A biomechanical investigation of dual growing rods used for fusionless scoliosis correction

Background The use of dual growing rods is a fusionless surgical approach to the treatment of early onset scoliosis (EOS), which aims of harness potential growth in order to correct spinal deformity. The purpose of this study was to compare the in-vitro biomechanical response of two different dual rod designs under axial rotation loading. Methods Six porcine spines were dissected into seven level thoracolumbar multi-segmental units. Each specimen was mounted and tested in a biaxial Instron machine, undergoing nondestructive left/right axial rotation to peak moments of 4Nm at a constant rotation rate of 8deg.s-1. A motion tracking system (Optotrak) measured 3D displacements of individual vertebrae. Each spine was tested in an un-instrumented state first and then with appropriately sized semi-constrained growing rods and ‘rigid’ rods in alternating sequence. Range of motion, neutral zone size and stiffness were calculated from the moment-rotation curves and intervertebral ranges of motion were calculated from Optotrak data. Findings Irrespective of test sequence, rigid rods showed significantly reduction of total rotation across all instrumented levels (with increased stiffness) whilst semi-constrained rods exhibited similar rotation behavior to the un-instrumented (P<0.05). An 11% and 8% increase in stiffness for left and right axial rotation respectively and 15% reduction in total range of motion was recorded with dual rigid rods compared with semi-constrained rods. Interpretation Based on these findings, the semi-constrained growing rods do not increase axial rotation stiffness compared with un-instrumented spines. This is thought to provide a more physiological environment for the growing spine compared to dual rigid rod constructs.

A novel ambiguity acceptance test threshold determination method with controllable failure rate

Ambiguity validation as an important procedure of integer ambiguity resolution is to test the correctness of the fixed integer ambiguity of phase measurements before being used for positioning computation. Most existing investigations on ambiguity validation focus on test statistic. How to determine the threshold more reasonably is less understood, although it is one of the most important topics in ambiguity validation. Currently, there are two threshold determination methods in the ambiguity validation procedure: the empirical approach and the fixed failure rate (FF-) approach. The empirical approach is simple but lacks of theoretical basis. The fixed failure rate approach has a rigorous probability theory basis, but it employs a more complicated procedure. This paper focuses on how to determine the threshold easily and reasonably. Both FF-ratio test and FF-difference test are investigated in this research and the extensive simulation results show that the FF-difference test can achieve comparable or even better performance than the well-known FF-ratio test. Another benefit of adopting the FF-difference test is that its threshold can be expressed as a function of integer least-squares (ILS) success rate with specified failure rate tolerance. Thus, a new threshold determination method named threshold function for the FF-difference test is proposed. The threshold function method preserves the fixed failure rate characteristic and is also easy-to-apply. The performance of the threshold function is validated with simulated data. The validation results show that with the threshold function method, the impact of the modelling error on the failure rate is less than 0.08%. Overall, the threshold function for the FF-difference test is a very promising threshold validation method and it makes the FF-approach applicable for the real-time GNSS positioning applications.

Parent feeding interactions and practices during childhood cancer treatment: A qualitative investigation

In the general population it is evident that parent feeding practices can directly shape a child’s life long dietary intake. Young children undergoing childhood cancer treatment may experience feeding difficulties and limited food intake, due to the inherent side effects of their anti-cancer treatment. What is not clear is how these treatment side effects are influencing the parent–child feeding relationship during anti-cancer treatment. This retrospective qualitative study collected telephone based interview data from 38 parents of childhood cancer patients who had recently completed cancer treatment (child’s mean age: 6.98 years). Parents described a range of treatment side effects that impacted on their child’s ability to eat, often resulting in weight loss. Sixty-one percent of parents (n = 23) reported high levels of stress in regard to their child’s eating and weight loss during treatment. Parents reported stress, feelings of helplessness, and conflict and/or tension between parent and the child during feeding/eating interactions. Parents described using both positive and negative feeding practices, such as: pressuring their child to eat, threatening the insertion of a nasogastric feeding tube, encouraging the child to eat and providing home cooked meals in hospital. Results indicated that parent stress may lead to the use of coping strategies such as positive or negative feeding practices to entice their child to eat during cancer treatment. Future research is recommended to determine the implication of parent feeding practice on the long term diet quality and food preferences of childhood cancer survivors.

Perceived barriers and facilitators to increasing physical activity among people with musculoskeletal disorders : a qualitative investigation to inform intervention development

Purpose Musculoskeletal conditions can impair people’s ability to undertake physical activity as they age. The purpose of this qualitative study was to investigate perceived barriers and facilitators to undertaking physical activity reported by patients accessing ambulatory hospital clinics for musculoskeletal disorders. Patients and methods A questionnaire with open-ended items was administered to patients (n=217, 73.3% of 296 eligible) from three clinics providing ambulatory services for nonsurgical treatment of musculoskeletal disorders. The survey included questions to capture the clinical and demographic characteristics of the sample. It also comprised two open-ended questions requiring qualitative responses. The first asked the participant to describe factors that made physical activity more difficult, and the second asked which factors made it easier for them to be physically active. Participants’ responses to the two open-ended questions were read, coded, and thematically analyzed independently by two researchers, with a third researcher available to arbitrate any unresolved disagreement. Results The mean (standard deviation) age of participants was 53 (15) years; n=113 (52.1%) were male. A total of 112 (51.6%) participants reported having three or more health conditions; n=140 (64.5%) were classified as overweight or obese. Five overarching themes describing perceived barriers for undertaking physical activity were "health conditions", "time restrictions", "poor physical condition", "emotional, social, and psychological barriers", and "access to exercise opportunities". Perceived physical activity facilitators were also aligned under five themes, namely "improved health state", "social, emotional, and behavioral supports", "access to exercise environment", "opportunities for physical activities", and "time availability". Conclusion It was clear from the breadth of the data that meaningful supports and interventions must be multidimensional. They should have the capacity to address a variety of physical, functional, social, psychological, motivational, environmental, lifestyle, and other perceived barriers. It would appear that for such interventions to be effective, they should be flexible enough to address a variety of specific concerns.

A strain-based failure criterion for pillar stability analysis

Strain-based failure criteria have several advantages over stress-based failure criteria: they can account for elastic and inelastic strains, they utilise direct, observables effects instead of inferred effects (strain gauges vs. stress estimates), and model complete stress-strain curves including pre-peak, non-linear elasticity and post-peak strain weakening. In this study, a strain-based failure criterion derived from thermodynamic first principles utilising the concepts of continuum damage mechanics is presented. Furthermore, implementation of this failure criterion into a finite-element simulation is demonstrated and applied to the stability of underground mining coal pillars. In numerical studies, pillar strength is usually expressed in terms of critical stresses or stress-based failure criteria where scaling with pillar width and height is common. Previous publications have employed the finite-element method for pillar stability analysis using stress-based failure criterion such as Mohr-Coulomb and Hoek-Brown or stress-based scalar damage models. A novel constitutive material model, which takes into consideration anisotropy as well as elastic strain and damage as state variables has been developed and is presented in this paper. The damage threshold and its evolution are strain-controlled, and coupling of the state variables is achieved through the damage-induced degradation of the elasticity tensor. This material model is implemented into the finite-element software ABAQUS and can be applied to 3D problems. Initial results show that this new material model is capable of describing the non-linear behaviour of geomaterials commonly observed before peak strength is reached as well as post-peak strain softening. Furthermore, it is demonstrated that the model can account for directional dependency of failure behaviour (i.e. anisotropy) and has the potential to be expanded to environmental controls like temperature or moisture.

The political in the age of the digital: propositions for empirical investigation

This article establishes whether there is a case for revising traditional accounts of politics and the public sphere given the ways in which digital technology is now being used in Western and non-Western settings to engage people politically. The article presents a case for framing this inquiry in terms of imaginaries. It then argues for a new political imaginary which helps to specify what is required for deliberative democratic practice in a way that shifts us away from the dominant liberal-utilitarian political imaginary that currently informs the political value systems of most Western nations. Drawing on the work of key political theorists such as Habermas and Dahlgren, five propositions or conditions for deliberative practice are identified that can be used in empirical investigation to help determine the democratic capacity and potential of new political communication and civic spaces being opened by means of digital media.

An Investigation into the Options for Increasing the Extent of Energy Efficiency Knowledge and Skills in Engineering Education

Society is increasingly calling for professionals across government, industry, business and civil society to be able to problem-solve issues related to climate change and sustainable development as part of their work. In particular there is an emerging realisation of the fundamental need to swiftly reduce the growing demand for energy across society, and to then meet the demand with low emissions options. A key ingredient to addressing such issues is equipping professionals with emerging knowledge and skills to address energy challenges in all aspects of their work. The Council of Australian Governments has recognised this need, signing the National Partnership Agreement on Energy Efficiency in July 2009, which included a commitment to assist business and industry obtain the knowledge, skills and capacity to pursue cost-effective energy efficiency opportunities.2 Engineering will play a critical part among the professions, with Engineers Australia acknowledging that, ‘The need to make changes in the way energy is used and supplied throughout the world represents the greatest challenge to engineers in moving toward sustainability.’

Profiled steel roof claddings under high wind forces

Profiled steel roof claddings in Australia and its neighbouring countries are commonly made of very thin high tensile steel and are crest-fixed intermittently with screw fasteners. The failure of the roof cladding systems was due to a local failure (dimpling of crests I pull-through) at the fasteners under wind uplift Cyclic wind uplift during cyclones causes fatigue cracking to occur at the fastener holes which leads to pull-through failures at lower load levels. At present the design of these claddings is entirely based on testing. In order to improve the understanding of the behaviour and the design and test methods of these claddings under wind uplift loading during storms and cyclones, a detailed investigation consisting of finite element analyses, static and fatigue experiments and cyclonic wind modelling was carried out on two-span roofing assemblies of three common roofing profiles. This paper presents the details of this investigation and its important results.

Acoustic emission activity from the two main types of small multi-cylinder diesel engine fuel injection systems

Effective fuel injector operation and efficient combustion are two of the most critical aspects when Diesel engine performance, efficiency and reliability are considered. Indeed, it is widely acknowledged that fuel injection equipment faults lead to increased fuel consumption, reduced power, greater levels of exhaust emissions and even unexpected engine failure. Previous investigations have identified fuel injector related acoustic emission activity as being caused by mechanisms such as fuel line pressure build-up; fuel flow through injector nozzles, injector needle opening and closing impacts and premixed combustion related pulses. Few of these investigations however, have attempted to categorise the close association and interrelation that exists between fuel injection equipment function and the acoustic emission generating mechanisms. Consequently, a significant amount of ambiguity remains in the interpretation and categorisation of injector related AE activity with respect to the functional characteristics of specific fuel injection equipment. The investigation presented addresses this ambiguity by detailing a study in which AE signals were recorded and analysed from two different Diesel engines employing the two commonly encountered yet fundamentally different types of fuel injection equipment. Results from tests in which faults were induced into fuel injector nozzles from both indirect-injection and direct-injection engines show that functional differences between the main types of fuel injection equipment results in acoustic emission activity which can be specifically related to the type of fuel injection equipment used.

An investigation of early career teachers’ perceptions of professional development opportunities and career advancement for teachers in rural and remote Queensland

It is generally accepted that to live and work in the remote regions of Australia requires specific skills and expertise to accommodate the shifting demands of outback life. For professionals assigned to such areas by employing bodies, this is particularly the case, and teachers are no exception. In addition to such personal attributes, professionals such as teachers must maintain currency in their professional practice both to serve their students appropriately and to ensure that they become eligible for future promotions and transfers possibilities. This study investigated whether teachers in rural and remote regions are disadvantaged in ways that could potentially affect their teaching careers in negative ways, in particular in terms of professional development and career advancement opportunities. Such opportunities are crucial if teachers are to provide an education of high relevance to rural and remote children who are already considered to be significantly disadvantaged in terms of educational provision. The data are presented in the form of a single teacher narrative, a composite tale aimed at telling the story of rural and remote teachers, professional development provision and career advancement opportunities. It was apparent that teachers in these contexts face serious challenges in terms of their professional and career development.

A micro-level investigation of the solid displacement method for porosity determination of dried food

Porosity is one of the key parameters of the macroscopic structure of porous media, generally defined as the ratio of the free spaces occupied (by the volume of air) within the material to the total volume of the material. Porosity is determined by measuring skeletal volume and the envelope volume. Solid displacement method is one of the inexpensive and easy methods to determine the envelope volume of a sample with an irregular shape. In this method, generally glass beads are used as a solid due to their uniform size, compactness and fluidity properties. The smaller size of the glass beads means that they enter into the open pores which have a larger diameter than the glass beads. Although extensive research has been carried out on porosity determination using displacement method, no study exists which adequately reports micro-level observation of the sample during measurement. This study set out with the aim of assessing the accuracy of solid displacement method of bulk density measurement of dried foods by micro-level observation. Solid displacement method of porosity determination was conducted using a cylindrical vial (cylindrical plastic container) and 57 µm glass beads in order to measure the bulk density of apple slices at different moisture contents. A scanning electron microscope (SEM), a profilometer and ImageJ software were used to investigate the penetration of glass beads into the surface pores during the determination of the porosity of dried food. A helium pycnometer was used to measure the particle density of the sample. Results show that a significant number of pores were large enough to allow the glass beads to enter into the pores, thereby causing some erroneous results. It was also found that coating the dried sample with appropriate coating material prior to measurement can resolve this problem.

Trial by media: An empirical investigation of corporate reputation and stock returns in Australia

This article examines whether investors are able to generate abnormal risk-adjusted returns in the Australian market based on media-specific firm reputational factors under market uncertainty between 2004 and 2012. The findings suggest that after controlling for crisis-centric time periods and market risk factors, contrarian trading strategies produce abnormal returns for poor corporate reputation firms but not for their good corporate reputation counterparts. Corporate reputation may be a driver of performance for poorly performing Australian firms and could be considered a stimulus for trading activity due to its explanatory capabilities.