École Normale Supérieure

About: École Normale Supérieure is a other organization based out in Paris, Île-de-France, France. It is known for research contribution in the topics: Population & Catalysis. The organization has 68439 authors who have published 99414 publications receiving 3092008 citations.

Recent Advances in the Description of Solvent Effects with the Polarizable Continuum Model

Abstract: Publisher Summary This chapter presents a set of methods addressed to the study of solvation problems at the quantum mechanical level with the use of polarizable continuum model (PCM). The chapter describes the evolution of continuous methods since the first proposals or the first formulation at a QM level, semiempirical, or ab initio. PCM belongs to the family of methods in which focuses on a limited portion of matter, the ‘solute’ (one or more molecules) while the remaining, and larger, portion of the solution, called here the ‘solvent’, is treated at a lower level of accuracy. PCM is a quantum mechanical (QM) method in which use is made of an effective Hamiltonian for the solute M , and the corresponding Schrodinger equation is generally (but not compulsory) treated at the ab initio level. PCM makes use of continuous solvent distributions to describe the solute-solvent interaction potential. The chapter demonstrates that PCM manages to treat not only the well known model based on a uniform isotropic dielectric description of the solvent, whose interactions are limited to the electrostatic terms, but also more complex models including interactions of different physical origin and other solvent distribution functions.

Fast multicolor 3D imaging using aberration-corrected multifocus microscopy

Abstract: Conventional acquisition of three-dimensional (3D) microscopy data requires sequential z scanning and is often too slow to capture biological events. We report an aberration-corrected multifocus microscopy method capable of producing an instant focal stack of nine 2D images. Appended to an epifluorescence microscope, the multifocus system enables high-resolution 3D imaging in multiple colors with single-molecule sensitivity, at speeds limited by the camera readout time of a single image.

Factors of success for end-user computing

Abstract: A two-phase study concerned with the factors of success associated with the development of computer applications by end users was conducted in 10 large organizations. During the first phase, in-depth interviews were used to refine a preliminary model of the factors of success for user development of computer applications (UDA). In the second phase, a questionnaire was administered to 272 end users experienced in developing applications. Statistical tests of the relationships in the model indicated that all but one of the derived hypotheses were substantiated. The result of this study is a field-verified model of the factors of success of UDA that provides a basis for implementation of UDA practices and policies in organizations, as well as for further research in end-user computing.

Gaps, rings, and non-axisymmetric structures in protoplanetary disks - From simulations to ALMA observations

Abstract: Aims. Recent observations by the Atacama Large Millimeter/submillimeter Array (ALMA) of disks around young stars revealed distinct asymmetries in the dust continuum emission. In this work we wish to study axisymmetric and non-axisymmetric structures that are generated by the magneto-rotational instability in the outer regions of protoplanetary disks. We combine the results of state-of-the-art numerical simulations with post-processing radiative transfer (RT) to generate synthetic maps and predictions for ALMA.Methods. We performed non-ideal global 3D magneto-hydrodynamic (MHD) stratified simulations of the dead-zone outer edge using the FARGO MHD code PLUTO. The stellar and disk parameters were taken from a parameterized disk model applied for fitting high-angular resolution multi-wavelength observations of various circumstellar disks. We considered a stellar mass of M∗ = 0.5 M⊙ and a total disk mass of about 0.085 M∗. The 2D initial temperature and density profiles were calculated consistently from a given surface density profile and Monte Carlo radiative transfer. The 2D Ohmic resistivity profile was calculated using a dust chemistry model. We considered two values for the dust-to-gas mass ratio, 10-2 and 10-4, which resulted in two different levels of magnetic coupling. The initial magnetic field was a vertical net flux field. The radiative transfer simulations were performed with the Monte Carlo-based 3D continuum RT code MC3D. The resulting dust reemission provided the basis for the simulation of observations with ALMA.Results. All models quickly turned into a turbulent state. The fiducial model with a dust-to-gas mass ratio of 10-2 developed a large gap followed by a jump in surface density located at the dead-zone outer edge. The jump in density and pressure was strong enough to stop the radial drift of particles at this location. In addition, we observed the generation of vortices by the Rossby wave instability at the jump location close to 60 AU. The vortices were steadily generated and destroyed at a cycle of 40 local orbits. The RT results and simulated ALMA observations predict that it is feasible to observe these large-scale structures that appear in magnetized disks without planets. Neither the turbulent fluctuations in the disk nor specific times of the model can be distinguished on the basis of high-angular resolution submillimeter observations alone. The same applies to the distinction between gaps at the dead-zone edges and planetary gaps, to the distinction between turbulent and simple unperturbed disks, and to the asymmetry created by the vortex.

A discursive perspective on legitimation strategies in multinational corporations

Abstract: Few studies have examined legitimation in multinational corporations from a discursive perspective. To complement the existing institutional literature, we adopt a critical discourse analysis perspective that allows us to examine the microlevel processes of discursive legitimation. We provide an example of a media text— dealing with a production unit shutdown—to demonstrate how this perspective elucidates the various textual strategies used to legitimate multinational corporations' actions and their controversial consequences.