Showing papers by "Australian National University published in 1982"

Booming Sector and De-Industrialisation in a Small Open Economy

Abstract: This paper presents a theoretical analysis of the 'Dutch Disease': the phenomenon whereby a boom in one traded goods sector squeezes porfitability in other traded goods sectors, both by directly bi ...

Nature and origin of A-type granites with particular reference to southeastern Australia

Abstract: In the Lachlan Fold Belt of southeastern Australia, Upper Devonian A-type granite suites were emplaced after the Lower Devonian I-type granites of the Bega Batholith. Individual plutons of two A-type suites are homogeneous and the granites are characterized by late interstitial annite. Chemically they are distinguished from I-type granites with similar SiO2 contents of the Bega Batholith, by higher abundances of large highly charged cations such as Nb, Ga, Y, and the REE and lower Al, Mg and Ca: high Ga/Al is diagnostic. These A-type suites are metaluminous, but peralkaline and peraluminous A-type granites also occur in Australia and elsewhere. Partial melting of felsic granulite is the preferred genetic model. This source rock is the residue remaining in the lower crust after production of a previous granite. High temperature, vapour-absent melting of the granulitic source generates a low viscosity, relatively anhydrous melt containing F and possibly Cl. The framework structure of this melt is considerably distorted by the presence of these dissolved halides allowing the large highly charged cations to form stable high co-ordination structures. The high concentration of Zr and probably other elements such as the REE in peralkaline or near peralkaline A-type melts is a result of the counter ion effect where excess alkali cations stabilize structures in the melt such as alkali-zircono-silicates. The melt structure determines the trace element composition of the granite. Separation of a fluid phase from an A-type magma results in destabilization of co-ordination complexes and in the formation of rare-metal deposits commonly associated with fluorite. At this stage the role of Cl in metal transport is considered more important than F.

A Regular Layout for Parallel Adders

Abstract: With VLSI architecture, the chip area and design regularity represent a better measure of cost than the conventional gate count. We show that addition of n-bit binary numbers can be performed on a chip with a regular layout in time proportional to log n and with area proportional to n.

The hydrophobic interaction is long range, decaying exponentially with distance

Abstract: The attractive interaction between organic nonpolar molecules, such as hydrocarbons, in water is unusually strong. This ‘hydrophobic interaction’1 is responsible for the very low solubility of hydrophobic molecules in water, and has a central role in micelle formation, biological membrane structure, and in determining the conformations of proteins2,3. It was once believed that because the interaction is so strong there is a ‘hydrophobic bond’ associated with it2,4; but it is now recognized that the interaction involves the configurational rearrangement of water molecules as two hydrophobic species come together5–9 and is therefore of longer range than a typical covalent bond. However, there has been no experimental information available concerning the distance dependence and effective range of this interaction. From measurements of the total force as a function of distance between two hydrophobic surfaces immersed in aqueous electrolyte solutions we have determined accurately the attractive component due to the hydrophobic interaction and found that the hydrophobic interaction has the same range as, but is about an order of magnitude stronger than, the van der Waals-dispersion force; and that in the range 0–10 nm it decays exponentially with distance with a decay length of ∼1 nm. The results can be roughly extrapolated to molecular interactions and show that the interaction free energy of two hydrophobic solute molecules of radius R (nm) in water at 21 °C is approximately given by ΔGH = −40R kJ mol−1, which is in agreement with previous estimates. However, the hydrophobic interaction is not due to a ‘hydrophobic bond’, and its long-range nature has obvious implications for the mechanism and rates of folding as well as the equilibrium conformations of proteins and other macromolecules.

Predictive Coding: A Fresh View of Inhibition in the Retina

Abstract: Interneurons exhibiting centre--surround antagonism within their receptive fields are commonly found in peripheral visual pathways. We propose that this organization enables the visual system to encode spatial detail in a manner that minimizes the deleterious effects of intrinsic noise, by exploiting the spatial correlation that exists within natural scenes. The antagonistic surround takes a weighted mean of the signals in neighbouring receptors to generate a statistical prediction of the signal at the centre. The predicted value is subtracted from the actual centre signal, thus minimizing the range of outputs transmitted by the centre. In this way the entire dynamic range of the interneuron can be devoted to encoding a small range of intensities, thus rendering fine detail detectable against intrinsic noise injected at later stages in processing. This predictive encoding scheme also reduces spatial redundancy, thereby enabling the array of interneurons to transmit a larger number of distinguishable images, taking into account the expected structure of the visual world. The profile of the required inhibitory field is derived from statistical estimation theory. This profile depends strongly upon the signal: noise ratio and weakly upon the extent of lateral spatial correlation. The receptive fields that are quantitatively predicted by the theory resemble those of X-type retinal ganglion cells and show that the inhibitory surround should become weaker and more diffuse at low intensities. The latter property is unequivocally demonstrated in the first-order interneurons of the fly's compound eye. The theory is extended to the time domain to account for the phasic responses of fly interneurons. These comparisons suggest that, in the early stages of processing, the visual system is concerned primarily with coding the visual image to protect against subsequent intrinsic noise, rather than with reconstructing the scene or extracting specific features from it. The treatment emphasizes that a neuron's dynamic range should be matched to both its receptive field and the statistical properties of the visual pattern expected within this field. Finally, the analysis is synthetic because it is an extension of the background suppression hypothesis (Barlow & Levick 1976), satisfies the redundancy reduction hypothesis (Barlow 1961 a, b) and is equivalent to deblurring under certain conditions (Ratliff 1965).

Diffusion of 40Ar in hornblende

Abstract: Measured radiogenic 40Ar loss from two compositionally contrasting hornblendes following isothermal-hydrothermal treatment have provided model diffusion coefficients in the temperature range of 750° C to 900° C. Eight experiments using a hornblende (77–600) with a Mg/(Mg +Fe) ratio of 0.72 yield a linear array on an Arrhenius plot with a slope corresponding to an activation energy of 66.1 kcal-mol−1 and a frequency factor of 0.061 cm2-sec−1, assuming spherical geometry for the mineral aggregate. Five experiments undertaken on a hornblende (M Mhb-1) with a Mg/(Mg+Fe) ratio of 0.36 show similar behavior to the Mgrich sample, suggesting that the diffusivity of Ar in hornblendes is not sensitive to the Mg/Fe ratio.

On Some Simple Estimates of an Exponent of Regular Variation

Abstract: SUMMARY We present a class of simple estimates of an exponent of regular variation. Unlike those proposed recently by de Haan and Resnick (1980), ours converge at an algebraic rather than a logarithmic rate, and unlike those considered by Teugels (1980), their form does not depend on the unknown exponent.

An explanation of 13 C/ 12 C variations in tree rings

Abstract: Variations in the 13C/12C ratio in trees are examined in the light of a simple expression relating the relative isotope composition of plant material, δp13 to δa13, the atmospheric isotope value, ca, the atmospheric CO2 concentration and ci, the internal concentration of CO2 in leaves. The expression gives good agreement with δp13 measurements where independent information on ci exists, such as seasonal growth, growth low in the canopy and in conditions of low humidity. The expression provides possible explanations for two previously unexplained phenomena: the absence of anticipated changes due to fossil fuel-induced changes in δa13, and regional differences in δp13 trends.

Recursive estimation of mixed autoregressive-moving average order

Abstract: SUMMARY The order, (p, q), of an autoregressive-moving average sequence, y(t), may be estimated- by minimizing a criterion, log &2 + (p + q) log T/T, with respect to p and q, where ^2 is the maximum likelihood estimate of the variance of the innovations, ?(t). It is suggested that, instead, a2 be estimated from a series of regressions of y(t) on y(t-1),y(t-2),...,y(t-p), 5(t-1),...,?(t-q), where the ?(t) are obtained by fitting a long autoregression to the data. It is shown how the sequence of regressions may, for p = q, be economically recursively calculated by embedding them in a sequence of bivariate autoregressions. Asymptotic properties of the procedure are established under very general conditions.

Molecular mechanisms of variation in influenza viruses

Abstract: Influenza is unique among the viruses in its capacity to vary. Because of antigenic variation, it has proved impossible to control influenza by vaccination, and variation in virulence, host range and transmissibility influence the spread and severity of influenza epidemics. This variation is caused by sequence changes in the genes of the virus and this review summarizes recent information on the structure of the genes and their products, the way in which these vary and the effects of the changes on the biological activities of the virus.

Random coefficient autoregressive models : an introduction

Abstract: 1 Introduction.- 1.1 Introduction.- Appendix 1.1.- Appendix 1.2.- 2 Stationarity and Stability.- 2.1 Introduction.- 2.2 Singly-Infinite Stationarity.- 2.3 Doubly-Infinite Stationarity.- 2.4 The Case of a Unit Eigenvalue.- 2.5 Stability of RCA Models.- 2.6 Strict Stationarity 37 Appendix 2.1.- 3 Least Squares Estimation of Scalar Models.- 3.1 Introduction.- 3.2 The Estimation Procedure.- 3.3 Strong Consistency and the Central Limit Theorem.- 3.4 The Consistent Estimation of the Covariance Matrix of the Estimates.- Appendix 3.1.- Appendix 3.2.- 4 Maximum Likelihood Estimation of Scalar Models.- 4.1 Introduction.- 4.2 The Maximum Likelihood Procedure.- 4.3 The Strong Consistency of the Estimates.- 4.4 The Central Limit Theorem.- 4.5 Some Practical Aspects.- Appendix 4.1.- Appendix 4.2.- 5 A Monte Carlo Study.- 5.1 Simulation and Estimation Procedures.- 5.2 First and Second Order Random Coefficient Autoregressions.- 5.3 Summary.- 6 Testing the Randomness of the Coefficients.- 6.1 Introduction.- 6.2 The Score Test.- 6.3 An Alternative Test.- 6.4 Power Comparisons 108 Appendix 6.1.- Appendix 6.1.- 7 The Estimation of Multivariate Models.- 7.1 Preliminary.- 7.2 The Least Squares Estimation Procedure.- 7.3 The Asymptotic Properties of the Estimates.- 7.4 Maximum Likelihood Estimation.- 7.5 Conclusion.- Appendix 7.1.- 8 An Application.- 8.1 Introduction.- 8.2 A Non-Linear Model for the Lynx Data.- References.- Author And Subject Index.

Human metallothionein genes--primary structure of the metallothionein-II gene and a related processed gene.

Abstract: The complete nucleotide sequence of two of the human metallothionein gene family has been compared. One is a functional metallothionein-II gene, the other a pseudogene, lacking introns, terminating in a poly(A) tail and flanked by two direct repeats. In addition, we have detected a size polymorphism associated with the processed gene in the population, examined, and we have observed a region of apparent secondary structure homology between of 5' flanking region of the functional metallothionein-II gene and that of a mouse metallothionein-I gene.

Free Ca2+ and cytoplasmic streaming in the alga Chara.

Abstract: Plant cells, like those of animals, contain the Ca2+-binding protein calmodulin1–4. By analogy with animal cells it has thus been suggested that the intracellular free Ca2+ concentration may have an important role in the regulation of plant cell activities. This suggestions has been supported by various physiological experiments, but so far direct evidence, invol ving measurements of intracellular Ca2+ levels, has not been obtained. We describe here measurements of intracellular Ca2+ in the giant alga Chara by microinjection of the protein aequorin, which emits blue light in proportion to Ca2+ concentration. Chara exhibit an ATP-dependent cytoplasmic streaming shown to be inhibited by Ca2+ (refs 5, 6). We report that Chara cells have a low free Ca2+ concentration, comparable with those of animal cells, and that action potentials which inhibit cytoplasmic streaming7 increase this Ca2+ concentration substantially.

Intermolecular potential functions and the properties of water

Abstract: A wide range of gas, liquid and solid state properties are calculated using most of the presently available potential functions for the water pair interaction. It is shown that no one model gives a satisfactory account of all three phases. We propose a new semi-empirical model that has some success as an effective pair potential in all three phases.

Alcohol dehydrogenase and glycerol-3-phosphate dehydrogenase clines in drosophila melanogaster on different continents.

Abstract: Some of the most persuasive evidence that natural selection can maintain allozymic variation derives from work on polymorphisms for electrophoretically "fast" and "slow" enzymes of alcohol dehydrogenase (ADH, EC 1.1.1.1.) and glycerol-3-phosphate dehydrogenase (GPDH, EC 1.1.1.8.) in Drosophila melanogaster. The ADH-F and ADH-S variants are encoded by the AdhF and Adhs alleles (11-50. 1; Grell et al., 1965) and the GPDH-F and GPDH-S variants by the GpdhF and Gpdhs alleles (11-20.5; Grell, 1967). Almost every wild population of D. melanogaster which has been investigated has been found to segregate for all four genes (e.g., Voelker et al., 1978). The frequencies of all the genes also show latitudinal clines in eastern United States and Mexico; Adhs and GpdhF decrease, and AdhF and Gpdhs increase in frequency with increasing distance from the equator (Berger, 1971; Johnson and Schaffer, 1973; Pipkin et al., 1973; Vigue and Johnson, 1973). The clines in North America are extensive, covering about 250 of latitude, and it has been suggested that they are maintained by latitude-related selection pressures (e.g., Pipkin et al., 1973; Vigue and Johnson, 1973). However, either stochastic processes or transient stages in the dynamics between migration and latitudinally invariant selection pressures can also produce gene frequency clines (Endler, 1973; Jacquard, 1974). Therefore, we have tested the hypothesis that latitudinally varying selection maintains the Adh and Gpdh clines in North America by testing for the presence of complementary latitudinal clines in Asia, Europe and Australasia. Our rationale is that if the North American clines are simply due to stochastic processes, then they are unlikely to recur in the southern hemisphere or elsewhere in the northern hemisphere. A second hypothesis which we have investigated is based on evidence for thermostability differences between the fast and slow allozymes at the two loci. GPDHF is more thermostable than GPDH-S at 39 C (Alahiotis et al., 1977) and ADH-S is generally more thermostable than ADHF at a variety of temperatures up to 44 C (Gibson, 1970; Vigue and Johnson, 1973; Day et al., 1974; but see also Oakeshott, 1976). Furthermore, in some laboratory tests, flies homozygous for Adhs are more likely to survive heat shock than AdhF homozygotes (Bijlsma-Meeles and van Delden, 1974; Johnson and Powell, 1974; but see Milkman, 1977). These results have led to the hypothesis that positive relationships between maximum temperature and Adhs and GpdhF gene frequencies underlie the latitudinal clines (Johnson and Powell, 1974; Alahiotis et al., 1977). We have tested this hypothesis by examining these relationships on the continents of Asia, Europe, Australasia and North America.

Spacelike hypersurfaces with prescribed boundary values and mean curvature

Abstract: We consider the boundary-value problem for the mean curvature operator in Minkowski space, and give necessary and sufficient conditions for the existence of smooth strictly spacelike solutions. Our main results hold for non-constant mean curvature, and make no assumptions about the smoothness of the boundary or boundary data.

The inversion relation method for some two-dimensional exactly solved models in lattice statistics

Abstract: The partition-functions-per-siteκ of several two-dimensional models (notably the eight-vertex, self-dual Potts and hard-hexagon models) can be easily obtained by using an inversion relation for local transfer matrices, together with symmetry and analyticity properties. This technique is discussed, the analyticity properties compared, and some equivalences (and nonequivalences) pointed out. In particular, the critical hard-hexagon model is found to have the sameκ as the self-dualq-state Potts model, withq=(3 + √5)/2 = 2.618 .... The Temperley-Lieb equivalence between the Potts and six-vertex models is found to fail in certain nonphysical antiferromagnetic cases.

Effect of salinity and humidity on δ13C value of halophytes—Evidence for diffusional isotope fractionation determined by the ratio of intercellular/atmospheric partial pressure of CO2 under different environmental conditions

Abstract: Seedlings of two mangrove species, Avicennia marina and Aegiceras corniculatum, were grown in a range of salinities and humidities in controlled environment chambers, and Phaseolus vulgaris plants were grown in the glasshouse. The fractionation of carbon isotopes in the three species was correlated with the ratio of intercellular and ambient partial pressures of CO2. The results are consistent with fractionation being due both to diffusion in air and to carboxylation in the leaf. It was concluded that the latter process discriminates against 13CO2 relative to 12CO2 by about 27‰.

Variations in the Geomagnetic Dipole 1: The Past 50, 000 Years

Abstract: An analysis has been made of all archeomagnetic intensity data for the past 50, 000 years. There are 1, 175 results from different parts of the world covering the past 12, 000 years but these are heavily biased to the region of the northern hemisphere between 0° and 90°E (64% of data). The global means show a broad maximum about 6, 500 years B. P. There is no evidence from data older than 7, 000 years that a quasi-cyclic variation with period about 104 years exists.A careful analysis of 472 dipole moments covering the 2, 000 year period between 1000 A. D. and 1000 B. C. shows that they have a normal distribution with standard deviation of 19.7%. The estimate of the standard deviation of results within each 1, 000-year-interval for the past 10, 000 years is 21.2%. Analysis of the present field suggests a standard deviation of dipole moments of 17.5% would apply if the present field is representative of the past. This suggests the standard deviation due to experimental errors in archeomagnetic results is about 10%, a value that concurs with independent analysis. The ten 1, 000-year-mean dipole moments have mean 8.75×1022Am2 and estimated standard deviation 18.0% which may be attributed to dipole intensity fluctuations.Over the period 15, 000 to 50, 000 years B. P. the earth's dipole moment was low, the 14 results available having mean value 4.44×1022Am2 with estimated standard deviation 26.5%. This is precisely the scatter to be expected from a combination of dipole intensity fluctuations of 18.0% non-dipole variations of 17.5% and experimental errors of 10% as deduced for the past 10, 000 years. The conclusion therefore is that variations in the non-dipole field always remain in the same proportion to the dipole field irrespective of its magnitude. Furthermore, the time scale of changes in the earth's dipole moment must be very much longer than has previously been supposed and must be at least 105 years.

The single‐crystal elastic moduli of stishovite

Abstract: The single-crystal elastic moduli of stishovite have been determined experimentally from measured Brillouin scattering spectra. They are C11 = 4.53 ± 0.04, C33 = 7.76 ± 0.05; C44 = 2.52 ± 0.02, C66 = 3.02 ± 0.03; and C12 = 2.11 ± 0.05, C13 = 2.03 ± 0.04 in units of mbar. The estimated aggregate (Voigt-Reuss-Hill) adiabatic moduli are K = 3.16 ± 0.04 and μ = 2.20 ± .03 mbar. Previous values of the isothermal bulk modulus, obtained from hydrostatic compression experiments, are in agreement with the Reuss value of KT = 3.06 ± .04 mbar (as corrected to isothermal conditions). Taken together, these results suggest that the pressure derivative of the bulk modulus for stishovite is low relative to other rutile structure oxides.

Photosynthesis and Inorganic Carbon Usage by the Marine Cyanobacterium, Synechococcus sp

Abstract: The marine cyanobacterium, Synechococcus sp. Nageli (strain RRIMP N1) changes its affinity for external inorganic carbon used in photosynthesis, depending on the concentration of CO(2) provided during growth. The high affinity for CO(2) + HCO(3) (-) of air-grown cells (K((1/2)) < 80 nanomoles [pH 8.2]) would seem to be the result of the presence of an inducible mechanism which concentrates inorganic carbon (and thus CO(2)) within the cells. Silicone-oil centrifugation experiments indicate that the inorganic carbon concentration inside suitably induced cells may be in excess of 1,000-fold greater than that in the surrounding medium, and that this accumulation is dependent upon light energy. The quantum requirements for O(2) evolution appear to be some 2-fold greater for low CO(2)-grown cells, compared with high CO(2)-grown cells. This presumably is due to the diversion of greater amounts of light energy into inorganic carbon transport in these cells.A number of experimental approaches to the question of whether CO(2) or HCO(3) (-) is primarily utilized by the inorganic carbon transport system in these cells show that in fact both species are capable of acting as substrate. CO(2), however, is more readily taken up when provided at an equivalent concentration to HCO(3) (-). This discovery suggests that the mechanistic basis for the inorganic carbon concentrating system may not be a simple HCO(3) (-) pump as has been suggested. It is clear, however, that during steady-state photosynthesis in seawater equilibrated with air, HCO(3) (-) uptake into the cell is the primary source of internal inorganic carbon.

Analysis of orientation bias in cat retina

Abstract: 1. Responses of cat retinal ganglion cells to a drifting sinusoidal grating stimulus were measured as a function of the grating orientation and spatial frequency. 2. The response at fixed frequency and contrast varied with orientation in the manner of a cosine function. A new measure was introduced to quantify this orientation bias in the response domain on an absolute scale of 0-100%. Under experimental conditions designed to maximize the effect, the mean bias for 250 cells was 16% and the range was 0-46%. In 70% of cells there was significant bias. 3. Orientation bias varied with spatial frequency and was maximal near the high-frequency limit. The majority of biassed cells preferred the same orientation at high and low frequencies but in some cells a reversal occurred: the orientation which gave maximum response at high frequencies gave minimum response at low frequencies. The greatest variation of cut-off frequency with orientation was ⅔ octave. 4. Orientation bias was due to neural, not optical, factors. Nevertheless, the phenomenon could often be imitated by deliberately introduced optical astigmatism of up to 4 dioptres for brisk-sustained units and over 10 dioptres for brisk-transient units. 5. The grating orientation preferred by cells varied systematically with position in the visual field. The central tendency was for the grating which yielded maximum response to lie parallel to the line joining the cell to the area centralis. This generalization failed for units within 2° of the centre of the area centralis. 6. Analysis of orientation bias indicates a functional asymmetry of receptive fields such that the centre mechanism, and sometimes also the surround mechanism, is elongated along the line joining cell to area centralis.