Hybrid graphene metasurfaces for high-speed mid-infrared light modulation and single-pixel imaging

During the past decades, major advances have been made in both the generation and detection of infrared light; however, its efficient wavefront manipulation and information processing still encounter great challenges. Efficient and fast optoelectronic modulators and spatial light modulators are required for mid-infrared imaging, sensing, security screening, communication and navigation, to name a few. However, their development remains elusive, and prevailing methods reported so far have suffered from drawbacks that significantly limit their practical applications. In this study, by leveraging graphene and metasurfaces, we demonstrate a high-performance free-space mid-infrared modulator operating at gigahertz speeds, low gate voltage and room temperature. We further pixelate the hybrid graphene metasurface to form a prototype spatial light modulator for high frame rate single-pixel imaging, suggesting orders of magnitude improvement over conventional liquid crystal or micromirror-based spatial light modulators. This work opens up the possibility of exploring wavefront engineering for infrared technologies for which fast temporal and spatial modulations are indispensable

Convergence of resistance and evolutionary responses in Escherichia coli and Salmonella enterica co-inhabiting chicken farms in China

Sharing of genetic elements among different pathogens and commensals inhabiting same hosts and environments has significant implications for antimicrobial resistance (AMR), especially in settings with high antimicrobial exposure. We analysed 661 Escherichia coli and Salmonella enterica isolates collected within and across hosts and environments, in 10 Chinese chicken farms over 2.5 years using novel data-mining methods. Most isolates within same hosts possessed same clinically relevant AMR-carrying mobile genetic elements (plasmids: 70.6%, transposons: 78%), which also showed recent common evolution. Machine learning revealed known and novel AMR-associated mutations and genes underlying resistance to 28 antimicrobials and primarily associated with resistance in E. coli and susceptibility in S. enterica. Many were essential and affected same metabolic processes in both species, albeit with varying degrees of phylogenetic penetration. Multi-modal strategies are crucial to investigate the interplay of mobilome, resistance and metabolism in cohabiting bacteria, especially in ecological settings where community-driven resistance selection occurs

Preparation of nano-sized calcium carbonate in solution mixing process

Discreet nano-sized precipitated calcium carbonate was prepared by a simple solution mixing process, in which sodium carbonate solution was injected into calcium chloride solution containing calcium hydroxide. The morphology, size, and structure of the as-prepared precipitated calcium carbonate and intermediate products were examined. The results indicated that the non-impurity additive of calcium hydroxide, temperature below 30 degrees C, and controlled injecting rate were essential to obtain nano-sized precipitated calcium carbonate in the solution mixing process. It was observed that the intermediate nanofibrils fragged into nanograins in the process. This method can provide a simpler method to study the formation mechanism of nano calcium carbonate

Simultaneous Determination of Coumarin and Its Derivatives in Tobacco Products by Liquid Chromatography-Tandem Mass Spectrometry

In this paper an analytical method based on high performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS) for the determination of coumarin and its derivatives in tobacco products was developed. The MS/MS fragmentation pathways of the eight coumarins were elucidated. The new analytical method was defined based on two main axes, an extraction procedure with acetonitrile and analyte detection performed by HPLC-MS/MS in electron impact mode. The excellent selectivity and sensitivity achieved in multiple reaction monitoring (MRM) mode allowed satisfactory confirmation and quantitation for the coumarin flavor additives. Under the optimized gradient elution conditions, it took only 4.5 min to separate all eight coumarins. Good linearity for all the analytes were confirmed by the correlation coefficient r2, ranging from 0.9987 to 0.9996. The limits of detection (LODs) and limits of quantitation (LOQs) of these compounds were in the range of 0.5–1.7 μg/kg and 1.7–5.2 μg/kg, respectively. The average recoveries at three spiked levels (LOQ, 1.5LOQ, 2LOQ) were all in the range of 69.6%–95.1% with RSDs (n = 6) lower than 5.3%. The method of HPLC-MS/MS developed in this study was initially applied to the research of coumarin flavor additives in tobacco products collected from the located market in Beijing from China and proved to be accurate, sensitive, convenient and practical