High-Sensitivity Dual Electrochemical QCM for Reliable Three-Electrode Measurements

An electrochemical quartz crystal microbalance (EC-QCM) is a versatile gravimetric technique that allows for parallel characterization of mass deposition and electrochemical properties. Despite its broad applicability, simultaneous characterization of two electrodes remains challenging due to practical difficulties posed by the dampening from fixture parasitics and the dissipative medium. In this study, we present a dual electrochemical QCM (dual EC-QCM) that is employed in a three-electrode configuration to enable consequent monitoring of mass deposition and viscous loading on two crystals, the working electrode (WE) and the counter electrode (CE). A novel correction approach, along with a three standard complex impedance calibration, is employed to overcome the effect of dampening while keeping high spectral sensitivity. Separation of viscous loading and rigid mass deposition is achieved by robust characterization of the complex impedance at the resonance frequency. Validation of the presented system is done by cyclic voltammetry characterization of Ag underpotential deposition on gold. The results indicate mass deposition of 412.2 ng for the WE and 345.6 ng for the CE, reflecting a difference of the initially-present Ag adhered to the surface. We also performed higher harmonic measurements that further corroborate the sensitivity and reproducibility of the dual EC-QCM. The demonstrated approach is especially intriguing for electrochemical energy storage applications where mass detection with multiple electrodes is desired.

Magnetoinductive waves in attenuating media

The capability of magnetic induction to transmit signals in attenuating environments has recently gained significant research interest. The wave aspect—magnetoinductive (MI) waves—has been proposed for numerous applications in RF-challenging environments, such as underground/underwater wireless networks, body area networks, and in-vivo medical diagnosis and treatment applications, to name but a few, where conventional electromagnetic waves have a number of limitations, most notably losses. To date, the effects of eddy currents inside the dissipative medium have not been characterised analytically. Here we propose a comprehensive circuit model of coupled resonators in a homogeneous dissipative medium, that takes into account all the electromagnetic effects of eddy currents, and, thereby, derive a general dispersion equation for the MI waves. We also report laboratory experiments to confirm our findings. Our work will serve as a fundamental model for design and analysis of every system employing MI waves or more generally, magnetically-coupled circuits in attenuating media.

Influence of gravity on torsional surface waves in a dissipative medium

The present paper deals with the possibilities of propagation of torsional surface waves in a viscoelastic medium under gravity field. During the study it will observe that the increase in gravity parameter will increase the velocity of the wave, the increase in viscoelastic parameter, decrease the velocity of the wave until the product of angular frequency and viscoelastic parameter is less than unity. It also notes that as the velocity increases, the curve becomes asymptotic in nature when the period of oscillation increases. In fact the maximum damping in velocity has been identified at this cut off point which may be considered as the point where a viscoelastic material becomes a viscous medium.The absorption coefficients have also been calculated for different values of the viscoelastic parameter and gravity field.

Distribution of the Earth's radiation belts protons over the drift frequency of particles

On the base of generalized data on the proton fluxes of the Earth's radiation belts (ERB) with energy from E ~ 0.2 MeV to 100 MeV at drift shells L from ~ 1 to 8, constructed stationary distributions of the ERB protons over the drift frequency fd of protons around the Earth. For this, direct measurements of proton fluxes of the ERB in the period 1961–2017 near the plane of the geomagnetic equator were used. The main physical processes in the ERB manifested more clearly in these distributions, and for protons with fd > 0.5 mHz at L > 3 distributions of the ERB protons in the space {fd, L} have a more orderly form than in the space {E, L}. It has been found also that the quantity of the ERB protons with fd ~ 1–10 mHz at L ~ 2 does not decrease, as for protons with E > 10–20 MeV (with fd > 10 mHz), but increases with an increase in solar activity. This means that the balance of radial transport and losses of the ERB low-energy protons at L ~ 2 is disrupt in advantage of transport: for these protons, the effect of an increase in the radial diffusion rates with increasing in solar activity overpowers the effect of an increase in the density of the dissipative medium.