Showing papers by "Australian National University published in 1976"

Geochemistry of eocene calc-alkaline volcanic rocks from the Kastamonu area, Northern Turkey

Abstract: Analytical data for Sr, Rb, Cs, Ba, Pb, rare earth elements, Y, Th, U, Zr, Hf, Sn, Nb, Mo, Ni, Co, V, Cr, Sc, Cu and major elements are reported for eocene volcanic rocks cropping out in the Kastamonu area, Pontic chain of Northern Turkey. SiO2% versus K2O% relationship shows that the analyzed samples belong to two major groups: the basaltic andesitic and the andesitic ones. High-K basaltic andesites and low-K andesites occur too. Although emplaced on continental type basement (the North Anatolian Crystalline Swell), the Pontic eocene volcanics show elemental abundances closely comparable with typical island arc calc-alkaline suites, e.g. low SiO2% range, low to moderate K2O% and large cations (Cs, Rb, Sr, Ba, Pb) contents and REE patterns with fractionated light and almost flat heavy REE patterns. ΣREE and highly charged cations (Th, U, Hf, Sn, Zr) are slightly higher than typical calc-alkaline values. Ferromagnesian elements show variable values. Within the basaltic andesite group the increase of K%, large cations, ΣREE, La/Yb ratio and high valency cations and the decrease of ferromagnesian element abundances with increasing SiO2% content indicate that the rock types making up this group developed by crystalliquid fractionation of olivine and clinopyroxene from a basic parent magma. Trace element concentration suggest that the andesite group was not derived by crystal-liquid fractionation processes from the basaltic andesites, but could represent a distinct group of rocks derived from a different parent magma.

Fast Multiple-Precision Evaluation of Elementary Functions

Abstract: Let ƒ(x) be one of the usual elementary functions (exp, log, artan, sin, cosh, etc.), and let M(n) be the number of single-precision operations required to multiply n-bit integers. It is shown that ƒ(x) can be evaluated, with relative error O(2-n), in O(M(n)log (n)) operations as n → ∞, for any floating-point number x (with an n-bit fraction) in a suitable finite interval. From the Schonhage-Strassen bound on M(n), it follows that an n-bit approximation to ƒ(x) may be evaluated in O(n log2(n) log log(n)) operations. Special cases include the evaluation of constants such as p, e, and ep. The algorithms depend on the theory of elliptic integrals, using the arithmetic-geometric mean iteration and ascending Landen transformations.

Pioneer neurones in an insect embryo.

Abstract: INSECT sense organs are produced by small groups of specialised epidermal cells1. The receptor neurones differentiate at the surface, so developing sensory axons grow inwards from the epidermis to the central nervous system (CNS). How do they find their way? During larval life the axons of newly differentiated sense cells combine with those of neighbouring receptors and thus are guided to the nearest branch of a peripheral nerve which carries them to the CNS2. At metamorphosis the axons of adult sensory neurones reach their central destination by growing along persistent larval nerves which are associated with the developing imaginal disks3–5. Thus with pathways to the ganglia already established, growth along existing nerves ensures the delivery of each generation of sensory axons to within a few hundred micrometres of their central targets. Just how the connection between the surface and the CNS is first established, whether by an outgrowth of nerves from the centre or by pioneering axons which grow inwards from the surface has never been shown, although some descriptions of embryonic development imply that the first axons to enter the developing appendages are growing outwards from the CNS6,7. Presumably these early centrifugal axons would provide a route for the later differentiating sensory fibres to follow in growth to the centre. Here, however, I report observations on the embryonic nervous system of Locusta migratoria which show that the first pathways between the epidermis and the central ganglia are formed by axons which grow inwards from peripheral neurones which differentiate early in embryonic life.

Some implications of the growth of the mineral sector

Abstract: The rapid growth of Australian mineral exports, through its effect on the balance of payments, is a significant force for structural change in other sectors. From the viewpoint of the rural sector which exports and the manufacturing sector which competes with imports, this force will be similar to that which would flow from very large tariff changes. Consequently, by observing the adjustments of the rural and manufacturing sectors to the rapid growth of mineral exports, it is possible to calculate indirect estimates of the effect of the Australian tariff on them. It is calculated that the mineral discoveries have had a much greater effect on these sectors than the recent across the board 25 per cent general reduction of tariffs.

Uptake and release of D- and L-aspartate by rat brain slices.

Abstract: — D-Aspartate is accumulated by slices of adult rat cortex by a high affinity uptake which is abolished if the sodium ions in the incubation medium are replaced by choline. A small uptake of D-aspartate takes place if the sodium ions are replaced by lithium ions. It appears likely that D-aspartate shares the same transport system with L-aspartate, and that the uptake of D-aspartate is into the same osmotically-sensitive particles as those which accumulate L-aspartate. D-Aspartate is released from cerebral cortex slices by raised potassium concentrations, provided calcium is present in the perfusing buffer. Both D- and L-aspartate produce gross hyperactivity when injected intraperitoneally into immature rats. Radioactive D-aspartate may be very useful in examining the neurotransmitter role of the naturally- occurring L-aspartate e.g. in studies of the autoradiographic localization of high affinity L-aspartate accumulation, its main advantage being that, unlike L-aspartate, D-aspartate does not undergo rapid metabolism.

Embryogenesis of an insect nervous system. I. A map of the thoracic and abdominal neuroblasts in Locusta migratoria.

Abstract: Maps of the thoracic and abdominal neuroblasts have been prepared by reconstruction from serial sections of timed Locusta migratoria embryos. The maps are bilaterally symmetrical, periodic and consistent for embryos of the same age, with a fundamental arrangementof 7 rows of 4–10 cells plus 1 median neuroblast per segment. A map of 60+1 cells isrepeated in each of the three thoracic segments, with an additional median cell developinglate at the anterior end of the prothorax. The arrangement in the abdomen is similar, with 56+ 1 cells per segment. Neuroblasts differentiate and subsequently degenerate in an anteroposteriorsequence, but construction of the thoracic ganglia involves a delayed degenerationof part of the original set in these segments. The maps show that the neuroblasts are as reliable in their number and arrangement as the adult cells they produce. The number of neuroblasts used in constructing the relatively complex thoracic ganglia is similar to that which produces the simpler abdominal ganglia. Some motorneurons have the same parent neuroblast. The maps are intended as a first step in an analysis of the relation between the progeny of different neuroblasts and the family of neurons which each neuroblast produces.

Morphometric analysis of rat superior cervical ganglion after axotomy and nerve growth factor treatment

Abstract: The changes in neuronal number, cell body size and nuclear size have been followed for 12 weeks after postganglionic axotomy of the rat superior cervical ganglion. Axotomy was carried out at 6 days post partum and treatment with nerve growth factor (NGF) was from 6-21 days. During normal development there is a 30% decrease in the number of neurons in the superior cervical ganglion; axotomy increases the loss of cells resulting in a 90% decrease by 28 days post partum. The normal decrease is prevented and the enhanced loss of cells after axotomy is decreased by administration of NGF. Thus the increased number of cells observed after NGF administration appears to be due to the survival of cells that otherwise would have degenerated. NGF causes a rapid enlargement of both the cell bodies and the nucleus in the normal and axotomized ganglia. This increase in size rapidly reverses after cessation of treatment. These changes in cell size may account for the previously observed changes in cell profile number with NGF. There is a large increase in the number of non-neuronal cells during normal development and axotomy prevents this increase. NGF treatment results in a 6 fold increase in the number of non-neuronal cells and it is suggested that these are required to support the massive fibre outgrowth that occurs in NGF treated ganglia. It is concluded that these results are consistent with a physiological role for NGF as the trophic substance supporting adrenergic neurons making the appropriate contact with their target cell.

Equivalence of the Potts model or Whitney polynomial with an ice-type model

Abstract: The partition function of the Potts model (1952) on any lattice can readily be written as a Whitney polynomial (1932). Temperley and Lieb (Proc. R. Soc., vol.A322, p.251 of 1971) have used operator methods to show that, for a square lattice, this problem is in turn equivalent to a staggered ice-type model. Here the authors rederive this equivalence by a graphical method, which they believe to be simpler, and which applies to any planar lattice. For instance, they also show that the Potts model on the triangular or honeycomb lattice is equivalent to an ice-type model on a Kagome lattice.

A problem of Paul Erdös on groups

Abstract: Let G be a group, and associate with G a graph 1 γ = Γ (G) as follows: the vertices of Γ are the elements of G, and two vertices g, h of Γ are joined by an undirected edge if, and only if, g and h do not commute as elements of G, that is [g, h] ≠ 1 [where [g, h] is the commutator g−1h−1gh, and 1 is the unit element of the groups that occur as well as the integer, according to context].We are interested in complete subgraphs of Γ, or equivalently in sets of elements of G no two of which commute.

Direct measurement of long range forces between two mica surfaces in aqueous KNO 3 solutions

Abstract: WE have constructed an apparatus for measuring the forces between two surfaces immersed in a liquid directly as a function of separation, and report initial results for the forces between two crossed cylindrical sheets of molecularly smooth muscovite mica in aqueous solutions of KNO3.

Inhibition of the uptake of GABA and related amino acids in rat brain slices by the optical isomers of nipecotic acid.

Abstract: — R(-)-Nipecotic acid was a more potent inhibitor than the S(+)-isomer of the uptake of GABA, (+)-nipecotic acid, and β-alanine in rat brain slices. (-)-Nipecotic acid was an order of magnitude more potent as an inhibitor of GABA uptake than as an inhibitor of β-alanine uptake, whereas the (+)-isomer was less selective. (–)-Nipecotic acid was a weak inhibitor of L-proline uptake and of rat brain acetylcholinesterase activity. Kinetic studies showed that both isomers of nipecotic acid were competitive inhibitors of GABA uptake when added at the same time as GABA, but non-competitive inhibitors when preincubated with the tissue for 15 min before addition of GABA. The apparent slope inhibition constants, which were not influenced by preincubation, indicated that (–)-nipecotic acid has an affinity for the carrier some 5 times higher than that for (+)-nipecotic acid. (–)-Nipecotic acid stimulated the release of preloaded radioactive GABA from rat brain slices. These observations indicate that (–)-nipecotic acid is a substrate-competitive inhibitor of GABA which combines with the GABA carrier and is taken up. (−)-Nipecotic acid and (+)-2,4-diaminobutyric acid, on the basis of their absolute structures and inhibition kinetics, are proposed to interact in a similar way with the GABA transport system.

A strong controllability and observability in linear multivariable control

Abstract: A particular family of strong controllability and observability properties is shown to be relevant to problems in linear multivariable control. Explicit interrelations are established between these system properties and several approaches to multivariable control: in particular, the abstract vector-space approach of Wonham and Morse, and the explicit algorithm approach of Silverman. The results are valid for systems over an arbitrary field.

Morphine, enkephalin and the substantia gelatinosa

Abstract: THE pentapeptide enkephalin interacts with opiate receptors of peripheral tissues1 and with stereospecific opiate receptors of brain homogenates2. Ejected from micropipettes in the vicinity of central neurones, it has depressant3–5 and excitant6 effects. These actions, however, cannot be related specifically to the analgesic effects of systematically administered opiates. In electrophoretic experiments, tissue concentrations are unknown and hence even antagonism by electrophoretic naloxone is not necessarily a sufficient test of relevance to the effects of systemic opiates. This report is concerned with the effects of morphine when administered electrophoretically into the substantia gelatinosa. The subsequent changes in the firing of neurones within Rexed laminae IV and V can be related to the effects of this compound given svstemically. Furthermore methion-ine enkephalin had an action similar to that of morphine.

Geochronology of Gran Canaria, Canary Islands: Age of Shield Building Volcanism and Other Magmatic Phases

Abstract: Forty-six new K-Ar age determinations are presented on whole rock samples and mineral separates from volcanic and subvolcanic rocks of Gran Canaria. The main subaerial shield building basaltic volcanism with estimated volume of about 1000 km3 was confined to the interval about 13.7 m.y. to 13.5 m.y. ago in the middle Miocene. Substantial volume (∼100 km3) of silicic volcanics (trachyte and peralkaline rhyolite) were erupted with no detectable time break following the basaltic volcanism, essentially contemporaneous with formation of a large collapse caldera at 13.4±0.3 m.y. ago. Trachytic to phonolitic volcanism continued intermittently in the waning states of activity until about 9 m.y. ago. Following a long hiatus there was resurgence of volcanism with eruption of about 100 km3 of basanitic to hauyne phonolitic rocks of the Roque Nublo Group between about 4.4 m.y. and 3.4 m.y. ago in the Pliocene. After a hiatus of less than 1.0 m.y., olivine nephelinite magmas were erupted and this activity continued intermittently until relatively recent times, the younger eruptives being mainly basanitic in composition. The volume of volcanic products in this phase probably does not exceed 10 km3. Thus the volume of all the resurgent volcanism comprises less than 10 percent of the subaerially exposed part of Gran Canaria. The results show that the subaerial main shield building phase of volcanism in Gran Canaria, consisting of mildly alkali to transitional basalts, occurred over a time interval that was less than 0.5 m.y. Magmatic evolution on Gran Canaria appears to be similar to that found on other basaltic volcanoes in oceanic regions. Thus volcanoes in the Hawaiian, Marquesas and Society Islands all were built by basaltic lavas in similar short-lived episodes of volcanism. In some Hawaiian volcanoes, a resurgent phase of volcanism of strongly undersaturated basalts of small volume is recognized following a long hiatus, again similar to that found on Gran Canaria. The relatively large volume of silicic lavas erupted in Gran Canaria immediately following the main basaltic shield building phase is, however, not matched in the Pacific volcanoes mentioned.

Some observations on instrumental variable methods of time-series analysis

Abstract: It. is becoming increasingly clear that in the area of environmental systems analysis, where systems are often badly defined and models are subject to considerable uncertainty, recursive methods of time-series analysis can be particularly useful both in the initial and critical stages of system identification, as well as in the final stages of parameter estimation and model validation. Of the existing methods of time-series analysis, those based upon the method of instrumental variables are amongst the simplest and. at the same time, demonstrably most useful in practical applications. This paper discusses the instrumental variable (IV) and approximate maximum likelihood (AML) methods of recursive time-series analysis and shows how they can be unified to some extent within the context of maximum likelihood estimation. In this manner the virtues and limitations of the existing IV and AML techniques become more apparent and possible procedures for improving their statistical efficiency are exposed.

Spin–echo diffusion coefficients of water to 2380 bar and −20°C

Abstract: The self‐diffusion coefficient of water has been measured by the steady‐gradient spin‐echo method at pressures up to 2380 bar and temperatures between 2 and −20°C in the stable liquid range using both strengthened glass and beryllium–copper pressure vessels. At low temperatures and high pressures the diffusion coefficient becomes almost independent of pressure. However, a rapid increase in DH2O with the first kilobar of applied pressure is inferred for the supercooled liquid from the relation of the new data to the 1 atm pressure diffusivity of supercooled water. The observations may be correlated with the high pressure low temperature thermodynamic properties of water in a manner consistent with the Adam–Gibbs entropy theory of liquid transport processes.

A method to correct adequately for the change in neuronal size when estimating neuronal numbers after nerve growth factor treatment.

Abstract: A method is described to compute the correct distribution of nuclear diameters in thick sections of superior cervical ganglia of rats from the observed distribution of nuclear profiles. This method is applicable to the problem of correcting for the differing diameters of cells observed after treatment with nerve growth factor (NGF). It overcomes the errors due to the failure to count small fragments of nuclei too thin to be seen and the multiple counting of nuclei in more than one section. It has been shown that the changes in number of neurons after NGF treatment were not as large as previously supposed. An estimate of the volume occupied by the cell bodies suggests that the numbers calculated here are correct.

Nonlinear least squares — the Levenberg algorithm revisited*

Abstract: One of the most succesful algorithims for nonlinear least squares calculations is that associated with the names of Levenberg, Marquardt, and Morrison. This algorithim gives a method which depends nonlinearly on a parameter γ for computing the correction to the current point. In this paper an attempt is made to give a rule for choosing γ which (a) permits a satisfactory convergence theorem to be proved, and (b) is capable of satisfactory computer implementation. It is beleieved that the stated aims have been met with reasonable success. The convergence theorem is both simple and global in character, and a computer code is given which appears to be at least competitive with existing alternatives.

Changes in cholesterol synthesis and excretion when cholesterol intake is increased.

Abstract: The metabolic responses to increased amounts of dietary cholesterol include, in man, a reduction in the synthesis and an increase in the re-excretion of cholesterol. The effectiveness of these compensating mechanisms in preventing increases in the plasma cholesterol concentration was studied in nine subjects. Cholesterol absorption, the excretion of bile acids, the excretion of endogenous neutral steroids, and the cholesterol balance (synthesis) were measured twice during intakes of cholesterol of about 250 and 750 mg/day. The sum of the compensating mechanisms (reduction in synthesis and increase in excretion of cholesterol) almost equalled the increase in absorbed cholesterol when the intake was raised by 500 mg (mean change in compensation, 226 mg/day; mean change in absorption, 230 mg/day). In three subjects in whom re-excretion of cholesterol was predominant and compensated for absorbed cholesterol, the plasma cholesterol levels rose substantially. In five others, in whom the predominant change was reduction in cholesterol synthesis, the rise in plasma cholesterol levels was not significant. At moderate intakes of cholesterol both compensating mechanisms prevented retention of dietary cholesterol in the body, though a rise in the plasma cholesterol level was prevented only when cholesterol synthesis was suppressed.

Hydrogen isotope discrimination in higher plants: Correlations with photosynthetic pathway and environment.

Abstract: The ratio of deuterium to hydrogen (expressed as δD) in hydrogen released as water during the combustion of dried plant material was examined. The δD value (metabolic hydrogen) determined on plant materials grown under controlled conditions is correlated with pathways of photosynthetic carbon metabolism. C3 plants show mean δD values of-132‰ for shoots and -117‰ for roots; C4 plants show mean δD values of -91‰ for shoots and-77‰ for roots and CAM plants a δD value of-75‰ for roots and shoots. The difference between the δD value of shoot material from C3 and C4 plants was confirmed in species growing under a range of glasshouse conditions. This difference in δD value between C3 and C4 species does not appear to be due to differences in the δD value (tissue water) in the plants as a result of physical fractionation of hydrogen isotopes during transpiration. In C3 and C4 plants the hydrogen isotope discrimination is in the same direction as the carbon isotope discrimination and factors contributing to the difference in δD values are discussed. In CAM plants grown in the laboratory or collected from the field δD values range from-75‰ to +50‰ and are correlated with δ(13)C values. When deprived of water, the δD value (metabolic hydrogen) in both soluble and insoluble material in leaves of Kalanchoe daigremontiana Hamet et Perr., becomes less negative. These changes may reflect the deuterium enrichment of tissue water during transpiration, or in field conditions, may reflect the different δD value of available water in areas of increasing aridity. Whatever the origin of the variable δD value in CAM plants, this parameter may be a useful index of the water relations of these plants under natural conditions.