Browsing by Author "Targan, S"
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Item Effects of supplementary cementing materials on the properties of cement and concreteTargan, S; Olgun, A; Erdogan, Y; Sevinc, VThe effect of bentonite, colemanite ore waste (CW), coal fly ash (FA) and coal bottom ash (BA) on the properties of cement and concrete has been investigated through a number of tests. The properties examined include setting time, bending strength, volume expansion, compressive strength and water consistency of the mortar. The result showed that setting time of the cements was generally accelerated when bentonite replaced a part of the cement. Bentonite exhibited a significant retarding effect when used in combination with CW in Portland cement at lower replacement level and showed an accelerating effect at higher replacement level. Although the inclusion of bentonite at replacement levels of 5-10% resulted in an increase in compressive strength at early ages, it decreased the compressive strength when used in combination with other materials. The results obtained were compared with Turkish standards and, in general, were found to be acceptable. (C) 2002 Elsevier Science Ltd. All rights reserved.Item Influence of natural pozzolan, colemanite ore waste, bottom ash, and fly ash on the properties of Portland cementTargan, S; Olgun, A; Erdogan, Y; Sevinc, VThis study has examined the effect of natural pozzolan (NP), colemanite ore waste (CW), coal fly ash (FA), and coal bottom ash (BA) on the properties of cement and concrete. The parameters studied included compressive strength, bending strength, volume expansion, and setting time. A number of cements were prepared (in the presence of fixed quantity of 10% FA, 10% BA, and 4% CW) by the replacement of Portland cement (PC) with NP in range of 5 - 30%. The results showed that the final setting time of cement pastes were generally accelerated when the NP replaced part of the cement. However, NP exhibited a significant retarding effect when used in combination with CW. The results also showed that the inclusion of NP at replacement levels of 5% resulted in an increase in compressive strength of the specimens compared with that of the control concrete. The replacement of PC by 10 - 15% of NP in the presence of fixed quantity of CW improves the bending strength of the specimens compared with control specimens after 60 days of curing age. (C) 2003 Elsevier Science Ltd. All rights reserved.Item Removal of lead from aqueous solutions by low cost and waste biosorbents (lemon, bean and artichoke shells)Ergüvenerler, F; Targan, S; Tirtom, VNSimple, fast, effective, low cost and waste biosorbents, lemon, bean and artichoke shells, were used to remove lead (II) ions from aqueous solution. The influence of pH, contact time, temperature and lead (II) concentration of the removal process was investigated. The sufficient contact time was deemed 10 minutes for bean and artichoke shells and 60 minutes for lemon shells for Pb(II) ions. The thermodynamic parameters, such as standard free energy (Delta G), standard enthalpy (Delta H), and standard entropy (Delta S) of the adsorption process were calculated as -5.6786, -5.5758, -3.1488 kJmol(-1) for Delta G, -7.2791, -20.285, -9.5561 kJ mol(-1) for Delta H, -0.00545, -0.05017, -0.02185 kJ mol(-1) K-1 for Delta S, respectively, for lemon, artichoke and bean shells. Maximum adsorption capacities of lead (II) were observed as 61.30 mg g(-1), 88.5 mg g(-1) and 62.81 mg g(-1), respectively, for lemon, bean and artichoke shells according to the Freundlich isotherm model at 20 degrees C. Scanning electron microscope (SEM) and energy-dispersive X-ray detector (EDX) were used to characterize the surface morphology of the adsorbents. Consequently, Pb(II) removal using lemon, bean and artichoke shells would be an effective method for the economic treatment of wastewater.Item Arsenic removal from aqueous system using modified chestnut shellTargan, S; Tirtom, VNNatural adsorbent chestnut shell treated with FeCl3 was prepared and employed by means of batch method for selective adsorption and removal of arsenic from aqueous system. The influences of different parameters, such as contact time, pH, temperature, and concentration of adsorbate, on adsorption performance of chestnut shell treated with FeCl3 was studied in order to optimize the adsorption conditions. Batch adsorption studies have shown that removal capacity of chestnut shell can be increased by FeCl3 treatment. The maximum adsorption capacity was found to be 0.885mgg(-1) As(III) of chestnut shell, which was treated with FeCl3. The adsorption data obtained follow a first-order rate expression and fit the Freundlich isotherm that has been used to obtain the thermodynamic parameters. In addition, the thermodynamic parameters, such as standard free energy (G degrees), standard enthalpy (H degrees), and standard entropy (S degrees), of the adsorption process were calculated. It was found that the adsorption of arsenic on chestnut shell was exothermic. The adsorbents were characterized by scanning electron microscopy.Item Evaluation of blends tincal waste, volcanic tuff, bentonite and fly ash for use as a cement admixtureAbali, Y; Bayca, SU; Targan, SThe evaluation of blends tincal waste (TW), fly ash (FA), bentonite (BE), volcanic tuff (VT) for use as a cement admixture was investigated. The properties examined include setting time, expansion, water requirement, specific surface and compressive strength of cement mixtures. The results revealed that the early compressive strength decrease with increasing tincal waste, due to tincal waste increasing initial setting time of the cement. The tincal waste and volcanic tuff of cement mixtures increased and there was reduction in compressive strength. The more the tincal waste increased the greater retardation there was initial setting time this may be attributed to containing high amount B2O3 and MgO content. The tincal waste and fly ash increased with expansion increased. Water requirement increased as the Blaine fineness of the cement mixtures increased. The results obtained were compared with standards and five batches were advised as suitable for the standard. (c) 2005 Published by Elsevier B.V.Item Comparative adsorption of Pb(II) and Cd(II) ions on chestnut shell in aqueous systemÇetinkaya, S; Targan, S; Tirtom, VNIn this study, high capacity Chestnut shell, a waste product from the chestnut sugar production industry, was successfully applied to remove Pb (II) and Cd (II) ions from aqueous solutions. Maximum adsorption capacities were found as 541.25mg/g and 75.86mg/g for Pb(II), and Cd(II) respectively. Several important parameters influencing the adsorption of Pb(II) and Cd(II) ions such as contact time, pH, temperature and effect of metal concentration were investigated systematically by batch experiments. Langmuir and Freundlich adsorption models were used to describe adsorption isotherms and constants. The thermodynamic parameters, such as standard free energy (G degrees), standard enthalpy (H degrees), and standard entropy (S degrees), of the adsorption process were calculated. The adsorbents were characterised by scanning electron microscopy. It has been observed from the experimental results that in case of both Cd (II) and Pb (II), pseudo 2nd order kinetic model. From the results, Chestnut Shell are considered as an effective, low cost and environmental friendly adsorbent for the removal of Pb (II) and Cd (II) from wastewater.Item Sulfate resistance of mortars with and without silica fume and natural pozzolanCanpolat, F; Yurdusev, MA; Targan, S; Yilmaz, KAn investigation was carried out on the effect of sulfate attack on the sulfate durability of mortars produced with natural zeolite and silica fume having pozzolanic character. Experiments were accomplished on the standard Rilem sand and portland cement mortars where the cement was replaced by various rates of natural zeolite (Z) and silica fume (SF) separately and together. 5% sodium sulfate solution and 5% magnesium sulfate solution were 5% sulfate exposures of mortars were initiated after 28 days of lime saturated water curing, compressive strength and density were determined at the beginning of exposure and at the 2nd, 7th, 28th, 90th days. Water and solutions were renewed after each period of experimental time, 14 days. Mass changes were determined at the time of renewing the solutions. The effects of sodium sulfate solutions on the properties of mortars were related to the zeolite and silica fume ratio. It is found that zeolite and silica fume replacement had caused significant increase in sulfate durability of mortars even at the highest sulfate concentration up to 90 days of exposure. The durability to sulfate attack was obtained with silica fume replacement 5-10%, but strength loss of 10-15% can be expected. Mortars with SF and Z were damaged in magnesium sulfate solution. The compressive strengths decreased with increasing SF and Z content. The test results showed that the use of Z and SF in concrete exposed to magnesium sulfate environment is not recommended.Item Current therapeutic approaches in childhood chronic hepatitis B infection: A multicenter studyDikici, B; Ozgenc, F; Kalayci, AG; Targan, S; Ozkan, T; Selimoglu, A; Doganci, T; Kansu, A; Tosun, S; Arslan, N; Kasirga, E; Bosnak, M; Haspolat, K; Buyukgebiz, B; Aydogdu, S; Girgin, N; Yagci, RVBackground and Aim: The aim of the present study was to compare the therapeutic efficacy of three different regimens in childhood chronic hepatitis B (CHB) infection. Methods: A total of 182 children with CHB infection were prospectively allocated to three random groups. Sixty-two patients in the first group received high-dose interferon (IFN)-alpha 2b (10 MU/m(2)) thrice/weekly alone for 6 months. In the second (n = 60) and third groups (n = 60), IFN-alpha was used for 6 months (5 MU/m(2)) thrice/weekly in combination with lamivudine (LAM) (4 mg/kg, maximum 100 mg/day) for 12 months. Lamivudine was started simultaneously with IFN in the second group, while it was started 2 months prior to IFN injections in the third group. Results: The initial mean alanine aminotransferase (ALT) values for the first, second and third groups were 109 +/- 93 IU/L, 101 +/- 64 IU/L and 92 +/- 42 IU/L, respectively (P > 0.05). At the end of the therapy, ALT values decreased to 82 +/- 111 IU/L, 38 +/- 41 IU/L and 29 +/- 16 IU/L in groups 1, 2 and 3, respectively. The mean ALT value of the first group was significantly different to the second and third groups (P = 0.046 and P = 0.002, respectively) at the end of the therapy and these differences were found to be sustained after 18 months. However, results in the second and third groups were similar (P > 0.05). There were no significant differences in HBeAg clearance and anti-HBe seroconversion at the initial stage, 12 months and 18 months between the three groups (P > 0.05). Hepatitis B virus (HBV) DNA clearance in the first group was different from the second and third groups, while the second and third groups had similar HBV DNA clearance ratios at 12 and 18 months. No significant difference was found in the complete response (normalization of ALT, clearance of HBV DNA and seroconversion of anti HBe) ratios of all groups (at 12 months: 28.8, 45.5, 35.8% and at 18 months 33.3, 49 and 34% in groups 1, 2 and 3, respectively, P > 0.05). Conclusions: Although the ALT normalization and HBV DNA clearance ratios of IFN plus LAM combination groups were better than the high-dose IFN-alpha monotherapy group, no significant difference was found in the complete response ratios of all three groups. (C) 2004 Blackwell Publishing Asia Pty Ltd.Item Chemical composition and biological activities of the essential oils of two endemic Nepeta speciesSarikurkcu, C; Ceylan, O; Targan, S; Zeljkovic, SCThe chemical composition, antioxidant activity and several enzyme inhibitions of the essential oils of two endemic Nepeta species, N. nuda subsp. glandulifera and N. cadmea were investigated for the first time. The major compounds of N. nuda subsp. glandulifera essential oil were geijerene (61.02%) and neointermedeol (6.07%). On contrary, essential oil of N. cadmea contained 70.94% of 4a beta,7 alpha,74 beta-nepetalactone. The oil of N. nuda subsp. glandulifera revealed better activity than the oil of N. cadmea against both reducing metal ions and radicals. Moreover, both oils have relatively weak but still noticeable activity against acetylcholinesterase and butyrylcholinesterase; weak activity against alpha-glucosidase, but quite high activity against alpha-amylase. On the other hand, both essential oils showed significant activity against tyrosinase. Presented results suggest that these two endemic species have strong potential to be used in food and pharmacological industries, and therefore they should to be investigated further.Item Influence of colemanite admixture on Portland cement durabilityErdogmus, E; Targan, S; Erdogan, Y; Avciata, U; Gencel, OIn this study, the compressive strength of mortar prepared by Portland cement (PC) and different proportions of blast furnace slag, fly ash and colemanite concentrator waste was examined at the end of the 2nd, 7th, 28th, 60th and 90th days. Moreover, some mortars were kept in 50 g/l sodium sulfate (Na2SO4) solution according to ASTM C1012 for 6 months to determine their sulfate resistance. The first length of some mortars made with alkali reactive sand together with additives mentioned above or PC according to ASTM C1260 was measured to detect their alkali-aggregate reaction resistance and then their final lengths were measured after being kept in 1 M sodium hydroxide (NaOH) solution at a temperature of 80 degrees C for 14 days. The results were compared both among themselves and with Portland cement. In addition, the microstructures of some samples scanned by scanning electron microscopy were photographed. It was found that all the additives had positive effects on sulfate and ASR resistance.Item Fatty acid composition, enzyme inhibitory, and antioxidant activities of the ethanol extracts of selected wild edible plants consumed as vegetables in the Aegean region of TurkeySarikurkcu, C; Targan, S; Ozer, MS; Tepe, BThe aim of this study was to evaluate the fatty acid composition, enzyme inhibitory, and antioxidant activities of the ethanol extracts of selected wild edible plants consumed as vegetable in the Aegean region of Turkey. In general, Mentha piperita L., Rumex patientia L., and R. acetosella L. exhibited quite strong antioxidant activities in the majority of test systems, whereas Urtica dioica L. and Eruca sativa Mill. show quite weak antioxidant activities. Enzyme inhibitory activities of the plants were found quite different than those of their antioxidant activities. Cardaria draba (L.) Desv., E. sativa, R. patientia, and E. cicutarium (L.) L'Her. showed the highest inhibitory activities on acetylcholinesterase, butyrylcholinesterase, -amylase, and -glucosidase, respectively. U. dioica also showed a promising inhibitory activity on these enzymes. In parallel to the experiments, total phenolic, flavonoid, flavonol, and saponin contents of the extracts were also determined. According to the results of these assays, M. piperita had the highest amounts of phenolics, flavonols, and saponins (162.36 mg gallic acid equivalents/g extract, 3.52 mg CEs/g extract and 761.54 mg QAEs/g extract, respectively). Opopanax hispidus (Friv.) Griseb. and Lepidium sativum L. were found to be rich in flavonoid compounds (121.18 and 104.21 mg Res/g extract, respectively). In general, a strong correlation was determined between the phytochemical profile and antioxidant activity of the plant species.