Replacing traditional nursery soil with spent mushroom substrate improves rice seedling quality and soil substrate properties.

Currently, large quantities of spent mushroom substrate (SMS) are produced annually. Because SMS has high water retention and nutrients, it has great potential to replace traditional topsoil for raising seedlings in agricultural production. However, few studies have examined the effects of substituting SMS for paddy soil on rice seedling growth and soil nutrients. SMS was mixed with rice soil in different proportions (20%, 50%, and 80%), and chemical fertilizer, organic fertilizer, and peat substrate were added in addition to equivalent nitrogen as a traditional seedling nursery method for comparison. Compared to traditional paddy soil (CK), the seedling qualities of the three SMS ratio treatments were all higher. Adding SMS at different ratios promoted rice seedling root growth, elevated the soluble protein concentration, and amplified the superoxide dismutase (SOD) enzymatic action in rice seedlings. Total porosity and aeration porosity of the soil increased by 17.40% and 32.90%, respectively. Soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) increased by 21.26-118.48%, 50.44-71.68%, and 23.08-80.17%, respectively. Besides, the relative abundance of Bacillus, Bacteroidetes, and other bacteria as well as the abundance of Ascomycota were all significantly increased. Adding 50% SMS increased the abundance of Pseudomonas by 8.42 times. The seedling quality of the 50% SMS treatment was even higher than chemical fertilizer and organic fertilizer treatments, only second to the peat substrate treatment. In summary, partial substitution of paddy soil with SMS can ameliorate substrate properties, improve seedling quality, and increase microbial diversity, indicating the suitability of SMS as a replacement for rice soil in seedling substrates. The 50% SMS ratio is the best. This study provides a basis for SMS to replace traditional rice soil in seedling cultivation.

Short-pulse-induced solute migration in the C49H43ClO6 + 1,2 dichloroethane solution.

Using the Z-scan technique with 532 nm 19 ps laser pulses separated by two time intervals τp-p's (0.1 s and 1.0 s) sandwiching the mass diffusion time constant of the C49H43ClO6 + 1,2 dichloroethane solution, we investigate short-pulse-induced solute migration in the sample by measuring its transmittance change with τp-p variation. Preparing the sample at two concentrations, we find that τp-p reduction, from 1.0 s to 0.1 s, increases its transmittance when input pulse energy ε1 exceeds a threshold εT, which is lower for the dilute solution than the concentrated one. At two ε1's above εT for the dilute solution, τp-p-reduction-induced transmittance increase in the dilute solution, as compared to that in the concentrated solution, is more at the lower ε1 and less at the higher ε1. This differs from continuous-wave-driven thermal diffusion which always causes a larger transmittance increase in the concentrated solution by inducing a larger temperature gradient. From this study, we predict that solute migration induced by short pulses at 1064 nm is one of the undesired heating effects occurring when this solution is used to simultaneously Q-switch and mode-lock Nd:YAG lasers.

Thermal lensing effect of CS2 studied with femtosecond laser pulses.

By chopping 820 nm 18 femtosecond (fs)-laser pulses, continuously generated by a self-mode locked Ti:Al2O3 laser at 82 MHz, into trains with both train-width and train-to-train separation considerably longer than the thermal diffusivity time constant τth of CS2, we conducted Z-scan measurements on it at various times relative to the leading pulse of each train (T's). As a result, we observed negative nonlinear refraction strengthening with T within τth and gradually stabilizing with T exceeding τth. We quantitatively explain the experimental results in terms of the thermal lensing effect. In particular, we attribute the heat generation to non-radiative relaxation of libration excited by individual 18 fs-pulses via stimulated Raman scattering. In contrast to the commonly held view of multi-photon excitation, we propose and verify a new heat-generating mechanism for the thermal lensing effect in CS2.

Shrinkage of picosecond laser beam by plasma reflection in super-resolution near-field structure of SiN/Sb/SiN thin film.

The transmittive and reflective Z-scan technique is used with a 10 Hz, frequency doubled, Q-switched, and mode-locked Nd:YAG laser to verify that the reflectivity of the super-resolution near-field structure of an SiN/Sb/SiN thin film increases as incident intensity decreases. This intensity-dependent reflection, called nonlinear reflection, reflects a TEM(00) mode laser beam more strongly at its periphery than at its center and so shrinks the transmitted laser beam. The observed nonlinear reflection is attributed to laser-induced change of carrier densities in Sb, to justify quantitatively the experimental results.

Kramers-Kronig relation between nonlinear absorption and refraction of C(60) and C(70).

Using the Z-scan technique with 532 nm 16 picosecond laser pulses, we observe reverse saturable absorption and positive nonlinear refraction of toluene solutions of both C(60) and C(70). By deducting the positive Kerr nonlinear refraction of the solvent, we notice that the solute molecules contribute to nonlinear refraction of opposite signs: positive for C(60) and negative for C(70). Attributing nonlinear absorption and refraction of both solutes to cascading one-photon excitations, we illustrate that they satisfy the Kramers-Kronig relation. Accordingly, we attest the signs and magnitudes of nonlinear refraction for both solutes at 532 nm by Kramers-Kronig transform of the corresponding nonlinear absorption spectra.

Solute migration caused by excited state absorptions.

Using the Z-scan technique, we find that migration of chloroaluminum phthalocyanine in liquid ethanol can be induced by the absorption of a 19 ps laser pulse with energy exceeding a threshold but not by that of a 2.8 ns pulse depositing more energy at the solute molecules. Considering each solute molecule as an oscillator confined within a potential well, we explain, in accordance with the five-energy-band model, that solute molecules excited by a 19 ps pulse retain more translational excess energy to overcome the potential well barrier compared with those excited by a 2.8 ns pulse of equal energy. Therefore, they are more likely to migrate out of the laser beam center, weakening the solution's absorption that we detect in the Z-scan measurements. Furthermore, we theoretically infer that the 19 ps pulse-induced solute migration tends to be nonquasistatic and experimentally verify that it cannot be attributed to the Soret effect, a quasistatic process.