A model of three-dimensional shear wave velocity variations in the mantle reveals a tilted low velocity anomaly extending from the core-mantle boundary (CMB) region beneath the southeastern Atlantic Ocean into the upper mantle beneath eastern Africa. This anomaly suggests that Cenozoic flood basalt volcanism in the Afar region and active rifting beneath the East African Rift is linked to an extensive thermal anomaly at the CMB more than 45 degrees away. In contrast, a low velocity anomaly beneath Iceland is confined to the upper mantle.

https://science.sciencemag.org/content/sci/286/5446/1925.full.pdf

Complex Shear Wave Velocity Structure Imaged Beneath Africa and Iceland.

Global tomographic images of mantle plumes and subducting slabs: Insight into deep Earth dynamics

Methods of manufacturing a liquid crystal device including depositing a layer of liquid crystal material on a substrate and imprinting a pattern on the layer of liquid crystal material using an imprint template are disclosed. The liquid crystal material can be jet deposited. The imprint template can include surface relief features, Pancharatnam-Berry Phase Effect (PBPE) structures or diffractive structures. The liquid crystal device manufactured by the methods described herein can be used to manipulate light, such as for beam steering, wavefront shaping, separating wavelengths and/or polarizations, and combining different wavelengths and/or polarizations.

Virtual and augmented reality systems and methods

The making and breaking of supercontinents: Some speculations based on superplumes, super downwelling and the role of tectosphere

Cenozoic rifting and volcanism in Europe have been associated with either passive or active mantle upwellings. Tomographic images show a low velocity structure between 660- and 2000-kilometer depth, which we propose to represent a lower mantle upwelling under central Europe that may feed smaller upper-mantle plumes. The position of the rift zones in the foreland of the Alpine belts and the relatively weak volcanism compared to other regions with plume-associated volcanism are probably the result of the past and present subduction under southern Europe.

A Lower Mantle Source for Central European Volcanism.

Effect of the mid-mantle viscosity and phase-transition structure on 3D mantle convection

A structured query can capture the complexity of object interactions (e.g. 'woman rides motorcycle') unlike single objects (e.g. 'woman' or 'motorcycle'). Retrieval using structured queries therefore is much more useful than single object retrieval, but a much more challenging problem. In this paper we present a method which uses scene graph embeddings as the basis for an approach to image retrieval. We examine how visual relationships, derived from scene graphs, can be used as structured queries. The visual relationships are directed subgraphs of the scene graph with a subject and object as nodes connected by a predicate relationship. Notably, we are able to achieve high recall even on low to medium frequency objects found in the long-tailed COCO-Stuff dataset, and find that adding a visual relationship-inspired loss boosts our recall by 10% in the best case.

Structured Query-Based Image Retrieval Using Scene Graphs

Recent geophysical evidence from seismology, mineral physics, viscosity inversion shows that the mantle between 400 and 1000 km is extremely complicated, with intermediate scale structures present regionally as seismic reflectors under the 660 km discontinuity and bent plume-like structures under the transition zone. We have studied the dynamics of the transition zone with two models, an axisymmetric spherical-shell (2-D) model with a horizontally averaged temperature- and pressure-dependent viscosity and a 3-D Cartesian model with a depth-dependent viscosity. Two mantle phase transitions have been employed in both models. Results of the 2-D axisymmetric model show that the interaction of the lower mantle plumes with the transition zone can result in a horizontal channel flow right underneath the 660 km and in the birth of secondary plume some distance away from the lower mantle plume. The strength of the secondary plume increases in strength with larger viscosity contrast across the 660 km discontinuity. In the 3-D model we have found that with the presence of a second low viscosity zone somewhere between 660 and 1000 km, many secondary instabilities are developed in the second asthenosphere and the mesoscale thermal structure developed can become quite complex. Many small-scale plumes can emanate from the transition zone. Occasionally a very large plume burst, with a near-surface radius exceeding 1000 km, can develop from the hot lower-mantle material trapped in the second asthenosphere. Both the viscosity and the phase transition structure between 660 km and 1000 km can exert a significant influence on the plume distribution and cause singular plume eruption events in the upper mantle. Plume instabilities originating below the 660 km discontinuity in the western Pacific might have launched a large hot upwelling into the upper mantle, thus precipitating the massive flood basalt volcanism in the Ontong-Java region.

/pdf/mesoscale-structures-in-the-transition-zone-dynamical-2b44mthwjz.pdf

Mesoscale structures in the transition zone : Dynamical consequences of boundary layer activities

A structured query can capture the complexity of object interactions (eg 'woman rides motorcycle') unlike single objects (eg 'woman' or 'motorcycle') Retrieval using structured queries therefore is much more useful than single object retrieval, but a much more challenging problem In this paper we present a method which uses scene graph embeddings as the basis for an approach to image retrieval We examine how visual relationships, derived from scene graphs, can be used as structured queries The visual relationships are directed subgraphs of the scene graph with a subject and object as nodes connected by a predicate re-lationhship Notably, we are able to achieve high recall even on low to medium frequency objects found in the long-tailed COCO-Stuff dataset, and find that adding a visual relationship-inspired loss boosts our recall by 10% in the best case

/pdf/structured-query-based-image-retrieval-using-scene-graphs-46v70drw0e.pdf

Many robotic and industrial systems require 3-D range-sensing capabilities for mapping, localization, navigation, and obstacle avoidance. Laser-scanning systems that mechanically trace a range-sensing beam over a raster or similar pattern can produce highly accurate models but tend to be bulky and slow when acquiring a significant field of view at useful resolutions. Stereo cameras can provide video-rate range images over significant fields of view but tend to have difficulty with scenes containing low or confusing textures. A new generation of active light, time-of-flight range sensors use a 2-D array of sensor elements to produce a 3-D range image at video rates. These sensors pose unique calibration challenges, requiring both the usual calibration of lens distortion (intrinsic calibration) and calibration of the time-of-flight range measurement (3-D calibration). We present our application of a photogrammetric calibration approach using inexpensive printed optical targets and off-the-shelf software to solve both intrinsic and range calibrations for the MESA Imaging SwissRanger SR-3100 range imaging sensor. Specific calibration issues stemming from this sensor's correlation of reflectivity with measured range are identified. We further present the integration of this otherwise grayscale 3-D sensor with an optical camera, providing a full-color, video-rate 3-D sensing solution.

Brigit Schroeder

Papers

Effect of the mid-mantle viscosity and phase-transition structure on 3D mantle convection

Structured Query-Based Image Retrieval Using Scene Graphs

Mesoscale structures in the transition zone : Dynamical consequences of boundary layer activities

Structured Query-Based Image Retrieval Using Scene Graphs

Photogrammetric calibration and colorization of the SwissRanger SR-3100 3-D range imaging sensor