Showing papers by "Macquarie University published in 2007"

The Chlamydomonas Genome Reveals the Evolution of Key Animal and Plant Functions

Abstract: Chlamydomonas reinhardtii is a unicellular green alga whose lineage diverged from land plants over 1 billion years ago. It is a model system for studying chloroplast-based photosynthesis, as well as the structure, assembly, and function of eukaryotic flagella (cilia), which were inherited from the common ancestor of plants and animals, but lost in land plants. We sequenced the approximately 120-megabase nuclear genome of Chlamydomonas and performed comparative phylogenomic analyses, identifying genes encoding uncharacterized proteins that are likely associated with the function and biogenesis of chloroplasts or eukaryotic flagella. Analyses of the Chlamydomonas genome advance our understanding of the ancestral eukaryotic cell, reveal previously unknown genes associated with photosynthetic and flagellar functions, and establish links between ciliopathy and the composition and function of flagella.

Gaze cueing of attention: visual attention, social cognition, and individual differences.

Abstract: During social interactions, people's eyes convey a wealth of information about their direction of attention and their emotional and mental states. This review aims to provide a comprehensive overview of past and current research into the perception of gaze behavior and its effect on the observer. This encompasses the perception of gaze direction and its influence on perception of the other person, as well as gaze-following behavior such as joint attention, in infant, adult, and clinical populations. Particular focus is given to the gaze-cueing paradigm that has been used to investigate the mechanisms of joint attention. The contribution of this paradigm has been significant and will likely continue to advance knowledge across diverse fields within psychology and neuroscience.

Amphibole “sponge” in arc crust?

Abstract: Pressure-temperature-time paths followed by arc magmas ascending through the lithosphere dictate the phase assemblage that crystallizes, and hence the compositions of liquid fractionates. Here we use La/Yb and Dy/Yb versus SiO2 relationships from selected volcanoes to show that amphibole is an important mineral during differentiation of arc magma. Production of intermediate and silicic arc magmas occurs as magmas stall and cool in the mid-lower crust, where amphibole is stable. Because amphibole is rarely a phenocryst phase, we term this “cryptic amphibole fractionation.” If this process is as widespread as our investigation suggests, then (1) amphibole cumulates may act as an effective filter for water dissolved in mantle-derived magmas; (2) amphibole cumulates may act as a fertile source of intracrustal melts and fluids; and (3) recycling of amphibole cumulates has the potential to return incompatible trace elements and water to the mantle.

Efficient Quantum Algorithms for Simulating Sparse Hamiltonians

Abstract: We present an efficient quantum algorithm for simulating the evolution of a quantum state for a sparse Hamiltonian H over a given time t in terms of a procedure for computing the matrix entries of H. In particular, when H acts on n qubits, has at most a constant number of nonzero entries in each row/column, and ||H|| is bounded by a constant, we may select any positive integer k such that the simulation requires O((log*n)t1+1/2k) accesses to matrix entries of H. We also show that the temporal scaling cannot be significantly improved beyond this, because sublinear time scaling is not possible.

Evaluation of the AR4 Climate Models’ Simulated Daily Maximum Temperature, Minimum Temperature, and Precipitation over Australia Using Probability Density Functions

Abstract: The coupled climate models used in the Fourth Assessment Report of the Intergovernmental Panel on Climate Change are evaluated The evaluation is focused on 12 regions of Australia for the daily simulation of precipitation, minimum temperature, and maximum temperature The evaluation is based on probability density functions and a simple quantitative measure of how well each climate model can capture the observed probability density functions for each variable and each region is introduced Across all three variables, the coupled climate models perform better than expected Precipitation is simulated reasonably by most and very well by a small number of models, although the problem with excessive drizzle is apparent in most models Averaged over Australia, 3 of the 14 climate models capture more than 80% of the observed probability density functions for precipitation Minimum temperature is simulated well, with 10 of the 13 climate models capturing more than 80% of the observed probability densit

The RAVE survey: constraining the local Galactic escape speed

Abstract: We report new constraints on the local escape speed of our Galaxy. Our analysis is based on a sample of high-velocity stars from the RAVE survey and two previously published data sets. We use cosmological simulations of disc galaxy formation to motivate our assumptions on the shape of the velocity distribution, allowing for a significantly more precise measurement of the escape velocity compared to previous studies. We find that the escape velocity lies within the range 498

Entanglement-free Heisenberg-limited phase estimation

Abstract: Measurement underpins all quantitative science. A key example is the measurement of optical phase, used in length metrology and many other applications. Advances in precision measurement have consistently led to important scientific discoveries. At the fundamental level, measurement precision is limited by the number N of quantum resources (such as photons) that are used. Standard measurement schemes, using each resource independently, lead to a phase uncertainty that scales as 1/square root N-known as the standard quantum limit. However, it has long been conjectured that it should be possible to achieve a precision limited only by the Heisenberg uncertainty principle, dramatically improving the scaling to 1/N (ref. 3). It is commonly thought that achieving this improvement requires the use of exotic quantum entangled states, such as the NOON state. These states are extremely difficult to generate. Measurement schemes with counted photons or ions have been performed with N < or = 6 (refs 6-15), but few have surpassed the standard quantum limit and none have shown Heisenberg-limited scaling. Here we demonstrate experimentally a Heisenberg-limited phase estimation procedure. We replace entangled input states with multiple applications of the phase shift on unentangled single-photon states. We generalize Kitaev's phase estimation algorithm using adaptive measurement theory to achieve a standard deviation scaling at the Heisenberg limit. For the largest number of resources used (N = 378), we estimate an unknown phase with a variance more than 10 dB below the standard quantum limit; achieving this variance would require more than 4,000 resources using standard interferometry. Our results represent a drastic reduction in the complexity of achieving quantum-enhanced measurement precision.

Buffers, barriers and blankets : the (dis)connectivity of catchment-scale sediment cascades

Abstract: Catchment configuration and the nature of connectivity within and between landscape compartments affect the operation of sediment cascades and geomorphic responses to disturbance events of differing magnitude and frequency. This paper introduces the concept of landform impediments, termed buffers, barriers and blankets, that impede sediment conveyance by limiting the connectivity between landscape compartments. Buffers restrict sediment delivery to channels, barriers inhibit sediment movement along channels, and blankets drape channel or floodplain surfaces affecting the accessibility of sediment to entrainment. These features operate as a series of switches which turn on/off processes of sediment delivery, determining the effective catchment area at any given time. Using previously documented examples, the role of these features in affecting the operation of sediment cascades in a low relief, passive landscape setting such as the Australian landmass is contrasted to examples from high relief, uplifting settings in New Zealand. The Australian examples are further explored by examining how changes to landscape connectivity brought about by human disturbance since European settlement have impacted upon landscape sensitivity and prospects for river recovery. This approach to analysis of impediments to sediment conveyance is generic and can be applied in any environmental setting.

The international entrepreneurial dynamics of accelerated internationalisation

Abstract: The initial stages of internationalisation, prior to firms having established their definitive sources of advantage, remain the relatively unexplored area of the international business (IB) literature. At these early stages, where firms are seeking to establish themselves, and new multinational firms are appearing to exploit new opportunities created by globalisation, the entrepreneurial aspects of internationalisation come to the fore. In this paper we aim to delineate an emerging field of IB scholarship: we use the appearance of international new ventures, and the phenomenon of accelerated internationalisation that they feature, to identify a set of issues that has slipped through the net of some of the existing IB frameworks. We propose that the salient features of accelerated and early internationalisation by the newly internationalising firm are best captured in a framework that is found at the intersection of entrepreneurial and internationalisation perspectives, which we propose be known as international entrepreneurial dynamics. We discuss such a framework in terms of entry points and pathways mapped by firms as they probe the IB arena, and the key factors that impinge on behaviour and strategic choices. In line with recent developments in the entrepreneurship literature, these are grouped into three milestones of entrepreneurial processes that extend across national boundaries: (1) the discovery of new opportunities; (2) the deployment of resources in the exploitation of these opportunities; and (3) the engagement with competitors. Implications for MNE and internationalisation theory are discussed.

Beyond ‘Do No Harm’: The Challenge of Constructing Ethical Relationships in Refugee Research

Abstract: This paper highlights some of the central ethical challenges involved in undertaking social science research with refugees in conflict and crisis situations. It focuses on two main sets of challenges: first the difficulties of constructing an ethical consent process and obtaining genuinely informed consent; and second taking fully into account and responding to refugee participants capacities for autonomy. The authors also discuss the challenges involved in applying the central normative principles governing ethics review processes-the principles of beneficence integrity respect for persons autonomy and justice-to the context of refugee research. It is argued that researchers should seek ways to move beyond harm minimization as a standard for ethical research and recognize an obligation to design and conduct research projects that aim to bring about reciprocal benefits for refugee participants and/or communities. Some of the methodological issues raised by this analysis are discussed in the conclusion. (authors)

Public Sector to Public Services: 20 Years of 'Contextual' Accounting Research

Abstract: Purpose - The purpose of this paper is to review and critique the field of public sector accounting research. Many nation states deliver essential public services. In recent times, many of these nations have been involved in programmes of "modernisation", which, in part, means that these public services now are significantly managed, delivered and governed by private and third sector organisations. Design/methodology/approach - The paper employs a literature-based analysis and critique of public sector accounting articles published in the selected journals from 1992 to 2006. From this, a descriptive meta-analysis of the characteristics of the research will be discussed. Finally, a conceptual analysis of the selected literature will be used to evaluate the field and address a possible future research agenda. Findings - The descriptive analysis highlights that among the research papers reviewed several interesting patterns emerged concerning public service research. Also, the dominance of Australasia and UK research was noted. The extent of research in different levels of government/jurisdiction indicated that the majority of research was organisationally based. Finally, when the various functional types of accounting are considered, management accounting remained the most researched area of interest. Research limitations/implications - The paper only considered research within eight selected journals and over the period 1992 to 2006. Therefore, for instance, US mainstream public sector accounting research has not been reviewed. Originality/value - The main implications of the paper are that "contextual" public service accounting research has a strong tradition and, through the process of reflection and critique of the body of work, several important insights are provided in order to highlight areas for further research and policy development.

Treating Anxiety Disorders in Children with High Functioning Autism Spectrum Disorders: A Controlled Trial

Abstract: A family-based, cognitive behavioural treatment for anxiety in 47 children with comorbid anxiety disorders and High Functioning Autism Spectrum Disorder (HFA) was evaluated. Treatment involved 12 weekly group sessions and was compared with a waiting list condition. Changes between pre- and post-treatment were examined using clinical interviews as well as child-, parent- and teacher-report measures. Following treatment, 71.4% of the treated participants no longer fulfilled diagnostic criteria for an anxiety disorder. Comparisons between the two conditions indicated significant reductions in anxiety symptoms as measured by self-report, parent report and teacher report. Discussion focuses on the implications for the use of cognitive behaviour therapy with HFA children, for theory of mind research and for further research on the treatment components.

Leaf trait relationships of native and invasive plants: community- and global-scale comparisons.

Abstract: Summary • Leaf carbon capture strategies of native and exotic invasive plants were compared by examining leaf traits and their scaling relationships at community and global scales • Community-level leaf trait data were obtained for 55 vascular plant species from nutrient-enriched and undisturbed bushland in Sydney, Australia. Global-scale leaf trait data were compiled from the literature for 75 native and 90 exotic invasive coexisting species. • At the community level, specific leaf area (SLA), foliar nitrogen and phosphorus (Nmass and Pmass) and N:P ratio were significantly higher for exotics at disturbed sites compared with natives at undisturbed sites, with natives at disturbed sites being intermediate. SLA, Nmass and Pmass were positively correlated, with significant shifts in group means along a common standardized major axis (SMA) slope. At the global scale, invasives had significantly higher Nmass, Pmass, assimilation rate (Amass and Aarea) and leaf area ratio (LAR) than natives. All traits showed positive correlations, with significant shifts in group means along a common slope. For a given SLA, invasives had higher Amass (7.7%) and Nmass (28%). • Thus, exotic invasives do not have fundamentally different carbon capture strategies from natives but are positioned further along the leaf economics spectrum towards faster growth strategies. Species with leaf traits enabling rapid growth will be successful invaders when introduced to novel environments where resources are not limited.

Bayesian integration of spatial information

Abstract: Spatial judgments and actions are often based on multiple cues. The authors review a multitude of phenomena on the integration of spatial cues in diverse species to consider how nearly optimally animals combine the cues. Under the banner of Bayesian perception, cues are sometimes combined and weighted in a near optimal fashion. In other instances when cues are combined, how optimal the integration is might be unclear. Only 1 cue may be relied on, or cues may seem to compete with one another. The authors attempt to bring some order to the diversity by taking into account the subjective discrepancy in the dictates of multiple cues. When cues are too discrepant, it may be best to rely on 1 cue source. When cues are not too discrepant, it may be advantageous to combine cues. Such a dual principle provides an extended Bayesian framework for understanding the functional reasons for the integration of spatial cues.

Magnetic fields in protoplanetary disks

Abstract: Magnetic fields likely play a key role in the dynamics and evolution of protoplanetary disks. They have the potential to efficiently transport angular momentum by MHD turbulence or via the magnetocentrifugal acceleration of outflows from the disk surface. Magnetically-driven mixing has implications for disk chemistry and evolution of the grain population, and the effective viscous response of the disk determines whether planets migrate inwards or outwards. However, the weak ionisation of protoplanetary disks means that magnetic fields may not be able to effectively couple to the matter. I examine the magnetic diffusivity in a minimum solar nebula model and present calculations of the ionisation equilibrium and magnetic diffusivity as a function of height from the disk midplane at radii of 1 and 5 AU. Dust grains tend to suppress magnetic coupling by soaking up electrons and ions from the gas phase and reducing the conductivity of the gas by many orders of magnitude. However, once grains have grown to a few microns in size their effect starts to wane and magnetic fields can begin to couple to the gas even at the disk midplane. Because ions are generally decoupled from the magnetic field by neutral collisions while electrons are not, the Hall effect tends to dominate the diffusion of the magnetic field when it is able to partially couple to the gas, except at the disk surfaces where the low density of neutrals permits the ions to remain attached to the field lines. For a standard population of 0.1 μm grains the active surface layers have a combined column Σactive≈2 g cm−2 at 1 AU; by the time grains have aggregated to 3 μm, Σactive≈80 g cm−2. Ionisation in the active layers is dominated by stellar X-rays. In the absence of grains, X-rays maintain magnetic coupling to 10% of the disk material at 1 AU (i.e. Σactive≈150 g cm−2). At 5 AU the Σactive≈Σtotal once grains have aggregated to 1 μm in size.

Formal Proofs for the Security of Signcryption

Abstract: Signcryption is an asymmetric cryptographic method that provides simultaneously both message confidentiality and unforgeability at a low computational and communication overhead. In this paper we propose realistic security models for signcryption, which give the attacker power to choose both messages/signcryptexts as well as recipient/sender public keys when accessing the signcryption/unsigncryption oracles of attacked entities. We then show that Zheng's original signcryption scheme is secure in our confidentiality model relative to the Gap Diffie-Hellman problem and is secure in our unforgeability model relative to a Gap version of the discrete logarithm problem. All these results are shown in the random oracle model.

Corporate Reporting of Intellectual Capital: Evidence from UK Companies

Abstract: This paper reports the results of an empirical investigation into the intellectual capital reporting (ICR) practices of UK companies in four distinct sectors. It differs from prior ICR studies in that it analyses a wide range of external corporate reporting media for their IC content. It finds major differences between the intellectual capital elements reported in each sector studied, and finds an overall sector effect which is at variance with the expected overall sector effect. The study also finds that a range of corporate media were used for communicating intellectual capital information, and that the annual reports were not a good proxy for the proportion of disclosures across all corporate media.

Top management support: mantra or necessity?

Abstract: This research provides evidence that top management support is the most important critical success factor for project success and is not simply one of many factors. The finding is justified in the context of the project management literature and the IS factor research on project success. There are implications for practice because it appears that the conventional technical and project management advice has less impact on project success than previously thought. Boards and top managers may have to personally accept that they have more influence on whether a project succeeds or fails. 2008 Elsevier Ltd and IPMA. All rights reserved.

Australian Sign Language: Auslan: An Introduction to Sign Language Linguistics

Abstract: 1. Signed languages and linguistics 2. Auslan in social context 3. Auslan and other signed languages 4. Phonetics and phonology: the building blocks of signs 5. Morphology: sign formation and modification 6. Lexicon: the structure of Auslan vocabulary 7. Syntax: the structure of sentences in Auslan 8. Semantics and pragmatics: sign meaning and sentence meaning 9. Discourse: structure and use above the sentence 10. Issues in the study of signed languages.

Heritable and experiential effects on boldness in a tropical poeciliid

Abstract: Consistent differences in human behaviour are often explained with reference to personality traits. Recent evidence suggests that similar traits are widespread across the entire animal kingdom and that they may have substantial fitness consequences. One of the major components of personality is the shyness–boldness continuum. Little is known about the relative contributions of genes and the environment in the development of boldness in wild animal populations. Here, we bred wild-caught fish (Brachyraphis episcopi) collected from regions of high- and low-predation pressure, reared their offspring in the laboratory under varying conditions and tested boldness utilising an open-field paradigm. First-generation laboratory-reared fish showed similar behaviour to their wild parents suggesting that boldness has a heritable component. In addition, repeated chasing with a net increased boldness in both high- and low-predation offspring, showing that boldness is also heavily influenced by life experiences. Differences between males and females were also sustained in the laboratory-reared generation indicating that sex differences in boldness are also heritable. We discuss these results with reference to the potential underlying genetic and hormonal mechanisms as well as the environmental influences that may be responsible for expression of boldness in wild animals.