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    Evaluation of early thyroidectomy complications
    (Bayrakol Medical Publisher, 2022) Karatas, Turgay; Selcuk, Engin Burak; Karatas, Mehmet; Yildirim, Atilla; Ozbag, Davut; Cay, Mahmut; Senol, Deniz
    Aim: Our aim in this study is to reveal the relationships between patient findings, surgical methods and early thyroidectomy complications. Material and Methods: The files and operative notes of 308 patients who underwent thyroidectomy within 10 years were reviewed retrospectively. Gender, age, preoperative diagnosis, primary or reoperated cases, the type of thyroidectomy [ bilateral subtotal (BST), bilateral total (BTT), unilateral subtotal (UST) and unilateral total (UTT)] and early postoperative complications (hypocalcemia, bleeding, nervus laryngeus recurrens (NLR) injury, infection and seroma) were recorded. The peculiarity of this study is that NLR neuromonitoring was not used in thyroidectomy operations. Results: Of the 308 patients who underwent thyroidectomy, 287 were females and 21 were males. Two hundred eighty three cases of multinodular goiter, 18 cases of nodular goiter and 7 thyroid cancers were operated; 180 BTT, 100 BST, 17 UTT + UST, 7 UST and 4 UTT were applied. Complications were seen in a total of 20 (6.49%) patients who underwent 19 BTT and 1 BST. The only complication in BST was bleeding. There were 10 (3.24%) hypocalcemia, 4 (1.29%) bleeding, 2 (0.649%) NLR injury, 2 (0.649%) infections and 2 (0.649%) seromas. In terms of the frequency of early thyroidectomy complications, hypocalcemia was the first (P=0.0047). In addition, the rates of hypocalcemia and NLR injury were higher in reoperated patients than in primary patients (P<0.05). Discussion: The most common complication was hypocalcemia. NLR injury and hypocalcemia rates were higher in reoperated cases who underwent BTT.
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    Experimental determination of electrical and thermo-physical characteristics of dielectric nanofluids based on volume fraction change
    (Elsevier Science Sa, 2023) Karatas, Mehmet; Bicen, Yunus
    Dielectric insulating fluids perform critical tasks such as electrical insulation and cooling functions in power system equipment. Improving the thermal properties of insulating fluids extends the service life of power equipment, while improving their dielectric properties ensures a reliable and safe electricity supply. Therefore, studies on enhancing the thermal and dielectric qualities of dielectric fluids using nanoparticles have become more popular in recent years. In this study, the dielectric and thermo-physical properties of mineral oil-based SiO2 nanoparticle suspensions, namely nanofluids, have been investigated. An approximately 25.6% enhance-ment in AC breakdown voltage level has been obtained at a 0.05% critical volume fraction. It has been noted that the level of the AC breakdown voltage decreases when the critical volume fraction is exceeded. The thermal conductivity of the prepared nanofluid has changed logarithmically in the positive direction according to the rising number of nanoparticles per unit volume. Thermal conductivity has increased by around 8.55% for the critical volume fraction value, whereas thermal diffusivity has increased by approximately 22%. Similarly, when the number of particles in the nanofluid rises, the viscosity increases nonlinearly. The viscosity increase, which is undesirable for heat transfer, has been determined to be around 10.64% for the crucial volume fraction. These findings indicate that dielectric nanofluids hold significant potential for the future. The SEM analysis, on the other hand, explains the difficulties of assuring the long-term stability of nanofluids in the volume fraction with the highest AC dielectric breakdown voltage.
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    Nanoparticle-enhanced dielectric oils for improved electrical insulation: Comparison of MgO, Al2O3, and SiO2-based dielectric nanofluids
    (Wiley, 2025) Karatas, Mehmet; Bicen, Yunus
    This study provides comprehensive and quantitative assessments of the electrical insulation, viscosity, thermal conductivity, flash point, acidity, and stability of dielectric nanofluids. In the experiment, naphthenic mineral oil was chosen as the base fluid. MgO, Al2O3, and SiO2 were preferred as nanoparticles. In the dielectric breakdown voltage (BDV) tests performed, increased values were observed at certain concentrations for each nanofluid, with the highest value in the SiO2-based nanofluid being 83.47 kV at a concentration rate of 0.05 g/L. Adding nanoparticles to the base oil increased the viscosity of all suspensions. Except for MgO-based dielectric nanofluid, the flash points of other nanofluids increased as compared to pure oil. Total acid number (TAN) values, on the other hand, increased for SiO2- and Al2O3-based nanofluids but decreased for MgO-based nanofluids. However, all values are quite below the standard limit of 0.25 mgKOH/g. The percentage transmittance values calculated from the ultraviolet and visible light (UV-vis) spectrophotometry results differed for each nanofluid. However, they were all lower than the base oil. In general, the results indicate that the use of dielectric nanofluids in electrical systems will be beneficial, provided that the problem of long-term stabilisation is solved.