Non-price competition in credit card markets through bundling and bank level benefits

The attempts to explain the high and sticky credit card rates have given rise to a vast literature on credit card markets. This paper endeavors to explain the rates in the Turkish market using measures of non-price competition. In this market, issuers compete monopolistically by differentiating their credit card products. The fact that credit cards and all other banking services are perceived as a bundle by consumers allows banks to deploy also bank level characteristics to differentiate their credit cards. Thus, credit card rates are expected to be affected by the features and service quality of banks. Panel data estimations also control for various costs associated with credit card lending. The results show significant and robust effects of the non-price competition variables on credit card rates.Credit Cards, Monopolistic Competition, Product Differentiation, Bundling, Bank Pricing Behavior, Regulation

The Failure of Price Competition In The Turkish Credit Card Market

The failure of competition and the consequent high and sticky interest rates in credit card markets have been the subject of a considerable amount of debate and research lately. This paper presents the first regression testing for the existence of price competition in a credit card market to be estimated free of dynamic panel bias using recent quarterly data from Turkey. The estimation reveals that even though the effect of the cost of funds on credit card rates is statistically significant, it is very weak. The paper thus provides empirical evidence for the failure of price competition in the Turkish credit card market.Credit Cards, Price Competition, System GMM, Banking

DMF-TONN: Direct Mesh-free Topology Optimization using Neural Networks

We propose a direct mesh-free method for performing topology optimization by integrating a density field approximation neural network with a displacement field approximation neural network. We show that this direct integration approach can give comparable results to conventional topology optimization techniques, with an added advantage of enabling seamless integration with post-processing software, and a potential of topology optimization with objectives where meshing and Finite Element Analysis (FEA) may be expensive or not suitable. Our approach (DMF-TONN) takes in as inputs the boundary conditions and domain coordinates and finds the optimum density field for minimizing the loss function of compliance and volume fraction constraint violation. The mesh-free nature is enabled by a physics-informed displacement field approximation neural network to solve the linear elasticity partial differential equation and replace the FEA conventionally used for calculating the compliance. We show that using a suitable Fourier Features neural network architecture and hyperparameters, the density field approximation neural network can learn the weights to represent the optimal density field for the given domain and boundary conditions, by directly backpropagating the loss gradient through the displacement field approximation neural network, and unlike prior work there is no requirement of a sensitivity filter, optimality criterion method, or a separate training of density network in each topology optimization iteration

Preživljavanje bakterije Listeria monocytogenes u Ayranu, tradicionalnom turskom fermentiranom napitku

Ayran is a traditional fermented dairy product produced by mixing milk or yoghurt, water and salt. In this study, survival of Listeria monocytogenes 1/2b was investigated in Ayran samples. For that purpose, Ayran samples produced from yoghurt (Group A and B) or directly form milk (Group C and D) were contaminated with 1 % concentration of 7 (A1, B1, C1 and D1 samples) or 5 (A2, B2, C2 and D2 samples) log cfu/mL of L. monocytogenes. So, eight different samples of Ayran were produced and stored at 4 ºC (Group A and C) or 20 ºC (Group B and D) for 21 days. According to the obtained results, there was no significant change in the number of viable cells of L. monocytogenes 1/2b in samples A1, A2, C1 and C2 after 21 days of the storage period. However, L. monocytogenes 1/2b cells of B1 and B2 samples were completely inhibited after 5 days of storage at 20 ºC. Similarly to that, L. monocytogenes 1/2b cells in samples D1 and D2 were also completely inhibited after 3 days of the storage. Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus viable cell counts were between 103-107 cfu/mL in all of the samples. Consequently, Ayran contaminated with L. monocytogenes may contribute to a risk for public health. But, due to low pH of approximately ≤3.90, Ayran is relatively safe from the risk of L. monocytogenes.Ayran je tradicionalni fermentirani mliječni proizvod koji se dobiva miješanjem mlijeka ili jogurta, te vode i soli. U ovom je istraživanju ispitivano preživljavanje soja Listeria monocytogenes 1/2b u uzorcima Ayrana. U tu su svrhu proizvedeni uzorci Ayrana iz jogurta (skupina A i B) ili izravno iz mlijeka (skupina C i D) te kontaminirani dodatkom 1 % kulture soja L. monocytogenes 1/2b u koncentraciji 7 (uzorci A1, B1, C1 i D1) ili 5 (uzorci A2, B2, C2 i D2) log cfu/mL. Time je proizvedeno ukupno 8 različitih uzoraka Ayrana koji su čuvani 21 dan na 4 °C (skupina A i C) odnosno na 20 °C (skupina B i D). Dobiveni rezultati pokazali su da u uzorcima A1, A2, C1 i C2 broj živih stanica soja L. monocytogenes 1/2b nije bio promijenjen na završetku skladištenja. Međutim, stanice L. monocytogenes u uzorcima B1 i B2 bile su potpuno inhibirane na kraju petog dana skladištenja na 20 °C. Slično tomu, u uzorcima D1 i D2 su stanice dodane kulture soja L. monocytogenes 1/2b također bile inhibirane nakon tri dana skladištenja. Pritom je broj živih stanica jogurtne kulture sastavljene od vrsta Streptococcus thermophilus i Lactobacillus delbrueckii ssp. bulgaricus u svim uzorcima bio između 103-107 cfu/mL. Prema tome, Ayran kontaminiran bakterijom L. monocytogenes može uzrokovati rizik za zdravlje potrošača. Međutim, zbog relativno niskog pH koji se kreće ispod 3,90, Ayran je relativno siguran proizvod kad se radi o prisustvu bakterijske vrste L. monocytogenes