Constraints on porosity and mass loss in O-star winds from modeling of X-ray emission line profile shapes

We fit X-ray emission line profiles in high resolution XMM-Newton and Chandra grating spectra of the early O supergiant Zeta Pup with models that include the effects of porosity in the stellar wind. We explore the effects of porosity due to both spherical and flattened clumps. We find that porosity models with flattened clumps oriented parallel to the photosphere provide poor fits to observed line shapes. However, porosity models with isotropic clumps can provide acceptable fits to observed line shapes, but only if the porosity effect is moderate. We quantify the degeneracy between porosity effects from isotropic clumps and the mass-loss rate inferred from the X-ray line shapes, and we show that only modest increases in the mass-loss rate (<~ 40%) are allowed if moderate porosity effects (h_infinity <~ R_*) are assumed to be important. Large porosity lengths, and thus strong porosity effects, are ruled out regardless of assumptions about clump shape. Thus, X-ray mass-loss rate estimates are relatively insensitive to both optically thin and optically thick clumping. This supports the use of X-ray spectroscopy as a mass-loss rate calibration for bright, nearby O stars.Comment: 20 pages, 20 figures. Accepted by Ap

Lessons from the unusual impacts of an abnormal winter in the USA

Economic impacts from the near record warm and snow-free winter of 2001–2 in the United States were assessed to ascertain their dimensions and relevance to issues like climate prediction and climate change. Unusual impacts resulted and embraced numerous sectors (heating/energy use, construction, tourism, insurance, government, and retail sales). Many outcomes were gains/benefits totalling $19.6 billion, with losses of$8.2 billion. Some economists identified the sizable positive impacts as a factor in the nation’s recovery from an on-going recession stemming from the terrorist attacks on 11 September 2001. Understanding the impacts of such a winter reveals how climate predictions of such conditions could have great utility in minimising the losses and maximising the gains. The results also have relevance to the global warming issue since most climate models project future average winter temperature and snowfall conditions in the United States to be similar to those experienced in 2001–2

Metropolitan bus service contracts (MBSC): Thoughts on the next round

This paper revisits a number of themes that have played a crucial role in the debate on alternative contracting regimes for the provision and bus and coach services. We have selected seven crucial issues to reflect on: (i) contractual regimes (in particular negotiated performance based contracts linked to benchmarking and competitive tendering); (ii) contract completeness (focussing on ex ante and ex post elements and what can be improved within the context of current contracts); (iii) building trust through partnership; (iv) number of contract areas (emphasising the crucial demand-side objective); (v) tactical or system level planning for bus services; (vi) asset ownership; and (vii) margins

Toric complete intersections and weighted projective space

It has been shown by Batyrev and Borisov that nef partitions of reflexive polyhedra can be used to construct mirror pairs of complete intersection Calabi--Yau manifolds in toric ambient spaces. We construct a number of such spaces and compute their cohomological data. We also discuss the relation of our results to complete intersections in weighted projective spaces and try to recover them as special cases of the toric construction. As compared to hypersurfaces, codimension two more than doubles the number of spectra with $h^{11}=1$. Alltogether we find 87 new (mirror pairs of) Hodge data, mainly with $h^{11}\le4$.Comment: 16 pages, LaTeX2e, error in Hodge data correcte

Environmental and social taxes: reforming road pricing in Australia

Pricing of road use, both in Australia and elsewhere, has long been recognised as an area where current arrangements are economically inefficient but also politically very difficult to change. The 2011 Australian Tax Forum provides an opportunity to revisit this question and lay out a pathway for change. This paper summarises some past analyses of the costs of road use in Australia, to demonstrate the broad extent of under-recovery of costs. The external costs, such as congestion, accidents and greenhouse gas emissions, which are the reason for the cost recovery gap are outlined. International experience with congestion charging, a key component (but not the whole) of road pricing reform is summarised, showing how sustained reductions in congestion levels and associated costs are achievable. That experience also shows the importance of political leadership to achieve implementation, often in the face of minority support pre-implementation. Some illustrative calculations of how Australian road use charges may need to increase, on average, under a reformed road pricing regime are presented. The paper concludes by arguing that an independently run two year community conversation around reforming road pricing, reporting to COAG, is the critical starting point if there is to be a successful implementation program.Australian Research Council Discovery Program Gran

Melbourne’s Public Transport Franchising: Lessons for PPPs

The paper reviews the recent franchising of public transport services in Melbourne, Australia, to assess the extent to which the objectives of the franchising were achieved. The major franchisee has failed only a short time into the franchise period. Some financial benefits from franchising have been realised, largely at the expense of franchisee shareholders. These savings are not sustainable. Some aspects of service delivery have improved. Overall, however, franchising has fallen well short of government expectations. The paper asks what can be learnt from this experience to improve future public/private partnerships in public transport. It is critical of the franchising process, in terms of unrealistic expectations and an insufficiently critical acceptance of competitive tendering to deliver outcomes. Changes in the nature of the relationship between the regulator and service provider are proposed, to incorporate a stronger planning focus, closer partnership basis and a greater reliance on negotiated contracts, along lines used in some infrastructure PPPs

Distribution and Habitat of Utilization of the Four-toed Salamander, Hemidactylium scutatum, in the Ouachita Mountains of Arkansas

Four-toed salamanders in Arkansas represent a disjunct population separated from their main range in the eastern United States and Canada. Until recently, the distribution of this species was documented by a few individual specimens collected or observed from widely spaced localities which has resulted in its being considered rare and vulnerable. Recent investigations of distribution and habitat utilization indicate this species may be more common than previously believed, but also reaffirms the need to protect riparian habitat, springs, ponds, woodland seeps and other preferred, moist habitats containing mossy areas used as primary egg deposition sites

High-order ENO schemes applied to two- and three-dimensional compressible flow

High order essentially non-oscillatory (ENO) finite difference schemes are applied to the 2-D and 3-D compressible Euler and Navier-Stokes equations. Practical issues, such as vectorization, efficiency of coding, cost comparison with other numerical methods, and accuracy degeneracy effects, are discussed. Numerical examples are provided which are representative of computational problems of current interest in transition and turbulence physics. These require both nonoscillatory shock capturing and high resolution for detailed structures in the smooth regions and demonstrate the advantage of ENO schemes

Advanced nickel-cadmium batteries for geosynchronous spacecraft

A nickel cadmium battery was developed that can be operated at 80 percent depth of discharge in excess of 10 years in a geosynchronous orbit application, and has about a 30 percent weight savings per spacecraft over present nickel cadmium batteries when used with a 1000 watts eclipse load. The approach used in the development was to replace nylon separators with inert polymer impregnated zirconia, use electrochemically deposited plates in place of conventional chemically precipitated ones, and use an additive to extend negative plate lifetime. The design has undergone extensive testing using both engineering and protoflight cell configurations