Atılım Academic Archive (Atılım University)
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The Relationship Between Concentric and Isometric Strength of Knee Flexor and Extensor Muscles and Postural Stability in Mild Stage Multiple Sclerosis Patients
Get PDFUnluer, Nezehat Ozgul/0000-0003-2314-0738Background Multiple sclerosis (MS) affects muscle strength and postural stability. However, the relationship between concentric and isometric strength of knee flexors and extensors and postural stability in mild stage MS is not well known. The aim of the study was to examine the relationship between concentric and isometric strength of knee flexors and extensors and postural stability in mild stage MS patients. Materials and Methods The study included 21 mild-stage MS patients with an EDSS score of 4 or less and 21 healthy controls. The concentric and isometric strength of knee flexors and extensors was measured with the Biodex System 4 Dynamometer, and postural stability with the Biodex Balance System under eyes-open and eyes-closed conditions on a rigid surface. Results Mild-stage MS patients had reduced concentric strength of knee extensors and flexors and increased postural sway compared with healthy controls (p 0.05). There was a moderate positive correlation between concentric strength of knee extensors and flexors and isometric strength of knee flexors and open-eye postural stability indexes in mild stage multiple sclerosis patients (p < 0.05). Conclusions While isometric strength of knee extensors and flexors was preserved, concentric strength of knee extensors and flexors was decreased, and postural stability was adversely affected in mild stage MS patients. The increase in the strength of the knee muscles was associated with an increase in their postural sway in mild stage MS patients.Science Citation Index Expande
Antioxidant Activity of Micractinium Sp. (Chlorophyta) Extracts Against H2o2 Induced Oxidative Stress in Human Breast Adenocarcinoma Cells
No full textScience Citation Index Expande
4D-Printed Continuous Fiber-Reinforced PLA/TPU Auxetic Composites: Mechanical Performance, Energy Absorption, Shape Recovery, and Reusability Evaluation
No full textThis study explores the mechanical performance, energy absorption, shape recovery, and reusability of 4D-printed continuous carbon fiber-reinforced auxetic composite structures based on PLA/TPU blends, designed for load-bearing applications. PLA-TPU mixtures with different TPU content were developed to optimize the balance between flexibility and strength, with carbon fibers incorporated to enhance the mechanical properties of the resulting composites. Thermo-mechanical characterization of the blends was conducted, followed by a detailed evaluation of the structures' mechanical behavior and energy absorption capacity under room temperature conditions, simulating practical industrial scenarios. The shape recovery performance of these composite structures was also investigated. To assess reusability, the programming-recovery cycle was repeated five times, analyzing the retention of mechanical properties and shape recovery over multiple cycles to determine durability. Results revealed that TPU integration provided sufficient flexibility for cold programming, while carbon fiber reinforcement significantly enhanced stiffness and strength. The 4D-printed composites exhibited consistent shape recovery and maintained mechanical integrity after five cycles, confirming their reusability. These findings demonstrate the potential of 4D-printed PLA/TPU-based carbon fiber-reinforced composites as smart, durable materials for load-bearing applications in industries such as biomedical engineering, automotive, and aerospace.Turkiye Bilimsel ve Teknolojik Arastirma Kurumu [221M067]Turkiye Bilimsel ve Teknolojik Arastirma Kurumu, 221M067, 221M067, 221M067, 221M067
Lifetime Prediction of Single Crystal Nickel-Based Superalloys
Get PDFKaftancioglu, Utku/0009-0009-6387-1990; BAYRAKTAR, Emin/0000-0003-0644-5249Single crystal nickel-based superalloys are extensively used in turbine blade applications due to their superior creep resistance compared to their polycrystalline counterparts. With the high creep resistance, high cycle fatigue (HCF) and low cycle fatigue (LCF) become primary failure mechanisms for such applications. This study investigates the fatigue life prediction of CMSX-4 using a combination of crystal plasticity and lifetime assessment models. The constitutive crystal plasticity model simulates the anisotropic, rate-dependent deformation behavior of CMSX-4, while the modified Chaboche damage model is used for lifetime assessment, focusing on cleavage stresses on active slip planes to include anisotropy. Both qualitative and quantitative data obtained from HCF experiments on single crystal superalloys with notched geometry were used for validation of the model. Furthermore, artificial neural networks (ANNs) were employed to enhance the accuracy of lifetime predictions across varying temperatures by analyzing the fatigue curves obtained from the damage model. The integration of crystal plasticity, damage mechanics, and ANNs resulted in an accurate prediction of fatigue life and crack initiation points under complex loading conditions of single crystals superalloys.TUBIdot;TAK 2244 Industrial PhD Program [119C037]This research was funded by the TUB & Idot;TAK 2244 Industrial PhD Program under project number [119C037]. Additionally, publication fees were covered by Turkish Aerospace Industries (TAI).Science Citation Index Expande
Serum Progesterone Variability on Embryo Transfer Day in Hormone Replacement Therapy Cycles Using Intramuscular Injections During Frozen Embryo Transfers
No full textPurpose To assess the intra-individual variability of serum progesterone (P) levels on embryo transfer (ET) day, when the same dose of intramuscular progesterone (IM-P) was used in two consecutive hormone replacement therapy (HRT) frozen embryo transfer (FET) cycles. Methods A total of 75 patients undergoing two consecutive HRT-FET cycles in one year performed at Bahceci Ankara IVF Center between November 2019 and February 2022 were retrospectively analyzed. Serum P levels were measured at the 117th-119th hours of support by a single laboratory. The two measurements of P levels performed on the day of the first and the second FET were compared to evaluate the intra-individual variability of serum P levels. Results Comparisons between the 1st and 2nd FET cycles revealed statistically significant intra-individual variation, with an average difference of -2.47 ng/mL (95% CI: -4.65 to -0.29, p = 0.027) between the two consecutive measurements. To assess their consistency, the limit of agreement was also tested with the Bland-Altman method, in which the mean difference (+ 1.96 x SD and -1.96 x SD) was -2.47 (16.1 and -21.1). Based on a previous study, the frequency of low P levels, as expressed by being > 20.6 ng/mL on ET day, was similar between the 1st and 2nd FET cycles (14.7% vs. 9.3%, p = 0.31). Notably, most patients had improved P levels in the second cycle if initially low, while decreases were rare among those with initially higher levels. Conclusion Serum P levels may vary within the same individual across FET cycles despite the use of the same dosage of IM-P. Increasing maternal age, high body mass index, and fluctuating estradiol levels on the day of ET were identified as risk factors contributing to this variability
Investigations on the Effect of Secondary Treatments on Ti48Al2Cr2Nb Alloy Manufactured by Electron Beam Powder Bed Fusion Method
No full textAs-built Ti48Al2Cr2Nb alloy samples produced by electron beam powder bed fusion (PBF-EB) exhibited notable brittleness. The low ductility was attributed to coarse gamma bands aligned perpendicular to the building and tensile direction. Additionally, variations in aluminum content and hardness between the coarse colonies and fine gamma/alpha(2) lamellae contribute to this phenomenon. Electron backscattered diffraction (EBSD) studies revealed a higher amount of dislocation density and inherent strain after PBF-EB manufacturing. Hence, usage of Ti48Al2Cr2Nb alloy in the as-built condition in aviation applications with high loads and demanding environments is not found to be viable. To eliminate these negative aspects and make PBF-EB produced Ti48Al2Cr2Nb alloy available for demanding applications, two distinct post-processing heat treatments; namely, hot isostatic pressing (HIP) and annealing heat treatment (HT) were employed at 1200 degrees C. A comprehensive characterization covering microstructure analysis, EBSD, fracture surface examination, as well as room and high-temperature tensile tests allowed determination of the effect of post-processes. HIPing altered the banded structure observed in the as-built samples by increasing the amount of alpha(2) phase and grain size. On the other hand, HT made the banded structure more pronounced without significantly increasing the amount of alpha(2) phase. HT also strengthened the texture, while HIPing introduced randomization of grains. On the other hand, complete recrystallization is achieved as a result of HT at 1200 degrees C for 2 h, whereas HIPing at the same temperature for 2 h induced only 80.5 % recrystallization. In both post-processes, dislocation density and inherent strain were reduced. Room temperature and high-temperature tensile tests demonstrated that both HIPing and HT eliminated the extreme brittleness of the as-built samples
Incidental Detection of Ectopic Liver Tissue During Elective Cholecystectomy: a Case Report
No full textEmral, Ahmet Cihangir/0000-0003-3976-1387Introduction Ectopic liver tissue (ELT) is a rare embryological anomaly most commonly found in the abdominal region, particularly on the gallbladder. It is generally asymptomatic and is often discovered incidentally during surgery or autopsy. Although histologically similar to the main liver, ELT should be excised due to the potential risk of malignancy.Case presentation This study presents a case of incidental ELT discovered during elective cholecystectomy in a 34-year-old female patient. Preoperative imaging revealed multiple gallstones, and during laparoscopic exploration, an ectopic liver tissue lesion was found on the gallbladder fundus. The lesion, measuring 10 x 5 mm, was excised en bloc with the gallbladder and sent for pathological examination, which showed no malignancy.Discussion The rarity and asymptomatic nature of ELT make it difficult to diagnose preoperatively, but its association with malignant transformation warrants careful management. In cases of suspected malignancy, further surgical approaches such as extended surgical margins and regional lymph node dissection should be considered.Conclusion This case underscores the importance of early detection and excision of ectopic liver tissue due to its potential for malignant transformation.Science Citation Index Expande
Tehlikeli Maddelerin İzinsiz Olarak Bulundurulması veya El Değiştirmesi Suçu (TCK M. 174)
No full textTCK m. 174 hükmünde kanun koyucu, üç farklı suç tipi düzenlemiştir. Bu suçların işlenebilmesi için, yasaklanan fiillerin yetkili makamların izni olmaksızın gerçekleştirilmesi gerekmektedir. Söz konusu iznin varlığının, hukuka uygunluk nedeni olduğu ileri sürülmekteyse de izin şartı, tipiklikte bir unsur olarak düzenlendiği için, bu çalışmada iznin varlığının, tipikliği kaldıran bir hal olduğu sonucuna ulaşılmıştır. Ayrıca TCK m. 174 hükmü kapsamında değerlendirilebilir bir fiilin, korunan hukuki varlığı tehlikeye atmaya elverişliliği olmasa dahi, salt yetkili makamdan izin alınmamış olması sebebiyle cezalandırılmasının, ihlal ilkesine aykırılık teşkil edebileceği sonucuna ulaşılmıştır. TCK m. 174/3 hükmüyle önemsiz tür ve miktarda patlayıcı maddeyi satın alan, kabul eden veya bulunduran kişinin cezalandırılacağı öngörülmüştür. Öte yandan, kanunun gerekçesinde bu fiillerin, meşru ihtiyaçları gidermek amacıyla gerçekleştirilebilecekleri belirtilerek yaratılan çelişki, bu çalışmada bir kanun değişikliği önerisiyle giderilmeye çalışılmıştır. TCK m. 174/1’in ikinci cümlesinde düzenlenen hazırlık suçunun maddi konusunun belirsiz olması ve karşılığında öngörülen müeyyidenin, TCK m. 174/1’in birinci cümlesinde düzenlenen suçun müeyyidesiyle aynı olması sebebiyle suçta ve cezada kanunilik, belirlilik ve orantılılık ilkelerini ihlal ettiği sonucuna ulaşılmıştır. Öte yandan, TCK m. 174/1’in birinci cümlesinde düzenlenen suç kapsamında, “bulundurma” seçimlik hareket olarak sayılmamış olmasına karşılık, uygulamada bu suç kapsamındaki maddelerin bulundurulmasından ceza verildiği gözlemlenmiş ve bu uygulamaların kanunilik ilkesine aykırı olduğu ortaya konulmuştur
Estimation of the Mean Radiant Temperature in Office Buildings Using an Artificial Neural Network Developed in a Phyton Environment
No full textThermal comfort describes an occupant's state of mind in a thermal environment, influenced by six parameters: air velocity, relative humidity, air temperature, mean radiant temperature (MRT), clothing value, and metabolic rate. MRT is the most problematic parameter since the obtaining process is difficult and time-consuming. MRT can be acquired by several methods such as calculations, measurements, assumptions, and software programmes. However, the methods have complexities and uncertainties. Comprehensive models are needed to obtain MRT. To this aim, this study presents an alternative method using one of the artificial intelligence methods, Artificial Neural Network (ANN), to predict MRT for indoor environments to abstain from the difficulties and complexities. A case building is selected in a university office building in Ankara, T & uuml;rkiye. The proposed model is developed and coded in a Python programming environment to predict the MRT using ANN. The results indicate that the ANN model, using only four inputs, predicts MRT with an R-2 value of 0.94 compared to the globe thermometer measurement method. The model's advantages over methods include simplicity, time efficiency and learning from the limited datasets such as difficulty in calculating terms like MRT.Emerging Sources Citation Inde
4D Printing of Reusable Mechanical Metamaterial Energy Absorber, Experimental and Numerical Investigation
Get PDFThis study investigates the compression behavior, energy absorption, shape memory properties, and reusability of 4D-printed smart mechanical metamaterials. Four structural configurations, i.e. honeycomb, re-entrant, and two modified re-entrant designs were developed to assess microstructure effects. Samples were fabricated using Polylactic Acid (PLA), a widely used shape memory polymer (SMP) in 4D printing, and polyethylene terephthalate glycol (PETG), an emerging SMP with demonstrated shape memory performance in recent studies. Cold-programming-induced shape recovery was evaluated at room temperature, simulating real-world conditions. Finite element simulations of compression and shape memory cycles matched experimental results well. Auxetic samples with negative Poisson's ratios showed superior energy absorption. However, only PETG demonstrated sufficient reusability, while PLA proved unsuitable for reusable designs. The PETG-3 modified re-entrant structure exhibited the best performance, with high energy absorption, delayed densification onset, and shape recovery and reusability factors of 0.95 and 0.96, respectively. Findings highlight the importance of considering both shape recovery and reusability when designing smart structures to address industrial challenges.Scientific and Technological Research Council of Turkey (TUEBITAK) [221M067]; Italian Ministry of University and Research [2022WFJ795, CUP F53C24001030001]This study was supported by the Scientific and Technological Research Council of Turkey (TUEBITAK) under Grant No. 221M067, which provided support to Ali Fallah, Qandeel Saleem and Bahattin Koc. Giulia Scalet acknowledges support from Italian Ministry of University and Research within the Call related to the scrolling of the final rankings of the PRIN 2022 call (Project StArT No 2022WFJ795, CUP F53C24001030001).Science Citation Index Expande