Catastrophic volcanism as a cause of shocked features found at the K/T boundary and in cryptoexplosion structures

The presence of quartz grains containing shock lamellae at the Cretaceous/Tertiary (K/T) boundary is viewed by many as the single most compelling evidence of meteoritic or cometary impact because there is no known endogenous mechanism for producing these features. Similarly the presence of shocked quartz, shatter cones, coesite and stishovite at cryptoexplosion structures is comonly taken as conclusive evidence of impact. However, several recent studies have cast doubt on this interpretation. It is argued that basaltic volcanism, although not normally explosive, can under exceptional circumstances produce overpressures sufficiently high to produce shock features. The exceptional circumstances include a high content of volatiles, usually CO2, and no preestablished pathway to the surface. Rapid cooling of the saturated basaltic magma can occur if it underlies a cooler more evolved magma in a chamber. Initial slow cooling and partial exsolution of the volatiles will cause the density of the basaltic magma to become less than that of the overlying magma, leading to overturning and mixing. Gas will escape the magma chamber along planar cracks once the pressure becomes sufficiently high. In the vicinity of the crack tip there is a smallscale deviatoric stress pattern which is thought to be sufficiently high to produce transient cracks along secondary axes in the quartz crystals, causing the planar features. The CO2-rich fluid inclusions which have been found along planar elements of quartz in basement rocks of the Vredefort Dome were likely to have been emplaced by such a process. If the mechanism described is capable of producing shocked features as above, it would require a reassessment of the origin of many cryptoexplosion structures as well as seriously weakening the case for an impact origin of the K/T event

Keep it SMPL: Automatic Estimation of 3D Human Pose and Shape from a Single Image

We describe the first method to automatically estimate the 3D pose of the human body as well as its 3D shape from a single unconstrained image. We estimate a full 3D mesh and show that 2D joints alone carry a surprising amount of information about body shape. The problem is challenging because of the complexity of the human body, articulation, occlusion, clothing, lighting, and the inherent ambiguity in inferring 3D from 2D. To solve this, we first use a recently published CNN-based method, DeepCut, to predict (bottom-up) the 2D body joint locations. We then fit (top-down) a recently published statistical body shape model, called SMPL, to the 2D joints. We do so by minimizing an objective function that penalizes the error between the projected 3D model joints and detected 2D joints. Because SMPL captures correlations in human shape across the population, we are able to robustly fit it to very little data. We further leverage the 3D model to prevent solutions that cause interpenetration. We evaluate our method, SMPLify, on the Leeds Sports, HumanEva, and Human3.6M datasets, showing superior pose accuracy with respect to the state of the art.Comment: To appear in ECCV 201

Inner Space Preserving Generative Pose Machine

Image-based generative methods, such as generative adversarial networks (GANs) have already been able to generate realistic images with much context control, specially when they are conditioned. However, most successful frameworks share a common procedure which performs an image-to-image translation with pose of figures in the image untouched. When the objective is reposing a figure in an image while preserving the rest of the image, the state-of-the-art mainly assumes a single rigid body with simple background and limited pose shift, which can hardly be extended to the images under normal settings. In this paper, we introduce an image "inner space" preserving model that assigns an interpretable low-dimensional pose descriptor (LDPD) to an articulated figure in the image. Figure reposing is then generated by passing the LDPD and the original image through multi-stage augmented hourglass networks in a conditional GAN structure, called inner space preserving generative pose machine (ISP-GPM). We evaluated ISP-GPM on reposing human figures, which are highly articulated with versatile variations. Test of a state-of-the-art pose estimator on our reposed dataset gave an accuracy over 80% on PCK0.5 metric. The results also elucidated that our ISP-GPM is able to preserve the background with high accuracy while reasonably recovering the area blocked by the figure to be reposed.Comment: http://www.northeastern.edu/ostadabbas/2018/07/23/inner-space-preserving-generative-pose-machine

The Ekman-Hartmann layer in MHD Taylor-Couette flow

We study magnetic effects induced by rigidly rotating plates enclosing a cylindrical MHD Taylor-Couette flow at the finite aspect ratio $H/D=10$. The fluid confined between the cylinders is assumed to be liquid metal characterized by small magnetic Prandtl number, the cylinders are perfectly conducting, an axial magnetic field is imposed \Ha \approx 10, the rotation rates correspond to \Rey of order $10^2-10^3$. We show that the end-plates introduce, besides the well known Ekman circulation, similar magnetic effects which arise for infinite, rotating plates, horizontally unbounded by any walls. In particular there exists the Hartmann current which penetrates the fluid, turns into the radial direction and together with the applied magnetic field gives rise to a force. Consequently the flow can be compared with a Taylor-Dean flow driven by an azimuthal pressure gradient. We analyze stability of such flows and show that the currents induced by the plates can give rise to instability for the considered parameters. When designing an MHD Taylor-Couette experiment, a special care must be taken concerning the vertical magnetic boundaries so they do not significantly alter the rotational profile.Comment: 9 pages, 6 figures; accepted to PR

Some closure operations in Zariski-Riemann spaces of valuation domains: a survey

In this survey we present several results concerning various topologies that were introduced in recent years on spaces of valuation domains

On the existence and structure of a mush at the inner core boundary of the Earth

It has been suggested about 20 years ago that the liquid close to the inner core boundary (ICB) is supercooled and that a sizable mushy layer has developed during the growth of the inner core. The morphological instability of the liquid-solid interface which usually results in the formation of a mushy zone has been intensively studied in metallurgy, but the freezing of the inner core occurs in very unusual conditions: the growth rate is very small, and the pressure gradient has a key role, the newly formed solid being hotter than the adjacent liquid. We investigate the linear stability of a solidification front under such conditions, pointing out the destabilizing role of the thermal and solutal fields, and the stabilizing role of the pressure gradient. The main consequence of the very small solidification rate is the importance of advective transport of solute in liquid, which tends to remove light solute from the vicinity of the ICB and to suppress supercooling, thus acting against the destabilization of the solidification front. For plausible phase diagrams of the core mixture, we nevertheless found that the ICB is likely to be morphologically unstable, and that a mushy zone might have developed at the ICB. The thermodynamic thickness of the resulting mushy zone can be significant, from $\sim100$ km to the entire inner core radius, depending on the phase diagram of the core mixture. However, such a thick mushy zone is predicted to collapse under its own weight, on a much smaller length scale ($\lesssim 1$ km). We estimate that the interdendritic spacing is probably smaller than a few tens of meter, and possibly only a few meters

Learning 3D Human Pose from Structure and Motion

3D human pose estimation from a single image is a challenging problem, especially for in-the-wild settings due to the lack of 3D annotated data. We propose two anatomically inspired loss functions and use them with a weakly-supervised learning framework to jointly learn from large-scale in-the-wild 2D and indoor/synthetic 3D data. We also present a simple temporal network that exploits temporal and structural cues present in predicted pose sequences to temporally harmonize the pose estimations. We carefully analyze the proposed contributions through loss surface visualizations and sensitivity analysis to facilitate deeper understanding of their working mechanism. Our complete pipeline improves the state-of-the-art by 11.8% and 12% on Human3.6M and MPI-INF-3DHP, respectively, and runs at 30 FPS on a commodity graphics card.Comment: ECCV 2018. Project page: https://www.cse.iitb.ac.in/~rdabral/3DPose

Radiography of the Earth's Core and Mantle with Atmospheric Neutrinos

A measurement of the absorption of neutrinos with energies in excess of 10 TeV when traversing the Earth is capable of revealing its density distribution. Unfortunately, the existence of beams with sufficient luminosity for the task has been ruled out by the AMANDA South Pole neutrino telescope. In this letter we point out that, with the advent of second-generation kilometer-scale neutrino detectors, the idea of studying the internal structure of the Earth may be revived using atmospheric neutrinos instead.Comment: 4 pages, LaTeX file using RevTEX4, 2 figures and 1 table included. Matches published versio

Collisional Broadening and Shift of D1 and D2 Spectral Lines in Atomic Alkali Vapor - Noble Gas Systems

The Baranger model is used to compute collisional broadening and shift of the D1 and D2 spectral lines of M + Ng, where M = K, Rb, Cs and Ng = He, Ne, Ar, using scattering phase shift differences which are calculated from scattering matrix elements. Scattering matrix elements are calculated using the Channel Packet Method where the collisions are treated non-adiabatically and include spin-orbit and Coriolis couplings. Non-adiabatic wavepacket dynamics are determined using the split-operator method together with a unitary transformation between adiabatic and diabatic representations. Scattering phase shift differences are thermally weighted and integrated over energies ranging from E = 0 Hartree up to E = 0.0075 Hartree and averaged over values of total angular momentum that range from J = 0.5 up to J = 400.5. Phase shifts are extrapolated linearly to provide an approximate extension of the energy regime up to E = 0.012 Hartree. Broadening and shift coefficients are obtained for temperatures ranging from T = 100 K up to T = 800 K and compared with experiment. Predictions from this research find application in laser physics and specifically with improvement of total power output of Optically Pumped Alkali Laser systems

Carrington-class Events as a Great Filter for Electronic Civilizations in the Drake Equation

The Drake equation is a calculation providing an upper bound on the likely number of intelligent species in our galaxy. In order to reconcile a potentially high occurrence of intelligent extraterrestrial species with the current non-observation of them, we frequently resort to some Great Filter which represents some inevitable, cataclysmic fate (such as nuclear war, pandemic, or asteroid impact) that tends to await enough worlds to negate the expectation that the galaxy ought to be teeming with intelligent life. This paper is intended to examine one potential Great Filter for electronic-based civilizations, the impact of a Carrington-class coronal mass ejection (CME) from the Sun. Carrington-class CMEs are classified as once in a century events caused by our Sun; this appears to place a time limit, following the development of a civilization dependent on electronic devices, either for hardening electronics against the geomagnetically induced currents that result from CMEs or for beginning interplanetary colonization