Temperature Dynamics in Rat Brains Exposed to Near-Field Waveguide Outputs at 2.8 GHz.

Biological effects in the microwave band of the radiofrequency (RF) spectrum are thermally mediated. For acute high-power microwave exposures, these effects will depend on transient time-temperature histories within the tissue. In this article, we summarize the transient temperature response of rats exposed to RF energy emanating from an open-ended rectangular waveguide. These exposures produced specific absorption rates of approximately 36 and 203 W/kg in the whole body and brain, respectively. We then use the experimentally measured thermal data to infer the baseline perfusion rate in the brain and modify a custom thermal modeling tool based upon these findings. Finally, we compare multi-physics simulations of rat brain temperature against empirical measurements in both live and euthanized subjects and find close agreement between model and experimentation. This research revealed that baseline brain perfusion rates in rat subjects could be larger than previously assumed in the RF thermal modeling literature, and plays a significant role in the transient thermal response to high-power microwave exposures. © 2021 Bioelectromagnetics Society.

Revisiting 35 and 94 GHZ Millimeter Wave Exposure to the Non-Human Primate Eye.

A previous study reported thermal effects resulting from millimeter wave exposures at 35 and 94 GHz on non-human primates, specifically rhesus monkeys' (Macaca mulatta) corneas, but the data exhibited large variations in the observed temperatures and uncertainties in the millimeter wave dosimetry. By incorporating improvements in models and dosimetry, a non-human primate experiment was conducted involving corneal exposures that agreed well with a three-layer, one-dimensional, thermodynamic model to predict the expected surface temperature rise. The new data indicated that the originally reported safety margins for eye exposures were underestimated by 41 ± 20% over the power densities explored. As a result, the expected minimal visible lesion thresholds should be raised to 10.6 ± 1.5 and 7.1 ± 1.0 J cm at 35 and 94 GHz, respectively, provided that the power density is less than 6 W cm for subjects that are unable to blink. If the blink reflex was active, a power density threshold of 20 W cm could be used to protect the eye, although the eyelid could be burned if the exposure was long enough.

Fatigue estimation using voice analysis.

In the present article, we present a means to remotely and transparently estimate an individual's level of fatigue by quantifying changes in his or her voice characteristics. Using Voice analysis to estimate fatigue is unique from established cognitive measures in a number of ways: (1) speaking is a natural activity requiring no initial training or learning curve, (2) voice recording is a unobtrusive operation allowing the speakers to go about their normal work activities, (3) using telecommunication infrastructure (radio, telephone, etc.) a diffuse set of remote populations can be monitored at a central location, and (4) often, previously recorded voice data are available for post hoc analysis. By quantifying changes in the mathematical coefficients that describe the human speech production process, we were able to demonstrate that for speech sounds requiring a large average air flow, a speaker's voice changes in synchrony with both direct measures of fatigue and with changes predicted by the length of time awake.

Assessing performance in complex team environments.

This paper provides a brief introduction to team performance assessment. It highlights some critical aspects leading to the successful measurement of team performance in realistic console operations; discusses the idea of process and outcome measures; presents two types of team data collection systems; and provides an example of team performance assessment. Team performance assessment is a complicated endeavor relative to assessing individual performance. Assessing team performance necessitates a clear understanding of each operator's task, both at the individual and team level, and requires planning for efficient data capture and analysis. Though team performance assessment requires considerable effort, the results can be very worthwhile. Most tasks performed in Command and Control environments are team tasks, and understanding this type of performance is becoming increasingly important to the evaluation of mission success and for overall system optimization.

Hypnotic efficacy of zaleplon for daytime sleep in rested individuals.

STUDY OBJECTIVES: The primary objective of this study was to determine whether zaleplon (10 mg) effectively promoted sleep during the daytime in well-rested individuals when compared to placebo. A secondary objective was to see if, while not expected, the use of zaleplon impacted the performance of well-rested individuals upon awakening. DESIGN: Repeated measures with 2 within-subject factors: drug (placebo/zaleplon) and trial (hourly testing during waking hours). Polysomnographic variables were recorded during a 3.5-hour nap following drug administration. Performance measures and subjective reports were collected during every waking trial of each session. SETTING: The study was conducted at the Chronobiology and Sleep Laboratory located at Brooks Air Force Base. PARTICIPANTS: Twelve participants, 6 men and 6 women. INTERVENTIONS: 10-mg zaleplon or placebo capsules, single afternoon dose. Drug administration was counterbalanced and double-blinded. MEASUREMENTS AND RESULTS: Zaleplon allowed participants to obtain significantly more slow-wave sleep than under placebo. There was also a trend for participants under zaleplon to accomplish a greater amount of sleep than under placebo. Performance was not adversely impacted following a 3.5-hour daytime sleep under zaleplon, nor were any undesirable symptoms induced. CONCLUSIONS: Zaleplon improves sleep quality when used by rested individuals to accomplish daytime sleep.

Performance following a sudden awakening from daytime nap induced by zaleplon.

BACKGROUND: Zaleplon appears to be a prime candidate for assisting individuals in obtaining sleep in situations not conducive to rest (i.e., a short period during the day). However, should an early unexpected awakening and return to duty be required, the effect on performance is not known. HYPOTHESIS: Zaleplon (10 mg) would negatively affect human performance for some duration, compared with placebo, after a sudden awakening from a short period (1 h) of daytime sleep. METHODS: There were 16 participants, 8 men and 8 women, who volunteered to participate in this study. The study was conducted using a counterbalanced, double-blind, repeated measures design. At 1 h prior to drug administration, and at each of 7 h postdrug, performance measures (cognition, memory, balance, and strength) and subjective symptom reports were recorded. RESULTS: Zaleplon had a statistically significant (p < 0.05) negative impact on balance through the first 2 h postdose when compared with placebo. In addition, symptoms related to "drowsiness" were statistically more prevalent under zaleplon than under placebo through the first 3 h postdrug. Of the eight measures of cognitive performance, six were significantly negatively impacted in the zaleplon condition through 2 h postdose when compared with placebo, with one remaining significantly degraded through 3 h postdose. Zaleplon also had a significantly negative impact on memory at 1 h and 4 h postdose. CONCLUSIONS: Zaleplon (10 mg), when used as a daytime sleep aid, causes drowsiness (and related symptoms) up to 3 h postdose, and may impact task performance, especially more complex tasks, for at least 2-3 h postdose.