Detailed comparison of the structures and kinematics of simulated and observed barred galaxies     

J. K. O'Neill  John Dubinski 《Monthly notices of the Royal Astronomical Society》2003,346(1):251-264

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Thaw modification of frost-fissure wedges,Richards Island,Pleistocene Mackenzie Delta,Western Arctic Canada     

Julian B. Murton  Hugh M. French 《第四纪科学杂志》1993,8(3):185-196

Thaw modification is the general process whereby frost-fissure wedges are modified during thaw, and by which frost-fissure pseudomorphs may develop. Specific processes of thaw modification are inferred from ice-wedge pseudomorphs, composite-wedge pseudomorphs and deformed sand wedges in the Pleistocene Mackenzie Delta: i.e. thermal erosion, collapse, subsidence, refreezing, loading, buoyancy, spreading, folding and shearing. Thaw modification is believed to result in selective preservation of pseudomorphs and wedges. Sand wedges are more likely to be preserved than are ice-wedge pseudomorphs or compositewedge pseudomorphs, because only those sand wedges that penetrate massive ice or icy sediments are prone to thaw modification. Furthermore, whereas ice wedges preferentially develop in ice-rich, fine-grained sediments (thaw-sensitive), their pseudomorphs appear to be selectively preserved in ice-poor, coarse-grained sediments (thaw-stable).  相似文献   

The relationship between X-ray variability amplitude and black hole mass in active galactic nuclei     

Paul M. O'Neill  Kirpal Nandra  Iossif E. Papadakis  T. J. Turner 《Monthly notices of the Royal Astronomical Society》2005,358(4):1405-1416

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Energetic ions in solar γ-ray flares     

Hugh S. Hudson 《Solar physics》1985,100(1-2):515-535

Solar flares emit line and continuum -radiation as well as neutrons and charged particles. These high-energy emissions require the presence of energetic ions within the magnetic structures of the flare proper. We have already learned a great deal about the location and mode of particle acceleration. The observations have now become extensive enough so that we can begin to study the dynamics of the energetic ions within the flare structures themselves. This paper reviews the -ray and neutron observations and the theory of their emission, and discusses on this basis the presence of energetic ions deep within the flaring atmosphere.  相似文献   

Evaluation of toxicity in tributaries of the Mersey estuary using the isopod Asellus aquaticus (L.)     

A. J. O'Neill  T. S. Galloway  M. A. Browne  A. Dissanayake  M. H. Depledge 《Marine environmental research》2004,58(2-5):327

Increasing numbers of industrial, agricultural and natural chemicals are present in sewage effluent and are known to elicit toxic effects in laboratory exposures, but little is known of their combined sub-lethal effect in the field. In this study, a combination of esterase activity and ventilation rate assays was performed to determine the neurological and physiological function of the freshwater crustacean Asellus aquaticus (L.) at sites above and below a sewage treatment works (STW). Cholinesterase and carboxylesterase activities were significantly inhibited (n=8, P<0.05) and ventilation rates increased (n=8, P=0.0001) in A. aquaticus at STW sites compared to those from reference sites, indicating a decrease in neurological and physiological function. The ecological relevance of these findings for the population dynamics of the organisms in the field is discussed.  相似文献   

Vertical habitat partitioning by large calanoid copepods in the oceanic subarctic Pacific during Spring   总被引：1，自引：0，他引：1  

David L. Mackas  Hugh Sefton  Charles B. Miller  Anne Raich 《Progress in Oceanography》1993,32(1-4)

The copepods Neocalanus plumchrus, N. flemingeri, N. cristatus, and Eucalanus bungii dominate the net zooplankton throughout the subarctic Pacific Ocean. All four species have an extensive seasonal ontogenetic vertical migration, completing most or all of their feeding and somatic growth in spring and early summer. We used stratified tows with MOCNESS and BIONESS instrumented net systems to resolve their upper ocean vertical distributions in May and June of 1984, 1987 and 1988. In each year the feeding copepodite stages of all four species were concentrated above the permanent halocline (roughly from 0 to 150m). However, the four species showed strong vertical species zonation and segregation within this layer. We consistently found a near-surface pair (N. plumchrus and N. flemingeri) and a subsurface pair (N. cristatus and E. bungii). The boundary between these groups shifts vertically, but was sharply defined and was very often coincident with a weak and transient thermocline marking the base of the layer actively mixed by surface wind and wave energy. Diel vertical migration was very limited during our sampling periods.The data suggest that the vertical distribution patterns of the copepods could be set by responses to the local intensity of turbulent mixing in the watercolumn. N. plumchrus and N. flemingeri occupied a stratum characterized by strong turbulence. N. cristatus and E. bungii occupied a stratum that was a local minimum in turbulence profiles. The depth of the boundary between the species pairs was deeper when winds and surface energy inputs were strong. The vertical partition pattern may also be determined by a difference in feeding strategy between the species pairs. N. plumchrus and N. flemingeri may feed on the enhanced protozoan population of the mixed layer, while N. cristatus and E. bungii feed on particle aggregates settling from above.  相似文献   

Characterizing Observed Environmental Variability With HF Doppler Radar Surface Current Mappers and Acoustic Doppler Current Profilers: Environmental Variability in the Coastal Ocean   总被引：3，自引：0，他引：3  

Josh T. Kohut Hugh J. Roarty Scott M. Glenn 《Oceanic Engineering, IEEE Journal of》2006,31(4):876-884

A network of high-frequency (HF) radars is deployed along the New Jersey coast providing synoptic current maps across the entire shelf. These data serve a variety of user groups from scientific research to Coast Guard search and rescue. In addition, model forecasts have been shown to improve with surface current assimilation. In all applications, there is a need for better definitions and assessment of the measurement uncertainty. During a summer coastal predictive skill experiment in 2001, an array of in situ current profilers was deployed near two HF radar sites, one long-range and one standard-range system. Comparison statistics were calculated between different vertical bins on the same current profiler, between different current profilers, and between the current profilers and the different HF radars. The velocity difference in the vertical and horizontal directions were then characterized using the observed root-mean-square (rms) differences. We further focused on two cases, one with relatively high vertical variability, and the second with relatively low vertical variability. Observed differences between the top bin of the current profiler and the HF radar were influenced by both system accuracy and the environment. Using the in situ current profilers, the environmental variability over scales based on the HF radar sampling was quantified. HF radar comparisons with the current profilers were on the same order as the observed environmental difference over the same scales, indicating that the environment has a significant influence on the observed differences. Velocity variability in the vertical and horizontal directions both contribute to these differences. When the potential effects of the vertical variability could be minimized, the remaining difference between the current profiler and the HF radar was similar to the measured horizontal velocity difference (~2.5 cm/s) and below the resolution of the raw radial data at the time of the deployment  相似文献   

Swimming endurance of haddock (Melanogrammus aeglefinus L.) at prolonged and sustained swimming speeds, and its role in their capture by towed fishing gears     

Breen  Mike; Dyson  Jamie; O'Neill  Finbarr G.; Jones  Emma; Haigh  Michael 《ICES Journal of Marine Science》2004,61(7):1071-1079

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Experimental method for quantifying resistance to the opening of netting panels   总被引：1，自引：0，他引：1  

Sala  A.; O'Neill  F. G.; Buglioni  G.; Lucchetti  A.; Palumbo  V.; Fryer  R. J. 《ICES Journal of Marine Science》2007,64(8):1573-1578

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An approach to aid INS using time-differenced GPS carrier phase (TDCP) measurements   总被引：1，自引：0，他引：1  

Ben K. H. Soon  Steve Scheding  Hyung-Kuen Lee  Hung-Kyu Lee  Hugh Durrant-Whyte 《GPS Solutions》2008,12(4):261-271

This paper presents a simple and effective approach that incorporates single-frequency, L1 time-differenced GPS carrier phase (TDCP) measurements without the need of ambiguity resolution techniques and the complexity to accommodate the delayed-state terms. Static trial results are included to illustrate the stochastic characteristics and effectiveness of the TDCP measurements in controlling position error growth. The formulation of the TDCP observation model is also described in a 17-state tightly-coupled GPS/INS iterative, extended Kalman filter (IEKF) approach. Preliminary land vehicle trial results are also presented to illustrate the effectiveness of the TDCP which provides sub-meter positional accuracies when operating for more than 10 min.  相似文献