How important is length? : mechanical testing and measurement of a cemented, polished, tapered femoral implant

Total hip arthroplasty (THA) has a proven clinical record for providing pain relief and return of function to patients with disabling arthritis. There are many successful options for femoral implant design and fixation. Cemented, polished, tapered femoral implants have been shown to have excellent results in national joint registries and long-term clinical series. These implants are usually 150mm long at their lateral aspect. Due to their length, these implants cannot always be offered to patients due to variations in femoral anatomy. Polished, tapered implants as short as 95mm exist, however their small proximal geometry (neck offset and body size) limit their use to smaller stature patients. There is a group of patients in which a shorter implant with a maintained proximal body size would be advantageous. There are also potential benefits to a shorter implant in standard patient populations such as reduced bone removal due to reduced reaming, favourable loading of the proximal femur, and the ability to revise into good proximal bone stock if required. These factors potentially make a shorter implant an option for all patient populations. The role of implant length in determining the stability of a cemented, polished, tapered femoral implant is not well defined by the literature. Before changes in implant design can be made, a better understanding of the role of each region in determining performance is required. The aim of the thesis was to describe how implant length affects the stability of a cemented, polished, tapered femoral implant. This has been determined through an extensive body of laboratory testing. The major findings are that for a given proximal body size, a reduction in implant length has no effect on the torsional stability of a polished, tapered design, while a small reduction in axial stability should be expected. These findings are important because the literature suggests that torsional stability is the major determinant of long-term clinical performance of a THA system. Furthermore, a polished, tapered design is known to be forgiving of cement-implant interface micromotion due to the favourable wear characteristics. Together these findings suggest that a shorter polished, tapered implant may be well tolerated. The effect of a change in implant length on the geometric characteristics of polished, tapered design were also determined and applied to the mechanical testing. Importantly, interface area does play a role in stability of the system; however it is the distribution of the interface and not the magnitude of the area that defines stability. Taper angle (at least in the range of angles seen in this work) was shown not to be a determinant of axial or torsional stability. A range of implants were tested, comparing variations in length, neck offset and indication (primary versus cement-in-cement revision). At their manufactured length, the 125mm implants were similar to their longer 150mm counterparts suggesting that they may be similarly well tolerated in the clinical environment. However, the slimmer cement-in-cement revision implant was shown to have a poorer mechanical performance, suggesting their use in higher demand patients may be hazardous. An implant length of 125mm has been shown to be quite stable and the results suggest that a further reduction to 100mm may be tolerated. However, further work is required. A shorter implant with maintained proximal body size would be useful for the group of patients who are unable to access the current standard length implants due to variations in femoral anatomy. Extending the findings further, the similar function with potential benefits of a shorter implant make their application to all patients appealing.

Testing a model of physical activity among mothers and fathers of young children: integrating self-determined motivation, planning, and the theory of planned behavior

Parents are at risk for inactivity; however, research into understanding parental physical activity (PA) is scarce. We integrated self-determined motivation, planning, and the theory of planned behavior (TPB) to better understand parental PA. Parents (252 mothers, 206 fathers) completed a main questionnaire assessing measures underpinning these constructs and a 1-week follow-up of PA behavior to examine whether self-determined motivation indirectly influenced intention via the TPB variables (i.e., attitude, subjective norm, and perceived behavioral control) and intention indirectly influenced behavior via planning. We found self-determined motivation on intention was fully mediated by the TPB variables and intention on behavior was partially mediated by the planning variables. In addition, slight differences in the model’s paths between the sexes were revealed. The results illustrate the range of important determinants of parental PA and provide support for the integrated model in explaining PA decision making as well as the importance of examining sex differences.

Wind-energy based path planning for unmanned aerial vehicles using Markov decision processes

Exploiting wind-energy is one possible way to extend flight duration for Unmanned Arial Vehicles. Wind-energy can also be used to minimise energy consumption for a planned path. In this paper, we consider uncertain time-varying wind fields and plan a path through them. A Gaussian distribution is used to determine uncertainty in the Time-varying wind fields. We use Markov Decision Process to plan a path based upon the uncertainty of Gaussian distribution. Simulation results that compare the direct line of flight between start and target point and our planned path for energy consumption and time of travel are presented. The result is a robust path using the most visited cell while sampling the Gaussian distribution of the wind field in each cell.

Coordinated tuning of DFIG-based wind turbines and batteries using bacteria foraging technique for maintaining constant grid power output

This paper proposes the use of battery energy storage (BES) system for the grid-connected doubly fed induction generator (DFIG). The BES would help in storing/releasing additional power in case of higher/lower wind speed to maintain constant grid power. The DC link capacitor is replaced with the BES system in a DFIG-based wind turbine to achieve the above-mentioned goal. The control scheme is modified and the co-ordinated tuning of the associated controllers to enhance the damping of the oscillatory modes is presented using bacterial foraging technique. The results from eigenvalue analysis and the time domain simulation studies are presented to elucidate the effectiveness of the BES systems in maintaining the grid stability under normal operation.

Improving stability of a DFIG-based wind power system with tuned damping controller

This paper focuses on the implementation of a damping controller for the doubly fed induction generator (DFIG) system. Coordinated tuning of the damping controller to enhance the damping of the oscillatory modes is presented using bacterial foraging technique. The effect of the tuned damping controller on converter ratings of the DFIG system is also investigated. The results of both eigenvalue analysis and the time-domain simulation studies are presented to elucidate the effectiveness of the tuned damping controller in the DFIG system. The improvement of the fault ride-through capability of the system is also demonstrated.

Impact of wind power development on transmission planning at Midwest ISO

The Midwest Independent Transmission System Operator (MISO) has experienced significant amounts of wind power development within the last decade. The MISO footprint spans the majority of the upper Midwest region of the country, from the Dakotas to Indiana and as far east as Michigan. These areas have a rich wind energy resource. States in the MISO footprint have passed laws or set goals that require load serving entities to supply a portion of their load using renewable energy. In order to meet these requirements, significant investments are needed to build the transmission infrastructure necessary to deliver the power from these often remote wind energy resources to the load centers. This paper presents some of the transmission planning related work done at MISO which was largely influenced by current and future needs for increased wind power generation in the footprint. Specifically, topics covered are generator interconnection, long-term planning coordination, and cost-allocation for new transmission lines.

Probability analysis of machine angle stability with non-gaussian wind power input

The security of power transfer across a given transmission link is typically a steady state assessment. This paper develops tools to assess machine angle stability as affected by a combination of faults and uncertainty of wind power using probability analysis. The paper elaborates on the development of the theoretical assessment tool and demonstrates its efficacy using single machine infinite bus system.

Security constrained economic dispatch considering wind energy conversion systems

The available wind power is stochastic and requires appropriate tools in the OPF model for economic and reliable power system operation. This paper exhibit the OPF formulation with factors involved in the intermittency of wind power. Weibull distribution is adopted to find the stochastic wind speed and power distribution. The reserve requirement is evaluated based on the wind distribution and risk of under/over estimation of the wind power. In addition, the Wind Energy Conversion System (WECS) is represented by Doubly Fed Induction Generator (DFIG) based wind farms. The reactive power capability for DFIG based wind farm is also analyzed. The study is performed on IEEE-30 bus system with wind farm located at different buses and with different wind profiles. Also the reactive power capacity to be installed in the wind farm to maintain a satisfactory voltage profile under the various wind flow scenario is demonstrated.

Effective planning approach to interconnect bulk quantities of wind generation

Over the past few years, the Midwest ISO has experienced a surge in requests to interconnect large amounts of wind generation, driven largely by a favorable political environment and an abundant wind resource in the Midwestern US. This tremendous influx of proposed generators along with a highly constrained transmission system adversely impacted interconnection queue processing, resulting in an unmanageable backlog. Under these circumstances, Midwest ISO successfully reformed the interconnection tariff to improve cycle times and provide increased certainty to interconnection customers. One of the key features of the reformed queue process is the System Planning and Analysis (SPA) phase which allows integration of the interconnection studies with regional transmission planning. This paper presents a brief background of the queue reform effort and then delves deeply in to the work performed at the Midwest ISO during the first SPA cycle - the study approach, the challenges faced in having to study over 50,000 MWs of wind generation and the effective solutions designed to complete these studies within tariff timelines.

Risk control in transmission system expansion planning with wind generators

With the advent of large-scale wind farms and their integration into electrical grids, more uncertainties, constraints and objectives must be considered in power system development. It is therefore necessary to introduce risk-control strategies into the planning of transmission systems connected with wind power generators. This paper presents a probability-based multi-objective model equipped with three risk-control strategies. The model is developed to evaluate and enhance the ability of the transmission system to protect against overload risks when wind power is integrated into the power system. The model involves: (i) defining the uncertainties associated with wind power generators with probability measures and calculating the probabilistic power flow with the combined use of cumulants and Gram-Charlier series; (ii) developing three risk-control strategies by specifying the smallest acceptable non-overload probability for each branch and the whole system, and specifying the non-overload margin for all branches in the whole system; (iii) formulating an overload risk index based on the non-overload probability and the non-overload margin defined; and (iv) developing a multi-objective transmission system expansion planning (TSEP) model with the objective functions composed of transmission investment and the overload risk index. The presented work represents a superior risk-control model for TSEP in terms of security, reliability and economy. The transmission expansion planning model with the three risk-control strategies demonstrates its feasibility in the case study using two typical power systems

More light at the end of the tunnel – apixaban in atrial fibrillation

Introduction: Subjects with atrial fibrillation are at risk of thromboembolic events. The vitamin K antagonists (e.g., warfarin) are useful at preventing coagulation in atrial fibrillation, but are difficult to use. One of the FXa inhibitors, oral apixaban, has been tested as an anticoagulant in atrial fibrillation. Areas covered: In ARISTOTLE (Apixaban for reduction in stroke and other thromboembolic events in atrial fibrillation) apixaban was compared to warfarin in subjects with atrial fibrillation, and shown to cause a lower rate of stroke or systemic embolism and of major bleeding, than warfarin. In the AVERROES (Apixaban versus acetylsalicylic acid [ASA] to prevent stroke in atrial fibrillations patients who have failed or are unsuitable for vitamin K antagonist treatment) trial, stroke or systemic embolism occurred less often with apixaban than aspirin, whereas the occurrence of major bleeding was similar in the groups. Expert opinion: Apixaban is much easier for subjects with atrial fibrillation to use than warfarin, as it does not require regular monitoring by a health professional, with dosage adjustment. In addition to replacing warfarin in subjects with atrial fibrillation who are unable or not prepared to use warfarin, apixaban has the potential to replace warfarin more widely in the prevention of thromboembolism in subjects with atrial fibrillation.

Development and testing of an iPad application for teaching self-management to heart failure patients. (Nursing/Allied Health Professional Investigator Award)- Abstract

Purpose: Heart failure (HF) is the leading cause of hospitalization and significant burden to the health care system in Australia. To reduce hospitalizations, multidisciplinary approaches and enhance self-management programs have been strongly advocated for HF patients globally. HF patients who can effectively manage their symptoms and adhere to complex medicine regimes will experience fewer hospitalizations. Research indicates that information technologies (IT) have a significant role in providing support to promote patients' self-management skills. The iPad utilizes user-friendly interfaces and to date an application for HF patient education has not been developed. This project aimed to develop the HF iPad teaching application in the way that would be engaging, interactive and simple to follow and usable for patients' carers and health care workers within both the hospital and community setting. Methods: The design for the development and evaluation of the application consisted of two action research cycles. Each cycle included 3 phases of testing and feedback from three groups comprising IT team, HF experts and patients. All patient education materials of the application were derived from national and international evidence based practice guidelines and patient self-care recommendations. Results: The iPad application has animated anatomy and physiology that simply and clearly teaches the concepts of the normal heart and the heart in failure. Patient Avatars throughout the application can be changed to reflect the sex and culture of the patient. There is voice-over presenting a script developed by the heart failure expert panel. Additional engagement processes included points of interaction throughout the application with touch screen responses and the ability of the patient to enter their weight and this data is secured and transferred to the clinic nurse and/or research data set. The application has been used independently, for instance, at home or using headphones in a clinic waiting room or most commonly to aid a nurse-led HF consultation. Conclusion: This project utilized iPad as an educational tool to standardize HF education from nurses who are not always heart failure specialists. Furthermore, study is currently ongoing to evaluate of the effectiveness of this tool on patient outcomes and to develop several specifically designed cultural adaptations [Hispanic (USA), Aboriginal (Australia), and Maori (New Zealand)].

In vitro primary cell culture as a physiologically relevant method for preclinical testing of human oncolytic adenovirus

Ad[I/PPT-E1A] is an oncolytic adenovirus that specifically kills prostate cells via restricted replication by a prostate-specific regulatory element. Off-target replication of oncolytic adenoviruses would have serious clinical consequences. As a proposed ex vivo test, we describe the assessment of the specificity of Ad[I/PPT-E1A] viral cytotoxicity and replication in human nonprostate primary cells. Four primary nonprostate cell types were selected to mimic the effects of potential in vivo exposure to Ad[I/PPT-E1A] virus: bronchial epithelial cells, urothelial cells, vascular endothelial cells, and hepatocytes. Primary cells were analyzed for Ad[I/PPT-E1A] viral cytotoxicity in MTS assays, and viral replication was determined by hexon titer immunostaining assays to quantify viral hexon protein. The results revealed that at an extreme multiplicity of infection of 500, unlikely to be achieved in vivo, Ad[I/PPT-E1A] virus showed no significant cytotoxic effects in the nonprostate primary cell types apart from the hepatocytes. Transmission electron microscopy studies revealed high levels of Ad[I/PPT-E1A] sequestered in the cytoplasm of these cells. Adenoviral green fluorescent protein reporter studies showed no evidence for nuclear localization, suggesting that the cytotoxic effects of Ad[I/PPT-E1A] in human primary hepatocytes are related to viral sequestration. Also, hepatocytes had increased amounts of coxsackie adenovirus receptor surface protein. Active viral replication was only observed in the permissive primary prostate cells and LNCaP prostate cell line, and was not evident in any of the other nonprostate cells types tested, confirming the specificity of Ad[I/PPT-E1A]. Thus, using a relevant panel of primary human cells provides a convenient and alternative preclinical assay for examining the specificity of conditionally replicating oncolytic adenoviruses in vivo.

Gene transfer vectors targeted to human prostate cancer : do we need better preclinical testing systems?

Destruction of cancer cells by genetically modified viral and nonviral vectors has been the aim of many research programs. The ability to target cytotoxic gene therapies to the cells of interest is an essential prerequisite, and the treatment has always had the potential to provide better and more long-lasting therapy than existing chemotherapies. However, the potency of these infectious agents requires effective testing systems, in which hypotheses can be explored both in vitro and in vivo before the establishment of clinical trials in humans. The real prospect of off-target effects should be eliminated in the preclinical stage, if current prejudices against such therapies are to be overcome. In this review we have set out, using adenoviral vectors as a commonly used example, to discuss some of the key parameters required to develop more effective testing, and to critically assess the current cellular models for the development and testing of prostate cancer biotherapy. Only by developing models that more closely mirror human tissues will we be able to translate literature publications into clinical trials and hence into acceptable alternative treatments for the most commonly diagnosed cancer in humans.