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871.
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. 相似文献
872.
DNA damage,signaling and repair: Protecting genomic integrity and reducing the risk of human disease
PingKun Zhou 《科学通报(英文版)》2011,56(30):3119-3121
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- 相似文献
873.
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. 相似文献
874.
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. 相似文献
875.
876.
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. 相似文献
877.
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. 相似文献
878.
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. 相似文献
879.
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. 相似文献
880.
本文对文峪金矿铜铅混合精矿进行了振动高梯度磁选分离铜铅的试验研究,并由此提出了浮-磁-重联合流程选矿新工艺,同时对新工艺进行了试验研究,取得很好的试验指标。研究结果表明,振动高梯度磁选的采用有可能使原现场整个分选工艺产生根本性的变革,从而提高生产指标,增加经济效益。 相似文献