The electronic structure and absorption spectrum of MnO 6 9− octahedra in manganian andalusite

The energy levels of MnO ₆ ^9? clusters, with D _4h approximated and C _2v actual symmetry of the M ₁ site of Mn³⁺-bearing andalusite, are calculated using the multiple scattering method. The energies of the electronic d-d transition of Mn³⁺ in the clusters with D _4h symmetry are calculated to be 6,000–7,000 cm^?1 (⁵ B _1g → ⁵ A _1g ), ～18,000 cm^?1 (⁵ B _1g → ⁵ B _2g ) and ～19,000 cm^?1 (⁵ B _1g → ⁵ E _g ). Apart from a splitting of the ⁵ E _g -level into two levels separated by 300–350 cm^?1, no significant changes of these transition energies are noted for the corresponding cluster with C _2v symmetry. The calculated transition energies give a good fit to the structure of the optical absorption spectra of Mn³⁺-bearing andalusites and support recent assignments of the major absorption bands observed in these spectra.     

The application of different analytical extractions and soil profile sampling in exploration geochemistry

This paper deals briefly with the principles of geochemical migration in the secondary (soil, sediment) environment, a knowledge of which is essential to a correct interpretation of exploration geochemical data. Examples are given which illustrate that the principles which apply in the more easily interpreted tropical areas, also apply in the more complicated glaciated regions. Any person employing exploration geochemistry in geomorphologically complicated areas, is well advised to study data from strictly residual soil areas where the fundamentals of geochemical migration are more easily observed. From this base it is easier to understand the additional complications of geochemistry in mountainous and glaciated terrain. Of the variety of exploration geochemical techniques which can be used, this paper deals specifically with two: soil profile sampling, and different strengths of acid extraction of metal from samples. Examples from the different environments are compared and contrasted.     

PCBs and chlorinated pesticides in the atmosphere and aquatic organisms of Ross Island, Antarctica

PCBs, p,p′-DDT, p,p′-DDE and lindane (γ-hexachlorocyclohexane) were monitored in the lower atmosphere of Ross Island, in Antarctica for 2 yr. Geometrical means were 15.2 pg m⁻³ for PCBs, 2.0 pg m⁻³ for p,p′-DDT, 1.0 pg m⁻³ for p,p′-DDE and 25.8 pg m⁻³ for lindane. Atmospheric levels of lindane were positively correlated with temperature, and a significant difference was found between spring-summer and summer-winter concentrations. No season related differences were found for the other chlorinated hydrocarbons, possibly owing to their lower vapour pressure and the cold climate. Periods with increased atmospheric levels of PCBs and DDT compounds were recorded. Lindane, p,p′-DDE and PCBs were present in fish and zooplankton sampled close to Ross Island. Pollutant levels in the zooplankton (on an extractable fat basis) were highest during the Antarctic spring and autumn and were inversely correlated to their fat content.     

Mapping of quick clay formations using geotechnical and geophysical methods

Quick clay has been involved in most serious, large clay slides in Sweden, Norway, and Canada. This paper describes geotechnical and geophysical methods that can be used to locate and map the extent of quick clay formations. Surface resistivity measurements and four different sounding methods have been tested. The results have been compared with sensitivities determined using fall-cone tests. The investigation shows that there is a correlation between sensitivity and electrical resistivity, which can be used to discriminate between marine clays that have been leached sufficiently to possibly form quick clay and those for which the salt content remains sufficiently high to prevent this. Although the most reliable evaluation of the variation in sensitivity was obtained by the CPT with additional measurement of total penetration force, this investigation suggests that any sounding method that uses a constant rate of advance into the ground and in which the penetration force applied on the top of the rods is measured may be used for quick clay mapping.     

SMART-1 mission description and development status

SMART-1 is the first of the Small Missions for Advanced Research in Technology of the ESA Horizons 2000 scientific programme. The SMART-1 mission is dedicated to testing of new technologies for future cornerstone missions, using Solar-Electric Primary Propulsion (SEPP) in Deep Space. The chosen mission planetary target is the Moon. The target orbit will be polar with the pericentre close to the South-Pole. The pericentre altitude lies between 300 and 2000 km, while the apocentre will extend to about 10,000 km. During the cruise phase, before reaching the Moon, the spacecraft thrusting profile allows extended periods for cruise science. The SMART-1 spacecraft will be launched in the spring of 2003 as an auxiliary passenger on an Ariane 5 and placed into a Geostationary Transfer Orbit (GTO). The expected launch mass is about 370 kg, including 19 kg of payload. The selected type of SEPP is a Hall-effect thruster called PPS-1350. The thruster is used to spiral out of the GTO and for all orbit maneuvers including lunar capture and descent. The trajectory has been optimised by inserting coast arcs and the presence of the Moon's gravitational field is exploited in multiple weak gravity assists.The Development Phase started in October 1999 and is expected to be concluded by a Flight Acceptance Review in January 2003. The short development time for this high technology spacecraft requires a concerted effort by industry, science institutes and ESA centres. This paper describes the mission and the project development status both from a technical and programmatic standpoint.     

Comparison of geotechnical uncertainties linked to different soil characterization methods

One of the essential inputs in settlement prediction models is the soil modulus, which may be obtained from laboratory tests or estimated from in situ measurements. The total uncertainty in predicting the confined modulus of a sandy soil is quantified with data from side-by-side in situ testing using the standard penetration test, the static cone penetration test, the light dynamic probing and the laboratory oedometer test. To estimate transformation errors, correlations are proposed between in situ and laboratory data. The results indicate that similar magnitudes of total uncertainties are associated with the in situ methods, which are approximately twice as high as those from the direct oedometer method. The quantified uncertainties are an important input for reliability-based designs of foundations under similar soil conditions.