We experimentally demonstrate PT-symmetric optical lattices with periodical gain and loss profiles in a coherently prepared four-level N-type atomic system. By appropriately tuning the pertinent atomic parameters, the onset of PT-symmetry breaking is observed through measuring an abrupt phase-shift jump between adjacent gain and loss waveguides. The experimental realization of such a readily reconfigurable and effectively controllable PT-symmetric waveguide array structure sets a new stage for further exploiting and better understanding the peculiar physical properties of these non-Hermitian systems in atomic settings.
State‐of‐the‐art photodetectors which apply hybrid perovskite materials have emerged as powerful candidates for next‐generation light sensing. Among them, lead‐based ones are the most popular beyond doubt on account of their unique and superior optoelectronic properties. Nevertheless, trade‐off toward commercialization exists between nontoxicity and high performance, with the poor stability of lead‐based perovskites, indicating that it is indispensable to substitute lead with nontoxic element meanwhile bringing about a comparable figure of merit of photodetectors and relatively long‐term stability. Herein, recent advances in lead‐free perovskite photodetectors are reviewed, analyzing the principle while designing new materials and highlighting some remarkable progress, which are comparable, even superior, to lead‐based photodetectors. Furthermore, their potential strategy in optical communication, image sensing, narrowband photodetection, etc., is examined and a perspective on developing new materials and photodetectors with superior properties for more practical applications is provided.
Currently, great attention is being paid to the utilization of biomass, such as feather keratins. It is imperative to extract and dissolve keratins from animal keratinous materials for exploitation of innovative biopolymers. However, most of the current processes are based on strong acid and alkali hydrolysis, chemical cleavage and other violent reactions, which are not eco-friendly and/or result in severe degradation and destruction of feather keratins. In this study, high density steam flash-explosion (HDSF) as an innovative pretreatment of biomass was firstly employed to treat feather waste. In HDSF treatment, steam with a powerful seepage force first penetrates into fibrous tissues and cells of feathers, and then quickly expands and breaks free of the structure upon an explosive decompression at supersonic speed (within 0.0875 s). HDSF effectively destabilized β-sheet crystals and intermolecular disulfide bonds without causing substantial damage to the keratin protein chain, dramatically increasing the extraction and dissolubility of feather keratins in polar solvents like water, salt solution and weak bases, as well as enzymatic accessibility. HDSF treatment could be a sustainable and practical pretreatment for extraction of feather keratin for exploitation of biomaterials and conversion of feathers to nutrient animal feed instead of the current chemical hydrolysis and hydrothermal treatment.
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