A continuous dimethylamino (CH3)2N ± (DMA) radical beam is produced in situ by the pyrolysis of dimethylnitrosamine (CH3)2NNO at 850 (0.5 ° C) in a double-heater inlet system on a double-chamber UPS machine-II which was built specifically to detect transient species. The HeI photoelectron spectrum (PES) of the (CH3)2N radical is recorded for the first time. To assign the PES bands of the (CH3)2N radical, the improved density functional theory (DFT) calculation based on the Amsterdam density functional (ADF) program package has been carried out according to C2v symmetry for the ground state of the neutral (CH3)2N radical and the equilibrium geometries of several ionic states of the cationic species. A sharp peak with the lowest ionization energy at 9.01 ± 0.02 eV comes from electron ionization of the HOMO(2b1) of the (CH3)2N radical, corresponding to the ionization of the (CH3)2N (X 2B1) to (CH3)2N+(X 1A1). The second band with vibration spacing 1980 ± 60 cm-1 comes from electron ionization of 1a2 orbital which is a strongly bound state for the (CH3)2N radical, corresponding to ionization of (CH3)2N (X 2B1) to the 3B1 state of (CH3)2N+ cation. The PES bands of the NO molecule clearly appears in the PE spectrum of the products pyrolyzed of the compound. The pyrolysis mechanism of the (CH3)2NNO compound is shown as follows:
Few‐shot segmentation is a challenging task due to the limited class cues provided by a few of annotations. Discovering more class cues from known and unknown classes is the essential to few‐shot segmentation. Existing method generates class cues mainly from common cues intra new classes where the similarity between support images and query images is measured to locate the foreground regions. However, the support images are not sufficient enough to measure the similarity since one or a few of support mask cannot describe the object of new class with large variations. In this paper, we capture the class cues by considering all images in the unknown classes, i.e., not only the support images but also the query images are used to capture the foreground regions. Moreover, the class‐level labels in the known classes are also considered to capture the discriminative feature of new classes. The two aspects are achieved by class activation map which is used as attention map to improve the feature extraction. A new few‐shot segmentation based on mask transferring and class activation map is proposed, and a new class activation map based on feature clustering is proposed to refine the class activation map. The proposed method is validated on Pascal Voc dataset. Experimental results demonstrate the effectiveness of the proposed method with larger mIoU values.
Motivated by the observations on the involvement of light-induced processes in the Drosophila melanogaster cryptochrome (DmCry) in regulation of the neuronal firing rate, which is achieved by a redox-state change of its voltage-dependent K+ channel Kvβ subunit hyperkinetic (Hk) reduced nicotinamide adenine dinucleotide phosphate (NADPH) cofactor, we propose in this work two hypothetical pathways that may potentially enable such coupling. In the first pathway, triggered by blue-light-induced formation of a radical pair [FAD•–TRP•+] in DmCry, the hole (TRP•+) may hop to Hk, for example, through a tryptophan chain and oxidize NADPH, possibly leading to inhibition of the N-terminus inactivation in the K+ channel. In a second possible pathway, DmCry's FAD•– is reoxidized by molecular oxygen, producing H2O2, which then diffuses to Hk and oxidizes NADPH. In this work, by applying a combination of quantum and empirical-based methods for free-energy calculations, we find that the oxidation of NADPH by TRP•+ or H2O2 and the reoxidation of FAD•– by O2 are thermodynamically feasible. Our results may have an implication in identifying a magnetic sensing signal transduction pathway, specifically upon Drosophila's Hk NADPH cofactor oxidation, with a subsequent inhibition of the K+ channel N-terminus inactivation gate, permitting K+ flux.
Although behavioral studies demonstrated light-induced magnetoreception in the insect Drosophila melanogaster, gaining insight into the possibility that a radical-pair mechanism accounts for the magnetic response of the cryptochrome (DmCry1) is complicated by a number of factors. In addition, the mechanism of magnetoreception for the cryptochrome from the garden warbler bird Sylvia borin (gwCry1a), which demonstrated a long-lived radical pair by transient optical absorption measurements, has also not been rationalized. To assess potential feasibility of a radical-pair mechanism in DmCry1 and gwCry1a, formed by excitation and electron transfer between a Trp-triad and flavin adenine dinucleotide (FAD), further separated by electron transfer within the triad, we applied a combination of theoretical methods, including homology modeling and molecular dynamics (MD) for structure refinement, high-level ab initio theory, and MD simulations using a polarizable force-field for prediction of pKₐ and the electron transfer rate. Calculated excitation energies, followed by electron transfer in model compounds of DmCry1 that assume proton transfer in conjunction with electron transfer from Trp (W420) to FAD and the predicted pKₐ for the proximate residue to FAD (Cys416), support a radical-pair mechanism. Furthermore, free-energy and reorganization energies for the Trp-triad in DmCry1 demonstrate facile electron transfer, explained by the local protein environment and exposure to solvent, which in turn enables a large enough distance separation for the radical-pair partners. Results for gwCry1a demonstrated the importance of accounting for relaxed excited-state geometries in validating the first stage of a radical-pair mechanism. This work provides insight into the so-called chemical compass mechanism to explain magnetic-field sensing in DmCry1 and gwCry1a, expanding on previous work on the cyrptochrome from the plant Arabidopsis thaliana (Solov’yov et al. J. Am. Chem. Soc. 2012, 134, 18046–18052. Solov’yov et al., Sci. Rep. 2014, 4, 1–8.).
Flavins are known to enhance extracellular electron transfer (EET) in Shewanella oneidensis MR-1 bacteria, which reduce electron acceptors through outer-membrane (OM) cytochromes c. Free-shuttle and bound-redox cofactor mechanisms were proposed to explain this enhancement, but recent electrochemical reports favor a flavin-bound model, proposing two one-electron reductions of flavin, namely, oxidized (Ox) to semiquinone (Sq) and semiquinone to hydroquinone (Hq), at anodic and cathodic conditions, respectively. In this work, to provide a mechanistic understanding of riboflavin (RF) binding at the multiheme OM cytochrome OmcA, we explored binding configurations at hemes 2, 5, 7, and 10. Subsequently, on the basis of molecular dynamics (MD) simulations, binding free energies and redox potential shifts upon RF binding for the Ox/Sq and Sq/Hq reductions were analyzed. Our results demonstrated an upshift in the Ox/Sq and a downshift in the Sq/Hq redox potentials, consistent with a bound RF-OmcA model. Furthermore, binding free energy MD simulations indicated an RF binding preference at heme 7. MD simulations of the OmcA-MtrC complex interfacing at hemes 5 revealed a small interprotein redox potential difference with an electron transfer rate of 10(7)-10(8)/s.
A continuous nitrate free radical (NO3) beam is produced in situ by the pyrolysis of pure gas phase N2O5 at 280 °C (±0.5 °C) in a double-heater inlet system on a double-chamber UPS Machine-II which was built specifically to detect transient species. The HeI photoelectron spectroscopy (PES) of the NO3 radical is recorded for the first time. Five obvious bands emerge on the PE spectrum of the NO3 radical. A very sharp peak with the lowest ionization energy at 12.55±0.01 eV originates from electron ionization of the HOMO for the NO3 radical, corresponding to the NO3+(1A1′)←NO3(2A2′) transition. To assign the bands of the PE spectrum of the NO3 radical, the improved density functional theory (DFT) calculation based on the Amsterdam density functional (ADF) program package has been carried out according to D3h symmetry for the neutral ground state of the NO3 radical and the equilibrium geometries of several ionic states of the cationic species. The ionization energies computed are in reasonable agreement with the PES experimental ionization energies. Both PES experimental and DFT calculation provide evidence on the lowest triplet and singlet states of the NO3+ cation.
In this paper, we propose a novel method for the annotation of the multispectral satellite images by incorporating a new graphical model. In order to obtain the annotated image, first, we use a set of images with defined semantic concepts to represent the training set. Second, the images are represented by several visual words based on the image features. At last, the model of discrete infinite logistic normal distribution is exploited to estimate probabilities of semantic classes for the regions in the test images, and categorize them into the semantic concepts. Experimental evaluation on the multispectral images demonstrates the good performance of the proposed method on the multispectral images annotation.
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