DGRec: Graph Neural Network for Recommendation with Diversified Embedding Generation

Graph Neural Network (GNN) based recommender systems have been attracting more and more attention in recent years due to their excellent performance in accuracy. Representing user-item interactions as a bipartite graph, a GNN model generates user and item representations by aggregating embeddings of their neighbors. However, such an aggregation procedure often accumulates information purely based on the graph structure, overlooking the redundancy of the aggregated neighbors and resulting in poor diversity of the recommended list. In this paper, we propose diversifying GNN-based recommender systems by directly improving the embedding generation procedure. Particularly, we utilize the following three modules: submodular neighbor selection to find a subset of diverse neighbors to aggregate for each GNN node, layer attention to assign attention weights for each layer, and loss reweighting to focus on the learning of items belonging to long-tail categories. Blending the three modules into GNN, we present DGRec(Diversified GNN-based Recommender System) for diversified recommendation. Experiments on real-world datasets demonstrate that the proposed method can achieve the best diversity while keeping the accuracy comparable to state-of-the-art GNN-based recommender systems.Comment: 9 pages, WSDM 202

Visualizing Graphene Based Sheets by Fluorescence Quenching Microscopy

Graphene based sheets have stimulated great interest due to their superior mechanical, electrical and thermal properties. A general visualization method that allows quick observation of these single atomic layers would be highly desirable as it can greatly facilitate sample evaluation and manipulation, and provide immediate feedback to improve synthesis and processing strategies. Here we report that graphene based sheets can be made highly visible under a fluorescence microscope by quenching the emission from a dye coating, which can be conveniently removed afterwards by rinsing without disrupting the sheets. Current imaging techniques for graphene based sheets rely on the use of special substrates. In contrast, the fluorescence quenching mechanism is no longer limited by the types of substrates. Graphene, reduced graphene oxide, or even graphene oxide sheets deposited on arbitrary substrates can now be readily visualized by eye with good contrast for layer counting. Direct observation of suspended sheets in solution was also demonstrated. The fluorescence quenching microscopy offers unprecedented imaging flexibility and could become a general tool for characterizing graphene based materials.Comment: J. Am. Chem. Soc., Article ASA

NMR Detection of Single-Walled Carbon Nanotubes in Solution

通讯作者地址: Sun,YP(通讯作者),Clemson Univ, Dept Chem, Clemson, SC 29634 USA 地址: 1. Clemson Univ, Dept Chem, Clemson, SC 29634 USA 2. Clemson Univ, Lab Emerging Mat & Technol, Clemson, SC 29634 USAThe detection of nanotube carbons in solution by C-13 NMR is reported. The highly soluble sample was from the functionalization of C-13-enriched single-walled carbon nanotubes (SWNTs) with diamineterminated oligomeric poly(ethylene glycol) (PEG(1500N)). The ferromagnetic impurities due to the residual metal catalysts were removed from the sample via repeated magnetic separation. The nanotube carbon signals are broad but partially resolved into two overlapping peaks, which are tentatively assigned to nanotube carbons on semiconducting (upfield) and metallic (downfield) SWNTs. The solid-state NMR signals of the same sample are similarly resolved. Mechanistic and practical implications of the results are discussed

Non-structured amino-acid impact on GH11 differs from GH10 xylanase.

The Aspergillus niger xylanase (Xyn) was used as a model to investigate impacts of un-structured residues on GH11 family enzyme, because the β-jelly roll structure has five residues (Ser1Ala2Gly3Ile4Asn5) at N-terminus and two residues (Ser183Ser184) at C-terminus that do not form to helix or strand. The N- or/and C-terminal residues were respectively deleted to construct three mutants. The optimal temperatures of XynΔN, XynΔC, and XynΔNC were 46, 50, and 46°C, and the thermostabilities were 15.7, 73.9, 15.5 min at 50°C, respectively, compared to 48°C and 33.9 min for the Xyn. After kinetic analysis, the substrate-binding affinities for birch-wood xylan decreased in the order XynΔC>Xyn>XynΔNC>XynΔN, while the K(cat) values increased in the order XynΔC<XynΔNC<Xyn<XynΔN. The C-terminal deletion increased the GH11 xylanase thermostability and T(opt), while the N- and NC-terminal deletions decreased its thermostability and optimal temperature. The C-terminal residues created more impact on enzyme thermal property, while the N-terminal residues created more impact on its catalytic efficiency and substrate-binding affinity. The impact of non-structured residues on GH11 xylanase was different from that of similar residues on GH10 xylanase, and the difference is attributed to structural difference between GH11 jelly-roll and GH10 (β/α)(8)

A Universal Strategy for Organic Fluid Phosphorescence Materials

It has become an accepted approach to construct room-temperature phosphorescence (RTP) materials by suppressing the non-radiative decay process. However, there is limited success in developing fluid phosphorescence materials due to the ultrafast non-radiation relaxation of vibration and collision of molecules in fluid matrixes. In this study, a universal strategy was proposed for pure organic phosphorescent fluid materials that are able to generate effective phosphorescent emissions at both room temperature (ΦRTP, 293 K ~ 30%) and even higher temperature (ΦRTP, 358 K ~ 4.53%). Based on these findings, a qualitative analytical method was developed for leak detection and a quantitative analytical technique was further validated to help visually identify the heat distribution of irregular surfaces. This advancement greatly empowers the current organic phosphorescent system offering an alternative approach to determine moisture and heat from non-invasive photoluminescence emission colors.</b

Recent advances and challenges in monitoring chromium ions using fluorescent probes

Chromium is among the most strategic and critical transition metal elements and has extensive applications in both industrial and biological contexts. The most stable oxidation states of chromium are trivalent chromium (Cr (III)) and hexavalent chromium (Cr(VI)). Cr(III) is recognized as an effective trace nutrient, whereas Cr(VI) in its highest oxidation state poses a toxic threat to human health due to its potent oxidizing capacities. To mitigate the risk of poisoning, efficient detection methods have been developed to meet testing requirements. Comparing with traditional methods, colorimetric and fluorescent techniques have emerged as simple, time-efficient, highly selective and sensitive, cost-effective and particularly well-suited for biological applications. Furthermore, these methods excel in distinguishing between trivalent and hexavalent chromium, even in low-level concentrations and complex matrices. Since the scarcity of fluorescent probes for chromium, most existing reviews merely touch upon this topic without providing comprehensive coverage. Therefore, this review aims to consolidate information on small molecular fluorescent probes and fluorescent materials serve as fluorescent probes for monitoring Cr2+, Cr3+, Cr2O72- and CrO42- in environmental settings and living cells. We anticipate that this review will promote the development of novel fluorescent probes for chromium detection, facilitating their applications in chemical, biological and medical domains

A Cocktail Approach Toward Tunable Organic Afterglow Systems

In this work, a cocktail approach toward tunable organic long-lived luminescence materials in solid, solution, and gel states is proposed. The tunable long-lived luminescence (τ > 0.7 s) is realized by controlling the energy transfer via manipulating the photo-induced isomerization of the energy acceptor (5). The afterglow can be regulated between blue and yellow emission upon irradiation of UV or visible light. And the “apparent lifetime” for the long-lived fluorescence is the same as the lifetime of the energy donor. The function is relying on the simple radiative energy transfer (reabsorption) between a long-lived phosphorescence and a highly efficient fluorescent isomer (5b), rather than the complicated communication between the excited state of the molecules such as Förster resonance energy transfer or Dexter energy transfer. The simple working principle endows this strategy with huge universality, flexibility, and operability. This work offers an extremely simple, feasible, and universal way to construct tunable afterglow materials in solid, solution, and gel states

Energy transfer-induced polymerization of acrylates

Photopolymerization of acrylate monomers has been the focus of research for quite a long time, but most of the researches concentrated on using exogenous radical species as means to achieve photo-induced polymerization. Herein, we exploit the energy transfer process between the luminescent molecule and the acrylate monomer to accomplish a two-component photoinduced polymerization reaction, and explored the universality of this strategy. Via the choice of thiochromanone as a template for the study, the photochemistry processes involved were explored in depth. The effect of radical polymerization processes was also excluded by time-resolved electron paramagnetic spectrum. As a result, it provides inspiration for further discussions on the roles played by monomers in photo-induced polymerization