Potassium promoted iron–zinc catalysts prepared by co-precipitation method(C–Fe–Zn/K),solvothermal method(S–Fe–Zn/K)and hydrothermal method(H–Fe–Zn/K)could selectively convert CO_2to light olefins,respectively....Potassium promoted iron–zinc catalysts prepared by co-precipitation method(C–Fe–Zn/K),solvothermal method(S–Fe–Zn/K)and hydrothermal method(H–Fe–Zn/K)could selectively convert CO_2to light olefins,respectively.The physicochemical properties of the obtained catalysts were determined by SEM,N_2physisorption,XRD,H_2-TPR,CO_2-TPD and XPS measurements.The results demonstrated that preparation methods had great influences on the morphology,phase structures,reduction and adsorption behavior,and hence the catalytic performance of the catalysts.The samples prepared by hydrothermal and co-precipitation method generated small uniform particles and led to lower specific surface area.In contrast,microspheres with larger specific surface area were formed by self-assembly of nanosheets using solvothermal method.ZnFe_2O_4was the only detectable phase in the fresh C–2Fe–1Zn/K,S–3Fe–1Zn/K and S–2Fe–1Zn/K samples.ZnFe_2O_4and ZnO co-existed with increasing Zncontent in S–1Fe–1Zn/K sample,while ZnO and Fe_2O_3could be observed over H–2Fe–1Zn/K sample.All the used samples contained Fe_3O_4,ZnO and Fe_5C_2.The peak intensity of ZnO was strong in the AR-H–2Fe–1Zn/K sample while it was the lowest in the AR-C–2Fe–1Zn/K sample after reaction.The formation of ZnFe_2O_4increased the interaction between iron and zinc for C–2Fe–1Zn/K and S–Fe–Zn/K samples,causing easier reduction of Fe_2O_3to Fe_3O_4.The surface basicity of the sample prepared by co-precipitation method was much more than that of the other two methods.During CO_2hydrogenation,all the catalysts showed good activity and olefin selectivity.The CO selectivity was increased with increasing Zncontent over S–Fe–Zn/K samples.H–2Fe–1Zn/K catalyst preferred to the production of C_5^+hydrocarbons.CO_2conversion of 54.76%and C_2~=–C_4~=contents of 57.38%were obtained on C–2Fe–1Zn/K sample,respectively.展开更多
Crop establishment largely depends on the methods of tillage for seedbed preparation. Seedbed conditions and related problems have recently attracted considerable interest for research. The intensity of the soil compa...Crop establishment largely depends on the methods of tillage for seedbed preparation. Seedbed conditions and related problems have recently attracted considerable interest for research. The intensity of the soil compaction achieved because of tillage is related to the working speed of the implement used. The effect of working speed on indices used for the evaluation of seedbed preparation （index of soil texture, actual tillage depth, soil bulk density and the proposed index of leveling） were investigated by applying four different systems of tillage and using different tillage implements. The relationships of the indices investigated to working speed are also presented graphically for all tillage implements used. All relationships were found to be linear with the working speed and the corresponding coefficients of determination were very close to unity. Useful conclusions, which may be used by extension services for the selection of the proper working speed of the implements used for seedbed preparation, are reached. Finally the general conclusion is that reciprocating harrows may be introduced into energetic tillage systems for seedbed preparation.展开更多
MI （mitral insufficiency） is the most common valvulopathy currently, with surgery being the gold standard treatment. However, about half of patients with severe MI have a high surgical risk because of their age or c...MI （mitral insufficiency） is the most common valvulopathy currently, with surgery being the gold standard treatment. However, about half of patients with severe MI have a high surgical risk because of their age or comorbidities, therefore surgery is contraindicated, In this context, Mitraclip appears, a device that allows the percutaneous treatment of MI and which is presented as a safe alternative and able to improve the quality of life for these patients. This work describes the first procedure performed at a referral hospital in western Parana-Brazil. It is a male patient with mitral valve insufficiency due to mitral prolapse, submitted to endovascular therapy due to the high surgical risk because of his advanced age, presence of comorbidities and left ventricular dysfunction. From this modality, partial regurgitation improvement and intense symptomatic relief were obtained, demonstrating the great potential of the MitraClip device to improve the quality of life of its patients.展开更多
基金Supports by the National Natural Science Foundation of China(21666030,21366025)National First-rate Discipline Construction Project of Ningxia(NXYLXK2017A04)
文摘Potassium promoted iron–zinc catalysts prepared by co-precipitation method(C–Fe–Zn/K),solvothermal method(S–Fe–Zn/K)and hydrothermal method(H–Fe–Zn/K)could selectively convert CO_2to light olefins,respectively.The physicochemical properties of the obtained catalysts were determined by SEM,N_2physisorption,XRD,H_2-TPR,CO_2-TPD and XPS measurements.The results demonstrated that preparation methods had great influences on the morphology,phase structures,reduction and adsorption behavior,and hence the catalytic performance of the catalysts.The samples prepared by hydrothermal and co-precipitation method generated small uniform particles and led to lower specific surface area.In contrast,microspheres with larger specific surface area were formed by self-assembly of nanosheets using solvothermal method.ZnFe_2O_4was the only detectable phase in the fresh C–2Fe–1Zn/K,S–3Fe–1Zn/K and S–2Fe–1Zn/K samples.ZnFe_2O_4and ZnO co-existed with increasing Zncontent in S–1Fe–1Zn/K sample,while ZnO and Fe_2O_3could be observed over H–2Fe–1Zn/K sample.All the used samples contained Fe_3O_4,ZnO and Fe_5C_2.The peak intensity of ZnO was strong in the AR-H–2Fe–1Zn/K sample while it was the lowest in the AR-C–2Fe–1Zn/K sample after reaction.The formation of ZnFe_2O_4increased the interaction between iron and zinc for C–2Fe–1Zn/K and S–Fe–Zn/K samples,causing easier reduction of Fe_2O_3to Fe_3O_4.The surface basicity of the sample prepared by co-precipitation method was much more than that of the other two methods.During CO_2hydrogenation,all the catalysts showed good activity and olefin selectivity.The CO selectivity was increased with increasing Zncontent over S–Fe–Zn/K samples.H–2Fe–1Zn/K catalyst preferred to the production of C_5^+hydrocarbons.CO_2conversion of 54.76%and C_2~=–C_4~=contents of 57.38%were obtained on C–2Fe–1Zn/K sample,respectively.
文摘Crop establishment largely depends on the methods of tillage for seedbed preparation. Seedbed conditions and related problems have recently attracted considerable interest for research. The intensity of the soil compaction achieved because of tillage is related to the working speed of the implement used. The effect of working speed on indices used for the evaluation of seedbed preparation （index of soil texture, actual tillage depth, soil bulk density and the proposed index of leveling） were investigated by applying four different systems of tillage and using different tillage implements. The relationships of the indices investigated to working speed are also presented graphically for all tillage implements used. All relationships were found to be linear with the working speed and the corresponding coefficients of determination were very close to unity. Useful conclusions, which may be used by extension services for the selection of the proper working speed of the implements used for seedbed preparation, are reached. Finally the general conclusion is that reciprocating harrows may be introduced into energetic tillage systems for seedbed preparation.
文摘MI （mitral insufficiency） is the most common valvulopathy currently, with surgery being the gold standard treatment. However, about half of patients with severe MI have a high surgical risk because of their age or comorbidities, therefore surgery is contraindicated, In this context, Mitraclip appears, a device that allows the percutaneous treatment of MI and which is presented as a safe alternative and able to improve the quality of life for these patients. This work describes the first procedure performed at a referral hospital in western Parana-Brazil. It is a male patient with mitral valve insufficiency due to mitral prolapse, submitted to endovascular therapy due to the high surgical risk because of his advanced age, presence of comorbidities and left ventricular dysfunction. From this modality, partial regurgitation improvement and intense symptomatic relief were obtained, demonstrating the great potential of the MitraClip device to improve the quality of life of its patients.
