Output Signal Research Articles

Cortical HFS-induced neo-Hebbian local plasticity enhances efferent output signal and strengthens afferent input connectivity.

High-frequency stimulation (HFS)-induced long-term potentiation (LTP) is generally regarded as a homosynaptic Hebbian-type LTP, where synaptic changes are thought to occur at the synapses that project from the stimulation site and terminate onto the neurons at the recording site. In this study, we first investigated HFS-induced LTP on urethane-anesthetized rats and found that cortical HFS enhances neural responses at the recording site through the strengthening of local connectivity with nearby neurons at the stimulation site, rather than through synaptic strengthening at the recording site. This enhanced local connectivity at the stimulation site leads to increased output propagation, resulting in signal potentiation at the recording site. Additionally, we discovered that HFS can also non-specifically strengthen distant afferent synapses at the HFS site, thereby expanding its impact beyond local neural connections. This form of plasticity exhibits a neo-Hebbian characteristic as it exclusively manifests in the presence of cholecystokinin (CCK) release, induced by HFS. The cortical HFS-induced local LTP was further supported by a behavioral task, providing additional evidence. Our results unveil a previously overlooked mechanism underlying cortical plasticity: synaptic plasticity is more likely to occur around the soma site of strongly activated cortical neurons, rather than solely at their projection terminals.Significance Statement This manuscript reveals that cortical HFS triggers the local release of CCK, a crucial neuromodulator for cortical plasticity, which is released at the HFS site from other cortical efferents rather than in a homosynaptic manner. Therefore, cortical HFS influences long-range cortical efferents through changes at the HFS location, not at the projection terminals. Additionally, the HFS-triggered locally released CCK strengthens long-range afferent synapses to the HFS site. This evidence suggests that a CCK-dependent neo-Hebbian mechanism underlies cortical plasticity.

A New Closed-Loop Control Paradigm Based on Process Moments

The paper presents a new control concept based on the process moment instead of the process states or the process output signal. The control scheme is based on separate control of reference tracking and disturbance rejection. The tracking control is achieved by additionally feeding the input of the process model by the scaled output signal of the process model. The advantage of such feedback is that the final state of the process output can be analytically calculated and used for control instead of the actual process output value. The disturbance rejection, including model imperfections, is controlled by feeding back the filtered difference between the process output and the model output to the process input. The performance of tracking and disturbance rejection is simply controlled by two user-defined gains. Several examples have shown that the new control method provides very good and stable tracking and disturbance rejection performance.

Comparison and performance optimization of two absolute circuit designs based on Multisim

Digital circuits are crucial in today's technology, underpinning infrastructure such as computing, communicating, and intelligent devices. Its high efficiency, accuracy and programmable capability drive the development of information processing, data transmission and automation systems. The application of digital circuits has promoted innovation in artificial intelligence, the Internet of Things and other fields, providing strong support for the intelligence and interconnection of modern society. The absolute value circuit is discussed in this paper. The absolute value circuit is implemented for converting the negative value of the input signal to a positive value, ensuring that the output signal is always non-negative. Its significance is to handle application scenarios that require non-negative values, such as signal processing, audio amplification, and sensor output. Through the absolute value circuit, negative value can avoid the negative effect on the subsequent circuit, and improve the stability and accuracy of the system. This paper first introduces all the gates used in the circuit, points out the functions of each gate circuit, and then puts forward two absolute value circuit designs, explaining their working principles, differences and advantages and disadvantages. Then the minimum delay is analyzed by the critical path logic and the sizes of each logic gate is given. Then the supply voltage is optimized after selecting the design with the smallest delay to reduce energy consumption.

All-fiber magnetic field sensor based on narrow-bandwidth laser internal cavity modulation with coated magnetic fluid

In this paper we present a magnetic probe structure based on magneto-fluidic and laser internal cavity modulation. We used a single-mode-no-core-single-mode fiber structure coated by a magnetic fluid as a sensing element, and inserted the sensing element in the inner cavity of a laser. Highly sensitive, high signal-to-noise ratio (SNR), narrow half-height width (FWHM) sensing signals have been obtained using intra-laser cavity modulation. The magnetic detection sensitivity of the sensor was improved, and a sensing system with a magnetic detection sensitivity of 1.76 × 10−3 mw/Oe and a linearity of 99.709% was achieved. The temperature sensitivity is 0.035 μW/°C. The limit error of the magnetic field sensor is ±0.006035%. Meanwhile, output signal index of the sensing system is FWHM<40pm.

Research on Composite Strain and Stress Sensors Based on Piezoresistive and Triboelectric Effects

Abstract In view of the problems that robotic arms find it difficult to effectively identify and grasp workpieces with different textures and hardness in complex industrial environments, and the low path planning accuracy of robotic arms in practical application scenarios, this paper proposes a composite sensor based on piezoresistive effect and triboelectric effect. The piezoresistive sensor and the triboelectric sensor simultaneously generate output signals, and the identification of different achieves high-precision dynamic monitoring of the robotic arm's gripping objects and joint movements. The base material of the piezoresistive sensor and the negative electrode material of the triboelectric sensor are both porous MXene/PDMS structures. The piezoresistive sensor enhances its conductivity by spin-coating CNT slurry on the surface of the base material and uses PVA hydrogel as the electrode. The triboelectric sensor uses copper as the positive electrode material. Experiments show that the developed sensor has a measurement range (0.015 kPa-70 kPa) and good repeatability. The experiment verifies that the composite sensor can be applied to the high-precision detection of robotic arm's flexible gripping and joint movements.

Engineering Acid-Promoted Two-Photon Ratiometric Nanoprobes for Evaluating HClO in Lysosomes and Inflammatory Bowel Disease.

HClO is considered a potential contributing factor and biomarker of inflammatory bowel disease (IBD). Accurate monitoring of lysosomal HClO is important for further developing specific diagnostic and therapeutic schedules for IBD. However, only rare types of fluorescent probes have been reported for detecting HClO in IBD so far. Herein, an acid-promoted two-photon semiconducting polymer dot (Lyso-RS Pdot) with dual emission in green and red channels and dual-sensing sites is successfully fabricated with two newly designed polymers NADE-PSMA and PFNA-10TBT as precursors. The red conjugated polymer PFNA-10TBT with pH-inert and HClO-sensitive units is employed to evaluate the HClO concentration in turn-off fluorescence. Meanwhile, the amphiphilic green fluorescent polymer NADE-PSMA sensitive to pH and HClO is employed to evaluate the pH value or HClO concentration in turn-on fluorescence. The resultant Lyso-RS Pdots not only display satisfactory performances for detecting HClO and pH but also achieve accurate two-photon imaging of HClO in lysosomes and the colon of IBD mice based on the distinguished properties such as ratiometric signal output, acid-promoted signal amplification, ultrafast response, and two-photon excitation. The results demonstrate that the HClO level in IBD mice is elevated, and the fast early diagnosis of IBD can be achieved through fluorescence imaging by the proposed Lyso-RS Pdots. This work may provide some solid perspectives for fluorescent diagnosis of H+ and HClO-related diseases.

Digitizing Low-Frequency Analog Control Circuit Using Bilinear Function Algorithm

In the past, low-frequency analog control circuits were largely used in analog control systems. With the rapid development of modern digital electronic technology, the digitization of traditional low-frequency analog control circuits while retaining the same functions as the original analog control systems has become an important trend in the field of electronic design. For this reason, this study aimed to develop an analog signal digitization model for control signals at a low frequency below 10 Hz. In terms of signal receiving and transmission requirements, the proposed model is configured with analog-to-digital converter (ADC), digital-to-analog converter (DAC), and pulse width modulation (PWM) functions. In the development environment, the input and output signals are first normalized and processed with PWM, enabling the digital signal processor to deal with analog signal receiving, processing, and external transmission. To replace the existing compensator in analog circuits, a digital compensator is used in the digital signal processor. Based on the bilinear function in MATLAB software, the parameter values demanded for the digital compensator can thus be obtained, achieving the automatic calculation of bilinear transformation in the system. Multisim simulation is then used to simulate analog circuit systems for comparison with the digitized outcomes. The experimental results reveal that the performance of the designed digital control circuit matches the simulation outcomes in both Bode gain (dB) and phase responses when the signal frequency is below 10 Hz. The effectiveness of the digitized analog control circuit for low-frequency control signals is therefore confirmed.

Direct detection method for cusp thickness in wavy thin-film flow using an optical waveguide film

The wave crest (cusp) of the disturbance wave in thin liquid film flow is an important factor contributing to heat/mass transfer, e.g., fuel rods in boiling water reactors, stator/rotor blades in steam turbines, and cleaning/drying wafer processes in semiconductor manufacturing. We developed a new technique for directly detecting the thickness of wave cusps using array-based sensing with an optical waveguide film (OWF). This technique, based on geometrical optics assumptions, simultaneously obtains information on liquid films’ thickness and their interfacial shape, i.e., whether or not the local interface is convex upward. We first performed a pseudo-film flow measurement using a metal specimen to confirm the basic principle. According to the results, a meaningful signal indicating the wave-cusp passage, along with a thickness signal, was detected simultaneously. The OWF signal processing for cusp thickness detection was newly established based on this fact. We then applied this technique to a wavy liquid film flow formed on a flat plate in the entry region. A series of experiments were performed over a wide range of air speeds (jG = 20–70 m/s). As a result, the cusp thicknesses of relatively large waves on the wavy interface were successfully extracted from the OWF output signal. Further, the major thickness variables (i.e., base film thickness, median film thickness, and cusp thickness) were compared with those of conventional thickness estimation methods, which showed reasonable agreement. This paper provides a framework for wavy thin-film flow measurements via OWF that is specialized for directly detecting local thickness profiles.Graphical abstract

Regulation of TADF by Internal and External Heavy Atom Effect in D-A MOF for Heterocrystal based Temperature-Compensated Photonic Device.

The application of temperature-compensated photonic device is hampered by poor accuracy and overly simplistic functions of propagation in photonic integrated circuits (PICs) field. Herein, we report a new library of donor-acceptor metal-organic framework (D-A MOF) with thermally activated delayed fluorescence (TADF) and the fabricating of temperature-compensated photonic device by virtue of the unique temperature response character of TADF emitters. Highly tunable through-space charge transfer (TSCT) of TADF was realized within the D-A MOFs through a novel strategy that synergistically combines the internal heavy atom effect (HAE) with an external HAE, induced by the incorporation of heavy atoms into different components, achieving the regulable photophysical indicators including adjustable PL wavelength (534 to 592 nm) and surging quantum yield (5.02%-47.39%). Further investigation of the impact of external HAE on TADF was conducted through crystal structures and Hirshfeld surface plots of four D-A regimes featuring substituent-based linkers. Notably, temperature-compensated photonic device based on heterocrystal was fabricated through integrating D-A MOFs with contrary temperature response. The emission signal output of the heterojunction remained nearly stable in 215 K to 295 K range, highlighting the promising potential application of TADF D-A MOF featuring sensitive temperature response in PICs field.

Hydroxyl Spillover in Fe-Se Dual-Site Catalysts for Mixed Plastics Assay.

The complex composition of real plastic wastes poses a significant challenge for their large-scale disposal. A responsive on-site compositional analysis of plastics is informative in choosing downstream processing methods. Nanocatalyst-based assay kit is highly qualified for this scene; however, there remain no efficient nanocatalysts for plastics due to their highly inert chemistry. Herein, we first unveiled the hydroxyl spillover effect in an Fe-Se dual-site catalyst (FeSe/NC) and devised a prototype colorimetric assay kit for mixed plastics. Experimental and theoretical results unveiled that Fe sites acted as the main active sites for H2O2 activation to produce adsorbed hydroxyl (*OH) intermediates, which subsequently desorb as hydroxyl radicals (•OH) and transfer to Se sites, supports, and even plastics for further catalysis. Specifically, •OH transferred to different plastics shows varying activities, where signal outputs were hereby used as the fingerprint for plastic identification. Moreover, the remaining *OH could respond to redox interferences in the samples for enhanced accuracy. In contrast to traditional techniques involving precise apparatus and complex pretreatments, our approach enables a rapid assay (∼10 min) of raw powdery mixed plastic wastes with an ultralow cost (0.0012 $). This discovery fills a crucial gap in the plastic assay, offering new technical guidance for diverse upcycling and recycling strategies to tackle the global plastic waste crisis.

Operando Photoelectrochemical Surface-Enhanced Raman Spectroscopy: Interfacial Mechanistic Insights and Simultaneous Detection of Patulin.

Comprehending the biosensing mechanism of the biosensor interface is crucial for sensor development, yet accurately reflecting interfacial interactions within actual detection environments remains an unsolved challenge. An operando photoelectrochemical surface-enhanced Raman spectroscopy (PEC-SERS) biosensing platform was developed, capable of simultaneously capturing photocurrent and SERS signals, allowing operando characterization of the interfacial biosensing behavior. Porphyrin-based MOFs (Zr-MOF) served as bifunctional nanotags, providing a photocurrent and stable Raman signal output under 532 nm laser irradiation. Aptamer was used to bridge the Zr-MOF and the silver-encased gold nanodumbbells (AuNDs@AgNPs). The simultaneous in situ acquisition of target-induced PEC and SERS signal responses facilitated the correlation of electron transfer information from the photocurrent with the distance information from the SERS signal. It revealed the biosensing mechanism in which target-induced aptamer conformational bending drove the Zr-MOF to approach the electrode. However, the increase in charge transfer observed through conventional electrochemical methods contradicts the conclusions drawn from the operando PEC-SERS analysis. Comprehensive analysis indicated that redox probes introduced during the non-in-situ measurement process became adsorbed within the MOF pores, potentially affecting the judgment of the biosensing mechanism. In addition, the operando PEC-SERS biosensor simultaneously obtained two independent signals, providing self-verification to improve the accuracy and reliability of patulin detection. The linear ranges were 1 pg mL-1-10 ng mL-1 for the PEC method and 1 pg mL-1-100 ng mL-1 for the SERS method, respectively. This work provides a powerful tool for determining the interface characteristics of biosensors.

Genetically Encoded Biosensors for Constrained Biological Functions in Probiotic Escherichia coli Nissle.

The probiotic Escherichia coli Nissle (EcN) is an exceptional strain that has attracted significant attention not only for its clinical efficacy in the treatment and prevention of gastrointestinal disorders but also as a burgeoning microbial chassis for living therapeutic applications. However, there is an immediate necessity to develop conditional expression systems that confine the activity of EcN specifically in the gastrointestinal tract, to avoid influencing the environment. Here, we constructed two genetically encoded interchangeable sensors responsive to body temperature at 37 °C, and small molecules such as protocatechuic acid (PCA), a metabolite found in green tea. By employing dCpf1 targeted deactivation of the LacI gene, we thereby coupled the above sensing modules with the Ptrc-lacO system and achieved improved signal outputs and relatively high ON/OFF ratios. Subsequently, we validated the biological function of engineering EcN using the enhanced green fluorescent protein (eGFP) in an animal model of mice. Taken together, the construction of genetically encoded sensors to restrict the biological functions of EcN would be applicable for the real-world implementation of living therapeutics or drug delivery.

Recent advances in centrifugal microfluidics for point-of-care testing.

Point-of-care testing (POCT) holds significant importance in the field of infectious disease prevention and control, as well as personalized precision medicine. The emerging microfluidics, capable of minimal reagent consumption, integration, and a high degree of automation, play a pivotal role in POCT. Centrifugal microfluidics, also termed lab-on-a-disc (LOAD), is a significant subfield of microfluidics that integrates crucial analytical steps onto a single chip, thereby optimizing the process and enabling high-throughput, automated analysis. By utilizing rotational mechanics to precisely control fluid dynamics without external pressure sources, centrifugal microfluidics facilitates swift operations ideal for urgent medical and field settings. This review provides a comprehensive overview of the latest advancements in centrifugal microfluidics for POCT, covering both theoretical principles and practical applications. We begin by introducing the fundamental operational principles, fluidic control mechanisms, and signal output detection methods. Subsequently, we delve into the typical applications of centrifugal microfluidic platforms in immunoassays, nucleic acid testing, antimicrobial susceptibility testing, and other tests. We also discuss the strengths and potential limitations of centrifugal microfluidic platforms, underscoring their transformative impact on traditional conventional procedures and their significant role in diagnostic practices.

Hydrogel-Gated MXene-Graphene Field-Effect Transistor for Selective Detection and Screening of SARS-CoV-2 and E. coli Bacteria.

Field-effect transistor (FET) biosensors have significantly attracted interest across various disciplines because of their high sensitivity, time-saving, and label-free characteristics. However, it remains a grand challenge to interface the FET biosensor with complex liquid media. Unlike standard liquid electrolytes containing purified protein content, directly exposing FET biosensors to complex biological fluids introduces significant sensing noise, which is caused by the abundance of nonspecific proteins, viruses, and bacteria that adsorb to the biosensor surfaces. In this work, we leverage the hydrogel encapsulation on an MXene-graphene-based FET, which selectively allows the permeation of viruses (e.g., SARS-CoV-2) and bacteria (e.g., E. coli), leading to the high-specificity detection of those biomarkers. The results demonstrated that hydrogel encapsulation could successfully detect the SARS-CoV-2 biomarker at 1 fg/mL while preventing the diffusion of E. coli biomarkers, and the obtained signal output amplitude is twice that of sensors without hydrogel encapsulation, demonstrating significant advantages over conventional bare sensors.

Optical and Electrical Dual-Mode Detection of a Carcinogenic Substance Based on Synergy of Liquid Crystals and Ionic Liquids.

Visual, sensitive, and selective detection of carcinogenic substances is highly desired in portable health protection and practical medicine production. However, achieving this goal presents significant challenges with the traditional single-mode sensors reported so far, as they have limited sensing mechanisms and provide only a single output signal. Here, we report an effective optical and electrical dual-mode sensor for the visual, sensitive, and selective detection of N-nitrosodiethylamine (NDEA), a typical volatile carcinogenic substance, leveraging the synergy of ionic liquid-doped liquid crystals (IL-LC). The optical mode derived from LCs provides the sensor with a visual identification recognizable by the naked eye, while the electrical mode derived from ILs offers a quantitative detection capability. It is noteworthy that the synergistic effect of the IL and LC enhances the performance of both optical and electrical modes. Unique sensing mechanisms derived from the interaction between NDEA and IL-LC endow the sensor with excellent selectivity. As a proof of concept, a portable kit based on a dual-mode sensor has been developed for the real-time and on-site analysis of N-nitrosamine impurities in pharmaceuticals. This work provides valuable insights and a theoretical foundation for developing portable multimode chemical sensors.

Design of high sensitivity magnetometer based on Diamond Nitrogen-Vacancy Centers and Weak Signal Output Module

Design of high sensitivity magnetometer based on Diamond Nitrogen-Vacancy Centers and Weak Signal Output Module

An enzyme-free immunosorbent assay of staphylococcal enterotoxin B using a three-way DNA junction amplifier with an automatic reset function.

A highly sensitive immunoadsorption assay without traditional horseradish peroxidase for signal amplification was developed, utilizing a three-way DNA junction amplifier instead. The formation of a three-way DNA junction and release of trigger DNA with recycling was accomplished by toehold-mediated strand displacement. The fluorescent dye N-methyl mesoporphyrin IX, with highly structure-specific binding affinity towards G-quadruplexes, was employed for label-free and simple signal output. High sensitivity was achieved for concentrations as low as 7.21 pg mL-1 by targeting Staphylococcal enterotoxin B for detection, and its applicability was confirmed by a recovery study of precooked dishes.

A multi-functional platform for stimulating and recording electrical responses of SH-SY5Y cells.

In recent years, multifunctional cell regulation on a single chip has become an imperative need for cell research. In this study, a novel multi-functional micro-platform integrating wireless electrical stimulation, mechanical stimulation and electrical response recording of cells was proposed. Controlling cell fate by photoexcited radio stimulation of cells on photosensitive films can precisely orchestrate biological activities. This is the first report of combining hydrogenated amorphous silicon (a-Si:H) photosensitive films and a 532 nm green laser for cell stimulation and electrical response recording. Remote wireless electrical stimulation of nerve cells through photoelectric effects based on photosensitive films evoked a change in membrane potential and promoted the neurite growth and neuronal differentiation. These effects were confirmed in a cell model of the human neuroblastoma cell line. The electrical response of cells demonstrated that the photocurrent generated by laser irradiation of the photosensitive film induced a redistribution of ions inside and outside the cell. Furthermore, a mechanical stimulus was applied to cells using a probe placed above them. The chip was used as a signal output to simultaneously obtain the electrical response of cells. The ability of photosensitive films to precisely excite cellular activity offers a novel prospect for wireless electrical stimulation. This work provides a promising strategy for the design of multi-functional biological devices based on a single chip.

Construction of a circularly polarized luminescence sensor based on self-assembly of carbon dots and G-quartet chiral nanofibers.

Circularly polarized luminescence (CPL) is a fascinating luminescence phenomenon that has garnered significant research attention for chiroptical applications. In this study, we developed a highly sensitive chiroptical sensor by co-assembling G-quartet nanofibers and nonchiral nitrogen sulfur-doped carbon dots (N-S-CDs) for dual ion detection. The N-S-CDs were synthesized using the one-step microwave method, and a helical G-quartet-based nanofiber structure (g-fiber) was simultaneously formed from guanosine 5'-monophosphate (GMP) in the presence of Sr2+. An adjustable helical G-quartet-based nanofiber provided an optimal chiral environment for CPL emission, with a dissymmetry factor (glum) reaching ±0.02. Notably, the left-handed (L-) and right-handed (R-) helical chirality of the complex was determined by switching between kinetic trap states and thermodynamic equilibrium during the reaction process. An optimized CPL sensor was developed based on chiral CDs/g-fiber composite materials, utilizing sensitive CPL as the signal output of dual detection for Hg2+ and I-. Similar limits of detection (LODs) were achieved for both L-/R-nanocomposites, with the best results being 83.5 nM for Hg2+ and 142.8 nM for I-. These values are comparable with or even better than those obtained with other optical analytical methods. Since CPL biosensors are relatively rare to date, our work presents a new horizon for the application of chiral CPL composites in biological assays.

Machine learning-assisted pattern recognition and imaging of multiplexed cancer cells via a porphyrin-embedded dendrimer array.

Early cancer detection plays a vital role in improving the survival rate of cancer patients, underscoring the importance of developing cancer detection methods. However, it is a great challenge to achieve simple, rapid, and accurate methods for simultaneously discerning various cancers. Herein we developed a 5-element porphyrin-embedded dendrimer-based sensor array, targeting the parallel discrimination of multiple cancers. The porphyrin-embedded dendrimers were modified with various functional groups to generate differentiated interactions with diverse cancer cells, which has been validated by fluorescence responses and laser confocal microscopy imaging. The dual-channel, five-element array, featuring ten signal outputs, achieved 100% accuracy in distinguishing between one human normal cell and six human cancerous cells, as well as in differentiating among mixed cells. Moreover, the screen 6-channel array can accurately distinguish 9 cells from mice and humans in minutes through optimization by multiple machine learning algorithms, including two normal cells and 7 cancerous cells with only 1000 cells, highlighting the significant potential of a porphyrin-embedded dendrimer-based parallel discriminating platform in early cancer diagnosis.