Factors affecting the elimination of PCBs in the marine copepod Acartia tonsa

The effects of feeding, egg laying, and fecal pellet production on the elimination of polychlorinated biphenyls (PCBs) from the marine copepod Acartia tonsa were studied in a series of experiments. Copepods were exposed to ¹⁴C-labelled Aroclor 1254 and allowed to depurate in clean seawater. Copepods fed during depuration eliminated PCBs more rapidly than unfed copepods whether or not the original PCB exposure medium had contained food. Both eggs and fecal pellets contained PCBs during depuration, with the weight specific concentration of PCB in the eggs (up to 407 ppm, dry weight) exceeding four times that in the females that produced them. Female copepods eliminated PCBs twice as rapidly as males, indicating that egg production is an important route for PCB elimination.     

Genetic variation in parthenogeneticArtemia from the Shandong Peninsula,P.R.C.

Results are presented of a survey of isozyme frequencies in parthenogeneticArtimia from six salterns in the Shandong Peninsula, P.R.C. Three of the eleven enzymes we scored using polyacryamide gel electrophoresis proved to be useful for analysis of electromorph frequency variation. These enzymes are tetrazolium oxidase (TO), lactate dehydrogenase (LDH), and malate dehydrogenase (MDH). Each of these systems showed extensive isozyme variation both within and between salterns. In addition, we have examined the possibility that electromorph frequencies may vary as the result of natural selection for adaptation to specific salinity, or salinity-associated environmental conditions. An indication of clinal variation was found in two series of ponds differing in salinity, however more extensive data are needed before it is possible to conclude that these patterns are the result of natural selection. Finally, the use of isozyme analyses such as ours, for unraveling taxonomic problems inArtemia is discussed.     

The low-eccentricity earth satellite orbit at the critical inclination

A solution to the orbital motion of an Earth satellite at the critical inclination and with near-zero eccentricity is developed by the von Zeipel method to the first order in the eccentricity, and to the first order in the higher gravitational harmonics, using elements which do not degenerate at zero eccentricity.     

Glacial deposits at Wylfa Head,Anglesey, North Wales: Evidence for Late Devensian deposition in a non-marine environment

The nature and origin of glacial sediments at Wylfa Head are described, and their significance with regard to sedimentary environments during Late Devensian deglaciation of the Irish Sea Basin is discussed. Recent models of deglaciation under glaciomarine conditions are challenged. The Quaternary sequence at Wylfa consists of eroded and glaciotectonically deformed bedrock, locally derived lodgement till, calcareous silt-rich lodgement till containing northern erratics, discontinuous units of orange-brown silty sand of possible aeolian origin, and grey laminated freshwater silts filling a small kettle hole. The till units thicken to the south where the surface is drumlinised. It is concluded that the landforms and deposits result from a warm-based Irish Sea glacier, which moved towards the southwest. Spatial variation in basal water pressure resulted from localised drainage through zones of more heavily jointed bedrock. Rapid glacial erosion occurred in areas where subglacial water pressure was relatively high, while deposition of the resulting basal sediment took place where water pressures were reduced. The glacier also carried basal calcareous silty till onshore, which was deposited by lodgement processes. None of the deposits at Wylfa are interpreted as glaciomarine in origin, and there is no evidence at this site for an isostatically induced marine transgression prior to deglaciation.     

A concept for a superconducting tunnelling junction based spectrograph

We describe a multi-order spectrograph concept suitable for 8-m class telescopes, using the intrinsic spectral resolution of superconducting tunnelling junction detectors to sort the spectral orders. The spectrograph works at low orders, 1–5 or 1–6, and provides spectral coverage with a resolving power of   R ≃ 8000  from the atmospheric cut-off at 320 nm to the long-wavelength end of the infrared H or K band at 1800 nm or 2400 nm. We calculate that the spectrograph would provide substantial throughput and wavelength coverage, together with high time resolution and sufficient dynamic range. The concept uses currently available technology, or technologies with short development horizons, restricting the spatial sampling to two linear arrays; however, an upgrade path to provide more spatial sampling is identified. All of the other challenging aspects of the concept – the cryogenics, thermal baffling and magnetic field biasing – are identified as being feasible.     

SUMMER MEASUREMENTS OF DISSOLVED ION CONCENTRATIONS IN ALPINE STREAMS,BLANCA PEAK REGION,COLORADO*

Chemical weathering is commonly assumed to be negligible in the denudation of alpine landscapes. Spot samples of dissolved ions from alpine streams on the Blanca Massif had minimum average concentrations in 1978 of 35.53 ppm (range: 14.9–75.6 ppm) and in 1979, 20.23 ppm (range: 7.35–35.0 ppm). Correlations between the variation in the concentration of dissolved ions (silica, pH, and minimum ion concentration) and the elevations and drainage-basin areas of sample sites were significant at the 0.05 level.