Context-free and context-sensitive dynamics in recurrent neural networks

Continuous-valued recurrent neural networks can learn mechanisms for processing context-free languages. The dynamics of such networks is usually based on damped oscillation around fixed points in state space and requires that the dynamical components are arranged in certain ways. It is shown that qualitatively similar dynamics with similar constraints hold for a(n)b(n)c(n), a context-sensitive language. The additional difficulty with a(n)b(n)c(n), compared with the context-free language a(n)b(n), consists of 'counting up' and 'counting down' letters simultaneously. The network solution is to oscillate in two principal dimensions, one for counting up and one for counting down. This study focuses on the dynamics employed by the sequential cascaded network, in contrast to the simple recurrent network, and the use of backpropagation through time. Found solutions generalize well beyond training data, however, learning is not reliable. The contribution of this study lies in demonstrating how the dynamics in recurrent neural networks that process context-free languages can also be employed in processing some context-sensitive languages (traditionally thought of as requiring additional computation resources). This continuity of mechanism between language classes contributes to our understanding of neural networks in modelling language learning and processing.

Protein disulfide isomerase: the structure of oxidative folding

Cellular functions hinge on the ability of proteins to adopt their correct folds, and misfolded proteins can lead to disease. Here, we focus on the proteins that catalyze disulfide bond formation, a step in the oxidative folding pathway that takes place in specialized cellular compartments. In the endoplasmic reticulum of eukaryotes, disulfide formation is catalyzed by protein disulfide isomerase (PDI); by contrast, prokaryotes produce a family of disulfide bond (Dsb) proteins, which together achieve an equivalent outcome in the bacterial periplasm. The recent crystal structure of yeast PDI has increased our understanding of the function and mechanism of PDI. Comparison of the structure of yeast PDI with those of bacterial DsbC and DsbG reveals some similarities but also striking differences that suggest directions for future research aimed at unraveling the catalytic mechanism of disulfide bond formation in the cell.

Space: Irrealis objects in technology policy and their role in a new political economy

In this article, I show how new spaces are being prefigured for colonization in new economy policy discourses. Drawing on a corpus of 1.3 million words collected from legislatures throughout the world, I show the role of policy language in creating the foundations of an emergent form of political economy: The analysis is informed by principles from critical discourse analysis (CDA), classical political economy and critical media studies. It foregrounds a functional aspect of language called process metaphor to show how aspects of human activity are prefigured for mass commodification by the manipulation of realis and irrealis spaces. I also show how the fundamental element of any new political economy, the property element, is being largely ignored. Current moves to create a privately owned global space, which is as concrete as landed property - namely, the electromagnetic spectrum - has significant ramifications for the future of social relations in any global knowledge economy.

Isolation and characterisation of a novel rabbit sulfotransferase isoform belonging to the SULT1A subfamily

Sulfotransferases (SULTs) catalyse the sulfonation of both endogenous and exogenous compounds including hormones, catecholamines. drugs and xenobiotics. While in most occasions, sulfonation is a detoxication pathway. in the case of certain drugs and carcinogens. it leads to metabolic activation. Since, the rabbit has been extensively used for both pharmacological and toxicological studies, the purpose of this study was to further characterise the sulfotransferase system of this animal. In the present study, a novel sulfotransferase isoform (GenBank Accession no. AF360872) was isolated from a rabbit liver cDNA lambdaZAP 11 library. The full-length sequence of the clone was 1138 bp long and contained a coding region of 888 bp encoding a cytosolic protein of 295 amino acids (deduced molecular weight 34,193 Da). The amino acid sequence of this novel SULT isoform showed >70% identity with members of the SULT1A subfamily of sulfotransferases from other species. Upon expression of the encoded rabbit sulfotransferase in Escherchia coli (E. coli), it was shown that the enzyme was capable of sulfonating both p-nitrophenot (K-m and V-max values of 0.15 muM and 897.5 nmol/min/mg protein. respectively) and dopamine (K-m and V-max values of 175.3 muM and 151.1 nmol/min/mg protein, respectively). Based on the sequence data obtained and substrate specificity, this new rabbit sulfotransferase was named rabSULT1A1. Immunoblotting was used to demonstrate that rabSULT1A1 protein is expressed in liver, duodenum, jejunum, ileum, colon and recturm. (C) 2002 Elsevier Science Ltd. All rights reserved.

Virtual learning communities beyond the classroom: perceptions of tertiary Chinese language and non-language learners

As class contact times are reduced as a result of fiscal restraints in the modern tertiary sector, language instructors are placed in the position of having to find new ways to provide experience and continuity in language learning. Extending 'learning communities'—sites of learner knowledge exchange, exposure to diverse learning styles and strategies, and mutual support—beyond the classroom is one solution to maintaining successful linguistic competencies amongst learners. This, however, can conflict with the diverse extra-curricular commitments faced by tertiary students. The flexibility of web-based learning platforms provides one means of overcoming these obstacles. This study investigates learner perceptions of the use of the WebCT platform's computer medicated communication (CMC) tools as a means of extending the community of learning in tertiary Chinese language and non-language courses. Learner responses to Likert and open-ended questionnaires show that flexibility and reduction of negative affect are seen as significant benefits to 'virtual' interaction and communication, although responses are notably stronger in the non-language compared with the language cohort. While both learner cohorts acknowledge positive learning outcomes, CMC is not seen to consistently further interpersonal rapport beyond that established in the classroom. Maintaining a balance between web-based and classroom learning emerges as a concern, especially amongst language learners. [Author abstract, ed]

Rapport-building through call in teaching Chinese as a foreign language: An exploratory study

Technological advances have brought about the ever-increasing utilisation of computer-assisted language learning ( CALL) media in the learning of a second language (L2). Computer-mediated communication, for example, provides a practical means for extending the learning of spoken language, a challenging process in tonal languages such as Chinese, beyond the realms of the classroom. In order to effectively improve spoken language competency, however, CALL applications must also reproduce the social interaction that lies at the heart of language learning and language use. This study draws on data obtained from the utilisation of CALL in the learning of L2 Chinese to explore whether this medium can be used to extend opportunities for rapport-building in language teaching beyond the face-to-face interaction of the classroom. Rapport's importance lies in its potential to enhance learning, motivate learners, and reduce learner anxiety. To date, CALL's potential in relation to this facet of social interaction remains a neglected area of research. The results of this exploratory study suggest that CALL may help foster learner-teacher rapport and that scaffolding, such as strategically composing rapport-fostering questions in sound-files, is conducive to this outcome. The study provides an instruction model for this application of CALL.

Quel role pour la langue de reference dans les representations des apprenants? Le cas de l'evaluation en langue etrangere

This research project explores learner’s representations of strategic L1 use in the foreign language classroom and highlights both the positive or negative roles attributed to the L1 in the language learning process - particularly with respect to language assessment - continuing to explore the relatively understudied domain of student representations within a scholarly context. Surveying a population of Australian (N=18) and French students (N=25), this study uses both questionnaire and interview responses in order to analyse the roles allocated to the L1 with respect to learning outcomes. The results indicate that students have a very balanced view of the L1 with respect to the learning of grammar, vocabulary and social aspects, yet its use in assessment aspects appears much more advantageous. The importance of this study and its findings is in recognizing the complex nature of learner representations in order to facilitate a discussion that is based more on the reality of language teaching, with the hope of renewing classroom practices.

Speech disorder in preschool children exposed to Cantonese and English

Speech disorder in monolingual Cantonese- or English-speaking children has been well described in the literature. There appear to be no reports, however, that describe speech-disordered children who have been exposed to both languages. Here we report on the error patterns of two preschool speech-disordered children who were learning two languages. Both children's first language was Cantonese, but they were also exposed to English through the media and child care. Their disorders were of unknown aetiology. The following questions were asked of the data: (a) Do bilingual children, suspected of having speech problems, make errors in Cantonese and English that reflect delay or disorder when compared with normative data on monolingual speech development in each language? (b) How does the children's speech differ from other bilingual children from the same language learning background? (c) Are the children's speech difficulties apparent in both languages? (d) Is the pattern of errors the same in both languages or do language-specific processes operate? The results bear on theories of acquisition, disorder and bilingualism; they also have clinical implications for speech-language pathologists whose caseloads include bilingual preschool children.

Perceptions of kanji learning strategies: Do they differ among Chinese character and alphabetic background learners

This study investigates three important issues in kanji learning strategies; namely, strategy use, effectiveness of strategy and orthographic background. A questionnaire on kanji learning strategy use and perceived effectiveness was administered to 116 beginner level, undergraduate students of Japanese from alphabetic and character backgrounds in Australia. Both descriptive and statistical analyses of the questionnaire responses revealed that the strategies used most often are the most helpful. Repeated writing was reported as the most used strategy type although alphabetic background learners reported using repeated writing strategies significantly more often than character background learners. The importance of strategy training and explicit instruction of fundamental differences between character and alphabetic background learners of Japanese is discussed in relation to teaching strategies. [Author abstract]