A Pressure Based Compressible Solver for Electric Arc-plasma Simulation

The electric arc discharge in a liquid medium is used in several applications such as the sterilization of the liquid by UV radiation, the fracturing of rocks by shock wave, the circuit breakers in oil bath or the forming of mechanical parts. Thus, describing the physics of the arc in a liquid and in particular its interaction with a liquid interface is an important issue to better characterize this type of configuration. However, such a challenging task requires to couple high-fidelity solver for compressible two-phase flows with liquid phase change and a plasma solver to describe the plasma and its interaction with the bubble. To study this type of medium, we use a compressible formulation of the fluid equations. For this purpose, a pressure based solver has been developed for the computation of the energy conservation equation. Moreover, our numerical model uses the immersed boundary method to simulate the solid electrodes. The numerical model is briefly described in this paper and the first results of the electric arc discharge in steam water are presented. To our knowledge this pressure based model has never been used to describe plasmas and electric arc discharge

xclim: xarray-based climate data analytics

xclim is a Python library that enables computation of climate indicators over large, hetero- geneous data sets. It is built using xarray objects and operations, can seamlessly benefit from the parallelization handling provided by dask, and relies on community conventions for data formatting and metadata attributes. xclim is meant as a tool to facilitate both climate science research and the delivery of operational climate services and products. In addition to climate indicator calculations, xclim also includes utilities for bias correction and statistical adjustment, ensemble analytics, model diagnostics, data quality assurance, and metadata standards compliance

Degradation of cellular mir-27 by a novel, highly abundant viral transcript is important for efficient virus replication in vivo.

Cytomegaloviruses express large amounts of viral miRNAs during lytic infection, yet, they only modestly alter the cellular miRNA profile. The most prominent alteration upon lytic murine cytomegalovirus (MCMV) infection is the rapid degradation of the cellular miR-27a and miR-27b. Here, we report that this regulation is mediated by the ∼1.7 kb spliced and highly abundant MCMV m169 transcript. Specificity to miR-27a/b is mediated by a single, apparently optimized, miRNA binding site located in its 3'-UTR. This site is easily and efficiently retargeted to other cellular and viral miRNAs by target site replacement. Expression of the 3'-UTR of m169 by an adenoviral vector was sufficient to mediate its function, indicating that no other viral factors are essential in this process. Degradation of miR-27a/b was found to be accompanied by 3'-tailing and -trimming. Despite its dramatic effect on miRNA stability, we found this interaction to be mutual, indicating potential regulation of m169 by miR-27a/b. Most interestingly, three mutant viruses no longer able to target miR-27a/b, either due to miRNA target site disruption or target site replacement, showed significant attenuation in multiple organs as early as 4 days post infection, indicating that degradation of miR-27a/b is important for efficient MCMV replication in vivo

Towards long-term standardised carbon and greenhouse gas observations for monitoring Europe's terrestrial ecosystems : a review

Research infrastructures play a key role in launching a new generation of integrated long-term, geographically distributed observation programmes designed to monitor climate change, better understand its impacts on global ecosystems, and evaluate possible mitigation and adaptation strategies. The pan-European Integrated Carbon Observation System combines carbon and greenhouse gas (GHG; CO2, CH4, N2O, H2O) observations within the atmosphere, terrestrial ecosystems and oceans. High-precision measurements are obtained using standardised methodologies, are centrally processed and openly available in a traceable and verifiable fashion in combination with detailed metadata. The Integrated Carbon Observation System ecosystem station network aims to sample climate and land-cover variability across Europe. In addition to GHG flux measurements, a large set of complementary data (including management practices, vegetation and soil characteristics) is collected to support the interpretation, spatial upscaling and modelling of observed ecosystem carbon and GHG dynamics. The applied sampling design was developed and formulated in protocols by the scientific community, representing a trade-off between an ideal dataset and practical feasibility. The use of open-access, high-quality and multi-level data products by different user communities is crucial for the Integrated Carbon Observation System in order to achieve its scientific potential and societal value.Peer reviewe

Application of a level set method for simulation of droplet collisions

Tanguy, S Berlemont, AA level set technique for interface tracking is presented, both for the continuum surface force formulation and the ghost fluid method approach. A projection method is used to solve incompressible Navier-Stokes equations that are coupled to a transport equation for the level set function, defined as the algebraic distance to interface. Results are presented for head-on droplet collisions in coalescence and reflexive regimes with a 2D axi-symmetric code, and for an off-center droplet collision in a separation regime for a large impact parameter with 3D code. Simulations provided realistic and various droplet collision behaviors and they correspond to experimental observations. (c) 2005 Elsevier Ltd. All rights reserved

Revisiting Hopenhayn and Nicolini’s optimal unemployment insurance with job search monitoring and sanctions

Photograph of from L to R: Carlton Beck, Bud Abbott and Lou Costello at KOCY Radio Station in Oklahoma City, OK. Photo taken by Meyers Photo Shop for the KOCY Acct., 1946

A level set method for vaporizing two-phase flows

Tanguy, Sebastien Menard, Thibaut Berlemont, AlainDevelopment and applications of numerical methods devoted to reactive interface simulations are presented. Emphasis is put on vaporization, where numerical difficulties arise in imposing accurate jump conditions for heat and mass transfers. We use both the Level Set Method and the Ghost Fluid Method to capture the interface motion accurately and to handle suitable jump conditions. A local vaporization mass flow rate per unit of surface area is defined and Stefan flow is involved in the process. Specific care has been devoted to the extension of discontinuous variables across the interface to populate ghost cells, in order to avoid parasitic currents and numerical diffusion across the interface. A projection method is set up to impose both the velocity field continuity and a divergence-free condition for the extended velocity field across the interface. The d(2) law is verified in the numerical simulations of the vaporization of an isolated static drop. Results are then presented for a water droplet moving in air. Vapor mass fraction and temperature fields inside and outside the droplet are presented. (c) 2006 Elsevier Inc. All rights reserved

Coupling level set/VOF/ghost fluid methods: Validation and application to 3D simulation of the primary break-up of a liquid jet

Menard, T. Tanguy, S. Berlemont, A.Numerical simulations are carried out to describe the dense zone of a spray where very little information is available, either from experimental or theoretical approaches. Interface tracking is ensured by the level set method and the ghost fluid method (GFM) is used to capture accurately sharp discontinuities for pressure, density and viscosity. The level set method is coupled with the VOF method for mass conservation. The level set-VOF coupling is validated on 2D and 3D test cases. The level set-ghost fluid method is applied to the Rayleigh instability of a liquid jet. Preliminary results are then presented for 3D simulation of the primary break-up of a turbulent liquid jet with the level set-VOF-ghost fluid method. (C) 2006 Published by Elsevier Ltd