Measurements of All-Particle Energy Spectrum and Mean Logarithmic Mass of Cosmic Rays from 0.3 to 30 PeV with LHAASO-KM2A

We present the measurements of all-particle energy spectrum and mean logarithmic mass of cosmic rays in the energy range of 0.3-30 PeV using data collected from LHAASO-KM2A between September 2021 and December 2022, which is based on a nearly composition-independent energy reconstruction method, achieving unprecedented accuracy. Our analysis reveals the position of the knee at 3.67±0.05±0.15  PeV. Below the knee, the spectral index is found to be -2.7413±0.0004±0.0050, while above the knee, it is -3.128±0.005±0.027, with the sharpness of the transition measured with a statistical error of 2%. The mean logarithmic mass of cosmic rays is almost heavier than helium in the whole measured energy range. It decreases from 1.7 at 0.3 PeV to 1.3 at 3 PeV, representing a 24% decline following a power law with an index of -0.1200±0.0003±0.0341. This is equivalent to an increase in abundance of light components. Above the knee, the mean logarithmic mass exhibits a power law trend towards heavier components, which is reversal to the behavior observed in the all-particle energy spectrum. Additionally, the knee position and the change in power-law index are approximately the same. These findings suggest that the knee observed in the all-particle spectrum corresponds to the knee of the light component, rather than the medium-heavy components.

To What Extent Do Iodomethane and Bromomethane Undergo Analogous Reactions?

Iodomethane and bromomethane (CH3I/CH3Br) are common chemicals, but their chemistry on nanometals is not fully understood. Here, we analyze the reactivity of Rhn+ (n = 3-30) clusters with halomethanes and unveil the spin effect and concentration dependence in the C-H and C-X bond activation. It is found that the reactions under halomethane-rich conditions differ from those under metal-rich conditions. Both CH3I and CH3Br undergo similar dehydrogenation on the Rhn+ clusters in the presence of small quantity reactants; however, different reactions are observed in the presence of sufficient CH3I/CH3Br, showing dominant Rh(CH3Br)x+ (x = 1-4) products but a series of RhnCxHyIz+ species (x = 1-4, y = 1-12, and z = 1-5) pertaining to H2, HI, or CH4 removal. Density functional theory calculations reveal that the dehydrogenation and demethanation of CH3Br are relatively less exothermic and will be deactivated by sufficient gas collisions if helium cooling takes away energy immediately; instead, the successive adsorption of CH3Br gives rise to a series of Rh(CH3Br)x+ species with accidental C-Br bond dissociation.

Investigation of Pb-B Bonding in PbB2(BO)n- (n = 0-2): Transformation from Aromatic PbB2- to Pb[B2(BO)2]-/0 Complexes with BB Triple Bonds

Boron has been found to be able to form multiple bonds with lead. To probe Pb-B bonding, here we report an investigation of three Pb-doped boron clusters, PbB2-, PbB3O-, and PbB4O2-, which are produced by a laser ablation cluster source and characterized by photoelectron spectroscopy and ab initio calculations. The most stable structures of PbB2-, PbB3O-, and PbB4O2- are found to follow the formula, [PbB2(BO)n]- (n = 0-2), with zero, one, and two boronyl ligands coordinated to a triangular and aromatic PbB2 core, respectively. The PbB2- cluster contains a BB double bond and two Pb-B single bonds. The coordination of BO is observed to weaken Pb-B bonding but strengthen the BB bond in [PbB2(BO)n]- (n = 1, 2). The anionic [PbB2(BO)2]- and its corresponding neutral closed-shell [PbB2(BO)2] contain a BB triple bond. A low-lying Y-shaped isomer is also observed for PbB4O2-, consisting of a central sp2 hybridized B atom bonded to two boronyl ligands and a PbB unit.

Bifunctional diatomic site catalysts supported by β12-borophene for efficient oxygen evolution and reduction reactions

Efficient bifunctional catalysts for oxygen evolution and reduction reactions (OERs/ORRs) are of great importance for sustainable and renewable clean energy, especially for metal-air batteries. Herein, we investigated β12-borophene with double-hole sites capped with 3d transition metal atoms to explore its catalyst performance for hydrogen evolution reactions (HERs), OERs and ORRs. It was found that the borophene is a good platform for diatomic site catalysts (DASCs) due to their advantage of stability over the corresponding single-atom catalysts (SACs) or clusters. The HER performance of DASCs on β12-BM was further improved compared to the SAC case. Furthermore, the supported FeNi DASC exhibited good catalytic performance for both OERs and ORRs, the overpotentials for which were 0.43 and 0.55 V, respectively, better than those of the corresponding supported Ni or Fe SAC due to synergistic effects. We herein propose a novel descriptor involving the Bader charges of coordinated atoms explicitly, behaving much better than the d-band center and integrated crystal orbital Hamilton population (-ICOHP) for DASCs. The synergistic effect of Fe-Ni pairs balanced the too strong binding of OH and further activated OH to achieve better catalytic performance. The results of this study can provide theoretical guidance for the design of efficient bifunctional electrocatalysts.

[(OB)2-M©B7O7-BO]- (M = Mn, Tc, Re): Chemically Stable and Triply Aromatic Ballet Rotors

Single-molecule nanorotors are generally constructed based on boron atoms to obtain structural fluxionality via possessing the delocalized multicenter bonds. However, the electron-deficient boron atoms are commonly exposed in these nanorotors, which leads to extremely high chemical reactivity, which blocks the synthesis in the condensed phase. In this work, we computationally designed a series of transition-metal-doped boron oxide clusters MB10O10- (in structural configuration of [(OB)2-M©B7O7-BO]-, M = Mn, Tc, Re, © means "centered" in a planar or quasi-planar hypercoordinate environment), which can be vividly named as "ballet rotors" to label their anthropomorphic dynamic rotational behaviors. The rotational fluxionality in ballet rotors originates from the completely delocalized nature of the bonding within their MB10 core moieties. Remarkably, compared with single-molecule nanorotors having bare boron atoms and the narrow HOMO-LUMO gaps (≤4.00 eV) as well as low vertical detachment energies (VDEs, ≤4.46 eV for anions), the ballet rotors possess significantly improved chemical stability, as evidenced sterically by the absence of exposed boron atoms and electronically by much wider HOMO-LUMO gaps (5.66-5.98 eV) as well as obviously higher VDEs between 5.36 and 5.47 eV. Specifically, the ballet rotors are mainly stabilized by the delicately placed peripheral oxygen atoms, which can compensate for all electron-deficient boron atoms via O → B π back bonds and sterically protect them. Simultaneously, they are additionally stabilized by aromatic stabilization effect from possessing the novel S + P + D triple aromaticity. We expect that the proposal of chemically stable ballet rotors in this work can arouse the rational design of nanorotors for experimental realization in the condensed phase.

Perfect cubic metallo-borospherenes TM8B6 (TM = Ni, Pd, Pt) as superatoms following the 18-electron rule

Transition-metal (TM)-doped metallo-borospherenes exhibit unique structures and bonding in chemistry which have received considerable attention in recent years. Based on extensive global minimum searches and first-principles theory calculations, we predict herein the first and smallest perfect cubic metallo-borospherenes Oh TM8B6 (TM = Ni (1), Pd (2), Pt (3)) and Oh Ni8B6- (1-) which contain eight equivalent TM atoms at the vertexes of a cube and six quasi-planar tetra-coordinate face-capping boron atoms on the surface. Detailed canonical molecular orbital and adaptive natural density partitioning bonding analyses indicate that Oh TM8B6 (1/2/3) as superatoms possess nine completely delocalized 14c-2e bonds following the 18-electron principle (1S21P61D10), rendering spherical aromaticity and extra stability to the complex systems. Furthermore, Ni8B6 (1) can be used as building blocks to form the three-dimensional metallic binary crystal NiB (4) (Pm3̄m) in a bottom-up approach which possesses a typical CsCl-type structure with an octa-coordinate B atom located exactly at the center of the cubic unit cell. The IR, Raman, UV-vis and photoelectron spectra of the concerned clusters are computationally simulated to facilitate their experimental characterization.

Benchmarking boron cluster calculations: Establishing reliable geometrical and energetic references for Bn (n = 1-4)

Using full configuration interaction (FCI) and multi-reference configuration interaction methods (MRCI), reliable geometrical and energetic references for Bn (n = 1-4) clusters were established. The accuracy of the computed results was confirmed by comparison with available experimental data. Benchmark calculations indicated that B97D3, B97D, VSXC, HCTH407, BP86 and CCSD(T) methods provided reasonable results for structural parameters, with mean absolute error (MAEs) within 0.020 Å. Among the tested density functional theory (DFT) methods, the VSXC functional showed the best performance in predicting the relative energies of B1 B4 with a MAE of 12.8 kJ mol-1 . Besides, B1B95, B971, TPSS, B3LYP, and BLYP functionals exhibited reasonable performance with MAE values of less than 15.0 kJ mol-1 . T1 diagnostic values between 0.035 and 0.109 at the CCSD(T) level revealed strong correlations in B2 B4 clusters, highlighting the need for caution in using CCSD(T) as an energy reference for small boron clusters. The methods of CCSDT, CCSDT(Q) and CCSDT[Q], which incorporate three-electron and four-electron excitations, effectively improved the accuracy of the energy calculations.

[Cs©C18]+ and [Na©C14]+: perfect planar alkaline-metal-centered polyynic cyclo[n]carbon complexes with record coordination numbers

Searching for the maximum coordination number (CN) in planar species with novel bonding patterns has fascinated chemists for many years. Using the experimentally observed polyynic cyclo[18]carbon D9h C18 and theoretically predicted polyynic cyclo[14]carbon D7h C14 as effective ligands and based on extensive first-principles theory calculations, we predict herein their perfect planar alkaline-metal-centered complexes D9h Cs©C18+ (1) and D7h Na©C14+ (4) which as the global minima of the systems possess the record coordination numbers of CN = 18 and 14 in planar polyynic species, respectively. More interestingly, detailed energy decomposition and adaptive natural density partitioning bonding analyses indicate that the hypercoordinate alkaline-metal centers in these complexes exhibit obvious transition metal behaviors, with effective in-plane (π-6s)σ, (π-7p)σ, and (π-5d)σ coordination bonds formed in Cs©C18+ (1) and (π-3s)σ, (π-3p)σ, and (π-3d)σ coordination interactions fabricated in Na©C14+ (4) to dominate the overall attractive interactions between the metal center and its cyclo[n]carbon ligand. Similarly, alkaline-metal-centered planar Cs Cs©C17B (2), C2v Cs©C17- (3), C2v Na©C13B (5), and C2v Na©C13- (6) have also been obtained with CN = 18, 17, 14, and 13, respectively.

Sc@B28-, Ti@B28, V@B28+, and V@B292-: Spherically Aromatic Endohedral Seashell-like Metallo-Borospherenes

Transition-metal-doped boron nanoclusters exhibit unique structures and bonding in chemistry. Using the experimentally observed seashell-like borospherenes C₂ B₂₈^-/0 and C_s B₂₉^- as ligands and based on extensive first-principles theory calculations, we predict herein a series of novel transition-metal-centered endohedral seashell-like metallo-borospherenes C₂ Sc@B₂₈^- (1), C₂ Ti@B₂₈ (2), C₂ V@B₂₈⁺ (3), and C_s V@B₂₉^2- (4) which, as the global minima of the complex systems, turn out to be the boron analogues of dibenzenechromium D_6h Cr(C₆H₆)₂ with two B₁₂ ligands on the top and bottom interconnected by four or five corner boron atoms on the waist and one transition-metal "pearl" sandwiched at the center in between. Detailed molecular orbital, adaptive natural density partitioning (AdNDP), and iso-chemical shielding surface (ICSS) analyses indicate that, similar to Cr(C₆H₆)₂, these endohedral seashell-like complexes follow the 18-electron rule in bonding patterns (1S²1P⁶1D¹⁰), rendering spherical aromaticity and extra stability to the systems.

Perfect Core-Shell Octahedral B@B38 + , Be@B38 , and Zn@B38 with an Octa-Coordinate Center as Superatoms Following the Octet Rule

The front cover artwork is provided by Prof. Si-Dian Li's group at Shanxi University, China. The image shows the smallest perfect core-shell octahedral borospherene O_h B@B₃₈ ⁺ and its endohedral metallo-borospherene analogs O_h Be@B₃₈ and O_h Zn@B₃₈ obtained at first-principles theory. Read the full text of the Research Article at 10.1002/cphc.202200947.

Heptacoordinate transition-metal-decorated metallo-borospherenes and multiple-helix metallo-boronanotubes

The recent discovery of lanthanide-metal-decorated metallo-borospherenes LM₃B₁₈^- (LM = La, Tb) marks the onset of a new class of boron-metal binary nanomaterials. Using the experimentally observed or theoretically predicted borospherenes as ligands and based on extensive first-principles theory calculations, we predict herein a series of novel chiral metallo-borospherenes C₂ Ni₆ ∈ B₃₉^- (1), C₁ Ni₆ ∈ B₄₁⁺ (3), C₂ Ni₆ ∈ B₄₂²⁺ (4), C₂ Ni₆ ∈ B₄₂ (5), and C₂ Ni₈ ∈ B₅₆ (6) as the global minima of the systems decorated with quasi-planar heptacoordinate Ni (phNi) centers in η⁷-B₇ heptagons on the cage surfaces, which are found to be obviously better favoured in coordination energies than hexacoordinate Ni centers in previously reported D_2d Ni₆ ∈ B₄₀ (2). Detailed bonding analyses indicate that these phNi-decorated metallo-borospherenes follow the σ + π double delocalization bonding pattern, with two effective (d-p)σ coordination bonds formed between each phNi and its η⁷-B₇ ligand, rendering spherical aromaticity and extra stability to the systems. The structural motif in elongated axially chiral Ni₆ ∈ B₄₂²⁺ (4), Ni₆ ∈ B₄₂ (5), and Ni₈ ∈ B₅₆ (6) can be extended to form the metallic phNi-decorated boron double chain (BDC) double-helix Ni₄ ∈ B₂₈ (2, 0) (P4̄m2) (8), triple-helix Ni₆ ∈ B₄₂ (3, 0) (P3̄m1) (9), and quadruple-helix Ni₈ ∈ B₅₆ (4, 0) (P4mm) (10) metallo-boronanotubes, which can be viewed as quasi-multiple-helix DNAs composed of interconnected BDCs decorated with phNi centers in η⁷-B₇ heptagons on the tube surfaces in the atomic ratio of Ni : B = 1 : 7.

Perfect Core-Shell Octahedral B@B38 + , Be@B38 , and Zn@B38 with an Octa-Coordinate Center as Superatoms Following the Octet Rule

Planar, tubular, cage-like, and bilayer boron clusters B_n ^+/0/- (n=3∼48) have been observed in joint experimental and theoretical investigations in the past two decades. Based on extensive global searches augmented with first-principles theory calculations, we predict herein the smallest perfect core-shell octahedral borospherene O_h B@B₃₈ ⁺ (1) and its endohedral metallo-borospherene analogs O_h Be@B₃₈ (2), and O_h Zn@B₃₈ (3) which, with an octa-coordinate B, Be or Zn atom located exactly at the center, turn out to be the well-defined global minima of the systems highly stable both thermodynamically and dynamically. B@B₃₈ ⁺ (1) represents the first boron-containing molecule reported to date which contains an octa-coordinate B center covalently coordinated by eight face-capping boron atoms at the corners of a perfect cube in the first coordination sphere. Detailed natural bonding orbital (NBO) and adaptive natural density partitioning (AdNDP) bonding analyses indicate that these high-symmetry core-shell complexes X@B₃₈ ^+/0/- (X=B, Be, Zn) as super-noble gas atoms follow the octet rule in coordination bonding patterns (1S² 1P⁶ ), with one delocalized 9c-2e S-type coordination bond and three delocalized 39c-2e P-type coordination bonds formed between the octa-coordinate X center and its octahedral O_h B₃₈ ligand to effectively stabilize the systems. Their IR, Raman, and UV-Vis spectra are computationally simulated to facilitate their spectroscopic characterizations.

Lanthanide/actinide boride nanoclusters and nanomaterials based on boron frameworks consisting of conjoined Bn rings (n = 7-9)

Extensive global minimum searches augmented with first-principles theory calculations performed in this work indicate that the experimentally observed perfect inverse sandwich lanthanide boride complexes D_7h La₂B₇^- (1), D_8h La₂B₈ (3), D_9h La₂B₉^- (7) can be extended to their actinide counterparts C_2v Ac₂B₇^- (1'), D_8h Ac₂B₈ (3'), D_9h Ac₂B₉^- (7') with a B_n monocyclic ring (n = 7-9) sandwiched by two Ac dopants. Such M₂B_n^-/0 inverse sandwiches (1/1', 3/3', 7/7') can be used as building blocks to generate the ground-state C₂ La₄B₁₃^- (2)/Ac₄B₁₃^- (2'), D₂ La₄B₁₅^- (4)/Ac₄B₁₅^- (4'), C_3v/C₃ La₄B₁₈ (5)/Ac₄B₁₈ (5'), O_h Ac₇B₂₄⁺ (6'), O_h Ac₇B₂₄, T_d Ac₄B₂₄ (8'), C₁ La₅B₂₄⁺ (9)/Ac₅B₂₄⁺ (9'), and T_d Ac₄B₂₉^- (10') which are based on boron frameworks consisting of multiple conjoined B_n rings (n = 7-9). Detailed bonding analyses show that effective (d-p)σ, (d-p)π and (d-p)δ coordination bonds are formed between the B_n rings and metal doping centers, conferring three-dimensional aromaticity and extra stability to the systems. In particular, the perfect body-centered cubic O_h Ac₇B₂₄⁺ (6') and O_h Ac₇B₂₄ with six conjoined B₈ rings can be extended in x, y, and z dimensions to form one-dimensional Ac₁₀B₃₂ (11'), two-dimensional Ac₃B₁₀ (12'), and three-dimensional AcB₆ (13') nanomaterials, presenting a B₈-based bottom-up approach from metal boride nanoclusters to their low-dimensional nanomaterials.

A bottom-up approach from medium-sized bilayer boron nanoclusters to bilayer borophene nanomaterials

Inspired by the experimentally observed bilayer B₄₈^-/0 and theoretically predicted bilayer B₅₀-B₇₂ and based on extensive density functional theory calculations, we report herein a series of novel medium-sized bilayer boron nanoclusters C₁ B₈₄ (I), C_2v B₈₆ (II), C₁ B₈₈ (III), C₁ B₉₀ (IV), C₁ B₉₂ (V), C₁ B₉₄ (VI), C_2v B₉₆ (VII), and C₁ B₉₈ (VIII) which are the most stable isomers of the systems reported to date effectively stabilized by optimum numbers of interlayer B-B σ bonds between the inward-buckled atoms on top and bottom layers. Detailed bonding analyses indicate that these bilayer species follow the universal bonding pattern of σ + π double delocalization, rendering three-dimensional aromaticity in the systems. More interestingly, the AA-stacked bilayer structural motif in B₉₆ (VII) with a B₇₂ bilayer hexagonal prism at the center can be extended to form bilayer C₂ B₁₂₈ (IX), D_2h B₂₁₄ (X), C_2v B₂₆₀ (XI), D_2h B₃₇₂ (XII), and D₂ B₈₂₈ (XIII) which contain one or multiple conjoined B₇₂ bilayer hexagonal prisms sharing interwoven zig-zag boron triple chains between them. Such bilayer species or their close-lying AB isomers can be viewed as embryos of the newly reported most stable freestanding BL-α⁺ bilayer borophenes and quasi-freestanding bilayer borophenes on Ag(111) which are composed of interwoven zig-zag boron triple chains shared by conjoined BL B₇₂ hexagonal prisms, presenting a bottom-up approach from medium-sized bilayer boron nanoclusters to two-dimensional bilayer borophene nanomaterials.

A family of superconducting boron crystals made of stacked bilayer borophenes

Monolayer borophenes tend to be easily oxidized, while thicker borophenes have stronger antioxidation properties. Herein, we proposed four novel metallic boron crystals by stacking the experimentally synthesized borophenes, and one of the crystals has been reported in our previous experiments. Bilayer units tend to act as blocks for crystals as determined by bonding analyses. Their kinetic, thermodynamic and mechanical stabilities are confirmed by our calculated phonon spectra, molecular dynamics and elastic constants. Our proposed allotropes are more stable than the boron α-Ga phase below 1000 K at ambient pressure. Some of them become more stable than the α-rh or γ-B₂₈ phases at appropriate external pressure. More importantly, our calculations show that three of the proposed crystals are phonon-mediated superconductors with critical temperatures of about 5-10 K, higher than those of most superconducting elemental solids, in contrast to typical boron crystals with significant band gaps. Our study indicates a novel preparation method for metallic and superconducting boron crystals dispensing with high pressure.

Compression-induced crimping of boron nanotubes from borophenes: a DFT study

Several borophenes have been prepared successfully, but the synthesis of boron nanotubes is still very difficult. Our results suggest that the high flexibility of borophene in combination with van der Waals interactions makes it possible to coil boron nanotubes from rippled borophenes, which is confirmed by ab initio molecular dynamics simulations. The plane structures transform into rippled structures almost without any barrier under very small compression and weak perturbations like molecular adsorption. The compression energies of the rippled structures increase linearly and slowly with the increase of the compression. This suggests how the geometry of the borophene evolves with compression. Based on the evaluation of the free energy of hydrogen adsorption, a stronger compression suggests the improved hydrogen evolution performance of the borophene and even makes it better than Pt catalysts. Meanwhile, good hydrogen evolution performance is also suggested for boron nanotubes. Our results suggest a novel preparation method for boron nanotubes from borophenes and a possible way to improve their hydrogen evolution performance.

Quasi-Freestanding Bilayer Borophene on Ag(111)

The lattice structure of monolayer borophene depends sensitively on the substrate yet is metallic independent of the environment. Here, we show that bilayer borophene on Ag(111) shares the same ground state as its freestanding counterpart that becomes semiconducting with an indirect bandgap of 1.13 eV, as evidenced by an extensive structural search based on first-principles calculations. The bilayer structure is composed of two covalently bonded v_1/12 boron monolayers that are stacked in an AB mode. The interlayer bonds not only localize electronic states that are otherwise metallic in monolayer borophene but also in part decouple the whole bilayer from the substrate, resulting in a quasi-freestanding system. More relevant is that the predicted bilayer model of a global minimum agrees well with recently synthesized bilayer borophene on Ag(111) in terms of lattice constant, topography, and moiré pattern.

Boron-lead multiple bonds in the PbB2O- and PbB3O2- clusters

Despite its electron deficiency, boron can form multiple bonds with a variety of elements. However, multiple bonds between boron and main-group metal elements are relatively rare. Here we report the observation of boron-lead multiple bonds in PbB₂O^- and PbB₃O₂^-, which are produced and characterized in a cluster beam. PbB₂O^- is found to have an open-shell linear structure, in which the bond order of B☱Pb is 2.5, while the closed-shell [Pb≡B-B≡O]^2- contains a B≡Pb triple bond. PbB₃O₂^- is shown to have a Y-shaped structure with a terminal B = Pb double bond coordinated by two boronyl ligands. Comparison between [Pb≡B-B≡O]^2-/[Pb=B(B≡O)₂]^- and the isoelectronic [Pb≡B-C≡O]^-/[Pb=B(C≡O)₂]⁺ carbonyl counterparts further reveals transition-metal-like behaviors for the central B atoms. Additional theoretical studies show that Ge and Sn can form similar boron species as Pb, suggesting the possibilities to synthesize new compounds containing multiple boron bonds with heavy group-14 elements.

Prediction of heptagonal bipyramidal nonacoordination in highly viable [OB-M©B7O7-BO]- (M = Fe, Ru, Os) complexes

Non-spherical distributions of ligand atoms in coordination complexes are generally unfavorable due to higher repulsion than for spherical distributions. To the best of our knowledge, non-spherical heptagonal bipyramidal nonacoordination is hitherto unreported, because of extremely high repulsion among seven equatorial ligand atoms. Herein, we report the computational prediction of such nonacoordination, which is constructed by the synergetic coordination of an equatorial hepta-dentate centripetal ligand (B₇O₇) and two axial mono-dentate ligands (-BO) in the gear-like mono-anionic complexes [OB-M©B₇O₇-BO]^- (M = Fe, Ru, Os). The high repulsion among seven equatorial ligand B atoms has been compensated by the strong B-O bonding. These complexes are the dynamically stable (up to 1500 K) global energy minima with the HOMO-LUMO gaps of 7.15 to 7.42 eV and first vertical detachment energies of 6.14 to 6.66 eV (being very high for anions), suggesting their high probability for experimental realization in both gas-phase and condensed phases. The high stability stems geometrically from the surrounded outer-shell oxygen atoms and electronically from meeting the 18e rule as well as possessing the σ + π + δ triple aromaticity. Remarkably, the ligand-metal interactions are governed not by the familiar donation and backdonation interactions, but by the electrostatic interactions and electron-sharing bonding.

La@[La5&B30]0/−/2−: endohedral trihedral metallo-borospherenes with spherical aromaticity

Extensive first-principles theory calculations predict the perfect endohedral metallo-borospherene D3h La@[La5&B30] (1) and its monoanion Cs La@[La5&B30]− (2) and dianion D3h La@[La5&B30]2− (3) which appear to be spherically aromatic in nature.

Predicting bilayer B50, B52, B56, and B58: structural evolution in bilayer B48-B72 clusters

The successive experimental observations of planar, cage-like, seashell-like, and bilayer B_n^-/0 clusters in the size range between n = 3-48 well demonstrate the structural diversity and rich chemistry of boron nanoclusters. Based on extensive global minimum search and density functional theory calculations, we predict herein the bilayer C₁ B₅₀ (I), C_2h B₅₂ (II), C₁ B₅₆ (IV), and C_2v B₅₈ (V) as the global minima of the systems to fill in the missing gap in the bilayer B_2n series between B₄₈-B₇₂. These highly stable species all contain a B₃₈ bilayer hexagonal prism at the center, with 2, 2, 3, and 3 effective interlayer B-B σ-bonds formed between inward-buckled atoms on the top and bottom layers, respectively. Our bilayer C₁ B₅₀ (I) and C₁ B₅₆ (IV) prove to be obviously more stable than the previously reported quasi-planar C_2v B₅₀ and C_2v B₅₆ with two adjacent B₆ hexagonal holes. Detailed bonding analyses indicate that these bilayer clusters follow the universal bonding pattern of σ + π double delocalization, making them three-dimensionally aromatic in nature. The bilayer B_2n species in the size range between B₄₈-B₇₂ evolve gradually on the waist around the B₃₈ or elongated B₄₆ bilayer hexagonal prism at the center.

The unified quantum mechanical structure of tubular molecular rotors with multiple equivalent global minimum structures: the 18*C2h → D9d case of La-[B2@B18]-La

La-[B₂@B₁₈]-La demonstrates decisive changes of the properties of molecular rotors, from multiple (here 18) equivalent individual global minimum structures to a quantum mechanical unified structure. This affects their geometries, their symmetries (18*C_2h → D_9d), the generation of energy bands, and high-resolution spectroscopy.

Metal-centered monocyclic carbon wheel clusters with record coordination numbers in planar species

The highest coordination number identified to date in planar species is CN = 10 in metal-centered monocyclic boron wheel clusters D_10h M©B₁₀⁻ (M = Ta and Nb) (Galeev et. al., Angew. Chem. Int. Ed., 2012, 51, 2101). Extensive global minimum searches and first-principles theory calculations performed herein indicate that the experimentally observed LaC₁₃⁺ and LaC₁₄⁺ possess the well-defined global minima of perfect metal-centered monocyclic carbon wheel D_13h La©C₁₃⁺ (1) and slightly off-centered C_2v La©C₁₄⁺ (4) (¹A₁) with record coordination numbers of CN = 13 and 11 in planar structures, respectively, further pushing the boundary of our understanding of chemical structures and bonding. Detailed molecular orbital, nucleus-independent chemical shift, and ring current analyses indicate that D_13h La©C₁₃⁺ (1) is σ + π dually aromatic in nature, with 14 totally delocalized in-plane σ electrons and 14 totally delocalized out-of-plane π electrons each matching the 4N + 2 aromatic rule (N_σ = N_π = 3). Similar σ + π dually aromatic metal-centered monocyclic wheel clusters D_13h Ca©C₁₃ (2), C_13v Ac©C₁₃⁺ (3), C_2v Y©B₆C₆⁺ (5), and C_2v Sc©B₅C₆ (6) have also been obtained with CN = 13, 13, 12, and 11, respectively. The results obtained in this work effectively enrich the chemical structures and bonding patterns of planar hypercoordinated complexes.

First-principle theory calculations reveal record coordination numbers of CN = 13 in D_13h La©C₁₃⁺, CN = 12 in C_2v Y©B₆C₆⁺, and CN = 11 in C_2v Sc©B₅C₆ in planar species, effectively enriching the chemical structures and bonding patterns of planar hypercoordinated complexes.

[Integration of clinical significance and statistical significance on clinical study results categorization: a Meta-epidemiology study]

Objective: Statistical significance plays an important role in the interpretation of clinical trial results. However, on the basis of obtaining statistical significance, the assessment of clinical significance is often neglected. This study attempted to propose a simple and unambiguous new classification method for study results, focusing on studies with statistical positive findings to evaluate whether the results have clinical significance. Methods: Our study subjects were the clinical studies in 2019 ACC and ESC annual meetings. Meta-epidemiology methods were used to extract the characteristic variable from each study. The primary evaluation indicators included target effect-size and observed effect-size. Based on the difference between the two indicators, the studies that had statistical significance were subdivided to identify studies with possible insufficient clinical significance; Furthermore, the theoretical threshold based on power analysis was proposed, which was used as the basis for the interpretation of study results. Results: There were 12 clinical studies included in the final analysis. All of them were published on top journals. Those studies had relative high quality on both study design and reporting. The correlation coefficient between the observed and target effect-size was 0.892. Among the 7 studies with statistical significance, two of them were classified as insufficient clinical significance. The counts was 1 (1/3) and 1 (1/4) for the studies reported in ACC and ESC respectively. Conclusions: The achievement of clinical significance is critical even in the study with positive results. This paper proposes a new classification standard that combines clinical significance with statistical significance and further suggests a method to evaluate the reliability of clinical study results in order to assist researchers in identifying potential risks caused by insufficient clinical significance, and provide some reference and help for the reasonable interpretation of clinical study results.

Interactions between water and rhodium clusters: molecular adsorption versus cluster adsorption

Understanding metal-water interactions and hydrogen-bonding in water droplets is important but highly challenging. Various transition metals may serve as effective coordination centers to water; however, not in all cases is water bonded to a metal center as single molecules. We report here the observations of gas-phase rhodium clusters and their interactions with water. A series of rhodium-water clusters, Rhn±,0(H2O)m (n = 3-30, m = 1-5), with isotope labels were detected by mass spectrometry after exposure to different water concentrations, among which Rh8+(H2O)4 and Rh9+(H2O)3 were prominent in the mass distributions, showing a size-dependent preference of water adsorption on rhodium clusters. Comprehensive density functional theory calculations reveal that the lowest energy structure of Rh9+(H2O)3 possesses a hydrogen-bonded cyclic (H2O)3 water trimer on the top of a tri-capped Rh9+ trigonal prism. The tri-capped Rh9+ trigonal prism and the cyclic (H2O)3 water trimer match in sizes, charge distributions, and orbital symmetries to form effective electrostatic cluster-cluster interactions. In contrast, Rh8+(H2O)4 contains four water molecules separately attached to a bi-capped octahedron, Rh8+, at four corners via single-molecule adsorption. The difference between covalent molecular adsorption and electrostatic cluster-cluster interaction in these two proto-typical rhodium hydrates is further demonstrated by detailed natural bonding orbital, electrostatic surface potential, and charge decomposition analyses.

Transition-metal-like bonding behaviors of a boron atom in a boron-cluster boronyl complex [(η7-B7)-B-BO]. Chem Sci 2021;12:8157-8164. [PMID: 34194706 PMCID: PMC8208299 DOI: 10.1039/d1sc00534k]

Boron displays many unusual structural and bonding properties due to its electron deficiency. Here we show that a boron atom in a boron monoxide cluster (B₉O⁻) exhibits transition-metal-like properties. Temperature-dependent photoelectron spectroscopy provided evidence of the existence of two isomers for B₉O⁻: the main isomer has an adiabatic detachment energy (ADE) of 4.19 eV and a higher energy isomer with an ADE of 3.59 eV. The global minimum of B₉O⁻ is found surprisingly to be an umbrella-like structure (C_6v, ¹A₁) and its simulated spectrum agrees well with that of the main isomer observed. A low-lying isomer (C_s, ¹A′) consisting of a BO unit bonded to a disk-like B₈ cluster agrees well with the 3.59 eV ADE species. The unexpected umbrella-like global minimum of B₉O⁻ can be viewed as a central boron atom coordinated by a η⁷-B₇ ligand on one side and a BO ligand on the other side, [(η⁷-B₇)-B-BO]⁻. The central B atom is found to share its valence electrons with the B₇ unit to fulfill double aromaticity, similar to that in half-sandwich [(η⁷-B₇)-Zn-CO]⁻ or [(η⁷-B₇)-Fe(CO)₃]⁻ transition-metal complexes. The ability of boron to form a half-sandwich complex with an aromatic ligand, a prototypical property of transition metals, brings out new metallomimetic properties of boron.

The global minimum of the B₉O⁻ cluster is found to have an umbrella-like structure, where the central B atom exhibits transition-metal-like bonding properties, coordinated by a η⁷-B₇ ligand on one side and a BO ligand on the other.

Perfect Spherical Tetrahedral Metallo-Borospherene Ta4B18 as a Superatom Following the 18-Electron Rule

Cage-like metallo-borospherenes exhibit unique structures and bonding. Inspired by the newly reported smallest spherical trihedral metallo-borospherene D 3h Ta3B12 - (1), which contains two equivalent B3 triangles interconnected by three B2 units on the cage surface, we present herein a first-principles theory prediction of the perfect spherical tetrahedral metallo-borospherene T d Ta4B18 (2), which possesses four equivalent B3 triangles interconnected by six B atoms, with four equivalent nonacoordinate Ta centers in four η9-B9 rings as integrated parts of the cage surface. As the well-defined global minimum of the neutral, Ta4B18 (2) possesses four 10c-2e B9(π)-Ta(dσ) and eight 10c-2e B9(π)-Ta(dδ) coordination bonds evenly distributed over four Ta-centered Ta@B9 nonagons, with the remaining 18 valence electrons in nine 22c-2e totally delocalized bonds following the 18-electron principle (1S21P61D10) of a superatom. Such a bonding pattern renders spherical aromaticity to the tetrahedral complex, which can be used as building blocks to form the face-centered cubic crystal Ta4B15 (3). The IR, Raman, and UV-vis spectra of Ta4B18 (2) are theoretically simulated to facilitate its future experimental characterizations.

B48-: a bilayer boron cluster

Size-selected negatively-charged boron clusters (B_n^-) have been found to be planar or quasi-planar in a wide size range. Even though cage structures emerged as the global minimum at B₃₉^-, the global minimum of B₄₀^- was in fact planar. Only in the neutral form did the B₄₀ borospherene become the global minimum. How the structures of larger boron clusters evolve is of immense interest. Here we report the observation of a bilayer B₄₈^- cluster using photoelectron spectroscopy and first-principles calculations. The photoelectron spectra of B₄₈^- exhibit two well-resolved features at low binding energies, which are used as electronic signatures to compare with theoretical calculations. Global minimum searches and theoretical calculations indicate that both the B₄₈^- anion and the B₄₈ neutral possess a bilayer-type structure with D_2h symmetry. The simulated spectrum of the D_2h B₄₈^- agrees well with the experimental spectral features, confirming the bilayer global minimum structure. The bilayer B₄₈^-/0 clusters are found to be highly stable with strong interlayer covalent bonding, revealing a new structural type for size-selected boron clusters. The current study shows the structural diversity of boron nanoclusters and provides experimental evidence for the viability of bilayer borophenes.

An oxygen-passivated vanadium cluster [V@V10O15]− with metal–metal coordination produced by reacting Vn− with O2

An oxygen-passivated vanadium cluster [V@V₁₀O₁₅]⁻ is reported by reacting V_n⁻ with O₂, giving rise to superatom features of metal–metal coordination and 3D aromaticity.

Donor-acceptor duality of the transition-metal-like B2 core in core-shell-like metallo-borospherenes La3&[B2@B17]- and La3&[B2@B18]. RSC Adv 2020;10:34225-34230. [PMID: 35519037 PMCID: PMC9056772 DOI: 10.1039/d0ra06769e]

Transition-metal doping induces dramatic structural changes and leads to earlier planar → tubular → spherical → core–shell-like structural transitions in boron clusters. Inspired by the newly discovered spherical trihedral metallo-borospherene D_3h La₃&B₁₈⁻ (1) (Chen, et al., Nat. Commun., 2020, 11, 2766) and based on extensive first-principles theory calculations, we predict herein the first and smallest core–shell-like metallo-borospherenes C_2v La₃&[B₂@B₁₇]⁻ (2) and D_3h La₃&[B₂@B₁₈]⁻ (3) which contain a transition-metal-like B₂ core at the cage center with unique donor–acceptor duality in La₃&B_n⁻ spherical trihedral shells (n = 17, 18). Detailed energy decomposition and bonding analyses indicate that the B₂ core in these novel complexes serves as a π-donor in the equatorial direction mainly to coordinate three La atoms on the waist and a π/σ-acceptor in the axial direction mainly coordinated by two B₆ triangles on the top and bottom. These highly stable core–shell complexes appear to be spherically aromatic in nature in bonding patterns. The IR, Raman, and photoelectron spectra of 2 and 3 are computationally simulated to facilitate their spectroscopic characterizations.

The smallest core–shell-like metallo-borospherenes C_2v La3&[B₂@B₁₇]⁻ and D_3h La₃&[B₂@B₁₈]⁻ have been predicted at first-principles theory level which contain a transition-metal-like B₂ core with unique donor–acceptor duality.

From inverse sandwich Ta2B7 + and Ta2B8 to spherical trihedral Ta3B12 -: prediction of the smallest metallo-borospherene

Transition-metal-doped boron nanoclusters exhibit interesting structures and bonding. Inspired by the experimentally discovered inverse sandwich D_6h Ta₂B₆ and spherical trihedral D_3h La₃B₁₈⁻ and based on extensive first-principles theory calculations, we predict herein the structural transition from perfect di-metal-doped inverse sandwich D_7h Ta₂B₇⁺ (1) and D_8h Ta₂B₈ (2) to tri-metal-doped spherical trihedral D_3h Ta₃B₁₂⁻ (3). As the smallest metallo-borospherene reported to date, Ta₃B₁₂⁻ (3) contains three octa-coordinate Ta atoms as integral parts of the cage surface coordinated in three equivalent η⁸-B₈ rings which share two eclipsed equilateral B₃ triangles on the top and bottom interconnected by three B₂ units on the waist. Detailed orbital and bonding analyses indicate that both Ta₂B₇⁺ (1) and Ta₂B₈ (2) possess σ + π dual aromaticity, while Ta₃B₁₂⁻ (3) is σ + π + δ triply aromatic in nature. The IR, Raman, and UV-vis or photoelectron spectra of the concerned species are computationally simulated to facilitate their future spectroscopic characterizations.

Structural transition from inverse sandwich Ta₂B₇⁺ (1) and Ta₂B₈ (2) with σ + π dual aromaticity to the smallest metallo-borospherene D_3h Ta₃B₁₂⁻ (3) which is σ + π + δ triply aromatic in nature.

Analysis of Driver-Passenger Relationship and Restoration of Accident Process Based on 3D Laser Scanning Technology

Abstract

Objective To discuss the application of 3D laser scanner and computer technology in restoration of the accident scene and reconstruction of the accident process, as well as identification of the driver-passenger relationship. Methods The scene of a traffic accident, the accident vehicle and the vehicle of the same type as accident vehicle were scanned using 3D laser scanner. The accident scene, traces and accident vehicle were integrated using computer technology to restore the accident scene, and the accident process was reconstructed and analyzed by combining the characteristics of the body injuries. Results By restoring the accident scene and reconstructing the accident process with 3D laser scanner, it was determined that Wu was in the driving seat at the time of the accident. Conclusion It is more objective and scientific to use 3D laser scanning technology to restore the accident scene, reconstruct the accident process and analyze the moving track of the driver and passengers in the vehicle. It will help to improve the accuracy of forensic identification of road traffic accidents.

Perfect cubic La-doped boron clusters La6&[La@B24]+/0 as the embryos of low-dimensional lanthanide boride nanomaterials

La-doped boron nanoclusters have received considerable attention due to their unique structures and bonding. Inspired by recent experimental observations of the inverse sandwich D_8h La₂B₈ (1) and triple-decker C_2v La₃B₁₄⁻ (2) and based on extensive global searches and first-principles theory investigations, we present herein the possibility of the perfect cubic La-doped boron clusters O_h La₆&[La@B₂₄]⁺ (3, ¹A_1g) and O_h La₆&[La@B₂₄] (4, ²A_2g) which appear to be the embryos of the metallic one-dimensional La₁₀B₃₂ (5) nanowire, two-dimensional La₃B₁₀ (6) nanosheet, and three-dimensional LaB₆ (7) nanocrystal, facilitating a bottom-up approach to build cubic lanthanide boride nanostructures from gas-phase clusters. Detailed molecular orbital and bonding analyses indicate that effective (d–p)σ, (d–p)π and (d–p)δ covalent coordination interactions exist in La₆&[La@B₂₄]^+/0 (3/4) clusters, while the 1D La₁₀B₃₂ (5), 2D La₃B₁₀ (6), and 3D LaB₆ (7) crystals exhibit mainly electrostatic interactions between the trivalent La centers and cubic B₂₄ frameworks, with weak but discernible coordination contributions from La (5d) ← B (2p) back-donations. The IR and Raman spectra of La₆&[La@B₂₄]^+/0 (3/4) and band structures of La₁₀B₃₂ (5) and La₃B₁₀ (6) are computationally simulated to facilitate their future characterizations.

Perfect cubic clusters O_h La₆&[La@B₂₄]^+/0 are predicted at first-principles levels to be the embryos of 1D La₁₀B₃₂, 2D La₃B₁₀, and 3D LaB₆ lanthanide boride nanomaterials in a bottom-up approach.

Sea-shell-like B31+ and B32: two new axially chiral members of the borospherene family

Since the discovery of the cage-like borospherenes D_2d B₄₀^−/0 and the first axially chiral borospherenes C₃/C₂ B₃₉⁻, a series of fullerene-like boron clusters in different charge states have been reported in theory. Based on extensive global minimum searches and first-principles theory calculations, we present herein two new axially chiral members C₂ B₃₁⁺ (I) and C₂ B₃₂ (VI) to the borospherene family. B₃₁⁺ (I) features two equivalent heptagons on the top and one octagon at the bottom on the cage surface, while B₃₂ (VI) possesses two equivalent heptagons on top and two equivalent heptagons at the bottom. Detailed bonding analyses show that both sea-shell-like B₃₁⁺ (I) and B₃₂ (VI) follow the universal σ + π double delocalization bonding pattern of the borospherene family, with ten delocalized π bonds over a σ skeleton, rendering spherical aromaticity to the systems. Extensive molecular dynamics simulations show that these novel borospherenes are kinetically stable below 1000 K. The IR, Raman, and UV-vis spectra of B₃₁⁺ (I) and B₃₂ (VI) are computationally simulated to facilitate their future experimental characterizations.

Two new axially chiral sea-shell-like boron clusters C₂ B₃₁⁺ (a) and C₂ B₃₂ (b) are presented at first-principles theory level to the borospherene family.

Planar B41- and B42- clusters with double-hexagonal vacancies

Since the discovery of the B₄₀ borospherene, research interests have been directed to the structural evolution of even larger boron clusters. An interesting question concerns if the borospherene cages persist in larger boron clusters like the fullerenes. Here we report a photoelectron spectroscopy (PES) and computational study on the structures and bonding of B₄₁^- and B₄₂^-, the largest boron clusters characterized experimentally thus far. The PE spectra of both clusters display broad and complicated features, suggesting the existence of multiple low-lying isomers. Global minimum searches for B₄₁^- reveal three low-lying isomers (I-III), which are all related to the planar B₄₀^- structure. Isomer II (C_s, ¹A') possessing a double hexagonal vacancy is found to agree well with the experiment, while isomers I (C_s, ³A'') and III (C_s, ¹A') both with a single hexagonal vacancy are also present as minor isomers in the experiment. The potential landscape of B₄₂^- is found to be much more complicated with numerous low-lying isomers (VII-XII). The quasi-planar structure VIII (C₁, ²A) containing a double hexagonal vacancy is found to make major contributions to the observed PE spectrum of B₄₂^-, while the other low-lying isomers may also be present to give rise to a complicated spectral pattern. Chemical bonding analyses show isomer II of B₄₁^- (C_s, ¹A') and isomer VIII of B₄₂^- (C₁, ²A) are π aromatic, analogous to that in the polycyclic aromatic hydrocarbon C₂₇H₁₃⁺ (C_2v, ¹A₁). Borospherene cage isomers are also found for both B₄₁^- and B₄₂^- in the global minimum searches, but they are much higher energy isomers.

Predicting lanthanide boride inverse sandwich tubular molecular rotors with the smallest core-shell structure

Lanthanide-boron binary clusters possess interesting structures and bonding which may provide insights into designing new boride nanomaterials. Inspired by the recently discovered mono-decker inverse sandwich D_9h La₂B₉^- (¹A'₁) (1) and based on the extensive first-principles theory calculations, we predict herein the possible existence of a series of bi-decker inverse sandwich di-lanthanide boron complexes including D_9d La₂[B₁₈] (³A_1g) (2), D_9d La₂[B₁₈]^2- (¹A_1g) (3), and C_2h La₂[B₂@B₁₈] (¹A_g) (4) which all contain a tubular B_n ligand (n = 18, 20) sandwiched by two La atoms at the two ends. In these novel clusters, La₂[B₂@B₁₈] (4) as a tubular molecular rotor with the smallest core-shell structure reported to date in boron-based nanoclusters possesses a B₂-bar rotating constantly and almost freely inside the B₁₈ tube around it at room temperature. Detailed bonding analyses indicate that these complexes are stablized by effective (d-p)σ, (d-p)π, and (d-p)δ coordination interactions between the La centers and B_n bi-decker ligand. Six multi-center fluxional σ-bonds between the B₂-core and B₁₈ tube in La₂[B₂@B₁₈] (4) are found to be responsible for its unique fluxional behaviors. The IR and Raman spectra of the concerned species are simulated to facilitate their experimental characterization.

Low-dimensional functional networks of cage-like B40 with effective transition-metal intercalations

As the first all-boron fullerene observed in experiments, cage-like borospherene B40 has attracted considerable attention in recent years. However, B40 has been proved to be chemically reactive and tends to coalesce with one another via the formation of covalent bonds. We explore herein the possibility of low-dimensional functional networks of B40 with effective transition-metal intercalations. We find that the four equivalent B7 heptagons on the waist of each B40 can serve as effective ligands to coordinate various transition metal centers in exohedral motifs. The intercalated metal atoms entail these networks with a variety of intriguing properties. The two-dimensional (2D) Cr2B40 network is a ferromagnetic metal while the 2D Zn2B40 network becomes semiconducting. In contrast, other 2D M2B40 (M = Sc, Ti, V, Mn, Fe, Co, Ni and Cu) networks and 1D CrB40 belong to nonmagnetic metals. The 3D Cr3B40 network is a magnetic metal. This work presents the viable possibility of assembling Mn&B40 metalloborospherenes into stable functional nanomaterials via effective transition-metal intercalations with potential applications in electronic and spintronic devices.

P4629Long-term outcomes in patients with ST-segment elevation myocardial infarction according to modalities of reperfusion therapy: data from china acute myocardial infarction (CAMI) registry

Background

Although primary percutaneous coronary intervention (pPCI) is the optimal reperfusion method for ST-segment elevation myocardial infarction (STEMI), it remains difficult to implement in many areas. Some STEMI patients have to accept fibrinolytic therapy and no reperfusion therapy instead.

Purpose

The aim of this study was to describe the impact of reperfusion therapy on the long-term outcomes of STEMI patients in China.

Methods

Using data from the China Acute Myocardial Infarction (CAMI) registry, we analyzed the 2-year outcomes of 18,075 STEMI patients symptom onset within 7 days from January 2013 to September 2014 according to the type of reperfusion therapy. The primary endpoint was a composite of major adverse cardiovascular event (MACE), defined as all-cause mortality, myocardial infarction or stroke.

Results

7798 (43%) were treated with pPCI and 1798 (10%) underwent fibrinolysis; 8479 (47%) did not receive any reperfusion. The 2-year MACE was 9.6% following pPCI, 15.7% following fibrinolysis, and 21.5% for patients without reperfusion therapy (P<0.0001). Adjusted hazard ratios for 2-year MACE were 0.71 (95% confidence interval [CI] 0.65–0.78, P<0.0001) for pPCI versus no reperfusion and 0.92 (95% CI 0.82–1.03, P=0.16) for fibrinolysis versus no reperfusion. Compared with patients without reperfusion, fibrinolysis only showed benefit in patients presented within 3 hours of symptom onset (HR 0.70, 95% CI 0.57–0.85, P=0.0005), whereas pPCI was associated with significantly decreased 2-year MACE rate in patients presented within 3 hours (HR 0.53, 95% CI 0.44–0.64, P<0.0001), 3–6 hours (HR 0.60, 95% CI 0.51–0.71, P<0.0001) and >6 hours (HR 0.86, 95% CI 0.76–0.97, P=0.01) of symptom onset.

Adjusted cumulative MACE rate

Conclusions

In a real-world setting, early reperfusion is the optimal strategy for STEMI. Fibrinolysis was not associated with better outcome in STEMI patients admitted >3 hours of symptom onset in Chinese real world setting.

Acknowledgement/Funding

Ministry of Science and Technology of China (Grant No. 2011BAI11B02)

[Prognosis factors analysis of 56 cases of non-Hodgkin's lymphoma originating from the nasopharynx]

Objective:To investigate the prognosis of non-Hodgkin's lymphoma originating from the nasopharynx.Method:The clinical data of 56 patients with a primary diagnosis of non-Hodgkin's lymphoma originating from the nasopharynx treated between January 2010 and December 2015 were studied.The association between clinical parameters and survival rate was evaluated by Kaplan-Meier method and Cox regression model.Result:The 1,3,5-year overall survival were 91.1%, 73.1%,and 49.6% respectively.Single factor analysis displayed that age,Ann-Arbor staging,iactate dehydrogenase,combined with B symptoms at the time of diagnosis,international prognostic index and the expression level of Ki-67 were related to the prognosis factors.Multivariate analysis showed that the international prognostic index greater than or equal to 2 points and the positive rate of Ki-67 greater than or equal to 60% were the independent risk factors for the prognosis of non-Hodgkin's lymphoma originating from the nasopharynx.Conclusion:International prognostic index and the expression level of Ki-67 may be independent prognostic factors for non-Hodgkin's lymphoma originating from the nasopharynx.

Predicting two-dimensional semiconducting boron carbides

Carbon and boron can mix to form numerous two-dimensional (2D) compounds with strong covalent bonds, yet very few possess a bandgap for functional applications. Motivated by the structural similarity between graphene and recently synthesized borophene, we propose a new family of semiconducting boron carbide monolayers composed of B₄C₃ pyramids and carbon hexagons, denoted as (B₄C₃)_m(C₆)_n (m, n are integers) by means of the global minimum search method augmented with first-principles calculations. These monolayers are isoelectronic to graphene yet exhibit increased bandgaps with decreasing n/m, due to the enhanced localization of boron multicenter bonding states as a consequence of the electronic transfer from boron to carbon. In particular, the B₄C₃ monolayer is even more stable than the previously synthesized BC₃ monolayer and has a direct bandgap of 2.73 eV, with the promise for applications in optical catalysis and optoelectronics. These results are likely to inform the on-going effort on the design of semiconducting 2D materials based on other light elements.

B31- and B32-: chiral quasi-planar boron clusters

Chirality plays an important role in nature. Nanoclusters can also exhibit chiral properties. We report herein a joint experimental and theoretical investigation on the geometric and electronic structures of B31- and B32- clusters, using photoelectron spectroscopy in combination with first-principles calculations. Two degenerate quasi-planar chiral C1 enantiomers (I and II, 1A) with a central hexagonal vacancy are identified as the global minima of B31-. For B32-, two degenerate boat-like quasi-planar chiral C2 structures (VI and VII, 2A) with a central hexagonal vacancy are also found as the global minima, with a low-lying chair-like Ci B32- (VIII, 2Au) also present in the experiment as a minor isomer. The chiral conversions in quasi-planar B31- and B32- clusters are investigated and relatively low barriers are found due to the high flexibility of these monolayer clusters, which feature multiple delocalized σ and π bonds over buckled molecular surfaces.

[A retrospective analysis of the efficacy and safety of imatinib in children with chronic myeloid leukemia during chronic phase]

Objective: To evaluate the efficacy and safety of imatinib in the treatment of newly diagnosed chronic myeloid leukemia during chronic phase (CML-CP) in children and to analyze the difference of the efficacy and safety between imported original imatinib (Gleevec) and domestic generic imatinib (Xinwei). Methods: Clinical data of 35 children with newly diagnosed CML-CP in Beijing Children's Hospital from January 2014 to January 2018 were collected, among which 15 cases were treated with the imported original imatinib (original drug group) and 20 cases were treated with the domestic generic imatinib (generic drug group). The hematological, cytogenetic and molecular reactions and safety of the treatments were monitored at months 3, 6 and 12. Chi square test or rank sum test was used for the comparison between two groups. Results: A total of 35 cases were treated for over 3 months, 31 cases were treated for over 6 months and 25 cases were treated for over 12 months. At 3 months, main cytogenetic response was obtained in 15 (100%) cases in the original drug group and 16 (80%) cases in the generic drug group respectively (χ(2)=3.387, P=0.119). At 6 months, complete cytogenetic response was obtained in 12 (80%) cases in the original drug group and 10 (63%) cases in the generic drug group (χ(2)=1.435, P=0.390). At 12 months, BCR-ABL(IS) ≤ 0.1% was obtained in 11 (92%) cases in the original drug group and 10 (77%) cases in the generic drug group (χ(2)=1.009, P=0.593). There was no significant difference at all stages (all P>0.05). Hematologic toxicity occurred in 7(20%) cases. The non-hematologic adverse reactions include nausea in 8 (23%) cases, pain in 8 (23%) cases, edema in 6 (17%) cases, emesis in 2 (6%) cases, fever in 2 (6%) cases, weakness in 1 (3%) case, rash in 1 (3%) case. The adverse reactions were easy to control and no drug toxicity related deaths occurred. There was no significant difference in the adverse reactions between original drug group and generic drug group (P>0.05). Conclusions: Imatinib had a good efficacy and safety in the early treatment of newly diagnosed CML-CP in children. The efficacy and safety of generic imatinib is similar to that of imported imatinib.

Probing the structures and bonding of size-selected boron and doped-boron clusters

Because of their interesting structures and bonding and potentials as motifs for new nanomaterials, size-selected boron clusters have received tremendous interest in recent years. In particular, boron cluster anions (Bn-) have allowed systematic joint photoelectron spectroscopy and theoretical studies, revealing predominantly two-dimensional structures. The discovery of the planar B36 cluster with a central hexagonal vacancy provided the first experimental evidence of the viability of 2D borons, giving rise to the concept of borophene. The finding of the B40 cage cluster unveiled the existence of fullerene-like boron clusters (borospherenes). Metal-doping can significantly extend the structural and bonding repertoire of boron clusters. Main-group metals interact with boron through s/p orbitals, resulting in either half-sandwich-type structures or substitutional structures. Transition metals are more versatile in bonding with boron, forming a variety of structures including half-sandwich structures, metal-centered boron rings, and metal-centered boron drums. Transition metal atoms have also been found to be able to be doped into the plane of 2D boron clusters, suggesting the possibility of metalloborophenes. Early studies of di-metal-doped boron clusters focused on gold, revealing ladder-like boron structures with terminal gold atoms. Recent observations of highly symmetric Ta2B6- and Ln2Bn- (n = 7-9) clusters have established a family of inverse sandwich structures with monocyclic boron rings stabilized by two metal atoms. The study of size-selected boron and doped-boron clusters is a burgeoning field of research. Further investigations will continue to reveal more interesting structures and novel chemical bonding, paving the foundation for new boron-based chemical compounds and nanomaterials.