Publications by authors named "Dohyun Park"

Cytotoxic chemotherapy that kills cancer cells can also elicit antitumor immune responses. Therefore, understanding the immunogenic context of cytotoxic chemotherapy can improve combination immunotherapies. In this study, we sought to improve our understanding of dendritic cell (DC) dynamics in cytotoxic chemotherapy-treated tumor tissues by developing three-dimensional (3D) microfluidic devices that enable high-resolution visualization of cellular dynamics.

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A novel method is presented for generating radiation using the beat wave of a bifrequency laser pulse to excite plasma oscillations in a plasma slab that has a density gradient. The plasma wave is localized where it is excited resonantly and becomes a plasma oscillator that produces a beam of radially polarized, terahertz radiation. Particle-in-cell simulations and a theoretical analysis are used to demonstrate its main characteristics, such as its narrow bandwidth.

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In modern bioprocessing, cell culture media is one of the most significant cost drivers, yet the nutrients and other critical factors in the media are often not fully utilized. With the renewed emphasis on reducing the cost of bioprocessing, there is much interest in reducing the overall use of cell culture media. In this work, we introduce a mesoscale microfluidic separation device based on the ion concentration polarization (ICP) process to regenerate the spent media for reuse by removing critical waste products from the cell culture that are known to inhibit the growth of the cells.

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As the physical size of a communication system for satellites or unmanned aerial vehicles demands to be reduced, a compact antenna with high directivity is proposed as a core element essential to the wireless device. Instead of using a horn or an array antenna, a unit planar antenna is combined with a surface-modulated lens to convert a low antenna gain to a high antenna gain. The lens is not a metal-patterned PCB but is dielectric, which is neither curved nor very wide.

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Microfluidic-based cytotoxic assays provide high physiological relevance with the potential to replace conventional animal experiments and two-dimensional (2D) assays. Here, a 3D method utilizing a microfluidic platform for analysis of lymphocyte cytotoxicity is introduced in detail, including platform design, cell culture method, real-time cytotoxic assay setup, and image-based analysis. A 2D experimental method is used for comparison, which effectively demonstrates the advantages of 3D microfluidic platforms in closely recapitulating immune responses within the tumor microenvironment.

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Silicon (Si) alkaline etching constitutes a fundamental process in the semiconductor industry. Although its etching kinetics on plain substrates have been thoroughly investigated, the kinetics of Si wet etching in nanoconfinements have yet to be fully explored despite its practical importance in three-dimensional (3-D) semiconductor manufacturing. Herein, we report the systematic study of potassium hydroxide (KOH) wet etching kinetics of amorphous silicon (a-Si)-filled two-dimensional (2-D) planar nanochannels.

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Divergent functionalization of α,β-unsaturated sulfones under copper catalysis is reported. Diastereoselective borylative allylation of alkenyl sulfones was achieved with a copper catalyst, allyl phosphate, bis(pinacolato)diboron, and LiOMe. In this method, the addition of a copper-boryl complex to alkenyl sulfone and subsequent allylic substitution rendered boroallylated products in good yield with excellent -diastereoselectivity.

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In electronic warfare systems, detecting low-probability-of-intercept (LPI) radar signals poses a significant challenge due to the signal power being lower than the noise power. Techniques using statistical or deep learning models have been proposed for detecting low-power signals. However, as these methods overlook the inherent characteristics of radar signals, they possess limitations in radar signal detection performance.

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Purpose: This study aims to clinically compare the fitness and trueness of zirconia crowns fabricated by different combinations of open CAD-CAM systems.

Materials And Methods: Total of 40 patients were enrolled in this study, and 9 different zirconia crowns were prepared per patient. Each crown was made through the cross-application of 3 different design software (EZIS VR, 3Shape Dental System, Exocad) with 3 different processing devices (Aegis HM, Trione Z, Motion 2).

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Disruption of mitochondrial function and protein homeostasis plays a central role in aging. However, how these processes interact and what governs their failure in aging remain poorly understood. Here, we showed that ceramide biosynthesis controls the decline in mitochondrial and protein homeostasis during muscle aging.

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We present a novel scheme to obtain robust, narrowband, and tunable THz emission using a nano-dimensional overdense plasma target, irradiated by two counter-propagating detuned laser pulses. So far, no narrowband THz sources with a field strength of GV/m-level have been reported from laser-solid interaction (mostly half-or single-cycle THz pulses with only broadband frequency spectrum). From two- and three-dimensional particle-in-cell simulations, we find that the strong plasma current generated by the beat ponderomotive force in the colliding region, produces beat-frequency radiation in the THz range.

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The development of short-wave infrared photodetectors based on various two-dimensional (2D) materials has recently attracted attention because of the ability of these devices to operate at room temperature. Although van der Waals heterostructures of 2D materials with type-II band alignment have significant potential for use in short-wave infrared photodetectors, there is a need to develop photodetectors with high photoresponsivity. In this study, we investigated the photogating of graphene using a monolayer-MoS2/monolayer-MoTe2 van der Waals heterostructure.

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The development of organs-on-a-chip has resulted in advances in the reconstruction of 3D cellular microenvironments. However, there remain limitations regarding applicability and manufacturability. Here, we present an injection-molded plastic array 3D universal culture platform (U-IMPACT) for various biological applications in a single platform, such as cocultures of various cell types, and spheroids (e.

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We guide the use of organ-on-chip technology in tissue engineering applications. Organ-on-chip technology is a form of microengineered cell culture platform that elaborates the in-vivo like organ or tissue microenvironments. The organ-on-chip platform consists of microfluidic channels, cell culture chambers, and stimulus sources that emulate the in-vivo microenvironment.

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Background: Pulse transit time and pulse wave velocity (PWV) are related to blood pressure (BP), and there were continuous attempts to use these to predict BP through wearable devices. However, previous studies were conducted on a small scale and could not confirm the relative importance of each variable in predicting BP.

Objective: This study aims to predict systolic blood pressure and diastolic blood pressure based on PWV and to evaluate the relative importance of each clinical variable used in BP prediction models.

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Recent advances in anticancer therapy have shown dramatic improvements in clinical outcomes, and adoptive cell therapy has emerged as a type of immunotherapy that can modulate immune responses by transferring engineered immune cells. However, a small percentage of responders and their toxicity remain as challenges. Three-dimensional (3D) models of the tumor microenvironment (TME) have the potential to provide a platform for assessing and predicting responses to therapy.

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Microfluidics offers promising methods for aligning cells in physiologically relevant configurations to recapitulate human organ functionality. Specifically, microstructures within microfluidic devices facilitate 3D cell culture by guiding hydrogel precursors containing cells. Conventional approaches utilize capillary forces of hydrogel precursors to guide fluid flow into desired areas of high wettability.

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Background: The aim of this study was to investigate the relationship between changes in breast density during menopause and breast cancer risk.

Methods: This study was a retrospective, longitudinal cohort study for women over 30 years of age who had undergone breast mammography serially at baseline and postmenopause during regular health checkups at Samsung Medical Center. None of the participants had been diagnosed with breast cancer at baseline.

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Background: Pill image recognition systems are difficult to develop due to differences in pill color, which are influenced by external factors such as the illumination from and the presence of a flash.

Objective: In this study, the differences in color between reference images and real-world images were measured to determine the accuracy of a pill recognition system under 12 real-world conditions (ie, different background colors, the presence and absence of a flash, and different exposure values [EVs]).

Methods: We analyzed 19 medications with different features (ie, different colors, shapes, and dosages).

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In vitro models are becoming more advanced to truly present physiological systems while enabling high-throughput screening and analysis. Organ-on-a-chip devices provide remarkable results through the reconstruction of a three-dimensional (3D) cellular microenvironment although they need to be further developed in terms of multiple liquid patterning principle, material properties, and scalability. Here we present a 3D anchor-based microfluidic injection-molded plastic array culture platform (Anchor-IMPACT) that enables selective, space-intensive patterning of hydrogels using anchor-island for high-throughput angiogenesis evaluation model.

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Semiconductors have long been perceived as a prerequisite for solid-state transistors. Although switching principles for nanometer-scale devices have emerged based on the deployment of two-dimensional (2D) van der Waals heterostructures, tunneling and ballistic currents through short channels are difficult to control, and semiconducting channel materials remain indispensable for practical switching. In this study, we report a semiconductor-less solid-state electronic device that exhibits an industry-applicable switching of the ballistic current.

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The field of microfluidics-based three-dimensional (3D) cell culture system is rapidly progressing from academic proof-of-concept studies to valid solutions to real-world problems. Polydimethylsiloxane (PDMS)-based platform has been widely adopted as in vitro platforms for mimicking tumor microenvironment. However, PDMS has not been welcomed as a standardized commercial application for preclinical screening due to inherent material limitations that make it difficult to scale-up production.

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The evolution of surface cleanliness and the electronic properties-Dirac voltage(V ), hysteresis and mobility (μ) of a graphene field-effect transistor (GFET)-were monitored by measuring lateral force microscopy and drain current (I ) as a function of gate voltage (V ), after mechanically cleaning the surface, scan-by-scan, with contact-mode atomic force microscopy. Both the surface cleanliness and the electronic properties evolved, showing a sudden improvement and then saturation for a mobility of around 2200 cm V s. We found that the mobility suppression of the as-fabricated GFET deviated from a randomly distributed impurities model, which predicted a greater mobility than obtained from the measured V .

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Adoptive cell transfer against solid tumors faces challenges to overcome tumor microenvironment (TME), which plays as a physical barrier and provides immuno-suppressive conditions. Classical cytotoxicity assays are widely used to measure killing ability of the engineered cytotoxic lymphocytes as therapeutics, but the results cannot represent the performance in clinical application due to the absence of the TME. This paper describes a 3D cytotoxicity assay using an injection molded plastic array culture (CACI-IMPACT) device for 3D cytotoxicity assay to assess killing abilities of cytotoxic lymphocytes in 3D microenvironment through a spatiotemporal analysis of the lymphocytes and cancer cells embedded in 3D extra cellular matrix (ECM).

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Microphysiological systems have emerged in the last decade to provide an alternative to in vivo models in basic science and pharmaceutical research. In the field of vascular biology, in particular, there has been a lack of a suitable in vitro model exhibiting a three-dimensional structure and the physiological function of vasculature integrated with organ-on-a-chip models. The rapid development of organ-on-a-chip technology is well positioned to fulfill unmet needs.

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