scholarly journals Commission 36: Theory of Stellar Atmospheres: (Theorie des Atmospheres Stellaires)

2000 ◽  
Vol 24 (1) ◽  
pp. 219-230
Author(s):  
R. Pallavicini ◽  
D. Dravins ◽  
B. Barbuy ◽  
L. Cram ◽  
I. Hubeny ◽  
...  
Keyword(s):  
Radiation Transfer ◽  
Accurate Determination ◽  
Stellar Atmospheres ◽  
Recent Past ◽  
Line Radiation ◽  
Chemical Enrichment ◽  
Elemental Abundances ◽  
The Galaxy ◽  
Made In

Consistently with a trend observed in recent past triennial reports, progress in the theory of stellar atmospheres continues to be made in two different directions: 1) the traditional areas of continuum and line radiation transfer, line blanketing, atomic physics and atmospheric structures controlled by the joint conditions of radiative and hydrostatic equilibrium, and 2) in areas of emerging interest such as oscillations, velocity fields, winds and mass loss, chromospheres, coronae and magnetic phenomena. Particular attention is devoted also to the accurate determination of stellar elemental abundances and their implications for stellar interior structure and evolution as well as for the chemical enrichment of the Galaxy.

scholarly journals 36. Theory of Stellar Atmospheres (Theorie des Atmospheres Stellaires

1997 ◽  
Vol 23 (1) ◽  
pp. 303-309
Keyword(s):  
Mass Loss ◽  
Atomic Physics ◽  
Radiation Transfer ◽  
Hydrostatic Equilibrium ◽  
Stellar Atmospheres ◽  
Recent Past ◽  
Line Radiation ◽  
Transfer Line ◽  
Made In ◽  
Magnetic Phenomena

Consistently with a trend observed in recent past triennial reports, progress in the theory of stellar atmospheres continues to be made in two different directions: (i) the traditional areas of continuum and line radiation transfer, line blanketing, atomic physics and atmospheric structures controlled by the joint conditions of radiative and hydrostatic equilibrium, and (ii) in areas of emerging interest such as oscillations, winds and mass loss, chromospheres, coronae and magnetic phenomena.

scholarly journals Microarcsec Astrometry: The Gaia Mission

1998 ◽  
Vol 11 (1) ◽  
pp. 581-582
Author(s):  
L. Lindegren ◽  
M.A.C. Perryman
Keyword(s):  
Accurate Determination ◽  
Distance Measurements ◽  
Profound Impact ◽  
Individual Stars ◽  
The Galaxy ◽  
Direct Distance ◽  
Scientific Potential ◽  
Space Astrometry ◽  
Small Instrument

The Hipparcos mission demonstrated the efficiency of space astrometry (in terms of number of objects, accuracy, and uniformity of results) and the fact that a relatively small instrument can have a very large scientific potential in the area of astrometry. However, Hipparcos could probe less than 0.1 per cent of the volume of the Galaxy by direct distance measurements. Using a larger instrument and more efficient detectors, it is now technically feasible to increase the efficiency of a space astrometry mission by several orders of magnitude, thus encompassing a large part of the Galaxy within its horizon for accurate determination of parallaxes and transverse velocities. Such a mission will have immediate and profound impact in the areas of the physics and evolution of individual stars and of the Galaxy as a whole.

scholarly journals III. On the determination, at sea, of the specific gravity of sea-water

1875 ◽  
Vol 23 (156-163) ◽  
pp. 301-308 ◽  
Keyword(s):  
Specific Gravity ◽  
Physical Condition ◽  
Sea Water ◽  
Accurate Determination ◽  
Actual Difference ◽  
Made In

In the investigation of the physical condition of the ocean the accurate determination of the specific gravity of the water holds a first place. The tolerably numerous observations which have been made in this direction, in a more or less connected manner, are sufficient to prove that the density of the water varies, not only with the latitude and longitude, but also with the distance from the surface of the source from which it is taken. This difference of density depends partly on an actual difference in saltness, and partly on a difference in temperature of the water.

scholarly journals Globular clusters in the Fornax cluster: A report from the FDS survey

2019 ◽  
Vol 14 (S351) ◽  
pp. 68-71
Author(s):  
Michele Cantiello ◽  
A. Venhola ◽  
M. Paolillo ◽  
R. D’Abrusco ◽  
A. Grado ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Accurate Determination ◽  
Galaxy Interactions ◽  
The Galaxy ◽  
The Status ◽  
Deep Survey ◽  
Dimensional Distribution ◽  
Fornax Cluster ◽  
Galaxy Luminosity Function

AbstractThe Fornax Deep Survey (FDS) is a multi-band imaging survey of the Fornax cluster of galaxies, executed with the ESO VLT Survey Telescope (VST). The survey is designed to reach unprecedented surface brightness and point-source magnitude depth over one virial radius of the cluster. The scientific objectives of the survey are numerous: the study of the galaxy luminosity function, derivation of galaxy scaling relations, determination of the properties of compact stellar systems, an accurate determination of distances and 3-D geometry of the Fornax cluster, analysis of diffuse stellar light and galaxy interactions, etc.In this contribute we give an overview on the interest of the survey on globular clusters (GC) populations, and present a report the status of the study of GCs also providing some preliminary results of our analysis, with particular regard to the two-dimensional distribution of GC candidates over ∼20 sq. degree area of Fornax centered on NGC 1399.

scholarly journals Discussion on the structure of atomic nuclei

1929 ◽  
Vol 123 (792) ◽  
pp. 373-390 ◽  
Keyword(s):  
Accurate Determination ◽  
Essential Point ◽  
Whole Numbers ◽  
Atomic Nuclei ◽  
Whole Number ◽  
Nuclear Atom ◽  
The Individual ◽  
The Masses ◽  
Made In

Sir Ernest Rutherford: It was on March 19, 1914, that the Royal Society held its last discussion on the constitution of the atom—just fifteen years ago. I had the honour to open the discussion on that occasion, and the other speakers were Mr. Moseley, Profs. Soddy, Nicholson, Hicks, Stanley Allen, S. P. Thomp­son. In my opening remarks I put forward the theory of the nuclear atom and the evidence in support of it, while Mr. Moseley gave an account of his X-ray investigations, which defined the atomic numbers of the elements, and showed how many gaps were present between hydrogen number 1 and uranium number 92. Prof. Soddy drew attention to the existence of isotopes in the radioactive series, and also to a remarkable observation by Sir Joseph Thomson and Dr. Aston, who had obtained two parabolas in the positive ray spectrograph of neon, and he suggested that possibly the ordinary elements might also consist of mixture of isotopes. I think you will find that the remarks and suggestions made in this discussion fifteen years ago have a certain pertinence to-day. In particular Hicks and Stanley Allen drew attention to the importance of taking into account the magnetic fields in the nucleus, although at that time we had very little evidence on that point, and even to-day our information is very scanty. What has been accomplished in the intervening period ? On looking back we see that three new methods of attack on this problem have been developed. The first, and in some respects the most important, has been the proof of the isotopic constitution of the ordinary elements, and the accurate determination of the masses or weights of the individual isotopes, mainly due to the work of Dr. Aston. This has led in a sense to an extension of the original ideas of Moseley. The experiments of the latter fixed the number of possible nuclear charges, while Aston has shown that there are a large number of species of atoms each defined by its nuclear charge, although their masses and their nuclear constitution may be different. The essential point brought out in the earlier work of Dr. Aston was that the masses of the elements are approxi­mately expressed by whole numbers, where oxygen is taken as 16—with the exception of hydrogen itself. But the real interest, as we now see it, is not the whole number rule itself, but rather the departures from it.

scholarly journals On a relation between the refractive and dispersive constants of the inert gases

1927 ◽  
Vol 114 (769) ◽  
pp. 659-661
Keyword(s):  
Accurate Determination ◽  
Inert Gases ◽  
Critical Temperatures ◽  
Philosophical Magazine ◽  
Empirical Relations ◽  
Five Elements ◽  
Made In

In 1911 I published in the ‘Philosophical Magazine’ a paper on new determinations of some constants of the inert gases, and drew attention to the remarkable empirical relations which subsist between (1) the calculated numbers of “dispersion” electrons in the atoms of these five elements, (2) their “viscosity diameters” as determined by Prof. A. O. Rankine, and (3) their critical temperatures. Since that time the figures used have undergone revision. The accurate determination of the value of ε by Millikan has enabled us to give absolute, instead of relative, values to the apparent numbers of dispersion electrons ( q , see Table I). Chapman has recalculated the viscosity diameters, and Rankine has revised Chapman’s values, in the light of corrections to be made in his own values of Sutherland’s constants for argon, krypton and xenon. But these alterations have not affected the validity of the relations then published.

scholarly journals Derivation of the Rotational Frequency of Massive Stars from Seismic Studies

2004 ◽  
Vol 215 ◽  
pp. 199-204 ◽  
Author(s):  
C. Aerts ◽  
R. Scuflaire ◽  
A. Thoul
Keyword(s):  
Main Sequence ◽  
High Spatial Resolution ◽  
Massive Stars ◽  
Accurate Determination ◽  
Rotation Frequency ◽  
Rotational Frequency ◽  
Current Status ◽  
B Stars ◽  
Made In

In this contribution we review the current status of the determination of the rotational frequency in non-radially pulsating B stars, i.e. β Cep stars and slowly pulsating B stars. Considerable progress is currently being made in the understanding of the non-radial oscillations of main-sequence B stars by means of high-temporal, high-spatial resolution spectroscopic time series. This has led to the detection of frequency multiplets, which are interpreted as rotationally splitted non-radial modes and which allow an accurate determination of the surface rotational frequency in some stars. We outline how our future goal, i.e. the derivation of the internal rotation frequency, can be achieved.

scholarly journals II. Magnetic survey of the east of France in 1869

1872 ◽  
Vol 162 ◽  
pp. 7-27
Keyword(s):  
Accurate Determination ◽  
Magnetic Survey ◽  
Sources Of Information ◽  
The West ◽  
Mean Values ◽  
The City ◽  
Central Station ◽  
Previous Occasion ◽  
Made In

This survey, which occupied a considerable portion of the months of August and September 1869, is a continuation of the series of observations made in the west of France during the preceding year. The instruments used were the same on both occasions, the only changes made for the second expedition being (1°) the substitution of a theodolite by Jones in lieu of Cooke’s transit-theodolite, which was slightly too heavy for carrying in the hand, and (2°) the procuring, through the kindness of Dr. Stewart, a second tripod stand similar to our own, which rendered the series of observations with two observers much more rapid than on the previous occasion. The observations were undertaken, as before, by the Rev. W. Sidgreaves and myself, the Vibrations and Deflections falling to his share, and the Declination and Chronometer comparisons remaining in my hands, whilst the Dip was in general observed by both. The method of reduction is almost identical with that adopted for the observations taken in the west of France. The geographical positions of the different stations have been calculated, as far as possible, from the data given in the 'Connaissance des Temps,’ but where this could not be done I have had recourse to the most reliable sources of information at my command. For the accurate determination of the positions of Mont Rolland (near Dôle), of N. D. de Myans (near Chambéry), of Mongré (near Villefranche-sur-Soane), of Iseure (near Moulins), and of our station at Marseilles I am indebted to the kindness of the Rev. N. Larcher, S. J., Membre de la Société Météorologique de France. The coordinates of Vaugirard were readily obtained from a good map of Paris, and for Issenheim and Monaco I have to depend on Cassini’s ‘Carte Générale de la France’ and on Philip’s 'Imperial Atlas.’ The Imperial Observatory at Paris is chosen as the natural position for the origin of coordinates, in lieu of our central station of observation at Vaugirard, which lies on the outskirts of the city; the resulting mean values will thus require no correction, and will be immediately comparable with those of most other observers.

Glomerular permeability in the fetal rabbit

1978 ◽  
Vol 36 (2) ◽  
pp. 681A-681B ◽  
Author(s):  
M. L. Monica ◽  
M. L. Zimny ◽  
S. G. McClugage
Keyword(s):  
New Zealand ◽  
Age Differences ◽  
Accurate Determination ◽  
Ethyl Carbamate ◽  
Lower Abdomen ◽  
Glomerular Permeability ◽  
Small Incision ◽  
New Zealand White Rabbits ◽  
Made In

The purpose of this study was to determine fetal age differences in glomerular permeability using a graded series of dextrans (Pharmacia, Inc., Uppsala, Sweden). The dextran fractions were highly purified and consisted of the following sizes: T-10, T-40 and T-110 (10,000, 40,000 and 110,000 M.W. respectively). The foundation for this study was the work of Caulfield and Farquhar, who showed, using a graded series of dextrans, that the basement membrane was the definitive barrier to permeability.A total of 120 fetuses of pregnant New Zealand white rabbits at the following periods of gestation: 20, 22, 24, 28 days and one day old neonates were utilized. Accurate determination of each fetus' developmental stage was based on weight and crown-rump measurements made at the time of sacrifice. Pregnant rabbits were anesthesized with 20% urethane (ethyl carbamate) and a longitudinal incision was made in the shaved lower abdomen. A small incision was placed in the exposed uterus which penetrated the amniotic sac allowing for removal of the fetus. Viability of the fetus was essential and each fetus remained attached to the placenta throughout the course of dextran injection.

THE IEC METHOD AND CONVERSION COEFFICIENTS OF THE 605-keV TRANSITION IN 134Ba

1966 ◽  
Vol 44 (3) ◽  
pp. 549-562 ◽  
Author(s):  
E. F. Zganjar ◽  
J. H. Hamilton
Keyword(s):  
Beta Decay ◽  
Photon Energy ◽  
Conversion Coefficient ◽  
Theoretical Calculations ◽  
Accurate Determination ◽  
A Value ◽  
Conversion Coefficients ◽  
Double Focusing ◽  
Made In

Tests of the internal–external method of measuring conversion coefficients in the Vanderbilt double-focusing spectrometer have been made in search of possible errors arising from scattering of photoelectrons in the converter for a photon energy of 605 keV. This scattering may affect the factor, f, which corrects for the anisotropic distribution of the photoelectrons. The 605-keV transition in 134Ba populated by the beta decay of 134Cs was used. An accurate determination of the K, L, and M conversion coefficients of the 2+ to 0+, 605-keV, E2 transition in 134Ba was made. Three uranium converters 1.12, 2.19, and 3.71 mg/cm2 thick were used. The results are compared with the new theoretical calculations of f which depend on the converter thickness and consequently consider the effect of scattering. For photons of energy 605 keV or greater, the IEC method used in the Vanderbilt double-focusing spectrometers is insensitive (< 5%) to scattering in uranium converters < 4 mg/cm2 thick. The K, L, and M conversion coefficients were determined to be (5.03 ± 0.20) × 10−3, (7.07 ± 0.50) × 10−4, and (1.64 ± 0.18) × 10−4, respectively. The respective theoretical values of Rose are 5.08 × 10−3, 6.92 × 10−4, and 2.77 × 10−4. Sliv and Band give a value of 5.10 × 10−3 for the K conversion coefficient.

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