Spiral waves of chemical activity

The Zhabotinsky-Zaikin reagent propagates waves of chemical activity. Reaction kinetics remain to be fully resolved, but certain features of wave behavior are determined by purely geometrical considerations. If a wave is broken, then spiral waves, resembling involutes of the circle, appear, persist, and eventually exclude all concentric ring waves.     

Scroll-shaped waves of chemical activity in three dimensions

Ferric ions catalyze the oxidation of malonate by bromate in acid solution, sometimes at a spatially uniform, steady rate, but sometimes in a self-regenerating three-dimensional wave which resembles a rotating scroll, often with its axis closed in a ring. In cross section perpendicular to the axis, one sees an involute spiral emerging from a thin cylindrical core. This "dissipative structure" organizes reaction stages periodically in space and time everywhere except along its rotation axis, which may therefore be a thermodynamically unique locus.     

Navigating complex labyrinths: optimal paths from chemical waves

The properties of excitable media are exploited to find minimum-length paths in complex labyrinths. Optimal pathways are experimentally determined by the collection of time-lapse position information on chemical waves propagating through mazes prepared with the Belousov-Zhabotinsky reaction. The corresponding velocity fields provide maps of optimal paths from every point in an image grid to a particular target point. Collisions of waves that were temporarily separated by obstacles mark boundary lines between Significantly different paths with the same absolute distance. The pathfinding algorithm is tested in very complex mazes with a simple reaction-diffusion model.     

Observation of backward pulse propagation through a medium with a negative group velocity

The nature of pulse propagation through a material with a negative value of the group velocity has been mysterious, as simple models seem to predict that pulses will propagate "backward" through such a material. Using an erbium-doped optical fiber and measuring the time evolution of the pulse intensity at many points within the fiber, we demonstrate that the peak of the pulse does propagate backward inside the fiber, even though the energy flow is always in the forward direction.     

Regional differences in the phase velocity and the quality factor q of mantle rayleigh waves

The phase velocity and the quality factor (Q) of mantle Rayleigh waves from the great Kurile Islands earthquake of 1963 have a close azimuthal correlation with each other and differ considerably among different paths. Serious error may be introduced in the interpretation of observed regionality in phase velocity if regional differences in Q are ignored.     

拟常曲率流形中具有常平均曲率的子流形

讨论了局部对称拟常曲率黎曼流形中具有常平均曲率向量的紧致无边子流形,给出了关于其第二基本形式模长平方S的积分不等式.     

平面曲线曲率计算公式的探讨

根据平面曲线曲率的定义,利用复合函数和含参变量函数求导数的公式证明了平面曲线的曲率计算公式,体现了数学定义的严肃性和定理证明的严密性。     

叶卷曲突变体的研究进展

介绍了卷叶突变体的类型,并从细胞水平、激素调控、分子遗传及环境因素等方面综述了叶卷曲突变体发生的机制。     

Curvature as a feature of pattern vision

Prolonged inspection of convex lines of one color and concave lines of another color can cause the appearance of oppositely colored aftereffects in curved, achromatic test lines. These effects, strongly dependent on radius of curvature, cannot be attributed to tilt or orientation. It is concluded that these results are not encompassed by models of the visual system that are based on rectilinear arrays and that curvature is a specific feature of human visual perception.     

软枣猕猴桃高效繁殖及栽培技术

软枣猕猴桃适应性强,易于种植管理。介绍了软枣猕猴桃的生物学特点、介绍了软枣猕猴桃的种苗繁殖先进技术、栽培管理技术要领、以及在软枣猕猴桃栽培过程中,遇到害虫取食,通过在实际中掌握了害虫的分布规律,对合理防控害虫,提高产量和品质至关重要。     

Shock waves in stellar atmospheres and breaking waves on an ocean beach

The phenomenon of ocean waves breaking on a beach is analogous to shock waves in the atmosphere of a pulsating star. In both cases a velocity discontinuity is clearly present. In stars the upper, expanding layer halts and falls back so as to interact with the rising gas at a shock. Similarly, a bore on a beach reaches its maximum extension before sliding back onto the next incoming wave. Analogous quantities such as the surface gravity of the star and the beach gradient in the ocean have similar effects on the flows and the nature of the discontinuity between them. Phenomena that are not analogous include the thermodynamic properties of the two media. Ocean observations may help solve some problems in shock phenomena associated with stellar pulsation.     

曲率的熵不等式的一种新证明

研究了关于曲率的积分不等式,利用纯分析的方法获得了一个不等式,它的一个直接结果就是曲率的熵不等式,并且证明了此不等式仅对圆成立.     

基于轮廓曲率和距离分析的重叠柑橘分割与重建

自然环境下重叠果实的精准识别是智能采摘面临的难题之一。针对自然环境中成熟的重叠柑橘,提出了一种基于轮廓曲率和距离分析的果实分割方法。首先,提取重叠柑橘果实轮廓并进行高斯平滑,通过曲率分析,找出异常的轮廓像素点;其次,依次连接相邻两个异常像素点,分析该线段上的像素点到轮廓的距离,在相邻两正常线段的交点处完成重叠柑橘轮廓分割,并通过寻找异常线段剔除对应的非柑橘轮廓像素点;在此基础上,采用最小二乘椭圆拟合方法,对获取的柑橘目标进行轮廓重建。结果表明：利用该方法所得到的重叠柑橘重建轮廓的平均误差、不重合度和时间分别为4.903%、5.593%、0.408 s,优于Hough变换算法和RANSAC算法,能够满足自然环境下成熟重叠柑橘果实的智能识别需求。     

水稻雄性不育系扦插繁殖与种子繁殖主要性状比较

[目的]探索水稻不同繁殖方式在农艺性状、经济性状、育性等方面的表现及存在的差异,为水稻不育系扦插繁殖在生产上的利用提供理论依据.[方法]以两个水稻细胞质雄性不育系和两个光温敏感核不育系为材料,采用茎节扦插繁殖和种子繁殖方法,调查两种繁殖方式的扦插(播种)期、始穗期、齐穗期、株高、每穗总粒数、有效穗数、穗长、株叶型及套袋自交结实率等.[结果]茎节扦插繁殖与种子繁殖相比,生育期大幅提前,株高降低,有效穗显著增多,穗长略短,穗粒数减少,植株形态表现紧束,长势旺,叶色浓,但群体整齐度较差;花粉育性及套袋自交结实率方面二者无差异.与细胞质雄性不育系相比,光温敏感核不育系扦插繁殖植株的上述性状表现相对较优.[结论]两种繁殖方式植株的农艺性状及经济性状存在一定差异,但不影响育性;光温敏感雄性不育系更适于扦插繁殖,可用于杂交种子生产.     

关于射影Ricci曲率的比较定理与共形不变性

主要研究了芬斯勒度量的射影Ricci曲率.首先,在一个完备的芬斯勒流形上,证明了关于芬斯勒度量的射影Ricci曲率的一个比较定理.其次,刻画了两个共形相关的芬斯勒度量的射影Ricci曲率的关系.在此基础上,证明了两个位似相关的芬斯勒度量的射影Ricci曲率是相等的.     

Comparison on major traits of cutting propagation and seed propagation in male sterile lines of rice

[目的]探索水稻不同繁殖方式在农艺性状、经济性状、育性等方面的表现及存在的差异,为水稻不育系扦插繁殖在生产上的利用提供理论依据.[方法]以两个水稻细胞质雄性不育系和两个光温敏感核不育系为材料,采用茎节扦插繁殖和种子繁殖方法,调查两种繁殖方式的扦插(播种)期、始穗期、齐穗期、株高、每穗总粒数、有效穗数、穗长、株叶型及套袋自交结实率等.[结果]茎节扦插繁殖与种子繁殖相比,生育期大幅提前,株高降低,有效穗显著增多,穗长略短,穗粒数减少,植株形态表现紧束,长势旺,叶色浓,但群体整齐度较差;花粉育性及套袋自交结实率方面二者无差异.与细胞质雄性不育系相比,光温敏感核不育系扦插繁殖植株的上述性状表现相对较优.[结论]两种繁殖方式植株的农艺性状及经济性状存在一定差异,但不影响育性;光温敏感雄性不育系更适于扦插繁殖,可用于杂交种子生产.