Intelligent manipulator with flexible link and joint: modeling and vibration control

This paper presents a finite-element (FE) model of a manipulator with a flexible link and flexible joint as well as embedded PZT actuators and proposes a corrected rebuilt reduced model (CRRM) to make its dynamic characteristics more consistent with reality and facilitate control design. The CRRM considers the holding torque of the manipulator driving motor and eliminates the response divergence induced by a fault of the mass matrix of the FE model. In order to reduce the dimensions and maintain the precision of the model, an iterated improved reduction system (IIRS) method is adopted. Additionally, a LQR controller is designed based on the output function of the improved model. The simulation results demonstrate that the CRRM is consistent with reality and the active controller has good performance in suppressing vibration of the manipulator with both the flexible link and the flexible joint

Dispersive Liquid-Phase Microextraction with Solidification of Floating Organic Droplet Coupled with High-Performance Liquid Chromatography for the Determination of Sudan Dyes in Foodstuffs and Water Samples

Dispersive liquid-phase microextraction with solidification of floating organic drop (SFO–DLPME) is one of the most interesting sample preparation techniques developed in recent years. In this paper, a new, rapid, and efficient SFO–DLPME coupled with high-performance liquid chromatography (HPLC) was established for the extraction and sensitive detection of banned Sudan dyes, namely, Sudan I, Sudan II, Sudan III, and Sudan IV, in foodstuff and water samples. Various factors, such as the type and volume of extractants and dispersants, pH and volume of sample solution, extraction time and temperature, ion strength, and humic acid concentration, were investigated and optimized to achieve optimal extraction of Sudan dyes in one single step. After optimization of extraction conditions using 1-dodecanol as an extractant and ethanol as a dispersant, the developed procedure was applied for extraction of the target Sudan dyes from 2 g of food samples and 10 mL of the spiked water samples. Under the optimized conditions, all Sudan dyes could be easily extracted by the proposed SFO–DLPME method. Limits of detection of the four Sudan dyes obtained were 0.10–0.20 ng g^–1 and 0.03 μg L^–1 when 2 g of foodstuff samples and 10 mL of water samples were adopted, respectively. The inter- and intraday reproducibilities were below 4.8% for analysis of Sudan dyes in foodstuffs. The method was satisfactorily used for the detection of Sudan dyes, and the recoveries of the target for the spiked foodstuff and water samples ranged from 92.6 to 106.6% and from 91.1 to 108.6%, respectively. These results indicated that the proposed method is simple, rapid, sensitive, and suitable for the pre-concentration and detection of the target dyes in foodstuff samples

Intelligent manipulator with flexible link and joint: modeling and vibration control

This paper presents a finite-element (FE) model of a manipulator with a flexible link and flexible joint as well as embedded PZT actuators and proposes a corrected rebuilt reduced model (CRRM) to make its dynamic characteristics more consistent with reality and facilitate control design. The CRRM considers the holding torque of the manipulator driving motor and eliminates the response divergence induced by a fault of the mass matrix of the FE model. In order to reduce the dimensions and maintain the precision of the model, an iterated improved reduction system (IIRS) method is adopted. Additionally, a LQR controller is designed based on the output function of the improved model. The simulation results demonstrate that the CRRM is consistent with reality and the active controller has good performance in suppressing vibration of the manipulator with both the flexible link and the flexible joint

Eggshell Membrane-Based Biotemplating of Mixed Hemimicelle/Admicelle as a Solid-Phase Extraction Adsorbent for Carcinogenic Polycyclic Aromatic Hydrocarbons

A new solid-phase extraction (SPE) format was demonstrated, based on eggshell membrane (ESM) templating of the mixed hemimicelle/admicelle of linear alkylbenzenesulfonates (LAS) as an adsorbent for the enrichment of carcinogenic polycyclic aromatic hydrocarbons (PAHs) in environmental aqueous samples. The LAS mixed hemimicelle/admicelle formation and SPE of the target PAHs were conducted simultaneously by adding the organic target and LAS through a column filled with 500 mg of ESM. The effect of various factors, including LAS concentration, solution pH, ionic strength, and humic acid concentration on the recoveries of PAHs were investigated and optimized. The results showed that LAS concentration and solution pH had obvious effect on extraction of PAHs, and the recoveries of PAHs compounds decreased in the presence of salt and humic acid. Under the optimized analytical conditions, the present method could respond down to 0.1–8.6 ng/L PAHs with a linear calibration ranging from 0.02 to 10 μg/L, showing a good PAHs enrichment ability with high sensitivity. The developed method was used satisfactorily for the detection of PAHs in environmental water samples. The mixed hemimicelle/admicelle adsorbent exhibited high extraction efficiency to PAHs and good selectivity with respect to natural organic matter and was advantageous over commercial C₁₈ adsorbent, for example, high extraction yield, high breakthrough volume, and easy regeneration

Magnetic Chitosan–Iron(III) Hydrogel as a Fast and Reusable Adsorbent for Chromium(VI) Removal

The magnetic chitosan–iron­(III) hydrogel (MCh-Fe) was synthesized and characterized by SEM, TG, XRD, and FT-IR and used to remove toxic chromium­(VI) (Cr^VI) from aqueous solution. The adsorption of Cr^VI onto the MCh-Fe adsorbent was fast and could reach equilibrium in less than 30 min. The adsorption was well described by the pseudo-second-order rate model. The equilibrium isotherm was better matched with the Langmuir model. The adsorption of Cr^VI onto MCh-Fe was an endothermic and spontaneous process. The loading capacity of Cr^VI on the adsorbent remained at a high level even after five cycles, showing that MCh-Fe can be used for repeated Cr^VI removal. Column adsorption results indicated that below 0.5 mg L^–1 Cr^VI was found in the effluent up to about 30 and 350 bed volumes for two wastewaters containing 115.0 and 5.6 mg L^–1 Cr^VI, respectively. The Cr^VI removal mechanism of MCh-Fe was also investigated

Biosorption of Multifold Toxic Heavy Metal Ions from Aqueous Water onto Food Residue Eggshell Membrane Functionalized with Ammonium Thioglycolate

A new biosorbent material from eggshell membrane was synthesized through thiol functionalization, which is based on the reduction of disulfide bonds in eggshell membrane by ammonium thioglycolate. The thiol-functionalized eggshell membrane was characterized, and its application as an adsorbent for removal of Cr­(VI), Hg­(II), Cu­(II), Pb­(II), Cd­(II), and Ag­(I) from aqueous water has been investigated. The experimental results revealed that the adsorption abilities of the thiol-functionalized eggshell membrane toward Cr­(VI), Hg­(II), Cu­(II), Pb­(II), Cd­(II), and Ag­(I) improved 1.6-, 5.5-, 7.7-, 12.4-, 12.7-, and 21.1-fold, respectively, compared with that of the eggshell membrane control. The adsorption mechanism and adsorption performance, including the adsorption capacity and the kinetics of the thiol-functionalized eggshell membrane for the target heavy metals, were investigated. The effects of solution pH, coexisting substances, and natural water matrices were studied. The thiol-functionalized eggshell membrane can be used as column packing to fabricate a column for real wastewater purification

Facile Low Temperature Hydrothermal Synthesis of Magnetic Mesoporous Carbon Nanocomposite for Adsorption Removal of Ciprofloxacin Antibiotics

A new magnetic mesoporous carbon composite (Fe₃O₄/C) was synthesized and characterized by XRD, nitrogen adsorption–desorption isotherms, FT-IR, TG, ζ potential, SEM, and TEM. The performance of using Fe₃O₄/C composite as an adsorbent for removal of antibiotics using ciprofloxacin (CIP) as a model was investigated. The Langmuir adsorption isotherm was applicable to fit the removal process. Kinetics of the CIP removal was found to follow a pseudo-second-order rate equation. The solution pH is critical for the adsorption of CIP on Fe₃O₄/C, and the maximum adsorption of CIP could be reached under neutral conditions. In addition, the Fe₃O₄/C adsorbent showed high magnetization and operational stability, and it could be readily separated from solution by applying an external magnetic field. After 10 recycle runs, over 85% of the adsorption capacity was retained. The high performance, low cost, and easily recyclable Fe₃O₄/C composite may become a promising adsorbent for water treatment

Visualization of the pH Response through Autofluorescent Poly(styrene-<i>alt</i>-<i>N</i>‑maleimide) Polyelectrolyte Brushes

Polyelectrolyte brushes can undergo reversible conformational transitions in response to changes in environmental pH and ionic strength. Therefore, they offer great potential for the design of “smart” surfaces and surface-based sensing devices. Herein, we report weak acidic polyelectrolyte brushes with pH-dependent autofluorescence based on alternating copolymers of styrene and tailor-made N-maleimides, which exhibit “clusteroluminescence” due to the through-space conjugation of π-chromophoric subfluorophores. Swelling behavior of the polyelectrolyte brushes was evaluated as a function of pH via in-solution atomic force microscopy (AFM) analyses. The correlation between the pH-induced conformational transitions and autofluorescence was confirmed with confocal laser scanning microscopy (CLSM) and two-photon laser scanning microscopy. Poly(styrene-alt-N-maleimide)-based well-defined, stable polyelectrolyte brushes, generating optical signals from conformational changes without conventional fluorophores, may enable the design of sensors and optoelectronic devices

CoFe₂O₄ Nanoparticles as Oxidase Mimic-Mediated Chemiluminescence of Aqueous Luminol for Sulfite in White Wines

Recently, the intrinsic enzyme-like activity of nanoparticles (NPs) has become a growing area of interest. However, the analytical applications of the NP-based enzyme mimetic are mainly concentrated on their peroxidase-like activity; no attempts have been made to investigate the analytical applications based on the oxidase mimic activities of NPs. For the first time, we report that CoFe₂O₄ NPs were found to possess intrinsic oxidase-like activity and could catalyze luminol oxidation by dissolved oxygen to produce intensified chemiluminescence (CL). The effect of sulfite on CoFe₂O₄ NP oxidase mimic-mediated CL of aqueous luminol was investigated. It is very interesting that when adding sulfite to the luminol–CoFe₂O₄ system, the role of sulfite in the luminol–CoFe₂O₄ NP–sulfite system depends on its concentration. At a relatively low concentration level, sulfite presents an inhibition effect on the luminol–CoFe₂O₄ NP system. However, it does have an enhancement effect at a higher concentration level. Investigations on the effect of the solution pH and luminol and CoFe₂O₄ NP concentrations on the kinetic characteristics of the studied CL system in the presence of trace sulfite suggested that the enhancement and inhibition of the luminol–CoFe₂O₄ NP–sulfite CL system also depended on the solution pH. It seems that the concentrations of luminol and CoFe₂O₄ NPs did not influence the CL pathway. The possible mechanism of the luminol–CoFe₂O₄ NP–sulfite CL system was also discussed. On this basis, a flow injection chemiluminescence method was established for the determination of trace sulfite in this study. Under the optimal conditions, the proposed system could respond down to 2.0 × 10^–8 M sulfite. The method has been applied to the determination of trace sulfite in white wine samples with satisfactory results. The results given by the proposed method are in good agreement with those given by the standard titration method

Co Nanoparticles Embedded in 2D N‑Doped Porous Carbon Nanosheets for Evaluating Acetylcholinesterase Activity

Here, we reported a facile strategy to prepare Co nanoparticles (NPs) encapsulated in two-dimensional (2D) N-doped porous carbon nanosheets (2D Co/NC) via pyrolyzing Zn/Co bimetallic metal–organic framework (MOF) nanosheets, which were prepared in aqueous solution. The successful synthesis of Zn/Co bimetallic MOF nanosheets and 2D Co/NC was demonstrated by various characterization techniques. The optimized 2D Co0.6/NC-700 and three-dimensional (3D) Co0.6/NC-700 show catalase- and oxidase-like activities. They can break down H2O2 into O2 and oxidize 3,3′,5,5′-tetramethylbenzidine (TMB) to a blue product, while the former displays superior performance to its 3D Co0.6/NC-700 aggregated nanoparticles. Specifically, the oxidase-mimicking activity and catalase-like activity of 2D Co0.6/NC-700 are 1.64-fold and 6.9-fold those of 3D Co0.6/NC-700, respectively. Relative to 3D Co0.6/NC-700 aggregates, the improvement of the catalytic activity of 2D Co0.6/NC-700 is likely ascribed to its 2D leaf-like structure with more accessible dispersed active sites and the interaction between Co NPs and N-doped carbon nanosheets. 2D Co0.6/NC-700 displayed superior oxidase-like activity with a low Michaelis–Menten constant (Km) of 0.35 mM. Interestingly, in the presence of both acetylcholinesterase (AChE) and acetylthiocholine (ATCh), the oxidase-like activity was suppressed because of the generation of thiocholine, which led to the fading of the TMB color reaction. On this basis, a colorimetric assay was developed for the determination of AChE activity. 2D Co0.6/NC-700 displayed excellent detection performance in AChE activity, with a linear detection range of 0.0002–0.8 U L–1 and a low detection limit of 0.0002 U L–1. Remarkably, the method showed good selectivity to AChE, and other coexisting substances had minor interference. The method was satisfactorily utilized to determine the AChE activity in real samples