Browsing by Author "Celik, A"

Now showing 1 - 7 of 7
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    Mechanical and fluoride release properties of titanium tetrafluoride-added glass-ionomer cement
    Pamir, T; Sen, BH; Celik, A
    The aim of this study was to determine the fluoride-release and mechanical properties of a water-hardening glass-ionomer cement (GIC) (ChemFil Superior) when titanium tetrafluoride (TiF4) was added. Three experimental groups were prepared with TiF4 added to the liquid component of the material in concentrations of 0.5, 1, and 2%. The control group was the original form of the cement and free of TiF4. After the specimens (4 nun in diameter X 6 mm in length) were prepared, their compressive strength, microhardness, modulus of elasticity, and fluoride release were measured. Data were analyzed using one-way analysis of variance (ANOVA) and post-hoc test (Bonferroni/Dunn correction). The addition of TiF4 into GIC significantly reduced fluoride release from the material with the exception of 1% TiF4 (p < 0.0083). Compressive strengths of 0.5 and 1% TiF4-added GICs were higher than that of the original GIC, but it was not statistically significant (p > 0.05). The differences among modulus of elasticity values of experimental and control groups were not significant (p > 0.05). Similarly, microhardness of GIC was not affected with TiF4 addition (p > 0.05).
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    Degradation of poplar and spruce wood chips using alkaline glycerol
    Demirbas, A; Celik, A
    Poplar and spruce wood chips were degraded by using glycerol as a solvent and alkaline glycerol with and without alkali media at different temperatures: 440, 450, 460, 470, 480, 490, and 500 K, then the results were compared with the other organic solvent systems. The degradation reactions were mainly occurred as delignification and partly decomposition of cellulose. The effects of solvent, temperature, catalyst, delignification time and wood species on the yield of delignification were discussed. Major byproducts from delignification rections of wood chips include lignin degradation products. Lignin and its degradation products can be utilized as fuels.
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    Determination of synthesis conditions of alkali calcium sulfonate
    Besergil, B; Celik, A
    In this study, alkali calcium sulfonate which is added to engine oils as a detergent-dispersant was obtained. A definite amount of Ca(OH)(2) and water was added to the mixture of neutral calcium sulfonate (NCS) and spindle-oil (SO), and the mixture was taken into an appropriate reactor. CO2-air mixture was passed through the mixture for definite periods at 85degreesC and the appropriate parameters affecting the qualities and efficiency of the product were determined. Thus, after the mixture of CO2 + air (having the ratio of 1/8.5) was passed through the mixture of 180 g NCS + 600 g SO + 60 g Ca(OH)(2) + 90 g water with the velocity of 108 L/h for 200 min, transparent alkali calcium sulfonate with a total base number value of 28.6 mg KOH/g was obtained.
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    An investigation of chromium(VI) ion removal from wastewaters by adsorption on residual lignin
    Celik, A; Dost, K; Sezer, H
    The aim of this study was to develop a low-cost method for effective removal of Cr(VI) ions from wastewater, but also to valuate this residual of major industry for its adsorption capacity. Therefore, the residual lignin produced from paper industry was utilised as an adsorption material and the effects of lignin amount used, pH of solution and contact time on removal capacity of chromium from wastewater were investigated. Analysis of Cr(VI) ions was performed with both spectrometric and volumetric standard methods. The results obtained from both methods were in good agreement with 2% relative error. Ninety-three % of Cr(VI) ions were adsorbed by 0.5 g residual lignin at pH 3 and 7 hours contact time. This result underlines that residual lignin could be used as a low-cost adsorbent material to remove Cr(VI) ions discharged into the environment with wastewaters.
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    Determination of synthesis conditions of neutral calcium sulfonate, so-called detergent-dispersant
    Celik, A; Besergil, B
    In this study, the conditions of obtaining neutral calcium sulfonate which is added to engine oils as a detergent-dispersant was studied. For this purpose, post-dodecyl benzene sulfonic acid, obtained from post-dodecyl benzene which remains as the bottom product during the production of dodecyl benzene sulfonate was used as the initial substance. Additionally, the reactor to be used in the production of neutral calcium sulfonate was designed and the amounts of spindle-oil, toluene, raw sulfonic acid solution and Ca(OH)(2) used during neutralization were determined.
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    Activation of peripheral opioid receptors has no effect on heart rate variability
    Ellidokuz, E; Kaya, D; Uslan, I; Celik, A; Esen, AM; Barutca, I
    Opioid receptors involved in regulating the motility of the gastrointestinal tract have been localized in both contractile and neuronal tissues. Trimebutine, a peripheral opioid receptor agonist, modulates gastrointestinal motor activity in both directions and also may act on cardiac tissue. This study investigated the effects of trimebutine in clinical doses on cardiac autonomic functions with heart rate variability. The effect of trimebutine on cardiac autonomic outflows was evaluated in 11 healthy subjects. Trimebutine (200 mg) or placebo was administered orally at random in a double-blind, cross-over manner. Continuous electrocardiography recordings were obtained before and after drug administration during three states: rest, controlled breathing, and a hand grip exercise. Heart rate variability analysis showed that there was no significant difference between subjects administered with placebo or trimebutine throughout rest, controlled breathing, or the hand grip exercise. We concluded that trimebutine, in clinical doses, has no significant effect on cardiac autonomic functions.
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    Removal of heavy metal ions from aqueous solutions via adsorption onto modified lignin from pulping wastes
    Celik, A; Demirbas, A
    The aim for this research is to study inexpensive and effective metal ion adsorbents from biomass sources of modified lignin to offer these adsorbents as replacements for existing commercial materials. The initial concentrations were increased up to 12.7 ppm for Pb2+, Cd2+, and Zn2+ in order to reach the plateau values which represent saturation of the active points which are available for interaction with metal ions on the lignin samples. The maximum adsorption capacities are 11.3, 17.5, and 7.7 mg per g of the lignin for Zn2+, Pb2+, and Cd2+, respectively. The maximum adsorption capacity is higher than 20 mg per g of the lignin for Cu2+ ion. The maximum adsorption percentage is 96.7 for Pb2+ for 4 h at 330 K and is 95.0 for Zn2+ for 10 h at 290 K. The adsorption of all heavy metal ions first increases with pH and almost reaches a plateau value around 4.0 for Cu2+, 4.5 for Zn2+, 5.0 for Pb2+. High adsorption at higher pH values implies that metal ions interact with lignin by ion exchange.