A matheuristic approach for the minimum broadcast time problem using a biased random-key genetic algorithm

The Minimum Broadcast Time (MBT) is a well-known data dissemination problem whose goal is to find a broadcast scheme that minimizes the number of steps needed to execute the broadcast operation. The problem has many applications in distributed systems and, in particular, the Industry 4.0 domain. Because Industry 4.0 applications rely primarily on the use of large-scale machine to machine communications, they need data dissemination techniques that combine high reliability with low communication latency. This work proposes a Biased Random-Key Genetic Algorithm and a matheuristic for the MBT. We carry out experiments with our algorithms on instances commonly used in the literature (hypercube, shuffle exchange, cube-connected cycles, de Bruijn, Harary graphs), and also on massive synthetic instances (up to 1000 vertices), allowing to cover many possibilities of real industry topologies. Our proposal is also compared with state-of-the-art exact methods and heuristics. Experimental results show that our algorithm is able to outperform the best-known heuristics for the MBT, and also that it is a very good alternative for large instances that cannot be solved by current exact methods.     

大蒜素水溶液稳定性及分解产物组成研究

大蒜素水溶液的稳定性对大蒜制品的加工极其重要。作者研究了体系温度、浓度、p H值对大蒜素水溶液稳定性以及分解产物组成的影响。研究结果显示:温度或浓度越高,大蒜素水溶液的稳定性越低;温度相对较低或大蒜素浓度较高时,大蒜素的分解产物越趋向于以3-乙烯基-1,2-二硫环己-4-烯和3-乙烯基-1,2-二硫环己-5-烯为主的环状物;反之,产物以二烯丙基二硫醚等直链化合物为主。溶液的酸性越强,大蒜素越稳定。采用氢谱表征了大蒜素与氘代乙酸的氢键作用,采用理论计算,发现大蒜素在酸性溶液中发生质子化后,O(13)与H(5)的键长变长,分子的能量降低,初步揭示大蒜素在酸性溶剂中稳定性更高的原因。     

1,2-二硬脂酰基-sn-甘油-3-磷脂酰丝氨酸的全合成

(S)-2-[(苄氧羰基)氨基]-3-羟基丙酸苄酯（Ⅰ）经亚磷酸二苯酯处理得到了(S)-2-[(苄氧羰基)氨基]-2-(苄氧羰基)乙基膦酸酯（Ⅱ）；化合物Ⅱ经新戊酰氯介导活化后，与(S)-(+)-2,2-二甲基-1,3-二氧戊环-4-甲醇（Ⅲ）缩合，并由碘氧化得到新化合物(R)-2,3-异亚丙基-sn-甘油基{(S)-2-[(苄氧羰基)氨基]-2-(苄氧羰基)-1-氧乙基}膦酸酯（Ⅳ）；然后，化合物Ⅳ在三氟乙酸的作用下脱除异丙叉基得到(R)-2,3-二羟基丙基-sn-甘油基{(S)-2-[(苄氧羰基)氨基]-2-(苄氧羰基)-1-氧乙基}膦酸酯（Ⅴ）；在1-乙基-(3-二甲氨基丙基)碳酰二亚胺盐酸盐（EDCI）的作用下，中间体Ⅴ与硬脂酸进一步乙酰化，以85.8%的产率得到了(R)-2,3-双(硬脂酰基)丙酰基{(S)-2-[(苄氧羰基)氨基]-2-(苄氧羰基)-1-氧乙基}膦酸酯（Ⅵ）；中间体Ⅵ经氢解得到了1,2-二硬脂酰基-sn-甘油-3-磷脂酰丝氨酸（Ⅶ）。对主要合成步骤的反应条件进行了优化，并进行了验证和放大实验。产物Ⅶ共经历5步反应，总产率为57.1%。采用FTIR、HRMS和...