Improving lateral resolution in ultrasound imaging through structured illumination techniques

기존의 초음파 이미징은 회절 한계로 인해 공간 분해능이 제한된다. 초음파 지역화 현미경(Ultrasound Localization Microscopy, ULM)은 조영제를 사용하여 이 회절 한계를 극복하고 초고해상도 이미징을 달성할 수 있으나, 주로 혈관 이미징에 제한되며 단일 고해상도 이미지를 생성하기 위해 수만 장의 저해상도 이미지를 획득해야한다. 이러한 문제를 해결하기 위해, 본 연구는 새로운 초음파 기반 구조화 조명 현미경(ultrasound-based Structured Illumination Microscopy, uSIM) 기법을 제안한다. 본 논문에서 제안한 기법은 초음파 시뮬레이션 및 인체조직 모사팬텀 실험에서 평가되었으며, 개선된 공간 분해능을 보여주었다. 실험 결과는 uSIM 기법이 특정 조직에 국한되지 않고 개선된 공간 분해능을 달성하며, 고해상도 이미지를 생성하는데 단 9장의 저해상도 영상만 필요함을 보여주었다. 본 기법은 다양한 의료용 초음파 진단 응용 분야에서 활용될 수 있을 것으로 기대한다. Conventional ultrasound imaging is limited by the diffraction limit, which constrains its spatial resolution. Although Ultrasound Localization Microscopy (ULM) can overcome this diffraction limit to achieve super-resolution imaging through the use of contrast agents, it is primarily restricted to vascular imaging and requires the acquisition of tens of thousands of low-resolution images to generate a single high-resolution image. To address these challenges, we propose a novel ultrasound-based Structured Illumination Microscopy (uSIM) technique. This method improves lateral resolution as evidenced by both in-silico and in-vitro phantom experiments. Our results demonstrate that uSIM achieves superior spatial resolution without being confined to specific tissues, requiring only nine images to reconstruct high-resolution image. This proposed technique is expected to be applicable in various medical ultrasound diagnostic applications.TRUEscopuskc

솔리드스테이트 나노포어를 이용한 생체분자의 단일분자 수준 분석

학위논문(박사)--서울대학교 대학원 :공과대학 재료공학부,2019. 8. 김기범.The nanopore is a biosensor capable of detecting small size molecules such as DNA, RNA, protein, and peptide with high sensitivity. Basically, a nanopore is a nanometersized pore formed on a thin, impermeable membrane, which can be lipid bilayers or solid-state thin films. When a biomolecule passes through a nanopore by an electric field, it generates a current drop, which is used to analyze physical and chemical properties of the passing molecule.This dissertation focuses primarily on improvements in solid-state nanopore devices and single-molecule level analysis of biomolecule using the nanopore device. Chapter 1 contains a general introduction to the nanopore technologies. First, the basic sensing principles of nanopore are described in detail, and two major classes of nanopores, biological nanopores and solid-state nanopores, are introduced. Biological nanopores such as α-hemolysin and MspA, are pore-shaped proteins which are inserted into lipid bilayers to form ion channels. Solid-state nanopores, developed to improve the limitations of biological nanopores, have the advantages of robustness, durability, chemical stability, and ability to tune the nanopore dimensions. Several limitations of solid-state nanopores for high detection sensitivity and studies to overcome them are also described in this chapter. In chapter 2, the fabrication processes for improving the membrane quality of low noise solid-state nanopore is described. A low noise solid-state nanopore platform has been developed using a quartz substrate to reduce the dielectric noise. However, the silicon nitride membrane used in the device had limitations in the membrane quality. Due to the transfer method, plasma-enhanced chemical vapor deposition (PECVD) silicon nitride had to be used, which caused pore expansion during the measurement and instability during high temperature cleaning. In addition, the polymer supporting layer used in the transfer process was not completely removed, but remained on the surface of the nanopore membrane, resulting in protein adsorption. Here, we developed a method for transferring high quality low-pressure chemical vapor deposition (LPCVD) silicon nitride to the low noise nanopore platform without a supporting layer. The nanopore membrane had a clean and uniform surface and exhibits excellent noise properties. In chapter 3, we explore the possibility of using peptide-based materials as a membrane in solid-state nanopore devices as an effort to develop a sequence-specific, programmable biological membrane platform. We use a tyrosine-mediated selfassembly peptide sheet. At the air/water interface, the 5mer peptide YFCFY selfassembles into a uniform and robust two-dimensional structure, and the peptide sheet is easily transferred to a low-noise substrate. The thickness of the peptide membrane can be adjusted to approximately 5 nm by an etching process, and the diameters of the peptide nanopores can be precisely controlled using a focused electron beam with an attuned spot size. The ionic current noise of the peptide nanopore is comparable to those of typical silicon nitride nanopores or multilayer two-dimensional materials. Using this membrane, we successfully observed translocation of double-stranded DNA (dsDNA)with sufficient signal-to-noise ratio (SNR) of ~30 and an elongated translocation speed of ~1 bp/μs. Our results suggest that the self-assembled peptide film can be used as a sensitive nanopore membrane and employed as a platform for applying biological functionalities to solid-state substrates. In chapter 4, we demonstrate a rapid identification of the location of zinc finger protein (ZFP), which is bound to a specific locus along the length of a dsDNA to a single protein resolution using a low noise solid-state nanopore. When ZFP labeled DNAs were driven through a nanopore by an externally applied electric field, characteristic ionic current signals arising from the passage of the DNA/ZFP complex and bare DNA were detected, which enabled us to identify the locations of ZFP binding site. We examined two DNAs with ZFP binding sites at different positions and found that the location of the additional current drop derived from the DNA/ZFP complex is wellmatched with a theoretical one along the length of the DNA molecule. These results suggest that the protein binding site on DNA can be mapped or that genetic information can be read at a single molecule level using solid-state nanopores. In chapter 5, we attempted to distinguish between three similar peptide sequences (~40 amino acids, ~5 kDa) that differed only by location or number of cysteine residues with solid-state nanopores. The cysteine residues are located at one end, one at the center, and at both ends for each of three peptides. We found that differentiation of the three types of peptides by nanopore signals was difficult. However, when the cysteine residue was labeled with a negatively charged molecule, Flamma® 496, the labeled peptides showed distinct signals for each peptides. Comparing the relative current blockades of labeled peptides with applied voltages, we found the label was able to change peptide conformations and the resulting ionic current signals from the three labeled peptides were distinguished based on relative current blockade, full width at half-maximum of the current blockade distribution, and single-molecule level peak shape analysis. Our results suggest that solid-state nanopores combined with a targeted labeling strategy could be used to obtain characteristic peptide signatures that could ultimately be used for protein identification.나노포어는 DNA, RNA, 단백질, 펩타이드 등의 작은 크기의 생체 분자들을 높은 정확도로 검지할 수 있는 바이오센서이다. 기본적으로, 나노포어는 지질 이중층이나 인공적으로 제작된 나노미터 두께 수준의 얇은 멤브레인에 형성된 수 나노미터 수준 직경의 구멍을 말한다. 전해질 수용액 내에 전압을 걸어주면 나노포어 멤브레인에 전기장이 생기고 나노포어를 통한 이온 전류가 발생한다. 이 때 수용액 내의 전하를 띤 생체 분자가 나노포어를 통과하며 이온 전류를 일시적으로 막게 된다. 이 때 발생하는 전류 하강의 크기, 지속 시간, 발생 빈도, 모양 등을 분석하여, 통과하는 생체분자의 크기, 모양, 표면 전하 등 생체 분자의 물리적, 화학적 특성을 파악할 수 있다. 이 학위 논문은 주로 기존 솔리드스테이트(solid-state) 나노포어 소자의 개선과, 개선된 나노포어 소자를 이용한 단일 분자 수준의 효율적인 생체 분자 분석에 대한 연구 결과를 담고 있다. 제 1장에서는 나노포어에 대한 전반적인 소개가 서술되어 있다. 먼저, 나노포어의 기본적인 생체 분자 검지 원리를 자세히 소개하고, 나노포어의 가장 큰 두 가지 분류인 단백질 나노포어와 솔리드스테이트 나노포어에 대해 소개한다. 알파헤모라이신(α-hemolysin) 혹은 MspA로 대표되는 단백질 나노포어는, 그 자체로 나노미터 크기의 포어를 갖고 있는 형태의 단백질이고, 보통 지질 이중층에 삽입하여 이온 통로를 형성한다. 솔리드스테이트 나노포어는 단백질 나노포어의 한계점인 물리적 견고성, 실험 지속성, 화학적 안정성, 고정된 크기의 나노포어 직경 등을 개선하고자 개발되었다. 이러한 솔리드스테이트 나노포어를 이용한 다양한 생체 분자 검지 예시들을 서술하고, 솔리드스테이트 나노포어가 갖고 있는 한계점들, 그리고 그것들을 극복하기 위한 연구 결과들을 소개한다. 제 2장에서는 저잡음 솔리드스테이트 나노포어 소자의 멤브레인 품질 향상을 위한 제작 공정의 개선을 서술한다. 기존 저잡음 솔리드스테이트 나노포어는 쿼츠를 나노포어 기판으로 사용하여 dielectric noise를 줄였지만, 해당 소자에 사용된 실리콘나이트라이드 멤브레인은 몇 가지 뚜렷한 한계점이 있었다. 이는 측정 중 나노포어가 단시간 내에 커지거나, 멤브레인이 고온의 클리닝 공정을 버티지 못하거나, 멤브레인 표면에 단백질들이 들러붙는 등의 측정 안정성 문제이다. 여기서는 안정성 측면에서 훌륭한 특성을 갖는 LPCVD 실리콘나이트라이드를 저잡음 나노포어 소자의 멤브레인으로 활용하는 제작 방법에 대해 서술하고, 제작된 나노포어 소자의 특성을 분석한다. 제 3장에서는 솔리드스테이트 나노포어 기판에 자가 조립 펩타이드 필름을 멤브레인 물질로 활용하는 하이브리드 나노포어에 대한 연구 결과를 소개한다. 물/공기 계면에서 우리가 사용한 tyrosine 기반 펩타이드인 YFCFY는 균일하고 안정성 있는 2D 구조를 형성하고, 그 자가 조립 펩타이드 필름은 저잡음 나노포어 기판에 쉽게 전사될 수 있다. 펩타이드 필름의 초기 두께는 10 nm 이상 이었지만, 에칭 과정을 통해 약 5 nm 수준으로 조절이 가능하다. 기존의 TEM을 이용한 나노포어 형성 방식을 이용해 펩타이드 멤브레인에 나노포어를 형성하는데 성공했고, 전자빔의 세기를 조절하여 1 nm 수준에서 정교하게 펩타이드 나노포어의 직경을 조절할 수 있었다. 펩타이드 나노포어의 이온 전류 잡음 특성은 일반적인 실리콘나이트라이드 나노포어 혹은 다중층의 2D 물질 나노포어와 유사한 수준으로, 나노포어로 활용되기에 충분했다. 펩타이드 나노포어를 통한 dsDNA의 통과를 약 30 정도의 훌륭한 신호대잡음비와 약 1 bp/μs의 느린 통과 속도로 검출할 수 있었다. 이 결과는 자가 조립 펩타이드 필름이 나노포어 멤브레인으로 사용될 수 있고, 솔리드스테이트 기판에 생물학적 기능성을 결합시킬 수 있는 가능성을 제시했다. 제 4장에서는 저잡음 솔리드스테이트 나노포어를 이용해 zinc finger protein (ZFP)이 dsDNA의 특정 염기 서열에 결합하는 것을 단일 분자 수준에서 빠르고 정확하게 검출한 결과를 소개한다. ZFP/DNA 결합체가 전기장에 의해 나노포어를 통과할 때, DNA만 통과할 때와는 확연히 다른 전류 하강 형태를 검출할 수 있었다. DNA가 나노포어를 통과할 때, ZFP가 결합된 부분에서 순간적으로 더 큰 전류 하강을 보여주고 이를 바탕으로 ZFP의 결합 여부 및 결합 위치를 확인할 수 있다. 총 길이와 ZFP 결합 위치가 다른 두 종류의 DNA에 대해, 실제 염기 서열 존재 위치와 나노포어 실험을 통해 얻어낸 ZFP 결합 위치가 일치하는 것을 확인했다. 이 결과는 단백질이 DNA에 결합하는 위치를 저잡음 솔리드스테이트 나노포어를 이용해 빠르게 검출하고, DNA의 특정 유전 정보를 단일 분자 수준에서 효율적으로 얻을 수 있음을 보여준다. 제 5장에서는 거의 같은 아미노산 서열로 구성된 세 종류의 유사한 펩타이드를 솔리드스테이트 나노포어로 구별한 결과를 소개한다. 세 종류의 펩타이드는 1개의 cystine의 위치 혹은 개수만 다른 약 40개의 아미노산으로 이루어진 약 5 kDa 수준의 작은 펩타이드이며, 첫번째 펩타이드는 cysteine이 한 쪽 끝에, 두번째 펩타이드는 중앙에, 마지막 펩타이드는 양 쪽 끝에 cysteine이 1개씩 존재한다. 세 종류의 펩타이드가 발생시키는 나노포어 전류 하강 신호는 구별이 힘들었지만, cysteine에 선택적으로 결합하는 음전하를 띠는 분자인 Flamma® 496을 붙인 labeled 펩타이드의 경우, 각각의 펩타이드가 뚜렷하게 구별되는 나노포어 신호를 나타냈다. 나노포어 멤브레인에 인가되는 전압에 따라 전류 하강 신호를 비교하여, label의 존재 위치에 따라 펩타이드의 통과 형태가 달라질 수 있음을 확인했다. 펩타이드의 나노포어 통과 형태에 따라, 전류 하강 크기, 전류 하강 크기의 분포, 그리고 단일 분자 수준에서의 픽 모양 분석을 통해 세 종류의 펩타이드를 구별할 수 있었다. 이 결과는 솔리드스테이트 나노포어와 표적화된 labeling 기술의 결합이 궁극적으로 단백질 동정에 사용될 수 있음을 제안했다.Abstract ···························································································· i Table of contents ················································································· v List of figures··················································································· viii CHAPTER 1. Introduction ························································· 1 1.1. Nanopore technologies····································································· 2 1.1.1. Basic principles and history of nanopores ········································ 2 1.1.2. Fabrication methods of solid-state nanopores ··································· 7 1.1.3. Biological applications of solid-state nanopores ······························· 13 1.2. Issues in solid-state nanopores··························································· 25 1.2.1. Spatial resolution ··································································· 25 1.2.2. Signal to noise ratio ································································ 30 References ······················································································· 36 CHAPTER 2. Enhancement of Solid-State Nanopore Membrane ················································································· 43 2.1. Introduction ················································································ 44 2.2. Results and discussion ···································································· 47 References ······················································································· 51 CHAPTER 3. DNA Translocation through a Nanopore in Ultrathin Self-assembled Peptide Membrane ··························· 53 3.1. Introduction ················································································ 54 3.2. Experimental details ······································································ 57 3.3. Results and discussion ···································································· 59 3.3.1. Peptide film characterization and nanopore formation ························ 59 3.3.2. Nanopore conductance measurements and noise characteristics ············ 65 3.3.3. DNA translocation through a peptide nanopore ································ 67 3.4. Summary ··················································································· 71 References ······················································································· 72 CHAPTER 4. Identifying the Location of a Single Protein along the DNA Strand Using Solid-State Nanopores··························· 81 4.1. Introduction ················································································ 82 4.2. Experimental details ······································································ 87 4.3. Results and discussion ···································································· 93 4.3.1. Translocation of short DNA (520 bp)/ZFP complex ·························· 93 4.3.2. Characterization of DNA/ZFP binding ·········································· 98 4.3.3. Translocation of long DNA (5605 bp)/ZFP complex and identifying the binding locations ·································································· 102 4.4. Summary ·················································································· 110 References······················································································ 111 CHAPTER 5. Differentiation of Selectively Labeled Peptides using Solid-State Nanopores ···················································· 119 5.1. Introduction ··············································································· 120 5.2. Experimental details····································································· 123 5.3. Results and Discussion ·································································· 125 5.3.1. Schematics of the experiments ·················································· 125 5.3.2. Electroosmotic capture of unlabeled peptides ································ 129 5.3.3. Nanopore measurement of three unlabeled peptides ························· 132 5.3.4. Capture rate of labeled peptides in the EO and EP directions ··············· 134 5.3.5. Stretching of labeled peptides in the EP direction ···························· 138 5.3.6. Nanopore measurement of three labeled peptides ···························· 141 5.3.7. Comparison of peak shapes of the three labeled peptides ···················· 144 5.4. Summary ·················································································· 149 References ····················································································· 150 CHAPTER 6. Summary and Conclusions······························· 157 Abstract (in Korean) ·········································································· 161 List of publications············································································ 165Docto

Self-healing performance of GGBFS based cementitious mortar with granulated activators exposed to a seawater environment

Concrete structures exposed to marine environments are susceptible to attack by harmful ions such as chloride, sulfate, etc. Ground granulated blast furnace slag (GGBFS) blended cementitious materials are used as a binder in coastal concrete structures. Cracks are generated at young ages due to shrinkage or other factors, which allow the ingress of harmful ions. Therefore, repair and maintenance of such structures is necessary to increase the service lives of these structures. Autogenous self-healing of the cement composites has proved to be an effective alternative method. It occurs when water comes in contact with the unhydrated cement particles and forms additional hydration products. In this study, cement mortar was prepared by replacing cement with GGBFS up to 50%. Granules of activators Ca(OH)(2) and Na2SO4 were made and incorporated at different dosages. Physical and self-healing performance of the mortar " specimens were evaluated via compressive strength, relative dynamic modulus of elasticity, ultrasonic pulse velocity and water permeability tests. The healing products were examined via electron microscopy, energy dispersive X-ray spectrometry, and microhardness tests. The results indicated that the specimens incorporating granulated Na2SO4 showed minimal self-healing performance while the self healing efficiency of the specimens with Ca(OH)(2) granules was significantly enhanced. (C) 2018 Elsevier Ltd. All rights reserved

소아에서 폐동맥판막 역류가 양심실의 용적과 기능에 미치는 조기 영향

학위논문 (석사)-- 서울대학교 대학원 : 의학과 흉부외과학전공, 2011.2. 김웅한.Maste

고정밀 동하중 측정장치 구현을 위한 견실설계

학위논문(석사)--서울대학교 대학원 :기계항공공학부,2006.Maste

APPARATUS AND METHOD FOR SUPPRESSING NOISE IN ULTRASOUND IMAGE BASED ON DEEP-LEARNING NETWORK WITHOUT REFERENCE DATA

본 개시의 일 실시 예에 따른 초음파 영상의 스페클 저감 방법은 프로세서에 의해, 스페클 패턴이 포함된 제1 초음파 영상을 제공 받는 단계 및 프로세서에 의해, 제1 초음파 영상을 딥러닝 기반의 학습 모델에 입력하여 스페클 패턴의 적어도 일부가 저감된 제2 초음파 영상을 획득하는 단계를 포함하고, 학습 모델은 스페클 패턴이 포함된 서로 다른 초음파 영상이 각각 입력 및 레이블(label)로 구성된 훈련 데이터로 훈련된 학습 모델일 수 있다

Sources separation of passive sonar array signal using recurrent neural network-based deep neural network with 3-D tensor

In underwater signal processing, separating individual signals from mixed signals has long been a challenge due to low signal quality. The common method using Short-time Fourier transform for spectrogram analysis has faced criticism for its complex parameter optimization and loss of phase data. We propose a Triple-path Recurrent Neural Network, based on the Dual-path Recurrent Neural Network's success in long time series signal processing, to handle three-dimensional tensors from multi-channel sensor input signals. By dividing input signals into short chunks and creating a 3D tensor, the method accounts for relationships within and between chunks and channels, enabling local and global feature learning. The proposed technique demonstrates improved Root Mean Square Error and Scale Invariant Signal to Noise Ratio compared to the existing method. 다양한 신호가 혼합된 수중 신호로부터 각각의 신호를 분리하는 기술은 오랫동안 연구되어왔지만, 낮은 품질의 수중 신호의 특성 상 쉽게 해결되지 않는 문제이다. 현재 주로 사용되는 방법은 Short-time Fourier transform을 사용하여 수신된 음향신호의 스펙트로그램을 얻은 뒤, 주파수의 특성을 분석하여 신호를 분리하는 기술이다. 하지만 매개변수의 최적화가 까다롭고, 스펙트로그램으로 변환하는 과정에서 위상 정보들이 손실되는 한계점이 지적되었다. 본 연구에서는 이러한 문제를 해결하기 위해 긴 시계열 신호 처리에서 좋은 성능을 보인 Dual-path Recurrent Neural Network을 기반으로, 다중 채널 센서로부터 생성된 입력신호인 3차원 텐서를 처리할 수 있도록 변형된 Tripple-path Recurrent Neural Network을 제안한다. 제안하는 기술은 먼저 다중 채널 입력 신호를 짧은 조각으로 분할하고 조각 내 신호 간, 구성된 조각간, 그리고 채널 신호 간의 각각의 관계를 고려한 3차원 텐서를 생성하여 로컬 및 글로벌 특성을 학습한다. 제안된 기법은, 기존 방법에 비해 개선된 Root Mean Square Error 값과 Scale Invariant Signal to Noise Ratio을 가짐을 확인하였다. © 2023 Acoustical Society of Korea. All rights reserved.TRU

Moving instrument driving system of change of driver's location

본 발명은 운전자 위치 변화에 따라 움직이는 운전 시스템에 관한 것으로, 운전자의 탑승 위치에 따라 조향 장치를 포함한 계기판이 자동으로 좌우로 움직일 수 있도록 함으로써, 차량의 무게 밸런스(balance)를 유지시킬 수 있고 차량의 안정성을 향상시킬 수 있다.본 발명에 의한 운전자 위치 변화에 따라 움직이는 운전 시스템은, 운전자의 탑승 위치를 감지하는 센서, 차량의 조향 장치를 좌우로 이동시키는 이동 수단, 계기판 및 어플리케이션 화면이 띄워지는 디스플레이 장치 및, 상기 센서에서 감지된 운전자의 탑승 위치에 따라, 상기 조향 장치가 차량의 중앙 또는 한쪽 방향으로 이동되도록 상기 이동 수단을 제어하고, 상기 계기판 화면이 상기 조향 장치가 위치한 방향에 표시되도록 상기 디스플레이 장치를 제어하는 제어부를 포함한다

Vehicle Dynamics And Analysis of a Three Wheel Electric Vehicle

에너지 가격의 상승으로 인해 도심형 전기자동차에 대한 연구가 이루어지고 있다. 작고 가벼운 도심형 전기자동차를 만들기 위해 바퀴 3개를 가지는 Three Wheel Electric Vehicle을 고려해 볼 수 있다. Three Wheel의 경우는 Four Wheel에 비해 무게가 가볍고 작은 차체로 만들 수 있어 고효율을 위한 자동차 구조가 될 수 있다. 하지만 Three Wheel Vehicle의 경우 기존 Four Wheel과 구조가 달라 차량의 거동이 기존 Four Wheel Vehicle과 상이하다. Three Wheel Vehicle Modeling을 위해 뒷바퀴의 Track 길이를 최소로 지정하여 하나의 바퀴로 만드는 모델링과 뒤 바퀴 하나만을 고려한 모델링을 생각해 볼 수 있다. 본 연구에서는 Four Wheel과 Three Wheel의 바퀴 수에 따른 변화 및 Three Wheel Vehicle의 뒷바퀴 구조에 따른 차량 거동을 분석하였다

Mechanical characteristics of carbon/carbon composite for aircraft brake disk

학위논문(석사) - 한국과학기술원 : 항공우주공학과, 1997.2, [ viii, 72 p. ]한국과학기술원 : 항공우주공학과