The two-body problem of a pseudo-rigid body and a rigid sphere

In this paper we consider the two-body problem of a spherical pseudo-rigid body and a rigid sphere. Due to the rotational and “re-labelling” symmetries, the system is shown to possess conservation of angular momentum and circulation. We follow a reduction procedure similar to that undertaken in the study of the two-body problem of a rigid body and a sphere so that the computed reduced non-canonical Hamiltonian takes a similar form. We then consider relative equilibria and show that the notions of locally central and planar equilibria coincide. Finally, we show that Riemann’s theorem on pseudo-rigid bodies has an extension to this system for planar relative equilibria.     

The hydrography and biology of a bloom of the coccolithophorid Emiliania huxleyi in the northern North Sea

In June/July 1994 a study was made of a small bloom of the coccolithophorid Emiliania huxleyi in an area of the North Sea to the east of the Shetland Islands. Observations on the hydrography of the study area indicated the bloom was associated with Atlantic water and was confined to an area in which a stable shallow mixed layer had formed. There was no evidence to suggest association of horizontal physical structure with the bloom development. High cell densities of >1– cells dm⁻³, together with low concentrations of PIC (<50 μg dm⁻³) and detached liths (2– liths cm⁻³) indicated that the bloom was studied at an early stage of development. Biochemical and physiological observations indicated active growth was taking place. The results presented are discussed in comparison with previous studies carried out in both oceanic and shelf seas.     

GPS relative positioning at a precision level of one part per billion

Six days of data from the GIG'91 experiment have been analyzed with a fiducial strategy. The results obtained with our orbital software GEOSAT, show daily horizontal and length repeatabilities at the level of 1 part in 10⁹ plus 2 mm for baseline lengths up to 4000 km. A direct comparison with results from the GIPSY software shows, with some exceptions, mean differences at the sub-cm level. After transformation to ITRF'90 the rms of the coordinate differences is 14.8 mm. Studies of orbital predictions and comparisons with external high precision orbits indicate a mean orbit precision and accuracy of around 35 cm in each cartesian coordinate. Correlations between the GEOSAT and GIPSY solutions indicate some common model deficiencies.     

Competition and Knowledge in Javanese Rural Business

The paper focuses on information flows and the need for change in cottage industries in rural Indonesia. The context for small-scale business entrepreneurs has changed dramatically during the last decade of economic liberalisation and crisis. Emerging market opportunities, as well as national and international competition, now challenge indigenous businesses in their different geographical settings, and new information is indispensable for survival and growth. The principal question in the paper is whether small-scale agribusiness entrepreneurs are able to identify and utilise existing knowledge for the purpose of improving their competitive strength. By using case studies taking an actor's perspective, the empirical data give insight into the small entrepreneurs' perceptions of their business environments and the hindrances to innovation. Theories on dual economies, path dependence and information asymmetry form the basis for analysing two cases of Javanese agribusiness. The paper concludes that a gap prevails between "traditional" and "modern" sectors of this society, and that cottage industries have much to gain from linking up with external agencies. Regional universities may play a crucial role in enhancing information flows and disseminating competence.     

Nitrate in groundwater and surface water related to land use in the Karup Basin,Denmark

The content and distribution of nitrate in groundwater and surface water in the Karup Basin area have been investigated and analyzed. In addition to existing analyses, chemical profiles of the groundwater of the upper part of the water table sand aquifer were measured at a number of sites. The profiles indicate, in general, an upper oxidation zone with nitrate and a lower reduction zone free of nitrate. However, below plantation areas, the nitrate content in the oxidation zone is significantly low as well. The eight profiles are graphed separately, and all results are finally plotted on a single map by a graphic method that takes into consideration both the concentration and the level of the sampled water. The great variation in the nitrate content of the water from one water-supply well to another can easily be explained by plotting the values on maps using this graphing procedure, in conjunction with an examination of the nitrate zonation found in the profiles. The influence of agricultural activities is significantly related to the concentration of nitrate in surface water and groundwater under such water table conditions and circumstances as are found in the Karup Basin.     

Pressure solution - The importance of the electrochemical surface potentials

“Pressure solution”, frequently found in clay-rich sandstone, is characterized by enhanced quartz dissolution at inter-grain contacts. The origin of pressure solution and many other related dissolution processes remains elusive. Using an Electrochemical Surface Forces Apparatus we visualized and measured the dissolution of silica glass surfaces close to an electrode surface. The dissolution rates correlate quantitatively with the electrode potential via the Butler-Volmer equation for corrosion. Our experimental results demonstrate that at low temperature, apparent pressure solution and many other mineral dissolution phenomena can be driven by electrochemical processes rather than a pressure-driven process. This finding highlights the role of electrochemical surface potentials in dissolution phenomena at dissimilar material interfaces, and provides new perspectives on pressure solution in particular and a new theoretical basis for predictive control of dissolution phenomena in general.     

Multi-Century Record of Anthropogenic Impacts on an Urbanized Mesotidal Estuary: Salem Sound,MA

Salem, MA, located north of Boston, has a rich, well-documented history dating back to settlement in 1626 ce, but the associated anthropogenic impacts on Salem Sound are poorly constrained. This project utilized dated sediment cores from the sound to assess the proxy record of anthropogenic alterations to the system and compared the proxy records to the known history. Proxies included bulk stable isotopes of organic matter, magnetic susceptibility, and trace metal concentrations. Our data reveal clear changes in organic matter composition and concentration associated with land use changes and twentieth century sewage disposal practices. Further, metal data correspond with local industrial activity, particularly the historic tanning industry in Peabody, MA. Although conservation practices of past decades have improved the state of Salem Sound, the stratigraphic record demonstrates that the environment is still affected by anthropogenic influences, and has not attained conditions consistent with pre-anthropogenic baseline. The approach and results of this study are applicable to coastal embayments that are being assessed for remediation, especially those with scant historic or monitoring data.