendicular to their basal plane. By combining this specific property with optimised surface chemistry, novel functional materials were developed, e.g., ferromagnetic ferrofluids and porous nanomagnets. We compared the interaction of chemically different phosphonic acids, hydrophobic and hydrophilic with 1–4 phosphonic groups, with BHF NPLs. A decrease in the saturation magnetisation after functionalising the BHF NPLs was correlated with the mass fraction of the nonmagnetic coating, whereas the saturation magnetisation of the NPLs coated with a tetraphosphonic acid at 80 °C was significantly lower than expected. We showed that such a substantial decrease in the saturation magnetisation originates from the disintegration of BHF NPLs, which was observed with atomic-resolution scanning transmission electron microscopy and confirmed by a computational study based on state-of-the-art first-principles calculations. Fe K-edge XANES (X-ray absorption near-edge structure) and EXAFS (Extended X-ray absorption fine structure) combined with Fourier-transformed infrared (FTIR) spectroscopy confirmed the formation of an Fe–phosphonate complex on the partly decomposed NPLs. Comparing our results with other functionalised magnetic nanoparticles confirmed that saturation magnetisation can be exploited to identify the disintegration of magnetic nanoparticles when insoluble disintegration products are formed.
Ključne besede: barium hexaferrite, Fe XANES, EXAFS, magnetic nanoparticles
Objavljeno v RUNG: 06.07.2023; Ogledov: 305; Prenosov: 1
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Voltage-Dependent FTIR and 2D Infrared Spectroscopies within the Electric Double Layer Using a Plasmonic and Conductive Electrode
Nan Yang, Matthew J. Ryan, Minjung Song, Andraž Mavrič, Martin T. Zanni, 2023, izvirni znanstveni članek

Opis: Strong electric fields exist between the electric double layer and charged surfaces. These fields impact molecular structures and chemistry at interfaces. We have developed a transparent electrode with infrared plasmonic enhancement sufficient to measure FTIR and two-dimensional infrared spectra at submonolayer coverages on the surface to which a voltage can be applied. Our device consists of an infrared transparent substrate, a 10–20 nm layer of conductive indium tin oxide (ITO), an electrically resistive layer of 3–5 nm Al2O3, and a 3 nm layer of nonconductive plasmonic gold. The materials and thicknesses are set to maximize the surface number density of the monolayer molecules, electrical conductivity, and plasmonic enhancement while minimizing background signals and avoiding Fano line shape distortions. The design was optimized by iteratively characterizing the material roughness and thickness with atomic force microscopy and electron microscopy and by monitoring the plasmon resonance enhancement with spectroscopy. The design is robust to repeated fabrication. This new electrode is tested on nitrile functional groups using a monolayer of 4-mercaptobenzonitrile as well as on CO and CC stretching modes using 4-mercaptobenzoic acid methyl ester. A voltage-dependent Stark shift is observed on both monolayers. We also observe that the transition dipole strength of the CN mode scales linearly with the applied voltage, providing a second way of measuring the surface electric field strength. We anticipate that this cell will enable many new voltage-dependent infrared experiments under applied voltages.
Ključne besede: two-dimensional infrared spectroscopy, infrared transparent substrate, voltage-dependent infrared experiments
Objavljeno v RUNG: 24.02.2023; Ogledov: 547; Prenosov: 0
.pdf Celotno besedilo (6,07 MB)

Classification of gamma-ray targets for velocity-dependent and subhalo-boosted dark-matter annihilation
Thomas Lacroix, Gaetán Facchinetti, Judit Pérez-Romero, Martin Stref, Julien Lavalle, David Maurin, Miguel Sánchez-Conde, izvirni znanstveni članek

Opis: Gamma-ray observations have long been used to constrain the properties of dark matter (DM), with a strong focus on weakly interacting massive particles annihilating through velocity-independent processes. However, in the absence of clear-cut observational evidence for the simplest candidates, the interest of the community in more complex DM scenarios involving a velocity-dependent cross-section has been growing steadily over the past few years. We present the first systematic study of velocity-dependent DM annihilation (in particular p-wave annihilation and Sommerfeld enhancement) in a variety of astrophysical objects, not only including the well-studied Milky Way dwarf satellite galaxies, but nearby dwarf irregular galaxies and local galaxy clusters as well. Particular attention is given to the interplay between velocity dependence and DM halo substructure. Uncertainties related to halo mass, phase-space and substructure modelling are also discussed in this velocity-dependent context. We show that, for s-wave annihilation, extremely large subhalo boost factors are to be expected, up to 10^11 in clusters and up to 10^6–10^7 in dwarf galaxies where subhalos are usually assumed not to play an important role. Boost factors for p-wave annihilation are smaller but can still reach 10^3 in clusters. The angular extension of the DM signal is also significantly impacted, with e.g. the cluster typical emission radius increasing by a factor of order 10 in the s-wave case. We also compute the signal contrast of the objects in our sample with respect to annihilation happening in the Milky Way halo. Overall, we find that the hierarchy between the brightest considered targets depends on the specific details of the assumed particle-physics model.
Ključne besede: dark matter theory, dwarf galaxies, galaxy clusters, gamma-ray theory
Objavljeno v RUNG: 27.01.2023; Ogledov: 601; Prenosov: 0
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Tehnologije in ogrodja za razvoj spletnih aplikacij na strani odjemalca
Martin Mitev, 2023, diplomsko delo

Opis: V diplomskem delu smo v vlogi mladega razvijalca raziskovali tehnologije in ogrodja za razvoj spletnih aplikacij na strani odjemalca. V njej smo opravili pregled teoretičnih izhodišč izbranega področja. Analizirali smo pomen tehnologij in ogrodij za razvoj spletnih aplikacij. Uporabili smo deskriptivno metodo raziskovanja, vsako tehnologijo in ogrodja smo podrobno opisali ter izpostavili prednosti in slabosti. Raziskovane tehnologije so bile sistemi za nadzor različic, linterji in urejevalniki kode, pregledovalniki tipov in enostranske spletne aplikacije. Zasnovali smo raziskovalni načrt in poiskali podatke na strokovnih spletnih platformah. Zbrane podatke smo uporabili pri izvedbi empirične raziskave najbolj razširjenih JavaScript ogrodij. Z rezultatom raziskave smo dobili vpogled v trg ogrodij, ki so na voljo razvijalcem in jih analizirali. Na osnovi vseh ugotovitev smo naredili sklop tehnologij in ogrodij za sodoben razvoj na strani odjemalca in zasledili naš cilj diplomskega dela. Dodajamo, da je skupnost razvijalcev na strokovnih platformah zelo pomembna, saj se na ta način izmenjuje znanje. Mreženje predstavlja temelj pri reševanju vsakodnevnih problemov, s katerimi se srečujejo razvijalci začetniki.
Ključne besede: tehnologije, ogrodje, razvoj, stran odjemalca, spletna aplikacija, koda
Objavljeno v RUNG: 23.01.2023; Ogledov: 765; Prenosov: 35
.pdf Celotno besedilo (810,97 KB)

Composition and diversity analysis of the lung microbiome in patients with suspected ventilator-associated pneumonia
Dominic Fenn, Mahmoud Abdel-Aziz, Pouline van Oort, Paul Brinkman, Waqar Ahmed, Timothy Felton, Antonio Artigas, Pedro Póvoa, Ignacio Martin-Loeches, Marcus Schultz, Paul Dark, Stephen Fowler, Iain R. White, 2022, izvirni znanstveni članek

Opis: Background: Ventilator-associated pneumonia (VAP) is associated with high morbidity and health care costs, yet diagnosis remains a challenge. Analysis of airway microbiota by amplicon sequencing provides a possible solution, as pneumonia is characterised by a disruption of the microbiome. However, studies evaluating the diagnostic capabilities of microbiome analysis are limited, with a lack of alignment on possible biomarkers. Using bronchoalveolar lavage fluid (BALF) from ventilated adult patients suspected of VAP, we aimed to explore how key characteristics of the microbiome differ between patients with positive and negative BALF cultures and whether any differences could have a clinically relevant role. Methods: BALF from patients suspected of VAP was analysed using 16s rRNA sequencing in order to: (1) differentiate between patients with and without a positive culture; (2) determine if there was any association between microbiome diversity and local inflammatory response; and (3) correctly identify pathogens detected by conventional culture. Results: Thirty-seven of 90 ICU patients with suspected VAP had positive cultures. Patients with a positive culture had significant microbiome dysbiosis with reduced alpha diversity. However, gross compositional variance was not strongly associated with culture positivity (AUROCC range 0.66–0.71). Patients with a positive culture had a significantly higher relative abundance of pathogenic bacteria compared to those without [0.45 (IQR 0.10–0.84), 0.02 (IQR 0.004–0.09), respectively], and an increased interleukin (IL)-1β was associated with reduced species evenness (rs = − 0.33, p < 0.01) and increased pathogenic bacteria presence (rs = 0.28, p = 0.013). Untargeted 16s rRNA pathogen detection was limited by false positives, while the use of pathogen-specific relative abundance thresholds showed better diagnostic accuracy (AUROCC range 0.89–0.998). Conclusion: Patients with positive BALF culture had increased dysbiosis and genus dominance. An increased caspase-1-dependent IL-1b expression was associated with a reduced species evenness and increased pathogenic bacterial presence, providing a possible causal link between microbiome dysbiosis and lung injury development in VAP. However, measures of diversity were an unreliable predictor of culture positivity and 16s sequencing used agnostically could not usefully identify pathogens; this could be overcome if pathogen-specific relative abundance thresholds are used.
Ključne besede: Microbiome, Next-generation sequencing, Ventilator-associated pneumonia
Objavljeno v RUNG: 26.10.2022; Ogledov: 618; Prenosov: 0
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