ALBERT

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: 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 effect of medium dissolved-oxygen tension on the molar growth yield, respiration and cytochrome content of Beneckea natriegens in chemostat culture (D 0·37 hr-1) was examined. The molar growth yield (Y), the specific rate of oxygen (qo2) and glucose consumption, and the specific rate of carbon dioxide evolution were independent of the dissolved-oxygen tension above a critical value (〈 2 mmHg). However, the potential respiration rate increased with reduction in the dissolved-oxygen tension at values of the dissolved-oxygen tension well above the critical value. Changes in the cytochrome content occurred at dissolved-oxygen tensions well above the critical value. An increase in cytochrome c relative to cytochrome b was observed as the dissolved-oxygen tension was decreased. Reduction of the dissolved-oxygen tension to less than 1 mmHg caused a switch to fermentative metabolism shown by the apparent rise in Y o2 and decrease in the molar growth yield from glucose. At this point the potential respiration rate (q o2) increased to its highest value, while the cytochrome pattern reverted to that observed at dissolved-oxygen tensions above 96 mmHg. There appeared to be no correlation between cytochrome content, potential q o2, in situ q o2, and cyanide sensitivity of the organism at various dissolved-oxygen tensions.

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 ommastrephid squids are large active animals occurring in most of the world's oceans. Luminous organs or bioluminescence have been observed only in members of the subfamily Sthenoteuthinae, containing the genera Ornithoteuthis, Symplectoteuthis (= Eucleoteuthis), Hyaloteuthis, Ommastrephes and Dosidicus. The light organs of Ommastrephes pteropus are small sub-spherical bodies randomly distributed over the ventral surface of the mantle, head, arms and tentacles (Roper, 1963) and are aggregated dorsally to form a large luminous patch (Clarke, 1965). Relatively little is known about the organs, capabilities and biochemistry of luminescence in cephalopods (Harvey, 1952; Herring, in Press), and the size of the light organ and availability of O. pteropus provide an unusual opportunity for such studies. Although among the molluscs the luminescent systems of the gastropod Latia and the bivalve Pholas have been partially characterized (Shimomura & Johnson, 1968; Henry, Isambert & Michelson, 1970, 1973) the only cephalopod system which has been investigated to date is that of the enoploteuthid Watasenia scintillans (Goto et al., 1974; Inoue et al., 1975). This investigation examines the anatomy and biochemistry of the dorsal light organ of O. pteropus, which differs markedly in these respects from the brachial organs of Watasenia.

Description: Squids (teuthoids) fall into two distinct groups according to their density in sea water. Squids of one group are considerably denser than sea water and must swim to stop sinking; squids in the other group are nearly neutrally buoyant. Analyses show that in almost all the neutrally buoyant squids large amounts of ammonium are present. This ammonium is not uniformly distributed throughout the body but is mostly confined to special tissues where its concentration can approach half molar. The locations of such tissues differ according to the species and developmental stage of the squid. It is clear that the ammonium-rich solution are almost isosmotic with sea water but of lower density and they are present in sufficient volume to provide the main buoyancy mechanism of these squids. A variety of evidence is given which suggests that squids in no less than 12 of the 26 families achieve near-neutral buoyancy in this way and that 14 families contain squids appreciably denser than sea water [at least one family contains both types of squid]. Some of the ammonium-rich squids are extremely abundant in the oceans.

Description: The ratio of compressional wavevelocityV p to shear wavevelocityV s , and Poisson’s ratio in marine sediments and rocks are important in modeling the sea floor for underwater acoustics,geophysics, and foundation engineering. V p and V s versus depth information was linked at common depths in terrigenous sediments (to 1000 m) and in sands (to 20 m) to yield data on V p vs V s , and V p /V s and Poisson’s ratios versus depth. Soft, terrigenous sediments usually grade with depth into mudstones and shales; V p /V s ratios vary from about 13 or more at the sea floor to about 2.6 at 1000 m. Poisson’s ratios vary from above 0.49 at the sea floor to about 0.41 at 1000 m. In sands, V p , V s , and V p /V s have very high gradients in the first few meters; below about 5 m, V p /V s ratios decrease from about 9 to about 6 at 20 m; Poisson’s ratios vary from above 0.49 at the surface to above 0.48 at 20 m. The mean value of V p /V s in 30 laboratory samples of chalk and limestone is 1.90 (standard error: 0.03); mean Poisson’s ratio is 0.31. Literature data on basalts from the sea floor are reviewed. Equations relating V p to V s are given for terrigenous sediments, sands, and basalts.

Description: Tables for the speed of sound in sea water are presented. These tables have been prepared from an empirical formula which was derived to fit measured sound‐speed data obtained over the temperature range −3°C to 30°C, the pressure range 1.033 kg/cm2 to 1000 kg/cm2, and the salinity range 33‰ to 37‰. The discrepancy of −3.0 m/sec found by Del Grosso at 1 atm., as compared to the tables of Kuwahara, is substantiated. In addition, the pressure coefficient of sound speed observed in the present work differs from that predicted by Kuwahara.