Prediction of erbium-nitrogen compounds as high-performance high-energy-density materials.

To explore high-energy-density materials, intense attention has been focused on how to stabilize the N-N bond in nitrogen-rich compounds. Here, we report several stable phases of erbium-nitrogen compounds ErNxas high-energy-density materials. Specifically, the phase diagrams of stable high-pressure structuresImmm-ErN2,C2-ErN3,P1--ErN4, andP1--ErN6, are theoretically studied by combining first-principles calculation with particle swarm optimization algorithm. In these erbium-nitrogen compounds, the N-N bonds are stabilized as diatomic quasi-molecule N2, helical-like nitrogen chains, armchair nitrogen chains, and armchair-anti-armchair nitrogen chains, respectively. Among them, theP1--ErN6harbors excellent stability at high thermal up to 1000 K. More importantly, theP1--ErN6has outstanding explosive performance with high-energy-density of 1.30 kJ g-1, detonation velocity of 10.87 km s-1, and detonation pressure of 812.98 kbar, which shows its promising application prospect as high-energy-density materials.

Excellent performance of a cryogenic Nd:YAlO3 laser with low wavefront distortion based on zero thermal expansion.

High-power solid-state lasers with good beam quality are attracting great attention on account of their important applications in industry and military. However, the thermal effects generated in the laser host materials seriously limit power scaling and degrade the beam quality. Thermal lensing and thermally induced wavefront deformation are the main causes of the beam quality deterioration. Here we investigate the performance of a zero thermal expansion (ZTE) solid-state laser gain material. In a proof-of-principle experiment, an ${a}$-cut rod ${\rm Nd}\!:\!{{\rm YAlO}_3}$ (Nd:YAP) perovskite crystal is chosen to be the gain medium for ZTE around 180 K. The laser performance spanning the temperature range from 80 to 290 K is studied. The maximum output power and minimum threshold pump power were obtained at a temperature of 180 K. Moreover, the measured thermal focal power and peak-to-valley value of the wavefront distortion also reach a minimum at this temperature, an additional benefit from the crystal's ZTE coefficient. We envisage that these results will open a new route towards the development of high-power and high-beam-quality lasers through the use of ZTE gain materials.

Development and Validation of a New Nomogram for Predicting Clinically Relevant Postoperative Pancreatic Fistula After Pancreatoduodenectomy.

BACKGROUND: There lacks an ideal model for accurately predicting clinically relevant postoperative pancreatic fistula (CR-POPF) after pancreatoduodenectomy (PD). This study aimed at developing a nomogram with high accuracy in predicting CR-POPF after PD. METHODS: A total of 1182 patients undergoing PD in the First Affiliated Hospital of Sun Yat-sen University (FAHSYSU, n = 762) and Fudan University Shanghai Cancer Center (FUSCC, n = 420) between January 2010 and May 2018 were enrolled. The patients from FAHSYSU were assigned as testing cohort, and those from FUSCC were used as external validation cohort. Univariate and multivariate logistic regression analyses were performed to determine the predictive factors for CR-POPF. Nomogram was developed on the basis of significant predictors. The performance of nomogram was evaluated by area under receiver operating characteristic (ROC) curve (AUC), calibration curve, and decision curve analysis. RESULTS: In testing cohort, 87 out of 762 patients developed CR-POPF. Three predictors were significantly associated with CR-POPF, including body mass index ≥24.0 kg/m2, pancreatic duct diameter <3 mm, and drainage fluid amylase on postoperative day 1 ≥2484 units/L (all p ≤ 0.001). Prediction of nomogram was accurate with AUC of 0.934 (95% confidence interval [CI]: 0.914-0.950) in testing cohort and 0.744 (95% CI: 0.699-0.785) in external validation cohort. The predictive accuracy of nomogram was better than that of previously proposed fistula risk scores both in testing and external validation cohort (all p < 0.05). CONCLUSIONS: The novel nomogram based on three easily available parameters could accurately predict CR-POPF after PD. It would have high clinical value due to its accuracy and convenience.

Long-term outcome and prognostic factors of combined hepatocellular carcinoma and cholangiocarcinoma after curative resection.

BACKGROUND: Combined hepatocellular carcinoma and cholangiocarcinoma (cHCC-CC) is a rare subtype of primary liver cancers. Its prognostic factors remain unclear. The study aimed to evaluate its long-term outcome and prognostic factors by retrospectively reviewing the series of cHCC-CC after curative resection from our institute. METHODS: A total of 55 pathologically confirmed cHCC-CC patients undergoing curative resections between January 2003 and January 2018 at the First Affiliated Hospital of Sun Yat-sen University (Guangzhou, China) were included. The clinicopathological and follow-up data were retrieved. Overall survival (OS) and recurrence-free survivals (RFS) were analysed by Kaplan-Meier curve. The independent prognostic factors were determined by using univariate and multivariate Cox analyses. RESULTS: There were 41 males and 14 females, with a median age of 51.0 (interquartile range, 44.0-60.0) years. The 1-, 3-, and 5-year OS and RFS rates in cHCC-CC were 80.0%, 25.5%, and 16.4%, respectively, and 52.7%, 21.8%, and 10.9%, respectively. The median OS and RFS were 24.9 and 14.5 months, respectively. Univariate and multivariate analyses revealed that elevated alpha-fetal protein (AFP) and/or CA19-9, vascular invasion, local extra-hepatic invasion, and lymph-node metastasis (LNM) were independent unfavorable prognostic factors for OS and RFS (all P < 0.005). Furthermore, elevated AFP and/or CA19-9 were independent unfavorable prognostic factors in various subgroups of cHCC-CC, including patients aged <60 years, positive hepatitis B surface antigen, cirrhosis, single tumor, tumor size ≥5 cm, no vascular invasion, no LNM, and no local extra-hepatic invasion (all P < 0.05). CONCLUSIONS: Elevated AFP and/or CA19-9, vascular invasion, local extra-hepatic invasion, and LNM were independent unfavorable prognostic factors for long-term survival of cHCC-CC undergoing curative resections. Patients with normal levels of AFP and CA19-9 had better prognosis.

Chemically modified phosphorene as efficient catalyst for hydrogen evolution reaction.

Hydrogen gas produced by electrolysis has been considered as an excellent alternative to fossil fuels. Developing non-noble metal catalysts with high electrocatalytic activities is an effective way to reduce the cost of hydrogen production. Recently, black phosphorus (BP) based materials have been reported to have good potential as electrocatalysts for hydrogen evolution reaction (HER). Herein, we systematically study the catalytic performance of monolayer BP (phosphorene) and several chemically modified phosphorenes (N/S/C/O doping and adsorbed NH2/OH functional groups) for HER on the basis of first-principles calculations. For pristine phosphorene, the armchair edge shows much better catalytic activity than the plane site and zigzag edge. The electronic states of phosphorene near the Fermi level are strongly influenced by chemical modifications. Both of doping heteroatoms into the lattice and introducing NH2/OH functional groups can effectively improve the catalytic performance of the plane site and zigzag edge site, but slightly degrade the armchair edge. These theoretical results shed light on the microscopic understanding of the active sites in BP based electrocatalysts for HER and pave the way for further improving their catalytic performance.

Regulating Second-Harmonic Generation by van der Waals Interactions in Two-dimensional Lead Halide Perovskite Nanosheets.

The flexible organic amine cations on the interfaces of two-dimensional (2D) hybrid organic-inorganic perovskite nanosheets could form relaxed structures, which would lead to exotic optoelectronic properties but are hard to understand. Here, the unusual interfacial relaxation of nanosheets exfoliated from an orthorhombic 2D lead halide perovskite, [(C6H5CH2NH3)2]PbCl4, is interrogated via ultrafast second-harmonic generation (SHG) spectroscopy. The in-plane SHG intensity anisotropy of these nanosheets is found to decrease with reducing layer thickness. Combined first-principles calculations and Monte Carlo simulations reveal that the induced second-order polarization arises primarily from the (C6H5CH2NH3)+ cations; and these organic amine cations form significantly reorganized conformations with decreasing nanosheet thickness due to weakened van der Waals interactions. Because the orientations of organic components at the interface determine their electric properties and specifically the dipolar susceptibility, the resulting structure leads to striking changes in the SHG properties.

Li6Na3Sr14Al11P22O90: an oxo-centered Al3 cluster based phosphate constructed from two types of (3,6)-connected kgd layers.

A novel and thermally stable aluminum phosphate Li6Na3Sr14Al11P22O90 (1) has been achieved by using a solid-state molten method, which contains an oxo-centered trinuclear cluster and an anti-Lowenstein's rule Al-O-Al linkage and is constructed from two types of (3,6)-connected kgd layers [Al(Al3O)(PO4)7]25- and [Al(PO4)2]3-. The good optical transparency in the whole UV range and excellent thermal stability make the title compound a potential optical window material.

Pb@Pb8 Basket-like-Cluster-Based Lead Tellurate-Nitrate Kleinman-Forbidden Nonlinear-Optical Crystal: Pb9Te2O13(OH)(NO3)3.

The first lead tellurate-nitrate nonlinear-optical (NLO) crystal, Pb9Te2O13(OH)(NO3)3, featuring a 3D anionic diamondlike toplogical structural motif formulated as [Pb9O13]8- constructed by unique nonanuclear basket-shaped Pb@Pb8O14 clusters has been hydrothermally achieved, in which the Pb@Pb8O14 cluster shows a core-shell structure with one PbO10 polyhedron enclosed by eight PbOx (x = 3 and 4) polyhedera via edge and face sharing. The hexavalent Te in TeO5(OH) octahedra is linked to a [Pb9O13]8- cluster to form a rare [Pb9Te2O13(OH)]3+ cationic framework. The compound demonstrates a powder second-harmonic-generation (SHG) response of about 1.2 times that of KH2PO4 (KDP) as well as a wide transparency range. Calculations on the local dipole moment and SHG coefficient reveal that the net polarization is zero because of a Kleinman-forbidden point group. Further analysis shows that the SHG response results from structure-induced variations by thermal vibrations of the lattice rather than the intrinsic dipole moment, which offers another insight on the design of new NLO materials.

[Effects of light intensity contrast on clonal integration of Spartina anglica].

We conducted a greenhouse experiment to test how clonal integration affected the growth responses of Spartina anglica to light intensity heterogeneity in light availability and whether such effects depended on contrast light intensity. The experiment had three homogeneous treatments and two heterogeneous treatments. In the homogeneous treatments, both ramets of a connected ramet pair were unshaded (high light intensity), moderately shaded (medium light intensity, 70% of the high light intensity) and deeply shaded (low light intensity, 30% of the high light intensity). In the heterogeneous treatments, one ramet of a pair was unshaded, but its connected ramet was either moderately shaded (low light intensity contrast) or deeply shaded (high light intensity contrast). In the homogeneous treatments, biomass of S. anglica was significantly higher in the high light intensity treatment than in the medium and low light intensity treatments. Number of leaves, root length, and total biomass were significantly higher in the shaded ramet in the heterogeneous treatment with low light intensity contrast than in the ramet in the homogeneous treatment with medium light intensity. Final size and mass were not significantly different between the unshaded ramet in the heterogeneous treatment with low light intensity contrast and the ramets in the homogeneous high light intensity treatment. These results suggested that clonal integration benefitted a shaded ramet with little cost to an unshaded ramet when contrast in light intensity was low. However, effects of clonal integration were not significant when contrast was high. It therefore appeared that effects of clonal integration on the growth of S. anglica did not increase with increasing light intensity contrast. In natural habitats, clonal integration might improve growth of S. anglica when its ramets are moderately shaded by other plants but not when they are deeply shaded.