Validating chemical and structural changes in painting materials by principal component analysis of spectroscopic data using internal mineral standards

This work shows the capability of principal component analysis (PCA) to detect molecular, chemical and mineralogical changes in historic painting materials subjected to a thermal ageing test (< 250 °C). To simulate the heat-induced alterations an ageing accelerated process was performed on two sets of samples containing two mineral phases (hydroxyapatite and quartz) and two organic compounds (collagen and albumin). The chosen minerals behaved as internal standards during the tests since they are stable and chemically inert at the tested temperatures. Raman microscopy (RM) was applied to characterise one set of samples made of bone, containing ca. 70% hydroxyapatite and 30% collagen. Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy was used to study the other set of samples made of four different quartz/albumin mixtures with quartz contents of 30%, 50%, 70% and 90% (w/w). The aim was to identify the ideal proportion of internal standard to be validated by ATR-FTIR and PCA, determined to be 70%. PCA analyses detected changes in the molecular structures of the organic components while the internal mineral standard remained stable. Moreover, the internal standard IR/Raman bands were constant during the tests and confirmed that the results of PCA analyses were independent of instrumental and technical factors, as well as sample collecting and handling. This demonstrates the potential benefits of our approach to study historical painting materials, which have suffered any type of heat-induced alteration.     

From resource to document: scaffolding content and organising student learning in teachers’ documentation work on the teaching of series

We examine teachers’ use of resources as they prepare to teach the topic of numerical series of real numbers, in order to identify how their personal relationship with mathematical content—and its teaching—interacts with their use of a commonly used textbook. We describe this interplay between textbook and personal relationship, a term coined in the Anthropological Theory of the Didactic (ATD, Chevallard, 2003), in terms of documentation work (resources, aims, rules of action, operational invariants), a key construct from the documentational approach (DA, Gueudet & Trouche, in Educational Studies in Mathematics, 71, 199–218, 2009). We do so in the case of five post-secondary teachers who use the same textbook as a main resource for teaching the topic. Documentational analysis of interviews with the teachers led to the identification of their aims and rules of action (the what and how of their resource use as they organise their teaching of the topic) as well as the operational invariants (the why for this organisation of their teaching). We describe the teachers’ documentation work in two sets of aims/rules of action: scaffolding mathematical content (series as a stepping stone to learning about Taylor polynomials and Maclaurin series), and organising student learning about series through drill exercises, visualisation, examples, and applications. Our bridging (networking) of theoretical constructs originating in one theoretical framework (personal relationship, ATD) with the constructs of a different, yet compatible, framework (documentation work, DA) aims to enrich the latter (teachers’ documentation work) with the individual agency (teachers’ personal relationships with the topic) provided by the former.     

Argumentation and indigenous knowledge: socio-historical influences in contextualizing an argumentation model in South African schools

This forum considers argumentation as a means of science teaching in South African schools, through the integration of indigenous knowledge (IK). It addresses issues raised in Mariana G. Hewson and Meshach B. Ogunniyi’s paper entitled: Argumentation-teaching as a method to introduce indigenous knowledge into science classrooms: opportunities and challenges. As well as Peter Easton’s: Hawks and baby chickens: cultivating the sources of indigenous science education; and, Femi S. Otulaja, Ann Cameron and Audrey Msimanga’s: Rethinking argumentation-teaching strategies and indigenous knowledge in South African science classrooms. The first topic addressed is that implementation of argumentation in the science classroom becomes a complex endeavor when the tensions between students’ IK, the educational infrastructure (allowance for teacher professional development, etc.) and local belief systems are made explicit. Secondly, western styles of debate become mitigating factors because they do not always adequately translate to South African culture. For example, in many instances it is more culturally acceptable in South Africa to build consensus than to be confrontational. Thirdly, the tension between what is “authentic science” and what is not becomes an influencing factor when a tension is created between IK and western science. Finally, I argue that the thrust of argumentation is to set students up as “scientist-students” who will be considered through a deficit model by judging their habitus and cultural capital. Explicitly, a “scientist-student” is a student who has “learned,” modeled and thoroughly assimilated the habits of western scientists, evidently—and who will be judged by and held accountable for their demonstration of explicit related behaviors in the science classroom. I propose that science teaching, to include argumentation, should consist of “listening carefully” (radical listening) to students and valuing their language, culture, and learning as a model for “science for all”.     

NARST: a lived history

In this Forum, we construct a history of the National Association for Research in Science Education (NARST) through the analysis of documents and through the personal perspectives of individuals. The history of NARST is inseparable from the biography of the individuals through whose lives it was produced and reproduced. The history of NARST is a living history that both shapes and was shaped by the biographies of its members.

Predictor variables of written picture naming in the deaf

Studies conducted in recent years on oral andwritten language production show that the ageat which words are learned is the main variablethat influences lexical access in both hearingpeople and people who have suffered brainlesions. No studies have been done with deafpeople and, since they use sign language inaddition to oral language, differencesregarding hearing people might be found intheir lexical organization. The aim of thisstudy was to test which variables determine thelexical production of deaf people. For thispurpose, 40 deaf people between the ages of 13and 58 years were asked to write individuallythe names of 100 pictures. The regressionanalyses performed on a total of 4000 responsesshow that the main predictor variable ofperformance was also age of acquisition. It isconcluded that the organization of the lexicalsystem in deaf people is similar to that of hearing people, although the phonologicalrepresentations of deaf people may be moreinaccurate.     

Giving priority to evidence in science teaching: A first‐year elementary teacher's specialized practices and knowledge

The purpose of this qualitative case study was to examine the nature of a first‐year elementary teacher's specialized practices and knowledge for giving priority to evidence in science teaching and to explore the possible sources from which this knowledge was generated. Data included three audiotaped interviews, six videotaped classroom observations, lesson plans, and samples of students' work. The findings of this study reveal that the teacher gave priority to evidence by frequently engaging students in collecting evidence through observations and investigations, recording and representing evidence, and using that evidence to construct explanations. The findings of this study also illustrate that critical experiences during preparation to teach and specific university coursework acted as sources through which the teacher's specialized knowledge for giving priority to evidence was generated. © 2005 Wiley Periodicals, Inc. J Res Sci Teach 42: 965–986, 2005     

Bridging memory-based collaborative filtering and text retrieval

When speaking of information retrieval, we often mean text retrieval. But there exist many other forms of information retrieval applications. A typical example is collaborative filtering that suggests interesting items to a user by taking into account other users’ preferences or tastes. Due to the uniqueness of the problem, it has been modeled and studied differently in the past, mainly drawing from the preference prediction and machine learning view point. A few attempts have yet been made to bring back collaborative filtering to information (text) retrieval modeling and subsequently new interesting collaborative filtering techniques have been thus derived. In this paper, we show that from the algorithmic view point, there is an even closer relationship between collaborative filtering and text retrieval. Specifically, major collaborative filtering algorithms, such as the memory-based, essentially calculate the dot product between the user vector (as the query vector in text retrieval) and the item rating vector (as the document vector in text retrieval). Thus, if we properly structure user preference data and employ the target user’s ratings as query input, major text retrieval algorithms and systems can be directly used without any modification. In this regard, we propose a unified formulation under a common notational framework for memory-based collaborative filtering, and a technique to use any text retrieval weighting function with collaborative filtering preference data. Besides confirming the rationale of the framework, our preliminary experimental results have also demonstrated the effectiveness of the approach in using text retrieval models and systems to perform item ranking tasks in collaborative filtering.