Kocaeli University
  • İzmit, Kocaeli, Turkey
Recent publications
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.
This paper introduces an innovative anchor-type longitudinal fin design that copes with the sluggish phase change process in shell-and-tube ice storage units by covering the regions between the conventional fins. The influence of these fins is studied on both melting and solidification processes. The simulations show that the melting process is much slower than the solidification process (up to 201.5%), and the presence of fins can be more influential on the melting process. The examined parameters for the fins are arc angle (θ), shank length (L sh), number of anchor-type fins (N f), and number of arcs on these fins (N a). The study reveals that at an identical PCM volume, this type of fin can improve the melting time by 1367.7 and 151.8% compared to when the bare tube and conventional longitudinal fins with the same length and number are used, respectively. On the other hand, these values for the solidification process are 544.2 and 89.5%, respectively. Furthermore, it was found that these fins manage to diminish the undesirable effects of natural convection by disrupting the un-wanted thermal stratification in the container by breaking the large circulation zone for the natural fluid flow in the container into several smaller circulation areas.
This work proposes a novel type of shell and tube latent thermal energy storage unit (LTESU). Effects of the thermal conductivity of PCM, the inlet temperature of heat transfer fluid (HTF), the inlet velocity of HTF and fin layout (fin length and distribution) on the thermal performance and exergy efficiency of the LTESU are numerically investigated. The transient numerical computation of the PCM phase transition process incorporates iterative by the finite volume method based on enthalpy-porosity technique. The results showed that the role of fin layout for enhancing the energy storage performance of LTESU is more predominant than that by the PCM thermal conductivity. The LTESU with fins has better heat storage intensity compared with the case of no-fins, where the heat storage intensity increased by 104.33% with non-uniform fin length and distribution and 61.06% with uniform fin length and distribution. In addition, the exergy efficiency of LTESU with reduced fin length and uniform distribution along the HTF flow direction (Case 1) has the greatest improvement, which is increased by 8.53% for Case 1 relative to the no-fins case. The findings reveal that adopting non-uniform length and distributed fins is an effective solution to attain higher thermal performance in LTESU.
The aim of present work is to analyze a U-type of evacuated tube solar collector in which phase change material (PCM) is employed to store surplus solar energy in daytime and reuse it at nighttime when the solar irradiation vanishes. Both charging and discharging processes are considered and modeled. Two critical points should be considered in designing the proposed collector; the stable requirement outlet temperature of the domestic solar collector during daytime (about 40°C) and assurance of a complete melting/solidification process to reach the maximum energy storage and release. Since the absorbed energy from solar radiation by heat transfer fluid and PCM in both day and nighttime strongly depends on the U-type tube's diameter, three values of which (namely, 6, 8, and 10 mm) are selected to attain the best case. The results show that the case with 6 mm diameter yields a 25% and 13.5% improvement in the liquid fraction and fluid outlet temperature, respectively, at 3:00 PM in the charging process, compared to other cases. Also, this case has achieved a 20% delay in the thermal energy release process and has increased the fluid outlet temperature by 24%, compared to other cases, at 9:00 PM in the discharging process.
A hybrid solar photovoltaic-thermal collector is the combination of a solar thermal unit and a photovoltaic panel for the simultaneous generation of heat and electricity. In these systems, a fluid is used to cool photovoltaic panels and, thus, prevent their reduction of electrical efficiency. The hot fluid leaving the system can also be used in various kinds of engineering applications, from agriculture to heating, ventilation and air conditioning units, and process heat in utilities. Coolants used in photovoltaic-thermal units include air, water and nanofluids, among which air is less efficient than water and nanofluids due to its low specific heat capacity. Although extensive research has been done on the exergy performance of photovoltaic-thermal units, the number of published review articles in this field is very limited. This paper presents a critical review with some recommendations for future research on the topic of exergy examination of water-based and nanofluid-based photovoltaic-thermal units. As a first step, the concept and mathematical exergy relations are introduced. Then, water-based and nanofluid-based photovoltaic-thermal units are exergetically discussed in detail, followed by the description of novel units. At the end of each section, some suggestions are presented for future exergy examination of those types of photovoltaic-thermal units.
We study the impact of the severe equatorial earthquakes on the ionospheric Equatorial Ionization Anomaly (EIA) to check the variations in the shape of electron concentrations along the earthquake longitudes as the possible precursors to the earthquakes by considering a case study of a strong Mw 7.3 seismic event from Honduras occurred in 2009. We have observed sharp increments in the atmospheric chemical potential and surface air temperature time series along with an abrupt decrease in the relative humidity simultaneously about 5–8 days before the impending earthquake indicating the procreation of the air ionization due to increased radon activity around the earthquake's epicenter. We further investigated the ionospheric conditions by estimating the total electron content (TEC) from 6 IGS stations. The results suggested that the 2 IGS stations operating within the earthquake preparation area (EPA) showed prominent TEC enhancements about 5 days before the impending earthquake, consistent with the seismic atmospheric circulations. The other 3 IGS stations, operating outside the EPA, did not show any perturbation. These TEC variations are quantified based on two different methods: (1) running interquartile method and (2) method of cognitive recognition (applied on station BOGT). Moreover, the TEC and electron density profiles, retrieved from station BOGT and the ISL probe of the DEMETER satellite, respectively, revealed that the local TEC enhancements further dispersed toward the magnetic equator at higher altitudes by developing an enormous two-hump-like EIA structure near the epicentral longitude that verifies the generation of the seismogenic electric field through air ionization. We believe that our multi-precursory analysis is another step forward in comprehending the seismic lithosphere–ionosphere interactions.
Large-scale usage of high and ultra-high strength steels is strongly linked to the availability of suitable joining techniques ensuring consistent properties throughout the welded structure. For conventional structural steels, fusion welding techniques, such as gas metal- or submerged arc welding, are well established and widely used. In many cases these welding processes can also be utilized for high and ultra-high strength steels. Likewise, high energy density welding processes, e.g. laser beam or electron beam welding, can also be suitable choices for welding these materials. However, constraints such as missing filler metals, missing standardization, and small processing windows, especially in terms of allowed heat input, still limit their application. In this review scientific literature on fusion welding of various ultra-high strength structural steel grades, i.e. steels with a yield strength in the range of 690 to 1300 MPa, is reviewed and discussed. The main focus lies on experimental results regarding mechanical properties, such as tensile strength, hardness, impact toughness, fatigue, etc. as well as residual stresses and microstructural transformations.
GNSS-IR enables the extraction of environmental parameters such as snow depth by analyzing signal-to-noise ratio, indicating the strength of the GNSS signal. We propose a machine learning (ML) classification approach for snow depth retrieval using the GNSS-IR technique. ML classifier algorithms were studied to classify the strong and weak ground reflections using input parameters (azimuth angle, satellite elevation angle, day of year, amplitude of reflected signal, epoch number, etc.) as independent variables. GPS data collected by UNAVCO AB39 and daily snow depth data from SNOTEL Fort Yukon for a 6-year period (2015–2020) were considered. The first 4-year data were trained by some well-known ML classifiers to weight the input data and then used to classify the strong and weak signals. Tree-based classifiers, Random Forest, AdaBoost, and Gradient Boosting overperformed the other classifiers since they have more than 70% accuracy, so we performed our analysis with these three methods. The last 2-year data were used to validate both trained models and snow depth retrievals. The results show that ML classifier algorithms perform better results than traditional GNSS-IR snow depth retrieval; they improve the correlations by up to 19%. Moreover, the root-mean-square errors decrease from 15.4 to 4.5 cm. This study has a novel approach to the use of ML techniques in GNSS-IR signal classification, and the proposed methods provide a critical improvement in accuracy compared to the traditional method.
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.
Several studies on vaccines and medicines against virus-based illnesses (COVID-19, SARS, MERS) are being conducted worldwide. However, virus mutation is an issue. Therefore, inactivation and disinfection of viruses are crucial. This paper presents a method for virus inactivation by physical techniques. The infrared (IR) technique is preferred over other disinfection techniques such as ultraviolet (UV) and chemical disinfectants (alcohol) due to the associated health and environmental benefits. In this study, IR sources with various wavelengths were characterized and a far infrared (FIR) source was used to inactivate viruses. FIR sources have a therapeutic effect on the human body and have been used in medical centers. Virus spread is highly affected by environmental conditions such as temperature, humidity, and airflow. A setup with IR sources, an IR camera, an automatically controlled humidity chamber, and an airflow unit was constructed to study the viability of viruses in stationary droplets as a function of relative humidity and temperature. Bacteriophage Phi6 was used as a model organism for studying enveloped viruses such as influenza and coronavirus. IR techniques were used for studying virus inactivation. The effect of various physical conditions such as temperature, humidity, and airflows was considered to study the effect of radiation on the stationary droplets of Phi6. All measurements were performed under laboratory conditions with controlled temperature and humidity. The IR camera system was used to measure the surface temperature of Phi6 suspension droplets. The samples subjected to IR radiation were processed for plaque assay preparation and counting. Measurements were carried out to reduce and eliminate droplets, which are one of the transmission pathways of viruses. IR was radiated in closed and open-air conditions with appropriate humidity and temperature. This study reports the effective inactivation of viruses by FIR. The inactivation rate under 50 %rh for IR radiated at 1.4 m height for 3 h in closed environmental chamber was 90%, and that under an airflow rate of 0.20 m/s for 10 min in open-air conditions at a height of 1.0 m was 45.7%.
Latent heat materials are widely investigated and successfully used in a variety of important applications as in the building industry and thermal engineering systems. In this paper a comprehensive review on phase change material (PCM) in relatively recent potential application such as photovoltaic (PV) panel cooling, applications in food, automotive; asphalt, and textile industries. The review is divided into seven sections. The first two sections give a general overview of PCMs, their potential in integrating intermittent systems, PCM characterization and enhancement techniques. In the third and subsequent sections applications in the PV panels cooling, food, textile, automotive and asphalt applications are presented. The results showed that application of PCM RT42 in a BiCPV system reduced the temperature by about 3.8 °C and increased the electrical efficiency by 7.7 %. The use of finned enclosures enhanced the performance of PV panels. A finned enclosure decreased the operating temperature by 6.1 °C and increased the efficiency by 5.3 %.The use of nanoparticles (SiC) dispersed into paraffin based PCM showed good thermal performance and increased the electrical efficiency by 13.7 %. Similar benefits are found in the food industry. The use of PCM in food containers reduced the energy consumption, the operational cost, and the emission by 86.7, 91.6, and 78.5 %, respectively. Penetration of PCM in the textile industry is relatively small. Applications in the textile industry showed that for a temperature rise from 20 to 28 °C, common silk took 13 s, the Outlast/silk took 20 s, and the treated fabric took 37 s. Application of PCM in the car industry for cooling batteries, and thermal insulation is continuously growing. It is shown that using PCM decreased the maximum and minimum battery temperature from 56.8 and 48.3 °C to 38.9 and 36.0 °C, respectively. Other application showed that the use of coconut oil as PCM for the thermal control of a vehicle decreased the passenger's cabin temperature by an average of 13 °C, while application on the roof of a parked car during 1 h in a sunny day can reduce the temperature by about 33 °C. The inclusion of PCM in the asphalt mixture can eliminate the destructive bonds that cause aging of the asphalt mixture, contribute to the prevention of low-temperature cracking and decrease the temperature fluctuations in the asphalt binder. This review can be of great help for system designers, practice engineers and researchers in the area of thermal energy storage and PCM based systems. Trends for future research are highlighted.
An analytical framework was proposed for analyzing long-term chemical pollution in a coastal region with limited environmental data. The framework consists of compiling and synthesizing the available knowledge including the chemical's properties and the environmentally relevant data, as well as the data obtained by past monitoring studies. The gathered data is analyzed to assess multimedia fate of the pollutant by using fugacity-based intermedia transport calculations. Uncertainty analysis by applying Monte Carlo simulations is an integrated part of the framework. Dispersion factor (k) values were adopted, enabling a unified and intuitive way to define lognormal uncertainty distributions. The proposed framework was applied to polycyclic aromatic hydrocarbon (PAH) pollution in Izmit Bay, a coastal region in Turkey, impacted by industrialization and population growth. The analysis showed the importance of atmospheric pollution as a PAH source and indicated that Izmit Bay sediments may be at steady state for most PAHs.
In this study, a new medium manganese (medium-Mn) steel alloy is developed for the hot stamping process and required material properties were obtained. The differences of microstructural and mechanical behaviors among typical 22MnB5 steel and medium-Mn steel are investigated during the hot stamping both in uncoated condition. The commercial Finite Element software PAM-STAMP is employed for the simulation of the hot stamping. ThermoCalc and JMatPro are used for the calculation of necessary thermophysical properties. The hot ductility and fracture behaviors of medium-Mn steel are investigated by Gleeble hot tensile experiments over the deformation temperatures of 600–900 °C and strain rates of 10− 3 and 10− 4 after annealing at different temperatures during the thermomechanical process. Dilatometer tests were conducted to obtain the phase transformations. Hot tensile testing and dilatometry studies indicated that the hot tensile behavior of medium-Mn steel is influenced by the microstructural alterations occurred via cooling or heating prior to the deformation. To validate the thickness distribution and the microstructural evolution, a prototype part is manufactured on a semi-industrial scale by hot stamping for both materials. A good correlation between simulation and experiments was observed. In addition, decarburization of the part is investigated. medium-Mn steel exhibited a lower decarburization layer. It was also seen that the higher hardenability of medium-Mn steel favors the martensitic transformation.
In this study, the polyvinyl alcohol (PVA) and sodium caseinate (SC) nanofibers were produced by a single-fluid electrospinning method from their blends. Afterward, the cross-linking process with two different methods was applied to the PVA/SC (70/30, v/v) ratio, which was selected according to the surface and mechanical properties of the electrospun mat. In the first method, different ratios (15%, 20%, 25%, and 30%) of glutaraldehyde (GLA) cross-linking agents were added to the PVA/SC solution and then, PVA/SC/GLA nanofibers were obtained. In the second method (in-situ method), the nanofibers obtained from the PVA/SC solution were cross-linked by dipping into the cross-linking solution. After, PVA/SC/GLA/Zinc oxide nanoparticles (ZnO NP) mats were obtained by adding ZnO NP at different rates to the PVA/SC/GLA (7030-25GLA) solution, which was chosen according to the results of thermal, mechanical, and moisture test. In addition, performing tests, a cytotoxicity test for fibroblast cell line (L929), and in vitro antibacterial test for Escherichia coli and Staphylococcus aureus were also applied to them. Therefore, the usability of PVA/SC/GLA/ZnO NP nanofibers as an antibacterial effective wound dressing was investigated. Due to the high toxic effect of GLA, it was found that PVA/SC/ZnO cross-linked nanofibers are not suitable for wound dressing use. However, it was determined that the PVA/SC nanofiber cross-linked by the in-situ method had high cell viability according to the cytotoxicity test result and thus could be used as a fibroblast tissue scaffold.
This study aimed to investigate the partial pressure of carbon dioxide (pCO2) and the serum total carbon dioxide (stCO2) gradients (ΔpCO2 and ΔstCO2) associated with the emergency treatment of ADHF and their relationship with major cardiac adverse events (MACE). This was a prospective observational study conducted in an academic emergency department (ED). Adult patient requiring emergency treatment for ADHF in the ED were included. The patients’ pCO2 and stCO2 levels were measured pre-treatment and at 6 h post-treatment. The ΔpCO2 and the ΔstCO2 and their relationship with MACE were evaluated. Ninety patients were included in the study. Five (5.5%) of the patients were in the low-risk group, 23 (25.6%) were in the intermediate-risk group, and 62 (68.9%) were in the high-risk group. The pCO2 and stCO2 levels were significantly higher in all the patients at the 6th hour following treatment (p = 0.018; p < 0.001, respectively). ΔstCO2 was significantly different between the risk groups (p = 0.037). No significant relations of ΔpCO2 and ΔstCO2 with MACE were detected (p = 0.989; p = 0.208, respectively). Although pCO2 and stCO2 significantly increased during the ADHF treatment, this change was not related to MACE.
Purpose To evaluate the corneal nerve fiber morphology in patients with multiple sclerosis (MS) by in vivo corneal confocal microscopy (CCM). Methods Retinal nerve fiber layer thickness (RNFLT), central macular thickness (CMT), corneal nerve fiber length (CNFL), corneal nerve fiber density (CNFD), corneal nerve branch density (CNBD) and corneal nerve fiber tortuosity (CNFT) were measured. Correlation of corneal nerve findings with duration and clinical severity of MS was calculated. Results CNFL (9.50 ± 0.60 vs. 11.20 ± 0.57 mm/mm², P = 0.046) and CNBD (57.46 ± 5.04 vs. 77.65 ± 3.41 no/mm², P = 0.001) were significantly lower with no significant difference in CNFD (21.24 ± 1.20 vs. 23.62 ± 0.95 no/mm², P = 0.125), CNFT (2.00 ± 0.15 vs. 1.73 ± 0.12, P = 0.180), CMT (269.57 ± 12.53 vs. 271.10 ± 18.84 μm, P = 0.716) or RNFLT (102.82 ± 6.98 vs. 105.33 ± 12.70 μm, P = 0.351) between patients with RRMS compared to controls. There was no significant correlation between CCM parameters with EDSS and duration of disease in MS patients. Conclusion The current study demonstrated that a decrease in CNFL, CNFD and CNBD in CCM analysis in the early course of MS.
The present study is aimed at exploring the links between academic self-efficacy, career decision-making self-efficacy, and academic major satisfaction, with career optimism as the mediator. The hypotheses based on this aim were tested on the data collected from a sample consisting of 411 senior engineering undergraduates attending a prestigious public university in Turkey. The results of structural equation modeling analyses indicate that career optimism mediates the relationship between academic self-efficacy and academic major satisfaction. Additionally, career optimism was found to have a mediating effect in the relationship between career decision-making self-efficacy and academic major satisfaction. Implications for theory and practice are presented.
Background Intraprocedural coronary angiography (CA) is recommended in patients undergoing ablation in aortic cusps to assess the relation of catheter tip and coronary ostia. In this report, we aimed to compare selective coronary angiography (SCA) through the contact force (CF)-sensing radiofrequency catheter with conventional coronary angiography (CCA) to guide ablation of premature ventricular contractions (PVC). Methods This was a retrospective observational cohort study of prospectively collected data of 87 consecutive patients undergoing PVC ablation at a single institution between February 2016 and June 2021. Forty-six patients (53%) underwent SCA and forty-one patients (47%) underwent CCA. Data were consecutively collected case-by-case and entered into a computerized database. Procedural characteristics, complications, and clinical outcomes were compared between the SCA and CCA groups. Results Successful ablation was achieved in seventy-seven (89%) patients. Total procedure and fluoroscopy time and radiation dose were significantly lower in SCA group (93 ± 22 min vs 102 ± 20 min, p = 0.042; 12 ± 3 min vs 14 ± 4 min, p = 0.030; 3292 ± 1221 μGy m² vs 3880 ± 1229 μGy m², p = 0.028, respectively). Median ambulation time was significantly longer in CCA group (6.8 ± 1 h vs 17.8 ± 1.8 h, p = 0.006). Conclusions Selective coronary angiography through the CF-sensing ablation catheter to assess the relation between the ablation site and the coronary ostia is feasible and safe. This technique precludes the requirement of an additional arterial access and decreases the total procedure and fluoroscopy time and radiation dose.
Background Diabetes education in Turkey is provided by diabetes nurse educators in almost all healthcare organizations. However, the education is not standardized in terms of learning content, duration, and methods. This multi-center study was performed to assess the self-care behaviors and glycemic control following education provided to the patients with type 2 diabetes mellitus by diabetes nurse educators. Methods This was a descriptive and cross-sectional study and included 1535 patients admitted to 28 public hospitals for the treatment of type 2 diabetes mellitus. The education was assessed by using a Patient Identification Form and Self-care Scale. Results The proportion of individuals who received diabetes education within the last year was 78.5%, with 46.7% of them having received it once. Of the patients, 84.8% reported that they received diabetes education individually. It was found that the proportion of individuals who received education about oral antidiabetics (78.5%) and glucose testing at home (78.5%) was higher than the proportion of individuals who received education about exercise (58.8%) and foot care (61.6%). The status of diabetes education, education intervals, and the correlation of the education method with self-care and glycemic control was evaluated. Self-care and glycemic control levels were better among the patients who received diabetes education thrice or more and in patients who received education both individually and in a group (p < 0.05). Conclusions Approximately three-quarters of individuals with type 2 diabetes mellitus received education by diabetes nurse educators in Turkey. Diabetes education is positively correlated with self-care and glycemic control levels among patients with type 2 diabetes mellitus. Efforts for generalization and standardized education for all diabetes patients are necessary.
In this article, the analysis of the inductive coupled CUK topology, which is a DC-DC converter, which is of great importance for power electronics and used in structures such as electric vehicles and PV systems, with Modified Nodal Analysis (MNA) and the modeling of the elements in the circuit structure will be explained. The numerical values of the semiconductors and passive circuit elements to be modeled will be given the voltage, and current at the output will be calculated. In addition, the graphs of the parameters analyzed and analyzed with MNA will be created with the code system written in the MATLAB environment and will be explained in this article.
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5,488 members
Esra Guzeldemir
  • Department of Periodontology
Can Aksu
  • Department of Anesthesiology and Reanimation
Elif Kacar
  • Department of Physics
Soner Polat
  • Department of Educational Sciences
Umuttepe Kampüsü, TR-41380, İzmit, Kocaeli, Turkey