Optimal Combinatorial Mechanism Design

We consider an optimal mechanism design problem with several heterogeneous objects and interdependent values. We characterize ex post incentives using an appropriate monotonicity condition and reformulate the problem in such a way that the choice of an allocation rule can be separated from the choice of the payment rule. Central to our analysis is the formulation of a regularity condition, which gives a recipe for the optimal mechanism. If the problem is regular, then an optimal mechanism can be obtained by solving a combinatorial allocation problem in which objects are allocated in a way to maximize the sum of "virtual" valuations. We identify conditions that imply regularity for two nonnested environments using the techniques of supermodular optimization.

Free to Choose: Testing the Pure Motivation Effect of Autonomous Choice

We conduct an experimental test of the long-standing conjecture that autonomy increases motivation and job performance. Subjects face a menu consisting of two projects: one risky and one safe. The probability that the risky project succeeds depends on the subject's effort. In one treatment, subjects choose a project from the menu; in the other treatment, they are assigned a project from the menu. Using a difference-in-difference approach that controls for selection effects, we show that autonomy (the right to choose a project) has a significant pure motivation effect on effort. The effect is consistent with aversion to anticipated regret, but not with standard expected-utility maximization. Futher, as predicted by regret theory, effort on the (chosen) risky project is increasing in the return to the (unchosen) safe project, and the pure motivation effect is greater, the riskier is the risky project. Finally, we find a significant negative relationship between the strength of the pure motivation effect and the subjects' expected earnings

Essays in mechanism design:

This dissertation consists of three essays in the theory of mechanism design under incomplete information. In the first essay, we analyze an implementation problem in which monetary transfers are feasible, valuations are interdependent and the set of available choices lies in a product space of lattices. This framework is general enough to subsume many interesting examples, including allocation problems with multiple objects. We identify a class of social choice rules which can be implemented in ex post equilibrium. We identify conditions under which ex post efficient social choice rules are implementable using monotone selection theory. The key conditions are extensions of the single crossing property and supermodularity. These conditions can be replaced with more tractable conditions in multiobject allocation problems with either two objects or two agents. I also show that the payments which implement monotone social decision rules coincide with the payments of (1) the classical Vickrey-Clarke-Groves mechanism with private values, and (2) the generalized Vickrey auction introduced by Ausubel [1999] in multiunit allocation problems. The second essay generalizes the analysis of optimal (revenue maximizing) mechanism design for the seller of a single object introduced by Myerson [1981]. We consider a problem in which the seller has several heterogeneous objects and buyers' valuations depend on each other's private information. We analyze two nonnested environments in which incentive constraints can be replaced with more tractable monotonicity conditions. We establish conditions under which these monotonicity conditions can be ignored, and show that several earlier analyses of the optimal mechanism design problem can be unified and generalized. In particular, problems with two complementary goods in Levin [1997] and multiunit auction problems in Maskin and Riley [1989] and Branco [1996] are special cases. The third essay considers the problem of selling internet advertising slots to advertisers. Under suitable conditions, we solve for the payments imposed by an optimal mechanism and show that it can be decentralized via prices using a linear assignment approach. At every configuration of private information, optimal mechanism can be interpreted as a menu consisting of a price for every slot.Ph. D.Includes bibliographical references (p. 69-70)by Levent Ulk

Nanofiltration and Reverse Osmosis for Reuse of Indigo Dye Rinsing Waters

WOS: 000277727100004A membrane based treatment strategy was developed for the possible recycling of rinsing wastewater from indigo dyeing to the process itself. Performances of three different nanofiltration (NF) (NF 270 and NF 90, Dow Film Tech, USA and NF 99, Alfa Laval, Denmark) and two different reverse osmosis (RO) (HR 98 PP and CA 995 PE, Alfa Laval, Denmark) membranes were investigated with wastewater collected from the first post-rinsing tank of indigo dyeing process of a denim manufacturing plant. Dead-end microfiltration with a 5 mu m filter was employed to remove coarse particles and minimize fouling of further NF and RO membranes. For NF and RO, a lab scale plate-and-frame membrane module was operated at a pressure of 5.07bar and at a 0.62m/s cross-flow velocity. The permeate quality from all the tested NF and RO membranes was acceptable for reuse in terms of COD and color. However, only the permeate from HR 98 PP RO and NF 90 membranes were with an acceptable conductivity. On the other hand, NF 270 membrane was superior to all the other NF and RO membranes in terms of the permeation rate. Flux declines obtained for all membranes were higher than 50% but fouling was not considerable and completely reversible. The good performance of NF 270 in terms of permeate quality (permeate conductivity, color, and COD values were 4.3mS/cm, 8 Pt-Co, and 87mg/L, respectively) together with a higher flux makes this membrane preferable over the other membranes to recycle denim textile rinsing wastewaters.Scientific and Technological Research Council of Turkey [CAYDAG-105Y088]The authors wish to express their gratitude to the Scientific and Technological Research Council of Turkey for funding the project (CAYDAG-105Y088) of which this study forms a part and also to METU Research Fund. Dow FilmTec (Minneapolis) and Alfalaval (Denmark) are thanked for supplying the membrane samples. Special thanks are extended to the textile mill administration for their technical support and for providing wastewater samples

Removal of disinfection by-product precursors by UF and NF membranes in low-SUVA waters

The performance of ultrafiltration (UF) and nanofiltration (NF) membranes on disinfection by-products (DBPs) precursor removal in a surface water having low-to-medium dissolved organic carbon (DOC) and specific ultraviolet absorbance (SUVA(254)) levels was evaluated. While higher molecular weight (HMW) DOC fraction was successfully rejected (> 90%), lower molecular weight (LMW) fraction could be removed only 1.5-30% by the tested four different membranes (two UF and two NF). This finding suggested that although NF and UF membranes with pore sizes of <= 1000 Da are highly effective on the removal of HMW NOM from waters having low-to-medium DOC and SUVA(254) levels, such membranes are not effective in these waters in rejecting LMW fractions (i.e., < 2000 Da). NF membranes provided THM and HAA formation reductions above 90%. However, DOC and UVA(254) rejections could not be directly linked to DBP formation reductions by the tested membranes. Due to higher rejection of DOC than the bromide ion in UF and NF separation, Br/DOC ratio increased which further increased the relative occurrence of brominated THM and HAA species over chlorinated ones. (c) 2008 Elsevier B.V. All rights reserved

Anti-hyperglycaemic and antioxidant effects of Bidens tripartita and quantitative analysis on its active principles

Objective(s): Bidens species are used for their antidiabetic properties traditionally in many countries. Aim of this study is to evaluate hypoglycaemic and antidiabetic activity of Bidens tripartita extract and to identify its active compounds through bioactivity guided isolation technique. Materials and Methods: Hypoglycaemic effects of B. tripartita extract and its sub-extracts were investigated in normal and glucose-hyperglycaemic rats. Streptozotocin induced diabetic rats were used to examine antidiabetic activity of the extract and its sub-extracts after acute and sub-acute administration. Additionally, in vitro enzyme inhibitory and antioxidant activities were evaluated. HPLC analyses were carried out to determine the active constituents of the extract and its sub-extracts. Results: Through in vivo bioactivity-guided fractionation process, ethyl acetate and n-buthanol sub-extracts were found to have potent antidiabetic activity. In vitro enzyme inhibitory activities of the same sub-extracts were found to be potent. The highest total phenol, flavonoid contents and radical scavenging activity was determined in ethyl acetate sub-extract. According to LC-MS analyses, chlorogenic acid, luteolin and 7-O-glucoside of luteolin (cynaroside) were determined as the main components of the active sub-extracts. Conclusion: According to our results, B. tripartita has potent antidiabetic activity and its active constituents might be beneficial for diabetes and its complications

The regulatory effects of clomiphene and tamoxifen on mTOR and LC3-II expressions in relation to autophagy in experimental polycystic ovary syndrome (PCOS)

Background Polycystic ovary syndrome (PCOS) is a metabolic disease that causes infertility due to anovulation in women in reproductive age. It is known that clomiphene citrate (CC) and tamoxifen citrate (TMX) induce ovulation in women with PCOS. In this study, we aimed to investigate the effects of CC and TMX on the autophagy pathway in PCOS. Methods and results Experimental PCOS model was induced by letrozole (1 mg/kg) in rats by gavage for 21 days. After the last letrozole administration, rats were treated TMX (1 mg/kg) or CC (1 mg/kg) for 5 days. At the end of the experimental procedures, rats in all groups were sacrificed and ovarian tissues were removed. It was observed that mRNA and protein expressions of LC3-II were significantly higher in TMX and CC groups than control and PCOS groups (p < 0.05), while mRNA and protein expressions of mTOR in TMX and CC groups were found significantly lower than control and PCOS groups (p < 0.05). Conclusions In conclusion, present study suggests that TMX and CC induce autophagy in ovaries with PCOS. Autophagy is a promising target for understanding pathophysiology of this disease and for developing more effective and safe new protocols for the treatment of PCOS-related anovulation.Ege University Research Fund [BAP-17-TIP-029]This study was supported by the Ege University Research Fund [Grant number BAP-17-TIP-029 (to Altug Yavasoglu)]