Recep Tayyip Erdoğan Üniversitesi Kurumsal Akademik Arşivi
DSpace@RTEÜ, Recep Tayyip Erdoğan Üniversitesi tarafından doğrudan ve dolaylı olarak yayınlanan; kitap, makale, tez, bildiri, rapor, araştırma verisi gibi tüm akademik kaynakları uluslararası standartlarda dijital ortamda depolar, Üniversitenin akademik performansını izlemeye aracılık eder, kaynakları uzun süreli saklar ve yayınların etkisini artırmak için telif haklarına uygun olarak Açık Erişime sunar.
Güncel Gönderiler
Enhanced carboniferous magmatism reveals the paleo-tethys dual subduction system: New detrital zircon evidence from western Türkiye
(Elsevier, 2026) Xin, Guang-Yao; Lei, Yi-Yang; Chu, Yang; Yang, Zhi-Li; Uysal, Ibrahim; Demir, Yılmaz; Xie, Gen
The tectonic evolution of the Paleo-Tethys Ocean in Türkiye is controversial, especially the polarity of subduction. This study reports new detrital zircon U-Pb ages and trace-element data from Mesozoic-Cenozoic sandstones of the Tavşanlı Zone and the Taurides Belt, both belonging to or tectonically associated with the Anatolide–Tauride Block (ATB), to assess the extent and significance of Carboniferous magmatism. All sampled sandstones show prominent Carboniferous zircon populations. The pooled Tavşanlı dataset has a dominant peak at ca. 304 Ma and a subordinate Cadomian component at ca. 554 Ma, which displays Pontide-affinity age spectra. Their occurrence within the Cretaceous subduction accretionary complex suggests sediment supply from the adjacent Pontides upper plate to the trench-forearc system or recycling of older Pontide-derived clastic material, rather than direct transport across a wide-open oceanic basin. In contrast, the pooled Taurides dataset is characterized by a ca. 320 Ma peak together with prominent Pan-African and Tonian-Grenvillian components at ca. 641 and 973 Ma, respectively, which predominantly records ATB sources. Zircon trace elements indicate a continental-arc affinity, and εHf(t) compilations reveal systematically different magma source characteristics between Pontides and ATB Carboniferous arcs. Integrated stratigraphic, petrologic, and geochronological evidence supports a dual-subduction model: northward subduction beneath Laurasia coexisting with southward subduction beneath Gondwana.
Biomechanical evaluation of cantilever length and arch form in the All-on-4 implant concept: a finite element analysis
(BioMed Central Ltd, 2026) Ok Bostan, Hilal; Yeşil, Zeynep
Background: This finite element analysis (FEA) was performed to evaluate the stress distribution and biomechanical performance of implants, cortical and trabecular bone tissues, and the titanium prosthetic framework in the All-on-4 implant concept. The aim of this study was to investigate the effects of different cantilever lengths and arch forms on the biomechanical behavior of these components. Methods: Digital models representing an edentulous mandible were created in three different arch forms: square, oval, and triangular. In each model, two anterior parallel implants and two posterior tilted implants were placed within the All-on-4 concept. Full arch fixed prostheses with a titanium framework were designed on the implants. For each arch form, cantilever lengths were applied as follows: 5, 10, and 15 mm. To physiologically simulate masticatory forces, the foodstuff loading method was employed. Occlusal loads consisting of a vertical component of 150 N and an oblique component of 100 N were applied to the posterior region. Maximum von Mises stress values were calculated for the implants and titanium framework, whereas maximum and minimum principal stresses were analyzed in the cortical and trabecular bone tissues. Results: In all arch forms, stress values obtained in the implant and titanium framework components under vertical loading were lower compared with those under oblique loading. In contrast, in the cortical and trabecular bone tissues, stress values observed under oblique loading conditions were lower than those under vertical loading. With an increase in cantilever length from 5 mm to 15 mm, stress values in the implant, framework, and bone tissues generally increased across all arch forms. Regardless of loading type, stress values were consistently lowest in the square arch form, followed by the oval and triangular arch forms. However, in the square arch form, higher maximum principal stress values were observed in the cortical bone in the 5 mm cantilever configuration compared with the 10 mm and 15 mm cantilever lengths. Conclusions: The biomechanical performance of the All-on-4 implant concept is influenced by arch form, cantilever length, and loading direction. Clinically, considering patient specific arch form and limiting cantilever length may reduce stress concentrations and support long term success.
Comparative performance of one-stage and two-stage deep learning models for instance segmentation of overhanging dental restorations on bitewing radiographs
(Nature Research, 2026) Hatipoğlu, Ömer; Başar, Özge; Mağat, Güldane; Altındağ, Ali; Pertek Hatipoğlu, Fatma
Accurate detection of overhanging dental restorations on bitewing radiographs is clinically important but remains challenging due to subtle marginal discrepancies. This study aimed to develop and compare deep learning–based instance segmentation models for the automated detection and classification of overhanging restorations, with a specific focus on the relative performances of one-stage and two-stage architectures. A total of 1236 anonymized bitewing radiographs were retrospectively collected and manually annotated using polygon-based segmentation by specialist dentists. The restorations were classified as ideal or overhanging based on established radiographic criteria. One-stage YOLO11-based segmentation models (YOLO11n-, YOLO11s-, and YOLO11m-seg) were compared with two-stage architectures implemented in Detectron2, including the Mask R-CNN, Cascade Mask R-CNN, and PointRend. All models were trained and evaluated using identical train–validation–test splits. Performance was assessed on an independent test set using COCO-style instance segmentation metrics (AP50–95, AP50, AP75, and AR@100), reported both overall and for the clinically relevant overhang class. Uncertainty was quantified using non-parametric bootstrap resampling (B = 200) to derive the 95% confidence intervals. All models achieved high AP50 values, indicating effective coarse localization of the restorations. However, two-stage architectures showed consistently higher AP-based point estimates than the one-stage YOLO-based models at stricter overlap thresholds. Cascade Mask R-CNN achieved the highest overall performance (AP50–95 = 0.703), while PointRend yielded the highest overhang-specific AP-based segmentation performance (Overhang AP50–95 = 0.743). YOLO-based models demonstrated lower AP50–95 values despite relatively strong AP50 performance, reflecting a reduced boundary precision. Increasing the YOLO model capacity did not improve performance. Two-stage instance segmentation models, particularly those incorporating boundary-aware refinement, showed higher AP-based performance than one-stage approaches for detecting overhanging dental restorations on bitewing radiographs in this dataset. These findings highlight the importance of architectural design over model scale alone and suggest that two-stage frameworks may offer advantages for precise evaluation of restoration margins in a controlled experimental setting. However, external validation across centers and imaging systems is required before their suitability for routine clinical decision support applications can be established.
Dynamic strength evolution and multiscale deterioration mechanism of sulfur-bearing cemented tailings backfill under impact loading
(Elsevier, 2026) Chen, Shunman; Li, Lang; Yılmaz, Erol; Yan, Rongfu; Hou, Chao; Wang, Yiming
Sulfur-bearing tailings are increasingly used in cemented tailings backfill (CTB), yet their dynamic response under impact loading remains poorly understood because previous studies have focused primarily on static behavior. To address this gap, this study systematically investigates the dynamic compressive strength (DCS) evolution and microstructural response of sulfur-bearing CTB under impact loading. The effects of elemental sulfur content (0–15 wt% of total solids), curing age (7–56 d), and impact energy (8–16 J) were evaluated through drop-weight impact tests, X-ray diffraction (XRD), scanning electron microscopy (SEM), and image-based porosity analysis. During 7–28 d of curing, DCS initially increased and then decreased with sulfur content, reaching an optimum at 6%. At 7 d and 8 J, 6% sulfur increased DCS by 32.0%. In contrast, after 56 d of curing, increasing sulfur content from 0% to 15% reduced DCS from 4.12 to 0.50 MPa, corresponding to an 87.9% decrease. At 28 d and 16 J, porosity decreased from 27.53% at 0% sulfur to 24.29% at 6%, but increased to 44.44% at 15%. Moderate sulfur content promoted hydration-product formation and pore refinement, whereas excess sulfur and prolonged curing induced gypsum and expansive ettringite accumulation, crystallization pressure, and microcracking. These findings reveal the microstructure-controlled mechanism governing the non-monotonic DCS evolution of sulfur-bearing CTB and provide guidance for its design and long-term stability assessment under dynamic loading.
The predictive role of strain parameters in predicting all-cause mortality in diabetic hypertensive patients with normal left ventricular systolic function in long-term follow-up
(Sakarya University, 2026) Özderya, Ahmet; Emre, Ender; Kalaycıoğlu, Ezgi; Yerlikaya, Murat Gökhan; Gökdeniz, Tayyar; Aktaş, Müjdat; Çetin, Mustafa
Objective: To demonstrate the relationship of all-cause mortality in the long term and speckle-tracking echocardiography parameters in a cohort of diabetic hypertensive cases that had preserved left ventricle ejection fraction (LV-EF). Methods: The study included 141 diabetic hypertensive cases with preserved LV-EF were retrospectively analyzed. After applying exclusion criteria, 121 patients were included. Two groups were formed according to out-of-hospital mortality status. Laboratory and echocardiography data were analyzed. Results: The mean age of the 121 patients was 58.4±8.04 years, and the median follow-up duration was 10.08 years. Echocardiographic left atrial strain parameters, namely left atrium reservoir phase strain (35.7±8.7 vs 29.8±7.3, p-value: 0.047), left atrium conduit phase strain (LAScd%) (17.6±5.8 vs 13.3±4.1, p-value: 0.028), and left atrium reservoir phase peak strain (1.5±0.4 vs 1.22±0.3, p-value: 0.037), were worse in the mortality group. In right ventricular strain evaluation, four-chamber right ventricular strain (RV4CSL%) (26.1±5.4 vs. 20.8±6.2, p-value: 0.005) was also worse in the mortality group. Multivariate analysis revealed that the mean daytime systolic blood pressure (odds ratio [OR]: 1.769, p-value: 0.028), LAScd% (OR: 0.820, p-value: 0.015), RV4CSL% (OR: 0.078, p-value: 0.043) independently predicted mortality. Kaplan-Meier analysis showed that LAScd%≤15.3 and RV4CSL%≤24.8 were predictive of mortality (p-values: 0.023 and 0.016, respectively). Conclusion: Strain parameters, assessed via echocardiography, can be useful diagnostic and follow-up tools for determining prognosis and guiding early risk factor management in diabetic hypertensive patients, especially in comparison to traditional volumetric parameters.
