The study of the preparation phase of large earthquakes is essential to understand the physical processes involved, and potentially useful also to develop a future reliable short-term warning system. ...Here we analyse electron density and magnetic field data measured by Swarm three-satellite constellation for 4.7 years, to look for possible in-situ ionospheric precursors of large earthquakes to study the interactions between the lithosphere and the above atmosphere and ionosphere, in what is called the Lithosphere-Atmosphere-Ionosphere Coupling (LAIC). We define these anomalies statistically in the whole space-time interval of interest and use a Worldwide Statistical Correlation (WSC) analysis through a superposed epoch approach to study the possible relation with the earthquakes. We find some clear concentrations of electron density and magnetic anomalies from more than two months to some days before the earthquake occurrences. Such anomaly clustering is, in general, statistically significant with respect to homogeneous random simulations, supporting a LAIC during the preparation phase of earthquakes. By investigating different earthquake magnitude ranges, not only do we confirm the well-known Rikitake empirical law between ionospheric anomaly precursor time and earthquake magnitude, but we also give more reliability to the seismic source origin for many of the identified anomalies.
The KLOE-2 experiment at the INFN Laboratori Nazionali di Frascati (LNF) completed its data-taking at the e+e− DAΦNE collider, which implements an innovative collision scheme based on a crab-waist ...configuration, and achieved the integrated luminosity of more than 5 fb−1 . KLOE-2 represents the continuation of KLOE with an upgraded detector and an extended physics program which includes, among the main topics, neutral kaon interferometry and test of discrete symmetries . Entangled neutral kaon pairs produced at DAΦNE are a unique tool to test discrete symmetries and quantum coherence at the utmost sensitivity, strongly motivating the experimental searches of possible CPT violating effects, which would constitute an unambiguous signal of New Physics. The status of the test of Time reversal and CPT simmetry in ϕ→KSKL→πv,3π0,(2π) decays with KLOE and KLOE-2 data will be discussed.
The debated question on the possible relation between the Earth's magnetic field and climate has been usually focused on direct correlations between different time series representing both systems. ...However, the physical mechanism able to potentially explain this connection is still an open issue. Finding hints about how this connection could work would suppose an important advance in the search of an adequate physical mechanism. Here, we propose an innovative information-theoretic tool, i.e. the transfer entropy, as a good candidate for this scope because is able to determine, not simply the possible existence of a connection, but even the direction in which the link is produced. We have applied this new methodology to two real time series, the South Atlantic Anomaly (SAA) area extent at the Earth's surface (representing the geomagnetic field system) and the Global Sea Level (GSL) rise (for the climate system) for the last 300 years, to measure the possible information flow and sense between them. This connection was previously suggested considering only the long-term trend while now we study this possibility also in shorter scales. The new results seem to support this hypothesis, with more information transferred from the SAA to the GSL time series, with about 90% of confidence level. This result provides new clues on the existence of a link between the geomagnetic field and the Earth's climate in the past and on the physical mechanism involved because, thanks to the application of the transfer entropy, we have determined that the sense of the connection seems to go from the system that produces geomagnetic field to the climate system. Of course, the connection does not mean that the geomagnetic field is fully responsible for the climate changes, rather that it is an important driving component to the variations of the climate.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
I extract a latent systematic risk factor, which is orthogonal to idiosyncratic risk and observable systematic risk, from credit spreads for 1764 Eurobonds across euro area non-financial firms over ...the 1999–2015 period. The extracted common latent factor negatively predicts stock market excess returns, the growth rate in real economic activity and economic sentiment. It predicts the financial crisis and the two economic recessions.
We study the macroeconomic effects of the 3-year long-term refinancing operations (LTROs) introduced by the ECB in December 2011 with the aim of reducing the obstacles to credit supply through the ...mitigation of liquidity and funding risks in the euro area banking system. Therefore, we interpret the measure as a credit supply shock, which is identified both recursively and with sign restriction methods using the euro area Bank Lending Survey (BLS). The size of the shock due to the LTROs is computed using both the April 2012 BLS and the special ad-hoc questions on the LTROs conducted in February 2012. The counterfactual exercises suggest that the 3-year LTROs lifted prospects for real GDP and loan provision to non-financial corporations and increased goods prices over the next two-to-three years, thereby avoiding a major credit crunch.
•The macroeconomic effects of the 3-year LTROs are studied.•The 3-year LTROs' shocks are identified using the euro area Bank Lending Survey.•The counterfactual exercises suggest that the 3-year LTROs was expansionary.•The 3-year LTROs avoided a major credit crunch in the euro area.
The geomagnetic storm that occurred on 25 August 25 2018, that is, during the minimum of solar cycle 24, is currently the strongest ever probed by the first China Seismo‐Electromagnetic Satellite ...(CSES‐01). By integrating the in situ measurements provided by CSES‐01 (orbiting at altitude of 507 km) and by Swarm A satellite (orbiting at ca., 460 km) with ground‐based observations (ionosondes, magnetometers, and Global Navigation Satellite System receivers), we investigate the ionospheric response at lower‐ and mid‐latitudes over Brazil. Specifically, we investigate the electrodynamic disturbances driven by solar wind changes, by focusing on the disturbances driving modifications of the equatorial electrojet (EEJ). Our proposed multisensor technique analysis mainly highlights the variations in the topside and bottomside ionosphere, and the interplay between prompt penetrating electric fields and disturbance dynamo electric fields resulting in EEJ variations. Thanks to this approach and leveraging on the newly available CSES‐01 data, we complement and extend what recently investigated in the Western South American sector, by highlighting the significant longitudinal differences, which mainly come from the occurrence of a daytime counter‐EEJ during both 25 and 26 August at Braziliian longitudes and during part of 26 August only in the Peruvian sector. In addition, the increased thermospheric circulation driven by the storm has an impact on the EEJ during the recovery phase of the storm. The observations at the CSES‐01/Swarm altitudes integrated with the ground‐based observation recorded signatures of equatorial ionospheric anomaly crests formation and modification during daytime coupled with the positive ionospheric storm effects at midlatitude.
Key Points
A detailed analysis of the storm‐triggered EEJ variations and the resulting ionospheric variability is provided
Counter‐electrojet found during 25 August daytime even under PPEF event
Use of CSES‐01 and Swarm A plasma density data in a multi‐instrument context to depict EIA crest signatures at different altitudes
•A novel generalized modelling approach for multiphase flows has been developed.•Suitable closures are selected as a function of the local interface morphology.•The switch between different closure ...models depends on the local mesh resolution.•Good predictions obtained for multiphase flows with different interfacial scales.
Multiphase flows are ubiquitous both in nature and industry. A broad range of interfacial scales, ranging from fine dispersions to large segregated interfaces, is often observed in such flows. Standard multiphase models rely on either the interface-averaging approach, which is suitable for the modelling of dispersed flows, or on the interface-resolving approach, which is ideal for large segregated interfaces. This results in the inability of such models to deal with complex multiscale flows, and different generalized hybrid modelling approaches having been proposed to overcome this shortcoming. This work presents a novel generalized multifluid modelling approach where large segregated interfaces are identified in the multifluid field from the local interface topology and resolution, avoiding the need for a-priori thresholds of the local volume fraction used in the majority of the models available in the literature. Interface compression and suitable modelling closures for drag and surface tension are activated in the large interfaces regions, whilst the model reverts to a standard multifluid formulation in the regions of small/dispersed interfaces. An assessment against different benchmark cases shows that the approach is as accurate as one-fluid interface-resolving techniques for large/segregated interfaces, while successfully recovering the expected multifluid behaviour for fully dispersed flows. Further, a prototypical multiscale flow has been simulated to demonstrate that the model can effectively switch between large-interface and dispersed-interface mode based on the local flow conditions and mesh size. It is concluded that the present approach represents a promising step towards the development of a comprehensive multiphase model capable of simulating complex multiscale flows of industrial interest.
A large earthquake of 7.8 magnitude occurred on 25 April 2015, 06:26 UTC, with the epicenter in Nepal. Here, taking advantage of measurements provided by the Swarm magnetic satellites, we investigate ...the possibility to detect some series of pre-earthquake magnetic anomalous signals, likely due to a lithosphere–atmosphere–ionosphere coupling, that can be a potential earthquake precursory pattern. Different techniques have been applied to Swarm data available during two months around earthquake occurrence. From the detected magnetic anomalies series (during night and magnetically quiet times or with an automatic detection algorithm), we show that the cumulative number of anomalies follows the same typical power-law behavior of a critical system approaching its critical time, and hence recovers as the typical recovery phase after a large event. The similarity of this behavior with the one obtained from seismic data analysis and the application of the analyses also to another period without significant seismicity do support a lithospheric-linked origin of the observed magnetic anomalies. We suggest that they might be connected to the preparation phase of the Nepal earthquake.
•Swarm magnetic data are analyzed in occasion of the large 2015 Nepal earthquake.•A statistical method is applied to detect earthquake related magnetic anomalies.•A temporal pattern of anomalies emerges as typical of critical systems.•The same pattern emerges from the seismic data.•This agreement suggests an internal origin of the found pattern.
Chebyshev polynomials have been recently proposed for designing public-key systems. Indeed, they enjoy some nice chaotic properties, which seem to be suitable for use in Cryptography. Moreover, they ...satisfy a semi-group property, which makes possible implementing a trapdoor mechanism. In this paper, we study a public-key cryptosystem based on such polynomials, which provides both encryption and digital signature. The cryptosystem works on real numbers and is quite efficient. Unfortunately, from our analysis, it comes up that it is not secure. We describe an attack which permits to recover the corresponding plaintext from a given ciphertext. The same attack can be applied to produce forgeries if the cryptosystem is used for signing messages. Then, we point out that also other primitives, a Diffie-Hellman like key agreement scheme and an authentication scheme, designed along the same lines of the cryptosystem, are not secure due to the aforementioned attack. We close the paper by discussing the issues and the possibilities of constructing public-key cryptosystems on real numbers.
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