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(上)

文章介绍了我国生物学家汤佩松先生和理论物理学家王竹溪先生42年前在植物生理学方面作出的一项具有重要历史意义的贡献．他们于1941年先于西方科学家二十多年提出解释植物细胞水分关系的热力学理论,首先引入了水势概念．然而这项贡献一直被埋没四十多年才得到承认．文章分析了汤佩松和王竹溪先生工作的内容、历史地位及其产生的背景,讨论了其在国内外的遭遇的原因及今日应当从中记取的教训．     

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     

How to introduce temperature to the 1D Sznajd model

We investigate the possibility of introducing temperature to the one dimensional Sznajd model and propose a natural extension of the original model by including other types of interactions. We characterise different kinds of equilibria into which the extended system can evolve. We determine the consequences of fulfilling the detailed balance condition and we prove that in some cases it is equivalent to microscopic reversibility. We found the equivalence of the model to the standard (inflow) model with interactions up to next nearest neighbors. It is shown that under some constraints there exists a Hamiltonian compatible with the dynamics and its form resembles that of the 1D ANNNI model. It appears however, that the standard approach of constructing temperature from the Hamiltonian fails. In this situation we propose a simple definition of the temperature-like quantity that measures the size of fluctuations in the system at equilibrium. The complete list of zero-temperature degenerated cases as well as the list of ground states of the derived Hamiltonian are provided.     

Diffusion of gases into the lung: How physics can help to understand physiology

In the human lung, the gas transfer between air and blood is achieved in terminal units that are called ‘acini’. Whereas convection is still the predominant transport phenomenon at the acinus entrance, most of the acinar surface is in fact accessed by diffusion. The transition between convection and diffusion, and thus the size of the diffusion unit, depends on the air velocity at the acinus entrance. In this paper, we present a gas transport model which takes into account both the diffusion into the acinus and the diffusion across the alveolar membrane. It is shown that the physiological sizes of the diffusion unit in the lung, at rest or at exercise, can be explained by physical arguments. In that sense, diffusion is the ‘dimensioning criterion’ of the lung at the acinar level. This approach shows that, due to diffusional screening at inspiration and at rest, there exists a permanent spatial inhomogeneity of oxygen and carbon dioxide partial pressure which reduces the effective surface efficiency of the human acinus to a value of only 30 to 40%. This model casts a new light on the properties of this physiological transport system. It permits in particular to understand how several diseases among which pulmonary edema may remain asymptomatic in their early stages.      

On the use of the method of wave images to introduce students to acoustics

A previous paper [Ginsberg, 2006, J. Acoust. Soc. Am. 119, 1954-1960] extended the d'Alembert solution of the one-dimensional wave equation to semi-infinite and finite length waveguides. The concept uses images of incident waves in order to describe reflection phenomena. Each image is algebraically related to an incident wave when the restriction to purely resistive terminations is met. The present paper extends the previous treatment from initial value problems to situations in which the particle velocity at a termination is specified. The discussion emphasizes the use of hand-drawn sketches as a method that will allow students at all levels to understand the basic processes of wave propagation and reflection. The number and complexity of the wave images is enhanced in a bounded waveguide, so simple numerical algorithms for evaluating the response of such systems also are discussed. The wave image technique is applied to a sequence of increasingly complicated systems. Suggestions are given regarding what material should be presented to students at various levels, and what students can be expected to garner from each case. The recommendation is that this solution method should be used to introduce students at all levels to basic acoustical phenomena.     

原子物理学中如何介绍量子理论的讨论

介绍了如何运用量子力学的基本原理讲授原子物理学的新的教学法。     

狄拉克方程的单旋量解法以及由此引起的认识上的差异

把狄拉克方程分解成了两个单旋量的联立方程组．指出现行的自旋理论仅考虑了其中的一个方程，是以一个单旋量代替双旋量来描述状态而建立起来的．笔者在认同现行自旋理论可以作为狄拉克方程的一种求解方法，因而同意其中的某些提法外，对于其主要的物理观念：微观粒子存在着独立于现实的位形空间之外的一个自旋空间，在这个自旋空间内禀着角动量S和磁矩μ；这个自旋理论是相对论性量子力学导出的必然结论等等看法予以否定．笔者认为，只有同时考虑两个单旋量的方程，同时计及两个单旋量，才能准确地描述状态，从而正确地描述客观规律．     

Peculiar meaning of the concept of the information depth in appearance potential spectroscopy

The information depth of APS is not related to the escape depth of the Auger electrons, because all electrons escaping from the target at a threshold potential can contribute to the signal without respect to the amount of energy they have lost. Nevertheless, the definition of the information depth proposed by the E-42 Committee of the American Society for Testing and Materials is still valid. Our paper presents and discusses results of a recent experimental investigation of the information depth of AEAPS and DAPS.     

Medium corrections to the first order optical potential for low-energy pion-4He scattering

We study the Pauli-principle corrections for low energy π-⁴He elastic scattering. In our approach we take into account explicitly the spin and isospin dependence of the Pauli-principle effect. Furthermore we discuss the combined effect of the Pauli-principle correction and the nuclear binding. Contrary to the Pauli principle we treat the binding corrections in an approximate way, using an effective mass for the residual nucleus. In our calculations we use the first-order optical potential of Celenza, Liu and Shakin. The Pauli-principle correction is found to have a considerable effect on the differential cross section. Our results indicate that the Pauli-principle corrections are largely compensated by the nuclear binding.     

耦合表象下的原子第一电离能的计算

以相对论的Xα方程为基础,提出了一种新的计算模型,即耦合表 象下的自旋极化模型。该模型综合地考虑了相对论效应和电子的自旋状态,把处于自旋混合 态的电子并入已有的自旋极化模型中。用此模型计算了第三周期至第六周期的ⅢA～ⅧA原子 的电离势。计算结果与自旋极化模型,自旋非极化模型的计算结果以及实验结果进行了比较 。该模型在一定程度上优于其它计算模型,在核电荷数较大的体系中计算结果更接近实验值 。