Due to their outstanding electrical contact properties,Cd-containing silver-matrix electrical contact materials can meet the requirements of high stability and long life for military defense and aerospace applications...Due to their outstanding electrical contact properties,Cd-containing silver-matrix electrical contact materials can meet the requirements of high stability and long life for military defense and aerospace applications.In order to further reduce the Cd content under the premise of meeting the high-performance requirements,in this study,high-purity intermediate Ti_(2)Cd powder of MAX phase(Ti_(2)CdC)was synthesized with a pressureless technique and then applied to reinforce the Ag matrix.The Cd content of the as-prepared Ag/Ti_(2)Cd composites was actually reduced by 38.31%compared with conventional Ag/CdO material.Based on the systematic study of the effect of heat treatment temperature on the physical phase,morphology,interface and comprehensive physical properties of Ag/Ti_(2)Cd composites,the preferred samples(heat treated at 400°C for 1 h)showed high density(97.77%),low resistivity(2.34μΩ·cm),moderate hardness(90.8HV),high tensile strength(189.9 MPa),and exhibited good electrical contact performance after 40000 cycles of arc discharging under severe conditions(DC 28 V/20 A).The results of microscopic morphological evolution,phase change and elemental distribution of the electrical contact surface show that the combination of high stability of Ti_(2)Cd reinforcing phase,good interfacial bonding with Ag matrix and improved melt pool viscosity in the primary stage of arc erosion,results in low and stable contact resistance(average value 13.20 mΩ)and welding force(average value 0.6 N),low fluctuation of static force(2.2-2.5 N).The decomposition and absorption energy of Ti_(2)Cd and the arc extinguishing effect of Cd vapor are the main reasons for the stable arcing energy and arcing time of electric contacts in the late stage of arc erosion.展开更多
Cognitive decline is a feature of normal and pathological aging. As the proportion of the global aged population continues to grow, it is imperative to understand the molecular and cellular substrates of cognitive agi...Cognitive decline is a feature of normal and pathological aging. As the proportion of the global aged population continues to grow, it is imperative to understand the molecular and cellular substrates of cognitive aging for therapeutic discovery. This review focuses on the critical role of neural extracellular matrix in the regulation of neuroplasticity underlying learning and memory in another under-investigated "critical period": the aging process. The fascinating ideas of neural extracellular matrix forming a synaptic cradle in the tetrapartite synapse and possibly serving as a substrate for storage of very long-term memories will be introduced. We emphasize the distinct functional roles of diffusive neural extracellular matrix and perineuronal nets and the advantage of the coexistence of two structures for the adaptation to the ever-changing external and internal environments. Our study of striatal neural extracellular matrix supports the idea that chondroitin sulfate proteoglycan-associated extracellular matrix is restrictive on synaptic neuroplasticity, which plays important functional and pathogenic roles in early postnatal synaptic consolidation and aging-related cognitive decline. Therefore, the chondroitin sulfate proteoglycan-associated neural extracellular matrix can be targeted for normal and pathological aging. Future studies should focus on the cell-type specificity of neural extracellular matrix to identify the endogenous, druggable targets to restore juvenile neuroplasticity and confer a therapeutic benefit to neural circuits affected by aging.展开更多
AIM: To evaluate the high sensitivity C-reactive protein(hs CRP), Fetuin-A and matrix γ-carboxyglutamate protein(MGP) as the main factors for vascular calcification and inflammation in serum of patients with advanced...AIM: To evaluate the high sensitivity C-reactive protein(hs CRP), Fetuin-A and matrix γ-carboxyglutamate protein(MGP) as the main factors for vascular calcification and inflammation in serum of patients with advanced age-related macular degeneration(ARMD) in comparison to healthy controls. METHODS: The subjects were 40 patients with choroidal neovascularization(CNV) having a mean age of70.9 ±9.1y and a matched group of 49 apparently healthy control subjects. The ARMD was diagnosed using a slitlamp with superfield lens, fundus photography and fluorescein angiography. Measurement of hs CRP was done by nephelometry method. Levels of Fetuin-A and MGP were measured by enzyme-linked immunosorbent assay(ELISA) technique.RESULTS: hs CRP [0.45(0.07-2.63) mg/L vs 0.25(0.03-1.2) mg/L, P =0.02)] and Fetuin-A levels(50.27 ±5.04 vs44.99±10.28 ng/m L, P =0.009) were higher in the patients than in the control groups. We could not find significant difference in MGP level between two groups(P =0.08).There was not a significant correlation between MGP with Fetuin-A and hs CRP among the patients(P =0.7, P =0.9respectively). A significant negative correlation of hs CRP with Fetuin-A was observed in both case and control groups(P =0.004, r =-0.33 and P =0.001, r =-0.54,respectively).CONCLUSION: Although our study shows that serum hs CRP and Fetuin-A is increased in CNV patients as well as negatively correlated with both study groups, their direct role on pathogenesis of ARMD required future studies.展开更多
基金This work was financially supported by the National Natural Science Foundation of China(52101064)Jiangsu Planned Projects for Postdoctoral Research Funds(2020Z158)Industry-University-Research Cooperation Projects(RH2000002728,RH2000002332,RH2100000263).
文摘Due to their outstanding electrical contact properties,Cd-containing silver-matrix electrical contact materials can meet the requirements of high stability and long life for military defense and aerospace applications.In order to further reduce the Cd content under the premise of meeting the high-performance requirements,in this study,high-purity intermediate Ti_(2)Cd powder of MAX phase(Ti_(2)CdC)was synthesized with a pressureless technique and then applied to reinforce the Ag matrix.The Cd content of the as-prepared Ag/Ti_(2)Cd composites was actually reduced by 38.31%compared with conventional Ag/CdO material.Based on the systematic study of the effect of heat treatment temperature on the physical phase,morphology,interface and comprehensive physical properties of Ag/Ti_(2)Cd composites,the preferred samples(heat treated at 400°C for 1 h)showed high density(97.77%),low resistivity(2.34μΩ·cm),moderate hardness(90.8HV),high tensile strength(189.9 MPa),and exhibited good electrical contact performance after 40000 cycles of arc discharging under severe conditions(DC 28 V/20 A).The results of microscopic morphological evolution,phase change and elemental distribution of the electrical contact surface show that the combination of high stability of Ti_(2)Cd reinforcing phase,good interfacial bonding with Ag matrix and improved melt pool viscosity in the primary stage of arc erosion,results in low and stable contact resistance(average value 13.20 mΩ)and welding force(average value 0.6 N),low fluctuation of static force(2.2-2.5 N).The decomposition and absorption energy of Ti_(2)Cd and the arc extinguishing effect of Cd vapor are the main reasons for the stable arcing energy and arcing time of electric contacts in the late stage of arc erosion.
基金supported in part by National Alliance for Research on Schizophrenia & Depression(NARSAD)Young Investigator Grant from Brain Behavorial Research Foundation,No.21365(to XHL)Ike Muslow Predoctoral Fellowship from Louisiana State University Health Sciences Center-Shreveport(to ADR)
文摘Cognitive decline is a feature of normal and pathological aging. As the proportion of the global aged population continues to grow, it is imperative to understand the molecular and cellular substrates of cognitive aging for therapeutic discovery. This review focuses on the critical role of neural extracellular matrix in the regulation of neuroplasticity underlying learning and memory in another under-investigated "critical period": the aging process. The fascinating ideas of neural extracellular matrix forming a synaptic cradle in the tetrapartite synapse and possibly serving as a substrate for storage of very long-term memories will be introduced. We emphasize the distinct functional roles of diffusive neural extracellular matrix and perineuronal nets and the advantage of the coexistence of two structures for the adaptation to the ever-changing external and internal environments. Our study of striatal neural extracellular matrix supports the idea that chondroitin sulfate proteoglycan-associated extracellular matrix is restrictive on synaptic neuroplasticity, which plays important functional and pathogenic roles in early postnatal synaptic consolidation and aging-related cognitive decline. Therefore, the chondroitin sulfate proteoglycan-associated neural extracellular matrix can be targeted for normal and pathological aging. Future studies should focus on the cell-type specificity of neural extracellular matrix to identify the endogenous, druggable targets to restore juvenile neuroplasticity and confer a therapeutic benefit to neural circuits affected by aging.
基金Supported by the vice-chancellor for research of Tabriz University of Medical Sciences, Tabriz, Iran
文摘AIM: To evaluate the high sensitivity C-reactive protein(hs CRP), Fetuin-A and matrix γ-carboxyglutamate protein(MGP) as the main factors for vascular calcification and inflammation in serum of patients with advanced age-related macular degeneration(ARMD) in comparison to healthy controls. METHODS: The subjects were 40 patients with choroidal neovascularization(CNV) having a mean age of70.9 ±9.1y and a matched group of 49 apparently healthy control subjects. The ARMD was diagnosed using a slitlamp with superfield lens, fundus photography and fluorescein angiography. Measurement of hs CRP was done by nephelometry method. Levels of Fetuin-A and MGP were measured by enzyme-linked immunosorbent assay(ELISA) technique.RESULTS: hs CRP [0.45(0.07-2.63) mg/L vs 0.25(0.03-1.2) mg/L, P =0.02)] and Fetuin-A levels(50.27 ±5.04 vs44.99±10.28 ng/m L, P =0.009) were higher in the patients than in the control groups. We could not find significant difference in MGP level between two groups(P =0.08).There was not a significant correlation between MGP with Fetuin-A and hs CRP among the patients(P =0.7, P =0.9respectively). A significant negative correlation of hs CRP with Fetuin-A was observed in both case and control groups(P =0.004, r =-0.33 and P =0.001, r =-0.54,respectively).CONCLUSION: Although our study shows that serum hs CRP and Fetuin-A is increased in CNV patients as well as negatively correlated with both study groups, their direct role on pathogenesis of ARMD required future studies.
