489 resultados para Intractable Likelihood
Error, Bias, and Long-Branch Attraction in Data for Two Chloroplast Photosystem Genes in Seed Plants
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Sequences of two chloroplast photosystem genes, psaA and psbB, together comprising about 3,500 bp, were obtained for all five major groups of extant seed plants and several outgroups among other vascular plants. Strongly supported, but significantly conflicting, phylogenetic signals were obtained in parsimony analyses from partitions of the data into first and second codon positions versus third positions. In the former, both genes agreed on a monophyletic gymnosperms, with Gnetales closely related to certain conifers. In the latter, Gnetales are inferred to be the sister group of all other seed plants, with gymnosperms paraphyletic. None of the data supported the modern ‘‘anthophyte hypothesis,’’ which places Gnetales as the sister group of flowering plants. A series of simulation studies were undertaken to examine the error rate for parsimony inference. Three kinds of errors were examined: random error, systematic bias (both properties of finite data sets), and statistical inconsistency owing to long-branch attraction (an asymptotic property). Parsimony reconstructions were extremely biased for third-position data for psbB. Regardless of the true underlying tree, a tree in which Gnetales are sister to all other seed plants was likely to be reconstructed for these data. None of the combinations of genes or partitions permits the anthophyte tree to be reconstructed with high probability. Simulations of progressively larger data sets indicate the existence of long-branch attraction (statistical inconsistency) for third-position psbB data if either the anthophyte tree or the gymnosperm tree is correct. This is also true for the anthophyte tree using either psaA third positions or psbB first and second positions. A factor contributing to bias and inconsistency is extremely short branches at the base of the seed plant radiation, coupled with extremely high rates in Gnetales and nonseed plant outgroups. M. J. Sanderson,* M. F. Wojciechowski,*† J.-M. Hu,* T. Sher Khan,* and S. G. Brady
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A plethora of methods for procuring building projects are available to meet the needs of clients. Deciding what method to use for a given project is a difficult and challenging task as a client’s objectives and priorities need to marry with the selected method so as to improve the likelihood of the project being procured successfully. The decision as to what procurement system to use should be made as early as possible and underpinned by the client’s business case for the project. The risks and how they can potentially affect the client’s business should also be considered. In this report, the need for client’s to develop a procurement strategy, which outlines the key means by which the objectives of the project are to be achieved is emphasised. Once a client has established a business case for a project, appointed a principal advisor, determined their requirements and brief, then consideration as to which procurement method to be adopted should be made. An understanding of the characteristics of various procurement options is required before a recommendation can be made to a client. Procurement systems can be categorised as traditional, design and construct, management and collaborative. The characteristics of these systems along with the procurement methods commonly used are described. The main advantages and disadvantages, and circumstances under which a system could be considered applicable for a given project are also identified.
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Risks and uncertainties are inevitable in engineering projects and infrastructure investments. Decisions about investment in infrastructure such as for maintenance, rehabilitation and construction works can pose risks, and may generate significant impacts on social, cultural, environmental and other related issues. This report presents the results of a literature review of current practice in identifying, quantifying and managing risks and predicting impacts as part of the planning and assessment process for infrastructure investment proposals. In assessing proposals for investment in infrastructure, it is necessary to consider social, cultural and environmental risks and impacts to the overall community, as well as financial risks to the investor. The report defines and explains the concept of risk and uncertainty, and describes the three main methodology approaches to the analysis of risk and uncertainty in investment planning for infrastructure, viz examining a range of scenarios or options, sensitivity analysis, and a statistical probability approach, listed here in order of increasing merit and complexity. Forecasts of costs, benefits and community impacts of infrastructure are recognised as central aspects of developing and assessing investment proposals. Increasingly complex modelling techniques are being used for investment evaluation. The literature review identified forecasting errors as the major cause of risk. The report contains a summary of the broad nature of decision-making tools used by governments and other organisations in Australia, New Zealand, Europe and North America, and shows their overall approach to risk assessment in assessing public infrastructure proposals. While there are established techniques to quantify financial and economic risks, quantification is far less developed for political, social and environmental risks and impacts. The report contains a summary of the broad nature of decision-making tools used by governments and other organisations in Australia, New Zealand, Europe and North America, and shows their overall approach to risk assessment in assessing public infrastructure proposals. While there are established techniques to quantify financial and economic risks, quantification is far less developed for political, social and environmental risks and impacts. For risks that cannot be readily quantified, assessment techniques commonly include classification or rating systems for likelihood and consequence. The report outlines the system used by the Australian Defence Organisation and in the Australian Standard on risk management. After each risk is identified and quantified or rated, consideration can be given to reducing the risk, and managing any remaining risk as part of the scope of the project. The literature review identified use of risk mapping techniques by a North American chemical company and by the Australian Defence Organisation. This literature review has enabled a risk assessment strategy to be developed, and will underpin an examination of the feasibility of developing a risk assessment capability using a probability approach.
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For the last two decades heart disease has been the highest single cause of death for the human population. With an alarming number of patients requiring heart transplant, and donations not able to satisfy the demand, treatment looks to mechanical alternatives. Rotary Ventricular Assist Devices, VADs, are miniature pumps which can be implanted alongside the heart to assist its pumping function. These constant flow devices are smaller, more efficient and promise a longer operational life than more traditional pulsatile VADs. The development of rotary VADs has focused on single pumps assisting the left ventricle only to supply blood for the body. In many patients however, failure of both ventricles demands that an additional pulsatile device be used to support the failing right ventricle. This condition renders them hospital bound while they wait for an unlikely heart donation. Reported attempts to use two rotary pumps to support both ventricles concurrently have warned of inherent haemodynamic instability. Poor balancing of the pumps’ flow rates quickly leads to vascular congestion increasing the risk of oedema and ventricular ‘suckdown’ occluding the inlet to the pump. This thesis introduces a novel Bi-Ventricular Assist Device (BiVAD) configuration where the pump outputs are passively balanced by vascular pressure. The BiVAD consists of two rotary pumps straddling the mechanical passive controller. Fluctuations in vascular pressure induce small deflections within both pumps adjusting their outputs allowing them to maintain arterial pressure. To optimise the passive controller’s interaction with the circulation, the controller’s dynamic response is optimised with a spring, mass, damper arrangement. This two part study presents a comprehensive assessment of the prototype’s ‘viability’ as a support device. Its ‘viability’ was considered based on its sensitivity to pathogenic haemodynamics and the ability of the passive response to maintain healthy circulation. The first part of the study is an experimental investigation where a prototype device was designed and built, and then tested in a pulsatile mock circulation loop. The BiVAD was subjected to a range of haemodynamic imbalances as well as a dynamic analysis to assess the functionality of the mechanical damper. The second part introduces the development of a numerical program to simulate human circulation supported by the passively controlled BiVAD. Both investigations showed that the prototype was able to mimic the native baroreceptor response. Simulating hypertension, poor flow balancing and subsequent ventricular failure during BiVAD support allowed the passive controller’s response to be assessed. Triggered by the resulting pressure imbalance, the controller responded by passively adjusting the VAD outputs in order to maintain healthy arterial pressures. This baroreceptor-like response demonstrated the inherent stability of the auto regulating BiVAD prototype. Simulating pulmonary hypertension in the more observable numerical model, however, revealed a serious issue with the passive response. The subsequent decrease in venous return into the left heart went unnoticed by the passive controller. Meanwhile the coupled nature of the passive response not only decreased RVAD output to reduce pulmonary arterial pressure, but it also increased LVAD output. Consequently, the LVAD increased fluid evacuation from the left ventricle, LV, and so actually accelerated the onset of LV collapse. It was concluded that despite the inherently stable baroreceptor-like response of the passive controller, its lack of sensitivity to venous return made it unviable in its present configuration. The study revealed a number of other important findings. Perhaps the most significant was that the reduced pulse experienced during constant flow support unbalanced the ratio of effective resistances of both vascular circuits. Even during steady rotary support therefore, the resulting ventricle volume imbalance increased the likelihood of suckdown. Additionally, mechanical damping of the passive controller’s response successfully filtered out pressure fluctuations from residual ventricular function. Finally, the importance of recognising inertial contributions to blood flow in the atria and ventricles in a numerical simulation were highlighted. This thesis documents the first attempt to create a fully auto regulated rotary cardiac assist device. Initial results encourage development of an inlet configuration sensitive to low flow such as collapsible inlet cannulae. Combining this with the existing baroreceptor-like response of the passive controller will render a highly stable passively controlled BiVAD configuration. The prototype controller’s passive interaction with the vasculature is a significant step towards a highly stable new generation of artificial heart.
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Work environments have previously been studied to identify the strategies, structures and processes which increase the likelihood of creativity, innovation and collaboration for productive workplaces. A number of perspectives have emerged which identify social and cognitive factors known to contribute to or to restrict innovation and collaboration. Recently more attention has been given to designing physical environments to encourage processes relevant to innovation such as creativity (McCoy & Evans, 2002) knowledge sharing (Hemlin, Allwood & Martin, 2008) and collaboration (Bozeman & Corley, 2004). Some attention has been given specifically to research and development environments (Boutellier et al, 2008) but little integration of this research has occurred. In the context of the construction of new purpose-built premises which will bring together under one roof separate public sector agencies engaged in research and development in agriculture, natural resource systems and the environment, this paper examines the extant literature and develops initial propositions for research relevant to the transition, collaboration and performance of research and development in new organizational environments where traditional boundaries have been redrawn.
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What an organisation does versus what it out-sources to the market is a classic boundaries of the firm question that has previously been dominated by efficiency arguments. However, a knowledge-based view suggests these boundaries are integral to the ability of a firm to deploy existing knowledge stocks efficiently, as well as develop new knowledge through learning that will drive future competitiveness. Furthermore, the nature of these boundaries, in respect of their permeability is critical in understanding the likelihood of knowledge flowing into and out of the organisation. Using these concepts, we present a case study of Main Roads Western Australia to illustrate how these principles have allowed it to start rebuilding its internal capabilities through repositioning its operational boundaries and via ensuring their boundaries are highly porous as they move more major projects into alliance contracts.
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This paper will summarise the findings from a study that explored the link between dwelling design, or type, and energy efficiencies in sub-tropical climates. An increasing number of government and private sector development companies are initiating projects that aim to deliver enhanced environmental outcomes at both sub-divisional and dwelling levels. The study used AccuRate, a new thermal modelling tool developed by CSIRO that responds to the need to improve ventilation modelling. The study found that dwellings developed in conjunction with the Departments of Housing and Public Works have set the benchmark. It provides a snapshot of the energy efficiency of a range of dwelling types found in recent subdivisions. However, the trend toward increasing urban densities may reduce the likelihood that cooling breezes will be available to cool dwellings. The findings are relevant to regulators, designers and industry in all states interested in reducing the energy used to cool dwellings in summer.
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The Guide contains the distilled findings from a major, two-year research project to explore those factors considered by industry practitioners to be critical to the successful adoption of ICT, both within their firms and between their firms and their trading partners. In the context of this project Critical Success Factors (CSFs) have been defined as, “Those things that absolutely, positively must be attended to in order to maximise the likelihood of a successful outcome for the stakeholder, defined in the stakeholder’s terms.” The guide includes: o Perceived benefits of ICT use across the head contractors’ sector o Types and levels of ICT used across the sector o Self-assessment tool o CSFs for high-level ICT users, including o Best Practice Profiles o Action Statements The material contained in this Guide has been generated following a number of principles: o For a given situation there is not a single ‘right answer’, but a number of solutions that have to be evaluated using a range of relevant factors. o Since there are as many solutions as there are ‘solvers’, factors for evaluation will ‘emerge’ from collective wisdom.
Resumo:
The Guide contains the distilled findings from a major, two-year research project to explore those factors considered by industry practitioners to be critical to the successful adoption of ICT, both within their firms and between their firms and their trading partners. In the context of this project Critical Success Factors (CSFs) have been defined as, “Those things that absolutely, positively must be attended to in order to maximise the likelihood of a successful outcome for the stakeholder, defined in the stakeholder’s terms.” The guide includes: o Perceived benefits of ICT use across the consultants’ sector o Types and levels of ICT used across the sector o Self-assessment tool o CSFs for medium- and high-level ICT users, including o Best Practice Profiles o Action Statements o Barriers to ICT use for low-level users o Action Statements The material contained in this Guide has been generated following a number of principles: o For a given situation there is not a single ‘right answer’, but a number of solutions that have to be evaluated using a range of relevant factors. o As there are as many solutions as there are ‘solvers’, factors for evaluation will ‘emerge’ from collective wisdom.
Resumo:
The Guide contains the distilled findings from a major, two-year research project to explore those factors considered by industry practitioners to be critical to the successful adoption of ICT, both within their firms and between their firms and their trading partners. In the context of this project Critical Success Factors (CSFs) have been defined as, “Those things that absolutely, positively must be attended to in order to maximise the likelihood of a successful outcome for the stakeholder, defined in the stakeholder’s terms.” The guide includes: o Perceived benefits of ICT use across the head contractors’ sector o Types and levels of ICT used across the sector o Self-assessment tool o CSFs for medium- and high-level ICT users, including o Best Practice Profiles o Action Statements The material contained in this Guide has been generated following a number of principles: o For a given situation there is not a single ‘right answer’, but a number of solutions that have to be evaluated using a range of relevant factors. o Since there are as many solutions as there are ‘solvers’, factors for evaluation will ‘emerge’ from collective wisdom.
Resumo:
The Guide contains the distilled findings from a major, two-year research project to explore those factors considered by industry practitioners to be critical to the successful adoption of ICT, both within their firms and between their firms and their trading partners. In the context of this project Critical Success Factors (CSFs) have been defined as, “Those things that absolutely, positively must be attended to in order to maximise the likelihood of a successful outcome for the stakeholder, defined in the stakeholder’s terms.” The guide includes: o Perceived benefits of ICT use across the subcontractors’ sector o Types and levels of ICT used across the sector o Self-assessment tool o CSFs for medium- and high-level ICT users, including o Best Practice Profiles o Action Statements o Barriers to ICT use for low-level users o Action Statements The material contained in this Guide has been generated following a number of principles: o For a given situation there is not a single ‘right answer’, but a number of solutions that have to be evaluated using a range of relevant factors. o As there are as many solutions as there are ‘solvers’, factors for evaluation will ‘emerge’ from collective wisdom.
Resumo:
Collaborative networks have come to form a large part of the public sector’s strategy to address ongoing and often complex social problems. The relational power of networks, with its emphasis on trust, reciprocity and mutuality provides the mechanism to integrate previously dispersed and even competitive entities into a collective venture(Agranoff 2003; Agranoff and McGuire 2003; Mandell 1994; Mandell and Harrington 1999). It is argued that the refocusing of a single body of effort to a collective contributes to reducing duplication and overlap of services, maximizes increasingly scarce resources and contributes to solving intractable or 'wicked’problems (Clarke and Stewart 1997). Given the current proliferation of collaborative networks and the fact that they are likely to continue for some time, concerns with the management and leadership of such arrangements for optimal outcomes are increasingly relevant. This is especially important for public sector managers who are used to working in a top-down, hierarchical manner. While the management of networks (Agranoff and McGuire 2001, 2003), including collaborative or complex networks (Kickert et al. 1997; Koppenjan and Klijn 2004), has been the subject of considerable attention, there has been much less explicit discussion on leadership approaches in this context. It is argued in this chapter that the traditional use of the terms ‘leader’ or ‘leadership’ does not apply to collaborative networks. There are no ‘followers’ in collaborative networks or supervisor-subordinate relations. Instead there are equal, horizontal relationships that are focused on delivering systems change. In this way the emergent organizational forms such as collaborative networks challenge older models of leadership. However despite the questionable relevance of old leadership styles to the contemporary work environment, no clear alternative has come along to take its place.
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Background - This study examined demographic profile, continuation rates and reasons for removal among Implanon® users accessing two family planning clinics in Queensland, Australia. Study Design - A retrospective chart audit of 976 women who attended for implant insertion over a 3-year period between May 2001 and May 2004. Results - Continuation rates showed that at 6 months after insertion, 94% of women continued, 74% continued at 1 year and 50% continued at 2 years. Metropolitan women were more likely than rural women to discontinue use because of dissatisfaction with bleeding patterns. Cox regression analysis showed that those attending the regional clinic experienced significantly shorter time to removal. Conclusions - Implanon® continuation rates and reasons for removal differ between clinics in metropolitan and rural locations. A cooling-off period did not affect the likelihood of continuation with Implanon®. Preinsertion counselling should emphasize potential changes in bleeding patterns.
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This paper explores the intentions and willingness of a sample of Australian consumers (N = 356) to use Complementary and Alternative Medicine (CAM). Participants considered using CAMs at least once in the next two months and rated the likelihood of certain consequences of CAM use, whether important others would approve, and if barriers would prevent them from using CAMs. People intending to use CAMs (high intenders) were more likely than those low on intention (low intenders) to endorse positive outcomes of CAM use and believe that important others would support their CAM use. High intenders were less likely than low intenders to believe that barriers would prevent use. Low intenders (n = 200) were also asked to consider their response to a free CAM trial. Those willing to accept a trial were more likely than those unwilling to believe that CAMs could improve health and less likely to believe that laziness would prevent use. These results identify important beliefs which may influence people’s decisions to use CAMs.
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Extended spectrum β-lactamases or ESBLs, which are derived from non-ESBL precursors by point mutation of β-lactamase genes (bla), are spreading rapidly all over the world and have caused considerable problems in the treatment of infections caused by bacteria which harbour them. The mechanism of this resistance is not fully understood and a better understanding of these mechanisms might significantly impact on choosing proper diagnostic and treatment strategies. Previous work on SHV β-lactamase gene, blaSHV, has shown that only Klebsiella pneumoniae strains which contain plasmid-borne blaSHV are able to mutate to phenotypically ESBL-positive strains and there was also evidence of an increase in blaSHV copy number. Therefore, it was hypothesised that although specific point mutation is essential for acquisition of ESBL activity, it is not yet enough, and blaSHV copy number amplification is also essential for an ESBL-positive phenotype, with homologous recombination being the likely mechanism of blaSHV copy number expansion. In this study, we investigated the mutation rate of non-ESBL expressing K. pneumoniae isolates to an ESBL-positive status by using the MSS-maximum likelihood method. Our data showed that blaSHV mutation rate of a non-ESBL expressing isolate is lower than the mutation rate of the other single base changes on the chromosome, even with a plasmid-borne blaSHV gene. On the other hand, mutation rate from a low MIC ESBL-positive (≤ 8 µg/mL for cefotaxime) to high MIC ESBL-positive (≥16 µg/mL for cefotaxime) is very high. This is because only gene copy number increase is needed which is probably mediated by homologous recombination that typically takes place at a much higher frequencies than point mutations. Using a subinhibitory concentration of novobiocin, as a homologous recombination inhibitor, revealed that this is the case.