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Koleksiyondaki öğeler
- 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 - MakaleAçık Erişim2018Scopus SJRQ2Natural convection in an enclosure with a discretely heated sidewall: Heatlines and flow visualization
Saglam, M.; Sarper, B.; Aydin, O.
Natural convection inside a rectangular enclosure is investigated experimentally and numerically. One of the sidewalls is heated discretely by two flush-mounted heat sources. The other sidewall is kept at a constant temperature, while the horizontal walls are unheated. Heat dissipation rates of the heat sources are equal to each other. The aspect ratio of the enclosure (AR) is 2 and the working fluid is air (Pr=0.71). The study is focused on the validation of the two and three dimensional computations under real test conditions against experiments for various modified Rayleigh number values. Experimental study is performed for various modified Rayleigh numbers in the range of 7.7×105 and 3.1×106 while numerical part covers the values between 104 and 5×106. Temperature measurements and flow visualization studies are performed in the experimental work, and streamlines, isotherms and heatlines are presented in the numerical part of the study. From the experimental and numerical studies, it is shown that two dimensional computations reflects the general characteristics of the problem, conduction and radiation heat transfer are not negligible, surface temperatures increase with the modified Rayleigh number and heatline approach is an important tool to analyze convective heat transfer.
AtıfScopus11WoS8OpenAlex8İncele - 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 - MakaleAçık Erişim2016Scopus SJRQ2Investigation of pozzolanic activity of volcanic rocks from the northeast of the Black Sea
Çullu, Mustafa; Bolat, Hakan; Vural, Alaaddin; Tuncer, Ertan
Mineralogical and chemical properties, as well as the pozzolanic activities, of the volcanic rocks in the northeast of the Black Sea were examined. Physical and mechanical tests were conducted on samples collected from the study area and the feasibility of using volcanic rocks as pozzolanic admixture in the concrete industry was investigated. Mortar samples containing admixture in the ratios of 0%, 10%, 20%, 30%, 40%, and 50% were prepared by keeping fineness of pozzolanic admixtures fixed. By using these mortar samples, prismatic mortar samples of 4×4×16 cm were prepared and the samples were cured in water. Their 7-, 28-, and 90-day tensile strengths, compressive strengths, and ultrasonic pulse velocity were determined. As a result, it was determined that volcanic rocks can be used to produce blended cement by considering their specific gravity, pozzolanic activities, and compressive strengths. It was noted that increase in trass rate significantly reduced tensile and compressive strength of cement in the early stage as expected.
AtıfScopus18WoS15OpenAlex19İncele - MakaleYalnız künye2016Scopus SJRQ1Antiproliferative and proapoptotic activity of Turkish propolis on human lung cancer cell line
Demir, Selim; Aliyazicioglu, Yuksel; Turan, Ibrahim; Misir, Sema; Mentese, Ahmet; Yaman, Serap Ozer; Akbulut, Kubra; Kilinc, Kagan; Deger, Orhan
Cancer is a heterogeneous disease, two of whose characteristic features are uncontrollable cell proliferation and insufficient apoptosis. Various studies have investigated the antiproliferative effects of propolis, a natural bee product, from different countries, and its cytotoxic effects have been attributed to its polyphenol contents. The purpose of this study was to show the cytotoxic effects, and possible mechanisms involved, of ethanolic extract of Turkish propolis (EEP) on the human lung cancer (A549) cell line. Cytotoxic activity of EEP on A549 cells was revealed using the MTT assay. Mechanisms involved in the cytotoxic action of EEP on A549 cells were then investigated in terms of apoptosis, mitochondrial membrane potential and cell cycle using flow cytometry, endoplasmic reticulum stress using RT-PCR, and caspase activity using luminometric analysis. EEP exhibited selective toxicity against A549 cells compared to normal fibroblast cells. We determined that EEP arrested the cell cycle of A549 cells at the G1 phase, induced endoplasmic reticulum stress, caspase activity, and apoptosis and reduced mitochondrial membrane potential. These results indicate that Turkish propolis is capable of reducing cancer cell proliferation and may have a promising role to play in the development of new anticancer drugs in the future.
AtıfScopus102WoS105OpenAlex123İncele - Kitap BölümüYalnız künye2017Giffen good or giffen behavior
Ipek, Egemen
AtıfOpenAlex9İncele - MakaleAçık Erişim2020Scopus SJRQ3Emplacement conditions of magma(s) forming Jurassic plutonic rocks in Gümüşhane (Eastern Pontides, Turkey)
Aydinçakir, Emre; Gündüz, Ramazan; Yücel, Cem
In this study, the petrography, mineral chemistry and crystallization conditions were reported for the Alemdar and Işıkdere plutons located in limited areas in the south of the Eastern Pontides. These plutons, which trend mostly in NE-SW directions, were emplaced by cutting the Early-Middle Carboniferous-aged Gümüşhane Granitoid and Early-Middle Jurassic Şenköy formation. Petrographically, the studied plutons are compositionally fine to medium grained quartz-diorite, quartz monzodiorite and tonalite. The rocks in the plutons have granular, poikilitic, monzonitic, graphic and rare porphyritic textures with consist of plagioclase, (An05-92), hornblende (Mg# = 0.52-0.81), biotite (Mg# = 0.32-0.67), orthoclase, quartz and Fe-Ti oxide. According to thermobarometric calculations, plutons have crystallization temperatures, pressures and oxygen fugacity values ranging from 541°C to 938°C, 0.1 to 4.4 kbar, and -23 to-12, respectively. The estimated water content calculated from amphibole is between 4.4 to 7.8%. It can be concluded that the studied plutons were emplaced at mid to shallow crustal depths (~4-15 km).
AtıfScopus12WoS11OpenAlex4TR Dizin7İncele - MakaleYalnız künye2021Scopus SJRQ1Static resistance of axially loaded multiplanar gap KK-joints of Circular Hollow sections at elevated temperatures
Wang, Y.C.; Ozyurt, E.
This paper presents the results of a numerical investigation of the behaviour, and proposes a method to calculate the static resistance of axially loaded Circular Hollow Section Double K-joints (DKK) at elevated temperatures. This type of joints is widely used in building construction, but currently, there is no method to calculate their static resistance at elevated temperatures. The numerical investigations of this paper cover a wide range of design parameters, including brace axial load combination, joint temperature, angles between brace members, longitudinal and transverse gap sizes, chord diameter to thickness ratio and brace diameter to chord diameter ratio. The results of this paper indicate that the ratio of joint elevated temperature resistance to ambient temperature resistance may be lower than the reduction factor for the yield strength of steel at elevated temperatures. There are two joint failure modes, one for small and one for large transverse gap. These failure modes and the demarcation between small and large gaps are independent of joint temperature. For joints with large gap, the ratio of joint resistance at elevated temperature to that at ambient temperature is close to the average of steel yield strength and Young's modulus reduction factors at elevated temperature. For joints with small gap, the joint resistance ratio follows the steel Young's modulus factor variation at elevated temperature if all four braces are under compression, but the trend changes to the average ratio of steel Young's modulus and yield strength reduction factors if the axial brace loads are balanced (compression in two brace members equal to tension force in the other two brace members). Linear interpolation can be applied between these two different loading cases.
AtıfScopus17WoS15OpenAlex17İncele - KitapYalnız künye2019Contemporary Debates on Politics and Public Administration in the Postmodern Era
Ugur, Ömer; Dogan, Kadir Caner
The volume provides a collection of articles on current debates in the fields of politics and public administration. The authors deal with frequently mentioned concepts of our era in political and public administration sciences.
AtıfScopus1OpenAlex6İncele - MakaleAçık Erişim2020Scopus SJRQ4Effect of the COVID-19 pandemic on eating habits and food purchasing behaviors of university students
Yılmaz, Hacı Ömer; Aslan, Ramazan; Unal, Cihan
COVID-19 disease, which has spread rapidly all over the world since the first case was detected in December 2019, has become the primary focus in every country. Radical measures have been taken by governments to prevent the spread of the disease. Precautions and social rules have required drastic changes to daily life activities everywhere. University students who have had to interrupt their educations are one of the affected groups by this disease sociologically, psychologically and physiologically. The aim of this study was planned and conducted to determine the effect of COVID-19 on university students' eating habits and food purchasing behaviors. The study was completed in April 2020 with 866 university students studying and training at the Faculty of Health Sciences, Gümüşhane, Turkey. Research data was obtained by online questionnaire. The questionnaire was prepared with information obtained from a literature review and the opinions of experts. It included questions about eating habits and food purchasing behaviors. The basic result of the study was that COVID-19 disease has caused significant changes in the eating habits and food purchasing behaviors of university students. Primarily, they now paid greater attention to hygiene when food purchasing, and had increased their consumption compared to previously, since they were now home 24 hours a day, seven days a week.
AtıfScopus30WoS22OpenAlex55İncele - Derleme MakaleYalnız künye2021Scopus SJRQ1Assessment of the relationship between renewable energy and employment of the United States of America: Empirical evidence from spectral Granger causality
Çelik, Orkun
In this study, the spectral Granger causality nexus between renewable energy generation and employment for the period February 1973–September 2019 in the USA is examined. The results obtained from the study expresses that there is no spectral Granger causality relationship between renewable energy generation and employment for aforementioned period in the USA. Furthermore, these findings support neutrality hypothesis, which means that there is no causality relation between the variables. In other words, renewable energy generation does not influence employment and employment does not have an effect on renewable energy generation.
AtıfScopus16WoS14OpenAlex20İncele - Kitap BölümüYalnız künye2020From efficiency discussions to democracy in public administration: A theoretical analysis
Dogan, Kadir Caner; Ugur, Omer
AtıfScopus2İncele - Kitap BölümüYalnız künye2020The Impact of Export Promotion Programs on the Technological Intensity of Export Products: The Case of Turkey
Mete, Emrullah; Yildiz, Gizem Akbulut
- MakaleAçık Erişim2021Scopus SJRQ3Experimental and numerical studies on predicting and improving the full-scale wastewater treatment plant hydrodynamics
Şibil, Rahim; Aras, Egemen; Kankal, Murat
This paper presents the results of both experimental and numerical studies on biological wastewater treatment plant (WWTP), oxidation ditches (OD) hydrodynamics to design and develop the desired flow conditions of the WWTP. Computational fluid dynamics (CFD) models were developed using CFD software, ANSYS Fluent (V13) with the three-dimensional, steady, incompressible flow based on the Reynolds-Averaged Navier-Stokes equations for flow field calculations in the combined ODs. Also, three different turbulence models [standard k–ε (ske), renormalization group k–ε (RNG), and realizable k–ε (real)] were performed for a comparative study. The numerical model was verified based on the experimental data in the relative errors for ske, RNG, and real 13%, 17%, and 18%, respec-tively. According to the parametric studies, the hydrodynamic characteristics of the existing WWTP were investigated. The maximum wastewater velocity occurred at the inlet and outlet, affecting the flow field in ODs. Moreover, the water velocity decreased as it moved away from the inlet and outlet locations at vertical and horizontal. It can also be noted that there was no homogeneous flow field distribution in ODs. Because the current OD model needs improvement hydrodynamically, a new original OD geometry was presented to eliminate the hydraulic weakness of existing WWTP by CFD analysis. The new original geometry provides a more homogeneous flow field in ODs that mean it will also help treatment efficiency and energy saving according to the operating principles of this facility.
AtıfScopus8WoS8OpenAlex8İncele - MakaleAçık Erişim2021Solving Bigeometric Volterra Integral Equations by Using Successive Approximations Method
Güngör, Nihan
In this study, the successive approximations method has been applied to investigate the solution for the linear bigeometric Volterra integral equations of the second kind in the sense of bigeometric calculus. The conditions to be taken into consideration for the bigeometric continuity and the uniqueness of the solution of linear bigeometric Volterra integral equations of the second kind are researched. Finally, some numerical examples are presented to illustrate successive approximations method.
AtıfScopus1OpenAlex1TR Dizin1İncele - MakaleYalnız künye2021Scopus SJRQ3The solutions of multiplicative Hermite differential equation and multiplicative Hermite polynomials
Yalçın, Numan
In this work, we give the power series solutions around an ordinary point, in the case of variable coefficients, homogeneous multiplicative differential equations of 2nd order. Further, we introduce the multiplicative Hermite differential equations, multiplicative Hermite polynomials and basic properties of these polynomials.
AtıfScopus17WoS18OpenAlex23İncele - MakaleAçık Erişim2025Scopus SJRQ3New Numerical Solutions for Caputo–Fabrizio Fractional Differential Multidimensional Diffusion Problems
Şahin, Yasin; Merdan, Mehmet
This study examined the multidimensional fractional diffusion equations that characterize the density dynamics in a diffusing medium utilizing the exact and analytical Aboodh transform decomposition method (ATDM). The Caputo–Fabrizio (CF) derivative is utilized to account for the fractional derivative that is being employed here. The suggested method handles nonlinear terms by combining the Adomian decomposition method (ADM) with the Aboodh transform (AT) and Adomian polynomials. Since the AT can only be applied to linear equations, ADM is a helpful technique for estimating solutions to nonlinear differential equations. In nonlinear systems, multidimensional diffusion problems which account for the production of stripes in two-dimensional systems are important. Additionally, we used MATLAB to compute numerical and graphical data that illustrate how the close-form analytical solution compares to the precise solution. Promising and appropriate for addressing multidimensional diffusion problems with fractional derivatives are the obtained results. The key benefit is that our devised approach does not depend on presumptions or constraints on variables that skew the actual issue. Overcoming fluctuating constraints that can make it difficult to discover the answer and represent the problem depends much on this technique. In the domains of science and technology, the approach presented in this work offers exceptional computational accuracy and convenience of use for analyzing and resolving intricate phenomena associated with CF fractional nonlinear partial differential equations.
AtıfScopus6WoS6OpenAlex6İncele - Derleme MakaleYayıncıda açık erişim2024Scopus SJRQ4Biochemical Processes During Cheese Ripening; [Peynir Olgunlaşmasında Biyokimyasal Olaylar]
Atasever, Mustafa; Mazlum, Halit
Cheese ripening entails specific biochemical changes that occur under certain conditions during storage. These changes allow different cheese varieties to develop their unique characteristics. The ripening process is influenced by both primary and secondary biochemical events. These are driven by coagulating enzymes, milk's natural enzymes, and the enzymes of both starter and non-starter microflora. The main biochemical events during cheese ripening include proteolysis, lipolysis, and the metabolism of citrate and lactate. Secondary biochemical reactions then process the primary metabolic products, such as lactic acid, fatty acids, and amino acids. This leads to the formation of volatile compounds like alcohols, aldehydes, ketones, acids, lactones, phenols, esters, and sulfur compounds, which play a crucial role in determining the cheese's quality. These processes give each cheese type its distinctive features, like aroma, taste, color, texture, and pore structure, influencing consumer preferences. This review provides insights into the biochemical events that occur during the cheese ripening period.
AtıfScopus13OpenAlex12İncele - MakaleAçık Erişim2025Scopus SJRQ2Multi-sensor data fusion based on the similarity measure and belief (Deng) entropy under neutrosophic evidence sets
Köseoğlu, Ali; Şahin, Rıdvan; Demir, Ümit
The Dempster–Shafer evidence theory is a very practical concept for handling uncertain information. The foundation of this theory lies in the basic probability assignment (BPA), which exclusively accounts for the degree of support attributed to focal elements (FEs). In this study, neutrosophic evidence sets (NESs) are defined to introduce additional probabilistic measures, aimed at addressing the uncertainty, imprecision, incompleteness, and inconsistency present in real-world information. The basic element of NESs is a neutrosophic basic probability assignment (NBPA), which consists of three components. The truth degree of FEs is represented by the first BPA, the second BPA represents the indeterminacy degree of FEs, and the last BPA characterizes the falsity degree of FEs. In NESs, each support degree of FEs is shown separately without any limitation. Therefore, the general concept of NESs is broader compared to traditional evidence sets and intuitionistic fuzzy evidence sets. Unlike the neutrosophic set (NS), the NBPA method assigns truth-support, uncertainty-support, and false-support degrees, as well as these support degrees, to single and multiple subsets in a discriminative framework. This paper aimed to develop some information measures for NESs, such as neutrosophic Deng entropy (NDE), neutrosophic cosine similarity measure, and neutrosophic Jousselme distance. Then, an improved method based on NDE and neutrosophic cosine similarity measure was established to combine contradictory evidence to increase the influence of reliable evidence on the one hand and to reduce the influence of unreliable evidence on the other hand. Finally, a case involving sensor data integration for target identification was studied to highlight the importance of these innovative ideas. The numerical example demonstrates that the proposed method provides more reliable and superior fusion performance compared to classical models, particularly in scenarios involving high conflict and uncertain information. However, the effectiveness of the method is partially influenced by the structure of the similarity matrix and the entropy parameters, which necessitates careful parameter tuning to achieve optimal results. These limitations are explicitly highlighted to serve as a guide for future improvements and broader applications of the method.
AtıfScopus1WoS1OpenAlex1İncele - MakaleYalnız künye2024Scopus SJRQ1Availability of sedimentary and volcanic rock deposits on Northeastern Turkey as concrete aggregates
Çavdar, Ahmet; Çavdar, Özlem
Turkey has large aggregate deposits; however, these deposits cannot be used effectively due to a lack of controls. This can lead to fatal errors, as in the 6 February 2023 Turkey-Syria earthquakes. The main motivation of this study is to investigate the availability of existing and new aggregate deposits as concrete aggregates in northeastern Turkey. Thus, the quality of aggregates in this region will be studied comparatively. This research was carried out with aggregate samples taken from 30 different rock quarries in 10 different provinces in this region of Turkey. First, the locations of 30 crushed rock aggregates were identified, and their petrographic, mineralogical, physical, geometric and durability properties were determined. Fifteen different test procedures were applied to 30 crushed rock samples. It was concluded that these rocks are generally sedimentary rock types and that 18 of these 30 samples are of limestone origin. To obtain high-strength concrete, in addition to quality cement, the aggregates used must also be of high quality. The use of aggregate resources mentioned in this study for building concrete will contribute to the production of high-strength concrete. These samples, which generally have sufficient physical, mechanical and durability properties, meet the limitations of the standards much better than concrete aggregates. High-statistical-performance regression equations were obtained for the physical and durability properties.
AtıfScopus3WoS3OpenAlex5İncele
