• The Korean Journal of Physiology
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• v.25 no.2
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• pp.211-221
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• 1991

Although the existence of nerve cells which determine the activity of sympathetic nervous system in ventrolateral medulla is advocated recently, there are wide varieties on the location and function of them according to authors. Present study aimed to identify and characterize the medullospinal tract cells in rostral and caudal medulla of cats .which branch to the lateral horn of the upper thoracic spinal cord. Cats were anesthetized with ${\alpha}-chloralose$. The upper thoracic spinal cord and floor of the IVth ventricle were exposed. Medullospinal tract cells in rostral and caudal medulla were identified by anti-dromic stimulation of the intermediolateral nucleus in the upper thoracic cord and then the location and physiological characteristics of these cells were studied. A total of seventy cells in medulla had constant latency and responded to high frequency stimulation to thoracic cord. Among them fifty-six cells were identified as medullospinal tract cells either by collision with spontaneous activities or activities evoked by sciatic nerve stimulation(27/56), or by determining the refractory period (29/56). Thirty-one of these cells branched to the contralateral thoracic spinal cord, twenty-one cells to the ipsilateral side and remaining four cells branched to both sides. The conduction velocity of cells branching to the contralateral side was $29{\pm}2.9\;m/sec$ and that of cells to the ipsilateral side was $39.1{\pm}6.0\;m/sec$. When medulla was devided into two by a horizontal plane at 3 mm rostral to the obex, fifty-one among seventy cells were in the rostral medulla and nineteen were in the caudal medulla. The conduction velocities of these two groups were $21.6{\pm}1.0\;and\;33.3{\pm}3.9\;m/sec$, respectively. In this study, we confirmed the existence of two groups of medullospinal tract cells in rostral and caudal ventrolateral medulla, which branch to the lateral horn of thoracic cord and these cells have relatively few spontaneous activities and rapid conduction velocity, so we concluded that these cells are different from the previously known sympatho-related cells in ventrolateral medulla.

• Journal of Korean Neurosurgical Society
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• v.42 no.3
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• pp.159-167
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• 2007

Vestibular schwannoma (VS) is a benign tumor typically originated in the schwann cell of vestibular nerve and usually accompany hearing symptom. Microsurgical removal and radiosurgery have a great role for the treatment of VS. Recently radiosurgery has been considered as an alternative or primary treatment for VS with the tremendous increase of patients who were treated with gamma knife radiosurgery (GKS) though microsurgery still takes the premier. By many published results, it is proved that GKS is a effective and noninvasive technique for VS, especially small sized tumors with satisfactory tumor control rate. The authors assumed that GKS can be expected to achieve satisfactory tumor control rate for small VS under 5cc in volume. A major interest regarding radiosurgery nowadays is to determine the optimal radiation dose for hearing preservation to improve the quality of life of patients. The more high radiation dose are used for effective tumor growth control, the more radiation-related complications like as hearing deficit, the impairment of other cranial nerve function are increased. Since 1990's the mean radiation dose for tumor margin was more than 18 Gy, but there were high complication rate in spite of good tumor growth control. After the year of 2000, under the influence of advanced neuro-imaging techniques and radiosurgical planning system which enable clinicians to do more precise planning, marginal dose for VS has been decreased to 12-13 Gy and the radiation-related complications has been reduced. But because there may be a unexpected radiation induced complications as time goes by after the latency period, optimal radiation dose for VS should be established on the basis of more long term follow-up observation.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.26 no.3
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• pp.238-244
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• 2000

The present study was aimed to investigate the effect of osseointegration according to implant placement timing in the distracted alveolar bone using intraoral distraction device. Six adult mongrel dogs of either sex, weighing about 15kg, were used. The animals were divided into 4-week and 8-week groups according to the timing of implant installation. The left upper and lower premolars and first molars were extracted and an alveoloplasty was performed to simulate an atrophic ridge. After 12 weeks of healing, a segmental osteotomy was made and an intraoral distraction device which was designed for augmentation of vertical height of the edentulous ridge was applied. Latency period was allowed for 5 days and then distraction was made at a rate of 1.2mm/day for 8 days. Four or eight weeks after distraction, implants were installed. Twelve weeks after implant installation, the animals were sacrificed. Macroscopic, radiographic, and histologic examinations of distracted alveolar ridge were performed. No significant abnormalities such as infection and dehiscence of overlying soft tissue were observed. Radiographically, there was slight bone resorption around the medial and distal edges of the alveolar bone segment, and a new bone deposition was observed in the neighboring alveolar crest area in the both groups. The satisfactory osseointegration was achieved in the distracted gap of the both groups, but fibrous tissue appeared on the buccal side of implant in the distracted gap in 4-week group. These results suggest that proper timing of implant installation is 8 weeks rather than 4 weeks after distraction when dental implant is to be placed onto the distracted bone.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.26 no.6
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• pp.620-627
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• 2000

The purpose of this study is to investigate the clinical and histologic changes in distraction osteogenesis according to different distraction rates in the rat's tibia. Eighteen adult rats underwent open osteotomy and attachment of an external unilateral distraction device in the middle of left tibia. Latency was allowed for 7 days before distracton began. The distraction device was activated with varying distraction rates of 0.5mm, 1mm, 2mm and same rhythm of twice a day until 5mm length gain was achieved. The animals were sacrificed at post-distraction 4, 8 weeks to observe the bony healing states. At each group, clinical, radiographic and histologic studies were done. The results obtained from this study were as follows: 1. The 0.5mm group showed excellent osteogenesis than other groups. The new bone was formed by intramembranous bone formation mostly and endochondral bone formation partly. 2. The 1mm group showed delayed osteogenesis and incomplete bony healing at 8 weeks. 3. The 2mm group showed weak osteogenesis and fibrous union or nonunion at 8 weeks. From these results, it could be stated that distraction rate of 0.5mm per day was most useful in rat's tibia. The rate of 1mm showed delayed bony healing and needed more consolidation period. Distraction osteogenesis is a excellent clinical method for regenerating local bone deficiencies in limbs and craniofacial area. The more studies needed for the higher animals and human about distraction rates and other biomechanical factors on the basis of this study.

• The KIPS Transactions:PartA
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• v.9A no.2
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• pp.197-206
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• 2002

Many researchers have been interested in the optimization of parallel programs through the latency hiding by overlapping the communication with the computation. We ana1yzed overlapping effects in the circular shift communication which is one of the collective communications being frequently used In many data parallel programs. We measured the time which can be possibly overlapped and the time which cannot be overlapped in over all circular shift communication period on an Ethernet switch-based clustered system. The result from each platform nay be used for the input of optimizing compilers. The previous performance models usually have two kinds of drawbacks one is only based on point-to-point communication, so it is not appropriate for analyzing the overall effects of collective communications. The other provides the performance of collective communication, but no overlapping effect. In this paper we extended the previous models and analyzed the experimental results of the extended model.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.6A
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• pp.506-514
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• 2009

To minimize energy consumption, most of MAC Protocols in WSNs exploit low duty cycling. Among those, RMAC [4] allows a node to transmit a data packet for multiple hops in a single duty cycle, which is made possible by exploiting a control frame named Pioneer (PION) in setting up the path. In this paper, we present a MAC Protocol called Hop Extended MAC (HE-MAC) that transmits the data packet for more multiple hops in a single duty cycle. It employs an EXP (Explorer) frame to set up the multiple hop transmission, which contains the information of the maximum hop that a packet can be transmitted. With the use of the information in EXP and an internal state of Ready to Receive (RTR), HEMAC extends the relay of the packet beyond the termination of the data period by two more hops compared to RMAC. Along with our proposed adaptive sleeping method, it also reduces power consumption and handles heavy traffic efficiently without experiencing packet inversion observed in RMAC. We analytically obtain the packet delivery latency in HE-MAC and evaluate the performance through ns-2 simulations. Compared to RMAC, HE-MAC achieves 14% less power consumption and 20% less packet delay on average for a random topology of 300 nodes.

• Journal of Oriental Neuropsychiatry
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• v.29 no.3
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• pp.121-134
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• 2018

Objectives: The purpose of this in vivo study is to observe anti-amnesic effects of Yeongkyekamjotanggayonggolmoryo (YGYM), a novel mixed herbal prescription, Ossis Mastodi and Ostreae Testa added Yeongkyekamjo-tang, on scopolamine induced amnesia in C57BL/6 mice through acetylcholine (ACh) and acetylcholinesterase (AChE) activity, Choline acetyltransferase (ChAT) mRNA expression, and antioxidant effects. Methods: Six groups, total 20 intact or 100 Sco treated mice were used in this study after one week of acclimatization period. Half the animals were used for passive avoidance task tests and hippocampus ACh content, AChE activity, and ChAT mRNA expression were measured. The other half was subjected to an underwater maze test and then the cerebral cortex antioxidant defense system was measured. Results: In the passive avoidance experiment, there was significant decrease in residence time in the bright room and in the underwater maze test, escape latency to escape from the esophagus significantly increased compared with the normal control group. At the final sacrifice, ACh content and ChAT mRNA expression decreased, AChE activity increased, and cerebral cortical MDA increased GSH content, SOD and CAT activity in Sco control mice, as compared to intact vehicle control mice. However, these Sco treatment-related memory loss through AChE activation destroyed the cerebral cortex antioxidant defense system, and was inhibited dose-dependently by 28 days consecutive oral pretreatments of YGYM extracts 500, 250, 125 mg/kg. Conclusions: In the above results, YGYM extract that oral administration of YGYM extracts alleviates the antioxidant defense system, through preservation of ACh mediated by upregulation of ChAT mRNA expression, and increase of AChE inhibition and brain antioxidant defense systems.

• Journal of Korean Neurosurgical Society
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• v.37 no.1
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• pp.8-15
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• 2005

Objective: We evaluate temporal correlations between postoperative symptomatic and electrophysiological improvements, and assessed the recovery time required for patients with carpal tunnel syndrome(CTS) before returning to routine activities. Methods: 30 CTS patients were treated via the endoscopic monoportal approach, from March 2001 to September 2003. We assessed the symptoms (hyperesthesia in the finger tips, or abnormal sensations and painful numbness or night pain) and electrophysiological changes in the preoperative state, 1 month and 6 months after surgery. We marked the times at which patients became able to return to activities of daily living and work, after undergoing endoscopic carpal tunnel release. Results: At the end of the follow-up period, high levels of achievement and good outcomes were observed, with respect to both the symptoms and electrophysiological studies. We discovered significant differences between the preoperative and postoperative periods, especially in terms of motor nerve onset latency from $4.50{\pm}1.43$ to $3.97{\pm}0.69$ and sensory nerve conduction velocity, the wrist-to-finger from $19.81{\pm}10.03$ to $28.18{\pm}11.01$ and wrist-to-palm from $23.34{\pm}13.40$ to $31.79{\pm}13.38$(P<0.05 for each comparison). The average time interval required before return to activities of daily living was 26.4 days, and time interval required before return to work was 48.08 days. Conclusion: Electrophysiological improvements are largely consistent with symptomatic relief, but there is some disparity between electrophysiological and symptomatic improvement.

• Journal of Korean Neurosurgical Society
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• v.63 no.4
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• pp.415-426
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• 2020

Arteriovenous malformations (AVMs) are congenital anomalies of the cerebrovascular system. AVM harbors 2.2% annual hemorrhage risk in unruptured cases and 4.5% annual hemorrhage risk of previously ruptured cases. Stereotactic radiosurgery (SRS) have been shown excellent treatment outcomes for patients with small- to moderated sized AVM which can be achieved in 80-90% complete obliteration rate with a 2-3 years latency period. The most important factors are associated with obliteration after SRS is the radiation dose to the AVM. In our institutional clinical practice, now 22 Gy (50% isodose line) dose of radiation has been used for treatment of cerebral AVM in single-session radiosurgery. However, dose-volume relationship can be unfavorable for large AVMs when treated in a single-session radiosurgery, resulting high complication rates for effective dose. Thus, various strategies should be considered to treat large AVM. The role of pre-SRS embolization is permanent volume reduction of the nidus and treat high-risk lesion such as AVM-related aneurysm and high-flow arteriovenous shunt. Various staging technique of radiosurgery including volume-staged radiosurgery, hypofractionated radiotherapy and dose-staged radiosurgery are possible option for large AVM. The incidence of post-radiosurgery complication is varied, the incidence rate of radiological post-radiosurgical complication has been reported 30-40% and symptomatic complication rate was reported from 8.1% to 11.8%. In the future, novel therapy which incorporate endovascular treatment using liquid embolic material and new radiosurgical technique such as gene or cytokine-targeted radio-sensitization should be needed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.11B
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• pp.968-980
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• 2008

Providing handover with guaranteed QoS for real-time multimedia service such as VoIP, video/audio streaming, and video conferencing in wireless LAN is a challenging task. In this paper, we present efficient layer 2 handover mechanism in wireless LAN, which can provide fast handover with guaranteed QoS for real-time multimedia service. To this end, the scanning period and the number of channels per scanning for handover are dynamically adapted to the type of applications and wireless networking environment, so that both the degradation of application service quality and signaling overhead are minimized simultaneously. The performance of the proposed mechanism is verified by the simulation. The simulation results show that the proposed mechanism guarantess QoS of each multimedia application with minimal power consumption.