1981. |
1982. Age-dependent moisture response of conifers near their cold range limitJan Tumajer, Grudd Håkan, Jernej Jevšenak, Andreas J. Kirchhefer, Francesco Marotta, Jiří Mašek, Kiara Maria Nowatzki, Nikolaus Obojes, Markus Stoffel, V. Treml, Jelena Lange, 2025, original scientific article Abstract: Growth dynamics of cold subarctic and subalpine forests are primarily sensitive to temperature, but growth responses may vary across regions or shift over tree ontogeny. Systematic assessments of spatial, interspecific, and demographic variation in temperature and moisture limitation of tree growth at cold distribution margins are essential for enhancing our understanding of how these ecosystems will evolve under climate regimes. To address this gap, we built a network of 22 tree-ring width chronologies from cold forests covering two regions (Fennoscandia, European Alps), three species (Pinus sylvestris, Pinus cembra, Larix decidua), and two age cohorts (45–100 and >150 years). We combined daily climate-growth correlations with the process-based Vaganov-Shashkin growth model to identify differences in critical growth factors between species and age cohorts. In addition, we assessed the coincidence of unusually wide and narrow tree rings with years of specific climatic anomalies. Although growing season temperature was the dominant growth-limiting factor, seasonal effects of water balance on tree growth were considerably large and varied systematically between regions, species, and particularly age cohorts. The growth of young P. sylvestris in Fennoscandia responded negatively to water balance and narrow rings coincided with wet years. In contrast, the growth of young P. cembra in the Alps was drought-limited. Old trees of all species and both age cohorts of L. decidua in the Alps showed limited sensitivity to water balance. The patterns of climate-growth responses in cohort chronologies based on tree age at the year of coring were similar to ontogenetic shifts of climate-growth responses if chronologies were based on the cambial age of individual rings. Our results stress the need to account for interspecific and demographic differences in sensitivity to climate in large-scale studies of cold forest ecosystems.
Keywords: boreal forest, Larix, subalpine forest, pinus, tree ring, Vaganov-Shashkin model
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1983. Efficient decoration of graphene oxide with a narrow size distribution of noble metal nanoparticles : green reduction and integration into a thermoelastic compositeDaniele Vella, Damjan Vengust, Polona Umek, Ali Rezaei, Matija Jezeršek, Aleš Mrzel, 2025, original scientific article Abstract: We have developed a significantly enhanced method for the effective and homogeneous decoration of graphene oxide (GO) and reduced graphene oxide (r-GO) flakes with gold (Au) and platinum (Pt) nanoparticles. This method involves the direct nucleation of nanoparticles on the surface of dispersed GO through a single-step reaction. By carefully controlling the stepwise introduction of gold and platinum complexes at elevated temperatures, without additional reducing agents, we successfully achieved a homogeneous distribution of Au and Pt nanoparticles, ∼ 20 nm and ∼ 3 nm in size, densely covering the GO sheets. The decoration yield in a mass ratio between Au and GO was up to 20 %. Reduced GO with attached gold and platinum nanoparticles was obtained using ascorbic acid as a reducing agent. Finally, we embedded Au-decorated r-GO in polydimethylsiloxane (PDMS) to form a composite. We show how this stable hybrid material composite can be spin-coated to form a thin thermoelastic film on a flexible substrate, enabling promising photoacoustic properties that could be exploited further in biomedical applications.
Keywords: graphene oxide, decoration, nanoparticles, nanocomposites
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1984. |
1985. Deformation properties and performance evaluation of reused ballast with waste tire-derived aggregatesStanislav Lenart, Siva Ram Karumanchi, 2025, original scientific article Abstract: The present study evaluates the shear strength characteristics, deformation properties, and degradation behavior of limestone-based reused ballast (RB) material by mixing crumbs of waste tire-derived aggregates (TDA), focusing on its suitability for railway infrastructure. Conventional large-scale direct shear tests and novel large-scale cyclic simple shear tests were performed to investigate the effects of tire-derived aggregate (TDA) content, with particle sizes varying between 22.4 mm and 50 mm. The results indicate that adding 5 % by the mass of TDA slightly reduced the friction angle from 46.6° to 44.5°, which is not a significant change compared to RB. However, increasing the TDA content to 10 % led to a notable decrease in the friction angle to 41°, highlighting the significant impact of higher TDA content on the shear strength behavior. Further, incorporating 5 % TDA improved the shear modulus and damping ratio relative to RB, which is attributed mainly to the similar larger particle sizes (22.4–50 mm) of TDA. Conversely, at 10 % TDA content, reductions in both shear modulus and damping ratio were observed. The ballast breakage index (BBI), evaluated through cyclic simple shear tests, showed a significant decrease from 15 % for RB to 9.5 % for the ballast sample containing 5 % TDA. Additionally, increased TDA content enhanced material durability, reducing Los Angeles abrasion (LAA) losses from an initial 33.5 to under 30 % at 5 % TDA. These findings demonstrate that incorporating 5 % by mass of TDA into RB material is optimal for enhancing deformation characteristics and reducing ballast degradation while maintaining adequate shear strength. This sustainable approach facilitates the recycling of waste materials, promotes a circular economy, and helps maintain safe and stable railway track conditions.
Keywords: reused ballast, rubber, cyclic simple shear tests, BBI, degradation
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1986. Curvature-dependent adsorption of surfactants in water nanodroplets and nanobubblesFabio Staniscia, Matej Kanduč, 2025, original scientific article Abstract: Hypothesis. Surfactants, molecules that readily adsorb to liquid interfaces and reduce surface tension, are paramount to numerous natural and technological processes: from cloud formation and climate modeling to the stability and reactivity of nanodroplets and nanobubbles. While surfactant adsorption at planar interfaces has been well-studied, their behavior at curved interfaces remains much less understood. Since curvature modifies interfacial thermodynamic properties, we hypothesize that it will also affect surfactant adsorption. Simulations. To test this hypothesis, we perform molecular dynamics simulations of short-chain surfactants at water–vapor interfaces with varying curvature, examining droplets, bubbles, and planar interfaces. Findings. The outcomes reveal a systematic dependence of adsorption on curvature, which is enhanced at droplet interfaces and reduced at bubble interfaces, with the effect becoming more pronounced for surfactants with longer alkyl tails. We attribute this curvature-dependent behavior to two key mechanisms: Laplace pressure and curvature-dependent surface tension. The breakdown of these contributions allows us to obtain a quantitative understanding and to predict the influence of curvature on adsorption.
Keywords: droplets, bubbles, molecular dynamics simulation
Published in DiRROS: 04.06.2025; Views: 446; Downloads: 219
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1987. |
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1989. Composition, microstructure and corrosion resistance of DED-LB additively manufactured Ti–6Al–4V alloy : comparison with wrought alloyIngrid Milošev, Peter Rodič, Barbara Kapun, Denis Sačer, Anish Nair, Davorin Kramar, Andrej Jeromen, Edvard Govekar, 2025, original scientific article Keywords: titanium alloys, directed-energy deposition by laser beam, simulated physiological solution
Published in DiRROS: 03.06.2025; Views: 561; Downloads: 330
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1990. |
