Comparison of the efficacy of different biodegradable membranes in guided bone/tissue regeneration: a systematic review and network meta-analysis.

Guided bone/tissue regeneration (GBR/GTR) is commonly used in dental treatment. The desired bone/tissue regeneration is achieved by placing a barrier membrane over the defect to avoid the downward growth of faster-growing connective and epithelial tissue into the defect. This review aimed to evaluate osteogenic properties, degradation characteristics, and postoperative complications of eight biodegradable membranes in animal experiments, including non-crosslinked collagen membrane (NCCM), crosslinked collagen membrane (CCM), silk membrane (SM), polylactic-co-glycolic acid, polylactic acid, polyethylene glycol hydrogel, polycaprolactone (PCL), and magnesium alloys. Seven electronic databases (PubMed, Embase, Web of Science, Cochrane Library, Science Direct, Wiley, Scopus and Google Scholar) were screened. Study selection, data extraction and quality assessment were made in duplicate. The SYRCLE assessment tool, CERQual (Confidence in the Evidence from Reviews of Qualitative Research) tool and GRADE tool were used to grade the risk of bias and level of evidence. A total of 2512 articles were found in the electronic database. Finally, 94 articles were selected, of which 53 were meta-analyzed. Surface under the cumulative ranking curve showed the best results for new bone formation in the magnesium barrier membrane group, followed by SM, PCL, NCCM, and CCM. Qualitative analysis showed good biocompatibility for natural polymer membranes and a longer degradation time for synthetic polymer membranes. In addition, 34 studies all showed high bias risks, while other studies had unclear bias risks. Natural polymer membranes were more effective for bone regeneration and magnesium alloys were proved to be promising barrier materials that warrant future research.

Improvement of the trace metal composition of medium for nitrite-dependent anaerobic methane oxidation bacteria: Iron (II) and copper (II) make a difference.

Nitrite-dependent anaerobic methane oxidation (n-damo) is a potential bioprocess for treating nitrogen-containing wastewater. This process uses methane, an inexpensive and nontoxic end-product of anaerobic digestion, as an external electron donor. However, the low turnover rate and slow growth rate of n-damo functional bacteria limit the practical application of this process. In the present study, the short- and long-term effects of variations in trace metal concentrations on n-damo bacteria were investigated, and the concentrations of trace metal elements of medium were improved. The results were subsequently verified by a group of long-term inoculations (90 days) and were applied in a sequencing batch reactor (SBR) (84 days). The results indicated that iron (Fe(II)) and copper (Cu(II)) (20 and 10 µmol L(-1), respectively) significantly stimulated the activity and the growth of n-damo bacteria, whereas other trace metal elements, including zinc (Zn), molybdenum (Mo), cobalt (Co), manganese (Mn), and nickel (Ni), had no significant effect on n-damo bacteria in the tested concentration ranges. Interestingly, fluorescence in situ hybridization (FISH) showed that a large number of dense, large aggregates (10-50 µm) of n-damo bacteria were formed by cell adhesion in the SBR reactor after using the improved medium, and to our knowledge this is the first discovery of large aggregates of n-damo bacteria.

Carrier phase shifted SPWM based on current sourced multi-modular converter for active power filter.

A novel current-source active power filter (APF) based on multi-modular converter with carrier phase-shifted SPWM (CPS-SPWM) technique is proposed. With this technique, the effect of equivalent high switching frequency converter is obtained with low switching frequency converter. It is very promising in current-source APF that adopt superconducting magnetic energy storage component.