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Enhanced Neurite Outgrowth by Intracellular Stimulation
Kim, Ilsoo,Lee, Hye Yeong,Kim, Hyungsuk,Lee, Eungjang,Jeong, Du-Won,Kim, Ju-Jin,Park, Seung-Han,Ha, Yoon,Na, Jukwan,Chae, Youngcheol,Yi, Seong,Choi, Heon-Jin American Chemical Society 2015 NANO LETTERS Vol.15 No.8
<P>Electrical stimulation through direct electrical activation has been widely used to recover the function of neurons, primarily through the extracellular application of thin film electrodes. However, studies using extracellular methods show limited ability to reveal correlations between the cells and the electrical stimulation due to interference from external sources such as membrane capacitance and culture medium. Here, we demonstrate long-term intracellular electrical stimulation of undamaged pheochromocytoma (PC-12) cells by utilizing a vertical nanowire electrode array (VNEA). The VNEA was prepared by synthesizing silicon nanowires on a Si substrate through a vapor–liquid–solid (VLS) mechanism and then fabricating them into electrodes with semiconductor nanodevice processing. PC-12 cells were cultured on the VNEA for 4 days with intracellular electrical stimulation and then a 2-day stabilization period. Periodic scanning via two-photon microscopy confirmed that the electrodes pierced the cells without inducing damage. Electrical stimulation through the VNEA enhances cellular differentiation and neurite outgrowth by about 50% relative to extracellular stimulation under the same conditions. VNEA-mediated stimulation also revealed that cellular differentiation and growth in the cultures were dependent on the potential used to stimulate them. Intracellular stimulation using nanowires could pave the way for controlled cellular differentiation and outgrowth studies in living cells.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2015/nalefd.2015.15.issue-8/acs.nanolett.5b01810/production/images/medium/nl-2015-01810h_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl5b01810'>ACS Electronic Supporting Info</A></P>
Two-Dimensionally Grown Single-Crystal Silicon Nanosheets with Tunable Visible-Light Emissions
Kim, Sung Wook,Lee, Jaejun,Sung, Ji Ho,Seo, Dong-jae,Kim, Ilsoo,Jo, Moon-Ho,Kwon, Byoung Wook,Choi, Won Kook,Choi, Heon-Jin American Chemical Society 2014 ACS NANO Vol.8 No.7
<P>Since the discovery of graphene, growth of two-dimensional (2D) nanomaterials has greatly attracted attention. However, spontaneous growth of atomic two-dimensional (2D) materials is limitedly permitted for several layered-structure crystals, such as graphene, MoS<SUB>2</SUB>, and <I>h</I>-BN, and otherwise it is notoriously difficult. Here we report the gas-phase 2D growth of silicon (Si), that is cubic in symmetry, <I>via</I> dendritic growth and an interdendritic filling mechanism and to form Si nanosheets (SiNSs) of 1 to 13 nm in thickness. Thin SiNSs show strong thickness-dependent photoluminescence in visible range including red, green, and blue (RGB) emissions with the associated band gap energies ranging from 1.6 to 3.2 eV; these emission energies were greater than those from Si quantum dots (SiQDs) of the similar sizes. We also demonstrated that electrically driven white, as well as blue, emission in a conventional organic light-emitting diode (OLED) geometry with the SiNS assembly as the active emitting layers. Tunable light emissions in visible range in our observations suggest practical implications for novel 2D Si nanophotonics.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2014/ancac3.2014.8.issue-7/nn501683f/production/images/medium/nn-2014-01683f_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn501683f'>ACS Electronic Supporting Info</A></P>
Factors associated with the risk of colorectal neoplasia in young adults under age 40
Ilsoo Kim,Han Hee Lee,Young Jae Ko,Ho Eun Chang,Dae Young Cheung,Bo-In Lee,Young-Seok Cho,Jin Il Kim,Myung-Gyu Choi 대한내과학회 2022 The Korean Journal of Internal Medicine Vol.37 No.5
Background/Aims: Recent epidemiologic studies have shown a continued increase in colorectal cancer incidence among younger adults. Little is known about the factors that contribute to the development of young-onset colorectal neoplasia (CRN). Methods: A cross-sectional analysis was performed for individuals younger than 40 years who underwent colonoscopy in Seoul St. Mary’s Hospital and its affiliated health screening center. High-risk CRN was defined as adenoma or sessile serrated lesion ≥ 10 mm, with three or more adenomas, villous histology, high grade dysplasia, or carcinoma. Results: Of these 13,621 included participants, 2,023 (14.9%) had one and more CRN. Young patients with CRN tended to be elderly, male, obese, smoker, having a habit of drinking, and having comorbidities such as hypertension, dyslipidemia, diabetes, and chronic kidney disease. In a multivariate analysis adjusted for age, sex, obesity, smoking status, and alcohol intake, old age (odds ratio [OR], 1.086; 95% confidence interval [CI], 1.054 to 1.119), male sex (OR, 1.748; 95% CI, 1.247 to 2.451), obesity (OR, 1.439; 95% CI, 1.133 to 1.828), and smoking (OR, 1.654; 95% CI, 1.287 to 2.127) were independent risk factors for overall CRN. Obesity and smoking as two modifiable factors increased the risk for high-risk CRN even more than for overall CRN (OR, 1.734; 95% CI, 1.168 to 2.575 and OR, 1.797; 95% CI, 1.172 to 2.753, respectively). Conclusions: Obesity and smoking were modifiable risk factors for CRN in young adults. They increased the risk for highrisk CRN even more than for overall CRN. A colonoscopy might be beneficial for young individuals with these factors.
Synthesis of p-type GaN nanowires.
Kim, Sung Wook,Park, Youn Ho,Kim, Ilsoo,Park, Tae-Eon,Kwon, Byoung Wook,Choi, Won Kook,Choi, Heon-Jin RSC Pub 2013 Nanoscale Vol.5 No.18
<P>GaN has been utilized in optoelectronics for two decades. However, p-type doping still remains crucial for realization of high performance GaN optoelectronics. Though Mg has been used as a p-dopant, its efficiency is low due to the formation of Mg-H complexes and/or structural defects in the course of doping. As a potential alternative p-type dopant, Cu has been recognized as an acceptor impurity for GaN. Herein, we report the fabrication of Cu-doped GaN nanowires (Cu:GaN NWs) and their p-type characteristics. The NWs were grown vertically via a vapor-liquid-solid (VLS) mechanism using a Au/Ni catalyst. Electrical characterization using a nanowire-field effect transistor (NW-FET) showed that the NWs exhibited n-type characteristics. However, with further annealing, the NWs showed p-type characteristics. A homo-junction structure (consisting of annealed Cu:GaN NW/n-type GaN thin film) exhibited p-n junction characteristics. A hybrid organic light emitting diode (OLED) employing the annealed Cu:GaN NWs as a hole injection layer (HIL) also demonstrated current injected luminescence. These results suggest that Cu can be used as a p-type dopant for GaN NWs.</P>
Neuron-like differentiation of mesenchymal stem cells on silicon nanowires.
Kim, Hyunju,Kim, Ilsoo,Choi, Heon-Jin,Kim, So Yeon,Yang, Eun Gyeong RSC Pub 2015 Nanoscale Vol.7 No.40
<P>The behavior of mammalian cells on vertical nanowire (NW) arrays, including cell spreading and the dynamic distribution of focal adhesions and cytoskeletal proteins, has been intensively studied to extend the implications for cellular manipulations in vitro. Prompted by the result that cells on silicon (Si) NWs showed morphological changes and reduced migration rates, we have explored the transition of mesenchymal stem cells into a neuronal lineage by using SiNWs with varying lengths. When human mesenchymal stem cells (hMSCs) were cultured on the longest SiNWs for 3 days, most of the cells exhibited elongated shapes with neurite-like extensions and dot-like focal adhesions that were prominently observed along with actin filaments. Under these circumstances, the cell motility analyzed by live cell imaging was found to decrease due to the presence of SiNWs. In addition, the slowed growth rate, as well as the reduced population of S phase cells, suggested that the cell cycle was likely arrested in response to the differentiation process. Furthermore, we measured the mRNA levels of several lineage-specific markers to confirm that the SiNWs actually induced neuron-like differentiation of the hMSCs while hampering their osteogenic differentiation. Taken together, our results implied that SiNWs were capable of inducing active reorganization of cellular behaviors, collectively guiding the fate of hMSCs into the neural lineage even in the absence of any inducing reagent.</P>
Kim, Ilsoo,Lee, Ki-Young,Kim, Ungkil,Park, Yong-Hee,Park, Tae-Eon,Choi, Heon-Jin Springer 2010 Nanoscale research letters Vol.5 No.10
<P>We report on bifurcate reactions on the surface of well-aligned Si<SUB>1−<I>x</I></SUB>Ge<SUB><I>x</I></SUB> nanowires that enable fabrication of two different coaxial heterostructure nanowires. The Si<SUB>1−<I>x</I></SUB>Ge<SUB><I>x</I></SUB> nanowires were grown in a chemical vapor transport process using SiCl<SUB>4</SUB> gas and Ge powder as a source. After the growth of nanowires, SiCl<SUB>4</SUB> flow was terminated while O<SUB>2</SUB> gas flow was introduced under vacuum. On the surface of nanowires was deposited Ge by the vapor from the Ge powder or oxidized into SiO<SUB>2</SUB> by the O<SUB>2</SUB> gas. The transition from deposition to oxidation occurred abruptly at 2 torr of O<SUB>2</SUB> pressure without any intermediate region and enables selectively fabricated Ge/Si<SUB>1−<I>x</I></SUB>Ge<SUB><I>x</I></SUB> or SiO<SUB>2</SUB>/Si<SUB>1−<I>x</I></SUB>Ge<SUB><I>x</I></SUB> coaxial heterostructure nanowires. The rate of deposition and oxidation was dominated by interfacial reaction and diffusion of oxygen through the oxide layer, respectively.</P>
소프트웨어 프로젝트에서 프로젝트 관리 성숙도가 3Baseline(범위, 일정, 원가)에 미치는 영향 연구
김일수 ( Ilsoo Kim ),이석주 ( Seoukjoo Lee ),최진영 ( Jinyoung Choi ) 한국정보처리학회 2012 한국정보처리학회 학술대회논문집 Vol.19 No.1
프로젝트 관리 성숙도(Project Management Maturity Model)란 프로젝트 관리 관련 업무 성숙도를 측정하는 것으로, 프로젝트 성공을 위해 관련 있는 업무가 어느 정도 수준으로 진행되고 있는가를 평가하는 목적으로 주로 사용된다. 본 논문에서는 프로젝트 관리 성숙도를 활용하여 프로젝트 관리 성숙도가 범위, 일정, 그리고 원가에 미치는 영향을 연구 하였다. 연구 결과로 프로젝트 관리 성숙도가 낮으면 범위 변경률이 커지고, 일정이 지연되며, 비용 또한 초과되는 것으로 나타났다. 본 연구의 성과를 토대로 기업이 프로젝트 관리 성숙도 향상을 위해 투자와 노력을 해야 한다는 것을 알 수 있다.