Selective Laser Melting of Al-Based Matrix Composites with Al2O3 Reinforcement: Features and Advantages

Aluminum matrix composites (AMC) are of great interest and importance as high-performance materials with enhanced mechanical properties. Al₂O₃ is a commonly used reinforcement in AMCs fabricated by means of various technological methods, including casting and sintering. Selective laser melting (SLM) is a suitable modern method of the fabrication of net-shape fully dense parts from AMC with alumina. The main results, achievements, and difficulties of SLM applied to AMCs with alumina are discussed in this review and compared with conventional methods. It was shown that the initial powder preparation, namely the particle size distribution, sphericity, and thorough mixing, affected the final microstructure and properties of SLMed materials drastically. The distribution of reinforcing particles tends to consolidate the near-melting pool-edges process because of pushing by the liquid–solid interface during the solidification process that is a common problem of various fabrication methods. The achievement of an homogeneous distribution was shown to be possible through both the thorough mixing of the initial powders and the precise optimization of SLM parameters. The strength of the AMCs fabricated by the SLM method was relatively low compared with materials produced by conventional methods, while for superior relative densities of more than 99%, hardness and tribological properties were obtained, making SLM a promising method for the Al-based matrix composites with Al₂O₃.     

预防性静滴钾离子、镁离子对急性心梗后并发室性心律失常的预防作用

目的 探究预防性静滴钾离子、镁离子对急性心梗后并发室性心律失常的预防作用。方法 选择2015年1月-2018年1月于西宁市第一人民医院进行治疗的78例急性心肌梗死患者为研究对象，按照随机数字表法将其均分为观察组与对照组，每组各39例患者。对照组患者进行常规急性心梗治疗，观察组患者在对照组基础上加用门冬氨酸钾镁进行治疗，对比两组治疗有效率，对比两组治疗前后血液流变学指标纤维蛋白原（Fib）、凝血酶原时间（PT）、血小板计数（Plt），对比两组治疗期间不良反应发生率及心律失常发生率。结果 治疗后，观察组患者治疗有效率为87.18%，对照组为76.92%，两组对比差异具有统计学意义（P<0.05）。治疗前两组患者Fib、PT以及Plt水平对比差异不具有统计学意义；治疗后，两组患者Plt及Fib水平低于治疗前，PT水平高于治疗前，差异有统计学意义（P<0.05）；治疗后观察组患者Plt及Fib水平低于对照组，PT水平高于对照组（P<0.05）。观察组患者不良反应发生率稍高于对照组，但对比差异不具有统计学意义。观察组心律失常发生率为7.69%，对照组为15.38%，两组对比差异具有统计学意义（P<0.05）。结论 预防性静滴钾离子与镁离子能够显著降低急性心梗患者心律失常发生率，同时有利于提高治疗有效率，改善其血流变指标，且安全性较高。     

Innovative Polymers for Next‐Generation Batteries

Lithium‐ion batteries are part of modern life, being present in daily‐used objects such as mobile phones, tablets, computers, watches, sport accessories, electric scooters, and cars. The next‐generation batteries require the development of innovative polymers that help to improve their performance in terms of power density, cyclability, raw materials' availability, low weight, printability, flexibility, sustainability, or security. This article highlights recent developments in the area of redox‐active, electronic/ionic conducting polymers. This includes the development of innovative binders for electrodes, polymer electrolytes, and redox polymers. All these new polymer developments are leading to new battery technologies such as metal–polymer batteries, organic batteries, polymer–air, and redox–flow batteries, which are expected to complement the current lithium‐ion technologies in the future.     

Objective evaluation of abutment tooth preparation for preformed metal crowns for primary molars in Japanese preclinical training

Evaluation of abutment tooth shape for preformed metal crowns for primary teeth in preclinical training depends on the subjective opinion of the instructor providing the training. Thus, the student's grade will likely vary according to teacher grading. In this study, we explored the potential for objective evaluation by comparing evaluations performed by teaching personnel (teacher grading) of abutment teeth for preformed metal crowns for primary teeth prepared by students at a dental school with evaluation by a three-dimensional (3D) laser morphometric system (system grading). The subjects of the evaluations were 139 abutment teeth for preformed metal crowns for primary teeth that had been prepared by fourth-year students at Asahi University School of Dentistry during preclinical pediatric dentistry training. A tooth prepared by a teacher following instruction criteria was used as the reference tooth, and system grade points were calculated from deductions made for insufficient and excessive cutting. Teacher grade points varied among teachers. We found that teachers prioritized contours of the margin, buccal and lingual sides, and adjacent surfaces in their evaluations. System grading showed that most students carried out insufficient cutting. The mean (SD) teacher and system grade points were 57.7 (9.7) and 75.7 (4.7), respectively, and these grade points were positively correlated (r = 0.500). System grading provides a simple 3D visual assessment of insufficient and excessive cutting that can be used for instructing students.     

All-ceramic restorations: A review of the literature

ObjectivesCeramics can simulate the visual character of the tooth substance successfully and are biocompatible materials. However, a wide range of ceramic materials and systems on the market are available for use in dentistry. Therefore, it is the aim of this article to provide an overview of dental ceramics, their classifications, methods of construction, and clinically relevant aspects that enable the reader to select the most appropriate ceramic for a particular clinical situation.Material and methodsThe PubMed (MEDLINE) search engine was used to gather the most recent information on dental ceramics. The search was restricted to a ten-year period (January 1, 2010–December 31, 2019) and only English-language studies. A Boolean search of the PubMed data set was implemented to combine a range of keywords: (ceramics OR all-ceramics OR dental porcelain OR polycrystalline OR porcelain fused to metal OR ceramometal OR procera OR e max OR zirconia OR In-ceram OR Inlays OR Onlays OR Overlays OR Endocrown) AND (survival rate OR success rate OR clinical outcomes OR classification) AND (humans). Studies were also obtained by manual searches and from Google Scholar.ResultsBy using this process, 2173 articles and studies were obtained. More studies were also obtained by manual searches and from Google Scholar. The most relevant published studies were chosen and used in the current review.ConclusionAll-ceramic restoration use has increased in recent years. This increase has been attributed to patients’ demand for good aesthetics and an improvement in the materials’ mechanical and aesthetic properties as well as to required minimally invasive tooth preparation and the methods of fabrication. The success of ceramic restorations depends on several factors, such as selection of material, restoration design, occlusion, and cementation media.     

基于UPLC-LTQ-Orbitrap-MS分析刺果番荔枝叶的化学成分

目的利用UPLC-LTQ-Orbitrap-MS技术对刺果番荔枝叶的化学成分进行定性分析。方法采用Waters Acquity UPLC HSS T 3色谱柱(2.1 mm×100 mm,1.8μm),流动相为0.1%甲酸水(A)和乙腈(B)梯度洗脱,流速为0.3 mL/min,进样量2μL,在电喷雾正负离子模式下采集数据。经Reaxys数据库检索番荔枝属类化合物信息,通过质谱信息比对各化合物的m/z值、保留时间、质谱特征碎片等,并结合文献数据对鉴定的化合物进行验证。结果根据各化合物的特征裂解规律,从刺果番荔枝叶中共鉴定出45个化合物,包括16个生物碱类,14个番荔枝内酯类,7个黄酮类和8个其他类化合物,其中以番荔枝内酯类和生物碱类成分居多,与文献报道番荔枝内酯与生物碱类化合物是发挥抗癌的主要活性成分一致。结论利用UPLC-LTQ-Orbitrap-MS技术对刺果番荔枝叶中的化学成分进行了快速、准确的定性分析,为刺果番荔枝叶的提取分离与药效物质基础的研究提供依据。