An experimental study on the effect of hexagonal boron nitride (h‐BN) underlay and cap layers on excitonic dynamics in monolayer WS2 is reported. A monolayer WS2 flake is fabricated by mechanical exfoliation. By using a dry transfer technique, three regions of the sample are obtained: WS2 directly on SiO2, WS2 on h‐BN, and WS2 sandwiched by two h‐BN flakes. Photoluminescence measurements show higher yield and narrower linewidth of the h‐BN/WS2/h‐BN region. Transient absorption measurements reveal that the top h‐BN layer enhances the exciton formation, prolongs the exciton lifetime, and slightly affects the exciton–exciton annihilation. By performing spatially resolved transient absorption measurements, exciton diffusion coefficients of about 100, 40, and 26 cm2 s−1 for the regions of WS2, h‐BN/WS2, and h‐BN/WS2/h‐BN, respectively, are obtained. The suppression of exciton diffusion by h‐BN is attributed to the additional phonon scattering mechanisms introduced by h‐BN, which decreases the exciton mean free path and thus the diffusion coefficient. The findings provide useful information for designing and understanding the effect of h‐BN layers interfacing with 2D semiconductors.

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PRV measurement could present the similar results as HRV analysis for sleep apnea patients during different sleep stages.

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Aim: To compare thermocoagulation and cryotherapy for treatment of high-grade cervical intraepithelial neoplasia (CIN). Methods: From May 2017 to May 2018, women with CIN2/3 were randomized to thermocoagulation or cryotherapy at Peking University Shenzhen Hospital. Follow-up at 4 and 8 months included cytology and human papillomavirus (HPV) testing. Women who were HPV-positive or had atypical squamous cells of undetermined significance or higher-grade disease underwent colposcopy/biopsy. Results: Among 149 women enrolled, 74 were randomized to thermocoagulation, and 75 to cryotherapy (excluded four were immediately referred for thermocoagulation due to large lesions). At follow-up, there was no difference between the thermocoagulation and cryotherapy groups in HPV-negative (4/8 months: 72.5%/86.2% vs 68.6%/80.6%) and pathology-negative (97.1%/98.5% vs 94.3%/92.3%) rates (all P > 0.05). The cytology-negative rate was similar for thermocoagulation and cryotherapy at 4 months (79.7% vs 78.9%, P > 0.05), but higher for thermocoagulation at 8 months (100% vs 88.7%, P < 0.05). No lesions were observed among the four referral women at follow-up. As compared with cryotherapy, thermocoagulation was associated with shorter duration of treatment and less vaginal discharge, but higher pain during application and longer bleeding after treatment. Conclusion: Thermocoagulation was as effective and safe as cryotherapy and might be easily applied to treat high-grade cervical lesions.

Abstract-A nationwide sample of university students completed a survey that asked questions about their perceptions of the factors that can cause problems which exist with online or general group work. Data were obtained from 173 students at more than 18 different universities in the United Kingdom. Three main problems that exist in group collaboration are identified through an extensive review of literature and addressed as problem scenarios in the survey. These include: poor motivation, lack of individual accountability and negative interdependence. Findings from the survey include that on average more than five factors are acknowledged by the students for each subcategory of problem, and for each scenario the factors that affect the group work are ranked by importance level. Furthermore, we find no statistically significant association between the students' backgrounds and their perceptions of the factors identified.

A comprehensive experimental study on optical properties and photocarrier dynamics in Bi2O2Se monolayers and nanoplates is presented. Large and uniform Bi2O2Se nanoplates with various thicknesses down to the monolayer limit are fabricated. In nanoplates, a direct optical transition near 720 nm is identified by optical transmission, photoluminescence, and transient absorption spectroscopic measurements and is attributed to the transition between the valence and conduction bands in the Γ valley. Time‐resolved differential reflection measurements reveal ultrafast carrier thermalization and energy relaxation processes and a photocarrier recombination lifetime of about 200 ps in nanoplates. Furthermore, by spatially resolving the differential reflection signal, a photocarrier diffusion coefficient of about 4.8 cm2 s−1 is obtained, corresponding to a mobility of about 180 cm2 V−1 s−1. A similar direct transition is also observed in monolayer Bi2O2Se, suggesting that the states in the Γ valley do not change significantly with the thickness. The temporal dynamics of the excitons in the monolayer is quite different from the nanoplates, with a strong saturation effect and fast exciton–exciton annihilation at high densities. Spatially and temporally resolved measurements yield an exciton diffusion coefficient of about 20 cm2 s−1.

˙OH selectively attacks the active sites opposite to phenolic hydroxyl groups and leads to bond-cleavage of ether bonds.