Search

Various features of scientific discourse have been characterized in the science education literature, and challenges students face in appropriating these features have been explored. Using the fram ...

Using self-generated analogies has been proposed as a method in a constructivist tradition for students to learn about a new subject, by use of what they previously know. We report on a group exercise on using self-generated analogies to make sense of two thermodynamic processes, reversible adiabatic expansion and free adiabatic expansion of an ideal gas. The participants (N = 8) were physics preservice teacher students at the fourth year of the teacher education program. A main finding was that work with self-generated analogies tended to be accompanied by the students assuming ownership for their learning, manifested in terms of actions of choice and control and the use of exploratory talk. Consequently, several self-generated analogies were elaborated and developed to a high-order relational structure. However, we also found that with the use of self-generated analogies in science teaching follows the risks of developing idiosyncratic explanations of the encountered phenomena or getting stuck in overly complex comparisons. Självgenererade analogier har förts fram som en metod i en konstruktivistisk tradition för att elever och studenter ska kunna lära sig något nytt genom att relatera till vad de redan vet. Vi redogör här för en gruppövning där självgenererade analogier användes för att förstå två termodynamiska processer: reversibel adiabatisk expansion, respektive fri adiabatisk expansion av en ideal gas. Åtta (N = 8) lärarstudenter på fjärde året av utbildningen med inriktning mot fysik på gymnasiet deltog i studien. Ett viktigt resultat var att vid arbete med självgenererade analogier tenderade studenterna att ta ägandeskap för sitt lärande, vilket tog sig uttryck i handlingar såsom aktiva val, kontroll över processen och explorativ dialog. Som en följd utvecklades flera av de självgenererade analogierna till ett stort strukturellt djup. Samtidigt såg vi att vid skapande av egna analogier löper studenter risken att utveckla egna förklaringar av de studerade fenomenen som inte svarar mot dem inom vetenskapen eller snärja in sig i alltför komplexa jämförelser.

This exploratory study in a classroom setting investigates first graders (age 78 years, N = 25) ability to perform analogical reasoning and create their own analogies for two irreversible natural phenomena: mixing and heat transfer. We found that the children who contributed actively to a full-class discussion were consistently successful at making analogical comparisons between known objects provided by a researcher and that some of the children could come up with their own analogies for the abstract natural phenomena with which they interacted. The use of full-class and small-group settings, shared laboratory experiences of the phenomena and childrens drawings as different kinds of scaffolding was found to be helpful for the childrens analogical reasoning. As an implication for science education, self-generated analogies are put forward as a potential learning tool within a constructivist approach to education.

Positron emission tomography (PET) radioligands that bind selectively to β-amyloid plaques (Aβ) are promising imaging tools aimed at supporting the diagnosis of Alzheimer’s disease and the evaluati ...

The presence of beta-amyloid plaques in brain is a hallmark of Alzheimer's disease (AD) and serves as a biomarker for confirmation of diagnosis postmortem. Positron emission tomography (PET) radioligands such as Pittsburgh compound B ([(11)C]-2-(3-fluoro-4-methylamino-phenyl)-benzothiazol-6-ol) (PIB) binds selectively to beta-amyloid and are promising new tools supporting the clinical diagnoses of AD. In addition, such methodology may be useful for evaluation of new drugs aiming at reduction of amyloid plaque load. The objective of this study is to develop a new amyloid selective PET radioligand with higher signal-to-background ratio when compared with existing amyloid PET ligands. The lead compound, AZD2184, (2-[6-(methylamino)pyridin-3-yl]-1,3-benzothiazol-6-ol) was found to have high affinity for amyloid fibrils in vitro (K(d): 8.4 +/- 1.0 nM). Two minutes after i.v. administration in rats, about 1% of the dose was in brain. In vitro autoradiography on cortical brain sections from amyloid-beta precursor protein/presenilin 1 (APP/PS1) mice and AD patients showed that while [(3)H]AZD2184 and [(3)H]PIB are mutually displaceable, [(3)H]AZD2184 displays a higher signal-to-background ratio primarily by virtue of lower background binding levels. The ratio of binding ability in prefrontal cortex (high plaque load) to subcortical white matter (background) was 4.5 for [(3)H]AZD2184 and 0.8 for [(3)H]PIB at 1 nM. In adjacent cortical sections from APP/PS1 mouse as well as from AD cortical tissue, [(3)H]AZD2184 and antibodies to human beta-amyloid labeled identical structures. In vivo administration of [(3)H]AZD2184 to APP/PS1 mice further showed that [(3)H]AZD2184 labels amyloid deposits with low non-specific background binding. Taken together, the pre-clinical profile of AZD2184 in relation to the reference ligand PIB, suggests that (11)C-labeled AZD2184 is a potential radioligand for PET-visualization of beta-amyloid deposits in the living human brain.

progressors respectively) (P