Gümüşhane ÜniversitesiGümüşhane ÜniversitesiAçık Erişim Arşivi · RDL Open

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  • MakaleAçık Erişim2026
    Comparison of Radiologic and Clinical Results of Short-Long Level Posterior Fusion in Lenke Type 5C Scoliosis

    Tas, Suleyman K.; Aydin, Abdurrahman; Yetkin, Cem; Albayrak, Akif; Kaygusuz, Mehmet A.

    Background: Lenke type 5C scoliosis is treated surgically with long-segment (nonselective) or short-segment (selective) level fusion. For Lenke type 5C scoliosis, no standardized criteria exist for selecting proximal and distal fusion levels. Studies report that short-segment level fusion patients with correct patient selection have a direct effect on the result of a well-balanced spine. Purpose: To compare the midterm and long-term radiologic and clinical outcomes of short-segment (selective) vs long-segment (nonselective) fusion in Lenke type 5C scoliosis. Design: Retrospective cohort study. Patient sample: This retrospective study evaluated patients who underwent posterior instrumentation for Lenke type 5C adolescent idiopathic scoliosis (AIS) at our institution between 2005 and 2016. Outcome measure: Physiologic measures: radiological evaluations included coronal, sagittal, and spinopelvic balance assessments as well as shoulder balance parameters on X-ray. Functional measures: clinical evaluations were performed using the SF-36 and SRS-22(r) scores. Methods: Patients with Lenke type 5C scoliosis who underwent selective (group 1) or nonselective (group 2) instrumentation were retrospectively analyzed. Group 1 included 47 patients (42 females and five males) with a mean age of 16.1 +/- 2.4 year (range, 12-22), and group 2 included 58 patients (53 females and five males) with a mean age of 16.3 +/- 3.4 yr (range, 12-24; P > .05). Radiological evaluations included coronal, sagittal, and spinopelvic balance assessments, as well as shoulder balance parameters. Clinical evaluations were performed using SF-36 and SRS-22(r) scores; results were compared between the two groups. Results: Both groups exhibited similar results in terms of coronal, sagittal, and spinopelvic balance as well as shoulder balance in many data after surgery (P > .05). Clinical outcomes, assessed via SF-36 mental health and SRS-22(r) scores, did not show statistically significant differences between groups (P > .05), except fort the physical role difficulty domain of the SF-36, where the selective fusion group (77.1 +/- 31.6) showed significantly better scores than nonselective group (58.2 +/- 36.1). However, the mean surgical time and transfusion requirement were significantly lower in the selective fusion group. Conclusion: When appropriately applied, selective fusion achieves comparable radiologic and clinical outcomes to nonselective fusion, with the added advantages of shorter surgical time and lower transfusion requirements.

    • SDG 3 · Sağlık ve Kaliteli Yaşam
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  • MakaleYalnız künye2026
    A comparison of the effects of different light intensities on the current-voltage characteristics of the Si3N4 interface with various thicknesses grown on the (Au: Ti)/n-GaAs (MS) structure

    Bucurgat, Mahmut; Özdemir, Ahmet Faruk; Altindal, Semsettin

    Different thicknesses of Si3N4 insulator layers were grown on an (Au: Ti)/n-GaAs (MS) reference structure to analyze the effect of these layers with/without illumination on the electrical characteristics and compare the results between these structures. With this motivation, current measurements were made as a function of voltage over +/- 3 V, either in the dark or at 20-100 mW cm- 2 illumination with an increment of 20 mW cm- 2. Some important electric and optoelectronic parameters, such as barrier height at zero bias, ideality factor, saturation current at reverse bias, photosensitivity, photoresponsivity, and detectivity, have been determined using currentvoltage data in relation to illumination intensity. To compare the calculation methods used, the basic electrical parameters, the barrier height at zero bias, the ideality factor, and the series resistance were calculated first using the Thermionic Emission Method and then, alternatively, using Cheung functions. Additionally, the dependence of energy of the interface states was investigated using forward bias current voltage data with the ideality factor and barrier height with/without different intensities of illumination, because of their reordering/restructuring in electric field effects and illumination. The voltage-dependent characteristics of resistance of these structures were also determined from Ohm's Law for each illumination intensity.

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  • MakaleYalnız künye2026
    Chemical characterization and bioactivity assessment of Erodium cedrorum subsp. salmoneum extracts supported by in silico analysis

    Yagi, Sakina; Zengin, Gokhan; Zoltan, Cziaky; Jeko, Josef; Ivashchanka, Yahor; Turecka, Katarzyna; Halasa, Rafal; Gucwa, Magdalena; Kochan-Jamrozy, Kinga; Stefanowicz-Hajduk, Justyna

    The growing interest in natural products, particularly as food additives and pharmaceutical raw materials, is making research into discovering new sources especially important. Erodium cedrorum subsp. salmoneum (family Geraniaceae) is used traditionally to cure many ailments like diabetes and gastro-intestinal diseases. Within this background, the current study was designed to investigate, for the first time, the chemical composition, antioxidant and enzyme inhibitory poroperties of different extracts from the aerial parts and roots of E. cedrorum. Results revealed that the aqueous extract of the aerial parts accumulated the highest total phenolic (85.35 mg GAE/g) and flavonoids (28.65 mg RE/g) contents. A total of 61 and 45 compounds, belonging mainly to phenolic acids and flavonoids, were tentatively identified in the aerial parts and roots extracts respectively. The aqueous extract from the aerial parts exerted the highest antiradical, ions reducing and chelation properties. The EtOH and 70% EtOH extracts of the two organs recorded the best anti-acetylcholinesterase activity (2.18 -2.41 mg GALAE/g; p >= 0.05) while those of the roots recorded respectively the best anti-butyrylcholinesterase and antityrosinase activities. The most potent antibacterial activity was exhibited by the 70% EtOH extracts from aerial parts and the pure EtOH extracts from roots. In contrast, ethyl acetate extracts from both plant parts showed only marginal activity. Among the tested strains, the highest susceptibility was observed against C. sporogenes ATCC 19404, C. bifermentans ATCC 638, S. aureus ATCC 6538, S. aureus ATCC 43300 (MRSA), C. diphtheriae PCM 506, and H. pylori ATCC 43504. The extracts were also examined for their anti-cancer potential on the HeLa, AGS and SKOV-3 cell lines, as well as a non-cancerous cell line. The ethyl acetate extract of the roots exhibited the most potent anti-cancer activity, with the lowest IC50 values. In addition, selected top-ranked complexes against AChE, alpha-amylase, representative bacterial and oncogenic targets were further evaluated by molecular docking and 100 ns molecular dynamics (MD) simulations, indicating overall conformational stability and persistent binding. In conclusion, these results position E. cedrorum as a valuable natural source of antioxidant and enzyme-inhibitory agents, meriting further exploration for drug development purposes.

    • SDG 3 · Sağlık ve Kaliteli Yaşam
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  • MakaleYalnız künye2026
    Late Cretaceous hybrid melt sources and flare-up magmatism in the eastern Sakarya Zone, NE Türkiye: Zircon Hf-O constraints and implications for VMS fertility

    Aydin, Faruk; Oguz-Saka, Simge; Karsli, Orhan; Dokuz, Abdurrahman; Moghadam, Hadi Shafaii; Zhao, Junxing; Schmitt, Axel K.

    Understanding melt source evolution during arc-back-arc magmatism is essential for resolving crustal growth processes and the development of felsic-hosted volcanogenic massive sulfide (VMS) systems. Here we integrate new zircon HfO isotope data with published geochronological and whole-rock geochemical datasets to reassess the petrogenesis of Late Cretaceous arc and back-arc magmatic flare-ups in the eastern Sakarya Zone (ESZ), NE T & uuml;rkiye. Two high-flux magmatic episodes are recognized: a Turonian-Santonian pulse (similar to 92-86 Ma) forming the lower volcanic sequence (LVS), and a younger Campanian pulse (similar to 84-75 Ma) forming the upper volcanic sequence (UVS), accompanied by contemporaneous arc-related granitoids. Zircons from both LVS and UVS display predominantly positive epsilon Hf(t) values (+2 to +12) coupled with mantle-like delta O-18 (5.0-5.6 parts per thousand), but contain abundant inherited Mesoproterozoic-Paleozoic cores and show variable two-stage model ages (T-DM (c) = 0.4-1.4 Ga). Together with the peraluminous affinity of many felsic units, these features indicate that the dacite-rhyolite suites hosting VMS deposits were generated by melting of compositionally heterogeneous lower crust variably hybridized by juvenile basaltic inputs. Arc granitoids likewise record a transition from dominantly juvenile, I-type magmatism during the Coniacian-Santonian to more evolved, crust-influenced signatures during the Campanian. We propose that both flare-ups reflect repeated episodes of basaltic underplating and deep-crustal heating, producing voluminous felsic magmas capable of sustaining long-lived hydrothermal systems. The spatial and temporal coincidence between felsic-dominated flare-ups and VMS mineralization suggests that hybridized felsic magmas, rather than purely juvenile mantle melts, played a central role in generating the physiochemical conditions required for metal-bearing hydrothermal fluids in the ESZ.

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  • MakaleAçık Erişim2025
    Pedogenic evidence sheds light on the post-Roman pedo-sedimentological and human history of Tarsus, the Roman capital of CE 60, Cilicia, Mersin, Türkiye

    Kapur, Selim; Akça, Erhan; Kadir, Selahattin; Previtali, Franco; Billor, Zeki; Zucca, Claudio; Casati, Enrico; Eren, Muhsin; Karagöz, Alptekin; Nazik, Atike

    The ancient city of Tarsus is underlying a sediment of 400 cm where the contemporary Tarsus grew. The diffusely stratified layers of the deposited sediment from the Kydnos (Tarsus) river overlying the Roman Road excavation site located in the heart of the modern city. The sediment is laden with technogenic materials. The profile of the stratigraphic layers represents a Pedocomplex (PDC) and its horizons are the Pedomembers (PDMs). All the PDMs were described and sampled for physical, chemical, mineralogical, micromorphological, and thermoluminescense analyses seeking pedogenic evidences. The origin of PDC materials is a fluvial and/or lagoon environment (archaeologically predicted date, about 60 CE, and they are calcareous, high in available P and some are high in total phosphorus contents). They have been partially modified by human activity in a settlement area, thus bringing some historical evidence suggesting that the site was part of the growing city after its abandonment. Thin sections show a vigorous biological degradation of the organic residues in the PDMs along with occasional evidence of soil-forming processes. The preliminary conclusions were extracted from the results obtained through the newly formed hydroxyapatite (Hap) determined by micromorphology, therefore proposing the new suffix pi for the WRB soil naming system. Primary, high temperature and clay minerals together with TL analyses of the layers, were conducted to reveal the provenance and weathering phases of the horizons. The seeds recovered from an inhabited layer helped to interpret the food and medicinal habits of the local society and the contemporary presence of the lagoon.

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  • MakaleYalnız künye2025
    Compositional variability and alteration dynamics of chromitites under greenschist metamorphism in the Kizildag ophiolite, southern Turkiye

    Akmaz, Recep Melih; Uysal, Ibrahim; Su, Ben-Xun; Sen, Ahmet D.; Hu, Wen-Jun; Seitz, Hans-Michael; Mueller, Dirk; Eslami, Alireza

    This study presents a complete alteration sequence in chromitites from the Kizildag ophiolite (southern T & uuml;rkiye), documenting three distinct chromite types that record processes related to Neotethyan subduction. Chromitites exhibit predominantly lenticular forms and occasionally banded textures, embedded within mantle peridotites and the mantle-crust transition zone, specifically harzburgite and dunite. Our analysis categorizes chromite grains into three groups: fresh, altered, and porous. Fresh chromites are characterized by high contents of Cr2O3 ranging from 42.69 to 57.08 wt% and Al2O3 from 12.46 to 25.34 wt%. In contrast, altered chromites, typically located along fractures or at the edges of fresh grains, show significant variability in chemical composition, with Cr2O3 content between 43.34 and 63.94 wt% and Al2O3 between 2.91 and 14.84 wt%. Porous chromites, distinguished by their porous structure, present Cr2O3 contents from 44.58 to 52.66 wt% and Al2O3 from 3.00 to 8.38 wt%. Notably, altered and porous chromites demonstrate substantial enrichments in Fe and trace elements such as Mn, Ni, Zn, Co, and Ga, indicating a shift due to metamorphic processes. The observed high Cr# (0.68-0.93) and low Mg# (0.25-0.65) values in rims of the altered and porous chromite further illustrate the metamorphic influence on chromite, with greenschist-facies conditions indicated by the Cr-Al-Fe3+ diagram at temperatures below 450 degrees C. The alteration dynamics reflect a progression that initiates with the olivine matrix and advances through reactions involving fresh chromites. This progression results in mass loss, the formation of chlorite, and the porous structures. Our findings contribute to the understanding of metamorphic alteration processes in chromitites and provide a detailed account of the geochemical trends (such as Fe/Mg exchange and trace element enrichment) that reflect greenschist-facies metamorphism. The evidence of chlorite formation and the prevalence of porous textures highlight the influence of metamorphic fluids over serpentinization, offering a model for chromite alteration in supra-subduction zones. This research elucidates the metamorphic history of chromitites in the Kizildag ophiolite.

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  • MakaleAçık Erişim2025
    A comprehensive and realistic performance evaluation of post-quantum security for consumer IoT devices

    Hanna, Yacoub; Bozhko, Jessica; Tonyali, Samet; Harrilal-Parchment, Ricardo; Cebe, Mumin; Akkaya, Kemal

    The computational capacity envisaged for quantum computers poses a significant threat to today's traditional cryptographic algorithms. Although they are not yet large enough to compromise current cryptographic protocols, one can practice retrospective decryption since data packets traveling through the Internet can be easily sniffed. This threat extends to wireless communication security within consumer IoT devices that use lightweight cryptography due to limited computational power. Thus, countermeasures against potential quantum attacks should be preemptively adopted. NIST is leading efforts to standardize several algorithms as quantum-resistant Key Exchange Mechanisms (KEMs) and Digital Signatures. In this paper, we investigate the viability of these Post-Quantum algorithms in the Transport Layer Security (TLS) of power-constrained IoT devices. Specifically, it focuses on two widely used IoT network protocol stacks, i.e., Bluetooth Low Energy (BLE) and Wi-Fi. To this end, we build a realistic IoT testbed running IP over BLE. Our evaluation considers the impact of several realistic factors for the first time, such as using a chain of certificates on the server side and incorporating certificate validation methods such as Online Certificate Status Protocol (OCSP) and Certificate Revocation Lists (CRL). We also evaluate the impact of mutual authentication between the server and the client. Utilizing the outcomes of this evaluation, we then propose a novel approach for IoT devices to dynamically choose the most efficient KEM algorithm for TLS based on the device's physical network interface. The performance results provide valuable insights with respect to the TLS latency and energy consumption of consumer IoT devices.

    • SDG 9 · Sanayi, Yenilikçilik ve Altyapı
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  • MakaleAçık Erişim2025
    Log-transformed approaches to variance estimation using auxiliary data

    Singh, Poonam; Sharma, Prayas; Singh, Anjali; Zaman, Tolga; Emam, Walid

    Reliable statistical inference requires accurate population variance estimate, especially in domains where measurement limitations and intrinsic variability impact data. Applying traditional estimators to skewed or heavy-tailed populations frequently results in inefficient results. We provide a novel class of generalized logarithmic variance estimators that use logarithmic transformations and auxiliary data to stabilize variance and improve estimator performance in order to overcome this constraint. We calculate the suggested estimators' bias and Mean Squared Error (MSE) expressions and assess their effectiveness using comprehensive Monte Carlo simulations with different sample sizes. The suggested estimator, Tr1-, produces a significant reduction in MSE up to 57% increase in efficiency (PRE) at n=600 when compared to the usual estimator. The suggested methodologies resilience and suitability for high-variability situations are further confirmed using real-world datasets. In every context, the findings show that the suggested estimators perform better than the current ones in terms of lower MSE and greater PRE. This research demonstrates how logarithmic transformations may be used to create variance estimators that are more accurate and effective, especially when auxiliary variables are provided.

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  • MakaleYalnız künye2025
    Subduction initiation of the Neotethyan Ocean recorded in chromite deposits: A case study of the Kızıldag ophiolite, southern Turkiye

    Uysal, Ibrahim; Akmaz, Recep Melih; Su, Ben-Xun; Demir, Yilmaz; Sen, Ahmet Dundar

    The chromitites of the K & imath;z & imath;lda & gbreve; ophiolite (KO) are primarily characterized by massive and disseminated textures within refractory mantle peridotites, predominantly harzburgite and dunite, with occasional occurrences of banded and nodular chromitites. Based on chromite composition, these chromitites can be classified into two groups exhibiting a broad compositional range: intermediate (0.55 <= Cr# < 0.70, TiO2 = 0.08-0.51 wt%) and high-Cr (0.70 <= Cr# <= 0.77, TiO2 = 0.05-0.28 wt%). The compositions of minor and trace elements align consistently with variations in Cr#. Total PGE (Os, Ir, Ru, Rh, Pt, Pd) contents in these chromitites are generally less than 500 ppb, with many samples showing enrichment of IPGE (Os, Ir, Ru) relative to PPGE (Rh, Pt, Pd). However, certain samples from both groups display elevated PGE concentrations (Sigma PGE(intermediate) = 718 ppb, Sigma PGE(High-Cr) = 866 ppb) compared to other samples. The dominant platinum group mineral inclusions in chromite are Ru-rich laurite [(Ru, Os)S-2], with a single osmiridium (Os-Ir alloy) grain also observed suggesting formation under high-temperature and low & fnof;S-2 conditions. Primary base metal mineral inclusions include millerite and pentlandite. Additionally, some chromite crystals contain single or multi-phase silicate inclusions, such as clinopyroxene, orthopyroxene, olivine, and amphibole. Parental melt compositions, calculated from Al2O3 and TiO2 contents of chromites, indicate that most high-Cr chromitites originated from boninitic melts, whereas intermediate chromitites and some high-Cr samples derived from melts with intermediate compositions. Trace element compositions of amphibole and clinopyroxene inclusions in the chromite crystals from the intermediate group further support crystallization from hydrous intermediate melts. It is proposed that the intermediate chromitite group formed from partial melts influenced by fluids from the subducted oceanic crust during the early stages of subduction initiation, while high-Cr chromitites originated from hydrous melts derived from a more depleted mantle wedge in later stages.

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  • MakaleAçık Erişim2024
    Late pleistocene glacial history of Mount Karadag, SW Turkiye

    Bayrakdar, Cihan; Çilgin, Zeynel; Saris, Faize; Yesilyurt, Serdar; Keserci, Ferhat; Büyükdeniz, Yusuf; Halis, Onur; Vockenhuber, Christof; Ivy-Ochs, Susan; Akçar, Naki

    Glacial landforms in the southwestern part of the Anatolian Peninsula are found at lower elevations than the rest, suggesting that glaciers were present during the Late Pleistocene. Karadag, located west of the Western Taurus Mountains, provides evidence of the climatic conditions that facilitated this extensive glaciation. It is characterized by numerous peaks exceeding 2300 m above sea level (asl), with the highest peak reaching 2418 m, making it the region's largest glaciation area. This high mountain mass is composed mainly of limestone and dolomite. This study focuses on the glacial landforms in Karadag to reconstruct the Late Pleistocene glacial chronology and palaeoclimate of the Western Taurus Mountains. We employed detailed UAV photogrammetry, extensive fieldwork and mapping, surface exposure dating with cosmogenic 36Cl, meteorological measurements, palaeoglacier reconstruction, and palaeo-equilibrium line altitude (pELA) calculations. Karadag, a topographic barrier to humid air masses from the Mediterranean Sea, ranks as the second wettest area in the Western Taurus Mountains. At a meteorological station we installed in Karadag, an annual precipitation of 1700 mm or more was recorded, highlighting its significant precipitation. In Karadag, we have identified two glacial valleys with a maximum length of 4.5 km and six cirques. The glaciers reached their maximum extent around 22.4 f 2.8 ka during the Last Glacial Maximum (LGM), facilitated by the lowering of the pELA to 2090 m. During the LGM, the glaciers covered an area of approximately 3.5 km2 and reached a maximum thickness of about 140 m. Sample TRKR 10 at 2015 m probably belongs to the LGM period. Although a single sample does not conclude definitive conclusions, the presence of the moraine at its highest position indicates the maximum thickness of the glacier. Following the LGM, two more significant glacier advances occurred during the Lateglacial (15.5 f 2.7 ka) and the Younger Dryas (12.4 f 1.1 ka). During the late Pleistocene glaciations, and especially during the LGM, Karadag probably received more precipitation than today, leading to the formation of glaciers at relatively lower elevations than on the Anatolian Peninsula.

    • SDG 13 · İklim Eylemi
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  • MakaleAçık Erişim2024
    Does structural change matter for sustainable development in newly industrialized countries? Fresh evidence from a new sustainability indicator

    Artan, Seyfettin; Erdogan, Sinan; Recepoglu, Muersit; Çakir, Suemeyra cay; Hayaloglu, Pinar; Çakir, Mehmet Ali

    The economic gap between developed and developing economies has been diminishing due to the recent rapid economic growth performance of developing economies. While achieving this swift growth level, developing economies have structurally transformed their economies. However, the impact of this structural change on environmental sustainability remains unclear. Therefore, this study focuses on the impacts of structural change, energy structure, and economic growth on the load capacity factor, a comprehensive sustainability indicator, in newly industrialized countries during 2000-2020. To this end, second-generation panel data techniques, which account for cross-sectional dependence and heterogeneity, are used to provide more robust and reliable estimates. The results show that economic growth, structural change, and fossil energy utilization decrease the load capacity factor while renewable energy utilization increases it. These findings underscore the need for energy efficiency and resource-conscious policies that align with environmental sustainability while promoting economic growth, highlighting their crucial role in the future of sustainable development.

    • SDG 7 · Erişilebilir ve Temiz Enerji
    • SDG 8 · İnsana Yakışır İş ve Ekonomik Büyüme
    • SDG 9 · Sanayi, Yenilikçilik ve Altyapı
    • SDG 13 · İklim Eylemi
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  • MakaleAçık Erişim2023
    Vaccination status of COVID-19 patients followed up in the ICU in a country with heterologous vaccination policy: A multicenter national study in Turkey

    Yildirim, Suleyman; Erkoyun, Erdem; Alpdog, Ozcan; Yilmaz, Huseyin Oguz; Yilmaz, Baris; Dönmez, Gul Erdal; Saritas, Aykut; Gökmen, Necati; Ergan, Begum; Bayrak, Vecihe

    Objective: Vaccination against severe acute respiratory syndrome coronavirus-2 (SARS-2) prevents the development of serious diseases has been shown in many studies. However, the effect of vaccination on outcomes in COVID-19 patients requiring intensive care is not clear.Methods: This is a retrospective multicenter study conducted in 17 intensive care unit (ICU) in Turkey between January 1, 2021, and December 31, 2021. Patients aged 18 years and older who were diagnosed with COVID-19 and followed in ICU were included in the study. Patients who have never been vaccinated and patients who have been vaccinated with a single dose were considered unvaccinated. Logistic regression models were fit for the two outcomes (28-day mortality and in-hospital mortality).Results: A total of 2968 patients were included final analysis. The most of patients followed in the ICU during the study period were unvaccinated (58.5%). Vaccinated patients were older, had higher Charlson comorbidity index (CCI), and had higher APACHE-2 scores than unvaccinated patients. Risk for 28-day mortality and in-hospital mortality was similar in across the year both vaccinated and unvaccinated patients. However, risk for in-hospital mortality and 28-day mortality was higher in the unvaccinated patients in quarter 4 adjusted for gender and CCI (OR: 1.45, 95% CI: 1.06-1.99 and OR: 1.42, 95% CI: 1.03-1.96, respectively) compared to the vaccinated group.Conclusion: Despite effective vaccination, fully vaccinated patients may be admitted to ICU because of disease severity. Unvaccinated patients were younger and had fewer comorbid conditions. Unvaccinated patients have an increased risk of 28-day mortality when adjusted for gender and CCI.

    • SDG 3 · Sağlık ve Kaliteli Yaşam
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  • MakaleAçık Erişim2023
    Ordovician S-type granites in the western Sakarya Zone, NW Turkey; linkage to a back-arc setting

    Karsli, Orhan; Sengun, Firat; Aydin, Faruk; Moghadam, Hadi S.; Dokuz, Abdurrahman; Griffin, William L.; Saka, Simge Oguz; Zack, Thomas

    Turkey's Early Paleozoic tectonic evolution has received much attention in recent years. Early Paleozoic intrusive rocks are mainly distributed across Europe, Turkey (Istanbul-Zonguldak Zone, Strandja Zone, and Tauride Block), and Iran. However, the Early Paleozoic rocks have not yet been identified in north Turkey's Sakarya Zone, and thus the Early Paleozoic paleogeography of the Sakarya Zone remains enigmatic. Here, we provide new field observations, petrography, geochemistry, and geochronology of the western Sakarya Zone to identify the nature, origin, and tectonic setting of the Ordovician magmatic rocks cropping out in the So center dot gut area (Bilecik, northwest Turkey). Our Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) U-Pb analyses on zircons suggest that the So center dot gut metagranites were emplaced at-484-461 Ma (except two zircons with ages of 490 and 494 Ma). There are abundant inherited zircon cores in the So center dot gut metagranites, with ages of >500 Ma to-2.2 Ga. The inherited Cadomian cores give concordant ages of 588 and 572 Ma. The So center dot gut metagranites are felsic and have high SiO2 (72-76 wt%) and K2O (4.1-5.3 wt%) contents, with high K2O/Na2O ratios (1.2-1.9), and low Mg# (17-35) values. The samples are Ca-poor (CaO = 0.52-0.68 wt%) and show peraluminous [A/CNK = molar Al2O3/(K2O + CaO + Na2O) = 1.15-1.28] and high-K calc-alkaline geochemical characters, with high modal content of muscovite (-10%), consistent with S-type compositions. The samples have low REE concentrations, with negative Eu anomalies. Ordovician zircon rims show epsilon Hf(t) values of +3.6 to-35.4, whereas inherited zircon cores have epsilon Hf(t) values of +33.9 to-26.1. Our data, in conjunction with previous studies, suggest that the So center dot gut metagranites were generated by fluid-absent muscovite-dehydration melting of metasediments accumulated in a back-arc setting. This back-arc basin was characterized by a denuded continental crust with abundant pelite-dominated sediments and minor input of juvenile mafic melts. Our results, combined with previously published data and paleogeographic reconstructions, allow us to conclude that the Ordovician S-type granites were formed by progressive back-arc extension and crustal thinning prompted by the rollback of the southward subducting oceanic-lithosphere slab. This led to the opening of the Rheic Ocean on the northern side of Gondwana in response to the final closure and termination of the Tornquist Ocean as a branch of the Iapetus Ocean. We argue that the Ordovician S-type granites from the northern side of Gondwana could signal significant crustal reworking away from any clear continental collision zone.

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  • MakaleYalnız künye2023
    Two-stage bimodal volcanism in a Late Cretaceous arc/back-arc setting, NE Turkey: Constraints from volcano-stratigraphy, zircon U-Pb and 40Ar/39Ar geochronology and whole-rock elemental and Sr-Nd-Pb isotope geochemistry

    Oguz-Saka, Simge; Aydin, Faruk; Karsli, Orhan; Dokuz, Abdurrahman; Aiglsperger, Thomas; Miggins, Daniel P.; Sen, Cuneyt; Kandemir, Raif; Sari, Bilal; Koppers, Anthony A. P.

    The eastern Blacksea magmatic arc (EBMA) in the eastern Sakarya Zone (ESZ) provides an excellent opportunity to investigate birth of an extensional intra-arc and back-arc settings in the Late Cretaceous over the Early Cretaceous northern passive margin of the Neotethys Ocean. Volcano-stratigraphy clearly shows that the Late Cretaceous volcanic activity of the EBMA occurred in two major phases. Bimodality, characterized by mafic/ basaltic rocks at the base and felsic/silicic types on top of it, is a typical feature of the lower (LVS) and upper (UVS) volcanic successions in the Giresun region of the ESZ. U-Pb and Ar-Ar ages support the volcanic suc-cession as two-stage (LVS: ca. 92-85 and UVS: ca. 83-67 Ma) bimodal volcanism. Both the volcanic successions are represented by similar rock types consisting of tholeiitic to calc-alkaline basalt-basaltic andesites and calc-alkaline to shoshonitic dacite-rhyolites. Basaltic (M1-and M2-series) and felsic/silicic (F1-and F2-series) sam-ples of the LVS and UVS have an arc-like signature with enriched large ion lithophile elements (LILEs) and light rare earth elements (LREEs) and depleted high field strength elements (HFSEs). Also, the felsic/silicic samples of the F1-and F2-series show prominent negative Sr and Eu anomalies (Eu/Eu* = 0.4 to 0.9), suggesting that plagioclase fractionation played a key role on the evolution of both felsic series. Bimodal rock series in two phases have a wide range of 87Sr/86Sr(i) (0.7048-0.7075) and 143Nd/144Nd(i) (0.5123-0.5127) ratios with var-iable epsilon Nd(i) values of-3.8 to +3.0. 206Pb/204Pb(i), 207Pb/204Pb(i) and 208Pb/204Pb(i) isotope ratios of the Giresun volcanic rocks vary in the range of 17.97-18.52, 15.55-15.65 and 37.53-38.56, respectively. Geochemical and isotopic data suggest that the parental magma of the M1-basaltic rocks were probably derived from a shallow (spinel-bearing) mantle metasomatized by slab/sediment-derived fluids. In contrast, the M2-basalts seem to have been originated from a deeper mantle source (spinel-garnet transition zone) enriched by slab/sediment-derived fluids and hydrous melts (bulk sediment) metasomatism with some contributions of lower/upper crustal materials. The least evolved basaltic samples in two phases are consistent with moderate (-10-15%) to high degree (-20-30%) partial melting of the metasomatized mantle. The silicic melts of the F1 -and F2-rocks series, on the other hand, were likely derived from melting of lower crustal materials consisting of meta-basalts/andesites and lesser amount of meta-sediments. Subsequently, these melts experienced FC +/- AFC and mixing processes during their ascent and emplacement to generate high-silica (rhyolitic) melts. Our data, combined with previous studies, suggest that two-stage bimodal volcanic rocks of the Late Cretaceous in the ESZ were formed in the transition from an extensional continental intra-arc to a back-arc setting during the north-ward subduction of the northern branch of Neotethys Ocean.

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  • MakaleYalnız künye2022
    Early Cambrian S-type granites in the Sakarya Zone, NE Turkey: A record for transition from subduction to post-collisional extension deduced from U-Pb zircon age and Nd-Hf isotopes

    Karsli, Orhan; Sengün, Firat; Dokuz, Abdurrahman; Aydin, Faruk; Kandemir, Raif; Kristoffersen, Magnus; Santos, Jose Francisco; Hofmann, Mandy; Duygu, Levent

    Cadomian realms have recently received much attention in the Alpine-Mediterranean orogenic belts, with discontinuous outcrops extending from the Alps to the Istanbul Zone, Menderes Massif, Taurides in Turkey and Iran as well. However, they have not been identified in the Sakarya Zone, northern Turkey to date. Here, we present, for the first time, zircon U-Pb geochronology, zircon Hf-isotopes and trace elements as well as whole-rock geochemistry and Nd-isotopes from the Karamese metagranitoid in the Yusufeli (Artvin) area, NE Turkey. The zircon U-Pb age data demonstrate that the Karamese metagranitoid intruded into the Precambrian basement units in the Early Cambrian (ca. 534-530 Ma). Zircon overgrowths in the Karamese metagranitoid interpreted as a result of metamorphic overprint yielded ages of 328 Ma. This age indicates that the Sakarya Zone experienced the Variscan metamorphic events at 328 Ma. The Early Cambrian metagranitoid shows that some rocks in the basement of the Sakarya Zone date back to Precambrian in age. The Karamese metagranitoid is an S-type granite, with high modal content of muscovite (similar to 10%). The samples show highly peraluminous [A/CNK = molar Al2O3/(CaO + K2O + Na2O) = 1.34-1.58] and medium-K calc-alkaline geochemical affinities. The Karamese metagranitoid displays low REE concentrations and a slight positive Eu anomaly and show slightly light REEs and LILEs enrichments, and HFSEs depletions. The samples have negative epsilon(Nd)(t) of -4.76 to -2.90 and epsilon(Hf) (t) of -4.75 to -1.08 values. These geochemical-isotopic characteristics reveal that the Karamase metagranitoid originated through fluid-absent muscovite dehydration melting of heterogeneous metasedimentary source rocks (mostly greywacke), with a minor input of juvenile mafic melt. We argue that the Early Paleozoic metagranitoids along the eastern Sakarya Zone is an expression of crustal thinning in the Cadomian orogenic belt in northern Gondwana, with the tectonic turnover from convergent margin to crustal extension possibly induced by break-off of Tornquist oceanic lithosphere which is a branch of Iapetus Ocean during Early Cambrian.

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  • MakaleAçık Erişim2021
    Chemical compositions by using LC-MS/MS and GC-MS and antioxidant activities of methanolic extracts from leaf and flower parts of Scabiosa columbaria subsp. columbaria var. columbaria L.

    Akar, Zeynep

    The members of the Scabiosa genus are one of the traditional medicinal plants used in the treatment of many diseases, in particular the treatment of scabies. In this study, it was aimed to determine antioxidant activities and chemical composition of methanolic extracts of leaves and flowers of Scabiosa columbaria subsp. columbaria var. columbaria. The phenolic contents of both parts of the plant were analyzed by LC-MS/MS. A total of 6 phenolic compounds were determined and chlorogenic acid was the major compound in both flower and leaf parts of the plants, with 5936.052 mg/g and 8021.666 mg/g, respectively. 6 different methods were used to determine the antioxidant activity of the plant parts. Both leaf and flower parts of the plant showed high antioxidant activity in all tested methods and the antioxidant activity values of the leaf part were measured higher than those of the flower part for four tests. The methanol extracts of the plant parts was analyzed with GC-MS and number of the essential oil compounds in the leaf and flower parts were determined as 17 and 13, respectively. Linalool compound was also found to be common in both parts of the plant. The major compounds of the essential oils were identified as 4Octadecenal (30.01%) in the flower and carvone (35.44%) in the leaf. In addition, terpene derivatives was determined as 90.32% of the highest essential oil group in the leaf, while this value was determined as 1.42% in the flower. For the flower, aromatics were determined as the main component group with 21.31%. (c) 2021 The Author. Published by Elsevier B.V. on behalf of King Saud University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

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  • MakaleYalnız künye2020
    Potential therapeutic effects of ethyl pyruvate and N-acetyl cysteine in an experimental rat model of corrosive esophageal

    Tatli, Ozgur; Pasli, Sinan; Imamoglu, Melih; Cicek, Mustafa; Yadigaroglu, Metin; Sahin, Aynur; Dilaver, Irem; Yulug, Esin; Karaca, Yunus

    Background and study aims: Esophageal burns due to ingestion of corrosive substances are frequently seen in both children and adults. However, there is no standard method of treatment to prevent associated mortality and morbidity. Therefore, this study aimed to evaluate the effects of known antioxidants, namely N-acetyl cysteine and ethyl pyruvate, on esophageal damage due to sodium hydroxide-induced corrosive burns. Materials and methods: Thirty-five female rats were randomly assigned to five equal groups. Group 1 was the sham group, while Group 2 was the control group. Group 3 received N-acetyl cysteine, Group 4 received ethyl pyruvate, and Group 5 received both N-acetyl cysteine and ethyl pyruvate. Rats in the burn groups were gavage-fed with 0.2mL of 25% NaOH. All esophagi were extracted on day 4 for histopathological evaluation. Results: Total histopathological damage scores were evaluated at the end of the study. Groups 3 and 5 were significantly different from the control group in terms of total histopathological scores (p = 0.001), while no significant difference was seen with Group 4. Stenosis index results in groups 3 and 5 were similar to those seen with total histopathological scores (p = 0.004). Conclusion: N-acetyl cysteine, alone or in combination with ethyl pyruvate, may be useful in the treatment of esophageal damage associated with corrosive substances and in achieving histopathological improvement in an experimental setting. (C) 2020 Pan-Arab Association of Gastroenterology. Published by Elsevier B.V. All rights reserved.

    • SDG 3 · Sağlık ve Kaliteli Yaşam
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  • MakaleYalnız künye2020
    Silurian to Early Devonian arc magmatism in the western Sakarya Zone (NW Turkey), with inference to the closure of the Rheic Ocean

    Karsli, Orhan; Sengün, Firat; Dokuz, Abdurrahman; Kandemir, Raif; Aydin, Faruk; Andersen, Tom

    The Rheic Ocean is the most significant Paleozoic ocean that detached peri-Gondwana terranes from the northern Gondwana margin throughout the closure of the Iapetus Ocean. The suture of the Rheic Ocean spreads from Mexico to the Middle East, and the timing of its final closure is well-documented by the rocks formed in the Variscan-Alleghanian-Ouachita orogeny which led to the formation of the supercontinent Pangaea. However, as robust paleomagnetic and quantitative data are mostly lacking, the onset and evolution of the subduction of the Rheic Ocean are highly speculative, and they require further confirmation. Recently, the well-preserved metagranitoids along the western Sakarya Zone (SZ) in Anatolia have been identified, and they provide new data that improve our knowledge on the evolution of the Early Paleozoic Rheic Ocean along the northern Gondwana. Here, we present new geochronological, in situ zircon Hf isotope, and whole-rock geochemical analyses of these metagranitoids from the western SZ to enhance our understanding of the subduction processes of the Rheic Ocean. IA-ICP-MS zircon U-Pb dating demonstrated that the Boziiyuk and Borcak metagranitoids from the western SZ were emplaced during the Silurian to Early Devonian (431 +/- 2.7 to 403 +/- 3.5 Ma). The both granitoids have medium- to high-K. calc-alkaline magmatic character, and exhibit peraluminous to slightly metaluminous geochemical signature. They show a typical arc pattern in terms of trace elements and have a uniform, moderate negative epsilon(Hf) (t) of -3.2 to -9.7, with Mesoproterozoic Hf depleted mantle model ages (T-DM1 = 12 to 1.4 Ga). The geochemical and isotopic characteristics are not consistent with those of depleted mantle melts and melts derived from the crustal rocks in an intracontinental environment. Instead, the parental magma is likely generated from the partial melting of a homogeneous and enriched mantle wedge source. We propose that the Silurian to Early Devonian arc-related magmatism is associated with a northward subduction episode of the Rheic Oceanic lithosphere beneath the peri-Gondwana terranes. Hence, we consider that the opening of Paleotethys Ocean formed in a back-arc basin of subduction in Andean style to the north rather than a continental rift to the south in response to south-directed and short-lived supra-subduction zone (SSZ)-type subduction during the Silurian to Early Devonian. (C) 2020 Elsevier B.V. All rights reserved.

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  • MakaleAçık Erişim2020
    Dynamic thermal modelling of PV performance and effect of heat capacity on the module temperature

    Tuncel, B.; Ozden, T.; Balog, R. S.; Akinoglu, B. G.

    One of the main weaknesses of Si-based Photovoltaic (PV) solar modules is the sensitivity of their efficiency to module (cell) temperature. Especially in locations with long hot seasons, the efficiency loss of PVs due to high temperatures should be considered carefully. Thermal modelling is a method to predict the performance of a PV module using essentially the 1st law of thermodynamics and available data. In this paper, a transient thermal model is described, which considers hourly meteorological data, including wind speed and direction, module parameters, and locational information. In transient analysis, the heat capacity value of PV panel is required, but it is not a parameter specified in the manufacturer's datasheet. Experiments on the heat capacity of PV modules are missing in the literature. The thermal model provides verified performance analysis for a poly-c-Si PV module installed in Ankara, Turkey, with a calculated heat capacity value. And a sensitivity analysis for the heat capacity of the transient thermal model is performed. It is found that the model results are almost invariant under changing module heat capacity values.

    • SDG 7 · Erişilebilir ve Temiz Enerji
    • SDG 13 · İklim Eylemi
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  • MakaleAçık Erişim2020
    Effect of ultrasonication treatment on structural, physicochemical and bioactive properties of pasteurized rosehip (Rosa canina L.) nectar

    Atalar, Ilyas; Saricaoglu, Furkan T.; Odabas, Halil I.; Yilmaz, Volkan A.; Gul, Osman

    The effect of ultrasonication process (US) on the physical and bioactive properties of pasteurized rosehip nectar was investigated. In order to solve sedimentation problem, two amplitude levels (50 and 100%) and different treatment times (5, 10, 15 and 30 min) were applied to rosehip nectars. Mean particle size decreased as amplitude and treatment time increased. US treatment caused to increase in redness and yellowness values of nectars and also color change was found noticeable as 1.9-2.6 at 100% amplitudes. US treated samples showed no sedimentation during storage for 15 days while control sample displayed 74% colloidal stability. All samples showed shear-thinning behavior and were characterized as weak gel network. Total phenolic and carotenoid contents and antioxidant activity was increased by US treatment, however, ascorbic acid content decreased. US treatment can be an alternative technology preventing sedimentation problems during shelf life with minimally affecting bioactive and physical properties of rosehip nectar.

    • SDG 2 · Açlığa Son
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