| 1. |
- Beal, Jacob, et al.
(author)
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Robust estimation of bacterial cell count from optical density
- 2020
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In: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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Journal article (peer-reviewed)abstract
- Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.
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| 2. |
- Chong, Hui, et al.
(author)
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Organo-ptii complexes for potent photodynamic inactivation of multi-drug resistant bacteria and the influence of configuration
- 2024
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In: Advanced Science. - : John Wiley & Sons. - 2198-3844. ; 11:14
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Journal article (peer-reviewed)abstract
- PtII based organometallic photosensitizers (PSs) have emerged as novel potent photodynamic inactivation (PDI) reagents through their enhanced intersystem crossing (ISC) processes. Currently, few PtII PSs have been investigated as antibacterial materials, with relatively poor performances reported and with structure-activity relationships not well described. Herein, a pair of configurational isomers are reported of Bis-BODIPY (4,4-difluoro-boradizaindacene) embedded PtII PSs. The cis-isomer (cis-BBP) displayed enhanced 1O2 generation and better bacterial membrane anchoring capability as compared to the trans-isomer (trans-BBP). The effective PDI concentrations (efficiency > 99.9%) for cis-BBP in Acinetobacter baumannii (multi-drug resistant (MDR)) and Staphylococcus aureus are 400 nM (12 J cm−2) and 100 nM (18 J cm−2), respectively; corresponding concentrations and light doses for trans-BBP in the two bacteria are 2.50 µM (30 J cm−2) and 1.50 µM (18 J cm−2), respectively. The 50% and 90% minimum inhibitory concentration (MIC50 and MIC90) ratio of trans-BBP to cis-BBP is 22.22 and 24.02 in A. baumannii (MDR); 21.29 and 22.36 in methicillin resistant S. aureus (MRSA), respectively. Furthermore, cis-BBP displays superior in vivo antibacterial performance, with acceptable dark and photoinduced cytotoxicity. These results demonstrate cis-BBP is a robust light-assisted antibacterial reagent at sub-micromolecular concentrations. More importantly, configuration of PtII PSs should be an important issue to be considered in further PDI reagents design.
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| 3. |
- Azimi Mousolou, Vahid, et al.
(author)
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Hierarchy of magnon mode entanglement in antiferromagnets
- 2020
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In: Physical Review B Condensed Matter. - : American Physical Society. - 0163-1829 .- 1095-3795. ; 102:22
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Journal article (peer-reviewed)abstract
- Continuous variable entanglement between magnon modes in Heisenberg antiferromagnets with Dzyaloshinskii-Moriya (DM) interaction is examined. Different bosonic modes are identified, which allows us to establish a hierarchy of magnon entanglement. We argue that entanglement between magnon modes is determined by a simple lattice-specific parameter, together with the ratio of the strengths of the DM and Heisenberg exchange interactions, and that magnon entanglement can be detected by means of quantum homodyne techniques. As an illustration of the relevance of our findings for possible entanglement experiments in the solid state, a typical antiferromagnet with the perovskite crystal structure is considered, and it is shown that long wave length magnon modes have a maximal degree of entanglement.
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| 4. |
- Azimi Mousolou, Vahid, et al.
(author)
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Magnon-magnon entanglement and its quantification via a microwave cavity
- 2021
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In: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 104:22
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Journal article (peer-reviewed)abstract
- Quantum magnonics is an emerging research field, with great potential for applications in magnon based hybrid systems and quantum information processing. Quantum correlation, such as entanglement, is a central resource in many quantum information protocols that naturally comes about in any study toward quantum technologies. This applies also to quantum magnonics. Here, we investigate antiferromagnetic coupling of two ferromagnetic sublattices that can have two different magnon modes. We show how this may lead to experimentally measurable bipartite continuous-variable magnon-magnon entanglement. The entanglement can be fully characterized via a single squeezing parameter or, equivalently, entanglement parameter. The clear relation between the entanglement parameter and the Einstein, Podolsky, and Rosen (EPR) function of the ground state opens up for experimental quantification magnon-magnon continuous-variable entanglement and EPR nonlocality. We propose a practical experimental realization to measure the EPR function of the ground state, in a setting that relies on magnon-photon interaction in a microwave cavity.
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| 5. |
- Chen, Hao, 1988, et al.
(author)
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A Permanent Magnet Brushless Doubly-Fed Electric Machine for Variable-Speed Constant-Frequency Wind Turbines
- 2023
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In: IEEE Transactions on Industrial Electronics. - 0278-0046 .- 1557-9948. ; 70:7, s. 6663-6674
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Journal article (peer-reviewed)abstract
- A permanent magnet brushless doubly-fed electric machine is presented in this paper. This machine is developed for variable-speed constant-frequency wind energy generation applications. Differing from conventional doubly-fed electric machines based on induction machines, a permanent magnet rotor provides the magnetic field excitations for both the control winding and the power winding in the presented machine. The operating principle of the presented machine for the variable-speed constant-frequency operation is revealed in detail. Compared to a counterpart machine, the presented machine exhibits significantly improved back- electromotive force, torque/power density, torque per magnet volume, efficiency, etc. Finally, a proof-of-concept prototype of the presented machine is fabricated, and the corresponding experimental results are provided to verify the fact that the presented machine is capable of achieving the variable-speed constant-frequency function.
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| 6. |
- Chen, Hao, 1988, et al.
(author)
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Design and Analysis of a Variable-Speed Constant-Amplitude Wind Generator for Stand-Alone DC Power Applications
- 2023
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In: IEEE Transactions on Industrial Electronics. - 0278-0046 .- 1557-9948. ; 70:8, s. 7731-7742
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Journal article (peer-reviewed)abstract
- This article presents the design and analysis of a permanent magnet (PM) wind generator, which consists of two sets of windings, and two rotors. The proposed PM wind generator is designed for variable-speed constant-amplitude voltage operation in dc power applications, in order to maximize the utilization of wind energy and make the electricity more accessible to stand-alone situations, e.g., remote areas and offshore islands. The operating principle of the variable-speed constant-amplitude voltage operation of the proposed PM wind generator is demonstrated in detail. A comparative study is carried out among the proposed generator, a conventional surface-mounted PM synchronous generator, and an existing counterpart generator used for the same application. The results show that compared to the conventional PM synchronous generator and the existing counterpart, the proposed PM wind generator exhibits the advantages of high induced voltage, high torque/power density, high efficiency, etc. Finally, the proposed PM wind generator is prototyped and manufactured. The validity of the variable-speed constant-amplitude operation of the proposed generator under both steady-state and dynamic conditions, is verified by experimental results.
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| 7. |
- Liu, Yuefei
(author)
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Dynamics of quantum entanglement and Bell nonlocality in magnetic systems
- 2024
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Doctoral thesis (other academic/artistic)abstract
- In this PhD thesis, the author first delves into the realm of quantum magnonics, focusing on the dynamics and properties of magnon modes and hybrid quantum models. The thesis introduce a comprehensive approach to studying both ferromagnetic and antiferromagnetic magnon systems using quantum mechanics tools, such as the second quantization of the spin Hamiltonian (Holstein-Primakoff transformation) and Bogoliubov transformation. This approach allows for the precise characterization of different coupling interactions, reflecting the symmetric properties of material lattice. Specifically, the author examines how these interactions enable the preparation of targeted isolated magnon (or boson) models, facilitating the control of vacuum and excited states. The thesis present a detailed analysis of the entanglement entropy of magnon modes in antiferromagnetic (AFM) materials , highlighting the role of exchange and Dzyaloshinskii-Moriya (DM) coupling terms. Moreover, the thesis propose a novel cavity magnonic setup that leverages the cavity photon degree of freedom for experimentally measuring entanglement in AFM magnon modes. Additionally, the thesis address the open system dynamics of magnon-magnon-phonon model in AFM lattice using the quantum Langevin equations. With the steady-state solution of quantum Langevin equations, one assess how external magnetic fields and temperature-dependent noise influence magnon-magnon entanglement in AFM lattice, leading to high-temperature entanglement in antiferromagnets under certain conditions.Transitioning interest from magnons to magnetic spin systems, part of the thesis analyze the spin dynamics described by the Landau-Lifshitz equations under the quantum framework, that is explore the implications of the Landau-Lifshitz equations for quantum dynamics. The author and his colleagues propose a quantum analog of the Landau-Lifshitz-Gilbert equation as an effective equation for qubit dynamics, which has no intrinsic information loss (preserves the purity of quantum states) and is faster than classical Landau-Lifshitz-Gilbert spin dynamics. It offers a promising direction for further theoretical, computational and experimental investigation. The dynamics of quantum correlation in dimer systems are studied, providing insights into the behavior of both pure and mixed states.This thesis not only advances our understanding of quantum entanglement and non-locality in quantum magnonics and spin dynamics but also sets the stage for future investigations into the quantum mechanical properties of novel materials and their applications in quantum information science. The methodologies and findings discussed here pave the way for developing more sophisticated quantum technologies and contribute to the broader field of quantum materials research.
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| 8. |
- Liu, Yuefei, et al.
(author)
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Quantum analog of Landau-Lifshitz-Gilbert dynamics
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Other publication (other academic/artistic)abstract
- The Landau-Lifshitz-Gilbert (LLG) and Landau-Lifshitz (LL) equations play an essential role for describing the dynamics of magnetization in solids. While a quantum analog of the LL dynamics has been proposed in [Phys. Rev. Lett. 110, 147201 (2013)], the corresponding quantum version of LLG remains unknown. Here, we propose such a quantum LLG equation that inherently conserves purity of the quantum state. We examine the quantum LLG dynamics of a dimer consisting of two interacting spin-1/2 particles. Our analysis reveals that, in the case of ferromagnetic coupling, the evolution of initially uncorrelated spins mirrors the classical LLG dynamics. However, in the antiferromagnetic scenario, we observe pronounced deviations from classical behavior, underscoring the unique dynamics of becoming a spinless state, which is non-locally correlated. Moreover, when considering spins that are initially correlated, our study uncovers an unusual form of transient quantum correlation dynamics, which differ significantly from what is typically seen in open quantum systems.
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| 9. |
- Liu, Yuefei, et al.
(author)
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Tunable phonon-driven magnon-magnon entanglement at room temperature
- 2023
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In: New Journal of Physics. - : IOP Publishing Ltd. - 1367-2630. ; 25:11
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Journal article (peer-reviewed)abstract
- We report the existence of entangled steady-states in bipartite quantum magnonic systems at elevated temperatures. We consider dissipative dynamics of two magnon modes in a bipartite antiferromagnet, subjected to interaction with a phonon mode and an external rotating magnetic field. To quantify the bipartite magnon-magnon entanglement, we use entanglement negativity and compute its dependence on temperature and magnetic field. We provide evidence that the coupling between magnon and phonon modes is necessary for the entanglement, and that, for any given phonon frequency and magnon-phonon coupling rate, there are always ranges of the magnetic field amplitudes and frequencies for which magnon-magnon entanglement persists at room temperature.
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