155,428 research outputs found
Ji-Won Byun
No full text학위논문(석사)--아주대학교 일반대학원 :의생명학과,2014. 2ABSTRACT ⅰ
TABLE OF CONTENTS ⅲ
LIST OF FIGURES ⅴ
Ⅰ. INTRODUCTION 1
A. Parkinsons disease and related genes 1
B. LRRK2 regulates actin dynamics and microglial motility 1
C. Focal adhesion kinase (FAK) as a master molecule that regulates adhesion and movement of cells 2
D. Specific aims 4
Ⅱ. MATERIAL AND METHODS 5
A. Transgenic mice 5
B. Cell culture 5
C. Time-lapse microscopy 6
D. Immunofluorescence staining 6
E. siRNA transfection 6
F. Immunoprecipitation (IP) assay 7
G. Western blot 7
H. In vivo stab wound assay 8
I. Immunohistochemistry 8
Ⅲ. RESULTS 10
Ⅳ. DISCUSSION 24
Ⅴ. CONCLUSION 26
REFERENCES 27
국문요약 31MasterParkinson’s disease (PD) is a neurodegenerative disease caused by dopaminergic neuronal death in the substantia nigra. Microglia are brain macrophages that continuously survey the microenvironment of the brain to find out and repair brain damage. Although PD associated genes are expressed in microglia, their roles in these cells are largely unknown. The present study revealed that LRRK2, a PD-associated gene, regulates the migration of microglia. LRRK2 was located in ruffles, an actin rich structure of moving cells, when ADP induced microglial movement. In immunoprecipation assay, LRRK2 interacted with focal adhesion kinase (FAK), a protein that regulates the adhesion and migration of cells. LRRK2 and FAK were co-localized with ruffles when microglia actively moved. The overexpression of LRRK2 reduced the phosphorylated FAK levels compared with that of the mock, which suggests that LRRK2 inhibits FAK activation. LRRK2 G2019S, a pathologic LRRK2 mutant, more significantly inhibited the FAK activation and the movement of microglia than non-transgenic LRRK2 did. Furthermore, microglial migration defects were also observed in stab-wounded LRRK2 G2019S TG mice brain. Taken together, these results suggest that LRRK2 suppresses microglial movement by inhibiting FAK activation. Importantly, mutations of LRRK2, such as G2019S, could increase the risk of PD development, since microglia could not properly respond to and repair brain damage
Jong Won Lee
No full text학위논문(박사)--아주대학교 일반대학원 :신경과학기술과정,2010. 2인간을 비롯한 동물들은 외부 시각 단서와 자신의 움직임에 근거하여 외부 공간을 표상한다는 것이 잘 알려져 있다. 그러나 다양한 감각 정보들이 어떻게 통합되어 외부 공간을 표상하는지는 잘 알려져 있지 않다. 이러한 과정에 해마 치상이 어떻게 관련되어 있는지 알아보기 위해, 치상 선택적 손상 모델인 백스 유전자 결손 생쥐를 이용해 신경 생리학적 실험과 행동 실험을 수행하였다. 그 결과 백스 유전자 결손 생쥐에서 해마 신경세포의 공간 발화율이 외부 단서와는 완전히 분리되어 발화하는 양상을 보였고, 외부 시각 단서보다는 노출된 전체 공간에 대하여 발화 양상을 유지하려는 경향을 보였다. 또한 전통적 공간 학습 과제에서는 대조군과 마찬가지로 학습을 잘 하나, 자신의 움직임에 근거한 정보 (추측 항법, dead reckoning) 와 외부 시각단서가 불일치했을 때 외부 시각단서에 근거한 공간 학습에서는 학습이 저해되었다. 이러한 결과들은 해마 치상이 외부 시각 단서를 내부 공간 표상에 통합하는데 있어서 역할을 한다는 것을 시사해준다. 또한 백스 유전자 결핍 생쥐는 이전에 방문했던 장소와 방문하지 않았던 장소를 구분하는 과제도 잘 수행하지 못하였는데, 이것은 해마 치상이 단지 시각 단서 뿐만 아니라 물체나 사건 (objects ,events) 등의 감각 정보를 내부 공간 정보에 연합 시키는데도 역할을 할 가능성이 높다는 것을 시사해 준다.ABSTRACT ⅰ
TABLE OF CONTENTS ⅲ
LIST OF FIGURES ⅴ
Ⅰ. INTRODUCTION 1
A. Spatial representation in the hippocampus 1
B. Dissociated streams of inputs into hippocampus 2
C. The role of distinct hippocampal subregions 5
1. DG 5
2. CA3 6
3. CA1 7
D. Bax knock-out mouse with impaired adult neurogenesis 8
Ⅱ. MATERIALS AND METHODS 11
A. NEUROPHYSIOLOGY 11
1. Animals 11
2. Behavioral paradigm 11
3. Unit recording 14
4. Analysis 15
5. Statistical analysis 16
6. Histology 18
B. BEHAVIOR 20
1. Spatial reference memory task in water maze 20
2. Spatial reference memory task on radial maze 20
3. Spatial working memory task on radial maze 21
4. Statistical analysis 22
Ⅲ. RESULTS 23
A. NEUROPHYSIOLOGY 23
1. Running speed 23
2. Theta EEG for control and Bax-KO mice 23
3. Characteristics of unit recording 24
4. Dependence of spatial firing on sensory cue 27
5. Relationship between spatial selectivity and cue-dependent firing 33
6. Similar rate remapping scores 36
B. BEHAVIOR 38
1. Performance in water maze 38
2. Performance in radial maze spatial reference memory task 40
3. Performance in spatial working memory task 43
Ⅳ. DISCUSSION 46
A. Role of DG in aligning internal spatial map to external landmark 46
B. Role of CA3 versus DG in aligning internal spatial map to external landmark 49
C. Strong influence of trisynaptic pathway on discharges of CA1 neurons 51
D. Role of DG in binding spatial and non-spatial information 52
Ⅴ. CONCLUSIONS 54
REFERENCES 55
국문요약 69MasterIt is well known that humans and animals form internal representations of external space based on their own body movement (dead reckoning) as well as external landmarks. It is poorly understood, however, how different types of information are integrated to form a unified representation of external space (i.e., cognitive map). To examine the role of dentate gyrus in this process, physiological and behavioral experiments were conducted using Bax knock-out (Bax-KO) mice in which newly generated granule cells continue to accumulate disrupting neural circuitry specifically in the dentate gyrus. Unlike Wild-type (WT) littermates, spatial firing of hippocampal neurons is completely dissociated from a distinct visual cue and instead, tended to stay constant relative to the recording room in Bax-KO mice. Moreover, whereas spatial learning was intact in Bax-KO mice in conventional spatial reference memory tasks, they were impaired in finding a target location based on visual landmarks when target locations predicted by dead reckoning and visual landmarks were made incongruent. These results suggest that the dentate gyrus is involved in aligning animal’s internal spatial representation to external landmarks, which is a necessary process for representing a distinct spatial map for each environment (i.e., remembering ‘where’). Bax-KO mice were also impaired in discriminating between previously visited and unvisited locations, which suggests a broader role of dentate gyrus in integrating different sources of information. Collectively, these results raise the possibility that the DG might be a region where the internal spatial representation is rapidly associated with the sensory information on external objects and events
In baseball, Bangor won the Class A state championship, Orono won the Class B, Y
No full textIn baseball, Bangor won the Class A state championship, Orono won the Class B, Yarmouth won the Class C and Ft. Fairfield won the Class D. In softball, Portland won the Class A championship, Oak Hill won the Class B, Madison won the Class C and Jonesport-Beals won the Class D
Sung-Won Lee
No full text학위논문(박사)--아주대학교 일반대학원 :컴퓨터공학과,2014. 2CHAPTER I INTRODUCTION １
I.A. Background １
I.B. Summary of the Thesis ２
CHAPTER II RELATED WORK ６
II.A. Taxonomy in Content-Centric Networking ６
II.B. In-network Caching ８
II.C. Content-based Routing １１
II.D. Position of Proposed Schemes １２
CHAPTER III LIGHTWEIGHT PREFIX-BASED ROUTING １３
III.A. Introduction １３
III.B. Problem Definition １５
III.C. Lightweight Prefix-based Routing (LPR) １８
III.C.1. Neighbor Discovery １８
III.C.2. Lightweight Route Discovery ２０
III.C.3. FIB Construction and Prefix-based Routing ２２
III.D. Performance Evaluation ２４
III.D.1. Simulation Environments ２４
III.D.2. Simulation Results ２６
CHAPTER IV PHEROMONE-BASED CACHE REPLACEMENT AND FORWARDING ２９
IV.A. Introduction ２９
IV.B. Problem Definition ３０
IV.C. Pheromone-based CCN (P-CCN) ３３
IV.C.1. Pheromone Estimation and Propagation ３４
IV.C.2. Pheromone-based Cache Replacement ３６
IV.C.3. Pheromone-based Forwarding ３８
IV.D. Performance Evaluation ４３
IV.D.1. Simulation Environments ４３
IV.D.2. Simulation Results ４５
CHAPTER V CACHE CAPACITY-AWARE CCN ４８
V.A. Introduction ４８
V.B. Problem Definition ４９
V.C. Cache Capacity-aware CCN (CC-CCN) ５４
V.C.1. Cache Capacity Estimation ５４
V.C.2. Selective Caching ５７
V.C.3. Cache-aware Routing ５９
V.D. Performance Evaluation ６１
V.D.1. Simulation Environments ６１
V.D.2. Simulation Results ６２
CHAPTER VI CONCLUSION AND FUTURE WORKS ６８
APPENDIX: OPNET CCN SIMULATOR ７２
A. Introduction ７２
B. Problem Definition ７２
C. OPNET CCN Simulator ７４
1. Node Models ７５
2. System Parameter Management ７８
3. CCN Topology Generation ７９
D. Verification of OPNET CCN Simulator ８０
1. CCN Traffic Generator ８０
2. CCN Route Support and Forwarding Engine ８２
3. Content Store (Cache Management) ８３DoctoralContent-Centric Networking (CCN) is a new, redesigned communication networking architecture of the Internet to replace traditional host-centric communication with content-centric communication. CCN proposes an architecture which is centered on the content itself, without regard to where it is physically located. The CCN architecture includes an in-network caching and a content-based routing as main features where every content has its own name as an identifier. Although content-centric networking embraces caching and content-based routing, there is little work on the comprehensive interaction between them. Most ongoing research on content-centric networking is centered on independent research item among emerging contents analysis, content naming, caching technology, and content-oriented routing. Therefore, we have an aim for synergy between cache management and content-based routing.
To reliably evaluate CCN performances, we developed OPNET CCN Simulator which is easy to configure diverse network environments. It covers most functionality of existing CCN simulators and overcome their drawbacks by providing GUI-based configuration, heterogeneous cache management and CCN topology generator software that allows users to generate diverse Internet-like topologies with node naming. Then, we propose the lightweight prefix-based routing protocol with a consideration of the complexity of the longest-prefix matching in CCN. The proposed scheme limits the area of route discovery to reduce the number of entries in the routing table and FIB with aggregation mechanism. Furthermore, the LPR provides a method of using inter-hierarchical connections to reduce overall route lengths.
As an interactive mechanism between cache replacement and cache-aware routing, the pheromone-based cache replacement and forwarding algorithm is proposed with a new metric, pheromone. This metric represents a degree of content concentration for a particular category. In addition, the metric is utilized to diverse the cached contents in the local area and to forward Interest to a router which has been expected to cache the required content. Then, the forwarding algorithm leads to concentrate contents of the particular category in the router even if cache miss occurs. In addition, the cache capacity-aware content centric networking is proposed for an interaction between cache replication and cache-aware routing. This proposal considers cache capacity as a main metric which is a supportable caching space and can be defined with a willingness degree by the previous proposal. The proposed scheme is composed of a selective caching and a cache-aware routing algorithm which provides deterministic cache-awareness without any control message. Then, with analysis about CCN performance under flash crowd, the CC-CCN mechanism is extended with flash crowd detection and related confrontational procedures to reduce network impact by flash crowd.
Simulation studies for each proposed scheme show that content-based routing mechanisms in both sides of server-aware and cache-aware routing need little control overhead and help cache hit ratio to be improved. In addition, a synergy effect between the proposed cache management algorithms and the cache-aware routing makes significant caching performance improvement and network load reduction even in flash crowd effect
Initial and Post-Initial Code Acquisition in the Non-Coherent Multiple Input/Multiple Output Aided DS-CDMA Downlink
No full textIn this paper, we investigate the issues of both initial and post-initial acquisition schemes in the multiple-input/multiple-output (MIMO)-aided direct-sequence code-division multiple-access (DS-CDMA) downlink when communicating over spatially uncorrelated Rayleigh channels. The associated mean acquisition time (MAT) performance trends are characterized as a function of the number of MIMO elements. Furthermore, we characterize both the initial and post-initial acquisition performance as a function of the relevant system parameters. Our findings suggest that increasing the number of transmit antennas in a MIMO-aided CDMA system results in combining the low-energy noise-contaminated signals of the transmit antennas, which ultimately increases the MAT by an order of magnitude when the signal-to-interference-plus-noise ratio (SINR) is relatively low, regardless of whether single- or multipath scenarios are considered. This phenomenon has a detrimental effect on the performance of Rake-receiver-based synchronization schemes when the perfectly synchronized system is capable of attaining its target bit-error-rate performance at reduced SINR values, as a benefit of employing multiple transmit antennas. Based on our analysis justified by information-theoretic considerations, our acquisition design guidelines are applicable to diverse noncoherent (NC) MIMO-assisted scenarios
MeSH term explosion and author rank improve expert recommendations
No full textInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
Differential Coherent Code Acquisition in the Multiple Transmit/Receive Antenna Aided DS-CDMA Downlink
No full textIn this contribution we investigate both differentially coherent and noncoherent code acquisition schemes in the multiple transmit/receive antenna aided DS-CDMA downlink, when communicating over uncorrelated Rayleigh channels. It is demonstrated that in contrast to our expectations, the achievable Mean Acquisition Time (MAT) degrades at low Ec/Io values, as the number of transmit antennas is increased in both differentially coherent and noncoherent code acquisition system scenarios, even though the degree of performance degradation depends upon the specific scheme considered. Ironically, our findings suggest that increasing the number of transmit antennas in a MIMO-aided CDMA system results in combining the low-energy, noise-contaminated signals of the transmit antennas, which ultimately increases the MAT by an order of magnitude, when the SINR is relatively low. Therefore our future research will be aimed at specifically designing acquisition schemes for MIMO systems
Initial synchronisation of wideband and UWB direct sequence systems: single- and multiple-antenna aided solutions
No full textThis survey guides the reader through the open literature on the principle of initial synchronisation in single-antenna-assisted single- and multi-carrier Code Division Multiple Access (CDMA) as well as Direct Sequence-Ultra WideBand (DS-UWB) systems, with special emphasis on the DownLink (DL). There is a paucity of up-to-date surveys and review articles on initial synchronization solutions for MIMO-aided and cooperative systems - even though there is a plethora of papers on both MIMOs and on cooperative systems, which assume perfect synchronization. Hence this paper aims to ?ll the related gap in the literature
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
THE MEXICAN PESO AND THE KOREAN WON REAL EXCHANGE RATES: EVIDENCE FROM PRODUCTIVITY MODELS
No full textUsing the U.S. as benchmark country, Korean data from 1970:1 to 2000:4 and Mexican data from 1983:1 to 2000:4 are decomposed into traded and non-traded sectors. We find that the traditional purchasing power parity (PPP) model performs remarkably well for the Peso and that the productivity model appears adequate for the Peso but not for the Won. As Mexican relative traded goods productivity rises, the nominal Peso appreciates (coefficients between -2.03 and -2.16). Conversely, as U.S. relative traded goods productivity rises, the Peso depreciates (coefficients between 2.06 and 2.48). Although predicting correctly the direction of change, such large magnitudes suggest only partial support for the theoretical mechanism in Mexico. Coefficients with contrary signs obtained in Korea may indicate competing models (neoclassical or Ricardian) are more appropriate to capture the relationship between productivity and exchange rates.Cointegration, Non-traded Goods, Traded Goods, Traditional PPP, Productivity Models
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