Both plume and arc : origin of Neoarchaean crust as recorded in Veligallu greenstone belt, Dharwar craton, India

Several profound changes, including those involving formation of the continental crust, occurred on Earth during the Neoarchaean Era. However, the tectonic settings associated with Neoarchaean crustal growth are not well understood and vigorously debated. The Neoarchaean Veligallu greenstone belt, eastern Dharwar craton hosts a variety of ultramafic, mafic and felsic volcanic rocks. Whole-rock elemental and Nd isotope data along with zircon U-Pb dating on these rocks provide significant insights into the origin and tectonic setting of Neoarchaean crust formation. The volcanism in the Veligallu belt started with similar to 2.67 Ga tholeiitic basalts derived from shallow melting of a slightly depleted mantle (epsilon(Ndt) = + 0.6 to + 1.1). Moderate negative Nb anomalies, slightly elevated Th/Yb and LREE, and an absence of evidence for crustal contamination are consistent with extraction of these basalts from a mantle source weakly metasomatized by subducted slab-derived fluids in an incipient oceanic arc setting. As the arc matured, clastic sediments started forming with concurrent emplacement of komatiites, komatiitic basalts and ferropicrites showing strong signatures of contamination with continental crust (negative Nb and Ti anomalies, LREE enrichment and negative epsilon(Ndt)). In the final stage (similar to 2.58 Ga), a variety of felsic volcanic rocks (sodic trachyandesite, high Mg# andesite, rhyolite, calc-alkaline andesite) formed. The rock association and distinct geochemical signatures (enrichment of LILE, negative Nb and Ti anomalies, Mesoarchaean Nd model ages and inherited older zircons) suggest a continental margin arc environment which contained older crust. The evolutionary history of the Veligallu belt implies that both the arcand plume-related processes, and their interplay contributed significantly to the growth of Neoarchaean crust.Peer reviewe

Progressor: Social navigation support through open social student modeling

The increased volumes of online learning content have produced two problems: how to help students to find the most appropriate resources and how to engage them in using these resources. Personalized and social learning have been suggested as potential ways to address these problems. Our work presented in this paper combines the ideas of personalized and social learning in the context of educational hypermedia. We introduce Progressor, an innovative Web-based tool based on the concepts of social navigation and open student modeling that helps students to find the most relevant resources in a large collection of parameterized self-assessment questions on Java programming. We have evaluated Progressor in a semester-long classroom study, the results of which are presented in this paper. The study confirmed the impact of personalized social navigation support provided by the system in the target context. The interface encouraged students to explore more topics attempting more questions and achieving higher success rates in answering them. A deeper analysis of the social navigation support mechanism revealed that the top students successfully led the way to discovering most relevant resources by creating clear pathways for weaker students. © 2013 Taylor and Francis Group, LLC

Negotiating topic changes:native and non-native English speakers in conversation

There is a tendency to view conversations involving non‐native speakers (NNSs) as inevitably fraught with problems, including an inability to handle topic management. This article, in contrast, will focus on effective topic changes made by non‐native speakers during informal conversations with native speakers of English. A micro‐analysis of ten conversations revealed several ways of shifting conversational topics; however, the article concentrates on those strategies which the participants used to effect a particular type of topic move, namely ‘marked topic changes’, where there is no connection at all with previous talk. The findings show how these topic changes were jointly negotiated, and that the non‐native speakers’ contributions to initiating new topics were competently managed

Motivational Social Visualizations for Personalized E-Learning

A large number of educational resources is now available on the Web to support both regular classroom learning and online learning. However, the abundance of available content produces at least two problems: how to help students find the most appropriate resources, and how to engage them into using these resources and benefiting from them. Personalized and social learning have been suggested as potential methods for addressing these problems. Our work presented in this paper attempts to combine the ideas of personalized and social learning. We introduce Progressor + , an innovative Web-based interface that helps students find the most relevant resources in a large collection of self-assessment questions and programming examples. We also present the results of a classroom study of the Progressor +  in an undergraduate class. The data revealed the motivational impact of the personalized social guidance provided by the system in the target context. The interface encouraged students to explore more educational resources and motivated them to do some work ahead of the course schedule. The increase in diversity of explored content resulted in improving students’ problem solving success. A deeper analysis of the social guidance mechanism revealed that it is based on the leading behavior of the strong students, who discovered the most relevant resources and created trails for weaker students to follow. The study results also demonstrate that students were more engaged with the system: they spent more time in working with self-assessment questions and annotated examples, attempted more questions, and achieved higher success rates in answering them

Promoting Client Participation and Constructing Decisions in Mental Health Rehabilitation Meetings

The chapter analyzes practices by which support workers promote client participation in mental health rehabilitation meetings at the Clubhouse. While promoting client participation, the support workers also need to ascertain that at least some decisions get constructed during the meetings. This combination of goals—promoting participation and constructing decisions—leads to a series of dilemmatic practices, the dynamics of which the chapter focuses on analyzing. The support workers may treat clients’ turns retrospectively as proposals, even if the status of these turns as such is ambiguous. In the face of a lack of recipient uptake, the support workers may remind the clients about their epistemic access to the content of the proposal or pursue their agreement or commitment to the idea. These practices involve the support workers carrying primary responsibility over the unfolding of interaction, which is argued to compromise the jointness of the decision-making outcome.The chapter analyzes practices by which support workers promote client participation in mental health rehabilitation meetings at the Clubhouse. While promoting client participation, the support workers also need to ascertain that at least some decisions get constructed during the meetings. This combination of goals—promoting participation and constructing decisions—leads to a series of dilemmatic practices, the dynamics of which the chapter focuses on analyzing. The support workers may treat clients’ turns retrospectively as proposals, even if the status of these turns as such is ambiguous. In the face of a lack of recipient uptake, the support workers may remind the clients about their epistemic access to the content of the proposal or pursue their agreement or commitment to the idea. These practices involve the support workers carrying primary responsibility over the unfolding of interaction, which is argued to compromise the jointness of the decision-making outcome.Peer reviewe

Laughter as medical providers' resource : negotiating informed choice in prenatal genetic counseling

This article aims to challenge the perception that in medical encounters laughter is an interactional resource primarily employed by patients. Drawing on 34 video-recorded prenatal genetic counseling (PGC) sessions collected in a Hong Kong hospital, and combining quantitative and qualitative methods, we illustrate that laughter is in fact frequently employed by the medical providers in our data. The particular focus of the article is on the ways in which laughter initiated by the medical providers assists interlocutors in negotiating informed choice, a crucial aspect of PGC sessions. Findings indicate that laughter initiated by the medical providers performs at least two PGC-specific functions: It assists the medical providers in olaughing offo and overcoming patients' resistance, and it helps them in dealing with patients' direct questions. Laughter is thus an important resource for the medical providers in pursuing the institutional goals of the interaction, namely negotiating informed choice with their patients