Gümüşhane ÜniversitesiGümüşhane ÜniversitesiAçık Erişim Arşivi · RDL Open

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Yeniden eskiyeEskiden yeniye
  • MakaleAçık Erişim2022
    Investigation of the effects of different extraction methods on some biological activities of Dactylorhiza romana subsp. georgica (Klinge) Soó ex Renz & Taubenheim

    Bozkir, Buğra; Acet, Tuba; Özcan, Kadriye

    Dactylorhiza romana subsp. georgica is found in Anatolia and is traditionally used by local people both as food and to alleviate various ailments. Although various biological activities of the plant have been partially investigated, these properties have not been comprehensively revealed in the light of scientific data. In this study, it was aimed to elucidate the antioxidant, antimicrobial, enzyme inhibition (alpha amylase, alpha glucosidase, and tyrosinase) and DNA protective activity and phenolic content of the extracts obtained from orchid tubers using different extraction methods. For this, the fresh and dry tubers of the plant were extracted with ethanol at different times in an ultrasonic water bath, shaker and their combinations with each other. ABTS, DPPH, and FRAP methods were used to determine the antioxidant properties of plant tubers. In addition, the phosphomolybdate method was used to determine the total antioxidant capacity. The spectrophotometric method was preferred to reveal the enzyme inhibition activity. The antimicrobial activity of the extracts was investigated by microdilution method. In addition, the phenolic content of the plant was analysed by HPLC. The DNA protective activity of the extracts was determined by using the pUC 19 plasmid. According to the results obtained, it was revealed that each extract exhibited various biological activities. According to the HPLC results, the highest phenolic component in the extracts was determined as p-hydroxybenzoic acid. As a result, it was observed that the biological activities of orchid tubers changed according to different extraction methods. Accordingly, due to the high biological activities of orchid tubers, they have a high potential for use in the food and pharmaceutical industries.

    • SDG 2 · Açlığa Son
    İncele
  • MakaleYalnız künye2022
    Effect of front, lateral and back dead layer thicknesses of a HPGe detector on full energy peak efficiency

    Kaya, Selim; Çeli̇k, Necati; Bayram, Tuncay

    As well known, High Purity Germanium (HPGe) detectors have a wide range of applications in every area where radiation detection and measurements are involved. One of the most important parameters in this respect is the determination of the full energy peak (FEP) efficiency. There are certain parameters affecting the so-called FEP efficiency. Perhaps the most important one is the thickness of dead layers of the crystal itself. In the current study, we investigated the effects of the thickness of front, lateral and back dead layer thicknesses of the detector crystal on the FEP efficiencies for the energy range 30 keV–5 MeV using EGS4 Monte Carlo simulation package. It was shown that the change in the thickness of the front dead layer has significant effect on the efficiency values for the energy interval 30–400 keV. The change in the thickness of the lateral and back dead layer was shown to have significant effects on the efficiencies for the energy intervals 2–3 MeV and 3–5 MeV, respectively. The results were checked using GEANT4 and a good agreement was observed.

    İncele
  • MakaleYalnız künye2022
    Major tectonic features and geodynamic setting of the Black Sea Basin: Evidence from satellite-derived gravity, heat flow, and seismological data

    Maden, Nafiz; Elmas, Ali

    The origin and development of the Black Sea Basin (BSB) remain controversial. In this study, we determined the main tectonic features of the BSB using satellite gravity, heat flow, and seismological data. Positive gravity anomalies are observed in the arc region due to high-density material, while negative gravity anomalies are seen in the trench region owing to the mass deficiency and sediments. The trench region has a relatively low heat flow anomalies along the Black Sea coasts. The Moho depth increases from 18.11 km in the Eastern Black Sea Basin (EBSB) to 51.83 km in the Eastern Anatolia Plateau (EAP) with an average of 34.13 ± 6.15 km. The lithosphere thickness changed between 78.48 km beneath Anatolia and 120.57 km below the EBSB with an average of 99.17 ± 8.17 km. The low heat flow and Moho temperature values indicate that the lithosphere is strong and cold beneath the BSB. The numerical results, therefore, provide evidence for southward subduction of the Tethys oceanic lithosphere below the Anatolian plate during the late Mesozoic-Cenozoic. Considering all geophysical and geological data, we conclude that the Black Sea Basin represents a relict basin, rather than a back-arc basin.

    İncele
  • MakaleAçık Erişim2022
    Zircon U[sbnd]Pb geochronology and petrology of the tholeiitic gabbro from the Kovanlık (Giresun) area: Constraints for the Late Cretaceous bimodal arc magmatism in the Eastern Pontides Orogenic Belt, NE Turkey

    Temizel, İrfan; Arslan, Mehmet; Abdioğlu Yazar, Emel; Aslan, Zafer; Kaygusuz, Abdullah; Baki Eraydın, Tuğba

    Mafic intrusions of the Eastern Pontides Orogenic Belt (EPOB) in NE Turkey are found rarely in varying ages, sizes and compositions. Of these, tholeiitic gabbro stocks, namely Kovanlık gabbro, consist of pyroxene gabbro and minor hornblende gabbro with a mainly granular texture. The pyroxene gabbro contains plagioclase, clino- and ortho-pyroxene, olivine, and Fe[sbnd]Ti oxides, whereas the hornblende gabbro includes mainly plagioclase, hornblende, rarely biotite and Fe[sbnd]Ti oxides. The clinopyroxene compositions of the pyroxene gabbro exhibit arc-related tholeiitic magmas. The Kovanlık gabbroic rocks have high U/Yb zircon ratios, implying continental arc-related tectonic settings. Zircon U[sbnd]Pb dating on the Kovanlık gabbro yielded a concordia age of ~92 Ma (Turonian). Petrochemically, the gabbroic rocks have a tholeiitic character and show arc- and MORB-like signatures. The gabbroic rocks show positive Rb, Ba, K, Pb, Sr, Ti and negative Nb, Ce, Nd, Hf, Zr anomalies in N-MORB normalized diagrams. The chondrite-normalized REE plots of the rocks show flat to feeble right-dipping REE patterns (LaN/LuN = 0.94–2.56) with positive Eu anomalies (EuN/Eu* = 1.15–2.14; except for two pyroxene gabbro samples). The gabbroic rocks have 87Sr/86Sr(i) ratios (0.704533 to 0.706265), εNd(i) values (4.04–4.85), 206Pb/204Pb (18.56–18.68) and 207Pb/204Pb (15.61–15.64) ratios. Low Nb/La and Nb/Y ratios, as well as high Sr/Yb and Ba/Rb ratios, indicate that source regions were modified by slab-derived fluids and/or melts. The obtained zircon dating, isotopic and geochemical data, as well as regional geology, revealed that the tholeiitic mafic magma derived from a spinel-lherzolite mantle at a relatively shallow depth, and the Kovanlık gabbro in the EPOB represents one of the first mafic intrusions of Late Cretaceous bimodal arc magmatism related to the roll-back of the northwards subducting Tethys oceanic plate.

    İncele
  • MakaleAçık Erişim2022
    COVID-DSNet: A novel deep convolutional neural network for detection of coronavirus (SARS-CoV-2) cases from CT and Chest X-Ray images

    Reis, Hatice Catal; Turk, Veysel

    COVID-19 (SARS-CoV-2), which causes acute respiratory syndrome, is a contagious and deadly disease that has devastating effects on society and human life. COVID-19 can cause serious complications, especially in patients with pre-existing chronic health problems such as diabetes, hypertension, lung cancer, weakened immune systems, and the elderly. The most critical step in the fight against COVID-19 is the rapid diagnosis of infected patients. Computed Tomography (CT), chest X-ray (CXR), and RT-PCR diagnostic kits are frequently used to diagnose the disease. However, due to difficulties such as the inadequacy of RT-PCR test kits and false negative (FN) results in the early stages of the disease, the time-consuming examination of medical images obtained from CT and CXR imaging techniques by specialists/doctors, and the increasing workload on specialists, it is challenging to detect COVID-19. Therefore, researchers have suggested searching for new methods in COVID- 19 detection. In analysis studies with CT and CXR radiography images, it was determined that COVID-19-infected patients experienced abnormalities related to COVID-19. The anomalies observed here are the primary motivation for artificial intelligence researchers to develop COVID-19 detection applications with deep convolutional neural networks. Here, convolutional neural network-based deep learning algorithms from artificial intelligence technologies with high discrimination capabilities can be considered as an alternative approach in the disease detection process. This study proposes a deep convolutional neural network, COVID-DSNet, to diagnose typical pneumonia (bacterial, viral) and COVID-19 diseases from CT, CXR, hybrid CT + CXR images. In the multi-classification study with the CT dataset, 97.60 % accuracy and 97.60 % sensitivity values were obtained from the COVID-DSNet model, and 100 %, 96.30 %, and 96.58 % sensitivity values were obtained in the detection of typical, common pneumonia and COVID-19, respectively. The proposed model is an economical, practical deep learning network that data scientists can benefit from and develop. Although it is not a definitive solution in disease diagnosis, it may help experts as it produces successful results in detecting pneumonia and COVID-19.

    • SDG 3 · Sağlık ve Kaliteli Yaşam
    İncele
  • MakaleYalnız künye2021
    Investigation of wear behavior of graphite additive composite coatings deposited by micro arc oxidation-hydrothermal treatment on AZ91 Mg alloy

    Küçükosman, Rıdvan; Emine Şüküroğlu, Ebru; Totik, Yaşar; Şüküroğlu, Süleyman

    Composite coatings were deposited on AZ91 magnesium alloys by micro arc oxidation (MAO) and the MAO-hydrothermal treatment (HT). The MAO process of Mg alloys was performed in the silicate/phosphate-based electrolyte with graphite particles size of 5-10 and 75 µm and then the obtained samples were submitted to hydrothermal treatment at 150°C in the graphite-ethanol mixture. The structural and morphological properties of composite coatings were analized X-ray diffraction (XRD) and scanning electron microscopy (SEM). The wear resistance was examined with ball-on-disc tribometer. The addition of graphite to the MAO electrolyte solution increased the coating thicknesses and compactness and the surface morphologies acquired relatively a homogeneous appearance. The coating surfaces were enriched in graphite by HT and the wear test results showed that the wear resistance of the graphite-doped MAO-HT composite coatings was significantly improved.

    İncele
  • MakaleYalnız künye2021
    Sodium silicate effect on setting properties, strength behavior and microstructure of cemented coal fly ash backfill

    Cavusoglu, Ibrahim; Yilmaz, Erol; Yilmaz, Ali Osman

    Representing an engineered mixture of coal fly ash, cement and water, cemented coal fly ash backfill (CCB) is typically employed for filling the openings created after coal excavation in the earth. A high rate of productivity for coal mines requires a high early-age strength backfill design. Therefore, the use of admixtures in CCB is key for accelerating the backfill setting time and augmenting short-and long-term strength. This study offers the effect of sodium silicate (SS) as an accelerator on early age mechanical and microstructure properties of CCB. SS-based admixture was used for a dosage of 0.5, 1 and 1.5 wt% in CCB that contains 25 wt% ordinary Portland cement OPC and 75 wt% coal fly ash. Backfill setting time was done by using the Vicat system while its strength and pore structure were measured by using the uniaxial compressive strength test, and scanning electron microscopy and Hg intrusion porosimetry. Results display that use of SS in CCB increases its short-term strength gain up to 14% and shortens the mining cycle by cutting its setting time up to 58%. The microstructure analyses also indicate that CCB formulated with SS has a finer pore structure than that without admixture. The outcomes of the present study will be advantageous to evaluate both setting time and strength behavior of CCB used in coal mines, thereby causing the effective backfill plan in terms of money saving and easy operation.

    • SDG 9 · Sanayi, Yenilikçilik ve Altyapı
    İncele
  • MakaleYalnız künye2021
    Performance evaluation of IEEE 802.15.7 CSK modulation under blue shift effect of optical receiver filters

    Küçük, Mehmet Ali; Türk, Kadir

    In recent years, the use of light-emitting diodes (LEDs) in lighting, which has higher energy efficiency and longer-lasting environmentally friendly lighting compared to conventional lighting devices, has accelerated the development of a promising new technology for short-range wireless optical transmission called visible light communication (VLC). Besides other applications, VLC switches the LEDs at very high speeds to simultaneously realize indoor lighting and data transmission. But the intensity and color of the lighting may vary because of data transmission. Color shift keying (CSK) modulation defined in the IEEE 802.15.7 VLC standard guarantees constant light intensity and color. The CSK receiver uses a band-pass optical filter to separate the light channels. However, the transition band of optical filters shifts towards the blue wavelength depending on the incidence angle of the light which is called the blue shift effect. In this paper, the performance of the CSK receiver is investigated for the first time under the blue shift effect in the case of single and multiple transmitter LED cells. The numerical results show that the blue shift effect significantly decreases system performance. To eliminate the distorting effect, various methods and an adaptive equalizer-based CSK receiver are proposed. The proposed structures provide notable improvement.

    İncele
  • Derleme MakaleAçık Erişim2021
    Microbulb and plantlet formation of a native bulbous flower, Lilium monodelphum M. Bieb, var. Armenum, through tissue culture propagation

    AZERİ, F.N.; Öztürk, G.

    The plant Lilium monadelphum M. Bieb. var. armenum (Mıscz. Ex Grossh) Davis et Henderson recognized as the caucasian lily grows in the Eastern Black Sea Region and is a perennial bulbous species belonging to the Liliaceae family. Its flowers, bulbs, and volatile oils are used in the perfume industry, as a folk medicine to treat eczema and abscess therapy, and as a tranquilizer among regional people respectively. Hence, it is commonly collected from the wild and could become endangered. In this study, we explored the optimal hormone treatment for efficient and rapid induction and production of this species in tissue culture. Explants taken from bulbs were cultured in Murashige and Skoog medium (MS medium, 1962) and modified with TDZ (thidiazuran) (0.5; 1.0; 2.0; 3.0; 5.0 mg/L), after which adventitious buds used for explants during the second stage were subcultured 4 different media supplemented with different concentrations of PAC (paclobutrazol) (0.1; 0.5; 1.0; 2.0 mg/L) to induce microbulbs formation. Microbulbs were cultured in a rooting medium containing IBA (0.5;1.0 mg/L). The highest bud regeneration was observed in medium containing 3.0 mg/L TDZ, 0.25 mg/L NAA and 0.1 mg/L GA3; the highest microbulb formation was observed in medium containing 2.0 mg/L PAC, 0.2 mg/L NAA, and 0.1 mg/L GA3. Besides, plant development from the microbulb was successful for roots in a medium containing 0.5 mg/I IBA and all of the plantlets obtained in tissue culture survived when transferred to the soil.

    İncele
  • MakaleYalnız künye2021
    Towards a circular economy: Investigating the critical success factors for a blockchain-based solar photovoltaic energy ecosystem in Turkey

    Erol, Ismail; Peker, Iskender; Ar, Ilker Murat; Turan, İsmet; Searcy, Cory

    Novel business models can be implemented through digital platforms to enable better circular economy (CE) performance in the renewable energy industry. For example, blockchain can assist in developing innovative business models throughout the solar photovoltaic energy ecosystem (SPVEE) to improve CE. Ranked fifth in total installed photovoltaic (PV) capacity, Turkey, as a developing country, should take the necessary steps and make progress towards achieving CE in the SPVEE. The solar PV industry requires further innovation to address the negative environmental impact of existing linear business models. To ensure favorable results, identifying and evaluating critical success factors (CSFs) are necessary. However, no study has investigated CSFs for SPVEE or any other renewable energy source to achieve a blockchain-based infrastructure towards increased CE performance. Therefore, the goal of this study is to identify and examine the CSFs to improve the performance of a blockchain-based SPVEE towards CE in Turkey. To this end, first, the CSFs for blockchain-based SPVEE were identified through both a literature review and the Nominal Group Technique (NGT). Then, Intuitionistic Fuzzy (IF)-DEMATEL was used to explore their interrelationships based on the expert data. Finally, IF-DELPHI was employed to validate the results. Our findings suggested that effective government incentive programs and regulations are significant for blockchain-based SPVEE towards CE in Turkey. The findings of this study assist macro and micro decision-making in the potential implementation of blockchain in Turkish SPVEE to improve CE. They are also invaluable for other countries and can be used as a reference point.

    • SDG 7 · Erişilebilir ve Temiz Enerji
    • SDG 9 · Sanayi, Yenilikçilik ve Altyapı
    • SDG 12 · Sorumlu Üretim ve Tüketim
    • SDG 13 · İklim Eylemi
    İncele
  • MakaleYalnız künye2021
    Nature of the Early Cretaceous lamprophyre and high-Nb basaltic dykes, NE Turkey: Constraints on their linkage to subduction initiation of Neotethyan oceanic lithosphere

    Karsli, Orhan; İlhan, Mehdi; Kandemir, Raif; Dokuz, Abdurrahman; Aydin, Faruk; Uysal, İbrahim; Duygu, Levent

    Late Mesozoic evolution of the Neotethys Ocean is critical and still remains unclear along the entire Sakarya Zone (SZ), Turkey, because previous interpretations of the Middle to Late Jurassic rifting of the SZ have not been consensually accepted. We identified, for the first time, the Early Cretaceous dykes intruded into the Late Jurassic and Late Carboniferous bodies in the Çamlıkaya (Erzurum) area in the SZ. Here, we present a data set of new field observations, 40Ar/39Ar geochronology, whole-rock geochemical and Sr–Nd isotopes to find out the tectonic setting of previously undated basic to intermediate igneous rocks. 40Ar/39Ar technique on the groundmass separations yielded the plateau ages of 128.78 ± 1.02 to 122.89 ± 0.82 Ma. The investigated dykes are compositionally divided into two sub-groups: calc-alkaline lamprophyres (CAL) and high-Nb alkaline basalts (HNB). They show enrichment in large ion lithophile elements (LILE: e.g., Rb, Ba, K) and depletion in high field strength elements (HFSE: Nb and Ti) as well as moderate fractionation of light rare earth elements relative to heavy rare earth elements. The HNB have high Mg# (47–66), and relatively unradiogenic Sr [87Sr/86Sr(t) = 0.70385 to 0.70510] and Nd [εNd(t) = +0.5 to +5.3] isotopic composition, whereas the CAL possess moderate to high Mg# (32–72), and relatively high Sr [87Sr/86Sr(t) = 0.70586 to 0.71379] and Nd [εNd(t) = +1.5 to −9.9] isotopic composition. Early Cretaceous high-angle subduction triggered upwelling of the asthenosphere at 126 Ma, which likely generated a heat anomaly. This anomaly has probably induced melting of the oceanic slab and the metasomatized mantle to form the CAL and HNB. The HNB were generated by low degrees of melting of mantle domain that was previously reacted by oceanic slab-related adakitic melts at the depths of the garnet stability field (≥70 km). However, the CAL were probably formed at shallower mantle levels within the garnet-amphibole field by a relatively higher degree of melting of the mantle, also modified by subducted slab sediments. A new field, age, and petrochemical data from the Early Cretaceous dykes, combined with the presence of Aptian deep-water sediments to the north and the Late Jurassic-Early Cretaceous platform carbonates deposited in the passive margin setting along the entire SZ, imply the initiation of active-margin magmatism in the SZ. We suggest that the coexistence of the Early Cretaceous CAL and HNB points to the formation of an Andean-type active margin above a north-dipping Neotethyan oceanic slab. Their emplacement ages are associated with the inception of the magmatic arc structure and refer to a significant geodynamic turnover from passive-margin to active-margin tectonics along the SZ.

    İncele
  • MakaleAçık Erişim2021
    Phenolic contents and biological activities of two endemic plants in Turkey

    Acet, Tuba; Çorbacı, Cengiz; Özcan, Kadriye

    In the paper, the phenolic compounds and biological activity of Corydalis oppositifolia DC. and Senecio cilicius Boiss., the endemic plants growing in Turkey, were investigated for the first time. The ethanol extract of C. oppositifolia exhibited more potent antimicrobial activity while the ethanol extract of S. cilicius exhibited the highest radical scavenging activity on ABTS (81.4±1.1a mg TE g−1 extract) and DPPH (23.4±0.2a mg TE g−1 extract). In C. oppositifolia, the highest total flavonoid and phenolic acid contents were found to be in the ethanol (94.2±3.5a mg QE g−1 extract) and methanol (320.5±3.3c mg GAE g−1 extract) extracts, respectively. In S. cilicius, the highest total flavonoid and phenolic acid contents were found to be in the methanol (56.9±0.9c mg QE g−1 extract) and ethanol (568.0±3.3a mg GAE g−1 extract) extracts, respectively. The ethanol extract of C. oppositifolia has the most prominent activity against α-amylase, AChE and BChE whereas the methanol extract of this plant displayed the highest inhibitory activity against α-glucosidase. HPLC analysis of the ethanol extracts revealed that the major flavonoids were kaempferol and quercetin whereas the major phenolic acids were protocatechuic acid, gallic acid, gentistic acid and 2,4-dihydroxybenzoic acid. The findings suggested that the plants and their extracts have the potential to be used in the treatment of diseases such as diabetes and Alzheimer's diseases.

    • SDG 3 · Sağlık ve Kaliteli Yaşam
    İncele
  • MakaleYalnız künye2020
    Determination of geological structures by geophysical and geotechnical techniques in Kırklartepe Dam Site (Turkey)

    Sari, Mahmut; Seren, Aysel; Alemdag, Selcuk

    In foundation research of engineering structures, application of geophysics methods before drilling work allows not only more economical studies but also a more detailed determination of underground sections. Especially in pre-feasibility studies on long tunnel routes, dam sites and lake areas, it has a vital importance in terms of structural safety to determine possible underground buried fault lines, lithology changes, anticlinal-synclinal structures and underground openings. By considering these effective factors, the alluvium/bedrock border and the positions of potential buried faults in the dam site and lake area in the Kırklartepe area of the province of Bayburt in northeastern Turkey were determined by comparison with geophysical and geotechnical methods. First of all, the resistivity of the dam axis location and the change of the Vp wave velocity by depth were determined by comparing the results between geophysical methods of electrical resistivity tomography (ERT) and seismic refraction tomography (SRT), respectively. Afterwards, from the foundation boreholes opened in the dam axis location, joint frequency and the other parameters determined by observations were obtained. With these parameters, 2-dimensional zoning profiles of the dam axis location were formed, and the alluvium-bedrock border and the locations of the buried faults were determined. Two potential faults in the NW-SE direction relative to the location of the dam axis were clearly revealed in the zoning profiles obtained in the ERT and SRT measurements. Additionally, the presence of these faults was determined as a result of examining the separation and joint frequency parameters from the drilling core samples collected from the BH_3 and BH_5 boreholes opened in the investigated area based on changes in the vertical and horizontal directions. In addition to these, in the ERT study, two potential faults other than the determined two were also detected. It was seen in the zoning profiles that these faults corresponded to right under the BH_2 borehole and 60 m SW of the BH_6 drilling. Consequently, in the zoning studies conducted at the examined site, the change in the lithology at the dam axis by depth (alluvium-bedrock border), lateral correlations of boreholes and potential faults were determined. It was recommended for the selected dam axis location to be constructed at a more suitable place in the NW direction in terms of engineering. Furthermore, with this study, it was revealed once again that it is highly essential to use geophysical and geotechnical together in conceptualizing large engineering structure projects.

    • SDG 9 · Sanayi, Yenilikçilik ve Altyapı
    İncele
  • MakaleYalnız künye2020
    Preparation and characterization of bacterial cellulose produced from fruit and vegetable peels by Komagataeibacter hansenii GA2016

    Güzel, Melih; Akpınar, Özlem

    This study focused on the investigation of bacterial cellulose production potency of some fruit and vegetable peels (cucumber, melon, kiwifruit, tomato, apple, quince and pomegranate) with Komagataeibacter hansenii GA2016. Fruit and vegetable peels were hydrolyzed, used for bacterial cellulose (BC) production and their chemical, physical, thermal and structural features were compared to BC from Hestrin–Schramm medium (HSBC) and plant cellulose (CP). Except for pomegranate peel hydrolysate, all the fruit and vegetable peel hydrolysates supplied to K. hansenii GA2016 supported the BC production. Among the fruit and vegetable peel hydrolysates, the highest BC production was observed in kiwifruit peel hydrolysate (11.53%), while the lowest production was observed in apple peel hydrolysate (1.54%). Water-holding capacities of the BCs were ranged from 627.50% to 928.79% and higher than HSBC (609.30%), average fiber diameters were ranged from 47.64 nm to 61.11 nm and thinner than HSBC (74.29) and CP (10,420 nm), crystallinities were ranged from 80.27% to 92.96%, thermal capacities BCs were higher than HSBC and CP. For the BC productions, utilization of the fruit and vegetable peels as the sole nutrient source could reduce the production costs and among the polysaccharides, increase the use of BC in industry.

    • SDG 2 · Açlığa Son
    • SDG 12 · Sorumlu Üretim ve Tüketim
    İncele
  • MakaleYalnız künye2020
    Effect of antimonite mineralization area on heavy metal contents and geochemical fractions of agricultural soils in Gümüşhane Province, Turkey

    Sungur, Ali; Vural, Alaaddin; Gundogdu, Ali; Soylak, Mustafa

    In this study, the possible impacts of an antimonite mineralization area on agricultural lands with regard to heavy metal concentrations were examined. In this scope, surface soil samples (0–20 cm) were taken from a total of 27 locations including eleven from the Avliyana antimonite mineralization area (Torul, Gümüşhane-NW Turkey) and its surroundings, eleven from agricultural areas and five from the control area. Wet digestion method was used with aqua regia procedure for determining the total heavy metal (Cd, Cr, Cu, Ni, Pb, Zn) concentrations of the soil samples. The geochemical fractions of heavy metals in soil samples were determined by way of a sequential extraction procedure. The total heavy metal contents of the soils were determined as: Ni > Cr > Zn > Cu > Pb > Cd for control soils, Cr > Ni > Zn > Cu > Pb > Cd for agricultural soils and Zn > Cu > Ni > Cr > Pb > Cd for mining area soils. It was determined that especially the values of Zn (57.6 ± 6.2 μg/g) and Cu (52.4 ± 5.8 μg/g) were high at the mineralization area due to hydrothermal alterations that are effective in the formation of mineralization. It was put forth as a result of sequential extraction that the heavy metals examined excluding Pb were observed dominantly in the residual fraction for all data set. On the other hand, it was determined that the non-residual mobile fractions reached from 11% Cr to 78% Pb in control soils, from 20% Cd to 88% Pb in agricultural soils and from 24% Cd to 87% Pb in mineralization area soils. Contamination signals due to mineralization area were monitored by way of the metal content in mobile fractions. Even though the metal concentrations determined in short term are not alarming for agricultural production, signals were observed especially for Cd, Pb, Cu, Ni and Zn elements to be more mobile in mineralization area soils in the long term due to the impact of environmental factors thereby being carried over to and accumulating in agricultural soils. In conclusion, while it is expected that the metal inputs due to mineralization areas may increase in the future, it is suggested to include plant analyses in future studies for determining the impact of the amount of bioavailable metal.

    • SDG 2 · Açlığa Son
    İncele
  • MakaleYalnız künye2020
    A study on the variations of recent seismicity in and around the Central Anatolian region of Turkey

    Öztürk, S.

    Variations of the recent seismicity in and around the Central Anatolian region of Turkey were evaluated based on the seismic b-value, standard normal deviate Z-value, GENAS modelling, annual probabilities and return periods of the earthquakes. The catalog includes 16,702 earthquakes between 1974 and 2019 with magnitudes from 1.0 to 6.3. Time distribution of b-value shows that there is a tendency to decrease after the year of 2002 and b-value decreased from 1.58 ± 0.03 to 1.25 ± 0.05 at the beginning of 2019. Annual probabilities for magnitude ranges of 3.0–4.0 have the values between 3 and 30. Return periods for magnitude levels of 5.0–5.5 have the values from 5 to 20 years, and a value of 80 years for magnitude level of 6.0. The GENAS results show the significant temporal variations in the number of earthquakes smaller and larger than specific magnitude intervals by supplying the beginning periods of increases and decreases in the earthquake activity rate. Remarkable reductions in region-time distribution of b-value at the beginning of 2019 were detected in the regions covering Niğde fault and its vicinity along the south, west, northwest and southwest directions, among the Mut Fault Zone, Karsantı-Karaisalı Fault Zone and Karataş-Osmaniye Fault Zone, in and around Sürgü fault and along its northwest direction, between Sürgü fault and East Anatolian Fault Zone. Significant seismic quiescence areas in Z-value distribution include the northwest ends of the Tuzgölü Fault Zone and study area including Akpınar fault, the northeast of Salanda fault, between Salanda fault and the Central Anatolian Fault Zone, the northeast parts of the Central Anatolian Fault Zone, the west of Malatya fault, between Sürgü fault and the East Anatolian Fault Zone, the southeast end of the Tuzgölü Fault Zone, Karsantı-Karaisalı Fault Zone and its vicinity, the southwest of Tuzgölü. Thus, these anomaly areas observed in the Central Anatolian region and its vicinity at the beginning of 2019 may be one of the most likely zones for the next strong/large earthquake occurrences.

    İncele
  • MakaleYalnız künye2019
    A novel endo-β-1,4-xylanase from Pediococcus acidilactici GC25; purification, characterization and application in clarification of fruit juices

    Adiguzel, Gulsah; Faiz, Ozlem; Sisecioglu, Melda; Sari, Bilge; Baltaci, Ozkan; Akbulut, Sumeyya; Genc, Berna; Adiguzel, Ahmet

    A novel extracellular xylanase was purified and characterized from Pediococcus acidilactici GC25 (GenBank number: MF289522). The purification was 4.6-fold with a yield of 43.61% through acetone precipitation, Q-Sepharose, and CM-Sepharose ion change chromatography. The molecular weight of the enzyme was 48.15 kDa, and the optimum pH and temperature were 7.0 and 40 °C, respectively. The maximum activity was observed between 20 and 50 °C. Although it was active within a wide pH range (pH 2.0–9.0), it retained over 85% of its activity after 24 h incubation; and over 70% of its activity after 168 h incubation in neutral and alkaline pH. It was observed that the enzyme showed high stability with K+, Ba2+, Cd2+, Co2+, Sr2+, Mg2+, Ca2+, Al3+, Zn2+, and Ni2+ ions. The Km and Vmax for the xylanase were 3.10 mg mL−1 and 4.66 U/mg protein, respectively. It was determined that treatment of different fruit juices with P. acidilactici GC25 xylanase improved the clarification. The highest increase in the reducing sugar amount and decrease in the turbidity was 24.47 ± 1.08 and 21.22 ± 0.58 for peach juice at 0.15 U/mL enzyme concentration. These results showed that the xylanase purified from P. acidilactici GC25 may have a wide potential in biotechnological processes of the food and baking industry.

    • SDG 12 · Sorumlu Üretim ve Tüketim
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  • MakaleYalnız künye2019
    Adakite-like parental melt generation by partial fusion of juvenile lower crust, Sakarya Zone, NE Turkey: A far-field response to break-off of the southern Neotethyan oceanic lithosphere

    Karsli, Orhan; Dokuz, Abdurrahman; Kandemir, Raif; Aydin, Faruk; Schmitt, Axel K.; Ersoy, E. Yalçın; Alyıldız, Cihangir

    The timing of major tectonic events and the driving mechanisms for magma generation during Late Cenozoic convergence and collision between Arabia and Eurasia still remain unknown. The Sakarya Zone (SZ) in northern Turkey is a critical member of this collisional assemblage. In the easternmost part of the SZ, we have recognized a Late Miocene volcanic suite termed the Çağirankaya volcanics which displays characteristic post-collisional geochemical features. Here, we report a new data set of zircon U–Pb ages, whole-rock major and trace element, as well as Sr–Nd isotope analyses for dacite and andesite samples from the Çağirankaya volcanics. Zircon U–Pb ages for a selected dacitic sample average 5.16 ± 0.11 Ma (mean square of weighted deviates, MSWD = 0.45, n = 35), confirming a late Miocene age of this volcanic episode. The high-K calc-alkaline andesites and dacites exhibit an adakite-like geochemical signature, and are characterized by high Sr (424 to 552 ppm), Sr/Y ratios (31–43), and low Mg# (42 to 46) values, along with low Y (12–14 ppm) and heavy rare earth element (HREE) concentrations, that resemble those in adakites formed by partial melting of hot oceanic slab during subduction. Isotopic compositions are near bulk Earth (87Sr/86Sr(t) = 0.70482 to 0.70489, εNd(t) = +1.08 to +1.33), which rules out a solely asthenospheric origin. Elevated Nb/Ta (14 to 17) and K2O/Na2O (0.6–1.0) imply a juvenile mafic lower crustal source composed of ~20% garnet-bearing amphibolite. Geochemical modeling suggests that adakite-like parental melts were generated in the absence of subduction and without large-scale delamination of lower continental crust. Instead, our findings suggest that Late Miocene adakite-like volcanic rocks in the SZ formed in a post-collisional intra-continental setting, which experienced far-field extension after the subducted slab of the southern Neotethyan branch became detached in the collision zone. Asthenospheric upwelling and underplating of basaltic magma provided the heat for partial melting of lower crustal amphibolite, forming minor amounts of adakite-like melts in the SZ.

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  • MakaleAçık Erişim2019
    Addressing the sneak-path problem in crossbar RRAM devices using memristor-based one Schottky diode-one resistor array

    Gül, Fatih

    Resistive random access memories (RRAMs) are favorable contenders in the race towards future technologies. Moreover, the desirable properties of memristor-based RRAM devices make them very good competitors in this field. The sneak paths problem poses one of the main difficulties in the construction of crossbar memory devices. This problem can be effectively suppressed by applying the 1diode-1resistor (1D1R) design structure. The Schottky diode has many advantages compared to the PN junction diode. The low-power (∼1 µW) ZnO active-layered thin-film (60 nm thick) one Schottky diode-one memristor device fabricated in this study included a top Ag electrode and a bottom Al electrode. The material makeup of the device was confirmed via energy dispersive X-ray spectroscopy (EDAX). The memristive and Schottky diode characteristics of the Ag/ZnO/Al device were resolved by measuring the time-dependent voltage/current. The characteristic pinched hysteresis memristive loops were observed at the first quadrant of the current-voltage plane, whereas the diode curves were seen at the third quadrant. Using the current-voltage curves, the height of the Schottky barrier, ideality factor and threshold voltage of the Schottky diode were found to be 0.68 eV, 3.75 and 0.49 V, respectively. After physical implementation and characterization of the one diode-one memristor device, its anti-crosstalk characteristics were investigated. Taking into account the 10% read margin, the maximum crossbar size was found to be 87.

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  • MakaleYalnız künye2019
    Jurassic acidic magmatism in a back-arc setting, eastern Sakarya Zone, Turkey: Geochemical constraints and an evolutionary model

    Dokuz, Abdurrahman; Sünnetçi, Kadir

    The Early Jurassic in the Sakarya Zone, Turkey, was dominated by basic magmatism. The products of this magmatic episode are found as basaltic lavas and pyroclastic rocks in the Şenköy Formation, which was deposited in an extensional basin, or as intrusives cutting Variscan crystalline basement rocks. The Olur (Erzurum) region in the easternmost part of the Sakarya Zone is one of the few locations where contemporaneous acidic rocks crop out, exposed in an area of ~50 km 2 . The acidic rocks in the eastern Sakarya Zone consist of dacitic lavas, rare pyroclastic rocks, and very rare pebble dikes. Porphyries and trondhjemites are their intrusive equivalents and crop out as dikes and small stocks within the underlying Variscan basement. These Early Jurassic rocks have modal K-feldspar contents of <10% and are trondhjemitic in character. Laser ablation–inductively coupled plasma–mass spectrometry U-Pb dating of zircons from two samples yielded formation ages for these rocks of 185.3 ± 1.0 and 184.1 ± 1.1 Ma (±2σ). Geochemically, the rocks are strongly peraluminous and display a medium- to low-K affinity and sodic compositions (K 2 O/Na 2 O = 0.03–0.49). Enrichment in large-ion lithophile elements and depletion in Nb, Ta, P, and Ti are regarded as signatures of a subduction-related setting. Moderately radiogenic I Sr ratios (0.70508–0.70877) and depleted mantle-like Ɛ Nd (t) values (−0.6 to +3.0) and Pb(t) isotopes suggest that the acidic rocks were derived from juvenile lower crust. Geochemical and isotope data imply that the partial melting of juvenile mafic lithologies of the lower crust produced K-poor tonalitic melts that later fractionated to trondhjemitic melts while ascending to the surface. Considering the available data, we suggest that the Early Jurassic bimodal magmatic rocks of the eastern Sakarya Zone were formed in a back-arc setting during the southward subduction of the Paleotethys oceanic lithosphere. These rocks are a prime example of the formation of shallow subduction products following Late Triassic ridge subduction.

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