The optimization of the strength distribution of the floating runway under wave loads was explored and the techniques needed to make this optimization possible were developed.

The "Hydrodynamic Influence Matrix" was defined to capture the hydrodynamic properties of the floating structure and to incorporate these into the motion equations of the floating structure. Great effort was made to improve the accuracy of the Hydrodynamic Influence Matrices for short waves.

A low-order panel method was developed first to compute the Hydrodynamic Influence Matrices, which were then incorporated into the finite-difference form of the motion equations for the floating-mat model. The spectra of the responses of the floating runway were computed by discretizing the incident wave spectrum into elemental waves and solving the finite-difference equations for each elemental wave. The low-order method required a huge number of variables to treat a realistic floating runway and the resulting numerical accuracy of the computation was insufficient.

A high-order method was then developed to improve the accuracy in the hydrodynamics computation for short waves. Double fifth order interpolation functions were used to represent the source distribution on a high-order panel. Analytically exact formulations and approximate formulations using asymptotic series were developed and combined to compute the singular integrations involving the Rankine part of the Green function and its gradient. Gaussian quadrature was used to compute the integrations involving the remnant part of the Green function. The high-order Hydrodynamic Influence Matrices were then computed with acceptable accuracy for waves with wavelength close to the panel dimension and were incorporated into the high-order motion equations for the floating-mat model. These were solved using a Galerkin method to get the responses of the floating runway in a wave system.

The optimization for the strength distribution of the floating runway was carried out based on consideration of the structural reliability using gradient projection method. Preliminary optimization results for various model structures and the full-size floating runway have been achieved. For the small model structures local optima satisfying the Kuhn-Tucker condition were found. For the large model structure and the full size floating runway preliminary optimized results with reduced total weight were presented as a reference for future work.

Silicon (Si) is the second most abundant element after oxygen in the earth’s crust and shows beneficial effects on plant growth and production by alleviating both biotic and abiotic stresses including diseases, pests, lodging, drought, and nutrient imbalance. Transporters involved in uptake and translocation of Si have been identified in Si-accumulating species including rice, barley and maize. Two kinds of transporters (influx and efflux) are involved in the Si uptake by the roots. The influx transporters (low silicon 1, lsi1) belongs to a Nod26-like major intrinsic protein (NIP) subfamily in aquaporin, while the efflux transporter (Lsi2) belongs to putative anion transporters. They are mainly expressed in the roots. Knockout of either Lsi1 or Lsi2 in rice results in defect of Si uptake, indicating that coupling of Lsi1 with Lsi2 is required for efficient uptake of Si in rice. Although the function of Lsi1 and Lsi2 is similar in rice, barley and maize, they show different expression pattern and cell-type specificity of localization. These differences may explain the differential Si uptake capacity among these species. On the other hand, Lsi6 is localized at the adaxial side of the xylem parenchyma cells in the leaf sheath and leaf blades of rice and maize. Knockout of rice Lsi6 does not affect the uptake of Si by the roots, but results in disordered deposition of silica in the shoots and increased excretion of Si in the guttation fluid, indicating that Lsi6 is a transporter responsible for the unloading of Si from the xylem.

Maize (Zea mays L.) is a Si-accumulating species although its accumulation is not as high as rice. However, the transporters involved in Si uptake and distribution are unknown. Here, we isolated and characterized three maize silicon transporter genes ZmLsi1, ZmLsi2 and ZmLsi6, which are homologues, respectively, of rice silicon transporter genes. Each transporter shared more than 80% between maize and rice at amino acid level. Both ZmLsi1 and ZmLsi6 showed Si influx transport activity, while ZmLsi2 showed efflux activity, when they were expressed in Xenopus laevis oocytes. mRNA of ZmLsi1 and ZmLsi2 was expressed mainly in the roots, while ZmLsi6 was also in the shoots. Immunostaining showed that ZmLsi1 was localized at the distal side of plasma membrane of root epidermis, hypodermis and cortex, while ZmLsi2 was only in the endodermis without polarity. In contrast, ZmLsi6 was localized at the xylem parenchyma cells of the leaf blades. These results suggest that ZmLsi1 and ZmLsi2 are involved in the uptake of Si from the roots and ZmLsi6 is responsible for transport of Si out of the xylem, therefore regulating Si distribution in the leaves.