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This paper studies the stabilization to an inverted pendulum under a delayed proportional-derivative-acceleration (PDA) feedback, which can be used to understand human balance in quiet standing. The closed-loop system is described by a neutral delay differential equation (NDDE). The optimal feedback gains (OFGs) that make the exponential decaying rate maximized are determined when the characteristic equation of the closed-loop has a repeated real root with multiplicity 4. Such a property is called multiplicity-induced dominancy of time-delay systems, and has been discussed intensively by many authors for retarded delay differential equations (RDDEs). This paper shows that multiplicity-induced dominancy can be achieved in NDDEs. In addition, the OFGs are delay-dependent, and decrease sharply to small numbers correspondingly as the delay increases from zero and varies slowly with respect to moderate delays. Thus, the inverted pendulum can be well-stabilized with moderate delays and relatively small feedback gains. The result might be understandable that the elderly with obvious response delays can be well-stabilized with a delayed PDA feedback controller. [ABSTRACT FROM AUTHOR]

This paper investigates the effect of double-frequency excitation on a fractional cerebral aneurysm model at the circle of Willis, where two kinds of external excitation are caused by the heart and arrhythmia respectively. Firstly, numerical analysis is performed on the proposed fractional model by using bifurcation diagrams and phase diagrams, and it is found that the periodic solution windows and chaotic solution windows switch more frequently than that resulted from single-frequency excitation, as a consequence of simultaneous resonances. Then, by using the method of multiple scales, the primary resonance response equation is obtained, and the effects of the system parameters on the amplitude of the fractional cerebral aneurysm model is analytically investigated. It is shown that double-frequency excitation changes the vibration patterns of the system under single-frequency excitation, and makes the primary resonance curve of the system deviate. Finally, the flexibility of using the amplitude-frequency equation to estimate the amplitude of the resonant solutions is verified numerically. [ABSTRACT FROM AUTHOR]

To overcome the deficiencies of traditional disturbance observers in the presence of measurement uncertainty, an integral‐type observer‐based control using measured signals is proposed. The integral‐type observer is in terms of an explicit integral‐algebra form of measured signals. As a combination of the integral‐type observer and high‐gain controller, the observer‐based control is a proportional‐integral‐derivative control with special combination of parameters for feedback linearization, simple in structure and easy in implementation. Without the observer, the high‐gain controller alone may not have good control performance, but the proposed observer‐based control works very well in stabilizing the system even when the observer performance is not good enough, due to the use of the high‐gain control. The main results are applied to the control of a two‐wheeled inverted pendulum. [ABSTRACT FROM AUTHOR]

Background: The risk factors for multi-drug resistant infection (MDRI) in the pediatric intensive care unit (PICU) remain unclear. It's necessary to evaluate the epidemiological characteristics and risk factors for MDRI in PICU, to provide insights into the prophylaxis of MDRI clinically. Methods: Clinical data of 79 PICU children with MDRI were identified, and 80 children in PICU without MDRI in the same period were selected as control group. The related children's characteristics, clinical care, microbiologic data, treatments provided, and outcomes of the patients with were reviewed and collected. Univariate and multivariate logistic regression analyses were performed to identify the potential risks of MDRI in PICU. Results: Of the diagnosed 79 cases of MDRI, there were28 cases of CR-AB, 24 cases of MRSA, 22 cases of PDR-PA,3 cases of VRE and 2 cases of CRE respectively. Univariate analyses indicated that the length of PICU stay, the duration of mechanical ventilation > 5 days, parenteral nutrition, coma, urinary catheter indwelling, invasive operation, 2 or more antibiotics use were associated with MDRIs (all p < 0.05); The logistic multiple regression analyses indicated that coma, parenteral nutrition, 2 or more antibiotics use and the duration of mechanical ventilation > 5 days were independent risk factors associated with MDRI (all p < 0.05). Conclusions: This present study has identified several potentially modifiable risk factors for MDRI in PICU, it's conducive to take appropriate measures targeting risk factors of MDRI for health care providers to reduce MDRI. [ABSTRACT FROM AUTHOR]

Summary: This paper studies the position control of uncertain mechanical systems with measurement uncertainty. Firstly, an observer using measurement signals is designed to estimate the unknown disturbances under an improved assumption of the uncertainties. The improved assumption can give smaller error estimation with same observer gain compared with the conventional assumption. Next, the essence of the observer and the method for selecting the observer gain are introduced. For the case when measurement uncertainties are not considered, the observer is allowed to have a large gain. As for the current case, it is shown that the observer with a large gain will lead to a failure. Then, by using the observed values, two switching controllers using measurement signals are proposed to realize the position control. The proposed control is a generalization of the sliding mode control without measurement uncertainty to the case with measurement uncertainty. Meanwhile, the features of the velocity change of the controlled system are discussed. Finally, as an application of the control design, the position control of a dynamic positioning system is investigated in details. The motion of the controlled system exhibits obviously three phases with different velocity features during the system moves to the target position: approximate acceleration phase, approximate uniform velocity phase, and approximate deceleration phase, and the velocity of the approximate uniform velocity phase can be easily adjusted with the change of the control gains. [ABSTRACT FROM AUTHOR]

This paper presents a control design method for implementing planar turning motion of a two-wheeled inverted pendulum with an input delay. The control task requires that the inverted pendulum is kept stabilized during the whole turning motion process along a pre-settled curve. Firstly, by using the theory of planar curve, key observations about the motion law of the two-wheeled mobile chassis are made and they are used to set up a dynamical trajectory tracking target. Then, by adjusting the parameters in the tracking target and the weights in the quadratic performance criterion, the optimal integral sliding mode controller based on a linear quadratic regulator is designed for keeping the vehicle body stabilized and tracking a circular path for the two-wheeled inverted pendulum. An illustrative example is given to demonstrate the validity of the theory with numerical simulation. [ABSTRACT FROM AUTHOR]

Despite the intensive studies on neurons, the control mechanism in real interactions of neurons is still unclear. This paper presents an understanding of this kind of control mechanism, controlling a neuron by stimulating another coupled neuron, with the uncertainties taken into consideration for both neurons. Two observers and a differentiator, which comprise the first-order low-pass filters, are first designed for estimating the uncertainties. Then, with the estimated values combined, a robust nonlinear controller with a saturation function is presented to track the desired membrane potential. Finally, two typical bursters of neurons with the desired membrane potentials are proposed in the simulation, and the numerical results show that they are tracked very well by the proposed controller. [ABSTRACT FROM AUTHOR]

In this paper, Chua’s circuit model with a fractional-order memristor is proposed and investigated from the viewpoint of nonlinear dynamics. Unlike the previous fractional-order models as generalizations of integer-order memristive Chua’s circuit in the literature, by replacing all the first-order derivatives in the system equation with fractional-order derivatives, the proposed model has only one fractional-order derivative in the system equation, introduced on the basis of a physical observation. Stability and bifurcation are analyzed for a sub-system, and numerical simulation is done for the whole circuit system. “Intermittent chaos” resulting from tangent bifurcation or grazing bifurcation is found numerically, for which limit cycle and chaotic attractor switch with very high frequency. This is a typical feature of nonsmooth dynamic systems, and the nonsmoothness is caused mainly by the fractional-order derivative. [ABSTRACT FROM AUTHOR]

This paper presents new observations of delayed AD (acceleration-derivative) controller in active vibration control and in bifurcation control of a Duffing oscillator. Based on the stability analysis of the linear delayed oscillator, it is found that combination of the two delays in acceleration feedback and velocity feedback has a significant influence on the stable region in the parameter plane of the gains. By calculating the real part of the rightmost characteristic roots of the controlled oscillator with fixed delays, it is shown that a delayed acceleration feedback with positive gain can work much better than the corresponding delayed negative acceleration feedback, which is used in classic control theory. For given feedback gains, by calculating the critical delay values, it is shown that a delayed positive acceleration feedback can result in a much larger stable delay interval than the corresponding delayed negative acceleration feedback does. As an application of these results to a delayed Duffing oscillator with acceleration-derivative feedback, a delayed positive acceleration feedback can be well used to postpone the occurrence of Hopf bifurcation in the delayed nonlinear oscillators. [ABSTRACT FROM AUTHOR]

In the dynamics analysis and synthesis of a controlled system, it is important to know for what feedback gains can the controlled system decay to the demanded steady state as fast as possible. This article presents a systematic method for finding the optimal feedback gains by taking the stability of an inverted pendulum system with a delayed proportional-derivative controller as an example. First, the condition for the existence and uniqueness of the stable region in the gain plane is obtained by using the D-subdivision method and the method of stability switch. Then the same procedure is used repeatedly to shrink the stable region by decreasing the real part of the rightmost characteristic root. Finally, the optimal feedback gains within the stable region that minimizes the real part of the rightmost root are expressed by an explicit formula. With the optimal feedback gains, the controlled inverted pendulum decays to its trivial equilibrium at the fastest speed when the initial values around the origin are fixed. The main results are checked by numerical simulation. [ABSTRACT FROM AUTHOR]

Fractional differential equations are more and more used in modeling memory (history-dependent, non-local, or hereditary) phenomena. Conventional initial values of fractional differential equations are defined at a point, while recent works define initial conditions over histories. We prove that the conventional initialization of fractional differential equations with a Riemann-Liouville derivative is wrong with a simple counter-example. The initial values were assumed to be arbitrarily given for a typical fractional differential equation, but we find one of these values can only be zero. We show that fractional differential equations are of infinite dimensions, and the initial conditions, initial histories, are defined as functions over intervals. We obtain the equivalent integral equation for Caputo case. With a simple fractional model of materials, we illustrate that the recovery behavior is correct with the initial creep history, but is wrong with initial values at the starting point of the recovery. We demonstrate the application of initial history by solving a forced fractional Lorenz system numerically. [ABSTRACT FROM AUTHOR]

This paper investigates the control of Back-and-Forth motion to fetch object and Lower-Raise-Head motion to avoid obstacle of the wheeled inverted pendulum system with an input delay. In controlling the Back-and-Forth motion, the linear optimal control theory is used because the tilt angle of the pendulum is forced to be small enough by minimizing a quadratic performance criterion with large weight of tilt angle error, and the controller is represented by using predictor-based feedback. In controlling the Lower-Raise-Head motion, linearized models do not work due to the strong nonlinearity caused by big tilt angle for avoiding obstacle. Without considering yaw movement, the wheeled inverted pendulum system is decoupled, the subsystem governing the state of the tilt angle is transformed into a simple linear system by using feedback linearization. With a properly chosen trajectory tracking target, the control of Lower-Raise-Head motion is solved on the basis of optimal trajectory tracking control for linear subsystems with an input delay. Numerical simulations illustrate the effectiveness of the proposed approaches. [ABSTRACT FROM AUTHOR]

The design problem of optimal feedback control for linear systems with input delays is very important in many engineering applications. Usually, the linear systems with input delays are firstly converted into linear systems without delays, and then all the design procedures are based on the delay-free linear systems. In this way, the feedback controllers are not designed in terms of the original states. This paper presents some new closed-form formula in terms of the original states for the delayed optimal feedback control of linear systems with input delays. We firstly reveal the essential role of the input delay in the optimal control design of the linear system with a single input delay: the input delay postpones the action of the optimal control only. Based on this fact, we calculate the delayed optimal control and find that the optimal state can be represented by a simple closed-form formula, so that the delayed optimal feedback control can be obtained in a simple way. We show that the delayed feedback gain matrix can be 'smaller' than that for the controlled system with zero input delay, which implies that the input delay can be considered as a positive factor. In addition, we give a general formula for the delayed optimal feedback control of time-variant linear systems with multiple input delays. To show the effectiveness and advantages of the main results, we present five illustrative examples with detailed numerical simulation and comparison. [ABSTRACT FROM AUTHOR]

Abstract: The Cu2O/SnO2/graphene (CSG) and SnO2/graphene (SG) nanocomposite photocatalysts were prepared by simple sol-gel growth method, and characterized by Fourier transform infrared spectra (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET) measurements, respectively. The photocatalytic efficiency of catalysts were evaluated by degradation of pendimethalin under visible light irradiation (λ > 420 nm), which conformed that CSG and SG exhibited better photocatalytic activity than SnO2 or graphene alone. An effort has been made to correlate the photoelectro-chemical behavior of these samples to the rate of photocatalytic degradation of pendimethalin. The results demonstrated that the cuprous oxide addition into SG materials could greatly improve the photoelectric activity. The mechanism of photocatalytic reaction is proposed based on the energy band theory and experimental results. The CSG catalyst with higher photocatalytic activity may have great potential in various fields. [Copyright &y& Elsevier]

Abstract: Silver nanoparticles modified graphene-carbon nanotubes/polyimide (Gr-CNTs/PI) films have been prepared by electrochemical reduction of silver nitrate on potassium hydroxide hydroxylated of Gr-CNTs/PI films surface. The as-prepared nanocomposites were characterized by transmission electron microscopy, scanning electron microscopy, X-ray diffraction analyzer and semiconductor characterization system. The lower content of Gr-CNTs (≤10 wt. %) doping in PI matrix can improve the conductivity of PI films more clearly than pure CNTs. The conductivity can be regulated by controlling Gr-CNTs content in PI matrix. These silver nanoparticles into Gr-CNTs/PI films presented here can act as deposition seeds which can initiate subsequent electroless silver or copper or electrodeposition other metal. [Copyright &y& Elsevier]

The electrocatalytic oxidation of ethanol is studied on the non-noble catalysts Ni-Co/graphene and Ni/graphene supported on glass carbon electrode (GCE) in alkaline medium. The synthesized materials are characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and scanning transmission electron microscopy. The elements of Ni-Co/graphene and Ni/graphene catalysts are characterized using energy-dispersive X-ray spectroscopy. The electrocatalytic properties of Ni-Co/graphene and Ni/graphene for ethanol oxidation are investigated by cyclic voltammetry, chronoamperometry, and Tafel plot. Compared with Ni/graphene catalyst, Ni-Co/graphene has the higher electroactivity and better stability for ethanol oxidation. The rate constant ( k) and charge-transfer coefficient ( α) are calculated for the electron exchange reaction of the modified GCE. The results indicate that Co addition could promote the oxidation reaction at the Ni/graphene catalyst. Our study demonstrates that the low-cost electrocatalyst Ni-Co/graphene has a great potential for real direct ethanol fuel cells' application. [ABSTRACT FROM AUTHOR]

Abstract: Poly(l-arginine)/graphene composite film modified electrode was successfully prepared via a facile one-step electrochemical method and used for simultaneous determination of uric acid (UA), xanthine (XA) and hypoxanthine (HX). The electrochemical behaviors of UA, XA and HX at the modified electrode were studied by cyclic voltammetry and differential pulse voltammetry (DPV), and showed that the modified electrode exhibited excellent electrocatalytic activity toward the oxidation of the three compounds. The calibration curves for UA, XA and HX were obtained over the range of 0.10–10.0, 0.10–10.0 and 0.20–20.0μM by DPV, respectively and the detection limits for UA, XA and HX were 0.05, 0.05 and 0.10μM (S/N=3), respectively. With good selectivity and high sensitivity, the modified electrode has been applied to simultaneous determination of UA, XA and HX in human urine with satisfactory result. [Copyright &y& Elsevier]

Abstract: This paper investigates the BIBO stability of a class of fractional-delay systems with rational orders, a stability that holds true if all the characteristic roots have negative real parts only. Based on the Argument Principle for complex functions as well as Hassard’s technique for ordinary time-delay systems, an explicit formula is established for calculating the number of characteristic roots lying in the closed right-half complex plane of the first sheet of the Riemann surface, and in turn a sufficient and necessary condition is obtained for testing the BIBO stability of fractional-delay systems. As shown in the illustrative examples, this stability criterion involves easy computation and works effectively. [Copyright &y& Elsevier]

This paper presents a study on the problem of Hopf bifurcation control of time delayed systems with weak nonlinearity via delayed feedback control. It focusses on two control objectives: one is to annihilate the periodic solution, namely to perform a linear delayed feedback control so that the trivial equilibrium is asymptotically stable, and the other is to obtain an asymptotically stable periodic solution with given amplitude via linear or nonlinear delayed feedback control. On the basis of the averaging method and the center manifold reduction for delayed differential equations, an effective method is developed for this problem. It has been shown that a linear delayed feedback can always stabilize the unstable trivial equilibrium of the system, and a linear or nonlinear delayed feedback control can always achieve an asymptotically stable periodic solution with desired amplitude. The illustrative example shows that the theoretical prediction is in very good agreement with the simulation results, and that the method is valid with high accuracy not only for delayed systems with weak nonlinearity and via weak feedback control, but also for those when the nonlinearity and feedback control are not small. [ABSTRACT FROM AUTHOR]

Provides nonlinear dynamics of controlled mechanical systems. Stability of linear systems; Development of speed and system performance; Scope of hydraulic actuators.

In this work, we analyzed freshly emitted particles from ship exhaust in the Guangzhou port region before and after the implementation of a clean fuel policy. We used a single particle aerosol mass spectrometer (SPAMS) to measure the changes in the chemical compositions of single particles and evaluate the role of V as a tracer for ship emissions. Particles from high sulfur fuel (S F) oil (HS) combustion ships consisted of 54.8% elemental carbon-vanadium-sulfate (EC-V-S) and 25.0% vanadium-sulfate (V-S) particles, while particles from low S F oil (LS) combustion ships were composed of 38.7% organic carbon-sulfate (OC-S) and 28.6% elemental and organic carbon (ECOC) particles. The sulfate-containing particles exhibited a moderate decrease from 95% in HS emissions to 78% in LS emissions, which still suggests the dominant role of sulfate in LS emissions after the implementation of a clean fuel policy. The V-containing particles showed a sharp decrease from 67% in HS emissions to 14% in LS emissions along with the decrease in the relative peak area (RPA) of V, suggesting a remarkable reduction in V in ship exhaust. The count of V-containing particles in urban Guangzhou in June 2017 was generally ten times lower than that in June 2016, which was in accordance with the sharp decrease in V-containing particles in LS emissions rather than in HS emissions. Despite the decrease in V in source-oriented ship emitted particles, the ubiquitous distribution of V in particles from lower S F combustion ships suggests V is still effective as a tracer of ship emissions in port regions after the implementation of the clean fuel policy. Furthermore, the particles from LS emissions were investigated in comparison to those from gasoline vehicles (GV), diesel vehicles (DV) and coal combustion (CC) sources to better resolve ship-related particles in port regions. Unlabelled Image • Freshly emitted single particles from ship exhaust in Guangzhou port before and after clean fuel policy were comparatively studied. • The ubiquitous distribution of V in particles from lower sulfur fuel (LS) combustion ships suggests V is still an effective tracer of ship emissions. • A moderate decrease of sulfate-containing particles in LS particles indicates the persistent dominance of sulfate in ship exhaust. [ABSTRACT FROM AUTHOR]

• ON particles increased as NO x enhancement at night. • ON particles were mainly produced via heterogeneous reactions between NO x and organics. • The decrease of ON particles was associated with photo-bleaching effect. Organic nitrogen (ON) compounds play a significant role in the light absorption of brown carbon and the formation of organic aerosols, however, the mixing state, secondary formation processes, and influencing factors of ON compounds are still unclear. This paper reports on the mixing state of ON-containing particles based on measurements obtained using a high-performance single particle aerosol mass spectrometer in January 2020 in Guangzhou. The ON-containing particles accounted for 21% of the total detected single particles, and the particle count and number fraction of the ON-containing particles were two times higher at night than during the day. The prominent increase in the content of ON-containing particles with the enhancement of NO x mainly occurred at night, and accompanied by high relative humidity and nitrate, which were associated with heterogeneous reactions between organics and gaseous NO x and/or NO 3 radical. The synchronous decreases in ON-containing particles and the mass absorption coefficient of water-soluble extracts at 365 nm in the afternoon may be associated with photo-bleaching of the ON species in the particles. In addition, the positive matrix factorization analysis found five factors dominated the formation processes of ON particles, and the nitrate factor (33%) mainly contributed to the production of ON particles at night. The results of this study provide unique insights into the mixing states and secondary formation processes of the ON-containing particles. [Display omitted] [ABSTRACT FROM AUTHOR]

A fractional-order model is proposed to describe the dynamic behaviors of the velocity of blood flow in cerebral aneurysm at the circle of Willis. The fractional-order derivative is used to model the blood flow damping term that features the viscoelasticity of the blood flow behaving between viscosity and elasticity, unlike the existing fractional models that use fractional-order derivatives to replace the integer-order derivatives as mathematical/logical generalization. A numerical analysis of the nonlinear dynamic behaviors of the model is carried out, and the influence of the damping term and the external power supply on the nonlinear dynamics of the model is investigated. It shows that not only chaos via period-doubling bifurcation is observed, but also two additional small period-doubling-bifurcation-like diagrams isolated from the big one are observed, a phenomenon that needs further investigation. [ABSTRACT FROM AUTHOR]

Many Dendrobium species, which hold a high status and value in traditional Chinese medicine, grow on barks and rocks in the wild, often encountering harsh environments and facing droughts. However, the molecular mechanisms underlying the shift in the photosynthetic pathway induced by drought remain unclear. To address this issue, three Dendrobium species with different photosynthetic pathways were selected for sequencing and transcriptome data analysis after drought treatment. The findings included 134.43 GB of sequencing data, with numerous Differentially Expressed Genes (DEGs) exhibiting different response mechanisms under drought stress. Gene Ontology (GO)–KEGG-based enrichment analysis of DEGs revealed that metabolic pathways contributed to drought tolerance and alterations in photosynthetic pathways. Phosphoenolpyruvate Carboxylase (PEPC) was subjected to phylogenetic tree construction, sequence alignment, and domain analysis. Under drought stress, variations were observed in the PEPC gene structure and expression among different Dendrobium species; the upregulation of Dc_gene2609 expression may be caused by dof-miR-384, which resulted in the shift from C3 photosynthesis to CAM, thereby improving drought tolerance in Dendrobium. This study revealed the expression patterns and roles of PEPC genes in enhancing plant drought tolerance and will provide an important basis for in-depth research on Dendrobium's adaptation mechanisms in arid environments. [ABSTRACT FROM AUTHOR]

The accurate detection and counting of flowers ensure the grading quality of the ornamental plants. In automated potted flower grading scenarios, low detection precision, occlusions and overlaps impact counting accuracy. This study proposed a counting method combining a deep learning algorithm with multiple viewpoints. Firstly, a flower detection model, PA-YOLO, was developed based on YOLOv5 by designing a two-scale detection branch, optimizing the number of bottlenecks and integrating a dynamic head framework. Next, PA-YOLO was used to detect grouped 360-viewpoint images of each potted plant to determine the optimal number of viewpoints for counting. The detection results indicated that PA-YOLO achieved a mean average precision (mAP) of 95.4% and an average precision (AP) of 91.9% for occluded blooms on our Phalaenopsis flower dataset. For the optimal number of viewpoints, the average counting accuracy of buds and blooms was highest at three viewpoints, with scores of 96.25% and 93.33%, respectively. The final counting accuracy reached 95.56% in flower counting tests conducted from three viewpoints. The overall results suggest that the proposed method can effectively detect and count flowers in complex occlusion and overlap environments, providing guidance for designing and implementing the vision component in an automated potted flower grading system. [ABSTRACT FROM AUTHOR]

Raloxifene (RXF) is a hormone-like medication used for treating postmenopausal osteoporosis and estrogen-dependent breast cancer, yet associated with bad low bioavailability due to poor solubility. This study was intended to develop cyclodextrin/chitosan nanoparticles (ccNPs) for oral delivery of RXF in order to enhance the oral bioavailability. RXF-loaded ccNPs (RXF-ccNPs) were prepared by cyclodextrin inclusion followed by complexation with chitosan. RXF-ccNPs were fully characterized by particle size, morphology and in vitro drug release. The oral delivery efficacy and transepithelial transport potential were evaluated by pharmacokinetics, in situ single-pass intestinal perfusion, cellular uptake and ex vivo imaging. The resulting RXF-ccNPs were around 165 nm in particle size with a narrow distribution. The oral bioavailability of RXF was enhanced by 2.6 folds through ccNPs compared to RXF suspensions in rats. It was shown that RXF-ccNPs could improve the intestinal permeability of RXF, increase the cellular uptake of RXF and facilitate its transport across the absorptive epithelia. The results indicate that our developed ccNPs based on sulfobutylether-β-cyclodextrin and oligochitosan are a promising vehicle to orally deliver poorly water-soluble drugs over and above RXF. [ABSTRACT FROM AUTHOR]

A coupled two-ring-network with time delay is developed to avoid the weakness of a simple ring topology. The divide and conquer algorithm is used to analyze the distribution of the eigenvalues of the adjacent matrix. The stability of the equilibrium and inter-layer synchronization of the periodic dynamics are studied, and the dynamical interactions between coupled rings which lead to complicated mirror and reflection waves are further analyzed. Special attention is paid on the generalized synchronization between two rings when the adjacent matrix has repeated eigenvalues. Numerical simulations verify the theoretical results, and show that the appropriate settings of the time delay and transverse coupling can guarantee the "backup and recovery" procedure. • A coupled rings model is developed to avoid the weakness of a ring topology. • A divide and conquer algorithm is used to give distributions of the eigenvalues. • Stability of the periodic solutions is analyzed when system has repeated eigenvalues. • The inter-layer synchronization in the coupled rings is analyzed. • The proposed model can be used to achieve the "back and recovery" procedure. [ABSTRACT FROM AUTHOR]

SUMMARY: Dendrobium officinale is edible and has medicinal and ornamental functions. Polysaccharides and flavonoids, including anthocyanins, are important components of D. officinale that largely determine the nutritional quality and consumer appeal. There is a need to study the molecular mechanisms regulating anthocyanin and polysaccharide biosynthesis to enhance D. officinale quality and its market value. Here, we report that high light (HL) induced the accumulation of polysaccharides, particularly mannose, as well as anthocyanin accumulation, resulting in red stems. Metabolome and transcriptome analyses revealed that most of the flavonoids showed large changes in abundance, and flavonoid and polysaccharide biosynthesis was significantly activated under HL treatment. Interestingly, DoHY5 expression was also highly induced. Biochemical analyses demonstrated that DoHY5 directly binds to the promoters of DoF3H1 (involved in anthocyanin biosynthesis), DoGMPP2, and DoPMT28 (involved in polysaccharide biosynthesis) to activate their expression, thereby promoting anthocyanin and polysaccharide accumulation in D. officinale stems. DoHY5 silencing decreased flavonoid‐ and polysaccharide‐related gene expression and reduced anthocyanin and polysaccharide accumulation, whereas DoHY5 overexpression had the opposite effects. Notably, naturally occurring red‐stemmed D. officinale plants similarly have high levels of anthocyanin and polysaccharide accumulation and biosynthesis gene expression. Our results reveal a previously undiscovered role of DoHY5 in co‐regulating anthocyanin and polysaccharide biosynthesis under HL conditions, improving our understanding of the mechanisms regulating stem color and determining nutritional quality in D. officinale. Collectively, our results propose a robust and simple strategy for significantly increasing anthocyanin and polysaccharide levels and subsequently improving the nutritional quality of D. officinale. Significance Statement: Dendrobium officinale is edible and has medicinal and ornamental functions. Polysaccharides and flavonoids are the predominant bioactive compounds produced by D. officinale. However, the relationship between anthocyanin biosynthesis and polysaccharide biosynthesis is unclear. Our study revealed a mechanism underlying the high‐light‐induced co‐regulation of anthocyanin biosynthesis and polysaccharide biosynthesis in D. officinale, improving our understanding of how plants coordinate anthocyanin and polysaccharide biosynthesis. [ABSTRACT FROM AUTHOR]

• The solid waste steel slag is recycled for the preparation of steel slag base geopolymer (SSGP). • Alkali activation effectively increases the specific surface area of the SSGP, which is about 4 times that of steel slag. • Adsorption may explain for the removal Zn and Ni ions. • SSGP achieved the maximum adsorption capacity of Zn and Ni ions was 145.43 and 69.97 mg/g, respectively. Geopolymer was successfully prepared by using the steel slag and sodium hydroxide. The changes in morphology, functional groups, specific surface area and crystal structure during geopolymerization were observed by SEM-EDS, FTIR, BET, XRD, VSM and other techniques. The results showed that the specific surface area of the geopolymer is nearly 3 times higher than that of the steel slag, which enhanced the adsorption capacity of the geopolymer. Steel slag base geopolymer easily achieved the maximum adsorption capacities of Zn (145.43 mg/g) and Ni ions (69.97 mg/g). These findings imply that the steel slag base geopolymer is a promising material for removing Zn and Ni. [ABSTRACT FROM AUTHOR]

With potential anti-tumor and antioxidant properties, the polysaccharide content of D. nobile is relatively lower than that of the other medicinal Dendrobium. To find high-content polysaccharide resources, the polysaccharide (DHPP-Ⅰs) was prepared from D. Second Love 'Tokimeki' (a D. nobile hybrid) and compared with DNPP-Ⅰs from D. nobile. DHPP-Is (Mn 31.09 kDa) and DNPP-Is (Mn 46.65 kDa) were found to be O-acetylated glucomannans (-Glcp-(1,4) and O-acetylated-D-Manp-(1,4) backbones), analogous to other Dendrobium polysaccharides. DHPP-Ⅰs had higher glucose content (31.1%) and a lower degree (0.16) of acetylation than DNPP-Ⅰs (15.8%, 0.28). Meanwhile, DHPP-Ⅰs and DNPP-Ⅰs had the same ability in the radical scavenging assay, which was milder than the control of Vc. Both DHPP-Is and DNPP-Is inhibited SPC-A-1 cell proliferation in vitro, with obvious differences in dose concentrations (0.5–2.0 mg/mL) and treatment times (24–72 h). Therefore, the antioxidant activity of DHPP-Ⅰs and DNPP-Ⅰs is not associated with distinction in anti-proliferative activity. As a glucomannan derived from non-medicinal Dendrobium, DHPP-Ⅰs has similar bioactivity to other medicinal Dendrobium, and this could serve as a starting point for studying the conformational–bioactivity relationship of Dendrobium polysaccharides. [ABSTRACT FROM AUTHOR]

The output of an accelerometer often has coupled components of displacement and acceleration, and is rarely used individually for balancing tasks. In order to balance a wheeled inverted pendulum like the Segway, the conventional control usually requires gyroscopes or a combination of accelerometers and gyroscopes. In this paper, we prove that even in the presence of time delay, a wheeled inverted pendulum can be well stabilized with only one accelerometer as the sensor when the mechanical structure is slightly modified. The key idea is the introduction of an additional damper that does not have a physical connection with the wheels. Moreover, we show that balancing can be achieved with an appropriately selected accelerometer position over a range of time delays. [ABSTRACT FROM AUTHOR]

For the stability analysis of time-delay systems, the available methods usually require the exact evaluation of some quantities. The definite integral stability method, originated from the Argument Principle or the Cauchy Theorem, is effective because it only requires a rough estimation of the testing integral over a finite interval to judge stability. However, no general rule is given in the literature for properly choosing the upper limit of the testing integral. In this paper, two simple algorithms are presented for finding the parameter-dependent critical upper limit and a parameter-independent upper limit without any restriction on the number of time delays. These results improve and complete the definite integral stability method. As illustrated by the numerical examples, the proposed algorithms work effectively and accurately. [ABSTRACT FROM AUTHOR]

A facile and green method was developed to synthesize the graphene–carbon nanotubes (Gr–CNTs) nanocomposite with a sandwich lamination structure. Pt nanoparticles were loaded on the as-synthesized Gr–CNTs nanocomposite to prepare an electrochemical sensor for determining bisphenol A (BPA) in thermal printing paper. The electrochemical behavior of BPA on the Pt/Gr–CNTs nanocomposite was investigated by cyclic voltammetry (CV) and chronocoulometry (CC). The direct determination of BPA was accomplished by using differential pulse voltammetry (DPV) under optimized conditions. The oxidation peak current was proportional to the BPA concentration in the range from 6.0 × 10−8 to 1.0 × 10−5 M and 1.0 × 10−5 to 8.0 × 10−5 M with a correlation coefficient of 0.987 and 0.998, respectively. The detection limit was 4.2 × 10−8 M (S/N = 3). The fabricated electrode showed good reproducibility, stability and selectivity. The proposed method was successfully applied to determine BPA in thermal printing papers samples and the results were satisfactory. [ABSTRACT FROM AUTHOR]

Abstract: The sandwich lamination structure of graphene-multi-walled carbon nanotubes (Gr-CNTs) nanocomposite has been fabricated through in situ facile and green method. Then Pt nanoparticles are fabricated on Gr-CNTs via a simple one-step chemical reduction method in ethylene glycol (EG) and water system. The Gr-CNTs nanocomposite increased the solubility of carbon nanotubes in water, and CNTs could effectively prevent the irreversible aggregation of graphene. The Pt/Gr-CNTs were further characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD), which indicated that the as-synthesized Pt nanoparticles were successfully dispersed on the surface of Gr-CNTs nanocomposite. Electrochemical study has proved that the Pt/Gr-CNTs nanocomposite has higher catalytic activity in neutral medium for methanol oxidation, which is hopefully used in various types of cells and biosensors in physiological medium. [Copyright &y& Elsevier]

This paper presents a systematic study on the dynamics of a controlled Duffing oscillator with delayed displacement feedback, especially on the local bifurcations of periodic motions with respect to the time delay. The study begins with the analysis of the stability switches of the trivial equilibrium of the system with various parametric combinations and gives the critical values of time delay, where the trivial equilibrium may change its stability. It shows that as the time delay increases from zero to the positive infinity, the trivial equilibrium undergoes a different number of stability switches for different parametric combinations, and becomes unstable at last for all parametric combinations. Then, the method of multiple scales and the numerical computation method are jointly used to obtain a global diagram of local bifurcations of periodic motions with respect to the time delay for each type of parametric combinations. The diagrams indicate two kinds of local bifurcations. One is the saddle-node bifurcation and the other is the pitchfork bifurcation, of which the former means the sudden emerging of two periodic motions with different stability and the latter implies the Hopf bifurcation in the sense of dynamic bifurcation. A novel feature, referred to as the property of "periodicity in delay", is observed in the global diagrams of local bifurcations and used to justify the validity of infinite number of bifurcating branches in the bifurcation diagrams. The stability of the periodic motions is discussed not only from the high-order approximation of the asymptotic solution, but also from viewpoint of basin of attraction, which gives a good explanation for coexisting periodic motions and quasi-periodic motions, as well as an overall idea of basin of attraction. Afterwards, a conventional Poincaré section technique is used to reveal the abundant dynamic structures of a tori bifurcation sequence, which shows that the system will repeat similar quasi-periodic motions several times, with an increase of time delay, enroute to a chaotic motion. Finally, a new Poincaré section technique is proposed as a comparison with the conventional one, and the results show that the dynamical structures on the two kinds of Poincaré sections are topologically symmetric in rotation. [ABSTRACT FROM AUTHOR]

ABSTRACT Background Nursing-sensitive indicators are considered effective tools for improving the quality of care in hospitals. However, these have not been used in paediatric intensive care units ( PICUs) in China. Aim To develop nursing-sensitive indicators for PICUs and to assess the quality of nursing in PICUs in China based on the nursing-sensitive indicators. Design Multi-centre, cross-sectional study. Methods Structure, process and outcome indicators were developed and measured from 1 January to 31 March 2014 in seven PICUs in China. Results The structure indicators showed that one nurse cared for an average of 2·8 patients in a PICU, and 44% of nurses had a bachelor's degree. The process indicators revealed that hand-washing compliance varied across PICUs, whereas pain management and physical restraint have not been adequately addressed in China. The outcome indicators revealed that the incidence rates of ventilator-associated pneumonia and central-line-associated blood stream infections were 2·96 and 0·7, respectively, per 1000 device days. Patients were intubated for a total of 4392 mechanical ventilator days, and 32 patients (7·29‰) had an unplanned extubation. Nurses were moderately satisfied in their jobs (3·1 ± 0·3), and parents reported that nurses provide high quality of care. Conclusions This study developed and used nursing-sensitive indicators to assess the quality of nursing in PICUs in China, which provided a reference for national and international comparisons of nursing quality in PICUs. Nursing staffing levels and education should be improved. Pain management and physical restraints should be regulated in China's PICUs. Nurse managers need to explore staff attitudes towards implementation of family-centred care. The development of a national database of nursing quality indicators can contribute to quality and safety improvement. Relevance to clinical practice This study developed a set of nursing-sensitive indicators, and these indicators were used to assess and improve the quality of nursing in PICUs. [ABSTRACT FROM AUTHOR]

CD1E, one of the most important glycolipid antigens on T cell membranes, is required for glycolipid antigen presentation on the cell surface. Cell-based recombinant expression systems have many limitations for synthesizing transmembrane proteins such as CD1E, including low protein yields and miss folding. To overcome these challenges, here we successfully synthesized high-quality soluble CD1E using an E.coli cell-free protein synthesis system (CFPS) with the aid of detergent. Following purification by Ni2+ affinity chromatography, we were able to obtain CD1E with ≥90% purity. Furthermore, we used the string website to predict the protein interaction network of CD1E and identified a potential binding partner━B2M. Similarly, we synthesized soluble B2M in the E.coli CFPS. Finally, we verified the interaction between CD1E and B2M by using Surface Plasmon Resonance (SPR). Taken together, the methods described here provide an alternative way to obtain active transmembrane protein and may facilitate future structural and functional studies on CD1E. Cell-based recombinant expression systems have many limitations for synthesizing transmembrane proteins such as CD1E, including low protein yields and miss folding. To overcome these challenges, here we successfully synthesized high-quality soluble CD1E using an E.coli cell-free protein synthesis system (CFPS) with the aid of detergent. Following purification by Ni2+ affinity chromatography, we were able to obtain CD1E with ≥90% purity. Furthermore, we used the Surface Plasmon Resonance (SPR) to verified the interaction between CD1E and B2M. The methods described here provide an alternative way to obtain active transmembrane protein and may facilitate future structural and functional studies on CD1E. [Display omitted] • Cell-based protein expression systems have limitations for producing membrane proteins, including low yields and solubility. • The cell-free protein expression system saves time and improves overall production of functional full-length proteins. • Proteins that can be used to study protein-protein interactions were successfully synthesized by the cell-free protein expression systems. • The SPR result reveals the precise affinity between CD1E and B2M. [ABSTRACT FROM AUTHOR]

[Display omitted] • Reveal the concentration characteristics of three different types of VOCs. • Explore the drivers of photochemically consumed VOCs to generate O 3. • Quantify the effect of photochemical consumed VOCs sources on O 3 formation. Ground-level ozone (O 3) pollution has received widespread attention because its rising trend and adverse ecological impacts. However, the extremely strong photochemical reactions of its precursor volatile organic compounds (VOCs) increase the difficulty of reducing VOCs emissions to alleviate O 3. Here, we carried out a one-year comprehensive observation in two representative cities, Tianjin (TJ, Northern China) and Guangzhou (GZ, Southern China). By revealing the concentration characteristics of three different types of VOCs, i.e., initial VOCs without photochemical reaction (In-VOCs), consumed VOCs (C-VOCs), and measured VOCs after the reaction (M-VOCs), we elucidated the important role of C-VOCs in the formation of O 3. Although the overall trends were similar in both cities, the average concentration level of VOCs in GZ was 8.2 ppbv higher than that in TJ, and the photochemical loss of VOCs was greater by 2.2 ppbv. In addition, various drivers affecting O 3 generation from C-VOCs were specifically explored, and it was found that most alkenes of TJ were key substances for rapid O 3 formation compared to aromatics of GZ. Meanwhile, favorable meteorological conditions such as high temperature (T > 31 °C in TJ, and T > 33 °C in GZ), low relative humidity (56% in TJ and 45% in GZ), and stable atmospheric environment (proper pressure and gentle wind speed) also contribute to the generation of O 3. More importantly, we combined chemical kinetics and receptor model to quantify the three-type VOCs source contributions and assess the potential impact of C-VOCs sources on O 3 production, thus proposing environmental abatement technologies corresponding to the three types of VOCs. The differences in the comparison results of the three-type VOCs highlight the need to reduce O 3 pollution from C-VOCs sources, which provides insights for future clean air policies development. [ABSTRACT FROM AUTHOR]

With structural diversity of water-soluble polysaccharides, their precise quantitative analysis by phenol‑sulfuric acid method becomes more difficult and challenging. In this study, the quantification analysis of dextran and glucose in phenol sulfuric acid method was compared in this paper. When the concentration is below 90 μg/mL, the quantification of glucose is close to theoretical value, however, glucose derivatives have significantly different absorption. Later, quantitative factors of water-soluble polysaccharide in RID measurement were investigated. The optimum temperature was 40 °C and linear range was 0.3125–10.0 mg/mL in RID for dextrans (1.0–500 kDa) and glucose derivatives. Method validation studies of the RID method were further performed and compared to conventional phenol sulfuric acid method, which demonstrated that RID measurement is more reliable and satisfactory method. The intervention of water-soluble impurity in RID response should be well control below 6% (w/w). By comparison, the RID measurement could well alleviate drawbacks in phenol‑sulfuric acid method. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: In this work, the multi-walled carbon nanotubes-COOH (MWCNTs-COOH)/graphene (GNs)/gold nanoparticles (AuNPs) composite materials were synthesized by in situ growth of AuNPs on the surface of the MWCNTs-COOH/GNs. And then, the Bilirubin oxidase (BUD) was immobilized on the surface of the film to construct a biosensor for determination of Bilirubin. Morphology of the nanomaterials was analyzed by field-emission scanning electron microscopy, high resolution transmission electron microscopy, Brunauer–Emmett–Teller, and X-ray photoelectron spectroscopy. The performance of the biosensor was studied by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and amperometric response (i–t). It was demonstrated that the nanocomposite materials exhibited enhanced fast electron transfer and excellent biocompatibility. In this assay, the MWCNTs-COOH/GNs/AuNPs composite film based biosensor showed prominently electrocatalytic activity for the detection of Bilirubin with a linear range from 1.33μM to 71.56μM and the low limit of detection (LOD) is 0.34μM based on a signal to noise ratio (S/N=3). Meanwhile, the apparent Michaelis–Menten constant (K m ) was 64.86μM. In addition, this biosensor exhibited satisfying reproducibility, stability, feasibility and fast responses. These results provide a novel way for exact detection of Bilirubin in biotechnology and clinical diagnosis, and broaden the application of graphene and carbon nanotubes in biomaterials. [Copyright &y& Elsevier]

Abstract: A new facile in situ direct synthesis method of graphene–aniline (Gr–aniline) nanocomplex by a charge-transfer self-assembly technology at organic–aqueous interface was developed in this work. The graphene nanosheets can be dissolved in aniline without any prior chemical functionalization, and then Gr–aniline is soluble in a variety of organic solvents. The graphene–polyaniline (Gr–PANI) nanocomposite was prepared by simultaneous electropolymerization of Gr–aniline, and palladium nanoparticles were loaded onto the Gr–PANI nanocomposite to be used as a new electrode material for electrochemical sensing. Hydroquinone (HQ) and catechol (CC) were used as probe molecule to evaluate the electrocatalytic activity of Pd/Gr–PANI nanocomposite. The Pd/Gr–PANI nanocomposite shows so excellent electro-catalytic activities toward the oxidation of HQ and CC isomers that the oxidation peaks of the two molecules were well and easily resolved. The excellent reproducibility, stability and selectivity of the Pd/Gr–PANI nanocomposite make it a potential candidate as electrochemical sensor for simultaneous determination of HQ and CC isomers. [Copyright &y& Elsevier]

Abstract: Well-dispersed PtPdAu ternary alloy nanoparticles were synthesized on graphene sheets via a simple one-step chemical reduction method in ethylene glycol (EG) and water system, in which EG served as both reductive and dispersing agent. The electrocatalytic activity of PtPdAu/G was tested by methanol oxidation reaction (MOR). The catalyst was further characterized by transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), which indicated that the as-synthesized PtPdAu nanoparticles with alloy structures were successfully dispersed on the graphene sheets. Electrocatalytic properties of the catalyst for MOR in alkaline have been investigated by cyclic voltammetry (CV), chronoamperometry and Tafel curves. The electrocatalytic activity and stability of PtPdAu/G were superior to PtPd/G, PtAu/G and Pt/G. In addition, the anodic peak current on PtPdAu/G catalyst was proportional to the concentration of methanol in the range of 0.05–1.00M. This study implies that the prepared catalyst have great potential applications in fuel cells. [Copyright &y& Elsevier]

Nanocomposites composed of cuprous oxide (CuO) and graphene were synthesized via reduction of copper(II) in ethylene glycol. This material possesses the specific features of both CuO and graphene. Its morphology was characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy. Cyclic voltammetry was used to evaluate the electrochemical response of a glass carbon electrode (GCE) modified with the nanocomposite towards dopamine (DA). Compared to the bare GCE, the CuO nanoparticles modified electrode and the graphene modified electrode, the nanocomposites modified electrode displays high electrocatalytic activity in giving an oxidation peak current that is proportional to the concentration of DA in the range from 0.1 to 10 μM,with a detection limit of 10 nM (S/ N = 3). The modified electrode shows excellent selectivity and sensitivity even in the presence of high concentration of uric acid and can be applied to determine DA in real samples with satisfactory results. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]