Multiple surface states,nontrivial band topology,and antiferromagnetism in GdAuAl_(4)Ge_(2)

Magnetic topological states of matter provide a fertile playground for emerging topological physics and phenomena.The current main focus is on materials whose magnetism stems from 3d magnetic transition elements,e.g.,MnBi_(2)Te_(4),Fe_(3)Sn_(2),and Co_(3)Sn_(2)S_(2).In contrast,topological materials with the magnetism from rare earth elements remain largely unexplored.Here we report rare earth antiferromagnet GdAuAl_(4)Ge_(2)as a candidate magnetic topological metal.Angle resolved photoemission spectroscopy(ARPES)and first-principles calculations have revealed multiple bulk bands crossing the Fermi level and pairs of low energy surface states.According to the parity and Wannier charge center analyses,these bulk bands possess nontrivial Z2 topology,establishing a strong topological insulator state in the nonmagnetic phase.Furthermore,the surface band pairs exhibit strong termination dependence which provides insight into their origin.Our results suggest GdAuAl_(4)Ge_(2)as a rare earth platform to explore the interplay between band topology,magnetism and f electron correlation,calling for further study targeting on its magnetic structure,magnetic topology state,transport behavior,and microscopic properties.

Development of an innovative nomogram of risk factors to predict postoperative recurrence of gastrointestinal stromal tumors

BACKGROUND There are many staging systems for gastrointestinal stromal tumors(GISTs),and the risk indicators selected are also different;thus,it is not possible to quantify the risk of recurrence among individual patients.AIM To develop and internally validate a model to identify the risk factors for GIST recurrence after surgery.METHODS The least absolute shrinkage and selection operator(LASSO)regression model was performed to identify the optimum clinical features for the GIST recurrence risk model.Multivariable logistic regression analysis was used to develop a prediction model that incorporated the possible factors selected by the LASSO regression model.The index of concordance(C-index),calibration curve,receiver operating characteristic curve(ROC),and decision curve analysis were used to assess the discrimination,calibration,and clinical usefulness of the predictive model.Internal validation of the clinical predictive capability was also evaluated by bootstrapping validation.RESULTS The nomogram included tumor site,lesion size,mitotic rate/50 high power fields,Ki-67 index,intracranial necrosis,and age as predictors.The model presented perfect discrimination with a reliable C-index of 0.836(95%CI:0.712-0.960),and a high C-index value of 0.714 was also confirmed by interval validation.The area under the curve value of this prediction nomogram was 0.704,and the ROC result indicated good predictive value.Decision curve analysis showed that the predicting recurrence nomogram was clinically feasible when the recurrence rate exceeded 5%after surgery.CONCLUSION This recurrence nomogram combines tumor site,lesion size,mitotic rate,Ki-67 index,intracranial necrosis,and age and can easily predict patient prognosis.

High-precision high-voltage detuning system for HIAF-SRing electron target

The development of a detuning system for the precision control of electron energy is a major challenge when electron targets are used in ion-storage rings.Thus,a high-precision,high-voltage,detuning system was developed for the electron target of a high-intensity heavy-ion accelerator facility-spectrometer ring(HIAF-SRing)to produce accurate electron-ion relative energies during experiments.The system consists of auxiliary,and high-voltage detuning power supplies.The front stage of the auxiliary power supply adopts an LCC resonant converter operating in the soft-switching state and an LC filter for a sinusoidal waveform output in the post-stage.The detuning power supply is a high-voltage pulse amplifier(HVPA)connected with a high-voltage DC(HVDC)module in series.In this paper,the design and development of the detuning system are described in detail,and the test bench is presented.The test results demonstrated that the detuning system conforms to the technical specifications of the dielectronic recombination(DR)experiment.Finally,a Fe15+DR spectrum was measured using the detuning system.The experimental data demonstrated a good experimental resolution and verified the reliability and feasibility of the design.

Flat Band and Z_(2)Topology of Kagome Metal CsTi_(3)Bi_(5)

The simple kagome-lattice band structure possesses Dirac cones,flat band,and saddle point with van Hove singularities in the electronic density of states,facilitating the emergence of various electronic orders.Here we report a titanium-based kagome metal CsTi_(3)Bi_(5)where titanium atoms form a kagome network,resembling its isostructural compound CsV_3Sb_5.Thermodynamic properties including the magnetization,resistance,and heat capacity reveal the conventional Fermi liquid behavior in the kagome metal CsTi_(3)Bi_(5)and no signature of superconducting or charge density wave(CDW)transition anomaly down to 85 m K.Systematic angle-resolved photoemission spectroscopy measurements reveal multiple bands crossing the Fermi level,consistent with the first-principles calculations.The flat band formed by the destructive interference of hopping in the kagome lattice is observed directly.Compared to Cs V_(3)Sb_(5),the van Hove singularities are pushed far away above the Fermi level in CsTi_(3)Bi_(5),in line with the absence of CDW.Furthermore,the first-principles calculations identify the nontrivial Z_(2)topological properties for those bands crossing the Fermi level,accompanied by several local band inversions.Our results suppose CsTi_(3)Bi_(5)as a complementary platform to explore the superconductivity and nontrivial band topology.

Erratum:Flat Band and Z_(2) Topology of Kagome Metal CsTi_(3)Bi_(5)[Chin.Phys.Lett.40,037102(2023)]

In our most recently published article,[1]an important reference[2]predicting CsTi_(3)Bi_(5) is missing and should be added,along with Ref.[3](originally Ref.[28]),to the introduction section.

Design of an efficient collector for the HIAF electron cooling system

A collector with high perveance,efficient recu-peration,and low secondary emissions is required for the 450-keV electron cooler in the HIAF accelerator complex.To optimize the collection efficiency of the collector,a simulation program,based on the Monte Carlo simulations,was developed in the world’s first attempt to calculate the electron collection efficiency.In this program,the backscattering electrons and secondary electrons generated on the collector surface are calculated using a Monte Carlo approach,and all electron trajectories in the collector region are tracked by the Runge–Kutta method.In this paper,the features and structure of our program are described.The backscattering electron yields,with various collector surface materials,are calculated using our pro-gram.Moreover,the collector efficiencies for various col-lector structures and electromagnetic fields are simulated and optimized.The measurement results of the collection efficiency of the HIAF collector prototype and the CSRm synchrotron are also reported.These experimental results were in good agreement with the simulation results of our program.

Ultralight and compressive SiC nanowires aerogel for high-temperature thermal insulation

Aerogels with excellent properties combination of ultralow density and great thermal insulation are drawing attention to applications in harsh conditions.Common aerogels,however,are usually constructed with nanoparticles with a weakness in physical combination.The silicon carbide nano wire(SiC_(NW)) is a kind of one-dimensional(1D) nano wire possessing the promising properties of flexibility,great thermal insulation,and stability at high temperatures.An aerogel constructed by the SiC_(NW) will produce a great material with a promising material,the amazing SiC_(NW) aerogel.Here,a novel SiC_(NW) aerogel was fabricated consisting of quantities of β-SiC_(NW) of15-40 nm in diameter and tens to hundreds of micrometers in length.This SiC_(NW) aerogel possessed an ultralow density of 5.82 mg·cm^(-3),high-temperature resistance,and great thermal insulation with its thermal conductivities of0.063 W·m^(-1)·K^(-1) at 100℃ and 0.243 W·m^(-1)·K^(-1) at900℃ in He.Furthermore,the thermal insulation applicability of this aerogel was simulated.This study provides a promising way for designing and fabricating other multifunctional nanowire aerogels for high-temperature thermal insulation.

Enhancement of electron–ion recombination rates at low energy range in the heavy ion storage ring CSRm

Recombination of Ar^(14+), Ar^(15+), Ca^(16+), and Ni^(19+) ions with electrons has been investigated at low energy range based on the merged-beam method at the main cooler storage ring CSRm in the Institute of Modern Physics, Lanzhou,China. For each ion, the absolute recombination rate coefficients have been measured with electron–ion collision energies from 0 meV to 1000 meV which include the radiative recombination(RR) and also dielectronic recombination(DR)processes. In order to interpret the measured results, RR cross sections were obtained from a modified version of the semiclassical Bethe and Salpeter formula for hydrogenic ions. DR cross sections were calculated by a relativistic configuration interaction method using the flexible atomic code(FAC) and AUTOSTRUCTURE code in this energy range. The calculated RR + DR rate coefficients show a good agreement with the measured value at the collision energy above 100 meV.However, large discrepancies have been found at low energy range especially below 10 meV, and the experimental results show a strong enhancement relative to the theoretical RR rate coefficients. For the electron–ion collision energy below 1 meV, it was found that the experimentally observed recombination rates are higher than the theoretically predicted and fitted rates by a factor of 1.5 to 3.9. The strong dependence of RR rate coefficient enhancement on the charge state of the ions has been found with the scaling rule of q^(3.0), reproducing the low-energy recombination enhancement effects found in other previous experiments.