bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of aspartate kinase and homoserine dehydrogenase from Corynebacterium glutamicum IWJ001 and systematic investigation of l-isoleucine biosynthesis
Authors: Dong Xunyan , Zhao Yue , Zhao Jianxun , Wang Xiaoyuan
Published: March 2016

Previously we have characterized a threonine dehydratase mutant TDF383V (encoded by ilvA1) and an acetohydroxy acid synthase mutant AHASP176S, D426E, L575W (encoded by ilvBN1) in Corynebacterium glutamicum IWJ001, one of the best l-isoleucine producing strains. Here, we further characterized an aspartate kinase mutant AKA279T (encoded by lysC1) and a homoserine dehydrogenase mutant HDG378S (encoded by hom1) in IWJ001, and analyzed the consequences of all these mutant enzymes on amino acids production in the wild type background. In vitro enzyme tests confirmed that AKA279T is completely resistant to feed-back inhibition by l-threonine and l-lysine, and that HDG378S is partially resistant to l-threonine with the half maximal inhibitory concentration between 12 and 14 mM. In C. glutamicum ATCC13869, expressing lysC1 alone led to exclusive l-lysine accumulation, co-expressing hom1 and thrB1 with lysC1 shifted partial carbon flux from l-lysine (decreased by 50.1 %) to l-threonine (4.85 g/L) with minor l-isoleucine and no l-homoserine accumulation, further co-expressing ilvA1 completely depleted l-threonine and strongly shifted carbon flux from l-lysine (decreased by 83.0 %) to l-isoleucine (3.53 g/L). The results demonstrated the strongly feed-back resistant TDF383V might be the main driving force for l-isoleucine over-synthesis in this case, and the partially feed-back resistant HDG378S might prevent the accumulation of toxic intermediates. Information exploited from such mutation-bred production strain would be useful for metabolic engineering.
CATALEPTON 9 AND HELLENISTIC POETRY
Authors: Kayachev Boris
Published: March 2016

The dating of Catalepton 9 has been the central issue of scholarship on that poem. The more particular questions of the poem's authorship, the identity of the addressee, and its chronological relation to other texts, both depend on and contribute to ascertaining the date of composition. The clearest exposition of the problem remains that by Richmond. Evidence provided by Catalepton 9 falls into two categories: literary and historical. Literary evidence encompasses two kinds of data: various formal features of the text and intertextual links with other poetry. While the poem's metre, language and style suggest a relatively early date of composition (before the Eclogues), the close textual parallels with the Eclogues, interpreted as borrowings from rather than sources of Virgil's poetry, point in the opposite direction. Historical indications are likewise ambivalent. On the one hand, it seems likely that the addressee is M. Valerius Messalla Corvinus (cos. 31 b.c.) and, further, that the occasion of composition is his (only) triumph in 27 b.c. (Catalepton 9.3 uictor adest, magni magnum decus ecce triumphi). On the other hand, the allusions to his military achievements (4–5, 41–54) are both too vague and exaggerated, and, if taken literally, do not fit well our Messalla at any particular point of his career (nor any other known member of the family). Richmond, following Birt and followed by Schoonhoven, believed that at least some of the historical references are ‘intended to be prophetic’. More recently, Peirano has attempted to explain this lack of precision by arguing that Catalepton 9 is not a real-life panegyric but a later biographical fiction, the real focus of which ‘is to be found […] in the relationship that the poem constructs between Virgil and his patron’.
The fiscal benefits of repeated cooperation: coalitions and debt dynamics in 36 democracies
Authors: Weisstanner David
Published: March 2016

Do coalition governments really suffer from short time horizons in fiscal policymaking, as posited by standard political-economy models? This article focusses on coalitions that have created high levels of familiarity through shared governing experiences in the past and that are likely to cooperate again in future governing coalitions. I argue that such coalitions have incentives to internalise the future costs of debt accumulation and reach credible agreements to balance their constituencies’ fiscal preferences. Moreover, sustaining broad coalitions should have electoral advantages to implementing controversial economic reforms, thus resulting in lower debt increases compared not only with less durable coalitions but also with single-party governments. Comparing 36 economically advanced democracies between (up to) 1962 and 2013, I estimate the effects of coalitions’ cooperation prospects on the dynamics of public debt. The findings indicate that long time horizons can help coalitions to overcome intertemporal coordination problems and to reach specific policy goals.
Lunar Igneous Activity and Differentiation
Authors: Fielder G.
Published: March 2016

One of the most significant advances in our understanding of the Moon has been the discovery, through the Surveyor, Orbiter and Apollo programmes, of widespread lunar igneous activity and differentiation.

Volcanic flows (Figure 1) in, and in the neighbourhood of, Tycho are up to 20 km long and up to 12 km wide. At least 5 flows, mapped by Strom and Fielder (1970) originated in, and breached, craters up to 100 km from the rim of Tycho. One flow (Figure 2) is essentially the same age as the ropy floor material of Tycho, since it is traversed by cracks that are indicative of marginal stretching of the floor unit. Other flows are found in what are probably lava lakes (Figure 3), and two flows derive from such lakes.
Seismology of the Moon and Implications on Internal Structure, Origin and Evolution
Authors: Ewing Maurice , Latham Gary , Press Frank , Sutton George , Dorman James , Nakamura Yosio , Meissner Rolf , Duennebier Frederich , Kovach Robert
Published: March 2016

The objective of the passive seismic experiment is to measure vibrations of the lunar surface produced by all natural and artificial sources of seismic energy and to use these data to deduce the internal structure and constitution of the Moon, the nature of tectonic processes which may be active within the Moon, the rate of strain energy release for the lunar body, and the numbers and masses of meteroroids striking the lunar surface. The instrument used is also capable of measuring changes in gravity and tidal tilts which occur in its vicinity. To accomplish these objectives, seismic data must be combined with data from laboratory measurements of the physical and chemical properties of surface rocks, and many other geophysical and geochemical measurements. Thus far, we have had the opportunity to record data from two lunar seismic stations which were installed by the astronauts during Apollo missions 11 and 12. The combined recording time from these stations is presently over 9 months, but there was no overlap to permit recording the same event at two stations. Results from the analysis of these data have been presented by the seismic experiment team in five previous papers.
Λ Doublet Radiation From Oh Excited Rotational States
Authors: Zuckerman B.
Published: March 2016

I will briefly summarize some recent observational results on Ʌ doublet maser radiation from OH excited rotational states. Combination of these results with interferometric observations should enable us to distinguish between the variety of pumping models that have been proposed for the ground state OH masers. I will not discuss pumping models since the time is limited and you would not believe me anyway.
Interstellar Molecules from Cool Stars*
Authors: Wickramasinghe N. C.
Published: March 2016

Problems relating to the formation of interstellar molecules have assumed an enhanced importance in recent years mainly because of the detection of a variety of molecular species in interstellar space. The interstellar molecules CH, CH+, CN were discovered several decades ago by their characteristic bands in optical stellar spectra, while OH, H2O, H2CO, HCN, HC3N, NH3 and CO were detected during the past few years by their spectral features in the radio waveband. The optical detection of interstellar H2 was reported only several weeks ago.
The Interpretation of Space Observations of Stars and Interstellar Matter
Authors: Morton Donald C.
Published: March 2016

This report will review space observations of stars and the interstellar medium and what we can expect to learn from instruments planned for the near future. Older observations are described in more detail by Underhill and Morton (1967), and Houziaux and Butler (1970). The interpretation of these measurements depends heavily on the results of theoretical and experimental atomic physics. Therefore the last section will describe some of the areas where new atomic data are essential for our understanding of space observations.

Rockets or satellites are necessary to detect all wavelengths between 0.1 and 3000 Å except for two bands from 2000 to 2200 Å and from 2700 to 3000 Å accessible at balloon altitudes. However, for most sources outside the solar system the bound-free absorption of atomic hydrogen will obliterate all wavelengths between 100 and 912 Å. For example, unit optical depth at 304 Å occurs at 12 parsecs even if the interstellar hydrogen density is as low as 0.1 atom cm-3.
Collision Strengths for Electron Excitation of Coronal Ions
Authors: Flower D. R.
Published: March 2016

Using general purpose computer programmes developed by Drs. Eissner and Nussbaumer at University College London for the solution of atomic structure and atomic collision problems, collision strengths have been obtained for transitions between terms of the ground and first few excited configurations of ions of interest in studies of the solar corona. The atomic structure programme is written in a configuration interaction representation and uses a scaled Thomas-Fermi potential as described by Eissner and Nussbaumer (1969). The bound state wave functions generated by the structure programme are used by the collision programme (Eissner, 1970) to calculate the R-matrix solution of the collision problem by means of the distorted wave approximation (Saraph et al., 1969). This approximation should be valid for highly ionized ions such as exist in the corona and this prediction is fully confirmed where comparison can be made with calculations using the more rigorous but more time-consuming close coupling method (Burke et al., 1966; Petrini, 1969).
A Comparative Study of Visual and Photoelectric Timing of Occultations
Authors: Morrison L. V.
Published: March 2016

The timing of occultations of stars by the Moon provide data for the following studies:

(a)

Lunar theory - Constants and secular changes of its orbit.

(b)

Fundamental star systems - Systematic corrections to equinox and obliquity; individual star corrections.

(c)

Rotation of Earth - Comparison of atomic and ephemeris time scales.

With these applications in mind we consider the analysis of the [O-C]’s from occultations.
Optical and Radio Occultation Analysis
Authors: Hazard C.
Published: March 2016

The study of occultations of radio sources by the Moon has proved a powerful method of studying the structure of radio sources with a resolution limit, in some cases, as small as 0″.1 and at the same time of obtaining positions of the radio components with an accuracy of the order of 0″.1 to 1″. Recent optical observations of occultations suggest that the method is likely to play an important role in the measurement of stellar diameters down to about 0″.001 and in the detection and measurement of binary star systems. Over the past several years considerable experience has been gained in the analysis of the occultation curves of radio sources and, since the problems encountered are common to both the optical and radio analysis, our conclusions on how best to analyse occultation curves may be of some interest to the optical workers and also to radio observers who have recently entered the field. Before discussing the methods of analysis and also before discussing some essential differences between the optical and radio work it is useful to consider in some detail the nature of the occultation curve of a simple source of small angular size. It is not proposed here to give a detailed account of the methods of analysis but to indicate the general principles along which the analysis should proceed so as to enable the choice of the most appropriate method in a particular case. A simple treatment of Scheuer’s convolution procedure is given and a simple derivation of the resolution limit imposed by the receiver bandwidth.
Lunar Occultation Theory and Techniques
Authors: Lang Kenneth R.
Published: March 2016

The formulae for the monochromatic radiation intensity at the Earth during the lunar occultation of an incoherent source are examined. It is shown that the oscillatory portion of the radiation intensity may be assigned an envelope amplitude and phase a+ each instant of time. Each complex number thus defined gives the amplitude and phase of one spatial Fourier component of the source brightness distribution. Resolution is limited by the maximum available spatial frequency, and is shown to depend on integration time, seeing, antenna aperture, bandwidth, and the signal-to-noise ratio of the observation. When observations are polychromatic, the monochromatic intensity is modified by a certain function of bandwidth and wavelength. This function is specified and theoretical occultation curves of a point source are given for various bandwidth-wavelength ratios. A new method of estimating a brightness distribution is illustrated by taking the inverse Fourier transform of the spatial Fourier components present in an occultation record of 3C 49. Restored distributions for the quasars 3C 273 and 3C 245 are also given. Source positions and/or lunar limb slopes may be determined from such distributions. When the width of single sources or the angular separation of double sources is all that is required, only the inner part of the envelope of the occultation record need be determined. Theoretical curves and envelopes are presented for use in comparisons with observed data.
New Techniques in X-Ray Astronomy
Authors: Jager C. de
Published: March 2016

A review is given of some modern developments in X-ray astronomy. Improved designs of proportional counters and other detectors are described. We further enumerate developments in solar X-ray spectrographs and heliographs, like the ‘gutter’ spectrograph, and the paraboloidal-hyperboloidal frustrum mirror system, the zone plate technique. We also give a review of instruments and collimating techniques for the detection of non-solar celestial X-ray sources.
The Place of Accurate Proper Motions in Galactic Research
Authors: Blaauw A.
Published: March 2016

Problems in galactic research for the solution of which highly accurate absolute proper motions are required are manyfold. The following selection seems of particular interest at the present moment. Problems for which only accurate relative proper motions are required are not considered here.
A Rotating Disk Model for a Quasar
Authors: Kahn F.D.
Published: March 2016

It has often been suggested that the energy supply of a quasar is derived from a central body with a mass of 109−1010M⊙. However, it is known that such bodies have no stable and static equilibrium configurations beyond a relatively low degree of condensation. Only a very limited amount of energy can be extracted before instability sets in. Basically the instability is due to the dominance of radiation pressure in supporting the mass against its self-gravitation.

But if a massive object is in rapid rotation, then it is partly supported by centrifugal force, and is much less liable to an instability of this kind. It is therefore interesting to investigate the properties of a rotating disk-like object with a mass of the order of 109−1010M⊙, and to see whether its overall properties match those of any quasar. The most important parameters are 2σ0, the mass per unit area of the disk, and Z, its half-thickness. In the case of the quasar 3C 273 B, assumed to be at a distance of 450 Mpc, the most suitable pair of values are σ0 = 107 gm/cm2 and Z = 1016 cm.
Origin of Binaries from a Consideration of Angular Momentum
Authors: Huang Su-Shu
Published: March 2016

According to various studies, more than one half of stars exist as members of binary and multiple systems. Therefore any theory for star formation must account for this fact. In other words, the problem of the origin of binaries has a far broader implication than is implied as a part of binary-star study. For this reason one cannot overexaggerate its importance.
A New Look at the Sun
Authors: Wild J. P.
Published: March 2016

I have the feeling that to most astronomers the Sun is rather a nuisance. The reasons are quite complex. In the first place the Sun at once halves the astronomer’s observing time from 24 to 12 hours, and then during most of the rest of the time it continues its perversity by illuminating the Moon. Furthermore I have met numerous astronomers who regard solar astronomy to be now, as always before, in a permanent state of decline - rather like Viennese music or English cricket. Nevertheless those who study the Sun and its planetary system occasionally make significant contributions. There were, for instance, Galileo and Newton who gave us mechanics and gravitation; Fraunhofer who gave us atomic spectra; Eddington and Bethe who pointed the way to nuclear energy; and Alfvén who gave us magneto-hydrodynamics. Perhaps the point to be recognized is that the Sun has more immediately to offer to physics rather than to astronomy. That is why it is quite rare that a solar man finds himself with a large captive audience of mainline astronomers: and so the responsibility weighs heavily on my shoulders tonight.
The Astronomy and Cosmology of Copernicus
Authors: Gingerich Owen
Published: March 2016

It was close to the northernmost coast of Europe, in the city of Toruń, that the King of Poland and the Teutonic Knights signed and sealed the peace of 1466, which made West Prussia part of Polish territory. And it was in that city, just seven years later and precisely 500 years ago, in 1473, that Nicholas Copernicus was born. We know relatively few biographical facts about Copernicus and virtually nothing of his childhood. He grew up far from the centers of Renaissance innovation, in a world still largely dominated by medieval patterns of thought. But Copernicus and his contemporaries lived in an age of exploration and of change, and in their lifetimes they put together a renewed picture of astronomy and geography, of mathematics and perspective, of anatomy, and of theology.

When Copernicus was ten years old, his father died, but fortunately his maternal uncle stepped into the breach. Uncle Lucas Watzenrode was then pursuing a successful career in ecclesiastical politics and in 1489 he became Bishop of Varmia. Thus Uncle Lucas could easily send Copernicus and his younger brother to the old and distinguished University of Krakow. The Collegium Maius was then richly and unusually endowed with specialists in mathematics and astronomy; Hartmann Schedel, in his Nuremberg Chronicle of 1493, remarked that “Next to St. Anne’s church stands a university, which boasts many eminent and learned men, and where numerous arts are taught; the study of astronomy stands highest there. In all Germany there is no university more renowned in this, as I know from many reports.” At the university the young Nicholas embraced the study of astronomy with a passion found only in the most exceptional of undergraduates. There he learned about the works of Sacrobosco, Regiomontanus, Ptolemy, and Euclid.
X-Ray Sources in Close Binary Systems
Authors: Rees M. J.
Published: March 2016

The discovery by Giacconi and his colleagues of variable X-ray sources in close binary systems certainly ranks as one of the highlights of astronomical research during the last 3 years. These remarkable objects have already been extensively studied, by optical and radio observations as well as in the X-ray band; and they seem likely to prove as significant and far-reaching in their implications as pulsars.

The ‘Third Uhuru Catalogue’ (Giacconi et al., 1973a) contains about 160 sources, of which about 100 lie in our Galaxy. Their distribution over the sky (together with other arguments) suggests that these sources have luminosities of the general order 1036–1038 erg s−1, and that their typical distances are ˜ 10kpc. These galactic sources generally display rapid variability. Little else is known about most of them, but they are probably of the same general class as systems such as Her X1, Cen X3, Cyg X1 and Cyg X3. These sources have been investigated in detail, and in all cases one infers a system where the X-ray source is orbiting around a relatively ordinary star. Six sources have been optically identified, and there are some others whose binary nature is established by the occurrence of an X-ray eclipse. Orbital periods range from 4.8 h (Cyg X3) up to ˜ 10 days.
The Correlation Between Kinematical Properties and Ages of Stellar Populations
Authors: Einasto J.
Published: March 2016

The spatial and kinematical properties of galactic populations are very conservative for time changes. Therefore the study of these properties gives us certain information on the past dynamical evolution of the Galaxy, in particular on the evolution of star generating medium (interstellar gas, as generally accepted). The detailed study of spatial structure of stellar populations in our Galaxy is possible in exceptional cases only. But the study of kinematical properties is possible practically for all populations, which makes these studies very useful for cosmogonic purpose.

In order to obtain adequate quantitative information for the study of dynamical history of the Galaxy the statistical data on stellar velocities are to satisfy the following requirements: populations under study must be physically homogeneous; statistical samples of stars must be free from selection effects, especially from velocity selection; information on r.m.s. errors of observed quantities must be known in order to correct the results for accidental observational errors; the data for the determination of the age of the sample must be available.
Solar Neighbourhood as the Local Macroscopic Volume Element Within the Galaxy
Authors: Agekjan T. A. , Ogorodnikov K. F.
Published: March 2016

The notion of the local Macroscopic Volume Element (MVE) is introduced in order to facilitate the application of hydro-dynamical methods of treating internal motions in stellar systems and in particular in our Galaxy. The MVE must characterize the properties of the stellar system in a given point within the system. Hence the diameter of the MVE must be taken as small as possible; it must, however, contain a sufficiently large number of stars in order that the laws of statistics might be applied. The greater is the local star density the smaller can be made the size of the MVE.

Modern catalogues of nearby stars by Gliese (1969) and Woolley et al. (1970) afford a good collection of data for a determination of local characteristics of the Galaxy in the immediate neighbourhood of the Sun. In the first section we discuss such characteristics as the local stellar density, the local luminosity function and the influence of observational selection upon them. In the second section we consider the local solar motion and the effect of the asymmetry of stellar motions. The responsibility for the content of paragraph 1 lies primarily upon T. A. Agekjan while that for paragraph 2 upon K. F. Ogorodnikov. We both are indebted to G. V. Ishkhanov and to L. V. Chuvicova for substantial help in numerical computations.
The Chemical Composition of the Envelopes of Novae
Authors: Antipova L. I.
Published: March 2016

There are two methods to study the chemical composition of the envelopes ejected by novae: (a) the analysis of the absorption spectra of novae; (b) the analysis of emission lines during the nebular stage.
Coordinated Campaign to Observe X-Ray Binaries
Authors: Kondo Yoji
Published: March 2016

The coordinated campaign to observe x-ray binaries sponsored by the IAU Commission 42 (Close Binary Stars) and Commission 44 (Astronomical Observations from Outside the Terrestrial Atmosphere) was initiated in January 1974 with Y. Kondo as its coordinator.

The main objectives of the campaign have been: (a) dissemination of information on satellite x-ray experiments and ground-based observing programs; (b) transmission of suggestions and recommendations from campaign participants; (c) designation of campaign dates for observation of specific objects. These functions have, in part, been performed through Campaign Circulars and Special Bulletins; the most recent, Circular No. 23, was issued a few weeks ago.
The Space Density of M Dwarfs - An Observational Program
Authors: Pesch Peter
Published: March 2016

In spite of extensive proper motion surveys, there remains some uncertainty about the space density and the kinematics of late-type dwarf stars. This uncertainty is primarily due to the unknown kinematic bias introduced by the proper motion discovery technique.

A spectrographic search, especially one using an objective prism on a Schmidt telescope, can identify significant numbers of intrinsically (and actually) faint stars, free from any kinematic bias. To find faint and cool stars, one chooses an objective prism with low dispersion and emulsions sensitive to the red and near photographic infrared. At low dispersions, in this wavelength region, there are no reliable luminosity criteria. Thus Sanduleak conducted his survey in the direction of the north galactic pole, with the expectation that very few remote giants would contaminate his results. A catalog of 273 probable dwarf stars of type M3 and later (Sanduleak, N. 1976, A.J., 81, 350) based on his objective prism survey in the direction of the north galactic pole is now available. Thanks to W.J. Luyten (1976, Proper Motion Survey with the Forty-Eight Inch Schmidt Telescope XLVI (Univ. Minnesota, Minneapolis)) proper motions have been measured for all of these stars.
The Frequency of Faint M Giant Stars at High Galactic Latitudes
Authors: Sanduleak N.
Published: March 2016

Based on the observations of M giant stars in the north galactic polar objective-prism survey of Upgren (1960) and the data summarized by Blanco (1965) the overall space density of all M-type giants as a function of distance from the galactic plane at the position of the sun can be approximated by,

where z is in kpc and ρ(z) is the number of stars per 106 pc3. This relationship is derived from the observed fall-off in space densities up to a distance of about 2 kpc.

The question arises as to the validity of extrapolation equation (1) to larger z distances so as to predict the number of faint M giants expected per unit area near the galactic poles. Adopting for the M giants a mean visual absolute magnitude of −1.0 (Blanco 1965), one finds that equation (1) predicts that less than one giant fainter than V~12 should be expected in a region of 200 square degrees. This expectation formed the hypothesis of a thesis study (Sanduleak 1965) in which it was assumed that the very faint M stars detected in a deep, infrared objective-prism survey at the NGP were main-sequence stars, since this could not be ascertained spectroscopically on the very low-dispersion plates used.
Objective-Prism Radial Velocities at High Latitudes
Authors: Stock J. , Osborn W. , Upgren A. R.
Published: March 2016

Stock and Osborn (1972, 1973) have shown that objective-prism spectra taken with a conventional prism may be measured to produce radial velocities of sufficient accuracy for statistical purposes. They are determined by means of a third-order power series in both x and y coordinates. The same spectral-line measures can also yield positions such that proper motions can be determined if first-epoch positions are also available. For many stars, both tangential and radial velocities can be obtained with about the same error which is of the order of ± 20 km/sec. The field distortions caused by the prism are large but are constant and predictable to the degree that measured residuals are similar in size to those for direct images (Stock and Upgren 1968). A survey of a high-latitude zone between −30° and −35° in declination is underway and a catalogue of about 3000 stars has already been compiled by Stock. For each star, the catalogue lists an accurate 1950 position, spectral and luminosity type, apparent photographic magnitude, relative radial velocity and its weight, and the number of plates on which the star was measured.
Boundary Conditions with Mass-Loss: General Considerations
Authors: Thomas Richard N.
Published: March 2016

I begin by stating very explicitly and unambiguously that I completely disagree with any idea that a stellar atmosphere can be in any sense a boundary of the star, or that the atmosphere sets boundary conditions on stellar structure. Such an idea is what underlies all the single-layer, LTE atmospheric models, which misdirected atmospheric studies for so many years by introducing a false separation between “normal” and “extended” atmospheric phenomena. On the contrary, I assert that a more correct physical picture for the atmosphere than as a boundary comes from the characterization of star and atmosphere as:

(1) The STAR is: a concentration of matter and energy, C (M, E), in its parental environment, the interstellar medium (ISM); with boundary conditions on stellar structure being set by the way one models (a) storage modes for matter and energy in the star and ISM, and (b) energy generation in the star.
Mass Loss in Stars of Moderate Mass by Stellar Winds and Effects on the Evolution
Authors: de Loore C.
Published: March 2016

Some 30 years ago it became clear that the solar corona is a plasma with a temperature of the order of 106K. As the underlying layers have only temperatures of 5000 K a mechanism had to be discovered, capable to explain this high temperature. A solution to the problem was found when it was realized that mechanical energy losses, by shock dissipation of wave energy can heat up a plasma to such high temperatures. This mechanical energy is formed in the deeper layers of the atmosphere and transported outwards. Dissipation becomes significant in regions where the density is sufficiently low.

Wave propagation in a compressible medium in the presence of gravity and magnetic fields has been treated as a general problem, among others by Ferraro and Plumpton [1958). Three basic parameters are present: compressibility of the medium, gravity and magnetic field.
[no title]
Authors: Harvey J.
Published: March 2016

If the Sun is observed like a star, without spatial resolution, its magnetic field seldom exceeds 1 Gauss. But with high spatial resolution the field is seen to be largely concentrated into kG structures. Observations of the structure and dynamics of solar magnetic fields can therefore provide a guide to the nature of magnetic fields of other stars which cannot be resolved. Solar activity and the structure of the chromosphere and inner corona are intimately linked with magnetism and a complete understanding of these features often depends on magnetic field details. There are unsolved physical problems involving solar magnetic fields which have challenged many physicists. For example, confinement of small-scale fields in kG structures is a problem of current interest (Parker, 1976; Piddington, 1976; Spruit, 1976). Solar observers are no less challenged since the Sun presents us with a complicated magnetic field having a range of scales from global to less than the scale of our best observations as illustrated in Figures 1, 2, and 3. This paper is a survey of observational techniques and results at the small-scale end of the spectrum of sizes in the solar photosphere. This topic has been frequently reviewed (e.g. Athay, 1976; Beckers, 1976; Deubner, 1975; Howard, 1972; Mullan, 1974; Severny, 1972; Stenflo, 1975) so that recent work is emphasized here.
Stellar Evolution and Close Binaries
Authors: Paczynski B.
Published: March 2016

A general scheme of evolution of close binaries is outlined. Many types of observed systems are classified according to their evolutionary status. Present theory can account reasonably well for the mass transfer between the two components. There is no satisfactory theory of mass and angular momentum loss from binary (as well as single) stars. Most close binaries sooner or later should develop extended common envelopes. A loss of a common envelope may remove a large fraction of mass and most of angular momentum from a binary, and leave as a remnant a very short period and highly evolved system. Binary nuclei of planetary nebulae, cataclysmic variables and some X-ray binaries are produced this way.

I shall present here a picture of the evolution of close binary systems (CBS) as it is understood now. This is not intended to be a review, and no attempt has been made to make the list of references complete. Usually I shall refer the first paper on a given subject and/or one of the recent ones, where a large number of other references can be found. There are many reviews and proceedings of various symposia that deal with close binaries. Here are some: Annual Review of Astronomy and Astrophysics (9, 183,14, 119,15, 127,16, 171, 241), IAU Symposia No. 73, 83, 88, IAU Colloquia No. 42, 46, 53. I shall try to emphasize what is known and what is not known, and how various observed systems fit into the theoretical evolutionary scheme. Because of my background I shall give more references to theoretical papers. Nevertheless, I am convinced that it was the theory of close binaries that was guided in its development by the observations, not other way around. In fact the theory predicted very few new phenomena and very few new types of binaries. But it managed to account, at least qualitatively, for the major evolutionary processes, and made it possible to arrange the observed systems into the evolutionary sequences.
Radio Continuum Observations of the Nucleus of our Galaxy and Other Normal Galaxies
Authors: Ekers R. D.
Published: March 2016

The radio properties of the nuclei of normal galaxies have been reviewed by Ekers (1974, 1978a, 1978b) and of the Galactic Centre by Oort (1977). In this report I will concentrate on material available since then. The following paper by Van der Hulst extends this review with more information on the structure of the central sources in normal galaxies.

No complete high resolution maps of Sgr A have been made since the “WORST” map (Ekers et al. 1975) so I will use it as a reference for the new information which is available. At the lower frequency of 327 MHz there have been a series of occultation measurements by Gopal-Krishna and Swarup (1976). These again show the separation into two components; a nonthermal Sgr A East and a thermal Sgr A West. In addition they show some spatial variation in the nonthermal spectral index and also suggest that the nonthermal source extends over the entire region of Sgr A. From observations using the RATAN telescope Parijskij (private communication) also suggests that the Sgr A East component might just be a peak on a more symmetrical nonthermal source which is centred on Sgr A West. RATAN observations are in progress in the wavelength range from 2-6 cm and these confirm the thermal nature of Sgr A West. As the VLA elements come into operation along more than one arm of the Y it becomes possible to use it to map Sgr A. 5 and 15 GHz maps (Brown, Lo and Johnston 1978 and private communication) with a resolution of a few seconds of arc resolve the Sgr A West source into a number of components with an overall size of ˜l’ × 30’ elongated along the galactic plane and centred on the Sgr A West point source (Balick and Brown 1974). The VLA maps of Sgr A West agree well with the inner contours of the WORST map and this distribution of emission is similar to that seen in the 53μ map (Harvey, Cambell and Hofmann’ 1976). Such an association is common in HII regions and is consistent with the thermal nature of Sgr A West.
IUE Observations of Novae
Authors: Sparks Warren M. , Wu Chi-Chao , Holm Albert V. , Schiffer Francis H.
Published: March 2016

In addition to offering observing time on a regular schedule, the International Ultraviolet Explorer (IUE) satellite is also being used to observe “targets of opportunity.” Novae represent one of the most exciting targets of opportunity and also one of the most difficult because of their rapid time behavior. During the first year of operation of IUE we were extremely fortunate to have three bright novae outbursts occur: Nova Cygni 1978, WZ Sagittae, and U Scorpii.

Nova Cyg 1978, a fast nova, reached a maximum apparent visual magnitude of 6.2 on September 12, 1978 (Slovak and Vogt 1979). Figure 1 shows the relative flux of Nova Cyg 1978 in the long ultraviolet wavelength range (1900-3200Å) at several different times. One day after maximum (Sept. 13), the nova is still in its absorption line phase. At this point it looks like a supergiant F star with mostly Fell absorption lines (also see Cassatella et al. 1979). Later spectra show the emergence of emission lines, which is the characteristic behavior of novae in the visual. Magnesium II at 2800Å is the strongest emission line in this part of the spectrum for at least a month after outburst. The last spectrum (Nov. 1) shows mainly semi-forbidden lines of carbon, nitrogen, and oxygen. It should also be noted that the slope of the continuum flattens as the nova evolves.
The Solar Corona
Authors: Chiuderi Claudio
Published: March 2016

Recent observations from space have shown that the solar corona is spatially a very structured medium and temporally a very dynamic one. The consequent changes in the current theoretical ideas about coronal physics are reviewed. The role of the magnetic fields in shaping and heating the coronal structures is especially underlined.
Theoretical Review of Secular Instabilities in the Sun
Authors: Gabriel M.
Published: March 2016

In this review we discuss the problems raised by the discovery that the sun was, in the past, unstable towards non-radial oscillations.

In 1972, Fowler (1972), in an attempt to explain the low-neutrino flux measured in Davis’ experiment (now 1.6 snu, while the standard solar model predicts 4.4 snu) suggested that the sun could have undergone, some 10 years ago, a change in structure because of sudden mixing of the inner core. During the same year Dilke and Gough (1972) suggested the sun is unstable to low-order gravity modes (g+ modes) of non-radial oscillation and that the mixing is triggered when the amplitude of the oscillation becomes large enough.
Shell Flashes
Authors: Sackmann I.-Juliana
Published: March 2016

Shell flashes will be discussed here with regard to three different stages of evolution: 1. normal stars, 2. white dwarfs accreting H-rich matter and 3. neutron stars accreting matter.

A shell flash Is a thermal instability, a nuclear run-away process, occurring inanynuclear burning shell, as long as It is sufficientlythinin geometrical extent and sufficiently thick for a high enough heat capacity. (in contrast to the off-center helium shell flash, another kind of shell flash which occurs for degenerate matter, the shell flash discussed here does take place for an Ideal gas including radiation pressure and does not require degeneracy.) The first shell flash discovered was theheliumshell flash, about 15 years ago, by Schwarzschild and Härm (1965); Hayashi, Hoshi, and Suglmoto (1965); and Weigert (1965, 1966).
The Large-Scale Structure of the Corona
Authors: Zirker Jack B.
Published: March 2016

The solar corona serves as a prototype of the outer atmospheres of all cool stars. Because of its nearness we can study this prototype in more detail than any other example. Considerable progress has been made recently in understanding how the large scale structure of the solar corona controls the genesis of the solar wind and the distribution of slow and fast wind streams throughout the three-dimensional space surrounding the sun. In this review we will discuss some of the progress made in this field during the last few years. We will emphasize the observational data and the inferences that can be made more or less directly from them. T. Holzer will discuss the theoretical aspects of stellar wind acceleration in another paper in this symposium.

The large scale structures of the solar corona consist essentially of three kinds: streamers, active regions and coronal holes. Figure 1 is a familiar photograph of the solar corona, obtained in white light at the total eclipse of 30 June 1973 by the High Altitude Observatory. The streamers are the petal-like structures extending out from the black lunar limb. They taper to narrow radial spikes that have been traced out as far as 10-12 solar radii (Keller, 1979). Daily measurements of the white light corona at the Mauna Loa Observatory (Hundhausen et al. 1979) and the Pic-du-Midi Observatory (Dollfus et al., 1977) since 1965 show that the streamers are fan-shaped structures that may extend 120° in solar longitude. We see them in various perspectives at the solar limb.
The Westerbork Survey of Rich Clusters of Galaxies
Authors: Valentijn Edwin A.
Published: March 2016

In the Westerbork Survey of Rich Clusters of galaxies (WSRC), seven nearby and rich clusters of galaxies have been observed with the Westerbork Synthesis Radio Telescope. The results obtained at different frequencies are published in several papers of a series, and Table 1 serves as a general reference to these publications. In these papers, both discussions on individual radio sources and the presentation of cluster radio luminosity functions (RLF) are given. Here we summarize some of the results of the WSRC which, from a statistical point of view, impose some constraints on the rate of the radio activity of galaxies and on the influence of the galaxy environments on their activity. The rate of radio activity of a sample of galaxies in a cluster can be described by the integral RLF of the cluster, which represents the fraction of galaxies that emit in the radio domain above a certain power. When it is presented as a function of the optical luminosities of the cluster galaxies, it is called the bivariate radio luminosity function (BRLF). The BRLFs are most suitable for representing in an unbiased way the rate of activity of a sample of galaxies, since they are presented in absolute parameters and are normalized to the optical luminosity function (or distribution) of the galaxy samples. This is important since, both inside and outside clusters, it has been shown that the RLF depends strongly on the optical luminosities.
Review of Recent Observations of Cluster X-Ray Sources Using the Einstein Observatory
Authors: Murray Stephen S.
Published: March 2016

In this contribution I shall review briefly some of the recent research being carried out at the Harvard-Smithsonian Center for Astrophysics in the study of X-ray emission from clusters of galaxies. This work is being done by several of us at CFA, and I particularly wish to thank Drs. Christine Jones, William Forman, and J. Patrick Henry for permission to discuss their results. The data have been obtained from the Einstein X-ray Observatory (HEAO-2) using the imaging instruments, and in particular the Imaging Proportional Counter (IPC). This gives X-ray images with about l½ arc minute resolution over a field of view of ½° × ½° and moderate energy resolution over a band from 0.5 to 3.0 keV. (For further details see Giacconi et al. 1979).
High Energy Astrophysics and Cosmology
Authors: Woltjer L.
Published: March 2016

A brief review is given of cosmological tests based on quasars, of source evolution and of the X-ray background. The cosmological tests are still inconclusive because of the limited material available and the possibility of serious selection effects. Quasars and other extra-galactic sources account for most or all of the background in the 1-10 kev range and very possibly also at higher X- and γ-ray energies.
A Review of Recent Ultraviolet Observations of Close Binaries from Space
Authors: Kondo Yoji
Published: March 2016

The reason for presenting this review at this Joint Meeting, in spite of the fact that there was, a few days ago, a special Joint Discussion on recent UV observations is partially that somehow the general subject of close binaries was overlooked at the Joint Discussion, although unique close binaries, such as cataclysmic binaries and X-ray binaries, were included. There exist a large number of vigorous research projects being carried out with UV telescopes in the field of close binaries. I shall concentrate on IUE results, although other satellite and balloon-borne telescopes have continued to produce interesting UV observations of close binaries.

There are a number of active IUE programs on this theme. In the time allocated to this review I shall only be able to present highlights of selected programs in the hope of giving a glimpse of what is going on. The programs on close binaries from the first year of IUE operations include those by P. Conti, M. Hack, J.B. Hutchings, R.H. Koch, Y. Kondo and G.E. McCluskey, M. Plavec, and J. Sahade. In the second year, additional astronomers are also observing close binaries with the IUE.
The Origin and Early History of the Sun and the Planetary System in the Context of Stellar Evolution
Authors: Herbig G. H.
Published: March 2016

A plausible scenario for the early history of the sun can be constructed by combining the results of stellar astronomy with lunar and meteoritic chronologies. The meteorites apparently contain material exposed to two nucleosynthetic events, one about 108 yr and another a few 106 yr before solidification. Following II. Reeves, these are associated with supernovae occurring in star clusters in molecular clouds that formed during passage through successive galactic arm shocks. The Orion Trapezium Cluster may be a modern example; its density is such that encounters between members would have been close enough and frequent enough to have had major effects upon their circumstellar ‘solar nebulae,’ as would recurrent FU Ori-like eruptions of the stars themselves. The lunar bombardment continued for 7 × 108 yr following formation of our sun. If this represented disk cleanup, disks must persist for that long, and hence circumstellar activity may still be in progress around some young stars in the solar vicinity. The observed time decay of axial rotation and surface activity in solar-type stars can be extended backwards, and indicates that the ultraviolet radiation of the young sun would have had major photochemical consequences upon the primitive earth.
Do Halo Field Stars and Globular Clusters Belong to the Same Population?
Authors: Kraft Robert P.
Published: March 2016

Obviously such transcendental issues as the helium content and age of the oldest stars depend on whether we are correct in our belief that the answer to this question is “yes” I hardly need say that over the past 40 years compelling affirmative arguments have been developed. Thus, for example, the solar motion of the common subdwarfs can be shown (e.g., Carney 1979) to be essentially identical with that of globular clusters (Kinman 1959) (Table 1), and the Fe-peak metallicities of giants and RR Lyraes in the halo field have been shown to be the same as those in clusters [see, e.g., recent reviews by Kraft (1979) and Freeman and Norris (1981)]. It is hard to believe that we would be incorrect in identifying the main sequence of a globular cluster with the main sequence defined by the trigonometric parallaxes, magnitudes and colors of subdwarfs having the same [Fe/H]. It might seem, therefore, that raising such an issue at this late date is equivalent to discussing a non-existent problem.
Eddington and Mass Loss
Authors: Tayler R. J.
Published: March 2016

This joint discussion is dedicated to the memory of Sir Arthur Eddington who was born 100 years ago. He laid the foundation of much work on stellar evolution, which was summed up in his book The Internal Constitution of the Stars (ICS) which appeared in 1926. Although he did no substantial work on mass loss from stars, the possibility of mass loss is mentioned in several places in ICS and I shall mention these and other aspects of Eddington’s work which are relevant to our present interest.