Topic tracking with Bayesian belief network

The task of topic tracking is to monitor a stream of stories and find all subsequent stories that discuss the same topic. Using Bayesian belief network we give three topic tracking models: a static topic model BSTM and two dynamic topic models BDTM-I, BDTM-II. BDTM-II merges the advantages of BSTM and BDTM-I, has better tracking performance than the former two, and effectively alleviates topic drift phenomenon. Applying unrelated coming stories to update BDTM-I and BDTM-II can filter noises existed in topics. Experiments on TDT corpora show that BSTM decreases (C_det)_norm by 5.5% comparing to VSM, BDTM-II decreases (C_det)_norm by 6.3% and 6.0% comparing to BSTM and BDTM-I respectively, using unrelated stories can improve the tracking performance.     

Geometric Phase for High-Temperature Master Equation

Geometric phase of mixed state is investigated for three-level system obeying a high-temperature master equation. The results show the Berry phase of mixed phase is strongly dependent on the initial condition. For the different initial angle, the turning region is different. In addition, the decrease of Berry phase is most slow around the coupling strength α=5 with an increasing of evolving time.     

Domino free radical photopolymerization based on phototriggered base proliferation reaction and redox initiation

A detailed evaluation of the kinetics of domino free radical photopolymerization (DFRP) based on phototriggered base proliferation reaction and redox initiation was described in the condition of eliminating the heat of polymerization via reacting in the thin polymer films. First, domino photoinitiating system made a substantial breakthrough in the photoefficiency of amine generation in contrast to photocaged base system, exhibiting marked improvement in the photosensitivity. Second, both the structural feature of base amplifier (BA) and reaction temperature as two important factors impacting the proliferation rate have been detailed. Third, different domino photoinitiating components, such as BAs, peroxides, and acrylates, were investigated in the thin polymer films. It is shown that both primary and secondary BAs are efficient catalysts for DFRP. Furthermore, polymerization rate shows a consistent dependence on the pK_a value of the proliferated amine. Finally, remarkable post conversion after irradiation was achieved in DFRP. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1560–1569     

One-pot synthesis of trifluoromethylated phthalans via intramolecular cyclization from 2-alkynylbenzaldehydes

An efficient tandem addition/cyclization procedure for the synthesis of trifluoromethylated phthalans under mild conditions was developed. This procedure involves tetrabutylammonium fluoride (TBAF)-promoted addition of Ruppert–Prakash reagent (TMSCF₃) to 2-alkynylbenzaldehyde to give 2-alkynylbenzylicalcohols, which would then undergo base-catalyzed selective 5-exo-dig cyclization to furnish the corresponding products.     

Simultaneous determination of three major lignans in rat plasma by LC‐MS/MS and its application to a pharmacokinetic study after oral administration of Diphylleia sinensis extract

A sensitive and selective liquid chromatography tandem mass spectrometry was developed and validated for the simultaneous determination of three major lignans (podophyllotoxin, epipodophyllotoxin, and 4′‐demethylpodophyllotoxin) in rat plasma using diphenhydramine as the internal standard. The analytes were detected using a triple quadrupole mass spectrometer that was equipped with an electrospray ionization source in the positive ion and selected reaction monitoring modes. The linearity of the calibration curve was good, with coefficients of determination (r²) >0.9914 for all of the analytes. The developed method was successfully applied for the simultaneous determination of the three lignans in rat plasma following oral administration of Diphylleia sinensis extract to rats. Copyright © 2013 John Wiley & Sons, Ltd.     

Quantification of multiple compounds containing heterogeneous elements in the mixture by one‐dimensional nuclear magnetic resonance spectroscopy of different nuclei using a single universal concentration reference

One‐dimensional (1D) quantitative NMR (qNMR) is a useful tool for concentration determination due to its experimental simplicity and the direct proportionality of the integrated signal area to the number of nuclei spin. For complex mixtures, however, signal overlapping often in one‐dimensional quantitative ¹H NMR (1D ¹H qNMR) spectrum limits the accurate quantification of individual compound. Here, we introduced employing joint 1D qNMR methods of different nuclei, such as ¹H and ³¹P (or/and ¹⁹F), to quantify multiple compounds in a complex mixture using a single universal concentration reference. When the concentration ratio of several compounds containing different elements in a complex mixture is of interest, the result calculated from measured intensities from 1D qNMR of different nuclei is independent of the gravimetric error from the reference. In this case, the common reference also serves as a ‘quantitative bridge’ among these 1D qNMR of different nuclei. Quantitative analysis of choline, phosphocholine, and glycerophosphocholine mixture is given as an example using trimethylphosphine oxide ((CH₃)₃P(O)) as concentration reference. Compounds containing multiple elements, such as tetramethylammonium hexafluorophosphate (N⁺(CH₃)₄PF₆^?), are proposed as the common concentration reference for ¹H, ¹³C, ¹⁵N, ³¹P, and ¹⁹F qNMR for the quantitative analysis of complex mixture containing these different elements. We anticipate that the proposed joint 1D qNMR approach using a universal concentration reference will be a valuable alternative for simultaneous quantification of multiple compounds in a complex mixture due to its accuracy and single and simple sample preparation. Copyright © 2014 John Wiley & Sons, Ltd.     

A continuum model for intermittent deformation of single crystal micropillars

Strain bursts are often observed during compression tests of single crystal micropillars. In this work, we formulate a new continuum model that accounts for the strain bursts within the framework of crystal plasticity. The strain bursts are separated from the loading stage (nearly elastic loading) by introducing a dimensionless constant in the continuum model, and are detected by load serrations. The boundary conditions in the context of micropillar compression are studied and they are shown to be changing and unpredictable as plastic deformation proceeds. To evaluate the validity of our model, finite element simulations of the uniaxial compression tests on nickel micropillars are performed. Our simulations produce clearly visible strain bursts during the plastic flow and the produced intermittent flows are comparable with the experimental observations. For the bulk crystal, a series of strain bursts is identified in the course of plastic flow, despite an apparently smooth stress–strain response. We also show that the intermittent flow is intensified in the micrometer-scale due to both increasing numbers of the successive strain bursts and increasing amplitude of the strain burst, when the specimen size decreases. Finally, we show that the occurrences of the strain bursts are always associated with negative values of the second-order work.