Paul Ehrenfest, Niels Bohr, and Albert Einstein: Colleagues and Friends

In May 1918 Paul Ehrenfest received a monograph from Niels Bohr in which Bohr had used Ehrenfest’s adiabatic principle as an essential assumption for understanding atomic structure. Ehrenfest responded by inviting Bohr, whom he had never met, to give a talk at a meeting in Leiden in late April 1919, which Bohr accepted; he lived with Ehrenfest, his mathematician wife Tatyana, and their young family for two weeks. Albert Einstein was unable to attend this meeting, but in October 1919 he visited his old friend Ehrenfest and his family in Leiden, where Ehrenfest told him how much he had enjoyed and profited from Bohr’s visit. Einstein first met Bohr when Bohr gave a lecture in Berlin at the end of April 1920, and the two immediately proclaimed unbounded admiration for each other as physicists and as human beings. Ehrenfest hoped that he and they would meet at the Third Solvay Conference in Brussels in early April 1921, but his hope was unfulfilled. Einstein, the only physicist from Germany who was invited to it in this bitter postwar atmosphere, decided instead to accompany Chaim Weizmann on a trip to the United States to help raise money for the new Hebrew University in Jerusalem. Bohr became so overworked with the planning and construction of his new Institute for Theoretical Physics in Copenhagen that he could only draft the first part of his Solvay report and ask Ehrenfest to present it, which Ehrenfest agreed to do following the presentation of his own report. After recovering his strength, Bohr invited Ehrenfest to give a lecture in Copenhagen that fall, and Ehrenfest, battling his deep-seated self-doubts, spent three weeks in Copenhagen in December 1921 accompanied by his daughter Tanya and her future husband, the two Ehrenfests staying with the Bohrs in their apartment in Bohr’s new Institute for Theoretical Physics. Immediately after leaving Copenhagen, Ehrenfest wrote to Einstein, telling him once again that Bohr was a prodigious physicist, and again expressing the hope that he soon would see both of them in Leiden.     

Guido Beck,Alexandre Proca,and the Oporto Theoretical Physics Seminar

We describe the pioneering attempts made by Ruy Luís Gomes (1905–1984) and other Portuguese physicists to develop a research and teaching seminar in theoretical physics at the University of Oporto in 1942–1944 under the leadership first of the refugee Austrian theoretical physicist Guido Beck (1903–1988) and then of the Romanian-French theoretical physicist Alexandre Proca (1896–1955). These efforts failed, however, owing to lack of sustained financial support from the Portuguese government and to the political repression of the Salazar regime, which dismissed Gomes and other prominent Portuguese physicists and other scientists from their university positions.     

Quirino Majorana’s Experiments on the Speed of Light and Gravitational Absorption

Quirino Majorana (1871–1957) was an outstanding Italian experimental physicist who investigated a wide range of phenomena during his long career in Rome,Turin, and Bologna. We focus on his experiments in Turin during 1916–1921 and in Bologna during 1921–1934 to test the validity of Albert Einstein’s postulate on the constancy of the speed of light and to detect gravitational absorption. These experiments required extraordinary skill, patience, and dedication, and all of them confirmed Einstein’s postulate and Isaac Newton’s law of universal gravitation to high precision. Had they not done so, Majorana’s fame among historians and physicists no doubt would be much greater than it is today. Giorgio Dragoni is Professor of History of Physics at the University of Bologna. Giulio Maltese is a Roman member of the Italian Society for the History of Physics and Astronomy. Luisa Atti is a Bolognese member of the Association for the Teaching of Physics.     

Thermodynamics as a science of symmetry

A new interpretation of thermodynamics is advanced; thermodynamics is the study of those properties of macroscopic matter that follow from the symmetry properties of physical laws, mediated through the statistics of large systems.The support of the John Simon Guggenheim Memorial Foundation is gratefully acknowledged. This work has also been supported in part by the National Science Foundation.Perrnanent address (on leave 1972–73 to Hebrew University of Jerusalem).     

Dirac's Claim and the Chemists

In 1929 Paul A. M. Dirac claimed that “the underlying physical laws necessary for the mathematical theory of ... the whole of chemistry are thus completely known, and the difficulty is only that the exact application of these laws leads to equations much too complicated to be soluble.” This sentence of Dirac's is cited frequently by historians and philosophers of chemistry in the context of discussions on the hypothetical reduction of chemistry to physics. But how did chemists themselves react to Dirac's claim? Did they feel threatened by physicists who felt they could do their job better than themselves? Did they feel indifferent, or did they simply not care? Was Dirac's paper often cited by chemists? Why was it cited? In this paper, I provide answers to these questions on the basis of an analysis of citations to Dirac's 1929 paper in the Science Citation Index. RID="*" ID="*"Ana Sim?es teaches history of science at the University of Lisbon. Her research is in the history of quantum chemistry and in the history of the sciences at the European peripheries.     

Introduction to biology and chromosomal instabilities in cancer

The recent decade has witnessed a surge of physicists to biology. Some of the activities of the participating groups focus on bona fide physics questions, posed on biological systems (such as the physics of molecular motors, for example). Another kind of research in which physicists take part alongside computer scientists and applied mathematicians, deals with questions that are of direct interest to biologists; they come under the umbrella of computational and systems biology. The topic of these lectures lies at the most biological end of this spectrum, addressing problems of clinical relevance which were posed and initiated by biologists.The objective of these lectures is to help the curious physicist to learn and to understand more about this emerging, highly interdisciplinary field of research, by providing brief introductions to molecular biology and cancer research. This is followed by a cursory review of some recent research done by the “Domany group” and its collaborations with biological and clinical labs. Furthermore, we mention (mainly in footnotes) a small subset of studies in which physicists have contributed to this field during the past years. A more detailed review of recent contributions by physicists is beyond the scope of this introductory text.The introductory nature of these lecture notes naturally induces a strong bias regarding publications cited; consequently, these lecture notes do not provide a fair, historically correct and updated review of relevant literature.     

Structural, electrical and optical properties of ZnS films deposited by close-spaced evaporation

ZnS films have been deposited on glass substrates by close-spaced evaporation (CSE) technique. The films were grown at different temperatures in the range, 200-350 °C. The layers have been characterized with X-ray diffractometer (XRD), atomic force microscope (AFM), energy dispersive analysis of X-rays (EDAX) and optical spectrophotometer to evaluate the quality of the layers for photovoltaic applications. The studies showed that the optimum substrate temperature for the growth of ZnS layers was 300 °C. The films grown at these temperatures exhibited cubic structure with nearly stoichiometric composition. The AFM data revealed that the films had nano-sized grains with a grain size of ∼40 nm. The optical studies exhibited direct allowed transition with an energy band gap of 3.61 eV. The other structural and optical parameters such as lattice stress, dislocation density, refractive index and extinction coefficient were also evaluated. The temperature-dependent conductivity measured in the range, 303-523 K showed a change in the conduction mechanism at 120 °C. The activation energy values evaluated using the temperature dependence of electrical conductivity are 7 and 29 meV at low and high temperature regions, respectively.     

C. V. Raman and the Discovery of the Raman Effect

In 1928 the Indian physicist C. V. Raman (1888-1970) discovered the effect named after him virtually simultaneously with the Russian physicists G. S. Landsberg (1890-1957) and L. I. Mandelstam (1879-1944). I first provide a biographical sketch of Raman through his years in Calcutta (1907-1932) and Bangalore (after 1932). I then discuss his scientific work in acoustics, astronomy, and optics up to 1928, including his views on Albert Einstein's light-quantum hypothesis and on Arthur Holly Compton's discovery of the Compton effect, with particular reference to Compton's debate on it with William Duane in Toronto in 1924, which Raman witnessed. I then examine Raman's discovery of the Raman effect and its reception among physicists. Finally, I suggest reasons why Landsberg and Mandelstam did not share the Nobel Prize in Physics for 1930 with Raman. RID="*" ID="*"Rajinder Singh is a Diplom-Physiker who is currently working on his doctoral thesis on C. V. Raman and the discovery of the Raman effect in the Department of Higher Education and History of Science in the Faculty of Physics at the University of Oldenburg, Germany.     

Two post-Alikhanian generations of physicists

Artem Alikhanian, famous Soviet physicist, was one of founders of experimental nuclear and cosmic-ray physics in USSR and in Armenia. A result of his activity is subsequent two generations of professional physicists presenting the real wealth of Armenian science.     

Ritz,Einstein, and the Emission Hypothesis

Just as Albert Einsteins special theory of relativity was gaining acceptance around 1908, the young Swiss physicist Walter Ritz advanced a competing though preliminary emission theory that sought to explain the phenomena of electrodynamics on the assumption that the speed of light depends on the motion of its source. I survey Ritzs unfinished work in this area and review the reasons why Einstein and other physicists rejected Ritzs and other emission theories. Since Ritzs emission theory attracted renewed attention in the 1960s, I discuss how the earlier observational evidence was misconstrued as telling against it more conclusively than actually was the case. Finally, I contrast the role played by evidence against Ritzs theory with other factors that led to the early rejection of his approach.     

Early Attempts to Detect the Neutrino at the Cavendish Laboratory

In the 1920s and early 1930s the Cavendish Laboratory in Cambridge was preeminent in experimental research on radioactivity and nuclear physics, with theoretical physics playing a subsidiary role in guiding, but not determining the course of experimental research. Soon after Wolfgang Pauli (1900–1958) proposed his neutrino hypothesis in 1930 to preserve conservation of energy and momentum in beta decay, experiments – the first of their kind – were carried out in the Cavendish Laboratory to detect Pauli’s elusive particle, but they were abandoned in 1936. I trace these early attempts and suggest reasons for their abandonment, which may contribute to an understanding of the complex way in which theoretical entities are accepted by physicists.     

Effect of p-d hybridization and structural distortion on the electronic properties of AgAlM2(M=S,Se,Te) chalcopyrite semiconductors

We report an ab initio calculation and study of the structural and electronic properties of AgAlM₂(M=S,Se,Te) chalcopyrite semiconductors using the density functional theory (DFT)-based self-consistent tight-binding linear muffin tin orbital (TB-LMTO) method. The calculated equilibrium values of the lattice constants, anion displacement parameter (u), tetragonal distortion (η=c/2a) and bond lengths are in good agreement with experimental values. Our study suggests these semiconductors to be direct band gap semiconductors with band gaps 1.98 eV, 1.59 eV and 1.36 eV, respectively. These values are in good agreement with experimental values, within the limitation of the local density approximation (LDA). Our explicit study of the effects of anion displacement and p-d hybridization show that the band gap increases by 9.8%, 8.2% and 5.1%, respectively, for AgAlM₂(M=S,Se,Te) due to former effect and decreases by 51%, 47% and 42%, respectively, due to latter effect.     

A Bratislavian from San Diego

Professor George Feher, born in Bratislava, Slovakia, left his country at the age of 17 in 1941. Since 1946 he has been living in USA. I met him in Jerusalem in September 1995. During one week we would sit together at breakfast time at the Hebrew University guesthouse. This week and many discussions with G. Feher were fascinating for me. Further we continued in our contacts, we exchanged letters, papers, essays. This way an idea to introduce George Feher to his former countrymen was born. Professor Feher as an experienced researcher in physics and biophysics, as a personality who met with William Shockley, Edward Teller and many other famous scientists, and moreover, as a personality collecting scientific humor and jokes, attracted the interest of Slovak scientific community. His life may be an inspiration especially for young people looking for examples of a true scientific career.     

Gerson Goldhaber: A Life in Science

I draw on my interviews in 2005–2007 with Gerson Goldhaber (1924–2010), his wife Judith, and his colleagues at Lawrence Berkeley National Laboratory. I discuss his childhood, early education, marriage to his first wife Sulamith (1923–1965), and his further education at the Hebrew University in Jerusalem (1942–1947) and his doctoral research at University of Wisconsin at Madison (1947–1950). He then was appointed to an instructorship in physics at Columbia University (1950–1953) before accepting a position in the physics department at the University of California at Berkeley and the Radiation Laboratory (later the Lawrence Berkeley Laboratory, today the Lawrence Berkeley National Laboratory), where he remained for the rest of his life. He made fundamental contributions to physics, including to the discovery of the antiproton in 1955, the GGLP effect in 1960, the psi particle in 1974, and charmed mesons in 1977, and to cosmology, including the discovery of the accelerating universe and dark energy in 1998. Beginning in the late 1960s, he also took up art, and he and his second wife Judith, whom he married in 1969, later collaborated in illustrating and writing two popular books. Goldhaber died in Berkeley, California, on July 19, 2010, at the age of 86.     

Structural stability and magnetic properties of Bi1−xLa(Pr)xFeO3 solid solutions

In this work, X-ray diffraction data taken on Bi_1−xLa_xFeO₃ solid solutions are used to verify the following structural phase transitions: “polar rhombohedral-antipolar orthorhombic” at x≈0.16 and “commensurate-incommensurate” within the orthorhombic phase at x≈0.18. In contrast, in the Bi_1−xPr_xFeO₃ series, the polar rhombohedral phase transforms into an antipolar orthorhombic one at x≥0.13. The polar rhombohedral phase near the morphotropic phase boundary exhibits an isothermal transformation into an antipolar orthorhombic phase, though the transformation occurs much faster in the case of La-doped compounds. The incommensurate structural phase was not detected in Bi_1−xPr_xFeO₃ solid solutions. The ternary structural phase diagram is constructed for (Bi,La,Pr)FeO₃ systems. In addition, the polar rhombohedral phase exhibits a magnetic field-induced transition from the modulated antiferromagnetic state into a homogeneous weak ferromagnetic state whereas the antipolar phase is a weak ferromagnetic state in the absence of an external field.     

Optical properties of GaN/AlN multiple quantum wells

Optical properties of GaN/AlN multiple quantum wells (MQW) have been investigated by Raman scattering, photoluminescence and photoluminescence excitation measurements. A careful examination of the Raman spectrum reveals the fact that the constituent layers of GaN/AlN MQWs are well strained. The experimental results of emission and absorption in MQWs were compared with the calculated solutions of the finite quantum well and the bound states involved in the optical transitions were identified. It is found that the interband transitions up to n=3 bound state can be observed in the strained GaN/AlN MQWs sample. The temperature dependence of the heavy-hole transitions shows an interesting phenomenon, in which the peak energy first increases with increasing temperature and then decreases with the temperature rapidly. The observation can be explained in a consistent way by the strain effects of lattice mismatch due to the interplay between the thermal expansion of GaN and AlN layers. Our results indicate that pseudomorphic GaN/AlN MQWs with good quality can be readily grown, and their applications in optoelectronics can be expected in the near future.     

条件愈苦,意志愈坚 --记王淦昌早年的科研活动

文章介绍了中国物理学家王淦昌早期的科研工作，特别是在抗日战争时期的科研成绩．王淦昌早期的科研贡献并不是在先进的实验仪器上，在条件优裕的实验室内完成的，而是在实验设备缺乏，科学文献不足等极端困难的环境中完成的．从王淦昌身上，可以看到那个时代中国优秀科学家脚踏实地、执志若金的奋斗精神．     

Magnetic and magnetotransport properties in Co5Cu95 melt-spun alloys

Giant magnetoresistance (GMR) has been observed in Co₅Cu₉₅ alloys fabricated by melt-spinning. The highest MR change of 28.0% occurs for Co₅Cu₉₅ after annealing at 450°C for 30 min. Based on the super-paramagnetic assumption, the average size of Co particles embedded in Cu matrix, ranging from 3.0 to 6.0 nm, has been determined by simulating the magnetization curves at 295 K which is higher than the blocking temperatures for the samples. Comparison with phenomenological theory for GMR indicates that the interfacial spin-dependent scattering is the dominant scattering mechanism underlying GMR origin in granular systems. Additionally, for the samples in as-quenched state or annealed at temperatureT _A=350°C, the electron hybridization and super-paramagnetic behaviors of fine Co particles may be responsible for the low value of MR change.     

A Conversation with William A. Fowler – Part II

Physicist William A.Fowler initiated an experimental program in nuclear astrophysics after World War II. He recalls here the Steady State versus Big Bang controversy and his celebrated collaboration with Fred Hoyle and Geoffrey and Margaret Burbidge on nucleosynthesis in stars. He also comments on the shift away from nuclear physics in universities to large accelerators and national laboratories.John Greenberg received his Ph.D. degree from the University of Wisconsin and was Caltech research fellow in history from 1980–1984. The Editors were saddened to learn that he died while this interview was in press. Requests for reprints may be directed to Judith R. Goodstein, Institute Archives 015A-74, Caltech, Pasadena, CA 91125 USA; e-mail: jrg@caltech.edu.     

Effects of growth temperature on Li-N dual-doped p-type ZnO thin films prepared by pulsed laser deposition

Li-N dual-doped p-type ZnO (ZnO:(Li,N)) thin films have been prepared by pulsed laser deposition. The introduction of Li and N was confirmed by secondary ion mass spectrometry measurements. The structural, electrical, and optical properties as a function of growth temperature were investigated in detail. The lowest room-temperature resistivity of 3.99 Ω cm was achieved at the optimal temperature of 450 °C, with a Hall mobility of 0.17 cm²/V s and hole concentration of 9.12 × 10¹⁸ cm⁻³. The ZnO:(Li,N) films exhibited good crystal quality with a complete c-axis orientation, a high transmittance (about 90%) in the visible region, and a predominant UV emission at room temperature. The two-layer-structure p-ZnO:(Li,N)/n-ZnO homojunctions were fabricated on a sapphire substrate. The current-voltage characteristics exhibited the rectifying behavior of a typical p-n junction.