Cypermethrin induces glutathione S-transferase activity in the shore crab,Carcinus maenas   总被引：2，自引：0，他引：2  

Gowlan BT  Moffat CF  Stagg RM  Houlihan DF  Davies IM 《Marine environmental research》2002,54(2):169-177

Cypermethrin is a synthetic pyrethroid that is particularly toxic to crustacea. It is therefore applied as a chemotherapeutant in the salmonid aquaculture industry for the treatment of sea lice infestations. After use, cypermethrin is released directly into the marine environment, to be diluted by fresh seawater. The shore crab, Carcinus maenas is found in the vicinity of fish farms, and may come into contact with released cypermethrin. The detoxification enzyme, glutathione S-transferase (GST) has been implicated in cypermethrin metabolism in terrestrial arthropods, but this has not yet been demonstrated in crustacea. In this paper we investigate the response of GST activity in Carcinus to cypermethrin exposure, and also the time course of the induction process. GST activity is significantly increased in Carcinus exposed to nominal concentrations of 50 and 500 ng/l of water-borne cypermethrin. Carcinus demonstrate a significant elevation in GST activity following intra-cephalothoracic injection with 10 ng of cypermethrin. GST activity returns to basal levels after 36 h. The potential application of GST activity in Carcinus as a biomarker of cypermethrin exposure is discussed.  相似文献   

Fossils explained 26: Trace fossils 4 – borings     

Stephen K. Donovan  Ron K. Pickerill 《Geology Today》1999,15(5):197-200

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Linearly Organized Turbulence Structures Observed Over a Suburban Area by Dual-Doppler Lidar   总被引：1，自引：1，他引：0  

Rob Newsom  Ron Calhoun  David Ligon  Jerry Allwine 《Boundary-Layer Meteorology》2008,127(1):111-130

Dual-Doppler lidar observations are used to investigate the structure and evolution of surface-layer flow over a suburban area. The observations were made during the Joint Urban 2003 (JU2003) field experiment in Oklahoma City, U.S.A. in the summer of 2003. This study focuses specifically on a 10-h sequence of scan data beginning shortly after noon local time on 7 July 2003. During this period two coherent Doppler lidars performed overlapping low elevation angle sector scans upwind and south of Oklahoma City’s central business district. Radial velocity data from the two lidars are processed to reveal the structure and evolution of the horizontal velocity field in the surface layer throughout the afternoon and during the evening transition period. The retrieved velocity fields clearly show a tendency for turbulence structures to be elongated in the direction of the mean flow throughout the entire 10-h study period. In order to quantify the observed anisotropy and its dependence on stability, integral length scales are estimated directly from the spatially resolved velocity retrievals. As the flow became more stably stratified the characteristic cross-stream dimension of the linear structures decreased. The streamwise component was consistently more anisotropic than the cross-stream component, and both velocity components exhibited maximum anisotropy under neutral conditions. The ratio of the streamwise to cross-stream length scale was estimated to be about eight for the streamwise component, and four for the cross-stream component under neutral conditions.  相似文献   

Magnetic behavior of magnetite and rocks stressed to failure — Relation to earthquake prediction     

Jacques Revol  Ron Day  Michael D. Fuller 《Earth and Planetary Science Letters》1977,37(2):296-306

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Thermodynamics of falling precipitation zones     

Claude Girard  Roland List 《Pure and Applied Geophysics》1975,113(1):1035-1053

A number of numerical experiments are performed in order to study the role of thermodynamics during the fall of precipitation zones. Thereby the air motion is handled in a Eulerian fashion, using the approximate equations for deep convection, and the precipitation-size particles are treated by a Lagrangian method. The results indicate that the behavior of a precipitation zone is greatly affected by both atmospheric stability and drop evaporation. Stable air strongly opposes downdraft development. Furthermore, air entrained downward by the zone becomes buoyant leading to a considerable updraft aloft. Evaporation, on the other hand, tends to counter the effect of stability and to cause a cool downdraft near the ground and a gust front. In spite of the many simplifications, particularly in the initial conditions, the results as seen by a surface observer show much realism.  相似文献   

Geography and the Social Sciences in Australia: an opportunity lost?1     

Ron Johnston 《The Australian geographer》2006,37(2):279-284

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Three-dimensional seismic reflection investigation of the upper crustal Winagami sill complex of northwestern Alberta, Canada     

J. Kim Welford  Ron M. Clowes 《Geophysical Journal International》2006,166(1):155-169

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RXTE spectroscopy of GRS 1915+105     

Jochen Greiner  Ed H. Morgan  Ron A. Remillard 《New Astronomy Reviews》1998,42(9-10)

The galactic superluminal motion source GRS 1915+105 has been extensively observed with the RXTE satellite over the last two years. More than 250 RXTE pointings have been performed until mid-May 1998 with more than 1.5 Msec exposure time on roughly a weekly basis. Here we report on first results of our spectral analysis of a major part of these pointed RXTE observations. We establish the existence of at least 5 spectral components and present the changes of these components over the last two years.  相似文献   

Evidence for a poleward meridional flow on the sun     

Ken Topka  Ron Moore  Barry J. LaBonte  Robert Howard 《Solar physics》1982,79(2):231-245

We define for observational study two subsets of all polar zone filaments, which we call polemost filaments and polar filament bands. The behavior of the mean latitude of both the polemost filaments and the polar filament bands is examined and compared with the evolution of the polar magnetic field over an activity cycle as recently distilled by Howard and LaBonte (1981) from the past 13 years of Mt. Wilson full-disk magnetograms. The magnetic data reveal that the polar magnetic fields are built up and maintained by the episodic arrival of discrete f-polarity regions that originate in active region latitudes and subsequently drift to the poles. After leaving the active-region latitudes, these unipolar f-polarity regions do not spread equatorward even though there is less net flux equatorward; this indicates that the f-polarity regions are carried poleward by a meridional flow, rather than by diffusion. The polar zone filaments are an independent tracer which confirms both the episodic polar field formation and the meridional flow. We find:

1. The mean latitude of the polemost filaments tracks the boundary of the polar field cap and undergoes an equatorward dip during each arrival of additional polar field.
2. Polar filament bands track the boundary latitudes of the unipolar regions, drifting poleward with the regions at about 10 m s^-1.
3. The Mt. Wilson magnetic data, combined with a simple model calculation, show that the filament drift expected from diffusion alone would be slower than observed, and in some cases would be equatorward rather than poleward.
4. The observation that filaments drift poleward along with the magnetic regions shows that fields of both polarities are carried by the meridional flow, as would be expected, rather than only the f-polarity flux which dominates the strength. This leads to the prediction that in the mid-latitudes during intervals between the passage of f-polarity regions, both polarities are present in nearly equal amounts. This prediction is confirmed by the magnetic data.

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Everywhere different? Globalisation and the impact of international migration on Sydney and Melbourne     

James Forrest  Michael Poulsen  Ron Johnston 《Geoforum》2003,34(4):499-510

Using a new approach to classifying migrant group concentrations, we test for evidence of the effects of globalisation, associated by some with ‘protopostmodernity’, on two Australian cities. Sydney is characterised as an emergent world city and a focus of ‘new economy’ activities. Melbourne is associated with ‘old economy’ activities, dominated by manufacturing. In the Australian context, the onset of globalisation also coincided with significant changes to immigration policy: the end of a ‘white Australia’ policy in the early 1970s in favour of a skills-based policy, regardless of race or ethnicity. We argue that the evidence of the spatial behaviour of ethnic groups for these two cities highlights the essential continuity of ethnic segregation and spatial assimilation processes in two cities where segregation levels and experience are fundamentally different from many overseas examples. We further argue for a need to recognise that context, and the ethnic experience, are everywhere different, both intra- and internationally.  相似文献