Sürdürülebilir Kalkınma Amaçları
Yazarlar
- Uzun, Sevda(77)
- Merdan, Mehmet(73)
- Duran, Celal(54)
- Ozdes, Duygu(50)
- Baltaci, Cemalettin(45)
- Kaygusuz, Abdullah(45)
- Kulakaç, Nurşen(39)
- Ashyralyyev, Charyyar(38)
- Karsli, Orhan(37)
- Demir, Selim(36)
- Öztürk, Serkan(36)
- Dokuz, Abdurrahman(35)
- Turan, Ibrahim(35)
- Araz, Onur(33)
- Kandemir, Raif(31)
- Sipahi, Ferkan(30)
- Topal, Fevzi(30)
- Kurt, Kemal(28)
- Peker, Iskender(28)
- Arslan, Mehmet(27)
- Baltacı, Cemalettin(27)
- Maden, Nafiz(27)
- Ozturk, Samet(27)
- Aydin, Aydanur(26)
- Vural, Alaaddin(26)
- Bayrakdaroglu, Serdar(25)
- Kurnaz, Muammer(25)
- Reis, Hatice Catal(25)
- Akar, Zeynep(24)
- Aydin, Faruk(24)
- Gücer, Mehmet Ali(24)
- Topal, Meryem(24)
- Yolcu, Halil(24)
- Yücel, Cem(24)
- Anaç, Halil(23)
- Kankal, Murat(23)
- Ürkek, Bayram(23)
- Aliyazicioglu, Yuksel(22)
- Günen, Mehmet Akif(22)
- Tuncer, Metin(22)
Yayınlar
- MakaleYalnız künye2017Scopus SJRQ2An Investigation of Corrosion Resistance and Antibacterial Sensitivity Properties of Nano-Ag-Doped TiO 2 Coating and TiO 2 Coating Grown on NiTi Alloy with the Micro-Arc Oxidation Process
Karabudak, Filiz; Yeşildal, Ruhi; Şüküroğlu, Ebru Emine; Şüküroğlu, Süleyman; Zamanlou, Hamid; Dikbaş, Neslihan; Bayındır, Funda; Şen, Sadri; Totik, Yaşar
In this study, TiO 2 coatings were grown with nano-Ag doped and micro-arc oxidation technique on NiTi shape memory alloy. The antibacterial sensitivity and corrosion resistance characteristics of both coatings were investigated. The microstructure and composition analyses of the coatings were performed with scanning electron microscope, energy dispersive X-ray spectrometry, and X-Ray diffraction (XRD). The XRD results showed that there were only TiO 2 crystal phases (anatase and rutile) on the coating. The results showed that a clean and dense oxide layer was grown on the surface successfully. The surface of nano-Ag-doped TiO 2-coated samples appear to be smoother than the surface of the coatings without Ag. The corrosion tests of the coated and uncoated samples were carried out in three different environments (simulated body fluid, synthetic saliva, and cola) at 37 ∘ which is human body temperature. The corrosion tests showed that the corrosion resistance of TiO 2-coated and nano-Ag-doped TiO 2-coated samples was much higher than the corrosion resistance of the NiTi substrate. Seven different bacteria including (S. aureus, L. monocytogenes, Bacillus subtilis, Salmonella enteritidis, Yersinia enterocolitica, and E. coli, P.aeruginosa) which have the human pathogen feature were used in the antibacterial susceptibility tests. The process was conducted based on the disk diffusion method to test the susceptibility of bacterial strains on the selected coated and uncoated samples, and antimicrobial activity was evaluated in the nano-Ag-doped TiO 2-coated material; P.aeruginosa, Y. enterocolitica, and E. coli (zone diameter of 8–14 mm) were found to be moderately susceptible; S. aureus, L. monocytogenes, B. subtilis, and S. enteritidis (zone diameters of 8–14 mm) were found to be resistant. The antimicrobial activity of the coating material NiTi was found to be sensitive for all antibacterial tests. According to the TiO 2-coated material results, S. aureus, P.aeruginosa, L. monocytogenes, E. coli were found to be moderately sensitive and Y. enterocolitica, S. enteritidis, and B. subtilis were found to be resistant.
AtıfScopus32WoS29OpenAlex32
İncele - MakaleYalnız künye2017Scopus SJRQ3Remote sensing technique for capturing and exploration of mineral deposit sites in Gumushane metallogenic province, NE Turkey
Vural, Alaaddin; Corumluoglu, Özsen; Asri, Ibrahim
This study examines the determination and confirmation of mineral deposits in the Gumushane Province,Turkey. Rather than using classical techniques, Remote Sensing (RS) and Geographic Information System GIS technologies are applied for this purpose. Mineral alteration traces on the ground are characteristic indicators of ore below the surface. These traces can be determined using RS techniques. The Crosta technique is one of the most important RS image analysis methods used for the determination of mineral alterations. The technique has shown particular usefulness around mine areas, which are rich in ore deposits and show hydrothermal alterations. Therefore, four separate mine fields covering a total area of 718 km2 in the southern part of Gumushane, which is rich in iron oxides, hydroxides and hydrothermal alteration, were chosen. The Crosta technique was applied to the satellite image of each area to explore the regional alterations. The determined locations could be confirmed as alteration areas. Within these four regions, some other locations showing similar alteration patterns were also determined using the Crosta technique. These locations represent good candidates for mineral exploration.
AtıfScopus15WoS12OpenAlex17İncele - MakaleYalnız künye2017Scopus SJRQ3Effect of dc field on ac-loss peak in a commercial Bi:2223/Ag tape
Öztürk, Ali; Düzgün, Ibrahim; Çelebi, Selahattin
Measurements of the ac susceptibility in a commercial Bi:2223/Ag tape for some different ac magnetic field amplitudes, Hac, in the presence of bias magnetic field Hdc directed along Hac are reported. It is found that the peak values of the imaginary component of ac susceptibility χ″max versus Hac trace a valley for the orientation where applied field Ha perpendicular to wide face of the tape total. We note that the observation of the valley depends on various parameters such as field dependence parameter n in the critical current density, in the simple power law expression jc = α(T)/Bn, choice of the bias field Hdc together with selected ac field amplitudes Hac, and dimension and geometry of sample studied. Our calculations based on critical state model with jc = α(1 - T/Tcm)p/Bn using the fitting parameters of n = 0.25, p = 2.2, Tcm = 108 K gives quite good results to compare the experimental and calculated curves.
AtıfScopus1WoS1OpenAlex1İncele - MakaleYayıncıda açık erişim2017Scopus SJRQ2Evaluation of the contraceptive effects of carprofen, flunixin meglumine and meloxicam in rats
Paksoy, Z.; Kirbas, A.
The objective of this study was to determine the suitability of carprofen, flunixin meglumine and meloxicam for use in emergency contraception. Forty-eight pregnant Sprague-Dawley rats were used as material. Five groups were subjected to treatments while one group served as a control. The numbers of animals in each group were equal (n = 8). Treatment groups were administered carprofen (10 mg/kg, single or double dose, s.c.), flunixin meglumine (5 mg/kg, single or double dose, i.m.) and meloxicam (2 mg/kg, a single dose, s.c.) on the third day after mating. The control group received saline. The rats were sacrificed on Day 7 of gestation. Luteal spots and implantation sites were recorded. Pre-implantation loss was calculated by subtracting the number of luteal spots from the number of implantation sites. Compared with the control, the administration of flunixin meglumine (double dose), carprofen (double dose) and meloxicam highly significantly decreased the implantation rate (P < 0.001). Single dose administration of flunixin meglumine and carprofen led to significant decreases (P < 0.01). In conclusion, this study indicates that carprofen, flunixin meglumine and meloxicam treatment cause a decline in implantation rate in rats.
AtıfScopus3WoS2OpenAlex2İncele - MakaleYalnız künye2017Scopus SJRQ2Genome reprogramming in Saccharomyces cerevisiae upon nonylphenol exposure
Bereketoglu, Ceyhun; Arga, Kazim Yalcin; Eraslan, Serpil; Mertoglu, Bulent
Bioaccumulative environmental estrogen, nonylphenol (NP; 4-nonylphenol), is widely used as a nonionic surfactant and can affect human health. Since genomes of Saccharomyces cerevisiae and higher eukaryotes share many structural and functional similarities, we investigated subcellular effects of NP on S. cerevisiae BY4742 cells by analyzing genome-wide transcriptional profiles. We examined effects of low (1 mg/l; <15% cell number reduction) and high (5 mg/l; >65% cell number reduction) inhibitory concentration exposures for 120 or 180 min. After 120 and 180 min of 1 mg/l NP exposure, 187 (63 downregulated, 124 upregulated) and 103 genes (56 downregulated, 47 upregulated), respectively, were differentially expressed. Similarly, 678 (168 repressed, 510 induced) and 688 genes (215 repressed, 473 induced) were differentially expressed in cells exposed to 5 mg/l NP for 120 and 180 min, respectively. Only 15 downregulated and 63 upregulated genes were common between low and high NP inhibitory concentration exposure for 120 min, whereas 16 downregulated and 31 upregulated genes were common after the 180-min exposure. Several processes/pathways were prominently affected by either low or high inhibitory concentration exposure, while certain processes were affected by both inhibitory concentrations, including ion transport, response to chemicals, transmembrane transport, cellular amino acids, and carbohydrate metabolism. While minimal expression changes were observed with low inhibitory concentration exposure, 5 mg/l NP treatment induced substantial expression changes in genes involved in oxidative phosphorylation, cell wall biogenesis, ribosomal biogenesis, and RNA processing, and encoding heat shock proteins and ubiquitin-conjugating enzymes. Collectively, these results provide considerable information on effects of NP at the molecular level.
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İncele - MakaleAçık Erişim2017Scopus SJRQ2Developing web based decision support system for evaluation occupational risks at shipyards
Cebi, Selcuk; Akyuz, Emre; Sahin, Yasin
In this study, a web based decision support system (WBDSS) has been developed to provide decision aid for risk analysis on occupational health and safety at shipyards. The system has been constructed as a modular structure to make its application easy for all kind of firms. The WBDSS is rule based and its database includes safety measures and risks for each tool and machine used in shipbuilding process. In addition, probability and hazard values have been involved in the case of violated measures. The frequencies of the violations that occurred in the work environment are entered to the system by the user. Hence, the system provides a decision support about the risks related to facilities and the cautions to be taken in the workplace. The developed WBDSS has the capability of determining accident, almost accident, and threat formation factors at workplace according to the changing parameters. In this aspect, it enables one to constantly monitor, check and evaluate risk preventive measures. Then, the capabilities of the suggested decision support system have been tested with different scenarios for shipyard processes. When the developed WBDSS is applied to all workplaces, it is aimed at providing a decrease in the number of accidents which cause death, occupational illness, injury, and temporary incapability.
AtıfScopus11WoS11OpenAlex12İncele - MakaleYalnız künye2017Scopus SJRQ1Comparison of low cost 3D structured light scanners for face modeling
Bakirman, Tolga; Gumusay, Mustafa Umit; Reis, Hatice Catal; Selbesoglu, Mahmut Oguz; Yosmaoglu, Serra; Yaras, Mehmet Cem; Seker, Dursun Zafer; Bayram, Bulent
This study aims to compare three different structured light scanner systems to generate accurate 3D human face models. Among these systems, the most dense and expensive one was denoted as the reference and the other two that were low cost and low resolution were compared according to the reference system. One female face and one male face were scanned with three light scanner systems. Point-cloud filtering, mesh generation, and hole-filling steps were carried out using a trial version of commercial software; moreover, the data evaluation process was realized using CloudCompare open-source software. Various filtering and mesh smoothing levels were applied on reference data to compare with other low-cost systems. Thus, the optimum reduction level of reference data was evaluated to continue further processes. The outcome of the presented study shows that low-cost structured light scanners have a great potential for 3D object modeling, including the human face. A considerable cheap structured light system has been used due to its capacity to obtain spatial and morphological information in the case study of 3D human face modeling. This study also discusses the benefits and accuracy of low-cost structured light systems.
AtıfScopus46WoS37OpenAlex42İncele - MakaleYalnız künye2017Scopus SJRQ2Geochemical and isotopic characteristics of stream and terrace sediments of the harsit stream, NE Turkey
Eker, Çiğdem Saydam
The current study compares and contrasts the elemental concentrations and the Nd, Sr and O isotopic compositions of sediments collected from the Harsit Stream bed sediments (HSBS) and terrace sediments (HSTS). There are positive correlations between Al2O3 and SiO2, TiO2, Na2O and Fe2O3, K2O in HSBS and between Al2O3 and Fe2O3, MnO in the HSTS samples. Major element components of HSBS and HSTS are comparable to average upper continental crust. Both types of sediments are generally classified as greywacke, based on chemical composition and O–Sr isotopic compositions. TheɛNd(0) andɛSr(0) values range from −0.6 to −5.7 and from 7.1 to 45, respectively, in HSBS; and from −0.7 to −4.4 and from 20 to 54, respectively, in HSTS. The δ18O values range from 8.8 to 11.8 (average 10.8) in HSBS and from 11.3 to 13.3 (average 12.2) in HSTS, which are generally controlled by detrital or authigenic minerals in the studied samples. The average chemical index of alteration (CIA) and, plagioclase index of alteration (PIA) values are high in HSTS, whereas the index of compositional variability (ICV) and weathering index (WIP) values are high in HSBS. Several minor differences were observed between HSBS and HSTS in terms of geochemistry and isotopic compositions that reflect different processes involved in their sedimentation.
AtıfScopus10WoS9OpenAlex10İncele - MakaleYalnız künye2017Scopus SJRQ1Stereo-based palmprint recognition in various 3D postures
Bingöl, Özkan; Ekinci, Murat
In order to increase performance in palmprint recognition systems, various devices are normally used to restrict the movement of the hand. These can cause problems, especially for those users with physical disabilities. They also cause significant hygiene problems in multi-user systems. Recently, studies on palmprint recognition systems have progressed towards the development of unconstrained, contactless and unrestricted background techniques. The most common problem encountered in these studies is the alignment arising from the free movement of the hand. Despite 3D hand-acquisition devices which offer extra recognition features to overcome this problem, the applicability of these devices is low because of their increased cost. In this study, a stereo camera was proposed. Although due to matching problems, it is difficult to achieve precise, distinct feature extraction in the unrestricted 3D environment used for palmprint recognition, the orientation of the hand in 3D space can be determined by obtaining depth information. In this study, the depth information was extracted by using the binocular stereo approach. First, the orientation of the hand was estimated by fitting a surface model associated with the eigenvectors of the depth information. Pose correction was then accomplished by establishing a relationship between the orientation and the images. The pose correction greatly relieved the perspective distortion that usually occurs within the various poses of the hands. Next, the region of interest was determined by performing segmentation on the corrected images using the Active Appearance Model (AAM). The palmprint features were then extracted via Gabor-based Kernel Fisher Discriminant Analysis. In order to demonstrate the performance of the proposed approach, a new dataset was compiled from stereo images within various scenarios collected from 138 different individuals. As a result of these experimental studies, the EER values, especially on the images captured from different hand orientations in 3D, were reduced from around 14–0.75%. With the help of this suggested approach, the palmprint recognition system was transformed into a more portable form by removing the closed-box mechanisms and equipment restricting movement of the hand. This system can automatically perform pose estimation, hand segmentation and recognition processes without any special intervention.
AtıfScopus34WoS24İncele - MakaleAçık Erişim2017Scopus SJRQ1ZnO and ZnO1−x based thin film memristors: The effects of oxygen deficiency and thickness in resistive switching behavior
Gul, Fatih; Efeoglu, Hasan
In this study, direct-current reactive sputtered ZnO and ZnO1−x based thin film (30 nm and 300 nm in thickness) memristor devices were produced and the effects of oxygen vacancies and thickness on the memristive characteristics were investigated. The oxygen deficiency of the ZnO1−x structure was confirmed by SIMS analyses. The memristive characteristics of both the ZnO and ZnO1−x devices were determined by time dependent current–voltage (I-V-t) measurements. The distinctive pinched hysteresis I-V loops of memristors were observed in all the fabricated devices. The typical homogeneous interface and filamentary types of memristive behaviors were compared. In addition, conduction mechanisms, on/off ratios and the compliance current were analyzed. The 30 nm ZnO based devices with native oxygen vacancies showed the best on/off ratio. All of the devices exhibited dominant Schottky emissions and weaker Poole-Frenkel conduction mechanisms. Results suggested that the oxygen deficiency was responsible for the Schottky emission mechanism. Moreover, the compliance currents of the devices were related to the decreasing power consumption as the oxygen vacancies increased.
AtıfScopus68WoS63OpenAlex71İncele - BildiriAçık Erişim2017Scopus SJRQ3K-Ar dating for determining the age of mineralization as alteration product: A case study of antimony mineralization vein type in granitic rocks of Gümüşhane area, Turkey
Vural, A.
Is it feasible to use K-Ar dating method in determination of the age of mineralization by utilizing alteration minerals? The purpose of this study was to examine the utility of the K-Ar dating method to accurately determine the age of mineralization. In ideal circumstances, dating of alteration products, such as illite and serisite minerals, gives the age of alteration event, which is indirectly associated with mineralization. In the study site, referred to as Avliyana, antimony mineralization (Gümüşhane, Turkey), stibnite (antimony) mineralizations of hydrothermal vein type were observed in granitic young intrusive rocks and the host rocks. In the study area, alteration was observed in the form of a small amount of weak silicification, argillitization (sericitization and illitization), hematitization, limonitization close to the mineralization and of epidotization and chloritization far from the mineralization. In order to determine the limits of the age of antimony mineralizations of the area, the K-Ar method was used to date illite and serisite minerals, which are alteration products related to mineralization. Two samples containing sericite and illite were collected from Avliyana antimonite mineralization. The alteration origin of these minerals was confirmed by supporting petrographic, XRD and scanning electron microscope studies. These samples were analysed for K-Ar dating.
AtıfScopus6WoS5OpenAlex11İncele - MakaleAçık Erişim2017Scopus SJRQ2Excited Muon Searches at the FCC-Based Muon-Hadron Colliders
Caliskan, A.; Kara, S.O.; Ozansoy, A.
We study the excited muon production at the FCC-based muon-hadron colliders. We give the excited muon decay widths and production cross-sections. We deal with the μp→μ∗q→μγq process and plot the transverse momentum and normalized pseudorapidity distributions of final state particles to define the kinematical cuts best suited for discovery. By using these cuts, we get the mass limits for excited muons. It is shown that the discovery limits obtained on the mass of μ∗ are 2.2, 5.8, and 7.5 TeV for muon energies of 63, 750, and 1500 GeV, respectively.
AtıfScopus14WoS8OpenAlex24İncele - MakaleAçık Erişim2017Scopus SJRQ2Effect of brewing conditions on antioxidant properties of rosehip tea beverage: study by response surface methodology
İlyasoğlu, Huri; Arpa, Tuba Eda
The aim of this study was to investigate the effects of brewing conditions (infusion time and temperature) on the antioxidant properties of rosehip tea beverage. The ascorbic acid content, total phenolic content (TPC), and ferric reducing antioxidant power (FRAP) of rosehip tea beverage were analysed. A two-factor and three-level central composite design was applied to evaluate the effects of the variables on the responses. The best quadratic models were obtained for all responses. The generated models were validated under the optimal conditions. At the optimal conditions, the rosehip tea beverage had 3.15 mg 100 mL−1 of ascorbic acid, 61.44 mg 100 mL−1 of TPC, and 2591 µmol of FRAP. The best brewing conditions for the rosehip tea beverage were found to be an infusion time of 6–8 min at temperatures of 84–86 °C.
AtıfScopus31WoS23OpenAlex33İncele - MakaleAçık Erişim2017Scopus SJRQ4The effect of sintering in different atmospheres on superconductivity parameters of YBCO
Başoǧlu, Mehmet
YBa2Cu3O7 (Y123) is a superconductor material discovered in 1987 and its transition temperature is above the liquid nitrogen temperature. It is known that superconductor samples produced by the solid-state reaction route are very often sintered in air atmosphere. However, in the presented work, Y123 was prepared by the same technique using a sintering ambient composed of a mixture of oxygen and argon gases for the first time. Critical current densities of the samples were calculated using results of magnetization measurements. It was obtained from magnetization analysis that all the samples exhibited superconductor character. It was also observed that the sample sintered in the 50% oxygen and 50% argon atmosphere showed the highest critical current density.
AtıfOpenAlex1
İncele - MakaleAçık Erişim2017Scopus SJRQ1A new colorimetric DPPH• scavenging activity method with no need for a spectrophotometer applied on synthetic and natural antioxidants and medicinal herbs
Akar, Zeynep; Küçük, Murat; Doğan, Hacer
2,2-Diphenyl-1-picrylhydrazyl (DPPH•) radical scavenging, the most commonly used antioxidant method with more than seventeen thousand articles cited, is very practical; however, as with most assays, it has the major disadvantage of dependence on a spectrophotometer. To overcome this drawback, the colorimetric determination of the antioxidant activity using a scanner and freely available Image J software was developed. In this new method, the mixtures of solutions of DPPH• and standard antioxidants or extracts of common medicinal herbs were dropped onto TLC plates, after an incubation period. The spot images were evaluated with Image J software to determine CSC50 values, the sample concentrations providing 50% colour reduction, which were very similar with the SC50 values obtained with spectrophotometric method. The advantages of the new method are the use of lower amounts of reagents and solvents, no need for costly spectrophotometers, and thus significantly lowered costs, and convenient implementation in any environment and situation.
AtıfScopus188WoS143OpenAlex169İncele - MakaleYalnız künye2017Scopus SJRQ1An injectable alginate-based hydrogel for microfluidic applications
Akay, Seref; Heils, Rene; Trieu, Hoc Khiem; Smirnova, Irina; Yesil-Celiktas, Ozlem
The objective of this study was to develop an injectable alginate based formulation for immobilizing enzymes into microfluidic systems. The gelation was induced upon lowering the pH by addition of D-glucono-δ-lactone (GDL) and release of Ca+ ions from solid CaCO3. The effects of GDL concentration on enzymatic activity and gelation time were investigated. The results indicated that increasing the GDL concentration increased both surface area and enzymatic activity. Also, chitosan was added to the formulation at different ratios to enhance the stability of enzyme during immobilization. For microfluidic application, 100 μl spiral coil single channel microchip was fabricated and alginate GDL mixture containing β-glucosidase was injected to the microchannel prior to gelation. Enzymatic conversion was performed by pumping substrate (pNPG) through the microchannel. The results indicated that the entire substrate was converted continuously during 24 h without any leakage or deactivation of immobilized enzyme.
AtıfScopus42WoS34OpenAlex38İncele - MakaleYalnız künye2017Scopus SJRQ1An Investigation of the Seismic Behaviour of an Ancient Masonry Bastion Using Non-Destructive and Numerical Methods
Altunisik, A.C.; Adanur, S.; Genc, A.F.; Gunaydin, M.; Okur, F.Y.
Determining the structural behavior of masonry structures is a challenge due to their lack of homogeneity. The seismic behavior of masonry structures is especially complex. The aim of this study was to examine the structural behavior of Zağanos Bastion using both experimental and numerical methods. The Operational Modal Analysis technique, including the Enhanced Frequency Domain Decomposition Method, and the Stochastic Subspace Identification Method were used to illustrate experimentally the dynamic characteristic of the bastion. A finite element model was developed using ANSYS software in order that the dynamic characteristics of the bastion, including natural frequencies and mode shapes, could be calculated numerically. Seismic analysis was carried out using the 1999 Kocaeli earthquake ground motion record to determine the linear and nonlinear seismic behavior of the bastion. The Turkish Earthquake Code and its general technical specifications were used to evaluate the seismic results. The results show that the maximum and minimum principal stresses exerted on the masonry components exceeded the code requirements at some points, but in general the requirements for the stresses were satisfied.
AtıfScopus22WoS22OpenAlex19İncele - MakaleAçık Erişim2017Scopus SJRQ2Reaction of 9-oxabicyclo[4.2.1]non-7-ene-1-ol with tetrazine: An unusually facile intramolecular rearrangement
Kaya, Afşin A.; Salamci, Emine; Menzek, Abdullah; Erdem, Safiye S.; Şahin, Ertan; Ecer, Kadriye
Reaction of (1S*,7R*)-9-oxabicyclo[4.2.1]non-7-en-1-ol (5) with dimethyl 1,2,4,5-tetrazine-3,6-dicarboxylate (6) produced (2R*,4R*)-dimethyl 4-(7-oxooxepan-2-yl)-1,4-dihydropyridazine-3,6-dicarboxylate (11) in a one-pot reaction involving cycloaddition at ambient conditions. The structure of the rearrangement product 11 was determined by X-ray crystallographic analysis. Its formation was discussed based on experimental studies and density functional theory calculations. The driving force of this unusually facile reaction was the stability of the caprolactone product 11 and the extremely exorgenic loss of N2. Structural factors facilitating this rearrangement were also explored employing PCM//M06-2X/6-31G(d, p) calculations.
AtıfScopus22WoS17OpenAlex22İncele - MakaleYalnız künye2017Scopus SJRQ1An on-line HPLC system for detection of antioxidant compounds in some plant extracts by comparing three different methods
Arslan Burnaz, Nesibe; Küçük, Murat; Akar, Zeynep
Echinacea (Echinacea purpurea), green tea (Camellia sinensis) and yaylacayi (Thymus praecox OPIZ subsp. grossheimii (Ronniger) Jalas) are herbs used in traditional medicine because of their beneficial health effects. A high performance liquid chromatography (HPLC) post-column method was developed by coupling HPLC with on-line antioxidant assays using diode array (DAD) and ultraviolet (UV) detectors. Thus antioxidant compounds and fifteen phenolic standards were detected in echinacea, green tea and yaylacayi methanol extracts simultaneously. Later on, the developed on-line HPLC coupled system was used to compare three different antioxidant methods, ABTS [2,2′-Azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid)], DPPH (2,2-diphenyl-1-picrylhydrazyl and FRAP (Ferric reducing antioxidant power). Eight compounds with antioxidant activity were identified as gallic acid, protocatechuic aldehyde, p-OH benzoic acid, chlorogenic acid, caffeic acid, vanillin, ferulic acid, and rosmarinic acid. For validation purposes, LOD (limit of detection) (0.36–14.68 μg/mL) and LOQ (limit of quantification) (1.35–48.92 μg/mL) values were calculated for six standards. The results showed that while the post-column ABTS and FRAP assays were repeatable, sensitive and supportive of each other, the post-column DPPH assay did not provide reliable results. Also due to the base-line noise and drifts in post-column DPPH assay, identification and quantitation of analytes could not be done accurately.
AtıfScopus46WoS42OpenAlex52İncele - Kitap BölümüYalnız künye2017Giffen good or giffen behavior
Ipek, Egemen
AtıfOpenAlex9İncele