Trophic Transfer of Halogenated Organic Pollutants in a Wetland Food Web: Insights from Compound-Specific Nitrogen Isotope of Amino Acids and Food Source Analysis.

A trophic position (TP) model (TPmix model) that simultaneously considered trophic discrimination factor and ßGlu/Phe variations was developed in this study and was first applied to investigate the trophic transfer of halogenated organic pollutants (HOPs) in wetland food webs. The TPmix model characterized the structure of the wetland food web more accurately and significantly improved the reliability of TMF compared to the TPbulk, TPAAs, and TPsimmr models, which were calculated based on the methods of stable nitrogen isotope analysis of bulk, traditional AAs-N-CSIA, and weighted ßGlu/Phe, respectively. Food source analysis revealed three interlocking food webs (kingfisher, crab, and frogs) in this wetland. The highest HOP biomagnification capacities (TMFmix) were found in the kingfisher food web (0.24-82.0), followed by the frog (0.08-34.0) and crab (0.56-11.7) food webs. The parabolic trends of TMFmix across combinations of log KOW in the frog food web were distinct from those of aquatic food webs (kingfisher and crab), which may be related to differences in food web composition and HOP bioaccumulation behaviors between aquatic and terrestrial organisms. This study provides a new tool to accurately study the trophic transfer of contaminants in wetlands and terrestrial food webs with diverse species and complex feeding relationships.

Accurate van der Waals force field for gas adsorption in porous materials.

An accurate van der Waals force field (VDW FF) was derived from highly precise quantum mechanical (QM) calculations. Small molecular clusters were used to explore van der Waals interactions between gas molecules and porous materials. The parameters of the accurate van der Waals force field were determined by QM calculations. To validate the force field, the prediction results from the VDW FF were compared with standard FFs, such as UFF, Dreiding, Pcff, and Compass. The results from the VDW FF were in excellent agreement with the experimental measurements. This force field can be applied to the prediction of the gas density (H2 , CO2 , C2 H4 , CH4 , N2 , O2 ) and adsorption performance inside porous materials, such as covalent organic frameworks (COFs), zeolites and metal organic frameworks (MOFs), consisting of H, B, N, C, O, S, Si, Al, Zn, Mg, Ni, and Co. This work provides a solid basis for studying gas adsorption in porous materials. © 2017 Wiley Periodicals, Inc.

Multi-pathway exposure assessment of organophosphate flame retardants in a southern Chinese population: Main route identification with compound-specificity.

In this study, we conducted comprehensive organophosphorus flame retardant (PFR) exposure assessments of both dietary and non-dietary pathways in a rural population in southern China. Skin wipes were collected from 30 volunteers. Indoor and outdoor air (gas and particles), dust in the houses of these volunteers, and foodstuffs consumed by these volunteers were simultaneously collected. The total PFR concentrations in dust, gas, and PM2.5 varied from 53.8 to 5.14 × 105 ng/g, 0.528 to 4.27 ng/m3, and 0.390 to 16.5 ng/m3, respectively. The forehead (median of 1.36 × 103 ng/m2) and hand (median of 920 ng/m2) exhibited relatively high PFR concentrations, followed by the forearm (median of 440 ng/m2) and upper arm (median of 230 ng/m2). The PFR concentrations in the food samples varied from 0.0700 to 10.9 ng/g wet weight in the order of egg > roast duck/goose and vegetable > pork > chicken > fish. Tris(1-chloro-isopropyl) phosphate (TCPP) was the main PFR in the non-diet samples, whereas the profiles of PFR individuals varied by food type. Among the multiple pathways investigated (inhalation, dermal exposure, dust ingestion, and food ingestion), dermal absorption and dust ingestion were the predominant pathways for tris(2-chloroethyl) phosphate (TCEP) and bisphenol A-bis(diphenyl phosphate) (BDP), respectively, whereas dietary exposure was the most important route for other chemicals.

Dissociation and ionization competing processes for H2+ in intense laser field: which one is larger?

Competition between dissociation and ionization of H(2)(+) in intense laser field has been investigated by using an accurate three-dimensional time-dependent wavepacket approach. The disagreement between the experiment and the former one-dimensional theory has been resolved. In a comparison of the calculated results with the available experimental data, a good agreement is reached, not only for the relative probabilities between dissociation and ionization but also for the two-peak structures and the peak energy locations for these two processes.

Quenching of OH(A(2)Sigma(+)) by H(2) through conical intersections: highly excited products in nonreactive channel.

Nonadiabatic quantum scattering calculations have been carried out for the reactive and nonreactive quenching of OH(A(2)Sigma(+)) in collisions with molecular H(2) on two new potential energy surfaces of the 1A' and 2A' states. Integral cross sections of the reactive and nonreactive quenching channels and the quantum state distributions of the nonreactive channel have been obtained. The theory reveals a high degree of rotational excitation of the quenched OH(X(2)II) products and vibrational excitation of the H(2) products. The calculated results are in good agreement with the existing experimental data. The topography of the potential energy surfaces in the conical intersection regions is provided in order to discuss the origin of the internal excitations of nonreactive products and the branching of the reactive and nonreactive channels.

Nonadiabatic quantum reactive scattering of the OH(A 2Σ+) + D2.

The seams of conical intersection exist between the ground (1 (2)A(')) and the first-excited (2 (2)A(')) electronic potential energy surfaces (PESs) of OH(A (2)Σ(+),X (2)Π) + H(2) system. This intersection induces the nonadiabatic quenching of OH(A (2)Σ(+)) by D(2). We present nonadiabatic quantum dynamics study for OH(A (2)Σ(+)) + D(2) on new five-dimensional coplanar PESs. The ab initio calculations of PESs are based on multireference configuration interaction (MRCI)/aug-cc-pVQZ level. A back-propagation neural network is utilized to fit the PESs and nonadiabatic coupling. High degrees of rotational excitation of quenched OH(X (2)Π) products are found in nonreactive quenching channel, and the quenched D(2) products are vibrationally excited up to quantum number v(2) (')=8. The theoretical results of nonadiabatic time-dependent wave-packet calculation are in good agreement with the existing experimental data.

Improved organic hydrogen carriers with superior thermodynamic properties.

By the incorporation of N atoms into naphthalene, we present a theoretical investigation to seek for improved organic hydrogen carriers with an explicit guideline, the release of H2 is found to be greatly favored thermodynamically and the corresponding cycloalkanes possess high hydrogen storage capacity, this offers extensive candidates for practical applications of the promising hydrogen energy.

Attosecond-resolution quantum dynamics calculations for atoms and molecules in strong laser fields.

A parallel quantum electron and nuclei wave packet computer code, LZH-DICP, has been developed to study laser-atom-molecule interaction in the nonperturbative regime with attosecond resolution. The nonlinear phenomena occurring in that regime can be studied with the code in a rigorous way by numerically solving the time-dependent Schrödinger equation of electrons and nuclei. Time propagation of the wave functions is performed using a split-operator approach, and based on a sine discrete variable representation. Photoelectron spectra for hydrogen and kinetic-energy spectra for molecular hydrogen ion in linearly polarized laser fields are calculated using a flux operator scheme, which testifies to the validity and the high efficiency of LZH-DICP.

(C6H5C2H4NH3)2GeI4: A Layered Two-Dimensional Perovskite with Potential for Photovoltaic Applications.

Recently, two-dimensional organic-inorganic perovskites have attracted increasing attention due to their unique photophysical properties and high stability. Here we report a lead-free, two-dimensional perovskite, (PEA)2GeI4 (PEA = C6H5(CH2)2NH3+). Structural characterization demonstrated that this 2D perovskite structure is formed with inorganic germanium iodide planes separated by organic PEAI layers. (PEA)2GeI4 has a direct band gap of 2.12 eV, in agreement with 2.17 eV obtained by density functional theory (DFT) calculations, implying that it is suitable for a tandem solar cell. (PEA)2GeI4 luminesces at room-temperature with a moderate lifetime, exhibiting good potential for photovoltaic applications. In addition, 2D (PEA)2GeI4 is more stable than 3D CH3NH3GeI3 in air, owing to the presence of a hydrophobic organic long chain. This work provides a direction for the development of 2D Ge-based perovskites with potential for photovoltaic applications.

Facile synthesis of tin phosphite nanosheets via exfoliated bulk crystals: Electronic structure and piezoelectric property.

Tin phosphite nanosheets were synthesized by a facile exfoliation method. SnHPO3 nanosheets with a thickness of ∼2.6nm readily form a stable colloidal suspension in ethanol using ultrasonic method. Structures and optical properties of the obtained nanosheets were investigated. The prepared SnHPO3 nanosheets exhibit an obvious blue-shift in UV absorbance compared with bulk SnHPO3 crystal materials. Moreover, the piezoelectric coefficients of SnHPO3 monolayer were calculated based on density functional theory, which are larger than that of h-BN monolayer, indicating this material could be a good candidate for designing electro-optical nano-devices.

Polygonatum odoratum lectin induces apoptosis and autophagy via targeting EGFR-mediated Ras-Raf-MEK-ERK pathway in human MCF-7 breast cancer cells.

Polygonatum odoratum lectin (POL), a mannose-binding GNA-related lectin, has been reported to display remarkable anti-proliferative and apoptosis-inducing activities toward a variety of cancer cells; however, the precise molecular mechanisms by which POL induces cancer cell death are still elusive. In the current study, we found that POL could induce both apoptosis and autophagy in human MCF-7 breast cancer cells. Subsequently, we found that POL induced MCF-7 cell apoptosis via the mitochondrial pathway. Additionally, we also found that POL induces MCF-7 cell apoptosis via EGFR-mediated Ras-Raf-MEK-ERK pathway, suggesting that POL may be a potential EGFR inhibitor. Finally, we used proteomics analyses for exploring more possible POL-induced pathways with EGFR, Ras, Raf, MEK and ERK, some of which were consistent with our in silico network prediction. Taken together, these results demonstrate that POL induces MCF-7 cell apoptosis and autophagy via targeting EGFR-mediated Ras-Raf-MEK-ERK signaling pathway, which would provide a new clue for exploiting POL as a potential anti-neoplastic drug for future cancer therapy.

Theoretical study of CO oxidation on cationic, neutral, and anionic AuM dimers (M = Pd and Ag).

The CO and O2 adsorption as well as CO oxidation on cationic, neutral, and anionic AuM dimers (M = Pd, Ag) are studied by density functional calculations. Our results show that CO and O2 are adsorbed more stably on AuPd dimers than on AuAg dimers with corresponding charge state. O2 is favorable to be adsorbed on Pd atom in AuPd(+), AuPd and AuPd(-) dimers. CO is adsorbed on Pd in AuPd and AuPd(-), while it is favorable to be adsorbed on Au in AuPd(+). For AuAg dimers, O2 is adsorbed on Ag in AuAg and AuAg(-), and it is adsorbed on Au in AuAg(+). CO is adsorbed on Ag in AuPd(-), while it is adsorbed on Au in AuAg and AuAg(+). The CO oxidation reaction is explored along two possible pathways: path-1 involves CO attacking the initial complexes of AuM dimers and O2, and path-2 is related to O2 interacting with the complexes of AuM dimers and CO. The charge state of AuM dimers has a substantial effect on CO oxidation. The reaction on AuPd(-) prefers path-1, and AuPd(+) mediated reaction proceeds along path-2, while CO oxidation on AuPd is difficult along both paths. For AuAg, both pathways are viable for AuAg(-) mediated reactions, while AuAg and AuAg(+) mediated reactions prefer path-2. Moreover, the energy barriers of CO oxidation on neutral AuAg is comparable with those on AuPd in all charge states while the energy barriers for AuAg(-) and AuAg(+) are considerably lower than those for all AuPd dimmers, indicating the impurity atom also plays a significant role in the catalytic activity. Furthermore, AuAg(-) is proposed to be the most active species due to the lowest barrier involved in the reaction.

Full six-dimensional nonadiabatic quantum dynamics calculation for the energy pooling reaction O(2)(a (1)Delta)+O(2)(a (1)Delta)-->O(2)(b (1)Sigma)+O(2)(X (3)Sigma).

Six new potential energy surfaces of four singlet states and two triplet states for the title oxygen molecule reaction along with the spin-orbit coupling among them have been constructed from the complete active space second-order perturbation theory with a 6-311+G(d) basis. Accurate integral cross sections are calculated with a full six-dimensional nonadiabatic time-dependent quantum wave packet method. The thermal rate constant based on the integral cross sections agrees well with the result of the experimental measurements, and the intersystem crossing effects are also discussed in this electronic energy-transfer process.

Spin-orbit effect in the energy pooling reaction O2(a 1Delta)+O2(a 1Delta)-->O2(b 1Sigma)+O2(X 3Sigma).

Five-dimensional nonadiabatic quantum dynamics studies have been carried out on two new potential energy surfaces of S(2)((1)A(')) and T(7)((3)A(")) states for the title oxygen molecules collision with coplanar configurations, along with the spin-orbit coupling between them. The ab initio calculations are based on complete active state second-order perturbation theory with the 6-31+G(d) basis set. The calculated spin-orbit induced transition probability as a function of collision energy is found to be very small for this energy pooling reaction. The rate constant obtained from a uniform J-shifting approach is compared with the existing theoretical and experimental data, and the spin-orbit effect is also discussed in this electronic energy-transfer process.

Nonadiabatic effects in the H+D2 reaction.

The state-to-state dynamics of the H+D2 reaction is studied by the reactant-product decoupling method using the double many-body expansion potential energy surface. Two approaches are compared: one uses only the lowest adiabatic sheet while the other employs both coupled diabatic sheets. Rotational distributions for the reaction H+D2 (upsilon = 0, j = 0)-->HD(upsilon' = 3, j')+D are obtained at eight different collision energies between 1.49 and 1.85 eV; no significant difference are found between the two approaches. Initial state-selected total reaction probabilities and integral cross sections are also given for energies ranging from 0.25 up to 2.0 eV with extremely small differences being observed between the two sets of results, thus showing that the nonadiabatic effects in the title reaction are negligible at least for small energies below 2.0 eV.

Quantum wave packet study of the H+ + D2 reaction on diabatic potential energy surfaces.

The exact three-dimensional nonadiabatic quantum dynamics calculations were carried out for the title reaction by a time-dependent wave packet approach based on a newly constructed diabatic potential energy surface (Kamisaka et al. J. Chem. Phys. 2002, 116, 654). Three processes including those of reactive charge transfer, nonreactive charge transfer, and reactive noncharge transfer were investigated to determine the initial state-resolved probabilities and reactive cross sections. The results show that a large number of resonances can be observed in the calculated probabilities due to the deep well on adiabatic ground surface and the dominant process is the reactive noncharge-transfer process. Some interesting dynamical features such as v-dependent and j-dependent behaviors of the probabilities are also revealed. In addition, a good agreement has been achieved in the comparison between the calculated quantum cross sections from the ground rovibrational initial state and the experimental measurement data.

A time-dependent wave-packet quantum scattering study of the reaction H2+(v = 0-2,4,6;j = 1) + He--> HeH+ + H.

The quantum scattering dynamics calculation was carried out for the titled reaction in the collision energy range of 0.0-2.4 eV with reactant H(2) (+) in the rotational state j = 1 and vibrational states v = 0-2, 4, and 6. The present time-dependent wave-packet calculation takes into account the Coriolis coupling (CC) and uses the accurate ab initio potential-energy surface of Palmieri et al. [Mol. Phys. 98, 1835 (2000)]. The importance of including the CC quantum scattering calculation has been revealed by the comparison between the CC calculation and the previous coupled state (CS) calculation. The CC total cross sections for the v = 2, 4, and 6 states show collision energy-dependent behaviors different from those based on the CS calculation. Furthermore, the collision energy dependence of the total cross sections obtained in the present CC calculation only exhibits minor oscillations, indicating that the chance is slim for reactive resonances in total cross sections to survive through the partial-wave averaging. The magnitude and profile of the CC total cross sections for v = 0-2 in the collision energy range of 0.0-2.5 eV are found to be consistent with experimental cross sections obtained recently by Tang et al. [J. Chem. Phys. 122, 164301 (2005)] after taking into account the experimental uncertainties.