25 Years of Self-organized Criticality: Concepts and Controversies

Introduced by the late Per Bak and his colleagues, self-organized criticality (SOC) has been one of the most stimulating concepts to come out of statistical mechanics and condensed matter theory in the last few decades, and has played a significant role in the development of complexity science. SOC, and more generally fractals and power laws, have attracted much comment, ranging from the very positive to the polemical. The other papers (Aschwanden et al. in Space Sci. Rev., 2014, this issue; McAteer et al. in Space Sci. Rev., 2015, this issue; Sharma et al. in Space Sci. Rev. 2015, in preparation) in this special issue showcase the considerable body of observations in solar, magnetospheric and fusion plasma inspired by the SOC idea, and expose the fertile role the new paradigm has played in approaches to modeling and understanding multiscale plasma instabilities. This very broad impact, and the necessary process of adapting a scientific hypothesis to the conditions of a given physical system, has meant that SOC as studied in these fields has sometimes differed significantly from the definition originally given by its creators. In Bak’s own field of theoretical physics there are significant observational and theoretical open questions, even 25 years on (Pruessner 2012). One aim of the present review is to address the dichotomy between the great reception SOC has received in some areas, and its shortcomings, as they became manifest in the controversies it triggered. Our article tries to clear up what we think are misunderstandings of SOC in fields more remote from its origins in statistical mechanics, condensed matter and dynamical systems by revisiting Bak, Tang and Wiesenfeld’s original papers

Press-fit stability of an osteochondral autograft: Influence of different plug length and perfect depth alignment.

BACKGROUND: Osteochondral autologous transplantation is used for the treatment of full-thickness articular cartilage lesions of a joint. Press-fit stability is an important factor for good survival of the transplanted plugs. MATERIAL AND METHODS: 36 plugs of three different lengths were transplanted in fresh-frozen human knees. On one condyle, 3 plugs were exactly matched to the depth of the recipient site ("bottomed" plugs) and on the opposite condyle 3 plugs were 5 mm shorter than the depth of the recipient site ("unbottomed" plugs). Plugs were left protruding and then pushed in until flush, and then to 2 mm below flush level, using a loading apparatus. RESULTS: Longer plugs needed higher forces to begin displacement. At flush level, bottomed plugs needed significantly higher forces than unbottomed plugs to become displaced below flush level (mean forces of 404 N and 131 N, respectively). Shorter bottomed plugs required higher forces than longer bottomed ones. INTERPRETATION: Bottomed plugs generally provide much more stability than unbottomed ones. Short bottomed plugs are more stable than long bottomed plugs. Thus, in clinical practice it is advisable to use short bottomed plugs. If, however, unbottomed plugs are still chosen, the longer the plug the higher the resulting stability will be because of higher frictional forces

Dendermonde, a city on two rivers: reflections about the projects d’amenagement after the First World War

peer reviewedThe First World War as well as being cause to destruction, was also an occasion of renewal for many residential areas, which exploited the post-war reconstruction to change their urban layout. It was the time when in Europe new approaches to architecture and urban planning were being discussed, based on the aesthetics. Meanwhile, in the Belgian context, the debate on the Art de Bâtir by C. Sitte began to consolidate, and, simultaneously, the first institutions of sites protection were born. Termonde, a settlement dating from the eleventh century, occupies a geographically strategic place of the Belgian territory: located north of the country, not far from the Dutch border and perfectly in the center of the triangle Ghent-Antwerp-Brussels, the city has always been one of the economy hubs in the nation. The Dendermonde industry has historically implanted in the urban area - crossed by the two rivers Escaut and Dendre - exploiting all the resources for industrial production. Despite the ravages of war and the many floods, thanks to government targeted actions, the city still managed to occupy a place of first importance in Flanders intensive industrialization, representing a crucial point of the 'water railway' which, starting from French Flanders and passing through Ghent and Antwerp, comes up to Germany. The objective of the study is to examine the situation of Dendermonde in the thirties of the twentieth century, by analyzing, in particular - on the basis of historical iconography of the early decades of the twentieth century and some local projects d’amenagement presented soon after the First World War up to the Concours pour l’urbanization de Termonde (1935) - measures, suggestions and reflections on the theme of conservation and redevelopment of the river landscape, in compliance with the historical archaeological persistence, geo-natural and landscape features of the town. In particular, we are going to examine the proposed interventions on the two streams of Dendermonde which aimed primarily at enhancing the ancient center. The projects related to the two rivers involved diversion, interception or slowdown operations. These transformations brought substantial changes to the urban features and to the natural historical landscape, thus altering the identity of places, and by deleting certain environmental values, or historical and aesthetic, without subtracting the character sometimes typically industrial, otherwise picturesque of the northern Europe ancient city

Characterizing Roman Artifacts to Investigate Gendered Practices in Contexts Without Sexed Bodies

This article concerns the characterization of Roman artifacts so that they can play a greater role in gendered approaches to Roman sites—sites that constitute lived spaces but lack actual references to sexed bodies. It commences with a brief discussion on gendered approaches in the two main strands of Roman archaeology—classical and provincial. Within the differing frameworks of the wider disciplines of classics and archaeology, both strands focus on contexts with sexed bodies—burials, figurative representation, and inscriptions. The discussion serves as a background for more integrated and more interrogative approaches to relationships between Roman artifacts and gendered practices, approaches that aim to develop interpretative tools for investigating social practice in contexts where no representational or biologically sexed bodies are evident. Three types of artifacts—brooches, glass bottles, and needles—are used to demonstrate how differing degrees of gender associations of artifacts and artifact assemblages can provide insights into gender relationships in settlement contexts. These insights in turn contribute to better understandings of gendered sociospatial practices across the Roman world

25 Years of Self-Organized Criticality: Solar and Astrophysics

Shortly after the seminal paper “Self-Organized Criticality: An explanation of 1/fnoise” by Bak et al. (1987), the idea has been applied to solar physics, in “Avalanches and the Distribution of Solar Flares” by Lu and Hamilton (1991). In the following years, an inspiring cross-fertilization from complexity theory to solar and astrophysics took place, where the SOC concept was initially applied to solar flares, stellar flares, and magnetospheric substorms, and later extended to the radiation belt, the heliosphere, lunar craters, the asteroid belt, the Saturn ring, pulsar glitches, soft X-ray repeaters, blazars, black-hole objects, cosmic rays, and boson clouds. The application of SOC concepts has been performed by numerical cellular automaton simulations, by analytical calculations of statistical (powerlaw-like) distributions based on physical scaling laws, and by observational tests of theoretically predicted size distributions and waiting time distributions. Attempts have been undertaken to import physical models into the numerical SOC toy models, such as the discretization of magneto-hydrodynamics (MHD) processes. The novel applications stimulated also vigorous debates about the discrimination between SOC models, SOC-like, and non-SOC processes, such as phase transitions, turbulence, random-walk diffusion, percolation, branching processes, network theory, chaos theory, fractality, multi-scale, and other complexity phenomena. We review SOC studies from the last 25 years and highlight new trends, open questions, and future challenges, as discussed during two recent ISSI workshops on this theme.Fil: Aschwanden, Markus J.. Lockheed Martin Corporation; Estados UnidosFil: Crosby, Norma B.. Belgian Institute For Space Aeronomy; BélgicaFil: Dimitropoulou, Michaila. University Of Athens; GreciaFil: Georgoulis, Manolis K.. Academy Of Athens; GreciaFil: Hergarten, Stefan. Universitat Freiburg Im Breisgau; AlemaniaFil: McAteer, James. University Of New Mexico; Estados UnidosFil: Milovanov, Alexander V.. Max Planck Institute For The Physics Of Complex Systems; Alemania. Russian Academy Of Sciences. Space Research Institute; Rusia. Enea Centro Ricerche Frascati; ItaliaFil: Mineshige, Shin. Kyoto University; JapónFil: Morales, Laura Fernanda. Canadian Space Agency; Canadá. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Nishizuka, Naoto. Japan National Institute Of Information And Communications Technology; JapónFil: Pruessner, Gunnar. Imperial College London; Reino UnidoFil: Sanchez, Raul. Universidad Carlos Iii de Madrid. Instituto de Salud; EspañaFil: Sharma, A. Surja. University Of Maryland; Estados UnidosFil: Strugarek, Antoine. University Of Montreal; CanadáFil: Uritsky, Vadim. Nasa Goddard Space Flight Center; Estados Unido