Search Results (4)

Salivary glands produce saliva through precisely coordinated epithelial ion transport processes. Ion channels are essential components of the molecular machinery that convert neural and hormonal signals into targeted ion and water flux. This review focuses on the integrated molecular and cellular mechanisms by which ion channels cooperate to generate salivary fluid under physiological conditions. Saliva formation proceeds through two sequential stages: isotonic primary fluid secretion by acinar cells, followed by ionic modification within the ductal epithelium. Parasympathetic stimulation activates muscarinic M1/3 receptors, initiating intracellular calcium signaling through inositol 1,4,5-trisphosphate-dependent release from the endoplasmic reticulum and sustained calcium entry via Orai1/TRPC channels. Elevated cytosolic calcium activates apical ANO1/TMEM16A chloride channels, the rate-limiting step in acinar fluid secretion, together with basolateral calcium-activated potassium channels that preserve the electrochemical driving force for chloride efflux. Chloride accumulation is maintained by Na⁺/K⁺-ATPase and the Na⁺-K⁺-2Cl⁻ cotransporter, while osmotic gradients drive water movement through apical aquaporin-5 and basolateral aquaporin-1/3. As primary saliva traverses the ductal system, epithelial sodium channels, CFTR, and additional ion transport pathways reabsorb sodium and chloride and secrete potassium and bicarbonate, producing hypotonic final saliva. By synthesizing calcium signaling, chloride and potassium conductance, sodium handling, and epithelial polarity into a unified framework, this review establishes ion channel integration as the fundamental basis of salivary gland fluid secretion. Full article

This study investigates the influence of prolonged electrolysis on the electrochemical performance and surface characteristics of NiFe-modified compressed graphite electrodes used in alkaline water electrolysis. The electrochemical experiment was conducted over a two-week period at a constant temperature of 60 °C. The electrodes were evaluated for changes in surface morphology and composition using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). The results demonstrated stable electrochemical performance with minimal current variation. However, significant structural changes occurred, including the formation of new microstructures on the cathode and the emergence of KHCO₃ (potassium bicarbonate) compound on both electrodes. Crystallographic analysis revealed an increase in crystallite size and tensile lattice strain on the cathode, while the anode exhibited compressive lattice strains and a reduction in crystallite size. These findings suggest that the observed changes were driven by electrochemical annealing processes, contributing to material redistribution and surface modifications during prolonged electrolysis. This study provides insight into optimizing NiFe-based catalysts for enhanced durability and efficiency in water splitting technologies. Full article

Using rapeseed straw as a raw material and potassium bicarbonate (KHCO₃) and urea (CO(NH₂)₂) as modification reagents, the pyrolysis raw materials were mixed in a certain proportion, and the unmodified biochar GBC800, KHCO₃-modified biochar KGBC800, and (KHCO₃)/(CO(NH₂)₂) co-modified biochar N-KGBC800 were, respectively, prepared using the one-pot method at 800 °C. The physicochemical properties, such as surface morphology, pore characteristics, functional group distribution, and elemental composition of the three biochars, were characterized, and the adsorption performance and mechanism of the typical antibiotic tetracycline (TC) in water were studied. The results showed that the surface of GBC800 was smooth and dense, with no obvious pore structure, and both the specific surface area and total pore volume were small; the surface of KGBC800 showed an obvious coral-like three-dimensional carbon skeleton, the number of micropores and the specific surface area were significantly improved, and the degree of carbonization and aromatization was enhanced; N-KGBC800 had a coral-like three-dimensional carbon skeleton similar to KGBC800, and there were also many clustered carbon groups. The carbon layer changed significantly with interlayer gaps, presenting a multi-level porous structure. After N doping, the content of N increased, and new nitrogen-containing functional groups were formed. When the initial TC concentration was 100 mg/L, pH ≈ 3.4, the temperature was 25 °C, and the dosage of the three biochars was 0.15 g/L, the adsorption equilibrium was reached before 720 min. The adsorption capacities of GBC800, KGBC800, and N-KGBC800 for TC were 16.97 mg/g, 294.86 mg/g, and 604.71 mg/g, respectively. Fitting the kinetic model to the experimental data, the adsorption of TC by the three biochars was more in line with the pseudo-second-order adsorption kinetic model, and the adsorption isotherm was more in line with the Langmuir model. This adsorption process was a spontaneous endothermic reaction, mainly chemical adsorption, specifically involving multiple adsorption mechanisms such as pore filling, electrostatic attraction, hydrogen bonds, n−π interaction, Lewis acid–base interaction, π−π stacking, or cation −π interaction between the aromatic ring structure of the carbon itself and TC. A biochar-adsorption column was built to investigate the dynamic adsorption process of tetracycline using the three biochars against the background of laboratory pure water and salt water. The adsorption results show that the Thomas model and the Yoon–Nelson model both provide better predictions for dynamic adsorption processes. The modified biochars KGBC800 and N-KGBC800 can be used as preferred materials for the efficient adsorption of TC in water. Full article

The traditional Solvay process and other modifications that are based on different types of alkaline material and waste promise to be effective in the reduction of reject brine salinity and the capture of CO₂. These processes, however, require low temperatures (10–20 °C) to increase the solubility of CO₂ and enhance the precipitation of metallic salts, while reject brine is usually discharged from desalination plants at relatively high temperatures (40–55 °C). A modified Solvay process based on potassium hydroxide (KOH) has emerged as a promising technique for simultaneously capturing carbon dioxide (CO₂) and reducing ions from reject brine in a combined reaction. In this study, the ability of the KOH-based Solvay process to reduce brine salinity at relatively high temperatures was investigated. The impact of different operating conditions, including pressure, KOH concentration, temperature, and CO₂ gas flowrate, on CO₂ uptake and ion removal was investigated and optimized. The optimization was performed using the response surface methodology based on a central composite design. A CO₂ uptake of 0.50 g CO₂/g KOH and maximum removal rates of sodium (Na⁺), chloride (Cl⁻), calcium (Ca²⁺), and magnesium (Mg²⁺) of 45.6%, 29.8%, 100%, and 91.2%, respectively, were obtained at a gauge pressure, gas flowrate, and KOH concentration of 2 bar, 776 mL/min, and 30 g/L, respectively, and at high temperature of 50 °C. These results confirm the effectiveness of the process in salinity reduction at a relatively high temperature that is near the actual reject brine temperature without prior cooling. The structural and chemical characteristics of the produced solids were investigated, confirming the presence of valuable products such as sodium bicarbonate (NaHCO₃), potassium bicarbonate (KHCO₃) and potassium chloride (KCl). Full article