Neural substrates of L2-L1 transfer effects on phonological awareness in young Chinese-English bilingual children.

The growing trend of bilingual education between Chinese and English has contributed to a rise in the number of early bilingual children, who were exposed to L2 prior to formal language instruction of L1. The L2-L1 transfer effect in an L1-dominant environment has been well established. However, the threshold of L2 proficiency at which such transfer manifests remains unclear. This study investigated the behavioral and neural processes involved when manipulating phonemes in an auditory phonological task to uncover the transfer effect in young bilingual children. Sixty-two first graders from elementary schools in Taiwan were recruited in this study (29 Chinese monolinguals, 33 Chinese-English bilinguals). The brain activity was measured using fNIRS (functional near-infrared spectroscopy). Bilingual children showed right lateralization to process Chinese and left lateralization to process English, which supports more on the accommodation effect within the framework of the assimilation-accommodation hypothesis. Also, compared to monolinguals, bilingual children showed more bilateral frontal activation in Chinese, potentially reflecting a mixed influence from L2-L1 transfer effects and increased cognitive load of bilingual exposure. These results elucidate the developmental adjustments in the neural substrates associated with early bilingual exposure in phonological processing, offering valuable insights into the bilingual learning process.

Solid Electrolyte Bimodal Grain Structures for Improved Cycling Performance.

The application of solid-state electrolytes in Li batteries is hampered by the occurrence of Li-dendrite-caused short circuits. To avoid cell failure, the electrolytes can only be stressed with rather low current densities, severely restricting their performance. As grain size and pore distributions significantly affect dendrite growth in ceramic electrolytes such as Li7La3Zr2O12 and its variants; here, a "detour and buffer" strategy to bring the superiority of both coarse and fine grains into play, is proposed. To validate the mechanism, a coarse/fine bimodal grain microstructure is obtained by seeding unpulverized large particles in the green body. The rearrangement of coarse grains and fine pores is fine-tuned by changing the ratio of pulverized and unpulverized powders. The optimized bimodal microstructure, obtained when the two powders are equally mixed, allows, without extra interface decoration, cycling for over 2000 h as the current density is increased from 1.0 mA·cm-2, and gradually, up to 2.0 mA·cm-2. The "detour and buffer" effects are confirmed from postmortem analysis. The complex grain boundaries formed by fine grains discourage the direct infiltration of Li. Simultaneously, the coarse grains further increase the tortuosity of the Li path. This study sheds light on the microstructure optimization for the polycrystalline solid-state electrolytes.

Three-Dimensionally Aligned Sulfur Electrodes by Directional Freeze Tape Casting.

Rational design of sulfur electrodes is exceptionally important in enabling a high-performance lithium/sulfur cell. Constructing a continuous pore structure of the sulfur electrode that enables facile lithium ion transport into the electrode and mitigates the reconstruction of sulfur is a key factor for enhancing the electrochemical performance. Here, we report a three-dimensionally (3D) aligned sulfur electrode cast onto conventional aluminum foil by directional freeze tape casting. The 3D aligned sulfur-graphene oxide (S-GO) electrode consisting of few micron thick S-GO layers with 10-20 µm interlayer spacings demonstrates significant improvement in the performance of the Li/S cell. Moreover, the freeze tape cast graphene oxide electrode exhibits homogeneous reconfiguration behavior in the polysulfide catholyte cell tests and demonstrated extended cycling capability with only 4% decay of the specific capacity over 200 cycles. This work emphasizes the critical importance of proper structural design for sulfur-carbonaceous composite electrodes.

Facile and Versatile Sol-Gel Strategy for the Preparation of a High-Loaded ZnO/SiO2 Adsorbent for Room-Temperature H2S Removal.

Preparation of well-dispersed ZnO nanograins is necessary to improve their reactivity toward room-temperature H2S removal. However, the challenge to design such a ZnO-based adsorbent with high ZnO loading is yet to be fulfilled. Herein, a facile sol-gel strategy is reported for the preparation of ZnO/SiO2 adsorbents for efficient H2S removal, by innovating a gel-drying method and simultaneously controlling ZnO grain formation through optimizing the molar ratio of ethylene glycol (EG)/nitrates in its precursors. The fabricated adsorbent embedded well-dispersed ZnO nanograins, of approximately 10-15 nm, into a SiO2 matrix (57 wt % ZnO loading) and thus yielded a high H2S removal capacity of 108.9 mg S/g sorbent. Therein, EG was used as a modifier for inhibiting the formation of a denser SiO2 network during the gel drying process and was used as a fuel for promoting the decomposition of nitrates and increasing the surface area of the composites in the subsequent calcination. Modulating the molar ratio of EG/nitrates ≤ 2 in precursors or traditional drying of the gel in an oven should be avoided because these would lead to the oxidation of EG by metallic nitrates and form carboxylate complexes during the gel-drying process. Although the produced ZnO grains had a very small size of less than 5 nm, a layer of monodentate ZnCO3 impurity was formed on the ZnO surface, which will drastically decrease the reactivity of ZnO toward H2S. According to the encouraging results from CuO and Co3O4, this strategy has proved to be versatile for the preparation of other metal oxide/SiO2 adsorbents.