ABSTRACT
We previously showed that death-associated protein kinase 1 (DAPK1) expression is increased in hippocampal tissue in a mouse model of major depressive disorde and is related to cognitive dysfunction in Alzheimer's disease. In addition, depression is a risk factor for developing Alzheimer's disease, as well as an early clinical manifestation of Alzheimer's disease. Meanwhile, cognitive dysfunction is a distinctive feature of major depressive disorder. Therefore, DAPK1 may be related to cognitive dysfunction in major depressive disorder. In this study, we established a mouse model of major depressive disorder by housing mice individually and exposing them to chronic, mild, unpredictable stressors. We found that DAPK1 and tau protein levels were increased in the hippocampal CA3 area, and tau was hyperphosphorylated at Thr231, Ser262, and Ser396 in these mice. Furthermore, DAPK1 shifted from axonal expression to overexpression on the cell membrane. Exercise and treatment with the antidepressant drug citalopram decreased DAPK1 expression and tau protein phosphorylation in hippocampal tissue and improved both depressive symptoms and cognitive dysfunction. These results indicate that DAPK1 may be a potential reason and therapeutic target of cognitive dysfunction in major depressive disorder.
ABSTRACT
Coating is one of the most important high-value-added application cases in geopolymer materials. However, efflorescence can easily cause discoloration and reduce the esthetic impression of the coating surface, thus limiting its application; hence, inhibition of efflorescence is one of the most important techniques in the application of geopolymer coatings. Efflorescence is a spontaneous behavior in a Na-based geopolymer, involving the migration of soluble alkalis. Alkalis are dissolved by water and diffuse to the material surface through nocuous pores, and then react with CO2 to produce white carbonate products. To inhibit efflorescence in geopolymer coating, this article reports a structure modification method using polydimethy siloxane (PS) and mica. To explore the inhibition mechanism, the effects of PS and mica on the pore structure, water absorption, alkali leaching, and efflorescence product were investigated. The experimental results showed that a harmful pore structure and instinctive water absorption of the geopolymer strongly contributed to efflorescence. PS and mica could reduce the pore size distribution and porosity and are helpful to establish a waterproof structure, leading to water absorption and the alkali leaching rate being significantly suppressed. Both high water glass and water content play a critical role in the increase of efflorescence, but even under a high content of water glass and water used in geopolymer coating, this method shows an 80-90% efflorescence reduction, which is much higher than that of other studies. In practical engineering, when the geopolymer coating is applied after modification, even if it is exposed to the field environment for a long time, there is no efflorescence deposit on the coating surface. It is feasible to limit water ingression in a geopolymer, which effectively blocks the efflorescence reaction process. This method is simple and practical and can be applied in practical engineering applications of geopolymer coatings conveniently.
ABSTRACT
As a highly hydrophobic and good environmental durable material, silicone nanofilaments have shown great advantages in the construction of superhydrophobic coatings. However, the synthesis of these materials has always been limited to the application of trifunctional organosilane monomers under the action of acidic catalysts. For the first time, long-chain polymeric hydrogenated siloxane-poly(methyl-hydrosiloxane) (PMHS) was used to synthesize rapidly silicone nanofilaments in situ under alkaline conditions. A dense silicone nanofilament coating was obtained by PMHS + geopolymer layer on a smooth iron sheet, and achieved by one-step brushing of PMHS on the surface of a just-solidified alkali-activated metakaolin-based geopolymer coating at 120 °C for an hour of sealed curing. This composite coating was followed by a superhydrophobic composite coating with a contact angle of approximately 161° and a rolling angle of 2°. Consistent with this, laser scanning confocal microscopy and field-emission scanning electron microscopy images show the presence of micro- and nanoscale features that enable the entrapment of air when exposed to water and endow excellent superhydrophobic properties. Because geopolymer material has good adhesion ability with metal, ceramic, or other materials, the composite superhydrophobic coating is expected to be widely used.
ABSTRACT
The adsorption and separation of hazard metal ions, radioactive nuclides, or minor actinides from wastewater and high-level radioactive waste liquids using functional silica-based nano/micro-particles modified with various inorganic materials or organic groups, has attracted significant attention since the discovery of ordered mesoporous silica-based substrates. Focusing on inorganic and organic modified materials, the synthesis methods and sorption performances for specific ions in aqueous solutions are summarized in this review. Three modification methods for silica-based particles, the direct synthesis method, wetness impregnation method, and layer-by-layer (LBL) deposition, are usually adopted to load inorganic material onto silica-based particles, while the wetness impregnation method is currently used for the preparation of functional silica-based particles modified with organic groups. Generally, the specific synthesis method is employed based on the properties of the loading materials and the silicon-based substrate. Adsorption of specific toxic ions onto modified silica-based particles depends on the properties of the loaded material. The silicon matrix only changes the thermodynamic and mechanical properties of the material, such as the abrasive resistance, dispersibility, and radiation resistance. In this paper, inorganic loads, such as metal phosphates, molybdophosphate, titanate-based materials, and hydrotalcite, in addition to organic loads, such as 1,3-[(2,4-diethylheptylethoxy)oxy]-2,4-crown-6-Calix{4}arene (Calix {4}) arene-R14 and functional 2,6-bis-(5,6-dialkyl-1,2,4-triazin-3-yl)-pyridines(BTP) are reviewed. More specifically, we emphasize on the synthesis methods of such materials, their structures in relation to their capacities, their selectivities for trapping specific ions from either single or multi-component aqueous solutions, and the possible retention mechanisms. Potential candidates for remediation uses are selected based on their sorption capacities and distribution coefficients for target cations and the pH window for an optimum cation capture.
ABSTRACT
The environment on the lunar surface poses some difficult challenges to building long-term lunar bases; therefore, scientists and engineers have proposed the creation of habitats using lunar building materials. These materials must meet the following conditions: be resistant to severe lunar temperature cycles, be stable in a vacuum environment, have minimal water requirements, and be sourced from local Moon materials. Therefore, the preparation of lunar building materials that use lunar resources is preferred. Here, we present a potential lunar cement material that was fabricated using tektite powder and a sodium hydroxide activator and is based on geopolymer technology. Geopolymer materials have the following properties: approximately zero water consumption, resistance to high- and low-temperature cycling, vacuum stability and good mechanical properties. Although the tektite powder is not equivalent to lunar soil, we speculate that the alkali activated activity of lunar soil will be higher than that of tektite because of its low Si/Al composition ratio. This assumption is based on the tektite geopolymerization research and associated references. In summary, this study provides a feasible approach for developing lunar cement materials using a possible water recycling system based on geopolymer technology.
