In this study, we report for the first time a novel silk fibroin (SF) nanofibrous films with robust mechanical properties that was fabricated by directly dissolving silk in CaCl2-formic acid solution. CaCl2-FA dissolved silk rapidly at room temperature, and more importantly, it disintegrated silk into nanofibrils instead of separate molecules. The morphology of nanofibrils crucially depended on CaCl2 concentrations, which resulted in different aggregation nanostructure in SF films. The SF film after drawing had maximum elastic modulus, ultimate tensile strength, and strain at break reaching 4 GPa, 106 MPa, and 29%, respectively, in dry state and 206 MPa, 28 MPa, and 188%, respectively, in wet state. Moreover, multiple yielding phenomena and substantially strain-hardening behavior was also observed in the stretched films, indicating the important role played by preparation method in regulating the mechanical properties of SF films. These exceptional and unique mechanical properties were suggested to be caused by preserving silk nanofibril during dissolution and stretching to align these nanofibrils. Furthermore, the SF films exhibit excellent biocompatibility, supporting marrow stromal cells adhesion and proliferation. The film preparation was facile, and the resulting SF films manifested enhanced mechanical properties, unique nanofibrous structures, and good biocompability.
Burn wounds are severely stressful events that can have a significant impact on the mental health of patients. However, the impact of burns on individuals with different personality traits can be different. The present study aimed to investigate the impact of dispositional optimism on the subjective well-being of burn patients, and mainly focused on the confirmation of the mediator role of psychological resilience. 410 burn patients from five general hospitals in Xi'an accomplished the revised Life Orientation Test, Connor-Davidson Resilience Scale, and Subjective Well-Being (SWB) scale. The results revealed that both dispositional optimism and psychological resilience were significantly correlated with SWB. Structural equation modelling indicated that psychological resilience partially mediated the relationship between dispositional optimism and SWB. The current findings extended prior reports and shed some light on how dispositional optimism influenced SWB. Limitations of the study were considered and suggestions for future studies were also discussed.
The objective of this experiment was to determine the effects of fiber level from alfalfa meal and collection period on intestinal nutrient and energy flow, and hindgut fermentation in growing pigs. Twenty-four pigs (initial BW = 21.4 ± 1.5 kg) were prepared by T-cannula insertion into the distal ileum and allotted to 4 treatments. The pigs were provided a corn-soybean meal control diet or a diet in which corn and soybean meal were partly replaced by 5%, 10%, or 20% alfalfa meal to give the graded levels of dietary fiber during two 10-d collection periods. The BW of pigs at the start of periods 1 and 2 were 32.2 ± 2.4 and 37.7 ± 4.2 kg, respectively. The final BW at the end of period 2 was 46.8 ± 4.0 kg. The apparent ileal digestibility (AID) and apparent total tract digestibility (ATTD) of nutrients and energy were measured. The VFA concentration was also determined in the ileal and fecal samples. Nutrient digestibility was not affected by inclusion of 5% alfalfa meal in the diet. The AID, ATTD, and hindgut fermentation of DM, carbohydrates (CHO), and GE decreased (linear, P < 0.05) as the level of alfalfa meal in the diet increased. The intestinal flow of DM, CHO, ADF, and GE increased (linear, P < 0.05) by increasing the level of dietary alfalfa. The pH in ileal digesta and concentration of acetate, propionate, and total VFA in the feces increased (linear, P < 0.01) as the level of alfalfa meal in the diet increased. From experiment period 1 to 2, ATTD and hindgut fermentation of CHO decreased (P < 0.01), whereas concentrations of propionate, valerate, and total VFA in ileal samples increased (P < 0.05). A multiple linear regression analysis, taking into account both soluble dietary fiber and insoluble dietary fiber intake, explained the variation (P < 0.01) in total tract flow of NDF (93%), ADF (84%), GE (73%), DM (71%), and CHO (62%). In conclusion, the diet containing 5% of alfalfa meal did not affect nutrient and energy digestion. Intestinal flow of CHO decreased during the 10-d collection period. The VFA concentration increased with fiber level and 10-d exposure to the experimental diets. Soluble and insoluble fibers from alfalfa meal have differential roles in nutrient digestion, which may help explain the variation observed in the intestinal flow of nutrients.
The variability of wind power generation increases the uncertainties in modern power system, affecting its physical operation. Owning to fast response capability, battery energy storage system (BESS) has offered an answer to this problem. In this paper, a novel sizing methodology is proposed for BESS planning, which strikes a balance between economic cost and wind smoothing performance. Firstly, a novel variable-interval reference signal optimization approach and a fuzzy control-based charging/discharging scheme are presented to smooth wind power, maintaining the state-of-health of BESS in the meanwhile. And then, power and energy capacities are determined according to a statistical model of charge/discharge power and the economic cost model respectively. Finally, case studies are carried out to demonstrate the performance of the proposed method. The impact from wind power forecasting error during real-time operation is also analyzed.
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