3,361 results match your criteria narrow spectral

Narrow-band high-lying excitons with negative-mass electrons in monolayer WSe.

Nat Commun 2021 Sep 17;12(1):5500. Epub 2021 Sep 17.

Department of Physics, University of Regensburg, Regensburg, Germany.

Monolayer transition-metal dichalcogenides (TMDCs) show a wealth of exciton physics. Here, we report the existence of a new excitonic species, the high-lying exciton (HX), in single-layer WSe with an energy of ~3.4 eV, almost twice the band-edge A-exciton energy, with a linewidth as narrow as 5. Read More

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September 2021

Broadly tunable, intracavity injection-seeded, hybrid optical parametric oscillator.

Opt Lett 2021 Sep;46(18):4502-4505

We report a novel, to the best of our knowledge, approach for injection seeding of pulsed optical parametric oscillators (OPOs), which can provide spectral control over the full tuning range. Bandwidth reduction down to single-mode operation is realized across the pulsed tuning range by deploying a hybrid design, where a continuous-wave (cw) OPO injection seeds the pulsed OPO in a single composite cavity. By exploiting two identical MgO-doped periodically poled lithium niobate crystals, the hybrid OPO provides signal pulses with a single-frequency linewidth as narrow as 7. Read More

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September 2021

Non-Hermitian topological phase transitions in superlattices and the optical Dirac equation.

Stefano Longhi

Opt Lett 2021 Sep;46(18):4470-4473

Optical superlattices with sublattice symmetry subjected to a synthetic imaginary gauge field undergo a topological phase transition in the Bloch energy spectrum, characterized by the change of a spectral winding number. For a narrow gap, the phase transition is of universal form and described by a non-Hermitian Dirac equation with Lorentz-symmetry violation. A simple photonic system displaying such a phase transition is discussed, which is based on light coupling in co-propagating gratings. Read More

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September 2021

kW-level monolithic single-mode narrow-linewidth all-solid photonic bandgap fiber amplifier.

Opt Lett 2021 Sep;46(18):4458-4461

Further power scaling of narrow-linewidth fiber lasers is critical for beam combining. Using all-solid photonic bandgap fibers with large effective mode areas and strong higher-order-mode suppression is an interesting approach. Previously, we demonstrated ∼400 single-frequency single-mode power at 1064 nm from a 50/400 photonic bandgap fiber amplifier, limited only by transverse mode instability (TMI). Read More

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September 2021

Prospective evaluation of optical coherence tomography for disease detection in the Casey mobile eye clinic.

Exp Biol Med (Maywood) 2021 Sep 15:15353702211037262. Epub 2021 Sep 15.

Casey Eye Institute, Oregon Health & Science University, OR 97239, USA.

This study was designed to evaluate iVue Spectral-domain optical coherence tomography (SD-OCT) effectiveness in screening for eye disease compared to clinical examination. Subjects were recruited from the Casey Eye Community Outreach Program Mobile Clinic during its routinely scheduled outreach clinics to indigent, underserved populations throughout Oregon. Macular optical coherence tomography interpretation and automated optical coherence tomography analysis were compared to the clinical examination, with specific attention to findings indicative of retinal abnormalities, risks for glaucoma, and narrow angles. Read More

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September 2021

Broadband infrared light source by simultaneous parametric down-conversion.

Sci Rep 2021 Sep 9;11(1):17986. Epub 2021 Sep 9.

Department of Physics, Science, Kyoto University, Kitashirakawa-Oiwake, Sakyo, Kyoto, 606-8224, Japan.

Spontaneous parametric down-conversion is an essential tool for a quantum light source in the infrared region ranging 2-5 µm for the purpose of material identification, chemical analysis, and gas sensing. So far, photon pairs from the process in a nonlinear crystal have low tunability and a narrow spectral range because of the phase-matching condition. Here, we propose a novel type of spontaneous parametric down-conversion processes that overcomes these challenges, where two photon pairs are simultaneously produced in the visible and infrared regions in periodically poled stoichiometric lithium tantalite. Read More

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September 2021

Ultrasensitive detection of endocrine disruptors via superfine plasmonic spectral combs.

Light Sci Appl 2021 Sep 7;10(1):181. Epub 2021 Sep 7.

Institute of Photonics Technology, Jinan University, Guangzhou, 510632, China.

The apparent increase in hormone-induced cancers and disorders of the reproductive tract has led to a growing demand for new technologies capable of detecting endocrine disruptors. However, a long-lasting challenge unaddressed is how to achieve ultrahigh sensitive, continuous, and in situ measurement with a portable device for in-field and remote environmental monitoring. Here we demonstrate a simple-to-implement plasmonic optical fiber biosensing platform to achieve an improved light-matter interaction and advanced surface chemistry for ultrasensitive detection of endocrine disruptors. Read More

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September 2021

Optimal frequency band selection using blind and targeted features for spectral coherence-based bearing diagnostics: A comparative study.

ISA Trans 2021 Aug 24. Epub 2021 Aug 24.

State Key Laboratory of Traction Power, Southwest Jiaotong University, Chengdu 610031, China. Electronic address:

Identifying a spectral frequency band with abundant fault information from spectral coherence is essential for improved envelope spectrum-based bearing diagnosis. Both blind features and targeted features have been employed to distinguish informative spectral frequency band of spectral coherence. However, how to select appropriate feature to correctly discriminate the optimal frequency band of spectral coherence in different scenarios is problematic. Read More

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Exploiting spatio-spectral aberrations for rapid synchrotron infrared imaging.

J Synchrotron Radiat 2021 Sep 9;28(Pt 5):1616-1619. Epub 2021 Aug 9.

Optical Sciences Center, Swinburne University of Technology, John Street, Melbourne, Victoria 3122, Australia.

The Infrared Microspectroscopy Beamline at the Australian Synchrotron is equipped with a Fourier transform infrared (FTIR) spectrometer, which is coupled with an infrared (IR) microscope and a choice of two detectors: a single-point narrow-band mercury cadmium telluride (MCT) detector and a 64 × 64 multi-pixel focal plane array (FPA) imaging detector. A scanning-based point-by-point mapping method is commonly used with a tightly focused synchrotron IR beam at the sample plane, using an MCT detector and a matching 36× IR reflecting objective and condenser (NA = 0.5), which is time consuming. Read More

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September 2021

Understanding the Effects of Optimal Combination of Spectral Bands on Deep Learning Model Predictions: A Case Study Based on Permafrost Tundra Landform Mapping Using High Resolution Multispectral Satellite Imagery.

J Imaging 2020 Sep 17;6(9). Epub 2020 Sep 17.

Department of Natural Resources and the Environment, University of Connecticut, Storrs, CT 06269, USA.

Deep learning (DL) convolutional neural networks (CNNs) have been rapidly adapted in very high spatial resolution (VHSR) satellite image analysis. DLCNN-based computer visions (CV) applications primarily aim for everyday object detection from standard red, green, blue (RGB) imagery, while earth science remote sensing applications focus on geo object detection and classification from multispectral (MS) imagery. MS imagery includes RGB and narrow spectral channels from near- and/or middle-infrared regions of reflectance spectra. Read More

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September 2020

Plate Waves Scattering Analysis and Active Damage Detection.

Tai-Ho Yu

Sensors (Basel) 2021 Aug 13;21(16). Epub 2021 Aug 13.

Department of Electronic Engineering, National United University, 2 Lien Da, Nan-Shih Li, Miaoli 36063, Taiwan.

This study investigates and evaluates the technology of using plate waves to detect the locations and sizes of circular holes and cracks in plates. Piezoelectric ceramic discs surface-mounted on both sides of an aluminum alloy plate were used as narrow-frequency plate wave actuators and sensors, and the antisymmetric plate wave signal was analyzed by wavelet transform in the time-frequency domain. The damage location and frequency spectrum characteristics were identified by the wave through time-of-flight difference and signal analysis of the damage scattered wave group. Read More

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Chronic Sensing of Subthalamic Local Field Potentials: Comparison of First and Second Generation Implantable Bidirectional Systems Within a Single Subject.

Front Neurosci 2021 10;15:725797. Epub 2021 Aug 10.

Department of Neurological Surgery, University of California, San Francisco, San Francisco, CA, United States.

Background: Many adaptative deep brain stimulation (DBS) paradigms rely upon the ability to sense neural signatures of specific clinical signs or symptoms in order to modulate therapeutic stimulation. In first-generation bidirectional neurostimulators, the ability to sense neural signals during active stimulation was often limited by artifact. Newer devices, with improved design specifications for sensing, have recently been developed and are now clinically available. Read More

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Ultranarrow and Tunable Fano Resonance in Ag Nanoshells and a Simple Ag Nanomatryushka.

Nanomaterials (Basel) 2021 Aug 10;11(8). Epub 2021 Aug 10.

National Laboratory of Solid State Microstructures, College of Physics, Nanjing University, Nanjing 210093, China.

We study theoretically the Fano resonances (FRs) produced by the near-field coupling between the lowest-order (dipolar) sphere plasmon resonance and the dipolar cavity plasmon mode supported by an Ag nanoshell or the hybrid mode in a simple three-layered Ag nanomatryushka constructed by incorporating a solid Ag nanosphere into the center of Ag nanoshell. We find that the linewidth of dipolar cavity plasmon resonance or hybrid mode induced FR is as narrow as 6.8 nm (corresponding to a high -factor of ~160 and a long dephasing time of ~200 fs) due to the highly localized feature of the electric-fields. Read More

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Accurate Measurement of Agatston Score Using kVp-Independent Reconstruction Algorithm for Ultra-High-Pitch Sn150 kVp CT.

Korean J Radiol 2021 Aug 19. Epub 2021 Aug 19.

Department of Radiology, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China.

Objective: To investigate the accuracy of the Agatston score obtained with the ultra-high-pitch (UHP) acquisition mode using tin-filter spectral shaping (Sn150 kVp) and a kVp-independent reconstruction algorithm to reduce the radiation dose.

Materials And Methods: This prospective study included 114 patients (mean ± standard deviation, 60.3 ± 9. Read More

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Wide-Range Color Tuning of Narrowband Emission in Multi-resonance Organoboron Delayed Fluorescence Materials through Rational Imine/Amine Functionalization.

Angew Chem Int Ed Engl 2021 Aug 18. Epub 2021 Aug 18.

INAMORI Frontier Research Center (IFRC), Kyushu University, 744 Motooka, Nishi-ku, Fukuoka, 819-0395, Japan.

Establishing a simple and versatile design strategy to finely modulate emission colors while retaining high luminescence efficiency and color purity remains an appealing yet challenging task for the development of multi-resonance-induced thermally activated delayed fluorescence (MR-TADF) materials. Herein, we demonstrate that the strategic introduction of electron-withdrawing imine and electron-donating amine moieties into a versatile boron-embedded 1,3-bis(carbazol-9-yl)benzene skeleton enables systematic hypsochromic and bathochromic shifts of narrowband emissions, respectively. By this method, effective electroluminescence color tuning was accomplished over a wide visible range from deep-blue to yellow (461-571 nm), using the same MR molecular system, without compromising very narrow spectral features. Read More

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Deep Search for Decaying Dark Matter with XMM-Newton Blank-Sky Observations.

Phys Rev Lett 2021 Jul;127(5):051101

Berkeley Center for Theoretical Physics, University of California, Berkeley, California 94720, USA.

Sterile neutrinos with masses in the keV range are well-motivated extensions to the Standard Model that could explain the observed neutrino masses while also making up the dark matter (DM) of the universe. If sterile neutrinos are DM then they may slowly decay into active neutrinos and photons, giving rise to the possibility of their detection through narrow spectral features in astrophysical x-ray data sets. In this Letter, we perform the most sensitive search to date for this and other decaying DM scenarios across the mass range from 5 to 16 keV using archival XMM-Newton data. Read More

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Invisibility Cloak Technology of Anti-Infrared Detection Materials Prepared Using CoGaZnSe Multilayer Nanofilms.

ACS Appl Mater Interfaces 2021 Aug 16;13(33):40145-40154. Epub 2021 Aug 16.

College of Science, Xi'an University of Architecture and Technology, Xi'an 710055, China.

The development of infrared stealth clothing technology and materials has been widely studied. However, the research of near-infrared stealth clothing still faces some challenges including complex preparation processes, narrow spectral ranges, and poor antidetection efficiency. To solve these questions, a CoGaZnSe multilayer film used for anti-near-infrared detection is designed and prepared by pulse laser deposition (PLD) at different pressures from 2 to 12 Pa. Read More

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Multifunctional Thio-Stabilized Gold Nanoparticles for Near-Infrared Fluorescence Detection and Imaging of Activated Caspase-3.

Curr Anal Chem 2021 ;17(8):1182-1193

Departments of Radiology, Washington University School of Medicine, St Louis, United States.

Background: Gold nanoparticles (AuNPs) are commonly used in nanomedicine because of their unique spectral properties, chemical and biological stability, and ability to quench the fluorescence of organic dyes attached to their surfaces. However, the utility of spherical AuNPs for activatable fluorescence sensing of molecular processes have been confined to resonance-matched fluorophores in the 500 nm to 600 nm spectral range to maximize dye fluorescence quenching efficiency. Expanding the repertoire of fluorophore systems into the NIR fluorescence regimen with emission >800 nm will facilitate the analysis of multiple biological events with high detection sensitivity. Read More

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January 2021

Broadband Fourier-transform silicon nitride spectrometer with wide-area multiaperture input.

Opt Lett 2021 Aug;46(16):4021-4024

Integrated microspectrometers implemented in silicon photonic chips have gathered a great interest for diverse applications such as biological analysis, environmental monitoring, and remote sensing. These applications often demand high spectral resolution, broad operational bandwidth, and large optical throughput. Spatial heterodyne Fourier-transform (SHFT) spectrometers have been proposed to overcome the limited optical throughput of dispersive and speckle-based on-chip spectrometers. Read More

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Simultaneous imaging of two-phase velocities in particle-laden flows by two-color optical phase discrimination.

Opt Lett 2021 Aug;46(16):3861-3864

In this Letter, we present a particle image/tracking velocimetry (PIV/PTV) technique for simultaneous velocity measurement of both fluid and particle phases, adopting newly developed optical phase discrimination methods and novel optical particles. Spherical acrylic (PMMA) particles of diameter ∼(100µ) were used as the particle phase, while fine : phosphors of diameter ∼(1µ) were used as the fluid tracer. Under Nd:YAG 355 nm laser excitation, both the laser-induced fluorescence (LIF) from PMMA and laser-induced phosphorescence (LIP) from : provided sufficiently strong signals for PIV imaging with two non-intensified cameras and were clearly separable for phase discrimination using spectral filters and temporal profiles. Read More

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Extreme Orientational Uniformity in Large-Area Floating Films of Semiconducting Polymers for Their Application in Flexible Electronics.

ACS Appl Mater Interfaces 2021 Aug 6;13(32):38534-38543. Epub 2021 Aug 6.

Organic Electronics Laboratory, Division of Materials Science, Nara Institute of Science and Technology, Takayama-cho 8916-5, Ikoma-shi 630-0196 Japan.

Layer-by-layer fabrication of uniformly oriented thin films over large areas by cost-effective solution-based approaches can open new horizons for the realization of high-performance organic circuits in various applications. In this work, fabrication of a large-area ≈40 cm film with uniform orientation is reported for poly(3,3‴-dialkylquaterthiophene) (PQT) using a unidirectional floating film transfer method (UFTM). Orientation characteristics and charge transport anisotropy were analyzed using polarized UV-vis spectral mapping and fabrication of bottom-gated organic field-effect transistors (OFETs) from different regions. Read More

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2D measurements of plasma electron density using coherence imaging with a pixelated phase mask.

Rev Sci Instrum 2021 Jul;92(7):073506

DIFFER - Dutch Institute for Fundamental Energy Research, De Zaale 20, 5612 AJ Eindhoven, The Netherlands.

In this paper, the pixelated phase mask (PPM) method of interferometry is applied to coherence imaging (CI)-a passive, narrowband spectral imaging technique for diagnosing the edge and divertor regions of fusion plasma experiments. Compared to previous CI designs that use a linear phase mask, the PPM method allows for a higher possible spatial resolution. The PPM method is also observed to give a higher instrument contrast (analogous to a more narrow spectrometer instrument function). Read More

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Achieving two-dimensional optical spectroscopy with temporal and spectral resolution using quantum entangled three photons.

J Chem Phys 2021 Jul;155(4):044101

Institute for Molecular Science, National Institutes of Natural Sciences, Okazaki 444-8585, Japan.

Recent advances in techniques for generating quantum light have stimulated research on novel spectroscopic measurements using quantum entangled photons. One such spectroscopy technique utilizes non-classical correlations among entangled photons to enable measurements with enhanced sensitivity and selectivity. Here, we investigate the spectroscopic measurement utilizing entangled three photons. Read More

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Unraveling 5correlated electronic states in paramagnetic PuSn.

Haiyan Lu Li Huang

J Phys Condens Matter 2021 Aug 17;33(43). Epub 2021 Aug 17.

Science and Technology on Surface Physics and Chemistry Laboratory, PO Box 9-35, Jiangyou 621908, People's Republic of China.

Plutonium-based compounds establish an ideal platform for exploring the interplay between long-standing itinerant-localized 5states and strongly correlated electronic states. In this paper, we exhaustively investigate the 5correlated electronic states of PuSndependence on temperature by means of a combination of the density functional theory and the embedded dynamical mean-field theory. It is found that the spectral weight of narrow 5band grows significantly and remarkable quasiparticle multiplets appear around the Fermi level at low temperature. Read More

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Low-threshold 1150  nm single-polarization single-frequency Yb-doped DFB fiber laser.

Opt Lett 2021 Aug;46(15):3705-3708

We demonstrate a stable single-polarization single-frequency distributed feedback Bragg (DFB) fiber laser at 1150 nm based on a 5 cm long Yb-doped fiber which, to the best of our knowledge, is the first demonstration of a Yb-doped fiber-based single-frequency laser with a wavelength longer than 1120 nm. The threshold is as low as 10 mW. The measured maximum output power is 10. Read More

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Lanthanide-Based Nanosensors: Refining Nanoparticle Responsiveness for Single Particle Imaging of Stimuli.

ACS Photonics 2021 Jan 16;8(1):3-17. Epub 2020 Oct 16.

Department of Materials Science and Engineering and Department of Radiology, Molecular Imaging Program, Stanford University, Stanford, California 94305, United States.

Lanthanide nanoparticles (LNPs) are promising sensors of chemical, mechanical, and temperature changes; they combine the narrow-spectral emission and long-lived excited states of individual lanthanide ions with the high spatial resolution and controlled energy transfer of nanocrystalline architectures. Despite considerable progress in optimizing LNP brightness and responsiveness for dynamic sensing, detection of stimuli with a spatial resolution approaching that of individual nanoparticles remains an outstanding challenge. Here, we highlight the existing capabilities and outstanding challenges of LNP sensors, en-route to nanometer-scale, single particle sensor resolution. Read More

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January 2021

Retrieving Sun-Induced Chlorophyll Fluorescence from Hyperspectral Data with TanSat Satellite.

Sensors (Basel) 2021 Jul 18;21(14). Epub 2021 Jul 18.

Key Laboratory of Agricultural Remote Sensing, Ministry of Agriculture and Rural Affairs, Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081, China.

A series of algorithms for satellite retrievals of sun-induced chlorophyll fluorescence (SIF) have been developed and applied to different sensors. However, research on SIF retrieval using hyperspectral data is performed in narrow spectral windows, assuming that SIF remains constant. In this paper, based on the singular vector decomposition (SVD) technique, we present an approach for retrieving SIF, which can be applied to remotely sensed data with ultra-high spectral resolution and in a broad spectral window without assuming that the SIF remains constant. Read More

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Phononic Thermal Transport along Graphene Grain Boundaries: A Hidden Vulnerability.

Adv Sci (Weinh) 2021 Sep 21;8(18):e2101624. Epub 2021 Jul 21.

Shenzhen JL Computational Science and Applied Research Institute, Shenzhen, 518131, China.

While graphene grain boundaries (GBs) are well characterized experimentally, their influence on transport properties is less understood. As revealed here, phononic thermal transport is vulnerable to GBs even when they are ultra-narrow and aligned along the temperature gradient direction. Non-equilibrium molecular dynamics simulations uncover large reductions in the phononic thermal conductivity (κ ) along linear GBs comprising periodically repeating pentagon-heptagon dislocations. Read More

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September 2021

retinopathy: biomarkers assessing vision loss.

Ophthalmic Genet 2021 Jul 22:1-11. Epub 2021 Jul 22.

Save Sight Institute, Faculty of Medicine and Health, The University of Sydney, Sydney, NSW, Australia.

Purpose: Mer tyrosine kinase-retinitis pigmentosa (RP) causes a primary defect in the retinal pigment epithelium, which subsequently affects rod and cone photoreceptors. The study aims to identify the most appropriate -RP biomarkers to measure disease progression for deciding the optimum therapeutic trial intervention time.

Materials And Methods: Patients' data from baseline (BL) and last follow-up (LFU) were reviewed. Read More

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Approaching Efficient and Narrow RGB Electroluminescence from D-A-Type TADF Emitters Containing an Identical Multiple Resonance Backbone as the Acceptor.

ACS Appl Mater Interfaces 2021 Aug 21;13(30):36089-36097. Epub 2021 Jul 21.

Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Joint International Research Laboratory of Carbon-Based Functional Materials and Devices, Soochow University, Suzhou, Jiangsu 215123, P. R. China.

Highly twisted electron donor (D)-electron acceptor (A)-type thermally activated delayed fluorescence (TADF) emitters can achieve high efficiency while suffering from serious structural relaxations and broad emissions. Multiple resonance (MR)-type TADF emitters can realize narrow emission. However, until now, only a few efficient MR-emitting cores are reported and custom tunning of their emission color remains a major challenge in their wider applications. Read More

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