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Although the elastocaloric effect was found in natural rubber as early as 160 years ago, commercial elastocaloric refrigeration based on polymer elastomers has stagnated owing to their deficient elastocaloric effects and large extension ratios. Herein, we demonstrate that polymer elastomers with uniform molecular chain-lengths exhibit enormous elastocaloric effects through reversible conformational changes. An adiabatic temperature change of −15.3 K and an isothermal entropy change of 145 J kg−1 K−1, obtained from poly(styrene-b-ethylene-co-butylene-b-styrene) near room temperature, exceed those of previously reported elastocaloric polymers. A rotary-motion cooling device is tailored to high-strains characteristics of rubbers, which effectively discharges the cooling energy of polymer elastomers. Our work provides a strategy for the enhancement of elastocaloric effects and could promote the commercialization of solid-state cooling devices based on polymer elastomers.

Higher education policy and talent training are failing to meet the ever-changing expectations of employers and society in Taiwan, resulting in a gap between university education and employment. We used social cognitive career theory to explore the relationships between problem-based learning, teachers' transformational leadership, and students' self-efficacy and employability. Participants were 619 undergraduates from 12 Taiwanese higher education institutions. We performed structural equation modeling and found that there were significant positive correlations between students' self-efficacy, problem-based learning, and employability, along with teachers' transformational leadership. Further, problem-based learning and the students' self-efficacy were key mediators of the relationship between teachers' transformational leadership and students' employability. Implications are discussed for related issues and future research involving models of students' employability.

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Compared to polyvinylidene fluoride (PVDF) and its copolymers, castor-oil-derived nylon-11 has been less explored over the past decades, despite its excellent piezoelectric properties at elevated temperatures. To utilize nylon-11 for future sensor or vibrational energy harvesting devices, it is important to control the formation of the electroactive δ′ crystal phase. In this work, nylon-11 films were first fabricated by solution-casting and were then uniaxially stretched at different stretching ratios (SR) and temperatures (Ts) to obtain a series of stretched films. The combination of two-dimensional wide-angle X-ray diffraction (2D-WAXD) and differential scanning calorimetry (DSC) techniques showed that the fraction of the δ′ crystal phase increased with the stretching ratio and acquired a maximum at a Ts of 80 °C. Further, it was found that the ferroelectric and piezoelectric properties of the fabricated nylon-11 films could be correlated well with their crystalline structure. Consequently, the stretched nylon-11 film stretched at an SR of 300% and a Ts of 80 °C showed maximum remanent polarization and a remarkable piezoelectric coefficient of 7.2 pC/N. A simple piezoelectric device with such a nylon-11 film was made into a simple piezoelectric device, which could generate an output voltage of 1.5 V and a current of 11 nA, respectively.

Background Colleges and universities in China have offered courses based on online teaching platforms as required by the Ministry of Education since the beginning of the COVID-19 pandemic. This emergency action was not an expedient measure, but a powerful impetus to improve extant education and implement teaching reform. Oral histopathology is a basic subject in oral medicine education, which combines theory with practice. The course aims to improve the ability of students to observe, think, analyze and identify oral diseases. Method We adjusted and modified the original Bridge-In, Outcomes, Pre-assessment, Participatory Learning, Post-assessment, and Summary (BOPPPS) teaching method to fit the characteristics and needs of oral histopathology. We then combined the characteristics of Small Private Online Courses (SPOCs) and a Flipped class to complete teaching material online, and assessed the effects of such teaching using a questionnaire and interviews. Fifty 5th-year undergraduates in stomatology at the School of Stomatology of Harbin Medical University of China participated in online classes. All were in the junior second half of the semester at the beginning of 2020. Teachers investigated from various medical colleges were responsible for delivering courses associated with stomatology or ophthalmology. Result & conclusion The results showed that the modified BOPPPS combined with SPOC and the Flipped class improved teaching satisfaction. Modified BOPPPS combined with SPOC and the Flipped class is a useful complement to offline teaching on 5th-year undergraduate oral histopathology learning in China during COVID-19, and it can meet the multiple needs of students participating in the course.

Advanced polymer dielectrics with high energy density at elevated temperatures are highly desired to meet the requirements of modern electronic and electrical systems under harsh conditions. Herein, we report a novel polyimide/magnesium oxide (PI/MgO) nanodielectric that exhibits high energy storage density (Ue) and charge–discharge efficiency (η) along with excellent cycling stability at elevated temperatures. Benefiting from the large bandgap of MgO and the extended interchain spacing of PI, the composite films can simultaneously achieve high dielectric constant and high breakdown strength, leading to enhanced energy storage density. The nanocomposite film doped with 0.1 vol% MgO can achieve a maximum Ue of 2.6 J cm−3 and a η of 89% at 450 MV m−1 and 150 °C, which is three times that of the PI film under the same conditions. In addition, embedding ultralow content of inorganic fillers can avoid aggregation and facilitate its large-scale production. This work may provide a new paradigm for exploring polymer nanocomposites with excellent energy storage performance at high temperatures and under a high electric field.

Development of advanced dielectric materials with both high‐electric energy density and high‐temperature resistant attributes is highly desirable in modern electronics and electrical systems. Herein, a series of polyimide (PI)‐based sandwich‐structured dielectric nanocomposite films have been attempted to develop the advanced high‐temperature resistant capacitor films, wherein the boron nitride nanosheets/PI nanocomposite acts as the outer layers and the zinc oxide (ZnO)/PI as the middle layer. Benefitting from the merits of both fillers and the unique structure, the resulting nanocomposite films can simultaneously achieve both high‐dielectric constant and high‐breakdown strength, as well as low‐electrical conduction loss, thus leading to improved discharged energy densities (Ue) and charge/discharge efficiency (η) at elevated temperatures. It is found that the sandwich‐structured nanocomposite film with 0.4 vol% ZnO (0.4ZnO/PI‐S) can deliver a maximum Ue of 5.29 J cm−3 at 400 MV m−1 and 150°C, which is about 1.9 times that of the pristine PI film. Moreover, outstanding dielectric stability over 10,000 charge/discharge cycles has been demonstrated in such PI‐based sandwich‐structured nanocomposite films at 150°C and 200 MV m−1. This research may provide a new paradigm to explore polymer nanocomposites having excellent energy storage and efficiency at elevated temperatures.