Search Results (330)

This study investigates the microstructural evolution, mechanical behavior, and electrochemical performance of CoCrFeNiNb and CoCrFeNiV HEAs fabricated via mechanical alloying and spark plasma sintering. Microstructural analyses reveal that the alloys have a face-centered cubic (FCC) matrix with Nb-enriched Laves and V-enriched σ phases. The CoCrFeNiNb HEA exhibits superior compressive strength and hardness than CoCrFeNiV due to uniform Laves phases distribution. Fracture surface analysis reveals that at lower sintering temperatures, the fracture is primarily caused by incomplete particle bonding, whereas at higher temperatures, brittle fracture modes dominated via transgranular cracking become predominant. The research results of potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) show that both alloys exhibited superior electrochemical stability in a 3.5 wt.% NaCl solution compared to the CoCrFeNi base alloy. X-ray photoelectron spectroscopy (XPS) analysis confirms the formation of stable oxide layers (Nb₂O₅ and V₂O₃) on the precipitated phases, acting as protective barriers against chloride ion penetration. The selective oxidation of Nb and V improves the integrity of the passive film, reducing the corrosion rates and enhancing the long-term durability. These findings highlight the critical role of precipitated phases in enhancing the corrosion resistance of HEAs, and emphasize their potential for use in extreme environments. Full article

Background/Objectives: Generating real-world data on the efficacy of multidisciplinary care in cardiometabolic risk management is essential to ensure that guidelines are both applicable and effective, especially in public healthcare settings, where organizational structures may impede healthcare professionals’ agility. This study aimed to generate data on patient follow-up and cardiometabolic risk management during the early years of a public university family medicine group in Québec (Canada) that provides multidisciplinary care to adults with cardiometabolic conditions, in order to evaluate the implementation and effectiveness of its care model. Methods: This was a retrospective longitudinal study. Patients treated at the clinic from 31 January 2020 (clinic opening) to 8 May 2024 (n = 96) were invited to consent to the use of their medical data for research. Results: A total of 52 patients consented and were included in the study. Upon entry at the clinic, >90% of patients had anthropometry and blood pressure (BP) measured, but plasma glucose and lipids were assessed among 50% and 79% of patients, respectively. A total of 36 patients completed the personalized multidisciplinary care program. No evidence of associations between the total number of appointments or appointments with the registered dietitian specifically with changes in BMI, waist circumference, and BP was found. However, each pharmaceutical intervention was associated with a −0.51 cm (95%CI: −1.03, 0.02; p = 0.06) change in waist circumference and a −1.49 mm Hg (95%CI: −2.56, −0.43, p = 0.01) change in diastolic BP. Conclusions: These data highlight the challenges of implementing a research-oriented clinic within Québec’s public healthcare system. Full article

Background Veno-venous extracorporeal membrane oxygenation (VV-ECMO) supports critically ill patients with respiratory failure. However, ECMO may induce systemic inflammation, hemolysis, and hemodilution, potentially resulting in endothelial activation and damage. Therefore, this study explored the longitudinal changes in circulating markers of inflammation, hemolysis, and endothelial activation and damage in patients with COVID-19 on VV-ECMO. Methods Plasma was obtained before, within 48 h as well as on day 4, week 1, and week 2 of ECMO support and after decannulation. Circulating markers were measured using Luminex, ELISA, and spectrophotometry. Human pulmonary endothelial cells were exposed to patient plasma, and in vitro endothelial permeability was assessed using electric cell-substrate impedance sensing. Results From April 2020 to January 2022, plasma was collected from 14 patients (71.4% male; age 54 (45–61) years). IL-6 levels decreased (1.238 vs. 0.614 ng/mL, p = 0.039) while ICAM-1 increased (667 vs. 884 ng/mL, p = 0.003) over time when compared to pre-ECMO. Angiopoietin-1 decreased after ECMO initiation (7.57 vs. 3.58 ng/mL, p = 0.030), whereas angiopoietin-2 increased (5.20 vs. 10.19 ng/mL, p = 0.017), particularly in non-survivors of ECMO. Cell-free hemoglobin decreased directly after VV-ECMO initiation but remained stable thereafter (55.29 vs. 9.19 mg/dL, p = 0.017). Moreover, the plasma obtained at several time points during the ECMO run induced in vitro pulmonary endothelial hyperpermeability. Conclusions This exploratory study shows that patients on VV-ECMO support due to COVID-ARDS exhibit progressive endothelial activation and damage but not inflammation and hemolysis. Larger prospective studies are necessary to elucidate pathophysiological pathways leading to endothelial activation and damage, thereby reducing organ failure in these critically ill patients. Full article

Background and Objectives: Sodium-glucose cotransporter 2 (SGLT2) inhibitors are increasingly used in type 2 diabetes (T2D) due to their cardiorenal benefits and weight-lowering effects. However, concerns have emerged regarding their potential adverse impact on lean mass and muscle strength particularly in patients at risk for sarcopenia. This study aimed to evaluate the effects of empagliflozin on skeletal muscle mass. Secondary objectives were to assess changes in glycemic control, body weight, fat mass and handgrip strength. Materials and Methods: In this 24-week real-world observational study, 31 adult patients with T2D were assigned to either empagliflozin or non-SGLT2i treatment groups. Patients did not receive a high-protein diet, a resistance exercise program or any other weight-reducing medications such as glucagon-like peptide-1 (GLP-1)-based therapies. Anthropometric measurements, body composition via bioelectrical impedance analysis (BIA), and handgrip strength testing were performed at baseline and after 6 months. Sarcopenia was defined according to EWGSOP2 criteria. Results: The empagliflozin group showed significant improvements in HbA1c, fasting plasma glucose, body weight, waist circumference, and fat mass (p < 0.05 for all). No significant changes were observed in the empagliflozin group after 6 months in appendicular skeletal muscle mass index (from 7.81 ± 1.33 kg/m² to 7.84 ± 1.38 kg/m², p = 0.154). No statistically significant changes were observed in handgrip strength in either group. Conclusions: Empagliflozin treatment over six months led to favorable changes in metabolic parameters and fat mass without detrimental effects on skeletal muscle mass or muscle strength. In clinical practice, the selection of antidiabetic therapies should consider individual glycemic targets, cardiovascular and renal risks, weight management, comorbidities and sarcopenia risk. Resistance exercises and adequate dietary protein intake should be recommended to preserve muscle mass in at-risk patients. Larger randomized trials are needed to confirm the long-term effects of SGLT2 inhibitors on body composition particularly in older adults. Full article

Thin, dense and nanocrystal bismuth oxide films were prepared by the in situ plasma-assisted reactive evaporation (ARE) method using lead doping. Thin films were deposited at room temperature and at 500 °C temperature on glass and silicon substrates. X-ray diffraction, SEM, EDS, and optical measurements were applied to characterize these bismuth oxide films. The results showed that it is possible to synthesize the δ-Bi₂O₃ phase thin films at a temperature lower than 729 °C using an plasma-assisted reactive evaporation (ARE) method and stabilize it (to room temperature) using the additives of lead oxide. The influence of lead oxide concentration on phase formation was investigated. The optimal amount of lead oxide dopant was determined. An excess of lead oxide concentration forms PbO and δ-Bi₂O₃ mixture phases and nanorods appear in films. The synthesized δ-Bi₂O₃ phase was metastable; it transformed into the β-Bi₂O₃ phase after thermal impact during impedance measurements. The cross section of thin film sample shows the dense and monolithic structure. Optical measurements show that the optical band gap increases with increasing lead concentration. It was found that the highest total ionic conductivity of (Bi_1−xPb_0.26)₂O₃ is 0.165 S/cm at 1073 K temperature and activation energy is ΔE_tot = 0.5 eV. Full article

Short-chain fatty acids (SCFAs) are microbial metabolites involved in immune regulation, energy metabolism, and intestinal barrier integrity. Among them, the role of hexanoic acid (C6), predominantly derived from dietary sources, remains poorly understood in chronic heart failure (CHF) and sarcopenia. A total of 636 patients with confirmed CHF were screened between 2019 and 2021. Sarcopenia was diagnosed in 114 patients, with 74 meeting the inclusion criteria for analysis. Plasma levels of SCFAs—including butanoic, propanoic, isobutyric, 2- and 3-methylbutanoic, hexanoic, pentanoic, and 4-methylpentanoic acids—were measured using HPLC-MS/MS. Muscle strength, mass, and physical performance were assessed using handgrip dynamometry, bioelectrical impedance analysis, and SPPB, respectively. All patients showed elevated SCFA levels compared to reference values. Butanoic acid levels exceeded reference values by 32.8-fold, propanoic acid by 10.9-fold, and hexanoic acid by 1.09-fold. Patients with plasma hexanoic acid levels above the 50th percentile had a seven-fold increased mortality risk (OR = 7.10; 95% CI: 1.74–28.9; p < 0.01). Kaplan–Meier analysis confirmed significantly lower survival in this group (p = 0.00051). The mean left ventricular ejection fraction was 41.2 ± 7.5%, and the mean SPPB score was 6.1 ± 1.8, indicating impaired physical performance. Elevated plasma hexanoic acid is associated with poor prognosis in CHF patients with sarcopenia. These findings suggest that C6 may serve as a potential prognostic biomarker and therapeutic target in this population. Full article

In this paper, we propose a multi-mode switchable ultra-wideband terahertz absorber based on patterned graphene and VO₂ by designing a graphene pattern composed of a large rectangle rotated 45° in the center and four identical small rectangles in the periphery, as well as a VO₂ layer pattern composed of four identical rectangular boxes and small rectangles embedded in the dielectric layer. VO₂ can regulate conductivity via temperature, the Fermi level of graphene depends on the external voltage, and the graphene layer and VO₂ layer produce resonance responses at different frequencies, resulting in high absorption. The proposed absorption microdevices have three modes: Mode 1 (2.52–4.52 THz), Mode 2 (3.91–9.66 THz), and Mode 3 (2.14–10 THz), which are low-band absorption, high-band absorption, and ultra-wideband absorption. At 2.96 THz in Mode 1, the absorption rate reaches 99.98%; at 8.04 THz in Mode 2, the absorption rate reaches 99.76%; at 5.04 THz in Mode 3, the absorption rate reaches 99.85%; and at 8.4 THz, the absorption rate reaches 99.76%. We explain the absorption mechanism by analyzing the electric field distribution and local plasma resonance, and reveal the high-performance absorption mechanism by using the relative impedance theory. In addition, absorption microdevices have the advantages of polarization insensitivity, incident angle insensitivity, multi-mode switching, ultra-wideband absorption, large manufacturing tolerance, etc., and have potential research and application value in electromagnetic stealth devices, filters and optical switches. Full article

Aluminum alloy AA6082 (Al-Si-Mg) is a lightweight alloy that requires thick barrier coatings to be protected from localized corrosion. Plasma Electrolytic Oxidation (PEO) coating is a common anodic surface treatment used for growing protective oxides; the main process variables of PEO are the composition of the electrolytic solution and the electrical input. This work focuses on the optimization of the electrical input by comparing different coatings produced by potentiostatic PEO at the effective potential of 350 V, applied by different combinations of voltage ramps with various slopes and maintenance times at the fixed potential. All processes lasted five minutes. The innovative character of this research work is the evaluation of the combined effect of the anodizing voltage and its different trends with time on the coating structure and morphology. The corrosion resistance of coated AA6082 is assessed in contact with chlorides, reproducing seawater. The resulting anodic coatings were compared in terms of structure, composition (thickness, XRD, SEM-EDS) and corrosion resistance (potentiodynamic polarization and electrochemical impedance spectroscopy), finding that longer maintenance at high anodizing potentials promotes localized high-energy plasma discharges, producing larger pores and thicker, but less protective coatings. Results show that the coating thickness increases with the maintenance time (maximum thickness value~17.6 μm). Shorter maintenance periods and longer voltage ramps lead to a lower surface porosity and enhanced corrosion performances of the oxide. The thinnest and least porous coating exhibits the best corrosion behavior (CR~1.1 μm/year). Full article

This study evaluates the wear and corrosion resistance of the Cu-50Ni-5Al alloy reinforced with CeO₂ nanoparticles for potential use as anodes in molten carbonate fuel cells (MCFCs). Cu–50Ni–5Al alloys were synthesized, with and without the incorporation of 1% CeO₂ nanoparticles, by the mechanical alloying method and spark plasma sintering (SPS). The samples were evaluated using a single scratch test with a cone-spherical diamond indenter under progressive normal loading conditions. A non-contact 3D surface profiler characterized the scratched surfaces to support the analysis. Progressive loading tests indicated a reduction of up to 50% in COF with 1% NPs, with specific values drop-ping from 0.48 in the unreinforced alloy to 0.25 in the CeO₂-doped composite at 15 N of applied load. Furthermore, the introduction of CeO₂ decreased scratch depths by 25%, indicating enhanced wear resistance. The electrochemical behavior of the samples was evaluated by electrochemical impedance spectroscopy (EIS) in a molten carbonate medium under a H₂/N₂ atmosphere at 550 °C for 120 h. Subsequently, the corrosion products were characterized using X-ray diffraction (XRD), scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS), and X-ray photoelectron spectroscopy (XPS). The results demonstrated that the CeO₂-reinforced alloy exhibits superior electro-chemical stability in molten carbonate environments (Li₂CO₃-K₂CO₃) under an H₂/N₂ atmosphere at 550 °C for 120 h. A marked reduction in polarization resistance and a pronounced re-passivation effect were observed, suggesting enhanced anodic protection. This effect is attributed to the formation of aluminum and copper oxides in both compositions, together with the appearance of NiO as the predominant phase in the materials reinforced with nanoparticles in a hydrogen-reducing atmosphere. The addition of CeO₂ nanoparticles significantly improves wear resistance and corrosion performance. Recognizing this effect is vital for creating strategies to enhance the material’s durability in challenging environments like MCFC. Full article

Plasma impedance monitoring in semiconductor manufacturing processes is performed using external sensors, such as voltage-current (VI) probes or directional couplers. Plasma chamber impedance measurements, conducted in non-50 Ω matched transmission lines, suffer from a lack of clean signals due to phase variations and the nonlinearity of plasma, thus, sensor calibration is required for each installment. In this study, we monitored plasma impedance in situ based on the position of the vacuum variable capacitor within the matching network, without employing an external VI probe. We observed changes in the matching position according to parameter variations and subsequently confirmed that the calculated plasma impedance also varied accordingly. This study demonstrates the feasibility of real-time plasma impedance monitoring under 50 Ω-matched conditions without the use of external sensors, thereby simplifying plasma diagnostics. Full article

Class-D power amplifiers driving variable loads, such as inductively coupled plasma (ICP), typically require an impedance matching network, which has a relatively slow matching speed, generally in the millisecond range. To address this issue, this paper proposes a solution that uses a fully digital control method for Class-D power amplifiers to directly drive ICP loads. This solution eliminates the need for an impedance matching network, reducing the overall output power regulation time to just tens of microseconds. Compared to traditional methods that use a VI probe to detect output power, the proposed method in this paper only requires measuring the resonant current in the loop to control the output power, thereby reducing costs and ensuring that the Class-D power amplifier achieves zero-voltage switching (ZVS) throughout the adjustment process. This paper provides a detailed introduction to the design method of the Class-D power amplifier and the overall digital control scheme and validates them via simulation and experimentation. The Class-D power amplifier prototype was designed using SiC MOSFETs, with a Xilinx ZYNQ-XC7Z100 FPGA as the control board. The output frequency varies around 4 MHz, successfully generating plasma. Full article

The purpose of this article is to evaluate and compare the mechanical and electrochemical properties of four new materials, composed of a B₄C ceramic matrix doped with 0.5%, 1%, 2% and 3% volumes of CoCrFeNiMo HEA with monolithic B₄C. The studied samples were obtained using the spark plasma sintering technique. The structure and hardness of the samples were analyzed via scanning electron microscopy (SEM) and a Vickers microhardness test. After immersion in artificial sea water to simulate a corrosive marine environment, corrosion potential, corrosion rate and electrochemical impedance spectroscopy tests were carried out to determine the samples’ electrochemical behavior. Tafel slopes and the equivalent circuit that fit the EIS experimental data were obtained. A denser microstructure and smaller grain size was achieved as the HEA content increase. According to the Vickers measurements, every sample showed a normal distribution. All studied samples exhibit great corrosion resistance in a two-step chemical interaction, influenced by the presence of the Warburg element. The research demonstrates that increasing the HEA content implies better performance of corrosion resistance and mechanical properties, confirming the materials’ potential use in corrosive environments and harsh mechanical applications. Full article

As one of the key components of high-voltage pulse modulators, the pulse-forming lines (PFLs) are moving in the direction of compact, solid-state, and stable working for a relatively long time. In this paper, a long-lifetime PFL, based on a glass ceramic with high relative permittivity, is studied numerically and experimentally. Specifically, based on a designed low-impedance PFL, dimension parameters of the thick electrode coating on the surface of the glass–ceramic dielectric were optimized to decrease the edge electric field enhancement which could lead to local discharge and plasma generation. The PFL was developed and experimentally studied in our laboratory. With charging voltage of 35 kV approximately, pulses with peak current over 4.4 kA were obtained on a matched dummy load. Importantly, the device has been successfully working over 2.8 million pulses with a repetitive rate of 50 Hz, which is suitable for potential applications including plasma science research. Full article

A Co-based composite powder, doped with rare earth Y, was crafted through a series of processes involving spray-drying, calcination, and low-temperature reduction. This powder was then blended with tungsten carbide (WC) powder and subjected to ball-milling. The resultant mixture was consolidated into a robust Y-doped WC-Co cemented carbide via the process of spark plasma sintering (SPS). The outcomes demonstrate that incorporating rare earth Y into Co powder to form a Co-Y₂O₃ composite powder via an innovative spray-drying, calcination, and low-temperature reduction process ensures uniform distribution of Y in the Co matrix. This uniform distribution refines the alloy’s grain structure during subsequent sintering, leading to enhanced performance. Within a specific range, increasing the Y content improves the overall alloy properties. It is notable that at a Y content of 1.5%, the alloy’s properties reach a state of stability, characterized by a density of 98.91%, a maximum hardness of 2120 Hv₃₀, and a fracture toughness of 8.24 MPa·m^1/2. The novel Y incorporation method has been shown to enhance the strength of the binder phase, impede the growth of WC grains, and thereby lead to a substantial improvement in the overall performance of the cemented carbide. Full article

Anodic aluminum oxide (AAO) is a promising material for sensor applications due to its unique nanoporous structure and high surface area. This study investigates enhancing AAO’s sensing capabilities by incorporating carbyne-enriched nanomaterials. This research aimed to create a novel surface acoustic wave (SAW) sensor with improved performance characteristics. AAO films were fabricated using a two-step anodization process, followed by carbyne-enriched coating deposition via ion-assisted pulse-plasma deposition. The dielectric properties of the resulting composite material were characterized using impedance spectroscopy, while the sensing performance was evaluated by exposing the sensor to various ethanol concentrations. The results showed a significant increase in capacitance and dielectric permittivity for the carbyne-filled AAO compared to pristine AAO, along with a 5-fold improvement in sensitivity to ethanol vapor. The increased sensitivity is attributed to the synergistic combination of the AAO’s high surface area and the carbyne’s unique electrical properties. This work demonstrates the successful fabrication and characterization of a novel high-sensitivity gas sensor, highlighting the potential of carbyne-enriched AAO for advanced sensor applications. Full article