Maximum Angular Separation Epochs for Exoplanet Imaging Observations

Direct imaging of exoplanets presents both significant challenges and significant gains. The advantages primarily lie in receiving emitted and, with future instruments, reflected photons at phase angles not accessible by other techniques, enabling the potential for atmospheric studies and the detection of rotation and surface features. The challenges are numerous and include coronagraph development and achieving the necessary contrast ratio. Here, we address the specific challenge of determining epochs of maximum angular separation for the star and planet. We compute orbital ephemerides for known transiting and radial velocity planets, taking Keplerian orbital elements into account. We provide analytical expressions for angular star--planet separation as a function of the true anomaly, including the locations of minimum and maximum. These expressions are used to calculate uncertainties for maximum angular separation as a function of time for the known exoplanets, and we provide strategies for improving ephemerides with application to proposed and planned imaging missions.Comment: 7 pages, 3 figures, 1 table, accepted for publication in the Astronomical Journa

Price Formation under Small Numbers Competition: Evidence from Land Auctions in Singapore

This paper examines the price formation process under small numbers competition using data from Singapore land auctions. The theory predicts that bid prices are less than the zero-profit asset value in these first-price sealed-bid auctions. The model also shows that expected sales price increases with the number of bidders both because each bidder has an incentive to offer a higher price and because of a greater likelihood that a high-value bidder is present. The empirical estimates are consistent with auction theory and show that the standard land attributes are reflected in auction prices as expected. Working Paper No. 04-0

Effect of organic, low-input and conventional production systems on yield and diseases in winter barley

The effect of organic, low-input and conventional management practices on barley yield and disease incidence was assessed in field trials over two years. Conventional fertility management (based on mineral fertiliser applications) and conventional crop protection (based on chemosynthetic pesticides) significantly increased the yield of winter barley as compared to organic fertility and crop protection regimes. Severity of leaf blotch (Rhynchosporium secalis) was highest under organic fertility and crop protection management and was correlated inversely with yield. For mildew (Erysiphe graminis), an interaction between fertility management and crop protection was detected. Conventional crop protection reduced severity of the disease, only under conventional fertility management. Under organic fertility management, incidence of mildew was low and application of synthetic pesticides in “low input” production systems had no significant effect on disease severity

List Price Information in Residential Appraisal and Underwriting

This article examines the usefulness of listing prices as leading indicators of house values and as predictors of the direction of housing markets. With Multiple Listing Service data from a large metropolitan area, we create two price indexes, using first listing price and then selling price as the dependent variable in the hedonic regressions. The market is then geographically and categorically segmented, and Granger causality tests are performed to analyze the leading aspect of list prices in the list price-sales price relationship. We find that different segments of the market perform quite differently over the time period of our study, suggesting that for data-based appraisal purposes care is needed in determining the manner and level of aggregation. We also find, however, that market list prices continue to convey important information about subsequent selling prices in most market segments.

N released from organic amendments is affected by soil management history

A ryegrass bioassay was conducted to investigate the effect of soil management history on nitrogen mineralisation from composted manure and pelleted poultry manure. Soils were used from 2 field experiments comparing conventional and organic/low input management systems. When composted manure was added, soils which had received high rates of composted FYM under biodynamic management released a greater amount of nitrogen for plant uptake than those with a history of mineral or fresh manure fertilisation, suggesting that biological preconditioning may result in greater efficiency of composted FYM as a nitrogen source for plants. “Native” N mineralisation was found to be related to total soil N content

Emergency and on-demand health care: modelling a large complex system

This paper describes how system dynamics was used as a central part of a whole-system review of emergency and on-demand health care in Nottingham, England. Based on interviews with 30 key individuals across health and social care, a 'conceptual map' of the system was developed, showing potential patient pathways through the system. This was used to construct a stock-flow model, populated with current activity data, in order to simulate patient flows and to identify system bottle-necks. Without intervention, assuming current trends continue, Nottingham hospitals are unlikely to reach elective admission targets or achieve the government target of 82% bed occupancy. Admissions from general practice had the greatest influence on occupancy rates. Preventing a small number of emergency admissions in elderly patients showed a substantial effect, reducing bed occupancy by 1% per annum over 5 years. Modelling indicated a range of undesirable outcomes associated with continued growth in demand for emergency care, but also considerable potential to intervene to alleviate these problems, in particular by increasing the care options available in the community

The devil in the deep: Expanding the known habitat of a rare and protected fish

The accepted geographic range of a species is related to both opportunity and effort in sampling that range. In deepwater ecosystems where human access is limited, the geographic ranges of many marine species are likely to be underestimated. A chance recording from baited cameras deployed on deep uncharted reef revealed an eastern blue devil fish (Paraplesiops bleekeri) at a depth of 51 m and more than 2 km further down the continental shelf slope than previously observed. This is the first verifiable observation of eastern blue devil fish, a protected and endemic southeastern Australian temperate reef species, at depths greater than the typically accepted depth range of 30 m. Knowledge on the ecology of this and many other reef species is indeed often limited to shallow coastal reefs, which are easily accessible by divers and researchers. Suitable habitat for many reef species appears to exist on deeper offshore reefs but is likely being overlooked due to the logistics of conducting research on these often uncharted habitats. On the basis of our observation at a depth of 51 m and observations by recreational fishers catching eastern blue devil fishes on deep offshore reefs, we suggest that the current depth range of eastern blue devil fish is being underestimated at 30 m. We also observed several common reef species well outside of their accepted depth range. Notably, immaculate damsel (Mecaenichthys immaculatus), red morwong (Cheilodactylus fuscus), mado (Atypichthys strigatus), white-ear (Parma microlepis) and silver sweep (Scorpis lineolata) were abundant and recorded in a number of locations at up to a depth of at least 55 m. This underestimation of depth potentially represents a large area of deep offshore reefs and micro habitats out on the continental shelf that could contribute to the resilience of eastern blue devil fish to extinction risk and contribute to the resilience of many reef species to climate change