ABSTRACT
Biological soil crusts (BSCs), as a pioneer for vegetation restoration and crucial component of surface landscape, greatly affect land surface process. To explore the development of BSCs and its effects on soil water infiltration in karst region, we investigated the development of BSCs and analyzed the infiltration processes with different BSCs coverages (0, 28%, 40%, 70%, 97%) and rainfall intensities (42 and 132 mm·h-1) in simulating rainfall experiments on a typical karst slope. The results showed that there were significant differences in the development of BSCs for different land use types, whereas the spatial variation of BSCs development on the slope was not obvious under the same land use type. Compared to the bare plot, the presence of BSCs significantly increased surface roughness, the initial runoff generation time, and soil water infiltration. In the cases of light (42 mm·h-1) and intensive (132 mm·h-1) rainfall, the initial infiltration rate of BSCs covered plots were 1.7-1.9 times and 1.2-1.9 times as that of bare plot, while the average infiltration rate in BSCs covered plots were 2.5-3.0 times and 1.4-3.3 times as that of bare plot, respectively. The BSCs coverage was significantly positively correlated with the initial runoff production time. The critical values of facilitating infiltration of BSCs coverage were between 65% and 70% under the test rainfall intensities. For heavy rainfall events, the inhibiting effects of BSCs on surface runoff were weakened. Horton model was the most reliable one for describing the infiltration process on karst slope with BSCs, followed by Kostiakov model and Philip model. In conclusion, the spatial variability of BSCs development on the karst slope was higher. The presence of BSCs had a significant effect on soil permeability in karst region.
Subject(s)
Soil , Water , Rain , Water/analysis , Water MovementsABSTRACT
The Aspergillus niger AS3.350 protease gene (pepD) was successfully cloned and expressed in Pichia pastoris KM71. The rPepD activity was 331.5 U/ml, and the optimum temperature and pH were 45⯰C and 8-9 respectively. In addition, enzyme activity was significantly inhibited by PMSF, EDTA, Mg2+, Fe2+ and Zn2+ ions, and stimulated by Ca2+ which selectively bound to the T302 and D323 residues. Mutation in either or both of the residues inhibited rPepD expression, indicating that binding to Ca2+ is necessary for PepD expression and activity. The rPepD showed a wide substrate range, and was particularly selective to those with hydrophobic amino acids. The degree of rPepD-mediated hydrolysis of soy protein isolate, corn flour and gluten meal were 8.7%, 38.1% and 33.6% respectively, which was higher than that by Alcalase, indicating that rPepD has potential applications in the food processing industry.
Subject(s)
Aspergillus niger/enzymology , Fungal Proteins/chemistry , Fungal Proteins/genetics , Peptide Hydrolases/chemistry , Peptide Hydrolases/genetics , Aspergillus niger/chemistry , Aspergillus niger/genetics , Calcium/metabolism , Cloning, Molecular , Enzyme Stability , Fungal Proteins/metabolism , Hydrogen-Ion Concentration , Peptide Hydrolases/metabolism , Pichia/genetics , Pichia/metabolism , Recombinant Proteins/chemistry , Recombinant Proteins/genetics , Recombinant Proteins/metabolism , TemperatureABSTRACT
PURPOSE: To investigate the anatomic morphology of root and root canal system of maxillary premolars by using cone-beam computer tomography (CBCT), in order to provide imaging basis for clinical treatment. METHODS: CB CT images of 720 patients (aged from 18 to 67 years) were included. They were divided into 5 groups according to their agesï¼18-28ï¼29-38ï¼39-48ï¼49-58 andï¼58 years old . The number of roots and root canals, root canal configuration, the distance between two orifices,root canal curvature,distance from apex to maxillary sinus,symmetry of the bilateral teeth and its relationship to age changes were analyzed statistically using SPSS21.0 software package. RESULTS: Double root canal of the first maxillary premolar accounted the most (89.72%), and type IV was the frequent type (57.78%) . The incidence of single root canal in the second maxillary premolar (53.06%) was slightly higher than double root canal (46.94%). Root canal type was mainly type I (53.06%). There was symmetrical distribution in the bilateral root and root canals of maxillary premolars. The detection rate of the single root canal was changed with age, and the distance between the two orifice was closely related to the root morphology. The detection rate of root curvature in maxillary first and second premolar was 32.53% and 21.50% in buccolingual direction. There was a certain proportion of S-type complex root canal.16.69% of the maxillary second premolar and maxillary sinus were closely related (d≤0.05 mm). CONCLUSIONS: The anatomical structure of root and root canal is complicated .The prevalence of the bilateral teeth presents symmetry and age-related changes.The curvature of root canal is complex, and the roots are closely related to maxillary sinus.
