Setting hospital infection control policy : a decision-making framework incorporating health economics and healthcare epidemiology

Background: Reducing rates of healthcare acquired infection has been identified by the Australian Commission on Safety and Quality in Health Care as a national priority. One of the goals is the prevention of central venous catheter-related bloodstream infection (CR-BSI). At least 3,500 cases of CR-BSI occur annually in Australian hospitals, resulting in unnecessary deaths and costs to the healthcare system between $25.7 and $95.3 million. Two approaches to preventing these infections have been proposed: use of antimicrobial catheters (A-CVCs); or a catheter care and management ‘bundle’. Given finite healthcare budgets, decisions about the optimal infection control policy require consideration of the effectiveness and value for money of each approach. Objectives: The aim of this research is to use a rational economic framework to inform efficient infection control policy relating to the prevention of CR-BSI in the intensive care unit. It addresses three questions relating to decision-making in this area: 1. Is additional investment in activities aimed at preventing CR-BSI an efficient use of healthcare resources? 2. What is the optimal infection control strategy from amongst the two major approaches that have been proposed to prevent CR-BSI? 3. What uncertainty is there in this decision and can a research agenda to improve decision-making in this area be identified? Methods: A decision analytic model-based economic evaluation was undertaken to identify an efficient approach to preventing CR-BSI in Queensland Health intensive care units. A Markov model was developed in conjunction with a panel of clinical experts which described the epidemiology and prognosis of CR-BSI. The model was parameterised using data systematically identified from the published literature and extracted from routine databases. The quality of data used in the model and its validity to clinical experts and sensitivity to modelling assumptions was assessed. Two separate economic evaluations were conducted. The first evaluation compared all commercially available A-CVCs alongside uncoated catheters to identify which was cost-effective for routine use. The uncertainty in this decision was estimated along with the value of collecting further information to inform the decision. The second evaluation compared the use of A-CVCs to a catheter care bundle. We were unable to estimate the cost of the bundle because it is unclear what the full resource requirements are for its implementation, and what the value of these would be in an Australian context. As such we undertook a threshold analysis to identify the cost and effectiveness thresholds at which a hypothetical bundle would dominate the use of A-CVCs under various clinical scenarios. Results: In the first evaluation of A-CVCs, the findings from the baseline analysis, in which uncertainty is not considered, show that the use of any of the four A-CVCs will result in health gains accompanied by cost-savings. The MR catheters dominate the baseline analysis generating 1.64 QALYs and cost-savings of $130,289 per 1.000 catheters. With uncertainty, and based on current information, the MR catheters remain the optimal decision and return the highest average net monetary benefits ($948 per catheter) relative to all other catheter types. This conclusion was robust to all scenarios tested, however, the probability of error in this conclusion is high, 62% in the baseline scenario. Using a value of $40,000 per QALY, the expected value of perfect information associated with this decision is $7.3 million. An analysis of the expected value of perfect information for individual parameters suggests that it may be worthwhile for future research to focus on providing better estimates of the mortality attributable to CR-BSI and the effectiveness of both SPC and CH/SSD (int/ext) catheters. In the second evaluation of the catheter care bundle relative to A-CVCs, the results which do not consider uncertainty indicate that a bundle must achieve a relative risk of CR-BSI of at least 0.45 to be cost-effective relative to MR catheters. If the bundle can reduce rates of infection from 2.5% to effectively zero, it is cost-effective relative to MR catheters if national implementation costs are less than $2.6 million ($56,610 per ICU). If the bundle can achieve a relative risk of 0.34 (comparable to that reported in the literature) it is cost-effective, relative to MR catheters, if costs over an 18 month period are below $613,795 nationally ($13,343 per ICU). Once uncertainty in the decision is considered, the cost threshold for the bundle increases to $2.2 million. Therefore, if each of the 46 Level III ICUs could implement an 18 month catheter care bundle for less than $47,826 each, this approach would be cost effective relative to A-CVCs. However, the uncertainty is substantial and the probability of error in concluding that the bundle is the cost-effective approach at a cost of $2.2 million is 89%. Conclusions: This work highlights that infection control to prevent CR-BSI is an efficient use of healthcare resources in the Australian context. If there is no further investment in infection control, an opportunity cost is incurred, which is the potential for a more efficient healthcare system. Minocycline/rifampicin catheters are the optimal choice of antimicrobial catheter for routine use in Australian Level III ICUs, however, if a catheter care bundle implemented in Australia was as effective as those used in the large studies in the United States it would be preferred over the catheters if it was able to be implemented for less than $47,826 per Level III ICU. Uncertainty is very high in this decision and arises from multiple sources. There are likely greater costs to this uncertainty for A-CVCs, which may carry hidden costs, than there are for a catheter care bundle, which is more likely to provide indirect benefits to clinical practice and patient safety. Research into the mortality attributable to CR-BSI, the effectiveness of SPC and CH/SSD (int/ext) catheters and the cost and effectiveness of a catheter care bundle in Australia should be prioritised to reduce uncertainty in this decision. This thesis provides the economic evidence to inform one area of infection control, but there are many other infection control decisions for which information about the cost-effectiveness of competing interventions does not exist. This work highlights some of the challenges and benefits to generating and using economic evidence for infection control decision-making and provides support for commissioning more research into the cost-effectiveness of infection control.

PDMS spreading morphological patterns on substrates of different hydrophilicity in air vacuum and water

In paper has been to investigate the morphological patterns and kinetics of PDMS spreading on silicon wafer using combination of techniques like ellipsometry, atomic force microscope (AFM), scanning electron microscope (SEM) and optical microscopy. A macroscopic silicone oil drops as well as PDMS water based emulsions were studied after deposition on a flat surface of silicon wafer in air, water and vacuum. our own measurements using an imaging ellipsometer, which also clearly shows the presence of a precursor film. The diffusion constant of this film, measured with a 60 000 cS PDMS sample spreading on a hydrophilic silicon wafer, is Df = 1.4  10-11 m2/s. Regardless of their size, density and method of deposition, droplets on both types of wafer (hydrophilic and hydrophobic) flatten out over a period of many hours, up to 3 days. During this process neighbouring droplets may coalesce, but there is strong evidence that some of the PDMS from the droplets migrates into a thin, continuous film that covers the surface in between droplets. The thin film appears to be ubiquitous if there has been any deposition of PDMS. However, this statement needs further verification. One question is whether the film forms immediately after forced drying, or whether in some or all cases it only forms by spreading from isolated droplets as they slowly flatten out.

Preventing consumer credit over-commitment and irresponsible lending in Australia

Mirroring the trends in other developed countries, levels of household debt in Australia have risen markedly in recent years. As one example, the total amount lent by banks to individuals has risen from $175.5 billion in August 1995 to $590.5 billion in August 2005.1 Consumer groups an~ media commentators here have long raised concerns about the risks of increasing levels of household debt and over-commitment, linking these issues at least in part to irresponsible lending practices. And more recently, the Reserve Bank Governor has also expressed concerns about the ability 'of some households to manage if personal or economic circumstances change.2

High fashion

High Fashion is a practice-led research enquiry that examines the processes involved in producing a no-budget film of high aesthetic standards that can confidently compete in the global film festival market, and to reflect on the production techniques tested during the making of the film. The practical outcome of the research is a twenty-five minute short drama. It incorporates a large cast and crew, original designer clothing, extravagant sets, and a popular soundtrack. The thesis considers how over one hundred professionals volunteered their time, expertise, and equipment to help produce the film. The thesis also examines the many obstacles encountered while producing the film and how these were overcome. It is written for the student filmmaker as a guide to "learn by doing."

Many Mount Barrens

Cibachrome photographic prints, Digital print, Acrylic Sheet , wire & card.--------- Total size: 170cm x 119cm x 15cm---------- The work employs a terrestrial photography and cartographic technique to represent a diversity of landscape types surrounding West Mt Barren in Western Australia. Sixteen views of West Mt Barren were captured over a two week period from map grid coordinates in the surround landscape. These images are configured in Many Mount Barrens in a manner which corresponds to the position from which they were recorded.---------- The work was exhibited at Eyes wide open (curators K Bradby and A Brandenberg) which was held at Gorepani Gallery, Albany WA to coincide with the first national screening on SBS Television of the Western Australian documentary A Million Acres a Year (Rijavec, F, Harrison, N & Bradby K (directors), Snakewood Films & Film Australia, c2003).

One-time-password-authenticated key exchange

To reduce the damage of phishing and spyware attacks, banks, governments, and other security-sensitive industries are deploying one-time password systems, where users have many passwords and use each password only once. If a single password is compromised, it can be only be used to impersonate the user once, limiting the damage caused. However, existing practical approaches to one-time passwords have been susceptible to sophisticated phishing attacks. ---------- We give a formal security treatment of this important practical problem. We consider the use of one-time passwords in the context of password-authenticated key exchange (PAKE), which allows for mutual authentication, session key agreement, and resistance to phishing attacks. We describe a security model for the use of one-time passwords, explicitly considering the compromise of past (and future) one-time passwords, and show a general technique for building a secure one-time-PAKE protocol from any secure PAKE protocol. Our techniques also allow for the secure use of pseudorandomly generated and time-dependent passwords.

Listening to late discovery adoption and donor offspring stories : adoption, ethics and implications for contemporary donor insemination practices

For most of the 20th Century a ‘closed’ system of adoption was practised throughout Australia and other modern Western societies. This ‘closed’ system was characterised by sealed records; amended birth certificates to conceal the adoption, and prohibited contact with all biological family. Despite claims that these measures protected these children from the taint of illegitimacy the central motivations were far more complex, involving a desire to protect couples from the stigma of infertility and to provide a socially acceptable family structure (Triseliotis, Feast, & Kyle, 2005; Marshall & McDonald, 2001). From the 1960s significant evidence began to emerge that many adopted children and adults were experiencing higher incidences of psychological difficulties, characterised by problems with psychological adjustment, building self-esteem and forming a secure personal identity. These difficulties became grouped under the term ‘genealogical bewilderment’. As a result, new policies and practices were introduced to try to place the best interests of the child at the forefront. These changes reflected new understandings of adoption; as not only an individual process but also as a social and relational process that continues throughout life. Secrecy and the withholding of birth information are now prohibited in the overwhelming majority of all domestic adoptions processed in Australia (Marshall & McDonald, 2001). One little known consequence of this ‘closed’ system of adoption was the significant number of children who were never told of their adoptive status. As a consequence, some have discovered or had this information disclosed to them, as adults. The first study that looked at the late discovery of genetic origins experiences was conducted by the Post Adoption Resource Centre in New South Wales in 1999. This report found that the participants in their study expressed feelings of disbelief, confusion, anger, sorrow and loss. Further, the majority of participants continued to struggle with issues arising from this intentional concealment of their genetic origins (Perl & Markham, 1999). A second and more recent study (Passmore, Feeney & Foulstone, 2007) looked at the issue of secrecy in adoptive families as part of a broader study of 144 adult adoptees. This study found that secrecy and/or lies or misinformation on the part of adoptive parents had negative effects on both personal identity and relationships with others. The authors noted that those adoptees who found out about their adoption as adults were ‘especially likely to feel a sense of betrayal’ (p.4). Over recent years, stories of secrecy and late discovery have also started to emerge from sperm donor conceived adults (Spencer, 2007; Turner & Coyle, 2000). Current research evidence shows that although a majority of couples during the donor assisted conception process indicate that they intend to tell the offspring about their origins, as many as two-thirds or more of couples continue to withhold this information from their children (Akker, 2006; Gottlieb, A. McWhinnie, 2001; Salter-Ling, Hunter, & Glover, 2001). Why do they keep this secret? Infertility involves a range of complex factors that are often left unresolved or poorly understood by those choosing insemination by donor as a form of family building (Schaffer, J. A., & Diamond, R., 1993). These factors may only impact after the child is born, when resemblance talk becomes most pronounced. Resemblance talk is an accepted form of public discourse and a social convention that legitimises the child as part of the family and is part of the process of constructing the child’s identity within the family. Couples tend to become focused on resemblance as this is where they feel most vulnerable, and the lack of resemblance to the parenting father may trigger his sense of loss (Becker, Butler, & Nachtigall, 2005).

The conceptualisation, sensitivity and measurement of holding costs and other selected elements impacting housing affordability (Literature review and research methodology for confirmation of PhD candidature)

It is widely held that strong relationships exist between housing, economic status, and well being. This is exemplified by widespread housing stock surpluses in many countries which threaten to destabilise numerous aspects related to individuals and community. However, the position of housing demand and supply is not consistent. The Australian position provides a distinct contrast whereby seemingly inexorable housing demand generally remains a critical issue affecting the socio-economic landscape. Underpinned by high levels of immigration, and further buoyed by sustained historically low interest rates, increasing income levels, and increased government assistance for first home buyers, this strong housing demand ensures elements related to housing affordability continue to gain prominence. A significant, but less visible factor impacting housing affordability – particularly new housing development – relates to holding costs. These costs are in many ways “hidden” and cannot always be easily identified. Although it is only one contributor, the nature and extent of its impact requires elucidation. In its simplest form, it commences with a calculation of the interest or opportunity cost of land holding. However, there is significantly more complexity for major new developments - particularly greenfield property development. Preliminary analysis conducted by the author suggests that even small shifts in primary factors impacting holding costs can appreciably affect housing affordability – and notably, to a greater extent than commonly held. Even so, their importance and perceived high level impact can be gauged from the unprecedented level of attention policy makers have given them over recent years. This may be evidenced by the embedding of specific strategies to address burgeoning holding costs (and particularly those cost savings associated with streamlining regulatory assessment) within statutory instruments such as the Queensland Housing Affordability Strategy, and the South East Queensland Regional Plan. However, several key issues require investigation. Firstly, the computation and methodology behind the calculation of holding costs varies widely. In fact, it is not only variable, but in some instances completely ignored. Secondly, some ambiguity exists in terms of the inclusion of various elements of holding costs, thereby affecting the assessment of their relative contribution. Perhaps this may in part be explained by their nature: such costs are not always immediately apparent. Some forms of holding costs are not as visible as the more tangible cost items associated with greenfield development such as regulatory fees, government taxes, acquisition costs, selling fees, commissions and others. Holding costs are also more difficult to evaluate since for the most part they must be ultimately assessed over time in an ever-changing environment, based on their strong relationship with opportunity cost which is in turn dependant, inter alia, upon prevailing inflation and / or interest rates. By extending research in the general area of housing affordability, this thesis seeks to provide a more detailed investigation of those elements related to holding costs, and in so doing determine the size of their impact specifically on the end user. This will involve the development of soundly based economic and econometric models which seek to clarify the componentry impacts of holding costs. Ultimately, there are significant policy implications in relation to the framework used in Australian jurisdictions that promote, retain, or otherwise maximise, the opportunities for affordable housing.

Preliminary review of over-regulation in Australian financial services

This article examines a preliminary review and the limited evidence of over-regulation in Australian financial services. The 1997 Wallis Report and the CLERP 6 paper resulted in the amendments to Ch 7 of the Corporations Act 2001 (Cth) by the Financial Services Reform Act. Nearly a decade later the system based upon 'one-size fits all' dual track regime and a consistent licensing regime has greatly increased the costs of compliance. In the area of enforcement there has not been a dramatic change to the effective techniques applied by ASIC over other agencies such as APRA. In particular there are clear economic arguments, as well as international experiences which state that a single financial services regulator is more effective than the multi-layered approach adopted in Australia. Finally, in the superannuation area of financial services, which is worth A$800 billion there is unnecessary dual licensing and duplicated regulation with little evidence of any consumer-member benefit but at a much greater cost

The vernacular terrain : Songzhang Art Museum, Beijing, China

The field was the curation of cross-cultural new media/ digital media practices within large-scale exhibition practices in China. The context was improved understandings of the intertwining of the natural and the artificial with respect to landscape and culture, and their consequent effect on our contemporary globalised society. The research highlighted new languages of media art with respect to landscape and their particular underpinning dialects. The methodology was principally practice-led. --------- The research brought together over 60 practitioners from both local and diasporic Asian, European and Australian cultures for the first time within a Chinese exhibition context. Through pursuing a strong response to both cultural displacement and re-identification the research forged and documented an enduring commonality within difference – an agenda further concentrated through sensitivities surrounding that year’s Beijing’s Olympics. In contrast to the severe threats posed to the local dialects of many of the world’s spoken and written languages the ‘Vernacular Terrain’ project evidenced that many local creative ‘dialects’ of the environment-media art continuum had indeed survived and flourished. --------- The project was co-funded by the Beijing Film Academy, QUT Precincts, IDAProjects and Platform China Art Institute. A broad range of peer-reviewed grants was won including from the Australia China Council and the Australian Embassy in China. Through invitations from external curators much of the work then traveled to other venues including the Block Gallery at QUT and the outdoor screens at Federation Square, Melbourne. The Vernacular Terrain catalogue featured a comprehensive history of the IDA project from 2000 to 2008 alongside several major essays. Due to the reputation IDA Projects had established, the team were invited to curate a major exhibition showcasing fifty new media artists: The Vernacular Terrain, at the prestigious Songzhang Art Museum, Beijing in Dec 07-Jan 2008. The exhibition was designed for an extensive, newly opened gallery owned by one of China's most important art historians Li Xian Ting. This exhibition was not only this gallery’s inaugural non-Chinese curated show but also the Gallery’s first new media exhibition. It included important works by artists such as Peter Greenway, Michael Roulier, Maleonn and Cui Xuiwen. --------- Each artist was chosen both for a focus upon their own local environmental concerns as well as their specific forms of practice - that included virtual world design, interactive design, video art, real time and manipulated multiplayer gaming platforms and web 2.0 practices. This exhibition examined the interconnectivities of cultural dialogue on both a micro and macro scale; incorporating the local and the global, through display methods and design approaches that stitched these diverse practices into a spatial map of meanings and conversations. By examining the contexts of each artist’s practice in relationship to the specificity of their own local place and prevailing global contexts the exhibition sought to uncover a global vernacular. Through pursuing this concentrated anthropological direction the research identified key themes and concerns of a contextual language that was clearly underpinned by distinctive local ‘dialects’ thereby contributing to a profound sense of cross-cultural association. Through augmentation of existing discourse the exhibition confirmed the enduring relevance and influence of both localized and globalised languages of the landscape-technology continuum.

Lifting the lifegiving dollar : case samples of creative practice in health and medical research philanthropy

This study aims to stimulate thought, debate and action for change on this question of more vigorous philanthropic funding of Australian health and medical research (HMR). It sharpens the argument with some facts and ideas about HMR funding from overseas sources. It also reports informed opinions from those working, giving and innovating in this area. It pinpoints the range of attitudes to HMR giving, both positive and negative. The study includes some aspects of Government funding as part of the equation, viewing Government as major HMR givers, with particular ability to partner, leverage and create incentives. Stimulating new philanthropy takes active outreach. The opportunity to build more dialogue between the HMR industry and the wider community is timely given the ‘licence to practice’ issues and questioned trust that applies currently somewhat both to science and to the charitable sector. This interest in improving HMR philanthropy also coincides with the launch last year by the Federal Government of Nonprofit Australia Limited (NAL), a group currently assessing infrastructure improvements to the charitable sector. History suggests no one will create this change if Research Australia does not. However, interest in change exists in various quarters. For Research Australia to successfully change the culture of Australian HMR giving, the process will drive the outcomes. Obviously stakeholder buy-in and partners will be needed and the ultimate blueprint for greater philanthropic HMR funding here will not be this document. Instead it will be the one that wears the handprint and ‘mindprint’ of the many architects and implementers interested in promoting HMR philanthropy, from philanthropists to nonprofit peaks to government policy arms. As the African proverb says, ‘If you want to go fast, go alone; but if you want to go far, go with others’.

Data muling over underwater wireless sensor networks using an autonomous underwater vehicle

We present algorithms, systems, and experimental results for underwater data muling. In data muling a mobile agent interacts with static agents to upload, download, or transport data to a different physical location. We consider a system comprising an Autonomous Underwater Vehicle (AUV) and many static Underwater Sensor Nodes (USN) networked together optically and acoustically. The AUV can locate the static nodes using vision and hover above the static nodes for data upload. We describe the hardware and software architecture of this underwater system, as well as experimental data. © 2006 IEEE.

A new multilevel converter configuration for high power and high quality applications

The Queensland University of Technology (QUT) allows the presentation of theses for the Degree of Doctor of Philosophy in the format of published or submitted papers, where such papers have been published, accepted or submitted during the period of candidature. This thesis is composed of ten published /submitted papers and book chapters of which nine have been published and one is under review. This project is financially supported by an Australian Research Council (ARC) Discovery Grant with the aim of investigating multilevel topologies for high quality and high power applications, with specific emphasis on renewable energy systems. The rapid evolution of renewable energy within the last several years has resulted in the design of efficient power converters suitable for medium and high-power applications such as wind turbine and photovoltaic (PV) systems. Today, the industrial trend is moving away from heavy and bulky passive components to power converter systems that use more and more semiconductor elements controlled by powerful processor systems. However, it is hard to connect the traditional converters to the high and medium voltage grids, as a single power switch cannot stand at high voltage. For these reasons, a new family of multilevel inverters has appeared as a solution for working with higher voltage levels. Besides this important feature, multilevel converters have the capability to generate stepped waveforms. Consequently, in comparison with conventional two-level inverters, they present lower switching losses, lower voltage stress across loads, lower electromagnetic interference (EMI) and higher quality output waveforms. These properties enable the connection of renewable energy sources directly to the grid without using expensive, bulky, heavy line transformers. Additionally, they minimize the size of the passive filter and increase the durability of electrical devices. However, multilevel converters have only been utilised in very particular applications, mainly due to the structural limitations, high cost and complexity of the multilevel converter system and control. New developments in the fields of power semiconductor switches and processors will favor the multilevel converters for many other fields of application. The main application for the multilevel converter presented in this work is the front-end power converter in renewable energy systems. Diode-clamped and cascade converters are the most common type of multilevel converters widely used in different renewable energy system applications. However, some drawbacks – such as capacitor voltage imbalance, number of components, and complexity of the control system – still exist, and these are investigated in the framework of this thesis. Various simulations using software simulation tools are undertaken and are used to study different cases. The feasibility of the developments is underlined with a series of experimental results. This thesis is divided into two main sections. The first section focuses on solving the capacitor voltage imbalance for a wide range of applications, and on decreasing the complexity of the control strategy on the inverter side. The idea of using sharing switches at the output structure of the DC-DC front-end converters is proposed to balance the series DC link capacitors. A new family of multioutput DC-DC converters is proposed for renewable energy systems connected to the DC link voltage of diode-clamped converters. The main objective of this type of converter is the sharing of the total output voltage into several series voltage levels using sharing switches. This solves the problems associated with capacitor voltage imbalance in diode-clamped multilevel converters. These converters adjust the variable and unregulated DC voltage generated by renewable energy systems (such as PV) to the desirable series multiple voltage levels at the inverter DC side. A multi-output boost (MOB) converter, with one inductor and series output voltage, is presented. This converter is suitable for renewable energy systems based on diode-clamped converters because it boosts the low output voltage and provides the series capacitor at the output side. A simple control strategy using cross voltage control with internal current loop is presented to obtain the desired voltage levels at the output voltage. The proposed topology and control strategy are validated by simulation and hardware results. Using the idea of voltage sharing switches, the circuit structure of different topologies of multi-output DC-DC converters – or multi-output voltage sharing (MOVS) converters – have been proposed. In order to verify the feasibility of this topology and its application, steady state and dynamic analyses have been carried out. Simulation and experiments using the proposed control strategy have verified the mathematical analysis. The second part of this thesis addresses the second problem of multilevel converters: the need to improve their quality with minimum cost and complexity. This is related to utilising asymmetrical multilevel topologies instead of conventional multilevel converters; this can increase the quality of output waveforms with a minimum number of components. It also allows for a reduction in the cost and complexity of systems while maintaining the same output quality, or for an increase in the quality while maintaining the same cost and complexity. Therefore, the asymmetrical configuration for two common types of multilevel converters – diode-clamped and cascade converters – is investigated. Also, as well as addressing the maximisation of the output voltage resolution, some technical issues – such as adjacent switching vectors – should be taken into account in asymmetrical multilevel configurations to keep the total harmonic distortion (THD) and switching losses to a minimum. Thus, the asymmetrical diode-clamped converter is proposed. An appropriate asymmetrical DC link arrangement is presented for four-level diode-clamped converters by keeping adjacent switching vectors. In this way, five-level inverter performance is achieved for the same level of complexity of the four-level inverter. Dealing with the capacitor voltage imbalance problem in asymmetrical diodeclamped converters has inspired the proposal for two different DC-DC topologies with a suitable control strategy. A Triple-Output Boost (TOB) converter and a Boost 3-Output Voltage Sharing (Boost-3OVS) converter connected to the four-level diode-clamped converter are proposed to arrange the proposed asymmetrical DC link for the high modulation indices and unity power factor. Cascade converters have shown their abilities and strengths in medium and high power applications. Using asymmetrical H-bridge inverters, more voltage levels can be generated in output voltage with the same number of components as the symmetrical converters. The concept of cascading multilevel H-bridge cells is used to propose a fifteen-level cascade inverter using a four-level H-bridge symmetrical diode-clamped converter, cascaded with classical two-level Hbridge inverters. A DC voltage ratio of cells is presented to obtain maximum voltage levels on output voltage, with adjacent switching vectors between all possible voltage levels; this can minimize the switching losses. This structure can save five isolated DC sources and twelve switches in comparison to conventional cascade converters with series two-level H bridge inverters. To increase the quality in presented hybrid topology with minimum number of components, a new cascade inverter is verified by cascading an asymmetrical four-level H-bridge diode-clamped inverter. An inverter with nineteen-level performance was achieved. This synthesizes more voltage levels with lower voltage and current THD, rather than using a symmetrical diode-clamped inverter with the same configuration and equivalent number of power components. Two different predictive current control methods for the switching states selection are proposed to minimise either losses or THD of voltage in hybrid converters. High voltage spikes at switching time in experimental results and investigation of a diode-clamped inverter structure raised another problem associated with high-level high voltage multilevel converters. Power switching components with fast switching, combined with hard switched-converters, produce high di/dt during turn off time. Thus, stray inductance of interconnections becomes an important issue and raises overvoltage and EMI issues correlated to the number of components. Planar busbar is a good candidate to reduce interconnection inductance in high power inverters compared with cables. The effect of different transient current loops on busbar physical structure of the high-voltage highlevel diode-clamped converters is highlighted. Design considerations of proper planar busbar are also presented to optimise the overall design of diode-clamped converters.

Exponential asymptotics with multiple stokes lines

When asymptotic series methods are applied in order to solve problems that arise in applied mathematics in the limit that some parameter becomes small, they are unable to demonstrate behaviour that occurs on a scale that is exponentially small compared to the algebraic terms of the asymptotic series. There are many examples of physical systems where behaviour on this scale has important effects and, as such, a range of techniques known as exponential asymptotic techniques were developed that may be used to examinine behaviour on this exponentially small scale. Many problems in applied mathematics may be represented by behaviour within the complex plane, which may subsequently be examined using asymptotic methods. These problems frequently demonstrate behaviour known as Stokes phenomenon, which involves the rapid switches of behaviour on an exponentially small scale in the neighbourhood of some curve known as a Stokes line. Exponential asymptotic techniques have been applied in order to obtain an expression for this exponentially small switching behaviour in the solutions to orginary and partial differential equations. The problem of potential flow over a submerged obstacle has been previously considered in this manner by Chapman & Vanden-Broeck (2006). By representing the problem in the complex plane and applying an exponential asymptotic technique, they were able to detect the switching, and subsequent behaviour, of exponentially small waves on the free surface of the flow in the limit of small Froude number, specifically considering the case of flow over a step with one Stokes line present in the complex plane. We consider an extension of this work to flow configurations with multiple Stokes lines, such as flow over an inclined step, or flow over a bump or trench. The resultant expressions are analysed, and demonstrate interesting implications, such as the presence of exponentially sub-subdominant intermediate waves and the possibility of trapped surface waves for flow over a bump or trench. We then consider the effect of multiple Stokes lines in higher order equations, particu- larly investigating the behaviour of higher-order Stokes lines in the solutions to partial differential equations. These higher-order Stokes lines switch off the ordinary Stokes lines themselves, adding a layer of complexity to the overall Stokes structure of the solution. Specifically, we consider the different approaches taken by Howls et al. (2004) and Chap- man & Mortimer (2005) in applying exponential asymptotic techniques to determine the higher-order Stokes phenomenon behaviour in the solution to a particular partial differ- ential equation.

Towards developing an integrated model of information behaviour

This paper presents the results from a study of information behaviors in the context of people's everyday lives undertaken in order to develop an integrated model of information behavior (IB). 34 participants from across 6 countries maintained a daily information journal or diary – mainly through a secure web log – for two weeks, to an aggregate of 468 participant days over five months. The text-rich diary data was analyzed using a multi-method qualitative-quantitative analysis in the following order: Grounded Theory analysis with manual coding, automated concept analysis using thesaurus-based visualization, and finally a statistical analysis of the coding data. The findings indicate that people engage in several information behaviors simultaneously throughout their everyday lives (including home and work life) and that sense-making is entangled in all aspects of them. Participants engaged in many of the information behaviors in a parallel, distributed, and concurrent fashion: many information behaviors for one information problem, one information behavior across many information problems, and many information behaviors concurrently across many information problems. Findings indicate also that information avoidance – both active and passive avoidance – is a common phenomenon and that information organizing behaviors or the lack thereof caused the most problems for participants. An integrated model of information behaviors is presented based on the findings.