Higher Education Admission Policy and Social Class of Ethnic Minority:The Case of Guangxi Zhuang Autonomous Region,China

Gaokao has been considered as the gatekeeper of intergenerational class reproduction in today’s slowing social mobility in China.In order to bolster the fairness of Gaokao,the Policy of Bonus Scores for Ethnic Minority Candidates(PBSEMC)has been issued,whose,however,effectiveness in promoting upward social class has not been adequately empirically explored.The difference-in-differences(DID)analysis based on cross-sectional data,which is distinct from the traditional DID analysis paradigm,was implemented to assess the Reform of PBSEMC in the Guangxi Zhuang Autonomous Region in 1988.The results showed that PBSEMC had a significant and positive impact on the social classes of ethnic minorities,and gender,residence type and occupation type were also relevant to social class,aligning with the previous literature.The PBSEMC is effective in improving the social classes of ethnic minorities.However,the PBSEMC policy should be made more precise,in order to benefit the candidates who are in genuine need of assistance.

Remote Learning in Higher Education During the Pandemic: A Study of the Experiences of Chinese International Students at United Kingdom and United States Universities in 2020/21

During the COVID-19 pandemic crisis,many universities around the world made a drastic change by transferring most of their offline classes to emergency remote learning(ERL).The aim of this study was to explore how Chinese students,who studied in United Kingdom(UK)and United States(US)universities during the 2020/21 academic year,perceive their experiences of remote learning.As the UK and the US have two relatively advanced education systems,the arrangements of their universities for ERL and their support for international students are worth exploring.Moreover,during the ERL,a portion of Chinese students had online classes in their home countries instead of the country in which their universities are located.Therefore,semi-structured interviews were carried out to explore the academic experiences and social interaction of students who studied in UK and US universities,while remaining in China.The data were analyzed using the thematic analysis method.The findings showed that ERL was perceived negatively by students despite its flexibility in areas of academic learning experiences and social interaction.

Low-Dimensional Halide Perovskites and Their Advanced Optoelectronic Applications

Metal halide perovskites are crystalline materials originally developed out of scientific curiosity. They have shown great potential as active materials in optoelectronic applications. In the last 6 years, their certified photovoltaic efficiencies have reached 22.1%. Compared to bulk halide perovskites, low-dimensional ones exhibited novel physical properties. The photoluminescence quantum yields of perovskite quantum dots are close to 100%. The external quantum efficiencies and current efficiencies of perovskite quantum dot light-emitting diodes have reached 8% and 43 cd A^(-1),respectively, and their nanowire lasers show ultralow-threshold room-temperature lasing with emission tunability and ease of synthesis. Perovskite nanowire photodetectors reached a responsivity of 10 A W^(-1)and a specific normalized detectivity of the order of 10^(12 )Jones. Different from most reported reviews focusing on photovoltaic applications, we summarize the rapid progress in the study of low-dimensional perovskite materials, as well as their promising applications in optoelectronic devices. In particular, we review the wide tunability of fabrication methods and the state-of-the-art research outputs of low-dimensional perovskite optoelectronic devices. Finally, the anticipated challenges and potential for this exciting research are proposed.

Hydroiodic Acid Additive Enhanced the Performance and Stability of PbS-QDs Solar Cells via Suppressing Hydroxyl Ligand

The recent emerging progress of quantum dot ink(QD-ink)has overcome the complexity of multiple-step colloidal QD(CQD)film preparation and pronouncedly promoted the device performance.However,the detrimental hydroxyl(OH)ligands induced from synthesis procedure have not been completely removed.Here,a halide ligand additive strategy was devised to optimize QD-ink process.It simultaneously reduced sub-bandgap states and converted them into iodide-passivated surface,which increase carrier mobility of the QDs films and achieve thicker absorber with improved performances.The corresponding power conversion efficiency of this optimized device reached 10.78%.(The control device was 9.56%.)Therefore,this stratege can support as a candidate strategy to solve the QD original limitation caused by hydroxyl ligands,which is also compatible with other CQD-based optoelectronic devices.

Lagrangian eddies in the Northwestern Pacifi c Ocean

The Lagrangian eddies in the western Pacifi c Ocean are identifi ed and analysed based on Maps of Sea Level Anomaly(MSLA)data from 1998 to 2018.By calculating the Lagrangian eddy advected by the AVISO velocity fi eld,we analyzed the variations in Lagrangian eddies and the average transport eff ects on diff erent time scales.By introducing the Niño coeffi cient,the lag response of the Lagrangian eddy to El Niño is found.These data are helpful to further explore the role of mesoscale eddies in ocean energy transfer.Through normalized chlorophyll data,we observed chlorophyll aggregation and hole eff ects caused by Lagrangian eddies.These fi ndings demonstrate the important role of Lagrangian eddies in material transport.The transportation volume of the Lagrangian eddy is calculated quantitatively,and several major transport routes have been identifi ed,which helps us to more accurately and objectively estimate the transport capacity of Lagrangian eddies in the western Pacifi c Ocean.

Improving the Performance of PbS Quantum Dot Solar Cells by Optimizing ZnO Window Layer

Comparing with hot researches in absorber layer,window layer has attracted less attention in PbS quantum dot solar cells(QD SCs). Actually, the window layer plays a key role in exciton separation, charge drifting, and so on.Herein, ZnO window layer was systematically investigated for its roles in QD SCs performance. The physical mechanism of improved performance was also explored. It was found that the optimized ZnO films with appropriate thickness and doping concentration can balance the optical and electrical properties, and its energy band align well with the absorber layer for efficient charge extraction. Further characterizations demonstrated that the window layer optimization can help to reduce the surface defects, improve the heterojunction quality, as well as extend the depletion width. Compared with the control devices, the optimized devices have obtained an efficiency of 6.7% with an enhanced V_(oc) of 18%, J_(sc) of 21%, FF of 10%, and power conversion efficiency of 58%. The present work suggests a useful strategy to improve the device performance by optimizing the window layer besides the absorber layer.

SARS-CoV-2 Surveillance Through China Influenza Surveillance Information System—China,December 1,2022 to February 12,2023

Introduction:The World Health Organization(WHO)proposed using influenza surveillance systems to carry out coronavirus disease 2019(COVID-19)surveillance due to the similarity between the two diseases in some respiratory symptoms.To assess the prevalence of COVID-19,we analyzed the influenzalike illness(ILI)and positive rate of severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)detections in ILI patients reported to the influenza Surveillance Information System(CNISIS)since late 2022.Methods:Data related to ILI were reported by national surveillance sentinel hospitals.Positive testing for SARS-CoV-2 and influenza viruses was conducted using real-time reverse transcription polymerase chain reaction(rRT-PCR)detection by the national influenza surveillance network laboratories.Surveillance data were reported to CNISIS.Results:Beginning on December 12,2022(Week 50),the ILI percentage increased dramatically,peaking in Week 51 at 12.1%.Subsequently,the ILI percentage began to decline rapidly from Week 52,2022,and by Week 6,2023(February 6-12),the ILI and ILI percentage had returned to the levels observed at the beginning of December 2022.From December 1,2022 to February 12,2023,115,844 specimens were tested for both SARS-CoV-2 and influenza virus.Of these,30,381(26.2%)were positive for SARSCoV-2 and 1,763(1.5%)were positive for influenza virus.The positive rate of SARS-CoV-2 tests peaked at 74.1%around December 23 and 25.Conclusions:Sentinel-based surveillance,previously established for influenza,is an effective way to track the circulation trend of SARS-CoV-2 during community-level epidemics.There was no coprevalence of SARS-CoV-2 and influenza virus during the outbreak of SARS-CoV-2,even during the winter influenza season.However,it is important to remain vigilant for the potential rise of influenza activities following the COVID-19 epidemic.

季节性流感疫苗和新型冠状病毒疫苗同时接种工作的思考和建议

在新型冠状病毒肺炎(新冠肺炎)全球大流行的环境下, 流感的流行强度、流行特征和人群的感染风险均呈现出新的特点, 且全球多地区已出现新冠肺炎和流感共同流行的情况。新冠肺炎和流感的传播方式、临床症状等方面相似, 流感病毒与新型冠状病毒对细胞的作用机制上也存在相似之处, 同时做好新冠肺炎和流感的防控工作具有较强可行性和重大现实意义。本文从流感疫苗接种预防共同感染、流感疫苗和新冠病毒疫苗同时接种等方面, 探讨了流感和新冠共同防控的相关策略和措施, 提出了相应的思考和建议, 以期为季节性流感疫苗和新型冠状病毒疫苗接种策略的制订提供科学支撑。

An easy synthesis of Ni-Co doped hollow C-N tubular nanocomposites as excellent cathodic catalysts of alkaline and neutral zinc-air batteries

Exploring high-activity electrocatalyst for oxygen reduction reaction (ORR) is of great significance for a variety of renewable energy conversion and storage technologies. Herein, we fabricated novel ORR electrocatalysts derived from Ni-Co nanoparticles encapsulated in hollow tubular C-N composites (ht-CN) through an easy and scalable pyrolysis route utilizing nickel acetate and cobalt acetate as metal precursors, 2-cyanoguanidine as the nitrogen source, and sucrose as the carbon source. Among the prepared nanocomposite catalysts with different molar ratios ofNi/Co, the catalyst Ni2Co3@ht-CN exhibits an outstanding ORR electroactivity comparable to Pt/C catalyst both in alkaline and neutral media. Home-made zinc-air battery with the Ni2Co3@ht-CN as cathode electrocatalyst presents excellent performance and superior durability either in neutral or alkaline medium. The Ni2Co3@ht-CN battery delivers an open circuit voltage of 1.08 V and a maximum power density of 47 mW cm^-2 in 0.5 mol L^-1 KNO3 solution, while 1.51 V and 314 mW cm^-2 in 6 mol L-^1 KOH solution. In addition, whether in neutral or alkaline solution, the constant current discharge curves of the Ni2Co3@ht-CN battery at different current densities exhibit higher voltage plateau and stability than the Pt/C battery. Results demonstrate the potential application of the catalysts of the present investigation to Zn-air batteries both in alkaline and neutral media.

Fabrication and properties of high quality InGaN-based LEDs with highly reflective nanoporous GaN mirrors

Distributed Bragg reflectors (DBRs) are essential components for the development of optoelectronic devices.In this paper, we first report the use of the nanoporous GaN (NP-GaN) DBR as a template for regrowth of InGaN-based light-emitting diodes (LEDs). The wafer-scale NP-GaN DBR, which is fabricated by electrochemical etching in a neutral solution, has a smooth surface, high reflectivity (>99.5%), and wide spectral stop band width (>70 nm). The chemical composition of the regrown LED thin film is similar to that of the reference LED, but the photoluminescence (PL) lifetime, PL intensity, and electroluminescence intensity of the LED with the DBR are enhanced several times compared to those of the reference LED. The intensity enhancement is attributed to the light reflection effect of the NP-GaN DBR and improved crystalline quality as a result of the etching scheme, whereas the enhancement of PL lifetime is attributable to the latter.