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Single bacteria identification with second-harmonic generation in MoS2by Young Chul Kim, Seung Won Jun, Yeong Hwan AhnBiosensors and Bioelectronics 2023, 241, 115675; https://doi.org/10.1016/j.bios.2023.115675AbstractTransition-metal dichalcogenides exhibit extraordinary optical nonlinearities, making them promising candidates for advanced photonic applications. Here, we present the microbial control over second-harmonic generation (SHG) in monolayer MoS2 and the identification of single-cell bacteria. Bacteria deposited on monolayer MoS2 induce a change in the SHG signal, in the form of anisotropic polarization responses that depend on the relative orientation of the bacteria with respect to the MoS2 crystallographic direction. The anisotropic enhancement is consistent with the presence of a tensile stress along the lateral direction of bacteria axis; SHG imaging is highly effective in monitoring biomaterial strain as low as 0.1%. We also investigate the ultraviolet-induced removal of single bacteria, through the SHG imaging of MoS2. By monitoring the transient SHG signals, we determine the rupture times for bacteria, which varies noticeably for each species. This allows us to distinguish specific bacteria that share habitats; SHG imaging is useful for label free identification of pathogens at the single cell levels such as E. coli and L. casei. This label-free detection and identification of pathogens at the single-cell level can have a profound impact on the development of diagnostic tools for various applications.Keywords: Second harmonic generation; Transition metal dichalcogenides; Bacteria; Label-free sensing; Microbial strain
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Interpretable classification for multivariate gait analysis of cerebral palsyby Changwon Yoon, Yongho Jeon, Hosik Choi, Soon-Sun Kwon & Jeongyoun AhnBioMedical Engineering OnLine 2023, 22, 109; https://doi.org/10.1186/s12938-023-01168-xAbstractBackgroundThe Gross Motor Function Classification System (GMFCS) is a widely used tool for assessing the mobility of people with Cerebral Palsy (CP). It classifies patients into different levels based on their gross motor function and its level is typically determined through visual evaluation by a trained expert. Although gait analysis is commonly used in CP research, the functional aspects of gait patterns has yet to be fully exploited. By utilizing the gait patterns to predict GMFCS, we can gain a more comprehensive understanding of how CP affects mobility and develop more effective interventions for CP patients.ResultIn this study, we propose a multivariate functional classification method to examine the relationship between kinematic gait measures and GMFCS levels in both normal individuals and CP patients with varying GMFCS levels. A sparse linear functional discrimination framework is utilized to achieve an interpretable prediction model. The method is generalized to handle multivariate functional data and multi-class classification. Our method offers competitive or improved prediction accuracy compared to state-of-the-art functional classification approaches and provides interpretable discriminant functions that can characterize the kinesiological progression of gait corresponding to higher GMFCS levels.ConclusionWe generalize the sparse functional linear discrimination framework to achieve interpretable classification of GMFCS levels using kinematic gait measures. The findings of this research will aid clinicians in diagnosing CP and assigning appropriate GMFCS levels in a more consistent, systematic, and scientifically supported manner.Keywords: Cerebral palsy; Functional sparse classification; GMFCS; Multivariate functional data; Sparse functional linear discriminant analysis
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Structural basis of aggregate binding by the AAA+ disaggregase ClpGby Panagiotis Katikaridis, Bernd Simon, Timo Jenne, Seongjoon Moon, Changhan Lee, Janosch Hennig, Axel MogkJournal of Biological Chemistry 2023, 299(11), 105336; https://doi.org/10.1016/j.jbc.2023.105336AbstractWe demonstrate the generation and control of polaritonic states in perovskite phonon polaritons, which are strongly coupled in the middle of a flexible Fabry–Perot cavity. We fabricated flexible perovskite films on a microporous substrate coated with graphene oxide, which led to a virtually free-standing film incorporated into the microcavity. Rabi splitting was observed when the cavity resonance was in tune with that of the phonons. The Rabi splitting energy increased as the film thickness increased, reaching 1.9 meV, which is 2.4-fold higher than the criterion for the strong coupling regime. We obtained dispersion curves for various perovskite film thicknesses exhibiting two polariton branches; clear beats between the two polaritonic branches were observed in the time domain. Flexible cavity devices with perovskite phonons enable macroscopic control over the polaritonic energy states through bending processes, which add an additional degree of freedom in the manipulation of polaritonic devices.Keywords: ATPase associated with diverse cellular activities (AAA); protein aggregation; molecular chaperone; stress; 70 kDa heat shock protein (Hsp70)
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Mechanical Control of Polaritonic States in Lead Halide Perovskite Phonons Strongly Coupled in THz Microcavityby H. S. Kim, A. A. Khan, J.-Y. Park, S. Lee, and Y. H. AhnThe Journal of Physical Chemistry Letters 2023, 14, 46, 10318–10327; https://doi.org/10.1021/acs.jpclett.3c02717AbstractWe demonstrate the generation and control of polaritonic states in perovskite phonon polaritons, which are strongly coupled in the middle of a flexible Fabry–Perot cavity. We fabricated flexible perovskite films on a microporous substrate coated with graphene oxide, which led to a virtually free-standing film incorporated into the microcavity. Rabi splitting was observed when the cavity resonance was in tune with that of the phonons. The Rabi splitting energy increased as the film thickness increased, reaching 1.9 meV, which is 2.4-fold higher than the criterion for the strong coupling regime. We obtained dispersion curves for various perovskite film thicknesses exhibiting two polariton branches; clear beats between the two polaritonic branches were observed in the time domain. Flexible cavity devices with perovskite phonons enable macroscopic control over the polaritonic energy states through bending processes, which add an additional degree of freedom in the manipulation of polaritonic devices.Keywords: Nucleic acids; DNA; RNA; Chaperone; Anti-aggregation activity
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Transport and localization properties of excitations in one-dimensional lattices with diagonal disordered mosaic modulationsby Ba Phi Nguyen and Kihong KimJournal of Physics A: Mathematical and Theoretical 2023, 56(47), 475701; https://doi.org/10.1088/1751-8121/ad03cdAbstractWe present a numerical study of the transport and localization properties of excitations in one-dimensional lattices with diagonal disordered mosaic modulations. The model is characterized by the modulation period κ and the disorder strength W. We calculate the disorder averages 〈𝑇〉, 〈ln𝑇〉, and 〈𝑃〉, where T is the transmittance and P is the participation ratio, as a function of energy E and system size L, for different values of κ and W. For excitations at quasiresonance energies determined by κ, we find power-law scaling behaviors of the form 〈𝑇〉∝𝐿−𝛾𝑎, 〈ln𝑇〉≈−𝛾𝑔ln𝐿, and 〈𝑃〉∝𝐿𝛽, as L increases to a large value. In the strong disorder limit, the exponents are seen to saturate at the values 𝛾𝑎∼0.5, 𝛾𝑔∼1, and 𝛽∼0.3, regardless of the quasiresonance energy value. This behavior is in contrast to the exponential localization behavior occurring at all other energies. The appearance of sharp peaks in the participation ratio spectrum at quasiresonance energies provides additional evidence for the existence of an anomalous power-law localization phenomenon. The corresponding eigenstates demonstrate multifractal behavior and exhibit unique node structures. In addition, we investigate the time-dependent wave packet dynamics and calculate the mean square displacement 〈𝑚2(𝑡)〉, spatial probability distribution, participation number, and return probability. When the wave packet's initial momentum satisfies the quasiresonance condition, we observe a subdiffusive spreading of the wave packet, characterized by 〈𝑚2(𝑡)〉∝𝑡𝜂 where η is always less than 1. We also note the occurrence of partial localization at quasiresonance energies, as indicated by the saturation of the participation number and a nonzero value for the return probability at long times.
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Converting the Bulk Transition Metal Dichalcogenides Crystal into Stacked Monolayers via Ethylenediamine Intercalationby Yeojin Ahn, Gyubin Lee, Namgyu Noh, Chulwan Lee, Duc Duy Le, Sunghun Kim, Yeonghoon Lee, Jounghoon Hyun, Chan-young Lim, Jaehun Cha, Mingi Jho, Seonggeon Gim, Jonathan D. Denlinger, Chan-Ho Yang, Jong Min Yuk, Myung Joon Han, and Yeongkwan KimNano Letters 2023, 23, 21, 9733–9739; https://doi.org/10.1021/acs.nanolett.3c02268AbstractWe report the synthesis of ethylenediamine-intercalated NbSe2 and Li-ethylenediamine-intercalated MoSe2 single crystals with increased interlayer distances and their electronic structures measured by means of angle-resolved photoemission spectroscopy (ARPES). X-ray diffraction patterns and transmission electron microscopy images confirm the successful intercalation and an increase in the interlayer distance. ARPES measurement reveals that intercalated NbSe2 shows an electronic structure almost identical to that of monolayer NbSe2. Intercalated MoSe2 also returns the characteristic feature of the monolayer electronic structure, a direct band gap, which generates sizable photoluminescence even in the bulk form. Our results demonstrate that the properties and phenomena of the monolayer transition metal dichalcogenides can be achieved with large-scale bulk samples by blocking the interlayer interaction through intercalation.Keywords: transition metal dichalcogenides; MoSe2; NbSe2; intercalation; bulk; monolayer
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Anhydrous Alum Inhibits α-MSH-Induced Melanogenesis by Down-Regulating MITF via Dual Modulation of CREB and ERKby Bong-Rim Shin, Uros Puc, Yu-Jin Park, Dong-Joo Kim, Chae-Won Lee, Woojin Yoon, Hoseop Yun, Chaeyoon Kim, Fabian Rotermund, Mojca Jazbinsek, O-Pil KwonAdvanced Science 2023, 10(34), 2304767; https://doi.org/10.1002/advs.202304767AbstractIn the development of new organic crystals for nonlinear optical and terahertz (THz) applications, it is very challenging to achieve the essentially required non-centrosymmetric molecular arrangement. Moreover, the resulting crystal structure is mostly unpredictable due to highly dipolar molecular components with complex functional substituents. In this work, new organic salt crystals with top-level macroscopic optical nonlinearity by controlling the van der Waals volume (VvdW), rather than by trial and error, are logically designed. When the VvdW of molecular ionic components varies, the corresponding crystal symmetry shows an observable trend: change from centrosymmetric to non-centrosymmetric and back to centrosymmetric. All non-centrosymmetric crystals exhibit an isomorphic P1 crystal structure with an excellent macroscopic second-order nonlinear optical response. Apart from the top-level macroscopic optical nonlinearity, new organic crystals introducing highly electronegative fluorinated substituents with strong secondary bonding ability show excellent performance in efficient and broadband THz wave generation, high crystal density, high thermal stability, and good bulk crystal growth ability.Keywords: crystal structure control; nonlinear optics; organic crystals; terahertz photonics; van der Waals volume
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