1,071 research outputs found

    The role of force dynamics and intentionality in the reconstruction of L2 verb meanings:A Danish-Spanish bidirectional study

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    This paper examines the role of force dynamics and intentionality in the description of placement events by two groups of native speakers of typologically and genetically different languages, Danish and Spanish, and by two groups of intermediate adult learners, Danish learners of L2 Spanish and Spanish learners of L2 Danish. The results of the study showed that (a) force dynamics and intentionality are important semantic components in both languages, but their distribution and relative focus differed crosslinguistically, and (b) the two learner groups had difficulties in reconstructing the meanings of the L2 verbs involving these two semantic components. Learning difficulties were observed when moving from a less to a more complex L2 system, when moving in the opposite direction, i.e., from a more to a less complex L2 system and when moving to an L2 system that is as complex as the learners native one

    How do differences in exposure affect English language learning? A comparison of teenagers in two learning environments

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    This study investigates whether potential differences in the weight of out-of-school and in-school learning environments affect the acquisition of L2 English by teenagers in two geographical contexts, more and less English-rich, and with less and more linguistic distance to English, respectively. Participants were two groups of 14-15-year-olds, from Denmark and Spain. Language measures included a listening comprehension test, a metalinguistic knowledge test, and a grammaticality judgment test. Data about out-of-classroom exposure was elicited via a questionnaire. The study showed that (a) the Danish group attained a significantly higher level in all language tests except for the metalinguistic knowledge test; (b) the Danish group engaged longer in out-of-school activities although the preference for some activities over others was similar in the two groups; and (c) the types of associations between out-of-school activities and language measures were different between the two groups. These results suggest that the potential influence of out-of-school activities on different language aspects is related to the particular context in which the L2 is learned and to the language proficiency of the learner

    Oral English performance in Danish primary school children: An interactional usage-based approach

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    Following the call in Sandlund, Sundqvist, and Nyroos (2016) for incorporating discursive approaches into the field of oral second language (L2) testing, this paper proposes an interactional usage-based approach to the analysis of oral L2 performance. Based on Eskildsen (2018a), we combine analytic tools from usage-based linguistics and conversation analysis. We draw on usage-based linguistics to analyze performance in terms of test-takers’ inventories of linguistic constructions and on conversation analysis to understand their interactional competence in terms of the relation between the linguistic constructions and the actions they are used to accomplish. Performance assessment is thus constructional and interactional. Participants in this pilot study were two Danish primary school children who performed two consecutive oral tasks: a semi-guided interview and a picture-elicited narrative task. Data were analyzed by means of cross-child comparisons and cross-task comparisons within each child. Our data confirm the observation from previous research that simple question-answer(-assessment) sequences dominate oral test formats, but also that the format is sometimes abandoned, which allows for the accomplishment of new social actions. Moreover, the picture-description task affords a different speech exchange system with the interviewer participating more as an active listener when the children do not voluntarily carry out the requested task

    Asymmetric Hydrogenation of 1-alkyl and 1-aryl vinyl benzoates: a broad scope procedure for the highly enantioselective synthesis of 1-substituted ethyl benzoates

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    The enantioselective hydrogenation of enol esters of formula CH2=C(OBz)R with rhodium catalysts based on phosphine-phosphite ligands (P-OP) has been studied. The reaction has a broad scope and it is suitable for the preparation of products possessing a wide variety of R substituents. For the cases where R is a primary alkyl high catalyst activity (S/C = 500) and enantioselectivities (95-99 % ee) were obtained with a catalyst characterized by an ethane backbone and a PPh2 fragment. In contrast, for R = tBu a catalyst possessing a benzene backbone provided the best results (97 % ee). Derivatives with a cycloalkyl R substituent were particularly difficult substrates for this reaction. A broader catalyst screening was required for these substrates, which identified a catalyst possessing a P(m-xylyl)2 fragment as the most appropriate one, affording enantioselectivities between 90 and 95 % ee. Outstanding enantioselectivities (99 % ee) and high catalyst activity (S/C = 500-1000) were also obtained in the case of substrates bearing a Ph or a fluoroaryl R substituent. In addition, the system is also appropriate for the preparation of other synthetically useful esters as those for R = benzyl, 2-phenylethyl or Nphthalimido alkyl chains. Likewise, the hydrogenation of divinyl dibenzoates proceeded with very high diastero- and enantioselectivity, generating rather low amounts of the meso isomer (3-6 %). On the other hand, substrates with Br- and MeO- substituents at the phenyl benzoate ring, suitable for further functionalization, have also been examined. The results obtained indicate no detrimental effect of these substituents in the hydrogenation. Alternatively, the methodology has been applied to the highly enantioselective synthesis of deuterium isotopomers of 1-octyl benzoate bearing CDH2, CD2H or CD3 fragments. Finally, as a practical advantage of the present system, it has been observed that the high performance of the catalysts is retained in high concentrated solutions or even in the neat substrate, then minimizing both the amount of solvent added and the volume of the reactionJunta de Andalucía 2009/FQM-4832CSIC 201480E03 1Ministerio de Ciencia e Innovación CTQ2010- 14796/BQ

    Apple Snail Perivitellin Precursor Properties Help Explain Predators’ Feeding Behavior

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    In contrast with vitellogenin maturation, it is unknown whether gastropod perivitellin precursors are subject to large structural changes. The gastropod reproductive tract includes an accessory organ, the albumen gland (AG), that produces and secretes perivitelline fluid. In the apple snail Pomacea canaliculata, the large, reddish-pink AG provides eggs with perivitellins that are defensive against predators. Although the AG makes a considerable contribution to apple snail biomass, field observations indicate that it is rejected by avian and mammalian predators, although the underlying reason remains unknown. By analyzing the structure-function properties of P. canaliculata perivitellin precursors, we provide insight into perivitellin maturation and its relationship with apple snail predator feeding behavior. Structural analysis using small-angle X-ray scattering, absorption and fluorescence spectroscopy, circular dichroism, electrophoresis, chromatography, and partial proteolysis showed that the size, shape, and structure of perivitellin precursors resemble those of egg mature forms. Functional analysis indicates that the precursors of the defensive perivitellins ovorubin (PcOvo) and perivitellin-2 (PcPV2) are highly stable and antinutritive, withstanding proteinase digestion and displaying structural stability of their quaternary structure under a wide pH range (4.0–10.0). Furthermore, AG extracts limit a predator’s ability to digest nutrients and are toxic to mice (median lethal concentration 96 h after administration: 5.9 mg/kg). Treated mice displayed neurologic signs similar to those produced by egg PcPV2. Results indicate that apple snails store active precursors of egg proteins inside the AG, providing evidence that gastropod perivitellin precursors do not experience the large structural processing of invertebrate vitellogenin maturation. These defensive proteins provide the apple snail AG with neurotoxic, antinutritive, and antidigestive activity, a likely explanation for the predators’ feeding behavior.Instituto de Investigaciones Bioquímicas de La PlataFacultad de Ciencias Naturales y Muse

    Apple Snail Perivitellin Precursor Properties Help Explain Predators’ Feeding Behavior

    Get PDF
    In contrast with vitellogenin maturation, it is unknown whether gastropod perivitellin precursors are subject to large structural changes. The gastropod reproductive tract includes an accessory organ, the albumen gland (AG), that produces and secretes perivitelline fluid. In the apple snail Pomacea canaliculata, the large, reddish-pink AG provides eggs with perivitellins that are defensive against predators. Although the AG makes a considerable contribution to apple snail biomass, field observations indicate that it is rejected by avian and mammalian predators, although the underlying reason remains unknown. By analyzing the structure-function properties of P. canaliculata perivitellin precursors, we provide insight into perivitellin maturation and its relationship with apple snail predator feeding behavior. Structural analysis using small-angle X-ray scattering, absorption and fluorescence spectroscopy, circular dichroism, electrophoresis, chromatography, and partial proteolysis showed that the size, shape, and structure of perivitellin precursors resemble those of egg mature forms. Functional analysis indicates that the precursors of the defensive perivitellins ovorubin (PcOvo) and perivitellin-2 (PcPV2) are highly stable and antinutritive, withstanding proteinase digestion and displaying structural stability of their quaternary structure under a wide pH range (4.0–10.0). Furthermore, AG extracts limit a predator’s ability to digest nutrients and are toxic to mice (median lethal concentration 96 h after administration: 5.9 mg/kg). Treated mice displayed neurologic signs similar to those produced by egg PcPV2. Results indicate that apple snails store active precursors of egg proteins inside the AG, providing evidence that gastropod perivitellin precursors do not experience the large structural processing of invertebrate vitellogenin maturation. These defensive proteins provide the apple snail AG with neurotoxic, antinutritive, and antidigestive activity, a likely explanation for the predators’ feeding behavior.Instituto de Investigaciones Bioquímicas de La PlataFacultad de Ciencias Naturales y Muse
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