치과용 임플란트로서의 지르코니아의 골적합성을 증가시키기 위한 졸 젤 법을 활용한 하이드록시아파타이트 코팅

학위논문(박사) -- 서울대학교대학원 : 공과대학 재료공학부, 2021.8. 김진영.다양한 이유로 상실되는 치아를 대체하기 위한 치과용 임플란트는 널리 사용되고 있는 경조직 임플란트이다. 치과용 임플란트로 가장 널리 사용되는 재료는 티타늄(Ti)으로 우수한 강도와 생체 친화성을 장점으로 가지고 있다. 하지만 이 티타늄은 금속 특유의 광채를 갖는 표면 때문에 심미적으로 거부감을 갖을 수 있으며, 금속에서의 비특이적 면역 반응과 침 등의 생체 물질에 의한 부식 등이 문제가 되고 있다. 한편 지르코니아는 우수한 기계적 물성과 미적 효과와 부식과 면역 반응에서 자유롭다는 점에서 최근 새로운 치과용 임플란트 소재로 주목 받고있다. 하지만 지르코니아는 상대적으로 낮은 골적합성을 가지고 있다는 단점이 존재한다. 하이드록시아파타이트는 인체 뼈의 대표적인 구성 물질로 체내에 많이 존재하는 생체 친화성 세라믹이다. 특유의 우수한 생체 친화성 덕분에 수많은 생체 재료의 표면을 코팅하기 위한 재료로 사용되고 있다. 지르코니아의 생체 적합성 향상을 위한 하이드록시아파타이트 (HA) 코팅 관련 연구가 많이 진행되었지만 두꺼운 두께와 고온 소결에서의 부산물 생성 등에 의한 안정성 저하가 문제가 되고 있다. 이 연구에서는 지르코니아의 생체 적합성을 증가시키기 위해 졸-젤법을 이용하여 하이드록시아파타이트를 코팅하고자한다. 졸-젤법을 이용하여 코팅층의 나노 및 마이크로 구조를 변화시켜 생체 적합성을 더욱 더 증진시키고, 소결 온도를 조절하여 부산물이 없는 얇고 안정적인 하이드록시아파타이트 코팅 층을 형성하고자 한다. 먼저 하이드록시아파타이트 코팅층의 표면 구조를 변화시키기 위해 소결온도 및 하이드록시아파타이트 졸의 에이징 시간을 조절하였고, 주사전자현미경 (SEM) 관찰을 통해 표면 구조를 관찰하여 소결온도가 나노 구조에, 에이징 시간이 마이크로 구조에 영향을 끼침을 알았다. 또한 투과전자현미경 (TEM) 관찰을 통해 에이징 시간에 따른 하이드록시아파타이트 졸 내의 입자 크기의 변화를 확인하였고, 이 변화가 코팅층의 마이크로 구조 변화의 원인임을 알 수 있었다. 집속 이온 빔 (FIB)을 통한 두께를 측정하였을 때, 코팅 층은 150 nm 정도, 마이크로 구조를 가지는 부분은 800 nm 정도의 크기를 가짐을 확인하였다. 또한 비접촉 3D 표면 분석을 통해 Ra가 마이크로 구조를 가질 경우 350 nm 정도로 마이크로 구조가 없을 때의 100 nm 정도보다 증가함을 확인하였다. 또한 X-선 회절 분석기 (XRD)와 X-선 광전자 분광법 (XPS)을 통해 소결 온도를 섭씨 800도로 진행했을 때 HA와 지르코니아 이외의 결정상은 없던 반면, 1000도로 진행했을 때 불순물인 칼슘 지르코네이트가 생성된 것을 확인하였다. 코팅층과 지르코니아의 접촉 강도는 Instron을 통한 tensile test로 진행되었고, 약 40 MPa 이상의 값을 가져 치과용 임플란트 응용 분야로 적절하였다. 이런 부분들을 종합하여 섭씨 800도 조건 하에 마이크로 구조의 형성을 조절하여 조골 세포를 통한 세포 실험을 진행하였고, 마이크로 구조를 가지는 경우가 세포 특성이 증가함을 확인하였다. 이를 바탕으로 생체 내 동물 실험을 비교군인 티타늄과 더불어 하이드록시 아파타이트가 코팅된 지르코니아와 지르코니아에 실행한 결과, 지르코니아의 골 적합성이 하이드록시 아파타이트 코팅에 의해 극적으로 향상됨을 입증했으며, 이는 기존 티타늄 임플란트와 비슷한 수준이었다. 이 연구를 통해 하이드록시 아파타이트를 통한 지르코니아의 골적합성 증가를 이뤄낼 수 있었다. 또한 하이드록시아파타이트 졸의 에이징 시간 및 소결 시간을 조절하여 코팅 층의 나노 및 마이크로 구조를 조절할 수 있었으며, 특히 소결 시간을 조절하여 지르코니아와 하이드록시아파타이트의 부산물인 칼슘 지르코네이트의 생성을 억제할 수 있었다. 이를 기반으로 생성한 졸 젤 기반 HA 코팅 지르코니아가 치과용 임플란트 재료로 사용하기에 큰 잠재력을 가지고 있음을 세포 실험 및 생체 내 동물 실험을 통해 입증하였다.Dental implants for replacing teeth lost for various reasons are widely used hard tissue implants. The most widely used material for dental implants is titanium (Ti), which has excellent strength and biocompatibility. However, titanium can have an aesthetic rejection because of its unique shiny surface, and non-specific immune reactions in the metal and corrosion by biomaterials such as saliva are problematic. Meanwhile, zirconia is attracting attention as a new dental implant material in that it is free from corrosion and immune reactions, as well as excellent mechanical properties and aesthetic effects. However, zirconia has a disadvantage in that it has relatively low bone compatibility. Hydroxyapatite is a biocompatible ceramic that exists in a large number of human bones as a representative component of human bone. Due to its unique excellent biocompatibility, it is used as a material for coating the surface of numerous biomaterials. There have been many studies related to hydroxyapatite (HA) coating for improving the biocompatibility of zirconia, but there is a problem with a thick thickness and deterioration of stability due to by-product formation in high-temperature sintering. In this study, to increase the biocompatibility of zirconia, we intend to coat hydroxyapatite using the sol-gel method. The sol-gel method is used to further improve biocompatibility by changing the nano and micro structures of the coating layer, and to form a thin and stable hydroxyapatite coating layer without by-products by controlling the sintering temperature. First, in order to change the surface structure of the hydroxyapatite coating layer, the sintering temperature and the aging time of the hydroxyapatite sol were adjusted, and the surface structure was observed through scanning electron microscope (SEM) observation. It was found to have an effect on the microstructure. In addition, through transmission electron microscopy (TEM) observation, the change in the particle size in the hydroxyapatite sol according to the aging time was confirmed, and this change was found to be the cause of the change in the microstructure of the coating layer. When the thickness was measured through a focused ion beam (FIB), it was confirmed that the coating layer had a size of about 150 nm, and the portion having a microstructure had a size of about 800 nm. In addition, through non-contact 3D surface analysis, it was confirmed that when Ra has a microstructure, it is about 350 nm, which is higher than about 100 nm when there is no microstructure. In addition, when the sintering temperature was 800 oC through X-ray diffraction analyzer (XRD) and X-ray photoelectron spectroscopy (XPS), there was no crystal phase other than HA and zirconia. It was confirmed that was generated. The contact strength between the coating layer and the zirconia was conducted by a tensile test through Instron, and had a value of about 40 MPa or more, which was suitable for dental implant applications. Cell experiments were conducted through osteoblasts by controlling the formation of microstructures under conditions of 800 oC, and it was confirmed that the in vitro cell characteristics increased when the microstructure was formed. Based on this, as a result of conducting in vivo animal experiments on zirconia and zirconia coated with hydroxyapatite along with titanium as a comparative group, it was proved that the bone compatibility of zirconia was dramatically improved by hydroxyapatite coating, which is similar to that of conventional titanium implants. Through this study, it was possible to achieve an increase in the bone compatibility of zirconia through hydroxyapatite. In addition, by controlling the aging time and sintering time of the hydroxyapatite sol, the nano and microstructure of the coating layer could be controlled. In particular, by controlling the sintering time, the formation of calcium zirconate, a by-product of zirconia and hydroxyapatite, could be suppressed. It was proved through in vitro cell experiments and in vivo animal experiments that the sol gel-based HA-coated zirconia produced based on this has great potential for use as a dental implant material.Chapter 1. Introduction 1 1.1. Biomaterials for dental implant 2 1.2. Hydroxyapatite coating for enhacing osseointegration 4 1.3. Issue of hydroxyapatite coating on zirconia Introduction 6 1.3.1. surface modification of hydroxyaptite coating layer 8 1.3.2. limitation of hydroxyapatite coating on zirconia 13 1.4. Purpose of this study 15 Chapter 2. Materials and methods 19 2.1. Materials for HA-coated zirconia 20 2.1.1. Preparation of the zirconia substrates 20 2.1.2. Ha sol synthesis 20 2.2. HA-coated zirconia preparation 21 2.3. Characterization of HA-coated zirconia 22 2.4. In-vitro osseointegration of the HA-coated zirconia 23 2.5. In-vivo osseointegration of the HA-coated zirconia 24 2.6. Statistical analysis 26 Chapter 3. Results and discussion 30 3.1. Control the surface morphology of the HA layer 31 3.1.1. Sintering temperature 31 3.1.2. HA sol aging time 33 3.2. Control the reaction of HA and zirconia by adjusting sintering temperature 37 3.2.1. Characteristics of HA coated zirconia with various sintering temperature 37 3.2.2. Coating stability of HA coated zirconia 40 3.3. Comparision of HA-coated zirconia with and without micro roughness 43 3.4. In-vitro osseointegration of the HA-coated zirconia 46 3.4.1. Osteoconductivity of roughness difference 46 3.4.2. Osteoconductivity of HA-coated zirconia 47 3.5. In-vivo osseointegration of the HA-coated zirconia 48 Chapter 4. Conclusions 68 4.1. Conclusions 69 Reference 73 Abstract in Korean 89박

의사결정 모델을 이용한 음소 분류과제의 선택과 반응시간 예측

학위논문 (석사)-- 서울대학교 대학원 : 뇌인지과학과, 2013. 2. 이상훈.Despite crucial roles of pre-lexical units in speech perception, modeling efforts so far have been heavily focused on information processing at lexical or post-lexical stages, impeding the mechanistic investigation of speech perception. Given this dearth of frameworks for studying pre-lexical units, the current study proposes a system-level neural model for phoneme classification. A lynchpin idea behind the proposed model is that the brain represents phonemes as probabilistic quantities, likelihoods. With this idea, our model bridges three well-known canonical computations in the brain – sensory encoding, likelihood decoding and evidence accumulation - along a cascade hierarchy of neural processing towards generating inputs to a next stage of speech perception. At the initial stage, sensory neurons with different tuning curves for physical properties relevant to phoneme discrimination compute individual likelihoods for the presence of those properties. Phoneme neurons at the following stage compute likelihoods for specific phonemes by summing the outputs of those sensory encoding neurons with weighting curves tuned for their preferred phonemes. At the final stage, evidence-accumulation neurons compute and accumulate over time evidence to reach a discrete phoneme classification by integrating outputs of phoneme neurons in a task-optimal manner over time. The accumulation-to-bound mechanism operating at this stage translates probabilistic information represented in the phoneme neurons output into concrete choices at a certain time. This translation allowed us to test the empirical viability of our model by assessing its capability of predicting actual patterns of choice fractions and reaction times exhibited by human listeners engaging in phoneme classification under various listening conditions. Using a small number of parameters, the model predicted not only the static, categorical structure of phoneme classification as a function of physical stimulus property, but also the adaptation-induced, dynamic changes in classification on an identical stimulus. Furthermore, the model was flexible enough to cover the wide range of individual differences in phoneme classification behavior. With these behavioral constraints in conjunction with neural and computational constraints exercised in model construction, our model provides a framework for studying neural mechanisms underlying initial stages of speech processing by generating hypotheses and predictions that are testable by neurophysiological and behavioral experiments.1. Introduction 1 1.1. Likelihood model of Phoneme Classification 5 2. Phoneme classification on a cyclic spectrum of stimuli varying in frequency modulation 9 2.1 Methods 9 2.2 Results 12 3. Dynamic changes in phoneme representation following adaptation 15 3.1 Methods 15 3.2 Results 23 4. Simultaneous fit of the likelihood model to phoneme classification responses with and without adaptation 24 5. Discussion 32 6. References 35Maste

초등학교 미술수업을 중심으로

학위논문(석사) -- 서울대학교대학원 : 사범대학 협동과정 미술교육전공, 2023. 8. 김형숙.This study aims to investigate the question, "What approach is needed for elementary students to experience perception more meaningfully in the aesthetic experience domain of the 2022 revised national art curriculum?" The purpose is to explore teaching and learning strategies for perception-centered aesthetic experiences. The theoretical foundation for this research involves a discussion of perception based on the ideas of the educational philosopher Dewey and the phenomenologist Merleau-Ponty. By integrating Dewey's principle of perception in aesthetic experience and Merleau-Ponty's theory of perception, the study develops new perception-centered aesthetic activities. Dewey and Merleau-Ponty share the common viewpoint that human "perception" is intimately connected to the body's "senses." Dewey considers perception as the origin of aesthetic experience, viewing it as an act of cognition where humans perceive the qualities of objects and find their own meanings within them through sensory organs' contact with the external world. Merleau-Ponty explains perception as knowledge through the "body." Here, the "body" serves as the perceiving subject and the source of knowledge and experience. Merleau-Ponty emphasizes capturing senses within the "field of phenomena," where the sensory experiences of objects become apparent. Combining Dewey and Merleau-Ponty's perspectives on perception, it can be summarized that "perception" is a process that occurs through "senses," and it requires the integration of sensory experiences and cognitive activities. To understand how perception is addressed in elementary art education, the study examines the concept of perception in the 2015 revised national art curriculum and the relevant chapters in the 2015 revised art textbooks. Additionally, the study examines how perception is addressed in the 2022 revised art and educational curriculum, which is based on the perceptual experience area. The content related to perception reflected in the curriculum serves as a guiding point for the development of new perceptual activities. The analysis of the 2015 revised art textbooks for 3rd and 4th grades (total of 10 volumes) reveals that the term "perception" is not explicitly mentioned. However, the term "senses" is present in chapters focusing on the exploration of characteristics of objects in the experiential domain and the exploration of material characteristics in the expressive domain. Therefore, two types of chapters utilizing "senses" to discover the qualities of objects (experience-centered chapters) and explore material characteristics (expression-centered chapters) can be considered as chapters addressing "perception." The study further analyzes the learning objectives and exploration methods in these perception-centered chapters, concluding whether they align with Dewey's concept of perception. In the 2015 revised 3rd and 4th grade art textbooks Volume 10, the units dealing with perception show the following common characteristics. First, in the case of experience-oriented units, there is a tendency to focus on 'visual' with the images in textbooks in the activities of observing the characteristics of objects or feeling them with the five senses. Second, in the limited situation of a classroom, 'sense' is often dealt with in a way that is recalled from past experiences and connected with a representative sense that matches the subject presented by the textbook. Third, in the expression-oriented units, it is common to explore the characteristics of materials using the senses and then move on to simple expression activities. Fourth, the method of explaining materials in expression-oriented units tends to be handled in terms of the function of materials. On the premise of viewing materials as tools for expression, this course focuses on how to use materials. The approach to addressing perception in the textbooks exhibits certain issues according to Dewey's perspective on perception: Firstly, there is a high possibility that activities focusing on "visual" aspects dominate those exploring "senses." Dewey emphasizes the need for the convergence of sensory organs to truly perceive the object (Dewey, 2016). Although the textbooks mention the utilization of various senses in activity objectives and instructions, since it is difficult to find aesthetic experience materials right away in the classroom, it is highly likely to become an exploration focusing only on the visual characteristics of the subject while looking at the images in the textbook. The practical constraints in the classroom often lead to a visual-focused exploration of object characteristics, making it difficult to integrate the diverse sensory experiences. Secondly, the textbooks' approach to addressing senses is often limited to re-recognition in which students recall past experiences and recognize the senses at the time. Depending on memory, it is expected that it will be difficult to move on to meaningful perception in the way that brings senses out of consciousness or matches the senses that come to mind by looking at images. Thirdly, the sequential transition from exploring material characteristics to expressive activities may deprive students of the time to reflect on their sensory experiences. However, if students engage in expressive activities without having time to interpret and signify sensory experiences, interaction with materials may become difficult to occur. Interaction with materials requires students to think back on sensory experiences. Fourthly, prescribing specific exploration methods for material characteristics may limit students' perception. Following the prescribed methods may hinder students from discovering the characteristics and the deeper essence of the material. As an alternative, the study establishes the "Perception-Centered Aesthetic Experience Principle" by integrating Dewey and Merleau-Ponty's perspectives on perception. Guided by Dewey's concept of "aesthetic experience," the principle sets the direction for perceptual learning. By reading Merleau-Ponty's theory of perception from an art educational perspective, essential elements are extracted. Based on this synthesis, the study develops five "Perception-Centered Aesthetic Activities" to enable students to experience rich perception in the classroom. The "Perception-Centered Aesthetic Experience Principle" consists of four aspects: "Perceiving Objects in Everyday Situations (Fields of Phenomena)," "Perceiving from Diverse Situations and Perspectives," "Utilizing Senses Holistically," and "Connecting Senses and Thinking." The principle introduces materials used as artistic expression tools and materials with a narrative, integrating them into the perceptual experience's subject matter. The five "Perceptual-Centric Aesthetic Activities" using these materials are as follows: "Materials with Narratives" refers to materials whose raw ingredients come from nature and are carefully harmonized with various elements and conditions of humans and the environment to create a complete substance. The term "narrative" here refers to the process through which materials are transformed from their natural state into usable materials. In this context, both conventional art materials and materials with narratives are utilized as subjects for aesthetic experiences. By understanding the narrative behind a material, one can grasp its essential dimension. This process allows us to go beyond the conventional perspective of seeing materials merely as tools for creation and discover new aspects of the materials, expanding our understanding of them. The materials with narratives introduced in this study include traditional handmade paper made from the bark of paper mulberry trees, charcoal made from burned wood, watercolor paints made from plant extracts, clay made from soil, and ink made from charred pine. This study introduces five perception-centered aesthetic experience activities" that approach and understand materials from various situations and perspectives for the purpose of guiding perception with narrative materials and expression materials. The first activity, Recognizing the creation process of materials, allows students to perceive the senses within the context by discovering the field of phenomena in the material creation process with narrative materials. Observe the interaction between humans and the environment that exists in the process of turning natural objects (raw materials) into materials. Recognize the existence of humans, the environment, and resources necessary for the creation of materials, and understand that materials are completed through the interaction between them. This is an attempt to discover the material in the field of phenomena in which the material is placed through the narrative of the material and to understand the material fundamentally, including the surrounding environment related to the material. It is an activity to understand the material more deeply by capturing the senses in vivid scenes of life and perceiving the field of various phenomena surrounding the material while watching a video of the material creation process. The second activity, Experience a new perspective of exploration through poetry is an activity in which students learn how to see an object through the poets eyes while reading poetry. The poet of the poem A Grain of Jujube introduced in this study reads beyond what is visible in the jujube through imagination to the invisible past of the jujube. The training of seeing things through the eyes of a poet can help students develop their eyes to perceive things more deeply. Therefore, through poetry, we want to create an art class that understands the way poets see objects and approaches and understands materials through the eyes of poets. The third activity, in the activity of Recognizing the artists attitude toward materials, we introduce artists who break away from the subject-tool relationship and breathe with materials and respect them as if they were life. Students pay attention to the way artists and materials meet while watching artist interviews and work videos. Through scenes in which humans and materials respond and interact with each other, students can get a glimpse of the possibility of newly encountering materials that have been taken for granted as a means of expression. The fourth activity, touching without purpose of expression activity is an activity to explore materials by paying attention to the physical properties felt by touching them freely with ones own sensory organs without accepting them based on the knowledge already possessed. Instead of a standardized order and method, in a free atmosphere, he touches the material to his heart's content and tries various movements, immersing himself in his senses and having time to realize the characteristics of the material himself. As such, it is expected that the sensory experience of immersion will enable students to vividly accept the senses and enable richer perception with materials. The fifth activity, Reflection on sensory experiences while writing a material exploration report is an activity in which students connect their senses and thoughts while organizing what they learned and felt while exploring materials. At the same time, he ruminates on the experience of sensing the material. It can be seen as a final step towards becoming an aesthetic experience while discovering new meanings. Aesthetic experience classes using 'perception-centered aesthetic experience activities' can be operated by selecting an appropriate activity out of 5 activities and reorganizing the order according to the selected materials and class conditions. By utilizing materials used as means of expression and materials with narratives, I think that students will be able to experience perception in the process of viewing and deeply understanding materials from various perspectives and situations. Furthermore, it is thought that the five perception-centered aesthetic experience activities can be learning activities that enable students to understand materials more deeply while closely interacting with materials beyond the fixed frame of recognizing materials only as tools of expression.본 연구는 2022 미술과 교육과정 미적 체험 영역에서 초등학생들이 지각(知覺)을 보다 의미 있게 경험하기 위해 어떠한 접근이 필요한가라는 질문에서 시작하여, 지각을 학습할 방안을 탐색하는 데 그 목적이 있다. 이에 대한 이론적 토대로 교육철학자 듀이(Dewey, J.)가 말하는 지각에 대해 고찰하고 구체적인 교수·학습 활동을 구상함에 있어 몸 현상학자 메를로-퐁티(Merleau-Ponty, M.)의 지각이론을 참조한다. 듀이와 메를로-퐁티는 인간의 지각을 몸의 감각과 긴밀하게 연결한다는 공통점이 있다. 듀이는 지각을 인간이 감각 기관을 통해 외부 세계를 접촉하며 대상의 질성을 포착하고 그 안에서 자신의 의미를 찾는 인식 작용으로 본다. 메를로-퐁티는 지각을 몸에 의한 앎으로 간주하며, 여기서 몸은 지각하는 주체로서 인식의 근원이자 지식과 경험의 원천이다. 듀이와 메를로-퐁티의 지각에 대한 관점을 종합하여 한마디로 요약하면, 지각은 감각을 통해 일어나고 감각 경험과 사고 작용의 연계가 필요하다. 현재 초등학교 미술교과에서 지각이 어떻게 다뤄지는지 검토할 목적으로 2015 및 2022 개정 교육과정의 지각 개념과 2015 개정 미술교과서의 지각을 다루는 단원을 분석한다. 2015 개정 교육과정에 의해 편찬된 3학년, 4학년 미술교과서 5종 총 10권 미술교과서를 분석한 결과, 교과서에는 지각이라는 용어가 언급되지 않고, 감각은 주변 대상의 특징을 발견하는 체험 영역의 단원과 표현 재료의 특징을 탐색하는 표현 영역의 단원에서 동원되는 것을 확인하였다. 따라서 본 연구에서는 감각을 활용하는 단원을 지각을 다루는 단원으로 보고, 단원의 교육 활동과 제시되는 탐색 대상 및 탐색 방법을 분석한다. 여기에 지각에 대한 듀이의 관점에 기초한 연구자의 해석을 덧붙인다. 2015 개정 3, 4학년 미술교과서 10권에서 지각을 다루는 단원들은 듀이가 말하는 지각 측면에서 다음과 같은 문제점을 동반한다. 첫째, 듀이는 대상을 제대로 지각하기 위해서는 여러 감각을 총체적으로 활용해야 한다고 주장하는 데 반해 교과서의 탐색 활동은 대부분 시각 중심으로 전개되는 경우가 많다. 둘째, 교과서에서 감각을 다루는 방식은 지나간 경험에서 감각을 떠올려 감각을 그대로 인식하는 재인에 그칠 우려가 있다. 감각을 기억에 의존하는 활동은 감각 자체를 깊이 탐색하기 어렵다는 한계를 갖는다. 셋째, 감각을 활용하여 재료의 특징을 탐색하고 곧바로 표현 활동으로 넘어가는 순서는 학생들이 자신의 감각 경험을 해석하고 반추할 기회를 뺏어버린다. 다시 말해 학생들의 감각 경험과 사고 작용의 연계가 이루어지지 않으면 결국 재료에 대한 반쪽짜리 앎에 그치게 되는 문제가 생긴다. 넷째, 규정된 탐색 방법은 학생들의 자유로운 사고를 방해하고 지각에 제한을 줄 수 있다. 학생들이 감각을 활용하여 대상의 특징을 몸소 깨닫고 대상을 깊이 이해하는 데 걸림돌이 된다. 이러한 문제점에 대한 대안으로, 듀이와 메를로-퐁티의 지각 관점을 고루 반영하여 지각 중심 미적 체험 원리를 설정한다. 지각 중심 미적 체험 원리는 일상적 경험상황(현상의 장) 속에서 대상을 지각하기, 다양한 상황과 관점에서 지각하기, 몸의 감각을 총체적으로 활용하기, 감각과 사고를 연결시키는 발문 활용하기와 같이 4가지이다. 여기에 표현 수단으로 쓰이는 재료, 서사가 있는 재료를 미적 체험의 대상으로 도입하여 구체적인 5가지 지각 중심 미적 체험 활동을 개발한다. 서사가 있는 재료는 재료의 그 원료가 자연에서 나며, 인간과 환경의 다양한 요소와 조건이 잘 조화되어 완성된 물질이다. 여기서 말하는 서사는 재료가 원료(자연)에서부터 재료로 만들어지기까지 과정을 의미한다. 표현 재료를 미적 체험의 소재로 활용하여 표현을 위한 도구로 보는 관습적인 시각을 탈피하고 재료의 서사를 통해 재료의 본질에 대해 이해한다. 이로써 재료의 새로운 모습을 발견하고 재료를 보는 시각을 확장하는 계기를 마련한다. 본 연구에서 소개하는 서사가 있는 재료로는 닥나무 껍질로 만든 전통 한지, 나무를 태워 만드는 도화용 숯 목탄, 식물을 빻아 나온 색물로 만든 수채화 물감, 흙으로 만든 찰흙, 소나무 그을음으로 만든 먹 등이 있다. 지각을 지도하기 위해 다양한 상황과 관점에서 서사가 있는 재료와 표현 재료에 접근하고 이해하는 5가지 을 소개한다. 첫 번째, 재료의 생성과정 알아보기 활동은 학생들이 서사가 있는 재료를 가지고 재료의 생성과정 속 현상의 장을 발견함으로써 감각을 상황 안에서 지각하도록 한다. 자연물(원료)에서 재료가 되는 과정에 존재하는 인간과 환경 사이의 상호작용을 관찰한다. 재료의 생성에 필요한 자원과 환경, 인간의 존재를 인지하고 이들 간의 상호작용을 통해 재료가 완성된 것임을 이해한다. 재료의 생성과정을 담은 영상을 보면서 생생한 삶의 장면에서 감각을 포착하고 재료를 둘러싼 다양한 현상의 장을 지각함으로써 재료를 더욱 깊이 이해해보는 활동이다. 두 번째, 시를 통하여 새로운 탐색 관점 경험하기 활동은 학생들이 시를 읽으면서 시인의 눈으로 대상을 보는 법을 배우는 활동이다. 본 연구에서 소개하는 시「대추 한 알」의 시인은 상상을 통해 대추에서 보이는 것 너머 보이지 않는 대추의 지나온 세월까지 읽어낸다. 시인의 눈으로 무언가를 보는 훈련은 학생들이 무언가를 더 깊이 지각하는 눈을 키우는 데 도움이 될 수 있다. 따라서 시를 통해 시인이 대상을 보는 방식을 이해하고 시인의 눈으로 재료에 접근하고 이해하는 미술수업을 만들고자 한다. 세 번째, 예술가의 재료 대하는 태도 알아보기 활동에서는 주체-도구의 관계를 탈피하여 재료와 함께 호흡하고 재료를 생명처럼 존중하는 태도를 보이는 예술가를 소개한다. 학생들은 예술가의 인터뷰와 작업 영상을 보면서 예술가와 재료가 만나는 방식에 주목한다. 인간과 재료가 서로 감응하며 상호작용하는 장면을 통해 학생들은 표현 수단으로 당연시 여겨왔던 재료를 새롭게 마주할 가능성을 엿볼 수 있다. 네 번째, 표현 목적 없이 만지기 활동은 재료를 이미 가지고 있는 지식에 의해 받아들이지 않고 자신의 감각 기관으로 자유롭게 만지면서 느껴지는 물리적 속성에 주목하여 재료를 탐색하는 활동이다. 정형화된 순서와 방법 대신 자유로운 분위기에서 재료를 마음껏 만져보고 다양한 움직임을 시도하면서 자신의 감각에 몰두하는 감각 경험은 학생들이 감각을 생생하게 수용하고 재료와 더불어 좀 더 풍성한 지각을 가능케 할 것으로 기대한다. 다섯 번째, 재료 탐구 보고서 쓰면서 감각 경험 반추하기 활동은 학생들이 재료를 탐구하면서 새로 알게 된 점과 느낀 점을 글로 정리하면서 자신의 감각과 사고를 연결하는 활동이다. 동시에 재료를 감각한 경험을 반추한다. 감각 경험에서 새로운 의미를 발견하면서 미적 경험이 되기 위한 마무리 단계로 볼 수 있다. 지각 중심 미적 체험 활동을 활용한 미적 체험 수업은 선택한 재료와 수업 조건에 따라 5가지 활동 중 적합한 활동을 선택하고 순서를 재구성하여 운영할 수 있다. 표현 수단으로 쓰이는 재료와 서사가 있는 재료를 활용하여 학생들이 다양한 관점과 상황에서 재료를 바라보고 깊이 이해하는 과정에서 지각을 경험할 수 있을 것으로 생각한다. 나아가 학생들이 재료를 표현 도구로만 인식하는 고정된 틀을 넘어 재료와 긴밀하게 상호작용할 수 있는 학습 활동이 될 수 있을 것으로 사료된다.Ⅰ. 서 론 1 1. 연구의 필요성과 목적 1 2. 연구 문제 8 3. 연구 방법 9 Ⅱ. 이론적 배경 13 1. 듀이의 경험에서 지각의 전제조건으로서 감각 13 2. 듀이의 경험에서의 지각 18 Ⅲ. 미술교육에서 지각에 대한 논의 26 1. 2015 개정 교육과정의 지각 개념 분석 26 2. 2015 개정 미술교과서의 지각 활동 분석 30 3. 2022 개정 교육과정의 지각 개념 분석 50 4. 듀이의 지각 관점에서 본 미술교육의 문제점 53 Ⅳ. 듀이를 넘어, 대안 탐색 56 1. 지각 중심 미적 체험을 위한 대안 56 2. 새로운 탐색 대상의 요건 65 1. 표현 수단으로 쓰이는 재료 65 2. 서사가 있는 재료 68 Ⅴ. 지각 중심 미적 체험 활동 및 교수·학습 지도안 72 1. 다양한 상황과 관점에서 재료 이해하기 72 1. 재료의 생성과정 알아보기 72 2. 시를 통하여 새로운 탐색 관점 경험하기 80 3. 예술가의 재료 대하는 태도 알아보기 84 4. 표현 목적 없이 만지기 86 5. 재료 탐구 보고서 쓰면서 감각 경험 반추하기 90 2. 지각 중심 미적 체험 수업의 교수·학습 지도안 98 1. <소재 1> 목탄 99 2. <소재 2> 찰흙 103 3. <소재 3> 물감 106 Ⅵ. 결론 109 참고문헌 113 Abstract 117석

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학위논문 (박사)-- 서울대학교 대학원 : 치의과학과, 2015. 2. 이인복.Objectives. The aim of the present study was to measure the polymerization shrinkage, modulus, and shrinkage stress of bulk-fill and conventional composites during polymerization and to investigate the relationship between tooth-composite interfacial debonding and polymerization shrinkage stress of the composites. Methods. Polymerization shrinkage, dynamic modulus, and shrinkage stress of two non-flowable bulk-fill: SonicFill (SF) and Tetric N-Ceram Bulk-Fill (TNB)two flowable bulk-fill: Filtek Bulk-Fill (FB) and SureFil SDR Flow (SDR)one non-flowable conventional: Filtek Z250 (Z250)and one flowable conventional: Filtek Z350 XT Flowable (Z350F) composites were measured using custom-made instruments. Acoustic emission (AE) analysis was performed to evaluate the tooth-composite interfacial debonding during polymerization of the composites in Class 1 cavities on extracted third molars. Results. Polymerization shrinkage (%) of Z350F (3.53) at 10 min was the highest, followed by FB (3.05), SDR (2.99), TNB (2.22), Z250 (2.09), and SF (2.05). Complex shear modulus (MPa) after 20 s of light-curing was highest in SF (996.2), followed by Z250 (831.8), TNB (723.6), Z350F (553.2), SDR (421.3), and FB (334.8). Polymerization shrinkage stress values (MPa) were: Z350F (3.51), TNB (2.42), Z250 (2.38), SF (2.36), FB (2.24), and SDR (1.68). The numbers of AE events were: Z350F (12.6), TNB (7.0), Z250 (7.0), FB (6.8), SF (6.6), and SDR (6.0). Z350F showed the highest polymerization shrinkage stress and AE event number (p 0.05). Conclusions. Composites that exhibited greater polymerization shrinkage stress generated more tooth-composite interfacial debonding. In contrast to similar outcomes among the non-flowable composites (conventional: Z250, bulk-fill: TNB and SF), the flowable bulk-fill composites (FB and SDR) demonstrated lower polymerization shrinkage stress and tooth-composite interfacial debonding than did the flowable conventional composite (Z350F).Contents Abstract (in English) 1. Introduction …………………………………………………… 1 2. Materials and Methods …………………………………… 5 3. Results ……………………………………………………… 12 4. Discussion …………………………………………………… 15 5. Conclusions ………………………………………………… 22 6. References …………………………………………………… 23 Table and Figures ……………………………………………… 29 Abstract (in Korean) …………………………………………… 40Docto

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Autophagy is critical for the maintenance of organelle function and intracellular nutrient environment. Autophagy is also involved in systemic metabolic homeostasis, and its dysregulation can lead to or accelerate the development of metabolic disorders. While the role of autophagy in the global metabolism of model organisms has been investigated mostly using site-specific genetic knockout technology, the impact of dysregulated autophagy on systemic metabolism has been unclear. Here, we review recent papers showing the role of autophagy in systemic metabolism and in the development of metabolic disorders. Also included are data suggesting the role of autophagy in human-type diabetes, which are different in several key aspects from murine models of diabetes. The results shown here support the view that autophagy modulation could be a new modality for the treatment of metabolic syndrome associated with lipid overload and human-type diabetes.ope

Income Tax Policy Suggestions for Improvement of the Elderly Employment

본 연구에서는 OECD가 출간한 『Taxing Wages』와 국세청이 출간한 『국세통계연보』를 이용하여 한국의 소득세 부담을 주요 외국과 비교하고 연령별 세부담 구조를 분석하였으며, 현행의 소득세제가 노년층의 고용에 미치는 영향에 대해 살펴보았다. 우리나라의 소득세 유효세율은 외국에 비하여 낮은 수준이지만, 청장년층에 비하여 소득이 낮은 50~60대 노년층의 유효세율이 오히려 높은 것으로 나타났다. 이는 현행의 소득세제하에서의 조세지원이 주로 소득공제로 이루어지므로 상대적으로 소득이 높은 청년층에 조세지원이 편중되기 때문이다. 또 가구전체의 세부담을 줄이기 위해 가구 내 소득이 가장 높은 가구원에게 소득공제를 집중하여 적용하는 세제상 이차거래로 인해 청장년층의 세부담이 줄어드는 점에도 기인한다. 소득이 낮고 노동공급 탄력성이 높은 노인층의 세부담을 줄이기 위해 인적공제제도 및 근로소득공제 개편과 조세지원방식을 소득공제에서 세액공제로 전환하는 방안을 제시하였다.We analyzed the age structure of effective income tax rates using Taxing Wages published by OECD and The Statistical Yearbook of National Tax of Korea. We found that the effective income tax rates of Korea are lower than those of most of OECD countries. However, the effective tax rates for the elderly are higher than those of non-elderly, because under the current income tax system, tax relieves are provided primarily through tax deductions, which benefit high-income earners more than low-income earners. It is also because of the tax arbitrage which allocates tax deductions to high-income earners within a household. Therefore, we suggest a structural revision of personal deduction, employment income deduction, and reinforcement of the role of tax credits, to improve the efficiency and equity by lowering tax burden of the elderly, who earn less than non-elderly and whose labor supply elasticity is high

Suppressive Effect of Autocrine FGF21 on Autophagy-Deficient Hepatic Tumorigenesis

Mice with hepatocyte-specific deletion of autophagy-related 7 (Atg7 ΔHep mice) develop hepatoma, suggesting that autophagy deficiency could be a factor in the initiation of tumorigenesis. We have shown that FGF21 is induced as a 'mitokine' when Atg7 is disrupted in insulin target tissues such as the liver, which could affect systemic metabolism through endocrine activity. Since FGF21 or other endocrine FGF such as FGF19 can affect tumor growth, we hypothesized that FGF21 produced by Atg7-knockout (KO) hepatocytes may affect the behavior of Atg7-KO hepatoma in an autocrine manner. We, thus, crossed Atg7 ΔHep mice with systemic Fgf21-KO (Fgf21 -/-) mice to generate Atg7 ΔHep Fgf21 -/- mice. The number and size of hepatoma of Atg7 ΔHep mice were significantly increased by additional Fgf21 KO. The proliferation of Atg7-KO hepatocyte was significantly increased by Fgf21 KO. pYAP1/YAP1 representing YAP1 degradation was significantly decreased in the liver of Atg7 ΔHep Fgf21 -/- mice compared to Atg7 ΔHep Fgf21 +/+ mice. Consistently, expression of YAP1/TAZ downstream genes was significantly increased in the liver of Atg7 ΔHep Fgf21 -/- mice compared to Atg7 ΔHep Fgf21 +/+ mice, which could explain the increased size of hepatoma in Atg7 ΔHep Fgf21 -/- mice. Accumulation of ROS and ROS-mediated DNA damage were increased in the liver of Atg7 ΔHep Fgf21 +/+ mice, which was further aggravated by additional Fgf21 KO probably due to the absence of positive effect of FGF21 on mitochondrial function, explaining the increased number of hepatoma in Atg7 ΔHep Fgf21 -/- mice compared to Atg7 ΔHep Fgf21 +/+ mice. These results show that FGF21 produced by autophagy-deficient hepatocytes could have autocrine or paracrine effects on the number and proliferation of autophagy-deficient hepatoma, suggesting that hormones or factors released from autophagy-deficient tumors can influence the behavior or prognosis of the tumor in addition to the effects on host metabolism.ope

An autophagy enhancer ameliorates diabetes of human IAPP-transgenic mice through clearance of amyloidogenic oligomer

We have reported that autophagy is crucial for clearance of amyloidogenic human IAPP (hIAPP) oligomer, suggesting that an autophagy enhancer could be a therapeutic modality against human diabetes with amyloid accumulation. Here, we show that a recently identified autophagy enhancer (MSL-7) reduces hIAPP oligomer accumulation in human induced pluripotent stem cell-derived β-cells (hiPSC-β-cells) and diminishes oligomer-mediated apoptosis of β-cells. Protective effects of MSL-7 against hIAPP oligomer accumulation and hIAPP oligomer-mediated β-cell death are significantly reduced in cells with knockout of MiTF/TFE family members such as Tfeb or Tfe3. MSL-7 improves glucose tolerance and β-cell function of hIAPP+ mice on high-fat diet, accompanied by reduced hIAPP oligomer/amyloid accumulation and β-cell apoptosis. Protective effects of MSL-7 against hIAPP oligomer-mediated β-cell death and the development of diabetes are also significantly reduced by β-cell-specific knockout of Tfeb. These results suggest that an autophagy enhancer could have therapeutic potential against human diabetes characterized by islet amyloid accumulation.ope

Comparison of Mechanical Property of Conventional Rods versus Growing Rods for Pediatric Early Onset Scoliosis

STUDY DESIGN: This is a mechanical study. OBJECTIVES: We wanted to investigate the mechanical properties of newly developed dual growing rods for obtaining approval for their clinical application. SUMMARY OF LITERATURE REVIEW: The current expandable spinal implant system appears effective for controlling progressive early onset scoliosis, and it allows for spinal growth and improving lung development. MATERIALS AND METHODS: We investigate the yield load and ultimate load during compression, tension and torsion of the growing rods and the conventional rods assembly using UHMWPE blocks, and the diameter of the rods was 6.0 mm and they expanded 5cm long. We also performed a fatigue test with growing rods, and the diameter of which was 6.0 mm and it expanded 2.5cm long. The guideline for the American Society for Testing Materials was followed during the entire mechanical test. With the growing rods and conventional rods, we tested for each mechanical property7 times with the new rods and blocks. RESULTS: The yield load of the growing rods and conventional rods were 845.2+/-18.2 (N) and 812.9+/-29.9 (N), respectively, and the ultimate load of the growing rods and conventional rods were 961.9+/-31.1 (N) and 914.9+/-25.6 (N), respectively, when compression force was applied. The yield load and ultimate load of the growing rods were statistically higher than those of the conventional rods (p0.05). The yield loads of the growing rods and conventional rods were 11.56+/-0.59 (Nm) and 12.46+/-0.71 (Nm), respectively, the ultimate loads of the growing rods and conventional rods were 16.97+/-0.94 (Nm) and 17.42+/-2.66 (Nm) during the torsion, respectively. The yield load and ultimate load of the growing rods were statistically lower than that of the conventional rods (p<0.05). CONCLUSIONS: The newly developed growing rods have a higher yield load and ultimate load under compression, a similar ultimate load under tension and a lower yield load and ultimate load under torsion. The differences of the yield load and ultimate load under torsion were minimal, and so the growing rods and conventional rods have similar mechanical propertiesope