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Koleksiyondaki öğeler
- MakaleAçık Erişim2019Scopus SJRQ2Preparation of gentiobiose-derived oligosaccharides by glucansucrase E81 and determination of prebiotic and immune-modulatory functions
İspirli, Hümeyra; Colquhoun, Ian J.; Şahin, Engin; Sagdic, Osman; Dertli, Enes
Gentiobiose-derived oligosaccharides were synthesized by the acceptor reaction of glucansucrase E81 obtained from Lactobacillus reuteri E81 with sucrose and gentiobiose as donor-acceptor sugars, respectively. The reaction products were monitored by TLC analysis and gentiobiose-derived oligosaccharides up to DP 8 were formed during the acceptor reaction as determined by ESI-MS/MS analysis. The glycosylation of the gentiobiose with α-(1 → 6) linkages and α-(1 → 3) linkages was shown by 1H and 13C NMR analysis confirming the structure of these gentiobiose-derived oligosaccharides. The in vitro prebiotic function of the oligosaccharides was determined in which probiotic strains were stimulated whereas no growth was observed in pathogen strains. Gentiobiose-derived oligosaccharides showed immune-modulatory functions in vitro and triggered the production of IL-4, IL12 and TNF-α cytokines in HT29 cells in a dose dependent manner. This study showed the production and functional characterisation of gentiobiose-derived oligosaccharides establishing a promising avenue for future applications.
AtıfScopus26WoS21OpenAlex22
İncele - MakaleAçık Erişim2019Scopus SJRQ2Modeling design parameters with taguchi experimental method for obtaining operating conditions for cu(Ii) removal through adsorption process
Serencam, Hüseyin; Özdemir, Akın; Teke, Çağatay; Uçurum, Metin
One of the environmental concerns deals with the removal process of pollutants in water and wastewater. In this paper, a removal process was used to eliminate pollutants in water and wastewater. The aim of this paper was to obtain an optimum adsorption condition for the highest metal ions adsorbed (MIA) mg/g. For this particular purpose, a Taguchi L18 design was conducted. In addition, the signal-to-noise ratio was analyzed for optimum adsorption levels. The analysis of variance was also performed to evaluate the effect of each adsorption condition on MIA (mg/g) values. Moreover, an optimization model was also proposed to find the best optimal setting of adsorption levels. Then, the confirmation tests were performed using optimum coded levels of the adsorption parameters for the verification purpose. The results of the experimental study showed a good performance that Cu(II) removal capacity was found to be 43.66 mg/g. To the best of our knowledge, this research is the first to study natural stone as an efficient, inexpensive and cheap adsorbent for the removal process.
AtıfScopus6WoS5OpenAlex6İncele - Kitap BölümüYalnız künye2022Gut effect on phytochemicals
Cebeci, Fatma
The gut microbiota play an important role for host nutritional, physiological, immunological functions like food digestion, vitamin production, protection of gut integrity, regulation of host immunity, and disease pathogenesis. Dietary phytochemicals are important factors to shape and change the human gut microbiota composition in diversity and abundance context. On the other hand, the microbial community of the gut provides a broad range of enzymes to host which are different from its own resources. This enables human gut microbiota to affect and direct the biosynthesis and metabolism of many bioactive compounds. Bioavailability of phytochemicals is important to benefit from health conferring effects of these compounds. Most of the phytochemicals are not absorbed well by the small intestine and pass through to the gut then gut microbiota acts on the compounds to form different metabolites. Therefore, elucidating the role of human gut microbiota on phytochemical metabolism is essential. This chapter discusses the studies reporting the gut microbial effect on different phytochemicals.
- MakaleAçık Erişim2020Scopus SJRQ2Switching linear quadratic Gaussian control of a flexible blade structure containing magnetorheological fluid
Sivrioglu, Selim; Bolat, Fevzi Cakmak
The present study suggests a new active control structure with a switching algorithm for control current of the electromagnetic actuator to suppress vibrations of a flexible blade element containing magnetorheological (MR) fluid. An identification model between MR fluid inside the blade and the electromagnetic actuator is utilized to derive the force equation. Since only one electromagnet is employed to suppress the blade vibration, a single-sided control actuation occurs in the proposed system. Therefore, the pulling force used for vibration control is generated by the actuator when the blade moves to downward direction. A switching linear quadratic Gaussian (LQG) controller that produces always a positive control input is designed to attenuate the blade vibrations. The LQG controller with switching is experimentally implemented under the impact and steady-state aerodynamic disturbances. The results of experiments show that the proposed switching controller is effective to attenuate vibrations of the flexible blade element.
AtıfScopus15WoS11OpenAlex13İncele - MakaleYalnız künye2020Scopus SJRQ1Probiotic properties of lactic acid bacteria strains isolated from pastırma
Topçu, Kübra Cinar; Kaya, Mükerrem; Kaban, Güzin
In this study, the probiotic properties of 80 lactic acid bacteria (LAB) strains isolated from pastırma, a dry-cured meat product, were investigated. For this purpose, strains were investigated for their resistance to bile salt and hydrophobicity abilities. In 6 strains selected as a result of these analyses, development at high salt concentrations, auto-aggregation and co-aggregation, resistance to low pH, and adhesion analyses were performed. The growth percentage of all strains decreased with increasing bile salt concentration at both 25 °C and 37 °C. P. pentosaceus K7, K41, K44, K51 and K81 and P. acidilactici K99 gave the highest values in terms of hydrophobicity ability. The highest auto-aggregation and the highest co-aggregation were found in P. pentosaceus K41 (17.62%) and P. pentosaceus K44 strain (26.23%), respectively. These six strains showed tolerance to high acidity even at pH 2. The strains significantly maintained their viability in the simulated gastric and intestinal fluids. Furthermore, the strains had low adhesion capacity in Caco-2 and HT-29 cell lines and generally showed resistance under gastrointestinal system conditions. As a result, P. pentosaceus K44, P. acidilactici K99 and P. pentosaceus K41 could be considered as probiotic strains.
AtıfScopus55WoS48OpenAlex50İncele - MakaleAçık Erişim2022Scopus SJRQ2Efficient bioreduction of cyclohexyl phenyl ketone by Leuconostoc pseudomesenteroides N13 biocatalyst using a distance-based design-focused optimization model
Özdemir, Akın; Şahin, Engin
Whole-cell biocatalysts have been a popular method for the preparation of chiral alcohols. Although asymmetric reduction of cyclohexyl(phenyl)methanone (1) by chemical catalysts is common, a biocatalytic asymmetric reduction is extremely rare. In this respect, we report herein that Leuconostoc pseudomesenteroides N13 was successfully employed as a biocatalyst to reduce 1 to (S)-cyclohexyl(phenyl)methanol ((S)-2). Furthermore, the use of a mathematical optimization strategy for asymmetric reduction of substrate 1 is not known in the current literature. The new distance-based design-focused optimization model was used to enhance the conversion of the substrate, enantiomeric excess (ee) of product, and yield. The distance-based design-focused optimization model identified the following optimal bioreduction conditions: pH=6.46, temperature=30°C, incubation period=72 hours, and agitation speed=199 rpm. Then it was stated that under these ideal conditions, (S)-2 may be produced with 99 % ee and 98.46 % conversion rate (cr). (S)-2 was achieved with 99% ee, and 99% cr as a consequence of the experimental reaction carried out under the indicated optimization conditions. It has been shown that Leuconostoc pseudomesenteroides N13 can be utilized as a biocatalyst in asymmetric reduction reactions. This study, in addition to being the first example of a bioreduction of substrate 1 by mathematical optimization, also demonstrates for the first time the distance-based design-focused model can be used in the bioreduction reaction.
AtıfScopus9WoS9OpenAlex8İncele - BildiriYalnız künye2020RoutingChain: A Proof-of-Concept Model for a Blockchain-Enabled QoS-Based Inter-AS Routing in SDN
Karakus, Murat; Guler, Evrim
A Software-Defined Networking (SDN) architecture and OpenFlow can help network administrators to provide end-to-end (E2E) Quality of Service (QoS)-guaranteed paths for flows among networks while providing finer-granular flow management along with global network view. In this context, we introduce a proof-of-concept for a blockchain-enabled QoS-based inter-Autonomous System (AS) routing framework, RoutingChain, that blends a QoS-concerned routing model and blockchain technology. This study's contributions can mainly be stated in five-fold: (i) Competitors-tailored routing coordination framework, (ii) eliminating centralized mediators while coordinating QoS-based inter-AS routing, (iii) an emerging use-case for blockchain technology in networking, (iv) reducing the number of QoS signaling-based message overhead, and (v) mitigating privacy/security concerns in inter-AS routing. Experimental results indicate that the blockchain technology can be applied on E2E QoS-based routing among networks. To the best of our knowledge, this is the first study exploiting the merits of blockchain technology to establish a novel coordination framework for QoS-enabled inter-AS routing in SDN.
AtıfScopus10WoS6OpenAlex12İncele - MakaleAçık Erişim2022Scopus SJRQ1Comparative seismic design optimization of spatial steel dome structures through three recent metaheuristic algorithms
Carbas, Serdar; Artar, Musa
Steel dome structures, with their striking structural forms, take a place among the impressive and aesthetic load bearing systems featuring large internal spaces without internal columns. In this paper, the seismic design optimization of spatial steel dome structures is achieved through three recent metaheuristic algorithms that are water strider (WS), grey wolf (GW), and brain storm optimization (BSO). The structural elements of the domes are treated as design variables collected in member groups. The structural stress and stability limitations are enforced by ASD-AISC provisions. Also, the displacement restrictions are considered in design procedure. The metaheuristic algorithms are encoded in MATLAB interacting with SAP2000 for gathering structural reactions through open application programming interface (OAPI). The optimum spatial steel dome designs achieved by proposed WS, GW, and BSO algorithms are compared with respect to solution accuracy, convergence rates, and reliability, utilizing three real-size design examples for considering both the previously reported optimum design results obtained by classical metaheuristic algorithms and a gradient descent-based hyperband optimization (HBO) algorithm.
AtıfScopus15WoS13OpenAlex15İncele - MakaleYalnız künye2021Scopus SJRQ1The Online Learning Experience of Theology Students in Turkey during the COVID-19 Pandemic: A New Disposition for RE?
Selçuk, Mualla; Sözen, Hasan; Şimşek, Vahdeddin; İpek, Yasemin
Through a quantitative research model, this study aims to understand the general attitudes of theology students in Turkey regarding online learning during the COVID-19 pandemic. In examining the determinant factors on their attitudes, research findings include: previous online education experience, the frequency of participating in synchronous courses, the qualifications of the instructor, the assessment and evaluation procedures, the orientation training programs and the infrastructure opportunities of the universities. Interpreting these factors enables the authors of this article to suggest a conversational relationship between RE and Islamic sciences with some shared objectives that leads to naming guiding principles in a manner that significantly supports students’ vocational journey.
AtıfScopus5WoS5OpenAlex19İncele - MakaleYalnız künye2021Scopus SJRQ1Development of gelatine-based edible film by addition of whey powders with different demineralisation ratios: Physicochemical, thermal, mechanical and microstructural characteristics
Sert, Durmuş; Üçok, Gamze; Kara, Ümmügülsüm; Mercan, E.M.İ.N.
The effects of using whey powders with different demineralisation rates on the physicochemical, thermal, mechanical, and microstructural properties of gelatine-based edible films were investigated. Films were produced from film-forming solutions (FFS) containing whey powder (WP) and 50, 70 and 90% demineralised whey powder (50DWP, 70DWP, 90DWP). The addition of whey powders increased the pH and particle size values of FFS. The zeta potential decreased significantly in the WP sample and gradually reduced depending on the demineralisation rate in the DWP samples. The addition of whey powders partially increased the density of the films. WP addition reduced the hydrophobicity of the film, while the addition of DWPs did not cause any change. The addition of whey powders decreased the L* and a* values of the films while increasing the b* values. Control was the most transparent, while 70DWP and 90DWP films had higher opacity. WP films had the most uniform and smooth surface. The highest degradation temperature (269.64 °C) was observed in the control sample. The weight loss of the control was 95%, whereas those of WP and DWP samples were 88–89%. WP addition reduced the tensile strength and increased the elasticity of the films.
AtıfScopus12WoS10OpenAlex12İncele - MakaleAçık Erişim2019Scopus SJRQ2Innovative trend analysis of total annual rainfall and temperature variability case study: Yesilirmak region, Turkey
Serencam, Uğur
It is well known that any kind of ordinary hydrometeorological parameter trend may have increasing or decreasing tendency systematically. Various methodologies are developed for possible trend identification such as the well-known Mann-Kendall test and recently Şen innovative trend analysis (ITA) approaches. The former has a set of assumptions, whereas the latter is almost without any restrictive assumption. The main purpose of this paper is to present precipitation and temperature trend behaviors by applying ITA in Yesilirmak drainage basin. Selected observation stations are mainly located at the Black Sea confluence region of Yesilirmak while few others at the middle and upper drainage basins. ITA provided visual inspection with quantitative trend slopes distinctively for low, medium, and high sub-levels with physical interpretations. Based on categorization, precipitation records have significant decreasing trends in low, medium, and high levels as an average − 3.4%, − 3.8%, and − 2.4%, respectively. In contrary to precipitation trend, and consistent to global expectation in climate change, temperature records have significantly strong increasing tendency along the basin. In sub-level of temperature, this strong trend tendencies are detected + 4.6%, + 4.8%, and + 7.2% from low to high ranges, respectively.
AtıfScopus40WoS36OpenAlex45İncele - Derleme MakaleAçık Erişim2021Scopus SJRQ2Investigation of the Effect of Inoculant and Casting Temperature on Fluidity Properties in the Production of Spheroidal Graphite Cast Iron
Çolak, Murat; Kaya, Sinan
Working with liquid metal makes the casting method very advantageous, but also presents some difficulties. One of the common challenges in the casting process is that the liquid metal may not fill the mold cavity completely. This is mainly due to the contact of the liquid metal with the mold surface in the mold cavity, the high heat transfer coefficient of the mold material, and the undercooling and solidification of the liquid metal during liquid movements. For this reason, the fluidity of the liquid metal is important for robust casting production. The fluidity is affected by many factors such as mold properties, casting temperature, and alloying elements. In this study, it is aimed to investigate the fluidity characteristics of GGG60 alloy. For this purpose, the effects of casting temperature, different inoculants, and different inoculant quantities were used in the new mold design, which has different cross-sectional thicknesses. The distance of the alloy in the cavities was also compared with FlowCast Casting simulation software.
AtıfScopus8WoS8OpenAlex9İncele - MakaleYayıncıda açık erişim2022Scopus SJRQ3Thiol disulfide homeostasis in primary dysmenorrhea
Savrun, Atakan; Savrun, Şeyda Tuba; Dirican, Ebubekir; Gökçen, Emre; Arıcı, Yeliz Kasko; Aygün, Ali; Korkmaz, Vakkas; Neşelioğlu, Salim; Erel, Özcan; Kıran, Tuğba Raika
Oxidative stress is defined as a result of the loss of balance between the production of free radical or reactive oxygen species and the antioxidant system. This study aimed to determine the level of thiol-disulfide homeostasis (TDH) in the serum of women with primary dysmenorrhea. The study group consisted of 42 subjects with primary dysmenorrhea, and the control group consisted of 30 volunteer women with demographic characteristics similar to the study group. Native thiol (SH), total thiol (TSH), disulphide (SS), and SH/SS parameters were measured for TDH of the subjects. The SH (p = 0.038) and SH/TSH (p = 0.046) levels were significantly higher while SS (p = 0.013), SS/SH (p = 0.042) and SS/TSH (p = 0.046) levels were lower in the study group than in the healthy control group. The SS cut-off value was determined as 17.85 in the study group (sensitivity = 61.9%, specificity = 43.3%). Therefore, the probability of dysmenorrhea may increase significantly when SS levels fall below this value. In subjects with dysmenorrhea, there was a decrease in SS levels and an increase in SH levels in order to protect the cells and tissues from the harmful effects of free radicals.
AtıfOpenAlex1İncele - MakaleYayıncıda açık erişim2020Scopus SJRQ3Determination of physicochemical and microbiological properties and fatty acid composition of butter produced in Trabzon, Turkey
Akgül, Halil İbrahim; Şengül, Mustafa; Ürkek, Bayram; Kotan, Tuba Erkaya
In this study, the some physicochemical properties, fatty acid compositions and microbiological properties of butter samples were studied. Butter samples (n = 30) were randomly collected from different local markets. Thus, butter samples were evaluated in terms of Turkish regulations, food safety and quality. The mean values of the butter samples for peroxide value (PV), iodine value (IV), saponification value (SV), Polenske value, Reichert-Meissl (RM) and Refractive index (RI) values were determined as 0.85 mEqO2 kg-1, 30.03, 220.09, 1.30, 25.60 and 1.4611, respectively. The moisture and fat values were not in harmony with Turkish Food Codex Butter, Other Milk Fat Based Spreadable Products and Anhydrous Milkfat Notification (the highest moisture content 16%, the lowest fat content 80%) in 23 and 13 butter samples, respectively. The salt values were coherent with Turkish Food Codex in all butter samples. Conjugated linoleic acid (CLA) rate of the butter samples was ranged from 0.15 to 1.32%. The average values of coliforms, total aerobic mesophilic bacteria (TAMB) and mould and yeasts counts were determined as 1.67, 6.33 and 5.22 log CFU g-1, respectively.
AtıfScopus13WoS10İncele - MakaleAçık Erişim2022Scopus SJRQ1Conventional and Microcellular Injection Molding of a Highly Filled Polycarbonate Composite with Glass Fibers and Carbon Black
Yilmaz, Galip; Devahastin, Apichart; Turng, Lih-Sheng
Conventional solid injection molding (CIM) and microcellular injection molding (MIM) of a highly filled polycarbonate (PC) composite with glass fibers and carbon black were performed for molding ASTM tensile test bars and a box-shape part with variable wall thickness. A scanning electron microscope (SEM) was used to examine the microstructure at the fractured surface of the tensile test bar samples. The fine and uniform cellular structure suggests that the PC composite is a suitable material for foaming applications. Standard tensile tests showed that, while the ultimate strength and elongation at break were lower for the foamed test bars at 4.0–11.4% weight reduction, their specific Young’s modulus was comparable to that of their solid counterparts. A melt flow and transition model was proposed to explain the unique, irregular “tiger-stripes” exhibited on the surface of solid test bars. Increasing the supercritical fluid (SCF) dosage and weight reduction of foamed samples resulted in swirl marks on the part surface, making the tiger-stripes less noticeable. Finally, it was found that an injection pressure reduction of 25.8% could be achieved with MIM for molding a complex box-shaped part in a consistent and reliable fashion.
AtıfScopus2WoS2OpenAlex3İncele - MakaleAçık Erişim2019Scopus SJRQ2Optimal Material Selection for Total Hip Implant: A Finite Element Case Study
Şensoy, Abdullah Tahir; Çolak, Murat; Kaymaz, Irfan; Findik, Fehim
The selection of most proper materials in engineering design is known as an important stage of the design process. In order to successfully complete this stage, it is necessary to have sufficient knowledge about the structure of materials, density, melting point, thermal expansion coefficient, tensile and yield strength, elongation, modulus of elasticity, hardness and many other properties. There are several selection systems that help the design engineer to choose most suitable material that meet the required properties. In the field of bioengineering, the selection of materials and the development of new materials for the clinical needs are increasingly important. In this study, the cases of optimal implant stabilization were investigated, material alternatives for hip prosthesis were evaluated, and optimal materials were determined. Using computerized tomography data with MIMICS software, virtual surgery was applied the hip bone and the implant was attached to bone. Boundary conditions and material properties have been defined, and finite element model has been created. FEA investigation of the mechanical behavior of the hip implant for various material alternatives determined by the CES software showed that the best material candidate is austenitic, annealed and biodurable stainless steel in terms of the micromotions at the implant–bone cement interface regarding osseointegration. This candidate showed 20.69% less strain value than the most commercially used hip implant material, Ti6Al4V. Therefore, the findings of this study suggest that the use of some specific stainless steel materials for implants may reduce the operation cost and increase the operation success for the total hip arthroplasty.
AtıfScopus36WoS28OpenAlex41İncele - MakaleYayıncıda açık erişim2020Scopus SJRQ1Temperature dependent current- and capacitance-voltage characteristics of W/n-Si structures with two-dimensional WS2 and three-dimensional WO3 interfaces deposited by RF sputtering technique
Baltakesmez, A.; Tekmen, S.; Güzeldir, B.
In this study, tungsten disulfide (WS2) and tungsten trioxide (WO3) thin films are deposited on n-Si by RF sputtering technique. The optical, morphological and structural characteristics of these films are investigated. The XRD patterns showed that highly crystallinity have been obtained with dominant characteristic diffraction peaks of the WS2 and WO3. The SEM images show that these films are nearly uniform and covered all surface of substrates. Furthermore, the WS2 film has two-dimensional (2D) vertical layers while the WO3 has three-dimensional (3D) structure. From the XPS spectra, it revealed that the peaks confirmed the formation of WS2 and WO3 phases. The Raman spectra presented that different vibrational modes and phases are characteristics of the WS2 and WO3 thin films. Electrical properties of W/n-Si metal-semiconductor (MS) and W/WS2/n-Si and W/WO3/n-Si metal-interfacial layer-semiconductor (MIS) diodes are investigated using current-voltage (I-V) and capacitance-voltage (C-V) characteristics at various temperatures. It was found that I-V and C-V characteristics are strongly dependent on temperature and the interfacial WS2 and WO3 layers are significant roles for the electrical properties of W/WS2/n-Si and W/WO3/n-Si devices.
AtıfScopus19WoS20OpenAlex17İncele - MakaleAçık Erişim2020Scopus SJRQ2Investigations of Strain Rate Effects on the Mechanical Properties of Hybrid Composite Laminate Under Varying Temperatures
Erbayrak, Engin; Gumus, Beril Eker; Yuncuoglu, Ercument Ugur; Kahraman, Yusuf
The mechanical behavior of hybrid composite laminates under varying strain rates and temperatures was investigated in this study. The hybrid composite laminate is constituted as a sequential stacking sequence of plain-woven carbon-fiber-reinforced epoxy (CFRE) and plain-woven glass-fiber-reinforced epoxy (GFRE) laminates. Vacuum-assisted resin transfer molding (VARTM) process was used to fabricate the composite laminates. Hybrid composite laminates (HCGFRE) were tested under four different strain rates (0.05 min−1, 0.5 min−1, 2.5 min−1, 5 min−1) and three different temperatures (RT, 60 °C, 100 °C). Microstructure analysis was performed to observe the voids, fiber delamination and matrix failure occurring in the composite laminate. In numerical analyses, continuum damage mechanics material model (MAT 58) was utilized in LS-DYNA® explicit finite element program to simulate the mechanical properties of CFRE, GFRE and HCGFRE laminates. It was determined that the tensile strength of all composite laminates is increasing by increasing the strain rates in all temperatures. The continuous damage mechanics material model (MAT 58) was found to be suitable for simulating woven composite laminate under different strain rates and temperatures. In microstructural study, it was not observed significant changes in the microstructure of composite laminates by changing strain rates.
AtıfScopus1WoS1OpenAlex3İncele - MakaleAçık Erişim2020Scopus SJRQ2Optical, morphological and nano-mechanical properties of chromium oxide thin films fabricated by radio frequency (RF) magnetron sputtering
Özen, Soner; Şenay, Volkan
In this research, two transparent chromium oxide thin films having different thickness values were simultaneously deposited on glass substrates by adjusting target-substrate distance by means of radio frequency (RF) magnetron sputtering technique. The effect of film thickness on optical, morphological and nano-mechanical properties of the produced thin films were analyzed by using UV-VIS spectrophotometer, interferometer, tensiometer and atomic force microscope. The transmittance and absorbance of the films were measured in the incident photon wavelength range of 300–1000 nm. The optical energy band gap value of the produced thin films was estimated to be approximately 4 eV from the obtained absorbance data via Tauc's method. According to the results obtained from nano-mechanical tests, the produced thin films were highly scratch resistant. From the wetting experiments, it was found that the surfaces of the films were hydrophilic.
AtıfScopus11WoS10OpenAlex11İncele - Kitap BölümüYalnız künye2021An Unsupervised Learning Framework to Analyze the Economic Impact of Covid-19: An Application on the Most Affected Countries
Özden, Erdemalp
