The Fauna of Certain Estuaries in West England and South Wales, with Special Reference to theTanaidacea, IsopodaandAmphipoda

1937 ◽  
Vol 21 (2) ◽  
pp. 647-662 ◽  
Author(s):  
G. I. Crawford
Keyword(s):  
Special Reference ◽  
Shallow Water ◽  
Brackish Water ◽  
South Wales ◽  
Full Day

Duringthe summer of 1935 Captain Nicholson of Saltash kindly put his motor-boat at my disposal and took me for seven full-day collecting trips on the estuaries of the Tamar and its confluents, the Tavy and Lynher. I also made some collections from land in the estuaries of the Plym and Exe (S. Devon), Taw (N. Devon), Camel (N. Cornwall), and Towy (S. Wales).All collecting was done intertidally or in shallow water and was practically confined to the brackish-water reaches. No gear was used except a hand-net of stramin, and a zinc sieve of 1-mm. mesh. More attention was paid to the Crustacean orders Tanaidacea, Isopoda, and Amphipoda than to the rest of the fauna, observations on which were only occasionally made.

Chemistry of the Bogan River, New South Wales, with Special Reference to the Sources of Dissolved Material

1978 ◽  
Vol 29 (4) ◽  
pp. 399 ◽  
Author(s):  
GL Muir ◽  
WD Johnson
Keyword(s):  
Special Reference ◽  
New South ◽  
New South Wales ◽  
Atmospheric Precipitation ◽  
Chemical Variation ◽  
Residual Method ◽  
South Wales

The chemistry of the Bogan River was studied, and the chemical variation along the river and the origin of the ions are discussed. Ionic dominances were: Na+ ≈ Ca2+ ≈ Mg2+; HCO3- > Cl- > SO42-. The contribution of salt from the sea, from dust and from soils has been assessed using a residual method. Atmospheric precipitation appears to be the main source of salts.

Methods of analysing competition with special reference to herbage plants: I. Establishment

1973 ◽  
Vol 81 (1) ◽  
pp. 77-89 ◽  
Author(s):  
J. Hill ◽  
Y. Shimamoto
Keyword(s):  
Special Reference ◽  
Lolium Perenne ◽  
Perennial Ryegrass ◽  
Natural Populations ◽  
Dry Weight ◽  
The Other ◽  
Replacement Series ◽  
Genotype Combination ◽  
South Wales ◽  
Gains And Losses

SummaryA diallel arrangement, which incorporated the essential features of the de Wit density replacement series, was employed to study the effects of competition amongst five genotypes of perennial ryegrass (Lolium perenne). Of the five genotypes concerned two were derived from S·24, two were collected from natural populations in South Wales, while the remaining genotype originated from S· 23. These five genotypes were grown as monocultures and in all ten binary combinations. Within each combination there were three mixture proportions, namely 75:25, 50:50 and 25:75. All mixtures and monocultures were represented by two boxes, one of which was cut at 3-week intervals (frequent cutting) the other being cut at 6-week intervals (infrequent cutting). At each cut all plants within the appropriate mixtures and monocultures were harvested individually and their dry weight recorded.The results obtained over the first 18 weeks of the experiment (i. e. the first three complete growing periods) establish that competition is occurring in nine of the ten binary combinations. Within these nine combinations competition may be classified into one of three groups: first, it may be compensatory, in which the gains and losses incurred by the two components counterbalance; secondly, it may be positive complete complementation, where the advantage gained by the stronger component is such that the mixture performance matches that of the better monoculture, and thirdly, it may be positive over-complementation, where the yield of the better monoculture is surpassed by the mixture. Further tests disclose that a long-leaved S· 24 genotype is the strongest competitor, while a short-leaved, prostrate, indigenous genotype proves to be by far the weakest competitor.Estimates of the equilibrium proportions for each genotype combination suggest that most combinations are expected to become monocultures of the strongest component, with only the combination between the long-leaved indigenous and longleaved S· 23 genotypes remaining a mixture at equilibrium. None of these equilibria coincides with the proportions required to achieve maximum productivity from a particular combination. The results are considered in relation to the known characteristics of these five perennial ryegrass genotypes, while the wider agronomic implications are also discussed.

Constitutive surfaces in fluid mechanics

1980 ◽  
Vol 88 (3) ◽  
pp. 517-546 ◽  
Author(s):  
M. J. Sewell ◽  
D. Porter
Keyword(s):  
Flow Stress ◽  
Shock Waves ◽  
Fluid Mechanics ◽  
Total Energy ◽  
Special Reference ◽  
Shallow Water ◽  
Gas Dynamics ◽  
Inviscid Fluid ◽  
Hydraulic Jumps ◽  
Shallow Water Theory

AbstractThe new concept of a constitutive surface is introduced into inviscid fluid mechanics, with special reference to compressible gas dynamics and to shallow water theory. The detailed shape of such surfaces is calculated, including the manner of their transition across singularities where the Mach or Froude number passes through unity. The calculation draws upon recent work describing the transition of a Legendre transformation through its singularity. For example, mass flow Q, total energy h and flow stress P are always related by part of a ‘swallowtail’ surface, regardless of the particular motion.The addition of dynamical conditions defines particle history tracks which always lie on constitutive surfaces even for unsteady flow, except that they may jump from one part to another of such a surface when shock waves or hydraulic jumps are passed through.Illustrations given include the steady flow of a general gas through a standing normal shock, general shallow water theory, and flow along a sloping-sided channel. Connections with existing literature are described.

scholarly journals Airborne Electromagnetic Sea Ice Thickness Sounding in Shallow, Brackish Water Environments of the Caspian and Baltic Seas

2006 ◽  
Author(s):  
Christian Haas
Keyword(s):  
Shallow Water ◽  
Water Depth ◽  
Brackish Water ◽  
Low Frequency ◽  
Ice Thickness ◽  
Sea Ice Thickness ◽  
Sea Floor ◽  
Airborne Electromagnetic ◽  
The Baltic ◽  
Engineering Projects

Ice engineering projects often rely on the knowledge of ice thickness in shallow, brackish water like in the Baltic and Caspian Seas. By means of field data and model results, the paper shows that helicopter-borne electromagnetic induction measurements using frequencies of 3.68 and 112 kHz can yield accurate thickness estimates with salinities as low as 3 ppt. The higher frequency yields the strongest EM signals. In addition, in shallow water the higher frequency is less sensitive to the sea floor signal, and can thus be used in water depths as shallow as 4 to 6 m, depending on flying altitude. Because the low frequency signal is very sensitive on shallow water depth, a combination of both signals will allow the retrieval of both ice thickness and water depth.

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