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Koleksiyondaki öğeler
- MakaleAçık Erişim2012Scopus SJRQ2The impact of heavy metals on the activity of carbonic anhydrase from rainbow trout (Oncorhynchus mykiss) kidney
Söyüt, Hakan; Beydemir, Şükrü
Many environmental and health problems have become a consequence of contamination of soil and water by toxic heavy metals and organic pollutants in the present age of technology. Heavy metals play vital roles in enzyme activities and other metabolic events with their bioaccumulative and nonbiodegradable properties among aquatic pollutants. Metal toxicity causes irregular metallothioneins protein synthesis, renal damage, and disruption of bone structure in humans and wildlife. In this study, we investigated in vitro effects of some metals on chemical-targeted carbonic anhydrase (CA) enzyme from rainbow trout kidney. The enzyme was purified with a specific activity of 17,285 EU × mg-1 and 31.7% yield and approximately 1800-fold using simple affinity purification method. Molecular weights of the subunit and native enzyme were estimated as 28.7 kDa and 26.9 kDa via sodium dodecyl sulfate polyacrylamide gel electrophoresis and Sephadex-G 200 column, respectively. Other kinetic properties of the enzyme were determined. Apparent Km, Vmax and kcat values were 0.40 mM, 0.097 μmol min-1 and 15.2 s-1 for p-nitrophenylacetate substrate, respectively. Inhibitory effects of cobalt, zinc, copper, cadmium and silver on CA activity were determined using the esterase method under in vitro conditions. IC50 and Ki values were calculated for metals. Ki values for Co2+, Zn2+, Cu2+, Cd2+ and Ag+ were 0.035, 1.2, 34.8, 103 and 257 from Lineweaver-Burk graphs, respectively. Consequently, in vitro inhibition rank order was determined as Co2+ > Zn2+ > Cu 2+ > Cd2+ > Ag+. The potential inhibitor for CA was found as Co2+ from these results.
AtıfScopus17WoS17OpenAlex17
İncele - BildiriYalnız künye2012Scopus SJRQ3Optimization of process parameters for removal of Cr(VI) by Hypnum cupressiforme using response surface methodology (RSM)
Özkan, Esra; Gürses, Ahmet; Açikyildiz, Metin; Güneş, Kübra
Response surface methodology was applied to optimize the removal of chromium ion by Hypnum cupressiforme from an aqueous solution. Experiments were analyzed using response surface methodology (RSM). The biosorption process was investigated as a function of five independent factors, sorption time, sorption temperature, initial ion concentration, sorbent dosage, and mixing rate. The optimum conditions for the chromium biosorption were found to be 760 min, 313K, 30mg/L, 0.01 mg/100mL, 107 min-1 respectively, for sorption time, sorption temperature, initial ion concentration, sorbent dosage, and mixing rate.
AtıfScopus2İncele - MakaleAçık Erişim2011Scopus SJRQ3A new species of Raphignathus Dugés (Acari, Raphignathidae) and newly discovered male of R. Fani Doǧan and Ayyildiz from Turkey
Dönel, Güldem; Doǧan, Salih
A new mite species, Raphignathus kelkitensis n. sp. and a newly discovered male of Raphignathus fani Doǧan and Ayyildiz from Turkey are described and illustrated.
AtıfScopus10WoS9OpenAlex8İncele - MakaleAçık Erişim2012Scopus SJRQ2Synthesis and carbonic anhydrase inhibitory properties of novel bromophenols including natural products
Balaydiin, Halis Türker; Soyut, Hakan; Ekinci, Deniz; Göksu, Sleyman; Beydemir, Şkrü; Menzek, Abdullah; Şahin, Ertan
(2-Bromo-3,4-dimethoxyphenyl) (3,4-dimethoxyphenyl)methanone (10) and its derivatives with Br, one dibromide and isomeric three tribromides, were synthesized. Demethylation of these compounds afforded a series of new bromophenols. Inhibition of human cytosolic carbonic anhydrase II (hCA II) isozyme by these new bromophenols and naturally occurring 3,4,6-tribromo-5-(2,5- dibromo-3,4-dihydroxybenzyl)benzene-1,2-diol (3), and 5,5′-methylenebis(3, 4,6-tribromo-benzene-1,2-diol) (4) was investigated. The synthesized compounds showed carbonic anhydrase inhibitory capacities with IC 50 values in the range of 0.7372 μM against hCA II. Some bromophenols investigated here showed effective hCA II inhibitory activity and might be used as leads for generating novel carbonic anhydrase inhibitors which are valuable drug candidates for the treatment of glaucoma, epilepsy, gastric and duodenal ulcers, neurological disorders, or osteoporosis.
AtıfScopus42WoS43OpenAlex41İncele - MakaleYalnız künye2010Scopus SJRQ2The first occurrence of the mite family linotetranidae (Acari: Tetranychoidea) in Turkey: Linotetranus anatolicus n. sp
Doǧan, Salih; Dönel, Güldem; Ali Bal, Durmus; Sezek, Fatih
A new species Linotetranus anatolicus Doan and Donel, n. sp. collected from soil, litter, oak bark and moss is herein described and figured. This is the first time that the family Linotetranidae has been recorded from Turkey.
AtıfScopus5WoS4OpenAlex6İncele - MakaleAçık Erişim2013Scopus SJRQ1Reference-plane invariant transmission-reflection method for measurement of constitutive parameters of liquid materials
Hasar, Ugur Cem; Barroso, Joaquim José; Kaya, Yunus; Ertugrul, Mehmet; Bute, Musa
We propose a new transmission-reflection method for measuring constitutive parameters of liquid samples inside an asymmetric measurement cell (a sample over a low-loss holder in vertical position inside an empty waveguide section). We derived reference-plane invariant expressions for constitutive parameters measurement of liquid samples from reference-plane dependent scattering parameters. In addition, we also applied a simple approach for unique determination of transformation factor and reference-plane distances. After, we also investigated how the performance of the proposed method could be improved by performing a differential uncertainty analysis. From this analysis, we found the following key results: (a) the accuracy of the proposed method could be enhanced for low-loss liquid samples by using thicker samples, and (b) the effect of constitutive parameters and the length of the (low-loss) sample holder on constitutive parameters measurements of liquid samples by the proposed method is a key parameter in increasing the accuracy of the measurements. Finally, we performed constitutive parameter measurements of distilled water and methanol to validate the proposed method and compared the proposed method with similar methods in the literature. From the measurements, we note that our method is especially useful for liquid sample measurements when the reference-plane transformation factors are not known a priori and/or if the measurements are carried out over a high frequency range.
AtıfScopus20WoS19OpenAlex22İncele - MakaleAçık Erişim2010Scopus SJRQ1Thermodynamics and kinetic studies of biosorption of a basic dye from aqueous solution using green algae Ulothrix sp.
Doǧar, Çetin; Gürses, Ahmet; Açikyildiz, Metin; Özkan, Esra
This study addresses removal of a basic dye, methylene blue, from aqueous solutions by using dried Ulothrix sp. biomass as biosorbent. The effects of the initial dye concentration, contact time, temperature, solution equilibrium pH, biosorbent dosage, and mixing rate on biosorption of the dye have been investigated. It was found that 30 min is sufficient in order to reach adsorption equilibrium. The amount of methylene blue adsorbed onto Ulothrix sp. increased with increasing equilibrium pH and mixing rate, in contrary, it decreased with increasing temperature and sorbent dosage. The process followed the pseudo-second-order kinetic model. The isosteric enthalpy and entropy values were calculated as -11.8 kJ/mol and 37.5 J/(mol K), respectively. In addition, the results suggest that the physical interactions between sorbent particles and sorbate ions play an important role for the adsorption of methylene blue onto the biosorbent.
AtıfScopus80WoS74OpenAlex85İncele - BildiriYalnız künye2009Investigation of the effect of a polypropylene fiber material on the shear strength and CBR characteristics of high plasticity Ankara clay
Mollamahmutoglu, M.; Yilmaz, Y.
Nowadays, many soil improvement methods have evolved with different materials used. In this study, a series of laboratory tests are carried out to investigate the effect of a polypropylene fiber material on the shear strength and California Bearing Capacity (CBR) characteristics of high plasticity Ankara clay. First, geotechnical properties of Ankara clay are presented. Then, results of unconfined compressive strength, triaxial strength (CU type) and CBR tests conducted on the various polypropylene fiber/clay mixtures (0.1%, 0.2%, 0.3% and 0.4% by dry weight) are given. Samples were compacted at optimum moisture contents and maximum dry unit weights obtained from the standard Proctor compaction effort. Standard Proctor compaction tests and CBR tests revealed that percentage of 19 mm length F type polypropylene fiber did not influence much the optimum moisture content, maximum dry unit weight and CBR values. Unconfined compression tests showed that inclusion of fiber content increased the axial strain at failure. Moreover, consolidated-undrained (CU) triaxial test results exhibited that due to inclusion of 19 mm length F type polypropylene fiber, the cohesion intercept decreased slightly but the internal angle of friction increased considerably.
AtıfScopus2İncele - BildiriAçık Erişim2012Scopus SJRQ1The relation of collector and storage tank size in solar heating systems
Çomakli, Kemal; Çakir, Uǧur; Kaya, Mehmet; Bakirci, Kadir
The most popular method to benefit from the solar energy is to use solar water heating systems since it is one of the cheapest way to benefit from the solar energy. The investment cost of a solar water heating system is very low, and the maintenance costs are nearly zero. Using the solar energy for solar water heating (SWH) technology has been greatly improved during the past century. A storage tank is used in many solar water heating systems for the conservation of heat energy or hot water for use when some need it. In addition, domestic hot water consumption is strongly variable in many buildings. It depends on the geographical situation, also on the country customs, and of course on the type of building usage. Above all, it depends on the inhabitants' specific lifestyle. For that reason, to provide the hot water for consumption at the desirable temperature whenever inhabitants require it, there must be a good relevance between the collectors and storage tank. In this paper, the optimum sizes of the collectors and the storage tank are determined to design more economic and efficient solar water heating systems. A program has been developed and validated with the experimental study and environmental data. The environmental data were obtained through a whole year of operation for Erzurum, Turkey.
AtıfScopus103WoS87OpenAlex108İncele - MakaleYalnız künye2008Scopus SJRQ1The removal of lignin and phenol from paper mill effluents by electrocoagulation
Uǧurlu, M.; Gürses, A.; Doǧar, Ç.; Yalçin, M.
This study aims to investigate the treatment of paper mill effluents using electrocoagulation. Removal of lignin, phenol, chemical oxygen demand (COD) and biological oxygen demand (BOD) from paper mill effluents was investigated at various current intensities by using different electrodes (Al and Fe) and at various electrolysis times (1.0, 2.5, 5.0 and 7.5 min). It was observed that the experiments carried out at 12 V, an electrolysis time of 2 min and a current intensity of 77.13 mA were sufficient for the removal of these pollutants with each electrode. The removal capacities of the process using an Al electrode were 80% of lignin, 98% of phenol, 70% of BOD, and 75% of COD after 7.5 min. Using an Fe electrode the removal capacities were 92%, 93%, 80% and 55%, respectively. In addition, it was found that removal of lignin, phenol, BOD and COD increased with increasing current intensity. In the experiments carried out at different current intensities, higher removal can be explained through a decrease in intra-resistance of solution and consequently an increase at the transfer speed of organic species to electrodes. It was also found that Al electrode performs higher efficiency than Fe electrode except for COD removal. However, the time required for removal of BOD was more than that of COD. The results suggest that electrocoagulation could be considered as an effective alternative to paper mill effluents treatment.
AtıfScopus257OpenAlex275İncele - BildiriAçık Erişim2012Scopus SJRQ2An evaluation index system for prediction of technology commercialization of investment projects
Altuntas, Serkan; Dereli, Turkay
Technology commercialization is a hot topic for governments, entrepreneurs, marketers and researchers due to the fact that its measurement is quite important for decision makers to know their possible growth potential in a dynamic and competitive environment. Having a high technology commercialization potential for invested technology is the engine of national development and growth as well. However, the measuring technology commercialization of any investment project is difficult because of the fact that there are some difficult questions, which should be answered exactly. For example, 'how will the technology be marketed in own sector?' 'Which factors are important for considered technology and affect technology commercialization?' 'Which scientific methods should be used for predication of technology commercialization potential properly?' and so on. The purpose of this study is to develop an evaluation index system for predicting the technology commercialization of the investment project. At the beginning of this study, a review of the technology commercialization literature is performed to address the factors which affect technology commercialization. Then, the evaluation index system proposed in this study can be used to prioritize investment projects in terms of their technology commercialization potential. It uses fuzzy multi-criteria decision making (FMCDM) methods and beta distribution to estimate the mean of each factor. Next, a solution approach to find an index value which shows technology commercialization potential is proposed. The proposed approach firstly finds interrelationships among the factors under fuzziness by using the fuzzy decision-making trial and evaluation laboratory (Fuzzy DEMATEL) method. Subsequently, it makes use of the fuzzy Analytic Network Process (Fuzzy ANP) method to determine the weights of factors. The values of all factors are then predicted by experts and assessed by beta distribution to estimate the mean of each factor with respect to the experts' opinion. Finally, a case study is presented to demonstrate the usefulness of the proposed approach.
AtıfScopus25WoS18OpenAlex34İncele - MakaleAçık Erişim2011Scopus SJRQ3The effects of silica fume and fly ash on the scaling resistance and flexural strength of pavement concretes
Yener, Engin; Hinislioǧlu, Sinan
The purpose of this study is to investigate the effects of Silica Fume (SF) and Fly Ash (FA) additives on the frost salt scaling resistance and flexural strength properties of pavement concrete. An attempt is also made to attain a more durable and higher strength concrete by a suitable combination of Ordinary Portland Cement (OPC), SF and FA. SF and FA are used as cement replacement in proportions of 0, 5, 10% and 0, 5, 10, 15% by weight respectively. Flexural strength is tested after 7, 28 and 91 days of the lime saturated water curing period. The experimental results indicate that using FA only decreases while SF only slightly increases 28-days flexural strength. On the other hand, using SF and FA together shows relatively more strength gain. Among all those tested, maximum 28 days flexural strength of 4.53 MPa is obtained for the mix proportions of 85% OPC + 10% FA and 5% SF. SF significantly decreases the amount of liquid absorption by capillary suction and has a significant effect on the scaling resistance. In addition, all the ternary mixtures showes better scaling resistance than the control mixture with 100% OPC.
AtıfScopus13WoS23İncele - MakaleYalnız künye2012Scopus SJRQ2Reflection and refraction of a harmonic SH wave at the interface of two dissimilar media with microheterogeneity
Altan, Burhanettin S.
Reflection and refraction of harmonic SH-waves from the interface of two dissimilar media with microheterogeneity is studied. The effect of the microheterogeneity on the overall behavior of the media is taken into account by adding higher order displacement gradients in the stress-strain relationship. It is found that a harmonic wave reflects back with the same angle of the incident wave, like in a classical case. However, it is found that the direction of propagation of the refracted wave is dependent on the wave number. It is also shown that the critical angle for which the incident wave cannot be transmitted to the other half plane is dependent on the wave number.
AtıfScopus1WoS1OpenAlex1İncele - BildiriYalnız künye2011A Novel approach for modeling mechanical behavior of porous media
Altan, Burhanettin S.; Mollamahmutoglu, Murat
A multi-scale novel homogenization technique is introduced to model mechanical behavior of open-cell porous media. The proposed method consists of primarily four components. The first component is based on two assumptions. First, a random porous structure can be approximated by superimposing regular grids that are interacting with each other at "junction" points. The second component consists of replacing each grid by an equivalent continuum. The forces at the junction points are also replaced by interacting body forces. The third component is to represent the equivalent media by single medium by expressing the "average stresses" in the elastic mixture in terms of the "average displacement" It is discussed how to extract the information about the geometrical and mechanical properties of the grids by comparing the analytical and experimental data for the dispersion of waves propagating in porous medium.
- MakaleYalnız künye2012Scopus SJRQ3Effect of magnetic flux distribution and magnetic powder addition on the magnetic levitation force of Sm123 superconductors
Abdioglu, M.; Ozturk, K.; Kutuk, S.; Bolat, S.; Yanmaz, E.
Sm123 and Sm211 were prepared by melt-powder-melt-growth and solid-state-reaction techniques, respectively, to have the nominal composition of (Sm123) 0.75 (Sm211) 0.25. After the preparation of this composition, the Fe-B magnetic powder (MP) was added to the composition for 0.000, 0.010, 0.015, 0.025, 0.050 wt.% to investigate the effect of MP addition on the levitation force density (LFD). Additionally, different permanent magnets (PM) were used as magnetic-field source to investigate the effect of magnetic-field gradient on the LFD of MP added superconductors. Our findings indicate that the MP addition acts as a flux pinning centre in the sample and enhances the LFD up to 0.025 wt.% adding amount, and the optimum flux gradient which produces a screening current in the sample occurs when the B/d (magnetic-field intensity/ diameter of PM) ratio is equal to 0.060. These results imply that the experimental data can be useful for fabricating process of superconducting samples with larger MLF values, and designing of superconducting magnets, flywheel energy storage and maglev systems.
AtıfScopus10WoS10OpenAlex10İncele - MakaleYalnız künye2011Scopus SJRQ2Engineering properties of medium-to-fine sands injected with microfine cement grout
Mollamahmutoglu, Murat; Yilmaz, Yuksel
This article investigates the penetrability of microfine cement suspensions prepared with Rheocem 900 with and without superplasticizer additive into various graded fine-to-medium sands into which chemical grout permeation is only possible. Initially, the basic rheological properties such as viscosity, setting time, and stability of microfine cement suspensions are studied. In addition, penetration performance of the suspensions into various graded fine to medium sand specimens under different grouting pressures is examined. Finally, the strength and permeability characteristics of various graded fine-to-medium sand specimens permeated with microfine cement suspensions are studied. It is found that a superplasticizer additive greatly increases the grouting performance of microfine cement and reduces the grouting pressure. Moreover, it is seen that the unconfined compressive strengths of sand specimens permeated with a cement grout without additive are slightly less than those of sand specimens permeated with cement grout and superplasticizer additive. Further-more, permeability tests on specimens permeated with cement grouts with or without a superplasticizer reveals that all specimens are impermeable (k<1 10 7 m=s).
AtıfScopus73WoS65İncele - BildiriYayıncıda açık erişim2011Identifying the secondary school students' misconceptions about functions
Cansiz, Şükrü; Küçük, Betül; Lşleyen, Tevfik
It is very important to identify and correct the mistakes that students make about mathematical concepts. The purpose of this study is to detect the secondary school students' misconceptions about functions in the 2009-2010 academic year. Research data was collected 61 students, included 9 th,10 th and 11 th grade students selected randomly, in Erzincan (2009-2010) academic year. Data collection tools consist of knowledge test and interviews. Frequency tables and percentages were used by analyzing students' explanations as answers to questions on the function information test. Pearson correlation was chosen to state the meaningful difference among the questions, if there is any, on the Function information test also included four different categories. Student, being believed to be in error, were interviewed with the help of data obtained from Function information test. As a result of the interview, it is most commonly observed that students make mistakes to understand whether a graphic is a function graphic or not, and about the demonstration of the table and function especially on the function information test.
AtıfScopus6WoS3OpenAlex12İncele - BildiriAçık Erişim2011Scopus SJRQ2Site-response effects on RC buildings isolated by triple concave friction pendulum bearings
Ates, Sevket; Yurdakul, Muhammet
The main object of this study is to evaluate the seismic response effects on a reinforced concrete building isolated by triple concave friction pendulum (TCFP) bearings. The site-response effects arise from the difference in the local soil conditions at the support points of the buildings. The local soil conditions are, therefore, considered as soft, medium and firm; separately. The results on the responses of the isolated building are compared with those of the non-isolated. The building model used in the time history analysis, which is a two-dimensional and eight-storey reinforced concrete building with and without the seismic isolation bearings and/or the local soil conditions, is composed of two-dimensional moment resisting frames for superstructure and of plane elements featuring plane-stress for substructure. The TCFP bearings for isolating the building are modelled as of a series arrangement of the three single concave friction pendulum (SCFP) bearings. In order to investigate the efficiency of both the seismic isolation bearings and the site-response effects on the buildings, the time history analyses are elaborately conducted. It is noted that the site-response effects are important for the isolated building constructed on soft, medium or firm type local foundation soil. The results of the analysis demonstrate that the siteresponse has significant effects on the response values of the structure-seismic isolation-foundation soil system.
AtıfScopus9OpenAlex7İncele - MakaleAçık Erişim2010Scopus SJRQ3Customer risk perceptions of internet banking - A study in turkey
Demirdogen, Osman; Yaprakli, Şükrü; Yilmaz, Mustafa Kemal; Husain, Jamaluddin
Technological developments in electronics have lead to the introduction of technology-based self-service systems resulting in the reorganization of several industries offering their services in electronic format known as "e-service" - electorinic banking iscalled internet banking?. With increasingly easier access to the internet, even in developing countries like Turkey over 18 % of all banking customers already use Internet Banking actively. Customers usually perceive risks in conducting transactions electronically, and particularly if the transactions involve money. Risk perception can beof six different types: time risk, finacial risk, performance risk, psychological risk, safety risk & confidentiality risk. It is generally considered that risk perception could be higher for electronic banking services. This study aims to understand the extent to which this consideration is valid as well as to determine the levels of risk perception differences among those using Internet Banking and those not using it. A survey was conducted among 350 academic staffs andtheir responses were analyzed statistically. This study showed that while customers used Internet Banking for a variety of different purposes such as to determine account balance, transfer money, or to pay invoices, etc., there was a significant relationship between the income level of customers and their risk perceptions. An analysis of the differences in risk perceptions between bank customers using Internet Banking (IB) and those not using IB showed that risk perceptions in terms of financial, psychological and safety risks among customer not using IB was more pronounced than those using IB. Customers not preferring to use internet banking thought that they would be swindled when using this service, and therefore, were particularly careful about high risk expectation during money transfers from and between accounts.
AtıfScopus16OpenAlex27İncele - MakaleYalnız künye2011Scopus SJRQ2The stigmaeid mites (Acari: Stigmaeidae) of kelkit valley (Turkey)
Dönel, Güldem; Doǧan, Salih
The stigmaeid mites collected from Kelkit Valley in Turkey are investigated. Nine new species, Cheylostigmaeus urhani sp. nov., Eustigmaeus varius sp. nov., Ledermuelleriopsis indiscretus sp. nov., Stigmaeus additicius sp. nov., S. angustus sp. nov., S. ayyildizi sp. nov., S. furcatus sp. nov., S. kelkitensis sp. nov. and Prostigmaeus integrius sp. nov., are described and illustrated. The following four stigmaeid species are new records for the Turkish fauna: Cheylostigmaeus salinus Evans, Eustigmaeus lacuna (Summers), Stigmaeus glabrisetus Summers and S. solidus Kuznetsov. Some known stigmaeid mites are recorded from new localities. This is the first record of the genus Prostigmaeus Kuznetsov in Turkey. Keys to Kelkit Valley genera and species of Stigmaeidae are included.
AtıfScopus50OpenAlex54İncele
