Control of stereochemistry plays a key role in medicinal chemistry, material and life science. As a prominent AIE luminogen, tetraphenylethene (TPE) derivatives have E/Z isomers which are challenging to separate even by HPLC. Herein, we designed oxetane-substituted TPE (TPE-2OXE) and separated pure isomers by simple column chromatography with high yields, as confirmed by mass spectrometry, IR and NMR spectroscopy. The isomerization of the two isomers can occur by photo-and thermo-activation. Importantly, (Z)-TPE-2OXE isomer solid shows bathochromic emission with a quantum yield 5 times higher than that of (E)-TPE-2OXE. The differences in emission wavelength and quantum yield are derived from distinct emission mechanisms of locally excited (LE) state emission of (E)-TPE-2OXE and charge transfer (CT) state emission of (Z)-TPE-2OXE. The two isomers are also good piezochromic luminescent materials, which have not only an obvious emission color shift but also significantly enhanced luminescence brightness by external force. In addition, (E)-TPE-2OXE solids show self-healing ability, which can crystallize spontaneously from ground amorphous state. The higher brightness of (E)-TPE-2OXE can be retained in solution, so fluorescent AIE nanodots are prepared from the two isomers. Cell-labeling experiments also show that (Z)-TPE-2OXE AIE dots have higher labeling brightness as compared to the (E)-TPE-2OXE isomer. The synthesis and distinct properties of E/Z isomers are beneficial to further development of new TPE derivatives for various applications.

By the end of 2012, China had launched 16 BeiDou-2 navigation satellites that include six GEOs, five IGSOs and five MEOs. This has provided initial navigation and precise pointing services ability in the Asia-Pacific regions. In order to assess the navigation and positioning performance of the BeiDou-2 system, Wuhan University has built up a network of BeiDou Experimental Tracking Stations (BETS) around the World. The Position and Navigation Data Analyst (PANDA) software was modified to determine the orbits of BeiDou satellites and provide precise orbit and satellite clock bias products from the BeiDou satellite system for user applications. This article uses the BeiDou/GPS observations of the BeiDou Experimental Tracking Stations to realize the BeiDou and BeiDou/GPS static and kinematic precise point positioning (PPP). The result indicates that the precision of BeiDou static and kinematic PPP reaches centimeter level. The precision of BeiDou/GPS kinematic PPP solutions is improved significantly compared to that of BeiDou-only or GPS-only kinematic PPP solutions. The PPP convergence time also decreases with the use of combined BeiDou/GPS systems.

The coronavirus disease (COVID-19) was first reported in China (Wuhan) at the end of 2019. It has rapidly spread over 216 countries, including the USA, UK, Europe, Russia, and many Asian countries. It has affected more than 4.5 million people, and around 0.3 million deaths have been reported globally. Many preventive measures have been adopted worldwide to mitigate its spread. The government of Pakistan has also taken many preventive measures to combat the COVID-19 outbreak, such as rapid response by governance, continuous monitoring of the pandemic spread in the affected areas, and integration of resources from multiple sectors, including health, education, defense, and media. According to global statistics, the number of COVID-19 cases in the country remained remarkably lower than the expected number for the first 169 days, as compared to other countries. A total of 286,674 confirmed cases, including 16,475 active, 6,139 deaths, and 264,060 (92%) recoveries were reported. The study finds that strict adherence to national policies, effective governance, and unity at the national level resulted in better outcomes. Hence, the preventive measures, rapid responses, and strategies adopted for combating the challenges could be adopted as a learning tool for other countries having similar work environments and financial constraints. This paper can help and guide governance/public actions in response to the possible rebound of coronavirus this fall/winter.

High-contrast fluorescence switching has been achieved in polymer films or fibers with non-invasive stimuli.

Urbanization is playing a key role in big cities of developing countries, which, in effect, is increasing the population. This study takes care of the mega infrastructure project (Orange Line Metro Train (OLMT)) to explore and identify the H&S (Health and Safety) factors that affect the local residents and the main key stakeholders working on the project. A Sequential Mixed-Method approach of the OLMT-project includes qualitative and quantitative methods were adopted. The data have been collected from the targeted population working on the OLMT-project through a questionnaire. The main key finding of the study indicates that poor planning and a lack of communication between the public and government led to frustration. The most significant factors that identified in the study were unsafe to work practice, project scope constraints, lack in technical and material support, unsafe/bad condition, health/environment degradation, declination and loss of resources and time, no proper emergency system, and negligence in adopting safety rules and laws. The study also revealed that the consensus should also be noticed between the key stakeholders (e.g., contractors, clients, safety officials, academia) in the second round of the Delphi survey of the project. The study findings will help the key stakeholders to prioritize their energies towards attaining zero levels of inadequate health and safety practices in infrastructure projects. The study outcomes can also be generalized for the other developing countries having a similar work scenario.

Recently,m etastable-state photoacids have been widely used to control protontransfer in numerousc hemical and biologicalp rocesses as well as applicationsw ith visible light. Generally,s ubstituents have ag reat influence on the photochemical properties of molecules, which will further affect their applications. Yet, the effects of substituents on metastable-state photoacids have not been studied systematically.I nt his work, 16 metastable-state photoacid derivatives were designeda nd synthesized on the basis of sub-stituents having al arge range of s-p electron-donor-acceptor capabilities. The effects of substituents on the color display [or maximuma bsorption band(s)], solubility,p K a values,d ark/photoacidity,p hotosensitivity,a nd relaxation kinetic(s) were investigated in detail.T his study will be helpful for the targeted design and synthesis of promisingp hotoacids and the application of their photocontrolled proton-release processes in functional materials/devices.Supporting Information and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

An AIE fluorescent switch exhibited multi-parameter detection properties for pH, sulfite anion and pressure with good linear relationships.

The products of Wuhan University with 5-min sampling are used to analyze the characteristics of BeiDou satellite clocks. Two nanoseconds root-mean-square (RMS) variations are obtained for 1-day quadratic fits in the sub-daily region. The relativistic effects of BDS clocks are also studied. General relativity predicts that linear variation of the semimajor axes of geostationary and inclined geosynchronous satellites causes a quadratic clock drift with a magnitude at the 10 -16 /day level. The observed drift is higher than what general relativity theory would produce. Several periodic terms are found in the satellite clock variations through spectrum analysis. In order to identify the origin of the BDS clock harmonics, a correlation analysis between the period or amplitude of the harmonics and properties of the satellite orbits is performed. It is found that the period of the harmonics is not exactly equal to the orbit period, but rather the ratio of the orbit period to clock period is almost the same as that of a sidereal day to solar day. The BDS clocks obey white frequency noise statistics for intervals from 300 s to several thousands seconds. For intervals greater than 10,000 s, all the BDS satellites display more complex, non-powerlaw behavior due to the effects of periodic clock variations.