Browsing by Author "Fitzmaurice, Brianna C."

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    Bacterial survival following shock compression in the GigaPascal range
    (Elsevier, 2017-09-01) Hazael, Rachael; Fitzmaurice, Brianna C.; Foglia, Fabrizia; Appleby-Thomas, Gareth J.; McMillan, Paul F.
    The possibility that life can exist within previously unconsidered habitats is causing us to expand our understanding of potential planetary biospheres. Significant populations of living organisms have been identified at depths extending up to several km below the Earth's surface; whereas laboratory experiments have shown that microbial species can survive following exposure to GigaPascal (GPa) pressures. Understanding the degree to which simple organisms such as microbes survive such extreme pressurization under static compression conditions is being actively investigated. The survival of bacteria under dynamic shock compression is also of interest. Such studies are being partly driven to test the hypothesis of potential transport of biological organisms between planetary systems. Shock compression is also of interest for the potential modification and sterilization of foodstuffs and agricultural products. Here we report the survival of Shewanella oneidensis bacteria exposed to dynamic (shock) compression. The samples examined included: (a) a "wild type" (WT) strain and (b) a "pressure adapted" (PA) population obtained by culturing survivors from static compression experiments to 750 MPa. Following exposure to peak shock pressures of 1.5 and 2.5 GPa the proportion of survivors was established as the number of colony forming units (CFU) present after recovery to ambient conditions. The data were compared with previous results in which the same bacterial samples were exposed to static pressurization to the same pressures, for 15 minutes each. The results indicate that shock compression leads to survival of a significantly greater proportion of both WT and PA organisms. The significantly shorter duration of the pressure pulse during the shock experiments (2-3 μs) likely contributes to the increased survival of the microbial species. One reason for this can involve the crossover from deformable to rigid solid-like mechanical relaxational behavior that occurs for bacterial cell walls on the order of seconds in the time dependent strain rate.
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    The effects of quasi-one-dimensional shock on Escherichia coli while controlling pressure and temperature
    (Elsevier, 2020-11-28) Fitzmaurice, Brianna C.; Appleby-Thomas, Gareth J.; Painter, Jonathan; Wood, David C.; Hazael, Rachael
    The response of microorganisms to high pressures is of growing interest in the literature, regarding areas of research including the sterilisation of foodstuffs, panspermia and, more generally, the study of extremophiles. When examining organisms under shock pressure, there are a number of caveats that need to be considered, including temperature and the nature of the shock wave front. Both of these caveats have been explored in this study through the application of the plate impact technique to create quasi-one-dimensional shock waves with controlled shock fronts through bacterial targets. This was achieved using typical planar flyer plates to study the dynamic pressure response of the bacterium, Escherichia coli NCTC 10538. Additionally, in order to create an adiabatic, off-Hugoniot loading path, a novel graded areal density flyer produced by the Surfi-Sculpt® approach was used to assess the effects of lowering temperature during shock on E. coli growth rates. The maximum temperature generated by a Surfi-Sculpt® flyer impact was 5 K less than that produced by the planar flyer analogue. Higher growth rates of bacterial colonies post-impact by the Surfi-Sculpt® flyer compared to those by the planar flyer were observed, with this behaviour determined to be a possible function of the nature, although temperature was also decreased with the use of this adiabatic ramp loading technique. In an effort to purposefully increase pressure and temperature for the E. coli samples, a modified form of a previously developed bacterial encapsulation system was also employed in this study, allowing pressures of up to 10 GPa and growth rates of up to 0.09% to be reached.
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    Investigation of the high-strain rate (shock and ballistic) response of the elastomeric tissue simulant Perma-Gel®
    (Elsevier, 2016-04-01) Appleby-Thomas, Gareth J.; Wood, David C.; Hameed, Amer; Painter, Jonathan; Le-Seelleur, Victoria; Fitzmaurice, Brianna C.
    For both ethical and practical reasons accurate tissue simulant materials are essential for ballistic testing applications. A wide variety of different materials have been previously adopted for such roles, ranging from gelatin to ballistics soap. However, while often well characterised quasi-statically, there is typically a paucity of information on the high strain-rate response of such materials in the literature. Here, building on previous studies by the authors on other tissue analogues, equation-of-state data for the elastomeric epithelial/muscular simulant material Perma-Gel® is presented, along with results from a series of ballistic tests designed to illustrate its impact-related behaviour. Comparison of both hydrodynamic and ballistic behaviour to that of comparable epithelial tissues/analogues (Sylgard® and porcine muscle tissue) has provided an insight into the applicability of both Perma-Gel® and, more generally, monolithic simulants for ballistic testing purposes. Of particular note was an apparent link between the high strain-rate compressibility (evidenced in the Hugoniot relationship in the Us-up plane) and subsequent ballistic response of these materials. Overall, work conducted in this study highlighted the importance of fully characterising tissue analogues – with particular emphasis on the requirement to understand the behaviour of such analogues under impact as part of a system as well as individually.
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    On differences in the equation-of-state for a selection of seven representative mammalian tissue analogue materials
    (Elsevier, 2017-10-10) Appleby-Thomas, Gareth J.; Fitzmaurice, Brianna C.; Hameed, Amer; Painter, Jonathan; Gibson, Michael C.; Wood, David C.; Hazael, Rachael; Hazell, Paul J.
    Tissue analogues employed for ballistic purposes are often monolithic in nature, e.g. ballistic gelatin and soap, etc. However, such constructs are not representative of real-world biological systems. Further, ethical considerations limit the ability to test with real-world tissues. This means that availability and understanding of accurate tissue simulants is of key importance. Here, the shock response of a wide range of ballistic simulants (ranging from dermal (protective / bulk) through to skeletal simulant materials) determined via plate-impact experiments are discussed, with a particular focus on the classification of the behaviour of differing simulants into groups that exhibit a similar response under high strain-rate loading. Resultant Hugoniot equation-of-state data (Us-up; P-v) provides appropriate feedstock materials data for future hydrocode simulations of ballistic impact events.
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    On the effects of powder morphology on the post-comminution ballistic strength of ceramics
    (Elsevier, 2016-10-29) Appleby-Thomas, Gareth J.; Wood, David C.; Hameed, Amer; Painter, Jonathan; Fitzmaurice, Brianna C.
    In this paper in order to try and elucidate the effects of particle morphology on ballistic response of comminuted systems, a series of experiments were carried out via the use of powder compacts with differing initial particle morphologies. This approach provided a route to readily manufacture comminuted armour analogues with significantly different microstructural compositions. In this study pre-formed `fragmented-ceramic' analogues were cold-pressed using plasma-spray alumina powders with two differing initial morphologies (angular and spherical). These compacts were then impacted using 7.62-mm FFV AP (Förenade Fabriksverken Armour Piercing) rounds with the subsequent depth-of-penetration of the impacting projectile into backing Al 6082 blocks used to provide a measure of pressed ceramic ballistic response. When material areal density was accounted for via differing ballistic efficiency calculations a strong indication of particle morphology influence on post-impact ceramic properties was apparent. These results were reinforced by a separate small series of plate-impact experiments, whose results indicated that powder morphology had a strong influence on the nature of compact collapse.
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    On the shock behaviour and response of Ovis Aries vertebrae
    (European Society of Biomechanics, 2016-07-10) Wood, David C.; Appleby-Thomas, Gareth J.; Fitzmaurice, Brianna C.; Franceskides, Constantinos; Shanker, Tobias; Zioupos, Peter; Samra, Amarjit
    When investigating a biological system during shock loading, it is best practice to isolate different components to fully comprehend each individual part [1,2] before building up the system as a whole. Due to the high acoustic impedance of bone in comparison to other biological tissues [3] the majority of the shock will be transmitted into this medium, and as such can cause large amounts of damage to other parts of the body potentially away from the impact area.
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    Pressure tolerance of Artemia cysts compressed in water medium
    (Taylor and Francis, 2019-02-04) Hazael, Rachael; Matsuda, Shinsuke; Mori, Yoshihisa; Fitzmaurice, Brianna C.; Appleby-Thomas, Gareth J.; Painter, Jonathan; Meersman, Filip; Richaud, Myriam; Galas, Simon; Saini, Naurang L.; Ono, Fumihisa; McMillan, Paul F.
    The high pressure tolerance of cysts of Artemia salina was investigated up to several GPa in water. No survival was observed after exposure to 1.0 GPa for 15 min. After exposure to 2.0 GPa for the same time duration, the hatching rate had recovered to 33%, but decreased to 8% following compression at 7.5 GPa. This contrasts with results using Fluorinert™ as the pressure-transmitting medium where 80–88% recovery was observed. The lower survival rate in water is accompanied by swelling of the eggs, indicating that liquid H2O close to the ice-VI crystallization pressure penetrated inside the eggs. This pressure exceeds the stability limit for proteins and other key biomolecules components within the embryos that could not be resuscitated. Rehydration takes several minutes and so was not completed for all samples compressed to higher pressures, prior to ice-VI formation, resulting in renewed survival. However H2O penetration inside the shell resulted in increased mortality
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    The shock response of biomaterials
    (Cranfield University, 2018) Fitzmaurice, Brianna C. ; Appleby-Thomas, Gareth J.; Painter, Jonathan
    The shock response of microorganisms is of particular interest to many different areas of research including, but not limited to: asteroid and meteoritic impacts and origins of life; food sterilisation; and deep-sea organisms. The primary interest behind the investigation presented in this thesis is the origins of life and how, if life began elsewhere in the universe, it could survive transfer from one planetary body to the next. This ties in with the theory of panspermia and suggests that life on Earth, or its building blocks, may have originated elsewhere in the universe and was transferred here via an asteroid or meteor. Aside from the many other caveats that travel through space would present to an organism, such as extreme temperatures and ionising radiation, to survive a meteoritic impact onto a planetary body would be to survive extreme shock pressures as well. The purpose of this investigation, therefore, was to examine a number of organisms under quasi-one-dimensional shock loading conditions in order to assess the organisms’ response to shock pressure. The microorganisms chosen were Escherichia coli NCTC 10538 and Saccharomyces cerevisiae ATCC 18824, two model organisms, a prokaryote and a eukaryote, respectively, whose biochemistry is well characterised. The shock loading experiments were carried out in a 50 mm bore single stage gas gun using the plateimpact technique. The bio-samples were contained within a capsule system that allowed them to be safely contained and retrieved after the shock so that their growth rates could be assessed. E. coli was subjected to shock pressures ranging from 0.55 to 10 GPa under various different shock conditions, yielding growth rates of 6% to 0.09%, respectively. S. cerevisiae was shock loaded to from 0.49 to 2.33 GPa with resulting growth rates ranging from 1.8% to zero growth. Additionally, to probe further into how life forms of varying complexity might respond to these shock pressures, the multicellular organism, Artemia salina, was shock loaded under the same conditions, but only up to a maximum pressure of 1.5 GPa. It was noted that Artemia cysts showed hatching rates of up to 18% at this pressure, but this was not always without residual damage to the shell and the embryo within. Since pressure gauges could not be attached to the target capsule due to the complexity of the set-up, validated numerical models had to be employed to interrogate the pressures occurring within the sample. This also gave an indication as to the type of loading occurring within the sample. It was also desired to measure temperatures occurring during shock loading and to explore methods to better control this so that samples could be shocked to a particular pressure, while still controlling temperature. This was achieved using a novel type of flyer plate called Surfi-Sculpt® while validated numerical models were again used to estimate peak temperatures inside the capsule containing the biological sample. From the findings of a variety of shock experiments carried out throughout this project, a number of mechanisms were proposed to explain some of the results seen, providing insight into how microorganisms in particular might survive high shock pressures.
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    Tolerance of Artemia to static and shock pressure loading
    (IOP Publishing, 2017-11-04) Fitzmaurice, Brianna C.; Appleby-Thomas, Gareth J.; Painter, Jonathan; Ono, Fumihisa; McMillan, Paul F.; Hazael, Rachael; Meersman, Filip
    Hydrostatic and hydrodynamic pressure loading has been applied to unicellular organisms for a number of years due to interest from food technology and extremophile communities. There is also an emerging interest in the response of multicellular organisms to high pressure conditions. Artemia salina is one such organism. Previous experiments have shown a marked difference in the hatching rate of these organisms after exposure to different magnitudes of pressure, with hydrostatic tests showing hatching rates at pressures up to several GPa, compared to dynamic loading that resulted in comparatively low survival rates at lower pressure magnitudes. In order to begin to investigate the origin of this difference, the work presented here has focussed on the response of Artemia salina to (quasi) one-dimensional shock loading. Such experiments were carried out using the plate-impact technique in order to create a planar shock front. Artemia cysts were investigated in this manner along with freshly hatched larvae (nauplii). The nauplii and cysts were observed post-shock using optical microscopy to detect motility or hatching, respectively. Hatching rates of 18% were recorded at pressures reaching 1.5 GPa, as determined with the aid of numerical models. Subjecting Artemia to quasi-one-dimensional shock loading offers a way to more thoroughly explore the shock pressure ranges these organisms can survive.