Exposure to blast shock waves via the ear canal induces deficits in vestibular afferent function in rats

The ears are air-filled structures that are directly impacted during blast exposure.In addition to hearing loss and tinnitus,blast victims often complain of vertigo,dizziness and unsteady posture,suggesting that blast exposure induces damage to the vestibular end organs in the inner ear.However,the underlying mechanisms remain to be elucidated.In this report,single vestibular afferent activity and the vestibuloocular reflex(VOR)were investigated before and after exposure to blast shock waves(~20 PSI)delivered into the left external ear canals of anesthetized rats.Single vestibular afferent activity was recorded from the superior branch of the left vestibular nerves of the blast-treated and control rats one day after blast exposure.Blast exposure reduced the spontaneous discharge rates of the otolith and canal afferents.Blast exposure also reduced the sensitivity of irregular canal afferents to sinusoidal head rotation at 0.5e2Hz.Blast exposure,however,resulted in few changes in the VOR responses to sinusoidal head rotation and translation.To the best of our knowledge,this is the first study that reports blast exposure-induced damage to vestibular afferents in an animal model.These results provide insights that may be helpful in developing biomarkers for early diagnosis of blast-induced vestibular deficits in military and civilian populations.

Traumatic brain injury induced by exposure to blast overpressure via ear canal

Exposure to explosive shockwave often leads to blast-induced traumatic brain injury in military and civilian populations.Unprotected ears are most often damaged following exposure to blasts.Although there is an association between tympanic membrane perforation and TBI in blast exposure victims,little is known about how and to what extent blast energy is transmitted to the central nervous system via the external ear canal.The present study investigated whether exposure to blasts directed through the ear canal causes brain injury in LongEvans rats.Animals were exposed to a single blast(0–30 pounds per square inch(psi))through the ear canal,and brain injury was evaluated by histological and behavioral outcomes at multiple time-points.Blast exposure not only caused tympanic membrane perforation but also produced substantial neuropathological changes in the brain,including increased expression of c-Fos,induction of a profound chronic neuroinflammatory response,and apoptosis of neurons.The blast-induced injury was not limited only to the brainstem most proximal to the source of the blast,but also affected the forebrain including the hippocampus,amygdala and the habenula,which are all involved in cognitive functions.Indeed,the animals exhibited long-term neurological deficits,including signs of anxiety in open field tests 2 months following blast exposure,and impaired learning and memory in an 8-arm maze 12 months following blast exposure.These results suggest that the unprotected ear canal provides a locus for blast waves to cause TBI.This study was approved by the Institutional Animal Care and Use Committee at the University of Mississippi Medical Center(Animal protocol#0932 E,approval date:September 30,2016 and 0932 F,approval date:September 27,2019).

CFD simulations of quenching process for partial oxidation of methane:Comparison of jet-in-cross-flow and impinging flow configurations

A new quenching process using the cold pyrolysis gas has been proposed for the partial oxidation(POX) of methane to recover the heat. The mixing of hot product gas and cold pyrolysis gas in milliseconds is critical to this new approach. Two most widely-used rapid mixing configurations, i.e. the jet-in-cross-flow(JICF) and impinging flow configurations, are compared in terms of mixing and quenching performances using computational fluid dynamics(CFD) coupled with detailed reaction mechanism Leeds 1.5. The mixedness, residence time distribution, temperature decreasing rate and loss ratio of acetylene during the quenching are systematically studied. The results show that the impinging flow has a more uniform mixing and narrower residence time distribution than the JICF.However, the temperature decreasing rate of the mainstream is faster in the JICF than in the impinging flow. The loss ratio of acetylene in the quenching process is 2.89% for the JICF and 1.45% for the impinging flow, showing that the impinging flow configuration is better and feasible for the quenching of POX of methane.