Solution processable CH3NH3PbI3 has received considerable attention for highly-efficient perovskite solar cells. However, the different solubility of PbI2 and CH3NH3I is problematic, initiating ...active solvent engineering research using dimethyl sulfoxide (DMSO). Here we investigated the pre-coordination of PbI2–DMSO powders for planar heterojunction perovskite solar cells fabricated by a low-temperature process (≤100 °C). Pre-coordination was carried out by simple mechanical mixing using a mortar and pestle. The composition of PbI2–DMSOx (x = 0, 1, or 2) in the powder mixture was investigated by gradually increasing mechanical mixing time, and a dominant composition of PbI2–DMSO1 was obtained after a 10 min mixing process. The pre-coordinated PbI2–DMSO powders were then blended with CH3NH3I in DMF to make the CH3NH3PbI3 film by toluene-assisted spin-coating and heat treatment. Compared with the one-step blending of CH3NH3I, PbI2, and DMSO in DMF, the pre-coordination method resulted in better dissolution of PbI2, larger grain size, and pinhole-free morphology. Consequently, absorption, fluorescence, carrier lifetime, and charge extraction were enhanced. The average open-circuit voltage (1.046 V), short-circuit current (22.9 mA cm−2), fill factor (73.5%), and power conversion efficiency (17.6%) were increased by 2–12% with decreased standard deviations (13–50%), compared with the one-step blending method. The best efficiency was 18.2%. The simple mechanical pre-coordination of PbI2–DMSO powders was very effective in enhancing the crystallinity of CH3NH3PbI3 and photovoltaic performance.
While the importance of task sequencing in task-based research and syllabus design has been emphasized, there is a gap in the literature regarding whether the order in which tasks are presented ...actually has a significant impact on L2 performance. The aim of the study was to investigate whether task sequencing actually had an effect on L2 written performance. A writing task with three levels of task complexity was given to 88 EFL learners, with one group carrying the three task versions out in the order of increasing task complexity (Simple-to-complex), and the other group in the order of decreasing task complexity (Complex-to-simple). It was found that the cognitive load of the task, as well as learners’ syntactic complexity and lexical diversity shown in their L2 writing, were significantly affected by task sequencing and its interaction with task complexity. Pedagogical implications are noted with regard to the differential effects that task sequencing has on L2 writing, as presenting tasks in the order of increasing task complexity resulted in greater syntactic complexity, while presenting tasks in decreasing task complexity led to greater lexical diversity.
Although extensive task-based research has focused on how the manipulation of task complexity affects L2 performance, less attention has been paid to its combined effects with those of L2 ...proficiency. In this study, 41 Korean learners of English carried out a written task with two levels of task complexity, operationalized as number of elements. Participants were divided into three groups, based on their level of L2 proficiency. Performance was assessed by syntactic complexity, lexical diversity, and accuracy measures. Significant interaction effects between L2 proficiency and task complexity were found on lexical diversity and accuracy measures, especially in the high-proficiency group. Findings are discussed in relation to Robinson’s Cognition Hypothesis and attentional resources available for task performance.
As a preliminary attempt to define an authentic list of English source words for loanwords, this study investigated how frequently, widely, and evenly the 200 source words listed in the 2015 RNCE are ...used in elementary school English textbooks. For this purpose, a corpus was created based on 10 elementary school textbooks and their supplementary e-textbooks. Examination of the distributional properties of the 200 source words in the corpus revealed two findings. First, elementary school English textbooks are not homogeneous with respect to the frequency of these source words. Second, out of the 200 source words, 26 were identified as representative source words of elementary school English textbooks. The usage coefficient of these source words is equal to or greater than 96, their dispersion figure is greater than .60, and their corresponding loanwords are true cognates. This indicates that 26 source words can be useful resources for Korean elementary school students learning English. KCI Citation Count: 0
Although recent studies of L2 writing development have called for the inclusion of metrics that measure phrasal embedding as well as clausal embedding as indicators of syntactic complexity, taskbased ...research on L2 written performance still shows a heavy dependence on length-based measures and clausal subordination. In this study, the written performance of 81 Korean learners of English was examined using traditional syntactic measures that most task-based studies rely on, clausal complexity measures, and noun phrasal complexity measures. Participants were randomly assigned to either a Closed group that carried out closed tasks (i.e., tasks with a predetermined answer), or an Open group that carried out open tasks (i.e., tasks without a predetermined answer). Task complexity was manipulated in terms of the number of elements. Generally in line with Kyle and Crossley’s findings (2018), the study revealed that including more encompassing measures of syntactic complexity helped in the understanding of learners’ interlanguage development, especially when considering their level of L2 proficiency.
Protein misfolding and/or aggregation has been implicated as the cause of several human diseases, such as Alzheimer’s and Parkinson’s diseases and familial amyloid polyneuropathy. These maladies are ...referred to as amyloid diseases, named after the cross-β-sheet amyloid fibril aggregates or deposits common to these disorders. Epigallocatechin-3-gallate (EGCG), the principal polyphenol present in green tea, has been shown to be effective at preventing aggregation and is able to remodel amyloid fibrils comprising different amyloidogenic proteins, although the mechanistic underpinnings are unclear. Herein, we work toward an understanding of the molecular mechanism(s) by which EGCG remodels mature amyloid fibrils made up of Aβ1–40, IAPP8–24, or Sup35NM7–16. We show that EGCG amyloid remodeling activity in vitro is dependent on auto-oxidation of the EGCG. Oxidized and unoxidized EGCG binds to amyloid fibrils, preventing the binding of thioflavin T. This engagement of the hydrophobic binding sites in Aβ1–40, IAPP8–24, or Sup35NMAc7–16 Y→F amyloid fibrils seems to be sufficient to explain the majority of the amyloid remodeling observed by EGCG treatment, although how EGCG oxidation drives remodeling remains unclear. Oxidized EGCG molecules react with free amines within the amyloid fibril through the formation of Schiff bases, cross-linking the fibrils, which may prevent dissociation and toxicity, but these aberrant post-translational modifications do not appear to be the major driving force for amyloid remodeling by EGCG treatment. These insights into the molecular mechanism of action of EGCG provide boundary conditions for exploring amyloid remodeling in more detail.
We report knitted fabrics made from highly conductive stretchable fibers. The maximum initial conductivity of fibers synthesized by wet spinning was 17460 S cm–1 with a rupture tensile strain of 50%. ...The maximum strain could be increased to 490% by decreasing the conductivity to 236 S cm–1. The knitted fabric was mechanically and electrically reversible up to 100% tensile strain when coated by poly(dimethylsiloxane). The normalized resistance of the poly(dimethylsiloxane)-coated fabric decreased to 0.65 at 100% strain.
Recent studies in task-based research have increasingly implemented ways to measure cognitive load in order to ensure that the tasks that were intended to be more complex placed greater cognitive ...load onto the learner, which in turn would lead to systematic changes in outcome measures. This study aims to introduce a more objective, indirect measure of cognitive load: time-on-task. In this study, 42 native speakers of English carried out three types of oral tasks that each had three levels of task complexity, operationalized as the number of elements. Cognitive load was measured by learner self-ratings, prospective time estimations, the dual task methodology, and time-on-task. Results of a series of correlational analyses and repeated-measures ANOVA showed that time-on-task, which can further be divided into time-on-planning and time-on-speech, proved to be a valid measure of cognitive load.
Previous research has shown that English loanwords that are true cognates can clearly be a valuable resource for Korean learners of English. This paper aimed to examine whether the 200 English source ...words in the 2015 RNCE and their Korean counterparts are true cognates, and whether the latter are in fact commonly used in everyday life. Careful scrutiny of the relationships to their Korean equivalents shows that some source words are phonologically or morphologically opaque and others fail to have a one-to-one correspondence in terms of meaning or usage. Moreover, the corpus-based investigation conducted in the present work shows that some of the 200 source words in the 2015 RNCE are ones whose Korean counterparts are not of high frequency and wide range. Because the selection of English source words listed in the RNCE has a substantial effect on English L2 learning, especially L2 vocabulary acquisition, more rigorous criteria must first be established on which the selection of such words can be based. KCI Citation Count: 3
Various perivascular drug delivery techniques have been demonstrated for localized post-treatment of intimal hyperplasia: a vascular inflammatory response caused by endothelial damages. Although most ...perivascular devices have focused on controlling the delivery duration of anti-proliferation drug, the confined and unidirectional delivery of the drug to the target tissue has become increasingly important. In addition, careful attention should also be paid to the luminal stability and the adequate exchange of vascular protein or cell between the blood vessel and extravascular tissue to avoid any side effect from the long-term application of any perivascular device. Here, a highly flexible and porous silk fibroin microneedle wrap (Silk MN wrap) is proposed to directly inject antiproliferative drug to the anastomosis sites while ensuring sufficient vascular exchanges. Drug-embedded silk MNs were transfer-molded on a highly flexible and porous silk wrap. The enhanced cell compatibility, molecular permeability, and flexibility of silk MN wrap guaranteed the structural integrity of blood vessels. Silk wrap successfully supported the silk MNs and induced multiple MN penetration to the target tissue. Over 28 days, silk MN wrap significantly inhibited intimal hyperplasia with a 62.1% reduction in neointimal formation.
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