Mapping the Energy Cascade in the North Atlantic Ocean: The Coarse-graining Approach

This is the final version of the article. Available from AMS via the DOI in this record.A coarse-graining framework is implemented to analyze nonlinear processes, measure energy transfer rates and map out the energy pathways from simulated global ocean data. Traditional tools to measure the energy cascade from turbulence theory, such as spectral flux or spectral transfer rely on the assumption of statistical homogeneity, or at least a large separation between the scales of motion and the scales of statistical inhomogeneity. The coarse-graining framework allows for probing the fully nonlinear dynamics simultaneously in scale and in space, and is not restricted by those assumptions. This paper describes how the framework can be applied to ocean flows. Energy transfer between scales is not unique due to a gauge freedom. Here, it is argued that a Galilean invariant subfilter scale (SFS) flux is a suitable quantity to properly measure energy scale-transfer in the Ocean. It is shown that the SFS definition can yield answers that are qualitatively different from traditional measures that conflate spatial transport with the scale-transfer of energy. The paper presents geographic maps of the energy scale-transfer that are both local in space and allow quasi-spectral, or scale-by-scale, dynamics to be diagnosed. Utilizing a strongly eddying simulation of flow in the North Atlantic Ocean, it is found that an upscale energy transfer does not hold everywhere. Indeed certain regions, near the Gulf Stream and in the Equatorial Counter Current have a marked downscale transfer. Nevertheless, on average an upscale transfer is a reasonable mean description of the extra-tropical energy scale-transfer over regions of O(10^3) kilometers in size.Financial support was provided by IGPPS at Los Alamos National Laboratory (LANL) and NSF grant OCE-1259794. HA was also supported through DOE grants de-sc0014318, de-na0001944, and the LANL LDRD program through project number 20150568ER. MH was also supported through the HiLAT project of the Regional and Global Climate Modeling program of the DOE’s Office of Science, and GKV was also supported by NERC, the Marie Curie Foundation and the Royal Society (Wolfson Foundation). This research used resources of the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231

The backbone of the climate network

We propose a method to reconstruct and analyze a complex network from data generated by a spatio-temporal dynamical system, relying on the nonlinear mutual information of time series analysis and betweenness centrality of complex network theory. We show, that this approach reveals a rich internal structure in complex climate networks constructed from reanalysis and model surface air temperature data. Our novel method uncovers peculiar wave-like structures of high energy flow, that we relate to global surface ocean currents. This points to a major role of the oceanic surface circulation in coupling and stabilizing the global temperature field in the long term mean (140 years for the model run and 60 years for reanalysis data). We find that these results cannot be obtained using classical linear methods of multivariate data analysis, and have ensured their robustness by intensive significance testing.Comment: 6 pages, 5 figure

Metallointercalator [Ru(dppz)2(PIP)]2+ Renders BRCA Wild-Type Triple-Negative Breast Cancer Cells Hypersensitive to PARP Inhibition

There is a need to improve and extend the use of clinically-approved poly(ADP-ribose) polymerase (PARP) inhibitors (PARPi), including for BRCA wild-type triple-negative breast cancer (TNBC). The demonstration that ruthenium(II) polypyridyl complex (RPC) metallo-intercalators can rapidly stall DNA replication fork progression provides the rationale for their combination alongside DNA damage response (DDR) inhibitors to achieve synergism in cancer cells. The aim of the present study was to evaluate use of the multi-intercalator [Ru(dppz)2(PIP)]2+ (dppz = dipyrido[3,2-a:2′,3′-c]phenazine, PIP = (2-(phenyl)imidazo[4,5-f][1,10]phenanthroline, Ru-PIP) alongside the PARP inhibitors (PARPi) olaparib and NU1025. Cell proliferation and clonogenic survival assays indicated a synergistic relationship between Ru-PIP and olaparib in MDA-MB-231 TNBC and MCF7 human breast cancer cells. Strikingly, low dose Ru-PIP renders both cell lines hypersensitive to olaparib, with a 300-fold increase in olaparib potency in TNBC; the largest non-genetic PARPi enhancement effect described to date. Negligible impact on the viability of normal human fibroblasts was observed for any combination tested. Increased levels of DNA double-strand break (DSB) damage and olaparib abrogation of Ru-PIP activated pChk1 signalling is consistent with PARPi-facilitated collapse of Ru-PIP-associated stalled replication forks. This results in enhanced G2/M cell-cycle arrest, apoptosis and decreased cell motility for the combination treatment compared to single-agent conditions. This work establishes that an RPC metallo-intercalator can be combined with PARPi for potent synergy in BRCA-proficient breast cancer cells, including TNBC

Generation and Structure of Solitary Rossby Vortices in Rotating Fluids

The formation of zonal flows and vortices in the generalized Charney-Hasegawa-Mima equation is studied. We focus on the regime when the size of structures is comparable to or larger than the deformation (Rossby) radius. Numerical simulations show the formation of anticyclonic vortices in unstable shear flows and ring-like vortices with quiescent cores and vorticity concentrated in a ring. Physical mechanisms that lead to these phenomena and their relevance to turbulence in planetary atmospheres are discussed.Comment: 3 pages in REVTeX, 5 postscript figures separately, submitted to Phys. Rev.

Inferring directed climatic interactions with renormalized partial directed coherence and directed partial correlation

ACKNOWLEDGMENTS This work was supported in part by Spanish MINECO/FEDER (FIS2015-66503-C3-2-P) and ITN LINC (FP7 289447). C.M. also acknowledges partial support from ICREA ACADEMIAPeer reviewedPublisher PD

Dispersive stabilization of the inverse cascade for the Kolmogorov flow

It is shown by perturbation techniques and numerical simulations that the inverse cascade of kink-antikink annihilations, characteristic of the Kolmogorov flow in the slightly supercritical Reynolds number regime, is halted by the dispersive action of Rossby waves in the beta-plane approximation. For beta tending to zero, the largest excited scale is proportional to the logarithm of one over beta and differs strongly from what is predicted by standard dimensional phenomenology which ignores depletion of nonlinearity.Comment: 4 pages, LATEX, 3 figures. v3: revised version with minor correction

Influence of turbulent advection on a phytoplankton ecosystem with nonuniform carrying capacity

In this work we study a plankton ecosystem model in a turbulent flow. The plankton model we consider contains logistic growth with a spatially varying background carrying capacity and the flow dynamics are generated using the two-dimensional (2D) Navier-Stokes equations. We characterize the system in terms of a dimensionless parameter, γ TB / TF, which is the ratio of the ecosystem biological time scales TB and the flow time scales TF. We integrate this system numerically for different values of γ until the mean plankton reaches a statistically stationary state and examine how the steady-state mean and variance of plankton depends on γ. Overall we find that advection in the presence of a nonuniform background carrying capacity can lead to very different plankton distributions depending on the time scale ratio γ. For small γ the plankton distribution is very similar to the background carrying capacity field and has a mean concentration close to the mean carrying capacity. As γ increases the plankton concentration is more influenced by the advection processes. In the largest γ cases there is a homogenization of the plankton concentration and the mean plankton concentration approaches the harmonic mean, 1/K -1. We derive asymptotic approximations for the cases of small and large γ. We also look at the dependence of the power spectra exponent, β, on γ where the power spectrum of plankton is k-β. We find that the power spectra exponent closely obeys β=1+2/γ as predicted by earlier studies using simple models of chaotic advection

Can Galvanic Vestibular Stimulation Reduce Simulator Adaptation Syndrome?

Electrical stimulation of the vestibular sensory system during virtual environment simulations has been proposed as a method to reduce the incidence of simulator adaptation syndrome (SAS). However, there is limited empirical evidence to support this hypothesis. It is especially important to provide vestibular stimulation in driving simulators because an absence of vestibular cues may alter driver behaviour and reduce vehicle control. This study examined the application of galvanic vestibular stimulation (GVS) as a technique to reduce symptoms of SAS and improve vehicular control in a fixed-based driving simulator. Nineteen participants drove two visually distinct virtual environments (high and low visual cues). In addition, each of these worlds was experienced with and without GVS. Post-drive scores on the Simulator Sickness Questionnaire (SSQ) were used to evaluate the effect of GVS on SAS. In addition, three driving variables were measured to examine driving performance: steering variability, lane departures, and average vehicular speed. GVS application while driving resulted in significant decreases in total SSQ and disorientation symptoms. Greater vehicular control was also observed (as shown by reduced steering variability) when GVS was used in combination with visual cues along the simulated edge of the road. These results support that GVS may be used in fixed-base driving simulators to create vestibular motion cues and reduce SAS