Intrinsic dynamics of emulsions: Experiments in microgravity on the International Space Station.

HYPOTHESIS: In order to understand the basic mechanisms affecting emulsion stability, the intrinsic dynamics of the drop population must be investigated. We hypothesize that transient ballistic motion can serve as a marker of interactions between drops. In 1G conditions, buoyancy-induced drop motion obscures these interactions. The microgravity condition onboard the International Space Station enable this investigation. EXPERIMENTS: We performed Diffusing Wave Spectroscopy (DWS) experiments in the ESA Soft Matter Dynamics (SMD) facility. We used Monte Carlo simulations of photon trajectory to support data analysis. The analysis framework was validated by ground-based characterizations of the initial drop size distribution (DSD) and the properties of the oil/water interface in the presence of surfactant. FINDINGS: We characterized the drop size distribution and found to be bi-disperse. Drop dynamics shows transient ballistic features at early times, reaching a stationary regime of primarily diffusion-dominated motion. This suggests different ageing mechanisms: immediately after emulsification, the main mechanism is coalescence or aggregation between small drops. However at later times, ageing proceeds via coalescence or aggregation of small with large drops in some emulsions. Our results elucidate new processes relevant to emulsion stability with potential impact on industrial processes on Earth, as well as enabling technologies for space exploration.

Ballistic Nerve Injuries: State of the Evidence and Approach to the Patient Based on Experience.

Nerve injuries secondary to gunshot wounds (GSWs) have been traditionally thought of as neurapraxic injuries with high likelihood of complete recovery. A review of the literature, however, highlights the misconceptions surrounding ballistic nerve injuries and their treatments. Contrary to this accepted dogma, approximately 30% to 60% of GSWs to the upper extremity may result in nerve injury requiring repair or reconstruction. Surgical exploration following ballistic injury reveals that 20% to 55% of nerves were lacerated requiring repair or grafting. Despite these numbers, outcomes after nerve repair or grafting are limited, and the limited data show evidence of poor functional recovery. In our experience, delayed exploration of GSW-related nerve injuries in patients without signs of functional recovery demonstrate large neuromas in continuity often requiring meticulous dissection and excision with resulting large gaps that require reconstruction. This has led us to explore options to identify patients with nerve deficits after GSWs who may benefit from earlier exploration. Others advocate for the exploration of all ballistic nerve injuries, which would represent a logistical challenge in high volume centers and may lead to unnecessary explorations of in continuity nerves. To facilitate identification of nerve injury following GSWs, we have explored the utilization of early ultrasound to identify patients with nerve lacerations that may benefit from early exploration (1-2 weeks after injury). Earlier exploration can lead to less technically challenging surgery, shorter nerve gaps, and more time for the nerve to recover. Herein, we present a series of cases to help illustrate this approach to the patient. Although early exploration and repair versus grafting of nerves may have benefits as outlined above, there are little to no data on outcomes of nerve repair or grafting in ballistic injuries in the more acute setting, 1 to 2 weeks after injury. Further research is needed both with regards to diagnosis and utilization of ultrasound, as well as postoperative outcomes in patients with ballistic nerve injuries to help guide our ever-evolving treatment protocols.

Deep infections after low-velocity ballistic tibia fractures are frequently polymicrobial and recalcitrant.

Objectives: To identify risk factors for developing a fracture-related infection in operatively treated ballistic tibia fractures and to report the microbiologic results of intraoperative cultures. Design: Retrospective review. Setting: Level 1 trauma center. Patients/Participants: One hundred thirty-three adults with operatively treated low-velocity ballistic tibia fractures, from 2011 to 2021. Intervention: One dose of prophylactic cefazolin or equivalent as well as perioperative prophylaxis. Main Outcome Measurements: Deep infection rate. Results: The deep infection rate was 12% (16/134) with no significant difference in injury characteristics, index surgical characteristics, or time to antibiotics between the groups (P > 0.05). Patients who were slightly older (35.5 vs. 27 median years, P = 0.005) and with higher median body mass indexes (BMIs) (30.09 vs. 24.51, P = 0.021) developed a deep infection. 56.3% of patients presented with signs of infection within the first 100 days after injury. Nine patients had polymicrobial infections. There were 29 isolated organisms, 69% were uncovered by first-generation cephalosporin prophylaxis (anaerobes, gram-negative rods, Enterococcus, methicillin resistant Staphylococcus Aureus [MRSA]), and 50% of patients developed recalcitrant infection and required a second reoperation where 6 organisms were isolated, half of which were not covered by first-generation prophylaxis (Enterococcus, Staphylococcus Aureus MRSA). Conclusions: We found a deep infection rate of 12% among ballistic tibia fractures receiving standard-of-care antibiotic prophylaxis. Increased age and body mass index were associated with deep infections. Half became recalcitrant requiring a second reoperation. 66.7% of isolated organisms were not covered by first-generation cephalosporin prophylaxis. Consideration should be given to treatment options such as broader prophylaxis or local antibiotic treatment. Level of Evidence: IV.

A response time model of the three-choice Mnemonic Similarity Task provides stable, mechanistically interpretable individual-difference measures.

Introduction: The Mnemonic Similarity Task (MST) is a widely used measure of individual tendency to discern small differences between remembered and presently presented stimuli. Significant work has established this measure as a reliable index of neurological and cognitive dysfunction and decline. However, questions remain about the neural and psychological mechanisms that support performance in the task. Methods: Here, we provide new insights into these questions by fitting seven previously-collected MST datasets (total N = 519), adapting a three-choice evidence accumulation model (the Linear Ballistic Accumulator). The model decomposes choices into automatic and deliberative components. Results: We show that these decomposed processes both contribute to the standard measure of behavior in this task, as well as capturing individual variation in this measure across the lifespan. We also exploit a delayed test/re-test manipulation in one of the experiments to show that model parameters exhibit improved stability, relative to the standard metric, across a 1 week delay. Finally, we apply the model to a resting-state fMRI dataset, finding that only the deliberative component corresponds to off-task co-activation in networks associated with long-term, episodic memory. Discussion: Taken together, these findings establish a novel mechanistic decomposition of MST behavior and help to constrain theories about the cognitive processes that support performance in the task.

Expanding bullets and ballistic gelatin - A restricted expansion experiment.

Ballistic gelatin has gained a status as standard method for terminal ballistic testing and experimenting. Variation considering the recipe and manufacturing of the blocks exists. The golden standard has been a cuboid gelatin block, dimensions varying according to the type and kinetic energy of the ammunition. Powerful ammunition requires larger gelatin blocks, making their handling and manufacturing difficult. This is the case especially with powerful, expanding hunting ammunition that leave most of their kinetic energy within the gelatin block. High speed cameras reveal that blocks tend to expand or swell significantly and even travel upon impact, potentially affecting to some basic values of terminal ballistics such as cavitation and energy transfer. In this study, we wanted to experiment new method to study terminal ballistics of high power, expanding ammunition by using cylinder shaped gelatin blocks. Secondly, we used a plastic tube around the gelatin cylinder to restrict the expansion/swelling. Thirdly we attached our gelatin target to a sturdy platform to restrict the movement of the cylinder and potentially improve the energy transfer of the bullet into the gelatin. To conduct our study we compared our experimental setting with a traditional, cuboid gelatin block. After the test firing the blocks underwent computed tomography scanning with clinical equipment. Three-dimensional reconstructions of gelatin cavitation and bullet fragment deposition were created. Our results clearly demonstrate that the restricted expansion of the block also clearly restricts the cavitation inside the gelatin. We believe that the method can be further developed, and it allows better potential for ballistic testing of heavy ammunition. In addition, it may aid in terminal ballistic reconstruction of forensic cases with gunshot trauma in anatomical structures fully enclosed by connective tissue such as brain and structures of the thorax.

Long-Range Ballistic Propagation of 80% Excitonic Fraction Polaritons in a Perovskite Metasurface at Room Temperature.

Exciton-polaritons, hybrid light-matter excitations arising from the strong coupling between excitons in semiconductors and photons in photonic nanostructures, are crucial for exploring the physics of quantum fluids of light and developing all-optical devices. Achieving room temperature propagation of polaritons with a large excitonic fraction is challenging but vital, e.g., for nonlinear light transport. We report on room temperature propagation of exciton-polaritons in a metasurface made from a subwavelength lattice of perovskite pillars. The large Rabi splitting, much greater than the optical phonon energy, decouples the lower polariton band from the phonon bath of the perovskite. These cooled polaritons, in combination with the high group velocity achieved through the metasurface design, enable long-range propagation, exceeding hundreds of micrometers even with an 80% excitonic component. Furthermore, the design of the metasurface introduces an original mechanism for unidirectional propagation through polarization control, suggesting a new avenue for the development of advanced polaritonic devices.

Analysis of ballistic trajectories and its association with clinical outcomes in civilian penetrating brain injury.

PURPOSE: Civilian penetrating brain injuries (PBI) caused by firearms are a medical emergency with high rates of morbidity and mortality. The aim of this study was to evaluate the association between trajectory vectors in CT brain angiography and clinical outcomes in patients with civilian gunshots. METHODS: This is a retrospective analytical cross-sectional study that includes patients over 15 years of age with PBI due to firearms, admitted from January 2019 to December 2021 at a University Hospital in Cali, Colombia. A brain CT with angio-CT was performed the first day of admission. An XYZ coordinate system centered on the Turk's saddle was developed. Trajectories of projectiles were plotted and compared to a patient 0 in a 3D-Slicer software. A bivariate analysis of the clinical and geometric characteristics of the trajectory was performed. Primary outcomes include mortality and disability at 6 months. RESULTS: Twenty-eight patients with a mean age of 27.39 ± 11.66 years were included. The vectors of non-survivors show a trend, crossing at a specific area. This area was designated as a "potential lethal zone" and inside this area, injuries around 25.3 mm from the circle of Willis, were associated with greater mortality (p < 0.005). CONCLUSIONS: In our study PBI avoiding the ventricular system, brain stem, dorsum sellae and the circle of Willis were associated with more survivability. A "potential lethal zone" was detected and associated with poor outcome after civilian PBI due to firearms. A better evaluation of the performance of this "potential lethal zone" in larger studies will be required.

The 2 stages of cartridge primer toolmark production and the implied impact of cartridge manufacturing tolerances.

Many methods of ballistic toolmark comparison rely upon comparison using 2D greyscale imaging. However, newly emerging analysis methods such as areal surface analysis now utilise an extra dimension of measurement allowing the surface heights/depths of unique toolmark features to be recorded in a densely populated (x,y,z) array for a 3D/areal quantitative comparative analysis. Due to this step change, the colloquialism in referring to the crater produced at the centre of the primer during firing as a "firing pin impression" has become a misnomer, leading some to believe that this toolmark is produced via a single process, where the critical variable is the condition of the firing pin. Furthermore, current forensic ballistic methodology relies on the microscopic differences between individual fired bullets and cartridge cases produced as a result of the manufacturing process of a particular firearm, in this case "matched toolmarks" confirm a ballistic match to a specific firearm. However, very rarely is it considered that the ammunition itself possesses minute differences produced during manufacture that could affect the ballistic match efficacy. This study examines the discharge process of conventional centrefire ammunition and concludes that the unique toolmarks upon the cartridge primer are definitively produced in two defined stages. This conclusion suggests that the factory loading and quality control tolerances of the cartridge itself should now be considered to be a more significant contributing factor to the production of cartridge primer toolmarks than has previously been accepted.

Biomimetic design and impact simulation of Al2O3/Al composite armor based on armadillo shell.

The advancement of lightweight protective armors holds critical importance for enhancing the maneuverability and combat capabilities of helicopters. Leveraging insights from bionics, it provides a new idea for high-performance armor design. In this study, a new type of composite armor was designed by referring to the structural characteristics of hard phase-protection, soft phase-buffering of unitization armadillo shell. Through the numerical study, the anti-ballistic performance of armor with varying thickness ratios of the dense ceramic layer to the interpenetrating layer is obtained, and the influence of different structures of armor on the anti-ballistic performance is analyzed. The results show that compared with the traditional laminated composite armor, the Al2O3/Al biomimetic composite armor not only improves the separation phenomenon caused by wave impedance mismatch, but also greatly improves the speed drop in resisting high-speed and penetrating bullets. When the thickness ratio is 2:1, the armor has higher ballistic protection performance.

Modified Epoxy Resin on the Burning Behavior and Mechanical Properties of Aramid Fiber Composite.

Aramid fiber/epoxy resin (AF/EP) composite has been heavily used as an impact protection material due to its excellent mechanical properties and lightweight merits. Meanwhile, it is also necessary to concern the flammability of matrix resin and the wick effect of aramid fiber, which would constitute a fire risk in harsh environments. In this work, a multifunctional flame-retardant modifier (EAD) was incorporated into the AF/EP system to improve the flame retardation. The addition of 5 wt% EAD made the AF/EP composite exhibit a high limiting oxygen index (LOI) value of 37.5%, self-extinguishment, as well as decreased total heat release and total smoke release. The results from thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA) demonstrated that the treated composites maintained good thermal stability. Due to the combined action of covalent and noncovalent bonds in the matrix-rich region, the interfacial bonding improved, which endowed AF/EP composite with strengthening and toughening effects. Compared with the control sample AF/EP, the tensile strength and ballistic parameter (V50) of the sample with 5 wt% EAD increased by 17% and 10%, accompanied with ductile failure mode. Furthermore, the flame-retardant mechanism was obtained by analyzing the actions in condensed and gaseous phases. Thanks to good compatibility and interfacial adhesion, the incorporation of EAD solved the inconsistent issue between flame retardancy and mechanical properties, which further expanded the application of AF/EP composite in the protection field.

Experimental Investigations on Shear Thickening Fluids as "Liquid Body Armors": Non-Conventional Formulations for Ballistic Protection.

Shear thickening fluids (STFs) have garnered attention as potential enhancers of protective capabilities and for the optimization of Kevlar® armor design. To assess the possible shear thickening properties and potential application in ballistic protection, ten formulations were developed by employing polyethylene glycol (PEG) or polypropylene glycol (PPG), along with fumed silica or Aerosil HDK®. Rheological characterization facilitated the identification of formulations displaying shear thickening behavior. The potential integration of the selected shear thickening fluids (STFs) into Kevlar®-based composites was investigated by studying the impact resistance of Kevlar® soft armor structures. Also, high-velocity impact testing revealed that the distance between aramid layers plays a crucial role in the impact resistance effectiveness of Kevlar®-STF composite structures and that there is a very narrow domain between optimal and undesired scenarios in which STF could facilitate the penetration of Kevlar. The introduction of STF between the Kevlar sheets disrupted this packing and the energy absorption capacity of the material was not improved. Only one formulation (PEG400, Aerosil 27 wt.%) led to a less profound traumatic imprint and stopped the bullet when it was placed between layers no.1 and no.2 from a total of 11 layers of Kevlar XP. These experimental findings align with the modeling and simulation of Kevlar®-STF composites using Ansys simulation software (Ansys® AutoDyn 2022 R2).

Hybrid Soft Ballistic Panel Packages with Integrated Graphene-Modified Para-Aramid Fabric Layers in Combinations with the Different Ballistic Kevlar Textiles.

The purpose of the research discussed in this article is to explore the possibility of creating hybrid soft ballistic panel (BP) package variants by integrating into their composition layers of graphene-modified para-aramid fabrics in combinations with the different ballistic Kevlar textiles to improve the durability of the first layers of the soft ballistic panel. To address this goal, the liquid-phase exfoliation (LPE) method was used for integrating dispersions into composites to solve a number of topical problems in the stages of the technological sequence development of processing methods and optimizing processing parameters in accordance with the processing specifics of aramid textiles to achieve the desired properties of modified ballistic fabric, including the provision of coating adhesion to the surface to be modified. To test the results, ballistic experiments were performed and the back-face signature (BFS) of bullet impact on a backing material was analysed according to standards. Bullet impacts on the first ballistic protective fabric layers were also studied.

Acute effects of voluntary isometric contractions at maximal shortening vs. ballistic stretching on flexibility, strength and jump.

Background: Isometric training is used in sport, conventional physical activity and rehabilitation. Understandably, there is a great deal of research related to its effect on performance. It is known that the length of the muscle at the moment of contraction is a determinant of strength levels. In the literature we find research on isometric training in short muscle lengths, although it has not been studied in maximally shortened positions or the acute effects that occur after its application. Ballistic stretching (BS) is also popular in sport. Their execution involves actively reaching maximally shortened muscle positions. So far, isometric training has not been compared with protocols involving ballistic stretching. Considering the above, the aim of the present study was to investigate the effects of BS and voluntary isometric contraction at maximal shortening (VICAMS) on range of motion, strength and vertical jump. Methods: The study involved 60 healthy, physically active individuals (40 and 52 years old) who were randomly assigned to three groups: BS, VICAMS and a control group (CG). To assess acute effects, before and after the intervention, active range of motion (AROM), maximal voluntary isometric force (MVIF) and countermovement jump height (CMJ) were determined. Results: Time main effects and time*group interactions were found for all variables (p < 0.001). Between-group differences were shown for the VICAMS group after the intervention, with statistically significant higher AROM values compared to the other groups. MVIF values were also higher in the VICAMS group. Intra-group differences were observed for the VICAMS and Ballistic groups, as values on all variables increased from baseline. For the CMJ, intra-group differences showed that both the VICAMS and BS groups improved values compared to baseline values. Conclusions: The application of VICAMS induced acute improvements over BS in AROM, MVIF and CMJ. These results are important for coaches seeking immediate performance improvement and offer an optimal solution to the warm-up protocol.

One Standard for All: Uniform Scale for Comparing Individuals and Groups in Hierarchical Bayesian Evidence Accumulation Modeling.

In recent years, a growing body of research uses Evidence Accumulation Models (EAMs) to study individual differences and group effects. This endeavor is challenging because fitting EAMs requires constraining one of the EAM parameters to be equal for all participants, which makes a strong and possibly unlikely assumption. Moreover, if this assumption is violated, differences or lack thereof may be wrongly found. To overcome this limitation, in this study, we introduce a new method that was originally suggested by van Maanen & Miletic (2021), which employs Bayesian hierarchical estimation. In this new method, we set the scale at the population level, thereby allowing for individual and group differences, which is realized by de facto fixing a population-level hyper-parameter through its priors. As proof of concept, we ran two successful parameter recovery studies using the Linear Ballistic Accumulation model. The results suggest that the new method can be reliably used to study individual and group differences using EAMs. We further show a case in which the new method reveals the true group differences whereas the classic method wrongly detects differences that are truly absent.

Visco-hyperelastic material model fitting to experimental stress-strain curves using a genetic algorithm and its application to soft tissue simulants.

Ballistic impacts on human thorax without penetration can produce severe injuries or even death of the carrier. Soft tissue finite element models must capture the non-linear elasticity and strain-rate dependence to accurately estimate the dynamic human mechanical response. The objective of this work is the calibration of a visco-hyperelastic model for soft tissue simulants. Material model parameters have been calculated by fitting experimental stress-strain relations obtained from the literature using genetic algorithms. Several parametric analyses have been carried out during the definition of the optimization algorithm. In this way, we were able to study different optimization strategies to improve the convergence and accuracy of the final result. Finally, the genetic algorithm has been applied to calibrate two different soft tissue simulants: ballistic gelatin and styrene-ethylene-butylene-styrene. The algorithm is able to calculate the constants for visco-hyperelastic constitutive equations with high accuracy. Regarding synthetic stress-strain curves, a short computational time has been shown when using the semi-free strategy, leading to high precision results in stress-strain curves. The algorithm developed in this work, whose code is included as supplementary material for the reader use, can be applied to calibrate visco-hyperelastic parameters from stress-strain relations under different strain rates. The semi-free relaxation time strategy has shown to obtain more accurate results and shorter convergence times than the other strategies studied. It has been also shown that the understanding of the constitutive models and the complexity of the stress-strain objective curves is crucial for the accuracy of the method.

Versatile Method of Engineering the Band Alignment and the Electron Wavefunction Hybridization of Hybrid Quantum Devices.

Hybrid devices that combine superconductors (S) and semiconductors (Sm) have attracted great attention due to the integration of the properties of both materials, which relies on the interface details and the resulting coupling strength and wavefunction hybridization. However, until now, none of the experiments have reported good control of the band alignment of the interface, as well as its tunability to the coupling and hybridization. Here, the interface is modified by inducing specific argon milling while maintaining its high quality, e.g., atomic connection, which results in a large induced superconducting gap and ballistic transport. By comparing with Schrödinger-Poisson calculations, it is proven that this method can vary the band bending/coupling strength and the electronic spatial distribution. In the strong coupling regime, the coexistence and tunability of crossed Andreev reflection and elastic co-tunneling-key ingredients for the Kitaev chain-are confirmed. This method is also generic for other materials and achieves a hard and huge superconducting gap in lead and indium antimonide nanowire (Pb-InSb) devices. Such a versatile method, compatible with the standard fabrication process and accompanied by the well-controlled modification of the interface, will definitely boost the creation of more sophisticated hybrid devices for exploring physics in solid-state systems.

The ballistic articular structure injury classification (BASIC) system: clarifying ballistic articular injuries.

PURPOSE: This study aims to (1) devise a classification system to categorize and manage ballistic fractures of the knee, hip, and shoulder; (2) assess the reliability of this classification compared to current classification schemas; and (3) determine the association of this classification with surgical management. METHODS: We performed a retrospective review of a prospectively collected trauma database at an urban level 1 trauma centre. The study included 147 patients with 169 articular fractures caused by ballistic trauma to the knee, hip, and shoulder. Injuries were selected based on radiographic criteria from plain radiographs and CT scans. The AO/OTA classification system's reliability was compared to that of the novel ballistic articular injury classification system (BASIC), developed using a nominal group approach. The BASIC system's ability to guide surgical decision-making, aiming to achieve stable fixation and minimize post-traumatic arthritis, was also evaluated. RESULTS: The BASIC system was created after analysing 73 knee, 62 hip, and 34 shoulder fractures. CT scans were used in 88% of cases, with 44% of patients receiving surgery. The BASIC classification comprises five subgroups, with a plus sign indicating the need for soft tissue intervention. Interrater reliability showed fair agreement for AO/OTA (k = 0.373) and moderate agreement for BASIC (k = 0.444). The BASIC system correlated strongly with surgical decisions, with an 83% concurrence in treatment choices based on chart reviews. CONCLUSIONS: Conventional classification systems provide limited guidance for ballistic articular injuries. The BASIC system offers a pragmatic and reproducible alternative, with potential to inform treatment decisions for knee, hip, and shoulder ballistic injuries. Further research is needed to validate this system and its correlation with patient outcomes. LEVEL OF EVIDENCE: Level III, Diagnostic Study.

Mechanisms of speed-accuracy trade-off in tennis topspin forehand of college players.

This study aimed to elucidate the mechanisms underlying the speed-accuracy relationship in a tennis topspin single-handed forehand groundstroke. Groundstrokes at three different speeds by nine college players were captured, with the variability of the ball landing position evaluated as indices of accuracy. Variabilities of ball launch variables (speed, launch angle, spin, etc.) and conversion ratios from these variabilities to the variability of the ball landing position were quantified. These variabilities and their conversion ratios could be influenced by different efforts exerted to generate ball speeds and different ball trajectories required to hit a target at each speed, respectively. The speed-accuracy trade-off was observed only in the hitting direction. While the variability of the spin axis increased, it had minimal influence on the ball landing position. Conversely, the conversion ratio in the hitting direction of the velocity elevation angle significantly increased, while its variability remained unchanged. Consequently, the geometrical requirements of ball trajectories can be responsible for the speed-accuracy trade-off. Therefore, even skilled players capable of maintaining consistent ball launch variables regardless of the shot speed should deliberately choose a moderately slower ball speed to avoid an inevitable increase in the variability of the ball landing position due to geometrical requirements.

Ballistic Gels in Experimental Fracture Setting.

Biomechanical tests typically involve bending, compression, or shear stress, while fall tests are less common. The main challenge in performing fall tests is the non-reproducible directionality of bone when tested with soft tissue. Upon removal of the soft tissue, the explanted bone's resistance to impact diminishes. Therefore, ballistic gels can fix specimens in reproducible directions and simulate periosteal soft tissue. However, the use of ballistic gels in biomechanical studies is neither standardized nor widespread. This study aimed to optimize a ballistic gel consistency that mimics the upper thigh muscle in sheep. Our results suggest a standardized and flexible evaluation method by embedding samples in ballistic gel. Compression tests were conducted using cylindrical pieces of gluteal muscle from sheep. Various compositions of agarose and gelatin mixtures were tested to achieve a muscle-like consistency. The muscle-equivalent ballistic gel was found to consist of 29.5% gelatin and 0.35% agarose. Bones remained stable within the ballistic gel setup after freeze-thaw cycles between -20 °C and +20 °C. This method reduces the variability caused by muscle and improves storage quality, allowing for tests to be conducted under consistent conditionsBallistic gels of agarose and gelatin are suitable for bone fracture models. They have muscle-like strength, fix fractures simultaneously, are inexpensive to produce, and can be stored to allow repeated measurements of the same object with changing questions.