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Cdk5 regulates N-cadherin-dependent neuronal migration during cortical development
Lee, Dong-Keun,Lee, Hojae,Yoon, Jiyoung,Hong, Sujeong,Lee, Yunjeong,Kim, Kyung-Tai,Kim, Jong Woon,Song, Mi-Ryoung Elsevier 2019 Biochemical and biophysical research communication Vol.514 No.3
<P><B>Abstract</B></P> <P>Cyclin-dependent kinase 5 (Cdk5) controls neuronal migration in the developing cortex when multipolar newborn neurons transform to become bipolar. However, by which mechanisms Cdk5 controls cell adhesion in migrating neurons are not fully understood. In this study, we examined the functional interaction between Cdk5 and N-cadherin (Ncad) in newborn neurons when they undergo the multipolar to bipolar transition in the intermediate zone (IZ). Detailed expression analysis revealed that both Cdk5 and Ncad were present in GFP-electroporated migrating neurons in the IZ. Misexpression of dominant negative Cdk5 into the embryonic brains stalled neuronal locomotion in the lower IZ in which arrested cells were round or multipolar. When Ncad was co-introduced with Cdk5DN, however, cells continue to migrate into the cortical plate (CP) and migrating neurons acquired typical bipolar morphology with a pia-directed leading process. Similarly, downregulation of CDK5 resulted in lesser aggregation ability, reversed by the expression of Ncad <I>in vitro</I>. Down-regulation of activity or protein level of CDK5 did not alter the total amount of NCAD proteins but lowered its surface expression in cells. Lastly, expression of CDK5 and NCAD overlapped in the IZ of the human fetal cortex, indicating that the role of Cdk5 and Ncad in neuronal migration is evolutionarily conserved.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Reduced Cdk5 activity inhibits the multipolar-bipolar transition of migrating neurons. </LI> <LI> Ncad expression rescues migration defects caused by the reduction of Cdk5 activity. </LI> <LI> Downregulation of Cdk5 impairs the membrane localization of Ncad. </LI> <LI> Cdk5 and Ncad are present in developing mouse and human brains. </LI> </UL> </P>
Theoretical-Analysis-Based Distributed Load Balancing Over Dynamic Overlay Clustering
Lee, Hojae,Kwon, Beom,Kim, Seonghyun,Lee, Inwoong,Lee, Sanghoon IEEE 2016 IEEE Transactions on Vehicular Technology VT Vol.65 No.8
<P>In multicell networks, unbalanced cell loading can lead to decreased system stability and reduced fairness among serviced users. In this paper, we propose theoretical-analysis-based distributed load balancing (DLB) over dynamic overlay clustering implemented over a multicell network. The proposed system is divided into two parts: DLB and overlay clustering. First, for DLB, we define the long-term expected load after deriving the long-term expected rate in terms of proportional fairness. We then introduce two algorithms: DLB for load dispersion and DLB for edge-rate enhancement (ERE). These algorithms operate in a distributed manner based on mathematical analyses and load balancing characteristics. Second, through overlay clustering, load balancing within each cluster is consecutively performed on neighboring clusters, which enables the algorithm to optimally approximate in a distributed manner. The simulation results show that approximately 90% of the near-optimal performance in terms of load variation and ERE can be achieved with low complexity by using the proposed schemes. In addition, we discuss aspects and tradeoffs of the load balancing system.</P>
Lee, Hojae,Kim, Jang-Ho Jay,Moon, Jae-Heum,Kim, Won-Woo,Seo, Eun-A Elsevier 2019 Construction & building materials Vol.226 No.-
<P><B>Abstract</B></P> <P>Recently, researches on additive manufacturing (AM) method have been actively carried out as the latest technique for building concrete structures in the construction field. It is known that the additive manufacturing method, also called 3D printing technique, is a method of constructing a structure by printing layers, and the adhesion strength in the interlayer between the layers plays a dominant role in the performance of the structure. In this study, we focused on the formation of interlayer of concrete structure built using additive manufacturing method. In this study, the position of the interlayer was analyzed using the computed tomography (CT) method and the correlation between porosity and tensile bond strength in the analyzed interlayer was tried. As a result of the CT analysis of 13 specimens extracted from the printed specimens, it was confirmed that the porosity was formed high in the interlayer. The porosity of the interlayer was at least 2.15% and 6.66% higher than the average porosity. After analyzing the porosity by CT, the tensile bond strength of the specimens was measured to confirm the tensile bond strength and location of the fracture surface. Tensile bond strengths were 2.58–3.77 MPa with an average of 2.80 MPa using 10 specimens. It was confirmed that all of the fracture surfaces occurred along the interlayer. It was confirmed that there was no correlation between the tensile bond strength and porosity of the test specimens used in this study. Six of the ten specimens failed in the other interlayer, but four specimens failed in the interlayer with the highest porosity. As a result of analysis of the fracture surfaces of six specimens without fracture at the highest porosity, the porosity at the fracture surface was 5.73–9.18%, which was higher by 0.6–3.3% than the average porosity. However, defects occurred during layer output were confirmed from the failure of six specimens. Through this study, we confirmed that the interlayer is the weakest when tensile stress is applied in the perpendicular direction of printing, and that it is necessary to review the defects when applying the printing method.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Pore distribution in the interlayer analyzed using X-ray Computed Tomography. </LI> <LI> Relationship between pore fraction and position of tensile bond fracture determined. </LI> <LI> Tensile bond strength of 6.27% of compressive strength obtained. </LI> <LI> Weakest layer occurred when tensile stress is perpendicular to printing direction. </LI> </UL> </P>
Mutual Interference Analysis of FBMC-Based Return Channel for Bidirectional T-DMB System
Lee, Hojae,Kwon, Beom,Jeon, Donghyun,Kim, Seonghyun,Lee, Sanghoon IEEE 2017 IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY Vol.66 No.5
<P>In this paper, we investigate an effective scheme for implementing the return channel by exploiting the guard band between orthogonal frequency-division multiplexing (OFDM) blocks for uplink transmission, which enables guaranteeing compatibility with legacy systems. In order to resolve the interference problem between the conventional broadcast channel and the return channel, we employ the filter bank-based multicarrier (FBMC) system. Toward this goal, the mutual interference between the return and OFDM channels is derived as a closed form through numerical analysis. Based on the mutual interference analysis and the channel condition, an adaptive modulation scheme is applied to increase data throughput. Through the simulation, it can be seen that more than 350 (500) kb/s/Channel can be achieved for the channel signal-to-noise ratio (SNR) of 20 dB (30 dB) when the quality of service constraint is lower than a bit error rate of <TEX>${\text 10}^-{\text 2}$</TEX> ( <TEX>$10^-{\text 4}$</TEX>). Consequently, the additional throughput above can be achieved in a given resource without the adverse effect to the legacy systems.</P>
Combinatorial Orthogonal Beamforming for Joint Processing and Transmission
Hojae Lee,Seonghyun Kim,Sanghoon Lee Institute of Electrical and Electronics Engineers 2014 IEEE Transactions on Communications Vol. No.
<P>Coordinated multiple point transmission (CoMP) technologies have recently been proposed to improve the performance of cell-edge users who suffer strong inter-cell interference. Nevertheless, as more transmitters get involved in cooperation, the complexity associated with the selection of multi-dimensional parameters increases exponentially. In this work, we investigate efficient multi-cell cooperation based on CoMP-joint processing and transmission (CoMP-JPT) with orthogonal beamforming using limited feedback. Through the utilization of combinatorial optimization, optimal user scheduling for joint transmission via multiple transmitters is accomplished, while the computational complexity is significantly reduced. In particular, a generalized beam assignment problem (GBAP) is formulated and solved using a combinatorial algorithm that is generalized in terms of the number of transmitters o\mathcal{B}o. The performance of the combinatorial orthogonal beamforming (COBF) scheme is mathematically analyzed so as to demonstrate its superiority and capability to maintain fairness among users in a multi-cell environment. In the simulation results, a performance gain of more than 50% for cell-edge users is obtained without a loss in the average throughput for the total number of users. In addition, the COBF method can reduce the complexity by more than 60% when compared to the conventional exhaustive search technique.</P>