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다중 전극 시스템을 사용한 PHMR 센서의 구동 전류 및 측정 방향에 따른 특성 분석
전창엽,임병화,김철기 한국자기학회 2023 韓國磁氣學會誌 Vol.33 No.2
This study investigated the offset voltage and phase shift of characteristic curves caused by current injection direction and voltage measurement direction in a planar Hall magnetoresistance sensor with a NiFe/IrMn bilayer structure. Using analytical methods, we separated the sensor signals to distinguish the offset voltage unrelated to the magnetic field and the offset voltage caused by the phase shift of magnetoresistance. We then analyzed the ratio of AMR signals and PHMR signals caused by phase shifts and changes in the sensitivity of the magnetic sensor. Under certain conditions, the current injection direction and voltage measurement direction increased the output voltage and exhibited high sensitivity. These results are expected to contribute to optimizing sensor design and fabrication processes and improving sensor performance.
Rise of the Visible Monkey: Sectioned Images of Rhesus Monkey
정범선,전창엽,허재원,정강진,하동환,곽규성,박진서 대한의학회 2019 Journal of Korean medical science Vol.34 No.8
Background: Gross anatomy and sectional anatomy of a monkey should be known by students and researchers of veterinary medicine and medical research. However, materials to learn the anatomy of a monkey are scarce. Thus, the objective of this study was to produce a Visible Monkey data set containing cross sectional images, computed tomographs (CTs), and magnetic resonance images (MRIs) of a monkey whole body. Methods: Before and after sacrifice, a female rhesus monkey was used for 3 Tesla MRI and CT scanning. The monkey was frozen and sectioned at 0.05 mm intervals for the head region and at 0.5 mm intervals for the rest of the body using a cryomacrotome. Each sectioned surface was photographed using a digital camera to obtain horizontal sectioned images. Segmentation of sectioned images was performed to elaborate three-dimensional (3D) models of the skin and brain. Results: A total of 1,612 horizontal sectioned images of the head and 1,355 images of the remaining region were obtained. The small pixel size (0.024 mm × 0.024 mm) and real color (48 bits color) of these images enabled observations of minute structures. Conclusion: Due to small intervals of these images, continuous structures could be traced completely. Moreover, 3D models of the skin and brain could be used for virtual dissections. Sectioned images of this study will enhance the understanding of monkey anatomy and foster further studies. These images will be provided to any requesting researcher free of charge
박정형,원진영,전창엽,임경섭,최원석,박성현,서진철,조지연,성중배,여현구,김근우,김유경,김민지,이경식,이영전 한국뇌신경과학회 2022 Experimental Neurobiology Vol.31 No.6
Till date, researchers have been developing animal models of Alzheimer’s disease (AD) in various species to understand the pathological charac- terization and molecular mechanistic pathways associated with this condition in humans to identify potential therapeutic treatments. A widely recognized AD model that mimics the pathology of human AD involves the intracerebroventricular (ICV) injection with streptozotocin (STZ). However, ICV injection as an invasive approach has several limitations related to complicated surgical procedures. Therefore, in the present study, we created a customized stereotaxic frame using the XperCT-guided system for injecting STZ in cynomolgus monkeys, aiming to establish an AD model. The anatomical structures surrounding the cisterna magna (CM) were confirmed using CT/MRI fusion images of monkey brain with XperCT, the c-arm cone beam computed tomography. XperCT was used to determine the appropriate direction in which the needle tip should be inserted within the CM region. Cerebrospinal fluid (CSF) was collected to confirm the accurate target site when STZ was injected into the CM. Cynomolgus monkeys were administered STZ dissolved in artificial CSF once every week for 4 weeks via intracisterna magna (ICM) injection us- ing XperCT-guided stereotactic system. The molecular mechanisms underlying the progression of STZ-induced AD pathology were analyzed two weeks after the final injection. The monkeys subjected to XperCT-based STZ injection via the ICM route showed features of AD pathology, includ- ing markedly enhanced neuronal loss, synaptic impairment, and tau phosphorylation in the hippocampus. These findings suggest a new approach for the construction of neurodegenerative disease models and development of therapeutic strategies.
한문기,차주홍,이호준,장철종,전창엽 대한전기학회 2017 Journal of Electrical Engineering & Technology Vol.12 No.5
In order to give hydrophobic surface properties on carbon steel, the fluorinated amorphous carbon films were prepared by using linear 2.45GHz microwave PECVD device. Two different process approaches have been tested. One is direct deposition of a-C:H:F films using admixture of Ar/CH4/CF4 working gases and the other is surface treatment using CF4 plasma after deposition of a- C:H film with Ar/CH4 binary gas system. Ar/CF4 plasma treated surface with high CF4 gas ratio shows best hydrophobicity and durability of hydrophobicity. Nanometer scale surface roughness seems one of the most important factors for hydrophobicity within our experimental conditions. The properties of a- C:H:F films and CF4 plasma treated a-C:H films were investigated in terms of surface roughness, hardness, microstructure, chemical bonding, atomic bonding structure between carbon and fluorine, adhesion and water contact angle by using atomic force microscopy (AFM), nano-indentation, Raman analysis and X-ray photoelectron spectroscopy (XPS).
Assessment of Hand Motor Function in a Non-human Primate Model of Ischemic Stroke
원진영,이경식,최치훈,전창엽,서진철,김건우,여현구,박정형,김유경,진영배,구본상,임경섭,이상일,김기진,최원석,박성현,김영현,허재원,이상래,차상훈,이영전 한국뇌신경과학회 2020 Experimental Neurobiology Vol.29 No.4
Ischemic stroke results from arterial occlusion and can cause irreversible brain injury. A non-human primate (NHP) model of ischemic stroke was previously developed to investigate its pathophysiology and for efficacy testing of therapeutic candidates; however, fine motor impairment remains to be well-characterized. We evaluated hand motor function in a cynomolgus monkey model of ischemic stroke. Endovascular transient middle cerebral artery occlusion (MCAO) with an angiographic microcatheter induced cerebral infarction.In vivo magnetic resonance imaging mapped and measured the ischemia-induced infarct lesion.In vivo diffusion tensor imaging (DTI) of the stroke lesion to assess the neuroplastic changes and fiber tractography demonstrated three-dimensional patterns in the corticospinal tract 12 weeks after MCAO. The hand dexterity task (HDT) was used to evaluate fine motor movement of upper extremity digits. The HDT was modified for a home cage-based training system, instead of conventional chair restraint training. The lesion was localized in the middle cerebral artery territory, including the sensorimotor cortex. Maximum infarct volume was exhibited over the first week after MCAO, which progressively inhibited ischemic core expansion, manifested by enhanced functional recovery of the affected hand over 12 weeks after MCAO. The total performance time decreased with increasing success rate for both hands on the HDT. Compensatory strategies and retrieval failure improved in the chronic phase after stroke. Our findings demonstrate the recov- ery of fine motor skill after stroke, and outline the behavioral characteristics and features of functional disorder of NHP stroke model, providing a basis for assessing hand motor function after stroke.
여현구,홍정주,이영전,이경식,전창엽,박정형,원진영,서진철,안유진,김건우,백승호,황은하,김그린,진영배,정강진,구본상,강필용,임경섭,김선욱,허재원,김영현,손영훈,김지수,최치훈,차상훈,이상래 한국뇌신경과학회 2019 Experimental Neurobiology Vol.28 No.4
The function of microglia/macrophages after ischemic stroke is poorly understood. This study examines the role of microglia/macrophages in the focal infarct area after transient middle cerebral artery occlusion (MCAO) in rhesus monkeys. We measured infarct volume and neurological function by magnetic resonance imaging (MRI) and non-human primate stroke scale (NHPSS), respectively, to assess temporal changes following MCAO. Activated phagocytic microglia/macrophages were examined by immunohistochemistry in post-mortem brains (n=6 MCAO, n=2 controls) at 3 and 24 hours (acute stage), 2 and 4 weeks (subacute stage), and 4, and 20 months (chronic stage) following MCAO. We found that the infarct volume progressively decreased between 1 and 4 weeks following MCAO, in parallel with the neurological recovery. Greater presence of cluster of differentiation 68 (CD68)-expressing microglia/macrophages was detected in the infarct lesion in the subacute and chronic stage, compared to the acute stage. Surprisingly, 98~99% of transforming growth factor beta (TGFβ) was found co-localized with CD68-expressing cells. CD68-expressing microglia/macrophages, rather than CD206+ cells, may exert anti-inflammatory effects by secreting TGFβ after the subacute stage of ischemic stroke. CD68+ microglia/macrophages can therefore be used as a potential therapeutic target.
황두섭,이정훈,이준오,전창엽,임유봉,장철종,장우석 한국정밀공학회 2012 International Journal of Precision Engineering and Vol. No.
For the mass production of silicon thin film solar cell, it is a key issue to increase deposition rate of microcrystalline silicon film on a large area substrate. One of the most effective methods to increase deposition rate of the film is using high frequency and high power plasma. However, high frequency plasma leads to plasma non uniformity in large area deposition, and high power plasma induces substrate heating during deposition of microcrystalline silicon film and degrades the film quality. In this study, we developed a shaped electrode for spatially uniform plasma and a susceptor cooling system for preventing substrate heating by plasma. And also we investigated the influences of deposition parameters on the microcrystalline silicon single junction cell efficiency with high frequency and high power plasma. Glass substrate was 1.1 m × 1.3 m and plasma excitation frequency was 40 MHz. Capacitively coupled parallel plates RF reactor with concave shaped electrode was used. For the high deposition rate of the microcrystalline films, plasma powers of 0.8~1.1W/cm2 were used. The highest deposition rate of microcrystalline silicon was 2nm/s. The increases of temperature of susceptor were monitored by two thermocouples which were installed at center and outer side of the susceptor. The temperature increases were suppressed to almost zero with liquid cooling systems. Multiple step deposition was performed which means the higher H2/SiH2 ratio at the initial stage of film growth was used and the ratio gradually decreased during deposition in order to eliminate the amorphous layer at the interface between substrate and film. We also achieved microcrystalline single junction cell efficiencies above 6% on large area substrate at high deposition rate of 1.5nm/s.
안유진,서진철,박정형,원진영,여현구,김건우,전창엽,허재원,이상래,이동석,이영전 한국실험동물학회 2020 Laboratory Animal Research Vol.36 No.2
To date, researchers have developed various animal models of Alzheimer’s disease (AD) to investigate its mechanisms and to identify potential therapeutic treatments. A widely recognized model that mimics the pathology of human sporadic AD involves intracerebroventricular (ICV) injection with streptozotocin (STZ). However, ICV injections are an invasive approach, which creates limitations in generalizing the results. In this study, we produced a rodent model of AD using STZ (3 mg/kg) injection via the cisterna magna (CM) once every week for 4 weeks, and analyzed at 4 weeks and 16 weeks after final injection. In the CM-STZ rodent model of AD, we observed increase in extracellular amyloid-beta (Aβ) deposition and decrease and abnormal morphology of post-synaptic protein, PSD95 in 16 weeks STZ-injected group. The model developed using our less-invasive method induced features of AD-like pathology, including significantly increased extracellular amyloid-beta deposition, and decreased synaptic protein in the hippocampus. These findings supporting the success of this alternative approach, and thus, we suggest this is a promising, less invasive model for use in future AD research.