High-pressure induces topology boosting thermoelectric performance of Bi2Te3.

Decoupling conductivity(σ)and Seebeck coefficient(S)by electronic topological transitions (ETT) under high pressure (2-4 GPa) is a promising method for bismuth telluride (Bi2Te3) to optimize thermoelectric (TE) performance. However, theScannot dramatically increase with increasingσwhen ETT occurs in Bi2Te3, which impedes optimizing TE performance by utilizing ETT in Bi2Te3. A new strategy of enhanced ETT by combining lattice distortions and high pressure is proposed in this work. The lattice distortions in Bi2Te3were introduced by high pressure and high temperature (HPHT) treatment to generate surplus dislocations. Thein-situmeasurements ofσandSat HPHT in Bi2Te3with lattice distortions show an enhanced ETT effect at 2 GPa, which causes decoupleσandSwith an anomalous increase in its|S|about 22%. The ETT effect causes the figure of merit (ZT) of Bi2Te3can be improved to 0.275 at 1.50-2.62 GPa, 460 K, it is more than 62% compared with 0.79 GPa, at 450 K. The excellent TE performance of Bi2Te3arising from the lattice distortions can result in local non-hydrostatic pressure which enhances ETT under high pressure. This work provides a new strategy to enhance ETT to decoupleσandS, and search for better TE materials from the pressure dimension in the future.

Accurate in situ measurements of thermoelectric transport properties at high pressure and high temperature.

Regulating electron structure and electron-phonon coupling by means of pressure and temperature is an effective way to optimize thermoelectric properties. However, in situ testing of thermoelectric transport performance under pressure and temperature is hindered by technical constraints that obscure the intrinsic effects of pressure and temperature on thermoelectric properties. In the present study, a new reliable assembly was developed for testing the in situ thermoelectric transport performance of materials at high pressure and high temperature (HPHT). This reduces the influence of thermal effects on the test results and improves the success rate of in situ experiments at HPHT. The Seebeck coefficient and electrical resistivity of α-Cu2Se were measured under HPHT, and the former was found to increase with increasing pressure and temperature; for the latter, although an increase in the pressure acted to lower the electrical resistivity, an increase in the temperature acted to increase it. On increasing pressure from 0.8 to 3 GPa at 333 K, the optimal power factor of α-Cu2Se was increased by ∼76% from 2.36 × 10-4-4.15 × 10-4 W m-1 K-2, and the higher pressure meant that α-Cu2Se had its maximum power factor at lower temperature. The present work is particularly important for understanding the thermoelectric mechanism under HPHT.

Psychological Distress and Its Association With Quality of Life in Organ Transplant Recipients During COVID-19 Pandemic.

Objectives: The coronavirus disease 2019 (COVID-19) pandemic may have an impact on the psychological distress of organ transplant recipients. We aimed to assess the status of psychological distress and its association with quality of life (QoL) in organ transplant recipients during the COVID-19 pandemic. Materials and Methods: A cross-sectional survey was carried out with 305 organ transplant recipients during March 30 and April 2, 2020, in Wuhan. Psychological distress comprised depression, anxiety, insomnia, and post-traumatic stress disorder (PTSD), which were assessed using the Patient Health Questionnaire-9, the seven-item Generalized Anxiety Disorder questionnaire, the Insomnia Severity Index, and Impact of event scale-revised. QoL was assessed using the Chinese version of the short Form 36-item health survey. Results: The prevalence of depression, anxiety, insomnia, and PTSD in organ transplant recipients was 13.4, 6.9, 11.8, and 30.5%, respectively. Organ transplant recipients with depression had significantly lower scores in all eight dimensions of QoL compared with participants without depression (all p < 0.05). Lower scores on the QoL dimensions of role physical, bodily pain, general health, vitality, role emotional, and mental health were found in organ transplant recipients with anxiety, insomnia, or PTSD compared with their counterparts without the respective disorder (all p < 0.05). Limitation: The cross-sectional study design limited us to make causal conclusion and the influence of potential confounders cannot be ruled out. Conclusions: Psychological distress was prevalent in organ transplant recipients during the COVID-19 pandemic, and those with depression, anxiety, insomnia, and PTSD had poorer QoL. Therefore, timely psychological counseling, COVID-19 related health education, and essential community medical services should be provided to organ transplant recipients to relieve their psychological distress, and to improve their QoL.