Intermittency in a Locally Forced Plane Couette Flow

International audienceThe plane Couette flow displays a globally subcritical transition to turbulence. When forced by a thin wire introduced in the central plane, the basic flow bifurcates towards a new state of streamwise vortices which break down through a complex spatiotemporal regime. When a bead is introduced in the central plane, only a few vortices are generated. Their destabilization occurs via a new type of temporal intermittency hard to understand within the framework of dynamical system

Thermodynamics of hydration and oxidation in the proton conductor Gd-doped barium cerate from density functional theory calculations

International audienceHydration and oxidation of gadolinium-doped barium cerate, a system with highly promising properties when used as electrolyte for protonic ceramic fuel cells, are investigated by means of density functional calculations. The energy landscape of oxygen vacancies and interstitial protons in this strongly distorted orthorhombic perovskite is computed. Although the most stable sites for protons are found in the close vicinity of the dopant, the picture of a very complex energy landscape emerges, in which some sites far away from Gd are found more stable than other ones in its close vicinity, due to the highly distorted geometry of the hostmaterials. The fully hydrated phase can be approximated by a structure with 16 local minima. Both hydration (water incorporation) and oxidation (oxygen incorporation) are found to be exothermic processeswith reaction enthalpies of−1.34 eV/H2Omolecule and −0.70 eV/O atom, respectively. The hole polaron resulting from the exothermic incorporation of oxygen is found localized on oxygens around the dopant (small polaron) and carries a spin magnetic moment. Finally, the competition between hydration and oxidation is studied and discussed as a function of oxygen and water partial pressures

On the decay of turbulence in plane Couette flow

The decay of turbulent and laminar oblique bands in the lower transitional range of plane Couette flow is studied by means of direct numerical simulations of the Navier--Stokes equations. We consider systems that are extended enough for several bands to exist, thanks to mild wall-normal under-resolution considered as a consistent and well-validated modelling strategy. We point out a two-stage process involving the rupture of a band followed by a slow regression of the fragments left. Previous approaches to turbulence decay in wall-bounded flows making use of the chaotic transient paradigm are reinterpreted within a spatiotemporal perspective in terms of large deviations of an underlying stochastic process.Comment: ETC13 Conference Proceedings, 6 pages, 5 figure

Management of the axilla in breast cancer:\ua0outcome analysis in a series of ductal versus lobular invasive cancers

Introduction: Axillary lymph node dissection (ALND) has been considered essential for the staging of breast cancer (BC). As the impact of tumor biology on clinical outcomes is recognized, a surgical de-escalation approach is being implemented. We performed a retrospective study focused on surgical management of the axilla in invasive lobular carcinoma (ILC) versus invasive ductal carcinoma (IDC). Materials and methods: 1151 newly diagnosed BCs, IDCs (79.6%) or ILCs (20.4%), were selected among patients treated at our Breast Cancer Unit from 2012 to 2018. Tumor characteristics and clinical information were collected and predictors of further metastasis after positive sentinel lymph node biopsy (SLNB) analyzed in relation to disease-free survival (DFS) and overall survival (OS). Results: 27.5% of patients with ILC had 65 3 metastatic lymph nodes at ALND after positive SLNB versus 11.48% of IDCs (p = 0.04). Risk predictors of further metastasis at ALND were the presence of > 2 positive lymph nodes at SLNB (OR = 4.72, 95% CI 1.15\u201319.5 p = 0.03), T3\u2013T4 tumors (OR = 4.93, 95% CI 1.10\u201322.2, p = 0.03) and Non-Luminal BC (OR = 2.74, 95% CI 1.16\u20136.50, p = 0.02). The lobular histotype was not associated with the risk of further metastasis at ALND (OR = 1.62, 95% CI 0.77\u20133.41, p = 0.20). Conclusions: ILC histology is not associated with higher risk of further metastasis at ALND in our analysis. However, surgical management decisions should be taken considering tumor histotype, biology and expected sensitivity to adjuvant therapies

Convective and absolute Eckhaus instability leading to modulated waves in a finite box

We report experimental study of the secondary modulational instability of a one-dimensional non-linear traveling wave in a long bounded channel. Two qualitatively different instability regimes involving fronts of spatio-temporal defects are linked to the convective and absolute nature of the instability. Both transitions appear to be subcritical. The spatio-temporal defects control the global mode structure.Comment: 5 pages, 7 figures (ReVTeX 4 and amsmath.sty), final versio

Critical exponents of directed percolation measured in spatiotemporal intermittency

A new experimental system showing a transition to spatiotemporal intermittency is presented. It consists of a ring of hundred oscillating ferrofluidic spikes. Four of five of the measured critical exponents of the system agree with those obtained from a theoretical model of directed percolation.Comment: 7 pages, 12 figures, submitted to PR

The melting curve of iron at extreme pressures: implications for planetary cores

Exoplanets with masses similar to that of Earth have recently been discovered in extrasolar systems. A first order question for understanding their dynamics is to know whether they possess Earth like liquid metallic cores. However, the iron melting curve is unknown at conditions corresponding to planets of several times the Earth's mass (over 1500 GPa for planets with 10 times the Earth's mass (ME)). In the density-temperature region of the cores of those super-Earths, we calculate the iron melting curve using first principle molecular dynamics simulations based on density functional theory. By comparing this melting curve with the calculated thermal structure of Super Earths, we show that planets heavier than 2ME, have solid cores, thus precluding the existence of an internal metallic-core driven magnetic field. The iron melting curve obtained in this study exhibits a steeper slope than any calculated planetary adiabatic temperature profile rendering the presence of molten metallic cores less likely as sizes of terrestrial planets increase

Elevated levels of eEF1A2 protein expression in triple negative breast cancer relate with poor prognosis

Eukaryotic elongation factor 1 alpha 2 (eEF1A2) is a translation factor selectively expressed by heart, skeletal muscle, nervous system and some specialized cells. Its ectopic expression relates with tumorigenesis in several types of human cancer. No data are available about the role of eEF1A2 in Triple Negative Breast Cancers (TNBC). This study investigated the relation between eEF1A2 protein levels and the prognosis of TNBC. A total of 84 TNBC diagnosed in the period 2002-2011 were included in the study. eEF1A2 protein level was measured in formalin-fixed paraffin-embedded tissues by immunohistochemistry in a semi-quantitative manner (sum of the percentage of positive cells x staining intensity) on a scale from 0 to 300. Cox regression assessed the association between eEF1A2 levels and disease-free survival (DFS) and breast cancer-specific survival (BCSS). Elevated values of eEF1A2 were associated with older age at diagnosis (p = 0.003), and androgen receptors positivity (p = 0.002). At univariate Cox analysis, eEF1A2 levels were not significantly associated with DFS and BCSS (p = 0.11 and p = 0.08, respectively) whereas adjusting for stage of disease, elevated levels of eEF1A2 protein resulted associated with poor prognosis (HR = 1.05, 95% CI: 1.01-1.11, p = 0.04 and HR = 1.07, 95% CI: 1.01-1.14, p = 0.03 for DFS and BCSS, respectively). This trend was confirmed analyzing negative versus positive samples by using categorized scores. Our data showed a negative prognostic role of eEF1A2 protein in TNBC, sustaining further investigations to confirm this result by wider and independent cohorts of patients

Evolution of turbulent spots in a parallel shear flow

The evolution of turbulent spots in a parallel shear flow is studied by means of full three-dimensional numerical simulations. The flow is bounded by free surfaces and driven by a volume force. Three regions in the spanwise spot cross-section can be identified: a turbulent interior, an interface layer with prominent streamwise streaks and vortices and a laminar exterior region with a large scale flow induced by the presence of the spot. The lift-up of streamwise streaks which is caused by non-normal amplification is clearly detected in the region adjacent to the spot interface. The spot can be characterized by an exponentially decaying front that moves with a speed different from that of the cross-stream outflow or the spanwise phase velocity of the streamwise roll pattern. Growth of the spots seems to be intimately connected to the large scale outside flow, for a turbulent ribbon extending across the box in downstream direction does not show the large scale flow and does not grow. Quantitatively, the large scale flow induces a linear instability in the neighborhood of the spot, but the associated front velocity is too small to explain the spot spreading.Comment: 10 pages, 10 Postscript figure