Vertical variations of the chlorophyll maximum during a red tide in a shallow lagoon     

Domenico Voltolina  Leslie N. Brown  Maurice G. Robinson 《Estuarine, Coastal and Shelf Science》1985,21(6):817-822

The results of eight sets of repeated observations on the vertical variations of the chlorophyll maximum layer in a shallow lagoon during a red tide show that these were more frequently hydrologically induced, rather than due to active vertical migrations of the red tide-forming organism. These results are discussed and compared to those existing in the literature, with special regard to the role of light and nitrogen in conditioning vertical migrations in red tide-forming dinoflagellates.  相似文献   

Effects of prolonged exposure to 4-tert-octylphenol on toxicity and indices of oestrogenic exposure in the sand goby (Pomatoschistus minutus, Pallas)   总被引：3，自引：0，他引：3  

Robinson CD  Brown E  Craft JA  Davies IM  Moffat CF 《Marine environmental research》2004,58(1):19-38

Alkylphenolic compounds are present in estuarine and marine environments. They are moderately bioaccumulative, and oestrogenic to fish following three week, in vivo, exposures. The effects of prolonged exposure are, as yet, unclear. Sand goby (Pomatoschistus minutus) were exposed to measured concentrations of 4-tert-octylphenol (OP) in a 28-day, dose-ranging study, and a six month temporal response study. Following 28-days exposure to measured 31+/-6 or 101+/-47 microg l(-1) OP (mean+/-SD), immature male sand goby showed elevated vitellogenin (VTG) mRNA expression. Plasma alkali-labile phosphate concentrations were elevated in both sexes and were higher in females than males. Although measured OP concentrations were variable, they were significantly different for each treatment and a range of concentration-dependent effects were observed. The LC(50) for chronic OP exposure (8 weeks) was 29+/-6 microg l(-1), and both sexes demonstrated concentration and duration dependent increases in VTG mRNA expression. Exposure to 28+/-20 microg l(-1) OP (median+/-95% CI) for 6 months inhibited development of male nuptial colouration and sperm duct glands. These findings are discussed in relation to environmental concentrations of alkylphenols and ecological concerns.  相似文献   

A Sensitivity Analysis of the Waterline Method of Constructing a Digital Elevation Model for Intertidal Areas in ERS SAR scene of Eastern England   总被引：1，自引：0，他引：1  

D. C. Mason  I. J. Davenport  R. A. Flather  C. Gurney  G. J. Robinson  J. A. Smith 《Estuarine, Coastal and Shelf Science》2001,53(6):759

A sensitivity analysis of the waterline method of constructing a Digital Elevation Model (DEM) of an intertidal zone using remote sensing and hydrodynamic modelling is described. Variation in vertical height accuracy as a function of beach slope is investigated using a set of nine ERS Synthetic Aperture Radar (SAR) images of the Humber/Wash area on the English east coast acquired between 1992 and 1994. Waterlines from these images are heighted using a hydrodynamic tide-surge model and interpolated using block kriging. On 1:500 slope beaches, an average block height estimation standard deviation of 18–22 cm is achieved. This rises to 27 cm on 1:100 slope beaches, and 32 cm on 1:30 slope beaches. The average heighting error at different slopes is decomposed into components due to waterline heighting error, inadequate sensor resolution and interpolation inaccuracy. It is shown that, at 1:500 slope, waterline heighting error and interpolation inaccuracy are the main error sources, whilst at 1:30 slope, errors due to inadequate sensor resolution become dominant. The ability of the technique to generate intertidal DEMs for almost the entire coastal zone in a complete ERS SAR scene covering 100×100 km is demonstrated.  相似文献   

Ionic activity coefficients in aqueous mixtures of NaCl and MgCl₂     

R. A. Robinson  R. G. Bates 《Marine Chemistry》1978,6(4):327-333

Methods developed earlier, based on hydration numbers for individual ionic species, have been extended to the calculation of ionic activity coefficients in aqueous systems of two electrolytes MX and NX₂ with a common unhydrated anion (X⁻). The data required include the mean activity coefficients of MX and NX₂ in the mixtures, together with the osmotic coefficient. The procedure is illustrated by a calculation of γ_Na, γ_Mg, and γ_Cl in a mixture of NaCl and MgCl₂ closely approximating the composition of seawater with salinity of 35‰.  相似文献   

The toxicity of one-hour silver exposures to early-life stages of the surf Spisula solidissima (Dillwyn)     

George A. Zoto  William E. Robinson 《Marine environmental research》1985,16(1):61-75

Early life stages of Spisula solidissima (1-, 4-, 8- and 12-h post-fertilization) were exposed to various concentrations of silver in solution (0, 4, 8, 24, 44, 124 and 278 μg liter^?1) for 1 h. An additional group of 1-h post-fertilized eggs was treated with 0, 4, 11 and 24 μg liter^?1 silver continuously for 48h. Results indicate that younger embryos are more susceptible to Ag. Exposure of one-hour-old embryos to silver for only 1 h gives results similar to a continuous 48-h exposure to the same concentration of Ag. The calculated EC₅₀ for 48-h continuously exposed embryos was similar to the EC₅₀ for 1-h post-fertilized embryos that were exposed to silver for only 1 h.  相似文献   

Propagation and absorption of cyclotron maser radiation in solar microwave spike bursts     

Z. Kuncic  P. A. Robinson 《Solar physics》1993,145(2):317-338

It has been argued that the loss-cone-driven electron cyclotron maser instability can account for the properties of millisecond microwave spike bursts observed during some solar flares. However, as it propagates outward from the corona, maser radiation undergoes gyroresonance absorption when its frequency is a harmonic of the local electron-cyclotron frequency. Existing analytical models using slab geometries predict that this absorption should be sufficiently strong to prevent the radiation from being seen at the observed levels, except under highly restrictive conditions or for unrealistic plasma parameters. A more comprehensive analysis is presented here to determine if and when maser radiation can escape to produce microwave spike bursts. This analysis employs numerical raytracing and incorporates propagation and absorption of fundamental maser emission in a realistic model of a coronal flux loop. It is found that ranges of physical conditions do exist under which maser radiation can escape to an observer and that these conditions are much more limiting for fundamental emission in the extraordinary ()-mode than in the ordinary (o)-mode. Detailed investigation implies that escaping radiation in the -mode is highly directional and chiefly observable toward the center of the solar disk, while escapingo-mode radiation is found to emerge from the corona over a much wider range of directions, with some cases corresponding to radiation observable near the solar limb.  相似文献   

Plasma processing of interstellar PAHs into solar system kerogen     

Wdowiak TJ  Lee W  Cronin J  Beegle LW  Robinson MS 《Planetary and Space Science》1995,43(10-11):1175-1182

Processes resulting in the formation of hydrocarbons of carbonaceous chondrites and the identity of the interstellar molecular precursors involved are an objective of investigations into the origin of the solar system and perhaps even life on earth. We have combined the resources and experience of an astronomer and physicists doing laboratory simulations with those of a chemical expert in the analysis of meteoritic hydrocarbons, in a project that investigated the conversion of polycyclic aromatic hydrocarbons (PAHs) formed in stellar atmospheres into alkanes found in meteorites. Plasma hydrogenation has been found in the University of Alabama at Birmingham Astrophysics Laboratory to produce from the precursor PAH naphthalene, a new material having an IR absorption spectrum (Lee, W. and Wdowiak, T.J., Astrophys. J. 417, L49-L51, 1993) remarkably similar to that obtained at Arizona State University of the benzene-methanol extract of the Murchison meteorite (Cronin, J.R. and Pizzarello, S., Geochim. Cosmochim. Acta 54, 2859-2868, 1990). There are astrophysical and meteoritic arguments for PAH species from extra-solar sources being incorporated into the solar nebula, where plasma hydrogenation is highly plausible. Conversion of PAHs into alkanes could also have occurred in the interstellar medium. The synthesis of laboratory analogs of meteoritic hydrocarbons through plasma hydrogenation of PAH species is underway, as is chemical analysis of those analogs. The objective is to clarify this heretofore uninvestigated process and to understand its role during the origin of the solar system as a mechanism of production of hydrocarbon species now found in meteorites. Results have been obtained in the form of time-of-flight spectroscopy and chemical analysis of the lab analog prepared from naphthalene.  相似文献   

Properties of metre-wavelength solar bursts associated with interplanetary type II emission     

R. D. Robinson  R. T. Stewart  H. V. Cane 《Solar physics》1984,91(1):159-168

A statistical analysis is used to determine the properties of metre-wavelength events which are associated with interplanetary type II bursts. It is found that the likelihood of an interplanetary type II burst is greatly increased if: (a) an associated metre-wavelength type II has a starting frequency less than 45 MHz; (b) a strong metre-wavelength continuum is present; (c) the type II contains herringbone fine structure; and (d) the metre-wavelength activity is accompanied by strong, long-lasting H and soft X-ray events.Visiting scientist at Division of Radiophysics, January 1983; previous address - NASA/Goddard Space Flight Center, Greenbelt, Maryland.  相似文献   

Spatial process and data models: Toward integration of agent-based models and GIS   总被引：8，自引：1，他引：8  

Daniel G. Brown  Rick Riolo  Derek T. Robinson  Michael North  William Rand 《Journal of Geographical Systems》2005,7(1):25-47

The use of object-orientation for both spatial data and spatial process models facilitates their integration, which can allow exploration and explanation of spatial-temporal phenomena. In order to better understand how tight coupling might proceed and to evaluate the possible functional and efficiency gains from such a tight coupling, we identify four key relationships affecting how geographic data (fields and objects) and agent-based process models can interact: identity, causal, temporal and topological. We discuss approaches to implementing tight integration, focusing on a middleware approach that links existing GIS and ABM development platforms, and illustrate the need and approaches with example agent-based models.  相似文献   

Dennis Curry, 1912-2001     

Eric Robinson 《Proceedings of the Geologists' Association. Geologists' Association》2002,113(1):89-90

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