Showing papers by "University of St Andrews published in 1971"

Non-linear resonant instability in boundary layers

Abstract: An investigation is made of resonant triads of Tollmien-Schlichting waves in an unstable boundary layer. The triads considered are those comprising a two-dimensional wave and two oblique waves propagating at equal and opposite angles to the flow direction and such that all three waves have the same phase velocity in the downstream direction. For such a resonant triad remarkably powerful wave interations take place, which may cause a continuous and rapid transfer of energy from the primary shear flow to the disturbance. It appears that the oblique waves can grow particularly rapidly and it is suggested that such preferential growth may be responsible for the rapid development of three-dimensionality in unstable boundary layers. The non-linear energy transfer primarily takes place in the vicinity of the critical layer where the downstream propagation velocity of the waves equals the velocity of the primary flow.The theoretical analysis is initially carried out for a general primary velocity profile; then, in order to demonstrate the essential features of the results, precise interaction equations are derived for a particular profile consisting of a layer of constant shear bounded by a uniform flow. Some exact solutions of the general interaction equations are presented, one of which has the property that the wave amplitudes become indefinitely large at a finite time. The possible relevance of the present theoretical model to the experiments of Klebanoff, Tidstrom & Sargent (1962) is examined.

Warm-Bodied Fish

Abstract: SYNOPSIS. Two groups of fishes, the tuna and the lamnid sharks, have evolved ounter-currentheat-exchange mechanisms for conserving metabolic heat and raising their body temperatures. Warm muscle can produce more power, and considering the other adaptations for fast swimming in these fish, it seems likely that the selective advantages of greater speed made possible by the warm muscle were important in the evolution of this system. Some tunas such as the yellowfin and skip jack are at a fixed temperature difference above the water, but bluefin tuna can thermoregulate. Telemetry experiments show that the bluefin tuna can maintain a constant deep body temperature during marked changes in the temperature of its environment.

Hydraulic Jumps in Turbidity Currents

Abstract: If uniform flow conditions are approached, turbidity currents should be supercritical (Froude number greater than unity) while passing through submarine canyons, and subcritical (Froude number less than unity) in the upper submarine fan channel. The change in flow regime requires that the current pass through a hydraulic jump in the vicinity of the canyon mouth. During the jump, the velocity of the flow would be reduced and its thickness markedly increased. The aspects of such hydraulic jumps are examined. The quantitative analysis of hydraulic jumps in turbidity currents is based upon solutions of the momentum flux equation and the equation resulting from the assumption of a continuity of sediment flux. It is found that for the average submarine canyon-channel system, the flow would more than double in thickness and its velocity would be halved during a hydraulic jump. The entrainment of water through the interface of the flow during the jump is significant in reducing the density of the current. The higher the initial Froude number, the greater the expected density reduction. However, the density reduction due to the jump is probably not sufficient to convert a high-density slide into a low-density turbidity current. There must be an initial density reduction by entrainment while the slide is passing through the canyon at high Froude number. Turbulence generated within the hydraulic jump would stir the flow and help to insure suspension of its sediment.

A metabolic theory of flooding tolerance: the significance of enzyme distribution and behaviour

Abstract: Summary The distribution and activity patterns of several enzymes of glycolytic and respiratory metabolism are considered in nineteen species of higher plants previously classified as tolerant or intolerant of experimental flooding. These results are combined with previous work on glycolysis, the inductive properties of alcohol dehydrogenase, and on tissue malic acid levels, to formulate a metabolic system of flooding tolerance. This system is based mainly on: (1) the control of glycolysis through the inductive and kinetic properties of alcohol dehydrogenase; and (2) a diversion from ethanol to malate accumulation, dependent upon the presence or absence of ‘malic’ enzyme.

Products of idempotents in certain semigroups of transformations

Abstract: In an earlier paper (5) a description was given in set-theoretic terms of the semigroup generated by the idempotents of a full transformation semigroup , one of the results being that if X is finite then every element of that is not bijective is expressible as a product of idempotents. In view of this it was natural to ask whether by analogy every singular square matrix is expressibleas a product of idempotent matrices. This is indeed the case, as was shown by J. A. Erdos (2). Magill (6) has considered products of idempotents in thesemigroup of all continuous self-maps of a topological space X, but a comparable characterization of products of idempotents in this case appears to be extremelydifficult, and no solution is available yet.

The Magnus or Robins effect on rotating spheres

Abstract: Robins showed in 1742 that a transverse aerodynamic force on a rotating sphere could be detected by suspending it as a pendulum. Differences of periodic time in conical pendulum motion with spin and orbit parallel and opposed have been found to give a reasonably accurate measure of the lift coefficient, and the results shown extend knowledge of the effect down to a Reynolds number of 2 × 103 and up to a ratio of 12 between the peripheral and translational velocities.

Distribution of biogenic amines in the slug,Limax maximus

Abstract: The distribution of monoamines inLimax maximus was studied by the histochemical fluorescent method of Falck and Hillarp. The number of 5-HT-containing and catecholamine-containing perikarya in the central nervous system is small compared with the non-fluorescent perikarya. However, all the ganglia except the proto-cerebral ganglia have some amine-containing neurons. There are relatively larger numbers of fluorescent cells in the cerebral, visceral, pedal and right parietal ganglia than in the other ganglia. A single, giant 5-HT-containing neuron was observed in each meta-cerebral ganglion. Monoamine neurons are localised in a number of peripheral tissues (heart, integument, tentacles, penis retractor muscle, sole of foot, kidney, alimentary canal, reproductive organs and tentacular, pharyngeal and cephalic retractor muscles). Neurons containing catecholamine are mostly associated with sensory structures such as the statocysts, the retina of the eye and the integument of the tentacles, whereas 5-HT-containing nerve fibres are mainly observed in muscle tissues.

Development and Deployment of Cilia, Basal Bodies, and other Microtubular Organelles in the Cortex of the Ciliate Nassula

Abstract: The basal bodies contain more internal structures than those described for other organisms. For example, they possess 2 different and separate cartwheel structures. In cilia the 2 central tubules terminate proximally in a different fashion. Three types of cilia have been distinguished. Each type possesses a different array of rootlet fibres. During binary fision one type develops 1 h before all the others while the ciliary shafts, but not the basal bodies, of a second type are being resorbed. These are later reformed when a third variety of cilia develop. Some new basal bodies and cilia are formed at least 30 min before they can be detected using silver staining. Studies of basal body morphogenesis based on this technique are pertinent to the separation of closely adjacent mature basal bodies rather than to their development. The arrangement and spacing of new basal bodies may be partly defined by their rootlet fibres which interconnect basal bodies before they attain their final positions in the cortex. Overlapping microtubules linking basal bodies apparently slide against each other during the final stages of basal body deployment. Heat shocks often inhibit the attachment of new basal bodies to the pellicle but ciliary and rootlet fibres assemble and grow out from the usual sites on these abnormally positioned basal bodies. The pellicle is highly impermeable to water and the fine structure of its innermost layer resembles that of the waterproofing epicuticle of some insects. A cuff of this pellicular material forms around the distal end of each new basal body and then seals it to the undersurface of the pellicle. The outer wall of the pellicular chamber so formed breaks down when the ciliary shaft is assembled. This ‘cytoplasm-lock’ mechanism may ensure that there is no marked change in the permeability of the pellicle when it is penetrated by outgrowing cilia. A new type of ciliary membranelle is described. Some of its modified cilia possess flanges attached to their outer fibres. These cilia may have a sensory role. Membranelle basal bodies are linked by fibres exhibiting a non-repeating polarized banding pattern which may be involved in defining the arrangement and spacing of these basal bodies. A ring of microfilaments encircles the narrow duct joining the contractile vacuole to its outlet pore. This ring may act as a sphincter and be involved in the control of water discharge. During binary fission contractile vacuole pores migrate posteriorly. They are apparently pulled by strands of microtubules and microfilaments attached at one end to a pore and anchored at the the other to more posteriorly situated basal bodies.

II. Sublethal Effects And Changes In Ecosystems - Assessment of the effects of pollutants on physiology and behaviour

Abstract: Many pollutants, even when present in the water in concentrations well below lethal levels, may cause marked changes in the physiology and behaviour of fish. The work reported deals mainly with salmonids. The responses to insecticides are particularly interesting. Of fundamental interest is the suggestion that DDT seems to act by interfering with the normal thermal acclimation mechanism(s), probably within the central nervous system. The results are not without practical significance. Some responses, including those induced by heavy metal ions from mining wastes, may cause long-term ecological changes of consequence.

The Christological Use of the Old Testament in the New Testament

Abstract: The use of the Old Testament by the New Testament – including its christological use – has engaged students of the Bible at least since the time of Jerome.1 In view of the immense erudition expended on it, by some of the best minds in their time, it seems remotely unlikely that anything new remains to be said. A fresh impetus has, however, been given to the subject – which has always been a highly specialized one – by the Dead Sea Scrolls, through the discovery of messianic Testimonies in the Cave 4 material and, more importantly, by the recognition that, hermeneutically, the New Testament belongs to the same tradition.

Formation of serotonin by isolated serotonin-containing neurons and by isolated non-amine-containing neurons.

Abstract: Isolated giant serotonin-containing neurons of the cerebral ganglia of Helix pomatia were shown to produce serotonin when incubated with 5-hydroxytryptophan (5-HTP) whereas cells of the buccal ganglia, which are non-amine-containing cells did not The rate of production was comparable to that for Ach in the isolated neurons of Aplysia The significance of these results is discussed

Microtubules and a Contractile Ring of Microfilaments Associated with a Cleavage Furrow

Abstract: A ring composed largely of microfilaments is situated underneath the pellicle and at the base of the cleavage furrow in the ciliate Nassula during binary fission. The microfilaments have diameters ranging from 4 to 10 nm. There are substantial indications that the ring actively constricts in a sphincter-like fashion and is the main contractile agent causing furrowing. As cleavage proceeds the ring thickens and the dense layer of the pellicle becomes progressively more deeply folded. The longitudinal axes of the folds are at right angles to the longitudinal axes of the microfilaments and the plane of the ring. Folds form only where the pellicle overlies the ring. Two distinct phases of cleavage have been distinguished. The furrow constricts the organism at a progressively more rapid rate until the cleavage constriction has a diameter of about 5 µm and the microfilaments plug the constriction. After this furrowing proceeds much more slowly. A girdle of several thousand microtubules embedded in a densely staining material forms between the ring and the pellicular folds during the final stages of cleavage. Constriction and severance of the narrow cleavage constriction joining daughter organisms during the final phase of cleavage involve mechanisms different from those acting during the earlier phase of furrow development.

Synaptic connections made by two serotonin-containing neurons in the snail (Helix pomatia) brain

Abstract: On decrit la disposition precise des contacts synaptiques realisee par deux gigantesques neurones contenant de la serotonine (GSC) avec d'autre neurones dans la cervelle de l'escargotHelix pomatia. Quelques neurones sont innerves deux fois par chaque GSC.

Vertical migration of Chaoborus flavicans in a Scottish loch

Abstract: SUMMARY The pattern of diel vertical migration of Chaoborus flavicans larvae in a shallow Scottish loch varies according to the instar and, in third and fourth instars, according to the season The planktonic phase of the migration is not exclusively concerned with predation, the larvae feeding at least equally actively in the benthos Although there is no conclusive evidence as to the role of vertical migration in Chaoborus flavicans, it has some of the characteristics of an epideictic display Upward and downward locomotion can be induced experimentally in a plankton wheel by manipulating light intensity alone However, the responses are complex and there is a great deal of individual variation, suggesting that additional factors are involved

Spectral intensity in some Scottish freshwater lochs

Abstract: Summary In the course of investigations on the ecology of submerged aquatic macrophytes a narrow-bandwidth spectroradiometer has been used to measure underwater spectral intensity (390–750 nm) in a series of lochs approaching the extremes in optical and chemical properties of Scottish fresh waters. Cosine response and immersion-effect properties of the collector were determined in the laboratory with a colUmated hght source. Diffuse attenuation coefficients, Ee, ranged from 0·55 in Loch Croispol, a calcareous loch, to 2·9 in Loch Leven, a lowland eutrophic loch. Underwater spectral intensity (1 m) relative to subsurface values show a proportional increase in short-wave radiation in the blue-green water of Loch Croispol, while the converse is true of the peaty brown water of Loch Uanagan. Attenuation coefficients were derived over 25 nm wavebands in Lochs Croispol, Leven and Uanagan. The water in the latter two lochs is optically similar although Leven is rich in phytopiankton and has an extinction peak at 675 nm. Uanagan represents the brown-water type of loch most common in Scotland. Loch Croispol has attenuation coefficients for shorter wave-lengths at least ten times lower than the other two lochs and only approaches their values at 750 nm. Croispol resembles Crater Lake, Oregon. The colour range at the maximum colonizable depths by rooted macrophytes of brown (Uanagan 4 m) to blue-green (Croispol 6 m) water is equivalent to 196·0 and 230·6 kJ/Einstein (48·2 and 55·6 kcal/Einstein). Red/far-red ratios even in plankton-rich water (Leven) were at least three times the value for sunlight (1·3) and within the total photic zone reached three-figure proportions. Possible implications for light-sensitive seeds of aquatic species and for morphogenesis and zonation are discussed.

Review of field studies on fish orientation

Abstract: Documented long-distance journeys of fishes are no longer a rarity. Some of the Pacific salmon travel from spawning streams to the open Pacific a thousand or more kilometers from their rivers,52 and coastal recaptures of salmon tagged in the ocean indicate routine return migrations at average speeds of 23-60 km/ day.37 Migrations of Atlantic salmon from both the British Isles and the North American coast to the west coast of Greenland are evident from tag returns in the explosive Greenland f i ~ h e r y . ~ , ~ ~ Although the controversy surrounding eel migrations in the Atlantic remains frequent transatlantic journeys of bluefin tuna are being do~umented,'~ and several transpacific crossings appear to be part of the life cycle of the Pacific albacore t ~ n a . 8 ~ Some of the more spectacular examples of long-distance journeys of fish are summarized in TABLE 1. In addition to the spectacular journeys of marine and diadromous fishes, there are also examples of homing on a smaller scale,23 and new evidence is accumulating rapidly. For species most familiar to the author, homing has been verified in the white sockeye ~ a l r n o n , ~ ~ ~ ~ ~ pink ~ a l m o n , ~ ~ ~ ~ ~ Atlantic salmon,13~8~ chum salmon,g2 lake trout,go and coho salmon in Lake Michigan.l1I A process of orientation is implied in migrations that cannot be explained in terms of passive transport by currents. NeaveS4 and Royce and coworkerse1 have concluded that the current velocities of 1-4 km/day (up to 10 km/day along the Aleutians) in the Alaska Gyre of the North Pacific\" cannot possibly account for the observed migrations of the sockeye and pink salmon. Passive transport can hardly be invoked for upstream migrations in rivers, nor can it be invoked for the rapid return of fish displaced in a variety of directions.

Stress detection at the autotomy plane in the decapod crustacea

Abstract: Situated in the basi-ischiopodite of the brachyuran Carcinus maenas are two receptors which resemble the chordotonal receptors of the limb articulations but are obviously not part of the series associated with the joints. The receptors have large numbers of bipolar neurons with their dendrites embedded in distinct connective tissue strands which insert onto discrete areas of thin or soft cuticle. The receptor strands do not span a limb joint nor do they attach to a muscle or its tendon. The receptors are referred to as cuticular stress detectors (CSD). CSD.1 lies proximal to the preformed breakage plane and the area of cuticle onto which the strand inserts, lies close to the attachment of the anterior levator muscle tendon (autotomiser muscle). CSD.2 which lies distal to the breakage plane is located in the ventral ischiopodite.

Determination of Amino Acids In Single Identd7iable Nerve Cells of Helix Pomatia

Abstract: Microchromatography of dansylated compounds was used to study the distribution of free amino acids, GABA, serotonin and 5-hydroxyindole in the metacerebral serotonergic cell and one of the giant cells in the buccal ganglia of Helix pomaiia. The distribution of some of the substances in each of the cell types varied depending upon the isolation procedure. Metacerebral cells dissected in the presence of nialamide contained large amounts of serotonin. The same neurons isolated in the absence of nialamide, but dissected with methylene blue contained no serotonin. The distribution of ornithine, glycine, alanine, arginine, e-lysine, α-amino-histidine and cystine in each cell type varied depending upon the method of isolation.Generally the distribution of dansylated substances is similar; GABA is present in each cell type but in low concentrations. However, there are some exceptions. The serotonergic cell contains less ornithine and more glycine than do the buccal cells. In addition the metacerebral cells have h...

Spatial Discrimination in the Cytoplasm during Microtubule Morphogenesis

Abstract: Patterns of microtubule formation and breakdown in the ciliate Nassula provide some indications of the ways in which the deployment of substances influencing microtubule assembly is related to control of tubule growth.

Observations on Some Valley Forms and Deposits in the Sani Pass Area, Lesotho

Abstract: Deposits located in hollows, reminiscent of nivation cirques and restricted to altitudes over 2 900 m, are described form an area south of Sani Pass. The deposits consist of layers of gravel with and without boulders, alternating with organic clays. It is postulated that these deposits provide evidence of former climatic fluctuations.