Showing papers in "Physics Today in 1983"
TL;DR: In this article, theoretical calculation of intermolecular forces is presented. But the present position of the current position is not the same as that of the index index of the previous position.
Abstract: Introduction Theoretical calculation of intermolecular forces Gas imperfections Molecular collisions The kinetic theory of non-uniform dilute gases The transport properties of gases and intermolecular forces Spectroscopic measurements Condensed phases Intermolecular forces: The present position Appendices Substance index Index.
923 citations
TL;DR: In this article, Rossiter describes the activities and personalities of numerous women scientists, including astronomers, chemists, biologists, and psychologists, who overcame extraordinary obstacles to contribute to the growth of American science.
Abstract: In volume one of this landmark study, focusing on developments up to 1940, Margaret Rossiter describes the activities and personalities of the numerous women scientists-astronomers, chemists, biologists, and psychologists-who overcame extraordinary obstacles to contribute to the growth of American science. This remarkable history recounts women's efforts to establish themselves as members of the scientific community and examines the forces that inhibited their active and visible participation in the sciences.
399 citations
TL;DR: In this paper, the authors considered the physics of magnetospheric radio emissions, plasma waves in the Jovian magnetosphere, theories of radio emissions and plasma waves, and magnetosphere models.
Abstract: Jupiter's magnetic field and magnetosphere are considered along with the ionosphere, the low-energy plasma in the Jovian magnetosphere, the low-energy particle population, high-energy particles, and spectrophotometric studies of the Io torus. Other topics explored are related to the phenomenology of magnetospheric radio emissions, plasma waves in the Jovian magnetosphere, theories of radio emissions and plasma waves, and magnetospheric models. Attention is also given to aspects of plasma distribution and flow, microscopic plasma processes in the Jovian magnetosphere, symbols and acronyms, coordinate systems, and selected physical parameters of Jupiter and Io.
380 citations
TL;DR: This paper presents a meta-thesis on the application of Linear Systems Theory to Radiographic Imaging, and its application to three-Dimensional Imaging.
Abstract: Preface to the Paperback Edition. Preface. List of Important Symbols. Named Functions. The Clinical Setting. Theory of Linear Systems. Theory of Random Processes. Application of Linear Systems Theory to Radiographic Imaging. Detectors. Classical Tomography. Computed Tomography. Multiplex Tomography. Three-Dimensional Imaging. Noise in Radiographic Images. Scattered Radiation. Appendix A: The Dirac Delta Function. Appendix B: The Fourier Transform. Appendix C: Interaction of Phtons with Matter. References. Author Index. Subject Index.
292 citations
TL;DR: Probabilistic and deterministic descriptions of macroscopic phenomena have coexisted for centuries as mentioned in this paper and no major confrontation ever arose between these seemingly contradictory world views were it not for the remarkable success of Laplace in elevating Newtonian determinism to the level of dogma in the scientific faith.
Abstract: Probabilistic and deterministic Descriptions of macroscopic phenomena have coexisted for centuries. During the period 1650–1750, for example, Newton developed his calculus of determinism for dynamics while the Bernoullis simultaneously constructed their calculus of probability for games of chance and various other many‐body problems. In retrospect, it would appear strange indeed that no major confrontation ever arose between these seemingly contradictory world views were it not for the remarkable success of Laplace in elevating Newtonian determinism to the level of dogma in the scientific faith. Thereafter, probabilitistic descriptions of classical systems were regarded as no more than useful conveniences to be invoked when, for one reason or another, the deterministic equations of motion were difficult or impossible to solve exactly. Moreover, these probabilistic descriptions were presumed derivable from the underlying determinism, although no one ever indicated exactly how this feat was to be accomplished.
230 citations
187 citations
85 citations
80 citations
[...]
TL;DR: In this article, it was shown that the laminar flow can be analyzed as a series of large swirls containing smaller swirls, and so forth, leading to a time-dependent flow pattern.
Abstract: Hydrodynamic systems often show an extremely complicated and apparently erratic flow pattern of the sort shown in figure 1. These turbulent flows are so highly time‐dependent that local measurements of any quantity that describes the flow—one component of the velocity, say—would show a very chaotic behavior. However, there is also an underlying regularity in which the motion can be analyzed (see figure 1 again) as a series of large swirls containing smaller swirls, and so forth. One approach to understanding this turbulence is to ask how it arises. If one puts a body in a stream of a fluid—for example, a piece of a bridge sitting in the stream of a river—then for very low speeds (figure 2a) the fluid flows in a regular and time‐independent fashion, what is called laminar flow. As the speed is increased (figure 2b), the motion gains swirls but remains time‐independent. Then, as the velocity increases still further, the swirls may break away and start moving downstream. This induces a time‐dependent flow pa...
66 citations
TL;DR: For a physical theory to be useful, we should be able to extract from it quantitative predictions for physical observables, and this process of practical application requires some approximation method that is both tractable and adequately accurate.
Abstract: For a physical theory to be useful, we should be able to extract from it quantitative predictions for physical observables. With most theories, this process of practical application requires some approximation method that is both tractable and adequately accurate. The lack of a useful approximation scheme can seriously impede progress in a field of research. Molecular quantum mechanics and critical phenomena, for example, have both suffered from this problem during periods of their development. The physics of strong interactions is in such a period today. Naturally, our inability to extract useful predictions from a promising theory is a strong incentive to develop novel approximation techniques.
TL;DR: In this article, the authors present a survey of the application of quantum theory in the field of particle physics and show that the model potential for atomic systems can be found in many applications.
Abstract: 1. Low-Energy Electron Collisions with Complex Atoms and Ions.- 1. Introduction.- 2. Theory of Electron Collisions with Atoms and Ions.- 2.1. Expansion of the Collision Wave Function.- 2.2. Expansion of the Target Wave Function.- 2.3. Variational Principles and the Derivation of the Coupled Integro-Differential Equations.- 2.4. Derivation of the Cross Section.- 2.5. Inclusion of Relativistic Effects.- 2.5.1. Use of the Breit-Pauli Hamiltonian.- 2.5.2. Use of the Dirac Hamiltonian.- 3. Numerical Solution of the Coupled Integro-Differential Equations.- 3.1. Early Work.- 3.1.1. Iterative Methods.- 3.1.2. Reduction to a System of Coupled Differential Equations.- 3.2. Reduction to a System of Linear Algebraic Equations.- 3.3. R-Matrix Method.- 3.4. Matrix Variational Method.- 3.5. Noniterative Integral Equations Method.- 3.6. New Directions.- 3.7. Illustrative Results.- 4. Computer Program Packages.- 4.1. Structure Packages.- 4.2. Collision Packages.- References.- 2. Numerical Methods for Asymptotic Solutions of Scattering Equations.- 1. Introduction.- 2. Specification of Asymptotic Forms.- 3. Travels in Intermedia.- 3.1. Numerical Integration of the Differential Equations.- 3.2. Noniterative Integration of the Phase-Amplitude Equations.- 4. At the Border of Asymptopia.- 4.1. Asymptopic Expansions.- 4.2. Iterative Techniques.- 4.2.1. The Iterated WBK (IWBK) Method.- 4.2.2. The Generalized Matricant.- 5. Concluding Remarks.- References.- 3. Collisions between Charged Particles and Highly Excited Atoms.- 1. Introduction.- 2. The Impact Parameter (IP) Method.- 3. The Sudden Approximation.- 4. Transitions between Levels with Quantum Defects.- 5. Transitions within the Degenerate Sea.- References.- 4. Proton Impact Excitation of Positive Ions.- 1. Introduction.- 2. Excitation of Fine-Structure Transitions.- 2.1. Semiclassical Theory.- 2.2. Quantal Theory.- 3. Excitation of Metastable Transitions.- 4. Charge-Transfer Ionization.- References.- 5. Long-Range Interactions in Atoms and Diatomic Molecules.- 1. Introduction.- 2. General Form of the Model Hamiltonian.- 3. Form of the Model Potential for Atomic Systems.- 3.1. The Exact Interaction between the Valence Electrons and the Core.- 3.2. Second-Order Perturbation Theory: The Static Contribution.- 3.3. The First Nonadiabatic Correction.- 3.4. The Second Nonadiabatic Correction.- 3.5. Nonadiabatic Corrections of Higher Order.- 3.6. Third-Order Perturbation Theory: The Static Contributions.- 3.7. Summary of Results.- 4. Form of the Model Potential for Diatomic Systems.- 4.1. The Exact Interaction between the Valence Electrons and the Cores.- 4.2. Second-Order Perturbation Theory: The Static Contributions.- 4.3. The First Nonadiabatic Correction.- 4.4. The Second Nonadiabatic Correction.- 4.5. Nonadiabatic Corrections of Higher Order.- 4.6. Third-Order Perturbation Theory: The Static Contribution.- 4.7. Summary of Results and the Separated Atom Limit.- 5. Addition Theorems for Solid Harmonics.- References.- 6. Applications of Quantum Defect Theory.- 1. Historical Survey.- 2. Mathematical Background to Quantum Defect Theory.- 2.1. Properties of Coulomb Wave Functions.- 2.2. Solutions of the Coupled Equations.- 2.2.1. All Channels Closed.- 2.2.2. Some Channels Open.- 3. Single-Channel Quantum Defect Methods: General Formulas in the Independent-Particle Approximation.- 3.1. Expressions for the Wave Functions.- 3.2. General Formulas for Radiative Transition Probabilities.- 3.3. Collision Cross Sections.- 3.3.1. Use of Extrapolated Quantum Defects.- 3.3.2. Use of Adjusted Calculated Quantum Defects.- 3.3.3. Use of Observed Quantum Defects in the Bethe Approximation.- 3.4. Summary.- 4. Applications to Simple Multichannel Problems.- 4.1. The Spectrum of Calcium.- 4.1.1. Bound States.- 4.1.2. Autoionizing States.- 4.2. Bound States of Complex Ions by Extrapolation of Calculated Scattering Parameters: Configurations 1s22s22pqnl.- 4.3. The Spectrum of the H2 Molecule.- 5. Extrapolation of the Generalized Reactance Matrix.- 5.1. Discussion of Extrapolation Methods.- 5.1.1. Restrictions on the Validity of Extrapolation Methods.- 5.1.2. Fitting Techniques.- 5.2. Applications.- 5.2.1. Collision Strengths in LS-Coupling.- 5.2.2. Collision Strengths for Excitations between Fine-Structure Levels.- 5.2.3. Photoionization Gross Sections.- 5.2.4. Electron Impact Ionization Cross Sections.- 6. Conclusions.- References.- 7. Electron-Ion Processes in Hot Plasmas.- 1. Introduction.- 2. Line Intensities.- 2.1. Level Populations.- 2.2. Forbidden Lines.- 2.3. Satellite Lines.- 3. Electron-Ion Processes.- 3.1. Introduction.- 3.2. The A+z + e System.- 3.3. Coupling between Open Channels.- 3.4. Resonance Contribution to Collisional Excitation.- 3.5. Approximate Methods for Strong Allowed Transitions.- 3.6. Relativistic Effects.- 3.7. Relativistic Effects in Autoionization.- 4. Conclusion.- A.1. Derivation of am(E) and b?i(E).- A.2. Resonances.- A.3. Gailitis Formula.- References.- 8. The University College Computer Package for the Calculation of Atomic Data: Aspects of Development and Application.- 1. Introduction.- 2. The Growth of Astronomical Observations.- 3. Some Aspects of the Genesis of the Programs.- 4. The C III Challenge.- 4.1. Collision Strengths and Transition Probabilities for the Interpretation of the Solar Spectrum.- 4.2. Excitation of C III by Recombination.- 4.2.1. Observations.- 4.2.2. Rate Coefficients from Detailed Balance Arguments.- 4.2.3. Improved Low-Temperature Coefficients.- References.- 9. Planetary Nebulae.- 1. Introduction.- 2. Observations.- 2.1. Optical.- 2.2. Infrared.- 2.3. Radio.- 2.4. Ultraviolet.- 2.4.1. NGC 7662.- 2.4.2. IC 418.- 2.4.3. The C/O Ratio in Planetary Nebulae.- 3. Models: Atomic Data.- 3.1. Charge Transfer.- 3.1.1. O+.- 3.1.2. O2+.- 3.1.3. Ne2+.- 3.2. Dielectronic Recombination.- 3.3. Photoionization and Radiative Recombination.- 3.4. Electron Collisional Excitation.- 3.5. Radiative Transition Probabilities.- References.- 10. Forbidden Atomic Lines in Auroral Spectra.- 1. Introduction.- 2. Beginnings.- 3. Seaton's Work.- 4. Refinement of Classical Theory.- 5. Advent of In Situ Measurements.- 6. N2(A3?u+)-O Excitation Transfer.- 7. Quenching.- 8. Coordinated Rocket and Satellite Measurements.- 9. ?3466 and ?10,400 of N I.- References.
TL;DR: A presentation of the fundamental principles governing nuclear explosions and their effects can be found in this paper, which is useful to those interested in carrying out this responsibility for education on nuclear war.
Abstract: The intensity of public debate on issues involving nuclear weapons and strategic policy is currently at an all‐time high. This is surely a welcome development. Although the issues are largely political, they cannot be addressed without some knowledge of the properties of nuclear weapons and of the destruction that their use could bring about It is our particular responsibility as technically trained citizens to be informed of the basic facts concerning nuclear weapons and to help our fellow citizens understand them so that they can contribute more effectively to the debate It is my hope that this article—a presentation of the fundamental principles governing nuclear explosions and their effects—will be useful to those interested in carrying out this responsibility for education on nuclear war.
TL;DR: In this article, it was shown that the vacuum exerts a pressure on the "bubbles", or bags, that we have to make to allow quarks to exist, and that this pressure keeps the bubbles from expanding.
Abstract: We have known for years that the nucleon must have a finite size. In the 1950s, with the development of quantitative calculational techniques in quantum electrodynamics, there were many attempts to describe the size of the nucleon, but none was successful. The advent of quark physics and the demonstration through high‐energy deep inelastic scattering of electrons by nucleons that there are three objects in the central nucleon core, and that these objects behave at high energies as if they are free and massless, gave impetus to a new description of nucleonic structure. Ever since Hendrik A. Lorentz's work on the theory of the electron, we have been trying to give elementary particles finite sizes to make their self energy finite. Whereas Lorentz introduced rods to hold his extended electron together (the method did not work), we now believe that the vacuum exerts a pressure on the “bubbles,” or “bags,” that we have to make to allow quarks to exist, and that this pressure keeps the bubbles from expanding. A...
TL;DR: The state of precollege education in the United States is in a state of crisis as discussed by the authors, which is confirmed by the number of editorials in our journals, the amount of legislation being proposed at all levels, the attention given the subject in the popular press, and the numbers of meetings held to discuss the crisis.
Abstract: Science and mathematics education in this country is in a precarious state. Most of our students do not learn nearly as much as they could and many of our teachers are ill prepared. That the state of affairs has deteriorated to the point of becoming a crisis is confirmed by the number of editorials in our journals, the amount of legislation being proposed at all levels, the attention given the subject in the popular press and the number of meetings held to discuss the crisis. Thus, for example, the National Academy of Sciences sponsored a national convocation (May 1982) to consider the state of precollege education in the United States. The topic also received special attention in October 1982 at The American Institute of Physics Corporate Associates meeting and at the Spring 1983 meeting of the AIP Assembly of Society Officers and the AIP Governing Board meeting.
TL;DR: In this article, the authors try to piece together the data from the original Big Bang experiment on their own to see if they can understand what happened in this experiment, which is the experiment that we call the Big Bang, which resulted in about 1090 bits of data spread out over 1028 cm3.
Abstract: 15 billion years ago, an experiment was carried out that related to the interaction between cosmology and particle physics and the unification of physics in general. This is the experiment that we call the Big Bang. It resulted in about 1090 bits of data spread out over 1028 cm3. We know the original apparatus had about 1019 GeV (see figure 1), but, unfortunately, the graduate student who designed this equipment is no longer around, and, as a result, she can't tell us exactly what she did. So we have to try to piece together the data on our own to see if we can understand what happened in this experiment. From some of the data that we've been able to assemble—for example, from observing the 3‐K background radiation—we know the early universe was hot and dense. We also know that about one‐quarter of the isotope helium‐4. This figure is really rather amazing. The sum total of all the other heavier elements (carbon, oxygen, iron and so on) makes up less than 2 percent of the mass of the Universe. Stars make ...
TL;DR: The possibility of counting the exact frequency of optical radiation or locking its oscillations to microwave standards is still very much in the development stage; however, its feasibility has already been demonstrated in experiments such as a recent measurement of the frequency of a visible laser emission, a feat that gained a recognition not often accorded scientists.
Abstract: Among the remarkable facts of modern technology, one of the most striking is that the possibility is at hand of making an exact count of cyclical events that occur at a rate of over 500 million in a microsecond; this will be the likely result of present work on the measurement of the frequency of optical radiation and the use of optical resonances at frequency standards. The actual counting of the exact frequency of optical radiation or locking its oscillations to microwave standards is still very much in the development stage; however, its feasibility has already been demonstrated in experiments such as a recent measurement of the frequency of a visible laser emission, a feat that gained a recognition not often accorded scientists: mention in the Guinness Book of Records for the highest frequency measured! A number of laboratories are actively engaged in setting up systems for precisely relating optical and microwave standards. The Institute for Semiconductor Physics in Novosibirsk, for example, has anno...
TL;DR: From this unique collection of documents emerges a fresh, intimate, often striking picture of the life of science in the United States in the era when American investigators became central to scientific advances in many fields as mentioned in this paper.
Abstract: From this unique collection of documents emerges a fresh, intimate, often striking picture of the life of science in the United States in the era when American investigators became central to scientific advances in many fields. Written in the course of the events described, these letters, memoranda, and other records for the most part previously unpublished convey personalities and issues with an immediacy hard to capture in conventional historical narratives."
TL;DR: In this article, it was shown that the forces between quarks are extremely simple and universal, and that these forces explain why free quarks cannot be seen, even though they have not been observed directly.
Abstract: Our understanding of the ultimate structure of matter has advanced greatly in the last few years. It was nearly twenty years ago that Murray Gell‐Mann and George Zweig gave us the key to much of this understanding with their revolutionary proposals that protons, neutrons and all other strongly interacting particles—the hadrons—are made of quarks, a theretofore unobserved kind of particle. Over the last ten years, this proposal has become firmly established even though we have not observed free quarks directly. More recent research has found that forces between quarks are extremely simple and universal—the same for all types of quarks—and that these forces explain why free quarks cannot be seen. In this article we will look at hadron spectroscopy, which has been one of the main venues for this great progress.
TL;DR: In the general public, the computer has changed from a remote and recalcitrant source of error on monthly bills to a friendly and increasingly common household appliance as discussed by the authors, and with the popular press full of the subject, it hardly seems necessary to tell an audience of physicists that a computer consists of a central processing unit, a high speed memory, mass storage disks and so on.
Abstract: In the eyes of the general public, the computer has changed from a remote and recalcitrant source of error on monthly bills to a friendly and increasingly common household appliance. Time magazine, which names a “Man of the Year,” in 1982 named the computer instead, and The New York Times runs a weekly computer column. With the popular press full of the subject, it hardly seems necessary to tell an audience of physicists that a computer consists of a central processing unit, a high‐speed memory, mass‐storage disks and so on. A large fraction of the total number of scientists active in research or development have ready access to computers. I can safely assume that my readers have some level of familiarity with the basic operation of modern computers and with a few uses of computers in their fields of specialization. In this article, then, I will address a set of topics of special concern to physicists in the hope that doing so will stimulate further discussion. One indisputable fact is that the presence o...
TL;DR: In the past year or so, the sale of microcomputers has increased from a few thousand to millions a year as mentioned in this paper, and they can be used to do large scale calculations in physics at a great savings in cost and added personal convenience for the researcher.
Abstract: In the past year or so, the sale of microcomputers has increased from a few thousand to millions a year. Today, you can walk into a toy store and buy a computer for a few hundred dollars. Most micros are probably used for recreation, and until recently they have not been taken very seriously by scientists. An ordinary personal computer can be used to do large‐scale calculations in physics at a great savings in cost and added personal convenience for the researcher.
TL;DR: The rapid availability of synchrotron radiation is revolutionizing some fields and is leading to a variety of new interdisciplinary collaborations as mentioned in this paper, which is having a profound effect on the many disciplines that make use of radiation in the x-ray and vacuum ultraviolet regions of the spectrum.
Abstract: Synchrotron radiation, with its remarkable properties and eminent suitability for scientific and technical applications, is having a profound effect on the many disciplines that make use of radiation in the x‐ray and vacuum ultraviolet regions of the spectrum. Indeed, the rapidly increasing availability of this radiation is revolutionizing some fields and is leading to a variety of new interdisciplinary collaborations. Seeking to take advantage of this incisive tool, scientists around the world are requesting time at synchrotron radiation facilities in such large numbers that the fast‐paced construction of new sources—including several in less‐developed countries—has yet to bring the level of availability up to that of demand.
TL;DR: Christoffel's life and work can be traced back to the International Christoffel Symposium, held on November 8-11, 1979 at Aachen and Monschau as discussed by the authors.
Abstract: This memorial volume is dedicated to E. B. Christoffel on the occasion of the 150th anniversary of his birth. Its aim is, on the one hand, to present the life of Christoffel and the scientific milieu in which he worked and, on the other hand, to present a survey of his work not only in its historical context but especially in the frame of contemporary mathematics and physics. For one thing, this book contains expanded versions of the twelve invited lectures given at the International Christoffel Symposium, held on November 8- 11, 1979 at Aachen and Monschau. For another, the scope of these papers has been broadened by soliciting some fourty-five additional invited articles, concerned either with further aspects of the work of Christoffel or with specia lized topics in fields in which Christoffel had worked. This should give the reader a greater opportunity to appreciate the richness of Christoffel's contributions to the mathematical and physical sciences, and not only its immediate impact but also its subsequent infiuence. It can be discerned that Christoffel did basic work not only in differential geometry or, better still, in classical tensor analysis, thereby supplying the mathematical foundations of Einstein's theory of general relativity, but also in a variety of other areas of mathematics. The scope of Christoffel's work can be appreciated from the following synopsis of the thirteen chapters into which the festschrift is divided. Chap."