Showing papers by "Lancaster University published in 1969"

Geomagnetic Variations and the Electrical Conductivity of the Upper Mantle

Abstract: Summary The electrical conductivity of the upper mantle can be determined by comparing the measured response of the Earth to magnetic variations of all frequencies with the theoretical response of particular conductivity distributions. On the basis of a limited amount of data the response has been estimated at frequencies in the range 0.003 to 0.25 c day−1. In this range of the geomagnetic spectrum, line spectra at frequencies of 1 and 2 c yr−1 and 1, 2, and 3 cycles per 27 days can be used. Investigations of the continuum spectrum show that it also occurs on a worldwide scale, and must correspond to a real geophysical process. Meaningful estimates of the response can therefore be made over the whole of the frequency range considered. The entire magnetic variation spectrum in the range 2 c yr−1 to 0.25 c day−1 appears to be generated by fluctuations in the strength of the ring current, and a P10 spherical harmonic adequately describes the variation of the magnetic field over the surface of the Earth.

Studies on the permeability to water of selected marine, freshwater and euryhaline teleosts.

Abstract: Measurements were made of the flux of tritiated water across various marine, freshwater and euryhaline teleosts. The effects of temperature, body size, species differences, salinity, stress and anaesthetization were studied. 2. The Q 10 of the flux of water across teleosts is approximately 1·90 and the flux is related to the 0·88 power of the body weight. 3. All of the freshwater species studied were more permeable to water than the marine species. Euryhaline teleosts appear to have about the same permeability as species to which they are most closely related. 4. While the flounder and the yellow eel are more permeable to water in fresh water than in sea water, the silver eel and the brown trout do not change their permeability and the 3-spined stickleback is less permeable to water in fresh water than in sea water. 5. While stress markedly increases the permeability to water of large brown trout, it has no effect on small brown trout and seems to decrease the water permeability of the plaice. 6. Anaesthetization has no effect on the water permeability of the goldfish but markedly increases the permeability to water of the silver eel. 7. The relationship between the flux of water and either the drinking rate in sea water or the urine flow in fresh water is discussed.

Auroral absorption of HF radio waves in the ionosphere: A review of results from the first decade of riometry

Abstract: In the decade since the International Geophysical Year, information about the ionospheric absorption of radio waves during periods of auroral and magnetic disturbance has been greatly increased by the use of the riometer technique. Such studies are important for their geophysical implications as well as in direct applications to radio propagation. The purpose of this paper is to summarize the state of knowledge of auroral radio absorption at about the end of 1968, and at the same time to give the major references through which the reader may be enabled to study any particular questions in greater depth.

Water balance in the eggs of the Atlantic salmon Salmo salar.

Abstract: 1. The rate of exchange of tritiated water across the vitelline membrane of the eggs of the Atlantic salmon has been examined under various conditions. 2. In eggs shed into isosmotic saline the rate constant of exchange is about 0.3-0.4/hr. 3. When eggs are shed into distilled water or isosmotic glucose rate constants as high as 0.8-1.0/hr. occur for short periods but the rate of exchange declines rapidly. 4. Low concentrations of sodium and more especially of calcium ions delay both the phase of rapid exchange and the phase of declining permeability. 5. The rate of formation of perivitelline fluid is greatest during the period of high permeability.

Aspects of the Physiology of Terrestrial Life in Amphibious Fishes: I. The Mudskipper, Periophthalmus Sobrinus

Abstract: 1. A study has been carried out of major aspects of the physiological adaptations for terrestrial life possessed by the amphibious mudskipper fish, Periophthalmus sobrinus, on the island of Nosy Be, Madagascar. 2. These fish can survive for approximately 1½ days out of water, if not exposed to severe dehydration or thermal stresses. Evaporative water-loss rates while out of water are relatively low. Upper lethal temperatures are only a few degrees above normal midday environmental temperatures. 3. These fish lack the symptoms of the ‘diving syndrome’. Metabolic rates (oxygen consumption), heart rates, and blood lactic acid concentrations are not affected by shifts of fish between water and air. 4. Rates of ammonia and urea production increase in fish out of water. The ratio of urea/ammonia also increases. 5. The generality of the results, also their physiological significance, are discussed.

The assessment of a method for the determination of absolute pollen frequencies

Abstract: Summary One method for the estimation of absolute pollen frequencies involves the addition of a known amount of an exotic pollen to a known quantity of sediment. From the observed ratio of indigenous to exotic pollen, the absolute quantity of indigenous per unit volume of sediment can be calculated. The pollen of Nyssa sylvatica was considered to be a suitable exotic for addition to northwestern European Post-glacial sediments to be measured by this method. A series of experiments was made to estimate the settling rate of fresh N. sylvatica pollen in pure glycerine, to determine the period of agitation required to produce an even suspension of N. sylvatica pollen in pure glycerine, to observe the effects of KOH treatment and acetolysis on a mixture of fresh N. sylvatica and Ailanthus eligantissima pollen and to estimate the experimental error of the method by using it to determine the quantity of pollen in a series of homogenized samples of gyttja. The value of the method for the estimation of absolute pollen frequencies is assessed.

A critical examination of the use of detached epidermis in studies of stomatal physiology

Abstract: Summary Although several workers have published accounts of stomatal studies with detached epidermis, there has not been general agreement as to whether the stomata continue to respond to environmental factors as they do in the intact plant. This paper reports a critical examination of the value of the technique, experiments having been carried out on material from Vida faba and two species of Commelina. The nature of the incubating medium was found to exert a considerable influence on the behaviour of the stomata. In Commelina, the presence of monovalent cations (K+, Na+) stimulated opening, but divalent cations (Ca2+, Mg2+) had an antagonistic effect suppressing opening or even preventing it altogether. In Vicia faba cations exerted less noticeable effects. pH changes affected aperture, but in Commelina the changes were of much smaller magnitude than those induced by the different cations. Factorial experiments were performed to determine the effect of detaching epidermis on the stomatal responses to environmental factors. In Vicia faba the light effect was very apparent on attached epidermis, but on detached epidermis the effect was largely obscured by stomatal opening that occurred in darkness; effects of CO2 concentration were detectable on epidermal strips, particularly in darkness, but were of smaller magnitude than those on attached epidermis. On the other hand, in Commelina, effects of both light and CO2 were of considerable magnitude when strips were immersed in media containing the cations that stimulated opening. The theory that the opening stimulated by monovalent cations is the outcome of their being actively taken up into the guard cells is discussed, and it is concluded that while this might apply to epidermal strips in media, there is inadequate evidence that such a mechanism is responsible for opening in the intact plant; there was no stimulation of opening on attached epidermis when pieces of leaf were immersed in media containing monovalent cations. Attempts are made to explain the difference in behaviour between Vicia faba and Commelina on the basis of the course of ion uptake into the cells of the epidermis; evidence of a possible difference in uptake was obtained from studies of the penetration by neutral red. It is concluded that epidermal strips from both species of Commelina are suitable for studies of stomatal responses to Hght and CO2 so long as they are incubated in a suitable medium. Epidermal strips from V. faba are unsuitable for studies of the light responses, and less satisfactory than Commelina for the responses to CO2.

Continuous and Köthe–Toeplitz duals of certain sequence spaces

Abstract: If (X, g) is a paranormed space, with paranorm g (see (2)), then we denote by X* the continuous dual of X, i.e. the set of all continuous linear functionals on X. If E is a set of complex sequences x = (xk) then E† will denote the generalized Kothe–Toeplitz dual of E

Sodium, chloride and water balance of the intertidal teleost, Pholis gunnellus.

Abstract: 1. Measurements were made of the regulation of the body ionic content, the fluxes of Na, Cl and water and the electrical potential across the intertidal teleost, Pholis gunnellus in 100% (410 mM-Na/1.) and 20% sea water. 2. The rates of the ion flux depended on the method of measurement. The flux of Cl is much below the flux of Na in 100% sea water. In 20% sea water the fluxes of Na and Cl are the same. 3. In 100% sea water only the Na flux has an exchange-diffusion component. There is no exchange-diffusion component of the flux of either ion in 20% sea water. 4. The electrical potential across Pholis changes from 18 mV. (inside positive) in 100% sea water to 6 mV (inside negative) in 100% sea water. Comparison with the Nernst potentials indicate that Cl is actively transported in both salinities while Na may possibly be actively transported in 100% sea water. 5. In 20% sea water the permeability to Na decreases to 51% of the permeability in 100% sea water, while the Cl permeability decreases to 82% and the water permeability remains at the sea-water level. 6. In both salinities the rate of diffusion of Na ions is greater than the rate of diffusion of Cl ions. 7. The osmotic permeability to water is approximately equal to the diffusional permeability to water in both salinities. 8. It is concluded that the passive movements of Na, Cl and water must be independent of each other and not via uncharged, water-filled pores.

The kidney and magnesium homeostasis

Abstract: Considerations of mineral homeostasis are usually concerned with the processes that regulate the concentration of metal in the blood. Early investigations of magnesium metabolism indicated wide variations in the magnesium level of plasma, but the development of accurate analytical methods has shown the concentration range to be more restricted than was originally thought. Measurements made by the technique of atomic absorption flamephotometry on the plasma from 176 subjects indicate a mean magnesium concentration of 2.00 mg/ 100 ml with a standard deviation of 0.145, giving a normal range of 1.72-2.28 mg/iOO ml. Individual variations in concentration occur within this range, and repeated determinations on the same subjects over a period of several weeks show that the concentration in each person fluctuates over a range of approximately 0.25 mg/ 100 ml. Although regulation of the magnesium concentration in plasma is important and large deviations from normal may result in clinical disorders, this forms only part of the problem of homeostasis. The magnesium concentration in soft tissues is about ten times higher than in the plasma but can fall by only a small amount before the metabolism of the tissue is disturbed. With the adult subject in metabolic equilibrium, however, the maintenance of normal magnesium levels in the extracellular and intracellular fluids can both be regarded as subsidiary to the equation of magnesium intake and excretion by the body.

Patterns of Buyer Behavior: Time for a New Approach?:

Abstract: Toothpaste brand purchases following a switch from a brand previously bought regularly are analyzed from consumer panel data. It is suggested that the results do not fit existing learning theory mo...

Modification of excitation-contraction coupling in locust skeletal muscle induced by caffeine.

Abstract: Potassium contractures were recorded isometrically in locust extensor tibialis muscles. The graphs relating contracture tension to external potassium, and contractute tension to depolarization were of sigmoid shape. In normal circumstances, peak contracture tension was obtained with 100 mM/1 potassium saline at a depolarization level of about −10 mV. At a concentration of 2 mM/1, caffeine considerably lowered the mechanical threshold of the muscle fibres such that peak contracture tension was obtained with 40 mM/1 potassium saline, at a depolarization level of only −30 mV. Withdrawal of calcium ions from caffeine containing salines resulted in a loss of the contractile response to depolarization, and the lowering of the mechanical threshold was abolished. These results are consistent with the view that caffeine may activate muscle in vivo by accelerating calcium release from the sarcoplasmic reticulum and by suppressing active calcium binding by the reticular calcium pump. Since caffeine can activate depolarized muscle it is suggested that caffeine short-circuits the normal excitation-contraction coupling channels to initiate a direct release of calcium ions from the sarcoplasmic reticulum without transient depolarization.

Absolute convexity in certain topological linear spaces

Abstract: For r > 0 a non-empty subset U of a linear space is said to be absolutely r -convex if x, y ∈ U and |λ| r + |μ| r ≤ 1 together imply λ x + μ y ∈ U , or, equivalently, x l , …, x n ∈ U and It is clear that if U is absolutely r -convex, then it is absolutely s -convex whenever s r . A topological linear space is said to be r -convex if every neighbourhood of the origin θ contains an absolutely r -convex neighbourhood of the origin. For the case 0 r ≤ 1, these concepts were introduced and discussed by Landsberg(2).

Recurrent Competitive Bidding

Abstract: A competitive bidding policy can be formulated if prior probability distributions of competitors' bids for future contracts have been determined A method for determining these prior probability distributions is described for markets where there are a large number of customers The identity of each winning company and its bid are assumed to be available to competitors and other customers so that the market reacts quickly to changes A real example of the use of the method is given The suppliers' general levels of bidding and their variation with individual types of customer are evaluated quantitatively The results are consistent with qualitative knowledge of the market

Correlates of school attainment at different ability levels

Abstract: Summary. Correlations between school attainment and various intellectual, personality and social variables are reported separately for the top and bottom thirds of the ability range. The ability groups were formed from an age-group of 2,538 Aberdeen children, who had been given tests yearly between the ages of 11 and 14. Results suggest that secondary school attainment is more difficult to predict in the high ability group than in the low ability group. But academic motivation is more closely related to school attainment for the high ability group. Among bright boys extraversion is negatively related to attainment, but in the low ability group the relationship is positive. Similar, but less extreme, differences exist among girls in this sample.

Operational Research and Decision-Making

Abstract: This paper was originally presented under the title "Decision" at the Third Operational Research Conference of the Universities of Lancaster and Sussex held at Windermere in April 1968. In it, the question of what is meant by "improved decision-making" is examined and the ways in which operational research can and does contribute to this are discussed. In the course of this the "American School" of Decision Analysis is reviewed. The paper concludes with some suggestions on computational procedures. This paper was written as a vehicle for discussion. In order to stimulate this, the authors have been deliberately provocative and presented an extreme point of view. The paper which follows this is a condensed version of some of the discussion which took place at the Conference. The authors would welcome further contributions.

Stomatal responses to light and carbon dioxide in the hart's-tongue fern, phyllitis scolopendrium newm.

Abstract: SUMMARY The stomata of Phyllitis scolopendrium differ from those of angiosperms in that the guard cells contain many chloroplasts, comparable in size and appearance with those of the mesophyll. Experiments are described showing that the stomata of this fern respond to light and darkness and changes in carbon dioxide concentration in the same way as those of angiosperms. The stomata opened widely in conditions in which there could be no net photosynthetic carbon dioxide fixation, and it is therefore concluded that substances produced from carbon dioxide by photosynthesis do not play a major role in the opening mechanism and possibly no direct role

Image Force in Metal-Oxide-Metal Tunnel Junctions

Abstract: Since it is necessary to supply energy to a metal in order to observe electron emission from a metal surface, it is evident that the potential energy of an electron within a metal is lower than that of an electron at rest outside the metal. Other theoretical arguments support this conclusion (1). It follows then that the electron must undergo a change in potential as it crosses the metal-vacuum interface. Figure 1 is the energy diagram of the model envisaged by Sommerfeld (2). The metal is represented by a potential energy well of depth V 0; the vacuum level represents the energy of an electron at rest within the metal. At 0°K the electrons, which exist in pairs in discrete energy levels, fill up the well to an energy n, the Fermi level. The distance ψ = V 0 − η from the Fermi level to the vacuum level is known as the work function of the metal, and represents the minimum energy required to free electrons from the interior of the metal at 0°K.