Non-tidal changes in the length of the day: 700 BC to AD 1982

Occultations and eclipses from ancient times down to the present are analysed to determine changes in the length of the day. By subtracting the expected tidal contribution from the observed changes, the non-tidal variations are obtained. The non-tidal varations are shown to occur on time-scales of decades and millennia.     

A poincaré model for the earth's fluid core

Abstract

The superconducting-gravimeter data of Melchior and Ducarme (1986) has been interpreted as internal motion in the Earth's core by Aldridge and Lumb (1987) using a Poincaré model. Several low-order modes with periods of 13–16 hours have been tentatively identified in the core which is taken to be an incompressible, homogeneous fluid within a rigid, rotating container. The identification is based on asymptotic values of the frequencies which change slowly with time while the modes decay with an e-folding time of about 280 days. The slow change in frequency with time implies a small temporal variation in the rotation rate of the core. This mean flow is a nonlinear effect often observed in laboratory experiments designed to excite Poincaré modes. Interaction among modes during free ringdown is also observed in those experiments and apparently in the data of Melchior et al. (1988) as well. Laboratory work thus provides the link to extend the Poincaré model to include viscous and nonlinear effects in order to interpret the gravimetric observations as core modes.     

Variability of monsoon circulation under different scenarios of carbon-cycle variations in the model atmosphere

The results of numerical experiments with the model of the Institute of Numerical Mathematics, RAN, aimed to reveal variability of the atmospheric global circulation under changing content of carbon dioxide, are analyzed. Variability of monsoon circulation is considered for different scenarios of carbon dioxide content in the model atmosphere. The monsoon circulation indices calculated from the zonal-wind speeds simulated in the upper and lower troposphere and model precipitation rates are studied.     

The nature and environments of compact steep spectrum radio sources from studies of their angular sizes

The angular sizes of compact steep spectrum sources in the Peacock and Wall sample were found to decrease steeply with redshift, similar to the angular size-redshift variation for extended sources. This, however, could be an artefact if the compact sources are not all of the same nature.Models such as those of Subramanian and Swarup with a beam power of 10³⁷ W were found to be compatible with compact sources being either young sources at an early stage of development or relatively weak sources in dense, active media where star formation is continuing.     

Wavelength Dependence of the Orbital Variability of the Eclipsing Nova-Like Object Dw Uma

Results of three-colour VRI CCD photometry are presented obtained during 11 nights in 2001. Twelve new minima timings are derived. The eclipse depth decreases with wavelength, being equal to 1.28, 1.13 and 1.02 for V, R and I, respectively. The instrumental magnitudes and colours are tabulated for the mid-eclipse, out-of-eclipse part and the eclipsed component. The V−R colour of the eclipsed component of emission is by 0.22 mag bluer than that for mid-eclipse, indicating a much higher temperature of the eclipsed region.     

Prospects of large-scale noble metal mineralization in the Upper Selemdzha minerogenic zone (by the example of the Malomyr and Sagur-Semertak ore clusters)

The Upper Selemdzha minerogenic zone, which has the potential for noble metal mineralization in the Upper Amur, has been studied. It is confined to the thick strata of Paleozoic terrigeneous-sedimentary rocks (sandstones, siltstones, clay schists, packages of their thin rhythmical interlayering, sedimentary breccias, and conglomerates) in the Tokura subzone of the Selemdzha-Kerbinsk zone in the Amur-Okhotsk area of the Mongol-Okhotsk system, overlain by Early Cretaceous volcanogenic sedimentary rocks and intruded by Early Cretaceous quartz diorites, granodiorites, and dacites. In the Malomyr and Sagur-Semertak ore clusters, there are a few known potential deposits of noble metals and ore occurrences; when studied and prospected, they can exhibit vein-veinlet noble metal mineralization with rich contents of gold and platinoids in ore columns and metasomatic deposits.     

Upper Jurassic overlapping-fans slope-apron system: Brae oilfield,North Sea

The Brae oilfield reservoir in the North Sea comprises Upper Jurassic resedimented conglomerates and sandstones interbedded with organic-rich silstone and mudstone thin-bedded turbidites. The system represents a series of small overlapping fans that form a thick (300 m) slope-apron accumulation of sediments deposited in a narrow (<10 km wide) belt along an active fault zone. The complex lateral and vertical distribution of facies was due mainly to variable tectonic activity, and partly also to sediment supply and sea-level changes.