1,354,117 research outputs found
Defect-Induced Magnetism in Graphene: An Ab Initio Study
No full textGraphene is an amazing two-dimensional system with exceptional physical and chemical properties. Potential applications in quantum information processing have been proposed for C-based materials, in particular for graphene system, where electron spin is a promising candidate for a solid-state qubit. The preservation of long spin coherence time is the fundamental feature to get for efficient working spin-qubit system. Despite graphene environment seems to suit the goal, defects in the structure, interactions with impurities and edge states can be a source of alteration of quantum information, since they could enhance the decoherence effects. The present work is a computational analysis of defective systems. It focuses on the investigations of various prototypical defect states (vacancies) and impurities interacting with graphene surface (hydrogen, boron, nitrogen, and oxygen) by means of density functional theory (DFT). We provide a preliminary study about the effects of these interactions. Vacancy-type defects give rise to a breaking of graphene symmetry, promoting a localized state with a magnetic moment whose magnitude is concentration-dependent. Hydrogen promotes a locally hybridization of the structure providing a localized magnetic moment and giving rise to an enhancement of spin-orbit interaction of about three orders of magnitude, showing the impact of hydrogen on spin-relaxation time. Among boron, nitrogen, and oxygen, the work has shown that the only one which returns a magnetic ground state is nitrogen. Boron
provides an n-doping of defective-graphene. Oxygen leads to a hybridization of carbon atoms bonding, but its electronic structure does not allow a magnetic system. In the particular case of a bridge-like adsorption site. Among the different configurations for the adsorption sites, the bridge-site is energetically the most stable one, showing as in the other configurations for nitrogen, a magnetic system. Nitrogen adatoms develop a magnetic order (at zero temperature) which is always ferromagnetic independently from the distance between two adjacent nitrogen atoms
Modelling of early-stage kilonova ejecta opacity reproducible in laboratory plasmas
No full textIn the framework of the multi-messenger astronomy, for a complete understanding of the heavy elements nucleosynthesis, investigation of the kilo- nova (KN) emission is crucial. The KN is a thermal transient signal following gravitational-wave events from the coalescence of compact objects. Modelling the KN light-curve is challenging: besides the difficulties in modelling the r-process synthesised elements, it requires several inputs, among which plasma ejecta opacity is still extremely uncertain. In this context, the PANDORA project aims at measuring, for the first time, opacities of a plasma resembling the plasma ejecta through which KN diffuses. In view of that, we present numerical estimates of argon plasma opacity perturbed by an external radiation flux under non local thermodynamic equilibrium. Simulations performed serve as demonstrator for further metallic elements, and their results underline that both thermodynamic parameters and radiation could impact on the opacity of the plasma
Euscarus cretensis: CARATTERIZZAZIONI D’ORDINE BROMATOLOGICO, ORGANOLETTICO, IGIENICO – SANITARIO, ISPETTIVO E VALUTAZIONE PRELIMINARE SULLA TRASFORMABILITA’ IN “KAMABOKO”
No full textInverse derivative operator and umbral methods for the harmonic numbers and telescopic series study
No full textThe formalism of differ-integral calculus, initially developed to treat differential operators of fractional order, realizes a complete symmetry between differential and integral operators. This possibility has opened new and interesting scenarios, once extended to positive and negative order derivatives. The associated rules offer an elegant, yet powerful, tool to deal with integral operators, viewed as derivatives of order-1. Although it is well known that the integration is the inverse of the derivative operation, the aforementioned rules offer a new mean to obtain either an explicit iteration of the integration by parts or a general formula to obtain the primitive of any infinitely differentiable function. We show that the method provides an unexpected link with generalized telescoping series, yields new useful tools for the relevant treatment, and allows a practically unexhausted tool to derive identities involving harmonic numbers and the associated generalized forms. It is eventually shown that embedding the differ-integral point of view with techniques of umbral algebraic nature offers a new insight into, and the possibility of, establishing a new and more powerful formalism
Inverse Derivative Operator and Umbral Methods for the Harmonic Numbers and Telescopic Series Study
No full textThe formalism of differ-integral calculus, initially developed to treat differential operators of fractional order, realizes a complete symmetry between differential and integral operators. This possibility has opened new and interesting scenarios, once extended to positive and negative order derivatives. The associated rules offer an elegant, yet powerful, tool to deal with integral operators, viewed as derivatives of order-1. Although it is well known that the integration is the inverse of the derivative operation, the aforementioned rules offer a new mean to obtain either an explicit iteration of the integration by parts or a general formula to obtain the primitive of any infinitely differentiable function. We show that the method provides an unexpected link with generalized telescoping series, yields new useful tools for the relevant treatment, and allows a practically unexhausted tool to derive identities involving harmonic numbers and the associated generalized forms. It is eventually shown that embedding the differ-integral point of view with techniques of umbral algebraic nature offers a new insight into, and the possibility of, establishing a new and more powerful formalism
Predicting β-decay rates of radioisotopes embedded in anisotropic ECR plasmas
No full textStudying in-plasma decay rates as a function of ionic charge state distribution (CSD) is the fundamental objective of the PANDORA project. To this effect, we present here two theoretical models to calculate β-decay lifetimes of radionuclide ions embedded in an energetic electron cyclotron resonance (ECR) plasma, starting from anisotropic electron distributions. The first model -designed as separate modules to implement various atomic processes like electron-ion reactions, ion-ion charge exchange collisions and ion loss dynamics sequentially- serves as a predecessor to a more robust second model aimed at coupling ion population kinetics with complex transport phenomena in an ECR plasma. The outputs from the models -in the form of space-resolved CSD and level populations- can be fed to an appropriate code based on known theories connecting atomic level configurations to decay lifetime to calculate the position-dependent β-decay rate
Theory of generalized trigonometric functions: From Laguerre to Airy forms
No full textWe develop a new point of view to introduce families of functions, which can be identified as generalization of the ordinary trigonometric or hyperbolic functions. They are defined using a procedure based on umbral methods, inspired by the Bessel Calculus of Bochner, Cholewinsky and Haimo. We propose further extensions of the method and of the relevant concepts as well and obtain new families of integral transforms allowing the framing of the previous concepts within the context of generalized Borel transform
Comments on the properties of Mittag-Leffler function
No full textThe properties of Mittag-Leffler function are reviewed within the framework of an umbral formalism. We take advantage from the formal equivalence with the exponential function to define the relevant semigroup properties. We analyse the relevant role in the solution of Schrödinger type and heat-type fractional partial differential equations and explore the problem of operatorial ordering finding appropriate rules when non-commuting operators are involved. We discuss the coherent states associated with the fractional Schödinger equation, analyze the relevant Poisson type probability amplitude and compare with analogous results already obtained in the literature
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Repeated derivatives of hyperbolic trigonometric functions and associated polynomials
No full textElementary problems as the evaluation of repeated derivatives of ordinary transcendent functionscan usefully be treated with the use of special polynomials and of a formalism borrowed from combinatorial analysis. Motivated by previous researches in this field, we review the results obtained by other authors and develop a complementary point of view for the repeated derivatives of sec(.), tan(.) and for their hyperbolic counterparts
- …
