Microstructural evolution of Mg-14Gd-0.4Zr alloy during compressive creep

The present work reports the creep behavior and microstructural evolution of the sand-cast Mg-14Gd-0.4Zr alloy(wt.%) prepared by the differential pressure casting machine. Their compressive creep tests at 250 ℃ were performed under various applied stresses(i.e., 60, 80 and100 MPa). Among them, the sand-cast Mg-14Gd-0.4Zr samples examined under 250 ℃/80 MPa for 39 and 95 h, respectively, were chosen to systemically analyze their creep mechanisms using high-angle annular dark field-scanning transmission electron microscopy(HAADF-STEM).The obtained results showed that the enhancement of creep resistance can be mainly attributed to the coherent β' and β'_F phases with an alternate distribution, effectively impeding the basal dislocations movement. However, with the creep time increasing, the fine β'+β'_F precipitate chains coarsened and transformed to semi-coherent β_1 phase and even to large incoherent β phase(surrounded by precipitate-free areas) in grain interiors. The precipitate-free zones(PFZs) at grain boundaries(GBs) were formed, and they could expand during creep deformation. Apart from the main cross-slip of basal and prismatic dislocations, type dislocations were activated and tended to distribute near the GBs. The aforementioned phenomena induced the stress concentrations, consequently leading to the increment of the creep strain.

Boosting Hydrogen Storage Performance of MgH_(2) by Oxygen Vacancy-Rich H-V_(2)O_(5) Nanosheet as an Excited H-Pump

MgH_(2) is a promising high-capacity solid-state hydrogen storage material,while its application is greatly hindered by the high desorption temperature and sluggish kinetics.Herein,intertwined 2D oxygen vacancy-rich V_(2)O_(5) nanosheets(H-V_(2)O_(5))are specifically designed and used as catalysts to improve the hydrogen storage properties of MgH_(2).The as-prepared MgH_(2)-H-V_(2)O_(5) composites exhibit low desorption temperatures(Tonset=185℃)with a hydrogen capacity of 6.54 wt%,fast kinetics(Ea=84.55±1.37 kJ mol^(-1) H_(2) for desorption),and long cycling stability.Impressively,hydrogen absorption can be achieved at a temperature as low as 30℃ with a capacity of 2.38 wt%within 60 min.Moreover,the composites maintain a capacity retention rate of~99%after 100 cycles at 275℃.Experimental studies and theoretical calculations demonstrate that the in-situ formed VH_(2)/V catalysts,unique 2D structure of H-V_(2)O_(5) nanosheets,and abundant oxygen vacancies positively contribute to the improved hydrogen sorption properties.Notably,the existence of oxygen vacancies plays a double role,which could not only directly accelerate the hydrogen ab/de-sorption rate of MgH_(2),but also indirectly affect the activity of the catalytic phase VH_(2)/V,thereby further boosting the hydrogen storage performance of MgH_(2).This work highlights an oxygen vacancy excited“hydrogen pump”effect of VH_(2)/V on the hydrogen sorption of Mg/MgH_(2).The strategy developed here may pave a new way toward the development of oxygen vacancy-rich transition metal oxides catalyzed hydride systems.

Risk factors for lymph node metastasis and evaluation of reasonable surgery for early gastric cancer

AIM: To give the evidence for rationalizing surgical therapy for early gastric cancer with different lymph node status. METHODS: A series of 322 early gastric cancer patients who underwent gastrectomy with more than 15 lymph nodes retrieved were reviewed in this study. The rate of lymph node metastasis was calculated. Univariate and multivariate analyses were performed to evaluate the independent factors for predicting lymph node metastasis. RESULTS: No metastasis was detected in No.5, 6 lymph nodes (LN) during proximal gastric cancer total gastrectomy, and in No.10, 11p, 11d during for combined resection of spleen and splenic artery and in No.15 LN during combined resection of transverse colon mesentery. No.11p, 12a, 14v LN were proved negative for metastasis. The global metastastic rate was 14.6% for LN, 5.9% for mucosa, and 22.4% for submucosa carcinoma, respectively. The metastasis in group Ⅱ?was almost limited in No.7, 8a LN. Multivariate analysis identified that the depth of invasion, histological type and lymphatic invasion were independent risk factors for LN metastasis. No metastasis from distal cancer (≤ 1.0 cm in diameter) was detected in group Ⅱ?LN. The metastasis rate increased significantly when the diameter exceeded 3.0 cm. All tumors (≤ 1.0 cm in diameter) with LN metastasis and mucosa invasion showed a depressed macroscopic type, and all protruded carcinomas were > 3.0 cm in diameter. CONCLUSION: Segmental/subtotal gastrectomy plus D1/D1 + No.7 should be performed for carcinoma (≤ 1.0 cm in diameter, protruded type and mucosa invasion).Subtotal gastrectomy plus D2 or D1 + No.7, 8a, 9 is the most rational operation, whereas No.11p, 12a, 14v lymphadenectomy should not be recommended routinely for poorly differentiated and depressed type of submucosa carcinoma (> 3.0 cm in diameter). Total gastrectomy should not be performed in proximal, so does combined resection or D2+/D3 lymphadenectomy.

Nanostructuring of Mg-Based Hydrogen Storage Materials:Recent Advances for Promoting Key Applications

With the depletion of fossil fuels and global warming,there is an urgent demand to seek green,low-cost,and high-efficiency energy resources.Hydrogen has been considered as a potential candidate to replace fossil fuels,due to its high gravimetric energy density(142 MJ kg^(-1)),high abundance(H_(2)O),and environmentalfriendliness.However,due to its low volume density,effective and safe hydrogen storage techniques are now becoming the bottleneck for the"hydrogen economy".Under such a circumstance,Mg-based hydrogen storage materials garnered tremendous interests due to their high hydrogen storage capacity(~7.6 wt%for MgH_(2)),low cost,and excellent reversibility.However,the high thermodynamic stability(ΔH=-74.7 kJ mol^(-1)H_(2))and sluggish kinetics result in a relatively high desorption temperature(>300℃),which severely restricts widespread applications of MgH_(2).Nano-structuring has been proven to be an effective strategy that can simultaneously enhance the ab/de-sorption thermodynamic and kinetic properties of MgH_(2),possibly meeting the demand for rapid hydrogen desorption,economic viability,and effective thermal management in practical applications.Herein,the fundamental theories,recent advances,and practical applications of the nanostructured Mg-based hydrogen storage materials are discussed.The synthetic strategies are classified into four categories:free-standing nano-sized Mg/MgH_(2)through electrochemical/vapor-transport/ultrasonic methods,nanostructured Mg-based composites via mechanical milling methods,construction of core-shell nano-structured Mg-based composites by chemical reduction approaches,and multi-dimensional nano-sized Mg-based heterostructure by nanoconfinement strategy.Through applying these strategies,near room temperature ab/de-sorption(<100℃)with considerable high capacity(>6 wt%)has been achieved in nano Mg/MgH_(2)systems.Some perspectives on the future research and development of nanostructured hydrogen storage materials are also provided.

Oxygen Vacancy-Rich 2D TiO_(2) Nanosheets:A Bridge Toward High Stability and Rapid Hydrogen Storage Kinetics of Nano-Confined MgH_(2)

MgH_(2) has attracted intensive interests as one of the most promising hydrogen storage materials.Nevertheless,the high desorption temperature,sluggish kinetics,and rapid capacity decay hamper its commercial application.Herein,2D TiO_(2) nanosheets with abundant oxygen vacancies are used to fabricate a flower-like MgH_(2)/TiO_(2) heterostructure with enhanced hydrogen storage performances.Particularly,the onset hydrogen desorption temperature of the MgH_(2)/TiO_(2) heterostructure is lowered down to 180℃(295℃ for blank MgH_(2)).The initial desorption rate of MgH_(2)/TiO_(2) reaches 2.116 wt% min^(-1) at 300℃,35 times of the blank MgH_(2) under the same conditions.Moreover,the capacity retention is as high as 98.5% after 100 cycles at 300℃,remarkably higher than those of the previously reported MgH_(2)-TiO_(2) composites.Both in situ HRTEM observations and ex situ XPS analyses confirm that the synergistic effects from multi-valance of Ti species,accelerated electron transportation caused by oxygen vacancies,formation of catalytic Mg-Ti oxides,and stabilized MgH_(2) NPs confined by TiO_(2) nanosheets contribute to the high stability and kinetically accelerated hydrogen storage performances of the composite.The strategy of using 2D substrates with abundant defects to support nano-sized energy storage materials to build heterostructure is therefore promising for the design of high-performance energy materials.

Burden of vitiligo on Chinese patients:An online survey

To the Editor:Vitiligo is a chronic disease that impacts many aspects of a patient’s life.The prevalence of vitiligo has been increasing,and currently involves up to 0.5%to 2%of all races worldwide.[1]Although this condition very rarely produces any direct physical discomfort,the cosmetic problems and disfiguring appearance resulting from the depigmented lesions severely affect the quality of life(QoL)in these individuals.

Clinical characteristics of 1327 patients with coronavirus disease 2019(COVID-19)in the largest Fangcang shelter hospital in Wuhan

To the Editor:Coronavirus disease 2019(COVID-19),a result of severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)infection,is highly infectious.[1]As COVID-19 spreads rapidly,and the majority of the patients develop mild to moderate form of the disease,we aimed to study the clinical characteristics of these patients admitted to Jianghan Fangcang shelter hospital,the largest Fangcang shelter hospital in Wuhan,China.