• 접착 및 계면
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• 제20권2호
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• pp.53-60
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• 2019

여러 종류의 용매와 상용화되어 있는 비공유결합성 분산제들을 이용하여 안정한 그래핀 분산액을 제조 하였다. 분산액은 3시간의 초음파 처리를 통하여 제조 되었으며, NMP 용매에서는 Tween 계열과 Span 계열과 Pluronic 계열의 분산제가 안정한 그래핀 분산액을 형성하였다. 또한 에탄올 용매에서는 질소를 포함한 분산제 종류가 안정한 분산액을 형성하였으며, 물과 dichloromethane에서는 모든 분산제에 대하여 대체로 불안정하였지만 poly(4-vinyl pyridine)과 sodium dodecyl sulfonate를 사용한 경우 일부 안정한 분산액을 형성 하였다. 또한 Poly(4-vinyl pyridine), poly(vinyl pyrrolidone), poly(2-(dimethylamino)ethyl methacrylate)를 이용하여 더 큰 용량의 그래핀 분산액을 제조하였다. 본 연구는 그래핀의 분산을 위한 여러 용매 및 분산제에 대한 기준을 제공할 수 있을 것으로 기대된다.

• Journal of Korean Neurosurgical Society
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• 제62권6호
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• pp.712-722
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• 2019

Objective : Although magnetic resonance guided focused ultrasound (MRgFUS) has been used as minimally invasive and effective neurosurgical treatment, it exhibits some limitations, mainly related to acoustic properties of the skull barrier. This study was undertaken to identify skull characteristics that contribute to optimal ultrasonic energy transmission for MRgFUS procedures. Methods : For ex vivo skull experiments, various acoustic fields were measured under different conditions, using five non-embalmed cadaver skulls. For clinical skull analyses, brain computed tomography data of 46 patients who underwent MRgFUS ablations (18 unilateral thalamotomy, nine unilateral pallidotomy, and 19 bilateral capsulotomy) were retrospectively reviewed. Patients' skull factors and sonication parameters were comparatively analyzed with respect to the cadaveric skulls. Results : Skull experiments identified three important factors related skull penetration of ultrasound, including skull density ratio (SDR), skull volume, and incidence angle of the acoustic rays against the skull surface. In clinical results, SDR and skull volume correlated with maximal temperature (Tmax) and energy requirement to achieve Tmax (p<0.05). In addition, considering the incidence angle determined by brain target location, less energy was required to reach Tmax in the central, rather than lateral targets particularly when compared between thalamotomy and capsulotomy (p<0.05). Conclusion : This study reconfirmed previously identified skull factors, including SDR and skull volume, for successful MRgFUS; it identified an additional factor, incidence angle of acoustic rays against the skull surface. To guarantee successful transcranial MRgFUS treatment without suffering these various skull issues, further technical improvements are required.

• 한국축산식품학회지
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• 제39권2호
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• pp.309-323
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• 2019

Fish oil consists of omega-3 fatty acids which play an important role in human health. Its susceptibility to oxidation causes considerable degradation during the processing and storage of food products. Accordingly, encapsulation of this ingredient through freeze drying was studied with the aim of protecting it against environmental conditions. Gum arabic (GA) was used as the wall material for fish oil nanoencapsulation where tween 80 was applied as the emulsifier. A water-in-oil (W/O) emulsion was prepared by sonication, containing 6% fish oil dispersed in aqueous solutions including 20% and 25% total wall material. The emulsion was sonicated at 24 kHz for 120 s. The emulsion was then freeze-dried and the nanocapsules were incorporated into probiotic fermented milk, with the effects of nanocapsules examined on the milk. The results showed that the nanoparticles encapsulated with 25% gum arabic and 4% emulsifier had the highest encapsulation efficiency (EE) (87.17%) and the lowest surface oil (31.66 mg/100 kg). Using nanoencapsulated fish oil in fermented milk significantly (p<0.05) increased the viability of Lactobacillus plantarum as well as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) contents. The fermented milk sample containing fish oil nanoencapsulated with 25% wall material and 4% emulsifier yielded the greatest probiotic bacterial count (8.41 Log CFU/mL) and the lowest peroxide value (0.57 mEq/kg). Moreover, this sample had the highest EPA and DHA contents. Utilizing this nanoencapsulated fish oil did not adversely affect fermented milk overall acceptance. Therefore, it can be used for fortification of low fat probiotic fermented milk.

• 한국물환경학회지
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• 제27권1호
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• pp.98-103
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• 2011

Photocatalysis using UV light and catalysts is an attractive low temperature and non-energy- intensive method for remediation of a wide range of chemical contaminants like chloroform (CF). Recently development of environmental friendly and sustainable catalytic systems is needed before such catalysts can be routinely applied to large-scale remediation or drinking water treatment. Titanium dioxide is a candidate material, since it is stable, highly reactive, and inexpensive. Diatoms are photosynthetic, single-celled algae that make a microscale silica shell with nano scale features. These diatoms have an ability to biologically fabricate $TiO_2$ nanoparticles into this shell in a process that parallels nanoscale silica mineralization. We cultivated diatoms, metabolically deposited titanium into the shell by using a two-stage photobioreactor and used this biogenic $TiO_2$ to this study. In this study we evaluated how effectively biogenic $TiO_2$ nanoparticles transform CF compared with chemically-synthesized $TiO_2$ nanoparticlesthe and effect of pretreatment of diatom-produced $TiO_2$ nanoparticles on photocatalytic transformation of CF. The rate of CF transformation by diatom-$TiO_2$ particles is a factor of 3 slower than chemically-synthesized one and chloride ion production was also co-related with CF transformation, and 79~91% of CF mineralization was observed in two $TiO_2$ particles. And the period of sonication and mass transfer due to particle size, evaluated by difference of oxygen tention does not affect on the CF transformation. Based on the XRD analysis we conclude that slower CF transformation by diatom-$TiO_2$ might be due to incomplete annealing to the anatase form.

• Current Applied Physics
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• 제18권11호
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• pp.1458-1464
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• 2018

An improved method for the preparation of g-$C_3N_4$ is described. Currently, heating (> $400^{\circ}C$) of urea is the common method used for preparing the g-$C_3N_4$. We have found that sonication of melamine in $HNO_3$ solution, followed by washing with anhydrous ethanol, not only reduce the crystallite size of g-$C_3N_4$ but also facilitate intriguing electronic structure and photoluminescence (PL) properties. Moreover, loading of metal (Pt and Ag) nanoparticles, by applying the borohydride reduction method, has resulted in multicolor-emission from g-$C_3N_4$. With the help of PL spectra and local electronic structure study, at C K-edge, N K-edge, Pt L-edge and Ag K-edge by X-ray absorption spectroscopy (XAS), a precise mechanism of tunable luminescence is established. The PL mechanism ascribes the amendments in the transitions, via defect and/or metal states assimilation, between the ${\pi}^*$ states of tris-triazine ring of g-$C_3N_4$ and lone pair states of nitride. It is evidenced that interaction between the C/N 2p and metal 4d/5d orbitals of Ag/Pt has manifested a net detraction in the ${\delta}^*{\rightarrow}LP$ transitions and enhancement in the ${\pi}^*{\rightarrow}LP$ and ${\pi}^*{\rightarrow}{\pi}$ transitions, leading to broad PL spectra from g-$C_3N_4$ organic semiconductor compound.

• 대한금속재료학회지
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• 제49권1호
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• pp.79-84
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• 2011

Double-walled carbon nanotubes (DWCNTs) with high purity were produced by the catalytic decomposition of tetrahydrofuran (THF) using a Fe-Mo/MgO catalyst at $800^{\circ}C$. The as-synthesized DWCNTs typically have catalytic impurities and amorphous carbon, which were removed by a two-step purification process consisting of acid treatment and oxidation. In the acid treatment, metallic catalysts were removed in HCl at room temperature for 5 hr with magnetic stirring. Subsequently, the oxidation, using air at $380^{\circ}C$ for 5 hr in the a vertical-type furnace, was used to remove the amorphous carbon particles. The DWCNT suspension was prepared by dispersing the purified DWCNTs in the aqueous sodium dodecyl sulfate solution with horn-type sonication. This was then air-sprayed on ITO glass to fabricate DWCNT field emitters. The field emission properties of DWCNT films related to transmittance were studied. This study provides the possibility of the application of large-area transparent CNT field emission cathodes.

• 대한금속재료학회지
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• 제48권4호
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• pp.335-341
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• 2010

High-quality single-walled carbon nanotubes (SWCNTs) were synthesized by catalytic decomposition of $C_2H_2$ using Fe-Mo/MgO catalyst at $800^{\circ}C$. The as-synthesized SWCNTs typically occurred in the form of a bundle with a diameter of 10~20 nm together with amorphous carbon and catalytic impurities, which were removed by a two-step purification process consisting of oxidation and an acid treatment. The oxidation step, using an $O_2$-Ar mixture at $380^{\circ}C$ for 5 hr in a vertical-type furnace and a $HNO_3$ treatment at $100^{\circ}C$ for one hour, was utilized to remove the amorphous carbon particles. Subsequently, metallic catalysts were removed in HCl at room temperature for 5 hr under magnetic stirring. The SWCNT suspension was prepared by dispersing the purified SWCNTs in an aqueous sodium dodecyl benzene sulfonate solution with horn-type sonication. This was then air-sprayed on glass to fabricate CNT field emitters. The samples had a turn-on field value of 4 V/${\mu}m$ and a current density of 0.67 mA/$cm^2$ at 9 V/${\mu}m$. Increasing the HCl treatment time improved the field emission properties.

• 한국음향학회지
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• 제41권5호
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• pp.501-506
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• 2022

공학적으로 제작된 미소기포 중 가스층과 유체층을 함께 내포하는 echogenic liposome은 수용성 약물 탑재에 용이하다. 또한 특정 위치에서 약물을 방출할 수 있다는 점에서 초음파 조영제의 기능을 넘어서 초음파 기반 약물전달(sonoporation)에 활용될 수 있다. 이에 따라, 본 논문에서는 이전 연구에서 제안된 echogenic liposome의 구조를 EF-TEM으로 재확인하였으며 sonoporation에서 약물전달 매개체로의 효과를 세포실험을 통하여 입증하였다. 세포실험은 유방암 조직인 MDA-MB-231 세포 대상으로 대표적 암치료제인 Doxorubicin을 지표 약물로 활용하였다. 비교군(1 그룹), Doxorubicin 그룹(2 그룹), Doxorubicin 과 일반 기포를 추가하여 sonoporation을 한 그룹(3 그룹), Doxorubicin을 echogenic liposome에 탑재하여 sonoporation을 적용한 그룹(4 그룹)으로 구분하여 진행한 실험결과, 4 그룹에서 약물 전달 효과가 초기부터 급격히 증가하였으며, 최종적으로 2 그룹과 3그룹에 비하여 최소 1.4 배 이상 효과적으로 종양 세포 괴사를 유도하였다. 따라서 sonoporation에서 echogenic liposome은 기존 일반적 미소기포보다 더 효율적인 약물 매개체라고 결론 내릴 수 있다.

• 한국축산식품학회지
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• 제42권6호
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• pp.1031-1045
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• 2022

Postbiotics are defined as probiotics inactivated by heat, ultraviolet radiation, sonication, and other physical or chemical stresses. Postbiotics are more stable than probiotics, and these properties are advantageous for food additives and pharmacological agents. This study investigated the immunostimulatory effects of heat-treated Lactiplantibacillus plantarum LM1004 (HT-LM1004). Cellular fatty acid composition of L. plantarum LM1004 isolated form kimchi was analyzed by gas chromatography-mass spectrometry detection system. The nitric oxide (NO) content was estimated using Griess reagent. Immunostimulatory cytokines were evaluated using enzyme-linked immunosorbent assay. Relative protein expressions were evaluated by western blotting. Phagocytosis was measured using enzyme-labelled Escherichia coli particles. L. plantarum LM1004 showed 7 kinds of cellular fatty acids including palmitic acid (C16:0). The HT-LM1004 induced release of NO and upregulated the inducible NO synthase in RAW 264.7 macrophage cells. Tumor necrosis factor-α and interleukin-6 levels were also increased compared to control (non-treated macrophages). Furthermore, HT-LM1004 modulated mitogen-activated protein kinase (MAPK) subfamilies including p38 MAPK, extracellular signal-regulated kinase 1/2, and c-Jun N-terminal kinase. Therefore, these immunostimulatory effects were attributed to the production of transcriptional factors, such as nuclear factor kappa B (NF-κB) and the activator protein 1 family (AP-1). However, HT-LM1004 did not showed significant phagocytosis of RAW 264.7 macrophage cells. Overall, HT-LM1004 stimulated MAPK/AP-1 and NF-κB expression, resulting in the release of NO and cytokines. These results will contribute to the development of diverse types of food and pharmacological products for immunostimulatory agents with postbiotics.

• 청정기술
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• 제15권2호
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• pp.69-74
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• 2009

초임계이산화탄소와 공용매의 혼합물을 사용하여 반도체 웨이퍼 기판으로부터 고농도이온주입 포토레지스트(HDIPR)를 제거하였다. 또한 고압 셀 내부에 초음파 장치를 부착하여 웨이퍼 표면에 물리적 힘을 제공함으로서 세정용액의 HDIPR에 대한 스트리핑 성능을 현저히 향상시키고, 제거 시간을 단축시켰다. 공용매의 종류 및 농도, 공정 온도, 압력 변화에 따른 HDIPR 스트리핑 특성을 조사하였으며, 웨이퍼 표면의 제거 전후의 상태 및 성분을 scanning electron microscopy 과 energy dispersive X-ray spectrometer를 이용하여 분석하였다. 10 w/w% 함량의 아세톤 공용매를 이용하여 공정압력 27.6 MPa과 온도 343 K 의 조건에서 3분의 초음파 처리시간을 거쳐 HDIPR을 완전히 제거할 수 있었다.