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391 results on '"Choi, Hongsoo"'

102. A Quantitative Electroencephalography Study on Cochlear Implant-Induced Cortical Changes in Single-Sided Deafness with Tinnitus

Author

Song, Jae-Jin, primary, Kim, Kyungsoo, additional, Sunwoo, Woongsang, additional, Mertens, Griet, additional, Van de Heyning, Paul, additional, De Ridder, Dirk, additional, Vanneste, Sven, additional, Lee, Sang-Youp, additional, Park, Kyung-Joon, additional, Choi, Hongsoo, additional, and Choi, Ji-Woong, additional

Published
2017
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110. Fabrication and Characterization of Magnetic Microrobots for Three-Dimensional Cell Culture and Targeted Transportation

Author

Kim Sangwon, Qiu Famin, Kim Samhwan, Ghanbari Ali, Moon Cheil, Zhang Li, Nelson Bradley J., and Choi Hongsoo

Subjects
Materials science, Fabrication, Biocompatibility, Magnetism, Polymers, Microrobots, Cell Culture Techniques, Magnetic manipulation, Nanotechnology, 02 engineering and technology, Photoresist, 010402 general chemistry, 01 natural sciences, Drug Delivery Systems, Microtechnology, Humans, General Materials Science, Three-dimensional cell culture, Targeted cell transportation, H671, Mechanical Engineering, Magnetic Phenomena, HEK 293 cells, technology, industry, and agriculture, Robotics, equipment and supplies, 021001 nanoscience & nanotechnology, Communications, 0104 chemical sciences, HEK293 Cells, Mechanics of Materials, Magnet, Feasibility Studies, 0210 nano-technology, human activities, Porosity, Maskless lithography
Abstract

Magnetically manipulated microrobots are demonstrated for targeted cell transportation. Full three-dimensional (3D) porous structures are fabricated with an SU-8 photoresist using a 3D laser lithography system. Nickel and titanium are deposited as a magnetic material and biocompatible material, respectively. The fabricated microrobots are controlled in the fluid by external magnetic fields. Human embryonic kidney 239 (HEK 239) cells are cultivated in the microrobot to show the possibility for targeted cell transportation., Advanced Materials, 25 (41), ISSN:0935-9648, ISSN:1521-4095

Published
2013

119. Feeding state regulates pheromone‐mediated avoidance behavior via the insulin signaling pathway in Caenorhabditis elegans.

Author

Ryu, Leesun, Cheon, YongJin, Huh, Yang Hoon, Pyo, Seondong, Chinta, Satya, Choi, Hongsoo, Butcher, Rebecca A., and Kim, Kyuhyung

Subjects
ANIMAL feeding, NEURAL transmission, PHEROMONES, AVOIDANCE (Psychology), CAENORHABDITIS elegans
Abstract

Abstract: Animals change sensory responses and their eventual behaviors, depending on their internal metabolic status and external food availability. However, the mechanisms underlying feeding state‐dependent behavioral changes remain undefined. Previous studies have shown that Caenorhabditis elegans hermaphrodite exhibits avoidance behaviors to acute exposure of a pheromone, ascr#3 (asc‐ΔC9, C9). Here, we show that the ascr#3 avoidance behavior is modulated by feeding state via the insulin signaling pathway. Starvation increases ascr#3 avoidance behavior, and loss‐of‐function mutations in daf‐2 insulin‐like receptor gene dampen this starvation‐induced ascr#3 avoidance behavior. DAF‐2 and its downstream signaling molecules, including the DAF‐16 FOXO transcription factor, act in the ascr#3‐sensing ADL neurons to regulate synaptic transmission to downstream target neurons, including the AVA command interneurons. Moreover, we found that starvation decreases the secretion of INS‐18 insulin‐like peptides from the intestine, which antagonizes DAF‐2 function in the ADL neurons. Altogether, this study provides insights about the molecular communication between intestine and sensory neurons delivering hunger message to sensory neurons, which regulates avoidance behavior from pheromones to facilitate survival chance. [ABSTRACT FROM AUTHOR]

Published
2018
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121. A microelectromechanical system artificial basilar membrane based on a piezoelectric cantilever array and its characterization using an animal model

Author

Jang, Jongmoon, primary, Lee, JangWoo, additional, Woo, Seongyong, additional, Sly, David J., additional, Campbell, Luke J., additional, Cho, Jin-Ho, additional, O’Leary, Stephen J., additional, Park, Min-Hyun, additional, Han, Sungmin, additional, Choi, Ji-Wong, additional, Hun Jang, Jeong, additional, and Choi, Hongsoo, additional

Published
2015
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127. Dumbbell Fluidic Tweezers for Dynamical Trapping and Selective Transport of Microobjects.

Author

Zhou, Qi, Petit, Tristan, Choi, Hongsoo, Nelson, Bradley J., and Zhang, Li

Subjects
NANOWIRES, FLUIDIC devices, MICROROBOTS, MAGNETIC actuators, FERROMAGNETIC materials
Abstract

Mobile microvortices generated by rotating nickel (Ni) nanowires (NW) have been reported as capable of inducing fluidic trapping that can be precisely focused and translated to manipulate microobjects. Here, a new design for significantly enhanced fluidic trapping is reported, which is a dumbbell (DB)-shaped magnetic actuator, assembled by a Ni NW and two polystyrene microbeads. In contrast to the single mode of tumbling trapping possessed by Ni NW, the magnetic dumbbell is able to perform dynamical trapping and implement on-demand transport of microobjects in three modes, i.e., tumbling, wobbling, and rolling. Experiments are conducted to demonstrate the robustness and efficacy of the fluidic trap by the DB actuator. And simulations using a finite element model compare the fluidic traps induced by NW and DB, followed by further discussion on the actuation and transport efficiency of NW and DB fluidic tweezers (FT). At last, some practical issues regarding the application of DB FT are addressed. [ABSTRACT FROM AUTHOR]

Published
2017
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129. Upshift of Phase Transition Temperature in Nanostructured PbTiO3 Thick Film for High Temperature Applications

Author

Ryu, Jungho, primary, Han, Guifang, additional, Song, Tae Kwon, additional, Welsh, Aaron, additional, Trolier-McKinstry, Susan, additional, Choi, Hongsoo, additional, Lee, Jong-Pil, additional, Kim, Jong-Woo, additional, Yoon, Woon-Ha, additional, Choi, Jong-Jin, additional, Park, Dong-Soo, additional, Ahn, Cheol-Woo, additional, Priya, Shashank, additional, Choi, Si-Young, additional, and Jeong, Dae-Yong, additional

Published
2014
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141. A low-complexity iterative MIMO detection and decoding scheme using dimension reduction.

Author

Shin, Sang‐Sik, Choi, Hongsoo, Jang, Jae‐Eun, and Choi, Ji‐Woong

Subjects
MIMO systems, DECODING algorithms, DEMODULATION, COMMUNICATION, BIT rate
Abstract

Spatial multiplexing multiple-input multiple-output is considered as a core advanced communication technology to increase data rate. Although it guarantees higher capacity, it gives huge burden on the receiver side especially when iterative detection and decoding (IDD) is employed. Therefore, the IDD receiver needs to be efficiently implemented considering the complexity as well as performance in practice. In this paper, we propose an IDD scheme employing dimension reduction soft demodulation (DRSD) principle based on maximum a posteriori criterion necessary for IDD operation. With separation into hard and soft streams in the DRSD, the proposed scheme employs all ordering successive interference cancellation with a simple modified slicing for hard detection to consider the effect of a priori information conveyed from past iteration, enabling complexity reduction. It can provide better trade-off between complexity and performance. [ABSTRACT FROM AUTHOR]

Published
2016
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148. Influence of mechanical coupling by SiO membrane on the frequency selectivity of microfabricated beam arrays for artificial basilar membranes.

Author

Song, Won, Jang, Jongmoon, Kim, Sangwon, and Choi, Hongsoo

Subjects
BASILAR membrane, VIBROMETERS, ACOUSTIC transducers, PIEZOELECTRIC materials, DEGREES of freedom
Abstract

Two types of microfabricated acoustic transducers-the resonator array of isolated beams (RAIB) and the resonator array of coupled beams (RACB)-were built using MEMS technology. The frequency selectivity of the two types of transducers was qualitatively compared using the transfer functions measured with a scanning laser Doppler vibrometer (SLDV). Each RAIB beam operated as a band-pass filter in the proximity to the corresponding resonance frequency, thereby showing the frequency-selective feature of the basilar membrane (BM). However, the frequency selectivity of RACB was poor because the SiO membrane, which mechanically coupled the neighboring beams, suppressed the independent response of each beam. The influence of the mechanical coupling of the SiO membrane was simulated using lumped parametric models. Simulation results showed that the coupling stiffness of the SiO membrane may significantly undermine the frequency selectivity of the resonator array. The comparison of the frequency-selective performance revealed that RAIB is a better option than RACB for mimicking the tonotopy of BM. [ABSTRACT FROM AUTHOR]

Published
2015
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150. Experimental study of a biomimetic artificial basilar membrane fabricated using piezoelectric micromachined beams.

Author

Sangwon Kim and Choi, Hongsoo

Abstract

The basilar membrane and hair cells are the main parts of the mammalian cochlea, which converts external sound into bioelectrical signals, in the inner ear,. Loss of hair cells on the basilar membrane in the cochlea is one of the main causes of hearing loss. An artificial basilar membrane (ABM) was developed as a MEMS acoustic sensor using a piezoelectric beam array based on MEMS technology. The lengths and thicknesses of the beams were calculated and determined prior to the design of the photomasks. An aluminum nitride (AlN) thin film was selected as the active piezoelectric layer for the ABM. The impedance magnitudes and phase angles of each beam are measured with an impedance analyzer and a probe station in air. The fabricated ABM contains 16 beams with various lengths ranging from 300 µm to 3300 µm along a trapezoidal shape in the array. The width of the beams is fixed at 200 µm and the thickness of the active AlN thin film is 500 nm. It is observed that the resonance frequencies tend to decreased from 233.3 kHz to 214.6 kHz as the beam length was increased. It is concluded that the fabricated AlN ABM can potentially be used as an acoustic sensor in a total implantable artificial cochlea. [ABSTRACT FROM PUBLISHER]

Published
2011
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