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Nitrogen oxide (NO x ) pollution presents a severe threat to the environment and human health. Catalytic reduction of NO x with H 2 using single-atom catalysts poses considerable potential in the remediation of air pollution; however, the unfavorable process of H 2 dissociation limits its practical application. Herein, we report that the in situ formation of Pt Ti cocatalytic sites (which are stabilized by Pt–Ti bonds) over Pt 1 /TiO 2 significantly increases NO x conversion by reducing the energy barrier of H 2 activation. We demonstrate that two H atoms of H 2 molecule are absorbed by adjacent Pt atoms in Pt–O and Pt–Ti, respectively, which can promote the cleave of H–H bonds. Besides, Pt Ti sites facilitate the adsorption of NO molecules and further lower the activation barrier of the whole de-NO x reaction. Extending the concept to Pt 1 /Nb 2 O 5 and Pd 1 /TiO 2 systems also sees enhanced catalytic activities, demonstrating that engineering the cocatalytic sites can be a general strategy for the design of high-efficiency catalysts that can benefit environmental sustainability.

At the end of 2019, the sudden attack of the COVID-19 brought huge challenges to the management, operation and development of listed companies. In view of the suddenness of the epidemic, the internal governance of listed companies is even more important! The index system, governance structure and performance, structure and behavior, structure and performance of the proposed hypotheses affected by the behavior of the index system, the 2019-2020 China GEM listed companies as a sample of equity concentration, and the human capital board of directors as the sample explanatory variable , Business performance, innovation performance are dependent variables, supervision and behavior, as an intermediary to encourage behavior, related test hypotheses, verify the path that Chinese companies listed in the GEM governance structure affect governance performance through behavior.

In this manuscript, ruthenium (Ru) nanoparticles functionalized with nitrene ligands through the ruthenium-nitrene (Ru N) π bonds are explored. By synthesizing the nitrene ligands with and without 15N-labelling, Ru N π bonds on Ru nanoparticles are evidenced by experimental and theoretically calculated FTIR spectra. The coordination of nitrene ligands on Ru nanoparticles surface, the interfacial charge delocalization and the impact of nitrene ligands on the catalytic performance of Ru nanoparticles are further characterized by magic-angle spinning solid-state carbon nuclear magnetic resonance spectroscopy (13C NMR) of 13CO-adsorbed Ru nanoparticles, photoluminescence and the hydrogenation of styrene.

The regulation of catalytic activity in the oxygen reduction reaction (ORR) is significant to the development of metal–air batteries and other oxygen involving energy conversion devices. Herein, we propose an atomic interface strategy to construct a single atom copper catalyst (denoted as Cu-SA/SNC) which exhibits enhanced ORR activity with a half-wave potential of 0.893 V vs. RHE in alkaline media. Moreover, synchrotron-radiation-based X-ray absorption fine structure (XAFS) investigations together with density functional theory (DFT) calculations reveal that the isolated bond-shrinking low-valence Cu (+1)–N4–C8S2 atomic interface moiety serves as an active site during the ORR process, and the synergistic mechanism between the Cu species and the carbon matrix at the atomic interface plays a critical role in boosting the ORR efficiency, by adjusting the reaction free energy of intermediate adsorption. This atomic interface concept may provide an alternative methodology for the rational design of advanced oxygen electrode materials and new probability to improve their catalytic performance.

Atomic-level insight into the unique catalytic capability of single-atom catalysts that distinguished from nanometer-sized counterparts is highly desirable for catalyst design and catalysis research. By synthesizing single Pd atoms supported on TiO2 as a catalyst, here we demonstrate a steric hindrance effect of single atoms induced by the unique isolation of single-atom active sites to achieve a remarkable enhancement on catalytic performance in the synthesis of dimethyl carbonate. Experimental results and density functional theory calculations reveal that such steric hindrance effect of single atoms favors the yield of the desired product dimethyl carbonate against further reacting with intermediates to form byproduct, because no extra Pd species around single Pd atoms provide active sites to further adsorb and activate substrates directly. The discovery of such steric hindrance effect is a valuable supplement to single-atom catalysis, and may promote single-atom catalysts to be widely applied in selective catalytic reactions.

Recently, a few in situ observations showed that reactant molecules can induce the hyper-fine surface change of catalyst under realistic conditions. However, hardly any report further illustrated that whether and how could this phenomenon affect the catalytic performance. Herein, using in situ TEM, we visually captured the reversible lattice expansion of Pt-WO3-x catalyst induced by NO in exemplified reduction of NO with H2. Results showed that the NO could adsorb on the oxygen vacancy sites and energetic favorably induced the reversible stretching of W-O-W bonds. 20% enhancement of catalytic activity was then correlated with this lattice expansion. Moreover, DFT calculations showed that the lattice expansion can reduce the adsorption energy of NO on Pt4 centers and also the energy barrier of the rate-determining step.

Development of single-site catalysts supported by ultrathin two-dimensional (2D) porous matrix with ultrahigh surface area is highly desired but also challenging. Here we report a cocoon silk chemistry strategy to synthesize isolated metal single-site catalysts embedded in ultrathin 2D porous N-doped carbon nanosheets (M-ISA/CNS, M = Fe, Co, Ni). X-ray absorption fine structure analysis and spherical aberration correction electron microscopy demonstrate an atomic dispersion of metal atoms on N-doped carbon matrix. In particular, the Co-ISA/CNS exhibit ultrahigh specific surface area (2105 m2 g−1) and high activity for C–H bond activation in the direct catalytic oxidation of benzene to phenol with hydrogen peroxide at room temperature, while the Co species in the form of phthalocyanine and metal nanoparticle show a negligible activity. Density functional theory calculations discover that the generated O = Co = O center intermediates on the single Co sites are responsible for the high activity of benzene oxidation to phenol.

The enhanced works of separation for the low adhesive (0 0 0 1)ZnO|(1 1 1)ZrO2 interfacess via Y-doping in ZnO slab were systematically studied using data-mining technique and density functional theory (DFT) study. The lattice constants in 31 types of doped wurtzite Zn0.9375X0.0625O were evaluated from DFT calculations. No linear correlation is found between the lattice constants and atomic radii. A support vector regression (SVR) for the lattice constants of 32 Zn0.9375X0.0625O has been performed. SVR method with leave-one-out cross-validation is used for evaluating the regression models. The correlation coefficient obtained by the models was 0.905. The accuracy of SVR model was higher than those of artificial neural network (ANN) and partial least square (PLS) methods. Zn0.9375Y0.0625O has the largest lattice constants among the investigated systems. In Y-ZnO(0 0 0 1) surface, a significant segregation phenomena occurs. Hence, dopant Y expands the lateral lattice and leaves the Zn-terminal surface intact. For coherent (0 0 0 1)Y-ZnO|(1 1 1)ZrO2 interfaces, Y-doping can enhance the work of separation significantly (∼82%) compared with the undoped (0 0 0 1)ZnO|(1 1 1)ZrO2 interfaces.

In-depth understanding of interfacial adhesive properties is required to access the long-term performance of substrate-film structures. The ZnO|ZrO 2 (or ZnO|YSZ) interfaces are of widely interests in experiments, however, the study on their adhesive strength is rare. Works of separation for (0 0 0 1)ZnO|(1 1 1)ZrO 2 interfaces have been investigated by using density functional calculations. Four coherent interface configurations were calculated to clarify the influence of atom termination and stacking sequence on the interfacial strength. The coherent interface model indicates that the small values for the work of separation are attributed to the large lattice mismatch between two slabs. Among the four configurations, interface model with Zr ZrO2 -O ZrO2 ⋯O ZnO B -Zn ZnO β stacking sequence has the largest work of separation, followed by the model with Zr ZrO2 -O ZrO2 ⋯Zn ZnO β -O ZnO B stacking sequence. We also construct “semicoherent interface” models to investigate the effect of strain. The Zr ZrO2 -O ZrO2 ⋯O ZnO B -Zn ZnO β sequence brings in some direct electrostatically repulsive anion-anion interactions across the interface, which causes significant distortion for the interface, especially on ZnO slab. Based on the “semicoherent interface” model with Zr ZrO2 -O ZrO2 ⋯Zn ZnO β -O ZnO B sequence, we elucidate that the interfacial adhesive strength for (0 0 0 1)ZnO|(1 1 1)ZrO 2 interface is very low.

For guidance for developing Fe/Co-Sn-based anode materials for lithium-ion batteries, the mechanical, thermodynamic and electronic properties of FeSn5 and CoSn5 intermetallic phases under pressures ranging from 0 to 30 GPa have been investigated systematically using first-principles total-energy calculations within the framework of the generalized gradient approximation. The pressure was found to have significant effects on the mechanical, thermodynamic and electronic properties of these compounds. In the selected pressure range, CoSn5 has a more negative formation enthalpy than FeSn5. Based on the calculated elastic constants, the bulk modulus, shear modulus, and Young’s modulus were determined via the Viogt-Reuss-Hill averaging scheme. The variations of specific heats at constant volume for FeSn5 and CoSn5 in a wide pressure (0 - 30 GPa) and temperature (0 - 1000 K) range are also predicted from phonon density of states calculation. The calculated results suggested that both FeSn5 and CoSn5 are mechanically stable at pressure from 0 to 30 GPa. FeSn5 is dynamically stable at pressure up to, 30 GPa, at least, however, CoSn5 is dynamically stable no higher than 15 GPa.

Purpose We evaluate the power of a next-generation sequencing-based ophthalmic targeted sequencing panel (NGS-based OTSP) as a genetics-testing tool for patients suspected of a wide range of hereditary eye diseases. Methods NGS-based OTSP encompasses 126 genes with identified mutations that account for the majority of Chinese families with hereditary eye diseases. A total of 568 probands suspected of having hereditary eye diseases underwent genetic testing by OTSP with targeted phenotype-driven analysis. Results NGS-based OTSP detected 329 potential pathogenic variants in 62 genes. These mutations might represent the genetic cause in 52% (293/568) of probands suspected of having hereditary eye diseases. Within the disease subgroups, the detection rates were 61% (124/202) for retinal degeneration disease, 53% (35/66) for eye tumors, 49% (53/108) for retinal vessel disease, 46% (13/28) for retinal detachment, 33% (19/58) for significant refractive error, 35% (16/46) for optic atrophy, 48% (11/23) for anterior segment dysgenesis, and 59% (22/37) for other hereditary eye diseases. These detection rates are comparable to those obtained in our previous study performed with whole exome sequencing. Mutations in the same gene were detected in different forms of hereditary eye diseases. The average turnaround time for OTSP is 30 days, and the average cost is 139 USD per patient. Conclusions NGS-based OTSP is a powerful tool for routine clinical genetic diagnostic testing in patients suspected of having hereditary eye diseases. Translational relevance NGS-based OTSP can be used as a routine clinical test to improve the genetic counseling and medical care of patients suspected of having hereditary eye diseases.

The mechanical, thermodynamic and electronic properties of FeSn5 and CoSn5 intermetallic phases at zero pressure have been systemically investigated by first-principles calculations using ultrasoft pseudopotential and generalized gradient approximation (GGA). The equilibrium lattice constants of FeSn5 and CoSn5 at zero pressure are in good agreement with the available experimental values. Thermodynamic and mechanical properties of FeSn5 and CoSn5 are predicted by calculating formation enthalpy, phonon density of states and elastic constants, respectively. Formation enthalpies calculation indicates that FeSn5 and CoSn5 are energetically unfavorable compare to FeSn2 and CoSn2. This may be the partial reason why FeSn5 and CoSn5 were hidden in the Fe/Co–Sn phase diagrams previously. FeSn5 and CoSn5 exhibit opposite relative incompressible behavior along a-axis and c-axis. Our results reveal that both FeSn5 and CoSn5 are mechanically and dynamically stable at 0 GPa. The quasi-harmonic model is employed to calculate the temperature dependence of specific heat at constant volume. In addition, the electron density of states and electron density difference are calculated to disclose the underlying electronic structure.

The emergence of big data technology has brought about a breakthrough change in agricultural product marketing concepts. Through analysis of agricultural product marketing channels, it has been found that the traditional single agricultural product marketing channel has hindered the development of the agricultural product market, and there are still intermediate links in the diverse marketing channels. There are many problems, such as lack of brand awareness. Therefore, the Internet, big data technology and artificial intelligence technology are needed to promote the diversified development of agricultural product marketing subjects, agricultural product wholesale markets, agricultural product transaction methods, agricultural product logistics and agricultural product brand building.

Noble metals play a momentous role in heterogeneous catalysis but still face a huge challenge in selectivity control. Herein, we report isolating contiguous Pt atoms and forming Pt-Zn intermetallic nanoparticles as an effective strategy to optimize the selectivity of Pt catalysts. Contiguous Pt atoms are isolated into single atoms and Pt-Zn intermetallic nanoparticles are formed which are supported on hollow nitrogen-doped carbon nanotubes (PtZn/HNCNT), as confirmed by aberration-corrected high-resolution transmission electron microscopy and X-ray absorption spectrometry measurements. Interestingly, this PtZn/HNCNT catalyst promotes the hydrogenation of 4-nitrophenylacetylene to 4-aminophenylacetylene with a much higher conversion ( > 99%) and selectivity (99%) than the comparison samples with Pt isolated-single-atomic-sites (Pt/HNCNT) and Pt nanoparticles (Pt/CN). Further density functional theory (DFT) calculations disclose that the positive Zn atoms assist the adsorption of nitro group and Pt-Zn intermetallic nanoparticles facilitate the hydrogenation on nitro group kinetically., Noble metals play a momentous role in heterogeneous catalysis but still face a huge challenge in selectivity control. Herein, the authors demonstrate that isolating contiguous Pt atoms and forming Pt-Zn intermetallic nanoparticles is an effective strategy to optimize the selectivity of Pt catalysts.

The structural, electronic and optical properties of hexagonal ferrites MFe 12 O 19 (M = Sr, Ba, Pb, Sr 0.5 Ba 0.5 , Sr 0.5 Pb 0.5 and Ba 0.5 Pb 0.5 ) are calculated by plane-wave pseudopotential density functional theory with general gradient approximation (GGA) and GGA+ U . The calculated lattice constants and band gaps are in good agreement with the available experimental and theoretical values. Lattice constants change corresponding to the cation radii at M-sites. The electronic structure shows that all the six hexaferrites are narrow gap semiconductors and Sr 2+ and Ba 2+ at M-sites have little contribution to the DOS at the vicinity of Fermi level due to the ionic bond interaction nature between M 2+ and O 2− . It should be noted that for Pb 2+ , comparing with the narrow localized s-states of Sr 2+ and Ba 2+ , there is a significant broadening of its s -states from −7 eV to the Fermi level, indicating its minority donation to the valence band near E f . The six MFOs (FO refers Fe 12 O 19 ) could be classified into two categories: Pb-containing hexaferrites (PFO, SPFO and BPFO) and others (SFO, BFO and SBFO). The former has larger static dielectric constants. This study will serve as the base for the investigation of the correlation among factors such as site preferences, properties and substitution strategies for MFOs.

To discuss the protection mechanism of DNA from radiation as well as assess the performance of PM6-DH2 on noncovalent interactions, the interaction of four nucleic acid bases (NABs) such as adenine (A), cytosine (C), guanine (G), and thymine (T), with Li@C(60) was extensively investigated with the-state-of-art theoretical methods describing noncovalent systems, like M06-2x, PBE-D, and PM6-DH2 methods. In the gas phase, the binding strength of NABs to Li@C(60) from M06-2x decreases in the sequence, GCAT. As dispersion was explicitly included, PBE-D relatively enhances the binding of A and T and corrects the sequence to, GAC∼T. PM6-DH2 predicted similar binding energies to those from PBE-D within 0.5 kcal/mol and the same binding sequence, suggesting that the PM6-DH2 method is promising for nano-scale systems. In the aqueous solution, binding of NABs-Li@C(60) is considerably decreased, and the M06-2X and PM6-D methods yield a different sequence from the gas phase, GATC. The encapsulation of Li atom results in a lower IP for Li@C(60) than those of NABs, and the dominant localization of single-occupied molecular orbital on Li@C(60) moiety of the complexes NABs-Li@C(60) further indicates that an electron would be ejected from Li@C(60) upon radiation and Li@C(60) is therefore able to protect DNA bases from radiation. In addition, it was revealed that Li prefers coordination with the hexagonal ring at Li@C(60) , which clarifies the existing controversy in this respect. Finally, Yang's reduced density gradient approach clearly shows that the weak and strong noncovalent interaction regions in the complexes, NABs-Li@C(60) and (NABs-Li@C(60) )(+).

The major objective of this paper is to address a controversial binding sequence between nucleic acid bases (NABs) and C60 by investigating adsorptions of NABs and their cations on C60 fullerene with a variety of density functional theories including two novel hybrid meta-GGA functionals, M05-2x and M06-2x, as well as a dispersion-corrected density functional, PBE-D. The M05-2x/6-311++G** provides the same binding sequence as previously reported, guanine(G) > cytosine(C) > adenine (A) > thymine (T); however, M06-2x switches the binding strengths of A and C, and PBE-D eventually results in the following sequence, G>A>T>C, which is the same as the widely accepted hierarchy for the stacking of NABs on other carbon nanomaterials such as single-walled carbon nanotube and graphite. The results indicate that the questionable relative binding strength is due to insufficient electron correlation treatment with the M05-2x or even the M06-2x method. The binding energy of G@C60 obtained with the M06-2x/6-311++G(d,p) and the PBE-D/cc-pVDZ is −7.10 and −8.07 kcal/mol, respectively, and the latter is only slightly weaker than that predicted by the MP2/6-31G(d,p) (−8.10kca/mol). Thus, the PDE-D performs better than the M06-2x for the observed NAB@C60 π-stacked complexes. To discuss whether C60 could prevent NABs from radiation-induced damage, ionization potentials of NABs and C60, and frontier molecular orbitals of the complexes NABs@C60 and (NABs@C60)+ are also extensively investigated. These results revealed that when an electron escapes from the complexes, a hole was preferentially created in C60 for T and C complexes, while for G and A the hole delocalizes over the entire complex, rather than a localization on the C60 moiety. The interesting finding might open a new strategy for protecting DNA from radiation-induced damage and offer a new idea for designing C60-based antiradiation drugs.

This paper proposes an economical resource management model based on QoS constraint, analyzed the significance of introducing QoS and SLA, and discussed the relationship between QoS and SLA management. Finally, the paper realized the mapping of QoS from application layer to resources layer through SLA negotiation, and implemented the optimal allocation of virtual machine resources by using the minimal strategy.

The interaction of molecules with inorganic substrates is a crucial issue forapplications in molecular electronics. It influences important factors suchas the immobilization efficiency and the charge injection through the inter-face. Moreover, mechanical aspects connected to the unfolding of biologicalmolecules are important.We hereby present recent efforts in our group to tackle these problems,based on density functional theory calculations. In particular, we discussour results on the adsorption of cytosine on Au(111) and on the interactionof guanine, in its natural and size-expanded forms, with small Au clusters.We find that cytosine binds to the Au(111) surface with a mechanism thatinvolves charge sharing, intermediate between chemisorption and physisorp-tion. The investigation of small complexes between guanine and gold clustersreveals the formation of hydrogen bonds: these configurations with unusualbonds are relevant at the corners of nanoparticles, while they can probably beneglected when DNA binds on flat extended metal surfaces.

The adsorptions of a glycine molecule as well as dehydrogenated radicals on the side walls of both intrinsic and boron-doped (B-doped) single-walled (8,0) carbon nanotubes (SWCNTs) were investigated by a density functional theory. A glycine molecule tends to physically adsorb on intrinsic SWCNT, yet chemically adsorb on B-doped SWCNT as a result of a somewhat chemical bond between the electron-rich nitrogen atom of the glycine molecule and the electron-scarce boron atom of the doped SWCNT. Opposite to the previous report (J. Phys. Chem. B 2006, 110, 6048-6050), it is found in the present study that both the N-centered and C-centered glycine radicals can form quite stable complexes with intrinsic as well as B-doped (8, 0) SWCNTs. When the B-doped SWCNT interacts with glycine radicals, although there is a competition between B and the neighbor C in the nanotube axis direction, glycine radicals preferentially bind to the C site. The encapsulations of a glycine molecule into SWCNTs with various diameters are also discussed. We find that the encapsulation process is endothermic for (8, 0) and (9, 0) SWCNTs, while it is exothermic for (10,0) SWCNT, indicating that the critical diameter of the zigzag SWCNT for the encapsulation is 7.83 Å, the diameter of (10,0).