Publications by authors named "Taewon Choi"

In this paper, a novel thermo-optic metagrating based on phase-change material (vanadium dioxide, VO) is proposed for broadband, polarization-independent, and non-dispersive transmission modulation at the telecommunication wavelengths. In the pursuit of concurrent attainment of multiple performance objectives, nanostructured VO metagratings are optimized numerically using inverse design algorithms. Notably, adjoint optimization pertaining to both phases of VO facilitates better modulation capabilities within free-form shaped VO metagratings compared to shape-optimized methods with predetermined designs.

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Article Synopsis
  • Slim cameras are crucial for modern devices like smartphones and AR/VR systems, but thinning them down is difficult due to bulky lens systems with empty spaces.
  • Researchers have developed an ultra-slim lens system utilizing metasurface folded optics, achieving a thickness of just 0.7 millimeters—two times thinner than standard designs.
  • This innovative lens technology offers high-quality imaging with a 10° field of view, paving the way for more compact camera solutions in consumer electronics.
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Article Synopsis
  • Deflectors play a crucial role in directing light in optical systems but often struggle with issues like size limitations and chromatic aberration due to traditional optics like prisms and mirrors.
  • Recent advancements using metasurfaces have faced challenges in terms of practical application and complex manufacturing, particularly in the near-infrared range.
  • The proposed single-layer metasurface uses a freeform design to eliminate chromatic aberration across the visible spectrum, achieving efficient light deflection at a precise angle and showing promise for use in technologies like AR/VR and high-quality cameras.
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Repetitive stimulation procedures are used in neuromodulation techniques to induce persistent excitatory or inhibitory brain activity. The directivity of modulation is empirically regulated by modifying the stimulation length, interval, and strength. However, bidirectional neuronal modulations using ultrasound stimulations are rarely reported.

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Objective: Focused ultrasound has been applied in brain therapeutics. Although focusing ultrasonic beams on multiple arbitrary regions under the guidance of magnetic resonance imaging(MRI) is needed for precise treatments, current therapeutic transducers with large pitch sizes have been optimized to focus on deep brain regions. While annular arrays can adjust the beam foci from cortical to deep regions, their circular shape may generate eddy current-induced magnetic flux during MRI.

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Bioresorbable vascular scaffold (BVS) has recently been spotlighted for its unique characteristics of absorbing into blood vessels and eventually disappearing. Although intravascular ultrasound (IVUS) is the most common guiding tool for stent deployment, the echogenicity of BVS struts has changed as the center of stent lumen and scanning rotation is not concentric, which may cause a critical erroneous measurement in practice. This study investigated the physical conditions for dimming the stent brightness in IVUS images using a finite-difference method (FDM) to numerically solve acoustic wave propagation through nonhomogeneous medium.

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Conventional acoustic brain stimulators that transmit low frequency (< 1 MHz) bursts in a pulse repetition frequency with large-sized transducers are barely compatible with small animal models because of broad beam width, possible stimulation of auditory pathways, and blocking of field-of-view for in vivo imaging of brain hemodynamics and neuronal activities. A miniaturized ultrasound stimulator with higher stimulation frequencies will enhance spatial specificity and enable simultaneous eliciting and monitoring brain activities. Moreover, the use of non-periodic pulse sequences may reduce unintended stimulations on auditory cortex, which might be caused by transmitting periodic bursting patterns.

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Rapid industrialization has significantly influenced people's lifestyles in the recent decades, and the influence of traditional culture is diminishing. Recently, several studies attempted to simultaneously utilize various sensors to record delicate and sophisticated performances of intangible cultural heritage (ICH). Although painting is one of the most common ICH of human history, few research studies have recorded traditional painting work.

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Asthma is a potentially life-threatening inflammatory disease of the lung characterized by the presence of large numbers of CD4+ T cells. These cells produce the Th2 and Th17 cytokines that are thought to orchestrate the inflammation associated with asthma. Bee venom (BV) has traditionally been used to relieve pain and to treat chronic inflammatory diseases.

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Ethnopharmacological Relevance: So-Shi-Ho-Tang (SSHT) or known as Sho-Saiko-To in Japanese and Xiao-Chai-Hu-Tang in Chinese has been used to treat chronic liver disease and other infections, and its hepatoprotective effects have been widely studied.

Aim Of The Study: We tried to investigate the immunomodulatory effect of SSHT on interferon (IFN)-gamma and interleukin (IL)-4 and their Th1/Th2 transcription factors in vivo and in vitro since these two cytokines are important in determining the type of cell-mediated inflammatory and humoral responses.

Materials And Methods: SSHT was orally given to BALB/c mice for 7 days and then injected with anti-CD3 mAb intravenously.

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Here, we confirmed that stable expression of B-cell lymphoma-xL (Bcl-xL) in N18TG neuroglioma cells could suppress c-Jun N-terminal protein kinase (JNK) activation, nuclear fragmentation, and cell death caused by etoposide treatment. Moreover, additional overexpression of JNK1 led to partially antagonize the antiapoptotic environment attained by Bcl-xL, implying that JNK1-involved pathway may play a role in down-regulation of the antiapoptotic effect of Bcl-xL. However, the antagonistic effect of JNK1 on the antiapoptotic action of Bcl-xL was significantly weaker than that on the action of Bcl-2.

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