20,695 research outputs found

    Calculating partial expected value of perfect information via Monte Carlo sampling algorithms

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    Partial expected value of perfect information (EVPI) calculations can quantify the value of learning about particular subsets of uncertain parameters in decision models. Published case studies have used different computational approaches. This article examines the computation of partial EVPI estimates via Monte Carlo sampling algorithms. The mathematical definition shows 2 nested expectations, which must be evaluated separately because of the need to compute a maximum between them. A generalized Monte Carlo sampling algorithm uses nested simulation with an outer loop to sample parameters of interest and, conditional upon these, an inner loop to sample remaining uncertain parameters. Alternative computation methods and shortcut algorithms are discussed and mathematical conditions for their use considered. Maxima of Monte Carlo estimates of expectations are biased upward, and the authors show that the use of small samples results in biased EVPI estimates. Three case studies illustrate 1) the bias due to maximization and also the inaccuracy of shortcut algorithms 2) when correlated variables are present and 3) when there is nonlinearity in net benefit functions. If relatively small correlation or nonlinearity is present, then the shortcut algorithm can be substantially inaccurate. Empirical investigation of the numbers of Monte Carlo samples suggests that fewer samples on the outer level and more on the inner level could be efficient and that relatively small numbers of samples can sometimes be used. Several remaining areas for methodological development are set out. A wider application of partial EVPI is recommended both for greater understanding of decision uncertainty and for analyzing research priorities

    Practice activity trends among oral and maxillofacial surgeons in Australia

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    © 2004 Brennan et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.BACKGROUND: The aim of this study was to describe practice activity trends among oral and maxillofacial surgeons in Australia over time. METHODS: All registered oral and maxillofacial surgeons in Australia were surveyed in 1990 and 2000 using mailed self-complete questionnaires. RESULTS: Data were available from 79 surgeons from 1990 (response rate = 73.8%) and 116 surgeons from 2000 (response rate = 65.1%). The rate of provision of services per visit changed over time with increased rates observed overall (from 1.43 ± 0.05 services per visit in 1990 to 1.66 ± 0.06 services per visit in 2000), reflecting increases in pathology and reconstructive surgery. No change over time was observed in the provision of services per year (4,521 ± 286 services per year in 1990 and 4,503 ± 367 services per year in 2000). Time devoted to work showed no significant change over time (1,682 ± 75 hours per year in 1990 and 1,681 ± 94 hours per year in 2000), while the number of visits per week declined (70 ± 4 visits per week in 1990 to 58 ± 4 visits per week in 2000). CONCLUSIONS: The apparent stability in the volume of services provided per year reflected a counterbalancing of increased services provided per visit and a decrease in the number of visits supplied.David S Brennan, A John Spencer, Kiran A Singh, Dana N Teusner and Alastair N Gos

    Panoramic Images for Situational Awareness in a 3D Chart-of-the-Future Display

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    Many early charts featured sketches of the coastline, providing a good picture of what the shore looked like from the bridge of a ship. These helped the mariner to distinguish one port from another during an approach and establish their rough position within that approach. More recent experimental 3D chart interfaces have incorporated 3D models of land topography and man-made structures to perform the same function. However, topography is typically captured from the air, by means of stereophotogrammetry or lidar and fails to present a good representation of what is seen from a vessel’s bridge. We have been conducting an investigation of ways to present photographic imagery to the mariner to better capture the utility of the early coastline sketches. Our focus has been on navigation in restricted waters, using the Piscataqua River as a test area. This is part of our “Chart-of-the-Future” project being conducted by The Data Visualization Research Lab at the UNH Center for Coastal and Ocean Mapping. Through our investigation, we have developed a new method for presenting photographic imagery to the mariner, in the form of a series of panoramic images progressing down the channel. The panoramas consist of images stitched almost seamlessly together into circular arcs, whose centers are intended to be close to the position of a vessel’s bridge during transit. When viewed from this center, there is no distortion, and distortion increases to a maximum between two panorama centers. Our preliminary trials suggest that panoramas can provide an excellent supplement to electronic navigation aids by making them visible in the context of what can be seen out the window. We believe panoramas will be especially useful both in familiarizing a mariner with an unfamiliar approach during planning, and in enhancing situational awareness at times of reduced visibility such as in fog, dusk, or nightfall

    The Copyright Tribunal as Exception-maker: Are Both Flexibility and Certainty Achievable?

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    This article proposes an approach to address the current fair use impasse in Australia. This is by the conferral of delegated legislative power upon the Copyright Tribunal of Australia for it to periodically determine new public interest exceptions. The reform would require, for separation of powers reasons, that the Tribunal be reconstituted to perform such a legislative function. The proposal is one that navigates a course between the current law and the open slather adoption of US-style fair use recommended by the Australian Law Reform Commission by creating a public interest rulemaking power within an existing Australian copyright institution. It is also proposed to use as the vehicle for the delegation of power an overhauled s 200AB, so that the three-step test no longer nakedly applies in domestic law, but instead operates as criteria to inform the legislative choices of the Tribunal

    Collide and Conquer: Constraints on Simplified Dark Matter Models using Mono-X Collider Searches

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    The use of simplified models as a tool for interpreting dark matter collider searches has become increasingly prevalent, and while early Run II results are beginning to appear, we look to see what further information can be extracted from the Run I dataset. We consider three `standard' simplified models that couple quarks to fermionic singlet dark matter: an ss-channel vector mediator with vector or axial-vector couplings, and a tt-channel scalar mediator. Upper limits on the couplings are calculated and compared across three alternate channels, namely mono-jet, mono-ZZ (leptonic) and mono-W/ZW/Z (hadronic). The strongest limits are observed in the mono-jet channel, however the computational simplicity and absence of significant tt-channel model width effects in the mono-boson channels make these a straightforward and competitive alternative. We also include a comparison with relic density and direct detection constraints.Comment: 32 pages, 8 figures; v2: minor changes, conclusion unchanged, matches published versio

    An acoustic charge transport imager for high definition television applications

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    In this report we present the progress during the second six month period of the project. This includes both experimental and theoretical work on the acoustic charge transport (ACT) portion of the chip, the theoretical program modelling of both the avalanche photodiode (APD) and the charge transfer and overflow transistor and the materials growth and fabrication part of the program

    An Assessment of the Economic, Environmental and Social Impacts of NSW Agriculture's Wheat Breeding Program

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    The Wagga wheat breeding program has been operating for over 100 years. In that time, it has released a flow of new wheat varieties for wheat growers in south-eastern Australia. Those varieties have led to increases in both yields and grain quality. The average annual rate of yield improvement in NSW has been 3.2% compared to the average for Australia of 2.4% with a significant proportion of these productivity gains arising from new varieties. In this analysis, the investment in that program from 1980 to 2003 has been evaluated. Given the lags inherent in wheat breeding investments, the benefits from those investments are being measured from 1993 to 2020. The broad structure of the program has remained relatively stable for most of the period since 1980. The program consists of 2-3 wheat breeders, one breeder-pathologist, and a cereal chemist, with appropriate technical and field support, totaling approximately 15 full-time equivalents per year. The costs of the program have averaged approximately 1.2millionperyearovertheperiod.InassessingtheWaggawheatbreedingprogramitisimportanttoconsiderhowtheindustrywouldhavedevelopedwithouttheprogram.ThebenefitsoftheprogramweremeasuredasthedifferenceinreturnsfromimprovedwheatvarietiesinNSWoverthatperiodandthereturnsthatwouldhavebeenachievedintheabsenceoftheWaggabreedingprogram.TheassumptionusedtodeterminetheimpactwithouttheWaggaprogramwasthattherateofyieldimprovementinNSWwouldhavebeenthesameasfortherestofAustralia.Forquality,withouttheWaggaprogramtheassumptionwasthatinsouthernNSWtheincreaseinqualitywouldhavebeen201.2 million per year over the period. In assessing the Wagga wheat breeding program it is important to consider how the industry would have developed without the program. The benefits of the program were measured as the difference in returns from improved wheat varieties in NSW over that period and the returns that would have been achieved in the absence of the Wagga breeding program. The assumption used to determine the impact without the Wagga program was that the rate of yield improvement in NSW would have been the same as for the rest of Australia. For quality, without the Wagga program the assumption was that in southern NSW the increase in quality would have been 20% slower, and in the north there would have been no change in the rate of quality improvement. Not all of those gains from new varieties in NSW are attributable to the Wagga wheat breeding program. Over half of all productivity gains are attributable to technologies other than new varieties and other breeding programs have contributed some of new varieties adopted. Wheat breeding within NSW was estimated to have increased the value of wheat per hectare (incorporating both yield and quality) by approximately 0.50% per year in southern NSW, and by approximately 0.15% per year in northern NSW. The share of the area sown to wheat in NSW of Wagga program varieties over the study period averaged around 46% in southern regions and 11% in northern regions. The benefits were projected into the future on the basis that the varieties released before 2003 will have a significant impact on production until 2013, but from then, these benefits will decline to zero by 2020. Based on these assumptions, the benefit-cost ratio found in the analysis was 8.4, with an internal rate of return of 16%. The Net Present Value of the total resources used in the program over the period since 1980 was estimated at 321 million. The economic benefits of the breeding program are shared by producers, processors and consumers in the wheat industry, some of whom live overseas. Because Australia is largely a price taker on world wheat markets and because the wheat processing and distribution sector in Australia is generally considered to be competitive, most of the benefits of the wheat breeding program are likely to remain with producers. However these gains are offset by declines in the world price in response to advancing technology throughout the world. These economic benefits have positive social consequences, largely through their contribution to the incomes of farmers and those who handle and process wheat in regional NSW. Some of these gains are in the form of new marketing and processing industries around the increasingly specialised industry segments resulting directly from the changes that have occurred in wheat varieties. Perhaps these new skills add to the social capital of towns in the wheat belt of NSW. In environmental terms, the wheat breeding program itself is not likely to have major impacts, since the wheat industry would have been very similar whether or not there was a Wagga breeding program. However, to the extent that improved productivity from the Wagga program's varieties has allowed an expansion of the wheat industry, there could be some negative environmental consequences of the breeding program, such as those arising from the clearing of land, increased cultivation and increased use of herbicides. On the other hand, the high levels of disease resistance developed and maintained has meant that wheat production is not associated with large-scale fungicide use, and hence the danger of chemical contamination of the environment is less than it would have been without the resistance developed in this program. Some of these environmental impacts affect the costs and incomes of wheat farmers and hence are reflected in economic benefits and some spill over to the broader community and have not been valued here. It is not clear that these social and environmental impacts would be much different without the Wagga breeding program, except through the extent to which the Wagga program has allowed the wheat industry in NSW to develop more than it otherwise would have. Without the Wagga program the slower gains in yield and quality would also be associated with some social and environmental impacts, and it is the difference that is critical in evaluating the Wagga program. The costs of this program have been met partly by the NSW taxpayers through NSW Agriculture and partly by the grains industry through levies from the Grains Research and Development Corporation (GRDC). The recent introduction of variety royalty payments ("end-point royalties") has not yet led to significant funding, but may be expected to do so in the future. The nature of the outputs of plant breeding programs is that there are large economic benefits that flow directly to producers, processors and consumers in the industry. However the social and environmental impacts on the broader community, while not explicitly valued here, are considered to be small relative to economic benefits and relative to some other programs of NSW Agriculture that have been evaluated. Hence it is appropriate that the industry, though GRDC levies and royalties on production, has increasingly funded the operations of the wheat breeding program. Recent institutional changes for the wheat breeding program have made it even more commercially-based for the future and less reliant on government funding. The new institutional arrangements for wheat breeding programs and the strengthening role of the private sector in supplying varieties traditionally supplied by the public sector mean that the place of public wheat breeding programs is being re-assessed. A key question is whether publicly-operated programs, can offer some additional benefits either to the industry or to the community, which would not result from the complete privatisation of the wheat breeding sector. While those issues have not been addressed directly in this analysis, the results indicate that past investments in public wheat breeding program at Wagga have certainly been a productive use of public funds over the past 20 years or so.Research and Development/Tech Change/Emerging Technologies,

    Trends in Pulse and Oilseed Crops in Winter Cereal Rotations in NSW

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    The key aims in this study are to assess the current level of importance of pulse and oilseed (broadleaf) crops in winter cereal rotations in NSW, and to identify recent trends. The production of broadleaf crops has increased in each region of NSW, but different crops have been favoured. Canola has played a key role in southern regions, and chickpea in the northern regions. In many areas, pulse crops have been grown more because of rotational benefits than their direct gross margins. If recent trends continue, the role of broadleaf crops will increase to 25% of the area sown to field crops in NSW by 2020. However, that will only be achieved with a focussed effort in both research and extension activities.broadleaf crop, oilseed, pulse, production, rotation, NSW, Agribusiness, Crop Production/Industries, Production Economics, Research and Development/Tech Change/Emerging Technologies, Q160,

    A Genome Sequence of Oceanimonas doudoroffii ATCC 27123T

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    Oceanimonas doudoroffii ATCC 27123T is an obligately aerobic Gram-negative rod of the class Gammaproteobacteria. It was first isolated from surface seawater off the coast of Oahu, HI, USA, in 1972. The predicted genome size is 3,832,938 bp (G+C content, 60.03%), which contains 3,524 predicted coding sequences
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