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Objective: Saccadic Intrusions (SIs) are abnormal eye movements during gaze fixation. Studies have indicated the clinical relevance of SIs, especially of square wave jerks (SWJ) in ALS. We used a software-based platform to extract SIs as a part of an interventional drug trial. The objective was to examine SIs' change over time as a potential biomarker of ALS disease progression. Methods: 28 ALS patients (61.95 ± 8.6 years) were assessed with the revised ALS Functional Rating Scale (ALSFRS-R) and with an oculometric test. Changes of SIs over time and correlations with ALSFRS-R and its bulbar subscale were calculated. A power calculation was conducted to understand the practical implications of results. Results: A significant increase of SWJ over trial duration was observed, with an increase in frequency (mean rise of 0.14 ± 0.28, p < 0.01), amplitude (0.001 ± 0.0016 degrees, p < 0.005), overall duration of SWJ (0.13 ± 0.25, in %, p < 0.01), and in their relative part out of all intrusions (0.18 ± 0.32, in %, p < 0.005). Negative correlations were found with the bulbar subscale (R=-0.43, −0.41, −0.39 and −0.47, respectively, p < 0.001). The required sample size for observing a 40% reduction in bulbar aspects when using the oculometric test (α = 0.05 and β = 0.8), was found to be 150 patients per arm, compared with 200 patients using the bulbar subscale. Conclusions: Evaluation of saccadic intrusions during fixation was able to detect disease progression over time, correlated with ALSFRS-R bulbar subscale. Eye movements can potentially serve as an objective biomarker in ALS clinical trials and reduce the required sample size to show clinical effect of therapies. [ABSTRACT FROM AUTHOR]

A new electrochemical sensor for the highly sensitive and selective determination of dopamine was developed, based on the use of a glassy carbon electrode modified with cobalt(II) polymer. Both electrochemical and morphological characterizations were investigated. Square wave voltammetry (SWV) was used for the determination of dopamine. From the SWV results obtained on the modified electrode under the optimized conditions, the successive addition of dopamine increased the anodic peak current. The results obtained show a linear response of the electrode modified with Co(II) polymer in a wide concentration range. Each concentration decade is characterized by a new calibration plot with a corresponding mathematical expression. The highest sensitivity (13.182) was obtained for the lowest concentration range, and the detection limit of 0.03 µM, calculated based on the 3 × sb/m criterion, indicates a very high sensitivity and great application potential. When analyzing a real sample, the modified electrode showed good electroanalytical activities in terms of oxidation of dopamine, good anti-interference ability, stability, reproducibility, and potential applicability in commercial pharmaceutical samples. [ABSTRACT FROM AUTHOR]

A novel approach was employed to craft innovative carbon-paste electrodes using cerium(IV) oxide (CeO2)-doped clay, aiming to modify graphite electrodes. The introduction of Ce involved the adsorption of Ce3+ ions onto an activated carbon (AC) clay mixture, showcasing an impressive adsorption capacity of 40.0 mg g−1, which surpasses that of clay alone. This step was undertaken to enhance the conductivity of raw clay and increase its electrochemical surface area. Sintering clay-CeO2 at 1000 °C resulted in the maximum electrochemical area when utilized as a 10 wt% dopant for graphite electrodes. Heavy metal ion analysis (HMI) involving Cd2+, Pb2+, Cu2+, and Hg2+ was conducted using five electrochemical techniques: Cyclic Voltammetry (CV), Square Wave Voltammetry (SWV), Normal Pulse Voltammetry (NPV), Differential Pulse Voltammetry (DPV), and Linear Sweep Voltammetry (LSV). SWV emerged as the optimal technique and was termed SWAdSV after the stripping process, displaying peak current responses for Cd2+ (74.7 µA), Pb2+ (42.4 µA), Cu2+ (36.0 µA), and Hg2+ (22.8 µA). Calibration curves were utilized to determine the Limit of Detection (LOD) and Limit of Quantification (LOQ) values for Cd2+, Pb2+, Cu2+, and Hg2+. The repeatability, expressed as %RSD, for the same electrode was found to be 1.70%, 2.04%, 1.14%, and 3.61% for Cd2+, Pb2+, Cu2+, and Hg2+. While the reproducibility, also expressed as %RSD, for different electrodes was determined to be 1.98%, 2.31%, 1.52%, and 1.89% for Cd2+, Pb2+, Cu2+, and Hg2+, respectively. [ABSTRACT FROM AUTHOR]

Detecting multiple targets in complex cellular and biological environments yields more reliable results than single-label assays. Here, we introduced an electrochemical biosensor equipped with computing functions, acting as a smart automaton to enable computing-based detection. By defining the logic combinations of miR-21 and miR-122 as detection patterns, we proposed the corresponding AND and OR detection automata. In both logic gate modes, miR-21 and miR-122 could be replaced with single-stranded FO or FA, modified with Fc, binding to the S chain on the electrode surface. This process led to a significant decrease in the square wave voltammetry (SWV) of Fc on the same sensing platform, as numerous ferrocene (Fc)-tagged DNA fragments escaped from the electrode surface. Experimental results indicated that both automata efficiently and sensitively detected the presence of the two targets. This strategy highlighted how a small amount of target could generate a large current signal decrease in the logic automata, significantly reducing the detection limit for monitoring low-abundance targets. Moreover, the short-stranded DNA components of the detection automata exhibited a simple composition and easy programmability of probe sequences, offering an innovative detection mode. This simplified the complex process of detection, data collection, computation, and evaluation. The direct detection result ("0" or "1") was exported according to the embedded computation code. This approach could be expanded into a detection system for identifying other sets of biomarkers, enhancing its potential for clinical applications. [ABSTRACT FROM AUTHOR]

In this research, we describe the first aptasensor for the detection of the Rift Valley Fever virus (RVFV). The process involved the selection of aptamers through the systematic evolution of ligands by the exponential enrichment (SELEX) technique. After 12 rounds of selection, 6 aptamers were selected and the corresponding binding affinities were assessed using fluorescence binding assays, revealing dissociation constants ranging from 15.45 to 40.98 nM. Notably, among the aptamers, RV2 and RV3 exhibited the highest binding affinities toward RVFV, with dissociation constants of 15.45 and 18.62 nM, respectively. Thiol-modified aptamers were subsequently immobilized onto screen-printed gold electrodes, facilitating the label-free detection of RVFV through square wave voltammetry. The voltammetric aptasensor demonstrated an excellent sensitivity, with a detection limit of 0.015 ng/mL. In addition, cross-reactivity assessments were conducted, where negligible response was obtained when the aptasensor was exposed to non-specific proteins. [ABSTRACT FROM AUTHOR]

In this study, the electrochemical properties of nepafenac, used after eye surgery operations, were investigated on a disposable pencil graphite electrode. Cyclic and square wave voltammetry techniques were used to investigate the electrochemical properties of nepafenac. Two peaks at potentials of approximately +0.33 V and +1.03 V in the anodic direction and two peaks at potentials of approximately +0.29 V and +0.08 V in the cathodic direction were observed on the surface of the disposable pencil electrode in acetate (pH 4.8) medium with the cyclic voltammetry technique. The analytical performance of the developed voltammetric technique had good linearity in the concentration range of 0.30 µM to 3.5 µM at pH 4.8. The LOD value of this voltammetric method in acetate (pH 4.8) medium was calculated as 0.035 µM (8.90 ng mL−1). For reproducibility, the relative standard deviation (RSD) values for Ia and IIa anodic peak current/potential were found to be 1.45%/0.43% and 1.28%/0.25%, respectively. The voltammetric method was successfully applied to urine and pharmaceutical preparations and the results were compared with the spectrophotometric method. [ABSTRACT FROM AUTHOR]

A novel bimetallic Fe/Co-metal–organic framework (MOF) hydrogel-based wearable sweat sensor was developed. Morphological and structural analysis of the hydrogel shows uniformly sized spines and spindle-shaped particles of the Fe/Co-MOF, and it has a high surface area (132.306 m2 g−1) and porosity (0.059 cm3 g−1) as confirmed by Brunauer–Emmett–Teller (BET) studies. The integration of the bimetallic MOF into a polyvinyl alcohol/chitosan (PVA/CS)-mixed matrix resulted in a multiple network hydrogel. The optimisation study investigated the effects of different pH of the PBS electrolyte, scan rates, and accumulation time in voltammetry. The electrochemical methods such as cyclic voltammetry (CV), square wave voltammetry (SWV), and electrochemical impedance spectroscopy (EIS) provided information on the redox behaviour, electrochemical stability, and catalytic activity of the hydrogel. The sensor demonstrates a wide linear detection range from 0.05 µM to 100 mM, a superior sensitivity of 0.02 mA mM−1 cm−2, and a lower limit of detection of 0.01 µM. Active sites distributed over the hydrogel surface, specifically Fe2+ and Co2+ within the MOF structure, catalyse the oxidation of l-lactic acid, resulting in electron transfer and the formation of pyruvic acid. Notably, the fabricated sensor exhibits high selectivity, effectively discriminating against interfering species such as uric acid, ascorbic acid, glucose, urea, dopamine, NaCl, and CaCl2. Real-time analysis conducted in a simulated sweat sample via the standard addition method resulted in good recovery percentages of a minimum of 98%. The work presented here is a versatile and simple platform for point-of-care testing, especially for athletes and military personnel. [ABSTRACT FROM AUTHOR]

An aptamer-based electrochemical sensor for the sensitive detection of staphylococcal enterotoxin type A (SEA) is presented. The truncated aptamer AptSEA1.4 used in this work was screened using computational techniques, which reduced the cost of the SELEX screening process. The aptamer-SEA interactions were confirmed by employing circular dichroism (CD) and fluorescence spectroscopy. Afterwards, for developing an electrochemical aptasensor, a fabricated GNR/FTO aptasensor was prepared and characterized using scanning electron microscopy-energy-dispersive X-ray analysis (SEM–EDX), atomic force microscopy (AFM), cyclic voltammetry (CV), and square wave voltammetry (SWV). A detailed investigation of aptamer and SEA interaction in the presence of various experimental conditions was also conducted through SWV and electrochemical impedance spectroscopy (EIS). The aptamer exhibits a strong affinity for SEA, with a dissociation constant (Kd) of 19.93 nM. The aptasensor is sensitive, with a lower limit of detection of 12.44 pg mL−1. It has good stability, repeatability, and specificity and has displayed highly specific and sensitive detection SEA in spiked packaged mixed fruit juice and milk, with a recovery of 95–110%. The aptasensor has high promise for detecting SEA in other food items. [ABSTRACT FROM AUTHOR]

Axial modification of boron (III) subphthalocyanine bromides with 4‐hydroxy‐benzoic acid successfully led to the formation of the macrocycles with anchored 4‐carboxyphenoxy group [RsPcPHBA] (R=tBu, H) in the axial position and to a new dimer [sPcPHBAsPc] as minor product. Tri‐tert‐butyl and unsubstituted subphthalocyanines bearing benzoate ([tBusPcBA], [sPcBA]), phenoxy‐group ([tBusPcOPh], [sPcOPh])) in the axial position, have been also investigated as well as control sPcs. All compounds were characterized by NMR, IR, UV‐Vis and mass spectrometry. The electrochemical properties were studied using cyclic voltammetry (CV) and square wave voltammetry (SWV). Singlet oxygen generation was systematically measured for all synthesized [RsPcX] by kinetic method of chemical trap decomposition (DPBF) and by determination of phosphorescence of singlet oxygen (at 1270 nm). Axially modified subphthalocyanines exhibit high quantum yields of singlet oxygen (1O2) generation (0.47–0.62). The observed exceptional photostability in oxygen‐saturated ethanol or toluene solutions and high 1O2 quantum yields allows to use [tBusPcPHBA] as photocatalysts of selective oxidative transformations of organic sulfides to sulfoxides. Loading the catalyst to 9.7 ⋅ 10−2 mol % made it possible to achieve complete conversion of the substrate (TON up to 1700). [ABSTRACT FROM AUTHOR]

Fluorescent molecules have enabled single-molecule detection of toxins, biomarkers, and pollutants under controlled conditions. Unfortunately, these fluorophores are typically organic molecules that degrade or become photobleached when applied to non-ideal systems. Noble metal nanoclusters, in particular gold nanoclusters (AuNCs), pose a solution to the problems of degradation and photobleaching. Despite the low fluorescence quantum yield of AuNCs without thiolated ligands, labeling these clusters with fluorescent ligands allows enhancement of the fluorescence intensity and manipulation of the emission wavelength. In this work, we explore the labeling of the bi-icosahedron Au25 (bi-Au25) nanocluster. The bi-Au25 nanocluster has unique stability and electrochemical properties making it an attractive, yet poorly studied, candidate for fluorescent labeling. In order to demonstrate its potential as a near-IR emitting nanocluster we synthesized and labeled the bi-Au25 with the novel fluorophore 6-(9-Anthryl)-5-hexyne-1-thiol, or simply anthracenethiol. Two common ligands used in the synthesis of bi-Au25 are hexanethiol and phenylethanethiol, and we spectroscopically verify the ability for the straight-chain alkane hexanethiol to block the labeling of bi-Au25, while the aromatic phenylethanethiol enables the labeling of the complex. These products are characterized with square wave voltammetry, UV-vis and fluorescence spectrophotometry, and NMR spectrometry. The fluorescently labeled bi-Au25 nanocluster demonstrates a 25x increase in NIR photoluminescence at ~ 810 nm when originally capped with phenylethanethiol, and not the long-chain alkanethiol. The quantum yield of this cluster has been improved from 0.0786% in the unlabeled cluster to 1.97% in the labeled product. [ABSTRACT FROM AUTHOR]

Through the manipulation of electrospinning solution properties, we tuned the morphology and porosity of electrospun titanium dioxide (TiO2) nanofibers. Using a modified glassy carbon electrode (GCE) with TiO2 nanofibers and Ag-coated carbon nanofibers (AgCNFs) with nafion as a binder, heavy metal ions (HMIs) have been detected with nanomolar detection limits using square wave anodic stripping voltammetry (SWASV). It has been determined how the Cd2+ current signal responds to changes in deposition potential, deposition time, buffer solution pH, and drop-cast volume. The estimated sensitivity of Cd2+ is 49.98 µA µM−1 and the limit of detection (LOD) is found to be 12.75 nM by the three-sigma (3σ) method. The TiO2/AgCNF/nafion/GCE electrode can simultaneously detect Cd2+, Pb2+, Cu2+, and Hg2+ ions without mutual interference. The sensitivities toward Cd2+, Pb2+, Cu2+, and Hg2+ are 39.59, 42.75, 15.67, and 10.52 µA µM−1, respectively. The LOD toward Cd2+, Pb2+, Cu2+, and Hg2+ are 40.14, 31.69, 93.31, and 208.26 nM, respectively. These quantities fall far short of the WHO's recommended guideline values. This combination of very porous TiO2 nanofiber with AgCNF leads to an innovative sensor platform that has very low LOD compared to the previous sensors that have been reported. [ABSTRACT FROM AUTHOR]

An efficient stable electrochemical method for the determination of thiophene as a sulfur model compound in gasoline has been investigated based on the electrodeposition of graphene oxide and dicyandiamide on graphite electrode by cyclic voltammetry. The electroactive layer performance was considered by linear sweep voltammetry and square wave voltammetry by examining scan rates and their relevant equations to evaluate the electrochemical parameters. This modified electrode has high electrocatalytic characteristics to irreversible electrooxidation of thiophene. The electron transfer coefficient (α) was equal to 0.78, the electron transfer rate constant (log KS) was 3.2 s−1, and the saturated adsorptive capacity of the electroactive substance at the electrode surface (Γmax) was 1.14 × 10−8 mol cm−2 at pH 8 at low working potential of 0.5 V versus Ag/AgCl reference electrode. Scanning electron microscopy of the surface revealed the nanostructure of electrodeposited films and the morphology. This sensor is capable of electrochemical response to thiophene over the concentration range from 25 to 250 nmol L−1 with a detection limit of 8.31 nmol L−1, and a quantification limit of 25.18 nmol L−1. The method's reliability was checked regarding the simulated gasoline samples and the desired response and sensitivity were provided. The wide dynamic range, low detection limit, favorable precision and accuracy, and fast response with no interferences confirm the ability of this sensor for thiophene determination. This nano-sensor can be used for electrochemical in-situ direct monitoring of liquid fuel desulfurization processes. [ABSTRACT FROM AUTHOR]

This report presents a new application for yttrium oxide (YOX) in the modification of carbon paste electrodes with excellent electroactivity for the independent detection of dopamine (DA) and ascorbic acid (AA). The surface of the YOX‐modified electrode was characterized with SEM and EDS. The electroactive properties of DP and AA were studied with cyclic voltammetry (CV), square wave voltammetry (SWV) and amperometry (Am). The activity of DA and AA increased by more than 100 % when YOX/CPE was used, which allowed us to obtain detection limits of 0.04 and 0.06 μmol/L for DA and AA, respectively. The usefulness of YOX/CPE was tested with real human urine, fresh orange juice and vitamin C tablets, and the results were acceptable. [ABSTRACT FROM AUTHOR]

In order to find an explanation for the mechanism in a plasma operated with an alternating voltage, or rather a square wave voltage, such a plasma was investigated. It was found that Penning ionization, charge transfer, and photoionization played a minor or even no role in the soft ionization mechanism of a FµTP. If the collision of plasma gases with air does not contribute to soft ionization, it should also be possible to use a separated plasma for soft ionization. Preliminary investigations show that it is possible to ignite a diagnosis gas with a plasma gas even when there is a barrier such as glass between those gases. A temporally and locally limited potential must be produced at the outer surface to achieve this. This potential should be sufficient to ionize the environment softly and to be able to use this so-called closed µ-tube plasma as a new ionization source. [ABSTRACT FROM AUTHOR]

The effects of occlusal splints on sport performance have already been studied, although their biomechanical impacts are often overlooked. We investigated the kinematical changes during running until exhaustion at severe intensity while wearing a mandibular advancement occlusal splint. Twelve trained runners completed (i) an incremental protocol on a track to determine their velocity corresponding to maximal oxygen uptake and (ii) two trials of square wave transition exercises at their velocity corresponding to maximal oxygen until exhaustion, wearing two occlusal splints (without and with mandibular advancement). Running kinematics were compared within laps performed during the square wave transition exercises and between splint conditions. The mandibular advancement occlusal splint increased the running distance covered (~1663 ± 402 vs. 1540 ± 397 m, p = 0.03), along with a noticeable lap effect in decreasing stride frequency (p = 0.04) and increasing stride length (p = 0.03) and duty factor (p < 0.001). No spatiotemporal differences were observed between splints, except for improved balance foot contact times in the mandibular advancement condition. An increased knee flexion angle at initial contact (p = 0.017) was noted along laps in the non-advancement condition, despite the fact that no differences between splints were found. Running patterns mainly shifted within laps rather than between conditions, indicating that a mandibular advancement occlusal splint had a trivial kinematical effect. [ABSTRACT FROM AUTHOR]

As a remote and non‐contact stimulus, light offers the potential for manipulating the polarization of ferroelectric materials without physical contact. However, in current research, the non‐contact write‐read (erase) process lacks direct observation through the stable current as output signal. To address this limitation, we investigated the photoinduced polarization switching capabilities of the cyanide‐bridged compound [Fe2Co] using visible light, leading to the achievement of rewritable polarization. By subjecting [Fe2Co] crystals to alternating irradiation with 785 nm and 532 nm light, the polarization changes exhibited a distinct square wave pattern, confirming the reliability of the writing and erasing processes. Initialization involved exposing specific crystal units to 532 nm light for storing "1" or "0" information, while reading was accomplished by scanning the units with 785 nm light, resulting in brief current pulses for "1" states and no current signal for "0" states. This research unveils new possibilities for optical storage systems, paving the way for efficient and rewritable data storage and retrieval technologies, such as the next‐generation memories. [ABSTRACT FROM AUTHOR]

This study explores the impact of different magnetic driving field waveforms on nanoparticle heating in magnetic hyperthermia. Our research, which shifts the usual focus from individual nanoparticle properties to interacting particle clusters, evidences that square waves induce more uniform and greater heating than sinusoidal waves. The sequential switching observed with sinusoidal waves, which additionally strongly depends on the alignment of the particle cluster with respect to the direction of the field, leads to less uniform heating within and among different clusters. In contrast, a square waveform leads to simultaneous particle switching, thereby homogenizing the heat and potentially mitigating hazardous hot spots. These findings reaffirm the potential advantages for magnetic hyperthermia treatments using non-harmonic field waveforms, offering more uniform heating and the possibility of reducing the applied field exposure. [ABSTRACT FROM AUTHOR]

The electrochemical detection of two pharmaceuticals, diclofenac (DCF) and carbamazepine (CBZ), was investigated as an oxidation current using boron‐doped nanocrystalline diamond (BDD) thin‐film electrodes. Both voltammetry and flow injection analysis with amperometric detection (FIA‐EC) were used to measure the drugs in standard solutions and a urine simulant. The oxidation potential for DCF was ca. 0.7 V vs. Ag/AgCl (3 M KCl) in 0.1 M phosphate buffer (pH 7.2) and was ca. 1.2 V for CBZ in 0.1 M perchloric acid. The DCF oxidation reaction was diffusion controlled at the detection potential with evidence of some surface fouling by reaction products. The CBZ oxidation reaction was also controlled by diffusion at the detection potential, but with no surface fouling. The voltammetric peak currents for both drugs increased linearly with the concentration in the micromolar range (r2≥0.994). FIA‐EC analysis of DCF and CBZ revealed a linear dynamic range from at least 0.1 to 100 μM with the actual minimum concentration detectable (S/N=3) being less than the lowest concentration measured. The recovery percentage for DCF in the urine simulant ranged from 94–108% and from 97–100% for CBZ, both assessed using square wave voltammetry. FIA‐EC data revealed that the BDD electrodes offer excellent intra and inter‐electrode repeatability with an RSD for DCF and CBZ of 4.90% and 3.81%, respectively. The BDD electrode provided good reproducibility and response stability over eight days of continuous use detecting both DCF and CBZ. Overall, BDD electrodes are a viable material  for the sensitive, selective, and reproducible electrochemical detection of these two pharmaceuticals. [ABSTRACT FROM AUTHOR]

Mercury is one of the most well‐known toxic contaminants of natural and anthropogenic origin in aquatic ecosystems that can bioaccumulate in vegetal and animal organisms. In this work, we propose a smart detection system for Hg(II) ions by square wave anodic stripping voltammetry at nanocomposite graphite screen‐printed electrodes, as an analytical tool to be applied in food quality control. The nanocomposite surfaces were obtained by the modification of screen‐printed graphite electrodes with poly(l‐aspartic acid) and gold nanoparticles and were characterized by means of electrochemical techniques. An exhaustive study of the experimental conditions involved both in the electropolymerization and in the voltammetric stripping measurements was addressed to develop a reliable method capable of measuring Hg(II) concentration in the low μg/L range, both in conventional and drop configurations. The sensor was integrated in a smart setup, comprising a Sensit Smart pocket instrument connected to a smartphone, thus proving its applicability for in situ analysis due to its cost‐effectiveness. The analytical significance of the developed sensor was assessed by detecting Hg(II) in novel food samples. [ABSTRACT FROM AUTHOR]

The paper presents a metamaterial with reconfigurable effective properties, intended to operate in alternating magnetic fields. The structure of a resonator, based on a series connection of a planar inductor and a lumped capacitor, is expanded using an additional capacitor with a MOSFET transistor. Due to the presence of the controllable active element, it is possible to dynamically change the phase of the current flowing through a meta-cell and shift a frequency response within an assumed range. Since the transistor is driven by the unipolar square wave with a changeable duty cycle and time delay, two closed-loop controllers were utilized to achieve a smart material, able to automatically attain and maintain the imposed resonant frequency. As a result, the complex effective magnetic permeability of the metamaterial can be smoothly changed, during its operation, via an electrical signal, i.e. by adjusting the parameters of a control signal of the active element. The design of the meta-cell, as well as the measuring, data operation and control part, are presented in detail. An illustrative system is examined in terms of achieving the user-defined resonance point of the metamaterial. Transient responses with estimated settling times and steady-state errors and the effective permeability characteristics for the exemplary cases are shown. The meta-cell is also tested experimentally to validate the theoretically determined effective properties. [ABSTRACT FROM AUTHOR]

The present study delves into the examination of the stereoscopic cells and wavefront structures characterizing the propagation of three-dimensional detonation waves within square ducts. Leveraging numerical solutions derived from three-dimensional reactive Euler equations, incorporating an induction-exothermic reaction kinetic model, this work reveals the distinct classification of three modes of detonation waves based on the direction of propagation and the phase characteristics of transverse shock waves on the wavefront. This paper delineates the presence of two different types of phenomena: duct wall slapping waves due to shock–wall collisions and internal slapping waves resulting from shock interactions. Furthermore, this investigation exposes the existence of two distinct types of triple-wave lines on the wavefront: the first comprising a strong Mach disk, a weak Mach disk, and a transverse shock wave; the second characterized by a weak Mach disk, an incident shock wave, and a transverse shock wave. Notably, the pressure behind the first type of triple-wave line is observed to be the highest. It elucidates the transition from two- to three-dimensional detonation waves, revealing that the prevalence of transverse shock waves on the wavefront in the rectangular and diagonal modes is twofold and quadruple, respectively, when compared to their two-dimensional counterparts within identical ducts/channels. [ABSTRACT FROM AUTHOR]

Adatoms on metallic surfaces appear to be inexpensive reversible surface alloys. Platinum nanostructured electrode (PtNPs) opens up new avenues in electrochemistry. The prepared platinum nanostructured on a tantalum substrate using a square wave potential regime was permitted to maintain an open circuit via a 1 × 10–3 M solution that included an ion of one element Sb, Sn, As, or Pb. As a result, the closeness of the permanently adsorbed adatoms on the previously described Pt-nanostructured electrodes was proved by energy-dispersive X-ray spectroscopy, cyclic voltammetry and scanning electron microscopy. The electrocatalytic properties of prepared adatoms on new platinum nanostructures deposited on tantalum supporting structures were tested by the examination of electrooxidation of formic acid and methanol in 0.5 M H2SO4. The results of the previously mentioned tools showed the electrocatalytic characteristics of the nanoparticles ready exterior were improved by the adatoms of the four systems with varying levels of progress. The optimum conditions were set at 100 Hz frequency, − 0.4 V, and 0.0 V below the square wave limits in addition, above at amplitude 0.4 V, to prepare nanostructured platinum deposits. The current peak (Ip) and the current of chronoamperometric (ICA) of HCOOH solution oxidation on Pt-nanostructured Snad (47 mAcm−2, 130 µAcm−2) have higher values than Asad (20 mAcm−2, 55 µAcm−2), Sbad (34 mAcm−2, 100 µAcm−2) and Pbad (24 mAcm−2, 30µAcm−2)-Pt electrode. [ABSTRACT FROM AUTHOR]

An electrochemical aptasensor was developed by utilizing a DNA walker driven by catalytic hairpin assembly (CHA) with kanamycin as the model analyte. Kanamycin bound to the aptamer, causes the release of DNA walker, triggers the CHA reaction, leads to the cyclic movement of the walker's long arm, and results in cascade amplification of the signal. The guanine-rich sequences of the double-stranded products produced by CHA were folded to form G-quadruplex structures, with electrochemical active molecules Hemin embedded, forms G-quadruplex/Hemin complexes in situ on the electrode surface, thereby achieving sensitive, efficient, and label-free detection of kanamycin with a limit of detection (LOD) of 0.27 pM (S/N = 3). Meaningfully, the aptasensor demonstrated high sensitivity and reliability in the detection of kanamycin in milk and livestock wastewater samples, suggesting that it has great potential for application in detecting antibiotics in food products and water samples from the environment. [ABSTRACT FROM AUTHOR]

In this study, nanoporous gold (NPG) was deposited on a screen-printed carbon electrode (SPCE) by the dynamic hydrogen bubble template (DHBT) method to prepare an electrochemical sensor for the simultaneous determination of Pb2+ and Cu2+ by square wave anodic stripping voltammetry (SWASV). The electrodeposition potential and electrodeposition time for NPG/SPCE preparation were investigated thoroughly. Scanning electron microscopy (SEM) and energy-dispersive X-ray diffraction (EDX) analysis confirmed successful fabrication of the NPG-modified electrode. Electrochemical characterization exhibits its superior electron transfer ability compared with bare and nanogold-modified electrodes. After a comprehensive optimization, Pb2+ and Cu2+ were simultaneously determined with linear range of 1–100 μg/L for Pb2+ and 10–100 μg/L for Cu2+, respectively. The limits of detection were determined to be 0.4 μg/L and 5.4 μg/L for Pb2+ and Cu2+, respectively. This method offers a broad linear detection range, a low detection limit, and good reliability for heavy metal determination in drinking water. These results suggest that NPG/SPCE holds great promise in environmental and food applications. [ABSTRACT FROM AUTHOR]

In electrocardiograms (ECGs), multiple forms of encryption and preservation formats create difficulties for data sharing and retrospective disease analysis. Additionally, photography and storage using mobile devices are convenient, but the images acquired contain different noise interferences. To address this problem, a suite of novel methodologies was proposed for converting paper-recorded ECGs into digital data. Firstly, this study ingeniously removed gridlines by utilizing the Hue Saturation Value (HSV) spatial properties of ECGs. Moreover, this study introduced an innovative adaptive local thresholding method with high robustness for foreground–background separation. Subsequently, an algorithm for the automatic recognition of calibration square waves was proposed to ensure consistency in amplitude, rather than solely in shape, for digital signals. The original signal reconstruction algorithm was validated with the MIT–BIH and PTB databases by comparing the difference between the reconstructed and the original signals. Moreover, the mean of the Pearson correlation coefficient was 0.97 and 0.98, respectively, while the mean absolute errors were 0.324 and 0.241, respectively. The method proposed in this study converts paper-recorded ECGs into a digital format, enabling direct analysis using software. Automated techniques for acquiring and restoring ECG reference voltages enhance the reconstruction accuracy. This innovative approach facilitates data storage, medical communication, and remote ECG analysis, and minimizes errors in remote diagnosis. [ABSTRACT FROM AUTHOR]

To prepare Mg–Al-Nd alloys electrochemically, the electrochemical co-reduction mechanism of Mg(II), Al(III), and Nd(III) was probed in the LiCl-NaCl-MgCl2-AlF3 melts on a molybdenum electrode by means of various electrochemical measurement techniques, i.e., cyclic voltammetry, square wave voltammetry, chronopotentiometry, and open circuit chronopotentiometry. It was found that Nd could deposit on pre-deposited Al metal and form Nd-Al intermetallics in the LiCl-NaCl-NdCl3-MgCl2-AlF3 system, and the electrochemical signal related to the formation of ternary intermetallics was not detected. The co-reduction of Mg(II), Al(III), and Nd(III) was carried out on molybdenum electrode by galvanostatic electrolysis to prepare Mg–Al-Nd alloy, and samples were characterized by X-ray diffraction, scanning electron microscopy (SEM) with energy-dispersive spectrometry (EDS), and inductively coupled plasma-atomic emission spectrometry (ICP-AES). The results indicate that the alloy products were comprised of Al2Nd intermetallic, Mg and Al phases, and the Mg–Al compound was not observed in the alloys. [ABSTRACT FROM AUTHOR]

The stochastic resonance (SR) phenomenon for a bistable system subject to signal-modulated noise and to multiplicative and additive noise is investigated. The signal is modelled as a random-phase asymmetric square-wave one. Based on adiabatic approximation condition and two-state theory, the system output signal-to-noise ratio (SNR) is deduced. It is found that double SR phenomenon occurs when the SNR varies with the asymmetry of the square-wave signal. One resonance peak appears when the SNR changes with the amplitude of the square-wave signal. Traditional SR can be observed on the curves of the SNRs vs. the strength of the signal-modulated noise and vs. the intensities of the multiplicative and additive noise. The non-monotonous dependence of the SNR on the system parameter is discussed. [ABSTRACT FROM AUTHOR]

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A novel, simple, rapid, and non-expensive analytical method based on square wave voltammogram at Pt-microelectrode coupled with partial least square multivariate calibration was used for the simultaneous quantitation of thymol (THY) and carvacrol (CAR) in thyme and oregano essential oils. Results demonstrated that the multivariate calibration method successfully exploited the first-order advantage, rendering highly satisfactory quantitative figures (average recoveries not statistically different than 100%). Moreover, the results agree well with those obtained from the official analytical method. Last, the method's environmental sustainability was asserted using the AGREE metric, highlighting its eco-friendly nature. More importantly, the proposed analytical procedure does not require previous sample preparation or electrode surface modification. The results underscore the suitability of the method for determining THY and CAR in essential oils at low concentrations (LOD ~ 7.6 µM) with REP% below 5.6%, meeting the requirements of the green analytical chemistry. [ABSTRACT FROM AUTHOR]

In this work, TiO2 spherical nanoparticles with a mean diameter of 10.08 nm (SD = 4.54 nm) were synthesized using Aloe vera extract. Rutile, brookite, and anatase crystalline phases were identified. The surface morphology of a carbon paste electrode does not change in the presence of nanoparticles; however, the surface chemical composition does. The voltammetric response to dicresyl dithiophosphate was higher when the electrode was modified with TiO2 nanoparticles. After an electrochemical response study from pH 1.0 to 12.0, pH 7.0 was selected for the electroanalysis. The electroactive area of the modified sensor was 0.036 cm2, while it was 0.026 cm2 for the bare electrode. The oxidation process showed mixed adsorption-diffusion control. The charge transfer resistance of the modified sensor (530.1 Ω, SD = 4.08 Ω) was much lower than that of the bare electrode (4298 Ω, SD = 8.53 Ω). The linear quantitative range by square wave voltammetry was from 5 to 150 μmol/L, with a limit of detection of 1.89 μmol/L and a limit of quantification of 6.26 μmol/L under optimal pulse parameters of 50 Hz frequency, 1 mV step potential, and 25 mV pulse amplitude. The sensor response was repeatable and reproducible over 30 days. The results on real flotation and synthetically contaminated soil samples were statistically equivalent to those obtained by UV-vis spectrophotometry. A dithiocarbamate showed an interfering effect on the sensor response to dithiophosphate. [ABSTRACT FROM AUTHOR]

This study explores the adsorption of Pb(II) from aqueous solutions using glutathione-modified carbon powder at room temperature. The graphite powder was modified through oxidation followed by surface immobilization of glutathione. The Pb(II) concentration was measured using square wave anodic stripping voltammetry (SWASV). Experiments were conducted with the following varying initial Pb(II) ion concentrations: 20.72 mg L−1, 41.44 mg L−1, 62.16 mg L−1, 82.88 mg L−1, 103.60 mg L−1, and 124.32 mg L−1. The effect of varying the glutathione-modified carbon powder dosage (12.5 mg, 25.0 mg, 50.0 mg, 75.0 mg, and 100.0 mg) on Pb(II) uptake was studied. The adsorption data were modeled using the Freundlich isotherm, resulting in a regression coefficient (R2) of 0.96, which signifies a good fit. The Freundlich constants obtained were KF = 3.54 × 10−5 (adsorption capacity) and n = 1.56 (adsorption intensity). At optimal conditions (10.0 mL of 20.72 mg L−1 Pb(II) solution with 100.0 mg of glutathione-modified carbon powder), the adsorption efficiency was 96.3%. The glutathione-modified carbon powder exhibits a high capacity for adsorbing Pb(II) from aqueous solutions. [ABSTRACT FROM AUTHOR]

Two sequences of DNA (single-strand DNA (ssDNA) and double-strand DNA (dsDNA)) modified disposable electrodes were designed to investigate the effect of antitumor agent drug idarubicine (IDA) on the DNA chain structure. The effect of IDA on DNA structure was analyzed by square wave voltammetry (SWV) depending on not only the guanine signal but also IDA oxidation response. The present study included the electrochemical investigation of IDA and the investigation of the biomolecular interaction between IDA and DNA. IDA was detected in buffer and urine using disposable pencil graphite electrodes (PGE) with SWV and cyclic voltammetry (CV)). The detection limit (LOD) of IDA in urine samples was 0.089 µg mL−1 with SWV under optimum conditions. For the biomolecular interaction of IDA and DNA, all electrochemical conditions, such as the concentration of DNA, concentration of IDA, interaction phase (at electrode surface/in solution phase), the interaction pH, and the interaction time were optimized. IDA interacted biomolecularly with DNA at the electrode surface and in solution phase using two methods. There is no previous electrochemical study performed on the interaction of IDA with ssDNA. Hence, the effect of IDA on both ssDNA and dsDNA was presented for the first time. [ABSTRACT FROM AUTHOR]

Voltammetric methods hold promise for the rapid and sensitive quantification of melatonin. This study reports the direct electrochemical quantification of melatonin using carbon nanotube (CNT) fiber cross‐sections as microelectrodes. Six identical highly densified CNT fiber cross‐sections were employed to quantify melatonin in the range of 0.05–100 μM. The limit of detection and quantification were 10 and 35 nM, respectively, with a sensitivity of 0.1322 nA/μM. Interference studies with uric acid, hypoxanthine, and ascorbic acid demonstrate its performance. Real‐world application was highlighted by measuring melatonin in food, pharmaceutical, and human urine samples. [ABSTRACT FROM AUTHOR]

The delay-Doppler map (DDM) is the signal power distribution of the Coarse/Acquisition code (C/A code) of the received Global Navigation Satellite System (GNSS) signal in different code phase delay and Doppler frequency. When the received signal is reflected from ocean surface, the DDM can be used to retrieve the ocean surface wind speed, which is the GNSS-reflectometry (GNSS-R) technique. Due to the signal power distribution in DDM is the correlation results of received and artificial C/A code from receiver in different code phase delay and Doppler frequency, the Woodward ambiguity function (WAF) occurs in the DDM. In the case of DDM, the WAF is the correlation results of two square waves in different code phase delay and Doppler frequency, and is approximated a triangular function and a sinc function in code phase delay and Doppler frequency axes, respectively. It means the correlation results not only show the code phase delay and Doppler frequency of the received signal but also influence the surrounding code phase delay and Doppler frequency values and cause the structure of DDM more complex. Using more bins in DDM in the wind speed retrieval process can reduce the influence of WAF but cause the spatial resolution to worsen. In order to use as less bins as possible in the retrieval process and not reduce the retrieval efficiency too much, a simple method to estimate bistatic radar cross section (BRCS) from DDM is developed in this study. Furthermore, a retrieval process is also developed for ocean surface wind speed retrieving by using less bins in the DDM from Cyclone Global Navigation Satellite System (CYGNSS) mission. Keypoints: Ocean surface wind speed retrieving. Better spatial resolution of ocean surface wind speed. Validation results confirms the retrieval process is useable [ABSTRACT FROM AUTHOR]

Electrochemical detection is favorable for the rapid and sensitive determination of heavy metal cadmium. However, the detection sensitivity needs to be further improved, and a portable, low-cost device is needed for on-site detection. Herein, an in-situ bismuth modified pre-anodized screen-printed carbon electrode (SPCE) was developed for Cd2+ determination by square wave anodic stripping voltammetry (SWASV). The in-situ bismuth modification enhances the enrichment of Cd2+, and together with pre-anodization improve the electron transfer rate of electrode, thus enhancing the detection sensitivity. The electrode modification method combines pre-anodization and in-situ bismuth deposition, which is very easy and effective. Furthermore, a self-made PSoC Stat potentiostat coupled with a stirring device was fabricated for portable and low-cost electrochemical detection. After comprehensive optimization, the developed method can reach a testing time of 3 min, a detection limit of 3.55 μg/L, a linear range of 5–100 μg/L, and a recovery rate of 91.7–107.1% in water and rice samples for Cd2+ determination. Therefore, our method holds great promise for the rapid, sensitive and on-site determination of Cd2+ in food samples. [ABSTRACT FROM AUTHOR]

Nanododecahedral ZIF-67 crystals were successfully synthesized by a simple coprecipitation method at room temperature and constructed with graphene oxide (GO) and Nafion as an electrochemical sensing platform for Cu2+. The properties of the electrode and the modified materials were analysed by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), square wave stripping voltammetry (SWSV), scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The experimental results show that the ZIF-67/GO/Nafion/GCE sensor platform has a stronger adsorption effect on Cu2+. It has high sensitivity (101.29 μA·μM−1) and a low detection limit (7.55 nM) in the linear range of 0.01 to 1.0 μM, as well as long-term stability, good repeatability and selectivity. The recovery rate was between 95.7 and 102.7% for real water samples. The method can be used for the trace analysis of Cu2+, which is valuable for the detection of trace metal ions in real water samples. [ABSTRACT FROM AUTHOR]

Screen-printed electrodes (SPEs) are reliable, portable, affordable, and versatile electrochemical platforms for the real-time analytical monitoring of emerging analytes in the environmental, clinical, and agricultural fields. The aim of this study was to evaluate the electrochemical behavior of gold screen-printed electrodes (SPGEs) modified with molecules containing amino (Tr-N) or α-aminophosphonate (Tr-P) groups for the selective and sensitive detection of the toxic metal ions Pb2+ and Hg2+ in aqueous samples. After optimizing the analytical parameters (conditioning potential and time, deposition potential and time, pH and concentration of the supporting electrolyte), anodic square wave stripping voltammetry (SWASV) was used to evaluate and compare the electrochemical performance of bare or modified electrodes for the detection of Hg2+ and Pb2+, either alone or in their mixtures in the concentration range between 1 nM and 10 nM. A significative improvement in the detection ability of Pb2+ ions was recorded for the amino-functionalized gold sensor SPGE-N, while the presence of a phosphonate moiety in SPGE-P led to greater sensitivity towards Hg2+ ions. The developed sensors allow the detection of Pb2+ and Hg2+ with a limit of detection (LOD) of 0.41 nM and 35 pM, respectively, below the legal limits for these heavy metal ions in drinking water or food, while the sensitivity was 5.84 µA nM−1cm−2 and 10 µA nM−1cm−2, respectively, for Pb2+ and Hg2+. The reported results are promising for the development of advanced devices for the in situ and cost-effective monitoring of heavy metals, even in trace amounts, in water resources. [ABSTRACT FROM AUTHOR]

AbstractSimple and highly sensitive voltammetric methods were developed using a poly(bromocresol purple) modified glassy carbon electrode to quantify cetirizine. Poly(bromocresol purple) film was synthesized on the surface of a glassy carbon electrode by cyclic voltammetry for 50 potential cycles in 0.1 M phosphate buffer at pH 6.0 containing 5.0 × 10−4 M of the monomer. Quantification of cetirizine exhibiting irreversible properties using the optimized conditions with a linear dependence between cetirizine concentration and peak currents from 0.2 to 100 µM for differential pulse voltammetry (DPV) and 0.1 to 100 µM for square wave voltammetry (SWV). Detection limits were 21.8 and 15.1 nM for DPV and SWV, respectively. Relative standard deviation (RSD) values below 0.98% indicated good precision. Recovery values from 100.12% to 100.90% with relative standard deviations below 1.14% for DPV and SWV in pharmaceutical formulations and urine samples demonstrated the high accuracy of the developed methods. The prepared modified electrode exhibited good fabrication reproducibility and suitable long-term stability. Finally, no interferences were observed in cetirizine determination in the presence of co-existing substances in the biological samples. [ABSTRACT FROM AUTHOR]

A novel electrochemical sensor based on multiwalled carbon nanotubes (MWCNTs) and 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6) hydrophobic ionic liquid for the rapid detection of Pb2+ and Cd2+ was developed. In this study, the BMIMPF6-MWCNTs composite, as well as BMIMPF6 and MWCNTs, were characterized using SEM. The electrochemical studies were performed using Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS). The BMIMPF6-MWCNTs/GCE exhibited excellent electrochemical activity. The effect of the pH value of 0.1 M NaAc/HAc buffer, deposition potential, and deposition time was investigated. Under the optimal conditions, the linear range for the modified sensors varies from 5 to 1850 µg L−1 for Pb2+ and 22 to 600 µg L−1 for Cd2+. The limit of detection (LOD) for Pb2+ and Cd2+ was 0.9 µg L−1 and 0.5 µg L−1, respectively, and the limit of quantification (LOQ) was 3 µg L−1 for Pb2+ and 1.7 µg L−1 for Cd2+. Moreover, this method showed excellent anti-interference performance, short analysis time, and practicability for determining Pb2+ and Cd2+. The electrochemical sensor was able to determine heavy metal ions in actual water samples without complex pretreatment, with acceptable recoveries from 98 to 110.8% for Pb2+ and 98.6 to 111.3% for Cd2+, demonstrating that the sensor based on BMIMPF6-MWCNTs/GCE can apply for Pb2+ and Cd2+ quantification. [ABSTRACT FROM AUTHOR]

The menstrual cycle is a loop involving the interplay of different organs and hormones, with the capacity to impact numerous physiological processes, including body temperature and heart rate, which in turn display menstrual rhythms. The advent of wearable devices that can continuously track physiological data opens the possibility of using these prolonged time series of skin temperature data to noninvasively detect the temperature variations that occur in ovulatory menstrual cycles. Here, we show that the menstrual skin temperature variation is better represented by a model of oscillation, the cosinor, than by a biphasic square wave model. We describe how applying a cosinor model to a menstrual cycle of distal skin temperature data can be used to assess whether the data oscillate or not, and in cases of oscillation, rhythm metrics for the cycle, including mesor, amplitude, and acrophase, can be obtained. We apply the method to wearable temperature data collected at a minute resolution each day from 120 female individuals over a menstrual cycle to illustrate how the method can be used to derive and present menstrual cycle characteristics, which can be used in other analyses examining indicators of female health. The cosinor method, frequently used in circadian rhythms studies, can be employed in research to facilitate the assessment of menstrual cycle effects on physiological parameters, and in clinical settings to use the characteristics of the menstrual cycles as health markers or to facilitate menstrual chronotherapy. [ABSTRACT FROM AUTHOR]

A Ti3C2TxMXene-based biosensor has been developed and the photocatalytic atom transfer radical polymerization (photo ATRP) amplification strategy applied to detect target miRNA-21 (tRNA). Initially, Ti3C2TxMXene nanosheets were synthesized from the Ti3AlC2 MAX precursor via selective aluminum etching. Then, functionalization of Ti3C2TxMXene nanosheets with 3-aminopropyl triethoxysilane (APTES) via silylation reactions to facilitate covalent bonding with hairpin DNA biomolecules specifically designed for tRNA detection. Upon binding with the tRNA, the hairpin DNA liberated the azide (N₃) group, initiating a click reaction to affix to the photo ATRP initiator. Through the ATRP photoreaction, facilitated by an organic photoredox catalyst and light, a significant amount of ferrocenyl methyl methacrylate (FMMA) monomer was immobilized on the electrode. Therefore, the electrochemical signal is amplified. The electrochemical efficacy of the biosensor was assessed using square wave voltammetry (SWV). Under optimized conditions, the biosensor demonstrated remarkable sensitivity in detecting tRNA, with a linear detection range from 0.01 fM to 10 pM and a detection limit of 2.81 aM. The findings elucidate that the developed biosensor, in conjunction with the photo ATRP strategy, offers reproducibility, stability, and increased sensitivity, underscoring its potential applications within the experimental medical sector of the biomolecular industry. [ABSTRACT FROM AUTHOR]

Surface functionalization strategy is becoming a crucial bridge from magnetic nanoparticles (MNPs) to their broad bio-application. To realize the multiple functions of MNPs such as magnetic manipulation, target capture, and signal amplification in their use of electrochemical biosensing, co-crosslinking strategy was proposed here to construct dual-functionalized MNPs by combining ultra-sensitive redox moieties and specific biological probes. In this work, MNPs with a TEM size of 10 nm were synthesized by co-precipitation for amination and PEGylation to maintain colloid stability once dispersed in high-ionic-strength buffer (such as phosphate-buffered saline). Then, MNPs@IgG were prepared via the bis(sulfosuccinimidyl) suberate (BS3) cross-linker to conjugate these IgG onto the MNP surface, with a binding efficiency of 73%. To construct dual-functionalized MNPs, these redox probes of ferrocene-NHS (Fc) were co-crosslinked onto the MNP surface, together with IgG, by using BS3. The developed MNPs@Redox@IgG were characterized by SDS‒PAGE to identify IgG binding and by square wave voltammetry (SWV) to validate the redox signal. Additionally, the anti-CD63 antibodies were selected for the development of MNPs@anti-CD63 for use in the bio-testing of exosome sample capture. Therefore, co-crosslinking strategy paved a way to develop dual-functionalized MNPs that can be an aid of their potential utilization in diagnostic assay or electrochemical methods. [ABSTRACT FROM AUTHOR]

This study introduces a simple, cost-effective, and rapid bismuth electrode-square-wave voltammetry method for determining the total sulfur content in automotive gasoline. Optimal conditions for the developed electrode, including various Bi ion concentrations, deposition times, and potentials, were established on a glassy carbon electrode. The results demonstrated that the highest response was achieved when the bismuth electrode was placed in an acetate buffer and a methanol:toluene (1:1 v/v) solvent. The method was validated with and without a 30-second electro-preconcentration step. The voltammetric method in conjunction with the preconcentration step exhibited a sensitivity of 571.81 nA mg L−1, a limit of detection (LOD) of 0.02 mg L−1, and a limit of quantification (LOQ) of 0.08 mg L−1. Without the preconcentration step, the method yielded a sensitivity of 421.89 nA mg L−1, an LOD of 0.03 mg L−1, and an LOQ of 0.11 mg L−1. The developed method was applied to quantify commercial fuel samples. The results showed that the electrochemical technique yielded a similar total sulfur content to that measured by the standard ASTM D2622 method, with an error of less than 7.5%. Moreover, the method proposed in this study had lower LOD and LOQ limits, meeting the EURO5 and EURO6 regulations. [ABSTRACT FROM AUTHOR]

Increasing the release of antibiotics in particular tetracycline in the environment is become one of the most concerns that threat human and animals' health. Regarding their low cost, sensitivity, portability, electrochemical sensors have received attention for tetracycline monitoring. With a nanostructure, diverse active functional sites, and good conductivity, green nanoparticles are considered now as an attractive material for sensors design. The objective of the present paper is then the design of electrochemical sensor functionalized with green nanoparticles based on gum Arabic for tetracycline detection. The green nanoparticles are synthesized by direct reduction of silver nanoparticle with gum Arabic polymer. The intrinsic properties of the obtained nanoparticles are examined using different techniques namely UV–Vis absorption (UV), X‐ray diffraction (XRD), transmission electron microscopy (TEM), and thermogravimetric TGA. To follow up, the sensor modification as well as tetracycline detection, cyclic voltammetry (CV) and square wave voltammetry are carried out. Correlation between the different results have demonstrated good dispersion and homogeneity of green nanoparticles, with good applicability in electrochemical measurements. In fact, the sensor has demonstrated wide concentrations range from 0.1 to 1250 nM with a limit of detection in the order of 0.056 nM, lower than those reported in the literature. The selectivity test, investigated against a various interfering with similar structure to tetracycline, have proven a good discrimination between all molecules. In addition, the sensor was successfully applied to real samples, and the found recovery rates are ranging from 90.4% to 106.9%. The obtained results confirm that green nanoparticles based on gum Arabic could commercially be viable for next generation of electrochemical sensor for tetracycline detection, and also could be applied for the detection of the variety of pharmaceutical pollutants in the environment. [ABSTRACT FROM AUTHOR]

Copyright of Control Theory & Applications / Kongzhi Lilun Yu Yinyong is the property of Editorial Department of Control Theory & Applications and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A nitrogen-doped nanocrystalline electrochemical graphite sensor for the sensitive determination of oleuropein (OL) from extra virgin olive oils (EVOOs) is presented. The sensor was developed by the deposition of nanocrystalline graphite (NCG) using plasma-enhanced chemical vapour deposition (PECVD) on silicon wafers. Scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and X-ray diffraction analysis (XRD) were used to characterise the microstructure and morphology of the developed materials. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and square wave voltammetry (SWV) were used to investigate the electrochemical properties of the material and the performance of the sensor. The developed sensor showed good analytical performance against OL over a concentration range of 5.00–500.00 µM, with a good detection limit of 3.93 µM and a good sensitivity of 0.057 µA µM−1. The reproducibility of the electrochemical sensor was excellent, with a relative standard deviation (RSD) of 8.56% for seven measurements. [ABSTRACT FROM AUTHOR]

Cardiovascular disease is one of the leading causes of premature death worldwide, and the determination of C-reactive protein (CRP) from human serum is of vital importance for the diagnosis of the disease. For this study, we have developed an electrochemical immunosensor based on onion-like carbon@polyacrylonitrile (OLC-PAN) for the detection of CRP antigens. This was accomplished by immobilizing CRP antibodies on a modified glassy carbon electrode (GCE). Several electrochemical techniques such as cyclic voltammetry (CV), square wave voltammetry (SWV), and electrochemical impedance spectroscopy (EIS) were employed to evaluate the electrochemical detection of the CRP antigen. This ultrasensitive method for CRP antigen detection exhibited a very good logarithmic plot from −4.52 to −12.05 g mL−1 and a limit of detection (LOD) of 0.9 fg mL−1. The high selectivity, sensitivity, and stability of the developed electrochemical immunosensor would facilitate miniaturization for point-of-care applications and the efficient diagnosis of cardiovascular diseases. [ABSTRACT FROM AUTHOR]

The amplitude of tooth passing frequency in frequency spectrum is an important indicator to judge machining quality and tool wear. In comparison to the amplitude of tooth passing frequency in acceleration spectrum, broaching force more directly reflects the tool wear and machining quality, but the broaching force measurement equipment is expensive and can change the dynamic structure of the machine. Therefore, this paper establishes a frequency spectrum prediction model of the broaching process using theoretical cutting force time history. This model combines the advantages of easy acquisition of vibration data, low cost, and no change in machine structure by the acceleration sensor, with the benefits of directly reflecting tool wear and machining quality through broaching force measurement equipment. In this paper, the theoretical cutting force model is developed based on the Johnson–Cook material law. Compared to the traditional method of directly applying FFT to obtain the broaching force spectrum, this paper innovatively divides the broaching force into square waves of equal width but varying amplitudes in the time domain. The frequency domain waveform of broaching force can be regarded as the vector superposition between the harmonic series corresponding to these time-domain square waves. Through the waveform image of numerical simulation, it can be concluded that the amplitude of tooth passing frequency used for tool wear diagnosis depends on the shape of tooth passing area in cutting force time history, which is affected by factors like tool wear and lubrication conditions. Any force changes caused by tool wear and broaching quality can be reflected in the broaching force spectrum. According to the characteristics of the dynamic equation, the frequency spectrum of acceleration can be obtained by substituting the broaching force in frequency domain into the dynamic equation. Through experimental analysis, it is shown that the numerical acceleration frequency spectrum obtained by the present model is consistent with the experimental acceleration frequency spectrum. [ABSTRACT FROM AUTHOR]