ABSTRACT
In order to reveal the mechanism of silicon (Si) fertilizer in improving nitrogen (N) and phosphorus (P) nutrient availability in paddy soil, we designed a series of soil culture experiments by combining application of varying Si fertilizer concentrations with fixed N and P fertilizer concentrations. Following the recommendations of fertilizer manufacturers and local farmers, we applied Si in concentrations of 0, 5.2, 10.4, 15.6, and 20.8 μg/kg. At each concentration of added Si, the availability of soil N and P nutrients, soil microbial activity, numbers of ammonia-oxidizing bacteria and P-decomposing bacteria which means that the organic P is decomposed into inorganic nutrients which can be absorbed and utilized by plants, and urease and phosphatase activity first increased, and then decreased, as Si was added to the soil. These indicators reached their highest levels with a Si application rate of 15.6 μg/kg, showing values respectively 19.78%, 105.09%, 8.34%, 73.12%, 130.36%, 28.12%, and 20.15% higher than those of the controls. Appropriate Si application (10.4 to 15.6 µg/kg) could significantly increase the richness of the soil microbial community involved in cycling of N and P nutrients in the soil. When the Si application rate was 15.6 μg/kg, parameters for characterizing microbial abundance such as sequence numbers, operational taxonomic unit (OTU) number, and correlation indices of microbial community richness such as Chao1 index, the adaptive coherence estimator (ACE) index, Shannon index, and Simpson index all reached maximum values, with amounts increased by 14.46%, 10.01%, 23.80%, 30.54%, 0.18%, and 2.64%, respectively, compared with the control group. There is also a good correlation between N and P mineralization and addition of Si fertilizer. The correlation coefficients between the ratio of available P/total P (AP/TP) and the number of ammonia-oxidizing bacteria, AP/TP and acid phosphatase activity (AcPA), AP/TP and the Shannon index, the ratio of available N/total amount of N (AN/TN) and the number of ammoniated bacteria, and AN/TN and AcPA were 0.9290, 0.9508, 0.9202, 0.9140, and 0.9366, respectively. In summary, these results revealed that enhancement of soil microbial community structure diversity and soil microbial activity by appropriate application of Si is the key ecological mechanism by which application of Si fertilizer improves N and P nutrient availability.
ABSTRACT
Objective:To investigate the wear characteristics of bovine enamel and lithium disilicate glass ceramic under simulated oral environment.Methods:18 cylindrical lithium disilicate glass-ceramic specimens with the length of 8 mm and diameter of 3 mm were randomly divided into 2 groups (n =9),9 lithium disilicate glass-ceramic specimens and 9 bovine enamel specimens were served as the antagonists respectively.The specimens were then loaded in a wear simulator and subjected to friction force of 10 N for 540 000 cycles in artificial saliva and room temperature(speed 100 r/min,turning radius of 2.5 mm,uniform circular motion) condition.During the testing,10 checkpoints were applied to measure the height loss of the specimens with 3D profilometer,then wear curves were plotted.Scanning electron microscopy were applied to investigate the worn surfaces at different wear stages.Results:At every checkpoints,bovine enamel wear height loss was larger than the lithium disilicate specimens (P ＜ 0.05);bovine enamel wear curve exhibits a runningin period,steady wear period and severe wear period 3 stages of wear,while wear curves of lithium disilicate glass ceramics exhibit onlyrunning-in period and steady wear period 2 wear stages.Both groups had the corresponding micro-morphological features in different periods.Conclusion:Bovine enamel and lithium disilicate glass ceramics show a phase dynamic evolution law under the simulated oral environment.Bovine enamel is more susceptible to wear than lithium disilicate,suggesting that clinical attention should be paid to prevent the excessive wear of natural teeth caused by lithium disilicate glass ceramic restorations.
ABSTRACT
Objective:To investigate the stress distribution in peri-implant bone with All-on-4 implant with various parameters by three-dimensional finite element method.Methods:An edentulous mandibular specimen was scanned by CT Mimcs.Geomagic,Uni-graphics,HyperMesh modeling software were used to establish All-on-4 implant finite element models with different inclination angles and corresponding cantilever lengths.1 50 N vertical static load was applied at the right end of the cantilever,peri-implant bone stress was analysed using Abaqus software.Results:When the distal implant inclined 0°with cantilever length of 1 9.5 mm,the peak stress in peri-implant cortical bone at the mesial and distal side was 25.526 MPa and 83.026 MPa respectively.When the distal implant in-clined 1 5°,30°and 45°with the cantilever length of 1 7.2 mm,1 3.3 mm and 9.8 mm,the stress in perio-implant cortical bone at distal side of the implant reduced by 1 2.4%,35.6% and 53.1 %,that at mesial side of the implant reduced by 1 3.6%,36.3% and 40.2%,respectively.Conclusion:From the perspective of the stress analysis,the design of All-on-4 distal implant with large incli-nation angle and short cantilever is superior to that with small inclination angle and long cantilever.
ABSTRACT
Malaria is the one of major diseases which threatens people’s life in Africa. Out of humanitarianism, Chinese scientists has contributed to research of Artemisinin and ACTS more than 30 years, China provides long-term antimalaria assistance to Africa and gain great achievements. In Moheli, the island of Comoros, the antimalaria group used a new strategy which universal medication and proactive intervention. They established not only an effective antimalaria system and reporting system but also a local antimalaria team. Furthermore, they enhanced publicity and put mass protection and treatment into effect. Finally, they achieved significant result. In order to apply those successful experience to other countries in Africa, this paper summed up those experience and inspirations.
ABSTRACT
Malaria is the one of major diseases which threatens people’s life in Africa. Out of humanitarianism, Chinese scientists has contributed to research of Artemisinin and ACTS more than 30 years, China provides long-term antimalaria assistance to Africa and gain great achievements. In Moheli, the island of Comoros, the antimalaria group used a new strategy which universal medication and proactive intervention. They established not only an effective antimalaria system and reporting system but also a local antimalaria team. Furthermore, they enhanced publicity and put mass protection and treatment into effect. Finally, they achieved significant result. In order to apply those successful experience to other countries in Africa, this paper summed up those experience and inspirations.