Penetration performance of protective materials from crossbow attack: a preliminary study.

Crossbow-related injuries resulting in serious and mortal consequences have increased in recent years, and although significant research exists for both injury and fatality on the human body, limited data exists on the lethality of the bolt and the failure modes of protective materials. This paper concerns itself with the experimental validation of four differing crossbow bolt geometries, their effects on material failure and potentially lethality. During this study, four different types of crossbow bolt geometries were tested against two protection mechanisms that differed in mechanical properties, geometry, mass and size. The results show that at 67 ms-1, ogive, field and combo tips do not provide lethal effect at 10-m range, whilst a broadhead tip will perforate both the para-aramid and a reinforced area of polycarbonate material consisting of two 3-mm plates at 63-66 ms-1. Although perforation was apparent with a more honed tip geometry, the chain mail layering within the para-aramid protection and friction caused by polycarbonate petalling on the arrow body reduced the velocity enough to demonstrate the materials under test are effective at withstanding crossbow attack. Subsequent calculation of the maximum velocity that arrows could achieve if fired from the crossbow within this study shows results close to the overmatch value of each material and therefore a requirement to advance the knowledge in this field to influence the development of more effective armour protection mechanisms.

Sustainable and economical alternatives to fragment capture materials in explosive and ballistic trials.

Strawboard has been utilised as a fragmentation capture material since the 1960s, mainly employed to capture fragments from explosives and explosive devices from arena trials of munitions. As this material has historically been calibrated to a known standard, it has a proven record of allowing research establishments to ascertain the velocity of a fragment based on the depth of penetration of the strawboard. During the time of calibration, strawboard was used as a common building material which was both widely available and relatively affordable; however, due to the recent economic crisis and geopolitical supply issues, this is no longer the case. Building on initial testing, this paper investigates alternatives to strawboard to determine if a cheaper, more readily available material can be used instead. The alternatives are compared and judged based on the NATO ARSP-03 guideline for capture material which includes metrics such as price and attainability, as well as assessing environmental impact and its ability to be used as a viable alternative to strawboard in an explosive environment. Based on these NATO guidelines, explosive fragmentation and ballistic experiments were conducted, and ten materials were tested based on the following criteria: Handling, Density, Flammability, Calibration, Cost and Availability. Medium Density Fibreboard (MDF) was found to be a suitable alternative to strawboard. The data demonstrates that it provides the same capture performance as strawboard at approximately a quarter of the cost and is far more readily available. Other materials also showed potential and further testing should be undertaken to validate these materials as alternatives to MDF.

Quantification of fragmentation capture materials and an assessment of the viability of economical alternatives: a preliminary study.

High pressure, high-temperature events need to be quantified experimentally. Where fragmentation occurs, i.e. against personal protective equipment, there is a requirement for both a reliable and repeatable measurement of numerous experimental metrics. Typically, the most critical is calculating the energy absorbed by the target material, to characterize target performance. This is achieved by detonating a device and capturing a proportion of the fragmentation in a suitable material that can achieve successful recovery of all fragmentation produced. Therefore, allowing the estimation of the target's response using the depth of penetration within the capture material which allows the calculation of energy absorption. The current standardized fragmentation capture material used within the UK is known as strawboard. Although effective, this material is both expensive and limited in its availability. This study explores the classification of strawboard to provide a suitable baseline to compare against medium density fibreboard (MDF) and flooring underlay, which represent two more economically friendly alternatives on the openmarket. It was found that the uniformity of response for the MDF material was better than that of strawboard, due to its reproducibility between batches and velocity ranges. To further explore this phenomena, high explosive trials were conducted, further demonstrating MDF to be a viable, reliable and cheaper alternative. This article is part of the theme issue 'Exploring the length scales, timescales and chemistry of challenging materials (Part 2)'.

A scanning electron microscopy study of projectile entry fractures in cortical bone; genesis and microarchitectural features.

The present paper presents a scanning electron microscope (SEM) analysis of the genesis and microarchitecture of experimentally induced cortical entry fractures in porcine scapulae impacted at velocities ranging from 54 to 897 m/s. SEM observation was conducted on polyurethane replicas cast from negative silicone moulds. Analysis of the sequence of fracture processes operative during projectile impact revealed the presence of ring cracks at the site of impact, confirming that penetration in sandwich bones is achieved by cone crack propagation. Despite impulsive loading, two forms of plastic deformation were identified in the cortical bone surrounding the entry fracture up to a maximum velocity of 871 m/s. Microscopic radial and concentric cracks were associated with projectile impact, and the role of pores and pits as stress concentrators was captured. Possible underlying mechanisms for the observed plastic deformation are described, and the diagnostic utility of SEM analysis is presented.

Photocatalytic water disinfection by simple and low-cost monolithic and heterojunction ceramic wafers.

In this work, the photocatalytic disinfection of Escherichia coli (E. coli) using dual layer ceramic wafers, prepared by a simple and low-cost technique, was investigated. Heterojunction wafers were prepared by pressing TiO2 and WO3 powders together into 2 layers within a single, self-supported monolith. Data modelling showed that the heterojunction wafers were able to sustain the formation of charged species (after an initial "charging" period). In comparison, a wafer made from pure TiO2 showed a less desirable bacterial inactivation profile in that the rate decreased with time (after being faster initially). The more favourable kinetics of the dual layer system was due to superior electron-hole vectorial charge separation and an accumulation of charges beyond the initial illumination period. The results demonstrate the potential for developing simplified photocatalytic devices for rapid water disinfection.

An assessment of a non-destructive magneto-optical imaging technique for the recovery of laser engraved marks from steel plates and firearm components.

The International Tracing Instrument (ITI) is a document adopted by United Nations Member States in 2005, which outlines challenges faced in the tracing of illicit weapons and offers suggestions to increase the success of tracing operations. A key provision of the ITI states that serial numbers must be recoverable if obliterated. This research, therefore, investigates two methods of recovering laser engraved marks on steel, due to the increase in firearms manufacturing relying on lasers to apply critical markings. This work uses 20 steel plates (CR4 grade), 6 AK-pattern rifle top covers, and a steel pistol slide to investigate the potential for visualising laser engraved marks. All samples had marks applied using a BWM-30F Fibre laser marking machine, in addition to any original manufacture's stamped marks on the pistol. All marks were removed using a grinding belt (plates) and a Dremel® rotary tool (slide and top covers) to average depths of 1200 µm (stamped) and 240 µm (laser engraved). Recovery of the marks was attempted using two techniques to compare the two techniques in their ability to recover laser engraved marks; Regula Forensics® Eddy Current Recovery kit, followed by traditional Fry's reagent. Both recovery techniques recovered 100 % (n = 6) of the stamped characters on the pistol slide, and 0 % (n = 509) of the laser engraved characters on the pistol, top covers and steel plates. Recommendations are made for forensic firearms examiners to avoid attempting the recovery of laser engraved marks using Fry's reagent to preserve the integrity of evidence. It is also suggested that manufacturers avoid laser engraving unique identifying marks on firearms, and to use more permanent methods, such as stamping, to remain compliant with politically binding documents such as the ITI.

Ballistic impact of hollow-point ammunition on porcine bone.

Identifying failure mechanisms in skeletal tissue allows a deeper understanding of the effects of specific projectile impacts on bone. While ballistic trauma in flat bones is largely researched, knowledge of how long bones react to gunshot impacts is limited in the literature. The impacts of deforming ammunition appear to produce higher levels of fragmentation; however, these have not been studied in depth. This study compares the damage to femora bone by HP 0.357 and 9 mm projectiles constructed with both full and semi-metal jackets. Impact experiments were undertaken on a single-stage light gas gun involving the use of a high-speed video camera and full reconstruction of the bones to ascertain fracture patterns occurring in the femora. Higher degrees of fragmentation are likened to the presence of semi-jacketed HP projectiles than jacketed HP projectiles. The observations of external facing beveled edges are believed to be associated with the increased separation of the jacket and lead core of projectiles. Additionally, experimentation has shown that the amount of kinetic energy lost postimpact is likely related to the presence or the absence of a metal jacket on an HP projectile. The observed data, therefore, suggest that the composition, rather than the configuration, of a projectile affects the type and extent of the damage.

The use of a predictive threat analysis to propose revisions to existing risk assessments for precursor chemicals used in the manufacture of home-made explosives (HME).

Improvised explosive devices (IEDs) have generated over 137,000 civilian casualties in the past decade, more than any other explosive weapon system in the same period with a far-reaching impact on personal security freedoms across 50 affected countries. The aim of this paper is to consolidate existing risk management processes to control the availability of chemical precursors used in the manufacture of home-made explosives (HME) and to recommend global standards for market regulations in their composition, sale and use. This will be achieved by assessing the current regional regulations for three common chemical precursors (hydrogen peroxide, ammonium nitrate and potassium chlorate), and proposing a risk management process to identify key precursor chemicals that require greater control.

In Vivo Water Dynamics in Shewanella oneidensis Bacteria at High Pressure.

Following observations of survival of microbes and other life forms in deep subsurface environments it is necessary to understand their biological functioning under high pressure conditions. Key aspects of biochemical reactions and transport processes within cells are determined by the intracellular water dynamics. We studied water diffusion and rotational relaxation in live Shewanella oneidensis bacteria at pressures up to 500 MPa using quasi-elastic neutron scattering (QENS). The intracellular diffusion exhibits a significantly greater slowdown (by -10-30%) and an increase in rotational relaxation times (+10-40%) compared with water dynamics in the aqueous solutions used to resuspend the bacterial samples. Those results indicate both a pressure-induced viscosity increase and slowdown in ionic/macromolecular transport properties within the cells affecting the rates of metabolic and other biological processes. Our new data support emerging models for intracellular organisation with nanoscale water channels threading between macromolecular regions within a dynamically organized structure rather than a homogenous gel-like cytoplasm.

Pressure as a Limiting Factor for Life.

Facts concerning the stability and functioning of key biomolecular components suggest that cellular life should no longer be viable above a few thousand atmospheres (200-300 MPa). However, organisms are seen to survive in the laboratory to much higher pressures, extending into the GPa or even tens of GPa ranges. This is causing main questions to be posed concerning the survival mechanisms of simple to complex organisms. Understanding the ultimate pressure survival of organisms is critical for food sterilization and agricultural products conservation technologies. On Earth the deep biosphere is limited in its extent by geothermal gradients but if life forms exist in cooler habitats elsewhere then survival to greater depths must be considered. The extent of pressure resistance and survival appears to vary greatly with the timescale of the exposure. For example, shock experiments on nanosecond timescales reveal greatly enhanced survival rates extending to higher pressure. Some organisms could survive bolide impacts thus allowing successful transport between planetary bodies. We summarize some of the main questions raised by recent results and their implications for the survival of life under extreme compression conditions and its possible extent in the laboratory and throughout the universe.

Water Dynamics in Shewanella oneidensis at Ambient and High Pressure using Quasi-Elastic Neutron Scattering.

Quasielastic neutron scattering (QENS) is an ideal technique for studying water transport and relaxation dynamics at pico- to nanosecond timescales and at length scales relevant to cellular dimensions. Studies of high pressure dynamic effects in live organisms are needed to understand Earth's deep biosphere and biotechnology applications. Here we applied QENS to study water transport in Shewanella oneidensis at ambient (0.1 MPa) and high (200 MPa) pressure using H/D isotopic contrast experiments for normal and perdeuterated bacteria and buffer solutions to distinguish intracellular and transmembrane processes. The results indicate that intracellular water dynamics are comparable with bulk diffusion rates in aqueous fluids at ambient conditions but a significant reduction occurs in high pressure mobility. We interpret this as due to enhanced interactions with macromolecules in the nanoconfined environment. Overall diffusion rates across the cell envelope also occur at similar rates but unexpected narrowing of the QENS signal appears between momentum transfer values Q = 0.7-1.1 Å(-1) corresponding to real space dimensions of 6-9 Å. The relaxation time increase can be explained by correlated dynamics of molecules passing through Aquaporin water transport complexes located within the inner or outer membrane structures.

Iron reduction by the deep-sea bacterium Shewanella profunda LT13a under subsurface pressure and temperature conditions.

Microorganisms influence biogeochemical cycles from the surface down to the depths of the continental rocks and oceanic basaltic crust. Due to the poor recovery of microbial isolates from the deep subsurface, the influence of physical environmental parameters, such as pressure and temperature, on the physiology and metabolic potential of subsurface inhabitants is not well constrained. We evaluated Fe(III) reduction rates (FeRRs) and viability, measured as colony-forming ability, of the deep-sea piezophilic bacterium Shewanella profunda LT13a over a range of pressures (0-125 MPa) and temperatures (4-37∘C) that included the in situ habitat of the bacterium isolated from deep-sea sediments at 4500 m depth below sea level. S. profunda LT13a was active at all temperatures investigated and at pressures up to 120 MPa at 30∘C, suggesting that it is well adapted to deep-sea and deep sedimentary environments. Average initial cellular FeRRs only slightly decreased with increasing pressure until activity stopped, suggesting that the respiratory chain was not immediately affected upon the application of pressure. We hypothesize that, as pressure increases, the increased energy demand for cell maintenance is not fulfilled, thus leading to a decrease in viability. This study opens up perspectives about energy requirements of cells in the deep subsurface.

Laboratory investigation of high pressure survival in Shewanella oneidensis MR-1 into the gigapascal pressure range.

The survival of Shewanella oneidensis MR-1 at up to 1500 MPa was investigated by laboratory studies involving exposure to high pressure followed by evaluation of survivors as the number (N) of colony forming units (CFU) that could be cultured following recovery to ambient conditions. Exposing the wild type (WT) bacteria to 250 MPa resulted in only a minor (0.7 log N units) drop in survival compared with the initial concentration of 10(8) cells/ml. Raising the pressure to above 500 MPa caused a large reduction in the number of viable cells observed following recovery to ambient pressure. Additional pressure increase caused a further decrease in survivability, with approximately 10(2) CFU/ml recorded following exposure to 1000 MPa (1 GPa) and 1.5 GPa. Pressurizing samples from colonies resuscitated from survivors that had been previously exposed to high pressure resulted in substantially greater survivor counts. Experiments were carried out to examine potential interactions between pressure and temperature variables in determining bacterial survival. One generation of survivors previously exposed to 1 GPa was compared with WT samples to investigate survival between 37 and 8°C. The results did not reveal any coupling between acquired high pressure resistance and temperature effects on growth.