An Experimental Study on the Heat Exchanger for Gas-Flinak Molten Salt

The Very High Temperature Reactor (VHTR), one of the most challenging next generation nuclear reactors, has recently drawn an international attention due to its higher efficiency and the operating conditions adequate for supplying process heat to the hydrogen production facilities. To make the design of VHTR complete and plausible, the designs of the Intermediate Heat Transport Loop (IHTL) as well as the Intermediate Heat Exchanger (IHX) are known to be one of the difficult engineering tasks due to its high temperature operating condition (up to 950°C). A type of compact heat exchangers such as Printed Circuit Heat Exchanger (PCHE) has been recommended for the IHX in the technical and economical respects. In this study, the Flinak molten salt, an eutectic mixture of LiF, NaF and KF (46.5:11.5:42.0 mole %) is considered as the heat transporting fluid. A double-pipe type heat exchanger was constructed using small diameter tubes to investigate the pressure drop and heat transfer characteristics of molten salt flow in minichannels. The outer and the inner diameters of the inner tube are 3.18 mm and 1.40 mm and of the outer tube are 6.35 mm and 4.57 mm, respectively. The length of test section is 500 mm. The molten salt flows through the inside of the inner tube and the gas flows through the annulus of 0.7 mm gap. For laminar flow of the molten Flinak in the 1.4 mm-inner diameter circular tube, the measured friction factors were close to the analytical result of 64/Re within the difference of -23 ~ +7%. The uncertainty in Flinak viscosity was considered to be the cause of this difference. The Flinak viscosity was calculated using the measured pressure drop and a new correlation of Flinak viscosity was proposed. The heat transfer data were successfully obtained for the counterflow of the double-pipe heat exchanger. Despite the sizable heat loss of the gas flow to the surroundings, the heat transfer coefficients of the Flinak flow in small channel were calculated using a modified LMTD method which accounted for the heat loss. The resulting Nu numbers were generally in the range of 3.66 and 4.36, which are the analytical values for laminar flow in circular tubes. A model heat exchanger was designed and fabricated to investigate the thermal performance of the plate-fin heat exchanger with minichannels. Minichannels were chemically etched on one side of a metal sheet and two of these sheets were diffusion-bonded to form a plate. Six plates and five off-set fin layers were then brazed to form the heat exchanger. The plates and fins were made of Inconel 600. To evaluate the pressure drop and heat transfer performance of the model heat exchanger, a series of tests were carried out using air and water. The water flows through the inside of the minichannels and the air flows through the fins. For laminar flow of the water in channels, the measured friction factors were close to 64/Re within the difference of ±8%. The heat transfer measurement was satisfactory such that the difference between the heat loss of water and the heat gain of air was -3.2 ~ +4.8%.1 . 서론 1 1.1 연구배경 1 1.2 연구목적 3 2. 선행연구 고찰 7 2.1 서론 7 2.2 열교환기 열유동 설계 방법 8 2.2.1 열 설계 8 2.2.2 압력손실 14 2.3 Flinak 물성치 16 2.3.1 융점 16 2.3.2 밀도 16 2.3.3 비열 17 2.3.4 점도 18 2.3.5 열전도도 20 3. Flinak 열수력 특성 실험 28 3.1 실험장치 28 3.1.1 용융염 장치 29 3.1.2 열교환 실험장치 30 3.1.3 계측장치 32 3.2 실험방법 34 3.3 실험결과 및 고찰 36 3.3.1 Flinak 제조 36 3.3.2 Flinak 용융 37 3.3.3 층류유동에서 Flinak 마찰계수 38 3.3.4 층류유동에서 Flinak 열전달계수 39 4. 열교환기 성능실험 59 4.1 실험장치 59 4.1.1 열교환기 60 4.1.2 순환형 풍동 실험장치 61 4.1.3 계측장치 62 4.2 실험방법 64 4.3 실험결과 및 고찰 64 4.3.1 열교환기 채널에서의 압력손실 64 4.3.2 열교환기 열전달량 66 5. 결론 78 참고문헌 8

A Study on the Mooring System for Floating Wave Energy Converter using Numerical Analysis

The aim of this study is to find and select a suitable mooring system to apply on to a floating wave energy system by studying the characteristics of its motion and response using a numerical analysis. The wave energy device converts the ocean wave motion into electrical energy. The waves influence the device's movement and in turn the device's motion influences the incoming waves. The behaviour of the device's motion is mainly affected by the type of mooring system that is attached to it. Therefore, as the mooring system has major influence on the output of the wave energy device, it is of high importance to study the response of the device with different mooring systems. The results are summarized as follows: 1. In previous studies, the wave energy device was manufactured and deployed for sea tests. In order to study the internal flow in the Power Take Off (PTO) system, a commercial Computational Fluid Dynamic (CFD) code, ANSYS CFX ver.14, was used for analysis on a 1:1 scale model. 2. At a period of 4 seconds, the power output obtained was 407W. As the period was increased, the power obtained decreased. At a period of 6 seconds, the power output was only 235W. The highest efficiency obtained was 46.7% and at a period of 4.5 seconds, the efficiency was much lower than that obtained at 4 seconds. As the length of the device and period of the wave have a direct effect on each other. This specific device design is not recommended for deployment in wave climates where a significant number of waves have a period of 4.5 seconds. 3. A numerical case was given the same conditions as the sea tests with a single point mooring, at case 5(λ/L=4.0) the pitch response amplitude operator (RAO) was 2.401 and the heave RAO was 2.154. As the λ/L ratio increases, the results show that the RAO values also increase. At case 5 (λ/L=4.0), the largest pitch angle seen was 20.1°. When compared to actual device, the motion numerical case was seen to be similar. 4. In an actual sea, the currents and wind will affect the wave energy device. Therefore, there is a need for the device to have a multiple point mooring system to avoid unnecessary yawing on the surface of the ocean. It was expected that adding more mooring points the system, the RAO values would decrease. However, from the results of the multiple point mooring analysis, the RAO values obtained were similar to the single point mooring results. Therefore, it can be seen from these results of the numerical model that multiple point mooring do not interfere greatly with the motion of the wave energy device. In addition, when installing additional mooring lines or selecting the most suitable mooring system for wave energy devices, the results obtained in this study is needed for the selection process.1. 서 론 1.1 연구배경 1.2 연구동향 1.3 연구목적 2. PTO 시스템의 수치해석 2.1 PTO 시스템 2.2 CFD에 의한 양방향 횡류터빈 모델 PTO 유동해석 2.2.1 형상 모델링 및 계산 격자 2.2.2 경계 조건 2.2.3 유동 해석 결과 2.3 요약 및 검토 3. 부유식 파력발전 장치 설계 3.1 개념 모델 및 구동원리 3.2 규칙파 이론과 해석 3.3 설계 파라미터 지정 3.3.1 장치의 길이 선정 3.3.2 장치의 폭 선정 3.4 계류 시스템 3.5 수치해석 기법 3.5.1 지배 방정식 3.5.2 이산화방법 3.5.3 난류모델 4. 계류시스템 특성 수치해석 4.1 수치해석 목적 4.2 단일 계류시스템을 적용한 파력발전장치 해석 4.2.1 형상 모델링 및 격자 4.2.2 경계조건 및 계산 조건 4.2.3 유동 해석 결과 4.3 다점 계류시스템을 적용한 파력발전장치 해석 4.3.1 형상 모델링 및 격자 4.3.2 경계조건 및 계산 조건 4.3.3 유동 해석 결과 4.4 요약 및 검토 5. 결론 참고문헌Maste

The function of keratinocyte derived laminin-5 as a regulator of melanoma cells

Although close association between melanocytes, the melanin-producing cells, and their neighboring keratinocytes has been well established, the exact regulatory mechanism still needs to be elucidated. We are now providing the evidence that laminin-5 expressed on keratinocytes is involved in the regulation of melanoma cell functions. A375 human melanoma cells attached and spread better on keratinocyte extracellular matrix (ECM) than that of human melanoma cells, suggesting the importance of keratinocyte derived ECM. Reduction of the expression of keratinocyte derived laminin-5, the major component of basement membrane, using siRNA diminished the keratinocyte ECM-mediated increased cell adhesion and spreading. Consistently, laminin-5, but neither laminin-1 nor fibronectin, promoted cell attachment and spreading of melanoma cells, confirming that keratinocyte derived lamin-5 is important for melanoma cell adhesion and spreading. While laminin-5 did not show any positive effects on migration and proliferation of melanoma cells, melanin production of mouse melanoma cells was markedly increased on laminin-5. Furthermore, laminin-5 enhanced a-melanocyte stimulating hormone-regulated melanin production in B16F10 cells. Taken together, these data strongly suggest that keratinocyte derived laminin-5 contributes to adhesion and melanin production in melanoma cells.;멜라닌 색소를 생성하는 멜라닌 세포와 케라틴 세포의 밀접한 관계를 잘 알려져 있으나, 이들 사이의 조절 기전은 아직 명확하지 않다. 본 연구자는 케라틴 세포가 생성하는 laminin-5가 흑색종 세포의 조절에 관여한다는 사실을 증명하고자 하였다. 사람 흑색종 세포인 A375는 케라틴 세포가 생성한 세포외기질에 효과적으로 부착 및 spreading을 하였으며, 이는 케라틴 세포가 생성한 세포외기질이 중요함을 시사한다. siRNA를 이용하여 기저막의 주요 구성성분인 laminin-5의 발현을 억제하였을 때, 케라틴 세포의 세포외기질은 흑색종 세포의 부착 및 spreading을 촉진하지 못하였다. 이는 흑색종 세포가 laminin-5에 의해 부착 및 spreading이 촉진되는 결과와 일치하며, 케라틴 세포에 의해 생성된 laminin-5가 세포 부착과 spreading에 중요함을 증명해 준다. Laminin-5가 흑색종 세포의 이동성이나 증식에는 큰 영향을 미치지 않았지만, 멜라닌 합성을 증가시켰다. 게다가, laminin-5는 a-melanocyte stimulating hormone에 의한 멜라닌합성과정을 더욱 촉진시켰다. 이러한 결과들은 케라틴 세포가 생성한 laminin-5가 흑색종 세포의 adhesion과 멜라닌 합성을 조절한다는 것을 뒷받침한다.Ⅰ. INTRODUCTION = 1 Ⅱ. MATERIALS AND METHODS = 7 1. Materials and antibodies = 7 2. Cell Culture and transfection = 7 3. RNA Extraction and Reverse Transcription Polymerase Chain Reaction (RT-PCR) = 8 4. Small interfering RNA (siRNA) = 10 5. Immunoblotting = 10 6. Fluorescence-activated cell sorting (FACS) = 11 7. Migration assay = 11 8. Wound healing assay = 12 9. Preparation of keratinocyte-derived extracellular matrix (ECM) and cell spreading assay = 12 10. Cell spreading assay = 13 11. Preparation and treatment of keratinocyte conditioned media = 13 12. MTT assay = 14 13. Melanin determination = 14 Ⅲ. RESULTS = 15 1. Extracellular matrix of keratinocyte promotes adhesion and spreading of melanoma cells. = 15 2. Laminin-5 promotes attachment and spread of melanoma cells among the other ECM molecules from keratinocyte. = 19 3. Melanoma cells are attached and spread on laminin-5 through integrin α6. = 25 4. Keratinocyte-derived laminin-5 regulates melanin synthesis of melanoma cells. = 30 5. Paracrine factor from keratinocytes regulates syndecan-2 mediated migration of melanoma. = 36 Ⅳ. DISCUSSION = 43 Ⅴ. REFERENCES = 47 국문초록 = 53 감사의 글 = 5

The Role of keratinocyte in regulation of melanoma function

피부 조직에서 멜라닌세포와 주변의 케라틴세포는 기능적으로 매우 밀접한 관계를 맺고 있다. 특히, 피부에서 가장 바깥쪽에 위치한 층의 대부분을 구성하고 있는 케라틴세포는 다양한 조절 메커니즘으로 멜라닌세포를 조절하고 있다. 크게 세가지 메커니즘이 제시되어 왔으며, 세포외기질, 수용성 인자 그리고 세포 결합 단백질에 의한 메커니즘이 그것이다. 케라틴세포 (HaCaT세포)가 합성하는 세포외기질 중 laminin-332는 악성흑색종 세포의 부착, focal adhesion 형성 및 세포이동성을 촉진하였으며 integrin alpha6가 이러한 세포현상에 receptor로 작용하였다. Integrin alpha6를 knockdown시킨 사람 악성흑색종 세포주인 A375세포는 laminin-332를 매개로 한 세포 부착 및 이동성이 감소하였다. 게다가 케라틴세포가 분비한 laminin-332는 악성흑색종 세포주인 B16F10과 MNT-1세포의 멜라닌 합성을 촉진시켰다. 그러나 예상과 달리, laminin-332에 의한 멜라닌 합성과정은 멜라닌 합성에 중요한 효소인 tyrosinase의 발현과 활성과 관련이 없었다. Laminin-332는 ERK의 활성을 촉진하여 tyrosinase의 기질인 L-tyrosine의 멜라닌세포나 악성흑색종 세포 내 유입 증가에 기여하였다. 따라서 케라틴세포가 합성한 laminin-332는 멜라닌세포 및 악성흑색종 세포의 멜라닌 합성을 비롯하여 세포 부착을 매개로 한 다양한 기능을 조절한다. 케라틴세포가 분비하는 수용성 인자 중 하나인 alpha-MSH는 악성흑색종 세포의 syndecan-2발현을 저해하여 악성흑색종 세포의 세포 이동성을 억제하였다. 흥미롭게도 alpha-MSH의 receptor인 MC1R 과발현은 syndecan-2발현 증가를 유도하여 세포이동성을 촉진하였다. MC1R의 발현은 p38 MAPK 활성을 억제하여 syndecan-2의 발현 및 세포이동성을 촉진하였으나, alpha-MSH는 반대 효과를 나타냈다. 이러한 결과는 케라틴세포가 alpha-MSH를 분비하여 악성흑색종 세포의 MC1R을 통한 이동성을 억제하고 있음을 제시한다. 또한 케라틴세포는 직접적인 세포간의 결합으로 악성흑색종 세포의 기능을 조절하였다. A375세포를 단독으로 배양 시 N-cadherin의 발현이 높았으나, HaCaT세포와 함께 배양 시 A375세포의 N-cadherin이 감소하였다. 그리고 A375-HaCaT을 함께 배양 하였을 때, ERK와 AKT의 활성이 감소하였으나 GSK3beta의 활성은 증가하였다. GSK3beta의 활성 억제로 N-cadherin의 발현이 증가하였으므로, 케라틴세포는 직접적 세포결합을 하여 GSK3beta활성조절을 통해 악성흑색종 세포의 N-cadherin의 억제자 역할을 한다는 것을 알 수 있다. 결론적으로 본 연구는 케라틴세포가 멜라닌세포 및 악성흑색종 세포를 다양한 메커니즘으로 조절하고 있음을 제시한다.;In human skin, melanocytes and its neighboring keratinocytes have a close functional interrelationship each other. Particularly, keratinocytes, the prevalent cell type of the uppermost layer of human skin, regulate melanocytes through various regulatory mechanisms. Three regulatory mechanisms have been provided, which are including extracellular matrix (ECM), soluble factors and cell adhesion molecules. Among ECMs derived from keratinocytes (HaCaT cells), laminin-332 promoted adhesion, focal adhesion formation and migration of melanoma cells and it was through the interaction with integrin alpha6. Consistently, knockdown of integrin alpha6 in human melanoma A375 cells reduced laminin-332-mediated adhesion and migration. In addition, keratinocyte-derived laminin-332 enhanced level of melanin in pigmented melanoma cell lines; B16F10 cells and MNT-1 cells. Unexpectedly, laminin-332-enhanced melanogenesis was independent on the expression and activation of tyrosinase, the key enzyme in melanogenesis. Instead, laminin-332 promoted ERK mediated uptake of L-tyrosine, a substrate of tyrosinase, into melanocytes and melanoma cells. Therefore, keratinocyte-derived laminin-332 seems to contribute to adhesion-mediated functions of melanocytes including melanin production. On the other hand, one of soluble factor secreted from keratinocytes, alpha-Melanocyte stimulating hormone (alpha-MSH), reduced migration of melanoma cells by downregulating syndecan-2 expression. Surprisingly, overexpression of melanocortin receptor 1 (MC1R), the receptor of alpha-MSH, enhanced syndecan-2 mediated migration. MC1R expression reduced p38 MAPK activity and subsequently increased syndecan-2 expression and cell migration, but the opposite effects were observed in cells treated with alpha-MSH. These results suggest that keratinocytes inhibit MC1R-mediated migration of melanoma cells by producing alpha-MSH. Besides, keratinocytes regulated melanoma cell functions through a direct interaction. Although mono-cultured A375 cells showed high levels of basal N-cadherin expression, A375-HaCaT co-culture induced reduction of levels of N-cadherin in A375 cells. In addition, A375-HaCaT co-culture reduced the activation of ERK and AKT, but enhanced the activity of GSK3beta. Since inhibition of GSK3betaabolished reduction of N-cadherin, keratinocytes seems to GSK3beta mediated negatively regulate levels of N-cadherin in melanoma cells by a direct interaction. Taken together, this research strongly suggests that keratinocyte contributes to the regulation of melanocytes and melanoma cells in various pathways.INTRODUCTION 1 CHAPTER I 21 I. INTRODUNCTION 22 II. MATERIALS AND METHODS 25 1. Materials and antibodies 25 2. Cell Culture and transfection 25 3. RNA Extraction and Reverse Transcription Polymerase Chain Reaction(RT-PCR) 26 4. Small interfering RNA (siRNA) 27 5. Immunoblotting 28 6. Cell spreading assay 28 7. Preparation of keratinocyte-derived extracellular matrix (ECM) and cell spreading assay 29 8. Immunofluorescence analysis 30 9. Transwell migration assay 30 10. Monitoring cell adhesion and migration 31 11. Preparation and treatment of keratinocyte conditioned media 32 12. Statistical Analysis 32 III. RESULTS 33 1. Keratinocyte-derived laminin-332 promotes the adhesion and spreading of melanoma cells 33 2. Integrin a6 regulates the laminin-332-mediated adhesion of melanoma cells 37 3. Laminin-332 promotes focal adhesion formation in melanoma cells 40 4. Laminin-332 enhances the migration of melanoma cells 43 5. Laminin-332 promotes adhesion and migration of melanocytes 45 6. Keratinocyte-derived soluble factors are not essential for the adhesion of melanoma cells 48 IV. DISCUSSION 51 CHAPTER II 56 I. INTRODUCTION 57 II. MATERIALS AND METHODS 59 1. Materials and antibodies 59 2. Cell culture and transfection 59 3. RNA extraction and reverse transcription polymerase chain reaction (RTPCR) 60 4. Small interfering RNA (siRNA) 61 5. Immunoblotting 62 6. Immunofluorescence analysis 62 7. Preparation of tissue culture plate coated with ECM substrate 63 8. Preparation of keratinocyte-derived ECM 64 9. Melanin determination 64 10. Tyrosinase activity assay 65 11. Intracellular tyrosine determination 66 12. Tyrosine uptake measurement 66 13. Statistical Analysis 67 III. RESULTS 68 1. Keratinocyte-derived laminin-332 promotes melanin synthesis of melanoma cells 68 2. Laminin-332 potentiates melanogenic response to a-MSH in melanoma cells 72 3. Laminin-332-mediated melanin synthesis is independent on tyrosinase 74 4. Laminin-332 promotes tyrosine uptake into melanoma cells 77 5. Laminin-332 promotes tyrosine uptake into melanoma cells via adhesiondependent MAP kinase activation 81 6. Laminin-332 regulates melanin synthesis in human primary melanocytes 85 IV. DISCUSSION 88 CHAPTER III 93 I. INTRODUNCTION 94 II. MATERIALS AND METHODS 98 1. Materials and antibodies 98 2. Cell culture and transfection 98 3. Synthesis of small interfering RNA constructs 99 4. RNA Extraction and Reverse Transcription-PCR 100 5. Immunoblotting 101 6. Flow cytometry 102 7. Construction of transcriptional syndecan-2 reporter plasmids 102 8. Luciferase assay 103 9. Transwell migration assay 103 10. Statistical Analysis 104 III. RESULTS 105 1. a-MSH inhibit melanoma cell migration by decreasing syndecan-2 expression 105 2. MC1R promotes migration of melanoma cells by controlling syndecan-2 expression 109 3. a-MSH negatively regulates MC1R mediated syndecan-2 expression and cell migration1 16 4. MC1R regulates syndecan-2 expression via inhibition of p38 activity 119 IV. DISCUSSION 124 CHAPTER IV 128 I. INTRODUCTION 129 II. MATERIALS AND METHODS 132 1. Materials and antibodies 132 2. Cell culture and transfection 132 3. RNA extraction and reverse transcription polymerase chain reaction (RTPCR) 133 4. Co-culture 134 5. Immunoblotting 134 6. Immunofluorescence analysis 135 III. RESULTS 136 1. Keratinocytes negatively regulate levels of N-cadherin of melanoma cells through cell-cell contacts 136 2. N-cadherin reduction in co-cultured melanoma cells is independent on both soluble and insoluble factors derived from keratinocytes 141 3. Snail expression is reduced in co-cultured melanoma cells 144 4. Keratinocytes regulate N-cadherin stability via AKT-GSK3b pathway in melanoma cells 146 IV. DISCUSSION 150 DISCUSSION 154 REFERENCES 170 논문개요 185 감사의 글 18

A Phonological Theory Using Unification-based Grammar Formalism

This paper has two purposes: one is to propose a new theory for phonological theory using unification-based grammar formalism, the other is to describe Korean phonology with a unification-based grammar called Korean Phrase Structure Grammar (KPSG). The approach of KPSG provides an explicit development model for contruction of a computational linguistic system. It has proven that the system theory is simpler then other system theories such those employing the traditional generative phonological approaches

Spirituality of Trans-Borders: A Narrative of Transformation of a Korean Sex Slave

Contemporary pastoral theology has been concerned about spirituality which would help to overcome splits and breakages of modernism. This paper intends to examine this issue through the narrative of a Korean sex slave during World War II and her subsequent conversion to Christianity. As a victim and agent of modernism, this sex slave showed spirituality of trans-borders: Christianity of trans-borders, motherhood of transborders, and deity of trans-borders. © 2009 Springer Science+Business Media, LLC

Local electrical characterizations of nanomaterials with scanning probe microscopy

학위논문(박사)--아주대학교 일반대학원 :에너지시스템학과,2016. 2Chapter 1 Introduction 1 Chapter 2 Theoretical background 3 2.1 Field-effect transistors and nanomaterials 3 2.2 1D- and 2D-nanomaterials 9 2.2.1 Single-walled carbon nanotube 9 2.2.2 Zinc oxide nanowire 14 2.2.3 Graphene oxide and its reduction 17 2.3 Atomic force microscopy 19 2.3.1 Brief history of atomic force microscopy 19 2.3.2 Electrical characterizations using AFM 20 2.3.3 Principles of AFM 21 2.3.4 Setup and operation modes of AFM 21 2.3.5 Principle of electrostatic force microscopy (EFM) 28 2.3.6 Principle of scanning gate microscopy (SGM) 30 Chapter 3 Local investigations of SWCNT-network devices using EFM and SGM 32 3.1 Introduction 32 3.2 Sample preparation 33 3.3 Experimental results and discussion 34 3.3.1 Investigating operation of SWCNT-network FETs 34 3.3.2 Local investigation of nitric acid vapor treatments on SWCNT networks 42 3.4 Conclusion 50 Chapter 4 Local characterizations of dielectrophoretically deposited CNTs 52 4.1 Introduction 52 4.2 Sample preparation 53 4.3 Experimental results and discussion 53 4.4 Conclusion 60 Chapter 5 Quantitative voltage profile inside 1D-nanomaterial devices 61 5.1 Introduction 61 5.2 Sample preparation 62 5.3 Experimental results and discussion 62 5.4 Conclusion 72 Chapter 6 Local conductance mapping of graphene oxide and reduced-graphene oxide during reduction process 74 6.1 Introduction 74 6.2 Sample preparation 75 6.3 Experimental results and discussion 75 6.4 Conclusion 94 Chapter 7 Conclusion 95 Bibliography/Reference 97 Publication list 107DoctoralIn this thesis, local electrical characterizations of nanomaterials and nanomaterial-based devices were carried out using scanning-probe-microscopy (SPM)-based techniques. For the experiments, various nanomaterials and nanodevices were synthesized and fabricated. Electrostatic force microscopy (EFM) and scanning gate microscopy (SGM) with a conventional electrical measurement, like IV characteristics, were employed to analyze the nanomaterials and the nanodevices. Firstly, operation of single-walled carbon nanotube (SWCNT) network FET devices was investigated using ac-EFM and SGM measurements. The device in this experiment has the apparent on-off ratio of 104, which is expected to be a FET based on semiconducting SWCNTs. However, SGM measurements show that localized segments of ~600 nm determines semiconducting characteristics of the whole device, and ac-EFM reveal that resistances are composed of resistances of electrode-SWCNT, SWCNT-SWCNT, and SWCNT segments with a kinked defect. Therefore, ac-EFM and SGM demonstrated the transfer characteristics of 1D network devices in nanoscale. Taking advantage of ac-EFM and SGM in nanoscale, we investigated the effects of nitric acid vapor treatment, as a doping method, through SWCNT-network FET devices. From SGM measurements before and after exposure of nitric acid vapor, p-type doping of the treatment is confirmed in nanoscale. Furthermore, additional current paths in metallic SWCNT network region after nitric acid vapor treatment are seen in ac-EFM images. As a result, nitric acid treatment can affect p-type doping and reduction of SWCNT-SWCNT resistances in the SWNCT networks. In dielectrophoretically-deposited CNT devices, SGM measurements with IV characteristics confirm metallic CNTs are well-separated from SWCNT dispersion because there are no gate responses in both IV and SGM measurements. Also, resistance of these DEP-deposited CNT devices is affected by connection among CNTs rather than at electrode-CNT junctions. Although EFM measurement provide relative differences of voltage in nanomaterials and nanodevices, quantitative analysis is, basically, difficult due to the local capacitive term in the EFM signal. Thus, we demonstrate a calibration procedure to obtain quantitative local voltage distributions of 1D-nanodevices. As voltage profiles are compared to IV characteristics, local resistances of electrode-SWCNT, electrode-ZnO nanowire, and defect in a SWCNT in the nanodevices are calculated. Moreover, photo-induced carrier concentrations of ZnO nanowires are also extracted from these results. Finally, 2D conductance mapping was carried out using EFM phase measurements. Graphene oxide is intrinsically an insulator. However, its conductivity can be recovered by reduction process. We find homogeneous electrical state of reduced graphene oxide is related to higher conductivity from EFM measurements in thermal and chemical reduction, and this result is confirmed again by combining EFM measurements and IV characteristics. In conclusion, EFM and SGM measurements can visualize electrical informations, such as electric potential differences, local perturbations’, and local conductivities, of the nanomaterials and the nanodevices, and these local measurements with nanoscale informations can compensate conventional characterizing tools for bulk samples. In addition, quantitative analysis through calibration of EFM images provides much detailed informations in nanoscale of the nanodevies. In even 2D nanomaterials, local conductance mapping is successfully carried out. Therefore, EFM and SGM techniques will be actively applied to various fields related to nanoscience and nanotechnology

Minireview: Syndecans and their crucial roles during tissue regeneration

Syndecans are transmembrane heparan sulfate proteoglycans, with roles in development, tumorigenesis and inflammation, and growing evidence for involvement in tissue regeneration. This is a fast developing field with the prospect of utilizing tissue engineering and biomaterials in novel therapies. Syndecan receptors are not only ubiquitous in mammalian tissues, regulating cell adhesion, migration, proliferation, and differentiation through independent signaling but also working alongside other receptors. Their importance is highlighted by an ability to interact with a diverse array of ligands, including extracellular matrix glycoproteins, growth factors, morphogens, and cytokines that are important regulators of regeneration. We also discuss the potential for syndecans to regulate stem cell properties, and suggest that understanding these proteoglycans is relevant to exploiting cell, tissue, and materials technologies

Keratinocyte-derived laminin-332 promotes adhesion and migration in melanocytes and melanoma

Melanocytes are highly motile cells that play an integral role in basic skin physiological processes such as wound healing and proper skin pigmentation. It has been postulated that surrounding keratinocytes contribute to melanocyte migration, but underlying mechanisms remain rather vague so far. In this study, we set out to analyze the specific potential contribution of keratinocyte components to melanocytes and melanoma cell migration-related processes. Our studies revealed that A375 human melanoma cell attachment, spreading, and migration are interestingly better supported by HaCaT keratinocyte extracellular matrix (ECM) than by self-derived A375 ECM. Moreover, HaCaT ECM caused increased integrin α6 expression, adhesion-mediated focal adhesion kinase phosphorylation, and focal adhesion formations. Similar effects were confirmed in human melanocytes. Furthermore, we found that keratinocyte-derived soluble factors did not appear to significantly contribute to these processes. Specific extrinsic factors that promoted melanoma migration were attributed to keratinocyte-derived laminin-332, whereas alternative ECM component such as laminin-111 and fibronectin functions appeared to have insignificant contributions. Taken together, these studies implicate extrinsic laminin-332 in promoting the high mobility property and perhaps invasiveness inherently characteristic of, and that are the menace of, melanocytes and melanomas, respectively. © 2011 by The American Society for Biochemistry and Molecular Biology, Inc

Syndecan-2 enhances E-cadherin shedding and fibroblast-like morphological changes by inducing MMP-7 expression in colon cancer cells

E-cadherin plays a mechanical role in mediating cell-cell interactions and maintaining epithelial tissue integrity, and the loss of E-cadherin function has been implicated in cancer progression and metastasis. Syndecan-2, a cell-surface heparan sulfate proteoglycan, is upregulated during the development of colon cancer. Here, we assessed the functional relationship between E-cadherin and syndecan-2. We found that stable overexpression of syndecan-2 in a human colorectal adenocarcinoma cell line (HT29) enhanced the proteolytic shedding of E-cadherin to conditioned-media. Either knockdown of matrix metalloproteinase 7 (MMP-7) or inhibition of MMP-7 activity using GM6001 significantly reduced the extracellular shedding of E-cadherin, suggesting that syndecan-2 mediates E-cadherin shedding via MMP-7. Consistent with this notion, enhancement of MMP-7 expression by interleukin-1 alpha treatment increased the shedding of E-cadherin. Conversely, the specific reduction of either syndecan-2 or MMP-7 reduced the shedding of E-cadherin. HT29 cells overexpressing syndecan-2 showed significantly lower cell-surface expression of E-cadherin, decreased cell-cell contact, a more fibroblastic cell morphology, and increased expression levels of ZEB-1. Taken together, these data suggest that syndecan-2 induces extracellular shedding of E-cadherin and supports the acquisition of a fibroblast-like morphology by regulating MMP-7 expression in a colon cancer cell line. (C) 2016 Published by Elsevier Inc