Gate tunability of stray-field-induced electron spin precession in a GaAs/InGaAs quantum well below an interdigitated magnetized Fe grating

Time-resolved Faraday rotation is used to measure the coherent electron spin precession in a GaAs/InGaAs quantum well below an interdigitated magnetized Fe grating. We show that the electron spin precession frequency can be modified by applying a gate voltage of opposite polarity to neighboring bars. A tunability of the precession frequency of 0.5 GHz/V has been observed. Modulating the gate potential with a gigahertz frequency allows the electron spin precession to be controlled on a nanosecond timescale

Performance Bounds for Parameter Estimation under Misspecified Models: Fundamental findings and applications

Inferring information from a set of acquired data is the main objective of any signal processing (SP) method. In particular, the common problem of estimating the value of a vector of parameters from a set of noisy measurements is at the core of a plethora of scientific and technological advances in the last decades; for example, wireless communications, radar and sonar, biomedicine, image processing, and seismology, just to name a few. Developing an estimation algorithm often begins by assuming a statistical model for the measured data, i.e. a probability density function (pdf) which if correct, fully characterizes the behaviour of the collected data/measurements. Experience with real data, however, often exposes the limitations of any assumed data model since modelling errors at some level are always present. Consequently, the true data model and the model assumed to derive the estimation algorithm could differ. When this happens, the model is said to be mismatched or misspecified. Therefore, understanding the possible performance loss or regret that an estimation algorithm could experience under model misspecification is of crucial importance for any SP practitioner. Further, understanding the limits on the performance of any estimator subject to model misspecification is of practical interest. Motivated by the widespread and practical need to assess the performance of a mismatched estimator, the goal of this paper is to help to bring attention to the main theoretical findings on estimation theory, and in particular on lower bounds under model misspecification, that have been published in the statistical and econometrical literature in the last fifty years. Secondly, some applications are discussed to illustrate the broad range of areas and problems to which this framework extends, and consequently the numerous opportunities available for SP researchers.Comment: To appear in the IEEE Signal Processing Magazin

MODULATING THE BIOSYNTHESIS OF A BIOACTIVE STEROIDAL SAPONIN, CHOLESTANOL GLUCOSIDE BY LASIODIPLODIA THEOBROMAE USING ABIOTIC STRESS FACTORS

Objective: The present study investigates the modulation of cholestanol glucoside (CG) biosynthesis by Lasiodiplodia theobromae in response to oxidative, osmotic and heat shock stresses.Methods: The fungal cultures were subjected to oxidative stress by supplementing the culture media with menadione or H2O2 to the desired final concentrations. Osmotic stress was implemented by the addition of the desired concentrations of NaCl or sorbitol. For heat-shock treatments, the fungal cultures were subjected to required temperature variations. Each stress treatment was carried out at different time points so as to include different stages of fungal growth.Results: Oxidative stress enhanced CG yield by the fungus by 1.8-fold (88.3±0.6 mg/l) where as osmotic and heat shock stresses proved to be poor enhancers of CG production.Conclusions: Our findings enable a cost-effective, large scale production of CG by L. theobromae and more over throws light on the possible antioxidant activity of the compound in the organism.Â

Optimized stray-field-induced enhancement of the electron spin precession by buried Fe gates

The magnetic stray field from Fe gates is used to modify the spin precession frequency of InGaAs/GaAs quantum-well electrons in an external magnetic field. By using an etching process to position the gates directly in the plane of the quantum well, the stray-field influence on the spin precession increases significantly compared with results from previous studies with top-gated structures. In line with numerical simulations, the stray-field-induced precession frequency increases as the gap between the ferromagnetic gates is reduced. The inhomogeneous stray field leads to additional spin dephasing.Comment: 4 pages, 2 figure

Social norms and e-motions in problematic social media use among adolescents

© 2020 The Authors Introduction: Being constantly connected on social media is a “way of being” among adolescents. However, social media use can become “problematic” for some users and only a few studies have explored the concurrent contribution of social context and emotion regulation to problematic social media use. The current study aimed to test: (i) the influence of friends (i.e., their social media use and group norms about social media use); and (ii) the effects of difficulties in emotion regulation and so-called “e-motions” on adolescents’ problematic social media use. Methods: A cross-sectional study was conducted in Italian secondary schools. An online questionnaire was administered to 761 adolescents (44.5% females; Mage = 15.49 years; SDage = 1.03). Results: Path analysis showed that social norms were directly associated with problematic social media use and friends’ social media use was associated with the frequency of social media use, which, in turn, was associated with problematic use. Difficulties in emotion regulation were directly and indirectly linked to problematic social media use via frequency of use and facilitating use of e-motions. Conclusions: These findings provide support for the importance of both peer influence and emotion regulation in this context. Social norms and emotion regulation should be considered in prevention programs addressing problematic social media use in adolescents