Prediction of photoperiodic regulators from quantitative gene circuit models

Photoperiod sensors allow physiological adaptation to the changing seasons. The external coincidence hypothesis postulates that a light-responsive regulator is modulated by a circadian rhythm. Sufficient data are available to test this quantitatively in plants, though not yet in animals. In Arabidopsis, the clock-regulated genes CONSTANS (CO) and FLAVIN, KELCH, F-BOX (FKF1) and their lightsensitive proteins are thought to form an external coincidence sensor. We use 40 timeseries of molecular data to model the integration of light and timing information by CO, its target gene FLOWERING LOCUS T (FT), and the circadian clock. Among other predictions, the models show that FKF1 activates FT. We demonstrate experimentally that this effect is independent of the known activation of CO by FKF1, thus we locate a major, novel controller of photoperiodism. External coincidence is part of a complex photoperiod sensor: modelling makes this complexity explicit and may thus contribute to crop improvement

Relative equity market valuation conditions and acquirers’ gains

We examine whether the relative equity market valuation conditions (EMVCs) in the merging firms countries help acquirers’ managers to time the announcements of domestic and foreign target acquisitions. After controlling for several deal- and merging firms-specific features we find that acquisition activity, as well as acquirers gains, are significantly higher during periods of high-EMVCs at home, irrespective of the domicile of the target. We also find that the higher foreign acquirers’ gains that reaped during periods of high-EMVCs at home are realized by deals of targets based in the RoW (=World-G7), rather than G6 (=G7-UK) countries, which is due to the low correlation of EMVCs between the U.K. (home) and the RoW countries. Moreover, acquisition of targets domiciled in the RoW (G6) countries yield higher (lower) gains than domestic targets during periods of high-EMVCs at home. This suggests that the relative EMVCs between the merging firms’ countries allow acquirers’ managers to time the market and acquire targets at a discount, particularly in countries in which acquirers’ stocks are likely to be more overvalued than the targets’ stocks

Statistical inference of the efficient frontier for dependent asset returns

Asset allocation, Mean–variance efficient frontier, Optimal portfolios, Asymptotic normality,