40 research outputs found

    Vibrationally-resolved X-ray spectra of diatomic systems: Time-independent and time-dependent simulations

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    We systematically investigated vibronic coupling effects in X-ray spectra of diatomic systems using time-independent (TI) and time-dependent (TD) methods. Under the TI framework, we studied 5 systems (N2_2, N2+_2^+, NO+^+, CO, CO+^+) in their lowest C/N/O 1s excited or ionized states, generating 10 X-ray absorption (XAS) or photoelectron (XPS) spectra using density functional theory (DFT) with two pure (BLYP, BP86) and two hybrid (B3LYP, M06-2X) functionals. Excellent agreement between theoretical and experimental spectra was found in most systems, except that in O1s XAS of CO and NO+^+, intensities of higher-energy peaks were underestimated. We established a connection between their complex vibronic structures and the significant geometrical changes induced by the O1s hole. Functional dependence in diatomic systems is generally more pronounced than in polyatomic ones. In all examined cases, pure functionals exhibit better or similar spectral accuracy to hybrid functionals, attributed to superior prediction accuracy in bond lengths and vibrational frequencies. With the TD wavepacket method, we simulated vibrationally-resolved XAS of CO+^+, NO+^+, and CO using potential energy curves (PECs) generated at both DFT and multiconfigurational levels. Both TD and TI generate similar C/O 1s XAS spectra of CO+^+. For O1s XAS of NO+^+ and CO, TD calculations significantly improved the corresponding TI results, demonstrating sensitivity to the anharmonic effect and the PEC quality. TI and TD approaches are complementary, with practical applications depending on the ease and accuracy of excited-state geometry optimization or PEC scanning, and the significance of anharmonicity. DFT with pure functionals is recommended for diatomic calculations due to its easy execution and reliable accuracy. TI is optimal for most scenarios, but TD is needed for problems with strong anharmonic effects.Comment: 11 figure

    Vibronic fine structure in the nitrogen 1s photoelectron spectra from Franck-Condon simulations II: Indoles

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    The vibronic coupling effect in nitrogen 1s X-ray photoelectron spectra (XPS) was systematically studied for a family of 17 bicyclic indole molecules by combining Franck-Condon simulations (including the Duschinsky rotation effect) and density functional theory. The simulated vibrationally-resolved spectra of 4 molecules agree well with available experiments. Reliable predictions for this family further allowed us to summarize rules for spectral evolution in response to three types of common structural changes (side chain substitution, CH↔\leftrightarrowN replacement, and isomerization). Interestingly, vibronic properties of amine and imine nitrogen are clearly separated: they show negative and positive Ξ”\DeltaZPE (zero-point vibration energy of the core-ionized with respect to the ground state), respectively, indicating flatter and steeper PESs induced by the N 1s ionization; amine N's show stronger mode mixing effects than imine N's; the 1s ionizations on two types of nitrogens led to distinct changes in local bond lengths and angles. The rules are useful for a basic understanding of vibronic coupling in this family, and the precise spectra are useful for future reference and data mining studies

    A novel camera calibration technique based on differential evolution particle swarm optimization algorithm

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    Camera calibration is one of the fundamental issues in computer vision and aims at determining the intrinsic and exterior camera parameters by using image features and the corresponding 3D features. This paper proposes a relationship model for camera calibration in which the geometric parameter and the lens distortion effect of camera are taken into account in order to unify the world coordinate system (WCS), the camera coordinate system (CCS) and the image coordinate system (ICS). Differential evolution is combined with particle swarm optimization algorithm to calibrate the camera parameters effectively. Experimental results show that the proposed algorithm has a good optimization ability to avoid local optimum and can complete the visual identification tasks accurately

    Activation of Sirt1 by Resveratrol Inhibits TNF-Ξ± Induced Inflammation in Fibroblasts

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    Inflammation is one of main mechanisms of autoimmune disorders and a common feature of most diseases. Appropriate suppression of inflammation is a key resolution to treat the diseases. Sirtuin1 (Sirt1) has been shown to play a role in regulation of inflammation. Resveratrol, a potent Sirt1 activator, has anti-inflammation property. However, the detailed mechanism is not fully understood. In this study, we investigated the anti-inflammation role of Sirt1 in NIH/3T3 fibroblast cell line. Upregulation of matrix metalloproteinases 9 (MMP-9), interleukin-1beta (IL-1Ξ²), IL-6 and inducible nitric oxide synthase (iNOS) were induced by tumor necrosis factor alpha (TNF-Ξ±) in 3T3 cells and resveratrol suppressed overexpression of these pro-inflammatory molecules in a dose-dependent manner. Knockdown of Sirt1 by RNA interference caused 3T3 cells susceptible to TNF-Ξ± stimulation and diminished anti-inflammatory effect of resveratrol. We also explored potential anti-inflammatory mechanisms of resveratrol. Resveratrol reduced NF-ΞΊB subunit RelA/p65 acetylation, which is notably Sirt1 dependent. Resveratrol also attenuated phosphorylation of mammalian target of rapamycin (mTOR) and S6 ribosomal protein (S6RP) while ameliorating inflammation. Our data demonstrate that resveratrol inhibits TNF-Ξ±-induced inflammation via Sirt1. It suggests that Sirt1 is an efficient target for regulation of inflammation. This study provides insight on treatment of inflammation-related diseases

    A Multi-Functional Fluorescence Sensing Platform Based on a Defective UiO-66 for Tetracycline and Moxifloxacin

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    In recent years, the excessive use and disordered discharge of antibiotics have had sustained adverse effects on ecological balance and human health. The convenient and effective detection of these “emerging pollutants” has become one of the research hotspots in the environmental field. In this study, a defective UiO-66 material, namely UiO-66-D, was constructed for the sensitive and selective sensing of tetracycline (TC) and moxifloxacin (MXF) in water. By utilizing a modulated synthesis approach with concentrated HCl, stable blue fluorescence at 400 nm was achieved for UiO-66-D. The as-prepared UiO-66-D could conduct the inner filter effect (IFE) within a short time (10 s) when sensing TC and MXF, and the fluorescence of the UiO-66-D was quenched. In particular, when sensing MXF, a ratiometric signal response was generated due to the combined effect of the IFE and the fluorescence of MXF itself. The sensitive and selective detection of TC and MXF using UiO-66-D was free from the interference of common anions and cations in water samples. The detection limit (LOD) for TC was determined to be 70.9 nM (0–115 μM), while for MXF, it was found to be 33.1 nM (0–24 μM). Additionally, UiO-66-D was successfully used to recognize TC and MXF in lake water with good recoveries, demonstrating that UiO-66-D exhibits substantial potential in the recognition of pollutants in environmental waters

    Transcription factor-based biosensor: A molecular-guided approach for advanced biofuel synthesis

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    As a sustainable and renewable alternative to petroleum fuels, advanced biofuels shoulder the responsibility of energy saving, emission reduction and environmental protection. Traditional engineering of cell factories for production of advanced biofuels lacks efficient high-throughput screening tools and regulating systems, impeding the improvement of cellular productivity and yield. Transcription factor-based biosensors have been widely applied to monitor and regulate microbial cell factory products due to the advantages of fast detection and in-situ screening. This review updates the design and application of transcription factor-based biosensors tailored for advanced biofuels and related intermediates. The construction and genetic parts selection principle of biosensors are discussed. Strategies to enhance the performance of biosensor, including regulating promoter strength and RBS strength, optimizing plasmid copy number, implementing genetic amplifier, and modulating the structure of transcription factor, have also been summarized. We further review the application of biosensors in high-throughput screening of new metabolic engineering targets, evolution engineering, confirmation of protein function, and dynamic regulation of metabolic flux for higher production of advanced biofuels. At last, we discuss the current limitations and future trends of transcription factor-based biosensors
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