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Showing papers in "Reports on Progress in Physics in 1976"


Journal ArticleDOI
TL;DR: In this paper, the X-ray small-angle scattering method was used for the analysis of biological structures composed of two kinds of molecules, such as ribosomes, nucleosomes and viruses.
Abstract: Neutron small-angle scattering provides a new tool for investigation of the structure of biological particles. The method is derived from X-ray small-angle scattering. The very large difference between the scattering amplitude of neutrons by hydrogen and deuterium gives the basis of this method, which is explained with reference to the X-ray technique, as both methods have a complementary aspect. Experimental results so far obtained are reviewed, with an emphasis on biological structures composed of two kinds of molecules, such as ribosomes, nucleosomes and viruses.

694 citations


Journal ArticleDOI
TL;DR: The chemical mechanisms that lead to the formation and destruction of molecules in the interstellar gas are reviewed in this paper, where detailed attention is given to gas-phase chemical processes and to the modifications they produce in the molecular compositions of interstellar clouds following the initial molecular formation.
Abstract: The chemical mechanisms that lead to the formation and destruction of molecules in the interstellar gas are reviewed. Grain surface catalysis is discussed briefly. Detailed attention is given to gas-phase chemical processes and to the modifications they produce in the molecular compositions of interstellar clouds following the initial molecular formation. The effects of chemical fractionation processes on the abundances of molecules containing different isotopes are explored. The review was completed in March 1976.

257 citations


Journal ArticleDOI
TL;DR: A review of principles governing alloy oxidation is presented together with the means by which practical oxidation-resistance alloys have been developed in this paper, where an attempt is made to show how the development of oxidation theory has contributed to this effort by a term now referred to as "informed empiricism".
Abstract: A review of principles governing alloy oxidation is presented together with the means by which practical oxidation-resistance alloys have been developed. The reactions involved are complex and involve acquiring data from many fields. Wagner developed the basic diffusional models for the formation of oxide scales, but these need to be expanded using detailed physical and metallurgical studies of the alloy phases, oxides and their defects, as well as the mode of scale formation and the structural relationships between alloy and oxide scale. At this time the engineering solutions have outstripped fundamental understanding, but an attempt is made to show how the development of oxidation theory has contributed to this effort by a term now referred to as 'informed empiricism'.

208 citations


Journal ArticleDOI
TL;DR: A detailed account of the techniques used to generate these resonance configurations from the purely nucleonic configurations is given in this paper, where two-and three-nucleon systems in which the resonance configurations appear to play a role are discussed.
Abstract: The present status of the theory of nucleon resonances in nuclei is reviewed. A detailed account is given of the techniques used to generate these resonance configurations from the purely nucleonic configurations. Situations in two- and three-nucleon systems in which the resonance configurations appear to play a role are discussed. Heavier nuclei are also mentioned. The effect of resonances in nuclear and neutron matter is also reviewed.

183 citations


Journal ArticleDOI
TL;DR: In this article, the theory of inner-shell excitation in slow ion-atom collisions over the past decade is described and the solution of the coupled equations for the excitation of K-shell electrons in collisions of first-row atoms is considered in detail, particularly the scaling properties.
Abstract: The development of the theory of inner-shell excitation in slow ion-atom collisions over the past decade is described. This theory recognizes that electrons in inner shells behave largely independently of other electrons and generalizes the coupled-state impact-parameter method used successfully for ion-atom collisions involving a single electron. The method utilizes one-electron molecular orbitals obtained from solutions of the stationary molecular Shcrodinger equation and the generation of such orbitals for inner-shell electrons is described. The solution of the coupled equations for the excitation of K-shell electrons in collisions of first-row atoms is considered in detail, particularly the scaling properties. A discussion is given of the limitations of the independent-electron method and the role played by the outer-shell electrons.

155 citations


Journal ArticleDOI
TL;DR: In this article, the authors discuss electron-ion collisions from an experimental viewpoint, with an emphasis on recent experiments and new techniques, such as ion traps and sequential mass spectrometry.
Abstract: The topic of electron-ion collisions is discussed, primarily from the experimental viewpoint, with an emphasis on recent experiments and new techniques. The methods used in crossed-beam experiments, ion traps and sequential mass spectrometry are described with their application to the measurement of cross sections for electron impact ionization and excitation of positive ions, detachment from negative ions and dissociation of simple molecular ions.

91 citations


Journal ArticleDOI
TL;DR: In this paper, the authors discuss the structure and composition of blood, its viscous properties and how these affect flow, and also the electrical, optical and thermal properties, which can be used to quantify flow.
Abstract: The paper discusses the structure and composition of blood, its viscous properties and how these affect flow, and also the electrical, optical and thermal properties, which can be used to quantify flow. The development of a flow profile is discussed for steady and pulsatile flow in major vessels. The various types of flowmeter which have been developed to take this profile into account are discussed. These include electromagnetic and ultrasonic flowmeters, indicator-dilution methods (including thermal dilution) and various pressure-sensing devices. In small vessels and in bulk tissue the concept of flow profile has no meaning and the measurement methods include indicator-transport methods using radioactive isotopes various forms of plethysmograph, calorimeters and thermal-conductivity probes. Each type of flow measurement method is discussed, together with its advantages and disadvantages.

55 citations


Journal ArticleDOI
TL;DR: In this article, the effects described arise as a consequence of two terms calculated by Josephson in the expression for the electrical current flowing between a pair of weakly coupled superconductors.
Abstract: The effects described arise as a consequence of two terms calculated by Josephson in the expression for the electrical current flowing between a pair of weakly coupled superconductors. One of these terms is present at zero voltage and represents a supercurrent which can cross such barriers as thin layers of insulator or normal metal; the other is an extra component of resistive current. The review sets out sufficient theoretical background to allow readers with no previous knowledge of superconductivity to understand the basic physics of the effects. It also caters for those wishing to learn enough to understand devices based on Josephson effects. The article concentrates on fundamentals, and early and recent experimental and theoretical developments in the understanding of Josephson weak links of all types are emphasized.

46 citations


Journal ArticleDOI
TL;DR: A review of the present status of the fusion phenomena occurring when two complex nuclei enter into collision and a composite nucleus is formed that may either form a compound nucleus or divide into two fragments, emitted after a considerable dissipation of kinetic energy.
Abstract: A review is presented of the present status of the 'fusion' phenomena occurring when two complex nuclei enter into collision and a composite nucleus is formed that may either form a compound nucleus or divide into two fragments, emitted after a considerable dissipation of kinetic energy.

42 citations


Journal ArticleDOI

38 citations


Journal ArticleDOI
TL;DR: A review of global induction studies of the Earth's crust and upper mantle using geomagnetic deep-sounding and magnetotelluric techniques is presented in this paper, with a discussion of studies in the UK and Kenya.
Abstract: In addition to a review of global induction studies of the Earth, the results of recent investigations of the electrical conductivity of the lunar interior are presented. Information on the magnetic environment of Venus, Mercury, Mars and Jupiter is tabulated, there being insufficient data to infer their electrical conductivity. Regional induction studies of the Earth's crust and upper mantle using geomagnetic deep-sounding and magnetotelluric techniques are summarised with a fuller discussion of studies in the UK and Kenya. The instrumentation used in observatory, field and laboratory studies is described.

Journal ArticleDOI
TL;DR: Experimental methods of studying hypernuclear ground states and continuum states observed in the recoilless Lambda production are reviewed in this article, where the Lambda particle is a unique probe of the nucleus; it interacts strongly with the nucleus and is distinguishable from the nucleons.
Abstract: Experimental methods of studying hypernuclear ground states and continuum states observed in the recoilless Lambda production are reviewed. These two types of hyper-nuclear states give the most direct information on the Lambda -nucleus interaction. The Lambda particle is a unique probe of the nucleus; it interacts strongly with the nucleus and is distinguishable from the nucleons. In light hypernuclei, gamma spectroscopy is a powerful tool in studying the bound excited states.

Journal ArticleDOI
TL;DR: In this paper, the main properties of the neutrino group (nu e, nu mu, nu e, Nu m, nu m, nu n, nu e, nu m, Nu e,nu m, Nu m ) are discussed.
Abstract: After a brief historical introduction, dealing with the development of the neutrino concept and the search for the free neutrino, the main properties of the various kinds of particles and antiparticles of the neutrino group ( nu e, nu mu , nu e, nu mu ) are listed. The article deals further only with the electron neutrinos nu e which are produced in the solar interior as a by-product of the thermonuclear reactions of hydrogen. An outline of the p-p chain and CNO cycle reactions inside the Sun is given, with the emphasis on the role of various branches of these processes in producing sufficiently energetic neutrinos which could be detected by Davis's method.

Journal ArticleDOI
TL;DR: The magnetic, remanence-carrying minerals in the Earth's crust are principally oxides and one group, the titanomagnetites and their derivatives which are ferrimagnetic spinels, occur mainly in igneous rocks as mentioned in this paper.
Abstract: The magnetic, remanence-carrying minerals in the Earth's crust are principally oxides. One group, the titanomagnetites and their derivatives which are ferrimagnetic spinels, occur mainly in igneous rocks. Haematite, a non-collinear antiferromagnet, is the remanence carrier in many sedimentary rocks. The combination of the geomagnetic field and a perturbation, present only at the time of formation of the rock, results in imprintation of a record of the field which is preserved over geological time. The retrieval and assessment of the recorded information requires a knowledge of the intrinsic properties of the minerals and the influence of microstructure, which is controlled by the environment in the host rock, on the magnetic properties.

Journal ArticleDOI
TL;DR: The Pt-Ir bar, international prototype of the metre, was one hundred times less precise as a length standard than the orange line of 86Kr by which the metre has been defined since 1960 as mentioned in this paper.
Abstract: The Pt-Ir bar, international prototype of the metre, was one hundred times less precise as a length standard than the orange line of 86Kr by which the metre has been defined since 1960. Molecular absorption lines which happen to coincide with gas laser radiations are being studied, two of which now have their wavelengths agreed internationally to serve as standards one hundred times more precise than the Kr radiation. The present time standard is the period of oscillation of the radiation corresponding to a hyperfine transition in 133Cs on which the definition of the second has been based since 1967, the preceding definitions based on the year (adopted in 1956) and on the mean solar day (before 1956) being 104 and 106 times less precise. Ways to further increase the precision and accuracy of these and other types of frequency standards as well as values for the speed of light, are discussed.

Journal ArticleDOI
TL;DR: In this paper, the theoretical techniques used to predict the potential energy surface of the deformed nucleus are described and the predictions are tested against theory and other properties of nuclei on the path to scission are discussed.
Abstract: As a fissioning nucleus passes from its ground state to the scission point-the point where it breaks into two fragments-the sequence of shapes it follows depends principally on the potential energy surface of the deformed nucleus The theoretical techniques used to predict the potential energy are described and the predictions are tested against theory Other properties of nuclei on the path to scission are also discussed: the structure of individual low-lying states, level densities at high excitation, and the magnitude of interstitial parameters may all be important in determining the nature of the fission process Finally, the current state of knowledge about specifically dynamical effects in fission is summarized

Journal ArticleDOI
TL;DR: In this paper, a rapid survey of traditional regularization schemes for quantum field theory is presented, including point-splitting, non-polynomial interactions, analytic regularization and dimensional continuation.
Abstract: Infinite integrals arising in perturbative expansions to quantum field theory have to be defined by means of a regularization procedure before they can be cancelled by a renormalization of the physical parameters in the theory. After a rapid survey of traditional regularization schemes the author describes fairly recent developments relying on point-splitting, non-polynomial interactions, analytic regularization and dimensional continuation. Among various critical tests of the schemes he considers vacuum polarization, scattering in an external field and the axial anomaly.

Journal ArticleDOI
TL;DR: The development of high-intensity electromagnets, hand in hand with the development of science, is traced since the discoveries of Oersted, particular emphasis being placed on normal conducting devices both continuously energized and pulsed.
Abstract: The development of high-intensity electromagnets, hand in hand with the development of science, is traced since the discoveries of Oersted, particular emphasis being placed on normal conducting devices both continuously energized and pulsed. Those aspects which most limit the performance of high-intensity electromagnets are reviewed and fundamental limitations, where they exist are pointed out. One of the most important limitations, that of mechanical strength, is treated in some depth, particularly the historical development of stress analysis. Finally, the author discusses the likely impact of magnetic technology, including superconducting technology, upon the future of our society.

Journal ArticleDOI
TL;DR: In this paper, the authors present a unified understanding of both two-body and multiparticle collisions. But they focus on the two-component model and cluster analysis, and do not discuss the dual unitary scheme.
Abstract: Hadron collisions are at present being investigated at energies such that production of many particles is a dominant effect. Some of the systematics that have come out of these studies are presented and related to the present understanding of the simpler two-body collisions. The data are discussed from two points of view, the inclusive point of view of the Regge-Mueller phenomenology and the exclusive point of view of the two-component model and cluster analysis. Finally, a possible theoretical framework, the dual unitary scheme, which may optimistically provide a unified understanding of both two-body and multiparticle collisions is outlined.