Virtual and augmented reality in a simulated naval engagement: Preliminary comparisons of simulator sickness and human performance.

The aim of this study was to compare simulator sickness symptoms while participants wore either a virtual reality (VR) or augmented reality (AR) headset. A secondary aim involved comparing how physical motion affects symptoms. During a simulation, participants wore VR and AR headsets while standing on a motion platform and firing at hostile ships under three motion conditions: No Physical Motion; Synchronous Motion, in which the physical and displayed motion were coupled; and Asynchronous Motion, in which the physical motion did not match the display.

Neuroendocrine function and associated mental health outcomes following mild traumatic brain injury in OEF-deployed service members.

Mild traumatic brain injury (mTBI) has been linked to mental health disorders (MHDs) and pituitary function alterations. Due to the complex relationship of mTBI, the neuroendocrine system, and MHDs, we propose that neuroendocrine dysfunction (NED) may play a role in negative long-term health outcomes. The goal of this study was to determine if blast-concussed service members (SMs) have a stronger likelihood of developing NED.

Direct Demonstration of Topological Stability of Magnetic Skyrmions Topology Manipulation.

Topological protection precludes a continuous deformation between topologically inequivalent configurations in a continuum. Motivated by this concept, magnetic skyrmions, topologically nontrivial spin textures, are expected to exhibit topological stability, thereby offering a prospect as a nanometer-scale nonvolatile information carrier. In real materials, however, atomic spins are configured as not continuous but discrete distributions, which raises a fundamental question if the topological stability is indeed preserved for real magnetic skyrmions.

Release of Munitions Constituents in Aquatic Environments Under Realistic Scenarios and Validation of Polar Organic Chemical Integrative Samplers for Monitoring.

Munitions constituents (MC) may be released into aquatic environments as a result of underwater military munitions (UWMM) corrosion and breach. The present study investigated the release of 2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) from Composition B fragments under 2 realistic exposure scenarios in a large flume with flow set at 15 cm/s: the first represented the release of MC from fully exposed Composition B, and the second represented release through a small hole, simulating a breached munition. Release of MC through a small hole was approximately 10 times lower than from exposed Composition B, demonstrating the strong influence of exposure to flow on release.

Effects of Dissolved Organic Carbon on Copper Toxicity to Embryos of Mytilus galloprovincialis as Measured by Diffusive Gradient in Thin Films.

Diffusive gradient in thin films (DGT) potentially better quantifies bioavailable copper (Cu) in seawater. Laboratory exposure of DGTs and Mytilus galloprovincialis embryos at varying concentrations of dissolved organic carbon and Cu were performed to resolve the degree to which mimicry of toxicity buffering occurs in passive sampler quantification. The results provide preliminary median effect concentrations (EC50s) ranging from 4.

Resilience of Central Pacific reefs subject to frequent heat stress and human disturbance.

Frequent occurrences of coral bleaching and associated coral mortality over recent decades have raised concerns about the survival of coral reefs in a warming planet. The El Niño-influenced coral reefs in the central Gilbert Islands of the Republic of Kiribati, which experience years with prolonged heat stress more frequently than 99% of the world's reefs, may serve as a natural model for coral community response to frequent heat stress. Here we use nine years of survey data (2004-2012) and a suite of remote sensing variables from sites along gradients of climate variability and human disturbance in the region to evaluate the drivers of coral community response to, and recovery from, multiple heat stress events.

Signal-to-noise ratio of auditory brainstem responses (ABRs) across click rate in the bottlenose dolphin (Tursiops truncatus).

Although the maximum length sequence (MLS) and iterative randomized stimulation and averaging (I-RSA) methods allow auditory brainstem response (ABR) measurements at high rates, it is not clear if high rates allow ABRs of a given quality to be measured in less time than conventional (CONV) averaging (i.e., fixed interstimulus intervals) at lower rates.

Spray-On Liquid-Metal Electrodes for Graphene Field-Effect Transistors.

Advancements in flexible circuit interconnects are critical for widespread adoption of flexible electronics. Non-toxic liquid-metals offer a viable solution for flexible electrodes due to deformability and low bulk resistivity. However, fabrication processes utilizing liquid-metals suffer from high complexity, low throughput, and significant production cost.

Stimulus bandwidth impact on auditory evoked potential thresholds and estimated upper-frequency limits of hearing in dolphins.

The frequency range of hearing is important for assessing the potential impact of anthropogenic noise on marine mammals. Auditory evoked potentials (AEPs) are commonly used to assess toothed whale hearing, but measurement methods vary across researchers and laboratories. In particular, estimates of the upper-frequency limit of hearing (UFL) can vary due to interactions between the unintended spread of spectral energy to frequencies below the desired test frequency and a sharp decline in hearing sensitivity at frequencies near the UFL.

Jittered echo-delay resolution in bottlenose dolphins (Tursiops truncatus).

Psychophysical methods similar to those employed with bats were used to examine jittered echo-delay resolution in bottlenose dolphins (Tursiops truncatus). Two dolphins were trained to produce echolocation clicks and report a change from electronic echoes with a fixed delay of ~ 12.6 ms (~ 9.

Dolphin echolocation behaviour during active long-range target approaches.

Echolocating toothed whales generally adjust click intensity and rate according to target range to ensure that echoes from targets of interest arrive before a subsequent click is produced, presumably facilitating range estimation from the delay between clicks and returning echoes. However, this click-echo-click paradigm for the dolphin biosonar is mostly based on experiments with stationary animals echolocating fixed targets at ranges below ∼120 m. Therefore, we trained two bottlenose dolphins instrumented with a sound recording tag to approach a target from ranges up to 400 m and either touch the target (subject TRO) or detect a target orientation change (subject SAY).

Dolphins maintain high echolocation vigilance for eight hours without primary (food) reinforcement.

Studies have demonstrated that dolphins can maintain continuous auditory or echolocation vigilance for up to 5 to 15 days when provided with continuous primary reinforcement (i.e., food reward after each correct detection).

Phase drift on networks of coupled crystal oscillators for precision timing.

Precise time dissemination and synchronization have been some of the most important technological tasks for several centuries. Since the early 1800s, it was realized that precise time-keeping devices having the same stable frequency and precisely synchronized can have important applications in navigation. In modern times, satellite-based global positioning and navigation systems such as the GPS use the same principle.

Comparison of maximum length sequence and randomized stimulation and averaging methods on the bottlenose dolphin auditory brainstem response.

The purpose of the present study was to compare auditory brainstem responses (ABRs) using two approaches that allow the use of high stimulation rates, but with different temporal variability in the interstimulus interval: maximum length sequences (MLS) and iterative randomized stimulation and averaging (I-RSA). ABRs were obtained to click stimuli in six bottlenose dolphins (Tursiops truncatus). In experiment 1, click level was held constant and click rate varied from 25 to 1250 Hz.

Bottlenose dolphin (Tursiops truncatus) discrimination of harmonic stimuli with range-dependent signal degradation.

The importance of perceived sound source distance has been noted in controlled exposure studies with free-ranging marine mammals. Different behavioral reactions have been observed for sonar exposures with a similar received level but differing source distances. This psychophysical study examined bottlenose dolphins' use of range-dependent acoustic features in classifying frequency-modulated tonal stimuli (∼10-kHz fundamental).

Effects of noise burst rise time and level on bottlenose dolphin (Tursiops truncatus) auditory brainstem responses.

Although the auditory brainstem response (ABR) is known to be an onset response, specific features of acoustic stimuli that affect the morphology of the ABR are not well understood. In this study, the effects of stimulus onset properties were investigated by measuring ABRs in seven bottlenose dolphins while systematically manipulating stimulus rise time and the amplitude of the sound pressure temporal envelope plateau. Stimuli consisted of spectrally pink (i.

Seroprevalence Survey for Microsporidia in Common Bottlenose Dolphin ( Tursiops truncatus): Example of a Quantitative Approach Based on Immunoblotting.

Little is known about microsporidiosis pathogenicity in cetaceans. Here we report seroprevalence of 76% for microsporidia in blood samples from common bottlenose dolphins ( Tursiops truncatus), from animals managed under human care ( n=108) or captured for health assessments ( n=13) and released.

Click reception in the harbor porpoise (Phocoena phocoena): Effects of electrode and contact transducer location on the auditory brainstem response.

Unlike terrestrial mammals that have unambiguous aerial sound transmission pathways via the outer ear and tympanum, sound reception pathways in most odontocetes are not well understood. Recent studies have used auditory brainstem response (ABR) measurements to examine sound reception pathways. This study sought to determine how sound source placements, recording electrode arrangements, and ABR peak analyses affect interpretations of sound reception in the harbor porpoise (Phocoena phocoena).

Field validation of POCIS for monitoring at underwater munitions sites.

The present study evaluated polar organic chemical integrative samplers (POCIS) for quantification of conventional munitions constituents, including trinitrotoluene (TNT), aminodinitrotoluenes, diaminonitrotoluenes, dinitrotoluene, and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in a field setting. The POCIS were deployed at varying distances from the commonly used explosive formulation composition B (39.5% TNT, 59.

Conditioned attenuation of auditory brainstem responses in dolphins warned of an intense noise exposure: Temporal and spectral patterns.

Conditioned reductions in hearing sensitivity were elicited in two bottlenose dolphins by pairing a 10-kHz tone (the conditioned stimulus) with a more intense tone (the unconditioned stimulus) at 20, 40, or 80 kHz. Hearing was assessed via noninvasive measurement of auditory brainstem responses (ABRs) to 20 - to 133-kHz tone bursts presented at randomized intervals from 1 to 3 ms. ABRs within each trial were obtained by averaging the instantaneous electroencephalogram, time-locked to tone burst onsets, over 2- to 3-s time intervals.

Performance of an in situ activated carbon treatment to reduce PCB availability in an active harbor.

In situ amendment of surface sediment with activated carbon is a promising technique for reducing the availability of hydrophobic organic compounds in surface sediment. The present study evaluated the performance of a logistically challenging activated carbon placement in a high-energy hydrodynamic environment adjacent to and beneath a pier in an active military harbor. Measurements conducted preamendment and 10, 21, and 33 months (mo) postamendment using in situ exposures of benthic invertebrates and passive samplers indicated that the targeted 4% (by weight) addition of activated carbon (particle diameter ≤74 µm) in the uppermost 10 cm of surface sediment reduced polychlorinated biphenyl availability by an average (± standard deviation) of 81 ± 11% in the first 10 mo after amendment.

Investigation of polar organic chemical integrative sampler (POCIS) flow rate dependence for munition constituents in underwater environments.

Munition constituents (MC) are present in aquatic environments throughout the world. Potential for fluctuating release with low residence times may cause concentrations of MC to vary widely over time at contaminated sites. Recently, polar organic chemical integrative samplers (POCIS) have been demonstrated to be valuable tools for the environmental exposure assessment of MC in water.

Timing and context of dolphin clicks during and after mine simulator detection and marking in the open ocean.

Two dolphins carrying cameras swam in the ocean as they searched for and marked mine simulators - buried, proud or moored. As the animals swam ahead of a boat they searched the ocean. Cameras on their harness recorded continuous sound and video.

Effects of vibratory pile driver noise on echolocation and vigilance in bottlenose dolphins (Tursiops truncatus).

Vibratory pile drivers, used for marine construction, can produce sustained, high sound pressure levels (SPLs) in areas that overlap with dolphin habitats. Dolphins rely on echolocation for navigation, detecting predators and prey, and to coordinate group behavior. This study examined the effects of vibratory pile driver noise on dolphin sustained target detection capabilities through echolocation.

A Study of Vertical Transport through Graphene toward Control of Quantum Tunneling.

Vertical integration of van der Waals (vdW) materials with atomic precision is an intriguing possibility brought forward by these two-dimensional (2D) materials. Essential to the design and analysis of these structures is a fundamental understanding of the vertical transport of charge carriers into and across vdW materials, yet little has been done in this area. In this report, we explore the important roles of single layer graphene in the vertical tunneling process as a tunneling barrier.