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Regeneration has been considered as an ideal way for the post-treatment of waste FCC catalyst (ECat). In this work, the degeneration mechanism of ECat was firstly researched and attributed to the increasing of strong acid sites accessibility of ECat in contrast with fresh FCC catalyst by adsorption FTIR. Based on the proposed degeneration mechanism, ECat was successfully regenerated through suitable weakening for strong acid sites by boron modification. Characterization and evaluation results suggested that, the strong acid sites of regenerated ECat (R-ECat) were apparently decreased by boron modification which had significantly improve the heavy oil catalytic cracking performance of R-ECat. Because of the excellent performance, R-ECat in this work could successfully substitute for partial fresh FCC catalyst in FCC unit, which would provide a practicable way for the reutilization of ECat. [ABSTRACT FROM AUTHOR]

Conventional mechanical machining of a composite material comprising an aluminum matrix reinforced with a high volume fraction of SiC particles (hereinafter referred to as an SiCp/Al composite) faces problems such as rapid tool wear, high specific cutting force, and poor surface integrity. Instead, a promising method for solving these problems is laser-induced oxidation-assisted milling (LOAM): under laser irradiation, the local workpiece material reacts with oxygen, thus forming loose and porous oxides that are easily removed. In the present work, the oxidation mechanism of SiCp/Al irradiated by a nanosecond pulsed laser is studied to better understand the laser-induced oxidation behavior and control the characteristics of the oxides, with laser irradiation experiments performed on a 65% SiCp/Al composite with various laser parameters and auxiliary gases (oxygen, nitrogen, and argon). With increasing laser pulse energy density, both the ablated groove depth and the width of the heat-affected zone increase. When oxygen is used as the auxiliary gas, an oxide layer composed of SiO2 and Al2O3 forms, and CO2 is produced and escapes from the material, thereby forming pores in the oxides. However, when nitrogen or argon is used as the auxiliary gas, a recast layer is produced that is relatively difficult to remove. Under laser irradiation, the sputtered material reacts with oxygen to form oxides on both sides of the ablated groove, and as the laser scanning path advances, the produced oxides accumulate to form an oxide layer. LOAM and conventional milling are compared using the same milling parameters, and LOAM is found to be better for reduced milling force and tool wear and improved machined surface quality. Highlights: •The governing laws and functional mechanism for the laser-induced oxidation of an SiCp/Al composite are investigated. •Laser-induced oxidation-assisted milling is effective for reduced milling force, tool wear, and machining damage. [ABSTRACT FROM AUTHOR]

Objective: The present study sought to establish an animal model to study the feasibility and safety of rapid retraction of maxillary anterior teeth en masse aided by alveolar surgery in order to reduce orthodontic treatment time., Method: Extraction of the maxillary canine and alveolar surgery were performed on twelve adult beagle dogs. After that, the custom-made tooth-borne distraction devices were placed on beagles' teeth. Nine of the dogs were applied compression at 0.5 mm/d for 12 days continuously. The other three received no force as the control group. The animals were killed in 1, 14, and 28 days after the end of the application of compression., Results: The tissue responses were assessed by craniometric measurement as well as histological examination. Gross alterations were evident in the experimental group, characterized by anterior teeth crossbite. The average total movements of incisors within 12 days were 4.63±0.10 mm and the average anchorage losses were 1.25±0.12 mm. Considerable root resorption extending into the dentine could be observed 1 and 14 days after the compression. But after consolidation of 28 days, there were regenerated cementum on the dentine. There was no apparent change in the control group. No obvious tooth loosening, gingival necrosis, pulp degeneration, or other adverse complications appeared in any of the dogs., Conclusions: This is the first experimental study for testing the technique of rapid anterior teeth retraction en masse aided by modified alveolar surgery. Despite a preliminary animal model study, the current findings pave the way for the potential clinical application that can accelerate orthodontic tooth movement without many adverse complications., Clinical Relevance: It may become a novel method to shorten the clinical orthodontic treatment time in the future.

Objective: To investigate the correlative factors influencing the stability of orthodontic treatment out of retention., Methods: Pre-treatment, post-treatment and 2 approximately 8 years out of retention study models of 74 cases with malocclusion were assessed by the PAR (Peer Assessment Rating) index., Results: (1) Out of retention, the relapse rate was 13.01% in weighted PAR total scores and the relapse rate was 6.38%, 15.56%, 28.86%, 22.41% in alignment, overjet, overbite and transverse buccal occlusion respectively. (2) The rate of great improvement was decreased from 77.03% after treatment to 64.86% out of retention. The PAR score increased in 53 cases (71.62%), unchanged in 6 cases (8.11%) and reduced in 15 cases (20.27%) out of retention. (3) The weighted total scores in the Begg appliance were higher than that in Edgewise out of retention (P < 0.05). (4) The alignment and PAR total scores out of retention were higher in class II malocclusion than in class I malocclusion (P < 0.05). (5) The weighted PAR total scores post-retention were higher in unilateral extraction than in other groups (P < 0.01)., Conclusions: (1) There was a trend that teeth relapsed to original position out of retention. The relapse rate was greater in alignment, overjet, overbite and transverse buccal occlusion. (2) The stability out of retention was not related to patient's age and sex, but was related to the types of appliance, malocclusion and extraction.