Search Results (35)

Boron carbide (B4C) is a widely recognized ceramic prized for its remarkable properties, including exceptional hardness, low density, and excellent chemical and mechanical stability. To date, limited research has explored the possible health risks associated with B4C nanoparticles (B4C-NPs). This study utilized a Caenorhabditis elegans (C. elegans) in vivo model to investigate the toxicological effects of B4C-NPs at concentrations of 40, 80, 160, and 320 mg/L. Larval nematodes were subjected to prolonged exposure, and their locomotion (head thrashing and body bending), reproduction (brood size), development (body length), lifespan, and gene expression (linked to oxidative stress, metal detoxification, apoptosis, and neurotransmitter synthesis) were assessed. Regarding survival rates, lethality was significantly increased to 5.41% at 320 mg/L of B4C-NPs and lifespan was significantly shortened across all concentrations compared with the controls. Development and reproduction showed slight reductions between 40 and 320 mg/L, while locomotion was markedly impaired at the doses from 80 to 320 mg/L. Gene expression related to antioxidants, apoptosis, cell cycle arrest, neurotransmitter synthesis, and metal detoxification rose significantly at 160–320 mg/L in C. elegans, suggesting that B4C-NPs may induce reproductive and neurological toxicity, delay development, reduce lifespan, and potentially cause genotoxicity in C. elegans. Full article

Solid-state DC circuit breakers provide crucial support for the safe and reliable operation of low-voltage DC distribution networks. A hardware topology based on a cascaded structure with dual-stage, current-limiting, small-capacity, solid-state DC circuit breakers has been proposed. The hardware topology uses a series–parallel configuration of cascaded SCR (thyristors) and MOSFETs (metal oxide semiconductor field-effect transistors) in the transfer branch, which enhances the breaking capacity of the transfer branch. Additionally, a secondary current-limiting circuit composed of an inductor and resistor in parallel is integrated at the front end of the transfer branch to effectively improve the current-limiting performance of the circuit breaker. Meanwhile, a dissipation branch is introduced on the fault side to reduce the energy consumption burden on surge arresters. For the power supply system of the hardware part, a capacitor-powered method is adopted for safety and efficiency, with a capacitor switch serially connected to the capacitor power supply for high-precision control of the power supply. Current detection branches are introduced into each branch to provide conditions for the on–off control of semiconductor switching devices and experimental data analysis. The high-frequency control of semiconductor devices is achieved using optocoupler signal isolation chips and high-speed drive chips through a microcontroller STM32. Simulation verification based on MATLAB/SIMULINK software and experimental prototype testing have been conducted, and the results show that the hardware topology is correct and effective. Full article

The controlled formation and stabilization of nanoparticles is of fundamental relevance for materials science and key to many modern technologies. Common synthetic strategies to arrest growth at small sizes and prevent undesired particle agglomeration often rely on the use of organic additives and require non-aqueous media and/or high temperatures, all of which appear critical with respect to production costs, safety, and sustainability. In the present work, we demonstrate a simple one-pot process in water under ambient conditions that can produce particles of various transition metal carbonates and sulfides with sizes of only a few nanometers embedded in a silica shell, similar to particles derived from more elaborate synthesis routes, like the sol–gel process. To this end, solutions of soluble salts of metal cations (e.g., chlorides) and the respective anions (e.g., sodium carbonate or sulfide) are mixed in the presence of different amounts of sodium silicate at elevated pH levels. Upon mixing, metal carbonate/sulfide particles nucleate, and their subsequent growth causes a sensible decrease of pH in the vicinity. Dissolved silicate species respond to this local acidification by condensation reactions, which eventually lead to the formation of amorphous silica layers that encapsulate the metal carbonate/sulfide cores and, thus, effectively inhibit any further growth. The as-obtained carbonate nanodots can readily be converted into the corresponding metal oxides by secondary thermal treatment, during which their nanometric size is maintained. Although the described method clearly requires optimization towards actual applications, the results of this study highlight the potential of bottom-up self-assembly for the synthesis of functional nanoparticles at mild conditions. Full article

Under the premise of using the solid-phase method to pre-sinter Bi₂O₃ and Sb₂O₃ into BiSbO₄ as a substitute for equal amounts of Bi₂O₃ and Sb₂O₃ in the formula, the effects of co-doping with In(NO₃)₃, Al(NO₃)₃, and Y(NO₃)₃ on the microstructure and electrical properties of ZnO varistors were studied. The experimental results show that with an increase in In³⁺-doped molar concentration, the leakage current of the ZnO varistor shows a rapid decrease and then a slow increase trend. However, the nonlinear coefficient is the opposite of it. With the combined effect of the rare earth element Y³⁺, the average grain size is significantly reduced, which leads to an increase in the voltage gradient. At the same time, a certain amount of doped In³⁺ and Al³⁺ is dissolved into the grains, resulting in a decrease in grain resistance and thus a low level of residual voltage. The varistor with 0.6 mol% In³⁺, 0.1 mol% Al³⁺, and 0.9 mol% Y³⁺ doping ratios exhibits excellent overall performance. The nonlinear coefficient is 62.2, with the leakage current being 1.46 µA/cm² and the voltage gradient being 558 V/mm, and the residual voltage ratio is 1.73. The prepared co-doped ZnO varistors will provide better protection for metal oxide surge arresters. Full article

This paper presents a literature review on the subject of Condition-Based Maintenance of surge arresters. Both a bibliometric analysis and traditional comprehensive research are presented. The bibliometric analysis is useful for obtaining insights about the literature. It quantitatively highlights relationships between journals, authors and keywords (related to the monitoring methods) and reveals future trends for research based on the timeline of the keywords. The traditional comprehensive literature review is also presented. It summarizes the methods, their advantages and disadvantages and also points to some known measurement issues of the methods. Both online (leakage current, harmonic components, temperature, partial discharges, power loss and the counting of discharges) and offline (reference voltage, residual voltage, insulation resistance, polarization/depolarization, return voltage, microscopy, spectrometry, X-ray, RUS and the recent application of FRA) methods have been qualitatively analyzed. Full article

Most existing methods aiming to solve the fault identification problem of metal oxide arresters (MOAs) are limited by strong subjectivity in judgment, the significant impact of environmental temperature and humidity on the online monitoring of the resistance current, and poor generalization ability. Therefore, in this article, we propose an MOA fault identification method that combines suppressing environmental temperature and humidity interference with a stacked autoencoder (SAE). Firstly, a functional relationship model between resistance current and environmental temperature and humidity is established. Then, a temperature and humidity interference suppression method based on weighted nonlinear surface modeling is proposed to normalize the resistance current to the same reference temperature and humidity conditions. Finally, an MOA fault identification method combining the suppression of environmental temperature and humidity interference with an SAE is proposed. Furthermore, a comprehensive comparison is conducted on the recall, accuracy, F₁-score, and average accuracy of support vector machine, random forest, logistic regression, and SAE classification algorithms in three different scenarios to demonstrate the effectiveness of the proposed method. The results indicate that environmental temperature and humidity interference suppression for resistive current prior to MOA fault classification significantly reduce the number of false alarms. Compared with other methods, the MOA fault identification method, which combines environmental temperature and humidity interference suppression with an SAE, has the highest average accuracy of 99.7%. Full article

Varistors processed from mixtures of certain metal oxides (as additives to the main component, zinc oxide, ZnO), called MOVs, represent the devices most used for overvoltage protection and are integrated into the construction of high-performance surge arresters. The manufacturing process of these powerful electronic devices is crucial for their electronic performance. For manufacturing temperature-related studies, we used two seven-varistor experimental series: one based on two added oxides and the other on five ones. The main goal of these series was to identify the suitable sintering temperature in the case of each chemical composition from the point of view of assessing the most important electric/electronic behavioral parameters. A simple study considering mass losses after the sintering process was carried out in order to provide a brief reference for the manufacturing engineers. Before performing these studies, each varistor was sintered at a different temperature. In order to draw a general set of conclusions about the impact of the sintering pressure on the main electrical and electronic performances, a second activity involved producing two additional smaller varistors series with similar chemical compositions (two main oxides and five main oxides as additives) all processed at two different sintering pressures 4900 N/cm² and 9800 N/cm². The electrical/electronic parameters considered for the assessment are the main current–voltage characteristics, the non-linearity logarithmic coefficient, and the normal operational leakage current. All electrical/electronic behavioral tests were performed according to the IEC standards and regulations for both types of varistor devices (seven different temperatures and two pressure values). We concluded that a sintering temperature of 1300 °C and a pressure of 4900 N/cm² are optimal for both types of varistors (with two and five additives). Full article

Aromatic ketones are important pharmaceutical intermediates, especially the pyridin-2-yl-methanone motifs. Thus, synthetic methods for these compounds have gained extensive attention in the last few years. Transition metals catalyze the oxidation of Csp³-H for the synthesis of aromatic ketones, which is arresting. Here, we describe an efficient copper-catalyzed synthesis of pyridin-2-yl-methanones from pyridin-2-yl-methanes through a direct Csp³-H oxidation approach with water under mild conditions. Pyridin-2-yl-methanes with aromatic rings, such as substituted benzene, thiophene, thiazole, pyridine, and triazine, undergo the reaction well to obtain the corresponding products in moderate to good yields. Several controlled experiments are operated for the mechanism exploration, indicating that water participates in the oxidation process, and it is the single oxygen source in this transformation. The current work provides new insights for water-involving oxidation reactions. Full article

This work presents an innovative application of Frequency Response Analysis (FRA) in order to detect early degradation of Metal Oxide Surge Arresters (MOSAs). This technique has been widely used in power transformers, but has never been applied to MOSAs. It consists in comparisons of spectra, measured at different instants of the lifetime of the arrester. Differences between these spectra are an indicator that some electrical properties of the arrester have changed. An incremental deterioration test has been performed on arrester samples (with controlled circulation of leakage current, which increases the energy dissipation over the device), and the FRA spectra correctly identified the progression of damage. Although preliminary, the FRA results seemed promising, and it is expected that this technology could be used as another diagnostic tool for arresters. Full article

IP6 (phytic acid) is a naturally occurring compound in plant seeds and grains. It is a poly-phosphorylated inositol derivative that has been shown to exhibit many biological activities that accrue benefits in health and diseases (cancer, diabetes, renal lithiasis, cardiovascular diseases, etc.). IP6 has been shown to have several cellular and molecular activities associated with its potential role in disease prevention. These activities include anti-oxidant properties, chelation of metal ions, inhibition of inflammation, modulation of cell signaling pathways, and modulation of the activities of enzymes and hormones that are involved in carbohydrate and lipid metabolism. Studies have shown that IP6 has anti-oxidant properties and can scavenge free radicals known to cause cellular damage and contribute to the development of chronic diseases such as cancers and cardiovascular diseases, as well as diabetes mellitus. It has also been shown to possess anti-inflammatory properties that may modulate immune responses geared towards the prevention of inflammatory conditions. Moreover, IP6 exhibits anti-cancer properties through the induction of cell cycle arrest, promoting apoptosis and inhibiting cancer cell growth. Additionally, it has been shown to have anti-mutagenic properties, which reduce the risk of malignancies by preventing DNA damage and mutations. IP6 has also been reported to have a potential role in bone health. It inhibits bone resorption and promotes bone formation, which may help in the prevention of bone diseases such as osteoporosis. Overall, IP6’s cellular and molecular activities make it a promising candidate for disease prevention. As reported in many studies, its anti-inflammatory, anti-oxidant, and anti-cancer properties support its inclusion as a dietary supplement that may protect against the development of chronic diseases. However, further studies are needed to understand the mechanisms of action of this dynamic molecule and its derivatives and determine the optimal doses and appropriate delivery methods for effective therapeutic use. Full article

In this study, commercially low-voltage MOVs are exposed to switching surges to analyse and model the relationship between the number of surges and the MOV grain barrier height response. Repeated slow-front overvoltage transients are used to degrade the protective qualities of metal oxide surge arrester devices, affecting their reliability and stability. A total of 360 MOVs with similar specifications from three different manufacturers are degraded under switching surges at a constant temperature of 60 °C. The reference voltage and C-V characteristics of MOVs are measured before and after the degradation process to analyse the MOVs’ conditions. Grain barrier heights are determined from the C-V characteristics curve. An F-statistical analysis is then applied to analyse the effects of number of surges on the grain barrier height. The T-test is used to assess the statistical difference between the tested groups. Linear regression analysis is then applied to model the relationship between the number of surges and MOV grain barrier height. The results obtained show that the number of surges has a significant impact on grain barrier height. MOV grain barrier height is found to decrease as the number of surges applied increases. Regression models obtained for the tested MOV groups across all three manufacturers agree and indicate that the reduction in grain barrier height results from an increased number of surges. Regression coefficients of a developed model indicate that for one surge applied, the MOV grain barrier height decreases by 0.024, 0.055, and 0.033 eV/cm for manufacturers X, Y, and Z, respectively. Therefore, there is a linear relationship between grain barrier height and the number of applied switching surges. Full article

Topical cariostatic agents have become a reasonable alternative for managing dental caries in young children. Silver diamine fluoride (SDF) is a practical topical approach to arrest caries and avoid extensive and risky dental treatment. However, the literature demonstrates a parental hesitation towards accepting SDF because of black unaesthetic tooth discolouration following application. The rapid oxidation of ionic silver darkens demineralised tooth structure permanently. In this regard, nano-metallic antimicrobials could augment or substitute for silver, and thereby enhance SDF aesthetic performance. Recently, biomedical research has drawn attention to selenium nanoparticles (SeNPs) due to their antimicrobial, antioxidant, and antiviral potencies. Various in vitro studies have examined the effect of SeNPs on the virulence of bacteria. This narrative review explores practical issues when using SDF and suggests future directions to develop it, focusing on antimicrobial metals. Several methods are described that could be followed to reduce the discolouration concern, including the use of nanoparticles of silver, of silver fluoride, or of selenium or other metals with antimicrobial actions. There could also be value in using remineralising agents other than fluoride, such as NPs of hydroxyapatite. There could be variations made to formulations in order to lower the levels of silver and fluoride in the SDF or even to replace one or both of the silver and fluoride components completely. Moreover, since oxidation processes appear central to the chemistry of the staining, adding SeNPs which have antioxidant actions could have an anti-staining benefit; SeNPs could be used for their antimicrobial actions as well. Future research should address the topic of selenium chemistry to optimise how SeNPs would be used with or in place of ionic silver. Incorporating other antimicrobial metals as nanoparticles should also be explored, taking into account the optimal physicochemical parameters for each of these. Full article

Metal oxide surge arresters (MOSAs) are a popular solution for dealing with overvoltages due to lightning and switching in power distribution networks. As a result, a MOSA’s performance and longevity have a significant impact on the quality of energy and the frequency of outages. A MOSA performance is determined by several elements such as leakage current, partial discharge, and thermal image measured in various ways. In this study, different techniques for diagnostic and condition monitoring of MOSAs are discussed, and each method’s advantages and disadvantages are investigated. Additionally, the results of practical tests on two 20 kV healthy and degraded MOSAs are investigated and compared. Full article

Interest in the third-row transition metal osmium and its compounds as potential anticancer agents has grown in recent years. Here, we synthesized the osmium(VI) nitrido complex Na[Os^VI(N)(tpm)₂] (tpm = [5-(Thien-2-yl)-1H-pyrazol-3-yl]methanol), which exhibited a greater inhibitory effect on the cell viabilities of the cervical, ovarian, and breast cancer cell lines compared with cisplatin. Proteomics analysis revealed that Na[Os^VI(N)(tpm)₂] modulates the expression of protein-transportation-associated, DNA-metabolism-associated, and oxidative-stress-associated proteins in HepG2 cells. Perturbation of protein expression activity by the complex in cancer cells affects the functions of the mitochondria, resulting in high levels of cellular oxidative stress and low rates of cell survival. Moreover, it caused G2/M phase cell cycle arrest and caspase-mediated apoptosis of HepG2 cells. This study reveals a new high-valent osmium complex as an anticancer agent candidate modulating protein homeostasis. Full article

With the rapid development of metal-organic frameworks (MOF), the toxicity and environmental safety of MOF materials should be thoroughly investigated. The behaviors and bio-effects of MOF materials after oral exposure are largely unknown. In this study, we performed a pilot toxicity evaluation of MOF-74(Co) nanoparticles (NPs) both in vitro and in vivo. The cell viability and cell cycle were monitored after LO2 cells were incubated with MOF-74(Co). The Co contents, bodyweight, serum biochemistry, histopathological changes, and oxidative stress parameters were measured after oral exposure to MOF-74(Co) NPs in mice. LO2 cells showed viability loss at 100 mg/L. The cell cycle arrest was more sensitive, which was observed even at 12.5 mg/L. MOF-74(Co) NPs led to a significant accumulation of Co in the liver and kidneys. No bodyweight loss was observed and the serum biochemical index was mainly unchanged. Except for slight inflammation, the histopathological images of the liver and kidneys after oral exposure to MOF-74(Co) NPs were normal compared to the control. Meaningful oxidative stress was found in the liver and kidneys. The results collectively indicated the low toxicity of MOF-74(Co) NPs after oral exposure in mice. Full article