Active Devices Research Articles

CM-Pf deep brain stimulation in polyneuromodulation for epilepsy.

Neuromodulation is a viable option for patients with drug-resistant epilepsies. We reviewed the management of patients with two deep brain neurostimulators. In addition, patients implanted with a device targeting the centromedian-parafascicular (CM-Pf) nuclear complex supplements this report to provide an illustrative case to implantation and programming a patient with three active devices. A narrative review using PubMed and Embase identified patients with drug-resistant epilepsy implanted with more than one neurostimulator was performed. Combinations of vagus nerve stimulation (VNS), deep brain stimulation (DBS), and responsive neurostimulation (RNS) were identified. We provide a background of a newly reported case of an adult with a triple implant eventually responding to CM-Pf DBS as the third implant following suboptimal benefit from VNS and RNS. In review of the literature, dual-device therapy is increasing in reports of use with combinations of VNS, RNS, and DBS to treat patients with drug-resistant epilepsy. We review dual-device implants with thalamic DBS device combinations, functional neural networks, and programming patients with dual devices. CM-Pf is a new target for DBS and has shown a variable response in focal epilepsy. We report the unique case of 28-year-old male with drug-resistant focal epilepsy who experienced a 75% seizure reduction with CM-Pf DBS as his third device after suboptimal responses to VNS and RNS. After 9 months, he also experienced seizure freedom from recurrent focal to bilateral tonic-clonic seizures. No medical or surgical complications or safety issues were encountered. We demonstrate safety and feasibility in an adult combining active VNS, RNS, and CM-Pf DBS. Patients with dual-device therapy who experience a suboptimal response to initial device use at optimized settings should not be considered a neuromodulation "failure." Strategies to combine devices require a working knowledge of brain networks.

Analytical and Antimicrobial Characterization of Zn-Modified Clays Embedding Thymol or Carvacrol.

Carvacrol and thymol are broad-spectrum natural antimicrobial agents. To reduce their volatility and improve their antimicrobial performance, synergistic systems were prepared loading the active molecules in zinc-modified clays. Montmorillonite (MMT) and zeolite (ZEO) were modified with zinc ions (ZnMMT and ZnZEO), with well-known antimicrobial properties, and then with carvacrol or thymol, reaching the 26 ± 3% and 33 ± 2% w/w of loading, respectively. The resulting hybrid materials were characterized by FT-IR, XPS, XRD, TGA, and GC-MS to evaluate carvacrol/thymol release in simulating food matrices. Antimicrobial assays carried out using spoiler and pathogenic bacterial strains showed that the antimicrobial activity of both thymol and carvacrol was largely preserved once they were loaded into Zn-modified clays. However, MMT hybrids showed an antibacterial activity significantly higher than ZEO hybrids at 50 mg/mL of thymol and carvacrol. For this reason, deeper antimicrobial evaluations were carried out only for ZnMMT composites. ZnMMT loaded with thymol or carvacrol produced inhibition zones against most of the target strains, also at 3.12 mg/mL, while the positive controls represented by the single molecule thymol or carvacrol were not active. The hybrid materials can be useful for applications in which the antimicrobial activity of natural molecules need to be displayed over time as requested for the control of microbial pathogens and spoilage bacteria in different applications, such as active packaging, biomaterials, and medical devices.

Experimental and numerical evaluation of the performance of an integrated activation device for neutron spectrum confirmation at THOR-BNCT

Experimental and numerical evaluation of the performance of an integrated activation device for neutron spectrum confirmation at THOR-BNCT

The effect of task processing management on energy consumption at the edge of Internet of things network with using reinforcement learning method

In this paper, the task processing approach at the edge of the Internet of Things (IoT) network in improving energy consumption was investigated. First, the subject of maximizing the use of energy is defined as the main problem and then based on the state of assignment of task processing from end devices at the edge of the network to smart gateways and local servers at the edge using possible low bandwidth and low battery consumption, the problem is divided into two subject which are obtained independently. After modeling by recombining these two sub-problems, the subject of maximizing the utility gain and battery life of the end devices is solved despite the limitations of processing time and energy resources.Considering that the environment of the problem and how the terminal devices are connected with the edge devices are unknown, a repetitive reinforcement learning algorithm has been used to create an optimal solution to maximize the operational benefit of the energy consumed in edge processing. The results achieved from the simulation show the increase in network load and processing overhead with the increase in the number of active devices. The suggested method, while increasing the edge processing speed, decreases the delay and maximizes the performance gain of the IOT edge system compared to the central cloud system. It should be noted that when the number of active end devices dramatically increases, the energy consumption and bandwidth at the network edge improves, and energy consumption at the network edge decreases lonely by 12.5%.

A review of applications of deployable structure

Simple and reliable deployable structures already play a role in every aspect of our daily lives, from shopping bags and baby carriages to large buildings such as balconies and stadium roofs. In recent decades, people have been more interested in the various applications of deployable structures, for example, aerospace engineering. This paper reviews some examples in the field of deployable structures, including from the basic elements to more complex ensembles such as planar double-chain linkages and deployable antennas. Due to its properties including lower cost, smaller volume, and multiple usages, deployable structures have been extensively applied to the design and manufacture of satellites and other devices for space activities. Sizeable space antennas, as a key technology currently developed for space probes, are reviewed in this paper by using formulas to explain their functions and highlight abilities. The system of paraboloid cable net is also reviewed due to some benefits. We have discussed and summarized some challenges in applying deployable structures, along with strategies for potential solutions.

Coherent coupling of localized surface plasmons and surface plasmons in borophene-based metamaterial

The strong coherent coupling in different electromagnetic modes can control the light-matter interaction more conveniently. Here, we theoretically researched the hybridization between the borophene surface plasmon (BSP) mode and the borophene localized surface plasmon (BLSP) mode in borophene grating structure. This coupling effect leads to the emergence of multiple hybrid modes. The absorption spectra of the system are investigated through finite difference time domain (FDTD) simulation and coupled oscillator model (COM). Results show that the coherent coupling of BSP and BLSP can be achieved by adjusting the carrier density of the borophene gratings. A Rabi splitting effect with frequency of 21.6 THz can be observed. Furthermore, we investigated the effects of geometric structural parameters, incident angle, and relaxation time on the correlated coupling spectra. Our work may deepen the understanding of light–matter interactions and provide a reference for borophene-based active photonic devices in the near-infrared region.

A mixer architecture using GaN-based split-gate nanowire transistor

Frequency mixer is an essential block in radio-frequency signal processing for frequency translation and phase comparison. The most common mixers are fabricated using passive elements which suffer from significant conversion loss and low isolation. Mixers using active devices are used less frequently and rather less matured on GaN technology. Here, we demonstrate a mixer based on GaN split-gate nanowire transistor, allowing low conversion loss and high isolation. A constriction is formed by electrostatic modulation of the effective gate width. The threshold voltage of the transistor is modified by one of the gate voltages through the width variation, while the other gate voltage biases the transistor in the saturation region. The nonlinear dependency of the transistor characteristics on the two gate voltages facilitates frequency translation. The mixing characteristics of this architecture are verified both experimentally and theoretically. The output power spectral density peaks at the difference frequency with a minimal conversion loss. Extremely high isolation is measured using three-port S-parameter measurements. The proposed architecture shows multiple benefits, additionally facilitating monolithic mixers on the GaN platform.

Teachers’ use of mobile devices in suburban under-resourced secondary schools in Nepal

This study examined how secondary teachers used mobile devices for teaching and learning activities in under-resourced secondary schools in Napal. Twelve secondary teachers from three schools in the suburbs of one Himalayan district in Nepal were interviewed using qualitative research methods. The information gathered through observation of their classes supplemented the information gathered through interviews. Findings show that using mobile devices is productive for developing digital content, getting access to internet resources, and delivering lessons in the classroom. The degree of teachers’ technological, pedagogical, and content knowledge was reflected in how they used their mobile devices for information access, language games, dictionaries, and specific learning applications. In the absence of desktop computers and laptops, this study demonstrated how mobile devices improved teachers’ teaching and learning activities. Teachers could exhibit a greater level of proficiency in using technology if they received training on its usage in teaching and learning, and administrative support.

Passively Broadband Tunable Dual Circular Dichroism via Bound States in the Continuum in Topological Chiral Metasurface.

Dynamic control for a strong circular dichroism (CD) response is essential in engineering applications such as polarization manipulation, sensing, and imaging. Here, we propose and experimentally demonstrate a broadband tunable dual CD response via bound states in the continuum (BICs) in two-dimensional topologically protected metasurfaces composed of all-dielectric Si chiral grating structures that generate a pair of mixed and degenerated BIC mode and circular dichroic mode (CDM) as an additional degree of freedom in CD manipulation. It is found that a singular CD peak of nearly 100% at 1.6 μm can be achieved by CDM when BIC is hidden under normal incidence, while the CD peak can be split into two in which peak wavelengths can be precisely and linearly tuned over a bandwidth of 180 nm by the incident angle when the BIC mode is excited under oblique incidence. Additionally, dynamic modulation of output polarization states from linear to circular can be arbitrarily achieved at the split CD peaks by controlling the incident angle when asymmetry perturbations on chiral gratings are introduced due to the decoupling of various polarization states at Γ point by BIC to different positions in K space. The proposed chiral grating metasurface exhibits unique angle-sensitive tunable CD spectral characteristics, making it ideal for hyperspectral and spin-selective wavefront shaping, and holds significant promise in various applications such as optical security, angle sensors, chiral lasers, nonlinear filters, and other active chiral optical devices.

Self-rotation-eversion of an anisotropic-friction-surface torus

Recent experiments have revealed a new end-to-end ribbon spiral structure capable of demonstrating two interconnected periodic zero-energy-mode self-rotation-eversion in reaction to constant temperature or constant light sources, yet its fabrication is challenging due to its intricate nature. Differently, this paper develops a light-fueled self-rotating and everting liquid crystal elastomer torus on an isotropic frictional plane, by imparting anisotropic frictional properties to the surface of the torus. Based on a mature dynamic liquid crystal elastomer model, we constructed the theoretical model of the torus system. The torus is capable of absorbing the illumination energy to counteract damping dissipation and produce zero-energy-mode self-eversion-rotation. Theoretical findings demonstrate that the angular velocity of self-eversion is influenced by light intensity, light penetration depth, gravitational acceleration and anisotropic friction surface. Moreover, there is a proportional relationship between the self-rotation and self-eversion angular velocities, which is determined by the anisotropic frictional surface. The detailed criterion for the self-rotation direction is also established. Theoretical findings exhibit several similar phenomena to experimental observations. This paper proposes a new simple strategy that utilizes anisotropic friction surface to control self-eversion-rotation, which has guiding significance for the application of soft robots, active devices, and energy harvesters.

Calcium Alginate as an Active Device Component for Light-Triggered Degradation of 2D MoS2-Based Transient Electronics.

Transient electronics technology has enabled the programmed disintegration of functional devices, paving the way for environmentally sustainable management of electronic wastes as well as facilitating the exploration of novel device concepts. While a variety of inorganic and/or organic materials have been employed as media to introduce transient characteristics in electronic devices, they have been mainly limited to function as passive device components. Herein, we report that calcium (Ca) alginate, a natural biopolymer, exhibits multifunctionalities of introducing light-triggered transient characteristics as well as constituting active components in electronic devices integrated with two-dimensional (2D) molybdenum disulfide (MoS2) layers. Ca2+ ions-based alginate electrolyte films are prepared through hydrolysis reactions and are subsequently incorporated with riboflavin, a natural photosensitizer, for the light-driven dissolution of 2D MoS2 layers. The alginate films exhibit strain-sensitive triboelectricity, confirming the presence of abundant mobile Ca2+ ions, which enables them to be active components of 2D MoS2 field-effect transistors (FETs) functioning as electrolyte top-gates. The alginate-integrated 2D MoS2 FETs display intriguing transient characteristics of spontaneous degradation upon ultraviolet-to-visible light illumination as well as water exposure. Such transient characteristics are demonstrated even in ambient conditions with natural sunlight, highlighting the versatility of the developed approach. This study emphasizes a relatively unexplored aspect of combining naturally abundant polymers with emerging near atom-thickness semiconductors toward realizing unconventional and transformative device functionalities.

Integrated erbium-doped waveguide amplifier on lithium niobate on insulator

The erbium-doped lithium niobate on insulator (Er:LNOI) has garnered significant attention as it combines outstanding gain property with integration capabilities, making it a promising solution for active devices on the versatile LNOI platform. This also paves a way for the development of appealing erbium-doped waveguide amplifiers. Here, we demonstrate an efficient integrated Er:LNOI micro-waveguide amplifier directly compatible with the lens fiber. In a 5.6-cm-long Er:LNOI micro-waveguide, we demonstrate a maximum internal net gain of 18.8 dB for 1531-nm signal light with 1460-nm pumping. Moreover, the maximum output signal power surpasses 20 mW, thereby confirming the practicality of the Er:LNOI micro-waveguide amplifier.

Compositional effects of hybrid MoS2–GO active layer on the performance of unipolar, low-power and multistate RRAM device

Currently, 2D nanomaterials-based resistive random access memory (RRAMs) are explored on account of their tunable material properties enabling fabrication of low power and flexible RRAM devices. In this work, hybrid MoS2–GO based active layer RRAM devices are investigated. A facile hydrothermal co-synthesis approach is used to obtain the hybrid materials and a cost-effective spin coating method adopted for the fabrication of Ag/MoS2–GO/ITO RRAM devices. The performance of the fabricated hybrid active layer RRAM device is analysed with respect to change in material properties of the synthesized hybrid material. The progressive addition of 0.5, 1.5, 2.5 and 4.5 weight % of GO to MoS2, results in a hybrid active layer with higher intermolecular interaction, in the case of Ag/MoS2–GO4.5/ITO RRAM device, resulting in a unipolar resistive switching RRAM behavior with low SET voltage of 1.37 V and high I on/I off of 200 with multilevel resistance states. A space charge limited conduction mechanism is obtained during switching, which may be attributed to the trap states present due to functional groups of GO. The increased number of conduction pathways on account of both Ag+ ions and oxygen vacancies (Vo 2+), participating in the formation of conducting filament, results in higher I on/I off. This is the first report of unipolar Ag/MoS2–GO/ITO RRAM devices, which are particularly important in realizing high density crossbar memories for neuromorphic and in-memory computing as well as enabling flexible 2D nanomaterials-based memristor applications.

Plasmon-mediated dynamics and lasing of nanoemitters enhanced by dispersing nanorings.

We investigate the plasmon-mediated nonlinear dynamics and the optics of a laser emission of random nanoemitters (NEs) embedded in a two-dimensional (2D) lattice of conducting nanorings (NRs) enhanced by plasmon-polariton (PP) excitations. The interaction of quantum NEs with the PP field in the NRs perturbs the dynamics of the electronic populations in NEs, leading to a significant dependence of laser generation (dynamics) on the plasma frequency ωp of PP. This results in a strong coupling of NE field emission with the PP field and sharp variations of the average current in the NR lattice. The phase transition in the system was found when the macroscopic structures of PP fields are excited simultaneously in different regions of the system if ωp (control parameter) reaches critical value ωc. We have established the analytical dependence of the PP current I = I(ωp/ωc) on the plasma frequency, which is in excellent agreement with the results of numerical simulations. This effect may allow the design of new types of PP active devices with the use of conducting NRs in modern nanoelectronics.

Perfect active absorption of water waves in a channel by a dipole source

This study investigates the potential use of an active device to efficiently absorb water waves propagating in a channel. The active device comprises a dipole source consisting of two sources in quasi-opposition of phase. We explore the feasibility of this approach to achieve perfect absorption of guided waves through interference phenomena. To accomplish this, we establish the law governing the waves emitted by the dipole source to optimize the absorption of specific incident waves. The validity of this law is demonstrated through numerical simulations and laboratory experiments, encompassing both the harmonic and transient regimes of the experimental set-up.

Antimicrobial Polymer Surfaces Containing Quaternary Ammonium Centers (QACs): Synthesis and Mechanism of Action.

Synthetic polymer surfaces provide an excellent opportunity for developing materials with inherent antimicrobial and/or biocidal activity, therefore representing an answer to the increasing demand for antimicrobial active medical devices. So far, biologists and material scientists have identified a few features of bacterial cells that can be strategically exploited to make polymers inherently antimicrobial. One of these is represented by the introduction of cationic charges that act by killing or deactivating bacteria by interaction with the negatively charged parts of their cell envelope (lipopolysaccharides, peptidoglycan, and membrane lipids). Among the possible cationic functionalities, the antimicrobial activity of polymers with quaternary ammonium centers (QACs) has been widely used for both soluble macromolecules and non-soluble materials. Unfortunately, most information is still unknown on the biological mechanism of action of QACs, a fundamental requirement for designing polymers with higher antimicrobial efficiency and possibly very low toxicity. This mini-review focuses on surfaces based on synthetic polymers with inherently antimicrobial activity due to QACs. It will discuss their synthesis, their antimicrobial activity, and studies carried out so far on their mechanism of action.

Combinatorial Analysis of Silver‐Palladium Alloy Thin Film Libraries

Combinatorial analysis of Ag–Pd alloy thin films shows the formation of a solid solution with the face‐centered cubic structure for all investigated alloy compositions. Using mixed matter theory and the high field model, oxide growth upon applying an anodic potential is indicated. Electrochemical impedance spectroscopy supports the idea of oxide formation based on a change in behavior correlated to a sharp increase in oxide formation as indicated by cyclic voltammetry measurements. After polarization at 4 V, a stable total impedance and increasingly less‐pronounced phase shift are detected in the frequency range of 100 mHz to 10 kHz, which encompasses the common range of application of active implantable medical devices (AIMD). Upon fitting the measured impedance data with the Randles circuit, capacitances are determined in the nF cm−2 range for the investigated alloys and attributed to the formed mixed oxide layer. Charge transfer resistances are found to be in the kΩ cm−2 range. No correlation between alloy composition and capacitance or resistance can be detected so far. These findings indicate a fundamental applicability of Ag–Pd alloys for use in AIMD.

Boost DC-DC converter with regenerative snubber

To accommodate the wide range of input voltages supplied by redundant batteries and ensure an adequate hold-up time for communication systems during utility power failures, power supplies used in 5 G base stations typically include a front-end boost converter as the first stage and a second-stage isolated converter. In this paper, a new topology for a regenerative snubber in boost converters is proposed. Compared to traditional active or passive snubber topologies, the proposed snubber offers the advantages of having fewer components and occupying less space. Moreover, it does not require additional active devices and can be driven by widely-used commercial PWM control integrated circuits, achieving a higher level of cost-effectiveness and offering increased industrial applications. The final prototype of a power supply for a networking switch hub (as used in 5 G base stations) is fabricated to demonstrate the feasibility of the proposed method.

High dynamic range structured illumination microscopy based on per-pixel coding

Abstract Structured illumination microscopy (SIM) can achieve optical sectioning with high resolution, and have aroused extensive research interest. In SIM, a set of high-contrast illumination patterns are projected onto the sample to modulate the surface height information, and then, a decoding algorithm is applied to the modulated pattern images for high-quality optical sectioning. Applied to samples with large dynamic range of reflectivity, however, SIM may fail to achieve high quality sectioning for accurate surface reconstruction. Herein, an active digital micromirror device (DMD) based illumination method using per-pixel coded strategy is proposed in SIM to realize high-quality measurement for surface with complex reflection characteristics. In this method, the mapping relationship between DMD and the camera is established pixels by pixels, which enables the illumination intensity on the sample surface can be flexibly modulated by DMD pixel-level modulation corresponding to reflectivity distribution of the surface, and allows the camera pixels always to have reasonable exposure intensity for high precision measurement. More importantly, we put forward an adaptive light intensity control algorithm to improves the signal-to-noise ratio of acquired images without compromising modulation depth of pattern and measurement efficiency. Extensive comparative experiments were conducted and demonstrated that the proposed method can retrieve the surface morphology information of micro-scale complex reflectivity surfaces with high accuracy.

Boosting the performance of dye-sensitized solar cells by employing Li-substituted NiO nanosheets as highly efficient electrocatalysts for reduction of triiodide

Dye-sensitized solar cells (DSSCs) exhibit considerable potential as a promising technology, particularly when addressing the challenge of replacing the costly Platinum (Pt) counter electrode (CE) with economically viable and chemically stable CE materials. This study examines the use of two-dimensional hexagonal-shaped nickel oxide nanosheets substituted with varying mol% of lithium (1, 3, and 5 %) (Li (1–5%)-NiO NSs) as the counter electrodes (CEs) for DSSCs. The facile hydrothermal method was employed for the preparation of NiO and Li (1–5 mol%)-NiO samples. The BET analysis of NiO and Li (1–5%)-NiO indicates that higher concentrations of Li1+ ions in Ni2+ ions sites lead to an increase in the overall surface area of NiO. This leads to an elevated number of exposed electrocatalytic active sites which resulted in enhancing the rate of reduction of I3− ions. The cyclic voltammetry (CV) result of 5 mol% of Li substituted NiO (5-LNO) shows outstanding electrocatalytic activity towards the redox reaction of I3−/I− redox mediator among the as-prepared CEs. The DSSCs assembled with 5-LNO CE show an excellent power conversion efficiency (η) of 5.84 % with short-circuit current (Jsc) of 18.76 mAcm−2, and open-circuit voltage (Voc) of 0.80 V which is higher than Pt-based CE (η of 4.05 % with Jsc of 10.16 mAcm−2, and Voc of 0.69 V). The DSSCs fabricated with 5-LNO CE exhibit excellent photovoltaic performance because of their high active surface area and enhanced electrical conductivity. The 5-LNO CE has low cost, significant electrocatalytic activity, less toxicity, and superior device efficiency than NiO, other Li (1–3%)-NiO, and Pt CEs, making it a suitable candidate for Pt-free DSSCs application.