Modelica - A Language for Physical System Modeling, Visualization and Interaction

Modelica is an object-oriented language for modeling of large, complex and heterogeneous physical systems. It is suited for multi-domain modeling, for example for modeling of mechatronics including cars, aircrafts and industrial robots which typically consist of mechanical, electrical and hydraulic subsystems as well as control systems. General equations are used for modeling of the physical phenomena, No particular variable needs to be solved for manually. A Modelica tool will have enough information to do that automatically. The language has been designed to allow tools to generate efficient code automatically. The modeling effort is thus reduced considerably since model components can be reused and tedious and error-prone manual manipulations are not needed. The principles of object-oriented modeling and the details of the Modelica language as well as several examples are presented

Quantum oscillations in the kinetic energy density: Gradient corrections from the Airy gas

We derive a closed form expression for the quantum corrections to the kinetic energy density (KED) in the Thomas-Fermi (TF) limit of a linear potential model system in three dimensions (the Airy gas). The universality of the expression is tested numerically in a number of three dimensional model systems: (i) jellium surfaces, (ii) hydrogen-like potentials, (iii) systems confined by an harmonic potential in one and (iv) all three dimensions, and (v) a system with a cosine potential (the Mathieu gas). Our results confirm that the usual gradient expansion of extended Thomas-Fermi theory (ETF) does not describe the quantum oscillations for systems that incorporate surface regions where the electron density drops off to zero. We find that the correction derived from the Airy gas is universally applicable to relevant spatial regions of systems of type (i), (ii), and (iv), but somewhat surprisingly not (iii). We discuss possible implications of our findings to the development of functionals for the kinetic energy density.Comment: 15 pages, 9 figure

Immunization of Rabbits with Purified Nicotinic Acetylcholine Receptor

Immunization of rabbits, rats and guinea pigs with nicotinic acetylcholine receptor from the electric organ of T. marmorata leads to a production of antibodies in these animais. Simultaneously a peripheral paralysis is seen, particularly .pronounced in rabbits. In rats the symptoms are transient. The antibody titres in rabbits are correlated to the visible symptoms. The highest antibody titres are found in the most affected animals. Electrophysiolog;ical, immunological and morphological analysis indicate disturbances of the neuromuscular function, probably on the post.synaptic site. Thymus reactions may also be involved as a thymit has been found in the immunized rabbits

Immunization of Rabbits with Purified Nicotinic Acetylcholine Receptor

Immunization of rabbits, rats and guinea pigs with nicotinic acetylcholine receptor from the electric organ of T. marmorata leads to a production of antibodies in these animais. Simultaneously a peripheral paralysis is seen, particularly .pronounced in rabbits. In rats the symptoms are transient. The antibody titres in rabbits are correlated to the visible symptoms. The highest antibody titres are found in the most affected animals. Electrophysiolog;ical, immunological and morphological analysis indicate disturbances of the neuromuscular function, probably on the post.synaptic site. Thymus reactions may also be involved as a thymit has been found in the immunized rabbits

Relativistic materials from an alternative viewpoint

Electrons in materials containing heavy elements are fundamentally relativistic and should in principle be described using the Dirac equation. However, the current standard for treatment of electrons in such materials involves density functional theory methods originally formulated from the Schr\"{o}dinger equation. While some extensions of the Schr\"{o}dinger-based formulation have been explored, such as the scalar relativistic approximation with or without spin-orbit coupling, these solutions do not provide a way to fully account for all relativistic effects of electrons, and the language used to describe such solutions are still based in the language of the Schr\"{o}dinger equation. In this article, we provide a different method for translating between the Dirac and Schr\"{o}dinger viewpoints in the context of a Coulomb potential. By retaining the Dirac four-vector notation and terminology in taking the non-relativistic limit, we see a much deeper connection between the Dirac and Schr\"{o}dinger equation solutions that allow us to more directly compare the effects of relativity in the angular and radial functions. Through this viewpoint, we introduce the concepts of densitals and Dirac spherical harmonics that allow us to translate more easily between the Dirac and Schr\"{o}dinger solutions. These concepts allow us to establish a useful language for discussing relativistic effects in materials containing elements throughout the full periodic table and thereby enable a more fundamental understanding of the effects of relativity on electronic structure

On the physics of frequency domain controlled source electromagnetics in shallow water, 2: transverse anisotropy

Author Posting. © The Authors, 2017. This article is posted here by permission of Oxford University Press for personal use, not for redistribution. The definitive version was published in Geophysical Journal International 211 (2017): 1046–1061, doi:10.1093/gji/ggx360.In recent years, marine controlled source electromagnetics (CSEM) has found increasing use in hydrocarbon exploration due to its ability to detect thin resistive zones beneath the seafloor. It is the purpose of this paper to evaluate the physics of CSEM for an ocean whose electrical thickness is comparable to or much thinner than that of the overburden using the in-line configuration through examination of the elliptically-polarized seafloor electric field, the time-averaged energy flow depicted by the real part of the complex Poynting vector, energy dissipation through Joule heating and the Fréchet derivatives of the seafloor field with respect to the sub-seafloor conductivity that is assumed to be transversely anisotropic, with a vertical-to-horizontal resistivity ratio of 3:1. For an ocean whose electrical thickness is comparable to that of the overburden, the seafloor electromagnetic response for a model containing a resistive reservoir layer has a greater amplitude and reduced phase as a function of offset compared to that for a halfspace, or a stronger and faster response, and displays little to no evidence for the air interaction. For an ocean whose electrical thickness is much smaller than that of the overburden, the electric field displays a greater amplitude and reduced phase at small offsets, shifting to a stronger amplitude and increased phase at intermediate offsets, and a weaker amplitude and enhanced phase at long offsets, or a stronger and faster response that first changes to stronger and slower, and then transitions to weaker and slower. By comparison to the isotropic case with the same horizontal conductivity, transverse anisotropy stretches the Poynting vector and the electric field response from a thin resistive layer to much longer offsets. These phenomena can be understood by visualizing the energy flow throughout the structure caused by the competing influences of the dipole source and guided energy flow in the reservoir layer, and the air interaction caused by coupling of the entire sub-seafloor resistivity structure with the sea surface. The Fréchet derivatives are dominated by preferential sensitivity to the vertical conductivity in the reservoir layer and overburden at short offsets. The horizontal conductivity Fréchet derivatives are weaker than to comparable to the vertical derivatives at long offsets in the substrate. This means that the sensitivity to the horizontal conductivity is present in the shallow parts of the subsurface. In the presence of transverse anisotropy, it is necessary to go to higher frequencies to sense the horizontal conductivity in the overburden as compared to an isotropic model with the same horizontal conductivity. These observations in part explain the success of shallow towed CSEM using only measurements of the in-line component of the electric field.This work was supported at WHOI by an Independent Research and Development award, and by the Walter A. and Hope Noyes Smith Chair for Excellence in Oceanography