Excitation dynamics involving homogeneous multistate interactions: one and two color VMI and REMPI of HBr.

Velocity map imaging (VMI) data and mass resolved REMPI spectra are complementarily utilized to elucidate the involvement of homogeneous multistate interactions in excited state dynamics of HBr. The H1Σ+(v' = 0) and E1Σ+(v' = 1) Rydberg states and the V1Σ+(v'= m + 7) and V1Σ+(v'= m + 8) ion-pair states are explored as a function of rotational quantum number in the two-photon excitation region of 79 100-80 700 cm-1. H+ and Br+ images were recorded by one- as well as two-color excitation schemes. Kinetic energy release (KER) spectra and angular distributions were extracted from the data. Strong-to-medium interactions between the E(1) and V(m + 8)/V(m + 7) states on one hand and the H(0) and V(m + 7)/V(m + 8) states on the other hand were quantified from peak shifts and intensity analysis of REMPI spectra. The effects of those interactions on subsequent photoionization and photolytic pathways of HBr were evaluated in one-color VMI experiments of the H+ and two-color VMI experiments of the Br+ photoproducts.

Conformational toggling controls target site choice for the heteromeric transposase element Tn7.

The bacterial transposon Tn7 facilitates horizontal transfer by directing transposition into actively replicating DNA with the element-encoded protein TnsE. Structural analysis of the C-terminal domain of wild-type TnsE identified a novel protein fold including a central V-shaped loop that toggles between two distinct conformations. The structure of a robust TnsE gain-of-activity variant has this loop locked in a single conformation, suggesting that conformational flexibility regulates TnsE activity. Structure-based analysis of a series of TnsE mutants relates transposition activity to DNA binding stability. Wild-type TnsE appears to naturally form an unstable complex with a target DNA, whereas mutant combinations required for large changes in transposition frequency and targeting stabilized this interaction. Collectively, our work unveils a unique structural proofreading mechanism where toggling between two conformations regulates target commitment by limiting the stability of target DNA engagement until an appropriate insertion site is identified.

Long term puzzles of the CH and CD energetics and related phenomena revisited; solutions sought through REMPI-photofragmentations of bromomethanes.

Ever since the pioneering work by Herzberg and Johns in 1969 (The Astrophysical Journal, 1969, 158, 399) the spectral assignment and the energetics of the fundamental molecular fragment CH, in the region of 63 000-65 000 cm(-1) (7.81-8.06 eV), have remained a puzzle to a large extent. The dissociation of bromoform and deuterated bromoform following two-photon resonance excitations to molecular Rydberg states forms the fragment species CH* and CD* in the excited state A(2)Δ(v' =0) as well as carbon and bromine atoms in the ground and first excited states, C/C* and Br/Br*. Further (1r + 1i)REMPI of CH* and CD* resonance excites the fragments to the energy region of concern, whereas the atom fragments were identified by further (2r + 1i)REMPI. Analysis based on spectral simulations, isotope shifts and comparison with other data allowed spectral identifications, assignments and partial characterization of four highly excited bound states for each of the molecular fragments (CH**/CD**); including the (3)(2)Π valence state and the (4)(2)Π Rydberg state, for the first time. Perturbations, shown as line-shifts, line-intensity and/or line-width alterations, due to the level-to-level state interactions between the bound states and predissociations by a repulsive state are recognized. Recording of C(+) signals in REMPI of several bromomethanes for a one-photon energy of about 40 333 cm(-1) allows the clarification of a mystery concerning a broad C(+) band frequently observed. This work, presented, demonstrates the usefulness of molecular REMPI for fragment analysis.

State interactions and illumination of hidden states through perturbations and observations of new states: High energy resonance enhanced multiphoton ionization of HI.

Hydrogen iodide, a Hund's case (c) molecule, serves as a benchmark compound for studying rich molecular state interactions between Rydberg and valence states as well as between Rydberg states at high energies (72,300-74,600 cm(-1)) by mass resolved resonance enhanced multiphoton ionization (REMPI). Perturbations in the spectra appearing as deformations in line-positions, line-intensities, and linewidths are found to be either due to near-degenerate or non-degenerate interactions, both homogeneous and heterogeneous in nature. Perturbation analyses allow indirect observation as well as characterization of "hidden states" to some extent. Furthermore, new observable spectral features are assigned and characterized.

Resonance-enhanced multiphoton ionization of CH2Br2: Rydberg states, photofragmentation, and CH spectra.

Mass-resolved (2 + n) resonance-enhanced multiphoton ionization (REMPI) spectra of CH2Br2 in the two-photon resonance excitation region from 71 200 to 82 300 cm(-1) were recorded and analyzed. Spectral structures allowed characterization of new molecular Rydberg states. C*((1)D2) was found to be an important intermediate in the photodissociation processes. A broad spectral feature peaking at about 80 663 cm(-1) in the C(+) spectrum and frequently seen in related studies is reinterpreted and associated with switching between three- and two-photon ionization of C*((1)D2). Analysis of band structures due to transitions from the A(2)Δ state of CH* that were seen in the CH(+) and C(+) REMPI spectra allowed characterization of three electronic states of CH, assigned as E(2)Π, D(2)Π, and F(2)Σ(+), which clarifies a long-term puzzle concerning the energetics of the CH radical. Predissociation of the E, D, and F states to form C*((1)D2) occurs. Bromine atomic lines were observed and are believed to be associated with bromine atom formation via predissociation of CH2Br2 Rydberg states.

Photofragmentation, state interaction, and energetics of Rydberg and ion-pair states: resonance enhanced multiphoton ionization of HI.

Mass resolved resonance enhanced multiphoton ionization data for hydrogen iodide (HI), for two-photon resonance excitation to Rydberg and ion-pair states in the 69,600-72,400 cm(-1) region were recorded and analyzed. Spectral perturbations due to homogeneous and heterogeneous interactions between Rydberg and ion-pair states, showing as deformations in line-positions, line-intensities, and line-widths, were focused on. Parameters relevant to photodissociation processes, state interaction strengths and spectroscopic parameters for deperturbed states were derived. Overall interaction and dynamical schemes to describe the observations are proposed.

Photofragmentations, state interactions, and energetics of Rydberg and ion-pair states: resonance enhanced multiphoton ionization via E and V (B) states of HCl and HBr.

(2 + n) resonance enhanced multiphoton ionization mass spectra for resonance excitations to diabatic E(1)Σ(+) (v') Rydberg and V (1)Σ(+) (v') ion-pair states (adiabatic B(1)Σ(+)(v') states) of H(i)Cl (i = 35,37) and H(i)Br (i = 79,81) were recorded as a function of excitation wavenumber (two-dimensional REMPI). Simulation analyses of ion signal intensities, deperturbation analysis of line shifts and interpretations of line-widths are used to derive qualitative and quantitative information concerning the energetics of the states, off-resonance interactions between the E states and V states, closest in energy as well as on predissociation channels. Spectroscopic parameters for the E(1)Σ(+) (v')(v' = 1) for H(35)Cl and v' = 0 for H(79)Br states, interaction strengths for E - V state interactions and parameters relevant to dissociation of the E states are derived. An overall interaction and dynamical scheme, to describe the observations for HBr, is proposed.

Global and Local Interactive Perception Network for Referring Image Segmentation.

The effective modal fusion and perception between the language and the image are necessary for inferring the reference instance in the referring image segmentation (RIS) task. In this article, we propose a novel RIS network, the global and local interactive perception network (GLIPN), to enhance the quality of modal fusion between the language and the image from the local and global perspectives. The core of GLIPN is the global and local interactive perception (GLIP) scheme. Specifically, the GLIP scheme contains the local perception module (LPM) and the global perception module (GPM). The LPM is designed to enhance the local modal fusion by the correspondence between word and image local semantics. The GPM is designed to inject the global structured semantics of images into the modal fusion process, which can better guide the word embedding to perceive the whole image's global structure. Combined with the local-global context semantics fusion, extensive experiments on several benchmark datasets demonstrate the advantage of the proposed GLIPN over most state-of-the-art approaches.

Migration and emission characteristics of trace elements in coal-fired power plant under deep peak load regulation.

The trace elements (TEs) have caused great harm to the environment due to the large consumption of coal, and their emission from the coal-fired power plant (CFPP) has become a hot issue. The deep peak load regulation (DPLR) become a trend in the CFPP, which will affect the migration and emission of TEs. To explore the effect of the DLPR on the migration and emission characteristics of typical TEs in a 330 MW CFPP, the TEs field tests were carried out during the regulation period. Results showed that a higher load enhanced the migration of Pb, Mn, and Cr from bottom ash to fly ash, while it had little effect on the other TEs. More importantly, >99 % of TEs (93 % of Se) could be captured by air pollution control devices (APCDs), and the emission risk of Se and Mn increased with the load. Compared with the other TEs, it is particularly noteworthy that Se has a higher gaseous proportion in the flue gas, and the emission factor sharply increased from 165 MW to 297 MW. In addition, part of the particulate selenium transformed into a gaseous state across the ESP. This work contributes to understanding the migration characteristic of TEs during the DPLR process of CFPP and provides guidance for TEs control in the CFPP.

Photofragmentations, state interactions, and energetics of Rydberg and ion-pair states: two-dimensional resonance enhanced multiphoton ionization of HBr via singlet-, triplet-, Ω = 0 and 2 states.

Mass spectra were recorded for one-colour resonance enhanced multiphoton ionization (REMPI) of H(i)Br (i = 79, 81) for the two-photon resonance excitation region 79,040-80,300 cm(-1) to obtain two-dimensional REMPI data. The data were analysed in terms of rotational line positions, intensities, and line-widths. Quantitative analysis of the data relevant to near-resonance interactions between the F(1)Δ(2)(v' = 1) and V(1)Σ(+)(v' = m + 7) states gives interaction strengths, fractional state mixing, and parameters relevant to dissociation of the F state. Qualitative analysis further reveals the nature of state interactions between ion-pair states and the E(1)Σ(+) (v' = 1) and H(1)Σ(+)(v' = 0) Rydberg states in terms of relative strengths and J' dependences. Large variety in line-widths, depending on electronic states and J' quantum numbers, is indicative of number of different predissociation channels. The relationship between line-widths, line-shifts, and signal intensities reveals dissociation mechanisms involving ion-pair to Rydberg state interactions prior to direct or indirect predissociations of Rydberg states. Quantum interference effects are found to be important. Moreover, observed bromine atom (2 + 1) REMPI signals support the importance of Rydberg state predissociation channels. A band system, not previously observed in REMPI, was observed and assigned to the k(3)Π(0)(v' = 0) ←← X transition with band origin 80,038 cm(-1) and rotational parameter B(v('))=7.238 cm(-1).

Cloning and expression of the first gene for biodegrading microcystin LR by Sphingopyxis sp. USTB-05.

Harmful cyanobacterial blooms are a growing environmental problem worldwide in natural waters, the biodegradation is found to be the most efficient method for removing microcystins (MCs) produced by harmful cyanobacteria. Based on the isolation of a promising bacterial strain of Sphingopyxis sp. USTB-05 for biodegrading MCs, we for the first time cloned and expressed a gene USTB-05-A (HM245411) that is responsible for the first step in the biodegradation of microcystin LR (MC-LR) in E. coli DH5alpha, with a cloning vector of pGEM-T easy and an expression vector of pGEX-4T-1, respectively. The cell-free extracts (CE) of recombinant E. coli DH5alpha containing USTB-05-A had high activity for biodegrading MC-LR. The initial MC-LR concentration of 40 mg/L was completely biodegraded within 1 hr in the presence of CE with a protein concentration of 0.35 mg/mL. Based on an analysis of the liquid chromatogram-mass spectrum (LC-MS), the enzyme encoded by gene USTB-OS-A was found to be active in cleaving the target peptide bond between 3-amino-9-methoxy-2,6, 8-trimethyl-10-phenyl-deca-4,6-dienoic acid (Adda) and arginine of MC-LR, and converting cyclic MC-LR to linear MC-LR as a first product that is much less toxic than parent MC-LR, which offered direct evidence for the first step on the pathway of MC-LR biodegradation by Sphingopyxis sp. USTB-05.

Two-dimensional resonance enhanced multiphoton ionization of H(i)Cl; i = 35, 37: state interactions, photofragmentations and energetics of high energy Rydberg states.

Mass spectra were recorded for (2 + n) resonance enhanced multiphoton ionization (REMPI) of HCl as a function of resonance excitation energy in the 88865-89285 cm(-1) region to obtain two-dimensional REMPI data. Band spectra due to two-photon resonance transitions to number of Rydberg states (Ω' = 0, 1, and 2) and the ion-pair state V((1)Σ(+)(Ω' = 0)) for H(35)Cl and H(37)Cl were identified, assigned, and analyzed with respect to Rydberg to ion-pair interactions. Perturbations show as line-, hence energy level-, shifts, as well as ion signal intensity variations with rotational quantum numbers, J', which, together, allowed determination of parameters relevant to the nature and strength of the state interactions as well as dissociation and ionization processes. Whereas near-resonance, level-to-level, interactions are found to be dominant in heterogeneous state interactions (ΔΩ ≠ 0) significant off-resonance interactions are observed in homogeneous interactions (ΔΩ = 0). The alterations in Cl(+) and HCl(+) signal intensities prove to be very useful for spectra assignments. Data relevant to excitations to the j(3)Σ(0(+)) Rydberg states and comparison with (3 + n) REMPI spectra allowed reassignment of corresponding spectra peaks. A band previously assigned to an Ω = 0 Rydberg state was reassigned to an Ω = 2 state (ν(0) = 88957.6 cm(-1)).

Two-dimensional (2+n) REMPI of CH(3)Br: photodissociation channels via Rydberg states.

(2+n) resonance enhanced multiphoton ionization (REMPI) spectra of CH(3)Br for the masses H(+), CH(m)(+), (i)Br(+), H(i)Br(+), and CH(m)(i)Br(+) (m = 0-3; i = 79, 81) have been recorded in the 66 000-81 000 cm(-1) resonance energy range. Signals due to resonance transitions from the zero vibrational energy level of the ground state CH(3)Br to a number of Rydberg states [Ω(c)]nl;ω (Ω(c) = 3/2, 1/2; ω = 0, 2; l = 1(p), 2(d)) and various vibrational states were identified. C((3)P) and C*((1)D) atom and HBr intermediate production, detected by (2+1) REMPI, most probably is due to photodissociation of CH(3)Br via two-photon excitations to Rydberg states followed by an unusual breaking of four bonds and formation of two bonds to give the fragments H(2) + C/C* + HBr prior to ionization. This observation is supported by REMPI observations as well as potential energy surface (PES) ab initio calculations. Bromine atom production by photodissociation channels via two-photon excitation to Rydberg states is identified by detecting bromine atom (2+1) REMPI.

Two-dimensional (2+n) resonance enhanced multiphoton ionization of HCl: state interactions and photorupture channels via low-energy triplet Rydberg states.

Mass spectra were recorded for (2+n) resonance enhanced multiphoton ionization (REMPI) of HCl as a function of resonance excitation energy in the 81,710-82,870 cm(-1) region to obtain two-dimensional REMPI data. Small but significant fragmentations and H(+), Cl(+), as well as HCl(+) formations are found to occur after resonance excitations to the triplet Rydberg states f (3)Delta(2)(v(') = 0), f (3)Delta(1)(v(') = 0), and g (3)Sigma(+)(1)(v(') = 0). Whereas insignificant rotational line shifts could be observed, alterations in relative ion signal intensities, due to perturbations, clearly could be seen, making such data ideal for detecting and analyzing weak state interactions. Model analysis of relative ion signal intensities, taking account of the major ion formation channels following excitations to Rydberg states, its near-resonance interactions with ion-pair states as well as dissociations and/or photodissociations were performed. These allowed verification of the existence of all these major channels as well as quantifications of the relative weights of the channels and estimates of state interaction strengths. The proposed mechanisms were supported by ion signal power dependence studies.

Cloning and Expression of Genes for Biodegrading Nodularin by Sphingopyxis sp. USTB-05.

Biodegradation is efficient for removing cyanobacterial toxins, such as microcystins (MCs) and nodularin (NOD). However, not all the microbial strains with the microcystin-biodegrading enzymes MlrA and MlrC could biodegrade NOD. Studies on genes and enzymes for biodegrading NOD can reveal the function and the biodegradation pathway of NOD. Based on successful cloning and expression of the USTB-05-A and USTB-05-C genes from Sphingopyxis sp. USTB-05, which are responsible for the biodegradation of MCs, the pathway for biodegrading NOD by these two enzymes was investigated in this study. The findings showed that the enzyme USTB-05-A converted cyclic NOD (m/z 825.4516) into its linear type as the first product by hydrolyzing the arginine and Adda peptide bond, and that USTB-05-C cut off the Adda and glutamic acid peptide bond of linearized NOD (m/z 843.4616) and produced dimeric Adda (m/z 663.4377) as the second product. Further, based on the homology modeling of enzyme USTB-05-A, site-directed mutants of USTB-05-A were constructed and seven crucial sites for enzyme USTB-05-A activity were found. A complete enzymatic mechanism for NOD biodegradation by USTB-05-A in the first step was proposed: glutamic acid 172 and histidine 205 activate a water molecule facilitating a nucleophilic attack on the arginine and Adda peptide bond of NOD; tryptophan 176 and tryptophan 201 contact the carboxylate side chain of glutamic acid 172 and accelerate the reaction rates; and histidine 260 and asparagine 264 function as an oxyanion hole to stabilize the transition states.

Two-dimensional (2+n) resonance enhanced multiphoton ionization of HCl: Photorupture channels via the F 1Delta2 Rydberg state and ab initio spectra.

Mass spectra were recorded for (2+n) resonance enhanced multiphoton ionization (REMPI) of HCl as a function of resonance excitation energy in the 82 600-88 100 cm(-1) region to obtain two-dimensional REMPI data. Analysis of ion-mass signal intensities for excitations via the F (1)Delta(2)(v(')=0-2) and the V (1)Sigma(+)(v(')) states as a function of rotational quantum numbers in the intermediate states either revealed near-resonance interactions or no significant coupling between the F (1)Delta(2) and the V (1)Sigma(+) states, depending on quantum levels. Ion-signal intensities and power dependence measurements allowed us to propose photoionization mechanisms in terms of intermediate state involvement. Based on relative ion-signal intensities and rotational line positions we quantified the contributions of Rydberg and valence intermediate states to the photoionization product formation and evaluated coupling strengths for state mixing. Time-dependent density functional theory (TD-DFT), equation-of-motion coupled cluster (EOM-CC), and completely renormalized EOM-CC calculations with various basis sets were performed to derive singlet state potential energy curves, relevant spectroscopic parameters, and to calculate spectra. Experimentally observed spectra and older calculations are compared with the reported ab initio results.

Inventory-transportation integrated optimization for maintenance spare parts of high-speed trains.

This paper presents a 0-1 programming model aimed at obtaining the optimal inventory policy and transportation mode for maintenance spare parts of high-speed trains. To obtain the model parameters for occasionally-replaced spare parts, a demand estimation method based on the maintenance strategies of China's high-speed railway system is proposed. In addition, we analyse the shortage time using PERT, and then calculate the unit time shortage cost from the viewpoint of train operation revenue. Finally, a real-world case study from Shanghai Depot is conducted to demonstrate our method. Computational results offer an effective and efficient decision support for inventory managers.

Subcritical carbon dioxide-water hydrolysis of sugarcane bagasse pith for reducing sugars production.

The aim of present study was to obtain total reducing sugars (TRS) by hydrolysis in subcritical CO2-water from sugarcane bagasse pith (SCBP), the fibrous residue remaining after papermaking from sugarcane bagasse. The optimum hydrolysis conditions were evaluated by L16(45) orthogonal experiments. The TRS yield achieved 45.8% at the optimal conditions: 200°C, 40min, 500rmin-1, CO2 initial pressure of 1MPa and liquid-to-solid ratio of 50:1. Fourier transform infrared spectrometry and two-dimensional heteronuclear single quantum coherence nuclear magnetic resonance were used to characterize hydrolysis liquor, treated and untreated SCBP, resulting in the removal of hemicelluloses to mainly produce xylose, glucose and arabinose during hydrolysis. The severity factors had no correlation to TRS yield, indicating that the simple kinetic processes of biomass solubilisation cannot perfectly describe the SCBP hydrolysis. The first-order kinetic model based on consecutive reaction was used to obtain rate constants, activation energies and pre-exponential factors.

Pathway for Biodegrading Nodularin (NOD) by Sphingopyxis sp. USTB-05.

Nodularin (NOD) is greatly produced by Nodularia spumigena and released into the environment when toxic cyanobacterial blooms happened in natural water body, which is seriously harmful to human and animals. The promising bacterial strain of Sphingopyxis sp. USTB-05 was found to have an ability in biodegrading NOD. Initially, 11.6 mg/L of NOD could be completely eliminated within 72 h by whole cells of USTB-05, and within 36 h by its crude enzymes (CEs) of 570 mg/L, respectively. During the enzymatic biodegradation process of NOD, two products were observed on the profiles of HPLC. Based on the analysis of m/z ratios of NOD and its two products on a rapid-resolution liquid chromatogram-mass spectrum (RRLC-MS), we suggested that at least two enzymes of USTB-05 participated in biodegrading NOD. The first enzyme hydrolyzed Arg-Adda peptide bond of cyclic NOD and converted it to linear NOD as the first product. The second enzyme was found to cut off the target peptide bond between Adda and Glu of linearized NOD, and Adda was produced as a second and dead-end product. This finding is very important in both basic research and the application of USTB-05 on the removal of NOD from a water environment.

Overexpression of afsR and Optimization of Metal Chloride to Improve Lomofungin Production in Streptomyces lomondensis S015.

As a global regulatory gene in Streptomyces, afsR can activate the biosynthesis of many secondary metabolites. The effect of afsR on the biosynthesis of a phenazine metabolite, lomofungin, was studied in Streptomyces lomondensis S015. There was a 2.5-fold increase of lomofungin production in the afsR-overexpressing strain of S. lomondensis S015 N1 compared with the wild-type strain. Meanwhile, the transcription levels of afsR and two important genes involved in the biosynthesis of lomofungin (i.e., phzC and phzE) were significantly upregulated in S. lomondensis S015 N1. The optimization of metal chlorides was investigated to further increase the production of lomofungin in the afsR-overexpressing strain. The addition of different metal chlorides to S. lomondensis S015 N1 cultivations showed that CaCl2, FeCl2, and MnCl2 led to an increase in lomofungin biosynthesis. The optimum concentrations of these metal chlorides were obtained using response surface methodology. CaCl2 (0.04 mM), FeCl2 (0.33 mM), and MnCl2 (0.38 mM) gave a maximum lomofungin production titer of 318.0 ± 10.7 mg/l, which was a 4.1-fold increase compared with that of S. lomondensis S015 N1 without the addition of a metal chloride. This work demonstrates that the biosynthesis of phenazine metabolites can be induced by afsR. The results also indicate that metal chlorides addition might be a simple and useful strategy for improving the production of other phenazine metabolites in Streptomyces.