Showing papers by "Curtin University published in 2008"

The Structure of Glycosaminoglycans and their Interactions with Proteins

Abstract: Glycosaminoglycans (GAGs) are important complex carbohydrates that participate in many biological processes through the regulation of their various protein partners. Biochemical, structural biology and molecular modelling approaches have assisted in understanding the molecular basis of such interactions, creating an opportunity to capitalize on the large structural diversity of GAGs in the discovery of new drugs. The complexity of GAG–protein interactions is in part due to the conformational flexibility and underlying sulphation patterns of GAGs, the role of metal ions and the effect of pH on the affinity of binding. Current understanding of the structure of GAGs and their interactions with proteins is here reviewed: the basic structures and functions of GAGs and their proteoglycans, their clinical significance, the three-dimensional features of GAGs, their interactions with proteins and the molecular modelling of heparin binding sites and GAG–protein interactions. This review focuses on some key aspects of GAG structure–function relationships using classical examples that illustrate the specificity of GAG–protein interactions, such as growth factors, anti-thrombin, cytokines and cell adhesion molecules. New approaches to the development of GAG mimetics as possible new glycotherapeutics are also briefly covered.

The SIESTA method; developments and applicability.

Abstract: Recent developments in and around the SIESTA method of first-principles simulation of condensed matter are described and reviewed, with emphasis on (i) the applicability of the method for large and varied systems, (ii) efficient basis sets for the standards of accuracy of density-functional methods, (iii) new implementations, and (iv) extensions beyond ground-state calculations.

Zircon M257 ‐ a Homogeneous Natural Reference Material for the Ion Microprobe U‐Pb Analysis of Zircon

Abstract: We introduce and propose zircon M257 as a future reference material for the determination of zircon U-Pb ages by means of secondary ion mass spectrometry. This light brownish, flawless, cut gemstone specimen from Sri Lanka weighed 5.14 g (25.7 carats). Zircon M257 has TIMS-determined, mean isotopic ratios (2s uncertainties) of 0.09100 ± 0.00003 for 206pb/238U and 0.7392 ± 0.0003 for 207pb/235U. Its 206pb/238U age is 561.3 ± 0.3 Ma (unweighted mean, uncertainty quoted at the 95% confidence level); the U-Pb system is concordant within uncertainty of decay constants. Zircon M257 contains ∼ 840 μg g−1 U (Th/U ∼ 0.27). The material exhibits remarkably low heterogeneity, with a virtual absence of any internal textures even in cathodoluminescence images. The uniform, moderate degree of radiation damage (estimated from the expansion of unit-cell parameters, broadening of Raman spectral parameters and density) corresponds well, within the “Sri Lankan trends”, with actinide concentrations, U-Pb age, and the calculated alpha fluence of 1.66 × 1018 g−1. This, and a (U+Th)/He age of 419 ± 9 Ma (2s), enables us to exclude any unusual thermal history or heat treatment, which could potentially have affected the retention of radiogenic Pb. The oxygen isotope ratio of this zircon is 13.9%o VSMOW suggesting a metamorphic genesis in a marble or calc-silicate skarn. Nous presentons et proposons a la communaute le zircon M257 qui pourrait devenir un materiau de reference pour la determination des âges U-Pb sur zircon par spectrometrie de masse a ions secondaires (SIMS). Ce specimen scie d'une gemme brun clair, sans defauts, provenant du Sri Lanka, pese 5.14 g (25.7 carats). Les moyennes des rapports isotopiques (et les incertitudes associees 2s) mesurees par TIMS sur ce zircon M257 sont 0.09100 ± 0.00003 en 206pb/238U et 0.7392 ± 0.0003 en 207pb/235U. Son âge 206pb/238U est de 561.3 ± 0.3 Ma (moyenne non ponderee, incertitude: 95% intervalle de confiance); le systeme U-Pb y est concordant, aux erreurs sur les constantes de desintegration pres. Le zircon M257 contient ∼ 840 μg g−1 U (Th/U ∼ 0.27). Ce materiel montre de tres faibles heterogeneites, avec une quasi absence de textures internes, meme a I'examen par cathodoluminescence. Le degre de dommage lie aux radiations (estime par I'expansion des parametres de la cellule unitaire, I'elargissement des parametres des spectres Raman et la densite) est modere et uniforme. II se correle bien, (sur I'alignement “Sri Lanka”) avec les concentrations en actinides, I'âge U-Pb et la fluence calculee de 1.66 × 1018 g−1 Ceci, couplea son âge (U+Th)/He de 419 ± 9 Ma (2s), nous permet d'exclure I'existence d'evenement thermique passe, ou de traitement par la chaleur, qui aurait potentiellement pu affecter le processus de retention de Pb radiogenique. Le rapport isotopique de I'oxygene de ce zircon est 13.9%o VSMOW, suggerant une genese par metamorphisme, au sein d'un marbre ou d'un skarn calco-silicate.

Reassessing the first appearance of eukaryotes and cyanobacteria

Abstract: The oldest widely accepted evidence for oxygenic photosynthesis on Earth comes from hydro-carbon biomarkers extracted from 2.7-billion-year-old shales in the Pilbara Craton of Australia, thought to be evidence of eukaryotes and photosynthetic cyanobacteria. This early date has caused controversy because of the long delay between this earliest appearance of oxygen-producing cyanobacteria and the 'great oxidation event' that caused the rise of atmospheric oxygen some 300 million years later. New work by Rasmussen et al. shows that the organic biomarkers are not of Archaean age and must have entered the rocks later, some time after about 2.2 billion years ago. The earliest unambiguous fossil evidence for eukaryotes and cyanobacteria thus reverts to 1.78–1.68 and 2.15 billion years, respectively. The oldest widely accepted evidence for oxygenic photosynthesis comes from hydrocarbon biomarkers extracted from 2.7-billion-year-old shales in the Pilbara Craton, Australia, thought to be evidence of eukaryotes and photosynthetic cyanobacteria. But evidence now shows that the organic biomarkers were not indigenous to the rocks containing them, and must have entered the rocks after ∼2.2 Gyr ago. The earliest unambiguous fossil evidence for eukaryotes and cyanobacteria thus reverts to 1.78–1.68 and 2.15 Gyr, respectively. The evolution of oxygenic photosynthesis had a profound impact on the Earth’s surface chemistry, leading to a sharp rise in atmospheric oxygen between 2.45 and 2.32 billion years (Gyr) ago1,2 and the onset of extreme ice ages3. The oldest widely accepted evidence for oxygenic photosynthesis has come from hydrocarbons extracted from ∼2.7-Gyr-old shales in the Pilbara Craton, Australia, which contain traces of biomarkers (molecular fossils) indicative of eukaryotes and suggestive of oxygen-producing cyanobacteria4,5,6,7. The soluble hydrocarbons were interpreted to be indigenous and syngenetic despite metamorphic alteration and extreme enrichment (10–20‰) of 13C relative to bulk sedimentary organic matter5,8. Here we present micrometre-scale, in situ 13C/12C measurements of pyrobitumen (thermally altered petroleum) and kerogen from these metamorphosed shales, including samples that originally yielded biomarkers. Our results show that both kerogen and pyrobitumen are strongly depleted in 13C, indicating that indigenous petroleum is 10–20‰ lighter than the extracted hydrocarbons5. These results are inconsistent with an indigenous origin for the biomarkers. Whatever their origin, the biomarkers must have entered the rock after peak metamorphism ∼2.2 Gyr ago9 and thus do not provide evidence for the existence of eukaryotes and cyanobacteria in the Archaean eon. The oldest fossil evidence for eukaryotes and cyanobacteria therefore reverts to 1.78–1.68 Gyr ago and ∼2.15 Gyr ago10,11, respectively. Our results eliminate the evidence for oxygenic photosynthesis ∼2.7 Gyr ago and exclude previous biomarker evidence for a long delay (∼300 million years) between the appearance of oxygen-producing cyanobacteria and the rise in atmospheric oxygen 2.45–2.32 Gyr ago1.

Some Recent Advances in Hydrolysis of Biomass in Hot-Compressed Water and Its Comparisons with Other Hydrolysis Methods†

Abstract: Biomass hydrolysis extracts, particularly sugars and other useful derivatives, are important products for further conversion to produce biofuels. The past 2 decades have witnessed significant research and development activities using hot-compressed water for the hydrolysis and conversion of cellulose, hemicellulose, and lignocellulosic biomass materials. This paper summarizes the decomposition mechanisms and hydrolysis products of these materials under various conditions in hot-compressed water. Key factors determining hydrolysis behavior in hot-compressed water are also discussed. Comparisons are made between hydrolysis in hot-compressed water and hydrolysis using other technologies, including acid hydrolysis, alkaline hydrolysis, and enzymatic hydrolysis. Advantages, disadvantages, typical operation conditions, products properties, and applicability are summarized. Key research issues on hydrolysis in hot-compressed water are identified, and future research prospects to further improve the technology ar...

Hopping hotspots: global shifts in marine biodiversity.

Abstract: Hotspots of high species diversity are a prominent feature of modern global biodiversity patterns. Fossil and molecular evidence is starting to reveal the history of these hotspots. There have been at least three marine biodiversity hotspots during the past 50 million years. They have moved across almost half the globe, with their timing and locations coinciding with major tectonic events. The birth and death of successive hotspots highlights the link between environmental change and biodiversity patterns. The antiquity of the taxa in the modern Indo-Australian Archipelago hotspot emphasizes the role of pre-Pleistocene events in shaping modern diversity patterns.

Science with ASKAP: The Australian square-kilometre-array pathfinder

Abstract: The future of cm and m-wave astronomy lies with the Square Kilometre Array (SKA), a telescope under development by a consortium of 17 countries. The SKA will be 50 times more sensitive than any existing radio facility. A majority of the key science for the SKA will be addressed through large-area imaging of the Universe at frequencies from 300 MHz to a few GHz. The Australian SKA Pathfinder (ASKAP) is aimed squarely in this frequency range, and achieves instantaneous wide-area imaging through the development and deployment of phase-array feed systems on parabolic reflectors. This large field-of-view makes ASKAP an unprecedented synoptic telescope poised to achieve substantial advances in SKA key science. The central core of ASKAP will be located at the Murchison Radio Observatory in inland Western Australia, one of the most radio-quiet locations on the Earth and one of the sites selected by the international community as a potential location for the SKA. Following an introductory description of ASKAP, this document contains 7 chapters describing specific science programmes for ASKAP. In summary, the goals of these programmes are as follows: The combination of location, technological innovation and scientific program will ensure that ASKAP will be a world-leading radio astronomy facility, closely aligned with the scientific and technical direction of the SKA. A brief summary chapter emphasizes the point, and considers discovery space.

Thermobarometric modelling of zircon and monazite growth in melt-bearing systems: examples using model metapelitic and metapsammitic granulites

Abstract: U–Pb age data collected from zircon and monazite are used to draw fundamental inferences about tectonic processes in the Earth. Despite the emphasis placed on zircon and monazite ages, the understanding of how to relate the timing of growth of zircon and monazite to an evolving rock system remains in its infancy. In addition, few studies have presented large datasets of geochronological data from zircon and monazite occurring in the same metamorphic rock sample. Such information is crucial for understanding the growth of zircon relative to monazite in a systematic and predictive manner, as per this study. The data that exist support the generally held conception that zircon ages tend to be older than monazite ages within the same rock. Here experimental data for zircon and monazite saturation in melt-bearing rocks are integrated with phase diagram calculations. The calculations constrain the dissolution and growth behaviour of zircon and monazite with respect to evolving pressure, temperature and silicate mineral assemblages in high-grade, melt-bearing, metasedimentary rocks. Several key results emerge from this modelling: first, that in aluminous metapelitic rocks (i.e. garnet + cordierite + sillimanite assemblages), zircon ages are older than monazite ages in the same rock; second, that the growth rate of accessory minerals is nonlinear and much higher at and near saturation than at lower temperatures; and third, that the difference in zircon and monazite ages from the same rock may be ascribed to differences in the temperature(s) at which zircon and monazite grow rather than differences in closure temperature systematics. Using our methodology the cooling rate of granulites from the Reynolds Range, central Australia, have been constrained at ∼4 °C Myr−1. This study serves as a first-pass template on which further research in applying the technique to a field study can be based.

Eight key issues for the decision support systems discipline

Abstract: This paper integrates a number of strands of a long-term project that is critically analysing the academic field of decision support systems (DSS). The project is based on the content analysis of 1093 DSS articles published in 14 major journals from 1990 to 2004. An examination of the findings of each part of the project yields eight key issues that the DSS field should address for it to continue to play an important part in information systems scholarship. These eight issues are: the relevance of DSS research, DSS research methods and paradigms, the judgement and decision-making theoretical foundations of DSS research, the role of the IT artifact in DSS research, the funding of DSS research, inertia and conservatism of DSS research agendas, DSS exposure in general ''A'' journals, and discipline coherence. The discussion of each issue is based on the data derived from the article content analysis. A number of suggestions are made for the improvement of DSS research. These relate to case study research, design science, professional relevance, industry funding, theoretical foundations, data warehousing, and business intelligence. The suggestions should help DSS researchers construct high quality research agendas that are relevant and rigorous.

Ti-in-zircon thermometry: applications and limitations

Abstract: The titanium concentrations of 484 zircons with U-Pb ages of ∼1 Ma to 4.4 Ga were measured by ion microprobe. Samples come from 45 different igneous rocks (365 zircons), as well as zircon megacrysts (84) from kimberlite, Early Archean detrital zircons (32), and zircon reference materials (3). Samples were chosen to represent a large range of igneous rock compositions. Most of the zircons contain less than 20 ppm Ti. Apparent temperatures for zircon crystallization were calculated using the Ti-in-zircon thermometer (Watson et al. 2006, Contrib Mineral Petrol 151:413–433) without making corrections for reduced oxide activities (e.g., TiO2 or SiO2), or variable pressure. Average apparent Ti-in-zircon temperatures range from 500° to 850°C, and are lower than either zircon saturation temperatures (for granitic rocks) or predicted crystallization temperatures of evolved melts (∼15% melt residue for mafic rocks). Temperatures average: 653 ± 124°C (2 standard deviations, 60 zircons) for felsic to intermediate igneous rocks, 758 ± 111°C (261 zircons) for mafic rocks, and 758 ± 98°C (84 zircons) for mantle megacrysts from kimberlite. Individually, the effects of reduced \( a_{{\rm TiO}_{2}}\) or \( a_{{\rm SiO}_{2}}\), variable pressure, deviations from Henry’s Law, and subsolidus Ti exchange are insufficient to explain the seemingly low temperatures for zircon crystallization in igneous rocks. MELTs calculations show that mafic magmas can evolve to hydrous melts with significantly lower crystallization temperature for the last 10–15% melt residue than that of the main rock. While some magmatic zircons surely form in such late hydrous melts, low apparent temperatures are found in zircons that are included within phenocrysts or glass showing that those zircons are not from evolved residue melts. Intracrystalline variability in Ti concentration, in excess of analytical precision, is observed for nearly all zircons that were analyzed more than once. However, there is no systematic change in Ti content from core to rim, or correlation with zoning, age, U content, Th/U ratio, or concordance in U-Pb age. Thus, it is likely that other variables, in addition to temperature and \( a_{{\rm TiO}_{2}}\), are important in controlling the Ti content of zircon. The Ti contents of igneous zircons from different rock types worldwide overlap significantly. However, on a more restricted regional scale, apparent Ti-in-zircon temperatures correlate with whole-rock SiO2 and HfO2 for plutonic rocks of the Sierra Nevada batholith, averaging 750°C at 50 wt.% SiO2 and 600°C at 75 wt.%. Among felsic plutons in the Sierra, peraluminous granites average 610 ± 88°C, while metaluminous rocks average 694 ± 94°C. Detrital zircons from the Jack Hills, Western Australia with ages from 4.4 to 4.0 Ga have apparent temperatures of 717 ± 108°C, which are intermediate between values for felsic rocks and those for mafic rocks. Although some mafic zircons have higher Ti content, values for Early Archean detrital zircons from a proposed granitic provenance are similar to zircons from many mafic rocks, including anorthosites from the Adirondack Mts (709 ± 76°C). Furthermore, the Jack Hills zircon apparent Ti-temperatures are significantly higher than measured values for peraluminous granites (610 ± 88°C). Thus the Ti concentration in detrital zircons and apparent Ti-in-zircon temperatures are not sufficient to independently identify parent melt composition.

Strategies for Design Science Research Evaluation

Abstract: Seminal works in the application of design science research (DSR) in IS emphasize the importance of evaluation. However, discussion of evaluation activities and methods is limited and typically assumes an ex post perspective, in which evaluation occurs after the construction of an IS artifact. Such perspectives can assume that the evaluation is an empirical process and its methods can be selected in the same way as empirical research methods. In this paper, we analyze a broader range of evaluation strategies, which includes ex ante (prior to artifact construction) evaluation. This broader view is developed as a strategic DSR evaluation framework, which expands evaluation choices for IS DSR researchers, and also adds emphasis to strategies for evaluating design processes in addition to design products, using well-known quality criteria as an important asset. The framework encompasses both ex ante and ex post orientations as well as naturalistic settings (e.g., case studies) and artificial settings (e.g., lab experiments) for DSR evaluation. The framework proposed offers a strategic view of DSR evaluation that is useful in analyzing published studies, and also in surfacing the evaluation opportunities that present themselves to IS DSR researchers.

Customer equity drivers and future sales

Abstract: Research on linking operational marketing inputs to customer attitudes and customer behavior has been gaining significance concomitant with the growing recognition that customers are market-based assets. In response to this, researchers and practitioners have proposed several conceptual models. Despite recent advances in research, the results are still inconclusive as to the relationship between customer attitude and future sales. A reason for this could be due to the paucity of studies combining survey-based data with behavioral data to understand better the drivers of customer behavior. With that in mind, the authors investigate the effects of customer perceptions of key marketing actions on customer attitudes and actual customer behavior as reflected by future sales. The authors propose that customer perceptions of value, brand, and relationship—“customer equity drivers”—affect loyalty intentions and future sales. The results of the study, which is based on a sample of 5694 customers of a large European do-it-yourself retailer, suggest that customer equity drivers can significantly predict future sales, even after the authors control for the current sales level.

Corporate social reporting and board representation: evidence from the Kenyan banking sector

Abstract: The paper examines the influence of gender and board representation on communication of corporate social reporting by Kenyan banks. The descriptive statistical analysis reveals that the level of corporate social disclosure by Kenyan banks is low with a mean of 15%, indicating that disclosure of corporate governance information is not of primary concern to Kenyan banks. In particular, there is a complete lack of disclosure on the categories of Recruitments, Employment of Special Groups, Assistance to Retiring Employees, Employees Productivity and Turnover. The results of multiple regression analysis indicate that board representation can fundamentally improve corporate communication. A higher level of women representation and independent directors greatly improves disclosure.

A four category scheme for coding and assessing the level of reflection in written work

Abstract: Where courses have as an aim the promotion of reflective practice, it will enhance the achievement of the goal if the level of reflective thinking is assessed. To do this in a satisfactory way requires a reliable protocol for assessing the level of reflection in written work. This article presents a protocol that can be used to guide the allocation of work to four categories, namely: habitual action/non‐reflection, understanding, reflection, and critical reflection. Intermediate categories can also be used. Detailed descriptors of each category to guide the process are provided. The protocol was tested by four assessors independently using it to grade a set of written work, and very good agreement was obtained.

Mesozoic decratonization of the North China block

Abstract: Cratons are old, stable parts of the continental crust that have survived at least since Proterozoic time and have not undergone strong magmatism or tectonism since their stabilization. Traditionally, the growth of continental crust in the North China craton is considered to have been complete by Paleoproterozoic time, Phanerozoic events being largely restricted to surrounding orogenic belts. However, the eastern part of the North China craton contains large volumes of Mesozoic igneous rocks, with widespread metamorphic core complexes and pull-apart basins. Hf isotope compositions of magmatic zircon grains from igneous rocks in the Liaodong Peninsula indicate that widespread late Mesozoic granitoids formed by partial melting of ancient crust, but with significant input of a mantle component via magma mixing and crustal assimilation. This magmatism has resulted from removal and modification of lithospheric mantle, accompanied by asthenospheric upwelling. The Hf isotopic signatures thus record the addition of juvenile crust beneath the eastern part of the North China craton, which appears related to major extension and possibly slab rollback of the Pacific plate. Whatever the mechanism, it is apparent that since ca. 200 Ma, ancient lithosphere beneath the eastern North China craton has been progressively reactivated and replaced, resulting in “decratonization.” Tertiary to Holocene volcanism in the area and major subsidence around the Gulf of Bohai suggest that the effects of the process are continuing. Similar processes probably operated in the geological past, leading to significant modification of continental crust and requiring reconsideration of mechanisms for continental breakup and dispersal and of continental growth rates.

Learning Environment, Attitudes and Achievement among Middle-school Science Students Using Inquiry-based Laboratory Activities

Abstract: This study compared inquiry and non-inquiry laboratory teaching in terms of students’ perceptions of the classroom learning environment, attitudes toward science, and achievement among middle-school physical science students. Learning environment and attitude scales were found to be valid and related to each other for a sample of 1,434 students in 71 classes. For a subsample of 165 students in 8 classes, inquiry instruction promoted more student cohesiveness than non-inquiry instruction (effect size of one-third of a standard deviation), and inquiry-based laboratory activities were found to be differentially effective for male and female students.

Conceptual change: a discussion of theoretical, methodological and practical challenges for science education

Abstract: Conceptual change views of teaching and learning processes in science, and also in various other content domains, have played a significant role in research on teaching and learning as well as in instructional design since the late 1970s. An important issue is whether conceptual change can provide a powerful framework for improving instructional practice in such a way that students’ levels of scientific literacy are significantly increased. In this article, the first section provides an overview on the development of conceptual change perspectives. In sections two to six, we examine the different ways that researchers have facilitated the collection of data and empirically evaluated learning as conceptual change based on these different theoretical perspectives. In section seven, we identify key issues of conceptual change with a deliberate emphasis on their contribution to improve instructional practice and conclude the article by posing challenges at theoretical, methodological and practical levels. We contend that conceptual change perspectives still have the potential to significantly improve instructional practice. However, it becomes also evident that actual practice is far from what conceptual change perspectives propose and that change of this practice will be a rather difficult and long-lasting process.

Adaptive Reuse and Sustainability of Commercial Buildings

Abstract: Purpose – To investigate the viability of adaptive reuse of commercial buildings and the impact it has on the sustainability of existing built environment in Western Australia.Design/methodology/approach – A survey of building owners in Western Australia and a review of literature concerning adaptive reuse of commercial buildings.Findings – The concept of adaptation is supported by building owners and there is a strong intuition/perception that adaptive reuse serves the key concepts of sustainability. Building owners are considering adaptive reuse as a viable option to demolition and redevelopment of existing facilities.Research limitations/implications – The use of a structured questionnaire limits the depth of responses in the study. A follow up study using interviews would allow further because it does not allow probing, prompting and clarification of the issues addressed.Practical implications – Results from this research has implications for building owners and managers as it will eventually provide ...

Social isolation and loneliness among older people: issues and future challenges in community and residential settings.

Abstract: Although often associated with older age, loneliness and social isolation are not well understood in terms of their prevalence, risk and protective factors. Evidence suggests that only a minority of community-dwelling older people are "severely" lonely or isolated, however a number of factors need to be considered to fully understand the extent and significance of the problem. Community-based studies have identified a variety of risk factors for loneliness/isolation including widowhood, no (surviving) children, living alone, deteriorating health, and life events (eg, loss and bereavement). Having a confidant has been identified as a protective factor for loneliness. However, evidence is often unclear or inconclusive, especially within residential settings. We identified the need to conduct more residential care-focused research; the importance of addressing a variety of methodological concerns; and the need for practitioners to develop intervention programs that are appropriately targeted, evidence-based and evaluated.

Joint learning and dictionary construction for pattern recognition

Abstract: We propose a joint representation and classification framework that achieves the dual goal of finding the most discriminative sparse overcomplete encoding and optimal classifier parameters. Formulating an optimization problem that combines the objective function of the classification with the representation error of both labeled and unlabeled data, constrained by sparsity, we propose an algorithm that alternates between solving for subsets of parameters, whilst preserving the sparsity. The method is then evaluated over two important classification problems in computer vision: object categorization of natural images using the Caltech 101 database and face recognition using the Extended Yale B face database. The results show that the proposed method is competitive against other recently proposed sparse overcomplete counterparts and considerably outperforms many recently proposed face recognition techniques when the number training samples is small.