MeSU computing platform addresses all research communities of Sorbonne-Université and its Alliance.
This page presents some examples of research works being performed with the help of MeSU.

Oceanography

The Mediterranean Sea is known for its important levels of plastic pollution, among the highest in the world oceans. However, plastic debris in the Mediterranean Sea does not accumulate in specific regions, making targeting of plastic difficult. In this study the authors identified the regions in which large amounts of plastic debris converges but then passes on, thus providing a novel paradigm to address this question. The research team developed a model, run on MeSU, that simulated trajectories of plastic particles released from coastal cities, rivers mouths and vessel routes, across the Mediterranean Sea, and validated it with in situ observations. The authors found that 20% of all plastic debris in the Mediterranean passed in less than 1% of its surface area, traveling hundreds of km.

The streaming of plastic in the Mediterranean Sea
Alberto Baudena, Enrico Ser-Giacomi, Isabel Jalón-Rojas, François Galgani, Maria Luiza Pedrotti
Nature Communications, 2022, DOI 10.1038/s41467-022-30572-5

Astrophysics

Spiral galaxies have the shape of a disk made up of a nucleus with some arms wrapped around it and are some of the most striking and interesting objects of the visible universe revealed by astronomy.  Thanks to computer simulations and theoretical calculations, we have reproduced the gravitational collapse of isolated clouds of particles with a small initial rotation speed, finding that they give rise systems that are qualitatively similar to spiral galaxies, whose arms are not stationary, i.e. they do not orbit like the planets around the Sun, which are in a state of equilibrium, but are phenomena generated by an out of equilibrium dynamics.

Transient spiral arms from far out of equilibrium gravitational evolution
David BenhaiemMichael JoyceFrancesco Sylos Labini, Astrophysical Journal, 851, 19 (2017), arXiv:1711.01913

Long-lived transient structure in collisionless self-gravitating systems
David BenhaiemFrancesco Sylos Labini, Michael Joyce,  Phys. Rev. E 99, 022125 , 2019 arXiv:1901.04456

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Molecular Chemistry

Evaluation of ligand electronic effects in organometallic complexes using photoelectron spectroscopy, DFT and energy decomposition analysis

Through their electronic and steric properties, ligands bound on metallic center play a crucial role in organometallic catalysis. They are indeed able to influence the net electron density on the metal and can therefore drive its behavior and reactivity. A detailed knowledge of the ligands effects on the metal center is thus decisive to access the finest tuning of the reaction systems. We are interested in the determination of these ligand effect by using photoelectron spectroscopy coupled to synchrotron radiation. This experimental approach gets us the access to the electronic structure of metal complexes. The spectra analysis requires the use of advanced DFT calculations to simulate the spectra and interpret them by means of orbitals structures. Another theoretical approaches, based on the metal-ligand analysis, helps us characterizing and quantifying the various contributions of the ligand to the bond.

Exploring Phosphine Electronic Effects on Molybdenum Complexes: A Combined Photoelectron Spectroscopy and Energy Decomposition Analysis Study
Héloïse Dossmann, David Gatineau, Hervé Clavier, Antony Memboeuf, Denis Lesage, Yves Gimbert
J. Phys. Chem. A 2020, 124, 42, 8753–8765

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Understanding the gold catalysis processes under visible light

In the past few years, the association of photocatalysis to organometallic catalysis has known an extraordinary growing success because it has opened many new perspectives in the synthesis processes: new molecules are formed, well-known reactions proceed more efficiently and/or with increased rates, etc. The principle of these reactions relies on the photoactivation of an organometallic complex which becomes then able to react in a different way and/or more efficiently towards an organic substrate. We are interested in developing such new processes using gold as a catalyzer. To get the finest tuning of our reactions, we need to accurately describe the mechanisms which are taking place. Theoretical approaches such as (time-dependent)-density-functional theory ((TD)-DFT) enable us to determine the structures of all molecules involved in the reaction and to characterize the energy-transfer processes which take place to photoactivate the organometallic complex.

Understanding the gold catalysis processes under visible light
Zhonghua Xia, Vincent Corcé, Fen Zhao, Cédric Przybylski, Agathe Espagne, Ludovic Jullien, Thomas Le Saux, Yves Gimbert, Héloïse Dossmann, Virginie Mouriès-Mansuy, Cyril Ollivier, Louis Fensterbank
Nature Chemistry, 2019, 11 797–805, https://doi.org/10.1038/s41557-019-0295-9

Funded by ANR Luxor (2020-2024)
Institut Parisien de Chimie Moléculaire (équipes MACO et CSOB)
Laboratoire PASTEUR, Ecole Normale Supérieure (Paris)

Graph Theory

Web search, drug design and traffic management are only a few examples of crucial applications that nowadays rely on the analysis of graphs. Involved graphs have become increasingly massive sometimes reaching trillions of edges such as the Web graph, Facebook, Internet or a human brain. Only quasi-linear time algorithms can process these massive graphs in a reasonable amount of time on the best supercomputers.

On the one hand, many important problems seem to require more than quadratic time to solve them in the worst case. On the other hand, it has been observed that many algorithms are much more efficient on real-world graphs than in such a worst case scenario. We suggest focusing on graph instances encountered in practice and design quasi-linear time algorithms for such real-world graphs by identifying, formalizing and leveraging their structural properties.

This research work is led by the ComplexNetworks LIP6 team.

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