A liquid helium temperature target with a 10 K vapor shield for shock compression experiment in the environment condition of 100 Pa

The shock compression experiment of liquid helium is an available way to gain properties of specimen at high temperatures and pressures.Based on Fluent,a thermal insulation analysis and design of a liquid helium temperature target in the environment condition of 100 Pa for shock compression experiment is performed.Then,a cryogenic target with a 10 K helium vapor shield and a separated vacuum interval is particularly developed.A lowest temperature of 3.63 K and a stable temperature of 3.70 K in the specimen cavity with an accuracy of 0.1 K are obtained by means of continuous flow and vacuum cooling.Both time-consuming and temperature stability are well-suited to the requirements of the shock compression experiment.The results show that the calculated and experimental data well-matched each other.The simulation method may be effective and feasible for the optimal design of the cryogenic target.     

DNA damage,signaling and repair: Protecting genomic integrity and reducing the risk of human disease

DNA is the genetic material that contains the "instructions" to not only guide the continuation of life but also govern the development, metabolism and functioning of living organisms. DNA damage occurs daily due to various exogenous (environ-     

Intrinsic abnormal electromagnetic medium based on polar lattice vibration

A new class of media with abnormal electromagnetic parameters has been attracting increasing attention because of its exotic properties and potential application. Currently, typical metamaterials are mainly composed of artificially designed metallic periodic structures. However, due to the limitations of available fabrication technologies, physical size and material effects, it is difficult to realize these abnormal properties by these artificial structures in the high-frequency regime. Therefore, it is important to find materials with intrinsic abnormal electromagnetic responses. In this field, a new mechanism based on the interaction between polar lattice vibrations and electromagnetic waves has been proposed. In this paper, we review progress in this field.     

Nonlinear Langevin model with product stochasticity for biological networks: The case of the Schnakenberg model

Langevin equation is widely used to study the stochastic effects in molecular networks, as it often approximates well the underlying chemical master equation. However, frequently it is not clear when such an approximation is applicable and when it breaks down. This paper studies the simple Schnakenberg model consisting of three reversible reactions and two molecular species whose concentrations vary. To reduce the residual errors from the conventional formulation of the Langevin equation, the authors propose to explicitly model the effective coupling between macroscopic concentrations of different molecular species. The results show that this formulation is effective in correcting residual errors from the original uncoupled Langevin equation and can approximate the underlying chemical master equation very accurately.     

Density and structure of undercooled liquid titanium

For liquid Ti, it is difficult to achieve high undercooling because of its chemical reactivity; as a result, there is little information available on its properties and structure in the undercooled state. In this study, we investigate the density and structure, using molecular dynamics method, for the undercooling and superheating ranges 0-743 K and 0-457 K. The density increases quadratically for undercooling. At the melting temperature, the density is 4.14 g/cm3, and first and second temperature coefficients are obtained. The pair correlation functions and coordination numbers indicate that the short range degree of order becomes increasingly significant with increasing undercooling.     

Generalized variation iteration solution of an atmosphere-ocean oscillator model for global climate

A box model of the interhemispheric thermohaline circulation (THC) in atmosphere-ocean for global climate is considered. By using the generalized variational iteration method, the approximate solution of a simplified nonlinear model is studied. The generalized variational iteration method is an analytic method, and the obtained analytic solution can be operated sequentially. The authors also diversify qualitative and quantitative behaviors for corresponding physical quantities.     

Temperature-induced fractionation of oxygen isotopes of diatom frustules and growth water in Lake Sihailongwan in Northeast China

Diatom oxygen isotopes have been widely applied in quantitative reconstruction of the paleoclimate and paleoenvironment, but have rarely been reported in China. In the present study, Lake Sihailongwan in Northeast China was selected for detailed investigation of oxygen isotopic fractionation between diatom frustules and lake water induced by growth temperature. This study involved a 2-year period of field monitoring of the lake water temperature at multiple depths and biweekly collections of traps for both sediment and water at shallow and bottom depths (7 and 49 m below the lake surface, respectively), diatom separation and purification of the trap sediments, and oxygen isotope measurement for diatom silica and lake water samples. The conditioned experiment conducted herein demonstrated that the laboratory device, methods and techniques used in this study were capable of generating reliable data for the typical oxygen isotope composition of diatom frustules. The data obtained revealed a prominent linear relationship between the oxygen isotope composition of the modern diatom and lake temperature during growth. The fractionation coefficient was about −0.185‰/°C−0.238‰/°C in the temperature range of 3.6–24°C, which is consistent with the observations from various aquatic environments and laboratory culture with different diatom taxa. These findings provide strong support for the dominant control of the growth temperature on the oxygen isotope fractionation between the diatom frustules and ambient water. A notable difference in the fractionation coefficient was observed between the surface and bottom diatom oxygen isotopes, suggesting that various depositional processes and taphonomic effects influenced the surface and bottom trap samples. Another factor leading to this difference may be that enrichment by evaporation and dilution by rainfall have a stronger influence on the surface. Overall, the results presented here demonstrate significant progress in evaluation of diatom oxygen isotopes in China and draw attention to the differences between surface and bottom diatom oxygen isotope compositions.     

Application of surface plasmon resonance in screening adsorbents and explaining adsorption phenomena using model polymers

A surface plasmon resonance (SPR) technique was developed as an online screening method to identify effective adsorbents for the peptide NH₂-Cys-Thr-Trp-Trp-COOH (CW-4). To validate the SPR technique, several linear polymers containing amino acid residues were synthesized as models of their corresponding adsorbents. SPR screening of all the linear polymers demonstrated that the linear polymer containing phenylalanine residues (PPhe) exhibited the highest affinity for CW-4 among the polymers tested. In accordance with the screening results from SPR, the adsorbent containing phenylalanine (APhe) exhibited the highest adsorption capacity for CW-4. An interesting observation was that the amounts of CW-4 adsorbed on 3 adsorbents were quite small, even though both SPR and isothermal titration calorimetry (ITC) experiments indicated the presence of interactions between CW-4 and the three polymers. A kinetic analysis performed using SPR technology suggested such a phenomenon was ascribed to the poor stability of the CW-4/polymer complexes; that is, CW-4 associates with the polymers quickly, but it also dissociated quickly. The combined results suggested that SPR was a promising tool to identify the optimal adsorbent for peptides, analyze the interactions contributing to adsorption and explain adsorption phenomena using polymer models.     

甲醇自发点火特性研究

从实验和数值模拟两方面探讨了甲醇的热点火特性。实验中应用快速压缩机得到了温度与点火延迟期的关系。计算中采用了基元化学反应动力学模型,给出了压力、温度、产物及主要中间反应体的变化历程。对助燃剂二叔丁基过氧化物的活化作用进行了理论分析。     

论高校实行设备有偿占有和有偿使用的可行性

本文针对我国高校实验设备利用率较低的现状,用价值工程的观点,从设备综合管理入手,采用设备折旧,实行设备有偿占有和有偿使用,从而提高设备的功能输出,有效地考核和提高设备的综合使用效益的可行性。并提出了以折旧为主线的实验设备有偿占有和有偿使用于系统功能评价框图。