scholarly journals A Survey for Red Variables in the Magellanic Clouds

1984 ◽  
Vol 108 ◽  
pp. 217-218 ◽  
Author(s):  
T. Lloyd Evans
Keyword(s):  
Large Amplitude ◽  
Small Amplitude ◽  
Magellanic Clouds ◽  
Carbon Stars

One LMC and two SMC fields of 0.3 sq. deg. have been searched for red variables. Carbon stars of V ~ 16–17 are common and are usually of small amplitude, while the LMC alone contains numerous faint M type variables of small amplitude. M giants of small amplitude generally have much shorter periods than carbon stars. The LMC contains numerous Miras with a P-L relation similar to that of galactic Miras, while the SMC has few Miras but many bright red variables of large amplitude which have a steeper P-L relation.

On nearly-commensurable periods in the restricted problem of three bodies, with calculations of the long-period variations in the interior 2:1 case

1966 ◽  
Vol 25 ◽  
pp. 197-222 ◽  
Author(s):  
P. J. Message
Keyword(s):  
Periodic Solution ◽  
Periodic Solutions ◽  
Large Amplitude ◽  
Restricted Problem ◽  
Small Amplitude ◽  
Minor Planets ◽  
Long Period ◽  
Numerical Integrations ◽  
Period Variations ◽  
The Mean

An analytical discussion of that case of motion in the restricted problem, in which the mean motions of the infinitesimal, and smaller-massed, bodies about the larger one are nearly in the ratio of two small integers displays the existence of a series of periodic solutions which, for commensurabilities of the typep+ 1:p, includes solutions of Poincaré'sdeuxième sortewhen the commensurability is very close, and of thepremière sortewhen it is less close. A linear treatment of the long-period variations of the elements, valid for motions in which the elements remain close to a particular periodic solution of this type, shows the continuity of near-commensurable motion with other motion, and some of the properties of long-period librations of small amplitude.To extend the investigation to other types of motion near commensurability, numerical integrations of the equations for the long-period variations of the elements were carried out for the 2:1 interior case (of which the planet 108 “Hecuba” is an example) to survey those motions in which the eccentricity takes values less than 0·1. An investigation of the effect of the large amplitude perturbations near commensurability on a distribution of minor planets, which is originally uniform over mean motion, shows a “draining off” effect from the vicinity of exact commensurability of a magnitude large enough to account for the observed gap in the distribution at the 2:1 commensurability.

Solitary Filaments of Coupled Electromagnetic Wave and Finite Amplitude Ion Fluctuations

1976 ◽  
Vol 31 (12) ◽  
pp. 1517-1519 ◽  
Author(s):  
P. K. Shukla ◽  
M. Y. Yu ◽  
S. G. Tagare
Keyword(s):  
Electromagnetic Wave ◽  
Electromagnetic Radiation ◽  
Plasma Density ◽  
Large Amplitude ◽  
Small Amplitude ◽  
Finite Amplitude ◽  
Nonlinear Coupling ◽  
Incoming Radiation

Abstract We show analytically that the nonlinear coupling of a large amplitude electromagnetic wave with finite amplitude ion fluctuations leads to filamentation. The latter consists of striations of the electromagnetic radiation trapped in depressions of the plasma density. The filamentation is found to be either standing or moving normal to the direction of the incoming radiation. Criteria for the existence of localized filaments are obtained. Small amplitude results are discussed.

scholarly journals Carbon stars in clusters in the Galaxy and the Magellanic Clouds

1983 ◽  
Vol 202 (1) ◽  
pp. 59-76 ◽  
Author(s):  
M. S. Bessell ◽  
P. R. Wood ◽  
T. Lloyd Evans
Keyword(s):  
Magellanic Clouds ◽  
Carbon Stars ◽  
The Galaxy

Air‐gun source instabilities

Geophysics ◽  
1987 ◽  
Vol 52 (9) ◽  
pp. 1229-1251 ◽  
Author(s):  
Bill Dragoset ◽  
Neil Hargreaves ◽  
Ken Larner
Keyword(s):  
Large Amplitude ◽  
Small Amplitude ◽  
Ocean Surface ◽  
Data Interpretation ◽  
Central Portion ◽  
Air Gun ◽  
Individual Signature ◽  
Band Limited ◽  
Zero Phase

The signature of an air‐gun array can change over a period of time or even from one shot to the next. If the signature variations are large, then deterministic deconvolution, with an operator designed from a single signature or from an average signature, could produce errors significant enough to affect data interpretation. Possible sources of air‐gun instability include changes in gun positions, firing times, and pressures, gun failures, and scattering from the fluctuating rough ocean surface. If an air‐gun array were perfectly stable, after application of signature deconvolution the residual signatures for a sequence of shots would be identically shaped, broadband, zero‐phase wavelets. In practice, air‐gun instabilities lead to two major defects in band‐ limited residual signatures: the central portion of the wavelet can become asymmetrical, and unsuppressed energy can occur in the residual bubble region. Processing experiments done with synthesized air‐gun array signatures show that of all types of air‐gun instabilities likely to occur, only gun dropouts cause signature variations severe enough to affect data interpretation. Gun dropouts produce unsuppressed residual bubble energy that can show up as phantom events on a stacked section or that can obscure small‐amplitude events following large‐amplitude events. Neither gun dropouts nor any other kind of air‐gun instability has a significant effect on resolution within the seismic band. Since gun dropouts do not happen on a shot‐to‐shot basis and other instabilities are unimportant, there is no practical benefit to be gained by deriving and applying individual signature deconvolution operators for each shot. The influence of gun dropouts can be minimized through other actions taken in acquisition and processing.

Surveys for Field Carbon Stars in the Magellanic Clouds

1994 ◽  
pp. 509-512
Author(s):  
M. Azzopardi ◽  
E. Rebeirot ◽  
B. E. Westerlund
Keyword(s):  
Magellanic Clouds ◽  
Carbon Stars

Pathway-Specific Targeting of GABAA Receptor Subtypes to Somatic and Dendritic Synapses in the Central Amygdala

2001 ◽  
Vol 86 (2) ◽  
pp. 717-723 ◽  
Author(s):  
Andrew J. Delaney ◽  
Pankaj Sah
Keyword(s):  
Gaba Receptors ◽  
Large Amplitude ◽  
Gaba Receptor ◽  
Small Amplitude ◽  
Inhibitory Synapses ◽  
Receptor Subtypes ◽  
Central Amygdala ◽  
Low Concentrations ◽  
Gabaa Receptor Subtypes ◽  
Minimal Stimulation

Neurons in the central amygdala express two distinct types of ionotropic GABA receptor. One is the classical GABAA receptor that is blocked by low concentrations of bicuculline and positively modulated by benzodiazepines. The other is a novel type of ionotropic GABA receptor that is less sensitive to bicuculline but blocked by the GABAC receptor antagonist (1,2,5,6-tetrohydropyridine-4-yl) methylphosphinic acid (TPMPA) and by benzodiazepines. In this study, we examine the distribution of these two receptor types. Recordings of GABAergic miniature inhibitory postsynaptic currents (mIPSCs) showed a wide variation in amplitude. Most events had amplitudes of <50 pA, but a small minority had amplitudes >100 pA. Large-amplitude events also had rise times faster than small-amplitude events. Large-amplitude events were fully blocked by 10 μM bicuculline but unaffected by TPMPA. Small amplitude events were partially blocked by both bicuculline and TPMPA. Focal application of hypertonic sucrose to the soma evoked large-amplitude mIPSCs, whereas focal dendritic application of sucrose evoked small-amplitude mIPSCs. Thus inhibitory synapses on the dendrites of neurons in the central amygdala express both types of GABA receptor, but somatic synapses expressed purely GABAA receptors. Minimal stimulation revealed that inhibitory inputs arising from the laterally located intercalated cells innervate dendritic synapses, whereas inhibitory inputs of medial origin innervated somatic inhibitory synapses. These results show that different types of ionotropic GABA receptors are targeted to spatially and functionally distinct synapses. Thus benzodiazepines will have different modulatory effects on different inhibitory pathways in the central amygdala.

scholarly journals Red Giant Stars: Comparison of Observations and Theory

1984 ◽  
Vol 108 ◽  
pp. 195-206
Author(s):  
Jeremy Mould
Keyword(s):  
Mass Loss ◽  
Parameter Space ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Magellanic Clouds ◽  
Asymptotic Giant Branch ◽  
Carbon Stars ◽  
Giant Stars ◽  
Theoretical Investigations ◽  
Red Giant

Recent observations in both the field and the clusters of the Magellanic Clouds suggest a higher mass loss rate during or at the end of the asymptotic giant branch phase than previously supposed. Recent theoretical investigations offer an explanation for the frequency of carbon stars in the Clouds, but a rich parameter space remains to be explored, before detailed agreement can be expected.

scholarly journals Surveys for Carbon Stars in External Galaxies

2000 ◽  
Vol 177 ◽  
pp. 51-58
Author(s):  
Marc Azzopardi
Keyword(s):  
Local Group ◽  
Galactic Halo ◽  
Magellanic Clouds ◽  
Carbon Stars ◽  
Molecular Absorption ◽  
Absorption Bands ◽  
Distant Galaxies ◽  
External Galaxies ◽  
Dwarf Spheroidals

Prominent molecular absorption bands in the spectra of carbon stars make their detection possible, even in relatively distant external galaxies. Although extensive surveys for carbon stars have been carried out mainly in the Magellanic Clouds and the dwarf spheroidals in the Galactic halo, more distant galaxies in the Local Group and beyond have been successfully searched for this kind of object.

scholarly journals Optical Variability of Twenty-Two Quasi-Stellar Objects

1972 ◽  
Vol 44 ◽  
pp. 171-178 ◽  
Author(s):  
R. J. Angione ◽  
H. J. Smith
Keyword(s):  
Large Amplitude ◽  
Small Amplitude ◽  
Secular Trends ◽  
Apparent Magnitude ◽  
Optical Variability ◽  
Stellar Objects ◽  
Light Fluctuations ◽  
Quasi Stellar Objects ◽  
One Year

Light fluctuations have been found in all 22 QSOs studied by measurement of plates from the Harvard collection, which cover the last eighty years. The conclusions of this study are: (i) There appear to be at least three general classes of variation: (a) erratic, small-amplitude variations, (b) erratic, large-amplitude variations, and (c) slow quasi-periodic variations, e.g. as in 3C 273; (ii) No significant differences were detected between the rates of rise and decline of luminosity; (iii) Definite secular trends over at least 50 years were found in 5 QSOs; (iv) No simple clearcut periods greater than one year have been found; (v) There may be a trend of decreasing amplitude of fluctuations in apparent magnitude with increasing luminosity.

The Formation of Carbon Stars in the Magellanic Clouds from Mass Transfer in Close Binaries

1999 ◽  
Vol 190 ◽  
pp. 381-382 ◽  
Author(s):  
Ju. Frantsman
Keyword(s):  
Mass Transfer ◽  
Binary Systems ◽  
Magellanic Clouds ◽  
Simulation Technique ◽  
Stage I ◽  
Close Binaries ◽  
Agb Stars ◽  
Carbon Stars ◽  
Population Simulation ◽  
Age Determinations

The presence of the carbon stars in the MC with luminosities higher or lower than predicted for thermally-pulsing (TP) AGB stars, can be explained by processes that happen during the early AGB (E–AGB) stage. I examine this assumption by means of a population simulation technique. I find that there must be TP–AGB C and S stars in the MC that formed as a result of mass transfer in binary systems. Their presence may influence the age determinations of MC clusters.

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