中国理论物理学家与生物学家结合的典范--回顾汤佩松和王竹溪先生对植物细胞水分关系研究的历史性贡献(下)

(上接 2 0 0 3年第 6期第 4 0 9页 )4　汤、王论文出现的主观与客观条件汤、王对植物生理学所作出的此一历史性贡献 ,是一位植物生理学家和一位理论物理学家合作的结果 .此一事实在一定的意义上表明 ,对于自然科学的某一特定领域一些基本问题的突破 ,根据问题所涉及知识领域的不同 ,往往是在多学科科学工作者的协作或具有不同专长的相同学科学者的合作下完成的 .自然科学史上这样的情况并不罕见 ,DNA双螺旋结构的创立是跨学科科学家协作的典型 ,低温超导中BCS理论的建立是同学科不同特长学者合作的范例 .汤、王二位先生能在 194 0年完成…     

记忆往往是靠不住的——对拙文“中国理论物理学家与生物学家结合的典范”的一处更正

2003年,我在《物理》发表了一篇文章,纪念我国理论物理学家王竹溪先生和生物学家汤佩松先生合作提出植物水势概念的历史功绩,文章的标题是《中国理论物理学家与生物学家结合的典范——回顾汤佩松和王竹溪先生对植物细胞水分关系研究的历史性贡献》,该文分(上)、(下)两部分分别刊登在2003年《物理》第32卷的第6期403—409页和第7期的477—483页.承读者和编辑部厚爱,这篇文章2005年经推荐曾获得第二届中国科协期刊优秀学术论文奖,并被一本书(杨舰、戴吾三编,《清华大     

The equivalent dipole potential of water for the electronic structure of threonine

The equivalent potential of water for the electronic structure of threonine (Thr) in solution is constructed by the first-principles, all-electrons, ab initio calculations. The main process of calculation consists of three steps. First, the geometric structure of the cluster containing Thr and water molecules is calculated by the free cluster calculation. Then, based on the obtained geometric structure, the electronic structure of Thr with the potential of water molecules is calculated using the self-consistent cluster-embedding method. Finally, the electronic structure of Thr with the potential of dipoles is calculated. The results show that the major effect of water on the electronic structure of Thr is to raise the occupied molecular orbitals near the Fermi level by about 0.01 Ry on average, and its energy gap is almost not changed. The effect of water on the electronic structure of Thr can be simulated by dipoles potential.     

How water and counterions diffuse into the hydrated montmorillonite

Molecular dynamics simulations have been performed to study the diffusive transport properties of water and counterions in 1-, 2- and 3-layer hydrated Wyoming-type montmorillonite (MMT). The considered counterions included in the clay are monovalent cations, such as Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, and divalent cations, such as Ca²⁺, Ni²⁺, Zn²⁺ and Pb²⁺. The diffusion simulation results of Li-, Na-, K-, Cs-MMT, based on NVE ensemble and SPC/E water model, compared well to available experimental quantities and previous simulations, which permit us to study the diffusion behaviour of heavy metal counterion including in the different hydrated montmorillonite. Our simulation results show that the diffusion coefficients of both water molecule and counterions increase versus the quantity of water content. At the same hydrated state, the diffusion of cations strongly depends on their size, weight and capacity of attracting water. Monovalent cations diffuse always much faster than divalent ones. Although the increasing of hydrate degree can raise the diffusion coefficient of divalent heavy cations, the activity of these heavy counterions is still very weak. The diffusion of cations in the interlayer space of clay is much weaker than that in bulk water. That means the presence of charged clay has great influence on the diffusion of cations, which change totally the diffusion behaviour of cations.     

Addendum to “On the exploitability of thermo-charged capacitors” [Physica A 390 (2011) 482–491]

In the article [Physica A 390 (2011) 482–491], an explicit discussion on contact potential (and its alleged consequences) arising between the inner metallic sphere of a thermo-charged spherical capacitor and its Ag–O–Cs coating is missing. This addendum aims to clarify this issue.     

Renormalization of the chemical potential due to multiphonon effects at the surface of metals

We study the relation between renormalization of the chemical potential due to multiphonon effects at the surface of Be(0001) and doping by solving the strong-coupling self-consistent equations of a two-dimensional(2D) electron-phonon interaction system.We present the quasiparticle dispersions and inverse lifetimes of a 2D electron system interacting with Einstein phonons under the different dopings(corresponding to chemical potentials).We find that the effect of electron-phonon interaction on electron structure is strongest at the half filling,but it has no effect on the chemical potential.However,the chemical potential shows distinct renormalization effects away from half filling due to the electron-phonon interaction.     

一个保守力作的功能等于势能的减少吗

通过实例说明一个保守力作的功,在一般情况下并不等于势能的减少,一个对保守力作用功才等于势能的减少。     

Experimental evaluation of the measurement errors of soil water content due to interference of two adjacent TDR probes

The objective of this experimental study was to determine the measurement errors caused by the interference effects when two TDR probes operate nearby in various distance apart for different soil types and soil water contents. The results will help to guide the design of an experimental apparatus which aims to study the coupled heat and moisture transfer in soils at high temperatures of higher than 40°C with the highest possible spatial resolution. The interference effect between two adjacent time domain reflectometry (TDR) probes has been evaluated and analyzed experimentally. It was observed that the distance between the probes, soil texture, and the water content of the testing soil is the key parameters which affect the interference and TDR probe capability of measurement. In this study, three types of soils were examined, namely FSJ#1 (silty clay), Matilda (loamy sand), and Ottawa sand C-190 (quartz sand). Three different volumetric water contents were evaluated for each soil. The interference effect was noticeable in all soil samples when the distances between the probes were 1 cm. For the samples with higher moisture content, the effect of interference on the TDRs’ electromagnetic waveform signals is more prominent. Interference was found in Matilda samples with degrees of saturations of 0.5 and higher even though the distances between the probes were greater than 1 cm; nevertheless, the determination of volumetric water content was not affected by the interference, because the interference only caused the two TDRs’ electromagnetic waveform signals to shift by the same length. No interference was observed in cases of FSJ#1 and Ottawa sand when the distances between the probes were greater than 1 cm. From the results, it was found that the sensitivity zone of our TDR equipment is a radius of about 10 mm surrounding the central needle of the TDR probe. In case of FSJ#1, when interference occurs, the measurement error of water content significantly increases from 9.3% to 15.5%, corresponding to the degree of saturation from 0.25 to 1.0.