External Signals Research Articles

Recent Advances in Artificial Sensory Neurons: Biological Fundamentals, Devices, Applications, and Challenges

AbstractSpike-based neural networks, which use spikes or action potentials to represent information, have gained a lot of attention because of their high energy efficiency and low power consumption. To fully leverage its advantages, converting the external analog signals to spikes is an essential prerequisite. Conventional approaches including analog-to-digital converters or ring oscillators, and sensors suffer from high power and area costs. Recent efforts are devoted to constructing artificial sensory neurons based on emerging devices inspired by the biological sensory system. They can simultaneously perform sensing and spike conversion, overcoming the deficiencies of traditional sensory systems. This review summarizes and benchmarks the recent progress of artificial sensory neurons. It starts with the presentation of various mechanisms of biological signal transduction, followed by the systematic introduction of the emerging devices employed for artificial sensory neurons. Furthermore, the implementations with different perceptual capabilities are briefly outlined and the key metrics and potential applications are also provided. Finally, we highlight the challenges and perspectives for the future development of artificial sensory neurons.

Mamba-VNPS: A Visual Navigation and Positioning System with State-Selection Space

This study was designed to address the challenges of autonomous navigation facing UAVs in urban air mobility environments without GPS. Unlike traditional localization methods that rely heavily on GPS and pre-mapped routes, Mamba-VNPS leverages a self-supervised learning framework and advanced feature extraction techniques to achieve robust real-time localization without external signal dependence. The results show that Mamba-VNPS significantly outperforms traditional methods across multiple aspects, including localization error. These innovations provide a scalable and effective solution for UAV navigation, enhancing operational efficiency in complex spaces. This study highlights the urgent need for adaptive positioning systems in urban air mobility (UAM) and provides a methodology for future research on autonomous navigation technologies in both aerial and ground applications.

Active noise control of refrigerator based on cascaded notch feedback algorithm

Refrigerators bring convenience to people, but the noise they produce can also affect people’s lives. Refrigerator noise is dominated by low-frequency noise, and the active noise control method is more effective for this kind of noise. However, the existing active noise control methods for refrigerators do not take into account factors such as the limited space and complex structure of the refrigerator compressor room, and external interference signals will be introduced to affect the noise reduction performance during the error signal collection. Given that, this paper proposes the cascade notch feedback algorithm, which can well reduce the influence of external interference signals to better achieve the refrigerator noise reduction. The algorithm consists of the cascaded notch filtering algorithm and the feedback algorithm. The cascade notch filtering algorithm is formed by cascading the adaptive notch filtering algorithm, which is used to deal with the main frequency and harmonic noise generated by the refrigerator. The feedback algorithm consists of a robust algorithm for dealing with external interference signals introduced during error signal collection. The simulation experiment proves that the algorithm has advantages in terms of noise reduction and computational cost compared with the adaptive notch filtering algorithm and the improved algorithm. The experimental test platform is set up to carry out the actual refrigerator noise reduction experiments under different conditions. The algorithm has the effect of noise reduction under different robust algorithms.

Effect of printing parameters and triply periodic minimal surfaces on electromagnetic shielding efficiency of polyvinylidene fluoride graphene nanocomposites

Electromagnetic interference (EMI) shielding is vital in safeguarding electronic devices from the harmful effects of external electromagnetic signals, a critical factor in ensuring the reliability and functionality of these systems. EMI, originating from a myriad of sources, can range from causing temporary disruptions to catastrophic system failures and potentially harmful consequences. This study delves into the EMI shielding capabilities of 3D printed Polyvinylidene Fluoride (PVDF)-graphene Triply Periodic Minimal Surface (TPMS) structures, fabricated using Material Extrusion (ME) process. The focus on TPMS structures stems from their unique geometrical configurations, offering promising potentials in enhancing EMI shielding effectiveness. Four distinct TPMS topologies—gyroid, Neovius, diamond, and I-WP were explored, with each demonstrating varying degrees of shielding effectiveness. 3D printed solid samples showed an average specific shielding effectiveness (SSE) of 13dB cm3/g, and Neovius triply periodic minimal surface (TPMS) structure exhibited an average SSE of 94dB cm3/g. Absolute shielding effectiveness (SSE/t) for solid samples and Neovius TPMS structure is around 66dB cm2/g and 62.5dB cm2/g respectively. Among the tested samples, those with a Neovius topology emerged as particularly promising, exhibiting high EMI shielding effectiveness suitable for commercial applications. Furthermore, the study investigates the impact of several design and printing parameters, including relative density/infill percentage, print orientation, and the size of unit cells, on total shielding effectiveness (SET). Results revealed SET variations ranging between 25dB and 75dB, suggesting that tuning the SET of these samples is feasible by adjusting these parameters. The study's findings, highlighting a strong correlation between SET and frequency influenced by unique geometrical characteristics and frequency-dependent interactions, underscore the potential of architected PVDF-graphene TPMS structures in EMI shielding applications. This opens new avenues for research and development in this field, paving the way for more advanced and effective EMI shielding solutions.

Improvement of visual servo system of industrial robot based on sliding mode control and deep reinforcement learning

Abstract. Visual servo system is more and more widely used in the field of industrial robots because it allows robots to sense external signals through sensors to convey control commands to themselves and complete tasks. However, the traditional visual servo has many limitations in the design of controller and image feature extraction, such as insufficient robustness and image extraction accuracy. This research focuses on the optimization of controller and image feature extraction, which can improve the overall performance and autonomy of the system by combining sliding mode control and Convolutional Neural Network (CNN). Sliding mode control performs well in terms of robustness and response speed, while CNN has excellent ability for image feature extraction. The research results show that the combination of the two and the visual servo has better performance in a variety of application scenarios, so this is also the development direction that industrial robots can adopt in the future.

GPR56: GPCR as a guardian against ferroptosis

Transmembrane receptor proteins are proficient in sensing external signals and initiating downstream pathways to control cell survival. Lin etal. demonstrated that GPR56, a G-protein-coupled receptor, can be activated by its agonist to suppress ferroptosis-a form of cell death-and effectively mitigate ferroptosis-associated liver damage.

Imitation learning with artificial neural networks for demand response with a heuristic control approach for heat pumps

The flexibility of electrical heating devices can help address the issues arising from the growing presence of unpredictable renewable energy sources in the energy system. In particular, heat pumps offer an effective solution by employing smart control methods that adjust the heat pump’s power output in reaction to demand response signals. This paper combines imitation learning based on an artificial neural network with an intelligent control approach for heat pumps. We train the model using the output data of an optimization problem to determine the optimal operation schedule of a heat pump. The objective is to minimize the electricity cost with a time-variable electricity tariff while keeping the building temperature within acceptable boundaries. We evaluate our developed novel method, PSC-ANN, on various multi-family buildings with differing insulation levels that utilize an underfloor heating system as thermal storage. The results show that PSC-ANN outperforms a positively evaluated intelligent control approach from the literature and a conventional control approach. Further, our experiments reveal that a trained imitation learning model for a specific building is also applicable to other similar buildings without the need to train it again with new data. Our developed approach also reduces the execution time compared to optimally solving the corresponding optimization problem. PSC-ANN can be integrated into multiple buildings, enabling them to better utilize renewable energy sources by adjusting their electricity consumption in response to volatile external signals.

Response of a Memristor to an External Noise Signal

Response of a Memristor to an External Noise Signal

News Sentiment and Liquidity Risk Forecasting: Insights from Iranian Banks

This study addresses the critical challenge of predicting liquidity risk in the banking sector, as emphasized by the Basel Committee on Banking Supervision. Liquidity risk serves as a key metric for evaluating a bank’s short-term resilience to liquidity shocks. Despite limited prior research, particularly in anticipating upcoming positions of bank liquidity risk, especially in Iranian banks with high liquidity risk, this study aimed to develop an AI-based model to predict the liquidity coverage ratio (LCR) under Basel III reforms, focusing on its direction (up, down, stable) rather than on exact values, thus distinguishing itself from previous studies. The research objectively explores the influence of external signals, particularly news sentiment, on liquidity prediction, through novel data augmentation, supported by empirical research, as qualitative factors to build a model predicting LCR positions using AI techniques such as deep and convolutional neural networks. Focused on a semi-private Islamic bank in Iran incorporating 4,288,829 Persian economic news articles from 2004 to 2020, this study compared various AI algorithms. It revealed that real-time news content offers valuable insights into impending changes in LCR, particularly in Islamic banks with elevated liquidity risks, achieving a predictive accuracy of 88.6%. This discovery underscores the importance of complementing traditional qualitative metrics with contemporary news sentiments as a signal, particularly when traditional measures require time-consuming data preparation, offering a promising avenue for risk managers seeking more robust liquidity risk forecasts.

Cariogenic potential of the Streptococcus mutans Cid/Lrg system: an in vivo animal case study.

In our prior study using a dual-species (Streptococcus mutans/Streptococcus gordonii) competitive mouse caries model to investigate the contribution of S. mutans LrgAB to in vivo fitness, S. mutans wild-type and ΔlrgAB mutants consistently outnumbered S. gordonii and had high caries scores, even though the ΔlrgAB mutant is highly sensitive to oxidative stress. To determine whether the highly cariogenic sucrose diet used in the previous study masked the contribution of LrgAB to competitive fitness of S. mutans against S. gordonii, we recapitulated our previous mouse caries experiment with a modification in which 4% sucrose drinking water was replaced with sterile water, hypothesized to decrease the frequency of exposure of mice to sucrose, a determinant in the cariogenicity of S. mutans. Given that both S. mutans ΔlrgAB and ΔcidB mutants are sensitive to oxidative stress and share similar transcriptional profiles, these strains, as well as wild-type UA159, were tested in this modified dual-species mouse caries model. When comparing between groups the colonization within molar dental biofilms of S. mutans strains, ΔlrgAB mutant was at a level similar to the wild type, whereas S. mutans ΔcidB was modestly lower than both wild-type and S. mutans ΔlrgAB. The severity of total sulcal caries in both the ∆cidB and ∆lrgAB mutant infections was significantly lower than that of wild type. These results demonstrate that the Cid/Lrg system aids in S. mutans fitness against S. gordonii and caries potential in vivo, a phenotype likely masked in our previous study by more frequent exposure to sucrose.IMPORTANCEThe development of a mature biofilm on the tooth surface is the central event in the pathogenesis of dental caries, which primarily requires that cariogenic organisms withstand the limited resources or environmental fluctuations experienced in the oral cavity. The sensitive and heterogeneous response of the cid and lrg operons to complex external signals has been hypothesized to trigger differentiation of the Streptococcus mutans biofilm community into distinct functional subpopulations to promote survival and persistence of the S. mutans community when challenged by an unfavorable environment. The study described herein enlightens our understanding of how Cid/Lrg contributes to S. mutans pathogenic potential in vivo (caries development), warranting further research regarding the adaptive role of Cid/Lrg system in human oral biofilms toward the development of anti-caries strategies directed at the Cid/Lrg system.

Molecular mechanism of flagellar motor rotation arrest in bacterial zoospores of Actinoplanes missouriensis before germination

Zoospores of the filamentous actinomycete Actinoplanes missouriensis swim vigorously using flagella and stop swimming to initiate germination in response to nutrient exposure. However, the molecular mechanisms underlying swimming cessation remain unknown. A protein (FtgA) of unknown function encoded by a chemotaxis gene cluster (che cluster-1) was found to be required for flagellar rotation arrest; the zoospores of ftgA-knockout mutants kept swimming awkwardly after germination. An ftgA-overexpressing strain exhibited a non-flagellated phenotype. Isolation of a suppressor strain from this strain and further in vivo experiments revealed that the extended N-terminal region of FliN, a component of the C-ring of the flagellar basal body, was involved in the function of FtgA; FliN-P101S canceled the flagellar rotation arrest by FtgA, as well as the negative effect of ftgA-overexpression on flagellation. Furthermore, bacterial two-hybrid assays suggested that FtgA interacted not only with the C-terminal core region of FliN but also with chemotaxis regulatory proteins CheA1 and CheW1-2, which are encoded by che cluster-1. We propose the following working model of motility regulation in A. missouriensis zoospores: the chemotaxis sensory complex initially captures FtgA to allow zoospores to swim and then releases FtgA to stop flagellar rotation (i.e., swimming) in response to external nutrient signals.

Controllable Autolytic Leaky E. coli Platform for the Recovery of Intracellular Proteins.

Escherichia coli is a commonly used platform for the production of heterologous proteins. Extraction and purification of intracellularly expressed recombinant proteins rely on efficient cell disruption. To facilitate downstream processing, controlled autolytic cells have been designed that lyse automatically to release intracellular proteins when triggered with an internal or external signal. In the cases when a weak promoter has to be adopted to control autolysis, cell lysis and product release progress slowly even in the presence of surfactants or other adjuvants. In this study, we report an improved autolytic E. coli strain controlled by a weak promoter with higher efficiency without the use of any facilitating chemical. Cell lysis was initiated upon arabinose-induced expression of T4 lysozyme with N-terminal fusion of amphipathic cell-penetrating peptides via a flexible peptide linker. Furthermore, genes involved in membrane permeability were individually deleted and screened for leaky phenotypes. Deletion of lpp (encoding Braun's lipoprotein) combined with the autolytic system caused 96% cell lysis in 4 h of induction and released 84% or 67% of mCherry or a super large Cas13a fusion protein (160.8 kDa), respectively, in 10 h of induction. This autolytic leaky strain shows great promise for protein recovery and library screening.

Age-associated imbalance in immune cell regeneration varies across individuals and arises from a distinct subset of stem cells.

The age-associated decline in immunity manifests as imbalanced adaptive and innate immune cells, which originate from the aging of the stem cells that sustain their regeneration. Aging variation across individuals is well recognized, but its mechanism remains unclear. Here, we used high-throughput single-cell technologies to compare mice of the same chronological age that exhibited early or delayed immune aging phenotypes. We found that some hematopoietic stem cells (HSCs) in earlyaging mice upregulated genes related to aging, myeloid differentiation, and stem cell proliferation. Delayed aging was instead associated with genes involved in stem cell regulation and the response to external signals. These molecular changes align with shifts in HSC function. We found that the lineage biases of 30% to 40% of the HSC clones shifted with age. Moreover, their lineage biases shifted in opposite directions in mice exhibiting an early or delayed aging phenotype. In earlyaging mice, the HSC lineage bias shifted toward the myeloid lineage, driving the aging phenotype. In delayedaging mice, HSC lineage bias shifted toward the lymphoid lineage, effectively counteracting aging progression. Furthermore, the anti-aging HSC clones did not increase lymphoid production but instead decreased myeloid production. Additionally, we systematically quantified the frequency of various changes in HSC differentiation and their roles in driving the immune aging phenotype. Taken together, our findings suggest that temporal variation in the aging of immune cell regeneration among individuals primarily arises from differences in the myelopoiesis of a distinct subset of HSCs. Therefore, interventions to delay aging may be possible by targeting a subset of stem cells.

Target Controllability: a Feed-Forward Greedy Algorithm in Complex Networks, Meeting Kalman's Rank Condition.

The concept of controllability within complex networks is pivotal in determining the minimal set of driver vertices required for the exertion of external signals, thereby enabling control over the entire network's vertices. Target controllability further refines this concept by focusing on a subset of vertices within the network as the specific targets for control, both of which are known to be NP-hard problems. Crucially, the effectiveness of the driver set in achieving control of the network is contingent upon satisfying a specific rank condition, as introduced by Kalman. On the other hand, structural controllability provides a complementary approach to understanding network control, emphasizing the identification of driver vertices based on the network's structural properties. However, in structural controllability approaches, the Kalman condition may not always be satisfied. In this study, we address the challenge of target controllability by proposing a feed-forward greedy algorithm designed to efficiently handle large networks while meeting the Kalman controllability rank condition. We further enhance our method's efficacy by integrating it with Barabasi et al.'s structural controllability approach. This integration allows for a more comprehensive control strategy, leveraging both the dynamical requirements specified by Kalman's rank condition and the structural properties of the network. Empirical evaluation across various network topologies demonstrates the superior performance of our algorithms compared to existing methods, consistently requiring fewer driver vertices for effective control. Additionally, our method's application to protein-protein interaction networks associated with breast cancer reveals potential drug repurposing candidates, underscoring its biomedical relevance. This study highlights the importance of addressing both structural and dynamical aspects of network controllability for advancing control strategies in complex systems. The source code is available for free at: Https://github.com/fatemeKhezry/targetControllability. Supplementary data are available at Bioinformatics online.

Potential Anti-tumor Effects and Apoptosis-Inducing Mechanisms of Saponins: A Review.

The search for effective cancer therapies highlights saponins, natural plant-derived compounds, as promising anticancer agents. These compounds induce apoptosis in cancer cells by activating caspases, essential enzymes for cell death. For example, Soyasapogenol B from Glycine max and Astragaloside IV from Astragalus membranaceus effectively trigger apoptosis in cancer cells. Additionally, saponins, such as Compound K from American ginseng and Saikosaponin from Bupleurum falcatum, affect extrinsic and intrinsic pathways, including mitochondrial release of cytochrome C and activation of caspase-9. Ziyuglycoside II also acts on both pathways and activates the ROS/JNK pathway. Understanding these mechanisms provides promising prospects for developing more specific and safer anticancer therapies. The review utilized the ScienceDirect, PubMed, and Google Scholar databases. It was found that original articles and reviews from journals indexed in these sources emphasized the antitumor capabilities of saponins and discussed their role in apoptosis induction and caspase activation. The activation of caspases by saponins in the apoptotic pathway involves two main pathways: the extrinsic pathway is initiated by external signals that activate caspase-8, while the intrinsic pathway starts with internal stimuli, causing the release of cytochrome c and the activation of caspase-9. These pathways both lead to the activation of effector caspases (caspases 3, 6, and 7), culminating in apoptosis, an essential process for maintaining cellular balance and eliminating damaged cells. Identifying saponins in the context of cancer and their mechanisms of action is an ever-evolving field. Future research may lead to more targeted and personalized therapies, highlighting the collaboration between basic and clinical research in this promising area of medicine.

Oviduct epithelial spheroids during in vitro culture of bovine embryos mitigate oxidative stress, improve blastocyst quality and change the embryonic transcriptome

BackgroundIn vitro embryo production is increasingly used for genetic improvement in cattle but bypasses the oviduct environment and exposes the embryos to oxidative stress with deleterious effects on further development. Here we aimed to examine the effect of oviduct epithelial spheroids (OES) on embryo development and quality in terms of morphology and gene expression during two co-culture times (4 days: up to embryonic genome activation at 8–16 cell stage vs. 7 days: up to blastocyst stage) and under two oxygen levels (5% vs. 20%).MethodsBovine presumptive zygotes produced by in vitro fertilization (day 0) using in-vitro matured oocytes were cultured in droplets of synthetic oviductal fluid (SOF) medium with or without (controls) OES for 4 or 7 days under 5% or 20% oxygen (4 treated and 2 control groups). Cleavage rates were evaluated on day 2 and blastocyst rates on days 7–8. Expanded blastocysts on days 7–8 were evaluated for total cell numbers and gene expression analysis by RNA-sequencing.ResultsUnder 20% oxygen, blastocyst rates and total cell numbers were significantly higher in the presence of OES for 4 and 7 days compared to controls (P < 0.05), with no difference according to the co-culture time. Under 5% oxygen, the presence of OES did not affect blastocyst rates but increased the number of cells per blastocyst after 7 days of co-culture (P < 0.05). Both oxygen level and OES co-culture had a significant impact on the embryonic transcriptome. The highest number of differentially expressed genes (DEGs) was identified after 7 days of co-culture under 20% oxygen. DEGs were involved in a wide range of functions, including lipid metabolism, membrane organization, response to external signals, early embryo development, and transport of small molecules among the most significantly impacted.ConclusionOES had beneficial effects on embryo development and quality under both 5% and 20% oxygen, mitigating oxidative stress. Stronger effects on embryo quality and transcriptome were obtained after 7 than 4 days of co-culture. This study shows the impact of OES on embryo development and reveals potential molecular targets of OES-embryo dialog involved in response to stress and early embryonic development.

Single pulse shaping for higher harmonic demodulation in terahertz time-domain spectroscopy

We present a simple, highly stable, low noise, and rapid detection scheme using higher harmonic demodulation applied to terahertz time domain spectroscopy (THz-TDS). The presence of higher harmonics in the detected periodic signal is because of the non-sinusoidal shape of a single pulse, which is controlled by an ultrafast current pre-amplifier. Instead of using external signal modulators, the use of the inherent repetition rate (frep) of the femtosecond laser and its harmonics as reference for the lock-in amplifier simplifies the setup, while allows rapid and low noise detection owing to the megahertz modulation frequencies. Unlike the signal detected at the fundamental frep, signals detected at higher harmonics have much lower offset and are unaffected by perturbations in the environment present during measurements, which is an essential characteristic for an analytical tool. Our proposed technique can be readily integrated to existing THz-TDS systems and is applicable to scans with rapid acquisition times and to scans that require long periods of time (e.g., hyperspectral imaging).

Suppression of Nonlinear Chorus Wave Growth by Active Control of Gyroresonant Interactions With Electron Hole Deformation

AbstractNonlinear gyroresonant acceleration is an essential mechanism for the formation of relativistic electrons in Earth's radiation belts, yet we still have only limited knowledge of how electron motion interacts nonlinearly with plasma waves. Here we demonstrate the compelling suppression of whistler‐mode chorus emissions as a resonant wave with energetic electrons by tuning an external transmitter signal in space plasmas. Through forcible modification of electron motions via phase trapping by the external waves, the nonlinear gyroresonant current is suppressed along with the electron hole deformation. Moreover, this can decrease the population of relativistic electrons due to the lack of coherent resonant waves seen by the phase‐organized electrons. Understanding such nonlinear wave suppression effects is crucial for a potential active control of Earth's plasma environment.

Ultra‐Low BER Encrypted Communication Based on Self‐Powered Bipolar Photoresponse Ultraviolet Photodetector

AbstractUnderwater visible light communication often faces risks such as susceptibility to external light source interference, signal distortion, and information leakage. The cuprous oxide modified gallium oxide nanorod arrays detector prepared in this study can generate bipolar photocurrents under dual‐wavelength ultraviolet light without external bias voltage. Based on it, the constructed self‐powered ultraviolet ASCII code communication system not only reduce power consumption but also significantly enhance anti‐interference capability. Furthermore, the developed solar‐blind ultraviolet AMI and HDB3 ternary code communication systems can realize non‐visible light secure communication and automatic error correction. Notably, the encrypted communication system assembled using the additive property of bipolar photocurrents can also significantly improve communication security and reliability, whose bit error rate is only 0.26‰. This achievement contributes to technical advancements in underwater channel encryption and provides valuable insights for the further application of encrypted communication coding techniques.

Mechanics of reproductive differentiation in the land plants: a paradigm shift?

This article addresses the physical mechanics of gametogenesis in vascular plants. The earliest events that initiate reproductive differentiation in the land plants are not well understood. How are the few cells that initiate reproductive differentiation specified and how is that information translated into action at the cellular level? In this article I propose a physical mechanism that resolves the problem of spatial targeting without invoking dependence on diffusible morphogens or other external signals. I suggest that the initiation of archesporial differentiation can instead be attributed to the confluence of organ geometry, surficial topography, and the physical mechanics of sporangial growth, resulting in the spontaneous emergence of an isotropic singularity that locates and precipitates archesporial differentiation. In discussing the logic of single-cell target selection and the limits of stochastic molecular signaling I propose that the sporangium would be better understood as a pressurized stress-mechanical lens that focuses turgor-generated growth forces on a central location, generating a physical singularity that locates and specifies the cell or cells that become the archesporium and initiates their transition from somatic proliferation to reproductive differentiation.