Emik S.,Istanbul University
Reactive and Functional Polymers | Year: 2014
A novel IPN type chelating resin, amino-functionalized poly (glycidyl methacrylate)/poly (acrylic acid), (pGMA/pAA), was synthesized by a combination of serial reactions including, conventional radical polymerization, amination and photopolymerization. To assess the efficacy and characteristics of the resin in removal of Cu (II), batch adsorption experiments were carried out, and the effects of different parameters such as contact time, adsorbent dosage, initial metal ion concentration, temperature, and pH on the adsorption process were investigated. The results showed that 0.5 g/L dosage and pH 5 are the optimum values to achieve the maximum adsorption capacity and the adsorption kinetic of Cu (II) was well represented by pseudo-second-order kinetic model. In addition, it was found that the adsorption was mainly controlled by the film diffusion mechanism, along with a considerable contribution of the intra-particle diffusion mechanism, and Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm models can be used for interpreting the adsorption process. Moreover, FT-IR analysis results and the mean free energies of adsorption clearly indicate that the ion exchange and chelation mechanisms took place as dominating mechanisms simultaneously during the adsorption process. It was also found to be that IPN resin could be used at least four times without losing its original activity. © 2013 Elsevier Ltd. All rights reserved.
Ozkaya E.,Istanbul University
Journal of the American Academy of Dermatology | Year: 2013
Background: Little is known about the characteristic features of oral mucosal fixed drug eruption (FDE). Objective: To present the clinical highlights and the differential diagnosis of oral mucosal FDE in a relatively large group of patients from Turkey. Methods: This was a methodological, retrospective, cross-sectional study of 61 patients with oral mucosal FDE. The causative drug was established mainly by oral provocation test. Results: The age range of 61 patients (38 females, 23 males) was 7 to 62 years. Naproxen and cotrimoxazole were the main inducers. Fourteen patients (23%) had a solitary oral lesion predominantly located on the dorsum of the tongue, or on the hard palate, the former statistically significantly associated with cotrimoxazole. Bullous/erosive (n = 47), aphthous (n = 12), and erythematous (n = 2) morphology were observed. A considerable number of patients were referred with a prior clinical diagnosis of herpes simplex and Behçet's disease; some of them were already receiving long-term treatment with acyclovir and colchicine, respectively. Limitations: The main limitation of the present study resides in its retrospective design. Conclusions: Isolated oral lesions, aphthous lesions, severe bullous/erosive lesions, and the absence of residual pigmentation are the main features that may cause difficulties in the differential diagnosis. It is important to differentiate dysmenorrhea-related monthly attacks of oral FDE in female patients caused by nonsteroidal anti-inflammatory drugs from menstruation-triggered attacks of herpes simplex infection, and isolated orogenital aphthous FDE from Behçet's disease, especially in countries with a high frequency of the disease in order to prevent irrelevant therapies. © 2013 by the American Academy of Dermatology, Inc.
Noyan N.,Istanbul University
Computers and Operations Research | Year: 2012
Traditional two-stage stochastic programming is risk-neutral; that is, it considers the expectation as the preference criterion while comparing the random variables (e.g., total cost) to identify the best decisions. However, in the presence of variability risk measures should be incorporated into decision making problems in order to model its effects. In this study, we consider a risk-averse two-stage stochastic programming model, where we specify the conditional-value-at-risk (CVaR) as the risk measure. We construct two decomposition algorithms based on the generic Benders-decomposition approach to solve such problems. Both single-cut and multicut versions of the proposed decomposition algorithms are presented. We adapt the concepts of the value of perfect information (VPI) and the value of the stochastic solution (VSS) for the proposed risk-averse two-stage stochastic programming framework and define two stochastic measures on the VPI and VSS. We apply the proposed model to disaster management, which is one of the research fields that can significantly benefit from risk-averse two-stage stochastic programming models. In particular, we consider the problem of determining the response facility locations and the inventory levels of the relief supplies at each facility in the presence of uncertainty in demand and the damage level of the disaster network. We present numerical results to discuss how incorporating a risk measure affects the optimal solutions and demonstrate the computational effectiveness of the proposed methods. © 2011 Elsevier Ltd. All rights reserved.
Pozan G.S.,Istanbul University
Journal of Hazardous Materials | Year: 2012
The aim of this work was to study combustion of toluene (1000ppm) over MnO 2 modified with different supports α-Al 2O 3 and γ-Al 2O 3 obtained from Boehmite, γ-Al 2O 3 (commercial), SiO 2, TiO 2 and ZrO 2 were used as commercial support materials. In view of potential interest of this process, the influence of support material on the catalytic performance was discussed. The deposition of 9.5MnO 2 was performed by impregnation over support. The catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), temperature programmed reduction and oxidation (TPR/TPO) and thermogravimetric analysis (TGA). The catalytic tests were carried out at atmospheric pressure in a fixed-bed flow reactor. 9.5MnO 2/α-Al 2O 3(B) (synthesized from Boehmite) catalyst exhibits the highest catalytic activity, over which the toluene conversion was up to 90% at a temperature of 289°C. Considering all the characterization and reaction data reported in this study, it was concluded that the manganese state and oxygen species played an important role in the catalytic activity. © 2012 Elsevier B.V.
Cura T.,Istanbul University
Expert Systems with Applications | Year: 2012
The clustering problem has been studied by many researchers using various approaches, including tabu searching, genetic algorithms, simulated annealing, ant colonies, a hybridized approach, and artificial bee colonies. However, almost none of these approaches have employed the pure particle swarm optimization (PSO) technique. This study presents a new PSO approach to the clustering problem that is effective, robust, comparatively efficient, easy-to-tune and applicable when the number of clusters is either known or unknown. The algorithm was tested using two artificial and five real data sets. The results show that the algorithm can successfully solve both clustering problems with both known and unknown numbers of clusters. © 2011 Elsevier Ltd. All rights reserved.