On the magnetohydrodynamic description of a two-component plasma in the Kerr metric

The magnetohydrodynamic equations describing an inviscid, fully ionized plasma in the vicinity of a rotating black hole are derived from a two-component plasma theory within the framework of the 3+1 split of the Kerr metric. Of central interest is the generalized Ohm's law. In the limit of quasi-neutral plasma it contains no new terms as compared with special relativity. Gravitomagnetic terms appear in Ohm's law only if the plasma is charged in its rest frame or the magnetohydrodynamic approximation is not applied. It is argued that a relativistic single-fluid description of a multiple-component plasma is possible only for cold (i.e. intrinsically non-relativistic) components. As seen by local stationary observers, close to the horizon the electron collision time becomes longer than dynamical timescales, i.e. the plasma appears to behave as particles.Comment: 8 pages, no figures, MNRAS, see also http://www.lsw.uni-heidelberg.de/~rkhanna/publications.htm

Investigation on the Electrical Properties of CdO/ZnO thin films using THz Spectroscopy

In this work, we study the electrical properties of transparent conducting oxides using physical and optical techniques. The objective is to characterize the conductivity of a series of cadmium oxide zinc-oxide thin films with varying cadmium concentrations using three methods. The Hall Effect estimates carrier concentration, sheet conductivity, and carrier mobility. Optical methods, such as FTIR spectroscopy, can provide estimates of the plasma frequency, which describes a metal’s transition from being transparent to opaque to light. THz spectroscopy extracts the complex conductivity of materials in the far infrared spectrum and provides insights on the optical transport properties of conductors. Our findings show that DC/AC measurements of the conductivity of Cd/ZnO thin films exhibit frequency independent conductivity, indicating that the films are homogeneous Drude metals

Perception of global facial geometry is modulated through experience

Identification of personally familiar faces is highly efficient across various viewing conditions. While the presence of robust facial representations stored in memory is considered to aid this process, the mechanisms underlying invariant identification remain unclear. Two experiments tested the hypothesis that facial representations stored in memory are associated with differential perceptual processing of the overall facial geometry. Subjects who were personally familiar or unfamiliar with the identities presented discriminated between stimuli whose overall facial geometry had been manipulated to maintain or alter the original facial configuration (see Barton, Zhao & Keenan, 2003). The results demonstrate that familiarity gives rise to more efficient processing of global facial geometry, and are interpreted in terms of increased holistic processing of facial information that is maintained across viewing distances

Political Economy : Variability and Consistency in the Development of Worker Owned Cooperatives

The relationship between worker cooperatives and their social and economic environment has sparked interest among the sociological community for the contradictions and harmony typical of these interactions. However, these studies do not examine how firm behavior varies and/or remains constant in different social conditions. With insights from economic sociology, neo-institutionalism, and social movements theory, the paper pursues this issue by answering the following question: how do worker cooperatives respond to different social conditions over time? Using interviews with members of eight worker cooperatives in a Midwestern metropolitan area, the author compares behavior in older and younger cooperatives to observe similarities and differences in their practices under different social conditions. The analysis demonstrates that differences in social support and market competition created variation among older and newer cooperatives. For instance, the decision to start worker-owned cooperatives reflected different political motivations that emerged from distinct socio-economic conditions. However, all firms eventually behaved like businesses because they framed economic activities as political activism, exposing them to fluctuations in the city’s political scene. As a result, these businesses created market niches, attract customers and competent workers, and copy other successful democratic enterprises to survive demographic fluctuations in the market

Notes regarding a pedagogical model for the distance learning of tradumática

The article presents a proposed plan of a pedagogical model for the distance learning of tradumática, based on an educational process that revolves around classes recorded in digital format and synchronous and asynchronous activities overseen by an educational supervisor