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- Andrews, Jennifer E., et al.
(author)
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SN 2017gmr : An Energetic Type II-P Supernova with Asymmetries
- 2019
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In: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 885:1
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Journal article (peer-reviewed)abstract
- We present high-cadence UV, optical, and near-infrared data on the luminous Type II-P supernova SN;2017gmr from hours after discovery through the first 180 days. SN;2017gmr does not show signs of narrow, high-ionization emission lines in the early optical spectra, yet the optical light-curve evolution suggests that an extra energy source from circumstellar medium (CSM) interaction must be present for at least 2 days after explosion. Modeling of the early light curve indicates a ?500 R progenitor radius, consistent with a rather compact red supergiant, and late-time luminosities indicate that up to 0.130;;0.026 M of Ni-56 are present, if the light curve is solely powered by radioactive decay, although the Ni-56 mass may be lower if CSM interaction contributes to the post-plateau luminosity. Prominent multipeaked emission lines of H? and [O i] emerge after day 154, as a result of either an asymmetric explosion or asymmetries in the CSM. The lack of narrow lines within the first 2 days of explosion in the likely presence of CSM interaction may be an example of close, dense, asymmetric CSM that is quickly enveloped by the spherical supernova ejecta.
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| 3. |
- Berton, Marco
(author)
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Effects of task complexity on the relationship between lexical richness and fluency in foreign language writing
- 2023
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Conference paper (peer-reviewed)abstract
- One of the most intriguing lines of investigation suggested by Foster (2020) refers to the relationship between free vocabulary use and fluency performance measures in speech. The hypothesis of a strong relationship between vocabulary and fluency had already been formulated also regarding writing, since one of the definitions proposed for writing fluency can be summarised as the speed of lexical retrieval while writing (Snellings et al. 2004). Thus, being a fluent writer, at least according to such slightly narrow definition, would be a consequence of being able to quickly access the mental lexicon in order to retrieve the lexical items needed.The present study investigates the written production in a narrative and a decision-making task by Swedish university students of Spanish as a foreign language. The relationship between lexical richness (diversity and sophistication) and fluency measures is analysed with the aim of finding possible changes due to the different degree of task complexity. The result showed that, when manipulating task complexity in both task types, the relationship between lexical richness and fluency turned out to be unclear, as it varied in unpredictable ways depending on the learners´ overall proficiency and passive vocabulary knowledge. Implications, limitations, and promising future lines of investigation will be discussed in light of previous research.
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| 4. |
- Berton, Marco, 1986-
(author)
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Riqueza léxica y expresión escrita en aprendices suecos de ELE : Proficiencia general, competencia léxica pasiva, tipo y complejidad de la tarea
- 2020
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Doctoral thesis (other academic/artistic)abstract
- The present study explored lexical richness in the written production of Swedish university students of Spanish as a foreign language. Two aspects of lexical richness were investigated in the study, i.e., diversity (the ability to use a varied lexical repertoire), and sophistication (the proportion of relatively infrequent words). The written data were elicited by means of two task types, namely a narrative task and a decision-making task. The main aim of the study was investigating the effect of the factors overall proficiency, passive vocabulary knowledge, manipulation of task complexity and task type on lexical richness. Moreover, the study inquired into the predicting power of the first three factors in relation to lexical richness within each task type. Overall proficiency was measured by means of a cloze test, while an estimation of passive vocabulary knowledge was obtained through a word recognition test. The effect of the manipulation of task complexity was examined by using two different versions of each task. The less complex version of the narrative task was based on a cartoon strip with a tight structure and no background events. On the contrary, in the more complex version the cartoon strip depicted a story without a clear sequence and with background events which are relevant to the story plot. Regarding the decision-making task, task complexity was manipulated by changing the number of elements involved. The task itself consisted in writing a message to a friend suggesting a holiday destination. To do so, the participants had to consider the friend´s needs and check them against the possibilities offered by a travel agency. The less complex version included two destinations, while the more complex one contained six. When analysing the effect of manipulating task complexity, structural complexity measures were included with the purpose of investigating if changes in lexical richness go hand in hand with or at the expense of changes in structural complexity. The results of the analysis of these three factors showed different patterns depending on the task type examined. These results suggest that overall proficiency seems to have an effect on lexical richness only in the narrative task, whereas passive vocabulary knowledge would influence lexical richness only in the decision-making task. The manipulation of task complexity apparently affected lexical diversity and structural complexity in the narrative task, on the one hand, and lexical sophistication in the decision-making task, on the other hand. When manipulating task complexity, the relationship between lexical richness and structural complexity turned out to be unclear, as it varied in unpredictable ways depending on the learners´ overall proficiency and passive vocabulary knowledge. The intrinsic complexity inherent to task type, i.e. the different cognitive load that different task types place on the learner, showed the most consistent effect in the study, as it was supported by all the measures of lexical richness and some measures of structural complexity. Finally, the regression model conformed by overall proficiency, passive vocabulary knowledge, and the manipulation of task complexity did not prove to be suitable to predict lexical richness in either of the task types under investigation in the study.
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