The g-modes of white dwarfs

The neutral g-modes of a degenerate fluid at zero temperature are analyzed. The g-modes of a degenerate fluid at finite but small temperatures are then expanded in terms of those of the zero temperature fluid. For nonrelativistic degenerate fluids it is found that (1) the g-eigenvalues are proportional to T mu(6)sub e mu(-1)sub i, where T is the internal temperature of the fluid, mu sub e and mu sub i are the mean molecular weights of electrons and ions, respectively; (2) the ion pressure is solely responsible for driving the g-modes. For white dwarfs of about a solar mass, the periods of the g-oscillations are in the range of a few hundredths of seconds

A novel underdetermined source recovery algorithm based on k-sparse component analysis

Sparse component analysis (SCA) is a popular method for addressing underdetermined blind source separation in array signal processing applications. We are motivated by problems that arise in the applications where the sources are densely sparse (i.e. the number of active sources is high and very close to the number of sensors). The separation performance of current underdetermined source recovery (USR) solutions, including the relaxation and greedy families, reduces with decreasing the mixing system dimension and increasing the sparsity level (k). In this paper, we present a k-SCA-based algorithm that is suitable for USR in low-dimensional mixing systems. Assuming the sources is at most (m−1) sparse where m is the number of mixtures; the proposed method is capable of recovering the sources from the mixtures given the mixing matrix using a subspace detection framework. Simulation results show that the proposed algorithm achieves better separation performance in k-SCA conditions compared to state-of-the-art USR algorithms such as basis pursuit, minimizing norm-L1, smoothed L0, focal underdetermined system solver and orthogonal matching pursuit

Troublesome trade-offs: balancing urban activities and values when securing a city-centre governmental quarter

Background Homeland security measures increasingly affect urban life and activities. Standoff distance, which prevents unscreened vehicles from approaching within a certain distance of a building, is a widely applied measure when protecting buildings against attacks with vehicle-borne improvised explosive devices. This measure both is rather inexpensive and has few negative externalities when implemented in rural areas. Unfortunately, sites with protection needs often are situated in city centres. Methods We apply the so-called Security Function Framework to illuminate the externalities or the ‘troublesome trade-offs’ between protecting a high-value site against vehicle-borne improvised explosive devices and protecting other urban values. Results This paper demonstrates that standoff creates challenges for other important values, such as functional office spaces for all employees, deliveries and emergency vehicle access. Simultaneously, standoff creates opportunities for reinforcing social-responsibility requirements, such as accessibility for pedestrians and environmental considerations. Conclusions Security measures can have both negative and positive externalities and planning might alleviate some of the negative ones

On synchronization of clocks in general space-times

  Einstein and transport synchronizations of infinitesimally spaced and distant clocks are considered in a general Riemannian space-time. It is shown that infinitesimally spaced clocks can always be synchronized. In general one can not find observers for whom distant clock are Einstein synchronized but transport synchronized observers do always exit. Whenever both procedures are possible, they are equivalent

Preventing plagiarism in academic literature, lessons learned from European union member states

Background and Objectives: Plagiarism is the most prevalent type of scientific misconduct, and various rules and strategies have been proposed to combat it in different countries. A review of other countrieschr('39') experiences in this area contributes to good policymaking. The present study was conducted to introduce preventive interventions of plagiarism in the leading countries. Methods: The present study was a qualitative review study of applied practices. In this study, preventive interventions of scientific plagiarism in the 27 European ::::::::union:::::::: countries were studied due to the appropriate coherence and structural similarity at national, organizational, and individual levels. The national-level interventions were analyzed using the content analysis method in mentioned countries. Results: The results of analyzing the national-level interventions were categorized into eight main themes, including reaching a national agreement on examples of scientific plagiarism and misconduct; policy development; monitoring and supervision; financial support development; development of databanks and software; compiling educational programs for faculty members and students; dissemination and use of successful experiences; and eventually establishment of laws related to scientific misconduct, plagiarism, and punishments activities. Conclusion: Using preventive interventions at a national level proves the commitment and determination of policymakers to control and prevent plagiarism. Proper use of preventive interventions at a national level strengthens the controlling and preventive infrastructures of this issue at the organizational level, and enhances moral commitment and professional skills among the countrychr('39')s researchers