β-Ga_(2)O_(3)晶体本征缺陷诱导的宽带超快光生载流子动力学

利用超快瞬态吸收光谱,针对氧化镓(β-Ga_(2)O_(3))晶体中本征缺陷诱导的载流子俘获和复合等动力学进行研究.实验发现,由本征缺陷诱导的宽带吸收光谱具有很强的偏振依赖性,特别是从不同探测偏振下的瞬态吸收光谱中可以提取出两个缺陷态吸收响应.该缺陷诱导的吸收响应归因于从价带到本征缺陷(镓空位)不同电荷态的光学跃迁,利用基于单缺陷的多能级载流子俘获模型拟合得到缺陷俘获空穴的速率远快于俘获电子,且缺陷态的吸收截面相较于自由载流子吸收截面大至少一个数量级.本文的研究结果不仅能明确本征缺陷与光生载流子动力学之间的关系,而且为β-Ga_(2)O_(3)在超快宽带光电子器件中的应用提供科学指导.

Atomistic simulation of defected magnesium hydroxide as flame retardants

The mechanical properties and the point defect energy of magnesium hydroxide（Mg（OH）2） were studied using the molecular dynamics. Moreover, the microelectronic structure of Mg（OH）2 with point defects in the bulk and on its surface were investigated using the first principles. The simulation results indicate that Mg（OH）2 was easily modified by other cations because of its strong, favorable interstitial and substitution defects via point defect energy calculation. Mg（OH）2 can provide high-efficiency flame retardancy because of the strong OH（OH Schottky defect） or H bond（H Frenkel defect and Schottky defect）. The potential model of Mg（OH）2 was established, and molecular dynamics simulation was used to investigate the relations between the crystal structure and the mechanical properties. Mg（OH）2 with special morphology such as nano-sheets was a prior consideration to maintain the composite mechanical properties. The detailed electronic structures of Mg（OH）2 with defects were determined. This work may provide theoretical guidance for choosing dopant element and reveal the element doping mechanism of Mg（OH）2.

A Kinetic Model of Dielectric Ageing

A kinetic model of dielectric ageing is presented. The central finding of this investigation is that there is a power-law relationship between the local electric field concentration and the rate of defect-tip initiated conducting crack growth. By applying such a power-law conducting crack growth rate expression to the evaluation of the life of solid dielectrics, the empirical classical ageing law of insulation materials can be derived theoretically as a lobical result. All the results are universal and agree with the experimental data of oxide films.

Unveiling Defect-Mediated Carrier Dynamics in Few-Layer MoS2 Prepared by Ion Exchange Method via Ultrafast Vis-NIR-MIR Spectroscopy

Defect-mediated processes in two-dimensional transition metal dichalcogenides have a significant influence on their carrier dynamics and transport properties,however,the detailed mechanisms remain poorly understood.Here,we present a comprehensive ultrafast study on defect-mediated carrier dynamics in ion exchange prepared few-layer MoS2 by femtosecond time-resolved Vis-NIR-MIR spectroscopy.The broadband photobleaching feature observed in the near-infrared transient spectrum discloses that the mid-gap defect states are widely distributed in few-layer MoS2 nanosheets.The processes of fast trapping of carriers by defect states and the following nonradiative recombination of trapped carriers are clearly revealed,demonstrating the mid-gap defect states play a significant role in the photoinduced carrier dynamics.The positive to negative crossover of the signal observed in the mid-infrared transient spectrum further uncovers some occupied shallow defect states distributed at less than0.24 e V below the conduction band minimum.These defect states can act as effective carrier trap centers to assist the nonradiative recombination of photo-induced carriers in few-layer MoS2 on the picosecond time scale.

Analytical Bond-order Potential for hcp-Y

The lattice parameters, elastic constants, cohesive energy, structural energy differences, as well as the properties of point defects and planar defects of hexagonal closepacked yttrium （hcpY） have been studied with ab initio density functional theory for constructing an ex tensive database. Based on an analytical bondorder poial scheme, empirical manybody interatomic potential for hcpY has been developed. The model is fitted to some properties of Y, e.g., the lattice parameters, elastic constants, bulk modulus, cohesive energy, vacancy formation energy, and the structural energy differences. The present potential has ability to reproduce defect properties including the selfinterstitial atoms formation energies, vacancy formation energy, divacancy binding energy, as well as the bulk properties and the thermal dynamic properties.

Energy Radiation of the Active Galactic Nuclei

In the Hellings Nordtvedt theory, we obtain some expressions of energy radiation and mass defect effect for a kind of the active galactic nuclei, which is meaningful to calculating the energy radiation in the procession of forming this kind of celestial bodies. This calculation can give some interpretation for energy source of the jet from the active galactic nuclei.

Clinical Observation on Acupuncture Intervention for Children with Attention Deficit Hyperactivity Disorder

Objective： To observe the effect of acupuncture for children with attention deficit hyperactivity disorder （ADHD）. Methods： A total of 36 cases were recruited in this study. Before treatment, a Chinese medical constitution survey was conducted on these children. Based on the survey findings, the children were divided in different groups for acupuncture intervention. Additionally, the heart rate variability and attention were detected respectively before treatment, in the 12th and 24th week after treatment. Results： ADHD kids commonly manifest as a body constitution of yang predominance and heat exuberance. The kids＇ Body Mass Indexes （BMI） are moderately correlated with attention deficit disorder （ADD）. After the treatment of 24 weeks, the ADHD scores were reduced from （10.94±1.98） to （8.56±2.48）, showing a statistical significance （P〈0.05）; in addition, the low frequency/high frequency （LF/HF） and normalized low frequency （nLF） between the two groups were also statistically different （P〈0.05）. Conclusion： Most ADHD kids present with a body constitution of yang predominance and heat exuberance. A well-controlled BMI is helpful for ADHD treatment. Acupuncture can be a supplementary therapy to improve the ADHD symptoms.

A molecular dynamics-based comparison of defect production in collision cascades during the bombardment of iron with different ions

We present a computer simulation study on the influence of incident ions on the energy transferred to primary knock-on atoms(PKAs)and defects produced in the cascade collision of irons.Three types of ions(H,Fe,and Xe,which are frequently used in irradiation experiments)with an energy of 3 MeV were simulated.According to the calculation results of SRIM,the average energy transferred to PKAs by Fe ions was the highest among the three types.Then,cascade collisions induced by PKAs with different energies were simulated by the molecular dynamics method.The maximum number of defects produced during irra-diation increased,and the time taken by defect number peak formation was extended with the increased energy of PKAs.The difference in radial distribution function between pre-and post-irradiation irons showed that a higher energy of PKA transferred resulted in a flatter curve.Besides,the law of defects varying in temperature was also investigated.All the researches imply that heavy ions can substitute for neutrons in irradiation experiments which is a practicable way,but the influence of conditions must be taken into account.

Point defects in L1_0 FePt studied by molecular dynamics simulations based on an analytic bond-order potential

The point defects and their related physical properties in L10 FePt are investigated by molecular dynamics simulations based on an analytic bond-order potential. The calculated results agree well with the experimental value, indicating that the analytic bond-order potential is suitable to describe the structural properties and surface energies of the FePt alloy in the L10 phase. However, the calculated vacancy formation energy of an Fe atom is higher than that of a Pt atom, which disagrees with some other previously calculated results. This result indicates that the analytic bond-order potential is unable to describe the related point defect properties. The analytic bond-order potential needs to be modified in order to study these defect properties of an FePt alloy.

Early fluid loading for septic patients： Any safety limit needed？

Early adequate fluid loading was the corner stone of hemodynamic optimization for sepsis and septic shock. Meanwhile, recent recommended protocol for fluid resuscitation was increasingly debated on hemodynamic stability vs risk of overloading. In recent publications, it was found that a priority was often given to hemodynamic stability rather than organ function alternation in the early fluid resusci- tation of sepsis. However, no safety limits were used at all in most of these reports. In this article, the rationality and safety of early aggressive fluid loading for septic patients were discussed. It was concluded that early aggressive fluid loading improved hemodynamics transitorily, but was probably traded off with a follow-up organ function impairment, such as worsening oxygenation by reduction of lung aeration, in a part of septic patients at least. Thus, a safeguard is needed against unnecessary excessive fluids in early aggressive fluid loading for set）tic patients.

DYNAMICS BEHAVIOR OF MUTATION DURING REPRODUCTION ON HIV-1 DRUG RESISTANCE

To study the transition dynamics of resistant-type human immunodeficiency virus 1 （HIV-1） in highly active antiretroviral therapy （HAART） and the affect of neutral mutation in the evolution of HIV-1, a mathematical model is proposed when mutation occurs mainly during reproduction. The derived results show that the resistant-type will certainly colonize in patients once mutation occurs. Furthermore, a neutral mutation is closely related to the colonized pattern of resistant-type HIV-1 quasispecies and there are some changes in the pattern of transmission dynamics when mutation occurs mainly during reproduction or in the absence of reproduction, which may lead to significant strategies for predicting or checking HIV-1 drug resistance in HAART.