Text messaging is a useful reminder tool

Introduction Longitudinal studies of adolescents must be ‘adolescent-friendly’, to collect data and to encourage maintenance in the study cohort. Text messaging may offer a feasible means to do both. Methods Adolescents in the Adolescent Rural Cohort, Hormones and Health, Education, Environments and Relationships (ARCHER) study (n=342) are sent automated text messages every 3 months, prompting biological specimen collection. Results A total of 99.2% of participants (or their parents) owned a mobile phone, of which 89.1% of participants responded to text messages and 97.3% of intended urine samples were collected. The average time to provide a urine sample after prompting correlated with time to reply to Short Message Service (SMS). Conclusions This study shows SMS can be used effectively in longitudinal research involving adolescents and is feasible and useful as a reminder tool for regular biological specimen collection.Australian National Health and Medical Research Counci

The shock compression of microorganism-loaded broths and emulsions: Experiments and simulations

By carefully selecting flyer plate thickness and the geometry of a target capsule for bacterial broths and emulsions, we have successfully subjected the contents of the capsule to simultaneous shock and dynamic compression when subjected to a flyer-plate impact experiment. The capsules were designed to be recovered intact so that post experimental analysis could be done on the contents. ANSYS® AUTODYN hydrocode simulations were carried out to interrogate the deformation of the cover plate and the wave propagation in the fluid. Accordingly, we have shown that microorganisms such as Escherichia coli, Enterococcus faecalis and Zygosaccharomyces bailii are not affected by this type of loading regime. However, by introducing a cavity behind the broth we were able to observe limited kill in the yeast sample. Further, on using this latter technique with emulsions it was shown that greater emulsification of an oil-based emulsion occurred due to the cavitation that was introduced

Penetration of a woven CFRP laminate by a high velocity steel sphere impacting at velocities of up to 1875 m/s

The impact of a woven 6 mm thick CFRP laminate has been subjected to impact by an annealed steel sphere up to velocities of 1875 m/s. It was observed that above a threshold impact energy, the percentage of kinetic energy dissipated by the laminate was constant. Further, the level of damage, as measured by C-Scan and through-thickness microscopy remained roughly constant as the impact energy was increased. However, the size of the hole formed increased. This suggested that the energy transferred to the target in the velocity range of interest became independent of the delamination. Consequently, the main energy transfer mechanism at the high velocities of impact is thought to be due to the cavity expansion and more importantly, the kinetic energy of the particulates

Penetration of a glass-faced transparent elastomeric resin by a lead-antimony- cored bullet

The penetration of the lead antimony-cored 7.62 mm × 51 mm bullet into a glass- faced polyurethane elastomeric polymer resin has been studied. The resulting craters in the resin contained elongated bullet core material that had a significant amount of porosity. A simple linear viscoelastic model was applied to AUTODYN-2D to describe the behaviour of the resin and numerical results of the penetration mechanism and depth-of-penetration appeared to match experimental observations well. Analysis of the high speed photography and a numerical model of this bullet penetrating a viscoelastic polymer showed that during the initial stages of penetration, the projectile is essentially turned inside out. Furthermore, the shape of the cavity was defined by the elastic relaxation of the polymer that led to compression of the core material. A weight analysis of the penetrated materials showed that using a thicker tile of glass resulted in better ballistic performanc

Modelling penetration events in tissue simulants

Tissue simulants are used widely in ballistics to approximate the effect of a projectile on the human body. Many materials classically chosen to investigate such interactions are selected either for their visual effect or on an apparent structural similarity with human tissue – classic examples are soap and gelatin respectively. In this paper, the authors begin to assess the high strain-rate, dynamic mechanical response of these flesh simulants with the aim of providing material properties and calibration data to inform future hydrocode models to aid in investigation of real wounding mechanisms. To this end, equations of state (EOS) for ballistic gelatin and soap have been measured and are presented here along with physical testing data; these results provide a case for the development of hydrocode models that could ultimately predict the outcome of simulant penetrations. CT scanning has provided a useful method of extracting the physical data required for ultimate model validation

An experimental investigation into the micro-mechanics of spall initiation and propagation in Ti–6Al–4V during shock loading

Titanium alloys have long been considered candidate materials for use in monolithic armor systems due to their excellent specific mechanical properties and relative ease of manufacture. However, high production costs combined with a propensity to fail due to adiabatic shear band formation and spallation have limited the adoption of titanium alloys in armor systems. In this paper, the spall behavior of the workhorse titanium alloy, Ti–6Al–4V, is investigated via a series of plate impact experiments. Back-scatter electron (BSE) microscopy and electron back-scatter diffraction (EBSD) are carried out on recovered specimens to investigate the nature of spall initiation and propagation. It is found that spall initiation occurs by the nucleation of voids at the grain boundaries between plastically hard/soft grains of the dominant hcp α phase. Further, it is shown that spall then propagates via the growth/coalescence of the nucleated voids into facets, followed by the coalescence of the facets through highly localized ductile bridging. A number of suggestions are made to improve the spall resistance of titanium alloys based on these observations

The dynamic behaviour of ballistic soap

Ballistic soap is used as a simulant to observe the effect of a projectile penetrating soft tissue; consequently information on its behaviour at high strain-rates is desirable. The Hugoniot equation-of-state for soap has been determined using the plate-impact technique at impact velocities of 81-967 m/s. The US-uP Hugoniot was linear, taking the form US = 1.99 + 2.04uP (?0 = 1.107 g/cc). In P-uP space the Hugoniot was observed to trend substantially above the predicted hydrodynamic response for Hugoniot stresses greater than 1.2 GPa, indicative of material strengthening. The lateral-stress response of soap was interrogated using embedded lateral manganin stress gauges. Gradients observed behind the shock for ?x > 1 GPa appeared to suggest continuation of the previously observed strengthening mechanism. It is proposed at higher values of ?x, increased compression of hydrocarbon chains acts to increase the materials resistance to shear, a phenomenon known as steric hindrance

On the response of ballistic soap to one-dimensional shock loading

The effects of projectile penetration into soft tissue are often studied using the tissue simulant ballistic soap. Consequently, a full understanding of the high strain-rate response of ballistic soap is desirable. Using the plate-impact technique, key shock parameters have been measured for impacts in the range 81-968 m/s, allowing derivation of the Hugoniot equation-of-state for soap in the US-uP and P-uP planes. A linear Hugoniot relationship was found in the US-uP plane, with the general form US = 2.05 + 1.75uP (?0 = 1.107 g/cc). In P-uP space an apparent strengthening phenomenon was observed, with the Hugoniot trending above the hydrodynamic response at impact stresses greater than 1.2 GPa. Embedded lateral manganin stress gauges were employed to interrogate the evolution of lateral stress within the soap. A gradient in lateral stress, whose magnitude increased incrementally with impact stress, was apparent behind the shock for ?x > 1 GPa. This appeared to suggest a continuation of the previously highlighted strengthening mechanism. It is proposed that at higher values of ?x, increased compression of hydrocarbon chains acts to increase the material's resistance to shear, a phenomenon consistent with steric hindrance

On the dynamic behaviour of three readily available soft tissue simulants

Plate-impact experiments have been employed to investigate the dynamic response of three readily available tissue simulants for ballistic purposes: gelatin, ballistic soap (both sub-dermal tissue simulants) and lard (adipose layers). All three materials exhibited linear Hugoniot equations-of-state in the US-uP plane. While gelatin behaved hydrodynamically under shock, soap and lard appeared to strengthen under increased loading. Interestingly, the simulants under test appeared to strengthen in a material-independent manner on shock arrival (tentatively attributed to a re-arrangement of the amorphous molecular chains under loading). However, material-specific behaviour was apparent behind the shock. This behaviour appeared to correlate with microstructural complexity, suggesting a steric hindrance effect