From pre-storm activity to magnetic storms: a transition described in terms of fractal dynamics

International audienceWe show that distinct changes in scaling parameters of the Dst index time series occur as an intense magnetic storm approaches, revealing a gradual reduction in complexity. The remarkable acceleration of energy release ? manifested in the increase in susceptibility ? couples to the transition from anti-persistent (negative feedback) to persistent (positive feedback) behavior and indicates that the occurence of an intense magnetic storm is imminent. The main driver of the Dst index, the VBSouth electric field component, does not reveal a similar transition to persistency prior to the storm. This indicates that while the magnetosphere is mostly driven by the solar wind the critical feature of persistency in the magnetosphere is the result of a combination of solar wind and internal magnetospheric activity rather than solar wind variations alone. Our results suggest that the development of an intense magnetic storm can be studied in terms of "intermittent criticality" that is of a more general character than the classical self-organized criticality phenomena, implying the predictability of the magnetosphere

The Atlantic blue crab Callinectes sapidus in southern European coastal waters: distribution, impact and prospective invasion management strategies

[EN] The native distribution of the blue crab Callinectes sapidus in the western Atlantic extends from Nova Scotia to Argentina. Introduced to Europe at the beginning of the 20th century, it is currently recorded almost ubiquitously in the Mediterranean and in the Black Sea. An overview of the occurrence, abundance, and ecological impact of the species in southern European waters is provided; additionally, we present a pragmatic assessment of its management scenarios, explicitly considering the dual nature of C sapidus as both an invasive species and a fishery resource. We emphasise that the ongoing expansion of C sapidus in the region may represent a stimulating challenge for the identification and implementation of future strategies in the management of invasive crustaceans. The impact of the invader could be converted into an enhancement of the services delivered by southern European coastal ecosystems, while mitigation costs could be transformed into profits for local populations. (C) 2017 Elsevier Ltd. All rights reserved.Funding from FUR 2013-2014 and 2014-2015 to G. M. is acknowledged. The European Fisheries Fund (FEP) Puglia Region (Italy) supported L. C. (CIP 04/OPI/010) as the scientific head of the MOLEVAR project (Pilot Project for the production of soft crabs from Carcinus aestuarii in Varano lagoon). The Portuguese Science Foundation (FCT) supported F. R. (SFRH/BPD/46761/2008) with a post-doctoral research grant from the Programa Operacional Potencial Humano/Fundo Social Europeu (POPH/FSE). F. R. and P. C. were also supported by the strategic MARE plan - Marine and Environmental Sciences Centre (UID/MAR/04292/2013).Mancinelli, G.; Chainho, P.; Cilenti, L.; Falco, S.; Kapiris, K.; Katselis, G.; Ribeiro, F. (2017). The Atlantic blue crab Callinectes sapidus in southern European coastal waters: distribution, impact and prospective invasion management strategies. Marine Pollution Bulletin. 119(1):5-11. https://doi.org/10.1016/j.marpolbul.2017.02.050S511119

Scaling similarities of multiple fracturing of solid materials

It has recently reported that electromagnetic flashes of low-energy <IMG WIDTH='12' HEIGHT='29' ALIGN='MIDDLE' BORDER='0' src='http://www.nonlin-processes-geophys.net/11/137/2004/npg-11-137-img1.gif' ALT='$gamma$'>-rays emitted during multi-fracturing on a neutron star, and electromagnetic pulses emitted in the laboratory by a disordered material subjected to an increasing external load, share distinctive statistical properties with earthquakes, such as power-law energy distributions (Cheng et al., 1996; Kossobokov et al., 2000; Rabinovitch et al., 2001; Sornette and Helmstetter, 2002). The neutron starquakes may release strain energies up to <IMG WIDTH='32' HEIGHT='16' ALIGN='BOTTOM' BORDER='0' src='http://www.nonlin-processes-geophys.net/11/137/2004/npg-11-137-img2.gif' ALT='$10^{46}$'>erg, while, the fractures in laboratory samples release strain energies approximately a fraction of an erg. An earthquake fault region can build up strain energy up to approximately <IMG WIDTH='32' HEIGHT='16' ALIGN='BOTTOM' BORDER='0' src='http://www.nonlin-processes-geophys.net/11/137/2004/npg-11-137-img3.gif' ALT='$10^{26}$'>erg for the strongest earthquakes. Clear sequences of kilohertz-megahertz electromagnetic avalanches have been detected from a few days up to a few hours prior to recent destructive earthquakes in Greece. A question that arises effortlessly is if the pre-seismic electromagnetic fluctuations also share the same statistical properties. Our study justifies a positive answer. Our analysis also reveals 'symptoms' of a transition to the main rupture common with earthquake sequences and acoustic emission pulses observed during laboratory experiments (Maes et al., 1998)

Unified approach to catastrophic events: from the normal state to geological or biological shock in terms of spectral fractal and nonlinear analysis

An important question in geophysics is whether earthquakes (EQs) can be anticipated prior to their occurrence. Pre-seismic electromagnetic (EM) emissions provide a promising window through which the dynamics of EQ preparation can be investigated. However, the existence of precursory features in pre-seismic EM emissions is still debatable: in principle, it is difficult to prove associations between events separated in time, such as EQs and their EM precursors. The scope of this paper is the investigation of the pre-seismic EM activity in terms of complexity. A basic reason for our interest in complexity is the striking similarity in behavior close to irreversible phase transitions among systems that are otherwise quite different in nature. Interestingly, theoretical studies (Hopfield, 1994; Herz and Hopfield 1995; Rundle et al., 1995; Corral et al., 1997) suggest that the EQ dynamics at the final stage and neural seizure dynamics should have many similar features and can be analyzed within similar mathematical frameworks. Motivated by this hypothesis, we evaluate the capability of linear and non-linear techniques to extract common features from brain electrical activities and pre-seismic EM emissions predictive of epileptic seizures and EQs respectively. The results suggest that a unified theory may exist for the ways in which firing neurons and opening cracks organize themselves to produce a large crisis, while the preparation of an epileptic shock or a large EQ can be studied in terms of ''Intermittent Criticality''

Evolving towards a critical point: A possible electromagnetic way in which the critical regime is reached as the rupture approaches

International audienceIn analogy to the study of critical phase transitions in statistical physics, it has been argued recently that the fracture of heterogeneous materials could be viewed as a critical phenomenon, either at laboratory or at geophysical scales. If the picture of the development of the fracture is correct one may guess that the precursors may reveal the critical approach of the main-shock. When a heterogeneous material is stretched, its evolution towards breaking is characterized by the appearance of microcracks before the final break-up. Microcracks produce both acoustic and electromagnetic(EM) emission in the frequency range from VLF to VHF. The microcracks and the associated acoustic and EM activities constitute the so-called precursors of general fracture. These precursors are detectable not only at laboratory but also at geophysical scales. VLF and VHF acoustic and EM emissions have been reported resulting from volcanic and seismic activities in various geologically distinct regions of the world. In the present work we attempt to establish the hypothesis that the evolution of the Earth's crust towards the critical point takes place not only in a mechanical but also in an electromagnetic sense. In other words, we focus on the possible electromagnetic criticality, which is reached while the catastrophic rupture in the Earth's crust approaches. Our main tool is the monitoring of micro-fractures that occur before the final breakup, by recording their radio-electromagnetic emissions. We show that the spectral power law analysis of the electromagnetic precursors reveals distinguishing signatures of underlying critical dynamics, such as: (i) the emergence of memory effects; (ii) the decrease with time of the anti-persistence behaviour; (iii) the presence of persistence properties in the tail of the sequence of the precursors; and (iv) the acceleration of the precursory electro-magnetic energy release. Moreover, the statistical analysis of the amplitudes of the electromagnetic fluctuations reveals the breaking of the symmetry as the theory predicts. Finally, we try to answer the question: how universal the observed electromagnetic critical behaviour of the failing system is

Sudden drop of fractal dimension of electromagnetic emissions recorded prior to significant earthquake

The variation of fractal dimension and entropy during a damage evolution process, especially approaching critical failure, has been recently investigated. A sudden drop of fractal dimension has been proposed as a quantitative indicator of damage localization or a likely precursor of an impending catastrophic failure. In this contribution, electromagnetic emissions recorded prior to significant earthquake are analysed to investigate whether they also present such sudden fractal dimension and entropy drops as the main catastrophic event is approaching. The pre-earthquake electromagnetic time series analysis results reveal a good agreement to the theoretically expected ones indicating that the critical fracture is approaching

Rapid rotational foam molding of integral skin polypropylene cellular composites

Rapid Rotational Foam Molding (RRFM) is a novel patent-pending process that was designed and developed to maximize the synergistic effects resulting from the deliberate combination of extrusion and rotational foam molding and thereby serve as a time-andenergy efficient technology for the manufacture of integral-skin rotationally molded foams of high quality. This thesis presents a thorough study of the scientific and engineering aspects related to the evolution of the RRFM process and its feasibility. This innovative processing technology was assessed and verified through a battery of planned experimental trials conducted utilizing an in-house custom-built industrial-grade lab-scale experimental setup. The experimental trials involved a variety of polypropylene (PP)- based foamable formulations with a chemical blowing agent (CBA) that were compounded and processed by utilizing an extruder and then foamed and injected as a foamed core, instantly, into the cavity of a suitable non-chilled rotationally molded hollow shell made of non-foamed pulverized PP grades. The investigated mold shapes included a cylindrical shaped mold and a rectangular flat shaped mold. The obtained moldings were examined for the quality of the skin surface, the skin-foam interface, and the achieved foam morphologies that were characterized in terms of foam density, average cell size, and average cell density. Optimal processing parameters were successfully determined for three different PP skin-foam formulation combinations. The accomplished reduction in processing time and energy consumption by implementing RRFM were substantial. A variety of processing impediments that hindered the efficiency of the single-charge conventional rotational foam molding practice were resolved by implementing RRFM; these include: the foam/skin invasion into the skin/foam layer of the manufactured article and the premature decomposition of CBA during compounding or subsequent rotational foam molding processing steps