We show the dielectrophoretic actuation of single-crystal diamond nanomechanical devices. Gradient radio-frequency electromagnetic forces are used to achieve actuation of both cantilever and doubly clamped beam structures, with operation frequencies ranging from a few MHz to ∼50MHz. Frequency tuning and parametric actuation are also studied.

As the available water supply for urban turfgrass management is becoming limited in Australia, it will be crucial to identify drought-resistant turfgrass species and water-saving management strategies. Eight (pre-)commercial turfgrasses grown in Australia, two each of four species including the bermudagrasses (Cynodon dactylon L.), the Queensland blue couches (Digitaria didactyla Willd), the seashore paspalums (Paspalum vaginatum Swartz.) and St Augustinegrasses (Stenotaphrum secundatum (Walt.) Kuntze) were evaluated in two lysimeter experiments. Shallow lysimeters (28 and 40 cm) were used to represent shallow soil profiles typical of urban environments. We measured gravimetric water use for the eight cultivars and calculated water use efficiency (WUE, clipping yield to water use ratio) and WUEr (ratio of WUE under drought to that under irrigated conditions). WUEr measured in both experiments correlated strongly with survival period and this relationship was not affected by soil type or cutting height. Using survival period as the criterion for drought resistance, the best were the bermudagrasses and the worst were the seashore paspalums and Queensland blue couches. The bermudagrass genotypes had the lowest water use, highest WUE and WUEr and the Queensland blue couches and seashore paspalums had the greatest water use, lowest WUE and WUEr. The possible mechanisms of drought resistance included lower water use and lower stomatal conductance as indicated by higher canopy temperature in the early stage of water deficit.

Increasing demand for scarce water resources in Australia has led to the selection of turfgrass genotypes with good drought tolerance. Here we describe the development of methodologies for screening green couch grasses (Cynodon spp.) grown in 40-cm PVC pots placed under rainout shelters. The drought tolerance of up to 8 genotypes including 4 commercial varieties (CT2, Grand Prix, Legend, and Winter Green) and 4 wild Australian ecotypes (1-1, 25-a-1, 40-1, and 81-1) was examined in 3 experiments conducted in 2007–08 and 2008–09. In the first experiment, all genotypes were grown with 2 soil types (clay and sandy soils) and 2 clipping heights (5 and 2 cm). Genotypic variation for survival period (defined as the period from the time water was withheld until 100% leaf firing had occurred) was high for the sandy soil × 2 cm clipping height treatment and, because retrieval of roots was easy, this combination was used in Expts 2 and 3 as the best system for screening drought tolerance. This method gave highly repeatable results across 2 years. Wild ecotype 81-1 had a significantly longer survival period than other genotypes, possibly associated with lower stomatal conductance early after water deficit was imposed, a greater root biomass at depth, and greater osmotic adjustment.