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"Cascaded Rocket" Nanosystems with Spatiotemporal Separation for Triple-Synergistic Therapy of Alzheimer's Disease
No full textAlzheimer's disease (AD) remains an incurable disease due to the intricate pathogenesis. The neuropathological hallmarks include extracellular amyloid-beta (A beta) plaques, tau phosphorylation and extensive oxidative stress in neurons, which facilitate the progression of AD. Based on the complex etiology, a spatiotemporally "cascaded rocket" delivery system (DPH/TPGAS NPs) with metal ion/enzyme responses is established in this study for triple-synergistic AD treatment. After targeting and permeating the blood-brain barrier (BBB), the histidine units in the DPH chelate excess metal ions at the extracellular microenvironment, restraining the formation of A beta aggregates, inducing the first-stage separation. Then, the remanent system targets neuronal cells and triggers the second separation with cathepsin B for reducing the level of phosphorylated tau and oxidative stress. Accordingly, the DPH/TPGAS NPs can achieve spatiotemporal drug release, which results in enhanced synergistic therapeutic effects both in the extracellular and intracellular region of the AD brain. After treating with DPH/TPGAS NPs, the memory deficits, levels of A beta and phosphorylated tau, inflammation and neuron damages are remarkably ameliorated in 3 x Tg-AD mice. Therefore, this "cascaded rocket" delivery system has great potential to serve as a powerful platform and provides a new horizon to the therapeutic strategy for AD and other brain diseases' treatments.</p
Efficient Extraction of Manganese from Low-Grade Pyrolusite by a Sawdust Pyrolysis Reduction Roasting-Acid Leaching Process
No full textIn this work, a novel method for extraction of manganese from low-grade pyrolusite by a sawdust pyrolysis reduction roasting-acid leaching process was explored. The reduction roasting was studied systematically, and the mechanism was also explored by thermodynamic and phase change analysis. Results indicate that sawdust was rapidly pyrolyzed at 250-450 degrees C to generate a large amount of reducing gases such as CO, CH4, and H-2, which gradually reduced MnO2 in low-grade pyrolusite to MnO. The reduction process of MnO2 was identified as MnO2 -> Mn2O3 -> Mn3O4 -> MnO. It was proved that MnO2 of low-grade pyrolusite could be reduced effectively to MnO at lower temperature and shorter duration time by sawdust pyrolysis. Meanwhile, the optimum leaching efficiency of 99.45% for manganese could be attained when sawdust dosage was 11% of the mass of low-grade pyrolusite, the roasting temperature was 500 degrees C, and the roasting time was 25 min
A Hybrid Experimental and Theoretical Approach to Optimize Recovery of Rare Earth Elements from Acid Mine Drainage Precipitates by Oxalic Acid Precipitation
No full textThe development of processing techniques for the extraction of rare earth elements and critical minerals (REE/CM) from acid mine drainage precipitates (AMDp) has attracted increased interest in recent years. Processes under development often utilize a standard hydrometallurgical approach that includes leaching and solvent extraction followed by oxalic acid precipitation and calcination to produce a final rare earth oxide product. Impurities such as Ca, Al, Mn, Fe and Mg can be detrimental in the oxalate precipitation step and a survey of the literature showed limited data pertaining to the REE precipitation efficiency in solutions with high impurity concentrations. As such, a systematic laboratory-scale precipitation study was performed on a strip solution generated by the acid leaching and solvent extraction of an AMDp feedstock to identify the optimal processing conditions that maximize REE precipitation efficiency and product purity while minimizing the oxalic acid dosage. Given the unique chemical characteristics of AMDp, the feed solution utilized in this study contained a moderate concentration of REEs (440 mg/L) as well a significant concentration (>7000 mg/L total) of non-REE contaminants such as Ca, Al, Mn, Fe and Mg. Initially, a theoretical basis for the required oxalic acid dose, optimal pH and predicted precipitation efficiency was established by solution equilibrium calculations. Following the solution chemistry calculations, bench-scale precipitation experiments were conducted and these test results indicate that a pH of 1.5 to 2, a reaction time of more than 2 h and an oxalic acid dosage of 30 to 40 g/L optimized the REEs recovery of at ~95% to nearly 100% for individual REE species. The test results validated the optimal pH predicted by the solution chemistry calculations (1.5 to 5); however, the predicted dosage needed for complete REE recovery (10 g/L) was significantly lower than the experimentally-determined dosage of 30 to 40 g/L. The reason for this discrepancy was determined to be due to the large concentration of impurities and large number of potential metal complexes that cause inaccuracies in the solution equilibrium calculations. Based on these findings, a hybrid experimental and theoretical approach is proposed for future oxalic acid precipitation optimization studies
Exploration of the Adsorption Kinetics of Surfactants at the Water-Oil Interface via Grand-Canonical Molecular Dynamics Simulations
No full textIt is well-known that surfactants tend to aggregate into clusters or micelles in aqueous solutions due to their special structures, and it is difficult for the surfactant molecules involved in the aggregation to move spontaneously to the oil-water interface. In this article, we developed a new grand-canonical molecular dynamics (GCMD) model to predict the saturated adsorption amount of surfactant with constant concentration of surfactant molecules in the bulk phase, which can prevent surfactants aggregating in the bulk phase and get the atomic details of the interfacial structural change with increase of the adsorption amount through a single GCMD run. The adsorption of anionic surfactant sodium dodecyl sulfate (SDS) at the heptane-water interface was studied to validate the model. The saturated adsorption amount obtained from the GCMD simulation is consistent with the experimental results. The adsorption kinetics of SDS molecules during the simulation can be divided into three stages: linear adsorption stage, transition adsorption stage, and dynamic equilibrium stage. We also carried out equilibrium molecular dynamics (EMD) simulations to compare with GCMD simulation. This GCMD model can effectively reduce the simulation time with correct prediction of the interfacial saturation adsorption. We believe the GCMD method could be especially helpful for the computational study of surfactant adsorption under complex environments or emulsion systems with the adsorption of multiple types of surfactants
Efficient Promotional Effects of Mo on the Catalytic Hydrogenation of Methyl Acrylate over Ni-Based Catalysts under Mild Conditions
No full textA series of Ni/gamma-Al2O3 and Ni-Mo/gamma-Al2O3 catalysts were prepared and evaluated for the hydrogenation of methyl acrylate to methyl propionate in a fixed-bed reactor. Physicochemical characterizations of these catalysts were carried out with Brunauer-Emmett-Teller analysis, X-ray diffraction, UV-vis diffuse reflectance spectroscopy, Raman spectroscopy, hydrogen temperature programed reduction, X-ray photoelectron spectroscopy, and transmission electron microscopy. It was noticed that Mo loaded onto the Ni/gamma-Al2O3 catalyst could not only promote the dispersion of Ni particles but also weaken the interaction between NiO and the gamma-Al2O3 support. The effect of the calcination temperature on Ni-Mo/gamma-Al2O3 catalysts is mainly due to the enhancement of the interaction between Ni species and gamma-Al2O3. The influence of the reduction temperature on the Ni-Mo/gamma-Al2O3 catalysts, as well as the reaction conditions, was also studied in detail. As a result, this hydrogenation process could be efficiently promoted on the optimal 10Ni-10Mo/gamma-Al2O3 catalyst with the highest yield of 94% and selectivity of 99.9%, and no deactivation behavior was observed after 130 h time-on-stream at 100 degrees C and 1.0 MPa
