Two-dimensional topological insulators feature helical edge states that are remarkably resistant to disorder, making them appeal for energy-efficient electronics and quantum information technologies. In this study, we develop a Te-rod-templated solution growth method to create Bi2Te3 nanoplates with a Corbino geometry. The resulting few-quintuple-layer hexagonal plates are single-crystalline and contain well-defined central pores. Using optimized magnetic force microscopy, we observe clear magnetic contrast at both the inner and outer edges. The signal depends strongly on tip height and oscillation amplitude, allowing us to distinguish genuine magnetic responses from electrostatic and topographic effects. By systematically varying the pore size, we find that edge contrast increases as the distance between edges decreases, suggesting stronger coupling between the inner and outer edge channels. These findings establish a geometry-controlled platform for tuning edge-localized magnetic behavior in Bi2Te3 and open a new path to explore edge interactions in two-dimensional topological insulators.

Advances in the development of flexible piezoelectric and thermoelectric materials have provided an important avenue for the exploration of energy scavenging through the thermodynamic-coupling of orthogonal energy-scavenging modalities. Hybrid thermo/piezo-electric generator devices (T/PEGs) based on flexible, layered, thin-film architectures, have shown a kind of thermodynamic entanglement of the piezoelectric and Seebeck effects in which the efficacy of the effects depend on each other. The hallmark of this coupled thermodynamics lies in the non-additive power generation characteristic of the combined effects. Thus, under some conditions, the power generation efficiency from such a combination hybrid device can be made to exceed that of its two components independently. In this work, we show that a basic coupled heat engine model can provide important insight into the origins of synergistic power generation. But, these models also suggest the emergence of other combined thermodynamic properties such as a kinetically driven Peltier-Caloric Effect (PCE) traced to Onsager reciprocity. We report the observation of this effect in T/PEG systems as a confirmation of this perspective of thermodynamic inseparability.

In this work, we examine the formation of iron-based magnetic domains on two-dimensional (2D) single-crystal bismuth telluride plates. Using solvothermal chemical methods, 2D bismuth telluride (Bi2Te3) single crystalline nanoplates were reacted with iron salts (FeCl2) to achieve electrical doping. The use of a reducing agent [L(+)-ascorbic acid] along with FeCl2 resulted in homogeneous dispersion of iron across the crystal, whereas non-reduced iron doping achieved edge growth of iron/iron oxide nanoparticles. High-resolution analytical electron microscopy was used to examine the iron nanoparticle accumulation and morphology at nanoplate edges for non-reduced materials and iron dispersions within the crystals in the case of reduction. Our analysis revealed little variation in the atomic uptake of iron in any form over a range of solution-dopant concentrations. However, structural analysis and transport measurements clearly indicate the tendency of the dopant nanoparticles to oxidize quickly. The Seebeck coefficient and power factor also express modifications with exposure to oxidation, providing an indirect probe of the dopant modification to the host Bi2Te3’s electronic properties. Importantly, however, magnetic force microscopy images show a distinct difference in the formation of magnetic phases with and without the use of reducing agents during iron doping. This suggests that oxidation post-doping does not form magnetic phases, whereas oxidation during the doping process is suitable for obtaining magnetically doped Bi2Te3 nanocrystals.

In this work, we present a solvothermal, in situ doping methodology for synthesizing crystalline doped 2D bismuth telluride (Bi2Te3) nanoplates. Isoelectronic antimony (Sb) substitution at the bismuth (Bi) site is chosen to minimize the lattice strain in the nanostructure. Using a combination of x-ray techniques and electron microscopy, we demonstrate that the rhombohedral crystal structure (space group R3̄m), characteristic of Bi2Te3 is preserved in few-quintuple-layer, hexagonal nanoplates. Our findings reveal a uniform dispersion of Sb within the nanoplates up to an atomic concentration of 1%. Beyond this threshold, a disordered SbTe alloy begins to form along the crystal edges in addition to Sb substitution at the Bi sites in the bulk, restricting further growth of the nanoplates. In addition, we examine the different stresses that develop within the nanoplates as lattice strain increases due to Sb substitution. This study provides fundamental insights into the dopant’s effect on the self-assembled growth of electronically relevant 2D crystals.

Motivated by the use of magnetohydrodynamic devices in fluid dynamic flow control research, the current work experimentally studied the actuation mechanism and the resulting aerodynamic interactions of magnetically driven low-current arc-plasma discharges. The investigation was conducted in the context of boundary-layer interactions in low-speed crossflow conditions through the use of coaxial and v-shaped geometries. Time-averaged velocity field measurements showed that the toroidal region of vorticity induced by the coaxial geometry in quiescent air resulted in the formation of a horseshoe vortex in crossflow. Similarly, the v-shaped actuator resulted in the formation of streamwise vortices. The resulting boundary layers had s-shaped streamwise velocity profiles as measured in the wall-normal direction characteristic for the flow downstream of a conventional vortex generator pair, due to the three-dimensional mixing induced by coherent vortex structures. A simplified model based on intermolecular momentum transfer through collisions is proposed to explain the fundamental discharge–air interactions and the induced flowfields. These results inform the applications of various magnetically driven discharges in the field of aerodynamic flow control.

Molybdenum sulfide (MoS2) is a transition metal dichalcogenide that can achieve ion transport, thanks to its interlayer spacing, 1T/2H surface properties, and inherent thermoelectric properties. In this study, nanosheets of 1T MoS2 were synthesized, deposited as thin film stacks, and utilized as a self-powered nano-channel membrane for the intercalation of sodium chloride ions. Controlled deposition of a NaCl solution droplet onto a thermally activated 1T MoS2 film caused a characteristic voltage spike and decay. These phenomena result from ion–surface interactions followed by Soret- and thermoelectric-induced transport and eventual intercalation within the film layers. Voltage decay curves were recorded for various NaCl droplet concentrations deposited onto MoS2 films subject to a range of temperature gradients (ΔT). Areas under the final decay curves were integrated; both higher salt concentration and greater ΔT were associated with larger integrated areas. A direct relationship between droplet voltage response and concentration was found, potentially allowing for 1T MoS2 to function as a sensor of solution ion concentrations.

The application of magnesium oxide (MgO) nanoparticles as a candidate material for antibacterial purposes has been limited by their relatively low antibacterial activity. In this study, antibacterial MgO nanoparticles were synthesised in one step using magnesium nitrate and citric acid as raw materials using an economical and environmentally friendly microwave-assisted solution combustion approach, while the effect of the pH of the reaction system (2, 4, and 7) on the structure and antimicrobial properties of the synthesised MgO nanoparticles was investigated. X-ray diffraction (XRD) analysis demonstrated the formation of cubic-phase MgO nanoparticles, and electron microscopy studies confirmed that MgO nanoparticles synthesised at a precursor solution pH of 4 had uniform size distribution with a small microcrystalline size (similar to 19 nm) and spherical granular morphology. In addition, the results of the plate colony counting method showed that the antibacterial rate of MgO-4 against Gram-negative Escherichia coli (10(6) CFU/mL) at a sample concentration of 100 mu g/mL was as high as 99.86 %, which showed excellent antibacterial performance. These findings provide valuable insights into how to increase the degree of oxygen adsorption on the sample surface to participate in the reaction, as well as a potential method for constructing nanomaterials with high antimicrobial activity.

A simplified plasmadynamics model is presented that examines radial and axial dependence of the current sheet structure of a coaxial quasi-steady self-field plasma accelerator, dominated by electromagnetic forces. Two radial electric field distributions are considered as limiting cases. In the first case, constant current flows between constant-radius electrodes; in the second case, constant current flows between electrodes and also extends downstream of the electrodes. Calculations for Teflon ([Formula: see text]) plasma show the distribution of plasma parameters inside the current sheet, as well as terminal values for kinetic efficiency, voltage, and impedance for both [Formula: see text] distributions. Evaluation of the validity of simplifying assumptions is presented, as is the behavior of previously developed accelerators as interpreted by the model.

Quantum computing has generated splashy headlines with pronouncements of “quantum supremacy”, but the reality is much more complicated than simple headlines can capture. Quantum computers are designed to use the interactions between quantum objects, such as electron spins, to perform useful computations. This paper will provide an overview of some of the engineering challenges involved in developing quantum computers and highlight some potential applications of interest to the mechanical engineering community. These challenges include the need to isolate the quantum bits — the logic elements used in quantum computers — from the environment to protect them from external sources of noise. In some quantum computer designs, this requires cooling the quantum bits to temperatures below 1 degree Kelvin, which requires specialized refrigeration systems. Potential future applications of quantum computers, particularly for mechanical engineers, rely on the promise of increased computational power for solving complex problems that have many degrees of freedom. This includes solving large systems of equations for finite element analysis and computational fluid dynamics, and in computational chemistry for materials optimization. Quantum computing is clearly a future technology — more development is needed before it will be used for engineering applications. That said, there are clear potential applications in mechanical engineering, and it will be a future technology that will be used for engineering analysis-based design optimization, digital twin development, and other relevant applications.

Abstract In this article, a novel photovoltaic/thermal (PV/T) geometry is introduced that allows for passive microlensing, IR collection, and photovoltaic deployment, as in previous implementations, together with spectral splitting. Stokes shifting dyes of the Coumarin family were dispersed in a thermal fluid in front of a single-junction amorphous silicon PV using a tubular focusing geometry. This architecture effectively shifts the high-energy UV flux into near bandgap photons for the Si, while capturing the released energy of the Stokes transition as heat. By combining this with the thermal fluid’s IR absorption and the PV, the system converts a surprising amount of the solar flux into collectable power, with a 71.05% thermal conversion efficiency and 2.07% electrical efficiency, leading to a total system efficiency of conversion of 73.1 percent. Temperatures and heat flow were then simulated to connect optical characteristics to thermal transport characteristics and allow for optimization under various circumstances. Impact statement The large entry cost of solar makes it unattainable for large segments of the world’s population. In this article, we present a photovoltaic/thermal (PV/T) system, made of low-cost, easily accessible materials that are simple to manufacture. Together, the components of the system harvest energy from nearly the entire solar spectrum using a photovoltaic, infrared absorbing thermal fluid and a Stokes shifting dye. The geometry of the PV/T acts as a passive microlens system while providing the additional benefit of keeping the PV cool. The modeling presented allows for optimization in specific applications. Graphical abstract

Adv. Energy Mater. 2017 , 7 , 1700513 The above article, published online on May 11, 2017, in Wiley Online Library, has been retracted by agreement between the corresponding author, the journal Editor in Chief Till von Graberg, and Wiley‐VCH GmbH. The retraction has been agreed on following concerns raised by a third party and a subsequent investigation at Wake Forest University. Data integrity issues were found in figures 6e and 7d. As a result, the editors consider the conclusions of this article invalid.

Adv. Mater. 2018, 30, 1705796 https://doi.org/10.1002/adma.201705796 The above article, published online on January 15, 2018, in Wiley Online Library (https://doi.org/10.1002/adma.201705796), has been retracted by agreement between the authors, the journal Editor in Chief Jos Lenders, and Wiley-VCH GmbH. The retraction has been agreed on following concerns raised by a third party and a subsequent investigation at Wake Forest University. Data integrity issues were found in Figures 1a, S2b, and S17. As a result, the authors consider the conclusions of this article invalid.

A plasma swirler, based on an existing Lorentz force driven gliding arcs, was developed as a flame holding and combustion enhancing device for premixed and diffusion flames. The device is intended to deliver the combined benefits of jet swirlers and plasma assisted combustion by providing fluidic mixing to augment flame stability, and high energy particles to enhance the combustion process. The current study focused on characterizing the fluid dynamic effects of the plasma swirler on an axial air jet ejected at various air flow rates in quiescent air. Schlieren imaging was used to study the thermal effects of the plasma on the axial air jet and qualitatively compare the turbulence levels in the actuated and unactuated jets. Time-averaged stereoscopic particle image velocimetry data were acquired across seven evenly-spaced planes perpendicular to the exit plane of the plasma swirler at three different axial flow rates, while maintaining constant plasma swirling parameters. These data were used to reconstruct three-component volumetric averaged velocity fields. Two-dimensional cross sections along with three-dimensional isosurfaces of the mean flow were used to describe the induced flow and flow turbulence levels, and characterize the vorticity created by the swirler.

This paper presents the development and initial experimental testing of a new compact, high-performance singlet oxygen generator (SOG). The generator uses a centrifugal design to assist in two-phase separation, a porous plate injection technique to create a froth and maximize chlorine utilization, and a closely coupled minimum length nozzle (MLN) to minimize transport losses. A high froth speed in the curved wall region is essential in order to attain a significant centrifugal force that pins the liquid component to the curved wall, which consequently results in a rapid and efficient separation of the vapor containing the excited oxygen that then flows into the nozzle. This generator operates without diluent and was demonstrated to perform at pressures greater than 350 Torr, which enables the technology to operate without the need for a pressure recovery system in an airborne chemical oxygen-iodine laser (COIL). The implementation of this froth SOG (FSOG) in combination with the use of a MLN allows the generation of large number densities of excited oxygen at a very high plenum pressure without the use of any diluent. Experimental results for this novel FSOG, along with the engineering logic behind it, are presented. Number densities greater than 5.3×1017 cm–3 were measured via calibrated spectroscopic analysis of the O2(1 Δ) emission about 1268 nm at the exit of a supersonic nozzle. To the authors’ knowledge, the FSOG produced a higher pressure and larger excited oxygen number density than any other SOG system reported.

Using an in-cell AMPK activation assay, we have developed structure-activity relationships around a hit pyridine dicarboxamide 5 that resulted in 40 (R419). A particular focus was to retain the on-target potency while also improving microsomal stability and reducing off-target activities, including hERG inhibition. We were able to show that removing a tertiary amino group from the piperazine unit of hit compound 5 improved microsomal stability while hERG inhibition was improved by modifying the substitution of the central core pyridine ring. The SAR resulted in 40, which continues to maintain on-target potency. Compound 40 was able to activate AMPK in vivo after oral administration and showed efficacy in animal models investigating activation of AMPK as a therapy for glucose control (both db/db and DIO mouse models).

Metal halide perovskites present specific challenges as emitters in large area, surface emission lighting devices. Among these challenges is the vast difference in carrier mobilities between the perovskite and many organic buffer layers typically used in such device fabrication as transport and blocking layers. This can make it difficult to engineer recombination to achieve white emitting devices generally. However, in this work, we introduce unique modulation of excitonic confinement within the perovskite layer of the device stack to control overall placement of the recombination zone. This results in a white light emitter that is bright and highly tunable, providing a path to realize white perovskite related light-emitting devices.