Significant therapeutic effects of adult human multipotent neural cells on spinal cord injury

Lee, Kee-Hang,Pyeon, Hee-Jang,Nam, Hyun,Won, Jeong-Seob,Hwang, Ji-Yoon,Lee, Kyung-A,Yeon, Je Young,Hong, Seung-Chyul,Nam, Do-Hyun,Lee, Kyunghoon,Lee, Sun-Ho,Joo, Kyeung-Min Elsevier 2018 Stem cell research Vol.31 No.-

<P><B>Abstract</B></P> <P>Neural stem cells are emerging as a regenerative therapy for spinal cord injury (SCI), since they differentiate into functional neural cells and secrete beneficial paracrine factors into the damaged microenvironment. Previously, we successfully isolated and cultured adult human multipotent neural cells (ahMNCs) from the temporal lobes of epileptic patients. In this study, we investigated the therapeutic efficacy and treatment mechanism of ahMNCs for SCI using rodent models. When 1 × 10<SUP>6</SUP> ahMNCs were transplanted into injured spinal cords at 7 days after contusion, the injection group showed significantly better functional recovery than the control group (media injection after contusion), which was determined by the Basso, Beattie and Bresnahan (BBB) score. Although transplanted ahMNCs disappeared continuously, remained cells expressed differentiated neural cell markers (Tuj1) or astrocyte marker (GFAP) in the injured spinal cords. Moreover, the number of CD31-positive microvessels significantly increased in the injection group than that of the control group. The paracrine pro-angiogenic activities of ahMNCs were confirmed by <I>in vitro</I> tube formation assay and <I>in vivo</I> Matrigel plug assay. Together, these results indicate that ahMNCs have significant therapeutic efficacy in SCI <I>via</I> replacement of damaged neural cells and pro-angiogenic effects on the microenvironment of SCI.</P> <P><B>Highlights</B></P> <P> <UL> <LI> ahMNCs are neural stem cell-like cells derived from adult human temporal lobes. </LI> <LI> ahMNCs have significant preclinical therapeutic effects on spinal cord injury. </LI> <LI> ahMNCs differentiate into astrocytes, neurons, and oligodendrocytes in damaged spinal cords. </LI> <LI> ahMNCs increase microvessel density significantly in damaged spinal cords. </LI> </UL> </P>

허브 네트워크에서의 장거리 공중 전술 통신을 위한 반복 정렬 기반의 자원 스케줄링 기법

이경훈(Kyunghoon Lee),이동훈(Dong Hun Lee),이대홍(Dae-Hong Lee),정성진(Sung-Jin Jung),최형진(Hyung-Jin Choi) 한국통신학회 2014 韓國通信學會論文誌 Vol.39 No.12(융합기술)

본 논문에서는 허브 네트워크 기반의 장거리 공중 전술 통신을 위한 새로운 자원 스케줄링 기법을 제안한다. 최근 세계 각국에서는 네트워크 중심전 (NCW, Network Centric Warfare)으로 변화하는 현대전의 흐름에 맞추어 공용데이터링크 (CDL, Common Data Link)의 전송속도 및 네트워킹 기능을 향상시키기 위한 기술 개발에 주력하고 있으며, 우리 군도 자립적인 차세대 대용량 CDL 기술 개발에 박차를 가하고 있다. CDL의 대표적 운용 구조인 허브 네트워크에서는 제한된 주파수 대역 내에서 다수의 UAV (Unmanned Aerial Vehicle)들과 대용량의 영상·전술 정보를 동시 다발적으로 교환하기 위해, hybrid FDMA(Frequency Division Multiple Access)/TDMA(Time Division Multiple Access) 구조를 고려할 수 있다. 그러나 UAV 별 상이한 왕복 시간 지연 (RTT,Round-Trip Time) 및 트래픽 크기로 인해 동일 주파수 대역을 점유하는 UAV 간 유휴 시간 자원이 발생하거나 불필요한 패킷 전송 지연이 발생할 수 있으며, 이는 장거리 운용 시 허브 네트워크의 자원 효율을 저하시킨다. 따라서 본 논문에서는 UAV 별 발생하는 RTT와 트래픽 크기를 기반으로 하는 반복적 정렬 알고리즘을 통해 UAV의 시간/주파수 자원을 스케줄링하는 기법을 제안한다. 성능 평가를 통해 제안 기법이 낮은 복잡도로 데이터 처리율과 패킷 지연 측면의 성능 향상이 가능함을 입증하였다. In this paper, a novel resource scheduling, which is used for hub network based long distance airborne tactical communication, is proposed. Recently, some countries of the world has concentrated on developing data rate and networking performance of CDL, striving to keep pace with modern warfare, which is changed into NCW. And our government has also developed the next generation high capacity CDL. In hub network, a typical communication structure of CDL, hybrid FDMA/TDMA can be considered to exchange high rate data among multiple UAVs simultaneously, within limited bandwidth. However, due to different RTT and traffic size of UAV, idle time resource and unnecessary packet transmission delay can occur. And these losses can reduce entire efficiency of hub network in long distance communication. Therefore, in this paper, we propose RTT and data traffic size based UAV scheduling, which selects time/frequency resource of UAVs by using iterative sorting algorithm. The simulation results verified that the proposed scheme improves data rate and packet delay performance in low complexity.

Model parameter identification of the Hansel-Spitttel flow stress equation by statistical regression

Kyunghoon Lee(이경훈),Woojin Song(송우진) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11

For forming simulation flow stress modeling is imperative in emulating the mechanical behavior of a material of interest. Flow stress models are typically determined by model parameter identification via least squares methods. Instead, this research tackles the same problem of model parameters identification by statistical regression. To determine the parameters of a flow stress model, this research presumes an additive noise model for experimental strain and stress measurements in a log space. Based on a probabilistic formulation, this research draws on the method of maximum likelihood to derive the parameters of a flow stress model. For illustration, we used the Hansel-Spittel flow stress equation with strain and stress measurements of AA1070 aluminum alloys. We found that the fitted Hansel-Spittel flow stress model agrees well with the strain and stress measurements.

Synthesis of iron nanoparticles with poly(1-vinylpyrrolidone-co-vinyl acetate) and its application to nitrate reduction

Lee, Nara,Choi, Kyunghoon,Uthuppu, Basil,Jakobsen, Mogens H.,Hwang, Yuhoon,Broholm, Mette M.,Lee, Woojin Techno-Press 2014 Advances in environmental research Vol.3 No.2

This study aimed to synthesize dispersed and reactive nanoscale zero-valent iron (nZVI) with poly(1-vinylpyrrolidone-co-vinyl acetate) (PVP/VA), nontoxic and biodegradable stabilizer. The nZVI used for the experiments was prepared by reduction of ferric solution in the presence of PVP/VA with specific weight ratios to iron contents. Colloidal stability was investigated based on the rate of sedimentation, hydrodynamic radius and zeta potential measurement. The characteristic time, which demonstrated dispersivity of particles resisting aggregation, increased from 21.2 min (bare nZVI) to 97.8 min with increasing amount of PVP/VA (the ratios of 2). For the most stable nZVI coated by PVP/VA, its reactivity was examined by nitrate reduction in a closed batch system. The pseudo-first-order kinetic rate constants for the nitrate reduction by the nanoparticles with PVP/VA ratios of 0 and 2 were 0.1633 and $0.1395min^{-1}$ respectively. A nitrogen mass balance, established by quantitative analysis of aqueous nitrogen species, showed that the addition of PVP/VA to nZVI can change the reduction capacity of the nanoparticles.

Propulsion System Modeling and Reduction for Conceptual Truss-Braced Wing Aircraft Design

Kyunghoon Lee,Taewoo Nam,Shinseong Kang 한국항공우주학회 2017 International Journal of Aeronautical and Space Sc Vol.18 No.4

A truss-braced wing (TBW) aircraft has recently received increasing attention due to higher aerodynamic efficiency compared to conventional cantilever wing aircraft. For conceptual TBW aircraft design, we developed a propulsion-and-airframe integrated design environment by replacing a semi-empirical turbofan engine model with a thermodynamic cycle-based one built upon the numerical propulsion system simulation (NPSS). The constructed NPSS model benefitted TBW aircraft design study, as it could handle engine installation effects influencing engine fuel efficiency. The NPSS model also contributed to broadening TBW aircraft design space, for it provided turbofan engine design variables involving a technology factor reflecting progress in propulsion technology. To effectively consolidate the NPSS propulsion model with the TBW airframe model, we devised a rapid, approximate substitute of the NPSS model by reduced-order modeling (ROM) to resolve difficulties in model integration. In addition, we formed an artificial neural network (ANN) that associates engine component attributes evaluated by object-oriented weight analysis of turbine engine (WATE++) with engine design variables to determine engine weight and size, both of which bring together the propulsion and airframe system models. Through propulsion-and-airframe design space exploration, we optimized TBW aircraft design for fuel saving and revealed that a simple engine model neglecting engine installation effects may overestimate TBW aircraft performance.

Microstructural Behavior of Nitriding Compound Layer for Nb-Carbonitride Coating Grown by Thermo-Reactive Diffusion Process

Kyunghoon Lee,강남현,Jong-Seong Bae,Chang-Woo Lee 대한금속·재료학회 2016 METALS AND MATERIALS International Vol.22 No.5

This study aims to understand the microstructural behavior of nitriding compound layer and its effect on Nb-carbonitride growth produced by the thermo-reactive diffusion (TRD) process. Gas nitriding was performed at 550 °C for 3 and 6 h, followed by TRD at 900 °C for 6 h. The nitriding compound layers had thicknesses of 10 and 16 μm for nitriding time of 3 and 6 h, respectively. The corresponding Nb-carbonitride layers produced by TRD were 7.2 and 11.2 μm thick, respectively. Reheating at 900 °C transformed the microstructure of the nitriding compounds to Fe3O4 and FeN0.0939. As reheating proceeded to 30 min, high concentration of nitrogen, initially existing in the nitride layer diffused to 80–90 μm into the substrate. Therefore, the TRD process produced NbN layer at the interfacial area due to intensively dissolved nitrogen from FeN0.0939. As the TRD proceeded, supply of C atoms from the base metal became competitive with the N diffusion. Thus, the TRD coating layer was grown to above the interface. Reheating at 900 °C for the 16-μm-thick nitride layer resulted in a nitrogen content ~0.4 at% higher than that for the 10-μm-thick nitride layer, thereby producing a thicker Nb-carbonitride layer.

A Comparative Study on Arrhenius-Type Constitutive Models with Regression Methods

Lee, Kyunghoon,Murugesan, Mohanraj,Lee, Seung-Min,Kang, Beom-Soo The Korean Society for Technology of Plasticity 2017 소성가공 : 한국소성가공학회지 Vol.26 No.1

A comparative study was performed on strain-compensated Arrhenius-type constitutive models established with two regression methods: polynomial regression and regression Kriging. For measurements at high temperatures, experimental data of 70Cr3Mo steel were adopted from previous research. An Arrhenius-type constitutive model necessitates strain compensation for material constants to account for strain effect. To associate the material constants with strain, we first evaluated them at a set of discrete strains, then capitalized on surrogate modeling to represent the material constants as a function of strain. As a result, disparate flow stress models were formed via the two different regression methods. The constructed constitutive models were examined systematically against measured flow stresses by validation methods. The predicted material constants were found to be quite accurate compared to the actual material constants. However, notable mismatches between measured and predicted flow stresses were revealed by the proposed validation techniques, which carry out validation with not the entire, but a single tensile test case.

Fatigue life of silver thin film on pet substrate under electrical current for flexible electronics applications

Kyunghoon Lee,이순복,장동원 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.12

It is important to prevent deterioration of electrical performance of flexible electronics under electro-mechanical condition. To explore the mechanism of degradation of flexible electrodes under electromechanical condition, the fatigue life of silver (Ag) thin films on polyethylene terephthalate (PET) substrates was investigated with respect to the resistance degradation induced by electrical current and the strain caused by cyclic mechanical stresses. Fatigue tests were conducted at different magnitudes of current on Ag/PET films with thicknesses. The fatigue life was analyzed at different currents, current densities, and powers. The results showed that for constant power, the fatigue life did not vary and was independent of the thickness of the silver film. Further, the current-induced degradation of fatigue life was analyzed by multi-physics analyses including electrical, thermal, and mechanical finite element analyses to observe strain localization induced by Joule heating.

Poor prognosis of hypocoagulability assessed by thrombin generation assay in disseminated intravascular coagulation

Lee, Kyunghoon,Kim, Ji-Eun,Kwon, Jihyun,Kim, Inho,Yoon, Sung-Soo,Park, Seonyang,Han, Kyou-Sup,Kim, Hyun Kyung Rapid Communications of Oxford Ltd 2014 Blood coagulation & fibrinolysis Vol.25 No.3

Overall assessment of the hemostatic system including procoagulant and anticoagulant changes may help assess the clinical status and prognosis of disseminated intravascular coagulation (DIC). The thrombin generation assay provides useful information about the global hemostatic status. Therefore, we measured several parameters of global hemostatic potential by the thrombin generation assay in patients suspected of having DIC. A total of 114 patients with suspected DIC were included. The thrombin generation assay was performed on the calibrated automated thrombogram using tissue factor with or without the addition of thrombomodulin, showing three parameters: lag time, endogenous thrombin potential (ETP), and peak thrombin. Both 1 and 5 pmol/l tissue factor-stimulated ETP and peak thrombin were well correlated with DIC severity. Interestingly, antithrombin level greatly affected ETP, whereas protein C influenced lag time. Prognostic analysis revealed that the area under the curve of peak thrombin stimulated by 1 pmol/l tissue factor was superior to that of D-dimer. Moreover, multivariate Cox analysis showed that the lag time and time to peak with both 1 and 5 pmol/l tissue factor were independent prognostic markers. ETP and peak thrombin well reflect DIC severity. Hypocoagulability manifesting as prolonged lag time and time to peak is expected to be an independent prognostic marker in DIC.

Propulsion System Modeling and Reduction for Conceptual Truss-Braced Wing Aircraft Design

Lee, Kyunghoon,Nam, Taewoo,Kang, Shinseong The Korean Society for Aeronautical and Space Scie 2017 International Journal of Aeronautical and Space Sc Vol.18 No.4

A truss-braced wing (TBW) aircraft has recently received increasing attention due to higher aerodynamic efficiency compared to conventional cantilever wing aircraft. For conceptual TBW aircraft design, we developed a propulsion-and-airframe integrated design environment by replacing a semi-empirical turbofan engine model with a thermodynamic cycle-based one built upon the numerical propulsion system simulation (NPSS). The constructed NPSS model benefitted TBW aircraft design study, as it could handle engine installation effects influencing engine fuel efficiency. The NPSS model also contributed to broadening TBW aircraft design space, for it provided turbofan engine design variables involving a technology factor reflecting progress in propulsion technology. To effectively consolidate the NPSS propulsion model with the TBW airframe model, we devised a rapid, approximate substitute of the NPSS model by reduced-order modeling (ROM) to resolve difficulties in model integration. In addition, we formed an artificial neural network (ANN) that associates engine component attributes evaluated by object-oriented weight analysis of turbine engine (WATE++) with engine design variables to determine engine weight and size, both of which bring together the propulsion and airframe system models. Through propulsion-andairframe design space exploration, we optimized TBW aircraft design for fuel saving and revealed that a simple engine model neglecting engine installation effects may overestimate TBW aircraft performance.