Direct Switching Research Articles

Coordinating directional switches of multiagent systems with delayed and nonlinear interactions

Coordinating directional switches of multiagent systems with delayed and nonlinear interactions

Effect of contact inhibition locomotion on confined cellular organization

Experiments performed using micro-patterned one dimensional collision assays have allowed a precise quantitative analysis of the collective manifestation of contact inhibition locomotion (CIL) wherein, individual migrating cells reorient their direction of motion when they come in contact with other cells. Inspired by these experiments, we present a discrete, minimal 1D Active spin model that mimics the CIL interaction between cells in one dimensional channels. We analyze the emergent collective behaviour of migrating cells in such confined geometries, as well as the sensitivity of the emergent patterns to driving forces that couple to cell motion. In the absence of vacancies, akin to dense cell packing, the translation dynamics is arrested and the model reduces to an equilibrium spin model which can be solved exactly. In the presence of vacancies, the interplay of activity-driven translation, cell polarity switching, and CIL results in an exponential steady cluster size distribution. We define a dimensionless Péclet number Q—the ratio of the translation rate and directional switching rate of particles in the absence of CIL. While the average cluster size increases monotonically as a function of Q, it exhibits a non-monotonic dependence on CIL strength, when the Q is sufficiently high. In the high Q limit, an analytical form of average cluster size can be obtained approximately by effectively mapping the system to an equivalent equilibrium process involving clusters of different sizes wherein the cluster size distribution is obtained by minimizing an effective Helmholtz free energy for the system. The resultant prediction of exponential dependence on CIL strength of the average cluster size and Q1/2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Q^{1/2}$$\\end{document} dependence of the average cluster size is borne out to reasonable accuracy as long as the CIL strength is not very large. The consequent prediction of a single scaling function of Q, particle density and CIL interaction strength, characterizing the distribution function of the cluster sizes and resultant data collapse is observed for a range of parameters.

Dual‐logic‐in‐memory implementation with orthogonal polarization of van der Waals ferroelectric heterostructure

AbstractThe rapid advancement of AI‐enabled applications has resulted in an increasing need for energy‐efficient computing hardware. Logic‐in‐memory is a promising approach for processing the data stored in memory, wherein fast and efficient computations are possible owing to the parallel execution of reconfigurable logic operations. In this study, a dual‐logic‐in‐memory device, which can simultaneously perform two logic operations in four states, is demonstrated using van der Waals ferroelectric field‐effect transistors (vdW FeFETs). The proposed dual‐logic‐in‐memory device, which also acts as a two‐bit storage device, is a single bidirectional polarization‐integrated ferroelectric field‐effect transistor (BPI‐FeFET). It is fabricated by integrating an in‐plane vdW ferroelectric semiconductor SnS and an out‐of‐plane vdW ferroelectric gate dielectric material—CuInP2S6. Four reliable resistance states with excellent endurance and retention characteristics were achieved. The two‐bit storage mechanism in a BPI‐FeFET was analyzed from two perspectives: carrier density and carrier injection controls, which originated from the out‐of‐plane polarization of the gate dielectric and in‐plane polarization of the semiconductor, respectively. Unlike conventional multilevel FeFETs, the proposed BPI‐FeFET does not require additional pre‐examination or erasing steps to switch from/to an intermediate polarization, enabling direct switching between the four memory states. To utilize the fabricated BPI‐FeFET as a dual‐logic‐in‐memory device, two logical operations were selected (XOR and AND), and their parallel execution was demonstrated. Different types of logic operations could be implemented by selecting different initial states, demonstrating various types of functions required for numerous neural network operations. The flexibility and efficiency of the proposed dual‐logic‐in‐memory device appear promising in the realization of next‐generation low‐power computing systems.image

Structural Basis of Directional Switching by the Bacterial Flagellum.

The bacterial flagellum is a macromolecular protein complex that harvests energy from ion-flow across the inner membrane to power bacterial swimming in viscous fluids via rotation of the flagellar filament. Bacteria such as Salmonella enterica are capable of bi-directional flagellar rotation even though ion flow is uni-directional. How uni-directional ion-movement through the inner membrane is utilized by this macromolecular machine to drive bi-directional flagellar rotation is not understood, but a chemotactic response regulator in the cytoplasm is known to reverse the direction of rotation. We here present cryo-EM structures of intact Salmonella flagellar basal bodies, including the cytoplasmic complexes required for power transmission, in conformations representing both directions of rotation. The structures reveal that the conformational changes required for switching the direction of rotation involve 180 degree rotations of both the N- and C-terminal domains of the FliG protein. Combining these models with a new, high-resolution, cryo-EM structure of the MotA5B2 stator, in complex with the C-terminal domain of FliG, reveals how uni-directional ion-flow across the inner membrane is used to accomplish bi-directional rotation of the flagellum.

Phase-change in topological chiral phononic crystal for directional coupling switch

Recently, acoustic valley Hall topological insulators have become a cutting-edge area of acoustic physics, where the topological phase transition in phononic crystals shows the presence of band inversion through the Dirac point in the momentum space. We developed a 2D hexagonal lattice chiral phononic crystal using reconfigurable construction by extending one side of the original rectangular rods. When the variation of the side length was from left to right, the topological phase transition is triggered by reopening the Dirac degeneracies beyond high-symmetry points in the first Brillouin zone. We numerically showed valley edge state’s propagation through the interface bent toward distinct chiral topological phononic crystals. Moreover, we assembled 2 × 2 cross-waveguides with a defect cavity based on double heterostructure interfaces. The simulated results verify that the phase change is achieved by the directional coupling switching. This research possibly paves the way for exploiting valley edge states to design the complex acoustic waveguide.

A singular stochastic control problem with direction switching cost

We introduce a new class of singular stochastic control problems in which the process controller not only chooses the push intensity, at a price proportional to the displacement caused by his action, but he can also change the allowable control direction, paying a fixed cost for each such switching. Singular control of the one-dimensional Brownian motion with quadratic instantaneous cost function and costly direction switching on the infinite time horizon is analyzed in detail, leading to a closed-form solution. This example is used as an illustration of qualitative differences between the class of problems considered here and classic singular stochastic control.

Anomalous Laser-Fluence Dependence of Electron Spin Excitation in CdS Colloidal Quantum Dots: Surface Effects.

Electron spin dynamics in CdS quantum dots (QDs) with hole acceptor 1-octanethiol organic molecules are investigated by time-resolved ellipticity spectroscopy. An anomalous dependence of laser fluences on electron spin excitation for the first time is reported. Increasing the laser fluence, the electron spin is switched from one direction to an antiparallel direction (spin direction switching, SDS) when adding enough 1-octanethiol hole acceptors in an air atmosphere. The analysis shows that the electron spin direction changes from heavy hole excitation defined to spin-orbit split hole excitation defined. In as-grown CdS QDs with native ligands, laser-fluence-dependent SDS phenomena are absent. Electron wave function spread into 1-octanethiol molecules is demonstrated to be important for the presence of SDS phenomena. The finding here thus reveals the importance of surface conditions on electron spin excitation processes in semiconductor QDs and that the surface can be used as an important factor to manipulate the spin.

Ferrocenyl-Substituted Triazatruxenes: Synthesis, Electronic Properties, and the Impact of Ferrocenyl Residues on Directional On-Surface Switching on Ag(111).

We report on seven new ferrocenyl-(1, 3)- and ferrocenylethynyl-modified N,N',N″-triethyltriazatruxenes (EtTATs) 4-7 as well as the dodecyl counterpart 2 of compound 1 and their use as molecular switching units when deposited on a Ag(111) surface. Such functional units may constitute a new approach to molecule-based high-density information storage and processing. Besides the five compounds 1-3, 6, and 7, where the 3-fold rotational symmetry of the triazatruxene (TAT) template is preserved, we also included 2-ethynylferrocenyl-TAT 4 and 2,2'-di(ethynylferrocenyl)-TAT 5, whose mono- and disubstitution patterns break the 3-fold symmetry of the TAT core. Voltammetric studies indicate that the ferrocenyl residues of compounds 1-7 oxidize prior to the oxidation of the TAT core. We have noted strong electrostatic effects on TAT oxidation in the 2,2',2″-triferrocenyl-TAT derivatives 1 and 2 and the 3,3',3″-isomer 3. The oxidized complexes feature multiple electronic excitations in the near-infrared and the visible spectra, which are assigned to dδ/δ* transitions of the ferrocenium (Fc+) moieties, as well as TAT → Fc+ charge-transfer transitions. The latter are augmented by intervalence charge-transfer contributions Fc → Fc+ in mixed-valent states, where only a part of the available ferrocenyl residues is oxidized. EtTAT was previously identified as a directional three-level switching unit when deposited on Ag(111) and constitutes a trinary-digit unit for on-surface information storage. The symmetrically trisubstituted compound 6 retains this property, albeit at somewhat reduced switching rates due to the additional interaction between the ferrocenyl residues and the Ag surface. In particular, the high directionality at low bias and the inversion of the preferred sense of the on-surface rocking motion with either a clockwise or counterclockwise switching sense, depending on the identity of the surface enantiomer, are preserved. Unsymmetrical substitution in mono- and diferrocenylated 4 and 5 alters the underlying ratchet potential in a manner such that a two-state switching between the two degenerate surface conformations of 4 or a pronounced suppression of switching (5) is observed.

Is part-night lighting a suitable mitigation strategy to limit Artificial Light at Night effects on the biological rhythm at the behavioral and molecular scales of the oyster Crassostrea gigas?

Artificial Light at Night (ALAN) is a fast-spreading threat to organisms, especially in coastal environments, where night lighting is increasing due to constant anthropization. Considering that ALAN affects a large diversity of coastal organisms, finding efficient solutions to limit these effects is of great importance but poorly investigated. The potential benefit of one strategy, in particular, should be studied since its use is growing: part-night lighting (PNL), which consists in switching off the lights for a few hours during nighttime. The aim of this study is to investigate the positive potential of the PNL strategy on the daily rhythm of the oyster Crassostrea gigas, a key species of coastal areas of ecological and commercial interest. Oysters were exposed to a control condition and three different ALAN modalities. A realistic PNL condition is applied, recreating a strategy of city policy in a coastal city boarding an urbanized bay (Lanton, Arcachon Bay, France). The PNL modality consists in switching off ALAN direct sources (5 lx) for 4 h (23−3 h) during which oysters are in darkness. Then, a PNL + skyglow (PNL + S) modality reproduces the previous one mimicking a skyglow (0.1 lx), an indirect ALAN source, during the direct lighting switch off, to get as close as possible to realistic conditions. Finally, the third ALAN condition mimics full-night direct lighting (FNL). Results revealed that PNL reduces some adverse effects of FNL on the behavioral daily rhythm. But, counterintuitively, PNL + S appears more harmful than FNL for some parameters of the behavioral daily rhythm. PNL + S modality is also the only one that affect oysters' clock and melatonin synthesis gene expression, suggesting physiological consequences. Thus, in realistic conditions, the PNL mitigation strategy might not be beneficial in the presence of skyglow, seeing worse for a coastal organism such as the oysters.

Nonlinear Quadratic Regulator Design With a Hybrid Switching Scheme for Wind Turbine Generators

This article proposes a new control scheme with a nonlinear quadratic regulator (NQR) associated with a hybrid switching stage for permanent magnet synchronous generator-based wind turbines (WTs). The proposed method shows a new approach combining a nonlinear optimal control method with a hybrid switching stage for WT generations (WTGs). As the WTG is a nonlinear system, NQR control design is directly employed to deal with the nonlinearity while a hybrid switching scheme can deal with constrained control inputs as discrete nonlinear characteristics of switch-mode power converters. A polynomial-based dynamic model is derived for the new NQR design. Unlike the previous state-dependent Riccatti equation (SDRE) technique where the solution of the nonlinear optimal controller is approximated, this technique finds the exact online solution of SDRE with nonlinear feedback gains flexibly depending on the tracking error. Then, the optimal control laws are implemented via a hybrid switching stage ensuring a smooth current regulation under a reduced switching frequency while avoiding any complicated modulator or finite state search. The proposed control design is investigated via comparative studies with linear quadratic regulator (LQR), direct switching, and space-vector pulse-width-modulation stages (SV-PWMs) implemented in both platforms of MATLAB/Simulink and real-time OPAL-RT. Comparative results exhibit flexible optimal performances via online hyper-parameter tuning to reduce the speed tracking error and low current ripples under a reduced switching frequency.

Sensitivity analysis of a dielectric loaded 1 × 2 directional coupler switch based on foundry process optical waveguides

Sensitivity analysis of a dielectric loaded 1 × 2 directional coupler switch based on foundry process optical waveguides

Manipulating nanoliter fluid circuits on an all-glass chip by the magnetic field

Actively controlled nanoliter fluid circuits are an urgently needed technology in electronics, biomedicine, chemical synthesis, and biosensing. The difficulty lies in how to drive the microfluid in an isolated and airtight manner in glass wafer. We used a magnetic oscillator pump to realize the switching of the circulation direction and controlling the flow rate of the 10nL fluid. Results of two-dimensional numerical simulations shows that the flow field can reach a steady state and a stable flow can be obtained. The contribution of each vibration cycle to the flow rate is proportional to the frequency, decays exponentially with the viscosity, is proportional to the 4.2 power of the amplitude, and is proportional to the radius. Compared with the existing fluid technology, this technology realizes the steering and flow control of a fully enclosed magnetic control fluid circuit as small as 10nL in hard materials for the first time.

Optogenetic control of migration of contractile cells predicted by an active gel model

Cell crawling on flat substrates stems from intracellular flows of the actin cytoskeleton that are driven by both actin polymerization at the front and myosin contractility at the back. Optogenetics makes it experimentally possible to spatially control contraction and possibly cell migration too. Here we theoretically analyze this situation using a one-dimensional active gel model that reflects the property of myosin II to assemble into minifilaments. Our model predicts bistability between sessile and motile solutions when cell adhesion and contractility are sufficiently large and in balance. We show that one can switch between the different states at realistic parameter values via optogenetic activation or inhibition of contractility, in agreement with recent experiments performed for neutrophils in microchannels. We predict the required activation strengths and initiation times, compare the effects of local and global increases of myosin II levels, and show that actin polymerization alone can affect a switch in direction only at high strength.

Bidirectional terahertz plasmonic switch based on periodically structured graphene

A plasmonic crystal structure is proposed and simulated based on graphene at terahertz frequency using the three-dimensional finite element method. The proposed model involves both an ON/OFF and a directional switch. Implementing a crystalline structure in graphene can enhance absorption since such a structure creates a bandgap wherein no propagation mode is allowed. Accordingly, the ON/OFF and directional switches can be designed with an extinction ratio higher than 30 dB. Other advantages of this structure are its high quality factor and small dimensions of 1 µm (for the ON/OFF switch) and 2 µm (for the directional switch).

An investigation of compliant contact force models applied for analysis of simultaneous, multi-zone impacts of particles

Compliant contact force models were developed and mainly used to investigate simple impacts of two bodies. It is therefore unclear how they will perform in more complex cases, where simultaneous, multi-zone impact may occur. The aim of this study is to investigate phenomena that occur in such impacts and to study the effectiveness of preselected contact force models in their modelling. For this purpose, the study addressed collisions that occur in a collinear system of 3 to 6 particles made of steel, aluminium, and bronze. The results obtained for each force model were referenced to the FEM analysis. To compare the performance of the models, the Benchmark Velocity Indicator (BVI) is proposed. The study showed that during simultaneous, multi-zone impact direct switch from the restitution to compression phases may occur and subsequent collision along the same normal may take place. Such phenomena are not incorporated in current compliant contact force models; therefore, the study showed the need for their further improvement. The best models proposed by Kogut and Etsion (KE) and Jackson and Green (JG) achieved average errors equal to 3.89% and 4.15%, respectively. However, the same models in their worst cases reached error values of 38.66% and 33.77%. The article concludes with proposals for future improvements.

Study on Active Disturbance Rejection Control of Permanent Magnet Synchronous Motor Based on Variable Structure Extended State Observer

Linear extended state observer (linear extended state observer, LESO) is the core component of linear active disturbance rejection control (linear active disturbance rejection control, LADRC), and its performance is critical to the control effect. The linear ADRC is applied to the speed loop of the permanent magnet synchronous motor control system with a double closed-loop control strategy. By adding a scale factor to the linear extended state observer, the utilization efficiency of the observed signal and the observation speed is improved. On this basis, a hybrid switching strategy is adopted to achieve a smooth transition between the traditional ESO and the improved ESO, avoiding the motor speed imbalance and motor chattering caused by direct switching. Finally, the improved ADRC strategy and the traditional ADRC strategy are compared and analyzed through simulation, which verifies the effectiveness and superiority of the improved strategy.

Utilization and Predictors of Adjuvant Metformin for Children and Adolescents on Mixed Receptor Antagonists (Second-Generation Antipsychotics)

To examine utilization and predictors of adjuvant metformin among pediatric recipients of second-generation antipsychotics (SGAs) (mixed receptor antagonist). This study used 2016-2021 data of a national electronic medical record database. Eligible participants were children aged 6 to 17 with a new SGA prescription for at least 90 days. Predictors of prescribing adjuvant metformin in general and to nonobese pediatric SGA recipients in particular were assessed using conditional logistic regression and logistic regression analyses, respectively. Of 30,009 pediatric SGA recipients identified, 2.3% (n= 785) received adjuvant metformin. Among 597 participants with a body mass index z score documented during the 6-month period before metformin initiation, 83% were obese, and 34% had either hyperglycemia or diabetes. Significant predictors for metformin prescribing were high baseline body mass index z score (odds ratio [OR] 3.5, 95% CI 2.8-4.5, p< .0001), having hyperglycemia or diabetes (OR 5.3, 95% CI 3.4-8.3, p< .0001), and undergoing a switch from a higher metabolic risk SGA to a lower risk one (OR 9.9, 95% CI 3.5-27.5, p= .0025) or a switch in the opposite direction (OR 4.1, 95% CI 2.1-7.9, p= .0051) compared with no switch. Nonobese metformin users were more likely to have a positive body mass index z score velocity before metformin initiation than their obese counterparts. Receiving the index SGA prescribed by a mental health specialist was associated with higher likelihood of receiving adjuvant metformin and receiving metformin before the development of obesity. Utilization of adjuvant metformin among pediatric SGA recipients is uncommon, and early introduction of the medication among nonobese children is rare.

Angiographic analysis of ophthalmic artery flow direction in children undergoing chemosurgery for retinoblastoma compared to age-matched controls.

Catheter-based intra-arterial chemotherapy (IAC) has revolutionized the treatment of retinoblastoma (RB). Variability in ophthalmic artery (OA) flow, either retrograde from external carotid artery branches, or anterograde from the internal carotid artery, necessitates multiple IAC techniques. We evaluated the direction of OA flow and identify OA flow reversal events over the course of IAC treatment as well in comparison to OA flow direction in non-RB children. We performed a retrospective analysis of OA flow direction in all RB patients treated with IAC, along with an age-matched control group who underwent cerebral angiography at our center from 2014 to 2020. IAC was administered to a total of 18 eyes (15 patients). Initial anterograde OA flow was demonstrated in 66% (n = 12) of eyes. Five OA reversal events were identified (3/5 anterograde-to-retrograde). All five events were in patients receiving multiagent chemotherapy. No correlation was found between OA flow reversal events and the initial IAC technique. A control group of 88 angiograms representing 82 eyes (41 patients) was utilized. The anterograde flow was observed in 76 eyes (86.4%). Our control group included 19 patients with sequential angiograms. One OA flow reversal event was identified. OA flow direction is dynamic in IAC patients. Anterograde and retrograde OA directional switches do occur and may necessitate delivery technique variation. In our analysis, all OA flow reversal events were associated with multiagent chemotherapy regimens. Both anterograde and retrograde OA flow patterns were observed in our control cohort, suggesting bidirectional flow can occur in non-RB children.

Multiple Magnetic Phase Transitions and Critical Behavior in Single-Crystal SmMn2Ge2

Magnetic materials with noncollinear spin configurations have engendered significant interest in condensed matter physics due to their intriguing physical properties. We direct our attention towards the magnetic properties and critical behavior of single-crystal SmMn2Ge2, an itinerant magnet with numerous temperature-dependent magnetic phase transitions. Notably, SmMn2Ge2 displays significant magnetic anisotropy with easy magnetization direction switching from the c axis to the ab plane as temperature decreases. The critical behavior of the ferromagnetic transition occurring above room temperature is thoroughly examined. Reliable and self-consistent critical exponents, including β = 0.292(2), γ = 0.924(8), and δ = 4.164(6), along with the Curie temperature T c = 347 K, are extracted through various methods, which provide evidence for the coexistence of multiple magnetic interactions in SmMn2Ge2. Further analysis reveals that the magnetic interaction of SmMn2Ge2 is a long-range type with the interaction distance decaying as J(r) ∼ r −4.35.

The Simple View of borrowing and code-switching

Aims and Objectives: In this paper, a novel approach to the distinction between borrowing and code-switching is proposed, called the Simple View of borrowing and code-switching. Under this view, listedness is seen as the key condition for classifying words or multiword units (MWUs) as borrowings. For MWUs, listedness is operationalized with mutual information (MI) scores: the higher the MI score of a given set of words, the higher the likelihood it is listed in the lexicon. Under the Simple View, the distinction between borrowing and code-switching is seen as a specific instantiation of the distinction between what belongs in the lexicon (fixed, arbitrary patterns) and what is computed online (productive rules), and should therefore be considered as part of the grammar. Methodology: Assumptions from the Simple View were tested on a corpus of switches of single words and MWUs from a Turkish-German code-switching corpus (87,000 words), which was transcribed in CHAT format. Data and analysis: The frequency of switches in either direction, and their morphosyntactic integration patterns were analysed with CLAN. The formulaicity of the MWUs was analysed with MI scores through Sketchengine. Findings: The MI scores of the donor language MWUs were found to be above 3, which is the cut-off point for formulaicity in Corpus Linguistics. Thus, the MWUs were found to be borrowings. In addition, MWUs were found to be more likely to be borrowed than single words. Originality: Insights about formulaic language from Corpus Linguistics and Second Language Acquisition were used to inform analyses of language contact phenomena, and new ways to test the model are proposed. Significance: The Simple View offers a unified approach to borrowing of lexical items and function words and opens a new avenue for research using neuroscientific methods to test whether items are listed in speakers’ mental lexicons.