Polaro–cryptic mirror of the lookdown as a biological model for open ocean camouflage

With no object to hide behind in 3D space, the open ocean represents a challenging environment for camouflage. Conventional strategies for reflective crypsis (e.g., standard mirror) are effective against axially symmetric radiance fields associated with high solar altitudes, yet ineffective against asymmetric polarized radiance fields associated with low solar inclinations. Here we identify a biological model for polaro–crypsis. We measured the surface-reflectance Mueller matrix of live open ocean fish (lookdown, Selene vomer) and seagrass-dwelling fish (pinfish, Lagodon rhomboides) using polarization-imaging and modeling polarization camouflage for the open ocean. Lookdowns occupy the minimization basin of our polarization-contrast space, while pinfish and standard mirror measurements exhibit higher contrast values than optimal. The lookdown reflective strategy achieves significant gains in polaro–crypsis (up to 80%) in comparison with nonpolarization sensitive strategies, such as a vertical mirror. Lookdowns achieve polaro–crypsis across solar altitudes by varying reflective properties (described by 16 Mueller matrix elements mij) with incident illumination. Lookdowns preserve reflected polarization aligned with principle axes (dorsal–ventral and anterior–posterior, m22 = 0.64), while randomizing incident polarization 45° from principle axes (m33 = –0.05). These reflectance properties allow lookdowns to reflect the uniform degree and angle of polarization associated with high-noon conditions due to alignment of the principle axes and the sun, and reflect a more complex polarization pattern at asymmetrical light fields associated with lower solar elevations. Our results suggest that polaro–cryptic strategies vary by habitat, and require context-specific depolarization and angle alteration for effective concealment in the complex open ocean environment

Fugitive emissions from the Bakken shale illustrate role of shale production in global ethane shift

Ethane is the second most abundant atmospheric hydrocarbon, exerts a strong influence on tropospheric ozone, and reduces the atmosphere’s oxidative capacity. Global observations showed declining ethane abundances from 1984 to 2010, while a regional measurement indicated increasing levels since 2009, with the reason for this subject to speculation. The Bakken shale is an oil and gas‐producing formation centered in North Dakota that experienced a rapid increase in production beginning in 2010. We use airborne data collected over the North Dakota portion of the Bakken shale in 2014 to calculate ethane emissions of 0.23 ± 0.07 (2σ) Tg/yr, equivalent to 1–3% of total global sources. Emissions of this magnitude impact air quality via concurrent increases in tropospheric ozone. This recently developed large ethane source from one location illustrates the key role of shale oil and gas production in rising global ethane levels.Key PointsThe Bakken shale in North Dakota accounted for 1–3% total global ethane emissions in 2014These findings highlight the importance of shale production in global atmospheric ethane shiftThese emissions impact air quality and influence interpretations of recent global methane changesPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/142509/1/grl54333.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/142509/2/grl54333-sup-0001-2016GL068703-SI.pd

A review of the effects of colour and light on non-image function in humans

This paper reviews current knowledge on non-image-forming aspects of vision. Developments in the last 20 years have included the discovery of a fifth class of human visual pigment (melanopsin), in addition to the three classes of photopsin to be found in the cones and rhodopsin in the rods in the human retina. Melanopsin is found in a small number of retinal ganglion cells which then, in addition to receiving input from rods and cones, are intrinsically photosensitive. These retinal ganglion cells send their input primarily to the hypothalamus, where they help to regulate the circadian system (daily rhythms of sleep patterns, body temperature, heart rate, etc.). The discovery of the anatomical basis of non-image-forming vision has led to a great deal of research into the effects of light on sleep, depression and mood, retinal photodamage and well-being, amongst other factors. Given that recent technological innovations in LED lighting now give us greater control over environmental lighting, it is timely to review the non-visual effects of light in humans in order to inform lighting design in the future

Optical scattering from nanoparticle aggregates

textNanometer-scale particles of the noble metals have been used for decades as contrast enhancement agents in electron microscopy. Over the past several years it has been demonstrated that these particles also function as excellent contrast agents for optical imaging techniques. The resonant optical scattering they exhibit enables scattering cross sections that may be many orders of magnitude greater than the analogous efficiency factor for fluorescent dye molecules. Biologically relevant labeling with nanoparticles generally results in aggregates containing a few to several tens of particles. The electrodynamic coupling between particles in these aggregates produces observable shifts in the resonance-scattering spectrum. This dissertation provides a theoretical analysis of the scattering from nanoparticle aggregates. The key objectives are to describe this scattering behavior qualitatively and to provide numerical codes usable for modeling its application to biomedical engineering. Considerations of the lowest-order dipole-dipole coupling lead to simple qualitative predictions of the behavior of the spectral properties of the optical cross sections as they depend on number of particles, inter-particle spacing, and aggregate aspect ratio. More comprehensive analysis using the multiple-particle T-matrix formalism allows the elaboration of more subtle cross-section spectral features depending on the interactions of the electrodynamic collective-modes of the aggregate, of individual-particle modes, and of modes associated with groups of particles within the aggregate sub-structure. In combination these analyses and the supporting numerical code-base provide a unified electrodynamic approach which facilitates interpretation of experimental cross section spectra, guides the design of new biophysical experiments using nanoparticle aggregates, and enables optimal fabrication of nanoparticle structures for biophysical applications.Physic

Model-Based Design of Optical Diagnostic Instrumentation

Biophotonics methods are attractive since they allow for the non-invasive diagnosis of cancer. Experiments were carried out to investigate the feasibility of detecting early pre-cancer using optical spectroscopy. However, optimization of instrumentation design parameters remains challenging because of the lack of metrics to evaluate the performance of certain design parameters. For example, although using angled-collection geometry has been shown to collect depth sensitive spatial origins, the performance of devices with angled-collection geometries are not well characterized or quantified. In this study, we use a polarization-sensitive Monte Carlo simulation (Pol-MC) to aid in the design of instrumentation for the early detection of epithelial cancer. The tissue is modeled in layers: (0) air outside the tissue, (1) epithelial layer, (2) thin pre-cancer layer of cells, (3) thin basement membrane, implemented as a thin transparent layer, and (4) the stroma, implemented as a thick layer of scattering material. We propose a new metric, Target Signal Ratio (TSR), to evaluate the proportion of signal that is scattered from a target layer, which is the basal/pre-cancer layer. This study is a proof-of-concept for the application of computational techniques to facilitate instrument design.Biomedical Engineerin

Fugitive emissions from the Bakken shale illustrate role of shale production in global ethane shift

Abstract Ethane is the second most abundant atmospheric hydrocarbon, exerts a strong influence on tropospheric ozone, and reduces the atmosphere's oxidative capacity. Global observations showed declining ethane abundances from 1984 to 2010, while a regional measurement indicated increasing levels since 2009, with the reason for this subject to speculation. The Bakken shale is an oil and gas-producing formation centered in North Dakota that experienced a rapid increase in production beginning in 2010. We use airborne data collected over the North Dakota portion of the Bakken shale in 2014 to calculate ethane emissions of 0.23 0.07 (2) Tg/yr, equivalent to 1-3% of total global sources. Emissions of this magnitude impact air quality via concurrent increases in tropospheric ozone. This recently developed large ethane source from one location illustrates the key role of shale oil and gas production in rising global ethane levels. Key Points: The Bakken shale in North Dakota accounted for 1-3% total global ethane emissions in 2014 These findings highlight the importance of shale production in global atmospheric ethane shift These emissions impact air quality and influence interpretations of recent global methane change

Reciprocity in autistic and typically developing children and adolescents with and without mild intellectual disabilities

The assessment of autism in individuals with mild intellectual disabilities (MID) is complicated because of the overlap between autistic traits and intellectual limitations. Impaired social emotional reciprocity is a core diagnostic criterion for autism. However, it is unknown whether reciprocal behaviour differs between MID individuals with or without an autism spectrum disorder (ASD). This study explored differences in reciprocal behaviour of 35 children and adolescents with MID (intelligence quotient 50–85): 15 with ASD (ASD-MID) and 20 with typical development (TD-MID) using the Interactive Drawing Test (IDT). ASD-MID participants showed a lower quality of reciprocal behaviour compared with TD-MID participants. The difference in quality of reciprocal behaviour between ASD-MID and TD-MID participants was not significantly related with Peabody Picture Vocabulary Test scores and thus not attributable to verbal capacity. The IDT is likely to reflect the child's inclination to display reciprocal behaviour in everyday situations, as its scale scores were meaningfully associated with the level of social cognition assessed with the Social Responsiveness Scale. Thus, the IDT seems well suited for measuring impairments in reciprocal behaviour in children and adolescents with MID

Data from: Open-ocean fish reveal an omnidirectional solution to camouflage in polarized environments

Despite appearing featureless to our eyes, the open ocean is a highly variable environment for polarization-sensitive viewers. Dynamic visual backgrounds coupled with predator encounters from all possible directions make this habitat one of the most challenging for camouflage. We tested open-ocean crypsis in nature by collecting more than 1500 videopolarimetry measurements from live fish from distinct habitats under a variety of viewing conditions. Open-ocean fish species exhibited camouflage that was superior to that of both nearshore fish and mirrorlike surfaces, with significantly higher crypsis at angles associated with predator detection and pursuit. Histological measurements revealed that specific arrangements of reflective guanine platelets in the fish’s skin produce angle-dependent polarization modifications for polarocrypsis in the open ocean, suggesting a mechanism for natural selection to shape reflectance properties in this complex environment