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Liger-Belair G.,CNRS Molecular and Atmospheric Spectrometry Group | Liger-Belair G.,University of Reims
European Physical Journal: Special Topics | Year: 2012

Bubbles in a glass of champagne may seem like the acme of frivolity to most of people, but in fact they may rather be considered as a fantastic playground for any physicist. Actually, the so-called effervescence process, which enlivens champagne and sparkling wines tasting, is the result of the fine interplay between CO 2 dissolved gas molecules, tiny air pockets trapped within microscopic particles during the pouring process, and some both glass and liquid properties. Results obtained concerning the various steps where the CO 2 molecule plays a role (from its ingestion in the liquid phase during the fermentation process to its progressive release in the headspace above the tasting glass as bubbles collapse) are gathered and synthesized to propose a self-consistent and global overview of how gaseous and dissolved CO 2 impact champagne and sparkling wine science. Physicochemical processes behind the nucleation, rise, and burst of gaseous CO 2 bubbles found in glasses poured with champagne and sparkling wines are depicted. Those phenomena observed in close-up through high-speed photography are often visually appealing. I hope that your enjoyment of champagne will be enhanced after reading this fully illustrated review dedicated to the science hidden right under your nose each time you enjoy a glass of champagne. © 2012 EDP Sciences and Springer. Source

Bonhommeau D.A.,CNRS Molecular and Atmospheric Spectrometry Group
Computer Physics Communications | Year: 2015

This new version of the MCMC2 program for modeling the thermodynamic and structural properties of multiply-charged clusters fixes some minor bugs present in earlier versions. A figure representing the required RAM per replica as a function of the cluster size (N&20000) is also provided as benchmark. New version program summary Program title:MCMC Catalogue identifier: AENZ-v1-2 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AENZ-v1-2.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 143653 No. of bytes in distributed program, including test data, etc.: 1396311 Distribution format: tar.gz Programming language: Fortran 90 with MPI extensions for parallelization. Computer: x86 and IBM platforms. Operating system:CentOS 5.6 Intel Xeon X5670 2.93 GHz, gfortran/ifort(version 13.1.0) + MPICH2;CentOS 5.3 Intel Xeon E5520 2.27 GHz, gfortran/g95 /pgf90 + MPICH2;Red Hat Enterprise 5.3 Intel Xeon X5650 2.67 GHz, gfortran + IntelMPI;IBM Power 6 4.7 GHz, xlf + PESSL (IBM parallel library).Has the code been vectorized or parallelized?: Yes, parallelized using MPI extensions. Number of CPUs used: Up to 999 RAM: (per CPU core) 10-20 MB. The physical memory needed for the simulation depends on the cluster size, the values indicated are typical for small or medium-sized clusters (N;300-400). The size of An+N clusters (N= number of particles, n= number of charged particles with n&N) should not exceed 1.6 (respectively 2.0) particles on servers with 2 GB (respectively 3 GB) of RAM per CPU core if n=0 (neutral clusters) or n=N ("fully-charged" clusters). For charged clusters composed of neutral and charged particles (e.g.; n=N/2), the maximum cluster size can drop to 1.4 and 1.8 on servers with 2 GB and 3 GB of RAM, respectively (see the figure given in Supplementary Material). Supplementary material: A figure showing the amount of RAM required per replica as a function of the size of A;bsubn+N clusters can be downloaded. Supplementary material related to this article can be found online at http://dx.doi.org/10.1016/j.cpc.2015.06.017. The following is the Supplementary material related to this article. Amount of RAM required per replica (in GB) as a function of the cluster size. The calculations have been performed without taking into account polarization Catalogue identifier of previous version: AENZ-v1-1 Journal reference of previous version: Comput. Phys. Comm. 185(2014)1188 Classification: 23. Does the new version supersede the previous version?: Yes Nature of problem: We provide a general parallel code to investigate structural and thermodynamic properties of multiply charged clusters. Solution method: Parallel Monte Carlo methods are implemented for the exploration of the configuration space of multiply charged clusters. Two parallel Monte Carlo methods were found appropriate to achieve such a goal: the Parallel Tempering method, where replicas of the same cluster at different temperatures are distributed among different CPUs, and Parallel Charging where replicas (at the same temperature) having different particle charges or numbers of charged particles are distributed on different CPUs. Reasons for new version: This new version of the MCMC2 program for modeling the thermodynamic and structural properties of multiply-charged clusters fixes some minor bugs present in earlier versions. A figure representing the required RAM per replica as a function of the cluster size (N&20000) is also provided as benchmark. Summary of revisions:Additional features of MCMC version 1.1.1: Same as in the previous version;Modifications or corrections to MCMC version 1.1 [2,3] Several minor bugs were fixed in this versioni. A default value for the integer "irand", used to select the type of random number generator (keyword SEED, subkeyword METHOD), was missing. It is set to 0.ii. The subkeyword "EVERY" used to define the frequency of statistics printing (keyword "STATISTICS") was missing and it has been implemented in the program. Before version 1.1.1, the choice entered into the setup file was simply ignored and the frequency was always set to its default value, namely a printing every 100 Monte Carlo sweeps.Some useless integers are removed from subroutines in lib4-pol.f90 and lib4-dampol.f90 and some test runs are slightly modified. In particular, in test run 2, the particle and probe diameters used to evaluate the number of surface particles were fixed to 0.8 and 1.2, respectively (see keyword "SURFACE"). Actually, the probe diameter should be smaller than the particle diameter [4] and the two values were therefore swapped.The subroutines dLJ-nopol-hom (in lib4-nopol.f90), dLJ-pol-hom (in lib4-pol.f90), and dLJ-dampol-hom (in lib4-dampol.f90) are renamed dLJ-nopol, dLJ-pol, and dLJ-dampol, respectively, to avoid any ambiguity. The suffix "Hom", that stood for "homogeneity" in order to indicate that Lennard-Jones interactions between particles were the same, was improper since homogeneity is commonly related to invariance by translation and all the properties of multiply charged clusters cannot be considered invariant by translation in the most general case. The renaming of the three subroutines has obviously no influence on the results and some related comments have been modified accordingly. Restrictions: The current version of the code uses Lennard-Jones interactions, as the main cohesive interaction between spherical particles, and electrostatic interactions (charge-charge, charge-induced dipole, induced dipole-induced dipole, polarization). Furthermore, the Monte Carlo simulations can only be performed in the NVT ensemble and the size of charged clusters should not exceed 2.0 particles on CPU cores with less than 3GB of RAM each. It is worth noting that the latter restriction is not significantly crippling since MCMC should be mainly devoted to the investigation of medium-sized cluster properties due to the difficulty to converge Monte Carlo simulations on large systems (N≥10) [1]. Unusual features: The Parallel Charging methods, based on the same philosophy as Parallel Tempering but with particle charges and number of charged particles as parameters instead of temperature, is an interesting new approach to explore energy landscapes. Splitting of the simulations is allowed and averages are accordingly updated. Running time: The running time depends on the number of Monte Carlo steps, cluster size, and the type of interactions selected (e.g.; polarization turned on or off, and method used for calculating the induced dipoles). Typically a complete simulation can last from a few tens of minutes or a few hours for small clusters (N;100, not including polarization interactions), to one week for large clusters (N≥1000 not including polarization interactions), and several weeks for large clusters (N≥1000) when including polarization interactions. A restart procedure has been implemented that enables a splitting of the simulation accumulation phase. References:E. Pahl, F. Calvo, L. Koci, P. Schwerdtfeger, Accurate Melting Temperatures for Neon and Argon from Ab Initio Monte Carlo Simulations, Angew. Chem. Int. Ed. 47 (2008) 8207-8210.D.A. Bonhommeau, M.-P. Gaigeot, MCMC2: A Monte Carlo code for multiply-charged clusters, Comput. Phys. Commun. 184 (2013) 873-884.D.A. Bonhommeau, M. Lewerenz, M.-P. Gaigeot, MCMC2 (version 1.1): A Monte Carlo code for multiply-charged clusters, Comput. Phys. Commun. 185 (2014) 1188-1191.M.A. Miller, D.A. Bonhommeau, C.J. Heard, Y. Shin, R. Spezia, M.-P. Gaigeot, Structure and stability of charged clusters, J. Phys.: Condens. Matter. 24 (2012) 284130. © 2015 Elsevier B.V. Source

Cordier D.,CNRS Molecular and Atmospheric Spectrometry Group
Monthly Notices of the Royal Astronomical Society | Year: 2016

The hydrocarbon seas of Titan, discovered by the Cassini/Huygens mission are among the most mysterious and interesting features of this moon. In the future, a possible dedicated planetary probe will certainly measure the speed of sound in this cryogenic liquid, as was planned in the case of Huygens landing in a sea. Previous theoretical studies of such acoustic measurements were based on simple models, leading in some cases to unphysical situations. Employed in a vast body of chemical engineering works, the state-of-the-art perturbed-chain statistical associating fluid theory (PC-SAFT) model has been recently introduced in studies aimed at Titan. Here, I revisit the issue of the speed of sound in Titan's liquids, in light of this theory. I describe, in detail, the derivation of the speed of sound from the chosen equation of state and the potential limitations of the approach. To make estimations of the composition of a ternary liquid mixture N2:CH4:C2H6 from speed-of-sound measurements an original inversion algorithm is proposed. It is shown that 50 measures between 90 and 100 K are enough to ensure an accuracy of the derived compositions of better than 10 per cent. The influence of the possible presence of propane is also investigated. © 2016 The Author. Source

Koskinen T.T.,University of Arizona | Harris M.J.,University College London | Yelle R.V.,University of Arizona | Lavvas P.,CNRS Molecular and Atmospheric Spectrometry Group
Icarus | Year: 2013

The detections of atomic hydrogen, heavy atoms and ions surrounding the extrasolar giant planet (EGP) HD209458b constrain the composition, temperature and density profiles in its upper atmosphere. Thus the observations provide guidance for models that have so far predicted a range of possible conditions. We present the first hydrodynamic escape model for the upper atmosphere that includes all of the detected species in order to explain their presence at high altitudes, and to further constrain the temperature and velocity profiles. This model calculates the stellar heating rates based on recent estimates of photoelectron heating efficiencies, and includes the photochemistry of heavy atoms and ions in addition to hydrogen and helium. The composition at the lower boundary of the escape model is constrained by a full photochemical model of the lower atmosphere. We confirm that molecules dissociate near the 1μbar level, and find that complex molecular chemistry does not need to be included above this level. We also confirm that diffusive separation of the detected species does not occur because the heavy atoms and ions collide frequently with the rapidly escaping H and H+. This means that the abundance of the heavy atoms and ions in the thermosphere simply depends on the elemental abundances and ionization rates. We show that, as expected, H and O remain mostly neutral up to at least 3Rp, whereas both C and Si are mostly ionized at significantly lower altitudes. We also explore the temperature and velocity profiles, and find that the outflow speed and the temperature gradients depend strongly on the assumed heating efficiencies. Our models predict an upper limit of 8000K for the mean (pressure averaged) temperature below 3Rp, with a typical value of 7000K based on the average solar XUV flux at 0.047AU. We use these temperature limits and the observations to evaluate the role of stellar energy in heating the upper atmosphere. © 2012 Elsevier Inc. Source

Alijah A.,CNRS Molecular and Atmospheric Spectrometry Group
Journal of Molecular Spectroscopy | Year: 2010

The results of full variational calculations for highly excited rovibrational states of H3+ are presented. The computed data have been adjusted, by comparison with experiment, to account for the neglect of non-adiabatic coupling in the calculations and for inaccuracies of the potential energy surface. Most data have been assigned by spectroscopic quantum numbers. Detailed tables of term values for J≤2 are provided. Some hitherto unassigned experimental lines could be identified. © 2010 Elsevier Inc. All rights reserved. Source

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