Development of a co-axial tri-rotor UAV.

This paper discusses the initial design requirements and development of a Small Unmanned Aerial Vehicle (SUAV), sometimes referred to as a Miniature Aerial Vehicle (MAV) or Micro Unmanned Aerial Vehicle (μUAV) as the backdrop to an entry for the MoD Grand Challenge Event 2008 (MoD GC 2008). A review of 61 SUAVs has been undertaken together with the development of a methodology for evaluation, review and rating against specific design criteria. This analysis concludes with a list of the top ten systems currently available which have been found to be best suited to the particular requirements of operating in the cluttered urban environment. Finally, we present a novel design of Co-Axial Tri-Rotor UAV (named HALO™) which has been developed by the i-Spy team at Middlesex University as our entry to the MoD GC 2008

Extended x-ray absorption fine structure study of porous GaSb formed by ion implantation

Porous GaSb has been formed by Ga ion implantation into crystalline GaSb substrates at either room temperature or −180 °C. The morphology has been characterized using scanning electron microscopy and the atomic structure was determined using extended x-ray absorption fine structure spectroscopy. Room-temperature implantation at low fluences leads to the formation of ∼20-nm voids though the material remains crystalline. Higher fluences cause the microstructure to evolve into a network of amorphous GaSb rods ∼15 nm in diameter. In contrast, implantation at −180 °C generates large, elongated voids but no rods. Upon exposure to air, the surface of the porous material is readily oxidized yielding Ga₂O₃ and metallic Sb precipitates, the latter resulting from the reduction of unstable Sb₂O₃. We consider and discuss the atomic-scale mechanisms potentially operative during the concurrent crystalline-to-amorphous and continuous-to-porous transformations

The Contribution of Network Organization and Integration to the Development of Cognitive Control

Cognitive control, which continues to mature throughout adolescence, is supported by the ability for well-defined organized brain networks to flexibly integrate information. However, the development of intrinsic brain network organization and its relationship to observed improvements in cognitive control are not well understood. In the present study, we used resting state functional magnetic resonance imaging (RS-fMRI), graph theory, the antisaccade task, and rigorous head motion control to characterize and relate developmental changes in network organization, connectivity strength, and integration to inhibitory control development. Subjects were 192 10–26-y-olds who were imaged during 5 min of rest. In contrast to initial studies, our results indicate that network organization is stable throughout adolescence. However, cross-network integration, predominantly of the cingulo-opercular/salience network, increased with age. Importantly, this increased integration of the cingulo-opercular/salience network significantly moderated the robust effect of age on the latency to initiate a correct inhibitory control response. These results provide compelling evidence that the transition to adult-level inhibitory control is dependent upon the refinement and strengthening of integration between specialized networks. Our findings support a novel, two-stage model of neural development, in which networks stabilize prior to adolescence and subsequently increase their integration to support the cross-domain incorporation of information processing critical for mature cognitive control

Neonatal exposure to monosodium glutamate results in dysmorphology of orofacial lower motor neurons

Glutamate is the most abundant excitatory neurotransmitter in the central nervous system, and is stored and released by both neurons and astrocytes. Despite the important role of glutamate as a neurotransmitter, high levels of extracellular glutamate can result in excitotoxicity and apoptosis. Monosodium glutamate (MSG) is a naturally occurring sodium salt of glutamic acid that is used as a flavour enhancer in many processed foods. Neonatal exposure to MSG has been shown to result in neurodegeneration in several forebrain regions, characterised by neuronal loss and neuroendocrine abnormalities. However, the brainstem effects of neonatal MSG exposure have not been investigated. It is therefore hypothesized that MSG exposure during the early postnatal period would impact brainstem lower motor neurons involved in feeding behaviour. The effect of neonatal MSG exposure on brainstem lower motor neurons was investigated by exposing rat pups to either 4 mg/g MSG or saline from postnatal day (P) 4 through 10. On P28, brains were preserved by vascular perfusion with fixative, frozen sectioned and stained for Nïssl substance. The number, size and shape of brainstem motor neurons were compared between MSG and saline-exposed animals. MSG exposure had no impact on the total number of neurons in the nuclei examined. However, MSG exposure was associated with a significant increase in the number of round somata in both the trigeminal and facial nuclei. Furthermore, MSG exposure resulted in significantly smaller neurons in all motor nuclei examined. These results suggest that neonatal exposure to MSG impacts the development of brainstem lower motor neurons which may impact feeding and swallowing behaviours in young animals.

Co–Au core-shell nanocrystals formed by sequential ion implantation into SiO₂

Co–Au core-shell nanocrystals (NCs) were formed by sequential ion implantation of Au and Co into thin SiO₂. The NCs were investigated by means of transmission electron microscopy and extended x-ray absorption fine structure spectroscopy. The latter reveals a bond length expansion in the Co core compared to monatomic Co NCs. Concomitantly, a significant contraction of the bond length and a significant reduction of the effective Au–Au coordination number were observed in the Au shells. Increased Debye-Waller factors indicate significant strain in the NCs. These experimental results verify recent theoretical predictions.P.K. and M.C.R. thank the Australian Research Council for support. P.K., B.H., B.J., and M.C.R. were supported by the Australian Synchrotron Research Program, funded by the Commonwealth of Australia via the Major National Research Facilities Program

Development of a novel platform for greater situational awareness in the urban military terrain

The conflicts in Afghanistan and Iraq and the more recent war in the Gaza Strip have emphasized the need for novel platforms which provide for greater situational awareness in the urban terrain. Without intelligent systems, which can accurately provide real-time information, collateral damage to property will result, together with unnecessary civilian deaths. This situation is exacerbated by the fact that within the next decade 75% of the world’s population will be living in urban areas. This paper outlines the current state of unmanned aerial vehicles throughout the world and presents a novel design of a multiple rotary wing platform which has great potential for both military and civilian application areas

A New Look at the Local White Dwarf Population

We have conducted a detailed new survey of the local population of white dwarfs lying within 20 pc of the Sun. A new revised catalog of local white dwarfs containing 122 entries (126 individual degenerate stars) is presented. This list contains 27 white dwarfs not included in a previous list from 2002, as well as new and recently published trigonometric parallaxes. In several cases new members of the local white dwarf population have come to light through accurate photometric distance estimates. In addition, a suspected new double degenerate system (WD 0423+120) has been identified. The 20 pc sample is currently estimated to be 80% complete. Using a variety of recent spectroscopic, photometric, and trigonometric distance determinations, we re-compute a space density of 4.8 ± 0.5 × 10−3 pc−3 corresponding to a mass density of 3.2 ± 0.3 × 10−3 M pc−3 from the complete portion of the sample within 13 pc. We find an overall mean mass for the local white dwarfs of 0.665 M, a value larger than most other non-volume-limited estimates. Although the sample is small, we find no evidence of a correlation between mass and temperature in which white dwarfs below 13,000 K are systematically more massive than those above this temperature. Within 20 pc 25% of the white dwarfs are in binary systems (including double degenerate systems). Approximately 6% are double degenerates and 6.5% are Sirius-like systems. The fraction of magnetic white dwarfs in the local population is found to be 13%

The galactic population of white dwarfs

Original paper can be found at: http://www.iop.org/EJ/conf DOI: 10.1088/1742-6596/172/1/012004 [16th European White Dwarfs Workshop]The contribution of white dwarfs of the different Galactic populations to the stellar content of our Galaxy is only poorly known. Some authors claim a vast population of halo white dwarfs, which would be in accordance with some investigations of the early phases of Galaxy formation claiming a top-heavy initial– mass– function. Here, I present a model of the population of white dwarfs in the Milky Way based on observations of the local white dwarf sample and a standard model of Galactic structure. This model will be used to estimate the space densities of thin disc, thick disc and halo white dwarfs and their contribution to the baryonic mass budget of the Milky Way. One result of this investigation is that white dwarfs of the halo population contribute a large fraction of the Galactic white dwarf number count, but they are not responsible for the lion's share of stellar mass in the Milky Way. Another important result is the substantial contribution of the – often neglected – population of thick disc white dwarfs. Misclassification of thick disc white dwarfs is responsible for overestimates of the halo population in previous investigations.Peer reviewe

The influence of annealing conditions on the growth and structure of embedded Pt nanocrystals

The growth and structure of Pt nanocrystals (NCs) formed by ion implantation in a-SiO₂ has been investigated as a function of the annealing conditions. Transmission electron microscopy and small-angle x-ray scatteringmeasurements demonstrate that the annealing ambient has a significant influence on NC size. Samples annealed in either Ar, O₂, or forming gas (95% N₂: 5% H₂) at temperatures ranging from 500 °C–1300 °C form spherical NCs with mean diameters ranging from 1–14 nm. For a given temperature, annealing in Ar yields the smallest NCs. O₂ and forming gas ambients produce NCs of comparable size though the latter induces H chemisorption at 1100 °C and above, as verified with x-ray absorption spectroscopy. This H intake is accompanied by a bond-length expansion and increased structural disorder in NCs of diameter >3 nm.We thank the Australian Synchrotron Research Program and the Australian Research Council for financial support