Resonant acoustic mixing of polymer bonded explosives

Current Polymer Bonded Explosive (PBX) formulation is limited by a compromise - optimised final properties against processability. While solid loading (explosive content) would ideally be maximised and plasticiser content would ideally be minimised, this would make the formulation too viscous to cast into its casing and require long and arduous mixing processes using conventional techniques. However, with Resonant Acoustic Mixing (RAM), PBX formulation does not have to be constrained. Instead of traditional mixing blades, mixing is achieved by the use of a vibrating platform to impart acoustic pressure waves (vibrations) into the mixture, agitating it. The added ability to mix in the end use casing (mixing ‘in-situ’) also renders casting obsolete in many scenarios. In order to maximise the benefits of RAM with regards to next generation formulation-optimised PBX manufacture (‘PBneXt’), the underlying mechanisms of how the technique works, how efficiency (time and energy required for homogeneity) can be determined and maximised, and how final material properties may change between casting and ‘in-situ’ processing methods, must be better understood. The research aim of the PhD is therefore to assess how mixing efficiency of RAM can be measured and optimised to maximise its benefits, with a focus on how aspects of machine control and mixing vessel design can be altered to improve the mixing mechanisms on which the technique relies. Areas investigated experimentally include the effects of acceleration and mixer intensity (linked to power draw) setting, mixer model and unit, vessel material (with regards to surface free energy and thermal properties), and vessel surface finish (with regards to roughness). It is found that by modifying these variables, the time and energy required for mixing can be substantially reduced. A comparison between material properties of composites mixed ‘in-situ’ and ‘mixed and cast’ is also undertaken. The findings are then reconciled with wider literature observations and recommendations are made as how to best implement RAM for ‘PBneXt’ manufacture, ultimately allowing for explosive compositions with improved performance, mechanical, safety, and ageing properties

Evaluating the Efficacy of an Active Compression Brace on Orthostatic Cardiovascular Responses

Orthostatic intolerance, one of the principle causes of syncope, can occur secondary to concomitant venous pooling and enhanced capillary filtration. We aimed to evaluate a prototype portable calf active compression brace (ACB) designed to improve orthostatic haemodynamic control. Fourteen healthy volunteers participated in a randomized, placebo controlled, cross-over, double-blind study. Testing consisted of head-upright tilting and walking on a treadmill conducted on two consecutive days with a pair of ACBs wrapped around both calves. The ACB was actuated on one test day, but not on the other (placebo). Wearability, comfort, and ambulatory use of the ACB were assessed using questionnaires. The average calf pressure exerted by the ACB was 46.3±2.2 mmHg and the actuation pressure was 20.7±1.7 mmHg. When considering the differences between ACB actuation and placebo during tilt after supine rest there were trends for a larger stroke volume (+5.20±2.34%, p = 0.05) and lower heart rate (-5.12±2.41%, p = 0.06) with ACB actuation, with no effect on systolic arterial pressure (+4.86±3.41%, p = 0.18). The decrease in stroke volume after ten minutes of tilting was positively correlated with the height:calf circumference (r = 0.464; p = 0.029; n = 22; both conditions combined). The increase in heart rate after ten minutes of tilting was negatively correlated with the height:calf circumference (r = -0.485; p = 0.022; n = 22; both conditions combined) and was positively correlated with the average calf circumference (r = 0.539; p = 0.009; n = 22; both conditions combined). Participants reported good ACB wearability and comfort during ambulatory use. These data verify that the ACB increased stroke volume during tilting in healthy controls. Active calf compression garments may be a viable option for the management of orthostatic intolerance

The effects of age and sex on mandibular bone graft donor sites

Objectives Intra‐oral bone grafting relies on 3‐Dimensional understanding of mandibular anatomy. This study assessed the bone volume at the two most common intra‐oral bone harvesting sites, the retromandibular and symphyseal regions, and assessed the impact of age and sex on the available bone at these sites. Materials and Methods Demographic and anatomical data were collected from Cone Beam Computer Tomographs (CBCT’s) of 200 randomly selected, fully dentate participants (100 male / 100 female) between the ages of 24 and 86 years. Statistical analysis was conducted with SPSS V25, using ANalysis of COVAriance (ANCOVA) to determine the effects of age and sex on the measurements at the donor sites. Results At retromandibular sites, women have a broader alveolar crest with a narrower mandible at the level of the IDC. There is a statistically significant difference, between the sexes, in bone width from the buccal cortex to the IDC. Men have a significantly greater distance from the outer buccal plate to the IDC. There is no difference in any measured dimension at the symphyseal region. There is a statistically significant reduction in bone volume with increasing age at both mandibular sites of 0.03 ‐ 0.05mm annually, irrespective of tooth loss. Conclusion Anatomical variability due to sex and bone reduction with age are both important findings in dental implantology, which must be considered when treatment planning and selecting bone grafting sites in the mandible. This study reinforces the importance of pre‐operative CBCT in planning bone grafting procedures

Determination and optimisation of Resonant Acoustic Mixing (RAM) efficiency in Polymer Bonded eXplosive (PBX) processing

An investigation into how the efficiency (time and energy required for homogeneity) of Resonant Acoustic Mixing (RAM) can be determined and optimised was undertaken. An idealised Polymer Bonded eXplosive (PBX) simulant based on glass microbeads (28.3 um D50, 62% v/v in binder and plasticiser) was used for mixing. Mixing evolution was monitored using machine output data, whereby the mixer ‘intensity’ (related to power draw) was plotted against time. Experiments were undertaken with three acceleration settings, three mixer units, and three vessel materials of low, medium, and high surface free energy. Different stages of the mixer ‘intensity’ profiles were found to correspond to discrete stages of mixing, as well as further rheological changes due to continued frictional heating, thus viscosity reduction, beyond homogeneity being achieved. Time to mixing completion was found to be repeatable within a standard deviation of +/- 10%, strongly dependent on acceleration setting, and additionally dependent on vessel material, though additional data is required to confirm this. A significant difference in mixing time was observed between different LabRAM units. Partial vacuum application without degassing was beneficial for mixing. Finally, a paradigm linking the ‘movement modes’ of mixing was constructed, based on literature observations and the experimental results

Torsion and vibration-torsion levels of the S1 and ground cation electronic states of para-fluorotoluene

We investigate the low-energy transitions (0–570 cm-1) of the S1 state of para-fluorotoluene (pFT) using a combination of resonance-enhanced multiphoton ionization (REMPI) and zero-kinetic-energy (ZEKE) spectroscopy and quantum chemical calculations. By using various S1 states as intermediate levels, we obtain zero-kinetic-energy (ZEKE) spectra. The differing activity observed allows detailed assignments to be made of both the cation and S1 low-energy levels. The assignments are in line with the recently-published work on toluene from the Lawrance group [J. Chem. Phys. 143, 044313 (2015)], which considered vibration-torsion coupling in depth for the S1 state of toluene. In addition, we investigate whether two bands that occur in the range 390–420 cm-1 are the result of a Fermi resonance; we present evidence for weak coupling between various vibrations and torsions that contribute to this region. This work has led to the identification of a number of misassignments in the literature, and these are corrected

Rapid discrimination between methicillin-sensitive and methicillin-resistant Staphylococcus aureus by intact cell mass spectrometry

Rapid, accurate discrimination between methicillin-sensitive Staphylococcus aureus (MSSA) and methicillin-resistant S. aureus (MRSA) strains is essential for appropriate therapeutic management and timely intervention for infection control. A rapid method involving intact cell mass spectrometry (ICMS) is presented that shows promise for identification, discrimination of MSSA from MRSA and typing. In ICMS, cells from a bacterial colony are emulsified in a chemical matrix, added to a sample slide, dried and analysed by matrix-assisted laser desorption ionisation time-of-flight mass spectrometry (MALDI-TOF-MS). This technique examines the chemistry of the intact bacterial cell surface, yielding spectra consisting of a series of peaks from 500 to 10 000, which represent the mass:charge (m:z) ratios. Each peak corresponds to a molecular fragment released from the cell surface during laser desorption. Specimens can be prepared in a few seconds from plate cultures and a spectrum can be obtained within 2 min. ICMS spectra for 20 staphylococcal isolates showed characteristic peaks, some of which were conserved at species level, some at strain level and some were characteristic of the methicillin susceptibility status of the strain. ICMS may have potential for MRSA identification and typing, and may improve infection control measures

Validating the Cambridge Protocol: Reliability of Hip Muscle Strength Measurements Using a Motorized Dynamometer and Electromyography

Background: Muscle weakness is common after injury in athletes and in the presence of hip pathology. It will cause abnormal hip biomechanics and can predict future injury. However, objective measurement of hip muscle strength is difficult to perform accurately and reliably. Therefore, it is challenging to determine when an athlete has returned to preinjury levels of strength. In addition, there is currently no standardized method of obtaining measurements, which prevents the data being compared or shared between research centers. Purpose: The purpose of this study is to comprehensively assess the inter- and intraobserver reliability of our standardized muscle strength measurement protocol. Study Design: Descriptive laboratory study. Level of Evidence: Level 3, inception cohort study. Methods: A total of 16 healthy male volunteers (age = 28.3 ± 7.9 years) were recruited. Those with a previous history of hip injuries or disorders were excluded. These volunteers underwent strength testing according to the Cambridge Protocol on 4 separate occasions, performed by 2 independent assessors. Maximal voluntary contractions, fatigue torque fluctuations, and electromyography measurements were recorded. Intra- and interobserver reliability was assessed using intraclass correlation coefficient (ICC). Results: Good-to-excellent correlation was seen for both intra- and interobserver reliability across almost all hip movements for maximal contractions: ICC ranged 0.78 to 0.93 and 0.78 to 0.96, respectively. The standard error of the mean for all hip movements was also extremely low at 2% to 3%. Conclusion: The Cambridge Protocol is a highly reliable method for objective measurement of hip muscle strength. We recommend future studies use this protocol, or the principles underpinning it, to enable data sharing and comparison across different studies. Clinical Relevance: This is a description and analysis of hip muscle strength measurement. If widely used, it will allow for accurate and objective strength assessment and closer monitoring of hip injuries and pathology

Structure-based design, synthesis and biological evaluation of a novel series of isoquinolone and pyrazolo[4,3-c]pyridine inhibitors of fascin 1 as potential anti-metastatic agents

Fascin is an actin binding and bundling protein that is not expressed in normal epithelial tissues but overexpressed in a variety of invasive epithelial tumors. It has a critical role in cancer cell metastasis by promoting cell migration and invasion. Here we report the crystal structures of fascin in complex with a series of novel and potent inhibitors. Structure-based elaboration of these compounds enabled the development of a series with nanomolar affinities for fascin, good physicochemical properties and the ability to inhibit fascin-mediated bundling of filamentous actin. These compounds provide promising starting points for fascin-targeted anti-metastatic therapies

The Effects of Processing Variables on Resonant Acoustic Mixed Polymer Bonded Explosives

Poster presented at the 2018 Defence and Security Doctoral Symposium.Polymer Bonded Explosives (PBXs) are composite materials which consist of high explosive crystals bound in a polymer matrix. During manufacture, the crystals are dispersed throughout a liquid prepolymer, which is then cured into a crosslinked elastomeric solid. Dispersion can be achieved with Resonant Acoustic Mixing (RAM), a novel mixing technique which uses a vibrating platform to create longitudinal acoustic pressure waves which agitate the mixture. This work describes the outcomes of a comparison between the effects of different mixing vessel surfaces on process efficiency, and a way in which RAM equipment can be modified to mix PBX samples ‘in-situ’, in their end-use cases.NOTE: This poster is based on preliminary data that has since been superseded, additional details on where to find current work will be included here in due course.MBD