Hyunwoo Kim

While verbs and argument structure constructions are essential for deriving sentence meaning, their roles in sentence processing remains less known. To address this issue, the present study explored how a verb’s lexical properties and the strength of verb–construction associations influence second language (L2) sentence processing. In two self-paced reading experiments, Korean-speaking learners of English and native English speakers read English argument structure constructions containing verbs with varying lexical properties and association strength. In both Experiment 1 (involving the prepositional dative construction) and Experiment 2 (involving the caused-motion construction), only the L2-English learners, and not the native speakers, spent more time integrating the target constructions with verbs of weaker associations than those with stronger associations. Furthermore, the learners exhibited greater difficulty with verb–construction integration when the verbs were less frequent and less concrete; L2 proficiency did not modulate these effects. Our findings support the constructionist approach, suggesting that both verbs and verb–construction associations play an instrumental role in sentence comprehension.

© 2015 Walker et al.Background: Carbohydrate binding modules bind polysaccharides and help target glycoside hydrolases catalytic domains to their appropriate carbohydrate substrates. To better understand how CBMs can improve cellulolytic enzyme reactivity, representatives from each of the 18 families of CBM found in Ruminoclostridium thermocellum were fused to the multifunctional GH5 catalytic domain of CelE, which can hydrolyze numerous types of polysaccharides including cellulose, mannan, and xylan. Since CelE is a cellulosomal enzyme, none of these fusions to a CBM previously existed. Results: CelEcc-CBM fusions were assayed for their ability to hydrolyze cellulose, lichenan, xylan, and mannan. Several CelEcc-CBM fusions showed enhanced hydrolytic activity with different substrates relative to the fusion to CBM3a from the cellulosome scaffoldin, which has high affinity for binding to crystalline cellulose. Additional binding studies and quantitative catalysis studies using nanostructure-initiator mass spectrometry were carried out with the CBM3a, CBM6, CBM30, and CBM44 fusion enzymes. In general, and consistent with observations of others, enhanced enzyme reactivity was correlated with moderate binding affinity of the CBM. Numerical analysis of reaction time courses showed that CelEcc-CBM44, a combination of a multifunctional enzyme domain with a CBM having broad binding specificity, gave the fastest rates for hydrolysis of both the hexose and pentose fractions of ionic-liquid pretreated switchgrass. Conclusion: We have shown that fusions of different CBMs to a single multifunctional GH5 catalytic domain can increase its rate of reaction with different pure polysaccharides and with pretreated biomass. This fusion approach, incorporating domains with broad specificity for binding and catalysis, provides a new avenue to improve reactivity of simple combinations of enzymes within the complexity of plant biomass.

© 2015. American Geophysical Union. All Rights Reserved. The impacts of droughts on the Amazon ecosystem have been broadly discussed in recent years, but a comprehensive understanding of the consequences is still missing. In this study, we show evidence of a fragile hydrological equilibrium in the western Amazon. While drainage systems located near the equator and the western Amazon do not show water deficit in years with average climate conditions, this equilibrium can be broken during drought events. More importantly, we show that this effect is persistent, taking years until the normal hydrological patterns are reestablished. We show clear links between persistent changes in forest canopy structure and changes in hydrological patterns, revealing physical evidence of hydrological mechanisms that may lead to permanent changes in parts of the Amazon ecosystem. If prospects of increasing drought frequency are confirmed, a change in the current hydroecological patterns in the western Amazon could take place in less than a decade.

This study investigated the role of cross-linguistic influence in L2 learners’ integration of a verb and a construction during online English sentence processing. In a self-paced reading task, L1-English speakers and Chinese-L1 learners of English read the English double-object and prepositional dative constructions with verbs whose Chinese translation equivalents are either compatible or incompatible with each dative form. When including only a subset of trials for which participants provided expected translations for the target sentences (i.e., translating the English prepositional dative construction into a Chinese prepositional dative sentence and translating the English double-object construction into a Chinese double-object sentence), the effect of cross-linguistic influence emerged only in a certain type of verbs. When including all trials in the analysis, we found the effect of cross-linguistic influence for all verb types. These results provide some evidence that the cross-linguistic activation of verbs can influence verb-construction integration in L2 processing. The study highlights how bilingual co-activation of verbs extends beyond the lexical and structural levels to influence the integration of multiple sources of information.