Magneto-elastic plane waves in a cosserat medium

Summary The propagation of plane waves in an electrically conducting cosserat medium placed in a magnetic field is investigated. The constitutive equations of cosserat elasticity developed recently byParia have been combined with the field equations of electromagnetism to obtain the basic equations for the problem. The results obtained in this investigation are in agreement with the corresponding results on magneto-elastic plane waves in Hookean solids when the cosserat constants are supposed to be absent.     

Clostridium perfringens as a potential indicator for the presence of sewage solids in marine sediments

Marine sediment cores collected from several depths of water and distances from a California sewage outfall were tested to see if sediments influenced by sewage solids were a reservoir of enteric pathogens, and if concentrations of indicator bacteria were related to the presence of sewage solids. Vertical distributions of microorganisms in marine sediments were determined; there was a decrease of indicator bacteria with increasing sediment depth. Aeromonas was randomly isolated, but none of the enteric bacterial pathogens or viruses were detected. While classic indicator bacteria were of little value in predicting the presence of pathogens, or relative amounts of sewage solids, Clostridium perfringens may be a suitable indicator. Clostridium perfringens concentrations were not related to the presence of pathogens in sediments.     

Large-Scale Structures in Comet Hale–Bopp

The plasma tails of comets clearly show the demarcation of the solar wind into distinct equatorial and polar regions (Brandt and Snow (2000), Icarus 148, 52–64).The boundary is determined by the maximum extent in latitude of the heliospheric current sheet (HCS). The observational record contains many well-observed equatorial comets, but observations of comets in the polar region are relatively rare. In addition to its size and brightness, comet Hale–Bopp had an orbital inclination of 89.4° and was well observed for months in the polar region. We document the comet's large-scale appearance throughout the apparition, including the polar region and its transition into the equatorial region. The bright dust tail hampered observations of the plasma tail, particularly near the head, but images taken with a CO⁺ filter show a very large disconnection event (DE) on May 7 and May 8, 1997. The time of disconnection is estimated at approximately May 4.0. This DE is associated with a crossing of the HCS. The model calculations of the HCS indicate that other crossings might have occurred in late April, but given the uncertainty in the calculation, the comet might have missed the HCS. Sparse observational coverage and the bright dust tail prevent further investigation of the potential earlier HCS crossings. The plasma tail shows anomalous orientations at the highest latitudes and possible explanations are discussed.     

Trace metals in the North Sea

The distribution of zinc, manganese, nickel, copper and cadmium in water and biological material has been measured in the southern North Sea and Straits of Dover, and off the north-east coast of England. These investigations provide baseline values against which future pollution changes can be measured.