Is the Kolmogoroff model applicable to large-scale turbulence?

We discuss the difficulties encountered when the Heisenberg-Kolmogoroff model for turbulence is applied to the large-scale turbulence in: (A) molecular clouds (specifically the velocity vs size relationship) and (B) stars (specifically, the estimate of convective fluxes).A new model for large-scale turbulence is, therefore, needed.     

A comparative study of the zooplankton in two adjacent embayments,Port Phillip and Westernport Bays,Australia

We report on a year's study of spatial and seasonal patterns of zooplankton abundance in Port Phillip and Westernport Bays, July 1982 to August 1983. These two bays, closely adjacent on the southern coast of Victoria, Australia, differ in several respects: Port Phillip is a nearly landlocked bay with a broad basin, while Westernport is an open tidal embayment with extensive mud and seagrass banks. Both bays have a resident zooplankton fauna distinct from that of Bass Strait. Although these resident communities have many species in common, patterns of abundance and dominance are quite different. We found that the holoplankton of Port Phillip was about half copepods, mostly Paracalanus indicus, with 23% Caldocera and 21% larvaceans. Westernport Bay zooplankton was dominated by Acartia tranteri, with no resident cladoceran fauna. Bass Strait species were more often found in Westernport than in Port Phillip Bay, but the resident community of Port Phillip Bay was more similar to that of Bass Strait than to that of Westernport.Although this study was undertaken in an exceptionally dry year, the available historical data show that the overall patterns found in 1982–1983 are typical for these bays. The differences in community composition probably relate to differences in depth profile, predator abundance, and suspended matter between the bays.     

Gravitational collapse of a dust ball — The external observer's point of view

The problem of collapse of a dust ball has been studied in detail from the point of view of an external observer (O). It is seen that although there is no material pressure from the point of view of the comoving observer, there is a non-vanishing material pressure in the ball from the point of view of O. In the early stages of collapse (w.r.t. O), this pressure is positive everywhere inside the ball, while during the later stages, if one goes outwards from the centre towards the surface of the ball, this pressure is negative up to a certain value of the radial coordinate, and then changes its sign thereafter. On the basis of this pressure, one can understand the physics of the whole scenario of collapse w.r.t. O; in particular, the important feature is that in the ultimate stages an event horizon is formed asymptotically and there is no collapse to a point (as takes place from the point of view of the comoving observer).     

Energy dissipation in oscillatory flow over rippled beds

Measurements of energy dissipation have been made with an oscillating tray apparatus similar to that of Bagnold (1946). Two different bed profiles were examined: one was sinusoidal and the other consisted of fins projecting perpendicularly fromthe plate in a regular two-dimensional pattern. The tests with the sinusoidal profile showed that significant variation in energy dissipation coefficient with Reynolds number occurs near the point at which vortex formation first starts to take place. It is suggested that Bagnold did not observe this effect because of the particular profile used in his tests. The tests with the finned beds showed that even when vortex formation is fully developed there is still some variation in energy dissipation coefficient with Reynolds number, at constant a/k_s, at high Reynolds numbers.     

Improved theoretical line ratios for Ciii in the Sun

The recent twelve-state R-matrix calculations of electron excitation rates in Ciii by Berrington are used to derive level populations applicable to the solar transition region. Line ratios R = I(2p ^{2 3} P ^e - 2s2p ³ P ^°)/I(2s2p ¹ P ^° - 2s ^{2 1} S ^e ) and R ₂=I(2p ^{2 1} S ^e - 2s2p ¹ P ^°)/I(2p ^{2 3} P ^e - 2s2p ³ P ^°) deduced from these data in conjunction with the relevent transition probabilities are found to be in much better agreement with the observed quiet Sun values than those determined from the level population calculations of Keenan et al.     

Volcanic style in the Strand Fiord Formation (Upper Cretaceous), Axel Heiberg Island, Canadian Arctic Archipelago

The Strand Fiord Formation is a volcanic unit of early Late Cretaceous age which outcrops on west-central and northwestern Axel Heiberg Island in the Canadian Arctic Archipelago. The formation is part of the thick Sverdrup Basin succession and immediately precedes the final basin foundering event. The Strand Fiord volcanics are encased in marine strata and thin southward from a maximum thickness of 789+ m on northwestern Axel Heiberg to a zero edge near the southern shore of the island. Tholeiitic icelandite flows are the main constituent of the formation with volcaniclastic conglomerates, sandstones, mudrocks and rare coal seams also being present. The lava flows range in thickness from 6 to 60 m and subaerial flows predominate. Both pahoehoe and aa lava types are common and the volcanic pile accumulated mostly by the quiet effusion of lavas. The volcaniclastic lithologies become more common near the southern and eastern edges of the formation and represent lahars and beach to shallow marine reworked deposits. The Strand Fiord volcanics are interpreted to represent the cratonward extension of the Alpha Ridge, a volcanic ridge that was active during the formation of the Amerasian Basin.     

The magnetic field of an infinite plane current sheet uniform except for two circular insertions of different uniform conductivities

Summary. The electrical system of currents excited by a uniform electric field of arbitrary direction in an infinite plane sheet of uniform conductivity except for two non-overlapping circular areas is obtained analytically. Using the method introduced by Ashour, the magnetic field of the system is also obtained. The components of this additional field are expressed as line integrals which are suitable for computation. The results reduce, in the special case of one insertion, to those obtained earlier by Ashour & Chapman.
As an illustration, numerical results are obtained for the special case of two equal insertions of zero conductivity.
The analysis and results obtained are useful in estimating the modification of the currents flowing in an ocean and their magnetic field by two islands.