Star–disc interactions in a galactic centre and oblateness of the inner stellar cluster     

L. &#;ubr  V. Karas  J.-M. Huré 《Monthly notices of the Royal Astronomical Society》2004,354(4):1177-1188

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Macrobenthic invertebrate responses to prolonged drought in South Africa's largest estuarine lake complex     

F. MacKay  D. Cyrus  K.-L. Russell 《Estuarine, Coastal and Shelf Science》2010

St Lucia, the largest estuarine lake complex of its type in Africa, is characterised by natural physico-chemical spatial and temporal fluctuations. This estuary functions as an important nursery area making use of a number of different habitat types and associated environmental conditions. The system has been subject to a number of natural episodic events such as cyclonic flooding and cyclical droughts, the most current has persisted since 2001, resulting in almost permanent mouth closure. Furthermore, high levels of evaporation have reduced lake levels and resulted in compartmentalisation of the system for up to several years at a time. St Lucia is sensitive to evaporation and therefore to vast salinity fluctuations and hypersaline conditions. The upper reaches in North Lake are particularly sensitive to drying out and extended hypersaline events. The macrobenthos has been well studied, but no studies have concentrated on the entire system for such an extent of time. Macrobenthic samples were initially collected in 2004, again in 2005 and biannually from 2006 to 2008. This study was part of a larger multidisciplinary programme aimed at determining the effects of long term drought conditions on the ecology of the St Lucia system, and increasing current understanding of the system response to future catastrophic climatic events. Three areas were sampled (North and South Lake and Estuary) at five sites per area, over five years. Data were analysed by representing communities through time series depictions and discriminating sites and sampling periods to test multidimensional relationships. Linkages between biological distribution and selected environmental forcing variables were investigated. The system was found to be highly variable and supporting a large number of different habitats and co-occurring environmental conditions. This variability makes it difficult to discern spatial or temporal patterns in environmental conditions and macrobenthic ecology. However, some level of resilience to wide ranging environmental changes associated with drought is maintained. This study was able to determine that there exists a core of taxa able to persist even under shallow depth conditions and prolonged hypersalinity. These taxa clearly have a self recruiting strategy and are therefore not reliant on mouth opening to re-establish local populations. This finding alone has important bearing for future studies and management of the system under similar adverse conditions.  相似文献   

Book review     

Vladimír Karas 《Earth, Moon, and Planets》1994,66(3):237-237

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Book reviews     

V. Karas  J. Horáček  John Dyson 《Astrophysics and Space Science》1991,179(2):335-337

The dispersive characteristic of hydromagnetic surface waves along a plasma-plasma interface when the upper fluid moves with a uniform velocity is discussed. The region of propagation of these waves is shifted above or below depending on whether the basic velocity (uniform)U0.  相似文献   

Turbidity and salinity in a tropical northern Australian estuary and their influence on fish distribution     

D.P. Cyrus  S.J.M. Blaber 《Estuarine, Coastal and Shelf Science》1992,35(6)

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The influence of turbidity on juvenile marine fish in the estuaries of Natal, South africa     

D.P. Cyrus  S.J.M. Blaber   《Continental Shelf Research》1987,7(11-12)

Results from field studies in Natal estuaries show that the distribution of juvenile marine fish is influenced by turbidity. Laboratory studies on turbidity preference, with other variables excluded, showed good correlation with the field data for eight of ten species tested. The importance of turbidity and other factors to juvenile fish is discussed in relation to the role which estuaries play as nursery areas for juveniles of numerous marine species.  相似文献   

Comparison of physical and chemical properties of maceral groups separated by density dradient centrifugation     

Jirina Karas  Ronald J. Pugmire  Warner R. Woolfenden  David M. Grant  Skeen Blair 《International Journal of Coal Geology》1985,5(4):315-338

Eight coals have been selected for study of the physical and chemical properties of the maceral group . The density-gradient centrifugation technique was employed to affect maceral group separation. The maximum reflectance method of Ting and Lo was used for estimating the reflectance of very small coal particles. The reflectograms were used to characterize the separated maceral fractions. The density, elemental composition, reflectance, NMR parameters of aromaticity, protonated aromatic carbon content and ƒ_stuggereda^stuggeredH of the maceral groups were compared. Variations in the aromatic structure of the maceral groups are discussed as well as the observation that ƒ_stuggereda and ƒ_stuggereda^stuggeredH change with particle density.  相似文献   

Characterization of coal maceral concentrates by curie-point pyrolysis mass spectrometry     

Henk L.C. Meuzelaar  Alice M. Harper  Ronald J. Pugmire  Jirina Karas 《International Journal of Coal Geology》1984,4(2):143-171

A set of 30 maceral concentrates consisting of 5 exinites (sporinites), 14 vitrinites and 11 inertinites (fusinites and semifusinites) was analyzed by Curie-point pyrolysis mass spectrometry in combination with computerized multivariate statistical analysis techniques. Seventeen samples, representing sink/flotation concentrates of 7 different coals, were obtained through the British National Coal Board, whereas the remaining samples represent cesium-chloride density-gradient centrifugation fractions of two different U.S. coals prepared at the University of Utah.It is found that vitrinites, (semi)fusinites and, to some extent, sporinites show qualitatively similar rank-related changes, such as a decrease in dihydroxybenzene signals and an increase in napthalene signals with increasing rank. In fact, the overall pyrolysis MS patterns of inertinities show a close similarity to those of vitrinites of corresponding carbon content (as obtained from higher rank coals).Notwithstanding these similarities, however, the presence of basic differences in maceral structure is indicated by relatively minor but characteristic peak series in the liptinite (sporinite) as well as inertinite samples. Whereas inertinite spectra show relatively pronounced peak series at the high mass end of the spectrum which can be tentatively identified as representative of polynuclear aromatic compounds, sporinites are characterized by series of branched aliphatic and/or alicyclic polyenic hydrocarbons, possibly representing isoprenoids and related biomarker compounds.  相似文献   

A Reservoir–Geomechanical Model to Study the Likelihood of Tensile and Shear Failure in the Caprock of Weyburn CCS Project with Regard to Interpretation of Microseismic Data     

Cyrus Khazaei  Rick Chalaturnyk 《Geotechnical and Geological Engineering》2017,35(6):2571-2595

According to poroelastic theory and also field observations, an increase in reservoir pore pressures can result in a decrease in horizontal stresses in the seal layers. This reduction is in favor of hydrofracture initiation and reactivation of weak planes and has to be studied in caprock integrity analyses. In this paper, a field scale reservoir–geomechanical (GEM-FLAC3D) model is developed for the Phase IB area of the Weyburn (Canada) CCS project that is located in Williston sedimentary basin. A one-way coupling has been conducted between the two codes for the period of CO₂ injection in Phase IB area from 2000 to 2010. Therefore, the reservoir pore pressures at selected timesteps are unidirectionally fed to the FLAC3D. In order to study the likelihood of tensile and shear failure in the seal layer on top as a result of stress transfer due to poroelastic effects, two margin ratios are defined for tensile and shear failure and their variations are studied above the reservoir upon changes in pore pressures within the reservoir. The results show that overall; the likelihood of shear failure has been about 25% greater than that of tensile failure in Weyburn. However, between 2008 and 2009, the pressures were high enough to trigger both tensile and shear mechanisms above the reservoir. A discussion is also presented on relevance of this study for interpretation of microseismic data with regard to failure margin ratios, magnitudes and distribution of events recorded in each year.  相似文献   

Habitat utilization by small flatfishes in a North Carolina estuary     

Harvey J. Walsh  David S. Peters  Digby P. Cyrus 《Estuaries and Coasts》1999,22(3):803-813

Distribution and abundance of flatfish species (<150 mm standard length) were related to habitat characteristics in the Newport River and Back Sound estuaries in North Carolina. Salinity, turbidity, depth, distance from marsh edge, benthic composition, and grain size were used to describe the different shallow water habitats from April through October 1994. One Scophthalmidae, seven Paralichthyidae, one Achiridae, and one Cynoglossidae species were collected during the study including juvenileParalichthys albigutta (gulf flounder),P. dentatus (summer flounder), andP. lethostigma (southern flounder) along with multiple age classes ofCitharichthys spilopterus (bay whiff),Etropus crossotus (fringed flounder),Symphurus plagiusa (blackcheek tonguefish), andTrinetes maculatus (hogchoker). Incidental catches ofAncylopsetta quadrocellata (ocellated flounder),C. macrops (spotted whiff), andScopthalmus aquosus (windowpane) were also made. Flatfish distributions among habitats varied by species, size within species, and season. Regardless of season, the highest densities of flatfishes were found in the upper estuary. All habitats were used by one or more species and most species occurred at several habitats. Some species were significantly more abundant at specific habitat types. Ontogenetic shifts in habitat utilization were found for several species. High densities of smallP. lethostigma, C. spilopterus, S. plagiusa, andT. maculatus occurred in the upper estuary on muddy substrates. LargeP. dentatus, C. spilopterus, S. plagiusa, andT. maculatus utilized sand flats and channels in the lower estuary.  相似文献