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．     

Work-Related Communicative Profile of Voice Teachers: Effects of Classroom Noise on Voice and Hearing Abilities

PurposeVocal instructors during their normal workday are exposed to high noise levels that can affect their voice and hearing health. The goal of this study was to evaluate the voice and hearing status of voice instructors before and after lessons and relate these evaluations with voice and noise dosimetry taken during lessons.MethodsEight voice instructors volunteered to participate in the study. The protocol included (1) questionnaires, (2) pre/post assessment of voice quality and hearing status, and (3) voice and noise dosimetry during lessons. Acoustic measurements were taken of the unoccupied classrooms.ResultsIn six of eight classrooms, the measured noise level was higher than the safety recommendations set by National Institute for Occupational Safety and Health. The background noise level and the reverberation time in the classrooms were in compliance with the national standard recommendations. We did not find a clear pattern comparing pre- and post-measurements of voice quality consistent among genders. In all subjects, the Sound Pressure Levels mean increased, and the standard deviation of fundamental frequency decreased indicating association to vocal fatigue. Previous studies link these changes to increasing vocal fatigue. The audiometric results revealed seven out of eight instructors have sensorineural hearing loss.ConclusionsThe interaction of the acoustic space and noise levels can contribute to the development of hearing and voice disorders for voice instructors. If supported by larger sample size, the results of this pilot study could justify the need for a hearing and voice conservation program for music faculty.     

Modeling Long-Range Dynamic Correlations of Words in Written Texts with Hawkes Processes

It has been clarified that words in written texts are classified into two groups called Type-I and Type-II words. The Type-I words are words that exhibit long-range dynamic correlations in written texts while the Type-II words do not show any type of dynamic correlations. Although the stochastic process of yielding Type-II words has been clarified to be a superposition of Poisson point processes with various intensities, there is no definitive model for Type-I words. In this study, we introduce a Hawkes process, which is known as a kind of self-exciting point process, as a candidate for the stochastic process that governs yielding Type-I words; i.e., the purpose of this study is to establish that the Hawkes process is useful to model occurrence patterns of Type-I words in real written texts. The relation between the Hawkes process and an existing model for Type-I words, in which hierarchical structures of written texts are considered to play a central role in yielding dynamic correlations, will also be discussed.     

Republication of: On the initial value problem of the equations of gravitation

This is an English translation of a paper by Karl Stellmacher, first published in German in 1938, in which he presented the first, correct and successful, formulation of the initial value problem for Einstein’s equations in vacuum and with a dust source. The paper has been selected by the Editors of General Relativity and Gravitation for re-publication in the Golden Oldies series of the journal. This republication is accompanied by an editorial note written by Helmut Friedrich and Stellmacher’s brief biography written by Hubert Goenner.     

Republication of: Quantum theory of weak gravitational fields

This is an English translation of a paper by Matvei Bronstein, first published in German in 1936 in a long-extinct Soviet journal, in which he presented the first attempt at quantizing a weak (linearized) gravitational field, rather modern in its approach. The paper has been selected by the Editors of General Relativity and Gravitation for re-publication in the Golden Oldies series of the journal. This republication is accompanied by an editorial note written by Stanley Deser and Alexei Starobinsky, and Bronstein’s brief biography written by Stanley Deser.     

Loop variables and gauge invariant exact renormalization group equations for (open) string theory

An exact renormalization group equation is written down for the world sheet theory describing the bosonic open string in general backgrounds. Loop variable techniques are used to make the equation gauge invariant. This is worked out explicitly up to level 3. The equation is quadratic in the fields and can be viewed as a proposal for a string field theory equation. As in the earlier loop variable approach, the theory has one extra space dimension and mass is obtained by dimensional reduction. Being based on the sigma model RG, it is background independent. It is intriguing that in contrast to BRST string field theory, the gauge transformations are not modified by the interactions up to the level calculated. The interactions can be written in terms of gauge invariant field strengths for the massive higher spin fields and the non-zero mass is essential for this. This is reminiscent of Abelian Born–Infeld action (along with derivative corrections) for the massless vector field, which is also written in terms of the field strength.     

多层光纤布拉格光栅的理论与实验研究

从理论和实验两方面研究了在非周期性多层光纤上写入布拉格光栅的光学特性。从耦合模理论出发,讨论了光纤具有多于一个光敏层的情况。在实验室自制的两类多层光纤上写入光栅的实验也表明,该类光栅具备有一般光栅的普遍光学特性,说明在使用多层光纤作为关键部分构建器件时,需要的各类光栅部件能够通过直接在该类光纤上写入光栅实现。紫外光在氢载掺铒多层光纤上写入光栅的实验说明分层的异种元素掺杂将导致芯区应力增加,从而辅助提高光纤的光敏性。     

光信息科学与技术专业实验室建设探讨

根据同济大学光信息科学与技术专业的教学计划,同时结合我校的科研条件,筹建了相应的专业实验室。介绍了同济大学光信息科学与技术专业实验室建设过程中的规划和7类实验项目的内容和意义,如光谱学系列实验、光学系统CAD设计系列、光学薄膜CAD设计系列、光学薄膜特性测试实验、激光系列实验、光电基础和光电探测系列实验和光纤光学与光纤通信系列实验。     

A Clifford Algebra Approach to the Classical Problem of a Charge in a Magnetic Monopole Field

The motion of an electric charge in the field of a magnetic monopole is described by means of a Lagrangian model written in terms of the Clifford algebra of the physical space. The equations of motion are written in terms of a radial equation (involving r=|r|, where r(t) is the charge trajectory) and a rotor equation (written in terms of an unitary operator spinor R). The solution corresponding to the charge trajectory in the field of a magnetic monopole is given in parametric form. The model can be generalized in order to describe the motion of a charge in the field of a magnetic monopole and other additional central forces, and as an example, we discuss the classical ones involving linear and inverse square interactions.     

Wronskian analysis of resonance tunnelling reactions

A Wronskian formalism is developed for resonance tunnelling reactions. It is shown how the S matrix can be written in terms of Wronskians between solutions of the Schrödinger equation representing incoming and outgoing waves. The method is an adaptation of the Jost function approach to elastic two-body scattering. Formal expressions are derived for the imaginary parts of the energy eigenvalues that arise from the application of complex boundary conditions used in a previous semiclassical analysis. When the imaginary parts are small, so that the resonance is sharp, the S matrix can be written in a Breit-Wigner resonance form. The theory unifies and extends the semiclassical analysis of resonance tunnelling reactions given previously.     

拉曼光谱阵列面扫描判断蓝色签字笔与印泥的时序研究

朱文时序的检验一直是公安司法鉴定的难点之一, 是文件检验工作者致力研究的难题之一。传统的检验方法灵敏度较低, 特别是对于蓝色签字笔与印文的先后顺序判断很难得到好的效果。为此, 寻求更为简单无损的方法成为了物证检验人员致力追求的目标。将拉曼光谱阵列面扫描成像技术拓展应用于蓝色签字笔与印泥印文先后顺序的研究中, 可以真正意义上实现对检材的无损检验和对检验结果的直观表述, 一方面可以深入研究拉曼光谱阵列面扫描成像技术的各项实验条件及方法特性, 拓展拉曼光谱技术在物证鉴定领域的应用范围; 另一方面也为朱文时序的判断研究提供一种新方法, 使实验结果更加准确可靠。     

Holographic recording by excitation of metastable electronic states in Na2[Fe(CN)5NO]·2H2O: a new photorefractive effect

Elementary holographic phase gratings can be written in single crystals of Na₂[Fe(CN)₅NO]·2H₂O, sodiumnitroprusside, by excitation of metastable electronic states in the blue–green spectral range. For light polarized parallel to the crystallographic a and b axes of the orthorhombic crystal the light-induced modulation of the refractive index reaches Δn≈2×10^-3 at λ=514.5 nm. Although the largest population of the metastable states is reached for light polarized parallel to the crystallographic c axis, a photorefractive response is not observed. In contrast to electro-optic photorefractive materials the photorefractive effect depends mono-exponentially on the exposure and on the modulation of the incident light interference pattern. Beam-coupling experiments demonstrate that written gratings are in phase with the interference pattern in correspondence with the fact that the excitation of the metastable electronic states is local. The width of the rocking curve shows that the holographic gratings are written completely over the volume of the crystal. Variations of the wavelengths within the excitation range as well as of the crystal thickness do not influence the maximum photorefractive response. Investigations on the grating vector of the written gratings show unambiguously that charge migration is not responsible for the photorefractive effect. Received: 18 November 1998 / Revised version: 26 January 1999 / Published online: 12 April 1999     

Republication of: A new class of vacuum solutions of the Einstein field equations

This reprinting of a paper by Kerr and Schild, first published in 1965 in a conference volume that is difficult to get hold of today, has been selected by the Editors of General Relativity and Gravitation for publication in the Golden Oldies series of the journal. It is the only publication showing how the Kerr solution was originally arrived at. In this reprint the editors have added several footnotes that update the references to the literature. The paper is accompanied by an editorial note written by A. Krasiński, E.Verdaguer and R. P. Kerr, and by the biography of Kerr written by A. Krasiński.     

Republication of: New solutions to Einstein’s equations of gravitation. B. Explicit determination of static,axially symmetric fields. By Rudolf Bach. With a supplement on the static two-body problem. By H. Weyl.

This is the English translation of the third of a series of 3 papers by Hermann Weyl (the third one jointly with Rudolf Bach), first published in 1917–1922, in which the authors derived and discussed the now-famous Weyl two-body static axially symmetric vacuum solution of Einstein’s equations. The English translations of the other two papers are published alongside this one. The papers have been selected by the Editors of General Relativity and Gravitation for re-publication in the Golden Oldies series of the journal. This republication is accompanied by an editorial note written by Gernot Neugebauer, David Petroff and Bahram Mashhoon, and by a brief biography of R. Bach, written by H. Goenner.     

Republication of: 3. On the theory of gravitation

This is the English translation of the first of a series of 3 papers by Hermann Weyl (the third one jointly with Rudolf Bach), first published in 1917–1922, in which the authors derived and discussed the now-famous Weyl two-body static axially symmetric vacuum solution of Einstein’s equations. The English translations of the other two papers are published alongside this one. The papers have been selected by the Editors of General Relativity and Gravitation for re-publication in the Golden Oldies series of the journal. This republication is accompanied by an editorial note written by Gernot Neugebauer, David Petroff and Bahram Mashhoon, and by a brief biography of R. Bach, written by H. Goenner.     

Republication of: 5. Comment on the axially symmetric solutions to Einstein’s equations of gravitation

This is the English translation of the second of a series of 3 papers by Hermann Weyl (the third one jointly with Rudolf Bach), first published in 1917–1922, in which the authors derived and discussed the now-famous Weyl two-body static axially symmetric vacuum solution of Einstein’s equations. The English translations of the other two papers are published alongside this one. The papers have been selected by the Editors of General Relativity and Gravitation for re-publication in the Golden Oldies series of the journal. This republication is accompanied by an editorial note written by Gernot Neugebauer, David Petroff and Bahram Mashhoon, and by a brief biography of R. Bach, written by H. Goenner.     

Algebraic programming of Hamiltonian formalism in general relativity: Application to inhomogeneous space-times

We describe the structure and the use of a program written in the algebraic programming languagereduce 2, giving the super-Hamiltonian and supermomenta constraints, as well as Hamilton's canonical equations in terms of the canonical variables, for vacuum relativistic space-times. The program uses as input the components of the spatial metric tensor and of the corresponding canonically conjugate momenta in a coordinate or in a spatial Cartan basis. The results of the application of the program to a series of inhomogeneous (cosmological as well as noncosmological) space-times are given: in particular, the constraints, the Dirac Hamiltonian and the canonical equations are explicitly written for axisymmetric space-times, constituting the starting point for the study of the dynamics and of the canonical quantization of these configurations.     

Republication of: On Hamilton’s canonical equations

This is an English translation of a paper by Władysław Ślebodziński, first published in French in 1931, in which he introduced the general definition of what is today called the Lie derivative of tensors (strangely enough, he gave no name to this object). The paper has been selected by the Editors of General Relativity and Gravitation for re-publication in the Golden Oldies series of the journal. This republication is accompanied by an editorial note written by Andrzej Trautman and Ślebodziński’s brief biography written by Witold Roter.     

Highly accurate film thickness measurement based on automatic fringe analysis

This paper describes an automated multiple-beam interferometry for measuring a calibrated step height of (27.00 ± 3.00) nm nominally. The fringes captured from the multiple-beam Fizeau–Tolansky interferometer were thinned by using a written program to obtain accurate measurement. We claim that multiple-beam interferometry based on automatic fringe thinning process can provide a real time solution for calibrating step heights precisely and with high accuracy. The uncertainty budget of the multiple-beam interferometry method due to incomplete parallelism of the incident beam and the inhomogeneity of the reflecting layers was calculated automatically with a written ray tracing program. The uncertainty budget in multiple-beam interferometry was estimated to be of the order of 3.00 nm.