Autonomous Learning by Simple Dynamical Systems with Delayed Feedbacks

A general scheme for construction of dynamical systems able to learn generation of the desired kinds of dynamics through adjustment of their internal structure is proposed. The scheme involves intrinsic time-delayed feedback to steer the dynamics towards the target performance. As an example, a system of coupled phase oscillators, which can by changing the weights of connections between its elements evolve to a dynamical state with the prescribed (low or high) synchronization level, is considered and investigated

Characterization and Application of Hard X-Ray Betatron Radiation Generated by Relativistic Electrons from a Laser-Wakefield Accelerator

The necessity for compact table-top x-ray sources with higher brightness, shorter wavelength and shorter pulse duration has led to the development of complementary sources based on laser-plasma accelerators, in contrast to conventional accelerators. Relativistic interaction of short-pulse lasers with underdense plasmas results in acceleration of electrons and in consequence in the emission of spatially coherent radiation, which is known in the literature as betatron radiation. In this article we report on our recent results in the rapidly developing field of secondary x-ray radiation generated by high-energy electron pulses. The betatron radiation is characterized with a novel setup allowing to measure the energy, the spatial energy distribution in the far-field of the beam and the source size in a single laser shot. Furthermore, the polarization state is measured for each laser shot. In this way the emitted betatron x-rays can be used as a non-invasive diagnostic tool to retrieve very subtle information of the electron dynamics within the plasma wave. Parallel to the experimental work, 3D particle-in-cell simulations were performed, proved to be in good agreement with the experimental results.Comment: 38 pages, 19 figures, submitted to the Journal of Plasma Physic

Design of Eco-Efficient Body Parts for Electric Vehicles Considering Life Cycle Environmental Information

The reduction of greenhouse gas (GHG) emissions over the entire life cycle of vehicles has become part of the strategic objectives in automotive industry. In this regard, the design of future body parts should be carried out based on information of life cycle GHG emissions. The substitution of steel towards lightweight materials is a major trend, with the industry undergoing a fundamental shift towards the introduction of electric vehicles (EV). The present research aims to support the conceptual design of body parts with a combined perspective on mechanical performance and life cycle GHG emissions. Particular attention is paid to the fact that the GHG impact of EV in the use phase depends on vehicle-specific factors that may not be specified at the conceptual design stage of components, such as the market-specific electricity mix used for vehicle charging. A methodology is proposed that combines a simplified numerical design of concept alternatives and an analytic approach estimating life cycle GHG emissions. It is applied to a case study in body part design based on a set of principal geometries and load cases, a range of materials (aluminum, glass and carbon fiber reinforced plastics (GFRP, CFRP) as substitution to a steel reference) and different use stage scenarios of EV. A new engineering chart was developed, which helps design engineers to compare life cycle GHG emissions of lightweight material concepts to the reference. For body shells, the replacement of the steel reference with aluminum or GFRP shows reduced lifecycle GHG emissions for most use phase scenarios. This holds as well for structural parts being designed on torsional stiffness. For structural parts designed on tension/compression or bending stiffness CFRP designs show lowest lifecycle GHG emissions. In all cases, a high share of renewable electricity mix and a short lifetime pose the steel reference in favor. It is argued that a further elaboration of the approach could substantially increase transparency between design choices and life cycle GHG emissions

Quantitative shadowgraphy and proton radiography for large intensity modulations

Shadowgraphy is a technique widely used to diagnose objects or systems in various fields in physics and engineering. In shadowgraphy, an optical beam is deflected by the object and then the intensity modulation is captured on a screen placed some distance away. However, retrieving quantitative information from the shadowgrams themselves is a challenging task because of the non-linear nature of the process. Here, a novel method to retrieve quantitative information from shadowgrams, based on computational geometry, is presented for the first time. This process can be applied to proton radiography for electric and magnetic field diagnosis in high-energy-density plasmas and has been benchmarked using a toroidal magnetic field as the object, among others. It is shown that the method can accurately retrieve quantitative parameters with error bars less than 10%, even when caustics are present. The method is also shown to be robust enough to process real experimental results with simple pre- and post-processing techniques. This adds a powerful new tool for research in various fields in engineering and physics for both techniques

Optical Probing of Ultrafast Laser-Induced Solid-to-Overdense-Plasma Transitions

Understanding the target dynamics during its interaction with a relativistic ultrashort laser pulse is a challenging fundamental multi-physics problem involving at least atomic and solid-state physics, plasma physics, and laser physics. Already, the properties of the so-called pre-plasma formed as the laser pulse's rising edge ionizes the target are complicated to access in experiments and modeling, and many aspects of this laser-induced transition from solid to overdense plasma over picosecond time scales are still open questions. At the same time, applications like laser-driven ion acceleration require precise knowledge and control of the pre-plasma because the efficiency of the acceleration process itself crucially depends on the target properties at the arrival of the relativistic intensity peak of the pulse. By capturing the dynamics of the initial stage of the interaction, we report on a detailed visualization of the pre-plasma formation and evolution. Nanometer-thin diamond-like carbon foils are shown to transition from solid to plasma during the laser rising edge with intensities < 10^16 W/cm^2. Single-shot near-infrared probe transmission measurements evidence sub-picosecond dynamics of an expanding plasma with densities above 10^23 cm^-3 (about 100 times the critical plasma density). The complementarity of a solid-state interaction model and a kinetic plasma description provides deep insight into the interplay of ionization, collisions, and expansion

New cladotherian mammal from southern Chile and the evolution of mesungulatid meridiolestidans at the dusk of the Mesozoic era

In the last decades, several discoveries have uncovered the complexity of mammalian evolution during the Mesozoic Era, including important Gondwanan lineages: the australosphenidans, gondwanatherians, and meridiolestidans (Dryolestoidea). Most often, their presence and diversity is documented by isolated teeth and jaws. Here, we describe a new meridiolestidan mammal, Orretherium tzen gen. et sp. nov., from the Late Cretaceous of southern Chile, based on a partial jaw with five cheek teeth in locis and an isolated upper premolar. Phylogenetic analysis places Orretherium as the earliest divergence within Mesungulatidae, before other forms such as the Late Cretaceous Mesungulatum and Coloniatherium, and the early Paleocene Peligrotherium. The in loco tooth sequence (last two premolars and three molars) is the first recovered for a Cretaceous taxon in this family and suggests that reconstructed tooth sequences for other Mesozoic mesungulatids may include more than one species. Tooth eruption and replacement show that molar eruption in mesungulatids is heterochronically delayed with regard to basal dryolestoids, with therian-like simultaneous eruption of the last premolar and last molar. Meridiolestidans seem endemic to Patagonia, but given their diversity and abundance, and the similarity of vertebrate faunas in other regions of Gondwana, they may yet be discovered in other continents.Fil: Martinelli, Agustín Guillermo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina. Universidad de Chile; ChileFil: Soto Acuña, Sergio. Universidad de Chile; ChileFil: Goin, Francisco Javier. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Kaluza, Jonatan Ezequiel. Universidad Maimónides; Argentina. Universidad de Chile; Chile. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; ArgentinaFil: Bostelmann, J. Enrique. Universidad Austral de Chile; ChileFil: Fonseca, Pedro H. M.. Universidade Federal do Rio Grande do Sul; BrasilFil: Reguero, Marcelo Alfredo. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Leppe, Marcelo. Instituto Antártico Chileno; ChileFil: Vargas, Alexander O.. Universidad de Chile; Chil

A new locality with ctenochasmatid pterosaurs (Pterosauria: Pterodactyloidea) in the Atacama Desert, Northern Chile

We describe a new locality with ctenochasmatid pterosaurs found in a tidal estuarine paleoenvironment of the Quebrada Monardes Formation (Lower Cretaceous). The new locality, which is named “Cerro Tormento”, is in Cerros Bravos in the northeast Atacama region, Northern Chile. Here, we describe four cervical vertebrae, one of them belonging to a small individual, the impression of a right scapulocoracoid, a left coracoid, an impression of a left humerus, an incomplete left humerus, a distal fragment of the right humerus, and impressions of a left femur and tibiotarsus. The presence of three humeri and a cervical vertebra belonging to a small pterosaur indicate that these materials represent more than one individual. The cervical vertebrae present diagnostic traits shared with ctenochasmatid pterosaurs, such as elongated vertebral centra, with integrated neural arch, low neural spines, and dorsally located neural canal. It is currently not possible to determine if there are one or more species represented. This finding is the second geographic occurrence of pterosaurs of the clade Ctenochasmatidae in the Atacama region, although it is currently uncertain if ctenochasmatids from both locations were contemporaneous. This suggests that the clade Ctenochasmatidae was widespread in what is now northern Chile. In addition, the presence of bones belonging to more than one individual preserved in Cerro Tormento suggest that pterosaur colonies were present at the southwestern margin of Gondwana during the Early Cretaceous.Fil: Alarcón Muñoz, Jhonatan Andrés. Universidad de Chile. Facultad de Ciencias Físicas y Matemáticas. Departamento de Geología; Chile. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Codorniú, Laura. Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Departamento de Geología; ArgentinaFil: González, Edwin. Servicio Nacional de Geología y Minería; ChileFil: Suárez, Mario E.. Atacama Fosil Research; ChileFil: Suárez, Manuel. Universidad Andrés Bello; ChileFil: Vicencio Campos, Omar. Atacama Fosil Research; ChileFil: Soto Acuña, Sergio. Universidad de Chile. Facultad de Ciencias Físicas y Matemáticas. Departamento de Geología; ChileFil: Kaluza, Jonatan Ezequiel. Fundación de Historia Natural Félix de Azara; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Vargas, Alexander O.. Universidad de Chile. Facultad de Ciencias Físicas y Matemáticas. Departamento de Geología; ChileFil: Rubilar Rogers, David. Museo Nacional de Historia Natural de Chile; Chil

Probing Minimal 5D Extensions of the Standard Model: From LEP to an e^+e^- Linear Collider

We derive new improved constraints on the compactification scale of minimal 5-dimensional (5D) extensions of the Standard Model (SM) from electroweak and LEP2 data and estimate the reach of an e^+e^- linear collider such as TESLA. Our analysis is performed within the framework of non-universal 5D models, where some of the gauge and Higgs fields propagate in the extra dimension, while all fermions are localized on a S^1/Z_2 orbifold fixed point. Carrying out simultaneous multi-parameter fits of the compactification scale and the SM parameters to the data, we obtain lower bounds on this scale in the range between 4 and 6 TeV. These fits also yield the correlation of the compactification scale with the SM Higgs mass. Investigating the prospects at TESLA, we show that the so-called GigaZ option has the potential to improve these bounds by about a factor 2 in almost all 5D models. Furthermore, at the center of mass energy of 800 GeV and with an integrated luminosity of 10^3 fb^-1, linear collider experiments can probe compactification scales up to 20-30 TeV, depending on the control of systematic errors.Comment: 28 pages, LaTeX, 9 eps figures, version published in Nuclear Physics

On new gravitational instantons describing creation of brane-worlds

By considering 5--dimensional cosmological models with a bulk filled with a pressureless scalar field; equivalently dust matter, and a negative cosmological constant, we have found a regular instantonic solution which is free from any singularity at the origin of the extra--coordinate. This instanton describes 5--dimensional asymptotically anti de Sitter wormhole, when the bulk has a topology R times S^4. Compactified brane-world instantons which are built up from such instantonic solution describe either a single brane or a string of branes. Their analytical continuation to the pseudo--Riemannian metric can give rise to either 4-dimensional inflating branes or solutions with the same dynamical behaviour for extra--dimension and branes, in addition to multitemporal solutions. Dust brane-world models with arbitrary dimensions (D >= 5) as well as other spatial topologies are also briefly discussed.Comment: 11 pages, 3 figures, LaTeX2e, accepted for publication in Classical and Quantum Gravit