多人数署名の証明可能安全性に関する研究

筑波大学 (University of Tsukuba)201

Content-Aware DataGuides for Indexing Large Collections of XML Documents

XML is well-suited for modelling structured data with textual content. However, most indexing approaches perform structure and content matching independently, combining the retrieved path and keyword occurrences in a third step. This paper shows that retrieval in XML documents can be accelerated significantly by processing text and structure simultaneously during all retrieval phases. To this end, the Content-Aware DataGuide (CADG) enhances the wellknown DataGuide with (1) simultaneous keyword and path matching and (2) a precomputed content/structure join. Extensive experiments prove the CADG to be 50-90% faster than the DataGuide for various sorts of query and document, including difficult cases such as poorly structured queries and recursive document paths. A new query classification scheme identifies precise query characteristics with a predominant influence on the performance of the individual indices. The experiments show that the CADG is applicable to many real-world applications, in particular large collections of heterogeneously structured XML documents

Towards Economic Models for MOOC Pricing Strategy Design

MOOCs have brought unprecedented opportunities of making high-quality courses accessible to everybody. However, from the business point of view, MOOCs are often challenged for lacking of sustainable business models, and academic research for marketing strategies of MOOCs is also a blind spot currently. In this work, we try to formulate the business models and pricing strategies in a structured and scientific way. Based on both theoretical research and real marketing data analysis from a MOOC platform, we present the insights of the pricing strategies for existing MOOC markets. We focus on the pricing strategies for verified certificates in the B2C markets, and also give ideas of modeling the course sub-licensing services in B2B markets

On the 7-azaindole in acetonitrile anhydrous solutions as an inappropriate photophysical model for DNA base pairs

Multiple Hydrogen-bonding is a fundamental issue to explain base-pairing in DNA structures, which was firstly described by Watson and Crick^1^ using stable keto tautomer forms. In their analysis, they considered the possibility of mutations via proton transfer reactions within a base pair. Such reactions can be induced by electronic excitation, for example, adenine-cytosine mispairing may be caused by double-proton phototautomerism.^2^ The 7-azaindole (7AI) doubly-hydrogen bonded dimer was firstly proposed as a suitable model for explaining the DNA base mispairing owing to excited state two-proton phototautomerization in 1969 by Taylor _et al_.^3^ The concerted nature of this excited state biprotonic transfer has been strongly supported by available evidence (see references 4-6 and references therein). Recently, Kwon and Zewail^7^ (K&Z) have reported femtosec time-resolved evidence on the stepwise mechanism in polar solvents, using very concentrated solutions of 7AI (0.1 M) in anhydrous acetonitrile, diethylether and dichloromethane on excitation at 320 nm. However, based on a careful spectroscopic analysis of the absorption and emission spectra of anhydrous 0.1 M 7-azaindole solutions in acetonitrile and butyronitrile, we demonstrate in this letter that the 7AI molecule does not form the doubly hydrogen bonded dimer at room temperature (rt) in acetonitrile, but it does generate another aggregate which emits fluorescence at ca. 500 nm. Consequently, the assertion of Kwon and Zewail^7,8^ that the rate of proton transfer in 7-azaindole dimers is significantly dependent on the solvent polarity and its stepwise mechanism for the process is not rightly stated as no C~2h~ dimer is formed in the medium used to record their femtosecond time resolved and fluorescence spectroscopic evidence (viz. 7-azaindole 0.1 M solution in acetonitrile at rt)