Cell surface binding, internalization, and biological effects of insulin-like growth factors (IGFs) I and I1 have been studied in primary neuronal cultures from developing rat brain (embryonic day 15). Two types of IGF binding sites are present on the cell surface. The IGF-I receptor cr-subunit (M, 125,000) binds IGF-I with a KD of 1 nM and IGF-I1 with 10 times lower affinity. The mannose-6-phosphate (Mand-

The surface precision of an antenna reflector can be improved using the actuation of piezoelectric materials to obtain a high-performance space antenna. In this study, the active shape control of a reflector with piezoceramic (lead zirconate titanate) actuators assembled on ribs is proposed by theoretical and experimental approaches. A finite element model of the integrated reflector–actuator system is established using piezoelectric constitutive equations and the virtual work’s principle. For a desired shape, a closed-loop iterative shape control method based on the influence coefficient matrix model is developed, which resolves the issue of high-precision shape control of the antenna reflector in the presence of model errors. The shape controller based on the proposed closed-loop shape control method is implemented on a planar hexagonal reflector with 30 lead zirconate titanate actuators. Experimental results demonstrate that the closed-loop control is an effective way to improve the surface precision of the reflector considering uncertainties.

Subject to the limited envelope size and carrying capacity of a rocket, it could be one of the most promising solutions to construct a large space structure through multilaunching and on-orbit assembly. Taking the antenna of the solar power satellite as the research objective, a novel vibration suppression strategy is developed in this article to guarantee high structural stability of the large space structure during on-orbit assembly. The concept of distributed control unit, together with the varying location relationship matrices, reflects the structural characteristics of the large space structure during on-orbit assembly. The explicit expression form of the control unit’s dynamic model is first derived based on the Newmark-β method. Then, the distributed adaptive model predictive controller is proposed to suppress the vibration of the large space structure aroused by weak impact among assembling modules. Through recalculating the control matrices efficiently at each assembly, the proposed controller achieves adaptive updating along with the varying large space structure. The feasibility of the proposed distributed adaptive model predictive controller is investigated in the numerical simulations, and the centralized fast model predictive controller is adopted for better comparison. The results demonstrate that the distributed adaptive model predictive controller can effectively suppress vibration of the large space structure during on-orbit assembly, with good adaptability, robustness, and computation efficiency.

In situ hybridization histochemistry was used to map cellular patterns of gene expression for the insulin-like growth factor (IGF) system in developing murine skeleton from embryonic day 15 (E15) through postnatal day 25 (P25). IGF-I receptor and IGF-II receptor messenger RNAs (mRNAs) are both selectively concentrated in developing chondrocytes and osteoblasts. IGF-II and IGF-binding protein-5 and -6(IGFBP-5 and -6) mRNAs are abundant in mesenchymal condensations and chondroblasts on E15. Chondrocyte IGF-II mRNA levels remain high, but IGFBP-5 and -6 mRNAs decline significantly as cartilage matures. Low levels of IGFBP-6 mRNA are detected in postnatal chondrocytes up to at least P25, but IGFBP-5 mRNA is no longer detected in chondrocytes after E18. IGF-I and IGFBP-2, -3, and -4 mRNAs are detected in surrounding mesenchymal tissue, but are not detected in mesenchymal condensations or chondrocytes at any stage of development. IGFBP-3 mRNA is localized in sprouting capillaries invading the perichondrium and periosteum throughout development. IGF-I, IGF-II, and IGFBP-2, -4, -5, and -6 mRNAs are detected in osteoblasts localized in zones of endochondral ossification from E18 to at least P25. IGFBP-1 mRNA is not detected in cartilage or bone cells at any stage of development. These data confirm the recent report by Shinar et al. that IGF-II, but not IGF-I, mRNA is detected in rat chondrocytes in vivo and show that this pattern also applies to the mouse. The present study demonstrates, for the first time, the cell-specific patterns of IGF-I and -II receptor and IGFBP-2 to -6 gene expression during the processes of chondro- and osteogenesis in vivo. Interestingly, IGF-II, both IGF receptors, and IGFBP-5 and -6 are simultaneously coexpressed in chondrocyte precursors early in skeletal development, suggesting functional interactions between these specific factors in chondrogenesis. Both IGFs, both IGF receptors, and IGFBP-2, -4, -5, and -6 are all expressed in osteoblasts, providing evidence for potential local interactions between these IGF system components in osteogenesis. Thus, 9 of 10 known components of the IGF system demonstrate dynamic cell-specific patterns of gene expression during chondro- and osteogenesis, supporting the view that the IGF system has a complex and integral role within the developing skeleton.