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[en] In the natural composites, the reinforcement particles are subtly organized into complex structures in matrix, and its various microstructures endow the biomaterials with a variety of excellent mechanical behaviors. Among the various reinforcement building blocks used in biomaterials, short fibers are the most ubiquitous reinforcement elements. Unfortunately, because of the limitation of fabrication technique, replication of these fiber-reinforced biological composites can be extremely difficult in practice. In this paper, we developed a fiber assembly 3D printing process, which can manipulate the orientation of fibers during 3D printing procedure. Benefiting from this technology, the reinforcement particles were manipulated remotely and the arrangement of reinforcement particles with higher degree of freedom was achieved. Subsequently, based on the herringbone-modified helicoidal architecture of mantis shrimp, the bio-inspired composites with various microstructures were reconstructed by 3D magnetic printing. In addition, the influence of microstructure type and parameters of bio-inspired composites on the properties of composites was studied systematically, and the quantitative relationship between microstructure and properties of the composites was established. The results show that the impact resistance and compression resistance of the composites can be significantly improved by the simple internal microstructures design, and the regression model established in this article can be used for accurate prediction of composites properties and the reliability is higher. In a word, this study opens a new route for the design of composites with unusual features.
[en] Lake Qinghai in the Qinghai-Tibet plateau is the largest lake in China. This study firstly reported the geochemistry of Cd in the lake. Water samples were collected from Lake Qinghai (n = 69) and Buha River (n = 12), while sediment (n = 22) and topsoil (n = 45) samples were collected from the lake and around the lake area, respectively. In addition, pore water samples (n = 20) were separated from sediment samples. Water samples were analyzed for pH, K, Na, Ca, Mg, Cl, S, and Cd, while sediment and topsoil samples were analyzed for K, Na, Ca, Mg, Al, Fe, Mn, S, Sc, and Cd. The average concentration of Cd was 0.014 μg L−1 in the water of Lake Qinghai and 0.007 μg L−1 in the water of Buha River. However, the average concentration of Cd was 0.320 μg L−1 in the sediment pore water, much higher than that in the lake water and river water. Cadmium concentration in the lake water might be mainly controlled by salinity, while it in the pore water might be mainly controlled by carbonate minerals. Cadmium concentration in the river water might be controlled by alkalinity and pH. The average concentration of Cd in the sediment was 0.284 mg kg−1. The enrichment of Cd in the lake sediment was significantly higher than that in the topsoil around the lake. Anthropogenic atmospheric deposition of Cd did not led to the increase in dissolved Cd level in the lake water, but led to its enrichment in the lake sediment.
[en] Objective: To investigate the feasibility of reducing CT scanning dose in the process of 125I radioactive seed implantation. Methods: GEMS phantom and 062 M phantom were scanned using GE Lightspeed RT large hole CT with 120 kV, 100 kV and 80 kV separately, and 150-10 mA (20 mA decreased progressively). The scanning dose, CT value and noise of the region of interest were recorded and the image quality was evaluated. Image signal-to-noise ratio (SNR) and contrast to noise ratio (CNR) values were calculated. Results: With the decreasing of tube voltage and current, the SNR values were reduced accorgingly. The values had significant difference with those of standard images except the images acquired with 120 kV, 150-70 mA and 100 kV, 150-90 mA (t = -9.294-3.717, P < 0.05). With the decreasing of the tube voltage and current, the CNR decreased significantly. The image quality was too low to evaluate while CNR lower than 2. The high contrast resolution of the CT images were not affected obviously with the tube voltage and current lowering. Conclusions: In the process of 125I radioactive seed implantation, it is feasible to choose lower tube voltage and tube current(100 kV, 70 mA) to scan the same area repeatedly except for the first scan with standard chest scanning parameters. The patient radiation dose has fallen dramatically. (authors)