Showing papers by "University of Wollongong published in 1987"

Identification of Cryptosporidium oocysts in river water

Abstract: Water samples were collected from four rivers in Washington State and two rivers in California and examined for the presence of Cryptosporidium oocysts. Oocyst-sized particles were concentrated from 20-liter samples of water by membrane filtration, centrifugation, and differential sedimentation. The particle concentrate was then deposited on a 25-mm-diameter membrane filter for oocyst identification by indirect immunofluorescence assay. The identification procedure had a limit of detection of about five oocysts per liter. Cryptosporidium oocysts were found in each of 11 river water samples examined. Concentrations ranged from 2 to 112 oocysts per liter. The finding of Cryptosporidium oocysts in all samples examined from six western rivers is noteworthy in light of recent reports indicating that Cryptosporidium sp. is a significant agent of human and animal disease. This finding suggests that waterborne oocysts of this parasite are more important than was previously recognized. More detailed studies are needed to define geographical and temporal distribution, to assess the viability of waterborne oocysts, and to determine the importance of water as a means of transmission.

Flicker Contrast Sensitivity in Normal and Specifically Disabled Readers

Abstract: Temporal contrast sensitivity for counterphase flicker was determined for specifically disabled and normal readers to investigate whether the two groups differ in the functioning of their transient systems. In experiment 1, temporal contrast sensitivity was measured over a range of temporal frequencies with a spatial frequency of 2 cycles deg-1. Disabled readers were less sensitive than the control subjects at all temporal frequencies. In experiment 2, temporal contrast sensitivity was measured at a temporal frequency of 20 Hz over a range of spatial frequencies. Disabled readers were less sensitive than the controls at all spatial frequencies, with the differences between the groups increasing as spatial frequency increased. Both these findings are interpreted as supporting the hypothesis of a transient-system deficit in the visual systems of disabled readers.

Public key cryptography

Abstract: We are going to devote most of our attention in this talk to the RSA Public Key Cryptosystem because it not only remains unbroken but it has some other useful features for digital signatures and authentication. We will briefly mention some other methods which have been compromised to some degree, and one, McEliece's which has not, but which are still valid when both keys are kept secret and some have other features which may be useful. Disciplines Physical Sciences and Mathematics Publication Details Seberry, J, Public key cryptography, Secure Data Communications Workshop, Digest of Papers, IEEE, Melbourne, 1987, 1-17. This conference paper is available at Research Online: http://ro.uow.edu.au/infopapers/1030 P"'f ' oJ! /'ltd, IUE j.}(}+lesh7 3/7/c7 PUBLIC KEY CRYPTOGRAPHY Jennifer Seberry University College The University of New South Wales Australian Defence Forces Academy Canberra INTRODUCTION We are going to devote most of our attention in this talk to the RSA Public Key Cryp~ tosystem because it not only remains unbroken but it has some other useful features for digital signatures and authentication. We will briefly mention some other methods which have been compromised to some degree, and one, McEliece' s which has not, but which are still valid when both keys are kept secret and some have other features which may be useful. PUBLIC KEY SYSTEMS A public key cryptosystem is a cryptographic system in which each encryption process is governed by not one but two keys. The two keys are inverses of each other, that is to say anything encrypted with one can be decrypted with the other and vice versa. The important additional property of a public key crptosystem is that given one of the keys, it is extremely difficult to find the other. This allows one of the keys to be made public while its inverse is kept secret, giving the systems their name. Public key cryptosystems have two very important properties. Because it is not necessary to keep both of the keys secret, one can be made readily available, published in a phonebook for example. Anyone wanting to transmit a confidential message can encrypt it in the public key of the addressee with assurance that only the addressee will be able to read it. Just as a message encrypted in a public key can be produced by anyone but can only be read by the holder of the corresponding secret key, a message encrypted in a secret key, a message encrypted in a secret key can be read by anyone. using the corresponding public key, but could only have been produced by the holder of the secret key. This gives it the fundamental property of a signature. Use is made of modular arithmetic. Mathematicians write the expression a :;b(mod m) (a is congruent to b modulo m) to denote the fact that the integer m divides exactly the difference of the integers a and b. For example, 32:; -4(mod 12). Note that if the remainder on dividing a by m is b, then a == b (mod m). Hence, 5124491" 12172(mod 21753). In fact, the remainder on dividing a by m is the only number b which is congruent to a modulo m such that 0 $; b < m. One very important cosequence of the definition of congruence is that if p (x) is any polynomial function of x with integer coefficients, then p (0)" p(b)(mod m) whenever 0" b(mod m). PUBLIC KEY DISTRIBUTION SYSTEM A public key distribution system is a mechanism which allows two people who have never had any prior secure contact to establish a secure channel "out of thin air", Public key distribution systems do not provide any signature mechanism but, at present, some are faster and more compact than public key cryptosystems which makes them better for many applications. The first practical public key distribution system makes use of the apparent difficulty of computing logarithms over a finite (Galois) field GF(q) with a prime number q of elements (the numbers (O,I, ... ,q-I) under arithmetic mod q). Let Y=axmod q,for 1

Movement of mammals through tunnels under railway lines

Abstract: Fragmentation of extensive natural ecosystems by roads, railways and other barriers poses major threats to populations of native animals. Attempts have been made to reduce the magnitude of these th...

The Hawkesbury Sandstone South of Sydney, Australia: Triassic Analogue for the Deposit of a Large, Braided River

Abstract: The Hawkesbury Sandstone is a Triassic sheet sandstone, extensively exposed in the Sydney Basin, New South Wales, particularly along the coast near Sydney. Unidirectional paleoflow in the sandstone, its freshwater biota, and abundant mudrock intraclasts indicate fluvial deposition. Sheet morphology, low paleocurrent variance, abundant erosion surfaces, and the paucity of in situ mudrocks point to a braided fluvial system. Three facies assemblages have been recognized: stratified sandstone, massive sandstone, and a minor mudrock assemblage. The stratified sandstone assemblage is dominated by stacked sets of planar cross-strata and minor trough cosets in sequences 6-23 m thick, bounded by erosion surfaces. Significant paleocurrent changes between channel sequences indicate that they were initiated by the avulsion of major channel systems. In some cases the channel sequences fine upward, with planar cross-stratal sets overlain by trough sets that decrease in magnitude upwards, fining up into mudrocks. The massive sandstone assemblage occurs principally as massive sandstone in elongate erosional features oriented transverse to paleoflow. The massive sandstone commonly contains large mudrock intraclasts and is attributed to failure of high channel banks and/or large bedforms during falling-water stages. The mudrock assemblage comprises rippled and horizontally laminated fine sandstone, siltstone, and shale, with minor mudstone. It is attributed primarily to floodplain deposition, but abandoned channel fills are also present. The Hawkesbury Sandstone does not conform to existing models for braided-fluvial deposition in that planar cross-strata accumulated in deeper parts of channels, whereas trough cross-strata formed in shallower water. The large scale of planar cross-strata (sets up to 7.5 m thick), mudrock intraclasts (up to 38 m long), bank-collapse scars (up to 11 m deep) and abandoned channel fills (up to 18 m deep) show that the Hawkesbury River was very large, with deep main channels and high but variable discharge.

Salt as an agent in the development of cavernous weathering

Abstract: A well-recognized spatial association exists between cavernous weathering and the presence of soluble salts Disaggregation of rock in caverns is attributed to mechanical pressures exerted by crystallization and/or hydration of salts However, scanning electron micrographic analysis demonstrates that solutional etching is the major weathering process in caverns in near-coastal locations in Western Australia and New South Wales, Australia It is suggested here that the breakdown of the caverned sandstone is caused by sodium chloride which increases the rate of quartz dissolution

Some aspects of an adaptive digital notch filter with constrained poles and zeros

Abstract: The paper derives the range of filter parameters which can be used for monitoring purposes in adaptive notch filtering applications. The nonconvergence problem associated with the stochastic Gauss-Newton algorithm is illustrated, and the paper proposes the use of a less efficient recursive estimation algorithm-the appropriate maximum likelihood method-to overcome this problem. Results from simulations are presented for demonstration purposes.

A Question of Properly Rights: Richard Owen's Evolutionism Reassessed

Abstract: When Vestiges of the Natural History of Creation, the anonymous evolutionary work which caused such a furore in mid-Victorian England, was published towards the close of 1844, Richard Owen, by then well-entrenched as the ‘British Cuvier’, received a complementary copy and addressed a letter to the author. This letter and how it should be interpreted have recently become the subject of historical debate, and this paper is directed at resolving the controversy. The question of Owen's attitude to the Vestiges argument is central to the larger historical problem of the views of this leading British morphologist and palaeontologist on the contentious issue of the ‘secondary causes’ of species. Owen wrote so little directly on this subject prior to 1858, that the letter in question, together with his two letters of 1848 to the rationalist publisher John Chapman, and the controversial conclusion to his On the Nature of Limbs (1849), constitute the major evidence that Owen in this period subscribed to a naturalistic theory of organic change. On the basis of this evidence, historians of biology have generally concurred with Owen's biographer grandson that Owen had a ‘certain leaning towards the theories enunciated by Robert Chambers [the Vestiges' author]’, but that his ‘official’ anti-transmutationist stance of the 1840s did not permit full public expression of his own views. As Ruse most recently summed up this historical consensus: Owen in the 1840s was ‘moving down a path not completely dissimilar from that followed by Chambers’, and he ‘tried to have matters two ways, praising Vestiges to its author and condemning it to its critics’.

Kriging without negative weights

Abstract: Under a constant drift, the linear kriging estimator is considered as a weighted average ofn available sample values. Kriging weights are determined such that the estimator is unbiased and optimal. To meet these requirements, negative kriging weights are sometimes found. Use of negative weights can produce negative block grades, which makes no practical sense. In some applications, all kriging weights may be required to be nonnegative. In this paper, a derivation of a set of nonlinear equations with the nonnegative constraint is presented. A numerical algorithm also is developed for the solution of the new set of kriging equations.

The Effects of Uncertainty Reporting on Lending Officers’ Perceptions of Risk and Additional Information Required

Abstract: This laboratory experiment investigates the perceptions which lending officers in Singapore have of risk and the additional information required when a client's financial reports receive a ‘subject to’ audit qualification. Using thirtyone bank lending officers in Singapore as subjects and a repeatedmeasurements ANOVA design, the conclusions of this study are that lending officers’ perceptions of risk and their demand for additional information required both increase as a result of a ‘subject to’ audit qualification.

An overview of the genre-based approach to the teaching of writing in Australia

Abstract: A significant educational development that has occurred in Australia in recent years has been the emergence of the genre-based approach to the teaching of writing. The theoretical basis of this approach lies in the systemic, functional model of language developd by M.A.K. Halliday and others. Thus it is an approach to writing which focuses on the relationship between written texts and the contexts in which written texts are produced. This paper traces the development of the genrebased approach. It discusses the meaning of the term “genre”, and describes the contribution of people such as Kress, Martin, Rothery and Christie to the theoretical development of the approach. It also describes some of the educational programs that have been developed to implement the genrebased approach. It is argued in this paper that the most significant contribution of the genre-based approach to writing is the development of an explicit understanding of the role of language in the educational context and a linguistic description of the major genres that children are expected to learn as they learn to write. It is in this area, that is, making the role of language explicit, that the genre-based approach differs most from other approaches such as the “growth model” of English teaching and “process writing” which have been influential in recent years.

The Holocene Prehistory of a coastal wetland system: Discovery Bay, Southeastern Australia

Abstract: Recent theories of socio-economic change in hunter-gatherer societies have referred to associated changes in intensity and mode of resource exploitation. These ideas are examined in the light of pollen and charcoal analyses of an Australian coastal wetland system which allow, at the local scale, (1) documentation of resource availability, (2) identification of resource use, particularly where fire technology is involved, and (3) examination of the effect of environmental change on the archeological record. Evidence of plant food management through fire around 6800 BP suggests a longer history of deliberate swamp exploitation than indicated by the archeological record, and lends support to models which propose long-term gradual change in zones of high productivity.

Compliant-skin tactile sensor

Abstract: A new design of robot tactile sensor is described which features a highly compliant structure. Sensor compliance accommodates a degree of inaccuracy in robot positioning, aids stable grasping and resists damage. Silicone rubber sheet forms the outer skin of the sensor which is supported by a core of polyurethane foam. Contact with external objects causes bending and stretch in the silicone rubber skin and this is detected by conductive rubber strain gage elements attached to the inner surface of the skin. The sensor construction is described and results obtained using prototype versions of the sensor are presented.

FF-Pad&#233; method of model reduction in frequency domain

Abstract: In this note the FF-Pade method based upon some new concepts in model reduction is presented. The new method will overcome the chief drawbacks of the current methods. Some typical examples are used to show convincingly that one has to break free from the conventional approaches in order to obtain better results in model reduction.

Crystallization kinetics of some iron-based metallic glasses

Abstract: The crystallization behaviour of a range of iron-based metallic glasses has been examined by isothermal differential scanning calorimetry, optical and transmission electron microscopy. It was found that the conventional procedure of applying the Johnson-Mehl-Avrami equation to determine reaction mechanisms, i.e. calculating a mean value of the Avrami exponent over a range of volume fraction transformed, can be misleading. The technique suggested by Calka and Radlinski, when used in conjunction with detailed metallography, is shown to be a more sensitive and reliable indicator of reaction mechanisms.

Sap feeding by the marsupial Petaurus australis: an enigmatic behaviour?

Abstract: The Yellow-bellied Glider, Petaurus australis, was observed to feed sporadically but extensively on eucalypt sap. Gliders extracted sap by making incisions into the bark with their procumbent lower incisor teeth and licking the resulting exudate. Less than 1% of possible trees were incised for sap. Sap flow and sap-sugar concentration were estimated for eight sap-site trees and eight non sap-site trees at intervals during an 18 month period. Measurements of sap-sugar concentration differed substantially among trees but fluctuated between sample periods independent of glider use. Sap flow measurements, were always higher for those trees currently 'in use' by gliders, although the particular sap-site trees comprising this group varied between sample periods. The variation in sap flow occurred indenpendent of the incidence of rainfall or the type of microhabitat the tree occupied. Experimental incising of trees, designed to mimic the effects of feeding by gliders, failed to show any effect on sap flow. This suggests that the incidence of sap feeding is determined by a tree's pattern of sap flow and that there may be trees with unusual patterns of sap flow which gliders select as the most favourable trees to incise.

Chronology and palaeoenvironment of the Cranebrook Terrace (near Sydney) containing artefacts more than 40,000 years old

Abstract: There is growing scientific and popular interest in the chronology, habitational environment and spatial extent of early human occupation of Australia. Lunettes adjacent to lakes in the semi-arid interior near Lake Mungo appear to have been occupied by at least 35,000 BP (Bowler 1976) Alluvial sites in the upper Swan River in Western Australia (Pearce and Barbetti 1981) and possibly Keilor in Victoria (Joyce and Anderson 1976) were peopled by about 40,000 BP (see review by White and O'Connell 1982:32-42). The oldest reported archaeological finds for coastal NSW are what are believed to be a selection of choppers and steep-edged scrapers found in association with alluvial gravels at the base of the Cranebrook Terrace of the Nepean River (Fig.l). StoGkton and Holland (1974), who described the site, obtained radiocarbon dates of 26,700 + 1700/1500 BP (GaK 3014) and >31,8OO BP (GaK 3445) for logs buried within the gravels. However, we now have reason to believe that these dates are minimum ages resulting from the contamination of ancient wood with younger carbon mobile within the groundwater. In this paper GCN and RWY are responsible for the geomorphology, stratigraphy and chronology, EDS for the archaeology. Because the artefacts were not found in a clearly defined habitation site, but rather were scattered throughout what was possibly a reworked gravel unit, their authenticity has not been universally accepted, although it has never been seriously questioned. Yet it was not the intention of Stockton and Holland (1974) to critically establish the absolute authenticity or antiquity of early human occupation of the Cranebrook Terrace. Their paper examined 'sites ranging across the Blue Mountains'. The Cranebrook Terrace is essentially outside their study location and was poorly dated. This most eastern aspect of their work has not been followed up except for a recent paper on an alluvial site nearby (Kohen et al 1984).

Thyroid Hormones, Membranes and the Evolution of Endothermy

Abstract: Marking the end of the “age of the reptiles” and the beginning of the “age of the mammals” at approximately 65 million years ago, is a geological layer rich in the unusual element, iridium. It has been proposed that this layer of iridium is the remains of an extraterrestrial body that hit the earth and changed the earth’s climate, resulting in both a short term cooling effect (possibly measured in months) as well as long term changes in the climate, such as greater latitudinal variation in temperature and the beginning of greater temporal variation in climate (the ushering in of seasons). Although the first mammals arose 200 million years ago, for the first two-thirds of their evolutionary history they were not the dominant land fauna and it was only after the extinction of the dominant reptile fauna at about 65 million years ago that they began an explosive adaptive radiation that led, among other species, to ourselves, a species through which evolution has begun to become conscious of itself.

Meta-Analysis of Pragmatic and Theoretical Research: A Critique

Abstract: Meta-analysis refers to a set of statistical procedures used to summarize and integrate many empirical studies that focus on one issue. This numerical method of integrating research findings is said to be superior to the narrative type of reviews because it is more objective, reliable, and rigorous. Moreover, the meta-analytic approach is supposedly capable of resolving research controversies, strengthening empirical hypotheses, and discovering new relationships among variables. In this study, these claims are examined and found to be wanting. Some objections to the use of meta-analysis as a means of substantiating theoretical assertions are raised with reference to the rationale of experimentation and to how knowledge evolves. It is concluded that it is inappropriate to apply meta-analysis to integrate theoretical research.