The paper deals with research focused on the use of fillers in the field of polymeric materials produced by additive technology SLA (stereolithography). The aim of the research is to evaluate 3D printing parameters, the mechanical properties (tensile strength, hardness), and the interaction of individual phases (polymer matrix and filler) in composite materials using SEM analysis. The tested fillers were cotton flakes and ground carbon fibres in different proportions. For the photosensitive resins, the use of cotton flakes as filler was found to have a positive effect on the mechanical properties not only under static but also under cyclic loading, which is a common cause of material failure in practice. The cyclic stress reference value was set at an amplitude of 5-50% of the maximum force required to break the pure resin in a static tensile test. A positive effect of fillers on the cyclic stress life of materials was demonstrated. The service life of pure resin was only 168 ± 29 cycles. The service life of materials with fillers increased to approximately 400 to 540 cycles for carbon fibre-based fillers and nearly 1000 cycles for cotton flake-based fillers, respectively. In this paper, new composite materials suitable for the use of SLA additive manufacturing techniques are presented. Research demonstrated the possibilities of adding cotton-based fillers in low-cost, commercially available resins. Furthermore, the importance of material research under cyclic loading was demonstrated.
- Klíčová slova
- 3D printing, carbon filler, cotton filler, cyclic loading, low cycle test, polymer composite,
- Publikační typ
- časopisecké články MeSH
Additive manufacturing (3D printing) has significantly changed the prototyping process in terms of technology, construction, materials, and their multiphysical properties. Among the most popular 3D printing techniques is vat photopolymerization, in which ultraviolet (UV) light is deployed to form chains between molecules of liquid light-curable resin, crosslink them, and as a result, solidify the resin. In this manuscript, three photopolymerization technologies, namely, stereolithography (SLA), digital light processing (DLP), and continuous digital light processing (CDLP), are reviewed. Additionally, the after-cured mechanical properties of light-curable resin materials are listed, along with a number of case studies showing their applications in practice. The manuscript aims at providing an overview and future trend of the photopolymerization technology to inspire the readers to engage in further research in this field, especially regarding developing new materials and mathematical models for microrods and bionic structures.
- Klíčová slova
- CDLP, CLIP, DLP, SLA, vat photopolymerization,
- Publikační typ
- časopisecké články MeSH
- přehledy MeSH
Complicated geometry in combination with surface treatment strongly deteriorates fatigue resistance of metallic dental implants. Mechanical properties of pure Ti grade 2, usually used for dental implant production, were shown to be significantly improved due to intensive grain refinement via Conform SPD. The increase of the tensile strength properties was accompanied by a significant increase in the fatigue resistance and fatigue endurance limit. However, the SLA treatment usually used for the implants' surface roughening, resulted in the fatigue properties and endurance limit decrease, while this effect was more pronounced for the ultrafine-grained comparing to the coarse-grained material when tested under tensile-tensile loading mode. The testing of the implants is usually provided under the bending mode. Even though different testing condition for the conventional specimens tests and implants testing was adopted, a numerical study revealed their comparable fatigue properties. The fatigue limit determined for the implants was 105% higher than the one for coarse-grained and only by 4 % lower than the one for ultrafine-grained Ti grade 2. Based on the obtained results, conventional specimens testing can be used for the prediction of the fatigue limit of the implants.
- Klíčová slova
- Dental implant, Fatigue, SLA treatment, Ti grade 2, Ultrafine-grained,
- MeSH
- pevnost v tahu MeSH
- povrchové vlastnosti MeSH
- testování materiálů MeSH
- titan * MeSH
- zubní implantáty * MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- titan * MeSH
- zubní implantáty * MeSH
- Klíčová slova
- EFL, ESL, FLL, L2 acquisition, SLA, human computer interaction,
- Publikační typ
- úvodníky MeSH
Drought stress can profoundly affect plant growth and physiological vitality, yet there is a notable scarcity of controlled drought experiments focused on herbaceous species of the forest understorey. In this study, we collected seeds from five forb and four graminoid species common in European temperate forests. Seeds were germinated under controlled glasshouse conditions and subjected to moderate drought stress for 5 weeks. We assessed biomass partitioning, stomatal and leaf morphology, leaf gas exchange, minimum leaf conductance (gmin), and chlorophyll fluorescence parameters. Comparison of the two ecological guilds revealed that graminoids had a higher R/S, improved WUE, greater carboxylation efficiency, and enhanced non-photochemical quenching under drought conditions compared to forbs. In contrast, forbs had significantly lower gmin, with higher total biomass and total leaf area. Despite these differences in morpho-physiological functional traits, both groups experienced a similar relative reduction in biomass after drought stress. Key predictors of biomass accumulation under drought included photochemical quenching, stomatal traits, total leaf area and gmin. A negative correlation between biomass and gmin suggests that plants with lower residual water loss after stomatal closure can accumulate more biomass under drought stress. Additionally, gmin was positively correlated with guard cell length, suggesting that larger stomata contribute to higher residual water loss. Contrasting strategies in morpho-physiological responses to drought define the differences between the two groups. In graminoids, drought resistance suggests greater emphasis on stress tolerance as a survival strategy. In contrast, forbs were able to maintain higher biomass and total leaf area, indicating a competitive strategy for maximizing resource acquisition.
- Klíčová slova
- Biomass partitioning, SLA, WUE, chlorophyll fluorescence, minimum leaf conductance, photosynthesis, stomatal morphology, water deficit,
- Publikační typ
- časopisecké články MeSH
The relict arctic-alpine tundra provides a natural laboratory to study the potential impacts of climate change and anthropogenic disturbance on tundra vegetation. The Nardus stricta-dominated relict tundra grasslands in the Krkonoše Mountains have experienced shifting species dynamics over the past few decades. Changes in species cover of the four competing grasses-Nardus stricta, Calamagrostis villosa, Molinia caerulea, and Deschampsia cespitosa-were successfully detected using orthophotos. Leaf functional traits (anatomy/morphology, element accumulation, leaf pigments, and phenolic compound profiles), were examined in combination with in situ chlorophyll fluorescence in order to shed light on their respective spatial expansions and retreats. Our results suggest a diverse phenolic profile in combination with early leaf expansion and pigment accumulation has aided the expansion of C. villosa, while microhabitats may drive the expansion and decline of D. cespitosa in different areas of the grassland. N. stricta-the dominant species-is retreating, while M. caerulea did not demonstrate significant changes in territory between 2012 and 2018. We propose that the seasonal dynamics of pigment accumulation and canopy formation are important factors when assessing potential "spreader" species and recommend that phenology be taken into account when monitoring grass species using remote sensing.
- Klíčová slova
- SLA, canopy, flavonoids, grasslands, orthophotos, phenolic compounds, remote sensing, secondary metabolism, species cover analysis, tundra,
- Publikační typ
- časopisecké články MeSH
Commercially pure Ti is a typical material for dental implants. Besides oral environmental effects, implants are seriously mechanically loaded during the lifetime. Mechanical resistance of coarse and ultra-fine grained Ti grade 4 was investigated. Significant grain size refinement resulting in the 65% increase of the proof stress is reported. The fatigue endurance limit increased from 523 MPa to 698 MPa due to grain refinement. The influence of sandblasting combined with acid etching on fatigue damage of both material states was analyzed. The surface treatment was proven as detrimental to the fatigue properties of both material states, due to reduction of the fatigue initiation stage. Nevertheless, the fatigue endurance limit of the surface-treated ultra-fine grained material remained higher than the fatigue endurance limit of the coarse-grained material without surface treatment. Reported results confirm better mechanical resistance of ultra-fine grained materials for dental implants in the comparison with coarse-grain one.
- Klíčová slova
- CP Ti grade 4, Fatigue, Fatigue crack initiation, SLA, UFG,
- MeSH
- povrchové vlastnosti MeSH
- testování materiálů MeSH
- titan * MeSH
- zubní implantáty * MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- titan * MeSH
- zubní implantáty * MeSH
Plant communities are being exposed to changing environmental conditions all around the globe, leading to alterations in plant diversity, community composition, and ecosystem functioning. For herbaceous understorey communities in temperate forests, responses to global change are postulated to be complex, due to the presence of a tree layer that modulates understorey responses to external pressures such as climate change and changes in atmospheric nitrogen deposition rates. Multiple investigative approaches have been put forward as tools to detect, quantify and predict understorey responses to these global-change drivers, including, among others, distributed resurvey studies and manipulative experiments. These investigative approaches are generally designed and reported upon in isolation, while integration across investigative approaches is rarely considered. In this study, we integrate three investigative approaches (two complementary resurvey approaches and one experimental approach) to investigate how climate warming and changes in nitrogen deposition affect the functional composition of the understorey and how functional responses in the understorey are modulated by canopy disturbance, that is, changes in overstorey canopy openness over time. Our resurvey data reveal that most changes in understorey functional characteristics represent responses to changes in canopy openness with shifts in macroclimate temperature and aerial nitrogen deposition playing secondary roles. Contrary to expectations, we found little evidence that these drivers interact. In addition, experimental findings deviated from the observational findings, suggesting that the forces driving understorey change at the regional scale differ from those driving change at the forest floor (i.e., the experimental treatments). Our study demonstrates that different approaches need to be integrated to acquire a full picture of how understorey communities respond to global change.
- Klíčová slova
- SLA, climate change, forest management, forestREplot, herbaceous layer, mesocosm experiment, nitrogen deposition, plant height, resurvey study,
- MeSH
- dusík MeSH
- ekosystém * MeSH
- lesy * MeSH
- rostliny MeSH
- stromy MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- dusík MeSH
The EUOS/SLAS challenge aimed to facilitate the development of reliable algorithms to predict the aqueous solubility of small molecules using experimental data from 100 K compounds. In total, hundred teams took part in the challenge to predict low, medium and highly soluble compounds as measured by the nephelometry assay. This article describes the winning model, which was developed using the publicly available Online CHEmical database and Modeling environment (OCHEM) available on the website https://ochem.eu/article/27. We describe in detail the assumptions and steps used to select methods, descriptors and strategy which contributed to the winning solution. In particular we show that consensus based on 28 models calculated using descriptor-based and representation learning methods allowed us to obtain the best score, which was higher than those based on individual approaches or consensus models developed using each individual approach. A combination of diverse models allowed us to decrease both bias and variance of individual models and to calculate the highest score. The model based on Transformer CNN contributed the best individual score thus highlighting the power of Natural Language Processing (NLP) methods. The inclusion of information about aleatoric uncertainty would be important to better understand and use the challenge data by the contestants.
- Klíčová slova
- Consensus, Descriptor based models, Graph neural networks, Kaggle challenge, OCHEM, Representation learning, Solubility prediction, Transformer CNN,
- MeSH
- algoritmy * MeSH
- chemické databáze MeSH
- konsensus MeSH
- neuronové sítě * MeSH
- rozpustnost MeSH
- Publikační typ
- časopisecké články MeSH
The present study describes the distinct bone marrow (BM) and peripheral blood (PB) monocyte subpopulations detected by seven-colour flow cytometry. Mononuclear phagocytes were identified as viable CD172a(+) SWC8(-) CD203a(-) mononuclear leukocytes. After that, monocyte subpopulations were differentiated by using CD14, CD163 and SLA-DR markers. Four distinct monocyte subpopulations were found in the BM and PB. Based on the discovered populations two possible maturation pathways have been proposed. The first pathway was characterised by release of CD14(hi) CD163(-) SLA-DR(-) BM monocytes into the PB where they matured into CD14(low) CD163(+) SLA-DR(+) monocytes. In the alternative pathway the monocytes finalised their phenotypical maturation in the BM and then they were released into the PB as CD14(low) CD163(+) SLA-DR(+) cells. In Salmonella-infected piglets, the population of CD14(low) CD163(+) SLA-DR(+) monocytes was elevated in the BM and mesenteric lymph nodes (MLN), suggesting the role of this population in pathogenesis of Salmonella infection in pigs.
- MeSH
- buňky kostní dřeně klasifikace cytologie MeSH
- membránové proteiny MeSH
- monocyty klasifikace cytologie MeSH
- nemoci prasat krev mikrobiologie MeSH
- prasata MeSH
- průtoková cytometrie metody veterinární MeSH
- Salmonella enteritidis MeSH
- salmonelová infekce u zvířat krev MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- membránové proteiny MeSH
