Steady-state Regulation Research Articles

A concurrent learning approach to monocular vision range regulation of leader/follower systems

This paper explores range and bearing angle regulation of a leader–follower using monocular vision. The main challenge is that monocular vision does not directly provide a range measurement. The contribution is a novel concurrent learning (CL) approach, called CL Subtended Angle and Bearing Estimator for Relative pose (CL-SABER), which achieves range regulation without communication, persistency of excitation or known geometry and is demonstrated on a physical, robot platform. A history stack estimates target size which augments the Kalman filter (KF) with a range pseudomeasurement. The target is followed to scale without drift, persistency of excitation requirements, prior knowledge, or additional measurements. Finite excitation is required to achieve parameter convergence and perform steady-state regulation using CL-SABER. Evaluation using simulation and mobile robot experiments in special Euclidean planar space (SE(2)) show that the new method provides stable and consistent range regulation, as demonstrated by the inter-rater reliability, including in noisy and high leader acceleration environments.

Optimal Steady-State Regulation by State Feedback

Optimal Steady-State Regulation by State Feedback

Regulatory properties of transcription factors with diverse mechanistic function.

Transcription factors (TFs) regulate the process of transcription through the modulation of different kinetic steps. Although models can often describe the observed transcriptional output of a measured gene, predicting a TFs role on a given promoter requires an understanding of how the TF alters each step of the transcription process. In this work, we use a simple model of transcription to assess the role of promoter identity, and the degree to which TFs alter binding of RNAP (stabilization) and initiation of transcription (acceleration) on three primary characteristics: the range of steady-state regulation, cell-to-cell variability in expression, and the dynamic response time of a regulated gene. We find that steady state regulation and the response time of a gene behave uniquely for TFs that regulate incoherently, i.e that speed up one step but slow the other. We also find that incoherent TFs have dynamic implications, with one type of incoherent mode configuring the promoter to respond more slowly at intermediate TF concentrations. We also demonstrate that the noise of gene expression for these TFs is sensitive to promoter strength, with a distinct non-monotonic profile that is apparent under stronger promoters. Taken together, our work uncovers the coupling between promoters and TF regulatory modes with implications for understanding natural promoters and engineering synthetic gene circuits with desired expression properties.

Reduced lactic acid strengthens microbial community stability and function during Jiang-flavour Baijiu fermentation

Unravelling the relationships between microbial community stability and function under environmental stress is critical to understanding microbial ecology but remains understudied in fermentation ecosystems. In this study, the relationship between lactic acid and microbial community was revealed during Jiang-flavour Baijiu fermentation using high-throughput sequencing and nontargeted metabolomics. Lactic acid was reduced by mono- and co-inoculation of lactic acid-degrading strains, Pichia kudriavzevii and Zygosaccharomyces bailii. Furthermore, reduced lactic acid strengthened microbial community stability, mainly characterized by higher network modularity and more positive interactions of species. Lactic acid had a significantly negative relation with network modularity (P = 0.03, Pearson's r = − 0.97). Moreover, the increase in network stability contributed to stronger community function, as indicated by the increase in ethanol, total esters, and total alcohols. Finally, metabolic function analysis showed that amino acid metabolism, starch and sucrose metabolism, pyruvate metabolism, the TCA cycle, nucleotide sugar metabolism, pyrimidine metabolism, and purine metabolism were the main pathways resulting in changes in microbial community stability and function. This study indicated that microbial community stability and function can be enhanced by the regulation of environmental factors and provided a possible strategy for the steady-state regulation of the microbial community in Baijiu fermentation.

Steady-state regulation of COPII-dependent secretory cargo sorting by inositol trisphosphate receptors, calcium, and penta EF hand proteins

Recently, we demonstrated that agonist-stimulated Ca2+ signaling involving IP3 receptors modulates ER export rates through activation of the penta-EF Hand proteins apoptosis-linked gene-2 (ALG-2) and peflin. It is unknown, however, whether IP3Rs and penta-EF proteins regulate ER export rates at steady state. Here we tested this idea in normal rat kidney epithelial cells by manipulation of IP3R isoform expression. Under standard growth conditions, spontaneous cytosolic Ca2+ oscillations occurred simultaneously in successive groups of contiguous cells, generating intercellular Ca2+ waves that moved across the monolayer periodically. Depletion of IP3R-3, typically the least promiscuous IP3R isoform, caused increased cell participation in intercellular Ca2+ waves in unstimulated cells. The increased spontaneous signaling was sufficient to cause increased ALG-2 and COPII coat subunit Sec31A and decreased peflin localization at ER exit sites, resulting in increased ER-to-Golgi transport of the COPII client cargo VSV-G. The elevated ER-to-Golgi transport caused greater concentration of VSV-G at ER exit sites and had reciprocal effects on transport of VSV-G and a bulk-flow cargo, though both cargos equally required Sec31A. Inactivation of client cargo sorting using 4-phenylbutyrate had opposing reciprocal effects on client and bulk-flow cargo and neutralized any effect of ALG-2 activation on transport. This work extends our knowledge of ALG-2 mechanisms and indicates that in normal rat kidney cells, IP3R isoforms regulate homeostatic Ca2+ signaling that helps determine the basal secretion rate and stringency of COPII-dependent cargo sorting.

High-Performance Electrochemiluminescence of a Coordination-Driven J-Aggregate K-PTC MOF Regulated by Metal-Phenolic Nanoparticles for Biomarker Analysis.

The elimination of aggregation-caused quenching of polycyclic aromatic hydrocarbons by metal-ligand coordination is of immense scientific interest in solid-state electrochemiluminescence (ECL) sensing. Herein potassium ion (K+)-mediated J-aggregate K-PTC MOF (PTCA, perylene-3,4,9,10-tetracarboxylic) was synthesized and employed to formulate an ECL immunosensor for biomarker detection. The coordination-driven aggregates are arranged in an end-to-end side mode, which overcomes the aggregation-caused quenching related to PTCA concentration. Compared with PTCA, K-PTC MOF shows a more stable ECL emission with an unprecedented red shift to 718 nm and is equipped with ECL activity for analytical applications at a voltage of -1.1 V. Considering the requirements of accurate detection, metal-phenolic bioactive nanoparticles (MPNPs) were synthesized for the construction of a sandwich sensing platform to realize the steady-state regulation of ECL. As proof of applicability, a constructive experiment was carried out with neuron-specific enolase (NSE), a marker of small cell lung cancer (SCLC), as a targeted analyte. With optimal requirements, the configuration can provide a detection range of 10 pg/mL to 50 ng/mL and a detection limit of 7.4 pg/mL, accompanied by sufficient practical analytical performance. Collectively, this paradigm provides a deeper understanding of the ECL characteristics of coordination-driven J-aggregation and provides more possibilities for the development of ECL patterns based on luminescent metal-organic frameworks.

A Novel Pre-Synchronization Control Method Based on Open-Loop Phase Detection for the Maritime VSC-HVDC System

Maritime island grids based on renewable energy are being rapidly developed, which poses a new challenge to the traditional pre-synchronization process of grid connection. Aiming at the problems of impulse current out of limit and long steady-state regulation time, a novel pre-synchronization control method is provided based on open-loop phase detection, which is realized by replacing the frequency detection method of the difference judgment part. The open-loop detection model of voltage phase and amplitude based on the synchronous rotating coordinate system is established first. Then the voltage phase is linearized to control the output frequency and finally reduces the voltage deviation through the compensation of virtual power to achieve the effect of a smooth grid connection. The novel pre-synchronization method has a fast response speed and no regulator effect, which can synchronize the actual values of output voltage amplitude, phase, and frequency. Simulation results verify the excellent performance of the proposed method in island stable operation and grid connection under disturbance.

D-Transform Based Control of Power Converters

The aim of this study is to present a very simple, intuitive and feasible tool: the D-transform between converters. This new method proposes to find a control equation of any pre-defined control law from one converter to another power converter. The central goal is to take maximum advantage of the robustness offered by the originator nonlinear control law. Although there is the possibility of more than one conversion, some candidates show good performance in terms of transient overshoot, settling time and steady-state regulation. The stability proof is disposed individually for each generated equation. The performance of D-Controllers is verified through Hardware In the Loop (HIL) simulations. A small overshoot under input and load perturbations is achieved for the buck-boost example. Finally, a experimental validation using a buck converter is given to illustrate the application method and the nonlinear control design.

Research Progress of Metabolomics in Asthma.

Asthma is a highly heterogeneous disease, but the pathogenesis of asthma is still unclear. It is well known that the airway inflammatory immune response is the pathological basis of asthma. Metabolomics is a systems biology method to analyze the difference of low molecular weight metabolites (<1.5 kDa) and explore the relationship between metabolic small molecules and pathophysiological changes of the organisms. The functional interdependence between immune response and metabolic regulation is one of the cores of the body’s steady-state regulation, and its dysfunction will lead to a series of metabolic disorders. The signal transduction effect of specific metabolites may affect the occurrence of the airway inflammatory immune response, which may be closely related to the pathogenesis of asthma. Emerging metabolomic analysis may provide insights into the pathogenesis and diagnosis of asthma. The review aims to analyze the changes of metabolites in blood/serum/plasma, urine, lung tissue, and exhaled breath condensate (EBC) samples, and further reveals the potential pathogenesis of asthma according to the disordered metabolic pathways.

Design and Application of Early Warning Model for Electric Vehicle Charging Safety

In order to improve the charging safety of electric vehicles, it is necessary to design the early warning model of charging safety, so as to overcome the overload defects in the charging process of electric vehicles. An electric vehicle charging safety warning model was proposed based on contactless charging design. The electromagnetic induction coil and electromagnetic coupler installed on the charging pile are used to design the electromagnetic coupling induction with the driving electric vehicle tire wire, and the electromagnetic coupling control and charging stability adjustment of the electric vehicle are carried out by using the inductive power transmission technology. According to the overload regulation of electric vehicle during charging, the overload interruption control of electric vehicle charging is carried out by mutual inductance coupling method, and the parameters such as resonance frequency, mutual inductance coefficient and coil internal resistance during charging are analyzed. The parameter steady-state regulation method is used for non-contact charging, and the electric vehicle charging safety early warning control is realized, and the parameter optimization design of electric power transmission system in the process of electric vehicle charging is carried out. According to the parameter optimization result, the electric vehicle charging safety early warning test is realized. The test results show that the proposed method has good control performance and can effectively realize the wireless energy transmission of 100W in 100cm, the charging efficiency and the charging safety are improved.

Optimal Steady-State Regulator Design for a Class of Nonlinear Systems With Arbitrary Relative Degree.

In this article, we consider the regulator design problem for a class of uncertain multi-input-multioutput (MIMO) nonlinear systems with arbitrary relative degree. The objective is to regulate the output of the nonlinear system to an optimal steady state that solves a constrained optimization problem, without computing the optimal solution in advance. By embedding saddle-point dynamics, both state and output-feedback-based regulators are proposed and the resulting closed-loop systems are modeled in standard singularly perturbed forms. By invoking the singular perturbation analysis, exponential stability is established under some regularity condition. Compared with the existing methods, the proposed regulators can deal with a class of nonlinear systems with uncertainties and arbitrary relative degree. Furthermore, the current results can include some recent works on the distributed optimization problem as special cases. Finally, the effectiveness of the proposed methods is validated through numerical simulations.

Distributed Optimal Steady-State Regulation for High-Order Multiagent Systems With External Disturbances

In this paper, a distributed optimal steady-state regulation problem is formulated and investigated for heterogeneous linear multi-agent systems subject to external disturbances. We aim to steer this high-order multi-agent network to a prescribed steady-state determined as the optimal solution of a resource allocation problem in a distributed way. To solve this problem, we employ an embedded control design and convert the formulated problem to two simpler subproblems. Then, both state-feedback and output feedback controls are presented under mild assumptions to solve this problem with disturbance rejection. Moreover, we extend these results to the case with only real-time gradient information by high-gain control techniques. Finally, numerical simulations verify their effectiveness.

Membrane Processing and Steady-State Regulation of the Alternative Peroxisomal Import Receptor Pex9p.

Import of peroxisomal matrix proteins with a type 1 peroxisomal targeting signal (PTS1) in Saccharomyces cerevisiae is facilitated by cytosolic import receptors Pex5p and Pex9p. While Pex5p has a broad specificity for all PTS1 proteins independent of the growth conditions, Pex9p is only expressed in fatty-acid containing media to mediate peroxisomal import of the two malate synthases, Mls1p and Mls2p, as well as the glutathione transferase Gto1p. Pex5p-cargo complexes dock at the peroxisomal membrane, translocate their cargo-protein via a transient pore and are recycled into the cytosol for a further round of import. The processing of Pex5p has been shown to require a complex network of interactions with other membrane-bound peroxins, as well as decoration with ubiquitin as signal for its ATP-dependent release and recycling. Here, we show that the alternative receptor Pex9p requires the same set of interacting peroxins to mediate peroxisomal import of Mls1p. However, while Pex5p is rather stable, Pex9p is rapidly degraded during its normal life cycle. The steady-state regulation of Pex9p, combining oleate-induced expression with high turnover rates resembles that of Pex18p, one of the two co-receptors of the PTS2-dependent targeting pathway into peroxisomes. Both Pex9p- and Pex18p-dependent import routes serve the fast metabolic adaptation to changes of carbon sources in baker’s yeast. By sequence similarities, we identified another Pex9p homolog in the human pathogenic fungus Candida glabrata, in which similar metabolic reprogramming strategies are crucial for survival of the pathogen.

Analysis of Unified Power Flow Controller Steady-State Power Flow Regulation Capability and Its Key Factors

As the latest generation of flexible AC transmission system (FACTS) devices, the unified power flow controller (UPFC) has comprehensive control capability and has played an important role in modern power systems. Research on UPFC steady-state power flow regulation capability is valuable for the design and operation of UPFC projects. To analyze the UPFC regulation capability, in this paper, the interaction between the UPFC and the external system is studied and the key factors of UPFC regulation capability are analyzed. It is demonstrated that the changes in the voltage magnitude and phase angle difference of UPFC-embedded line terminals will hinder the UPFC from regulating the power flow and decrease the UPFC regulation capability. Therefore, the UPFC power flow regulation capability is not only related to the parameters of the UPFC and its installation line, but also related to grid parameters. To analyze the UPFC active power flow regulation capability in practical power grids, the relationship between the UPFC regulation capability and grid parameters is deduced, and an estimation method is proposed to calculate the regulation range. Then, the estimation method is applied in the Chuxiong Power Grid and compared with power flow calculations. The results verify the UPFC power flow regulation characteristics given by the analysis and the effectiveness of the estimation method. Besides, it is shown that the estimation method can lower the requirements for the power flow calculation program, and reduce computation load.

Control Oriented Modeling of Soft Robots: The Polynomial Curvature Case

The complex nature of soft robot dynamics calls for the development of models specifically tailored on the control application. In this letter, we take a first step in this direction by proposing a dynamic model for slender soft robots, taking into account the fully infinite-dimensional dynamical structure of the system. We also contextually introduce a strategy to approximate this model at any level of detail through a finite dimensional system. First, we analyze the main mathematical properties of this model in the case of lightweight and non lightweight soft robots. Then, we prove that using the constant term of curvature as control output produces a minimum phase system, in this way providing the theoretical support that existing curvature control techniques lack, and at the same time opening up to the use of advanced nonlinear control techniques. Finally, we propose a new controller, i.e., the PD-poly, which exploits information on high order deformations, to achieve zero steady state regulation error in presence of gravity and generic nonconstant curvature conditions.

Application of high-fat cell model in steady-state regulation of vascular function.

In order to effectively apply the high-fat cell model to the regulation of vascular homeostasis and the repair of vascular endothelial cell injury, and to provide a new theoretical basis for the treatment of vascular homeostasis imbalance in the future, in this study, the mouse thoracic aorta tissue is extracted by using mouse endothelial cells. Western blotting and immunofluorescence resonance energy transfer (Immuno-FRET) are then used to verify the distribution and physical coupling properties of TRPV4 and Nox2 in cells. Finally, mouse mesenteric endothelial cells are isolated and cultured to induce FFA high-fat cell model. The results show that the nucleic acid expression levels of TRPV4 and Nox2 in RNA are significantly different from those of TRPV4 and Nox2 in protein. The relative values of TRPV4 and Nox2 in the control group are relatively low (0.8 ± 0.11). However, the relative values of TRPV4 and Nox2 are higher in the FFA high-fat cell model induced by the experimental group, and the values are (1.7 ± 0.8). Obviously, the relative values of TRPV4 and Nox2 in the experimental group are higher than those in the control group. The expression of reactive oxygen species (ROS) in vascular endothelial cells of control group is (1.0 ± 0.16), and that in FFA group is (2.5 ± 0.46). The expression of ROS in FFA cell model with HC067047A inhibitor is (1.5 ± 0.38). In the FFA cell model with apo inhibitor, ROS expression is (1.2 ± 0.23). Thus, in the FFA high-fat cell model induced successfully, the physical coupling of TRPV4 and Nox2 increases in primary endothelial cells, and the increase of physical coupling of TRPV4 and Nox2 results in the increase of ROS expression, which also means the imbalance of ROS homeostasis in vascular endothelial cells and the change of vascular endothelial cell permeability. The expression levels of TRPV4 and Nox2 are used as indicators of whether the vascular function is stable or unbalanced, thus providing a new theoretical basis for the treatment of cardiovascular diseases.

Quantifying Dynamic Regulation in Metabolic Pathways with Nonparametric Flux Inference

One of the central tasks in systems biology is to understand how cells regulate their metabolism. Hierarchical regulation analysis is a powerful tool to study this regulation at the metabolic, gene-expression, and signaling levels. It has been widely applied to study steady-state regulation, but analysis of the metabolic dynamics remains challenging because it is difficult to measure time-dependent metabolic flux. Here, we develop a nonparametric method that uses Gaussian processes to accurately infer the dynamics of a metabolic pathway based only on metabolite measurements; from this, we then go on to obtain a dynamical view of the hierarchical regulation processes invoked over time to control the activity in a pathway. Our approach allows us to use hierarchical regulation analysis in a dynamic setting but without the need for explicitly time-dependent flux measurements.

Transcriptome analysis for identifying possible causes of post-reproductive death of Sepia esculenta based on brain tissue.

The subpeduncle lobe/olfactory lobe-optic gland axis is called the endocrine regulation center of cephalopods. However, little is known about the mechanism of the subpeduncle lobe/olfactory lobe-optic gland axis regulate the sexual maturation and post-reproductive death of Sepia esculenta Hoyle. The primary objective of this study was to provide basic information for revealing the mechanism of the subpeduncle lobe/olfactory lobe-optic axis regulating the rapid post-reproductive death of S. esculenta. In this paper, Illumina sequencing based transcriptome analysis was performed on the brain tissue of female S. esculenta in the three key developmental stages: growth stage (BG), spawning stage (BS), and post-reproductive death stage (BA). A total of 66.19Gb Illumina sequencing data were obtained. A comparative analysis of the three stages showed 2609, 3333, and 170 differentially expressed genes (DEGs) in BG-vs-BA, BG-vs-BA, and BS-vs-BA, respectively. The Gene Ontology (GO) enrichment analysis of DEGs revealed that the regulation of cyclin-dependent protein serine/threonine kinase activity, oxidative phosphorylation, and respiratory chain were significantly enriched. The significant enrichment analysis of the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway identified pathways associated with the regulation of death, such as the mammalian target of rapamycin (mTOR) signaling pathway, AMPK signaling pathway, oxidative phosphorylation, and cell cycle. The post-reproductive death of S. esculenta was found to be a complex energy steady-state regulation network system. The mTOR acted as an energy receptor and had a key role in regulating energy homeostasis.

Bidirectional DC–DC Converter for Modular Residential Battery Energy Storage Systems

A novel bidirectional dc–dc converter based on the quasi- Z -source (qZS) topology is presented in this paper. During battery discharge, it operates as the conventional qZS full-bridge converter with a synchronous voltage doubler rectifier. During battery charging, it operates as the half-bridge converter with a synchronous full-bridge rectifier and LC filter. A relay is used for reconfiguration between those two modes. The operation principle is explained, and design guidelines are provided. A prototype with a nominal power of 300 W is used for verification of steady-state regulation characteristics and efficiency measurements in the input voltage range compatible with an eight-cell LiFePO4 battery. Closed-loop control system for the converter application in dc microgrids is presented and tested in two control scenarios: dc-bus signaling and direct reference defined by a master controller through a communication channel.

Quantum Mechanical/Molecular Mechanical Analysis of the Catalytic Mechanism of Phosphoserine Phosphatase.

Phosphoserine phosphatase (PSP), a member of the haloacid dehalogenase (HAD) superfamily that comprises the vast majority of phosphotransferases, is likely a steady-state regulator of the level of d-serine in the brain. The proposed catalytic cycle of PSP consists of a two-step mechanism: formation of a phospho-enzyme intermediate by phosphate transfer to Asp11 and its subsequent hydrolysis. Our combined quantum mechanical/molecular mechanical (QM/MM) calculations of the reaction pathways favour a dissociative mechanism of nucleophilic substitution via a trigonal-planar metaphosphate-like configuration for both steps, associated with proton transfer to the leaving group or from the nucleophile. This proton transfer is facilitated by active site residue Asp13 that acts as both a general base and a general acid. Free energy calculation on the reaction pathways further support the structural role of the enzymatic environment and the active site architecture. The choice of a proper reaction coordinate along which to bias the free energy calculations can be guided by a projection of the canonical reaction coordinate obtained from a chain-of-state optimisation onto important internal coordinates.