Morphological plasticity and adaptation level of distylous Primula nivalis in a heterogeneous alpine environment

Plant populations at high elevation face extreme climatic conditions and resource limitations. The existence of distylous species at different elevations can help us investigate their adaptation to high altitudes, the evolution of their morphological characteristics, as well as their responses to limited resources. Here, 17 populations of Primula nivalis at different elevations were evaluated regarding variations in plant morphological characteristics, biomass allocation, and morphological plasticity in a heterogeneous environment. Our results demonstrate that heterogeneous environments can affect plant morphological characteristics and resource allocation in each sexual morph of these plants. Moreover,environmental variations reduced morphological plasticity in the two plant morphs, and the plasticity of long style(LS) plants was greater than that of short style(SS) plants. There were significant negative correlations between morphological characteristics and elevation, rainfall, temperature, and sunshine,and these are the main variables that affect morphological characteristics and resource allocation of both morphs of P. nivalis plants in heterogeneous environments. The morphological characteristics of P. nivalis plants transplanted from high to lower elevations were not significantly different in either population.LS plants had greater morphological plasticity and adaptability in heterogeneous environments than SS plants. Elevational gradients and heterogeneous environments differentiated both morphs of P. nivalis plants with regards to morphology as well as adaptations. LS plants showed a higher level of adaptability than SS plants.

Projected Runge-Kutta methods for constrained Hamiltonian systems

Projected Runge-Kutta （R-K） methods for constrained Hamiltonian systems are proposed. Dynamic equations of the systems, which are index-3 differential-algebraic equations （DAEs） in the Heisenberg form, are established under the framework of Lagrangian multipliers. R-K methods combined with the technique of projections are then used to solve the DAEs. The basic idea of projections is to eliminate the constraint violations at the position, velocity, and acceleration levels, and to preserve the total energy of constrained Hamiltonian systems by correcting variables of the position, velocity, acceleration, and energy. Numerical results confirm the validity and show the high precision of the proposed method in preserving three levels of constraints and total energy compared with results reported in the literature.

Up-regulation and time course of protein kinase C immunoreactivity during persistent inflammation of the rat spinal cord

BACKGROUND： It has been reported that activation and/or translocation of protein kinase C （PKC） is related to hyperalgesia, and changes in PKC expression in the dorsal horn of spinal cord take place during inflammatory pain. OBJECTIVE： To observe PKC changes in the dorsal horn of spinal cord using immunohistochemistry and to measure the time-course during persistent pain produced by chemical stimulation with a right hind-paw injection of formalin. DESIGN： Randomized controlled animal experiment. SETTING： Institute of Basic Medical Science, Hebei Medical University MATERIALS： The present experiment was performed at the Department of Pathophysiology, Institute of Basic Medical Science, Hebei Medical University between September 2000 and June 2002. Forty-two Sprague-Dawley rats, weighing 260-280 g, irrespective of gender, were provided by the Center of Animal Experimentation at Hebei Medical University. PKC antibody was provided by Sigma, USA. Immunohistochemistry kits were purchased from Zhongshan Biotechnology Company, Beijing. HPIAS-1000 definition multicolor system was provided by Qianping Wuxiang Project Company of Tongji Medical University. Animal use during experimentation was consistent with the standards of Animal Ethics Committee. METHODS： Sprague-Dawley rats were divided randomly into control （n = 6） and experimental groups （n = 36）. Experimental rats were given an intracutaneous injection of 5% formalin into the planta surface of the right hind-paw. Animals with inflammatory pain were anesthetized and sacrificed to obtain the L5 spinal region at 1, 3, 12 hours, 1, 3, and 7 days after formalin treatment, with 6 rats in each time group. The spinal cords at the L5 region were collected from the control group following sodium chloride injections into the planta surface of the right hind-paw, identical to the experimental group. MAIN OUTCOME MEASURES： Pain reaction of experimental rats after formalin treatment. PKC-positive neurons, and distribution of PKC-immunoreactive particles, in the ipsi- and contralateral dorsal horn were investigated during different stages of inflammatory pain using immunohistochemistry. RESULTS： All 42 rats were included in the final analysis, without any loss. Pain reaction： consistent with previous findings, it was determined that a unilateral injection of formalin into the hind-paw resulted in significant edema and induced a series of nociceptive responses, such as licking, biting, or shaking the injected paw. The maximal inflammation change was observed 1 day after formalin injection and changes did not disappear until the day 7. Number of the PKC positive neurons： results demonstrated that the number of PKC immunoreactive neurons in the dorsal horn increased slightly after formalin injection at 1 hour, compared with the control group. PKC immunoreactivity was up-regulated at day 1, reduced at day 3, and appeared to recover at day 7. The number of PKC-positive neurons in the contralateral side was less than the ipsilateral side at each time sampled. Distribution of PKC immunoparticles over the neurons： PKC immunoreactivity was observed in the nucleus and cytoplasm, as well as on or near the membrane of neurons and synaptosomes in the spinal cord of the control group. PKC activated and translocated from nucleus to the membrane-associated site following formalin treatment. Significant changes were observed at 1 hour and 1 day. The intensity of staining was stronger in the ipsilateral side than the contralateral side at all time points following formalin injection （P 〈 0.01）, whereas the expression patterns of PKC immunoreactivity in the nuclei were very similar in the right and left hemispheres. CONCLUSION： PKC expression in the dorsal horn of the spinal cord peaked at 1 hour and 24 hours, and was very obvious at 24 hours. Protein kinase C expression in the spinal cord increased bilaterally, although it was greater in the ipsilateral hemisphere. In addition, PKC expression at the neuronal membrane and synaptosome was significantly increased. These results indicate that PKC expression is activated in the dorsal horn of the spinal cord during hyperalgesia.

Novel orbit-attitude combination mode for solar power satellites to reduce mass and fuel

Solar power satellite receives great attention because it can release the energy crisis and environmental problems in the future.However,the launch and maintenance costs are tremendous due to the large system mass and large fuel consumption to counteract space perturbations.To reduce mass and fuel,a novel quasi-Sun-pointing attitude in Sun-frozen orbit is proposed.The Sun-frozen orbit has a nonzero eccentricity vector that always points towards the Sun.The quasi-Sun-pointing attitude is a periodic solution of the Sun-pointing attitude angle.Although about 3%electricity must be given up because of the variation of Sun-pointing attitude angle,little control action is required to deal with the solar radiation pressure and gravity-gradient torque.The algorithm to obtain initial conditions is proposed.The influences of system parameters and structural flexibilities are studied.Simulation results reveal that the quasi-Sun-pointing attitude in Sunfrozen orbit dramatically reduce fuel consumption,the dry mass,and complexity of the control system.In addition,structural vibration is hardly induced by the gravity-gradient torque.Thus,the bending stiffness as well as the mass of the supporting structure can be reduced.

Natural hybridization and reproductive isolation between two Primula species

Natural hybridization frequently occurs in plants and can facilitate gene flow between species, possibly resulting in species refusion. However, various reproductive barriers block the formation of hybrids and maintain species integrity. Here, we conducted a field survey to examine natural hybridization and reproductive isolation （RI） between sympatric populations of Primula secundiflora and P. poissonii using ten nuclear simple sequence repeat （SSR） loci. Although introgressive hybridization occurred, species boundaries between P. secundiflora and P. poissonii were maintained through nearly complete reproductive isolation. These interfertite species provide an excellent model for studying the RI mechanisms and evolutionary forces that maintain species boundaries.