221. Effect of Nb, Ta, and Ti microalloying on the secondary hardening of Mo-W tool steelJaka Burja, Aleš Nagode, Klemen Grabnar, Jože Medved, Tilen Balaško, 2024, original scientific article Keywords: hot work tool steel, microalloying, tempering, heat treatment, carbides
Published in DiRROS: 25.11.2024; Views: 106; Downloads: 712
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222. $S$-packing colorings of distance graphs with distance sets of cardinality $2$Boštjan Brešar, Jasmina Ferme, Přemysl Holub, Marko Jakovac, Petra Melicharová, 2025, original scientific article Abstract: For a non-decreasing sequence $S=(s_1,s_2,\ldots)$ of positive integers, a partition of the vertex set of a graph $G$ into subsets $X_1,\ldots, X_\ell$, such that vertices in $X_i$ are pairwise at distance greater than $s_i$ for every $i\in\{1,\ldots,\ell\}$, is called an $S$-packing $\ell$-coloring of $G$. The minimum $\ell$ for which $G$ admits an $S$-packing $\ell$-coloring is called the $S$-packing chromatic number of $G$. In this paper, we consider $S$-packing colorings of the integer distance graphs with respect two positive integers $k$ and $t$, which are the graphs whose vertex set is $\mathbb{Z}$, and two vertices $x,y\in \mathbb{Z}$ are adjacent whenever $|x-y|\in\{k,t\}$. We complement partial results from two earlier papers, thus determining all values of the $S$-packing chromatic numbers of these distance graphs for all sequence $S$ such that $s_i\le 2$ for all $i$. In particular, if $S=(1,1,2,2,\ldots)$, then the $S$-packing chromatic number is $2$ if $k+t$ is even, and $4$ otherwise, while if $S=(1,2,2,\ldots)$, then the $S$-packing chromatic number is $5$, unless $\{k,t\}=\{2,3\}$ when it is $6$; when $S=(2,2,2,\ldots)$, the corresponding formula is more complex.
Keywords: S-packing coloring, S-packing chromatic number, distance graph, distance coloring
Published in DiRROS: 22.11.2024; Views: 137; Downloads: 69
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223. Estimating the effective char depth in structural timber elements exposed to natural fires, considering the heating and cooling phaseAndrea Lucherini, Daniela Šejnová Pitelková, Vladimír Mózer, 2025, original scientific article Abstract: This research study investigates the effect of different heating and cooling regimes on the effective cross-section of timber elements exposed to natural fires. An advanced calculation method based on a 1D finite-difference heat transfer model and effective thermo-physical properties is adopted to analyse the heat penetration and the consequent reduction in mechanical properties. In particular, the research focuses on the evolution and penetration speed of the char depth (300 ◦C isotherm) and zero-strength layer (determined through in-depth temperatures and reduced mechanical properties). Results reveal how the char depth mainly develops during the heating phase, with non-negligible contributions from the cooling phase. In contrast, the zero-strength layer increases throughout the whole fire exposure, particularly during cooling and, possibly, after the end of the cooling phase. In general, the heating phase contributes about 2/3 to the total effective char depth, while the cooling phase about 1/3. The most challenging conditions were found for the fires of the longest durations (heating and overall), corresponding to low ventilation and high fuel load density conditions. The study emphasises the necessity of incorporating the cooling phase in performance-based methodologies for fire-safe timber structures to avoid under-estimating heat penetration effects.
Keywords: timber structures, fire safety, charring, zero-strength layer, natural fire, heating, cooling, structural fire engineering, performance-based design
Published in DiRROS: 22.11.2024; Views: 138; Downloads: 434
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225. Prolonged cultivation enhances the stimulatory activity of hiPSC mesenchymal progenitor-derived conditioned mediumDarja Marolt Presen, Vanessa Goeschl, Dominik Hanetseder, Laura Ogrin, Alexandra-Larissa Stetco, Anja Tanšek, Laura Poženel, Bella Bruszel, Goran Mitulović, Johannes Oesterreicher, Johannes Zipperle, 2024, original scientific article Published in DiRROS: 22.11.2024; Views: 152; Downloads: 938
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227. Investigation of the hyporheic zone of two gravel-bed rivers after reservoir drainingMaja Zagmajster, Nataša Mori, Gregor Bračko, Anton Brancelj, Špela Di Batista Borko, Teo Delić, Žiga Fišer, Klemen Koselj, Simona Prevorčnik, Valerija Zakšek, Cene Fišer, 2024, original scientific article Abstract: Dams and reservoirs are a common and globally widespread anthropogenic disturbance with documented negative effects on riverine and riparian habitats. The two most well-known impacts of river damming are longitudinal fragmentation of surface running waters and a shift from lotic habitats towards habitats with lentic characteristics that affect the benthic and pelagic communities. However, there is very little empirical evidence about the effects of damming on the aquatic fauna inhabiting interstitial habitats extending in and alongside the river-bed (i.e., hyporheic zone). In this study, we investigated the patterns in the interstitial community composition upstream, downstream and within the reservoir that was formed 80 years ago, when the river was dammed for the hydropower production. We used the rare opportunity to directly access the bottom of the reservoir drained due to dam maintenance in January 2018, to compare physical, chemical and faunistic data from the reservoir area, with those from downstream and upstream reaches of the two gravel bed rivers that are flowing into the reservoir. We sampled the interstitial invertebrate communities at seven locations, using a Bou-Rouch pump at two depths (30–60 cm and 60–90 cm within the river bed) and at three sampling points within each location. At the same sampling points we measured also physical and chemical parameters (temperature, conductivity, oxygen and pH). The interstitial water from the deepest point of the drained reservoir had substantially lower oxygen concentration, lower pH, and higher conductivity than water from the other sampling localities. This was also the site where taxa richness was lowest, and only one obligate groundwater species (i.e. stygobiont) was found. Most probably, the changes in morphology of the river channel and speed of water flow due to damming, which increased sedimentation rate and clogging of interstitial habitat, resulted in such large differences in environmental conditions and invertebrate community composition. This study provides rare empirical evidence of the effects of damming on the river interstitial habitats and fauna within the reservoir area. We recommend that environmental impact assessments conducted prior dam constructions should include also assessment of the effect of river damming on the interstitial communities. These organisms are playing important role in driving important ecosystem processes, such as organic matter degradation on one hand, and on the other hand, are composed of many rare and endangered species that need to be protected.
Keywords: damming, interstitial habitats, subterranean fauna, invertebrate communities, stygobionts, dam, hydropower, environmental impact
Published in DiRROS: 22.11.2024; Views: 143; Downloads: 82
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228. Vibrational noise disrupts Nezara viridula communication, irrespective of spectral overlapRok Janža, Nataša Stritih Peljhan, Aleš Škorjanc, Jernej Polajnar, Meta Virant-Doberlet, 2024, original scientific article Abstract: Insects rely on substrate vibrations in numerous intra- and interspecific interactions. Yet, our knowledge of noise impact in this modality lags behind that in audition, limiting our understanding of how anthropogenic noise affects insect communities. Auditory research has linked impaired signal perception in noise (i.e., masking) to spectral overlap. We investigated the impact of noise with different spectral compositions on the vibrational communication of the stink bug Nezara viridula, examining courtship behaviour and signal representation by sensory neurons. We found negative effects of vibrational noise regardless of spectral overlap, challenging common expectations. Noise impaired the ability of males to recognize the female signal and localise its source: overlapping noise decreased sensitivity of receptor neurons to the signal and disrupted signal frequency encoding by phase-locking units, while non-overlapping noise only affected frequency encoding. Modelling neuronal spike triggering in sensory neurons linked disrupted frequency encoding to interference-induced alterations of the signal waveform. These alterations also affected time delays between signal arrivals to different legs, crucial for localisation. Our study thus unveils a new masking mechanism, potentially unique to insect vibrosensory systems. The findings highlight the higher vulnerability of vibration-mediated behaviour to noise, with implications for insect interactions in natural and anthropogenically altered environments.
Keywords: biotremology, vibrations, noise, communication, neurons, masking, entomology, neurobiology
Published in DiRROS: 21.11.2024; Views: 155; Downloads: 2482
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229. Initial glutathione depletion during short-term bed rest : pinpointing synthesis and degradation checkpoints in the γ-glutamyl cycleFilippo Giorgio Di Girolamo, Filippo Mearelli, Mariella Sturma, Nicola Fiotti, Kaja Teraž, Alja Ivetac, Alessio Nunnari, Pierandrea Vinci, Boštjan Šimunič, Rado Pišot, Gianni Biolo, 2024, original scientific article Abstract: Hypokinesia triggers oxidative stress and accelerates the turnover of the glutathione system via the γ-glutamyl cycle. Our study aimed to identify the regulatory checkpoints controlling intracellular glutathione levels. We measured the intermediate substrates of the γ-glutamyl cycle in erythrocytes from 19 healthy young male volunteers before and during a 10-day experimental bed rest. Additionally, we tracked changes in glutathione levels and specific metabolite ratios up to 21 days of bed rest. Using gas chromatography-mass spectrometry and the internal standard technique, we observed a 9 ± 9% decrease in glutathione levels during the first 5 days of bed rest, followed by an 11 ± 9% increase from the 5th to the 10th day, nearly returning to baseline ambulatory levels. The cysteinyl-glycine-to-glutathione ratio, reflecting γ-glutamyl cyclotransferase activity (a key enzyme in glutathione breakdown), rose by 14 ± 22% in the first 5 days and then fell by 10 ± 14% over the subsequent 5 days, again approaching baseline levels. Additionally, the γ-glutamyl cysteine-to-cysteine ratio, indicative of γ-glutamyl cysteine synthetase activity (crucial for glutathione synthesis), increased by 12 ± 30% on day 5 and by 29 ± 41% on day 10 of bed rest. The results observed on day 21 of bed rest confirm those seen on day 10. By calculating the ratio of product concentration to precursor concentration, we assessed the efficiency of these key enzymes in glutathione turnover. These results were corroborated by directly measuring glutathione synthesis and degradation rates in vivo using stable isotope techniques. Our findings reveal significant changes in glutathione kinetics during the initial days of bed rest and identify potential therapeutic targets for maintaining glutathione levels.
Keywords: antioxidant, muscle unloading, glutathion turnover, γ-glutamyl cycle, gamma-glutamyl cycle
Published in DiRROS: 21.11.2024; Views: 164; Downloads: 1121
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230. Acute effects of high-intensity interval training on microvascular circulation : a case control study in uveal melanomaMichael Mendes Wefelnberg, Johanna Hubert, Freerk T. Baumann, Damir Zubac, 2024, original scientific article Abstract: Objectives: The aim of this study was to explore the acute effects of high-intensity interval training (HIIT) on the microvascular circulation and vascular tumor microenvironment (TME) in a patient with uveal melanoma (UM). Additionally, the acceptance of the applied diagnostics and the exercise protocol in a clinical ophthalmic-oncology setting were evaluated. Methods: This case-control study included a young adult male patient with UM previously treated with radiation and an age-matched healthy control. Participants underwent a baseline assessment of dynamic retinal vessel analysis (DRVA) and cardiopulmonary exercise testing (CPET) to determine endothelial function and intensity for HIIT. Optical coherences tomography angiography (OCTA) was performed before, immediately and 30 min after one session of HIIT. The primary outcome were changes in ocular vessel parameters and whole body oxygen uptake. Results: The UM patient exhibited lower arterial dilation and constriction in the affected eye compared to his healthy eye and both eyes of the healthy control. OCTA revealed heterogeneous patterns of vascular response to HIIT in both participants. The tumor eye showed an increase followed by a significant decrease in vessel density post-exercise, while the healthy control exhibited minor increases. Conclusions: The findings of this study highlighted the potential of UM combined with OCTA and DRVA as a model for examine exercise-induced vascular effects within the TME. However, a pre-treated UM as well as detailed image analyses and further research with longitudinal, randomized controlled designs are essential to validate these findings and address methodological limitations. Such investigations could refine integrative cancer treatment.
Keywords: uveal melanoma, endothelial dysfunction, aerobic exercise, oxygen kinetics
Published in DiRROS: 21.11.2024; Views: 127; Downloads: 477
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