WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7150
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Article Evaluation of Partially Reduced Keratins Extracted From Wool Fibers as a Hydrogel Forming Biomaterial(inst Tecnologia Parana, 2024) Top, Ayben; Top, Ayben; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyIn this study, it was aimed to prepare low-cost hydrogel from reduced keratin. Keratin proteins were obtained from Merino wool via three extraction methods. In the first method, keratins were reduced using sodium sulfide. In the second method, keratins extracted with the first method were precipitated with HCl. Urea, EDTA, and sodium sulfide were used in the third method. Extraction yields of method 1, method 2, and method 3 were determined as 44 +/- 2, 27 +/- 1, and 42 +/- 2 %, respectively. For all extraction methods, the average value of the free thiol amounts was obtained as 0.06 +/- 0.02 mmol SH/g keratin. A considerable portion of the highly polydisperse keratins was separated between similar to 40 kDa and similar to 60 kDa in the SDS-PAGE gel, and this fraction corresponds to alpha-keratin proteins with low sulfur content. A strong band at similar to 1654 +/- 1 cm(-1) detected in the FTIR spectra of the keratins confirms mainly alpha-helical secondary structure. The self- standing hydrogel was obtained upon incubating 15 wt. % keratin solution at 37 degrees C. Storage modulus and loss modulus of the hydrogel were determined as 1.3 +/- 0.08 kPa and 0.1 +/- 0.015 kPa, respectively. The keratin hydrogel is not cytotoxic to L929 mouse fibroblast cells, suggesting that this affordable hydrogel can be applied as a drug delivery/encapsulation system and in wound healing.Article Citation - WoS: 2Citation - Scopus: 2Effects of Mix-Design Variables on the Workability, Rheology and Stability of Self-Consolidating Concrete(Pontificia Universidad Catolica de Chile, Escuela de Construccion Civil, 2022) Erdem, Tahir Kemal; Erdem, T.K.; 01. Izmir Institute of Technology; 03.03. Department of Civil Engineering; 03. Faculty of EngineeringThis study investigates the effects of basic mix design variables such as water/cement ratio (w/c), slump flow, coarse-to-total aggregate ratio (CA/TA), and maximum aggregate size (Dmax) on the main characteristics of self-consoli-dating concrete. The w/c of the mixtures was either 0.42 or 0.50. The CA/TA ranged between 0.45 and 0.53. Slump flow was adjusted to 550, 650 or 720 ±20 mm by varying the superplasticizer content. Dmax was varied as 10, 15 and 20 mm. V-funnel, L-box, rheometer, sieve segregation tests and a new test method, recently developed by the authors, for dynamic segregation resistance were performed. The effect of each variable on the test results were effectively summarized in a table. Increasing the w/c, CA/TA and Dmax decreased the superplasticizer demand and increased the flowability. When the slump flow, w/c and CA/TA were higher, viscosity was found to be lower. Higher values of CA/TA and Dmax were found to reduce the passing ability. Increasing the slump flow (or superplasticizer content), CA/TA and Dmax disturbed the sta-bility. Generally, the effects of w/c and slump flow on the SCC characteristics were more pronounced when compared to those of CA/TA and Dmax. Good correlations were obtained between several test results © Copyright (c) 2022 Alami, M. and Erdem, T. This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivatives 4.0 International LicenseArticle Citation - WoS: 63Correlating Rheology of Self-Consolidating Concrete To Corresponding Concrete-Equivalent Mortar(American Concrete Institute, 2009) Erdem, Tahir Kemal; Erdem, Tahir Kemal; Khayat, Kamal H.; Yahia, Ammar; 03.03. Department of Civil Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyThe investigation reported in this paper seeks to develop a methodology to evaluate the rheological parameters and thixotropy of self-consolidating concrete (SCC) using those of concrete-equivalent mortar (CEM). The mixture proportioning of CEMs are derived from their corresponding concrete mixtures by eliminating the coarse aggregate fraction and replacing it by a certain mass of sand of the same surface area. SCC mixtures with water-cementitious material ratios (w/cm) of 0.35, 0.38, and 0.42 and coarse aggregate-total aggregate volume ratios (CA/A) of 0.44 to 0.53 were investigated. The mixtures with a w/cm (if 0.38 and 0.42 incorporated low and moderate dosages, respectively, of a viscosity-modifying admixture to enhance stability For each SCC, the dosage of high-range water-reducer (HRWR) was varied to cover a wide range of slump flow consistencies ranging between 570 and 730 mm (22.4 and 28.7 in.). All SCC mixtures were proportioned with 450 kg/m(3) (758.5 lb/yd(3)) of ternary silica fume-ground granulated blast-furnace slag cement. A simple method is also proposed to determine the HRWR demand of SCC from that of the corresponding CEM. Test results showed that a good correlation can be established between the yield stress, plastic viscosity, and thixotropy of SCC and their corresponding CEM mixtures. Both thixotropy and plastic viscosity of SCC mixtures and their corresponding CEM mixtures are shown to vary primarily with variations in the w/cm and relative volume of coarse aggregate.