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AbstractWe examine the stock return predictability of out‐of‐the‐money (OTM) put‐to‐call trading volume ratio (OTMPC). Our numerical analysis predicts that in the US equity option market, informed investors rarely write OTM options because the leverage effect is not sufficient to compensate for transaction costs. OTMPC thus captures the informed investors' OTM put purchase volume relative to their OTM call purchase volume. After controlling for existing empirical proxies for informed option trading, we find that OTMPC predicts future stock returns and corporate news. The return predictability offers implementable stock portfolio strategies. Our findings suggest that market inefficiency can emerge from uninformed investors' limited knowledge about how transaction costs influence the trading strategies of informed investors.

Nitrogen flow rate is one of the important growth parameters for the growth of group-III nitride nanowires in plasma-assisted molecular beam epitaxy. However, nitrogen flow rate has received less attention compared to the group-III metal fluxes since its effects are not as prominent as that of the metal fluxes. In this study, we investigated the effects of nitrogen flow rate on the morphology and composition of AlGaN nanowires. Reducing the nitrogen flow rate improved the structural uniformity and increased the Al composition. We present a composition change model and show that excess nitrogen suppresses Ga desorption by recombining the Ga atoms, thereby causing a change in the composition of AlGaN. It was confirmed that the influence of the nitrogen flow rate on the Al composition varied with the growth temperature. These results provide insights into the role of nitrogen flow rate on the growth of AlGaN nanowires and suggest that more sophisticated growth control is possible by considering the nitrogen flow rate. ; This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. NRF-2017R1A2B2011858); Gwangju institute of science technology (GIST) also funded this experiment through Amano Center for Advanced LEDs.