311. Computation of leaky waves in layered structures coupled to unbounded media by exploiting multiparameter eigenvalue problemsHauke Gravenkamp, Bor Plestenjak, Daniel A. Kiefer, Elias Jarlebring, 2025, original scientific article Abstract: We present a semi-analytical approach to compute quasi-guided elastic wave modes in horizontally layered structures radiating into unbounded fluid or solid media. This problem is of relevance, e.g., for the simulation of guided ultrasound in embedded plate structures or seismic waves in soil layers over an elastic half-space. We employ a semi-analytical formulation to describe the layers, thus discretizing the thickness direction by means of finite elements. For a free layer, this technique leads to a well-known quadratic eigenvalue problem for the mode shapes and corresponding horizontal wavenumbers. Incorporating the coupling conditions to account for the adjacent half-spaces gives rise to additional terms that are nonlinear in the wavenumber. We show that the resulting nonlinear eigenvalue problem can be cast in the form of a multiparameter eigenvalue problem whose solutions represent the wave numbers in the plate and in the half-spaces. The multiparameter eigenvalue problem is solved numerically using recently developed algorithms. Matlab implementations of the proposed methods are publicly available.
Keywords: guided waves, plates, soil dynamics, half-space, leaky waves, semi-analytical method
Published in DiRROS: 11.10.2024; Views: 156; Downloads: 2365
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312. Long-term assessment of the population trends and body condition of Carabus variolosus nodulosus in SloveniaEva Vera Jiménez, 2024, master's thesis Abstract: To gain insight into the current population trends of Carabus variolosus nodulosus in Slovenia and assess the body condition of individuals, data from 17-year monitoring program were analyzed across five geographically distinct regions. The number of beetles captured per trap was recorded, and measurements of live specimens were taken to calculate both national and regional population trends, along with a body condition index. Additionally, linear mixed-effects models were used to examine the potential impact of sex and disturbances on body condition, and to explore the correlation between body condition and population density. The results indicated an overall stable population trend with marked regional differences. No correlation was found between body condition and population density or disturbances, though significant differences in body condition between sexes were observed. This study underscores the importance of long-term and multi-scale monitoring to detect stress factors and potential local extinctions that might otherwise remain undetected and proposes sampling efforts for future monitoring schemes for reliable trend assessments of the species.
Keywords: scaled mass index, long-term monitoring, ground beetle, body condition, zoology, master thesis
Published in DiRROS: 10.10.2024; Views: 182; Downloads: 45
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314. Selection on the vascular-remodeling BMPER gene is associated with altitudinal adaptation in an insular lizardNina Guerra Serén, Catarina Pinho, Rodrigo Megía-Palma, Prem Aguilar, Anamarija Žagar, Pedro Andrade, Miguel A. Carretero, 2024, original scientific article Abstract: High altitude imposes several extreme constraints on life, such as low oxygen pressure and high levels of ultraviolet radiation, which require specialized adaptations. Many studies have focused on how endothermic vertebrates respond to these challenging environments, but there is still uncertainty on how ectotherms adapt to these conditions. Here, we used whole-genome sequencing of low-altitude (100–600 m) and high-altitude (3,550 m) populations of the wide-ranging Tenerife lizard Gallotia galloti to uncover signatures of selection for altitudinal adaptation. The studied populations show reduced differentiation, sharing similar patterns of genetic variation. Selective sweep mapping suggests that signatures of adaptation to high altitude are not widespread across the genome, clustering in a relatively small number of genomic regions. One of these regions contains BMPER, a gene involved with vascular remodeling, and that has been associated with hypoxia-induced angiogenic response. By genotyping samples across 2 altitudinal transects, we show that allele frequency changes at this locus are not gradual, but rather show a well-defined shift above ca. 1,900 m. Transcript and protein structure analyses on this gene suggest that putative selection likely acts on noncoding variation. These results underline how low oxygen pressure generates the most consistent selective constraint in high-altitude environments, to which vertebrates with vastly contrasting physiological profiles need to adapt in the context of ongoing climate change.
Keywords: high altitude, adaptations, ectotherms, whole-genome sequencing, selective sweep, BMPER gene, hypoxia, genomics
Published in DiRROS: 08.10.2024; Views: 189; Downloads: 76
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315. Phytoplankton morphological traits and biomass outline community dynamics in a coastal ecosystem (Gulf of Trieste, Adriatic Sea)Ivano Vascotto, Patricija Mozetič, Janja Francé, 2024, original scientific article Abstract: Trait-based ecology has recently gained increasing importance in phytoplankton research. In particular, the taxonomic and morphological traits, such as size and shape of phytoplankton cells, can help to unveil the ecological processes and their drivers in the pelagic domain. Our study aims to shed light on the trophodynamics of phytoplankton communities in a coastal ecosystem in the northern Adriatic Sea (Gulf of Trieste) using data on individual traits such as biomass, size and shape of phytoplankton taxa during a one-year study. The phytoplankton parameters were investigated at the levels of the whole community, groups, and individual cells, analysing also the probability distributions of biomass and size of the latter level. The results showed good agreement between abundance and biomass data, as well as individual size and biomass with differences partly explained by cell shapes. We have emphasized the role of the local freshwater source in bottom-up control, alternating with top-down control of phytoplankton dynamics through taxonomic and morphological diversity. The predominant bimodal and non-power law distribution, especially during and around the biomass peaks, confirmed the importance of nano- and microphytoplankton size classes and the role of blooms in destabilizing the trophic webs. We suggest that the analyses of distribution types of individual cell size and biomass can be appropriate to spot ecological processes driving to unconstrained phytoplankton proliferation or to periods of trophic web stability.
Keywords: phytoplankton, biomass, taxonomic traits, morphological traits, Northern Adriatic, trophodynamics, pelagic domain
Published in DiRROS: 08.10.2024; Views: 180; Downloads: 593
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316. Comparing the effects of pristine and UV–VIS aged microplastics : behavioural response of model terrestrial and freshwater crustaceansPrimož Zidar, Dana Kühnel, Andrijana Sever Škapin, Tina Skalar, Damjana Drobne, Luka Škrlep, Branka Mušič, Anita Jemec Kokalj, 2024, original scientific article Abstract: Physico-chemical properties of microplastics (MPs) change during weathering in the environment. There is a lack of knowledge about the effects of such environmentally relevant MPs on organisms. We investigated: 1) the physico-chemical changes of MPs due to UV–VIS weathering, and 2) compared the effect of pristine and aged MPs on the behaviour of the water flea Daphnia magna and terrestrial crustacean Porcellio scaber. Dry powders of MPs were produced from widely used polymer types: disposable three-layer polypropylene (PP) medical masks (inner, middle and outer), polyester textile fibres, car tires and low-density polyethylene (LDPE) bags and were subjected to accelerated ultraviolet–visible (UV–VIS) ageing. Our results show that the extent of transformation depends on the type of polymer, with PP showing the most changes, followed by LDPE, textile fibres and tire particles. Obvious fragmentation was observed in PP and textile fibres. In the case of PP, but not polyester textile fibres, changes in FTIR spectra and surface properties were observed. Tire particles and LDPE did not change in size, but clear changes were observed in their FTIR spectra. Most MPs, aged and pristine, did not affect the swimming of daphnids. The only effect observed was a significant increase in path length and swimming speed for the pristine tire particles when the recording was done with particles remaining in the wells. After transfer to a clean medium, this effect was no longer present, suggesting a physical rather than chemical effect. Similarly, woodlice showed no significant avoidance response to the MPs tested, although there was a noticeable trend to avoid soils contaminated with pristine polyester textile fibers and preference towards the soils contaminated with aged MP of the middle mask layer. Overall, the apparent changes in physico-chemical properties of MPs after accelerated ageing were not reflected in their effects on woodlice and daphnids.
Keywords: Daphnia magna, Porcellio scaber, polyethylene, polypropylene, weathering, FTIR
Published in DiRROS: 08.10.2024; Views: 189; Downloads: 1443
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317. Controlling the optoelectronic properties of nitrogen-doped carbon quantum dots using biomass-derived precursors in a continuous flow systemKiem G. Nguyen, Matej Huš, Ioan-Alexandru Baragau, Elisa G. Puccinelli, James Bowen, Tobias Heil, Adela Nicolaev, Deborah Andrews, Muhammad Tariq Sajjad, Steven Dunn, Suela Kellici, 2024, original scientific article Published in DiRROS: 08.10.2024; Views: 168; Downloads: 971
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