Showing papers by "Australian National University published in 1991"
TL;DR: The Iasp91 traveltime tables as mentioned in this paper are derived from a radially stratified velocity model which has been constructed so that the times for the major seismic phases are consistent with the reported times for events in the catalogue of the International Seismological Centre (ISC) for the period 1964-1987.
Abstract: SUMMARY
Over the last three years, a major international effort has been made by the Sub-Commission on Earthquake Algorithms of the International Association of Seismology and the Physics of the Earth's Interior (IASPEI) to generate new global traveltime tables for seismic phases to update the tables of Jeffreys & Bullen (1940). The new tables are specifically designed for convenient computational use, with high-accuracy interpolation in both depth and range. The new iasp91 traveltime tables are derived from a radially stratified velocity model which has been constructed so that the times for the major seismic phases are consistent with the reported times for events in the catalogue of the International Seismological Centre (ISC) for the period 1964–1987. The baseline for the P-wave traveltimes in the iasp91 model has been adjusted to provide only a small bias in origin time for well-constrained events at the main nuclear testing sites around the world.
For P-waves at teleseismic distances, the new tables are about 0.7s slower than the 1968 P-tables (Herrin 1968) and on average about 1.8–1.9 s faster than the Jeffreys & Bullen (1940) tables. For S-waves the teleseismic times lie between those of the JB tables and the results of Randall (1971).
Because the times for all phases are derived from the same velocity model, there is complete consistency between the traveltimes for different phases at different focal depths. The calculation scheme adopted for the new iasp91 tables is that proposed by Buland & Chapman (1983). Tables of delay time as a function of slowness are stored for each traveltime branch, and interpolated using a specially designed tau spline which takes care of square-root singularities in the derivative of the traveltime curve at certain critical slownesses. With this representation, once the source depth is specified, it is straightforward to find the traveltime explicitly for a given epicentral distance. The computational cost is no higher than a conventional look-up table, but there is increased accuracy in constructing the traveltimes for a source at arbitrary depth. A further advantage over standard tables is that exactly the same procedure can be used for each phase. For a given source depth, it is therefore possible to generate very rapidly a comprehensive list of traveltimes and associated derivatives for the main seismic phases which could be observed at a given epicentral distance.
3,177 citations
TL;DR: In this article, the authors describe elevation data sources, digital elevation model structures, and the analysis of digital elevation data for hydrological, geomorphological, and biological applications.
Abstract: The topography of a catchment has a major impact on the hydrological, geomorphological. and biological processes active in the landscape. The spatial distribution of topographic attributes can often be used as an indirect measure of the spatial variability of these processes and allows them to be mapped using relatively simple techniques. Many geographic information systems are being developed that store topographic information as the primary data for analysing water resource and biological problems. Furthermore, topography can be used to develop more physically realistic structures for hydrologic and water quality models that directly account for the impact of topography on the hydrology. Digital elevation models are the primary data used in the analysis of catchment topography. We describe elevation data sources, digital elevation model structures, and the analysis of digital elevation data for hydrological, geomorphological, and biological applications. Some hydrologic models that make use of digital representations of topography are also considered.
2,855 citations
TL;DR: In this article, the authors used the atomic force microscope to measure the forces between a planar surface and an individual colloid particle, a silica sphere of radius 3.5 µm, attached to the force sensor in the microscope and measured in solutions of sodium chloride.
Abstract: THE forces between colloidal particles dominate the behaviour of a great variety of materials, including paints, paper, soil, clays and (in some circumstances) cells. Here we describe the use of the atomic force microscope to measure directly the force between a planar surface and an individual colloid particle. The particle, a silica sphere of radius 3.5 µm, was attached to the force sensor in the microscope and the force between the particle and the surface was measured in solutions of sodium chloride. The measurements are consistent with the double-layer theory1,2 of colloidal forces, although at very short distances there are deviations that may be attributed to hydration forces3–6 or surface roughness, and with previous studies on macroscopic systems4–6. Similar measurements should be possible for a wide range of the particulate and fibrous materials that are often encountered in industrial contexts, provided that they can be attached to the microscope probe.
1,900 citations
TL;DR: In this article, a quantitative model has been developed for IAB petrogenesis with the transfer of trace elements from the slab to the mantle wedge being modelled with empirical slab-fluid partition coefficients whilst the mantlewedge to arc-crust transfer is constrained by melt-solid partitioning.
1,327 citations
TL;DR: Analysis of plants sampled from high and low altitudes along latitudinal gradients from the equator to the polar ends of plant distribution suggests that both temperature and atmospheric pressure are responsible for the altitudinal trends in 13C discrimination.
Abstract: In an earlier paper we provided evidence that carbon isotope discrimination during photosynthesis of terrestrial C3 plants decreases with altitude, and it was found that this was associated with greater carboxylation efficiency at high altitudes. Changing partial pressures of CO2 and O2 and changing temperature are possible explanations, since influences of moisture and light were reduced to a minimum by selective sampling. Here we analyse plants sampled using the same criteria, but from high and low altitudes along latitudinal gradients from the equator to the polar ends of plant distribution. These data should permit separation of the pressure and temperature components (Fig. 1). Only leaves of fully sunlit, non-water-stressed, herbaceous C3 plants are compared. The survey covers pressure differences of 400 mbar (ca. 5000 m) and 78 degrees of latitude (ca 25 K of mean temperature of growth period). When habitats of similar low temperature (i.e. high altitude at low latitude and low altitude at polar latitude) are compared, discrimination increases towards the pole (with decreasing altitude and thus increasing atmospheric pressure). Latitudinally decreasing temperature at almost constant atmospheric pressure (samples from low altitude) is associated with a decrease in discrimination. So, polar low-altitude plants have δ13C values half way between humid tropical lowland and tropical alpine plants. It is unlikely that latitudinal changes of the light regime had an effect, since low and high altitude plants show contrasting latitudinal trends in δ13C although local altitudinal differences in overall light consumption were small. These results suggest that both temperature and atmospheric pressure are responsible for the altitudinal trends in 13C discrimination. Temperature effects may partly be related to increased leaf thickness (within the same leaf type) in cold environments. Theoretical considerations and laboratory experiments suggest that it is the oxygen partial pressure that is responsible for the pressure related change in discrimination. The study also provided results of practical significance for the use of carbon isotope data. Within a community of C3 plants, discrimination in species of similar life form, exposed to similar light, water and ambient CO2 conditions ranges over 4‰, with standard deviations for 10–30 species of ±0.6 to 1.2‰. This natural variation has to be taken into account by using a sufficient sample size and standardization of sampling in any attempt at ecological site characterization using carbon isotope data. Evidence of a pronounced genotypic component of this variation in 13C discrimination in wild C3 plant species is provided. Correlations with dry matter partitioning, mesophyll thickness and nitrogen content are also present.
555 citations
TL;DR: The bulk chemical composition of pyrolite is derived from experimental and petrological studies of the complementary relationships between basaltic magmas and refractory peridotites as discussed by the authors.
470 citations
01 Oct 1991
TL;DR: In this article, two complementary delineation criteria are presented which provide guidelines to the design of relatively short, low-loss tapered fibres and devices, which are used to explain anomalous loss effects in depressed-cladding and W-fibres, as well as the difficulty in fabricating low loss devices by tapering such fibres.
Abstract: Two complementary delineation criteria are presented which provide guidelines to the design of relatively short, low-loss tapered fibres and devices. They are used to explain anomalous loss effects in depressed-cladding and W-fibres, as well as the difficulty in fabricating low-loss devices by tapering such fibres. Practical application of the criteria to couplers, beam expanders and abrupt taper filters is summarised. The accompanying paper provides both experimental and theoretical justification for the delineation criteria.
447 citations
TL;DR: In this paper, it was hypothesized that the perceived social category membership of others becomes salient as a description and explanation of their behaviour where their attitudes "fit" the social categorization, defined as the degree to which the attributes of others are perceived to correlate with group membership in a normatively consistent direction.
Abstract: It was hypothesized that the perceived social category membership of others becomes salient as a description and explanation of their behaviour where their attitudes ‘fit’ the social categorization. Fit is defined as the degree to which the attributes of others are perceived to correlate with group membership in a normatively consistent direction. In Expt 1 subjects viewed tape—slide presentations of six‐person groups where gender composition (‘solo’ or ‘collective’) and the pattern of agreement (‘deviance’ or ‘conflict’) were manipulated in a 2 × 2 design to produce a correlation between gender and attitudes in the solo/deviance and collective/conflict conditions. In Expt 2, subjects viewed videos of a group of three arts and three science students in which the normative consistency of an arts target person (‘consistent’ or ‘inconsistent’) and the pattern of agreement (‘consensus' or ‘conflict’ or ‘deviance’) were manipulated in a 2 × 3 design to produce a normative correlation between faculty membership and attitudes in the consistent/conflict condition. Salience was measured by stereotyping in terms of, and attributions to, social category memberships. The results of both experiments were largely consistent with predictions. 1991 The British Psychological Society
429 citations
TL;DR: In this article, a wide range in structural styles on passive margins is predicted by five models which incorporate detachment faults linked to flat ductile shear zones, and ductile stretching of the thermal lithosphere below the shear zone.
Abstract: The inherent asymmetry of extension by detachment leads to contrasting and conjugate classes of passive margins. Upper-plate margins comprise crust above a deeper detachment. Lower-plate margins comprise the footwall of the detachment, overlain by faulted upper plate remnants. Such margins have distinctive architectures, structural styles, uplift-subsidence paths and thermal histories. The wide range in structural styles on passive margins is predicted by five models which incorporate detachment faults linked to flat ductile shear zones, and ductile stretching of the thermal lithosphere below the shear zones. These models provide explanations for enigmatic structural and morphological features of passive margins such as marginal plateaux, outer highs, unstructured synrift sag basins, and perched rift basins. Numerical modelling of isostatic uplift-subsidence histories shows that different patterns of uplift-subsidence behaviour can be explained by variations in detachment geometry and change in the amount of lithospheric stretching. Voluminous igneous underplating is predicted if anomalously hot asthenosphere is uplifted. The arrival of such mantle derived melts may cause significant additional uplift. Upper-plate margins undergo thermally induced uplift, with permanent uplift due to igneous underplating. This uplift may be the origin of passive margin mountains in the adjacent hinterlands. Marginal plateaux are emergent or very shallowly submerged throughout the extension history, with postrift subsidence to intermediate water depths. The lithosphere is extended below a midcrustal detachment, but with little extension of the upper-plate. The pattern of subsidence on an Atlantic margin requires an extended upper plate superimposed on progressively more stretched subdetachment lithosphere. Conjugate margins are described from the Tasman Sea, the Atlantic Ocean and the Great Southern Ocean, illustrating both the principle of complementary asymmetry and the different patterns of uplift or subsidence on opposing passive margins.
381 citations
TL;DR: There are several additional features, derived from both clinical and pathology information, which have had prognostic significance shown by appropriately constructed multivariate analyses and can be used to formulate a more accurate prognostic index than that provided by a description of anatomical tumour spread.
Abstract: The purpose of tumour staging for colorectal cancer (CRC) is to help define clinical management, facilitate communication between physicians, provide a basis for stratification and analysis of treatment results in prospective studies, and provide some prognostic information for patients and their families. The World Congresses of Gastroenterology, Digestive Endoscopy, and Coloproctology, Working Party on staging for CRC studied six commonly used systems to review their strengths and weaknesses. Although it was concluded that defining a new staging system was unnecessary, it was recognized that there is a need to define a terminology to describe the full anatomic extent of spread of CRC. Furthermore, we note that there are several additional features, derived from both clinical and pathology information, which have had prognostic significance shown by appropriately constructed multivariate analyses and which can be used to formulate a more accurate prognostic index than that provided by a description of anatomical tumour spread. Thus the Working Party came to two principal conclusions. First, a standard format should be adopted for the collection of the essential data required for prospective studies, and we recommend the 'International Documentation System (IDS) for CRC' for this purpose. Second, a nomenclature which describes the full anatomical extent of tumour spread and residual tumour status in CRC has been defined and should be adopted, from which all currently used staging systems can be derived. We have called this nomenclature the 'International Comprehensive Anatomical Terminology (ICAT) for CRC'. In the event that these recommendations are adopted, we envision that there will be improved clarity in the documentation of treatment outcome for patients with CRC and improved communication of results derived from prospective studies. Furthermore, an acceptance of IDS and ICAT would set the scene to develop a prognostic index for individual patients with CRC by the expansion of anatomical clinicopathology staging information to include additional factors which have independent prognostic significance.
381 citations
TL;DR: In this paper, it was shown that plumes do not provide the ultimate driving force for continental break-up (these come from the plate-scale motions), but the extra gravitational potential that they impose means that they play an important role in determining both where and when continental breakup does occur.
TL;DR: In this paper, an ion microprobe study on zircons from volcanic rocks within the three basins of the Kaapvaal Craton of southern Africa is presented.
TL;DR: In this paper, a 52m drill core from a postglacial reef at Huon Peninsula, Papua New Guinea, spanning the interval from 7,000 to 11,000 14C yr BP was used to show that coral growth kept pace while the relative sea level rose by 50m.
Abstract: DATING of coral reef terraces can provide a record of changes in sea level, which should be pronounced during the transition between glacial and interglacial periods. Cores drilled from coral reefs at Barbados in the equatorial west Atlantic1have revealed the sea-level changes that occurred during the Younger Dry as event at the end of the Last Glacial Maximum (∼11,000 yr BP). It has not been known, however, whether Pacific coral reefs can grow at a rate sufficient to keep up with the rise in sea level during such a transition. Here we report results obtained from a 52-m drill core from the post-glacial reef at Huon Peninsula, Papua New Guinea, spanning the interval from 7,000 to 11,000 14C yr BP, which show that coral growth kept pace while the relative sea level rose by 50m. Although the tectonic environment is very different from that at Barbados, the two records compare well when corrections are made for local tectonic uplift, showing that sea-level rise was similar at both locations. The rate of rise was greatest between 9,000 and 10,00014C yr BP, corresponding to the time of the Younger Dryas.
TL;DR: The motion-sensitive mechanisms mediating range perception appear to be qualitatively different from those that mediate the well-known optomotor response in insects, or those involved in motion detection and ocular tracking in man.
Abstract: When negotiating a narrow gap, honeybees tend to fly through the middle of the gap, balancing the distances to the boundary on either side. To investigate the basis of this “centering response,” bees were trained to fly through a tunnel on their way to a feeding site and back, while their flight trajectories were filmed from above. The wall on either side carried a visual pattern. When the patterns were stationary vertical gratings, bees tended to fly through the middle of the tunnel, i.e. along its longitudinal axis. However, when one of the gratings was in motion, bees flying in the same direction as the moving grating tended to fly closer to while bees flying in the opposite direction tended to fly closer to the stationary grating. This demonstrates, directly and unequivocally, that flying bees estimate the distances of surfaces in terms of the apparent motion of their images. A series of further experiments revealed that the distance to the gratings is gauged in terms of their apparent angular speeds, and that the visual system of the bee is capable of measuring angular speed largely independently of the spatial period, intensity profile, or contrast of the grating. Thus, the motion-sensitive mechanisms mediating range perception appear to be qualitatively different from those that mediate the well-known optomotor response in insects, or those involved in motion detection and ocular tracking in man.
TL;DR: In vitro susceptibility of the human malaria parasite Plasmodium falciparum to killing by nitric oxide and related molecules is investigated and nitrosothiol derivatives of cysteine and glutathione were found to be about a thousand times more active than nitrite.
Abstract: We have investigated the in vitro susceptibility of the human malaria parasite Plasmodium falciparum to killing by nitric oxide and related molecules. A saturated solution of nitric oxide did not inhibit parasite growth, but two oxidation products of nitric oxide (nitrite and nitrate ions) were toxic to the parasite in millimolar concentrations. Nitrosothiol derivatives of cysteine and glutathione were found to be about a thousand times more active (50% growth inhibitory concentration, approximately 40 microM) than nitrite.
TL;DR: The noble-gas elemental and isotopic composition in the primordial Earth is significantly different from that of the present atmosphere, and provides an important clue to the origin and history of the Earth and its atmosphere.
Abstract: THE noble-gas elemental and isotopic composition in the Earth is significantly different from that of the present atmosphere, and provides an important clue to the origin and history of the Earth and its atmosphere. Possible candidates for the noble-gas composition of the primordial Earth include a solar-like component, a planetary-like component (as observed in primitive meteorites) and a component similar in composition to the present atmosphere. In an attempt to identify the contributions of such components, we have measured isotope ratios of helium and neon in fresh basaltic glasses dredged from Loihi seamount and the East Rift Zone of Kilauea1–3. We find a systematic enrichment in 20Ne and 21Ne relative to 22Ne, compared with atmospheric neon. The helium and neon isotope signatures observed in our samples can be explained by mixing of solar, present atmospheric, radiogenic and nucleogenic components. These data suggest that the noble-gas isotopic composition of the mantle source of the Hawaiian plume is different from that of the present atmosphere, and that it includes a significant solar-like component. We infer that this component was acquired during the formation of the Earth.
TL;DR: A 26-item informant questionnaire (IQCODE) was found to perform at least as well as the MMSE against all diagnoses and significantly better when judged against the algorithmic ICD-10 diagnoses.
Abstract: A 26-item informant questionnaire (IQCODE) and the Mini-Mental State Examination (MMSE) were compared as screening tests for dementia in a sample of 69 patients. Dementia diagnoses were made by both a clinician and a research interview using a computer algorithm to meet DSM-III-R and ICD-10 (Draft) criteria. The IQCODE was found to perform at least as well as the MMSE against all diagnoses and significantly better when judged against the algorithmic ICD-10 diagnoses. Also, the IQCODE was found to be uncontaminated by pre-morbid ability as estimated from the National Adult Reading Test and to have very high test-retest reliability after a delay of a day or more.
TL;DR: The teleological notion of function was introduced in this article, where the teleological concept of function is used to define the notion of functions in the teleology of the human body.
Abstract: (1991). The teleological notion of ‘function’. Australasian Journal of Philosophy: Vol. 69, No. 4, pp. 454-468.
TL;DR: Gold-bearing quartz vein systems in metamorphic terranes are one of the most important types of lode gold resource in central Victoria as mentioned in this paper, which is restricted to narrow, structurally-controlled domains in a low grade metamorphosed quartz-rich turbidite sequence.
TL;DR: The result is a bandwidth selector with the, by nonparametric standards, extremely fast asymptotic rate of convergence of n−½ where n → ∞ denotes sample size.
Abstract: A bandwidth selection method is proposed for kernel density estimation. This is based on the straightforward idea of plugging estimates into the usual asymptotic representation for the optimal bandwidth, but with two important modifications. The result is a bandwidth selector with the, by nonparametric standards, extremely fast asymptotic rate of convergence of n−½ where n → ∞ denotes sample size. Comparison is given to other bandwidth selection methods, and small sample impact is investigated.
TL;DR: In this article, the main structural cause of ferroelectricity in Bi4Ti3O12 and Bi3TiNbO9 is shown to be the a-axis displacement of Bi atoms in the perovskite A sites with respect to the chains of TiO6 octahedra.
TL;DR: A new phase unwrapping algorithm is described that uses local phase information to mask out those parts of the field that cause inconsistencies in the unwraps and can produce an approximately correct unwrapped.
Abstract: A new phase unwrapping algorithm is described that uses local phase information to mask out those parts of the field that cause inconsistencies in the unwrapping. Unlike earlier techniques, which produce only a consistent unwrapping of the phase in the presence of discontinuities, this technique can produce an approximately correct unwrapping. The technique is tolerant of discontinuities and noise in the phase and is fast, efficient, and simple to implement. In the absence of discontinuities an rms signal-to-noise ratio in the wrapped phase of <2:1 can be tolerated.
TL;DR: In this article, a questionnaire survey of a sample of 133 first year overseas students mainly from Singapore, Malaysia and Hong Kong, most of whom were studying for a Bachelor of Business degree, and 76 Australian born first year students mainly of British and European origin from the same classes, showed that compared to local students the overseas group had significantly greater difficulties adjusting to academic requirements, particularly with regard to managing the demands of study, specifically study methods, independent learning, language skills, participation and time management.
Abstract: Overseas students bring to Australia a very different cultural, social and intellectual experience from that which awaits them. Reviews of previous studies suggest that their beliefs, values and attitudes to knowledge, to styles of learning and study can lead to study shock. A questionnaire survey of a sample of 133 first year overseas students mainly from Singapore, Malaysia and Hong Kong, most of whom were studying for a Bachelor of Business degree, and 76 Australian born first year students mainly of British and European origin from the same classes, showed that compared to local students the overseas group had significantly greater difficulties adjusting to academic requirements, particularly with regard to managing the demands of study, specifically study methods, independent learning, language skills, participation and time management. The overseas students manifested significantly higher degrees of various stress indicators than did the local students. More academic and counselling support...
TL;DR: The existence of stable undesirable equilibria for the Godard algorithm is demonstrated through a simple autoregressive (AR) channel model and it is shown that attaining the global minimum of the mean cost necessarily implies correct equalization.
Abstract: The existence of stable undesirable equilibria for the Godard algorithm is demonstrated through a simple autoregressive (AR) channel model. These undesirable equilibria correspond to local but nonglobal minima of the underlying mean cost function, and thus permit the ill-convergence of the Godard algorithms which are stochastic gradient descent in nature. Simulation results confirm predicted misbehavior. For channel input of constant modulus, it is shown that attaining the global minimum of the mean cost necessarily implies correct equalization. A criterion is also presented for allowing a decision at the equalizer as to whether a global or nonglobal minimum has been reached. >
TL;DR: Foraminifera, Pteropoda, corals, Gastropoda, and Pelecypoda have been found to yield large variations in boron concentration that range from 1 ppm in gastropod shells to 80 ppm in corals.
TL;DR: It is revealed that the relatively small chemical differences between CTx-1, CTX-2 andCTX-3 give rise to significant structure-activity and pharmacokinetic differences that are comparable to mouse lethality.
TL;DR: The method used is a switching argument recently used by us to uniformly generate random graphs with given degree sequences to determine the asymptotic number of unlabelled graphs with a given degree sequence.
Abstract: We determine the asymptotic number of labelled graphs with a given degree sequence for the case where the maximum degree iso(|E(G)|1/3). The previously best enumeration, by the first author, required maximum degreeo(|E(G)|1/4). In particular, ifk=o(n
1/2), the number of regular graphs of degreek and ordern is asymptotically
$$\frac{{(nk)!}}{{(nk/2)!2^{nk/2} (k!)^n }}\exp \left( { - \frac{{k^2 - 1}}{4} - \frac{{k^3 }}{{12n}} + 0\left( {k^2 /n} \right)} \right).$$
Under slightly stronger conditions, we also determine the asymptotic number of unlabelled graphs with a given degree sequence. The method used is a switching argument recently used by us to uniformly generate random graphs with given degree sequences.
TL;DR: History of depression was found to be associated with AD, although the effect was confined to late onset cases, and no association was found with the three major life events considered in the pooled analysis: death of spouse, death of a child and divorce.
Abstract: Data from case-control studies of Alzheimer's disease (AD) were pooled to examine the possible roles of history of depression, anti-depressant treatment and adverse life events as risk factors. History of depression was found to be associated with AD, although the effect was confined to late onset cases. The association held for episodes of depression more than 10 years before AD onset, as well as for episodes occurring within a decade of onset. No association was found with anti-depressant treatment. However, data were only available from two studies, limiting the power of the analysis. Also, no association was found with the three major life events considered in the pooled analysis: death of spouse, death of a child and divorce.
25 Mar 1991-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the authors describe the design and modes of operation of a novel ball mill device in which the ball movement pattern is controlled by an external magnetic field, and examples of applications of this ball mill to the synthesis of Ni-Zr alloys, high melting point intermetallics, MgZn alloys and aluminium-based alloys are given.
Abstract: We describe the design and modes of operation of a novel ball mill device in which the ball movement pattern is controlled by an external magnetic field. Examples of applications of this ball mill to the synthesis of NiZr alloys, high melting point intermetallics, MgZn alloys and aluminium-based alloys are given. In particular, various modes of operation may result in a different path for the solid state reaction occurring during milling.