Efficient production of ZnO nanowires by a ball milling and annealing method

ZnO powder was mechanically milled in a ball mill. This procedure was found to greatly increase its evaporation ability. The anomalous evaporation behaviour was caused by the disordered structure of the milled material and was not related to the increase in its surface area after milling. ZnO nanowires were synthesized by evaporation of this milled precursor. Nanowires with smooth and rough surfaces were present in the sample; the latter morphology was dominant. A green emission band centred at 510 nm was dominant in the cathodoluminescence spectrum of the nanowires.

One-dimensional nanomaterials synthesized using high-energy ball milling and annealing process

One-dimensional (1D) nanomaterials including nanotubes, nanowires and nanorods have many new properties, functionalities and a large range of promising applications. A major challenge for these future industrial applications is the large-quantity production. We report that the ball milling and annealing process has the potential to achieve the mass production. Several examples including C, BN nanotubes and SiC, Zn nanowires are presented to demonstrate such capability. In addition, both size and structure of 1D nanomaterials can be controlled by varying processing conditions. New growth mechanisms involved in the process have been investigated and the high-energy ball milling has an important role in the formation of these 1D nanomaterials.

‘Be yourself and have a ball’ : using a school and community based health education model to build young women’s resilience and connectedness

Recognition of the important role schools play in the promotion of student wellbeing can be seen in the growing number of polices and programs being implemented in schools across the Australia. This paper reports on some initial data from focus group interviews with year 9 and 10 girls involved in the pilot of a health and physical activity intervention designed to connect them to their local community and reconnect them with their school and their peers. The aim of the program was to build connectedness and resilience by engaging young women in non-traditional physical activities whilst providing them with a sound understanding of health issues relevant to adolescent girls. Situated in a relatively isolated rural community 200 kilometers south east of Melbourne the program was overwhelmingly delivered by regional and local agencies in conjunction with the local secondary school. The intervention was built on a partnerships model designed with the purpose of increasing participation and access for young women whilst building a sustainable program run in partnership between the school and local agencies and services. The initial data from this pilot indicates the program is having a positive impact on the young women’s sense of self and their bodies, their relationships with their peers and in reducing bullying behaviour amongst the girls. However the data raises some important questions around the adequacy of school-based health education, and the sustainability of approaches designed to be delivered by outside agencies rather than classroom teachers.

Older people playing ball : what is the risk of falling and injury?

Increasing physical activity amongst seniors is important for public health, yet guidance is needed to minimise injury risks. To describe the incidence of falls/injuries in a walking team ball game (Lifeball) designed for seniors, a prospective cohort study was undertaken amongst community dwelling Lifeball participants in Australia. Players completed a telephone survey soon after commencing Lifeball (2004) and 12 months later (2005). Attendance and incident records were audited for the period. Subjects joined a Lifeball group with opportunity to play at least once per week. Baseline was completed by 284 players aged between 40 and 96 years (mean 67 years), with most (83.8%, 238/284) female. Of 263 followed up, the average attendances was 25, with 19.3% attending on fewer than 4 occasions and 14.3% attending 52 or more times. Most (93.9%) reported no injuries requiring medical attention. However, 16 (6.1%) had injuries requiring medical attention and their 27 injuries represent an injury rate of 3.3 per 1000 hours of participation. Twenty participants (7.6%) had a Lifeball fall equating to a fall rate of 2.8 per 1000 hours of participation. Falls in Lifeball were not associated with measured predictors (age, gender, falls history, perceived falls risk or hours played). Incident records showed a trip/stumble involving rushing, walking backwards, or overextending (all against rules) as common falling causes. Lifeball is not ‘risk free’ however due to a lack of comparative data it is difficult to compare injury rate to relevant activities. Prevention of injury should concentrate on enforcing safety rules.

Reactive ball milling to produce nanocrystalline ZnO

Ball milling of zinc powders in oxygen atmosphere leads to nanocrystalline ZnO. The average grain size has a value of 9 nm. The zinc oxidation proceeds gradually. It is compared with the combustion oxidation reactions of metals (Zr, Ti, Fe and Sn) reported previously. We propose a new parameter ΔH/C_p(metal) instead of simplified adiabatic temperature to judge if the mechanochemical oxidation of a particular metal happens via gradual or combustion reaction.

Maximum likelihood estimation for rician distributed data in analytical q-ball imaging

Analytical q-ball imaging is widely used for reconstruction of orientation distribution function (ODF) using diffusion weighted MRI data. Estimating the spherical harmonic coefficients is a critical step in this method. Least squares (LS) is widely used for this purpose assuming the noise to be additive Gaussian. However, Rician noise is considered as a more appropriate model to describe noise in MR signal. Therefore, the current estimation techniques are valid only for high SNRs with Gaussian distribution approximating the Rician distribution. The aim of this study is to present an estimation approach considering the actual distribution of the data to provide reliable results particularly for the case of low SNR values. Maximum likelihood (ML) is investigated as a more effective estimation method. However, no closed form estimator is presented as the estimator becomes nonlinear for the noise assumption of the Rician distribution. Consequently, the results of LS estimator is used as an initial guess and the more refined answer is achieved using iterative numerical methods. According to the results, the ODFs reconstructed from low SNR data are in close agreement with ODFs reconstructed from high SNRs when Rician distribution is considered. Also, the error between the estimated and actual fiber orientations was compared using ML and LS estimator. In low SNRs, ML estimator achieves less error compared to the LS estimator.

Promoting a team ball game (Lifeball) to older people : who does this game attract and who continues?

Issue addressed: To describe the demographic and health-related characteristics (physical activity, self-reported health status, quality of life and falls history) of older people who enroll in a team-based game, Lifeball, and examine associations between continuation and participant characteristics. Reasons for stopping, participants' perceptions of the game and changes in health-related characteristics over 12 months were examined.

Methods: Telephone surveys were conducted with a cohort of Lifeball players at: baseline, soon after commencing playing and 12 months later.

Results: At baseline, participants were aged 40 to 96 years (mean 67). Most were female (84%), in good to excellent health (86%) and reported being sufficiently (>150 minutes per week) physically active (69%). Almost half (43%) were still playing 12 months later (continuers). Continuers were more likely to perceive Lifeball had helped them to: feel fitter and healthier (91%); improve their social life (73%); and be more active (53%). No significant changes in continuers' physical activity, self-reported health status and quality of life measures were reported. The main reason for stopping playing was illness/injury unrelated to Lifeball.

Conclusions: Lifeball mainly appealed to healthy, active older people.

Growth of V2O5 nanorods from ball-milled powders and their performance in cathodes and anodes of lithium-ion batteries

The two-stage procedure of ball milling and annealing in air represents a prospective method of preparing nanorods of V₂O₅ with electrochemical properties suitable for the application in lithium-ion batteries. Commercially purchased V₂O₅ powder is milled in a ball mill as the first step of the synthesis. The as-milled precursor is subsequently annealed in air to produce the morphology of nanorods via solid-state recrystallization. We have recently investigated intermediate stages of the formation of nanorods, and this paper summarizes the synthesis method including the description of the current understanding of the growth mechanism. The obtained V₂O₅ nanorods have been assessed as an electrode material for both anodes and cathodes of lithium-ion batteries. When used in cathodes, the nanorods demonstrate a better retention of capacity upon cycling than that of the commercially available powder of V₂O₅. When used in anodes, the performances of nanorods and the reference V₂O₅ powder are similar to a large extent, which is related to a different operating mechanism of V₂O₅ in anodes. The experimentally observed capacity of V₂O₅ nanorods in an anode has stabilized at the level of about 450 mAh/g after few cycles.

Maximum-likelihood based estimation for Q-ball imaging using diffusion-weighted MRI data

Q-ball imaging has been presented to reconstruct diffusion orientation distribution function using diffusion weighted MRI. In this thesiis, we present a novel and robust approach to satisfy the smoothness constraint required in Q-ball imaging. Moreover, we developed an improved estimator based on the actual distribution of the MR data.

Large-scale mechanical peeling of boron nitride nanosheets by low-energy ball milling

Mechanical cleavage by Scotch tape was the first method to produce graphene and is still widely used in laboratories. However, a critical problem of this method is the extremely low yield. We have tailored ball milling conditions to produce gentle shear forces that produce high quality boron nitride (BN) nanosheets in high yield and efficiency. The in-plane structure of the BN nanosheets has not been damaged as shown by near edge X-ray absorption fine structure measurements. The benzyl benzoate acts as the milling agent to reduce the ball impacts and milling contamination. This method is applicable to any layered materials for producing nanosheets.