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The excited state intramolecular proton transfer (ESIPT) dynamics and photophysical properties of 4-( N , N -dimethylamino)-3-hydroxyflavone (DMAF) in acetonitrile (ACN) and ethanol (EtOH) were investigated by density-functional theory (DFT) and time-dependent density-functional theory (TDDFT) methods at B3LYP/6-31G (d,p) level. The calculation results show that hydrogen bond in the first excited state (S 1 ) is strengthened, which can facilitate the process of proton transfer. The absorption and emission spectra obtained through the vertical excitation energies agree well with the experiment, which confirm the rationality of the choice of theoretical methods. In addition, the frontier molecular orbitals (MOs) analysis indicates the intramolecular charge transfer, which can reveal the tendency of ESIPT reaction. In order to explore the mechanism of the ESIPT process, the potential energy curves of the ground state (S 0 ) and the S 1 state have been constructed. Based on the energy potential barrier of 3.48 kcal/mol for DMAF molecule and 5.48 kcal/mol for 4-( N , N -dimethylamino)-3-hydroxyflavone/ethanol (DMAF-EtOH) complex in the S 1 state, we can find that the proton transfer occurs more easily in acetonitrile solvent. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we propose an algorithm for computing and maintaining recently frequent patterns which is more stable and smaller than the data stream and dynamically updating them with the incoming transactions. Our study mainly has two contributions. First, a regression-based data stream model is proposed to differentiate new and old transactions. The novel model reflects transactions into many multiple time granularities and can automatically adjust transactional fading rate by defining a fading factor. The factor defines a desired life-time of the information of transactions in the data stream. Second, we develop RFIMiner, a single-scan algorithm for mining recently frequent patterns from data streams. Our algorithm employs a special property among suffix-trees, so it is unnecessary to traverse suffix-trees when patterns are discovered. To cater to suffix-trees, we also adopt a new method called Depth-first and Bottom–up Inside Itemset Growth to find more recently frequent patterns from known frequent ones. Moreover, it avoids generating redundant computation and candidate patterns as well. We conduct detailed experiments to evaluate the performance of algorithm in several aspects. Results confirm that the new method has an excellent scalability and the performance meets the condition which requires better quality and efficiency of mining recently frequent itemsets in the data stream. [Copyright &y& Elsevier]

Highlights • Sulfide significantly decreases the long-term strength of CPB. • A certain amount of sulfide improves the early strength of CPB. • Pore size distribution effects the strength of CPB. • Sulfide content is important for mining stability. Abstract With the production of a large amount of metal tailings, backfill is one of the best models for waste management and has been widely used in many mines. Metal deposit, especially lead-zinc mines, usually contain sulfide minerals, mainly pyrite. Sulfide attack would cause the strength degradation of cemented materials and decrease the structural stability. This study aimed to understand the effect of sulfide on the long-term strength of lead-zinc tailings cemented paste backfill (CPB). CPB specimens with four sulfur contents (2 wt%, 5 wt%, 10 wt%, 15 wt%) were prepared to investigate their physicochemical characteristics in 28–360 days. Scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) analyses of the CPB specimens were also conducted to obtain valuable information. The results showed that the highest strength of CPB was achieved at curing 90 days. Sulfide showed early strength agent property and the early strength of CPB with sulfur content of 5 wt% was improved. The internal system of CPB was alkaline, and sulfate mainly involved in cement hydration reaction. SEM observed that CPB specimens had compact structures, and calcium silicate hydrate (C-S-H) was produced. After 90 days, under the influence of sulfide, the strength of all the CPB specimens decreased, and the strength of CPB specimen with the highest sulfur content decreased the most. The pH value of the solution continuously decreased and eventually became acidic. A large amount of sulfate accumulated. The hydrated calcium silicate decomposed in the acidic environment. The number of expansive ettringite and gypsum products increased, and the number of large pores increased. Sulfide reactivity includes sulfate and acid attack. Large internal defects lead the strength and stability deterioration. This study compared the differences between sulfide erosion and sulfate attack, then provided some advice for the disposal of high sulfide tailings. [ABSTRACT FROM AUTHOR]