Density of excess modes below the first phonon mode in four-dimensional glasses

Glasses are known to possess low-frequency excess modes beyond the Debye prediction.For decades,it has been assumed that evolution of low-frequency density of excess modes D(ω) with frequency ω follows a power-law scaling:D(ω)~ω~γ.However,it remains debated on the value of γ at low frequencies below the first phonon-like mode in finitesize glasses.Early simulation studies reported γ=4 at low frequencies in two-(2D),three-(3D),and four-dimensional(4D)glasses,whereas recent observations in 2D and 3D glasses suggested γ=3.5 in a lower-frequency regime.It is uncertain whether the low-frequency scaling of D(ω)~ω^(3.5) could be generalized to 4D glasses.Here,we conduct numerical simulation studies of excess modes at frequencies below the first phonon-like mode in 4D model glasses.It is found that the system size dependence of D(ω) below the first phonon-like mode varies with spatial dimensions:D(ω) increases in2D glasses but decreases in 3D and 4D glasses as the system size increases.Furthermore,we demonstrate that the ω^(3.5)scaling,rather than the ω~4 scaling,works in the lowest-frequency regime accessed in 4D glasses,regardless of interaction potentials and system sizes examined.Therefore,our findings in 4D glasses,combined with previous results in 2D and 3D glasses,suggest a common low-frequency scaling of D(ω)~ ω^3.5) below the first phonon-like mode across different spatial dimensions,which would inspire further theoretical studies.

Thyroid Nodule Prevalence and Iodine Nutrition:Influencing Factors in Coastal Areas

Iodine is an essential trace element for human health.The thyroid gland uses iodine for the synthesis of thyroid hormones.Most iodine comes from food and drinking water,and approximately 85%is excreted through the urine.Therefore,urinary iodine content is an important indicator for judging the iodine nutrition level of a population[1].A thyroid nodule is a discrete mass resulting from the abnormal proliferation of thyroid cells.Iodine deficiency in the general population has dramatically diminished after implementing universal salt iodization(USI)policies.However,the incidence of thyroid nodules has been reported to be increasing following the implementation of USI,leading some to question the plausibility of USI.This data from Zhao et al.

The State Equations Methods for Stochastic Control Problems

The state equations of stochastic control problems,which are controlled stochastic differential equations,are proposed to be discretized by the weak midpoint rule and predictor-corrector methods for the Markov chain approximation approach. Local consistency of the methods are proved.Numerical tests on a simplified Merton's portfolio model show better simulation to feedback control rules by these two methods, as compared with the weak Euler-Maruyama discretisation used by Krawczyk.This suggests a new approach of improving accuracy of approximating Markov chains for stochastic control problems.

Nonperturbative effects of attraction on dynamical behaviors of glass-forming liquids

We investigate systematically the effects of the inter-particle attraction on the structure and dynamical behaviors of glass-forming liquids via molecular dynamics simulations.We find that the inter-particle attraction does not influence the structure,but greatly affects the dynamics and dynamical heterogeneity of the system.After the system changes from a purely repulsive glass-forming liquid to an attractive one,the dynamics slows down and the dynamical heterogeneity becomes greater,which is found interestingly to be associated with larger cooperative rearrangement regions(CRRs).Additionally,the structures of CRRs are observed to be compact in attractive glass-forming liquids but string-like in purely repulsive ones.Our findings constitute an important contribution to the ongoing study of the role of attractions in properties of glasses and glass-forming liquids.

Absolute Structure Determination of Chiral Organic Nanocrystals Using Zone-Axis Electron Diffraction

Enantiomorphic identification of chiral molecules is essential in organic chemistry and the pharmaceutical industry,as two enantiomorphic structures can show distinctively different properties.Here,we illustrate the absolute structural determination of organic nanocrystals using zone-axis electron diffraction by taking advantage of electron multiple scattering.Two enantiomorphs are distinguished by comparing the reflection intensities of Friedel pairs in the zone-axis electron diffraction pattern,after confirming the absolute indices of reflections by locating relative positions of diffraction spots from two patterns that deviate from a certain angle.We demonstrate the protocol with successful applications in two chiral drug nanocrystals.

多元铜基硫族半导体纳米晶的发光性能及其在电致发光器件中的应用进展

半导体纳米晶(又称为半导体量子点)由于其色纯度高和尺寸依赖的发光性能等优势,在照明和显示方面受到了科学界和产业界的广泛关注.目前,基于半导体量子点的电致发光器件所使用的发光材料以镉基硫族化合物量子点为主,然而镉元素对环境和人体都有一定的危害.因此,开发一种环境友好且光电性能良好的无镉半导体纳米晶是非常必要的.近年来,多元铜基硫族半导体纳米晶由于其毒性低、组分可调的发光特性及其在光电子器件领域的潜在应用受到了广泛关注.本文详细综述了多元铜基硫族半导体纳米晶的组分、表面配体、晶体结构和纳米结构等因素对其发光特性的影响,着重阐述了多元铜基硫族半导体纳米晶在电致发光器件中的研究进展,最后对多元铜基硫族半导体纳米晶的发展进行了展望.

Accumulation and potential sources of heavy metals in soils of the Hetao area,Inner Mongolia,China

Soil contamination by heavy metals is a problem in agricultural irrigation systems.To assess the accumulation and sources of heavy metals in the Yongji irrigation district of the Hetao area,Inner Mongolia,China,195 soil samples from 39 sites(0–100 cm)were collected,and Zn,Cu,Pb,Cr,and Cd concentrations were analyzed.The mean concentrations were 107.17,32.48,12.31,53.53,and 0.22 mg kg-1,respectively,with no significant differences between soil depths(P>0.05).Concentrations of Zn,Cu,and Cd were higher than the background levels,with moderate accumulation;the contamination factor(CF)values were 1.9,1.7,and 1.9,respectively,and the geoaccumulation index(Igeo)was>0.Concentrations of Pb and Cr were lower than,or close to,the background levels(CF<1,Igeo<0),indicating that they originated from a natural source.The monomial potential ecological risk index(Eri)for Zn,Cu,Pb,and Cr was low;Eri for Cd was 55.73,implying a moderate risk.The grade of potential ecological risk index of the five heavy metals(RI)was low,declining from south to north.The studied soils were contaminated with Zn,Cu,and Cd;principal component(PC)analysis implicated the enrichment of Cd and partial Cu(high loading in PC 2)was related to agricultural activities;Zn and partial Cu,closely associated with PC 3,may have originated from irrigation water from the Yellow River.Future agricultural development should focus on fertilizer and pesticide application and the quality of irrigation water.

Cuckoo search with varied scaling factor

Cuckoo search （CS）, inspired by the obligate brood parasitic behavior of some cuckoo species, iteratively uses L6vy flights random walk （LFRW） and biased/selective random walk （BSRW） to search for new solutions. In this study, we seek a simple strategy to set the scaling factor in LFRW, which can vary the scaling factor to achieve better performance. However, choosing the best scaling factor for each problem is intractable. Thus, we propose a varied scal- ing factor （VSF） strategy that samples a value from the range [0,1] uniformly at random for each iteration. In addition, we integrate the VSF strategy into several advanced CS vari- ants. Extensive experiments are conducted on three groups of benchmark functions including 18 common test functions, 25 functions proposed in CEC 2005, and 28 functions intro- duced in CEC 2013. Experimental results demonstrate the ef- fectiveness of the VSF strategy.

Stochastic Multi-Symplectic Integrator for Stochastic Nonlinear Schrodinger Equation

In this paper we propose stochastic multi-symplectic conservation law for stochastic Hamiltonian partial differential equations,and develop a stochastic multisymplectic method for numerically solving a kind of stochastic nonlinear Schrodinger equations.It is shown that the stochasticmulti-symplecticmethod preserves themultisymplectic structure,the discrete charge conservation law,and deduces the recurrence relation of the discrete energy.Numerical experiments are performed to verify the good behaviors of the stochastic multi-symplectic method in cases of both solitary wave and collision.

Sequential quadratic programming enhanced backtracking search algorithm

In this paper, we propose a new hybrid method called SQPBSA which combines backtracking search optimization algorithm （BSA） and sequential quadratic programming （SQP）. BSA, as an exploration search engine, gives a good direction to the global optimal region, while SQP is used as a local search technique to exploit the optimal solution. The experiments are carried on two suits of 28 functions proposed in the CEC-2013 competitions to verify the performance of SQPBSA. The results indicate the proposed method is effective and competitive.

A Symplectic Based Neural Network Algorithm for Quantum Controls under Uncertainty

Robust quantum control with uncertainty plays a crucial role in practical quantum technologies.This paper presents a method for solving a quantum control problem by combining neural network and symplecticfinite difference methods.The neural network approach provides a framework that is easy to establish and train.At the same time,the symplectic methods possess the norm-preserving property for the quantum system to produce a realistic solution in physics.We construct a general high dimensional quantum optimal control problem to evaluate the proposed method and an approach that combines a neural network with forward Euler’s method.Our analysis and numerical experiments confirm that the neural network-based symplectic method achieves significantly better accuracy and robustness against noises.

Solution-processed electroluminescent whitelight-emitting devices based on AIE molecules and Cu-In-Zn-S nanocrystals

Solution process is a key technique for the manufacture of large-area and low-cost semiconducting devices and,thus, attracts a lot of attention from both academia and industry. Herein, we realized solution-processed lightemitting diodes(excluding a cathode) based on aggregation-induced emission(AIE) molecules of tetraphenylethylene-4Cl(TPE-4Cl) and cadimum-free semiconductor nanocrystals(NCs) for the first time. By mixing Cu-In-Zn-S NCs and TPE-4Cl as an emissive layer, a new type of environmentally friendly white-light-emitting diodes(WLEDs) was prepared through a solution-processed technique. After systematical optimization of the asprepared WLEDs, the corresponding color rendering index can reach up to 87 with a maximum luminance of262 cd/m2. This study may pave a new road to realize AIE-based WLEDs through a solution-processed technique.