The characteristics of multi-substrates (low and high C/N) anaerobic digestion: focus on energy recovery and the succession of methanogenic pathway.

Anaerobic digestion of common rural wastes (human feces (HF), food waste (FW) and lawn grass (LG)) were studied considering the specific methane yield, process parameters and microbial characteristics (mainly microbial community and pathogenic bacteria). The results showed that co-digestion of multiple substrates obtained high digestion performance when the total solid (TS) was 4%. The optimal co-digestion ratio of HF, FW, and LG was 33-56%, 21-38% and 20-40%, respectively. The digestion system containing HF underwent ammonia inhibition, which leads to the succession of the methanogenesis pathway from the acetoclastic pathway to the hydrogenotrophic pathway. Simultaneously, the dominant methanogenic archaea changed from Methanosaeta to Methanobacterium and Methanosarcina. Co-digestion reduced Salmonella's absolute concentration. The recovered energy and nitrogen could meet 52-109 % energy demand of rural community and all nitrogen demand in lawn fertilization, respectively. The main rural organic wastes could be recycled by anaerobic digestion, considering the flexibility of substrate ratio.

Biomechanical Evaluation of Seven Fixation Methods for Sagittal Split Ramus Osteotomy with Four Advancement Levels by Finite Element Analysis.

Background: Mandibular sagittal split ramus osteotomy (SSRO) is a routine surgery to correct mandibular deformities, such as mandibular retrusion, protrusion, deficiency, and asymmetry. However, nonunion/malunion of the fragments and relapse caused by fixation failure after SSRO are major concerns. Rigid fixation to maintain postosteotomy segmental stabilization is critical for success. Additionally, understanding the biomechanical characteristics of different fixation methods in SSRO with large advancements is extremely important for clinical guidance. Therefore, the aim of the present study was to evaluate the biomechanical characteristics of different SSRO methods by finite element analysis. Methods: SSRO finite element models with 5-, 10-, 15-, and 20-mm advancements were developed. Seven fixation methods, namely, two types of bicortical screws, single miniplate, dual miniplates, grid plate, dual L-shaped plates, and hybrid fixation, were positioned into the SSRO models. Molar and incisal biomechanical loads were applied to all models to simulate bite forces. We then investigated the immediate postoperative stability from four aspects, namely, the stability of the distal osteotomy segment, osteotomy regional stability, stress distribution on the mandible, and implant stress performance. Results: The stability of the distal osteotomy segment and osteotomy region decreased when the advancement increased. All seven fixation methods displayed favorable biomechanical stability under minor advancement (5 mm). With large advancements, bicortical screws, dual miniplates, and grid plates provided better stability. The von Mises stress was concentrated around the screws close to the osteotomy region for the proximal segment for all fixation methods, and the von Mises stress on implants increased with larger advancements. With small advancements, five fixation methods endured tolerable maximum stresses of <880 MPa. A single miniplate and dual L-shaped plates generally suffered high stresses using larger advancements. The biomechanical characteristics were similar under molar and incisal loads. Conclusions: The current study investigated the biomechanical properties of seven fixation devices after SSRO under molar and incisal loads. Generally, bicortical screws, grid plates, and dual miniplates provided better biomechanical stability using finite element analysis.

Comparative study on the characteristics and environmental risk of potentially toxic elements in biochar obtained via pyrolysis of swine manure at lab and pilot scales.

Pyrolysis is considered as a promising method to immobilize potentially toxic elements (PTEs) in animal manures. However, comparative study on characteristics and environmental risk of PTEs in biochar obtained by pyrolysis of animal manure at different reactors are lacking. In this study, swine manure was pyrolyzed at 300-600 °C in a lab-scale or pilot-scale reactor with the aim to investigate their effects on characteristics and environmental risk of As, Cd, Cu, Ni, Pb, and Zn in swine manure biochar. Results showed that biochars produced from pilot scale had lower pH and carbon (C) content but higher oxygen (O) content than those from lab scale. Biochars from pilot scale had higher total PTEs (except Cd) concentrations and releasable PTEs (except Pb) but lower CaCl2-extractable PTEs and phytotoxicity germination index (GI) to radish seedings than those from lab scale. Chemical speciation analysis indicated that PTEs in biochar produced from pilot-scale fast pyrolysis at 400 °C had higher percentage of more stable fraction (F5 fraction) and lower potential ecological risk index (RI) than those from lab-scale slow pyrolysis. These findings demonstrated that bioavailability and potential ecological risk of PTE in swine manure biochar were greatly decrease in the pilot-scale pyrolysis reactor and the optimum temperature was 400 °C considering the lowest potential ecological risk index.

Combined effects of arbuscular mycorrhizae fungus and composted pig manure on the growth of ryegrass and uptake of Cd and Zn in the soil from an e-waste recycling site.

Little attention has been paid to the combined effects of arbuscular mycorrhizae (AM) fungus and composted manure on heavy metal bioavailability and its uptake by plants grown in heavy metal-contaminated soils from electronic-waste (e-waste) recycling sites. A greenhouse pot experiment was conducted to investigate the effects of AM fungus, composted pig manure (CM) and AM fungus + CM (ACM) on the growth of ryegrass and uptake of Cd and Zn in the soil collected from an e-waste recycling site. The calcium chloride (CaCl2) and Tessier sequential extraction procedure were adopted to evaluate the bioavailability and chemical speciation of Cd and Zn in the soil. Results showed that the application of CM and ACM significantly increased the pH but decreased the CaCl2-extractable Cd and Zn concentrations in the rhizosphere and bulk soils. ACM treatment significantly shifted Cd from exchangeable fraction to other more stable fractions, and transformed the exchangeable Zn fraction to the carbonate-bound and reducible iron and manganese-bound fractions. Furthermore, the application of ACM can enhance the growth of plant shoots, and decrease the uptake of Cd and Zn in the ryegrass plants. This work suggests that AM fungus in combination with CM amendment may be a potential method for not only remediation of soil Cd and Zn pollution, but also reduction of Cd and Zn uptake by ryegrass grown in the soil from e-waste recycling sites.

Virtual Reality and Three-Dimensional Printed Models Improve the Morphological Understanding in Learning Mandibular Sagittal Split Ramus Osteotomy: A Randomized Controlled Study.

Background: The mandibular sagittal split ramus osteotomy (SSRO) is a routine operation performed to correct mandibular deformity including mandibular retrusion, protrusion, deficiency, and asymmetry. The SSRO remains a challenging procedure for junior surgeons due to a lack of adequate morphological knowledge necessary for success in clinical practice. Virtual reality (VR) and three-dimensional printed (3DP) models have been widely applied in anatomy education. The present randomized, controlled study was performed to evaluate the effect of traditional educational instruments, VR models, and 3DP models on junior surgeons learning the morphological information required to perform SSRO. Methods: Eighty-one participants were randomly assigned to three learning groups: Control, VR, and 3DP. Objective and subjective tests were used to evaluate the learning effectiveness of each learning instrument. In the objective test, participants were asked to identify 10 anatomical landmarks on normal and deformed models, draw the osteotomy line, and determine the description of SSRO. In the subjective test, participants were asked to provide feedback regarding their subjective feelings about the learning instrument used in their group. Results: The objective test results showed that the VR and 3DP groups achieved better accuracy in drawing the osteotomy line (p = 0.027) and determining the description of SSRO (p = 0.023) than the Control group. However, there was no significant difference among the three groups regarding the identification of anatomical landmarks. The VR and 3DP groups gave satisfactory subjective feedback about the usefulness in learning, good presentation, and enjoyment. The Control and 3DP groups reported positive feelings about ease of use. Conclusion: The current findings suggest that VR and 3DP models were effective instruments that assisted in the morphological understanding of SSRO-related anatomical structures. Furthermore, 3DP models may be a promising supplementary instrument to bridge the gap between conventional learning and clinical practice.