A threshold-based approach to calorimetry in helium droplets: Measurement of binding energies of water clusters

Helium droplet beam methods have emerged as a versatile technique that can be used to assemble a wide variety of atomic and molecular clusters. We have developed a method to measure the binding energies of clusters assembled in helium droplets by determining the minimum droplet sizes required to assemble and detect selected clusters in the spectrum of the doped droplet beam. The differences in the droplet sizes required between the various multimers are then used to estimate the incremental binding energies. We have applied this method to measure the binding energies of cyclic water clusters from the dimer to the tetramer. We obtain measured values of D(0) that are in agreement with theoretical estimates to within ～20%. Our results suggest that this threshold-based approach should be generally applicable using either mass spectrometry or optical spectroscopy techniques for detection, provided that the clusters selected for study are at least as strongly bound as those of water, and that a peak in the overall spectrum of the beam corresponding only to the cluster chosen (at least in the vicinity of the threshold) can be located.     

The influence of coating structure on micromachine stiction

Stiction and friction in micromachines is commonly inhibited through the use of silane coupling agents such as 1H-, 1H-, 2H-, 2H-perfluorodecyltrichlorosilane (FDTS). FDTS coatings have allowed micromachine parts processed in water to be released without debilitating capillary adhesion occurring. These coatings are frequently considered as densely-packed monolayers, well-bonded to the substrate. In this paper, it is demonstrated that FDTS coatings can exhibit complex nanoscale structures, which control whether micromachine parts release or not. Surface images obtained via atomic force microscopy reveal that FDTS coating solutions can generate micellar aggregates that deposit on substrate surfaces. Interferometric imaging of model beam structures shows that stiction is high when the droplets are present and low when only monolayers are deposited. As the aggregate thickness (tens of nanometers) is insufficient to bridge the 2 m gap under the beams, the aggregates appear to promote beam–substrate adhesion by changing the wetting characteristics of coated surfaces. Contact angle measurements and condensation figure experiments have been performed on surfaces and under coated beams to quantify the changes in interfacial properties that accompany different coating structures. These results may explain the irreproducibility that is often observed with these films.     

Adelaide

Excluding Darwin in the Northern Territory, Adelaide was the last of the Australian state capital cities to be founded, with first settlement taking place in 1836. Adelaide already has a population of almost a million people and forms an urban area stretching for about 50 kilometres north-south by 20 kilometres east-west, a local area of 652 km ². As Adelaide's population increases beyond one million, new conditions and challenges necessitate more complex and comprehensive measures to plan and develop the city.     

Correlation between maximum latewood density of annual tree rings and NDVI based estimates of forest productivity

In boreal conifers, maximum latewood density (MXD) of annual rings varies in response to warm-season temperatures. Vegetation productivity can be estimated using the Normalized-Difference Vegetation Index (NDVI) calculated from satellite sensor data. Ground measurements related to productivity are required in order to evaluate these estimates. MXD from three boreal sites was compared with estimates of net primary productivity (NPP) for 1982-1990 produced by the CASA (Carnegie-Ames-Stanford-Approach) model from FASIR (Fourier adjustments, solar zenith angle correction, interpolation at high latitudes, and reconstruction of tropical values) NDVI. All three density series correlated significantly with the CASA estimates, suggesting that in boreal conifers MXD may be an appropriate index for productivity or canopy growth in regions where productivity is strongly temperature-related.     

The Local Impacts of Urban Consolidation in Sydney

The processes of urban consolidation are described, detailed and reviewed in three local government areas in Sydney since 1980. This provides an integrated account and analysis of how market forces and planning policies have actually delivered dwelling stock on the ground. Distinctive aspects of urban consolidation in each local government area are reviewed.     

Microtubule‐Templated Biomimetic Mineralization of Lepidocrocite

Protein microtubules (MTs) 25 nm in diameter and tens of micrometers long have been used as templates for the biomimetic mineralization of FeOOH. Exposure of MTs to anaerobic aqueous solutions of Fe²⁺ buffered to neutral pH followed by aerial oxidation leads to the formation of iron oxide coated MTs. The iron oxide layer was found to grow via a two‐step process: initially formed 10–30 nm thick coatings were found to be amorphous in structure and comprised of several iron‐containing species. Further growth resulted in MTs coated with highly crystalline layers of lepidocrocite with a controllable thickness of up to 125 nm. On the micrometer size scale, these coated MTs were observed to form large, irregular bundles containing hundreds of individually coated MTs. Iron oxide grew selectively on the MT surface, a result of the highly charged MT surface that provided an interface favorable for iron oxide nucleation. This result illustrates that MTs can be used as scaffolds for the in‐situ production of high‐aspect‐ratio inorganic nanowires.     

Embodied and Operational Energy Consumption in the City

This study shows how estimates of energy consumption can be extracted from existing data sets and efficiently related to characteristics of the real property making up the discrete areas of the city. The study suggests that embodied energy consumption may be more significant than previously thought and suggests how estimates of embodied and operational energy may be used as a development control tool in the planning system.