Instant Switching Research Articles

A self-stiffening compliant intracortical microprobe

Utilising a flexible intracortical microprobe to record/stimulate neurons minimises the incompatibility between the implanted microprobe and the brain, reducing tissue damage due to the brain micromotion. Applying bio-dissolvable coating materials temporarily makes a flexible microprobe stiff to tolerate the penetration force during insertion. However, the inability to adjust the dissolving time after the microprobe contact with the cerebrospinal fluid may lead to inaccuracy in the microprobe positioning. Furthermore, since the dissolving process is irreversible, any subsequent positioning error cannot be corrected by re-stiffening the microprobe. The purpose of this study is to propose an intracortical microprobe that incorporates two compressible structures to make the microprobe both adaptive to the brain during operation and stiff during insertion. Applying a compressive force by an inserter compresses the two compressible structures completely, resulting in increasing the equivalent elastic modulus. Thus, instant switching between stiff and soft modes can be accomplished as many times as necessary to ensure high-accuracy positioning while causing minimal tissue damage. The equivalent elastic modulus of the microprobe during operation is ≈ 23 kPa, which is ≈ 42% less than the existing counterpart, resulting in ≈ 46% less maximum strain generated on the surrounding tissue under brain longitudinal motion. The self-stiffening microprobe and surrounding neural tissue are simulated during insertion and operation to confirm the efficiency of the design. Two-photon polymerisation technology is utilised to 3D print the proposed microprobe, which is experimentally validated and inserted into a lamb’s brain without buckling.

Instant switching control between two types of plasma-driven liquid flows

Plasma-driven liquid flows that are generated in bulk liquid by plasma irradiation are one of the key factors in understanding the interaction between plasma and liquid. In this work, the direction of the plasma-driven liquid flow was successfully switched and controlled only by changing the frequency of argon plasma jet generation. The liquid flow could switch in the opposite direction within 3 s after the frequency change. Changes in the emission spectra with frequency have an important effect on the liquid flows, with results from current waveforms indicating that the frequency also changes the characteristics of the plasma jet.

Temporally modulated metamaterial based on a multilayer graphene structure

The recently developed concept of time-varying metamaterials paves the way for advanced methods of electromagnetic property modulation, such as magnet-free isolators, frequency converters, and other nonreciprocal photonic components. Here, we analyze the metamaterial based on the periodically arranged temporally modulated graphene layers via a steplike graphene Fermi level. The material properties are described by the effective medium theory. The electromagnetic wave temporal scattering phenomenon caused by rapid steplike graphene Fermi level switching is considered. It is demonstrated that the frequency of scattered waves increases as the Fermi level grows rapidly and vice versa. The relation between the amplitudes of forward- and backward-scattered waves is found using the Laplace transform technique. The proposed concept allows us to efficiently generate frequency harmonics under instant switching of the graphene Fermi level at a few meV. Our investigation provides a basement for the realization of temporally modulated multilayer structures based on functional tunable materials as power-efficient frequency converters.

A Portable Ultrawideband Confocal Raman Spectroscopy System with a Handheld Probe for Skin Studies.

Confocal Raman spectroscopy (CRS) has shown potential in non-invasive skin analysis. However, current CRS systems have various limitations including a narrow detection band, large size, non-flexibility, slowness, and complexity, which hinder their clinical applications. Herein, we developed a portable ultrawideband CRS system with a fiber-based handheld probe to acquire the Raman spectra in both fingerprint and high wavenumber regions in a fast and quasi-simultaneous way. Dual-wavelength excitation with a dual-passband laser cleaning filter and high-speed fiber array multiplexer was adopted instead of a specialized grating and detector to achieve instant switching between the detection regions and improve system robustness. Preliminary in vivo results demonstrated its depth profiling capability in an ultrawide detection range for stratum corneum thickness, natural moisturizing factor, and water content quantification, indicating its great potential in a wide range of clinical and cosmeceutical applications.

Impact of the Ferroelectric Stack Lamination in Si Doped Hafnium Oxide (HSO) and Hafnium Zirconium Oxide (HZO) Based FeFETs: Toward High-Density Multi-Level Cell and Synaptic Storage

A multi-level cell (MLC) operation as a 1–3 bit/cell of the FeFET emerging memory is reported by utilizing optimized Si doped hafnium oxide (HSO) and hafnium zirconium oxide (HZO) based on ferroelectric laminates. An alumina interlayer was used to achieve the thickness independent of the HSO and HZO-based stack with optimal ferroelectric properties. Various split thicknesses of the HSO and HZO were explored with lamination to increase the FeFET maximum memory window (MW) for a practical MLC operation. A higher MW occurred as the ferroelectric stack thickness increased with lamination. The maximum MW (3.5 V) was obtained for the HZO-based laminate; the FeFETs demonstrated a switching speed (300 ns), 10 years MLC retention, and 104 MLC endurance. The transition from instant switching to increased MLC levels was realized by ferroelectric lamination. This indicated an increased film granularity and a reduced variability through the interruption of ferroelectric columnar grains. The 2–3 bit/cell MLC levels and maximum MW were studied in terms of the size-dependent variability to indicate the impact of the ferroelectric area scaling. The impact of an alumina interlayer on the ferroelectric phase is outlined for HSO in comparison to the HZO material. For the same ferroelectric stack thickness with lamination, a lower maximum MW, and a pronounced wakeup effect was observed in HSO laminate compared to the HZO laminate. Both wakeup effect and charge trapping were studied in the context of an MLC operation. The merits of ferroelectric stack lamination are considered for an optimal FeFET-based synaptic device operation. The impact of the pulsing scheme was studied to modulate the FeFET current to mimic the synaptic weight update in long-term synaptic potentiation/depression.

Metal Ion Mediated Instant Z → E Isomerization of Azobenzene Macrocycles in the Absence of Light.

The classical photoswitch azobenzenes reversibly interconvert between the E- and the Z-isomers with light. Here, we report a pair of new macrocyclic azobenzenes characterized thoroughly by spectroscopic methods and single crystal X-ray diffraction structures, and one of the compounds displays a quantitative conversion of the E- to the Z-form. These compounds, besides their normal photoswitching behavior, display an unusual instant switching of the Z-form to the E-isomer in the presence of Cu2+ ions in the dark under 273 K. The Cu2+ complex can stay in the Z-form under constant UV radiation. However, it reverts to the E-form as soon as the exposure to the UV is ceased. The same phenomenon is also observed with Ag+ ions albeit it is a bit slower. This unusual instant switching of the azobenzene systems with metal ions prompted the detailed studies to unravel the reason behind this behavior.

Реализация игровых технологий при дистанционном обучении русскому языку как иностранному

The possibilities of implementing game technologies for distance learning of Russian as a foreign language using online services are considered. The relevance of the work is due to the development of education digitalization and the high didactic potential of gaming. The purpose of this study is to formulate guidelines for the selection of Web 2.0 services for the implementation of gaming technologies aimed at the development of linguistic, communicative, linguistic-cultural competences of foreign students in the course of distance learning of their Russian language. The study analyzed the techniques and methods of using online game tasks in teaching Russian as a foreign language from the standpoint of the following features: methodic tasks, distance learning format, the number of players, the presence of automatic verification of answers, the nature of the choice, the presence of a creative component, the possibility of instant switching of the game template within one content, translation features. It is concluded that many traditional game tech-niques that have become habitual in face-to-face work can be applied in distance learning. Online tools make it possible to organize manipulative play activities, team play, and communication in a digital environment in a form that is fun for students. The results of this study are essential both for understanding the methodoic features of the organizing distance learning process in general, and for the effective use of gaming technologies when teaching Russian to foreigners.

Kinetic-contact-driven gigantic energy transfer in a two-dimensional Lennard-Jones fluid confined to a rotating pore.

A two-dimensional Lennard-Jones system in a circular and rotating container has been studied by means of molecular dynamics technique. A nonequilibrium transition to the rotating stage has been detected in a delayed time since an instant switching of the frame rotation. This transition is attributed to the increase of the density at the wall because of the centrifugal force. At the same time the phase transition occurs, the inner system changes its configuration of the solid-state type into the liquid type. Impact of angular frequency and molecular roughness on the transport properties of the nonrotating and rotating systems is analyzed.

Technique of Training of Volleyball Players of 14-15 Years to Competitions Taking into Account Properties of Attention

Work is devoted by studying of a technique of preparation for competitive activity of volleyball players of 14-15 years taking into account properties of attention. Continuous interactions of players with a ball and among themselves promote improvement of deep and peripheral sight, accuracy and orientation in space. Besides, the volleyball develops also instant switching of attention from one object on another, increases muscular feeling and ability to fast alternations of tension and relaxations of muscles, and also ability to focus attention on the most important point in various game situations. Research helped to define, what properties of attention are most developed at players of various roles and who demand improvement. Having introduced the technique including 38 psycho-technical games-exercises we drew a conclusion, they can be used as a development tool of properties of attention as by the end of research in experimental group the gain of indicators of properties of attention was observed.

The smooth switching gain-scheduled control with H<SUP align="right">∞</SUP> performance to the application of TORA systems

The function of switching logics is crucial to the operation of switching control systems. This paper investigates the smooth switching control approach for linear parameter varying systems, in which the control law for neighbouring subsystems is smoothly switched or scheduled in the overlapped region instead of employing the usual instant switching methods. The proposed approach is designed in terms of the achieved ∞ performance level under control input and system output variable constraints. The control law is constructed based on the parameterised linear matrix inequality conditions. The effectiveness of the proposed approach is demonstrated by disturbance attenuation of the non-linear translational oscillator with rotational actuator systems in a quasi-linear parameter varying system representation.

Time delay of microdialysis in vitro

Background:Microdialysis is a specific and local sampling method to collect free molecules from the extracellular fluid, however, there are no reports on time delay issues of microdialysis applications.Aims:This study was to check the time gap between the start of target molecule changes in detected fluid and corresponding stable concentration formation in the sampled dialysate.Materials and Methods:A designated microdialysis system for free calcium ion was set up in vitro and perfused with saline. The dialysate was diluted synchronously, and collected in a vial every 10 min. The free calcium concentration [Ca++] of the sample was measured by an atomic absorption spectrophotometer. A signal-switching method was introduced to mimic the target molecule [Ca++] changes in the detected fluid, standard calcium solution and saline.Results:There was a notable lag in dialysates [Ca++] for both uprising and down going course in spite of instant switching between the detected fluids. The recovery time (RT) of the microdialysis system was extrapolated to be 20 min for [Ca++] detection.Conclusions:With 10 min sampling interval, [Ca++] time delay of the microdialysis system existed, and could not be estimated precisely beforehand. The signal-switching method was applicable for RT calibration in vitro with a dedicated microdialysis system.

An instant-switching ∆–Σ fractional-N frequency synthesizer with adjustable duty cycles

A Phase-Locked Loop (PLL)-based frequency synthesizer (FS) with adjustable duty cycle is presented. By employing digital processing circuitry and the ?---Σ fractional-N technique, the FS is capable of generating arbitrary frequencies in a wide frequency range, and capable of adjusting the clock duty cycles. In addition, the switching between different frequencies is instant except when a very fine frequency resolution is required. The adjustable duty cycle and instant switching are desired features in applications such as time-interleaved Analog-to-Digital-Converters (ADCs), switched-capacitor circuits, and DC---DC converters. The design was fabricated using a 0.13 μm CMOS process. This paper gives the theories, analysis, implementation, and measurement results of this FS.

Josephson Junction Comparator as a Quantum-Limited Detector for Flux Qubit Readout

We have applied the Langevin-Heisenberg-Lax formalism for dissipative quantum systems to a balanced Josephson junction comparator operating as a fast, single-shot detector of state of a flux (rf-SQUID) qubit. Earlier experiments and theoretical analysis have shown that such a detector may reach quantum- limited resolution when it measures signal from a high-impedance (current) source. In this work, we have calculated the flux resolution of a detector for a signal source with finite inductive impedance (e.g., a flux qubit) for both an instant switching of the comparator, and for its switching with a realistic SFQ driver. The results show that the flux resolution may be quite high: for typical experimental parameters, the signal-to-noise ratio may be on the order of 10, at 10-ps-scale measurement time. Moreover, the natural energy measure of the resolution, Eout, may be made (within a narrow range of parameters) smaller than planck/2. This situation is similar to the case of continuous flux measurements using SQUIDs. In both cases, a more adequate sensitivity measure requires an account of the fluctuation back-action of the detector on the signal source. In this work we have shown that in the case of single-shot measurements, the back-action effects as characterized by the information/dephasing measure, may be brought down to their fundamental limit by at least two methods: coupling quenching and feedback compensation.

A Neural Circuit Model of Flexible Sensorimotor Mapping: Learning and Forgetting on Multiple Timescales

Volitional behavior relies on the brain's ability to remap sensory flow to motor programs whenever demanded by a changed behavioral context. To investigate the circuit basis of such flexible behavior, we have developed a biophysically based decision-making network model of spiking neurons for arbitrary sensorimotor mapping. The model quantitatively reproduces behavioral and prefrontal single-cell data from an experiment in which monkeys learn visuomotor associations that are reversed unpredictably from time to time. We show that when synaptic modifications occur on multiple timescales, the model behavior becomes flexible only when needed: slow components of learning usually dominate the decision process. However, if behavioral contexts change frequently enough, fast components of plasticity take over, and the behavior exhibits a quick forget-and-learn pattern. This model prediction is confirmed by monkey data. Therefore, our work reveals a scenario for conditional associative learning that is distinct from instant switching between sets of well-established sensorimotor associations.

Electrokinetic-driven microfluidic system in poly(dimethylsiloxane) for mass spectrometry detection integrating sample injection, capillary electrophoresis, and electrospray emitter on-chip

A novel microsystem device in poly(dimethylsiloxane) (PDMS) for MS detection is presented. The microchip integrates sample injection, capillary electrophoretic separation, and electrospray emitter in a single substrate, and all modules are fabricated in the PDMS bulk material. The injection and separation flow is driven electrokinetically and the total amount of external equipment needed consists of a three-channel high-voltage power supply. The instant switching between sample injection and separation is performed through a series of low-cost relays, limiting the separation field strength to a maximum of 270 V/cm. We show that this set-up is sufficient to accomplish electrospray MS analysis and, to a moderate extent, microchip separation of standard peptides. A new method of instant in-channel oxidation makes it possible to overcome the problem of irreversibly bonded PDMS channels that have recovered their hydrophobic properties over time. The fast method turns the channel surfaces hydrophilic and less prone to nonspecific analyte adsorption, yielding better separation efficiencies and higher apparent peptide mobilities.

Translocation Mechanism of Long Sugar Chains across the Maltoporin Membrane Channel

Maltoporin allows permeation of long maltodextrin chains. It tightly binds the amphiphilic sugar, offering both hydrophobic interactions with a helical lane of aromatic residues and H bonds with ionic side chains. The minimum-energy path of maltohexaose translocation is obtained by the conjugate peak refinement method, which optimizes a continuous string of conformers without applying constraints. This reveals that the protein is passive while the sugar glides screw-like along the aromatic lane. Near instant switching of sugar hydroxyl H bond partners results in two small energy barriers (of ∼4 kcal/mol each) during register shift by one glucosyl unit, in agreement with a kinetic analysis of experimental dissociation rates for varying sugar chain lengths. Thus, maltoporin functions like an efficient translocation “enzyme,” and the slow rate of the register shift (∼1/ms) is due to high collisional friction.

Monolayer control of chemical beam etching

An etching process with real-time monitoring of each monolayer removed is demonstrated. This etching capability which we refer to as monolayer chemical beam etching (ML-CBET) is achieved by employing in-situ reflection high energy electron diffraction (RHEED) intensity oscillation monitoring during etch. The etching is accomplished by injecting AsCl 3 or PCl 3 gas directly into the growth chamber at a temperature comparable to the typical growth temperature in the same system. This permits instant switching from etching to growth and vice versa in the same experimental run. The combination of growth and etch in a single chamber with both controllable at atomic scale presents a very powerful processing method for the fabrication of intergrated devices that require multiple steps of etch and regrowth. We have also identified the roughening mechanism during etch and present the methods to obtain excellent morphology through a migration enhanced smoothing mechanism.

In-situ dry etching of InP using phosphorus trichloride and regrowth inside a chemical beam epitaxial growth chamber

We have extended the capability and versatility of a chemical beam epitaxial (CBE) system by demonstrating reactive chemical beam etching (CBET) of InP using phosphorus tri-chloride (PCI 3) as the gaseous etching beam injected directly into the growth chamber. This permits instant switching from etching to growth (and vice versa) in the same run for the first time in CBE. We investigated CBET of InP at various substrate temperatures between ∼ 400 and 580°C, under different PCI 3 fluences, and etching conditions. Excellent surface morphology was obtained at high temperatures (≳530−570°C) and under an etching rate of ≲6 Å/s. We also found that upon addition of trimethylindium flow equivalent to a growth rate of 1 Å/s during CBET, a dramatic improvement in surface morphology was obtained even at a high net etching rate of 10 Å/s. The surface morphology obtained under such conditions is indistinguishable from that of the original substrate surface. Using SiO 2 as a mask, selective-area etching and etching followed immediately by regrowth having excellent etched and regrown morphologies were obtained. For CBET of GaAs, we employed arsenic tri-chloride (AsCl 3) in a similar manner. Furthermore, PCl 3 and AsCl 3 may be used as alternative etching gases to hydrogen chloride or carbon tetrachloride in a metalorganic vapor phase epitaxial reactor.

Monolayer chemical beam etching

We have developed an etching process with real-time counting of each monolayer removed, thus achieving etching with monolayer precision and control. This is an exact reversal of molecular beam epitaxy or more specifically in this case, chemical beam epitaxy (CBE). This new etching capability which we refer to as monolayer chemical beam etching (ML-CBET) is achieved by employing in-situ reflection high energy electron diffraction (RHEED) intensity oscillation monitoring during etching. Etching is accomplished in high vacuum by injecting AsCl 3 directly into a CBE growth chamber impinging on a heated GaAs substrate surface. Having both epitaxial growth and etching integrated in the same process and both capable of ultimate control down to the atomic layer precision represents a very powerful combination. This permits instant switching from growth to etching and vice versa, clean regrown interfaces critical for device applications, direct modification of surface chemistries during etching or growth, and high temperature etching (500–570°C for InP and 500–650°C for GaAs) unachievable in conventional etching processes. The temperature and flux dependence of etching rates are also studied using RHEED oscillations. Results indicate that ML-CBET is predominantly via a layer-by-layer mechanism under the present etching conditions studied.

Monolayer chemical beam etching: Reverse molecular beam epitaxy

We have developed an etching process with real-time counting of each monolayer removed, thus achieving etching with monolayer precision and control. This is an exact reversal of molecular beam epitaxy or more specifically in this case, chemical beam epitaxy (CBE). This new etching capability which we refer to as monolayer chemical beam etching (ML-CBET) is achieved by employing in situ reflection high-energy electron diffraction (RHEED) intensity oscillation monitoring during etching. Etching is accomplished in high vacuum by injecting AsCl3 directly into a CBE growth chamber impinging on a heated GaAs substrate surface. Having both epitaxial growth and etching integrated in the same process and both capable of ultimate control down to the atomic layer precision represents a very powerful combination. This permits instant switching from growth to etching and vice versa, clean regrown interfaces critical for device applications, direct modification of surface chemistries during etching or growth, and high temperature etching (500–570 °C for InP and 500–650 °C for GaAs) unachievable in conventional etching processes. The temperature and flux dependence of etching rates are also studied using RHEED oscillations. Results indicate that ML-CBET is studied predominantly via a layer-by-layer mechanism under the present etching conditions.