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The performance of oxygen reduction reaction (ORR) catalysts, typically evaluated by potential scanning techniques, fails to capture the significant activity decay occurring at longer time scales. To meet the 65% peak energy efficiency target, the continuous decay of Pt/C ORR catalyst, commonly referred to as “transient performance loss”, is studied at 0.8 V by chronoamperometry under membrane electrode assembly (MEA) testing conditions. Based on the results from the time-resolved cyclic voltammetry (CV), surface oxidation was identified as the primary cause of the transient loss. The reduction of surface oxide was observed to occur at 0.6 V, and the recovery of cathode performance can hence be achieved at equal or lower potentials. In addition, the effects of operating temperature and cathode humidity were also studied. The coverage of Pt surface oxides and the extent of the transient loss were both significantly reduced as temperature decreased. However, the benefit of a lower operating temperature came at the cost of slower recovery kinetics. In terms of the impact of humidity, the presence of liquid water was identified as the critical factor leading to a much more severe performance loss over time.

We demonstrated transmissive- and reflective-type Fresnel lenses based on dye-doped liquid crystal using photoalignment technique. The former is a polarization-independent and electrically tunable. The maximum diffraction efficiency reaches 37%, which approaches the theoretical limit ~ 41 %. Such a lens functions as a half-wave plate, and this feature could be well preserved under the applied voltage. The reflective-type Fresnel lens is based on dye-doped cholesteric liquid crystals (DDCLC). The formed lens persists without any external disturbance, and its focusing efficiency, analyzed using circularly polarized light, is ~ 23.7 %, which almost equals the measured diffraction efficiency of the used Fresnel-zone-plate mask (~ 25.6 %). The lens is thermally erasable, and rewritable. Notably, both of the transmissive- and reflective-type Fresnel lenses are switchable between focusing and defocusing states, upon application of a voltage. In addition, these devices are simple to fabricate, and have fast switching responses between focusing and defocusing state.

This article is to review the book Children, Language, and Literacy: Diverse Learners in Diverse Times, published in 2009, by Celia Genishi and Anne Haas Dyson. This book aims to explore the central premise that “diversity is the norm” through examining classroom activities that unfold young children’s interaction and learning as well as teachers’ instructional design and strategies. It provides insights into diverse child-centered curricula where children’s flexibility and adaptability in literacy development are stressed. Key focuses throughout this book rest on various dialects of English, sociolinguistic flexibility, pedagogies, assessments, flexible and play-based curricula. As expected, this book would contribute to studies of early childhood literacy, language diversity, and bilingual education. Specifically, it would benefit intended audiences: teachers and educators of young children, particularly teachers working with English language learners, emergent bilinguals, and special needs learners.