Publications by authors named "ChangHwan Lee"

A topological crystalline insulator (TCI) constitutes a valid candidate for optoelectronic applications owing to its broad spectral absorption, ultrafast response, and excellent stability. Thus far, the upscaling of the synthetic approach for TCIs has not been accomplished. Here, we proposed the one-step upscaling of a 6 in.

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Mechanical force is an essential feature for many physical and biological processes, and remote measurement of mechanical signals with high sensitivity and spatial resolution is needed for diverse applications, including robotics, biophysics, energy storage and medicine. Nanoscale luminescent force sensors excel at measuring piconewton forces, whereas larger sensors have proven powerful in probing micronewton forces. However, large gaps remain in the force magnitudes that can be probed remotely from subsurface or interfacial sites, and no individual, non-invasive sensor is capable of measuring over the large dynamic range needed to understand many systems.

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This study characterizes the influence of self-assembly conditions on the aggregation pathway and resulting photophysical properties of one-dimensional aggregates of the simple imide-substituted perylene diimide, N, N'-didodecyl-3,4,9,10-perylenedicarboximide (ddPDI). We show that ddPDI, which has symmetric alkyl chains at the imide positions, assembles into fibers with distinct morphology, emission spectra, and temperature-dependent behavior as a function of preparation conditions. In all conditions explored, aggregates are one-dimensional; however, assembly conditions can bias formation to either J-like or H-like aggregates.

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Optical technologies enable real-time, noninvasive analysis of complex systems but are limited to discrete regions of the optical spectrum. While wavelengths in the short-wave infrared (SWIR) window (typically, 1700-3000 nm) should enable deep subsurface penetration and reduced photodamage, there are few luminescent probes that can be excited in this region. Here, we report the discovery of lanthanide-based upconverting nanoparticles (UCNPs) that efficiently convert 1740 or 1950 nm excitation to wavelengths compatible with conventional silicon detectors.

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Studies of letter transposition effects in alphabetic scripts provide compelling evidence that letter position is encoded flexibly during reading, potentially during an early, perceptual stage of visual word recognition. Recent studies additionally suggest similar flexibility in the spatial encoding of syllabic information in the Korean Hangul script. With the present research, we conducted two experiments to investigate the locus of this syllabic transposition effect.

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Upconverting nanoparticles (UCNPs) exhibit unique nonlinear optical properties that can be harnessed in microscopy, sensing, and photonics. However, forming high-resolution nano- and micropatterns of UCNPs with large packing fractions is still challenging. Additionally, there is limited understanding of how nanoparticle patterning chemistries are affected by the particle size.

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A major factor driving stem cell decline is stem cell niche aging, but its molecular mechanism remains elusive. We use the Caenorhabditis elegans distal tip cell (DTC), the mesenchymal niche that employs Notch signaling to regulate germline stem cells (GSCs), as an in vivo niche aging model and delineate the molecular details of the DTC/niche aging process. Here, we demonstrate that a drastic decrease in C.

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Photon avalanching nanoparticles (ANPs) exhibit extremely nonlinear upconverted emission valuable for subdiffraction imaging, nanoscale sensing, and optical computing. Avalanching has been demonstrated with Tm-, Pr-, or Nd-doped nanocrystals, but their emission is limited to a few wavelengths and materials. Here, we utilize Gd-assisted energy migration to tune the emission wavelengths of Tm-sensitized ANPs and generate highly nonlinear emission from Eu, Tb, Ho, and Er ions.

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Materials whose luminescence can be switched by optical stimulation drive technologies ranging from superresolution imaging, nanophotonics, and optical data storage, to targeted pharmacology, optogenetics, and chemical reactivity. These photoswitchable probes, including organic fluorophores and proteins, can be prone to photodegradation and often operate in the ultraviolet or visible spectral regions. Colloidal inorganic nanoparticles can offer improved stability, but the ability to switch emission bidirectionally, particularly with near-infrared (NIR) light, has not, to our knowledge, been reported in such systems.

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Upconverting nanoparticles (UCNPs) compose a class of luminescent materials that utilize the unique wavelength-converting properties of lanthanide (Ln) ions for light-harvesting applications, photonics technologies, and biological imaging and sensing experiments. Recent advances in UCNP design have shed light on the properties of local color centers, both intrinsic and controllably induced, within these materials and their potential influence on UCNP photophysics. In this review, we describe fundamental studies of color centers in Ln-based materials, including research into their origins and their roles in observed photodarkening and photobrightening mechanisms.

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An 8-week feeding trial was conducted to evaluate the effects of various dietary levels of garlic juice processing waste (GJPW) on the growth, feed utilization, digestive and antioxidant enzyme activity, growth- and antioxidant-related gene expression, and resistance to infection of juvenile black rockfish (). A total of 450 juvenile rockfish were randomly distributed into 30 L rectangular tanks (30 fish per tank). Five experimental diets were prepared in triplicate.

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Neck contrast-enhanced CT (CECT) is a routine tool used to evaluate patients with cervical lymphadenopathy. This study aimed to evaluate the ability of convolutional neural networks (CNNs) to classify Kikuchi-Fujimoto's disease (KD) and cervical tuberculous lymphadenitis (CTL) on neck CECT in patients with benign cervical lymphadenopathy. A retrospective analysis of consecutive patients with biopsy-confirmed KD and CTL in a single center, from January 2012 to June 2020 was performed.

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Greater word length effects have been reported when a word was presented in the left visual field (LVF) than when presented in the right visual field (RVF). The current study employed 2 experiments to examine the visual-perceptual loci of asymmetric word length effect while testing the physical and linguistic length effects and the effect of visual angle increase at the RVF. Experiment 1 showed significant effects on the number of strokes in both VHFs (visual half fields) with the added significance of the number of syllables in the LVF, suggesting both parafoveal fields were affected by the physical length factors in contrast with the linguistic length factors, inducing asymmetric word length effects in the symmetrically presented word recognition in parafoveal vision.

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Notch signaling is crucial to animal development and homeostasis. Notch triggers the transcription of its target genes, which produce diverse outcomes depending on context. The high resolution and spatially precise assessment of Notch-dependent transcription is essential for understanding how Notch operates normally in its native context in vivo and how Notch defects lead to pathogenesis.

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A long-standing biological question is how DNA cis-regulatory elements shape transcriptional patterns during metazoan development. Reporter constructs, cell culture assays and computational modeling have made major contributions to answering this question, but analysis of elements in their natural context is an important complement. Here, we mutate Notch-dependent LAG-1 binding sites (LBSs) in the endogenous Caenorhabditis elegans sygl-1 gene, which encodes a key stem cell regulator, and analyze the consequences on sygl-1 expression (nascent transcripts, mRNA, protein) and stem cell maintenance.

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Plant-derived feed additives provide cost effective and environmentally friendly alternatives to antibiotics for improving fish performance in aquaculture. An 8-week feeding trial was conducted to evaluate the effects of dietary ginger residue from juice extraction (GRJE) on juvenile black rockfish () growth performance, antioxidant enzyme activities, and resistance to Streptococcus iniae infection. Juvenile rockfish ( = 450; initial weight = 2.

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Reinforced concrete (RC) columns of old existing buildings are vulnerable to earthquakes because the hoops comprising their transverse reinforcement are widely spaced and anchored using 90° hooks. This study extensively evaluated the seismic behavior of RC columns with such non-seismic details. Experiments were conducted by applying lateral cyclic loads to five full-scale column specimens with various transverse reinforcement details subjected to low axial loads.

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Background: The digital health care field is expanding from the daily monitoring of chronic diseases to the detection of acute diseases, such as arrhythmia. Wolff-Parkinson-White (WPW) syndrome, a congenital cardiac disorder due to accessory pathways, causes tachycardia, syncope, and even sudden death.

Case Presentation: We presented a 26-year-old female office worker with WPW syndrome managing the disease with a wearable device and discussed its significance in occupational medicine.

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Background: Coronavirus disease 2019 (COVID-19) has infected many individuals worldwide. Individuals in contact with unspecified people during their work, may be at risk of occupational exposure. On June 22, 2020, 1,435 overseas patients were identified in the Republic of Korea.

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Energy conversion to generate hot electrons through the excitation of localized surface plasmon resonance (LSPR) in metallic nanostructures is an emerging strategy in photovoltaics and photocatalytic devices. Important factors for surface plasmon and hot electron generation are the size, shape, and materials of plasmonic metal nanostructures, which affect LSPR excitation, absorbance, and hot electron collection. Here, we fabricated the ordered structure of metal-semiconductor plasmonic nanodiodes using nanosphere lithography and reactive ion etching.

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Hot electron flux, generated by both incident light energy and the heat of the catalytic reaction, is a major element for energy conversion at the surface. Controlling hot electron flux in a reversible manner is extremely important for achieving high energy conversion efficiency. Here we demonstrate that hot electron flux can be controlled by tuning the Schottky barrier height.

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Various seismic analysis methods are being used to predict the response of structures to earthquakes. Although nonlinear dynamic analysis (NDA) is considered an ideal method to represent the most realistic behavior of a structure among these various methods, correct results can be derived only when the analysis model is carefully developed by a knowledgeable person. It is particularly important to properly implement the behavior characteristics depending on the reversed cyclic load in the NDA of a building made of reinforced concrete (RC) moment frames.

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A new type of composite voided slab, the TUBEDECK (TD), which utilizes the structural function of profiled steel decks, has recently been proposed. Previous studies have confirmed that the flexural strength of TD slabs can be calculated based on the full composite contribution of the steel deck, but for long-span flexural members, the deflection serviceability requirement is often dominant. Herein, we derived a novel deflection prediction approach using the results of flexural tests on slab specimens, focusing on TD slabs.

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Avalanche phenomena use steeply nonlinear dynamics to generate disproportionately large responses from small perturbations, and are found in a multitude of events and materials. Photon avalanching enables technologies such as optical phase-conjugate imaging, infrared quantum counting and efficient upconverted lasing. However, the photon-avalanching mechanism underlying these optical applications has been observed only in bulk materials and aggregates, limiting its utility and impact.

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