Trion dynamics and charge photogeneration in MoS2 nanosheets prepared by liquid phase exfoliation.

Since excitonic quasiparticles, including excitons, trions and charges, have a great influence on the photoelectric characteristics of two-dimensional (2D) transition metal dichalcogenides (TMDs), systematic explorations of the trion dynamics and charge photogeneration in 2D TMDs are important for their future optoelectronic applications. Here, broadband femtosecond transient absorption spectroscopic experiments are performed first to investigate the peak shifting and broadening kinetics in MoS2 nanosheets in solution prepared by liquid phase exfoliation (LPE-MoS2, ∼9 layers, 9L), which reveal that the binding energies for the A-, B-, and C-exciton states are ∼77 meV, ∼76 meV, and -70 meV (the energy difference between free charges and excitons; the negative sign for C-excitons means a spontaneous dissociation nature in band-nesting regions), respectively. Then, the trion dynamics and charge photogeneration in LPE-MoS2 nanosheets have been studied in detail, demonstrating that they are comparable to those in chemical vapor deposition grown MoS2 films (1L-, 3L- and 7L-MoS2). These experimental results suggest that LPE-TMD nanosheets also have the potential for use in charge-related optoelectronic devices based on 2D TMDs.

A 3-D Full Convolution Electromagnetic Reconstruction Neural Network (3-D FCERNN) for Fast Super-Resolution Electromagnetic Inversion of Human Brain.

Three-dimensional (3-D) super-resolution microwave imaging of human brain is a typical electromagnetic (EM) inverse scattering problem with high contrast. It is a challenge for the traditional schemes based on deterministic or stochastic inversion methods to obtain high contrast and high resolution, and they require huge computational time. In this work, a dual-module 3-D EM inversion scheme based on deep neural network is proposed. The proposed scheme can solve the inverse scattering problems with high contrast and super-resolution in real time and reduce a huge computational cost. In the EM inversion module, a 3-D full convolution EM reconstruction neural network (3-D FCERNN) is proposed to nonlinearly map the measured scattered field to a preliminary image of 3-D electrical parameter distribution of the human brain. The proposed 3-D FCERNN is completely composed of convolution layers, which can greatly save training cost and improve model generalization compared with fully connected networks. Then, the image enhancement module employs a U-Net to further improve the imaging quality from the results of 3-D FCERNN. In addition, a dataset generation strategy based on the human brain features is proposed, which can solve the difficulty of human brain dataset collection and high training cost. The proposed scheme has been confirmed to be effective and accurate in reconstructing the distribution of 3-D super-resolution electrical parameters distribution of human brain through noise-free and noisy examples, while the traditional EM inversion method is difficult to converge in the case of high contrast and strong scatterers. Compared with our previous work, the training of FCERNN is faster and can significantly decrease computational resources.

Spin-Valley Depolarization in van der Waals Heterostructures.

The appearance of van der Waals heterostructures offers a new solution to valleytronics. Here, we observe the spin-valley depolarization process of electrons and holes in type-II MoS2-WSe2 heterostructures simultaneously for the first time by valley-resolved broad-band femtosecond pump-probe experiments. The different depolarization paths between electrons and holes make them have different spin-valley polarization lifetimes. The spin-valley depolarization pathway of holes is mainly dominated by a phonon-assisted intervalley scattering process, while intra- and intervalley coupling can trigger additional depolarization pathways for electrons. The hole polarization lifetime can be further prolonged to more than three times in trilayer heterostructure 2MoS2-WSe2. For MoS2-WS2 that has strong orbital hybridization of Mo and W atoms, both electrons and holes lose the spin-valley polarization extremely soon after charge separation, behaving similarly to intraexcitons in a monolayer. Our work advances the basic understanding of spin-valley depolarization of van der Waals heterostructures and facilitates the effort toward longer lifetime valleytronic devices for information transfer and storage applications.

Dynamics of Strong Coupling Between Free Charge Carriers in Organometal Halide Perovskites and Aluminum Plasmonic States.

We have investigated a strong coupled system composed of a MAPbIxCl3-x perovskite film and aluminum conical nanopits array. The hybrid states formed by surface plasmons and free carriers, rather than the traditional excitons, is observed in both steady-state reflection measurements and transient absorption spectra. In particular, under near upper band resonant excitation, the bleaching signal from the band edge of uncoupled perovskite was completely separated into two distinctive bleaching signals of the hybrid system, which is clear evidence for the formation of strong coupling states between the free carrier-plasmon state. Besides this, a Rabi splitting up to 260 meV is achieved. The appearance of the lower bands can compensate for the poor absorption of the perovskite in the NIR region. Finally, we found that the lifetime of the free carrier-SP hybrid states is slightly shorter than that of uncoupled perovskite film, which can be caused by the ultrafast damping of the SPs modes. These peculiar features on the strong coupled hybrid states based on free charge carriers can open new perspectives for novel plasmonic perovskite solar cells.

Chinese patent herbal medicine (Shufeng Jiedu capsule) for acute upper respiratory tract infections: A systematic review and meta-analysis.

BACKGROUND: Shufeng Jiedu capsule has been widely used in China for acute upper respiratory tract infections (AURTIs). The aim of this study was to evaluate its effectiveness and safety for AURTIs. METHODS: Randomized controlled trials comparing SFJD with conventional drug for patients with AURTIs were included. Eight databases were searched from their inceptions to February 2021. Data was synthesized using risk ration (RR) or mean difference (MD) with their 95% confidence interval (CI). The primary outcome was resolution time of typical symptoms. RESULTS: Twenty-five RCTs involving 3410 patients were included. SFJD in combination with conventional drug was associated with; in common cold shortening the duration of fever (MD -1.54 days, 95% CI [-2.15,-0.92], I 2 = 80%, n = 385, 3 trials) and cough (MD -1.22 days, 95% CI [-1.52, -0.93]); in herpangina, shortening the duration of fever (MD -0.68 days, 95% CI [-1.15, -0.21], I2  = 68%, n = 140, 2 trials) and blistering (MD -0.99 days, 95% CI [-1.23, -0.76], n = 386, 3 trials); in acute tonsillitis and acute pharyngitis shortening the duration of fever (MD -1.13 days, 95% CI [-1.36, -0.90], I 2 = 33%, n = 688, 7 trials) and sore throat (MD -1.13 days, 95% CI [-1.40, -0.86], I 2 = 84.1%, n = 1194, 10 trials). SFJD also improving their cure rate with a range (1-5 days). No serious adverse events were reported. CONCLUSION: Low certainty evidence suggests that SFJD appears to shorten the duration of symptoms in AURTIs, improve cure rate and seems safe for application. However, high quality placebo controlled trials are warranted to confirm its benefit.