Thermally Activated Photoluminescence Induced by Tunable Interlayer Interactions in Naturally Occurring van der Waals Superlattice SnS/TiS2.

van der Waals (vdW) superlattices, comprising different 2D materials aligned alternately by weak interlayer interactions, offer versatile structures for the fabrication of novel semiconductor devices. Despite their potential, the precise control of optoelectronic properties with interlayer interactions remains challenging. Here, we investigate the discrepancies between the SnS/TiS2 superlattice (SnTiS3) and its subsystems by comprehensive characterization and DFT calculations. The disappearance of certain Raman modes suggests that the interactions alter the SnS subsystem structure. Specifically, such structural changes transform the band structure from indirect to direct band gap, causing a strong PL emission (∼2.18 eV) in SnTiS3. In addition, the modulation of the optoelectronic properties ultimately leads to the unique phenomenon of thermally activated photoluminescence. This phenomenon is attributed to the inhibition of charge transfer induced by tunable intralayer strains. Our findings extend the understanding of the mechanism of interlayer interactions in van der Waals superlattices and provide insights into the design of high-temperature optoelectronic devices.

Crosstalk between metabolism and cell death in tumorigenesis.

It is generally recognized that tumor cells proliferate more rapidly than normal cells. Due to such an abnormally rapid proliferation rate, cancer cells constantly encounter the limits of insufficient oxygen and nutrient supplies. To satisfy their growth needs and resist adverse environmental events, tumor cells modify the metabolic pathways to produce both extra energies and substances required for rapid growth. Realizing the metabolic characters special for tumor cells will be helpful for eliminating them during therapy. Cell death is a hot topic of long-term study and targeting cell death is one of the most effective ways to repress tumor growth. Many studies have successfully demonstrated that metabolism is inextricably linked to cell death of cancer cells. Here we summarize the recently identified metabolic characters that specifically impact on different types of cell deaths and discuss their roles in tumorigenesis.

Broadband phase noise measurement of single-frequency lasers by the short-fiber recirculating delayed self-heterodyne method.

Characterization of single-frequency lasers (SFLs) requires a precise measurement of their phase noise. However, there exists a contradiction between the frequency range and laser phase noise measurement sensitivity in the delay self-heterodyne method. Achieving a broadband and highly sensitive phase noise measurement often requires overlapping the results obtained from different delay lengths. In this study, we present a precisely designed short-fiber recirculating delayed self-heterodyne (SF-RDSH) method that enables the broadband and highly sensitive laser phase noise measurement in a compact setup. By designing the length of the delay fiber based on a theoretical model, the RDSH technique with a shortest delay length of 200 m enables a highly sensitive laser phase noise measurement from 1 Hz to 1 MHz for the first time, to our knowledge. In the experiment, we demonstrate the broadband phase noise measurement of an SFL by analyzing the 1st and 10th beat notes.

Laser-sustained plasma of high radiance in the ultraviolet spectral range based on the reservoir effect of the annular beam.

Laser-sustained plasma (LSP) featured by high radiance in the ultraviolet (UV) spectral range is found to be powerful in high resolution inspection and spectroscopy applications. In this paper, we demonstrate significant enhancement of UV radiance in LSP excited by a high power focused annular laser beam of small F-number. A two-dimensional refractive index distribution in the plasma region is established to obtain the propagation path of the annular beam. Subsequently, the spatial distribution of the annular beam power density is calculated to establish the quantitative relationship between laser power and plasma dimension. Theoretical analysis of a "reservoir" effect constructed by the annular beam is carried out. Abrupt plasma dimension change is observed when the laser power exceeds the "reservoir" boundary. The new model is then validated by experiments. LSP with the highest reported UV radiance to our knowledge has been achieved. This work paves what we believe is a novel way of generating high radiance UV sources by spatial manipulation of excitation laser beam.

Strain-Dependent Band Splitting and Spin-Flip Dynamics in Monolayer WS2.

Triggered by the expanding demands of semiconductor devices, strain engineering of two-dimensional transition metal dichalcogenides (TMDs) has garnered considerable research interest. Through steady-state measurements, strain has been proved in terms of its modulation of electronic energy bands and optoelectronic properties in TMDs. However, the influence of strain on the spin-orbit coupling as well as its related valley excitonic dynamics remains elusive. Here, we demonstrate the effect of strain on the excitonic dynamics of monolayer WS2 via steady-state fluorescence and transient absorption spectroscopy. Combined with theoretical calculations, we found that tensile strain can reduce the spin-splitting value of the conduction band and lead to transitions between different exciton states via spin-flip mechanism. Our findings suggest that the spin-flip process is strain-dependent, provides a reference for application of valleytronic devices, where tensile strain is usually existing during their design and fabrication.

Investigation of the laser-sustained plasma of a Xenon lamp driven by an annular beam.

Higher brightness UV light sources based on laser-sustained plasma (LSP) finds critical applications in high-resolution optical inspection and measurement. An annular beam focused with a low F-number is proposed for the first time to investigate its effect in realizing high-brightness LSP compared with Gaussian beams. We experimentally verified that the annular laser beam sustained a nearly laterally symmetric plasma with a longitudinal length less than 600 µm plasma length, where the length-width ratio was four times smaller than that driven by a TEM00 Gaussian beam. Theoretical analysis further explored that the annular beam's transmission path could limit the plasma's longitudinal growth, like a "reservoir". Furthermore, the "reservoir" effect is favorable for effectively increasing the plasma temperature and the effective power ratio of UV from 8% to 15%. This work paves a novel way of generating high-brightness UV sources by spatial manipulation of infrared pumping beam.

Moving Object Detection Based on Fusion of Depth Information and RGB Features.

The detection of moving objects is one of the key problems in the field of computer vision. It is very important to detect moving objects accurately and rapidly for automatic driving. In this paper, we propose an improved moving object detection method to overcome the disadvantages of the RGB information-only-based method in detecting moving objects that are susceptible to shadow interference and illumination changes by adding depth information. Firstly, a convolutional neural network (CNN) based on the color edge-guided super-resolution reconstruction of depth maps is proposed to perform super-resolution reconstruction of low-resolution depth images obtained by depth cameras. Secondly, the RGB-D moving object detection algorithm is based on fusing the depth information of the same scene with RGB features for detection. Finally, in order to evaluate the effectiveness of the algorithm proposed in this paper, the Middlebury 2005 dataset and the SBM-RGBD dataset are successively used for testing. The experimental results show that our super-resolution reconstruction algorithm achieves the best results among the six commonly used algorithms, and our moving object detection algorithm improves the detection accuracy by up to 18.2%, 9.87% and 40.2% in three scenes, respectively, compared with the original algorithm, and it achieves the best results compared with the other three recent RGB-D-based methods. The algorithm proposed in this paper can better overcome the interference caused by shadow or illumination changes and detect moving objects more accurately.

Fringe-width encoded patterns for 3D surface profilometry.

This paper presents a new fringe projection method for surface-shape measurement that uses novel fringe-width encoded fringe patterns. Specifically, the projection patterns are adjusted with the width of the fringe as the codeword. The wrapped phase with coding information is obtained by using the conventional wrapped phase calculation method, and the fringe order can be identified from the wrapped phase. After the fringe order is corrected based on the region growing algorithm, the fringe order and the wrapped phase can be directly used to reconstruct the surface. Static and dynamic measurements demonstrated the ability of the method to perform 3D shape measurement with only three projected patterns, single camera and projector in the least case.

BF3·OEt2-mediated cyclization of ß,γ-unsaturated oximes and hydrazones with N-(arylthio/arylseleno)succinimides: an efficient approach to synthesize isoxazoles or dihydropyrazoles.

A highly efficient BF3·OEt2-mediated cyclization of ß,γ-unsaturated oximes and tosylhydrazones with N-(arylthio/arylseleno)succinimides has been established for the construction of N-heterocycles in a one-step manner. This metal-free cyclization provides direct access to isoxazoles and dihydropyrazoles in good to excellent yields at room temperature. The mechanistic experiments support the formation of a cationic species PhS+ which plays a critical role in this cyclization process.

Construction of a combined enzyme system of graphene oxide and manganese peroxidase for efficient oxidation of aromatic compounds.

Manganese peroxidase (MnP) from Irpex lacteus F17 has potential use as a biocatalyst in the field of environmental biotechnology because of its unique properties and ability to decompose harmful aromatic compounds. However, its requirement of harsh acidic reaction conditions and its insufficient catalytic activity restrict its practical applications. Here, we combine graphene oxide (GO) and MnP to construct an efficient enzyme system (GO-MnP) with improved catalytic efficiencies and a wide pH range for the oxidation of aromatic substances and dye decolorization. We found that the Michaelis constant (Km) of GO-MnP for Mn2+ was 2.8 times lower and the catalytic efficiency (kcat/Km) of GO-MnP was 4.5 times higher than those of MnP, and that the decolorization of various dyes by GO-MnP was significantly improved over the pH range of 4.5-5.5. A comparison of the midpoint redox potentials also reflects the strong oxidation ability of GO-MnP. Furthermore, we demonstrated that, in the GO-MnP system, the MnP activity is mainly determined by the amounts of epoxy and carboxyl groups in GO, based on an analysis of the functional group changes in GO and reduced GO associated with different reduction degrees as shown by X-ray photoelectron spectroscopy.

Comparative Transcriptome Analysis Provides Insights Into Yellow Rind Formation and Preliminary Mapping of the Clyr (Yellow Rind) Gene in Watermelon.

As an important appearance trait, the rind color of watermelon fruit affects the commodity value and further determines consumption choices. In this study, a comparative transcriptome analysis was conducted to elucidate the genes and pathways involved in the formation of yellow rind fruit in watermelon using a yellow rind inbred line WT4 and a green rind inbred line WM102. A total of 2,362 differentially expressed genes (DEGs) between WT4 and WM102 at three different stages (0, 7, and 14 DAP) were identified and 9,770 DEGs were obtained by comparing the expression level at 7 DAP and 14 DAP with the former stages of WT4. The function enrichment of DEGs revealed a number of pathways and terms in biological processes, cellular components, and molecular functions that were related to plant pigment metabolism, suggesting that there may be a group of common core genes regulating rind color formation. In addition, next-generation sequencing aided bulked-segregant analysis (BSA-seq) of the yellow rind pool and green rind pool selected from an F2 population revealed that the yellow rind gene (Clyr) was mapped on the top end of chromosome 4. Based on the BSA-seq analysis result, Clyr was further confined to a region of 91.42 kb by linkage analysis using 1,106 F2 plants. These results will aid in identifying the key genes and pathways associated with yellow rind formation and elucidating the molecular mechanism of rind color formation in watermelon.

Room temperature iron(ii)-catalyzed radical cyclization of unsaturated oximes with hypervalent iodine reagents.

Here, we disclose an iron(ii)-catalyzed I-O bond cleavage of Koser's hypervalent iodine reagents (HIRs) that initiated the radical cyclization of unsaturated oximes at room temperature. This strategy is successfully applied for the construction of the isoxazoline backbone in an efficient manner. In particular, the direct introduction of a TsO group into products facilitates their late-stage transformations in organic synthesis.

Visible-Light Photoredox-Catalyzed Regioselective Sulfonylation of Alkenes Assisted by Oximes via [1,5]-H Migration.

We herein report a visible-light photoredox-catalyzed regioselective sulfonylation of alkenes with sulfonyl hydrazides assisted by oximes at room temperature, which affords a variety of sulfones in good yields. The initial mechanistic experiments demonstrate that the hydroxyl group within oximes plays a crucial role in this sulfonylation.

Sediment records of polybrominated diphenyl ethers (PBDEs) in Huaihe River, China: Implications for historical production and household usage of PBDE-containing products.

In recent decades, rapid development of industrialization and urbanization caused adverse impact on the aqueous ecology and environment of the Huaihe River basin, China. In this work, three 210Pb-dated sediment cores extracted from the middle reach of Huaihe River in Anhui Province, China were analyzed to elucidate the temporal trends and sources of polybrominated diphenyl ethers (PBDEs). Source diagnostics indicated that commercial Deca-BDE, Penta-BDE and Octa-BDE products and debromination of higher brominated BDE compounds were likely the PBDE sources in the Huaihe River. The prevalence of BDE-47 in the sediment cores was attributed to the extensive use of commercial Bromkal 70-5DE and Bromkal DE-71 in the region. BDE-28 was another congener that was prevalent in all sediment samples, suggesting that reductive debromination occurred in the sediments. Dramatic increase of PBDE concentrations in both three cores since the post-1980s could be attributed to the rapid expansion of production of electronic and telecommunication equipment and household usage in China. PBDE temporal trends in core S1 located at rural area mainly reflected the regional and national inputs deriving from long distance atmospheric transport, and the positive correlations between PBDE concentration in core S1 and gross domestic product (GDP) and household appliances production volumes (HPVs) were observed. PBDE inputs at site S3 mainly include the transport of contaminated water and re-suspended fine sediment particles from the upstream site S2, which was located in the industrial area and adjacent to e-waste recycling area. The government efforts to protect the environment and improve the e-waste management resulted in the progressive decrease trends in PBDE concentrations in cores S2 and S3.