Social Collaborative Filtering by Trust Yang, Bo; Lei, Yu; Liu, Jiming ...
IEEE transactions on pattern analysis and machine intelligence,
08/2017, Volume:
39, Issue:
8
Journal Article
Peer reviewed
Recommender systems are used to accurately and actively provide users with potentially interesting information or services. Collaborative filtering is a widely adopted approach to recommendation, but ...sparse data and cold-start users are often barriers to providing high quality recommendations. To address such issues, we propose a novel method that works to improve the performance of collaborative filtering recommendations by integrating sparse rating data given by users and sparse social trust network among these same users. This is a model-based method that adopts matrix factorization technique that maps users into low-dimensional latent feature spaces in terms of their trust relationship, and aims to more accurately reflect the users reciprocal influence on the formation of their own opinions and to learn better preferential patterns of users for high-quality recommendations. We use four large-scale datasets to show that the proposed method performs much better, especially for cold start users, than state-of-the-art recommendation algorithms for social collaborative filtering based on trust.
Non-methane volatile organic compounds (NMVOCs) are
important ozone and secondary organic aerosol precursors and play important
roles in tropospheric chemistry. In this work, we estimated the total ...and
speciated NMVOC emissions from China's anthropogenic sources during
1990–2017 by using a bottom-up emission inventory framework and
investigated the main drivers behind the trends. We found that anthropogenic
NMVOC emissions in China have been increasing continuously since 1990 due to
the dramatic growth in activity rates and absence of effective control
measures. We estimated that anthropogenic NMVOC emissions in China increased
from 9.76 Tg in 1990 to 28.5 Tg in 2017, mainly driven by the persistent
growth from the industry sector and solvent use. Meanwhile, emissions
from the residential and transportation sectors declined after 2005, partly
offsetting the total emission increase. During 1990–2017, mass-based
emissions of alkanes, alkenes, alkynes, aromatics, oxygenated volatile organic compounds (OVOCs)
and other species increased by 274 %, 88 %, 4 %, 387 %, 91 % and
231 %, respectively. Following the growth in total NMVOC emissions, the
corresponding ozone formation potential (OFP) increased from 38.2 Tg of O3
in 1990 to 99.7 Tg of O3 in 2017. We estimated that aromatics accounted
for the largest share (43 %) of the total OFP, followed by alkenes
(37 %) and OVOCs (10 %). Growth in China's NMVOC emissions was mainly
driven by the transportation sector before 2000, while industry and solvent
use dominated the emission growth during 2000–2010. Since 2010, although
emissions from the industry sector and solvent use kept growing, strict
control measures on transportation and fuel transition in residential stoves
have successfully slowed down the increasing trend, especially after the
implementation of China's clean air action since 2013. However, compared to
large emission decreases in other major air pollutants in China (e.g.,
SO2, NOx and primary PM) during 2013–2017, the relatively flat
trend in NMVOC emissions and OFP revealed the absence of effective control
measures, which might have contributed to the increase in ozone during the
same period. Given their high contributions to emissions and OFP, tailored
control measures for solvent use and industrial sources should be developed,
and multi-pollutant control strategies should be designed to mitigate both
PM2.5 and ozone pollution simultaneously.
Upon heating, polyesters decompose to small molecules and release flammable volatiles and toxic gases, primarily through chain scission of their ester linkages, and therefore exhibit poor fire‐safety ...properties, thus restricting their applications. Reported herein is an end‐group‐capturing effect of (bis)oxazoline groups, generated from the thermal rearrangement of the N‐(2‐hydroxyphenyl)phthalimide (HPI) moiety which was incorporated into the polyester chain by copolymerization. These copolyesters, as a result, exhibit high efficiency in retarding decomposition by capturing the decomposed products, particularly for the carbonyl‐terminated fragments, thus increasing the fire‐safety properties, such as self‐extinguishing, anti‐dripping, and inhibiting heat release and smoke production. The successful application of this method in both semi‐aromatic and aliphatic polyesters provide promising perspectives to designing versatile fire‐safe polymers.
Captured: End‐group capture of benzoxazole from the thermal rearrangement of a hydroxy‐containing phthalimide group contributes to the fire‐safety features of polyesters. This novel strategy exhibits applicability and efficiency for both semi‐aromatic and aliphatic polyesters, providing a new design approach to fire‐safe polymers.
It remains unclear whether the necessity of calcified mellitus induced by high inorganic phosphate (Pi) is required and the roles of autophagy plays in aldosterone (Aldo)‐enhanced vascular ...calcification (VC) and vascular smooth muscle cell (VSMC) osteogenic differentiation. In the present study, we found that Aldo enhanced VC both in vivo and in vitro only in the presence of high Pi, alongside with increased expression of VSMC osteogenic proteins (BMP2, Runx2 and OCN) and decreased expression of VSMC contractile proteins (α‐SMA, SM22α and smoothelin). However, these effects were blocked by mineralocorticoid receptor inhibitor, spironolactone. In addition, the stimulatory effects of Aldo on VSMC calcification were further accelerated by the autophagy inhibitor, 3‐MA, and were counteracted by the autophagy inducer, rapamycin. Moreover, inhibiting adenosine monophosphate‐activated protein kinase (AMPK) by Compound C attenuated Aldo/MR‐enhanced VC. These results suggested that Aldo facilitates high Pi‐induced VSMC osteogenic phenotypic switch and calcification through MR‐mediated signalling pathways that involve AMPK‐dependent autophagy, which provided new insights into Aldo excess‐associated VC in various settings.
Biochar draws increasing attention as soil amendment, carbon sink, slow-release fertilizer, and adsorbent. Herein, it was interesting to find out that among 11 kinds of commercial biochar, 3 of them ...facilitated ferrate oxidation of sulfamethoxazole (SMX). With the addition of biochar, oxidation rates of 5 kinds of organic pollutants (including antibiotics, pharmaceuticals, and personal care product) increased by 3–14 times, and the total organic carbon (TOC) removal ratio increased by 2.4–8 times. Radical scavenging experiment, electron spin resonance (ESR) analysis, and probe compound (sulfoxide) oxidation experiment showed that no radical but intermediate iron species Fe(IV) and Fe(V) participated in the oxidation reactions. Redox-active moieties (phenolic hydroxyl) on biochar interact with ferrate as electron shuttle and enhance the formation of intermediate iron species through electron transfer. The intermediate iron species not only interacted with organic pollutants and accelerated their transformation, but also corrupted (oxidized) the physical structure of biochar and expanded its surface area and pore volume. Increase of surface area and pore volume of the spent biochar in turn resulted in the improved adsorption capacity. In addition to eliminating emerging organic pollutants, ferrate/biochar removed 8.7%–31.6% of TOC in authentic water and decreased the formation potential of 20 kinds of chlorinated disinfection by-products (DBPs) by 9.2%–23.9%.
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•Biochar reacted with Fe(VI) with the formation of Fe(IV)/Fe(V).•Fe(IV)/Fe(V) was more reactive with organic pollutants compared with Fe(VI).•Biochar enhanced Fe(VI) oxidation of SMX, CBZ, CIP, DCF, and DEET.•Fe(IV)/Fe(V) corrupted structure of biochar and facilitated the adsorption of TOC.
Hydroxylamine showed an outstanding performance on enhancing the oxidation of pollutants in Fe(II) involved advanced oxidation processes, while the detailed reaction schemes have not been fully ...revealed. Specific functions of hydroxylamine in the oxidation of benzoic acid with Fe(II)/persulfate (PDS) system were explored. With the addition of hydroxylamine, degradation kinetics of benzoic acid deviated from both two-stage kinetics and pseudo first order kinetics, but could be interpreted well with binomial regression analysis. Degradation rate constant (kobs) of benzoic acid was calculated and showed the same variation trend with hydroxylamineFe(III)2/(Fe(II)H+)2, the value of which was changed during reaction processes. A detailed kinetic model for simulating the degradation profile of benzoic acid with hydroxylamine acceleration was proposed for the first time and indicated that interactions of hydroxylamine and Fe(III) were fast equilibrium reactions, which was a dominant factor influencing the oxidation kinetics of benzoic acid in Fe(II)/hydroxylamine/PDS system. Comparative study showed that when 1.4 mM of ascorbic acid was added into Fe(II)/PDS system, degradation kinetics of benzoic acid was similar to that enhanced by hydroxylamine. However, when 0.6 mM or 1.0 mM of ascorbic acid was added, oxidation kinetics still presented as the two-stage profile. Kinetic simulations indicated that Fe(II) was produced slower from Fe(III)-ascorbic acid complexes than that with hydroxylamine, which caused the difference in oxidation kinetics. This study could improve our understanding about the effect of hydroxylamine and other reductants in promoting pollutants elimination in Fe(II)/PDS system.
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•Kinetic variations were compared in Fe(II)/persulfate system with and without hydroxylamine.•Kinetic models with fast equilibrium of hydroxylamine and Fe(III) were built to simulate degradation process.•Fast equilibrium of hydroxylamine and Fe(III) was a dominant factor for the enhanced oxidation of pollutants.
Air pollution control has become one of the top priorities of China's “Ecological Civilization” development. As a quick response to the 2013 PM2.5 episodes, the Chinese Government issued the “Air ...Pollution Prevention and Control Action Plan” as the national strategy and roadmap for air quality improvements consisting of phased quantitative targets and concrete measures. Taking this into account, this study explores the spatiotemporal variations of the five conventional pollutants—PM2.5, PM10, SO2, NO2, and O3—as well as the Air Quality Index and primary pollutants in 338 Chinese cities from 2013 to 2017 in order to comprehensively understand China's current air pollution situation and evaluate the effectiveness of the Action Plan. The results indicate that: (1) the overall air quality has been significantly improved, with the concentrations of PM2.5, PM10, and SO2 decreasing noticeably, although the still high PM level, the dramatically increasing O3 concentration, and the stagnant amounts of NO2 present further challenges, along with the intensification of regional compound air pollution problems; (2) in contrast to the three key regions under the Action Plan exhibiting significant decreases in PM and SO2, the Fen-Wei Plain (FWP) is suffering from serious compound pollution, suggesting that there is an urgent need for the development of a regional joint prevention and control mechanism in the FWP and similar areas; (3) with the exception of the common pollution hot spots mainly concentrated in the FWP as well as Beijing-Tianjin-Hebei (BTH) and its surrounding regions, the distribution of each pollutant exhibited remarkable spatial heterogeneity due to their distinctive emission sources, a finding that strongly indicates the need for regionally differentiated management; and (4) the most frequent primary pollutant at the national level was O3, followed by PM2.5 and PM10. In the Wuhan Metropolitan Area (WHM), Changsha-Zhuzhou-Xiangtan Metropolitan Area (CZT), and Sichuan-Chongqing Region (CY), PM2.5 pollution is playing the dominant role, while in the FWP, BTH, Yangtze River Delta region (YRD), and Pearl River Delta region (PRD), the synergistic control of PM2.5 and O3 pollutants is urgently needed as soon as possible, which will require that more attention be paid to emission mitigation in the transportation sector, as well as the synergistic control of NOx and VOC emissions.
•Overall air quality improved dramatically, but non-attainment is still widespread.•Regional compound air pollution problems are intensifying, dominated by PM and O3.•Spatial disparity of pollutants requires regionally differentiated management.•Fen-Wei Plain suffers from the most serious air pollution along with 2 + 26 cities.•Synergistic control of NOx and VOCs is greatly needed.
A synergistic catalytic method combining photoredox catalysis, hydrogen‐atom transfer, and proton‐reduction catalysis for the dehydrogenative silylation of alkenes was developed. With this approach, ...a highly concise route to substituted allylsilanes has been achieved under very mild reaction conditions without using oxidants. This transformation features good to excellent yields, operational simplicity, and high atom economy. Based on control experiments, a possible reaction mechanism is proposed.
A synergistic catalytic method of combining photoredox catalysis, hydrogen‐atom transfer, and proton‐reduction catalysis for the dehydrogenative silylation of alkenes was developed. The reaction features high regioselectivity, excellent tolerance of functional groups, wide substrate scope, and mild reaction conditions. Moreover, this oxidant‐free system offers a cleaner and more efficient method beyond traditional catalysis, which requires either stoichiometric or excess amounts of oxidants.
•MnOx/biochar and FeOx/biochar significantly improved ozonization of ATZ.•Enhanced formation of •OH was observed in the catalytic ozonation systems.•Increased Lewis acid sites and electron transfer ...contributed for the O3 catalyzation.•Toxicity of ATZ had been largely eliminated after the heterogeneous catalytic ozonation.
After reaction with permanganate or ferrate, the resulted Mn-loaded and Fe-loaded biochar (MnOx/biochar and FeOx/biochar) exhibited excellent catalytic ozonation activity. O3 (2.5 mg/L) eliminated 48% of atrazine (ATZ, 5 μM) within 30 min at pH 7.0, while under identical conditions, ozonation efficiency of ATZ increased to 83% and 100% in MnOx/biochar and FeOx/biochar (20 mg/L) heterogeneous catalytic systems, respectively. Radical scavenger experiment and electron paramagnetic resonance (EPR) analysis confirmed that hydroxyl radical (•OH) was the dominant oxidant. Total Lewis acid sites on MnOx/biochar and FeOx/biochar were 3.5 and 4.1 times of that on the raw biochar, which induced enhanced adsorption of O3 and its subsequent decomposition into •OH. Electron transfer via redox pairs on MnOx/biochar and FeOx/biochar was observed by cyclic voltammetry scans, which also functioned in the improved catalytic capacity. Degradation pathways of ATZ in MnOx/biochar and FeOx/biochar ozonation systems were proposed, with 34.6% and 44.8% of dechlorination effect accomplished within 30 min of reaction, which was improved by 4.1 and 5.3 times compared to pure ozonation. After 12-hour treatment, acute toxicity of ATZ oxidation products was reduced from 38.3% of pure ozonation system to 14.5% and 6.3% of activated ozonation systems with MnOx/biochar and FeOx/biochar, respectively. Mn-loaded biochar and Fe-loaded biochar have great potential for heterogeneous catalytic ozonation of polluted water.
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Nonalcoholic fermentation could improve the organoleptic quality and functionality of fruit juice, and lactic acid bacteria (LAB)-fermented fruit juice has been proven to be beneficial to human ...health. However, LAB exhibit strain specificity with different food matrices. In the present study, the effects of L. plantarum and L. acidophilus on the physicochemical characteristics, antioxidant activity and metabolomics of loquat juices were investigated. Both LAB strains fermentation could significantly enhance the antioxidant activity of loquat juice. L. acidophilus grows faster than L. plantarum in loquat juice, but L. plantarum fermentation more effectively increased the total flavonoid content. Nontargeted metabolomics analysis based on UHPLC-Q Exactive HF-X/MS were performed to reveal the different metabolic profiles between LAB fermentation. A total of 776 metabolites were identified and annotated. The significant differentially regulated metabolites were concentrated mainly in lipids and lipid-like molecules; organic acids and derivatives; amino acids, peptides, and analogs; phenolic compounds and terpenoids. The regulation of metabolites plays a very important role in the flavor reconstruction and functional improvement of loquat juices. In addition, the metabolic profiles between L. plantarum- and L. acidophilus-fermented loquat juices were different, and the application of cofermentation of these two strains may be considered in future studies.
•L. plantarum and L. acidophilus were selected to prepared functional loquat juice.•Both strains fermentation could enhance the antioxidant activity of loquat juice.•L. acidophilus grows faster than L. plantarum in loquat juice fermentation.•L. plantarum fermentation more effectively increased the total flavonoid content.•Nontargeted metabolomics were used to reveal the differences of metabolic profiles.
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