Following the mysterious health attacks on U.S. diplomats in Cuba in 2016, the cause of concussion-like symptoms concurrent with strange noises heard by the diplomats remains undetermined. A wide range of possible causes of the sensations have been proposed: pulsed microwave exposure, infrasound acoustic devices, pesticides/neurotoxins, and even mass hysteria (psychogenic illness). Here, we numerically examine the pulsed microwave exposure hypothesis and the simulated mechanical response of brain tissue. A computational model is used to examine the influence of various spatially varying temperature gradients and pulse durations on the mechanical response of brain tissue. We show that a stress-focusing effect due to a rapid temperature increase may result in brain tissue strains larger than the initially applied thermal strains.
Source: Amy Dagro, Justin Wilkerson, A computational investigation of strain concentration in the brain in response to a rapid temperature rise, Journal of the Mechanical Behavior of Biomedical Materials, Volume 115, 2021, 104228, ISSN 1751-6161,
According to the authors their results show that a rapid temperature rise can result in concentrated strains that exceed the strains associated with pure thermal expansion. Although the simulations show that injury thresholds could be exceeded in the case of rapidly applied large temperatures (e.g.,6°C applied in 1 μs), it is unlikely that a microwave source could generate such a large temperature increase in these short timescales. At more reasonable temperature magnitudes, the strains are likely to be below conventional injury thresholds however, the associated pressures are large and comparable with stresses seen in blast and ballistic loading.