Solvable Hydrodynamics of Quantum Integrable Systems

The conventional theory of hydrodynamics describes the evolution in time of chaotic many-particle systems from local to global equilibrium. In a quantum integrable system, local equilibrium is characterized by a local generalized Gibbs ensemble or equivalently a local distribution of pseudo-momenta. We study time evolution from local equilibria in such models by solving a certain kinetic equation, the "Bethe-Boltzmann" equation satisfied by the local pseudo-momentum density. Explicit comparison with density matrix renormalization group time evolution of a thermal expansion in the XXZ model shows that hydrodynamical predictions from smooth initial conditions can be remarkably accurate, even for small system sizes. Solutions are also obtained in the Lieb-Liniger model for free expansion into vacuum and collisions between clouds of particles, which model experiments on ultracold one-dimensional Bose gases.Comment: 6+5 pages, published versio

Essais de génotoxicité in vitro et in vivo applicables à l'environnement hydrique

Cet article est une revue des essais in vitro et in vivo utilisés pour évaluer le caractère génotoxique des micropolluants des milieux environnementaux relatifs aux eaux continentales et marines, rejets liquides d'origine domestique, industrielle ou agricole, sédiments de rivières et boues de stations de traitement d'épuration.Les essais in vitro réalisés sur cellules eucaryotes ou procaryotes sont fondés sur la détection des mutations géniques et chromosomiques, ou la mesure des adduits à l'ADN. Ils constituent des systèmes d'épreuve miniaturisés qui requièrent des volumes d'échantillons faibles; ils se prêtent ainsi au dépistage à grande échelle de la génotoxicité et à l'étude des concentrats et des extraits préparés à partir des milieux contaminés. Ils sont cependant moins bien adaptés à la prédiction de l'impact des micropolluants sur l'environnement.La recherche de conditions d'essai plus proches de la réalité environnementale a conduit au développement des essais in vivo réalisés sur organismes supérieurs, mollusques, poissons ou amphibiens, qui évaluent un potentiel génotoxique à partir d'études cytogénétiques ou d'études du caryotype des organismes exposés.Les critères de génotoxicité étudiés in vitro peuvent être utilisés dans le cadre d'études écoépidémiologiques, sur le terrain, afin d'évaluer l'impact réel des micropolluants présents dans les milieux environnementaux sujets à des contaminations d'origines diverses.This review deals with in vitro and in vivo genotoxicity bioassays carried out to evaluate the genotoxic potential of polluted environmental samples : continental and marine waters, domestic and industrial wastewaters, aquatic sediments and sludges of urban or industrial wastewater treatment plants.The end-points of the in vitro and in vivo assays are : genetic alterations, i.e. reverse and forward mutations, DNA adducts or chramosomic damages, i.e. chromosomic aberrations (AC), micronuclei (MN) and sister chromatid exchanges (SCE).The in vitro assays generally detect adverse effects on DNA only alter concentration or extraction of micropollutants. They constitute miniaturized tools, rapid and easy to use, thus well-suited for large screening studies. In vitro genotoxicity bioassays requiring only small volumes of samples are therefore systems of choice for testing concentrates or extracts from environmental contaminated samples. Among the in vitro assays reviewed, the Salmonella typhimurium gene mutation test is the most often used to assess the genotoxic potential of contaminated samples. However, genotoxicity tests performed on eukaryotic cell cultures are more relevant than those using bacteria for evaluating environmental pollution. The use of fish cell fines appears superior to the use of mammalian cells for assessing an aquatic impact.In vitro bioassays, whether performed on prokaryotic or eukaryotic cells, are limited for predicting the possible impact of genotoxic pollutants on the environment. It is clear that it is difficult to extrapolate in vitro bioassay results to higher organisms in which the response obtained integrates effects of complex metabolizing systems, hormonal regulation and immunological defenses.Therefore, genotoxicity studies performed with aquatic organisms such as molluscs (Mytilus sp.), fish (Umbra pygmaea, Notobranchius rachowi) or amphibians (Pleurodeles waltl) appear more representative of environmental conditions. The genotoxicity end-points of in vivo assays are mainly cytogenetic damage such as the SCE, AC or MN but also take into account DNA adducts. Direct testing of environmental samples without preconcentration is possible with in vivo assays. This means that factors such as bioavailability and metabolism will be integrated direcrly in the response of these assays. Hence, these in vivo assays are more sensitive titan in vitro genotoxicity tests. However, in vivo tests require important volumes of sample and it will be difficult or almost impossible to apply them for testing concentrates or sample extracts, generally only available in small quantities. An interesting area of application of in vivo assays is field studies and ecoepidemioiogy. In this respect, they would constitue an a posteriori control system of pollution effects, assuming that suitable control areas are available to eliminate the influence of confounding factors.As a general conclusion, if is important to emphasize the interest of using both in vitro and in vivo bioassays for evaluating the genotoxicity of contaminated environmental samples. This rationale is based on the fact that in vitro bioassays are well adapted for genotoxicity screening or concentrates and extracts testing, white in vivo tests are interesting because of their better representativity in terms of environmental conditions of exposure to pollutants

Traffic jams and intermittent flows in microfluidic networks

We investigate both experimentally and theoretically the traffic of particles flowing in microfluidic obstacle networks. We show that the traffic dynamics is a non-linear process: the particle current does not scale with the particle density even in the dilute limit where no particle collision occurs. We demonstrate that this non-linear behavior stems from long range hydrodynamic interactions. Importantly, we also establish that there exists a maximal current above which no stationary particle flow can be sustained. For higher current values, intermittent traffic jams form thereby inducing the ejection of the particles from the initial path and the subsequent invasion of the network. Eventually, we put our findings in the broader context of the transport proccesses of driven particles in low dimension

Helium Cryoplant Off-line Commissioning and Operator Training: Two Applications of the PROCOS Simulation System at CERN

The off-line commissioning step, through reliable simulation of physical models, aims to correct and validate control systems before their implementation into real equipments. It prepares and minimizes plant commissioning phase and at the same time validates the efficiency of the new process control logic. This paper describes how different CERN/UNICOS cryogenic control systems have been pre-commissioned off-line, using the CERN cryogenic simulation environment PROCOS. Some examples are reported. Additionally the presented simulation environment will be used for operator training. The second part of the paper will presents the simulation platform and the first feedback from the operation crew

Dehydration‐driven mass loss from packs of sintering hydrous silicate glass particles

Glass sintering involves the densification of packs of particles and the expulsion of the interparticle pore gas. The pore space begins as a convolute interconnected interparticle network, and ends as distributed isolated bubbles; two configurations that are separated by the percolation threshold. Here, we perform experiments in which (i) the particles are initially saturated in H2O at 871 K, and (ii) they are then heated non-isothermally at different rates to temperatures in excess of 871 K. In step (ii), H2O becomes supersaturated and the particles diffusively lose mass as they sinter together. We use thermogravimetry to track the loss of mass with time. We find that the mass loss is initially well predicted by solutions to Fick's second law in spherical coordinates with the appropriate material and boundary conditions. However, as the sintering pack crosses the percolation threshold at a time predicted by sintering theory, we find that the mass loss deviates from simple diffusional solutions. We interpret this to be the result of an increase in the diffusion distance from the particle-scale to the scale of the sintering pack itself. Therefore, we conclude that the open- to closed-system transition that occurs at the percolation threshold is a continuous, but rapid jump for diffusive and other transport properties. We use a capillary Peclet number Pc to parameterize for this transition, such that at low Pc diffusive equilibrium is achieved before the sintering-induced transition to closed system, whereas at high Pcthere is a “diffusion crisis” and disequilibrium may be maintained for longer relative timescales that depend on the system size

Bethe-Boltzmann hydrodynamics and spin transport in the XXZ chain

Quantum integrable systems, such as the interacting Bose gas in one dimension and the XXZ quantum spin chain, have an extensive number of local conserved quantities that endow them with exotic thermalization and transport properties. We discuss recently introduced hydrodynamic approaches for such integrable systems from the viewpoint of kinetic theory and extend the previous works by proposing a numerical scheme to solve the hydrodynamic equations for finite times and arbitrary locally equilibrated initial conditions. We then discuss how such methods can be applied to describe nonequilibrium steady states involving ballistic heat and spin currents. In particular, we show that the spin Drude weight in the XXZ chain, previously accessible only by rigorous techniques of limited scope or controversial thermodynamic Bethe ansatz arguments, may be evaluated from hydrodynamics in very good agreement with density-matrix renormalization group calculations