Generation of highly symmetric, cylindrically convergent shockwaves in water

We report on pulsed power driven, exploding copper wire array experiments conducted to generate cylindrical convergent shockwaves in water employing μs risetime currents >550 kA in amplitude and with stored energies of >15 kJ—a substantial increase over previous results. The experiments were carried out on the recently constructed Mega-Ampere-Compression-and-Hydrodynamics facility at Imperial College London in collaboration with colleagues of Technion, Israel. 10 mm diameter arrays consisting of 60 × 130 μm wires were utilized, and the current and voltage diagnostics of the load region suggested that ∼8 kJ of energy was deposited in the wires (and the load region close to the wires) during the experiments, resulting in the formation of dense, highly resistive plasmas that rapidly expanded driving the shockwaves in water. Laser-backlit framing images of the shockfront were obtained at radii 50:1. Framing images and streak photographs showed that the velocity of the shockwave reached ∼7.5 km s−1 at 0.1 mm from the axis. 2D hydrodynamic simulations that match the experimentally obtained implosion trajectory suggest that pressures >1 Mbar are produced within 10 μm of the axis along with water densities of 3gcm−3 and temperatures of many 1000 s of Kelvin. Under these conditions, Quotidian Equation of State suggests that a strongly coupled plasma with an ionization fraction of ∼0.7 would be formed. The results represent a “stepping stone” in the application of the technique to drive different material samples into high pressure, warm dense matter regimes with compact, university scale generators, and provide support in scaling the technique to multi-mega ampere currents

The Transformation of Citizenship in Complex Societies

The main purpose of this paper is to propose a theoretical framework for understanding the transformation of citizenship in complex societies. To this end, the paper is divided into six sections. The first section elucidates the main reasons for the renaissance of the concept of citizenship in the contemporary social sciences. The second section argues that a comprehensive sociological theory of citizenship needs to account for the importance of four dimensions: the content, the type, the conditions, and the arrangements of citizenship. The third section suggests that in order to understand the sociological significance of T.H. Marshall’s account of legal, political, and social rights we need to explore the particular historical contexts in which citizenship rights became ideologically and institutionally relevant. The fourth section offers some critical reflections on the main shortcomings of the Marshallian approach to citizenship. The fifth section draws an analogy between the transformation of social movements and the transformation of citizenship. The sixth section sheds light on the fact that contemporary citizenship studies are confronted with a curious paradox: the differentiation of citizenship has led to both the relativistic impoverishment and the pluralistic enrichment of contemporary accounts of ‘the social’ and ‘the political’.The paper concludes by arguing that, under conditions of late modernity, the state’s capacity to gain political legitimacy increasingly depends on its ability to confront the normative challenges posed by the ubiquity of societal complexity

Building the genomic nation: ‘Homo Brasilis’ and the ‘Genoma Mexicano’ in comparative cultural perspective

This article explores the relationship between genetic research, nationalism and the construction of collective social identities in Latin America. It makes a comparative analysis of two research projects – the ‘Genoma Mexicano’ and the ‘Homo Brasilis’ – both of which sought to establish national and genetic profiles. Both have reproduced and strengthened the idea of their respective nations of focus, incorporating biological elements into debates on social identities. Also, both have placed the unifying figure of the mestizo/mestiço at the heart of national identity constructions, and in so doing have displaced alternative identity categories, such as those based on race. However, having been developed in different national contexts, these projects have had distinct scientific and social trajectories: in Mexico, the genomic mestizo is mobilized mainly in relation to health, while in Brazil the key arena is that of race. We show the importance of the nation as a frame for mobilizing genetic data in public policy debates, and demonstrate how race comes in and out of focus in different Latin American national contexts of genomic research, while never completely disappearing

Electron beam generation in a diode having a ferroelectric plasma cathode controlled by optic fibers

An electron diode having a ferroelectric plasma cathode (FPS) controlled by optic fibers was operated at a repetition rate of 0.5 Hz during 1 hour, when an accelerating pulse of ~250 kV in amplitude and ~250 ns in duration is applied. The application of the fiber optic decoupling allows easy control and synchronization of the FPS operation with the firing of the HV generator. It was shown that the use of the FPS with fast fall time of the driving pulse allows reproducible generation of an electron beam having a current amplitude of ~1 kA and uniform cross-sectional current density distribution. It was shown also that in the case of the driving pulse ringing, the application of the accelerating pulse during the fall in the negative ringing leads to a plasma pre-filled mode of diode operation due to intense ion emission from the FPS. When the accelerating pulse is applied during the rise in the positive driving pulse ringing, one obtains diode operation with limited plasma emission ability. Only when the accelerating pulse is applied during the fall in the positive ringing of the driving pulse does one obtain diode operation in space-charge limited mode. This dependence of the diode operation on the timing of the accelerating pulse application with respect to the driving pulse is explained by processes related to the screening of ferroelectric bounded surface charges by the plasma charged particles