Understanding the interfacial structures-chemistry relationships in solid oxide fuel cells (SOFC)

Issued as final reportUnited States. Dept. of Energ

Effects of the antimicrobial agent Triclosan on bacterial resistance to disinfection in wastewater treatment processes

2-(2,5-Dichlorophenoxy)-5-chlorophenol or Triclosan is a widely used antimicrobial agent included in a multitude of products, such as soap, toothpaste, and personal care products.;The objective of this research was to investigate the effects of Triclosan on the resistance of activated sludge bacteria to conventional disinfection processes applied in wastewater treatment processes, such as chlorination and UV.;Specific Aim 1. A complex bacterial community collected from an active sludge was acclimated over several sub-cultures in the presence of different concentrations of Triclosan (from 0.0 to 20 mg L-1) and then exposed to sub-lethal doses of chlorine and UV irradiation. Determination of bacterial viability by direct counting and flow-cytometry showed that microbial communities exposed to Triclosan exhibited an increased susceptibility to chlorination and UV by comparison to non-exposed bacteria.;Specific Aim 2. In order to determine the origin of the change of susceptibility observed in Specific Aim 1, we characterized the microbial communities by construction of gene library and restriction fragment length polymorphism (RFLP). Results showed that acclimation on Triclosan resulted in a significant reduction of the bacterial diversity, suggesting that the change of susceptibility to disinfection could be explained, at least partly, by a change of the bacterial community structure. To investigate whether exposure to Triclosan could select bacterial species with a lower susceptibility to chlorination, two highly resistant strains were isolated from Triclosan-acclimated cultures and identified as Pseudomonas fluorescens and Serratia marcescens, which are opportunistic pathogens previously documented as highly resistant to Triclosan. This time, flow cytometry results showed that one of the strains, S. marcescens, exhibited a significant decrease of susceptibility to chlorination after acclimation in the presence of high concentration of Triclosan.;Specific Aim 3. In order to investigate further the relative susceptibility to chlorination of different species in Triclosan-exposed activated sludge bacteria, the microbial community structure was characterized by terminal-restriction fragment length polymorphism (T-RFLP) after sorting dead and living bacteria by flow-cytometry. Our preliminary results showed again that acclimation on Triclosan resulted in a significant reduction of the bacterial diversity, and, more importantly, that several species in Triclosan-acclimated bacterial suspensions exhibited a much higher resistance to chlorination.;Our results provide the first evidence that acclimation on sub-lethal doses of the antimicrobial agent Triclosan can result in decreasing susceptibility of opportunistic pathogens, which could have potential important implication for public health. In addition, our experiments combining flow-cytometry for dead-living bacteria sorting with T-RFLP for microbial community structure characterization opens the way for further research on the effect of antimicrobial agents on the relative susceptibility of different pathogens to disinfection systems

유기 전계 효과 트랜지스터를 위한 1,5-Naphthyridine-2,6 dione (NTD) 유도체의 구조 - 성질에 관한 연구

학위논문(석사)--서울대학교 대학원 :공과대학 재료공학부,2019. 8. Park, Soo Young.초 록 유기 전계 효과 트랜지스터를 위한 1,5-Naphthyridine-2,6-dione (NTD) 유도체의 구조 - 성질에 관한 연구 유기 전계 효과 트랜지스터(OFETs) 는 유연성 및 용액 공정성의 이점 때문에 주목을 받고있다. 유기 트랜지스터의 장점을 살펴보면 공정이 쉽고 저비용제작이 가능하며, 가벼우면서도 좋은 유연성을 가진다는 장점을 가지고 있어서센서, 메모리, 디스플레이 백플레인 등에 다양하게 적용하고 있다. 최근, 연구자들이 트랜지스터에 적용되는 물질 중에 락탐 작용기를 포함하는 물질들에 많은 관심은 갖고 있다. 락탐 작용기를 포함하는 물질들은 독특한 전자-당김 효과에 의한 높은 전자 친화력을 가지게 되어서 LUMO 레벨이 더 안정화될 수 있고, N-원자 위치에 용해성이 있는 사슬을 도입해서 용해도를 조절하는 것도 가능하다. 또한, 평평한 구조에 기인한 강한 파이-파이 상호작용이 있어서 좋은 전자-받개 빌딩 블록으로 많은 연구를 진행하고 있다. 그중에 가장 대표적인 소재는 디케토피롤로피롤(DPP)로써 많이 연구되고 있지만, DPP는 평면성이 부족하기 때문에 트랜지스터의 성능을 더 향상시키기 어려운 문제가 있다. 최근 새로운 전자-받개 비스-락탐 기반의 빌딩 블록인 3,7-dithiophen-2-yl-1,5-dialkyl-1,5-naphthyridine-2,6-dione(NTDT)이 성공적으로 개발된 바 있다. 잘 알려져 있고 많이 쓰이는 비스-락탐 구조인 2,5-dioctyl-3,6-di(thiophen-2-yl)pyrrolo[3,4-c]pyrrole-1,4-dione(DPPT)와 달리, NTDT는 이차원 분자간 상호 작용 (2D) CH‧‧‧O = C이 있으며, 평면성이 높은 분자 구조 및 강한 분자간 π-π 스태킹으로 인한 층상구조와 높은 전자이동도, 높은 결정성을 가지므로 유기 전계-효과 트랜지스터로의 소자 적용이 유리하다. 그러나 NTDT가 트랜지스터 소자에서 괜찮은 이동도를 보여 주었지만 여전히 개선의 여지는 많이 남아있으며, 이를 위해 NTDT 유도체에 대한 구조-물성 상관관계에 대한 연구가 필요한 상황이다. 본 연구에서는 주로 NTDT 유도체의 평면성와 결정성이 OFET 소자의 성능에 미치는 효과를 탐구하였다. 우리는 NTDT 양쪽에 티오펜고리의 다른 위치에 헥실 사슬을 도입해서 NTDT 유도체를 디자인하고 합성했다. 광학적, 전기화학적 특성은 자외선-가시광선 분광법, 발광 분광법 및 순환 전압 전류 (CV)을 통해 측정하였고, 밀도범합수 이론 (DFT)을 사용하여 이론적인 에너지 레벨을 계산해서 연구하였다. 헥실기의 치환 위치에 따라서 NTDT 유도체의 분자 평탄도에 영향을 미치므로 광전자 및 열적 특성이 다른 것을 확인하였다. 또한 형광사진을 보면 알킬기의 치환에 관계없이 용액에서의 형광 효율은 모두 100%정도으로 높고 균일하게 나온 반면 고체 상태 필름의 경우 hexyl기의 치환 위치에 따라 상이한 ΦPL 값을 가지고 있는 것을 확인할 수가 있습니다. 합성된 물질을 이용해서 유기전계효과 트렌지스터의 성능을 측정한 결과을 보면 다 p형 소자의 특성이 나타나고 온도를 조절한 후에 Octyl_NTDT_αhexyl이 70도에서 최대 정공이동도이 0.44 cm2 V-1 s-1을 보여주었다,또한 NTD가 분자간 상호작용이 커서 용해도 낮은 문제가 있기 때문에 본연구에서 알킬 사슬을 도입해서 용액공정용 트랜지스터을 측정해봤고 최대 정공이동도 9.11×10–2 cm2 V−1 s−1을 보여주었다. 따라서, 진공증착 및 용액공정으로 제작한 OFET 장치에서 NTDT 유도체의 헥실기 치환 위치와 소자 성능 간에 상관 관계가 있음을 확인하였다. 주요어: 디케토피롤로피롤, 단분자,구조특성관계, 유기저계효과 트랜지스터Abstract Study on structure-property relationship of 1,5-naphthyridine-2,6-dione (NTD) derivatives for organic field-effect transistors Organic field-effect transistors (OFETs) have attracted great attention due to their advantages of flexibility and solution processability. Many researchers have made great efforts on development of high-performance organic semiconductor materials and exploring their structure-property relationships to optimize the device performances. Among many organic semiconductors, organic molecules containing bis-lactam functional groups have been drawing special attention for high-performance OFET materials because of their high electron affinity, tunable solubility, and strong π-π interaction. Recently, a novel bis-lactam-based small molecule, 1,5-dioctyl-3,7-di(thiophene-2-yl)-1,5-naphthyridine-2,6-dione (NTDT), was developed. In comparison with the well-known bis-lactam-based semiconducting material such as 2,5-dioctyl-3,6-di(thiophen-2-yl) pyrrolo[3,4-c]pyrrole-1,4-dione (DPPT), NTDT exhibited more favorable thin-film morphology and electronic coupling structures for charge transport due to two-dimensional (2D) C-H‧‧‧O=C intermolecular interaction, highly planar molecular structure, and strong intermolecular π–π stacking. Although NTDT showed promising hole mobility in the OFET devices, there is still much room for further improvement. Therefore, studying structure-property relationships of NTDT derivatives is highly desired. This study aims to investigate the effect of molecular planarity and crystallinity on the performance of OFET devices using NTDT-based semiconductors. In this work, we designed and synthesized a series of NTDT derivatives bearing additional two hexyl side chains at three different positions (α, β, and γ) in the thiophene rings of NTDT. Their optoelectronic properties were thoroughly investigated by UV-vis absorption, photoluminescence, and cyclic voltammetry (CV) measurements as well as theoretical calculation using density functional theory (DFT) method. It was found that the substitution position of the hexyl chains influenced molecular planarity of the NTDT derivatives, which significantly altered their optoelectronic and thermal properties as well as crystallinity in the solid state. Interestingly, the photoluminescence quantum yields (ΦPL) of the NTDT series were unity in solution state regardless of the substitution of additional hexyl chains. In contrast, in films, the NTDT derivatives showed different ΦPL values depending on the substitution position of the hexyl chains. Finally, vapor-deposited and solution-processed OFET devices were fabricated using the NTDT derivatives. In the vapor deposited devices, Octyl-NTDT-αhexyl showed the best hole mobility (μh) up to 0.44 cm2 V-1 s-1 among the series, while Octyl-NTDT-βhexyl showed the best μh as high as 9.11×10-2 cm2 V−1 s−1 in the solution-processed devices. In contrast, the μh of Octyl-NTDT-γhexyl was significantly low in both devices due to the twisted molecular structure. Through X-ray diffraction (XRD) studies, it was revealed that there was a correlation between the substitution position, crystallinity, and device performance of the NTDT derivatives. Keywords:1,5-naphthyridine-2,6-dione, Small molecule, D-A structure, Structure-Property Relationship, Organic Field-Effect Transistor.Contents Abstract ⅰ List of Table v List of Schemes vi List of Figures vii Chapter 1 Introduction 1 1.1 Organic field-effect transistors (OFETs) 1 1.1.1 Introduction of OFETs 1 1.1.2 Operation principle of OFETs 3 1.1.3 Device characterization 10 1.1.4 Organic semiconductors for OFETs 16 1.2. Organic semiconductors containing lactam moiety 23 1.2.1 Introduction of Diketopyrrolopyrrole (DPP) 26 1.2.2 Introduction of 1,5-naphthyridine-2,6-dione (NTD) 28 1.3 Research Objective 29 1.4 Bibliography 31 Chapter 2 Study on Structure-Property Relationship of 1,5-naphthyridine-2,6-dione (NTD) cores with Tuning Alkyl Group 36 2.1 Introduction 36 2.2 Experimental 40 2.2.1 Synthesis 40 2.2.2 Instruments and measurements 45 2.2.3 Fabrication and evaluation of OFETs 46 2.3 Results and Discussion 48 2.3.1 Theoretical molecular orbital calculation used density functional theory (DFT) 48 2.3.2. Optical and electrochemical properties of NTD-based Small molecules 51 2.3.3 Thermal stability of molecules 65 2.3.4 Vacuum deposited OFETs performance 68 2.3.5 XRD and GIWAX analysis of Vacuum deposited film 73 2.3.6 Solution process OFETs performance 78 2.3.7 XRD analysis for Solution processed OFETs 81 2.4 Conclusion 84 2.5 Bibliography 85 Abstract in Korean 87Maste

CEG 7200-01: Information Security

This course gives a comprehensive study of security vulnerabilities· in information systems and the basic techniques for developing secure applications and practicing safe computing. Topics include: Conventional encryption; Data Encryption Standard; Advanced Encryption Standard; Hashing functions and data integrity; Basic Number Theory; Public-key encryption (RSA); Digital signature; Security standards and applications; Access Control; Management and analysis of security. After taking this course, students will have the knowledge of several well-known security standards and their applications; and the students should be able to increase system security and develop secure applications

CEG/EE 260 Digital Computing Hardware/Switching Circuits

We will discuss and cover basic digital, combinational and sequential logic systems. Labs will be used to gain valuable practical experience in implementing elementary circuits and logic designs

CS 400-01: Data Structures and Software Design

This is a fundamental course for students majoring in Computer Science. Students will learn: basic algorithm analysis techniques; asymptotic complexity; big-0 and big-Omega notations; efficient algorithms for discrete structures including lists, trees, stacks, and graphs; fundamental computing algorithms including sorting, searching, and hashing techniques

CEG 260: Digital Computer Hardware Switching Circuits

We will discuss and cover basic digital, combinational and sequential logic systems. Labs will be used to gain valuable practical experience in implementing elementary circuits and logic designs

CS 790-01: Information Security

This course gives a comprehensive study of security vulnerabilities in information systems and the basic techniques for developing secure applications and practicing safe computing. Topics include: Conventional encryption; Data Encryption Standard; Advanced Encryption Standard; Hashing functions and data integrity; Basic Number Theory; Public-key encryption (RSA); Digital signature; Security standards and applications; Access Control; Management and analysis of security. After taking this course, students will have the knowledge of several well-known security standards and their applications; and the students should be able to increase system security and develop secure applications

Structural Analysis and Deletion Mutagenesis Define Regions of QUIVER/SLEEPLESS that Are Responsible for Interactions with Shaker-Type Potassium Channels and Nicotinic Acetylcholine Receptors.

Ly6 proteins are endogenous prototoxins found in most animals. They show striking structural and functional parallels to snake α-neurotoxins, including regulation of ion channels and cholinergic signaling. However, the structural contributions of Ly6 proteins to regulation of effector molecules is poorly understood. This question is particularly relevant to the Ly6 protein QUIVER/SLEEPLESS (QVR/SSS), which has previously been shown to suppress excitability and synaptic transmission by upregulating potassium (K) channels and downregulating nicotinic acetylcholine receptors (nAChRs) in wake-promoting neurons to facilitate sleep in Drosophila. Using deletion mutagenesis, co-immunoprecipitations, ion flux assays, surface labeling and confocal microscopy, we demonstrate that only loop 2 is required for many of the previously described properties of SSS in transfected cells, including interactions with K channels and nAChRs. Collectively our data suggest that QVR/SSS, and by extension perhaps other Ly6 proteins, target effector molecules using limited protein motifs. Mapping these motifs may be useful in rational design of drugs that mimic or suppress Ly6-effector interactions to modulate nervous system function