The outbreak of Coronavirus Disease 2019 has posed a serious threat to global public health, calling for the development of safe and effective prophylactics and therapeutics against infection of its causative agent, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), also known as 2019 novel coronavirus (2019-nCoV). The CoV spike (S) protein plays the most important roles in viral attachment, fusion and entry, and serves as a target for development of antibodies, entry inhibitors and vaccines. Here, we identified the receptor-binding domain (RBD) in SARS-CoV-2 S protein and found that the RBD protein bound strongly to human and bat angiotensin-converting enzyme 2 (ACE2) receptors. SARS-CoV-2 RBD exhibited significantly higher binding affinity to ACE2 receptor than SARS-CoV RBD and could block the binding and, hence, attachment of SARS-CoV-2 RBD and SARS-CoV RBD to ACE2-expressing cells, thus inhibiting their infection to host cells. SARS-CoV RBD-specific antibodies could crossreact with SARS-CoV-2 RBD protein, and SARS-CoV RBD-induced antisera could cross-neutralize SARS-CoV-2, suggesting the potential to develop SARS-CoV RBD-based vaccines for prevention of SARS-CoV-2 and SARS-CoV infection.

The anti-hyperglycemic effect of metformin is believed to be caused by its direct action on signaling processes in hepatocytes, leading to lower hepatic gluconeogenesis. Recently, metformin was reported to alter the gut microbiota community in humans, suggesting that the hyperglycemia-lowering action of the drug could be the result of modulating the population of gut microbiota. However, the critical microbial signaling metabolites and the host targets associated with the metabolic benefits of metformin remained elusive. Here, we performed metagenomic and metabolomic analysis of samples from individuals with newly diagnosed type 2 diabetes (T2D) naively treated with metformin for 3 d, which revealed that Bacteroides fragilis was decreased and the bile acid glycoursodeoxycholic acid (GUDCA) was increased in the gut. These changes were accompanied by inhibition of intestinal farnesoid X receptor (FXR) signaling. We further found that high-fat-diet (HFD)-fed mice colonized with B. fragilis were predisposed to more severe glucose intolerance, and the metabolic benefits of metformin treatment on glucose intolerance were abrogated. GUDCA was further identified as an intestinal FXR antagonist that improved various metabolic endpoints in mice with established obesity. Thus, we conclude that metformin acts in part through a B. fragilis–GUDCA–intestinal FXR axis to improve metabolic dysfunction, including hyperglycemia.

As an exotic state of quantum matter, topological insulators have promising applications in new-generation electronic and optoelectronic devices. The realization of these applications relies critically on the preparation and properties understanding of high-quality topological insulators, which however are mainly fabricated by high-cost methods like molecular beam epitaxy. We here report the successful preparation of high-quality topological insulator Bi2Se3/Si heterostructure having an atomically abrupt interface by van der Waals epitaxy growth of Bi2Se3 films on Si wafer. A simple, low-cost physical vapor deposition (PVD) method was employed to achieve the growth of the Bi2Se3 films. The Bi2Se3/Si heterostructure exhibited excellent diode characteristics with a pronounced photoresponse under light illumination. The built-in potential at the Bi2Se3/Si interface greatly facilitated the separation and transport of photogenerated carriers, enabling the photodetector to have a high light responsivity of 24.28 A W(-1), a high detectivity of 4.39 × 10(12) Jones (Jones = cm Hz(1/2) W(-1)), and a fast response speed of aproximately microseconds. These device parameters represent the highest values for topological insulator-based photodetectors. Additionally, the photodetector possessed broadband detection ranging from ultraviolet to optical telecommunication wavelengths. Given the simple device architecture and compatibility with silicon technology, the topological insulator Bi2Se3/Si heterostructure holds great promise for high-performance electronic and optoelectronic applications.

Recently, we witnessed a tremendous effort to conquer the realm of acoustics as a possible playground to test with sound waves topologically protected wave propagation. Acoustics differ substantially from photonic and electronic systems since longitudinal sound waves lack intrinsic spin polarization and breaking the time-reversal symmetry requires additional complexities that both are essential in mimicking the quantum effects leading to topologically robust sound propagation. In this article, we review the latest efforts to explore with sound waves topological states of quantum matter in two-and three-dimensional systems where we discuss how spin and valley degrees of freedom appear as highly novel ingredients to tailor the flow of sound in the form of one-way edge modes and defect-immune protected acoustic waves. Both from a theoretical stand point and based on contemporary experimental verifications, we summarize the latest advancements of the flourishing research frontier on topological sound. arXiv:1807.09544v1 [cond-mat.mes-hall] 25 Jul 2018Recently, another discrete degree of freedom, namely the valley, has also been proposed to realize a topological state, known as the valley Hall effect (VHE), which is related to valleytronics 9,10 . Valley refers to the two energy extrema of the band structure in momentum space, at which the Berry curvature exhibits opposite signs and therefore its integral over the full Brillouin zone is zero, while the integral within each valley is non-zero. As a result, the system shows a valley-selective topologically non-trivial property (Fig. 1(d)). It is