Zero-point quantum swing of magnetic couples

Quantum fluctuations are ubiquitous in physics. Ranging from conventional examples like the harmonic oscillator to intricate theories on the origin of the universe, they alter virtually all aspects of matter -- including superconductivity, phase transitions and nanoscale processes. As a rule of thumb, the smaller the object, the larger their impact. This poses a serious challenge to modern nanotechnology, which aims total control via atom-by-atom engineered devices. In magnetic nanostructures, high stability of the magnetic signal is crucial when targeting realistic applications in information technology, e.g. miniaturized bits. Here, we demonstrate that zero-point spin-fluctuations are paramount in determining the fundamental magnetic exchange interactions that dictate the nature and stability of the magnetic state. Hinging on the fluctuation-dissipation theorem, we establish that quantum fluctuations correctly account for the large overestimation of the interactions as obtained from conventional static first-principles frameworks, filling in a crucial gap between theory and experiment [1,2]. Our analysis further reveals that zero-point spin-fluctuations tend to promote the non-collinearity and stability of chiral magnetic textures such as skyrmions -- a counter-intuitive quantum effect that inspires practical guidelines for designing disruptive nanodevices

A Multi-Agent Architecture for the Design of Hierarchical Interval Type-2 Beta Fuzzy System

This paper presents a new methodology for building and evolving hierarchical fuzzy systems. For the system design, a tree-based encoding method is adopted to hierarchically link low dimensional fuzzy systems. Such tree structural representation has by nature a flexible design offering more adjustable and modifiable structures. The proposed hierarchical structure employs a type-2 beta fuzzy system to cope with the faced uncertainties, and the resulting system is called the Hierarchical Interval Type-2 Beta Fuzzy System (HT2BFS). For the system optimization, two main tasks of structure learning and parameter tuning are applied. The structure learning phase aims to evolve and learn the structures of a population of HT2BFS in a multiobjective context taking into account the optimization of both the accuracy and the interpretability metrics. The parameter tuning phase is applied to refine and adjust the parameters of the system. To accomplish these two tasks in the most optimal and faster way, we further employ a multi-agent architecture to provide both a distributed and a cooperative management of the optimization tasks. Agents are divided into two different types based on their functions: a structure agent and a parameter agent. The main function of the structure agent is to perform a multi-objective evolutionary structure learning step by means of the Multi-Objective Immune Programming algorithm (MOIP). The parameter agents have the function of managing different hierarchical structures simultaneously to refine their parameters by means of the Hybrid Harmony Search algorithm (HHS). In this architecture, agents use cooperation and communication concepts to create high-performance HT2BFSs. The performance of the proposed system is evaluated by several comparisons with various state of art approaches on noise-free and noisy time series prediction data sets and regression problems. The results clearly demonstrate a great improvement in the accuracy rate, the convergence speed and the number of used rules as compared with other existing approaches

Modelling the effect of carbon on deformation behaviour of twinning induced plasticity steels

In this article, a physical model describing the deformation behaviour of Twinning Induced Plasticity(TWIP) steels has been extended to include the effect of carbon content. The experimental validation and the analysis show that carbon mainly controls the maximum number of dislocations piled up at the twin boundary, resulting in the increase of back-stresses (i.e. kinematic hardening) and therefore the work hardening rate. This explanation seems to be in agreement with recent TEM observations. © The Author(s) 2011. This article is published with open access at Springerlink.com. © Springer Science+Business Media, LLC 2011.published_or_final_versionSpringer Open Choice, 21 Feb 201

Dynamical amplification of magnetoresistances and Hall currents up to the THz regime

Spin-orbit-related effects offer a highly promising route for reading and writing information in magnetic units of future devices. These phenomena rely not only on the static magnetization orientation but also on its dynamics to achieve fast switchings that can reach the THz range. In this work, we consider Co/Pt and Fe/W bilayers to show that accounting for the phase difference between different processes is crucial to the correct description of the dynamical currents. By tuning each system towards its ferromagnetic resonance, we reveal that dynamical spin Hall angles can non-trivially change sign and be boosted by over 500%, reaching giant values. We demonstrate that charge and spin pumping mechanisms can greatly magnify or dwindle the currents flowing through the system, influencing all kinds of magnetoresistive and Hall effects, thus impacting also dc and second harmonic experimental measurements.Comment: 19 pages, 4 figures, Supplementary Informatio

JUpdate: A JSON Update Language

Although JSON documents are being used in several emerging applications (e.g., Big Data applications, IoT, mobile computing, smart cities, and online social networks), there is no consensual or standard language for updating JSON documents (i.e., creating, deleting or changing such documents, where changing means inserting, deleting, replacing, copying, moving, etc., portions of data in such documents). To fill this gap, we propose in this paper an SQL-like language, named JUpdate, for updating JSON documents. JUpdate is based on a set of six primitive update operations, which is proven complete and minimal, and it provides a set of fourteen user-friendly high-level operations with a well-founded semantics defined on the basis of the primitive update operations

Polyphenols content, antioxidant and antimicrobial activities of extracts of some wild plants collected from the south of Tunisia

25 wild plants were collected from the south of Tunisia. The dried aerial parts were extracted under a continuous reflux set-up in a Soxhlet extractor with hexane, ethyl acetate, methanol and water. The extracts were screened for total phenolic content, antioxidant and antimicrobial activities. Total phenolic contents were determined using a spectrophotometric technique, based on the Folin-Ciocalteau reagent and calculated as pyrogallol equivalents (PyE) per 100 g of dry weight (dw). Total phenolic content ranged from traces to 2225 ± 267 mg PyE/100 g dw in Periploca angustifolia hexane extract and Erodium glaucophyllum methanol extract, respectively. Total flavonoids and flavonols weremeasured by a colorimetric assay and expressed as mg of rutin equivalents (RuE) per 100 g dw and mg of quercetin equivalents (QuE) per 100 g dw respectively. The highest amounts of flavonoids of 315 mgRuE/100 g dw and of flavonols of 63 mg QuE/100 g dw was recorded in the ethyl acetate extract of Acacia radiana. The antioxidant capacity of all extracts was evaluated with the (1,1-diphenyl-2-picrylhydrazyl, DPPH and 2,2'-azino-bis [3-ethylbenzthiazoline-6-sulphonic acid]) ABTS tests. Several extracts showed antioxidant capacity higher than (butylated hydroxytoluene) BHT. Different trend was observed for each antioxidant system with respect to solvents used. All tested plants showedantimicrobial activity, but this activity depended closely on the nature of the solvent used and of the microorganism tested. Rhanterium suaveolens ethyl acetate extract showed the largest spectre of antibacterial activity and Bassia indica ethyl acetate extract showed the highest antifungal activity.Interestingly, some of the collected plants had a high phenolic content and powerful antioxidant and antimicrobial activities. These plants may serve as sources of antioxidants with new chemotypes and potential beneficial health properties

Multisensors Systems Architecture

This paper deals with the architectures and models of fusion used to combine and integrate data into a multisensors system. There are various approaches with which a designer can develop or adapt his own model of fusion coming from two domains of applications, the military domain of the data fusion and the domain of the civil robotics or more generally the design of intelligent computerized autonomous systems. The first model is the functional JDL model, which describes applications of target tracking applied to the battlefield, then in a second time some different models are chosen to exhibit the evolution of the manners to think the fusion systems. Some fundamental principles are then exhibited about the design of multi-sensors systems related to either functional architecture or hardware architecture.Ce papier propose une synthèse sur les architectures et modèles de fusion utilisés pour combiner et intégrer des données dans un système multicapteurs de fusion de données. Il existe différentes approches avec lesquelles un concepteur peut développer ou adapter son propre modèle de fusion issues de deux domaines dans lesquels la recherche est active, le domaine militaire de la fusion de données et le domaine de la robotique civile ou plus généralement de la conception de systèmes autonomes informatiques intelligents. Le modèle fonctionnel intitulé JDL apporte une vision systémique de la fusion de données appliquée au suivi de cibles dans un champ de bataille, des modèles différents montrent l’évolution des façons de penser en ce qui concerne les systèmes de fusion. Un certain nombre de principes fondamentaux sont ensuite décrits concernant la conception d’un système de fusion multi-capteurs tant sur le plan de son architecture fonctionnelle que matérielle