Peroxycarbenium-mediated C-C bond formation: applications to the synthesis of hydroperoxides and peroxides

The Lewis acid-mediated reaction of alkene nucleophiles with peroxyacetals provides an effective route for the synthesis of homologated peroxides and hydroperoxides. In the presence of Lewis acids such as TiCl(4), SnCl(4), and trimethylsilyl triflate, peroxyacetals and peroxyketals undergo reaction with allyltrimethylsilane, silyl enol ethers, and silyl ketene acetals to afford homoallyl peroxides, 3-peroxyketones, and 3-peroxyalkanoates, respectively. Reactions of peroxyacetals are Lewis acid dependent; TiCl(4) promotes formation of ethers while SnCl(4) and trimethylsilyl triflate promote formation of peroxides. Lewis acid-promoted reactions of silylated hydroperoxyacetals furnish silylated hydroperoxides, which can be deprotected to homologated hydroperoxides. Hydroperoxyketals undergo Lewis acid-mediated allylation to furnish 1,2-dioxolanes via attack of hydroperoxide on the intermediate carbocation. Lewis acid-mediated cyclization of unsaturated peroxyacetals furnishes 1,2-dioxanes, 1,2-dioxepanes, and 1,2-dioxacanes through 6-endo/exo, 7-endo/endo, and 8-endo/endo pathways. The corresponding reactions involving 6-endo/endo and 5-endo/exo pathways were unsuccessful.     

Dynamic Hierarchical Packing of Wireless Switches Using a Seed, Repair and Replace Genetic Algorithm

Suppose that items of equipment are to be added to a supply station (e.g., new switch modules are to be added to a telecommunications switch) over time to meet growing demand requirements. Both supply and demand have multiple components: an item of equipment supplies different amounts of several resources, and demand may be expressed in terms of the vector of resources required. There are several different types of equipment to choose among, each type supplying known amounts of each resource per unit of equipment. The supply station is organized into bays, shelves, or other capacitated containers so that when the cumulative amount of equipment added exceeds the holding capacity of the installed containers, new containers must be added, creating a relatively large jump in cumulative costs. Thus, it is desirable to sequentially pack items of equipment into the available containers, by choosing which types of equipment to install when, so as to minimize the total cost of covering demand in each period. We discuss an instance of this problem arising from wireless telephony and describe the performance of a conventional branch-and-bound optimization algorithm for solving it. The branch-and-bound approach works well on small instances of the problem, and has been used successfully in practical planning. However, it can take CPU-days to run, thus preventing development of a useful interactive planning tool. Therefore, we introduce a novel seed, repair, and replace genetic algorithm (SRR-GA) for solving dynamic packing problems of this type. We contrast its performance with the branch-and-bound algorithm's on both hand-generated and randomly-created dynamic packing problems, finding that the SRR-GA is two to three orders of magnitude faster and produces solutions of equal or better quality on practical problems. Variations of the dynamic packing problem and of the SRR-GA for solving it are mentioned, and the paper concludes by suggesting other potential applications of the SRR-GA to hard combinatorial optimization problems.     

Ion‐Responsive Behavior of Ionic‐Liquid Surfactant Aggregates with Applications in Controlled Release and Emulsification

We propose a simple but efficient, rapid, and quantitative ion‐responsive micelle system based on counter‐anion exchange of a surfactant with an imidazolium unit. The ion‐exchange reaction results in the amphiphilic‐to‐hydrophobic transition of the imidazolium salt, leading to the destruction of the micelles, which has been successfully applied to controlled release and emulsification. The proposed design offers a novel alternative stimulus to control these smart physical aggregates besides pH, temperature and light—with extra advantages. Our finding greatly benefits both fundamental research and industry.     

An experimental and numerical study of shock interaction with a gas column seeded with droplets

Shock Waves - This work presents an experimental and numerical consideration of the flow developing after a planar shock wave accelerates a cylindrical column of heavy gas seeded with glycol...     

Neural correlates of semantic and syntactic processes in the comprehension of case marked pronouns: Evidence from German and Dutch

Background  

It is well known that both semantic and syntactic information play a role in pronoun resolution in sentences. However, it is unclear what the relative contribution of these sources of information is for the establishment of a coreferential relationship between the pronoun and the antecedent in combination with a local structural case constraint on the pronoun (i.e. case assignment of a pronoun under preposition governing). In a prepositional phrase in German and Dutch, it is the preposition that assigns case to the pronoun. Furthermore, in these languages different overtly case-marked pronouns are used to refer to male and female persons. Thus, one can manipulate biological/syntactic gender features separately from case marking features.     

ICP-AES法测定色漆可溶性金属含量

用ICP-AES法测定了色漆中的“可溶性”金属铬、镉、铅元素，考察了不同酸度对分析结果的影响，优化了测试条件。进行了回收率和精密度试验。并用原子吸收光谱国标方法进行对照，结果一致。