Ultrathin graphitic structures and carbon nanotubes in a purified synthetic graphite

A new class of carbon structure is reported, which consists of microscale graphitic shells bounded by curved and faceted planes containing two to five layers. These structures were originally found in a commercial graphite produced by the Acheson process, followed by a purification treatment. The particles, which could be several hundreds of nanometres in size, were frequently decorated with nanoscale carbon particles, or short nanotubes. In some cases, nanotubes were found to be seamlessly connected to the thin shells, indicating that the formation of the shells and that of the nanotubes are intimately connected. The structures are believed to form during a purification process which involves passing an electric current through the graphite in the presence of a reactive gas. In support of this, it is shown that similar particles can be produced in a standard carbon arc apparatus. With their extremely thin graphene walls and high surface areas, the new structures may have a range of useful properties

Structural transformation of graphite by arc-discharge

The formation of novel structures by the passage of an electric current through graphite is described. These structures apparently consist of hollow three-dimensional graphitic shells bounded by curved and faceted planes, typically made up of two graphene layers. The curved structures were frequently decorated with nano-scale carbon particles, or short nanotubes. In some cases, nanotubes were found to be seamlessly connected to the thin shells, indicating that the formation of the shells and the nanotubes is intimately connected. Small nanotubes or nanoparticles were also sometimes found encapsulated inside the hollow structures, while fullerene-like particles were often seen attached to the outside surfaces. With their high surface areas and structural perfection, the new carbon structures may have applications as anodes of lithium ion batteries or as components of composite materials

An integrated approach for evaluating coastal vulnerability in a changing climate

Coastal hazards such as flooding and erosion threaten many coastal communities and ecosystems. With documented increases in both storm frequency and intensity and projected acceleration of sea level rise, incorporating the impacts of climate change and variability into coastal vulnerability assessments is becoming a necessary, yet challenging task. We are developing an integrated approach to probabilistically incorporate the impacts of climate change into coastal vulnerability assessments via a multi-scale, multi-hazard methodology. By examining the combined hazards of episodic flooding/inundation and storm induced coastal change with chronic trends under a range of future climate change scenarios, a quantitative framework can be established to promote more sciencebased decision making in the coastal zone. Our focus here is on an initial application of our method in southern Oregon, United States. (PDF contains 5 pages

Outside the Wall: Hydrodynamics of Type I Supernovae Interacting with a Partially Swept-Up Circumstellar Medium

Explaining the observed diversity of supernovae (SNe) and the physics of explosion requires knowledge of their progenitor stars, which can be obtained by constraining the circumstellar medium (CSM). Models of the SN ejecta colliding with CSM are necessary to infer the structure of the CSM and tie it back to a progenitor model. Recent SNe I revealed CSM concentrated at a distance $r\sim10^16$ cm, for which models of SN interaction are extremely limited. In this paper, we assume the concentrated region is a "wall" representing swept-up material, and unswept material lies outside the wall. We simulate one-dimensional hydrodynamics of SNe Ia & Ib impacting 300 unique CSM configurations using RT1D, which captures the Rayleigh-Taylor instability. We find that the density ratio between the wall and ejecta -- denoted $A_0$ or "wall height" -- is key, and higher walls deviate more from self-similar evolution. Functional fits accounting for $A_0$ are presented for the forward shock radius evolution. We show that higher walls have more degeneracy between CSM properties in the deceleration parameter, slower shocks, deeper-probing reverse shocks, slower shocked ejecta, less ejecta mass than CSM in the shock, and more mixing of ejecta into the CSM at early times. We analyze observations of SN 2014C (Type Ib) and suggest that it had a moderately high wall ($10 < A_0 < 200$) and wind-like outer CSM. We also postulate an alternate interpretation for the radio data of SN 2014C, that the radio rise occurs in the wind rather than the wall. Finally, we find that hydrodynamic measurements at very late times cannot distinguish the presence of a wall, except perhaps as an anomalously wide shock region.Comment: 17 pages, 13 figures, accepted to Ap

Habermas, Human Agency, and Human Genetic Enhancement: The Grown, the Made, and Responsibility for Actions

Recent developments in genomic science hold out the tantalizing prospect of soon being able to treat and prevent a wide variety of medical conditions through gene therapy. In time, it may be possible to use similar techniques not simply to combat disease but also to enhance, or improve on, normal human functioning

The Dynamic Effects of Skilled Labour Targeting in Immigration Programs

We consider the impact of the recent trend in immigration policies towards selecting migrants on the basis of skills. The analysis uses an inter-temporal general equilibrium model with endogenous skill formation. The model is calibrated to a steady state benchmark that represents Australia in 2000-2001. We then consider the impact of the increase in skilled migrants of approximately 20 thousand per year, which corresponds to the increase in flows of migrant Professionals in Australia since 2000. We find that this generates substantial crowding out of the higher Education sector in Australia. Moreover we show that, when this shock is anticipated as a permanent policy change, there is very little net increase in the stock of skilled labour due to falling student enrollments of 12%. Paradoxically, in this case, the decline in students increases the number of unskilled workers in the economy such that the ratio skilled to unskilled workers in the economy actually falls and the skill premium increases.Immigration; Human Capital; Computable General Equilibrium Models

Dynamic Adjustments to Terms of Trade Shocks: The USA Productivity Boom and Australia

How has the USA’s “new economy” productivity boom affected Australia? We consider this question using a dynamic multi-sector growth model of the Australian and USA economies. We find that productivity growth in the USA durables sector generates small but important gains to Australia. We find that the transmission of growth is generated through increased export demand for Agriculture. Consequently we find that the USA’s productivity growth tends to favour Australia’s traditional export sectors. Likewise it increases the relative demand for less skilled labour in Australia and reduces the demand for skilled labour and higher education.Terms of Trade; Productivity; Economic Growth; Human Capital; Computable General Equilibrium Models

Dynamic Gains and Market Access Insurance: Another look at the AUSFTA

We use a dynamic computable general equilibrium model to revisit the dynamic benefits of the Australia-USA Free Trade Agreement and, in particular, to evaluate the insurance value of this agreement in the face of regional and global trade wars. The insurance benefits are quantified by comparing the status quo against alternative scenarios where some or all regions raise tariffs by 10 percent, both permanently and temporarily. These insurance gains are found to be as much as four times larger than the traditional status quo efficiency gains.Trade policy; Computable General Equilibrium; Human Capital; Dynamics

Imaging the atomic structure of activated carbon

The precise atomic structure of activated carbon is unknown, despite its huge commercial importance in the purification of air and water. Diffraction methods have been extensively applied to the study of microporous carbons, but cannot provide an unequivocal identification of their structure. Here we show that the structure of a commercial activated carbon can be imaged directly using aberration-corrected transmission electron microscopy. Images are presented both of the as-produced carbon and of the carbon following heat treatment at 2000 degrees C. In the 2000 degrees C carbon clear evidence is found for the presence of pentagonal rings, suggesting that the carbons have a fullerene-related structure. Such a structure would help to explain the properties of activated carbon, and would also have important implications for the modelling of adsorption on microporous carbons

Material and Structural Aspects of Bone in Osteogenesis Imperfecta

Bone fragility is a fundamental problem in individuals with osteogenesis imperfecta (OI). The mechanisms behind this fragility, however, are not yet well understood. Multiple factors appear to contribute to the increased fracture risk in OI. At the structural level, bone mass deficiency can result in increased stress levels within bones. The underlying mineral and collagen abnormalities that define OI are also believed to result in compromised material-level properties. The variability of collagen biochemical irregularities causing OI and the corresponding heterogeneity of disease severity result in abnormalities that are not easily generalized within the OI population. The aims of this chapter are to introduce basic mechanical notions pertaining to the strength of structures and materials, and to present a synthesis of existing literature regarding the mechanical properties of bones in OI