EDDINGTON'S “Internal Constitution of the Stars” was published in 1926 and gives what now ranks as a classical account of his own researches and of the general state of the theory at that time. Since then, a tremendous amount of work has appeared. Much of it has to do with the construction of stellar models with different equations of state applying in different zones. Other parts deal with the effects of varying chemical composition, with pulsation and tidal and rotational distortion of stars, and with the precise relations between the interior and the atmosphere of a star. The striking feature of all this work is that so much can be done without assuming any particular mechanism of stellar energy-generation. Only such very comprehensive assumptions are made about the distribution and behaviour of the energy sources that we may expect future knowledge of their mechanism to lead mainly to more detailed results within the framework of the existing general theory. An Introduction to the Study of Stellar Structure By S. Chandrasekhar. (Astrophysical Monographs sponsored by The Astrophysical Journal.) Pp. ix+509. (Chicago: University of Chicago Press; London: Cambridge University Press, 1939.) 50s. net.

An Introduction to the Study of Stellar Structure

Many-particle charged-particle plasma simulations using spatial meshes for the electromagnetic field solutions, particle-in-cell (PIC) merged with Monte Carlo collision (MCC) calculations, are coming into wide use for application to partially ionized gases. The author emphasizes the development of PIC computer experiments since the 1950s starting with one-dimensional (1-D) charged-sheet models, the addition of the mesh, and fast direct Poisson equation solvers for 2-D and 3-D. Details are provided for adding the collisions between the charged particles and neutral atoms. The result is many-particle simulations with many of the features met in low-temperature collision plasmas; for example, with applications to plasma-assisted materials processing, but also related to warmer plasmas at the edges of magnetized fusion plasmas. >

Particle-in-Cell Charged Particle Simulations, plus Monte Carlo Collisions with Neutral Atoms, PIC-MCC

Molecular simulations and chemoinformatics are used quite extensively to identify new adsorbents for CO 2 . The use of those digital tools is far less common in the search for new solvents (absorption) to capture CO 2 . This is primarily related to the complexity of the absorption process, mainly due to its reactive nature. This talk will highlight several recent significant advances in computer-aided experimental developments in the field of absorption. First, we focus on physical solvents. We developed a machine-learning tool to predict the absorption capacity of CO 2 as well as its selectivity with respect to other gases. We validated the tool with new experimental datapoints and identify a new class of pure low-viscous amines with high absorption capacity and selectivity. Second, we switch to chemical solvents, and, more specifically, to tertiary amines. New industrial solvents are often a mixture of amines with a high capacity and a relatively low regeneration energy (e.g. tertiary amines) and an activator, piperazine, which increases the overall CO 2 absorption rate. The search for new tertiary amines with better kinetics is thus of paramount importance. We have developed a novel computational approach which combines kinetic experiments, molecular simulations and machine learning for the in silico screening of hundreds of prospective candidates and identify a class of tertiary amines which, when mixed with piperazine, absorbs CO 2 faster than a typical commercial solvent. The approach is validated experimentally. Finally, we show how molecular simulations can be used to improve the overall process simulation of the CO 2 capture unit.

心臓病診療プラクティス 16. 心不全を癒す

The current understanding of some important nonlinear collective processes in quantum plasmas with degenerate electrons is presented. After reviewing the basic properties of quantum plasmas, model equations (e.g., the quantum hydrodynamic and effective nonlinear Schrodinger-Poisson equations) are presented that describe collective nonlinear phenomena at nanoscales. The effects of the electron degeneracy arise due to Heisenberg’s uncertainty principle and Pauli’s exclusion principle for overlapping electron wave functions that result in tunneling of electrons and the electron degeneracy pressure. Since electrons are Fermions (spin-1/2 quantum particles), there also appears an electron spin current and a spin force acting on electrons due to the Bohr magnetization. The quantum effects produce new aspects of electrostatic (ES) and electromagnetic (EM) waves in a quantum plasma that are summarized in here. Furthermore, nonlinear features of ES ion waves and electron plasma oscillations are discussed, as well as the trapping of intense EM waves in quantum electron-density cavities. Specifically, simulation studies of the coupled nonlinear Schrodinger and Poisson equations reveal the formation and dynamics of localized ES structures at nanoscales in a quantum plasma. The effect of an external magnetic field on the plasma wave spectra and develop quantum magnetohydrodynamic equations are also discussed. The results are useful for understanding numerous collective phenomena in quantum plasmas, such as those in compact astrophysical objects (e.g., the cores of white dwarf stars and giant planets), as well as in plasma-assisted nanotechnology (e.g., quantum diodes, quantum free-electron lasers, nanophotonics and nanoplasmonics, metallic nanostructures, thin metal films, semiconductor quantum wells, and quantum dots, etc.), and in the next generation of intense laser-solid density plasma interaction experiments relevant for fast ignition in inertial confinement fusion schemes.

/pdf/colloquium-nonlinear-collective-interactions-in-quantum-1nqlatefgo.pdf

Colloquium : nonlinear collective interactions in quantum plasmas with degenerate electron fluids

The Zakharov-Kuznetsov (ZK) equation is an isotropic nonlinear evolution equation, first derived for weakly nonlinear ion-acoustic waves in a strongly magnetized lossless plasma in two dimensions. In the present study, by applying the extended direct algebraic method, we found the electric field potential, electric field and magnetic field in the form of traveling wave solutions for the two-dimensional ZK equation. The solutions for the ZK equation are obtained precisely and the efficiency of the method can be demonstrated. The stability of these solutions and the movement role of the waves are analyzed by making graphs of the exact solutions.

Stability analysis for Zakharov-Kuznetsov equation of weakly nonlinear ion-acoustic waves in a plasma

Magnetosonic waves are intensively studied due to their importance in space plasmas and also in fusion plasmas where they are used in particle acceleration and heating experiments. This work considers magnetosonic waves propagating obliquely at an angle θ to an external magnetic field in an electron–positron–ion plasma, using the effective one-fluid magnetohydrodynamic model. Two separate modes (fast and slow) for the waves are discussed in the linear approximation, and the Kadomstev–Petviashvilli soliton equation is derived by using reductive perturbation scheme for these modes in the nonlinear regime. It is observed that for both the modes the angle θ, positron concentration, ion temperature, and plasma β-value affect the propagation properties of solitary waves and behave differently from the simple electron–ion plasmas. Likewise, current density, electric field, and magnetic field for these waves are investigated, for their dependence on the above mentioned parameters.

Effects of positron concentration, ion temperature, and plasma β value on linear and nonlinear two-dimensional magnetosonic waves in electron-positron-ion plasmas

By considering the one-dimensional quantum hydrodynamic model for a three-species ultracold quantum dusty plasma, the properties of dust-ion-acoustic waves are studied. The dispersion relation in the linear regime and the Korteweg–de Vries equation in the nonlinear regime are derived by incorporating quantum corrections. The quantum-mechanical effects through quantum diffraction and quantum statistics as well as the role of immobile charged dust particulates are studied both analytically and numerically. It is found that the amplitude and width of the dust ion acoustic solitary waves are significantly affected by the quantum corrections and concentration of the dust particles.

Linear and nonlinear dust ion acoustic waves in ultracold quantum dusty plasmas

Using the effective one fluid quantum magnetohydrodynamic (QMHD) model, magnetosonic waves propagating obliquely to an external magnetic field are studied in an electron-ion (e-i) Fermi plasma. In the linear approximation, the effect of quantum corrections on the fast and slow magnetosonic waves are discussed. It is shown that the system of QMHD equations admit the Kadomstev–Petviashvilli soliton due to the balance between nonlinearity and dispersion caused by the obliqueness and quantum diffraction effects. It is observed that for both modes, the angle θ, the electron quantum diffraction, and statistic effects modify the shape of the solitary structure. It is also found that the results obtained for the quantum plasma differ significantly from the classical e-i plasmas.

Parametric studies of nonlinear magnetosonic waves in two-dimensional quantum magnetoplasmas

The longitudinal response function for a thermal electron gas is calculated including two quantum effects exactly, degeneracy, and the quantum recoil. The Fermi-Dirac distribution is expanded in powers of a parameter that is small in the nondegenerate limit and the response function is evaluated in terms of the conventional plasma dispersion function to arbitrary order in this parameter. The infinite sum is performed in terms of polylogarithms in the long-wavelength and quasistatic limits, giving results that apply for arbitrary degeneracy. The results are applied to the dispersion relations for Langmuir waves and to screening, reproducing known results in the nondegenerate and completely degenerate limits, and generalizing them to arbitrary degeneracy.

Dispersion in a thermal plasma including arbitrary degeneracy and quantum recoil

Obliquely propagating magnetosonic waves in multicomponent quantum magnetoplasma

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