Shot noise in magnetic tunnel junctions from first principles

We compute the shot noise in ballistic and disordered Fe/MgO/Fe tunnel junctions by a wave function-matching method. For tunnel barriers with no more than 5 atomic layers we find a suppression of the Fano factor as a function of the magnetic configuration. For thicker MgO barriers the shot noise is suppressed up to a threshold bias indicating the onset of resonant tunneling. We find excellent agreement with recent experiments when interface disorder is taken into accountComment: 5 pages,5 figure

Spin-transfer torques in anti-ferromagnetic metals from first principles

In spite of the absence of a macroscopic magnetic moment, an anti-ferromagnet is spin-polarized on an atomic scale. The electric current passing through a conducting anti-ferromagnet is polarized as well, leading to spin-transfer torques when the order parameter is textured, such as in anti-ferromagnetic non-collinear spin valves and domain walls. We report a first principles study on the electronic transport properties of anti-ferromagnetic systems. The current-induced spin torques acting on the magnetic moments are comparable with those in conventional ferromagnetic materials, leading to measurable angular resistances and current-induced magnetization dynamics. In contrast to ferromagnets, spin torques in anti-ferromagnets are very nonlocal. The torques acting far away from the center of an anti-ferromagnetic domain wall should facilitate current-induced domain wall motion.Comment: The paper has substantially been rewritten, 4 pages, 5 figure

From cyber-security deception to manipulation and gratification through gamification

Over the last two decades the field of cyber-security has experienced numerous changes associated with the evolution of other fields, such as networking, mobile communications, and recently the Internet of Things (IoT) [3]. Changes in mindsets have also been witnessed, a couple of years ago the cyber-security industry only blamed users for their mistakes often depicted as the number one reason behind security breaches. Nowadays, companies are empowering users, modifying their perception of being the weak link, into being the center-piece of the network design [4]. Users are by definition "in control" and therefore a cyber-security asset. Researchers have focused on the gamification of cyber- security elements, helping users to learn and understand the concepts of attacks and threats, allowing them to become the first line of defense to report anoma- lies [5]. However, over the past years numerous infrastructures have suffered from malicious intent, data breaches, and crypto-ransomeware, clearly showing the technical "know-how" of hackers and their ability to bypass any security in place, demonstrating that no infrastructure, software or device can be consid- ered secure. Researchers concentrated on the gamification, learning and teaching theory of cyber-security to end-users in numerous fields through various techniques and scenarios to raise cyber-situational awareness [2][1]. However, they overlooked the users’ ability to gather information on these attacks. In this paper, we argue that there is an endemic issue in the the understanding of hacking practices leading to vulnerable devices, software and architectures. We therefore propose a transparent gamification platform for hackers. The platform is designed with hacker user-interaction and deception in mind enabling researchers to gather data on the techniques and practices of hackers. To this end, we developed a fully extendable gamification architecture allowing researchers to deploy virtualised hosts on the internet. Each virtualised hosts contains a specific vulnerability (i.e. web application, software, etc). Each vulnerability is connected to a game engine, an interaction engine and a scoring engine

Sub-Kelvin Lateral Thermal Transport in Diffusive Graphene

In this work, we report on hot carrier diffusion in graphene across large enough length scales that the carriers are not thermalized across the crystal. The carriers are injected into graphene at one site and their thermal transport is studied as a function of applied power and distance from the heating source, up to tens of micrometers away. Superconducting contacts prevent out-diffusion of hot carriers to isolate the electron-phonon coupling as the sole channel for thermal relaxation. As local thermometers, we use the amplitude of the Universal Conductance Fluctuations, which varies monotonically as a function of temperature. By measuring the electron temperature simultaneously along the length we observe a thermal gradient which results from the competition between electron-phonon cooling and lateral heat flow

Reliability and clinical usefulness of the personality inventory for DSM-5 in clinically referred adolescents. A preliminary report in a sample of Italian inpatients

Background The DSM-5 Alternative Model of Personality Disorders (AMPD) provides the opportunity to integrate the needed developmental perspective in the assessment of personality pathology. Based on this model, Krueger and colleagues (2012) developed the Personality Inventory for DSM-5 (PID-5), which operationalizes the proposed DSM-5 traits. Methods Eighty-five consecutively admitted Italian adolescent inpatients were administered the Italian translation of the PID-5, in order to obtain preliminary data on PID-5 reliability and clinical usefulness in clinically referred adolescents. Results With the possible exception of the PID-5 Suspiciousness scale, all other PID-5 scales evidenced adequate internal consistency reliability (i.e., Cronbach's α values of at least .70, most being greater than .80). Our data seemed to yield at least partial support for the construct validity of the PID-5 scales also in clinical adolescents, at least in terms of patterns of associations with dimensionally assessed DSM-5 Section II PDs that were also included in the DSM-5 AMPD (excluding Antisocial PD because of the participants' minor age). Finally, our data suggested that the clinical usefulness of the PID-5 in adolescent inpatients may extend beyond PDs to profiling adolescents at risk for life-threatening suicide attempts. In particular, PID-5 Depressivity, Anhedonia, and Submissiveness trait scales were significantly associated with adolescents' history of life-threatening suicide attempts, even after controlling for a number of other variables, including mood disorder diagnosis. Discussion As a whole, our study may provide interesting, albeit preliminary data as to the clinical usefulness of PID-5 in the assessment of adolescent inpatients

Absorbate-Induced Piezochromism in a Porous Molecular Crystal

Atmospherically stable porous frameworks and materials are interesting for heterogeneous solid–gas applications. One motivation is the direct and selective uptake of pollutant/hazardous gases, where the material produces a measurable response in the presence of the analyte. In this report, we present a combined experimental and theoretical rationalization for the piezochromic response of a robust and porous molecular crystal built from an extensively fluorinated trispyrazole. The electronic response of the material is directly determined by analyte uptake, which provokes a subtle lattice contraction and an observable bathochromic shift in the optical absorption onset. Selectivity for fluorinated absorbates is demonstrated, and toluene is also found to crystallize within the pore. Furthermore, we demonstrate the application of electronic structure calculations to predict a physicochemical response, providing the foundations for the design of electronically tunable porous solids with the chemical properties required for development of novel gas-uptake media

Unlocking CO Depletion in Protoplanetary Disks II. Primordial C/H Predictions Inside the CO Snowline

CO is thought to be the main reservoir of volatile carbon in protoplanetary disks, and thus the primary initial source of carbon in the atmospheres of forming giant planets. However, recent observations of protoplanetary disks point towards low volatile carbon abundances in many systems, including at radii interior to the CO snowline. One potential explanation is that gas phase carbon is chemically reprocessed into less volatile species, which are frozen on dust grain surfaces as ice. This mechanism has the potential to change the primordial C/H ratio in the gas. However, current observations primarily probe the upper layers of the disk. It is not clear if the low volatile carbon abundances extend to the midplane, where planets form. We have run a grid of 198 chemical models, exploring how the chemical reprocessing of CO depends on disk mass, dust grain size distribution, temperature, cosmic ray and X-ray ionization rate, and initial water abundance. Building on our previous work focusing on the warm molecular layer, here we analyze the results for our grid of models in the disk midplane at 12 au. We find that either an ISM level cosmic ray ionization rate or the presence of UV photons due to a low dust surface density are needed to chemically reduce the midplane CO gas abundance by at least an order of magnitude within 1 Myr. In the majority of our models CO does not undergo substantial reprocessing by in situ chemistry and there is little change in the gas phase C/H and C/O ratios over the lifetime of the typical disk. However, in the small sub-set of disks where the disk midplane is subject to a source of ionization or photolysis, the gas phase C/O ratio increases by up to nearly 9 orders of magnitude due to conversion of CO into volatile hydrocarbons.Comment: Accepted for publication in ApJ, 15 pages, 10 figures, 3 table

Consistency in Formulation of Spin Current and Torque Associated with a Variance of Angular Momentum

Stimulated generally by recent interest in the novel spin Hall effect, the nonrelativistic quantum mechanical conserved currents, taken into account of spin-orbit coupling, are rigorously formulated based on the symmetries of system and Noether' theorem. The quantum mechanical force on the spin as well as the torque associated with the variance of angular momentum are obtained. Consequently, the kinetic interpretation of the variances of spin and orbit angular momentum currents implies a torque on the "electric dipole" associated with the moving spin. The bearing of the force and the torque on the properties of spin current in a two-dimensional electron gas with the Rashba spin-orbit interaction is discussed.Comment: 4 pages, no figur