The Fe-N-C material represents an attractive oxygen reduction reaction electrocatalyst,and the FeN_(4)moiety has been identified as a very competitive catalytic active site.Fine tuning of the coordination structure of...The Fe-N-C material represents an attractive oxygen reduction reaction electrocatalyst,and the FeN_(4)moiety has been identified as a very competitive catalytic active site.Fine tuning of the coordination structure of FeN_(4)has an essential impact on the catalytic performance.Herein,we construct a sulfur-modified Fe-N-C catalyst with controllable local coordination environment,where the Fe is coordinated with four in-plane N and an axial external S.The external S atom affects not only the electron distribution but also the spin state of Fe in the FeN_(4)active site.The appearance of higher valence states and spin states for Fe demonstrates the increase in unpaired electrons.With the above characteristics,the adsorption and desorption of the reactants at FeN_(4)active sites are optimized,thus promoting the oxygen reduction reaction activity.This work explores the key point in electronic configuration and coordination environment tuning of FeN_(4)through S doping and provides new insight into the construction of M-N-C-based oxygen reduction reaction catalysts.展开更多
Deep underground projects(e.g., coal mines), are often faced with complex conditions such as high stress and extremely soft rock. The strength and rigidity of the traditional support system are often insufficient,whic...Deep underground projects(e.g., coal mines), are often faced with complex conditions such as high stress and extremely soft rock. The strength and rigidity of the traditional support system are often insufficient,which makes it difficult to meet the requirements of ground control under complex conditions. As a new support form with high strength and rigidity, the confined concrete arch plays an important role in controlling the rock deformation under complex conditions. The section shape of the tunnel has an important impact on the mechanical properties and design of the support system. However, studies on the mechanical properties and influence mechanism of the new confined concrete arch are rarely reported. To this end, the mechanical properties of traditional U-shaped steel and new confined concrete arches are compared and comparative tests on arches of circular and straight-leg semicircular shapes in deep tunnels are conducted. A large mechanical testing system for underground engineering support structure is developed. The mechanical properties and influence mechanism of confined concrete arches with different section shapes under different loading modes and cross-section parameters are systematically studied. Test results show that the bearing capacity of the confined concrete arch is 2.10 times that of the U-shaped steel arch, and the bearing capacity of the circular confined concrete arch is 2.27 times that of the straight-leg semicircular arch. Among the various influencing factors and their engineering parameters,the lateral stress coefficient has the greatest impact on the bearing capacity of the confined concrete arch,followed by the steel pipe wall thickness, steel strength, and core concrete strength. Subsequently, the economic index of bearing capacity and cost is established, and the optimization design method for the confined concrete arch is proposed. Finally, this design method is applied to a high-stress tunnel under complex conditions, and the deformation of the surrounding rock is effectively controlled.展开更多
China's Mars probe,named Tianwen-1,including an orbiter and a landing rover,will be launched during the July-August 2020 Mars launch windows.Selected to be among the rover payloads is a Subsurface Penetrating Rada...China's Mars probe,named Tianwen-1,including an orbiter and a landing rover,will be launched during the July-August 2020 Mars launch windows.Selected to be among the rover payloads is a Subsurface Penetrating Radar module(RoSPR).The main scientific objective of the RoSPR is to characterize the thickness and sub-layer distribution of the Martian soil.The RoSPR consists of two channels.The low frequency channel of the RoSPR will penetrate the Martian soil to depths of 10 to 100 m with a resolution of a few meters.The higher frequency channel will penetrate to a depth of 3 to 10 m with a resolution of a few centimeters.This paper describes the design of the instrument and some results of field experiments.展开更多
Oral mucositis is a common morbidity induced by radiation therapy and chemo-radiotherapy for head and neck malignancies. This often results in treatment delays, premature treatment cessation and increased cost. New tr...Oral mucositis is a common morbidity induced by radiation therapy and chemo-radiotherapy for head and neck malignancies. This often results in treatment delays, premature treatment cessation and increased cost. New treatments of oral mucositis are emerging but effective remedies remain limited. Between February 2007 and May 2008, 21 patients with head and neck malignancies were treated with a supersaturated calcium phosphate oral rinse (Caphosol) that was performed for 4-10 times daily, each consisting of two one-minute rinses. There were 21 matched patients who received supportive care without the oral rinse. All patients in the two groups were treated with intensity modulated radiation therapy (IMRT) for average prescription doses of 66 Gy in 33 fractions. The effects of this rinse vs. supportive care on mucositis, PEG tube requirements, hospitalization, xerostomia, analgesic requirements and weight was respectively evaluated. We have observed statistically significant decreases in the incidence of radiation induced oral mucositis (p=0.0002) with WHO grade 3 (38% vs. 52%) and 4 mucositis (0% vs. 19%), need for PEG tube placement (33% vs. 57%) and hospitalization (0% vs 19%). There was also a favorable impact on the incidence of grade 3 (29% vs. 43%) xerostomia in the treated patients but it was statistically insignificant (p=0.58). Incremental costs related to treatment of oral mucositis were reduced considerably. Our data suggest that use of a supersaturated calcium phosphate oral rinse is an effective treatment for mucositis in patients undergoing IMRT. It may also be helpful in the reduction of hospitalization and PEG tube requirements.展开更多
基金supported by the National Key Research and Development Program of China(Grant No.2020YFA0715000)the National Natural Science Foundation of China(Grant No.52127816)+2 种基金supported by the U.S.Department of Energy(DOE),Office of Energy Efficiency and Renewable Energy,Vehicle Technologies Officethe DOE Office of Science by UChicago Argonne LLC under contract no.DE-AC02-06CH11357the Advanced Photon Source(APS),a U.S.Department of Energy(DOE)Office of Science User Facility,operated for the DOE Office of Science by Argonne National Laboratory under Contract No.DE-AC02-06CH11357
文摘The Fe-N-C material represents an attractive oxygen reduction reaction electrocatalyst,and the FeN_(4)moiety has been identified as a very competitive catalytic active site.Fine tuning of the coordination structure of FeN_(4)has an essential impact on the catalytic performance.Herein,we construct a sulfur-modified Fe-N-C catalyst with controllable local coordination environment,where the Fe is coordinated with four in-plane N and an axial external S.The external S atom affects not only the electron distribution but also the spin state of Fe in the FeN_(4)active site.The appearance of higher valence states and spin states for Fe demonstrates the increase in unpaired electrons.With the above characteristics,the adsorption and desorption of the reactants at FeN_(4)active sites are optimized,thus promoting the oxygen reduction reaction activity.This work explores the key point in electronic configuration and coordination environment tuning of FeN_(4)through S doping and provides new insight into the construction of M-N-C-based oxygen reduction reaction catalysts.
基金supported by the National Natural Science Foundation of China (Nos. 42277174, 42077267, and 52074164)the Natural Science Foundation of Shandong Province, China (No. ZR2020JQ23)+2 种基金Major Scientific and Technological Innovation Project of Shandong Province, China (No. 2019SDZY04)the Project of Shandong Province Higher Educational Youth Innovation Science and Technology Program, China (No. 2019KJG013)the opening project of State Key Laboratory of Explosion Science and Technology, Beijing Institute of Technology (No. KFJJ21-02Z)。
文摘Deep underground projects(e.g., coal mines), are often faced with complex conditions such as high stress and extremely soft rock. The strength and rigidity of the traditional support system are often insufficient,which makes it difficult to meet the requirements of ground control under complex conditions. As a new support form with high strength and rigidity, the confined concrete arch plays an important role in controlling the rock deformation under complex conditions. The section shape of the tunnel has an important impact on the mechanical properties and design of the support system. However, studies on the mechanical properties and influence mechanism of the new confined concrete arch are rarely reported. To this end, the mechanical properties of traditional U-shaped steel and new confined concrete arches are compared and comparative tests on arches of circular and straight-leg semicircular shapes in deep tunnels are conducted. A large mechanical testing system for underground engineering support structure is developed. The mechanical properties and influence mechanism of confined concrete arches with different section shapes under different loading modes and cross-section parameters are systematically studied. Test results show that the bearing capacity of the confined concrete arch is 2.10 times that of the U-shaped steel arch, and the bearing capacity of the circular confined concrete arch is 2.27 times that of the straight-leg semicircular arch. Among the various influencing factors and their engineering parameters,the lateral stress coefficient has the greatest impact on the bearing capacity of the confined concrete arch,followed by the steel pipe wall thickness, steel strength, and core concrete strength. Subsequently, the economic index of bearing capacity and cost is established, and the optimization design method for the confined concrete arch is proposed. Finally, this design method is applied to a high-stress tunnel under complex conditions, and the deformation of the surrounding rock is effectively controlled.
基金support from the China National Space Administration.
文摘China's Mars probe,named Tianwen-1,including an orbiter and a landing rover,will be launched during the July-August 2020 Mars launch windows.Selected to be among the rover payloads is a Subsurface Penetrating Radar module(RoSPR).The main scientific objective of the RoSPR is to characterize the thickness and sub-layer distribution of the Martian soil.The RoSPR consists of two channels.The low frequency channel of the RoSPR will penetrate the Martian soil to depths of 10 to 100 m with a resolution of a few meters.The higher frequency channel will penetrate to a depth of 3 to 10 m with a resolution of a few centimeters.This paper describes the design of the instrument and some results of field experiments.
文摘Oral mucositis is a common morbidity induced by radiation therapy and chemo-radiotherapy for head and neck malignancies. This often results in treatment delays, premature treatment cessation and increased cost. New treatments of oral mucositis are emerging but effective remedies remain limited. Between February 2007 and May 2008, 21 patients with head and neck malignancies were treated with a supersaturated calcium phosphate oral rinse (Caphosol) that was performed for 4-10 times daily, each consisting of two one-minute rinses. There were 21 matched patients who received supportive care without the oral rinse. All patients in the two groups were treated with intensity modulated radiation therapy (IMRT) for average prescription doses of 66 Gy in 33 fractions. The effects of this rinse vs. supportive care on mucositis, PEG tube requirements, hospitalization, xerostomia, analgesic requirements and weight was respectively evaluated. We have observed statistically significant decreases in the incidence of radiation induced oral mucositis (p=0.0002) with WHO grade 3 (38% vs. 52%) and 4 mucositis (0% vs. 19%), need for PEG tube placement (33% vs. 57%) and hospitalization (0% vs 19%). There was also a favorable impact on the incidence of grade 3 (29% vs. 43%) xerostomia in the treated patients but it was statistically insignificant (p=0.58). Incremental costs related to treatment of oral mucositis were reduced considerably. Our data suggest that use of a supersaturated calcium phosphate oral rinse is an effective treatment for mucositis in patients undergoing IMRT. It may also be helpful in the reduction of hospitalization and PEG tube requirements.
基金financially supported by Shenzhen Fundamental Research Program(JCYJ20190809114409397)the Fundamental Research Funds for the Central Universities(WUT:2020Ⅲ029 and 2020IVA100)。
