While eye sensitivity in the American horseshoe crab Limulus polyphemus has long been known to be under the control of an endogenous circadian clock, only recently has horseshoe crab locomotion been shown to be contro...While eye sensitivity in the American horseshoe crab Limulus polyphemus has long been known to be under the control of an endogenous circadian clock, only recently has horseshoe crab locomotion been shown to be controlled by a separate clock system. In the laboratory, this system drives clear activity rhythms throughout much of the year, not just during the mating season when horseshoe crabs express clear tidal rhythms in the field. Water temperature is a key factor influencing the expression of these rhythms： at 17~C tidal rhythms are expressed by most animals, while at I l^C expression of circatidal rhythms is rarely seen, and at 4~C rhythms are suppressed. Neither long （16：8 Light：Dark） nor short （8：16） photoperiods modify this behavior at any of these temperatures. Synchronization of these circatidal rhythms can be most readily effeeted by water pressure cycles both in situ and in the lab, while temperature and current cycles play lesser, but possibly contributory, roles. Interestingly, Light：Dark cycles appear to have synchronizing as well as ＂masking＂ effects in some individuals. Evidence that each of two daily bouts of activity are independent suggests that the Limulus circatidal rhythm of locomotion is driven by two （circalunidian） clocks, each with a period of 24.8h. While the anatomical locations of either the circadian clock, that drives fluctuations in visual sensitivity, or the circatidal clock, that controls tidal rhythms of locomotion, are currently unknown, preliminary molecular analyses have shown that a 71 kD protein that reacts with antibodies directed against the Drosophila PERIOD （PER） protein is found in both the pro- tocerebrum and the subesophageal ganglion展开更多
Using the global magnetohydrodynamics(MHD) simulation model, we investigated the effects of the interplanetary magnetic field(IMF) clock angle on the shape of bow shock, including its rotational asymmetry and subsolar...Using the global magnetohydrodynamics(MHD) simulation model, we investigated the effects of the interplanetary magnetic field(IMF) clock angle on the shape of bow shock, including its rotational asymmetry and subsolar point. For general northward IMF( z component Bz > 0), the rotational symmetry of the bow shock is broken by the effects of fast magnetosonic Mach number(Mms), and the cross-sectional line of the bow shock is an ellipse with the semi-major axis along the direction perpendicular to the IMF. The ratio or D-value between semi-major and semi-minor axis can be used to illustrate the extent of asymmetry of the bow shock. On the basis of the multiple parameters fitting, we obtain the changing relationship of both semi-axes with the clock angle and the distance away from the Earth. For general southward IMF(Bz < 0), the cross sectional line of the bow shock is highly asymmetrical under the multiple effects of magnetopause and Mms. The effects of IMF clock angle on subsolar point depend mainly on the changing subsolar point of magnetopause as an obstacle. The distance of subsolar point of bow shock from the Earth increases with the increasing IMF clock angle for Bz > 0, and decreases with the increasing IMF clock angle for Bz < 0.展开更多
文摘While eye sensitivity in the American horseshoe crab Limulus polyphemus has long been known to be under the control of an endogenous circadian clock, only recently has horseshoe crab locomotion been shown to be controlled by a separate clock system. In the laboratory, this system drives clear activity rhythms throughout much of the year, not just during the mating season when horseshoe crabs express clear tidal rhythms in the field. Water temperature is a key factor influencing the expression of these rhythms： at 17~C tidal rhythms are expressed by most animals, while at I l^C expression of circatidal rhythms is rarely seen, and at 4~C rhythms are suppressed. Neither long （16：8 Light：Dark） nor short （8：16） photoperiods modify this behavior at any of these temperatures. Synchronization of these circatidal rhythms can be most readily effeeted by water pressure cycles both in situ and in the lab, while temperature and current cycles play lesser, but possibly contributory, roles. Interestingly, Light：Dark cycles appear to have synchronizing as well as ＂masking＂ effects in some individuals. Evidence that each of two daily bouts of activity are independent suggests that the Limulus circatidal rhythm of locomotion is driven by two （circalunidian） clocks, each with a period of 24.8h. While the anatomical locations of either the circadian clock, that drives fluctuations in visual sensitivity, or the circatidal clock, that controls tidal rhythms of locomotion, are currently unknown, preliminary molecular analyses have shown that a 71 kD protein that reacts with antibodies directed against the Drosophila PERIOD （PER） protein is found in both the pro- tocerebrum and the subesophageal ganglion
基金supported by the National Natural Science Foundation of China(Grant Nos.41231067,41374172)the National Basic Research Program of China(Grant No.2012CB825602)the Specialized Research Fund for State Key Laboratories of China
文摘Using the global magnetohydrodynamics(MHD) simulation model, we investigated the effects of the interplanetary magnetic field(IMF) clock angle on the shape of bow shock, including its rotational asymmetry and subsolar point. For general northward IMF( z component Bz > 0), the rotational symmetry of the bow shock is broken by the effects of fast magnetosonic Mach number(Mms), and the cross-sectional line of the bow shock is an ellipse with the semi-major axis along the direction perpendicular to the IMF. The ratio or D-value between semi-major and semi-minor axis can be used to illustrate the extent of asymmetry of the bow shock. On the basis of the multiple parameters fitting, we obtain the changing relationship of both semi-axes with the clock angle and the distance away from the Earth. For general southward IMF(Bz < 0), the cross sectional line of the bow shock is highly asymmetrical under the multiple effects of magnetopause and Mms. The effects of IMF clock angle on subsolar point depend mainly on the changing subsolar point of magnetopause as an obstacle. The distance of subsolar point of bow shock from the Earth increases with the increasing IMF clock angle for Bz > 0, and decreases with the increasing IMF clock angle for Bz < 0.
