The adsorption behaviour of isobutane on Pt(533): A combined RAIRS and TPD study

The adsorption of isobutane on a Pt(533) stepped surface has been investigated using temperature programmed desorption (TPD) and reflection absorption infrared spectroscopy (RAIRS). Isobutane exists in two monolayer states and one multilayer phase on the Pt(533) surface. The most stable desorption state is caused by isobutane desorbing from the terrace planes. The orientation of isobutane in this state was determined from RAIRS measurements. The second monolayer phase probably belongs to isobutane molecules with only two hydrogen atoms in direct contact with the surface. RAIRS spectra also showed there was little bond weakening due to metal adsorbate interaction

Some Applications of a Two-Fluid Model

International audienc

A Method To Accelerate LES Explicit Solvers Using Local Time-Stepping

International audienceIn practical flow congurations, a large disparities of geometrical length scales are often encountered. Inside a combustor, for example, the ratio between the diameter of the injection holes and the size of the entire combustion chamber may present several orders of magnitude. When considering an explicit solver for fully compressible Navier-Stokes equations, the global time step is constrained through a CFL-like condition by the size of the smallest cells in the overall computational domain. Local renement of the injector leads to an inhomogeneous mesh and the former restriction drastically alters the overall solver effciency. A new local time-stepping (LTS) method is proposed to address this issue. The domain is divided into subgrids composed of cells that have similar sizes. Flow equations are simultaneously advanced on each subgrid which have a local time step adapted to satisfy the local CFL condition. The accuracy of the method has been veried on a simple convection case using a test code. The method has also been implemented in a large eddy simulation (LES) explicit solver and successfully tested for an acoustic wave propagation. It has been nally used in the two-dimensional large eddy simulation of a turbulent jet

SAMHD1 acts at stalled replication forks to prevent interferon induction

SAMHD1 was previously characterized as a dNTPase that protects cells from viral infections. Mutations in SAMHD1 are implicated in cancer development and in a severe congenital inflammatory disease known as Aicardi-Goutieres syndrome. The mechanism by which SAMHD1 protects against cancer and chronic inflammation is unknown. Here we show that SAMHD1 promotes degradation of nascent DNA at stalled replication forks in human cell lines by stimulating the exonuclease activity of MRE11. This function activates the ATR-CHK1 checkpoint and allows the forks to restart replication. In SAMHD1-depleted cells, single-stranded DNA fragments are released from stalled forks and accumulate in the cytosol, where they activate the cGAS-STING pathway to induce expression of pro-inflammatory type I interferons. SAMHD1 is thus an important player in the replication stress response, which prevents chronic inflammation by limiting the release of single-stranded DNA from stalled replication forks