30 research outputs found
복숭아혹진딧물의 피레스로이드와 카바메이트계 살충제 저항성요인의 분자적 진단
Get PDF학위논문 (석사)-- 서울대학교 대학원 : 농생명공학부, 2012. 8. 이시혁.The green peach aphid (Myzus persicae) is an economically serious pest of agricultural and horticultural crops all over the world and developed resistance almost all kinds of insecticides. In this study, target site mutations were investigated by sequencing the voltage-gated sodium channel (vgsc) and acetylcholinesterase (ace) genes in 7 and 10 local strains collected in 2010 and 2011, respectively. In addition, leaf dip bioassay was conducted to determine LC50 values of bifenthrin and methomyl. Based on the mutation survey, quantitative sequencing (QS) was employed for investigation of resistance allele frequencies in local strains. Mutation survey of the vgsc revealed that M918L and L1014F mutations were present in local strains. Especially, M918L mutation showed a higher correlation than L1014F between the resistance allele frequency and actual resistance level. Thus, QS using newly identified M918L mutation should facilitate the detection and monitoring of pyrethroid resistance levels in the field.
As putative mutations for target site insensitivity to carbamates, frequencies of A301S and S431F mutations in ace were investigated by sequencing. However, only S431F mutation was revealed in local strains. QS was employed to detect S431F mutation frequency. Correlation analysis of mutation allele frequency versus actual resistance level revealed that S431F mutation itself does not appear to play a significant role.
To identify whether higher expression of M. persicae carboxylesterase (CbE) E4 is due to gene duplication, gene copy number was determined by quantitative real-time PCR. To determine CbE E4 quantity, Western blotting in conjunction with activity staining were conducted. Correlation analysis was carried out to investigate the possible connection between CbE expression level and its gene copy number, activity and protein quantity. Qualitative changing from point mutation was considered and mutation survey was conducted by PCR. However, new mutation G134C was revealed in oxyanion hole. To predict the functions of this mutation, altered CbE E4 3D structure was predicted and correlation analysis was conducted using sequence chromatogram of G134C mutation. Finally, we expect that altered CbE E4 might play a significant role to hydrolyze and/or sequestrate the carbamate insecticide in M. persicae.TABLE OF CONTENTS
ABSTRACT i
LIST OF TABLES ix
LIST OF FIGURES xi
LITERATURE REVIEW 1
1. Myzus persicae 1
2. Insecticide resistance monitoring 2
3. Carboxylesterase (CbE) as co-resistance factor 3
CHAPTER 1.
Pyrethroid resistance monitoring in local strains of Myzus persicae and characterization of the voltage-gated sodium channel gene 4
Abstract 5
1. Introduction 6
2. Materials and methods 7
2.1 M. persicae strain 7
2.2 Pyrethroid resistance monitoring 7
2.2.1 Local strain genotyping for the detection of resistance mutation 8
2.2.2 Bioassay of local strains by bifenthrin 9
2.2.3 Establishment of QS protocol for the detection of resistance allele frequency 10
2.2.4 Correlation analysis between the vgsc mutation frequency and bifenthrin resistance ratios. 11
2.2.5 Analysis of exon-intron structure in partial genomic DNA fragment of vgsc 11
2.2.6 Analysis of vgsc gene copy number ratio by quantitative real-time PCR(qPCR) 12
3. Results 13
3.1 Bifenthrin resistance level in local strains 13
3.2 Genotypes of the vgsc mutation sites 14
3.3 Establishment of QS protocol 15
3.4 Correlation between the two vgsc mutations and bifenthrin resistance levels 18
3.5 Exon-intron structure of vgsc genomic DNA fragments 22
3.6 vgsc gene copy number ratio 22
4. Discussion 23
CHAPTER 2.
Carbamate resistance monitoring in local strains of M. persicae and characterization of the acetylcholinesterase gene 25
Abstract 26
1. Introduction 27
2. Materials and methods 28
2.1 M. persicae strain 28
2.2 Carbamate resistance monitoring 28
2.2.1 Local strain genotyping for the detection of acetylcholinesterase mutation 28
2.2.2 Bioassay of local strains by methomyl 29
2.2.3 Establishment of the QS protocol to predict resistance allele frequency 30
2.2.4 Correlation analysis between the ace mutation frequency and methomyl resistance ratios 31
3. Results 32
3.1 Methomyl resistance level in local strains 32
3.2 Genotypes of the ace mutation sites 32
3.3 Establishment of QS protocol 38
3.4 Correlation between the ace mutation and methomyl resistance levels 38
4. Discussion 39
CHAPTER 3.
Characterization of carboxylesterase (E4) as a nonspecific metabolic resistance factor in M. persicae 41
Abstract 42
1. Introduction 43
2. Materials and methods 44
2.1 Quantitative real-time PCR (qCR) of Carboxylesterase (CbE) E4 gene 44
2.2 Generation of anti-CbE E4 polyclonal antibody 45
2.3 Activity staining and Western blotting 46
2.4 Mutation survey of CbE E4 gene of local strains 47
2.5 3D structure modeling 47
2.6 Correlation between insecticide resistance ratio, gene copy number and expression levels 47
3. Results 48
3.1 Gene copy number of CbE E4 in local strains 48
3.2 CbE E4 expression levels in local strains 48
3.3 Comparison of CbE E4 sequences among local strains 50
3.4 Three-dimensional (3D) modeling of CbE E4 55
3.5 Determination of correlation factor related with insecticide resistance 56
4. Disscussion 57
LITERATURE CITED 59
KOREAN ABSTRACT 68Maste
티타늄 산화막을 기반으로 하는 저항 스위칭 메모리의 리셋 전환시의 점진적 스위칭 동작과 그 메커니즘에 관한 연구
No full textDRAM 및 NAND 플래시 메모리와 같이 상업화된 메모리들은 수십 년 동안 다양하고 넓은 분야에서 활용되어 왔고 그 수요는 폭발적으로 증가해 오고 있다. 그러나, 최근에, 이러한 상업화된 메모리들은 가까운 미래에 기술적, 물리적 한계에 도달할 것으로 예상된다. 종래의 메모리들의 한계를 극복하기 위해, 3차원 구조 기술, 다층 셀 (MLC) 기술 및 새로운 메모리 연구를 포함한 새로운 접근이 시도되고 있다. 새로운 메모리 중에서, 저항 변화 메모리 (RRAM)는 단순한 구조, 기존의 CMOS 공정과의 호환성, 그리고 3차원 구조와 MLC 동작으로의 확장성 때문에 최근에 관심을 많이 끌고 있으며 그에 대한 연구 보고서들도 급격히 증가하고 있다.
MLC는 평탄한 구조를 기반으로 하는 메모리 셀의 스케일링 한계를 극복할 수 있는 유용한 기술 중의 하나이다. NAND 플래시 메모리의 경우, MLC 기술이 이미 폭넓게 사용되고 있다. 따라서, 새로운 메모리 연구 분야에서도 MLC의 가능성이 필수적으로 고려되어야 한다. RRAM의 경우, 리셋 전환 시의 점진적인 스위칭 현상은 MLC를 실현할 수 있는 중요한 특성들 중 하나이다.
이 논문에서는, 티타늄 산화막을 기반으로 하는 RRAM 셀의 점진적인 리셋 스위칭 특성이 산화량 효과와 스케일링 효과와 함께 연구되었다. 티타늄 산화막이 산소 이온을 적게 함유했을 때, 점진적인 리셋 스위칭 동작이 더욱 쉽게 얻어질 수 있고 ON/OFF 전류비도 증가한다. 전기적 분석으로부터 리셋 전환시의 점진적인 스위칭은 앏은 전도성 필라멘트들 혹은 전도성 필라멘트 가지들의 순차적인 끊어짐 때문이라는 것을 알 수 있었고 그 메카니즘에 대한 모델을 세웠다. 여러 가지 분석을 통해 리셋 전환시의 타입을 결정하는 요소가 컴플라이언스 파워라는 사실을 알 수 있었다. 약 40 nm 지름의 바닥 길이를 가지는 스케일된 RRAM 셀에서도 점진적인 스위칭 현상이 여전히 관찰되며 이것은 전도성 필라멘트의 작은 가지들의 순차적인 끊어짐 또는 줄어듦 때문이다. 즉, 40 nm 설계 룰까지는 심지어 ON/OFF 전류비가 증가된 상태로 점진적인 리셋 스위칭 동작을 이용한 MLC 동작이 사용 가능하다. 그러나, 더욱 작아진 셀에서는 작은 가지를 가지는 전도성 필라멘트가 제한되는 효과 때문에 점진적인 스위칭이 더 이상 일어나지 않을 것으로 예상한다.Commercial memories such as dynamic random access memory (DRAM) and NAND flash memory have been utilized in various and wide fields for several decades and demand for the memories has been rising explosively. However, in recent years, these commercial memories are expected to face the technical and physical limits in near future. In order to overcome limits of conventional memories, novel approaches including 3-dimensional (3D) structure technology, multi-level cell (MLC) technology, and emerging new memory research have been conducted. Among emerging new memories, resistive random access memory (RRAM) has attracted more interests and its research reports have been exponentially increasing recently because of its simple structure, conventional CMOS process compatibility, and extendibility to the 3D structure and MLC operation.
MLC is one of the useful technologies which can overcome the scaling limits of planar-structure-based memory cell. In NAND flash memory field, MLC technology has already been utilized extensively. Accordingly, in the emerging new memory research, the applicability of MLC should be considered. In RRAM, gradual switching phenomenon in reset transition is one of the important properties which are able to realize the MLC.
In this Ph. D. thesis, the gradual reset switching characteristics of TiO2-based RRAM cell are investigated with the effect of oxidation amount and scaling. When TiO2 film contains less oxygen ions (more oxygen vacancies), the gradual reset switching behavior is more easily achieved and the ON/OFF current ratio is increased. The electrical analysis results indicate that the gradual switching in reset transition is due to the sequential rupturing of thin conductive filaments (CFs) or CF branches and the model about the mechanism is established. By using various analyses, it is found that the factor determining the reset type (abrupt and gradual) is the compliance power during forming and set process. In about 40 nm bottom diameter RRAM cell, the gradual switching phenomenon is still observed and is due to the sequential rupturing or the shrinking of micro-branches of conductive filament. That is, to the 40 nm design rule, MLC operation can be employed by using the gradual reset switching behavior with even increased ON/OFF current ratio. However, in further shrunk cell, it is expected that the gradual switching would vanish because of the confinement effect of the conductive filament with micro-branches.CONTENTS
Abstract i
Contents iv
Chapter 1
Introduction 1
1.1 Memory and Emerging New Memory 1
1.2 Motivation 10
1.3 Thesis Scope and Organization 12
Chapter 2
RRAM Technology Overview 14
2. 1 Introduction 14
2. 2 Classification of RRAM 16
2. 3 Electrical Parameters 20
2. 4 Current Issues 22
Chapter 3
Effect of Oxidation Amount on Gradual Reset Switching Behavior in TiO2-Based RRAM Cell and its Modeling 24
3. 1 Introduction 24
3. 2 Experimental Procedure 26
3. 3 Electrical Characteristics and Analysis 31
3. 4 Summary 52
Chapter 4
Gradual Reset Switching Behavior in Scaled RRAM Cell 53
4. 1 Introduction 53
4. 2 Experimental Procedure 55
4. 3 Electrical Characteristics and Analysis 68
4. 4 Summary 93
Chapter 5
Conclusion 94
Bibliography 96
Abstract in Korean 108
List of Publication 111
List of Patent 124Docto
