Abslracf-In this paper, we propose a collision detection system based on a nonlinear adaptive impedance control law. The colUsion detection system detects collisions of a manipulator with its environment without using external sensors. The adaptive impedance control law is employed to estimate the dynamic parameters of the manipulator, and allows the manipulator to have interaction with its environment. The system detects collisions based on the difference between the actual input torque to the manipulator and the reference input torque, which is calculated based on the estimated parameters of the manipulator dynamics. The manipulator stops when a collision is detected. The proposed collision detection system is implemented in an industrial manipulator and experimental results illustrate the validity of the proposed system. 0-7803-7736-2/03/$17.00 02003 IEEE

Summary 1.Cleistogamy is a mating system found in approximately 300 species of flowering plants. Cleistogamous plants produce closed (cleistogamous, CL) flowers that require obligate selfpollination and open (chasmogamous, CH) flowers that allow for outcross-pollination. CL and CH flowers are induced by various environmental factors; this appears to be an adaptive mating strategy in unpredictable environments. 2. We examined the molecular basis of CL and CH flowering in Cardamine kokaiensis , which is closely related to the model flowering plant Arabidopsis thaliana . CL and CH flowering should be regulated by gene expression that is dependent on environmental conditions. By elucidating the molecular basis of CL and CH flowering, we can determine the changes in gene regulatory networks involved in the transition from CH to CL flowering. Furthermore, these results may help clarify the molecular evolutionary mechanisms leading to cleistogamy. 3. We regulated CL and CH flowering of C. kokaiensis using chilling treatments in a growth chamber. In a control treatment without chilling, C. kokaiensis produced CH and intermediate (INT) flowers. Long chilling of seedlings led to INT flowers, while long chilling of seeds induced the formation of CL flowers. Chilling seeds, and to a lesser extent of seedlings, induced early flowering and small plant size at flowering. 4. We also conducted a cross-species microarray analysis to compare gene expression patterns between CL and CH flowers using genomic DNA-based probe-selection strategy in an A. thaliana microarray. In this result, 69 genes, including genes related to floral development, auxin, flowering time, cold-stress, and drought-stress, were differentially expressed between CL and CH flowers. 5. Synthesis . This is the first report on the molecular basis of cleistogamy. We hypothesize that the interaction between the genetic network of the chilling response and that of floral development has been important in the evolution of cleistogamy in C. kokaiensis . Our results help to clarify the molecular basis for the evolution of plant mating systems that depend on environmental conditions.

Aims. It is well known that convective motions in the photosphere are suppressed by magnetic fields. However, it has been difficult to study the interaction between convection and small magnetic features, such as G-band bright points (GBPs) or pores with polarimetric measurements, because of the available spatial resolution (∼1 ). This situation is changed by the advent of the SpectroPolarimeter (SP) aboard the Hinode satellite, which has 0. 3 spatial resolution. Methods. We analyzed the pore and its surrounding region in NOAA 10940 near the disk center. We obtained the field strength and filling factor through the Milne-Eddington inversion of the Stokes profiles. We also derived the line-of-sight velocity by the shift of the line core. Using these physical parameters, we investigated the physical conditions needed to suppress the convection. Results. We found that the convection is suppressed, not by the strength of the magnetic field itself, but by high concentration of magnetic flux tubes. We also found that GBPs and pores are distinguished in terms of the filling factor ( f ); f 0.6 for GBPs and f = 0.8-0.9 for pores.

Although the sizes of individual flowers within one plant vary, few studies to date have investigated correlations among floral traits at the intra-plant level. Variations of the pleiotropic genes or linkage disequilibrium of genes, those have been said to create larger correlations between some combinations of traits than others at the inter-plant level, cannot predict intra-plant level correlations. In this study, correlations between several combinations of floral traits, including the number and volume of pollen grains and ovules, were investigated at both intra-and inter-plant levels in Iris gracilipes. The pattern of intra-plant level correlations was similar to that of inter-plant level correlations with some exceptions; correlations between functionally related traits tended to be larger than others at both levels. For example, correlations between sepal and petal size, and between petaloid style and filament length were large at both levels. This may be explained by the genetic and the developmental relationships between some combinations of traits, rather than by (co)variations of the peculiar properties of the individual plants such as genetic variations.