Search Results (13)

Pyrene (Pr) was used to improve the electrochemical and electrochromic properties of polythiophene copolymerized with 3,4-ethylenedioxythiophene (EDOT). The corresponding product, poly(3,4-ethylenedioxythiophene-co-Pyrene) (P(EDOT-co-Pr)), was successfully synthesized by electrochemical polymerization with different monomer concentrations in propylene carbonate solution containing 0.1 M lithium perchlorate (LiClO₄/PC (0.1 M)). The homopolymer and copolymer films were analyzed by Fourier transform infrared spectroscopy (FT-IR), color-coordinate and colorimetric methods, cyclic voltammetry (CV), spectroelectrochemistry (SEC), and UV–visible spectroscopy (UV-Vis). Homopolymer poly(3,4-ethylenedioxythiophene) (PEDOT) and the P(EDOT-co-Pr) copolymer were investigated, which included examining their colorimetric, electrochemical, and electrochromic characteristics. The color shifts resulting from redox reactions of the polymers were also observed. The copolymers with different monomer concentrations achieved multicolor shifts, such as light purple, dark blue, dark red, green, and earthy yellow. Moreover, P(EDOT-co-Pr) had a small optical bandgap (1.74–1.83 eV), excellent optical contrast (31.68–45.96%), and high coloring efficiency (350–507 cm² C⁻¹). In particular, P(EDOT1-co-Pr3) exhibited outstanding cycling stability, retaining 91% of its initial optical contrast after cycling for 10,000 s, and it is expected to be a promising candidate copolymer for electrochromic applications. Full article

Bacteria respond to metal pollution through sensors that control the uptake and the detoxification machineries. Specificity in metal recognition is therefore a prerequisite for triggering the appropriate response, particularly when facing a mixture of metals. In response to Cu⁺, the purple bacterium Rubrivivax gelatinosus induces the efflux Cu⁺-ATPase CopA by the Cu⁺ regulator CopR. However, genetic analyses have suggested the presence of additional regulators. Here, we show that CadR, the Cd²⁺ sensor, is involved in Cd²⁺ and Cu⁺ tolerance and demonstrate that CopR and CadR share common target genes. Interestingly, expression of the Cu⁺ detoxification and efflux (CopI/CopA) system was induced by Cd²⁺ and downregulated in the double mutant copRcadR⁻. This double mutant was more sensitive to low Cu⁺ concentration than the single copR⁻ mutant, and accumulation of coproporphyrin III pointed to a significantly decreased expression of CopA. Furthermore, analyses of Cd²⁺ toxicity in the cadR⁻ mutant suggested that although CopR is Cu⁺ selective, CopR is involved in Cd²⁺ response since the addition of Cu⁺ alleviates Cd²⁺ toxicity. Based on our current knowledge of metal transport across the inner membrane, Cd²⁺ and Cu⁺ do not share common efflux routes nor do they share common regulators. Nevertheless, the crosstalk between Cd²⁺ and Cu⁺ tolerance systems is demonstrated in the present study. The modulation of Cu⁺ detoxification by a Cd²⁺ regulator in vivo places emphasis on the relaxed selectivity, under elevated metal concentration, in MerR regulators. Full article

Developing flame-retardant epoxy resins (EPs) is essential to broaden their industrial applications, as their inherent flammability restricts their widespread use. In this study, commercial cerium oxide (CeO₂) nanoparticles were modified with oleic acid and successfully assembled onto the surface of pyrophosphate piperazine (PAPP) through a simple solvophobic effect, constructing an integrated superstructure flame retardant, CeO₂@PAPP, with enhanced performance integration. Compared to traditional simple blends, the EP composite with 10 wt% CeO₂@PAPP displayed superior flame retardancy, thanks to the more subtle synergistic effects between flame retardant components and their favorable interface interactions. The EP composite achieved a UL-94 V-0 rating and increased the limiting oxygen index (LOI) to 34.2%. Significant reductions of 56.3% in peak heat release rate (PHRR) and 38.2% in total heat release (THR) were observed. Furthermore, total smoke release (TSR), carbon monoxide yield (COPR), and carbon dioxide yield (CO₂PR) decreased by 52.2%, 50.2%, and 67.3%, respectively. Through comprehensive and detailed characterization, it was discovered that the assembled integrated CeO₂@PAPP flame retardant can perform better in both the gas phase and condensed phase, resulting in superior flame-retardant properties. This study offers an effective strategy for developing highly flame-retardant EPs, thereby expanding their potential applications across various industries. Full article

The alkali digestion pretreatment method in the United States Environmental Protection Agency (USEPA) Method 3060A could underestimate the content of Cr(VI) in Cr-contaminated soils, especially for soils mixed with chromite ore processing residue (COPR), which leads to a misjudgment of the Cr(VI) level in soils after remediation, causing secondary pollution to the environment. In this study, a new pretreatment method to analyze Cr(VI) concentration in contaminated soils was established. The impacts of soil quality, particle size, alkali digestion time and the rounds of alkali digestion on Cr(VI) detection in contaminated soils was explored and the alkali digestion method was optimized. Compared with USEPA Method 3060A, the alkaline digestion time was prolonged to 6 h and multiple alkali digestion was employed until the amount of Cr(VI) in the last extraction was less than 10% of the total amount of Cr(VI). Because Cr(VI) in COPR is usually embedded in the mineral phase structure, the hydration products were dissolved and Cr(VI) was released gradually during the alkaline digestion process. The amount of Cr(VI) detected showed high correlation coefficients with the percentage of F1 (mild acid-soluble fraction), F2 (reducible fraction) and F4 (residual fraction). The Cr(VI) contents detected by the new alkaline digestion method and USEPA Method 3060A showed significant differences for soil samples mixed with COPR due to their high percentage of residual fraction. This new pretreatment method could quantify more than 90% of Cr(VI) in Cr-contaminated soils, especially those mixed with COPR, which proved to be a promising method for Cr(VI) analysis in soils, before and after remediation. Full article

Lead–zinc smelting slag (LZSS) is regarded as a hazardous waste containing heavy metals that poses a significant threat to the environment. LZSS is rich in aluminosilicate, which has the potential to prepare alkali-activated materials and solidify hazardous waste, realizing hazardous waste cotreatment. In this study, the experiment included two parts; i.e., the preparation of alkali-activated LZSS (pure smelting slag) and chromite ore processing residue (COPR) solidification/stabilization. Single-factor and orthogonal experiments were carried out that aimed to explore the effects of various parameters (alkali solid content, water glass modulus, liquid–solid ratio, and initial curing temperature) for alkali-activated LZSS. Additionally, compressive strength and leaching toxicity were the indexes used to evaluate the performance of the solidified bodies containing COPR. As a result, the highest compressive strength of alkali-activated LZSS reached 84.49 MPa, and when 40% COPR was added, the strength decreased to 1.42 MPa. However, the leaching concentrations of Zn and Cr from all the solidified bodies were far below the critical limits (US EPA Method 1311 and China GB5085.3-2007). Heavy-metal ions in LZSS and COPR were immobilized successfully by chemical and physical means, which was detected by analyses including environmental scanning electron microscopy with energy-dispersive spectrometry, Fourier transform infrared spectrometry, and X-ray diffraction. Full article

The cooling coefficient of performance (COP_R) and energy efficiency ratio (EER) of refrigerant R-134a compressors (single- and double-compressors) with different refrigerant tonnage (200, 250, 300, 380, 500, and 700 RT) for centrifugal and Maglev centrifugal compressors change with different operating performance load percentages (10–100%), and constant-frequency and variable-frequency operation, resulting in performance differences. In particular, a water chiller can have a fixed cooling water inlet temperature of 32 °C and a variable cooling water inlet temperature between 18.33 °C and 32 °C. According to the actual test results, the commercial performance code program and parameter table of the water chiller were established. Based on the performance matching of different load chillers, the on-site load capacity was analyzed and the effective water chiller performance and model matching were determined as the best choice for the ton_R number of the deicing machine and unit matching, providing a reference for a future large water chiller that cannot be used on site for a single unit ton_R. To achieve energy-saving benefits, different types of compressors, different refrigeration ton_R operation, constant-frequency unit and variable-frequency unit alternate operation, and different operating performance load percentage operation can be allocated. Finally, the results show that, when the cooling water inlet temperature is fixed, the Maglev variable-frequency centrifugal compressor water chiller is better than the constant-frequency centrifugal water chiller, and also better than the variable-frequency centrifugal water chiller. The larger the freezing ton_R of the variable-frequency centrifugal water chiller, the smaller the difference between COP_R and EER. When the cooling water inlet temperature changes, the Maglev variable-frequency centrifugal water chiller is better than the constant-frequency centrifugal water chiller, and it is also better than the variable-frequency centrifugal water chiller. The larger the freezing ton_R of the variable-frequency centrifugal water chiller, the smaller the difference between COP_R and EER. Moreover, the operating performance of the constant-frequency centrifugal water chiller is between 60% and 90%, which can maintain relatively high COP_R and EER values. The operating performance of the variable-frequency centrifugal water chiller is between 40% and 70%, which can maintain relatively high COP_R and EER values. Compared with the constant-frequency and variable-frequency, the Maglev variable-frequency centrifugal water chiller can maintain higher COP_R and EER values when the operating performance is between 10% and 100%. When the operating performance is between 10% and 70%, it can maintain very high COP_R and EER values. When the water chiller is selected in the field, the energy-saving of COP_R and EER will be given priority. Therefore, the load capacity can be used to effectively manage the water chiller performance and model selection, so that the operation performance can reach the best percentage and energy saving can be achieved. Full article

Thirty-five thousand people die as a result of more than 2.8 million antibiotic-resistant infections in the United States of America per year. Pseudomonas aeruginosa (P. aeruginosa) is classified a serious threat, the second-highest threat category of the U.S. Department of Health and Human Services. Among others, the World Health Organization (WHO) encourages the discovery and development of novel antibiotic classes with new targets and mechanisms of action without cross-resistance to existing classes. To find potential new target sites in pathogenic bacteria, such as P. aeruginosa, it is inevitable to fully understand the molecular mechanism of homeostasis, metabolism, regulation, growth, and resistances thereof. P. aeruginosa maintains a sophisticated copper defense cascade comprising three stages, resembling those of public safety organizations. These stages include copper scavenging, first responder, and second responder. Similar mechanisms are found in numerous pathogens. Here we compare the copper-dependent transcription regulators cueR and copRS of Escherichia coli (E. coli) and P. aeruginosa. Further, phylogenetic analysis and structural modelling of mexPQ-opmE reveal that this efflux pump is unlikely to be involved in the copper export of P. aeruginosa. Altogether, we present current understandings of the copper homeostasis in P. aeruginosa and potential new target sites for antimicrobial agents or a combinatorial drug regimen in the fight against multidrug resistant pathogens. Full article

This experiment examined changes in body sway after Wingate test (WAnT) in 19 adolescents practicing alpine skiing, subjected to the same type of training load for 4–5 years (10 girls and nine boys). The postural examinations were performed with eyes open (EO), eyes closed (EC), and sway reverenced vision (SRV) in the medial-lateral (ML) and anterior-posterior (AP) planes. The displacement of center of foot pressure (CoP), range of sway (RS), mean sway velocity (MV), way length, and surface area were measured in bipedal upright stance before and after the WAnT to assess the influence of fatigue on postural balance. There were no significant differences in WAnT parameters between girls and boys. Relative peak power (RPP), relative total work (RWtot) were (girls vs. boys) 8.89 ± 0.70 vs. 9.57 ± 1.22 W/kg, p < 0.05 and 227.91 ± 14.98 vs. 243.22 ± 30.24 W/kg, p < 0.05 respectively. The fatigue index (FI) was also on similar level in both genders; however, blood lactate concentration (BLa) was significantly higher in boys (10.35 ± 1.16 mM) than in girls (8.67 ± 1.35 mM) p = 0.007. In the EO examination, statistically significant differences between resting and fatigue conditions in the whole group and after the division into girls and boys were found. In fatigue conditions, significant gender differences were noted for measurements in the ML plane (sway path and RS) and RS in the AP plane. Comparison of the three conditions shows differences between EO vs. EC and SRV in AP plane measured parameters, and for RS in ML plane in rest condition in girls. The strong correlations between FI and CoP parameters mainly in ML plane in the whole group for all examination conditions were noted. By genders, mainly RS in ML plane strongly correlates with FI (r > 0.7). No correlation was found between BLa and CoP parameters (p > 0.06). The presented results indicate that subjecting adolescents of both genders to the same training may reduce gender differences in the postural balance ability at rest but not in fatigue conditions and that girls are significantly superior in postural balance in the ML plane than boys. It was also shown that too little or too much information may be destructive to postural balance in young adolescents. Full article

Copper is widely used as antimicrobial in agriculture and medicine. Copper tolerance mechanisms of pathogenic bacteria have been proven to be required for both copper tolerance and survival during bacterial infections. Here, we determined both copper-tolerant phenotype and genotype in A. baumannii originated from clinical and environmental samples. Using copper susceptibility testing, copper-tolerant A. baumannii could be found in both clinical and environmental isolates. Genotypic study revealed that representative copper-related genes of the cluster A (cueR), B (pcoAB), and D (oprC) were detected in all isolates, while copRS of cluster C was detected in only copper-tolerant A. baumannii isolates. Moreover, we found that copper-tolerant phenotype was associated with amikacin resistance, while the presence of copRS was statistically associated with bla_NDM-1. We chose the A. baumannii strain AB003 as a representative of copper-tolerant isolate to characterize the effect of copper treatment on external morphology as well as on genes responsible for copper tolerance. The morphological features and survival of A. baumannii AB003 were affected by its exposure to copper, while whole-genome sequencing and analysis showed that it carried fourteen copper-related genes located on four clusters, and cluster C of AB003 was found to be embedded on genomic island G08. Transcriptional analysis of fourteen copper-related genes identified in AB003 revealed that copper treatment induced the expressions of genes of clusters A, B, and D at the micromolar level, while genes of cluster C were over-expressed at the millimolar levels of copper. This study showed that both clinical and environmental A. baumannii isolates have the ability to tolerate copper and carried numerous copper tolerance determinants including intrinsic copper tolerance (clusters A, B, and D) and acquired copper tolerance (cluster C) that could respond to copper toxicity. Our evidence suggests that we need to reconsider the use of copper in hospitals and other medical environments to prevent the selection and spread of copper-tolerant organisms. Full article

This study investigates the applicability of the Leven–Marquardt algorithm, Bayesian regularization, and a scaled conjugate gradient algorithm as training algorithms for an artificial neural network (ANN) predictively modeling the rate of CO and H₂ production by methane dry reforming over a Co/Pr₂O₃ catalyst. The dataset employed for the ANN modeling was obtained using a central composite experimental design. The input parameters consisted of CH₄ partial pressure, CO₂ partial pressure, and reaction temperature, while the target parameters included the rate of CO and H₂ production. A neural network architecture of 3 13 2, 3 15 2, and 3 15 2 representing the input layer, hidden neuron layer, and target (output) layer were employed for the Leven–Marquardt, Bayesian regularization, and scaled conjugate gradient training algorithms, respectively. The ANN training with each of the algorithms resulted in an accurate prediction of the rate of CO and H₂ production. The best prediction was, however, obtained using the Bayesian regularization algorithm with the lowest standard error of estimates (SEE). The high values of coefficient of determination (R² > 0.9) obtained from the parity plots are an indication that the predicted rates of CO and H₂ production were strongly correlated with the observed values. Full article

In this paper, we present narrow-band substrate integrated waveguide (SIW) millimeter wave band-pass filters, designed using cyclo-olefin polymers (COP). The structures were molded, drilled, and metalized with a laser direct structuring (LDS) process. COP are a type of thermoplastic with low dielectric losses in the millimeter waveband, typically 7.5 × 10⁻⁴ at 40 GHz for the COP RS420-LDS from Zeon^®. The body of the filter was realized using a molding process that facilitates the combination of thin 50 Ω microstrip access lines with high thickness microwave cavities through 3D transitions, thus making high quality factors attainable. The simulations and experimental results are presented and discussed. Full article

The metal‐specific CzcRS two‐component system in Pseudomonas aeruginosa is involved in the repression of the OprD porin, causing in turn carbapenem antibiotic resistance in the presence of high zinc concentration. It has also been shown that CzcR is able to directly regulate the expression of multiple genes including virulence factors. CzcR is therefore an important regulator connecting (i) metal response, (ii) pathogenicity and (iii) antibiotic resistance in P. aeruginosa. Recent data have suggested that other regulators could negatively control oprD expression in the presence of zinc. Here we show that the RNA chaperone Hfq is a key factor acting independently of CzcR for the repression of oprD upon Zn treatment. Additionally, we found that an Hfq‐dependent mechanism is necessary for the localization of CzcR to the oprD promoter, mediating oprD transcriptional repression. Furthermore, in the presence of Cu, CopR, the transcriptional regulator of the CopRS two‐component system also requires Hfq for oprD repression. Altogether, these results suggest important roles for this RNA chaperone in the context of environment‐sensing and antibiotic resistance in P. aeruginosa. Full article

The Klip River has suffered from severe anthropogenic effects from industrial activities such as mining. Long-term exposure to heavy metal pollution has led to the development of heavy metal resistant strains of Pseudomonas sp. KR23, Lysinibacillus sp. KR25, and E. coli KR29. The objectives of this study were to characterize the genetics of copper and chromate resistance of the isolates. Copper and chromate resistance determinants were cloned and sequenced. Open reading frames (ORFs) related to the genes CopA and CopR were identified in E. coli KR29, PcoA in Lysinibacillus sp. KR25 and none related to chromate resistance were detected. The 3D-models predicted by I-TASSER disclose that the PcoA proteins consist of β-sheets, which form a part of the cupredoxin domain of the CopA copper resistance family of genes. The model for PcoR_29 revealed the presence of a helix turn helix; this forms part of a DNA binding protein, which is part of a heavy metal transcriptional regulator. The bacterial strains were cured using ethidium bromide. The genes encoding for heavy metal resistance and antibiotic resistance were found to be located on the chromosome for both Pseudomonas sp. (KR23) and E. coli (KR29). For Lysinibacillus (KR25) the heavy metal resistance determinants are suspected to be located on a mobile genetic element, which was not detected using gel electrophoresis. Full article