Kinematic validation of a quasi-geostrophic model for the fast dynamics in the Earth’s outer core

We derive a quasi-geostrophic (QG) system of equations suitable for the description of the Earth’s core dynamics on interannual to decadal timescales. Over these timescales, rotation is assumed to be the dominant force and fluid motions are strongly invariant along the direction parallel to the rotation axis. The diffusion-free, QG system derived here is similar to the one derived in Canet et al. but the projection of the governing equations on the equatorial disc is handled via vertical integration and mass conservation is applied to the velocity field. Here we carefully analyse the properties of the resulting equations and we validate them neglecting the action of the Lorentz force in the momentum equation. We derive a novel analytical solution describing the evolution of the magnetic field under these assumptions in the presence of a purely azimuthal flow and an alternative formulation that allows us to numerically solve the evolution equations with a finite element method. The excellent agreement we found with the analytical solution proves that numerical integration of the QG system is possible and that it preserves important physical properties of the magnetic field. Implementation of magnetic diffusion is also briefly considered

Plesio-geostrophy for Earth’s core: I. Basic equations, inertial modes and induction

An approximation is developed that lends itself to accurate description of the physics of fluid motions and motional induction on short time scales (e.g. decades), appropriate for planetary cores and in the geophysically relevant limit of very rapid rotation. Adopting a representation of the flow to be columnar (horizontal motions are invariant along the rotation axis), our characterization of the equations leads to the approximation we call plesio-geostrophy, which arises from dedicated forms of integration along the rotation axis of the equations of motion and of motional induction. Neglecting magnetic diffusion, our self-consistent equations collapse all three-dimensional quantities into two-dimensional scalars in an exact manner. For the isothermal magnetic case, a series of fifteen partial differential equations is developed that fully characterizes the evolution of the system. In the case of no forcing and absent viscous damping, we solve for the normal modes of the system, called inertial modes. A comparison with a subset of the known three-dimensional modes that are of the least complexity along the rotation axis shows that the approximation accurately captures the eigenfunctions and associated eigenfrequencies

Propagation and reflection of diffusionless torsional waves in a sphere

We consider an inviscid and perfectly conducting fluid sphere in rapid rotation and permeated by a background magnetic field. Such a system admits normal modes in the form of torsional oscillations, namely azimuthal motions of cylinders coaxial with the rotation axis. We analyse this system for a particular background magnetic field that provides a new closed form normal mode solution. We derive Wentzel–Kramers–Brillouin–Jeffreys (WKBJ) approximations to the normal modes, and focus particularly on the reflections that take place on the rotation axis and at the equator. We propose a procedure to calculate the reflection coefficients and we discuss the analogy of our findings with well-known seismological results. Our analytical results are tested against numerical calculations and show good agreement

Self-Positioning Smart Buoys, The \u27Un-Buoy\u27 Solution: Logistic Considerations Using Autonomous Surface Craft Technology and Improved Communications Infrastructure

Moored buoys have long served national interests, but incur high development, construction, installation, and maintenance costs. Buoys which drift off-location can pose hazards to mariners, and in coastal waters may cause environmental damage. Moreover, retrieval, repair and replacement of drifting buoys may be delayed when data would be most useful. Such gaps in coastal buoy data can pose a threat to national security by reducing maritime domain awareness. The concept of self-positioning buoys has been advanced to reduce installation cost by eliminating mooring hardware. We here describe technology for operation of reduced cost self-positioning buoys which can be used in coastal or oceanic waters. The ASC SCOUT model is based on a self-propelled, GPS-positioned, autonomous surface craft that can be pre-programmed, autonomous, or directed in real time. Each vessel can communicate wirelessly with deployment vessels and other similar buoys directly or via satellite. Engineering options for short or longer term power requirements are considered, in addition to future options for improved energy delivery systems. Methods of reducing buoy drift and position-maintaining energy requirements for self-locating buoys are also discussed, based on the potential of incorporating traditional maritime solutions to these problems. We here include discussion of the advanced Delay Tolerant Networking (DTN) communications draft protocol which offers improved wireless communication capabilities underwater, to adjacent vessels, and to satellites. DTN is particularly adapted for noisy or loss-prone environments, thus it improves reliability. In addition to existing buoy communication via commercial satellites, a growing network of small satellites known as PICOSATs can be readily adapted to provide low-cost communications nodes for buoys. Coordination with planned vessel Automated Identification Systems (AIS) and International Maritime Organization standards for buoy and vessel notificat- - ion systems are reviewed and the legal framework for deployment of autonomous surface vessels is considered

PI3kinases in diabetes mellitus and its related complications

Recent studies have shown that phosphoinositide 3-kinases (PI3Ks) have become the target of many pharmacological treatments, both in clinical trials and in clinical practice. PI3Ks play an important role in glucose regulation, and this suggests their possible involvement in the onset of diabetes mellitus. In this review, we gather our knowledge regarding the effects of PI3K isoforms on glucose regulation in several organs and on the most clinically-relevant complications of diabetes mellitus, such as cardiomyopathy, vasculopathy, nephropathy, and neurological disease. For instance, PI3K α has been proven to be protective against diabetes-induced heart failure, while PI3K γ inhibition is protective against the disease onset. In vessels, PI3K γ can generate oxidative stress, while PI3K β inhibition is anti-thrombotic. Finally, we describe the role of PI3Ks in Alzheimer’s disease and ADHD, discussing the relevance for diabetic patients. Given the high prevalence of diabetes mellitus, the multiple effects here described should be taken into account for the development and validation of drugs acting on PI3Ks

The Jason II virtual control van system, data acquisition system, web-based event logger, and SeaNet

Scientific underwater remotely operated vehicles (ROVs) collect data from multiple video cameras and scientific instruments. This integrated information is often only available in an ROV control-van during operations. Although all the data is logged, it is difficult for scientists to re-create a combined display of this data and have the ability to review and access an entire cruise dataset easily. We introduce a methodology of taking continuous real-time information snapshots (infosnaps) during interesting events and at regular time intervals for complete data coverage. These infosnaps capture four simultaneous video sources, vehicle data, instrument data, and event data as entered by scientists. The infosnaps are automatically cataloged and immediately accessible and searchable via a web-browser. We developed, built, and deployed the Jason II Virtual Control Van system on seven Jason cruises. The system has captured over 50,000 control-van infosnaps, containing more than 200,000 images co-registered with vehicle telemetry and scientific instrument data. The Virtual Control Van is designed for both scientific collaboration and public/educational outreach. It has been integrated with the SeaNet system to provide remote on-shore access. The report describes the Jason II Virtual Control Van system and includes instructions for setting up the system in the field.Funding was provided by the W. M. Keck Foundation under Grant No. 991735

Probing neutrino masses with CMB lensing extraction

We evaluate the ability of future cosmic microwave background (CMB) experiments to measure the power spectrum of large scale structure using quadratic estimators of the weak lensing deflection field. We calculate the sensitivity of upcoming CMB experiments such as BICEP, QUaD, BRAIN, ClOVER and PLANCK to the non-zero total neutrino mass M_nu indicated by current neutrino oscillation data. We find that these experiments greatly benefit from lensing extraction techniques, improving their one-sigma sensitivity to M_nu by a factor of order four. The combination of data from PLANCK and the SAMPAN mini-satellite project would lead to sigma(M_nu) = 0.1 eV, while a value as small as sigma(M_nu) = 0.035 eV is within the reach of a space mission based on bolometers with a passively cooled 3-4 m aperture telescope, representative of the most ambitious projects currently under investigation. We show that our results are robust not only considering possible difficulties in subtracting astrophysical foregrounds from the primary CMB signal but also when the minimal cosmological model (Lambda Mixed Dark Matter) is generalized in order to include a possible scalar tilt running, a constant equation of state parameter for the dark energy and/or extra relativistic degrees of freedom.Comment: 13 pages, 4 figures. One new figure and references added. Version accepted for publicatio