| 1. |
- Klionsky, Daniel J., et al.
(författare)
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Guidelines for the use and interpretation of assays for monitoring autophagy
- 2012
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Ingår i: Autophagy. - : Informa UK Limited. - 1554-8635 .- 1554-8627. ; 8:4, s. 445-544
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Forskningsöversikt (refereegranskat)abstract
- In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process vs. those that measure flux through the autophagy pathway (i.e., the complete process); thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from stimuli that result in increased autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field.
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| 2. |
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| 3. |
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| 4. |
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| 5. |
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| 6. |
- Kristan, Matej, et al.
(författare)
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The Ninth Visual Object Tracking VOT2021 Challenge Results
- 2021
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Ingår i: 2021 IEEE/CVF INTERNATIONAL CONFERENCE ON COMPUTER VISION WORKSHOPS (ICCVW 2021). - : IEEE COMPUTER SOC. - 9781665401913 ; , s. 2711-2738
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Konferensbidrag (refereegranskat)abstract
- The Visual Object Tracking challenge VOT2021 is the ninth annual tracker benchmarking activity organized by the VOT initiative. Results of 71 trackers are presented; many are state-of-the-art trackers published at major computer vision conferences or in journals in recent years. The VOT2021 challenge was composed of four sub-challenges focusing on different tracking domains: (i) VOT-ST2021 challenge focused on short-term tracking in RGB, (ii) VOT-RT2021 challenge focused on "real-time" short-term tracking in RGB, (iii) VOT-LT2021 focused on long-term tracking, namely coping with target disappearance and reappearance and (iv) VOT-RGBD2021 challenge focused on long-term tracking in RGB and depth imagery. The VOT-ST2021 dataset was refreshed, while VOT-RGBD2021 introduces a training dataset and sequestered dataset for winner identification. The source code for most of the trackers, the datasets, the evaluation kit and the results along with the source code for most trackers are publicly available at the challenge website(1).
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| 7. |
- Alimena, Juliette, et al.
(författare)
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Searching for long-lived particles beyond the Standard Model at the Large Hadron Collider
- 2020
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Ingår i: Journal of Physics G. - : IOP Publishing. - 0954-3899 .- 1361-6471. ; 47:9
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Tidskriftsartikel (refereegranskat)abstract
- Particles beyond the Standard Model (SM) can generically have lifetimes that are long compared to SM particles at the weak scale. When produced at experiments such as the Large Hadron Collider (LHC) at CERN, these long-lived particles (LLPs) can decay far from the interaction vertex of the primary proton-proton collision. Such LLP signatures are distinct from those of promptly decaying particles that are targeted by the majority of searches for new physics at the LHC, often requiring customized techniques to identify, for example, significantly displaced decay vertices, tracks with atypical properties, and short track segments. Given their non-standard nature, a comprehensive overview of LLP signatures at the LHC is beneficial to ensure that possible avenues of the discovery of new physics are not overlooked. Here we report on the joint work of a community of theorists and experimentalists with the ATLAS, CMS, and LHCb experiments-as well as those working on dedicated experiments such as MoEDAL, milliQan, MATHUSLA, CODEX-b, and FASER-to survey the current state of LLP searches at the LHC, and to chart a path for the development of LLP searches into the future, both in the upcoming Run 3 and at the high-luminosity LHC. The work is organized around the current and future potential capabilities of LHC experiments to generally discover new LLPs, and takes a signature-based approach to surveying classes of models that give rise to LLPs rather than emphasizing any particular theory motivation. We develop a set of simplified models; assess the coverage of current searches; document known, often unexpected backgrounds; explore the capabilities of proposed detector upgrades; provide recommendations for the presentation of search results; and look towards the newest frontiers, namely high-multiplicity 'dark showers', highlighting opportunities for expanding the LHC reach for these signals.
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| 8. |
- An, Junghwa, et al.
(författare)
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Permanent Genetic Resources added to Molecular Ecology Resources Database 1 October 2009-30 November 2009
- 2010
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Ingår i: Molecular Ecology Resources. - : Wiley. - 1755-098X .- 1755-0998. ; 10:2, s. 404-408
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Tidskriftsartikel (refereegranskat)abstract
- This article documents the addition of 411 microsatellite marker loci and 15 pairs of Single Nucleotide Polymorphism (SNP) sequencing primers to the Molecular Ecology Resources Database. Loci were developed for the following species: Acanthopagrus schlegeli, Anopheles lesteri, Aspergillus clavatus, Aspergillus flavus, Aspergillus fumigatus, Aspergillus oryzae, Aspergillus terreus, Branchiostoma japonicum, Branchiostoma belcheri, Colias behrii, Coryphopterus personatus, Cynogolssus semilaevis, Cynoglossus semilaevis, Dendrobium officinale, Dendrobium officinale, Dysoxylum malabaricum, Metrioptera roeselii, Myrmeciza exsul, Ochotona thibetana, Neosartorya fischeri, Nothofagus pumilio, Onychodactylus fischeri, Phoenicopterus roseus, Salvia officinalis L., Scylla paramamosain, Silene latifo, Sula sula, and Vulpes vulpes. These loci were cross-tested on the following species: Aspergillus giganteus, Colias pelidne, Colias interior, Colias meadii, Colias eurytheme, Coryphopterus lipernes, Coryphopterus glaucofrenum, Coryphopterus eidolon, Gnatholepis thompsoni, Elacatinus evelynae, Dendrobium loddigesii Dendrobium devonianum, Dysoxylum binectariferum, Nothofagus antarctica, Nothofagus dombeyii, Nothofagus nervosa, Nothofagus obliqua, Sula nebouxii, and Sula variegata. This article also documents the addition of 39 sequencing primer pairs and 15 allele specific primers or probes for Paralithodes camtschaticus.
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| 9. |
- Anchordoqui, Luis A., et al.
(författare)
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The Forward Physics Facility : Sites, experiments, and physics potential
- 2022
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Ingår i: Physics reports. - : Elsevier. - 0370-1573 .- 1873-6270. ; 968, s. 1-50
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Tidskriftsartikel (refereegranskat)abstract
- The Forward Physics Facility (FPF) is a proposal to create a cavern with the space and infrastructure to support a suite of far-forward experiments at the Large Hadron Collider during the High Luminosity era. Located along the beam collision axis and shielded from the interaction point by at least 100 m of concrete and rock, the FPF will house experiments that will detect particles outside the acceptance of the existing large LHC experiments and will observe rare and exotic processes in an extremely low-background environment. In this work, we summarize the current status of plans for the FPF, including recent progress in civil engineering in identifying promising sites for the FPF and the experiments currently envisioned to realize the FPF's physics potential. We then review the many Standard Model and new physics topics that will be advanced by the FPF, including searches for long-lived particles, probes of dark matter and dark sectors, high-statistics studies of TeV neutrinos of all three flavors, aspects of perturbative and non-perturbative QCD, and high-energy astroparticle physics.
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| 10. |
- Chen, Zhen, et al.
(författare)
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Design, Synthesis, and Evaluation of Reversible and Irreversible Monoacylglycerol Lipase Positron Emission Tomography (PET) Tracers Using a "Tail Switching" Strategy on a Piperazinyl Azetidine Skeleton
- 2019
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Ingår i: Journal of Medicinal Chemistry. - : American Chemical Society (ACS). - 0022-2623 .- 1520-4804. ; 62:7, s. 3336-3353
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Tidskriftsartikel (refereegranskat)abstract
- Monoacylglycerol lipase (MAGL) is a senile hydrolase that degrades 2-arachidonoylglycerol (2-AG) in the endocannabinoid system (eCB). Selective inhibition of MAGL has emerged as a potential therapeutic approach for the treatment of diverse pathological conditions, including chronic pain, inflammation, cancer, and neurodegeneration. Herein, we disclose a novel array of reversible and irreversible MAGL inhibitors by means of "tail switching" on a piperazinyl azetidine scaffold. We developed a lead irreversible-binding MAGL inhibitor 8 and reversible-binding compounds 17 and 37, which are amenable for radiolabeling with C-11 or F-18. [C-11]8 ([C-11]MAGL-2-11) exhibited high brain uptake and excellent binding specificity in the brain toward MAGL. Reversible radioligands [C-11]17 ([C-11]PAD) and [F-18]37 ([F-18]MAGL-4-11) also demonstrated excellent in vivo binding specificity toward MAGL in peripheral organs. This work may pave the way for the development of MAGL-targeted positron emission tomography tracers with tunability in reversible and irreversible binding mechanisms.
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| 11. |
- Cheng, Ran, et al.
(författare)
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In Vitro and in Vivo Evaluation of C-11-Labeled Azetidinecarboxylates for Imaging Monoacylglycerol Lipase by PET Imaging Studies
- 2018
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Ingår i: Journal of Medicinal Chemistry. - : American Chemical Society (ACS). - 0022-2623 .- 1520-4804. ; 61:6, s. 2278-2291
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Tidskriftsartikel (refereegranskat)abstract
- Monoacylglycerol lipase (MAGL) is the principle enzyme for metabolizing endogenous cannabinoid ligand 2-arachidonoyglycerol (2-AG). Blockade of MAGL increases 2-AG levels, resulting in subsequent activation of the endocannabinoid system, and has emerged as a novel therapeutic strategy to treat drug addiction, inflammation, and neurodegenerative diseases. Herein we report a new series of MAGL inhibitors, which were radiolabeled by site-specific labeling technologies, including C-11-carbonylation and spirocyclic iodonium ylide (SCIDY) radio fluorination. The lead compound [C-11]10 (MAGL-0519) demonstrated high specific binding and selectivity in vitro and in vivo. We also observed unexpected washout kinetics with these irreversible radiotracers, in which in vivo evidence for turnover of the covalent residue was unveiled between MAGL and azetidine carboxylates. This work may lead to new directions for drug discovery and PET tracer development based on azetidine carboxylate inhibitor scaffold.
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| 12. |
- Duan, S., et al.
(författare)
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Effects of Plasmon Modes on Resonant Raman Images of a Single Molecule
- 2020
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Ingår i: The Journal of Physical Chemistry Letters. - : NLM (Medline). - 1948-7185. ; 11:2, s. 407-411
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Tidskriftsartikel (refereegranskat)abstract
- Localized surface plasmons (LSPs) are excellent light sources at the nanoscale. How to precisely describe the interaction between LSPs and molecules has become an important issue. We present here a comprehensive study on the dependence of resonant Raman images on LSP modes generated by two typical nanostructures. Theoretical calculations demonstrate that the Raman images are sensitive to not only the spatial distribution but also the phase of the localized field, which should be attributed to the quantum nature of the interaction between LSP modes and molecules. We also find that the rotation of noncylindrical symmetry modes could affect the details of images, which offers an extra means to extract molecular information. Our findings extend the understanding of the LSP-matter interaction, which would be useful for the rational design of nanostructures and thus further applications of LSPs.
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| 13. |
- Duan, Sai, et al.
(författare)
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Gauge invariant theory for super high resolution Raman images
- 2017
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Ingår i: Journal of Chemical Physics. - : American Institute of Physics (AIP). - 0021-9606 .- 1089-7690. ; 146:19
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Tidskriftsartikel (refereegranskat)abstract
- The use of a highly localized plasmonic field has enabled us to achieve sub-nanometer resolution of Raman images for single molecules. The inhomogeneous spatial distribution of plasmonic field has become an important factor that controls the interaction between the light and the molecule. We present here a gauge invariant interaction Hamiltonian (GIIH) to take into account the nonuniformity of the electromagnetic field distribution in the non-relativistic regime. The theory has been implemented for both resonant and nonresonant Raman processes within the sum-over-state framework. It removes the gauge origin dependence in the phenomenologically modified interaction Hamiltonian (PMIH) employed in previous studies. Our calculations show that, in most resonant cases, the Raman images from GIIH are similar to those from PMIH when the origin is set to the nuclear charge center of the molecule. In the case of nonresonant Raman images, distinct differences can be found from two different approaches, while GIIH calculations provide more details and phase information of the images. Furthermore, the results from GIIH calculations are more stable with respect to the computational parameters. Our results not only help to correctly simulate the resonant and nonresonant Raman images of single molecules but also lay the foundation for developing gauge invariant theory for other linear and nonlinear optical processes under the excitation of non-uniform electromagnetic field. Published by AIP Publishing.
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| 14. |
- Duan, Sai, et al.
(författare)
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Identification of Water Hexamer on Cu(111) Surfaces
- 2020
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 142:15, s. 6902-6906
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Tidskriftsartikel (refereegranskat)abstract
- While being considered as the building block of ice on a hydrophobic metal surface, the global minimum of the water hexamer is still elusive, which has impeded our understanding of water/metal interfaces. Herein, we comprehensively investigate water hexamer on Cu(111) theoretically and propose the boat configuration as the new in situ adsorption configuration from the scanning tunneling microscope experiments. All existing experimental measurements can therefore be well reproduced. Calculations in high-level theories reveal that the boat configuration is indeed the global minimum under experimental conditions, solving a long-standing discrepancy.
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| 15. |
- Fu, Jiahong, et al.
(författare)
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Effect of an impinging jet on the flow characteristics and thermal performance of mainstream in battery cooling of hybrid electric vehicles
- 2022
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Ingår i: International Journal of Heat and Mass Transfer. - : Elsevier BV. - 0017-9310. ; 183
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Tidskriftsartikel (refereegranskat)abstract
- The novel concept of impinging jet cooling, i.e., an active-passive air cooling strategy, was proposed to achieve improved battery thermal management in hybrid vehicles, and this method is supported by excess high pressure discharged air. To comprehensively realize the active-passive combined cooling behavior, a rectangular channel with a jet impingement hole was utilized to experimentally and numerically study the flow characteristics and thermal performance of the joint cooling mechanism. The numerical results were confirmed by the experimental data in this work, the maximum deviations of the offset and Nusselt numbers are 18.8% and 7.5%, respectively. The thermal transport performs much better under the interaction between the mainstream and impinging jet, i.e., the average Nusselt number and maximum Nusselt number can be increased by 0.43-16.55, 5.73-34.42, respectively, at inlet pressures of the impinging jet in the range of 1–6 bar. The values of Nu/Nu0/(f/f0) 1/3 are improved by 1.52–3.33. The jet fluid was deflected under the influence of the mainstream and a vortex can be induced, which is beneficial for the heat transfer performance. The jet fluid closely reached the heated plane at a relatively large volume flow rate and the heat transfer performance was excellent once the jet fluid touched the heated plane. The thermal boundary layer becomes thinned under the impact of the impinging jet but the magnitude of the reduction is relatively slight.
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| 16. |
- Gong, Zu-Yong, et al.
(författare)
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Harvesting of surface plasmon polaritons : Role of the confinement factor
- 2020
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 153:9
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Tidskriftsartikel (refereegranskat)abstract
- Surface plasmon polaritons (SPPs) are propagating waves generated at the interface of a metal (metamaterial) and a dielectric. The intensity of SPPs often exponentially decays away from the surface, while their wavelengths can be tuned by the confinement effect. We present here a computational method based on quantum-mechanical theory to fully describe the interaction between confined SPPs and adsorbed molecules at the interface. Special attention has been paid to the roles of the confinement factor. Taking a prototype dye sensitized solar cell as an example, calculated results reveal that with the increase in the confinement factor in metal/dielectric interfaces, the breakdown of the conventional dipole approximation emerges, which allows efficient harvesting of SPPs with low excitation energies and, thus, increases the efficiency of the solar energy conversion by dye molecules. Furthermore, at the metamaterial/dielectric interface, SPPs with large confinement factors could directly excite the dye molecule from its ground singlet state to the triplet state, opening an entirely new channel with long-living carriers for the photovoltaic conversion. Our results not only provide a rigorous theory for the SPP-molecule interaction but also highlight the important role played by the momentum of the light in plasmon related studies.
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| 17. |
- Guo, Yaxiao, et al.
(författare)
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Molybdenum and boron synergistically boosting efficient electrochemical nitrogen fixation
- 2020
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Ingår i: Nano Energy. - : Elsevier Ltd. - 2211-2855 .- 2211-3282. ; 78
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Tidskriftsartikel (refereegranskat)abstract
- Ammonia production consumes ~2% of the annual worldwide energy supply, therefore strategic alternatives for the energy-intensive ammonia synthesis through the Haber-Bosch process are of great importance to reduce our carbon footprint. Inspired by MoFe-nitrogenase and the energy-efficient and industrially feasible electrocatalytic synthesis of ammonia, we herein establish a catalytic electrode for artificial nitrogen fixation, featuring a carbon fiber cloth fully grafted by boron-doped molybdenum disulfide (B-MoS2/CFC) nanosheets. An excellent ammonia production rate of 44.09 μg h–1 cm–2 is obtained at −0.2 V versus the reversible hydrogen electrode (RHE), whilst maintaining one of the best reported Faradaic efficiency (FE) of 21.72% in acidic aqueous electrolyte (0.1 M HCl). Further applying a more negative potential of −0.25 V renders the best ammonia production rate of 50.51 μg h–1 cm–2. A strong-weak electron polarization (SWEP) pair from the different electron accepting and back-donating capacities of boron and molybdenum (2p shell for boron and 5d shell for molybdenum) is proposed to facilitate greatly the adsorption of non-polar dinitrogen gas via N≡N bond polarization and the first protonation with large driving force. In addition, for the first time a visible light driven photo-electrochemical (PEC) cell for overall production of ammonia, hydrogen and oxygen from water + nitrogen, is demonstrated by coupling a bismuth vanadate BiVO4 photo-anode with the B-MoS2/CFC catalytic cathode.
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| 18. |
- Li, Yong, et al.
(författare)
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Buoyancy and Thermal Acceleration of Supercritical n-Decane in a Rectangular Channel
- 2022
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Ingår i: Journal of Thermophysics and Heat Transfer. - 0887-8722. ; 36:2, s. 419-430
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Tidskriftsartikel (refereegranskat)abstract
- In this work, supercritical n-decane flowing in ducts with different orientations is thoroughly investigated in terms of secondary flow, wall shear stress, and thermal acceleration. It is known that the secondary flow strength hardly plays a role in cases of flowing upward, flowing downward, or flowing horizontally at a small heat flux/mass flux. Still, an attachment point can be found at the center for cases of flowing upward and flowing downward, and this enhances the heat transfer. For a large heat flux/mass flux, thermal transport depends not only on the secondary flow strength but also on the secondary flow structure. Besides, a separation point is found at the center for flowing up/downward cases, and the more adjacent the attachment point is to the heated wall, the more serious is the thermal transport. The wall shear stress is beneficial to heat transfer but also relies on the distribution profile. Thermal acceleration can really diminish or even restrain the HTD phenomenon, but it is not the reason to cause the difference of heat transfer behavior for channels with different orientations.
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| 19. |
- Li, Yong, et al.
(författare)
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竖直矩形通道内超临界正癸烷振荡特性的大涡模拟
- 2022
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Ingår i: Nanjing Hangkong Hangtian Daxue Xuebao/Journal of Nanjing University of Aeronautics and Astronautics. - 1005-2615. ; 54:2, s. 281-289
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Tidskriftsartikel (refereegranskat)abstract
- Active generative cooling based on supercritical hydrocarbon fuel is regarded as one of the most promising methods for scramjet thermal management. A large eddy simulation method is used to explore the transient change law of the initial flow, and heat transfer behaviors of supercritical hydrocarbon fuel is in rectangular channels. An oscillation effect can be proved in the convective heat transfer process, i.e., the temperature and velocity distributions fluctuate strongly. By monitoring the velocity variation rule of 10-4 s time scale, the approximate trigonometric frequency and amplitude are present in this oscillation. At the initial heating condition, the high-temperature fluid, which is close to the heated wall, flows into the low-temperature region under the effect of buoyancy force. As the fluid temperature gradually reaches the pseudo-critical value, its thermo-physical properties change dramatically. The friction factor oscillates as well as the fluid kinetic energy. Correspondingly, the enhanced vortex is induced away from the heated wall. Over time, the enhanced vortex begins to move to the heated wall and the low-temperature fluid impinges on the wall. Consequently, the thermal transport is enhanced.
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| 20. |
- Liang, Zhen-pu, et al.
(författare)
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单分子层修饰生物芯片基片的电化学研究
- 2005
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Ingår i: Journal of Wuhan University (Natural Science Edition). - 1671-8836. ; :2, s. 249-252
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Tidskriftsartikel (refereegranskat)abstract
- A biotin-avidin modified biochip has been constructed, and its electrochemistry characteristics were studied with K4Fe(CN)(6).3H2O and ferrocene as the indicators by cyclic voltammograms. Electrochemical experiments showed that this biochip has high response signal, reproducibility,uniformity and low background signal; the ferrocene can be used as high efficiency electron medium. And these results were discussed in this paper.
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| 21. |
- Liu, Kui, et al.
(författare)
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Kallikrein genes are associated with lupus and glomerular basement membrane-specific antibody-induced nephritis in mice and humans
- 2009
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Ingår i: Journal of Clinical Investigation. - 0021-9738 .- 1558-8238. ; 119:4, s. 911-923
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Tidskriftsartikel (refereegranskat)abstract
- Immune-mediated nephritis contributes to disease in systemic lupus erythematosus, Goodpasture syndrome (caused by antibodies specific for glomerular basement membrane [anti-GBM antibodies]), and spontaneous lupus nephritis. Inbred mouse strains differ in susceptibility to anti-GBM antibody-induced and spontaneous lupus nephritis. This study sought to clarify the genetic and molecular factors that maybe responsible for enhanced immune-mediated renal disease in these models. When the kidneys of 3 mouse strains sensitive to anti-GBM antibody-induced nephritis were compared with those of 2 control strains using microarray analysis, one-fifth of the underexpressed genes belonged to the kallikrein gene family,which encodes serine esterases. Mouse strains that upregulated renal and urinary kallikreins exhibited less evidence of disease. Antagonizing the kallikrein pathway augmented disease, while agonists dampened the severity of anti-GBM antibody-induced nephritis. In addition, nephritis-sensitive mouse strains had kallikrein haplotypes that were distinct from those of control strains, including several regulatory polymorphisms,some of which were associated with functional consequences. Indeed, increased susceptibility to anti-GBM antibody-induced nephritis and spontaneous lupus nephritis was achieved by breeding mice with a genetic interval harboring the kallikrein genes onto a disease-resistant background. Finally, both human SLE and spontaneous lupus nephritis were found to be associated with kallikrein genes, particularly KLK1 and the KLK3 promoter, when DNA SNPs from independent cohorts of SLE patients and controls were compared. Collectively, these studies suggest that kallikreins are protective disease-associated genes in anti-GBM antibody-induced nephritis and lupus.
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| 22. |
- Liu, Xuan, et al.
(författare)
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Increased southerly and easterly water vapor transport contributed to the dry-to-wet transition of summer precipitation over the Three-River Headwaters in the Tibetan Plateau
- 2023
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Ingår i: Advances in Climate Change Research. - 1674-9278 .- 2524-1761. ; 14:4, s. 502-510
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Tidskriftsartikel (refereegranskat)abstract
- The Three-River Headwaters (TRH) region in the Tibetan Plateau is vulnerable to climate change; changes in summer (June–August) precipitation have a significant impact on water security and sustainability in both local and downstream areas. However, the changes in summer precipitation of different intensities over the TRH region, along with their influencing factors, remain unclear. In this study, we used observational and ERA5 reanalysis data and employed a precipitation categorization and water vapor budget analysis to quantify the categorized precipitation variations and investigate their possible linkages with the water vapor budget. Our results showed an increasing trend in summer precipitation at a rate of 0.9 mm per year (p < 0.1) during 1979–2020, with a significant dry-to-wet transition in 2002. The category ‘very heavy precipitation’ (≥10 mm d−1) contributed 65.1% of the increased summer precipitation, which occurred frequently in the northern TRH region. The dry-to-wet transition was caused by the effects of varied atmospheric circulations in each subregion. Southwesterly water vapor transport through the southern boundary was responsible for the increased net water vapor flux in the western TRH region (158.2%), while southeasterly water vapor transport through the eastern boundary was responsible for the increased net water vapor flux in the central TRH (155.2%) and eastern TRH (229.2%) regions. Therefore, we inferred that the dry-to-wet transition of summer precipitation and the increased ‘very heavy precipitation’ over the TRH was caused by increased easterly and southerly water vapor transport.
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| 23. |
- Sun, Jie, et al.
(författare)
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Thermomechanical performances of sandwich panels with multi-layer multi-row lightening holes : Comparative study on corrugated-core and X-core
- 2023
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Ingår i: Thermal Science and Engineering Progress. - 2451-9049. ; 43
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Tidskriftsartikel (refereegranskat)abstract
- In the present study, corrugated-core and X-core sandwich panels with multi-layer and multi-row lightening holes are designed from the perspective of extending the thermal short-circuit path. The thermal insulation performance and load-bearing capacity of the integrated thermal protection structure are investigated and enhanced by sequential thermal–mechanical coupling method. For the corrugated-core sandwich structure, heat proofing effect of schemes altering the quantity of lightening holes along the vertical and lateral directions is relatively similar. Compared to a solid corrugated panel, the maximum temperature of the bottom panel is reduced by up to 86.7 K after arranging the lightening holes. Under the joint effect of temperature load and aerodynamic pressure load, the equivalent stress of double-layer lightening holes at the bolted joints is slightly above the material yield strength. X-panel with three kinds of lightening holes decreases the maximum temperature by 54 K, 60 K and 76 K, respectively, compared to that without lightening holes. Increasing the number of lightening holes along the thickness direction has a noticeable effect on the insulation performance within the safety limits. Special X-shaped structure enhances the structural stability, which has a maximum deformation of merely 0.29 mm. Overall temperature of the X panel is lower than that of the corrugated plate by 39–63 K and has better uniformity of the temperature distribution on the bottom panel. These findings enlighten that passive thermal protection technologies could focus on the direction of setting multiple barriers along the direction of temperature transfer.
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| 24. |
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| 25. |
- Xie, Zhen, et al.
(författare)
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Finding the true pathway for reversible isomerization of a single azobenzene molecule tumbling on Au(111) surface
- 2020
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Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3364 .- 2040-3372. ; 12:19, s. 10474-10479
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Tidskriftsartikel (refereegranskat)abstract
- Switchable trans-cis isomerization of azobenzene (AB) and its derivatives on metallic surfaces have offered rich possibilities to functionalize molecular devices. However, the lack of a good understanding of the isomerization pathway has severely limited our ability for rational design. One of the long-debated issues is the cis configuration of the parental AB on the Au(111) surface, for which the experimentally inferred structure differs from the theoretically predicted global minimum. Here, we theoretically identify a new in situ metastable configuration for cis-AB on Au(111) that can reproduce all the observations reported in the scanning tunneling microscopy experiments. It reveals that the bistability of AB on the Au(111) surface is attributed to the significantly increased kinetic stability of the newly discovered cis-AB isomer. A fascinating tumbling pathway that overcomes two energy barriers stimulated by tunneling electrons for the trans-cis AB isomerization on Au(111) has been verified, suggesting a new type of molecular motion based on the AB systems.
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| 26. |
- Xie, Zhen
(författare)
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High Resolution Tip-Enhanced Raman Images of Single Molecules from First Principles Simulations
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- With the precise control of spatially confined plasmon (SCP), tip-enhanced Raman spectroscopy (TERS) has achieved sub-nanometer resolution, leading to the chemical and physical characterization of the single molecule by optical Raman images. In the high resolution TERS measurements, the SCP spatial distribution generates the position-dependent Raman images. The position dependence challenges the conventional response theory, because the assumption of interactions between the molecule and the uniform electromagnetic field does not hold anymore. Moreover, as an emerging technology, potential applications of high resolution TERS are required to be fully explored. In this thesis, the developed theory for modeling high resolution Raman images is presented. By taking a series of typical molecular systems as examples, we theoretically predict some fine applications of single-molecule TERS.The first part of the thesis introduces the development of Raman spectroscopy and images. To achieve the final target of single molecule characterization, high spatial resolution single-molecule TERS is established and improved. As a nondestructive measuring tool, Raman imaging technology offers the means to study single molecules with unprecedented spatial resolution.The high resolution Raman images theory with detailed derivations is given in the second part of the thesis. The key factor is to take the inhomogeneous spatial distribution of SCP field into account, when we construct the interaction Hamiltonian between the localized light field and the molecule. This makes the numerical simulations of Raman images feasible.Other parts of the thesis give some theoretical predictions for potential applications of the emerging Raman imaging technology. Specifically, resonance Raman images can visualize the geometric changes of a single molecule switch and the intramolecular structure in real space. Since the localized plasmonic field can affect the electron transition, the excited quantum states can thus be effectively manipulated. This breaks down the intrinsic spatial selection rule imposed in conventional spectra. In addition, an effective linear response algorithm is used to simulate nonresonance Raman images. The unique superiority of spatial vibration resolution from non-resonance cases provides rich information about the single molecule. By constructing images from different vibrational modes, the spatial chemical distribution within a single molecule can be visualized. All these findings will facilitate fine applications of the emerging TERS technology in the coming years.
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| 27. |
- Xie, Zhen, et al.
(författare)
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Lighting up long-range charge-transfer states by a localized plasmonic field
- 2017
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Ingår i: Nanoscale. - : Royal Society of Chemistry. - 2040-3364 .- 2040-3372. ; 9:46, s. 18189-18193
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Tidskriftsartikel (refereegranskat)abstract
- The long-range charge-transfer states in a donor-acceptor system exhibit well separated electron-hole pairs, but are often difficult to achieve by optical means owing to a very small overlap between the wave functions of the donor and acceptor. We have found that the introduction of a spatially confined plasmon can enhance the transition probability to the long-range charge-transfer states as it can effectively break the intrinsic symmetry selection rule imposed on the system. Meanwhile, the intensity borrowed from local excitations could also be selectively promoted, allowing the manipulation of the excited quantum states. In addition, our calculations reveal that the donor and acceptor moieties can be unambiguously visualized in real space by tip-enhanced resonance Raman images. These findings can benefit light-harvesting and also be readily extended to diverse optical processes.
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| 28. |
- Xie, Zhen, et al.
(författare)
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Molecular tumbling on Au(111) surface : a new pathway for reversible isomerization of a single azobenzene molecule
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The switchable trans-cis isomerization of azobenzene (AB) and its derivatives on metallic surfaces has offered rich possibilities to functionalize molecular devices. However, the lack of good understanding on isomerization pathway has severely limited our ability for rational design. One of long debated issues is the cis configuration of parental AB on Au(111) surface, for which the experimentally inferred structure differs from the theoretically predicted global minimum. Here, we theoretically predict a new in-situ metastable configuration for cis-AB on Au(111) that can reproduce the observations reported in the scanning tunneling microscopy experiments. The calculated potential energy surface indicates that the stability of the newly discovered cis-AB isomer is kinetically much superior than that of the cis global minimum, which well explains the bistability of AB on Au(111) surface. Accordingly, we reveal a fascinating tumbling pathway that overcomes two energy barriers stimulated by tunneling electrons for the trans-cis AB isomerization on Au(111), suggesting a new type of molecular motor based on the AB systems.
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| 29. |
- Xie, Zhen, et al.
(författare)
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Monitoring Hydrogen/Deuterium Tautomerization in Transient Isomers of Single Porphine by Highly Localized Plasmonic Field
- 2019
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Ingår i: The Journal of Physical Chemistry C. - : AMER CHEMICAL SOC. - 1932-7447 .- 1932-7455. ; 123:17, s. 11081-11093
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Tidskriftsartikel (refereegranskat)abstract
- Inner proton transfer between two trans isomers (tautomerization) in porphyrins plays a crucial role in many biological systems as well as molecular nanotechnology. Although the stepwise mechanism of tautomerization is well accepted, the involved intermediate cis-isomer has not been directly detected owing to its short lifetime and the extremely low intensities of corresponding hydrogen vibrations. Here, taking a single porphine as the prototype, we theoretically demonstrate that Raman intensities of the hydrogen vibrations become accessible under the highly localized plasmonic field because of the symmetry breaking effect. In addition, with the ultrafast incident excitations, we find that Raman signals of cis-porphine could be distinguished from the stable trans isomer, suggesting a general protocol for the direct characterization of transient isomers. Moreover, calculated results reveal that the position of inner hydrogen/deuterium can be unambiguously visualized from Raman images of the corresponding stretching modes, providing a unique optical means for the chemical monitoring of tautomerization in porphine and its derivatives.
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| 30. |
- Xie, Zhen, et al.
(författare)
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Theoretical modeling of tip-enhanced resonance Raman images of switchable azobenzene molecules on Au(111)
- 2018
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Ingår i: Nanoscale. - : ROYAL SOC CHEMISTRY. - 2040-3364 .- 2040-3372. ; 10:25, s. 11850-11860
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Tidskriftsartikel (refereegranskat)abstract
- With a highly localized plasmonic field, tip-enhanced Raman spectroscopy (TERS) images have reached atomic-scale resolution, providing an optical means to explore the structure of a single molecule. We have applied the recently developed theoretical method to simulate the TERS images of trans and cis azobenzene as well as its derivatives on Au(111). Our theoretical results reveal that when the first excited state is resonantly excited, TERS images from a highly confined plasmonic field can effectively distinguish the isomer configurations of the adsorbates. The decay of the plasmonic field along the surface normal can be further used to distinguish different nonplanar cis configurations. Moreover, subtle characteristics of different molecular configurations can also be identified from the TERS images of other resonant excited states with a super-high confined plasmonic field. These findings serve as good references for future TERS experiments on molecular isomers.
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| 31. |
- Yang, Xun, et al.
(författare)
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Diamond Based Optical Metasurfaces for Broadband Wavefront Shaping in Harsh Environment
- 2024
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Ingår i: Laser and Photonics Reviews. - 1863-8899 .- 1863-8880. ; In Press
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Tidskriftsartikel (refereegranskat)abstract
- Metasurface enables a new class of “meta-optics” that can manipulate light at subwavelength scale. Despite that versatile metasurfaces have been demonstrated based on a wide range of materials, the vulnerability of conventional materials to harsh environments, i.e., low resistance to corrosion, low transparency at short wavelength, and lack of thermal/mechanical stability, greatly limit their applications in extreme conditions. Diamond is well-known for exceptional properties, including the highest thermal conductivity, high damage resistance, extraordinary hardness, and chemical inertness. Therefore, diamond based metasurface is generally expected to benefit from its material merits for extreme use. However, the performance of diamond metasurface in harsh environments remains unexplored up to date. To address this question, this work is designed to study the suitability of single-crystal diamond based metasurface for broadband applications under harsh environments. As an example, diamond metasurfaces with representative functionalities, including holographic wavefront-shaping, DUV-focusing, are investigated under high-temperature, acid/alkali, and abrasive conditions, respectively. The findings prove the capability of diamond metasurfaces for applications in broadband and harsh conditions, which not only provides a practical and scalable scheme to encode on-demand functionalities into diamond, but also unlocks a capable candidate to develop robust, large bandwidth, and durable meta-optics for advanced wavefront shaping under extreme conditions.
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| 32. |
- Yang, Zhen, et al.
(författare)
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Synthesis and coordination of a dipyrrin appended N-confused porphyrin
- 2023
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Ingår i: Journal of Porphyrins and Phthalocyanines. - : World Scientific. - 1088-4246 .- 1099-1409. ; 27:1, s. 285-292
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Tidskriftsartikel (refereegranskat)abstract
- A hexapyrrane P6 with a terminal N-confused pyrrole was synthesized by acid-catalyzed [3+3] condensation followed by oxidation with DDQ, which did not afford the expected N-confused hexaphyrin. In stead, a rearranged product, i.e., α-dipyrrin appended N-confused porphyrin 1 was obtained in a yield of 46%. Chelation of 1 with Pt(II) afforded the peripheral complex 1-Pt, which was further coordinated with Rh(I) in the cavity to afford the corresponding bimetallic complex 1-Pt-Rh. Both 1-Pt and 1-Pt-Rh exhibit split Soret-like bands and noticeable Q-like bands tailing to the NIR region up to ca. 1200 nm. Single crystal X-ray diffraction analyses of 1 and 1-Pt revealed that the peripheral coordination of Pt(II) slightly modifies the interplanar angle between the porphyrin macrocycle and the dipyrrin unit, which may modulate the absorption spectra. The results of this work compose an interesting example of synthesizing porphyrinoids appended with conjugated peripheral chains by the oxidative ring closure reaction of an oligopyrrane containing a terminal N-confused pyrrole, and such compounds may be used for both inner and peripheral coordination to afford complexes with tunable NIR absorption.
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| 33. |
- Yu, Wenjin, et al.
(författare)
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Deep Learning-Based Classification of Cancer Cell in Leptomeningeal Metastasis on Cytomorphologic Features of Cerebrospinal Fluid
- 2022
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Ingår i: Frontiers in Oncology. - : Frontiers Media SA. - 2234-943X. ; 12, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- Background: It is a critical challenge to diagnose leptomeningeal metastasis (LM), given its technical difficulty and the lack of typical symptoms. The existing gold standard of diagnosing LM is to use positive cerebrospinal fluid (CSF) cytology, which consumes significantly more time to classify cells under a microscope.Objective: This study aims to establish a deep learning model to classify cancer cells in CSF, thus facilitating doctors to achieve an accurate and fast diagnosis of LM in an early stage.Method: The cerebrospinal fluid laboratory of Xijing Hospital provides 53,255 cells from 90 LM patients in the research. We used two deep convolutional neural networks (CNN) models to classify cells in the CSF. A five-way cell classification model (CNN1) consists of lymphocytes, monocytes, neutrophils, erythrocytes, and cancer cells. A four-way cancer cell classification model (CNN2) consists of lung cancer cells, gastric cancer cells, breast cancer cells, and pancreatic cancer cells. Here, the CNN models were constructed by Resnet-inception-V2. We evaluated the performance of the proposed models on two external datasets and compared them with the results from 42 doctors of various levels of experience in the human-machine tests. Furthermore, we develop a computer-aided diagnosis (CAD) software to generate cytology diagnosis reports in the research rapidly.Results: With respect to the validation set, the mean average precision (mAP) of CNN1 is over 95% and that of CNN2 is close to 80%. Hence, the proposed deep learning model effectively classifies cells in CSF to facilitate the screening of cancer cells. In the human-machine tests, the accuracy of CNN1 is similar to the results from experts, with higher accuracy than doctors in other levels. Moreover, the overall accuracy of CNN2 is 10% higher than that of experts, with a time consumption of only one-third of that consumed by an expert. Using the CAD software saves 90% working time of cytologists.Conclusion: A deep learning method has been developed to assist the LM diagnosis with high accuracy and low time consumption effectively. Thanks to labeled data and step-by-step training, our proposed method can successfully classify cancer cells in the CSF to assist LM diagnosis early. In addition, this unique research can predict cancer’s primary source of LM, which relies on cytomorphologic features without immunohistochemistry. Our results show that deep learning can be widely used in medical images to classify cerebrospinal fluid cells. For complex cancer classification tasks, the accuracy of the proposed method is significantly higher than that of specialist doctors, and its performance is better than that of junior doctors and interns. The application of CNNs and CAD software may ultimately aid in expediting the diagnosis and overcoming the shortage of experienced cytologists, thereby facilitating earlier treatment and improving the prognosis of LM.
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| 34. |
- Zhu, Liping, et al.
(författare)
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A similar to 30,000-year record of environmental changes inferred from Lake Chen Co, Southern Tibet
- 2009
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Ingår i: Journal of Paleolimnology. - : Springer Science and Business Media LLC. - 0921-2728 .- 1573-0417. ; 42:3, s. 343-358
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Tidskriftsartikel (refereegranskat)abstract
- Climatic and environmental changes since the last glacial period are important to our understanding of global environmental change. There are few records from Southern Tibet, one of the most climatically sensitive areas on earth. Here we present a study of the lake sediments (TC1 core) from Lake Chen Co, Southern Tibet. Two sediment cores were drilled using a hydraulic borer in Terrace 1 of Lake Chen Co. AMS C-14 dating of the sediments showed that the sequence spanned > 30,000 years. Analyses of present lake hydrology indicated that glacier melt water is very important to maintaining the lake level. Sediment variables such as grain size, TOC, TN, C/N, Fe/Mn, CaCO3, and pollen were analyzed. Warm and moderately humid conditions dominated during the interval 30,000-26,500 cal year BP. From 26,500 to 20,000 cal year BP, chemical variables and pollen assemblages indicate a cold/dry environment, and pollen amounts and assemblages suggest a decline in vegetation. From 20,000 to 18,000 cal year BP, the environment shifted from cold/dry to warm/humid and vegetation rebounded. The environment transitioned to cold/humid during 16,500-10,500 cal year BP, with a cold/dry event around 14,500 cal year BP. After 10,500 cal year BP, the environment in this region tended to be warm/dry, but exhibited three stages. From 10,500 to 9,000 cal year BP, there was a short warm/humid period, but a shift to cold/dry conditions occurred around 9,000 cal year BP. Thereafter, from 9,000 to 6,000 cal year BP, there was a change from cold/dry to warm/humid conditions, with the warmest period around 6,000 cal year BP. After 6,000 cal year BP, the environment cooled rapidly, but then displayed a warming trend. Chemical variables indicate that a relatively warm/dry event occurred around 5,500-5,000 cal year BP, which is supported by time-lagged pollen assemblages around 4,800 cal year BP. Our lake sediment sequence exhibits environmental changes since 30,000 cal year BP, and most features agree with records from the Greenland GISP2 ice core and with other sequences from the Tibetan Plateau. This indicates that environmental changes inferred from Lake Chen Co, Southern Tibet were globally significant.
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| 35. |
- Zou, Jiazhi, et al.
(författare)
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Porphyrins containing a tetraphenylethylene-substituted phenothiazine donor for fabricating efficient dye sensitized solar cells with high photovoltages
- 2022
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Ingår i: Journal of Materials Chemistry A. - : ROYAL SOC CHEMISTRY. - 2050-7488 .- 2050-7496. ; 10:3, s. 1320-1328
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Tidskriftsartikel (refereegranskat)abstract
- With the aim to enhance the photovoltages and efficiencies of dye sensitized solar cells (DSSCs) based on porphyrin dyes, a dialkoxy-substituted highly twisted tetraphenylethylene (TPE) moiety has been introduced into the donor unit of a porphyrin dye to suppress dye aggregation and charge recombination. Thus, based on our previously reported porphyrin dye XW43, a dialkoxy-TPE moiety has been introduced into the phenothiazine donor to afford XW71. Compared with the diethyleneglycol substituent in XW43, the bulkier dialkoxy-TPE unit in XW71 is more beneficial for suppressing charge recombination. The alkoxy chains on the TPE moieties in XW71 are extended outward from the molecule and folded toward the porphyrin macrocycle, respectively, favorable for suppressing dye aggregation and charge recombination. As a result, the V-OC was dramatically improved from 0.750 V (XW43) to 0.765 V (XW71). On this basis, the substituents surrounding the porphyrin macrocycle have been optimized to further improve the V-OC and the efficiencies. Thus, XW72 and XW73 have been synthesized by replacing the dodecyloxy moieties on the meso-phenyl substituents of XW71 with two diethyleneglycol (DEG) chains and double straps, respectively. As a result, XW72 and XW73 exhibit a gradually improved V-OC of 0.772 V and 0.777 V, respectively, and a high power conversion efficiency (PCE) of 11.0% has been achieved for XW73. Upon coadsorption and cosensitization, the efficiency can be further enhanced to an outstanding value of 12.3% for the XW73 + CDCA + XC3 system.
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| 36. |
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- 2019
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Tidskriftsartikel (refereegranskat)
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