Exposure to short-wavelength light influences refractive development and inhibits myopic development in many animal models. Retinal mechanisms underlying this response remain unknown. This study used ...a mouse model of lens-induced myopia to evaluate the effect of different wavelength light on refractive development and dopamine levels in the retina. A possible retinal pathway is tested using a mutant mouse with dysfunctional cones.
Wild-type C57BL/6J (WT) and ALS/LtJ/Gnat2cpfl3 (Gnat2-/-) mice were exposed to one of three different light conditions beginning at postnatal day 28: broad-spectrum "white" (420-680 nm), medium wavelength "green" (525 ± 40 nm), and short wavelength "violet" (400 ± 20 nm). One-half of the mice received hyperopic lens defocus. All mice were exposed to the light for 4 weeks; animals were measured weekly for refractive error and axial parameters. Retinal dopamine and the dopamine metabolite 3,4-dihydroxyphenylacetic acid were measured by HPLC.
In WT mice, short-wavelength violet light induced hyperopia and violet light inhibited lens-induced myopia when compared with mice exposed to white light. Hyperopia could be attributed to shallower vitreous chambers in WT animals. There were no changes in the levels of dopamine or its metabolite. In Gnat2-/- mice, violet light did not induce hyperopia or inhibit lens-induced myopia.
These findings show that short-wavelength light slows refractive eye growth, producing hyperopic responses in mice and inhibiting lens-induced myopia. The lack of inhibition in mice with dysfunctional cones suggests that cone signaling plays a role in the hyperopic response to short-wavelength (violet) light.
A visible atmospheric optical depth of 0.9 was measured by the Spirit rover at Gusev crater and by the Opportunity rover at Meridiani Planum. Optical depth decreased by about 0.6 to 0.7% per sol ...through both 90-sol primary missions. The vertical distribution of atmospheric dust at Gusev crater was consistent with uniform mixing, with a measured scale height of 11.56 ± 0.62 kilometers. The dust's cross section weighted mean radius was 1.47 ± 0.21 micrometers (µm) at Gusev and 1.52 ± 0.18 µm at Meridiani. Comparison of visible optical depths with 9-µm optical depths shows a visible-to-infrared optical depth ratio of 2.0 ± 0.2 for comparison with previous monitoring of infrared optical depths.
The Mars Exploration Rover Opportunity has investigated the landing site in Eagle crater and the nearby plains within Meridiani Planum. The soils consist of fine-grained basaltic sand and a surface ...lag of hematite-rich spherules, spherule fragments, and other granules. Wind ripples are common. Underlying the thin soil layer, and exposed within small impact craters and troughs, are flat-lying sedimentary rocks. These rocks are finely laminated, are rich in sulfur, and contain abundant sulfate salts. Small-scale cross-lamination in some locations provides evidence for deposition in flowing liquid water. We interpret the rocks to be a mixture of chemical and siliciclastic sediments formed by episodic inundation by shallow surface water, followed by evaporation, exposure, and desiccation. Hematite-rich spherules are embedded in the rock and eroding from them. We interpret these spherules to be concretions formed by postdepositional diagenesis, again involving liquid water.
Building on an exercise that identified potential harms from simulated investigational releases of a population suppression gene drive for malaria vector control, a series of online workshops ...identified nine recommendations to advance future environmental risk assessment of gene drive applications.
Overflights of the Mars Exploration Rovers (MER) by the Mars Global Surveyor (MGS) provide a unique opportunity to examine some of the basic properties of dust aerosols, starting with one of the most ...fundamental, the indices of refraction (m = n + ik) in the infrared. The upward‐viewing geometry of the Miniature Thermal Emission Spectrometer (Mini‐TES) and the combined contemporaneous observations from both MER and MGS are powerful tools. Their use allows atmospheric retrievals to directly determine n and k while offering constraints for the menagerie of other radiative transfer input parameters. We exploit these coordinated observing campaigns, along additional data sources, to carry out series of radiative transfer analyses that ultimately return the set of refractive indices. We apply the resulting m to a larger sample of Mini‐TES data to both further validate our approach and retrieve several other aerosol properties, including dust optical depth, dust size, and a measure of the vertical mixing profile. We find good agreement with the empirical approach of Smith et al. (2006), in terms of both the optical depths themselves and the frequency dependence of their extinction cross section and single scattering albedo. The retrieved dust sizes vary from near 1.3 μm to 1.8 μm within the selected sample, with a precision estimated to be ≃0.1–0.2 μm. The vertical mixing profile evolves from well‐mixed to appreciably confined by LS ∼ 30°. For Spirit (MER‐A), there is an abrupt transition back to a more well‐mixed vertical profile with the onset of regional dust activity at LS ∼ 140°. We discuss the lack of a definitive detection of water ice clouds in Mini‐TES observations and the potential effects of vertical gradients in particle size distribution. Finally, as part of coordinated overflight analyses, an atmospherically corrected TES Lambert albedo map is derived and presented in Appendix A.
Reports of plastics, at higher levels than previously thought, in the water that we drink and the air that we breathe, are generating considerable interest and concern. Plastics have been recorded in ...almost every environment in the world with estimates on the order of trillions of microplastic pieces. Yet, this may very well be an underestimate of plastic pollution as a whole. Once microplastics (<5 mm) break down in the environment, they nominally enter the nanoscale (<1,000 nm), where they cannot be seen by the naked eye or even with the use of a typical laboratory microscope. Thus far, research has focused on plastics in the macro- (>25 mm) and micro-size ranges, which are easier to detect and identify, leaving large knowledge gaps in our understanding of nanoplastic debris. Our ability to ask and answer questions relating to the transport, fate, and potential toxicity of these particles is disadvantaged by the detection and identification limits of current technology. Furthermore, laboratory exposures have been substantially constrained to the study of commercially available nanoplastics; i.e., polystyrene spheres, which do not adequately reflect the composition of environmental plastic debris. While a great deal of plastic-focused research has been published in recent years, the pattern of the work does not answer a number of key factors vital to calculating risk that takes into account the smallest plastic particles; namely, sources, fate and transport, exposure measures, toxicity and effects. These data are critical to inform regulatory decision making and to implement adaptive management strategies that mitigate risk to human health and the environment. This paper reviews the current state-of-the-science on nanoplastic research, highlighting areas where data are needed to establish robust risk assessments that take into account plastics pollution. Where nanoplastic-specific data are not available, suggested substitutions are indicated.
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