Showing papers by "Curtin University published in 2003"

Atlas of Zircon Textures

Abstract: The mineral zircon is extremely variable both in terms of external morphology and internal textures. These features reflect the geologic history of the mineral, especially the relevant episode(s) of magmatic or metamorphic crystallization (and recrystallization), strain imposed both by external forces and by internal volume expansion caused by metamictization, and chemical alteration. The paper presents a selection of both the most typical, but also of the less common, features seen in zircon, categorized according to the different geological processes responsible for their formation. The atlas is intended as a general guide for the interpretation of zircon characteristics, and of related isotopic data. Zircon has become one of the most widely used minerals for the extraction of information on the prehistory and genesis of magmatic, metamorphic and sedimentary rocks. Much of the geological usefulness of zircon stems from its suitability as a geochronometer based on the decay of U (and Th) to Pb, but in addition it is also the major host of the radiogenic isotopic tracer Hf, and it is used to determine oxygen isotopic compositions and REE and other trace element abundances, all of which yield useful clues concerning the history of the host rock, and in some case, the parent rock in which the precursor zircon crystallized. One of the major advantages of zircon is its ability to survive magmatic, metamorphic and erosional processes that destroy most other common minerals. Zircon-forming events tend to be preserved as distinct structural entities on a pre-existing zircon grain. Because of this ability, quite commonly zircon consists of distinct segments, each preserving a particular period of zircon-formation (or consumption). A long experience and modern instrumentation and techniques have provided the “zircon community” the means to image and interpret preserved textures, and hence to decipher the history and evolution of a rock. One …

Conceptual Change: A Powerful Framework for Improving Science Teaching and Learning

Abstract: In this review, we discuss (1) how the notion of conceptual change has developed over the past three decades, (2) giving rise to alternative approaches for analysing conceptual change, (3) leading towards a multiperspective view of science learning and instruction that (4) can be used to examine scientific literacy and (5) lead to a powerful framework for improving science teaching and learning

Lu–Hf and Sm–Nd isotope systems in zircon

Abstract: As a significant carrier of uranium, thorium and the rare earth elements (REEs) at ppm level, and hafnium at the percent level, zircon hosts a remarkable number of long-lived radioactive isotopes and their stable decay products. These include 238U, 235U and 232Th which decay via intermediate steps to 206Pb, 207Pb and 208Pb, respectively, 176Lu which decays to 176Hf, 147Sm which decays to 143Nd, and 138La which undergoes branched decay to 138Ce and 138Ba. This combination makes zircon one of the most versatile minerals available to the geochronologist. Whilst the majority of rock-dating studies involving zircon have utilized the U–Pb and Th–Pb decay schemes, as discussed in previous chapters, an increasing number of investigations are targeting the complementary age information available in the lesser known decay schemes. This chapter reviews the history of application of the Lu–Hf and Sm–Nd isotope systems in zircon and, in its conclusions, speculates on potential future use of the La–Ce system. 176Lu is an unstable radionuclide that undergoes spontaneous β− decay to stable 176Hf, with a half-life of approximately 35 billion years. Variations in the abundance of 176Hf are conventionally expressed with respect to 177Hf whose natural abundance is constant. Thus, the basic age equation for the Lu–Hf dating method, as applied to any closed system, is as follows: \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \[(^{176}Hf/^{177}Hf)\_{t}\ =\ (^{176}Hf/^{177}Hf)\_{initial}\ +\ (^{176}Lu/^{177}Hf)_{t}\ {\cdot}\ (e^{{\lambda}t}\ {-}\ 1)\] \end{document} where t is the elapsed time, and λ is the 176Lu β− decay constant. The exact value of the decay constant λ is currently under review. Most geological studies have either used the value 1.94 × 10−11 y−1, originally calculated from the slope of a Lu–Hf isochron for the 4.56 Ga eucrite achondrite meteorites (Patchett and Tatsumoto 1980a, Tatsumoto et al. 1981), or …

Fine and gross motor ability in males with ADHD

Abstract: In the this study, both fine and gross motor ability of males with attention-deficit-hyperactivity disorder (ADHD) were compared with a group of control children. Three groups of males with the following ADHD subtypes: predominantly inattentive (ADHD-PI; n = 50), hyperactive/impulsive (ADHD-HI; n = 16), or combined (ADHD-C; n = 38) were compared with 39 control males. Mean ages for the control group were 10 years 4 months (SD 1 year 4 months, range 7 years 8 months to 12 years 11 months); for the ADHD-PI group, 10 years (SD 1 year 2 months, range 7 years 10 months to 13 years); for the ADHD-HI group, 9 years 11 months (SD 1 year 2 months), range 7 years 11 months to 12 years 6 months); and for the ADHD-C group 10 years 2 months (SD 1 year 4 months, range 8 to 13 years). The Australian Disruptive Behaviours Scale and Connors' Parent Rating Scale-Revised were used to assess ADHD symptomatology. Verbal IQ was estimated using two verbal subtests of the Wechsler Intelligence Scale for Children, and movement ability was assessed using the Movement Assessment Battery for Children (MABC) and the Purdue Pegboard test. Findings demonstrated that the children with ADHD had significantly poorer movement ability than control children. A high percentage of these children displayed movement difficulties consistent with developmental coordination disorder (DCD). In addition, the current study found that the type and degree of movement difficulty differed between subtypes. The Total Impairment score, as derived from the MABC, was less severe for the ADHD-HI group than the other two ADHD groups, but more severe than for the control group. Males with ADHD-PI and ADHD-C had significantly poorer fine motor ability (p < 0.001) than control males, whereas the ADHD-HI group did not differ significantly from any of the other groups. As children with ADHD only and the control group did not differ significantly on fine motor ability but were significantly better than children categorized with both ADHD and DCD, it was argued that poorer fine motor ability found in children with ADHD could not be attributed to deficits in attention and concentration, but rather to factors relating to their motor ability.

Chemical optimisation of the compressive strength of aluminosilicate geopolymers synthesised by sodium silicate activation of metakaolinite

Abstract: High strength cements can be synthesised by alkali activation of materials rich in Al2O3 and SiO2. In this study, amorphous aluminosilicate polymers produced by sodium silicate activation of metakaolinite were studied, with particular reference to chemical optimisation of the compressive strength according to the relative concentrations of Si, Al and Na in the polymer. The sodium silicate was manufactured from silica fume and sodium hydroxide. The compressive strengths of polymers with Si∶Al molar ratios of 1.0–3.0 and Na∶Al molar ratios of 0.5–2.0 were considered. The polymers were cured at 75 °C for 24 h and their compressive strengths measured after aging for 7 days. The strength was found to depend systematically on the relative amounts of Si, Al and Na, with the maximum being 64 ± 3 MPa for an Si∶Al∶Na molar ratio of 2.5∶1∶1.3. X-Ray diffraction/scattering data indicate qualitatively that the bonding network in the amorphous aluminosilicate alters systematically with composition.

Proterozoic basement provinces of southern and southwestern Australia, and their correlation with Antarctica

Abstract: Abstract Three Precambrian basement provinces extend from the southern coast of Australia into East Antarctica when reconstructed in a Gondwana configuration. These are, from east to west, the Mawson Craton, and the Albany-Fraser and Pinjarra Orogens. The Mawson Craton preserves evidence for tectonic activity from the late Archaean until the earliest Mesoproterozoic. It is exposed in the Gawler Craton of South Australia, the Terre Adélie and King George V Land coastline of East Antarctica, and the Miller Range of the central Transantarctic Mountains. It may form a significant part of the ice-covered East Antarctic Shield, although insufficient data are available to constrain its lateral extent. The Mawson Craton underwent late Palaeoproterozoic tectonism along its eastern margin (the Kimban Orogeny) and the occurrence of c. 1700Ma eclogites in the Transantarctic Mountains implies that this was, in part, a collisional event, although elsewhere it was characterized by low P/T metamorphism. The western margin of the Mawson Craton collided with a continental fragment comprising the Nawa Domain of the Gawler Craton, the Coompana Block and the Nornalup Complex of Western Australia at c. 1560Ma during the Kararan Orogeny. The western edge of the Nornalup Complex later collided with the Biranup and Fraser Complexes and Yilgarn Craton to form the Albany-Fraser Orogen during two stages of tectonism at c. 1350–1260 and 1210–1140Ma. The Pinjarra Orogen truncates the western margin of the Yilgarn Craton and Albany-Fraser Orogen, and contains allochthonous 1100–1000Ma gneissic blocks transported along the craton margin during at least two stages of Neoproterozoic transcurrent movement. It divides East Gondwana into Australo-Antarctic and Indo-Antarctic domains, which are distinct continental fragments with different Proterozoic histories that were juxtaposed by oblique collision at 550–500Ma during the assembly of Gondwana. The path taken by the Pinjarra Orogen beneath the Antarctic ice sheet is unknown, but it is of similar width and length to the East African Orogen, and must have been a fundamental Neoproterozoic boundary of critical importance to supercontinent assembly and breakup.

Lumbar repositioning deficit in a specific low back pain population

Abstract: STUDY DESIGN A cross-sectional observational design study was conducted to determine lumbar repositioning error in 15 subjects who had chronic low back pain with a clinical diagnosis of lumbar segmental instability and 15 asymptomatic participants. OBJECTIVE To determine whether individuals with lumbar segmental instability have a decreased ability to reposition their lumbar spine into a neutral spinal position. SUMMARY OF BACKGROUND DATA Proprioception of the lumbar spine has been investigated in individuals who have low back pain with variable results. The testing procedure's lack of sensitivity and the nonhomogeneity of groups may be responsible for the conflicting findings. METHODS Repositioning accuracy of the lumbar spine was assessed using the 3Space Fastrak to determine error in 15 participants with lumbar segmental instability and 15 asymptomatic subjects. The participants were assisted into a neutral spinal sitting posture and then asked to reproduce this position independently over five trials separated by periods of relaxed full lumbar flexion. RESULTS Lumbosacral repositioning error was significantly greater in participants with lumbar segmental instability than in the asymptomatic group (t[28] = 2.48; P = 0.02. There also was a significant difference between the groups at each individual sensor. CONCLUSIONS The results of this study indicate that individuals with a clinical diagnosis of lumbar segmental instability demonstrate an inability to reposition the lumbar spine accurately into a neutral spinal posture while seated. This finding provides evidence of a deficiency in lumbar proprioceptive awareness among this population.

High intensity anthropogenic sound damages fish ears

Abstract: Marine petroleum exploration involves the repetitive use of high-energy noise sources, air-guns, that produce a short, sharp, low-frequency sound. Despite reports of behavioral responses of fishes and marine mammals to such noise, it is not known whether exposure to air-guns has the potential to damage the ears of aquatic vertebrates. It is shown here that the ears of fish exposed to an operating air-gun sustained extensive damage to their sensory epithelia that was apparent as ablated hair cells. The damage was regionally severe, with no evidence of repair or replacement of damaged sensory cells up to 58 days after air-gun exposure.

`Agon'izing Over Consensus: Why Habermasian Ideals cannot be `Real'

Abstract: I explore the core Habermasian concept of rational consensus-formation and its counterfactuality before introducing the possibility of permanence of conflict, non-reciprocity and domination (i.e. of agonism) which may productively explain some of the powergames enacted in planning decision-making. In so doing I draw on the concept of agonism and introduce the political into Habermas' moral theorization. Where the personal and the political intersect there is a role for psychology. I illustrate how Habermas' communicative theorizing was itself partly developed from a psychoanalytical tradition before introducing some of the concepts popularized by Jacques Lacan. I conclude that development of communicative planning theory could usefully retain some of Habermas' psychological foundations while turning to the work of Lacan as a basis for an enhanced understanding of the realities of planning practice.

Classroom Learning Environments

Abstract: The study of learning environments has gained much recognition internationally in the last 30 years as a significant field of educational research (Fraser, 1998a). This trend is also evident in Asia, where this field has attracted the attention of educational researchers especially over the previous decade. The way in which studies in various Asian countries covering different types of learning environments have gained momentum in the last decade is illustrated in Goh and Khine’s (2002) book. With the ensuing enthusiasm in learning environment research, studies began to emerge in countries such as Singapore, Korea, Taiwan and Indonesia, some of which can be regarded as pioneering in the field. Those studies focussed on students’ and teachers’ perceptions of classroom learning environments and science laboratory classes. Overall, much progress has been achieved in the conceptualisation, assessment and investigations of learning environment (Fraser, 1994, 1998a).

Zero-Inflated Negative Binomial Mixed Regression Modeling of Over-Dispersed Count Data with Extra Zeros

Abstract: In many biometrical applications, the count data encountered often contain extra zeros relative to the Poisson distribution. Zero-inflated Poisson regression models are useful for analyzing such data, but parameter estimates may be seriously biased if the nonzero observations are over-dispersed and simultaneously correlated due to the sampling design or the data collection procedure. In this paper, a zero-inflated negative binomial mixed regression model is presented to analyze a set of pancreas disorder length of stay (LOS) data that comprised mainly same-day separations. Random effects are introduced to account for inter-hospital variations and the dependency of clustered LOS observations. Parameter estimation is achieved by maximizing an appropriate log-likelihood function using an EM algorithm. Alternative modeling strategies, namely the finite mixture of Poisson distributions and the non-parametric maximum likelihood approach, are also considered. The determination of pertinent covariates would assist hospital administrators and clinicians to manage LOS and expenditures efficiently.

Linking growth episodes of zircon and metamorphic textures to zircon chemistry: an example from the ultrahigh-temperature granulites of Rogaland (SW Norway)

Abstract: In-situ U-Th-Pb analyses by ion-microprobe on zircon in intact textural relationships are combined with backscatter and cathodoluminescence imaging and trace element analyses to provide evidence for growth episodes of zircon. This approach helps: (a) to unravel the polymetamorphic history of aluminous migmatitic and granitoid gneisses of the regional contact aureole around the Rogaland anorthosite-norite intrusive complex; and (b) to constrain the age of M 2 ultrahigh-temperature (UHT) metamorphism and the subsequent retrograde M 3 event. All samples yield magmatic inherited zircon of c. 1035 Ma, some an additional group at c. 1050 Ma. This suggests that loss of Pb by volume diffusion in non-metamict zircon is not an important factor even under extreme crustal conditions. Furthermore, the identical inheritance patterns in aluminous (garnet, cordierite ± osumilite-bearing) migmatites and orthogneisses indicate a metasomatic igneous instead of a sedimentary protolith for the migmatite. Results for the M 1 metamorphic event at c. 1000 Ma BP are consistent in all samples, including those from outside the orthopyroxene-in isograd. The latter do not show evidence for zircon growth during the M 2 metamorphic episode. Zircon intergrown with or included within M 2 metamorphic minerals (magnetite, spinel, orthopyroxene) give an age of 927 ± 7 Ma (2 σ, n = 20). The youngest observed results are found in zircon outside M 2 minerals, some overgrown by M 3 mineral assemblages (late garnet coronas, garnet + quartz and orthopyroxene + garnet symplectites) and yield a slightly younger pooled age of 908 ± 9 Ma (2 σ, n = 6). These textures are relative time markers for the crystallization of zircon overgrowths during discrete stages of the UHT event. These youngest age groups are consistent with the emplacement age of the Rogaland intrusive complex and the last magmatic activity (Tellnes dyke intrusion), respectively. This is direct and conclusive evidence for UHT metamorphism in the regional aureole being caused by the intrusions, and corrects earlier notions that the events are not linked. Trace element behaviour of zircon (Tb/U and Y content) has been tracked through time in the samples and shows variations both within and between samples. This heterogeneous behaviour at all scales appears to be common in metamorphic rocks and precludes the use of ‘rules of thumb’ in the interpretation of zircon chemistry, but chemical tracers are useful for recognition of zircon growth or recrystallization during metamorphism.

Policy statement of the “informal science education” ad hoc committee

Abstract: Cet article informe de la politique developpee par un comite charge de developper la recherche sur l'education scientifique extra-scolaire, dans des institutions pedagogiques, telles que les zoos, musees, aquariums, et a travers les moyens de communication et d'information de masse, tels que les journaux, la television, l'Internet.

Waist–hip ratio is the dominant risk factor predicting cardiovascular death in Australia

Abstract: Objective To evaluate clinical measures of obesity for their ability to predict death from cardiovascular disease (CVD) and coronary heart disease (CHD), in parallel with conventional cardiovascular risk factors. Design, participants and setting Cross-sectional analysis of an age- and sex-stratified sample of 9206 adults aged 20-69 years from Australian capital cities (1989 Australian Risk Factor Prevalence Survey). Blood pressure, fasting serum lipid levels, smoking, history of heart disease or diabetes, and obesity as measured by body mass index (BMI), waist circumference and waist-hip ratio were recorded. These data were linked with the National Death Index to determine causes of death of the 473 survey subjects who had died to 31 December 2000. Main outcome measures Hazard ratios for the risk factors predicting CVD mortality and CHD mortality. Results Of the modifiable risk factors, obesity, as measured by waist-hip ratio, is a dominant, independent, predictive variable for CVD and CHD deaths in Australian men and women. Self-reported angina/myocardial infarction in both sexes, and cigarette smoking in women, are also independent risk factors. Conclusions Obesity assessed by waist-hip ratio is a better predictor of CVD and CHD mortality than waist circumference, which, in turn, is a better predictor than BMI. The recognition of central obesity is clinically important, as lifestyle intervention is likely to provide significant health benefits.

An Application of Branch and Cut to Open Pit Mine Scheduling

Abstract: The economic viability of the modern day mine is highly dependent upon careful planning and management. Declining trends in average ore grades, increasing mining costs and environmental considerations will ensure that this situation will remain in the foreseeable future. The operation and management of a large open pit mine having a life of several years is an enormous and complex task. Though a number of optimization techniques have been successfully applied to resolve some important problems, the problem of determining an optimal production schedule over the life of the deposit is still very much unresolved. In this paper we will critically examine the techniques that are being used in the mining industry for production scheduling indicating their limitations. In addition, we present a mixed integer linear programming model for the scheduling problems along with a Branch and Cut solution strategy. Computational results for practical sized problems are discussed.

Mesozoic crust-mantle interaction beneath the North China craton: A consequence of the dispersal of Gondwanaland and accretion of Asia

Abstract: We present evidence from zircons entrained within lower-crustal xenoliths in the Cenozoic Hannuoba Basalt of multiple melting events beneath the North China craton in the late Mesozoic. Peak activity was between 180 and 80 Ma, the upper crustal signature of which was the generation of voluminous granitoids and related volcanic rocks, emplacement of dioritic and lamprophyric dikes, and widespread gold mineralization. The process involved partial loss of mantle lithosphere, accompanied by wholesale rising of asthenospheric mantle beneath eastern China. We correlate these events with lithospheric thinning resulting from the breakup and dispersal of Gondwanaland, accompanied by a major mantle overturn, fueled by the destruction of oceanic lithosphere and triggered by its sinking into the lower mantle during the subsequent accretion of Asia.

In Situ FTIR-ATR Examination of Poly(acrylic acid) Adsorbed onto Hematite at Low pH

Abstract: The adsorption of water-soluble polymers (e.g., flocculants, coagulants) onto mineral particles is typically characterized by “trains” of adsorbed polymer segments with “loops” and “tails” of unadsorbed polymer segments that extend into the solution. Ex situ spectroscopic studies carried out in the past have been complicated by the way in which the unadsorbed segments of the polymer interact with the surface of the substrate upon drying. In this study, an in situ Fourier transform infrared attenuated total reflection technique was used to examine the interaction of poly(acrylic acid) and hematite at pH 2. A hematite colloid was deposited onto a ZnSe crystal, and the poly(acrylic acid) solution was subsequently pumped across the coated crystal at a known rate. Polymer adsorption was irreversible and could be described by a Langmuir isotherm, the rate of curvature of which suggested that the adsorption was weak. The mode of adsorption was shown to be bidentate chelate complexation by the carboxylate functio...

Power imbalance between nurses and patients: a potential inhibitor of partnership in care

Abstract: The Patient's Charter identifies the need for nurses to respect patients' rights to influence their care, and contemporary nursing practice advocates that nurses work in partnership with patients. Hence nurses are encouraged to share their power and facilitate empowerment in their patients by giving them information and support. However, the literature indicates that nurses are not very successful in making patients feel empowered to make informed decisions. This study, conducted in 1998, provides some answers as to why this may be the case. The aim of the study was to explore and describe nurses' and patients' views regarding partnership in care in hospital. Using the grounded theory approach, participants were drawn from four hospitals in Western Australia. A purposive sample of 33 nurses and 32 patients were interviewed in-depth. Participant observation was also conducted and field notes were written. The interviews were transcribed verbatim and analysed using the constant comparative method. The findings showed that nurses viewed involving patients in care as requiring them to give patients information and to share their decision-making powers with them. With the exception of a few, the majority of nurses were unwilling to share their decision-making powers. This created a situation of power imbalance with subsequent little patient input. Factors identified included nurses' beliefs that they "know best", the view that patients lacked medical knowledge and the perceived need for nurses to hold onto their power and maintain control. If nurses and patients are to work as partners, it is important that nurses make every effort to equalize the power imbalance. One way to do this is for nurses to share and give information to patients readily and to be open in their communication with them.

Experimental hydrothermal alteration of partially metamict zircon

Abstract: We present the results of a series of hydrothermal experiments on grains from two partially metamict zircon samples from Sri Lanka in the temperature range 350 to 650 °C and with different solutions (2 M AlCl 3 , 2 M CaCl 2 , pure H 2 O, and a multi-cation solution). Under these conditions, sharply bounded reaction fronts penetrated into the zircon grains and developed complex lobate and rim structures that resemble structures found in natural zircon systems. The reaction zones are characterized by a marked increase in the cathodoluminescence intensity, a decrease of the back-scattered electron emission, and an increased degree of structural order, as revealed by micro-Raman and infrared spectroscopy. Sensitive high-resolution ion microprobe and electron microprobe measurements revealed that the altered areas gained solvent cations (e.g., Ca 2 + , Ba 2 + , Mg 2 + , Al 3 + ) from the solution and lost variable amounts of Zr, Si, Hf, the REE, U, Th as well as radiogenic Pb. A comparison between "dry" and "hydrothermal" annealing trends shows that the kinetics of structural recovery, including recrystallization of the amorphous phase in metamict zircon, is strongly enhanced under hydrothermal conditions. This finding suggests that water "catalyzes" structural recovery processes in metamict zircon. We found that the structure of the reacted areas does not resemble that of crystalline zircon, i.e., is still characterized by a temperature-dependent degree of disorder, which would not be expected if the reaction is controlled by a coupled dissolution and re-precipitation process. Instead, the alteration process can be described best by a diffusion-reaction-recrystallization model. In this model, it is postulated that the diffusion of water into the metamict structure is the driving force for moving recrystallization fronts. We found that the rate and the extent of solid-state recrystallization of the amorphous phase is an important factor in determining the mobility of trace elements. This interpretation is indicated by the observation that trace elements, including U and Th, were preferentially lost during the reaction with a fluid at low temperatures, where recrystallization of the amorphous material was slow or not activated at all. The observed chemical alteration patterns are believed to reflect a competition between the kinetics of long-range diffusion and ion exchange and the kinetics of the short-range diffusion necessary for the recrystallization process.

A modification to the Goldstein radar interferogram filter

Abstract: We present a modification to the adaptive Goldstein radar interferogram filter which improves the quality of interferometry products. The proposed approach makes the Goldstein filter parameter alpha dependent on coherence, such that incoherent areas are filtered more than coherent areas. This modification minimizes loss of signal while still reducing the level of noise.

Toward an agenda for advancing research on science learning in out-of-school settings

Abstract: The question, ‘‘What constitutes a reasonable, useful agenda for research into science learning in out-of-school, free-choice environments?’’ has surfaced with increasing frequency over the past 10 years or so. One event that helped move the agenda forward was the National Science Foundation–funded conference, ‘‘Public Institutions for Personal Learning: Understanding the Long-term Impact of Museums,’’ held in Annapolis in 1994. The proceedings of this conference, published by the American Association of Museums (Falk & Dierking, 1995), reflected a large step forward in setting out the research issues and questions involved. Although focused on museums (a generic term including all kinds of museums, botanical gardens, aquaria, zoos, and science and other interpretative centers), the issues discussed are applicable to a wide range of non-museum contexts. The Annapolis conference was conceived as a forum for frontline researchers in a variety of fields representing the physical, social, and personal dimensions of learning. The goal was to discuss how the thinking and modalities of their disciplines might shed insights into the nature of learning and be used to define and lay out a long-term research agenda in museums. At about the same time, a small group of science museum practitioners held several meetings under the auspices of the Association of Science and Technology Centers (ASTC) and the Institute of Museum Studies (IMS) to start thinking about a research agenda in their area of expertise. The results of the think tank meetings were published in six successive ASTC newsletters during 1996 (and are now available at http:/ /www.astc.org/resource/educator/educmain.htm#theories).