Abstract: Oceanic domains form via the break-up of the continental lithosphere resulting from extensional tectonic processes that eventually create passive margins. Whether active rifting and subsequent volcanic break-up occur within the oceanic lithosphere remains ambiguous. New seismic reflection data from the southern Bay of Bengal, where multiple mantle plumes were active during the late Cretaceous, provide visual evidence for resolving this issue. The studied seismic profile reveals an ∼300-km-wide anomalous crustal domain characterized by basement highs, irregular Moho depth fluctuations, and a thick pile of well-organized upper crustal dipping reflections. These features resemble those of volcanic passive margins, i.e., stacked volcanoclastic layers, seaward-dipping reflectors, underplating and failed rifting centers. Here, we document a similar setting within an intraoceanic domain, which is consistent with the active rifting model, with an excess magma supply presumably associated with active mantle upwelling. The structures described in the present study require a multistage dynamic process during local impingement of the northward-drifting Indian oceanic lithosphere by mantle upwelling, with a transition from thermal doming, intense volcanic eruptions and magmatic underplating, to lithospheric extension and necking, and finally to an incipient but failed rift. The volcanism initiated at ∼84–85 Ma, and volcanics were emplaced on young oceanic lithosphere with an age of ∼7–8 Ma. The active mantle upwelling that promoted the intraoceanic rifting was likely driven by a weak or pulsed branch of the Kerguelen Plume, which is also involved in producing the Ninety-East Ridge. These findings help further understand the processes dominating lithospheric breakup and extend some concepts seaward from passive margins to the interior of the oceanic lithospheric domain.

Abstract: Objective: To document the aspect, topography and morphometry of normal human choroidal arteries in the posterior pole by laser Doppler holography (LDH) and OCT. Design: Cross-sectional study. Subjects: Fifty-four eyes of 27 healthy subjects. Methods: A prototypic LDH system captured the laser Doppler shift of the choroidal circulation within the central 20°. Doppler shifts were filtered to extract high velocity vessels. Images of choroidal arteries identified by LDH were subsequently registered with en face and cross-sectional OCT images. Subsequently, the diameters of macular choroidal arteries and their correlation to central choroidal thickness was measured on OCT B-scans. Main Outcome Measures: Spatial disposition, distribution, and diameters of choroidal arteries. Results: Choroidal arteries were identified by LDH and OCT from their emergence from short posterior ciliary arteries (sPCAs), and could be traced to second and third divisions. In the 8 eyes that underwent LDH, 7 of 8 (88%) showed a horizontal first-order artery within 0.5 disc diameter from the fovea. OCT B-scans showed that first-order arteries were located along the sclera-choroid interface; around arteries, the choroidal tissue formed a pyramid-shaped avascular structure with a posterior base contiguous and isoreflective to the sclera. In a cohort of 49 eyes, the diameter of horizontal submacular arteries (average [± standard deviation] 136.3 μm [±47]; range, 70–209 μm) was weakly correlated to central choroidal thickness (P = 0.09). Conclusions: First-order choroidal arteries emerging from sPCAs are located along the sclerochoroidal interface and are surrounded by a pyramid-shaped avascular space, which contributes to differentiate them from veins. The majority of normal eye show a submacular first-order artery running horizontally toward the temporal periphery. These results will pave the way for a better knowledge of diseases affecting the choroidal circulation. Financial Disclosure(s): Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Abstract: The maximum deposition eigenchannel provides the largest possible power delivery to a target region inside a diffusive medium by optimizing the incident wavefront of a monochromatic beam. It originates from constructive interference of scattered waves, which is frequency sensitive. We investigate the spectral width of the maximum deposition eigenchannels over a range of target depths using numerical simulations of a 2D diffusive system. Compared to tight focusing into the system, power deposition to an extended region is more sensitive to frequency detuning. The spectral width of enhanced delivery to a large target displays a rather weak, nonmonotonic variation with target depth, in contrast to a sharp drop of focusing bandwidth with depth. While the maximum enhancement of power deposited within a diffusive system can exceed that of power transmitted through it, this comes at the cost of a narrower spectral width. We investigate the narrower deposition width in terms of the constructive interference of transmission eigenchannels within the target. We further observe that the spatial field distribution inside the target region decorrelates more slowly with spectral detuning than the power decay of the maximum deposition eigenchannel. Additionally, absorption increases the spectral width of deposition eigenchannels, but the depth dependence remains qualitatively identical to that without absorption. These findings hold for any diffusive waves, including electromagnetic waves, acoustic waves, pressure waves, mesoscopic electrons, and cold atoms.