179 research outputs found

    Deep Learning on Recommender Systems

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    The so-called cold-start problem has haunted the recommender systems community for years. The problem happens when a user rated/clicked/liked a few number of items. Classic approaches, such as collaborative filtering, assume that a user has a fair amount of actions so that the preferences of the user can be inferred. As a result, traditional methods cannot effectively model the interests of cold users due to the scarcity of data. In this dissertation, I will introduce our recent works on employing deep learning methods for alleviating the cold-start problem for recommendation. In the first part, we focus on utilizing review data to build deep learning models to ease the cold start problem. In the second part, I present an spectral approach to discover users' interests from the spectral domain of the user-item bipartite graph. In the third part, I introduce a recurrent method designed to capture users' evolving interests from dynamic graphs. In the fourth part, we propose to model users and items with probability distributions, rather than the popular vectors. With distribution-based representations, the proposed model is able to alleviate the cold-start problem and therefore, delivers the start-of-the-art performances in three real-world datasets

    Gold Nanoparticle-Catalyzed Clock Reaction of Methylene Blue and Hydrazine for Visual Chronometric Detection of Glutathione and Cysteine

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    A visual chronometric assay for glutathione (GSH) and cysteine (Cy) is reported based on a gold nanoparticle (AuNP)-catalyzed clock reaction of methylene blue and hydrazine. The blue MB is reduced to colorless leucomethylene blue (LMB) by hydrazine in the presence of AuNPs as the nanocatalysts, and it is again oxidized back to MB by oxygen under shaking. Therefore, a periodic oscillation is observed between blue MB and colorless LMB. However, when GSH or Cy is added to the clock reaction system, the catalytic activity of AuNPs decreases because of the inhibition of the formation of gold-hydride species, leading to a long reaction time from MB to LMB. The chronometric assay displays a good linear range of 10 to 330 μM for GSH and 20 to 400 μM for Cy, respectively. The limit of detection is estimated to be 8 and 10 μM at a 3σ, respectively. Different concentrations of GSH/Cy can be visually detected by observing the height of the blue solution under different reaction time points. In addition, the present assay shows good selectivity, and it is successfully applied for detecting GSH/Cy in fetal bovine serum

    Attachment and Detachment Processes of Individual Lysozyme Molecules on a Surface of a Monoclinic Lysozyme Crystal Studied by Fluorescent Single-Molecule Visualization

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    On a {101̅} face of a monoclinic crystal of hen egg-white lysozyme (HEWL), we visualized the attachment and detachment processes of individual fluorescent-labeled HEWL (F-HEWL) molecules by a fluorescent single-molecule visualization technique. We measured the changes in number density of F-HEWL molecules, whose positions were not changed for longer than a certain residence time, as a function of an adsorption time. We first confirmed that under an equilibrium condition, there was an “induction period” (∼120 min) of the attachment/detachment processes, during which period the number density remained constant. After the induction period, the number density increased linearly with the adsorption time, as it was recently found on a tetragonal HEWL crystal [Dai, G. L. Cryst. Growth Des 2011, 11­(1), 88−92]. In addition, we performed similar measurements under a supersaturated condition. Then we found that supersaturation significantly enhanced the attachment process after the induction time. The attachment/detachment processes finally reached a steady state, in which the attachment rate was higher than the detachment one. Moreover, we also found that in a rare case, an F-HEWL molecule adsorbed on a step laterally moved following the advancement of a growing step

    Allylic C–S Bond Construction through Metal-Free Direct Nitroalkene Sulfonation

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    A metal-free, open-flask protocol was developed for the preparation of allylic sulfones through direct condensation of sodium arylsulfinates and β,β-disubstituted nitroalkenes. The key step of this process was the Lewis base-promoted equilibrium between nitroalkenes and allylic nitro compounds. Through this process, the readily available conjugated nitroalkenes can be easily converted into allylic nitro compounds, which contain more reactive CC bonds toward the sulfonyl radical addition. As a result, allylic sulfones were prepared in excellent yields with a broad substrate scope under mild conditions

    Catalyst-free three-component approach to efficient synthesis of chromeno[4,3-<i>b</i>]pyrrol-4(1<i>H</i>)-one derivatives

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    <p>A mild, efficient, and environmentally benign one-pot synthesis of functionalized chromeno[4,3-<i>b</i>]pyrrol-4(1<i>H</i>)-ones by a three-component domino reaction of 4-aminocoumarins, arylglyoxal monohydrates, and 1,3-dicarbonyl compounds in refluxing ethanol without the use of catalyst is reported. The present protocol features operational simplicity, short reaction time, good yields, and the absence of aqueous workup procedure and chromatographic separation.</p

    Amino acid sequences of selected phage clones from 12-mer peptide library.

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    <p>After the fourth round of panning, 60 phage clones were randomly selected. The phage clones were sequenced and three phage clones (Sp25, INp42 and INp55) lacked the exogenous sequence. 18 different peptide sequences were obtained and designated VP1 to VP18. The frequency represents the number of the peptide sequence appeared in the whole selected phage clones. Here, Mp represents phages recovered from an acid elution fraction, Sp represents a specific elution by VIP, INp represents phages recovered from a lysate fraction.</p

    Bypass shortens the lifespan of stored red blood cells in a rat model of cardiopulmonary bypass.

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    (a, b) Absolute numbers of (a) monocytes and (b) neutrophils that phagocytosed FITC-labeled stored red blood cells at the indicated time points after 2-h bypass or sham bypass. (c) Absolute numbers of FITC-labeled red blood cells over time after bypass or sham bypass. a Pvs. bypass group. (d) Percentages of splenic macrophages labeled by FITC at 24 h after 2-h bypass or sham bypass. Data are mean ± SD (n = 6 animals per condition).</p

    Inhibiting caspase-3 did not improve oxidative stress in red blood cells.

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    Cells were pretreated with caspase-3 inhibitor Z-DEVD-FMK or vehicle (DMSO), then mixed with plasma from rats that underwent bypass. (a) The inhibitor Z-DEVD-FMK inhibited caspase-3 in stored red blood cells. (b) Representative micrographs of the suspensions of red blood cells in plasma. Reactive oxygen species (ROS) were stained using DCFH-DA (green). (c-f) Levels or activity of (b) ROS, (c) malonic dialdehyde (MDA), (d) l-glutathione (GSH) and (e) superoxide dismutase (SOD) were assayed in the suspensions. Data are mean ± SD (n = 10 animals per condition).</p

    Screening of a Specific Peptide Binding to VPAC1 Receptor from a Phage Display Peptide Library

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    <div><h3>Background/Purpose</h3><p>The VPAC1 receptor, a member of the vasoactive intestinal peptide receptors (VIPRs), is overexpressed in the most frequently occurring malignant tumors and plays a major role in the progression and angiogenesis of a number of malignancies. Recently, phage display has become widely used for many applications, including ligand generation for targeted imaging, drug delivery and therapy. In this work, we developed a panning procedure using a phage display peptide library to select a peptide that specifically binds to the VPAC1 receptor to develop a novel targeted probe for molecular imaging and therapy.</p> <h3>Methods</h3><p>CHO-K1 cells stably expressing VPAC1 receptors (CHO-K1/VPAC1 cells) were used to select a VPAC1-binding peptide from a 12-mer phage peptide library. DNA sequencing and homologous analysis of the randomly selected phage clones were performed. A cellular ELISA was used to determine the most selectively binding peptide for further investigation. Binding specificity to the VPAC1 receptor was analyzed by competitive inhibition ELISA and flow cytometry. The binding ability of the selected peptide to CHO-K1/VPAC1 cells and colorectal cancer (CRC) cell lines was confirmed using fluorescence microscopy and flow cytometry.</p> <h3>Results</h3><p>A significant enrichment of phages that specifically bound to CHO-K1/VPAC1 cells was obtained after four rounds of panning. Of the selected phage clones, 16 out of 60 shared the same peptide sequence, GFRFGALHEYNS, which we termed the VP2 peptide. VP2 and vasoactive intestinal peptide (VIP) competitively bound to the VPAC1 receptor. More importantly, we confirmed that VP2 specifically bound to CHO-K1/VPAC1 cells and several CRC cell lines.</p> <h3>Conclusion</h3><p>Our results demonstrate that the VP2 peptide could specifically bind to VPAC1 receptor and several CRC cell lines. And VP2 peptide may be a potential candidate to be developed as a useful diagnostic molecular imaging probe for early detection of CRC.</p> </div

    The minimal underlying data set about the manuscript.

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    The minimal underlying data set about the manuscript.</p