• 대한의용생체공학회:의공학회지
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• 제40권5호
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• pp.158-164
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• 2019

The interbody fusion cage used to replace the degenerative intervertebral disc is largely composed of titanium-based biomaterials and biopolymer materials such as PEEK. Titanium is characterized by osseointergration and biocompatibility, but it is posed that the phenomenon such as subsidence can occur due to high elastic modulus versus bone. On the other hand, PEEK can control the elastic modulus in a similar to bone, but there is a problem that the osseointegration is limited. The purpose of this study was to implement titanium material's stiffness similar to that of bone by applying cellular structure, which is able to change the stiffness. For this purpose, the cellular structure A (BD, Body Diagonal Shape) and structure B (QP, Quadral Pod Shape) with porosity of 50%, 60%, 70% were proposed and the reinforcement structure was suggested for efficient strength reinforcement and the stiffness of each model was evaluated. As a result, the stiffness was reduced by 69~93% compared with Ti6Al4V ELI material, and the stiffness most similar to cortical bone is calculated with the deviation of about 12% in the BD model with 60% porosity. In this study, the interbody fusion cage made of Ti6Al4V ELI material with stiffness similar to cortical bone was implementing by applying cellular structure. Through this, it is considered that the limitation of the metal biomaterial by the high elastic modulus may be alleviated.

• 한국추진공학회지
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• 제18권5호
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• pp.54-61
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• 2014

본 연구에서는 비정렬격자계를 사용하는 2차원 축대칭 DSMC 법을 사용하여 로켓 노즐에서 사출되는 플룸을 해석하였다. 오리피스의 출구 전압에 대한 배압의 비율이 높은 경우와 낮은 경우의 플룸에 대하여 해석을 실시하여 저고도와 고고도를 대표하는 두 가지 조건에서 플룸 유동의 차이를 관찰하였다. 저고도 플룸은 Mach disc 등 복잡한 유동 구조를 보인 반면 고고도 플룸은 단순 팽창만을 보였으며, 유동이 상류 방향으로 심하게 꺾였다. 또한 고도 20 km의 대기 조건에서 소형 로켓 노즐에서 사출되는 플룸에 대한 해석을 수행하여 연속체 해석 결과와 비교하였으며 과소팽창되는 로켓 플룸의 유동구조가 잘 나타났다. 또한, 플룸 내부에 국지적인 천이 유동이 발생할 수 있음을 확인하였다.

• 통합자연과학논문집
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• 제7권1호
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• pp.25-38
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• 2014

Amyloid-${\beta}$-peptide ($A{\beta}$) is important in the pathogenesis of Alzheimer's disease (AD). Calpain ($Ca^{2+}$-dependent protease) and caspase-8 (the initiating caspase for the extrinsic, receptor-mediated apoptosis pathway) have been implicated in $AD/A{\beta}$ toxicity. We found that $A{\beta}$ promoted degradation of calpastatin (the specific endogenous calpain inhibitor); calpastatin degradation was prevented by inhibitors of either calpain or caspase-8. The results implied a cross-talk between the two proteases and suggested that one protease was responsible for the activity of the other one. In neuron-like differentiated PC12 cells, calpain promotes active caspase-8 formation from procaspase-8 via the $A{\beta}$ and CD95 pathways, along with degradation of the procaspase-8 processing inhibitor caspase-8 (FLICE)-like inhibitory protein, short isoform (FLIPS). Inhibition of calpain (by pharmacological inhibitors and by overexpression of calpastatin) prevents the cleavage of procaspase-8 to mature, active caspase-8, and inhibits FLIPS degradation in the $A{\beta}$-treated and CD95-triggered cells. Increased cellular Ca2+ per se results in calpain activation but does not lead to caspase-8 activation or FLIPS degradation. The results suggest that procaspase-8 and FLIPS association with cell membrane receptor complexes is required for calpain-induced caspase-8 activation. The results presented here add to the understanding of the roles of calpain, caspase- 8, and CD95 pathway in $AD/A{\beta}$ toxicity. Calpain-promoted activation of caspase-8 may have implications for other types of CD95-induced cell damage, and for nonapoptotic functions of caspase-8. Inhibition of calpain may be useful for modulating certain caspase-8-dependent processes.

• 폴리머
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• 제34권4호
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• pp.352-356
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• 2010

2개의 종횡비에 의해 특징지어진 3차원 타원체를 사용하여 PP복합체의 충전제 형태와 함량이 열팽창률에 미 치는 영향에 대해 Lee와 Paul에 의해 제안된 이론적인 값과 실험적인 결과값이 비교분석되었다. 충전제의 형태는 구형에 황산바륨을, 섬유형에는 유리섬유를, 판상형에는 운모를 사용하였다. 실험의 결과로서 구형을 갖는 황산바륨 은 종횡비가 1의 값을 갖고 이론과 같이 열팽창률이 감소하였다. 유리섬유의 경우 함량증가에 따라 종횡비는 42, 37, 25, 20으로 감소하였으며 종단방향에선 열팽창률이 감소하였지만 수직방향에서는 증가하였다. 운모의 경우 그 함량증가에 따라 모두 종단방향과 횡단방향에서 감소하고 수직방향에서 증가하였다. 종횡비의 값은 각각, $\rho_\alpha$=13.5, $\rho_\beta$=1.8이었다.

• 유기물자원화
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• 제19권3호
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• pp.63-72
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• 2011

본 연구에서는 benzalkonium chloride 처리에 따라 바이오가스 생산이 억제되는 정도를 평가하였다. 바이오가스 생산 억제 수준은 10 ppm, 40 ppm, 80ppm의 benzalkonium chloride가 처리되었을 때 각각 10%, 30-40%, 70% 이상이었다. Benzalkonium chloride의 처리에 따라 저해되는 효소를 알아내기 위하여 효소 활성을 분석하였으며 산성/알칼리 포스파타아제, 프로테아제는 메탄 생산량과 음의 상관관계를 나타내었다. ${\alpha}$-글루코시다아제는 실험기간 동안 메탄 생성량과 상대적으로 낮은 음의 상관성을 보였으며(p<0.01, r=-426), 다른 효소와의 상관성도 상대적으로 낮았다. 메탄생성률(ml/day)은 benzalkonium chloride및 산성 포스파타아제와 유의한 상관성을 나타내었다. Benzalkonium chloride가 대장균에 미치는 영향을 원판확산법을 통하여 분석하였다. Benzalkonium chloride의 농도가 높을수록 세균증식 억제대가 확장되었으며, 이를 통하여 benzalkonium chloride가 초산생성균의 증식을 억제함으로써 혐기소화조에 영향을 미칠 수 있다는 것을 확인하였다.

• Tribology and Lubricants
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• 제34권6호
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• pp.217-225
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• 2018

In this study, we spray a Ni-Cr composite powder onto AISI 4340 steel using the high velocity oxygen fuel method. We subsequently subject the Ni-Cr coating (as-sprayed) to ultrasonic nanocrystal surface modification (UNSM) process to improve the tribological performance. This study aims at increasing the wear resistance and durability of the Ni-Cr coating by altering the surface integrity and microstructure via the UNSM process. The UNSM process reduces the surface roughness of the as-sprayed coating by about 64%, which is explained by observing the elimination of high peaks and valleys and filling up micro-pores. Furthermore, a change in the microstructure of the coating due to continuous high-frequency strikes to the surface by a tip can lead to an increase in hardness from about 48 to 60 HRC. Furthermore, we investigate the characterization of the friction and wear behavior of Ni-Cr coating by a ball-on-disc tribometer in the dry conditions. We determine that after the UNSM process, there is a significant reduction in the friction coefficient of the as-sprayed coating from approximately 1.1 to 0.75. This is owing to the increased hardness and smoothed surface roughness. In addition, we investigate the surface morphology and wear track of the coatings before and after the UNSM process using a scanning electron microscope, energy dispersive spectrometer, and three-dimensional laser scanning microscope. We observe that the wear track of the Ni-Cr coating after the UNSM process is lower than that of the as-sprayed one. Thus, we confirm that the UNSM process has a significant influence on the improvement of the tribological performance of the Ni-Cr composite coating.

• Journal of Acupuncture Research
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• 제36권4호
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• pp.230-237
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• 2019

Background: The purpose of this study was to investigate the clinical efficacy of Korean medicine combination treatments for recurring back pain after medical procedures. Methods: This was a retrospective study performed on 311 patients admitted to Daejoen Jaseng hospital who were diagnosed with lumbar spine herniated intervertebral discs. The patients were divided into 2 groups according to whether or not they had undergone at least one medical procedure on the lumbar spine. They were assessed with Numeric Rating Scale (NRS), Oswestry Disability Index (ODI) and EuroQol-5 Dimensions Index (EQ-5D) before and after treatment. Results: Patients who experienced a medical procedure on the lumbar spine in the prehospital phase (Group A), statistically significantly improved EQ-5D and ODI scores. The NRS scores also decreased however it was not statistically significant. Patients who had not undergone a medical procedure on the lumbar spine in the prehospital phase (Group B) had statistically significantly improved ODI and NRS scores. The average EQ-5D score decreased however, there was no statistically significant difference before and after scores in Group B. There was no statistically significant difference in variation in EQ-5D, ODI, and NRS scores before and after treatment between the groups. Conclusion: The results of this study indicated that even after a bilateral procedure and surgery, when pain in patients with lumbar spine herniated intervertebral disc did not decrease, (as in failed back surgery syndrome), Korean medicine combination treatment of postoperative pain was helpful and there was improvement in daily life.

• The Korean Journal of Pain
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• 제34권4호
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• pp.454-462
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• 2021

Background: This study was performed to reveal the relationships between the cross-sectional areas (CSAs) of the paraspinal muscles and the severity of low back pain (LBP), including the level of disability. Methods: This single-center cross-sectional study was conducted on 164 patients with chronic LBP. The effects of demographic characteristics, posture, level of physical activity, disc herniation type, and sarcopenia risk on the CSAs of paraspinal muscles were evaluated along with the relationship between the CSAs and severity of pain and disability in all patients. The CSAs of paraspinal muscles were evaluated using the software program Image J 1.53. Results: A negative significant correlation was found between age and the paraspinal muscle's CSA (P < 0.05), whereas a positive correlation was present between the level of physical activity and the CSA of the paraspinal muscle at the L2-3 and L3-4 levels. The CSAs of paraspinal muscles in patients with sarcopenia risk was significantly lower than those in patients without sarcopenia risk (P < 0.05). The CSAs of paraspinal muscles at the L2-3 and L3-4 levels in obese patients were significantly higher than those in overweight patients (P = 0.028, P = 0.026, respectively). There was no relationship between the CSAs of paraspinal muscles and pain intensity or disability. Conclusions: Although this study did not find a relationship between paraspinal CSAs and pain or disability, treatment regimens for preventing paraspinal muscles from atrophy may aid pain physicians in relieving pain, restoring function, and preventing recurrence in patients with chronic LBP.

• Journal of Korean Neurosurgical Society
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• 제64권6호
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• pp.864-872
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• 2021

Objective : The aim of our study is to investigate the cytotoxic, antioxidant, and antimicrobial effects of newly synthesized boron compounds in U87MG glioblastoma cell treatment. Methods : We synthesized boron glycine monoester (BGM) and boron glycine diester (BGD) structures containing boron atoms and determined their cytotoxic activities on glioblastoma by the MTT method. The inhibitory concentration 50 (IC₅₀) value was calculated with GraphPad Prism 5.0 program. The IC₅₀ values were administered 48 hours on U87MG glioblastoma cell. Catalase (CAT), acid phosphatase (ACP) and alkaline phosphatase (ALP) enzyme activity, malondialdehyde (MDA), total glutathione (GSH), and total protein levels were detected using spectrophotometric methods. We determined the antimicrobial activities of BGM and BGD with the disc diffusion method. Results : After 48 hours of BGM and BGD application to U87MG glioblastoma cells, we found the IC₅₀ value as 6.6 mM and 26 mM, respectively. CAT and ACP enzyme activities were decreased in BGM and BGD groups. MDA which is a metabolite of lipid peroxidation was increased in both boron compounds groups. GSH level was reduced especially in BGD group. BGM and BGD have been found to be antimicrobial effects. Conclusion : Boron compounds, especially the BGM, can provide a new therapeutic approach for the treatment of glioblastoma with their anticancer, antioxidant, and antimicrobial effects.

• Journal of Korean Neurosurgical Society
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• 제64권3호
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• pp.447-459
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• 2021

Objective : Oblique lateral interbody fusion (OLIF) is becoming the preferred treatment for degenerative lumbar diseases. As beginners, we performed 143 surgeries over 19 months. In these consecutive cases, we analyzed the learning curve and reviewed the complications in our experience. Methods : This was a retrospective study; however, complications that were well known in the previous literature were strictly recorded prospectively. We followed up the changes in estimated blood loss (EBL), operation time, and transient psoas paresis according to case accumulation to analyze the learning curve. Results : Complication-free patients accounted for 43.6% (12.9%, early stage 70 patients and 74.3%, late stage 70 patients). The most common complication was transient psoas paresis (n=52). Most of these complications occurred in the early stages of learning. C-reactive protein normalization was delayed in seven patients (4.89%). The operation time showed a decreasing trend with the cases; however, EBL did not show any significant change. Notable operation-induced complications were cage malposition, vertebral body fracture, injury to the ureter, and injury to the lumbar vein. Conclusion : According to the learning curve, the operation time and psoas paresis decreased. It is important to select an appropriately sized cage along with clear dissection of the anterior border of the psoas muscle to prevent OLIF-specific complications.