ALBERT

Description: In this paper we examine the steady, two-dimensional convective motion which occurs in a horizontal circular cylinder whose wall is non-uniformly heated. One observes several qualitatively different physical phenomena depending on the wall temperature distribution and the value of the Rayleigh number. The low-Rayleigh-number behaviour for the single convective cell heated from below is related to the classical Rayleigh stability problem. The critical Rayleigh number for the single circular cell is approximately five times the value for Rayleigh's multi-celluar configuration. The flow which exhibits a nearly parabolic velocity profile near the critical Rayleigh number, gradually changes to a rigidly-rotating-core behaviour as the Rayleigh number increases. The speed of core rotation is a function of the Prandtl number, whereas the boundary-layer thickness is primarily a function of the Rayleigh number. When the heating is from side to side, the solution shows that as the Rayleigh number increases the core motion is progressively arrested leaving a narrow circulating band of fluid adjacent to the wall. An oblique heating produces a hybrid phenomenon, a low-Rayleigh-number behaviour which is characteristic of the sideways heating case and a high-Rayleigh-number interior motion characteristic of the bottom heating case. To determine the core motion in the high-Rayleigh-number limit, Batchelor's work concerning the uniqueness of incompressible, exactly steady, closed streamline flows with small viscosity is extended to include flows with small thermal conductivity.

Description: The results of an examination of one quarry within the gneisses of the Bartica Assemblage are described and the validity of these results throughout the whole of the Bartica Assemblage is discussed. The foliation and banding of the gneisses at Kereti Quarry are mainly the results of tectonism; concomitant metamorphism within the Amphibolite Facies was succeeded by a two-phase metasomatism involving successive additions of Na and K. These results appear valid throughout the Bartica Assemblage and it is further suggested that the main rock type distribution in the Bartica Assemblage is also controlled by tectonism.

Description: Textural differences in the occurrence of microcline define augen gneisses, subhedral porphyroblastic gneisses and euhedral porphyroblastic gneisses within the Bartica Assemblage, British Guiana. The introduction of microcline is metasomatic and the nature of the porphyroblasts appears to be a reflection of tectonic control during their development.

Description: Theories of the origin of microseisms have in the past generally been expressed in terms of the Green functions of the elastic systems considered. An alternative approach based on spectral transfer functions and the local energy-balance equation of the seismic field is proposed. The method enables a rigorous analysis of the statistical aspects of the problem, which could be treated only approximately and under restrictive conditions in terms of the far-field representations used previously. Three suggested origins of microseisms are considered: (1) the action of ocean waves on coasts, originally proposed by Wiechert; (2) atmospheric pressure fluctuations, as suggested by Gherzi, Scholte, and others; and (3) nonlinear interactions between ocean waves as proposed by Longuet-Higgins. In all cases appreciable microseisms are generated only by Fourier components of the random exciting fields that have the same phase velocities as free modes of the elastic system. The effect of pressure fluctuations associated with turbulence in the atmosphere is found to be negligible. The theory for Wiechert's and Longuet-Higgins' mechanisms is in good agreement with recent measurements by Haubrich et al.

Description: The energy flux in a finite-depth gravity-wave spectrum resulting from weak non-linear couplings between the spectral components is evaluated by means of a perturbation method. The fifth-order analysis yields a fourth-order effect comparable in magnitude to the generating and dissipating processes in wind-generated seas. The energy flux favours equidistribution of energy and vanishes in the limiting case of a white, isotropic spectrum. The influence on the equilibrium structure of fully developed wave spectra and on other phenomena in random seas is discussed briefly.

Description: The larvae of the Japanese commercial octopod, Octopus (Octopus) vulgare CUVIER, were successfully reared from the swimming larvae just after hatching to the benthic young octopus in 33 to 40 days on a diet of the zoea larvae of the shrimp, Palaemon serrifer. The rearing experiments were carried out at the Hyogo Prefectural Fisheries Experimantal Station from June to September, 1962. At a start of experiments 200 individuals of the octopus larvae were kept in a glass vessel containing about 8 litre of sea-water. During the early 20 days period the sea-water of each vessel was aerated and renewed every 3rd or 4th day, and after this period the method was changed for the use of running water. The results obtained are summarized as follows: 1) From just after hatching, the larvae of the octopus were fed on the larvae of Paleamon of 2 to 4mm body-length. (See table 1) After transforming into benthic stage, they were given a small piece of ovaries, tests and hepatic glands of the crab, Charybdis japoniea. Three or four days after transforming, they were fed on small shripms and young crabs, Gaetice depressus (DE HAAN) of 5 to 7mm carapace-width. It was observed that the young octopus of 30mm total-length ate 4 or 5 young crabs in a day. 2) The survival rate of the octopus larvae was found as low as 9 percent through the free-swimming stage. However, it would be conceivably possible to raise this survival rate much higher if sufficient food supply is secured during the rearing experiments. 3) The growth of the octopus larvae in 90 days after hatching at water temperature 24.7°C (23.0~26.7°C) can be seen in Table 4 and Fig. 1. It was found that the larvae settled on the bottom 33 to 40 days after hatching, when they attained a size ranging 10~15mm in total-length (3.8~5.7mm in body-length). Once the swimming larvae transformed into the benthic young octopus, they bcame nocternal and fed on foods mainly at night. A considerable mortality occured among the young octopus, which was caused by cannibalism and creeping out of the rearing water. 4) The numbers of suckers found on each arm were 3 at the hatching, 5 (4~6) at 10 days, 9 (6~12) at 20 days, 19 (16~22) at 30 days, 24 (21~27) at 40 days and 22~23 when a majority of octopus larvae grew to the benthic stage.