The prolonged effect of film mulch and P application on lucerne forage yield in a semiarid environment.

Introduction: Limited water and soil phosphorus (P) availability often hampers lucerne productivity in semiarid regions. Plastic film mulch and P application typically enhance young lucerne (2-3 years) productivity by increasing soil water use and P availability. However, the prolonged impact of film mulch and P application on lucerne productivity as the stand ages remains unclear. Methods: This study conducted a 9-year field experiment on the semiarid Loess Plateau to investigate how film mulch and P application affect lucerne forage yield, soil water content, and soil fertility. The field experiment used a split-plot design with randomized blocks, in which the whole plots were with (M1) and without plastic film mulch (M0), and the split plots were four P rates (0 (P0), 9.7 (P1), 19.2 (P2), and 28.8 (P3) kg P ha-1). Results and discussion: The M1 treatment produced significantly higher lucerne forage yields than the M0 treatment during the first five years, but the yield-increasing effect of film mulch gradually diminished over time, with no effect in Years 6-8, and lower yields than the M0 treatment in Year 9. Phosphorus fertilization significantly increased forage yield after Year 3 in the M0 treatment, but only in Years 3-5 in the M1 treatment. In Years 2-5, film mulch significantly increased soil organic carbon, total nitrogen (N), inorganic N, and microbial biomass carbon in P0, P1, and P2 but not in P3. However, in Years 7-9, film mulch significantly decreased soil available potassium (K), organic carbon mineralization, lucerne density, and shoot K concentration, but did not reduce soil N and P availability at any level P of application. Moreover, plastic film mulch significantly increased the soil water content at 0-300 cm deep from Year 7 onwards. In conclusion, film mulch ceased to enhance lucerne production beyond year 6, which could not be attributed to soil water content, N or P availability but was partially associated with reduced soil K availability. Consequently, future research should focus on soil K availability, and K addition should be considered after five years in lucerne pastures mulched with plastic film in semiarid areas.

Effect of loading history on material properties of human heel pad: an in-vivo pilot investigation during gait.

BACKGROUND: This study was aimed to develop a novel dynamic measurement technique for testing the material properties and investigating the effect of continuous compression load on the structural and mechanical properties of human heel pad during actual gait. METHODS: The dual fluoroscopic imaging system (DFIS) and dynamic foot-ground contact pressure-test plate were used for measuring the material properties, including primary thickness, peak strain, peak stress, elastic modulus, viscous modulus and energy dissipation rate (EDR), both at time zero and following continuous loading. Ten healthy pilot subjects, aged from 23 to 72 (average: 46.5 ± 17.6), were enrolled. A "three-step gait cycle" is performed for all subjects, with the second step striking at a marked position on the force plate with the heel to maintain the location of the tested foot to be in the view of fluoroscopes. The subjects were measured at both relaxed (time-zero group) and fatigue (continuous-loading group) statuses, and the left and right heels were measured using the identical procedures. RESULTS: The peak strain, peak stress, elastic modulus, and EDR are similar before and after continuous load, while the viscous modulus was significantly decreased (median: 43.9 vs. 20.37 kPa•s; p < 0.001) as well as primary thicknesses (median: 15.99 vs. 15.72 mm; p < 0.001). Age is demonstrated to be moderately correlated with the primary thicknesses both at time zero (R = -0.507) and following continuous load (R = -0.607). The peak stress was significantly correlated with the elastic modulus before (R = 0.741) and after continuous load (R = 0.802). The peak strain was correlated with the elastic modulus before (R = -0.765) and after continuous load (R = -0.801). The correlations between the viscous modulus and peak stress/ peak strain are similar to above(R = 0.643, 0.577, - 0.586 and - 0.717 respectively). The viscous modulus is positively correlated with the elastic modulus before (R = 0.821) and after continuous load (R = 0.784). CONCLUSIONS: By using dynamic fluoroscopy combined with the plantar pressure plate, the in vivo viscoelastic properties and other data of the heel pad in the actual gait can be obtained. Age was negatively correlated with the primary thickness of heel pad and peak strain, and was positively correlated with viscous modulus. Repetitive loading could decrease the primary thickness of heel pad and viscous modulus.

Research of a new metal chelating carrier preparation and papain immobilization.

A new type of magnetic metal chelating carrier (PCMM-IDA-Cu2+) was prepared for the immobilization of papain, using chitosan as raw material, nano Fe3O4 as magnetic material, SiO2 as porogen, iminodiacetic acid (IDA) as a chelating ligand, and binding with transition metal ion (Cu2+). The resulting products were well characterized by optical microscopy, scanning electron microscopy (SEM), vibrating sample magnetometer (VSM), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). The BBD (Box-Behnken Design) of RSM (Response Surface Methodology) was applied to analyze the optimum enzyme immobilization conditions. The results showed that the enzyme immobilization capacity was 94.18mg/g of PCMM-IDA-Cu2+, with 7.976U/mg of relative immobilized enzyme activity under the optimum conditions (pH6.73, 1.56mg enzyme/15.0mg carrier, 30.9°C), and the recovery of enzyme activity was reached 87.21%. Compared with the free papain, the immobilized papain displayed enhanced enzyme activity, superior enzymatic properties, good operational stability and reusability. It is worth mentioning that the novel carriers exhibited selectively biological adsorption capacity, and this technique is an alternative method for the immobilization of enzyme, making the process more efficient and economic.