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Deming Xia

Bio: Deming Xia is an academic researcher from Dalian University of Technology. The author has contributed to research in topics: Medicine & Hydrogen bond. The author has an hindex of 5, co-authored 12 publications receiving 123 citations.

Papers
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Journal ArticleDOI
TL;DR: It is revealed for the first time that water has a negative role in the ·OH-initiated degradation of TCPP by modifying the stabilities of prereactive complexes and transition states via forming hydrogen bonds, which unveils one underlying mechanism for the observed persistence ofTCP in the atmosphere.
Abstract: Tris(2-chloroisopropyl) phosphate (TCPP), a widely used organophosphate flame retardant, has been recognized as an important atmospheric pollutant. It is notable that TCPP has potential for long-range atmospheric transport. However, its atmospheric fate is unknown, restricting its environmental risk assessment. Herein we performed quantum chemical calculations to investigate the atmospheric transformation mechanisms and kinetics of TCPP initiated by ·OH in the presence of O2/NO/NO2, and the effects of ubiquitous water on these reactions. Results show the H-abstraction pathways are the most favorable for the titled reaction. The calculated gaseous rate constant and lifetime at 298 K are 1.7 × 10–10 cm3molecule–1 s–1 and 1.7 h, respectively. However, when considering atmospheric water, the corresponding lifetime is about 0.5–20.2 days. This study reveals for the first time that water has a negative role in the ·OH-initiated degradation of TCPP by modifying the stabilities of prereactive complexes and transi...

72 citations

Journal ArticleDOI
TL;DR: Qualitative structure-activity relationship models were developed that can differentiate PAEs with the departure of the leaving group as the rate-determining step in the hydrolysis and estimate kB values, which provides a promising way to predict hydrolytic kinetics of PAEs.
Abstract: Many phthalate esters (PAEs) are chemicals of high production volume and of toxicological concern. The second-order rate constant for base-catalyzed hydrolysis (kB) is a key parameter for assessing environmental persistence of PAEs. However, the kB values for most PAEs are lacking, and the experimental determination of kB encounters various difficulties. Herein, density functional theory (DFT) methods were selected by comparing empirical kB values of five PAEs and five carboxylic acid esters with the DFT-calculated ones. Results indicate that PAEs with cyclic side chains are more vulnerable to base-catalyzed hydrolysis than PAEs with linear alkyl side chains, followed by PAEs with branched alkyl side chains. By combining experimental and DFT-calculated second-order rate constants for base-catalyzed hydrolysis of one side chain in PAEs (kB_side chain), quantitative structure–activity relationship models were developed. The models can differentiate PAEs with the departure of the leaving group (or the nucleo...

32 citations

Journal ArticleDOI
TL;DR: Two models for predicting logK were developed with multiple linear regression (MLR) and support vector machine (SVM) algorithms that have satisfactory goodness-of-fit, robustness and predictive ability and performs slightly better than the MLR model.

31 citations

Journal ArticleDOI
TL;DR: An accelerated solvent extraction with in-cell clean-up method coupled to ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was developed and offered comparable extraction efficiency for sulfonamides from sea cucumber, but higher for other categories of antibiotics.

25 citations

Journal ArticleDOI
TL;DR: In this article, a semi-empirical quantum chemical (QC) method was selected to calculate pKa of the parabens, and density functional theory (DFT) was used to calculate second-order base-catalyzed hydrolysis kinetics (kB) values.
Abstract: Parabens for which the molecules contain hydrolytic and ionizable groups, are emerging pollutants due to their ubiquity in the environment However, lack of pKa and second-order base-catalyzed hydrolysis kinetics (kB) values limits their environmental persistence assessment Herein, six parabens were selected as reference compounds for which the pKa and kB values were measured experimentally A semiempirical quantum chemical (QC) method was selected to calculate pKa of the parabens, and density functional theory (DFT) methods were selected to calculate kB for neutral and anionic forms of the parabens, by comparing the QC-calculated and determined values Combining the QC-calculated and experimental pKa and kB values, quantitative structure-activity relationships with determination coefficients (R2) being 0947 and 0842 for the pKa and kB models, respectively, were developed, which were validated and could be employed to efficiently fill the kB and pKa data gaps of parabens within applicability domains The base-catalyzed hydrolysis half-lives were estimated to range from 6 h to 152 × 106 years (pH 7-9, 25 °C), further necessitating the in silico models due to the tedious and onerous experimental determination, and the huge number of hydrolyzable and ionizable chemicals that may be released into the environment

17 citations


Cited by
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01 Feb 1995
TL;DR: In this paper, the unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio using DFT, MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set.
Abstract: : The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

1,652 citations

Journal ArticleDOI
TL;DR: In this paper, the types and structures of organic pollutants, and the classes of nanomaterials and their application for the remediation of organic contaminants in water are systematically summarized.

339 citations

Posted Content
TL;DR: The projector augmented wave (PAW) method as mentioned in this paper is an all-electron method for efficient ab-initio molecular dynamics simulations with the full wave functions, which extends and combines the traditions of existing augmented wave methods and the pseudopotential approach.
Abstract: A brief introduction to the projector augmented wave method is given and recent developments are reviewed. The projector augmented wave method is an all-electron method for efficient ab-initio molecular dynamics simulations with the full wave functions. It extends and combines the traditions of existing augmented wave methods and the pseudopotential approach. Without sacrificing efficiency, the PAW method avoids transferability problems of the pseudopotential approach and it has been valuable to predict properties that depend on the full wave functions.

275 citations

Journal ArticleDOI
TL;DR: It is hoped that the joint efforts of the scientific community and political circles will lead to the formation of a unified standard for the extraction and analysis of antibiotics in food, so as to allow comprehensive monitoring of residual antibiotics and ensure human health.
Abstract: The abundant use of antibiotics leads to antibiotic residues in frequently consumed foods. Residual antibiotics in food may have adverse effects on humans by directly causing disease via low-dose exposure and indirect harm via antibiotic resistance. However, the current methods for antibiotic extraction and analysis in food have not yet formed a uniform standard, and only a few data exist regarding the residual antibiotic condition in various types of foods. Hence, we review the literature since 2008 to summarize analytical methods and residue status of antibiotics in food. Then, we discuss the causes of antibiotic residues in food and the possible hazards to human health. We hope that the joint efforts of the scientific community and political circles will lead to the formation of a unified standard for the extraction and analysis of antibiotics in food, to allow for comprehensive monitoring of residual antibiotics and ensure human health.

210 citations

Journal ArticleDOI
TL;DR: In this review, a comprehensive survey on progress in fast sample preparation techniques for complex sample in the last 2 years has been composed from more than 180 references, including field-assisted, materials-based rapid mass transfer, microfluidic, and multistep integration techniques.
Abstract: Sample preparation is a critical step in complex sample analysis which effect to sensitivity, selectivity, speed, and accuracy of analytical results. The goal of sample preparation is separation and enrichment. Separation and enrichment are entropy reduction procedures which cannot happen spontaneously. On account of consuming over two thirds of analysis time, sample preparation becomes the bottleneck issue in analytical chemistry. Therefore, fast sample preparation has been received much attention. In this review, a comprehensive survey on progress in fast sample preparation techniques for complex sample in the last 2 years has been composed from more than 180 references. Four approaches for entropy reduction of sample preparation system were generalized, they are energy exchange acceleration, materials-based acceleration, size reduction acceleration, and integration acceleration. Moreover, we highlight the most interesting acceleration techniques, including field-assisted, materials-based rapid mass tra...

86 citations