Showing papers in "Science & Engineering Faculty in 1999"

Ethylenedione : An intrinsically short-lived molecule

Abstract: Ethylenedione C2O2 is one of the elusive small molecules which have remained undetected even after numerous attempts with different experimental techniques, This is surprising, since theoretical studies predicted the triplet state of C2O2 to be stable towards spin-allowed dissociation and hence long-lived. Here we report a comprehensive study of charged and neutral ethylenedione by means of charge reversal and neutralization -reionization mass spectrometry. These experimental results, in conjunction with theoretical calculations, suggest that neutral ethylenedione is intrinsically short-lived rather than being elusive, Both the singlet and triplet states of C2O2 are predicted to dissociate rapidly into two ground-state CO molecules, and for the triplet species, this dissociation involves facile curve-crossing to the singlet surface within a few nanoseconds.

The salt dependence of DNA recognition by NF-kappaB p50 : a detailed kinetic analysis of the effects on affinityand specificity

Abstract: *This article is free to read on the publisher's website* The binding kinetics of NF-kappaB p50 to the Ig-kappaB site and to a DNA duplex with no specific binding site were determined under varying conditions of potassium chloride concentration using a surface plasmonresonance biosensor. Association and dissociation rate constants were measured enabling calculation of the dissociation constants. Under previously established high affinity buffer conditions, the k a for both sequences was in the order of 10(7) M-1s-1whilst the k d values varied 600-fold in a sequence-dependent manner between 10(-1) and 10(-4 )s-1, suggesting that the selectivity of p50 for different sequences is mediated primarily through sequence-dependent dissociation rates. The calculated K D value for the Ig-kappaB sequence was 16 pM, whilst the K D for the non-specific sequence was 9.9 nM. As the ionic strength increased to levels which are closer to that of the cellular environment, the binding of p50 to the non-specific sequence was abolished whilst the specific affinity dropped to nanomolar levels. From these results, a mechanism is proposed in which p50 binds specific sequences with high affinity whilst binding non-specific sequences weakly enough to allow efficient searching of the DNA.

On the realization of the current-driven dust ion-acoustic instability

Abstract: The current-driven dust ion-acoustic instability in a collisional dusty plasma is studied. The effects of dust-charge variation, electron and ion capture by the dust grains, as well as various dissipative mechanisms leading to the changes of the particles momenta, are taken into account. It is shown that the threshold for the excitation of the dust ion-acoustic waves can be high because of the large dissipation rate induced by the dusts. © 1999 American Institute of Physics.

Construction of interstellar cumulenes and heterocumulenes : Mass spectrometric studies

Abstract: The last few years have brought an increasing interest in the chemistry of rite interstellar and circumstellar environs. Many of the molecular species discovered in remote galactic regions have been dubbed 'non-terrestrial' because of their unique structures (Thaddeus et al, 1993). These findings have provided a challenge to chemists in many differing fields to attempt to generate these unusual species in the laboratory of particular recent interest have been the unsaturated hydrocarbon families, CnH and CnH2, which have been pursued by a number of diverse methodologies. A wine range of heterocumulenes, including CnO, HCnO, CnN, HCnN, CnS, HCnS, CnSi and HCnSi have also provided intriguing targets for laboratory experiments. Strictly the term cumulene refers to a class of compounds that possess a series of adjacent double bonds, with allene representing the simplest example (H2C=C=CH2). However for many of the non-terrestrial molecules presented here, the carbon chain cannot be described in terms of a single simple valence structure, and so we use the terms cumulene and heterocumulene in a more general sense: to describe molecular species that contain an unsaturated polycarbon chain. Mass spectrometry has proved an invaluable tool in the quest for interstellar cumulenes and heterocumulenes in the laboratory it has the ability in its many forms, to (i) generate charged analogs of these species in the gas phase, (ii) probe their connectivity, ion chemistry, and thermochemistry, and (iii) in some cases, elucidate the neutrals themselves. Here, we will discuss the progress of these studies to this time. (C) 1999 John Wiley & Sons, Inc.

Workplace experiences of information literacy

Abstract: The idea of information literacy, broadly deÞned as the ability to recognise information needs and identify, evaluate and use information e¤ectively, has been of growing concern in the education sectors for a number of years; whilst in the workplace, employers and managers have perhaps attended more to the need for computer and information technology skill. New descriptions of information literacy, that may be of value to the business sector, are now beginning to appear as a result of qualitative research into how professional employees experience the e¤ective use of information. This paper summarises the outcomes of an investigation into the experience of information literacy amongst various types of professionals; and explores the possible di¤erences and interrelations between individual and organisational information literacy suggested by these outcomes. Seven di¤erent ways of experiencing information literacy were identiÞed. These experiences are closely related to important workplace processes such as environmental scanning, information management, corporate memory, and research and development; conÞrming that information literacy should be considered a signiÞcant part of the character of learning organisations as well as being a key characteristic of the organisationOs employees. Implications of individual and organisational information literacy for beginning and continuing professional education are explored.

Generation of two isomers of C5H from the corresponding anions. A theoretically motivated mass spectrometric study

Abstract: Molecular orbital calculations have predicted the stability of a range of connectivities for the radical C5H potential surface. The most energetically favorable of these include the linear C4CH geometry and two ring-chain structures HC2C3 and C2C3H The corresponding anions are also shown to be theoretically stable, and furthermore, a fourth isomer, C2CHC2, is predicted to be the most stable anion connectivity. These results have motivated experimental efforts. Methodologies for the generation of the non-ring-containing isomeric anions C4CH and C2CHC2 have been developed utilizing negative ion mass spectrometry. The absolute connectivities of the anions have been established using deuterium labeling, charge reversal, and neutralization reionization techniques. The success of the latter experiment confirms theoretical predictions of stability of the corresponding neutral species. This is the first reported observation of the neutral C2CHC2 species that calculations predict to be substantially less stable than the C4CH connectivity but still bound relative to isomerization processes.

Molecular co-crystals of 2-aminothiazole derivatives

Abstract: A series of molecular adducts of 2-aminothiazole derivatives - 2-aminothiazole, 2-amino-2-thiazoline and 2-aminobenzothiazole with the carboxylic-acid-substituted heterocyclics indole-2-carboxylic acid, N-methylpyrrole-2-carboxylic acid and thiophene-2-carboxylic acid - have been prepared and characterized using X-ray powder diffraction and in five cases by single-crystal X-ray diffraction methods. These five compounds are the adducts of 2-amino-2-thiazolium with indole-2-carboxylate [(C3H7N2S)+(C9H6NO2)-], and N-methylpyrrole-2-carboxylate [(C3H7N2S)+-(C6H6NO2)-], 2-aminobenzothiazolium with indole-2-carboxylate [(C7H7N2S)+(C9H6NO2)-], N-methylpyrrole-2-carboxylate [(C7H7N2S)+(C6H6NO2)-] and thiophene-2-carboxylate [(C7H7N2S)+(C5H3O2S)-]. All complexes involve proton transfer, as indicated by IR spectroscopy, while the five crystal structures display similar hydrogen-bonding patterns with the dominant interaction being an graph set dimer association between carboxylate groups and the amine/heterocyclic nitrogen sites. Futhermore, in each case a subsiduary interaction between an amino proton and a carboxylate oxygen completes a linear hydrogen-bonded chain. In addition to this, the indole-2-carboxylate molecules in the adduct structure with 2-amino-2-thiazolium form associated dimers which add to the hydrogen-bonding network.

Frame-rate stereopsis using non-parametric transforms and programmable logic

Abstract: A frame-rate stereo vision system, based on non-parametric matching metrics, is described. Traditional metrics, such as normalized cross-correlation, are expensive in terms of logic. Non-parametric measures require only simple, parallelizable, functions such as comparators, counters and exclusive-or, and are thus very well suited to implementation in reprogrammable logic.

Local buckling behaviour of steel plate elements supported by a plastic foam material

Abstract: Sandwich panels comprising steel facings and a polystyrene foam core are increasingly used as roof and wall claddings in buildings in Australia. When they are subjected to loads causing bending and/or axial compression, the steel plate elements of their profiled facing are susceptible to local buckling. However, when compared to panels with no foam core, they demonstrate significantly improved local buckling behaviour because they are supported by foam. In order to quantify such improvements and to validate the use of available design buckling stress formulae, an investigation using finite element analyses and laboratory experiments was carried out on steel plates that are commonly used in Australia of varying yield stress and thickness supported by a polystyrene foam core. This paper presents the details of this investigation, the buckling results and their comparison with available design buckling formulae.

Pull-through strength of high tensile steel cladding systems

Abstract: The profiled steel roof and wall cladding systems in Australia are commonly made of very thin high tensile steels, and are crest-fixed with screw fasteners. A review of current literature and design standards indicated the need to improve the understanding of the behaviour of crest-fixed steel cladding systems under wind uplift/suction loading, in particular, the local failures. Therefore a detailed experimental study using a series of small scale tests and some two-span cladding tests was conducted to investigate the local pull-through and dimpling failures in the commonly used steel cladding systems. The applicability of the current design formulae for the pull-through strength of crest-fixed steel classing systems was investigated first. An improved design formula was then developed in terms of the thickness and ultimate tensile strenth of steel cladding material and diameter of screw head or washer. This paper presents the details of this investigation and its results. A review of current design and test methods is also included.

Group dynamics and software engineering

Abstract: This paper reports on an experiment that was conducted to determine the extent to which group dynamics impacts on the effectiveness of software development teams. The experiment was conducted on software engineering project students at the Queensland University of Technology (QUT).

A real-time software architecture for robotics and automation

Abstract: This paper describes a software architecture for real-world robotic applications We discuss issues of software reliability, testing and realistic off-line simulation that allows the majority of the automation system to be tested off-line in the laboratory before deployment in the field A recent project, the automation of a very large mining machine is used to illustrate the discussion

High-frequency electrostatic surface oscillations in a dust-contaminated plasma

Abstract: High-frequency electrostatic surface waves at the interface of a dusty plasma and a dielectric wall are investigated. The effects of ionization, recombination, and dust-charge variation are taken into account in a self-consistent manner, so that the system considered is closed. It is shown that a coupling of the surface waves and the dust-charge relaxation mode leads to anomalous damping and frequency downshift of the waves.

Three-dimensional modeling of steel portal frame buildings

Abstract: The realistic strength and deflection behavior of industrial and commercial steel portal frame buildings are understood only if the effects of rigidity of end frames and profiled steel claddings are included. The conventional designs ignore these effects and are very much based on idealized two-dimensional (2D) frame behavior. Full-scale tests of a 1212 m steel portal frame building under a range of design load cases indicated that the observed deflections and bending moments in the portal frame were considerably different from those obtained from a 2D analysis of frames ignoring these effects. Three-dimensional (3D) analyses of the same building, including the effects of end frames and cladding, were carried out, and the results agreed well with full-scale test results. Results clearly indicated the need for such an analysis and for testing to study the true behavior of steel portal frame buildings. It is expected that such a 3D analysis will lead to lighter steel frames as the maximum moments and deflections are reduced.

An efficient approach to constrained via minimization for two-layer VLSI routing

Abstract: Constrained Via Minimization is the problem of reassigning wire segments of a VLSI routing so that the number of vias is minimized. In this paper, a new approach is proposed for two-layer VLSI routing. This approach is able to handle any types of routing, and allows arbitrary number of wire segments split at a via candidate.

ESR measurements of the partitioning of some new spin probes in n-octanol-water

Abstract: The stable free radical 1,1,3,3-tetramethylisoindolin-2-yloxyl (TMIO) has proved to be very suitable for use as a spin probe for a number of applications. Because it is soluble mainly in non-polar liquids, there is a need for new derivatives that can be used in a variety of environments. This has been done by introducing substituents in the 5-position of the aromatic ring, namely carboxyl (CTMIO), trimethylamino (TMTMIOI) and sodium sulphonate (NaTMIOS). An accurate ESR method was developed for the measurement of partition coefficients in n-octanol–water. For comparison purposes the method was also applied to some Tempo derivatives. The effect of temperature on the rotational correlation times and the nitrogen-14 hyperfine coupling constant of some of the spin probes was investigated. There is evidence for dimerization of CTMIO to form a biradical

Embedding reflective practice in professional practice with portfolios

Abstract: Completing a professional portfolio as part of coursework gives beginning library and information professionals a tool which helps them bridge the gap between being a student and a practitioner. Portfolios require them to reflect on their learning outcomes, so that they can communicate these to employers, and encourage them to design strategies for professional development. Portfolios promote reflective practice and may continue to be used in the workplace. They are also a useful mechanism for established librarians who wish to record their professional growth, plans and contributions. The idea may even be applied to monitoring the achievements and performance of whole libraries or smaller units within libraries. The first part of this paper reviews portfolios as a tool for reflecting on, showcasing and developing the practice of entry level library and information professionals. Examples of portfolio contents, and reactions to the process, in this part of the paper come from students, (now colleagues), who have recently completed the Graduate Diploma of Information Studies [GDLIS] at the Queensland University of Technology [QUT]. The potential of portfolios as a reflective professional development tool raises interesting possibilities for organisations, educational programs and professional associations. For example, LIS educators could consider strengthening the role of portfolios in courses; organisations could use them as part of the employee selection process; and professional associations such as ALIA could use them as one mechanism for recognising professional status, or establish them as a recommended professional development tool. These roles for the portfolio form the focus of the second half of this paper.

The effect of near-sheath dusts on a surface-wave-sustained gas discharge

Abstract: The effect of near-sheath dusts on the rf power loss in a surface-wave-sustained gas discharge is studied. The planar plasma is bounded by a dielectric and consists of an inhomogeneous near-wall transition layer (sheath), a dusty plasma layer and an outer dust-free plasma. The discharge is maintained by high-frequency axially symmetrical surface waves. The surface-wave power loss from the most relevant dissipative mechanisms in typical discharge plasmas is analysed.

Robot control of a 3,500 tonne mining machine

Abstract: The mining industry is highly suitable for the application of robotics and automation technology since the work is arduous, dangerous and often repetitive. This paper describes the development of an automation system for a physically large and complex field robotic system - a 3,500 tonne mining machine (a dragline). The major components of the system are discussed with a particular emphasis on the machine/operator interface. A very important aspect of this system is that it must work cooperatively with a human operator, seamlessly passing the control back and forth in order to achieve the main aim - increased productivity.

The influence of small amounts of N2 in SF6 on prebreakdown discharges

Abstract: Pre-breakdown discharge activity in SF6 and SF6 +2% N2 at 1 bar absolute has been investigated to assess the feasibility of adding small amounts of N2 to SF6 to improve the luminosity of the pre-breakdown discharges. It has been shown that small amounts of N2 does not significantly alter the breakdown strength of the mixture but will have a profound influence on the pre-breakdown discharge activity under 50 Hz voltages and lightning impulse voltages. This influence is attributed to the following three mechanisms: 1. The increased availability of free electrons due to the lower ionisation potential of the N2 compared to SF6 2. The removal of high energy electrons from the discharge by electron scattering due to negative ion resonance in N2, thus effectively increasing the attachment of SF6. 3. The creation of longer lived SF6- ions by the attachment of the scattered low energy electrons from N2 thus effectively enhancing the negative ion space charge.

Generation of three isomers of C 7 H - in the gas phase. A joint experimental and theoretical study a

Abstract: Three anion isomers of formula C7H have been synthesised in the mass spectrometer by unequivocal routes. The structures of the isomers are \[HCCC(C-2)(2)](-), C6CH- and C2CHC4-. One of these, \[HCCC(C-2)(2)](-), is formed in sufficient yield to allow it to be charge stripped to the corresponding neutral radical.

Compressional Alfvén cross-field surface waves in inhomogeneous dusty plasmas

Abstract: Compressional Alfven surface waves in an inhomogeneous dusty plasma are studied. The inhomogeneiry is modeled by two distinct regions of dusty plasmas with different ion densities. The stationary external magnetic field is along the interface between the two plasmas. The dispersion properties of cross-field surface waves, impossible in dust-free plasmas, are obtained for the constant dust charge case. The existence of the surface waves is due to an imbalance in the electron and ion Hall currents in a dusty plasma © 1999 American Institute of Physics.