Showing papers by "Australian National University published in 1984"

U‐Pb geochronology of zircons from lunar breccia 73217 using a sensitive high mass‐resolution ion microprobe

Abstract: U-Pb age determinations on four lunar zircons from existing thin-sections of one highland breccia, 73217, using the recently constructed ion microprobe SHRIMP, are reported. The analytical reproducibility of SHRIMP is demonstrated, and procedures for measuring Pb/U, Th/U, and corecting for initial Pb are explained. Electron microprobe analyses for the zircons are alsoar reported. The results show that the four zircons survived the lunar cataclysm without any identifiable effects on their U-Pb systematics. All four indicate a single age of 4356 +23 or -14 m.y. The zircons have experienced small variable amounts of Pb loss since crystallization, from almost zero up to about 10 percent. If this occurred during one later event, then age of the latter is between 1100 and 2300 m.y.

Eight-vertex SOS model and generalized Rogers-Ramanujan-type identities

Abstract: The eight-vertex model is equivalent to a “solid-on-solid” (SOS) model, in which an integer heightl i is associated with each sitei of the square lattice. The Boltzmann weights of the model are expressed in terms of elliptic functions of period 2K, and involve a variable parameter η. Here we begin by showing that the hard hexagon model is a special case of this eight-vertex SOS model, in which η=K/5 and the heights are restricted to the range 1⩽l i⩽4. We remark that the calculation of the sublattice densities of the hard hexagon model involves the Rogers-Ramanujan and related identities. We then go on to consider a more general eight-vertex SOS model, with η=K/r (r an integer) and 1⩽l i⩽r−1. We evaluate the local height probabilities (which are the analogs of the sublattice densities) of this model, and are automatically led to generalizations of the Rogers-Ramanujan and similar identities. The results are put into a form suitable for examining critical behavior, and exponentsβ, α, $$\bar \alpha $$ are obtained.

Characterization of DNA sequences through which cadmium and glucocorticoid hormones induce human metallothionein-IIA gene.

Abstract: Deletion experiments have defined two stretches of DNA (genetic elements), lying close to the promoter for a human gene for metallothionein, that separately mediate the induction of the gene by heavy metal ions, particularly cadmium, and by glucocorticoid hormones. The element responsible for induction by cadmium is duplicated, yet a single copy is fully functional; the element responsible for induction by glucocorticoid hormones is coincident with the DNA-binding site for the glucocorticoid hormone receptor.

Easy riders, joint production, and public goods*

Abstract: The conventional wisdom on pure public good provision has certain accepted propositions:' (i) As group or community size increases, easy (or free) riding2 and its associated suboptimality also increase (Olson, I965). (2) The stability of Nash (or Nash-Cournot) equilibrium solely depends on the sign and magnitude of an inycome effect (see, for example, Breton, I970, p. 574; Olson and Zeckhauser, I966; Pauly, I970, p. 574; Williams, I966, p. 2I). (3) Nash behaviour always leads to inefficiency for public goods (Pauly, I970). (4) A model with identical individuals has a symmetric equilibrium where everyone provides the same equilibrium quantity of a pure public good (Olson, I965). (5) There is no measure for the extent of easy riding. These are important propositions that are universally used and accepted in public finance. This article explores the comparative statics of the demand for a marketed good that jointly provides public and private outputs or characteristics. Once joint products are admitted to the analysis of public goods, we demonstrate that propositions (I)-(4) no longer hold. In particular, the analysis shows that the consumption relationship of the jointly produced outputs influences the slope of the expenditure reaction paths, the stability of equilibria, and the departure of Nash equilibria from optimality (i.e. the extent of easy riding). When the joint products are complements in a Hicksian sense, particularly interesting results follow including the possibilities of positively sloped reaction paths and of reduced easy riding as the size of the community is increased. Thus, an agent's public expenditures may increase in response to increased public expenditures of others, even when all goods are normal with positive income elasticities. Such a result may well apply to an activity like philanthropy, where charitable activities provide private as well as public benefits to contributors (see, Sugden, I982; Posnett and Sandler, I983). Even in the absence ofjointness, this article demonstrates that propositions (i) and (4) are not valid. Furthermore, a simple, but useful, geometric technique is presented. This device can generate reaction paths and an index of easy riding, whose existence disproves proposition (5). Additionally, we derive the stability conditions for an n-person public good model. In Section V the theoretical results are applied to the study of a military alliance, where an arsenal jointly produces private and public outputs. This

Molecular cloning of cDNA for murine interleukin-3.

Abstract: The cDNA sequence for murine interleukin-3, one of the colony stimulating factors that regulate haematopoiesis, codes for a polypeptide of 166 amino acids including a putative signal peptide. The predicted amino acid sequence indicates that formation of mature interleukin-3 involves proteolytic removal of not only the signal peptide but additional ammo-terminal amino acids.

Very efficient plasma generation by whistler waves near the lower hybrid frequency

Abstract: Experimental results are presented which show that r.f. power at frequencies near the lower hybrid frequency couples resonantly into a standing whistler wave. For an input power flux of less than 5 W cm-2 densities above 1012 cm-3 with close to 100% ionization have been achieved. Measured density, temperatures and wave fields are presented and are used as input parameters for a theoretical model.

Genetic Covariation Between Neuroticism and the Symptoms of Anxiety and Depression

Abstract: A genetic analysis of the trait of neuroticism and symptoms of anxiety and depression in 3,810 pairs of adult MZ and DZ twins is reported. Differences between people in these measures can be explained simply by differences in their genes and in their individual environmental experiences. There is no evidence that environmental experiences that are shared by cotwins, such as common family environment or social influences, are important. There are differences between the sexes in gene action affecting neuroticism, and genetic effects become more pronounced with age in females. The lack of evidence for dominance variance affecting neuroticism contrasts well with the detection of considerable genetical nonadditivity for extraversion in the same sample and reinforces the view that these two traits are not only statistically, but also genetically, quite independent. An analysis of the causes of covariation between anxiety, depression, and neuroticism shows that additive gene effects are more important causes of covariation than environmental factors. Genetic variation in symptoms of anxiety and depression is largely dependent on the same factors as effect the neuroticism trait. However, there is also evidence for genetic variation specific to depression.

Photosynthetic and stomatal responses of two mangrove species, Aegiceras corniculatum and Avicennia marina to long term salinity and humidity conditions.

Abstract: Gas exchange characteristics were studied in two mangrove species, Aegiceras corniculatum (L.) Blanco and Avicennia marina (Forstk.) Vierh. var australasica (Walp.) Moldenke, grown under a variety of salinity and humidity conditions. The assimilation rate was measured as a function of the intercellular CO2 concentration [A(ci) curve]. The photosynthetic capacity decreased with increase in salinity from 50 to 500 millimolar NaCl, as shown by decline in both the initial linear slope and the upper plateau of the A(ci) curve, with A. corniculatum being the more sensitive species. The decline in photosynthetic capacity was enhanced by increase in the leaf to air vapor pressure difference from 6 to 24 millibars, but this treatment caused a decrease in only the upper plateau of the A(ci) curve. Stomatal conductance was such that the intercellular CO2 concentration obtaining under normal atmospheric conditions occurred near the transition between the lower linear and upper plateau portions of the A(ci) curves. Thus, stomatal conductance and photosynthetic capacity together co-limited the assimilation rate, which declined with increasing salinity and decreasing humidity. The marginal water cost of carbon assimilation was similar in most treatments, despite variation in the water loss/carbon gain ratio.

New approaches to direct gradient analysis using environmental scalars and statistical curve-fitting procedures

Abstract: The conceptual framework of direct gradient analysis (DGA) is discussed in relation to the functional, factorial approach to vegetation. Both approaches use abstract simplified environment gradients with which to correlate vegetation response. Environmental scalars based on physical process models of environment and/ or known biological growth processes can be incorporated to make analyses less location specific. An example of an environmental scalar (radiation index) for converting aspect and slope measurements to the more biologically relevant radiation input at a site is given.

The fluid dynamics of evolving magma chambers

Abstract: Recent developments in petrology indicate that fluid dynamic effects are of fundamental importance in controlling magma genesis. The forms of convection in magma chambers arise from compositional variations caused by processes such as fractional crystallization, partial melting and contamination, as well as from thermal effects. These processes, together with phase changes such as volatile exsolution, generally cause much larger density changes in magmas than the thermal effects arising from associated temperature changes. Magmas exhibit a wide range of convective phenomena not encountered in one-component fluids that are due to these compositional changes and to the differences between the diffusivities of chemical components and heat. When crystallization occurs in such multi-component systems, fluid immediately adjacent to the growing crystals is generally either depleted or enriched in heavy components and can convect away from its point of origin. Experimental studies of convection in crystallizing systems together with theoretical analyses suggest that convective separation of liquid from crystals is the dominant process of fractionation in magmas. This paper provides a synopsis of these new ideas on convection in magmas and their application to the interpretation of igneous rocks. Crystal settling is shown to be an inadequate and, in many situations, improbable mechanism for fractional crystallization. The convective motions in chambers are usually sufficiently vigorous to keep crystals in suspension, although settling can occur from thin fluid layers and within the boundary layers at the margins of a magma chamber. We propose that convective fractionation, a term introduced to embrace a wide variety of convective phenomena caused by crystallization, is the dominant mechanism for crystal fractionation. The process enables compositional and thermal gradients to be formed in magma chambers both by closed-system crystallization and by repeated replenishment in open systems. During crystallization along the margins of a chamber, highly fractionated magmas can be generated without requiring large amounts of crystallization, because the removal and concentration of chemical components affects only a small fraction of the total magma. These convective effects also give insights into many features observed in layered intrusions, including the various types of layering and the formation of different kinds of cumulate rock.

Cation distributions and thermodynamic properties of binary spinel solid solutions.

Abstract: A general model is presented to enable the calculation of the cation distribution and thermodynamic properties of any binary solid solution between oxide spinels containing 2+,3+ and 4+ cations. The model includes the effect of disordering enthalpy which depends linearly on the degree of disorder. In addition there are important contributions to the thermodynamic properties from the size mismatch of the substituting cations, which may be accounted for adequately using the simplest possible approach, that of a strictly regular solution. The regular solution parameter, W, depends on the difference in volume of the substituting cations. The model has been tested against the extensive literature data on spinel solutions; in the great majority of cases agreement with experimental observation is good. The model may be used to explain a diverse array of phenomena associated with the cation distribution in spinel solutions, to discriminate among conflicting experimental data, to extrapolate experimental data to other temperatures and pressures, and to predict the properties of unstudied systems.

Nonlinear-response theory for steady planar Couette flow

Abstract: We present a simplified derivation of the Yamada-Kawasaki formula for the nonlinear adiabatic response of the stress tensor to planar Couette flow. This formally exact expression is then used to prove the validity of two nonequilibrium molecular-dynamics algorithms that have been used to study fluids undergoing planar Couette flow, very far from equilibrium.

Decomposing Differences between Groups: A Cautionary Note on Measuring Discrimination

Abstract: Somewhat divergent approaches to finding the components of group differences (for example, the difference in average earnings across gender or racial groups) have grown up in the literatures of economics and sociology. Both, however, are variants of the same underlying approach. This article illustrates different approaches and draws attention to the conditions under which two, three, or four components of the income gap between groups can be usefully distinguished. The two central issues are which standard one uses to evaluate endowment differences between groups, and whether the scales used to operationalize underlying concepts have arbitrary zero-points or not. This latter difficulty has often been neglected in empirical applications using variables such as education, region, occupation, industry, and marital status. In such cases, the choice of a comparison group is inherently arbitrary, and nothing other than an arbitrary decomposition of the residual group difference can result.

Effects of partial defoliation, changes of irradiance during growth, short-term water stress and growth at enhanced p(CO2) on the photosynthetic capacity of leaves of Phaseolus vulgaris L.

Abstract: The response of CO2-assimilation rate to the intercellular partial pressure of CO2 (p(CO2)) is used to analyse the effects of various growth treatments on the photosynthetic characteristics of P. vulgaris. Partial defoliation caused an increase in CO2-assimilation rate at all intercellular p(CO2). A change in the light regime for growth from high to low light levels caused a decrease of CO2-assimilation rate at all intercellular p(CO2). Growth in a CO2-enriched atmosphere resulted in lowered assimilation assimilation rates compared with controls at comparable intercellular p(CO2). Short-term water stress initially caused only a decline in the CO2-assimilation rate at high intercellular p(CO2), but not at low intercellular p(CO2). Except under severe water stress, changes in the initial slope of the response of CO2-assimilation rate to intercellular p(CO2) were in parallel to those of the in-vitro activity of ribulose-1,5-bisphosphate (RuBP) carboxylase. From the results, we infer that partial defoliation, changes in the light regime for growth, and growth in a CO2-enriched atmosphere cause parallel changes in RuBP-carboxylase (EC 4.1.1.39) activity and the “capacity for RuBP regeneration”, whereas short-term water stress initially causes only a decline in the RuBP-regeneration capacity.

On the rate of Poisson convergence

Abstract: Let X1, …, Xn be independent Bernoulli random variables, and let pi = P[Xi = 1], λ = Σi=1n pi and Σi=1n Xi. Successively improved estimates of the total variation distance between the distribution ℒ(W) of W and a Poisson distribution Pλ with mean λ have been obtained by Prohorov[5], Le Cam [4], Kerstan[3], Vervaat[8], Chen [2], Serfling[7] and Romanowska[6]. Prohorov, Vervaat and Romanowska discussed only the case of identically distributed Xi's, whereas Chen and Serfling were primarily interested in more general, dependent sequences. Under the present hypotheses, the following inequalities, here expressed in terms of the total variation distancewere established respectively by Le Cam, Kerstan and Chen:(Kerstan's published estimate of ([3], p.174, equation (1)) is a misprint for , the constant 2·1 appearing twice on p. 175 of his paper.) Here, we use Chen's [2] elegant adaptation of Stein's method to improve hte estimates given in (1·1), and we complement these estimates with a reverse inequality expressed in similar terms. Second order estimates, and the case of more general non-negative integer valued X's, are also discussed.

Emplacement and cooling of komatiite lavas

Abstract: We propose that komatiite lavas were emplaced as turbulent flows, accompanied by vigorous forced convection with cooling rates often in excess of hundreds of °C h−1. They melted and assimilated up to 10% of the ground over which they flowed, forming deep channels. Nickel sulphide mineralization may have resulted from incorporation of sulphur-rich sediment. After emplacement, high cooling rates persisted, resulting in spinifex textures due to compositional convection.

Housing Careers, Life Cycle and Residential Mobility: Implications for the Housing Market:

Abstract: The concept of a housing career provides a useful way of integrating the residential mobility and filtering literatures in understanding the operation of the housing market. Using data from a survey in Adelaide, the paper examines these careers in terms of moves to and from both rental accommodation and home ownership. It shows how the progression of households through the stock is influenced by the circumstances that prompt moves, economic resources, and stage in the family life cycle. The results suggest that acceleration and postponement of advancement along housing careers provide the principal mechanisms by which household demand adjusts to available housing supply over the short term.

Unsupported radiogenic Pb in zircon: a cause of anomalously high Pb-Pb, U-Pb and Th-Pb ages

Abstract: Ion microprobe U-Th-Pb isotopic analyses of zircons from a granodioritic orthogneiss from the Napier Complex, Mount Sones, Enderby Land, Antarctica, have identified an unambiguous example of unsupported radiogenic Pb in a 3,950 Ma-old crystal. At one 40 μm spot on the crystal an unusually large heterogeneity in Pb content was found, the concentration of radiogenic Pb ranging from 5 to 50 percent higher than could have been generated in 3,950 Ma by radioactive decay of the co-existing U and Th. This relative excess of radiogenic Pb is attributed to Pb gain rather than to U and Th loss because first, the Pb content varied by more than the U or Th contents and secondly, changes in the Pb/U, Pb/Th and Pb isotopic composition correlated directly with changes in the Pb concentration. The individual 207Pb/206Pb apparent ages ranged from 4,000 Ma to 4,145 Ma, all greater than the inferred age of the crystal. A correlation between 207Pb/206Pb and Pb/U shows that the Pb excess has not resulted from recent Pb movement. The spot apparently gained radiogenic Pb about 2,500 Ma ago, at the same time as the majority of the other zircons in the rock suffered substantial Pb loss. The Pb movement occurred in response to a discrete geologic event. Reverse discordance is a phenomenon that must be considered when interpreting zircon U-Pb ages, especially 207Pb/206Pb ages of single crystals or portions of crystals.

Chapter 18 Dynamic specification

Abstract: Publisher Summary Dynamic specification denotes the problem of appropriately matching the lag reactions of a postulated theoretical model to the autocorrelation structure of the associated observed time-series data. As such, the issue is inseparable from that of stochastic specification if the finally chosen model is to have a purely random error process as its basic innovation. The subject-matter has advanced rapidly and offers an opportunity for critically examining the main themes and integrating previously disparate developments. A statistical-theory based model considers the joint density of the observables and seeks to characterize the processes whereby the data were generated. Thus, the focus is on means of simplifying the analysis to allow valid inference from submodels. This chapter also discusses that given the paucity of dynamic theory and the small sample sizes currently available for most time series of interest, as against the manifest complexity of the data processes, all sources of information have to be utilized. Attempt to resolve the issue of dynamic specification first involves developing the relevant concepts, models, and methods that is the deductive aspect of statistical analysis, prior to formulating inference techniques. An alternative interpretation is that by emphasizing the econometric aspect of time-series modeling, the analysis applies howsoever the model is obtained and seeks to be relatively neutral as to the economic theory content.

Magneto-chiral birefringence and dichroism

Abstract: It was pointed out recently that the absorption coefficient of a chiral molecule should be shifted slightly in a magnetic field parallel to a light beam in any polarization state. This suggestion is developed further by considering an analogous refractive index shift and by discussing these magneto-chiral phenomena in the unified context of effects generated by the ‘magnetic’ (time-odd) parts of the complex optical activity tensors. Explicit expressions, in terms of molecular property tensors, are derived for the difference in refractive index and absorption coefficient of a chiral molecule in a magnetic field parallel and antiparallel to the light beam, and magneto-chiral analogues of the Faraday A-, B- and C-terms introduced. A rough estimate of the magneto-chiral birefringence indicates that it should be observable using a modified Rayleigh refractometer. The feasibility of observing magneto-chiral dichroism A-, B- and C-terms in different types of chiral molecules is also considered. The magneto-chira...

Effects of milk protein genetic variants on milk yield and composition.

Abstract: Effects of genetic variants of the milk proteins, alpha S1-casein, beta-casein, kappa-casein and beta-lactoglobulin (beta-lg), on milk yield and composition, particularly the protein composition, were investigated in milk samples from 289 Jersey and 249 Friesian cows in eight commercial herds. Milk protein genotypes had no significant effect on yields over a complete lactation of milk and fat, but significant differences in fat content were detected for beta-casein (B, A1B, A2 greater than A1A2) and beta-lg (B, AB greater than A) variants. Significant differences between beta-lg variants were also found with total solids (B, AB greater than A), casein (B, AB greater than A), whey protein (A greater than AB greater than B) and beta-lg (A greater than AB, AC greater than B greater than BC) concentrations. Casein genotypes were not significantly different in total protein and casein concentrations but many differences were found in casein composition. alpha S1-Casein variants significantly affected alpha S1-casein (BC greater than B) and kappa-casein (B greater than BC) concentrations. beta-Casein variants affected concentration and proportion of beta-casein (A1B, A2B greater than A1, A1A2, A2, B), alpha S1-casein (A1, A2 greater than B) and kappa-casein (B greater than A2) and concentration of whey protein (A1 greater than most other beta-casein variants). kappa-Casein variants affected concentration and proportion of kappa-casein (B greater than AB greater than A), proportion of alpha S1-casein (A greater than AB greater than B) and concentrations of beta-lg (A greater than AB, B) and alpha-lactalbumin (A, AB greater than B). Differences in milk composition were found between breeds, herds and ages, and with stage of lactation. The potential use of milk protein genotypes as an aid in dairy cattle breeding is discussed.