| 311. |
- Liu, Fei, et al.
(författare)
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Draft genomes of four enterotoxigenic Escherichia coli (ETEC) clinical isolates from China and Bangladesh
- 2015
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Ingår i: Gut Pathogens. - : Springer Science and Business Media LLC. - 1757-4749. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- © 2015 Liu et al. Abstract Background: Enterotoxigenic Escherichia coli (ETEC) is an important pathogen that causes childhood and travelers' diarrhea. Here, we present the draft genomes of four ETEC isolates recovered from stool specimens of patients with diarrhea in Beijing, China and Dhaka, Bangladesh, respectively. Results: We obtained the draft genomes of ETEC strains CE516 and CE549 isolated in China, and E1777 and E2265 isolated in Bangladesh with a length of 5.1 Mbp, 4.9 Mbp, 5.1 Mbp, and 5.0 Mbp, respectively. Phylogenetic analysis indicated that the four strains grouped with the classical Escherichia coli phylogenetic groups A and B1 and three of them including a multi drug-resistant Chinese isolate (CE549) belonged to two major ETEC lineages distributed globally. The heat stable toxin (ST) structural gene (estA) was present in all strains except in strain CE516, and the heat labile toxin (LT) operon (eltAB) was present in all four genomes. Moreover, different resistance gene profiles were found between the ETEC strains. Conclusions: The draft genomes of the two isolates CE516 and CE549 represent the first genomes of ETEC reported from China. Though we revealed that ETEC is uncommon in Beijing, China, however, when it does occur, multi-drug resistance and ESBL positive isolates might pose a specific public health risk. Furthermore, this study advances our understanding of prevalence and antibiotic resistance of ETEC in China and adds to the number of sequenced strains from Bangladesh.
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| 312. |
- Liu, Hao, et al.
(författare)
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Graphene oxide for nonvolatile memory application by using electrophoretic technique
- 2020
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Ingår i: Materials Today Communications. - : Elsevier BV. - 2352-4928. ; 25
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Tidskriftsartikel (refereegranskat)abstract
- The experimental work presented here, for the first time using electrophoretic technique to fabricate graphene oxide (GO)-based resistive random access memory (RRAM). By using electrophoretic technique, nonvolatile RRAM devices with Aluminum (Al)/GO/Indium tin oxide (ITO) cross-bar sandwich-like structure were fabricated. The fabricated devices show typical bipolar resistant switching behavior with ON/OFF ratio more than 10, retention time more than 102 s, and transition voltage less than 1.7 V. The switching mechanism for the devices is ascribed to the formation and rupture of the conducting filament induced by the diffusion of oxygen ions. The results show that the electrophoretic technique holds great potential for film manufacturing for RRAM.
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| 313. |
- Liu, Haichun, et al.
(författare)
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Phase angle encoded upconversion luminescent nanocrystals for multiplexing applications
- 2017
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Ingår i: Nanoscale. - : Royal Society of Chemistry. - 2040-3364 .- 2040-3372. ; 9:4, s. 1676-1686
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Tidskriftsartikel (refereegranskat)abstract
- Lanthanide-doped upconversion nanoparticles (UCNPs) are increasingly used as luminescent candidates in multiplexed applications due to their excellent optical properties. Inthepast,several encodingidentities havebeen proposedforUCNPs,includingemissioncolour,intensity ratio between different emissionbands, colourspatial distribution, and luminescencelifetime.In this paper, a new optical encoding dimension for upconversion nanomaterials is developed by exploring their luminescence kinetics, i.e., the phase angle of upconversion luminescence in response to a harmonic-wave excitation. Our theoretical derivation shows that the phase angle is governed jointly by the rise and decay times, characterizing the upconversion luminescence kinetics. Experimentally, a full set of methods are developed to manage the upconversion luminescence kinetics, through which the rise and decay times can be manipulated dependently or independently. Furthermore,a large phase-angle space is achieved in which tens of unique codes can be potentially generated in the same colour channel. Our work greatly extends the multiplexing capacity of UCNPs,and offers newopportunities for their applicationsin a wide range such as microarray assays, bioimaging, anti-counterfeiting, deep tissue multiplexed labelling/detectionand high-density data storage.In addition, the development of thisluminescence kinetics-based optical encoding strategy is also instructive for developing multiplexing techniques using other cascade luminescent systems that inherently lack multi-spectral channels, such as triplet-triplet annihilation molecule pairs.
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| 314. |
- Liu, Haichun, et al.
(författare)
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Photon Upconversion Kinetic Nanosystems and Their Optical Response
- 2018
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Ingår i: Laser & Photonics reviews. - : John Wiley & Sons. - 1863-8880 .- 1863-8899. ; 12:1
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Forskningsöversikt (refereegranskat)abstract
- Lanthanide-doped photon upconversion nanoparticles (UCNPs) are capable of converting low-intensity near-infrared light to UV and visible emission through the synergistic effects of light excitation and mutual interactions between doped ions. UCNPs have attracted strong interest as unique spectrum converters and found a multitude of applications in areas like biomedical imaging, energy harvesting and information technology. UCNPs are distinct from many other types of luminescent materials in terms of the involvement of a host lattice and multiple optical centers, i.e., trivalent lanthanide ions with manyfolds of accessible long-lived energy states, in individual nanoparticles. The mutual interactions between these optical centers, i.e., sequential energy transfers, make them operate as an integrated unit and co-determine the luminescence kinetics and other optical properties of the individual nanoparticle. Thus, each nanoparticle consititutes a kinetic optical system. In this work, we explore UCNPs from the outset of being such kinetic optical systems and review their physical formation, the underlying photophysics, macroscopic statistical description, and their response to various optical stimuli in the spectral, polarization, intensity, temporal and frequency domains, and demonstrate ways that their optical output can be optimized by manipulating the excitation schemes. Our review highlights upconversion nanotechnology as an interdisciplinary field across chemistry, physics and biomedical engineering, with great future possibilities, flexibility and ramifications. We outline some of the potential directions of upconversion nanoparticle research.
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| 315. |
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| 316. |
- Liu, Qingyun, 1993-, et al.
(författare)
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High throughput decoding approach for luminescencekinetics-based optical encoding of lanthanide upconversion nanoparticles
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Lanthanide upconversion nanoparticles (UCNPs) are increasingly explored to develop high-security-level anti-counterfeiting and multiplexing applications, due to the availability of ample encoding dimensions. Among other applications, upconversion luminescence(UCL) kinetics-based optical encoding is particularly attractive as it provides an almost unlimited encoding capacity due to the ease of manipulating the UCL kinetics by chemical engineering. However, current decoding methods limit its applications because of a typically low throughput and high cost of the system. In this Letter, we propose a novel decoding approach for UCL kinetics-based optical encoding, which utilizes a pulsed excitation source with adjustable pulse duration and a low time-resolution and large-area detector. We develop a theoretical fitting model and show how fingerprint time constants of the UCNPs (the encoding identities) can be extracted from the correlation between the averaged UCL intensity and the pulse duration. Our new approach provides a high-throughput and cost-effective solution to decode UCL kinetics.
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| 317. |
- Liu, Yong, et al.
(författare)
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One-Pot Catalytic Conversion of Raw Lignocellulosic Biomass into Gasoline Alkanes and Chemicals over LiTaMoO6 and Ru/C in Aqueous Phosphoric Acid
- 2015
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Ingår i: ACS Sustainable Chemistry and Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 3:8, s. 1745-1755
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Tidskriftsartikel (refereegranskat)abstract
- Lignocellulosic biomass is a renewable feedstock that has the potential to replace the diminishing fossil fuels. Herein, we reported the simultaneous conversion of cellulose, hemicellulose and lignin from raw biomass into gasoline alkanes (hexanes and pentanes) and monophenols and related hydrocarbons over layered LiTaMoO6 and Ru/C in aqueous phosphoric acid medium. Specifically, gasoline alkanes were directly yielded from the carbohydrate components, based on hemicellulose and cellulose, and the total yield could be up to 82.4%. Notably, the lignin fraction could also be transformed into monophenols, related alcohols and hydrocarbons by the one-pot reaction. It suggested that the hydrocracking of monophenol fraction could be performed in this catalytic system. The total yield of volatile products was 53% based on the lignin fraction. In this paper, the influences of phosphoric acid concentration, substrate ash and the amino acids derived from the biogenic impurities were investigated and different raw biomass substrates were tested. Furthermore, the catalysts could be reused for several runs to convert raw biomass without pretreatment.
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| 318. |
- Liu, Yan Rong, et al.
(författare)
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Electron-rotation coupling in diatomics under strong-field excitation
- 2020
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Ingår i: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - : American Physical Society. - 2469-9926 .- 2469-9934. ; 102:3
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Tidskriftsartikel (refereegranskat)abstract
- The photoexcitation and photodissociation of diatomic molecules by intense pulse lasers has been the subject of extensive investigations over the past decades. However, the usually employed theoretical framework neglects the coupling between the molecular rotational angular momentum (R) and the angular momentum of the electrons projected onto the molecular axis Omega = Lambda + Sigma, which results in the known Lambda-doubling phenomenon in high-resolution electronic spectra of diatomic molecules. While neglecting this coupling is an excellent approximation in the weak-field or perturbative regime owing to the large mass difference between the rotating atoms and the electrons, the approximation breaks down for intense laser pulses because of the repeated Rabi cycling of the electronic transitions, which can have a significant effect on the rotational degrees of freedom of the molecule. By correcting the transition dipole matrix elements and introducing angular basis sets based on Wigner D functions, the conventional theoretical treatment is generalized to a universal description valid for both the weak- and strong-field regimes. The theoretical treatment developed here is applied to the vertical bar(1)Sigma > to vertical bar(1)Pi > transitions in diatomic systems. Our results reveal that, for field intensities resulting in about one Rabi cycling for extreme ultraviolet or x-ray transitions, the theoretical predictions by the conventional theoretical frame need to be corrected when considering observables such as the molecular alignment and the angular distribution of the photofragments.
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| 319. |
- Liu, Yan Rong, et al.
(författare)
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Electron-rotation coupling in UV photodissociation of aligned diatomics
- 2022
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Ingår i: Physical Review Research. - : American Physical Society (APS). - 2643-1564. ; 4:1
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the effect of electron-rotation coupling (R -Omega coupling) on fs UV photodissociation dynamics of aligned diatomic molecules. We consider the showcase of ground-state MeH+ ((1)Sigma(+)) pumped by an fs IR pulse, which initiates rotational dynamics leading to field-free molecular alignment. A time-delayed fs UV pulse probes the degree of alignment of the rotational wave packet in the framework of photodissociation spectroscopy. The molecular alignment correlates directly with the angular distribution of the photofragments in the dissociative (1)Pi state, as it is shown in our simulations comparing the cases when the R -Omega coupling is included and ignored. We show how the angular distribution of the photofragment is strongly affected by the R -Omega coupling at various delay times with specific molecular alignment. It was shown that increases of the fs UV pulse intensity and the degree of alignment enhance the effect of R -Omega coupling on the angular distribution of the photofragments. On the contrary, an increase of the initial temperature tends to reduce the effect of R -Omega coupling, which is explained by the fact that such an effect turns smaller as the increasing of magnetic state vertical bar M-0 vertical bar for each initial rotational state J(0); furthermore, higher excited rotational state J(0) contains more magnetic states M-0, and the results have been averaged over all degenerated M-0 states.
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| 320. |
- Liu, Yan Rong, et al.
(författare)
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Photodissociation dynamics of the NH molecule under intense VUV pulses
- 2020
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Ingår i: Physical Review Research. - : American Physical Society (APS). - 2643-1564. ; 2:4
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Tidskriftsartikel (refereegranskat)abstract
- Photodissociation dynamics of the NH molecule excited from the triplet ground X-3 Sigma(-) to 2(3)Pi state by resonant intense VUV pulses have been comprehensively investigated by the recently proposed theoretical treatment involving the electron-rotation coupling. The rotational dynamics are described by the Wigner D functions, and the electronic transition operators are refined with respect to the changes of the projection of the total orbital angular momentum onto the molecular axis Delta Lambda. The kinetic energy release (KER) spectra and the angular distribution of photofragments are obtained by averaging over nine degenerate initial angular states, computed separately. We have shown that the KER spectra are not very sensitive to the electron-rotation coupling for different pulse intensity and energy detuning from the resonance. The angular distribution of the photofragments, on the contrary, is strongly affected by the electron-rotation coupling at the small angles between the molecular axis and laser polarization. The influence of the electron-rotational coupling shows different trends for positive and negative detunings from the resonance at variation of the pulse intensity, which is explained by sufficient changes of the rotational wave packet dynamics caused by different phases of the initial rotational states.
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