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Lee, Sukjun,Lim, Donghyun,Lee, Eunyoung,Lee, Nakyung,Lee, Hong-gun,Cechetto, Jonathan,Liuzzi, Michel,Freitas-Junior, Lucio H.,Song, Jin Sook,Bae, Myung Ae,Oh, Sangmi,Ayong, Lawrence,Park, Seung Bum American Chemical Society 2014 Journal of medicinal chemistry Vol.57 No.17
<P>New antimalarial agents that exhibit multistage activities against drug-resistant strains of malaria parasites represent good starting points for developing next-generation antimalarial therapies. To facilitate the progression of such agents into the development phase, we developed an image-based parasitological screening method for defining drug effects on different asexual life cycle stages of <I>Plasmodium falciparum</I>. High-throughput screening of a newly assembled diversity-oriented synthetic library using this approach led to the identification of carbohybrid-based 2-aminopyrimidine compounds with fast-acting growth inhibitory activities against three laboratory strains of multidrug-resistant <I>P. falciparum</I>. Our structure–activity relationship study led to the identification of two derivatives (<B>8aA</B> and <B>11aA</B>) as the most promising antimalarial candidates (mean EC<SUB>50</SUB> of 0.130 and 0.096 μM against all three <I>P. falciparum</I> strains, selectivity indices >600, microsomal stabilities >80%, and mouse malaria ED<SUB>50</SUB> values of 0.32 and 0.12 mg/kg/day, respectively), targeting all major blood stages of multidrug-resistant <I>P. falciparum</I> parasites.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jmcmar/2014/jmcmar.2014.57.issue-17/jm5009693/production/images/medium/jm-2014-009693_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jm5009693'>ACS Electronic Supporting Info</A></P>
Relationship between subjective pain scale and muscle recruitment patterns of low back
Nakyung Lee,Gwanseob Shin 대한인간공학회 2014 대한인간공학회 학술대회논문집 Vol.2014 No.11
Objective: The main objective of this study was to investigate the relationship between self-reported back pain severity and muscle recruitment patterns while conducting common physical exercises. Background: Non-specific low back pain has been one of major concerns in various occupational environments. Reliable and quantitative assessment of the severity of non-specific low back pain is important in injury prevention as well as rehabilitation of injured individuals. While self-reported questionnaires such as the Oswestry Low Back Disability questionnaire have been frequently used to assess the severity of non-specific low back pain, no quantitative and objective assessment tool or system has yet been developed. Method: Twenty seven participants who had low back pain symptoms were grouped into three groups by their Oswestry disability score (less than 22; 23-30; greater than 30), and participated in a laboratory experiment. Myoelectric signals (EMG) of the lumbar erector spinae muscles and abdominal muscles were collected from each participant during common physical exercises, including walking, plank, bird-dog, and isometric back extension. Mean amplitude of each muscle, bilateral difference between left and right side muscles, and co-contraction ratio between abdominal and low back muscles were compared between the three Oswestry score groups. Results: Significant differences between score groups were observed only from the bird-dog exercise. Greater bilateral difference of the L2 lumbar erector spinae muscles and smaller bilateral difference of the recturs abdominal muscles were observed from groups with higher Oswestry scores. Conclusion: Severity of non-specific low back pain could be quantitatively assessed from the evaluation of muscle recruitment patterns in non-symmetric exercises such as bird-dog. Application: Results of this pioneering study could be used to develop reliable and easyto-use low back health monitoring systems.
Assessment of low back muscle fatigue during normal gait
Nakyung Lee,Seobin Choi,Gwanseob Shin 대한인간공학회 2015 대한인간공학회 학술대회논문집 Vol.2015 No.10
Development of low back muscle fatigue has been evaluated by analyzing electromyography (EMG) measured during isometric back extension exercises which cannot be easily administered in non-laboratory settings. The objective of this study was to explore whether the changes in muscle activation pattern induced by muscle fatigue could be identified during normal walking, which can be easily done in daily life. Nineteen subjects participated in an experiment and conducted normal walking trials on a treadmill with a fatigue generating Biering-Sorensen test in between. Eight EMG sensors were bilaterally attached to back and abdominal muscles. Muscle activation levels and integrated EMG of the walking trials were compared between before and after the fatigue development. In result, it was found that the EMG amplitudes and the integrated EMG of the lumbar erector spinae muscles were increased significantly after the fatigue development. Results of this study suggest that muscle fatigue development could be monitored in a daily activity and it may lead to the development of wearable health monitoring systems with surface EMG sensors.
Use of antagonist muscle EMG in the assessment of neuromuscular health of the low back
Nakyung Lee,Gwanseob Shin,Hwayeong Kang 대한인간공학회 2014 대한인간공학회 학술대회논문집 Vol.2014 No.5
Surface electromyography (SEMG) has been frequently used in ergonomics and kinesiology research to assess the amount of physical efforts of skeletal muscles and resultant biomechanical stresses on body joints. The use of surface EMG as a diagnostic method in non-laboratory settings, however, has been limited due to its sensitivity to noises and difficulty in detecting signals from deep muscles. The objective of this study was to determine EMG variables and data collection methods that could identify changes in the spinal stability after pain-free 10-min static stooping. Twenty two subjects conducted simple physical tasks before and immediately after 10-min stooping, and their EMG variables were compared between pre- and post-stooping. In results, mean normalized amplitude of agonist muscles did not vary significantly after stooping, but the amplitude of antagonist muscles decreased after stooping. Decrements in the antagonist muscle activity were significant for flank and isometric back extension exercises (p<0.05). Findings of this study suggest the possibility of using surface EMG in the evaluation of spinal stability and low back health status in simple exercise postures. Changes in the amplitude of antagonist muscles may be indicative of changes in the spinal stability, and the sensitivity of the indicator can be improved, if measured in flank or back extension exercises where required moment to maintain a posture is primarily generated from the agonist muscles.
Use of Antagonist Muscle EMG in the Assessment of Neuromuscular Health of the Low Back
( Nakyung Lee ),( Gwanseob Shin ),( Hwayeong Kang ) 한국감성과학회 2014 춘계학술대회 Vol.2014 No.-
Surface electromyography (SEMG) has been frequently used in ergonomics and kinesiology research to assess the amount of physical efforts of skeletal muscles and resultant biomechanical stresses on body joints. The use of surface EMG as a diagnostic method in non-laboratory settings, however, has been limited due to its sensitivity to noises and difficulty in detecting signals from deep muscles. The objective of this study was to determine EMG variables and data collection methods that could identify changes in the spinal stability after pain-free 10-min static stooping. Twenty two subjects conducted simple physical tasks before and immediately after 10-min stooping, and their EMG variables were compared between pre- and post-stooping. In results, mean normalized amplitude of agonist muscles did not vary significantly after stooping, but the amplitude of antagonist muscles decreased after stooping.
Joint Localization and Velocity Estimation for Pulse Radar in the Nearfield Environments
Lee Nakyung,Hyunwoo Park,Daesung Park,Bukeun Byeon,Sunwoo Kim 사단법인 항법시스템학회 2023 Journal of Positioning, Navigation, and Timing Vol.12 No.3
In this paper, we propose an algorithm that jointly estimates the location and velocity of a near-field moving target in a pulse radar system. The proposed algorithm estimates the location and velocity corresponding to the outcome of orthogonal matching pursuit (OMP) in a 4-dimensional (4D) location-velocity space. To address the high computational complexity of 4D parameter joint estimation, we propose an algorithm that iteratively estimates the target’s 2D location and velocity sequentially. Through simulations, we analyze the estimation performance and verify the computational efficiency of the proposed algorithm.