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Perlitleşmemiş Obsidiyen Genleşmesi: Hidrasyon ve Oluşum Özellikleri / Unperlitized Obsidian Expansion: Hydration and Formation Characteristics
No full textMagma ile su etkileşimi, volkanik patlamalarda patlamanın şiddetini belirleyen en önemli parametrelerden biri olarak tanımlanmaktadır. Bununla birlikte, patlama ile oluşan volkanik ürünlerde rastlanılan su içeriğinin volkanizma sırasında veya sonrasında gelişip gelişmediğinin belirlenmesinde çeşitli kısıtlamalar bulunmaktadır. Bu çalışma, Nevşehir Acıgöl Maar’ından örneklenen obsidiyenin, perlitik doku sahibi olmadan ısıl işlem ile genleşmesinin nedeni ve özellikleri ile termal ayrışma özelliklerinin belirlenmesi amacıyla gerçekleştirilmiştir. Bantlı obsidiyenin genleştirilmesi sırasında geçirmiş olduğu fiziksel ve kimyasal değişimler, çeşitli analitik yöntemler ile incelenmiştir. Bu kapsamda, su bileşenlerinde meydana gelen değişimler FT-IR analizi ile gözlemlenmiştir. Örnekte gerçekleşen kütle kaybının değeri TG-DTA yöntemi ile ölçülmüş olup genleştirme deneyi sonucunda oluşan üründe genleşmeye bağlı meydana gelen dokusal değişimler üç boyutlu tomografik görüntüleme tekniği ile belirlenmiştir. Sonuç olarak bir volkan camının termal olarak ayrışması, uçucu gazlar ile birincil ve ikincil su türlerinin farklı sıcaklıklarda çeşitli süreçler sonucunda salınması ile meydana gelmektedir. Bu çalışma ile su içeren riyolitik bileşime sahip obsidiyenin, su ve uçucu bileşenlerin kimyasal olarak gevşek bir şekilde bağlandığı yerlerde çeşitli oranlarda genişleyen gözenekler oluşturabildiği deneysel olarak gösterilmiştir.Magma-water interaction is defined as one of the most important parameters determining the explosivity of volcanic eruptions. However, accurately quantifying the water content in volcanic products formed during syn-eruptive or post-eruptive processes remains a significant challenge. This study investigated the thermal expansion and decomposition behavior of obsidian sampled from the Nevşehir Acıgöl Maar, which was subjected to heat treatment without exhibiting perlitic texture development, in order to elucidate the underlying mechanisms and characteristics of the process. The physical and chemical changes that the banded obsidian experienced during its expansion were analyzed using various analytical methods. In this context, FT-IR analysis was used to observe modifications in water components. The mass loss in the sample was quantified using the TG-DTA method, while the textural changes occurring during the obsidian expansion experiment were determined through three-dimensional tomographic imaging technique. The results show that thermal decomposition of volcanic glass involves the release of volatiles and both primary and secondary water species across a range of temperatures. This study demonstrates experimentally that hydrous rhyolitic obsidian can generate vesicles that expand at varying rates, particularly in regions where water and volatiles are loosely bound within the glass structure
Do bioactive restoratives prevent demineralization of adjacent proximal enamel? a laboratory study
No full textAIM: The aim of this laboratory study was to evaluate the preventive effect of various bioactive restorative materials on proximal enamel surfaces adjacent to approximal restorations under erosive conditions. Materials and methods: Sixty sound human proximal enamel specimens were prepared and randomly assigned to four groups (n = 15). Each specimen was placed adjacent to an approximal restoration prepared using one of the following materials: Cention Forte (Ivoclar Vivadent AG, Liechtenstein), Equia Forte HT (GC Europe, Belgium), Beautifil II (Shofu, Japan), and Filtek Z550 (3 M ESPE, USA) as the control. All specimens were subjected to an erosive challenge by immersion in Coca-Cola for 15 min, three times daily for seven consecutive days. Surface roughness (Ra) and microhardness (VHN) values were measured at baseline and after the erosive challenge using a contact profilometer and a Vickers microhardness tester, respectively. Representative specimens (n = 3 per group) were imaged using scanning electron microscopy (SEM) to visualize surface changes, and were further analyzed by energy-dispersive X-ray spectroscopy (EDS) to determine elemental composition (F, Ca, P). Data were analyzed using one-way ANOVA followed by Tukey's post hoc test (alpha = 0.05). Results: Surface roughness increased significantly in all groups after the erosive challenge, with Cention Forte and Equia Forte HT exhibiting significantly lower roughness values than Filtek Z550 (p < 0.05). A significant reduction in microhardness was observed in all groups except for Equia Forte HT when compared to baseline (p < 0.05). Specimens adjacent to the resin composite showed a greater decrease in microhardness compared to those in contact with Equia Forte HT and Cention Forte (p < 0.05). EDS analysis revealed no statistically significant differences in elemental composition among the groups. Conclusion: Compared to resin composite, bioactive materials such as Equia Forte HT and Cention Forte demonstrated greater potential in preserving the integrity of proximal enamel adjacent to approximal restorations under erosive conditions
Transoral Robotic Surgery (TORS) for Head and Neck Cancer in the Elderly Population: Functional Outcomes, Survival, and Complications
No full textComparison of System Identification Methods for Close-Proximity Sensing Soft Antennae
No full textThe design and manufacturing of compliant structures using soft materials are gaining importance due to their unique advantages in robotics and sensing applications. This study presents research conducted to analyze the close-proximity depth perception capabilities of low-cost, soft robotic antennae produced in a laboratory environment for use in insect-like robots. The characteristic properties of these antennae in both the time and frequency domains have been determined using different methods, and the advantages of these methods over one another have been discussed
Assessment of Flood Risk Mitigation Measures Based on Economic and Social Performance: A Case Study From Agva, Turkiye
No full textIn this study, flood mitigation measures, both structural and nature-based ones, are proposed, and their social and economic performances are quantified using a multi-criteria decision analysis framework. The effectiveness of the selected measures is evaluated through numerical modeling. As a case study, flood inundation areas and flood hazard maps are determined in the A & gbreve;va District of Istanbul using high-resolution LIDAR data in a 2D hydrodynamic model for different flood scenarios. The numerical model is calibrated against measured discharges at the river gauging station in the river basin. For the social and economic assessment, a total of seven criteria are assessed: number of affected inhabitants, number of affected cultural items, number of public institutions under flood, expected annual damage, investment cost of measures, annual maintenance cost, and benefit-cost ratio. The overall score of each flood mitigation measure alternative is computed, and their performance is compared for different strategies. For our case study, the implementation of a levee exhibits the highest economic and social performance for flood risk management
Lernerperspektiven zu Deutsch als Tertiärsprache nach Englisch: Eine empirische Untersuchung
No full textPolygenic discrimination of leaf morphotypes in alpine Heldreichia bupleurifolia (Brassicaceae) across its natural range
No full textBackground and Aims Leaf morphology is a critical adaptive trait in plants, yet its genetic basis and environmental drivers remain poorly resolved in natural populations. Heldreichia bupleurifolia, a polymorphic alpine species in Turkey, exhibits three distinct leaf morphotypes (entire, mixed, lobed/dissected) across a west-to-east geographical gradient. This study aims to investigate genome-wide patterns of genetic variation associated with these morphotypes, identify candidate loci and pathways involved in phenotypic differentiation, and examine potential environmental correlates/drivers.Methods Using RADseq, we generated 61 286 high-confidence single nucleotide polymorphisms from 131 individuals across 20 populations. Genetic structure was analysed via principal components analysis, while morphotype differentiation was assessed using discriminant analysis of principal components (DAPC) and random forest (RF) classification. Gene Ontology enrichment analysis identified biological pathways linked to candidate loci. Field observations correlated morphotypes with substrate type.Results Three genetic clusters aligned with a west-to-east geographical gradient, with limited congruence to traditional subspecies classifications. DAPC and RF achieved perfect discrimination among morphotypes, identifying 167 loci (90 from DAPC, 83 from RF; five shared) localized to protein-coding regions. Enriched pathways included ion homeostasis and transmembrane transport, critical for nutrient-poor alpine soils. Lobed/dissected-leaved populations exclusively occupied volcanic substrates, while entire/mixed-leaved groups occurred on limestone, highlighting substrate-driven selection.Conclusion Our findings suggest that genetic differentiation among morphotypes may involve stress-related processes, particularly ion transport and homeostasis. The enrichment of these functions among candidate loci, alongside observed correlations between morphotypes and substrate types, also hints at a possible contribution of edaphic conditions. While these associations are correlative and require further validation, they underscore potential links between genotype, phenotype and environment, and highlight the value of integrating genomic and ecological data in alpine plant conservation