Gazi University
  • Ankara, Republic of Turkey, Turkey
Recent publications
COVID-19 pandemic created a need to improvise and redefine blended learning to be executed fully online. Background information on the effectiveness of fully online blended learning activities, especially for surgical disciplines is limited. This study describes a fully online blended learning course format on spinal surgery and aims to provide data regarding it effectiveness. Fully online blended courses on three topics of spinal surgery designed as six-week asynchronous and followed by 3-day live parts. Learning gaps (LGs) were identified with a survey at the beginning of asynchronous part, at its end, and at the end of the live part. The effectiveness of the asynchronous and live parts was assessed by LGs and a quiz, login statistics of learners and faculty and a post-course survey. Participants' LGs decreased in all courses, statistically significant in two. Faculty and learner login rates significantly correlated with each other. Faculty and learner satisfaction was very high. A fully online blended learning course can be delivered effectively on spine surgery with a high participant and faculty satisfaction rate. The asynchronous part contributes to learning significantly.
Background: We aimed to evaluate the features of primary membranous nephropathy (MNP) in Turkish people. Methods: This is a retrospective analysis of patients with biopsy-proven primary MNP. We obtained the data collected between 2009 and 2019 in the primary glomerulonephritis registry of the Turkish Society of Nephrology Glomerular Diseases Study Group (TSN-GOLD). Patients with a secondary cause for MNP were excluded. Clinical, demographic, laboratory, and histopathological findings were analyzed. Results: A total of 995 patients with primary MNP were included in the analyses. Males constituted the majority (58.8%). The mean age was 48.4 ± 13.9 years. The most common presentation was the presence of nephrotic syndrome (81.7%) and sub nephrotic proteinuria (10.3%). Microscopic hematuria was detected in one-third of patients. The median estimated glomerular filtration rate (eGFR) was 100.6 mL/min/1.73 m2 (IQR, 75.4-116.3), and median proteinuria was 6000 mg/d (IQR, 3656-9457). Serum C3 and C4 complement levels were decreased in 3.7 and 1.7% of patients, respectively. Twenty-four (2.4%) patients had glomerular crescents in their kidney biopsy samples. Basal membrane thickening was detected in 93.8% of cases under light microscopy. Mesangial proliferation and interstitial inflammation were evident in 32.8 and 55.9% of the patients, respectively. The most commonly detected depositions were IgG (93%), C3 complement (68.8%), and kappa and lambda immunoglobulin light chains (70%). Although renal functions were normal at presentation, vascular, interstitial, and glomerular findings were more prominent on biopsy in hypertensive patients. No significant effect of BMI on biopsy findings was observed. Conclusions: Despite some atypical findings, the main features of primary MNP in Turkey were similar to the published literature. This is the largest MNP study to date conducted in Turkish people.
Poor chromatographic resolution is one of the main challenges in chromatographic analysis. Partially separated chromatographic peaks frequently occur, due to the nature of analytes and the demand for fast analysis using high flow rates and shorter columns. Modelling of chromatographic three‐way data using suitable chemometric tools enables resolving co‐eluted peaks without using additional experimental efforts. In this paper, parallel factor analysis (PARAFAC) was applied to chromatographic data for the quantitative resolution of a quaternary mixture at the co‐elution condition of acetaminophen, aspirin, ascorbic acid, and guaifenesin in a spectrochromatogram. The spectrochromatograms of the calibration set, validation set and real samples were arranged as a three‐way array. In the next step, the PARAFAC model was implemented to decompose the spectrochromatographic array into trilinear components, corresponding to spectral, chromatographic and relative concentration profiles of the analytes. The chromatographic and spectral modes were used for the qualitative analysis of components, while the analytes in commercial tablets were quantified from their individual profiles in their concentration mode. This study indicated that the application of PARAFAC model provided a novel strategy for solving overlapping peaks in a chromatogram to perform the analysis of multicomponent mixtures with a very short runtime and without additional efforts.
Background Patients are the most important stakeholders in the care of any disease and have an educational need to learn about their condition and the treatment they should receive. Considering this need for patient-focused materials, we present a directed approach for mucopolysaccharidosis (MPS) VI and MPS IVA, a pair of rare, inherited diseases that affects multiple organs and parts of the body. Independent guidelines on the treatment of these diseases were recently published, providing evidence- and expertise-driven recommendations to optimize patient management. However, while healthcare providers may have the training and knowledge to understand these guidelines, patients and their caregivers can find the technical content challenging. Hence, we aimed to develop plain language summaries (PLS) of the MPS VI and MPS IVA guidelines with patients as the primary audience. Results A review of the guidelines by an expert team identified six domains of information relevant to patients: The multidisciplinary team, regular tests and check-ups, disease-modifying and supportive treatments, general anesthetics, ear-nose-throat/respiratory care, and surgeries. This information was adapted into a series of infographics specific to either MPS VI or MPS IVA, designed to appeal to patients and clearly present information in a concise manner. Conclusions The use of patient-friendly materials, like the infographics we have developed, has the potential to better inform patients and engage them in their care. We issue a “call to arms” to the medical community for the development of similar PLS materials in rare diseases intended to inform and empower patients.
This consensus statement by a panel of Fabry experts aimed to identify areas of consensus on conceptual, clinical and therapeutic aspects of Fabry disease (FD) and to provide guidance to healthcare providers on best practice in the management of pediatric and adult patients with FD. This consensus statement indicated the clinical heterogeneity of FD as well as a large number of pathogenic variants in the GLA gene, emphasizing a need for an individualized approach to patient care. The experts reached consensus on the critical role of a high index of suspicion in symptomatic patients and screening of certain at-risk groups to reveal timely and accurate diagnosis of FD along with an increased awareness of the treating physician about the different kinds of pathogenic variants and their clinical implications. The experts emphasized the crucial role of timely recognition of FD with minimal delay from symptom onset to definite diagnosis in better management of FD patients, given the likelihood of changing the disease’s natural history, improving the patients’ quality of life and the prognosis after enzyme replacement therapy (ERT) administered through a coordinated, multidisciplinary care approach. In this regard, this consensus document is expected to increase awareness among physicians about unique characteristics of FD to assist clinicians in recognizing FD with a well-established clinical suspicion consistent with pathogenic variants and gender-based heterogeneous clinical manifestations of FD and in translating this information into their clinical practice for best practice in the management of patients with FD.
Background/aim Certain constituents in migraine food triggers and non-steroidal anti-inflammatory drugs (NSAIDs) inhibit sulfotransferases (SULTs) that detoxify drugs/chemicals and play role in the metabolism of neurotransmitters. We aimed to dissect SULT1A1 modulation of CSD susceptibility and behavior in an in vivo experimental model using hesperidin, a SULT1A1 inhibitor found in citrus fruits (known migraine triggers) and mefenamic acid (SULT1A1 inhibitor), an NSAID to simulate medication overuse. Methods Hesperidin was used as SULT1A1 inhibitor found in citrus fruits, known migraine triggers and mefenamic acid (NSAID), another SULT1A1 inhibitor, was used to induce MO in rats. The groups were; 1) Hesperidin (ip) or its vehicle-DMSO (ip) 2) Chronic (4 weeks) mefenamic acid (ip) or its vehicle (ip) 3) Chronic mefenamic acid+hesperidin (ip) or DMSO (ip). CSD susceptibility was evaluated and behavioral testing was performed. SULT1A1 enzyme activity was measured in brain samples. Results Single-dose of hesperidin neither changed CSD susceptibility nor resulted in any behavioral change. Chronic mefenamic acid exposure resulted in increased CSD susceptibility, mechanical-thermal hypersensitivity, increased head shake, grooming and freezing and decreased locomotion. Single dose hesperidin administration after chronic mefenamic acid exposure resulted in increased CSD susceptibility and mechanical-thermal hypersensitivity, increased freezing and decreased locomotion. SULT1A1 enzyme activity was lower in mefenamic acid and mefenamic acid+hesperidin groups compared to their vehicles. Conclusion Mefenamic acid and hesperidin have synergistic effect in modulating CSD susceptibility and pain behavior. Sulfotransferase inhibition may be the common mechanism by which food triggers and NSAIDs modulate migraine susceptibility. Further investigations regarding human provocation studies using hesperidin in migraine patients with medication overuse are needed.
Mathematical understanding is considered to have a multidimensional structure and an important place in mathematics teaching. The focus of the assessments in mathematics courses is on the multidimensional evaluation of mathematical understanding. However, a review of related literature shows the lack of studies on assessing mathematical understanding using multidimensional structures. For this reason, the current study attempted to develop a scale for assessing teachers' mathematical understanding. The instrument development model, an exploratory sequential mixed methods model, has been used in line with this aim during the scale’s development. The study’s qualitative data were collected through a mathematical understanding assessment form and semi-structured interviews developed by the authors. Qualitative data emerged from 17 mathematics teachers working in middle schools or high schools who were determined using the easy access sampling method. Five themes were arrived at from the content analysis with the obtained qualitative data: applying rules, transferring knowledge, generating questions and solutions, generalizing, and exploring information. The initial version of the instrument prepared in accordance with these themes was applied to a total of 501 primary school mathematics preservice teachers from nine different universities in Turkey during the 2018 spring semester. Cronbach’s alpha (α) assessment was performed for the scale’s reliability. Item-total correlations were calculated as item statistics. Exploratory and confirmatory factor analyses were applied to test the scale’s construct validity. The item loadings for the scale were seen to vary between.431 and.759 in this process; the reliability of the sub-dimensions and the scale’s fit indices were seen to be at sufficient levels. As a result of all the performed analyses, a scale form consisting of 21 items and five sub-dimension was obtained. The results from the scale development process show that the preservice teachers took into account the factor of transferring knowledge the most and the factor of producing questions and solution pathways the least.
Shell and Helically Coiled Tube Heat Exchangers (SHCTHEXs) are utilized in energy conversion applications in industry and in various engineering systems. They are generally composed of a helically coiled tube and a shell covering it. This coiled structure of tubes, provides better heat transfer and takes less space. There is an ongoing interest in research on this type of heat exchangers. In this study, a new design was created modifying a simple type of conventional shell and helically coiled heat exchanger, by integrating discs and rings. These rings and discs were attached to the helically coiled tubes with the aim of performing as baffles restricting the shell side flow and creating turbulence. The thermal performance of a conventional heat exchanger was improved by this modification. The study was carried out both numerically and experimentally. At first step, two SHCTHEXs, one conventional; one modified, were designed with same overall geometric dimensions. Then created solid models were numerically simulated with same boundary conditions using ANSYS Fluent. Simulations were performed with various flow rates and the results were reported. According to the simulations, compared to the conventional one, with the modified heat exchanger 7.1% increase in average amount of heat transfer rate and around 20% increase in overall heat transfer coefficient were obtained. With the promising results taken by simulations, the modified heat exchanger was fabricated with the same dimensions and it was experimentally tested with same conditions in laboratory to verify the simulation results. Experimental results were in harmony with the simulations with little differences. The average differences between simulation and experimental values in terms of average amount of heat transfer rate were obtained as 2.4% for 3 l/min hot fluid flow rate and 3.5% for 4 l/min hot fluid flow rate. Overall heat transfer coefficient of modified SHCTHEX with circular baffles achieved in the range of 1050–1400 W/m²K. General outcomes of this study exhibited successful design of baffled SHCTHEX.
The multi-floor facility layout problem (MFLP) is one of the most important and complex facility layout problems that has many applications in designing the facilities of manufacturing and service sectors. In this study, a hybrid version of the Dantzig-Wolfe decomposition algorithm is proposed to solve the MFLP for the first time. The proposed solution approach is performed in two steps. In the first step, a mathematical formulation is applied to assign the departments to the floors in a way that the departments with higher material flow between them be located on the same or closer floors. In the second step, the output of the first step is considered and the MFLP is decomposed into a master problem and some sub-problems to form the Dantzig-Wolfe decomposition algorithm and find the optimal layout of each floor separately. Then the integrated layout of multiple floors is formed easily. The proposed algorithm is evaluated using some sample problems from the literature and some newly generated test problems. The obtained results show the superiority of the proposed algorithm compared to the approaches of the literature.
In this study, it was aimed to control the HCCI combustion phase. For this purpose, low and high reactivity pure fuels and their mixtures in various ratios were tested. Reference n-heptane was chosen as the high reactivity fuel, while heavy naphtha was used as the low reactivity fuel. Detailed combustion analysis was performed using in-cylinder pressure data. IMEP, the start of combustion, combustion duration, indicated thermal efficiency, MPRR and COVimep maps were examined at different engine speeds and lambda values. Almost zero NOx and soot emissions were observed under all test conditions. On the other hand, CO and HC emissions were analyzed comparatively. It has been determined that HN75 fuel provides optimum operating conditions for HCCI combustion and also causes low CO and HC emissions. Indicated thermal efficiency was obtained at about 36% and in a wide operating range in the use of HN75 and HN100 fuels. This study shows that heavy naphtha fuel significantly improved combustion phase control in HCCI engines. Particularly remarkable results were obtained in terms of performance and emission values at 50% and 75% mixing ratios with n-heptane.
The aim of this study is to examine the effects of commercial rhizobacteria inoculant on eggplant plants grown under drought stress conditions. Commercial inoculant containing Azotobacter chroococum and Azotobacter vinelandii rhizobacteria species was applied to eggplant plants by root inoculation and the plants were exposed to different levels of drought stress (moderate drought stress-MS and severe drought stress-SS). To determine the growth-promoting ability of inoculation with rhizobacteria, changes in plant morphology (shoot-root fresh and dry weights, shoot length and diameter) and physiology (relative water content-RWC, stomatal conductivity-gs, K, Ca, Mg and Na accumulations in shoot and root, photosynthetic pigment contents) were investigated. To determine the impacts of the inoculant on the potential of increasing the drought tolerance of eggplant, besides the enzyme activities of superoxide dismutase (SOD), catalase (CAT) and glutathione reductase (GR), non-enzymatic antioxidant activities such as antochiyanin, total phenolic substance, proline were investigated. In addition, H2O2 and malondialdehyde (MDA) contents were analyzed to resolve whether drought stress causes oxidative damage in eggplant. The increase in the severity of drought caused a decrease in plant growth and shoot-root fresh and dry weights. Nevertheless, these adverse effects of drought stress were alleviated by inoculation. Decreased RWC, gs values of plants under drought stress, and especially K, Ca and Mg accumulations and protein contents in the root increased significantly with inoculation. On the other hand, Chlorophyll (Chl) (Chl a, Chl b, Chl a + b) and carotenoid contents were significantly increased in leaves under uninoculated MS and SS. Inoculation with rhizobacteria reduced the increase in photosynthetic pigment contents. Depending on the severity of stress, higher levels of total phenolic compounds and proline were accumulated in inoculated plants compared to uninoculated plants. However, higher SOD, CAT, and GR enzymatic activities were observed in inoculated stressed plants, and membrane lipid peroxidation was reduced. These results were found to be important in that the commercial bacterial inoculant has the potential to diminish the negative effects of drought stress in eggplant and supports the stress tolerance of the plant by mitigating the drought-related oxidative damage.
In this study, the combustion, performance, and emission results of the HCCI engine under different fuel and engine parameters conditions were examined experimentally and statistically. Engine speed, excess air ratio, and fuel types with different fusel oil concentrations were used as variable parameters. The engine speed was determined as 1000 and 1200 rpm, excess air ratio 1.7 and 2.1, and fusel oil ratio in fuel was determined as 15% and 30%. When the HCCI engine was operated with these input parameters, the effective torque indicated thermal efficiency, maximum pressure increase rate, COVimep, HC, CO, and NOx values were examined. Experiments were carried out in line with the determined experimental series, and the data obtained were analyzed. Optimization has been made to determine the optimum input parameters by inputting the targeted response parameters from the HCCI engine. After the optimization study, it was concluded that the optimum response parameters, engine speed was 1262.44 rpm, excess air ratio was 1.91631, and was obtained by using F30 fuel. Under optimum input parameters, the effective torque is 5.751 Nm, ITE 34.089%, MPRR 7.257%, COVimep 4.009%, CA50 7 ° CA, HC 454.185 ppm, CO 0.0727%, and NOx 0.000169486 ppm.
Some Dianthus specimens collected from Sakarya and Bolu Provinces (Turkey) provinces are proposed as a new species. Dianthus nezahatiae Hamzaoğlu (Caryophyllaceae) is naturally distributed in subalpine meadow habitats between the altitude range of 1450 and 1620 m a.s.l. Dianthus nezahatiae is differed from D. akdaghensis Gemici et Leblebici in respect to its inner bracts are 1.7−2.1 mm wide, the apex of the epicalyx scales is attenuate–rounded, the petal collar is almost half of the claw width, and the capsule is longer than calyx. In this paper description of the species, comparison with its close taxon, photographs, the distribution map, and its habitat preference are given.
This paper presents a family of implicit-explicit (IMEX) time stepping scheme for the optimal control problem of the unsteady Navier-Stokes equations (NSE). The main feature of this kind of optimal control problem is that stabilization terms are proportional to discrete curvature of the solutions. First and second order optimality conditions are used for optimality of the curvature based stabilized Navier-Stokes equations. Complete stability and error analyses of state, adjoint and control variables are presented. Numerical experiments verify theoretical findings and illustrate the improvement of approximate solutions enhancing the efficiency of numerical scheme.
This study presents a comparison of three different S‐band thulium‐doped fiber amplifiers (TDFA) designs. The gain performances of the amplifiers are analyzed based on each scheme, separately. With −20 dBm input power, to provide ground‐state and excited‐state absorptions, the 1050 nm pump is used in all designs. The thulium‐doped fiber (TDF) lengths are optimized for maximum gain by using the single parameter single result optimization of Optisystem 18.0 software. A reflector is integrated into the double‐pass and dual‐stage triple‐pass TDFA to allow double propagation. Compared to double‐pass TDFA, in dual‐stage triple‐pass TDFA design, gain values increased without changing the stable bandwidth. 42.77 dB gain is demonstrated for two optimized TDF lengths; L1: 5 m and L2: 4.8 m, while noise figure values are higher than the other schemes. This comparison is important to show that the dual‐stage triple‐pass TDFA design could be suitable for obtaining higher gain in wider stable bandwidth in the fiber optic communication systems.
This paper proposes and implements, a harmonic analysis technique used in microgrids for inverter power control when measured voltage and current signals are passed over a communication link with considerable latency. Using frequency-shifting and filtering techniques, the measurement is converted to magnitude and phase information and passed over an asynchronous communication link to another controller, where the original waveform is recovered with delay compensation. The method allows accurate power calculations and grid synchronization over distributed prosumer controllers. The proposed method can work at different execution rates, depending on real time (RT) workload, and is shown to be robust against step changes, harmonics and communication delays. The method is demonstrated with two PHIL experiments at the CoSES, TU Munich lab in grid connected and island mode.
The risk assessment of submarine pipeline is carried out considering vertical and horizontal displacements under hydrodynamic forces. The stability of the pipeline is assessed according to limit-state functions using Monte Carlo (MC) simulation. The effects of subsea topography, hydrodynamic loads of waves and currents, pipe-soil interaction, and characteristics of hazardous materials carried by the pipeline were examined. The failure probability obtained by the MC simulation was defined by the exceedance probability of the displacement limit state. The novel part of this paper is the MC simulation which is coupled with a 3-D hydrodynamic numerical model (Hydrotam-3D) developed by Balas (Balas and Ozhan, 2000). The effects of pipe-soil interactions and environmental parameters such as wave-induced currents can be obtained by this model coupling. The most important parameters that affect the results of the simulations are obtained. Hydrodynamic loads that depend on the combined actions of waves and currents are obtained by the hydrodynamic numerical model (Hydrotam-3D) and they are used in the MC simulation, to increase the reliability of the pipeline design.
This paper presents a combined usage of axiomatic design principles and simulation in developing and comparison of alternative assembly systems for airplane fuselage panels. In the application, four assembly system alternatives are obtained with axiomatic design methodology; and their performance results are obtained using simulation. The simulation results are made available for system designers to see each alternative’s capabilities and make a comparison among the alternatives. The application of the proposed combined application of axiomatic design principles and simulation provides a reference guide for system designers to apply in designing other assembly systems’ design.
Background Although several renal biopsy registry reports have been published worldwide, there are no data on primary glomerular disease trends in Turkey. Methods Three thousand eight-hundred fifty-eight native kidney biopsy records were assessed in the Turkish Society of Nephrology Primary Glomerulopathy Working Group (TSN-GOLD) Registry. Secondary disease and transplant biopsies were not recorded in the registry. These records were divided into four periods, before 2009, 2009 to 2013, 2013–2017, and 2017–current. Results A total of 3858 patients (43.6% female, 6.8% elderly) were examined. Nephrotic syndrome was the most common biopsy indication in all periods (58.6%, 53%, 44.1%, 51.6%, respectively). In the whole cohort, IgA nephropathy (IgAN) (25.7%) was the most common PGN with male predominance (62.7%), and IgAN frequency steadily increased through the periods (× 2 = 198, p < 0.001). MGN was the most common nephropathy in the elderly (> 65 years), and there was no trend in this age group. An increasing trend was seen in the frequency of overweight patients (× 2 = 37, p < 0.0001). Although the biopsy rate performed with interventional radiology gradually increased, the mean glomeruli count in the samples did not change over the periods. Conclusions In Turkey, IgAN is the most common primary glomerulonephritis, and the frequency of this is increasing.
Institution pages aggregate content on ResearchGate related to an institution. The members listed on this page have self-identified as being affiliated with this institution. Publications listed on this page were identified by our algorithms as relating to this institution. This page was not created or approved by the institution. If you represent an institution and have questions about these pages or wish to report inaccurate content, you can contact us here.
9,182 members
Hakan Ciftci
  • Department of Physics
Abdullah Hasbenli
  • Department of Biology
Information
Address
Teknikokullar, 06500, Ankara, Republic of Turkey, Turkey
Head of institution
Gazi University
Website
www.gazi.edu.tr
Phone
+903122028571
Fax
+903122213202