89,483 results

  • Robust Mode Delay Dependent H??? Control of Discrete-Time Systems with Random Communication Delays

    Chae, S; Rasool, F; Nguang, SK; Swain, Akshya (2010)

    Journal article
    The University of Auckland Library

    This study considers stability and robust mode delay-dependent H controller design for discrete-time systems with random communication delays. Communication delays between sensors and controllers are modelled by a finite state Markov process. Based on Lyapunov???Krasovskii functional, a novel methodology for designing a mode delay-dependent state feedback controller has been proposed. The authors also show that the existing delay-dependent approach is a special case of the mode delay-dependent approach proposed in this study. The mode delay-dependent controller is obtained by solving linear matrix inequality optimisation problems using the cone complementarity linearisation algorithm. The effectiveness of the proposed design methodology is verified by a numerical example.

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  • El inventario fon??mico nasal del espa??ol: un estudio comparativo

    Pi??eros, Carlos (2011)

    Journal article
    The University of Auckland Library

    This paper investigates the composition of the Spanish phonemic nasal inventory using the UPSID (UCLA Phonological Segment Inventory Database) as a framework of comparison. It was found that the inventory /m, n, V/ agrees with a predominant crosslinguistic tendency ???the inclusion of /m/ and /n/??? but disagrees with another predominant crosslinguistic tendency ???the selection of /n/ to complete the nasal triad???. The Optimality-theoretic analysis proposed herein is based on the assumption that, in addition to an articulation markedness dimension, there is also a perception markedness dimension, both of which are formalized in terms of negative constraints and assumed to be subject to a universal hierarchical order. The number of nasal consonants and the place features that they may have depend on the rank that individual grammars assign to FAITH(nasal place) ???the pertinent faithfulness principle??? with respect to the members of two universal markedness hierarchies. According to this approach, absolute domination of FAITH(nasal place) by both markedness hierarchies leads to the absence of nasal consonants, while the gradual promotion of this faithfulness constraint allows for nasal inventories that are gradually more populated. Yet, regardless of how highly FAITH(nasal place) is promoted, the fixed internal order of the markedness hierarchies rules out the possibility of generating nasal inventories comprising exclusively marked units (e. g. the triad /b, V, n/). Only in those inventories were the least marked units are present can the most marked units arise as well.

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  • A Wireless Power Pick-up Based on Directional Tuning Control of a Magnetic Amplifier

    Hsu, J; Hu, Aiguo; Swain, Akshya (2009)

    Journal article
    The University of Auckland Library

    This paper proposes a novel inductor-capacitor-inductor wireless power pickup with directional tuning control (DTC) for a magnetic amplifier. The proposed technique allows the power pickup to achieve full-range tuning/detuning operation to regulate power flow and maintain the output voltage to be constant. The method eliminates the tedious fine-tuning process associated with traditional fixed power pickup tuning methods and eases the component selection. Moreover, it can overcome the online circuit parameter variations and automatically achieve the maximum power transfer capacity when required. In order to meet dynamic load demands, a magnetic amplifier is used as a variable inductor and is controlled by a novel DTC algorithm to change the tuning condition of the power pickup. The effectiveness of the proposed power pickup and its applicability to general wireless power transfer applications have been demonstrated by both simulation and experimental results.

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  • Diflavin oxidoreductases activate the bioreductive prodrug PR-104A under hypoxia.

    Guise, Christopher; Abbattista, Maria; Nair, Smitha; Lambie, NK; Su, J; Li, D; Wilson, William; Dachs, GU; Patterson, Adam (2012)

    Journal article
    The University of Auckland Library

    The clinical agent PR-104 is converted systemically to PR-104A, a nitrogen mustard prodrug designed to target tumor hypoxia. Reductive activation of PR-104A is initiated by one-electron oxidoreductases in a process reversed by oxygen. The identity of these oxidoreductases is unknown, with the exception of cytochrome P450 reductase (POR). To identify other hypoxia-selective PR-104A reductases, nine candidate oxidoreductases were expressed in HCT116 cells. Increased PR-104A-cytotoxicity was observed in cells expressing methionine synthase reductase (MTRR), novel diflavin oxidoreductase 1 (NDOR1), and inducible nitric-oxide synthase (NOS2A), in addition to POR. Plasmid-based expression of these diflavin oxidoreductases also enhanced bioreductive metabolism of PR-104A in an anoxia-specific manner. Diflavin oxidoreductase-dependent PR-104A metabolism was suppressed >90% by pan-flavoenzyme inhibition with diphenyliodonium chloride. Antibodies were used to quantify endogenous POR, MTRR, NDOR1, and NOS2A expression in 23 human tumor cell lines; however, only POR protein was detectable and its expression correlated with anoxic PR-104A reduction (r(2) = 0.712). An anti-POR monoclonal antibody was used to probe expression using human tissue microarrays; 13 of 19 cancer types expressed detectable POR with 21% of cores (185 of 874) staining positive; this heterogeneity suggests that POR is a useful biomarker for PR-104A activation. Immunostaining for carbonic anhydrase 9 (CAIX), reportedly an endogenous marker of hypoxia, revealed only moderate coexpression (9.6%) of both CAIX and POR across a subset of five cancer types.

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  • Identification of human reductases that activate the dinitrobenzamide mustard prodrug PR-104A: a role for NADPH:cytochrome P450 oxidoreductase under hypoxia.

    Guise, Christopher; Wang, AT; Theil, A; Bridewell, David; Wilson, William; Patterson, Adam (2007)

    Journal article
    The University of Auckland Library

    Hypoxia is a common trait found in many solid tumours and thus represents a therapeutic target with considerable potential. PR-104, a hypoxia-activated prodrug currently in clinical trial, is a water-soluble phosphate ester which is converted in vivo to the corresponding alcohol, PR-104A. This 3,5-dinitrobenzamide-2-nitrogen mustard is activated by reduction to the corresponding 5-hydroxylamine (PR-104H) and 5-amine (PR-104M) in hypoxic cells. The clinical effectiveness of PR-104 will depend in part on the expression of reductases within tumours that can effect this reduction. Here, we evaluate the roles of NADPH:cytochrome P450 oxidoreductase (CYPOR; E.C.1.6.2.4) and NAD(P)H:quinone oxidoreductase (NQO1; E.C.1.6.99.2) as candidate PR-104A reductases. A weak correlation was observed between NQO1 activity and aerobic cytotoxicity in a panel of eight tumour cell lines. However, overexpression of human NQO1 did not increase cytotoxicity of PR-104A or the formation of PR-104H/M, showing that PR-104A is not a substrate for NQO1. Overexpression of human CYPOR did, however, increase the hypoxic cytotoxicity of PR-104A, and its metabolism to PR-104H and PR-104M, demonstrating it to be a PR-104A reductase. To assess the contribution of CYPOR to overall activation of PR-104A in hypoxic SiHa cells, a combination of siRNA transfection and antisense expression were used to suppress CYPOR protein by 91% (+/-3%), a phenotype which conferred 45% (+/-7%) decrease in cytotoxic potency of PR-104A. Regression analysis of all CYPOR depletion data was found to correlate with cytoprotection and metabolism (p<0.001). Residual PR-104A reductase activity could be inhibited by the flavoprotein inhibitor diphenyliodonium. We conclude that CYPOR is an important PR-104A reductase, but that other flavoenzymes also contribute to its activation in hypoxic SiHa cells.

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  • Direct positive selection for improved nitroreductase variants using SOS triggering of bacteriophage lambda lytic cycle

    Guise, Christopher; Grove, JI; Hyde, EI; Searle, PF (2007)

    Journal article
    The University of Auckland Library

    Expression of prodrug-activating enzymes that convert non-toxic substrates to cytotoxic derivatives is a promising strategy for cancer gene therapy. However, their catalytic activity with unnatural, prodrug substrates is often suboptimal. Efforts to improve these enzymes have been limited by the inability to select directly for increased prodrug activation. We have focussed on developing variants of Escherichia coli (E. coli) nitroreductase (NTR) with improved ability to activate the prodrug 5-(aziridin-1-yl)-2,4-dinitrobenzamide (CB1954), and describe here a novel, direct, positive selection for improved enzymes that exploits the alternative life cycles of bacteriophage lambda. In lambda lysogens of E. coli, the activation of the prodrug CB1954 by NTR triggers the SOS response to DNA damage, switching integrated lambda prophages into lytic cycle. This provides a direct, positive selection for phages encoding improved NTR variants, as, upon limiting exposure of lysogenized E. coli to CB1954, only those encoding the most active enzyme variants are triggered into lytic cycle, allowing their selective recovery. We exemplify the selection by isolating highly improved ???turbo-NTR??? variants from a library of 6.8 10 5 clones, conferring up to 50-fold greater sensitivity to CB1954 than the wild type. Carcinoma cells infected with adenovirus expressing T41Q/N71S/F124T-NTR were sensitized to CB1954 concentrations 40- to 80-fold lower than required with WT-NTR

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  • Hippocampal atrophy in relapsing-remitting and primary progressive MS: a comparative study

    Anderson, Valerie; Fisniku, LK; Khaleeli, Z; Summers, MM; Penny, SA; Altmann, DR; Thompson, AJ; Ron, MA; Miller, DH (2010-09)

    Journal article
    The University of Auckland Library

    Background: In multiple sclerosis (MS), demyelination and neuroaxonal damage are seen in the hippocampus, and MRI has revealed hippocampal atrophy. Objectives: To investigate and compare hippocampal volume loss in patients with relapsing???remitting MS (RRMS) and primary progressive MS (PPMS) using manual volumetry, and explore its association with memory dysfunction. Methods: Hippocampi were manually delineated on volumetric MRI of 34 patients with RRMS, 23 patients with PPMS and 18 controls. Patients underwent neuropsychological tests of verbal and visuospatial recall memory. Linear regression was used to compare hippocampal volumes between subject groups, and to assess the association with memory function. Results: Hippocampal volumes were smaller in MS patients compared with controls, and were similar in patients with RRMS and PPMS. The mean decrease in hippocampal volume in MS patients was 317 mm3 (9.4%; 95% CI 86 to 549; p = 0.008) on the right and 284 mm3 (8.9%; 95% CI 61 to 508; p = 0.013) on the left. A borderline association of hippocampal volume with memory performance was observed only in patients with PPMS. Conclusion: Hippocampal atrophy occurs in patients with RRMS and PPMS. Factors additional to hippocampal atrophy may impact on memory performance.

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  • The clinical profile of right temporal lobe atrophy

    Chan, D; Anderson, Valerie; Pijnenburg, Y; Whitwell, J; Barnes, J; Scahill, R; Stevens, JM; Barkhof, F; Scheltens, P; Rossor, MN; Fox, NC (2009-05)

    Journal article
    The University of Auckland Library

    Frontotemporal lobar degeneration is currently associated with three syndromic variants. Disorders of speech and language figure prominently in two of the three variants, and are associated with left-sided frontotemporal atrophy. The detailed characterization of these syndromes contrasts with the relative paucity of information relating to frontotemporal lobar degeneration primarily affecting the right cerebral hemisphere. The objective of this study was to identify the clinical profile associated with asymmetrical, predominantly right-sided, temporal lobe atrophy. Twenty patients with predominant right temporal lobe atrophy were identified on the basis of blinded visual assessment of the MRI scans. The severity of right temporal lobe atrophy was quantified using volumetric analysis of the whole temporal lobes, the amygdala and the hippocampus. Profiles of cognitive function, behavioural and personality changes were obtained on each patient. The pattern of atrophy and the clinical features were compared with those observed in a group of patients with semantic dementia and predominant left-sided temporal lobe atrophy. The mean right temporal lobe volume in the right temporal lobe atrophy group was reduced by 37%, with the mean left temporal lobe volume reduced by 19%. There was marked atrophy of the right hippocampus and right amygdala, with mean volumes reduced by 41 and 51%, respectively (left hippocampus and amygdala volumes were reduced by 18 and 33%, respectively). The most prominent cognitive deficits were impairment of episodic memory and getting lost. Prosopagnosia was a symptom in right temporal lobe atrophy patients. These patients also exhibited a variety of behavioural symptoms including social disinhibition, depression and aggressive behaviour. Nearly all behavioural disorders were more prevalent in the right temporal lobe atrophy patient group than the semantic dementia group. Symptoms particular to the right temporal lobe atrophy patient group included hyper-religiosity, visual hallucinations and cross-modal sensory experiences. The combination of clinical features associated with predominant right temporal lobe atrophy differs significantly from those associated with the other syndromes associated with focal degeneration of the frontal and temporal lobes and it is, therefore, proposed that this right temporal variant should be considered a separate syndromic variant of frontotemporal lobar degeneration.

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  • Tissue-Specific Mathematical Models of Slow Wave Entrainment in Wild-Type and 5-HT2B Knockout Mice with Altered Interstitial Cells of Cajal Networks

    Du, Peng; O'Grady, Gregory; Gibbons, SJ; Yassi, R; Lees-Green, R; Farrugia, G; Cheng, Leo; Pullan, Andrew (2010-05-05)

    Journal article
    The University of Auckland Library

    Gastrointestinal slow waves are generated within networks of interstitial cells of Cajal (ICCs). In the intact tissue, slow waves are entrained to neighboring ICCs with higher intrinsic frequencies, leading to active propagation of slow waves. Degradation of ICC networks in humans is associated with motility disorders; however, the pathophysiological mechanisms of this relationship are uncertain. A recently developed biophysically based mathematical model of ICC was adopted and updated to simulate entrainment of slow waves. Simulated slow wave propagation was successfully entrained in a one-dimensional model, which contained a gradient of intrinsic frequencies. Slow wave propagation was then simulated in tissue models which contained a realistic two-dimensional microstructure of the myenteric ICC networks translated from wild-type (WT) and 5-HT2B knockout (degraded) mouse jejunum. The results showed that the peak current density in the WT model was 0.49 ??A mm???2 higher than the 5-HT2B knockout model, and the intracellular Ca2+ density after 400 ms was 0.26 mM mm???2 higher in the WT model. In conclusion, tissue-specific models of slow waves are presented, and simulations quantitatively demonstrated physiological differences between WT and 5-HT2B knockout models. This study provides a framework for evaluating how ICC network degradation may impair slow wave propagation and ultimately motility and transit.

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  • A Multiscale Model of the Electrophysiological Basis of the Human Electrogastrogram

    Pullan, Andrew; O'Grady, Gregory; Du, Peng; Cheng, Leo (2010)

    Journal article
    The University of Auckland Library

    The motility of the stomach is coordinated by an electrical activity termed ???slow waves???, and slow-wave dysrhythmias contribute to motility disorders. One major method for clinically evaluating gastric dysrhythmias has been electrogastrography (EGG); however, the clinical utility of EGG is limited partly due to the uncertainty regarding its electrophysiological basis. In this study, a multiscale model of gastric slow waves was generated from a biophysically based continuum description of cellular electrical events, coupled with a subject-specific human stomach model and high-resolution electrical mapping data. The model was then applied using a forward-modeling approach, within an anatomical torso model, to define how slow wave activity summates to generate the EGG potentials. The simulated EGG potentials were shown to be spatially varying in amplitude (0.27???0.33 mV) and duration (9.2???15.3 s), and the sources of this variance were quantified with respect to the activation timings of the underlying slow wave activity. This model constitutes an improved theory of the electrophysiological basis of the EGG, and offers a framework for optimizing the placement of EGG electrodes, and for interpreting the EGG changes occurring in disease states.

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  • Bilingual dictionaries in tests of L2 writing proficiency: Do they make a difference?

    East, Martin (2007)

    Journal article
    The University of Auckland Library

    Whether test takers should be allowed access to dictionaries when taking L2 tests has been the subject of debate for a good number of years. Opinions differ according to how the test construct is understood and whether the underlying value system favours process-orientated assessment for learning, with its concern to elicit the test takers' best performance, or product-focused assessment of learning, with its emphasis on the discriminatory power of the test. One key study into bilingual dictionaries and writing tests (Hurman & Tall, 1998) concluded that dictionary use improves test scores. This study was influential in a recent decision to ban dictionaries in several high-stakes L2 examinations in the UK. Research into dictionary use in reading tests has suggested, however, that dictionary availability makes no statistically significant difference to test scores. This article presents the findings of a further study into bilingual dictionary use in writing tests that also indicated no significant difference to scores. Considering this finding alongside those of studies other than Hurman and Tall's casts some doubt on whether the UK ban was fully justified. (Contains 8 tables and 5 footnotes.)

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  • Language evaluation policies and the use of support resources in assessments of language proficiency

    East, Martin (2008)

    Journal article
    The University of Auckland Library

    This paper reviews the arguments for and against the inclusion of support resources in high-stakes assessments of L2 language proficiency. It explores how these arguments have shaped centralised language-in-education planning and policy decisions and looks at what has happened at the local level as a consequence of these decisions. Regardless of whether support resources are included in or excluded from the assessment the paper proposes some of the language planning issues that need to be borne in mind both centrally and locally, seen in the light of the important requirement to develop students' communicative language ability.

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  • Promoting positive attitudes towards foreign language learning: a New Zealand initiative

    East, Martin (2009)

    Journal article
    The University of Auckland Library

    This paper reports on the effectiveness of a tailored undergraduate course at a tertiary institution in New Zealand constructed to challenge, and encourage changes to, monolingual ???English-only??? attitudes. The course was designed to provide knowledge and promote understanding of the phenomenon of English as a global language, and the place of, and implications for, languages other than English in that context. Working with two cohorts of students, a pre- and post-treatment design was used whereby participants completed an attitudinal questionnaire at the start of the course and the same questionnaire at the end. They were also asked what they thought about languages in a globalised world. The questionnaires were analysed to determine if there had been any shift in attitudes by the end of the course. Findings are presented and discussed in terms of the effectiveness of this course to promote positive attitudes towards foreign language learning in New Zealand-based students. It raises the question of whether similar courses could be planned for use by secondary and other tertiary students as part of initiatives to help them to recognise that speaking languages other than English is normative in today's world.

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  • Moving towards us-others reciprocity: Implications of glocalisation for language learning and intercultural communication

    East, Martin (2008)

    Journal article
    The University of Auckland Library

    Learning new languages potentially gives people vital skills to build more successful relationships, and understanding the social influences at work today may help us to know which type of language education is most beneficial. This article explores three social influences--globalisation, localisation and glocalisation--from the perspective of their effect on language use. It is suggested that glocalisation provides the most useful term to describe the reality of social interaction at the start of the 21st century and that language education should be shaped by the impact of this social influence on language use. (Contains 4 notes.)

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  • Gray matter atrophy rate as a marker of disease progression in AD

    Anderson, Valerie; Schott, JM; Bartlett, JW; Leung, KK; Miller, DH; Fox, NC (2010-12-14)

    Journal article
    The University of Auckland Library

    Global gray matter (GM) atrophy rates were quantified from magnetic resonance imaging (MRI) over 6- and 12-month intervals in 37 patients with Alzheimer's disease (AD) and 19 controls using: (1) nonlinear registration and integration of Jacobian values, and (2) segmentation and subtraction of serial GM volumes. Sample sizes required to power treatment trials using global GM atrophy rate as an outcome measure were estimated and compared between the 2 techniques, and to global brain atrophy measures quantified using the boundary shift integral (brain boundary shift integral; BBSI) and structural image evaluation, using normalization, of atrophy (SIENA). Increased GM atrophy rates (approximately 2% per year) were observed in patients compared with controls. Although mean atrophy rates provided by Jacobian integration were smaller than those from segmentation and subtraction of GM volumes, measurement variance was reduced. The number of patients required per treatment arm to detect a 20% reduction in GM atrophy rate over a 12-month follow-up (90% power) was 202 (95% confidence interval [CI], 118-423) using Jacobian integration and 2047 (95% CI 271 to > 10 000) using segmentation and subtraction. Comparable sample sizes for whole brain atrophy were 240 (95% CI, 142-469) using the BBSI and 196 (95% CI, 110-425) using SIENA. Jacobian integration could be useful for measuring GM atrophy rate in Alzheimer's disease as a marker of disease progression and treatment efficacy.

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  • E/Z-Rubrolide O, an Anti-inflammatory Halogenated Furanone from the New Zealand Ascidian Synoicum n. sp.

    Pearce, Allison; Chia, EW; Berridge, MV; Maas, E; Page, MJ; Webb, VL; Harper, JL; Copp, Brent (2007)

    Journal article
    The University of Auckland Library

    Bioassay-directed fractionation of extracts of a Synoicum n. sp. ascidian from New Zealand led to the isolation of the principal anti-inflammatory component, which was identified by spectroscopic methods as a new member of the rubrolide family, rubrolide O (1), existing as a mixture of E/Z isomers.

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  • Detecting treatment effects on brain atrophy in relapsing remitting multiple sclerosis: sample size estimates

    Anderson, Valerie; Bartlett, JW; Fox, NC; Fisniku, L; Miller, DH (2007-11)

    Journal article
    The University of Auckland Library

    Brain atrophy, thought to reflect neuroaxonal degeneration, may be considered an objective marker of disease progression in multiple sclerosis (MS). Our objective was to estimate sample sizes required for parallel group placebo-controlled trials of disease-modifying treatments in relapsing remitting MS (RRMS), using brain atrophy on MRI as the outcome measure. In addition, we investigated how brain atrophy measurement method and trial duration affect sample sizes. Thirty-three patients with RRMS and 16 controls had T1-weighted volumetric MR imaging acquired at baseline and up to six repeat time-points (six monthly intervals). Brain atrophy was quantified between baseline and each repeat image using four methods: segmented brain volume difference, BBSI, SIENA and ventricular enlargement. Linear mixed models were fitted to data from each subject group and method. Sample size calculations were performed using mean and variance estimates from these models. For a 2 year trial, a treatment slowing atrophy rate by 30% required 123 subjects in each treatment arm if using SIENA to measure atrophy, 157 for the BBSI, 140 for ventricular enlargement and 763 for segmented brain volume difference. For a given effect size and method, sample sizes were statistically significantly reduced the longer the trial duration. Our estimations suggest that brain atrophy could provide an additional outcome measure to clinical assessment for monitoring treatment effects in RRMS although the relationship between atrophy and subsequent disability, and potential confounding factors to atrophy measurement must be further investigated.

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  • A systematic review of tools that support peer assessment

    Luxton-Reilly, Andrew (2009)

    Journal article
    The University of Auckland Library

    Peer assessment is a powerful educational technique that provides significant benefits to both staff and students. Traditionally, peer assessment has been conducted using pen-and-paper in small classes. More recently, online tools have been developed to enable peer assessment to be applied in large class. In this article, the tools that support peer assessment are reviewed and analysed, revealing the common features and significant differences. Future directions for research on peer assessment tools are suggested.

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  • Contributing Student Pedagogy

    Hamer, John; Cutts, Q; Jackova, J; Luxton-Reilly, Andrew; McCartney, R; Purchase, Helen; Riedesel, C; Saeli, M; Sanders, K; Sheard, J (2008)

    Journal article
    The University of Auckland Library

    A Contributing Student Pedagogy (CSP) is a pedagogy that encourages students to contribute to the learning of others and to value the contributions of others. CSP in formal education is anticipatory of learning processes found in industry and research, in which the roles and responsibilities of 'teacher' and 'student' are fluid. Preparing students for this shift is one motivation for use of CSP. Further, CSP approaches are linked to constructivist and community theories of learning, and provide opportunities to engage students more deeply in subject material. In this paper we advance the concept of CSP and relate it to the particular needs of computer science. We present a number of characteristics of this approach, and use case studies from the available literature to illustrate these characteristics in practice. We discuss enabling technologies, provide guidance to instructors who would like to incorporate this approach in their teaching, and suggest some future directions for the study and evaluation of this technique. We conclude with an extensive bibliography of related research and case studies which exhibit elements of CSP.

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  • (Re)making space for kiwi: beyond ???fortress conservation??? in Northland

    Blue, Lyndsay; Blunden, G (2010)

    Journal article
    The University of Auckland Library

    Mainstream conservation has been long dominated globally by the pro-tected area paradigm. This approach has been widely challenged in recent years, and new conservation initiatives have emerged. The situation is mirrored in New Zealand, where ongoing biodiversity loss has prompted reappraisal. Within this context, we highlight the plight of kiwi, focusing on Northland and efforts there to (re)make space for this iconic bird which is at risk of extinction. While the state has primarily responded by fortifying ???islands??? on public conservation land, Far North communities are working in a variety of ways and localities, both within and beyond ???the fortress???, to secure a future for the ???people???s bird???.

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