Switching Structure Research Articles

Label free ultrasensitive detection of NS1 based on electrochemical aptasensor using polyethyleneimine aggregated AuNPs

To date, NS1 viral diagnostic technologies have been considered as time-consuming, expensive and too complex to be widely deployed, particularly in developing countries. In view of this, anelectrochemical methodwas exploited to detectdengue virus based on NS1-specific aptamer and cationic polymer-induced aggregation ofgold nanoparticles(AuNPs).The basic principle of this assay is classical based on the gradual aggregation of AuNPs controlled by the specific interactions among polyethyleneimine (PEI), aptamer and NS1. The aggregation of AuNPs was induced by the cationic polymer, which was controlled by the interaction of aptamer and cationic polymer forming “duplex” structure. This non-specific interaction between aptamer and polymer was expected to limit the flexibility of the aptameric chain and consequently renders the aptamer to be more accessible to the target molecule (NS1). This accession of NS1 was responsible for the quadruplexe formation due to strong obligatory electrostatic interaction with aptamer. This structural switching between aptamer/polymer duplex and aptamer/target complex was the base to design this electrochemical aptasensor. This cationic polymer and aptamer assisted dispersion-aggregation phenomenon renders change in their electrochemical response which could eventually probe the sensitive detection of NS1 protein. The as prepared electrochemical aptasensor successfully detected NS-1 protein with enhanced limit of detection (0.3 ng mL−1) and linear range (3–160 ng mL−1). Human real serum analysis indicated the actual applicability of our E-Apts. Using this electrochemical aptasensor, we demonstrate the highly sensitive and specific detection of Dengue virus. The low-cost and flexibility inherent in this analytical technique could be an important step towards effective diagnostic technology for the detection of Dengue virus and other infectious diseases.

Out-of-plane carrier spin in transition-metal dichalcogenides under electric current

Absence of spatial inversion symmetry allows a nonequilibrium spin polarization to be induced by electric currents, which, in two-dimensional systems, is conventionally analyzed using the Rashba model, leading to in-plane spin polarization. Given that the material realizations of out-of-plane current-induced spin polarization (CISP) are relatively fewer than that of in-plane CISP, but important for perpendicular-magnetization switching and electronic structure evolution, it is highly desirable to search for new prototypical materials and mechanisms to generate the out-of-plane carrier spin and promote the study of CISP. Here, we propose that an out-of-plane CISP can emerge in ferromagnetic transition-metal dichalcogenide monolayers. Taking monolayer [Formula: see text] and [Formula: see text] as examples, we calculate the out-of-plane CISP based on linear-response theory and first-principles methods. We deduce a general low-energy model for easy-plane ferromagnetic transition-metal dichalcogenide monolayers and find that the out-of-plane CISP is due to an in-plane magnetization together with intrinsic spin-orbit coupling inducing an anisotropic out-of-plane spin splitting in the momentum space. The CISP paves the way for magnetization rotation and electric control of the valley quantum number.

A 65–81 GHz CMOS Dual-Mode VCO Using High Quality Factor Transformer-Based Inductors

This paper presents a wide-tuning range dual-mode millimeter wave (mm-wave) voltage controlled oscillator (VCO) incorporating high quality-factor (Q) transformer-based variable inductors. A high Q switched inductor with two different values is proposed by constructing the load of a transformer of a high Q fixed capacitor in series with a lossless switch structure that does not add any loss to the LC-tank as implemented by changing the signals mode across the capacitor. By choosing a proper center frequency for each mode and sufficient frequency overlap, a wide frequency tuning range (FTR) mm-wave VCO can be designed. It provides almost twice higher tuning range while keeping phase noise (PN) nearly the same as the two-mode VCO designed with two standalone inductors. Fabricated in a 65 nm CMOS process, the VCO demonstrates the measured FTR of 22.8% from 64.88 to 81.6 GHz range. The measured peak PN at 10 MHz offset is -114.63 dBc/Hz and the maximum and minimum corresponding figures of merit FOM and FOMT are -173.9 to -181.84 dB and -181.07 to -189 dB, respectively. The VCO cores consume 10.2 mA current from 1 V power supply, and the occupied area is 0.146 ×0.205 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .

Missense mutations affecting Ca2+-coordination in GCAP1 lead to cone-rod dystrophies by altering protein structural and functional properties

Guanylate cyclase activating protein 1 (GCAP1) is a neuronal calcium sensor (NCS) involved in the early biochemical steps underlying the phototransduction cascade. By switching from a Ca2+-bound form in the dark to a Mg2+-bound state following light activation of the cascade, GCAP1 triggers the activation of the retinal guanylate cyclase (GC), thus replenishing the levels of 3′,5′-cyclic monophosphate (cGMP) necessary to re-open CNG channels. Here, we investigated the structural and functional effects of three missense mutations in GCAP1 associated with cone-rod dystrophy, which severely perturb the homeostasis of cGMP and Ca2+. Substitutions affect residues directly involved in Ca2+ coordination in either EF3 (D100G) or EF4 (E155A and E155G) Ca2+ binding motifs. We found that all GCAP1 variants form relatively stable dimers showing decreased apparent affinity for Ca2+ and blocking the enzyme in a constitutively active state at physiological levels of Ca2+. Interestingly, by corroborating spectroscopic experiments with molecular dynamics simulations we show that beside local structural effects, mutation of the bidentate glutamate in an EF-hand calcium binding motif can profoundly perturb the flexibility of the adjacent EF-hand as well, ultimately destabilizing the whole domain. Therefore, while Ca2+-binding to GCAP1 per se occurs sequentially, allosteric effects may connect EF hand motifs, which appear to be essential for the integrity of the structural switch mechanism in GCAP1, and perhaps in other NCS proteins.

Design of Step down Structure RF-MEMS Shunt Capacitive Switch for Low-Pull-In Voltage

In this paper, designs and simulations of a new RF MEMS step-down structure of a capacitive shunt switch using different meandering methods are presented. The beam and dielectric materials are taken as gold and silicon nitride for the proposed switch. The switch required actuation voltage is 7.9 V for the non-uniform one meander technique.

MASGQF with application to SINS alignment

To effectively improve the computation efficiency in the strapdown inertial navigation system (SINS) alignment process, the authors propose a marginalised adaptive sparse-grid quadrature filter (MASGQF). The filtering method combines the virtues of marginalisation technique and accuracy level switching structure to decrease the computational burden and improve the filtering precision simultaneously. With the adaptation criterion and the predefined tolerance value, different integration rules corresponding to the different accuracy levels nested in the proposed filtering method can be adjusted autonomously. It is proved that the MASGQF is exponentially bounded by theoretical analysis. The performance comparison of different filtering methods is demonstrated by the numerical results of the simulation and offline experiment. On the basis of the data performance of the online test, the validity of the proposed MASGQF is verified in the SINS alignment application.

Autonomous navigation control based on improved adaptive filtering for agricultural robot

Under the complex agricultural operation environment, reliable navigation system is the basic guarantee to realize the agricultural robot automated operation. This study focuses on improving navigation accuracy and control accuracy and conducts related research on autonomous navigation control of agricultural robots. This article discusses the advantages of using strict convergence criteria and combining Sage–Husa adaptive filtering with strong tracking Kalman filtering and then proposes an improved adaptive Kalman filter algorithm. The new algorithm can effectively suppress the filter divergence, improve the dynamic performance of the filter, and ensure its better filtering accuracy and strong adaptive ability to improve navigation accuracy of GPS. Further variable structure switching method is used to prevent proportional integral differential (PID) controller integral saturation phenomenon, which effectively solves the controller over-saturation problem. And combining this method with an improved adaptive filtering algorithm not only can effectively inhibit control interference but also achieve the anti-saturation effect, thereby enhancing the stability and accuracy of the control system. Finally, the simulation and experiment of the new method show that the proposed method greatly improves the ability of the filter to suppress divergence and control precision.

Modeling of Clos Switching Structures with Dynamically Variable Number of Active Switches in the Spine Stage

This article proposes a new analytical model of a switching structure using a Clos network topology. The assumption is that, in the structure under consideration, it is possible to switch off temporarily a certain number of spine switches (those in the middle stage of the switching fabric) depending on the current intensity of the offered traffic to reduce power consumption. The solution presented in the article can be used in present-day multiservice switching fabrics and in networks connecting servers in data centers. The developed analytical model allows the value of blocking probabilities for different stream classes of multiservice traffic to be evaluated in switching structures (switching fabrics) with a variable number of switches in the middle stage. The results obtained on the basis of the analytical model are compared with the results obtained as a result of relevant simulation experiments for a selected structure of the switching fabric. The study confirms high accuracy of the proposed model. This model can be used in further works to evaluate the effectiveness of energy-saving switching fabrics and the networks of data centers, as well as to construct energy-saving control algorithms that would control these switching structures, that is, algorithms that would change the topology of the switching fabric depending on changes in the offered traffic.

Low-temperature chemical fabrication of WO3 gasochromic switchable films: a comparative study of Pd and Pt nanoparticles dispersed WO3 films based on their structural and chemical properties

Pd nanoparticles dispersed WO3 (Pd-WO3) gasochromic switchable films were prepared using our method combining UV irradiation and H2 gas flow at room temperature. Structural, chemical and optical switching properties of the films were evaluated and compared with those of the Pt-WO3 films prepared using the same method. It was found that the distribution of catalysts in the Pd-WO3 films was different from that in the Pt-WO3 films. The Pd-WO3 films exhibited large difference in optical transmittance in their colored and bleached states, which was similar to that of the Pt-WO3 films. However, the coloring of the Pd-WO3 films by H2 gas was a little slower than that of the Pt-WO3 films, although the bleaching of these films by air was similarly fast. It was speculated that the difference in the gasochromic properties between the Pd-WO3 and the Pt-WO3 films is likely due to the difference in the distributions of catalysts between the Pd-WO3 and the Pt-WO3 films.

Use of the “Via-In-Pad” Method to Ensure the High-Density Layout of the Conductive Pattern when Designing Multilayer Switching Structures

The application features of the Via-in-Pad method when implementing a high-density conductive pattern of multilayer switching structures in electronics is considered herein. The composition method for vias and contact pads for the tracing ability improvement is proposed, and the assessment methodology for the effective area utilization for BGA components is presented. The experimental study of the pressure sensor housing was carried out, which showed that the application of this method made it possible to reduce the number of vias by 40% and place more contact pads per unit area, which frees up the gaps for BGA tracing, reduces the pattern density and microwave signal paths. The obtained results confirmed the possibility of reduction of the usable space by 25%, which makes it possible to arrange more pads per unit area, to free up the gaps for BGA tracing, to reduce the time for drilling the workpieces, to reduce the number of used drills, and also provides the best heat removal from the components. The disadvantage is the large internal resistance of the transitions created by the Via-in-Pad method, in contrast to the standard ones, which can negatively affect the flow of critical signals. By comparing the resistances from the metallization layer of the via in the MPCB with a flexible flat cable and in the MPCB designed using the Via-in-Pad method, it was found that the Via-in-Pad method made it possible to increase the layout efficiency of multilayer printed circuit boards.

Photovoltaic Equalizer Based on Single-Input Multi-Output Push-Pull Converter

Component mismatch often happens in the module-series photovoltaic system(including centralized, string, multi-strings PV system) due to partial shadowing, which causes a large loss of power generation. Photovoltaic equalizer can process the differential power under the condition of mismatching through parallel power electronic converter without changing the existing photovoltaic system architecture, so that all the modules can work near their maximum power points, which can greatly improve the power generation of the system under the condition of mismatching. This paper proposes a photovoltaic equalizer based on single-input multi-output push-pull converter. The topology has the advantages of simple structure and less switching devices. Firstly, the paper introduces the partial shadowing problem of photovoltaic modules and the principle of photovoltaic equalizer. Then, the topological structure and working principle of the proposed photovoltaic equalizer system are analyzed in detail. Finally, the simulation and verification of the designed photovoltaic equalizer are carried out. The simulated results show that the proposed equalizer can greatly improve the generation capacity of photovoltaic system under mismatching conditions, and the maximum increment can be up to 41%.

АЛГОРИТМЫ БЕЗДАТЧИКОВОГО ОТКАЗОУСТОЙЧИВОГО УПРАВЛЕНИЯ ВЕНТИЛЬНО-ИНДУКТОРНЫМ ЭЛЕКТРОДВИГАТЕЛЕМ НАСОСА ДЛЯ ДОБЫЧИ НЕФТИ

Актуальность.Нефтегазовая отрасль России сегодня одна из самых быстро развивающихся в стране. Высокие темпы развития предполагают внедрениеновых технологий и значительную модернизацию технологических комплексов, входящих в состав производственной базы. В частности, исполнительных двигателей насосов добычи и транспортировки ископаемого топлива. Надёжное и бесперебойное функционирование двигателя насоса является конкурентным преимуществом. Для снижения вероятных простоев оборудования и недоотпуска нефти предлагается использовать современный вентильно-индукторный электродвигатель в качестве исполнительного двигателя насоса добычи нефти. Существующие разработки показывают конкурентные преимущества этого типа электродвигателя при доработке системы управления и применении алгоритмов отказоустойчивого управления. Повысить отказоустойчивость и расширить области применения вентильно-индукторного электродвигателя позволяет использование бездатчикового управления. На сегодняшний день в технической литературе данная тематика проработана недостаточно глубоко, а математическая и имитационная модели бездатчикового управления вентильно-индукторным электроприводом в аварийном неполнофазном режиме работы ранее рассмотрены не были. Цель: разработка алгоритмов отказоустойчивого бездатчикового управления исполнительным вентильно-индукторным электродвигателем в неполнофазных режимах работы; обеспечение корректности переключения структуры управления при обрыве фазы; повышение отказоустойчивости вентильно-индукторного электродвигателя насоса в аварийных режимах работы путем подключения алгоритмов отказоустойчивого управления при переключении структуры управления. Объект:четырехфазный вентильно-индукторный электродвигатель насоса добычи или транспортировки нефти в аварийных неполнофазных режимах работы. Методы: математическое и имитационное моделирование, программирование в среде MatlabSimulink. Результаты. Разработаны математическая и имитационная модели бездатчикового отказоустойчивого четырехфазного вентильно-индукторного электропривода в аварийном режиме работы. Получен алгоритм бездатчикового отказоустойчивого управления насосом с вентильно-индукторным электродвигателем в аварийном режиме работы. Получены характеристики насоса добычи нефти в неполнофазном режиме работы исполнительного вентильно-индукторного электродвигателя с применением алгоритма отказоустойчивого управления.

Effects of impulse delays on Lp-stability of a class of nonlinear time-delay systems

In this paper, a nonlinear time-delay system with delayed impulses and external disturbances is considered. The robustness problem of Lp-stability with respect to impulse-delays is addressed. In order to circumvent the technical difficulties caused by delayed impulses, the impulses-delayed system is modeled as an impulse-delay free system with switching impulses by means of an augmentation method. Based on the switching structure of the augmented system, a time-dependent Lyapunov function is constructed from the original Lyapunov function for the impulse-delay free case. Then by employing the new designed Lyapunov function combined with the use of Razumikhin-type arguments, sufficient conditions for exponential stability and Lp-stability are derived. The developed results characterize the relationship among the impulse intervals, the size of impulse-delays, and the level of Lp-gain. Two numerical examples are presented to illustrate the effectiveness of the developed methodology.

Comprehensive Spectral Analysis of PWM Waveforms With Compensated DC-Link Oscillations

In the available literature, including reference books on the topic, the spectral analysis of voltage waveforms obtained through the use of pulse width modulation (PWM) relies on the assumption of an ideally flat voltage across the dc-link of a considered switching structure. Nevertheless, certain converter families (e.g., modular multilevel converter, characterized by the presence of distributed and floating dc-links), feature low-frequency oscillations of dc voltage within their switching stages. On these terms, the flat dc-link assumption cannot be considered valid from both theoretical and practical viewpoints. In case carrier-based modulation is employed, unless properly compensated through the modulation signal adjustments, the above mentioned voltage oscillations cause undesirable distortion of the converter currents. However, the very same adjustments of modulation signals introduce additional challenges in the spectral analysis of the voltage across the ac terminals of an observed switching stage. This article provides the ac terminals voltage analysis of a single half-bridge experiencing dc-link oscillations, which are compensated through the modulation signal generation process. PWM with the conventional triangular carrier is considered, while all the results are presented in a generalized form, making them easily extendable to cascaded structures. All of the presented results were experimentally validated.

Redox-Induced Structural Switching through Sporadic Pyridine-Bridged CoIICoII Dimer and Electrocatalytic Proton Reduction.

The homodinuclear CoII helicate complex [CoII(DQPD)]2 (1) was prepared by treating [Co(H2O)6](ClO4)2 with the deprotonated form of the ligand N2,N6-bis(quinolin-8-yl)pyridine-2,6-dicarboxamide (DQPDH2). Complex 1 represents a discrete homodinuclear helicate complex with two CoII centers having a distorted-octahedral geometry through an unprecedented pyridine bridge. Complex 1, upon treatment with H2O2, undergoes oxidation at one of the CoII centers followed by a structural deformation to generate the mixed-valence complex [CoIIICoII(DQPD)2](ClO4) (2·ClO4). In complex 2, the bridging through the central pyridine collapses along with the formation of Co(III) octahedral and Co(II) tetrahedral environments. Complexes 1 and 2 interconvert to one another. The effective magnetic moments for complexes 1 and 2 are respectively 5.88 and 4.30 μB. Complexes 1 and 2 have been employed for electrocatalytic proton reduction using AcOH as the proton source in 95/5 (v/v) DMF/H2O. A TOF of 30000 mmol of H2 h-1 (mol of 1)-1 at a potential of -1.7 V vs SCE was achieved. A resting-state analysis has been carried out to support the mechanism for the catalytic proton reduction.

3D modeling of graphene oxide based nanoelectromechanical capacitive switch

The present work deals with 3D modeling of a novel configuration of a double clamped nanoelectromechanical (NEM) capacitive switch. In the proposed work, graphene oxide (GO) as a dielectric has been used as suspended beam material in NEM switch for the first time. Analysis of von Mises stress, pull-in, and pull-out voltages are investigated using COMSOL Multiphysics, for standard and perforated GO NEM switch structures. The actuation voltages of 5.4 V and 3.35 V are evaluated for standard and perforated beam structures respectively for the beam lengths of 1 µm and widths of 0.3 µm. The actuation voltage and von Mises stress value have reduced by making perforations in the beam. The von Mises stress comparative analysis of GO and graphene NEM switch exhibits that GO is a better choice for beam material as GO NEM switch withstand less von Mises stress than graphene NEM switch. The variation in capacitance including the fringing field capacitance is calculated as the beam is pulled down by the actuating electrode.

The domain structure and local switching of LiNbO3 thin films deposited on Si(001) by radio-frequency magnetron sputtering

Ferroelectric domain structure and local switching were studied in LiNbO3 thin films deposited by radio-frequency magnetron sputtering technique on Si (001) substrates in Ar and Ar(60%)+O2(40%) environments. The noticeable difference in surface morphology and ferroelectric domain structure of the investigated films was found. The films sintered in pure Ar environment demonstrated pronounced <0001> texture; nevertheless, neither piezoresponse nor ferroelectric domains were obtained. Films sintered in Ar(60%)+O2(40%) environment possessed the switchable ferroelectric domain structure but disordered grain orientation. The films sintered in Ar after thermal annealing in air preserve <0001> texture and possess self-poled switchable domain structure.

Substrate and Product-Assisted Catalysis: Molecular Aspects behind Structural Switches along Organic Hydroperoxide Resistance Protein Catalytic Cycle

Bacteria contain a large repertoire of enzymes to decompose oxidants, such as hydroperoxides. Among them, organic hydroperoxide resistance (Ohr) proteins play central roles in the bacterial response to fatty acid peroxides and peroxynitrite (Alegria et al. Ohr Plays a Central Role in Bacterial Responses against Fatty Acid Hydroperoxides and Peroxynitrite. Proc. Natl. Acad. Sci. USA 2017, 114, E132) and present distinct structural and biochemical features in comparison with mammalian Cys-based peroxidases. The molecular events associated with the high reactivity of Ohr enzymes toward hydroperoxides and its reducibility by lipoylated proteins (or dihydrolipoamide) are still elusive. Here, we report six crystallographic structures of two Ohr paralogs from Chromobacterium violaceum, including the complex with dihydrolipoamide. Comparison of these six structures with the other few Ohr structures available in public databases revealed conserved features in the active site, such as a hydrophobic collar. Together with classical, hybrid quantum-classical molecular dynamics simulations and point mutation analyses, we show that Ohr undergoes several structural switches to allow an energetically accessible movement of the loop containing the catalytic Arg, which is stabilized in the closed state when the catalytic Cys is reduced. The structure of Ohr in complex with its substrate (dihydrolipoamide) together with molecular simulations allowed us to characterize the reductive half of the catalytic pathway in detail. Notably, dihydrolipoamide favors Arg-loop closure, thereby assisting enzyme turnover. The conserved physicochemical properties of the Ohr active site and the mechanisms revealed here provide relevant information for the identification of inhibitors with therapeutic potential.

Ultrasensitive Electrochemical Dnazyme Based Sensing Platform for Clinical Detection of Uropathogenic Escherichia coli

Urinary tract infections (UTIs) are one of the most ubiquitous bacterial infection diseases affecting half of the global population at least once in their lifetime. Given the occurrence of the false positive result in Dipstics and the time-consuming identification of bacteria using culturing method to detect UroPathogenic Escherichia coli (UPEC), there is the need for a point-of-care diagnostic platform that is reliable, sensitive, specific, cost-effective, fast and easy to use. With the advent electrochemical methods coupled with the specific biorecognition elements, the detection of any biomarker has become possible with one touch. Among many biorecognition molecules, DNAzymes are gaining attention due to their robustness, stability, specificity, and the ease of selection without prior knowledge of the biomarker. Their structure switching and functionality (RNA cleaving) can be utilized with redox active species (like methylene blue) to design highly sensitive and selective electrochemical assays for pathogen detection.In this work, we have developed a dual signaling electrochemical DNAzyme based platform for specific and sensitive detection of Escherichia coli (E.coli) in UTI patient urine samples. The two on-chip working electrodes named as release channel and capture channel are integrated with DNAzyme-redox barcode and DNA probe respectively. In the presence of the bacterial target the DNAzyme catalyzes the cleavage of the redox DNA barcode in the release channel, which is subsequently translated into a redox signal upon hybridization with the probe on the capture channel. The differential signal generated by the two channels in the sensor demonstrated the sensitive detection of 10 CFU for E.coli in buffer and urine. Additionally, the sensor specifically detected E. coli in the presence of a panel of other gram positive and negative bacteria. Clinical validation of the assay was performed using 40 E.coli+ and E.coli- patient urine delineating a clinical sensitivity of 100% and specificity of 78% in a 30 minute testing time. This cost effective, reagent-free, time-efficient, and amplification-free electrochemical assay is suitable for detecting a wide range of pathogens, also alleviates the additional knowledge requirement of the biomarker as compared to other protein and aptamer-based assay. With the advancement in the chip fabrication and microfluidics, this assay can also be multiplexed with other pathogen for simultaneous detection of multiple pathogens in a single urine sample.

Mechanical Regulation Triboelectric Nanogenerator with Controllable Output Performance for Random Energy Harvesting

AbstractRecycling of random mechanical energy in the environment has become an important research hotspot. The triboelectric nanogenerators (TENGs) were invented to harvest energy, and have been widely applied due to their simple structure, small size, and low cost. This paper reports a mechanical regulation triboelectric nanogenerator (MR‐TENG) for the first time with controllable output performance used to harvest random or irregular energy in the environment. It comprises a transmission unit, switch structure, generator unit, flywheel, and shell. Random linear motion or rocking motion is transferred via the transmission unit to the flywheel. The rotor of the generator unit fixed on the flywheel and the stator of the generator unit fixed on the shell combine. By controlling the storage and release of energy in the flywheel, the switch structure assists the flywheel to convert random or irregular energy into a controllable and stable energy output. The MR‐TENG can generate an open‐circuit voltage of 350 V, a short‐circuit current of 12 μA, a transfer charge of 130 nC, and a peak power of 2.52 mW. Furthermore, a thermometer and more than 300 light emitting diodes (LEDs) are separately powered by this MR‐TENG in simulated water waves, demonstrating its potential application in water wave energy harvesting.