Esin Cakan

The use of 18F-FDG PET ratios in the differential diagnosis of common malignant brain tumors.

OBJECTIVE This study examined the use of positron emission tomography (PET) ratios to improve the diagnostic ability of 18F-FDG PET/computed tomography (CT) in the differentiation of enhancing brain metastases, central nervous system lymphomas, and gliomas. MATERIALS AND METHODS Seventy-six patients with malignant brain tumors and available magnetic resonance imaging and PET/CT examinations were included. RESULTS Among standardized uptake value (SUV)-related parameters tested, tumor maximum SUV to ipsilateral cortex maximum SUV ratio (Tmax:WMimax) and maximum SUV (SUVmax) proved to be the two most valuable parameters for differential diagnosis. CONCLUSION In addition to SUVmax, Tmax:WMimax also seems to provide helpful information for the differential diagnosis of lymphomas from other malignant brain tumors.

On the Nonlinear Causality between Inflation and Inflation Uncertainty in the G3 Countries

This study examines the dynamic relationship between monthly inflation and inflation uncertainty in Japan, the US and the UK by employing linear and nonlinear Granger causality tests for the 1957: 01–2006: 10 period. Using a generalised autoregressive conditional heteroskedasticity (GARCH) model to generate a measure of inflation uncertainty, the empirical evidence from the linear and nonlinear Granger causality tests indicate a bidirectional causality between the series. The estimates from both the linear vector autoregressive (VAR) and nonparametric regression models show that higher inflation rates lead to greater inflation uncertainty for all countries as predicted by Friedman (1977). Although VAR estimates imply no significant impact, except for Japan, nonparametric estimates show that inflation uncertainty raises average inflation in all countries, as suggested by Cukierman and Meltzer (1986). Thus, inflation and inflation uncertainty have a positive predictive content for each other, supporting the Friedman and Cukierman-Meltzer hypotheses, respectively.

Herd behaviour in the Turkish banking sector

This study looks for evidence of investor herding in the Turkish banking sector. We apply the methodology of Chang et al. (2000) to daily stock returns between 2007 and 2012 and find evidence of herding. This result is robust under model specifications that control for market and firm fundamentals. Herding behaviour shows asymmetric effects, and investors herd only in rising markets.

Policy regime change and structural break in the velocity of money: the Turkish evidence

The integration properties of Turkish velocity series are investigated by employing recently developed procedures (Zivot and Andrews (1992) and Perron (Journal of Econometrics, 80, 355–85, 1997)) which allows stationarity around an endogenously estimated structural break point under the alternative hypothesis. The evidence suggests that real currency balances and currency velocity are stationary around a broken trend. The estimated break point coincides with a major policy regime change in Turkey. Broad money velocity and real broad money balances are found to be nonstationary even after allowance for a broken mean and trend.

Did large institutional investors flock into the technology herd? An empirical investigation using a vector Markov-switching model

ABSTRACT This article investigates whether large non-bank institutional investors herded during the dot-com bubble of the 1990s. We use the vector Markov-switching model of Hamilton and Lin (1996) to analyse the technology stockholdings of 115 large institutional investors from 1980 to 2012. By imposing different restrictions on the elements of the transition probability matrix, we are able to test for various lead/lag scenarios that might have existed between the technology stockholding of each investor and that of the residual market. We find that only 17.4% of the investors in our sample herded during the dot-com bubble. Thus, during the dot-com bubble, herding among large institutional investors was not an especially widespread phenomenon. Among those investors that herded, 80% herded during the run-up, 10% during the collapse and 10% during both phases of the dot-com bubble. About 23% of all investors in our sample exited from the technology sector before the bubble collapsed. These results seem to support Abreu and Brunnermeier’s (2003) theory of bubbles and crashes.

The international REIT’s time-varying response to the U.S. monetary policy and macroeconomic surprises

Abstract International real estate markets and the ever increasing role of the U.S. economic and policy developments have played a central role both in international portfolio management as well as broader economic policy making. In this paper, we measure the extent of time-varying impact of the U.S. monetary policy and macroeconomic news on the international Real Estate Investment Trusts (REITs) stock returns. Results suggest that there has been significant variation both across time and across countries in the impact of U.S. news on the global REIT stocks. Further, the country’s stock market capitalization to GDP ratio has strong connections with the time-varying nature of the impact of the U.S. news on the global REIT stock returns.