Shock Waves最新文献

Blast deafness and balance disorders are common consequences of modern warfare and terrorist actions. A predictive evaluation system can assist commanders in quickly gathering information on the incapacitation of combat personnel. However, a critical challenge to this goal was to clarify the dose–response relationship between the blast parameters and the severity of auditory and vestibular dysfunction. This paper describes the algorithms for a prediction model. We performed blast experiments to obtain data on animal auditory/vestibular dysfunction under different overpressures. Peak overpressure and positive phase duration of the blast wave were obtained by pressure measurements. The severity of auditory and vestibular dysfunction was established by the auditory brainstem response test, behavioral rating, and vestibular-evoked myogenic potentials tests. Test data were analyzed using receiver operating characteristic (ROC) curves and logistic regression analysis to obtain the overpressure limits for auditory/vestibular function and logistic regression curves for severity separately. The ROC curve analysis showed that the overpressure limit for the auditory function was 32.635 kPa and the vestibular function was 96.275 kPa. Logistic regression fitted curves illustrated the dose–response relationship between the coefficient K, normalized by peak overpressure and positive phase duration, and the risk probability of auditory and vestibular disfunction. The prediction model for the risk of auditory and vestibular disfunction severity (mild/moderate/severe) has been established based on the overpressure limit and dose–response relationship.

Blast-induced traumatic brain injury has long been a prevalent health issue. There is growing concern for repeated exposures to low-level blasts with studies suggesting effects on neurological impairments and long-term health problems. The purpose of this study was to expand our understanding of the neurophysiological consequences of repetitive mild blast from a range of occupational exposure levels. We studied shock waves of peak overpressures ranging from 45 to 270 kPa and impulses of 54 to 295 kPa(cdot )ms. We observed the effects of these shock waves in organotypic hippocampal slice cultures generated from neonatal rat pups. This model allowed us to isolate the effects of blast on neuronal function without the confounding factors of scaling and peripheral systemic input. We found that blast severity and inter-blast interval were both integral in understanding non-injurious limits for blast exposure. With higher blast severity, the inter-blast interval needed to be extended to avoid deficits in long-term potentiation (LTP), a form of synaptic plasticity. Furthermore, blast exposures too close in time synergistically affected LTP negatively, producing a dose response with more exposures leading to greater deficits in LTP. Overall, even the lowest blast tested was capable of producing functional deficits under the appropriate conditions. These findings can aid in the improvement of safety and training protocols to set occupational exposure limits to avoid neurological impairments and negative long-term health effects.

The transition between Mach reflection (MR) and regular reflection (RR) of gaseous detonations in argon-diluted stoichiometric hydrogen–oxygen was investigated experimentally using a wedge with a concave–convex surface. The continuous MR triple-point trajectory was recorded using the smoked foil technique, from which the transition angles for ({textrm{MR}}leftrightarrow {textrm{RR}}) transitions could be determined. Similar to the reflection of a non-reacting shock wave, the non-stationary hysteresis phenomenon was found for detonation reflection, i.e., the ({textrm{MR}}rightarrow {textrm{RR}}) transition angle was much larger than that for ({textrm{RR}} rightarrow {textrm{MR}}) transition. In addition, the ({textrm{RR}} rightarrow {textrm{MR}}) transition angle on the convex surface was smaller than that for detonation reflection over a single half-cylinder. This is opposite to what is found for non-reacting shock wave reflection.

Brain injuries in warfighters due to low-level blasts, even while wearing a helmet, are common. Understanding how the form of a shock wave changes when impacting a head donning a helmet may present solutions to reducing shock loading on the head, thereby reducing the prevalence of blast-induced traumatic brain injury. A manikin with PCB piezoelectric transducers throughout the head was exposed to low-pressure free-field blasts using an RDX-based explosive charge designed to output a side-on overpressure of 4 pounds per square inch (psi) [27.5 kilopascals (kPa)] with and without a helmet. Orientations of 0, 45, 90, 135, and 180 degrees were evaluated to observe changes in overpressure versus time (p(t)) waveforms. The waveforms were compared to schlieren imagery in which a shock wave impacted 3D-printed silhouettes of a warfighter donning a helmet, showing shock wave flow under the helmet at 0-, 90-, and 180-degree orientations. It was found that trapped shock waves under the helmet create regions of high overpressure and increase the duration of exposure, resulting in higher impulses imparted onto the head. While wearing a helmet, the 90-degree orientation resulted in the greatest reduction in overall peak overpressure, with an 8% decrease compared to the 0-degree orientation. In contrast, the 180-degree orientation led to an increase by 30%. For impulse, the 90-degree orientation showed the greatest reduction, with a decrease of 21%. The 0-degree orientation had the highest overall impulse among all orientations when wearing a helmet.

Evidence suggests that low-level blast (LLB) overpressure exposure from military heavy weapons training is associated with subclinical adverse brain health and performance (H &P) outcomes. Existing DOD safety policies related to blast overpressure exposure are not specific to LLB-related brain health effects. This study sought to synthesize the available literature and analyze the relevancy of a specific blast metric to LLB exposures and the manifestation of adverse brain H &P outcomes. A literature search yielded 311 unique articles, from which 220 were identified as human studies on LLB published from 2010 to 2021. After more exhaustive exclusion criteria were applied, 14 articles met the criteria for inclusion. Findings on brain H &P changes were examined in relation to quantified LLB measurements (e.g., peak overpressure) to identify trends. Overall, the included studies suggested that alterations of reaction time, a metric for neurocognitive performance, as well as symptom reporting can occur following cumulative LLB exposures above 4 psi (27.6 kPa). Biomarkers and neurosensory changes have not demonstrated consistent associations with LLB exposures. These findings suggest that cumulative blast overpressure exposures above 4 psi (27.6 kPa) based on current measurement methodologies for body-worn sensors may be associated with adverse brain H &P outcomes. Current research efforts seek to better quantify LLB exposure, the relationships between LLB (e.g., intensity, duration, dose) and brain health, as well as to assess brain H &P domains more comprehensively. These efforts will serve to promote a better understanding of the interaction between LLB exposures and adverse brain H &P outcomes.

The neurological consequences of combat blast-induced neurotrauma (BINT) pose important clinical concerns for military service members and veterans. Previous studies have shown that low-intensity blast (LIB) results in BINT with multifaceted characteristics in mice exposed to open-field blast in prone position. Although the prone position is natural for rodents, experimental models of blast using this position do not represent common scenarios of human standing while being exposed to blast during deployment or military training. In this study, we used our previously developed BINT mouse model of open-field LIB with mice in an upright position and then used quantitative proteomics and multiple bioinformatic approaches to analyze brain tissue taken from multiple subregions during the acute post-injury phase. We identified: (1) region-specific BINT-induced proteome changes, which were significantly and differently influenced by animal positioning (upright vs. prone): the upright positioning caused more significant protein alterations in cortex and cerebellum, which were less significant in striatum as compared to prone position; (2) synapse- and mitochondrion-related damage contributed to BINT in both positions; and (3) some molecular signatures were exclusively and/or oppositely regulated in two positions. This study delineates the molecular signatures of the position-dependent blast effects, indicating the importance of brain–body position for BINT translational studies and for modeling the location and extent of position-related blast injuries.

Towards a better characterization of the increasing blast overpressure threat, person-borne sensors are being considered for large military population segments potentially subjected to explosive blast and firing of crew served weapons. Training and field data, tracked longitudinally across a soldier’s entire career, can help with the diagnosis of blast injuries and the improvement of standard operating procedures for both explosive forced entry and large weapons firing. However, a current challenge with person-born blast dosimeters resides with the position of the overpressure sensors themselves. Often, the sensors are not fully exposed to the blast locally, resulting in pressure measurements not representative of the blast conditions surrounding an individual. While fielding multiple individual and uncoupled dosimeter units around the body increases the likeliness of catching the representative blast exposure, issues arise from differences in internal clock, potential partial triggering, and the complexity of merging data from different sources. Instead, integrating multiple overpressure sensors pointing in different directions, within a single device that captures and records all data simultaneously, proves highly beneficial for data analysis and interpretation. This paper presents algorithms that combine the overpressure data collected from such multiple coupled sensors for each blast event to minimize the effect of blast directionality. In particular, an algorithm estimating the equivalent side-on blast overpressure is presented, facilitating injury estimates from existing established blast injury models adapted for the outputs from the blast dosimeters. An algorithm is also presented that estimates the orientation or provenance of an explosive blast relative to the soldier.

This note presents a vapor-based seeding apparatus, named the external alkali seeding instrument (EASI), which is designed to introduce alkali metal vapors into experimental facilities without using precursors or large auxiliary equipment. The device vaporizes small amounts of alkali metals, potassium in this work, which are then carried away by an inert gas. In a benchtop flow cell, carrier gas flow rate (6–(200~hbox {cm}^3/hbox {s})) and device temperature (150–(250,^{circ }hbox {C})) most strongly affected potassium-vapor concentrations. Higher values of either quantity lead to increased potassium-vapor concentrations. When using the EASI to seed a shock tube experiment, vapor-phase potassium was detected immediately after the incident and reflected shockwaves using a laser absorption diagnostic. Mole fraction time histories stay within a factor of 2 over the test time as compared with those from a precursor-based seeding approach, which may span multiple orders of magnitude. This suggests potassium is nearly homogeneously distributed throughout the test gas. This design can be extended to other low-vapor-pressure elements, such as other alkalis or sulfur, with minimal modifications. The EASI simplifies seeding for laboratory experiments targeting potassium and other alkali metals—enabling advances in fundamental spectroscopy, diagnostic development, and chemical kinetics.