The Expansion of the Distance Between Two Arbitrary Gravitating Points as Applied to Specific Models of Celestial Bodies

For the complete system of biharmonic functions a suitable representation in spheroidal coordinates is found. It is used for expanding the distance between two arbitrary gravitating points and its inverse quantity in appropriate series. Such expansions can be of interest and useful in a number of problems of celestial mechanics and stellar dynamics.     

The equatorial Atlantic oscillation and its response to ENSO

An internal equatorial Atlantic oscillation has been identified by analyzing sea surface temperature (SST) observations. The equatorial Atlantic oscillation can be viewed as the Atlantic analogue of the El Niño/Southern Oscillation (ENSO) phenomenon in the equatorial Pacific, but it is much less vigorous. The equatorial Atlantic oscillation is strongly influenced by the Pacific ENSO with the equatorial Atlantic sea surface temperature lagging by about six months. This lag can be explained by the dynamical adjustment time of the equatorial Atlantic to low-frequency wind stress variations and the seasonally varying background state, which favours strongest growth of perturbations in summer. Results of an extended-range simulation with a coupled ocean-atmosphere GCM support this picture.     

Demographic transition in Sri Lanka: a spatial perspective

Demographic transition theory involves a lagging fertility transition induced by a leading mortality transition. This article focuses on the linkage between the mortality and fertility transitions in Sri Lanka; it discusses the measurement of areal fertility, demonstrates the use of a measure not commonly used in population geography, and shows areal association between past mortality and recent fertility. The Coale or Princeton fertility indices allow a reasonably good view of structural and behavioral aspects of fertility; the Coale indices examine the contribution of structure to total fertility and the contribution of marital fertility. Although recent fertility decline has been less rapid than the post-war mortality decline, Sri Lanka's crude birth rate in 1975 was the 5th lowest in Asia. Sri Lanka experienced very high crude death rates in 1930, and quite low rates in 1950 and in subsequent years. This demonstrates an association between historic mortality and recent fertility, and that association can be linked deductively to demographic transition theory. In 1930, malaria was endemic throughout the Dry Zone of Sri Lanka, and hyperendemic in several districts. The Spearman rank correlation coefficients reveal the strongest relationship between malaria and nuptiality; this lends evidence to the notion that structural influences on fertility--such as delayed marriage--are more important than influences on marital fertility--such as coital frequency. The evidence suggests that mortalily decline in Sri Lanka led to an increase in fertility in those areas where malaria had been concentrated. This suggests the possibility that measures constituting malaria control or eradication also stimulate increased fertility; therefore, anti-malarial programs must be integrated with family planning.     

A methodology for making initial estimates of groundwater recharge from groundwater vulnerability mapping

Recharge to an aquifer can be estimated by first calculating the effective rainfall using a soil moisture budgeting technique, and then by applying a recharge coefficient to indicate the proportion of this effective rainfall that contributes to groundwater recharge. In the Republic of Ireland, the recharge coefficient is determined mainly by the permeability and thickness of the superficial deposits (subsoils) that overlie the country’s aquifers. The properties of these subsoils also influence groundwater vulnerability, and a methodology has been developed for determining the recharge coefficient using the groundwater vulnerability classification. The results of four case studies have been used to develop a quantified link between subsoil permeability, aquifer vulnerability, recharge and runoff. Recharge and runoff coefficients are each classed into three groupings: high, intermediate and low. A high recharge coefficient equates to a low runoff coefficient, and vice versa. A GIS-based tool enables preliminary estimates of recharge to be made using these recharge coefficient groupings. Potential recharge is calculated as the product of effective rainfall and recharge coefficient. The actual recharge is then calculated taking account of the ability of the aquifer to accept the available recharge. The methodology could be applied to other temperate climate zones where the main aquifers have a substantial covering of superficial deposits.     

New variable stars on digitized Moscow collection plates. The field of 66 Ophiuchi

In the course of a program to digitize the astronomical plates of the Sternberg Astronomical Institute’s plate stacks, we are developing algorithms for searching for new variable stars and studying them using digitized photographic plates. We have discovered and studied 480 new variable stars in a 10° × 10° field of view centered on 66 Ophiuchi. The digitized plate negatives used are from the 40-cm astrograph, and are 30 × 30 cm in size. These stars include three new Cepheids of the Galaxy’s spherical component, 157 eclipsing binaries, 11 high-amplitude δ Scuti stars (HADSs), 144 RR Lyrae stars, 110 irregular variables (109 LB and one white star), and 55 semi-regular red variables. New important information has been obtained for 43 known variables, which we have classified and derived or improved their light elements; an erroneous identification of the Mira V404 Oph has been corrected. We have also identified more than 50 suspect brightness variables; a program of CCD observations of these suspected variables has been initiated. Our discoveries of new variable stars were performed in a star field with a large number of known variables, detected earlier photographically or using CCD techniques. The discovery of hundreds of new variables in a well-studied region of sky demonstrates that archive photographs possess a large information potential that has remained unrealized.     

Enhancement of a hypoplastic model for granular soil–structure interface behaviour

Modelling of interfaces in geotechnical engineering is an important issue. Interfaces between structural elements (e.g., anchors, piles, tunnel linings) and soils are widely used in geotechnical engineering. The objective of this article is to propose an enhanced hypoplastic interface model that incorporates the in-plane stresses at the interface. To this aim, we develop a general approach to convert the existing hypoplastic model with a predefined limit state surface for sands into an interface model. This is achieved by adopting reduced stress and stretching vectors and redefining tensorial operations which can be used in the existing continuum model with few modifications. The enhanced interface model and the previous model are compared under constant-load, stiffness and volume conditions. The comparison is followed by a verification of two the approaches for modelling the different surface roughness. Subsequently, a validation between available experimental data from the literature versus simulations is presented. The new enhanced model gives improved predictions by the incorporation of in-plane stresses into the model formulation.     

Magnetic cleansing of weathered/tarry oiled feathers--the role of pre-conditioners

Iron powder has previously been demonstrated to be effective in the removal, via magnetic harvesting, of a wide variety of oil contaminants from feathers and plumage. This study investigates the efficacy of magnetic cleansing for the removal from feathers of tarry contamination that has been allowed to weather. Clusters of feathers from Mallard duck (Anas platyrhnchos) and Little Penguin (Eudyptula minor) were completely immersed in a tarry contaminant and allowed to weather from one to fourteen days. The contaminant was removed using a magnetic cleansing protocol and the removal efficacy assessed gravimetrically. For one, seven and fourteen days of weathering, a final removal (after fourteen treatments) of more than 99% and 97% was achieved for duck feathers and penguin feathers, respectively. Repeating the experiments (for a seven-day weathering period) for both duck and penguin feathers, with the judicious application of a pre-conditioner (olive oil), further improved removal efficacy. A convenient method to screen for improved pre-conditioning agents is suggested.     

Rainfall‐induced consolidation and sealing effects on soil erodibility during concentrated runoff for loess‐derived topsoils

Flume experiments simulating concentrated runoff were carried out on remolded silt loam soil samples (0·36 × 0·09 × 0·09 m³) to measure the effect of rainfall‐induced soil consolidation and soil surface sealing on soil erosion by concentrated flow for loess‐derived soils and to establish a relationship between soil erodibility and soil bulk density. Soil consolidation and sealing were simulated by successive simulated rainfall events (0–600 mm of cumulative rainfall) alternated by periods of drying. Soil detachment measurements were repeated for four different soil moisture contents (0·04, 0·14, 0·20 and 0·31 g g^?1). Whereas no effect of soil consolidation and sealing is observed for critical flow shear stress (τ_cr), soil erodibility (Kc) decreases exponentially with increasing cumulative rainfall depth. The erosion‐reducing effect of soil consolidation and sealing decreases with a decreasing soil moisture content prior to erosion due to slaking effects occurring during rapid wetting of the dry topsoil. After about 100 mm of rainfall, Kc attains its minimum value for all moisture conditions, corresponding to a reduction of about 70% compared with the initial Kc value for the moist soil samples and only a 10% reduction for the driest soil samples. The relationship estimating relative Kc values from soil moisture content and cumulative rainfall depth predicts Kc values measured on a gradually consolidating cropland field in the Belgian Loess Belt reasonably well (MEF = 0·54). Kc is also shown to decrease linearly with increasing soil bulk density for all moisture treatments, suggesting that the compaction of thalwegs where concentrated flow erosion often occurs might be an alternative soil erosion control measure in addition to grassed waterways and double drilling. Copyright © 2007 John Wiley & Sons, Ltd.