Quantitative assessment of steroid amount in the tissue after epidural steroid injection: a new rabbit model

Jungheum Cho,Joon Woo Lee,Eugene Lee,Yusuhn Kang,Ha Ra Cho,Dong Yoon Kim,Myoung Jin Ho,Myung Joo Kang,Yong Seok Choi 대한통증학회 2019 The Korean Journal of Pain Vol.32 No.4

Background: To develop a rabbit epidural steroid injection (ESI) model for analyzing steroid retention in the tissue, and to assess the difference in steroid retention in the model according to the location and time elapsed after ESI. Methods: Fluoroscopy-guided ESI was performed using the interlaminar approach between the lowest two lumbar segments in 13 female New Zealand white rabbits. Four rabbits were allocated to each of three different groups according to the time of sacrifice: 3, 7, and 15 days post-ESI; the remaining rabbit was sacrificed immediately post-ESI to obtain baseline data. After sacrifice, two segments were harvested: the lowest two lumbar vertebrae and another two lumbar vertebrae immediately above these. The residual steroid amount (RSA) and residual steroid concentration (RSC) in the collected spinal columns were analyzed. A linear mixed model was used to compare RSAs and RSCs between the injected and adjacent segments, and among the number of days until sacrifice; P < 0.05 was considered statistically significant. Results: Both RSA and RSC of the injected segment were significantly higher than those of the adjacent segment (P < 0.001, both). The RSA and RSC significantly decreased over time (P = 0.009 and P = 0.016, respectively). Conclusions: The developed rabbit ESI model verified that significantly more steroid was retained at the injected segment than at the adjacent segment and the residual steroid decreased over time. This model could be useful not only for comparing current steroid medications, but also for developing new, better steroid formulations.

Interface between Oxide Coatings and Plasma‐damaged Polymers and Its Effects on Coating Adhesion and Structure

Yun, Jungheum,Bae, Tae‐,Sung,Lee, Sunghun,Lee, Seunghun,Rha, Jongjoo,Lee, Gun‐,Hwan WILEY‐VCH Verlag 2012 Plasma Processes and Polymers Vol.9 No.2

<P><B>Abstract</B></P><P>The chemical and morphological features of the interface between plasma‐treated polymer substrates and oxide coatings are investigated to clarify the influence of the interfacial features on the adhesive and cohesive properties in the polymer–oxide system. It is found that one‐dimensional polymer protrusions and polymer–oxide composite structures develop sequentially in the early growth stages of silicon oxide films on both acrylate hard coat and bare polyethylene terephthalate surfaces exposed to strong plasma‐ion irradiation. These interfacial nanostructures cause a dramatic decrease in the wettability of the polymers with silicon oxide films, thus leading to a weak boundary layer, which results in adhesion failures at the polymer–oxide interface. </P>

Light trapping in bendable organic solar cells using silica nanoparticle arrays

Yun, Jungheum,Wang, Wei,Kim, Soo Min,Bae, Tae-Sung,Lee, Sunghun,Kim, Donghwan,Lee, Gun-Hwan,Lee, Hae-Seok,Song, Myungkwan The Royal Society of Chemistry 2015 ENERGY AND ENVIRONMENTAL SCIENCE Vol.8 No.3

<P>A highly efficient light-scattering layer, composed of quasi-periodic discrete silica nanoparticles directly deposited onto polymer substrates to produce bendable organic solar cells (OSCs) with enhanced light absorption, is reported. A silica nanoparticle layer (SNL) underwent self-assembly on a highly flexible and heat-sensitive polymer at room temperature during fabrication, which employed a unique plasma-enhanced chemical vapour deposition technique. Such efficient light-scattering SNLs have not been realizable by conventional solution-based coating techniques. SNLs were optimized by precisely controlling dimensional parameters, specifically, the nanoparticle layer thickness and interparticle distance. The optimized SNL exhibited an improved transmission haze of 16.8% in the spectral range of 350–700 nm, where reduction of the total transmission was suppressed to 2%. Coating light-scattering SNLs onto polymer substrates is a promising method for improving the light harvesting abilities of OSCs by enhancing the light absorption of photoactive polymer layers. This SNL-based flexible OSC exhibited a record power conversion efficiency (PCE) of 7.4%, representing a 13% improvement, while reducing the thickness of the photoactive polymer layer by 30%.</P> <P>Graphic Abstract</P><P>A highly efficient light-scattering layer based on a silica nanoparticle array was fabricated on a flexible polymer substrate by employing a direct vacuum deposition process at room temperature, facilitating a power conversion efficiency of 7.42% from a flexible organic solar cell. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c4ee01100g'> </P>

Preparation of Flexible Organic Solar Cells with Highly Conductive and Transparent Metal-Oxide Multilayer Electrodes Based on Silver Oxide

Yun, Jungheum,Wang, Wei,Bae, Tae Sung,Park, Yeon Hyun,Kang, Yong-Cheol,Kim, Dong-Ho,Lee, Sunghun,Lee, Gun-Hwan,Song, Myungkwan,Kang, Jae-Wook American Chemical Society 2013 ACS APPLIED MATERIALS & INTERFACES Vol.5 No.20

<P>We report that significantly more transparent yet comparably conductive AgO<SUB><I>x</I></SUB> films, when compared to Ag films, are synthesized by the inclusion of a remarkably small amount of oxygen (i.e., 2 or 3 atom %) in thin Ag films. An 8 nm thick AgO<SUB><I>x</I></SUB> (O/Ag = 2.4 atom %) film embedded between 30 nm thick ITO films (ITO/AgO<SUB><I>x</I></SUB>/ITO) achieves a transmittance improvement of 30% when compared to a conventional ITO/Ag/ITO electrode with the same configuration by retaining the sheet resistance in the range of 10–20 Ω sq<SUP>–1</SUP>. The high transmittance provides an excellent opportunity to improve the power-conversion efficiency of organic solar cells (OSCs) by successfully matching the transmittance spectral range of the electrode to the optimal absorption region of low band gap photoactive polymers, which is highly limited in OSCs utilizing conventional ITO/Ag/ITO electrodes. An improvement of the power-conversion efficiency from 4.72 to 5.88% is achieved from highly flexible organic solar cells (OSCs) fabricated on poly(ethylene terephthalate) polymer substrates by replacing the conventional ITO/Ag/ITO electrode with the ITO/AgO<SUB><I>x</I></SUB>/ITO electrode. This novel transparent electrode can facilitate a cost-effective, high-throughput, room-temperature fabrication solution for producing large-area flexible OSCs on heat-sensitive polymer substrates with excellent power-conversion efficiencies.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2013/aamick.2013.5.issue-20/am401845n/production/images/medium/am-2013-01845n_0009.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am401845n'>ACS Electronic Supporting Info</A></P>

Fabrication of a Completely Transparent and Highly Flexible ITO Nanoparticle Electrode at Room Temperature

Yun, Jungheum,Park, Yeon Hyun,Bae, Tae-Sung,Lee, Sunghun,Lee, Gun-Hwan American Chemical Society 2013 ACS APPLIED MATERIALS & INTERFACES Vol.5 No.1

<P>We report the fabrication of a highly flexible indium tin oxide (ITO) electrode that is completely transparent to light in the visible spectrum. The electrode was fabricated via the formation of a novel ITO nanoarray structure, consisting of discrete globular ITO nanoparticles superimposed on an agglomerated ITO layer, on a heat-sensitive polymer substrate. The ITO nanoarray spontaneously assembled on the surface of the polymer substrate by a simple sputter coating at room temperature, without nanolithographic or solution-based assembly processes being required. The ITO nanoarray exhibited a resistivity of approximately 2.3 × 10<SUP>–3</SUP> Ω cm and a specular transmission of about 99% at 550 nm, surpassing all previously reported values of these parameters in the case of transparent porous ITO electrodes synthesized via solution-based processes at elevated temperatures. This novel nanoarray structure and its fabrication methodology can be used for coating large-area transparent electrodes on heat-sensitive polymer substrates, a goal unrealizable through currently available solution-based fabrication methods.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2013/aamick.2013.5.issue-1/am302341p/production/images/medium/am-2012-02341p_0009.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am302341p'>ACS Electronic Supporting Info</A></P>

Adhesive and Structural Failures of Oxide Coatings on Plasma‐Treated Polymers

Yun, Jungheum,Lee, Sunghun,Bae, Tae‐,Sung,Yun, Youngmok,Lee, Seunghoon,Kwon, Jung‐,Dae,Lee, Gun‐,Hwan WILEY‐VCH Verlag 2011 Plasma Processes and Polymers Vol.8 No.9

<P><B>Abstract</B></P><P>This study discloses (i) the chemical and morphological modifications in acrylate hard‐coat and bare polyethylene terephthalate polymers occurring in the course of Ar plasma treatments and (ii) the effects of these modifications on the adhesion, barrier performance, and cohesion of silicon oxide coatings deposited on the polymers. It is concluded that the deterioration in these coating properties is dominated by the formation of nanoscopic globular polymer protrusions on the polymer surface as a result of plasma treatment. The protrusions evolve even under very mild plasma conditions in which an ion fluence of less than 1 × 10<SUP>16</SUP> ions · cm<SUP>−2</SUP> is applied with low‐energy ion irradiation of 6 eV. The polymer protrusions dictate the nucleation and subsequent growth of a coating by promoting the development of a three‐dimensional granular morphology in the coating. At the initial oxide nucleation stage, the wetting behavior of silicon oxide on the polymer surface in the presence of nanoscopic protrusions is directly limited by the area number density and size of the protrusions. Incomplete wetting of the protrusions with a silicon oxide coating hinders adhesion between the oxide and the polymer surface. The reduction in the contact area between the oxide and the protrusions is identified as the reason that a weak boundary layer forms at the oxide–polymer interface. Furthermore, the formation of nanoscopic defects, predominantly pinholes, is inevitable in the granular coating morphology on the polymer protrusions and weakens the oxide coating's barrier performance and cohesion strength. Variations in the polar surface free energy and chemical composition of the plasma‐treated polymer surface are irrelevant to the wetting dynamics whenever the protrusions develop on the polymer surface. The effects of the polar surface free energy and chemical composition are valid only to the extent that the plasma treatment improves the wettability of a polymer surface without protrusion formation. </P>

Forensic investigation of Microsoft PowerPoint files

Park, Jungheum,Lee, Sangjin Elsevier 2009 Digital investigation Vol.6 No.1

<P><B>Abstract</B></P><P>Nowadays, many electronic documents reside in individual systems and on public networks. Electronic documents contain important information such as private data and trade secrets. Because of this, electronic documents can be used as digital evidence in forensic investigations. Until now, forensic examiners have looked at the contents of an electronic document using specific applications, a procedure which fails to provide them with information about how an electronic document was created. Research into the process by which an electronic document is written can help forensic examiners discover the relationships among several electronic documents and the traces of past work in some special cases. This paper demonstrates new methods for investigating Microsoft PowerPoint files that include some useful information about their own writing process.</P>

Reduction of Defects in SiO_<i>x</i>Vapor Permeation Barriers on Polymer Substrates by Introducing a Sputtered Interlayer

Yun, Jungheum,Lee, Sunghun,Jeong, Yujeong,Lee, Hong-Rim,Kwon, Jung-Dae,Lee, Gun-Hwan IOP Publishing 2009 Japanese journal of applied physics Vol.48 No.r5

Appendiceal Visualization on 2-mSv CT vs. Conventional-Dose CT in Adolescents and Young Adults with Suspected Appendicitis: An Analysis of Large Pragmatic Randomized Trial Data

Cho Jungheum,Kim Youngjune,Lee Seungjae,Min Hooney Daniel,Ko Yousun,Chee Choong Guen,Kim Hae Young,Park Ji Hoon,Lee Kyoung Ho 대한영상의학회 2022 Korean Journal of Radiology Vol.23 No.4

Objective: We compared appendiceal visualization on 2-mSv CT vs. conventional-dose CT (median 7 mSv) in adolescents and young adults and analyzed the undesirable clinical and diagnostic outcomes that followed appendiceal nonvisualization. Materials and Methods: A total of 3074 patients aged 15–44 years (mean ± standard deviation, 28 ± 9 years; 1672 female) from 20 hospitals were randomized to the 2-mSv CT or conventional-dose CT group (1535 vs. 1539) from December 2013 through August 2016. A total of 161 radiologists from 20 institutions prospectively rated appendiceal visualization (grade 0, not identified; grade 1, unsure or partly visualized; and grade 2, clearly and entirely visualized) and the presence of appendicitis in these patients. The final diagnosis was based on CT imaging and surgical, pathologic, and clinical findings. We analyzed undesirable clinical or diagnostic outcomes, such as negative appendectomy, perforated appendicitis, more extensive than simple appendectomy, delay in patient management, or incorrect CT diagnosis, which followed appendiceal nonvisualization (defined as grade 0 or 1) and compared the outcomes between the two groups. Results: In the 2-mSv CT and conventional-dose CT groups, appendiceal visualization was rated as grade 0 in 41 (2.7%) and 18 (1.2%) patients, respectively; grade 1 in 181 (11.8%) and 81 (5.3%) patients, respectively; and grade 2 in 1304 (85.0%) and 1421 (92.3%) patients, respectively (p < 0.001). Overall, undesirable outcomes were rare in both groups. Compared to the conventional-dose CT group, the 2-mSv CT group had slightly higher rates of perforated appendicitis (1.1% [17] vs. 0.5% [7], p = 0.06) and false-negative diagnoses (0.4% [6] vs. 0.0% [0], p = 0.01) following appendiceal nonvisualization. Otherwise, these two groups were comparable. Conclusion: The use of 2-mSv CT instead of conventional-dose CT impairs appendiceal visualization in more patients. However, appendiceal nonvisualization on 2-mSv CT rarely leads to undesirable clinical or diagnostic outcomes.

NIST의 디지털 포렌식 도구 검증 체계 소개

Park, Jungheum,Lyle, James R.,Guttman, Barbara 한국정보보호학회 2016 情報保護學會誌 Vol.26 No.5

정보 통신 기술이 빠르게 발전하고 디지털 기기가 보급됨에 따라 다양한 유형의 사건을 해결하는데 있어서 디지털 증거가 핵심적인 요소로 활용되고 있다. 이에 잠재적인 디지털 증거를 수집, 추출, 복구, 분석하기 위한 디지털 포렌식(Digital Forensics) 기술의 연구 개발이 전 세계적으로 매우 활발하게 진행되어 왔다. 활발한 연구 개발의 결과, 보다 효율적인 디지털 포렌식 활동을 지원하기 위해서 여러 도구(S/W, H/W)들이 공개되고 있으며 현재 다양한 목적으로 널리 활용되고 있다. 이와 같이 디지털 포렌식 도구의 활용이 일반화되었고 특히 동일(또는 유사한) 기능을 제공하는 여러 도구가 존재함에 따라서 각각의 도구가 제공하는 기능의 범위와 구현의 정확성 등에 대한 검증의 필요성이 제기되었다. 이러한 요구에 맞춰 1999년 미국 국립표준기술연구소(NIST)에서 디지털 포렌식 도구 검증 체계를 구축하였고, 현재까지도 활발하게 진행되고 있다. 본 논문에서는 NIST에서 수행 중인 CFTT와 CFReDS 프로젝트를 소개하고, 진행 현황과 향후의 발전 방향을 설명한다.